Tobacco plants accumulating high levels of soluble sugars due to the cytosolic expression of an inorganic pyrophosphatase from Escherichia coli were ušed to study adaptation to the osmotic stress that these plants are continuously faced with. In the course of differential RNA screening between wild type and transgenic plants three cDNA dones could be isolated, which after sequencing were identified as pathogenesis-related proteins (PR-proteins). Two cDNAs, PRlb and PR-P, belong to the acidic PRl and PR3 groups of PR-proteins, and the third cDNA, SAR8.2, has so far been associated with systemic acquired resistance in tobacco plants. The expression of PR-proteins transcripts in generál was well correlated with the steady- state level of total soluble sugars present in the tobacco plants. The induction of PR protein transcripts resulted in an accumulation of corresponding proteins. Moreover, the complete set of acidic PR-proteins induced by potato virus Y was also present in the sugar-accumulating transgenic plants. The induction of PR-proteins might be a generál response to the osmotic stress in tobacco plants.
An ICR outbred suckling mouse model of cryptosporidiosis was used to explain some of the variability associated with experimental Cryptosporidium parvum infections in neonate mice. Fourty four groups of 12 mice each, ranging in age from 4-12 days, each received 1.0 x 104 CsCl purified oocysts per os in 5 pm PBS. At 6 days post-inoculation (PI), mice were killed by C02 overdose and individually weighed. Intestines were then homogenized and oocysts were quantified by hemacytometer. Results revealed that both age and weight have pronounced effects on numbers of oocysts produced in vivo, with larger and older mice producing higher numbers of parasites. Mice 8-9 days of age at the time of inoculation displayed the least amount of weight dependent variability, produced the highest numbers of oocysts, and were judged to be superior over other ages for pharmaceutical screening. Significant reductions in numbers of oocysts occurred in mice inoculated at 10 days of age, and only a few oocysts were found in mice inoculated at 11-12 days of age. These studies suggest that at least some data on Cryptosporidium generated from suckling mouse studies to date are probably unreliable and should be viewed skeptically.
Infections of Unicauda clavicauda (Kudo, 1920) Davis, 1944 (Myxozoa) are described from Notropis hudsonius (Clinton) in Montana. Plasmodia form beneath scales of the body and produced spores within a loosely-defined matrix. Fixed spores are oval in front view, 11-14 pm long and 9-10.5 pm wide, and contain a posterior appendage that is up to 26 pm long. The polar capsules are 4-6 pm long and 2.5-4 pm wide. The study represents the first report of U. clavicauda since the original species description and a new host and geographical record. The taxonomic history of Unicauda Davis, 1944 is summarised and it is concluded the following 10 species are valid members of the genus: U. aristichthydis Zhao et Ma, 1995, U. brachyura (Ward, 1919), U. caudatus (Gogebashvili, 1965), U clavicauda, U. crassicauda (Kudo, 1934), U. lumae Rahemo, 1976, U. macrura (Gurley, 1893), U. magna Minchew, 1981, U. pelteobagrus Ma, 1998, and U. wuhanensis Xiao et Chen, 1993. All of these species have circular, subcircular, or oval spores in frontal view and all parasitise fish of the superorder Ostariophysi. As a group they are known from temperate freshwater locations in North America, Europe and Asia. A list of 16 species described or transferred to Unicauda at one time or another, but not recognised as members of the genus in the present study, is provided.
Under boron (B) deficiency, the CO2 exchange rate, chloropliyll (Clil) and oil contents significantly decreased, whereas Clil alb ratio, leaf area ratio and leaf stem ratio significantly increased. When B-deficient plants had been siipplied witli tlie control solution for 3 weeks, there was a partial recoveiy in sonie growtli and yield parameters. In leaves of deficient plants, •^C02 incoiporation in sugars, ainino acids and organic acids decreased, whereas in stems the incoiporation of these three fractions was higher than in the Controls. Upon recovery (3 weeks) the pattenis of '‘*C02 incoiporation in sugars, amino acids and organic acids in leaves and stems were similar to those in conPol plants. In leaves of the B-deficient plants, [U-’‘*C] saccharose incoiporation was very high with respect to Controls, and a major portion was in ethanol soluble fraction. The incoiporation was significantly higher in sugars and organic acids than in amino acids. A substantial portion of labellcd saccharose remained in the stem and it was significantly higher than in control plants. Under B- deficiency, the levels of primaiy metabolites and their partitioiiiiig between leaf and stem significantly influenced the essential oil accumulation.
Light-induced Ca2+ concentration oscillations in cytoplasm of oat protoplasts were shown to be controlled by inhibitors of Ca^"*" pumps, sodium vanadate and tuBHQ. The sources of Ca^'*' released into cytoplasm under the action of radiant energy are vacuole and endoplasmic reticulum, but not mitochondria. The manifestation of Ca^'*' oscillations depends on the concentrations of oat protoplasts in the suspension which suggests the propagation of a signál between the cells and synchronization of their light-induced Ca2+ oscillation response.
Cd2+ and Ni2+ dififerently affected the rates of net photosynthesís (P^) and transpiration (E), chlorophyll (Chl) content, and stomatal conductance (gj in different leaves of wheat. and Chl content in the top leaf were affected more than the lower leaves by Ni2+, whereas the deleterious effect of Cd^"*" was more pronounced in the third leaf. Ni2+ and Cd2+ slightly decreased the relative water content and leaf water potential of all the leaves after 2 d of treatment. However, this reduction was relatively more severe under Cd^^ treatment than with Ni2+ particularly in the top leaf after 4 d of the treatment.