Molecular basis for the special properties of proteins and enzymes from Halobacterium marismortui

Abstract Three proteins from Halobacterium marismortui , malate dehydrogenase (hMDH), glutamate dehydrogenase (hGDH) and ferredoxin (hFD) were purified and characterized with respect to their molecular masses, amino acid composition and, for hFD only, primary structure. Striking features of halophilic proteins are: the high excess of acidic over basic residues; acidic clusters in the sequence. Low-salt concentration causes inactivation and changes in structural parameters of hMDH and hGDH. Reactivation of hMDH involves long-lived stable intermediates. The salt concentration optimum of enzymic activity is independent of salt nature. The high capacity of halophilic proteins to retain water and salt is due to unique molecular properties, studied by physico-chemical techniques.     

Hypoplasia and health status: a comparison of two lifestyles

Enamel hypoplasia was recorded for the primary and permanent teeth of Natufians (terminal Pleistocene Hunter-Gatherers) and Early Arabs (Subsistence farmers). Minimal hypoplasia was found in the primary teeth of the Natufians, but in the Early Arab population, 31% of upper first primary molars showed enamel defects. In the permanent teeth, the Early Arab population again showed a significantly higher frequency of hypoplasia, with all teeth affected. In the Natufians, only later developing teeth showed enamel defects. These findings suggest that health status in the Early Arab population was poor throughout life, affecting pregnant mothers, their foetuses, young infants and children. These results confirm other studies that have shown deterioration in health status of early agriculturalists relative to hunter- gatherers. Comparisons of these findings with those of recent populations indicate that health status in the Natufians was comparable to that of modern populations with subsistence diets and mediocre health care. Health status in the Early Arab population was comparable to that of modern populations suffering from severe malnutrition and chronic disease.     

Anatomical aspects of hormonal regulation of abscission in citrus – The shoot-peduncle abscission zone in the non-abscising stage

Although mature citrus fruits [ Citrus sinensis (L.) Osbeck cv. Shamouti] did not abscise at the peduncle-shoot abscission zone (AZ–A) when incubated in ethylene environment, abscission processes did occur in a limited number of cell layers situated in the inner bark, the starch sheath region, and in the pith of AZ–A. These processes were regulated by 2,4-D and ethylene treatments. Cells responding to the "separation processes", particularly in the ethylene treatment, underwent either (a) cell wall swelling, dissolving and breakdown, or (b) growth and expansion in a radial plane. Further away from the dissolving area, the response of some cells of the mid and outer bark took the form of divisions or growth in a circumferential plane, while other cells remained unchanged. Non-responding tissues of the outer bark formed a "sleeve" of undissolved cells, and the vascular cylinder produced no abscission in AZ–A. It is concluded that the partial cell wall dissolution in AZ–A explains the increased activity of cellulase and polygalacturonase in the non-abscising AZ–A of the mature fruit (Greenberg et al. 1975. Physiol. Plant. 37: 1–7).     

The interaction of phagocytes and the large-sized parasite Cryptococcus neoformans: Cytochemical and ultrastructural study

Summary The yeast Cryptococcus neoformans may develop under certain conditions a large polysaccharide capsule 50–100 M in diameter and therefore cannot be phagocytosed by either polymorphonuclear cells (PMN's) or mononuclear phagocytes (MN's). The cellular defense mechanism — in various animals — against the yeast is composed by formation of ringlike structure of PMN's or MN's cells which surround the C. neoformans. Ring structures develop either in vivo or in vitro in tissue culture; destruction of the yeast occurs within 36–72 hours.Several hydrolases, such as acid phosphatase, -glucuronidase and non-specific esterase were found to be released from the phagocytic cells into the enclosed yeast. Considerable reduction of NBT used as a marker for oxidative activity was observed in MN rings at contact regions of the MN cells and the yeast. Electron microscopic studies indicate that the phagocytic cells in the ring structure have many pseudopodes penetrating into the polysaccharide capsule of the yeast. Disintegration of the capsule was observed as well as phagocytosis of its material. A possible analogy between normal phagocytosis of small-sized bodies and the ring structure obtained when large bodies are involved is discussed.     

Effects of light, temperature, gibberellin (GA3) and their interaction on coleoptile and leaf elongation of tall, semi-dwarf and dwarf wheat

Near-isogenic wheat lines differing in height-reducing (Rht) alleles, in each of two cultivars, were used to investigate the effects of light intensity and of their interaction with temperature and GA₃ application, on the elongation of the coleoptile and the first seedling leaf. Darkness caused a conspicuous increase in the lengths of the coleoptile and of the sheath and lamina of the first leaf, in GA₃ treated and untreated seedlings of all genotypes grown at 11 and 25°C. The genotype effects and the effects of light intensity and GA₃ application on leaf length were ascribed entirely to their effects on the rate of leaf elongation since the duration of leaf elongation was not affected by these factors. Temperature elevation from 11 to 25°C caused a 55% shortening of the duration of leaf elongation and a concomitant increase in elongation rate, which diminished with increased genotypic dwarfness. Accordingly, temperature elevation resulted in a significant reduction in leaf-length of the light-grown dwarf genotypes and the dark-grown dwarf and semi-dwarf genotypes. It is suggested that this temperature × light × genotype interaction effect is due to environmental dependent upper limits of elongation rate set by the Rht alleles.Abbreviations PAR Photosynthetic Active Radiation     

Induced diploid gynogenesis and polyploidy in the ornamental (koi) carp Cyprinus carpio L.

The results of a series of experiments conducted in our laboratory on the ornamental common carp (koi), aimed at optimizing heat-shock chromosome-set manipulation procedures, are described. The timing of heat-shock initiation was expressed in the relative unit of embryological age (₀) in order to standardize this parameter, the absolute time for heat-shock initiation being calculated from duration of one ₀ at two different pre-treatment water temperatures. Heat shocks were applied within the periods of 0.05–0.60 ₀ and 1.20–2.20 ₀ which, respectively, cover the successive phases of the 2nd meiotic division and the 1st cleavage. The highest production of diploid gynogenetic offspring was observed when heat shocks were initiated at 0.15–0.25 ₀ and at 1.5 ₀, after insemination, corresponding to anaphase of meiosis-II, and metaphase of the 1st cleavage, respectively. Similar results were obtained irrespective of the different pre-treatment water temperatures, thus confirming the possibility of standardizing heat-shock timing by ₀.