Peptidergic co-transmission inAplysia: Functional implications for rhythmic behaviors

Despite their ubiquitous presence in the central and peripheral nervous systems, the behavioral functions of peptide co-transmitters remain to be elucidated. The marine molluscAplysia, whose simple nervous system facilitates the study of the neural basis of behavior, was used to investigate the role of peptidergic co-transmission in feeding behavior. Several novel modulatory neuropeptides were purified, and localized to identified cholinergic motorneurons. Physiological and biochemical studies demonstrated that these peptides are released when the motorneourons fire at frequencies that occur during normal behavior, and that the peptides modify the relationship between muscle contraction amplitude and relaxation rate so as to maintain optimal motor output when the intensity and frequency of feeding behavior change.     

Insulin-like effect of dichloroacetic acid on hexose transport in Swiss 3T3 cells

Summary Hexose transport in Swiss 3T3 cells was increased by treatment with dichloroacetic acid as well as by treatment with insulin. Neither extra-nor intracellular Ca²⁺ was found to be involved in their stimulatory action. On the other hand, the removal of intracellular Mg²⁺ resulted in a loss of the stimulation. These results suggest that dichloroacetic acid stimulates the hexose transport in Mg²⁺-dependent manner, similar to that of insulin.This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, and the Ministry of Health and Welfare of Japan.     

Effects of kallidinogenase on urinary kallikrein excretion and plasma prostanoid concentrations in patients with essential hypertension

The effects of kallidinogenase on urinary kallikrein excretion, plasma immunoreactive prostanoids and platelet aggregation were investigated in patients with essential hypertension. Urinary kallikrein excretion and plasma 6-keto PGF1 alpha concentration were significantly decreased in these patients. Significant decreases in blood pressure, as well as significant increases of urinary kallikrein excretion and plasma 6-keto PGF1 alpha concentration after kallidinogenase administration were also observed.     

Serotonin is localized in endothelial cells of coronary arteries and released during hypoxia: A possible new mechanism for hypoxia-induced vasodilatation of the rat heart

Summary In this report we demonstrate the immunocytochemical localization of serotonin in endothelial cells of rat coronary vessels and a significant increase in the release of serotonin into the perfusate of Langendorff rat heart preparations during hypoxia. It is suggested that serotonin, localized in endothelial cells, is released during hypoxia and could provide part of a pathophysiological mechanism for vasodilatation to protect the heart from damage due to hypoxia.This research was supported by the British Heart Foundation and the excellent technical assistance of Jon Bokor is gratefully acknowledged.     

Evidence for no relationship of the pineal activity with the neonatal shrinkage of Leydig cells in the rat

Summary The collective volume of Leydig cells in prenatally pinealectomized newborn rats declined as sharply as in intact newborn rats. Also, the collective volume in pups born in the dark declined in a fashion similar to that in pups born in the light. The results indicate that neither the pineal gland nor the light is responsible for the neonatal shrinkage of Leydig cells.This study was supported in part by a Grant-in Aid for Scientific Research (No. 548067) from the Ministry of Education, Science and Culture of Japan.     

Bombesin-like immunoreactivity in the pancreas of man and other mammalian species

Summary Bombesin-like immunoreactivity has been measured in pancreatic tissues of man (12.4±1.2 pmol/g), pig (15.8±3.2), calf (4.3±0.9), rat (8.5±1.2) and guinea-pig (2.8±0.6) by a specific radioimmunoassay. Gel filtration of the pancreatic extracts revealed 2 major immunoreactive peaks: the earlier peak was eluted in the position of porcine gastrin-releasing peptide, and the later peak was eluted just after the amphibian bombesin standard. Immunocytochemistry demonstrated the presence of bombesin-like immunoreactivity in nerves in the rat pancreas, particularly in the exocrine pancreas, and occasionally in the peri-insular spaces. Isolated rat pancreatic islets were found to contain small quantities of bombesin-like immunoreactivity (0.037±0.003 fmol/islet) suggesting that mammalian bombesin-like peptides may be invovled in the regulation of endocrine as well as exocrine pancreatic secretion.Acknowledgments. We are grateful to Dr. A. V. Edwards, Physiological Laboratory, Cambridge, U. K. for providing the calf tissues, and the British Diabetic Association, U. K. for support.To whom reprint requests should be addressed.     

Plasma adenosine concentrations are elevated in Dahl salt-sensitive rats

We measured plasma levels of adenosine in Dahl salt-sensitive rats (DS) and Dahl salt-resistant rats (DR) to examine the potential role of adenosine in cardiovascular regulation in this type of hypertension. Plasma adenosine concentrations were significantly higher in DS than in DR. The NaCl content in the diet did not affect plasma adenosine concentration in either DS or DR. Significant positive correlation was found between adenosine concentrations and systolic blood pressure when the data for DS and DR were analyzed together. These results suggest that adenosine may play an important role in the pathophysiology of hypertension in DS.     

The phorbol ester TPA induces metamorphosis in Red Sea coral planulae (Cnidaria: Anthozoa)

Controlled experiments on the metamorphosis of marine invertebrate larvae require artificial inducers. These inducers can be used for studying the involvement of known signal transduction pathways in settlement and metamorphosis. The ability of the tumor-promoting phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate) to induce metamorphosis in planulae of the Red Sea soft coral speciesHeteroxenia fuscescens, Xenia umbellata, Dendronephthya hemprichii, Litophyton arboreum andParerythropodium fulvum fulvum, and the stony coralStylophora pistillata, was examined by using various concentrations of TPA. The chemical induced metamorphosis in all six species. The effect was unspecific and concentration-related. For all the corals except forX. umbellata the highest mean percentages of metamorphosis were obtained with 8.1×10^–7–10^–9 M TPA. ForX. umbellata, the percentage of metamorphosis was lower, and was obtained within a wider TPA concentration range. The present results, along with previous studies on Hydrozoa and Scyphozoa, demonstrate that TPA is the first common artificial inducer for these classes of Cnidaria. TPA is known to activate the enzyme protein kinase C (PKC) and therefore plays an important role in studying the phosphatidylinositol signal transduction system. Evidence for the involvement of this pathway in triggering metamorphosis has already been reported for Hydrozoa and Scyphozoa. Our results suggest that PKC is also involved in initiating metamorphosis in Anthozoa.     

Localization of pyruvate carboxylase in the cells of Neurospora crassa

The cell wall of Neurospora crassa was digested enzymatically and the cytosolic and the mitochondrial fractions were separated. The activity of pyruvate carboxylase (EC 6.4.1.1) was detected entirely in the cytosolic fraction. This indicates that the location of pyruvate carboxylase of N. crassa is in the cytosol, but is not in the mitochondria; this is different from the situation in animal tissues.