Design,synthesis, and effects of novel phenylpyrimidines as glucagon receptor antagonists

The hormone glucagon increases blood glucose levels through increasing hepatic glucose output. In diabetic patients, dysregulation of glucagon secretion contributes to hyperglycemia. Thus, the inhibition of glucagon receptor is one target for the treatment of hyperglycemia in type 2 diabetes. Here we designed and synthesized a series of small molecules based on phenylpyrimidine. Of these, the compound (R)-7a most significantly decreased the glucagon-induced cAMP production and glucagon-induced glucose production during in vitro and in vivo assays. In addition, (R)-7a showed good efficacy in glucagon challenge tests and lowered blood glucose levels in diabetic db/db mice. Our results suggest that the compound (R)-7a could be a potential glucose-lowering agent for treating type 2 diabetes.     

Compound 4880 is a selective and powerful inhibitor of calmodulin-regulated functions

Compound $\text{48}\text{80}$, a condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde, is composed of a family of cationic amphiphiles differing in the degree of polymerization. Compound $\text{48}\text{80}$ was found to be a potent inhibitor of the calmodulin-activated fraction of brain phosphodiesterase and red blood cell Ca²⁺-transport ATPase, with IC₅₀ values of 0.3 and 0.85 μg/ml, respectively. However, the basal activity of both enzymes is not at all suppressed by the drug at concentrations up to 300 μg/ml. Inhibition of Ca²⁺ transport into inside-out red blood cell vesicles by compound $\text{48}\text{80}$ follows a similar pattern in that basal, calmodulin-independent, transport is also not affected by the drug. Kinetic analysis revealed that the stimulation of Ca²⁺-transport ATPase induced by calmodulin is inhibited by compound $\text{48}\text{80}$ according to a competitive mechanism. It was demonstrated that the inhibitory constituents of compound $\text{48}\text{80}$ bind to calmodulin in a Ca²⁺-dependent fashion. Comparison of the specificity of several anti-calmodulin drugs showed that compound $\text{48}\text{80}$ is the most specific inhibitor of the calmodulin-dependent fraction of red blood cell Ca²⁺-transport ATPase that has been described hitherto. In addition, compound $\text{48}\text{80}$ was found to be a rather specific inhibitor of the calmodulin-induced activation of Ca²⁺-transport ATPase when compared with the stimulation induced by an anionic amphiphile or by limited proteolysis. Half-maximal inhibition of the activity stimulated by oleic acid or mild tryptic digestion required 8- and 32-times higher concentrations of compound $\text{48}\text{80}$, respectively, compared with the calmodulin-dependent fraction of the ATPase activity. Moreover, calmodulin-independent systems as rabbit skeletal muscle sarcoplasmic reticulum Ca²⁺-transport ATPase or calf cardiac sarcolemma (Na⁺ + K⁺)-transport ATPase are far less influenced by compound $\text{48}\text{80}$ as compared with trifluoperazine and calmidazolium. Because of its high specificity compound $\text{48}\text{80}$ is proposed to be a promising tool for studying calmodulin-dependent processes.     

Dual Signalling by the Adenosine A2a Receptor Involves Activation of Both N- and P-Type Calcium Channels by Different G Proteins and Protein Kinases in the Same Striatal Nerve Terminals

Abstract: Many G_s-linked receptors have been reported to use multiple signalling pathways in transfected cells but few in their normal cell environment. We show that the adenosine A_2a receptor uses two signalling pathways to increase the release of acetylcholine from striatal nerve terminals. One pathway involves activation of G_s, adenylyl cyclase, protein kinase A, and P-type calcium channels; the other is mediated by a cholera toxin-insensitive G protein, protein kinase C, and N-type calcium channels. The effects of these two pathways are not additive, the second pathway being inhibited by the first; but they are equally sensitive to the A_2a receptor antagonist KF17837. This demonstrates that the A_2a receptor activates two signalling systems in striatal cholinergic neurons.     

Relationship between reaction time of eye movement and activity of the neck extensors

This study investigated the relationship between the reaction time of eye movement (RTEM) and activity of the superficial neck extensor muscles when the shoulder girdle elevator muscles contracted isometrically. The results were compared with those of a previous study in which the subjects's head was fixed and loaded with the neck flexed. When the shoulder girdle elevator muscles contracted isometrically, RTEM decreased significantly in comparison to RTEM at rest. This demonstrated that the reaction time significantly decreased not only as a result of the neck in flexion, which activated the deep and superficial neck extensor muscles, but also from contraction of the shoulder girdle elevator muscles which mainly activated the superficial extensor muscles. The relationship between RTEM and relative muscle load of the shoulder girdle elevator muscles showed that RTEM decreased up to 30% loading, and with loading above 40% the RTEM was longer than with 30%. The relative muscle load for the shortest RTEM demonstrated a subject-to-subject variance ranging from 24.7% to 49.6%. The difference between RTEM at rest and at their shortest reaction time was approximately 20 ms, which was consistent with the data for the neck in flexion. However, the relative muscle load for the shortest RTEM differed between the current and previous studies. The parameters obtained in this study were higher than for those in the previous study.     

Effects of photoperiod and temperature on sexual recrudescence in the male weakfish,Cynoscion regalis

Synopsis Male weakfish,Cynoscion regalis, were collected in the south-west portion of Delaware Bay from April through August of 1992. Histological examination of testes collected from these specimens was used as a baseline for comparison with laboratory data. Weakfish testes were found to be of the unrestricted, continuous spermatogenic type and spermatogenesis was apparently prenuptial. The effects of photoperiod and temperature on gonadal maturation were studied in the laboratory using fish collected in June and July 1991. These fish were exposed to two months of simulated winter conditions prior to assignment to one of four experimental photoperiod/temperature regimes. The treatments included combinations of long day (LD,15 h light) or short day (SD, 9 h light) and high (HT, 20° C) or low (LT, 13° C) water temperatures. The four treatment groups were LD/HT, LD/LT, SD/HT, SD/LT. The LD/HT group was the only one to mature fully, expressing increased plasma androgen levels, increased gonadosomatic index (GSI) and advanced spermatogenesis, as well as hypertrophy of the sonic muscles, a seasonally expressed secondary sexual characteristic of male weakfish. High temperatures promoted the later stages of spermatogenesis, which were apparently inhibited by low temperatures. The presence of an endogenous annual cycle is suggested by the partial maturation of the testes and sonic muscles in all treatment groups, regardless of photoperiod/temperature regime.     

TNRNFLRFamide and SDRNFLRFamide modulate muscles of the stomatogastric system of the crab Cancer borealis

The effects of the extended FLRFamide-like peptides, TNRNFLRFamide and SDRNFLRFamide, were studied on the stomach musculature of the crab Cancer borealis. Peptide-induced modulation of nerve-evoked contractions was used to screen muscles. All but 2 of the 17 muscles tested were modulated by the peptides. In several muscles of the pyloric region, peptides induced long-lasting myogenic activity. In other muscles, the peptides increased the amplitude of nerve-evoked contractions, excitatory junctional potentials, and excitatory junctional currents, but produced no apparent change in the input resistance of the muscle fibers. The threshold concentration was 10^–10 M for TNRNFLRFamide and between 10^–9 M to 10^–8 M for SDRNFLRFamide. The absence of direct peptidecontaining innervation to these muscles and the wide-spread sensitivity of these muscles to the peptides suggest that TNRNFLRFamide and SDRNFLRFamide may be released from neurosecretory structures to modulate stomatogastric musculature hormonally. We speculate that hormonally released peptide will be crucial for maintaining appreciable muscle contraction in response to low-frequency and low-intensity motor discharge.Abbreviations cpv muscles cardiopyloric valve muscles - CG commissural ganglion - DG neuron dorsal gastric neuron - dgn dorsal gastric nerve - dvn dorsal ventricular nerve - EJC excitatory junctional current - EJP excitatory junctional potential - FaRPs FMRF-amide related peptides - gm muscles gastric mill muscles - lvn lateral ventricular nerve - mvn medial ventricular nerve - p muscles pyloric muscles - STG stomatogastric ganglion     

Ultrastructural and histochemical comparison in two haplotaxids

Pelodrilus leruthi Hrabe, 1958 and Haplotaxis gordioides Hartman, 1821 have been investigated from a histochemical point of view. A different distribution and number of fast and slow fibres has been detected in the two species. Pelodrilus leruthi specimens living in different caves, show some differences in the body wall muscle thickness and in the structure of the ventral nerve cord. A correlation with their different life styles is proposed.     

Body wall muscles in oligochaetes

Longitudinal body wall muscles in tubificids, enchytraeids, lumbriculids, haplotaxids and lumbricids are always histologically and ultrastructurally distinguishable from one another. Some structural peculiarities, as those typical of lumbriculids, may be used as taxonomic tools. The longitudinal body wall muscles in all oligochaetes belong to slow and fast contracting fibre types. Two possible phylogenetic patterns for the formation of slow fibres are discussed.     

Regulation of gap junctional coupling in isolated pancreatic acinar cell pairs by cholecystokinin-octapeptide,vasoactive intestinal peptide (VIP) and a VIP-antagonist

Cholecystokinin-octapeptide (CCK-OP) induces a time- and dose-dependent decrease of gap Junctional conductance in isolated pairs of pancreatic acinar cells. In double whole-cell experiments, the time course could be described by the latency and the half-life time (t _1/2 ) of cell-to-cell uncoupling. The latency shows a biphasic dependence on [CCK-OP] with a minimum of about 50 sec at 10^–9 m CCK-OP. In the presence of vasoactive intestinal peptide (VIP), the biphasic relationship is shifted to lower CCK-OP concentrations. The increase of latency at high concentrations of CCK-OP (> 10⁰⁹ m) was blocked by addition of a VIP-antagonist. t _1/2 decreases monophasically with increasing [CCKOP]. Addition of GTPS to the pipette solution suppresses the [CCK-OP] dependence of the latency and potentiates the uncoupling phase. The kinetic data are discussed in terms of CCK binding to receptors of high and low affinity. Evidence is presented that secretion and cell-to-cell coupling are not related by an all-ornone process, but that for physiological CCK-OP concentrations, gap junctional uncoupling follows secretion.The authors would like to thank Dipl. Biol. F. Mendez for his support in software development for analysis of gap junctional conductance. The work was supported by the Graduiertenkolleg Biochemische Pharmakologie, the Herrmann und Lilly Schilling Stiftung and the Sonderforschungsbereich 156 of the Deutsche Forschungsgemeinschaft.     

Fine Structure of the Head and Cervical Region of Ceramonema carinatum (Chromadorida: Ceramonematidae)

Structure of the head and cervical region of Ceramonema carinatum (Chromadorida: Ceramonematidae) was described from transmission electron microscopy of serial transverse and longitudinal sections of two females. An unbroken massive cortical layer encompasses the head, except where three thin liplets surround the mouth. A large flask-shaped buccal cavity, with simpler less dense cuticle identical with that of the pharynx, abuts the body cuticle just within the mouth. Myoepithelial ceils constituting the buccal and pharyngeal regions were described. Sixteen head sensilla, the amphids, and dorsal and ventral internal sensilla were identified and described, each with associated sheath and socket cells. Ultrasturcture of the head was compared with that of other nematodes. Arrangement of sensilla resembled that of Monhysterida and Rhabditida with some significant variations, such as prominent longitudinally arranged intracellular organelles containing many microtubules associated with the amphids. The buccal cavity was almost entirely pharyngeal in character. A well-developed system of structural fibrils and abundant hemidesmosomes were notable features.