Effects of G2-checkpoint dynamics on low-dose hyper-radiosensitivity

Journal of Mathematical Biology - In experimental studies, it has been found that certain cell lines are more sensitive to low-dose radiation than would be expected from the classical...     

Activation of cytosolic phospholipase A2 in Her14 fibroblasts by hydrogen peroxide: a p42/44(MAPK)-dependent and phosphorylation-independent mechanism

Reactive oxygen species (ROS) have been implicated in the pathogenesis of diseases as well as various normal cellular processes. It has been suggested that ROS function as mediators of signal transduction, given that they can mimic growth factor-induced signaling. The ROS H2O2 has been reported to activate phospholipase A2 (PLA2) and, therefore, we investigated if and through which pathway ROS activate cytosolic PLA2 (cPLA2) in Her14 fibroblasts. cPLA2 was activated concentration-dependently by H2O2 in a transient manner. In addition, the lipophilic cumene hydroperoxide was shown to induce cPLA2 activity in the same manner. H2O2-induced cPLA2 activity in Her14 cells was partially phosphorylation-dependent, which was mediated through the Raf-MEK-p42/44(MAPK) pathway and occurred partially through a phosphorylation-independent mechanism. ROS can lead to changes in the (micro) viscosity of membranes due to the presence oxidized lipids, thereby increasing the substrate availability for cPLA2. In support of this, treatment of Her14 cells with H2O2 induced lipid peroxidation time-dependently as determined from degradation of lipid arachidonate and linoleate and the formation of aldehydic degradation products. Furthermore, H2O2 induced translocation of cPLA2 to the membrane fraction in a calcium-independent fashion, with a concomitant increase in cPLA2 activity. Collectively, the results suggest that oxidative stress-induced cPLA2 activity is partially phosphorylation-dependent and is further increased due to increased substrate availability by the action of ROS on membranes.     

Characterization of green seed,an enhancer of abi3-1 in Arabidopsis that affects seed longevity

Seeds are usually stored in physiological conditions in which they gradually lose their viability and vigor depending on storage conditions, storage time, and genotype. Very little is known about the underlying genetics of seed storability and seed deterioration. We analyzed a mutant in Arabidopsis disturbed in seed storability. This mutant was isolated as a grs (green-seeded) mutant in an abi3-1 (abscisic acid 3) mutant background. Genetic and physiological characterization showed that the monogenic grs mutant was not visibly green seeded and mapped on chromosome 4. This enhancer mutation did not affect the ABA sensitivity of seed germination or seed dormancy but was found to affect seed storability and seedling vigor. Seed storability was assessed in a controlled deterioration test, in which the germination capacity of the mutant decreased with the duration of the treatment. The decrease in viability and vigor was confirmed by storing the seeds in two relative humidities (RHs) for a prolonged period. At 60% RH, the mutant lost germinability, but storage at 32% RH showed no decrease of germination although seed vigor decreased. The decrease in viability and vigor could be related to an increase in conductivity, suggesting membrane deterioration. This was not affected by light conditions during imbibition, expected to influence the generation of active oxygen species. During seed maturation, ABI3 regulates several processes: acquiring dormancy and long-term storability and loss of chlorophyll. Our results indicate that GRS is a common regulator in the latter two but not of dormancy/germination.     

Substituted azoloquinolines and -quinazolines as new potent farnesyl protein transferase inhibitors

A series of (4-chlorophenyl)--(1-methyl-1H-imidazol-5-yl)azoloquinolines and -quinazolines was prepared. These compounds displayed potent Farnesyl Protein Transferase inhibitory activity and tetrazolo[1,5-a]quinazolines are promising agents for oral in vivo inhibition.     

Responses ofBacillus subtilis spores to space environment: Results from experiments in space

Onboard of several spacecrafts (Apollo 16, Spacelab 1, LDEF), spores ofBacillus subtilis were exposed to selected parameters of space, such as space vacuum, different spectral ranges of solar UV-radiation and cosmic rays, applied separately or in combination, and we have studied their survival and genetic changes after retrieval. The spores survive extended periods of time in space — up to several years —, if protected against the high influx of solar UV-radiation. Water desorption caused by the space vacuum leads to structural changes of the DNA; the consequences are an increased mutation frequency and altered photobiological properties of the spores. UV-effects, such as killing and mutagenesis, are augmented, if the spores are in space vacuum during irradiation. Vacuum-specific photoproducts which are different from the spore photoproduct may cause the synergistic response of spores to the simultaneous action of UV and vacuum. The experiments provide an experimental test of certain steps of the panspermia hypothesis.Presented at the Session Water in the Solar System and Its Role in Exobiology during the 26th General Assembly of the European Geophysical Society, 22–26 April 1991 in Wiesbaden, Germany     

The ventricular system in neuroendocrine mechanisms

Summary This investigation has utilized a correlative scanning-transmission electron microscopic technique in the analysis of the primate cerebral ventricular system. This approach has demonstrated a complex network of supraependymal cellular elements upon the walls of the third cerebral ventricle in direct contact with the ventricular lumen. Type I neuronal-like cells and type II histiocytic-like cells with potential phagocytic capabilities have been observed in large numbers throughout the third ventricle. Type I neuron-like cells are discussed in the context that they may represent a population of receptor-cells which serve to assess ambient changes in the composition of bioactive peptides in the cerebrospinal fluid and may serve as a supraependymal network that integrates the endocrine hypothalamus with other circumventricular organs which may also be sites of neuroendocrine transduction.Supported by USPHS Program Project Grant NS-11642Career Development Awardee GM K04 70001     

Silage studies. IV. The microflora on the surface of some fodder plants at different stages of maturity

Summary A comparison is made of the bacterial populations on the surface of some fodder plants and the populations on corresponding plant materials after collecting into a silo.Estimations are made of the total number of bacteria and fungi, and of the number of lactic acid bacteria and spore-forming anaerobes.The equilibrium between acidifying and ammonifying organisms is discussed. Antibiotic phenomena within the floras have been studied.These studies are still in progress. We are indebted to the Swedish Foundation: Fonden för främjande av forsknings- och försöksverksamheten på jordbrukets område for generous financial support. We also gratefully acknowledge the encouraging interest and support of ProfessorRagnar Nilsson.     

Über Glykoproteideinschlüsse in den Trophoblastzellen der menschlichen Plazenta und die Frage ihres Zusammenhangs mit der Bildung von Gonadotropin

Summary In some of the basophilic trophoblastic cells of the basal plate and islands of the mature human placenta there are glycoprotein inclusions, many of which are within vacuoles. As established by the histochemical results these inclusions are composed of a neutral mucopolysaccharide and a basophilic protein with SH groups. They gradually increase in number from the 4th month of pregnancy and are not influenced by labor. From the first to the fourth month of gestation small vacuoles, initially infra-nuclear but later supranuclear, may be seen in the syncitial cells of the villi; these likewise contain glycoprotein granules. The same inclusions are to be found in some trophoblastic cells of the chorionic plate and of the chorion laeve, and in an occasional epithelial cell of the amnion.On the basis of the histochemical behavior of these inclusions, their similarity with the -granules of the hypophysis, and the obvious high activity of the trophoblastic cells which bear them, it is postulated that these inclusions contain gonadotropin. Their occurrence during pregnancy parallels the biochemical concentration and immunofluorescent histological demonstration of gonadotropin in the placenta. Thus, at the end of pregnancy the basal trophoblastic cells of the human placenta appear to form at least two different hormones: relaxin, probably represented morphologically by the acidophilic protein inclusions (described elsewhere), and gonadotropin most likely represented by the basophilic glycoprotein inclusions.