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Biomedical subjects

K West

Publications and source records attributed to K West.

At least 19 recordsLinked to original sources
PubMed2002

Correlation lengths of the wigner-crystal order in a two-dimensional electron system at high magnetic fields.

The insulator terminating the fractional quantum Hall series at low Landau level filling nu is generally taken to be a pinned Wigner crystal (WC), and exhibits a microwave resonance that is interpreted as a WC pinning mode. For a high quality sample at several densities, n, we find maxima in resonance peak frequency, f(pk), vs magnetic field, B. L, the correlation length of WC order, is calculated from f(pk). For each n, L vs nu tends at low nu toward a line with positive intercept; the fit is accurate over as much as a factor of 5 range of nu. The linear behavior is interpreted as due to B compressing the electron wave functions, to alter the effective electron-impurity interaction.

Journal Article↗
PubMed2002

Long-range transport in excitonic dark states in coupled quantum wells.

During the past ten years, coupled quantum wells have emerged as a promising system for experiments on Bose condensation of excitons, with numerous theoretical and experimental studies aimed at the demonstration of this effect. One of the issues driving these studies is the possibility of long-range coherent transport of excitons. Excitons in quantum wells typically diffuse only a few micrometres from the spot where they are generated by a laser pulse; their diffusion is limited by their lifetime (typically a few nanoseconds) and by scattering due to disorder in the well structure. Here we report photoluminescence measurements of InGaAs quantum wells and the observation of an effect by which luminescence from excitons appears hundreds of micrometres away from the laser excitation spot. This luminescence appears as a ring around the laser spot; almost none appears in the region between the laser spot and the ring. This implies that the excitons must travel in a dark state until they reach some critical distance, at which they collectively revert to luminescing states. It is unclear whether this effect is related to macroscopic coherence caused by Bose condensation of excitons.

Journal Article↗
PubMed2002

Death certification: an audit of practice entering the 21st century.

AIMS: Death certification, a legal duty of doctors, continues to be poorly performed despite Royal College recommendations and increased education at an undergraduate level. Therefore, the current performance of certifying doctors was audited within a large teaching hospital entering the new century. METHODS: A total of 1000 completed certificate counterfoils were examined retrospectively for appropriateness of completion and the ability to construct a logical cause of death cascade. RESULTS: Only 55% of certificates were completed to a minimally accepted standard, and many of these failed to provide relevant information to allow adequate ICD-10 coding. Nearly 10% were completed to a poor standard, being illogical or inappropriately completed. CONCLUSIONS: The results show no improvement in the state of certification. Possible interventions to improve outcomes are discussed; however, in light of a recent high profile legal case a current Home Office review of death certification may suggest the passing of statutory law to ensure accurate completion.

Cause of Death↗
PubMed2001

Induction of T lymphocyte responses to dengue virus by a candidate tetravalent live attenuated dengue virus vaccine.

Development of a safe and immunogenic tetravalent dengue virus (DV) vaccine has been designated as a priority by the World Health Organization. We characterized the T cell response to DV induced by a candidate live attenuated tetravalent DV vaccine as part of a phase I study. Proliferation and cytotoxic T lymphocyte (CTL) responses to multiple DV serotypes were detected in six of six and four of four subjects studied, respectively. Proliferation responses were higher to DV serotypes 1 and 3 than to serotypes 2 and 4. CTL responses were higher to DV serotypes 2 and 3 than to serotype 1, and included serotype cross-reactive responses. Production of interferon-gamma, but not IL-4, was observed in response to DV stimulation. This candidate vaccine is immunogenic for both CD4+ and CD8+ T lymphocytes. However, T cell responses to the four DV serotypes were not equivalent, suggesting that the vaccine could be further optimized.

Antibodies, Viral↗
PubMed2001

Effect of maternal antibodies on induction and persistence of vaccine-induced immune responses against bovine viral diarrhea virus type II in young calves.

OBJECTIVE: To determine the effect of maternally derived antibodies on induction of protective immune responses against bovine viral diarrhea virus (BVDV) type II in young calves vaccinated with a modified-live bovine viral diarrhea virus (BVDV) type I vaccine. DESIGN: Blinded controlled challenge study. ANIMALS: 24 neonatal Holstein and Holstein-cross calves that were deprived of maternal colostrum and fed pooled colostrum that contained a high concentration of (n = 6) or no (18) antibodies to BVDV. PROCEDURE: At 10 to 14 days of age, 6 seropositive and 6 seronegative calves were given a combination vaccine containing modified-live BVDV type I. All calves were kept in isolation for 4.5 months. Six calves of the remaining 12 untreated calves were vaccinated with the same combination vaccine at approximately 4 months of age. Three weeks later, all calves were challenged intranasally with a virulent BVDV type II. RESULTS: Seronegative unvaccinated calves and seropositive calves that were vaccinated at 2 weeks of age developed severe disease, and 4 calves in each of these groups required euthanasia. Seronegative calves that were vaccinated at 2 weeks or 4 months of age developed only mild or no clinical signs of disease. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that a single dose of a modified-live BVDV type-I vaccine given at 10 to 14 days of age can protect susceptible young calves from virulent BVDV type II infection for at least 4 months, but high concentrations of BVDV-specific maternally derived antibodies can block the induction of the response.

Animals↗
PubMed2001

Efficacy of an inactivated respiratory syncytial virus vaccine in calves.

OBJECTIVE: To determine whether an inactivated bovine respiratory syncytial virus (BRSV) vaccine would protect calves from infection with virulent BRSV. DESIGN: Randomized controlled trial. ANIMALS: 27 nine-week-old calves seronegative for BRSV exposure. PROCEDURE: Group-1 calves (n = 9) were not vaccinated. Group-2 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing a minimum immunizing dose of antigen. Group-3 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing an amount of antigen similar to that in a commercial vaccine. All calves were challenged with virulent BRSV on day 42. Clinical signs and immune responses were monitored for 8 days after challenge. Calves were euthanatized on day 50, and lungs were examined for lesions. RESULTS: Vaccination elicited increases in BRSV-specific IgG and virus neutralizing antibody titers and in production of interferon-gamma. Virus neutralizing antibody titers were consistently less than IgG titers. Challenge with BRSV resulted in severe respiratory tract disease and extensive pulmonary lesions in control calves, whereas vaccinated calves had less severe signs of clinical disease and less extensive pulmonary lesions. The percentage of vaccinated calves that shed virus in nasal secretions was significantly lower than the percentage of control calves that did, and peak viral titer was lower for vaccinated than for control calves. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the inactivated BRSV vaccine provided clinical protection from experimental infection with virulent virus and decreased the severity of pulmonary lesions. Efficacy was similar to that reported for modified-live BRSV vaccines.

Animals↗
PubMed2001

Spatial and temporal variance of river discharge on Okinawa (Japan): inferring the temporal impact on adjacent coral reefs.

Land-use changes and associated river discharges in coastal tropical regions present a global threat to coral reef environments. This study investigated the temporal variation in biological oxygen demand (BOD5) and suspended particulate matter (SPM) at the mouths of seven rivers on Okinawa Island (Japan) over 20 years. We report strong positive relationships between human population densities within river catchment areas and both average BOD5 concentration (r2 = 0.968; p < 0.001) and SPM (r2 = 0.659; p < 0.003) at the mouths of the rivers. At the reef adjacent to one river (Hija River, 50.2 km2 catchment area) we applied moving window analysis to assess an optimal sampling strategy for elucidating transitional boundaries in coral composition from the river mouth to a point where the effect of river discharge was minimal. The optimal window width for Okinawan rivers was five 1 m2 quadrats spaced over 5 m intervals. This sampling strategy clearly showed dissimilarity spikes in coral community composition up to 400 m from the Hija River mouth, beyond which no significant differences in coral composition were detected using analysis of similarities (ANOSIM). We developed a simple diffusion model linking the rivers' maximum discharge rate, and the average concentration of BOD5 and SPM with the spatial impact on the coral communities. The diffusion model can aid in predicting negative shifts in coral communities expected to result from detrimental land-use changes and is an important tool for monitoring coral reefs.

Animals↗
PubMed2001

Spongiotic vesicular dermatitis as a cutaneous reaction pattern in seven horses.

Over a 6-year period seven adult horses of different breeds and genders developed multifocal, exudative, oozing dermatitis characterized histologically by epidermal spongiotic vesicles and perivascular eosinophilic, neutrophilic and mixed mononuclear inflammation. Three horses were pruritic. Systemic disease was not noted. Two horses had a history of recurrent urticaria (hives) and one horse had nodules or welt-type lesions that progressed to exudative, oozing lesions. Interepithelial immunoglobulin (Ig)G was detected by avidin-biotin complex-peroxidase staining, but the pattern of staining was more consistent with epithelial oedema than specific IgG deposition associated with pemphigus. The exudative oozing lesions developed under circumstances suggesting that dermal oedema progressed to intracellular and intercellular epidermal oedema, which in turn progressed to the spongiotic vesicular epidermal lesions.

Animals↗
PubMed2001

Association of porcine circovirus 2 with reproductive failure in pigs: a retrospective study, 1995-1998.

In order to determine if vertically transmitted porcine circovirus (PCV) has played a role in reproductive failure in pigs in areas of endemic infection, archival fixed tissues were examined by polymerase chain reaction (PCR) and immunohistochemistry. Tissues tested were from routine cases of abortion or reproductive failure submitted between 1995 and 1998 to the diagnostic laboratory at the Western College of Veterinary Medicine, Saskatoon. They originated from 29 high-health herds in the provinces of Alberta and Saskatchewan and comprised a total of 36 individual submissions. Porcine circovirus type 1 (PCV1) was not detected by PCR in any submitted tissues. Porcine circovirus type 2 (PCV2) was not detected by PCR or immunohistochemistry in any of the submitted tissue. The effect of extended formalin fixation on the detection of PCV2 by PCR was assessed and fixation for up to one week had no gross effect on sensitivity of detection using this PCR technique. Failure to detect porcine circoviruses in cases of reproductive failure prior to 1999 in areas of endemic infections, suggests that reproductive disease may be a new clinical manifestation of PCV2 infection, and that vertical transmission may not have been the primary mechanism of initial dissemination of the virus in the pig population.

Abortion, Veterinary↗
PubMed2001

Multiple porcine circovirus 2-associated abortions and reproductive failure in a multisite swine production unit.

Porcine circovirus type 2 was detected in several stillborn and nonviable neonatal piglets presenting with chronic passive congestion, cardiac hypertrophy, and severe diffuse myocarditis. The presence of the virus in the heart and other tissues of affected piglets was confirmed by polymerase chain reaction, immunohistochemistry, and virus isolation techniques. Other reproductive losses and associated infectious agents in the herd are discussed.

Abortion, Veterinary↗
PubMed2000

Overexpression of the human VPAC2 receptor in the suprachiasmatic nucleus alters the circadian phenotype of mice.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) belong to a superfamily of structurally related peptide hormones that includes glucagon, glucagon-like peptides, secretin, and growth hormone-releasing hormone. Microinjection of VIP or PACAP into the rodent suprachiasmatic nucleus (SCN) phase shifts the circadian pacemaker and VIP antagonists, and antisense oligodeoxynucleotides have been shown to disrupt circadian function. VIP and PACAP have equal potency as agonists of the VPAC(2) receptor (VPAC(2)R), which is expressed abundantly in the SCN, in a circadian manner. To determine whether manipulating the level of expression of the VPAC(2)R can influence the control of the circadian clock, we have created transgenic mice overexpressing the human VPAC(2)R gene from a yeast artificial chromosome (YAC) construct. The YAC was modified by a strategy using homologous recombination to introduce (i) the HA epitope tag sequence (from influenza virus hemagglutinin) at the carboxyl terminus of the VPAC(2)R protein, (ii) the lacZ reporter gene, and (iii) a conditional centromere, enabling YAC DNA to be amplified in culture in the presence of galactose. High levels of lacZ expression were detected in the SCN, habenula, pancreas, and testis of the transgenic mice, with lower levels in the olfactory bulb and various hypothalamic areas. Transgenic mice resynchronized more quickly than wild-type controls to an advance of 8 h in the light-dark (LD) cycle and exhibited a significantly shorter circadian period in constant darkness (DD). These data suggest that the VPAC(2)R can influence the rhythmicity and photic entrainment of the circadian clock.

Amino Acid Sequence↗
PubMed2000

Adjuvant use of epsilon-aminocaproic acid (Amicar) in the endovascular treatment of cranial arteriovenous fistulae.

We report our experience with the use of the antifibrinolytic agent epsilon-aminocaproic acid (EACA), Amicar, as an adjuvant to endovascular treatment of cranial arteriovenous fistulae. We also review applications of antifibrinolytic agents to neurovascular disorders and discuss the mechanism of action, dosing strategy, contraindications, and possible complications associated with the use of EACA. We identified 13 patients with cranial arteriovenous fistulae (five direct carotid cavernous fistulae [CCF], seven dural arteriovenous fistulae [DAVF], and one vein of Galen malformation) who received EACA as an adjunct to endovascular treatment. In all cases embolic coils were the primary embolic agent. We reviewed the modes of initial endovascular therapy and angiographic findings immediately thereafter and the response to EACA. Two direct CCF and two DAVF were completely thrombosed on follow-up angiography, and two DAVF demonstrated diminished flow after EACA therapy. Seven fistulae did not respond to EACA. Four of eight tightly coiled fistulae thrombosed, while none of five loosely coiled fistulae thrombosed. None of four cases with a residual fistula separate from the coil mass underwent thrombosis with EACA, while four of nine cases without a separate fistula thrombosed. There was no morbidity related to EACA therapy. EACA may thus be useful as an adjunct to endovascular treatment of cranial arteriovenous fistulae. Loose or incomplete coil packing of the fistula predicts a poor response to EACA therapy.

Adolescent↗
PubMed2000

Is the grass greener? Early results of the Nuss procedure.

BACKGROUND/PURPOSE: Minimal access surgery (MIS, Nuss Procedure) is gaining acceptance rapidly as the preferred method for pectus excavatum repair. This shift in operative management has followed a single institution's evaluation of the procedure. This report describes an additional experience with the Nuss procedure. METHODS: Twenty-one patients with pectus excavatum underwent repair by the Nuss Procedure. The patients ranged in age from 5 to 15 years (average, 8.2 years). There were 19 boys and 2 girls. RESULTS: In 1 patient (age 5 years) the MIS procedure was aborted because of persistence of chest wall asymmetry. The other 20 patients had completion of their procedure without intraoperative complication. The operating times ranged from 45 to 90 minutes; however, there was an additional anesthetic set-up time (average, 45 minutes). All cases utilized a single support bar (11 to 17 inches). Patients underwent extubation in the operating room and were admitted to a ward bed with an epidural catheter in place for pain control and received intravenous analgesia. The hospital stay ranged from 4 to 11 days and averaged 4.9 days. Early postoperative complications included ileus (n = 1), bilateral pleural effusion (n = 2), atelectasis (n = 1), fungal dermatitis (n = 1), pneumothorax (n = 1), and flipped pectus bar (n = 2). Delayed complications included flipped pectus bar (n = 2), marked pectus carinatum requiring bar removal (n = 1), mild carinatum (n = 1), mild bar deviation (n = 1), progressive chest wall asymmetry (n = 3) with 1 requiring bar removal and open pectus repair, pleural effusion (n = 1), and chronic persistent pain requiring bar removal (n = 1). The length of follow-up is 3 to 20 months with an average of 12.3 months. CONCLUSIONS: The Nuss Procedure is quick, minimally invasive, and a technically easy method to learn; however, our data indicate there is a significant learning curve. Although previous reports suggest that few complications occur, we believe further assessment of patient selection regarding age, presence of connective tissue disorder, and severe chest wall asymmetry are still needed. Long-term follow-up also will be required to assure both health professionals and the public that this is the procedure of choice for patients with pectus excavatum.

Adolescent↗
PubMed2000

Osseous morphology and spatial relationships of the temporomandibular joint: comparisons of normal and anterior disc positions.

The objective of this study was to determine differences in spatial relationships and osseous morphology between temporomandibular joints with normal and anterior disc positions. Magnetic resonance imaging was employed to determine disc position in 335 temporomandibular joints in 175 subjects (106 female and 69 male) between the ages of 7.27 years and 20.0 years (mean age: 13.08 years). Twelve tomographic variables were measured from preorthodontic tomograms of the same individuals. Tomographic data were cross-referenced with MRI data for those with normal and full anterior disc displacement. Independent sample t-tests revealed significant differences for all measures of joint space, condylar position, and morphology of the articular eminence (P < .05) between joints with normal disc position and with full anterior disc displacement. This study indicated that measures of joint space and eminence morphology might provide diagnostic information for the assessment of joint status in the adolescent population.

Adolescent↗
PubMed2000

After the call. The latest post-exposure medical management info.

Ensuring proper post-exposure medical evaluation and treatment remains essential for the health and wellness of your personnel, risk management and OSHA compliance. Departments must ensure that the medical provider designated to manage post-exposure treatment knows the current post-exposure medical treatment protocols and that the medical facilities involved offer the most up-to-date, fastest testing methods available. With all the new recommendations and testing methods, HCWs can receive accurate information post-exposure in a 24-hour time-frame. The HIV issue can be resolved in less than one hour. This is exciting progress.

Anti-HIV Agents↗