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Biomedical subjects

L Bitensky

Publications and source records attributed to L Bitensky.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1985

Electrochemical detection of depressed circulating levels of vitamin K1 in osteoporosis.

If gamma-carboxylation, by the vitamin K1 - cycle, of glutamate residues of bone-matrix peptides is essential for the formation of bone, the circulating levels of this vitamin might indicate the potential efficiency of this process. Methods involving HPLC with electrochemical detection have very recently been developed for assaying the low levels of vitamin K1 that occur in normal plasma. Using such methods, we found that the circulating levels of vitamin K1 in osteoporotic patients (who had sustained either spinal crush-fractures or fractures of the neck of the femur) were significantly lower than those of age-matched control subjects.

Aged↗
PubMed1984

Use of microscopic interferometry for measuring changes in water content of small samples of tissue.

Oedema following periods of ischaemic arrest and subsequent reperfusion has been shown experimentally and clinically to affect the functional state of the heart. Tissue water content has been measured in myocardial sections by microscopic interferometry and densitometry, and the results correlated with those obtained by wet and dry weight analysis (r = 0.87; p less than 0.001). Microscopic interferometry also revealed the distribution of the water in the tissue. Experimentally induced ischaemic arrest in isolated rat hearts resulted in predominantly intra-fibrillar oedema, whilst subsequent reperfusion resulted in interfibrillar oedema. Microscopic interferometry facilitates accurate measurement of water content in tissue samples as small as 2 mg wet weight and shows (as conventional wet/dry weight analysis cannot) the distribution of the water in the tissue.

Animals↗
PubMed1984

Possible mechanism for target cell lysis by cytotoxic T-cells.

The mechanism of the lysis of target cells by cytotoxic T-cells (Tc) is still obscure; there is no evidence for transfer of material from the Tc and prior to lysis, despite intimate contact, the plasma membranes of both types of cell appear to remain intact. The effects on the target cell lysosomes of brief contact between anti-viral Tc and targets bearing both the appropriate histocompatibility and viral antigens, have been examined cytochemically. Both the distribution of acid phosphatase activity and the percentage bound lysosomal naphthylamidase activity indicated that, in virus-infected target cells exposed to Tc, the lysosomal membranes became totally labilized. Thus the contact between Tc and targets appears to cause sufficient perturbation of the target plasma membrane as to cause the intracellular release of some agent that activates 'suicide capsule' lysosomes.

Acid Phosphatase↗
PubMed1984

Effects on fracture healing of an antagonist of the vitamin K cycle.

The anticoagulant, dicumarol, inhibits the vitamin K cycle by blocking the conversion of the vitamin K epoxide. The effects of dicumarol on ossification have been tested by feeding it to rats in which a closed fracture of the metatarsals had been induced; the effects were studied up to 12 days postfracture. At 12 days, treatment with dicumarol caused a highly significant decrease in the amount of bone produced, without affecting the total size of the callus. Quantitative cytochemistry of unfixed, undemineralized sections showed that dicumarol also markedly affected the periosteal activities of glucose 6-phosphate dehydrogenase and of alkaline phosphatase in the first 2 mm from the fracture measured at 3 and 5 days postfracture when normally, new bone is first formed. In contrast, dicumarol had little effect on these activities in the fully formed callus.

Alkaline Phosphatase↗
PubMed1983

Aerobic glycolysis of bone and cartilage: the possible involvement of fatty acid oxidation.

The apparent paradox of aerobic glycolysis has been investigated in bone and in cartilage. A new cytochemical procedure for hydroxyacyl dehydrogenase (HOAD) activity showed that the maximal activity of this enzyme in both tissues was equivalent to the maximal activity of glyceraldehyde 3-phosphate dehydrogenase (GAPD). The sum of these activities gave a measure of the maximum amount of acetyl-coenzyme A that could be produced. In these tissues, but not in liver which does not exhibit aerobic glycolysis, this summed value exceeded the maximal activity of succinate dehydrogenase (SDH). Consequently, it suggested that where fatty acid oxidation is sufficient to supply all the acetyl-coenzyme A required for the Krebs' cycle, that derived from fatty acid oxidation may inhibit pyruvate dehydrogenase causing accumulation of pyruvate which must be converted to lactate if pentose-shunt activity is to be maintained.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1983

Metabolic changes in the cells of the callus during fracture healing in the rat.

Unfixed, undecalcified sections from closed fractures of rat metatarsals have been studied by quantitative cytochemistry from the first week after fracture to late in the fracture-healing process. Alkaline phosphatase activity appeared to be related to calcification. Glucose 6-phosphate dehydrogenase activity was associated with proliferation and with calcification. Studies made with the critical electrolyte Alcian blue technique suggested that whether the ossification process is of the endochondral or membranous type might be predetermined in the relatively undifferentiated callus.

Alkaline Phosphatase↗
PubMed1983

Synthesis of arachidonate cyclo-oxygenase products by rheumatoid and nonrheumatoid synovial lining in nonproliferative organ culture.

Specimens of human rheumatoid and nonrheumatoid synovial lining were maintained in nonproliferative organ culture for 20 hours. The culture fluids were then assayed for prostaglandin E(2) (PGE(2)), thromboxane B(2) (TXB(2)), and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)) by specific radioimmunoassay. The presence of each of these substances was confirmed by gas chromatography and mass spectrometry. Rheumatoid tissue produced significantly more of each cyclo-oxygenase product than nonrheumatoid tissue.

6-Ketoprostaglandin F1 alpha↗
PubMed1983

A modified tetrazolium reaction for identifying malignant cells from gastric and colonic cancer.

When non-malignant cells were reacted for glucose-6-phosphate dehydrogenase activity, with neotetrazolium chloride as the indicator of the activity, oxygen competed with the neotetrazolium and nullified the reaction. In contrast, about 30% of the activity was retained in malignant cells, in sections and in smears, from cancer of the stomach or colon. This could provide the basis of a qualitative (black-or-white) functional test for distinguishing malignant cells in these conditions.

Colonic Neoplasms↗
PubMed1983

Changes in crystal size and orientation of acidic glycosaminoglycans at the fracture site in fractured necks of femur.

The aim of this study was to try to elucidate the increased susceptibility of the neck of femur to fracture. Quantitative polarised light microscopy has been applied to fresh, undecalcified sections of samples of bone taken from the site of fracture, in specimens taken at operation from patients with fractures of the femoral neck or osteoarthritic femoral heads or from the equivalent site from otherwise normal subjects at necropsy. In all 21 specimens of fractured necks of femur, but in none of the other specimens, relatively large crystals (up to 2.5 X 0.5 micrometres) were found close to the site of fracture; the properties of these crystals were compatible with their being apatite. Measurement of the natural birefringence of the collagen showed no difference in the orientation of the collagen in all three types of specimen. However, the orientation of acidic glycosaminoglycans, measured by the birefringence of alcian blue bound to these moieties, was 45 per cent lower in the specimens from fractured necks of femur than in the other specimens, even though the total content of acidic glycosaminoglycans was unchanged. Although the decreased orientation was most marked close to the site of fracture, it was still apparent 15 millimetres from that site. These changes were unlikely to be simply the sequelae of fracture since they were not found in traumatic fractures of other bones. Thus it is conceivable that changes in the orientation of the ground substance allow formation of relatively large crystals of apatite and that such crystals, in the microcrystalline mass of apatite, are the cause of the increased fragility of such bones.

Aged↗
PubMed1982

The involvement of the pentose shunt in thyroid metabolism after stimulation with TSH or with immunoglobulins from patients with thyroid disease. 1. The generation of NADPH in relation to stimulation of thyroid growth.

It has been shown previously that both thyrotrophin (TSH), and also immunoglobulins (Ig) derived from patients with goitrous Graves' disease, stimulate DNA-synthesis in guinea-pig thyroid tissue maintained in vitro. Here we describe the use of the same in vitro system and methods of quantitative cytochemistry to test the effect of these substances on the generation of NADPH, which is another indicator of the potential for growth. As could be predicted by its trophic action, TSH stimulated the generation of NADPH by glucose 6-phosphate dehydrogenase. The Ig-fraction from normal subjects depressed this activity. The Ig-fraction from Graves' disease patients with goitres stimulated the generation of NADPH, whereas the Ig from patients with Graves' disease but with minimal enlargement of the thyroid gland behaved like normal Ig. A similar lack of stimulation was found with Ig from patients with Pendred's syndrome, other dyshormonogenetic goitres, and autonomous single adenomas. In all specimens tested, there was good correlation between the amount of DNA-synthesis, measured by Feulgen cytophotometry, and the activity of glucose 6-phosphate dehydrogenase activity that generated NADPH. These results support the concept that there is a distinct type of autoantibody that influences thyroid growth.

Animals↗
PubMed1982

The involvement of the pentose shunt in thyroid metabolism after stimulation with TSH or with immunoglobulins from patients with thyroid disease. II. The reoxidation of NADPH and stimulation of hormone synthesis.

Reducing equivalents derived from the tissue re-oxidation of NADPH (NADPH-diaphorase) have been implicated in the peroxidation that is involved in the organification of iodine in the production of thyroid hormones. Immunoglobulin (Ig) fractions from patients with thyroid diseases and from normal controls, in a standard dose of 125 micrograms/ml and 0.3 microunits/ml thyrotrophin (TSH) were incubated with segments of guinea-pig thyroid gland maintained in vitro. A quantitative cytochemical study was made on how these fractions influenced the enzyme activity. A good correlation was found between the ability of such Ig fractions to stimulate the NADPH-diaphorase activity and (1) the degree of hyperthyroidism in the patients and (2) the amount of T3 secreted by the thyroid segments in vitro.

Animals↗
PubMed1982

Circulating levels of biologically active parathyroid hormone in rheumatic diseases.

There has been doubt as to whether elevated levels of parathyroid hormone, reported previously by radioimmunoassay, reflect increased concentrations of the biologically active hormone. The application of a recently developed, highly sensitive bioassay has shown considerable disparity between bioactivity and immunoreactivity in 5 rheumatic conditions and in normal subjects. Six patients with chondrocalcinosis had elevated levels; 3 of these did not have hypercalcaemia or any obvious cause other than possible subclinical hyperparathyroidism. One patient, assayed during an acute episode, had an elevated concentration of the hormone which reverted to normal when she was asymptomatic. Most patients with osteoarthrosis (13 our of 15) had low normal levels; 2 showed unexplained slightly elevated concentrations. Of 6 patients with haemochromatosis 3 had elevated levels, though this may have been related to the associated presence of diabetes mellitus. A third of patients with ankylosing spondylitis (10 out of 30) showed elevated parathyroid hormone levels but without hypercalcaemia. A number of spondylitic patients also showed anomalous results in this assay, possibly due to the presence of an antagonist. This would be consistent with the absence of clinical or biochemical evidence of hyperparathyroidism.

Adult↗
PubMed1982

Feulgen-hydrolysis profiles in cells exfoliated from the cervix uteri: a potential aid in the diagnosis of malignancy.

By varying the time of hydrolysis for the Feulgen reaction, done under conditions that protect the backbone of the DNA, it is possible to distinguish three species of DNA that are characterised by their lability to acid hydrolysis. The most labile DNA was found, in greatest proportions, in malignant cells; this may be helpful in diagnostic cytology. The fact that the cytologically normal cells, in grade V smears, also show this labile DNA may well facilitate cytological screening even in those smears that contain very few neoplastic cells.

Cervix Uteri↗
PubMed1982

Inhibition of cytochemical bioactivity of parathyroid hormone by plasma in pseudohypoparathyroidism type I.

Despite the high circulating levels of immunoreactive PTH in patients with pseudohypoparathyroidism type I (PSPI) the levels of bioactive PTH (bioPTH) have been found to be close to the normal range. To elucidate this dissociation, we have studied the recovery of the biological activity of bovine PTH added to the plasma of patients with either PSPI, or with hypoparathyroidism (PTX), primary hyperparathyroidism (HPT) or of normal subjects. In PSPI (n = 10) the recovery of biological activity was 5.6% +/- 3.6 (mean +/- SEM) whereas in PTX (n = 7), in HPT (n = 4) and in normal subjects (n = 8) it was 79% +/- 5, 75% +/- 9 and 68% +/- 4, respectively. In another PSPI patient, who had undergone total parathyroidectomy, bioPTH was undetectable but the recovery from the plasma of added PTH was 84%. Thus we have found inhibition of PTH bioactivity by plasma of PSPI patients which was absent after parathyroidectomy.

Animals↗