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Biomedical subjects

G Williams

Publications and source records attributed to G Williams.

At least 523 records · Page 29Linked to original sources
PubMed1989

Penile response to intracavernosal vasoactive intestinal polypeptide alone and in combination with other vasoactive agents.

Intracavernosally injected vasoactive intestinal polypeptide (VIP) (2 micrograms and 4 micrograms) resulted in penile tumescence even in men with predominantly organic impotence. Papaverine and phentolamine were successful in inducing erections in all subjects studied but the addition of VIP to this combination improved the erectile response further. A combination of papaverine and VIP produced penile rigidity similar to that with papaverine and phentolamine. While intracavernosal VIP alone produced disappointing penile responses, its combination with papaverine potentiated the response to this drug, probably by increasing venous outflow resistance.

Adult↗
PubMed1989

Histamine and duodenal ulceration in renal transplant recipients.

Six of 25 renal transplant recipients had a duodenal ulcer at endoscopy. Histamine concentration and the activity of histamine methyltransferase, the degrading enzyme of histamine, were measured in gastric mucosal biopsies obtained at endoscopy and compared with patients with duodenal ulcer but not undergoing transplant and with patients with an apparently normal stomach and duodenum. Histamine concentrations in the corpus (no ulcer, median: 151 nmol/g; DU, median: 122 nmol/g) and in the antrum (no ulcer, median: 118 nmol/g; with DU, median: 113 nmol/g) of renal transplant patients, irrespective of ulcer diagnosis, and in patients with a chronic duodenal ulcer (median corpus histamine: 137 nmol/g and median antral histamine: 126 nmol/g) were not different from one another but significantly lower than the corresponding values in normal subjects (median corpus histamine: 241 nmol/g, p less than 0.01, and median antral histamine: 178 nmol/g, p less than 0.05). Histamine concentration in the corpus was significantly higher than in the antrum in all three groups of patients (p less than 0.05). There were no significant differences in histamine methyltransferase activity in any of the groups studied. Mucosal histamine and histamine methyltransferase activity were significantly correlated in the corpus (p less than 0.05) and antrum (p less than 0.02). Plasma concentration of histamine after transplant was higher in the patients who subsequently were discovered to have a duodenal ulcer (p less than 0.05). The occurrence of ulcer after transplantation was not related to the serum creatinine level. The uniform depletion of gastric histamine and increase in circulatory histamine after renal transplantation may be a factor in the pathogenesis of duodenal ulcer disease in this clinical situation.

Adult↗
PubMed1989

Two-monthly depot gonadotropin releasing hormone agonist (buserelin) for treatment of prostatic cancer.

The agonist analogues of gonadotropin-releasing hormone provide an alternate medical therapy for prostatic cancer. Current methods of administration of these analogues by daily injection or nasal spray is sub-optimal in an elderly population. We have performed a pharmacological and endocrine evaluation of a new depot preparation of one such analogue, buserelin, active for 2 months. Thirty patients with advanced symptomatic prostatic cancer were treated. Serum testosterone was suppressed for the duration of treatment which ranged up to 14 months. The release characteristics of the depot were consistent and showed minimal variation between patients. This 2-month preparation of buserelin offers and advantage to the patient with prostatic cancer, over current treatment regimens.

Adult↗
PubMed1989

Increased neuropeptide Y concentrations in specific hypothalamic regions of streptozocin-induced diabetic rats.

Untreated streptozocin-induced diabetic (STZ-D) rats have previously been shown to have significantly increased hypothalamic concentrations of neuropeptide Y (NPY), a regulatory peptide that powerfully stimulates eating and drinking and inhibits secretion of several pituitary hormones when injected centrally. Tissue NPY concentrations have been measured by radioimmunoassay in selected hypothalamic regions microdissected from fresh, unfixed brain slices to localize diabetes-associated NPY changes precisely within the hypothalamus. Significant (35-200%) increases in NPY concentrations (P less than .01 vs. matched nondiabetic controls) were found in specific hypothalamic regions between 3 and 14 wk after induction of STZ-D. These regions included the paraventricular and ventromedial nuclei and lateral hypothalamic area, major appetite-regulating areas that are sensitive to the hyperphagic and polydipsic actions of NPY. Increased NPYergic activity in these areas may, at least partly, drive the increased eating and drinking characteristic of STZ-D. NPY concentrations were also increased in the arcuate nucleus and medial preoptic area. Because both of these regions are important in modulating pituitary hormone secretion, local NPY increases may be involved in the impaired secretion of luteinizing hormone, thyroid-stimulating hormone, growth hormone, and prolactin known to occur in STZ-D. Our finding of NPY increases in specific hypothalamic nuclei associated with functional changes found in STZ-D suggests that this peptide may have a role in the altered metabolic and neuroendocrine regulation of the syndrome.

Animals↗
PubMed1989

The shock of the new.

Explore the source record for details and available documents.

Attitude of Health Personnel↗
PubMed1988

Isolation and characterisation of GLP-1 7-36 amide from rat intestine. Elevated levels in diabetic rats.

Glucagon-like peptide-1 (GLP-1) was purified to homogeneity by HPLC and anion-exchange chromatography. A molecular mass of 3297.4 Da was obtained by FAB mass spectrometry which corresponded exactly to GLP-1 7-36 NH2, providing evidence that amidation occurs at an arginine residue during the post-translational processing of GLP-1. The distribution of GLP-1 7-36 NH2-like immunoreactivity (GLP-1 7-36 NH2 IR) was determined in the rat gastrointestinal tract. Highest concentrations were found in terminal ileum and colon. Streptozocin-induced diabetic rats, who showed a significant increase in food intake, had a significant increase of GLP-1 7-36 NH2 IR in the colon.

Animals↗
PubMed1988

Ion binding to cytochrome c.

This paper is a further study of ion binding to protein surfaces and builds on the studies of the binding of [Cr(CN)6]3- and [Fe(edta)(H2O)]- previously reported [Williams et al. (1982) FEBS Lett. 15, 293-299; Eley et al. (1982) Eur. J. Biochem. 124, 295-303]. In the present paper the binding of polyaminocarboxylate complexes of gadolinium have been studied. Eight ion-binding sites have been identified on the surface of cytochrome c. These exhibit different binding specificities which, in some cases, are not full understood. However it is clear that simple outer-sphere interactions are not the sole determining factor for the association of metal ion complexes with proteins. The NMR paramagnetic difference spectrum method has been shown to be good at locating binding sites and revealing qualitative differences in their relative affinities for a range of complex types. However the use of relaxation probes is not a good method for the quantitative determination of binding constants; for this, isostructural shift probes must be sought.

Amino Acids↗
PubMed1988

Variability in vibration perception threshold among sites: a potential source of error in biothesiometry.

Vibration perception threshold was measured with a biothesiometer by a single observer at both medial malleoli and both big toes in 110 diabetic patients aged 15-65 selected at random and in 64 non-diabetic subjects aged 20-65. The vibration perception threshold showed appreciable individual variation both between contralateral sites and between ipsilateral sites, differing by at least 30% between the big toes in 26 (24%) of the diabetic patients and 16 (25%) of the non-diabetic group. Variability between sites was significantly greater in the diabetics than the normal subjects. The vibration perception threshold exceeded published normal values at one or more sites in 22 of the diabetic patients but at all four sites in only four. The wide variability in vibration perception threshold among sites may be due to the tissue characteristics locally and, in diabetic patients, possibly to asymmetric neuropathy. Biothesiometer readings at single or unilateral sites may be unrepresentative or misleading.

Adolescent↗
PubMed1988

A pharmacological analysis of the rat spinal cord serotonin (5-HT) autoreceptor.

The pharmacological characteristics of the presynaptic 5-HT receptor associated with the modulation of 5-HT release were investigated in a preparation of rat spinal cord synaptosomes (nerve terminals) superfused with a Tris-buffered Krebs solution containing fluoxetine (1 microM). The 5-HT receptor agonists serotonin (1-100 nM), lysergic acid diethylamide (10 nM-1 microM) and the 5-HT1B receptor agonists 1-(m-trifluoromethylphenyl)piperazine (100 nM-1 microM) and 1-(m-chlorophenyl) piperazine (100 nM-3 microM) concentration dependently decreased [3H]5-HT release, while 8-hydroxy-2-(di-n-propylamino)tetralin, a selective 5-HT1A receptor agonist, was inactive. The actions of the effective agonists were reversed by quipazine, an antagonist with high affinity for 5-HT1B binding sites, but not by spiperone, a 5-HT1A receptor antagonist. Furthermore, mesulergine, a 5-HT1C receptor antagonist was ineffective in reversing the action of 5-HT on [3H]5-HT release. These data indicate that the rat spinal cord nerve terminal autoreceptor has characteristics similar to the 5-HT1B binding site.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

The construction of computer tomographic phantoms and their application in radiology and radiation protection.

In order to assess human organ doses for risk estimates under natural and man made radiation exposure conditions, human phantoms have to be used. As an improvement to the mathematical anthropomorphic phantoms, a new family of phantoms is proposed, constructed from computer tomographic (CT) data. A technique is developed which allows any physical phantom to be converted into computer files to be used for several applications. The new human phantoms present advantages towards the location and shape of the organs, in particular the hard bone and bone marrow. The CT phantoms were used to construct three dimensional images of high resolution; some examples are given and their potential is discussed. The use of CT phantoms is also demonstrated to assess accurately the proportion of bone marrow in the skeleton. Finally, the use of CT phantoms for Monte Carlo (MC) calculations of doses resulting from various photon exposures in radiology and radiation protection is discussed.

Bone Marrow↗