Nyctohemeral Rhythm in the Levels of S-Adenosylmethionine in the Rat Pineal Gland and Its Relationship to Melatonin Biosynthesis

Abstract: Liquid chromatographic techniques that permit the simultaneous analysis of S -adenosylmethionine, melatonin, and its intermediary metabolites N -acetyl-5-hydroxytryptamine and 5-hydroxytryptamine within individual pineal glands have been developed. S -Adenosylmethionine has been shown to undergo a marked nyctohemeral rhythm in the pineal gland of the rat, with maximal levels occurring during the light period and minimal levels during the dark period. Detailed studies of the temporal relationships between the levels of S -adenosylmethionine and those of melatonin and its intermediary metabolites suggest that an association exists between the levels of S -adenosylmethionine and the status of the biosynthesis of melatonin. Exposure of animals to continuous light and the administration of the β-adrenoreceptor antagonist propranolol were both found to inhibit the induction of melatonin synthesis and prevent the reduction in the levels of S -adenosylmethionine during the dark period. As a corollary the induction of melatonin biosynthesis following the administration of the β-adrenoreceptor agonist isoproterenol during the light period was accompanied by a marked decrease in the levels of S -adenosylmethionine in the pineal gland. The significance of the link between the nyctohemeral rhythms in the levels of S -adenosylmethionine and the biosynthesis of melatonin in the pineal gland is discussed in the context of the therapeutic efficacy of S -adenosylmethionine as an antidepressant.     

Left ventricular aneurysm: Twenty-year surgical experience with 1572 patients at the Texas Heart Institute

From January 1958 through December 1979, 1572 patients underwent surgery for left ventricular aneurysm (LVA) in our institution. The series included 1365 men and 207 women, with a ratio of 6.5:1. Ages ranged from 25 to 79 years, with a mean of 54.7 years. Most patients were in NYHA functional Class III or IV, and all had sustained at least one documented myocardial infarction. During the first decade, LVA resection alone was performed, but after the advent of aortocoronary bypass (ACB) surgery, the majority of patients underwent ACB along with LVA resection. Some required additional septoplasty, mitral valve replacement, annuloplasty, or aortic valve replacement. In all groups, the mortality was higher for women than for men. Early deaths were due primarily to acute or progressive myocardial failure secondary to recurrent myocardial infarction. Follow-up information for 6 months to 8 years was obtained by means of questionnaires submitted to patients and referring physicians. Of 475 patients who underwent LVA resection and ACB and who responded, 92.2% were either improved or asymptomatic.     

Interaction of antimicrobial peptides with biological and model membranes: structural and charge requirements for activity

Species right across the evolutionary scale from insects to mammals use peptides as part of their host-defense system to counter microbial infection. The primary structures of a large number of these host-defense peptides have been determined. While there is no primary structure homology, the peptides are characterized by a preponderance of cationic and hydrophobic amino acids. The secondary structures of many of the host-defense peptides have been determined by a variety of techniques. The acyclic peptides tend to adopt helical conformation, especially in media of low dielectric constant, whereas peptides with more than one disulfide bridge adopt beta-structures. Detailed investigations have indicated that a majority of these host-defense peptides exert their action by permeabilizing microbial membranes. In this review, we discuss structural and charge requirements for the interaction of endogenous antimicrobial peptides and short peptides that have been derived from them, with membranes.     

Cellular calcium mobilization in response to phosphoinositide delivery

Intracellular calcium [Ca(2+)](i) is mobilized in many cell types in response to activation of phosphoinositide (PIP(n)) signaling pathways involving PtdIns(4,5)P(2) or PtdIns(3,4,5)P(3). To further explore the relationship between increases in intracellular PIP(n) concentrations and mobilization of [Ca(2+)](i), each of the seven phosphorylated phosphoinositides (PIP(n)s) were delivered into cells and the metabolism and physiological effects of the exogenously administered PIP(n)s were determined. The efficient cellular delivery of fluorophore-tagged and native PIP(n)s was accomplished using histone protein, neomycin, and dendrimeric polyamines. PtdIns(4,5)P(2) fluorophore-tagged analogs with short- and long-acyl chains were substrates for cellular enzymes in vitro and for phospholipases in stimulated fibroblasts. PtdIns(4)P, PtdIns(3,4)P(2) and PtdIns(4,5)P(2), each induced calcium mobilization rapidly after exogenous addition to fibroblasts. PtdIns(3,4,5)P(3) induced a significant, but smaller increase in intracellular calcium. These observations suggest that PIP(n)s other than PtdIns(4,5)P(2) or PtdIns(3,4,5)P(3) may have direct roles in signaling involving [Ca(2+)](i).     

Effect of Oxygen on the Induction of Tryptophan Hydroxylase by Adrenergic Agents in Organ Cultures of Rat Pineal Glands

Rat pineal glands, cultured under 95% air and 5% CO2, lost 50% of their tryptophan hydroxylase activity within 5 h. This loss was accelerated by the addition of cycloheximide or puromycin to the medium. Activity was, however, largely maintained in 95% O2 and 5% CO2. Under these conditions, L-noradrenaline (100 microM), L-isoproterenol (10 microM), and dibutyryl cyclic AMP (1 mM) induced enzyme activity. They failed to do so when 95% air and 5% CO2 was used. Noradrenaline induced serotonin N-acetyltransferase activity with either atmosphere.     

Terpenoids inhibit Candida albicans growth by affecting membrane integrity and arrest of cell cycle

Anti-Candida potential of six terpenoids were evaluated in this study against various isolates of Candida albicans (n = 39) and non-C. albicans (n = 9) that are differentially susceptible to fluconazole. All the six terpenoids tested, showed excellent activity and were equally effective against isolates of Candida sps., tested in this study. Linalool and citral were the most effective ones, inhibiting all the isolates at ≤0.064% (v/v). Five among the six terpenoids tested were fungicidal. Time dependent kill curve assay showed that MFCs of linalool and eugenol were highly toxic to C. albicans, killing 99.9% inoculum within seven min of exposure, while that of citronellal, linalyl acetate and citral required 15 min, 1 h and 2 h, respectively. FIC index values (Linalool - 0.140, benzyl benzoate - 0.156, eugenol - 0.265, citral - 0.281 and 0.312 for linalyl acetate and citronellal) and isobologram obtained by checker board assay showed that all the six terpenoids tested exhibit excellent synergistic activity with fluconazole against a fluconazole resistant strain of C. albicans. Terpenoids tested arrested C. albicans cells at different phases of the cell cycle i.e. linalool and LA at G1, citral and citronellal at S phase and benzyl benzoate at G2-M phase and induced apoptosis. Linalool, citral, citronellal and benzyl benzoate caused more than 50% inhibition of germ tube induction at 0.008%, while eugenol and LA required 0.032 and 0.016% (v/v) concentrations, respectively. MICs of all the terpenoids for the C. albicans growth were non toxic to HeLa cells. Terpenoids tested exhibited excellent activity against C. albicans yeast and hyphal form growth at the concentrations that are non toxic to HeLa cells. Terpenoids tested in this study may find use in antifungal chemotherapy, not only as antifungal agents but also as synergistic agents along with conventional drugs like fluconazole.     

A new pyrimidine-specific ribonuclease from bovine seminal plasma that is active on both single and double-stranded polyribonucleotides and that can distinguish between Mg2+-containing and Mg2+-depleted naturally occurring RNAs

The purification to homogeneity of a new ribonuclease, named RNAase SPL, from bovine seminal plasma is described. This nuclease, like the bovine pancreatic RNAase A, is pyrimidine specific. Its activity on single-stranded synthetic polyribonucleotides such as poly(rU) is significantly higher than that of RNAase A. However, unlike RNAase A, RNAase SPL is highly active on a double-stranded RNA such as poly[r(A · U)], and shows extremely limited activity on naturally occurring RNAs, such as Escherichia coli RNA, prepared with Mg²⁺ present throughout the isolation procedure. Under conditions of limiting hydrolysis in which RNAase A degrades 60 to 90% of total E. coli RNA to acid-soluble material and the remaining to material having a molecular weight lower than that of transfer RNA, RNAase SPL does not yield any acid-soluble products: it does not appear to degrade tRNA or 5 S RNA, and causes only a small number of nicks in the remaining RNAs to yield a limiting digest containing products with molecular weights ranging between 10,000 and 150,000. Absence of Mg²⁺ during the isolation procedure, or heat denaturation of the RNA makes it as susceptible to RNAase SPL as it is to RNAase A.The above and other related observations reported here support the view that there are Mg²⁺-dependent structural features, besides single and doublestrandedness, in naturally occurring RNAs, that can be distinguished by using the two nucleases RNAase SPL and RNAase A.     

DIURNAL RHYTHM AND TURNOVER OF TRYPTOPHAN HYDROXYLASE IN THE PINEAL GLAND OF THE RAT

Tryptophan hydroxylase in the pineal gland of the rat was found to undergo a diurnal rhythm in activity with an elevated activity at night. The rhythm was abolished in constant light. Cycloheximide (15 mg/kg, i.p.), administered both at night and during the day, caused a rapid decay in activity suggesting that tryptophan hydroxylase was subject to a rapid turnover in vivo. The primary site of control appeared to be at the level of translation since actinomycin D had no effect. Some relevant properties of the enzyme were studied. Thiol-containing compounds were shown to substantially protect pineal tryptophan hydroxylase from inactivation at 0°C but provided little protection at higher temperatures. The inactivation process appeared to be independent of oxygen. The activity of the enzyme, lost after ageing at 0°C. could be recovered by incubation with dithiothreitol under anaerobic conditions. Fresh enzyme, or enzyme inactivated at 37°C could not be activated by this process. A re-examination of the action of p-chlorophenylalanine (PCPA) on pineal tryptophan hydroxylase revealed that an irreversible inactivation occurred within 6h (25% of initial activity) followed by a recovery within 24 h. The rapid turnover of the enzyme is the probable reason for the failure of previous studies to observe an irreversible inhibition of this enzyme by PCPA.     

Seminalplasmin

The importance of seminal plasma in fertilization was appreciated as early as 1677 and would thus hardly seem a source for the search of antibacterial agents. The observation that seminal plasma had the ability to inhibit the growth of microorganisms in 1940 led to a systematic search for molecules possessing antimicrobial activity in addition to factors that might have a role in reproductive physiology. Extensive investigations led to the discovery in bovine seminal fluid of a 47-residue peptide, possessing potent antimicrobial activity as well as calcium transport modulatory properties in bovine sperm. We describe in this article the two, apparently unrelated, biological activities of this peptide.