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Biomedical subjects

K Lang

Publications and source records attributed to K Lang.

At least 19 recordsLinked to original sources
PubMed1992

Intracranial microdialysis of salicylic acid to detect hydroxyl radical generation through dopamine autooxidation in the caudate nucleus: effects of MPP+.

Ringer's solution containing salicylic acid (5 nmol/microliters/min) was infused directly through an intracranial microdialysis probe to detect the generation of hydroxyl radicals (.OH) reflected by the formation of dihydroxybenzoic acids (DHBA) in the caudate nucleus of anesthetized rats. Brain dialysate was assayed for dopamine, 2,3-, and 2,5-DHBA by a high-pressure liquid chromatography-electrochemical (HPLC-EC) procedure. 1-Methyl-4-phenylpyridinium ions (MPP+, 0 to 150 nmol) increased dose-dependently the release of dopamine and the formation of DHBA. A positive linear correlation between the release of dopamine and the formation of 2,3- or 2,5-DHBA was observed (R2 = .98). The present results demonstrate the validity of the use of not only 2,3-DHBA but also 2,5-DHBA as an in vivo index of oxidative damage generated by reactive .OH radicals. In conclusion, the present study demonstrates a novel use of intracranial microdialysis of salicylic acid to assess the oxidative damage elicited by .OH in living brain.

1-Methyl-4-phenylpyridinium↗
PubMed1990

Role of two proline-containing turns in the folding of porcine ribonuclease.

Unfolded ribonuclease (RNase) from porcine pancreas consists of a mixture of fast and slow-refolding species. The equilibrium distribution of these species differs strongly from other homologous RNases, because an additional proline residue is present at position 115 of the porcine protein. The major slow-folding species of porcine RNase contains incorrect proline isomers at Pro93 and at Pro114-Pro115. Both positions are presumably part of beta-turn structures in the native protein, as deduced from the structure of the homologous bovine RNase A. The folding kinetics of these molecules depend strongly on the conditions used. Under unfavorable conditions (near the unfolding transition), refolding is virtually blocked by the presence of the incorrect proline peptide bonds and partially folded intermediates with incorrect isomers could not be detected. As a consequence, folding is very slow under such conditions and the re-isomerization of Pro114-Pro115 is the first and rate-limiting step of folding. Under strongly native conditions (such as in the presence of ammonium sulfate), refolding is much faster. A largely folded intermediate accumulates with the turns around Pro93 and Pro114-Pro115 still in the non-native conformation. These results suggest that incorrect proline isomers strongly influence protein folding and that, under favorable conditions, the polypeptide chain can fold with two beta-turns locked into a non-native conformation. We conclude, therefore, that early formation of correct turn structure is not necessarily required for protein folding. However, the presence of incorrect turns, locked-in by non-native proline isomers, strongly decreases the rate of refolding. Alternative pathways of folding exist. The choice of pathway depends on the number and distribution of incorrect proline isomers and on the folding conditions.

Ammonium Sulfate↗
PubMed1990

Coronary reperfusion studies with pro-urokinase in acute myocardial infarction: evidence for synergism of low dose urokinase.

Pro-urokinase is a single chain precursor of two chain urokinase, which has been shown to induce fibrin-selective plasminogen activation. In the present study, thrombolytic efficacy of 9 million U of glycosylated pro-urokinase administered intravenously was compared with that of a combined regimen utilizing 4.5 million U of pro-urokinase and 0.2 million U of urokinase. Seventy-five patients with a first myocardial infarction were randomized to receive high dose pro-urokinase (n = 40, group A) or the combination therapy (n = 35, group B). Reperfusion of the infarct-related artery was assessed by repeat coronary angiography. Thrombolysis in Myocardial Infarction trial (TIMI) grade II or III reperfusion was achieved in 73% of group A patients compared with 66% of group B patients (p = NS). A trend toward faster reopening of the infarct-related artery was observed in patients in group B. Coronary artery reocclusion occurred in 5 (10%) of 49 patients in whom angiography was repeated within 36 h after the start of therapy. Clot-selective thrombolysis was indicated by a minimal fibrinogen decline (15% and 13%, respectively, in groups A and B). Alpha 2-antiplasmin levels, however, decreased more rapidly in patients in group B (p less than 0.05). This finding and the equivalent reperfusion rate in the combined treatment group strongly suggest synergistic interaction between these two thrombolytic agents. In summary, the high incidence of reperfusion, the low rate of early reocclusion and the paucity of side effects, particularly with regard to bleeding complications, indicate that pro-urokinase possesses the characteristics of an ideal thrombolytic agent.

Drug Synergism↗
PubMed1979

[Sulfites in infusion solutions].

9 commercially available high-calorie carbohydrate solutions were investigated for their sulfite content. It became evident that 6 manufacturers of infusion solutions add varying amounts of sulfite to their solutions. We consider such an addition to be unnecessary and risky from the toxicological point of view.

Carbohydrates↗
PubMed1978

Diagnosis of dissecting aortic aneurysm with suprasternal echocardiography.

A 33 year old woman with Marfan's syndrome and aortic root dissection was studied with precordial and suprasternal echocardiography. The precordial approach revealed some typical features of aortic root dissection. With suprasternal echocardiography it was possible to visualize the characteristic diagnostic feature of this disease: within the aortic lumen an m-shaped pattern--the aortic intimal flap--moving downward to the posterior aortic wall during systole. The diagnosis was confirmed with aortic cineangiography and intraoperative findings. Thus, suprasternal echocardiography can be a useful method of detecting aortic root dissection, especially in patients with aortic arch dissection alone.

Adult↗
PubMed1977

[The use of sugar substitutes in parenteral feeding].

Parenteral administration of hydrocarbons is particularly indicated after heavy trauma or operations. In this case, fructose and the sugar substitutes sorbitol and xylitol play an important role as they can be metabolized independently from insulin. In this comprehensive review, the objectives and goals of parenteral nutrition as well as the metabolic processes of sugar substitutes in the human organism and their effects and the tolerances are discussed.

Amino Acids↗
PubMed1976

[Cardiac arrhythmias in the chronic phase of myocardial infarction (author's transl)].

Incidence and type of arrhythmia, using continuous ECG monitoring, were examined in 79 patients six weeks to 24 months after acute myocardial infarction, the findings being compared with arrhythmias at rest and on exercise, and correlated with signs of heart failure and coronary insufficiency. Arrhythmias were revealed in 16% (n = 13 at rest) and 19% (n = 10 of 52) on exercise. But continuous ECG monitoring revealed it in 86% (n = 68). On the other hand, arrhythmias may occur in the resting ECG but be rare on continuous monitoring. Ventricular extrasystoles were the most common arrhythmia, often multifocal and giving rise to bigeminy, only rarely as a result of exercise. Such extrasystoles usually showed right or right and left bundle conduction delays. Their frequency increased with increasing age of the patient. They were particularly frequent in patient who already had cardiac symptoms at rest, in patients with a large heart, and those who could not easily be exercised. Arrhythmias were more frequent a year after infarction than shortly before discharge from hospital or six months after infarction.

Adult↗