Unusual growth pattern in the Frasnian alveolitids (Tabulata) from the Holy Cross Mountains (Poland)

Abstract: Growth periodicity is a phenomenon occurring in fossil and modern corals. The most apparent feature is growth banding, and environmental changes are broadly accepted as controls on this phenomenon. If environment controls the growth, then all corallites within a colony should repeat the same growth pattern, as individuals are clones and must have shared the same environment. A study on several species of Alveolitidae (Anthozoa, Tabulata) from the Late Devonian (Early Frasnian) of the Holy Cross Mountains (Poland) shows that the growth pattern varies between neighbouring individuals within the same corallum. This contradicts observations of closely related Favositida as demonstrated on Pachyfavosites sp. from the Givetian of Avesnois, France, where neighbouring individuals repeat the same pattern. Therefore, environmental control on growth rhythm in Alveolitidae can be excluded; the causes of differences between individuals remain unknown.     

The mechanism of the hyperglycaemic action of synthetic peptides related to the C-terminal sequence of human growth hormone

Synthetic part sequences of human pituitary growth hormone (hGH 176–191 and hGH 177–191) corresponding to residues 176–191 or 177–191 of the hormone have been tested for their effects on glycogen and pyruvate metabolism in the rat, both in vivo and in vitro. When injected, the peptides caused transient increases in blood glucose and lactate, while decreasing the activity ratio of glycogen synthase in muscle, adipose tissue and liver and of pyruvate dehydrogenase in muscle and adipose tissue, but not in liver. These decreases were associated with the conversion of the enzymes from their active to their inactive forms, since the peptides did not affect the total amount of either the synthase or the dehydrogenase. The time course of the effect on the enzymes was similar to that for the effect on blood metabolites, and responses for synthase were produced over the range 0.07–7 nmols hGH 177–191/kg body weight. Phosphorylase activity was not affected by the peptides, nor was the capacity to dispose of injected L-lactate. Experiments with adipocytes and hepatocytes showed that the peptides also affected glycogen synthase and pyruvate dehydrogenase activities in vitro. The peptides had no effect on the overall rate of gluconeogenesis from lactate by hepatocytes. However, at times corresponding to those at which glycogen synthase was inactivated, the peptides caused increased incorporation of lactate into free glucose and decreased incorporation into glycogen. It was concluded that the peptides acted directly on their target tissues, and that the observed hyperlactataemia was the result of the inactivation of pyruvate dehydrogenase. The addition lactate increased the flux through the gluconeogenic pathway, and appeared as glucose because the peptide also inactivated glycogen synthase. Thus, the hyperglycaemia produced by hGH 177–199 and related peptides is explicable in terms of a modified Cori Cycle.     

Effects of varying the hostplant and environmental conditions on the feeding and reproduction of Aphis fabae

The reproduction of apterous virginoparae of A. fabae on field beans is primarily controlled by nutrition of both the larval and adult stages. The kind of hostplant and the lighting conditions under which it is grown affect the aphid's fecundity and reproductive rate. Plants grown under mercury fluorescent lamps provide the aphids with better or more nutrients of the right kind so that they reproduce better than aphids living on plants grown in daylight in glasshouses.Nutrition during larval life also affects the early reproductive rate and fecundity of the aphids. Aphids that grew quickly as larvae reproduced faster during early adult life than slow developers. Fast developers were heavier and larger but did not contain more embryos than slow developers as adults and probably received a more nutritious food supply during their larval lives.

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Zusammenfassung Die Fortpflanzung ungeflügelter Virginoparer von Aphis fabae auf Ackerbohnen wird primär durch die Ernährung der Larven und Erwachsenen gesteuert. Die Art der Wirtspflanze und die Beleuchtungsbedingungen, unter denen sie sich entwickeln, beeinflussen die Gesamt-Fruchtbarkeit und die Reproduktionsrate der Blattläuse. Pflanzen, die unter Quecksilber-Fluoreszenz-Lampen (Leuchtstoffröhren) aufwuchsen, bieten den Blattläusen offensichtlich bessere oder mehr Nahrungsstoffe der erforderlichen Art, so daß sie sich besser fortpflanzen als Läuse, die auf Pflanzen leben, die im Gewächshaus unter Tageslicht aufgezogen wurden.Auch die Ernährungsverhältnisse während des Larvallebens beeinflussen die anfängliche Reproduktionsrate und die Fruchtbarkeit der Blattläuse. Manche Blattläuse, die sich rascher als andere entwickeln, hatten im frühen Adultstadium eine höhere Reproduktionsrate als die Langsam-Entwickler. Schnell-Entwickler waren schwerer und größer als Langsam-Entwickler und erhielten während ihres Larvallebens wahrscheinlich eine nahrhaftere Kost.

     

A Role for Protein Kinase Bβ/Akt2 in Insulin-Stimulated GLUT4 Translocation in Adipocytes

Insulin stimulates glucose uptake into muscle and fat cells by promoting the translocation of glucose transporter 4 (GLUT4) to the cell surface. Phosphatidylinositide 3-kinase (PI3K) has been implicated in this process. However, the involvement of protein kinase B (PKB)/Akt, a downstream target of PI3K in regulation of GLUT4 translocation, has been controversial. Here we report that microinjection of a PKB substrate peptide or an antibody to PKB inhibited insulin-stimulated GLUT4 translocation to the plasma membrane by 66 or 56%, respectively. We further examined the activation of PKB isoforms following treatment of cells with insulin or platelet-derived growth factor (PDGF) and found that PKBbeta is preferentially expressed in both rat and 3T3-L1 adipocytes, whereas PKBalpha expression is down-regulated in 3T3-L1 adipocytes. A switch in growth factor response was also observed when 3T3-L1 fibroblasts were differentiated into adipocytes. While PDGF was more efficacious than insulin in stimulating PKB phosphorylation in fibroblasts, PDGF did not stimulate PKBbeta phosphorylation to any significant extent in adipocytes, as assessed by several methods. Moreover, insulin, but not PDGF, stimulated the translocation of PKBbeta to the plasma membrane and high-density microsome fractions of 3T3-L1 adipocytes. These results support a role for PKBbeta in insulin-stimulated glucose transport in adipocytes.