Effect of protein content on low temperature inactivation of the extracellular proteinase from Pseudomonas fluorescens 22F

The formation of cholic acid and chenodeoxycholic acid through cleavage of the side chains of CoA esters of 3alpha,7alpha,12alpha-trihydroxy-5beta-choles tan-26-oic acid and 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid is believed to occur in peroxisomes. Recently, we found a new peroxisomal enzyme, D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein, and suggested that this bifunctional protein is responsible for the conversion of 3alpha,7alpha,12alpha-trihydroxy-5beta-cholest-2 4-en-26-oyl-CoA and 3alpha,7alpha-dihydroxy-5beta-cholest-24-en-26-oyl-CoA to their 24-oxo-forms. In the present study, the products of this bifunctional protein reaction were analyzed by gas chromatography-mass spectrometry, and the formation of 24-oxo-27-nor-cholestanes was confirmed. Previously, we found a new thiolase in Caenorhabditis elegans, P-44, and suggested that P-44 and sterol carrier protein x, a peroxisomal protein, constitute a second group of 3-oxoacyl-CoA thiolases. The production of cholic acid and chenodeoxycholic acid from the precursors on incubation with the bifunctional protein and sterol carrier protein x or P-44 was confirmed by gas chromatography.     

Chemical denaturation and modification of ovalbumin alters its dependence on ubiquitin conjugation for class I antigen presentation

Class I presentation of microinjected native OVA by a temperature-sensitive ubiquitin conjugation mutant, ts85, but not wild-type murine cells, was markedly inhibited following incubation at a nonpermissive temperature. In contrast, the nonpermissive temperature did not affect class I presentation of a minimal OVA peptide expressed in the cytosol. Therefore, these results provide a second example in which a temperature sensitive mutation in the ubiquitin conjugation pathway inhibits MHC class I presentation of native OVA. Surprisingly, incubation at the nonpermissive temperature did not inhibit class I presentation of chemically denatured and alkylated OVA microinjected into the cytosol of mutant cells. Similarly, the presentation of endogenously synthesized OVA (which is expressed from a recombinant vaccinia virus and, presumably, is misfolded in the cytosol) was also not inhibited in both mutant cell lines. Methylation of the lysine groups in denatured OVA, which blocks ubiquitin conjugation, reduced but did not eliminate the presentation of denatured OVA, providing evidence for both ubiquitin-dependent and ubiquitin-independent pathways for class I presentation. In contrast, a proteasome inhibitor blocked class I presentation of all forms of OVA, while a control peptide aldehyde was not inhibitory. These results indicate that modification of the structure of a protein can influence its requirements for ubiquitin conjugation for efficient class I presentation, with the key alteration possibly being the loss of proper conformation. However, regardless of the form of the Ag, the proteasome appears to be required for generating peptides from both endogenously synthesized and microinjected OVA for class I presentation.     

The lives of female physicians

Survey data from 113 female physicians, 634 male physicians, and 41 female dentists were compared. Instruments designed to assess work satisfaction, work stress, marital satisfaction, family competence, and psychiatric symptoms and treatment were used, thereby exploring important life domains concurrently. The results suggest that female physicians are much more like both male physicians and female dentists than anticipated. Generally, female physicians describe high levels of work satisfaction, moderate levels of work stress, average-to-high levels of marital satisfaction, and relatively low levels of psychiatric distress. Their lower levels of practice income remain something of an enigma as gender remains the most powerful predictor of income and is not replaced in statistical analyses by specialty, hours worked, or other significant variables. Finally, female physicians who find higher levels of satisfaction in work also report higher levels of marital satisfaction and fewer psychiatric symptoms. For these women, a highly satisfying medical career does not apparently need to be experienced at the cost of marital or personal distress.     

TGF-beta knockout and dominant-negative receptor transgenic mice

Use of homologous recombination and transgenic technologies have provided mouse models to study the physiological roles of the three mammalian TGF-beta isoforms, and their regulation in the context of the intact animal. Mice harboring null mutations for TGF-beta isoforms demonstrate that each exerts discrete nonoverlapping functions during development. TGF-beta1 null mice reveal a crucial role for this cytokine in modulation of the immune system, with evidence for altered development, activation and function of various immune cell populations. New approaches to tissue- and cell-restricted disruption of TGF-beta signaling pathways in transgenic mice carrying dominant-negative mutant TGF-beta receptors will be discussed.     

Effects of ligand priming and multiple-dose injection on tissue uptake of 111In-pentetreotide in rats

In patients undergoing somatostatin receptor scintigraphy, treatment with octreotide (Sandostatin) is usually discontinued 24-48 h before and after injection with the radioligand 111In-pentetreotide ([111In-DTPA(O)]octreotide) (Octreoscan) because octreotide competes with radioligand for the same receptors. However, D?rr et al. and Soresi et al. reported improved visualization of carcinoid and small cell lung cancer lesions, respectively, during continued octreotide treatment. We found that intravenous administration of unlabeled octreotide to rats inhibited the binding of an optimal dose (0.5 microg) of 111In-pentetreotide to somatostatin receptors in pancreas and adrenals in a mass- and time-dependent way. Pretreatment with unlabeled octreotide never increased receptor binding of 111In-pentetreotide. Administration of 100 microg of octreotide decreased receptor-bound radioactivity if given simultaneously with or 10 or 20 min after injection of the radioligand, but had no effect if given 30 min after the radioligand. These findings indicate rapid processing of receptor-bound octreotide and suggest that octreotide treatment of patients undergoing 111In-pentetreotide scintigraphy may be reinitiated as soon as 1 h after radioligand administration.