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Biomedical subjects

C R Kennedy

Publications and source records attributed to C R Kennedy.

At least 37 records · Page 2Linked to original sources
PubMed2001

Diuretic therapy for newborn infants with posthemorrhagic ventricular dilatation.

BACKGROUND: Intraventricular hemorrhage remains a serious complication of premature birth and post hemorrhagic hydrocephalus still has no satisfactory treatment. Acetazolamide and furosemide, which both reduce the production of cerebrospinal fluid, have been suggested as non-invasive therapies to reduce hydrocephalus and the need for ventriculo-peritoneal (V-P) shunting. OBJECTIVES: The aim of this review was to determine whether the use of acetazolamide and furosemide improves outcome, especially shunt dependence, in infants developing post-hemorrhagic ventricular dilatation. SEARCH STRATEGY: The standard search strategy of the Cochrane Collaboration was used. SELECTION CRITERIA: Randomised, or quasi-randomised trials, of acetazolamide and/or furosemide compared with standard therapy in infants with IVH or post-hemorrhagic ventricular dilatation DATA COLLECTION AND ANALYSIS: Data were extracted independently by each author and were analysed by the standard methods of the Cochrane Collaboration using relative risk (RR) and risk difference (RD), a fixed effect model and sensitivity analyses where appropriate. MAIN RESULTS: There were two eligible trials: one randomized 16 infants and the other, 177. Neither showed a decreased risk for V-P shunt or for V-P shunt or death associated with acetazolamide and furosemide therapy. The larger trial showed that acetazolamide and furosemide treatment resulted in a borderline increase in the risk for motor impairment at one year (RR 1.27, CI 1.02 to 1.58; RD 0.16, CI 0.02 to 0.31), but did not significantly affect the risk for the combined outcome of delay, disability or motor impairment among survivors, or the risk of the combined outcome of death, delay, disability or impairment at one year. The larger trial showed that diuretic treatment increased the risk for nephrocalcinosis (RR 5.31, CI 1.90 to 14.84; RD 0.19, CI 0.09 to 0.29); meta-analysis confirmed this result. REVIEWER'S CONCLUSIONS: Acetazolamide and furosemide therapy is neither effective nor safe in treating post hemorrhagic ventricular dilatation. Acetazolamide and furosemide cannot be recommended as therapy for post hemorrhagic hydrocephalus.

Acetazolamide↗
PubMed2001

Interspecific interactions between larval digeneans in the eyes of perch, Perca fluviatilis.

The changes in prevalence and abundance of the three species of metacercariae in the humour of the eyes of perch Perca fluviatilis in Slapton Ley, Devon, have been monitored over a period of 29 years. Earlier studies had revealed that Diplostomum gasterostei was originally the sole occupant of this niche, but Tylodelphys clavata colonised in 1973 and T. podicipina in 1976. A decline in the number of perch with heavy infections of D. gasterostei was significantly negatively correlated with population abundance of T. clavata and a decline in recruitment rate of D. gasterostei coincided with the population increase in T. podicipino over the period 1976-1979. It was suggested that the decline in population size of D. gasterostei was due to inter-specific competition, but this hypothesis could not be tested experimentally. Subsequent investigations, reported here, confirmed the decline when the data set was extended to 1985. A severe decline in the perch population over the winter of 1984/1985 resulted in the disappearance of D. gasterostei and T. podicipina and this was followed by a slow recovery from 1990 onwards. This natural experiment provided an opportunity to test the hypothesis. Only T. clavata survived throughout the perch crash and the population continued at pre-crash levels up to 1999. Its congener T. podicipina did not re-appear until 1994 and was probably a re-introduction: it did not attain pre-crash levels until 1999. It is likely that D. gasterostei survived the crash as it re-appeared in 1991, but was confined to young of the year fish and barely approached pre-crash levels even in 1999. Its continual low levels cannot be explained by changes in the lake or in densities of snail intermediate or bird definitive hosts. New data revealed that the suspensory ligaments of the eye were the preferred site of all three species and that the eye was partitioned out between them. The data from the post-crash period do not refute but rather confirm earlier conclusions that inter-specific competition is responsible for the decline in D. gasterostei and this remains the preferred hypothesis.

Animals↗
PubMed2001

Metapopulation and community dynamics of helminth parasites of eels anguilla Anguilla in the River Exe system.

The possibility that much of the spatial and temporal variation in helminth communities in freshwater fish can be explained in terms of metapopulation theory was tested by examining helminth component communities of eels sampled from 3 localities in the River Exe and 5 of its tributaries on 2 occasions at an interval of 3 years. Four specific predictions of metapopulation theory in relation to community dynamics were tested. The prediction that parasite species could be recognized as common and rare and that this was sensitive to scale was met. The prediction that core species would be more widely distributed and have a higher dispersal ability was met only in part. The prediction that similarity between communities would increase with connectivity and decrease with distance apart was not met. The final prediction that species would go locally extinct and be replaced by rescue effects was not met. There was evidence of local extinctions; not of eel specialists but of species using other fish species as their principal definitive hosts. Eel helminth communities were heavily dominated by 3 species of eel specialists which were relatively stable and responsible for most of the similarity and its changes in space and time. It was concluded that metapopulation theory did not provide a very satisfactory explanation for the changes in the helminth communities in eels and reasons for this included the inherent difficulty of applying metapopulation theory to parasites and the fact that the helminth communities in eels in the River Exe were atypical in being dominated by eel specialists.

Air Sacs↗
PubMed2001

Long-term dynamics of Ligula intestinalis and roach Rutilus rutilus: a study of three epizootic cycles over thirty-one years.

Data are presented on 2 full epizootic cycles and the start of a third of Ligula intestinalis in roach Rutilus rutilus in a small lake, and the relationships of these cycles to the densities of rudd, Scardinius erythrophthalmus, and Great Crested Grebes, Podiceps cristatus, over 31 years. The parasite was introduced to the lake by P. cristatus in 1973 at a time when the roach population had increased in response to eutrophication to a level at which individual fish growth was stunted and the hithero dominant rudd population had declined in numbers as a consequence of inter-specific competition with roach. Ligula prevalence peaked at 28% in only 2 years: thereafter parasite-induced host mortality caused a decline in the roach population, releasing fish from stunting and allowing the rudd population to recover. The consequent improved growth of roach individuals and their short life-span reduced Ligula transmission rates and prevalence levels declined to approximately 1% although Ligula nevertheless persisted for a further 10 years. Following a massive winter-kill of the fish populations in 1984-1985, fish and Ligula numbers declined to barely detectable levels and the parasite disappeared from samples. Rudd recovered first, then roach and interspecific competition again led to a decline in rudd numbers. This increase in roach numbers led to a decrease in roach growth rates, which coincided with the re-colonization of the lake by Ligula. This second epizootic of Ligula peaked within 2 years in 1991-1992, when up to 78% of roach were infected with a maximum abundance of 2.2 parasites and intensity of 21 parasites. Heavy parasite-induced mortality of roach led to a decline in numbers, an improvement in individual growth rate and a reduction of Ligula transmission rates such that the epizootic died out in 1996. Similar conditions of roach numbers and growth prevailed at the start of a third cycle in 1998. The course of events over the second cycle was so similar to that of the first that it confirms the interpretations of that cycle. Comparison with other localities shows that epizootics of Ligula always coincide with rapid increases in roach numbers, for whatever cause, and stunted growth, which together attract piscivorous birds. At the start of a cycle Ligula is a major determinant of the population dynamics of the roach, but at the end of the cycle the fish population dynamics determine those of the parasite. The cycles are not regulated and the roach-Ligula system is inherently unstable.

Animals↗
PubMed2001

Helminth communities in eels Anguilla anguilla from Adriatic coastal lagoons in Italy.

The composition and diversity of the total and intestinal component and infra-communities were determined in eels Anguilla anguilla from three shallow lagoons on the Adriatic coast of Italy to determine whether the helminth communities would differ in composition and structure from those in eels from lagoons on the Tyrrhenian coast. The lagoons differed in respect of their management regimes and the extent of freshwater influx. Both freshwater and marine species of helminths were found in the eels in all three lagoons, but the freshwater component was richer in Valle Figheri. A suite of three digenean eel specialist species occurred in all three lagoons, of which any two members dominated each community. This conferred a high degree of similarity between the communities of the three lagoons. The same three species also dominated helminth communities in eels in lagoons along the Tyrrhenian coast of Italy, and compositional similarity levels were similar within and between western and eastern groups. Species richness was higher in the component communities of the eels of the Adriatic lagoons when compared to the Tyrrhenian ones, but diversity and dominance indices were of a similar order of magnitude and range. Intestinal helminth communities were richer and more diverse in two of the Adriatic lagoons because the proportion of eels with zero or one helminth species was, unusually, in the minority. It was nevertheless concluded that infracommunity structure was similar in eels from both western and eastern lagoons and that the hypothesis that it would differ in Adriatic lagoons could not be supported. The findings provide further evidence of the similarity in composition and structure of helminth communities in eels from coastal lagoons throughout Europe.

Anguilla↗
PubMed2001

The effects of meiosis activating sterol on in-vitro maturation and fertilization of human oocytes from stimulated and unstimulated ovaries.

The object of this study was to assess functional maturation in vitro by obtaining data on the fertilization and embryonic competence of human oocytes with or without exposure to meiosis activating sterol (MAS) during maturation in vitro. Immature oocytes were either collected from unstimulated patients with polycystic ovaries (PCO) during gynaecological surgery, or were donated by patients undergoing a cycle of intracytoplasmic sperm injection (ICSI) treatment including ovarian stimulation with gonadotrophins. PCO oocytes had variable cumulus cover, which was retained during culture while those from ICSI patients were cultured without cumulus. The study included 119 oocytes from PCO patients and 72 from ICSI patients. The oocytes were allowed to mature in vitro for up to 46 h in the presence or absence of MAS. Mature oocytes were inseminated by ICSI with fertile donor spermatozoa and embryo development was monitored in vitro. MAS (30 microg/ml) significantly increased the survival of oocytes from PCO patients (P < 0.01) but did not significantly affect the proportion completing maturation in vitro. For the ICSI patients, >90% of oocytes survived in all culture groups, regardless of MAS addition, however MAS (10 or 30 microg/ml) significantly increased the proportion of oocytes maturing in vitro (P < 0.05). The apparent tendency towards improved subsequent development in vitro will require larger numbers of oocytes for evaluation. Oocytes from ICSI patients matured more rapidly in vitro than those from PCO patients. Our results show positive effects of MAS on human oocytes, confirming previous data in mice. This work may have implications for the future clinical application of IVM.

Adult↗
PubMed2001

Colonisation and extinction in relation to competition and resource partitioning in acanthocephalans of freshwater fishes of the British Isles.

This paper challenges two paradigms long held in relation to the ecology of parasites in freshwater systems: (1) autogenic species are poorer colonisers than allogenic ones; and (2) parasites with direct life cycles are more successful colonisers than those with complex life cycles. Using new and existing data for Acanthocephala in freshwater fish from the British Isles, it is suggested that all six species present have been able to colonise and persist successfully, in spite of the supposed limitations of their autogenic life-style. It is proposed that these parasites have overcome these limitations by a variety of means, which apply equally to all species considered. Foremost among these is the utilisation of a migratory fish host as either a preferred or a suitable host in their life cycle, allowing colonisation of new areas and rescue effects in established areas, whilst equally important is the use of a common and widespread crustacean as the intermediate host. In addition, all six species appear to exhibit resource partitioning by host at either or both the larval and adult stages, thus reducing the potential for competition and further facilitating colonisation and survival. This hypothesis is supported by data from previous studies both on acanthocephalans from Europe and North America and on other autogenic parasites. It also provides an explanation for the apparently atypical host utilisation patterns of some acanthocephalan species in areas on the edge of their distributions, notably in Ireland.

Acanthocephala↗
PubMed2001

Randomized, controlled trial of acetazolamide and furosemide in posthemorrhagic ventricular dilation in infancy: follow-up at 1 year.

OBJECTIVE: Posthemorrhagic ventricular dilation (PHVD) is a complication of intraventricular hemorrhage in preterm infants and is associated with a high risk of long-term disability. Furosemide and acetazolamide are used widely in the treatment of PHVD in the hope of avoiding the need for placement of a ventriculoperitoneal shunt, but these drugs have not been evaluated in a controlled trial. This article reports a multicenter, randomized, controlled trial designed to test the hypothesis that these drugs would reduce the rate of shunt placement (or death) and increase survival to 1 year of age without disability. METHODS: Between 1992 and 1996, 177 infants who were less than 3 months past term and had ventricular width >4 mm above the 97th centile following intraventricular hemorrhage were assigned randomly to either standard therapy or standard therapy plus drug therapy with acetazolamide (100 mg/kg/d) plus furosemide (1 mg/kg/d). Infants who were enrolled in the trial had a median gestational age of 28.6 weeks and were enrolled at a mean postnatal age of 3.6 weeks. Forty-four percent were reported to have a cerebral parenchymal lesion on ultrasound scan at randomization. The primary outcome measure of death or shunt placement (known in all but 1 infant) occurred in 56 of 88 infants who were allocated to drug plus standard therapy compared with 46 of 88 who were allocated to standard therapy. The risk ratio was 1.23 (95% confidence interval: 0.95-1.59). Neurodevelopmental outcome information at a corrected age of 1 year (known in all but 3 of 149 surviving infants) included disability or neuromotor impairment in 54 of 67 infants (81%) who were allocated to drug plus standard therapy and 52 of 69 infants (66%) who were allocated to standard therapy. Seventy-two of 85 infants (85%) who were allocated to drug therapy either died or were disabled or impaired at 1 year compared with 62 of 89 infants (70%) who were treated with standard therapy (risk ratio: 1.22; 95% confidence interval: 1.03-1.4376). The excess risk of these adverse outcomes was greater among infants who did not have a cerebral parenchymal lesion seen on ultrasound examination at trial entry. CONCLUSIONS: These results suggest that the use of acetazolamide and furosemide in preterm infants with PHVD is ineffective in decreasing the rate of shunt placement and is associated with increased neurologic morbidity. This treatment therefore cannot be recommended.

Acetazolamide↗
PubMed2000

Effect of salinity on hatching, survival and infectivity of Anguillicola crassus (Nematoda: Dracunculoidea) larvae.

The effect of salinity on hatching, larval survival and infectivity of Anguillicola crassus was studied under experimental conditions using eggs obtained from naturally infected eels. Egg hatching rate, second-stage larval survival and larval infectivity were maximal in fresh water and declined with increase in salinity. Larvae survived up to 100 d in fresh water, 70 d in 50 % sea water and 40 d in 100% sea water. Infectivity experiments demonstrated that salinity influenced transmission success throughout the life cycle by decreasing total infectivity of the larval population in utero within female A. crassus and when larvae were free-living in the aquatic environment. Infectivity was age-dependent in relation to salinity. Larvae were infective to intermediate and paratenic hosts for up to 80 d in fresh water, 21 d in 50% sea water and up to 8 d in 100% sea water. The data confirm field observations that infection levels decrease with an increase in salinity. The study contributes to experimental verification of the colonization abilities of A. crassus and supports the hypothesis that A. crassus can be disseminated and transmitted in brackish water. The importance of regular monitoring and stringent hygiene practices in the transportation of eels is emphasized.

Air Sacs↗
PubMed2000

A clinical and genetic study of a manifesting heterozygote with X-linked myotubular myopathy.

X-linked myotubular myopathy (XLMTM) characteristically causes severe or fatal muscle weakness in male infants. Mutations in the gene MTM1, encoding the protein myotubularin, can be identified in most families. Prior to this report, XLMTM was thought not to cause symptomatic manifestations in female carriers. We describe an adult female from a large family with typical XLMTM. The patient had progressive disabling muscle weakness of later onset and lesser severity than that observed in affected males. The distribution of weakness resembled typical XLMTM with facial weakness, marked limb-girdle weakness, respiratory muscle involvement and dysphagia. Analysis of the MTM1 gene identified a heterozygous missense mutation (G378R) within the highly conserved tyrosine phosphatase site of myotubularin. We did not identify significantly skewed X-inactivation. We conclude that XLMTM is capable of causing significant disability in heterozygotes.

Female↗
PubMed2000

Physiological status of wild European eels (Anguilla anguilla) infected with the parasitic nematode, Anguillicola crassus.

The effect of the parasitic swimbladder nematode, Anguillicola crassus, on the physiological status of wild European eels (Anguilla anguilla) was investigated during an 18 month survey (February 1995 until September 1996), and compared with that of wild uninfected eels collected over the same time-period. Despite the occurrence of up to 15 blood-feeding adults in the swimbladder lumen of the infected eels and as many as 25 additional larvae in the swimbladder wall, there were no major differences in hormonal, metabolic or osmoregulatory status of the 2 groups of eels. Wild European eels appear to adapt to chronic parasitism with Anguillicola crassus. The possible adverse effects of additional simultaneous stressors are discussed.

Air Sacs↗
PubMed2000

Survival and transmission of Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974 (Nematoda) in seawater eels.

The study aims were to quantify the survivorship of Anguillicola crassus in eels in seawater and investigate transmission in estuarine (50% seawater) and marine (100% seawater) simulated conditions. Most A. crassus were able to survive and reproduce in 50% and 100% seawater eels for up to 6 months and therefore could survive during the spawning migration of eels to the Sargasso Sea. Up to 10% of the parasite metapopulation were damaged after long-term exposure to 50% or 100% seawater. Transmission of A. crassus was completed in 50% and 100% seawater in the laboratory, although infection levels in 100% seawater hosts were always lower. Transmission in estuaries is ecologically possible since the copepod Eurytemora affinis is susceptible to infection and is the dominant autochthonous species in most tidal estuaries in the Northern hemisphere. Transmission at sea is unlikely due to lack of suitable intermediate hosts. The data support the suggestion that dissemination of A. crassus has been facilitated by natural movement of eels in coastal waters. It is possible that A. crassus could impair the success of the eel spawning migration to the Sargasso Sea, although there is no direct evidence to support this.

Air Sacs↗
PubMed2000

Richness and diversity of intestinal metazoan communities in brown trout Salmo trutta compared to those of eels Anguilla anguilla in their European heartlands.

The hypothesis that intestinal helminth communities in freshwater brown trout are dissimilar in composition and structure to those in the European eel was tested by an analysis of component communities from 72 localities and of infracommunities from 34 localities in the British Isles and Norway. Derived indices were then compared with published data from eels. Composition of helminth communities differed considerably between the two hosts as a group of 4 species occurred commonly in trout and so gave greater predictability to the community composition. These 4 species were trout specialists and in 97% of the localities a trout specialist dominated the community rather than a generalist acanthocephalan as is typical for eels. By contrast all measures of community structure and indices of richness and diversity indicated that helminth communities in trout were isolationist in character, species poor and exhibited low diversity at both component and infracommunity levels. All values of indices for trout helminth communities were strikingly similar to those obtained from eels. Evidence of interspecific interactions within the trout helminth communities and a limit of 4 to infracommunity species richness further enhanced the similarities and suggested a common determinant of community structure. The hypothesis was thus supported in respect of species composition but refuted in respect of community structure.

Anguilla↗
PubMed2000

Structure-function analyses of eicosanoid receptors. Physiologic and therapeutic implications.

Prostaglandins (PGs) are ubiquitous lipid mediators derived from cyclooxygenase (COX) metabolism of arachidonic acid that exert a broad range of physiologic activities including modulation of inflammation, ovulation, and arterial blood pressure. The physiologic actions of PGs are mediated in part by their interaction with specific G-protein-coupled PG receptors. Eight PG receptors have been cloned, including four for the major COX metabolite, PGE2. The physiologic roles of the PGE2 receptors have been investigated utilizing subtype-selective agonists, localization of receptor mRNA expression, and creation of mice with targeted disruption of PG receptor genes. These analyses have delineated discrete roles for the various PG receptor subtypes. Recent studies on mice lacking the PGE2 EP2 receptor have implicated the PGE2 EP2 receptor subtype in arterial dilatation and salt-sensitive hypertension, and also indicate that this receptor plays a key role in female fertility. The EP2 receptor may thus prove to be a productive target for pharmacological intervention in the treatment of hypertension and infertility.

Animals↗