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Biomedical subjects

T Burke

Publications and source records attributed to T Burke.

At least 73 records · Page 4Linked to original sources
PubMed1997

Fluorescent dye assay for detection of DNA in recombinant protein products.

A homogeneous fluorescence-based DNA detection system has been developed to measure DNA in protein solutions. The technique relies on the increase in fluorescence of a dye molecule when it intercalates into double-stranded (ds) DNA. The increased fluorescence is a direct measurement of the amount of DNA in the sample. The analysis time required per sample is less than 5 min. The dye has absorbance and emission maxima at 485 and 530 nm, respectively. The assay is linear from 98 pg/mL to 200 ng/mL of DNA in buffers containing no proteins with typical relative standard deviation values of less than 2.4%. The assay performance was evaluated under various matrix conditions, including buffers, pH, ionic salts, detergents, denaturants and organic solvents. Each reagent was tested at several concentrations to determine how the slope and linearity (r value) of the standard curve were affected. Even in the presence of matrix components and protein, the assay was able to quantitatively detect picogram to nanogram levels of DNA. The fluorescence can be removed by DNase treatment. This method is specific for dsDNA with RNA emitting less than 2% intensity of an equivalent mass of DNA.

Buffers↗
PubMed1997

Noninvasive genetic tracking of the endangered Pyrenean brown bear population.

Pyrenean brown bears Ursus arctos are threatened with extinction. Management efforts to preserve this population require a comprehensive knowledge of the number and sex of the remaining individuals and their respective home ranges. This goal has been achieved using a combination of noninvasive genetic sampling of hair and faeces collected in the field and corresponding track size data. Genotypic data were collected at 24 microsatellite loci using a rigorous multiple-tubes approach to avoid genotyping errors associated with low quantities of DNA. Based on field and genetic data, the Pyrenean population was shown to be composed at least of one yearling, three adult males, and one adult female. These data indicate that extinction of the Pyrenean brown bear population is imminent without population augmentation. To preserve the remaining Pyrenean gene pool and increase genetic diversity, we suggest that managers consider population augmentation using only females. This study demonstrates that comprehensive knowledge of endangered small populations of mammals can be obtained using noninvasive genetic sampling.

Animals↗
PubMed1997

Effectiveness of light-curing units in vocational training practices. A project administered by the Research Committee of the Faculty of General Dental Practitioners (UK).

A project has been organised by the Research Committee of the Faculty of General Dental Practitioners (UK) in conjunction with vocational training advisers in which vocational dental practitioners (VDPs) tested the effectiveness of the light-curing units in their surgeries using Heliotests (Ivoclar-Vivadent) and Z100 Composite (3M). The VDPs also completed a questionnaire giving details of their light-curing units. The mean incremental depth stated as being used by the respondents was 2.6 mm; 43.5% of the participants' light-curing units (n = 63) were found to produce a depth of cure less than this figure. However, no correlation was found between reported post-operative clinical problems and cure depth lower than 2.6 mm. A negative correlation between depth of cure and age of light-curing unit was noted, with older units tending to cure the composite samples to less depth than newer units (p = 0.002). One-fifth of the participating VDPs' practices had some means of checking curing-light effectiveness. Greater awareness of the need to monitor practice light-curing units is therefore required.

Composite Resins↗
PubMed1997

Chicken microsatellite markers isolated from libraries enriched for simple tandem repeats.

The total number of microsatellite loci is considered to be at least 10-fold lower in avian species than in mammalian species. Therefore, efficient large-scale cloning of chicken microsatellites, as required for the construction of a high-resolution linkage map, is facilitated by the construction of libraries using an enrichment strategy. In this study, a plasmid library enriched for tandem repeats was constructed from chicken genomic DNA by hybridization selection. Using this technique the proportion of recombinant clones that cross-hybridized to probes containing simple tandem repeats was raised to 16%, compared with < 0.1% in a non-enriched library. Primers were designed from 121 different sequences. Polymerase chain reaction (PCR) analysis of two chicken reference pedigrees enabled 72 loci to be localized within the collaborative chicken genetic map, and at least 30 of the remaining loci have been shown to be informative in these or other crosses.

Animals↗
PubMed1996

Schizophrenia and neurological soft signs: gender differences in clinical correlates and antecedent factors.

Although it is recognized that patients with schizophrenia demonstrate more neurological soft signs (NSS) than control subjects, the significance and clinical correlates of these signs remain poorly defined. The present study examined 48 patients with DSM-III-R schizophrenia for evidence of NSS. The majority (98%) of patients demonstrated at least one NSS, although the range of scores was wide. There was no relationship between current dosage of neuroleptic medication and NSS score. Among males, there was a significant relationship between NSS and duration of illness. Males whose mothers experienced obstetric complications had higher NSS scores, while females with a family history of schizophrenia exhibited higher scores. These relationships in schizophrenia between NSS and factors of etiological importance wuch as obstetric complications and family history require further evaluation. The present findings are in accord with a body of evidence which suggests that gender may influence the impact of genetic and environmental factors on the neurology of the disorder.

Adolescent↗
PubMed1996

Topographical disorientation following unilateral temporal lobe lesions in humans.

Studies of the non-human temporal lobe, particularly the hippocampus, confirm its significant role in learning and memory, particularly allocentric spatial mapping of the environment. The role of the human temporal lobes in topographical orientation was investigated by examining the formation of representations of a large-scale real-world environment after unilateral left and right temporal lobe surgery. Patients and normal control subjects viewed videotape presentations of overlapping routes through a novel urban area. Topographical orientation was then assessed across a range of parameters. Right temporal lobe lesions alone gave rise to deficits in making proximity judgements. However, on all other topographical orientation tasks both right and left temporal lobe lesion groups were impaired relative to the normal control group, but the two patient groups did not differ significantly from each other. These findings suggest that such is the nature of remembering and way-finding in the environment that the integrity of both human temporal lobes is required.

Adult↗
PubMed1996

Adenocarcinoma in situ of the cervix: significance of cone biopsy margins.

OBJECTIVE: To evaluate the treatment and outcome of patients with adenocarcinoma in situ of the cervix, with special emphasis on cone biopsy margins. METHODS: Sixty-one women with adenocarcinoma in situ of the cervix treated between April 1984 and December 1993 were identified. Medical records and histologic material were reviewed. Mixed lesions with both adenocarcinoma in situ and squamous cervical intraepithelial neoplasia (CIN) were included. RESULTS: The mean age of the patients was 35.9 years. Fifty-five of the 61 (90%) patients had cone biopsies, and 44 of these 55 (80%) subsequently had hysterectomies. Eight women (13%) had associated invasive cancer. Among 50 patients in whom the status of the margins was confirmed, 23 (46%) had positive margins and 27 (54%) had negative margins. Of 23 women with positive margins, 19 had hysterectomies and ten of the 19 (53%) had residual disease in the uterus. Of 27 patients with negative cone margins, 21 had hysterectomies, and seven of the 21 (33%) had residual disease in the uterus. Two women with negative margins who did not have hysterectomies developed recurrent disease. Fifty-five of the total series of 61 patients followed-up for a median of 57 months (range 17-132) had no evidence of disease at last follow-up. CONCLUSION: Women with adenocarcinoma in situ of the cervix often have residual disease in the uterus, regardless of whether the margins on cone biopsy are positive or negative.

Adenocarcinoma↗
PubMed1996

Gamma radiation-sterilized, triple-lumen catheters coated with a low concentration of chlorhexidine were not efficacious at preventing catheter infections in intensive care unit patients.

In a randomized, double-blind trial, gamma radiation-sterilized, chlorhexidine-coated triple-lumen catheters were compared with uncoated control catheters for their ability to prevent catheter infection in 254 intensive care unit patients. The chlorhexidine coating was not efficacious, and a rabbit model demonstrated that reduction of chlorhexidine activity by gamma radiation sterilization was the likely explanation for the failure.

Bacteremia↗
PubMed1996

Neuropsychological assessment in multiple sclerosis: methodological issues and concerns.

A brief overview of research findings in five key areas pertaining to the study of neuropsychological aspects of multiple sclerosis is presented. The areas covered are: (1) general and specific cognitive deficits (2) prevalence of these deficits (3) attempts to correlate these deficits with clinicopathological features (4) attempts to investigate the relationship between deficits and abnormalities detected on magnetic resonance scanning and (5) longitudinal studies of cognitive deficits and MS. Based on this review, methodological issues that continue to hinder comparison between research reports, and across research centres, are outlined. Problem areas identified are (1) patient selection (2) selection of control subjects (3) lack of consensus regarding test selection (4) problems with statistical procedures (5) the relationship between depression and cognition (6) problems with measuring disability and MR abnormalities and (7) lack of longitudinal data.

Humans↗
PubMed1996

Mechanism of clocinnamox blockade of opioid receptors: evidence from in vitro and ex vivo binding and behavioral assays.

In behavioral experiments, the cinnamoylaminomorphinone clocinnamox (CCAM) has been shown to act as an insurmountable antagonist of mu, but not delta or kappa opioid agonists. In contrast, CCAM displayed only moderate mu selectivity (29:6:1 for mu:delta:kappa) in radioligand displacement experiments using mouse brain membranes. In the present study, the apparent discrepancy between the high mu selectivity of the insurmountable functional antagonism of CCAM and its only moderate mu selectivity in in vitro binding experiments was resolved by in vitro washout experiments and ex vivo binding experiments involving all three opioid receptor types. In the ex vitro washout experiments, CCAM-mediated mu receptor binding inhibition could not be reversed even after allowing for 8 hr hr dissociation, whereas the CCAM inhibition of delta and kappa receptor binding was time-dependently reversed. In the ex vivo binding experiments, 1 hr pretreatment of mice with 10 mg/kg of CCAM i.p. decreased ex vivo [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin ([3H]DAMGO) binding (tested at > or = 5 * Kd) by 90%, paralleled by an 88% decrease in mu receptor density in equilibrium saturation binding assays. Ex vivo [3H]DAMGO binding returned to control levels with a T1/2 of 2.7 to 4.2 days (independent of the CCAM dose), the effect being predominantly due to a recovery of mu receptor density. The CCAM inhibition of ex vivo [3H]DAMGO binding was dose-dependent and could be prevented in part by simultaneous administration of the protein synthesis inhibitor cylcoheximide. In contrast to the ex vivo binding of [3H]DAMGO, ex vivo binding of p-[3H]CI-[D-Pen2, D-Pen5]enkephalin or (-)-[3H]bremazocine (in the presence of 1 microM DAMGO and 1 microM [D-Pen6, D-Pen5]enkephalin) was not affected by CCAM pretreatment. Finally, ex vivo [3H]DAMGO binding inhibition data correlated well with mu receptor population changes estimated by Black and Leff analysis of behavioral (antinociception) experiments (T1/2 of receptor reappearance, 3.2 days). Thus, although CCAM reversibly interacted with mu, delta and kappa opioid receptors, only binding to mu receptors was wash-resistant. Binding of methoclocinnamox, a codeinone CCAM precursor with mu agonistic activity, seemed to be at least partially reversible, even at mu receptors.

Animals↗
PubMed1995

Histologic characterization of uterine papillary serous adenocarcinoma.

Uterine papillary serous adenocarcinoma (UPSC) is one of the most aggressive endometrial tumors. UPSC has been associated with an increased propensity for extrauterine spread. Survival rates of not more than 50% are commonly reported even for tumors which appear to be confined to the uterus. Small areas of UPSC can be found in otherwise well-differentiated endometrial lesions and yet still determine the overall prognosis. In the present study we evaluated histologic criteria that might be helpful in diagnosing small-volume UPSC, including silver-stained nucleolar organizer regions (AgNOR) which have prognostic importance in a variety of tumors, and nuclear size which has been used for prognostication in endometrial cancer. We examined 25 UPSC specimens and compared them to grade III (GIII, n = 10) and grade I (GI, n = 10) typical endometrial adenocarcinoma using the following parameters: mean AgNOR count per cell was UPSC 6, GIII 6.0, and GI 4.3; mean AgNOR area was UPSC 1.28 microns2, GIII 1.35 microns2, and GI 0.86 microns2; total AgNOR area per cell was UPSC 7.5 microns2, GIII 8.13 microns2, GI 4.47 microns2; and nuclear size was UPSC 66.9 microns2, GIII 60.3 microns2, GI 34.8 microns2. All differences between UPSC or GIII tumors and GI lesions were statistically significant. Overexpression of p53, as determined histochemically, was seen in 64% of the UPSC specimens. UPSC is characterized by high AgNOR count and area per cell, large nuclear size, and a high rate of p53 overexpression. Evaluation of these parameters in biopsy material may aid in selecting high-risk patients for adjuvant therapy trials.

Cystadenocarcinoma, Papillary↗
PubMed1995

Patterns of genetic variability at individual minisatellite loci in minke whale Balaenoptera acutorostrata populations from three different oceans.

The genetic variability at six cloned minisatellite loci was analyzed in minke whale populations from the North Atlantic, North Pacific, and Antarctic Oceans. Three loci displayed only a few different alleles in each of the three populations, with heterozygosity ranging from 0.00 to 0.47, and three loci revealed many different alleles in at least two fo the three populations, with heterozygosity ranging up to 0.98. Using small sample sizes, samples from two adjacent Antarctic Management Areas were not found to differ significantly in allele frequencies at any of the six loci. The use of principal coordinate analysis to detect multilocus disequilibria was explored. No significant evidence was found of intrapopulation heterogeneity within the pooled Antarctic sample. Pronounced interoceanic differences were observed at every locus, confirming the existence of genetic isolation found earlier using more conventional marker systems. The populations from the three oceans appear to have diverged to such a degree that the hypervariable loci have had time to evolve independently and arrive at different evolutionary stages in different populations. The frequency of undetected "null" alleles is remarkably high in minke whale populations compared to human populations and is probably a result of the cloning protocol used. Minisatellite loci are shown to provide a powerful population genetic tool, supplying levels of resolution appropriate to different degrees of evolutionary divergence.

Alleles↗
PubMed1995

Medicinal chemistry of difluoropurines.

A series of over 70 difluoropurine analogs was synthesized by varying the C-2, 6 and 8 substituents about the purine ring system. After initial in vitro and in vivo screening, testing concentrated on the 2,6-diaminopurine analog (dFdAP) and the guanosine analog (dFdG). dFDAP appears to be a prodrug for dFdG. Both compounds significantly inhibited mammary tumor growth in mice, caused a moderate inhibition in ovarian and lymphosarcoma models, and demonstrated no activity in lung and melanoma models. This is a narrower spectrum of activity than that of gemcitabine (dFdC). The antitumor activity of dFdAP in human xenografts that are refractory to standard clinical agents was comparable or superior to that of gemcitabine. However, during the preliminary toxicology testing, dFdG was associated with several deaths caused by cardiac toxicity. Therefore, although dFdG is a potentially useful oncolytic, further investigation is required.

2-Aminopurine↗
PubMed1995

Reproducibility of computed tomography measurement of visceral adipose tissue area.

OBJECTIVE: The purpose of the current study is to examine the reproducibility of CT measurement of the cross-sectional area of abdominal adipose tissue. DESIGN: Sixteen healthy pre-menopausal women, ranging from lean to obese, underwent duplicate cross-sectional CT scans of the abdomen at the level of the 4th lumbar vertebral disc space. Subjects stood after the initial scan and were then re-positioned prior to repeat CT scanning. RESULTS: There was a high degree of reproducibility in measurement of overall cross-sectional adipose tissue (AT) and in the partitioning of this into subcutaneous and visceral AT. The excellent reproducibility is demonstrated by a high correlation between duplicate measurements (r = 0.99, P < 0.01), and by small precision errors; 1.2% of the mean value for total AT cross-sectional area, 1.9% for subcutaneous AT area, and 3.9% for visceral AT area. CONCLUSION: Measurement of abdominal AT area by cross-sectional CT scanning is not only an accurate determination of this adipose depot but can also be repeated with a high degree of precision.

Adipose Tissue↗