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Biomedical subjects

W Ritter

Publications and source records attributed to W Ritter.

At least 109 records · Page 6Linked to original sources
PubMed1989

[Alterations of teeth and jaws in children with chronic renal failure].

Dental examination of 50 children with chronic renal failure revealed enamel hypoplasia in 26 (52%), retardation of dental age in 18 (36%) and delay of dental eruption in 16 (32%) cases. In comparison to normal children the prevalence of caries was significantly lower. Half of the children showed radiologic changes in the jaw-bones already during preterminal stage of renal insufficiency. The possible role of the dentist concerning early diagnosis of renal failure is discussed.

Adolescent↗
PubMed1989

The molecular structure of indium-DTPA.

The x-ray structural characterization of Na2In(DTPA).7 H2O is described. The structure is notable for two reasons. It is the first In3+-complex with relevance to antibody attachment to be structurally characterized. Surprisingly, the complex has coordination number eight and is the first monomeric In3+-complex with such a high coordination number. The potentially octadentate ligand binds through three amino groups and five deprotonated carboxylate groups to the metal ion. The ligand atoms surround the central indium atom in a slightly distorted Archimedian antiprismatic configuration. High resolution nuclear magnetic resonance studies in solution show that this high coordination number also pertains in aqueous medium. Consequently, one may conclude that octadentate ligands are optimal for the thermodynamic and kinetic stabilization of In3+ in living systems. It is also indicated that bifunctional diethylenetriaminepentaacetic acid (DTPA) is superior to amide bound (= sevendentate) DTPA in antibody labeling.

Chemical Phenomena↗
PubMed1988

Effects of the amount of stimulus information processed on negative event-related potentials.

Event-related potentials were recorded during simple reaction time and 3 discrimination conditions which varied in the amount of stimulus information that needed to be processed. It was found that NA became longer in duration as the amount of stimulus information that required processing was increased. Using sequential topographic mapping, it was concluded that there are at least 3 overlapping deflections that comprise NA. The experimental effect appeared to be mainly on the third deflection of NA. The problem of overlap between NA and later positive-going components, P380 and P3b, is discussed in terms of their relative latencies and scalp distributions.

Adult↗
PubMed1988

The N2 component elicited by stimulus matches and multiple targets.

This paper examines two methodological issues concerning the N2 component of human event-related potentials. The first issue concerns the circumstance that the most common way to obtain N2 in discrimination tasks is with an infrequent deviant stimulus that mismatches a frequent, standard stimulus. In these studies it is not possible to disentangle the effects of stimulus probability and stimulus mismatch on N2. In the present study it was found that, if two stimuli regularly alternate, N2 is elicited by infrequent repetitions of either stimulus. Thus, N2 is elicited by infrequent stimulus matches as well as infrequent stimulus mismatches. The second issue concerns the effect of stimulus probability on N2. Whereas previous research has established that the amplitude of N2 is inversely related to stimulus probability, the present study found that the number of possible targets in a visual discrimination task also has effects on N2 amplitude, with the overall probability of targets kept constant. Increasing the number of targets was associated with an increase in the duration of N2 and a differential enhancement of N2 at fronto-central as opposed to posterior-lateral recording sites. The latter results provide further evidence for the existence of two visual N2 components and tentative grounds for differentiating N2 from N400.

Adult↗
PubMed1988

Praziquantel pharmacokinetics and side effects in Schistosoma japonicum-infected patients with liver disease.

Praziquantel undergoes extensive first-pass hepatic biotransformation, but there is little information on its disposition or toxicity when administered to patients with liver disease. To define the influence of liver disease on the pharmacokinetics of praziquantel, we administered it orally to 30 patients with proven Schistosoma japonicum infection whose liver disease was carefully assessed as being severe, moderate, or absent. Both the peak plasma concentration of praziquantel and the bioavailability (measured as the area under the plasma concentration time curve) were significantly greater in the two groups of patients with liver disease (P less than .005), as were the concentrations of the two identified metabolites of praziquantel. Mild side effects were associated with high peak concentrations of praziquantel, but a syndrome of severe abdominal pain followed by bloody diarrhea was not. Our results indicate that the side effects and bioavailability of praziquantel are increased in the presence of liver disease.

Biological Availability↗
PubMed1987

Oral nafazatrom in man: effect on inhaled antigen challenge.

The effect of oral nafazatrom (Bay g6575, 2 X 3 g) or placebo on inhaled antigen challenge was assessed in a double-blind study. In four subjects antigen challenge resulted in an immediate fall of 93.2 +/- 3.36% in airflow at 40% of vital capacity (Vp40) and a 45.85 +/- 4.95% reduction in forced partial expiratory volume at one second (FEV1). Neither nafazatrom nor placebo had any effect on baseline lung function or that after challenge. Leukotriene B4 was generated by ex vivo stimulus of blood with ionophore A23187, and quantified by high performance liquid chromatography (h.p.l.c.)-radioimmunoassay. No inhibition of LTB4 formation occurred ex vivo following oral nafazatrom, although addition of 10(-5) M nafazatrom to blood in vitro significantly inhibited LTB4 release. Peak plasma nafazatrom levels during the study ranged from 3.3 X 10(-7) M to 1.47 X 10(-6) M which are below the concentration (10(-5) M) at which significant 5-lipoxygenase inhibition occurs in vitro. Oral nafazatrom is ineffective as a 5-lipoxygenase inhibitor in man, probably because of poor bioavailability after administration.

Adult↗
PubMed1986

Topography of visual event-related potentials during geometric and phonetic discriminations.

Event-related potentials (ERPs) were obtained to letters during 3 tasks that involved a SIMPLE RESPONSE (SR) to each letter presentation, a FORM discrimination of the letters that formed a closed loop, and a RHYME discrimination of the letters that rhymed with the letter 'v'. The first task only required detection of the letters, the FORM task required a visual-spatial analysis, and the RHYME task, a grapheme-phoneme conversion of the letters followed by a determination of rhyming characteristics. The SR ERPs were morphologically different from the discriminative ERPs, notably by the absence of N2 and P3. The difference wave forms between the discrimination and SR conditions and between the targets and non-targets indicated differential topographies of components associated with the FORM and RHYME tasks in the 300 msec latency region. In both of these tasks, components exhibited distributions localized primarily in the occipital regions, whereas in the RHYME task they extended more anteriorly and encompassed temporo-parietal regions. Thus, although the stimulus presentation was visual, the requirement of a visual-auditory conversion in the RHYME task resulted in activity that was more proximal to auditory regions than when only a FORM analysis of the letters was required.

Adult↗
PubMed1986

Pharmacokinetics of ciprofloxacin. 1st communication: absorption, concentrations in plasma, metabolism and excretion after a single administration of [14C]ciprofloxacin in albino rats and rhesus monkeys.

The absorption, disposition, metabolism and excretion of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-[U-14C]piperazinyl)-3- quinoline carboxylic acid (ciprofloxacin, Bay o 9867; designated tradename: Ciprobay) were studied following a single intraduodenal (rat), oral and intravenous (rat, monkey) administration, respectively, in the dose range 5 to 30 mg/kg body weight. Ciprofloxacin was absorbed partially (30 to 40%) in both species. Peak plasma concentrations of radioactivity were measured approximately 1 h (rat) or 2 h (monkey) after oral dosing. Terminal half-lives ranging from 26 to 44 h were determined for the elimination of radioactivity from the plasma (observation time up to 48 h after dosing). Nearly identical concentrations of the unchanged drug and total radioactivity were found during the first 7 or 8 h for the monkey after intravenous injection and for the rat also after oral administration, respectively. After reaching maximum concentration of 0.25 microgram/ml after administration of 5 mg/kg to rats and 0.88 microgram/ml after dosing with 30 mg/kg to a rhesus monkey, the unchanged drug was eliminated from plasma corresponding to half-lives ranging from 3 h (rat) and 4.4 h (monkey). The radioactivity was rapidly and completely excreted in both species. After intravenous administration about 51% (rat) and 61% (monkey), respectively, was excreted via the kidney. After oral dosing renal excretion amounted to 6-14% (rat) and 30% (monkey), respectively. Maximum residues in the body (exclusive gastrointestinal tract) of 1% of dose occurred in both species. In urine and feces of rats predominantly the unchanged drug and a conjugate were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Pharmacokinetic fundamentals of vaginal treatment with clotrimazole.

Pharmacokinetic studies with clotrimazole in rats and in humans, following oral and intravenous administration, have shown that clotrimazole is rapidly metabolized. After vaginal treatment with clotrimazole, the small fraction absorbed into the systemic circulation--between 3% and 10% of the dose--is subjected to metabolism and excretion as after oral or intravenous administration. The vaginal availability of clotrimazole is largely dependent on the formulation applied. In contrast, up to 3 days after single application of a vaginal tablet containing 500 mg clotrimazole together with lactic acid, fungicidal amounts of clotrimazole were measured in vaginal fluid, i.e., the single dose serves as a depot in the vagina for at least 3 days. Thus the single-dose treatment of vaginal mycosis with clotrimazole offers the advantage of combining a high availability in the vagina with a low availability of systemic circulation and is a means of solving the problem of the patient's noncompliance.

Administration, Oral↗
PubMed1985

Effects of expectation on negative potentials during visual processing.

ERPs were recorded during several RT tasks: simple RT; oddball choice RT; a LIE condition in which subjects were told stimuli would infrequently change, but did not; differential responding to two equiprobable stimuli that were randomized in one condition and alternated in another condition. Subtracting ERPs elicited during simple RT from those elicited during the other conditions, it was found that a negative component, NA, was enhanced, relative to simple RT, in all the other RT tasks. The data of the LIE condition indicated that NA was enhanced by the expectation that unpredictable stimulus changes would occur, even when they did not. The data of the 50/50 alternating RT condition indicated that stimulus changes by themselves enhance NA, even when they are predictable. There appear to be several deflections that comprise NA. NA was obtained with a variety of subtractions that balanced stimulus probability, the structure of the stimulus sequence and task instructions. Similar results were obtained whether subjects made a finger lift response or counted stimuli.

Adult↗
PubMed1985

[Thin-layer densitometric determination of clotiazepam in tablets and blood plasma].

Quantitative determination of 7-ethyl-5-(2-chlorophenyl)-1-methyl-1,3-dihydro-2H-thieno[2,3-e]1, 4-diazepin-2-one (clotiazepam, Trecalmo) as pure substance and after extraction from tablets can be carried out by high performance thin-layer densitometry in absorbance at 243 nm. Detection limit was 10 ng/spot, and inaccuracy +/- 1.8% in the microgram range. For determination of clotiazepam in blood plasma, a more sensitive method was developed by fluorodensitometry above 460 nm after excitation at 313 nm. Analytical parameters are: detection limit 2.5 ng/ml, inaccuracy between 25 and 300 ng/ml +/- 5%, and imprecision at a concentration of 100 ng/ml +/- 5%. Plasma level determination up to 12 samples can be achieved in about 5 h. Thus, for determination of only a few samples, the HPTLC method is less time-consuming than the gas chromatographic assay.

Animals↗
PubMed1985

Effects of haemodialysis on the pharmacokinetics of muzolimine.

UNLABELLED: High ceiling diuretics allow a better control of fluid balance in dialysis patients with a minimum urine flow of 500 ml/day. The pharmacokinetics of the high ceiling, long acting diuretic muzolimine (M) was investigated in 6 patients on regular dialysis therapy. METHODS: Concentrations of unchanged M in plasma were determined by high performance thin-layer chromatography (HPTLC) after a single oral dose of 240 mg up to 26 h: A) during and after the performance of dialysis lasting for 3 h, B) 20 h after finishing haemodialysis therapy (non-blind randomized cross-over study). RESULTS: The M plasma levels and the M half-lives did not differ between the two treatment groups (half-life A: 5.1 +/- 0.24 h; B: 4.8 +/- 0.51 h). The M peak concentrations were between 2 and 5 micrograms/ml and were reached 2 h post administration or even earlier. The mean M plasma levels 24 h after administration were in the same range (A: 0.33 +/- 0.16 microgram/ml; B: 0.33 +/- 0.11 microgram/ml).

Adult↗
PubMed1985

Effects of muzolimine and of a combination of hydrochlorothiazide/triamterene in healthy subjects and in nephrotic patients.

The diuretic effects of 30 mg muzolimine and 25 mg hydrochlorothiazide/50 mg triamterene were comparable in healthy subjects and nephrotic patients (serum albumin less than 32 g/l, creatinine clearance greater than 50 ml/min/1.73 m2). A single daily dose of 30 mg muzolimine or 25 mg hydrochlorothiazide/50 mg triamterene was sufficient in the majority of the investigated nephrotic patients. The different diuretic effects which were observed in nephrotic patients were not related to the severity of hypalbuminemia, but rather to differences in preceding diuretic treatment. Plasma levels and urinary excretion of unchanged muzolimine were comparable in healthy subjects and nephrotic patients after one day of diuretic treatment; after seven days of treatment plasma levels of muzolimine were significantly lower and urinary excretion significantly higher in nephrotic patients than in control subjects.

Adolescent↗
PubMed1985

Pharmacodynamic and pharmacokinetic correlation of muzolimine with and without aluminium hydroxide.

The objective of the reported study was to investigate whether aluminium hydroxide administered in addition to muzolimine interferes with the pharmacodynamics or the pharmacokinetics of the drug. For this purpose a cross-over study in 6 healthy male volunteers was carried out in which each subject received muzolimine and after a wash-out period muzolimine together with Aludrox. To avoid interferences of a psychological nature a third period with placebo was added. The administrations were randomised. The excreted urinary volume was measured, and blood was taken at relevant times in order to follow the pharmacokinetic profile. These are the results: Urinary excretion after the oral administration of muzolimine was within normal limits compared with the literature. There was no change in elimination with respect to either extent or time characteristics after the combined administration of Aludrox. There was no change in the pharmacokinetic profile either.

Aluminum Hydroxide↗
PubMed1985

Food and muzolimine interaction.

The influence of food on the bioavailability of muzolimine was investigated in a non-controlled cross-over study. Six healthy volunteers received 40 mg muzolimine directly after a standardized American breakfast (non-fasting volunteers) and, one week later, after an overnight fast with breakfast 90 min after drug intake (fasting volunteers). The concentrations of muzolimine in plasma and urine were determined between 0 and 48 h after administration. Results (means +/- SEM): in the fasting volunteers, the areas under the muzolimine plasma level curves (0-32 h) were higher than in the non-fasting volunteers (3002 +/- 390 vs. 2038 +/- 344 ng X h/ml, p less than 0.001), the peak concentrations were higher (332 +/- 36 vs. 176 +/- 38 ng/ml, p less than 0.05) and appeared earlier (1.8 +/- 0.2 h vs. 4.0 +/- 0.5 h, p less than 0.01). Also, the urinary volumes and sodium excretion were higher in the fasting volunteers than in the non-fasting volunteers. Hence, the bioavailability of muzolimine is reduced if administered after a meal which should be considered in the treatment schedule.

Adult↗
PubMed1985

Pharmacokinetics of muzolimine after oral administration with and without aluminium hydroxide in healthy volunteers.

The pharmacokinetics of muzolimine administered with and without aluminium hydroxide was investigated in volunteers (randomized non-blind cross-over study). Six healthy male volunteers aged 20 to 28 years with a mean body weight of 68 +/- 8 kg received 40 mg muzolimine after a standardized breakfast without and with 1760 mg aluminium hydroxide (Aludrox) administered 10 min before breakfast. Muzolimine concentrations were determined in plasma and urine between 0.5 and 48 h post dosing. The data were analysed using a two- or three-compartment open model. The pharmacokinetic parameters of muzolimine, e.g. absorption half-life, peak concentration, time to reach peak concentration, AUC and mean time, obtained with both treatment regimens, did not show any significant difference (analysis of variance). As a conclusion, the pharmacokinetics of muzolimine is not altered by the ingestion of aluminium hydroxide, which might be important for patients with advanced renal failure.

Adult↗