Search PubMed⌕ Search

Biomedical subjects

S Peterson

Publications and source records attributed to S Peterson.

At least 73 records · Page 4Linked to original sources
PubMed1997

A novel assay for hepatitis B e markers.

The evaluation of a novel assay that allows simultaneous testing for hepatitis B e antigen and its antibody in a single well is described. The results of routine application and sequential studies on patients with acute hepatitis B and chronic hepatitis B treated with interferon are presented. The specificity and sensitivity of the assay and its ability to be used to follow the response of a patient during the whole seroconversion episode has been evaluated. The assay proved to give useful information about the reactivity of the sample, especially in those patients who were changing their "e" status.

Biomarkers↗
PubMed1995

CDK4/cyclin D1/PCNA complexes during staurosporine-induced G1 arrest and G0 arrest of human fibroblasts.

We have shown that staurosporine (STSP) arrests normal human diploid fibroblasts in the G1 phase of the cell cycle at a time approximately 3 h after release from low-serum-induced G0 arrest. This initial temporal mapping of the STSP-induced restriction point was based on flow cytometric analyses that measured the onset of DNA synthesis after release from STSP and low-serum treatment. Here we show that the STSP-mediated arrest point distinctly differs from low-serum G0 arrest. We have found that cyclin D1 is expressed in STSP-arrested G1 fibroblasts but not in low-serum-arrested G0 fibroblasts, whereas cyclin-dependent kinase 4 (cdk4) and proliferating cell nuclear antigen (PCNA) are equivalently expressed under conditions of both STSP treatment and serum deprivation. Cdk4/cyclin D1/PCNA complexes are also formed in STSP-arrested G1 fibroblasts, but they are absent in serum-deprived G0 cells. The formation of cdk4/cyclin D1/PCNA complexes was found to coincide with the transcription and synthesis of cyclin D1, which indicates that the lack of available cyclin D1 is the limiting factor in cdk4/cyclin D1/PCNA complex formation in serum-deprived fibroblasts. This conclusion was further supported by the observation that cyclin D1-GST fusion protein binds cdk4 and PCNA when added to G0 cell extracts. Circumstantial evidence obtained in our studies and by other investigators suggests that STSP-induced arrest may be due to the inhibition of cdk-activating kinase.

Alkaloids↗
PubMed1995

Effects of rhIGF-I administration on bone turnover during short-term fasting.

Insulin-like growth factor-I (IGF-I) is a nutritionally dependent bone trophic hormone which stimulates osteoblast function and collagen synthesis in vivo and in vitro. We hypothesized that in the fasting state, IGF-I levels would decline significantly and would establish a model in which we could investigate the effects of IGF-I administration on bone turnover. We therefore studied 14 normal women ages 19-33 (mean, 24 +/- 4 [SD] years) during a complete 10-d fast. After 4 d of fasting, subjects were randomized to receive rhIGF-I or placebo subcutaneously twice a day for 6 d. Bone turnover was assessed using specific markers of formation (osteocalcin and type I procollagen carboxyl-terminal propeptide [PICP]) and resorption (pyridinoline, deoxypyridinoline, type I collagen crosslinked N-telopeptide [N-telopeptide] and hydroxyproline). Serum levels of PICP and osteocalcin decreased from 143 +/- 52 to 60 +/- 28 ng/ml (P = 0.001) and from 7.6 +/- 5.4 to 4.2 +/- 3.1 ng/ml (P = 0.001) respectively with 4 d of fasting. Urinary excretion of pyridinoline and deoxypyridinoline decreased from 96 +/- 63 to 47 +/- 38 nmol/mmol creatinine (P < 0.05) and from 28 +/- 17 to 14 +/- 11 nmol/mmol creatinine (P < 0.05) respectively. Mean IGF-I levels decreased from 310 +/- 81 to 186 +/- 78 ng/ml (P = 0.001). In the second part of the experimental protocol, serum osteocalcin and PICP levels increased 5- and 3-fold, respectively with rhIGF-I administration and were significantly elevated compared with the placebo group at the end of treatment (20.9 +/- 17.3 vs. 5.9 +/- 6.4 ng/ml for osteocalcin [P < 0.05] and 188 +/- 45 vs. 110 +/- 37 ng/ml for PICP [P < 0.05]). In contrast, all four markers of bone resorption, including urinary pyridinoline, deoxypyridinoline, N-telopeptide and hydroxyproline were unchanged with rhIGF-I administration. This report is the first to demonstrate that bone turnover falls rapidly with acute caloric deprivation in normal women. RhIGF-I administration uncouples bone formation in this setting by significantly increasing bone formation, but not resorption. These data suggest a novel use of rhIGF-I to selectively stimulate bone formation in states of undernutrition and low bone turnover.

Adult↗
PubMed1994

The effects of changes in temperature or ionic strength on isolated rabbit and fish skeletal muscle thick filaments.

Although the skeletal muscles of different vertebrate species have been assumed to be generally similar, recent X-ray diffraction and mechanical studies have demonstrated differences in the responses of these muscles to changes in physiological conditions. X-ray diffraction studies have indicated that lowering the temperature and lowering ionic strength may affect the crossbridge arrangement of rabbit thick filaments. Similar X-ray diffraction studies on the structural effects of lowering ionic strength in frog and fish muscles are less clear in interpretation, while lowering the temperature appears to have little effect in these muscles. In the present study we have compared the effects of lowering the temperature or ionic strength on the crossbridge order of isolated rabbit and fish thick filaments as observed in the electron microscope. In agreement with the X-ray results, rabbit filaments show a distinct loss of crossbridge order when stained at 4 degrees C compared to 25 degrees C, whereas fish thick filaments appear similar at both temperatures. Rabbit thick filaments, when diluted to one-fourth of the normal ionic strength (while maintaining constant EGTA and ATP concentration), showed a strong tendency to bind to actin filaments, while similarly-treated fish filaments showed little tendency to aggregate or become disordered. These results appear to support the X-ray diffraction results of other investigators, and the idea that effects of ionic strength or temperature on muscle may vary with species.

Actin Cytoskeleton↗
PubMed1994

Identification of bacteriophage T4 prereplicative proteins on two-dimensional polyacrylamide gels.

Bacteriophage T4 makes a large number of prereplicative proteins, which are involved in directing the transition from host to phage functions, in producing the new T4 DNA, and in regulating transcriptional shifts. We have used two-dimensional gel electrophoresis (nonequilibrium pH gradient electrophoresis gels in the first dimension and sodium dodecyl sulfate-polyacrylamide gradient slab gels in the second) to identify a number of new prereplicative proteins. The products of many known genes are identified because they are missing in mutants with amber mutations of those genes, as analyzed by us and/or by previous workers. Some have also been identified by running purified proteins as markers on gels with labeled extracts from infected cells. Other proteins that are otherwise unknown are characterized as missing in infections with phage carrying certain large deletions and, in some cases, are correlated with sequence data.

Bacteriophage T4↗
PubMed1994

Long term outcome of an attachment-based program for conduct disorder.

There is increasing concern among professionals and the public about the level of violence and antisocial behaviour among our youth. This has been coupled with confusion and a sense of helplessness about which types of interventions are most effective in responding to these difficulties. Some professionals and advocacy groups are calling for tougher disciplinary responses to violence and antisocial behaviour, including changes in the Young Offenders Act. Yet, such interventions are rarely effective in producing the desired reductions in these behaviours. Other professionals have called for better forms of treatment. However, few treatments have been shown to be effective in bringing about long term reductions either in aggressive behaviour or in the concomitant psychological difficulties experienced by these youths. In this paper, a description is presented of an approach to understanding conduct disorder that focuses on attachment as an organizing principle of behaviour and affect. Also, a description is presented of a community-oriented program that is based on attachment theory, as well as the results of the program evaluation at six, 12 and 18 months following discharge. The findings replicate and extend earlier findings reported by Holland et al (1) on the effectiveness of this approach.

Adolescent↗
PubMed1994

Konzo in the Central African Republic.

We identified a new focus of konzo, an upper motor neuron disease, in a part of western Central African Republic. Interviews and high serum levels of thiocyanate indicate that cyanide exposure from insufficiently processed cassava may cause konzo. Abrupt onset, nonprogressive course, and seronegativity to HTLV-I clearly differentiate konzo from HTLV-I-associated myelopathy in tropical countries.

Adolescent↗
PubMed1993

A quantitative study of levodopa-induced dyskinesia in Parkinson's disease.

The present study addressed the question of whether the emergence and severity of levodopa-induced dyskinesia was related to the therapeutic benefits derived from levodopa. Eight PD patients with clinically observed levodopa-induced dyskinesia were studied prior to and for two hours following a single dose of Sinemet (carbidopa/levodopa). Quantitative instrumental procedures were used to assess upper extremity dyskinesia, rigidity and bradykinesia. Results indicated that all patients exhibited significant reduction in their parkinsonism within 45 minutes following treatment. Reduction in bradykinesia, but not rigidity appeared to coincide with the emergence of dyskinesia. There was a significant relationship between severity of dyskinesia and the degree of improvement in movement velocity but not rigidity. Further analyses revealed that this relationship depended largely on the age of the patient. These findings are discussed as they pertain to a unified model of basal ganglia movement disorders which places dyskinesia and bradykinesia at opposite extremes along a continuum.

Aged↗
PubMed1993

Attachment and conduct disorder: the Response Program.

An increasing number of youths are being identified as suffering from behavioural problems that cause difficulties in their family and peer relations which in turn reduces their chances of academic and vocational success. There is growing concern regarding their level of aggressiveness. The common diagnosis given to these disaffiliated youths is conduct disorder. To date, most treatment programs for conduct disorder have been unsuccessful. A review of recent studies indicates that the disruption of attachment may be an important feature that underlies the wide range of symptoms that are typically found in youths with conduct disorder. A community-oriented program designed to ensure long term care for these youths is described in this paper, and the findings of a six month follow-up evaluation are presented. Results indicated that communities, caregivers, and youths responded positively to the program; caregivers reported significant reductions in a broad range of psychiatric symptoms in youths, and youths reported a significant reduction in symptoms of conduct disorder.

Adolescent↗
PubMed1993

Effects of exercise on plasma lipids and lipoproteins of women.

This review summarizes the cross-sectional and training studies (acute and chronic) that have examined the relationship between exercise and plasma lipid and lipoproteins in women. Because women experience major fluctuations in reproductive hormones throughout the life cycle, the effects of the endogenous sex steroid status on the association between exercise and plasma lipoproteins also are addressed. In general, cross-sectional studies report a positive association between exercise and high density lipoprotein-cholesterol (HDL-C) in both pre- and postmenopausal women. Women on hormone replacement therapy who report exercising have higher HDL-C than sedentary women on hormone replacement therapy. Results from longitudinal training studies have been inconsistent because of experimental design, i.e., inadequate type, duration, and intensity of exercise intervention, lipid measurements made across the menstrual cycle, and studies carried out in women with high baseline HDL-C. Since lipids vary approximately 10-25% throughout the menstrual cycle, menstrual phase should be controlled when determining lipid changes after an exercise intervention. In approximately half of the intervention studies, an increase in HDL-C was demonstrated; the magnitude of the response that can be expected is approximately 10%. The responsiveness of pre- versus postmenopausal women to an exercise intervention is unknown. Studies are needed to clarify the interactive effects of exercise and sex hormones on plasma lipoproteins in women of all ages. This information will be useful in developing intervention programs to reduce the risk of coronary heart disease in women.

Adult↗