Influence of auxin on phosphate absorption and metabolism of phosphorylated compounds in aged potato tuber discs (Solanum tuberosum)

Ageing of potato tuber discs markedly increases the rate of phosphate uptake. This increase is partially prevented by the presence of indoleacetic acid (IAA: 50 μ M ) in the ageing medium. ³²P distribution among the various phosphorylated fractions (P₁, organic soluble phosphate, acid-insoluble phosphate) was carried out after 24 h of ageing in the presence of IAA. An equal inhibition of the labelling rates of each of the different fractions is induced by the hormone. No important effect on respiration and ATP content was observed. Moreover, IAA neither changes the total phospholipid content nor the relative distribution of ³²P between the components. These results support the hypothesis that IAA acts specifically on the development of uptake mechanisms during the ageing period.     

Sweet taste involves several distinct receptor mechanisms

Measures of human sensitivities to various sweet compounds conductedat threshold (91 subjects, 7 sweeteners) and at suprathresholdlevels (9 subjects, 12 sweeteners) show interindividual differences.Multidimensional analysis indicates that sweet taste can berepresented in a tridimensional continuum if 12 compounds areconsidered. Results are speculatively interpreted as indirectevidence for the existence of several receptor sites cooperatingin sweet taste chemoreception.     

Secondary mouse mixed lymphocyte reaction (MLR) in vitro: Correlation between primed cells reactivity and serological typing for Ia specificities

B10.M (H-2^f) spleen lymphocytes were cultured for 14 days with X-irradiated B10.P (H-2 ^p ) lymphocytes. These primed cells were then tested for their capacity to respond to a secondary stimulation induced by a panel of mouse cells carrying differentH-2 haplotypes. The third-party cells induced various degrees of proliferation which could be expressed as a percentage of the proliferation induced by the primary stimulating strain (relative response = RR) and could then be classified according to the RR. Anti-Ia antibodies present in a B10.M anti-B10.P serum were studied by the dye exclusion lymphocytotoxicity technique (LCT) against the same panel, after absorption of H-2K, D antibodies on B10.P platelets. The strain panel could then be classified according to the LCT titers of the absorbed immune serum. A significant correlation (r=0.96,P<0.01) was found between both classifications. According to the Ia chart, the public specificities involved were Ia.6, 7, and 13, but these did not fully explain either the primed cell reactivity or the LCT results. An unexpected crossreactivity was observed between B10.P and B10. Absorption-elution experiments with A.TH anti-A.TL serum demonstrated that B10 and B10.P share the Ia.3 antigen. These results indicate that the structure(s) recognized by the primed lymphocytes is the Ia antigen(s).Abbreviations used in this paper RR Relative response - LCT Dye exclusion lymphocytotoxicity technique - MLR Mixed lymphocyte reaction - PC Primed cell - MHC Major histocompatibility complex - PLT Primed lymphocytes typing test     

Possible involvement of the yeast POLIII DNA polymerase in induced gene conversion

Summary In Saccharomyces cerevisiae, three different DNA polymerase complexes, POLI, POLII and POLIII, are known to be involved in DNA replication. The catalytic subunit of POLIII is encoded by the essential CDC2 gene. The existence of different thermosensitive non-complementing mutants of CDC2 offers the possibility of using a genetic approach to investigate the involvement of POLIII in induced gene conversion. When cdc2 heteroallelic cells were irradiated and incubated under restrictive conditions, almost no induction of thermoresistant cells could be detected, suggesting an essential role for POLIII in mitotic gene conversion events.     

Cytoplasmic events in human meiotic arrest as revealed by immunolabelling of spermatocyte proacrosin

Abstract. Proacrosin appears in the Golgi complex as early as the mid-pachytene stage and immediately thereafter initiates partition to be equally distributed in sper-matids. The anti-proacrosin monoclonal antibody 4D4 (mAb 4D4) was used as a marker of these cytoplasmic events in ten men exhibiting spermatogenesis arrest in three specific stages: (i) leptotene/zygotene spermatocyte I with impaired chromosome pairing (six cases), (ii) early pachytene I (one case) and (iii) metaphase/anaphase I (three cases). Prophase arrest stages were identified on testis sections stained by silver nitrate. MAb 4D4 labelling revealed two types of leptotene/zygotene arrest depending on whether proacrosin was expressed or not. The data obtained enabled us to distinguish between: (i) nuclear blockages due to chromosome and/or nuclear matrix anomalies, when cytoplasmic events were either inhibited or not inhibited, and (ii) nuclear anomalies due to microtubular disturbances. In this latter case, cytokinesis was impaired as early as the prophase I, thus indicating a relationship between the Golgi partitioning and the microtubule network. Data show that meiotic arrest investigations, by means of an appropriate marker of the cytoplasmic events, provide valuable information on spermatogenic developmental processes.     

Degradation and fermentation of cellulose by the rumen anaerobic fungi in axenic cultures or in association with cellulolytic bacteria

Three rumen anaerobic fungi—Neocallinastix frontalis MCH3,Piromyces (Piromonas) communis FL, andCaecomyces (Sphaeromonas) communis FG10—were cultured on cellulose filter paper alone or in association with one of two rumen cellulolytic bacteria,Ruminococcus flavefaciens 007 andFibrobacter succinogenes S85. Cocultures ofN. frontalis orP. communis andR. flavefaciens were markedly less effective than the fungal monocultures in degrading cellulose but more effective than the bacterial monocultures.R. flavefaciens had an antagonistic effect against both of the fungal species. In contrast, no interaction was observed between the two fungal species andF. succinogenes. Cellulose was more effectively degraded by the cocultureC. communis-R. flavefaciens than by the corresponding fungal and bacterial monocultures. The effectiveness of degradation of the cocultureC. communis-F. succinogenes was comparable to that of the bacterial strains but greater than that of the fungi; no interaction was observed between these two microorganisms.     

Impact of phosphate concentration on the metabolome of biofilms of the marine bacterium Pseudoalteromonas lipolytica

Metabolomics - Recent advances in high-throughput methodologies in the ‘omics’ and synthetic biology fields call for rapid and sensitive workflows in the metabolic phenotyping of...