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Biomedical subjects

M A Perry

Publications and source records attributed to M A Perry.

71 records · Page 4Linked to original sources
PubMed1982

Role of exchange vessels in the regulation of intestinal oxygenation.

The contribution of changes in capillary exchange capacity to local regulation of oxygen uptake was assessed in the cat small intestine. Oxygen extraction, oxygen uptake, and the capillary filtration coefficient (KF,C) were measured at blood flows ranging between 4 and 70 ml.min-1.100 g-1. Blood flow was altered via pump perfusion or partial arterial occlusion. Both oxygen extraction and capillary exchange capacity (KF,C) increased progressively as blood flow was reduced in a stepwise fashion. Oxygen uptake remained constant between blood flows of 30 and 70 ml.min-1.100 g-1, yet it decreased progressively as blood flow was reduced below 30 ml.min-1.100 g-1. These findings support the hypothesis that intrinsic modulation of intestinal oxygen extraction is mediated by vascular elements that govern capillary exchange capacity.

Animals↗
PubMed1982

Pancreatic circulation: intrinsic regulation.

The purpose of the present study was to characterize the intrinsic mechanisms involved in the regulation of blood flow and oxygenation in the totally isolated, perfused canine pancreas. Arterial pressure, venous outflow pressure, blood flow, arteriovenous oxygen difference, and capillary filtration coefficient were measured during graded arterial pressure reductions and venous pressure elevation. Reductions in arterial pressure caused pancreatic blood flow and vascular resistance to decrease, whereas venous pressure elevation resulted in a decreased blood flow and increased vascular resistance. The reductions in blood flow produced by arterial and venous pressure alterations were associated with increases in oxygen extraction and capillary filtration coefficient. During the same pressure perturbations, oxygen uptake remained constant between blood flows of 40-100 ml.min-1.100 g-1, yet decreased progressively as blood flow was reduced below 40 ml.min-1.100 g-1. Arterial occlusion resulted in a postocclusive reactive hyperemia, the magnitude of which was related to the duration of occlusion. The findings of this study suggest that intrinsic regulation of pancreatic blood flow can be attributed to both metabolic and myogenic mechanisms. Resistance and exchange vessels both appear to play a role in the regulation of oxygen delivery to the pancreatic parenchyma.

Animals↗
PubMed1982

Exclusion phenomenon in the liver interstitium.

Measurements were made of hepatic interstitial fluid volume and the proportion of that space occupied by 125I-labeled lactoglobulin, albumin, and gamma-globulin in anesthetized cats. 51Cr-red blood cells and 99mTc-diethylenetriaminepentaacetic acid were used to estimate tissue blood volume and extracellular volume, respectively. Hepatic lymph was assumed to represent the interstitial fluid of the liver. The degree of exclusion of each protein increased with increasing molecular size. At normal hepatic venous pressures, the excluded volume fraction for cat albumin was 0.41. Elevation of hepatic venous pressure by 12.5 mmHg caused a fourfold increase in hepatic lymph flow with an increase in interstitial volume and a reduction in albumin exclusion. When the exclusion of heterologous (human) albumin was studied in the cat liver, much higher values were obtained than with homologous albumin. This effect may be due to polymerization of commercial human albumin on storage.

Animals↗
PubMed1982

Autoregulation of intestinal capillary filtration rate.

To determine whether intestinal capillary filtration rate, capillary pressure, or both are autoregulated in the cat ileum, the following parameters were measured under isovolumetric conditions: lymph flow, capillary pressure, capillary filtration coefficient, and lymph and plasma oncotic pressures. Superior mesenteric arterial pressure was reduced in 25-mmHg steps from 125 to 25 mmHg. As arterial pressure was reduced, lymph flow, capillary pressure, and the transcapillary oncotic pressure gradient decreased while the capillary filtration coefficient increased. Over the arterial pressure range of 75-125 mmHg, capillary pressure decreased in a fashion expected from a rigid system; however, capillary pressure was slightly autoregulated at lower arterial pressures. Lymph flow fell proportionately more than capillary pressure over the entire arterial pressure range. The results of this study indicate that intestinal capillary pressure and capillary filtration rate are poorly autoregulated in the cat when arterial pressure is reduced. Changes in interstitial fluid pressure play a major role in preventing interstitial dehydration in the cat ileum when arterial pressure is reduced.

Animals↗
PubMed1981

Effects of bradykinin on intestinal transcapillary fluid exchange.

Bradykinin (50 micrograms.L-1) increases intestinal lymph flow sixfold when infused intraarterially into the cat ileum. The capillary filtration coefficient and capillary pressure increase and interstitial fluid pressure rises from negative to positive values. A slight increase in lymph:plasma protein concentration occurs with a resulting fall in the transcapillary oncotic pressure gradient. These results indicate that the effect of bradykinin on intestinal lymph flow is attributable, at least in part, to increased capillary pressure, exchange vessel surface area, and a reduction in the effective transcapillary oncotic pressure gradient.

Animals↗
PubMed1981

Permeability of intestinal capillaries to small molecules.

The permeability of capillaries in the isolated, vascularly perfused cat ileum was studied with the double-indicator diffusion technique. The molecules studied were raffinose, inulin, and beta-lactoglobulin A. Plasma flow through the tissue was increased by local intra-arterial infusions of isoproterenol (a selective mucosal vasodilator) or adenosine (a dilator of the muscularis vasculature). The permeability-surface area product (PS) for all solutes increased with increasing plasma flow. At the highest plasma flow acquired with isoproterenol, PS values for raffinose, inulin, and beta-lactoglobulin A were approximately 40, 20, and 4 ml.min-1.100 g-1, respectively. These data suggest that capillaries in the mucosa-submucosa of the ileum are at least five to seven times more permeable to raffinose and inulin than has been reported for skeletal muscle capillaries. Selective vasodilation of the muscularis region with adenosine reduced PS values for raffinose and inulin at each flow rate studied. The data are consistent with equivalent pore radii of approximately 60 A for capillaries in the mucosa-submucosa and 40 A in the muscularis of the small intestine.

Animals↗
PubMed1981

Interstitium-to-blood movement of macromolecules in the absorbing small intestine.

The relative roles of diffusion and convection in the transport of plasma proteins across intestinal capillaries were estimated for absorbing and nonabsorbing segments of cat ileum. Diffusive, convective, and net protein fluxes were estimated with steady-state lymph and plasma protein concentrations, lymph flow, net transmucosal volume flow, and phenomenological transport equations. The results acquired indicate that convection accounts for approximately 80-90% of total net transcapillary solute movement at normal and increased capillary filtration rates. When the intestinal capillaries are converted from filtering to absorbing vessels by enhancing transmucosal water movement, the convective and diffusive protein fluxes occur in opposite directions, i.e., significant quantities of plasma proteins move from interstitium to blood by convection. These findings suggest that the magnitude of the capillary protein leakage during absorption is far greater than predicted using lymphatic protein flux changes. The massive movement of plasma proteins into and out of the mucosal interstitium during absorption may be advantageous for the removal of protein-bound nutrients (e.g., fatty acids).

Animals↗
PubMed1981

Autoregulation of gastric blood flow and oxygen uptake.

The purpose of this study was to determine whether the ability of the stomach to autoregulate blood flow and oxygen uptake is altered by sympathetic denervation. Blood flow, oxygen extraction, local arterial pressure, and venous pressure were continuously monitored in sympathetically innervated and denervated autoperfused dog stomach preparations. As perfusion pressure was reduced in increments from 120 to 20 mmHg in innervated preparations, blood flow and oxygen uptake decreased while oxygen extraction and vascular resistance increased. Reductions in perfusion pressure in denervated preparations resulted in a decrease in blood flow, oxygen uptake, and vascular resistance, whereas oxygen extraction increased. The ability of the stomach to regulate blood flow and oxygen uptake was significantly improved after denervation, i.e., vascular resistance decreased and oxygen uptake remained relatively constant when arterial pressure was reduced. Oxygen uptake in denervated stomachs was generally higher than that in innervated stomachs. Autoregulation of gastric blood flow therefore appears to be improved by denervation. The better autoregulation observed after denervation may result either from a reduction in sympathetic tone and/or the increase in gastric oxygen demand.

Animals↗
PubMed1981

Permeability of gastric capillaries to small and large molecules.

The permeability of capillaries in the stomach to small and large solutes was studied with the double-indicator diffusion technique in the dog stomach and by analysis of steady-state lymph and plasma samples in the cat stomach. The effective pore radius in gastric capillaries determined by indicator diffusion was 53 A, whereas steady-state lymph samples predicted a small-pore radius of 47 A. At the highest plasma flow rates studied (achieved by intra-arterial infusion of isoproterenol), indicator diffusion estimates of the permeability-surface area product for raffinose, inulin, and beta-lactoglobulin A were 140, 70, and 8 ml . min-1 . 100 g-1, respectively. The lymph studies indicate that gastric capillaries are more permeable than capillaries in the intestine and colon to albumin and larger molecules. The calculated effective large-pore radius of gastric capillaries was 250 A. The osmotic reflection coefficients (sigma d) ranged from 0.73 +/- 0.03 for albumin to 0.91 +/- 0.02 for beta-lipoprotein (120-A radius). The sigma d for total plasma protein was 0.78 +/- 0.03, indicating a substantial transcapillary oncotic pressure gradient, despite the greater permeability of these capillaries for macromolecules.

Animals↗
PubMed1979

IQ measurement in children with skeletal dysplasia.

We have reviewed the IQ studies on 68 children with skeletal dysplasia. These data should provide useful information for the counseling of parents with newborn affected children. Previous studies have documented retardation and hydrocephalus in association with achondroplasia. Some parents report that they were given a poor prognosis for their child's mental development early in his or her life. This study shows that the 34 children with achondroplasia and 34 with other skeletal dysplasia performed intellectually in the same range as other children.

Achondroplasia↗
PubMed1977

The catabolism of intravenously injected heparan N-[35S] sulphate in the rat.

The metabolic fate of heparan N-[(35)S]sulphate was studied in rats. Heparan sulphate was obtained from either bovine aorta or lung and labelled with (35)S by desulphation and subsequent resulphation in vitro. Experiments in which heparan N-[(35)S]sulphate was administered intravenously to either free-range or wholly anaesthetized rats with ureter cannulae established that substantial desulphation occurs in vivo, with elimination of inorganic [(35)S]sulphate in urine. Oligosaccharides labelled with (35)S, possible intermediates in heparan sulphate degradation, could not be detected in urine or blood. The general distribution of radioactivity after administration of heparan N-[(35)S]sulphate, as demonstrated by whole-body radioautography, suggested that desulphation was not restricted to one organ in particular. Support for this view was obtained in experiments in which heparan N-[(35)S]sulphate was administered to animals after the removal of kidneys, liver, spleen, pancreas or gastrointestinal tract. In all cases inorganic [(35)S]sulphate was still produced. The ability of rats of desulphate heparan N-[(35)S]sulphate was progressively impaired by increasing concentrations of heparin administered simultaneously. It was concluded that heparan sulphate is metabolized at a number of sites in the body by a sequence of degradative events leading to the formation of inorganic sulphate. It is also concluded that at least some of these events are common to heparan sulphate and heparin.

Animals↗
PubMedDate not supplied

Peritoneal dialysis solutions and feline splanchnic blood flow.

Splanchnic blood flow is generally considered to be one of the major factors governing the efficiency of peritoneal dialysis; however, few direct measurements of blood flow have been made during peritoneal dialysis. The radioactive microsphere technique was used to assess the effects of 1.5 and 4.25 g/100 ml dextrose-Dianeal solutions on blood flow to various tissues in the abdominal cavity. The effects of dialysis solution on blood flow through the superior mesenteric and coeliac arteries were measured by electromagnetic flowmetry. The results indicate that the commercial peritoneal dialysis solutions dramatically increase blood flow to the mesentery, omentum, intestinal serosa and parietal peritoneum. These changes are not accompanied by significant alterations in blood perfusion in the major abdominal organs (liver, stomach, intestine, pancreas, spleen). Peritoneal dialysis solutions do not significantly alter blood flow through the coeliac and superior mesenteric arteries. These findings indicate that commercial dialysis solutions improve perfusion to the peritoneum without significantly altering splanchnic blood flow.

Animals↗
PubMedDate not supplied

How can the uptake of cervical cytology screening be improved?

BACKGROUND: Cervical cancer remains a killer, despite a screening programme designed to detect cases in the early stages of development. A number of factors appear to influence a woman's decision to attend for a smear test. This literature review considers these factors, and whether nurses can play a part in reducing the death rate by dispelling the misapprehensions and misinformation that deter vulnerable women from attending. CONCLUSION: There is a great need for modification and improvement of the present screening programme if all women who are at risk from cervical cancer are to be encouraged to attend for screening. The attitude of those who conduct smear tests is often crucial in gaining women's confidence--an unpleasant experience might deter a patient from attending again. Other barriers to attendance include administrative errors and lack of knowledge. Given the impact of mass advertising and health promotion campaigns in other areas, such as smoking cessation, there is clearly a need for a similar strategy to be applied to cervical screening.

Attitude to Health↗