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Biomedical subjects

F Wright

Publications and source records attributed to F Wright.

At least 73 records · Page 4Linked to original sources
PubMed1989

Responses by general practitioners in Avon to proposals for general practice in the white paper Working for Patients.

OBJECTIVE: To determine the views of Avon's general practitioners about the general practice proposals within the government's white paper Working for Patients. DESIGN: Postal questionnaire survey. SETTING: A county in south west England. SUBJECTS: All general practitioner principals (n = 537) under contract with Avon Family Practitioner Committee. MEASUREMENTS AND MAIN RESULTS: 492 doctors (92%) responded to the survey. More than three quarters of the respondents were opposed to the government's proposals on budgets for specific surgical procedures, prescribing, and diagnostic tests; and between 63% and 93% felt negative about advantages that might accrue from the proposals. Over three quarters of general practitioners were in favour of family practitioner committees monitoring work load, prescribing, and referrals. General practitioners in large, potentially budget holding practices held similar views to doctors in smaller practices. CONCLUSIONS: Avon's general practitioners substantially reject most of the government's proposals about general practice in the white paper Working for Patients.

Attitude of Health Personnel↗
PubMed1989

Androgen receptor in sexual differentiation.

Androgens play an essential role in sexual differentiation and their action is mediated by the androgen receptor (AR). The normal AR is a soluble protein, highly thermolabile, with a mol. wt of 90 kDa and a pI of 5.2 as determined by 2 dimensional (2D) gel electrophoresis. It is regulated by androgens in culture conditions but the physiological relevance of this regulation remains controversial. The presence of a functional AR is an absolute requirement for male sexual differentiation and its absence results in complete insensitivity. However, androgen insensitivity (complete or partial) can develop in the presence of a normal androgen binding capacity and there is no correlation between the clinical and the biochemical findings. A number of qualitative abnormalities have been described to explain the failure of androgen action in these cases: they all emphasize the extreme instability of the abnormal AR. It is difficult at the present time to determine whether these abnormalities result from structural mutations of the AR gene, transcriptional or post-transcriptional abnormalities. Further elucidation of these defects awaits for an antibody and/or a cDNA probe for the AR.

Animals↗
PubMed1989

Increased thromboxane biosynthesis during coronary thrombolysis. Evidence that platelet activation and thromboxane A2 modulate the response to tissue-type plasminogen activator in vivo.

Platelet activation is markedly increased during coronary thrombolysis and limits the response to thrombolytic therapy. A possible mediator of platelet activation in this setting is thromboxane (TX) A2, a potent platelet agonist formed in greatly increased amounts during coronary thrombolysis in man. To address this hypothesis, we examined the role of TXA2 in modulating the response to intravenous tissue-type plasminogen activator (t-PA) in a chronic canine model of coronary thrombosis. Reperfusion occurred in 60 +/- 5 minutes and was complicated by spontaneous reocclusion. The times to reperfusion and reocclusion were platelet-dependent. Consistent with a role for TXA2 in this process, TXA2 biosynthesis, determined a excretion of its enzymatic metabolite, 2,3-dinor-TXB2, was markedly increased during coronary thrombolysis. Furthermore, inhibition of TXA2 by aspirin, given alone or in combination with a TXA2/prostaglandin endoperoxide receptor antagonist, accelerated reperfusion and partly inhibited cyclic flow variations during reperfusion. The delay in reperfusion and reocclusion induced by TXA2 appeared to be mediated by platelet aggregation since the F(ab')2 fragment of 7E3, a monoclonal antibody to the platelet GPIIb/IIIa, also accelerated reperfusion and prevented reocclusion without altering TXA2 biosynthesis. These finding suggest that platelet aggregation limits the response to coronary thrombolysis and that platelet activation in this setting is partly TXA2-dependent.

Angiography↗
PubMed1989

The early natural history of subfoveal neovascular membranes in eyes with age-related macular degeneration.

During the course of age-related macular degeneration, the visual prognosis is abruptly changed when the presence of a subretinal neovascular membrane (SRNVM) is established by intravenous fluorescein angiography (IVFA). Patients who have been alerted to this condition may notice distortion on the Amsler grid and report within days of the onset of symptoms. Unfortunately most patients either do not notice the early changes in central vision or incorrectly attribute these symptoms to the development of cataracts and defer proper retinal evaluation for several months. We reviewed our records to determine the natural history of those SRNVMs which on initial IVFA either originated or extended into the foveal portion of the macula. Our results clearly indicate that treatment must be undertaken early in the course of this disease to maintain useful visual function for as long as possible.

Aged↗
PubMed1988

Codon usage patterns in Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Drosophila melanogaster and Homo sapiens; a review of the considerable within-species diversity.

The genetic code is degenerate, but alternative synonymous codons are generally not used with equal frequency. Since the pioneering work of Grantham's group it has been apparent that genes from one species often share similarities in codon frequency; under the "genome hypothesis" there is a species-specific pattern to codon usage. However, it has become clear that in most species there are also considerable differences among genes. Multivariate analyses have revealed that in each species so far examined there is a single major trend in codon usage among genes, usually from highly biased to more nearly even usage of synonymous codons. Thus, to represent the codon usage pattern of an organism it is not sufficient to sum over all genes as this conceals the underlying heterogeneity. Rather, it is necessary to describe the trend among genes seen in that species. We illustrate these trends for six species where codon usage has been examined in detail, by presenting the pooled codon usage for the 10% of genes at either end of the major trend. Closely-related organisms have similar patterns of codon usage, and so the six species in Table 1 are representative of wider groups. For example, with respect to codon usage, Salmonella typhimurium closely resembles E. coli, while all mammalian species so far examined (principally mouse, rat and cow) largely resemble humans.

Amino Acids↗
PubMed1988

"Silent" sites in Drosophila genes are not neutral: evidence of selection among synonymous codons.

The patterns of synonymous codon usage in 91 Drosophila melanogaster genes have been examined. Codon usage varies strikingly among genes. This variation is associated with differences in G+C content at silent sites, but (unlike the situation in mammalian genes) these differences are not correlated with variation in intron base composition and so are not easily explicable in terms of mutational biases. Instead, those genes with high G+C content at silent sites, resulting from a strong "preference" for a particular subset of the codons that are mostly C-ending, appear to be the more highly expressed genes. This suggests that G+C content is reduced in sequences where selective constraints are weaker, as indeed seen in a pseudogene. These and other data discussed are consistent with the effects of translational selection among synonymous codons, as seen in unicellular organisms. The existence of selective constraints on silent substitutions, which may vary in strength among genes, has implications for the use of silent molecular clocks.

Animals↗
PubMed1987

[Androgen insensitivity syndromes].

The syndromes of androgen resistance illustrate a special field of endocrinology, that is pathology of target-tissues. These syndromes are responsible for male pseudohermaphroditism and provoke in XY subjects, with a normal testicular androgen secretion, abnormalities in the phenotype with all the possibilities from an "idealistically" female phenotype in the testicular feminization syndrome to an almost normal male phenotype in the mildest forms of the incomplete syndrome. Understanding of these syndromes has strongly benefited of progress in biochemistry and molecular biology concerning the mechanism of action of androgens. On the other hand, understanding androgen mechanism expanded markedly from parallel clinical observation and biochemical investigation permitted by methodological progress: plasma hormones assays, 5 alpha-reductase and androgen receptor qualitative and quantitative determinations. The complete form of the testicular feminization syndrome seems to be due--in most cases--to an absence of the androgen receptor whereas the incomplete forms of the syndrome are related either to insufficient amount or qualitative alteration of the receptor or to a defect of 5 alpha-reductase, the key-enzyme which transforms testosterone to its active metabolite dihydrotestosterone in androgen target-cells. In some cases (approximately equal to 10%) the mechanism of androgen insensitivity could not be identified. The abnormality might be downstream the receptor at various possible steps = binding of the complex androgen-receptor to the chromatin, transcription or post-transcription process. These cases can be useful models for understanding the ultimate steps of the androgen mechanism of action.

Androgen-Insensitivity Syndrome↗
PubMed1986

Contribution of plasma androstenedione to 5 alpha-androstanediol glucuronide in women with idiopathic hirsutism.

To confirm that plasma delta 4 androstenedione (delta 4) is the main precursor for 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide (Adiol G) in patients with idiopathic hirsutism (IH), delta 4 was cutaneously applied to five normal women and five women with IH. Several parameters of androgen metabolism were assayed basally and throughout the studies. Those included plasma delta 4, testosterone, and dihydrotestosterone as well as urinary Adiol G and testosterone glucuronide excretion. Under basal conditions plasma testosterone, delta 4, and dihydrotestosterone did not differ significantly between the two groups of subjects. Urinary Adiol G excretion was significantly higher (P less than 0.01) in IH patients [123 +/- 36 (SE) micrograms/24 h] than in the normal women group (45 +/- 20 micrograms/24 h). After percutaneous administration of delta 4, plasma delta 4 increased in both groups by nearly 600% and there was a 300% increase in Adiol G excretion in IH patients (336 +/- 57 micrograms/24 h), whereas only a 50% increase occurred in normal women (65 +/- 17 micrograms/24 h). We postulate that plasma delta 4 may be the main precursor accounting for the increased production of urinary Adiol G in women with IH, in whom hirsutism may be due to a high 5 alpha-reductase activity. Indeed, 5 alpha-reductase as measured in vitro in pubic skin was significantly higher in hirsute patients (224 +/- 66 fmol/mg skin X h) than in normal women (45 +/- 15 fmol/mg skin X h).

Adolescent↗
PubMed1986

Androgen insensitivity in oligospermic men: a reappraisal.

Androgen insensitivity has been reported to be present in as many as 40% of patients with severe oligospermia. In order to evaluate further the role of androgen resistance in male infertility we studied 24 men with severe oligospermia. Plasma T and LH were measured by RIA and the T X LH product was calculated. Fibroblasts were grown from genital skin obtained during testicular biopsies and androgen receptor maximal binding capacity (BMAX) and affinity (KD) were measured in fibroblast monolayers. Pubic skin 5 alpha-reductase activity, an androgen-dependent enzyme, was measured in skin homogenates. Plasma T values were in the upper normal range [7.0 +/- 1.7 (SEM) ng ml-1] whereas the T X LH product was high (greater than 50) in only six patients. Mean BMAX and KD values for the androgen receptor were normal [BMAX: 788 +/- 259 fmol mg DNA-1 (patients, n = 20), 726 +/- 227 (normal men, n = 20), and KD: 0.27 +/- 0.24 (patients, n = 20), 0.18 +/- 0.09 (normal men, n = 15), respectively]. However, four men had supranormal KD values. The mean BMAX was also normal when the group of men with sperm densities below 10(6) per ejaculate was considered separately. Public skin 5 alpha-reductase activity was normal in all but four patients (patients: 177.1 +/- 91 fmol/mg skin/h, n = 30, normal men: 210 +/- 45, n = 20 patients). In conclusion, androgen receptor BMAX levels were normal in all patients studied, regardless of the sperm density and the T X LH product. Pubic skin 5 alpha-reductase activity was also normal in all but four patients. In these four patients, a qualitative defect of the androgen receptor cannot be excluded. In this group of patients with severe oligospermia, infertility did not seem to be related to quantitative abnormality of the androgen receptor as was previously reported.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1985

Familial male pseudohermaphroditism with gynaecomastia due to 17 beta-hydroxysteroid dehydrogenase deficiency. A report of 3 cases.

Three sisters with male pseudohermaphroditism due to 17 beta-hydroxysteroid dehydrogenase deficiency are described. On the basis of a 46 XY karyotype and female phenotype all subjects were thought to have the testicular feminization syndrome. At puberty the two older patients developed signs of virilization and gynaecomastia. In these patients the plasma androstenedione level was 4-5 times higher than normal, whilst the plasma testosterone level was low compared to the normal range and, under basal conditions, their plasma androstenedione to testosterone ratio was 20-25 times higher than normal. Interestingly, in the third, prepubertal case, the basal androstenedione to testosterone ratio was normal but became six times higher than normal after hCG stimulation. These data support the diagnosis of male pseudohermaphroditism due to 17 beta-hydroxysteroid dehydrogenase deficiency and underline the diagnostic value of the hCG stimulation test prepubertally.

17-Hydroxysteroid Dehydrogenases↗
PubMed1985

Decreased urinary 5 alpha-androstane-3 alpha,17 beta-diol glucuronide excretion in patients with benign prostatic hyperplasia.

Urinary testosterone and 3 alpha-androstanediol (3 alpha diol G) glucuronides together with plasma testosterone, 5 alpha-dihydrotestosterone (DHT), and delta 4-androstenedione (delta 4) were measured in 43 normal young men (18-36 yr old), 23 elderly men without clinically evident prostatic pathology (54-89 yr old), 68 elderly men with benign prostatic hyperplasia (BPH group; 54-91 yr old), and 26 elderly men with well differentiated cancer of the prostate (K group; 63-97 yr old). Plasma testosterone decreased slightly with age in all 3 elderly groups (from 591 to 438, 479, and 444 ng/100 ml, respectively). Plasma DHT, on the contrary, was significantly (P less than 0.01) higher in the BPH group than in the other three groups (68 vs. 30, 37, and 32 ng/100 ml, respectively). Plasma delta 4 was significantly lower (P less than 0.01) in the elderly K group than in all other groups (59 vs. 109, 83, and 78 ng/100 ml, respectively). Urinary testosterone glucuronide decreased with age in all 3 elderly groups (from 109 to 55, 38, and 44 micrograms/24 h, respectively) as a result of decreased androgen production rates with age. All 3 elderly groups also had decreased urinary 3 alpha diol G, from 194 to 123, 55, and 118 micrograms/24 h, respectively. The group of elderly patients with BPH had the lowest mean urinary 3 alpha diol G excretion together with the highest mean plasma DHT. This low urinary 3 alpha diol G excretion, which reflects a decrease in both androgen production and DHT metabolism, suggests a decrease in 3 alpha-hydroxysteroid dehydrogenase activity, which, in turn, could explain the increased DHT availability and tissue retention in most target organs. Moreover, the extent of these modifications in androgen metabolism specific to the BPH condition raises the question of an overall alteration of androgen metabolism in patients with BPH which could be the cause of the disease.

Adenocarcinoma↗