Effect of amphotericin B on membrane-associated photosynthetic reactions in maize chloroplasts.

Superoxide dismutase of anaerobic purple sulfur bacterium, Chromatium vinosum, was purified to a homogeneous state. The enzyme contains two atoms of iron per mole and has a molecular weight of 41,000. It is composed of two identical subunits. Amino acid composition, absorption spectra, and the reaction rate constant with O₂^? are also similar to those of the Fe-superoxide dismutases from aerobes. The enzyme is sensitive to hydrogen peroxide and methylene blue-sensitized photooxidation. The functional and evolutional aspects of superoxide dismutase in anaerobes are discussed.     

Observations on the photohydrogen producing activity during the synchronous cell cycle of Scenedesmus obliquus

In anaerobically adapted samples of synchronized cultures of the unicellular green alga Scenedesmus obliquus it was observed that both the rate and the maximum volume of hydrogen produced in the light changed in a parallel fashion over the life cycle. These two parameters of cells of the 16th h were 3 times greater than the comparable values for cells of the 8th h. Although both photosystems are involved in photohydrogen production the patterns seen over a complete life cycle (24 h) for hydrogen metabolism was inverse to that noted for changes in the photosynthetic capacity. The provision of either glucose, ethanol or acetate to 8th and 16th h cultures enhanced photohydrogen production of the 8th to the same level as the 16th h. From these findings, and also from the observation that the starch content is low at the 8th but 4 fold at the 16th h, it is apparent that in autotrophic cultures an endogenous organic compound, and not water, serves as the electron donor for photohydrogen production. Since free glucose was not detected the natural substrate is most likely starch. From experiments with monochromatic light and observations on the inhibitory action of DCMU and DBMIB on photohydrogen production we conclude that the major portion of the machinery for photohydrogen production in Scenedesmus requires both PS I and PS II participation and the input of electrons from the natural substrate proceeds through PS II.The alternate possibility that glucose, acetate and ethanol also act as inhibitors of reactions, most probably photophosphorylation, which compete with photohydrogen production was suggested by some experiments. The subsequent modulation of hydrogenase activity was discussed as a possible reason for the enhancement of photohydrogen production.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - Chl chlorophyll - DCMU 3-(3, 4-dichlorophenyl)-1,1-dimethyl-urea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - NAD nicotinamide adenine dinucleotide - PSI photosystem I - PSII photosystem II - PCV packed cell volume     

Genetic analysis of Azotobacter vinelandii mutant strains unable to fix nitrogen.

Transformation was used to perform ratio test crosses with mutant strains of Azotobacter vinelandii unable to fix N2. Mutations that simultaneously eliminated both components of nitrogenase (nif-1 and nif-2) were tightly linked. The nif-45 mutation that resulted in the absence of an active molybdenum cofactor was closer to nif-1 and nif-2 than to any of the other nif mutations. Strains that lacked component I carried mutations that were closely linked to each other. Mutations that probably were located in the structural genes for components I and II appeared to be relatively close to each other on the A. vinelandii genome.     

Ribosomal RNA genes of Saccharomyces cerevisiae. I. Physical map of the repeating unit and location of the regions coding for 5 S, 5.8 S, 18 S, and 25 S ribosomal RNAs.

The organization of the ribosomal DNA repeating unit from Saccharomyces cerevisiae has been analyzed. A cloned ribosomal DNA repeating unit has been mapped with the restriction enzymes Xma 1, Kpn 1, HindIII, Xba 1, Bgl I + II, and EcoRI. The locations of the sequences which code for 5 S, 5.8 S, 18 S, and 25 S ribosomal RNAs have been determined by hybridization of the purified RNA species with restriction endonuclease generated fragments of the repeating unit. The position of the 5.8 S ribosomal DNA sequences within the repeat was also established by sequencing the DNA which codes for 83 nucleotides at the 5' end of 5.8 S ribosomal RNA. The polarity of the 35 S ribosomal RNA precursor has been established by a combination of hybridization analysis and DNA sequence determination and is 5'-18 S, 5.8 S, 25 S-3'.     

Structural components of influenza C virions.

The genome RNA species of influenza type C virions were analyzed by polyacrylamide gel electrophoresis. The pattern obtained was found to resemble those of other influenza viruses. Six RNA species were resolved, with estimated sizes ranging from 0.37 X 10(6) to 1.25 X 10(6) daltons. The internal ribonucleoproteins of influenza C virions were found to sediment heterogeneously in glycerol velocity gradients as demonstrated previously with influenza A/WSN virus. The ribonucleoproteins possessed diameters of 12 to 15 nm, with lengths ranging from 30 to 100 nm. Of the three major virion polypeptides (molecular weights, 88,000, 66,000, and 26,000), only the largest is glycosylated. Similar polypeptide species were present in influenza C virions of five different strains. All three major proteins of influenza C virions possess electrophoretic mobilities distinguishable from those of the major polypeptides of influenza A/WSN. The 66,000-dalton protein is associated with the ribonucleoprotein components. Two additional glycosylated polypeptides, with estimated molecular weights of 65,000 and 30,000, were detected in virions grown in embryonated eggs, but not in virus particles obtained from chicken embryo fibroblasts.     

Morning versus evening power output and repeated-sprint ability

We investigated the effect of time-of-day on both maximal sprint power and repeated-sprint ability (RSA). Nine volunteers (22+/-4 yrs) performed a RSA test both in the morning (07:00 to 09:00 h) and evening (17:00 to 19:00 h) on different days in a random order. The RSA cycle test consisted of five, 6 sec maximal sprints interspersed by 24 sec of passive recovery. Both blood lactate concentration and heart rate were higher in the evening than morning RSA (lactate values post exercise: 13+/-3 versus 11+/-3 mmol/L(-1), p<0.05). The peak power developed during the first sprint was higher in the evening than morning (958+/-112 vs. 915+/-133 W, p<0.05), but this difference was not apparent in subsequent sprints, leading to a higher power decrement across the 5x6 sec test in the evening (11+/-2 vs. 7+/-3%, p<0.05). Both the total work during the RSA cycle test and the power developed during bouts 2 to 5 failed to be influenced by time-of-day. This suggests that the beneficial effect of time-of-day may be limited to a single expression of muscular power and fails to advantage performance during repeated sprints.     

Integrative genomics revealed RAI3 is a cell growth-promoting gene and a novel P53 transcriptional target

In this study, differential gene expression between normal human mammary epithelial cells and their malignant counterparts (eight well established breast cancer cell lines) was studied using Incyte GeneAlbum 1-6, which contains 65,873 cDNA clones representing 33,515 individual genes. 3,152 cDNAs showed a > or =3.0-fold expression level change in at least one of the human breast cancer cell lines as compared with normal human mammary epithelial cells. Integration of breast tumor gene expression data with the genes in the tumor suppressor p53 signaling pathway yielded 128 genes whose expression is altered in breast tumor cell lines and in response to p53 expression. A hierarchical cluster analysis of the 128 genes revealed that a significant portion of genes demonstrate an opposing expression pattern, i.e. p53-activated genes are down-regulated in the breast tumor lines, whereas p53-repressed genes are up-regulated. Most of these genes are involved in cell cycle regulation and/or apoptosis, consistent with the tumor suppressor function of p53. Follow-up studies on one gene, RAI3, suggested that p53 interacts with the promoter of RAI3 and repressed its expression at the onset of apoptosis. The expression of RAI3 is elevated in most tumor cell lines expressing mutant p53, whereas RAI3 mRNA is relatively repressed in the tumor cell lines expressing wild-type p53. Furthermore, ectopic expression of RAI3 in 293 cells promotes anchorage-independent growth and small interfering RNA-mediated depletion of RAI3 in AsPc-1 pancreatic tumor cells induces cell morphological change. Taken together, these data suggest a role for RAI3 in tumor growth and demonstrate the predictive power of integrative genomics.     

A combined genomewide linkage scan of 1,233 families for prostate cancer-susceptibility genes conducted by the international consortium for prostate cancer genetics

Evidence of the existence of major prostate cancer (PC)–susceptibility genes has been provided by multiple segregation analyses. Although genomewide screens have been performed in over a dozen independent studies, few chromosomal regions have been consistently identified as regions of interest. One of the major difficulties is genetic heterogeneity, possibly due to multiple, incompletely penetrant PC-susceptibility genes. In this study, we explored two approaches to overcome this difficulty, in an analysis of a large number of families with PC in the International Consortium for Prostate Cancer Genetics (ICPCG). One approach was to combine linkage data from a total of 1,233 families to increase the statistical power for detecting linkage. Using parametric (dominant and recessive) and nonparametric analyses, we identified five regions with “suggestive” linkage (LOD score >1.86): 5q12, 8p21, 15q11, 17q21, and 22q12. The second approach was to focus on subsets of families that are more likely to segregate highly penetrant mutations, including families with large numbers of affected individuals or early age at diagnosis. Stronger evidence of linkage in several regions was identified, including a “significant” linkage at 22q12, with a LOD score of 3.57, and five suggestive linkages (1q25, 8q13, 13q14, 16p13, and 17q21) in 269 families with at least five affected members. In addition, four additional suggestive linkages (3p24, 5q35, 11q22, and Xq12) were found in 606 families with mean age at diagnosis of 65 years. Although it is difficult to determine the true statistical significance of these findings, a conservative interpretation of these results would be that if major PC-susceptibility genes do exist, they are most likely located in the regions generating suggestive or significant linkage signals in this large study.     

Molecular and biologic characteristics of Toxoplasma gondii isolates from wildlife in the United States

Toxoplasma gondii isolates can be grouped into 3 genetic lineages. Type I isolates are considered more virulent in outbred mice and have been isolated predominantly from clinical cases of human toxoplasmosis, whereas types II and III isolates are considered less virulent for mice and are found in humans and food animals. Little is known of genotypes of T. gondii isolates from wild animals. In the present report, genotypes of isolates of T. gondii from wildlife in the United States are described. Sera from wildlife were tested for antibodies to T. gondii with the modified agglutination test, and tissues from animals with titers of 1:25 (seropositive) were bioassayed in mice. Toxoplasma gondii was isolated from the hearts of 21 of 34 seropositive white-tailed deer (Odocoileus virginianus) from Mississippi and from 7 of 29 raccoons (Procyon lotor); 5 of 6 bobcats (Lynx rufus); and the gray fox (Urocyon cinereoargenteus), red fox (Vulpes vulpes), and coyote (Canis latrans) from Georgia. Toxoplasma gondii was also isolated from 7 of 10 seropositive black bears (Ursus americanus) from Pennsylvania by bioassay in cats. All 3 genotypes of T. gondii based on the SAG2 locus were circulating among wildlife.