Complementation of a Schizosaccharomyces pombe mutant lacking the beta subunit of the mitochondrial ATPase by the ATP2 gene of Saccharomyces cerevisiae

A chimeric plasmid carrying the structural gene (ATP2) for the mitochondrial ATPase beta subunit of Saccharomyces cerevisiae has been used to complement a mutant of Schizosaccharomyces pombe lacking the beta subunit (Boutry, M., and Goffeau, A. (1982) Eur. J. Biochem. 125, 471-477). Transformation with ATP2 restored the growth rate of S. pombe mutant on glycerol as well as the mitochondrial ATPase and 32Pi-ATP exchange activities to approximately 20% of the parental strain. Mitochondria prepared from the transformant contained a normal amount of a hybrid F1-ATPase consisting of the S. cerevisiae beta subunit assembled with the remaining subunits of the S. pombe ATPase complex. The presence of the S. cerevisiae beta subunit in the S. pombe ATPase complex conferred a sensitivity to the energy transfer inhibitors citreoviridin and oligomycin which was like that of the intact S. cerevisiae enzyme. The S. cerevisiae beta subunit assembled into the hybrid ATPase complex was the same size as the mature subunit in S. cerevisiae. These data indicate that the mechanism of mitochondrial import and the assembly of the cytoplasmically synthesized subunits is similar or identical in these evolutionary divergent yeasts. In addition, this study provides a new approach for the construction of hybrid mitochondrial ATPase complexes which can be used to examine the function of selected subunits in energy transduction.     

Distinguishing behavioral interactions from visual cues as causes of adult sex change in a coral reef fish

Two experiments tested the hypothesis that adult female-to-male sex reversal in protogynous fish is induced by the loss of close-contact behavioral interactions between males and females, and not by the loss of simple visual cues from the male. Twenty-six laboratory groups of Anthias squamipinnis were manipulated so that females within each group (1) retained chemical and acoustic access to a male, (2) were denied behavioral access to a male, and (3) were either allowed or denied visual access to a male alone or to a male interacting with another female. At least one female subsequently changed sex in each of 22 groups. While acoustic and chemical cues were not completely eliminated as possible causes, sex change is apparently induced by loss of male-female behavioral interaction in combination with continued interaction between females.     

Relationships among New World species of Hibiscus section furcaria (Malvaceae)

Seventeen species ofHibiscus sectionFurcaria are native to the New World, of which 12 (one diploid, nine tetraploids, one octoploid and one decaploid) have been studied cytotaxonomically. New chromosome counts (2n=4x=72) are reported forH. cucurbitaceus, H. flagelliformis, H. kitaibelifolius, andH. laxiflorus. Seventeen types of tetraploid interspecific hybrids (seven new to this study) all showed complete meiotic chromosome homology (genome formulaGGPP) and normal floral development. That all hybrids were nevertheless almost completely sterile suggests a cytoplasmic component to the genetic differentiation of the species. The diversification of the tetraploid species in habits, habitats and geographical ranges is considerable, despite their similar genome constitutions. A key to 17 native and four introduced African species is presented.Hibiscus cerradoensis sp. nov. is described.     

Chlorobium limicola forma thiosulfatophilum: Biocatalyst in the Production of Sulfur and Organic Carbon from a Gas Stream Containing H2S and CO2

Chlorobium limicola forma thiosulfatophilum (ATCC 17092) was grown in a 1-liter continuously stirred tank reactor (800-ml liquid volume) at pH 6.8, 30°C, saturated light intensity, and a gas flow rate of 23.6 ml/min from a gas cylinder blend consisting of 3.9 mol% H₂S, 9.2 mol% CO₂, 86.4 mol% N₂, and 0.5 mol% H₂. This is the first demonstration of photoautotrophic growth of a Chlorobium sp. on a continuous inorganic gas feed. A significant potential exists for applying this photoautotrophic process to desulfurization and CO₂ fixation of gases containing acidic components (H₂S and CO₂).     

Effects of Metals on Methanogenesis, Sulfate Reduction, Carbon Dioxide Evolution, and Microbial Biomass in Anoxic Salt Marsh Sediments

The effects of several metals on microbial methane, carbon dioxide, and sulfide production and microbial ATP were examined in sediments from Spartina alterniflora communities. Anaerobically homogenized sediments were amended with 1,000 ppm (ratio of weight of metal to dry weight of sediment) of various metals. Time courses in controls were similar for CH₄, H₂S, and CO₂, with short initial lags (0 to 4 h) followed by periods of constant gas production (1 to 2 days) and declining rates thereafter. Comparisons were made between control and experimental assays with respect to initial rates of production (after lag) and overall production. Methane evolution was inhibited both initially and overall by CH₃HgCl, HgS, and NaAsO₂. A period of initial inhibition was followed by a period of overall stimulation with Hg, Pb, Ni, Cd, and Cu, all as chlorides, and with ZnSO₄, K₂CrO₄, and K₂Cr₂O₇. Production of CO₂ was generally less affected by the addition of metals. Inhibition was noted with NaAsO₂, CH₃HgCl, and Na₂MoO₄. Minor stimulation of CO₂ production occurred over the long term with chlorides of Hg, Pb, and Fe. Sulfate reduction was inhibited in the short term by all metals tested and over the long term by all but FeCl₂ and NiCl₂. Microbial biomass was decreased by FeCl₂, K₂Cr₂O₇, ZnSO₄, CdCl₂, and CuCl₂ but remained generally unaffected by PbCl₂, HgCl₂, and NiCl₂. Although the majority of metals produced an immediate inhibition of methanogenesis, for several metals this was only a transient phenomenon followed by an overall stimulation. The initial suppression of methanogenesis may be relieved by precipitation, complexation, or transformation of the metal (possibly by methylation), with the subsequent stimulation resulting from a sustained inhibition of competing organisms (e.g., sulfate-reducing bacteria). For several environmentally significant metals, severe metal pollution may substantially alter the flow of carbon in sediments.     

Multiple Molecular Forms of Enkephalins in the Guinea Pig Hippocampus

Abstract: The combined techniques of HPLC and radioimmunoassay were used to identify and quantitate enkephalin-related peptides in the guinea pig hippocampus. Both met- and leu-enkephalin were identified, in approximately a 2:1 ratio, as well as a third enkephalin-like molecule that is neither met- nor leu-enkephalin. The third enkephalin elutes earlier than met- or leu-enkephalin from a reversed-phase column, has a molecular weight similar to the other enkephalins, and is as active as these enkephalins are in inhibiting binding of labeled opiates to rat brain membranes. All regions of the hippocampus (dentate gyrus, CA1–2, CA3–4, and subiculum) contain all three immunoreactive peptides. Immunocytochemical techniques, using antisera raised against met-enkephalin, show with one antiserum immunoreactivity in the granule cell-mossy fiber system, and with the other scattered immunoreactive cells mostly in the CA2 region. Enkephalins are not confined to the mossy fiber system, as previously suggested, but may be a component of another hippocampal innervation.     

Hypoxanthine: Guanine phosphoribosyltransferase mutants in Saccharomyces cerevisiae

Summary Yeast mutants lacking activity of the enzyme hypoxanthine: guanine phosphoribosyltransferase (H:GPRT) have been isolated by selecting for resistance to 8-azaguanine in a strain carrying the wild type allele, ade4 ⁺ of the gene coding for amidophosphoribosyltransferase (PRPPAT), the first enzyme of de novo purine synthesis. The mutants excrete purines and are cross-resistant to 8-azaadenine. They are recessive and represent a single complementation group, designated hpt1. Ade4-su, a prototrophic allele of ade4 with reduced activity of PRPPAT, is epistatic to hpt1, suppressing purine excretion and resistance to azaadenine but not resistance to azaguanine. The genotype ade2 hpt1 does not respond to hypoxanthine. Hpt1 complements and is not closely linked to the purine excreting mutants pur1 to pur5. Hpt1 and pur6, a regulatory mutant of PRPPAT, are also unlinked but do not complement, suggesting a protein-protein interaction between H:G-PRT and PRPPAT. Mycophenolic acid (MPA), an inhibitor of de novo guanine nucleotide synthesis, inhibits the growth of hpt1 and hpt1 ⁺. Xanthine allows both genotypes to grow in the presence of MPA whereas guanine only allows growth of hpt1 ⁺. Activity of A-PRT, X-PRT and H:G-PRT is present in hpt ⁺. Hpt1 lacks activity of H:G-PRT but has normal A-PRT and X-PRT.     

Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans

In six spontaneously breathing anesthetized subjects [halothane approximately 1 maximum anesthetic concentration (MAC), 70% N2O-30% O2], we measured flow (V), volume (V), and tracheal pressure (Ptr). With airway occluded at end-inspiration tidal volume (VT), we measured Ptr when the subjects relaxed the respiratory muscles. Dividing relaxed Ptr by VT, total respiratory system elastance (Ers) was obtained. With the subject still relaxed, the occlusion was released to obtain the V-V relationship during the ensuing relaxed expiration. Under these conditions, the expiratory driving pressure is V X Ers, and thus the pressure-flow relationship of the system can be obtained. By subtracting the flow resistance of equipment, the intrinsic respiratory flow resistance (Rrs) is obtained. Similar measurements were repeated during anesthesia-paralysis (succinylcholine). Ers averaged 23.9 +/- 4 (+/- SD) during anesthesia and 21 +/- 1.8 cmH2O X 1(-1) during anesthesia-paralysis. The corresponding values of intrinsic Rrs were 1.6 +/- 0.7 and 1.9 +/- 0.9 cmH2O X 1(-1) X s, respectively. These results indicate that Ers increases substantially during anesthesia, whereas Rrs remains within the normal limits. Muscle paralysis has no significant effect on Ers and Rrs. We also provide the first measurements of inspiratory muscle activity and related negative work during spontaneous expiration in anesthetized humans. These show that 36-74% of the elastic energy stored during inspiration is wasted in terms of negative inspiratory muscle work.     

Distribution of immunoreactive somatostatin in the primate hypothalamus

Immunocytochemical methods were used to compare the localization of somatostatin (SRIF) in the human and rhesus monkey hypothalamus. The distribution of SRIF-containing cell bodies and fibers is similar in the two species. Perikarya are located predominantly in the periventricular region and to a lesser extent in the ventromedial nucleus. Fibers occur in dense clusters within the periventricular region, ventromedial nucleus, arcuate nucleus, median eminence, and pericommissural area of both species. Analysis of serial sections suggests that fibers originate from cells in the periventricular region, extend ventrally through the ventromedial and arcuate nuclei to terminate around the portal vessels of the infundibular stalk, and thereby participate in the regulation of anterior pituitary function. Somatostatinergic fibers are also found surrounding non-immunoreactive perikarya in the ventromedial nucleus and periventricular region of both primates. This arrangement may support somatostatin's postulated role as a neurotransmitter or neuromodulator. The strong similarity between the localization of hypothalamic SRIF in the human and rhesus monkey supports the use of the rhesus monkey as a model for the study of somatostatin as a neuroendocrine regulatory in the human.