Heat shock proteins in Sorghum bicolor and Pennisetum americanum I. genotypic and developmental variation during seed germination

Abstract The capacity to synthesize heat shock proteins (HSPs) during seed germination of sorghum (Sorghum bicolor) and pearl millet (Pennisetum americanum) has been examined. HSP synthesis is detectable in a thermotolerant genotype of sorghum during the first hour of imbibition of the seed under high temperature stress. A non-coordinate control of HSP synthesis during germination was revealed. Genotypic differences were manifest in the stage of germination at which the ability to synthesize HSPs was first apparent and this related to the thermosensitivity of that genotype.     

Effects of repeated short-term cold exposures on cold induced thermogenesis of women

The effects of repeated exposures to resting cold air (10°C) on the shivering and thermogenic responses of women to standard cold stress were investigated. Ten women, aged 18 to 34 years, were divided into two groups of five women each. One group, the acclimated (A) was exposed ten times within 2 weeks, the first and the last exposures being the pre-and post-tests respectively. The second group, the control (C) was exposed twice within 18 days. Measurements of rectal and skin temperatures, oxygen uptake, time to onset of shivering (TOS), and perceived cold were performed during all exposures. Shivering responses were evaluated by electromyography and visually. A significant (P<0.05), increase was seen in TOS (from 26.2 min to 55.6 min), and a significant decrease was seen in thermoregulatory heat production (from 14.78 kcal/h to –2.64 kcal/h) in group A; these changes were evident after about five exposures. It is concluded that the women became cold acclimated as a result of the repeated short-term resting cold air exposures.Research supported by Capes/Brazil, and by the Universidade Federal de Minas Gerais/Brazil     

Effects of wearing two different types of clothing on body temperatures during and after exercise

The experiment was conducted to investigate the human thermoregulatory responses during rest, exercise and recovery atT _a 20°C and 60% R.H. under the conditions of wearing two different types of clothing. Six healthy men wore two types of clothing: one covering the whole body area except the head (Type A, weight 1656 g), and the other covering only the trunk, upper arms and thighs (Type B, weight 996 g). The level of rectal temperature was kept significantly higher in Type B than in Type A during rest and recovery. The increased and decreased rates of rectal temperature during exercise and recovery were significantly greater in Type A than in Type B, respectively. These findings are discussed from the viewpoint of the differences of skin temperatures of the extremities between Type A and Type B.     

Allozyme diversity and the evolution ofCrepidiastrum (Compositae) on the Bonin (Ogasawara) Islands

The genusCrepidiastrum is distributed in East Asia and includes 7 species. In the Bonin Islands, three species ofCrepidiastrum occur, and all of them are endemic to the islands. For detecting the origin and speciation of these endemic species, electrophoretic studies have been done in three endemic species of the Bonin Islands as well as in the remaining four species ofCrepidiastrum, andYoungia denticulata which is considered to be closely related toCrepidiastrum. A total of 386 individuals were sampled from 14 populations. As a result, 17 loci of 10 enzyme systems were resolved and gene frequencies for each population were calculated. The genetic variability was low in island species, as reported in some oceanic island plants. Four groups were recognized in the dendrogram generated by the UPGMA method. The Bonin endemics were clustered together, suggesting a monophyletic origin.C. ameristophyllum andC. linguaefolium were found to be genetically very similar, and this may suggest recent and rapid speciation within the islands.     

Protection of photosynthetic O2 evolution against heat inactivation: the role of chloride,pH and coupling status

Heat inactivation of photosynthetic O₂ evolution was studied in isolated thylakoids from spinach (Spinacia oleracea) and mangrove (Avicennia marina) leaves. Different temperatures, salt, pH and uncoupler effects were investigated. From these results and others in the literature it was concluced that chloride loss from the membrane and, more specifically, the oxygen-evolving complex of photosystem II, may be the cause of inhibition of oxygen evolution during heat inactivation.Abbreviations Hepes 4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol - Tricine N-2-hydroxy-1, 1-bis (hydroxymethyl) ethyl glycine - EDTA ethylenediaminetetraacetic acid - FeCN K-ferricyanide     

Intra- and interspecific variation in body size ofProtohermes (Megaloptera: Corydalidae)

The life history of three populations ofProtohermes grandis and two populations ofProtohermes immaculatus (Megaloptera: Corydalidae) was compared. In general, the larvae lived in stream riffles for 2 years and the adults appeared in summer. Adult body size differed between these closely related species and also between the populations ofP. grandis. Dwarfism occurred inP. immaculatus, a species that is endemic to the small, isolated island, Amami Island. The population ofP. grandis on Yaku Island, located between Amami Island and the mainland Kyushu, had an intermediate body size between that ofP. immaculatus and the mainland population ofP. grandis. Despite being an insular population,P. grandis on Tsushima Island had a similar body size to mainlandP. grandis. In these populations with large adults, some larvae lived in the streams for 3 years. The size distribution of benthic animals, which are the prey available toProtohermes larvae, differed between the streams studied. The density of large prey was lowest on Amami Island, intermediate on Yaku Island, and highest on the mainland and Tsushima Island. Different size distributions of available prey may be caused by the differences of benthic fauna; most of Ecdyonuridae and Ephemerellidae (large mayflies) and Perlidae (large stoneflies) were not found on Amami and Yaku Islands. Thus, there is a tendency to dwarfism in the populations ofProtobermes inhabiting streams where the density of large prey is low.     

Molecular responses of plants to an increased incidence of heat shock

Abstract. Climatic change as a result of the greenhouse effect is widely predicted to increase mean temperatures globally and, in turn, increase the frequency with which plants are exposed to heat shock conditions, particularly in the semi-arid tropics. The consequences of extreme high-temperature treatments on plants have been considered, particularly in relation to the synthesis of heat shock proteins (HSPs) and the capacity to acquire thermotolerance. The heat shock response is described using results obtained with seedlings of the tropical cereals, sorghum ( Sorghum bicolor ) and pearl millet ( Pennisetum glaucum ). A gradual temperature increase, as would occur in the field, is sufficient to induce thermotolerance. The synthesis of HSPs is a transient phenomenon and ceases once the stress is released. Despite the persistence of the HSPs themselves, de novo synthesis of HSPs is required for the induction of thermotolerance each time high temperatures are encountered. The effect of a repeated, diurnal heat shock was investigated and genotypic differences found in the ability to induce the heat shock response repeatedly.