Acquisition of native beta-strand topology during the rapid collapse phase of protein folding

The 98 residue C-terminal domain of the cell-surface receptor protein CD2 (CD2.D1) has a beta-sandwich fold belonging to the immunoglobulin superfamily but lacking the usual disulfide bridges. Kinetic studies on the folding/unfolding of CD2.D1 reveal that folding proceeds through a rapidly formed intermediate state [Parker, M. J., & Clarke, A. R. (1997) Biochemistry 36, 5786-5794]. To characterize the structural properties of this intermediate we have performed a series of amide hydrogen exchange studies using the pH competition method, in which folding and exchange are initiated simultaneously. The complex beta-sheet topology of this molecule makes it an ideal object for examining the acquisition of backbone hydrogen bonds made between sequence-local and sequence-distant segments of the chain during folding. The pattern of protected amides in the intermediate reveal that the essential features of the beta-sheet topology of CD2.D1 are defined early in the folding pathway, before the development of intimate side chain interactions characteristic of the native state. The results are discussed in light of current issues concerning the mechanistic relevance of kinetic protein folding intermediates.     

Increased cerebral blood volume in HIV-positive patients detected by functional MRI

OBJECTIVE: To study changes in cerebral hemodynamics related to HIV infection. BACKGROUND: Cerebral injury is a well-known manifestation of HIV infection. Physiologic changes in the HIV brain may precede structural changes and may be detected by functional MRI (fMRI). METHODS: Dynamic contrast fMRI was used to measure the cerebral blood volume (CBV) in 13 patients infected with HIV and in 7 healthy control subjects. RESULTS: Significant increases in dynamic CBV were found in the deep (p < 0.001) and cortical gray matter (p < 0.05) of HIV-positive (HIV+) patients. Patients with definite cognitive impairment showed significantly greater increases in CBV in the deep gray matter (DGM) compared with those without impairment. In one patient with rapidly progressive cognitive impairment, these abnormalities reversed and paralleled clinical improvement after initiation of zidovudine monotherapy. CONCLUSIONS: This study supports the hypothesis that HIV infection is associated with significant cerebral hemodynamic changes, particularly in the DGM, that may contribute to cognitive dysfunction in AIDS. Functional MRI may be useful for early detection of cerebral injury and for the assessment of novel therapies.     

A five year study. Fluoride release of four reinforced composite resins

PURPOSE: The purpose of this study was to record the fluoride released measured in parts per million of four fluoride composite resins for five years. MATERIALS AND METHODS: Four fluoridated composites were separated into four groups. Two composite resins with high viscosity were core materials, Ti-Core with titanium (group 1) and Ti-Core Natural (group 2) and the other two resins studied were low viscosity post cements Flexi-Flow cement with titanium (group 3) and Flexi-Flow Natural (group 4). The fluoride release was studied under four experimental conditions. Three replications were studied in each condition. Fluoride release was measured for 260 weeks (5 years). STATISTICAL METHODS: A one-way analysis of variance (ANOVA) was used to compare the average weekly release followed by a Student-Newman-Keuls (SNK) pairwise multiple comparison test. All results were considered statistically significant if p < 0.05. RESULTS: The ANOVA analysis released a significant statistical interaction between group and week (p < 0.0001). Further analysis showed that the average weekly release for Ti-Core with titanium did not differ from Ti-Core Natural, and that Ti-Core with titanium and Ti-Core Natural differed from both Flexi-Flow Natural and Flexi-Flow with titanium, which were not different from one another. CONCLUSIONS: Ti-Core with titanium (Group 1) and Ti-Core Natural (Group 2) released a greater amount of fluoride than Flexi-Flow with titanium (Group 3) and Flexi-Flow Natural (Group 4). The fluoride released from these fluoridated resin composites are similar to reported ranges of other fluoride releasing dental restoration materials.     

Fatigue testing of PVC pipe fittings

The fatigue resistance of 6 inch Schedule 40 PVC solvent-bonded pipe fittings was investigated. It has often been assumed that the performance of PVC fittings is comparable to that of the corresponding pipe. The results of this study indicate that the fatigue performance of PVC fittings is much lower than that of the pipe. Several fittings were exposed to a repetitive surge cycle of 90 to 180 psig at a rate of 0.111 hertz. Failures of several tees occurred between 13,000 and 16,000 cycles, much sooner than the predicted lifetime of pipe under these conditions.     

Treatment of colorectal cancer: hepatic metastasis

Almost one-third of patients dying from colorectal cancer have tumor limited to the liver. Systemic chemotherapy is the appropriate palliative management of patients with metastases to the liver and other sites. For many patients with isolated hepatic metastases, systemic chemotherapy is also the most appropriate treatment. However, results with systemic chemotherapy indicate that one-third or less of patients will respond to such treatments, and long-term survival is rare. In this report we provide information concerning the natural history of colorectal hepatic metastases, followed by the expected benefits with systemic chemotherapy. This information provides background for the regional therapeutic strategies of surgical resection, cryosurgery, and hepatic artery chemotherapy. We discuss the selection factors appropriate for such treatments, morbidity and mortality, and the potential long-term benefits of such approaches. The last section focuses on surgical considerations in hepatic resection and hepatic artery chemotherapy.     

Effects of phenobarbital and diazepam on imipramine-induced changes in blood pressure, heart rate and rectal temperature of rats

To investigate the safety of anticonvulsants in doses found equipotent in suppressing imipramine induced convulsions, the effects of diazepam (1.8 mg/kg) or phenobarbital (40 mg/kg) following a toxic dose of imipramine (50 mg/kg) on heart rate, blood pressure and body temperature were examined in male Wistar rats. Administration of imipramine alone resulted in significant decreases in blood pressure, heart rate and rectal temperature. Phenobarbital or diazepam alone failed to significantly affect any of these parameters apart from a slight reduction in rectal temperature seen with phenobarbital. Diazepam given after imipramine antagonized the imipramine-induced decrease in heart rate but increased the hypotensive and hypothermic effects. Phenobarbital failed to significantly affect the imipramine-induced changes in any of the physiological parameters studied. The present data suggests that phenobarbital may be preferable to diazepam in treatment of imipramine-induced convulsions.     

Document-based peer review in a psychology training clinic: A preliminary report of a statewide program.

14 licensed psychologists evaluated 20 5-session treatment reports completed by graduate students at a psychology training clinic. The review report ratings indicate that psychologists were impressed with the services provided and proposed at the training clinic. The review program is seen as supplementing the clinic's educational and quality assurance activities. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of the immunospecificity of the porin Om1 of Vibrio anguillarum serotype O1

PURPOSE: To evaluate the relationship between indicators of physical activity and health-related fitness in youth 9-18 yr. METHODS: A cross-sectional sample of 356 boys and 284 girls 9-18 yr of age from phase I of the Quebec Family Study was studied. The sample was divided into three age groups by gender, 9-12, 13-15, and 16-18 yr of age. Physical activity variables included two estimates of activity, estimated daily energy expenditure (EE) and estimated moderate-to-vigorous physical activity (MVPA), and one estimate of inactivity, time spent watching television per day (TVTIME). Health-related fitness variables were the sum of six skin folds (SUM), number of sit-ups in 1 min (SITUP), physical work capacity at 150 beats x min(-1) (PWC150), and static strength of the leg (LMS). Partial canonical correlation was used to quantify the relationship between standardized (z-transformed) activity variables and health-related fitness items, controlling for age. RESULTS: There is a weak to moderate association between physical activity and fitness in youth. The first activity canonical variate is a function of positive loadings for EE and MVPA, with a smaller, negative loading for TVTIME. The first fitness variate generally includes positive loadings for PWC150 and SITUP, with a small negative loading for the SUM and a small positive loading for LMS. The first canonical correlations indicate that the variance shared by the fitness and activity variates ranges from 11 to 21%. CONCLUSION: There is a significant relationship between activity and health-related physical fitness, but a large part of the variability (80-90%) in fitness is not accounted for by physical activity as measured in this study.