Molecular and cytological characteristics of nuclear DNA and chromatin for angiosperm systematics: DNA diversification in the evolution of four orchids

The species- and genus-specific DNA content, average base composition of nuclear DNA, presence or absence of satellite DNA, the percentage of heterochromatin and other characteristics of nuclear DNA and nuclear structure allow to deduce the molecular changes which accompanied, or more probably caused, cladogenesis in the orchids studied. It is suggested that saltatory replication (generative amplification) of certain DNA sequenes, diversification of reiterated DNA sequences, and loss of DNA play an important role in the evolution of orchids.—The relationship between changes of genome composition and of nuclear structure and ultrastructure is discussed on the basis of cot curves, heterochromatin staining with Giemsa (C banding), electron microscopy of nuclei, and molecular hybridization in situ.Some aspects of this paper have been presented at the Helsinki Chromosome Conference, August 1977 (Nagl & Capesius 1977).     

Inhibition of protein kinase activity from Trypanosoma cruzi and Trypanosoma gambiense by 3'-deoxyadenosine.

3'-Deoxydadenosine was found to be a potent inhibitor of nucleoside-stimulated protein kinase activity from culture forms of Trypanosoma cruzi and bloodstream forms of Trypanosoma gambiense. The type of inhibition by 3'-deoxyadenosine was competitive with respect to ATP. The inhibition constants for 3'-deoxyadenosine were determined to be 0.11mM and 0.085mM for the enzyme from T. cruzi and T. gambiense, respectively. The apparent Km value for ATP was 0.2mM for both enzymes. 2'-Deoxyadenosine was less effective as inhibitor of the protein kinase activity. The inhibition constants were calculated to be 0.8mM and 0.67mM, respectively.     

Contributions of subterranean termites to the “economy” of Chihuahuan desert ecosystems

Summary We examined the role of subterranean termites in decomposition of cattle dung, various herbaceous plant species and wood in a Chihuahuan desert ecosystem. From July–September, termites removed dung at a rate of 0.63 g day^-1 accounting for a percent mass loss of 19.5–100%. During the autumn subterranean termites consumed more than 50% of the leaves of the shrub Larrea tridentata, the grass Erioneuron pulchellum and annual plant Lepidium lasiocarpum and Baileya multiradiata but used very little of two other annuals Eriastrum diffusum and Eriogonum trichopes. Yucca inflorescence stalks on plots with termites lost 23% of their original mass in 30 months while those on termite free soils lost 11%. Elimination of termites resulted in reduction of fluff grass, Erioneuron pulchellum biomass, thereby affecting the structure of the ecosystem.     

On the population genetics of beta2-glycoprotein I.

Beta2-glycoprotein I typings on 152 healthy Germans and 150 patients with atopic diseases did not show any differences in the serum protein concentrations or in the phenotype and gene frequencies. Compared to these German samples, Philippinos (n = 88) as well as healthy Negroes from South Africa (n = 192) revealed statistically significant lower concentrations of this serum protein. They differ also from the Germans with regard to phenotype and gene frequencies. A most striking result was found in the comparison of healthy and leprous Negroes (n = 250) from South Africa. In these, quite different and statistically significant beta 2-Glycoprotein I concentrations, respectively, phenotype and gene frequencies were seen, which may be due to this disease. The possible reasons for these observations as well as for the observed population differences are discussed.     

Resistenzphysiologische Grundlagen der evolutiven Kälteakklimatisation von Sproßpflanzen

Gradations in cold resistance of plants with different latitudinal and altitudinal distribution, and the various categories of chilling and freezing resistance are hypothesized to be evolutionary steps of adaptive responses to increasing low temperature stress and annual seasonality. The gradual lowering of the critical phase transition temperature of biomembrane lipids, the capacity of persistent supercooling of tissues, and the development of a dormancy linked freezing-tolerance are considered to be essential mechanisms resulting in improved acclimatation to low temperature climates.

     

Use of 13C in biosynthetic studies. The labelling pattern in tenellin enriched from isotope-labelled acetate, methionine, and phenylalanine

The biogenetic origin of the carbon atoms in tenellin has been established by adding 13C-enriched compounds to cultures of Beauveria bassiana, and determining the isotopic distribution in the metabolite by 13C nuclear magnetic resonance spectrometry. Tenellin is formed by condensation of an acetate-derived polyketide chain with a phenylpropanoid unit that may be phenylalanine. Alternate carbon atoms of the polyketide chain were labelled with sodium [1(-13C)]- and [2-(13C]-acetate; sodium [1,2-(13C)]acetate was incorporated as intact two-carbon units, the presence of which in tenellin was apparent from coupling between adjacent 13C-enriched carbons. Substituent methyl groups of the polyketide-derived alkenyl chain were labelled with L-[Me-13C]methionine. The labelling patterns from DL-[carboxy-13C]phenylalanine and DL-[alpha-13C]phenylalanine indicated a rearrangement of the propanoid component at some stage in the synthesis. The mass spectrum of tenellin from cultures administered L-[15N]phenylalanine showed isotopic enrichment similar to that obtained with 13C- or 14C-labelled phenylalanine. During incorporation of L-[carboxy-14C, beta-3H]phenylalanine 96% of the tritium label was lost, discounting the possibility of a 1,2-hydride shift during biosynthesis of the metabolite.     

Rat hepatic uroporphyrinogen III cosynthase: Purification,properties, and inhibition by metal ions

Rat hepatic uroporphyrinogen III cosynthase has been isolated and purified 50-fold with a 36% yield by ammonium sulfate fractionation and sequential chromatography on DEAE-Sephacel and Sephadex G-100SF. Inhibition of uroporphyrinogen III formation with increasing porphobilinogen concentration was observed. Cosynthase was shown to be thermolabile, and a time-dependent loss of enzyme activity during reaction with uroporphyrinogen I synthase and porphobilinogen was observed. The pH optimum for the complete system (synthase and cosynthase) was pH 7.8 in 50 mm Tris-HCl or 50 mm sodium phosphate buffer. Various metals (KCl, NaCl, MgCl₂, CaCl₂) increased formation of Uroporphyrinogen III. Heavy metals including ZnCl₂, CdCl₂, and CuCl₂ were shown to selectively inhibit cosynthase activity, whereas other metals (HgCl₂, PbCl₂) were less selective and inhibited both synthase and cosynthase at similar concentrations.     

Phytoplankton and zooplankton of the Westport River Estuary,Massachusetts (USA)

Zooplankton and phytoplankton samples were simultaneously collected at approximately biweekly intervals over most of an annual cycle in the Westport River Estuary, Massachusetts. Phytoplankton numbers were overwhelmingly dominated throughout the study by athecate nanoplankton <5 µm in diameter. The zooplankton was primarily composed of copepod nauplii. Periods of occurrence of other zooplankters such as adult copepods, marine cladocerans, meroplankters and ctenophores were similar to those recorded for adjacent estuaries. Our results emphasize the abundance of smaller plankters that have been historically undersampled.