Ammonification rates and 210Pb in sediments from a lagoon under a wet tropical climate: Marica,Rio de Janeiro state,Brazil

The ammonification rates in surficial sediments of the Marica lagoon (Rio de Janeiro, Brazil) were estimated using two methods:

Coordinate pretranslational control of cAMP-dependent protein kinase subunit expression during development in the water mold Blastocladiella emersonii.

The aquatic fungus Blastocladiella emersonii provides a system for studying the regulation of expression of regulatory (R) and catalytic (C) subunits of cAMP-dependent protein kinase (PKA). Blastocladiella cells contain a single PKA with properties very similar to type II kinases of mammalian tissues. During development cAMP-dependent protein kinase activity and its associated cAMP-binding activity change drastically. We have previously shown that the increase in cAMP-binding activity during sporulation is due to de novo synthesis of R subunit and to an increase in the translatable mRNA coding for R (Marques et al., Eur. J. Biochem. 178, 803, 1989). In the present work we have continued these studies to investigate the mechanism by which the changes in the level of kinase activity take place. The C subunit of Blastocladiella has been purified; antiserum has been raised against it and used to determine amounts of C subunit throughout the fungus' life cycle. A sharp increase in C subunit content occurs during sporulation and peaks at the zoospore stage. Northern blot analyses, using Blastocladiella C and R cDNA probes, have shown that the levels of C and R mRNAs parallel their intracellular protein concentrations. These results indicate a coordinate pretranslational control for C and R subunit expression during differentiation in Blastocladiella.     

5,8,11,14-Eicosatetraynoic acid-induced destruction of mitochondria in human prostate cells (PC-3)

Summary Culturing human prostate PC-3 cells for 4, 24, or 72 h in the presence of 5,8,11,14-eicosatetraynoic acid (ETYA), an inhibitor of arachidonic acid metabolism and cholesterol biosynthesis, markedly altered the morphology and reduced the number of mitochondria in the treated cells. Using quantitative electron microscopic morphometry, we documented changes in the number, form, area, matrix density, and integrity of the cristae and limiting membranes of mitochondria in cells cultured with ETYA. The inhibition of cholesterol synthesis or the substitution of ETYA for polyunsaturated fatty acids in the inner membrane may participate in the disruption of the mitochondria, which resembles the morphologic sequelae of oxidative stress. If sufficiently extensive, these changes could contribute to the inhibition of cellular proliferation by ETYA.     

Revision and affinities ofGalium (Rubiaceae) in Madagascar

The only representatives ofRubiaceae-Rubieae in Madagascar are five species ofGalium. G. thunbergianum andG. chloroionanthum are essentially afromontane species, ± widely distributed in both the African mainland and Madagascar. The new speciesG. andringitrense andG. ankaratrense are endemic to Madagascar but show close affinities to two afromontane—afroalpine groups from the African mainland, theG. simense—G. ruwenzoriense andG. glaciale complex respectively.G. polyacanthum (new combination) exhibits certain primitive morphological traits and appears to be an old Madagascan endemic without close allies. New chromosome counts for populations from the African mainland demonstrate thatG. chloroionanthum andG. simense are 4x (x=11). Distribution patterns and origins of theGalium species in Madagascar and their relationships with African taxa are discussed.     

The effect of sterols and haemin on the growth of the rumen ciliate Ophryoscolex caudatus and some other Entodiniomorphid protozoa

Seven isolates of Ophryoscolex caudatus have been cultured anaerobically in vitro (at a population density of 56/ml) for an average of 18 months each in the presence of bacteria on a reduced buffered salts medium containing prepared fresh rumen fluid with the daily addition of ground wheat and dried grass and with twice weekly dilution of the culture with an equal volume of fresh medium. The ground wheat and dried grass could be replaced by ground wheat coated with β-sitosterol, stigmasterol, ergosterol or α-spinasterol and with β-sitosterol the population density increased to 110/ml. Haemin further increased the population density obtained in the presence of sterol by 9–160%. The population density of cultures of Epidinium ecaudatum caudatum was also increased by sterols and haemin, that of Polyplastron multivesiculatum by sterols only, and some sterols and haemin, under certain conditions, increased that of Entodinium caudatum.     

Thin-layer separation and quantification of bile acids

A method has been developed for quantification of total free and conjugated bile acids separated on silica gel HR coated thin-layer chromatography plates. Aliquots of bile acid solutions are applied to channeled plates which are developed with either ethyl acetate: isooctane: glacial acetic acid 10:10:2 v/v for free bile acid separation, or chloroform:methanol:glacial acetic acid:water 130:50:4:8 v/v for conjugated bile acid separation. Bile acids are determined directly in serial areas of silica gel by treating gel areas suspended in tris buffer with resazurin reagent. The method is quantitative and as little as 0.1 μg of bile acid is readily determined. Application of the method to determinations of bile acids in crude fecal extracts is described.     

Identification of the protein products of the rrnC, ilv, rho region of the Escherichia coli K-12 chromosome

Summary Two methods have been used to identify the protein products of the Escherichia coli K-12 ilv region at 84 min and the flanking rrnC (counterclockwise) and rho (clockwise) loci. First, a set of dilv specialized transducing phages, including some phages that carry rho and others that carry part of rrnC, was used to infect UV irradiated cells. The proteins produced by the infecting dilv phage were selectively labelled with radioactive amino acids and identified by SDS gel electrophoresis and autoradiography. Second, restriction enzyme fragments were cloned from the dilv phage into pBR322 and the plasmid specific gene products produced in maxicells were similarly identified by SDS gel electrophoresis and autoradiography. The proteins produced were correlated with specific genes and restriction enzyme fragments present in the dilv phage and the pBR322 derivatives. Several ilv gene products that have previously been refractory to protein purification attempts have been identified for the first time by this technique. The presence of mutations at the ilvO site is shown to activate the cryptic ilvG gene and to result in the production of a 62,000 dalton protein. A 15,000 dalton protein of unknown function is synthesized from a DNA segment between ilv and rrnC. The rho gene was cloned from dilv phage into pBR322 and shown to be dominant to a rho mutation on the host cromosome. The rho gene product and four additional proteins coded by genes near or between rho and ilv have been detected.