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Biomedical subjects

L Bitensky

Publications and source records attributed to L Bitensky.

At least 19 recordsLinked to original sources
PubMed1992

Chondrocytic monoamine oxidase activity in the development of natural murine osteoarthritis.

Most of the male STR/ORT mice develop osteoarthritis (OA) involving the medial tibial plateau. A peculiarity of two chondroprotective drugs is the presence of a nitrogen atom so that cleavage of the molecule could generate a molecule that might act as an inhibitor of monoamine oxidase (MAO). Direct examination showed abnormal localization of MAO in the potentially osteoarthritic cartilage indicating possible abnormal response to catecholamines. In normal cartilage, the direct effect of excessive concentration of adrenaline caused considerable oedema, as measured by microscopic interferometry. It is therefore suggested that the excess of water found in the matrix of osteoarthritic cartilage may be related to disturbance of the MAO activity.

Animals↗
PubMed1991

Depressed levels of circulating menaquinones in patients with osteoporotic fractures of the spine and femoral neck.

Vitamin K1 functions in the conversion of glutamate residues, present in certain bone peptides, into the putatively active gamma-carboxyglutamate form. We have shown previously that the circulating levels of vitamin K1 are depressed in osteoporotic patients. However, it is known that menaquinones (vitamin K2:MK) may be more effective than vitamin K1 in this conversion of the inactive to active form of glutamate residues. A procedure for measuring such menaquinones has now demonstrated a marked deficiency of MK-7 and MK-8 in patients with osteoporotic fractures. It is suggested that estimates of circulating levels of K1, MK-7, and MK-8 might provide a biochemical risk marker of osteoporotic fractures.

Aged↗
PubMed1991

The effect of menadione epoxide on the experimental immune arthritis in the rabbit.

It was shown previously that the experimentally induced arthritis in the rabbit can be largely nullified by subsequent treatment with menadione (by gavage). It is now shown that menadione epoxide, as is produced in the vitamin K cycle, also exerts a beneficial effect histologically and biochemically. Such treatment decreased both the glucose 6-phosphate dehydrogenase and the 6-phosphogluconolactonase activities in the synovial lining cells of the challenged joints towards values found in the unchallenged joints; it had only equivocal effects on the 6-phosphogluconate dehydrogenase activity. The results indicated that the epoxide might be interfering primarily with the lactonase activity.

Animals↗
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↗
PubMed1978

Quantitative cytochemistry: the basis of sensitive bioassays, for comparison of bio-and immuno-reactive hormone values.

Cytochemistry now extends biochemistry down to the single-cell level. Special procedures have been developed for cutting sections of uniform thickness with no measurable or detectable artifact. The cytochemical bioassays use chromogenic reactions with the immediate precipitation of the resulting chromophore so that biochemical activity can be related to the individual cells constituting a tissue. This activity, in individual cells, is measured by scanning and integrating microdensitometry which also increases the sensitivity of cytochemical measurement over that of conventional biochemistry. A hormone, or indeed any biologically active substance, acting on its target cell, causes a change in the chemical activity of that cell that mediates the physiological effect of the hormone. By cytochemical methods one can assess such changes in the target cells even if these constitute only a small part of the target-organ; thus such methods are ideally suited to measuring chemical changes of this sort induced by the hormone. Such cytochemical bioassay of polypeptide hormones, done as "within-animal" assays, are about 1000-f0ld more sensitive than the equivalent radioimmunoassays and are as precise. Thus they have two advantages: (a) bioreactive hormone is measured rather than a composite of antigenic determinants characteristic of part of the hormone molecule and (b) their increased sensitivity allows discrimination between low normal and subnormal concentrations of the circulating hormone.

Animals↗