Chymotryptic-like hydrolysis of luliberin (LH-RF) by an adenohypophyseal enzyme of high molecular weight

An enzyme that hydrolyzes the fluorogenic chymotrypsin substrate glutaryl-Gly-Gly-Phe-β-naphthylamide has been partially purified from extracts of bovine anterior pituitaries. Like chymotrypsin, this enzyme hydrolyzes the neuropeptide Luliberin (LH-RF, <Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂) at the carboxyl-side of Trp and Tyr, but it differs from the pancreatic protease by its high molecular weight, insensitivity towards OH-reactive agents and other enzymechemical parameters. It seems, however, to be identical to the “cation-sensitive neutral endopeptidase”. In the course of this study evidence has also been obtained that LH-RF is not degraded by the cystinyl-arylamidase.     

SV40 chromatin structure is not essential for viral gene expression

The biological activity and the fate of SV40 DNA (minichromosomes, DNA I, DNA II, DNA III) were tested in culture cells by immunofluorescence staining and blot analysis. Following microinjection of 2-4 circular SV40 molecules (minichromosomes, DNA I, DNA II) into the cytoplasm or the nuclei of monkey and rat cells, T- and V-antigen synthesis was demonstrable in nearly every recipient cell. Only linear DNA induced T-antigen synthesis with a very low efficiency after cytoplasmic injection. This low activity correlates with a rapid degradation of DNA III in the recipient cells. Further modifications observed immediately after injection are relaxation of superhelical molecules and formation of high-Mr DNA. Assembly of the injected DNA into SV40 chromatin-like structure, however, occurred only late after early viral gene expression.     

Pitcher geometry facilitates extrinsically powered ‘springboard trapping' in carnivorous Nepenthes gracilis pitcher plants

Carnivorous pitcher plants capture insects in cup-shaped leaves that function as motionless pitfall traps. Nepenthes gracilis evolved a unique ‘springboard'' trapping mechanism that exploits the impact energy of falling raindrops to actuate a fast pivoting motion of the canopy-like pitcher lid. We superimposed multiple computed micro-tomography images of the same pitcher to reveal distinct deformation patterns in lid-trapping N. gracilis and closely related pitfall-trapping N. rafflesiana. We found prominent differences between downward and upward lid displacement in N. gracilis only. Downward displacement was characterized by bending in two distinct deformation zones whist upward displacement was accomplished by evenly distributed straightening of the entire upper rear section of the pitcher. This suggests an anisotropic impact response, which may help to maximize initial jerk forces for prey capture, as well as the subsequent damping of the oscillation. Our results point to a key role of pitcher geometry for effective ‘springboard'' trapping in N. gracilis.     

Effect of gibberellic Acid on crown gall tumor induction in aging primary pinto bean leaves

Gibberellic acid was tested for its effect on tumor induction by Agrobacterium tumefaciens in primary pinto bean (Phaseolus vulgaris) leaves in various stages of development. The hormone was found to promote tumor induction in partially aged leaves but did not effect tumor induction in very young leaves or in fully matured leaves. It is suggested that the natural loss of susceptibility to tumor induction in maturing pinto bean leaves is associated with a concomitant loss of endogenous gibberellins and/or a sensitivity to gibberellins.     

Resveratrol,an Ingredient of Wine,Acts Synergistically with Ara-C and Tiazofurin in HL-60 Human Promyelocytic Leukemia Cells

Resveratrol (RV), a naturally occurring stilbene derivative, is a potent free radical scavenger causing a number of biochemical and antineoplastic effects. It was shown to induce differentiation and apoptosis in leukemia cells and was also identified as an inhibitor of ribonucleotide reductase (RR), a key enzyme of DNA synthesis.

In this study, we report about the biochemical effects of RV in HL-60 human promyelocytic leukemia cells. RV effectively inhibited in situ RR activity. Furthermore, incubation of HL-60 cells with RV significantly decreased intracellular dCTP, dTTP, dATP and dGTP concentrations. In growth inhibition and clonogenic assays, RV acted synergistically with both Ara-C and tiazofurin in HL-60 cells. We conclude that RV could become a viable candidate as one compound in the combination chemotherapy of leukemia and therefore deserves further in vitro and in vivo testing.     

A registry for exposure and population health in the Altai region affected by fallout from the Semipalatinsk nuclear test site

A registry of the rural population in the Altai region exposed to fallout from nuclear tests at the Semipalatinsk test site (STS) was established more than four decades after the first Soviet nuclear explosion on August 29, 1949. Information about individuals living in an exposed and a control area was collected using all available local sources, such as kolkhoz documentation, school registries, medical treatment records and interviews with residents. As a result, a database comprising an exposed group of 39 179 individuals from 53 Altai region villages, 6769 external and 3303 internal controls was compiled. For several settlements, effective dose estimates reached the level of 1.5 Sv, while the average effective dose estimate in the exposed group was 340 mSv. Dosimetric data, vital status information and health records gathered at rayon and village medical facilities are held in the registry. Cause-of-death information for deceased residents is obtained from death registration forms archived at the Altai region vital statistics office. At present, a follow-up of approximately 40% of the population exposed in 1949 has been done. More will be added by searching for migrants to the larger towns of the Altai region, i.e. Barnaul, Rubtsovsk and Biisk. In order to assess the influence of radiation exposure, analytical studies with a case-control design for stomach and lung cancer are currently being prepared. The number of known cases is sufficient to detect an odds ratio of 1.5 at the 95% confidence level. Epidemiological studies in populations affected by fallout from STS may be equally important to the atomic bomb survivors’ study for the direct quantification of radiation effects. The range of exposure rates experienced will extend the acute high-dose-rate findings from Hiroshima/Nagasaki towards acute and protracted lower exposures, which are more relevant for radiation protection issues. Received: 3 March 1999 / Accepted in revised form: 8 June 1999     

Differential influence of Pomphorhynchus laevis (Acanthocephala) on the behaviour of native and invader gammarid species.

Although various species of acanthocephalan parasites can increase the vulnerability of their amphipod intermediate hosts to predation, particularly by altering their photophobic behaviour, their influence on the structure of amphipod communities and the success of invader species has so far received little attention. We compared the prevalence and behavioural influence of a fish acanthocephalan parasite, Pomphorhynchus laevis, in two species of amphipods, Gammarus pulex and Gammarus roeseli in sympatry in the river Ouche (Burgundy, eastern France). There, G. pulex is a resident species, whereas G. roeseli is a recent coloniser. Both uninfected G. pulex and G. roeseli were strongly photophobic, although less so in the invading species. However, there was no significant difference in reaction to light between infected and uninfected G. roeseli, whereas infected G. pulex were strongly photophilic. We discuss our results in relation to the parasite's ability to manipulate invading host species, the possibility that resistant individuals have been selected during the invasion process, and the role that acanthocephalan parasites can play in shaping the structure of amphipod communities.