Determination of the solution conformation of adenosein 2':3'-monophosphate by nuclear magnetic resonance with lanthanide probes.

The aqueous solution conformation of adenosine 2':3'-monophosphate at pH 2.5 has been determined by a nuclear magnetic resonance method utilizing lanthanide ions as shift and relaxation probes. The ribose conformation is best described as a rapid equilibrium of 2'-endo(3'-exo) and 3'-endo(2'-exo) conformations in a ratio of approximately 2 to 1. The orientation of the base relative to ribose is restricted to a narrow range about chiCN=-70 degrees.     

Effects on Sperm Morphology by Alleles at the Pink-Eyed Dilution Locus in Mice

Sperm head morphology was analyzed in all genotypic combinations for alleles dark pink-eye (p^d) and p-sterile alleles, p^6H, p^bs (p -black-eyed sterile) and p^25H. Three of these, p^6H, p^bs and p^25H, were radiation induced; homozygotes and heterozygotes of these three alleles are male sterile, whereas p^d/— genotypes are fertile. Sperm heads were examined by light microscopy and assigned to one of five classes: A. normal and near-normal, B. triangulate and oblate, C. spatulate, D. elongate, and E. filamentous. Males of each sterile genotype had grossly abnormal sperm and each sterile genotype differed from all other sterile genotypes and from fertile genotypes in at least one class, except p^6H/p^6H compared to p^bs/p^bs.Frequency distribution profiles (1) revealed a complex pattern of allelic interaction and do not support a deletion-complementation hypothesis, (2) do not show simple bimodality, which might suggest post-meiotic (haploid) gene expression, and (3) together with unpublished breeding data, show that p^25H is not a remutation of p^6H.     

Modification of ribonucleic acid by vitamin B6. 1. Specific interaction of pyridoxal 5'-phosphate with transfer ribonucleic acid.

Whole tRNA preparation obtained from a human cell line (HT-29) of colon carcinoma and purified specific Escherichia coli tRNA were reacted with pyridoxal 5'-phosphate, reduced by sodium borohydride and digested with RNase A and snake venom phosphodiesterase. Two-dimensional chromatography of the pyridoxal 5'-phosphate treated tRNA digest showed that pyridoxal 5'-phosphate binds specifically to GMP, presumably in the form of a Schiff base with the exocyclic amino group of the purine. The reaction of pyridoxal 5'-phosphate with whole tRNA was competitively inhibited by N-acetoxy-2-acetylaminofluorene. This suggests that binding occurred primarily to the G20 base residue at the unpaired region of the dihydrouridine loop (Fujimura et al., 1972). The modification of tRNA by pyridoxal 5'-phosphate resulted in the inhibition, to varying extent (10-80%), of amino acid acceptance in the aminoacyl-tRNA synthetase reaction. Defects in codon recognition by pyridoxal 5'-phosphate modified amino acid acylated tRNAs in the presence of the corresponding guanine-containing polynucleotide triplets were observed by the ribosomal binding assay.     

Nutrition and carbon metabolism of Methanococcus voltae.

Methanococcus voltae is a heterotrophic, H2-oxidizing methanogenic bacterium. In complex medium, this bacterium has a doubling time of 1.2 h at its temperature optimum of 38 degrees C. In defined medium, optimal growth is obtained with 0.75 mM isoleucine, 0.75 mM leucine, 2.5 mM acetate, 5 mM NH4Cl, 84 mM MgSO4, 0.4 M NaCl, 1 mM CaCl2, 10 microM Fe2O3, and 0.2 microM NiCl2. In addition, pantothenate, sodium selenate, and cobalt stimulate growth. Optimal growth is obtained between pH 6.0 and 7.0 with either H2 or formate as the electron donor. The volatile fatty acids 2-methylbutyrate and isovalerate can substitute for isoleucine and leucine, respectively. Cellular carbon is derived from acetate (31%), isoleucine (22%), leucine (25%), and carbon dioxide (23%). The amino acids and fatty acids are incorporated almost exclusively into protein. A comparison of the incorporation of U-14C-amino acids and 1-14C-fatty acids indicated that the fatty acids are degraded during incorporation into cell protein. The distribution of carbon from the amino acids suggests that acetyl coenzyme A is not a major intermediate in the degradation of these compounds. Thus, M. voltae may convert isoleucine and leucine to other amino acids by a unique mechanism. The lipid carbon is derived largely from acetate. Thus, the isoprenoid lipids are synthesized de novo from acetate rather than by degradation of leucine. The carbon in the nucleic acids is derived from carbon dioxide (45%), the C-1 of acetate (25%), the C-2 of acetate (22%), and isoleucine and leucine (7%). This labeling pattern is consistent with known biochemical pathways.     

Malate dehydrogenase. Kinetic studies with meso-tartrate and 2-keto-3-hydroxysuccinate, comparison of the mitochondrial and supernatant pig heart enzymes.

Initial rate, product inhibition, and isotope rate kinetic studies of pig heart mitochondrial and supernatant malate dehydrogenases, acting upon the nonphysiological substrates, meso-tartrate and 2-keto-3-hydroxysuccinate, are reported. The measured spontaneous keto-enol equilibrium for 2-keto-3-hydroxysuccinate in 0.05 m Tris-acetate (pH 8.0) at 25 °C favors the enol form, dihydroxyfumarate, with an apparent equilibrium constant of 0.036. The enzyme-catalyzed reaction favors meso-tartrate with an apparent equilibrium constant of 1.25 × 10^?6, M^?1 at pH 8.0. The mechanism apparently remains ordered bi bi for both enzymes when these nonphysiological substrates are used, and the chemical-converting hydride transfer step becomes more rate limiting for both enzymes. This conclusion is supported by $\text{V}{}_{\mathrm{<mtext>H</mtext>}}\text{V}{}_{\mathrm{<mtext>D</mtext>}}$ and $\text{(}\text{V}{}_{\mathrm{<mtext>H</mtext>}}\text{K}{}_{\mathrm{<mtext>H</mtext>}}\text{)}\text{V}{}_{\mathrm{<mtext>D</mtext>}}\text{K}{}_{\mathrm{<mtext>D</mtext>}}$ values of 2.6 and 3.1, respectively, for the mitochondrial enzyme and 1.9 and 2.9, respectively, for the supernatant enzyme.     

Properties of bilayer membranes in the phase transition or phase separation region

The increase in passive permeability of bilayer membranes near the phase transition temperature is usually explained as caused by either the increase in the amount of ‘boundary lipid’ present in the membrane, or by the increase in lateral compressibility of the membrane. Since both the amount of ‘boundary lipid’ and the lateral compressibility show a similar anomaly near the transition temperature, it is difficult to distinguish experimentally between the two proposed mechanisms.We have examined some details of both of the proposed pictures. The fluid-solid boundary energy, neglected in previous work, has been computed as a function of the domain size. For a single component uncharged lipid bilayer, the results rule out the existence of even loosely defined solid domains in a fluid phase, or vice versa. Thermodynamic fluctuations, which are responsible for anomalous behaviour near the phase transition temperature, are not intense enough to approximate the formation of a domain of the opposite phase.Turning next to lateral compressibility of bilayer membranes we have considered two-component mixtures in the phase separation region. We present the first calculation of lateral compressibility for such systems. The behaviour shows interesting anomalies, which should correlate with existing and future data on transport across membranes.     

Isolation of a cytomegalovirus from salivary glands of white-lipped marmosets (Saguinus fuscicollis).

Minced salivary glands from seven white-lipped marmosets (Saguinus fuscicollis and Saguinus nigricollis) and one cotton-topped marmoset (Saguinus oedipus) were cocultivated with marmoset cell cultures. A viral agent, designated SSG, was isolated from two Saguinus fuscicollis. Slowly progressing foci of rounded, vacuolated, refractile cells were first observed at 40-43 days incubation. Electron microscopy revealed intranuclear herpesvirus nucleocapsids and intracytoplasmic and extracellular enveloped particles. Infected cells stained with hematoxylin and eosin contained eosinophilic intranuclear and cytoplasmic inclusion bodies. SSG could be passaged in cell cultures only using viable whole cells; infectious cell-free virus was not detected in either culture supernatants or cell lysates. SSG replicated in marmoset fibroblastic but not in marmoset epithelioid or human fibroblastic cell cultures. Plasma antibodies to SSG were detected by indirect immunofluorescence assays in 16 of 56 (28.6%) adult wild-caught marmosets but were absent in 40 colony-born, hand-reared marmosets. Antigenic cross-reactivity of SSG with a rhesus monkey (Macaca mulatta) cytomegalovirus (bidirectional) and with a human cytomegalovirus (unidirectional) was also demonstrated by indirect immunofluorescence assays. SSG was identified as a herpesvirus by morphology and was classified as a cytomegalovirus by its site of isolation, biologic properties in vitro, and antigenic characteristics.     

The effects of mefloquine on Escherichia coli.

Mefloquine, a quinoline-4-methanol antimalarial drug, also possesses bactericidal activity. Mefloquine causes rapid loss of bacterial viability, cell and spheroplast lysis, cessation of macromolecular synthesis, release of macromolecular constituents, and inhibition of the oxidation of NADH by isolated $\text{E. coli}$ membranes. Results are consistent with the hypothesis that mefloquine is a membrane-active drug.     

Sexual maturation among members of a transported troop of Japanese macaques (Macaca fuscata)

Data on the sexual maturation of a transported natural troop of Japanese macaques were collected during the 1973–74 and 1974–75 breeding seasons. Analysis of the data revealed that the sexual maturation of many monkeys was delayed one to two years. It is suggested that the delay of sexual maturation is related to a failure of the pubescent-aged monkeys to attain appropriate weight levels after transportation. This study was partially supported by a University of Oregon, Department of Anthropology PHS Biomedical Science Grant 50-262-1112.