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Biomedical subjects

V Williams

Publications and source records attributed to V Williams.

At least 37 records · Page 2Linked to original sources
PubMed1996

Comparison of measures of exposure to asbestos in former crocidolite workers from Wittenoom Gorge, W. Australia.

Determinations of exposure-response relationships between crocidolite and the major asbestos-related diseases in the Wittenoom cohort have previously depended on the validity of estimates of airborne exposure to asbestos. This work aims to validate the airborne exposure measurements by obtaining measurements of the concentrations of uncoated crocidolite fibers and asbestos bodies retained in the lungs of individual workers, and to estimate the half-life of crocidolite fibers in the lungs. Samples of lung tissue, excluding tumor, of all former Wittenoom workers known to have died in Western Australia (WA) were sought from teaching hospitals, pathology departments, and the Coroner's pathologist. The lung specimens were processed using Pooley's method with TEM for counts of fibers of all types and using Smith and Naylor's method with conventional light microscopy for asbestos bodies (AB). Multiple linear regression was utilized to examine the associations between crocidolite concentrations in the lung and duration of employment at Wittenoom, time since last employed at Wittenoom, nature of job, estimated average fiber concentration at the worksite, and estimated cumulative crocidolite exposure (CCE) in fiber-years/ml for each subject. Lung tissue from 90 cases was processed and there was good agreement between counts of crocidolite fibers, asbestos bodies, and CCE. Correlations were 0.77 for AB and fibers, 0.54 for AB and CCE, and 0.58 for CCE and fibers, after log transformation. The half-life of crocidolite fibers in the lung was estimated at 92 months (95% CI 55-277 months). Previous estimates of airborne exposure to Wittenoom crocidolite have been reasonably reliable. The relatively simple technique of light microscopy for counting ABs in lung tissue also provides a useful and reliable indication of the level of past occupational exposure to crocidolite in subjects whose exposure has been only to crocidolite. The half-life of crocidolite fibers in the lungs of former Wittenoom workers is about 7-8 years.

Adult↗
PubMed1996

Pseudomonas fluorescens adhesion and transport through porous media are affected by lipopolysaccharide composition.

The objectives of this work were (i) to use transposon mutagenesis to produce mutants of Pseudomonas fluorescens that were altered in adhesion ability and transport through porous media and (ii) to identify the alterations in surface characteristics that were responsible for the changes in attachment. Mutants of P. fluorescens were generated with TnphoA, which enabled identification of mutants that were altered in surface proteins. Transposon mutants were screened for alterations in adhesion ability by attachment assays on hydrophobic polystyrene and water-wettable polystyrene. Four TnphoA mutants with increased adhesion to the hydrophobic surface and decreased adhesion to the water-wettable surface were obtained. Transport of the strains through porous media was evaluated by passing suspensions of each mutant and the parent through columns containing quartz sand and determining the number of cells retained in the columns. The mutants all demonstrated increased adhesion and retention in the columns. Southern analysis demonstrated two types of mutants with separate transposon insertion sites. Polyacrylamide gel electrophoresis of the strains demonstrated that the O antigen on the lipopolysaccharide was either attenuated or absent. Lack of this polysaccharide, and the consequent increased exposure of the lipid moiety of the lipopolysaccharide, is probably responsible for the increase in adhesion to the hydrophobic substrata and retention in the sand column. This work combined with previous studies of attachment of P. fluorescens demonstrates that more than one type of polymer can mediate the adhesion of this organism to nonbiological surfaces.

Bacterial Adhesion↗
PubMed1996

Cocaine-associated intracranial hemorrhage: absence of vasculitis in 14 cases.

Complications associated with the use of cocaine are varied, and include cerebral hemorrhage and ischemia, with vasculitis and vasospasm as possible etiologies. We reviewed selected brain samples from 14 autopsy cases of cocaine-related cerebrovascular disease. Intracerebral or subarachnoid hemorrhage was present in 12 cases. Intracranial arterioles were either normal or showed nonspecific changes. From these observations, we suggest that intracranial hemorrhages occur in the absence of readily detectable vascular abnormalities.

Adult↗
PubMed1995

Asbestos bodies in lung tissue following exposure to crocidolite.

A series of 206 necropsies in Western Australia (WA) have had routine counts made of asbestos bodies in samples of lung tissue using conventional light microscopy. Thirty-two cases had worked in the asbestos industry at Wittenoom, WA and (log) counts of asbestos bodies in their lung tissue correlated well with estimates of their (log) cumulative airborne exposure to crocidolite fibers (r = 0.60). There was no association between the number of asbestos bodies and time since exposure to asbestos ceased. In subjects without known exposure to asbestos, there was a weak but nonsignificant increase in number of asbestos bodies with increasing age, with 26% of cases having no asbestos bodies present. It is concluded that the relatively simple technique of light microscopy for counting of asbestos bodies in lung tissue provides a reliable indication of the level of past occupational exposure to crocidolite in subjects whose exposure has been only to crocidolite. This could be extremely useful in follow-up studies of cohorts that lack reliable measures of airborne exposure to crocidolite asbestos.

Adult↗
PubMed1995

Accuracy of interpretation of cranial computed tomography scans in an emergency medicine residency program.

STUDY OBJECTIVES: To determine the concordance of emergency physicians and radiologists in interpreting cranial computed tomography (CT) scans. The study also sought to determine the clinical significance of misinterpretations of cranial CT scans by emergency physicians. DESIGN: Prospective cohort study. SETTING: A county hospital emergency medicine residency program. PARTICIPANTS: Five hundred fifty-five patients undergoing CT scanning during emergency department evaluation. RESULTS: Forty-nine percent (272) of the indications for CT scanning were for trauma, 14.2% (79) were for cerebrovascular accident, 25.1% (139) were for headache, 15.1% (84) were for seizure, and 13.7% (76) were for miscellaneous reasons. The radiologists interpreted 46.1% (256) of the CT scans as abnormal. The most frequent abnormalities were scalp hematoma, 15.2% (39); infarction, 14.1% (36); calcification, 6.3% (16); contusion, 6.3% (16); parenchymal hemorrhage, 5.1% (13); and mass, 5.1% (13). Nonconcordance between radiologists and emergency physicians was found in 38.7% (206) of the cases. Potentially clinically significant misinterpretations were found in 24.1% (131) of the total sample. These misinterpretations included 62 missed major findings (11.4% of total sample): 25 new infarcts, 10 mass lesions, 8 cases of cerebral edema, 8 parenchymal hemorrhages, 5 contusions, 4 subarachnoid hemorrhages, 1 epidural hematoma, and 1 subdural hematoma. However, on chart review, only three patients (0.6%) were found to have been managed inappropriately, and none had an adverse outcome. CONCLUSION: The misinterpretation rate of cranial CT scans by emergency physicians is of potential clinical concern. However, clinical mismanagement is rare. We recommend that more formal education in CT interpretation be included in residency training and continuing medical education programs for emergency physicians.

Brain Diseases↗
PubMed1995

Biochemical markers of cerebral injury in patients with minor head trauma and ethanol intoxication.

OBJECTIVE: To determine whether biochemical markers can selectively identify those intoxicated patients with presumed minor head injuries who are likely to have CT evidence of intracranial injury. METHODS: Patients presenting to the ED with simultaneous presumed minor head trauma and ethanol intoxication were prospectively entered into this cross-sectional study. Following phlebotomy, all patients received cranial CT. Associations between the presence of an abnormal CT scan for injury and serum levels of the following biochemical markers were sought: serum catecholamines, creatine kinase-brain band (CK-BB), and serum amylase. Serum levels are reported as mean +/- SEM. RESULTS: Nine of the 107 patients (8.4%; 95% CI 3.9-15.4%) had evidence of intracranial injury on CT. Mean serum CK-BB (16.1 +/- 3.7 vs 13.2 +/- 9.6 ng/mL), serum norepinephrine (913 +/- 117 vs 1,089 +/- 76 pg/mL), and serum amylase (64.9 +/- 14.8 vs 84 +/- 4.7 U/L) levels were not significantly different in patients with and without CT evidence of intracranial injury, respectively. Mean serum epinephrine (298 +/- 54 vs 167 +/- 18 pg/mL; p = 0.03) and serum dopamine (218 +/- 50 vs 130 +/- 9 pg/mL; p = 0.014) levels were significantly elevated in the group with intracranial injury on CT. A threshold level of serum dopamine > or = 140 pg/mL yields a sensitivity of 89% (95% CI 52-100%) and a specificity of 80% (95% CI 70-87%) for CT-evident injury. A threshold level of serum epinephrine > or = 218 pg/mL yields a sensitivity of 89% (95% CI 52-100%) and a specificity of 80% (95% CI 70-87%) for CT-evident injury. CONCLUSION: Elevated serum epinephrine and dopamine levels are associated with intracranial CT-evident injury for ethanol-intoxicated patients with presumed minor head injuries. The potential use of these biochemical markers to guide a more selective approach to cranial CT scanning warrants further evaluation.

Alcoholic Intoxication↗
PubMed1994

Comparative study on the procoagulant from the venom of Australian brown snakes (Elapidae; Pseudonaja spp.).

The procoagulant was isolated from the venom of four clinically significant species of brown snake; Pseudonaja affinis, P. inframacula, P. nuchalis, and P. textilis. HPLC elution profiles and PAGE showed a high degree of homology between the procoagulants from the four species. Antiserum from the CSL Ltd (Brown Snake Antivenom) produced a single band against all four procoagulants. The specific activity of the procoagulant varied between species, while inhibitory studies indicated that the procoagulants were serine proteases with a sialic acid component which also contributes to the coagulant action.

Animals↗
PubMed1993

Neurosurgical intensive care unit organization and function: an American experience.

This article describes the organization and function of a university-based neurosurgical intensive care unit. The unit's success has been based in part on its physical structure and in larger part on its organization. Patients are comanaged by a team of neurosurgeons and anesthesiologist intensive care specialists, who receive twice-weekly input from all other participating patient care specialists, including nurses, physical therapists, social workers, and others. This type of approach promotes teamwork and fosters mutual respect among the team. It also improves patient care and, frequently, outcome.

Critical Care↗
PubMed1993

Comparison of CNS adverse effects between astemizole and chlorpheniramine in children: a randomized, double-blind study.

OBJECTIVE: To assess the central nervous system side effects of chlorpheniramine and astemizole in children. DESIGN: Prospective, randomized, double-blind cross-over study. SETTING: Children were recruited from the out-patient allergy clinic and from respondents to an advertisement in a local newspaper. The study was conducted in the outpatient clinics of the ambulatory care services of the Children's Hospital of Eastern Ontario. PATIENTS, PARTICIPANTS: Children 8-16 years of age, with isolated allergic rhinitis or hay fever, were eligible for the study. We excluded children with: (1) chronic conditions (specifically asthma, atopic dermatitis, learning disabilities, or current treatment with oral corticosteroid medication); (2) known allergy to the study medications; (3) recent use of any antihistamine medication. One hundred and three children entered the study and 92 completed it. INTERVENTIONS: Children were stratified by age and randomly allocated to treatment with one of the two medication sequences. Over a period of 13 weeks both groups had 1 week of baseline studies, 3 weeks of one study medication, either chlorpheniramine or astemizole, a 6-week wash-out period and then 3 weeks of the other study medication for a second treatment period. MAIN OUTCOME MEASURES: Attention span (continuous performance test), short-term auditory and visual memory (visual aural digit span test), visual memory for geometric shapes (Benton visual retention test), motor coordination and visual-motor integration (grooved pegboard test), tapping speed and fine motor coordination (finger tapping test), physical side effects (such as sleepiness and dizziness), and compliance. RESULTS: One hundred and three patients were enrolled in the study, 92 (89%) completed the study. There were no significant drug effects on the visual retention test and the continuous performance test. On the visual aural digit span test, patients treated with astemizole scored higher than at baseline. There were no clinical or statistical differences in adverse effects between the two medications or between each medication and baseline. CONCLUSIONS: The two antihistamines studied had no adverse effects on the performance of children.

Adolescent↗
PubMed1993

Effectiveness of combined triazolam-behavioral therapy for primary insomnia.

The authors examined sleep improvement in subjects with primary insomnia who received triazolam plus behavioral therapy (N = 8) or triazolam plus sleep-related information (N = 7). At follow-up, total sleep and restedness in the morning showed greater improvement with combined triazolam-behavioral therapy and returned toward baseline in the control subjects.

Adult↗
PubMed1992

Variation in the composition of the venom from a single specimen of Pseudonaja textilis (common brown snake) over one year.

Venom was collected over a 12-month period from a single specimen of Pseudonaja textilis. No trends in the weight of venom extracted or protein content were noted. Amidolytic activity, coagulant and esterolytic activity showed a decrease over the summer months, while a rise in phosphodiesterase and 5' nucleotidase activity was noted at this time. Precipitin lines developed against the venoms by brown snake antivenom showed variability over the 12-month period. Gel filtration and SDS-polyacrylamide gel electrophoresis profiles showed quantitative and minor qualitative differences; however, the variation noted in the activities of these venoms was not predictable from these profiles.

Animals↗
PubMed1992

Influence of solid surface, adhesive ability, and inoculum size on bacterial colonization in microcosm studies.

Microcosm studies were performed to evaluate the effect of solid surfaces, bacterial adhesive ability, and inoculum size on colonization success and persistence of Pseudomonas fluorescens and Xanthomonas maltophilia, each with a Tn5 insertion that conferred resistance to kanamycin and streptomycin. Two types of microcosms were used: (i) a simple system that was colonized by Aeromonas hydrophila and a coryneform and (ii) a complex system produced from lake water enrichment cultures. Simple microcosms contained 100 ml of peptone- and yeast extract-supplemented artificial lake water or 60 ml of peptone- and yeast extract-supplemented artificial lake water with 70 g of 3-mm glass beads. Complex microcosms contained 100 ml of lake water with no nutrient additions or 100 ml of lake water with 70 g of glass beads. The microcosms were incubated for 35 days at 20 degrees C. In lake water enrichment microcosms, the presence of beads increased the abilities of P. fluorescens or X. maltophilia to colonize, but their numbers decreased with time in microcosms both with and without beads. The adhesiveness of the bacteria, measured in an in vitro assay, did not relate to colonization success. In simple microcosms, the inoculum size (10, 10, or 10) of P. fluorescens did not influence colonization success. However, in complex microcosms, an inoculum of 10 cells was insufficient to ensure colonization by P. fluorescens, while 10 cells resulted in colonization of liquid and beads. Simple microcosm studies, utilizing only a few species, were poor models for complex natural systems. In complex enrichment systems, colonization of surfaces resulted in higher numbers of organisms but did not noticeably promote persistence. Adhesiveness of a particular organism may be a relatively minor factor influencing its ability to colonize solid surfaces in complex natural environments.

Journal Article↗
PubMed1991

Snake venom variability: methods of study, results and interpretation.

The causes and implications of venom variability are discussed with a review of the literature. Venom variability may have an impact on both primary venom research and management of snakebite, including selection of antivenoms and selection of specimens for antivenom production. Choice of venom is reviewed, including venom collection, maintenance, and pooled venom versus venom milked from individual specimens, the latter being more reliable in many applications. Intraspecific variability resulting in clinical variability of envenomation occurs and is reviewed. Venom variability is considered at several levels; interfamily, intergenus, interspecies, intersubspecies and intraspecies, geographical variation, between individual specimens, and in individual specimens, due to seasonal variation, diet, habitat, age-dependent change, and sexual dimorphism. It is concluded that venom researchers must be aware of venom variability both in selecting their sources of venom and in interpretation of results. Producers of antivenom must utilize an understanding of such variability in selecting sources of venom for antivenom production to ensure representation of all venom types required within each antivenom. Furthermore, clinicians treating snakebite should understand the influence of venom variability on both the presentation of envenomation and the treatment implications.

Animals↗
PubMed1991

Efficacy of behavioral versus triazolam treatment in persistent sleep-onset insomnia.

OBJECTIVE: This study compared differential effects of behavioral therapy and triazolam in a clinical population with sleep-onset insomnia. Triazolam was hypothesized to decrease sleep latency and frequency and duration of awakening, with some effects during the first night's administration. But at follow-up, sleep measures were predicted to return to baseline levels. Behavioral treatment was hypothesized to effect sleep after 2 or more weeks of training which persisted at follow-up. METHOD: Thirty patients with average sleep latencies of 81.48 minutes, who reported chronic insomnia for an average of 2.6 years, were randomly assigned to one of two treatment groups: behavioral stimulus control/relaxation training and triazolam. RESULTS: Both treatments decreased sleep latency but differentially. Triazolam was effective immediately but maintained only some gains at follow-up. Behavioral treatment decreased sleep latency beginning the second week, when subjects expected no improvement, with gains maintained at follow-up. Comparisons showed that triazolam group latencies returned toward baseline, while behavioral group gains were maintained at follow-up. CONCLUSIONS: Triazolam treatment showed superior immediate treatment effects, while behavioral treatment showed superior treatment effects at follow-up, effects that accrued during the training period and differentially persisted at follow-up. One treatment strategy implied by these results would be to combine these two interventions concurrently. This would seem to use the immediate effects produced by the medication until the behavioral skills were learned, at which point medication would be terminated. This strategy could offer immediate relief and sustained effects at drug termination.

Adult↗
PubMed1990

Variation in venom composition and reactivity in two specimens of yellow-faced whip snake (Demansia psammophis) from the same geographical area.

Gel filtration chromatography and SDS-PAGE of venom from two specimens of Demansia psammophis showed little similarity. Amidolytic activity of the venoms, however, was in the same order of reactivity against various chromogenic substrates. The venom from both snakes produced precipitin lines with brown snake antivenom but the venom detection kit (Commonwealth Serum Laboratories) identified one venom as brown snake (Pseudonaja sp.) and the other as tiger snake (Notechis sp.). These results raise questions about the phylogeny of this species.

Animals↗