Renal and intrarenal blood flow distribution in swine during severe exercise

It is known that a compensatory reduction and diversion of renal flow occurs in severe exercise in humans but not in dogs. We investigated this in miniature swine by measuring changes in total renal blood flow (TRF) and intra-renal blood flow (IRBF) distribution with tracer microspheres (15 +/- 5 mum) at rest and during steady-state exercise at 4.8-7.2 kph and 0% grade, and during severe exercise at 4.8-7.2 kph and 10% grade. We measured heart rate and cardiac output (Q) via implanted probes. TRF was determined as a percent of Q and as ml/100 g per min. IRBF was determined for the outer cortex, inner cortex, outer medulla, and inner medulla. Our results show that renal blood flow is significantly (P less than 0.05) reduced in pigs with exercise. Steady-state exercise reduced flow to about 66% of control and severe exercise reduced renal flow to 30% of control. IRBF was unchanged throughout. These results show that the exercising pig augments blood flow to skeletal muscle by reducing blood flow to kidneys, a response known to occur in man.     

Endothelium-smooth muscle interactions in blood vessels

1. Blood vessel tone is determined both by smooth muscle and endothelial functions. In coronary arteries taken from rat (Fisher-Lewis) cardiac transplanted hearts, the inducible form of NOS (iNOS) in smooth muscle is more active, while acetylcholine-induced nitric oxide production in the endothelium is greatly diminished. This causes a greatly reduced myogenic constriction, in pressurized septal arteries taken from immunologically challenged transplanted hearts. 2. The sarcoplasmic reticulum (SR) of smooth muscle and the endoplasmic reticulum (ER) of endothelial cells sequester Ca2+ from the cytoplasm. This reduces the intracellular concentration of free Ca2+, which is necessary for the activation of cellular processes. The release of Ca2+ from internal stores occurs through ryanodine and IP3 recoptors located on the SR membrane. 3. The superficial SR/ER also interacts with ion exchangers and pumps in the plasma membrane. This allows for the superficial SR/ER to function in Ca2+ extrusion; for example, inhibition of the SR/ER Ca(2+)-ATPase (SERCA) partially inhibits the rate of loss Ca2+ from the cell. Recent data suggest that the SR Ca(2+)-ATPase and the Na(+)-Ca2+ exchanger of smooth muscle cells function in series; that is, Ca2+ uptake by the SR followed by release towards the exchanger to mediate extrusion. This interaction between the SERCA of the superficial SR and ion exchangers and pumps creates intracellular Ca2+ gradients. 4. The SERCA of the superficial, peripherally distributed SR/ER also serves to regulate Ca2+ entry from the extracellular space. This occurs in part by inhibition of the superficial buffer barrier function of the SR as well as by depletion of stimulated Ca2+ entry. 5. Ca2+ entry is also regulated in endothelial and smooth muscle cells by the membrane potential. Membrane hyperpolarization increases the driving force for Ca2+ entry into endothelial cells, which lack voltage-gated Ca2+ channels, and reduces open state probability of voltage-gated Ca2+ channels in vascular smooth muscle cells. The two cell types have electrical contact and interact in a dynamic manner to regulate blood vessel diameter.     

Relationship between intrarenal distribution of blood flow and renin secretion during ureteral occlusion

The present study was undertaken to evaluate the relationship between renin secretion from the denervated kidney and intrarenal distribution of blood flow during reductions in renal perfusion pressure by partial constriction of the aorta with and without ureteral occlusion in the anesthetized dog. In addition, renin contents in different zones of the kidney were measured. A reduction in renal arterial pressure from normal pressure (125-135 mmHg) to 77 mm Hg resulted in significant increase in renin secretion and redistribution of cortical blood flow. A further reduction of renal arterial pressure to 51 mmHg produced a marked increase in renin secretion rate (RSR) without further changes in the intrarenal distribution pattern of blood flow. The pressure reductions during ureteral occlusion increased RSR without any change in the distribution pattern of blood flow, and a decrease in the amounts of extractable renin was found in the outer cortex of the experimental kidney. These findings suggest that renin release occurs mainly in the outer cortex, and this process may be stimulated when the mechanism of autoregulation fails as the perfusion presure approaches to the lower range of autoregulation in the outer cortex.     

Basement membrane of blood vessels during distraction osteogenesis

A canine model of distraction osteogenesis has recently been developed that permitted the evaluation of bone formation and its vascularization during bifocal callotasis. In this model, the authors examined the composition of the blood vessels during distraction osteogenesis of the mandible for laminin and for Type IV collagen, both constituents of the vascular basement membrane. At the fibrous distraction site, at the juncture of the free cortical surface and the regenerated bone, and at the abutting cortical surfaces at the distal margin of the defect, laminin and Type IV collagen were present in all vessels.     

Gadolinium-enhanced magnetic resonance angiography of abdominal blood vessels

Contrast enhanced (CE) magnetic resonance angiography (MRA) provides high resolution angiograms within 20-40 sec. The technique is based on the acquisition of heavily T1-weighted three-dimensional (3D) gradient-echo data sets (FISP) with ultrashort echo-(< 2ms) and repetition times (< 5 ms) during arterial phase of an intravenously injected bolus of a T1-shortening agent such as Gd-DTPA. For MR-angiography of abdominal vessels CE-MRA is better suited than "time-of flight" (TOF) and phase-contrast (PC) MRA because motional artifacts can be obviated with breath-held acquisitions. We have optimised the technique and evaluated its potential for angiography of the abdominal aorta and its branches as well as the portal vein and its tributaries. Whilst CE-MRA provides reliable diagnostic accuracy in the aorta and the proximal sections of its branches, small peripheral arteries cannot be assessed accurately. The portal vein and its tributaries can often be depicted better with CE-MRA than with conventional angiography but, like conventional angiography, CE-MRA is hampered by slow and reversed flow, conditions under which TOF or "true FISP" MRA may perform bst. We have also investigated FLASH-echo-planar imaging (EPI) hybrid techniques, a further technical development which due to shorter acquisition times of 12-15 sec. allows semi-dynamic imaging of the arterial and venous phase and provide better vessel contrast due to the use of fat-suppression.     

The individualization of activities of blood vessels]

Due to its short half life and high tryptophan content, prealbumin has been considered a sensitive indicator of protein and/or energy deficiency. In addition, prealbumin diminishes during the acute phase response elicited by either infection or tissue injury. Serum levels of prealbumin were determined in undernourished children with or without associated clinical infection and in their infected or non-infected controls matched for age, sex, race and socioeconomical conditions. Serum levels of prealbumin were significantly lower in undernourished than in control children without overt infections. On the other hand, the concentrations of serum prealbumin diminished significantly and to similar levels both in undernourished and control children with associated clinical infection as compared with those observed in non infected children belonging to the similar nutritional status. A positive correlation was found between prealbumin level and the Z-scores of weight-for-age, height-for-age and weight-for height in children without associated infections, which disappeared in clinically infected patients. Thus, prealbumin is a marker of undernutrition in the absence of infection and could be an earlier and more sensitive indicator of actual undernutrition caused by the metabolic effects of acute phase cytokines, than the anthropometrical measurements used here.     

The intrarenal renin-angiotensin system

In this article, we have discussed the localization of components of the renal renin-angiotensin system, as well as the existing information on the regulation of this axis and the effects of Ang II on renal function. All the components of the renin-angiotensin system are present in both fetal and adult kidney. In the adult kidney, renin is principally localized to jg cells of the distal afferent arteriole, where release is stimulated by increases in intracellular cAMP and inhibited by increases in cytosolic calcium. Four distinct stimuli mediating renin release are (1) NaCl sensed at the macula densa, (2) the sympathetic nervous system, (3) humoral factors, with Ang II, vasopressin, endothelin, and adenosine inhibiting renin release, and (4) changes in intrarenal blood pressure. Alterations in renal renin gene expression have been reported in pathophysiological states, such as salt depletion, diabetes mellitus, ureteral obstruction, Bartter's syndrome, and with high protein feeding. The highest renal concentrations of mRNA for the renin substrate angiotensinogen are found in the PT, where the protein is localized to subapical granules. Both salt depletion and androgens upregulate renal angiotensinogen mRNA. Of interest, renal angiotensinogen mRNA levels are lower in SHR than in normotensive WKY rats. As with angiotensinogen, renal ACE is mainly localized to the PT, with highest concentration on the brush border. The mechanisms of regulation of both renal angiotensinogen and ACE require further study. Using recently developed specific nonpeptide Ang II receptor antagonists, it appears that adult renal Ang II receptors are principally of the AT1 class, whereas fetal kidney Ang II receptors are of the AT2 subtype. By binding to AT1 receptors, Ang II exerts constrictive effects on both afferent and efferent arterioles, with increased effect reported on efferent arterioles. Glomerular Ang II receptors are localized to mesangial cells, mediating contractile responses resulting in changes in glomerular surface area and Kf, and potentially regulating mesangial sieving and phagocytosis. These receptors are reduced with salt restriction or in experimental diabetes. The highest concentrations of tubular Ang II receptors are found in PT, on both brush border and basolateral membranes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Developmental failures of blood vessels within central nervous system

Improved prevention and detection methods, as well as advances in medical treatment have resulted in a trend of increasing numbers of cancer survivors. Today, there are over 8 million cancer survivors, 5 million of whom were diagnosed 5 or more years ago. Cancer, once thought of as an acute disease, is increasingly being classified as a chronic disease. This article reviews physical, psychological, and social aspects of cancer survivorship, as well as other issues related to a diagnosis of cancer.     

Special surgery of blood vessels injuries in abdominal trauma

The analysis of the results of treatment of 41 victims with large vessels injuries in abdominal trauma was carried out. According to their location, all the injured vessels were divided in 5 groups: 1) on median line above the mesocolon (9 cases); 2) on median line under the mesocolon (14 cases); 3) in superior lateral part of the abdominal cavity (2); 4) in interior-lateral part of abdominal cavity (8); 5) in the region of hepato-duodenal ligament and retrohepatic area (13). Combined vascular injuries were observed in 5 patients. Basic aspects of diagnosis, surgical policy and treatment are discussed, 14 patients died.     

Overproduction of nitric oxide in pathophysiology of blood vessels

Sustained production of large amounts of nitric oxide (NO) is induced in blood vessels by inflammatory stimuli as a result of the expression of the inducible form of NO-synthase (NOS-2). This happens in systemic inflammatory reactions like septic shock and in local reactions produced by endothelium denudation and atherosclerosis. NOS-2 activity in blood vessels may protect tissues by virtue of the vasodilating, anti-thrombotic and leukocyte adhesion inhibitory effects of NO. It may also participate in vascular remodeling as a result of the antiproliferative and pro-apoptotic actions of NO. However excessive production of NO in blood vessels is involved in circulatory failure that takes place in systemic inflammatory reactions and it may be cytotoxic for surrounding tissues. For these reasons, inhibition of NO overproduction has been proposed in the treatment of septic shock. Selective inhibitors of NOS-2 activity or NO trapping agent, or both, might prove to be valuable drugs in the treatment of some inflammatory diseases. The conditions in which NO shifts from a tissue protective to a damaging role are not well elucidated. Recent findings suggest that the interactions with superoxide radicals, thiols, and metals (particularly with Fe2+) may be important not only in buffering excess NO produced by NOS-2, but also in channeling it from physiologically to pathophysiologically relevant targets. It has also been found recently that adventitial cells may play an important part in vascular NO production and generation of NO stores in the media layer. The ultimate effect of NO in blood vessels might depend on its site of production, local concentration, and interactions with other tissue components.     

Early changes in iris blood vessels in exfoliation syndrome

PURPOSE: To look for possible changes in iris blood vessels that might precede the formation of true exfoliation material, and to correlate these changes, if present, to aging of the iris. METHODS: Iris blood vessels of 10 clinically normal irises from 10 eyes (ages: 1 day-80 years), 4 irises with exfoliation (ages: 64-80 years) and 3 irises from primary open-angle glaucoma (POAG) (ages: 27-65 years) were examined with an electron microscope. RESULTS: Pronounced multilayering of the basal lamina around the vessels, abnormal excessive formation of microfibrils, presence of atrophic invaginations in the outer cell membranes of endothelial cells containing interlacing basal lamina, and an apparent decrease in the perivascular collagen fibers were evident in exfoliative iris vessels devoid of true exfoliation material. Similar, but much milder, changes were evident in normal aged and POAG irises. CONCLUSIONS: Abnormal elastic tissue and/or basal lamina production plays a role early in the formation of exfoliation material around iris blood vessels.