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Biomedical subjects

R Hayes

Publications and source records attributed to R Hayes.

At least 145 records · Page 8Linked to original sources
PubMed1986

Bed-nets (mosquito-nets) and morbidity from malaria.

A study was undertaken in the Farafenni area of The Gambia to determine the relation between morbidity from malaria in children and the use of bed-nets (mosquito-nets). From comparisons of parasite and spleen rates in bed-net users and in non-users it seemed that bed-nets had a strong protective effect. However, the prevalence of malaria in the study population was also influenced by ethnic group and place of residence, and the association of bed-net use with these two confounding factors accounted for some of the differences observed between bed-net users and non-users. Nevertheless, a significant inverse correlation between splenomegaly and the use of bed-nets remained. This suggests that bed-nets give Gambian children some protection against malaria and that the use of bed-nets, either untreated or treated with an insecticide such as permethrin, should be investigated further as a means of malaria control in Africa.

Adolescent↗
PubMed1986

Partner support and the use of coping techniques in labour.

This study examined the relationship between partner support, use of pain control techniques and epidural anaesthesia in 80 primiparous women. It was found that the use of psychological 'pain control' techniques did not reduce the intensity of labour pain, nor did their use enable women to do without an epidural anaesthesic. However, the use of techniques did correlate with reduced frequency of anaesthesia when women were consistently supported and encouraged throughout labour, and when the labour was relatively short.

Adult↗
PubMed1986

Molecular organization of the sex steroid-binding protein (SBP) of human plasma.

Several years ago this laboratory presented evidence that SBP is a dimer composed of two subunits having similar molecular weights. The question of whether or not these subunits are identical and therefore products of a single gene remained unanswered. We now report that the two polypeptide chains are identical and that SBP is a homodimer. The experimental approach was to reduce and [14C]alkylate cystine residues in human SBP, digest the product with trypsin or cyanogen bromide and determine the number of unique amino acid sequences around each [14C]carboxymethylcysteine residue. Only four unique sequences were found when all the radioactive peptides were analyzed. Since there are eight half-cystine residues per dimer, the results support a homodimeric structure.

Amino Acid Sequence↗
PubMed1985

Human vascular smooth muscle responses mediated by alpha 2 mechanisms in vivo and in vitro.

The effects of compounds with alpha 2-agonist and alpha 2-antagonist properties on human forearm blood flow and on isolated human arterial segments have been studied. The findings from these studies in vivo and in vitro did not provide evidence in support of the hypothesis that postsynaptic alpha 2-receptors mediate smooth muscle contraction in the tissues under investigation. The constriction of the forearm vascular bed in response to low intra-arterial doses of idazoxan (RX 781094), an alpha 2-antagonist, provides evidence for a physiological role for a presynaptic alpha 2 autoregulatory mechanism. The variability of the forearm vascular responses to higher doses of idazoxan highlights the pitfalls that may have misled previous authors in their interpretation of the results of similar studies. A U-shaped dose-response curve to compounds with mixed alpha 2- and alpha 1-antagonist properties may be constructed, which emphasizes the importance of the dose-dependent selectivity of these antagonists at alpha 2- and alpha 1-receptors. The effect of idazoxan on the responses of arterial segments in vitro to exogenous catecholamines was dependent on the integrity of the endothelium, and provides evidence that alpha 2-receptors may mediate release of the endothelium-derived relaxing factor.

Adrenergic alpha-Agonists↗
PubMed1985

In vivo and in vitro studies of alpha 2-adrenoceptor responses in human vascular smooth muscle.

To assess the role of alpha 2-receptor mechanisms in the control of vascular tone in humans, the pharmacological activities of RX 781094, an alpha 2-antagonist, and UK 14304, an alpha 2-agonist, have been investigated with the additional use of an alpha 1-antagonist, doxazosin. The effects of these agents on human forearm blood flow have been studied. In addition, some preliminary observations on the effects of these alpha 2-selective agents on isolated human arterial segments have been made. The alpha 2 agonist, UK 14304, produced a dose-dependent reduction in forearm blood flow, but the antagonism of this response by both doxazosin and RX 781094 at a dose which must be regarded as nonselective casts doubt on the hypothesis that alpha 2-receptors may be located postsynaptically in human vascular smooth muscle. These observations may be explained by UK 14304 having partial alpha 1-agonist activity. RX 781094 infused at low doses produced a dose-dependent reduction in forearm blood flow, which is interpreted as evidence for a presynaptic alpha 2 autoregulatory mechanism in the vasculature. Observations on isolated arterial segments (mesenteric, renal, splenic, gastric, and brachial) obtained during surgical procedures and mounted under tension in tissue baths did not provide evidence for a postsynaptic alpha 2-receptor mediating vasoconstriction. In contrast, the potentiation of the adrenaline response in the presence of the alpha 2 antagonist, RX 781094, supports the possibility that, in humans, an extrajunctional alpha 2-receptor may serve as the adrenergic mechanism for the release of an endothelial derived relaxing factor.

Adult↗
PubMed1984

Course-related depressive syndromes in schizophrenia.

The authors evaluated 20 patients, diagnosed by Research Diagnostic Criteria after 1 week of hospitalization as having schizophrenia, weekly throughout their hospitalization. Four patients developed syndromes of depression after resolution of their psychoses: three manifesting a "minor" and one a "major" postpsychotic depressive syndrome. Four other patients went on to develop syndromes equivalent to major depression at a time when they were still actively psychotic, and their cross-sectional diagnoses were therefore changed to schizoaffective disorder, depressed type. The authors discuss the implications of these findings for diagnosis.

Adult↗
PubMed1982

Medroxyprogesterone acetate and homozygous sickle-cell disease.

The haematological and clinical effects of medroxyprogesterone acetate in homozygous sickle-cell (SS) disease were assessed in a 2-year controlled crossover trial completed by 23 patients. Haematological indices remained steady during the placebo phase, but during the medroxyprogesterone-acetate phase fetal haemoglobin, total haemoglobin, red-cell mass, and red-cell survival rose significantly, and reticulocytes, irreversibly-sickled-cell counts, and total bilirubin fell significantly. Painful crises were significantly less frequent during the medroxyprogesterone-acetate than the placebo phase. These results are compatible with an inhibition of in-vivo sickling in patients with SS disease during medroxyprogesterone-acetate treatment. The mechanisms of such an effect require further study.

Adult↗
PubMed1982

Third-party consent to medical procedures.

The issue of consent to medical procedures is a particularly complex one when the patient is incapable of giving valid consent (because of age, mental disability, or physical state). A medical practitioner who proceeds with treatment without valid consent may be liable to legal action or disciplinary proceedings. Third-party consent can be given by parents legally appointed guardians. Consent is not required if emergency treatment is necessary to preserve the life of the patient. It is extremely doubtful whether valid third-party consent can be given for procedures which are not essential for the preservation of life or health.

Australia↗
PubMed1982

A survey of leptospirosis in febrile patients mainly from hospitals and clinics in Trinidad.

Acute and convalescent sera were obtained from 202 febrile patients, most of whom were admitted to or attended hospitals or clinics in northern Trinidad during the 12 months from mid-February 1977 to mid-February 1978. Laboratory tests confirmed that 10 of the patients were suffering from current leptospirosis while another 54 had serological evidence of previous leptospiral infections. Antibodies to strains of the Icterohaemorrhagiae serogroup were most commonly found, followed by those to the Hebdomadis and Autumnalis serogroups. Isolates were obtained from the blood of two and the urine of three of the 10 current cases. Four of these strains were identified as belonging to copenhageni serovar of the Icterohaemorrhagiae serogroup and one to serovar brasiliensis of the Bataviae serogroup. Seven of the patients suffering from leptospirosis were males, all rural dwellers, and all except one under 20 years of age. Two of the three female patients were over 60 years old and were urban dwellers. It was not possible to identify the sources of infection with certainty, although dogs may have been responsible for three of the Icterohaemorrhagiae and one of the Canicola infections. Of the 192 patients who were not currently infected, serological evidence of previous infection was obtained in 31 (40%) males and 23 (21%) females and was most common among farmers and rural workers.

Adolescent↗
PubMed1982

The influence of drugs on the overflow of noradrenaline and the identification of receptors in guinea-pig atria.

1 Salbutamol (1.0 microM) and isoprenaline (1.2 nM) significantly increased the fractional release of tritiated noradrenaline from driven left atria but phentolamine (10 microM) failed to do so. Butoxamine (4.0 microM) blocked the increase in overflow produced by isoprenaline. Isoprenaline (1.2 nM), phentolamine (10.0 microM) and salbutamol (1.0 microM) failed to increase the overflow of tritiated noradrenaline from spontaneously beating atria. 2 Spontaneously beating atria were therefore used to identify the receptors mediating chronotropism and inotropism. 3 There was no clear relationship between inotropism and chronotropism. 4 The inotropic effects of both dobutamine (0.04-4.0 microM) and isoprenaline (0.11-9.0 nM) were inhibited by practolol (4.0 microM) and by butoxamine (4.0 microM). The chronotropic effects were inhibited only by practolol (4.0 microM). 5 Both inotropic and chronotropic effects of noradrenaline (3.0-200 nM) were antagonized by practolol (4.0 microM), but not by butoxamine (4.0 microM). Thus both functions appeared to be mediated by beta 1-adrenoceptors when noradrenaline was the agonist. 6 Inotropic responses to salbutamol (0.45-7.5 microM) were inhibited by both practolol (4.0 microM) and by butoxamine (4.0 microM), but chronotropic responses were antagonized only by butoxamine (4.0 microM), Thus salbutamol acts on both beta 1-and beta 2-adrenoceptors to produce an inotropic response but only on beta 2-adrenoceptors to produce its chronotropic response. 7 It is concluded that both beta 1- and beta 2-adrenoceptors can mediate chronotropism and inotropism in guinea-pig isolated atria. Determination of the postsynaptic effects of drugs should be carried out on spontaneously beating rather than driven atria to obviate modification of the responses by noradrenaline release from sympathetic neurons.

Albuterol↗
PubMed1979

Kinetics and time dependence of the effect of far red light on the photoperiodic induction of flowering in wintex barley.

Flowering in the long day plant Hordeum vulgare L. var. Wintex barley was enhanced by the addition of far red light to the main light portion of the photoperiod. Far red energy was provided to produce quantum flux ratios (660/730 nm) and phytochrome photoequilibria (Pfr/total phytochrome) equivalent to those reported both beneath a leaf canopy and outside a canopy at twilight. The photoperiodic requirement for long days can be completely eliminated by the addition of far red light. However, both the effect of extending the photoperiod without far red and the addition of far red to 12-hour photoperiods were suboptimal. Maximal stimulation was achieved only when far red was added to continuous light. The duration of the period of maximal apex elongation rate, as well as the reduction of the time required for floral initiation, were saturated by three inductive cycles. When far red energy was provided intermittently during 3 days of continuous light, the ability to respond varied in a circadian manner. This enhancement of flowering by far red appears to be mediated by the "high irradiance response" of phytochrome.

Journal Article↗
PubMed1975

Control factors in the release of gastrin by direct electrical stimulation of the vagus.

The release of gastrin by direct electrical stimulation of the vagus was studied together with the relative effects on the response of antral and duodenal acidification. As expected, gastrin levels increased to three times the normal simulated response following antral neutralization. In contrast, duodenal acidification failed to influence the vagal release of gastrin when the antrum was neutralized although it had a minor effect when the antrum was acidified. Thus the antral pH dominates over duodenal pH as a factor in controlling gastrin release. Surprisingly, atropine in doses which blocked acid release and produced marked cardiac effects failed to inhibit the release of gastrin from the antrum on vagal stimulation. This suggests that, using this model, vagal release of gastrin, if cholinergic, is highly resistant to atropine.

Animals↗