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Biomedical subjects

L Bitensky

Publications and source records attributed to L Bitensky.

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

Evidence for cell division in synoviocytes in acutely inflamed rabbit joints.

DNA synthesis has been measured both by Feulgen cytophotometry, quantified by the DNA synthesis index, and by tritiated thymidine autoradiography, quantified by the labelling index. In the early acute inflammation resulting from the intra-articular challenge of ovalbumin in sensitised rabbits both indices rose considerably, so that at least 1 in 10 synoviocytes was heavily labelled 3 days after challenge. The results are compatible with the concept that even such apparently differentiated synoviocytes are capable of cell division.

Animals↗
PubMed1981

Dissociation of parathyroid hormone bioactivity and immunoreactivity in pseudohypoparathyroidism type I.

Circulating levels of parathyroid hormone (PTH) in six patients with pseudohypoparathyroidism type I (PSPI) have been measured by two immunoassays and by cytochemical bioassay and compared with measurements in normal subjects and patients with clinically defined hyper- and hypoparathyroidism. In all PSPI patients, the levels of immunoreactive PTH were in the hyperparathyroid range, whereas the bioactive levels were either in the normal or close to the normal range. In one patient from whom the dihydrotachysterol therapy was withdrawn, both immunoreactive and bioactive PTH concentrations increased. The finding that the PTH measured by RIA in these PSPI patients may have reduced biological activity may explain some of the clinical findings of hypoparathyroidism in this syndrome.

Adult↗
PubMed1980

A cytochemical section-bioassay for thyrotropin.

A cytochemical section-bioassay of thyrotropin has been developed which retains the sensitivity of the earlier segment-assay (10(-4) microunits/ml) and allows a considerable increase in the rate at which these within-animal bioassays can be done. The index of precision (n=23) was 0.11 +/- 0.06; intra-assay variation was 1.3%; inter-assay variation was 10.9 +/- 6%. Fiducial limits (p = 0.95) ranged from 65-150% to 78-127%. The system is also capable of detecting thyroid-stimulating immunoglobulins.

Aminopeptidases↗
PubMed1980

A cytochemical bioassay for arginine vasopressin: preliminary studies.

A new method of measuring vasopressin activity is described. It depends on the finding that the Na+-K+-ATPase activity, measured cytochemically, in the thick ascending limb of the loop of Henle in rat renal tissue maintained in vitro, responded to increasing concentrations of synthetic arginine vasopressin in a log-dose related fashion. The limit of sensitivity was 0.002 pg/ml (2 x 10(-15) mol/l). The dose-responses were reproducible; the inter-assay coefficient of variation was 6.4% at a vasopressin concentration of 0.02 pg/ml. Normal plasma stimulated this Na+-K+-ATPase activity, the stimulation being reduced by 98% when the plasma had been treated with an antiserum specific for vasopressin. Measured in this system, the circulating levels of plasma vasopressin, in healthy adults after 18h dehydration, was 4.0 +/- 0.3 pg/ml (mean +/- SEM; n = 4) and fell to 0.6 +/- 0.1 pg/ml following a water load. Absolute plasma vasopressin values obtained by the cytochemical bioassay were comparable to those measured by radioimmunoassay (r = +0.97, p less than 0.001).

Adenosine Triphosphatases↗
PubMed1980

DNA synthesis in human rheumatoid and nonrheumatoid synovial lining.

The DNA content per nucleus has been measured in the lining cells of 12 specimens of rheumatoid and 12 of nonrheumatoid synovial tissue. Optimal conditions for this reaction on these cells have been defined, and an index of DNA synthesis has been applied to give a quantitative measure of the degree of synthesis. This has given evidence of some DNA synthesis in both types of synoviocytes, compatible with the amount found in a slowly self-replacing tissue. There was no difference in the amount of synthesis in the rheumatoid and nonrheumatoid synoviocytes.

Adolescent↗
PubMed1980

Lysosomal naphthylamidase activity as a possible aid in cytological screening.

Lysosomal naphthylamidase activity has been measured microdensitometrically in cells in samples obtained by cervical and vaginal irrigation from 22 cases cytologically graded I and II, 28 graded III (moderate to severe dysplasia), 22 graded IV (carcinoma in situ), and 15 cases (grade V) of invasive carcinoma. There was a statistically significant difference in this activity in the cells from cases of grade V as against those in the relatively normal samples (grades I and II; p < 0.001) and as against those of grade IV (p < 0.005). The method is sufficiently robust for routine use provided that it is recognised that elevated activities can be found as a consequence of other factors such as previous surgical intervention and infection with herpes simplex.

Aminopeptidases↗
PubMed1980

Inhibition of parietal cell function by human gammaglobulin containing gastric parietal cell antibodies.

Parietal cell antibodies (PCA) are found in up to 90% of sera from pernicious anaemia patients but it is often stated that they could represent an epiphenomenon without being directly responsible for the achlorhydria. In the present studies a direct effect of these antibodies on the secretory function of gastric acid-secreting cells has been demonstrated in two different experimental systems. In one set of experiments IgGs containing PCA activity were shown to inhibit acid secretion specifically in the living gastric mucosa of the bull frog suspended as a diaphragm between two chambers. The other system demonstrated their inhibition of carbonic anhydrase activity in a cytochemical bioassay for human G17-gastrin, suggesting a blocking effect on the gastrin receptors in the canalicular microvilli or the cell membrane. These experiments suggest a direct pathogenic role for PCA in autoimmune fundal gastritis and in pernicious anaemia.

Anemia, Pernicious↗
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↗