Comparative cardiac toxicity of the i.v. administered benzimidazole pyridazinon derivative Pimobendan and its enantiomers in female Beagle dogs.

The new positive-inotropic and vasodilatating drug Pimobendan (racemate), 4,5-dihydro-6-[2-(4-methoxyphenyl)-1H-benzimidazole-5-yl]-5-methyl-3 (2-H)-pyridazinone, and its enantiomers were investigated with regard to their cardiotoxicity in young adult female Chbb: Beagle dogs. The racemate and the (-)-isomer (eutomer) were intravenously injected once daily for 4 consecutive weeks at doses of 0.25, 0.75 and 2.25 mg/kg, and the (+)-isomer (distomer) at doses of 0.75, 2.25 and 6.75 mg/kg, respectively. Clinical signs, hematological, clinico-chemical, ophthalmologic and electrophysiological parameters were monitored. Plasma concentration-time profiles of the parent compound and the major metabolite UD-CG 212 were established on day 1 and in week 4 using an HPLC assay. Partial areas under the curves from 0.08 h to 1 h (AUC0.08-1 h) as well as the plasma concentration at time point 0.5 h/C0.5 h) were used for statistical calculations. Necropsy and histopathologic examination were performed after completion of the treatment period. Reduction of the blood pressure occurred already at low dosages of the racemate and the eutomer, but only in high dose distomer-treated animals. A tendency to tachycardia developed only in high dose females receiving the racemate. Consequently, with respect to the pharmacological effects and the adverse events, the racemate is equivalent to the eutomer. Plasma concentrations of parent compound and metabolite were dose-linear for racemate, eutomer and distomer within the dose range 0.25-2.25 mg/kg.d at both time points. There were no significant effects of form or repeated administration. A moderate increase of AUC0.08 1 h and C0.5 h could be seen on day 23 for the distomer indicating a stereoselektive metabolism of the latter. Histologic changes of the valvular and parietal endocardium being termed jet lesion were observed after administration of the racemate (> or = 0.75 mg/kg.d) and the eutomer (> or = 0.25 mg/kg.d) at distinctly lower doses than after the distomer (> or = 2.25 mg/kg.d). Furthermore, extent and severity of the morphologic lesions were found to be higher in dogs exposed to the racemate or the eutomer than in those receiving the distomer. The results gave evidence that the so-called cardiotoxicity by Pimobendan in dogs resulted from the exaggerated pharmacodynamic effect but not from the chemical nature of the compound per se. They corroborate also the previously raised assumption that the exaggerated pharmacodynamic activity of cardiotonic compounds in the broadest sense accounts for their morphologic adverse effects in experimental animals.

Duration of action and pharmacokinetics of the oral antidiabetic drug gliquidone in patients with non-insulin-dependent (type 2) diabetes mellitus.

The duration of action and the pharmacokinetics of gliquidone (1-cyclohexyl-3-[[4-[2-(3,4-dihydro-7-methoxy-4,4-dimethyl-1, 3-dioxo-2(1H)-isochinolyl)ethyl]phenyl]-sulfonyl]-urea, AR-DF 26 SE, CAS 33342-05-1, Glurenorm, Beglynor) were investigated in 32 patients with non-insulin-dependent (type 2) diabetes mellitus over 16 h. In a single-blinded cross-over design vs. placebo, one 30 mg tablet gliquidone was administered 15 min before breakfast. Concomitant to the measurement of glucose and insulin, the gliquidone plasma levels of 20 subjects were determined by a new specific liquid chromatographic (HPLC) assay method with fluorescence detection, and the pharmacokinetic parameters calculated. Following the gliquidone administration, the mean plasma glucose profiles of the responders were up to 15% lower than with placebo (p < 0.005) between 8 a.m. and 6 p.m., representing a duration of the blood sugar-lowering effect of 8 to 10 h. Insulin values were raised, with peaks over 40% higher, during or shortly after meals. Subsequently, the insulin levels returned to approximately the same levels obtained with placebo during the postprandial phase. Plasma concentrations of gliquidone showed pronounced interindividual variability. The mean maximum concentration in plasma Cmax was 0.65 microgram/ml, (range: 0.12-2.14 micrograms/ml, coefficient of variation (CV): 82%). The median time to reach maximum plasma concentrations tmax was 2.25 h (range: 1.25-4.75 h). The areas under the plasma concentration-time curve from zero time to infinity (AUC0-infinity) and the mean terminal elimination half-lives (t1/2 beta) were computed from those patients (N = 8) who exhibited at least five plasma levels above the limit of quantitation in the terminal log-linear phase using a two-compartment model: the mean AUC0-infinity was 5.1 micrograms.h/ml (range: 1.5-10.1 micrograms.h/ml, CV 56%). The dominant half-life t1/2 alpha derived from therapeutically relevant plasma levels of gliquidone (> 80 ng/ml) was approximately 1.2 h (range: 0.4-3.0 h. CV: 71%) and the mean terminal half-life t1/2 beta was approximately 8 h (range: 5.7-9.4 h, CV: 17%). From the pharmacodynamic behavior as well as from the pharmacokinetic parameters it can be deduced that gliquidone belongs to the class of short-acting sulfonylureas used in antidiabetic therapy.

Ambroxol improves the broncho-spasmolytic activity of clenbuterol in the guinea-pig.

The effects of ambroxol on the spasmolytic action of clenbuterol were investigated on acetylcholine-induced bronchospasm in guinea-pigs. Ambroxol (50 mg kg-1 day-1) or vehicle was administered orally for 14 days. Approximately 45 min after the final dose on day 14, the animals were anaesthetized and the spasmolytic effects of clenbuterol (3, 6 or 12 micrograms kg-1 injected intravenously) were determined by use of acetylcholine (40 micrograms kg-1, i.v.)-induced bronchoconstriction. For both vehicle- and ambroxol-treated animals, a positive linear relationship was observed between the log-dose of clenbuterol and the percent inhibition of bronchospasm. The calculated ED25 of clenbuterol (i.e., the dose producing 25% inhibition of the acetylcholine-induced bronchospasm) was 3.98 micrograms kg-1 (3.29 to 4.82 micrograms kg-1, 95% confidence interval) in the presence of ambroxol and 5.81 micrograms kg-1 (4.98 to 6.79 micrograms kg-1) in the absence of ambroxol. The linear regressions with or without ambroxol differed from each other (P < 0.001) but ran parallel (covariance analysis), enabling us to calculate a relative potency, the value of which was 1.46 (1.16 to 1.84). These results demonstrate that the spasmolytic activity of clenbuterol is significantly improved in animals pretreated with ambroxol.

[H-NMR spectroscopy. Specificity of microbial sialidases against complex substrates]. / 1H-NMR-Spektroskopie. Spezifität mikrobieller Sialidasen gegenüber komplexen Substraten.

The specificities of one viral and five bacterial sialidases were investigated by 1H-NMR-spectroscopy with substrates or substrate mixtures containing two sialic acid residues of different linkage types. This technique allows - in contrast to the methods used before - the simultaneous determination of the rates of hydrolysis of both NeuAc linkages in a single experiment. The substrate specificities of the enzymes are discussed on the basis of the relation of the rate constants k/k'. The data obtained are more exact and more informative than those of separate experiments as reported previously. Among the enzymes investigated, i.e. sialidases of fowl plague virus (FPV = VKH), Clostridium perfringens (CP), Vibrio cholerae (VC), Bifidobacterium bifidum var. pennsylvanicum (BBif), Bifidobacterium lactentis (BLac), and Arthrobacter ureafaciens (AU), the activity of the viral sialidase VKH shows the highest, the activities of the Bifidobacterium sialidases the lowest dependence on the nature and on the linkage type of the different substrates. All sialidases preferentially cleave the NeuAc alpha 2-3-Gal linkage with the exception of the enzyme of Arthrobacter ureafaciens (AU) which shows a higher affinity to alpha 2-6 linkages. However, this does not apply to the side-arm-linked NeuAc alpha 2-6 structure in NeuAc alpha 2-3 Gal beta 1-3 (NeuAc alpha 2-6)-GlcNAc beta 1-3Gal beta 1-4Glc (Substrate B). This substrate in generally cleaved very slowly and is hardly affected by the viral enzyme. After the alpha 2-3 linkage, the alpha 2-8 bond in NeuAc alpha 2-8 NeuAc alpha 2-3 Gal beta 1-4Glc(Substrate A) is most susceptible for the sialidases VKH, CP and VC. An elongation of the carbohydrate chain (Substrate D) is accompanied by a reduction of the rate of cleavage for all enzymes. The experiments with alpha 1-acid glycoprotein, fetuin, and with the glycopeptides obtained by proteolytic degradation of the latter, revealed the same specificity towards the alpha 2-3 and the alpha 2-6 linkages as the oligosaccharides. Influenced by the chemical nature and the size of the substrate, NeuAc is released from the native alpha 1-acid glycoprotein more quickly than from the corresponding glycopeptide. All sialidases investigated so far are strictly exo-enzymes as could be demonstrated by the cleavage of NeuAc alpha 2-8 NeuAc alpha 2-3 Gal beta 1-4Glc (Substrate A).

A newly discovered sialidase from Gardnerella vaginalis.

A sialidase (neuraminidase, acylneuraminosyl hydrolase, EC 3.2.1.18) has been discovered and isolated from Gardnerella vaginalis (ex. Haemophilus vaginalis), a possibly pathogenic inhabitant of the female genital tract. Bacteria were grown in peptone-yeast-extract medium with 2.0 mM N-acetylmannosamine as enzyme inductor under CO2 atmosphere. Sialidase activity was found in the bacterial sediment and in the culture medium. The enzyme was liberated from the cells by ultrasonic treatment. Purification was performed by 60-80% ammonium sulfate precipitation and by column chromatography on Sepharose CL-6B and Sephadex G 200. The enzyme revealed a molecular weight in the range of Mr 75 000 and a pH optimum at 5.5. Among the different types of NeuAc-containing glycoconjugates, the enzyme exhibits its highest activities towards the globular glycoproteins alpha 1-acid glycoprotein and fetuin. Taking their cleavage rate as 100, it is around 55 for II3NeuAc-Lac, 45 for bovine submaxillary mucin, 35 for II6NeuAc-Lac and IV3, III6NeuAc2-LcOse4. The rates for III8,II3NeuAc2-Lac, gangliosides and colominic acid are below 20. Due to its specificity pattern, the enzyme may play a role in the pathogenic process of G. vaginalis infections.

Fucose containing oligosaccharides from human milk. I. Separation and identification of new constituents.

Neutral oligosaccharides isolated from pooled human milk were subjected to fractionation on high-performance thin-layer chromatography (HPTLC) plates, Iatrobeads, and reverse-phase chromatography after borohydride reduction and peracetylation. By the combined HPLC and HPTLC separation a mixture of pooled human milk oligosaccharides was separated into 101 fractions. These fractions were characterized by field desorption or fast atom bombardment (FAB)-mass spectrometry. Each of the carbohydrate constituents, the peracetylated glucitol, the galactose, the glucosamine, and the fucose contribute specific mass increments to the molecular weight of the oligosaccharide. Therefore, the exact carbohydrate composition can be calculated from the molecular weight determined by mass spectrometry. Among the fractions obtained one trifucosyl-lacto-N-tetraose, five monofucosyl-, eleven difucosyl-, and nine trifucosyl-lacto-N-hexaoses, one monofucosyl-, eight difucosyl-, seven trifucosyl-, four tetrafucosyl-, and two pentafucosyl-lacto-N-octaoses, one trifucosyl-, and two difucosyl-lacto-N-decaoses could be identified. FAB spectra furnished additional data on structural features of the isolated oligosaccharides.

[1H-NMR spectroscopy--a potent method for the determination of substrate specificity of sialidases (author's transl)]. / 1H-NMR-Spektroskopie--Eine aussagekräftige Methode zur Bestimmung der Substratspezifität von Sialidasen.

We describe here the application of 1H-NMR spectroscopy to determine the substrate specificity of sialidases using a 1:1 mixture of NeuAc alpha 2-3Gal beta 1-4Glc and NeuAc alpha 2-6Gal beta 1-4Glc, one viral and five bacterial sialidases. This method utilizes the separate signals in NMR spectra, characteristic for the different alpha ketosidically linked NeuAc residues and also for bound and free NeuAc. The signals generally most suitable for these purposes are those of H3a, H3e and NCOCH3. By observation and integration of these signals we can follow--qualitatively and quantitatively--which and how many NeuAc residues of the substrates are hydrolized. In contrast to the generally used colorimetric tests it is now possible to investigate with this method substrates containing two or more NeuAc residues and to determine the corresponding rate constants for hydrolysis of the differently bound NeuAc molecules. The six sialidases used show large differences in their specificity as compared with our "model substrate": The sialidase from fowl plague virus hydrolizes NeuAc alpha 2-3Gal beta 1-4Glc nearly 18 times and the enzyme from Clostridium perfringens four times, from Vibrio cholerae two times faster than NeuAc alpha 2-6Gal beta 1-4Glc. On the contrary, the sialidase from Arthrobacter ureafaciens hydrolizes the alpha 2-6 linkage six times faster than the alpha 2-3 linkage. The sialidases from Bifidobacterium show no obvious differences in their specificities relative to the linkage.

Neuraminidases of Bacteroidaceae die neuraminidasen von bacteroidaceen.

Neuraminidases can be detected in members of the anaerobic gram-negative non-sporing rods (Bacteroidaceae), especially in the genus Bacteroides. B. fragilis, the most virulent species, has the highest neuraminidase activity, while the other intestinal species exhibit markedly lower activities or the enzyme is completely absent. Members of the Bacteroides oralis group, so far investigated, degrade only substrates of lower molecular weight.

Partial purification and properties of neuraminidase from Bifidobacterium lactentis.

Bifidobacterium lactentis 659 a gram-positive, nonsporeforming anaerobic bacterium originally isolated from the feces of breast-fed infants produces neuraminidase after enzyme induction with 2mM N-acetylmannosamine added to the culture medium. Bacteria were transferred and grown in a medium containing casein hydrolysate, lactose, sodium acetate, amino acids, vitamins, salts and 2% human milk for 48 h at 37 degrees C under N2/CO2 atmosphere. Two subcultures derived from the original strain B. lactentis 659 were investigated separately because of different growth characteristics. However, their taxonomic identity was not doubtful. Neuraminidase was liberated from the bacterial sediments by ultrasonic treatment in 0.15M NaCl and was isolated by 60% ammonium sulfate precipitation, dialysis, concentration, and column chromatography on Sepharose CL-6B and Sephadex G-100. The enzyme exhibits a molecular weight of 38000 and a pH optimum in the range of pH 5--6 in barbital/acetate buffers. Starch gel electrophoresis and neuraminidase-specific staining with NeuAc alpha 2 leads to (3-methoxyphenyl) glycoside revealed two major and three minor enzyme bands. Michaelis constants (Km) were determined to be 7.1 mM for the (alpha 2 leads to 3) linkage of II3NeuAc-Lac, 7.5mM for the (alpha 2 leads to 6) linkage of II6Neu-Ac-Lac and 15mM for the (alpha 2 leads to 8) linkage in II3(leads from 2NeuAc8)2-Lac. Among the different groups of naturally occurring NeuAc-containing substrates, i.e. glycoproteins, gangliosides and oligosaccharides, B. lactentis neuraminidase cleaves oligosaccharides preferentially without remarkable differences between (alpha 2 leads to 3) and (alpha 2 leads to 6) linkages. Globular glycoproteins and mucins are poor substrates and gangliosides are practically not affected. In contrast, enzyme activity towards synthetic NeuAc glycosides is very high. The enzyme is activated by 50% with 50mM Ca2 and inhibited by 20mM EDTA accordingly. In general, B. lactentis neuraminidase shows a substrate specificity pattern similar to those found in other non-pathogenic and non-invasive representatives of the human bacterial flora. The potential biological role of intestinal Bifidobacteria will be discussed.

Neuraminidase production by Propionibacterium acnes-strains isolated from patients with acne vulgaris, seborrheic eczema and healthy subjects.

Among cutaneous propionibacteria, synthesis of neuraminidase is highest in strains of the species P, acnes. In the present study, neuraminidase activity was discovered in 90.0% of P. acnes strains isolated from acne lesions compared with 72.7% of strains from normal human skin. Neuraminidase-positive strains from acne lesions, moreover, produced statistically significant higher amounts of the enzyme (X = 727 microunits/ml bacterial suspension) than isolates from normal skin (X - 392 microunits/ml). Whereas the moderate production of neuraminidase by strains from patients with seborrheic eczema is probably of no causative importance, the enzyme has to be discussed a potential etiologic factor in acne vulgaris.

Isolation, purification, and properties of neuraminidase from Propionibacterium acnes.

Neuraminidase activity was discovered in 32 of 38 strains of Propionibacterium acnes. Enzyme production was studied in yeast extract bouillon of different pH containing various amounts of human milk as neuraminidase inductor. Enzyme activity was found in the bacterial sediments as well as in the culture filtrates. Since neither ultrasonic treatment nor lysozyme incubation of bacterial sediments did release reasonable amounts of enzyme, culture filtrates were used for enzyme preparation. Neuraminidase was isolated by 40% ammonium sulfate precipitation, dialysis, concentration and repeated gel chromatography on Sephadex G-100. The enzyme posesses a molecular weight of about 33 000 and a pH-optimum around 5.0. The Michaelis constants are 1.8 x 10(-3) M for alpha 2 leads to 3 linked N-acetylneuraminic acid (NeuAc) in II3NeuAc-Lac, 3.7 x 10(-3) M for the alpha 2 leads to 6 linkage in II6NeuAc-Lac, and 2.1 x 10(-3) M for the alpha 2 leads to 8 linkage of II3 (comes from 2 alpha NeuAc8)2-Lac, respectively. Among the different groups of naturally occurring NeuAc-containing substrates, i.e. oligosaccharides, glycolipids and glycoproteins, the enzyme exhibits its highest activity towards low molecular weight oligosaccharides. Activity is considerably lower on glycoproteins. Glycolipids (gangliosides) are only little attacked under conditions used in the test. However, there is no remarkable specificity towards one of the different linkage types of N-acetylneuraminic acid. In general, the enzyme reveals a specificity pattern similar to that found in other bacteria of low pathogenicity towards man.

Properties and substrate specificities of two neuraminidases from Trichomonas fetus.

Trichomonas fetus, a protozoon belonging to the class of flagellates causes vaginal infections in cows, leading to sterility or abortion in early stage of pregnancy. Two neuraminidases were isolated from the culture medium and purified by various procedures of gel chromatography, ion exchange chromatography, and by affinity chromatography on N-(4-nitrophenyl)-oxamic acid-Sepharose 4B. The molecular weights of the two neuraminidases were determined as 320 000 (enzyme I) and 38 000 (enzyme II) respectively. However, enzyme I seems to consist of two isoenzymes containing four subunits of almost equal molecular weight. The pH optima of both enzymes depend on the substrates and range from pH 4.7 to 5.5. Due to the type of substrate, the Michaelis constants (Km) vary between 5.0 x 10(-2)M and 6.6 x 10(-3)M for enzyme I and between 1.4 x 10(-2)M and 4.9 x 10(-3)M for enzyme II. Among the different groups of NeuAc-containing substrates, i.e. glycoproteins, glycolipids, oligosaccharides and synthetic ketosides, enzyme I preferably cleaves high molecular weight glycoprotein type substrates whereas enzyme II shows higher affinities to low-molecular weight oligosaccharides. The ganglioside II3NeuAcGgOse4Cer is susceptible to both enzymes only after removal of the lipophilic ceramide residue. Both enzymes show differences in the specificity towards alpha 2 leads 3 to 3, alpha 2 leads to 6, and alpha 2 leads to 8 glycosidic linkages of NeuAc. Taking the rate of cleavage of the alpha 2 leads to linkage in II3NeuAc-Lac as 100, enzyme I reveals 65 for the alpha 2 leads to 6 linkage in II6NeuAc-Lac, and 15 for the alpha 2 leads to 8 linkage in II3(comes from 2 alpha NeuAc8)2-Lac, whereas enzyme II exhibits values around 50 for both the alpha 2 leads to 6- and the alpha 2 leads to 8-linked substrates. The activity of neuraminidase I and II is not influenced by Ca2 but is inhibited by Cu2, Hg2, ann 4-hydroxymercurisulfonic acid. The inhibition by Hg2 and by the latter is reversible with enzyme I by addition of dithioerythritol.

Uptake and distribution of orally applied N-acetyl-(14C)neuraminosyl-lactose and N-acetyl-(14C)neuraminic acid in the organs of newborn rats.

N-acetyl-(14C)neuraminosyl-(alpha,2 leads to 3)lactose enzymatically prepared of CMP-NeuNAc and lactose by a particulate enzyme fraction from lactating rat mammary gland was applied orally to newborn rats and examined for uptake and distribution in relation to those of free N-acetyl-(14C)neuraminic acid. The neonates were allowed to stay with their mother before and during the incubation time up to 6 h. Within this time 70% of the given dose was excreted while 30% was retained in the body. (14C)NeuNAc-lactose activity appeared 1.5 h after application in blood, urine, and tissues and attained maximum values after 3 and 6 h, respectively. The highest uptake occurred in liver, spleen, and brain. The absorption of the trisaccharide was delayed by 30 min compared with free (14C)NeuNAc. The time courses of the curves show a slower but higher accumulation in the tissues suggesting a better utilization of the (14C)NeuNAc from (14C)NeuNAc-lactose or pecularities in the absorption of the trisaccharide by the organs.

[Gas chromatographic mass spectrometric analysis of neurtral and acid oligosaccharides from human milk as their trimethylsilyl derivatives (author's transl)]. / Gaschromatographisch-massenspektrometrische Analyse neutraler und saurer Oligosaccharide der Frauenmilch als Trimethylsilyläther

Gas chromatography and the 20 eV mass spectra of the human milk oligosaccharides fucosido-galactose, fucosido-lactose, di-fucosido-lactose, 3'-N-acetylneuraminyl-lactose, 6'-N-acetylneuraminyl-lactose and of N-acetyllactosamine as pertrimethylsilyl (TMS) ethers are described. The gas chromatographic separation of the L-fucose containing oligosaccharides was performed on Silicone SE 30. The sialic acid containing sugars were separated on DEXSIL 300. The correlations between oligosaccharide structures and mass spectrometric fragmentation patterns are discussed.

[Michaelis constants of neuraminidases of pathogenic and apathogenic microorganisms (author's transl)]. / Michaelis-Konstanten von Neuroaminidasen bei pathogenen und apathogenen Mikroorganismen

The Km-values of neuraminidases from different pathogenic and apathogenic microorganisms have been determined on low and high molecular substrates. The substrate specificity and the affinity to the different types of substrates in relation to the pathogenicity of the microorganisms are discussed.