Effect of angiotensin II receptor blockage on osteopontin expression and calcium oxalate crystal deposition in rat kidneys. (73/363)

Hyperoxaluria leads to calcium oxalate (CaOx) crystallization and development of tubulointerstitial lesions in the kidneys. Treatment of hyperoxaluric rats with angiotensin II (Ang II) type I receptor blocker (ARB) reduces lesion formation. Because Ang II mediates osteopontin (OPN) synthesis, which is involved in both macrophage recruitment and CaOx crystallization, it was hypothesized that ARB acts via OPN. Hyperoxaluria was induced in 10-wk-old male Sprague-Dawley rats, and they were treated with ARB candesartan. At the end of 4 wk, kidneys were examined for crystal deposits, ED-1-positive cells, and expression of OPN mRNA. PCR was used to quantify OPN, renin, and angiotensin-converting enzyme (ACE) mRNA in kidneys. RIA was used to determine renal, plasma, and urinary OPN; plasma renin; Ang II and ACE; and renal Ang II. For evaluating oxidative stress, malondialdehyde was measured. Urinary calcium, oxalate, creatinine, and albumin were also determined. Despite similar urinary calcium and oxalate levels, kidneys of hyperoxaluric rats on candesartan had fewer CaOx crystals, fewer ED-1-positive cells, reduced OPN expression, and reduced malondialdehyde than hyperoxaluric rats. Urinary albumin excretion and serum creatinine levels improved significantly on candesartan treatment. mRNA for OPN, renin, and ACE were significantly elevated in hyperoxaluric rats. OPN synthesis and production increased with hyperoxaluria but to a lesser extent in candesartan-treated hyperoxaluric rats. These results show for the first time that oxalate can activate the renal renin-angiotensin system and that oxalate-induced upregulation of OPN is in part mediated via renal renin-angiotensin system.  (+info)

Raphides in palm embryos and their systematic distribution. (74/363)

BACKGROUND AND AIMS: Raphides are ubiquitous in the palms (Arecaceae), where they are found in roots, stems, leaves, flowers and fruits. Their occasional presence in embryos, first noticed over 100 years ago, has gone largely unexamined. METHODS: Embryos from 148 taxa of palms, the largest survey of palm embryos to date, were examined using light microscopy of squashed preparations under non-polarized and crossed polarized light. RESULTS: Raphides were found in embryos of species from the three subfamilies Coryphoideae, Ceroxyloideae and Arecoideae. Raphides were not observed in the embryos of species of Calamoideae or Phytelephantoideae. The remaining subfamily, the monospecific Nypoideae, was not available for study. CONCLUSIONS: Within the Coryphoideae and Ceroxyloideae, embryos with raphides were rare, but within the Arecoideae, they were a common feature of the tribes Areceae and Caryoteae.  (+info)

Canine urolithiasis: a look at over 16 000 urolith submissions to the Canadian Veterinary Urolith Centre from February 1998 to April 2003. (75/363)

The purpose of this study was to report on the age, sex, breed, and mineral composition of 16 647 canine bladder uroliths submitted to the Canadian Veterinary Urolith Centre between February 1998 and April 2003. Each urolith submission was accompanied by a questionnaire. Of the submissions, approximately 43.8% were struvite and 41.5% oxalate. Struvite uroliths were most common in female dogs. Mixed breed dogs predominated, followed by the shih tzu, bichon frise, miniature schnauzer, Lhasa apso, and Yorkshire terrier. Oxalate uroliths were most common in males and in the miniature schnauzer, bichon frise, Lhasa apso, shih tzu, and Yorkshire terrier. Urate uroliths were most common in male Dalmations. Other urolith types, including cystine, xanthine, silica, and calcium phosphate, were less commonly reported. A review of risk factors for the various uroliths is presented, along with some recommendations for treatment and prevention.  (+info)

Calcium channels are involved in calcium oxalate crystal formation in specialized cells of Pistia stratiotes L. (76/363)

BACKGROUND AND AIMS: Pistia stratiotes produces large amounts of calcium (Ca) oxalate crystals in specialized cells called crystal idioblasts. The potential involvement of Ca(2+) channels in Ca oxalate crystal formation by crystal idioblasts was investigated. METHODS: Anatomical, ultrastructural and physiological analyses were used on plants, fresh or fixed tissues, or protoplasts. Ca(2+) uptake by protoplasts was measured with (45)Ca(2+), and the effect of Ca(2+) channel blockers studied in intact plants. Labelled Ca(2+) channel blockers and a channel protein antibody were used to determine if Ca(2+) channels were associated with crystal idioblasts. KEY RESULTS: (45)Ca(2+) uptake was more than two orders of magnitude greater for crystal idioblast protoplasts than mesophyll protoplasts, and idioblast number increased when medium Ca was increased. Plants grown on media containing 1-50 microM of the Ca(2+) channel blockers, isradipine, nifedipine or fluspirilene, showed almost complete inhibition of crystal formation. When fresh tissue sections were treated with the fluorescent dihydropyridine-type Ca(2+) channel blocker, DM-Bodipy-DHP, crystal idioblasts were intensely labelled compared with surrounding mesophyll, and the label appeared to be associated with the plasma membrane and the endoplasmic reticulum, which is shown to be abundant in idioblasts. An antibody to a mammalian Ca(2+) channel alpha1 subunit recognized a single band in a microsomal protein fraction but not soluble protein fraction on western blots, and it selectively and heavily labelled developing crystal idioblasts in tissue sections. CONCLUSIONS: The results demonstrate that Ca oxalate crystal idioblasts are enriched, relative to mesophyll cells, in dihydropyridine-type Ca(2+) channels and that the activity of these channels is important to transport and accumulation of Ca(2+) required for crystal formation.  (+info)

Renal epithelial cells constitutively produce a protein that blocks adhesion of crystals to their surface. (77/363)

Attachment of newly formed crystals to renal tubular epithelial cells appears to be a critical step in the development of kidney stones. The present study was undertaken to identify autocrine factors released from renal epithelial cells into the culture medium that inhibit adhesion of calcium oxalate crystals to the cell surface. A 39-kDa glycoprotein that is constitutively secreted by renal cells was purified by gel filtration chromatography. Amino acid microsequencing revealed that it is novel and not structurally related to known inhibitors of calcium oxalate crystallization. Hence, it was named crystal adhesion inhibitor, or CAI. Immunoreactive CAI was detected in diverse rat tissues, including kidney, heart, pancreas, liver, and testis. Immunohistochemistry revealed that CAI is present in the renal cell cytosol and is also on the plasma membrane. Importantly, CAI is present in normal human urine, from which it can be purified using calcium oxalate monohydrate crystal affinity chromatography. CAI could be an important defense against crystal attachment to tubular cells and the subsequent development of renal stones in vivo.  (+info)

Dependence of oxalate absorption on the daily calcium intake. (78/363)

Two to 20% of ingested oxalate is absorbed in the gastrointestinal tract of healthy humans with a daily 800 mg calcium intake. Calcium is the most potent modifier of the oxalate absorption. Although this has been found repeatedly, the exact correlation between calcium intake and oxalate absorption has not been assessed to date. Investigated was oxalate absorption in healthy volunteers applying 0.37 mmol of the soluble salt sodium [(13)C(2)]oxalate in the calcium intake range from 5 mmol (200 mg) calcium to 45 mmol (1800 mg) calcium. Within the range of 200 to 1200 mg calcium per day, oxalate absorption depended linearly on the calcium intake. With 200 mg calcium per day, the mean absorption (+/- SD) was 17% +/- 8.3%; with 1200 mg calcium per day, the mean absorption was 2.6% +/- 1.5%. Within this range, reduction of the calcium supply by 70 mg increased the oxalate absorption by 1% and vice versa. Calcium addition beyond 1200 mg/d reduced the oxalate absorption only one-tenth as effectively. With 1800 mg calcium per day, the mean absorption was 1.7% +/- 0.9%. The findings may explain why a low-calcium diet increases the risk of calcium oxalate stone formation.  (+info)

Calcium phosphate and calcium oxalate crystal handling is dependent upon CLC-5 expression in mouse collecting duct cells. (79/363)

Defects in an intracellular chloride channel CLC-5 cause Dent's disease, an inherited kidney stone disorder. Using a collecting duct model, mIMCD-3 cells, we show expression of dimeric mCLC-5. Transient transfection of antisense CLC-5 reduces CLC-5 protein expression. Binding of both calcium phosphate (hydroxyapatite) and calcium oxalate monohydrate (COM) crystals overlaid onto mIMCD-3 cultures was affected by altered CLC-5 expression. Calcium phosphate crystal agglomerations (>10 microm) were minimal in control (9%) and sense (13%) CLC-5-transfected cells, compared to 66% of antisense CLC-5-transfected cells (P<0.001). Small calcium phosphate crystals (<10 microm) were found associated with 45% of sense CLC-5-treated cells, of which the majority (11/14 cells) appeared to be internalised within the cell. Calcium oxalate agglomerations (>10 microm) were also largely absent for controls or sense mCLC-5 transfectants (11% and 9% of cells, respectively) with COM crystal agglomerates predominating in antisense CLC-5 transfectants (66%, P<0.0001). We conclude that collecting duct cells with reduced CLC-5 expression lead to a tendency to form calcium crystal agglomeration, which may help explain the nephrocalcinosis and nephrolithiasis seen in Dent's disease.  (+info)

The relationship of 3' vitamin D receptor haplotypes to urinary supersaturation of calcium oxalate salts and to age at onset and familial prevalence of nephrolithiasis. (80/363)

BACKGROUND: Idiopathic hypercalciuria (IHc) and idiopathic hypocitraturia are frequently associated with calcium nephrolithiasis. We investigated the relationship of vitamin D receptor (VDR) polymorphisms (BsmI, TaqI and FokI) to urinary supersaturation of calcium oxalate salts in recurrent calcium oxalate stone formers with IHc and the clinical relevance of this relationship. METHODS: The study included 110 Caucasian stone formers with IHc and 127 unrelated healthy controls without history of nephrolithiasis. Age at onset of nephrolithiasis, familial history score (FHS) and the ion activity product of calcium oxalate salts in urine (AP(CaOx)) were tabulated. BsmI, TaqI and FokI VDR polymorphisms were evaluated in all participants. RESULTS: Patients and controls were classified as homozygous (bbTT and BBtt) or heterozygous in relation to BsmI and TaqI polymorphisms. Compared with BBtt patients, bbTT homozygous stone formers showed lower citrate excretion (1.91+/-0.89 vs 3.46+/-1.39 mmol/24 h, P = 0.004) and higher AP(CaOx) (2.02+/-0.51 vs 1.53+/-0.53, P = 0.006). Among controls, there were similar differences in citrate excretion and AP(CaOx) between the two groups, but they were not statistically significant. Compared with BBtt, bbTT patients showed lower mean age at onset of nephrolithiasis (29.7+/-12.1 vs 38.1+/-12.7 years, P = 0.008) and higher values of FHS (2.45+/-1.9 vs 0.83+/-0.7, P = 0.006). Similar results were obtained for individual BsmI and TaqI alleles. The analysis of FokI alleles was not informative. CONCLUSIONS: Recurrent calcium oxalate stone formers with IHc and the bT VDR haplotype have more aggressive kidney stone diseases as indicated by a higher familial incidence and lower mean age at onset. This clinical severity is associated with the higher urinary supersaturation of calcium oxalate salts and abnormalities of renal citrate handling.  (+info)