The primary structure of a procaryotic glycoprotein. Cloning and sequencing of the cell surface glycoprotein gene of halobacteria

The hexagonally patterned surface layer of halobacteria consists of a true glycoprotein. This procaryotic glycoprotein has recently been shown to exhibit novel features with respect to saccharide structure and saccharide biosynthesis. The primary structure and the location of glycosylation sites were determined by cloning and sequencing of the glycoprotein gene of Halobacterium halobium. According to the predicted amino acid sequence, the glycoprotein is synthesized with a N-terminal leader sequence of 34 amino acid residues reminiscent of eucaryotic and procaryotic signal peptides. A hydrophobic stretch of 21 amino acid residues at the C terminus probably serves as a transmembrane domain. 14 threonine residues are clustered adjacent to this membrane anchor and linked to these threonines are all the disaccharides of the cell surface glycoprotein. 12 N-glycosylation sites are distributed over the polypeptide chain.     

Lipase production of Staphylococcus carnosus in a dialysis fermentor

Summary In a newly constructed one-vessel dialysis fermentor, a strain of Staphylococcus carnosus TM300 carrying the lipase secretion plasmid pLipPS1 was used to investigate exoenzyme and biomass production. The bacterial culture grows in an inner compartment of 21 volume, separated from a 101 nutrient broth compartment by a conventional dialysis membrane. In order to avoid substrate depletion and to prolong the growth phase, a highly concentrated nutrient broth was used. The biomass production reached 60 g cell dry weight/l. The increase in extracellular lipase concentration was directly coupled with the increase of cell mass and reached a value of 230 mg/l culture supernatant. Harvesting the cells in the late growth phase, the lipase content was about 30% of the total exoproteins in the supernatant.     

Effects of naloxone on regional blood flow distribution in canine hemorrhagic shock

The opiate antagonist naloxone increases arterial pressure, maximal left ventricular dp/dt and cardiac output when administered to dogs subjected to hemorrhagic shock. The purpose of this study was to investigate regional blood flow changes associated with naloxone treatment in anesthetized hypovolemic and normovolemic dogs. Hypovolemic dogs (n = 10) were bled over 30 min (t = -30 to t = 0) to a pressure of 45 mm Hg which was maintained for 1 hr. At t = 60, five dogs received naloxone (2 mg/kg + 2 mg/kg X hr), and five received an equal volume of saline. Regional blood flows were determined at t = -30, 45, and 90 min using 15-micron microspheres. Normovolemic dogs (n = 10) were subjected to the same protocol except they were not bled. During hypovolemia, naloxone produced significant increases in myocardial, intestinal, hepatic, and adrenal blood flows whereas saline treatment did not. No significant changes in skin, muscle, fat, pancreatic, renal, or brain flows were detected. The increases in blood flow were not associated with significant changes in vascular resistance. Naloxone had no significant effects on any hemodynamic parameter during normovolemia. The beneficial effects of naloxone in hemorrhagic shock include increased blood flow to vital organs due to increased perfusion pressure which is secondary to improved cardiac performance.     

A zinc finger protein, essential for chromosome segregation, constitutes a putative DNA binding subunit of the Saccharomyces cerevisiae kinetochore complex, Cbf3.

A multisubunit protein complex, Cbf3, is a component of the Saccharomyces cerevisiae kinetochore. Cbf3 was recently shown to be essential for chromosome segregation in vivo and for movement of centromere DNA (CEN) along microtubules in vitro. Cbf3 contains three proteins, Cbf3a, Cbf3b and Cbf3c. Here the characterization of Cbf3b is described. Cbf3b contains an N-terminal Zn2Cys6 type zinc finger domain, a C-terminal acidic domain and a putative coiled coil dimerization domain. Cbf3b is essential for growth. Mutations within the zinc finger domain result in cells that exhibit a G2-M cell cycle delay and increased chromosome loss in each mitotic cell division. Therefore, Cbf3b has an essential function in chromosome segregation and the zinc finger domain executes part of this function presumably by providing the specific interaction between Cbf3 and CEN. Finally, data are provided to show that Cbf3c is encoded by CTF13, a gene that had been cloned recently by complementing a temperature sensitive mutant that exhibits chromosome loss as a result of a defective centromere.     

The steroid antagonist RU38486 is metabolized by the liver microsomal P450 mono-oxygenases

Microsomal preparations from adult male rat liver actively oxidized RU38486 into the 11 beta-monodemethylated, 11 beta-didemethylated and 17 alpha-hydroxylated derivatives, metabolites which are known to be formed in vivo. These oxidative reactions were inhibited at different degrees by P450 chemical inhibitors. Pretreatment of the animals by P450 mono-oxygenase prototype inducers led to drastic changes in RU38486 metabolization. Methylcholanthrene treatment carried out a significant decrease while phenobarbital markedly increased the metabolic activity of the liver microsomes. Moreover, antibodies to methylcholantrene-inducible P450 forms did not affect the metabolic activity while a complete blockade-of RU38486 oxidation was observed in the presence of antibodies to phenobarbital- inducible forms. The present results demonstrate that liver P450 mono-oxygenases are engaged in different oxidative steps of RU38486 metabolism and that phenobarbital-inducible but not methylcholanthrene-inducible P450 forms are active in RU38486 degradation.     

Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

     

Occurrence of anastomoses of the intrahepatic bile ducts

Eighty-four human livers were investigated with regard to the existence of vascular communications within their biliary tracts. Even with the help of a most subtle technique we could not detect any junctions between the bile ducts, so that there is no evidence of primary anastomoses between the main lobes, between the segments, or inside the segments. In case of chronic biliary obstruction only the major ducts, e.g., up to the fourth generation, are amplified. There is an inflammatory reaction around the smaller vessels, followed by fibrosis and shrinking of the connective tissue. That is why the formation of secondary anastomoses cannot happen under pathological conditions.