Secreted phospholipase A2-IIA modulates key regulators of proliferation on astrocytoma cells

Human group IIA secreted phospholipase A₂ (sPLA₂-IIA) has been characterized in numerous inflammatory and neoplastic conditions. sPLA₂-IIA can either promote or inhibit cell growth depending on the cellular type and the specific injury. We have previously demonstrated that exogenous sPLA₂-IIA, by engagement to a membrane structure, induces proliferation and activation of mitogen-activated protein kinases cascade in human astrocytoma cells. In this study, we used human astrocytoma 1321N1 cells to investigate the key molecules mediating sPLA₂-IIA-induced cell proliferation. We found that sPLA₂-IIA promoted reactive oxygen species (ROS) accumulation, which was abrogated in the presence of allopurinol and DPI, but not by rotenone, discarding mitochondria as a ROS source. In addition, sPLA₂-IIA triggered Ras and Raf-1 activation, with kinetics that paralleled ERK phosphorylation, and co-immunoprecipitation assays indicated an association between Ras, Raf-1 and ERK. Additionally, Akt, p70 ribosomal protein S6 kinase, and S6 ribosomal protein were also phosphorylated upon sPLA₂-IIA treatment, effect that was abrogated by N -acetylcysteine or LY294002 treatment indicating that ROS and phosphatidylinositol 3 kinase are upstream signaling regulators. As the inhibitors N -acetylcysteine, PD98059, LY294002 or rapamycin blocked sPLA₂-IIA-induced proliferation without activation of the apoptotic program, we suggest that inhibition of these intracellular signal transduction elements may represent a mechanism of growth arrest. Our results reveal new potential targets for therapeutic intervention in neuroinflammatory disorders and brain cancer in particular.     

Influence of Different Intensities of Pesticide Management on the Structure of Ground Beetle Communities (Coleoptera; Carabidae) During a Crop Rotation

Investigations were lead through in the years 1992 to 1995 at Halle (Saale) on a stand 24ha in size. Aim of the survey was to record the effects of graduate intensities of pest management on ground beetles. For this purpose 6 plots were installed on the field, 72 ‐ 200m each. Two plots served as control areas, without any application of pesticides. On two other plots intensive chemical pest management was applied. On the last two plots treatments were lead through considering the economic thresholds for weeds, fungal and insect pests according to the rules of integrated pest management. Ground beetles were sampled by using pitfall traps. In 1992 complementary methods to the pitfall trap catches, pick up of beetles after pesticide applications and semi-field-tests, on all plots were lead through. The graduate pest management was carried out 1992 and 1993 in winter wheat and 1994 in sugar beet stands. The last crop in 1995 was summer barley. In this year all plots were treated conventionally. In 1992 the differences between the total catches of ground beetles on the experimental sites were not high. In the following year most species were predominant on the control sites. In 1994 in sugar beet mechanical weed control was carried out on the control plots. The intensity of pesticide management between intensive and integrated plots differs only small. The amounts of ground beetles reached similar values on all experimental sites. In contrast to the expections the trap catches of ground beetles in the final investigations in summer barley were highest in the plots which had been treated integrated in the years before. The smallest amount was sampled in the former intensively managed sites. Renunciation of pesticides often is connected with economic losses which are not tolerable. If management is conducted considering the economic thresholds corresponding to the principles of integrated pest management negative effects on the economy of nature should not be expected for the longer term.     

Rab and Arf proteins at the crossroad between membrane transport and cytoskeleton dynamics

The intracellular movement and positioning of organelles and vesicles is mediated by the cytoskeleton and molecular motors. Small GTPases like Rab and Arf proteins are main regulators of intracellular transport by connecting membranes to cytoskeleton motors or adaptors. However, it is becoming clear that interactions between these small GTPases and the cytoskeleton are important not only for the regulation of membrane transport. In this review, we will cover our current understanding of the mechanisms underlying the connection between Rab and Arf GTPases and the cytoskeleton, with special emphasis on the double role of these interactions, not only in membrane trafficking but also in membrane and cytoskeleton remodeling. Furthermore, we will highlight the most recent findings about the fine control mechanisms of crosstalk between different members of Rab, Arf, and Rho families of small GTPases in the regulation of cytoskeleton organization.     

Expression of the inducible nitric oxide synthase gene in diaphragm and skeletal muscle

Thompson, Marita, Lisa Becker, Debbie Bryant, Gary Williams,Daniel Levin, Linda Margraf, and Brett P. Giroir. Expression ofthe inducible nitric oxide synthase gene in diaphragm and skeletal muscle. J. Appl. Physiol. 81(6):2415-2420, 1996.Nitric oxide (NO) is a pluripotent molecule thatcan be secreted by skeletal muscle through the activity of the neuronalconstitutive isoform of NO synthase. To determine whether skeletalmuscle and diaphragm might also express the macrophage-inducible formof NO synthase (iNOS) during provocative states, we examined tissuefrom mice at serial times after intravenous administration ofEscherichia coli endotoxin. In thesestudies, iNOS mRNA was strongly expressed in the diaphragm and skeletalmuscle of mice 4 h after intravenous endotoxin and was significantlydiminished by 8 h after challenge. Induction of iNOS mRNA was followedby expression of iNOS immunoreactive protein on Western immunoblots.Increased iNOS activity was demonstrated by conversion of arginine tocitrulline. Immunochemical analysis of diaphragmatic explants exposedto endotoxin in vitro revealed specific iNOS staining in myocytes, inaddition to macrophages and endothelium. These results may be importantin understanding the pathogenesis of respiratory pump failure duringseptic shock, as well as skeletal muscle injury during inflammation ormetabolic stress.

     

Protein gene product 9.5-immunoreactive nerve fibres and cells in human skin

Summary Sections of human skin were processed according to the indirect immunofluorescence technique with a rabbit antiserum against human protein gene product 9.5 (PGP 9.5). Immunoreactivity was detected in intraepidermal and dermal nerve fibres and cells. The intraepidermal nerves were varicose or smooth with different diameters, running as single processes or branched, straight or bent, projecting in various directions and terminating in the stratum basale, spinosum or granulosum. The density of the intraepidermal nerves varied between the different skin areas investigated. PGP 9.5-containing axons of the lower dermis were found in large bundles. They separated into smaller axon bundles within the upper dermis, entering this portion of the skin perpendicular to the surface. Then they branched into fibres mainly arranged parallel to the epidermal-dermal junctional zone. However, the fibres en route to the epidermis traversed the upper dermis more or less perpendicularly. Furthermore, immunoreactive dermal nerve fibres were found in the Meissner corpuscles, the arrector pili muscles, hair follicles, around the eccrine and apocrine sweat glands and around certain blood vessels. Such fibres were also observed around most subcutaneous blood vessels, sometimes heavily innervating these structures. Numerous weakly-to-strongly PGP 9.5-immunoreactive cells were found both in the epidermis and in the dermis.     

Localization of ribosomal cistrons in metaphase chromosomes of Vicia faba (L.)

Tritiated ribosomal RNA (rRNA) was prepared from the roots of Vicia faba after incubation in ³H-uridine. Separation of the nucleic acids by MAK chromatography yielded fractions of specific activity of 4–5 × 10⁵ dpm/μg. 4 + 5S, 18S and 25S RNA fractions were used for cytological hybridization on squash preparations of Vicia faba root tip meristems. Autoradiographs of the 18S and 25S RNA preparations exhibited a clear labelling in the secondary constriction of the satellite (SAT) chromosomes after exposition times of 28 weeks.