PubMed Health⌕ Search

Biomedical subjects

L Bitensky

Publications and source records attributed to L Bitensky.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1977

Pentose-shunt oxidation in the periosteal cells in healing fractures.

The activity of pentose-shunt dehydrogenases is very low in periosteal cells of normal rat metatarsals, but increases one day post-fracture and rises linearly over the next two days. By four days post-fracture, the distribution of this activity along the bone shows two centres of high activity: the first in the region of proliferation to form callus and the second at the site where new bone is first seen, one day later. The high rate of generation of NADPH would be expected to reduce glutathione; reduced glutathione has been shown to inhibit alkaline phosphatase activity in these cells.

Alkaline Phosphatase↗
PubMed1977

Effect of glucocorticoids on the hexose monophosphate pathway in human rheumatoid synovial lining cells in vitro and in vivo.

Human rheumatoid synovial lining cells have up to four times the capacity to oxidize glucose 6-phosphate, the first step of the hexose monophosphate pathway, as do the nonrheumatoid cells. The reducing equivalents produced by this system have many significant metabolic effects. Exposure of these cells by 10(-5) M prednisolone in vitro, or to 6 mg/day in vivo, causes some depression of this activity in the rheumatoid synovial lining cells; less than this dose of steroid, or the administration of nonsteroidal drugs in vivo, has little or no effect. The depression of activity produced by 6 mg/day does not bring this activity down to the value found in nonrheumatoid synoviocytes.

Adult↗
PubMed1977

Myocardial preservation during aortic valve surgery. Assessment of five techniques by cellular chemical and biophysical methods.

Five different types of myocardial protection were employed in this series of 168 patients undergoing aortic valve replacement. Two methods of assessing myocardial preservation were used: cellular biological estimations and quantitative polarization measurements. Both parameters showed that either of two methods, continuous perfusion at 32 degrees C. with a beating heart or cardioplegic hypothermic arrest, protected the myocardum best. Intermittent perfusion at 30 degrees C. with a fibrillating heart was the worst means of preservation. Our investigations (both clinical and experimental) have also shown that changes in birefringence, indicative of deteriorating myocardial function, are often detectable before parallel cytochemical changes are apparent.

Adenosine Triphosphatases↗
PubMed1977

Cold cardioplegia or continuous coronary perfusion? Report on preliminary clinical experience as assessed cytochemically.

Myocardial preservation by continuous coronary perfusion is compared with cold cardioplegia. The 1 L. of St. Thomas' cardioplegic protective solution used for infusion into the coronary arteries was at 4 degrees C. and had a normal electrolyte content except for raised concentrations of magnesium and potassium and the addition of procaine. Myocardial preservation was assessed by cytochemical grading of myocardial biopsy specimens and also by the requirement for significant inotropic support postoperatively. In aortic valve replacements with an aortic occlusion time of 1 1/2 hours, both techniques afforded a similar degree of preservation, except that the inner half of the myocardium was markedly better preserved by cold cardioplegia. After 2 hours in double valve replacements, a single cardioplegic infusion was not as effective as continuous coronary perfusion, but this could be corrected by a second infusion of the cardioplegic solution after an hour.

Aortic Valve↗
PubMed1976

Changes in alkaline phosphatase activity in periosteal cells in healing fractures.

The quantitative changes in alkaline phosphatase activity in the periosteal cells close to the fracture in rat metatarsal bones has been measured during the first 5 days postfracture. This study has been made possible by two technological advances, firstly the development of cryostat microtomy for cutting unfixed, undemineralised bone, and secondly the use of scanning and integrating microdensitometry for quantifying the activity in each periosteal cell. The results showed a loss of alkaline phosphatase activity close to the fracture site, with activity rising to normal values 0.8-1.0 mm from the site. No alkaline phosphatase activity was found in the cells which proliferated from the periosteum. It is suggested that reduced glutathione could cause such inhibition.

Alkaline Phosphatase↗