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Biomedical subjects

B Voigt

Publications and source records attributed to B Voigt.

At least 55 records · Page 3Linked to original sources
PubMed1989

The influence of the rotational energy of a flywheel on the load pulse sum during pedalling on a cycle ergometer.

Employing seven male subjects, the influence of four different ergometer flywheels with the moments of inertia at the crankshaft (J') = 5.5, 10.5, 16.5, and 19.5 kg.m2 on 6-min load pulse sum (LPS), the heart rate integrated over 6-min was investigated. The J' was demonstrated to influence LPS at each of the corresponding rotational energies of the flywheels (75, 144, 226 and 276 J at 50 rev.min-1) in the four work-load steps (50, 100, 150 and 200 W). Between the values J' = 5.5 kg.m2 and 10.5 kg.m2 the LPS decreases, to rise again in the range J' = 10.5 kg.m2-19.5 kg.m2. For equal work-loads the minimum LPS was reached at a J' of 10.5 kg.m2. For the workloads of 100, 150 and 200 W it was possible to show statistically significant differences. The moment of inertia of ergometer flywheels J has a smoothing effect on the fluctuations of the rotational speed which are unavoidable during work on a cycle ergometer. The flywheel stores the leg forces acting on the pedals as rotational energy and opposes any rotational acceleration. If the J used is too small, equalization of the fluctuations of the rotational speed remains unsatisfactory. Flywheels with larger J require larger torques at the crankshaft for acceleration. For the most effective delivery of work to a cycle ergometer, an optimal rotational energy of the flywheel was found. For equal physical work, smaller or larger rotational energies require a larger expenditure of biological energy. A J' = 11 +/- 2 kg.m2 was incorporated into the draft for the German standard DIN 13,405 -- cycle-type ergometers.

Adult↗
PubMed1988

[Synthesis of N-alpha-(arylsulfonyl)-4-amidino-phenylalanyl-prolines and N-alpha-(arylsulfonylglycyl)-4-amidino-phenylalanyl-prolines and testing of them as inhibitors of serine proteinases. 33. Synthetic inhibitors of serine proteinases].

The headline compounds were prepared by the reaction of N alpha-(arylsulfonyl)- and N alpha-(arylsulfonylglycyl)-4-cyanophenylalanines to the L- and D-proline derivatives. These compounds were transformed in a usual manner in the amidino compounds. The substitution of the pyrrolidine residue by L-proline in this type of inhibitors decreased the activity against serine proteases, especially against thrombin. In the case of the D-proline derivatives the decrease of the inhibitor activity against thrombin was very high.

Chemical Phenomena↗
PubMed1988

[Synthetic inhibitors of serine proteinases. 34. The effect of modification of the amidino function of N-alpha-substituted 4-amidinophenylalanine amides on inhibitory activity].

Cyclic amides of N alpha-arylsulfonylated 4-amidinophenylalanine are selective inhibitors of thrombin. The exchange of the amidino function for an aminomethyl residue does not influence the selectivity and potency of their inhibitory activity. In contrast, the modification of the amidino function of the N alpha-arylsulfonylaminoacylated compound N alpha-(2-naphthylsulfonylglycyl)-4-amidinophenylalanine piperidide results in a drastic loss of inhibitory activity. Only the oxamidino derivative possesses considerable high affinity for thrombin. Obviously, in tight binding inhibitors of thrombin structural variation results in any case in a loss of inhibitory activity.

Amidines↗
PubMed1987

[Synthetic inhibitors of serine proteinases. 32. Inhibition of trypsin, plasmin and thrombin by amides of N-alpha-substituted 4-amidinophenylalanine. Effect of various amino acids and blocking groups of the n-alpha residue on inhibitory activity].

Cyclic amides of N alpha-arylsulfonylated 4-amidinophenylalanine are specific, highly potent inhibitors of thrombin. Introduction of amino acids between the arylsulfonyl blocking group and amino nitrogen influence particularly the antithrombin activity. By the use of glycine as spacer the compounds become tight binding thrombin inhibitors, while introduction of other omega-amino acids, Gly-Gly, L-Pro, Gly-L-Pro or L-Pro-Gly, reduces the specificity and potency of thrombin inhibition. Substitution of the arylsulfonyl blocking group for a heteroarylsulfonyl residue or an aryl residue causes a decrease in antithrombin activity, while substitution for a benzoyloxycarbonyl blocking group has only slight influence. It is concluded that the N alpha-moiety is of decisive importance for the antithrombin activity of derivatives of 4-amidinophenylalanine.

Amidines↗
PubMed1986

[Synthesis of N-alpha-(arylsulfonyl-L-prolyl)- and N alpha-(benzyloxycarbonyl-L-prolyl)-D,L-4-amidinophenylalanine amides as inhibitors of thrombin].

N alpha substituted 4-cyanophenylalanines were prepared by reaction of the acid chloride, the activated ester and the mixed anhydride of Tos-Pro-OH, 2-naphthylsulfonyl-L-proline and Z-Pro-OH, respectively, with cyanophenylalanine. These acids were transferred into the amides via the 4-nitrophenyl esters or the mixed anhydrides. The cyano compounds were converted via the thioamides and the thioimidic esters into the amidines by common way. The exchange of the glycine residue by prolin in compounds former described caused a decreased antithrombin effect.

Chemical Phenomena↗
PubMed1986

[Synthesis of N-alpha-(tosylglycylprolyl)-4-amidinophenylalanine amides as thrombin inhibitors].

N alpha-(Tosylprolylglycyl)-4-cyanphenylalanine was synthesized by the reaction of an activated ester and a mixed anhydride, respectively, of Tos-Pro-Gly-OH with 4-cyanophenylalanine. N alpha-(Tosylglycylprolyl)-4-cyanophenylalanine was prepared by reaction of Tos-Gly-Cl with N alpha-prolyl-4-cyanophenylalanine. These acids were transferred into the amides. The cyano compounds were converted into the desired amidines via the thioamides and the thioimidic esters.

Amidines↗
PubMed1985

[Synthesis of N-alpha-benzyloxycarbonyl-4-amidinophenylalanine amides as thrombin inhibitors].

Based on 4-cyanophenylalanine, the title compounds had been obtained by benzyloxycarbonylation of the amino group, subsequent formation of the activated ester by 4-nitrophenol, its aminolysis and at least change of the cyano function to the amidine function via thiocarbamides and thioimid acid esters. The inhibitor effect against thrombin of the pyrrolidid 16 is analogous to those of the adequate N alpha-tosyl compound.

Chemical Phenomena↗
PubMed1985

[Synthesis of N alpha-(benzoylglycyl)- and N alpha-(benzyloxycarbonylglycyl)-4-amidinophenylalanine amides as thrombin inhibitors].

The 4-nitrophenyl esters of hippuric acid and benzyloxycarbonylglycine had been aminolyzed by racemic 4-cyanphenylalanine into the compounds 3 and 4. After activation as 4-nitrophenyl esters and following reaction with amines the amides 7-14 were formed. These cyano compounds were converted into the amidines via the thioamides 15-22 and the thioimidic esters 23-30. The piperidide 35 was most effective against thrombin.

Antithrombins↗
PubMed1984

Inhibition of bovine and human thrombins by derivatives of benzamidine.

Thirty-four derivatives of benzamidine were tested for their inhibitory activities on bovine and human thrombins using the chromogenic peptide substrate N-D-Phe-Pip-Arg-pNA. The inhibition constants of small molecular size inhibitors of comparatively low affinity as well as those of tight binding inhibitors did not differ significantly with different species. Accordingly, the active site of bovine thrombin seems to correspond largely to that of human thrombin.

Amidines↗
PubMed1984

[Determination of free and bound ergosterol in microorganisms].

A method for the quantitative determination of free and esterified ergosterol in lipid fractions from biomasses grown on hydrocarbons as sole carbon source is described. Column chromatography was used for the fractionation of lipids. Esterified ergosterol was determined in the benzene fraction and free ergosterol in the methanol fraction by known methods.

Chromatography, Gel↗
PubMed1984

[Synthesis of N alpha-(tosyl-beta-alanyl)- and N alpha-(tosyl-epsilon-aminocapronyl)amidinophenylalanineamides as strongly effective inhibitors of thrombin].

The headline compounds were prepared for further determination of structure-activity-relationships. By conversion of cyanophenylalanines with the acidic chloride of tosyl-beta-alanine resp. tosyl-epsilon-aminocapronic acid and aminolysis of the following prepared p-nitrophenylic esters the cyano compounds would get the desired structure, which were converted over the thioamides and thioimidic esters in the amidines by the common way. At the preparation of epsilon-aminocapronic acid derivatives occurred difficulties because of simultaneous formation of the N-tosyl-epsilon-caprolactame. The preparation of corresponding aminobutyric acid derivatives wasn't possible. The prolongation of the C-chain of the branchless amino acid decreased the antithrombine effect.

Aminocaproates↗
PubMed1984

[Synthesis of N alpha-(arylsulfonylglycylglycyl)-4-amidinophenylalanine amides as thrombin inhibitors].

The headline compounds were prepared using N-arylsulfonylglycylglycine-4-nitrophenyl esters. Firstly these compounds were aminolized with 4-cyanphenyl alanine and thereby the N alpha-(arylsulfonylglycylglycyl)-4-cyanphenyl alanines got were transferred into the 4-nitrophenyl esters After aminolysis the desired hydroiodides of the headline compounds starting from the cyano compounds were prepared via the carbamoyl compounds and the thiomidic acid methyl ester hydroiodides. The arylsulfonylglycylglycine rest caused a decreasing of the inhibitor activity.

Amidines↗
PubMed1984

Affinity sorbents containing benzamidine derivatives for biomedical application.

Affinity sorbents for trypsin have been obtained by immobilization of 4-amidinophenylalkylcarboxylic acids on macroporous silica gel. Frontal chromatography was used to measure the dissociation constants of the trypsin-immobilized inhibitor complexes (Kd). The Kd value has been found to increase 50-100 fold on immobilization. A commercial trypsin preparation was purified on the obtained biospecific sorbent. Applicability of the affinity sorbent containing 4-amidinophenylacetic acid was demonstrated by hemoperfusion in dogs with acute pancreatitis. The sorbent with immobilized low molecular mass trypsin inhibitor has the capacity to greatly reduce the level of proteases in blood without altering the concentration of protease inhibitors: this results in efficient treatment.

Acute Disease↗
PubMed1984

[Computer tomographic diagnosis of endocrine orbitopathy].

On the basis of 52 CT analyses of endocrine orbitopathy the involvement and changes in density and width of the orbital structures are worked out. The differential diagnostic value of CT in inflammatory, tumorous or vascular ophthalmopathy is discussed.

Adult↗
PubMed1984

[Synthesis of N-alpha-(arylsulfonylglycyl)amidinophenylalanine amides as highly active inhibitors of thrombin].

The headline compounds were prepared from purified cyanophenylalanines after presenting arylsulfonylglycyl residues, activation of the carboxyl group by formation of the p- nitrophenylester followed by aminolysis and transfer of a cyano in an amidine function. Besides some esters and an acid were synthetized with the basic structure mentioned in the headline . The p-compounds with a cycloaliphatic amide component proved as "tight binding inhibitors". The greatest antithrombin effect shows N alpha-(2- naphthylsulphonylglycyl )-4- amidinophenylalaninpiperidi d with a Ki-value of 6 X 10(-9) mol/l using S-2238 as a substrate.

Phenylalanine↗