The effects of electronic nicotine vapor on voluntary alcohol consumption in female and male C57BL/6 J mice.

SIGNIFICANCE: Alcohol drinking and nicotine vaping often co-occur and dependence on both substances is common. However, the impact of nicotine vaping on alcohol consumption is not fully understood. METHODS: We examined the effects of nicotine vaping on ethanol drinking in female and male C57BL/6 J mice using an electronic nicotine delivery system and intermittent access two-bottle choice (IA-2BC) drinking. Mice were exposed to electronic nicotine vapor (3%) or propylene glycol/vegetable glycerol (PG/VG) control for 3 h sessions daily for 4 weeks and voluntary alcohol consumption was monitored. Nicotine vapor exposure was stopped and voluntary alcohol drinking was measured for a 2 week abstinence period. We also examined the effects of alcohol and nicotine on locomotion, temperature, and nicotine metabolism. RESULTS: Following acute nicotine vapor exposure, alcohol drinking was increased in males but not in females. Thermoregulation was disrupted following nicotine vapor exposure and voluntary drinking. Male and female mice displayed increased locomotor activity immediately following chronic nicotine vapor exposure, and an anxiolytic effect was seen in males. In nicotine vapor abstinence, female mice displayed increased alcohol consumption. Locomotor activity and anxiolytic effects remained elevated in male but not female mice. Female mice displayed higher levels of serum nicotine and hydroxycotinine, suggesting impaired metabolism following chronic drinking and nicotine vapor exposure. CONCLUSION: Collectively, these results suggest that while both male and female ethanol-drinking mice experience the stimulatory effects of nicotine vapor, only in males is there a parallel increase in ethanol drinking and only females display impairments in nicotine metabolism after drinking.

Experimental dissection of flagellar surface motility in Chlamydomonas.

Experiments have explored the possible relationships between the flagellar surface motility of chlamydomonas, visualized as translocation of polystyrene beads by paralyzed (pf) mutants (Bloodgood, 1977, J. Cell Biol. 15:983-989), and the capacity of gametic flagella to participate in the mating reaction. While vegetative and gametic flagella bind beads with equal efficiencies and are capable of transporting them along entire flagellar lengths, beads on vegetative flagella are primarily associated with the proximal half of the flagella whereas those of gametic flagella exhibit no such preference. This difference may relate to the "tipping" response of gametes during sexual flagellar agglutination (Goodenough and Jurivich, 1978, J. Cell Biol. 79:680-693). Colchicine, vinblastine, chymotrypsin, cytochalasins B and D, and anti-beta-tubulin antiserum are all able to inhibit the binding of beads to the flagellar suface. Trysin digestion and an antiserum directed against whole chlamydomonas flagella have no effect on the ability of flagella to bind beads, but the beads remain immobile. These results suggest that at least two flagellar activities participate in surface motility: (a) bead binding, which may involve a tubulin-like component at the flagellar surface; and (b) bead translocation, which may depend on a second component (e.g. an ATPase) of the flagellar surface. Surface motility is shown to be distinct from gametic adhesiveness per se, but it may participate in concentrating dispersed agglutinins, in driving them toward the flagellar tips, and/or in generating a signal-to-fuse from the flagellar tips to the cell body. Directly supporting these concepts is the observation that bound beads remain immobilized at the flagellar tips during the "tip-locking" stage of pf x pf matings, and the observation that bound ligands such as antibody fail to be tipped by trypsinized flagella.

Flagellar tip activation stimulated by membrane adhesions in Chlamydomonas gametes.

Membrane adhesions between the flagella of mating-type "plus" and "minus" gametes of Chlamydomonas reinhardi are shown to stimulate a rapid change in the ultrastructure of the flagellar tips, designated as flagellar tip activation (FTA). A dense substance, termed fibrous tip material (FTM), accumulates between the flagellar membrane and the nine single A microtubules of the tip. The A microtubules then elongate, growing into the distal region of the tip, increasing tip length by 30%. This study describes FTA kinetics during normal and mutant matings, presents experiments designed to probe its role in the mating reaction, and offers the following conclusions: (a) FTA is elicited by agents that cross-link flagellar membrane components (including natural sexual agglutinins, antiflagellar antisera, and concanavalin A) but not by flagellar adherence to polylysine-coated films. (b) FTA is reversed by flagellar disadhesion. (c) Gametes can undergo repeated cycles of FTA during successive rounds of adhesion/disadhesion. (d) FTA, flagellar tipping, and sexual signaling are simultaneously blocked by colchicine and by vinblastine, suggesting that tubulinlike molecules, perhaps exposed at the membrane surface, are involved in all three responses. (e) FTA is not blocked by short exposure to chymotrypsin, by cytochalasins B and D, nor by concanavalin A, even though all block cell fusion; the response is therefore autonomous and experimentally dissociable from later stages in the mating reaction. (f) Under no experimental conditions is mating-structure activation observed to occur unless FTA also occurs. This study concludes that FTA is a necessary event in the sexual signaling sequence, and presents a testable working model for its mechanism.

Effect of methotrexate with 5-methyltetrahydrofolate rescue and dietary homocystine on survival of leukemic mice and on concentrations of liver adenosylamino acids.

We have increased significantly the survival time of DBA/2 mice bearing methionine-dependent L1210 or L5178Y leukemia cells by i.p. administration of lethal doses of methotrexate (five daily doses of 25 mg/kg body weight) followed by rescue with 5-methyl tetrahydrofolate (five daily doses of 20 mg/kg body weight). The mice were maintained on a semipurified choline- and cyst(e)ine-free diet containing 0.32% L-methionine. We further increased significantly the survival time of the treated animals bearing L5178Y cells, but not those bearing L1210 cells, by substitution of 0.86% DL-homocystine for the methionine in the diet. We have examined the effects of both diets in mice treated with methotrexate and 5-methyl tetrahydrofolate, singly and in combination, on the concentrations of S-adenosylmethionine and S-adenosylhomocysteine in the liver, a tissue highly active in the metabolism of these amino acids. The substitution of homocystine for methionine in the diet of untreated animals led to a significant increase in S-adenosylhomocysteine and decrease in S-adenosylmethionine in the liver, with a resultant profound decrease in the ratio of S-adenosylmethionine to S-adenosylhomocysteine which was not further altered significantly by administration of methotrexate.

Cloning and base sequence analysis of a cDNA encoding mouse lung thioether S-methyltransferase.

Thioether S-methyltransferase catalyzes transfer of the methyl group from S-adenosylmethionine to X in compounds of the structure R-X-R', where X may be sulfur, selenium, or tellurium, and R and R' may be various organic groups. To obtain a cDNA clone of thioether S-methyltransferase, a mouse lung cDNA library in lambda gt11 was screened with a 99 base-pair probe obtained by performing the polymerase chain reaction on oligo(dT) primed, reverse transcribed, mouse lung RNA using two degenerate primers designed from partial amino-acid sequences of the enzyme. The entire coding and 3'-untranslated regions were obtained and sequenced. The predicted protein contains 264 amino-acid residues and has a calculated M(r) of 29,460. The amino-acid sequence of thioether S-methyltransferase contains three motifs characteristic of many methyltransferases and has a high level of identity with the amino-acid sequences of nicotinamide N-methyltransferase and phenylethanolamine N-methyltransferase. However, in spite of the fact that they are both mammalian cytosolic sulfur methyltransferases, the sequences of thioether S-methyltransferase and thiopurine S-methyltransferase share little identity.

S-phase modulation by irinotecan: pilot studies in advanced solid tumors.

Two studies of irinotecan (CPT-11) followed 24 h later by an antimetabolite were conducted. The objectives of the studies were: (1) to determine whether the increase in S-phase in tumor cells seen 24 h after CPT-11 administration in animal studies is seen in advanced solid tumors in patients, (2) to determine the dose of CPT-11 required to produce this effect, (3) to compare two methods (immunohistochemistry, IHC, for cyclin A, and DNA flow cytometry, FC) for evaluating S-phase in tumor biopsies from patients, and (4) to establish the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of CPT-11, given 24 h before gemcitabine (GEM, 1000 mg/m(2)). In one study CPT-11 was followed 24 h later by 5-fluorouracil (5-FU), 400 mg/m(2) per week for 4 weeks every 6 weeks. Tumor biopsies were obtained before and 24 h after CPT-11 administration before administration of 5-FU and assayed for S-phase by IHC for cyclin A and by FC. The starting dose of CPT-11 was 80 mg/m(2) per week with subsequent exploration of 40 and 60 mg/m(2) per week to establish the dose-effect relationship of the increase in tumor cells in S-phase. In the second study, CPT-11 was given 24 h before GEM 1000 mg/m(2) per week for 2 weeks every 3 weeks. Doses of 20-80 mg/m(2) were explored to establish the MTD and DLT and to study tumor cell S-phase in selected patients. CPT-11 80 mg/m(2) produced a mean increase in S-phase by IHC for cyclin A of 137%. Lesser increases were seen with 40 and 60 mg/m(2). CPT-11 followed 24 h later by 5-FU 400 mg/m(2) per week for 4 weeks was well tolerated. In the study of CPT-11 followed by GEM 1000 mg/m(2), 60 mg/m(2) of CPT-11 was the MTD.

Effect of prenylcysteine analogues on chemoattractant receptor-mediated G protein activation.

The hypothesis that carboxylmethylation of gamma subunits plays a role in G protein activation was tested by examining the ability of N-acetyl-S-farnesyl-L-cysteine (AFC) and its methyl ester (AFC-ME) to inhibit G protein-mediated signalling in intact HL-60 granulocytes and isolated HL-60 plasma membranes. Incubation of HL-60 granulocytes with AFC or AFC-ME inhibited superoxide release stimulated by fMet-Leu-Phe, but not by opsonized bacteria. AFC-ME, but not AFC, inhibited NaF- and PMA-stimulated superoxide release. Addition of AFC to HL-60 membranes inhibited fMet-Leu-Phe-, leukotriene B4- (LTB4) and C5a-stimulated GTP gamma S binding and GTP hydrolysis more potently than it inhibited basal guanine nucleotide exchange. AFC-ME inhibited basal- and ligand-stimulated G protein activation with equal potency, but less potently than AFC. AFC also inhibited mastoparan-stimulated GTP gamma S binding. Binding of fMet-Leu-Phe and LTB4 to HL-60 membranes was completely inhibited by AFC, while AFC-ME inhibited ligand binding by less than 50%. Neither AFC nor AFC-ME inhibited pertussis toxin or cholera toxin-catalysed ADP-ribosylation of alpha i. It was concluded that AFC interrupts signal propagation in G protein-dependent pathways by multiple mechanisms, including inhibition of ligand-receptor interactions, of receptor-G protein coupling and of guanine nucleotide binding to G proteins. Carboxylmethylation alters the specificity of AFC interruption of signal propagation in intact cells and isolated membranes.

Effect of gamma subunit carboxyl methylation on the interaction of G protein alpha subunits with beta gamma subunits of defined composition.

A baculovirus expression system was used to determine the contribution of carboxyl methylation of specific G protein gamma subunits to the interaction between alpha and beta gamma subunits. beta gamma subunits were carboxyl methylated by a membrane bound methyltransferase in Sf9 cells, and periodate-oxidized adenosine inhibited this methylation by 90%. Carboxyl methylation of beta(1) gamma(2), beta(2) gamma(3), and beta(2) gamma(7) enhanced pertussis toxin-catalyzed ADP-ribosylation of alpha(i2) and alpha(i3) by about 2-fold. On the other hand, methylation did not enhance membrane attachment of beta gamma subunits. These results suggest that methylation of isoprenylated gamma subunits is required for optimal G protein-mediated signal transduction, but not membrane attachment.

Alprazolam-ritonavir interaction: implications for product labeling.

BACKGROUND: Pharmacokinetic interactions involving antiretroviral therapies may critically influence the efficacy and toxicity of these drugs, as well as pharmacologic treatments of coincident or complicating diseases. The viral protease inhibitor ritonavir is of particular concern since it both inhibits and induces the activity of cytochrome P450 3A (CYP3A) isoforms. METHODS: The inhibitory effect of ritonavir on the metabolism of alprazolam, a CYP3A-mediated reaction in humans, was tested in vitro using human liver microsomes. In a double-blind clinical study, volunteer subjects received 1.0 mg of alprazolam concurrent with low-dose ritonavir (four doses of 200 mg) or with placebo. RESULTS: Ritonavir was a potent in vitro inhibitor of alprazolam hydroxylation. The 50% inhibitory concentration was 0.11 micromol/L (0.08 microg/mL); this is below the usual therapeutic plasma concentration range (generally exceeding 2 microg/mL). In the clinical study, ritonavir reduced alprazolam clearance to 41% of control values (P < .001), prolonged elimination half-life (mean values, 30 versus 13 hours; P < .005), and magnified benzodiazepine agonist effects such as sedation and performance impairment. CONCLUSION: Consistent with in vitro results, administration of low doses of ritonavir for a short duration of time resulted in large impairment of alprazolam clearance and enhancement of clinical effects. Removal from product labeling of a warning against coadministration of ritonavir and alprazolam was based on a previous study only of extended exposure to ritonavir, in which CYP3A induction offset inhibition. Kinetic interactions involving antiretroviral therapies may be complex and time dependent. Product labeling should reflect this complexity.

Sequential methylation of 2-mercaptoethanol to the dimethyl sulfonium ion, 2-(dimethylthio)ethanol, in vivo and in vitro.

Thioether methyltransferase (S-adenosyl-L-methionine: thioether S-methyltransferase; EC 2.1.1.96) catalyzes the methylation of X in compounds of the type R-X-R'(X = S, Se, Te), yielding a methyl onium ion. Previous results using mice have demonstrated a role for thioether methyltransferase in the conversion and clearance of thioethers by methylation to more water-soluble methyl sulfonium ions suitable for excretion in the urine. A potential major physiological source of thiethers is reactions catalyzed by microsomal thiol methyltransferase (S-adenosyl-L-methionine: thiol S-methyltransferase; EC 2.1.1.9), which has been shown to methylate a diverse range of aliphatic sulfhydryl compounds. This study provides evidence for the sequential methylation of the aliphatic thiol, 2-mercaptoethanol, first to the methyl thioether, 2-(methylthio)ethanol, by thiol methyltransferase followed by methylation of this methyl thioeter to the dimethyl sulfonium ion, 2-(-dimethylthio)ethanol, by thioether methyltransferase. This sequence of reactions was demonstrated in vivo by injecting mice i.p. with radioactive 2-mercaptoethanol and analyzing the labeled methylated products, 2-(methylthio)ethanol and 2(dimethylthio)ethanol, in the urine by HPLC. In addition, the system converting 2-mercaptoethanol to 2-(dimethylthio)ethanol was reconstituted in vitro using solubilized mouse liver microsomes as a source of thiol methyltransferase and purified thioether methyltransferase from mouse lung. The results of these in vivo and in vitro studies established the sequential methylation of 2-mercaptoethanol by these two enzymes.

CNS sites involved in sympathetic and parasympathetic control of the pancreas: a viral tracing study.

The viral transneuronal tracing method was used to identify the CNS cell groups that regulate the parasympathetic and sympathetic outflow systems of the pancreas. Pseudorabies virus (PRV) was injected into the pancreas of vagotomized rats and after 6 days survival, the pattern of transneuronal labeling in the CNS sympathetic regulatory regions was determined. The converse experiment was performed in order to elucidate the central parasympathetic cell groups that regulate the pancreas. Immunohistochemical methods were used to identify putative neuropeptide- and catecholamine-containing CNS neurons involved in these regulatory circuits. The major finding of this study indicates that five brain regions, viz., paraventricular hypothalamic nucleus, perifornical hypothalamic region, A5 catecholamine cell group, rostral ventrolateral medulla, and lateral paragigantocellular reticular nucleus, contain a considerable amount of overlap in cell body labeling. In addition, the ventrolateral part of the periaqueductal gray matter and gigantocellular reticular nucleus, ventral part also showed a similar overlap, but the numbers of neurons found in these areas were considerably lower than the five major regions. These data suggest that these brain regions may provide parallel and possibly redundant, autonomic pathways affecting glucagon and adrenaline release.

Role of tyrosine kinase, ODC, and p34cdc2 kinase and cyclin B-associated cdc2 in jejunal enterocyte proliferation, maturation, and exfoliation in diabetic and DFMO-treated rats.

BACKGROUND: Several signal transduction pathways involved in rapidly proliferating cells of the intestine are currently not well understood. In the jejunum, crypt enterocytes are constantly replicating, lower villi are maturing, and upper villi are constantly shed. Type I diabetes is associated with jejunal mucosal hyperplasia, and administration of diflouromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), causes hypoplasia. Phosphorylation of proteins controls cellular proliferation and/or exfoliation. Cell division cycle kinase (p34cdc2) and cyclin B-associated p34cdc2 kinase regulate the cell cycle during the transition from G2-M phase. Our aims were to: 1) investigate the activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated p34cdc2 kinase and 2) phosphorylate proteins at tyrosine residues in jejunal upper villi, lower villi, and crypt enterocytes of DFMO-treated control and diabetic rats. METHODS: Diabetes was induced by streptozotocin. DFMO was administered in drinking water in both control and diabetic groups for 10 days after the induction of diabetes. Jejunal enterocytes were isolated and kept frozen at -70 degrees C until ready to process. RESULTS: Diabetic rats showed jejunal mucosal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content compared to control rats. Diabetic crypt enterocytes showed significant increases in activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated cdc2 as well as increased phosphorylation of proteins at tyrosine residues compared to control rats. DFMO prevented diabetes-induced jejunal hyperplasia, and decreased the activities of these enzymes and phosphorylation of proteins at tyrosine residues in both diabetic and control rats. Phosphorylation of a 14 kd protein became prominent in crypt, upper villi, and lower villi enterocytes of DFMO-treated diabetic and control groups. CONCLUSION: Diabetic jejunal mucosal hyperplasia appears to involve activation of complex signal transduction pathways such as tyrosine kinase, ODC, p34cdc2 kinase, and cyclin B. These enzymes are involved in proliferation and/or exfoliation of jejunal enterocytes. Our results also suggest that tyrosine phosphorylation of a 14 kd protein may be involved in cell exfoliation and that jejunal mucosal hypoplasia may be a synergistic effect caused by down regulation of the above enzymes.

Effects of diabetes and difluoromethylornithine treatment on hyperplasia, activity of MAP-kinase, and activity and association with cyclin B of p34cdc2 kinase in rat jejunal mucosa.

BACKGROUND: The different signal transduction pathways of rapidly proliferating cells of the intestine are not clearly understood. We report here a possible signaling pathway that involves regulation of activity of two closely related kinases, MAP-K (mitogen-activated protein kinase) and p34cdc2 kinase, during hyperplasia of diabetic jejunal mucosa. Our aim was to investigate the activity and phosphorylation of MAP-K and activity and association of p34cdc2 kinase with cyclin B during diabetes-induced jejunal mucosal hyperplasia in vivo. METHODS: We studied untreated and difluoromethylornithine (DFMO) treated control rats and rats with streptozotocin-induced type I diabetes. Assays were done 10 days after the induction of diabetes. In diabetic rats there was jejunal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content as well as increased activities of MAP-K and p34cdc2 kinase and association of the latter with cyclin B as compared to corresponding values in control rats. Administration of DFMO, an irreversible inhibitor of the proliferation-associated enzyme ornithine decarboxylase (ODC), prevented diabetes-I induced jejunal hyperplasia and decreased all of the above enzymic parameters in both diabetic and control rats. In our previous in vivo study, DFMO administration also blocked diabetic jejunal hyperplasia and in addition decreased ornithine decarboxylase and tyrosine kinase activities jejunal and tyrosine phosphorylation of proteins. CONCLUSION: Thus the jejunal mucosal hyperplasia found in diabetes appears to involve activation of signal transduction pathways involving tyrosine kinases, MAP-K, p34cdc2 kinase, and cyclin B.

Ion chromatographic analysis of the purity and synthesis of sulfonium and selenonium ions.

The use of single-column ion chromatography with conductometric detection was shown to be useful for the analysis of sulfonium and selenonium ions. A Hamilton PRP X-200 cation column was eluted with either solvent A (5 mM nitric acid in 30% methanol) or solvent B (4 mM nitric acid). With solvent B, trimethylsulfonium ion was separated from trimethylselenonium ion. With solvent A, amounts of trimethylsulfonium ion from 2 to 250 nmol were detected with a linear response. The retention times and response factors for a series of sulfonium ions with various organic groups were determined. In general the ions with more hydrophobic groups eluted later, but all had similar response factors. The method was shown to be useful for optimizing conditions for the synthesis of methylsulfonium ions, specifically the reaction of methyl iodide with diallyl sulfide.