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Biomedical subjects

R E Parker

Publications and source records attributed to R E Parker.

17 recordsLinked to original sources
PubMed1992

Hydrostatic pulmonary edema in sheep. Effects of bronchial artery embolization on the plain chest radiograph.

RATIONALE AND OBJECTIVES: The bronchial circulation may influence pulmonary edema. This study evaluates possible effects of bronchoesophageal artery embolization on the plain film manifestations of hydrostatic pulmonary edema in sheep. METHODS: Anteroposterior and lateral chest radiographs were obtained during the induction of pulmonary edema both before and after embolization of the bronchoesophageal artery in six adult sheep. Interstitial lines and perivascular, segmental bronchial, proximal bronchial, carinal, tracheal, and parenchymal edema were evaluated. RESULTS: Only parenchymal edema was graded consistently. Though edema increased with left atrial pressure before embolization (P < .001), there was no similar change afterward. The embolized animals tended to be more edematous by the first film. CONCLUSION: Rather than any protective effect, bronchoesophageal artery embolization may increase edema. This model may be inappropriate for further investigation of the bronchial circulation in the development of human pulmonary edema.

Animals↗
PubMed1992

Evaluating flux of labeled albumin into the pulmonary interstitium of sheep lungs.

A noninvasive method was used to measure the movement of 131I-labeled albumin across the pulmonary microvascular barrier of a blood-perfused in situ sheep lung lymph preparation. After injection of labeled albumin into the blood, external measurements of gamma activity were taken for 2 h. The interstitial concentrations were calculated by applying the external activities and sampled lung lymph concentrations to a mass transport model. For the external activities and lymph activities to yield the same quantitative results, two modifications were necessary. First, lymph concentrations were corrected for transport delay from the lymphatic system. Second, externally detected radioactivity had to be corrected for the contribution of unbound nuclide. Application of a mathematical model to the data indicated the extravascular distribution volume for albumin was 79% of the pulmonary blood volume, and the extravascular distribution volume for radiolabeled iodide was 4.42 times greater than the pulmonary blood volume. The permeability-surface area product for iodide in the lung was estimated to be 0.274 ml.min-1.g blood-free dry lung wt-1. The transport delay in the lymphatic system was approximately 30-45 min and represented a volume of 1.44-2.80 ml.

Albumins↗
PubMed1992

Effects of Perilla ketone on the in situ sheep lung.

We studied the effects of three different doses (15, 20, and 25 mg/kg) of Perilla ketone (PK) on the blood-perfused in situ sheep lung while obtaining external measurements of lung transvascular protein flux. Lymph flow and lymphatic protein clearance increased significantly after all doses of PK. Severe pulmonary edema was confirmed by high postmortem wet-to-dry lung weight ratios and increased extravascular lung water from multiple indicator-dilution studies. Urea permeability-surface area product and effective diffusivity from multiple indicator-dilution studies also increased after PK infusion. Because we observed no evidence of increased capillary pressure or increased microvascular surface area after PK, we conclude that PK significantly increased pulmonary microvascular permeability. Certain aspects of the in situ PK response appeared to be dose dependent. The lungs responded rather quickly to high doses of PK, but an apparent latency period was noted with low doses of PK. Postmortem wet-to-dry lung weight ratios were always high but did not suggest dose dependence. However, times of postmortem measurements were not the same for all doses of PK. The external scan technique appeared to be sensitive to changes that occurred in the lung after PK. Externally detected albumin interstitial-to-plasma mass (mass I/P) ratios were substantially higher after PK than during control in situ studies. In some experiments, final mass I/P ratios increased above 4 approximately 2.0 h after PK compared with control values of 0.2 and 0.4. A delay time between injection and change in mass I/P slope was also observed, which decreased with increasing dose of PK. PK causes a permeability injury in the in situ sheep lung and provides a useful model for studying the sensitivity of permeability measurement techniques such as the external gamma-ray detection method.

Albumins↗
PubMed1992

Canine pulmonary filtration coefficient calculated from optical, radioisotope, and weight measurements.

Three independent methods were used to estimate filtration coefficient (Kf) in isolated dog lungs perfused with low-hematocrit (Hct) blood. Pulmonary vascular pressure was increased by 12-23 cmH2O to induce fluid filtration. Average Kf (ml.min-1 x cmH2O-1 x 100 g dry wt-1) for six lungs was 0.26 +/- 0.05 (SE) with use of equations describing conservation of optically measured protein labeled with indocyanine green. Good agreement was found when a simplified version of the multiequation theory was applied to the data (0.24 +/- 0.05). Both optical estimates were lower than those predicted by constant slope (0.55 +/- 0.07) or extrapolation (1.20 +/- 0.15) techniques, which are based on changes in total lung weight. Subsequent studies in five dog lungs investigated whether the higher Kf from weight analyses could be caused by prolonged pulmonary vascular filling. We found that 51Cr-labeled red blood cells (RBCs), monitored over the lung, continued to accumulate for 30 min after vascular pressure elevations of 9-16 cmH2O.Kf was determined by subtracting computed vascular filling from total weight change (0.28 +/- 0.06) and by perfusate Hct changes determined from radiolabeled RBCs (0.23 +/- 0.04). These values were similar to those obtained from analysis of optical data with the complete model (0.30 +/- 0.06), the simplified version (0.26 +/- 0.05), and from optically determined perfusate Hct (0.16 +/- 0.03). However, constant slope (0.47 +/- 0.04) and extrapolation (0.57 +/- 0.07) computations of Kf were higher than estimates from the other methods. Our studies indicate that prolonged blood volume changes may accompany vascular pressure elevations and produce overestimates of Kf with standard weight measurement techniques. However, Kf computed from optical measurements is independent of pulmonary blood volume changes.

Albumins↗
PubMed1979

Vascular responses in canine subcutaneous adipose tissue to hypothalamic stimulation.

The present studies investigated vascular responses to electrical stimulation of the posterior hypothalamus in isolated but perfused and innervated subcutaneous adipose tissue in adult dogs. Three groups of dogs were distinguished: in one, electrical stimulation elicited vasodilation; in another, vasoconstriction, and in a third, neither significant vasodilation nor vasoconstriction occurred. Histological examination revealed that electrode placements were in the medial posterior hypothalamus, the lateral posterior hypothalamus, and the medial septal region, respectively. Hypothalamic stimulation failed to alter concentrations of free fatty acids or glycerol in venous blood from subcutaneous fat. Local beta-adrenergic block (propranolol) reversed the vasodilation to vasoconstriction while local alpha-adrenergic block (dihydroergotamine) abolished the vaso constrictor response. These results suggest that selective stimulation of the posterior hypothalamus results in neurogenic activation of both alpha- and beta-adrenergic mechanisms in adipose tissue vasculature. beta-Adrenergic vasodilation appears to predominate if the electrode is located medially, and alpha-adrenergic vasoconstriction appears to predominate if the electrode is located in the lateral posterior hypothalamus.

Adipose Tissue↗
PubMed1979

The effect of fluid volume loading on exclusion of interstitial albumin and lymph flow in the dog lung.

The excluded volume fraction for interstitial albumin (FE) was estimated in the lungs of seven mongrel dogs during steady state conditions following intravenous infusions of Ringer's solution, amounting to 0, 5, 10, and 15% of body weight (BW). We estimated the tissue blood volume with 51Cr red cells, extracellular space with 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA), and the albumin pool with 125I human serum albumin. A prenodal tracheobronchial lymphatic was cannulated for recording lymph flow (QL), total protein (CL), and albumin [CL(A)] concentrations. From these measurements, we calculated the extravascular albumin content (QA) and 99mTc-DTPA space (VI) of lung tissue samples collected at the successive volume expansions. The apparent tissue concentration of albumin (CApp = QA/VI) decreased from a control value (mean +/- SE) of 0.89 +/- 0.06 to 0.46 +/- 0.04 g/dl following the 15% BW infusion, whereas CL(A) decreased from 1.43 +/- 0.16 to 0.50 +/- 0.07 g/dl for the same volume expansion. By assuming that pulmonary lymph represented tissue fluid, we calculated a control FE of 0.38 +/- 0.02 using the equation, FE = 1 - [CApp/CL(A)]. FE decreased following successive infusions to 0.28 +/- 0.03, 0.16 +/- 0.02, and 0.10 +/- 0.02. These data indicate a significant contribution by the decrease in FE to the total decrease in tissue albumin concentration as interstitial fluid volume increased. Somewhat unexpectedly, the mean steady state QL increased by only 2.1-fold following the 5% BW expansion, but did not further increase following subsequent volume expansions. This has been attributed to a nonlinear interstitial compliance, sequestration of interstitial fluid, or possible deterioration of the experimental preparation.

Albumins↗
PubMed1979

Permselectivity of cat blood-lymph barrier to endogenous macromolecules.

The restrictive properties of liver blood-lymph barrier to endogenous plasma protein fractions of varying molecular size were studied at different hepatic venous pressures (and lymph flows) using steady-state lymph to plasma protein concentration ratios. At control hepatic venous pressures (0-2 mmHg) the lymph to plasma venous concentration ratios of the various protein fractions indicate significant selectivity by the liver blood-lymph barrier to macromolecules on the basis of molecular size. The sieving observed was consistent with equivalent pore radii of 180-250 A. The transsinusoidal oncotic pressure gradient ranged between 4.0 and 8.0 mmHg at control venous pressures. As venous pressure was increased, liver lymph flow and lymph to plasma protein concentration ratio increased while the blood-lymph oncotic pressure gradient decreased. Liver lymph flow was linearly related to hepatic venous pressure. At lymph flow less than or equal to 10 x control, there is no longer a sieving effect on plasma protein; findings consistent with por radii in excess of 1000 A. The results of this study suggest that maximal sieving by the liver blood-lymph barrier occur at normal capillary filtration rates and support the possibility that the interstitium is the rate limiting barrier for blood to lymph transport of macromolecules in the liver.

Animals↗
PubMed1979

Vertical gradient in regional vascular resistance and pre to post capillary resistance ratios in the dog lung.

The ratios of pre-capillary (Ra) and post-capillary (Rv) resistances to total vascular resistance (RT) were measured at different vertical distances in the lungs of supine dogs. Capillary pressures were estimated as the algebraic sum of the alveolar absorption pressure for Tyrode's solution and the plasma colloid osmotic pressure. Segmental resistance fractions (Ra/RT, Rv/RT) were calculated using the pressure drops between arterial, capillary, and venous pressures at each vertical distance within the lung. In a second group of animals, total vascular resistance was calculated at each lung level using regional blood flow as measured by radiolabelled microspheres and the corresponding regional vascular pressures. The total vascular resistance was lowest in Zone III portions of the lung, but Ra/RT and Rv/RT were constant throughout this zone (n = 22) averaging .63 +/- .02 (SEM) and .37 +/- .02 (SEM, respectively, resulting in Ra/Rv of 1.70). Total vascular resistance increased markedly in Zone II portions of the lung, but the relative contribution of Ra/RT decreased from .62 +/- .07 (SEM) to .45 +/- .05 (SEM). Thus Ra/Rv decreased from 1.70 to .82 in Zone II. The absolute values of pre- and post-capillary resistances were lowest in Zone III but post-capillary resistance increased to a greater degree than pre-capillary resistance up Zone II.

Animals↗
PubMed1978

Picture processing during recognition.

This study investigated the processing of information during picture recognition. The subjects studied a single target picture and then were given a series of same-different recognition trials during which eye fixations were monitored. Distractors for the test trials were systematic transformations of the target picture. The results indicated that during recognition, information is encoded from a wide area and utilized both to direct additional eye fixations and to reach response decisions. The data also suggested that some of the processes involved in picture recognition are active simultaneously.

Attention↗
PubMed1978

Effects of adenosine on intestinal hemodynamics, oxygen delivery, and capillary fluid exchange.

Systemic arterial pressure, superior mesenteric arterial and venous pressures, blood flow, arteriovenous oxygen difference, lymph flow, and intestinal volume were monitored continuously from an autoperfused loop of cat ileum to determine the effects of locally infused adenosine on intestinal hemodynamics, oxygen consumption, and capillary fluid exchange. The results indicate that adenosine, inosine, and hypoxanthine are vasodilators in the intestinal circulation. Local infusion of adenosine significantly reduces vascular resistance, but lymph flow, lymph oncotic pressure, and lymphatic protein flux remained unchanged from control, and the intestinal volume rapidly became constant after an initial blood volume shift. Intestinal oxygen consumption decreased significantly in both autoperfused and constant flow preparations. Pretreatment with aminophylline prevented the reduction in oxygen consumption and greatly attenuated the vasodilatory effect of adenosine. The reactive hyperemic response to 60-s arterial occlusions was virtually unchanged following aminophylline treatment. Adenosine depressed oxygen utilization of mucosal and muscularis strips in vitro and caused a significant redistribution of blood flow from the mucosal-submucosal layer to the muscularis in autoperfused preparations. The results of this study indicate that adenosine significantly reduces vascular resistance and oxygen consumption, yet does not alter fluid exchange in the small intestine.

Adenosine↗
PubMed1977

Noradrenaline reversal in canine subcutaneous adipose tissue.

Although adrenaline reversal is a well known phenomenon, fewer investigations have demonstrated reversal of the vascular response to noradrenaline (NA). The present studies compared subcutaneous adipose tissue vascular responses to intra-arterial NA with those of sympathetic nerve stimulation. Both NA and electrical stimulation produced vasoconstriction in adipose tissue which was reversed to beta-adrenergically mediated vasodilation following local alpha-adrenergic block.

Adipose Tissue↗
PubMed1976

Acute changes in high energy phosphates, nucleotide derivatives, and contractile force in ischaemic and nonischaemic canine myocardium following coronary occlusion.

Studies of ischaemic myocardium following occlusion of coronary arterial branches revealed a substantial decline in creatine phosphate, adenosine triphosphate, and total adenine nucleotide contents over 40 min. Contents of nucleotide breakdown derivatives increased significantly but transiently. Contractile force declined rapidly and stabilized at a low level. In nonischaemic muscle following occlusion creatine phosphate, adenosine triphosphate, and total nucleotide contents declined rapidly, although not to the degree seen in ischaemic muscle. Contents of derivatives increased only slightly. Contractile force increased.

Adenine Nucleotides↗
PubMed1976

Memory for descriptive and spatial information in complex pictures.

Memory for several kinds of information in complex pictures was studied. Stimuli were line drawings of either real-world scenes or unorganized collections of objects. Memory was tested by recognition and reconstruction tests, given immediately and/or after a week. Organization of the pictures had little effect on memory for size, orientation, or physical appearance of objects in the pictures. There was only a small loss of these types of descriptive information over a week's time. Organization of the pictures had a major effect on memory for location of objects in the pictures. Memory for location on the horizontal dimension declined markedly for both types of pictures over a week. Performance remained high on the vertical dimension for organized pictures, and systematic distortion occurred on this dimension for unorganized pictures. Reconstruction data were compared with the performance of subjects who had not seen the pictures before. It was concluded that real-world schemata do not affect encoding of some types of descriptive information, but play an important role in both encoding and memory for spatial information.

Female↗