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Biomedical subjects

G Hart

Publications and source records attributed to G Hart.

At least 145 records · Page 8Linked to original sources
PubMed1989

Needle-exchange in central London: operating philosophy and communication strategies.

Despite a large number of needle-exchange schemes in the U.K., there are few accounts of how particular agencies attract injecting drug users. This paper describes a busy scheme in London, the take-up of services by clients, and the operating philosophy of the staff. From November 1987 to October 1988 The Exchange saw a mean of 257 clients per month, making an average three visits per client each month. An average of 8,950 needles and syringes were dispensed and 6,918 returned monthly, giving an average return rate of 77%. The Exchange also served as a referral agency to clients; 533 referrals were made, 63.4% of which were to drug and non-medical services, 36.6% to health services, and 9.2% to HIV services. To account for the take-up of services the paper describes The Exchange's open access policy, the staff's communication strategies and their adoption of the philosophy of harm-minimization in relation to injecting drug use. It is argued that these must be seen as integral to needle-exchange if it is to succeed as a comprehensive service.

Adolescent↗
PubMed1989

Modulation of lentivirus replication by antibodies. Non-neutralizing antibodies to caprine arthritis-encephalitis virus enhance early stages of infection in macrophages, but do not cause increased production of virions.

Non-neutralizing antibodies to caprine arthritis-encephalitis virus (CAEV) enhance the early stages of the virus life cycle but do not potentiate enhanced production of virus particles by macrophages. In primary macrophages used for these studies, there was enhancement in binding, internalization and uncoating of virus pretreated with non-neutralizing sera in comparison to virus pretreated with a non-immune serum. However, this did not lead to enhanced production of virus particles. Failure of non-neutralizing sera to inactivate CAEV may be due in part to low avidity of the antibodies for the virus particles which contain sialic acids on their envelopes, because desialylation of the particles made them neutralizable. The non-neutralizing antibodies probably bound to most of the native virus particles which were then internalized via Fc receptor-mediated endocytosis and degraded. Sialylated particles that failed to bind antibodies probably caused the infection. Thus there was no true enhancement of infection. The previously reported increase in severity of lesions in animals immunized with inactivated CAEV particles prior to challenge with live virus suggested enhancement of infection but in the light of our finding this may have been caused by factors other than an increase in production in the number of infectious virus particles.

Animals↗
PubMed1989

Heterosexual sexual behaviour in a sample of homosexually active men.

Three hundred and fifty six homosexually active men were recruited in 1988 for a study by interview of sexual behaviour. Thirty two per cent had homosexual passive anal sex in the previous month and 60% in the year before interview. Anal sex and unprotected anal sex were more common with regular than non-regular partners. Heterosexual sex was reported by 4% of men in the last month and 10% for the last year. Sixteen per cent of heterosexually active men reported anal sex with a female partner. Fewer men described themselves as bisexual than would be expected from the sample's recent sexual histories. More attention is needed to the definition and measurement of "bisexuality" to understand its role in HIV transmission.

Adolescent↗
PubMed1989

Growth hormone-releasing factor-induced growth hormone secretion from perifused rat anterior pituitary cells: lack of influence of glucose concentration, and normal responses in pituitary cells from diabetic animals.

The mechanism responsible for the suppression of GH secretion in hyperglycaemia and hypoglycaemia in rats has been investigated using perifusion of anterior pituitary cells. When perifused with Krebs-Ringer bicarbonate containing normal (5 mmol/l), high (20 mmol/l) and low (1 mmol/l) concentrations of glucose, the GH responses to GH-releasing factor (GRF) were 85 +/- 5, 85.5 +/- 5.4 and 89 +/- 3.0 (S.E.M.)% respectively compared with the initial response to GRF at 5 mmol/l in each column. The mean GH response to GRF from anterior pituitary cells of normal rats was 6.58 +/- 0.88 micrograms/three pituitaries, which was not statistically different form that of cells from rats with streptozotocin-induced diabetes (5.40 +/- 0.68 micrograms/three pituitaries). It is concluded that GH suppression in diabetic rats and during hypoglycaemia is not mediated by changes in the GH response to GRF.

Animals↗
PubMed1989

Foramen magnum decompression in an infant with homozygous achondroplasia. Case report.

Homozygous achondroplasia is a rare yet distinct clinical entity. Most infants succumb to an early death as a result of respiratory compromise due to upper airway obstruction, thoracic cage deformity, and/or cervicomedullary compression. The successful cervicomedullary decompression of a 16-week-old infant with homozygous achondroplasia is described. This report suggests that homozygous achondroplasia is not universally fatal and that these infants are potentially viable if managed by aggressive respiratory and surgical measures.

Achondroplasia↗
PubMed1988

Patterns of selective involvement of thigh muscles in neuromuscular disease.

In 14 patients with limb girdle muscular dystrophy, polymyositis, and type 3 spinal muscular atrophy, CT scans of the thigh muscles were correlated with single fiber EMG studies in vastus lateralis, semimembranosus and biceps femoris muscles. There was a relation between the extent of CT scan abnormality and increased fiber density in the three muscles studied, except in the most severely affected muscles in which in some muscles the fiber density values were lower than expected. These results were independent of the underlying pathology. Correlative CT/SFEMG studies provide insights into the pattern of selective involvement of certain muscles in neuromuscular disorders.

Adult↗
PubMed1988

An analysis of spontaneous and chemotherapy-associated changes in skeletal osteosarcomas.

Microscopically assessed changes observed in large sections of osteosarcomas from patients who had undergone pre-operative chemotherapy (PCT) (n = 22), or no chemotherapy (n = 22), were examined either quantitatively, semiquantitatively, or qualitatively. Eight tumour characteristics were associated with the treatment mode by way of a stepwise logistic analysis. Minimal amount of viable tumour tissue (less than 10 per cent) and strong fibroblastic proliferation were each proved to be associated with PCT. These two variables in combination indicated a good response to PCT. The discrimination between PCT and non-PCT patients based on statistical analysis was superior to discrimination based on 'overall impression'.

Adolescent↗
PubMed1987

Intravenous urography as a prognostic indicator in vesical carcinoma.

A retrospective analysis of 1378 cases of urinary bladder tumor, showed that unilateral or bilateral ureteric obstruction seen on an intravenous urogram at presentation, was significantly associated with both decreased overall survival and tumor-free interval. A tumor shadow shown on standard projections did not correlate with survival. At 24 months only 35% of the ureteric obstruction group were tumor-free as compared with 65% of the unobstructed group. Survival at 5 years was 27% in the obstructed ureter group and 73% in the non-obstructed group. This difference although less marked, persists at 9-year follow-up.

Adult↗
PubMed1987

Factors affecting intracellular sodium during repetitive activity in isolated sheep Purkinje fibres.

1. Intracellular Na+ activity (aiNa) was measured using neutral-carrier Na+-sensitive micro-electrodes in voltage-clamped sheep Purkinje fibres during and after 4 min sequences of depolarizing pulses applied to around 0 mV, at a rate of 2.5 Hz. After trains of pulse duration 50 ms the mean increase in aiNa was 0.65 +/- 0.3 mM (mean +/- S.D., n = 18) whereas with longer pulse durations this rise became progressively smaller. At pulse durations of 300 ms a fall in aiNa was usually found. 2. Recovery of aiNa after a pulse sequence followed a roughly exponential time course. The half-time of decline after a rise in aiNa using 50 ms pulses was 111 +/- 52 s (n = 10), compared with a half-time of 318 +/- 116 s (n = 6) for recovery from a fall in aiNa during a sequence of 300 ms pulses. 3. Application of 2 mM-Cs+ to block the pace-maker current (if) resulted in a decrease in resting aiNa by 0.85 +/- 0.45 mM (n = 6) and an outward current shift. Na+ loading during a depolarizing pulse train was greater in 2 mM-Cs+ than in control solution. The rise in aiNa produced by a train of 50 ms pulses in Cs+ was 1.15 +/- 0.4 mM (n = 10). At short pulse durations in the presence of Cs+, Na+ loading at the end of a pulse train increased as a function of pulse duration, becoming maximal at a duration of approximately 50 ms and then diminishing at longer pulse durations. 4. Application of 2.5 X 10(-5) M-tetrodotoxin (TTX) produced a fall in resting aiNa of 0.55 +/- 0.2 mM (n = 6) and an outward current shift, suggesting that a TTX-sensitive component of steady-state Na+ current exists at potentials in the region -65 to -80 mV. 5. TTX greatly reduced the rise in aiNa during a depolarizing pulse train at all pulse durations tested. A fall in aiNa was now found after trains of shorter pulse duration than in control solution. Similar results were obtained in the absence of TTX if the pulse train was initiated from a holding potential which was positive to the Na+ current (iNa) threshold. When iNa had been blocked, using either TTX or a low holding potential, the mean rise in aiNa after a train of 50 ms pulses was 0.25 +/- 0.2 mM (n = 8).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1987

Effects of repetitive activity on developed force and intracellular sodium in isolated sheep and dog Purkinje fibres.

1. When cardiac muscle is stimulated after a rest there is a gradual increase in force development over several minutes. The origin of this 'force staircase' was investigated in experiments on sheep and dog Purkinje fibres. Particular attention was paid to the possible role of changes in the intracellular Na+ activity (aNAi). 2. The first line of evidence for a role for aiNa came from a comparison of sheep and dog Purkinje fibres generating action potentials: after a change in the stimulus rate the slow changes of both aNai and force were monophasic in sheep but biphasic in dog preparations. 3. In the remaining experiments changes in aNai and force in sheep preparations were measured during 4 min trains of voltage-clamp pulses at a frequency of 2.5 Hz. 4. A number of these voltage-clamp experiments also indicated that changes in aNai are involved. Depending on the preparation and the duration of the pulses aNai rose or fell during a train-a rise in aNai was always associated with a gradual rise in force, whereas a fall in aNai was usually accompanied by a gradual fall in force. The addition of tetrodotoxin (TTX) or the use of a low holding potential reduced the progressive rises of both aNai and force, whereas the inclusion of a 10 mV hyperpolarization between pulses potentiated the progressive rises of both. 5. The effect of TTX on the staircase was more marked the longer the pulses during the train; this possibly indicates that the effect of aNai on the force staircase is complex and is more marked with longer pulses. 6. A rise in aNai was shown not to be the only factor underlying the progressive increase in force, because in many preparations a gradual rise in force occurred in spite of no change or even a fall of aNai. 7. It is concluded that an increase in aNai is involved in the slow increase in force during the staircase accompanying a train of action potentials, and that other factors are also involved; various possibilities are discussed.

Action Potentials↗
PubMed1987

Use of the maximal ST/HR slope to estimate myocardial ischaemia after recent myocardial infarction.

Fifty two patients were examined 4-6 weeks after myocardial infarction to assess whether factors other than coronary artery narrowing affect the maximal ST/HR slope which is used as an index of myocardial ischaemia. The slope was compared with indices of myocardial scarring or cardiac enlargement derived from x ray and echocardiographic and angio-cardiographic investigations. In 35 (67%) patients the slope failed to predict the severity of myocardial ischaemia attributable to coronary artery narrowing: in 14 (27%) patients the slope overestimated the findings of coronary angiography and in 21 (40%) patients the slope underestimated the findings of coronary angiography. In the remaining 17 (33%) patients the slope accorded with the assessment of myocardial ischaemia by coronary angiography. Underestimation by the slope was associated with significantly poorer left ventricular function and a lower ejection fraction, indicating a greater degree of myocardial scarring. To assess whether overestimation was related to cardiac enlargement with better preservation of ventricular function a follow up examination was performed six months after infarction. In the overestimated group 11 patients were followed up and seven of them showed a reduction in the maximal ST/HR slope which correlated with a reduction in the cardiothoracic ratio. This suggested that cardiac enlargement had contributed to myocardial ischaemia. The results suggest that if the maximal ST/HR slope is an index of exercise induced myocardial ischaemia after recent infarction, it is subject to the influences of coronary artery narrowing as well as those of scarring and cardiac enlargement.

Adult↗
PubMed1987

Significance of plasma retinol binding protein levels in recurrence of breast tumors in women.

Plasma retinol-binding protein (RBP), prealbumin, vitamin A (total) and beta-carotene levels were studied in premenopausal women with node-positive breast carcinoma receiving adjuvant chemotherapy. Plasma levels were measured prior to chemotherapy and at monthly intervals during the chemotherapy course. The results showed that significantly lower RBP levels during the course of the study were associated with early tumor recurrence. Patients who maintained a disease-free status for 24 months or longer had significantly higher plasma RBP levels than those who had tumor metastasis at distant sites within 24 months after beginning chemotherapy. RBP levels were not associated with adjuvant chemotherapy (CMF)-induced hormonal changes (amenorrhea vs. no amenorrhea), or family history of breast cancer. In contrast, breast cancer patients with a prior history of benign breast disease had significantly lower RBP levels than did healthy, premenopausal women. Reduced RBP levels in these patients are due to neither an inadequate dietary intake of beta-carotene, nor to severe protein malnutrition.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

Induced abortion trends in South Australia, 1970-84.

Following legislative amendments extending the grounds for abortion in South Australia the abortion rate rose from 6.0/1000 in 1970, to 9.9/1000 in 1971, to 13.2/1000 in 1984. However, rates differ widely by marital status among young women, the age pattern varies markedly for different marital status groups, and trends over time differ for different age/marital status groups. Collection of detailed age and marital status data on every live birth and abortion is recommended in order to provide the most informative analysis of abortion trends.

Abortion, Induced↗
PubMed1987

Modification by cis-diamminedichloroplatinum (II) of the radiation dose-response curve for intestinal crypt cells in mice.

The effect of cis-diamminedichloroplatinum (II) (c-DDP) on the shape of the radiation dose-response curve for mouse duodenal crypt cells was investigated. A priming X-ray dose was followed 18 h later by graded test doses (single doses or five equal fractions at 3-h intervals) with or without c-DDP. Curves were fitted by a linear quadratic (LQ) relationship. The drug modified the dose-response curve by enhancing both the alpha and the beta terms. Repair kinetics were analyzed in split-dose experiments. c-DDP caused a minor, nonsignificant decrease in the rate of repair after irradiation. The survival ratio after split-dose irradiation, when the same X-ray doses were given, was actually slightly increased by the drug. This paradoxical effect can be explained by the fact that c-DDP mainly increased the beta term in the LQ relationship. There was no significant increase in crypt cell survival when split-drug doses were given alone at increasing intervals, suggesting no cellular repair after c-DDP treatment. The data are discussed in the light of the recently proposed "lethal and potentially lethal" (LPL) unified repair model of Curtis.

Animals↗
PubMed1986

Assessment of the effect of nifedipine on myocardial ischaemia by using the ST segment/heart rate slope.

Nifedipine is used in patients with stable angina of effort and any resulting change in symptoms is attributed to several effects of nifedipine. However, there have been indications in such patients that one effect of nifedipine could be an increase in the severity of myocardial ischaemia, and the present report involves a trial the results of which could explain this effect. In the present trial, the effect of nifedipine on myocardial ischaemia was assessed by using the maximal ST/heart rate slope. This slope was used as an index of myocardial ischaemia because, in our hands in patients with angina, an increase or a decrease in the value of the slope respectively indicated an increase or a decrease in the severity of myocardial ischaemia as assessed by coronary arteriography. The maximal ST/heart rate slope was obtained at least twice in each of 23 patients with stable angina, with and without nifedipine; two patients were examined twice and three other patients were examined after an increased dose. Nifedipine resulted in an increase in the slope in 24 of the 28 comparisons, no change in three and a decrease in one comparison; there was a statistically significant (P less than 0.005; n = 28; paired t-test) increase in the maximal ST/heart rate slope. A further increase in the slope was obtained by increasing the dose of nifedipine in two out of three patients. The increase in the maximal ST/heart rate slope occurred in the absence of any effect of nifedipine on the initial level of ST segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Clinical aspects of induced abortion in South Australia from 1970-1984.

Clinical changes, and their implication, in medically induced abortion within South Australia from 1970-1984 were assessed by analysis of legally required reports provided by operating practitioners. In the past 15 years vacuum aspiration has largely replaced dilatation and curettage for early abortions, and intrauterine chemical methods have greatly decreased the use of hysterotomy for late abortions. A marked improvement in gestational pattern has also occurred, and recorded complication rates have been halved for all gestational ages. Sterilization rates at the time of abortions increased with increasing age and with increasing gravidity, but the total rates, adjusted for age and gravidity of patients, have changed little in the past 15 years.

Abortion, Induced↗
PubMed1986

Dissociation between force and intracellular sodium activity with strophanthidin in isolated sheep Purkinje fibres.

1. We have recorded membrane potential, intracellular Na activity (aiNa) and force of contraction in sheep Purkinje fibres. Force and aiNa were recorded continuously and simultaneously during exposure to strophanthidin and its subsequent washing off. 2. Exposure to strophanthidin in concentrations of 1.5 X 10(-7), 5 X 10(-7) and 10(-5) M caused an increase in force of contraction which was temporally dissociated from the increase of aiNa. 3. There was hysteresis in the relationship between force and aiNa when the period of increasing force was compared to the period of decreasing force. When force increased on exposure to strophanthidin, the same aiNa was always associated with a higher force than when force was decreasing while washing off the drug. 4. For the same rise of aiNa higher doses of strophanthidin produced larger rises of force than lower doses. 5. When diphenylhydantoin was present in the bathing solution at concentrations of 10(-5) and 10(-4) M, the relation between force and aiNa with 10(-5) M-strophanthidin had a less steep slope, but still displayed hysteresis. 6. The relationship between force and aiNa during changes of the bathing K concentration also displayed a hysteresis, which was in the same direction as that found with strophanthidin. 7. These results are discussed in relation to proposed mechanisms of action of strophanthidin and more generally in relation to the factors linking force of contraction and aiNa. We conclude that in sheep Purkinje fibres the increase of force caused by strophanthidin is not solely due to an increase of aiNa, and that other interventions can also result in hysteresis between force and aiNa.

Action Potentials↗