Assimilation of different cyanobacteria as food and the consequences for internal energy stores of juvenile roach

Juvenile roach Rutilus rutilus fed on the cyanobacterium Aphanizomenon were able to maintain liver glycogen and muscle protein concentrations. In contrast, internal energy stores of fish fed on the cyanobacterium Microcystis were degraded. Liver glycogen, however, was higher than in starved fish, suggesting that roach was able to obtain some nutrients (probably carbohydrates) from the mucus cover of Microcystis . Weak assimilation of radiolabeled Microcystis by roach was detectable, and assimilation rates increased with increasing proportion of Aphanizomenon in a mixture of both cyanobacteria. It is concluded that the incomplete digestion of Microcystis was the main reason for the negative growth rates of roach when fed on this cyanobacterium species.     

Abnormal swellings in the tegument of the acanthocephalan parasite Metechinorhynchus salmonis

A yellow mass up to 1 mm in diameter was found in the tegument of acanthocephalans of the species Metechinorhynchus salmonis taken from the intestine of adult coho and chinook salmon, Oncorhynchus kisutch and O. tschawytscha, in a tributary to Lake Ontario. Histochemical and ultrastructural observations indicated that it consisted of colored phospholipid bodies in a matrix containing glycogen. No protozoan, bacterial, or viral pathogen was found, suggesting that the abnormality was due to a metabolic dysfunction. Five to ten percent of the worms found were affected.     

High-resolution structural-omics of human liver enzymes

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Preliminary characterization of glycogen phosphorylase activating hormone and adipokinetic hormone from Manduca sexta corpora cardiaca

ABSTRACT. An attempt was made to separate glycogen phosphorylase activating hormone (GPAH) and adipokinetic hormone (AKH) from the corpora cardiaca (CC) of the moth Manduca sexta (Lepidoptera: Sphingidae) by separating extracts of CC on various chromotographic media, but it was not possible to conclude whether GPAH and AKH are activities of one or of two different peptides. Both activities elute together from glass beads, from Sephadex G-25 and from Sephadex LH-20 columns. In the separation experiments with glass beads and G-25 the activities eluted as a single peak, but using LH-20 we found two peaks exhibiting both activities. The major peak eluted at 1.25 × V_t, which is very similar to locust AKH, while the smaller second peak eluted at O.74 × V _t. Cross injections of CC extracts from M. sexta into Locusta migratoria and CC extracts from L. migratoria into M. sexta suggest that GPAH and the AKH from M. sexta are not identical with the decapeptide AKH from locusts.     

Electrostatic effects in the control of glycogen phosphorylase by phosphorylation.

Electrostatic effects are important in the initial activation mechanism of glycogen phosphorylase by phosphorylation. Analysis of the electrostatic surface potential of glycogen phosphorylase with the program GRASP shows that in the unphosphorylated state, the N-terminal 20 residues, which include a number of basic amino acids, are located close to a position on the surface of the molecule that is highly acidic. Upon phosphorylation by phosphorylase kinase at Ser 14, the N-terminal residues change their position and conformation so that the Ser-P is directed away from the acidic patch and to an intersubunit site where 2 arginines bind the phosphate. This recognition site is created through tertiary and quaternary structural changes that accompany the activation mechanism.     

Comparative analysis of glycogen and trehalose accumulation in methylotrophic and nonmethylotrophic yeasts

Trehalose and glycogen accumulate in certain yeast species when they are exposed to unfavorable growth conditions. Accumulations of these reserve carbohydrates in yeasts provide resistance to stress conditions. The results of this study indicate that certain Pichia species do not accumulate high levels of glycogen and trehalose under normal growth conditions. However, depending on the Pichia species, both saccharides accumulate at high levels when the Pichia cells are exposed to unfavorable or stress-inducing growth conditions. Growth in glycerol or methanol medium mostly led to trehalose accumulation in Pichia species tested in this study. It was shown that the metabolic pathways for glycogen and trehalose biosynthesis are present in Pichia species. However, it appears that the biosynthesis of trehalose and glycogen may be regulated in different manners in Pichia species than in the yeast S. cerevisiae. Published in Russian in Mikrobiologiya, 2006, Vol. 75, No. 6, pp. 737–741. The text was submitted by the author in English.     

Development of imaginal competence to adipokinetic hormone in Locusta: lipid and carbohydrate levels, and glycogen phosphorylase activity in precocene-induced adultiforms

Abstract. Adipokinetic responses to injection of synthetic adipokinetic hormone I (sAKH) were investigated in precocene-induced fifth-instar adultiforms and in chemically allatectomized but morphogenetically normal adults of Locusta migratoria (L.). The results were compared with data on normal fifth (=last)-instar nymphs and normal adults. Chemical allatectomy did not affect the resting level of lipid in the haemolymph, nor the slight decrease of haemolymph carbohydrate concentration induced by sAKH. The effects of chemical allatectomy on sAKH-induced hyperlipaemia, the resting level of haemolymph carbohydrate, total glycogen phosphorylase specific activity, as well as sAKH-induced phosphorylase activation in the fat body, were mostly minor and probably indirect. The concentrations of lipid and carbohydrate in the haemolymph, and sAKH-induced activation of fat body glycogen phosphorylase were more or less similar in normal fifth-instar nymphs, normal adults and fifth-instar adultiforms. Thus, precocious metamorphosis did not affect markedly those parameters which show no or slight changes during normal metamorphosis. In contrast, parameters which change substantially during normal metamorphosis (sAKH-induced hyperlipaemia, sAKH-induced changes in haemolymph carbohydrate level and total glycogen phosphorylase activity) showed similar changes in the course of precocious metamorphosis; the values for fifth-instar adultiforms were similar to those obtained for normal adults, but differed markedly from those found in normal fifth-instar nymphs. Thus, accelerated (precocious) morphological adult development is strongly correlated with accelerated imaginal target competence to AKH and with relevant physiological development.     

The rate-limiting step for glucose transport into the hypothalamus is across the blood–hypothalamus interface

Specialized glucosensing neurons are present in the hypothalamus, some of which neighbor the median eminence, where the blood–brain barrier has been reported leaky. A leaky blood–brain barrier implies high tissue glucose levels and obviates a role for endothelial glucose transporters in the control of hypothalamic glucose concentration, important in understanding the mechanisms of glucose sensing We therefore addressed the question of blood–brain barrier integrity at the hypothalamus for glucose transport by examining the brain tissue-to-plasma glucose ratio in the hypothalamus relative to other brain regions. We also examined glycogenolysis in hypothalamus because its occurrence is unlikely in the potential absence of a hypothalamus–blood interface. Across all regions the concentration of glucose was comparable at a given plasma glucose concentration and was a near linear function of plasma glucose. At steady-state, hypothalamic glucose concentration was similar to the extracellular hypothalamic glucose concentration reported by others. Hypothalamic glycogen fell at a rate of ∼1.5 μmol/g/h and remained present in substantial amounts. We conclude for the hypothalamus, a putative primary site of brain glucose sensing that: the rate-limiting step for glucose transport into brain cells is at the blood–hypothalamus interface, and that glycogenolysis is consistent with a substantial blood -to- intracellular glucose concentration gradient.