Evolution of the expression of the Gld gene in the reproductive tract of Drosophila.

During the preadult development of Drosophila melanogaster, the GLD (glucose dehydrogenase) gene (Gld) is expressed in a variety of tissues, including the immature reproductive tract. At the adult stage the expression of Gld becomes largely restricted to the reproductive tract of males and females. We examined the expression of GLD in the adult reproductive tract of 50 species in the genus Drosophila, as well as in those of a few representative species from four other closely related genera. GLD exhibits considerable organ-specific diversity in the reproductive tract of males and females. Among these species, five male GLD phenotypes and six female GLD phenotypes were found. In contrast, the preadult expression of GLD in representative species from each distinct adult pattern type was determined and found to be highly conserved in both the immature reproductive tract and non-reproductive organs. Moreover, the set of reproductive organs that express GLD during preadult development is equivalent to the sum of the five male and six female adult GLD phenotypes. To initially define the contribution of cis- versus trans-acting factors responsible for differences in adult GLD expression between two of these species--D. melanogaster and D. pseudoobscura--we transferred the D. pseudoobscura Gld to the genome of D. melanogaster and investigated its expression. GLD expression patterns of these transformants displayed characteristics that are unique to both species, suggesting the presence of both cis- and trans-acting differences between these two species.     

DETERMINATION OF GUSTATORY SUCROSE THRESHOLD IN WATER BY USE OF A LINEAR SUCROSE GRADIENT

A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)).     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Temporal Stability of Allozyme Frequencies in a Natural Population of DROSOPHILA MELANOGASTER

Seasonal patterns of allozyme variation are examined for 12 polymorphic enzyme loci in Drosophila melanogaster. The data derive from a total of 56 samples taken from a natural population in the Summer and Fall of 1978 and 1979. Samples were obtained at approximately five-day intervals and assayed for 6-phosphogluconate dehydrogenase (6Pgd), phosphoglucomutase (Pgm) and glucose-6-phosphate dehydrogenase (G6pd). The remaining nine enzymes were assayed in an average of eight samples per season. None of the loci exhibit regular seasonal cycles of gene-frequency change, although 6Pgd does show significant, but irregular, frequency oscillations. There is also little evidence for gene-frequency differences between years, although 6Pgd is again exceptional in showing significant frequency changes between years. In addition, genotypic frequency distributions are usually consistent with random mating expectations. With the notable exception of 6Pgd, the data give a strong impression of gene-frequency homogeneity within and among years, despite obvious seasonal changes in climate and in the distribution of breeding sites.     

GCN2 in the Brain Programs PPARγ2 and Triglyceride Storage in the Liver during Perinatal Development in Response to Maternal Dietary Fat

The liver plays a central role in regulating lipid metabolism and facilitates efficient lipid utilization and storage. We discovered that a modest increase in maternal dietary fat in mice programs triglyceride storage in the liver of their developing offspring. The activation of this programming is not apparent, however, until several months later at the adult stage. We found that the perinatal programming of adult hepatic triglyceride storage was controlled by the eIF2α kinase GCN2 (EIF2AK4) in the brain of the offspring, which stimulates epigenetic modification of the Pparγ2 gene in the neonatal liver. Genetic ablation of Gcn2 in the offspring exhibited reduced hepatic triglyceride storage and repressed expression of the peroxisome proliferator-activated receptor gamma 2 (Pparγ2) and two lipid droplet protein genes, Fsp27 and Cidea. Brain-specific, but not liver-specific, Gcn2 KO mice exhibit these same defects demonstrating that GCN2 in the developing brain programs hepatic triglyceride storage. GCN2 and nutrition-dependent programming of Pparγ2 is correlated with trimethylation of lysine 4 of histone 3 (H3K4me3) in the Pparγ2 promoter region during neonatal development. In addition to regulating hepatic triglyceride in response to modest changes in dietary fat, Gcn2 deficiency profoundly impacts the severity of the obese-diabetic phenotype of the leptin receptor mutant (db/db) mouse, by reducing hepatic steatosis and obesity but exacerbating the diabetic phenotype. We suggest that GCN2-dependent perinatal programming of hepatic triglyceride storage is an adaptation to couple early nutrition to anticipated needs for hepatic triglyceride storage in adults. However, increasing the hepatic triglyceride set point during perinatal development may predispose individuals to hepatosteatosis, while reducing circulating fatty acid levels that promote insulin resistance.     

Insulin Secretion and Ca2+ Dynamics in β-Cells Are Regulated by PERK (EIF2AK3) in Concert with Calcineurin

Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) (EIF2AK3) is essential for normal development and function of the insulin-secreting β-cell. Although genetic ablation of PERK in β-cells results in permanent neonatal diabetes in humans and mice, the underlying mechanisms remain unclear. Here, we used a newly developed and highly specific inhibitor of PERK to determine the immediate effects of acute ablation of PERK activity. We found that inhibition of PERK in human and rodent β-cells causes a rapid inhibition of secretagogue-stimulated subcellular Ca²⁺ signaling and insulin secretion. These dysfunctions stem from alterations in store-operated Ca²⁺ entry and sarcoplasmic endoplasmic reticulum Ca²⁺-ATPase activity. We also found that PERK regulates calcineurin, and pharmacological inhibition of calcineurin results in similar defects on stimulus-secretion coupling. Our findings suggest that interplay between calcineurin and PERK regulates β-cell Ca²⁺ signaling and insulin secretion, and that loss of this interaction may have profound implications in insulin secretion defects associated with diabetes.     

Delimitation of the maritime boundary in the gulf of Maine area

The compulsory dispute settlement regime included in the 1982 Law of the Sea Convention is recognized as one of the most comprehensive in a modern international convention. Yet, in the recent application of this regime, the question has arisen as to whether the procedural prerequisites associated with the LOS Convention's compulsory dispute settlement mechanism are so arduous as to avoid binding and compulsory jurisdiction in most instances. This article addresses that question by examining, in particular, the reasoning of the Southern Bluefin Tuna arbitration tribunal, which found Article 281 of Section 1 of the LOS Convention to bar jurisdiction to the compulsory dispute settlement mechanism prescribed by the Convention, and offers suggestions as to how states might distinguish or overcome the barriers imposed by the Southern Bluefin Tuna tribunal in future cases.     

PERK eIF2 alpha kinase is required to regulate the viability of the exocrine pancreas in mice

Background

The lymphatic system complements the blood circulatory system in absorption and transport of nutrients, and in the maintenance of homeostasis. Angiopoietins 1 and 2 (Ang1 and Ang2) are regulators of both angiogenesis and lymphangiogenesis through the Tek/Tie-2 receptor tyrosine kinase. The response of endothelial cells to stimulation with either Ang1 or Ang2 is thought to be dependent upon the origin of the endothelial cells. In this study, we examined the effects of the angiopoietins on lymphatic, venous and arterial primary endothelial cells (bmLEC, bmVEC and bmAEC, respectively), which were isolated and cultured from bovine mesenteric vessels.

Results

BmLEC, bmVEC and bmAEC cell populations all express Tie-2 and were shown to express the appropriate cellular markers Prox-1, VEGFR3, and Neuropilin-1 that define the particular origin of each preparation. We showed that while bmLECs responded slightly more readily to angiopoietin-2 (Ang2) stimulation, bmVECs and bmAECs were more sensitive to Ang1 stimulation. Furthermore, exposure of bmLECs to Ang2 induced marginally higher levels of proliferation and survival than did exposure to Ang1. However, exposure to Ang1 resulted in higher levels of migration in bmLECs than did to Ang2.

Conclusion

Our results suggest that although both Ang1 and Ang2 can activate the Tie-2 receptor in bmLECs, Ang1 and Ang2 may have distinct roles in mesenteric lymphatic endothelial cells.     

PERK is responsible for the increased phosphorylation of eIF2alpha and the severe inhibition of protein synthesis after transient global brain ischemia

Reperfusion after global brain ischemia results initially in a widespread suppression of protein synthesis in neurons that is due to inhibition of translation initiation as a result of the phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF2). To address the role of the eIF2alpha kinase RNA-dependent protein kinase-like endoplasmic reticulum kinase (PERK) in the reperfused brain, transgenic mice with a targeted disruption of the Perk gene were subjected to 20 min of forebrain ischemia followed by 10 min of reperfusion. In wild-type mice, phosphorylated eIF2alpha was detected in the non-ischemic brain and its levels were elevated threefold after 10 min of reperfusion. Conversely, there was no phosphorylated eIF2alpha detected in the non-ischemic transgenic mice and there was no sizeable rise in phosphorylated eIF2alpha levels in the forebrain after ischemia and reperfusion. Moreover, there was a substantial rescue of protein translation in the reperfused transgenic mice. Neither group showed any change in total eIF2alpha, phosphorylated eukaryotic elongation factor 2 or total eukaryotic elongation factor 2 levels. These data demonstrate that PERK is responsible for the large increase in phosphorylated eIF2alpha and the suppression of translation early in reperfusion after transient global brain ischemia.