Biomedical subjects

B Jasani

Publications and source records attributed to B Jasani.

At least 163 records · Page 9Linked to original sources

PubMed1983

A simple post-embedding system for the rapid demonstration of tissue antigens under the electron microscope.

A simple and versatile technique for the preparation of ultra-thin sections, which can be stained immunohistochemically directly on electron microscope grids, is presented. An anti-hapten immunoperoxidase procedure has been adapted for use on tissue fixed in a purified monomeric glutaraldehyde--picric acid mixture, and embedded in 'L R White', a recently formulated plastic resin. This plastic tolerates the use of partial dehydration of tissue, resulting in higher antigenic yields. In addition, no etching of ultra-thin sections is necessary, and the whole immunostaining procedure can be completed in less than 2 h. A comparison of commonly used fixatives is discussed. High-resolution micrographs showing general staining (uranyl acetate--lead citrate) of rat pancreas, and immunostaining of insulin and TSH in storage granules in perfusion-fixed rat tissue and of lambda-chain immunoreactive cells in immersion-fixed human tonsil are included as examples.

Animals↗

PubMed1983

Receptor secretion hypothesis for regulation of hormone action.

It is well established that modulation of target cell responses to hormonal stimulation can occur through variation of the number of effective hormone receptors per cell. Recent experimental evidence suggests that an alternative or additional autoregulatory mechanism may operate via secretion by the cell of 'receptors' which can bind to, and thereby regulate, the concentration of free hormone in the extracellular space. We present here a brief general analysis of this 'receptor-secretion' model, together with an example which shows that it can readily account for the phenomenon of self-limiting growth seen in many tissues in response to sustained hormonal stimulation. The biological significance of the model is discussed, and the close analogy with B-lymphocyte regulation pointed out. Finally, two important implications are considered, for the pathogenesis of nodular hyperplasia and tumours in hormonally-controlled tissues.

Homeostasis↗

PubMed1983

Factor VIII as a marker of endothelial cells in follicular carcinoma of the thyroid.

Factor VIII-related antigen is a recognised marker of endothelial cells. A brief immunocytochemical study of its distribution in follicular carcinoma of the thyroid and its value in the recognition of vascular invasion by this tumour has been carried out. Ten cases of follicular carcinoma of the thyroid were studied. In each strong endothelial staining was found in the majority of vessels in the adjacent normal thyroid. Lymphatic endothelium was negative. In eight of the 10 cases the staining of vessels within the tumour was absent or very weak. Staining was also absent in the majority of vessels completely occluded by tumour, but was present in the endothelium of vessels only partly occluded by tumour. It is concluded that factor VIII-related antigen staining has only limited value in the recognition of vascular invasion in follicular carcinoma. The absence of vascular staining in the tumour leads us to suggest that inhibition of factor VIII production by the tumour could be a possible mechanism which facilitates vascular invasion and metastasis.

Adenocarcinoma↗

PubMed1983

Metal compound intensification of the electron-density of diaminobenzidine.

Diaminobenzidine (DAB), commonly used in immunocytochemistry as the substrate for peroxidase, has a low electron density. DAB has a known affinity for the salts of some metals and therefore an examination of the ability of six metal compounds (including osmium tetroxide) to increase the electron density associated with DAB deposits has been undertaken. Ultra-thin sections of unosmicated rat pituitary gland, embedded in L. R. White resin, were immunostained by a hapten sandwich immunoperoxidase method, using antibodies to ACTH and TSH. The unintensified electron density of the DAB polymer reaction product on the specific endocrine granules was compared with the electron density resulting from the use of each of the six metal compounds. Lead and silver nitrate gave unsatisfactory results, while phosphotungstic acid and uranyl acetate produced a limited increase in specific electron density under the conditions used. Gold chloride was found to give the highest electron density to the specific endocrine granules, followed closely by osmium tetroxide. Background staining was greater when osmium was used. We conclude that several metal compounds may be used to intensify the electron density of DAB, but of the ones tested, gold chloride, which is safer, more stable, and cheaper than osmium tetroxide, was clearly the best. This approach not only increases the electron density of the DAB reaction product, but allows of the possibility of quantitation using energy dispersive X-ray analysis.

3,3'-Diaminobenzidine↗

PubMed1982

Automated cell counting in tissue sections: a new approach by 'multiple grey-level analysis'.

A system is described for the automated quantitation in tissue sections of the follicular and stromal cell populations of the thyroid gland, using a computer-linked TV image analyser. The paper illustrates how the problems of variable staining intensity and clustering of images (nuclei) may be overcome by a novel approach, in which multiple analyses of each field are made at increasing grey-level thresholds, and then 'synthesized' by computer to give a composite image. Discrimination between cell (nuclear) types was by a single minimum width criterion. The results were highly reproducible and correlated well with counts obtained by a comparable manual method.

Animals↗

PubMed1981

Use of monoclonal antihapten antibodies for immunolocalisation of tissue antigens.

The applicability of a hapten-antihapten sandwich technique incorporating a monoclonal antihapten bridge antibody to localisation of tissue antigen is described. The results show that the method is both versatile and selective and has the potential of being even more sensitive than currently used immunoperoxidase methods.

Animals↗

PubMed1981

Effect of goitrogen administration on the circadian rhythm of serum thyroid stimulating hormone in the rat.

Adult male rats were fed a goitrogen, aminotriazole, for 74 days at a dose known to suppress thyroid function completely. At the end of this period, these animals along with matched controls were killed in groups of seven at 3 hourly intervals throughout a 24 hour period, and serum TSH, T3, T4 and albumin assayed. No significant circadian rhythms of T3, T4 or albumin were found in either, but a highly significant rhythm of TSH was demonstrated both in controls and goitrogen treated groups, with a diminished relative amplitude in the latter. The results indicate that a significant diurnal rhythm of serum TSH persists in the rat despite long-term blockade of thyroid hormone synthesis and that the existence of this rhythm is therefore independent of the presence of circulating T3 or T4.

Amitrole↗

PubMed1980

Endotoxin-induced appearance of peroxidase-positive cells in the white pulp of the mouse spleen.

Endotoxin (1-10 microgram intravenously) increased the number of strongly peroxidase-positive cells in the white pulp of the mouse spleen, demonstrable by the Graham-Karnovsky technique. The increase was greatest after 10 h, the cells being found most frequently around the central vessels of the white pulp. The appearance of such cells at this critical immunological site may relate to the known adjuvant activity of endotoxin in promoting immune responses against protein antigens.

Animals↗

PubMed1979

Further studies on the structural requirements for polypeptide-mediated histamine release from rat mast cells.

Structure-activity studies have been performed on a series of naturally occurring and 'tailor-made' polypeptides, by measurement of ability to induce selective histamine release from normal rat peritoneal mast cells in vitro. Compounds investigated include corticotropin and melittin derivatives, mast-cell-degranulating peptide from bee venom, polymyxin B, bradykinin and various synthetic poly(amino acids) and short-chain peptides. It was confirmed that a cluster of four basic residues (lysine or arginine) was optimal for histamine release by corticotropin and melittin polypeptides, provided that the C-terminal carboxyl group was substituted (by, for instance, amidation). In contrast, the presence of a free C-terminal carboxyl group or nearby dicarboxylic acid residues led to a considerable diminution in histamine-releasing activity. Likewise, polypeptides comprised essentially of acidic amino acids were inactive. On the basis of these observations it has been possible to predict that synthetic peptides comprising a particular sequence within the Fc region of human immunoglobulin E, the immunoglobulin class particularly involved in mediation of allergic reactions of the immediate type, would possess potent histamine-releasing activity when similarly made to react with normal rat mast cells. The further study of such a structure should throw new light on the molecular basis of allergen-antibody triggering of mast cells.

Adrenocorticotropic Hormone↗

PubMed1979

An investigation of the optimal conditions for the in vivo production of immunologically sensitised rat mast cells.

Experiments were designed to develop an optimal method for inducing in vivo production of sensitised peritoneal mast cells. Rats of different strains were sensitised with whole egg-white and killed at suitable intervals to harvest the peritoneal mast cells. Release of histamine was induced in vitro by both whole egg-white and its major protein constituents, and assayed by a standard spectrofluorometric method. Wistar rats showed higher levels of sensitisation than black-hooded Lister rats; it was more convenient to harvest erythrocyte-free peritoneal mast cells from males than females. Very young (less than 150 g) and very old (greater than 300 g) rats showed sub-optimal sensitisation. Optimal sensitisation was obtained by simultaneous administration of antigen (doses of 50 micrograms whole egg-white and above) and adjuvant (1.0 ml pertussis vaccine); mast cells harvested between 20 and 50 days after the sensitising dose exhibited maximal histamine release upon in vitro challenge with 'whole' egg-white (100 micrograms). Routine use of plastic ware, and ice-cold phosphate-buffered saline (pH 7.2) for handling cells and avoidance of heparin and excessive centrifugation ensured optimal preservation of histamine-releasing capacity of the harvested peritoneal mast cells.

Aging↗

PubMed1978

Characterization of two acid proteinases found in rabbit skin homografts.

Two types of acid proteinase activity found in rabbit skin homografts were characterized by studying the effect of temperature, pH and polyacrylamide-gel electrophoresis. Their chromatographic behaviour was characterized on DEAE-cellulose, Sephadex G-75, G-100 and G-200, and their molecular weights were estimated by gel filtration. One of the acid proteinases in the homograft resembled cathepsin D (EC 3.4.23.5) of normal skin. The other acid proteinase differed from cathepsin D with respect to heat inactivation, pH optimum and molecular weight; it was not inactivated on heating at 60 degrees C for 60 min, its pH optimum was 2.5 and its molecular weight measured by Sephadex G-100 chromatography was 100 000. In all these respects, the heat-stable proteinase resembles cathepsin E (EC 3.4.23.5) of rabbit polymorphonuclear leucocytes.

Animals↗

PubMed1978

Mechanism of impaired glucose tolerance in patients with neoplasia.

The disappearance rate (k) of i.v. glucose was measured in cachectic and non-cachectic cancer patients and tumour-free controls. The respective k values were found to be 1.06 +/- 0.27 (mean +/- s.d.), 1.64 +/- 0.34 and 1.63 +/- 0.23. Of the other parameters measured, only plasma albumin level was found to vary significantly amongst the 3 categories, the mean level being the lowest in cachectic cancer patients. The means of total plasma protein, fasting blood glucose and plasma liver enzyme concentrations were similar in the 3 groups. Glucagon, a potent insulin secretogogue, failed to augment the fasting insulin level in cachectic but did so in non-cachectic cancer patients. Taken together, the findings suggest that the reduced glucose tolerance in patients with neoplasia is due to impairment of insulin release exhibited predominantly by ill-nourished advanced cancer patients having a moderate to sever degree of hypoalbuminemia.

Adult↗

PubMed1977

Topical thrombin and control of wound haematoma.

The frequency of wound haematoma was investigated in 45 prophylactically heparinised patients undergoing abdominal surgery. Thrombin was applied locally to the wound in 15 patients, and in these patients wound haematoma was significantly less common than in the controls.

Abdomen↗

PubMed1974