Effects of starvation and Ca++ on glucose-induced accumulation of cyclic 3′,5′-AMP in pancreatic islets

Summary Exposure to glucose in the presence of 3-isobutyl-1-methylxanthine leads to accumulation of cAMP in islets microdissected fromob/ob-mice. This process is dependent on extracellular Ca⁺⁺ but differs markedly from the glucose action on insulin release in the same in vitro system in disappearing after 18 h of starvation.Supported by the Swedish Medical Research Council (No. 12x562).     

Pancreatic polypeptide: A possible role in the regulation of food intake in the mouse. Hypothesis

Summary Pancreatic polypeptide (PP) is a recently identified hormone produced by pancreatic endocrine cells. The islets of genetically obese mice (ob/ob, C57 BL/6J), which are suspected to lack a circulating satiety factor, contain relatively few of the PP-producing cells. Administration of bovine pancreatic polypeptide (bPP) reduces food intake and suppresses body weight gain in the hyperphagic obese mice. It is postulated that PP participates in the regulation of food intake in a manner as yet undefined.This work was supported by grant No. 3.553.75 from Swiss National Science Foundation. We thank Mrs M. Eissler and Mr R. Cuche for their valuable help.     

Abhängigkeit der Leukozytenwanderung und ihrer Steigerung durch Proteuslipo-polysaccharide von der Glucosekonzentration des Milieus

Summary The migration of leucocytes from the buffy coat is influenced by the glucose concentration in the medium, stimulation of migration results from concentrations of glucose up to 2%.. Higher concentrations of glucose up to 8%. have no effect. The stimulating effect of a constant concentration PLPS increases considerably over the whole range of glucose concentrations up to 8%.. Optimal stimulation by PLPS depends therefore on the glucose concentration.     

Interaction of mitochondrial porin with cytosolic proteins.

Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

Interaction of mitochondrial porin with cytosolic proteins

Summary Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver, cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver, and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

The effects of decreased glucose concentrations on the in vitro development of the post-blastocyst mouse embryo in a fetal calf serum-or bovine serum albumin-supplemented medium

Summary Decreasing the glucose concentration from 1.0 mg/ml to 0.25 mg/ml has no detrimental effects on postblastocyst embryo development when either dialyzed fetal calf serum (20%) or bovine serum albumin (4.0 mg/ml) is used to supplement Eagle's Basal Medium (BME). Development is reduced in both serum-and BSA-supplemented BME devoid of glucose in comparison to glucose controls. Serum-supplemented media support better overall development than BSA-supplemented media.     

The denaturation of proteins: Two state? Reversible or irreversible?

Zusammenfassung Untersuchungen der Denaturie-rungsvorgänge sind für ein Verständnis der Proteinstruktur und -funktion von grosser Bedeutung. Es werden Methoden besprochen, die am ehesten geeignet sind, die Fragen zu beleuchten, ob die Denaturierung einen Zwei-Formen-Prozess darstellt und ob sie reversibel oder irreversibel ist. Sie werden an Beispielen der Harnstoffdenaturierung genetischer Varianten des Rinder--Lactoglobulins erläutert. Es wird ausserdem erörtert, in wieweit sich die Schlussfolgerungen auf die Denaturierung anderer Proteine übertragen lassen.     

Stimulation of glucagon and inhibition of insulin secretion evoked from carotid baroreceptors

Summary The influence from carotid baroreceptors on portal immuno-reactive glucagon and insulin levels and on arterial plasma glucose concentration was studied in vagotomized cats by sectioning of the sinus nerves. Such a complete elimination of the afferent baroreceptor discharge caused a prompt and pronounced increase in the glucose and glucagon levels, whereas the insulin concentration significantly decreased. The role of vascular baroreceptors in the hyperglycemic response to hemorrhage is discussed.     

Dissociation of obesity,hypercholesterolemia and diabetes from atherosclerosis in ob/ob mice

Summary Genetically obese, diabetic and hypercholesterolemic C57BL/6J-ob/ob mice were placed on Purina Laboratory Chow containing 2% cholesterol for up to 4 months. They developed higher plasma cholesterol levels and accumulated an increased quantity of cholesterol in the liver but failed to develop atherosclerotic lesions in the aorta as would be expected in an obese, diabetic and hypercholesterolemic human adult.Acknowledgments. We wish to thank Mr. Willis M. Overton for his excellent technical assistance.     

Stimulation of glucagon and inhibition of insulin secretion evoked from carotid baroreceptors.

The influence from carotid baroreceptors on portal immuno-reactive glucagon and insulin levels and on arterial plasma glucose concentration was studied in vagotomized cats by sectioning of the sinus nerves. Such a complete elimination of the afferent baroreceptor discharge caused a prompt and pronounced increase in the glucose and glucagon levels, whereas the insulin concentration significantly decreased. The role of vascular barorecptors in the hyperglycemic response to hemorrhage is discussed.     

Some thoughts on the importance of insulin in the regulation of the blood glucose level

Insulin can influence rates of glucose utilization by muscle and possibly other tissues via both direct and indirect effects. It can control the rate of fatty acid mobilization from adipose tissue and the rate of fatty acid oxidation in muscle, and the latter inhibits glucose utilization and oxidation. Insulin may influence the levels of insulin-like growth factors I and II, both of which have effects on rates of glucose utilization by muscle. The intertissue cycle between glucose and lactate — the Cori cycle, which is influenced by insulin — may provide another novel mechanism for control of blood glucose. How far other anti-insulin hormones affect these processes is not clear.     

Glucose does not influence the insulin-like growth factor (IGF) binding to carrier proteins (IGFBPs): Analysis of rat and human serum by western ligand blotting

The insulin-like growth factors (IGFs) circulate bound to specific proteins (termed IGFBP-1 through IGFBP-6) that modulate IGF bioactivity in tissues. The aim of this study was to analyse the effects of glucose on IGF binding to IGFBPs in rat and human serum by means of western ligand blotting. Serum samples were incubated with increasing concentrations of glucose (0 to 50 mmol/l), and EDTA (25 mmol/l) was added to inhibit protease activity. To analyse the effect of glucose on protection of IGFBPs from protease activity, serum from pregnant women (reported to be very rich in proteolytic activity against IGFBPs) was added to rat serum previously incubated with glucose. Glucose did not affect the¹²⁵I-IGF binding to rat and human serum IGFBPs. The intensity of IGFBP-3 bands decreased considerably during the incubation. This appeared to be due to endogenous protease activity, since the decrease was blocked by addition of EDTA. The incubationi of rat serum with pregnant human serum produced a marked attenuation of IGFBP-3 and disappearance of IGFBP-4 bands. In conclusion, our study shows that glucose does not influence the IGF binding to IGFBP-3 either in rat or in human serum, confirms the presence of endogenous proteolytic activity in normal non-pregnant serum, and demonstrates that glucose has no protective action against protease activity.     

Demonstration of specific and non-specific agglutinogens in the normal bone marrow erythroblasts

Zusammenfassung Es wurde untersucht, ob die Erythroblasten im menschlichen Knochenmark spezifische und unspezifische Antigene, entsprechend den Erythrozyten, besitzen. Diese Eigenschaft wurde auch bei den unreifsten basophilen Erythroblasten beobachtet.     

大理岩单轴受压全过程细观损伤量化研究

设计基于SEM的大理岩细观损伤全程数字化跟踪试验方案,对四川锦屏大理岩试样进行了单轴压缩细观损伤的全程试验。基于数字图像处理技术,对微裂纹的萌生、生长及贯通过程进行定量分析,提取试样在受荷过程中微裂纹的面积、方位角、长度、宽度和周长基本几何数据。然后利用统计学理论对获取到的32组试样微裂纹的损伤全过程的细现信息进行了统计分析,得到在单轴压缩过程中微裂纹的方位角、长度和间距服从变参数的广义极限分布这一结论,最后引入G Swoboda损伤理论,模拟得到单轴压缩试验的应力一应变关系,并与实际试验的结果进行了比较。结果显示可以较准确模拟单轴压缩力学状态下的应力一应变关系。     

Updating ARMA predictions for temporal aggregates

This article develops and extends previous investigations on the temporal aggregation of ARMA predications. Given a basic ARMA model for disaggregated data, two sets of predictors may be constructed for future temporal aggregates: predictions based on models utilizing aggregated data or on models constructed from disaggregated data for which forecasts are updated as soon as the new information becomes available. We show that considerable gains in efficiency based on mean‐square‐error‐type criteria can be obtained for short‐term predications when using models based on updated disaggregated data. However, as the prediction horizon increases, the gain in using updated disaggregated data diminishes substantially. In addition to theoretical results associated with forecast efficiency of ARMA models, we also illustrate our findings with two well‐known time series. Copyright © 2004 John Wiley & Sons, Ltd.     

Reversible impairment of hepatobiliary function induced by streptozotocin in the rat

The effect of streptozotocin (SZ) on hepatobiliary function was studied in rats on the 1st, 7th and 15th days of treatment. Serum glucose increased significantly on the 1st day, and then remained high. Bile flow, bile acids output and BSP biliary excretion were significantly decreased on the 1st day of treatment, whereas serum sorbitol dehydrogenase was increased. All the parameters tested apart from serum glucose tended to normalize with time. The results suggested a transient toxic effect of SZ on the hepatocyte.     

Effect of epinephrine upon irreversible disposal and recycling of glucose in dogs

Summary Irreversible utilization and recycling of glucose during epinephrine-induced hyperglycemia were studied in adrenal-demedullated dogs exposed to neutral or cold ambient temperature. Whatever the ambient temperature, most of the extra glucose mobilized by epinephrine is recycled rather than irreversibly utilized by the peripheral tissues.This work was supported by a grant from Université Claude Bernard (U.E.R. Lyon Nord and U.E.R. Biologie Humaine).J. Schellhorn was on leave from the University of Chile. The authors thank D. Rougier and G. Dallevet for their excellent technical assistance.     

High glucose-induced enzyme activity changes in cultured cell lines established from the kidneys of Chinese hamsters with aglycosuria or spontaneous glycosuria

Summary Chinese hamster kidney epithelial-like cells derived from highly inbred nondiabetic (AV) and diabetic (XA) genetic sublines were passaged in medium containing 100 or 400 mg/dl glucose. The effect of high medium glucose on the activities of 5 enzymes involved in glucose metabolism was followed and significant glucose-dependent difference was observed. The effects, however, were opposite in cells derived fromAV andXA sublines.     

Kinetic analysis and simulation of glucose transport in plasma membrane vesicles of glucose-repressed and derepressed Saccharomyces cerevisiae cells

In this study experimental data on the kinetic parameters investigated by other authors 1-5, 11 together with own data on plasma membrane vesicles, have been subjected to a computer simulation based on the equations describing facilitated diffusion. The simulation led to an ideal fit describing the above data. From this it can be concluded that glucose is transported by facilitated diffusion, and not by active transport as was postulated by Van Steveninck 14,15. The simulation method also demonstrates that the fast sampling technique used by these authors 1-5, 11 underestimated the fluxes. Thus, the parameters given do not contribute to the understand of glucose transport under different metabolic conditions. The K value of plasma membrane vesicles prepared from glucose-repressed cells is around 7 mM. Derepression, particularly by galactose, causes a highly significant increase in affinity as shown by a decrease in the K value to 2 mM. The highest affinity was measured in a triple kinaseless mutant grown on glycerol with a K value of 1 mM. It seems, therefore, that the kinetic parameters derived from initial uptake rates of glucose in intact cells 1-5, 11 using single flux analysis, such as Eadie-Hofstee- or Lineweaver-Burk-plots, are in error.