Search PubMed⌕ Search

Biomedical subjects

J L Matthews

Publications and source records attributed to J L Matthews.

At least 73 records · Page 4Linked to original sources
PubMed1981

Calcitonin and phosphate.

This report summarizes the relationship of calcitonin to phosphate. The hypocalcemic action of calcitonin is dependent upon phosphate, while the hypophosphatemic action is independent of calcium. Calcitonin moves phosphate into bone cells and bone fluid in contrast to reducing the movement of calcium from bone to blood. Calcitonin acts rapidly and at low doses on the osteocytes and lining cells at bone surfaces. Morphological changes can be identified within 7 min. This action causes the accumulation of an electron-dense material both in bone lining cells and their microenvironment. It is postulated that both the hypocalcemic action of calcitonin and its ability to cause an accumulation of material at bone surfaces may result from the movement of phosphate into these areas. The biochemical action which could produce the phosphate movement is unknown. The possibility is suggested that calcitonin increases phosphate transport into bone cells.

Adult↗
PubMed1981

Influence of parathyroid hormone on bone cell ultrastructure.

A study in rats demonstrated that morphologic changes in the bone osteocytes and osteoblasts are produced following parathyroid hormone (PTH) injection into thyroparathyroidectomized animals. It further showed that similar changes occur in normal rats as the result of of extended fasting. Plasma calcium concentrations were determined at sacrifice to ascertain that these changes in bone occurred at times when plasma calcium is rising as the result of parathyroid hormone stimulation. Tibias from these animals were removed and prepared for morphologic observation using both transmission (TEM) and scanning (SEM) electron microscopy. Specific structural features characterized bone cells stimulated by exogenous or endogenous PTH. The most significant morphologic alterations involved surface microvilli and blebs as determined by SEM. TEM studies showed alterations in the cisternae of the rough endoplasmic reticulum (RER). Additionally, cell shape varied markedly from the control cuboidal morphology. These morphologic changes occurred during peak periods of plasma calcium change and returned to control morphology as plasma calcium levels normalized. Use of an extracellular electron-dense tracer (lanthanum) confirmed the patency of the intercellular channels and the presence of a fluid space between the bone cell plasma membranes and the mineralized surface. PTH stimulation modified cell activity such that the tracer material entered the cell more readily, possibly by inducing increased pinocytosis (endocytosis). This study supports the concept that the osteocytes and lining cells on the surface of bone play a role in maintenance of plasma calcium concentrations.

Animals↗
PubMed1980

Immunopathology of periodontal disease. I. Immunologic profiles in periodontitis and juvenile periodontitis.

Eleven patients with periodontitis, ten patients with juvenile periodontitis and ten control subjects were studied to compare systemic and local immunologic responses and various other blood parameters. A more intensified immunologic response was seen in juvenile periodontitis as compared to periodontitis or controls as evidenced by: (1) greater number of plasma cells and lymphocytes in biopsy specimens of involved gingiva stained by Harris hematoxylin and eosin; (2) significant decrease in serum C4 levels and slightly elevated serum IgG levels as determined by radial immunodiffusion; (3) marked increase of positive fluorescing cells in biopsy specimens stained with antihuman immunoglobulin conjugate and an increase in complement deposition in the same tissues as determined by immunofluorescence. No significant differences among the two groups of patients and control subjects were observed with respect to complete blood counts, coagulation studies, or blood glucose levels. These findings suggest that the immunologic responses in periodontitis and juvenile periodontitis are qualitatively similar, but that the intensity of the response is greater in juvenile periodontitis.

Adolescent↗
PubMed1978

Calcium localization in normal rachitic, and D3-treated chicken epiphyseal chondrocytes utilizing potassium pyroantimonate-osmium tetroxide.

Normal, rachitic, and vitamin D3-replete chicken growth plates were studied utilizing the potassium pyroantimonate-osmium tetroxide procedure. A marked membrane and mitochondrial calcium was revealed in all specimens in the maturing and early hypertrophic zones which disappeared as heavy matrix mineralization began. The most significant difference shown in the specimens was in the marked intracellular lipid content of chondrocytes in all zones of the rachitic and D3-replete growth plates. There was negligible lipid present in normal specimens. It is suggested that as most of the mechanisms postulated as necessary for calcification are present in rachitic chicks, perhaps the increased intracellular lipid pool results from the formation of abnormal lipids for insertion into the plasma membrane and thus prevents normal calcium transport. Chains of intracellular vesicles were also visualized in maturing and hypertrophic chondrocytes. These were more often seen in rachitic growth plates and in increased numbers in the early D3-replete specimens. The etiology is unknown at the present time.

Animals↗
PubMed1977

The effect of cytochalasin B on the endosteal lining cells of mammalian bone. A scanning electron microscopic study.

The lining osteoblasts of the rat tibial endosteum were treated for various times (between 1 and 60 min) and increasing doses (3.87-38.7 microgram/ml) with the macrolide fungal metabolite cytochalasin B (CB). Dimethylsulfoxide (DMSO) served as the vehicle for CB and was administered to control tissues. An in vitro incubation system and scanning electron microscopy (SEM) were used to evaluate the effects of CB. The drug initiated cell rounding (contraction), nuclear protrusion, bleb formation, and the subsequent clustering of blebs and microvilli into aggregates. All CB-induced aberrations of the surface structure were readily reversible when tissues were washed with CB-free media. DMSO had no significant effect on cell surface morphology. The reversible structural changes brought about by CB are explained in terms of alterations of the subplasmalemmal cortical microfilament system of osteoblasts. The potential use of CB in evaluating the bone cell cytoskeleton and its relationship to the physiology of the cellular functional membrane (endosteum) of bone is discussed.

Animals↗