Primary electron donors for Azotobacter chroococcum nitrogenase

Augmentation mammaplasty by the transaxillary approach seems to be a safe and anatomically sound procedure which produces consistent results with a low complication rate. Our experiences with this procedure and our modifications in the technique are described. Two instruments which were designed to facilitate the procedure are reported. An anatomical justification for the transaxillary method is made.     

NADP-Isocitrate dehydrogenase from Pseudomonas nautica: kinetic constant determination and carbon limitation effects on the pool of intracellular substrates

Variations of intracellular concentrations of isocitrate and NADP+ were measured throughout all growth phases of the marine bacterium Pseudomonas nautica. The intracellular isocitrate concentration tracked the intracellular protein concentration throughout all phases of growth. It rapidly increased in early exponential phase to a maximum and fell to nearly zero in parallel with pyruvate exhaustion in the culture medium. The intracellular NADP+ and protein concentrations increased in parallel during the exponential phase but were poorly correlated. Even after carbon exhaustion, the intracellular NADP+ concentration stayed high, as did protein levels. The results demonstrated that the intracellular isocitrate concentration, but not the intracellular NADP+ concentration, was affected by the carbon availability in the culture. They also suggest that, because of its variability, isocitrate, but not NADP+, plays the larger role in the control of the respiratory CO2 production rate (RCO2). From initial rate studies, bisubstrate Michaelis constants and the dissociation constant were determined for NADP+-specific isocitrate dehydrogenase (IDH) from P. nautica. These studies support the hypothesis that the mechanism of IDH's activity involves the ordered addition of the substrates, D-isocitrate and NADP+. Furthermore, the results support the use of a bisubstrate enzyme kinetic equation to model RCO2 in P. nautica.     

Greater improvement in summer than with light treatment in winter in patients with seasonal affective disorder

OBJECTIVE: The authors sought to compare the degree of mood improvement after light treatment with mood improvement in the subsequent summer in patients with seasonal affective disorder. METHOD: By using the Seasonal Affective Disorder Version of the Hamilton Depression Rating Scale, the authors rated 15 patients with seasonal affective disorder on three occasions: during winter when the patients were depressed, during winter following 2 weeks of light therapy, and during the following summer. They compared the three conditions by using Friedman's analysis of variance and the Wilcoxon signed ranks test. RESULTS: The patients' scores on the depression scale were significantly higher after 2 weeks of light therapy in winter than during the following summer. CONCLUSIONS: Light treatment for 2 weeks in winter is only partially effective when compared to summer. Further studies will be necessary to assess if summer's light or other factors are the main contributors to this difference.     

Cross-sectional assessment of ELISA reactivity in leprosy patients, contacts, and normal population using the semisynthetic antigen natural disaccharide octyl bovine serum albumin (ND-O-BSA) in Cebu, The Philippines

An indirect enzyme-linked immunosorbent assay (ELISA) using natural disaccharide octyl bovine serum albumin (ND-O-BSA) as antigen was used in testing leprosy patients, contacts and a normal population in Cebu, The Philippines, from 1985 to 1989. A total of 1413 persons were studied. The results suggested that ELISA reactivity and the bacterial index (BI) correlate in a general way. In multibacillary (MB) leprosy, positivity ranges from 54.2% to 92.3% among patients with a BI of < 2+ to > 4+ on the Ridley scale, with an overall average of 84.5%. Paucibacillary (PB) leprosy patients have a low degree of reactivity, with only 15.0% ELISA positive. The test is more efficient in detecting MB than PB leprosy. The contacts of MB leprosy showed 6.5% positivity; contacts of PB leprosy, 7.0% positivity. The normal population showed 1.7% positive ELISA or 17 per thousand population, which is very much less than that of the household contacts. However, because the normal population is a much larger population than the household contact population in a community, more new leprosy cases would emanate from it. Leprosy workers are concerned about the transmission of the disease to household contacts. However, for the reason stated above, we should be more concerned with the silent spread of the disease to the normal population in the community.(ABSTRACT TRUNCATED AT 250 WORDS)     

A method for shape optimization of a hip prosthesis to maximize the fatigue life of the cement

The long term success of total joint replacement can be limited by fatigue failure of the acrylic cement and the resulting disruption of the bone-cement interface. The incidence of such problems may be diminished by reduction of the fatigue notch factor in the cement, so that stress concentrations are avoided and the fatigue crack initiation time maximized. This study describes a method for numerical shape optimization whereby the finite element method is used to determine an optimal shape for the femoral stem of a hip prosthesis in order to minimize the fatigue notch factor in the cement layer and at interfaces with the bone and stem. A two-dimensional model of the proximal end of a femur fitted with a total hip prosthesis was used which was equivalent to a simplified three-dimensional axisymmetric model. Software was developed to calculate the fatigue notch factor in the cement along the cement/stem and cement/bone interfaces and in the proximal bone. The fatigue notch factor in the cement at the cement/stem interface was then minimized using the ANSYS finite element program while constraining the fatigue notch factor at the cement/bone interface at or below its initial level and maintaining levels of stress in the proximal bone to prevent stress shielding. The results were compared with those from other optimization studies.     

Direct measurement of the contributions of type I and type II 5'-deiodinases to whole body steady state 3,5,3'-triiodothyronine production from thyroxine in the rat

Production of T3 from T4 in tissues is catalyzed by two 5'-deiodinases, type I (D1) and type II (D2), but the quantitative contribution of each pathway to whole body T3 production is not well established. In the presence of propylthiouracil (PTU), D1, but not D2, can be effectively blocked, providing an experimental probe for addressing this problem. Decades ago, this approach provided indirect estimates ranging from 23-44% contribution by D2, based on plasma T3 appearance rate comparisons (PAR3 = PCR3 [T3]p) in periodically T4-injected athyreotic rats vs. controls. Two, more recent studies, using constant infusions of T4 for replacement, achieved 22% and 65% estimates, respectively, from PAR3 comparisons. We have revisited this problem more directly and precisely, with two major differences in experiment design. We used direct whole body steady state measurements of T3 production, instead of indirect plasma-only data (PAR3). We also used (euthyroid) physiological doses of both T4 (0.9 microg/day x 100 g BW) and T3 (0.15 microg/day x 100 g BW) for replacement in two thyroidectomized rat groups, instead of T4 only, in a 7-day constant steady state, dual tracer infusion protocol. The first group also had chronically implanted 150-mg PTU pellets (TXR-PTU); the other had implanted 0.1 N NaOH placebo pellets (TXR-EU); each delivered their product at constant rates. A third euthyroid intact group was used as the controls. The completeness of D1 inhibition was ascertained in a fourth group, identically treated with 150-mg PTU pellets, in which negligible D1 activity was found in liver and kidney using labeled rT3 as substrate for the 5'-D assays and minimal (1 mM) dithiothreitol as cofactor. In the TXR-PTU group, the percentage of T4 converted to T3 was 11.8%, compared with 23.4% (P < 0.0005) in the TXR-EU group, and 22.7% (P = NS) in controls. Thus, in euthyroid steady state, D2 contributes about half of the T3 produced from T4.