Infraspecific variation in Cerastium alpinum s. lat. (Caryophyllaceae) in Central Norway

Within Cerastium alpinum s. lat., several taxa have been circumscribed. Three infraspecific taxa are currently recognized in Nordic literature, but the opinions have varied about their taxonomic levels and relations to each other. Populations of these three taxa — alpinum, glabratum and lanatum — were investigated in Central Norway to elucidate taxonomic relationships on a regional scale. Morphometric analyses (PCA ordination) based on two data sets; one with 61 characters, and one without the 35 indumentum characters, gave different results. The former partly support the use of a higher rank for glabratum , but this analysis may put too much weight on indumentum characters. The reduced data set gave a more continuous transition between the three taxa, with no special status for glabratum. Crossing experiments between the taxa indicated full cross compatibility as far as relative seed set was concerned. Finally, vegetation analysis (DCA ordination) indicated that the three taxa have somewhat different ecological demands. This suggests that they, in spite of hybridization abilities, normally are maintained as separate entities due to habitat differences. A delimitation of three infraspecific taxa at the same level within C. alpinum s. lat. is thus supported by this study. Whether these taxa should be treated as subspecies or varieties strongly depends upon the definitions of these categories. Viewed in a wide geographical context, however, the arguments for subspecific rank are strengthened.     

Changes in the population dynamics of Keratella cochlearis (Gosse), Kellicottia longispina (Gosse) and Polyarthra vulgaris Carlin in a fertilized enclosure

The population dynamics of phytoplankton and zooplankton in a fertilized enclosure were studied from April 1977 to June 1978. During the first spring period, the rotifers Keratella cochlearis, Kellicottia longispina, and Polyarthra vulgaris were scarce. During the following spring, all three species were abundant. An attempt is made to explain these differences. Food resource competition from cladocerans, and the low food quality and possible inhibitory effects of Coccomyxa sp. were found to be the most likely factors limiting the growth of these rotifers during the first spring period.     

Biosynthesis of the neural cell adhesion molecule: characterization of polypeptide C

The biosynthesis of the neural cell adhesion molecule (N-CAM) was studied in primary cultures of rat cerebral glial cells, cerebellar granule neurons, and skeletal muscle cells. The three cell types produced different N-CAM polypeptide patterns. Glial cells synthesized a 135,000 Mr polypeptide B and a 115,000 Mr polypeptide C, whereas neurons expressed a 200,000 Mr polypeptide A as well as polypeptide B. Skeletal muscle cells produced polypeptide B. The polypeptides synthesized by the three cell types were immunochemically identical. The membrane association of polypeptide C was investigated with methods that distinguish peripheral and integral membrane proteins. Polypeptide C was found to be a peripheral membrane protein, whereas polypeptides A and B were integral membrane proteins with cytoplasmic domains of approximately 50,000 and approximately 25,000 Mr, respectively. The affinity of the membrane binding of polypeptide C increased during postnatal development. The posttranslational modifications of polypeptide C were investigated in glial cell cultures, and it was found to be N-linked glycosylated and sulfated.     

Large Pseudomonas phages isolated from barley rhizosphere

Abstract: Five bacteriophages infecting common fluorescent pseudomonads ( Pseudomonas fluorescens and Pseudomonas putida ) were isolated from barley rhizosphere soil. Morphological and molecular characteristics of the phages are described together with selected phage-host interactions. All phages belonged to the Myoviridae family with isometrical heads on contractile tails; 4 of them were unusually large and had complex protein and DNA profiles. The large phages had estimated genome sizes of 200 kb or more. Restriction enzyme analyses and DNA-DNA hybridizations showed that all isolates represented different phage species. None of the isolates were observed to establish lysogeny with the main host strain, P. putida MM1. The large phages multiplied slowly on their hosts, producing very small plaques; one-step growth experiments with one of the large phages (Psp 4) hence demonstrated a long latent period (2.5 h) and a very small burst size (10 particles). One of the large phages (Psp 3) was abundant in the rhizosphere (approx. 10⁴ pfu g⁻¹ soil) and had a particularly broad host range which extended to both fluorescent ( Pseudomonas aeruginosa, P. fluorescens, P. putida and Pseudomonas chlororaphis ) and non-fluorescent (Pseudomonas stutzeri) Pseudomonas spp. occurring in soil. The ecological importance of the large Pseudomonas phages must be further studied, but their slow multiplication rates suggested a possible mechanism of balanced phage-host co-existence in the rhizosphere.     

On the origin of Z-band material and myofilaments in myoblasts from the human atrial wall

Summary The origin of cardiac myofibrils in cells from the atrial wall in human embryos was studied. Z-band substance appears throughout the cytoplasm as irregular electron dense patches in a network of thin filaments. The thin and thick filaments are synthesized as separate units in the sarcoplasm and are later aggregated into myofibrils. Complexes of Z substance and thin filaments occur numerously at different stages of myofibrillar organisation. Thick filaments are formed in close proximity to free ribosomes and are later incorporated in an hexagonal pattern into the Z-band/thin filament complex.This work was supported by grants from The Norwegian Council on Cardiovascular Disease and from The Norwegian Research Council for Science and the Humanities     

Microbial biomass and activity in subsurface sediments from Vejen,Denmark

Subsurface sediment samples were collected from 4 to 31 m below landsurface in glacio-fluvial sediments from the Quaternary period. The samples were described in terms of pH, electrical conductivity, chloride concentration, organic matter content, and grain size distribution. Viable counts of bacteria varied from 0.5 to 1,203 x 103 colony forming units/g dry weight (gdw); total numbers of bacteria acridine orange direct counts (AODC) varied from 1.7 to 147 × 10⁷ cells/gdw; growth rates (incorporation of [³H]-thymidine) varied from 1.4 to 60.7 × 10⁴ cells/(gdw · day); and rate constants for mineralization of ¹⁴C-labelled compounds varied from 0.2 to 2.3 × 10^–3 ml/(dpm · day) for acetate, and from 0 to 2.0 × 10^–3 ml/(dpm · day) for phenol. Sediment texture influenced the total number of bacteria and potential for mineralization; with increasing content of clay and silt and decreasing content of sand, AODC increased and the mineralization rate declined. Intrinsic permeability calculated from grain size correlated positively with mineralization rate for acetate. Statistical correlation analysis showed high correlations between some of the abiotic parameters, but it was not possible to point out a single abiotic parameter that could explain the variation of size and activity of the microbial population. The microbial data obtained in these geologically young sediments were compared to literature data from older sediments, and this comparison showed that age and type of geological formation might be important for the size and activity of the microbial populations.Offprint requests to: H.-J. Albrechtsen.     

Some molecular properties of NAD(P)H dehydrogenase from rat liver

NAD(P)H dehydrogenase (EC 1.6.99.2) purified from rat liver cytosol revealed three discrete bands, of mol.wts. about 27000, 18000 and 9000, when subjected to polyacrylamidegel electrophoresis in the presence of sodium dodecyl sulphate. Elution of the bands from the gel and individual re-electrophoresis on separate gels showed that the 27000-mol.wt. band yielded three bands similar to those obtained with the intact enzyme, whereas the 18000-mol.wt. band retained its characteristic mobility. Amino acid analysis of native enzyme and protein extracted from each of the three bands from sodium dodecyl sulphate/polyacrylamide gels suggests that the native enzyme is composed of two subunits and that each subunit consists of two dissimilar non-covalently bound polypeptides, so that altogether the enzyme is composed of four polypeptides, two of mol.wt. 18000 and two of mol.wt. 9000. NAD(P)H dehydrogenase was active over a wide pH range with no sharp optimum. The same K(m) value for NADH but different values for V(max.) were obtained for the enzyme purified from Sprague-Dawley and Wistar rats. In immunodiffusion, however, the enzymes from the two rat strains showed a reaction of complete identity. NAD(P)H dehydrogenase was effectively inhibited by thiol-blocking reagents, indicating that the activity is dependent on free thiol group(s). By amino acid analysis six cysteine residues were found per mol of enzyme. Guanidino-group- and amino-group-selective reagents had only moderate inactivating effects on the enzyme activity.