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Biomedical subjects

M Marsh

Publications and source records attributed to M Marsh.

At least 109 records · Page 6Linked to original sources
PubMed1988

Effects of physical exercise for elderly patients with physical impairments.

Exercise is known to preserve many physiological responses in the healthy elderly, yet those with physical impairments are often discouraged from exercising. The authors studied the effects of a closely supervised exercise program designed specifically for elders with health problems and functional limitations. Tests, selected for their relevance to clinical patient management, included the Self Evaluation of Life Function questionnaire, treadmill performance, and tests of autonomic nervous system and neuromotor functions. Ambulatory volunteers, aged 64 to 83 years, with noncardiac health problems, were randomly assigned to a control group (CG; n = 17) or a 16-week exercise group (EG; 3 hr/wk, n = 18). Nine of the control and 13 of the exercise subjects completed the study. All EG dropouts were due to illness. EG attendance averaged 87%, and subjects trained at a heart rate (HR) of 103 +/- 5 beats/min (SD) (98% of prescription HR). Though EG test responses showed a tendency to improve, none reached statistical significance. This result was affected by the small number completing the study and the variability inherent in such a sample. Though these impaired elderly subjects enthusiastically and safely participated with high attendance and at an exercise intensity adequate to expect benefit, measurable training effects were not demonstrated.

Aged↗
PubMed1987

Rapid analytical and preparative isolation of functional endosomes by free flow electrophoresis.

Endosomes are prelysosomal organelles that serve as an intracellular site for the sorting, distribution, and processing of receptors, ligands, fluid phase components, and membrane proteins internalized by endocytosis. Whereas the overall functions of endosomes are increasingly understood, little is known about endosome structure, composition, or biogenesis. In this paper, we describe a rapid procedure that permits analytical and preparative isolation of endosomes from a variety of tissue culture cells. The procedure relies on a combination of density gradient centrifugation and free flow electrophoresis. It yields a fraction of highly purified, functionally intact organelles. As markers for endosomes in Chinese hamster ovary cells, we used endocytosed horseradish peroxidase, FITC-conjugated dextran, and [35S]methionine-labeled Semliki Forest virus. Total postnuclear supernatants, crude microsomal pellets, or partially purified Golgi fractions were subjected to free flow electrophoresis. Endosomes and lysosomes migrated together as a single anodally deflected peak separated from most other organelles (plasma membrane, mitochondria, endoplasmic reticulum, and Golgi). The endosomes and lysosomes were then resolved by centrifugation in Percoll density gradients. Endosomes prepared in this way were enriched up to 70-fold relative to the initial homogenate and were still capable of ATP-dependent acidification. By electron microscopy, the isolated organelles were found to consist of electron lucent vacuoles and tubules, many of which could be shown to contain an endocytic tracer (e.g., horseradish peroxidase). SDS PAGE analysis of integral and peripheral membrane proteins (separated from each other by condensation in Triton X-114) revealed a unique and restricted subset of proteins when compared with lysosomes, the unshifted free flow electrophoresis peak, and total cell protein. Altogether, the purification procedure takes 5-6 h and yields amounts of endosomes (150-200 micrograms protein) sufficient for biochemical, immunological, and functional analysis.

Animals↗
PubMed1987

Effects of tolazamide and exogenous insulin on pattern of postprandial carbohydrate metabolism in patients with non-insulin-dependent diabetes mellitus. Results of randomized crossover trial.

To determine whether therapy with exogenous insulin or sulfonylureas results in a postprandial pattern of carbohydrate metabolism in patients with non-insulin-dependent diabetes mellitus (NIDDM) that resembles that in nondiabetic individuals, we employed a dual-isotope technique combined with forearm catheterization to examine meal disposition in NIDDM patients, before and after 3 mo of therapy with tolazamide and after 3 mo of therapy with exogenous insulin, with a randomized crossover design. Results were compared with those observed in nondiabetic subjects. Although both forms of therapy improved chronic glycemic control (glycosylated hemoglobin concentration went from 9.6 +/- 0.7 to 7.6 +/- 0.5 and 7.1 +/- 0.2%, respectively, P less than .01), exogenous insulin resulted in a lower postprandial glycemic response than tolazamide (P less than .001). Both agents comparably increased (P less than .01) fasting and integrated postprandial insulin concentrations. However, the initial rate of postprandial increase was greater with exogenous insulin (P less than .05). Tolazamide (P less than .05) but not exogenous insulin increased postprandial C-peptide concentrations. However, tolazamide did not improve the deficient early insulin release. Both agents (P less than .05) lowered postabsorptive hepatic glucose release (from 2.8 +/- 0.3 to 2.3 +/- 0.2 mg . kg-1 . min-1), but not to normal rates (1.8 +/- 0.1 mg . kg-1 . min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1987

Effects of experimental diabetes, uremia, and malnutrition on wound healing.

The strength of linear wounds was studied in normal and diabetic rats in the first 8 wk after wounding. The strength of wounds from diabetic animals was found to be reduced compared with normal controls but could be improved by insulin treatment, especially when excellent metabolic control was achieved. There appeared to be both quantitative and qualitative defects in the formation of wound tissues in diabetic animals, because wound strength was not normalized when the thinner skin of diabetic animals was taken into consideration. This was different from the findings in rats with renal failure or malnutrition: in these two conditions, wound strength appeared reduced but was normalized when adjusted for skin thickness. Increased activity of aldose reductase did not appear to be an important factor in the impairment of wound healing in diabetes, because wound strength was not corrected by treatment with sorbinil, an aldose reductase inhibitor. The precise mechanism of abnormal wound strength in diabetes remains to be studied further, but careful control of diabetes, maintenance of nutrition, and treatment of systemic illness are important factors in the promotion of wound healing.

Animals↗
PubMed1986

Kinetics of endosome acidification detected by mutant and wild-type Semliki Forest virus.

The fusogenic properties of Semliki Forest virus (SFV) and its mutants were used to follow the kinetics of acidification during the endocytic uptake of virus by BHK-21 cells. It has previously been shown that the low pH of endocytic vacuoles triggers a conformational change in the SFV spike glycoprotein, activating membrane fusion and initiating virus infection. This conformational alteration was here shown to occur in endosomes and to follow the same time course as the intracellular fusion reaction, demonstrating that fusion occurs rapidly after virus exposure to endosome acidity. The kinetics of endosome acidification were monitored using wild type (wt) SFV and fus-1, an SFV mutant with a lower fusion pH threshold. The results presented here demonstrated that wt and mutant virus were internalized with a t1/2 of 10 min, and that endosomes were acidified to the wt threshold of pH 6.2 with a t1/2 of 15 min. In contrast, endosome pH reached the fus-1 threshold of 5.3 with a much longer t1/2 of 45 min. The subsequent degradation of SFV in lysosomes had a t1/2 of 90 min. It was found that after the initial uptake of virus from the plasma membrane, its transit through the endocytic pathway, exposure to endosome acidity and eventual delivery to lysosomes were markedly asynchronous.

Animals↗
PubMed1986

Transport of macrophage Fc receptors and Fc receptor-bound ligands to lysosomes.

Mouse macrophage Fc receptors specific for IgG1/IgG2b mediate the binding and pinocytic uptake of soluble IgG-containing antibody-antigen complexes. Internalization of these multivalent IgG complexes is accompanied not only by the intracellular degradation of the ligand, but also by a net decrease in the number of plasma membrane Fc receptors and an accelerated rate of receptor turnover. In contrast, internalized receptors bound to a monovalent ligand, the high affinity Fab fragment of the antireceptor mAb 2.4G2, escape degradation by rapidly recycling to the cell surface. In this paper, we have characterized the intracellular pathway involved in the endocytosis and transport of Fc receptors in the J774 macrophage cell line. The results show that the uptake of multivalent ligands follows the normal pathway of receptor-mediated endocytosis: internalization in clathrin-coated pits and coated vesicles, delivery to endosomes, and finally to acid hydrolase-rich lysosomes. Immunoprecipitation of radiolabeled receptor from Percoll density gradients showed that endocytosis of the IgG complexes also results in the concomitant transport of the receptor to lysosomes. Although uptake of the monovalent Fab fragment had no detectable effect on intracellular receptor distribution, preparations of 2.4G2 Fab rendered multivalent by adsorption to colloidal gold were as effective as the IgG complexes at causing lysosomal accumulation of internalized receptors. Thus, it is likely that the down-regulation and degradation of Fc receptors which occurs during the endocytosis of antibody-antigen complexes is due to the transport of internalized receptors to lysosomes. Moreover, the ability of certain Fc receptor-bound ligands to interfere with receptor recycling and trigger lysosomal transport seems to depend on ligand valency rather than on the presence or absence of Fc domains on intact IgG molecules.

Animals↗
PubMed1986

Three-dimensional structure of endosomes in BHK-21 cells.

The organization of the endosome compartment in BHK-21 cells was studied by using horseradish peroxidase as a fluid-phase marker and Semliki Forest virus as an adsorptive marker. Stereo pairs of semithin sections (0.2-0.5 micron) and computer-aided reconstruction and tracing of serial thin sections (CARTOS) were used to obtain three-dimensional images of the labeled compartments. Two types of labeled organelles could be observed: small vesicles and tubules (approximately equal to 50 nm in diameter) and large complex structures consisting of central vesicular elements (with diameters up to 0.5 micron) and associated systems of radiating tubules. The large endosomes were located either in the peripheral cytoplasm or in the perinuclear region, and, importantly, they existed as independent organelles and not as an interconnected reticulum. Each endosomal vacuole had two to seven tubules oriented in random directions from the central vesicle. The tubules were 60-100 nm in diameter and up to 4 micron in length. Morphometric estimates indicated that 60-70% of the endosomal membrane was in the tubules, in contrast to 30-40% of the volume. No structural continuity between endosomes and Golgi cisternae was observed, although elements of the two systems were frequently found in close proximity.

Animals↗
PubMed1986

The prevention and reversibility of tissue non-enzymatic glycosylation in diabetes.

The time course of non-enzymatic glycosylation (NEG) of liver, kidney, tail collagen, and haemoglobin was studied in diabetic rats. Increased NEG of liver, kidney, and collagen was detectable within 4 weeks of diabetes. The abnormal NEG of liver, kidney, and haemoglobin present after 4 weeks of untreated diabetes could be normalized by 4-8 weeks of intensive insulin therapy given by continuous subcutaneous infusion. However, the same treatment was ineffective in reversing the abnormal NEG and thermal stability of tail collagen. The differences in the development and reversibility of these tissue changes may be due to different tissue turnover rates. Insulin therapy, given from the onset of diabetes, was effective in preventing the development of collagen abnormalities. This suggests that early and vigorous treatment of diabetes is necessary to prevent collagen changes which are potentially irreversible.

Animals↗
PubMed1986

Abnormalities of granulation tissue and collagen formation in experimental diabetes, uraemia and malnutrition.

The formation of granulation tissue and collagen was studied in rats made diabetic with streptozotocin. Granulation tissue was harvested from the inside of steelmesh cylinders implanted in the back of diabetic and control animals. Four weeks after implantation there was a reduction in the quantity of granulation tissue and its collagen content in diabetic animals compared to controls. Rats with renal failure or malnutrition but no diabetes also formed less granulation tissue but in these animals the content of collagen in the granulation tissue was normal. These results suggest that the decrease of collagen, but not granulation tissue, in diabetes is a relatively specific phenomenon which was not due to the toxic effects of streptozotocin as the changes were prevented by insulin treatment. The hydroxyproline/proline ratio of diabetic collagen was found to be normal, excluding defective hydroxylation of proline as an important factor in the reduction of collagen in diabetes. Treatment with an aldose reductase inhibitor did not prevent the abnormalities of granulation tissue and collagen in diabetes, making it unlikely that increased activity of this enzyme played an important pathogenetic role. The observed reduction of granulation tissue mass and collagen content in diabetes may be important factors in the impairment of wound healing in diabetes.

Aldehyde Reductase↗
PubMed1985

Glycoproteins of the lysosomal membrane.

Three glycoprotein antigens (120, 100, and 80 kD) were detected by mono- and/or polyclonal antibodies generated by immunization with highly purified rat liver lysosomal membranes. All of the antigens were judged to be integral membrane proteins based on the binding of Triton X-114. By immunofluorescence on normal rat kidney cells, a mouse monoclonal antibody to the 120-kD antigen co-stained with a polyclonal rabbit antibody that detected the 100- and 80-kD antigens as well as with antibodies to acid phosphatase, indicating that these antigens are preferentially localized in lysosomes. Few 120-kD-positive structures were found to be negative for acid phosphatase, suggesting that the antigen was not concentrated in organelles such as endosomes, which lack acid phosphatase. Immunoperoxidase cytochemistry also showed little reactivity in Golgi cisternae, coated vesicles, or on the plasma membrane. Digestion with endo-beta-N-acetylglucosaminidase H (Endo H) and endo-beta-N-acetylglucosaminidase F (Endo F) demonstrated that each of the antigens contained multiple N-linked oligosaccharide chains, most of which were of the complex (Endo H-resistant) type. The 120-kD protein was very heavily glycosylated, having at least 18 N-linked chains. It was also rich in sialic acid, since neuraminidase digestion increased the pI of the 120-kD protein from less than 4 to greater than 8. Taken together, these results strongly suggest that the glycoprotein components of the lysosomal membrane are synthesized in the rough endoplasmic reticulum and terminally glycosylated in the Golgi before delivery to lysosomes. We have provisionally designated these antigens lysosomal membrane glycoproteins lgp120, lgp100, lgp80.

Animals↗
PubMed1984

Biliary proteins. Unique inhibitors of cholesterol crystal nucleation in human gallbladder bile.

The onset time for cholesterol crystal nucleation of supersaturated normal human gallbladder biles is consistently prolonged when compared with biles from patients with cholesterol gallstone disease. Investigation of the factor(s) responsible for the suspended supersaturation (metastability) of normal human biles revealed that model bile solutions of cholesterol saturation index (CSI) and molar lipid composition identical to individual gallbladder bile specimens had much shorter crystal nucleation times, i.e., exhibited decreased metastability. Unsaturated normal biles, after supplementation with lecithin, cholesterol, and sodium taurocholate to a 'standard' supersaturated lipid composition, also demonstrated nucleation times three- to 15-fold longer than the comparable standard model bile. Total lipid extracts of normal biles, however, when similarly supplemented, did not differ in nucleation time from the control model solution. Gallbladder biles were fractionated by gel chromatography and the eluted fractions were pooled into two fractions. The fractions eluting in about the first 25% of the included volume when mixed with the supersaturated standard model bile induced a modest increase in nucleation time of approximately 1.5 times the control value. The fractions eluting in the second 25% of the included volume and which contained all of the bile lipids, were concentrated and supplemented with lipids to the standard composition. The nucleation times of these supplements were 3-10 times longer than the control nucleation times. Delipidated bile protein mixtures, purified by discontinuous sucrose gradient centrifugation, were recombined with purified lipids at the standard composition used previously. The nucleation times of these mixtures were significantly prolonged to the same extent as those associated with the second chromatographic fraction. These observations demonstrate that the delayed onset (inhibition) of cholesterol crystal nucleation observed in normal human gallbladder bile is produced by a factor(s) present in the biliary protein fraction.

Anticholesteremic Agents↗
PubMed1984

A day rehabilitation stroke program.

An innovative approach to the rehabilitation of the stroke patient was initiated at Riverside Methodist Hospital to accommodate an increasing number of patients. Patients spend six hours a day several days a week attending a day rehabilitation program at which all necessary therapies are provided. A year-end analysis of the program substantiates the original hypothesis that stroke patients would show significant improvement with treatment in a specialized day rehabilitation facility.

Adolescent↗
PubMed1983

Penetration of Semliki Forest virus from acidic prelysosomal vacuoles.

To identify and characterize the intracellular site from which the penetration of Semliki Forest virus (SFV) to the cytosolic compartment of the host cell occurs, we determined the time course and temperature dependence of nucleocapsid uncoating and infection in BHK-21 cells. At 37 degrees C the genome release to the cytosol was detected within 5-7 min after virus endocytosis, whereas delivery of the virus particles to secondary lysosomes occurred within 15-20 min. At temperatures of 15 degrees -20 degrees C virus particles were internalized by endocytosis, but they were not delivered to the secondary lysosomes. Nevertheless, at 20 degrees C nucleocapsid uncoating and infection occurred, indicating that secondary lysosomes are not required for SFV penetration. We conclude that the penetration reaction occurs in prelysosomal endocytic vacuoles (endosomes). As SFV penetration by membrane fusion requires a pH less than 6 and the presence of cholesterol in the target membrane, the data indicate that endosomes are acidic and contain cholesterol.

Animals↗