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Biomedical subjects

C R Kennedy

Publications and source records attributed to C R Kennedy.

At least 91 records · Page 5Linked to original sources
PubMed1994

X-linked adrenoleukodystrophy with non-diagnostic plasma very long chain fatty acids.

Measurement of plasma very long chain fatty acids is widely recognised as a sensitive screening test for X-linked adrenoleukodystrophy (X-ALD). This test has particular importance because of the highly variable clinical expression of X-ALD. In this affected family the progressive childhood form of X-ALD was accompanied by "non-diagnostic" concentrations of plasma very long chain fatty acids. The implications for diagnosis of X-ALD are discussed.

Adrenoleukodystrophy↗
PubMed1994

Feasibility of otoacoustic emission detection followed by ABR as a universal neonatal screening test for hearing impairment.

The feasibility of attempting a two-stage universal screening test for auditory impairment was assessed at a large district maternity hospital. The first stage was measurement of otoacoustic emissions using the Programmable Otoacoustic Emission Measurement System. Those failing the first stage proceeded to automated analysis of auditory brainsteam responses. A single tester working for 6 h on 6 days per week attempted to test all babies born between the hours of midday and midnight for 2 weeks and then all babies born between midnight and midday for a further 2 weeks. Of 217 babies born during the study periods, one infant died and three were still receiving intensive care at the end of the study. Of the remaining 213 infants, auditory testing was undertaken in 201 infants (94%). Eight infants (4%) who failed the first stage of the screening test did not undergo the second stage. Of those 193 infants completing the screen, one (0.5%) failed the screen unilaterally. There were no bilateral failures. Three testers, working two and a half whole-time equivalents, should be adequate to achieve a coverage of 90% and a specificity of 99% for this screen in this clinical setting.

Cross-Sectional Studies↗
PubMed1994

A comparison of neonatal evoked otoacoustic emissions obtained using two types of apparatus.

The transient evoked otoacoustic emission (TEOAE), generated by a click and recorded in the ear canal is influenced by many factors. Of these, the form of the stimulus, the characteristics of the microphone, amplifiers and filter are probably the major ones. In addition, the acoustical loading of the ear canal by the probe may interact with the TEOAE measurement. Data presented here were obtained from 64 babies tested on each of 3 days post partum. The differences in the TEOAEs produced by the ILO88 and POEMS instruments can be quite marked. The ILO88 TEOAEs consistently have larger high frequency components than do the emissions from the POEMS system. The ILO88 system also gives higher correlations between repeat recordings. Such differences point out the need for explicit standards in probe design.

Equipment Design↗
PubMed1993

Maximum local helminth parasite community richness in British freshwater fish: a test of the colonization time hypothesis.

The investigation of Price & Clancy (1983), which demonstrated a significant positive correlation between total helminth species number per host species and geographical range of freshwater fish host species in Britain, was re-examined using a different measure of parasite species richness. Re-calculation of the correlations between the two parameters after controlling for the effect of the composition of the list of fish by excluding, on biological and distributional grounds, 2 species of agnathans and 7 species of introduced teleosts, and for the effect of sampling effort by using helminth richness in the richest component community of each fish species rather than check-list data, reveals no significant relationship between helminth species richness and host range. Habitat and an omnivorous host diet now appear more significant determinants of helminth richness than the accumulation of parasites by predation. The findings provide little support for the interpretation of the relationship between helminth species richness and host range in terms of island biogeographic theory, but do support an alternative explanation in terms of the colonization time hypothesis, i.e. that helminth species richness is related to the time since the fish host arrived in Britain.

Analysis of Variance↗
PubMed1993

The mitochondrial DNA transfer RNA(Lys)A-->G(8344) mutation and the syndrome of myoclonic epilepsy with ragged red fibres (MERRF). Relationship of clinical phenotype to proportion of mutant mitochondrial DNA.

The mitochondrial DNA (mtDNA) transfer RNA (tRNA)Lys A-->G(8344) mutation was identified in seven patients. These patients and their relatives were assessed clinically; in one family the mutation was deduced to be present in four generations. The phenotype in index cases was consistent with the syndrome of myoclonic epilepsy with ragged red fibres, with the core clinical features of myoclonus, ataxia and seizures. Amongst other features, progressive external ophthalmoplegia, Leigh's syndrome and stroke-like episodes were observed, well recognized in mitochondrial myopathies but novel manifestations of this genotype. Samples of blood and muscle were analysed for the proportion of mutant mtDNA using an oligonucleotide hybridization technique. The proportion of mutant mtDNA in blood was significantly greater in symptomatic than asymptomatic cases. Furthermore, the proportion of mutant mtDNA in blood correlated with age of onset of disease and clinical severity assessed by a simple scale. Study of disease associated with the tRNA(Lys) A-->G(8344) mutation provides further insight into the pathogenesis and transmission of mitochondrial diseases. Quantification of the proportion of mtDNA in tissues demonstrates that this is a major factor determining the course of disease, but other, as yet unidentified factors are also likely to play a role.

Adult↗
PubMed1993

External- and middle-ear factors affecting evoked otoacoustic emissions in neonates.

Babies without any of the known risk factors for hearing impairment were taken from normal maternity wards and tested daily for 3 days post-partum. Tympanometric and evoked otoacoustic emission data were obtained from 121 babies. Middle-ear pressure and middle-ear compliance values were obtained with a Grason Stadler Middle-Ear Analyser (GSI-33) using a 1000-Hz probe tone. All babies had their evoked emissions measured on the Programmable Otoacoustic Emissions Measurement System (POEMS) equipment. The middle-ear compliance, the proportion of normally shaped tympanograms, the middle-ear pressure and the proportion passing EOAE testing all improved over the 3 days. However, the statistically significant factors affecting the pass rate appeared to be only the middle-ear pressure (for a small number of babies) and the degree of obstruction of the external ear canal. Whilst both these factors play a part in determining emission pass/fail rates they do not fully account for the observed changes in pass rate. There are developmental and other mechanisms which must contribute to the increase in pass rate as the baby matures.

Acoustic Impedance Tests↗
PubMed1992

Species richness in helminth communities: the importance of multiple congeners.

Using data sets derived from published literature, the contribution of congeneric species to helminth component community richness is evaluated. Consideration of the frequency distribution of congeners in relation to host and parasite groups reveals that the distributions are unimodal, that singletons are the commonest class and that the frequency of occurrence of congeners decreases with increasing number of species per genus. Congeners may be found in any group of hosts or parasites, but are more common amongst cestodes of aquatic birds. Two patterns of occurrence of congeneric species are recognized: one in which from a few to multiple congeners are found within a single helminth genus, exemplified by dactylogyrid monogeneans and cloacinid nematodes, and the other in which there is a simultaneous occurrence of congenerics and confamilials such that there are several genera involved, but each represented by fewer species, exemplified by strongyles in horses. The question of whether these patterns can be considered examples of species flocks is discussed. We conclude that multiple congeners and species flocks are interesting phenomena but, except in isolated cases, they make insignificant contributions to community richness.

Animals↗
PubMed1991

Potential interactions between Acanthocephalus anguillae and Pomphorhynchus laevis in their natural hosts chub, Leuciscus cephalus and the European eel, Anguilla anguilla.

Chub and eels were experimentally infected via intermediate hosts harbouring cystacanths, with Pomphorhynchus laevis alone, or Acanthocephalus anguillae alone, or simultaneously with mixtures of both species in varying proportions, and sampled at 7, 56 or 112 days post-infection. Examination of chub revealed that both species showed low establishment and growth rates, differing markedly from British field data, where chub is apparently one of the most important hosts, and preventing further meaningful experiments. Both species showed higher establishment rates in eels, but A. anguillae both grew faster and matured to a greater extent than P. laevis, reflecting field data. No evidence of any interactions, competitive or otherwise, was found in the mixed infections in eels at low or high infection levels. The results were interpreted with regard to British field data and current theories of the role of interspecific competition in structuring fish helminth communities.

Acanthocephala↗
PubMed1991

Site availability and density-dependent constraints on the acanthocephalan Pomphorhynchus laevis in rainbow trout, Oncorhynchus mykiss (Walbaum).

Threshold density levels were investigated experimentally in rainbow trout, Oncorhynchus mykiss, for the acanthocephalan Pomphorhynchus laevis. Fifty small fish 120-150 mm long were infected with 50 cystacanths each every 4 weeks for 16 weeks, and samples of up to 10 fish examined at 1, 5, 9, 13 and 17 weeks after the original infection. The mean intestinal length was found to have increased significantly over this period, from a mean of 125 to 173 mm and the mean number of parasites recovered increased after each interval of 4 weeks, and significantly from 19.30 to 86.40 per fish over the 17 weeks. The distribution of the parasites in the alimentary tract of O. mykiss was unaltered, indicating that the favourable region for establishment had remained unchanged. The failure to detect any manifestations of competition is discussed, and the relevance of conventional approaches to experimental investigations of both intra- and interspecific competition in fish was queried, and contrasted to the situation in birds and mammals.

Acanthocephala↗
PubMed1991

Herpes simplex encephalitis with relapse.

Three children are described in whom herpes simplex encephalitis (HSE) followed a clearly biphasic course. The secondary deterioration may be due to a resurgence of the viral infection and calls into question the adequacy of current treatment regimens for HSE. Alternatively, a postinfectious neuroallergic process may be active in which case immunomodulatory treatment might be more appropriate than further antiviral treatment.

Acyclovir↗
PubMed1991

Otoacoustic emissions and auditory brainstem responses in the newborn.

The auditory function of 370 infants, drawn from both low and high risk groups, was tested before postnatal discharge using three tests: standard auditory brain stem responses (ABR), automated analysis of ABR, and automated analysis of evoked otoacoustic emissions (OAE). All infants failing any neonatal test had further audiological evaluation. Follow up information was also available on those who passed neonatal tests. Automated OAE testing of both ears was quickest (median 12.5 minutes) and least invasive (no scalp electrodes). Bilateral failure rates (and upper 95% confidence limits) with a stimulus 35-36 dB above normal hearing threshold level (nHL) were 3.0% (4.6) with automated OAE, 3.2% (5.1) with ABR, and 2.7% (4.4) with automated ABR. Automated OAE was the test most sensitive for subsequently confirmed hearing impairment. Sequential testing with automated OAE followed, in those failing this test, by automated ABR would have provided a screening test for substantial hearing impairment with a specificity greater than 99% in this population. Possible application as a universal screen is discussed.

Audiometry, Evoked Response↗
PubMed1990

Interactions between the acanthocephalans Pomphorhynchus laevis and Acanthocephalus anguillae in rainbow trout: testing an exclusion hypothesis.

Rainbow trout were infected simultaneously with cystacanths of the two acanthocephalan species Pomphorhynchus laevis and Acanthocephalus anguillae in the laboratory. Infections consisted of varying proportions of the two species (from 0 to 100%) at low (20 cystacanths) and high (60 cystacanths) levels. Fish were sacrificed at 7, 56 and 112 days post-infection (p.i.) and the parasites recovered. At low-level infections there was a high degree of overlap in the range of intestine occupied by the two species (44.12%) and no evidence for interspecific competition affecting either species. At high-level infections the establishment of both species was unaffected by the presence or number of individuals of the other species. The survivorship and the range of intestine occupied by A. anguillae were found to be reduced in the presence of P. laevis. The interaction was one-sided, as P. laevis remained unaffected by A. anguillae, and so indicated interference competition. The possibility that both intraspecific and interspecific competition are implicated in explaining the distribution of the two species in the British Isles is discussed.

Acanthocephala↗
PubMed1990

Hyperinsulinaemic hypoglycaemia in small for dates babies.

Blood glucose concentrations were measured prospectively in 27 small for dates infants in the first 48 hours after birth: 10 infants became hypoglycaemic. Of these, five had inappropriately raised plasma insulin concentrations. Plasma free fatty acids were lower and carbohydrate intake higher in these five infants, further supporting the diagnosis of hyperinsulinism. The hypoglycaemia recurred in four of the five hyperinsulinaemic infants, but in none of those who were not hyperinsulinaemic. Hyperinsulinism is common in small for dates babies. It is important to recognise this because hypoglycaemia is likely to recur and appropriate treatment is needed to prevent long term sequelae.

C-Peptide↗