In vivo visualization of hemodialysis-induced alterations in leukocyte-endothelial interactions.
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BACKGROUND: The aim of this study was to develop a model for hemodialysis (HD) in small animals using conventional dialysis equipment that would allow the intravital microscopic observation of leukocyte-endothelial interactions in vivo. METHODS: Cuprophan dialyzers were adapted to obtain a similar ratio of membrane area to blood volume as in clinical HD. A silicone ring was inserted into the dialyzer's inlet to limit the number of blood-perfused capillaries. Rabbits were dialyzed for one hour without a dialysate flow. RESULTS: Extracorporeal circulation with the cuprophan dialyzer resulted in a transient leukopenia and complement activation. At the nadir of leukopenia, leukocytes that rolled along the venular wall were scarcely observed, whereas rolling was abundant (54 +/- 9 per min) prior to extracorporeal circulation. The adhesion of leukocytes to the vascular endothelium was not induced. After 60 minutes, rolling of leukocytes was still reduced by 73 +/- 5.5%, despite the full recovery of circulating leukocyte counts. Extracorporeal circulation without a dialyzer also tended to reduce leukocyte rolling, although systemic leukocyte counts were not affected. CONCLUSIONS: The use of adapted conventional cuprophan hemodialyzers in rabbits yielded a transient leukopenia similar to that in clinical HD. Using intravital microscopy, we demonstrated impairment of leukocyte-endothelial interactions. In addition, our data indicate that tissues, in which leukocytes can roll and adhere, are not automatically sites of leukocyte sequestration during HD-induced leukopenia. (+info)
The spleen of the one humped camel (Camelus dromedarius) has a unique histological structure.
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The histology and structure of 38 spleens of the dromedary (aged 0.5-15 y) were studied in relation to age. The spleen was found to have a thick capsule (292+/-106 mm) divided into an outer layer (113+/-39 mm) composed mainly of connective tissue and an inner layer (180+/-81 mm) consisting mainly of smooth muscle cells. Vascular and avascular trabeculae extend from the capsule, the former containing arteries and nerves but no trabecular veins, the latter being divided structurally into primary and secondary trabeculae. Subcapsular and peritrabecular blood sinuses around primary and vascular trabeculae are unique to the camel spleen. The central artery emerges from the periarterial lymphatic sheath and branches into up to 4 penicilli which extend as sheathed arterioles (42+/-8 microm). These are found near or surrounded by blood sinusoids of the red pulp. A wide marginal zone surrounds the white pulp and contains sheathed arteries but no marginal sinuses. The red pulp is characteristically divided into cords by secondary trabeculae and contains venous sinusoids of different sizes. The camel spleen is of a sinusal type that can store blood. The thick muscular capsule and trabeculae pump the stored blood according to the body's need. Both closed and open circulations are found. The venous return is unique as the blood flow is from the venous sinusoids of the red pulp to the peritrabecular sinuses to the subcapsular sinuses to the splenic vein. No significant structural differences related to age were found. (+info)
Do fluid administration and reduction in norepinephrine dose improve global and splanchnic haemodynamics?
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We studied global and splanchnic haemodynamics in patients with septic shock, while reducing norepinephrine doses by progressive fluid loading administration. Ten patients (six female, four male, aged 39-86 yr, mean 61 yr) were assessed using a transpulmonary thermo-dye dilution technique to measure cardiac output, intrathoracic blood volume and total blood volume. Splanchnic blood flow was measured by the steady state indocyanine green technique using a hepatic venous catheter. Gastric mucosal blood flow was estimated by regional carbon dioxide tension (PRCO2). Hydroxyethylstarch was infused in two stages while maintaining mean arterial pressure, allowing a reduction in norepinephrine dose from 0.54 to 0.33 to 0.21 microgram kg-1 min-1. Mean (SD) heart rate significantly decreased, from 104 (13) to 94 (15) beats min-1. Total blood volume index (mean (SD)) increased from 2650 (638) to 3655 (885) ml m-2, intrathoracic blood volume index from 888 (204) to 1050 (248) ml m-2 and cardiac index from 3.6 (1.0) to 4.0 (0.9) litres min-1 m-2. Splanchnic blood flow did not change significantly--either absolute (from 0.81 to 0.98 litres min-1 m-2) or fractional (from 22.3% to 23.9%). Gastric mucosal (PRCO2) increased from 7.5 (2.5) to 9.0 (2.8) kPa. The PCO2 gap, i.e. the difference between regional and end-tidal PCO2, increased from 3.1 (2.5) to 4.0 (2.9) kPa. Marked individual variation in responses suggests that norepinephrine dose reduction by fluid loading in patients with stabilized septic shock does not necessarily increase global or splanchnic blood flow. (+info)
Effects of hormone replacement therapy on hemodynamic responses of postmenopausal women to passive heating.
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To examine the influence of chronic hormone replacement therapy (HRT) on the central and peripheral cardiovascular responses of postmenopausal women to direct passive heating, seven women taking estrogen replacement therapy, seven women taking estrogen and progesterone therapy, and seven women not taking HRT were passively heated with water-perfused suits to their individual limit of thermal tolerance. Measurements included heart rate (HR), cardiac output, blood pressure, skin blood flow, splanchnic blood flow, renal blood flow, esophageal temperature, and mean skin temperature. Cardiac output was higher in women taking estrogen and progesterone therapy than in women not taking HRT (7.12 +/- 0.70 vs. 5.02 +/- 0. 57 l/min at the limit of thermal tolerance, respectively; P < 0.05) because of a higher HR. However, when the HR data were plotted as a percentage of the maximum HR or percentage of HR reserve, there were no differences among the three groups of women. Neither splanchnic nor renal blood flow differed among the groups of women. These data suggest that HRT has little effect on the cardiovascular responses to direct passive heating. (+info)
Free and peptide amino acid net flux across the rumen and the mesenteric- and portal-drained viscera of sheep.
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This experiment was conducted to determine the significance of the peptide amino acid (PAA) contribution to amino acid (AA) net flux in the portal vein and to evaluate the capacity for peptide absorption in the different segments of the gastrointestinal tract of ruminants. Four sheep (64+/-3 kg BW) were fitted with catheters and blood flow probes, allowing AA net flux measurements across the portal- (PDV) and mesenteric (MDV)-drained viscera and the rumen. Sheep were fed at maintenance a diet containing hay and extruded peas (70:30). Peptide absorption was investigated by a dose infusion of a mixture of peptides (casein hydrolysate, Pro-Phe, beta-Ala-His, Gly-Gly) into the rumen. Control and postinjection net fluxes of plasma free amino acids (FAA) and PAA were determined. The concentration of plasma PAA was determined by quantification of amino acids before and after acid hydrolysis of samples first submitted to chemical deproteinization and ultrafiltration (3-kDa cut-off filter). During the control period a significant net release (12 mmol/h) of PAA was observed across the PDV, which accounted for 35% of the sum of FAA and PAA net fluxes. This PDV flux of PAA mainly resulted from a MDV release of PAA (15 mmol/h). The net flux of total PAA across the ruminal wall was not significantly different from zero, but uptake of peptide Ile and release of peptide Gly were observed. The injection into the rumen of the peptide mixture increased the net release of peptide essential AA (EAA) across the MDV (P < .05) and the PDV (P < .10), and of peptide Pro and Phe across the non-MDV (P < .10). Peptide Ile uptake by the rumen tissues was decreased by the injection (P < .05). Significant increases in peptide Pro and Gly arterial concentrations were observed (P < .05). The 3-Ala-His and Gly-Gly arterial concentrations and net fluxes across the PDV were not affected by their injections into the rumen. This study showed that PAA may contribute significantly to AA flux across the PDV of sheep, and that part of this flux can probably be attributed to peptide absorption from the gut lumen. When high concentrations of peptides are generated in the rumen the possibility of peptide absorption before the jejunum has to be considered. (+info)
Sphingosine-1-phosphate reduces rat renal and mesenteric blood flow in vivo in a pertussis toxin-sensitive manner.
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Sphingolipids such as sphingosine-1-phosphate (SPP) and sphingosylphosphorylcholine constrict isolated rat intrarenal and mesenteric microvessels in vitro. The present study investigates their effects on the cardiovascular system in vivo in anaesthetized rats. The animals were given intravenous or intrarenal arterial bolus injections of sphingolipids (0.1-100 microg kg(-1)) with subsequent measurements of mean arterial pressure, heart rate and renal and mesenteric blood flows (RBF, MBF) using a pressure transducer and electromagnetic flow probes, respectively. Intravenous injection of SPP rapidly (within 30 s), transiently and dose-dependently reduced RBF (maximally -4.0+/-0.3 ml min(-1)) and MBF (maximally -1.4+/-0.2 ml min(-1)), without affecting mean arterial pressure or heart rate. Other sphingolipids had no significant effect. Intrarenal arterial SPP administration caused greater blood flow reductions (maximally -6.4+/-0.3 ml min(-1)) than systemic administration. Upon intrarenal administration, sphingosylphos- phorylcholine also lowered RBF (maximally -2.8+/-0.6 ml min(-1)), while the other sphingolipids remained without effect. Pretreatment with pertussis toxin (PTX, 10 microg kg(-1)) 3 days before the acute experiment abolished the SPP-induced reductions of RBF and MBF. These data demonstrate, that SPP is a potent vasoconstrictor in vivo, particularly in the renal vasculature, while the other structurally related sphingolipids had little if any effects. The PTX-sensitivity strongly suggests that the effects of SPP on renal and mesenteric blood flow are mediated by receptors coupled to G(i)-type G-proteins. (+info)
Splanchnic haemodynamic disturbances in perinatal sepsis.
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AIM: To determine the effect of perinatal bacterial infection on the neonatal splanchnic circulation. SUBJECTS/SETTING: 76 premature infants with appropriate birth weight for gestation admitted for neonatal intensive care. METHODS: Doppler ultrasound was used to measure blood flow velocity and pulsatility index in the superior mesenteric artery and coeliac axis during the first 24 hours of life. Babies were classified according to the results of blood and surface cultures, as well as the presence or absence of maternal prolonged membrane rupture. RESULTS: Infection status had a significant effect on pulsatility index in both arteries, with that in the coeliac axis being reduced from 1.27 to 0.80 in babies with infection (p < 0.0001). Coeliac axis blood flow velocity was significantly increased in those with infection (from 34.6 to 46.5 cm/s; p < 0.05). CONCLUSION: As early as the first day of postnatal life, infected neonates show a pattern of splanchnic hyperaemia similar to that found in adult systemic inflammatory response syndrome. (+info)
Systemic hypoxia increases leukocyte emigration and vascular permeability in conscious rats.
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We recently observed that acute systemic hypoxia produces rapid increases in leukocyte adherence in the mesenteric microcirculation of the anesthetized rat Wood JG, Johnson JS, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 1734-1740, 1999; Wood JG, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 873-881, 1999. Hypoxia-induced leukocyte adherence is associated with an increase in reactive oxygen species (ROS) generation and is attenuated by antioxidants or interventions that increase tissue levels of nitric oxide (NO). These results suggest that the acute effects of hypoxia on leukocyte-endothelial interactions are caused by a change in the ROS-NO balance. The present experiments were designed to extend our observations of the initial microcirculatory response to hypoxia; specifically, we wanted to determine whether the response to systemic hypoxia involves increased microvascular permeability and leukocyte emigration and whether ROS generation and decreased NO levels contribute to these responses. At this time, there is conflicting evidence, from in vitro studies, regarding the effect of hypoxia on these indexes of vascular function. Our studies were carried out in the physiological setting of the conscious animal, in which a prolonged hypoxic exposure is possible without the adverse effects that may develop under anesthesia. The central observation of these studies is that conscious animals exposed for 4 h to environmental hypoxia show increased microvascular permeability and emigration of leukocytes into the extravascular space of the mesenteric circulation. Furthermore, these events are dependent on increased ROS generation and, possibly, a subsequent decrease in tissue NO levels during systemic hypoxia. Our results show that systemic hypoxia profoundly affects vascular endothelial function through changes in the ROS-NO balance in the conscious animal. (+info)