Hypermotility induced by vasoactive intestinal peptide in the rat: its reciprocal action to cholecystokinin octapeptide

Intracerebroventricular administration of vasoactive intestinal peptide (VIP) shortened the duration of pentobarbital-induced sleep and produced significant hypermotility in the rat. Although hypermotility induced by methamphetamine was not potentiated by central administration of VIP, L-DOPA-induced hypermotility in pargyline-pretreated rats was markedly enhanced by VIP and this hypermotility was suppressed by simultaneous administration of cholecystokinin octapeptide (CCK-8) in a dose-related manner. Apomorphine-induced hypermotility was also potentiated by VIP. These results suggest that VIP may stimulate postsynaptic dopaminergic receptor, causing an increase in motility, and that a possible reciprocal interaction exists between VIP and CCK-8.     

Induction of selective phosphorylation of a fat body protein of Sarcophaga peregrina larvae by 20-hydroxyecdysone.

20-Hydroxyecdysone was shown to induce selective phosphorylation of a fat body protein of Sarcophaga peregrina larvae with a molecular mass of 30 kDa. This phosphorylation was not associated with synthesis of new protein. Fractionation of 32P-labelled fat body by differential centrifugation showed that this protein was mainly present in the membrane-rich fraction, although we could not specify the membrane. Thus, 20-hydroxyecdysone may modify the function of the fat body by inducing phosphorylation of a specific membrane protein.     

Characterization of Gd3+ and Tb3+ binding sites on Ca2+,Mg2+-adenosine triphosphatase of sarcoplasmic reticulum

Interaction between Gd3+ and Tb3+ ions and Ca2+,Mg2+-ATPase of sarcoplasmic reticulum was studied. Three classes of lanthanide-ion binding sites with different affinities were distinguished. Binding of Gd3+ to the site with the highest affinity seemed to occur at less than 10(-6)M free Gd3+ and resulted in severe inhibition of ATPase activity. The reaction rates of both E-P formation and decomposition in the forward direction were inhibited in parallel with this binding, whereas ADP-dependent decay of E-P in the backward direction was not. At these Gd3+ concentrations, Ca2+-binding to the transport site was not inhibited. Binding of Gd3+ and Tb3+ to the Ca2+-transport site did occur, but more than 10(-5)M free Gd3+ or Tb3+ was required for effective competition with Ca2+ for that site. Gd3+ bound to the transport site in place of Ca2+ did not activate the E-P intermediate formation. Addition of 10(-1)M Tb3+ to a suspension of sarcoplasmic reticulum membranes resulted in marked enhancement of Tb3+ fluorescence, which is due to an energy transfer from aromatic amino acid residues of ATPase to Tb3+ ions bound to the low affinity site of the enzyme. Gd3+ and Mn2+ competed with Tb3+ for that site, but Ca2+, Zn2+, and Cd2+ did not.     

Guanine nucleotide binding protein involved in muscarinic responses in the pig coronary artery is insensitive to islet-activating protein.

In an attempt to identify the nature of guanine nucleotide binding protein(s) (G-protein) involved in the acetylcholine (ACh)-induced (muscarinic) response of pig coronary-artery smooth muscle, we studied the effect of ADP-ribosylation of specific membrane protein(s) catalysed by islet-activating protein (IAP; pertussis toxin). The ACh-stimulated and guanine nucleotide-dependent activities of phosphatidylinositol 4,5-bisphosphate (PIP2) phosphodiesterase (PDE), assessed by the production of inositol 1,4,5-trisphosphate (IP3) from exogenously applied PIP2, were not modified, in either IAP-treated or non-treated cell homogenates used as the enzyme source. In intact tissues, pretreatment with up to 100 ng of IAP/ml inhibited neither the ACh-induced decrease in the amount of inositol phospholipids nor the increase in the amounts of phosphatidic acid and of inositol phosphates. IAP treatment increased the amount of cyclic AMP accumulated by isoprenaline. These observations suggest that G-protein which couples the muscarinic receptor to PIP2-PDE is insensitive to IAP. Such being the case, the nature of this protein(s) probably differs from that required for the regulation of adenylate cyclase activities (Ni or Gi).     

Wavelength-dependence of the relative rate constants for the main geometric and structural photoisomerization of bilirubin IX alpha bound to human serum albumin. Demonstration of green light at 510 nm as the most effective wavelength in photochemical changes from (ZZ)-bilirubin IX alpha to (EZ)-cyclobilirubin IX alpha via (EZ)-bilirubin.

The kinetics for the quantitatively important reaction: (Formula: see text) that is, the photochemical interconversion between bilirubin and its geometric and structural photoisomers bound to human serum albumin in aqueous solution when various wavelengths of monochromatic light were used, were assayed by h.p.l.c. In order to clarify the wavelength-dependence of the relative rate constants in the individual steps, a light-source with a half-bandwidth of 10 nm was used at increments of 20 nm, in the range from 410 nm to 550 nm. We describe for the first time studies on the wavelength-dependence of rate constants in geometric and structural photoisomerization reactions in vitro of (ZZ)-bilirubin or (EZ)-bilirubin bound to human serum albumin, especially the relative rate constants of cyclization of (EZ)-bilirubin into (EZ)-cyclobilirubin. Because studies in vitro have demonstrated that the wavelengths from 350 to 450 nm are mutagenic, the results obtained indicated that the safest and ideal light-source for phototherapy is green light of 510 nm, which keeps (ZE)-bilirubin concentrations as low as possible, as shown by a maximal value of k2 at 510 nm and a relatively low value of k1 at 510 nm. This light-source still ensures the substantial absorption of (ZZ)-bilirubin, which is the precursor of (EZ)-bilirubin, the intermediate in (EZ)-cyclobilirubin formation and, furthermore, as shown by the maximal value of k5 and a considerable value of k4 at 510 nm, promotes the cyclization of (EZ)-bilirubin derived from (ZZ)-bilirubin even though k3 at 510 nm also shows a peak value.     

Reactions of the hydrated electron with pyrimidine nucleosides halogenated at the sugar moiety: e.s.r. and spin-trapping with 2-methyl-2-nitrosopropane

Free radicals produced by the reactions of hydrated electrons with pyrimidine nucleosides halogenated at the sugar moiety (2'-chloro-2'-deoxyuridine and 2'-chlorothymidine) were studied by e.s.r. and spin-trapping. 2-Methyl-2-nitrosopropane was used as the spin-trap. The usual spin-trapping technique was extended to frozen and deoxygenated systems to avoid contamination of the trapped radicals with side-products by spin-trapping 2-methyl-2-nitrosopropane itself. When this method was applied to 2'-chloro-2'-deoxyuridine, a free radical at the C-2' position of the sugar moiety was spin-trapped together with a free radical at the C-5 position of the base moiety. This indicates that hydrated electrons both add to the base moiety and eliminate halogen anions from the halogenated sugar moiety. In the case of 2'-chlorothymidine, however, only a free radical attributed to H-addition at the C-6 position of the thymine base was observed. No radicals produced by the reaction of hydrated electrons with the halogenated sugar could be spin-trapped.     

A possible role of protein kinase C in signal-induced lysosomal enzyme release

In platelets, activation of protein kinase C and mobilization of Ca2+ were selectively induced by the addition of 1-oleoyl-2-acetyl-glycerol and a low concentration of A23187, respectively (Kaibuchi, K., Takai, Y., Sawamura, M., Hoshijima, M., Fujikura, T. and Nishizuka, Y. (1983) J. Biol. Chem. 258, 6701-6704). Using this procedure evidence was obtained suggesting that the protein phosphorylation and Ca2+ mobilization were both essential and synergistically effective to cause release of lysosomal acid hydrolases such as N-acetylglucosaminidase. A similar observation was made for the lysosomal enzyme release from rat neutrophils.     

Clinical Use of a New Mitral Disc Valve

A disc valve of new design was used successfully for the replacement of the mitral valve in patients with rheumatic mitral valve disease. This valve would appear to have the following advantages over the mitral ball valve prosthesis:• Lower left atrial pressure after replacement.• Elimination of the hazard of left ventricular outflow tract obstruction with mitral valve replacement.• Decreased incidence of thromboembolization.• Abolition of possibility of ventricular septal irritation.Despite the better outlook for this valve compared with the ball valve for mitral valve substitution, the mitral valve should always be repaired whenever feasible. Repair is possible in the majority of patients.     

Alterations in migrating cranial neural crest cells in embryos of mice fed retinoic acid

Alterations in migrating neural crest cells induced by all-trans retinoic acid (RA) were studied morphologically and immunohistochemically in the cranial portion of 8-day-old mouse embryos which were derived from dams given 60, 40 or 0 mg kg of RA and killed 2 to 8 h later. Additionally, the embryos exposed to 4 mg/kg of actinomycin D (AD) on day 8 of gestation for 5 h were examined similarly. Light microscopy revealed that RA was cytotoxic and caused the appearance of pleomorphic nuclei, extra-large nucleoli and cytoplasmic budding which replaced lamellipodia and spike-like projections. Electron microscopy revealed pleomorphic nuclei containing nucleoli with major granular portions frequently surrounded with heterochromatin, monosomes, and phagosomes. A monosomal distribution pattern was different from that seen in the neural crest cells exposed to AD. The latter showed incomplete polyribosomal dispersion with fewer nucleolar components. Fewer neural crest cells with choline acetyltransferase-like immunoreactivity were detected in RA- and AD-exposed embryos than in the controls. These findings suggest that excess RA inhibits acetylcholine synthesis of the migrating neural crest cells, in a manner different from AD, and that it enhances phagocytosis. These phenomena modify the characteristics of neural crest cells resulting in craniofacial malformations.