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Biomedical subjects

G Evans

Publications and source records attributed to G Evans.

At least 253 records · Page 14Linked to original sources
PubMed1987

Metabolism of glucose into glutamate via the hexose monophosphate shunt and its inhibition by 6-aminonicotinamide in rat brain in vivo.

The treatment of rats for 4 h with 6-aminonicotinamide (60 mg kg-1) resulted in an 180-fold increase in the concentration of 6-phosphogluconate in their brains; glucose increased 2.6-fold and glucose 6-phosphate, 1.7-fold. Moreover, lactate decreased by 20%, glutamate by 8% and gamma-aminobutyrate by 12%, and aspartate increased by 10%. No significant changes were found in glutamine and citrate. In blood, 6-phosphogluconate increased 5-fold; glucose, 1.4-fold and glucose 6-phosphate, 1.8-fold. The metabolism of glucose in the rat brain, via both the Embden-Meyerhof pathway and the hexose monophosphate shunt, was investigated by injecting [U-14C]glucose or [2-14C]glucose, and that via the hexose monophosphate shunt alone by injecting [3,4-14C]glucose. The total radioactive yield of amino acids in the rat brain was 5.63 mumol at 20 min after injection of [U-14C]glucose, or 5.82 mumol after injection of [2-14C]glucose; by contrast, it was 0.62 mumol after injection of [3,4-14C]glucose. The treatment of rats with 6-aminonicotinamide showed significant decreases in these values, owing to decreases in the radioactive yields of glutamate, glutamine, aspartate, gamma-aminobutyrate, and alanine+glycine+serine. Glutamate isolated from the brain contained approximately 43% of its radioactivity in carbon 1 after injection of [3,4-14C]glucose, in contrast to 13% and 18% after injection of [U-14C]glucose and [2-14C]glucose, respectively, in both the control and treated rats. The calculations based on these findings showed that approximately 69% of the 14C-labelled glutamate was formed from [14C]acetyl coenzyme A (acetyl CoA) and the residual 31% by 14CO2 fixation of pyruvate after injection of [3,4-14C]glucose in both control and treated rats. The results gave direct evidence that glutamate and gamma-aminobutyrate in the brain were formed by metabolism of glucose via the hexose monophosphate shunt as well as via the Embden-Meyerhof pathway. From the radioactive yields of glutamate formed via [14C]acetyl CoA it was estimated that approximately 7.8% of the total glucose utilized was channelled via the hexose monophosphate shunt. Assuming that [14C]glutamate formed by carbon-dioxide fixation of pyruvate was also dependent on the metabolism of glucose through the hexose monophosphate shunt, the estimated value was approximately 9.5% of the total glucose converted into glutamate. The results of the present investigation, taken in conjunction with other findings, suggest that the utilization of glucose via the hexose monophosphate shunt is functionally important in the rat brain.

6-Aminonicotinamide↗
PubMed1987

Detection of Pneumocystis carinii by fluorescent-antibody stain using a combination of three monoclonal antibodies.

A combination of three monoclonal antibodies, two prepared against human and one against rat Pneumocystis carinii, was used in an indirect fluorescent-antibody stain (IFA) to diagnose P. carinii in both bronchoalveolar lavage and lung biopsy specimens. This combination of monoclonal antibodies was specific for P. carinii and yielded bright fluorescence of both P. carinii cysts and trophozoites. A total of 126 specimens from 93 patients were stained for P. carinii by a toluidine blue O stain and the monoclonal IFA. Forty-five (35.7%) of these were positive for P. carinii by toluidine blue O, and 43 (34.1%) were positive by IFA. There was 98.4% agreement between both methods, with no false-positive and two false-negative occurrences by IFA. An IFA procedure with monoclonal antibodies such as those used in these studies can provide a simple, fast, and sensitive method for diagnosing P. carinii pneumonia by microbiology laboratories.

Acquired Immunodeficiency Syndrome↗
PubMed1986

A comparison of conservative treatment and silicone replacement arthroplasty in Kienböck's disease.

Two forms of treatment of Kienböck's disease were compared in a total of thirty-seven wrists. Sixteen had been treated conservatively and were followed-up for an average of twenty years. Twenty-one had undergone silicone replacement arthroplasty an average of five years prior to review. Clinical results of conservative treatment showed four (25%) good, six (37.5%) fair and six (37.5%) with a poor result. Radiological deterioration was seen in only a quarter of cases. After silicone replacement there were nine (43%) good and seven (33%) fair. Five (24%) cases had a very poor result associated with dislocation of the prosthesis but design improvements have made this less frequent. Radiological abnormalities were noted in more than half of cases treated by silicone replacement arthroplasty. These included carpal collapse, scapho-lunate diastasis and generalised degenerative changes in the carpus. There were two cases with cyst formation in the capitate which closely resembled previous reports of silicone synovitis.

Adolescent↗
PubMed1986

A monoclonal antibody to a cell wall component of Candida albicans.

A heterologous fusion between mouse myeloma cells and rat lymphocytes resulted in the isolation of a rat immunoglobulin M monoclonal antibody with both agglutinating and precipitating activity. Indirect immunofluorescence and direct agglutination tests showed that the corresponding antigen was present in the cell wall of the three Candida species considered to be the most pathogenic, C. albicans, C. tropicalis, and C. glabrata, and also in the cell wall of C. guilliermondii. The antigen appeared to be predominantly polysaccharide in nature. Precipitation by counterimmunoelectrophoresis suggested that the epitope is shared by at least two separate molecules with different electrophoretic mobilities. Presence of this epitope varied from strain to strain within a given species and may be related to the morphological stage in the cell cycle. Antigen was shown to be present in the cytoplasm, in the periplasmic space, and at the cell surface of C. albicans. Indirect immunofluorescence also suggested that antigen is excreted from the cell.

Agglutination↗
PubMed1986

Studies of the effect of 1,25-dihydroxycholecalciferol on the proliferation and differentiation of the human promyelocytic leukaemia cell line HL-60.

Treatment of the human promyelocytic leukaemia cell line HL-60 with 1,25(OH)2D3, the active metabolite of vitamin D3, led to a dose- and time-dependent inhibition of growth and 3H-TdR incorporation at the population level. A similar effect was noted at the single cell level in clonogenic assays and autoradiographic experiments. Flow cytometry indicated that there was an arrest of cells in the G0/G1 phase of the cell cycle. Parallel to the loss of proliferative capacity 1,25(OH)2D3 induced differentiation of HL-60 into monocyte/macrophages as measured by the enzyme NSE and the macrophage membrane antigen recognised by the monoclonal antibody EB11 as well as by morphological changes. These findings reinforce the concept of concordant induction of differentiation and loss of proliferative capacity and demonstrate that the latter occurs not only at the population level but also at the single cell level in this system. In limiting dilution assays in liquid culture there was evidence for positive interactions between HL-60 cells as untreated cells gave less colonies at low dilutions than would have been expected by Poisson statistical analysis. In the presence of 10(-8) M 1,25(OH)2D3 more complex growth parameters were noted indicating the involvement of both positive and negative cellular interactions.

Calcitriol↗
PubMed1985

A microcomputer-based method for physiologically interpretable measurement of the rewarding efficacy of brain stimulation.

Determination of the function relating rate of pressing to the number of pulses in a train of fixed duration (the rate-frequency function) yields a physiologically interpretable measure of changes in the rewarding efficacy of the stimulation, because the number of action potentials in the reward-relevant first stage axons is directly proportional to the number of pulses in the train. We describe a system, based on a low cost microcomputer, which permits determination of 16-data-point rate-frequency functions in 4-6 animals simultaneously in less than 10 minutes. We give an empirical and theoretical justification for using the curve-shift measurement procedure in drug and lesion work, where the experimental treatments must be presumed to have substantial effects on performance factors.

Animals↗
PubMed1984

Blood thiamine and thiamine phosphate ester concentrations in alcoholic and non-alcoholic liver diseases.

Thiamine state was investigated in patients with alcoholic liver disease, patients with various non-alcoholic liver diseases, and controls using a direct technique (thiochrome assay) to measure thiamine, thiamine monophospate, and the active coenzyme thiamine pyrophosphate in whole blood after isolating the fractions by ion exchange chromatography. Overall nutrition was similar in all groups as assessed by anthropometry, and no patient had clinical evidence of thiamine deficiency. There was no significant difference among the groups in mean concentration of any form of thiamine. The scatter was much greater in patients with alcoholic liver disease but only 8.7% had biochemical thiamine deficiency (defined as a blood concentration of the active coenzyme greater than 2 SD below the mean control value). An unexpected finding was of abnormally high total thiamine concentrations (greater than 2 SD above the mean control value) in 17.4% of patients with alcoholic liver disease, the highest concentrations being found in two patients with severe alcoholic hepatitis and cirrhosis. The ratio of phosphorylated to unphosphorylated thiamine was calculated as an index of phosphorylation and, although the mean did not differ significantly among the groups, the range was greatest in alcoholic liver disease. The lowest ratios occurred in the two patients with severe alcoholic hepatitis, but neither had evidence of thiamine pyrophosphate deficiency. Contrary to studies using indirect assay techniques, these results suggest that thiamine deficiency is unusual in well nourished patients with alcoholic liver disease. The new finding of unexpectedly high thiamine concentrations in some patients may be due to abnormalities of hepatic storage or release in liver disease, particularly in severe alcoholic hepatitis. There was no convincing evidence of impaired thiamine phosphorylation in any patients with liver disease. Conclusions from studies using indirect assays on the prevalence and mechanisms of thiamine deficiency in liver diseases may not be valid.

Adult↗
PubMed1984

Introducing a general prompting and recording system: its effect on client and staff behavior in an institutional ward.

This study describes the evaluation of a "low-key" approach to training staff in procedures designed to increase the degree of independence of mentally handicapped people. Training leaflets describing a method of giving graded prompts to residents were distributed to staff on a hospital ward. Subsequently, checklists were introduced on which staff recorded the amount of assistance they gave residents in a variety of self-help skills. Time-sampling observations provided data on residents' engagement in such skills and their degree of independence. The amount of staff prompting was not affected by the interventions. The introduction of each intervention increased the frequency with which staff allowed residents to do tasks independently, but the effect did not persist. The amount of residents' independent activity increased prior to the introduction of the leaflets, remained stable after their introduction, and increased further when checklists were introduced. These results are discussed in terms of the training materials used and the role of supervisors in staff training.

Activities of Daily Living↗
PubMed1984

Androgen inhibition of FSH-stimulated progesterone production by granulosa cells of prepubertal pigs.

Androgens have been reported to stimulate progesterone production by granulosa cells of several species, and to act synergistically with FSH in stimulation of progesterone accumulation by rat granulosa cells. Studies were undertaken to examine the effect of androgens on FSH-stimulated progesterone production in culture by granulosa cells derived from prepubertal pig ovaries. When included in 24-h culture with FSH, both androstenedione and testosterone caused a reduction in progesterone accumulation, but dihydrotestosterone and androsterone did not. Granulosa cells were cultured for 24 h with FSH and [14C]progesterone with or without testosterone; testosterone did not affect the rate of overall metabolism of [14C]progesterone and it was therefore concluded that testosterone inhibited progesterone synthesis, rather than enhancing its catabolism. 17 beta-Estradiol also inhibited FSH-stimulated progesterone accumulation. To determine whether the action of testosterone was mediated by conversion to estradiol, granulosa cells were cultured with FSH and testosterone with or without an aromatase inhibitor (4-acetoxy-androstenedione). The aromatase inhibitor failed to prevent the testosterone-induced reduction in progesterone accumulation, although it markedly inhibited estradiol accumulation. These results indicate that theca-derived androgens can inhibit FSH-stimulated progesterone production by granulosa cells in the prepubertal pig, independently of estradiol.

Androgens↗
PubMed1984

Reduction of sperm transport in ewes by superovulation treatments.

Oestrus was synchronized in ewes by (a) withdrawal of an intravaginal progestagen sponge after 12 days or (b) injection of PGF-2 alpha on Day 11 of the oestrous cycle. In addition, ewes were treated with (a) no hormone, (b) 1500 i.u. PMSG 48 h before sponge removal or PG injection, or (c) 24 mg porcine pituitary FSH in multiple injections commencing 48 h before sponge removal or PG injection, in a 2 X 3 factorial design. Ewes were inseminated with 0.2 ml fresh undiluted semen into the neck of the cervix 48 h after sponge removal or PG injection. Normally cyclic ewes were similarly inseminated within 12 h of observed standing oestrus. At 24 h after insemination one uterine horn and one oviduct were flushed for recovery of spermatozoa and ova. When compared with naturally cyclic ewes, PG synchronization resulted in a marked reduction in the numbers of spermatozoa recovered (P less than 0.05), and sponge synchronization led to a small, non-significant, reduction. Within the synchronized ewes, PMSG and FSH resulted in an equivalent superovulatory response, but there was a marked reduction in sperm recovery when compared with unstimulated animals (P less than 0.01), with the greatest reduction attributable to PMSG treatment. Spermatozoa were recovered from fewer ewes treated with PMSG than with FSH (P less than 0.05). Despite the observed impairment of sperm transport, a high fertilization rate was observed within each group and there were no differences between treatments.

Animals↗
PubMed1984

Reduction in fertilization rate in vitro of oocytes from immature rats induced to superovulate.

Immature female rats (65-70 g) were injected with 4 i.u. PMSG (control) or superovulated with 8, 16, 24 or 40 i.u. PMSG and were killed 68-70 h later, shortly after the normally expected time of ovulation. Oocytes were recovered from the oviducts and inseminated in vitro. After 18 h oocytes were counted and classed as degenerate or 1-cell. Mean numbers of oocytes recovered were 8.2, 26.8, 50.7, 38.7 and 38.5 for each dose of PMSG respectively. The 1-cell oocytes were assessed for sperm penetration of the vitellus and pronuclear development and later for development to the 2-cell stage. Fertilization rates at the 1-cell stage were 76.8, 62.9, 53.6, 52.2 and 44.5% for the rats treated with 4, 8, 16, 24 and 40 i.u. respectively (P less than 0.001). On average, 91% of fertilized 1-cell oocytes developed to the 2-cell stage and there was no difference between treatments in this respect. Significantly more of the unfertilized oocytes were degenerate in the rats treated with 24 or 40 i.u. PMSG (34.6 and 50.4%) than in those treated with 4, 8 or 16 i.u. (7.0, 13.9, and 7.5%) (P less than 0.001). When rats were killed 63-65 h after PMSG, just before the normally expected time of ovulation, some of the rats treated with 24 and 40 i.u. PMSG had partly ovulated: of the oocytes recovered from the oviducts only 12.3% (24 i.u.) and 26.6% (40 i.u.) were fertilized. These results demonstrate that proportionately fewer oocytes recovered from superovulated rats are competent to undergo in-vitro fertilization than are oocytes recovered from control rats.

Animals↗
PubMed1984

Intrauterine insemination enhances fertility of frozen semen in superovulated ewes.

Superovulated ewes were inseminated with fresh or frozen semen in a factorial experiment which compared two techniques of artificial insemination; i.e. conventional cervical deposition and intrauterine deposition at laparoscopy. Similar fertilization rates resulted from insemination with fresh semen at cervical (81% of ova from 11/11 ewes) and intrauterine (83% of ova from 10/12 ewes) sites. These results approached those observed in a naturally-mated group (95% of ova from 5/5 ewes). In ewes inseminated with frozen semen, fertilization rate was markedly reduced (P less than 0.05) after cervical insemination (11% of ova from 3/11 ewes) and partly restored (P less than 0.05) after intrauterine insemination (50% of ova from 8/11 ewes).

Animals↗