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Biomedical subjects

M Barrett

Publications and source records attributed to M Barrett.

At least 37 records · Page 2Linked to original sources
PubMed1995

Metabolism of herbicides by cytochrome P450 in corn.

Cytochrome P450 monooxygenases (P450) have long been considered a potentially important enzyme system for the detoxification of herbicides in corn and other crop plants. Only recently has herbicide metabolism by P450 in corn microsomes been conclusively demonstrated. Fourteen herbicides in six chemical families have been shown to be metabolized by P450 in corn. P450 is now considered of equal importance to glutathione S-transferases for the metabolism of herbicides in corn. P450 metabolism of herbicides in corn is characterized as an inducible enzyme activity which primarily catalyses hydroxylations and demethylations of the herbicide substrates. Induction of the herbicide metabolizing activity is specific, with only slight changes in the total P450 level accompanying several-fold induction of herbicide metabolism. Turnover rates for herbicide metabolism can equal those for drug metabolism. Microsomes isolated from both shoots and roots metabolize herbicides, although the majority of activities are most fully characterized in microsomes isolated from shoots of young etiolated seedlings. Many questions concerning the P450 metabolism of herbicides in corn remain. These include determining how many P450s are involved in herbicide metabolism and how their levels are regulated. Evidence is gathering that, for a number of the herbicides presently known to be metabolized by P450 in corn, there may be relatively few or even one P450 which metabolizes all the herbicide substrates.

Cytochrome P-450 Enzyme Inhibitors↗
PubMed1994

Physical activity and risk of breast cancer in the Framingham Heart Study.

The authors analyzed data from the Framingham Heart Study to evaluate the association between physical activity and breast cancer risk. Physical activity was ascertained by a physician-administered questionnaire from 2,321 women at the fourth biennial examination conducted in 1954-1956. Breast cancers were identified by self-report, surveillance of admissions to Framingham Union Hospital, and review of death records; all but one were histologically confirmed. During 28 years of follow-up, 117 breast cancer cases were diagnosed among the 2,307 women with data on physical activity and reproductive history (a potential confounder). Analysis was performed using Cox proportional hazards models with age as the underlying time variable. Models were adjusted for age at physical activity assessment, menopausal status, age at first pregnancy, parity, education, occupation, and alcohol ingestion. We observed a gradient of increasing risk of breast cancer with increasing physical activity (trend p = 0.06). The relative risk for women in the highest versus lowest activity quartile was 1.6 (95% confidence interval 0.9-3.0; p = 0.13). Although both moderate-to-heavy leisure and occupational activities were associated with an increased risk, the association was marginally significant only for leisure activity (p = 0.06). Our findings do not support a protective effect of physical activity during adulthood for breast cancer, but suggest an increased risk among more active women.

Adult↗
PubMed1994

The drawings of children and young people with Down's syndrome: a case of delay or difference?

This study compared the performance of 29 children and young people with Down's Syndrome with the performance of 29 verbal-mental-age-matched children without learning difficulties on four drawing tasks and four picture-selection tasks. All eight tasks involved the graphic depiction of a perceptually-present array in which one object was partially occluded by another object. It was found that all participants performed better on the picture-selection tasks than on the drawing tasks, and that the individuals with Down's Syndrome performed significantly worse than the children without learning difficulties on all eight tasks. However, it was also found that the performance of the children without learning difficulties correlated strongly with their verbal mental age, but that the performance of the individuals with Down's Syndrome did not show the same correlation with verbal mental age. Other systematic differences between the drawings of the individuals with Down's Syndrome and those of the children without learning difficulties also occurred. The findings suggest that the drawing development of children and young people with Down's Syndrome may not just be delayed relative to that of children who do not have learning difficulties but may exhibit a qualitatively different pattern.

Adolescent↗
PubMed1993

Cancer associated haemolytic uraemic syndrome developing prior to treatment with cytotoxic agents.

The haemolytic uraemic syndrome has been reported in children and adults with neoplasias treated with mitomycin C and occasionally in adults prior to chemotherapeutic treatment, but it has not been reported in a child prior to the use of cytotoxic drugs. This case report concerns the development of the haemolytic uraemic syndrome in a 7-year-old male child with a metastatic hepatocellular carcinoma. The child had persisting haemolysis and renal impairment, and died three weeks after presentation. Though our experience with similar tumours suggested the outlook would be poor, we had hoped to provide palliative chemotherapy. This proved impossible as optimal chemotherapy could not be used because of the renal impairment.

Anemia, Hemolytic↗
PubMed1991

Early lexical development and maternal speech: a comparison of children's initial and subsequent uses of words.

In Harris, Barrett, Jones & Brookes (1988), we reported the results of a detailed analysis of the initial uses of the first 10 words which were produced by four children. The present paper reports the results of an analysis of the subsequent uses of these 40 words. This analysis reveals that seven qualitatively different patterns of change occurred between the children's initial and subsequent uses of these words; the particular patterns of change which occurred support Barrett's (1986) model of early lexical development. In addition, it was found that, although there was a strong relationship between maternal speech and the children's initial word uses, the relationship between maternal speech and the children's subsequent word uses was very much weaker. These findings indicate that the role of linguistic input in early lexical development may decline quite sharply once the child has established initial uses for words.

Child Language↗
PubMed1991

A thesis is born.

Explore the source record for details and available documents.

Academic Dissertations as Topic↗
PubMed1990

In vitro comparison of mezlocillin and piperacillin plus tobramycin or gentamicin versus 100 gram-negative nosocomial bloodstream isolates.

We compared the in vitro activity of mezlocillin and piperacillin, alone and in combination with tobramycin or gentamicin, against clinical isolates of gram-negative bacilli from hospitalized patients with 100 distinct episodes of nosocomial bacteremia. The minimum inhibitory concentrations (MICs) necessary to inhibit 50% and 90% of isolates showed that piperacillin was most active against Pseudomonas aeruginosa. The MIC needed to inhibit 90% of isolates also showed that mezlocillin was more active against Enterobacter cloacae. Activities of the two acylaminopenicillins were comparable against the rest of the isolates. Combining the acylaminopenicillins with either gentamicin or tobramycin decreased the MICs fourfold or more for both combinations. Synergy occurred more frequently with mezlocillin-gentamicin (12%), followed by piperacillin-tobramycin (9%), mezlocillin-tobramycin (6%), and piperacillin-gentamicin (5%). Antagonism for Enterobacteriaceae isolates was observed most frequently with the combination of piperacillin plus tobramycin (20%), followed by mezlocillin plus tobramycin (17.6%), piperacillin plus gentamicin (12.9%), and mezlocillin plus gentamicin (8.2%). There are very few differences in the activities of mezlocillin and piperacillin combined with either gentamicin or tobramycin versus nosocomial gram-negative bloodstream isolates.

Drug Synergism↗
PubMed1990

Services and charges by PPO physicians for PPO and indemnity patients. An episode of care comparison.

Physicians who participate in preferred provider organizations (PPOs) usually agree to various types of utilization review and sometimes discount their charges or agree to accept lower fees. This study was performed to determine whether they provided more or fewer services to their PPO patients than to their indemnity patients and whether the discounting resulted in lower expenditures for each episode of illness. In 1984, Metropolitan Life offered PPO coverage to Dade County (Florida) school board employees and dependents but only a standard indemnity plan to Dade County government employees and dependents. Episodes of care were examined for patients with chest pain, hypertension, joint pain, gastrointestinal or liver disorders, and lower back pain cared for by physicians who treated patients in both the PPO and indemnity employee groups. For PPO patients, charges per physician service were the same or lower, but total physician charges during an episode were higher. For services such as laboratory tests, diagnostic x-rays, and room and board, PPO and indemnity patients' charges were not significantly different.

Fees, Medical↗
PubMed1990

Vancomycin resistance in Staphylococcus haemolyticus causing colonization and bloodstream infection.

The increase in the incidence of infections due to beta-lactam-resistant coagulase-negative staphylococci has resulted in expanded use of vancomycin for such infections. Despite this, coagulase-negative staphylococci have remained susceptible to vancomycin in recent years. This report describes a strain of Staphylococcus haemolyticus with increased resistance to vancomycin (MIC, 8.0 to 16 micrograms/ml). S. haemolyticus was initially isolated from a patient with acute leukemia and neutropenia in surveillance throat and stool cultures. The microdilution vancomycin MICs for these isolates were 1.0 to 2.0 micrograms/ml. Subsequent S. haemolyticus isolates from the bloodstream and tracheal aspirate occurred in the setting of prolonged empirical vancomycin therapy. MICs for these isolates were 8.0 to 16 micrograms/ml. Further vancomycin resistance (MIC, 32 micrograms/ml) could be selected for in vitro in all four isolates. Restriction endonuclease analysis of plasmid DNA indicated that the isolates were very closely related and likely to be of the same strain. We conclude that colonization with a vancomycin-susceptible strain of S. haemolyticus was subsequently linked to a nosocomial bloodstream infection with an apparently identical strain with intermediate levels of vancomycin resistance. Prolonged empirical vancomycin therapy was temporally associated with this episode.

Aged↗
PubMed1989

Clinical evaluation of a direct fluorescent monoclonal antibody test for detection of Pseudomonas aeruginosa in blood cultures.

A direct fluorescent monoclonal antibody test (DFA; Genetic Systems Corp., Seattle, Wash.) was evaluated for the detection of Pseudomonas aeruginosa in 178 blood culture broths obtained from 128 patients. The DFA identified 44 (98%) of 45 blood cultures positive for P. aeruginosa and was negative in 131 (98%) of 133 blood cultures which grew gram-negative rods other than P. aeruginosa. Upon further investigation, saline suspensions of the organism from the false-negative blood culture were strongly (4+) DFA positive. The false-positive reactions were not due to cross-reactivity, as shown by lack of DFA staining of the non-P. aeruginosa isolates following subculture to agar media. The specificity of the reagent was further demonstrated by directly staining culture isolates including 10 serotypes of P. aeruginosa (all positive) and 57 selected gram-negative bacilli including eight species of Pseudomonas that were not P. aeruginosa (all negative). DFA staining of blood culture broths was easy to perform and read with minimal background fluorescence. The DFA method can be performed in 50 min and appears promising as a rapid method for the identification of P. aeruginosa bacteremia.

Antibodies, Monoclonal↗
PubMed1989

The immune response of the sheep popliteal lymph node to a purified phenoloxidase from larval cuticle of the sheep ectoparasite, Lucilia cuprina.

The popliteal lymph node of the sheep can mount a strong immune response to a phenoloxidase, enzyme A, purified from larval cuticle of a major sheep ectoparasite, the sheep blowfly, Lucilia cuprina. Continuous sampling from a cannulated efferent lymphatic allowed monitoring of changes in both cellular output (total cells and large blast cells) and specific antibody production (by ELISA) following primary and secondary challenge with antigen. Anti-enzyme A antibodies in lymph selectively precipitated enzyme A but not a second cuticular phenoloxidase, enzyme B, a finding that will prove useful in immunolocalization of the enzymes and in elucidating their origins. The implications for immunization of sheep against L. cuprina are discussed.

Animals↗
PubMed1988

Development of the quantitative micro-test for slime production by coagulase-negative staphylococci.

The macro-test for slime production by coagulase-negative staphylococci was adapted to a spectrophotometric micro-test assay to obtain more objective and quantitative information on slime production. A total of 135 isolates of coagulase-negative staphylococci (70 macro-test-positive and 65 macro-test-negative) were tested by both methods. The quantitative micro-test optical density readings were (mean +/- SD) 1.176 +/- 0.294 and 0.130 +/- 0.095 for the macro-test-positive and -negative groups, respectively. The micro-test was reproducible and demonstrated quantitative differences in slime production among the different species of coagulase-negative staphylococci. Aside from Staphylococcus epidermidis, the majority of the coagulase-negative staphylococci had very low optical density readings, indicating little or no slime production under the conditions employed in this assay. This test allows one to study the relative production of slime by different strains and species of coagulase-negative staphylococci, and may be useful in studying the effects of different conditions, such as antibiotic exposure, on slime production.

Bacterial Proteins↗
PubMed1988

Quality assurance review: improving diagnostic accuracy of percutaneous needle biopsy.

Adequate pathologic slide preparation of percutaneous fine-needle biopsy (PFNB) specimens is necessary to maximize sensitivity and yield a tissue diagnosis. We present a quality control review of our biopsy technique and results in 71 aspiration biopsies done in 59 patients. Immediate cytology slide preparation in the radiology suite enabled us to increase our diagnostic yield from 53% to 84%, and allowed us to preserve PFNB, rather than open biopsy, as the primary diagnostic modality. We recommend regular review of biopsy techniques to confirm adequate diagnostic yields of these procedures.

Biopsy, Needle↗
PubMed1987

Use of the maximal-operant principle to motivate children's intrinsic interest.

The present research examined the hypothesis that in contrast to theory and research indicating that tangible reward decreases subsequent interest in enjoyable academic activities, rewards are perceived by adults as effective techniques to maximize long- and short-term subsequent interest for academic tasks of both high and low initial interest level. The results of our first three studies demonstrated that college students and parents view tangible reward as more effective than other less controlling techniques to enhance intrinsic motivation and value rewards more for intrinsically interesting academic behaviors in comparison with others (e.g., prosocial behaviors). Our fourth study supported the hypothesis that adults do not subscribe to the minimal-sufficiency analysis of increasing intrinsic motivation but prefer a maximal-operant principle in which the likelihood of producing long-term interest in academic tasks is assumed to vary positively with the size of a reward. Our fifth and sixth studies investigated illusory correlation as one mechanism that may perpetuate beliefs about the assumed positive relation between tangible reward and intrinsic interest in academic tasks.

Achievement↗
PubMed1987

Needle biopsy evaluation of class II major histocompatibility complex antigen expression for the differential diagnosis of cyclosporine nephrotoxicity from kidney graft rejection.

Twenty needle biopsies from 14 patients were taken at times of renal dysfunction, and frozen sections were stained for class I and class II major histocompatibility complex (MHC) antigen expression using the immunoperoxidase technique and monomorphic mouse monoclonal antibodies. Eight of the 9 biopsies taken during periods of dysfunction attributed to cyclosporine toxicity had normal levels of class II expression. In contrast, 9 of the 10 biopsies taken during episodes of rejection had easily recognized increases in class II expression. In the one case where no definite clinical diagnosis was possible, no class II induction was present. Class I levels were less definitive but tended to be markedly raised in the cases of rejection, and only mildly raised in the cases of nephrotoxicity. Biopsy results can be available within 1 1/2-2 hr. The test is therefore likely to be of value in the correct diagnosis of the cause of renal dysfunction and thereby improve the management of cyclosporine-treated renal transplant patients.

Antibodies, Monoclonal↗