Carbon Dioxide Effects on Carbohydrate Status and Partitioning in Rice

The atmospheric carbon dioxide (CO₂) concentration has beenrising and is predicted to reach double the present concentrationsometime during the next century. The objective of this investigationwas to determine the long-term effects of different CO₂ concentrationson carbohydrate status and partitioning in rice (Oryza sativaL cv. IR-30). Rice plants were grown season-long in outdoor,naturally sunlit, environmentally controlled growth chamberswith CO₂ concentrations of 160, 250, 330, 500, 660, and 900µmolCO₂ mol¹ air. In leaf blades, the priority between the partitioningof carbon into storage carbohydrates or into export changedwith developmental stage and CO₂ concentration. During vegetativegrowth, leaf sucrose and starch concentrations increased withincreasing CO₂ concentration but tended to level off above 500µmolmol^–1 CO₂. Similarly, photosynthesis also increased withCO2 concentrations up to 500µmol mol^–1 and thenreached a plateau at higher concentrations. The ratio of starchto sucrose concentration was positively correlated with theCO₂ concentration. At maturity, increasing CO₂ concentrationresulted in an increase in total non-structural carbohydrate(TNC) concentration in leaf blades, leaf sheaths and culms.Carbohydrates that were stored in vegetative plant parts beforeheading made a smaller contribution to grain dry weight at CO₂concentrations below 330µmol mol^–1 than for treatmentsat concentrations above ambient Increasing CO₂ concentrationhad no effect on the carbohydrate concentration in the grainat maturity Key words: CO₂ enrichment, starch, sucrose     

Nucleotide sequence and distinctive characteristics of the env gene of endogenous feline leukemia provirus.

Nucleotide sequence analysis of the env gene of two different endogenous feline leukemia virus (FeLV) loci, CFE-6 and CFE-16, of domestic cats revealed the following characteristics. (i) Both proviruses contain an open reading frame in the env region; (ii) whereas the full complement of the exogenous FeLV env is generally present in CFE-6 DNA, it is truncated in CFE-16 DNA such that the 5' half of the gp70 domain and the untranslated region 3' to the p15E domain have been fused by an internal deletion, resulting in loss of the C-terminal half of the gp70- and all of the p15E-coding sequences; (iii) endogenous env is highly homologous to large sequence domains conserved in all three exogenous FeLV subgroups (A, B, and C) but is similar to FeLV-B sequence domains in the variable regions detected in these viruses; and (iv) there are four other sequence domains, one residing at the C terminus of gp70 and three scattered in p15E, which are unique for the endogenous env, thereby distinguishing it from the FeLV-B gene.     

The crystal violet nuclei staining technique leads to anomalous results in monitoring mammalian cell cultures

Nuclear counts determined by crystal violet staining from samples of stationary or microcarrier cultures of hybridomas, CHO or Vero cells were consistently and significantly higher than cell concentrations determined by the trypan blue or Coulter counter methods. This difference was attributed to the presence of a significant proportion of binucleated cells, which are assumed to be 35% of the cell population in the stationary phase of Vero cultures. The proportion of such cells during exponential growth was variable. However, continuous sub-culture of these cells induced a degree of synchrony during growth which resulted in a cyclic variation of the difference between the cell and nuclei counting techniques. This data indicates that care should be taken in interpreting cell culture profiles based solely on crystal violet nuclei staining counts.     

A METHOD FOR ISOLATION OF CAMPYLOBACTER SPP. (JEJUNI, COLI AND LARI) FROM SHELLFISH AND THE MARINE ENVIRONMENT

A method has been developed to detect thermophilic species of Campylobacter in shellfish, marine and tributary waters, sediment and farm runoff by-products such as manure and silage. The method consists of a 48 h enrichment incubation and subcultured to selective agars. Presumptive colonies confirmed with a latex agglutination (antibodies) to common flagellar antigens of C. jejuni, C. coli and C. lardi. Over an 8 year period, West Coast estuaries (Washington, Oregon, and California) were sampled, resulting in analysis of a total of 512 samples. Results suggest that Campylobacter spp. are well distributed in the marine environment. Two enrichment broths were compared for the recovery of campylobacters from environmental samples. The method described in the Food and Drug Administration Bacteriological Analytical Manual (FDA/BAM) (1984), was compared to a modified method. Use of the modified method described here resulted in higher recovery rates of Campylobacter spp. Recoveries of campylobacters from sediment, shellfish, and water were 10,13, and 28% higher for the modified method, respectively.     

Selective intra-lysosomal concentration of niobium in kidney and bone marrow cells: a microanalytical study

Niobium is used as an alloy in the industrial and biomedical fields. The concentration of the toxic element in organs of a number of animal species has been defined by using radioactive niobium (⁹⁵Nb). However, tissue lesions induced by niobium have only been studied at the light microscopy level. In this study, we used an electron probe X-ray analyzer equipped with a transmission electron microscope to define the localization of this element in kidney and bone marrow cells. Results demonstrated that niobium is located in the lysosome and that this element coprecipitates with phosphate. In kidney, lysosomes and precipitates are eliminated in the tubular lumen. In contrast, precipitates appear to be eliminated more slowly from the lysosomes of bone marrow macrophages. These processes therefore correspond to one of the mechanisms by which lysosomes eliminate certain toxic mineral elements and thus play a role in the more general process of the body's defenses.     

GENETIC VARIATION AND JUVENILE SURVIVAL IN RED DEER

The survival of red deer (Cervus elaphus L.) calves to two years of age was examined in relation to electrophoretic variation in a population on the Scottish island of Rhum. Survival was analyzed using logistic analysis in which the “phenotypic” factors birth weight, birth date, subdivision of the study area, cohort, and sex, which affect the probability of a calf's survival, were taken into account. All three polymorphic loci examined, Mpi, Idh-2, and Trf (each with two detected alleles) are significantly associated with juvenile survival. At Mpi, there is selection against one allele, f (or an allele at a linked locus), and there are indications that this effect is stronger in females than males. For Idh-2, overall, the heterozygote class survives better than the two homozygotes, which survive equally well. However, again there is a difference between the sexes; female heterozygotes survive much better than homozygotes, whereas male homozygotes survive better than heterozygotes, and the difference in survival is smaller. Furthermore, there is an interaction involving Mpi, Idh-2, and survival in which Mpi^f carriers that are also Idh-2 homozygotes survive very badly compared with other Mpi-Idh-2 combinations, which all survive equally well. For Trf, the heterozygote class survives best, and there is also a difference in survival between the two homozygote classes. Genotype frequencies in the adult population are consistent with the results for calf survival, in that the Mpi^f frequency is lower in succeeding cohorts of surviving adults, whereas no significant gene frequency change is apparent for Idh-2 or Trf.     

A New Malaria Parasite Plasmodium (Sauramoeba) heischi in Skinks (Mabuya striata) from Nairobi, with a Brief Discussion of the Distribution of Malaria Parasites in the Family Scincidae

ABSTRACT. A new species of malaria parasite, Plasmodium (Sauramoeba) heischi , is described from African skinks (Mabuya striata). Eleven individuals of 90 specimens collected in Nairobi were found to be infected. The new parasite is a large species, characterized by spindle-shaped gametocytes, the female often with a subterminal nucleus. The schizonts produce up to 65 nuclei and cause great hypertrophy and distortion of the host cell. Although similar to P. (Sauramoeba) giganteum in dimensions and merozoite numbers, P. heischi is easily distinguished by gametocyte and schizont shapes.     

Photosynthetic response and adaptation to high temperature in desert plants : a comparison of gas exchange and fluorescence methods for studies of thermal tolerance

The temperature threshold for the onset of irreversible loss of photosynthetic capacity of leaves was examined in studies of net CO₂ exchange and by chlorophyll fluorescence techniques. Close agreement was found between the temperature threshold for a dramatic increase in the fluorescence of chlorophyll from intact leaves and the leaf temperature at which the capacity for photosynthetic CO₂ fixation (measured at rate saturating light intensity by infrared gas analysis) began to be temperature unstable (i.e. decline with time of exposure to a constant temperature). This decline in CO₂ uptake was not a result of a stomatal response yielding a reduced intercellular CO₂ concentration at high temperature, and it is interpreted as an indication of progressive damage to some essential component(s) of the leaf. The temperature-dependent change in chlorophyll fluorescence apparently also indicated the onset of this damage. The fluorescence assay could be conducted with discs of leaves collected from remote locations and kept moist while they were transported to a central location, allowing assessment of the high temperature tolerance of leaves which developed under natural field conditions. These assays were verified using a mobile laboratory to study gas exchange of attached leaves in situ. The high temperature sensitivity of leaves of plants growing under natural conditions were similar to those of the same species grown in controlled environments of similar thermal regimes. High temperature in controlled environment studies brought about acclimation responses which increased the threshold for high temperature damage as measured by gas exchange. Studies of fluorescence versus temperature confirmed that this method could be used to quantify these responses, and permitted the kinetics of the acclimation response to be examined. Gas exchange studies, while providing similar estimates of thermal stability, required more time, more elaborate instrumentation, and are particularly difficult to conduct with field plants growing in situ.     

Sub-antarctic House mice: colonization, survival and selection

House mice have colonized and survived successfully on a number of Sub-Antarctic islands, where the mean annual temperature is only about 5°C, but where there is little seasonal fluctuation in climate. Surprisingly this allows almost continuous breeding. On at least two islands (Macquarie and Marion), there are significant changes in gene frequency in electro-phoretically detected enzymes between young (less than three months of age) and old animals from the same population. This indicates natural selection acting in opposite directions at different stages of the life cycle. However the genetical compositions of the Macquarie and Marion populations are more distinct from each other than either is from most British samples. This means that detailed studies of the Sub-Antarctic mouse populations are likely to reveal much about local adaptation, while comparison between the responses of different populations may lead to important generalisations about the possible reaction to evolutionary challenges of a species living close to its physiological limit.