Long convoluted tubules in the nephrons. They collect filtrate from blood passing through the KIDNEY GLOMERULUS and process this filtrate into URINE. Each renal tubule consists of a BOWMAN CAPSULE; PROXIMAL KIDNEY TUBULE; LOOP OF HENLE; DISTAL KIDNEY TUBULE; and KIDNEY COLLECTING DUCT leading to the central cavity of the kidney (KIDNEY PELVIS) that connects to the URETER.
The renal tubule portion that extends from the BOWMAN CAPSULE in the KIDNEY CORTEX into the KIDNEY MEDULLA. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the U-shaped LOOP OF HENLE.
Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.
Straight tubes commencing in the radiate part of the kidney cortex where they receive the curved ends of the distal convoluted tubules. In the medulla the collecting tubules of each pyramid converge to join a central tube (duct of Bellini) which opens on the summit of the papilla.
The outer zone of the KIDNEY, beneath the capsule, consisting of KIDNEY GLOMERULUS; KIDNEY TUBULES, DISTAL; and KIDNEY TUBULES, PROXIMAL.
The functional units of the kidney, consisting of the glomerulus and the attached tubule.
The portion of renal tubule that begins from the enlarged segment of the ascending limb of the LOOP OF HENLE. It reenters the KIDNEY CORTEX and forms the convoluted segments of the distal tubule.
The internal portion of the kidney, consisting of striated conical masses, the renal pyramids, whose bases are adjacent to the cortex and whose apices form prominent papillae projecting into the lumen of the minor calyces.
A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.
Slender tubular or hairlike excretory structures found in insects. They emerge from the alimentary canal between the mesenteron (midgut) and the proctodeum (hindgut).
An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.
One or more layers of EPITHELIAL CELLS, supported by the basal lamina, which covers the inner or outer surfaces of the body.
Pathological processes of the KIDNEY or its component tissues.
Biosynthesis of GLUCOSE from nonhexose or non-carbohydrate precursors, such as LACTATE; PYRUVATE; ALANINE; and GLYCEROL.
The transference of a kidney from one human or animal to another.
Accumulation of a drug or chemical substance in various organs (including those not relevant to its pharmacologic or therapeutic action). This distribution depends on the blood flow or perfusion rate of the organ, the ability of the drug to penetrate organ membranes, tissue specificity, protein binding. The distribution is usually expressed as tissue to plasma ratios.
Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.
Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.
The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)
Histochemical localization of immunoreactive substances using labeled antibodies as reagents.
Abrupt reduction in kidney function. Acute kidney injury encompasses the entire spectrum of the syndrome including acute kidney failure; ACUTE KIDNEY TUBULAR NECROSIS; and other less severe conditions.
Established cell cultures that have the potential to propagate indefinitely.
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
The end-stage of CHRONIC RENAL INSUFFICIENCY. It is characterized by the severe irreversible kidney damage (as measured by the level of PROTEINURIA) and the reduction in GLOMERULAR FILTRATION RATE to less than 15 ml per min (Kidney Foundation: Kidney Disease Outcome Quality Initiative, 2002). These patients generally require HEMODIALYSIS or KIDNEY TRANSPLANTATION.
A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue.
Hereditary diseases that are characterized by the progressive expansion of a large number of tightly packed CYSTS within the KIDNEYS. They include diseases with autosomal dominant and autosomal recessive inheritance.
Tumors or cancers of the KIDNEY.
Laboratory tests used to evaluate how well the kidneys are working through examination of blood and urine.
Stones in the KIDNEY, usually formed in the urine-collecting area of the kidney (KIDNEY PELVIS). Their sizes vary and most contains CALCIUM OXALATE.
Kidney disorders with autosomal dominant inheritance and characterized by multiple CYSTS in both KIDNEYS with progressive deterioration of renal function.
The ability of the kidney to excrete in the urine high concentrations of solutes from the blood plasma.
The volume of water filtered out of plasma through glomerular capillary walls into Bowman's capsules per unit of time. It is considered to be equivalent to INULIN clearance.

Dietary magnesium, not calcium, regulates renal thiazide receptor. (1/551)

This study reports for the first time a relationship between dietary Mg and the renal thiazide-sensitive Na-Cl cotransporter (TZR, measured by saturation binding with 3H-metolazone). Ion-selective electrodes measured plasma ionized magnesium (PMg++), calcium (PCa++), and potassium (PK+). Restricting dietary Mg for 1 wk decreased PMg++ 18%, TZR 25%, and renal excretion of magnesium (UMg) and calcium (UCa) more than 50% without changing PCa++, PK+, or plasma aldosterone. A low Mg diet for 1 d significantly decreased PMg++, TZR, UMg and UCa. Return of dietary Mg after 5 d of Mg restriction restored PMg++ and TZR toward normal. In the control, Mg-deficient, and Mg-repleting animals, TZR correlated with PMg++ (r = 0.86) and with UMg (r = 0.87) but not UCa (r = 0.09). Increasing oral intake of Mg for 1 wk increased PMg++ 14%, TZR 32%, UMg 74%, and UCa more than fourfold without changing PCa++ or PK+. In contrast, increasing dietary Ca content from 0.02% to 1.91% did not change TZR, but increased UCa fivefold without changing PCa++. Hormonal mediators (if any) involved in the relationship between dietary Mg and TZR remain to be elucidated, as does the relationship between TZR and tubular reabsorption of Mg.  (+info)

Cellular distribution of cytochromes P-450 in the rat kidney. (2/551)

The distribution of several cytochrome P-450 (P-450) isoenzymes between proximal tubular (PT) and distal tubular (DT) cells of the rat kidney was determined. Western blot analysis of microsomes prepared from liver and kidney cortical homogenates revealed that CYP2E1 protein was expressed in rat kidney microsomes at approximately 10% of hepatic levels. Microsomes from renal cortical, PT, and DT cells all expressed CYP2E1, with DT microsomes expressing slightly higher levels than PT microsomes. In contrast, chlorzoxazone hydroxylation activity was markedly higher in microsomes from PT cells than in those from DT cells. Northern blot analysis of total RNA from PT and DT cells exhibited a pattern of CYP2E1 mRNA distribution similar to that of CYP2E1 protein. CYP2C11 protein expression in renal cortical microsomes was approximately 10% of that in liver microsomes but was significantly higher in microsomes from PT cells than in those from DT cells. CYP3A1/2 was not detected in microsomes from either cortical, PT, or DT cells, but was detected in microsomes isolated from total liver or kidney cortical homogenates. CYP2B1/2 expression was detected in all tissues tested. The peroxisomal proliferator clofibrate enhanced the level of CYP2B1/2 in microsomes from both total liver and kidney cortical homogenates but not in microsomes from cortical, PT, or DT cells. CYP4A2/3 protein and CYP4A mRNA expression were detected in microsomes from total liver and kidney cortical homogenates and from renal cortical, PT, and DT cells using Western and Northern blot analyses, respectively. Lauric acid hydroxylation activity, an indicator of CYP4A, was comparable in PT and DT cells. Clofibrate elevation of CYP4A in cortical, PT, and DT microsomes was not as great as that detected in total kidney cortical microsomes. These results establish the distribution of several P-450 isoenzymes between different cell populations of the rat kidney. Furthermore, these results present evidence that the level of induction of certain P-450 isoenzymes in the kidney is cell type-specific.  (+info)

Identification and characterization of ligands for L-selectin in the kidney. III. Characterization of L-selectin reactive heparan sulfate proteoglycans. (3/551)

L-Selectin, a leukocyte adhesion molecule, mediates leukocyte rolling on the endothelium and plays a critical role in leukocyte recruitment at inflammatory sites as well as in lymphocyte homing. We have previously shown that L-selectin reactive chondroitin sulfate and heparan sulfate proteoglycans (HSPGs) are both expressed in the distal tubules of the kidney and that versican is one of the chondroitin sulfate-type ligands. In the present study, we characterized the heparan sulfate-type ligand(s) in more detail. The molecular sizes of HSPGs were approximately 600 kDa with core protein sizes of 160 and 180 kDa. Western blotting analysis showed that L-selectin reactive HSPGs were neither agrin nor perlecan, major basement membrane HSPGs in the kidney. The binding to L-selectin was mediated by the lectin domain of L-selectin in a Ca2+-dependent manner and required heparan sulfate side chains, but not sialic acid. To our knowledge, this is the first biochemical characterization of the L-selectin reactive heparan sulfate proteoglycan(s) in the distal tubules of the kidney.  (+info)

Expression of 25(OH)D3 24-hydroxylase in distal nephron: coordinate regulation by 1,25(OH)2D3 and cAMP or PTH. (4/551)

Previous studies using microdissected nephron segments reported that the exclusive site of renal 25-hydroxyvitamin D3-24-hydroxylase (24OHase) activity is the renal proximal convoluted tubule (PCT). We now report the presence of 24OHase mRNA, protein, and activity in cells that are devoid of markers of proximal tubules but express characteristics highly specific for the distal tubule. 24OHase mRNA was undetectable in vehicle-treated mouse distal convoluted tubule (DCT) cells but was markedly induced when DCT cells were treated with 1,25 dihydroxyvitamin D3 [1,25(OH)2D3]. 24OHase protein and activity were also identified in DCT cells by Western blot analysis and HPLC, respectively. 8-Bromo-cAMP (1 mM) or parathyroid hormone [PTH-(1-34); 10 nM] was found to potentiate the effect of 1, 25(OH)2D3 on 24OHase mRNA. The stimulatory effect of cAMP or PTH on 24OHase expression in DCT cells suggests differential regulation of 24OHase expression in the PCT and DCT. In the presence of cAMP and 1, 25(OH)2D3, a four- to sixfold induction in vitamin D receptor (VDR) mRNA was observed. VDR protein, as determined by Western blot analysis, was also enhanced in the presence of cAMP. Transient transfection analysis in DCT cells with rat 24OHase promoter deletion constructs demonstrated that cAMP enhanced 1, 25(OH)2D3-induced 24OHase transcription but this enhancement was not mediated by cAMP response elements (CREs) in the 24OHase promoter. We conclude that 1) although the PCT is the major site of localization of 24OHase, 24OHase mRNA and activity can also be localized in the distal nephron; 2) both PTH and cAMP modulate the induction of 24OHase expression by 1,25(OH)2D3 in DCT cells in a manner different from that reported in the PCT; and 3) in DCT cells, upregulation of VDR levels by cAMP, and not an effect on CREs in the 24OHase promoter, is one mechanism involved in the cAMP-mediated modulation of 24OHase transcription.  (+info)

Localization of rat CLC-K2 chloride channel mRNA in the kidney. (5/551)

To gain insight into the physiological role of a kidney-specific chloride channel, CLC-K2, the exact intrarenal localization was determined by in situ hybridization. In contrast to the inner medullary localization of CLC-K1, the signal of CLC-K2 in our in situ hybridization study was highly evident in the superficial cortex, moderate in the outer medulla, and absent in the inner medulla. To identify the nephron segments where CLC-K2 mRNA was expressed, we performed in situ hybridization of CLC-K2 and immunohistochemistry of marker proteins (Na+/Ca2+ exchanger, Na+-Cl- cotransporter, aquaporin-2 water channel, and Tamm-Horsfall glycoprotein) in sequential sections of a rat kidney. Among the tubules of the superficial cortex, CLC-K2 mRNA was highly expressed in the distal convoluted tubules, connecting tubules, and cortical collecting ducts. The expression of CLC-K2 in the outer and inner medullary collecting ducts was almost absent. In contrast, a moderate signal of CLC-K2 mRNA was observed in the medullary thick ascending limb of Henle's loop, but the signal in the cortical thick ascending limb of Henle's loop was low. These results clearly demonstrated that CLC-K2 was not colocalized with CLC-K1 and that its localization along the nephron segments was relatively broad compared with that of CLC-K1.  (+info)

Expression of the polymeric immunoglobulin receptor and excretion of secretory IgA in the postischemic kidney. (6/551)

The humoral mucosal immune response of the kidney involves the transport of secretory IgA (S-IgA) through renal epithelial cells by the polymeric immunoglobulin receptor (pIgR). The pIgR is cleaved and released as free secretory component (FSC) or attached to IgA (S-IgA). We examined the effects of an ischemic model of acute renal failure (ARF) on the expression of pIgR and the secretion of FSC and S-IgA in the urine. Kidney pIgR mRNA levels decreased in ischemic animals by 55% at 4 h and by 85% at 72 h compared with controls. pIgR protein expression in the medullary thick ascending limb (TAL) decreased within 24 h and was nearly undetectable by 72 h. Urinary S-IgA and FSC concentrations decreased by 60% between days 3 and 6. pIgR mRNA and pIgR protein in the kidney returned to approximately 90% of control levels and urinary FSC and S-IgA concentrations returned to approximately 55% of control levels by day 7. We demonstrate that ischemic ARF decreases renal mucosal S-IgA transport in vivo and may contribute to the increased incidence of urinary tract infections.  (+info)

Role of tyrosine phosphorylation in the reassembly of occludin and other tight junction proteins. (7/551)

After the simulation of anoxia by ATP depletion of MDCK cell monolayers with metabolic inhibitors, the tight junction (TJ) is known to become structurally perturbed, leading to loss of the permeability barrier. Peripheral TJ proteins such as zonula occludens 1 (ZO-1), ZO-2, and cingulin become extremely insoluble and associate into large macromolecular complexes (T. Tsukamoto and S. K. Nigam. J. Biol. Chem. 272: 16133-16139, 1997). For up to 3 h, this process is reversible by ATP repletion. We now show that the reassembly process depends on tyrosine phosphorylation. Recovery of transepithelial electrical resistance in ATP-replete monolayers was markedly inhibited by the tyrosine kinase inhibitor, genistein. Indirect immunofluorescence revealed a decrease in staining of occludin, a membrane component of the TJ, in the region of the TJ after ATP depletion, which reversed after ATP repletion; this reversal process was inhibited by genistein. Examination of the Triton X-100 solubilities of occludin and several nonmembrane TJ proteins revealed a shift of occludin and nonmembrane TJ proteins into an insoluble pool following ATP depletion. These changes reversed after ATP repletion, and the movement of insoluble occludin, ZO-1, and ZO-2 back into the soluble pool was again via a genistein-sensitive mechanism. Rate-zonal centrifugation analyses of detergent-soluble TJ proteins showed a reversible increase in higher density fractions following ATP depletion-repletion, although this change was not affected by genistein. In 32P-labeled cells, dephosphorylation of all studied TJ proteins was observed during ATP depletion, followed by rephosphorylation during ATP repletion; rephosphorylation of occludin was inhibited by genistein. Furthermore, during the ATP repletion phase, tyrosine phosphorylation of Triton X-100-insoluble occludin, which is localized at the junction, as well as ZO-2, p130/ZO-3 (though not ZO-1), and other proteins was evident; this tyrosine phosphorylation was completely inhibited by genistein. This indicates that tyrosine kinase activity is necessary for TJ reassembly during ATP repletion and suggests an important role for the tyrosine phosphorylation of occludin, ZO-2, p130/ZO-3, and possibly other proteins in the processes involved in TJ (re)formation.  (+info)

D-Serine is reabsorbed in rat renal pars recta. (8/551)

D-Serine normally contributes up to 3% to total plasma serine and up to 23% in chronic renal failure. D-Serine is metabolized by tubular D-amino acid oxidase (D-AAO), and high D-serine plasma levels are nephrotoxic; both events are localized in the straight part of the proximal tubule. We therefore investigated if and how D-serine is reabsorbed there. We microinfused 14C-labeled D- or -L-serine + [3H]inulin into early proximal (EP), late proximal (LP), or early distal (ED) tubule sections of superficial nephrons and into long loops of Henle (LLH) of rats in vivo and in situ. The fractional reabsorption (FR) of the 14C label was determined from the 14C:3H ratio in the final urine. At 0.36 mM, FR of D-[14C]serine was 86% (EP), 90% (LP), and approximately 0 (ED, LLH). FR of D-serine could be saturated and inhibited by L-serine (and vice versa). D-methionine, but not D-glutamate or D-arginine, blocked FR of D-serine (LP). We conlude that filtered D-serine is able to enter the pars recta cells, thereby getting access to D-AAO. The uptake carrier has a very low stereospecificity and is, therefore, different from that in the proximal convolution. The colocalization of exclusive reabsorption and metabolism makes the pars recta the tubule site for the recycling of the carbon structure of D-amino acids and, at the same time, the target of D-serine nephrotoxicity.  (+info)

Kidney tubules are the structural and functional units of the kidney responsible for reabsorption, secretion, and excretion of various substances. They are part of the nephron, which is the basic unit of the kidney's filtration and reabsorption process.

There are three main types of kidney tubules:

1. Proximal tubule: This is the initial segment of the kidney tubule that receives the filtrate from the glomerulus. It is responsible for reabsorbing approximately 65% of the filtrate, including water, glucose, amino acids, and electrolytes.
2. Loop of Henle: This U-shaped segment of the tubule consists of a thin descending limb, a thin ascending limb, and a thick ascending limb. The loop of Henle helps to concentrate urine by creating an osmotic gradient that allows water to be reabsorbed in the collecting ducts.
3. Distal tubule: This is the final segment of the kidney tubule before it empties into the collecting duct. It is responsible for fine-tuning the concentration of electrolytes and pH balance in the urine by selectively reabsorbing or secreting substances such as sodium, potassium, chloride, and hydrogen ions.

Overall, kidney tubules play a critical role in maintaining fluid and electrolyte balance, regulating acid-base balance, and removing waste products from the body.

The proximal kidney tubule is the initial portion of the renal tubule in the nephron of the kidney. It is located in the renal cortex and is called "proximal" because it is closer to the glomerulus, compared to the distal tubule. The proximal tubule plays a crucial role in the reabsorption of water, electrolytes, and nutrients from the filtrate that has been formed by the glomerulus. It also helps in the secretion of waste products and other substances into the urine.

The proximal tubule is divided into two segments: the pars convoluta and the pars recta. The pars convoluta is the curved portion that receives filtrate from the Bowman's capsule, while the pars recta is the straight portion that extends deeper into the renal cortex.

The proximal tubule is lined with a simple cuboidal epithelium, and its cells are characterized by numerous mitochondria, which provide energy for active transport processes. The apical surface of the proximal tubular cells has numerous microvilli, forming a brush border that increases the surface area for reabsorption.

In summary, the proximal kidney tubule is a critical site for the reabsorption of water, electrolytes, and nutrients from the glomerular filtrate, contributing to the maintenance of fluid and electrolyte balance in the body.

A kidney, in medical terms, is one of two bean-shaped organs located in the lower back region of the body. They are essential for maintaining homeostasis within the body by performing several crucial functions such as:

1. Regulation of water and electrolyte balance: Kidneys help regulate the amount of water and various electrolytes like sodium, potassium, and calcium in the bloodstream to maintain a stable internal environment.

2. Excretion of waste products: They filter waste products from the blood, including urea (a byproduct of protein metabolism), creatinine (a breakdown product of muscle tissue), and other harmful substances that result from normal cellular functions or external sources like medications and toxins.

3. Endocrine function: Kidneys produce several hormones with important roles in the body, such as erythropoietin (stimulates red blood cell production), renin (regulates blood pressure), and calcitriol (activated form of vitamin D that helps regulate calcium homeostasis).

4. pH balance regulation: Kidneys maintain the proper acid-base balance in the body by excreting either hydrogen ions or bicarbonate ions, depending on whether the blood is too acidic or too alkaline.

5. Blood pressure control: The kidneys play a significant role in regulating blood pressure through the renin-angiotensin-aldosterone system (RAAS), which constricts blood vessels and promotes sodium and water retention to increase blood volume and, consequently, blood pressure.

Anatomically, each kidney is approximately 10-12 cm long, 5-7 cm wide, and 3 cm thick, with a weight of about 120-170 grams. They are surrounded by a protective layer of fat and connected to the urinary system through the renal pelvis, ureters, bladder, and urethra.

Collecting kidney tubules, also known as collecting ducts, are the final portion of the renal tubule in the nephron of the kidney. They collect filtrate from the distal convoluted tubules and glomeruli and are responsible for the reabsorption of water and electrolytes back into the bloodstream under the influence of antidiuretic hormone (ADH) and aldosterone. The collecting ducts then deliver the remaining filtrate to the ureter, which transports it to the bladder for storage until urination.

The kidney cortex is the outer region of the kidney where most of the functional units called nephrons are located. It plays a crucial role in filtering blood and regulating water, electrolyte, and acid-base balance in the body. The kidney cortex contains the glomeruli, proximal tubules, loop of Henle, and distal tubules, which work together to reabsorb necessary substances and excrete waste products into the urine.

A nephron is the basic structural and functional unit of the kidney. It is responsible for filtering blood, reabsorbing necessary substances, and excreting waste products into the urine. Each human kidney contains approximately one million nephrons.

The structure of a nephron includes a glomerulus, which is a tuft of capillaries surrounded by Bowman's capsule. The glomerulus filters blood, allowing small molecules like water and solutes to pass through while keeping larger molecules like proteins and blood cells within the capillaries.

The filtrate then passes through the tubular portion of the nephron, which includes the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. The tubular portion reabsorbs necessary substances like water, glucose, amino acids, and electrolytes back into the bloodstream while excreting waste products like urea and creatinine into the urine.

Overall, nephrons play a critical role in maintaining fluid and electrolyte balance, regulating blood pressure, and removing waste products from the body.

Distal kidney tubules are the final segment of the renal tubule in the nephron of the kidney. The nephron is the basic unit of the kidney that filters blood and produces urine. After the filtrate leaves the glomerulus, it enters the proximal tubule where most of the reabsorption of water, electrolytes, and nutrients occurs.

The filtrate then moves into the loop of Henle, which is divided into a thin and thick descending limb and a thin and thick ascending limb. The loop of Henle helps to establish a concentration gradient in the medullary interstitium, allowing for the reabsorption of water in the collecting ducts.

The distal tubule is the last segment of the renal tubule before the filtrate enters the collecting duct. It is a relatively short structure that receives filtrate from the thick ascending limb of the loop of Henle. The distal tubule plays an important role in regulating electrolyte and water balance by actively transporting ions such as sodium, potassium, and chloride.

The distal tubule also contains specialized cells called principal cells and intercalated cells that are responsible for secreting or reabsorbing hydrogen and potassium ions to maintain acid-base balance. Additionally, the distal tubule is a site of action for several hormones, including aldosterone, which stimulates sodium reabsorption and potassium excretion, and vasopressin (antidiuretic hormone), which promotes water reabsorption in the collecting ducts.

The kidney medulla is the inner portion of the renal pyramids in the kidney, consisting of multiple conical structures found within the kidney. It is composed of loops of Henle and collecting ducts responsible for concentrating urine by reabsorbing water and producing a hyperosmotic environment. The kidney medulla has a unique blood supply and is divided into an inner and outer zone, with the inner zone having a higher osmolarity than the outer zone. This region of the kidney helps regulate electrolyte and fluid balance in the body.

Glutamine is defined as a conditionally essential amino acid in humans, which means that it can be produced by the body under normal circumstances, but may become essential during certain conditions such as stress, illness, or injury. It is the most abundant free amino acid found in the blood and in the muscles of the body.

Glutamine plays a crucial role in various biological processes, including protein synthesis, energy production, and acid-base balance. It serves as an important fuel source for cells in the intestines, immune system, and skeletal muscles. Glutamine has also been shown to have potential benefits in wound healing, gut function, and immunity, particularly during times of physiological stress or illness.

In summary, glutamine is a vital amino acid that plays a critical role in maintaining the health and function of various tissues and organs in the body.

Malpighian tubules are specialized excretory structures found in the circulatory system of many arthropods, including insects. They are named after Marcello Malpighi, an Italian physician and biologist who was one of the first to describe them. These tubules play a crucial role in eliminating waste products and maintaining water and ion balance within the insect's body.

Functionally, Malpighian tubules are analogous to the vertebrate kidneys as they filter the hemolymph (insect blood) and reabsorb necessary substances while excreting waste materials. The main waste product excreted by these tubules is uric acid, which is a less toxic form of nitrogenous waste compared to urea or ammonia, making it more suitable for terrestrial arthropods.

Malpighian tubules originate from the midgut epithelium and extend into the hemocoel (insect body cavity). They are lined with a single layer of epithelial cells that contain microvilli, increasing their surface area for efficient filtration. The tubules receive nutrient-rich hemolymph from the hemocoel through open-ended or blind-ended structures called ostia.

The filtrate formed by Malpighian tubules passes through a series of cellular transport processes involving both active and passive transport mechanisms. These processes help in reabsorbing water, ions, and nutrients back into the hemolymph while concentrating waste products for excretion. The final waste-laden fluid is then released into the hindgut, where it gets mixed with fecal material before being eliminated from the body through the anus.

In summary, Malpighian tubules are vital excretory organs in arthropods that filter hemolymph, reabsorb essential substances, and excrete waste products to maintain homeostasis within their bodies.

Sodium-Potassium-Exchanging ATPase (also known as Na+/K+ ATPase) is a type of active transporter found in the cell membrane of many types of cells. It plays a crucial role in maintaining the electrochemical gradient and membrane potential of animal cells by pumping sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, using energy derived from ATP hydrolysis.

This transporter is composed of two main subunits: a catalytic α-subunit that contains the binding sites for Na+, K+, and ATP, and a regulatory β-subunit that helps in the proper targeting and functioning of the pump. The Na+/K+ ATPase plays a critical role in various physiological processes, including nerve impulse transmission, muscle contraction, and kidney function.

In summary, Sodium-Potassium-Exchanging ATPase is an essential membrane protein that uses energy from ATP to transport sodium and potassium ions across the cell membrane, thereby maintaining ionic gradients and membrane potentials necessary for normal cellular function.

Epithelium is the tissue that covers the outer surface of the body, lines the internal cavities and organs, and forms various glands. It is composed of one or more layers of tightly packed cells that have a uniform shape and size, and rest on a basement membrane. Epithelial tissues are avascular, meaning they do not contain blood vessels, and are supplied with nutrients by diffusion from the underlying connective tissue.

Epithelial cells perform a variety of functions, including protection, secretion, absorption, excretion, and sensation. They can be classified based on their shape and the number of cell layers they contain. The main types of epithelium are:

1. Squamous epithelium: composed of flat, scalelike cells that fit together like tiles on a roof. It forms the lining of blood vessels, air sacs in the lungs, and the outermost layer of the skin.
2. Cuboidal epithelium: composed of cube-shaped cells with equal height and width. It is found in glands, tubules, and ducts.
3. Columnar epithelium: composed of tall, rectangular cells that are taller than they are wide. It lines the respiratory, digestive, and reproductive tracts.
4. Pseudostratified epithelium: appears stratified or layered but is actually made up of a single layer of cells that vary in height. The nuclei of these cells appear at different levels, giving the tissue a stratified appearance. It lines the respiratory and reproductive tracts.
5. Transitional epithelium: composed of several layers of cells that can stretch and change shape to accommodate changes in volume. It is found in the urinary bladder and ureters.

Epithelial tissue provides a barrier between the internal and external environments, protecting the body from physical, chemical, and biological damage. It also plays a crucial role in maintaining homeostasis by regulating the exchange of substances between the body and its environment.

Kidney disease, also known as nephropathy or renal disease, refers to any functional or structural damage to the kidneys that impairs their ability to filter blood, regulate electrolytes, produce hormones, and maintain fluid balance. This damage can result from a wide range of causes, including diabetes, hypertension, glomerulonephritis, polycystic kidney disease, lupus, infections, drugs, toxins, and congenital or inherited disorders.

Depending on the severity and progression of the kidney damage, kidney diseases can be classified into two main categories: acute kidney injury (AKI) and chronic kidney disease (CKD). AKI is a sudden and often reversible loss of kidney function that occurs over hours to days, while CKD is a progressive and irreversible decline in kidney function that develops over months or years.

Symptoms of kidney diseases may include edema, proteinuria, hematuria, hypertension, electrolyte imbalances, metabolic acidosis, anemia, and decreased urine output. Treatment options depend on the underlying cause and severity of the disease and may include medications, dietary modifications, dialysis, or kidney transplantation.

Gluconeogenesis is a metabolic pathway that occurs in the liver, kidneys, and to a lesser extent in the small intestine. It involves the synthesis of glucose from non-carbohydrate precursors such as lactate, pyruvate, glycerol, and certain amino acids. This process becomes particularly important during periods of fasting or starvation when glucose levels in the body begin to drop, and there is limited carbohydrate intake to replenish them.

Gluconeogenesis helps maintain blood glucose homeostasis by providing an alternative source of glucose for use by various tissues, especially the brain, which relies heavily on glucose as its primary energy source. It is a complex process that involves several enzymatic steps, many of which are regulated to ensure an adequate supply of glucose while preventing excessive production, which could lead to hyperglycemia.

Kidney transplantation is a surgical procedure where a healthy kidney from a deceased or living donor is implanted into a patient with end-stage renal disease (ESRD) or permanent kidney failure. The new kidney takes over the functions of filtering waste and excess fluids from the blood, producing urine, and maintaining the body's electrolyte balance.

The transplanted kidney is typically placed in the lower abdomen, with its blood vessels connected to the recipient's iliac artery and vein. The ureter of the new kidney is then attached to the recipient's bladder to ensure proper urine flow. Following the surgery, the patient will require lifelong immunosuppressive therapy to prevent rejection of the transplanted organ by their immune system.

Tissue distribution, in the context of pharmacology and toxicology, refers to the way that a drug or xenobiotic (a chemical substance found within an organism that is not naturally produced by or expected to be present within that organism) is distributed throughout the body's tissues after administration. It describes how much of the drug or xenobiotic can be found in various tissues and organs, and is influenced by factors such as blood flow, lipid solubility, protein binding, and the permeability of cell membranes. Understanding tissue distribution is important for predicting the potential effects of a drug or toxin on different parts of the body, and for designing drugs with improved safety and efficacy profiles.

Electron microscopy (EM) is a type of microscopy that uses a beam of electrons to create an image of the sample being examined, resulting in much higher magnification and resolution than light microscopy. There are several types of electron microscopy, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and reflection electron microscopy (REM).

In TEM, a beam of electrons is transmitted through a thin slice of the sample, and the electrons that pass through the sample are focused to form an image. This technique can provide detailed information about the internal structure of cells, viruses, and other biological specimens, as well as the composition and structure of materials at the atomic level.

In SEM, a beam of electrons is scanned across the surface of the sample, and the electrons that are scattered back from the surface are detected to create an image. This technique can provide information about the topography and composition of surfaces, as well as the structure of materials at the microscopic level.

REM is a variation of SEM in which the beam of electrons is reflected off the surface of the sample, rather than scattered back from it. This technique can provide information about the surface chemistry and composition of materials.

Electron microscopy has a wide range of applications in biology, medicine, and materials science, including the study of cellular structure and function, disease diagnosis, and the development of new materials and technologies.

Epithelial cells are types of cells that cover the outer surfaces of the body, line the inner surfaces of organs and glands, and form the lining of blood vessels and body cavities. They provide a protective barrier against the external environment, regulate the movement of materials between the internal and external environments, and are involved in the sense of touch, temperature, and pain. Epithelial cells can be squamous (flat and thin), cuboidal (square-shaped and of equal height), or columnar (tall and narrow) in shape and are classified based on their location and function.

I believe there might be a misunderstanding in your question. "Dogs" is not a medical term or condition. It is the common name for a domesticated carnivore of the family Canidae, specifically the genus Canis, which includes wolves, foxes, and other extant and extinct species of mammals. Dogs are often kept as pets and companions, and they have been bred in a wide variety of forms and sizes for different purposes, such as hunting, herding, guarding, assisting police and military forces, and providing companionship and emotional support.

If you meant to ask about a specific medical condition or term related to dogs, please provide more context so I can give you an accurate answer.

Immunohistochemistry (IHC) is a technique used in pathology and laboratory medicine to identify specific proteins or antigens in tissue sections. It combines the principles of immunology and histology to detect the presence and location of these target molecules within cells and tissues. This technique utilizes antibodies that are specific to the protein or antigen of interest, which are then tagged with a detection system such as a chromogen or fluorophore. The stained tissue sections can be examined under a microscope, allowing for the visualization and analysis of the distribution and expression patterns of the target molecule in the context of the tissue architecture. Immunohistochemistry is widely used in diagnostic pathology to help identify various diseases, including cancer, infectious diseases, and immune-mediated disorders.

Acute kidney injury (AKI), also known as acute renal failure, is a rapid loss of kidney function that occurs over a few hours or days. It is defined as an increase in the serum creatinine level by 0.3 mg/dL within 48 hours or an increase in the creatinine level to more than 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days, or a urine volume of less than 0.5 mL/kg per hour for six hours.

AKI can be caused by a variety of conditions, including decreased blood flow to the kidneys, obstruction of the urinary tract, exposure to toxic substances, and certain medications. Symptoms of AKI may include decreased urine output, fluid retention, electrolyte imbalances, and metabolic acidosis. Treatment typically involves addressing the underlying cause of the injury and providing supportive care, such as dialysis, to help maintain kidney function until the injury resolves.

A cell line is a culture of cells that are grown in a laboratory for use in research. These cells are usually taken from a single cell or group of cells, and they are able to divide and grow continuously in the lab. Cell lines can come from many different sources, including animals, plants, and humans. They are often used in scientific research to study cellular processes, disease mechanisms, and to test new drugs or treatments. Some common types of human cell lines include HeLa cells (which come from a cancer patient named Henrietta Lacks), HEK293 cells (which come from embryonic kidney cells), and HUVEC cells (which come from umbilical vein endothelial cells). It is important to note that cell lines are not the same as primary cells, which are cells that are taken directly from a living organism and have not been grown in the lab.

Messenger RNA (mRNA) is a type of RNA (ribonucleic acid) that carries genetic information copied from DNA in the form of a series of three-base code "words," each of which specifies a particular amino acid. This information is used by the cell's machinery to construct proteins, a process known as translation. After being transcribed from DNA, mRNA travels out of the nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. Once the protein has been synthesized, the mRNA may be degraded and recycled. Post-transcriptional modifications can also occur to mRNA, such as alternative splicing and addition of a 5' cap and a poly(A) tail, which can affect its stability, localization, and translation efficiency.

Molecular sequence data refers to the specific arrangement of molecules, most commonly nucleotides in DNA or RNA, or amino acids in proteins, that make up a biological macromolecule. This data is generated through laboratory techniques such as sequencing, and provides information about the exact order of the constituent molecules. This data is crucial in various fields of biology, including genetics, evolution, and molecular biology, allowing for comparisons between different organisms, identification of genetic variations, and studies of gene function and regulation.

Chronic kidney failure, also known as chronic kidney disease (CKD) stage 5 or end-stage renal disease (ESRD), is a permanent loss of kidney function that occurs gradually over a period of months to years. It is defined as a glomerular filtration rate (GFR) of less than 15 ml/min, which means the kidneys are filtering waste and excess fluids at less than 15% of their normal capacity.

CKD can be caused by various underlying conditions such as diabetes, hypertension, glomerulonephritis, polycystic kidney disease, and recurrent kidney infections. Over time, the damage to the kidneys can lead to a buildup of waste products and fluids in the body, which can cause a range of symptoms including fatigue, weakness, shortness of breath, nausea, vomiting, and confusion.

Treatment for chronic kidney failure typically involves managing the underlying condition, making lifestyle changes such as following a healthy diet, and receiving supportive care such as dialysis or a kidney transplant to replace lost kidney function.

A kidney glomerulus is a functional unit in the nephron of the kidney. It is a tuft of capillaries enclosed within a structure called Bowman's capsule, which filters waste and excess fluids from the blood. The glomerulus receives blood from an afferent arteriole and drains into an efferent arteriole.

The process of filtration in the glomerulus is called ultrafiltration, where the pressure within the glomerular capillaries drives plasma fluid and small molecules (such as ions, glucose, amino acids, and waste products) through the filtration membrane into the Bowman's space. Larger molecules, like proteins and blood cells, are retained in the blood due to their larger size. The filtrate then continues down the nephron for further processing, eventually forming urine.

Polycystic Kidney Disease (PKD) is a genetic disorder characterized by the growth of multiple cysts in the kidneys. These cysts are fluid-filled sacs that can vary in size and can multiply, leading to enlarged kidneys. The increased size and number of cysts can result in reduced kidney function, high blood pressure, and eventually kidney failure.

There are two main types of PKD: Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Autosomal Recessive Polycystic Kidney Disease (ARPKD). ADPKD is the most common form, affecting approximately 1 in every 500 people. It typically develops in adulthood. On the other hand, ARPKD is a rarer form, affecting about 1 in every 20,000 children, and it often presents in infancy or early childhood.

In addition to kidney problems, PKD can also affect other organs, such as the liver and the heart. It's important to note that while there is no cure for PKD, various treatments can help manage symptoms and slow down the progression of the disease.

Kidney neoplasms refer to abnormal growths or tumors in the kidney tissues that can be benign (non-cancerous) or malignant (cancerous). These growths can originate from various types of kidney cells, including the renal tubules, glomeruli, and the renal pelvis.

Malignant kidney neoplasms are also known as kidney cancers, with renal cell carcinoma being the most common type. Benign kidney neoplasms include renal adenomas, oncocytomas, and angiomyolipomas. While benign neoplasms are generally not life-threatening, they can still cause problems if they grow large enough to compromise kidney function or if they undergo malignant transformation.

Early detection and appropriate management of kidney neoplasms are crucial for improving patient outcomes and overall prognosis. Regular medical check-ups, imaging studies, and urinalysis can help in the early identification of these growths, allowing for timely intervention and treatment.

Kidney function tests (KFTs) are a group of diagnostic tests that evaluate how well your kidneys are functioning by measuring the levels of various substances in the blood and urine. The tests typically assess the glomerular filtration rate (GFR), which is an indicator of how efficiently the kidneys filter waste from the blood, as well as the levels of electrolytes, waste products, and proteins in the body.

Some common KFTs include:

1. Serum creatinine: A waste product that's produced by normal muscle breakdown and is excreted by the kidneys. Elevated levels may indicate reduced kidney function.
2. Blood urea nitrogen (BUN): Another waste product that's produced when protein is broken down and excreted by the kidneys. Increased BUN levels can suggest impaired kidney function.
3. Estimated glomerular filtration rate (eGFR): A calculation based on serum creatinine, age, sex, and race that estimates the GFR and provides a more precise assessment of kidney function than creatinine alone.
4. Urinalysis: An examination of a urine sample to detect abnormalities such as protein, blood, or bacteria that may indicate kidney disease.
5. Electrolyte levels: Measurement of sodium, potassium, chloride, and bicarbonate in the blood to ensure they're properly balanced, which is essential for normal kidney function.

KFTs are often ordered as part of a routine check-up or when kidney disease is suspected based on symptoms or other diagnostic tests. Regular monitoring of kidney function can help detect and manage kidney disease early, potentially preventing or slowing down its progression.

Kidney calculi, also known as kidney stones, are hard deposits made of minerals and salts that form inside your kidneys. They can range in size from a grain of sand to a golf ball. When they're small enough, they can be passed through your urine without causing too much discomfort. However, larger stones may block the flow of urine, causing severe pain and potentially leading to serious complications such as urinary tract infections or kidney damage if left untreated.

The formation of kidney calculi is often associated with factors like dehydration, high levels of certain minerals in your urine, family history, obesity, and certain medical conditions such as gout or inflammatory bowel disease. Symptoms of kidney stones typically include severe pain in the back, side, lower abdomen, or groin; nausea and vomiting; fever and chills if an infection is present; and blood in the urine. Treatment options depend on the size and location of the stone but may include medications to help pass the stone, shock wave lithotripsy to break up the stone, or surgical removal of the stone in severe cases.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a genetic disorder characterized by the growth of multiple cysts in the kidneys. These cysts are fluid-filled sacs that can vary in size and can multiply, leading to enlarged kidneys. The increased size and number of cysts can eventually result in reduced kidney function, high blood pressure, and potentially kidney failure.

ADPKD is an autosomal dominant disorder, meaning it only requires one copy of the altered gene (from either the mother or father) to have the disease. Each child of an affected individual has a 50% chance of inheriting the mutated gene. The two genes most commonly associated with ADPKD are PKD1 and PKD2, located on chromosomes 16 and 4, respectively.

Symptoms can vary widely among individuals with ADPKD, but they often include high blood pressure, back or side pain, headaches, increased abdominal size due to enlarged kidneys, blood in the urine, and kidney failure. Other complications may include cysts in the liver, pancreas, and/or brain (berries aneurysms).

Early diagnosis and management of ADPKD can help slow down disease progression and improve quality of life. Treatment typically includes controlling high blood pressure, managing pain, monitoring kidney function, and addressing complications as they arise. In some cases, dialysis or a kidney transplant may be necessary if kidney failure occurs.

Kidney concentrating ability refers to the capacity of the kidneys to increase the concentration of solutes, such as urea and minerals, and remove waste products while reabsorbing water to maintain fluid balance in the body. This is primarily regulated by the hormone vasopressin (ADH), which signals the collecting ducts in the nephrons of the kidneys to absorb more water, resulting in the production of concentrated urine. A decreased kidney concentrating ability may indicate a variety of renal disorders or diseases, such as diabetes insipidus or chronic kidney disease.

Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the glomeruli each minute. The glomeruli are the tiny fibers in the kidneys that filter waste from the blood. A lower GFR number means that the kidneys aren't working properly and may indicate kidney disease.

The GFR is typically calculated using a formula that takes into account the patient's serum creatinine level, age, sex, and race. The most commonly used formula is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. A normal GFR is usually above 90 mL/min/1.73m2, but this can vary depending on the individual's age and other factors.

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