Molecular approaches to problems in biogeochemical cycling

Summary By using molecular probe techniques in combination with activity and expression measurements, it is possible to estimate bacterial populations in nature. This information can be expooited to study a number of important environmental problems. For instance, it will be possible to study ecosystem perturbation and microbial competition, by altering an ecosystem or a laboratory model of an ecosystem, and assessing corresponding changes in key activities and populations. In addition, regulation of activities in the laboratory can be compared to the response of activities and populations in situ, to develop an understanding of the key parameters that control these processes in nature. These types of approaches are important steps for determining the role of microorganisms in geochemical cycling, in both specific habitats and on a global basis.     

Ammonium uptake usingUlva (Chlorophyta) in intensive fishpond systems: mass culture and treatment of effluent

A vegetative clone ofUlva lactuca L. was selected for mass culture and nutrient uptake experiments with fish pond wastewater. Growth rates of over 55 g dry wt. d^?1 per 6001(1 m²) tank were obtained. Growth rate was linked to stocking density, tank flushing rates and aeration induced thallus movement. The plants could not survive on the macronutrients provided by a weekly pulse of wastewater. A continuous supply of fish pond wastewater was required to maintain good growth rates. An ‘uncoupling’ of growth rate and thallus nitrogen content was observed. The plants were able to store nitrogen from a pulsed ammonium supply and allot the nitrogen reserves to new tissue growth. Plants with slower growth rates or a continuous supply of ammonium had higher thallus nitrogen content.Ulva efficiently removed up to 85% of the ammonium from fish pond wastewater in darkness or light independently of temperature fluctuations.     

Calicotyle urolophi n. sp. (Monogenea: Monocotylidae) from stingarees,Urolophus spp. (Elasmobranchii: Urolophidae) taken in coastal waters of Southern Australia

Calicotyle urolophi n. sp. is proposed for calicotylines found in the cloaca of three stingaree species, Urolophus cruciatus, U. bucculentus and U. paucimaculatus, collected off the southeastern coast of Tasmania. Variations in the soft body parts were observed between specimens taken from U. cruciatus and U. bucculentus but were not considered sufficient for separation into two species. C. urolophi is differentiated from other Calicotyle spp. found in the South Pacific by the configuration of the tubular male copulatory organ, the structure of the intestinal caeca and the arrangement of the vaginae. Amended diagnoses for the subfamily Calicotylinae and the genus Calicotyle are provided.     

Deregulation of arginine biosynthesis in Synechococcus sp. PCC7942

Summary In order to deregulate arginine biosynthesis in Synechococcus sp. PCC7942, d-arginine-resistant cell lines were selected following ethyl methanesulfonate mutagenesis of wild-type (WT) cells. Three of these arginine-producing mutant (APM) cell lines, APM1, APM31 and APM40, were putative regulatory mutants based upon secretion of l-arginine into their growth medium. HPLC of lyophilized post-harvest supernatants of APM 31 and 40 resolved two predominant amino acids, arginine and citrulline. In-vitro activity of N-acetylglutamate kinase (NAGK), the proposed regulatory enzyme of the arginine pathway, was about 100-fold less sensitive to l-arginine inhibition in extracts from APM 31 and 40 than the enzyme in WT extracts. The enzyme from APM 1 was 20-fold less sensitive to l-arginine inhibition than WT. The most likely site of mutation in each of the APM cell lines is in the gene for NAGK, rendering the enzymes insensitive to l-arginine feedback control. These strains can be utilized for the phototrophic production of arginine. Offprint requests to: S. E. Bingham     

Cationic probes: Specificity of distribution of metal-binding sites in bovine sperm

Salts of transition elements that alter the rate of sperm cell movement act at or near calcium-binding sites. After living bull sperm cells had been preincubated in VO₄^3?, Ni²⁺, Zn²⁺, Mn²⁺, and also La³⁺, they were then fixed. Crisply defined organelles and the absence of particulate deposits in the morphological controls contrasted sharply with the treated specimens; the latter contained regions of increased electron density, the nature and distribution of which depended on the test substance, reflecting the differential affinities of the specific ions. La³⁺ formed fine dense areas, mainly at the exocytic surface of the plasma membrane. VO₄^3? marks the cell surface but also left particulate densities within the cell. Ni²⁺ caused a nearly uniformly dense deposit at the surface and on the satellite fibers and axonemal microtubules. Zn²⁺ formed less uniform but coarser deposits, while in Mn²⁺ the distribution was similar to that in Zn²⁺ but much denser in the axonemal matrix and on the satellite fibers. Verapamil restricted the size and number of the opacities, while procaine permitted a similar distribution of slightly larger size reaction product. The differences in size and distribution of the enhanced densities were consistent and replicable for the individual assay substances. Vanadate, which specifically inhibits Na, K-ATPase, bound to ouabain-sensitive enzyme loci, however, completely disrupting the axonemal complex. This suggests that an important role of dynein in flagellar motion may relate to intracellular transport of Ca²⁺.     

Restriction fragment polymorphisms as probes for plant diversity and their development as tools for applied plant breeding

Summary Maize and tomato cDNA clones have been hybridized in Southern blotting experiments to plant genomic DNA prepared from different lines to detect restriction fragment polymorphisms (RFPs). In maize we have found that a high degree of genetic variability is present, even among domestic inbred lines. Most randomly chosen maize cDNA clones can be used to detect elements of this variability. Similar levels of polymorphism are observed when genomic DNA is digested with any of a number of different restriction enzymes and probed with individual clones. When a clone is hybridized to genomic DNAs prepared from several different maize lines, a number of different alleles are often detected at a single locus. At the same time one clone can often detect more than one independently segregating locus by cross hybridization to related sequences at other loci. As expected these markers are inherited as simple codominant Mendelian alleles from one generation to the next and colinkage of these markers can be demonstrated in the progeny from a heterozygous parent. In similar studies with tomato, remarkably different results were found. Few RFPs were demonstrable among domestic Lycopersicon esculentum lines although a higher level of variability could be detected when comparing esculentum with its wild Lycopersicon relatives. These results are discussed in relation to the applied uses of RFPs in plant breeding as well as the inherent variability of different plant genomes.This work was supported in part by funds from Sandoz Ltd. (Basel, Switzerland) and its subsidiary company, Northrup King Co. (Minneapolis, Minn., U.S.A.) as well as by NSF SBIR grant #BSR-8360870.     

Decay and synthesis of ribosomal proteins during Dictyostelium discoideum development

Summary Ribosome turnover is a prominent process during cell differentiation in Dictyostelium discoideum. At the end of 24 h of development on filters, the cells contain only 30% of the ribosome content of vegetatively growing cells. We determined the relative rates of synthesis and decay of each of the ribosomal proteins during this period. Approximately 80% of the total vegetative cell ribosomal proteins were degraded during the course of fruiting body construction. Ribosomal RNA and protein degradation apparently occurred coordinately during development. Although all ribosomal proteins decayed during development, some were more stable and a few less stable than the average. In addition, all the ribosomal proteins were synthesized during this period. Most ribosomal proteins were synthesized at the same rate as other cellular proteins, although a number were made at lower or higher rates. It was estimated that about 35% of the ribosomes in developed cells represented those, that were made during cell differentiation. Differential decay and/or synthesis of ribosomal proteins could account for the observed difference in protein content of ribosomes from growing amoebae and late development cells and spores.Paper No. 4 in the series, Studies on Ribosomal Proteins in Dictyostelium discoideum. Paper No. 3 is Ramagopal and Ennis (1982)     

Orbitally magnetized organic solids

The preparation is discussed of polymeric organic solids in which large ring-like delocalized electronic orbitals can be made to enclose or trap magnetic flux. The situation is analogous to snapping shut a loop of superconductor while it is in a magnetic field. The operation of the Meissner effect acts to retain the trapped flux and create remant magnetization.     

Topographical distribution of the gonadotrophs,mammotrophs, somatotrophs and thyrotrophs in the pituitary gland of the baboon (Papio cynocephalus)

The identification and regionalization of four pituitary parenchymal cell types, gonadotrophs, mammotrophs, somatotrophs and thyrotrophs, were studied in the baboon (Papio cynocephalus) hypophysis using immunocytochemistry. The gonadotrophs were homogeneously distributed throughout the entire pars distalis. Both mammotrophs and somatotrophs predominate at the superior and inferior poles of the organ. The medial and anteromedial regions are populated by mammotrophs and thyrotrophs, while the lateral and posterior portions of the pars distalis contain large numbers of somatotrophs.     

Study of Chromosomes in the Newborn after Ultrasonic Fetal Heart Monitoring in Labour

The effect of continuous-wave ultrasound on the chromosomes of newborn infants has been investigated. Twenty-four women were studied during labour. The fetal heart was monitored by a Sonicaid FM2 monitor applied to the abdomen, and continuous monitoring undertaken for intervals varying from 1 hour 5 minutes to 9 hours 25 minutes. There was no increase in the number of chromosome aberrations in cultures of blood taken from the insonated babies when compared with controls.