Toxicity Assessment of Volatile Organic Compounds in Poplar Trees

A method is described to assess the toxicity of selected volatile organic compounds (VOCs) in poplar trees. The method is illustrated for a specific aqueous mixture of VOCs that contaminates the groundwater at a site for which phytoremediation was being considered. The VOC mixture contained a variety of aromatic compounds, chlorinated aliphatics, and alcohols. Poplar tree cuttings planted in 50-gallon barrels in the greenhouse were watered via subirrigation. The subirrigant contained either a low (42 mg/L), medium (85 mg/L), or high (169 mg/L) dose of the VOC mixture, or water only (experimental control). Phytotoxicity was evaluated by measuring the physiological parameters of stomatal conductance, shoot elongation, and biomass production. Two experiments are briefly described: (1) The poplar tree cuttings were allowed to become established in the barrels and then treated to gradually increasing concentrations of the VOC mixture until the final dose was reached. The objective was to establish a detailed dose-response relationship. (2) The poplar tree cuttings were given the low, medium, or high dose of the VOC mixture immediately after planting. The aim of this experiment was to determine if the VOC mixture would be inhibitory to root development. Phytotoxic effects were not observed in either experiment.     

Erbliches Pankreaskarzinom

The dismal prognosis for ductal pancreatic adenocarcinoma is mainly attributable to advanced tumor stages at the time of diagnosis. Familial pancreatic cancer is an established hereditary tumor syndrome that is responsible for about 3% of pancreatic cancer cases. Therefore, analysis of family history may help to identify individuals at increased risk for the development of pancreatic cancer. In addition to family history, such high risk individuals can be identified by screening for mutations in tumor predisposition genes and/or analyses of exogenous risk factors. Invasive screening methods for the identification of early pancreatic cancer could also be applied to provide the option of a timely curative pancreatectomy. The benefit of a clinical, genetically based screening approach for individuals at high riskis currently being investigated in prospective studies.     

Isolation of hydrogenase from the thermophilic cyanobacterium Mastigocladus laminosus

Summary A soluble, cytoplasmic hydrogenase was detected and partially purified from Mastigocladus laminosus. It was found to be unstable but could be stabilized to some extent by Mg⁺⁺; 50% of the activity remained after one week in air at 4 °C.     

The sudden recruitment of gamma-tubulin to the centrosome at the onset of mitosis and its dynamic exchange throughout the cell cycle, do not require microtubules.

gamma-Tubulin is a centrosomal component involved in microtubule nucleation. To determine how this molecule behaves during the cell cycle, we have established several vertebrate somatic cell lines that constitutively express a gamma-tubulin/green fluorescent protein fusion protein. Near simultaneous fluorescence and DIC light microscopy reveals that the amount of gamma-tubulin associated with the centrosome remains relatively constant throughout interphase, suddenly increases during prophase, and then decreases to interphase levels as the cell exits mitosis. This mitosis-specific recruitment of gamma-tubulin does not require microtubules. Fluorescence recovery after photobleaching (FRAP) studies reveal that the centrosome possesses two populations of gamma-tubulin: one that turns over rapidly and another that is more tightly bound. The dynamic exchange of centrosome-associated gamma-tubulin occurs throughout the cell cycle, including mitosis, and it does not require microtubules. These data are the first to characterize the dynamics of centrosome-associated gamma-tubulin in vertebrate cells in vivo and to demonstrate the microtubule-independent nature of these dynamics. They reveal that the additional gamma-tubulin required for spindle formation does not accumulate progressively at the centrosome during interphase. Rather, at the onset of mitosis, the centrosome suddenly gains the ability to bind greater than three times the amount of gamma-tubulin than during interphase.     

NADP-dependent dehydrogenases in rat liver parenchyma. II. Comparison of qualitative and quantitative G6PDH distribution patterns with particular reference to sex differences.

Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25 +/- 1.56 U/g dry weight in zone 1 and 2.08 +/- 0.46 U/g dry weight in zone 3 of male and 7.21 +/- 1.03 U/g dry weight in zone 1 and 11.10 +/- 2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.     

NADP-dependent dehydrogenases in rat liver parenchyma

Summary Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25±1.56 U/g dry weight in zone 1 and 2.08±0.46 U/g dry weight in zone 3 of male and 7.21±1.03 U/g dry weight in zone 1 and 11.10±2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.Supported by a grant from the SFB 46 (Molgrudent)