Glycogen synthesis from pyruvate in the periportal and from glucose in the perivenous zone in perfused livers from fasted rats

The isolated liver of 24 h fasted rats was perfused in a non-recirculating manner in the orthograde or retrograde direction with media containing glucose and/or gluconeogenic precursors. Glycogen formation was determined biochemically and demonstrated histochemically. With glucose as the only exogenous substrate glycogen was formed exclusively in the perivenous area during both orthograde and retrograde perfusion. With gluconeogenic precursors as the exogenous substrates glycogen was deposited in the periportal zone during orthograde perfusion and in the intermediate zone during retrograde perfusion. Supply of glucose and gluconeogenic substrates initiated glycogen synthesis only in the upstream region, i.e. in the periportal zone during orthograde and in the perivenous zone during retrograde perfusion. This localization of glycogen synthesis was probably due to an unavoidable, insufficient oxygen supply of the respective downstream area. In general, the results confirm the hypothesis that periportal and perivenous glycogen was synthesized from different substrates.     

Acanthocefalan eggs in animal coprolites from archaeological sites from Brazil

An important point in paleoparasitology is the correct diagnosis of the origin of coprolites found in archaeological sites. The identification of human and animal coprolites, through the study of the shape, size, characteristics after rehydration, alimentary contents, and the presence of parasites, has proved to be accurate for human coprolites. For non-human ones we compared coprolites with recent faeces of animals collected near the archaeological sites, following the methodology above mentioned. In this paper anteaters coprolites (Tamandua tetradactyla; Myrmecophaga tridactyla) with eggs of Gigantorhynchus echinodiscus (Archiancanthocephala; Gigantorynchidae) were identified.     

Extrapolations from species to species and from various cell types in assessing risks from chemical mutagens

Strategies for estimating human mutation frequencies can be based on extrapolations of dose: mutation ratios in other species.     

Reconstructing land cover from pollen assemblages from small lakes in Denmark

A calibration data set of AD 1800 pollen assemblages and land cover from 30 lake sites (3.5–33 ha) in Denmark is analysed. Canonical ordination (RDA) shows that the distance-weighted land cover of woodland, heathland and open field explain the highest proportion of the variation in the pollen data. Four different distance-weighting functions, 1, 1/d, 1/d² and an approximation of the Sugita model of pollen dispersal, are applied to the land-cover data, and the 1/d function results in the strongest correlation between distance-weighted land cover and pollen proportions. Partial least squares (PLS) calibration is applied, and land cover around nine test sites (not included in the calibration data set) is reconstructed from pollen assemblages. The Extended R-value (ERV) model is applied to the pollen proportions and distance-weighted plant abundance inferred from the maps. Pollen productivity and background components are estimated from the calibration data set and used to reconstruct plant abundance around the test sites. The reconstructed land cover and plant abundance are compared with historical maps, and the performance of the two models is compared. Root-mean-squared errors for the two models are within the same ranges but tend to be slightly lower for the ERV model. Division of the data set into two regional subsets does not improve the reconstructions.     

Glycogen synthesis from glucose and fructose in hepatocytes from diabetic rats

In rat hepatocytes, the basal glycogen synthase activation state is decreased in the fed and diabetic states, whereas glycogen phosphorylase a activity decreases only in diabetes. Diabetes practically abolishes the time- and dose-dependent activation of glycogen synthase to glucose especially in the fed state. Fructose, however, is still able to activate this enzyme. Glycogen phosphorylase response to both sugars is operative in all cases. Cell incubation with the combination of 20 mM glucose plus 3 mM fructose produces a great activation of glycogen synthase and a potentiated glycogen deposition in both normal and diabetic conditions. Using radiolabeled sugars, we demonstrate that this enhanced glycogen synthesis is achieved from both glucose and fructose even in the diabetic state. Therefore, the presence of fructose plays a permissive role in glycogen synthesis from glucose in diabetic animals. Glucose and fructose increase the intracellular concentration of glucose 6-phosphate and fructose reduces the concentration of ATP. There is a close correlation between the ratio of the intracellular concentrations of glucose 6-phosphate and ATP (G6-P/ATP) and the activation state of glycogen synthase in hepatocytes from both normal and diabetic animals. However, for any given value of the G6-P/ATP ratio, the activation state of glycogen synthase in diabetic animals is always lower than that of normal animals. This suggests that the system that activates glycogen synthase (synthase phosphatase activity) is impaired in the diabetic state. The permissive effect of fructose is probably exerted through its capacity to increase the G6-P/ATP ratio which may partially increase synthase phosphatase activity, rendering glycogen synthase active.     

Proline synthesis from glutamate in mitochondria from the blowfly Aldrichina grahami

• 1.1. Glutamyl kinase in a homogenate of blowfly abdomens was not inhibited by proline and its analogues, and was found only in the mitochondrial fraction.
• 2.2. Proline was biosynthesized from glutamate only in a cell-free system prepared from blowfly abdomen.

     

Lipoprotein lipase from rainbow trout differs in several respects from the enzyme in mammals

Previously we found lipase activity with characteristics similar to lipoprotein lipase (LPL) in tissues from rainbow trout [Biochim. Biophys. Acta 1255 (1995) 205], whereas no equivalent to the related hepatic lipase could be found. An equivalent to apolipoprotein CII was also identified and characterized [Gene 254 (2000) 189]. We present here the full nucleotide sequence for LPL from rainbow trout (Oncorhynchus mykiss) and have investigated some properties of the enzyme. In contrast to what has been found in mammals, LPL mRNA was expressed in livers of adult trout. This indicates that trout LPL carries out functions that hepatic lipase has evolved to take over in mammals. Trout LPL was unstable at 37 degrees C compared with bovine and human LPL. Two sequence differences that may relate to the instability are that trout LPL lacks the disulfide bridge in the C-terminal domain and lacks Pro(258). This residue is conserved in LPL from all mammals and has been shown to be critical for enzyme stability at 37 degrees C. On chromatography on heparin-Sepharose trout and chicken LPL eluted at higher salt concentration than bovine (or other mammalian) LPL. The C-terminal end of LPL has been implied in heparin binding and the higher heparin affinity of the trout and chicken enzymes may be because they have 17 and 15 extra amino acid residues at the C-terminal end, of which three residues are positively charged.     

Plant Regeneration from Protoplasts Derived from Suspension Cultures in Leymus racemosus

Calli initiated from mature embryos of Leymus racemosus (Lam. Tzvel. =L. giganteus were transferred onto the AA and DM media to produce friable embryogenic callus,from which embryogenic suspension cultures were established. Protoplasts were isolated from the embryogenic suspension cultures and were cultured either in thin-layer liquid medium or in double-layer (agar/liquid) medium. When visible calli were formed they were transferred onto the NBI agar medium or into the MBL liquid medium for further proliferation. These calli were transferred onto differentiation media of NBII and NR, where green spots were developed. Plants with both shoots and roots can be recovered from these green spots on MS Ⅱ medium containing 0.5 mg/L NAA. The results showed that the Km8p basal medium was favourable to the culture of L. racemosus protoplasts during the early stages of culture. In addition, the composition of the media added to the cultures had a marked influence on the growth of protoplasts, indicating that the nutritional requirements in this plant were different at various stages of protoplast growth and differentiation.     

Decline in mortality from coronary heart disease in Finland from 1969 to 1979.

The trends in mortality from coronary heart disease in the 1970s and the differences in trends between counties within Finland were calculated from official mortality statistics among the population aged 35 to 64 years. During this period coronary mortality declined by a mean of 1.1% for men and 2.3% for women annually in the whole of Finland. A community based cardiovascular control programme was started in 1972 in North Karelia, a county in the east of Finland. The decline in coronary mortality in this county between 1969 and 1979 was 24% in men and 51% in women. The decline in the rest of Finland over the same period was 12% in men and 24% in women. The decline in North Karelia was greater than that in other counties of Finland for both men and women and that difference exceeded random variation, with over 95% likelihood for both sexes. Even with adjustment for rates before 1974 with cross-county multiple regression analyses the difference persisted. Although further studies are needed, the changes in coronary mortality in North Karelia suggest that the preventive programme has been effective.     

Hepatozoonosis in foxes from Portugal

Hepatozoon, sp. is described for the first time in foxes (Vulpes vulpes silacea) in Portugal. Of 301 foxes examined, 143 (48%) were infected. The gametocyte was the predominant stage of the life cycle and was found in every organ except the bone marrow, where schizonts were the most abundant stage. The morphological similarity of this parasite's gametocytes to Hepatozoon canis is emphasized.     

Lipogenesis from n-butyrate in colonocytes

Cell membranes of colonic epithelial cells (CEC) in ulcerative colitis show structural abnormalities which are specific to the disease and which suggest impaired lipogenesis in CECs. Lipogenesis from [1-¹⁴C]-n-butyrate, the chief oxidative fuel of colonic epithelial cells, was measured in isolated CECs under control conditions, with or without glucose and in the presence of mercaptoacetate, a major reducing agent in the colonic lumen- Glucose significantly (p < 0.01) stimulated lipogenesis from [1-¹⁴C]-butyrate which was reversed by 5 mM mercaptoacetate. Mercaptoacetate significantly diminished CEC thiolase activity (EC 2.3.1.9). 5-Aminosalicylic acid reversed the adverse effects of mercaptoacetate in the saponifiable fraction of extracted lipids. Changes in lipogenesis due to colonic luminal reducing agents would affect the barrier function of CECs a feature relevant to the disease process of ulcerative colitis.     

Rabies in bats from Alabama

Data on rabies virus infection in bats that were submitted to the Alabama Department of Public Health from 1995-2005 were analyzed. Demographic factors, such as species and sex, and temporal aspects, such as yearly and monthly trends, were investigated. Thirteen species of bats were submitted, and of those, individuals from seven species were rabid; prevalence was highest in Lasiurus borealis and Pipistrellus subflavus and lowest in Eptesicus fuscus and Nycticeius humeralis. There was no difference in prevalence of rabies between sexes or years. Statistically, more rabid bats were submitted in August, September, and November; and fewer were submitted in March, June, and July. Results were similar to those from other regions of North America; these data from Alabama can help to present a more complete view of rabies in bats in North America.     

Splicing from the outside in

A new study in this issue of Molecular Cell (Pleiss et al., 2007b) shows that changes in the environment rapidly alter the splicing efficiency of specific pre-mRNAs in yeast.