Cytosolic acidification as a signal mediating hyperosmotic stress responses in Dictyostelium discoideum

Background  

Dictyostelium cells exhibit an unusual response to hyperosmolarity that is distinct from the response in other organisms investigated: instead of accumulating compatible osmolytes as it has been described for a wide range of organisms, Dictyostelium cells rearrange their cytoskeleton and thereby build up a rigid network which is believed to constitute the major osmoprotective mechanism in this organism. To gain more insight into the osmoregulation of this amoeba, we investigated physiological processes affected under hyperosmotic conditions in Dictyostelium.     

Genetic diversity of Clostridium perfringens type A isolates from animals, food poisoning outbreaks and sludge

Background  

Clostridium perfringens, a serious pathogen, causes enteric diseases in domestic animals and food poisoning in humans. The epidemiological relationship between C. perfringens isolates from the same source has previously been investigated chiefly by pulsed-field gel electrophoresis (PFGE). In this study the genetic diversity of C. perfringens isolated from various animals, from food poisoning outbreaks and from sludge was investigated.     

Diet specialization in a fluctuating population of Saduria entomon: a consequence of resource or forager densities?

Intraspecific competition has been shown to favor diet specialization among individuals. However, the question whether the competition takes the form of interference or exploitative in driving diet specialization has never been investigated. We investigated individual diet specialization in the isopod Saduria entomon, in relation to forager and resource biomasses in a system that exhibits predator–prey fluctuations in density. We found that individual diet specialization was only affected by the biomass of their preferred prey (Monoporeia affinis) and not by Saduria biomass; diet specialization was higher when Monoporeia biomass was low compared to when there were high Monoporeia biomass. Population diet breadth increased at low Monoporeia biomass whereas individual diet breadths were marginally affected by Monoporeia biomass. Overall, this led to the increase in diet specialization at low Monoporeia biomass. This study shows that predator–prey dynamics might influence diet specialization in the predator and that resource biomass, not forager biomass might be important for individual diet specialization.     

Studies on the Proteolytic Enzymes of Black Aspergilli

The specificity of crystalline Asp. Saitoi proteinase on oxidized lysozyme has been investigated by application of the Sanger DNP-method.

It was found that this proteinase has a much broader specificity as compared with pepsin and Bac. subtilis proteinase.     

Interference between Hieracium pilosella and Arrhenatherum elatius in colliery spoils of north of France

Summary On colliery heaps in northern France, a tall grassland community dominated by Arrhenatherum elatius, give place to a thin grassland community in which Hieracium pilosella is very abundant. It has been claimed that Hieracium pilosella is an allelopathic species and this phenomenon has been investigated as an explanation of this phase of plant succession. The importance of osmotic pressure in tested plant extracts is demonstrated and may be responsible for presumed allelopathy. Two phytotoxic compounds have been revealed in roots+rhizomes of Hieracium pilosella (umbelliferon and apigenin-glucoside). A third phytotoxic compound was exuded by roots in hydroponic cultures (7-glucoside-umbelliferon or skimin). However no toxicity of soil has been found and no phytotoxic compounds appeared to be present in the soil under Hieracium pilosella. Experimental mixed cultures (sterile or non-sterile conditions) reveal suppression of Hieracium pilosella by Arrhenatherum elatius rather than the reverse. Allelopathy cannot be invoked to explain this plant succession.     

Molecular and physical organization of highly repetitive, undermethylated DNA from Pennisetum glaucum

A HaeIIl monomer of a repetitive DNA family from Pennisetum glaucum (L.) R. Br. cv. Massue has been cloned and characterized. The repeat is 137 bp long and is organized in head-to-tail orientation in tandem arrays. The HaeIII monomer contains 55% A+T residues. The distribution of this highly repetitive sequence in different Pennisetum species and in other cereals was investigated. The HaeIII satellite is present in all Pennisetum species investigated but absent from other genera examined. In situ hybridization revealed a centromeric localization of this sequence on all seven chromosome pairs and indicated chromosome-specific differences in copy number. Methylation was investigated by comparative restriction enzyme analysis (Msp/HpaII) which showed a greater extent of methylation of the internal C of the enzyme recognition site 5-CCGG. A South-Western analysis, using an anti-methylcytosine antibody to examine the methylation status in P. glaucum confirmed that the sequence is not highly methylated.     

The twisted pharynx phenotype in <Emphasis Type="Italic">C. elegans</Emphasis>

Background  

The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development. Several C. elegans mutants have been reported to exhibit a twisted pharynx phenotype but no careful studies have been made to directly address this phenomenon. In this study, the twisting mutants dig-1, mig-4, mnm-4 and unc-61 are examined in detail and the nature of the twist is investigated.     

<Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> invades epithelial cells and outer membrane protein A mediates interactions with epithelial cells

Background  

Acinetobacter baumannii is a nosocomial pathogen of increasing importance, but the pathogenic mechanism of this microorganism has not been fully explored. This study investigated the potential of A. baumannii to invade epithelial cells and determined the role of A. baumannii outer membrane protein A (AbOmpA) in interactions with epithelial cells.     

Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli

Summary The effect on translational fidelity of a particular mutation in the gene coding for protein S5 (rpxE) has been investigated. This mutation has the opposite effect of a restrictive strA mutation; in vivo, it relieves the restriction imposed by strA on the suppression of T4 nonsense mutants and results in hypersensitivity to streptomycin; in vitro, the presence of the altered S5 protein in 30S ribosomes results in increased intrinsic misreading. It is concluded that this mutation, ramC₃₁₉, acts as a ribosomal ambiguity mutation similar to certain mutations of protein S4 (ramA).     

Sclerophylly in Quercus cerris L. var. cerris and Phillyrea latifolia L. and edaphic relations of these species

In this study foliar sclerophyll indexes, N %, P % and K % concentrations and correlations between sclerophyll index and these parameters were investigated in Quercus cerris L. var. cerris and Phillyrea latifolia L. In addition to this soil samples were collected and some physical and chemical analysis were carried out in these samples. Finally it has been determined that sclerophyll index was correlated with leaf N % concentrations in Q. cerris var. cerris and P. latifolia and leaf K % concentration in Q. cerris var. cerris.     

Penetration and Reproduction of Meloidogyne javanica on Leguminous Crops

The use of antagonist plants is one of the most effective methods in the management of root–knot nematodes, and several plants recommended for this purpose are nitrogen‐fixing plants that act as green manure because of the amount of mass produced. The mode of action of some species has already been investigated, but this has yet to be elucidated for many plants researched as antagonists. Thus, this study aimed to assess the penetration and reproduction of Meloidogyne javanica on the root system of three species of crotalaria, as well as Mucuna deeringiana, Cajanus cajan, Canavalia ensiformis, Macrotyloma axillare and Stylosanthes capitata, with soya bean used as control treatment. Thus, plants inoculated with the nematode were assessed 5, 10, 15 and 20 days after inoculation (DAI), for nematode penetration and development. After 60 days of inoculation, the nematode reproduction factor (RF) was assessed. The plants did not prevent M. javanica penetration, which differed at varying degrees, according to the time of assessment and the plant species investigated. However, the nematode reproduction was impaired in all the leguminous crops assessed, with (RF)<1 in all the plants, while in soya bean the RF values were 2.85 and 2.56, in the respective experiments.     

Reproductive Compensation: A Review of the <Emphasis Type="Italic">Gryllus</Emphasis> spp.—<Emphasis Type="Italic">Ormia ochracea</Emphasis> Host-Parasitoid System

Calling male field crickets (Gryllus spp.) are acoustically located and subsequently parasitized by the parasitoid fly, Ormia ochracea (Diptera: Tachinidae). Parasitism by O. ochracea results in cricket death. The reproductive compensation hypothesis posits that when a host’s residual reproductive value decreases, it would be adaptive for that host to shift its resources into current reproduction. Reproductive compensation has not been observed in the cricket-fly system. Here we review the studies to date that have investigated reproductive compensation in the cricket-fly interaction, in an attempt to understand why crickets do not compensate for their future reproductive losses. We conclude that the cricket-fly interaction may not be an ideal system in which to investigate reproductive compensation and furthermore, that reproductive compensation has been poorly investigated in this system.     

Phytosociological investigations of a Pinus pinea L. forest in the Eastern Mediterranean Region (K. Maraş – Turkey)

In this study the phytosociological structures of Pinuspinea L. forests occuring in K. Mara province in theeastern-mediterranean region have been investigated. The vegetation of theresearch area has been studied according to the Braun-Blanquet (1932) methodanda Gastridio ventricosi-Pinetum pineaeassociation has been recognised.     

Mass emergence of a specialist sawfly species on unpalatable herbs under severe feeding pressure by sika deer

In recent years, the increase in sika deer populations has had a significant impact on forest ecosystems. Many studies have reported that this increase has led to the dominance of plants unpalatable to the deer; however, few studies have investigated the effects of this dominance on the specialist sawfly species that feed on the unpalatable plants. We observed the mass emergence of Aglaostigma amoorensis (Hymenoptera: Tenthredinidae), a rare specialist sawfly of the false helleborine Veratrum plants unpalatable to sika deer, in areas under severe feeding pressure by sika deer. An exponential increase in the number of emergent A. amoorensis adults was observed to occur with an increase in Veratrum album patch sizes. In addition, the increase in the A. amoorensis density had a negative effect on reproductive success of V. album. Our findings suggest that the relative abundance of specialist sawfly to the host‐plant abundance has changed for successive years after sika deer irruption.     

Development of a bifunctional crosslinking agent with potential for the preparation of immunotoxins

A new protein crosslinking agent, 2,3-dibromopropionyl-N-hydroxysuccinimide ester, has been synthesized and characterized. The potential use of this compound as a temperature-controllable heterobifunctional crosslinking agent has been investigated using model systems and its reactivity compared with that of chlorambucil-N-hydroxysuccinimide ester. The coupling of¹⁴C-labeled phenylethylamine to lysozyme has been used to illustrate the feasibility of the use of this crosslinking agent for the synthesis of immunotoxins.     

Regulatory and structural properties differentiating the chromosomal and the bacteriophage-associated <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 Cu,Zn Superoxide Dismutases

Background  

Highly virulent enterohemorrhagic Escherichia coli O157:H7 strains possess three sodC genes encoding for periplasmic Cu, Zn superoxide dismutases: sodC, which is identical to the gene present in non-pathogenic E. coli strains, and sodC-F1 and sodC-F2, two nearly identical genes located within lambdoid prophage sequences. The significance of this apparent sodC redundancy in E. coli O157:H7 has not yet been investigated.     

Phylogenetic relationships of the enigmatic species Serratula chinensis and Serratula forrestii (Asteraceae - Cardueae)

The phylogenetic relationships of the Chinese species Serratula forrestii and S. chinensis within the subtribe Centaureinae (Asteraceae – Cardueae) were investigated based on nuclear ribosomal DNA external and internal transcribed spacer sequences. Results indicated that Serratula s. l. is clearly polyphyletic, none of the two species showing close affinities to either Serratula s. str. or Klasea, a genus traditionally included in Serratula. Serratula forrestii has a basal position within the subtribe and has retained most plesiomorphic character states. Serratula chinensis is related to the genera of the Rhaponticum group. Its chromosome number was determined as 2n = 26, and the relationship between this species and the Rhapon-ticum group is discussed from a morphological and karyological point of view.