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Biomedical subjects

R M Sykes

Publications and source records attributed to R M Sykes.

At least 37 records · Page 2Linked to original sources
PubMed1992

gamma-Aminobutyric acid immunoreactive structures in the nucleus tractus solitarius: a light and electron microscopic study.

gamma-Aminobutyric acid immunoreactive perikarya and boutons in the nucleus tractus solitarius of the cat were examined at both the light and electron microscopic level. Immunoreactive neurones were found predominantly in the parvocellular subdivision of the nucleus tractus solitarius and to a lesser degree in all the other subdivisions of the nucleus tractus solitarius and the dorsal vagal motonucleus. All the immunoreactive perikarya observed were similar in size and morphology. gamma-Aminobutyric acid immunoreactive boutons were observed throughout the nucleus tractus solitarius. However, in contrast to its high content of immunoreactive perikarya the parvocellular subdivision contained the lowest density of immunoreactive boutons. Ultrastructural examination of immunoreactive boutons in the different regions of the nucleus tractus solitarius revealed that they formed synaptic specializations, predominantly with dendritic shafts, all of which were of the symmetric type. This pattern of innervation was observed throughout the medial, commissural, ventrolateral and parvocellular subdivisions of the nucleus tractus solitarius.

Animals↗
PubMed1992

Indications for lumbar puncture in children presenting with convulsions and fever of acute onset: experience in the Children's Emergency Room of the University of Benin Teaching Hospital, Nigeria.

A total of 522 children, aged 1 month to 6 years, who presented with convulsions and fever of acute onset at the Children's Emergency Room of the University of Benin Teaching Hospital over a 1-year period, were prospectively evaluated. Bacterial meningitis was diagnosed in 22 (4.2%) on bacteriological and/or biochemical evidence. The causative organisms were cultured from the CSF in 13 (Neisseria meningitidis = 7, Streptococcus pneumoniae = 5 and Haemophilus influenzae = 1) and identified by Gram stain only in three (Gram-positive diplococci = 2 and Gram-negative diplococci = 1). No organisms were identified in the CSF of six of the children with meningitis. The prevalence of meningitis declined sharply after 6 months of age. Six of the children with bacterial meningitis lacked classical meningeal signs but had other indications for lumbar puncture. The following were significantly associated with meningitis: age under 6 months; focal or multiple seizures; absence of a past or family history of seizures; unrousable coma; and an extracranial focus of infection. It is concluded that bacterial meningitis occurs in a good proportion of children, even beyond infancy, with convulsions associated with fever of acute onset, and that decision on the need for lumbar puncture should be guided by clinical features such as age and the presence of complex febrile seizures.

Acute Disease↗
PubMed1992

Relative contribution of bacteraemia and malaria to acute fever without localizing signs of infection in under-five children.

Six-hundred-and-forty-two previously healthy children aged 1 month to 5 years with fever of acute onset, without localizing signs of infection, were prospectively recruited over 1 year. Sixty-three per cent had malaria, 4 per cent bacteraemia, and 7 per cent malaria and bacteraemia. Neither infection was identified in 27 per cent. Malaria was the predominant infection irrespective of season, temperature on presentation, or age (except under 6 months). Although Gram-negative bacteraemia was overall commoner than Gram-positive bacteraemia, Staphylococcus aureus was the commonest single organism (43 per cent) in bacteraemic patients. The prevalence of malaria increased with age while that of bacteraemia decreased with age (P < 0.0005). The prevalence of an identifiable infection increased with the temperature on presentation (P < 0.025). It is concluded that although malaria is the predominant infection in previously healthy under-5 children with acute fever without specific localizing signs of infection, bacteraemia (alone or associated with malaria) occur with an importantly high frequency. It is recommended that while presumptive treatment for malaria is justified in such children, evaluation for bacteraemia should be given consideration.

Acute Disease↗
PubMed1992

Convulsions with fever as a presenting feature of bacterial meningitis among preschool children in developing countries.

The authors report 522 infants and young children aged between one month and six years who presented with convulsions and fever as emergencies in Nigeria. 22 had bacterial meningitis, six of whom lacked the usual signs of meningitis. Although features of complex febrile convulsions were significantly associated with bacterial meningitis, it is concluded that, as an aid to the early diagnosis of bacterial meningitis, all preschool children convulsing with fever in developing countries should have a lumbar puncture. This may reduce the contribution of meningitis to chronic neurological disabilities. The necessity for such a policy is illustrated by a case report of a young infant with convulsions and fever caused by meningitis, seen at a general hospital.

Age Factors↗
PubMed1991

Efferent connections of lobule IX of the posterior cerebellar cortex in the rabbit--some functional considerations.

The Purkinje cell projection from the cardiovascular region of sublobule b of the uvula (medial area of zone A) has been investigated using anterograde tracing methods in the rabbit. The importance of the integrity of the identified pathways in mediating the cardiovascular responses from the uvula has been studied in subsequent lesioning experiments. Wheat germ agglutinin-conjugated horseradish peroxidase or tritiated amino acids were microinjected into sublobule IXb. This resulted in anterogradely labelled Purkinje cell axons in both the inferior and superior cerebellar peduncle. In agreement with previous studies in rabbit we also found labelled fibres at the level of the fastigial nucleus and vestibular complex. However, the labelled fibres we observed in the parabrachial nucleus have not been reported in previous studies except in the prosimian primate. Projections from IXb showed terminal-like patterns of label in the ventromedial region of the caudal fastigial nucleus, the dorsal areas of the superior and inferior vestibular nuclei and in the medial and lateral divisions of the parabrachial nucleus. Labelled fibres were also seen coursing in the lateral vestibular nucleus. Lesioning experiments have revealed that the integrity of the superior cerebellar peduncle is essential for the expression of the cardiovascular responses (bradycardia and depressor response) elicited from the uvula in the anaesthetized rabbit. In contrast, the pattern of cardiovascular response evoked in a decerebrate rabbit (tachycardia and pressor response) was abolished when the inferior cerebellar peduncle was lesioned.

Amino Acids↗
PubMed1991

Localization of [125I]endothelin binding sites in the region of the carotid bifurcation and brainstem of the cat: possible baro- and chemoreceptor involvement.

We have demonstrated by autoradiography, displaceable binding for [125I]endothelin-1 ([125I]ET-1), [125I]endothelin-2 ([125I]ET-2), and [125I]endothelin-3 ([125I]ET-3) in the cat carotid bifurcation as well as in the nucleus of the tractus solitarius, where baroreceptor and chemoreceptor afferents from the carotid body and sinus terminate. There was also significant binding in the nodose and superior cervical ganglia. Barosensory and chemosensory discharge was recorded from filaments of the carotid sinus nerve in cats anesthetized with pentobarbitone. Intra-carotid injection of ET-1 or ET-3 (4-402 pmoles) caused transient dose-related depression of baroreceptor discharge without any immediate effects on systemic blood pressure (BP) or heart rate; there was a delayed biphasic effect on BP. ET-1 had little effect on chemosensory discharge during the first 15 s post-injection, but there was a delayed (45-90 s) dose-related increase in discharge. The effects of all three ETs were qualitatively similar, and ET enhanced chemoexcitation evoked by either acetylcholine or sodium cyanide. Our results show that (a) ET binding sites are located in the baroreceptor and chemoreceptor afferent pathways and (b) ETs can influence afferent activity of baroreceptors and chemoreceptors. Further studies are needed to determine the significance of these findings, particularly with regard to reflex control of the cardiovascular system.

Animals↗
PubMed1991

Autoradiographic localization of [125I]endothelin binding sites in human blood vessels and coronary tissue: functional correlates.

The distribution of endothelin-1 (ET-1) receptors on human vascular tissue has been studied. High- and low-resolution autoradiography was used to determine the distribution of [125]ET binding sites in human blood vessels and ventricular myocardium. Dense, displaceable [125I]ET binding was associated with cardiac myocytes and the smooth muscle layer of all vessels were examined. There was also dense binding to vasa vasora. There was increased [125I]ET binding to atheromatous coronary arteries and vein graft, which was associated with the tunica media and vasa vasora or regions of neovascularization. Vasoconstrictor and positive inotropic activity of ET-1 has been established in vitro. The vasoconstrictor effect of ET-1 is likely to be mediated via the binding sites identified on vascular smooth muscle. The striking perivascular [125I]ET-1 binding suggests that ET-1 may also have constrictor activity on vasa vasora. There is experimental evidence that ET-1 has mitogenic activity on vascular smooth muscle cells in culture. The increased binding to both smooth muscle and regions of neovascularization in atheromatous vessels suggests that ET-1 may play a role in atherosclerosis.

Adolescent↗
PubMed1991

Distribution of 125I-labelled insulin-binding sites in peripheral tissues of the normal and diabetic rat: an autoradiographic study.

In-vitro autoradiography was used to demonstrate the regional distribution of 12I-labelled insulin-binding sites in the liver, kidney and heart of normal rats and rats made diabetic with streptozotocin. The distribution of insulin-binding sites in the liver of control rats was uniformly high, while in the kidney of control rats there was weak 125I-labelled insulin binding in the medulla and dense binding in the cortex. In the hearts of control rats a high density of 125I-labelled insulin-binding sites was evident both in the atrial and ventricular muscle. Non-ketotic diabetes mellitus caused a marked increase in 125I-labelled insulin-binding sites in both the liver and kidney with the former tissue exhibiting a time-dependent (7 to 62 days) increase. There was no apparent effect of diabetes on insulin-binding sites in the heart. Since experimental diabetes causes (1) a decrease in circulating insulin concentration and (2) impaired insulin action at many target tissues, the increase in 125I-labelled insulin-binding sites observed in the present study may represent a compensatory 'up regulation' of insulin receptors.

Animals↗
PubMed1990

Functional and autoradiographic evidence for endothelin 1 receptors on human and rat cardiac myocytes. Comparison with single smooth muscle cells.

This study aimed to determine whether receptors for endothelin were present on the cardiac myocyte as well as on vascular smooth muscle cells. Low- and high-resolution autoradiography was performed using 125I-endothelin 1 on intact rat myocardium and samples of human ventricle obtained from explanted hearts at the time of transplant. In addition to specific binding to the smooth muscle of the blood vessel lumen, there was considerable binding associated with cardiac myocytes. To discover whether there was any functional correlate for this binding, muscle cells were isolated enzymatically from human and rat ventricle and from rat femoral artery, and their contractile characteristics were studied. Single cardiac cells were superfused with physiological saline at 32 degrees C, and their length change was displayed continuously on a chart recorder. Endothelin 1 had a pronounced effect on shortening in both rat and human myocytes. The contraction amplitude was approximately doubled in both cases, from 4.1 +/- 0.8% cell length to 8.1 +/- 1.3% for rat (mean +/- SEM, n = 9, p less than 0.001), and from 2.1 +/- 0.5% to 4.0 +/- 0.5% in human (n = 10, p less than 0.001). In rat, the magnitude of the effect was comparable to that of the alpha-adrenoceptor agonist phenylephrine. The maximum contraction amplitude of the human cells, produced by raising extracellular calcium to greater than 10 mM, was 11.4 +/- 1.1% cell length (n = 9), significantly greater than that produced by endothelin (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Autoradiographic demonstration of [3H] loperamide binding to opioid receptors in rat and human small intestine.

Loperamide has an anti-diarrhoeal action which has been suggested to be mediated by opioid receptors associated with gut motility. There is now evidence to suggest that loperamide also affects intestinal transport. In this study we have used in vitro autoradiography to localize [3H] loperamide binding sites in both rat and human small intestine and the displacement of [3H] loperamide binding by mu- and delta-selective ligands.

Animals↗
PubMed1989

Cerebrospinal fluid/serum lactic acid in febrile convulsions.

Cerebrospinal fluid/serum lactic acid was prospectively assayed in 42 patients with febrile convulsions. Patients were divided into two groups for analytical purposes. Those with brief febrile seizures (30 patients) and the remaining 12 patients had prolonged febrile seizures. CSF and serum lactic acid values were within normal range in patients with brief seizures while elevated values were obtained in patients with prolonged seizures. The mean CSF lactic acid on admission was significantly higher (P less than 0.001) in patients with prolonged seizures than corresponding values in those with brief seizures. Mean serum lactic acid on admission was also significantly higher in patients with prolonged febrile seizures compared to the corresponding mean value in patients with brief seizures (P greater than 0.001). Patients who recovered with neurological deficits had significantly higher CSF lactic acid on admission (P greater than 0.001). Similarly 8 patients who had recurrent febrile convulsions had significantly higher CSF lactate on admission. It is suggested that measurement of CSF lactate can be used as a biochemical marker to identify children with prolonged seizures and those who are likely to have recurrent febrile seizures.

Biomarkers↗
PubMed1988

Rectal diazepam solution in the treatment of convulsions in the children's emergency room.

Rectal diazepam solution was administered to 55 convulsing children in the Children's Emergency Room. In 71%, the convulsion ceased within 5 min, and in 7%, between 5 and 10 min. In 16%, rectal diazepam was ineffective but there was a rapid response to intravenous diazepam. Convulsions that had lasted less than 15 min before treatment responded more often (81%) than those that had lasted more than 15 min (46%). Four children had transient respiratory depression. Though intravenous diazepam is superior, rectal diazepam solution is adequate for controlling most acute convulsions in children, and has the advantage that it can be administered by paramedical workers.

Administration, Rectal↗
PubMed1986

Autoradiographic localization of opioid receptor types in the rat small intestine.

The selective mu and delta ligands [3H]DAGO and [3H]DPDPE have been used to investigate the distribution of specific opioid subtypes in the rat small intestine by in vitro autoradiography. There was a greater density of [3H]DPDPE binding at regions of the villi and crypts than [3H]DAGO binding. These results suggest that the opioid receptors located in these regions are predominantly of the delta subtype.

Animals↗
PubMed1986

Tuberculoma of the eye; a case report.

A case of tuberculoma of the eye is reported occurring in a 3-year-old girl. Clinically presenting as a case of leucocoria a pre-operative diagnosis of retinoblastoma was made, necessitating enucleation of the eye. Post-operatively a diagnosis of intraocular tuberculosis was made. The differential diagnosis is discussed and the importance of inclusion of intraocular tuberculoma in the differential diagnosis of retinoblastoma is stressed.

Child, Preschool↗
PubMed1984

Neurological diseases as seen at the outpatient Paediatric Neurology Clinic in Benin City.

There is a paucity of literature about the pattern of neurological diseases in children attending out-patient departments in Africa. In this study more boys than girls presented at our clinic. Almost all the principal diseases seen are eminently preventable. There appears to be no effective immunization programme. There is need for epidemiological studies to ascertain the true incidence of subacute sclerosing panencephalitis in view of the high incidence of measles in the community.

Adolescent↗