Axial Diffusivity of the Corona Radiata at 24 Hours Post-Stroke: A New Biomarker for Motor and Global Outcome

Fractional anisotropy (FA) is an effective marker of motor outcome at the chronic stage of stroke yet proves to be less efficient at early time points. This study aims to determine which diffusion metric in which location is the best marker of long-term stroke outcome after thrombolysis with diffusion tensor imaging (DTI) at 24 hours post-stroke. Twenty-eight thrombolyzed patients underwent DTI at 24 hours post-stroke onset. Ipsilesional and contralesional FA, mean (MD), axial (AD), and radial (RD) diffusivities values were calculated in different Regions-of-Interest (ROIs): (1) the white matter underlying the precentral gyrus (M1), (2) the corona radiata (CoRad), (3) the posterior limb of the internal capsule (PLIC) and (4) the cerebral peduncles (CP). NIHSS scores were acquired at admission, day 1, and day 7; modified Rankin Scores (mRS) at 3 months. Significant decreases were found in FA, MD, and AD of the ipsilesional CoRad and M1. MD and AD were also significantly lower in the PLIC. The ratio of ipsi and contralesional AD of the CoRad (CoRad-rAD) was the strongest diffusion parameter correlated with motor NIHSS scores on day 7 and with the mRS at 3 months. A Receiver-Operator Curve analysis yielded a model for the CoRad-rAD to predict good outcome based on upper limb NIHSS motor scores and mRS with high specificity and sensitivity. FA values were not correlated with clinical outcome. In conclusion, axial diffusivity of the CoRad from clinical DTI at 24 hours post-stroke is the most appropriate diffusion metric for quantifying stroke damage to predict outcome, suggesting the importance of early axonal damage.     

The Mr 17500 region of the A chain of urokinase is required for interaction with a specific receptor in A431 cells

We have found the existence of specific receptors for the plasminogen activator, urokinase, in A431 human epidermoid carcinoma cells, cultures in plasminogen-free conditions. Two subsets of receptors have been recognized on the basis of 125I-labelled urokinase binding analysis: about 1 X 10(3) high-affinity (Kd = 5.0 X 10(-11) M) and 1 X 10(5) low-affinity (Kd = 9 X 10(-9) M) receptors per cell. The electron microscopic observation of a urokinase: ferritin conjugate has shown single and clustered receptors at the cell surface. Down-regulation of the receptors (T1/2 = 3.77 h) follows the binding of urokinase. The binding does not involve an intact catalytic site and is inhibited by a monoclonal antibody against the Mr 17500 proteolytic fragment of the A chain of urokinase.     

Involvement of chondroitin sulphate in preventing adhesive cellular interactions

Glycosaminoglycans isolated from native non-adhesive surfaces of both endothelial and mesothelial origin and from endothelial cells cultured in vitro were analyzed by electrophoresis and characterized by chemical and enzymatic breakdown. All the surfaces examined expose in vivo chondroitin 6-sulphate as the main glycosaminoglycan. Under in vitro culture, the exposure of chondroitin sulphate is reduced. Paper chromatography of hydrolysis products upon degradation by chondroitinase AC shows equal amounts of both 6- and 4-sulphated disaccharides. At the same time, the surfaces lose their non-adhesiveness to leukocytes. The addition of fibroblast growth factor to endothelial monolayers restores both non-adhesiveness to leukocytes and exposure of chondroitin sulphate. These results seem to indicate that the exposure of chondroitin sulphate is important in preventing cellular adhesion.     

Convenient Model To Describe the Combined Effects of Temperature and pH on Microbial Growth

A new model in which the maximum microbial specific growth rate ((mu)(infmax)) is described as a function of pH and temperature is presented. The seven parameters of this model are the three cardinal pH parameters (the pH below which no growth occurs, the pH above which no growth occurs, and the pH at which the (mu)(infmax) is optimal), the three cardinal temperature parameters (the temperature below which no growth occurs, the temperature above which no growth occurs, and the temperature at which the (mu)(infmax) is optimal), and the specific growth rate at the optimum temperature and optimum pH. The model is a combination of the cardinal temperature model with inflection and the cardinal pH model (CPM). The CPM was compared with the models of Wijtzes et al. and Zwietering et al. by using previously published data sets. The models were compared on the basis of the usual criteria (simplicity, biological significance and minimum number of parameters, applicability, quality of fit, minimum structural correlations, and ease of initial parameter estimation), and our results justified the choice of the CPM. Our combined model was constructed by using the hypothesis that the temperature and pH effects on the (mu)(infmax) are independent. An analysis of this new model with an Escherichia coli O157:H7 data set showed that there was a good correspondence between observed and calculated (mu)(infmax) values. The potential and convenience of the model are discussed.     

Mitochondrial abnormalities in some human muscular diseases and in experimental ischemic myopathy

Morphologic abnormalities have been observed in two cases of human polymyositis and in three cases of ocular myopathies. Similar findings can be observed in experimental ischemic myopathy. "Ragged red" fibres, with anomalous distribution of oxidative enzymes, mitochondrial alterations, with presence of intracristal paracrystalline inclusions and degenerative myofibrillar changes are the similar features. The similarity between some of these alterations, expecially mitochondrial changes, is remarkable, but it is difficult to correlate them to the primary etiology of described human myopathies.     

Selective localization of receptors for urokinase amino-terminal fragment at substratum contact sites of an in vitro-established line of human epidermal cells.

We have shown the presence of surface receptors for the amino-terminal fragment (ATF) of human urokinase-type plasminogen activator (u-PA) on an in vitro-established cell line of human epidermal origin by both radio-binding assays with human 125I-u-PA-ATF and transmission electron microscopy of a gold-u-PA complex. On the basis of cross-linking experiments with 125I-u-PA-ATF and subsequent autoradiography of the gels we have observed that such receptors are not spontaneously released into the culture medium. The treatment with phosphatidylinositol-specific phospholipase C induces the release of the receptor, which behaves as a glycosyl phosphatidyl inositol(GPI)-anchored protein. Phase-partitioning experiments on cell lysates have shown that the receptor partitions into the detergent phase. By detaching cell monolayers with the chelating agent EDTA we have prepared the cell-substratum contact sites of these cells, which represent only the 3.5% of the surface membrane of monolayered cells. Such plasma membrane remnants are highly selected since they contain about 43% of total u-PA-ATF binding sites. Such binding sites show the same biochemical and morphological characteristics of u-PA-ATF receptors observed in the monolayered cells, thus indicating that u-PA is selectively concentrated at the level of cell-substratum contacts. This is likely to enable directional proteolysis for cell migration and invasion.     

Selective exposure of mucopolysaccharides is involved in macrophage physiology.

Surface and intracellular mucopolysaccharides of guinea-pig peritoneal macrophages maintained in suspension and monolayer culture were studied. At least five classes of compound (hyaluronic acid, heparan sulfate, dermatan sulfate, chondroitin 4-sulfate and chondroitin 6-sulfate) were resolved and characterized by electrophoresis and enzymatic degradation. The results reported here suggest that modulation of mucopolysaccharide exposure is involved in macrophage physiology. The possible biological role of surface mucopolysaccharides in macrophage activity is discussed.