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Biomedical subjects

W Z Potter

Publications and source records attributed to W Z Potter.

16 recordsLinked to original sources
PubMed1992

Idazoxan down-regulates beta-adrenoceptors on C6 glioma cells in vitro.

Incubation of the C6 cells with 10 microM idazoxan (an alpha 2-adrenoceptor antagonist and putative antidepressant) for 5 days in vitro resulted in a 23% reduction of beta-adrenoceptor number and a 37% decrease in isoproterenol-induced cyclic AMP accumulation. In contrast, post-receptor stimulated cyclic AMP accumulation (by the use of forskolin or cholera toxin) was unaffected. The desensitization of the beta-adrenoceptor was accompanied by an increase in the KL/KH ratio for this receptor. Chronic in vitro treatment of C6 glioma cells with idazoxan did not significantly affect cholera or pertussis toxin catalyzed ribosylation of Gs and Gi/Go in these cells. Similarly, idazoxan did not alter either the basal levels of protein kinase C (PKC) alpha, or its cytoplasm to membrane translocation. These results suggest that idazoxan may have direct postsynaptic effects, the site of which may be at the level of receptor/G protein interaction.

Adrenergic alpha-Antagonists↗
PubMed1992

Cerebrospinal fluid neurochemistry in children and adolescents with obsessive-compulsive disorder.

Cerebrospinal fluid hormones, monoaminergic metabolites, and dynorphin A (1-8 sequence) were examined in 43 children with severe, primary obsessive-compulsive disorder. Cerebrospinal fluid levels of 5-hydroxyindoleacetic acid were positively correlated with one of eight obsessive-compulsive disorder severity ratings and three of seven measures of improvement following 5 weeks of treatment with clomipramine hydrochloride. Arginine vasopressin concentration was significantly and negatively correlated with several ratings of obsessive-compulsive disorder symptom severity, while oxytocin concentration was positively correlated with depressive symptoms. The ratio of arginine vasopressin to oxytocin was also negatively correlated with obsessive-compulsive disorder and depressive symptoms. Comorbid affective disorder was associated with decreased arginine vasopressin concentrations, while concomitant anxiety disorder was associated with increased oxytocin. Dynorphin A (1-8 sequence), homovanillic acid, corticotropin, 3-methoxy-4-hydroxyphenylglycol, and corticotropin releasing hormone were not significantly related to obsessive-compulsive disorder symptoms. These results seem to indicate that arginine vasopressin may be related to obsessive-compulsive disorder symptom severity, while 5-hydroxyindoleacetic acid might be associated with drug response.

Adolescent↗
PubMed1992

In vivo evidence that lithium inactivates Gi modulation of adenylate cyclase in brain.

In vivo microdialysis of cyclic AMP from prefrontal cortex complemented by ex vivo measures was used to investigate the possibility that lithium produces functional changes in G proteins that could account for its effects on adenylate cyclase activity. Four weeks of lithium administration (serum lithium concentration of 0.85 +/- 0.05 mM; n = 11) significantly increased the basal cyclic AMP content in dialysate from prefrontal cortex of anesthetized rats. Forskolin infused through the probe increased dialysate cyclic AMP, but the magnitude of this increase was unaffected by chronic lithium administration. Inactivation of the inhibitory guanine nucleotide binding protein Gi with pertussis toxin increased dialysate cyclic AMP in control rats, as did stimulation with cholera toxin (which activates the stimulatory guanine nucleotide binding protein Gs). The effect of pertussis toxin was abolished following chronic lithium, whereas the increase in cyclic AMP after cholera toxin was enhanced. In vitro pertussis toxin-catalyzed ADP ribosylation of alpha i (and alpha o) was increased by 20% in prefrontal cortex from lithium-treated rats, but the alpha i and alpha s contents (as determined by immunoblot) as well as the cholera toxin-catalyzed ADP ribosylation of alpha s were unchanged. Taken together, these results suggest that chronic lithium administration may interfere with the dissociation of Gi into its active components and thereby remove a tonic inhibitory influence on adenylate cyclase, with resultant enhanced basal and cholera toxin-stimulated adenylate cyclase activity.

Adenylate Cyclase Toxin↗
PubMed1979

Binding of imipramine to plasma protein and to brain tissue: relationship to CSF tricyclic levels in man.

The possible clinical significance of the plasma protein binding of tricyclic antidepressants has been evaluated using imipramine (IMI), a typical tricyclic. Using equilibrium dialysis, the in vitro binding of IMI to plasma was compared to that of brain tissue. Cerebrospinal fluid (CSF) IMI was used as an independent measure of 'free' drug in the central nervous system. Intrinsic metabolic clearances were calculated on the basis of steady-state plasma IMI concentrations. There were three significant results: (1) variations in plasma binding are not great; (2) plasma protein binding does not limit the entry of IMI into the CSF; (3) variations in metabolism (intrinsic clearance) account for almost all variations in CSF concentrations of drug. It is concluded that measurement of free tricyclic antidepressant is not indicated in studies of clinical efficacy.

Animals↗
PubMed1979

Comparative pharmacokinetics of zimelidine and desipramine in man following acute and chronic administration.

Single dose and steady-state pharmacokinetics of zimelidine and desipramine were compared in eight depressed patients who were subjects in a double-blind crossover study. Within the same patient, there was no relationship between the pharmacokinetics of desipramine (pharmacokinetically similar to all other tricyclic antidepressants) and those of zimelidin, a bicyclic antidepressant. The weight-corrected dose of zimelidine gives a reasonable index of the concentration of its active metabolite norzimelidine, which predominates over zimelidine by a ratio of approximately 3 to 1. The variation in steady-state concentration of norzimelidine for a given dose of zimelidine in adults is about twofold and can be reduced by correcting for weight.

Adolescent↗
PubMed1979

Hydroxylated metabolites of tricyclic antidepressants: preclinical assessment of activity.

Studies investigating a possible relationship between the plasma concentration of tricyclic antidepressants and clinical response have measured only the tertiary and secondary amine forms of these drugs. The present study shows that the hydroxy metabolites of tricyclic antidepressants might also be active. Hydroxylated imipramine, desipramine, chlorimipramine, and nortriptyline inhibit the uptake of norepinephrine and serotonin into synaptosomes to the same extent as do their parent compounds. Hydroxylated nortriptyline and imipramine reverse or prevent reserpine-induced motor retardation and ptosis. Following chronic imipramine, significant steady-state concentrations of unconjugated hydroxylated metabolites are present in rat tissues including the cerebrospinal fluid. Accounting for steady-state concentrations of hydroxylated metabolites of tricyclic antidepressants in man may help to clarify whether there is a relationship between active drug concentration and clinical effect.

Animals↗
PubMed1978

Imipramine and desipramine in plasma and spinal fluid: relationship to clinical response and serotonin metabolism.

In a double-blind study of depressed patients treated with imipramine hydrochloride, levels of imipramine and desipramine were measured in plasma and in CSF. Levels of both drugs in CSF were approximately 10% of plasma levels, but the levels in the two body fluids were highly correlated. The levels of both drugs were approximately equal in plasma, but desipramine predominated in CSF (imipramine/desipramine ratio of 0.8). The imipramine-induced alteration in CSF levels of the serotonin metabolite (5-hydroxy-indoleacetic acid [5HIAA]) correlated with imipramine levels but not with desipramine. For the group of patients showing a clear antidepressant response, the mean drug levels were nearly double those of the nonresponder group, a difference that did not quite reach statistical significance in this relatively small sample. The desipramine levels showed no responder-nonresponder difference, while the ratio of imipramine/desipramine was significantly higher among the responders. On the average this particular patient group had relatively low pretreatment levels of 5HIAA in CSF, an observation that may partially account for the relatively low overall response rate to imipramine.

Adult↗
PubMed1976

Biochemical changes after hepatic injury by allyl alcohol and N-hydroxy-2-acetylaminofluorene.

Administration of hepatotoxic doses of allyl alcohol and N-hydroxy-2-acetylaminofluorene (N-OH-AAF) TO adult male rats produced periportal necrosis and functional derangement of the hepatic endoplasmic reticulum within 24 h. The rates of N-demethylation of ethylmorphine and p-hydroxylation of aniline were decreased 6 h following allyl alcohol administration, but cytochromes P-450 and b5 were unchanged. In contrast, administration of NOH-AAF decreased cytochromes P-450 and b5 and the rate of aniline p-hydroxylation, but did not change the rate of N-demethylation of ethylmorphine or the activities of cytochrome c reductase and glucose-6-phosphatase. No decrease was observed in the activity of the cytosol enzyme, DT diaphorase, following allyl alcohol treatment. The changes by these periportal hepatotoxins were compared with those produced both by central and midzonal hepatotoxins and with changes occurring in the liver after surgical partial hepatectomy.

Acetaminophen↗
PubMed1976

Biochemical changes after hepatic injury from toxic doses of acetaminophen or furosemide.

The effects of hepatotoxic doses of acetaminophen and furosemide on the function and composition of hepatic endoplasmic reticulum were compared from 3 to 24 h after administration. Acetaminophen caused a significant decrease in microsomal protein concentration as early as 3 h after its administration, but furosemide did not affect the microsomal protein concentration until 24 h after the dose. Both acetaminophen and furosemide decreased the concentrations of cytochrome P-450 and cytochrome b5 in microsomes, and the activity of microsomal ethylmorphine N-demethylase and aniline hydroxylase. Glucose-6-phosphatase and UDP-glucuronyl transferase were not significantly affected by acetaminophen or furosemide administration, and neither diene conjugation nor hepatic triglycerides were increased. Incorporation of 3H-L-leucine into liver proteins was decreased by 50% after the administration of either acetaminophen or furosemide.

Acetaminophen↗
PubMed1976

Metabolic activation of furosemide to a chemically reactive, hepatotoxic metabolite.

The possibility that furosemide-induced hepatic necrosis results from the formation of a chemically reactive hepatotoxic metabolite has been examined. Hepatotoxic doses of 3H-furosemide or 14C-furosemide were administered to normal mice and to mice pretreated with piperonyl butoxide, cobalt chloride, alpha-naphthylisothiocyanate or phenobarbital. Mice were killed at various time intervals and tissues were examined for necrosis, for free furosemide concentrations and for covalently bound metabolites of furosemide. Little furosemide was covalently bound to muscle, whereas the amount of covalently bound material in liver usually paralleled the severity of live necrosis after alteration by the pretreatments. The severity of hepatic necrosis failed to correlate with furosemide concentrations in liver or plasma. Furosemide was shown to be metabolically activated to an arylating intermediate by a cytochrome P-450 mixed function oxidase in hepatic microsomes. Additional experiments demonstrated that the furan ring of furosemide was the portion activated.

Alanine Transaminase↗
PubMed1975

Increased incidence of isoniazid hepatitis in rapid acetylators: possible relation to hydranize metabolites.

Approximately 10% to 20% of isoniazid recipients manifest biochemical evidence of liver injury. A smaller number of patients develop clinically overt hepatitis. Isoniazid is metabolized in man at extremely variable rates, and the rate is under genetic control. Two separate clinical studies have noted a possible relation between susceptibility of patients to isoniazid liver injury and rapid metabolism (acetylation) of the drug. For this reason, 21 patients who had recovered from probable isoniazid hepatitis and 5 patients who previously had manifested biochemical evidence of mild isoniazid liver injury were genetically phenotyped as rapid or slow isoniazid acetylators by the sulfamethazine method. The rapid phenotype was found in 86% of patients with probable hepatitis and in 60% of the possible ones, whereas the expected frequency was 45%. Eximination of isoniazid metabolites revealed that rapid acetylators hydrolze much more isoniazid to isonic otinic hydrazine moiety than do slow acetylators. The hydrazine moiety liberated from isoniazed is primarily acetylhydrazine, and studies in animals show this metabolite to be converted to a potent acylating agent that produces liver necrosis. We suggest that release of the hepatotoxic hydrazino moiety of isoniazid in man is responsible for isoniazid liver injury.

Acetylation↗