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An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
Endothelial cells that make up brain capillaries and constitute the blood-brain barrier become different from peripheral endothelial cells in response to inductive factors found in the nervous system. We have established a cell culture model of the blood-brain barrier by treating brain endothelial cells with a combination of astrocyte-conditioned medium and agents that elevate intracellular cAMP. These cells form high resistance tight junctions and exhibit low rates of paracellular leakage and fluid-phase endocytosis. They also undergo a dramatic structural reorganization as they form tight junctions. Results from these studies suggest modes of manipulating the permeability of the blood-brain barrier, potentially providing the basis for increasing the penetration of drugs into the central nervous system.
Two cDNAs encoding an abundant chicken muscle extracellular matrix (ECM)-associated laminin-binding protein (LBP) have been isolated and sequenced. The predicted primary amino acid sequence includes a probable signal peptide and a site for N-linked glycosylation, but lacks a hydrophobic segment long enough to span the membrane. The COOH terminus consists of an unusual repeat of 33 consecutive aspartate residues. Comparison with other sequences indicates that this protein is different from previously described LBPs and ECM receptors. RNA blot analysis of LBP gene expression showed that LBP mRNA was abundant in skeletal and heart muscle, but barely detectable in other tissues. Blots of chicken genomic DNA suggest that a single gene encodes this LBP. The amino acid sequence and mRNA distribution are consistent with the biochemical characterization described by Hall and co-workers (Hall, D. E., K. A. Frazer, B. C. Hahn, and L. F. Reichardt. 1988. J. Cell Biol. 107:687-697). These analyses indicate that LBP is an abundant ECM-associated muscle protein with an unusually high negative charge that interacts with both membranes and laminin, and has properties of a peripheral, not integral membrane protein. Taken together, our studies show that muscle LBP is a secreted, peripheral membrane protein with an unusual polyaspartate domain. Its laminin and membrane binding properties suggest that it may help mediate muscle cell interactions with the extracellular matrix. We propose the name "aspartactin" for this LBP.
A major laminin-binding protein (LBP), distinct from previously described LBPs, has been isolated from chick and rat skeletal muscle (Mr 56,000 and 66,000, respectively). The purified LBPs from the two species were shown to be related antigenically and to have similar NH2-terminal amino acid sequences and total amino acid compositions. Protein blots using laminin and laminin fragments provided evidence that this LBP interacts with the major heparin-binding domain, E3, of laminin. Studies on the association of this LBP with muscle membrane fractions and reconstituted lipid vesicles indicate that this protein can interact with lipid bilayers and has properties of a peripheral, not an integral membrane protein. These properties are consistent with its amino acid sequence, determined from cDNAs (Clegg et al., 1988). Examination by light and electron microscopy of the LBP antigen distribution in skeletal muscle indicated that the protein is localized primarily extracellularly, near the extracellular matrix and myotube plasmalemma. While a form of this LBP has been identified in heart muscle, it is present at low or undetectable levels in other tissues examined by immunocytochemistry indicating that it is probably a muscle-specific protein. As this protein is localized extracellularly and can bind to both membranes and laminin, it may mediate myotube interactions with the extracellular matrix.
The purpose of this article is to present the community hospital perspective of trauma care in the non-trauma facility. Non-trauma community hospitals in regions with-out trauma systems or with exclusive trauma systems that sporadically receive trauma patients often do so without adequate training, resources and skills for the immediate care and resuscitation of the trauma patient. A case study provides an opportunity to explore the community hospital experience in caring for the trauma patient without trauma teams, trauma educated staff, 24-hour-a-day surgical services, staffing patterns conducive to the immediate and possibly continual needs of the trauma patient, and potential limitations in the rapid access to blood products. The fact that trauma systems do not exist in many areas of the United States requires that federal and state agencies pay special attention to involvement of the community hospital in the development of an inclusive trauma system.
The development of neurons depends in large part on interactions with molecules in their environment. These include chemotropic and trophic factors, cell adhesion molecules (CAMs), and molecules anchored in the extracellular matrix (ECM). The number of identified proteins in each of these classes has expanded dramatically in recent years (Reichardt and Tomaselli 1991; Grenningloh et al.; Takeichi et al.; Yancopoulos et al.; all this volume). Proteins in each class have now been shown to influence major steps in neural development, including neuronal survival and differentiation, axon growth and guidance, and synapse formation. Subclasses of neurons have been shown to differ dramatically in their responses to some of these proteins, providing a potential molecular basis for determining their individual phenotypes. The same classes of molecules also regulate proliferation and differentiation of glia. Clearly, identifying these morphogenic molecules and their receptors is important for understanding neural development.
An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
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