Biomedical subjects

David T Burke

Publications and source records attributed to David T Burke.

At least 37 records · Page 2Linked to original sources

PubMed2004

Reading habits of physical medicine and rehabilitation resident physicians.

OBJECTIVE: To investigate the focus and extent of the resident physician reading habits, to compare how these change over the years of their training, and to compare these habits with those of physiatrists in practice. DESIGN: A total of 1,076 surveys were sent to 80 physical medicine and rehabilitation residency programs accredited by the Accreditation Council for Graduate Medical Education. The questionnaire contained a list of 36 journals pertinent to the field of Physical Medicine and Rehabilitation. Resident physicians were asked to indicate which journals they read during the past year and how extensively they read them. Respondents were also asked whether they participated in a journal club and if they read as much as they would like. RESULTS: A total of 324 surveys (30.1%) were completed correctly. At least half of the surveyed resident physicians scanned or read six journals:Archives of Physical Medicine and Rehabilitation (85.2%), American Journal of Physical Medicine and Rehabilitation (80.6%), Journal of the American Medical Association (68.8%), New England Journal of Medicine (60.5%), American Journal of Sports Medicine (50.9%), and Rehab in Review (49.7%). Most resident physicians (93.9%) responded that they do not read as much as they would like, and 90.1% of resident physicians participate in some form of journal club. CONCLUSION: Most resident physicians in the field of physical medicine and rehabilitation tend to scan for important articles within one of six journals, with most of these physicians noting that they do not read as much as they would like. As the resident physicians advance in postgraduate-year level, the number of journals that they scan increases. The reading habits of the resident physicians were quite similar to those noted in our previous study of the reading habits of practicing physiatrists.

Adult↗

PubMed2004

Apathy and depression in cross-cultural survivors of traumatic brain injury.

The disturbance of motivation and its relationship to depression continues to spark contradictory findings among European and North American populations. Could a cross-cultural study shed some light on the situation? This study aims to detect the prevalence of apathy and to test whether the Apathy Evaluation Scale (AES) can spot the presence or absence of depression in survivors of traumatic brain injury (TBI) in Oman. Eighty subjects who sustained a TBI were given an Arabic version of the AES and were also interviewed with the semistructured Composite International Diagnostic Interview (CIDI). The authors found that the incidence of apathy and depression among Omani people who sustained TBI is similar to that reported elsewhere. The AES has poor discriminatory power in identifying cases of depression. These findings emphasize the importance of developing assessment tools that are culturally sensitive in light of the rising incidence of TBI in developing countries such as Oman.

Adolescent↗

PubMed2003

Quantitative trait loci for insulin-like growth factor I, leptin, thyroxine, and corticosterone in genetically heterogeneous mice.

Genotype information was collected at 87 loci in a group of 1,108 UM-HET3 mice bred as the progeny of [BALB/cJ x C57BL/6J]F1 mothers and [C3H/HeJ x DBA/2J]F1 fathers, for which thyroxine (T4), insulin-like growth factor I (IGF-I), and leptin levels had been measured at 4 and 15 mo of age. The data provided significant evidence for quantitative trait loci (QTL) modulating IGF-I levels on chromosomes 1, 3, 8, 10, and 17; for loci affecting T4 on chromosomes 4, 15, and 17; and for leptin on chromosome 3. Fecal levels of corticosterone at 17 mo of age were influenced by a QTL on chromosome 1. Nine other gene/hormone associations reached a nominal P < 0.01, providing suggestive but not statistical evidence for additional QTL. QTL with an influence on a given hormone were in nearly all cases additive, with little or no evidence for epistasis. Of the 12 strongest QTL, 5 had effects that were age dependent, having more effect in 15-mo-old than in 4-mo-old mice in all but one case; the other QTL had effects that were apparently age-independent. These results show that the genetic controls over late-life hormone levels are complex and dependent on effects of genes that act both early and late in the life course.

Aging↗

PubMed2003

Selective extraction of size-fractioned DNA samples in microfabricated electrophoresis devices.

We have designed and constructed a microfabricated device for separation of double-stranded DNA fragments using a crosslinked sieving medium and spatially selective extraction of the desired fraction. Based on measuring the width and spacing of migrating bands, a narrow side channel is constructed perpendicular to the separation channel to collect the DNA fragments of interest. This selective collection technique was tested using a 100 base pair double-stranded DNA ladder. We successfully demonstrate selective extraction of the desired fragment with minimal interference from the adjacent bands in an electric field of 31 V/cm. We also achieve extraction of multiple DNA fragments using an array of microelectrodes in this side channel. The device uses cross-linked polyacrylamide gel matrix, allowing the separation to be performed in a distance of 1 cm or less and at a low electric field strength. Together with on-chip electrode, this design is amenable to integration with reaction chambers into a single device for portable genetic-based analysis.

DNA↗

PubMed2003

Light-induced molecular cutting: localized reaction on a single DNA molecule.

A short focused pulse of light was used to selectively cut lambda-phage DNA molecules at specific restriction sites. Lambda DNA (48.5 kbp) was stretched and placed in a solution containing a restriction enzyme (Sma 1), caged magnesium ions (using a DM-Nitrophen complex), and a chelating agent (EDTA). When a pulse of UV light was directed at a particular location on the stretched DNA molecule, magnesium ions were released into solution. A series of binding reactions then occur in which the enzyme and the chelating agent compete for free Mg2+ ions. Since Sma 1 functions only in the presence of Mg2+, as is true of most endonucleases, the site(s) in the vicinity of the pulse (typically approximately 6 microm) were cut while other sites (three total for this DNA/enzyme pair) were not. The ratio of the concentration of the chelating agent to that of the magnesium ions was used to control the radius of this reaction zone with higher ratios leading to smaller, localized reaction areas. This optically based reaction mechanism could be useful to understand single molecule enzymatic kinetics, and when coupled with other DNA analysis techniques, this could be used to construct complex genotyping and sequencing devices that would analyze parts of single DNA molecules.

Bacteriophage lambda↗

PubMed2003

A versatile microfabricated platform for electrophoresis of double- and single-stranded DNA.

We demonstrate a versatile microfabricated electrophoresis platform, incorporating arrays of integrated on-chip electrodes, heaters, and temperature sensors. This design allows a range of different sieving gels to be used within the same device to perform separations involving both single- and double-stranded DNA over distances on the order of 1 cm. We use this device to compare linear and cross-linked polyacrylamide, agarose, and thermo-reversible Pluronic-F127 gels on the basis of gel casting ease, reusability, and overall separation performance using a 100 base pair double-stranded DNA ladder as a standard sample. While cross-linked polyacrylamide matrices provide consistently high-quality separations in our system over a wide range of DNA fragment sizes, Pluronic gels also offer compelling advantages in terms of the ability to remove and reload the gel. Agarose gels offer good separation performance, however, additional care must be exercised to ensure consistent gel properties as a consequence of the need for elevated gel loading temperatures. We also demonstrate the use of denaturing cross-linked polyacrylamide gels at concentrations up to 19% to separate single-stranded DNA fragments ranging in size from 18 to 400 bases in length. Primers differing by 4 bases at a read length of 30 bases can be separated with a resolution of 0.9-1.0 in under 20 min. This level of performance is sufficient to conduct a variety of genotyping assays including the rapid detection of single nucleotide polymorphisms (SNPs) in a microfabricated platform. The ability to use a single microelectrophoresis system to satisfy a wide range of separation applications offers molecular biologists an unprecedented level of flexibility in a portable and inexpensive format.

Acrylic Resins↗

PubMed2003

A mysterious temporal penetrating head wound without fracture.

Unwitnessed head injuries are often diagnostic and management dilemmas. Low-velocity penetrating head wounds are rare. This paper describes a case of an accidental low-velocity penetrating head wound through the soft tissue of the temporal region. This lesion resulted in a deep intra-cerebral haemorrhage, after the initial assessment revealed no evidence of skull fracture, missile or missile track. The diagnostic evaluation and medical course of this case are presented. This is the first case in the medical literature of a brain injury by an object that penetrated the calvarium at low velocity but which did not produce a fracture of the skull. The evolving diagnostic dilemma is outlined to its conclusion, through 3 years of follow-up observation.

Adult↗

PubMed2003

Age-associated activation of epigenetically repressed genes in the mouse.

Epigenetic control of gene expression is a consistent feature of differentiated mammalian cell types. Epigenetic expression patterns are mitotically heritable and are stably maintained in adult cells. However, unlike somatic DNA mutation, little is known about the occurrence of epigenetic change, or epimutation, during normal adult life. We have monitored the age-associated maintenance of two epigenetic systems--X inactivation and genomic imprinting--using the genes Atp7a and Igf2, respectively. Quantitative measurements of RNA transcripts from the inactive and active alleles were performed in mice from 2 to 24 months of age. For both genes, older animal cohorts showed reproducible increases in transcripts expressed from the silenced alleles. Loss of X chromosome silencing showed cohort mean increases of up to 2.2%, while imprinted-gene activation increased up to 6.7%. The results support the hypothesis that epigenetic loss of gene repression occurs in normal tissues and may be a contributing factor in progressive physiological dysfunction seen during mammalian aging. Quantitatively, the loss of epigenetic control may be one to two orders of magnitude greater than previously determined somatic DNA mutation.

Adenosine Triphosphatases↗

PubMed2003

Effects of methylphenidate on heart rate and blood pressure among inpatients with acquired brain injury.

OBJECTIVE: The purpose of this study was to evaluate the effects of methylphenidate on heart rate and blood pressure in patients with acquired brain injury. DESIGN: The records of 60 consecutive hospitalized patients with acquired brain injury were reviewed for treatment with methylphenidate. Seventeen patients met the inclusion criteria. Systolic blood pressure, diastolic blood pressure, and heart rate recordings were compared before and after the introduction of methylphenidate. RESULTS: There was no significant difference in mean systolic blood pressure, diastolic blood pressure, and heart rate when patients received (118 mm Hg, 74 mm Hg, and 88 bpm) and did not receive (118 mm Hg, 73 mm Hg, and 86 bpm) methylphenidate. It was unclear whether there was a true trend toward medication effect on heart rate and blood pressure during the peak dose period. CONCLUSIONS: This retrospective study points to safe sympathetic effects of methylphenidate, yet future prospective studies are warranted to clarify the effects of methylphenidate on heart rate and blood pressure in the acquired brain injury population.

Adult↗

PubMed2003

Upper-extremity deep vein thrombosis.

Upper-extremity deep vein thrombosis (UEDVT) was an understudied disease until recently. Previously thought of as benign, UEDVT has been shown in recent studies to pose a significant risk for pulmonary embolus and death. This article reviews the epidemiology, risk factors, clinical features, diagnostic tests, treatment options, complications, and prevention strategies for patients with UEDVT.

Anticoagulants↗

PubMed2003

Quantitative trait loci for femoral size and shape in a genetically heterogeneous mouse population.

UNLABELLED: The aim of this study was to examine the genetic effects on cortical bone geometry. Genotypes from 487 mice were compared with geometric traits obtained from microCT. We found 14 genetic markers that associate with geometric traits, showing the complexity of genetic control over bone geometry. INTRODUCTION: Previous studies have shown that genetic background affects bone characteristics, particularly bone mineral density, in both mouse and human populations. Much less is known, however, about the effects of polymorphic genes on bone size, shape, and mechanical integrity. In this study, we investigated the genetic determinants of geometric properties of cortical bone in mice. MATERIALS AND METHODS: This study used a genetically heterogeneous mouse population, which is denoted UM-HET3 stock and is derived as the progeny of (BALB/cJ X C57BL/6J) F1 females and (C3H/HeJ X DBA/2J) F1 males. The experimental group consisted of 487 female UM-HET3 mice. Genotypic data from 99 polymorphic genetic loci was obtained from the mice at 4 weeks of age. At 18 months of age, the mice were humanely killed, and the right femurs were scanned with microcomputed tomography to assess geometric properties of cortical bone. A permutation-based test was used to detect significant associations between genetic markers and geometric traits. This test generates experiment-wise p values, which account for the effect of testing multiple hypotheses. An experiment-wise p < or = 0.05 was considered statistically significant. RESULTS: Fourteen genetic markers were found to significantly associate with one or more geometric traits. Two markers (D3Mit62 and D4Mit155) were associated with traits describing bone size; 2 (D12Mit167 and D14Mit170) were linked with traits describing bone shape; and 10 (D1Nds2, D5Mit95, D6Mit216, D7Mit91, D8Mit51, D9Mit110, D11Mit83, D15Mit100, D15Mit171, and D17Mit46) were associated with both size and shape. CONCLUSIONS: Our results indicate that the genetic control of cortical bone geometry is complex and that femoral size and shape may be influenced by different, although overlapping, groups of polymorphic loci.

Animals↗

PubMed2003

Eye-movements and ongoing task processing.

This study tests the relation between eye-movements and thought processing. Subjects were given specific modality tasks (visual, gustatory, kinesthetic) and assessed on whether they responded with distinct eye-movements. Some subjects' eye-movements reflected ongoing thought processing. Instead of a universal pattern, as suggested by the neurolinguistic programming hypothesis, this study yielded subject-specific idiosyncratic eye-movements across all modalities. Included is a discussion of the neurolinguistic programming hypothesis regarding eye-movements and its implications for the eye-movement desensitization and reprocessing theory.

Choice Behavior↗

PubMed2002

Electrostretching DNA molecules using polymer-enhanced media within microfabricated devices.

In this paper, we demonstrate immobilization and stretching of single lambda-phage DNA molecules within microfluidic systems using ac fields. We present a novel "thiol-on-gold"-based immobilization technique for fixing one specific end (3' end) of a DNA molecule onto a gold electrode. A polymer-enhanced medium (approximately 3.75 wt % linear polyacrylamide in Tris-HCl) is used to obtain fully stretched configurations (21 microm) of fluorescently stained lambda-DNA molecules. We also present an optimized microelectrode design with pointed electrodes and an electrode spacing of 20 microm for stretching DNA molecules with an ac field (1 MHz, 3 x 10(5) V/m). Finally, using these techniques, we immobilize a single DNA molecule at one electrode edge, stretch the molecule, and fix the other end at an adjacent electrode edge, forming a bridge between two electrodes within a microfabricated device.

Acrylic Resins↗

PubMed2002

Cross-linked polyacrylamide gel electrophoresis of single-stranded DNA for microfabricated genomic analysis systems.

Microfabricated devices are poised to offer inexpensive self-contained alternatives to conventional benchtop-scale laboratory equipment for performing a variety of important DNA analysis assays. In order to realize the dramatic cost savings possible through photolithographic fabrication techniques, these devices must occupy an extremely compact footprint on the silicon wafer. This requirement implies that electrophoretic separations must be performed over ultrashort distances. Employing cross-linked polyacrylamide gels in place of conventional uncross-linked sieving media offers a convenient strategy to achieve this goal. In this paper, we show how the increased resolving power offered by cross-linked polyacrylamide gels, along with improved sample injection techniques, can be exploited to enhance separation performance in microscale systems. We use these techniques to perform high-resolution gel electrophoresis of single-stranded DNA fragments in microfabricated devices over separation distances of 1.5 cm or less. The results presented here are in agreement with theoretical predictions and suggest that it is possible to perform DNA sequencing on compact microchips. More importantly, the separation performance demonstrated in this work is already more than adequate to perform a number of important genomic assays imposing less stringent resolution requirements than sequencing. Successfully adapting even a few of these assays to the microdevice format has the potential to provide a new generation of inexpensive and portable devices suitable for direct end-user applications.

Acrylic Resins↗

PubMed2002

Microdevice-based measurements of diffusion and dispersion in cross-linked and linear polyacrylamide DNA sequencing gels.

We use microfabricated gel electrophoresis devices incorporating integrated on-chip electrodes, heaters, and temperature sensors to measure diffusion and dispersion of single-stranded DNA fragments in cross-linked and uncross-linked polyacrylamide gels. The microdevice format allows a complete set of diffusion and dispersion data to be collected in approximately one hour. These results are compared with corresponding data obtained in a macroscale DNA sequencer, and the effects of gel composition and initiation chemistry are explored. Although the diffusion and dispersion data exhibit similar qualitative trends both on chip and on the macroscale, the magnitudes of the coefficients measured in the microdevice are somewhat higher. This discrepancy is likely due to altered polymerization kinetics arising as a consequence of using a UV-initiated polymerization chemistry to cast the on-chip gels as opposed to the standard chemical polymerization employed on the macroscale. We also find that reductions in the magnitudes of diffusion and dispersion coefficients are achieved at higher polymer concentrations and at operating temperatures in the vicinity of 50 degrees C. Finally, we find that cross-linked polyacrylamide gels yield significantly lower diffusion and dispersion coefficients than linear polyacrylamide. These findings can be used to identify rational strategies to improve separation performance in both micro- and macroscale gel electrophoresis systems.

Cross-Linking Reagents↗

PubMed2002

Deliberate self-poisoning in Oman.

OBJECTIVE: To describe the demographics, precipitating factors, substances and methods used for deliberate self-harm in Oman. METHODS: Data were extracted from the Accident and Emergency (A & E) records of patients treated at the A & E units in Muscat from 1993 to 1998. Data were obtained form the history, and clinical findings resulting form deliberate self-harm. RESULTS: During the 5-year study period, 123 persons presented to various hospitals in the Muscat area with injuries that resulted form deliberate self-harm. Most of these cases were women, students and unemployed. There was a high incidence of family, marital and psychiatric or social problems. The methods of self-harm were most often analgesics (such as paracetamol) and non-pharmaceutical chemicals. CONCLUSIONS: The rate of self-injurious behaviour is low in Oman, compared with other countries, including other Islamic countries. The data illustrate a rising rate and a tendency to ingest toxic doses of analgesics or non-pharmaceutical chemicals.

Acculturation↗

PubMed2002

Big mice die young: early life body weight predicts longevity in genetically heterogeneous mice.

Small body size has been associated with long life span in four stocks of mutant dwarf mice, and in two varieties of dietary restriction in rodents. In this study, small body size at ages 2-24 months was shown to be a significant predictor of life span in a genetically heterogeneous mouse population derived from four common inbred mouse strains. The association was strongest for weights measured early in adult life, and somewhat weaker, though still statistically significant, at later ages. The effect was seen both in males and females, and was replicated in an independent population of the same genetic background. Body size at ages 2-4 months was correlated with levels of serum leptin in both males and females, and with levels of IGF-I and thyroid hormone in females only. A genome scan showed the presence of polymorphic alleles on chromosomes 2, 6, 7 and 15 with significant effects on body weight at 2-4 months, at 10-12 months, or at both age ranges, showing that weight gain trajectory in this stock is under complex genetic control. Because it provides the earliest known predictor of life span, body weight may be usefully included in screens for induced mutations that alter aging. The evidence that weight in 2-month-old mice is a significant predictor of life span suggests that at least some of the lethal diseases of old age can be timed by factors that influence growth rate in juvenile rodents.

Animals↗

PubMed2002

Cutoff score on the apathy evaluation scale in subjects with traumatic brain injury.

This cross-sectional study was designed to determine a cutoff score on the Apathy Evaluation Scale (AES) that predicts a clinician's designation of a subject with TBI as apathetic or not. Forty-five outpatients with TBI completed the AES-S, and 37 family members, friends, or significant others filled out the AES-I. Three clinicians prospectively gave their impressions of the presence or absence of apathy and retrospectively chose the degree of apathy on a 7-point subjective rating scale. The data was analysed by logistic regression and Receiver Operating Characteristic (ROC) curve. Sensitivity and specificity were calculated. No cutoff score on the AES-S or AES-I was found to have reasonable sensitivity and specificity with respect to the ability to predict the clinician's designation of a subject as apathetic. The AES requires further study if it is to be used to measure apathy following TBI.

Adolescent↗