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Biomedical subjects

A Nicoll

Publications and source records attributed to A Nicoll.

At least 19 recordsLinked to original sources
PubMed1992

EPSPs in rat neocortical pyramidal neurones in vitro are prolonged by NMDA receptor-mediated currents.

We investigated the influence of 2-amino-5-phosphonovalerate (APV), a selective antagonist of the N-methyl-D-aspartate (NMDA) receptor, on the time course of small excitatory postsynaptic potentials (EPSPs) in pyramidal neurones in layer 2/3 of adult rat visual cortex in vitro. Time constants of the voltage decay following the EPSPs (T(s)) and after brief (2 ms) pulses of current injected at the soma (T(p)) were determined from semilogarithmic plots of averages of 100-250 trials. The mean T(s)/T(p) ratio decreased from 1.53 +/- 0.29 (S.D.) to 1.10 +/- 0.08 on addition of 50 microM APV to the bathing medium (P less than 0.001; n = 23), but there was no significant change in EPSP peak amplitude or rise-time. These results suggest that the time course of many small EPSPs, even at negative membrane potentials and in the presence of Mg2+, can be prolonged by NMDA receptor-mediated currents.

2-Amino-5-phosphonovalerate↗
PubMed1992

Heterosexually acquired HIV-1 infection: cases reported in England, Wales and Northern Ireland, 1985 to 1991.

By the end of 1991, there had been 417 reports of AIDS and 1620 reports of HIV-1 infection in persons in England, Wales and Northern Ireland who probably acquired their infection through sexual intercourse between men and women. Between 1986 and 1991, the proportion of AIDS cases attributable to heterosexual transmission increased from 2% to 14% and of diagnosed HIV-1 infections from 4% to 23%. Reported HIV-1 infections inadequately reflect the extent of infection as only individuals choosing to be tested can be reported. HIV-1 infection acquired during heterosexual intercourse may be the result of transmission from partners who were infected by routes other than heterosexual transmission (first generation transmission) or of transmission from infected partners who were themselves infected through heterosexual intercourse (second generation transmission). Of the 417 cases in which AIDS was acquired through heterosexual intercourse, 42 (10%) were categorised as due to first generation transmission, 328 (79%) as second generation transmission--abroad, and 47 (11%) as second generation transmission--UK. Transmission categories could be allocated to 1438 of the 1620 reports of HIV infection: 17% were categorised as first generation, 74% as second generation--abroad, and 9% as second generation--UK. Heterosexual transmission of HIV infection is increasing, both in individuals acquiring their infection abroad as well as those who become infected in the United Kingdom.

Acquired Immunodeficiency Syndrome↗
PubMed1992

The epidemiology of HIV-1 infection in urban areas, roadside settlements and rural villages in Mwanza Region, Tanzania.

OBJECTIVE: To determine the prevalence of HIV-1 infection and to identify the most important risk factors for infection. DESIGN: A cross-sectional population survey carried out in 1990 and 1991 in Mwanza Region, Tanzania. METHODS: Adults aged 15-54 years were selected from the region (population, 2 million) by stratified random cluster sampling: 2434 from 20 rural villages, 1157 from 20 roadside settlements and 1554 from 20 urban wards. Risk factor information was obtained from interviews. All sera were tested for HIV-1 antibodies using enzyme-linked immunosorbent assay (ELISA); sera non-negative on ELISA were also tested by Western blot. RESULTS: The response rate was 81%. HIV-1 infection was 1.5 times more common in women than in men; 2.5% of the adult population in rural villages, 7.3% in roadside settlements and 11.8% in town were infected. HIV-1 infection occurred mostly in women aged 15-34 years and men aged 25-44 years. It was associated with being separated or widowed, multiple sex partners, presence of syphilis antibodies, history of genital discharge or genital ulcer, travel to Mwanza town, and receiving injections during the previous 12 months, but not with male circumcision. CONCLUSION: This study confirms that HIV-1 infection in this region in East Africa is more common in women than in men. The results are consistent with the spread of HIV-1 infection along the main roads. There is no evidence that lack of circumcision is a risk factor in this population.

Adolescent↗
PubMed1991

Synaptic transmission between individual pyramidal neurons of the rat visual cortex in vitro.

Synaptic transmission between pairs of neurons in layer 2/3 of in vitro slices from the rat visual cortex was studied by dual intracellular recording. The intrinsic electrophysiological properties of these neurons suggested that they were pyramidal cells. More than 1/3 of the total number of synaptically connected neurons were stained by intracellular iontophoresis of biocytin, and all had pyramidal morphology. Postsynaptic potentials (PSPs) were evoked by single action potentials (elicited by current injection) in presynaptic cells. Measurements of PSP latency, amplitude, and shape were made on spike-triggered averages. Forty-eight synaptic connections were found out of a possible total of 549, equivalent to a probability of about 0.09. For these 48 connections, the distance between the 2 impalement sites ranged from 50 to 340 microns. All PSPs were depolarizing at rest (-74 +/- 5 mV, mean +/- SD), and all 14 of the PSPs that were also recorded with the postsynaptic cell depolarized to around action potential threshold (about -55 mV) remained depolarizing. PSPs had short latencies (1.2 +/- 0.6 msec, mean +/- SD), suggesting that they were mediated by monosynaptic pathways. Peak amplitudes of the averaged PSPs varied widely (range, 0.05-2.08 mV), but the majority were less than 0.5 mV. PSPs decayed exponentially with time constants that were correlated with, but slightly longer than, the membrane time constants of the postsynaptic cells measured using injected current pulses. Four cell pairs were connected reciprocally, and 6 examples of convergent input were found in which a single cell was postsynaptic to more than 1 presynaptic cell. Trial-to-trial fluctuations in PSP amplitude were analyzed for 16 synaptic connections. The amplitude of the PSP evoked by a presynaptic action potential fluctuated more than could be accounted for by the background noise.

Action Potentials↗
PubMed1991

The effect of neonatal monocular enucleation on the optic nerves of the rat.

It is known that removal of one eye in the rat in early postnatal life results in an aberrant ipsilateral projection from the remaining eye. We have estimated the number of optic nerve fibres in 36 days old Black and White Hooded rats that had been unilaterally enucleated at birth. There was no significant difference in the transverse cross-sectional area of the optic nerves of control and enucleated rats. Control animals had an average of about 109,000 myelinated fibres and about 11,000 unmyelinated fibres. The mean minimum diameter of the myelinated fibres was 0.73 microns. The corresponding values in the unilaterally enucleated animals were not significantly different from control animals. These results are discussed in the context of the previously reported increased ipsilateral projection in unilaterally enucleated rats.

Animals↗
PubMed1990

Autosomal dominant osteopetrosis type II with "malignant" presentation: further support for heterogeneity?

The osteopetroses are a heterogeneous group of disorders characterised by generalised bony sclerosis. The autosomal dominant form usually has a "benign" prognosis, in contrast to the "malignant" course of the autosomal recessive variety. In this paper we describe a kindred in which the phenotypic spectrum varied from an asymptomatic condition in adults to a severely affected infant, presenting with anaemia, hepatosplenomegaly, hydrocephalus and blindness. The findings in this family are reported and discussed to elucidate further the possible genetic heterogeneity in autosomal dominant osteopetrosis.

Adult↗
PubMed1990

Discovering anaemia at child health clinics.

Children at three inner city child health clinics were offered haemoglobin estimation by fingerprick blood test when attending for immunisation against measles. Of the 98 immunised, 92 (94%) participated in the study, together with 58 other children. Anaemia (haemoglobin concentration less than 110 g/l) was found in 33 of 130 overall (25%), and in 17 of 44 Asian children (39%). The method of testing was acceptable to parents and staff.

Anemia, Hypochromic↗
PubMed1990

HIV and infant feeding practices: epidemiological implications for sub-Saharan African countries.

In industrialized countries HIV-1-seropositive mothers who are nursing infants are advised to use artificial feeds, whilst HIV-infected women in the developing world are recommended to breast-feed. Current evidence is insufficient even to estimate the attributable risk associated with breast-feeding. There is a possibility that the policy promoted in industrialized societies will eventually become established in urban and peri-urban areas of sub-Saharan Africa. This may be defensible for some elite urban mothers providing safe artificial feeding. However, calculations of the consequence of any population-level change to bottle-feeding indicate that it would result in more deaths from infectious causes, substantially adding to the child deaths directly attributable to HIV-1 infection. These data demonstrate that there is a clear need for policy-makers and health care workers to undertake further promotion of breast-feeding despite the AIDS epidemic.

Africa↗
PubMed1988

The epidemiology and service implications of congenital and constitutional anomalies in ethnic minorities in the United Kingdom.

The literature on the incidence in the UK of congenital and constitutional anomalies in populations deriving from Africa, the Caribbean, the Far East, the Indian subcontinent and the Mediterranean is reviewed. These groups represent an increasing proportion of the whole child population. Comparison with the white population and between groups reveals that the burden of impairment varies with country of origin. Some of the reasons implicated include different gene frequencies and mating patterns, age/parity distribution and uptake of preventive services. Comparisons with prevalence at birth in the countries of origin are made where possible. In general, populations with high rates in their country of origin retain their high rates (e.g. central nervous system anomalies among births to parents deriving from the Indian subcontinent). There is a general lack of data on the prevalence of handicapping conditions such as cerebral palsy, as well as the associated health needs and service utilisation amongst ethnic minorities.

Africa↗
PubMed1988

Whooping cough and unrecognised postperinatal mortality.

Trends in postperinatal infant mortality from respiratory causes and the sudden infant death syndrome in England and Wales for 1968 to 1984 were examined. These were compared by time series analysis with changes in the incidence of specific infective diseases and organisms for the same period. Discontinuity was found in association with the occurrence of whooping cough between 1977 and 1982. Associations with the general incidence of respiratory infections and other specific organisms were less evident. An estimate of excess mortality is 460 to 700 deaths, a substantial increase over the certified mortality from whooping cough.

Disease Outbreaks↗
PubMed1988

Developmental screening and surveillance.

This article reviews the practice of and state of knowledge concerning developmental screening and surveillance of preschool children in the UK. It includes testing for defects of hearing and vision but does not constitute a "how-to-do-it" guide. This is available elsewhere (Egan et al, 1969; Sheridan, 1975).

Child Development↗
PubMed1987

Congenital rubella in babies of south Asian women in England and Wales: an excess and its causes.

The incidence of congenital rubella was found to be 2.3 times higher in Asian than non-Asian births in England and Wales. This was attributed in part to higher susceptibility to rubella in Asian than non-Asian women, as shown by antenatal serological data from public health laboratories in Leeds, Luton, and Manchester. Examination of the ethnic origin of pregnant women requesting laboratory testing after contact with rubella or rash and of women with laboratory confirmed rubella in pregnancy also suggested that the disease was being underdiagnosed in pregnant Asian women. Failure to prevent congenital rubella by termination of infected pregnancies may therefore contribute to the increased incidence of the syndrome in Asians. Health education programmes about the dangers of rubella in pregnancy and of the need for vaccination can readily be promoted in the Asian community through existing ethnic organisations. Protection of other ethnic minorities likely to be at similar increased risk may require a vaccination programme aimed at national elimination of rubella.

Asia↗