PubMed Health⌕ Search

Biomedical subjects

P W West

Publications and source records attributed to P W West.

At least 19 recordsLinked to original sources
PubMed2000

Reduced visual acuity impairs place but not cued learning in the Morris water task.

The Morris water task is a standard method for testing spatial learning in rodents. In a place version of the task, animals utilize multiple visual cues to learn the location of a hidden platform. The ability of animals to locate a cued platform is often used to qualitatively test for possible non-cognitive contributions to deficient place learning, including reduced visual function. We investigated the role of visual acuity in water maze performance quantitatively by depriving rats of pattern vision during a critical period for visual plasticity, which reduced their acuity by approximately 27% and then tested them in typical place and cued platform configurations of the Morris water task. Animals with reduced visual acuity had a significant deficit in place learning, but eventually reached the same escape latency as non-deprived animals. Deprived and non-deprived animals, however, did not differ in their ability to locate a cued platform following place learning. These data indicate that reduced visual acuity in rats can influence measurement of their place learning and that a typical cued platform version of the task cannot detect a modest, but significant, visual deficit.

Animals↗
PubMed2000

Behavioral assessment of visual acuity in mice and rats.

We have developed a simple computer-based discrimination task that enables the quick determination of visual acuities in rodents. A grating is displayed randomly on one of two monitors at the wide end of a trapezoidal-shaped tank containing shallow water. Animals are trained to swim toward the screens, and at a fixed distance, choose the screen displaying the grating and escape to a submerged platform hidden below it. Both mice and rats learn the task quickly. Performance falls below 70% when the spatial frequency is increased beyond 0.5 cycles in most C57BU6 mice, and around 1.0 cycles per degree (cpd) in Long-Evans rats.

Adaptation, Physiological↗
PubMed2000

Experience-dependent plasticity of visual acuity in rats.

Rats have become a popular model for investigating the mechanisms underlying ocular dominance plasticity; however, no quantitative assessment of the effects of visual deprivation on behavioural acuity has been reported in this species. We measured the spatial acuity of monocularly and binocularly deprived rats with a visual discrimination task. The average spatial acuity of normal rats and rats deprived of vision after postnatal day 40 was approximately 1 cycle/degree. Monocular deprivation up to postnatal day 40 resulted in a 30% decrease in acuity and there was no recovery after 8 months. Identical binocular deprivation produced a comparable but significantly smaller reduction in acuity. The deleterious effects of monocular and binocular deprivation on visual acuity indicate that the development of cortical receptive field properties related to spatial tuning are affected by both monocular and binocular deprivation. The similarities in the effects of visual deprivation on visual acuity between rats and other mammals confirm that rats are a good model system for studying the cellular and molecular mechanisms underlying experience-dependent visual plasticity.

Age Factors↗
PubMed2000

Extended-spectrum beta-lactamase-producing Klebsiella spp.

Extended-spectrum beta-lactamases (ESBLs) are associated particularly with Klebsiella spp. These enzymes have arisen by mutation of the genes coding for clavulanate-sensitive, plasmid-mediated beta-lactamases such as TEM-1, TEM-2 and SHV-1. Amino acid changes in ESBLs confer enhanced hydrolysis of oxyimino-aminothiazolyl beta-lactams and aztreonam. Enzyme hyperproduction and loss of porins contribute to hydrolytic efficiency. ESBLs are highly susceptible to inhibition by clavulanate, and their presence can be detected by the disc-approximation test, using amoxycillin/clavulanate and an ESBL-susceptible antibiotic. Other manual procedures have been used and commercial tests to detect the enzymes include Etest, Vitek and Dade Microscan products. The epidemiology of ESBLs is complex, and epidemic and sporadic strains may be encountered in the same hospital. Spread between hospitals--even countries--has been documented. ESBL activity is carried on large plasmids that often carry determinants for resistance to aminoglycosides and other antibiotics, and this is transmissible to Escherichia coli and other species of Enterobacteriaceae in which ESBLs have been detected.

Humans↗
PubMed1998

Speciation of presumptive viridans streptococci from early onset neonatal sepsis.

Twenty isolates resembling viridans streptococci, 16 from blood and four from gastric aspirates, from 17 cases of early onset neonatal sepsis were identified by the API20 Strep, Rapid ID 32 Strep and conventional tests plus hydrolysis of methylumbelliferyl glycoside substrates. Nineteen of the isolates were identified as species of viridans streptococci and one as a Leuconostoc sp. Ten of the isolates were Streptococcus oralis, three S. mitis biotype 1, two S. mitis biotype 2 and one each of S. sanguis, S. vestibularis, S. salivarius and S. intermedius. The Rapid ID 32 Strep and conventional plus methylumbelliferyl tests gave the same species identity for 17 of the isolates. S. intermedius was identified by the Rapid ID 32 Strep as S. constellatus and S. salivarius as S. equinus, with S. salivarius at lower probability. The API20 Strep failed to identify S. vestibularis and identified S. salivarius as S. defectivus. The absence of certain critical tests, including urea hydrolysis, does not allow the API20 Strep to identify all the currently recognised species of viridans steptococci. The species distribution was unexpected and the incidence of S. oralis and other viridans streptococci in vaginal swabs from prenatal patients is being investigated further.

Bacteremia↗
PubMed1996

Plasmid-mediated multidrug resistance in Salmonella typhi in Kuwait.

Multidrug resistant Salmonella typhi infection is common in Kuwait. Between January 1993 and December 1994, 266 strains of S. typhi were isolated from blood of suspected typhoid fever cases attending the Infectious Disease Hospital, Kuwait. Of these, 205 strains were isolated from patients from the Indian sub-continent, 105 (45%) of which showed resistance to one or more drugs; 91 of these resistant strains showed resistance to the oral antimicrobials ampicillin, chloramphenicol, tetracycline and co-trimoxazole (ACTCo). All 266 isolates were sensitive to fluoroquinolones and cephalosporines. The minimum inhibitory concentrations (MIC) for ampicillin, chloramphenicol and tetracycline in resistant strains were > 1000 micrograms/ml. All 91 strains with ACTCo resistance pattern transferred their resistance to a recipient E. coli strain, whereas none of the remaining 14 strains with different resistance patterns transferred theirs. This paper reaffirms that multidrug resistant S. typhi is quite common in Kuwait and that such resistance is encoded by auto-transferring plasmids.

Anti-Bacterial Agents↗
PubMed1996

Comparison of five methods for the determination of arginine hydrolysis by viridans streptococci.

Seventy-eight clinical isolates and four control strains of viridans streptococci were tested in parallel for arginine hydrolysis by five different methods. These comprised two commercial systems, the API20 STREP and Vitek GPI card, two published methods, one based on ammonia production and one on alkalisation of Møeller's decarboxylase medium, and a method based on alkalisation of a phenol-red broth medium dispensed into microtitration plates. The clinical isolates were speciated by their biochemical reactions in the API20 STREP and API20 ZYM systems. One strain produced only a weak reaction for arginine hydrolysis in the medium by ammonia production, but otherwise the results with this medium, the API20 STREP and the microtitration plate method were identical. Tests with the Møeller decarboxylase medium and Vitek GPI card gave negative results with isolates that were positive by other methods. Inoculum size was shown to influence arginine hydrolysis obtained with Streptococcus sanguis NCTC 7863 and S. milleri 10713.

Adult↗
PubMed1990

Childhood shigellosis: clinical and bacteriological study.

Ninety-three children with shigellosis were hospitalized in a regional hospital in Kuwait during the year 1988. S. flexneri was the most common isolate (54%) followed by S. sonnei (39%) and S. boydii (7%). In addition to the gastrointestinal manifestations, 14 patients (15%) developed generalized convulsions. The benign and self-limiting nature of the convulsions associated with shigellosis means that neither diagnostic procedure nor drug therapy are usually necessary. The disease was self-limiting in 41% and antimicrobial usage did not seem to shorten the duration of symptoms or hospital stay. All shigellae isolated were sensitive to gentamicin and amikacin, 56% were resistant to three or more antimicrobial agents, 32 were resistant to five or more. These findings may indicate the need for better control of antibiotic use, particularly in developing countries.

Amikacin↗
PubMed1990

Childhood bacterial meningitis in Kuwait.

A total of 110 cases of bacterial meningitis were studied over a 7-year period. The attack rate was 3.2/100,000 overall and 13/100,000 in children under 12 years. Haemophilus influenzae was the most common pathogen (44.3%), followed by Streptococcus pneumoniae (20.9%) and Neisseria meningitidis (12.7%). The mean patient age was 2.7 years, but 44/49 cases of H. influenzae meningitis were in children under 2 years, an attack rate of 31/100,000. The mortality was 22.4% for neonates and 6.5% for other children, and was associated with coma at presentation and unusual microorganisms. Neurological sequelae were detected in 19% of surviving children.

Age Factors↗
PubMed1988

Evaluation of a latex kit reagent for the detection and identification of pneumococci.

The ability of a commercial latex kit to detect pneumococcal antigen in 50 CSF samples, 150 ear swabs and 80 sputum samples was investigated. Results were compared with microscopic and culture findings. 18/19 culture-positive specimens were latex-positive. 7 latex-positive specimens yielded organisms other than S. pneumoniae which agglutinated the latex, 4 Klebsiella spp, 2 Staphylococcus aureus and 1 Haemophilus influenzae. For 11 other specimens latex agglutination was positive and culture negative. S. pneumoniae was recovered from the blood of 1 of these patients and, in 2 further cases, microscopy showed poorly stained organisms which had some resemblance to S. pneumoniae. For 10 different strains of S. pneumoniae suspensions containing between 10(4) and 10(7) organisms per ml were required to agglutinate the latex.

Antigens, Bacterial↗
PubMed1978

Field tests of a permeation-type personal monitor for vinyl chloride.

A passive dosimeter-type personal monitor for vinyl chloride has undergone extensive field testing. Collaborative studies by a number of laboratories confirm the accuracy, reliability, convenience and general acceptability of personal monitors utilizing gas permeation for sample collection and quantification. Data are generated as timeweighted averages and response is linear from 5 ppb to 50 ppm. The monitors which weigh only 35 g are unaffected by variations in environmental conditions.

Charcoal↗