Heterogeneity of glucagon receptors of rat hepatocytes: a synthetic peptide probe for the high affinity site

A glucagon analog with the following sequence has been synthesized: His- Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg -Leu-Gln-Glu-Phe-Leu-Gln-Trp-Ala-Leu-Gln-Thr. When interacting with rat hepatocytes, the analog mimics, in part, the activities of glucagon in receptor binding and inhibition of carbohydrate incorporation into glycogen. Comparison of the binding of the analog with that of glucagon demonstrates the existence of two distinct homogeneous populations of glucagon receptors. The synthetic analog acts as a specific probe for those receptors that have a high affinity for glucagon.     

Bidentate peptides: highly potent new inhibitors of enkephalin degrading enzymes

Three series of bidentates bearing an hydroxamic or an N-Acyl-N-hydroxy amino group on structures related to Phe-Gly or Phe-Ala exhibit strong inhibitory potency against purified enkephalinase with IC50 values in the 4 to 15 nM range. As with thiol-containing inhibitors, such as thiorphan, the most active compounds are those in which a methylene spacer separates the benzyl P1' moiety from the Zn coordinating residue. Formation of a bidentate complex with the metal enzyme is clearly demonstrated by a loss of potency of three order of magnitude following the removal of one component of the bidentate group. All the compounds studied are unable to interact with angiotensin converting enzyme (IC50 greater than 10,000 nM). Moreover, compounds of the general formula HONHCO-CH2-CH(CH2 phi)-CONH-CH(R)-COOH belonging to the most active series of enkephalinase blockers (IC50 approximately 4 nM) behave also as highly potent and competitive inhibitors (IC50 approximately 10 nM) of a Tyr-Gly releasing dipeptidylaminopeptidase purified from rat brain. The pure steroisomer [(R)-3-(N-hydroxy)carboxamido-2-benzylpropanoyl]-L-alanine designated kelatorphan, exhibits also a relatively good inhibitory potency against aminopeptidases (IC50 approximately 10 microM) and can be considered as the first virtually complete inhibitor of enkephalin metabolism. This very interesting property of inhibiting all three enzymes of enkephalin metabolism could enhance the required selectivity for a possible clinical use of these inhibitors as new analgesic and psychoactive drugs.     

The effects of mating,exogenous juvenile hormone and a juvenile hormone analogue on pheromone titre,calling and oviposition in the omnivorous leafroller moth (Platynota stultana)

Mating in Platynota stultana resulted in the termination of calling, the gradual reduction of pheromone in the pheromone glands to non-detectable levels (<0.1 ng/♀) within 14 h, and oviposition of the first batch of eggs 20–24 h after copulation. Decapitation of virgin females resulted in a similar decline in pheromone titre, and also eliminated oviposition and calling. Pheromone production appears to be controlled via the head. Mating probably terminates neural or hormonal input required for pheromone production and/or removes neural or hormonal inhibition of pheromone degradation. A juvenile hormone analogue (ZR-512) and juvenile hormones I, II and III applied exogenously to virgin females elicited oviposition comparable to mated females and terminated calling within 48 h. The juvenile hormone analogue also appeared to block pheromone production in virgin females. These results suggest that juvenile hormone may be involved in the switch from virgin to mated behaviour in this species.     

Urinary catecholamine responses to basic types of physical activity

Urinary adrenaline, noradrenaline, heart rate, and subjective ratings were obtained from 9 healthy males during six different physical activities, ranging in intensity from lying down to running. Heart rate, subjective ratings and noradrenaline excretion reflected the work load in the different conditions. Adrenaline, on the other hand, failed to show this relationship. There was no significant increase in adrenaline excretion even at the highest work load (corresponding to a heart rate of 160 bpm). It was concluded that urinary adrenaline may safely be used as an indicator of mental factors even in situations with different levels of physical activity.     

Cyclic nucleotide phosphodiesterases in larval brain of wild type and dunce mutant strains of Drosophila melanogaster: isoenzyme pattern and activation by Ca2+/calmodulin

Like adult heads and whole flies, larval brains of wild type Drosophila melanogaster contain two major soluble cyclic nucleotide phosphodiesterases, forms I and II. Larval brains of the learning-defective mutant strain, dunceM11, contain only the form I enzyme. In both wild type and dunce strains the form I enzyme is activated by Ca2+/calmodulin. A time-dependent loss of this Ca2+ activation was observed.     

Characterization of black-pigmented Bacteroides strains isolated from animals

The aims of the study were: the isolation of strains of black-pigmented Bacteroides from the gingival sulcus of different animals, their biochemical and immunological characterization and comparison of their properties for classification within the genus. A total of 104 strains, isolated from cats, dogs, racoons and a jaguar, were characterized on the basis of fermentation of carbohydrates, metabolic end products, haemagglutination studies, enzymatic activities, catalase production and indirect immunofluorescence. No differences were observed between the strains regardless of their animal origin. The strains did not ferment carbohydrates, produce phenylacetic acid, show an array of enzyme activities or agglutinate sheep red blood cells. They were catalase-positive and so differed from the human oral strains of Bact. gingivalis. Immunofluorescence microscopy revealed that the animal strains shared at least one major antigen with Bact. gingivalis but none with Bact. asaccharolyticus. Apart from their catalase activity, the animal strains isolated were similar to those of human Bact. gingivalis strains.     

Vasopressin-immunoreactive cells in the dorsomedial hypothalamic region,medial amygdaloid nucleus and locus coeruleus of the rat

Summary Recently, the existence of a vasopressin-immunoreactive cell group was described in the bed nucleus of the stria terminalis (van Leeuwen and Caffé 1983). In the present investigation additional nuclei containing vasopressin-immunoreactive cells were found, after colchicine pretreatment, in the dorsomedial hypothalamus, medial amygdaloid nucleus and the locus coeruleus.Vasopressin-immunoreactive cells in the dorsomedial hypothalamus and medial amygdaloid nucleus are small (8–14 m and 10–14 m, respectively), while those in the locus coeruleus are medium-sized (20–25 m). Incubation with anti-bovine neurophysin II and anti-rat neurophysin revealed staining of the same cell group in the above-mentioned areas. None of these cell groups show stained cells after incubation with anti-oxytocin and anti-bovine neurophysin I. When sections of the homozygous Brattleboro rat, which shows a deficiency in vasopressin synthesis, are incubated with anti-vasopressin, anti-bovine neurophysin II, or anti-rat neurophysin, no immunoreactivity can be observed in these brain regions.The above-mentioned cell groups may contribute to the vasopressinergic innervation of brain sites that have been reported to persist after lesioning of the suprachiasmatic, paraventricular and bed nuclei of the stria terminalis.     

Demonstration of an ATPase at the cell surface of intact normal and neoplastic human cells in culture

An ATPase reaction has been studied at the surface of intact normal and neoplastic human cells in culture. For this purpose a sensitive method has been developed which permits repeated monitoring of enzyme activity without interference with cellular viability. Experiments could be performed with the cells cultured in a single dish. The cells were firmly attached to the supporting medium throughout the experiment. The incubation medium could easily be separated from the cells at the end of the reaction. There was no diffusion of the surface-located ATPase into the incubation medium. Another advantage was the possibility of microscopic control of the appearance of the cells during the reaction. High ATPase activity was found in glia-like cells derived from normal adult brain cells while lines from gliomas had very low activity. One SV40 transformed glia line had an extremely low ATPase activity in contrast to the uninfected cells. Normal fibroblasts and sarcoma cells had about the same low activity as the glioma cells.