Calcitonin- and somatostatin-positive cells in thyroid gland of pigs at different ages

Immunohistochemical studies were carried out on calcitonin-, somatostatin- and serotonin-reactive cells in newborn pigs and pigs at 3 weeks and 7 months old. The aim of these studies was to examine if the expression of various bioactive substances by parafollicular cells in the pig thyroid varied during development. The volume density of the follicular epithelium was nearly the same in newborn and 3-week-old piglets and significantly lower in 7-month-old animals. The volume density of calciton-in-positive cells, expressed as a percentage of the follicular epithelium density, was similar in young animals, being 12.10% and 13.03% in newborn and 3-week-old piglets, respectively. A small but significant increase to 14.40% was seen in 7-month-old pigs. Somatostatin-positive cells formed a much smaller population at all time points, but these also showed a significant increase with age (0.13%, 0.17% and 0.52% of follicular epithelium density in newborn, 3-week- and 7-month-old pigs, respectively). However the changes in the volume density of somatostatin-positive cells correlated inversely with thyroid activity, the density being highest when the activation index was lowest, suggesting that thyroid activity may be regulated by an increase in the synthesis of this inhibitory peptide. Serotonin-positive cells were extremely rare at all time points and their volume density was not calculated.     

Localization of C-S lyase activity in the root cells ofAlbizzia lophanta

Summary The distribution of C-S lyase activity in root cells ofAlbizzia lophanta Benth. plantlets was investigated histochemically. H₂S formed upon cleavage of exogenously applied L-cysteine was precipitated by Pb⁺⁺ in a capture reaction at the site of its formation. Enzyme activity was found to be localized at the root tip and in a layer of cortex cells adjacent to the endodermis throughout the whole length of the root. Distinct areas within the exodermis, distributed in a regular pattern on the root surface, also exhibited the specific reaction. In vivo roots ofAlbizzia lophanta actively excrete the strongly smelling methylene dithiol, formed by enzymatic cleavage of djenkolic acid, the natural substrate of C-S lyase inAlbizzia. The physiological meaning of this compound, as well as the localization and intracellular distribution of C-S lyase activity are discussed.     

Lipid composition of Daucus carota roots

Lipids extracted from Daucus carota roots were analyzed and the fatty acid composition of the triglycerides and phospholipids determined. Compariso     

Naloxone's effect on the inotropic and chronotropic responses of isolated, electrically stimulated or spontaneously beating rat atria

Experiments were conducted to determine (i) how naloxone administration alone could modify the inotropic (in electrically stimulated (ES) rat atria) and both the inotropic and chronotropic responses (in spontaneously beating (SB) rat atria) isolated from normotensive and hypotensive (hemorrhaged) rats, and (ii) how naloxone administration would modify the inotropic and chronotropic responses of isolated rat atria previously administered an opiate agonist (morphine), a muscarinic agonist (carbachol), or an alpha- and beta-adrenergic agonist (noradrenaline). Naloxone (51-340 microM) added to ES atria caused a delayed but dose-related decrease in atrial tension (AT), whereas in SB atria, naloxone caused atrial heart rate (AHR) to fall and atrial tension (AT) to increase. Naloxone (68-340 microM), given to SB atria from acutely hypotensive rats, caused a similar increase in atrial tension as seen in the "normotensive" isolated (SB) atria and a similar decrease in atrial heart rate. Morphine sulphate (MS), 37-375 microM, administered to ES atria caused a delayed fall in AT; which was further decreased when naloxone (340 microM) was also added. In the SB atria, morphine caused a dose-related decrease in atrial heart rate whereas atrial tension increased. In SB preparations, atrial heart rate fell even further when naloxone was added to morphine compared with when morphine sulphate was given alone, whereas atrial tension was increased. Noradrenaline (3 or 12 microM) caused a positive, dose-related inotropic response in the ES atria, effects not influenced by the addition of naloxone. In the SB atria, naloxone caused no change in the dose-related increases in atrial tension and heart rate when combined with the lower dose of noradrenaline but decreased AT when combined with 12 microM noradrenaline, compared with when this dose of noradrenaline was given alone. Carbachol (683 nM-1.37 microM) caused a dose-related decrease in atrial tension in ES atria, which was reversed completely by the addition of naloxone. In SB atria, carbachol decreased both atrial tension and heart rate, and with the addition of naloxone (340 microM), a further slight drop in atrial heart rate occurred, but concurrently, a marked rise in atrial tension was observed. The results indicate that naloxone can act with receptors directly within atrial tissue to cause changes in atrial tension and heart rate. The comparable delayed responses of morphine and naloxone suggest their effects are mediated by nonopiate receptors which, in time, cause decreases in calcium influx into the atria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gut hormones in tropical malabsorption.

Concentrations of various gut hormones were measured after a test breakfast in eight patients with severe tropical malabsorption and 12 controls. The patients with tropical malabsorption had greatly raised basal plasma motilin and enteroglucagon concentrations, but their postprandial release of both gastric inhibitory polypeptide and insulin was significantly reduced. The pattern of gut hormone release differed from that found in coeliac disease. The measurement of gut hormones, each of which has a specific site and function, thus throws new light on the pathophysiology of tropical malabsorption and may suggest approaches of treatment.     

Subunit IV of yeast cytochrome c oxidase: cloning and nucleotide sequencing of the gene and partial amino acid sequencing of the mature protein.

The six small subunits (IV-VII, VIIa, VIII) of yeast cytochrome c oxidase are encoded by nuclear genes and imported into the mitochondria. We have isolated the gene for subunit IV from a yeast genomic clone bank and determined its complete nucleotide sequence. We have also isolated subunit IV from purified yeast cytochrome c oxidase and determined most of its amino acid sequence which confirms the positioning of approximately 90% of the amino acid residues. The sequence comparison shows that the coding sequence of the gene lacks introns and that subunit IV is made as a precursor with an amino-terminal extension of 25 residues, five of which are basic and none of them acidic. Precursor processing involves cleavage of a Leu-Gln bond.     

Apolipoprotein D modulates arachidonic acid signaling in cultured cells: implications for psychiatric disorders

Deficiencies in arachidonic acid (AA) parameters have been reported in schizophrenic patients. AA is a primary binding ligand for apolipoprotein D (apoD), which is increased in response to antipsychotic drug treatment and elevated in subjects with schizophrenia and bipolar disorder. In this study, we investigated whether apoD might modulate AA signaling/mobilization in cultured embryonic kidney (HEK) 293T cells. Immunofluorescent labeling revealed both cytosolic and membrane-bound expression of apoD protein in apoD-transfected cells. In cells expressing apoD, phorbal 12-myristate 13-acetate-induced AA release was inhibited compared to controls and membrane levels of AA were elevated, as indicated by the amount of AA maximally incorporated into membrane phospholipids. In addition, exogenous apoD added directly to the incubation media prevented cellular uptake of free [3H]AA. These results suggest that apoD acts to stabilize membrane-associated AA by preventing release and sequestering free AA in the cell. These actions of apoD may be beneficial to psychiatric patients.     

Interbacterial macromolecular transfer by the Campylobacter fetus subsp. venerealis type IV secretion system

We report here the first demonstration of intra- and interspecies conjugative plasmid DNA transfer for Campylobacter fetus. Gene regions carried by a Campylobacter coli plasmid were identified that are sufficient for conjugative mobilization to Escherichia coli and C. fetus recipients. A broader functional range is predicted. Efficient DNA transfer involves the virB9 and virD4 genes of the type IV bacterial secretion system encoded by a pathogenicity island of C. fetus subsp. venerealis. Complementation of these phenotypes from expression constructions based on the promoter of the C. fetus surface antigen protein (sap) locus was temperature dependent, and a temperature regulation of the sap promoter was subsequently confirmed under laboratory conditions. Gene transfer was sensitive to surface or entry exclusion functions in potential recipient cells carrying IncPα plasmid RP4 implying functional relatedness to C. fetus proteins. The virB/virD4 locus is also known to be involved in bacterial invasion and killing of cultured human cells in vitro. Whether specifically secreted effector proteins contribute to host colonization and infection activities is currently unknown. Two putative effector proteins carrying an FIC domain conserved in a few bacterial type III and type IV secreted proteins of pathogens were analyzed for secretion by the C. fetus or heterologous conjugative systems. No evidence for interbacterial translocation of the Fic proteins was found.