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Biomedical subjects

R Y Chen

Publications and source records attributed to R Y Chen.

79 records · Page 5Linked to original sources
PubMed1977

Plasma volume, red cell volume, and thoracic duct lymph flow in hypothermia.

The effects of hypothermia on plasma volume (125I-albumin), red blood cell volume (51 Cr-RBC), and capillary permeability (thoracic duct lymph flow and protein concentration) were determined on dogs anesthetized with pentobarbital, paralyzed with succinylcholine, and mechanically ventilated. Red blood cell volume and plasma protein concentration did not change significantly after cooling. Reductions in plasma volume and total plasma proteins indicate that whole plasma was excluded from the effective circulating blood volume. Except for a lesser increase in hematocrit, chronically splenectomized dogs showed essentially the same changes as normal dogs in response to hypothermia. Following application of ice bags, there was a biphasic response in lymph flow. The early increase in lymph flow accompanying a slight decrease in plasma volume was attributable to transcapillary fluid loss into interstitial space, probably due to cold-induced sympathetic activity. The later decrease in lymph flow in hypothermia resulted from a decrease of lymph production secondary to a decrease in available capillary diffusion area. This decrease in lymph flows and the continued reduction in plasma volume suggest an intravascular sequestration of whole plasma.

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Gastric arteriolar and venular responses to nitrogenous and nonnitrogenous vasodilating agents in the rat.

We made in vivo microvascular observations to simultaneously compare the actions of various direct vasodilators on the resistance and capacitance vessels without confounding systemic hemodynamic effects. The responses of gastric submucosal arteriolar and venular diameters to the topical application of 10(-7) 10(-5), and 10(-3) M of the vasodilators nitroglycerin (NTG), sodium nitroprusside (SNP), hydralazine (HYD), and adenosine (ADN), and acetylcholine (ACh) were studied in 6 rats for each agent using in vivo microscopy. The basal diameters of arterioles, 37 +/- 2 microns (mean +/- SE), were maximally dilated to 86 +/- 2 microns by 10(-3) M ADN, NTG, SNP or ACh, while with 10(-3) M HYD dilation was just 55%. The basal diameters of venules, 36 +/- 2 microns, were maximally dilated only to 51 +/- 1 micron by 10(-3) M ADN, NTG or SNP, while those by 10(-3) M HYD and ACh were 60 and 71%, respectively. We observed that: (1) NTG and SNP were the strongest arteriolar and venular dilators, but at low dose (10(-7) M), NTG was more effective than SNP. (2) Gastric submucosal venules had considerably less dilating capacity than arterioles. (3) ADN was as effective as NTG and SNP for both arteriolar and venular dilation at 10(-3) M. It was less potent at lower concentrations. (4) ACh was as potent as ADN, NTG and SNP in dilating arterioles, but it was notably less potent in dilating venules. (5) HYD was the weakest arteriolar and venular dilator among all agents studied, and its action on venules was slightly greater than that on arterioles.

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Effects of sphere size and injection site on regional cerebral blood flow measurements.

Regional cerebral blood flows and shunting of microspheres with four different sizes (9,12, 16 and 25 microns) into the superior sagittal sinus were determined in twelve dogs. Venous blood was collected from the superior sagittal sinus for 120 min after the injection of microspheres, and the dogs were then sacrificed immediately. Results on blood flow measurements and venous shunting determinations were similar between left ventricular and left atrial injections. Blood flows measured by 12, 16 and 25 microns spheres were comparable in various brain tissues, except the choroid plexus. 9 microns spheres underestimated blood flows in all regions studied: by 13-19 percent in the cerebral cortex, midbrain, brain stem and cerebellum, by 34-42 percent in the cortical white matter, corpus callosum and cervical cord, and by 64-81 percent in pituitary gland and choroid plexus. These results probably reflect regional difference in microvascular architecture. Venous shunting of 9, 12, 16 and 25 microns spheres during a 24 hr period were 23.6 +/- 2.5, 12.6 +/- 1.2, 4.8 +/- 1.4, and 4.0 +/- 1.2 percent (mean +/- SEM), respectively, with respect to the arterial delivery. Although most of the venous shunting occurred during the first 3 min after the injection of microspheres, it continued 3-60 min after the injection. Beyond 60 min, the venous shunting became minimal for 16 and 25 microns spheres, while significant amount of 9 microns spheres continued to appear in sagittal sinus. This time dependent shunting indicates that some microspheres may be transiently trapped in the microcirculation and become gradually dislodged with time. Failure to consider this time dependence may underestimate the shunting of microspheres through the microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

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Regional cerebral blood flow and oxygen consumption of the canine brain during hemorrhagic hypotension.

The sequential changes in systemic and cerebral hemodynamics, systemic and cerebral oxygen transport and consumption rates, and the regional blood flows (measured with 15 micron microspheres) to the cortical and subcortical brain tissues were determined in nine dogs subjected to graded hemorrhage (10 ml/kg X 4 at 15 min intervals). As hemorrhage progressed, both mean arterial pressure and cardiac output decreased progressively. In contrast to the systemic circulation, the mean cerebral blood flow (mCBF) was well maintained by cerebral vasodilation and the cerebral O2 consumption rate (CMRO2) increased during the first three stages of hemorrhage. At 40 ml/kg of hemorrhage, there were significant reduction in mCBF and CMRO2 despite the increase in O2 extraction, suggesting the occurrence of cerebral hypoxia and decompensation of the cerebral circulation. There were remarkable regional variations in the responses of regional cerebral blood flows (rCBF) to hypovolemia, resulting in a significant redistribution of cerebral blood flow. The fractions of cardiac output supplying the diencephalon (thalamus and hypothalamus), the brain stem (pons and medulla oblongata) and the cervical spinal cord increased after hemorrhage up to 40 ml/kg. The redistribution of rCBF favors those areas where neurons related to cardiovascular control are located. These findings have significant implications relating to hemodynamic regulation during hemorrhagic hypotension.

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PubMedDate not supplied

Decrease in cerebral blood flow in rats after experimental subarachnoid hemorrhage: a new animal model.

There continues to be a need for good animal models of experimental subarachnoid hemorrhage (SAH). The rat would be an ideal subject in which to study SAH since it is inexpensive and easier to use than the larger laboratory animals. The present study was undertaken to determine if alterations of cerebral blood flow could be produced in the rat after experimental SAH, and thereby justify using the rat as a model for further study of SAH. Rats weighing between 450 and 500 grams underwent insertion of a cannula into the cisterna magna at least 5 days prior to physiological testing. One group of rats then received a 0.3 cc injection of fresh autologous arterial blood into the cisterna magna to simulate a SAH. Another group of rats received injection of an equal volume of mock CSF (buffered saline) into the cisterna magna. A third group of rats had no subarachnoid injections. In all three groups, blood flow to the cerebral hemispheres was measured with the labeled microsphere technique. Rats with experimental SAH showed a 40% decrease of cerebral blood flow, whereas rats with saline injections showed only a 15% decrease. Control rats had no changes of cerebral blood flow. These studies demonstrate that the rat is a potential experimental model for investigations into SAH.

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