The effects of insulin on choline kinase activity in cultured rat liver cells

The effect of insulin on phosphatidylcholine biosynthesis in cultured rat liver cells was assessed by measuring changes in the activity of the first enzyme in the choline pathway of phosphatidylcholine biosynthesis, choline kinase (ATP: cholinephosphortransferase, EC 2.7.1.32), in the presence or absence of the hormone. Choline kinase specific activity in liver cells incubated for 18 hours in the presence of 10^?7M insulin increased two-fold from 3.4 ± 0.3 nmoles phosphorylcholine formed/min/mg protein to 7.5 ± 0.6 nmoles/min/mg protein. This effect was dose dependent and reversed by the addition of actinomycin D and cycloheximide. It is concluded that the increase in specific activity is due to synthesis of new enzyme rather than activation of existing enzyme.     

Rad52 recruitment is DNA replication independent and regulated by Cdc28 and the Mec1 kinase

Recruitment of the homologous recombination machinery to sites of double‐strand breaks is a cell cycle‐regulated event requiring entry into S phase and CDK1 activity. Here, we demonstrate that the central recombination protein, Rad52, forms foci independent of DNA replication, and its recruitment requires B‐type cyclin/CDK1 activity. Induction of the intra‐S‐phase checkpoint by hydroxyurea (HU) inhibits Rad52 focus formation in response to ionizing radiation. This inhibition is dependent upon Mec1/Tel1 kinase activity, as HU‐treated cells form Rad52 foci in the presence of the PI3 kinase inhibitor caffeine. These Rad52 foci colocalize with foci formed by the replication clamp PCNA. These results indicate that Mec1 activity inhibits the recruitment of Rad52 to both sites of DNA damage and stalled replication forks during the intra‐S‐phase checkpoint. We propose that B‐type cyclins promote the recruitment of Rad52 to sites of DNA damage, whereas Mec1 inhibits spurious recombination at stalled replication forks.     

Acanthocephaloides cyrusi n. sp. (Acanthocephala: Arhythmacanthidae) from southeast African teleost fishes

A new species,Acanthocephaloides cyrusi, is described from the fishesSolea bleekeri andPomadasys commersoni from Lake St. Lucia, Natal, South Africa. It is distinguished from the other species in the genus by the more marked sexual dimorphism in length, the arrangement of hooks, the proboscis with the longest hooks at the anterior-most extremity and the greater size of the proboscis hooks and body spines. An acanthella, which may represent this species, was found in the tanaidApseudes digitalis.     

Macvicaria taksengi n. sp. (Digenea: Opecoelidae) in marine teleosts from Pinang,Malaysia

Summary A new species, Macvicaria taksengi (Opecoelidae: Plagioporinae), is described from the fishes Otolithes ruber and Sillago sihama from Pinang, Malaysia. It differs from most other members of the genus in the position of the ovary relative to the testes and the anterior position of the genital pore. A brief discussion on the Indo-West Pacific forms of the genus Macvicaria and related genera includes references to several new combinations: M. [Lebouria] isaitschikowi (Layman, 1930), M. [Plagioporus] sillagonis (Yamaguti, 1938), M. [Plagioporus] chrysophrys (Nagaty & Abdel Aal, 1969) and M. [Plagioporus (Plagioporus)] longisaccus (Fischthal & Kuntz, 1964).     

A review of the genus Parahemiurus Vaz & Pereira, 1930 (Digenea: Hemiuridae)

The genus Parahemiurus Vaz & Pereira, 1930 (syn.: Daniella Sahai & Srivastava, 1977) is defined, its major morphological characters discussed and a key to species given. The species P. merus (Linton, 1910) (syns: P. parahemiurus Vaz & Pereira, 1930, P. sardiniae Yamaguti, 1934, P. seriolae Yamaguti, 1934, P. platichthyi Lloyd, 1938, P. atherinae Yamaguti, 1938, P. harengulae Yamaguti, 1938, P. noblei King, 1962) and P. anchoviae Pereira & Vaz, 1930 are described. Other species recognized are P. clupeae Yamaguti, 1953, P. [originally Daniella] madrasensis (Sahai & Srivastava, 1977) n. comb. (syns: P. dussumieriai Hafeezullah, 1981, P. indicus Ahmad, 1981), P. ecuadori Manter, 1940, P. engraulisi Gupta & Jahan, 1977 (syns: P. cameroni Gupta & Ahmad, 1977, P. puriensis Ahmad, 1981, P. simhai Gupta & Gupta, 1978, P. tricanthusi Gupta & Puri, 1984) and P. yanamense Hafeezullah, 1980. Forms considered species inquirendae are P. arripidis Lebedev, 1971, P. clupeae of King (1964), P. dogieli Skrjabin & Guschanskaya, 1953, P. pseudosciaenae Shen, 1985 and P. trachichthodi Lebedev, 1968. Host and locality information is given in detail for all species. The complete life-cycle is not known, but metacercariae are reported in chaetognaths and teleosts. The definitive hosts of Parahemiurus spp. most frequently reported belong in the families Clupeidae and Carangidae and the genus is most commonly reported in temperate and subtropical waters.     

Chiral assay methods for lifibrol and metabolites in plasma and the observation of unidirectional chiral inversion following administration of the enantiomers to dogs

Lifibrol, a new drug for the treatment of hypercholesterolemia, contains a stereogenic center bearing a secondary alcohol group. A normal-phase achiral–chiral HPLC separation of the enantiomers of lifibrol and two of its metabolites was developed and validated for quantitation in dog plasma. A silica and a Chiralcel OD-H column were operated in series and all six enantiomeric components and internal standard were directly separated. An initial solid-phase extraction (phenyl) clean-up step and a column-switching step to eliminate late-eluting compounds were also utilized. The solid-phase extraction step was automated using a robotic system. Assay development, validation, and application of the method to a bioavailability study of the racemate and enantiomers of lifibrol in dogs are described. The lower limit of quantitation was 0.0125 μg/ml for each enantiomer of lifibrol using 200 μl of dog plasma with UV detection (255 nm). In dog plasma following oral or intravenous administration of the racemate, the (R)/(S) ratio of the enantiomers of lifibrol was greater than one and increased with time. Following administration of the individual enantiomers, chiral inversion of the (S)-enantiomer but not the (R)-enantiomer was observed. © 1994 Wiley-Liss, Inc.     

Paleoecology of a low-diversity silurian community from the tofta beds of Gotland

The Silurian (Wenlockian) Tofta Beds at Galgberget 1, Gotland, Sweden, formed in a protected intertidal setting. Massive fenestral limestone at this locality contains a low diversity community dominated by stromatoporoids, calcareous algae, and ostracods, with less common rugose corals, bryozoans, brachiopods, and trilobites. Abundance of stromatoporoids, which form about 40% of sediment volume, suggests reef-like conditions. The Tofta community differs from typical Silurian reef communities, however, in its low diversity, very limited tiering, and absence of groups such as crionozoans and tabulates. These differences are possibly due to intertidal conditions which precluded upward growth of a mound structure and subjected the community to periodic desication.     

An aberrant plastid ribosomal RNA gene cluster in the root parasite Conopholis americana

The plastid ribisomal RNA (rRNA) operon of the achlorophyllous root parasite Conopholis americana was completely sequenced. Full-length rRNA genes are retained in the gene cluster, but significant divergence has occurred in the 16S, 23S and 5S genes. Both the 16S–23S intergenic spacer and the 4.5S–5S intergenic spacer have suffered substantial deletions, including the two tRNA genes typically found in prokaryotic and plastid 16S–23S spacers.     

Expression of a group II phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus in Escherichia coli: Recovery and renaturation from bacterial inclusion bodies

A synthetic gene encoding the Group 11 phospholipase A₂ (PLA₂) from the venom of Agkistrodon piscivorus piscivorus has been constructed and expressed with high efficiency in Escherichia coli. No enzymatic activity was recovered when the polypeptide contained the initiator Met residue. Replacement of an Asn residue penultimate to the initiator Met with Ser or Gly permitted removal of the initiator Met by the endogenous methionine aminopeptidase. The amino-terminal serine (N-Ser) and amino-terminal glycine PLA₂'s were isolated from intracellular inclusion bodies and were renatured with 25% recovery. Automated Edman degradation confirmed the removal of the initiator Met and confirmed the sequence of the first 40 residues of N-Ser PLA₂. The recombinant proteins were purified to apparent homogeneity and showed the same specific activity as the wild-type protein. N-Ser PLA₂ demonstrated the same kinetics of activation as the wild type enzyme on large vesicles of zwitterionic lipid.