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Biomedical subjects

S Whitaker

Publications and source records attributed to S Whitaker.

At least 19 recordsLinked to original sources
PubMed2003

Multiple-interval timing in rats: Performance on two-valued mixed fixed-interval schedules.

Three experiments studied timing in rats on 2-valued mixed-fixed-interval schedules, with equally probable components, Fixed-Interval S and Fixed-Interval L (FI S and FI L, respectively). When the L:S ratio was greater than 4, 2 distinct response peaks appeared close to FI S and FI L, and data could be well fitted by the sum of 2 Gaussian curves. When the L:S ratio was less than 4, only 1 response peak was usually visible, but nonlinear regression often identified separate sources of behavioral control, by FI S and FI L, although control by FI L dominated. Data were used to test ideas derived from scalar expectancy theory, the behavioral theory of timing, and learning to time.

Animals↗
PubMed1999

Cellular growth in biofilms.

In this paper we develop a macroscopic evolutionary equation for the growth of the cellular phase starting from a microscopic description of mass transport and a simple structured model for product formation. The methods of continuum mechanics and volume averaging are used to develop the macroscopic representation by carefully considering the fluxes of chemical species that pertain to cell growth. The concept of structured models is extended to include the transport of reacting chemical species at the microscopic scale. The resulting macroscopic growth model is similar in form to previously published models for the transport of a single substrate and electron donor and for the production of cellular mass and exopolymer. The method of volume averaging indicates under what conditions the developed growth model is valid and provides an explicit connection between the relevant microscopic model parameters and their corresponding macroscopic counterparts.

Biofilms↗
PubMed1998

Hu23F2G, an antibody recognizing the leukocyte CD11/CD18 integrin, reduces injury in a rabbit model of transient focal cerebral ischemia.

Neutrophils are known to mediate injury in acute ischemic stroke especially during reperfusion. Migration of neutrophils into regions of ischemic injury involves binding to the endothelial cell's intercellular adhesion molecule (ICAM-1) through the leukocyte integrin, CD11/CD18. We studied the potential for neuroprotection with a humanized antibody that binds to and blocks the functions of the CD11/CD18 integrin in a rabbit model of transient focal ischemia. Fifteen New Zealand White rabbits underwent transorbital occlusion of the left middle cerebral, anterior cerebral, and internal carotid arteries using aneurysm clips for 2 h, followed by 6 h of reperfusion. Treatment with a maximally saturating dose (4 mg/kg) of a humanized CD11/CD18 monoclonal antibody (Hu23F2G, ICOS Corp., Bothell, WA) (n = 8) or placebo (n = 7) was administered 20 min after occlusion and given as a single intravenous bolus. Hemispheric ischemic neuronal damage (IND) as seen on hematoxylin- and eosin-stained sections was significantly reduced in Hu23F2G-treated animals by 57% (Hu23F2G: 15 +/- 6.9%; placebo: 35 +/- 5%; mean +/- SEM, P < 0.05, t-test). Immunohistochemical staining with neutrophil elastase confirmed the presence of neutrophils within regions of IND in control brains. Treatment with Hu23F2G resulted in marked reduction of neutrophil infiltration. (No. of neutrophils/IND area: Hu23F2G 36.1 +/- 36.7 cm-2, placebo 460.6 +/- 101.8 cm-2, P = 0.001. ) Antagonism of neutrophil migration at the level of the CD11/CD18 integrin reduces ischemic injury in experimental stroke.

Animals↗
PubMed1995

A polycistronic transcript in transformed cells encodes the dihydrofolate reductase of herpesvirus saimiri.

Herpesvirus saimiri, an oncogenic gamma herpesvirus of primates, is the only eukaryotic virus that carries the entire metabolic gene set for a complex biochemical synthesis. Every element of the thymidine synthesis gene cascade is present in the virus, and their function is probably related to the uniquely high A + T content of the genome. Although one member of the gene set, dihydrofolate reductase (DHFR), is mapped in a region required for oncogenesis, very little is known of the expression and function of this gene in transformed cells. We report the expression of the DHFR sequence on a novel, unique tricistronic transcript in virally transformed tumor cells. The DHFR sequence is the first open reading frame on a 5.3 kb minor transcript. Alpha-amanitine sensitivity indicates that it is an RNA polymerase II transcript, and since it is also polyadenylated it appears to be a functional, relatively unstable (half-life 3 hr) mRNA. Initiation of transcription uniquely overlaps with the HSUR3 small RNA gene. Expression of the small transcript appears to be alpha-amanitine resistant, implicating polymerase III transcription. Together with the remarkably low-level expression of HSUR3 in tumor cells, the data may indicate transcription interference between two different RNA polymerases, with unusual overlapping regulation and initiation.

Base Sequence↗
PubMed1995

Audit of pre-employment assessments by occupational health departments in the National Health Service.

Pre-employment health assessment of applicants to the National Health Service (NHS) is one of the functions of occupational health departments in the NHS. This paper describes the results of a process and outcome audit of this activity, concentrating on the current practice of occupational health departments. The audit was carried out by 40 NHS occupational health units who provided information on a standard questionnaire on all pre-employment assessments undertaken over a three-month period. This produced 9139 questionnaire returns. The analysis showed that the most common method of assessment was the use of a self-administered questionnaire alone (49.4%). A self-administered questionnaire followed by a nurse interview as standard practice was the next most common method (34.1%), but referral to a physician was uncommon. The outcome of the assessments for 98% of all applicants was 'fit for work'. A total of 120 individuals (1.3%) were assessed as 'fit to work, but with some restriction' and 65 individuals (0.7%) were considered 'unfit'. The most common reasons for rejection were abnormal body mass index (40%), skin conditions (21.5%) and psychiatric conditions (10.8%). The most common reasons for restriction were musculoskeletal conditions (27.5%), skin conditions (15%) and abnormal body mass index and psychiatric conditions (both 10.8%). The audit identified wide variation between occupational health departments in the NHS in the practice of restriction and rejection. A decision on the value of pre-employment assessment in the NHS mus take into consideration the ability of the process to achieve its aim, the time and manpower involved in the process, and the probability of low restriction and rejection rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Employment↗
PubMed1995

The art and science of home infant apnea monitoring in the 1990s.

The use of home apnea monitoring (HAM) continues as an accepted or recommended intervention for infants with certain signs and symptoms or medical diagnoses. Results of HAM in terms of case outcomes versus cost-effectiveness and efficacy remain matters of controversy in relation to the limited number of studies that show conflicting results. There are no studies that document the effectiveness of apnea monitoring. When an apnea monitor is prescribed, nursing can provide quality care through education and emotional support of families using HAM.

Apnea↗
PubMed1993

Ataxia telangiectasia: an investigation of the repair defect in the cell line AT5BIVA by plasmid reconstitution.

The ataxia telangiectasia cell line, AT5BIVA, exhibited low repair fidelity measured by the reconstitution of transfected linear plasmid. This assay involves transfecting a linear plasmid containing two selectable marker genes: one gene (neo) is undamaged and marks transfection and the other gene (gpt) is cleaved to test functional repair. The proportion of transfected cells which have a functionally intact gpt gene gives a measure of repair fidelity. Southern analysis of individual transfected clones showed that integrated plasmids in AT5BIVA had a high frequency of sequence rearrangement. Blunt or staggered-ended termini of a linear plasmid did not determine the type of misrepair. A variety of sizes of deletions and sequence insertions were found at and around the cleavage site. Loss of intact sequence occurred similarly following transfection by linear or circular plasmid (misrepair or rearrangement error). This suggests that the action of excess exonuclease activity upon, or lack of protection of, exposed DNA termini is not the sole mechanism of misrepair. Erroneous rearrangement of circular plasmid could involve any location along the plasmid. Rearrangement of transfected circular plasmid occurred in multiple copies of the same abnormal size, suggesting that error-prone recombination rather than degradation of presumed nicked circular plasmid was the underlying mechanism. It is hypothesized that misrepair in ataxia-telangiectasia arises by error-prone recombination.

Ataxia Telangiectasia↗
PubMed1993

The reduction of aggression in people with learning difficulties: a review of psychological methods.

The literature on the reduction of aggression in people with learning difficulties is reviewed. The methods of reducing aggression identified were predominantly evaluated in staffed settings and with target behaviours more frequent than once a day. This contrasts with the findings of a recent survey that found the majority of aggressive individuals to live in the community and show aggression less than once a day. It is argued that the reasons for this disparity are as follows. That it is easier to do a controlled study in staffed settings with high-frequency aggression. That it is more difficult to do an analysis of the target behaviour if it is low frequency or if the subject is in the community; and that the methods that have been traditionally used to reduce aggression may not be effective with all subjects in all settings. It is suggested that it may be necessary to develop and evaluate a new technology for reducing aggression.

Adolescent↗
PubMed1993

PEA: working towards standards of good practice in the NHS.

At the beginning of the year Stuart Whitaker described a pilot study for the national audit of pre-employment assessment in the NHS. Having completed the project he now presents its findings with a call for the introduction of standards of good practice.

Employment↗
PubMed1990

Prognostic significance of tumor ploidy in patients with advanced ovarian carcinoma.

Fresh tumor specimens obtained from 53 consecutive patients with FIGO Stage III ovarian carcinoma were analyzed by flow cytometry. All patients were treated by a standard protocol: maximal tumor excision and cisplatin/cyclophosphamide/adriamycin chemotherapy, and followed-up for at least 24 months. Thirty-two percent of tumors were diploid (DNA index = 1.00) and 68% aneuploid (DNA index greater than 1.00), with more aneuploid tumors being associated with larger residual tumor and poor cellular differentiation. Patients with diploid tumors were found to survive significantly better than those with aneuploid tumors, in terms of survival rate (65% versus 31%), median survival time (33 months versus 13 months), and mean disease-free interval (17.8 months versus 8.2 months). The influence of the amount of residual tumor after primary surgery on survival was only significant in patients with diploid tumors. Our results support previous findings that tumor ploidy is an important prognostic indicator in ovarian cancer. We found aneuploidy to be associated with a poorer clinical outcome in Stage III disease, regardless of the amount of residual tumor after primary surgery and the degree of cellular differentiation.

Adenocarcinoma↗