The infrared dichroism of transmembrane helical polypeptides

Polarized attenuated total internal reflectance techniques were applied to study the infrared dichroism of the amide I transition moment in two membrane-bound peptides that are known to form oriented transmembrane helices: gramicidin A in a supported phospholipid monolayer and Ac-Lys2-Leu24-Lys2-amide (L24) in oriented multibilayers. These studies were performed to test the ability of these techniques to determine the orientation of these peptides, to verify the value of optical parameters used to calculate electric field strengths, to examine the common assumptions regarding the amide I transition moment orientation, and to ascertain the effect of surface imperfections on molecular disorder. The two peptides exhibit marked differences in the shape and frequency of their amide I absorption bands. Yet both peptides are highly ordered and oriented with their helical axes perpendicular to the membrane surface. In the alpha-helix formed by L24, there is evidence for a mode with type E1 symmetry contributing to amide I, and the amide I transition moment must be more closely aligned with the peptide C=O (< 34 degrees) than earlier studies have suggested. These results indicate that long-standing assumptions about the orientation of amide I in a peptide require some revision, but that in general, infrared spectroscopy yields reliable information about the orientation of membrane-bound helical peptides.     

Chronic d-fenfluramine treatment reduces fat intake independent of macronutrient preference

The origin of hematopoietic stem cells (HSCs) and their growth factor requirement are poorly understood. Here we describe a new in vitro culture system of the aorta-gonad-mesonephros (AGM) region, where long-term repopulating HSCs first arise. We demonstrate that oncostatin M (OSM) is expressed in the AGM and is absolutely required for the expansion of multipotential hematopoietic progenitors in vitro. In addition, OSM enhances the formation of endothelial cell clusters. Thus, OSM appears to be a key cytokine for the development of multipotential hematopoietic progenitors in the AGM, possibly acting on common precursor cells between HSCs and endothelial cells. By using the AGM culture derived from macrophage colony-stimulating factor (M-CSF)-deficient op/op mutant embryos, we also show a pivotal role for M-CSF in fetal myelopoiesis.     

Distribution of bacteria with the arylsulfate sulfotransferase activity

We herein report a simple method using intestinal clamps to prevent intraoperative contamination during an immediate mucocutaneous suture of the intestinal stoma. Using this technique, a protruded intestinal stoma can be constructed reliably without soiling. The technique can be used both for constructing an end as well as a loop intestinal stoma.     

In situ localization and quantification of mRNA for 92-kD type IV collagenase and its inhibitor in aneurysmal, occlusive, and normal aorta

Ninety-two-kilodalton type IV collagenase (MMP-9) is present in aortic aneurysms and may be important to the pathogenesis of this disease. Alteration in expression of MMP-9 or its inhibitor, the tissue inhibitor of metalloproteinase type 1 (TIMP-1), could increase degradation of extracellular matrix and lead to aneurysm formation. The purpose of this study was (1) to measure tissue levels of MMP-9 and TIMP-1 mRNA in aneurysmal (AAA), atherosclerotic occlusive (AOD), and normal (NL) human infrarenal aorta; (2) to test for their expression by cultured AAA and NL vascular smooth muscle cells (VSMCs); and (3) to locate in situ the cells responsible for mRNA production within AAA, AOD, and NL aortic wall. Total RNA extracted from AAA (n = 8), AOD (n = 8), and NL (n = 7) tissue was subjected to Northern analysis. Signals for MMP-9 and TIMP-1 were normalized to alpha-tubulin. Mean values +/- SEM were compared by ANOVA. NL and AAA VSMCs were cultured, passaged, and grown to confluence before RNA extraction and Northern analysis. In situ hybridization with digoxigenin-labeled RNA probes localized cells responsible for MMP-9 and TIMP-1 mRNA expression within sections of AAA (n = 5), AOD (n = 2), and NL (n = 2) aorta. MMP-9 mRNA levels were significantly greater in AAA (0.855 +/- 0.180) than NL (0.046 +/- 0.23) (P < .02), but differences between AOD (0.406 +/- 0.196) and AAA or AOD and NL were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene targeting--homing in on alpha 2-adrenoceptor-subtype function

The alpha-adrenoceptor was subdivided into three subtypes: alpha 2A-, alpha 2B- and alpha 2C-adrenoceptors almost ten years ago. Since then, the search has been on to discover and develop subtype-selective agonists and antagonists, but as yet no major breakthrough has been made. In the past year, several strains of genetically engineered mice have become available, either overexpressing, totally lacking or expressing heavily modified alpha 2-adrenoceptor subtypes. Ewen MacDonald, Brian Kobilka and Mika Scheinin describe how these mice may be utilized to elucidate the physiological functions of the receptor subtypes and the properties of future subtype-selective drugs.     

Species differences in the physical and transport properties of airway secretions

Four cases of severe Lepiota poisoning, including three which developed toxic fulminant hepatitis treated by orthotopic hepatic transplantation, are reported here. The toxicity of the Lepiota is discussed as well as the indications for hepatic transplantation in poisonings due to amatoxin-containing mushrooms.