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At least 487 records · Page 27Linked to original sources
PubMed1986

Role of calcium ion antagonists of the bladder detrusor muscle: in vitro and in vivo study.

Calcium (Ca2+) ions play an important role in the contractility of the detrusor. Most of the neurotransmitters and modulators act on the detrusor through altering the final intracellular concentration of Ca2+. We studied three commonly used Ca2+ antagonists on their effect of detrusor contractility in vitro: verapamil, nifedipine and segontin. All three inhibited the detrusor-induced contraction in a dose-dependent fashion. Verapamil showed noncompetitive inhibition. Segontin showed a competitive inhibition on both phasic and tonic contractions of the detrusor strips. Nifedipine selectively inhibited the phasic contraction noncompetitively but competitively suppressed the tonic contraction. The in vivo application of verapamil on the bladder of rabbits with multiple-sclerosis-like disease showed a significant increase in bladder capacity. The study shows the possibility of the potential use of Ca2+-antagonist to suppress the problem of bladder instability.

Animals↗
PubMed2006

Deficiency in phylloquinone (vitamin K1) methylation affects prenyl quinone distribution, photosystem I abundance, and anthocyanin accumulation in the Arabidopsis AtmenG mutant.

Phylloquinone (vitamin K(1)) is synthesized in cyanobacteria and in chloroplasts of plants, where it serves as electron carrier of photosystem I. The last step of phylloquinone synthesis in cyanobacteria is the methylation of 2-phytyl-1,4-naphthoquinone by the menG gene product. Here, we report that the uncharacterized Arabidopsis gene At1g23360, which shows sequence similarity to menG, functionally complements the Synechocystis menG mutant. An Arabidopsis mutant, AtmenG, carrying a T-DNA insertion in the gene At1g23360 is devoid of phylloquinone, but contains an increased amount of 2-phytyl-1,4-naphthoquinone. Phylloquinone and 2-phytyl-1,4-naphthoquinone in thylakoid membranes of wild type and AtmenG, respectively, predominantly localize to photosystem I, whereas excess amounts of prenyl quinones are stored in plastoglobules. Photosystem I reaction centers are decreased in AtmenG plants under high light, as revealed by immunoblot and spectroscopic measurements. Anthocyanin accumulation and chalcone synthase (CHS1) transcription are affected during high light exposure, indicating that alterations in photosynthesis in AtmenG affect gene expression in the nucleus. Photosystem II quantum yield is decreased under high light. Therefore, the loss of phylloquinone methylation affects photosystem I stability or turnover, and the limitation in functional photosystem I complexes results in overreduction of photosystem II under high light.

Anthocyanins↗
PubMed2000

Electrophysiologic effects of lercanidipine on repolarizing potassium currents.

Blockade of cardiac repolarizing potassium channels by drugs may result in QT-interval prolongation, eventually degenerating into "torsades de pointes," a life-threatening arrhythmia. Lercanidipine (LER) is a recently introduced lipophilic calcium antagonist with no cardiodepressant activity and long-lasting antihypertensive action. Its chemical structure is characterized by the presence of a diphenylpropylaminoalkyl group, which is present in some of the drugs that have been reported to cause QT-interval prolongation. Our previous data demonstrated that LER blocks L-type calcium channels without affecting sodium current; however, no data are available concerning its effects on cardiac potassium channels. Transient outward (I(to)), delayed rectifier (I(K)), background currents, and action potential (AP) profile were measured from patch-clamped ventricular myocytes isolated from rat, guinea pig, or human hearts using enzymatic dissociation procedures. LER did not affect I(K) (and I(Kr)) density and activation curve in guinea pig myocytes; the reversal potential of the background current (I(K1)) and its slope were not changed by the drug. Maximal diastolic potential (MDP) and duration of the AP measured at -60 mV (APD(-60)) were not significantly changed. I(to) density and activation curves measured in rat myocytes were similar in the absence and presence of 1 or 10 microM LER. Finally, the effect of LER was tested in human ventricular myocytes: superfusion with 1 microM LER did not affect MDP and APD(-60). I(to) density and the midpoint of activation and inactivation curves were similar in the absence and presence of LER. In conclusion, our data demonstrate that LER does not affect repolarizing potassium currents and action potential profile recorded from guinea pig, rat, and human ventricular myocytes. It is unlikely that LER could cause QT prolongation in vivo.

Action Potentials↗
PubMed2002

Precursor medications as a source of methamphetamine and/or amphetamine positive drug testing results.

Medical Review Officer interpretation of laboratory results is an important component of drug testing programs. The clinical evaluation of laboratory results to assess the possibility of appropriate medical use of a drug is a task with many different facets, depending on the drug class considered. This intercession prevents the reporting of positive results unless it is apparent that drugs were used illicitly. In addition to the commonly encountered prescribed drugs that yield positive drug testing results, other sources of positive results must be considered. This review describes a series of compounds referred to as "precursor" drugs that are metabolized by the body to amphetamine and/or methamphetamine. These compounds lead to positive results for amphetamines even though neither amphetamine nor methamphetamine were used, a possibility that must be considered in the review of laboratory results. Description of the drugs, their clinical indications, and results seen following administration are provided. This information allows for the informed evaluation of results with regard to the potential involvement of these drugs.

Amphetamine↗
PubMed1985

Calcium antagonists stimulate sperm motility in ejaculated human semen.

Three calcium antagonists, diltiazem, flunarizine and verapamil stimulated human sperm motility in vitro. Among them, diltiazem induced the largest amplitude of motility increase. The concentration-response curve of diltiazem was similar in shape to those of calcium chelators. EGTA, a calcium chelator, potentiated the stimulatory effect of diltiazem while A23187, a calcium ionophore, antagonized it. These observations supported our previous hypothesis that an increased concentration of calcium ion was detrimental to human sperm motility. Whether calcium antagonists could be used in the treatment of subfertile patients awaits further investigation.

Calcimycin↗
PubMed1976

On the decrease of myocardial oxygen consumption induced by chloracyzine.

The effects of chloracyzine (2-chloro-10-(3-diethylaminopropionyl)-phenothiazine hydrochloride; antianginal drug) on myocardial oxygen consumption were studied in open-chest cats and cat isolated hearts using oximetry and polarography respectively. It was found that chloracyzine produced a decrease in myocardial oxygen consumption accompanied by a reduction in coronary blood flow preceded by transient coronary dilatation. Chloracyzine produced an insignificant increase in arterial pressure; heart rate increased slightly in the open-chest experiments but not in the isolated heart. It is suggested that reduced oxygen uptake after chloracyzine is realized through improved efficiency in the use of oxygen.

Aminophylline↗