Induction of rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase mRNA by refeeding and insulin

The effects of fasting/refeeding and untreated or insulin-treated diabetes on the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and its mRNA in rat liver were determined. Both enzymatic activities fell to 20% of control values with fasting or streptozotocin-induced diabetes and were coordinately restored to normal within 48 h of refeeding or 24 h of insulin administration. These alterations in enzymatic activities were always mirrored by corresponding changes in amount of enzyme as determined by phosphoenzyme formation and immunoblotting. In contrast, mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase did not decrease during starvation or in diabetes, but there was a 3-6-fold increase upon refeeding a high carbohydrate diet to starved rats or insulin treatment of diabetic rats. The decrease of the enzyme in starved or diabetic rats without associated changes in mRNA levels suggests a decrease in the rate of mRNA translation, an increase in enzyme degradation, or both. The rise in enzyme amount and mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase with refeeding and insulin treatment suggests an insulin-dependent stimulation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene expression. Northern blots of RNA from heart, brain, kidney, and skeletal muscle probed with restriction fragments of a full-length cDNA from liver showed that only skeletal muscle contained an RNA species that hybridized to any of the probes. Skeletal muscle mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase was 2.0 kilobase pairs but in contrast to the liver message (2.2 kilobase pairs) was not regulated by refeeding.     

Plasma volume, osmolarity, total protein and electrolytes during treadmill running and cycle ergometer exercise

While haemoconcentration due to loss of plasma volume is well established during cycling, the existence of similar changes during running remains contentious. This study compared the changes in plasma volume and associated blood indices during 60 min of running and cycling at the same relative intensity (approximately 65% VO2max), with all changes referenced to blood indices obtained after 30 min seated at rest on a cycle ergometer. Plasma osmolarity increased similarly with both forms of exercise but was less than predicted for water loss alone, such that there was a net loss of sodium during exercise and of potassium postexercise, with essentially no loss of protein. Plasma volume decreased similarly (approximately 6.5%) in both exercise trials, but while that with cycling was initiated by exercise itself and was essentially maximal within 5 min, the reduction in plasma volume in the running trial was induced by adopting the upright posture and was complete before exercise began. These data would indicate that different mechanisms are responsible for the changes in plasma volume induced by running and cycling, while the similarity of change would suggest that there is a lower limit to any reduction in plasma volume, regardless of mechanism. Furthermore, the observation that the changes in plasma volume were complete before or early in exercise, would imply that oral water ingestion during prolonged exercise, which is essential for thermoregulation, may be more concerned with homeostasis of extravascular water rather than plasma volume.     

Measurement of blood volume in fetal and neonatal sheep using red blood cells labelled with 99m technetium

Blood volume has been measured in fetal and neonatal sheep using red blood cells labelled with 99mTc. The calculated volumes were highly correlated with simultaneous measurements made using the standard 51Cr labelled red cell method, although in absolute terms the 99m Tc method provided volumes which on average exceeded by a small percentage those determined with the 51Cr method. Measurements using the 99mTc method were also made at different ages in fetal and neonatal sheep and, while no correlation could be demonstrated between blood volume and either fetal or neonatal age, neonatal blood volumes were highly correlated with body weight. The 99mTc method is considered to be a reliable technique for measuring perinatal blood volumes in sheep with the short half-life of the isotope offering additional advantages.     

Phylogenetics, genome diversity and origin of modern leopard, Panthera pardus

Leopards, Panthera pardus, are widely distributed across southern Asia and sub-Saharan Africa. The extent and phylogeographic patterns of molecular genetic diversity were addressed in a survey of 77 leopards from known geographical locales representing 13 of the 27 classical trinomial subspecies. Phylogenetic analysis of mitochondrial DNA sequences (727 bp of NADH5 and control region) and 25 polymorphic microsatellite loci revealed abundant diversity that could be partitioned into a minimum of nine discrete populations, tentatively named here as revised subspecies: P. pardus pardus, P. p. nimr, P. p. saxicolor, P. p. fusca, P. p. kotiya, P. p. delacouri, P. p. japonensis, P. p. orientalis and P. p. melas. However, because of limited sampling of African populations, this may be an underestimate of modern phylogeographic population structure. Combined phylogeographic and population diversity estimates support an origin for modern leopard lineages 470,000-825,000 years ago in Africa followed by their migration into and across Asia more recently (170,000-300,000 years ago). Recent demographic reductions likely have led to genetic impoverishment in P. p. orientalis and in the island subspecies P. p. kotiya.     

Inefficient serotype knock down leads to stable coexistence of different surface antigens on the outer membrane in Paramecium tetraurelia

Expression of surface antigens is usually mutually exclusive, meaning that only one protein is present on the cell surface. With the RNAi feeding technology we induce serotype shifts in Paramecium tetraurelia which are demonstrated to be incomplete, meaning that the cells remain in a shifting state. The coexpression of "old" and "new" protein on the surface can be detected to be stable for more than 15 divisions over a 5-day feeding procedure, a time period different from that reported for temperature-induced shifts. A characteristic heterogenic distribution of the different surface antigens is demonstrated by double indirect-immunofluorescent-staining and we show antigen transport mechanisms related to the tips of cilia. Therefore, we discuss release mechanisms, potential sorting mechanisms for glycosylphosphatidylinositol-anchored proteins and the localizations of surface antigens, which are important for the reported classical immobilization reaction.     

Cryopreservation of spermatozoa from wild-born Namibian cheetahs (Acinonyx jubatus) and influence of glycerol on cryosurvival

Sperm cryopreservation is a valuable tool for the genetic management of ex situ populations. This study was conducted to assess: (1) semen characteristics of wild-born cheetahs; and (2) the impact of three types of glycerol influence (duration of exposure, temperature, and method of addition) on sperm cryosensitivity. To evaluate the impact of duration of glycerol exposure, spermatozoa were incubated in Test Yolk Buffer (TYB) with 4% glycerol at ambient temperature (approximately 22 degrees C) for 15 vs. 60 min before cryopreservation. To evaluate the influence of temperature and method of glycerol addition, spermatozoa were resuspended at ambient temperature either in TYB with 0% glycerol followed by addition of 8% glycerol (1:1 v/v; at ambient temperature vs. 5 degrees C) or directly in TYB with 4% glycerol. All samples were cryopreserved in straws over liquid nitrogen vapor and evaluated for sperm motility and acrosomal integrity after thawing. Semen samples (n = 23; n = 13 males) contained a high proportion (78%) of pleiomorphic spermatozoa. Ejaculates also contained a high proportion of acrosome-intact (86%) and motile spermatozoa (78%). Immediately after thawing, a significant proportion of spermatozoa retained intact acrosomes (range, 48-67%) and motility (range, 40-49%). After thawing, incubation in glycerol for 60 min at ambient temperature before freezing decreased (p < 0.05) sperm motility and acrosomal integrity at one time-point each (pre-centrifugation and post-centrifugation, respectively). However, method or temperature of glycerol addition had no (p > 0.05) impact on sperm cryosurvival. In summary, (1) wild-born cheetahs produce high proportions of pleiomorphic spermatozoa but with a high proportion of intact acrosomes; and (2) resuspension in 4% glycerol, followed by exposure for up to 60 min at ambient temperature, had minimal effect on sperm motility and acrosomal integrity after cryopreservation. Results indicate the feasibility of cryopreserving cheetah spermatozoa under field conditions, providing a user-friendly method to capture and store gametes to enhance genetic management.     

Chromosomal Localization, Embryonic Expression, and Imprinting Tests for Bmp7 on Distal Mouse Chromosome 2

Murine Bmp7 has been assigned to distal Chromosome 2 by interspecific backcross mapping. The map location suggests close linkage to classical mouse mutations and places Bmp7 within a chromosome region thought to contain one or more unidentified imprinted genes. A direct test suggests that Bmp7 is not imprinted. An examination of embryonic RNA expression patterns shows that Bmp7 is expressed in a variety of skeletal and nonskeletal tissues. Both embryonic expression patterns and the human chromosomal sublocalization inferred from its mouse location make Bmp7 a candidate for the gene affected in some patients with Holt-Oram syndrome.