Ca2+ sensitization of myocardial force and actomyosin ATPase by (D-Ala2, Met5) enkephalinamide.

The presence of proenkephalin mRNA and proenkephalin peptides in cardiac muscle cells suggests the local production of enkephalins in the myocardium. Yet, the effects of these peptides on the function of the contractile proteins are unknown. The effects of (D-Ala2, Met5) enkephalinamide (DALA) on the activity of the actin stimulated Ca, Mg-myosin ATPase in myofibrils and on the contractility and the activity of the related actomyosin ATPase of chemically skinned muscle fibres from pig myocardium were studied. In this article, it is shown that the myofibrillar actomyosin ATPase as well as the contractility and the actomyosin ATPase in skinned fibres are sensitized to Ca2+ ions by DALA. 10(-11) -10(-6) mol/l DALA decrease the effective concentration of Ca2+ stimulating the myofibrillar ATPase activity by 50% (EC50) from 4.0.10(-5) to 1.5.10(-5) mol/l (p < 0.05). The magnesium dependent myosin ATPase activity at low Ca2+ concentration (10(-9) mol/l) is increased. The EC50 values of Ca2+ for both force development and the related actomyosin ATPase activity of skinned fibres are decreased by DALA (10(-11) -10(-5) mol/l) from 2.5.10(-6) to 2.0.10(-6) mol/l (contractions; p < 0.01) and from 2.0.10(-6) to 1.3.10(-6) mol/l (ATPase activity; p < 0.01). The tension cost (ATPase/tension) of the fibres is unchanged by DALA. In conclusion, the results demonstrate a Ca2+ sensitization of the contractile proteins by low concentrations of DALA, indicating a direct regulatory involvement of enkephalins in the regulation of myocardial contractility. These results correspond with the positive inotropic effects of enkephalins in isolated heart muscle cells.

Spin trapping evidence for radical generation by isolated hearts and cultured heart cells.

The spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been applied to monitor the generation of free oxy-radicals in samples derived from isolated hearts and heart cells. .OH was trapped in the effluent of isolated hearts in the early phase of reperfusion following an ischemia time of only 10 min. Radical detection was possible even when the cardioactive DMPO was added to the effluent after draining off the heart, demonstrating that the short-lived .OH was generated by components released from the affected heart. These results support the hypothesis that radicals are of relevance for reperfusion injury. By omitting antioxidants commonly used for incubation media of cultured cells, it was possible for the first time to demonstrate the formation of .OH in the incubation solution of cardiac cells.

[Cumulative functional rates of orthoptic dialysis fistulas and interposition grafts]. / Kumulative Funktionsraten von orthotopen Dialysefisteln und Interponaten.

The function of 221 dialysis shunts was investigated retrospectively in 111 patients of an outpatient haemodialysis centre. The mean age of the patients was 58 years. Of 221 recorded shunts, 171 were direct arteriovenous fistulas, while 50 were interposition grafts. The longest observation period was almost 20 years (227 months). The cumulative function rate was evaluated by the life table method; primary patency (until first revision) was differentiated from total function (revisions included). The direct fistulas as compared to the grafts had a significantly (P less than 0.05) higher primary function rate (median 35 vs. 13 months) and after 36 months also a significantly longer total function (median 76 vs. 28 months). Complications were significantly (P less than 0.05) more frequent in grafts than in fistulas (61/50 vs 120/171). Surgical revisions of fistulas failed significantly more often (P less than 0.05) than revisions of grafts (137/171 versus 26/50). Grafts on the forearm had significantly worse results as compared to grafts or fistulas on the upper arm (P = 0.03). In contrast to age, sex and underlying disease of patients a blood pressure less than 130/70 mmHg was a significant risk factor for shunt failure (P = 0.002). Analysis of primary function shows (clearer than the total patency rate) that a direct fistula is a better vascular access in haemodialysis patients than a graft.

Effect of troxerutin and methionine on spin trapping of free oxy-radicals.

The cardioprotective agents troxerutin and methionine are radical scavengers and compete with the DMPO adduct formation of .OH generated by the Fenton reaction. The concentration of trapped .O2- generated by the xanthine oxidase/hypoxanthine reaction is lowered in the presence of troxerutin. The decay of DMPO-OH is decreased by troxerutin compared to the control. In the presence of methionine a carbon-centered radical is produced. The investigations support the opinion that the scavenging of oxygen derived free radicals is of importance for the cardioprotective action of these agents.

[Potential filaricides. Suramin analogs]. / Potentielle Filarizide. Suramin-Analoge.

A series of suramin analogues has been synthesized in which the methyl groups of suramin have been replaced by hydrogen, alkyl, phenyl, and fluoro substituents, or which contain more than two methyl groups. The substances have been screened against Dipetalonema viteae in Meriones unguiculatus, Litomosoides carinii in Sigmodon hispidus and L. carinii in Mastomys natalensis, respectively. Small structural modifications have a marked influence on the antifilarial activity. There are marked differences between antifilarial and trypanocidal activities. A symmetrical molecule structure seems not to be essential for the antifilarial activity.

Two new fluorescent retrograde neuronal tracers which are transported over long distances.

Two new fluorescent retrograde neuronal tracers are reported: Nuclear Yellow (Hoechst S 769121), which mainly labels the neuronal nucleus; and Fast Blue (diamidino compound 253/50), which mainly labels the neuronal cytoplasm. Both tracers appear to be transported effectively over long distances in rat and cat.

Studies on the induction of petite mutants in yeast by analogues of berenil. Characterization of three mutants resistant to the compound Hoe 15,030.

Compound Hoe 15,030 is an analogue of berenil which is as effective as berenil in inducing petite mutants in Saccharomyces cerevisiae. Hoe 15,030 has greater stability than berenil in aqueous solution, and is less toxic to yeast at high drug concentrations. Mutants of S. cerevisiae strain J69-1B have been isolated which are resistant to the petite inducing effects of Hoe 15,030. Three mutant strains (HR7, HR8 and HR10) were characterized and each was shown to carry a recessive nuclear mutation determining resistance to Hoe 15,030. The degree of resistance to Hoe 15,030 is different for each mutant, and each was found to be co-ordinately cross-resistant both to berenil and to another analogue of berenil, Hoe 13,548. However, the three mutants show no cross-resistance to other unrelated petite inducing drugs, including ethidium bromide, euflavine and 1-methyl phenyl neutral red. Further studies on the mutants revealed that each strain exhibits characteristic new properties indicative of changes in mitochondrial membrane functions concerned with the replication (and probably also repair) of mitochondrial DNA. Thus, mutant HR7 is hypersensitive to petite induction by the detergent sodium dodecyl sulphate under conditions where the parent J69-1B is unaffected by this agent. Mutant HR8 is even more sensitive to sodium dodecyl sulphate than is HR7, and additionally shows a markedly elevated spontaneous petite frequency. Isolated mitochondria from strains HR8 and HR10 (but not HR7) show resistance to the inhibitory effects of Hoe 15,030 on the replication of mitochondrial DNA in vitro.

Action of p-(4-amidino-phenoxy)-benzaldehyde-p-amidino-phenylhydrazone dihydrochloride on Leishmania donovani infections in the golden hamster.

The chemotherapeutic effect of a new diamidine, HOE 668, the p-(4-amidino-phenoxy)-benzaldehyde-p-amidino-phenylhydrazone dihydrochloride, was compared with that of known anti-leishmanial drugs in golden hamsters infected with Leishmania donovani. The effect of HOE 668 against visceral leishmaniasis proved superior to that of pentamidine isethionate and the pentavalent antimonial drugs, sodium stibogluconate and N-methylglucamine antimoniate. However, HOE 668 can be used only experimentally because of its toxicity. Its very good anti-leishmanial action qualifies HOE 668 as a standard compound in screening tests.

Diarylamidine derivatives with one or both of the aryl moieties consisting of an indole or indole-like ring. Inhibitors of arginine-specific esteroproteases.

A series of 62 diarylamidine derivatives was evaluated for their antiproteolytic activity. In all but two of the compounds one or both of the amidino-substituted aryl moieties was either an indole or an indole-like ring. The latter included indene, benzimidazole, benzofuran, benzol[beta]thiophene, and several other related nitrogen-containing heterocycles. Several of the compounds exhibited considerable inhibitory potency against thrombin, trypsin, and pancreatic kallikrein. An outstanding inhibitor of trypsin was found in bis(5-amidino-2-benzimidazolyl)methane (compound 42) with a Ki value of 1.7 X 10(-8) M(pH. 8.1, 37 degrees C). Another derivative, 1,2-di(4-amidino-2-benzofuranyl)ethane (compound 21), proved to be a highly effective inhibitor of the overall blood clotting process. From a general structure-activity standpoint these compounds demonstrate that minor structural variations of low-molecular-weight inhibitors can result in significant changes in specificity and potency with regard to antiproteolytic activity.

Specific inhibition of platelet agglutination and aggregation by aromatic amidino compounds.

A series of aromatic amidino compounds were investigated for their inhibitory effect on platelet agglutination and platelet aggregation. Agglutination of fresh or fixed platelets was produced by bovine plasma or by human plasma in combination with ristocetin, while aggregation of fresh platelets was induced by ADP, thrombin or collagen. Highly effective inhibitors were found for both types of platelet clumping, but there was no parralelism between the inhibitory activities in the two test system. 5-(5-amidino-2-benzimidazolyl)-2-(4-hydroxybenzene)benzimidazole suppressed agglutination exclusively. Pentamidine, on the other hand, strongly blocked the aggregation reaction, but did not interfere with agglutination, even at high concentrations. Compounds which inhibited aggregation also prevented the liberation of serotonin from the platelets.