Über Geweihentwickelung und Geweihbildung

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Salinx repens L.

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Grosswardein bis jetzt beobachteten Phaner ogamen

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Long-Time Respiration of Contaminated Soil Samples during Laboratory Storage under Different Conditions

Soil samples have to be stored during transportation and investigation in the laboratory if they are not analyzed directly at the site. Existing standards and investigations give no recommendations on handling and storage of soil materials for (eco-)toxicological investigations. The objective of this investigation was to determine if microbial turnovers and losses of volatile organic compounds mainly cause storage-dependent changes in soil samples. Furthermore, recommendations are given for storage of soil reserve samples for toxicological investigations. During 18 months of storage, the microbial respiration of six highly contaminated soil samples was determined. Physicochemical characteristics, such as contaminant and nutrient content, were analyzed before and after storage. From the investigations it can be concluded that the oxygen consumption depends on the storage temperature, organic matter content, nutrient content, and total content of toxic substances. Based on the results, a flow scheme was derived that could be a useful tool for a sequential approach to determine the storage capacity of contaminated soil samples and sites for toxicological investigations.     

Cl transport in the frog cornea: An electron-microprobe analysis

Summary The intracellular electrolyte concentrations of the bullfrog corneal epithelium have been determined in thin freezedried cryosections using the technique of electron-microprobe analysis. Under control conditions, transepithelial potential short-circuited and either side of the cornea incubated in Conway's solution, the mean intracellular concentrations (in mmol/kg wet weight) were 8.0 for Na, 18.4 for Cl and 117.3 for K. These values are in good agreement with ion activities previously obtained by Reuss et al. (Am. J. Physiol. 244:C336–C347, 1983) under open-circuit conditions. From a comparison of the chemical concentrations and activities of Na and K a mean intracellular activity coefficient of 0.75 is calculated. For small ions no significant differences between nuclear and cytoplasmic concentration values were detectable. The Cl concentrations in the different epithelial layers were virtually identical and showed parallel changes at varying states of Cl secretion, suggesting that the epithelium represents a functional syncytium. For Na a concentration gradient between theouter and inner epithelial layer was observed, which can be accounted for by two different models of epithelial cooperation. The behavior of the intracellular Na and Cl concentrations after removal of Na, Cl or K from the outer or inner bathing medium provides support for a passive electrodiffusive Cl efflux across the apical membrane and a Na-coupled Cl uptake across the basolateral membrane. The results are inconclusive with regard to the exact mechanism of Cl uptake, indicating either a variable stoichiometry of the symporter or the presence of more than one transport system. Furthermore, a dependence of intracellular Cl on HCO₃ and CO₂ was observed. Extracellular measurements in corneal stroma demonstrated that ion concentrations in this space are in free equilibrium with the inner bath.     

Tumorigenesis in colorectal tumors from patients with hereditary non-polyposis colorectal cancer

Tumorigenesis of colorectal cancer in patients with hereditary non-polyposis colorectal cancer (HNPCC) has been postulated to follow a different pathway from that of sporadic colorectal tumors. A characteristic of HNPCC-associated tumors is the replication error phenotype. We studied tumorigenesis in 8 fresh-frozen and 67 paraffin-embedded colorectal tumors derived from 29 families with HNPCC or a familial aggregation of colorectal cancer. By using intragenic markers, inactivation of the wild-type allele of hMLH1 was shown to occur through loss of heterozygosity and not through a somatic point mutation. Microsatellite instability is very common and occurs early in almost all colorectal tumors from HNPCC patients. Transforming growth factor β type II receptor (TβRII) mutations occur in these tumors at a high frequency. Of colorectal cancers from families with HNPCC, 63% have frameshift mutations in TβRII, compared with 10% of sporadic colorectal cancers. APC and K-RAS mutations appear to be as frequent in the HNPCC tumors as in the sporadic counterpart. Received: 3 March 1997 / Accepted: 23 June 1997     

Nonlinear mathematical models for the origin of asymmetry in biological molecules

The origin of chemical chirality is probably associated with a difference in the initial concentrations of two separate populations of primeval organic molecules and possibly even two types of primeval organisms and amplified by nonlinear kinetic processes leading to the death of one population. This theory, as originally developed by F. C. Frank of the University of Bristol, is reviewed in this paper with additional derivations, discussions and generalizations. The possible effect of asymmetry in the rate constant is compared to the role of statistical fluctuations, and it is shown, that within the simple model investigated here that the role of statistical fluctuations is much more important for the death of one isomer. In the unlikely absence of any fluctuations, the nonlinear kinetic processes amplify the asymmetry in the rate constant and lead to the death of one enanthiomorph. The role of spatial diffusion is discussed, and it is shown that in the presence of a local excess of one enanthiomorph this excess would have spread in space and grown, destroying the opposite enanthiomorph. If the total population of both enanthiomorphs was exactly composed of equal parts of both types, but local fluctuation increased one type at one place and decreased the same type at a different location, the diffusion and growth rate would have caused spatial separation in the population of both enanthiomorphs. For generalnth order nonlinear symmetric rate processes (incorporating multitudes of reactions and general diffusion), it is shown that if initially two populations of enanthiomorphs were exactly the same at all locations, then for all times both populations would have increased and remained equal to each other. Mathematical model was constructed for stereoscopic autocatalysis suggested by Calvin. It was found that under certain special local conditions in the presence of large fluctuation it is possible indeed to have growth of only one type of isomer. Various approximate methods and numerical solutions are presented in order to facilitate the handling of nonlinear rate equations.     

Association of red cell glucose-6-phosphate dehydrogenase with haemoglobinopathies

A total of 1,112 randomly selected Saudi Arabs, of both sexes, living in Jeddah and the surrounding areas were screened for the phenotypic distribution of red cell glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). They were also investigated for haemoglobin and for thalassaemia. Phenotyping of the haemoglobins and the red cell enzymes was carried out by starch gel electrophoresis and the dye-decolouration screening test, while the investigation for thalassaemia was carried out by globin-chain biosynthesis, followed by column chromatography. The red cell Gd- alleles were significantly associated with the sickle-cell gene in both the males (chi 2(1): AS-28.80; SS-4.89) and females (chi 2(1): AS-10.99; SS-13.16). A similar association was also observed between G6PD deficiency and thalassaemias in males (chi 2(1): alpha-thalassaemia - 3.13; beta-thalassaemia - 11.06) and females (chi 2(1): alpha-thalassaemia - 6.63). However, no such association was detected between red cell 6PGD types and haemoglobin genes. The results suggest that the red cell G6PD deficiency, sickle-cell and thalassaemia genes might have evolved as a result of the same ecological factor, probably malaria.     

Myriophyllum quitense and myriophyllum ussuriense (Haloragaceae) in British Columbia,Canada

Myriophyllum quitense andM. ussuriense are added to the flora of British Columbia, Canada.Myriophyllum quitense has not been previously reported in Canada, and this is the first report ofM. ussuriense for the North American continent. Problems with the identification of these species, and their distributions and habitats are discussed. The somatic chromosome numbers of 2n=42 forM. quitense and 2n=21 forM. ussuriense were found. A key for the identification ofMyriophyllum taxa growing in British Columbia is given.