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Biomedical subjects

S E Anderson

Publications and source records attributed to S E Anderson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Muscle protein synthesis in response to testosterone administration in wether lambs.

A method has been developed based on stable isotopes and biopsy procedures which allows the large-dose procedure for measurement of protein synthesis to be applied in serial studies to farm species. Measurements of total nitrogen retention and protein synthesis in m. longissimus dorsi and m. vastus lateralis were made in five wether lambs (40-44 kg) infused intravenously, successively, with vehicle (10 d); testosterone (15 d; 9 mg/d); vehicle (15 d). N retention was improved by testosterone infusion (+2.9 g N/d; a 96% improvement total over control periods). Muscle protein synthesis was not significantly altered by exogenous hormone administration, nor were RNA:protein, RNA:DNA or protein:DNA. The implication of the developed procedure for dynamic studies in accessible tissues of large animals is discussed.

Animals↗
PubMed1990

Na-H exchange in myocardium: effects of hypoxia and acidification on Na and Ca.

Historically, increase in cell Na content during ischemic and hypoxic episodes were thought to result from impaired ATP production causing decreased Na(+)-K(+)-ATPase activity. Here we report the results of testing the alternate hypothesis that hypoxia-induced Na uptake is 1) the result of increased entry, as opposed to decreased extrusion 2) via Na-H exchange operating in a pH regulatory capacity and that cell Ca accumulation occurs via Na-Ca exchange secondary to collapse of the Na gradient. We used 23Na-, 19F-, and 31P-nuclear magnetic resonance (NMR) to measure intracellular Na content (Nai), Ca concentration [( Ca]i), pH (pHi), and high-energy phosphates in Langendorff-perfused rabbit hearts. When the Na(+)-K(+)-ATPase was inhibited by ouabain and/or K-free perfusion, hearts subjected to hypoxia gained Na at a rate greater than 10 times that of normoxic controls [during the first 12.5 min Nai increased from 7.9 +/- 5.8 to 34.9 +/- 11.0 (SD) meq/kg dry wt compared with 11.1 +/- 16.3 to 13.6 +/- 9.0 meq/kg dry wt, respectively]. When normoxic hearts were acidified using a 20 mM NH4Cl prepulse technique, pHi rapidly fell from 7.27 +/- 0.24 to 6.63 +/- 0.12 but returned to 7.07 +/- 0.10 within 20 min, while Na uptake was similar in rate and magnitude to that observed during hypoxia (24.5 +/- 13.4 to 132.1 +/- 17.7 meq/kg dry wt). During hypoxia and after NH4Cl washout, increases in [Ca]i were similar in time course to those observed for Na.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1989

Evidence that the production of acetate in rat hepatocytes is a predominantly cytoplasmic process.

By using [1-14C]butyrate, the fluxes of butyrate to acetate and fatty acids were measured in rat hepatocytes. Both fluxes were inhibited to a similar extent by (-)-hydroxycitrate, with no significant effect on butyrate uptake. These results indicate that acetate formation takes place in the cytoplasm, presumably via ATP-stimulated acetyl-CoA hydrolase. Since acetate formation occurred despite a net uptake of acetate, the results are also consistent with the operation of a substrate cycle between acetate and acetyl-CoA, recently proposed by other workers, and suggest that this cycle is cytoplasmic.

Acetates↗
PubMed1989

New NMR probe designs for neonatal, immature and adult heart research. With a brief review.

We present three new radiofrequency probes for nuclear magnetic resonance (NMR) research with perfused rabbit hearts at different maturational ages. The objective of the double-tunable, cylindrical-window probe design was to achieve a highly homogeneous magnetic field throughout the 16, 25 or 30 mm diameter usable volume for consistency of comparison of measurements obtained from neonate, immature and adult rabbit hearts, respectively. This probe design tunes to 23-Sodium for rapid shimming and then, to 31-Phosphorus for measurements of pH and high energy phosphate metabolites. All three probes yielded excellent signal-to-noise ratios and radiofrequency operating characteristics. We introduce these new probes here in the context of a brief review of other state-of-the-art designs for in vitro and in vivo cardiovascular research.

Animals↗
PubMed1988

Na/H exchange-dependent cell volume and pH regulation and disturbances.

1. The role of Na/H exchange in cell volume and pH regulation is discussed. In addition the roles of Cl/HCO3 exchange and system buffers are evaluated as they relate to Na/H exchange-dependent changes in cell salt and water content and intracellular pH. 2. Data obtained from studies of Amphiuma red blood cells showed that in addition to previously reported Na/H exchange dependent volume regulation the pathway is also involved in regulating cell pH. 3. These data showed that in contrast to volume activated Na/H exchange, when the pathway is pH activated it does not deactivate as a function of cell volume. 4. Given what appeared to be mutually exclusive volume and pH regulatory functions of the Na/H exchange, we hypothesized that the pathway might play a role in hypoxic cell swelling (cytotoxic edema). 5. In studies performed on perfused rabbit hearts employing 23Na NMR we were able to observe that relative to normoxic controls hypoxic hearts exhibited a five-fold increase in intracellular Na content when the Na-K pump was inhibited by ouabain and/or K-free perfusate. 6. These studies lead us to conclude that hypoxia-induced Na uptake is the result of an increased inward Na leak as opposed to decreased Na pumping. 7. Based upon studies with a variety of inhibitors of dissipative Na transport, we conclude that the increased inward Na leak in hypoxic hearts is via Na/H exchange.

Amiloride↗
PubMed1988

Dynamic NMR measurement of volume regulatory changes in Amphiuma RBC Na+ content.

23Na nuclear magnetic resonance (NMR) and conventional chemical methods were employed to measure Na+ fluxes in Amphiuma red blood cells (RBC) during volume regulation. Paramagnetic shift reagents [dysprosium triethylenetetraminehexaacetic acid (DyTTHA) and dysprosium tripolyphosphate (Dy(TPP)2)] were used to alter extracellular Na+ magnetic resonance. Data are presented describing 23Na resonance dependence on shift reagent, sodium and calcium concentration. We confirmed that the shift reagents neither enter the cells nor alter intracellular Na+, K+, and Cl-concentrations under control conditions when extracellular calcium was maintained greater than 0.5 mM. We also confirmed that the shift reagent complexes chelate calcium [Dy(TPP)2 much more so than DyTTHA] and that their toxic effects could be alleviated by adjusting calcium in the cell's suspension medium to control levels. In parallel experiments, where volume-activated Na+ fluxes ranged from 0.3 to 3 mmol Na+/kg dry cell solid (DCS) x minute in cells containing from 30 to 150 mmol Na+/kg DCS, changes in intracellular sodium measured by 32Na NMR were within 4% of those measured by conventional destructive methods. Finally, we present data that are consistent with the interpretation that 6 mmol Na+/kg DCS plus 16% of intracellular Na+ is NMR invisible.

Animals↗
PubMed1987

Measurement of the rate of substrate cycling between acetate and acetyl-CoA in sheep muscle in vivo. Effects of infusion of acetate.

1. The rate of substrate cycling between acetate and acetyl-CoA in sheep hindlimb muscle was measured from the decrease of [14C]acetate specific radioactivity across the tissue in vivo. 2. The rate of cycling was 0.005-0.015 mumol/min per g and, in two of the three sheep investigated, was approximately doubled as a result of infusing 2 mol acetate/day intravenously. 3. The results indicate that this cycle contributes only approx. 0.5% of the total heat produced by the animal and would probably make only a relatively small contribution to any heat increment of feeding associated with diets producing large amounts of acetate.

Acetates↗
PubMed1987

23Na rotating frame imaging in the perfused rabbit heart using separate transmitter and receiver coils.

One-dimensional spatial localization of sodium absorption in the perfused rabbit heart was obtained using 23Na rotating frame imaging. A Dadok-type coil was used as the receiver and a circular surface coil as the transmitter allowing regularly shaped slices and homogeneous reception sensitivity. The short time of spatial labeling in this technique results in minimal intensity losses due to relaxation processes.

Animals↗
PubMed1987

A microcomputer-based system for processing 31-phosphorus nuclear magnetic resonance spectra from studies of cardiac metabolism in immature hearts.

We designed an interactive microcomputer-based digital data processing system for analysis of 31-phosphorus nuclear magnetic resonance (31P-NMR) spectra from studies of cardiac metabolism in immature and neonatal hearts. This system included a digitizing tablet (Kurta Series Two), a microcomputer (IBM PC XT) and a graphics plotter (Hewlett-Packard 7470A) used in conjunction with a Nicolet 1280 NMR signal processing computer. We obtained 31P spectra from isolated perfused rabbit hearts with a Nicolet NT-200 4.7 Tesla superconducting NMR spectrometer operated in the pulsed Fourier transform mode. The small size of the hearts resulted in increased noise in spectra and demanded comparison of methods used to quantitate changes in inorganic phosphorus, phosphocreatine and ATP during ischemic stress. We performed microcomputer operations and interfacing functions with a software package written in BASIC. This system simplified documentation, data filing and statistical data processing. Our microcomputer system displayed and made hard copies of digitized spectra and results of analyses. Errors in data entry were rectified directly with this program. Consistent data reduction improved the precision of the physiological results and reduced the influence of noise on 31P spectra from neonatal hearts weighing about 0.5 g. The system flexibility extends its application to NMR spectra analysis for other in vivo organ systems, and signal processing in other biological research.

Animals↗
PubMed1987

Tissue-fluid pressure measured in perfused rabbit hearts during osmotic transients.

To resolve discrepancies between models used to calculate myocardial capillary solute permeability we measured tissue-fluid pressure (Pi), perfusion pressure (Pp), and heart weight continuously after a step change in the NaCl or inulin concentration of crystalloid solutions perfusing isolated rabbit hearts. Linear regression analysis of the mean values for near steady-state Pi plotted against Pp showed significantly different (P less than 0.01) slopes of 0.77 and 0.40, respectively, for the inner and outer halves of the left ventricular free wall. Tissue compliance (Tcm) was measured as the fractional change in whole heart weight divided by the concurrent change in Pi. For NaCl and inulin osmotic transients Tcm values were 0.005 +/- 0.001 (SE) and 0.014 +/- 0.004 ml X cmH2O-1 X g tissue-1, respectively. A model for heart weight change based on the Starling hypothesis predicts significantly different tissue compliance (Tcc) values of 0.031 +/- 0.004 and 0.040 +/- 0.005 ml X cmH2O-1 X g tissue-1 for the same transients, respectively. This model shows myocardial capillary permeability for inulin and NaCl are overestimated by 25% if tissue compliance is not included in the analysis. The discrepancy between Tcm and Tcc is discussed.

Animals↗
PubMed1987

Monoclonal antibody purified beta 2-microglobulin: heterogeneity revealed by radioimmunoassay.

A monoclonal antibody, CMRF1, to human beta 2-microglobulin (beta 2m) was used to purify antigen to develop an in-house beta 2m radioimmunoassay. This immunoadsorption purified material was used to prepare a rabbit anti-beta 2m serum and was radiolabelled for the radioimmunoassay. The assay compared favourably with a widely used commercial radioimmunoassay but the immunological potency of the in-house standard was lower than that of the commercial reagent. This potency difference was not accounted for by antigenic denaturation. Subsequent two-dimensional gel electrophoresis revealed a second 12,000 dalton protein with a higher isoelectric point than beta 2m in the immunoadsorption purified material, which was also present, although in lesser amounts, in the commercial product. The different relative content of the additional 12,000 dalton protein appeared to explain the immunological potency difference between the in-house and the commercial standard. These results strengthen suggestions that there may be some heterogeneity or polymorphism in human beta 2m.

Antibodies, Monoclonal↗
PubMed1986

The inheritance of abnormal sialoglycoproteins found in a Gerbich negative individual.

The Gerbich blood group antigens are probably expressed on one or more of the minor erythrocyte (beta, beta 1, or gamma) sialoglycoproteins which are lacking in some rare individuals having the Gerbich negative phenotype. A monoclonal antibody, CMRF-10, which recognises a trypsin-sensitive site on both the beta and beta 1 sialoglycoproteins, was tested for binding to erythrocytes from a Gerbich negative individual, OM. Erythrocytes from OM bound CMRF-10 in similar amounts to normal erythrocytes even though membranes from OM were shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis to lack both the beta and gamma sialoglycoproteins found in normal red blood cells. Instead, abnormal sialoglycoproteins which migrated as two bands with apparent molecular weights within the range 29,500-32,500 daltons were identified and purified using CMRF-10. Subsequent electrophoretic analysis of OM's two children failed to reveal any abnormal sialoglycoproteins. This suggests that in this instance the Gerbich negative phenotype may result from other mechanisms, possibly defective glycosylation, rather than a crossover involving the gene coding for the primary protein structure of the sialoglycoproteins.

Aged↗
PubMed1983

Effects of thermal applications on the abdominal temperature of dogs.

The results of thermal applications to the abdomens of unrestrained, unanesthetized dogs are reported. A silicone rubber envelope through which water circulated at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, or 50 degrees C was applied. Skin surface, subcutaneous, intraperitoneal, intestinal, and colonic temperatures were measured after 90 minutes. Pad applications at 0 degrees, 10 degrees, 20 degrees, and 30 degrees C significantly lowered skin surface and subcutaneous temperatures, while pad applications at 40 degrees and 50 degrees C significantly increased subcutaneous and skin surface temperatures. None of the pad applications had a significant effect on intraperitoneal, intestinal, or colonic temperatures. The findings indicate that a wide range of thermal applications to the abdominal skin of the dog do not alter deep abdominal temperatures.

Abdomen↗
PubMed1980

Histoplasma capsulatum endocarditis.

Endocarditis is a rare manifestation of disseminated Histoplasma capsulatum infection. A 22-year-old man presented with a seven month history of fever, weight loss, and progressive aortic insufficiency. The diagnosis of H. capsulatum was suggested by a diagnostic rise in complement fixation titers and positive echocardiographic findings. The diagnosis was confirmed prior to surgery by positive bone marrow culture. Progressive congestive heart failure necessitated replacement of the aortic valve which subsequently grew H. capsulatum. In this case, a combination of amphotericin B therapy and valve replacement was curative.

Adult↗