Inactivation and oxidative modification of Cu,Zn superoxide dismutase by stimulated neutrophils: the appearance of new catalytically active structures.

Bovine superoxide dismutase (SOD) was inactivated during incubation with phorbol myristate acetate-stimulated neutrophils. In addition, stimulated neutrophils were able to disrupt the SOD structure. Inactivation and structural damage were dependent on the action of hypochlorous acid, an oxidant generated by the myeloperoxidase-hydrogen peroxide-chloride system of neutrophils. Incubation of SOD with stimulated neutrophils lead to long-wavelength fluorescence (ex, 350 nm; em, 450 nm) and the appearance of new structural forms with other isoelectric points. These additional forms possess catalytic activity. Generation of catalytically active new forms of SOD demonstrates the inaccessibility of the active centre of SOD to hypochlorite and may be a reason for the successful application of SOD during anti-inflammatory therapy.     

Effects of neurotropin on seizure activity in picrotoxin kindling]

It is shown that both intracerebral and intraperitoneal neurotropin administration resulted in a decrease of seizure susceptibility of preliminary picrotoxin--kindled rats. On the other hand, neurotropin did not change the course of kindling development. Under conditions of acute picrotoxin--induced seizures it was observed that preliminary cycloheximide (protein-synthesis blocker) administration abolished anticonvulsant properties of neurotropin. It is concluded that anticonvulsant effects of neurotropin are realized via modulation of endogenous peptides synthesis and, in particular, cerulein.     

Species loss leads to community closure

Global extinction of a species is sadly irreversible. At a local scale, however, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its doors for re-invasion of species lost from it. Previous studies of how communities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly generated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was removed from the community, the cascading species loss was recorded and frequently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size (and not only trophic structure) and that the reintroduction of the original species lost often is impossible. Hence, species loss does not simply leave a void potentially refilled, but permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders.     

Specific Features of the Formation of a Halo during Pathogenesis as a Response of Cereal Epidermal Cells to Penetration of Powdery Mildew Causative Agents

A cytophysiological study was carried out of the functional status of a halo as a response of the host plant to contact with a powdery mildew pathogen. Interactions of the powdery mildew causative agents with barley, wheat, wheat–wheat-grass hybrids, wheat-aegilops lines, and aegilops with different genotypic resistance lead to the expression of haloes during pathogens, which are induced by infection pegs of the primary growth tubes, appressoria, and hyphal lobes. Haloes are visualized using cytochemical reactions to proteins and scanning electron microscopy. The observed differences in the size of haloes and intensity of their staining (uniform or zonal) are related, to a great extent, to individual reactions of the plant cell at the penetration site and, to a lesser extent, to the level of genotypic resistance. An analysis of electron microscopy and cytochemistry studies suggests that the halo as a physiologically active zone is localized at the level of the plant cell plasmalemma. Active taxis of the cell organelles to the site of infection during the formation of a halo suggests that some kind of informational signals to changes in the cell metabolism are spread from the halo zone, which lead to compatible or incompatible interactions.     

Evolutionary trends in Mio-Pliocene Leporinae, based onTrischizolagus (Mammalia, Lagomorpha)

New material ofTrischizolagus dumitrescuae from Moldova and Ukraine is described. The variation of p3 inTrischizolagus shows the gradual shift of morphotype frequencies from the ‘Hypolagus’ pattern in Turolian through the mixture of three patterns (including ‘Nekrolagus’ morphotype) in Early Ruscinian to the dominant ‘Alilepus’ pattern in the Late Ruscinian samples. These transformations took place parallel to that of the North AmericanNekrolagus. Probably North AmericanSylvilagus, Brachylagus, andRomerolagus had an North American origin fromNekrolagus, whereas Eurasiatic and AfricanOryctolagus, Caprolagus, Nesolagus, andPoelagus could have originated in the Old World fromTrischizolagus.     

Phytochrome A regulates red-light induction of phototropic enhancement in Arabidopsis.

Phytochrome A (phyA) and phytochrome B photoreceptors have distinct roles in the regulation of plant growth and development. Studies using specific photomorphogenic mutants and transgenic plants overexpressing phytochrome have supported an evolving picture in which phyA and phytochrome B are responsive to continuous far-red and red light, respectively. Photomorphogenic mutants of Arabidopsis thaliana that had been selected for their inability to respond to continuous irradiance conditions were tested for their ability to carry out red-light-induced enhancement of phototropism, which is an inductive phytochrome response. We conclude that phyA is the primary photoreceptor regulating this response and provide evidence suggesting that a common regulatory domain in the phyA polypeptide functions for both high-irradiance and inductive phytochrome responses.     

Studies on the frequency and associations of equine leucocyte antigens in sarcoid and summer dermatitis

The equine leucocyte antigen (ELA) types and the clinical diagnosis for equine sarcoid and summer dermatitis were evaluated in 2026 horses representing five breeds. Data were analysed in unrelated animals and in family material. In the case of equine sarcoid, a strong association was observed between the ELA class II DW13 antigen and its effect on Swiss (cP < 0·001), French (cP < 0·0001) and Irish (cP < 0·01) Warmblood horses. The class I antigen A3 occurred more frequently in sarcoid-affected French horses (cP < 0·001). These results confirm our earlier findings (Gerber et al. 1988). Among Freiberger horses, which lack the ELA DW13 and A3 specificities, a breed-specific class I antigen, ABe108, displayed an increased frequency (cP < 0·05) in the affected group. Among Arabian horses, a tendency for increased frequency of the A1 antigen was observed in the affected animals, but the number of affected horses is too small for statistical significance. The Mendelian segregation in diseased half-siblings by ELA DW13 heterozygous stallions showed a strong association (P < 0·0001) between the inherited DW13 antigen and susceptibility to the sarcoid effect. In the case of summer dermatitis, previously published data (Marti et al. 1992) have been extended. The ELA types in four multiple-case families, founded by the same stallion, were analysed for an association with the effect of sarcoid. Eight out of nine ELA-typed affected offspring inherited the paternal haplotype A15, DW23 in contrast to nonaffected offspring where three out of 12 displayed these antigens (P < 0·005). Moreover, the ELA haplotypes of 11 out of 12 informative affected half-siblings sired by another stallion inherited the paternal haplotype A3, W12, DW23 (P < 0·05). Our findings demonstrate statistically significant associations between certain ELA antigens and two equine diseases. It is still unknown if the major histocompatibility complex (MHC) molecules themselves or another linked gene(s) play a role in the pathogenesis of these conditions.     

Aerobic heat shock activates trehalose synthesis in embryos of Artemia franciscana.

Encysted embryos (cysts) of the brine shrimp, Artemia franciscana, contain large amounts of trehalose which they use as a major substrate for energy metabolism and biosynthesis for development under aerobic conditions at 25 degrees C. When cysts are placed at 42 degrees C (heat shock) these pathways stop, and the cysts re-synthesize the trehalose that was utilized during the previous incubation at 25 degrees C. Glycogen and glycerol, produced from trehalose at 25 degrees C, appear to be substrates for trehalose synthesis during heat shock. Anoxia prevents trehalose synthesis in cysts undergoing heat shock. These results are consistent with the view that trehalose may play a protective role in cells exposed to heat shock, and other environmental insults, in addition to being a storage form of energy and organic carbon for development.