Abortive Infection of L Cells by Influenza B Virus: Defect in Bud Formation

Host-dependent restriction of influenza B virus replication in L cells was analysed in comparison with productive infection in MDCK or 1–5C-4 cells. The synthesis and intracellular distribution of virus-specific proteins and the production of cytoplasmic ribonucleoproteins in nonpermissive L cells were similar to those in permissive MDCK cells. However, an electron microscopic study of infected L cells showed neither extracellular virions nor budding virus particles on the cell surface, in contrast to MDCK cells which produced numerous virus particles. PAGE analysis of the plasma membrane isolated from the cells demonstrated no significant difference in the composition of viral polypeptides between permissive 1-5C-4 and nonpermissive L cells. It was noted that the abortiveness of influenza B virus infection in L cells may be due to a defect in host cell function involved in the initiation of virus budding.     

Determination of guanine by high-performance liquid chromatography with electrochemical detection: application to DNA and RNA assays

A highly sensitive assay for guanine was developed using high-performance liquid chromatography with electrochemical detection (ECD). Guanine was susceptible to the electrochemical oxidation, and ECD response was proportional to the amount of guanine in the range 0.25-4 pmol of guanine. The ECD of guanine was applicable to the analysis of nucleic acids. DNA and RNA were hydrolyzed in 0.03 and 3 M HCl, respectively, and guanine liberated from the nucleic acids was separated on a reverse-phase column and determined by ECD. The method allowed detection of 0.2 ng of calf thymus DNA or tRNA. An application of the method is shown for DNA and RNA assays in trichloroacetic acid extracts of rat adrenal and liver.     

Involvement of prostaglandin-induced proteins in the inhibition of herpes simplex virus replication

Cyclopentenone prostaglandin (PG), delta7-PGA1 was found to induce several polypeptides in human embryonic fibroblast (HEF) cells which were noticed to be dose-related and appeared after 1 h of treatment with a peak at around 5 h and gradual disappearance after 12 h. PG-induced proteins were almost identical in terms of molecular weights with those induced by heat-shock at 42 degrees C. Regarding the mechanism of inhibition of herpes simplex virus (HSV) replication by PG in cell culture, dot blot hybridization has revealed that the level of immediate early (IE) mRNA of the virus was reduced after PG treatment with time dependence. And this delayed inhibitory effect of delta7-PGA1 on HSV was shown to be associated with the production and accumulation of the induced polypeptides.     

Regional distribution of DNA and RNA in rat brain: A sensitive determination using high-performance liquid chromatography with electrochemical detection

DNA and RNA contents in 20 brain regions or nuclei of the rat were determined by a highly sensitive method using high-performance liquid chromatography with electrochemical detection. The high DNA and RNA contents were found in the hypothalamic nuclei, especially the median eminence-arcuate nucleus. These results may be available for the preparation of nucleic acids as the regional control.     

Constitution of Mitochondrial and Chloroplast Genomes in Male Sterile Tobacco Obtained by Protoplast Fusion of Nicotiana tabacum and N. debneyi

Chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) of malesterile tobacco plants obtained by fusion of Nicotiana tabacumprotoplasts and X-irradiated N. debneyi protoplasts were analyzed.Digestion of cpDNA isolated from ten male sterile lines withfour restriction endonucleases (EcoRI, XhoI, SmaI and HindIII)indicated that these lines possessed either one or the otherparental chloroplast genome. Neither mixture of two types ofcpDNA nor unique restriction fragments were detected in anyof the cases examined. The genetic constitution of chloroplastgenomes identified by restriction analysis of cpDNA showed goodagreement with that based on isoelectric focusing of the largesubunit of the Fraction I protein. The mtDNA from five fusion-derivedmale sterile plants showed banding patterns quite differentfrom each other and from the parental plants. Each plant exhibitednew restriction fragments not found in the parental species.These findings indicate that recombinational events in the mitochondrialgenomes take place rather frequently in the mixed cytoplasmsafter protoplast fusion, whereas the mixed chloroplasts becomesegregated to homogeneity. (Received June 19, 1987; Accepted October 5, 1987)     

Increase in the frequency of gamma-ray induced chromosomal aberrations in mammalian cells by post-treatment with novobiocin

The effect of novobiocin (an inhibitor of DNA topoisomerase and polymerase) on the frequency of chromosomal aberrations was examined in Chinese hamster V79 cells irradiated with gamma-rays in the plateau phase of growth and subcultured in the presence of novobiocin until the first mitosis after irradiation. Novobiocin alone affected cell survival, DNA synthesis and the mitotic frequency of unirradiated cells in a dose-dependent manner, without causing any significant increase in the frequency of chromosome- or chromatid-type aberrations. The frequency of chromosome-type aberrations induced by gamma-radiation was not influenced by novobiocin at 200 microM, but the frequency of chromosome deletions (but not rings and dicentrics) showed a two-fold increase when 300 microM novobiocin was present. Irradiation produced a low level of chromatid-type aberrations and post-treatment with novobiocin at concentrations greater than 100 microM significantly increased the frequency of chromatid gaps and breaks. The results support the idea that different radiation-induced lesions lead to chromosome- as opposed to chromatid-type aberrations.     

Glucagon-related peptides in the rat hypothalamus

Summary Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism.     

Molecular and enzymatic properties of 1,2-α-d-mannosidase fromAspergillus saitoi

The molecular properties, such as molecular weight, N-and C-terminal amino acids, amino acid composition, and circular dichroism, of 1,2--mannosidase isolated from the culture filtrate ofAspergillus saitoi were determined.The enzyme had aK _m of 0.67 mM andk _cat of 1.27/s with mannobiose at pH 50.0 and 30°C. The anomeric configuration of the reaction products of the enzyme was examined by studying the -anomer. A single Manl2Man linkage in intact Taka-amylase A fromAspergillus oryzae was hydrolyzed, producing free mannose.