Interaction of iodinated vinculin, metavinculin and α-actinin with cytoskeletal proteins

Iodinated vinculin, metavinculin and α-actinin were used to probe the interaction of these proteins with electrophoretically separated cytoskeletal proteins. Using the gel overlay technique, we detected strong binding of ¹²⁵I-vinculin and ¹²⁵I-metavinculin to α-actinin, 175 kDa polypeptide, talin, vinculin and metavinculin themselves, and moderate binding to actin.¹²⁵I-α-actinin was capable of interacting with vinculin and metavinculin. The specific binding of ¹²⁵-I-α-actinin to vinculin and metavinculin immobilized on a polysterene surface was also demonstrated. We suggest that the ability of vinculin and α-actinin to form a complex may be realized in microfilament-membrane linkages.     

Resistance of Spirulina platensis to Ammonia at High pH Values

Spirulina platensis is an alkalophilic cyanobacterium, exhibitingoptimal growth at pH 9.0 to 10.0. It grows well at pH 11.5 butnot at pH 7.0. Unlike many other photosynthetic microorganisms,it is capable of utilizing ammonia³ even at high pH values,and is resistant to the ammonia-mediated uncoupling of photosynthesis.The entry of ammonia into the cells is pH-dependent, and islimited by a relatively high average internal pH. This highpH value appears to be maintained predominantly by a high intrathylakoidpH. (Received November 20, 1990; Accepted July 3, 1991)     

Expression of alpha 1 integrin, a laminin-collagen receptor, during myogenesis and neurogenesis in the avian embryo.

In this study, we have examined the spatiotemporal distribution of the alpha 1 integrin subunit, a putative laminin and collagen receptor, in avian embryos, using immunofluorescence microscopy and immunoblotting techniques. We used an antibody raised against a gizzard 175 x 10(3) M(r) membrane protein which was described previously and which we found to be immunologically identical to the chicken alpha 1 integrin subunit. In adult avian tissues, alpha 1 integrin exhibited a very restricted pattern of expression; it was detected only in smooth muscle and in capillary endothelial cells. In the developing embryo, alpha 1 integrin subunit expression was discovered in addition to smooth muscle and capillary endothelial cells, transiently, in both central and peripheral nervous systems and in striated muscles, in association with laminin and collagen IV. alpha 1 integrin was practically absent from most epithelial tissues, including the liver, pancreas and kidney tubules, and was weakly expressed by tissues that were not associated with laminin and collagen IV. In the nervous system, alpha 1 integrin subunit expression occurred predominantly at the time of early neuronal differentiation. During skeletal muscle development, alpha 1 integrin was expressed on myogenic precursors, during myoblast migration, and in differentiating myotubes. alpha 1 integrin disappeared from skeletal muscle cells as they became contractile. In visceral and vascular smooth muscles, alpha 1 integrin appeared specifically during early smooth muscle cell differentiation and, later, was permanently expressed after cell maturation. These results indicate that (i) the expression pattern of alpha 1 integrin is consistent with a function as a laminin/collagen IV receptor; (ii) during avian development, expression of the alpha 1 integrin subunit is spatially and temporally regulated; (iii) during myogenesis and neurogenesis, expression of alpha 1 integrin is transient and correlates with cell migration and differentiation.     

A survey of histoplasmosis and blastomycosis in U.A.R. (Egyptian sector) a preliminary report

Summary A selected group of 525 individuals with pulmonary diseases, granulomas and other medical conditions was tested for histoplasmin and blastomycin dermal reactions. No positive results were observed. Few doubtful positive reactions were recorded (3 to histoplasmin and 7 to blastomycin). None of the patients with chronic cutaneous granulomas exhibited any reaction.Although the number of subjects studied is small, these preliminry findings suggest the probable absence of histoplasmosis and blastomycosis in Egypt.     

Intracellular Synthesis of Myxovirus Neuraminidase in Chick Embryo Cell Monolayer Culture I. Neuraminidase Activity, Hemagglutinin Synthesis, and Content of Cell-bound Sialic Acid in Newcastle Disease Virus-infected Cells

Neuraminidase (Nase) activity of chick embryo monolayer cell homogenates was determined by its rate of splitting of neuraminlactose, free neuraminic acid (NA) being determined by the thiobarbituric acid assay. Noninfected cells were found to have no detectable amount of Nase activity. Newcastle disease virus (NDV)-infected cells (multiplicity of infection, 20 to 75 plaque-forming units per cell) displayed a high level of Nase synthesis, the rate of synthesis being parallel to that of hemagglutinin (HA) synthesis (with a 1.5 hr delay in the latter). An "eclipse" of the Nase and HA activities associated with the virus that was adsorbed onto cells was observed. The data provide evidence that the Nase is not incorporated into the viral envelope from a pre-existing cell supply but that its synthesis is coded by the viral genome. The content of cell-bound sialic acid, determined simultaneously in infected-cell homogenates, showed characteristic features allowing certain conclusions concerning the renewal of NA-terminating cell receptors during the course of infection, and the intracellular action of the Nase of the virus introduced into cells by the inoculum and that of the newly synthesized Nase at different stages of infection.     

M protein (M1) of influenza virus: antigenic analysis and intracellular localization with monoclonal antibodies.

A panel of 16 monoclonal antibodies recognizing M protein (M1) of influenza virus was generated. Competition analyses resulted in localization of 14 monoclonal antibodies to three antigenic sites. Three monoclonal antibodies localized to site 1B recognized a peptide synthesized to M1 (residues 220 to 236) with enzyme-linked immunosorbent assay titers equivalent to or greater than that seen with purified M1; therefore, site 1B is located near the C terminus of M1. Sites 2 and 3 localize to the N-terminal half of M1. Antigenic variation of M proteins was seen when the monoclonal antibodies were tested against 14 strains of type A influenza viruses. Several monoclonal antibodies showed specific recognition of A/PR/8/34 and A/USSR/90/77 M proteins and little or no reactivity for all other strains tested. Immunofluorescence analysis with the monoclonal antibodies showed migration of M protein to the nucleus during the replicative cycle and demonstrated association of M protein with actin filaments in the cytoplasm. Use of a vaccinia virus recombinant containing the M-protein gene demonstrated migration of M protein to the nucleus in the absence of synthesis of gene products from other influenza virus RNA segments.     

Isolation and Characterization of the Plasma Membrane by Two-Phase Partitioning from the Alkalophilic Cyanobacterium Spirulina platensis

Partition in aqueous dextran-polyethylene glycol two-phase systemwas used to isolate the plasma membranes from the alkalophiliccyanobacterium Spirulina platensis. The upper phase containeda colorless membranes obtained in relatively short time, 3–4h. This fraction had a different protein profile than that ofthe thylakoid fraction obtained in the lower phase. It did notcontain cytochrome c-oxidase activity, but retained characteristicMg²⁺-ATPase activity that is sensitive to vanadate, stimulatedby K⁺, and has a pH optimum near 8.5. These data support ourassumption that the upper phase of the gradient consist of theplasma membrane of S. platensis. (Received November 25, 1993; Accepted April 12, 1994)     

Down's syndrome,Edwards' syndrome,Patau's syndrome —synthesis of glycosaminoglycans

Synthesis of glycosaminoglycans (GAGS) by fibroblasts derived from seven patients with Down's syndrome, five patients with Edwards' syndrome, and two patients with Patau's syndrome were studied in cell culture. The aneuploid strains were compared with diploid fibroblasts from age-matched controls. In terms of hyaluronic acid and sulfated GAG synthesis, the amount of synthesized hyaluronic acid was not significantly different between postnatal aneuploid strains and controls.