Calculation of effective diffusivities for biofilms and tissues.

In this study we describe a scheme for numerically calculating the effective diffusivity of cellular systems such as biofilms and tissues. This work extends previous studies in which we developed the macroscale representations of the transport equations for cellular systems based on the subcellular-scale transport and reaction processes. A finite-difference model is used to predict the effective diffusivity of a cellular system on the basis of the subcellular-scale geometry and transport parameters. The effective diffusivity is predicted for a complex three-dimensional structure that is based on laboratory observations of a biofilm, and these numerical predictions are compared with predictions from a simple analytical solution and with experimental data. Our results indicate that, under many practical circumstances, the simple analytical solution can be used to provide reasonable estimates of the effective diffusivity.     

Synthesis of 6(α,β)-aminocholestanols as ergosterol biosynthesis inhibitors

Δ⁷-5-Desaturase catalyses one of the last steps in ergosterol biosynthesis in fungi. Moreover Δ⁵-unsaturation is necessary for the sparking function. Synthesis of three pairs of C-6 epimeric cholestanol derivatives are described as potential growth inhibitors. Preliminary results suggest that 6β-aminocholestanol is a potent antifungal agent.     

Sulfhydryl-reagent inhibition of olfaction in a moth and effects of exposure to pheromone compounds or a pheromone analogue

The effects on olfaction of N-ethylmaleimide (NEM), a specificreagent of free sulfhydryl groups, were studied in the mothMamestra brassicae. The antennae of male M.brassicae bear twotypes of specialist receptor neurons involved in pheromone communication.One type is tuned to (Z)-11-hexadecenyl acetate (Z11-16:Ac),the main pheromone component; the second type is tuned to (Z)-9-tetradecenylacetate (Z9-14:Ac), an interspecific inhibitor not producedby the females of this species. Vapours of NEM irreversiblyinhibited the electro-antennographic (EAG) responses to Z11-16:Acand Z9-14:Ac. When Zll-16:Ac was applied before and during NEMtreatment, the responses to Z9-14:Ac were preserved and someprotection was observed in the responses to Zll-16:Ac. In return,Z9-14:Ac partially prevented the disappearance of responsesto Zll-16:Ac but not to Z9-14:Ac. A third compound, hexadecylacetate (16:Ac), found in the pheromone gland, but not detectedby the antennal receptors, did not prevent the inhibition causedby NEM.     

Orthologs of key vertebrate neural genes are expressed during neurogenesis in the annelid Platynereis dumerilii

SUMMARY The molecular mechanisms underlying the formation and patterning of the nervous system are relatively poorly understood for lophotrochozoans (like annelids) as compared with ecdysozoans (especially Drosophila ) and deuterostomes (especially vertebrates). Therefore, we have undertaken a candidate gene approach to study aspects of neurogenesis in a polychaete annelid Platynereis dumerilii . We determined the spatiotemporal expression for Platynereis orthologs of four genes ( SoxB, Churchill, prospero / Prox , and SoxC) known to play key roles in vertebrate neurogenesis. During Platynereis development, SoxB is expressed in the neuroectoderm and its expression switches off when committed neural precursors are formed. Subsequently, Prox is expressed in all differentiating neural precursors in the central and peripheral nervous systems. Finally, SoxC and Churchill are transcribed in patterns consistent with their involvement in neural differentiation. The expression patterns of Platynereis SoxB and Prox closely resemble those in Drosophila and vertebrates—this suggests that orthologs of these genes play similar neurogenic roles in all bilaterians. Whereas Platynereis SoxC , like its vertebrate orthologs, plays a role in neural cell differentiation, related genes in Drosophila do not appear to be involved in neurogenesis. Finally, conversely to Churchill in Platynereis , vertebrate orthologs of this gene are expressed during neuroectoderm formation, but not later during nerve cell differentiation; in the insect lineage, homologs of these genes have been secondarily lost. In spite of such instances of functional divergence or loss, the present study shows conspicuous similarities in the genetic control of neurogenesis among bilaterians. These commonalities suggest that key features of the genetic program for neurogenesis are ancestral to bilaterians.     

Immunocytochemical characterisation of endophytic bacteriaAzospirillum brasilense, Herbaspirillum seropedicae, Burkholderia ambifaria andGluconacetobacter diazotrophicus

In the present work an immunocytochemical characterisation of four endophytic bacterial species has been made by using polyclonal antiserum produced against each of the four bacterial strains previously heated at 60 °C. The aim of this researchsito identify common elements among bacteria associated with their endophytic behaviour. Analysis of extracts of each strain by immunoblotting and ELISA confirmed the presence of proteins from different bacterial strains made up of common epitopes. However, antisaproduced againstHerbaspirillum seropedicae andBurkholderia ambifaria show a high number of bands recognised on each extracts, while antisera againstAzospirillum brasilense andGluconacetobacter diazotrophicus show a low number of bands recognised on each extract. Immunogold labelling showed that epitopes are located both on the cell wall and in the cytoplasm; most likely they could be preursor cell wall proteins synthesized inside the cytoplasm and subsequently transported onto cell wall. Finally, the common bands amog bacterial strains revealed by immunoblotting could play a role as active hydrolases involved in host tissue penetration.     

Nucleotide sequence and characterization of a maize cytoplasmic ribosomal protein S11 cDNA

We isolated a Zea mays cDNA encoding the 40S subunit cytoplasmic ribosomal protein S11. The nucleotide sequence was determined and the derived amino acid sequence compared to the corresponding Arabidopsis thaliana protein showing an homology of 90%. This ribosomal protein is encoded by a small multigene family of at least two members. The mRNA steady-state level is about one order of magnitude higher in rapidly growing parts of the plant such as the roots and shoots of seedlings compared to fully expanded leaf tissue.     

Characterization of a monoclonal antibody to human proacrosin and its use in acrosomal status evaluation.

Among the monoclonal antibodies (MAb) selected after immunization of mice with a detergent-insoluble fraction from human spermatozoa, MAb 4D4 was found to stain in immunofluorescence the principal part of the acrosome of human spermatozoa. Acrosome reaction induced decreased and spotty 4D4 immunofluorescence staining. Immunoelectron microscopy before or after embedding revealed that the epitope defined by MAb 4D4 was sequestered in the anterior acrosomal matrix and, after the acrosome reaction, remained partly bound on matrix elements attached to the inner acrosomal membrane. Western blot analysis of sperm extracts showed that the epitope defined by MAb 4D4 was located on a 55 KD polypeptide in whole cells and on 55 and 50 KD polypeptides in non-ionic detergent fractions. Human proacrosin-enriched fraction obtained by FPLC purification exhibited several proteolytic activities against gelatin in gel enzymography: a 50 KD major band and two minor bands in the 20-30 KD area; the 50 KD polypeptide reacted with MAb 4D4 in Western blots. Furthermore, the 4D4-immunoprecipitated polypeptide from sperm extract showed that the 50 KD band exhibited proteolytic activity with an optimal pH at 8.0 that was strongly inhibited by soybean trypsin inhibitor and ZnCl2. MAb 4D4 also reacted with the acrosome of the monkey Macaca fascicularis but not with the acrosome of any of the other non-primate mammalian species examined so far. Various shape defects of the acrosomal principal region were revealed by 4D4 labeling of spermatozoa with head anomalies from infertile patients. MAb 4D4 also recognized proacrosin in paraffin-embedded human testis sections. These data make the monoclonal antiproacrosin antibody 4D4 an efficient tool for evaluation of the acrosomal status of human spermatozoa and spermatids.