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Biomedical subjects

D Brown

Publications and source records attributed to D Brown.

At least 919 records · Page 51Linked to original sources
PubMed1985

Detection of surface-bound ligands by freeze-fracture autoradiography.

This article describes a new freeze-fracture autoradiographic technique for the detection of radioactive ligands associated with the surface of cells in monolayer or suspension culture. Since freeze-fracture replicas are produced in the conventional way, all membrane features normally seen in freeze-fracture are retained, and autoradiographic grains produced by the labeled ligands are seen superimposed on unaltered exoplasmic membrane fracture faces. To assess the feasibility and resolution of this technique, we compared the surface distribution of alpha 2-macroglobulin and cholera toxin, labeled either with 125I or with colloidal gold, on 3T3-L1 fibroblasts. Both by autoradiography and cytochemical gold labeling, alpha 2-macroglobulin was associated specifically with coated pits, whereas cholera toxin was preferentially found over smaller, apparently non-coated membrane invaginations. Together with data on the surface localization of 125I-transferrin on HL-60 myelomonocytic cells, these results demonstrate the application of this technique for the accurate determination of ligand distribution over large areas of plasma membrane. The simplicity and reproducibility of the method should now allow freeze-fracture autoradiography to become a standard technique for investigating the distribution of both endogenous and exogenous cell surface-associated molecules, as well as the redistribution of such molecules under different experimental conditions.

Animals↗
PubMed1985

Effects of inhibitory and stimulatory photoperiods and sexual maturation on the ability of hamster testes to respond to hCG in vitro.

The decrease in gonadal weight produced in adult golden hamsters by exposure to short photoperiods was accompanied by a marked reduction in the ability of the testes to produce testosterone from endogenous precursors in vitro, both without and with hCG stimulation. These changes were significant after 4-7 weeks in short photoperiod (5L: 19D) and were even more pronounced after 17-20 weeks. Production of testosterone in vitro by testes of immature hamsters was comparable to values obtained in adult animals with short photoperiod-induced gonadal atrophy. Delay of sexual maturation induced by daily injections of bromocriptine was accompanied by a further decrease in testicular testosterone production in vitro. Exposure of gonadally-regressed adult hamsters to a long, stimulatory photoperiod (14L: 10D) produced a rapid and marked increase in testicular testosterone production, which was coincident with the previously demonstrated increase in serum gonadotrophin levels after 1-5 days of photostimulation. Furthermore, testosterone production in vitro by regressed testes of animals exposed to short photoperiod was increased significantly by one large dose of hCG administered 26 h before killing the animals. It is concluded that the suppressive effects of short photoperiods on the ability of the hamster testis to produce testosterone and to respond to hCG stimulation are due to reductions in endogenous LH, FSH and prolactin release, with a consequent loss of testicular LH/hCG receptors and decreased activity of enzymes involved in the biosynthesis of testosterone.

Animals↗
PubMed1985

Sexual behaviour in a centre for epilepsy.

The sexual behaviour and hormonal profiles in 97 patients with chronic epilepsy from an epilepsy centre were studied. Sexual behaviour relating to numbers of sexual contacts, orgasms, spontaneous erections, and early morning erections, whether there was difficulty in obtaining or maintaining an erection, or in ejaculation, was assessed at interview. Hormonal profiles consisted of LH, FSH, prolactin, total testosterone, free testosterone, and SHBG. Information was obtained relating to type of seizure, seizure frequency, age of onset, likely pathology, IQ, and medication. The study showed that this patient group was profoundly hyposexual and had a high level of sexual dysfunction. Serum free testosterone levels were low, and it is suggested that the high level of sexual dysfunction and lack of sexual interest may well have a hormonal basis. The reasons for this are discussed.

Adolescent↗
PubMed1985

'Psychic sensitivity', mystical experience, head injury and brain pathology.

The 'psychic' experiences of 17 students (sensitives) from the College of Psychic Studies were compared with those of 17 church-going control subjects, who were matched for age, sex, and approximate intellectual level. At interview, 67 items of information relating to the medical history, family history, 'psychic gifts', head injuries, and mystical experiences were obtained. The shortened WAIS, the Benton Visual Retention Test, with tests of both dominant (Wechsler Logical Memory) and non-dominant temporal lobe function (the Rey-Osterreith Test) were given. The results showed that the sensitive population contained more single or divorced people, and people who had sometime consulted a psychiatrist. They had experienced more head injuries and serious illnesses than the controls. Sixty-six per cent showed evidence of right hemisphere and right temporal lobe dysfunction and, of these, 35 per cent had poor visual memories. There was evidence to suggest that some 'psychic' experiences were associated with brain dysfunction. Despite an increased occurrence of head injury, no clear correlation with the onset of 'psychic' sensitivity was found. Mystical experiences showed a trend towards being related to non-dominant hemisphere dysfunction. Vagueness about the position of the sensitive's 'psychic helper' in physical space was also associated with non-dominant hemisphere dysfunction.

Adult↗
PubMed1985

An immunocytochemical study of malignant melanoma and its differential diagnosis from other malignant tumours.

A series of 41 fresh and 36 routinely processed malignant melanomas were immunostained with a panel of 12 monoclonal antibodies reactive against a range of epithelial, lymphoid, and melanoma associated antigens. The aim of the study was to determine whether this panel of antibodies would be useful in diagnostically difficult cases for differentiating melanomas from other tumours, particularly carcinomas and lymphomas. The results confirmed that most unequivocal malignant melanomas can be identified by positivity for S100 protein and for the antigen recognised by antibody NK1/C3, and by negativity for epithelial and lymphoid antigens. The incidence of melanomas expressing cytokeratin antigens was higher, however, particularly in cryostat sections than has previously been reported. It is therefore suggested that a panel of antibodies with more than one marker in each category should be used for identifying melanomas in clinical practice.

Antibodies, Monoclonal↗
PubMed1985

Lectin-gold cytochemistry reveals intercalated cell heterogeneity along rat kidney collecting ducts.

The lectin-gold technique was used to detect Helix pomatia and Dolichos biflorus lectin binding sites directly on semithin and thin sections of rat kidney collecting ducts. Intercalated cell apical plasma membranes and the membranes of apical cytoplasmic vesicles were heavily labeled in the cortex and outer stripe of the outer medulla but were negative or very weakly labeled in the inner stripe and inner medulla. In contrast, clear cell apical membranes were labeled along the entire length of the collecting duct. Double labeling of semithin cryostat sections with a specific antibody and lectin-gold complexes was used to demonstrate that the intercalated cells in all regions studied contained carbonic anhydrase, even though the lectin binding differed. These results indicate that, in terms of their glycocalyx composition, intercalated cells represent a heterogeneous population in different regions of the collecting duct.

Animals↗
PubMed1985

Lack of intramembranous particle clusters in collecting ducts of mice with nephrogenic diabetes insipidus.

We suggested previously, on the basis of indirect evidence, that in two strains of mice with nephrogenic defects of urinary concentration the deficiency arose from an inadequate rise in water permeability of the collecting duct system. In this study we tested the question further by assuming that the frequency of intramembranous particle (IMP) clusters seen by freeze-fracture can be used as a morphological marker of vasopressin-induced water permeability. Three genotypes of mice were studied: 1) DI +/+ Severe, with florid, vasopressin-resistant diabetes insipidus; 2) DI +/+ Nonsevere, with an intermediate deficiency of urinary concentration; and 3) normal, VII +/+ mice. In addition, we examined a group of DI +/+ Severe mice that had been injected with exogenous 1-desamino-8-D-arginine vasopressin (DDAVP) subcutaneously for 3 days. Since the results in this group did not differ from those in untreated DI +/+ Severe mice, all data for this genotype were combined. IMP clusters within luminal membranes of inner medullary collecting duct principal cells were quantified by freeze-fracture electron microscopy. Urinary osmolality and percentage of cells showing clusters were, respectively: 203 +/- 43 mosmol/kg H2O and 0% in DI +/+ Severe mice; 1,133 +/- 86 and 33 +/- 4 in DI +/+ Nonsevere mice; and 2,234 +/- 190 and 52 +/- 5 in VII +/+ animals. With the exception of one animal, there was no overlap of the data, which were significantly different from one another for each variable. We conclude that in DI +/+ Severe mice, both endogenous and exogenous vasopressin are unable to increase the water permeability of medullary collecting ducts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The cytoskeleton of Xenopus oocytes and its role in development.

Much is known about determinative events in early amphibian embryos, perhaps more than any other animal group. However, as yet, little attention has been focused on the cytoarchitecture of the oocyte, and the way in which this could regulate asymmetries in the egg, which in turn could lead to developmentally important interactions. The changing cytoarchitecture of the Xenopus oocyte is described with the emphasis on the following: -firstly the polarity; the oocyte is not radially symmetrical at early stages of oogenesis, but shows marked polarity. Secondly, several cytoskeletal elements change their distribution during oogenesis, and again during maturation to form a fertilizable egg. Thirdly, monoclonal antibody methods show that the oocyte develops several asymmetries which are retained in the egg and early embryo, and may be lineage related.

Animals↗
PubMed1985

Multicenter clinical evaluation of a hydrocolloid dressing for leg ulcers.

The need for a moist environment for the normal healing process led to the development of occlusive dressings. Results from this study support the contention that a moist wound environment is favorable to the healing process in humans as well as in animal models. Hydrocolloid dressings are effective in the practical daily management of chronic and even refractive ulcerations of the lower extremities and offer a time-saving treatment alternative with a high degree of patient acceptability.

Adolescent↗
PubMed1985

The effects and effectiveness of gamma-hydroxybutyrate in patients with narcolepsy.

Thirty patients with polysomnographically confirmed narcolepsy were treated with GHB (gamma-hydroxybutyrate) for up to 30 weeks. The number of nightly awakenings significantly decreased, while Stages 3 and 4 sleep substantially increased. The clinical symptoms of cataplexy, sleep paralysis, hypnogogic hallucinations, daily naps, and sleep attacks all showed significant improvements. Daytime sleepiness, while not completely eliminated, was controlled with lower doses of stimulant medication than patients were taking before the study. No patient developed tolerance to the drug, and no serious side effects were noted.

Adult↗
PubMed1985

Ultrastructural localization of glycocalyx domains in human kidney podocytes using the lectin-gold technique.

The lectin-gold technique was used to reveal Helix pomatia lectin (HPL)-binding sites in human kidney glomeruli. HPL-binding sites were associated mainly with podocyte foot process bases, and extended over the lamina rara externa of the glomerular basement membrane. In addition, kidneys from blood group A1 donors showed labeling of capillary endothelial cells and erythrocytes. After neuraminidase digestion of the sections prior to incubation with HPL-gold complexes, HPL-binding sites appeared on previously negative regions of the glomerulus. This increase in labeling was particularly striking at the level of the podocyte-free surface (adjacent to the urinary space) in all kidneys, and on capillary endothelial cells from donors of blood groups other than A1. These results demonstrate the existence of two distinct glycocalyx domains in human kidney podocytes, and show the application of the lectin-gold technique for the high resolution, ultrastructural detection and quantification of lectin-binding sites in human material.

Adult↗