An analysis of the association of collagen based on structural models.

The existence and distribution of vertical, interacting edges on cylindrical surfaces, which were derived from the basic structural features of the collagen molecule, have been examined as a function of the angle θ of the superhelix. Over the range θ = 26°–33° and near θ = 36°, the strongest intermolecular association was detected at 29.95°. This model exhibited three similar, self-interacting edges, separated by approximately 120°. The potential for three similar but nonidentical edges lies in the geometry of the collagen molecule, but the existence of such edges and their ability to self-associate is dependent upon the unique amino acid sequence. The relative strengths of association of each edge with itself and with the other edges are not identical, but the present analysis does not permit a judgment as to whether this variation could result in functional specificity in such interactions. All three chains participate in each edge though their contribution to the relative interaction strength is not identical. These edges showed distinct maxima when displaced past one another by integral intervals of D, where D = 233 residue positions (quarter-stagger). The strongest relative interaction occurs at a displacement of 1D.     

Factors affecting the colonisation of a root system by fluorescent Pseudomonads: The effects of water,temperature and soil microflora

The colonisation of a radish root system by strains ofPseudomonas fluorescens, selected for their ability to promote potato and radish growth under different environmental conditions is reported. In pot experiments colonisation of different parts of the root system was measured at different temperatures, in different watering regimes and in sterile and recropped soil. Root colonisation was extensive but populations were highest on the upper root system and their distribution throughout the root system was greatly affected by environmental factors. percolation of water through the soil and partial soil sterilisation enhanced colonisation but the effects of temperature and recropping were complex. Growth promotion was unpredictable and there was no simple relationship between PGPR colonisation and stimulation of plant growth.     

Increased Production of Paired Helical Filament Epitopes in a Cell Culture System Reduces the Turnover of τ

Abstract: To investigate the regulation of posttranslational modifications of τ that might be pertinent to the production of the paired helical filament (PHF) of Alzheimer's disease, we incubated human neuroblastoma cells with the protein phosphatase inhibitor okadaic acid. This treatment results in increased immunoreactivity of τ with the monoclonal antibodies Alz-50, PHF-1, T3P, and NP8, a reduction in Tau-1 immunoreactivity, and an elevation in apparent molecular weight of τ. Moreover, our data demonstrate that accumulation of phosphates in τ leads to a decrease in the turnover rate of τ in the neuroblastoma cells. It is suggested that similar build-up of hyperphosphorylated τ in the neuronal perikarya may represent an early event in PHF formation. The present system facilitates the investigation of regulatory mechanisms governing the occurrence of PHF epitopes, their effects on neuronal cell metabolism, and possible pharmacological intervention.     

Reproductive Dynamics and Potential Annual Fecundity of South Pacific Albacore Tuna (Thunnus alalunga)

The reproductive biology of albacore tuna, Thunnus alalunga, in the South Pacific Ocean was investigated with samples collected during broad-scale sampling between 2006 and 2011. Histology was done in a single laboratory according to standard protocols and the data analysed using generalized linear mixed-effects models. The sex ratio of albacore was female biased for fish smaller than approximately 60 cm FL and between 85 and 95 cm, and progressively more male biased above 95 cm FL. Spawning activity was synchronised across the region between 10°S and 25°S during the austral spring and summer where sea surface temperatures were ≥24 °C. The average gonad index varied among regions, with fish in easterly longitudes having heavier gonads for their size than fish in westerly longitudes. Albacore, while capable of spawning daily, on average spawn every 1.3 days during the peak spawning months of October to December. Spawning occurs around midnight and the early hours of the morning. Regional variation in spawning frequency and batch fecundity were not significant. The proportion of active females and the spawning fraction increased with length and age, and mature small and young fish were less active at either end of the spawning season than larger, older fish. Batch fecundity estimates ranged from 0.26 to 2.83 million oocytes with a mean relative batch fecundity of 64.4 oocytes per gram of body weight. Predicted batch fecundity and potential annual fecundity increased with both length and age. This extensive set of reproductive parameter estimates provides many of the first quantitative estimates for this population and will substantially improve the quality of biological inputs to the stock assessment for South Pacific albacore.