Further evidence for entry of infectious bovine rhinotracheitis virus into bovine kidney cells

The penetration of bovine kidney cells by infectious bovine rhinotracheitis virus, a member of the herpesvirus group, was investigated using the direct immunoferritin labeling technique. Electron microscopic examination of infected cells after 10 min at 37°C revealed fusion between viral envelope and cell membrane; the former reacted with the ferritin particles conjugated with antiviral antibody. However, shortly after penetration of the nucleocapsid, viral-specific antigenic sites on the plasma membrane were not detected by the immunoferritin technique. Antigenically reactive structures in a disorganized array were frequently detected extracellularly, situated above the penetration sites as indicated by the internalized nucleocapsids.     

DNA translocation by the restriction enzyme from E. coli K

The restriction endonuclease Eco K binds to a host specificity site and then proceeds to cleave the DNA at sites that may to several thousand bases away. It does this by translocating the DNA past the enzyme in an ATP-dependent reaction that results in the formation of highly twisted loop intermediates. DNA cleavage can occur on either side of the host specificity site.     

Characterization of the spontaneous murine B cell leukemia (BCL1). III. Evidence for monoclonality by using an anti-idiotype antibody.

We have raised an anti-idiotypic antibody against the cell surface IgM of the murine BCL1 tumor cells. This antiserum reacts exclusively with the IgM expressed on the tumor cells and detects a unique population of cells in the spleen and blood of the tumor-bearing mice. When these cells are stimulated in vitro with LPS, they secrete an IgM bearing the same idiotype as the cell surface Ig. These results are discussed in terms of a model for the immunotherapy of a chronic lymphocytic leukemia-like syndrome in mice.     

Metabolism of prostaglandins in spontaneously hypertensive rats: NAD"-dependent 15-hydroxyprostaglandin dehydrogenase activity is decreased in kidney and increased in lung.

Renal, pulmonary and gastric NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase activities were determined in both spontaneously hypertensive and normotensive rats at 6 and 12 weeks of age. Renal enzyme activity in hypertensive rats was only 30–40% of that present in normotensive controls at both ages. In contract, pulmonary enzyme activity in hypertensive animals was twice as active as that in normal controls. There was no significant difference in gastric enzyme activity. NAD⁺-dependent 9-hydroxyprostaglandin dehydrogenase activity, the enzyme responsible for the conversion of vasoinactive PGF metabolites to PGE metabolites, also failed to show any difference in two types of rat kidneys. The results indicate that, in hypertension, prostaglandin inactivation is impaired in kidney but is facilitated in lung.     

中国显脉长蝽属两新种记述(半翅目:长蝽科)

本文记述长蝽科显脉长蝽属两新种。此属是一个小属,全世界已知20余种,过去在我国只记载一种,现又发现两个新种。文中所用长度单位为毫米。     

Preparation of new ω-aldehydroalkyl 1-thio-d-glycopyranosides,and their coupling to bovine serum albumin by reductive alkylation

Synthesis of two ω-aldehydoalkyl 1-thioglycosides of d-glucopyranose and of d-galactopyranose is described. 3-Oxopropyl and 2-oxoethyl 1-thioglycosides were prepared by treating a tetra-O-acetyl-1-thioaldose with either acrolein or 2-bromoacetaldehyde, followed by O-deacetylation under mild conditions. These ω-aldehydoalkyl 1-thioglycosides were successfully attached to bovine serum albumin (BSA) by reductive alkylation as described previously. With the 3-oxopropyl 1-thioglycosides, much higher levels of sugar attachment (e.g., ～80 mol of sugar per mol of BSA) were attained than hitherto possible with any sugar derivative tested.     

Mutational analysis of the transin (rat stromelysin) autoinhibitor region demonstrates a role for residues surrounding the "cysteine switch"

The family of mammalian extracellular matrix metalloproteases (MMPs) are secreted by cells in an inactive (latent) proenzyme form. A highly conserved amino acid sequence, PRCGVPDV, is found near the COOH-terminal end of the pro-domain of these MMPs and believed to act as an "autoinhibitor." Recent studies (Springman, E. B., Angleton, E. L., Birkedal-Hansen, H., and Wart, H. E. V. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 364-368) indicate the Cys of this sequence ligands to the active-site zinc keeping the proenzyme in an inactive state, and mutational analysis (Sanchez-Lopez, R., Nicholson, R., Gesnel, M. C., Matrisian, L. M., and Breathnach, R. (1988) J. Biol. Chem. 263, 11892-11899) suggests that the conserved residues surrounding this Cys are required for latency. We have constructed 16 new site-directed mutations of the PRCGVPDV autoinhibitor region of the MMP transin (rat stromelysin) and tested whether these mutant enzymes are produced in a latent or activated form. We find that the conserved Arg as well as the Cys are essential for maintaining latency. The Cys cannot be replaced by other zinc-liganding amino acids, and the Arg cannot be replaced by Lys. Residues immediately surrounding the Cys are sensitive to even conservative amino acid substitutions. We show that a synthetic peptide PRCGVPDV is capable of acting as a weak inhibitor of transin and that replacement of the Cys with a Ser abolishes inhibition by the peptide. A review of the current knowledge of MMP substrate specificity in combination with these new results suggests that the PRCGVPDV sequence does not inhibit activity by mimicking the known substrates of the protease.     

Induction of erythropoietin responsiveness in murine hematopoietic cells by the gag-myb-ets-containing ME26 virus.

ME26 virus, which was generated by inserting the coding region of the acute avian leukemia-inducing virus E26 into a murine retrovirus vector, encodes a 135-kDa gag-myb-ets fusion protein. Amphotropic murine leukemia virus pseudotypes of ME26 virus induce a high incidence of erythroleukemia 2 to 4 months after injection into newborn NFS/N mice. Spleen cells from the majority of these mice proliferate to high levels in the presence of the erythroid hormone erythropoietin (Epo) and can easily be established as permanent Epo-dependent cell lines. The cell lines contain multiple copies of ME26 viral DNA and express viral message and protein. An Epo receptor mRNA of normal size can be detected in these cells, and binding studies reveal a single class of lower-affinity Epo receptor with an affinity for Epo that is in the range of that previously reported for erythroid cells. The ME26 virus-induced Epo-dependent cell lines, however, appear more immature than previously described erythroid cell lines and more closely resemble early hematopoietic precursor cells, suggesting that the virus may be activating the Epo receptor in hematopoietic cells that do not normally express it. Consistent with this idea, we are able to infect an interleukin-3-dependent myeloid cell line, FDC-P2, with ME26 virus and convert it to Epo dependence. The ME26 virus-infected FDC-P2 cells, even before growth on Epo, showed a large increase in the amount of Epo receptor mRNA. However, no ME26 viral integrations can be detected adjacent to the Epo receptor gene, indicating that the virus is not activating the Epo receptor gene by promoter/enhancer insertion. Our results are more consistent with the hypothesis that the gag-myb-ets-encoded viral fusion protein, which is known to bind DNA, is directly or indirectly activating the expression of the Epo receptor gene in these cells.     

The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions.

Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gp120 and gp41, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.