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Biomedical subjects

A Turner

Publications and source records attributed to A Turner.

At least 37 records · Page 2Linked to original sources
PubMed2002

Effects of immunocontraception on population, longevity and body condition in wild mares (Equus caballus).

Contraception is becoming a common approach for the management of captive and wild ungulates yet there are few data for contraceptive effects on entire populations. Management-level treatment of mares with porcine zona pellucida (PZP) vaccine resulted in zero population growth of the Assateague Island wild horse population within 1 year of initiation of treatment. Contraceptive efficacy was 90% for mares treated twice in the first year and annually thereafter. For mares given a single initial inoculation, contraceptive efficacy was 78%. The effort required to achieve zero population growth decreased, as 95, 83 and 84% of all adult mares were treated in each of the first 3 years, compared with 59 and 52% during the last 2 years. Mortality rates for mares and foals after the initiation of management-level treatments decreased below historic and pretreatment mortality rates of approximately 5%. Two new age classes have appeared among treated animals (21-25 years and > 25 years), indicating an increase in longevity among treated animals. Body condition scores for all horses, all adult mares and non-lactating mares increased significantly between summer 1989 and autumn 1999 but did not change significantly in lactating mares. These results provide reliable data for the construction of realistic models for contraceptive management of free-roaming or captive ungulate populations.

Animals↗
PubMed2002

Reversibility of action and safety during pregnancy of immunization against porcine zona pellucida in wild mares (Equus caballus).

Contraceptive management of publicly valued wildlife species requires safeguards to ensure that these populations are preserved in a healthy state. In addition, reversibility of contraceptive effects and safety in pregnant animals are major concerns. A population of wild horses has been immunized against porcine zona pellucida (PZP) over a 12 year period on Assateague Island National Seashore, MD (ASIS). Mares initially received one or two 65 microg inoculations and once a year 65 microg booster inoculations, all delivered by dart. All young mares aged > 2 years were treated with PZP for 3 consecutive years regardless of whether they have bred successfully and they were then removed from treatment until they had foaled. All mares vaccinated for 1 or 2 consecutive years became fertile again and 69% of mares treated for 3 consecutive years returned to fertility. All five mares treated for 4 or 5 consecutive years have also returned to fertility, but over longer periods of time. Mares treated for 7 consecutive years have not returned to fertility, but several, while still infertile, have started ovulating again. There was no difference in survival rates between foals born to treated and untreated mares, and PZP treatment of pregnant mares did not affect subsequent fertility of their female offspring.

Animals↗
PubMed2001

Sediment-water partitioning of inorganic mercury in estuaries.

The sediment-water partitioning and speciation of inorganic mercury have been studied under simulated estuarine conditions by monitoring the hydrophobicity and uptake of dissolved 203Hg(II) in samples from a variety of estuarine environments. A persistent increase in the distribution coefficientwith increasing salinity is inconsistent with inorganic speciation calculations, which predict an increase in the concentration of the soluble HgCl4(2-) complex (or reduction in sediment-water distribution coefficient) with increasing salinity. Partition data are, however, defined by an empirical equation relating to the salting out of nonelectrolytes via electrostriction and are characterized by salting constants between about 1.4 and 2.0 L mol(-1). Salting out of the neutral, covalent chloro-complex, HgCl2(0), is predicted but cannot account for the magnitude of salting out observed. Since Hg(II) strongly complexes with dissolved (and particulate) organic matter in natural environments, of more significance appears to be the salting out of Hg(II)-organic complexes. Operational measurements of the speciation of dissolved Hg(II) using Sep-Pak C18 columns indicate a reduction in the proportion of hydrophobic (C18-retained) dissolved Hg(II) complexes with increasing salinity, both in the presence and absence of suspended particles. Ratios of hydrophobic Hg(ll) before and after particle addition suggest a coupled salting out-sorption mechanism, with the precise nature of Hg(II) species salted out being determined bythe characteristics and concentrations of dissolved and sediment organic matter.

Absorption↗
PubMed2001

Ligand dependence of metal-metal bonding in the d(3)d(3) dimers M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I).

The ligand dependence of metal-metal bonding in the d(3)d(3) face-shared M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I) dimers has been investigated using density functional theory. In general, significant differences in metal-metal bonding are observed between the fluoride and chloride complexes involving the same metal ion, whereas less dramatic changes occur between the bromide and iodide complexes and minimal differences between the chloride and bromide complexes. For M = Mo, Tc, and Re, change in the halide from F to I results in weaker metal-metal bonding corresponding to a shift from either the triple metal-metal bonded to single bonded case or from the latter to a nonbonded structure. A fragment analysis performed on M(2)X(9)(3-) (M = Mo, W) allowed determination of the metal-metal and metal-bridge contributions to the total bonding energy in the dimer. As the halide changes from F to I, there is a systematic reduction in the total interaction energy of the fragments which can be traced to a progressive destabilization of the metal-bridge interaction because of weaker M-X(bridge) bonding as fluoride is replaced by its heavier congeners. In contrast, the metal-metal interaction remains essentially constant with change in the halide.

Journal Article↗
PubMed2001

Yeast 2 microm plasmid copy number is elevated by a mutation in the nuclear gene UBC4.

The copy number of the Saccharomyces cerevisiae endogenous 2 microm plasmid is under strict control to ensure efficient propagation to the daughter cell without significantly reducing the growth rate of the mother or the daughter cell. A recessive mutation has been identified that resulted in an elevated but stable 2 microm plasmid copy number, which could be complemented by a genomic DNA clone containing the UBC4 gene, encoding an E2 ubiquitin-conjugating enzyme. A ubc4::URA3 deletion resulted in the same elevated 2 microm plasmid copy number. An analysis of the endogenous 2 microm transcripts revealed that the steady-state abundance of REP1, REP2, FLP and RAF were all increased 4-5-fold in the mutant. Analysis of the mutant ubc4 allele identified a single base pair mutation within the UBC4 coding region, which would generate a glutamic acid to lysine amino acid substitution within a region of conserved tertiary structure located within the first alpha-helix of Ubc4p. These investigations represent the first molecular characterization of a mutation within a Saccharomyces cerevisiae nuclear gene shown to affect 2 microm steady-state plasmid copy number and implicate the ubiquitin-dependent proteolytic pathway in host control of 2 microm plasmid copy number.

Blotting, Southern↗
PubMed2001

In Southern Africa, brown oculocutaneous albinism (BOCA) maps to the OCA2 locus on chromosome 15q: P-gene mutations identified.

In southern Africa, brown oculocutaneous albinism (BOCA) is a distinct pigmentation phenotype. In at least two cases, it has occurred in the same families as tyrosinase-positive oculocutaneous albinism (OCA2), suggesting that it may be allelic, despite the fact that this phenotype was attributed to mutations in the TYRP1 gene in an American individual of mixed ancestry. Linkage analysis in five families mapped the BOCA locus to the same region as the OCA2 locus (maximum LOD 3.07; theta=0 using a six-marker haplotype). Mutation analysis of the human homologue of the mouse pink-eyed dilution gene (P), in 10 unrelated individuals with BOCA revealed that 9 had one copy of the 2.7-kb deletion. No other mutations were identified. Additional haplotype studies, based on closely linked markers (telomere to centromere: D15S1048, D15S1019, D15S1533, P-gene 2.7-kb deletion, D15S219, and D15S156) revealed several BOCA-associated P haplotypes. These could be divided into two core haplotypes, suggesting that a limited number of P-gene mutations give rise to this phenotype.

Albinism, Oculocutaneous↗
PubMed2001

Regulation of histone acetylation and transcription by INHAT, a human cellular complex containing the set oncoprotein.

Acetylation of histones by p300/CBP and PCAF is considered to be a critical step in transcriptional regulation. In order to understand the role of cellular activities that modulate histone acetylation and transcription, we have purified and characterized a multiprotein cellular complex that potently inhibits the histone acetyltransferase activity of p300/CBP and PCAF. We have mapped a novel acetyltransferase-inhibitory domain of this INHAT (inhibitor of acetyltransferases) complex that binds to histones and masks them from being acetyltransferase substrates. Endogenous INHAT subunits, which include the Set/TAF-Ibeta oncoprotein, associate with chromatin in vivo and can block coactivatormediated transcription when transfected in cells. We propose that histone masking by INHAT plays a regulatory role in chromatin modification and serves as a novel mechanism of transcriptional regulation.

Acetylation↗
PubMed2001

Visual signal detection measured by event-related potentials.

Signal Detection tasks typically involve within-subject signal changes. Such a procedure does not lend itself to event-related potential (ERP) experiments where the need for averaging necessitates the maintenance of consistent stimulus parameters. In the present ERP study we adopt a novel approach to thresholding that allows within-subject signal manipulation. The Signal Detection task required the identification of letter targets, formed from dots, in a random dot field. ERP waveforms were segmented into three windows corresponding to N1, N2, and P300 components. Analysis shows that ERP variations are dependent on both task demands and response characteristics for N1, N2, and P300 components.

Adolescent↗
PubMed2001

The influence of salting out on the sorption of neutral organic compounds in estuaries.

The relative (unsaturated) solubility and sorption of 2,2',5,5'-tetrachlorobiphenyl have been studied along an estuarine salinity gradient. The aqueous compound was salted out with increasing salinity and an aqueous salting constant of about 0.0021 g(-1) was derived. Sorption of the compound to estuarine particles increased with increasing salinity for a range of particle concentrations, but the magnitude of this effect (sorption salting constants of about 0.005-0.011 g(-1)) indicated that salting out of the aqueous phase was not solely responsible. It is suggested that the hydrophobicity of sediment organic matter is enhanced by its interaction with seawater ions through a reduction in the charge of the particle surface and, possibly, modification of the structure of the organic matter. Examination of literature data on the sorption of neutral organic compounds to estuarine sediment indicates a general increase in sorption with increasing salinity which can be empirically defined by a salting equation. Although charge reduction of estuarine particles is a general observation, it is not possible to establish the general significance of this effect (or any other form of salting out of sediment organic matter) on the sorption of organic compounds in estuaries because appropriate site- and compound-specific aqueous salting constants are unavailable. Increased sorption at high salinities has obvious implications for the disposal and transport of organic chemicals in estuaries. However, the inverse dependency of sediment-water partitioning on particle concentration is likely to be of at least equal significance in macrotidal environments where sediment resuspension occurs. An empirical model, combining the effects of salinity and particle concentration, is proposed for deriving first-order estimates of the partitioning of neutral organic compounds in estuaries.

Absorption↗
PubMed2001

Corrosive esophagitis in children: a 30-year review.

Caustic ingestion with resultant corrosive esophagitis in the pediatric population comprises a heterogeneous group in terms of offending agent, location of burn and the degree of damage. Consequently, the treatment of these injuries has also varied over the years and the optimal management remains controversial. Another area of concern that is seldom reported in the otolaryngology literature is the socioeconomic impact of such injuries both on the child and on the family. We report a 30-year retrospective review of aerodigestive tract caustic injuries at The Hospital for Sick Children. Eighty patients were identified with an age range from 1 month to 16 years. Early and late complications are reviewed including 23 patients (29%) that developed medical complications and 16 patients (20%) that developed severe esophageal strictures. Five of these children required repeat prograde dilatation, while 11 children required gastrostomy and stringing with subsequent retrograde dilatation. All the 11 children required esophageal replacement surgery. The economic and social consequences to the child and family were also noted with particular attention to hospital costs, parental absenteeism from work, and the need for job relocation. A partial cost analysis using a child with a severe injury is presented as an example. Psychological aspects such as attempted murder, jail terms and attempted suicides are also documented. We also present an analysis of those children requiring esophageal replacement surgery, and examine the possible role of esophageal stents in recalcitrant strictures.

Adolescent↗
PubMed2001

Investigation of an outbreak of ciprofloxacin-resistant Neisseria gonorrhoeae using a simplified opa-typing method.

Ciprofloxacin-resistant gonococci have been isolated from patients in the United Kingdom since 1993. Until recently, evidence has suggested that the majority of infections are not endemic but have been acquired abroad. In October 1999, increasing numbers of ciprofloxacin resistant isolates of the non-requiring auxotype were reported in Oldham and Rochdale (Northwest England). These and similar isolates from elsewhere in England and Wales were genetically characterized using a simplified opa-typing method (a non-radioactive PCR-RFLP method targeting the opa family of genes). Of 73 isolates studied, 24 had unique opa-types (10 from infections acquired abroad), whilst the remaining 49 were indistinguishable (none were known to be acquired abroad). This cluster included 31 isolates from Oldham and Rochdale, 16 from elsewhere in the north of England, and 2 from Southern England and South Wales with known epidemiological links to cases from Manchester and Rochdale respectively. This study illustrates the potential for spread of an antibiotic resistant clone of N. gonorrhoeae both locally and nationally and demonstrates that endemic acquisition of ciprofloxacin-resistant gonococci is now a significant problem in the United Kingdom.

Antigens, Bacterial↗
PubMed2001

Partitioning of mercury onto suspended sediments in estuaries.

Radiochemical partitioning experiments using 203Hg have been undertaken with mixtures of river, seawater and sediment samples taken from three geochemically contrasting UK estuaries: the Plym, Beaulieu and Mersey. Species of dissolved Hg were determined using reversed-phase C18 chelating columns and particulate species were determined by sequential leaching with 1 M NH4OAc and 1 M HCl. Mercury had a high particle reactivity with partition coefficients, KDs, ranging from 10(4) to 5 x 10(5) ml g(-1), depending on salinity, the chemical composition of the end-member waters, and on the physico-chemical characteristics of the sediment. Dissolved organic matter present in the waters (humic substances and/or anthropogenic compounds) was found to be the main factor governing the forms of dissolved Hg and their reactivity. From the spiked 203Hg, up to 95% of the dissolved metal was retained on the C18 columns for the Mersey waters, whereas this fraction was < 60% in the Plym and Beaulieu waters. Quasi-irreversible adsorption of Hg onto particles from each estuary was observed over a time-scale of a few hours and < 20% of total particulate Hg was released by the sequential leach. In this paper, physico-chemical processes are proposed to explain the estuarine behaviour of Hg and the results are discussed in terms of Hg availability in estuarine systems.

Adsorption↗
PubMed2001

Proliferation of lens epithelial cells on the Acrysof intraocular lens: clinical and histological features of a case.

Postoperative deposits on the surface of intraocular lenses (IOLs) have been demonstrated in vivo for many IOL material types. The Acrysof acrylic lens develops a granular material extending from the capsulorhexis margin onto the IOL's anterior surface during the first 4 weeks after surgery in a significant proportion of cases. Complete resolution of this membrane occurs by 3 months in almost all cases. The case is presented of an 81-year-old woman who had a persisting membrane coverng the IOL surface at 6 months. This membrane was removed surgically and pathology showed the constituent cells to be of lens epithelial cell origin.

Acrylic Resins↗
PubMed2001

A neuropsychological-neuropathological case study of variant Creutzfeldt-Jakob disease.

We report the first neuropsychological-neuropathological case study of a patient with variant Creutzfeldt-Jakob disease (vCJD) who was seen at the early stages of the disease, and whose cognitive functioning was monitored in the following months until his death. At presentation, his neuropsychological profile included impaired ability to retain new episodic information, deficits on tests of retrieval from semantic memory, and impairments on tests of memory for public knowledge, such as famous personalities. Tests of executive function were also performed poorly. Picture recognition memory and autobiographical memory were relatively spared, as was performance on tests of face perception and complex copying ability. Neuropsychological testing may be useful in monitoring the progression of vCJD, and we provide evidence to show a steady rate of decline in perceptual and naming tasks over a 4-month period. Post-mortem findings showed neuronal loss in the caudate, putamen, dorsal thalamus, cerebellum and occipital cortex. Spongiform changes were found throughout the brain, including the entorhinal cortex and anterior thalamus. Prion protein accumulation was noted in the hippocampus. We hypothesize that primary subcortical damage to structures in the thalamus and neostriatum, together with secondary frontal lobe dysfunction, combine to yield the pattern of neuropsychological impairment and neuropsychological sparing that was found.

Adult↗
PubMed2001

The differential assessment of children's attention: the Test of Everyday Attention for Children (TEA-Ch), normative sample and ADHD performance.

"Attention" is not a unitary brain process. Evidence from adult studies indicates that distinct neuroanatomical networks perform specific attentional operations and that these are vulnerable to selective damage. Accordingly, characterising attentional disorders requires the use of a variety of tasks that differentially challenge these systems. Here we describe a novel battery, the Test of Everyday Attention for Children (TEA-Ch), comprising nine subtests adapted from the adult literature. The performance of 293 healthy children between the ages of 6 and 16 is described together with the relationships to IQ, existing measures of attention, and scholastic attainment. This large normative sample also allows us to test the fit of the adult model of functionally separable attention systems to the observed patterns of variance in children's performance. A Structural Equation Modelling approach supports this view. A three-factor model of sustained and selective attention and higher-level "executive" control formed a good fit to the data, even in the youngest children. A single factor model was rejected. There are behavioural and anatomical grounds to believe that Attention Deficit Disorder (ADD) is particularly associated with poor self-sustained attention and behavioural control. The TEA-Ch performance of 24 boys diagnosed with ADD presented here is consistent with this view. When performance levels on WISC-III subtests were taken into account, specific deficits in sustained attention were apparent while selective attention performance was within the normal range.

Activities of Daily Living↗
PubMed2001

Antibiotic prophylaxis to prevent post-abortal upper genital tract infection in women with bacterial vaginosis: randomised controlled trial.

OBJECTIVE: To determine the prevalence of bacterial vaginosis in women undergoing first trimester suction termination of pregnancy and to evaluate the efficacy of metronidazole in reducing the risk of post abortal pelvic infection in women with bacterial vaginosis. DESIGN: Randomised double-blind placebo-controlled trial. SETTING: Two teaching hospitals and one district general hospital. SAMPLE: Two hundred and seventy-three women with bacterial vaginosis undergoing termination of pregnancy. METHODS: Women with bacterial vaginosis, diagnosed using modified Spiegel's criteria, were individually randomised to receive either a 2 g metronidazole suppository or identical placebo per-operatively. Participants, doctors and investigators were blinded to treatment allocation. Participants were asked to complete a questionnaire about post-operative symptoms, visits to the general practitioner, antibiotic treatment, readmission to hospital, contraception and emotional response after one month. RESULTS: The prevalence of bacterial vaginosis was 29.3% (326/1,111). Intention-to-treat analysis showed that post-operative upper genital tract infection developed in 12/142 (8.5%) women allocated to metronidazole and 21/131 (16.0%) women randomised to placebo, a difference of 7.6% (95% confidence intervals -15.4 to +0.2%; relative risk 0.53. 0.27 to 1.03, P = 0.055). The effect of prophylaxis was similar when the analysis was restricted to women receiving the allocated treatment and with complete follow up. There was no difference in the risk of readmission to hospital and the frequencies of self reported symptoms in the two groups were similar. CONCLUSION: This randomised placebo-controlled trial among women with bacterial vaginosis provides weak evidence that metronidazole decreases the risk of upper genital tract infection after first trimester suction termination of pregnancy but a chance finding could not confidently be excluded. Large well-conducted randomised trials with long term outcome measures are now needed to determine the most effective antibiotic combinations and strategy for prevention of post-abortal pelvic infection.

Abortion, Induced↗
PubMed2001

Oxidative stress in the fetal lamb brain following intermittent umbilical cord occlusion: a path analysis.

OBJECTIVE: To evaluate the relative contribution of cord occlusion length intervals between occlusions and experimental duration on oxidative stress in the fetal lamb brain. DESIGN: Acute, partially exteriorised fetal lambs with intermittent total cord occlusion. SETTING: The Vivarium of Westmead Hospital, University of Sydney, Australia and The Chinese University of Hong Kong. MAIN OUTCOME MEASURES: Arterio-venous differences in the concentration of organic hydroperoxides, measured in paired samples of carotid arterial and jugular venous blood, as an index of oxidative stress in the brain. METHODS: Thirty-two fetal lambs were exposed to graded hypoxia, induced by intermittent total umbilical cord compression of 30 seconds, 60 seconds and 90 seconds duration, occurring every minute for a total of 27 occlusions over 81 minutes. Three sham experiments were also performed. In addition to organic hydroperoxides, carotid arterial blood samples were also assayed in 15 animals (two sham) for oxygen saturation, pH, hypoxanthine, xanthine and urate concentrations. A causal model for oxidative stress was defined: occlusions leading to hypoxia with a rise in hypoxanthine; reperfusion during intervals between occlusions leading to the accelerated production of xanthine and uric acid and the generation of oxygen free radicals, which in turn, are responsible for the rise in lipid peroxidation. Path analysis was performed to assess the strength of the relationships between these variables and the cord occlusion length, the interval between occlusions and the duration of the experiment. RESULTS: Sham experiments showed no change in organic hydroperoxide production. Following 30-second umbilical cord occlusions a sixfold drop in mean organic hydroperoxides was observed between carotid arterial and jugular venous levels. In contrast, following occlusions of 60 seconds duration (or longer) a median 20-fold increase in organic hydroperoxide production was observed. Path analysis revealed a strong indirect pathway from occlusion length --> hypoxanthine --> urate and weak positive pathways from oxygen saturation --> urate and from interval between occlusions --> urate. After accounting for these pathways reflecting oxidative stress, a strong direct path remained from time from first occlusion --> organic hydroperoxide production. CONCLUSIONS: Peroxidation of lipids in the brain occurs under conditions of severe hypoxia and reperfusion associated with intermittent umbilical cord occlusions of 60 seconds or longer. The path analysis supported the causal model as originally defined, with the exception that the indirect pathway via pH was found to be trivial.

Animals↗