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Biomedical subjects

D Loew

Publications and source records attributed to D Loew.

At least 37 records · Page 2Linked to original sources
PubMed1997

Gene cloning of rat and mouse platelet glycoprotein V: identification of megakaryocyte-specific promoters and demonstration of functional thrombin cleavage.

Platelet glycoprotein (GP) V is a major surface protein cleaved during thrombin-induced platelet activation. GPV associates noncovalently with the GPIb-IX complex to form GPIb-V-IX, a receptor for von Willebrand factor and thrombin. We describe the cloning of the genes coding for rat and mouse GPV and compare them with the human gene. The two rodent genes have a similar structure and resemble the human GPV gene with a coding sequence (approximately 1,700 nucleotides) entirely contained in one exon and a single intron (approximately 900 nucleotides) in the 5' untranslated region. Both genes have megakaryocyte-type promoters with conserved tandem Ets and GATA recognition motifs and lack a TATA box. The mature rat and mouse proteins comprise 551 amino acids, have 70% sequence identity, and contain an additional 8-amino acid intracellular segment as compared with the human protein. As in human GPV, there is an NH2-terminal leucine-rich region of 15 repeats and a thrombin cleavage recognition sequence. Whereas the rat and human thrombin cleavage sites are similar, the mouse cleavage site resembles that of the human thrombin receptor. Functionality of these sites was demonstrated by thrombin cleavage of synthetic peptides and analysis by high-performance liquid chromatography (HPLC) or mass spectrometry. Cleavage of native rat GPV was confirmed by means of a polyclonal antibody directed against the new NH2-terminal peptide exposed after thrombin cleavage. This antibody specifically recognized thrombin-activated rat platelets by fluorescence-activated cell sorting (FACS) analysis. In addition, we raised monoclonal antibodies specific for rat GPV (88 kD), which recognized the NH2-terminal soluble fragment (70 kD) liberated after thrombin cleavage. Knowledge of these rodent GPV genes and availability of species-specific peptides and antibodies will be essential to further studies aiming to define the exact in vivo function of platelet GPV using animal models of thrombosis and gene inactivation experiments.

Amino Acid Sequence↗
PubMed1997

[L-tryptophan. An essential amino acid for structural and functional metabolism].

Since the nineteen-sixties, L-Tryptophan has been used with success to treat depressive states and sleep disorders. When, in 1989, the substance was suspected of causing severe adverse reactions (EMS), approval for its use was initially suspended. It has since been shown that the undesired side effects were due not to L-Tryptophan itself, but to contaminations of the basic substance, and the suspension of approval was therefore lifted. In September 1996, L-Tryptophan was re-introduced onto the market as Ardeytropin. The present paper takes a look at the substance L-Tryptophan and discusses in particular its biochemical significance and its biokinetics/pharmacokinetics. The pharmacological basis for the use of L-Tryptophan to treat sleep disorders and depression is examined.

Amino Acids, Essential↗
PubMed1997

Is the biopharmaceutical quality of extracts adequate for clinical pharmacology?

According to definition, an extract is a multi-substance mixture from a medicinal plant obtained by extraction of specific parts of the plant. Corresponding to the active ingredients in each case, each extract exhibits, qualitatively and quantitatively, a specific content spectrum, so that an extract is not just any extract. With an increasing demand for demonstrating the clinical efficacy of plant-based substances, extracts or extract fractions, we necessarily confront the problem of phytogenerics, i.e. extract-identical preparations for exchange versus the innovator. Up to now, pharmacognosic experts, phytochemists, and pharmacists have dealt with the problem as to the bioequivalence of phytopharmaceuticals within the context of pharmaceutical and biopharmaceutical/technological equivalence. In the meantime, however, from a number of plant extracts, the active ingredients determining their efficacy are known and analytical methods have been established, so that bioavailability/bioequivalence studies similar to those for chemical/synthetic substances are now possible.

Guidelines as Topic↗
PubMed1997

[Planning, realization and evaluation of post-marketing surveillance studies. Recommendations of the Society for Phytotherapy].

Post-marketing-surveillance studies with herbal drugs usually are prospective prescription-epidemiological studies, which should allow statements on quality, efficacy and safety. Until now neither laws nor concrete normative guidelines for the methodology and the evaluation of post-marketing-surveillance studies are existing which could be used for pharmacovigilance. In the present paper guidelines for planning, realisation and evaluation are presented which should allow studies of high quality. The essential components required for the investigational plan are focussed. Also recommendations on the obligatory, optional and special components of the study protocols are made. Additionally statistical methods which allow the evaluation of the therapeutic efficacy are presented.

Humans↗
PubMed1997

[Therapeutic trial, clinical research and therapeutic freedom--medical aspects].

In the history of medicine, the approach has changed from prevention to curative medicine- hand in hand with the availability of the pharmacologic findings. Prior to the era of a medicine based on natural science, drugs were found by an empirical trial- and error approach resulting in a steadily growing of drugs. With the upcoming natural sciences, medicine reached new levels in drug treatment by extensive and systematic research in experimental and clinical trials. For scientific and regulatory acceptance, national and international guidelines and the rules of "Good Clinical Practice" have to be met. On the basis of the respect for the "Oath of Hippocrates", the commitment to "salus aegroti suprema lex", the responsibility of "nil nocere" and the duty of information are elementary. The regulations of the "social legislation" define rights and duties of patients and physicians. In spite of all these rules, the physicians' autonomy is undeniable because of individualism of patients in contrast to the clinical trials based on national and international guidelines.

Clinical Trials as Topic↗
PubMed1996

Characterization of novel cysteine-rich antimicrobial peptides from scorpion blood.

We have isolated, from the hemolymph of unchallenged scorpions of the species Androctonus australis, three distinct antimicrobial peptides, which we have fully characterized by Edman degradation, electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization mass spectrometry. Two are novel molecules: (i) androctonin, a 25-residue peptide with two disulfide bridges, active against both bacteria (Gram-positive and Gram-negative) and fungi and showing marked sequence homology to tachyplesins and polyphemusins from horseshoe crabs; and (ii) buthinin, a 34-residue antibacterial (Gram-positive and Gram-negative) peptide with three disulfide bridges. The third peptide contains 37 residues and three disulfide bridges and clearly belongs to the family of anti-Gram-positive insect defensins. We have synthesized androctonin and explored its activity spectrum and mode of action.

Amino Acid Sequence↗
PubMed1996

The effects of a special Agnus castus extract (BP1095E1) on prolactin secretion in healthy male subjects.

The effects of three doses of a special Agnus castus extract (BP1095E1)--extracts from 120 mg, 240 mg and 480 mg of drug per day--were examined within the framework of a placebo-controlled clinical study of tolerance and prolactin secretion in 20 healthy male subjects during a period of 14 days. There was good tolerance during the study as regards the following: adverse effects, the effects on blood pressure and heart rate, blood count, Quick's test, clinical chemistry as well as testosterone, FSH and LH values. During each study phase the 24-hour prolactin secretion profile was measured from the penultimate to the final day, and the amount of prolactin release was monitored an hour after TRH stimulation on the last day. A significant increase in the 24-hour profile was registered with the lowest dose in comparison to placebo, the opposite being the case with the higher doses, i.e. a slight reduction. In contrast to the administration of placebo, the 1-hour AUC after TRH stimulation resulted in a significant increase with the lowest dose and a significant reduction with the highest dose. The results suggest effects of the special Agnus castus extract which are dependent on the dose administered and the initial level of prolactin concentration.

Adult↗
PubMed1996

Pharmacokinetics of thiamine derivatives especially of benfotiamine.

Pharmacokinetic data of orally administered lipid-soluble thiamine analogues like benfotiamine are reviewed and assessed. It is quite clear that benfotiamine is absorbed much more better than water-soluble thiamine salts: maximum plasma levels of thiamine are about 5 times higher after benfotiamine, the bioavailability is at maximum about 3.6 times as high as that of thiamine hydrochloride and better than other lipophilic thiamine derivates. The physiological activity (alphaETK) increased only after benfotiamine was given. Due to its excellent pharmacokinetic profile benfotiamine should be preferred in treatment of relevant indications.

Absorption↗
PubMed1995

Absorption behavior of sulpiride described using Weibull functions.

Deconvolution absorption profiles of oral sulpiride formulations were calculated from plasma concentration-time data obtained in an open, 3-period study with a crossover of the 2 oral formulations in 12 healthy volunteers following single intravenous (100 mg) and oral (2 x 50 mg capsules, 200 mg tablets) application of sulpiride. A model based on 2 Weibull-functions, and applied using NONMEM, described the complex absorption profiles more satisfactorily than a first order absorption model or a model based on a single Weibull-function.

Absorption↗
PubMed1993

Variability in the stereoselective disposition of ibuprofen in patients with rheumatoid arthritis.

1. Patients suffering from rheumatoid arthritis received oral doses of 600 mg racemic ibuprofen (n = 25; RAC) or 400 mg (S)-ibuprofen (n = 25; S-IBU) in a double-blind, randomized parallel-group study. 2. The pharmacokinetic parameters of (S)-ibuprofen were not statistically different between treatments (P > 0.05). Comparing (S)- and (R)-ibuprofen within the group receiving the racemate significantly higher Cmax (20.3 +/- 5.3 vs 17.7 +/- 4.4 micrograms ml-1; P < 0.02; 95% confidence interval for differences (CI): 0.5-4.6), AUC (86.2 +/- 23.5 vs 67.6 +/- 26.6 micrograms ml-1 h; P < 0.001; CI: 9.5-27.6), mean residence time (4.5 +/- 1.1 vs 4.1 +/- 1.2 h; P < 0.01; CI: 0.1-0.6) and renal clearance (0.8 +/- 0.6 vs 0.0 +/- 0.0 ml min-1; P < 0.001; CI: 0.5-1.0) values were observed for the (S)-enantiomer. 3. No difference was found (P > 0.05) between treatments in the percentage of the dose recovered in the urine as (R)- or (S)-ibuprofen plus metabolites (S-IBU: 80.2 +/- 8.47 vs RAC: 74.1 +/- 14.0%). 4. Interindividual variation in the pharmacokinetics of (S)-ibuprofen following administration of the racemate was similar to that following the administration of the single isomer suggesting that chiral inversion is not a major factor contributing to variability in the disposition of this drug.

Arthritis, Rheumatoid↗
PubMed1991

S-ibuprofen versus ibuprofen-racemate. A randomized double-blind study in patients with rheumatoid arthritis.

Ibuprofen (ibu) is a racemic 2-arylpropionic acid non-steroidal anti-inflammatory drug whose activity is due mainly to the S-enantiomer. So far only the racemic compound is in clinical use. A double-blind randomized trial was carried out for a 2-week period in 50 patients with classical rheumatoid arthritis (RA) (Steinbrocker II-III) to compare the effectiveness and tolerance of S-ibu (400 mg T.I.D.) with that of the racemic compound (600 mg T.I.D.). Ritchie-index, limitation of movement, joint pain on pressure and pain at night decreased significantly in both groups. Due to lack of effectiveness, the dose had to be increased in 3 patients from the S-ibu group as well as in 6 patients from the racemic group resulting in mean daily doses of 1220 mg S-ibuprofen and 1870 mg racemic ibu. No statistically significant difference could be found between both groups concerning efficacy and unwanted effects. Therefore, S-ibu given alone may be advantageous because the metabolic load to the human body is reduced and patients are more likely to comply with drug doses of 1.2 g/day as compared to 1.8 g/day.

Adult↗
PubMed1991

Bioequivalence between two furosemide-spironolactone formulations: a pharmacokinetic and pharmacodynamic approach.

Two formulations of the drug combination furosemide (20 mg)-spironolactone (100 mg) were tested for bioequivalence in a randomized crossover trial in 12 healthy volunteers. By comparing the AUC values derived from drug serum concentrations, bioequivalence was only achieved for canrenone, the main metabolite of spironolactone, but not for furosemide. A significant difference in the tmax values indicates sustained release of furosemide from one of the formulations. By contrast, bioequivalence was achieved if pharmacodynamic criteria, such as urine volume and Na+ and Cl- excretion over a period of 12 hours, were used. Fractional measurements of urinary volume and electrolyte excretion (0 to 3 h, 3 to 6 h, 6 to 12 h) correlated with the different tmax values for both formulations. These data indicate that bioequivalence is more conclusively verified on the basis of pharmacodynamic parameters than on the basis of pharmacokinetic parameters. These considerations are applicable in particular to drugs displaying large inter-individual variations in serum levels and/or a poor correlation between serum levels and effect.

Adult↗
PubMed1991

Pharmacokinetics of the analgesic o-carbamoylphenoxyacetic acid.

The pharmacokinetics of o-carbamoylphenoxyacetic acid was studied in 9 male healthy subjects following a single i.m. administration of 1000 mg of this compound in form of its sodium salt. Venous blood specimens were drawn up to the 10th h p.a. and the plasma concentration of o-carbamoylphenoxyacetic acid and its metabolite salicylamide were determined using a specific HPLC-assay. Following injection, o-carbamoylphenoxyacetic acid was rapidly distributed in the body since the maximal plasma concentration occurred within 0.37 +/- 0.08 h and was determined with 23.5 +/- 7.51 micrograms/ml in mean. In the following, the plasma concentration declined rapidly as well according to the mean terminal elimination half-life of 0.93 +/- 0.23 h. By contrast, plasma concentration of the metabolite salicylamide was comparatively low. Mean maximal plasma concentration amounted to only 0.18 +/- 0.03 microgram/ml and the peak concentration occurred 1.08 +/- 0.43 h after injection. The mean of the individual areas under the plasma concentration time profiles AUC(O-t) was 30.2 +/- 3.96 micrograms x h/ml for the parent compound and 0.69 +/- 0.14 microgram x h/ml for the metabolite. The relative mass portion of salicylamide vs o-carbamoylphenoxyacetic acid in systemic circulation was estimated with 0.008 comparing mean Cmax and with 0.023 comparing the mean areas AUC(O-t). A possible interpretation of these findings might be that a relatively stable ether bond exists in o-carbamoylphenoxyacetic acid which has to be cleaved during the formation of salicylamide. Due to the moderate rate of metabolic conversion, only minor quantities of salicylamide appeared in the systemic circulation. Furthermore, its peak concentration occurred at a time 2-3 times later than that of the parent compound.

Adult↗
PubMed1990

Pharmacokinetics of S(+)- and R(-)-ibuprofen in volunteers and first clinical experience of S(+)-ibuprofen in rheumatoid arthritis.

S(+)-, R(-)- or racemic ibuprofen was administered orally to volunteers in doses of 150 mg, 300 mg and 500 mg pure S(+)-, 300 mg pure R(-)- and 600 mg racemic ibuprofen. The pharmacokinetic parameters in humans showed that S(+)-ibuprofen was not inverted to R(-)-ibuprofen, whereas R(-)-ibuprofen was inverted to S(+)-ibuprofen to a variable degree. S(+)-ibuprofen and R(-)-ibuprofen given alone more rapidly reached significantly higher maximal plasma concentrations than after the same doses of the racemic compound. The elimination half-lives and clearance values for all three forms of ibuprofen were comparable. The mean residence time of S(+)-ibuprofen after R(-)- and racemic ibuprofen was significantly longer than after administration of the pure S(+)-enantiomer. Judged by the AUC, the bioavailability of S(+)-ibuprofen was independent of the dose within the range tested. Administration of S(+)-ibuprofen to 6 rheumatic patients showed that the pharmacokinetic behaviour of S(+)-ibuprofen in patients was similar to that found in volunteers. S(+)-ibuprofen proved to be an effective analgesic antirheumatic drug in the dose range 1 to 1.5 g/day.

Adult↗
PubMed1989

High-performance liquid chromatographic determination of ibuprofen, its metabolites and enantiomers in biological fluids.

An isocratic high-performance liquid chromatographic method to determine racemic ibuprofen (assay I) and its major metabolites (assay II) in biological fluids (plasma, urine, bile) using a conventional reversed-phase column is described. A third assay using beta-cyclodextrin as stationary phase (Cyclobond I) for the separation of the ibuprofen enantiomers is also described. A wavelength of 220 nm was used to monitor the substances. The sensitivity of the method was 0.1 microgram/ml for all three assays. The method was demonstrated to be suitable for stereoselective pharmacokinetic studies of ibuprofen in humans and animals.

Bile↗
PubMed1989

Pharmacological differences between R(-)- and S(+)-ibuprofen.

Ibuprofen (IBU) is a non-steroidal anti-inflammatory drug exhibiting optical isomerism. Only the racemate is in clinical use. In in vitro studies it has been demonstrated that only the S(+)-enantiomer inhibits the PG synthetase system. Nevertheless, it is widely believed that the sole use of the active isomer does not comprise any advantages since the inactive isomer is converted within the human body. In a triple cross-over study (300 mg S(+), 300 mg R(-), 600 mg racemic IBU; n = 8), we could show that the converted R(-)-IBU after racemate administration provides for only one third of the AUC of S(+)-IBU obtained after S(+)-application. Highest S(+)-peak plasma levels were reached after S(+)-IBU, lower ones after racemate. We, therefore, studied 4 patients with classical rheumatoid arthritis treated with 2-3 doses of 500 mg of S(+)-IBU/day over a two week period. Significant clinical recovery (Ritchie-index p less than 0.01; analogue scale pain p less than 0.05, motion p less than 0.01) was reached after one week. The results indicate that a reduction of dose and of metabolic load is possible if the S(+)-enantiomer is administrated.

Administration, Oral↗
PubMed1987

[Plasma kinetics and elimination of folic acid].

The plasma kinetics and elimination of folic acid were studied in 11 healthy subjects after saturation with a multivitamin preparation. A radioassay was utilized for the determination of folic acid. After the i.m. injection of 1.1 mg folic acid sodium, a maximum plasma level of 63.7 +/- 14.3 nmol/l was reached after 0.69 +/- 0.26 h. The elimination half-life time amounted to 1.53 +/- 0.46 h. Based on the injected amount of folic acid, the cumulative increase in elimination within 24 h amounted to 9.4% +/- 3.1%. Within the first 6 h 81.4% +/- 6.1% of the administered folic acid appeared in the urine and in the following 4 h 17.3% +/- 5.4%.

Adult↗