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Biomedical subjects

H J Förster

Publications and source records attributed to H J Förster.

At least 19 recordsLinked to original sources
PubMed1991

Clenbuterol plasma concentrations after repeated oral administration and its effects on cardio-respiratory and blood lactate responses to exercise in healthy Standardbred horses.

To evaluate the effects of clenbuterol on cardio-respiratory parameters and blood lactate relation to exercise tolerance, experimental horses performed standardized exercise tests on a high-speed treadmill before and after administration of the drug. Clenbuterol was administered in feed to six healthy Standardbreds at a dose rate of 0.8 micrograms/kg b.wt twice daily for 5.5 days. Each horse was tested twice, without and with a respiratory mask, during two consecutive days. One week elapsed between the baseline tests without drug and the tests with clenbuterol treatment (each horse served as its own control). The results show an unchanged heart rate response to exercise 2 h after the last clenbuterol administration. The blood lactate response and the arterial oxygen tension during exercise did not differ before and after drug treatment. The oxygen uptake as well as pulmonary ventilation relative to the work load performed was essentially unaffected. The arterial pH during exercise was significantly increased (P less than 0.05) following clenbuterol treatment. Plasma levels of clenbuterol were maximal 2 h post-administration with values between 0.45 and 0.75 ng/ml. The plasma half-life of elimination was 10.4 h (+/- 2.25 SD). In conclusion, clenbuterol did not cause any major effects on the cardio-respiratory and blood lactate parameters studied in healthy horses performing submaximal exercise tolerance tests.

Administration, Oral↗
PubMed1990

[Results of physiologic occupational studies of intensive care unit nurses].

Continuous measures of the pulse by wireless telemeter to value the degree of work were performed by 6 nurses in intensive care unit during work in shifts about 476 hours. Work activity and time were registed simultaneously. In the outcome is ascertained that the work of these nurses is middle heavy on an average with heavy or very heavy short portions. To reduce or to avoid the latter proposals are recommended.

Adult↗
PubMed1986

Metabolic fate of [14C]-brotizolam in the rat, dog, monkey and man.

The metabolism of brotizolam (2-bromo-4-(2-chlorophenyl)-9-methyl-6H-thieno [3,2-f]-1,2,4-triazolo[4,3-a]-1,4-diazepine, We 941, Lendormin) was studied in the bile of the rat and in the urine of the dog, rhesus monkey and man using 14C-labeled substance. Concentration, fractionation and purification of the metabolites were performed using thin layer chromatography, column chromatography or high pressure liquid chromatography. Metabolites were structurally characterized by thin layer chromatography, high pressure liquid chromatography, mass spectrometry and nuclear magnetic resonance spectrometry using reference compounds. Hydroxylation at different sites of the brotizolam molecule and subsequent conjugation were the metabolic pathways preferred by far in the species studied. Unchanged brotizolam was excreted in minute amounts only, if at all. In man and monkey We 964 (brotizolam hydroxylated in the methyl group) and We 1061 (brotizolam hydroxylated in the diazepine ring) represented the main metabolites. In the rat, the main metabolites were We 1061 and a brotizolam hydroxylated in the phenyl ring. The main metabolites found in the dog were We 964 and We 1064, an isomeric compound of We 1061. Since We 1061 is irreversibly transformed in an alkaline medium to We 1064, the latter could be formed due to the clean-up processes. Thus, in the dog also We 1061 was probably the metabolite which was actually excreted renally. The proposed structures of minor metabolites are presented.

Animals↗
PubMed1985

[Thrombolytic treatment of peripheral arterial circulatory disorders with streptokinase].

The purpose of these investigations is to refer to the possibility of the reconstructive treatment of arterial obstructions by means of streptokinase. New application methods improved the chances of success of fibrinolysis. They run about 50%. The local application of smaller doses of streptokinase confines the contraindications to a certain extent. Obstruction in the pelvic area which are not older than three months and such ones in the femoropopliteal part up to 6 weeks are to be regarded as indication to the fibrinolysis. In the care of patients with arterial obstructive diseases importance should, therefore, be attached to the fact that thrombotic shifts should be recognized in time an the possibility of a fibrinolytic therapy is tested within the periods mentioned.

Aged↗
PubMed1985

[Biochemical studies with oxitropium bromide. 1. Pharmacokinetics and metabolism in the rat and dog].

The bronchospasmolytic drug (8r)-6 beta, 7 beta-epoxy-8-ethyl-3 alpha-[(-)-tropoyloxy]-1 alpha H, 5 alpha H-tropanium bromide (oxitropium bromide, Ba 253 BR, Ventilat) was tested pharmacokinetically as a 14C labelled substance in rats and dogs. Following oral administration low concentrations of radioactivity persisting over several hours were measured in the blood of dogs and rats. The active ingredient which can be separated from the metabolites by thin layer chromatography and quantified via the radioactivity reaches a maximum in the rat plasma after 1 to 2 h; it is then eliminated from the blood with a half-life of approx. 4 h. Following intravenous administration the radioactivity measured directly (active ingredient + metabolites) is distributed rapidly into the tissue of the rat and the dog. The distribution phase is followed by a relatively fast elimination phase ending in the terminal elimination phase approx. 1 h after administration. Rats and dogs eliminate the radioactivity mainly with the feces after oral administration, whereas following intravenous administration the rat eliminates about half with the feces and half via the kidneys. Biliary excretion of the rat is 12% after oral and 14% after intravenous administration. The rat absorbs 14% and the dog 28% of dose. Five metabolites have been demonstrated in the urine of the rat and the dog. Metabolism takes place exclusively in the tropaic acid part of the molecule and by hydrolysis of the compound.

Animals↗
PubMed1981

Pharmacokinetics and metabolism of 14C-labelled alinidine in man and dogs.

Radioactively labelled alinidine was administered intravenously (10 mg) and orally (40 mg) to 5 healthy volunteers and beagle dogs (3 animals for each administration route: 0.1 mg/kg body weight i.v. and 1 mg/kg body weight p.o.). Alinidine was totally absorbed in both species. Regardless of the route of administration man excreted the drug via the kidneys within 12 hours, almost entirely in the unchanged form. The blood plasma curves in man followed a multiexponential decline (t 1/2 alpha : 35 sec, t 1/2 beta : 44 min, t 1/2 gamma : 210 min). The maximum plasma levels of the drug were recorded in man, 45 min after oral administration. However, the rather slow decline of plasma radioactivity observed in dogs, corresponded well with the delayed urinary excretion of alinidine (50% of the administered dose) in this species. Dogs metabolized the drug extensively; seven different metabolites including the parent compound were isolated from canine urine. considerable interindividual differneces were found concerning the quantitive but not the qualitative metabolic pattern of alinidine in dogs. Structural analysis by mass spectrometry revealed oxidation, hydroxylation, and cleavage products of alinidine, altered in its imidazolin and/or allylic moiety. In both species no traces of clonidine were found, which was a predicted metabolite formed by the removal of the allylic sidechain of alinidine.

Administration, Oral↗
PubMed1981

Development of a RIA for clonidine and its comparison with the reference methods.

A radioimmunoassay for clonidine was optimized by introducing, as a tracer ligand, an iodinized clonidine derivative specifically labeled with more than 500 Ci/mMol. The detection limit of clonidine was 10 pg/ml. The high assay specificity was demonstrated by a double isotope technique. The intraassay coefficient of variance (VK) was less than 4% for any concentration, the interassay VK did not exceed 8.3%. The assay reliability was increased when the plasma samples were diluted 1:5, prior to analysis, in normal human blood plasma, which was also used for the preparation of the calibration samples. In a comparative manner, this assay system was subjected to double-blind accuracy control tests, including all other reference methods so far described for clonidine analysis in blood plasma samples. The RIA technique presented here turned out to be the most sensitive and most reliable method, requiring, moreover, the smallest volumes of blood plasma (0.05 ml). This procedure was appropriate for routine tests, since one technician could perform 500 sample analyses a day. The advantages and disadvantages of each method are discussed.

Chromatography, Gas↗
PubMed1979

[Plasma levels, renal excretion and metabolism of orciprenaline after administration in sustained-release form (author's transl)].

A newly developed sustained-release form of orciprenaline-sulfate (Alupent) was tested in 13 patients. Determination of 3H-radioactivity in blood, urine and faeces was used to elucidate its pharmacokinetic properties. Maximum plasma levels of radioactivity were obtained between 8 and 12 h after administration. 10.7 +/- 2.5% of the administered radioactivity were excreted in urine over a period of 72 h. Orciprenaline was mainly excreted as the sulfate-conjugate. Approximately five percent of the radioactivity were excreted as 4,6,8-trihydroxy-N-isopropyl-tetrahydroisoquinoline--the condensation product of formaldehyde and orciprenaline.

Biotransformation↗
PubMed1978

The on column methylation of clonidine and p-hydroxyclonidine with trimethylanilinium hydroxide.

The structures of the methylated clonidine derivatives formed by on column methylation with trimethylanilinium hydroxide are revised. The almost exclusive formation of derivatives of phenylimino-N,N-dimethylimidazolidine structure is explained in terms of a fast kinetically controlled reaction of substrate anions. The reliability of a stable isotope dilution assay for clonidine is discussed in view of these results.

Aniline Compounds↗
PubMed1978

[Metabolic degradation of clonidine (author's transl)].

From the urine of dogs treated with 14C-clonidine (Catapres) 6 radioactive substances were isolated and their chemical structures identified. The presence of unchanged clonidine, p-hydroxy-clonidine, and dichlorophenylguanidine was confirmed and three new metabolites were detected: 1-(2,6-dichloro-4-hydroxyphenyl)-guanidine; 2-[(2,6-dichlorophenyl)-imino-a1-imidazolidine-4-one; 2-[2,6-dichloro-4-hydroxyphenyl)-imino]-imidazolidine-4-one. The splitting of the imidazolidine ring and the hydroxylation of the phenyl ring are the two principal routes of metabolism. A comparison of the metabolic patterns in the urines of dog, rat, and man showed that the 6 identified compounds were eliminated by all three specieis, the relative amounts, hoever, were different. Man eliminated clonidine mainly in the unchanged form; the dog metabolized the compound most readily of the 3 species investigated.

Animals↗
PubMed1978

[A new method for the determination of thrombocyte function in patients and in preserved blood].

In a circulating thrombocytic plasma the pressure in front of a defined mesh filter depends on the combined capacity of adhesion and aggregation of thrombocytes. A new clinical in vitro test is based on this principle which comes nearest to the conditions to be found in hemostasis dependent on thrombocytes. Judging from the preliminary results of investigations performed on stored blood, blood donors, patients with thrombocytopenia, disturbances of blood flow and patients under anticoagulant therapy, the time until the pressure rise after administering ADP and the maximal pressure amplitude proved to be the most significant parameters of the new procedure.

Blood Preservation↗
PubMed1978

[Results of a new platelet function test in various clinical diseases and in preserved blood].

In healthy persons, patients with thrombocytopenia and patients with arterial disturbances of blood flow with and without administration of Falithrom the pressure recording was carried out after the combined aggregation and adhesion of thrombocytes. The reaction time particularly observed after administration of ADP revealed marked differences in the groups examined, likewise the maximal pressure amplitude in front of the pumped through filter. When Falithrom was administered the thrombocyte functions were clearly impaired. The reduction of the capacity of platelets to obstruct filter pores can impressively be proved even in those thrombocytes stored in ACD-AG-plasma.

Adenosine Diphosphate↗
PubMed1978

[Studies of thrombocyte function in CPD blood].

The CPD stabilizer according to Gibson with an addition of 1.25 mMol adeninesulfate and 2.50 mMol guanosine is used in blood storage for better preserving 2.3-bis-phosphoglycerate of erythrocytes. Here platelet-rich CPD plasma was investigated before and during a 3 days storage at 4 degrees C or room temperature with regard to preserving the global thrombocyte function. The latter consists in the ability to seal blood vessels and is tested by means of pressure registration in combined thrombocyte-aggregation-adhesion (DKTA method) as an ability to close the pores of a sieve by adding 10(-5) mM/l of ADP. At room temperature this thrombocyte function is approximately 0 following 3 days of storage in CPD plasma excess without shaking. When stored at 4 degrees C it is preserved to a slight degree. Loss of thrombocyte function will depend on pH, thus being particularly evident at room temperature.

Blood Platelets↗
PubMed1978

[Postoperative changes of the thrombocyte number and function].

In 30 patients the number of thrombocytes was determined 24-48 hours after surgical interventions and compared with the normal range. The function of thrombocytes was determined by the method of pressure registration in combined thrombocyte-aggregation-adhesion (DKTA method). In spite of the occurring thrombocytosis there is a tendency towards a decrease of response in most cases and thus of haemostatic function of blood platelets. The influence of the thrombocyte function caused by fibrinolytic split products or by a change of prostaglandine metabolism is discussed.

Blood Cell Count↗
PubMed1977

[Methods and quality of information from myocardial scintigrams in the diagnosis of myocardial infarct].

There is an increasing importance of scintigraphy for the assessment of microcirculation in the myocardium. In animal experiments advantages and disadvantages of negative and positive representation of ischemic myocardiac areas were tried, after experimental infarction in particular. The results by computer scintigraphy prove that positive representation reveals an information on site and extent of an infarction.

Coronary Circulation↗
PubMed1976

[Studies on the pharmacokinetics and biotransformation of ipratropium bromide in the rat and dog].

The pharmacokinetics of the bronchodilator (8r)-3alpha-hydroxy-8-isopropyl-1alphaH,5alphaH-tropanium-bromide-(+/-)-tropate (ipratropiumbromide, Sch 1000, Atrovent) were studied in the rat and the dog after administering radioactive material (14C). The blood level of Sch 1000 following oral dosing showed plateaus in both the rat and the dog over a period of 2--8 h following administration. Subsequent elimination from the blood occurs with a half-life of 7h (rat) and 10 (dog). The half-life of elimination following i.v. administration is 1.9 h (rat) and 3.4 h (dog). In the rat biliary excretion occurs to the extent of 3.2% following oral dosing and 17.7% following i.v. application. In the same species renal excretion is 5.5% following oral administration and 58% following i.v. administration. Renal excretion in the dog, on the other hand, averaged 28% following oral and 55% following i.v. dosing, respectively. On the basis of a comparison of the areas under the blood level curves and also from the renal excretion following oral and i.v. dosing, i.e. disregarding absorption by gastrointestinal tissue, absorption was calculated as being 12% in the rat and 38% in the dog. Absorption in the rat after 1--3 h was calculated at 17--35% including the gastrointestinal tissue. Four metabolites and the unchanged substance could be detected in the 8-h urine of the rat. In the urine of the dog, the percentage of unchanged substance fell from a maximum of 81% (after 1 h) to 20% (after 47 h) in terms of radioactivity in the urine.

Administration, Oral↗