Postexercise rehydration: effect of Na(+) and volume on restoration of fluid spaces and cardiovascular function.

Our purpose was to study the interaction between Na(+) content and fluid volume on rehydration (RH) and restoration of fluid spaces and cardiovascular (CV) function. Ten men completed four trials in which they exercised in a 35 degrees C environment until dehydrated by 2. 9% body mass, were rehydrated for 180 min, and exercised for an additional 20 min. Four RH regimens were tested: low volume (100% fluid replacement)-low (25 mM) Na(+) (LL), low volume-high (50 mM) Na(+) (LH), high volume (150% fluid replacement)-low Na(+) (HL), and high volume-high Na(+) (HH). Blood and urine samples were collected and body mass was measured before and after exercise and every hour during RH. Before and after the dehydration exercise and during the 20 min of exercise after RH, cardiac output was measured. Fluid compartment (intracellular and extracellular) restoration and percent change in plasma volume were calculated using the Cl(-) and hematocrit/Hb methods, respectively. RH was greater (P < 0.05) in HL and HH (102.0 +/- 15.2 and 103.7 +/- 14.7%, respectively) than in LL and LH (70.7 +/- 10.5 and 75.9 +/- 6.3%, respectively). Intracellular RH was greater in HL (1.12 +/- 0.4 liters) than in all other conditions (0.83 +/- 0.3, 0.69 +/- 0.2, and 0.73 +/- 0.3 liter for LL, LH, and HH, respectively), whereas extracellular RH (including plasma volume) was greater in HL and HH (1.35 +/- 0.8 and 1.63 +/- 0.4 liters, respectively) than in LL and LH (0.83 +/- 0.3 and 1.05 +/- 0.4 liters, respectively). CV function (based on stroke volume, heart rate, and cardiac output) was restored equally in all conditions. These data indicate that greater RH can be achieved through larger volumes of fluid and is not affected by Na(+) content within the range tested. Higher Na(+) content favors extracellular fluid filling, whereas intracellular fluid benefits from higher volumes of fluid with lower Na(+). Alterations in Na(+) and/or volume within the range tested do not affect the degree of restoration of CV function.     

Artificial Triple Wolbachia Infection in Aedes albopictus Yields a New Pattern of Unidirectional Cytoplasmic Incompatibility

Obligately intracellular Wolbachia bacteria infect numerous invertebrates and often manipulate host reproduction to facilitate the spread of infection. An example of reproductive manipulation is Wolbachia-induced cytoplasmic incompatibility (CI), which occurs commonly in insects. This CI has been the focus both of basic scientific studies of naturally occurring invasion events and of applied investigations on the use of Wolbachia as a vehicle to drive desired genotypes into insect populations (“gene drive” or “population replacement” strategies). The latter application requires an ability to generate artificial infections that cause a pattern of unidirectional incompatibility with the targeted host population. A suggested target of population replacement strategies is the mosquito Aedes albopictus (Asian tiger mosquito), an important invasive pest and disease vector. Aedes albopictus individuals are naturally “superinfected” with two Wolbachia types: wAlbA and wAlbB. Thus, generating a strain that is unidirectionally incompatible with field populations requires the introduction of an additional infection into the preexisting superinfection. Although prior reports demonstrate an ability to transfer Wolbachia infections to A. albopictus artificially, including both intra- and interspecific Wolbachia transfers, previous efforts have not generated a strain capable of invading natural populations. Here we describe the generation of a stable triple infection by introducing Wolbachia wRi from Drosophila simulans into a naturally superinfected A. albopictus strain. The triple-infected strain displays a pattern of unidirectional incompatibility with the naturally infected strain. This unidirectional CI, combined with a high fidelity of maternal inheritance and low fecundity effects, suggests that the artificial cytotype could serve as an appropriate vehicle for gene drive.Wolbachia spp. are maternally inherited, obligately intracellular bacteria that commonly infect invertebrates, including ∼20% of insect species (2). A hypothesized explanation for the evolutionary success of Wolbachia is its ability to affect host reproduction; cytoplasmic incompatibility (CI) is one of the most widely reported effects (25). Unidirectional CI can occur when the Wolbachia infection type present in a male differs from that in his mate. Although the precise mechanism is unknown, a lock/key model has been proposed in which the Wolbachia infection modifies the sperm during spermatogenesis (27). If the male inseminates a female lacking a compatible Wolbachia type, the modified sperm fail to achieve karyogamy. In contrast, “rescue” of the modified sperm occurs in embryos from females infected with compatible Wolbachia types. Thus, in populations that include both infected and uninfected individuals, Wolbachia-infected females can mate successfully with all males in the population. In contrast, uninfected females can reproduce successfully only with uninfected males. This pattern of unidirectional CI allows Wolbachia to spread rapidly through host populations.Previous studies of insects with multiple Wolbachia types have demonstrated that unidirectional CI can be additive (4, 5). Multiple Wolbachia infection types within an individual male may independently modify sperm, requiring a similar combination of infection types in female mates for compatibility. Additive unidirectional CI can result in repeated population replacement events, in which single- or double-infection cytotypes are replaced by a Wolbachia “superinfection” (i.e., individuals harboring two or more infections).The concept of population replacement has attracted attention for its potential applications. A frequently referenced strategy is based on the replacement of natural populations with modified populations that are refractory to disease transmission (1, 4, 8, 12, 22). A Wolbachia-based population replacement strategy requires the generation of artificial infection types that differ from those of the targeted populations.Aedes albopictus (Skuse) (Diptera: Culicidae), the Asian tiger mosquito, is native to Asia and is a globally invasive insect. Examples of introduction and establishment include North and South America (11), and recent invasions have extended to Africa, Australia, and Europe (9). In addition to being an invasive pest, this mosquito is an aggressive daytime human biter and has been implicated as a vector of animal (20) and human (11) disease. Recent reports have highlighted its role as a primary vector during recent chikungunya virus epidemics (17, 21).Aedes albopictus populations are naturally infected with two Wolbachia types: wAlbA and wAlbB (13, 24). Therefore, to employ Wolbachia as a vehicle for population replacement, an additional, incompatible infection must be introduced into the natural infection types. Previously, Wolbachia strain wRi was successfully established in A. albopictus by microinjecting the cytoplasm of Drosophila simulans (Riverside) into the embryos of aposymbiotic (i.e., without Wolbachia) A. albopictus mosquitoes (28). As hypothesized, the resulting artificial infection displayed a pattern of bidirectional CI when these mosquitoes were crossed with the naturally double infected strain. Thus, the modification/rescue mechanism(s) of the wRi infection is known to differ from those of the naturally occurring infection types. Therefore, we hypothesized that individuals harboring the combined wRi, wAlbA, and wAlbB infections would be unidirectionally incompatible with the naturally infected mosquitoes.To develop a strain appropriate for an applied population replacement strategy, we have performed experiments to generate an artificial triple infection. Following embryonic microinjection, experiments were designed to examine individuals across generations for the hypothesized unidirectional CI pattern, to determine the stability and segregation of the different infection types, and to characterize the relative fitness of triple-infected individuals.     

The structure of a putative scaffolding protein of immature poxvirus particles as determined by electron microscopy suggests similarity with capsid proteins of large icosahedral DNA viruses

Orf virus, the prototype parapoxvirus, is responsible for contagious ecthyma in sheep and goats. The central region of the viral genome codes for proteins highly conserved among vertebrate poxviruses and which are frequently essential for viral proliferation. Analysis of the recently published genome sequence of orf virus revealed that among such essential proteins, the protein orfv075 is an orthologue of D13, the rifampin resistance gene product critical for vaccinia virus morphogenesis. Previous studies showed that D13, arranged as "spicules," is necessary for the formation of vaccinia virus immature virions, a mandatory intermediate in viral maturation. We have determined the three-dimensional structure of recombinant orfv075 at approximately 25-A resolution by electron microscopy of two-dimensional crystals. orfv075 organizes as trimers with a tripod-like main body and a propeller-like smaller domain. The molecular envelope of orfv075 shows unexpectedly good agreement to that of a distant homologue, VP54, the major capsid protein of Paramecium bursaria Chlorella virus type 1. Our structural analysis suggests that orfv075 belongs in the double-barreled capsid protein family found in many double-stranded DNA icosahedral viruses and supports the hypothesis that the nonicosahedral poxviruses and the large icosahedral DNA viruses are evolutionarily related.     

Isolation of a human ceruloplasmin cDNA clone that includes the N-terminal leader sequence

A number of cDNA clones encoding human ceruloplasmin were identified using two mixed oligonucleotide probes. One of these clones was shown by DNA sequence analysis to span from the complete N-terminal leader sequence to 114 amino acids short of the C-terminus. The leader sequence consists of 19 primarily hydrophobic amino acids. Northern blot analysis of RNA from human liver showed two species of ceruloplasmin mRNA; a minor species of 3600 nucleotides and a major one of 4400 nucleotides.     

Antithrombin III mRNA in adult rat liver and kidney and in rat liver during development

Using Northern blots the size of antithrombin III (AT III) mRNA in rat liver was found to be 1650 nucleotides. Adult rat kidney also contained a slightly smaller mRNA at about 20% the level in liver. The ontogeny of AT III mRNA in the liver was assessed by dot blot hybridization. The mRNA was detectable at the earliest age examined (14th day of gestation) at about 15% of the adult levels. After the 17th day of gestation the levels of antithrombin III mRNA rise reaching 50% of adult levels at birth. After birth the mRNA levels rise to 75% of adult levels by the 5th day and reach adult levels by 40 days after birth. We suggest that foetal AT III is produced by both the foetal liver and by placental transfer of the maternal inhibitor.     

Placental metabolite profiles in late gestation for healthy mice

Metabolomics - The study of lipoprotein metabolism at the population level can provide valuable information for the organisation of lipoprotein related processes in the body. To use this...     

Regulation of fermentative capacity and levels of glycolytic enzymes in chemostat cultures of Saccharomyces cerevisiae

Regulation of fermentative capacity was studied in chemostat cultures of two Saccharomyces cerevisiae strains: the laboratory strain CEN.PK113-7D and the industrial bakers’ yeast strain DS28911. The two strains were cultivated at a fixed dilution rate of 0.10 h⁻¹ under various nutrient limitation regimes: aerobic and anaerobic glucose limitation, aerobic and anaerobic nitrogen limitation on glucose, and aerobic ethanol limitation. Also the effect of specific growth rate on fermentative capacity was compared in glucose-limited, aerobic cultures grown at dilution rates between 0.05 h⁻¹ and 0.40 h⁻¹. Biomass yields and metabolite formation patterns were identical for the two strains under all cultivation conditions tested. However, the way in which environmental conditions affected fermentative capacity (assayed off-line as ethanol production rate under anaerobic conditions) differed for the two strains. A different regulation of fermentative capacity in the two strains was also evident from the levels of the glycolytic enzymes, as determined by in vitro enzyme assays. With the exception of phosphofructokinase and pyruvate decarboxylase in the industrial strain, no clear-cut correlation between the activities of glycolytic enzymes and the fermentative capacity was found. These results emphasise the need for controlled cultivation conditions in studies on metabolic regulation in S. cerevisiae and demonstrate that conclusions from physiological studies cannot necessarily be extrapolated from one S. cerevisiae strain to the other.