PubMed Health⌕ Search

Biomedical subjects

L Bitensky

Publications and source records attributed to L Bitensky.

At least 37 records · Page 2Linked to original sources
PubMed1987

Altered organization of non-collagenous bone matrix in osteoporosis.

In osteoporosis it is postulated that while the amount of bone is diminished, the quality of the bone is unaltered. Recently relatively novel methods of analysis have shown that, at the fracture site of osteoporotic subcapital fractures, there is a marked change in the molecular orientation of components of the non-collagenous bone matrix. These procedures, now applied to iliac crest biopsies, confirm earlier findings of altered orientation of the proteoglycans at the subcapital fracture site but show that very similar changes occur even in the iliac crests from patients with both types of osteoporotic proximal femoral fracture. Thus, whereas the amount of these acidic moieties of the non-collagenous bone matrix was unchanged, the molecular orientation was markedly altered, albeit not to the same extent as that found at the fracture site. These results imply that the quality of the bone, as well as the quantity, may be generally affected in osteoporosis.

Adult↗
PubMed1987

Major components of bone in subcapital and trochanteric fractures. A comparative study.

Quantitative polarised light microscopy was applied to sections of unfixed, undecalcified bone taken at operation from patients with two types of proximal femoral fracture, subcapital and trochanteric. Specimens were also taken from the equivalent sites in otherwise normal subjects at autopsy, and from various other sites of traumatic fractures; these two latter groups acted as controls. Analysis of the 57 specimens disclosed changes in the nature of the bone at the site of subcapital fractures, namely the presence of relatively large crystals of hydroxyapatite and a change in the molecular orientation, but not total content, of the acidic proteoglycans of the bone matrix. Our results have confirmed and extended the findings of others on subcapital fractures, and have also shown very similar changes in the trochanteric fractures. It thus appears that the bony changes in the two types of proximal femoral fracture are not as different as has been suggested.

Adult↗
PubMed1986

Enzymic heterogeneity of normal canine articular cartilage.

Articular cartilage is generally considered to be an homogeneous tissue. It has now been shown that, although different regions of the medial tibial cartilage of the dog have very similar oxidative enzymic activities, each region is heterogeneous with respect to these activities. The conventional histological delineation of this cartilage has been modified, to take into account a narrow band (designated zone 2a), just below the most superficial spindle-shaped cells, that has higher oxidative enzymic activity than any other. Changes in the activity in this zone might be diluted by the lack of change in other zones if measured by conventional biochemical procedures which could not measure the activities of the different zones separately.

Alcohol Oxidoreductases↗
PubMed1985

Altered orientation of glycosaminoglycans and cellular changes in the tibial cartilage in the first two weeks of experimental canine osteoarthritis.

Changes in the cellularity and in the nature of the matrix were studied in the cartilages of the tibial plateau in experimentally induced arthritis in the dog, 7 and 14 days after section of the anterior cruciate ligament. Samples from the different regions of these cartilages were chilled and sectioned in a cryostat, with a variable microtome chuck to allow precise orientation of the specimens. The samples were examined by normal light microscopy, by microscopic interferometry, and by quantitative polarized light microscopy. The orientation of the glycosaminoglycans was assessed by the new "induced birefringence" method. The results indicated that only the region of the medial tibial cartilage that was unprotected by the meniscus was affected, showing increased water content, loss of superficial cells, and a decrease in orientation of the glycosaminoglycans. Whereas the birefringence of the collagen was unaffected, the superficial area that lacked oriented glycosaminoglycans was markedly increased; this may be a useful indicator of early osteoarthritic changes.

Alcian Blue↗
PubMed1979

Microdensitometry.

Microdensitometry, or microspectrophotometry, is the measurement of the concentration or mass of a chromophore in microscopically defined regions, and is governed by well-established laws of physics. Initially it proved of value in Feulgen cytophotometry of the relative amounts of DNA in individual nuclei of isolated cells. It has now achieved wide applicability to the measurement of cellular biochemical activity by means of stoichiometric chromogenic reactions. The validity of some of these measurements has been confirmed by comparative biochemical and microdensitometric assays. Thus microdensitometry, even of heterogeneously distributed chromophores, can be precise, provided that the technique is operated with due regard to its limitations within the laws of physics. The potential errors include: variation in thickness of tissue sections (path-length); scatter; glare; diffraction; occlusion of light by optically dense particles; and the inhomogeneity error. However, under correct conditions for the cytochemical reactions and for operating the microdensitometer, these potential errors become small or negligible. Thus the highly sensitive cytochemical bioassay of thyrotropin exemplifies the precision that can be achieved by controlled use of microdensitometry.

Animals↗
PubMed1979

Glycolytic activity in human synovial lining cells in rheumatoid arthritis.

It was conceivable that the previously reported elevated pentose-shunt activity in human rheumatoid synoviocytes could be at the expense of glycolytic activity. To test this possibility the activities of glyceraldehyde 3-phosphate and lactate dehydrogenase, the two dehydrogenase enzymes of the latter pathway, have been investigated in the synovial lining cells in fresh sections of nonrheumatoid and rheumatoid synovial tissue. To measure the activity solely in the lining cells, apart from that in underlying infiltrating cells, quantitative cytochemical reactions have been used; the activities were measured by microdensitometry. The results showed highly and significantly increased activity of both enzymes in the rheumatoid cells. Increased activity was also found in synoviocytes in nonrheumatoid synovial tissue after trauma, so that the increased activity of these enzymes is not characteristic of the rheumatoid condition. However, the results indicate that the increased pentose shunt activity in rheumatoid synovial lining cells is not at the expense of glycolytic activity but may be part of an enhanced potential for utilising glucose 6-phosphate in these cells.

Adolescent↗
PubMed1979

Metabolic alterations in human synovial lining cells in pigmented villonodular synovitis.

Synovial tissue from 3 patients with villonodular synovitis has been examined by quantitative cytochemistry. Considerable changes in the metabolism of the synoviocytes have been observed. These included a massive rise in the activity of glucose 6-phosphate dehydrogenase to levels even greater than those found in rheumatoid arthritis, and a significant rise in the activity of 2 glycolytic enzymes, glyceraldehyde 3-phosphate and lactate dehydrogenase. Lysosomal napthhylamidase showed raised activity with no latency. The sulphydryl content in the synoviocytes was raised, as was the amount of available phospholipid. This pattern of metabolic alterations is similar to that found in human rheumatoid synoviocytes.

Adult↗
PubMed1979

Thyrotropin secretion in patients with central hypothyroidism: evidence for reduced biological activity of immunoreactive thyrotropin.

TSH concentration was measured in plasma before and after TRH administration (200 micrograms, iv) in 89 patients with documented hypothyroidism consequent to various hypothalamic-pituitary disorders. Basal plasma TSH was less than 1.0 microI/ml in 34.8%, between 1.0-3.6 microU/ml in 40.5% and slightly elevated (3.7-9.7 microU/ml) in 24.7% of the cases. The plasma TSH response to TRH was absent in 13.5%, impaired in 16.8%, normal in 47.2%, and exaggerated in 22.5% of the cases, with delayed and/or prolonged pattern of response in 65% of the cases. The dilution curves of several plasmas drawn before and after TRH were parallel to those obtained with TSH standard preparation. After gel filtration, the elution pattern of TRH-stimulated plasmas from 4 patients did not show any major difference from that of pooled plasmas from normal subjects given TRH or from that of patients with primary hypothyroidism. Plasma TSH values determined by cytochemical bioassay on both basal and TRH-stimulated samples of 5 patients were markedly lower than those obtained by RIA. The serum T3 response to TRH was absent or low in 40 out of 53 patients in whom it was evaluated. The administration of T3 (100 micrograms/day for 3 days) or dexamethasone (3 mg/day for 5 days) respectively suppressed or reduced both basal and TRH-induced plasma TSH levels. Two patients became hypothyroid shortly after pituitary surgery in spite of basal and TRH-induced plasma TSH levels similar to or higher than those before surgery. Though thyroid atrophy due to chronic understimulation could explain the low T3 response to TRH in secondary hypothyroidism, it is difficult to reconcile thyroid understimulation with normal or increased plasma TSH unless the immunoreactive material has low biological activity. Present data suggest that several patients with hypothyroidism consequent to hypothalamic-pituitary diseases secrete a material which is immunologically similar to pituitary standard TSH and responds to stimulatory and suppressive agents in a manner similar to normal TSH but has low or absent biological activity. Thus, hypothyroidism due to insufficient TSH stimulation can be termed central hypothyroidism and can be due 1) to pituitary insufficiency (secondary hypothyroidism), 2) to a hypothalamic defect (tertiary hypothyroidism), or 3) to the secretion of biologically inactive TSH.

Biological Assay↗
PubMed1978

A sensitive bioassay of parathyroid hormone in plasma.

Understanding of calcium metabolism in health and disease has been retarded by the lack of an adequately sensitive bioassay of parathyroid hormone. The problem of dissociation of bioactivity and immunoactivity, well recognized for other polypeptide hormones, is exaggerated in the case of parathyroid hormone by the disproportionately long half-time in the circulation of the immunoreactive fragments. A new method of assaying the biological activity of parathyroid hormone in plasma has been developed, based on the cytochemical methods which have yielded highly sensitive bioassays of other polypeptide hormones. It depends on the stimulation of glucose 6-phosphate dehydrogenase activity in the distal convoluted tubules of segments of guinea-pig kidney maintained in vitro, and measured by microdensitometry. The limit of sensitivity of the assay is 5 fh/ml (bPTH); the index of precision is 0.09 +/- 0.04 (mean +/- SEM; n = 11).

Animals↗
PubMed1978

Altered phospholipids in human rheumatoid synoviocytes.

A specific cytochemical reaction for freely available phospholipids has shown a raised concentration of such phospholipids in the lining cells of human synovial membranes removed from rheumatoid joints. Quantitative measurement, by microdensitometry, of the amount of reaction-product per cell showed that the rheumatoid synoviocytes contained almost three times the amount of free phospholipids present in the equivalent nonrheumatoid cells; statistically the difference was highly significant. Evidence from studies in which the bound phospholipids were 'unmasked' by methanol-chloroform confirmed the view that the increased content of freely available phospholipids was related to altered lipid-protein binding rather than to an increase in total phospholipids.

Adolescent↗
PubMed1978

Mitochondrial oxidative activity in human rheumatoid synovial lining cells.

The activities of two mitochondrial enzymes, succinate dehydrogenase and cytochrome oxidase, have been measured by quantitative cytochemistry and microdensitometry in the synoviocytes of rheumatoid and non-rheumatoid synovial lining cells. Although both tended to be higher in the former, there was no statistically significant difference in the activities of either enzyme in these tissues. However, when cytochrome oxidase activity was measured without exogenous cytochrome c, the activity in the rheumatoid synoviocytes was highly significantly elevated. It is suggested that these findings may indicate only that the cytochrome c-cytochrome oxidase complex in the rheumatoid cells is more stable, possibly because of the increased availability of phospholipids in these cells.

Arthritis, Rheumatoid↗
PubMed1978

The effect of zinc on alkaline phosphatase activity in rheumatoid synovial tissue.

To examine the reported beneficial effect of zinc in rheumatoid arthritis, rheumatoid synovial tissue has been maintained in vitro in non-proliferative culture with or without zinc sulphate in the culture medium. Alkaline phosphatase activity was measured by microdensitometry of the cytochemical reaction in cryostat sections; the activity in blood vessels was measured separately from that in the supporting tissue below the synovial surface. Zinc enhanced this activity optimally at concentrations of between 10(-5) and 10(-4) mol/l.

Aged↗