Discriminative stimulus,antagonist, and rate-decreasing effects of cyclorphan: Multiple modes of action

The discriminative effects of cyclorphan were studied in pigeons trained to discriminate 0.32 mg/kg ethylketazocine, 1.8 mg/kg cyclazocine, or 32 mg/kg naltrexone from saline. A fourth group of pigeons was administered 100 mg/kg/day morphine and trained to discriminate 0.1 mg/kg naltrexone from saline. Cyclorphan produced dose-related ethylketazocine-appropriate responding that reached a maximum of 83% of the total session responses at 0.3 mg/kg. Higher cyclorphan doses produced less ethylketazocine-appropriate responding. In pigeons trained to discriminate cyclazocine from saline, maximum drug-appropriate responding of greater than 90% occured at 5.6–10.0 mg/kg cyclorphan. In narcotic-naive pigeons trained to discriminate 32 mg/kg naltrexone from saline, cyclorphan produced a maximum of less than 50% drug-appropriate responding. In contrast, in pigeons chronically administered morphine and trained to discriminate 0.1 mg/kg naltrexone from saline, 1.0 mg/kg cyclorphan resulted in 100% drug-appropriate responding. In pigeons responding under a multiple fixed-interval, fixed-ratio schedule of food delivery, cyclorphan produced a complete dose-related reversal of the rate-decreasing effects of 10 mg/kg morphine, the maximally effective antagonist doses being 1.0–3.2 mg/kg. Higher cyclorphan doses (10 mg/kg) resulted in response rate decreases that were not reversed by naloxone (1 mg/kg). Thus, cyclorphan has discriminative effects that are similar to those of both ethylketazocine and, at 20-fold higher doses, cyclazocine. In addition, in morphine-treated pigeons, cyclorphan, across the same range of doses that produce ethylketazocine-appropriate responding, has discriminative effects that are similar to those of naltrexone, an effect that is probably related to the antagonist action of the drug.     

Catalytic hydrogenations of several 18-oxygenated 3-keto- 4 -steroids

Hydrogenations of the monoketal 2, dihydroaldosterone acetate 4a and aldosterone in the presence of palladium on charcoal are surprisingly easily carried to the tetrahydro stage; this is the basis of a facile synthesis of 3β,5α- and 3β,5β-tetrahydroaldosterone.     

Prolonged blood glucose reduction in mrp-2 deficient rats (GY/TR(-)) by the glucose-6-phosphate translocase inhibitor S 3025

Chlorogenic acid derivatives are potent inhibitors of hepatic glucose production by inhibition of the glucose-6-phosphate translocase component of the hepatic glucose-6-phosphatase system. The pharmacological proof of concept was clearly demonstrated during i.v. infusion of potent derivatives (S 4048, S 3483) in rats. However, the blood glucose lowering effect of S 4048 after bolus i.v. injection lasted only 60-90 min. Plasma clearance of S 4048 was very high, and the parent compound was rapidly and efficiently excreted into the bile of Wistar and GY/TR(-) rats, indicating that mrp-2 was not involved in this hepatobiliary elimination process. About 72% of the total administered radioactivity appeared in the bile within 20 min after i.v. bolus injection of the radiolabeled analogue [(3)H]S 1743 in a Wistar rat. However, in GY/TR(-) rats the dicarboxylic analogue of S 4048, S 3025, was cleared from the plasma less rapidly than its parent compound and its biliary elimination was comparatively low. In contrast, S 3025 exhibited comparable pharmacokinetics and biliary elimination profile as S 4048 in Wistar rats, suggesting that biliary elimination of S 3025 is facilitated by mrp-2, functionally absent in GY/TR(-) rats. Targeting to mrp-2 resulted in a significantly prolonged reduction of blood glucose levels in GY/TR(-) rats after i.v. bolus administration of S 3025.     

Upregulation of hepatic glucose 6-phosphatase gene expression in rats treated with an inhibitor of glucose-6-phosphate translocase

The multicomponent hepatic glucose 6-phosphatase (Glc-6-Pase) system catalyzes the terminal step of hepatic glucose production and plays a key role in the regulation of blood glucose. We used the chlorogenic acid derivative S 3483, a reversible inhibitor of the glucose-6-phosphate (Glc-6-P) translocase component, to demonstrate for the first time upregulation of Glc-6-Pase expression in rat liver in vivo after inhibition of Glc-6-P translocase. In accordance with its mode of action, S 3483-treatment of overnight-fasted rats induced hypoglycemia and increased blood lactate, hepatic Glc-6-P, and glycogen. The metabolic changes were accompanied by rapid and marked increases in Glc-6-Pase mRNA (above 35-fold), protein (about 2-fold), and enzymatic activity (about 2-fold). Maximal mRNA levels were reached after 4 h of treatment. Glycemia, blood lactate, and Glc-6-Pase mRNA levels returned to control values, whereas Glc-6-P and glycogen levels decreased but were still elevated 2 h after S 3483 withdrawal. The capacity for Glc-6-P influx was only marginally increased after 8.5 h of treatment. Prevention of hypoglycemia by euglycemic clamp did not abolish the increase in Glc-6-Pase mRNA induced by S 3483 treatment. A similar pattern of hypoglycemia and possibly of associated counterregulatory responses elicited by treatment with the phosphoenolpyruvate carboxykinase inhibitor 3-mercaptopicolinic acid could account for only a 2-fold induction of Glc-6-Pase mRNA. These findings suggest that the significant upregulation of Glc-6-Pase gene expression observed after treatment of rats in vivo with an inhibitor of Glc-6-P translocase is caused predominantly either by S 3483 per se or by the compound-induced changes of intracellular carbohydrate metabolism.     

A High Power‐Density,Mediator‐Free,Microfluidic Biophotovoltaic Device for Cyanobacterial Cells

Biophotovoltaics has emerged as a promising technology for generating renewable energy because it relies on living organisms as inexpensive, self‐repairing, and readily available catalysts to produce electricity from an abundant resource: sunlight. The efficiency of biophotovoltaic cells, however, has remained significantly lower than that achievable through synthetic materials. Here, a platform is devised to harness the large power densities afforded by miniaturized geometries. To this effect, a soft‐lithography approach is developed for the fabrication of microfluidic biophotovoltaic devices that do not require membranes or mediators. Synechocystis sp. PCC 6803 cells are injected and allowed to settle on the anode, permitting the physical proximity between cells and electrode required for mediator‐free operation. Power densities of above 100 mW m^‐2 are demonstrated for a chlorophyll concentration of 100 μM under white light, which is a high value for biophotovoltaic devices without extrinsic supply of additional energy.     

Appropriateness of the Zucker Diabetic Fatty rat as a model for diabetic microvascular late complications

Male obese Zucker Diabetic Fatty (ZDF) rats develop type 2 diabetes around eight weeks of age, and are widely used as a model for human diabetes and its complications. The objective of the study was to test whether the complications manifested in the kidney and nerves of ZDF rats really correspond to human diabetic complications in their being related to the hyperglycaemic state. Four groups of ZDF rats were used. One lean (Fa/?) and one obese (fa/fa) untreated group served as non-diabetic and diabetic controls. In two further groups of obese (fa/fa) rats, diabetes was prevented by pioglitazone or delayed by food restriction. All rats were monitored up to 35 weeks of age with respect to their blood glucose, HbA1c and insulin levels, their kidney function (urinary glucose excretion, renal glucose filtration, glomerular filtration rate, albumin/creatinine ratio), and their nerve function (tactile and thermal sensory threshold and nerve conduction velocity). Pioglitazone prevented the development of diabetes, while food restriction delayed its onset for 8-10 weeks. Accordingly, kidney function parameters were similar to lean non-diabetic rats in pioglitazone-treated rats and significantly improved in food-restricted rats compared with obese controls. Kidney histology paralleled the functional results. By contrast, nerve functional evaluations did not mirror the differing blood glucose levels. We conclude that the ZDF rat is a good model for diabetic nephropathy, while alterations in nerve functions were not diabetes-related.     

CB1 receptor antagonist AVE1625 affects primarily metabolic parameters independently of reduced food intake in Wistar rats

The objective of the present study was to investigate in fed Wistar rats whether the cannabinoid-1 (CB1) receptor antagonist AVE1625 causes primary effects on metabolic blood and tissue parameters as well as metabolic rate, which are independent of reduced caloric intake. After single administration to rats postprandially, AVE1625 caused a slight dose-dependent increase in basal lipolysis. Six hours after single administration, liver glycogen content was dose-dependently reduced to approximately 60% of that of untreated controls. These findings demonstrate a primary acute effect of AVE1625 on induction of 1) lipolysis from fat tissue (increased FFA) and 2) glycogenolysis from the liver (reduced hepatic glycogen). Measured by indirect calorimetry, AVE1625 caused an immediate increase in total energy expenditure, a long-lasting increase of fat oxidation, and a transient increase of glucose oxidation, which were consistent with the acute findings on metabolic blood and tissue parameters. We conclude that, in addition to the well-investigated effects of CB1 receptor antagonists to reduce caloric intake and subsequently body weight, this pharmacological approach is additionally linked to inherently increased lipid oxidation. This oxidation is driven by persistently increased lipolysis from fat tissues, independently of reduced caloric intake, and might significantly contribute to the weight-reducing effect.     

Role of elongation and secondary pathways in S6 amyloid fibril growth

The concerted action of a large number of individual molecular level events in the formation and growth of fibrillar protein structures creates a significant challenge for differentiating between the relative contributions of different self-assembly steps to the overall kinetics of this process. The characterization of the individual steps is, however, an important requirement for achieving a quantitative understanding of this general phenomenon which underlies many crucial functional and pathological pathways in living systems. In this study, we have applied a kinetic modeling approach to interpret experimental data obtained for the aggregation of a selection of site-directed mutants of the protein S6 from Thermus thermophilus. By studying a range of concentrations of both the seed structures, used to initiate the reaction, and of the soluble monomer, which is consumed during the growth reaction, we are able to separate unambiguously secondary pathways from primary nucleation and fibril elongation. In particular, our results show that the characteristic autocatalytic nature of the growth process originates from secondary processes rather than primary nucleation events, and enables us to derive a scaling law which relates the initial seed concentration to the onset of the growth phase.