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Biomedical subjects

A Hope

Publications and source records attributed to A Hope.

18 recordsLinked to original sources
PubMed1992

Respiratory effects of warm and dry air at increased ambient pressure.

We have measured in 7 divers forced vital capacity (FVC), forced expired volume in 1 s (FEV1), and forced midexpiratory flow rate (FEF25-75%) before and after exposure to dry or humid breathing gas of 35.3 degrees-36.8 degrees C (air) when diving to pressures of 117-600 kPa. The response was compared with the subjects' reactivity to pharmacologic bronchoprovocation with methacholine. Baseline FEV1 and FEF25-75% decreased in accordance with increasing gas density. Relative to baseline, there was a significant reduction after the dives in FEV1 of 4.0 +/- 6.1% (P less than 0.05) and in FEF25-75% of 8.6 +/- 9.7% (P less than 0.01) with exposure to dry breathing gas. By analysis of variance the reduction in the lung function variables below baseline were related to the breathing gas characteristic (dry/humid) (P less than 0.01), bronchial hyperreactivity (P less than 0.02), and ambient pressure (P less than 0.02) independently of each other. There was no significant change in FVC after the exposures. Humid breathing gas was considered more comfortable than dry breathing gas, and the upper comfort limit for breathing gas temperature was higher with humid breathing gas. Convective respiratory heat loss was negligible in these experiments, indicating that dry gas itself had a significant bronchoconstrictive effect. Bronchial hyperreactivity may cause increased risk of development of bronchial obstruction and air trapping during diving.

Adult↗
PubMed1991

Symptomatic intraventricular xanthogranulomata. A report of 2 cases.

Intraventricular xanthogranulomata may occasionally be seen as incidental findings at post-mortem. It is however, exceptionally rare for them to become symptomatic, but if they do, it is usually attributable to obstruction of the CSF pathways. Two further symptomatic cases are presented and the literature is reviewed. Treatment is surgical excision, but stereotactic biopsy should be avoided due to the often impenetrable nature of the capsule.

Adult↗
PubMed1989

Lipomatous meningioma--an uncommon tumor with distinct radiographic findings.

A case of lipomatous (lipoblastic) meningioma is described. Atypical radiographic features of low density on computed tomography scanning and high intensity on T1-weighted magnetic resonance imaging corresponded to the presence of adipose tissue within the tumor. A review of the literature indicates few similar reported cases.

Adipose Tissue↗
PubMed1989

Dural punctures.

Explore the source record for details and available documents.

Dura Mater↗
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↗