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Biomedical subjects

A Hope

Publications and source records attributed to A Hope.

54 records · Page 3Linked to original sources
PubMed1983

The effect of water deprivation on local renal blood flow and filtration in the laboratory rat.

The effects of longlasting dehydration on total and local renal blood flow and glomerular filtration rate have not been studied previously in the laboratory rat. We therefore determined zonal renal blood flow (ZRBF) in cortical and medullary zones by the 125I-iodoantipyrine and H2 gas washout techniques. After 8 days of water deprivation renal blood flow (RBF) was reduced by 65% and renal vascular resistance (RVR) had increased by 110%. Half the RVR increase could be ascribed to increased blood viscosity as reflected by increased hematocrit (42 to 60%). Fractional ZRBF decreased by 5% in the outer half and increased by 5% in the inner half of the cortex. Measurements of the relative single nephron glomerular filtration rate (sngfr) of superficial and deep nephrons, determined by the 14C-ferrocyanide technique, indicated no detectable changes in filtrate distribution. Both ZRBF and sngfr heterogeneity had increased in dehydrated as compared to control rats. In one rat studied with the H2 gas washout method, local ischemia and intermittent blood flow occurred. Similarly, cortical patches of nonfiltering nephrons were observed in another rat. These findings suggest that the increased heterogeneity of intrarenal flow and filtration may involve, and in part be due to, intermittent local changes in blood flow.

Animals↗
PubMed1982

Effect of adriamycin on blood flow in renal tumour and normal renal tissue.

The effect of adriamycin (Adm) on local blood flow was simultaneously measured in neoplastic tumour, diameter 3-5 mm, and intact tissue in rat kidneys using the H2 gas washout technique. Constant rate i.v. infusion of Adm, 0.3-6 mg/kg/min for 3-15 min, increased mean arterial blood pressure (AP) by 20%, a maximum already obtained at the lower infusion rate, without affecting heart rate. Control tumour flow averaged 0.9 (0.4-1.1) ml/min/g. Flow was inversely related to Adm infusion rate in both tissues, but tumour flow tended to be relatively less affected. In another series of experiments total renal blood flow (RBF) was recorded electromagnetically during constant rate infusion of Adm into the renal blood stream, 0.03-3 mg/kg/min for 3-20 min. AP increased and RBF decreased during the first 2 min of infusion, whereafter steady levels were maintained. Both parameters returned to control levels within 4 min after completed infusion, irrespective of infusion rate and duration. High i.a. infusion rates, 2-3 mg/kg/min, almost stopped RBF but gave no further AP increase (max at approximately 0.5 mg/kg/min), indicating a direct constrictor effect on renal vessels. On the other hand, the AP response persisted when renal circulation was excluded, suggesting a general pressor response evoked by Adm. A 60% RBF reduction was obtained by 1 mg/kg/min i.a. as compared to 4-6 mg/kg/min i.v. infusions. This indicates that a several times higher Adm concentration was maintained in renal blood during i.a. infusion. Taken together with the recovery time, this observation also suggests a post-infusion blood clearance of Adm with an initial half-time of about 2 min or less. This was confirmed in additional experiments where [3H]-labelled Adm was determined in timed blood samples.

Animals↗
PubMed1981

Incomplete and flow dependent extraction of 86Rb in the rat kidney. Errors in local flow estimation.

Renal uptake of 86Rb, lasting for 30s after intravenous bolus injection, and uptake of 15 micrometer radioactive microspheres (Ms) simultaneously injected in the left ventricle were measured in rats. Calculated from renal blood flow (RBF) determined by Ms and 86Rb clearance, the renal extraction ratio of 86Rb (ERb) was 0.81 +/- 0.07 (SD). With increasing RBF, ERb decreased significantly. Total body 86Rb extraction ratio nearly equalled ERb as determined 30s after injection. In another group of rats 86Rb was injected into an extracorporal circuit from the carotid artery perfusing the left kidney only. Renal recovery of 86Rb averaged 0.76 +/- 0.13 15-20s after injection. As in the first group, ERb was inversely related to RBF. At increased RBF, calculated local cortical flow is seriously underestimated unless ERb as well as ERb flow dependency are taken into account. However, the relative local flow rates calculated for cortical zones are not appreciably affected by ERb and its flow dependency.

Animals↗
PubMed1981

Total and local renal blood flow and filtration in the rat during reduced renal arterial blood pressure.

Discrepancies concerning the lower pressure limit of renal blood flow (RBF) autoregulation, different autoregulatory adjustments in deep and superficial renal zones and dissociation of RBF and filtrate production stimulated the present study. Autoregulation of renal blood flow was investigated at reduced renal arterial blood pressure (RAP) in Sprague-Dawley rats using 4 different flow methods: uptake of 125I-iodoantipyrine (I-Ap) and 86Rb, local detection of hydrogen gas washout rate (H2) and, in the autoperfused kidney, electromagnetic flowmetry (FM). With I-Ap and 86Rb, RBF was maintained at a RAP as low as 80 mmHg, compared to contralateral RBF. However, with the other two methods where each kidney serves as its own control, a 15% RBF reduction was obtained at this RAP. This discrepancy (p less than 0.001) infers a contralateral renal vasoconstriction during ipsilateral renal hypotension and vasodilation. Arterial blood pressure increased during unilateral renal hypotension, suggesting that contralateral renal constriction was part of a general increase in total body vascular resistance. Following abrupt RAP reduction RBF was immediately readjusted (2-3 s) and maintained for up to 40 min. No significant change in intrarenal blood flow distribution was observed with I-Ap. Superficial and deep cortical single nephron glomerular filtration rates were equally reduced at lowered RAP as determined by the ferrocyanide technique. However, a dissociation between the autoregulation of RBF and glomerular filtration rate (GFR) in the direction of less well maintained GFR was observed. Renal arterial acetylcholine infusion increased RBF by about 40% and effectively abolished RBF autoregulation.

Acetylcholine↗
PubMed1980

Distribution of blood flow in the dog kidney. II. Saturation rates of inert diffusible tracers versus uptake of 15 mu microspheres during vasodilation and vasoconstriction.

While 15 mu microspheres (Ms) in principle provide a measure of glomerular flow, uptake rate of inert diffusible tracers indicates "effective" or "nutrient" flow, i.e. essentially postglomerular capillary flow. Paired measurements of glomerular and postglomerular flow were made in tissue samples from outer, middle and inner cortex (C1, C2, C3) and medullary zones. After a control Ms injection, renal vascular conductance (RVC) was altered in one kidney whereupon a second Ms injection was made, immediately followed by infusion of the 125I-iodoantipyrine and tritiated water. RVC was increased maximally by i.a. infusion of acetylcholine with and without reduced renal arterial pressure, whereas moderate vasodilation was produced by lowering renal arterial or rising ureteral pressure. RVC was reduced by i.a. or i.v. infusion of angiotensin II. Within a mean RVC range of 50 to 180% of control the fractional distribution of zonal postglomerular flow remained unaltered, in agreement with previous results obtained from local H2 gas desaturation rate. Glomerular flow was about 20% higher in C1, equal in C2 and 40% lower in C3 as compared to postglomerular flow in control kidneys. This disparity nearly disappeared during maximal vasodilation and tended to increase during vasoconstriction. The results might suggest a variable net postglomerular effective flow in radial direction through the renal cortex. Alternatively, the fractional redistribution of Ms might reflect a variable degree of Ms skimming at the afferent arteriolar inlets along the interlobular arteries.

Acetylcholine↗
PubMed1979

Fluid transport and the dimensions of cells and interspaces of living Necturus gallbladder.

The volume of the cells and lateral intercellular spaces were measured in living Necturus gallbladder epithelium. Under control conditions, the volume of the lateral spaces was 9% of the cell volume. Replacement of mucosal NaCl by sucrose or tetramethylammonium chloride (TMACl) caused intercellular spaces to collapse. During mucosal NaCl replacement, cell volume decreased to 79% of its control value. When NaCl was reintroduced into the mucosal bath, the intercellular spaces reopened and the cells returned to control volume. The NaCl active transport rate, calculated from the rate of cell volume decrease, was 266 pM/cm2.s, close to the observed rate of transepithelial salt transport. It was calculated from the decrease in cell volume that all of the intracellular NaCl was transported out of the cell during removal of mucosal NaCl. The flux of salt across the apical membrane, calculated from the rate of cell volume increase upon reintroducing mucosal NaCl, was 209 pM/cm2.s, in good agreement with estimates by other methods. The electrical resistance of the tight junctions was estimated to be 83.9% of the total tissue resistance in control conditions, suggesting that the lateral intercellular spaces normally offer only a small resistance to electrolyte movement.

Animals↗
PubMed1979

Partition of 125I-iodoantipyrine among erythrocytes, plasma, and renal cortex in the dog.

The tissue/blood partition coefficient, lambda tb, defined as the amount of blood having the same tracer content as one unit of tissue at diffusion equilibrium, was determined for 125I-iodoantipyrine (I-Ap) and tritiated water (THO) in the dog kidney cortex. Measurements were made after in vivo equilibration for 75 to 300 s and with liver circulation excluded. In 18 kidneys, lambda tb for I-Ap averaged 1.38 (S.D. 0.13) w/w (weight/weight), without significant correlation to hematocrit (range: 23-43) or to urine pH (range 5.5-8.6). The lambda tb for THO averaged 0.97 (S.D. 0.06) v/w (volume/weight), close to the relative water contents. Erythrocyte/plasma partition for I-Ap was 0.82 w/w, compared to a water partition of 0.72. Thus, at diffusion equilibrium the apparent I-Ap concentration in renal cortical and red cell water exceeds that of plasma water by 14 and 60%, respectively. It follows that I-Ap cannot be used as a general indicator for total tissue water content. When used for measurement of local blood flow and modum Kety, lambda tb must be determined for each tissue and species.

Animals↗
PubMed1979

Distribution of blood flow in the dog kidney. I. Saturation rates for inert diffusible tracers, 125I-iodoantipyrine and tritiated water, versus uptake of microspheres under control conditions.

Disparate reports on intrarenal blood flow distribution prompted a direct comparison between microspheres (Ms) and inert diffusible tracers (DT). The "tissue sampling technique" for estimating local flow with DT (Kety) was adapted for the dog kidney, using 125I-iodoantipyrine (1-Ap) and tritiated water (THO). Ms (15 micron) were injected 2-3 min prior to 10-15 s DT infusion made during continuous 1 s arterial blood sampling. Tracers were measured in 7 to 20 samples from each of the following zones: Outer, middle and inner cortex (C1, C2, C3), outer and inner halves of outer medulla (OM1, OM2), and inner medulla (IM). I-Ap and THO gave closely similar flow distribution, and average total renal blood flow (RBF) of 3.90 and 3.78 as compared to 3.94 ml/min . g with Ms. Flow in C2 (ml/min . g) was similar with all tracers, and in per cent thereof average local flows were: C1 102, C3 70, OM1 34, OM2 12, and IM 2 with DT versus 117, 53, 12, 3, and 0 with Ms. Zonal flow fractions of total RBF obtained with DT were: C1 0.41, C2 0.33, and C3+medulla 0.26 versus 0.51, 0.33 and 0.16 with Ms. Thus, a Ms surplus in C1 relative to DT flow, representing 10% of total RBF, matched a Ms deficit in C3+medulla. This disparity might result from: (1) Failure of Ms to enter deep afferent arterioles in proportion to blood flow, (2) diffusion of DT from deep portions of the interlobular arteries, and/or (3) postglomerular inward flow of blood and DT.

Animals↗
PubMed1979

Dimensions of cells and lateral intercellular spaces in living Necturus gallbladder.

The size and shape of the cells and lateral intercellular spaces were measured in living Necturus gallbladder epithelium. Interspace volume was determined as a function of the transepithelial hydrostatic pressure difference. The compliance of the lateral membranes of the gallbladder cells was calculated from the interspace pressure-volume curves in both the presence and absence of fluid transport. Cell and interspace volume were studied when the NaCl in the mucosal bath was substituted by equiosmolar quantities of sucrose. The cells decreased in volume after the removal of mucosal NaCl and increased to control volume when the mucosal perfusate was 100 NaCl Ringer. The interspaces collapsed when fluid transport was inhibited by the removal of mucosal NaCl and reopened when NaCl was reintroduced to the mucosal bath. The rate of change of cell volume was used to calculate the active transport rate and the flux of NaCl across the apical membrane. The magnitude of the cell volume change during NaCl replacement indicated that all intracellular NaCl was readily accessible to be transported out of the cell.

Animals↗
PubMed1978

Size and shape of the lateral intercellular spaces in a living epithelium.

The lateral intercellular spaces of Necturus gallbladder epithelium were seen and measured while the living tissue was perfused in a new chamber. The compliance of the lateral cell membranes was calculated from the measured pressure-volume characteristics of the lateral intercellular spaces.

Animals↗
PubMed1977

Intrarenal distribution of blood flow and glomerular filtration during chronic unilateral ureteral obstruction.

Paired hydronephrotic (HN) and hypertrophic (HT) rat kidneys were studied after 6 days with complete unilateral ureteral obstruction without exposing the kidneys. Total HN renal blood flow (RBF), estimated by total microsphere (MS) uptake and from local 125I-antipyrine (Ap) uptake, averaged about 3/4 of control. HN kidney GFR was reduced to about 1/2 of control level as estimated from inulin clearance of HT kidney times the HN to HT ratio for mean single nephron filtration rate, determined by 14C-ferrocyanide. Whereas blood flow (Ap) was proportionately reduced in outer and inner cortex (OC and IC), fractional flow to the outer medulla (OM) was doubled as compared to controls (p less than 0.01). Filtration was well preserved in deep as compared to superficial glomeruli with a smaller deep nonfiltering fraction (p less than 0.02). Thus the results oppose the current concept that HN is characterized by disproportionate circulatory damage to IC and OM with little or no filtration in deep nephrons. In HT kidneys average RBF (MS) and GFR rose by about 1/2. Whereas total blood flow (Ap) rose proportionately in OC and IC, it remained at control level in OM, indicating dissociation between the total RBF and GFR and the effective blood flow to the OM zone.

Animals↗
PubMedDate not supplied

Effect of reduced perfusion pressure and acetylcholine on local blood flow in tumors in the rat kidney.

The local blood flow (LBF) in a sarcoma and a hepatoma implanted into the rat kidney was examined during renal vasodilation, with and without increased total renal blood flow (RBF). Both tumor types had a control LBF of about 0.7 ml/min per g, i.e. 35 per cent or less as compared with the renal LBF, as simultaneously determined by the H2 gas clearance technique. The RBF averaged 4.6 ml/min per g as recorded electromagnetically. During about 20 mmHg reduction of renal arterial pressure the tumor LBF was maintained relative to the renal LBF, whether the RBF was autoregulated or not. Provided neoplastic vessels account for most of the vascular resistance to tumor blood flow, they must therefore possess autoregulatory ability. The tumor LBF was maintained when the RBF was maximally increased by continuous renal arterial infusion of acetylcholine. This may suggest that a neoplastic vessel vasodilatory response to acetylcholine prevented reduction of the tumor flow.

Acetylcholine↗
PubMedDate not supplied

Lifestyle and cancer: the relative effects of a workplace health promotion program across gender and social class.

A self-administered cross-sectional survey was used to assess the relative impact of a health promotion program on blue- and white-collar workers of both sexes. The program operated in five different types of organizations and consisted of exercise, nutrition, smoking, stress, breast and testicular self-examination. Significant positive improvements occurred on at least five health behaviors for female workers reporting and four behaviors for male workers, with the greatest gains among blue-collar women. Several study limitations are noted suggesting a cautious interpretation of the results.

Adult↗