Formulation of a coupled mechanism between solute diffusion,phosphatase-kinase reactions and membrane potentials for the primary active transport of phosphorylated substrates through biological membranes

Coupled interrelations occurring between a phosphatase/kinase reaction sequence acting in unstirred layers and on both sides of a charged biomembrane pore structure are presented as a plausible kinetic model for the primary active transport of phosphorylated molecules. Simulations conducted at the cell level and with credible numerical values demonstrate that the enzymes positions strongly regulate the membrane permeability for the transported substrate. Depending on both the enzymes positions (more or less far from the membrane) and the membrane charges, the membrane may appear either impervious, either permeable or able to actively transport a phosphorylated substrate. Globally all happens as if, in function of the enzymes positions, a permanent pore may be regulated, changing from a more closed to a more open conformation.     

Comparative Molecular Evolution of Primary (<Emphasis Type="BoldItalic">Buchnera</Emphasis>) and Secondary Symbionts of Aphids Based on Two Protein-Coding Genes

A+T content, phylogenetic relationships, codon usage, evolutionary rates, and ratio of synonymous versus non-synonymous substitutions have been studied in partial sequences of the atpD and aroQ/pheA genes of primary (Buchnera) and secondary symbionts of aphids and a set of selected non-symbiotic bacteria, belonging to the five subdivisions of the Proteobacteria. Compared to the homologous genes of the last group, both genes belonging to Buchnera behave in a similar way, showing a higher A+T content, forming a monophyletic group, a loss in codon bias, especially in third base position, an evolutionary acceleration and an increase in the number of non-synonymous substitutions, confirming previous results reported elsewhere for other genes. When available, these properties have been partly observed with the secondary symbionts, but with values that are intermediate between Buchnera and free living Proteobacteria. They show high A+T content, but not as high as Buchnera, a non-solved phylogenetic position between Buchnera, and the other γ-Proteobacteria, a loss in codon bias, again not as high as in Buchnera and a significant evolutionary acceleration in the case of the three atpD genes, but not when considering aroQ/pheA genes. These results give support to the hypothesis that they are symbionts at different stages of the symbiotic accommodation to the host.     

Vegetation development on pumice at Mount St. Helens, USA

This study explores early vegetation development on pumice at Mount St.Helens. We monitored species annually in a grid of 200 contiguous100-m² plots between 1989 and 1999. Of interestwere how vegetation changed and if it became more homogeneous over time.Speciesrichness and cover increased annually. Diversity(H) stabilized by 1996 and began to decline aslong-livedstress-tolerant species such as Agrostis pallens, Carexmertensii and Penstemon cardwellii began todominate. Protected sites had more species and higher cover than did exposedones. Plots next to relict vegetation had more species and cover than diddistant plots. The vegetation initially was dominated by species with gooddispersal, but subsequently those with poor dispersal became dominant. Wecompared species expansion patterns to a model based on random colonization.Theresults implied that populations with poor dispersal derived from a fewcolonists that then produced seeds for local expansion. Detrendedcorrespondenceanalysis showed a pronounced shift in species composition. This analysis alsoshowed that species composition was becoming more homogeneous over time.However, significant heterogeneity remained and some plots are diverging fromothers. As yet, this vegetation is not developing towards a regional vegetationtype. Rather, an unusual community with Agrostis spp.,Carex spp., Penstemon cardwellii, Lupinuslepidus, Anaphalis margaritacea and Salixcommutata has developed. The accumulation phase of primarysuccessionis nearly complete. The next phase, in which vertical structure develops asSalix and conifers mature, has scarcely begun. It shouldbemarked by the invasion of forest understory species and loss of subalpinemeadowspecies. Assembly rules based on biotic interactions may then become evident.     

p130/p107 expression distinguishes adipogenic potential in primary myoblasts based on age

Recent investigations have provided significant evidence that many mesodermally derived tissues contain stem cell-like precursors capable of being stimulated to undergo differentiation into a variety of cellular lineages. We have recently reported that primary myoblasts isolated from 23-month-old mice have an increased adipogenic potential when compared to their 8-month-old counterparts. To further characterize the degree of adipocyte differentiation in these myoblasts, we examined early and late markers of adipocyte differentiation. Within the first 24h of adipocyte differentiation, expression of p130 and p107, two members of the retinoblastoma tumor suppressor gene family, are regulated and this event is an important one early in adipogenesis. Consistent with the increased adipogenic potential of the older myoblasts and in contrast to the younger cells, the p130:p107 pattern of expression is very similar to that observed in adipogenesis where there is a transient increase in p107 expression accompanied by a decrease in p130 expression. Interestingly, while these older cells accumulated lipid and expressed genes associated with lipid metabolism, they failed to express adipsin and leptin, two well-established markers of terminal adipocyte differentiation. These results suggest that older myoblasts are capable of initiating and progressing through the adipogenic program to a point where they express genes associated with lipid metabolism, but do not reach a terminally differentiated state. This finding may have important metabolic implications in the aging population.     

Optimization of protoplast isolation from NaCl stressed primary, secondary and tertiary calli derived from mature seeds of Bangladeshi indica rice cultivar Binnatoa

A standardized protocol was developed for the isolation of protoplasts from salt stressed primary, secondary and tertiary calli of the moderately salt tolerant indica rice land race Binnatoa. Calli were induced from mature seeds using MS2 callus induction media supplemented with 0, 50 and 100 mM NaCl. Subsequently cultures were maintained in the same medium for 1–2 passages with or without salt stress at the same concentrations. Large numbers of protoplasts (about 1.57–2.10×10⁵/ml) with high viability were isolated from both control and salt stressed (50 and 100 mM NaCl) secondary and tertiary calli compared with the primary calli. The mannitol concentraion in the isolation and washing media was gradually increased, based on salt concentrations in which 13–15% was the most compatible for the control and 50 mM NaCl stressed calli and 17% for the 100 mM NaCl stressed calli. Isolated protoplasts at a density of 1–1.5×10⁵/ml were cultured in MS1₁₅ medium by liquid culture or agarose droplets. The first division of protoplasts was observed 4–5 days after culture using either method. The agarose droplet method led to sustained division of protoplasts and microcolonies formed within 2 weeks. Although no microcalli or protocalli were observed the procedure described provides a method for the isolation of salt-stressed protoplasts in indica rice which avoids the need for laborious and time-consuming suspension cultures. Subsequent regeneration from calli, derived from these protoplasts is reported in a further publication.     

Do the habitats,mouth morphology and diets of the mullids Upeneichthys stotti and U. lineatus in coastal waters of south-western Australia differ?

Two benthic carnivorous goatfish (Mullidae), Upeneichthys stotti (max total length, L _T= 179 mm) and U. lineatus (max L _T= 257 mm), were trawled from the inner continental shelf waters of Western Australia. U. stotti was found almost exclusively offshore at 20–35 m depth, while U. lineatus was most abundant inshore at 5–15 m depth. Smaller individuals of both species ate small, thin-shelled mysids, tanaids and amphipods, while larger fish ate large, hard-bodied isopods, carid decapods and brachyuran crabs. Classification and ordination of the mean volumetric percentage contributions of the prey (dietary samples) of both species from all sites and in each season did not lead to a clear separation between these two species. However, ordination demonstrated that the dietary samples of the two species were distinct when the two species were found together, and when fish of sequential 20-mm length intervals were used. The interspecific size-class differences were consistent with the results obtained using Schoener's overlap index, for which values >0·6 were recorded for only two of the 45 possible interspecific pairwise comparisons. Since these interspecific differences occurred despite virtually identical mouth sizes and morphologies, the two species must feed in a slightly different manner and/or in different microhabitats. While most comparable-sized fish ate tanaids and amphipods, U. stotti ate more relatively mobile epibenthic mysids, cumaceans and carid decapods, whereas U. lineatus ate more larger and slower-moving burrowing bivalves, onuphid polychaetes and brachyuran crabs. The partial partitioning of habitats, when combined with differences in the diet, would help facilitate the co-existence of these two mullids when they are abundant.     

Construction of RFLP-based maps of foxtail millet, Setaria italica (L.) P. Beauv.

 An RFLP-based map consisting of 160 loci was constructed in an intervarietal cross of foxtail millet [Setaria italica (L.) P. Beauv.], Longgu 25×Pagoda Flower Green. The map comprises nine linkage groups, which were aligned with the nine foxtail millet chromosomes using trisomic lines, and spans 964 cM. The intraspecific map was compared to an interspecific map, constructed in a S. italica×S. viridis cross. Both the order of the markers and the genetic distances between the loci were highly conserved. Deviations from the expected 1 : 2 : 1 Mendelian segregation ratios were observed in both the intra- and inter-specific populations. The segregation data indicate that chromosome VIII in the Longgu 25×Pagoda Flower Green cross carries a gene that strongly affects gamete fertility. Received: 18 December 1996 / Accepted: 4 August 1997     

Field performance of cell-suspension-derived Lolium perenne L. regenerants and their progenies

 Two sets of plants (Lb and Lc), regenerated from different single-genotype-derived embryogenic suspension cultures of Lolium perenne cv Citadel, were evaluated for agronomic traits in a modified polycross design in the field. Seed from the primary regenerated plants was harvested to evaluate morphological and phenological traits of corresponding progenies in a replicated field experiment. When compared to seed-grown plants of the same cultivar, primary regenerants of the Lb set showed a significant delay in ear emergence and a more-erect growth habit, while primary regenerants from the Lc set showed a significantly higher seed yield. However, progenies of regenerated plants did not differ from those of seed-grown plants. Embryogenic suspension cells of L. perenne have the potential for producing fertile, well-performing, material which can be integrated into breeding programs. Received: 3 November 1997 / Accepted: 25 November 1997     

乐陵金丝小枣区生态环境地质特征

乐陵金丝小枣区生态环境地质研究表明,层状沉积的河流相及其变异体,心、底土层层位为壤质、粘壤质的土体构型,以不稳定原生矿物为主的土壤,中性或微碱性的重碳酸盐型地球化学环境,钾素丰富、理化性状良好的潮土、褐土化潮土、盐化潮土为该枣区生态环境地质特征的重要标志．对枣生长发育适宜区进行了划分．