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Biomedical subjects

J D Foster

Publications and source records attributed to J D Foster.

83 records · Page 5Linked to original sources
PubMed1981

Myogenesis in adult mammalian skeletal muscle in vitro.

An injury to adult mammalian skeletal muscle is followed by regeneration, which involves a process believed to be similar to the differentiation of muscle fibres in the embryo. The origin of these differentiating myogenic cells is conjectural. The aim of the present study was to examine the source of myogenic cells and the process of myogenesis in adult skeletal muscle. Mononucleated cells were released from adult rat leg muscle mince after incubation with 0.1% pronase for 50-60 minutes at 37 degrees C. The ultrastructural studies revealed that the freshly dissociated mononucleated cells consisted of at least two populations of cells: myogenic satellite cells and non-myogenic fibroblastic cells. These cells were plated in growth media at various densities in cell culture dishes and incubated for 3 weeks in a balanced air atmosphere at 37 degrees C. The culture was routinely examined with a phase contrasted microscope for evidence of myogenic activities of the plated cells. At selected time intervals, the cell cultures were processed for autoradiography and scanning and transmission electron microscopy (SEM and TEM). Attachment of cells to the dish began soon after plating, with flattening of some non-muscle cells. The round- to spindle-shaped cells, indicative of myoblasts, began to appear within 24 hours. DNA synthesis and cell proliferation were observed in myogenic and non-myogenic cells within 24 hours of culture. SEM revealed that at 72 hours some myoblasts aligned and fused with one another, forming myotubes. Quantitation of autoradiographs indicated that the maximum number of labelled myotubes were present in the 3 days old culture, and thereafter, the labelled myotubes decreased in number and were absent in the 7 days old culture. Within 5-7 days the myotubes became larger and showed contractility. TEM of 6 to 21 day culture revealed that the myotubes contained well differentiated myofibrils, T-tubules and sarcoplasmic reticulum. It was evident from our studies that the mononucleated cells, having satellite cell morphology, were capable of differentiating into fully formed muscle fibres. This study lends support to the satellite cell hypothesis for regeneration of the skeletal muscle.

Animals↗
PubMed1980

The platelet estimate: is it being ignored?

A study was undertaken to determine whether the platelet estimate included in the routine CBC is being utilized as a guide to ordering quantitative platelet counts. Requisition slips and results were reviewed for a one-month period. The data showed that platelet estimates were not being used properly. In fact, much of the time the platelet count was being ordered with the CBC. The smear estimate and quantitative count agreed in 96% of specimens. The platelet count is a costly procedure and should be reserved for those occasions when the platelet estimate is abnormal.

Blood Cell Count↗
PubMedDate not supplied

Influence of documented lead poisoning on environmental modification programs in Newark, New Jersey.

Data from the Newark, New Jersey Childhood Lead Poisoning Program suggest that the major consequence of the program has been early intervention rather than the amelioration of environmental contamination. During 1975 to 1976, the authors investigated housing for 253 black and Hispanic children with blood levels over 60 microgram/100 ml. Of these, 115 had moved or had given incorrect addresses and were lost to follow-up, 22 were in the same homes but did not make themselves available and in 16 instances, the houses were boarded up or had been destroyed by fire. Of the remaining 100 children, 31% suffered from symptoms potentially related to lead poisoning and 57% of the children were still living in the same dwelling in which the child was affected. Only one-fourth of the houses had been properly abated, i. e., the problem of environmental lead had been corrected, and one-fourth of the houses were not investigated at all by health authorities. These data support the concern that lead poisoning will not be effectively combated until the environmental issue is fully addressed.

Child↗
PubMedDate not supplied

Retinopathy in mice with experimental scrapie.

Scrapie is a naturally occurring neurological disease of adult sheep and goats with an incubation period of several years. Some strains of the causal agent can infect laboratory mice in which the incubation period, as well as the severity and distribution of vacuolar degeneration in the brain, varies according to the strain of the agent and the genotype of the mouse. Retinopathy, involving the partial or complete loss of the photoreceptor layer, was observed in a number of murine scrapie models but was absent in others. The severity of retinopathy depended on both the strain of scrapie and the genotype of mouse used. Some scrapie strains (22C, 87A and 87V) produced minimal or no retinal pathology, others (ME7, 22A and 22L) produced changes in the retinae of only certain mouse genotypes, while the strains 79A and 139A produced degeneration of the photoreceptor layer in every mouse genotype investigated. The severity of retinopathy in the various models did not correlate with the overall intensity of vacuolar degeneration in the brain, with the severity of vacuolation in the centres in the brain controlling pupillary constriction, or with the incubation period.

Animals↗
PubMedDate not supplied

The correlation of electroretinographic and histopathological findings in the eyes of mice infected with the 79A strain of scrapie.

Retinal degeneration was produced using the 79A strain of scrapie injected intracerebrally into mice of the MM inbred strain, and studied by electroretinography and light and electron microscopy during the preclinical and clinical phases of the disease. The changes in the electroretinogram (ERG), detectable in some mice at 118 days postinjection (d.p.i.), appeared to coincide with the earliest morphological evidence of photoreceptor damage. In the early stages there was a progressive reduction of b-wave amplitude without marked loss of retinal sensitivity or significant change in a- and b-wave peak implicit times. Extinction of the ERG, observed in half the mice examined at 144 d.p.i., approximated to a stage of the retinopathy in which the outer nuclear layer was reduced to about four rows of nuclei. Early morphological changes suggested that the primary lesion involved the integrity of the photoreceptor as a whole, the electrophysiological findings reflecting a primary loss of light sensitive tissue rather than impairment of the transduction mechanism or neurotransmission.

Animals↗
PubMedDate not supplied

Inhibition of glucose-6-phosphate phosphohydrolase by 3-mercaptopicolinate and two analogs is metabolically directive.

3-Mercaptopicolinae (3-MP) blocks gluconeogenesis from lactate, pyruvate, alanine, and other substrates through its inhibition of phosphoenolpyruvate carboxykinase. Nevertheless, we observed increased glycogenesis, net glucose uptake, and glucose-6-P levels in livers perfused with glucose in the presence of 3-MP. In perfusions with 20 mM dihydroxyacetone, increased glycogenesis and decreased glucose production were observed with 3-MP. These metabolic effects suggested additional site(s) of action of 3-MP. Further studies showed that 3-MP inhibits glucose-6-P phosphohydrolase activity of intact liver microsomes. Several compounds with structural similarities to 3-MP (2-mercaptonicotinic acid, picolinic acid, cysteine, reduced glutathione, nicotinic acid, quinolinic acid, tryptophan, and pyridine) were tested for their effect on glucose-6-P phosphohydrolase activity. Two of these compounds, 2-mercaptonicotinic acid and picolinic acid, were found to inhibit. In perfusions including 7.5 mM fructose, the addition of 3-MP, 2-mercaptonicotinic acid, or picolinic acid increased glycogenesis, decreased glucose production, and increased hepatic glucose-6-P concentrations. These observations indicate that the inhibition of glucose-6-P phosphohydrolase may play a role in enhanced glycogenesis from glucose, dihydroxyacetone, and fructose in isolated livers from 48-h fasted rats perfused with 3-MP or certain sulfhydryl-containing and sulfhydryl-devoid analogs.

Animals↗