Responses of ligamentous fibroblasts to mechanical stimulation

Mechanical stimulation, as provided by physiotherapy or controlled motion is essentially the only factor able to improve anterior cruciate ligament (ACL) healing. We investigate the cellular effects of such stimulus. Two types of stimulations are applied on canine ACL fibroblasts: repetitive stretch of an elastomeric adhesion substrate and a laminar flow of culture media over the culture surface. Cell orientation, proliferation rate, synthesis and type of collagen as well as proteoglycans (PG) synthesis and hydrodynamic characteristics have been studied. According to our results, the fibroblasts tend to align perpendicularly to the deformation axis of their substrate, and along a laminar flow. The shear stress induced by the laminar flow does not modify significantly proliferation rate nor extracellular matrix synthesis. Substrate stretching however, increases proliferation rate, collagen synthesis, mostly type III, and PG synthesis, principally of small sizes. The characteristics of fibroblasts submitted to repeated deformation match those of fibroblasts from ligament scar tissues. Their orientation perpendicular to substratum deformation differs from the one usually encountered in the undamaged tissue: aligned on the ligament axis.     

High speed p-type SiGe modulation-doped field-effect transistors

We report on the fabrication and characterization of high-speed p-type modulation-doped field-effect transistors (MODFETs) with 0.7-μm and 1-μm gate-lengths having unity current-gain cut-off frequencies (f_T) of 9.5 GHz and 5.3 GHz, respectively. The devices were fabricated on a high hole mobility SiGe heterostructure grown by ultra-high-vacuum chemical vapor deposition (UHV-CVD). The dc maximum extrinsic transconductance (g_m) is 105 mS/mm (205 mS/mm) at room temperature (77 K) for the 0.7-μm gate length devices. The fabricated devices show good pinch-off characteristics and have a very low gate leakage current of a few μA/mm at room temperature and a few nA/mm at 77 K     

High performance analog VLSI computational circuits

Simple linear voltage/current-controlled voltage-to-current (V-T) converters, which are to first-order insensitive to the threshold voltage variation, are introduced. The circuits can be used as basic building blocks to construct simple analog computational circuits, which can perform functions such as square rooting, squaring, multiplication, sum of squares, difference of squares, etc. Some of the key features are: good linearity, floating inputs [high common-mode rejection ratio (CMRR)], simplicity, and good transconductance tuning range. The circuits can be realized with CMOS devices in saturation, however, BiCMOS devices extend their speed and input voltage range. Realistic simulations and experimental results clearly demonstrate the claims     

Hepatobiliary cystadenoma. A study of five cases with reference to histogenesis

Hepatobiliary cystadenoma is a rare hepatic lesion characterized by a multiloculated cyst lined by cuboidal or columnar epithelial cells. Four cases of hepatobiliary cystadenoma with mesenchymal stroma (HCMS) and one case of hepatobiliary cystadenoma with intracystic epithelial component were studied by light microscopy, immunohistochemical methods, and electron microscopy. Similar studies were conducted on six fetal gallbladder tissues, representing the biliary tree, and two adult ovarian tissues. By light microscopy, the columnar epithelium of the five cases of hepatobiliary cystadenoma was similar to the epithelium of the developing gallbladder. The spindle cell stroma of the HCMS and the subepithelial spindle cells of the developing gallbladders showed similar reactivity to smooth-muscle actin. Vimentin reactivity was strongly positive in the stroma of the HCMS, and in the fetal gallbladders it was only noted in the subepithelial spindle cells of the 15-week gestation fetal gallbladder tissues. By electron microscopy, the epithelium lining the hepatic lesions showed characteristic gastrointestinal features and was identical to the epithelia lining the embryonic gallbladders. Furthermore, the mesenchymal stroma of the HCMS recapitulated the features found in subepithelial tissues in developing gallbladders. Although the ovarian stroma resembled the stroma of the HCMS by light microscopy, the immunohistochemical reactions and the electron microscopic studies showed dissimilarities. This study supports the hypothesis that the hepatobiliary cystadenomas arise from ectopic embryonic tissues destined to form the adult gallbladder.     

ACAT inhibitors derived from hetero-Diels-Alder cycloadducts of thioaldehydes

Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds.     

Oxygenation in the rabbit myocardium: assessment with susceptibility-dependent MR imaging

PURPOSE: To determine the feasibility of using hemoglobin (Hb) desaturation as an indicator of myocardial oxygenation. MATERIALS AND METHODS: High-resolution gradient-echo nuclear magnetic resonance (MR) images of isolated, blood-perfused rabbit hearts were obtained at various blood oxygenation levels. The hearts were perfused at 37 degrees C with a Langendorff apparatus modified for nuclear MR imaging. The perfusate contained bovine red blood cells in a cardioplegic solution that eliminated motion artifacts and minimized arteriovenous oxygenation differences. Hb saturation was varied (7%-100%) randomly. Perfusion pressure was continuously monitored, and blood samples were obtained. RESULTS: There was a substantial correlation between image signal intensity in the myocardium and Hb saturation in the blood, believed to be due to susceptibility effects of the paramagnetic species deoxyhemoglobin. CONCLUSION: Direct and noninvasive determination of regional Hb saturation with susceptibility-dependent MR imaging may provide information regarding regional myocardial O2 content.     

Cell cycle. The NIMA kinase joins forces with Cdc2

The NIMA and Cdc2 protein kinases cooperate to regulate mitosis in Aspergillus nidulans. NIMA-related pathways have now begun to emerge in higher eukaryotes.