[Influence of spontaneous ventricular premature beat coupling interval on the value of heart rate turbulence]. / Vliv vazebného intervalu spontánní komorové extrasystoly na hodnoty turbulence srdecního rytmu.

UNLABELLED: The heart rate turbulence is promising marker of a sudden cardiac death. The aim of the study is to evaluate the influence of the ventricular premature beat (VPB) coupling interval on the values of turbulence onset (TO) and turbulence slope (TS) parameters in the three groups of patients--"healthy" with ventricular premature beats, pts post myocardial infarction (MI) and pts with chronic heart failure with the left ventricle ejection fraction (LVEF) < 0.35. PATIENTS AND METHODS: 382 pts were examined: healthy--149, post MI--123 and LVEF < 0.35 - 110. The distribution ofVPB was analyzed and the values ofTO and TS were evaluated according to the coupling intervals of VPB--in the intervals 00-50, 51-100 (% of RR interval) and in the intervals 34-66 and 67-100 (% of RR interval). RESULTS: The coupling interval of spontaneous ventricular premature beats cause the statistically significant variability HRT values in all three groups of pts. CONCLUSION: The values of TO in the groups of post MI pts and pts with chronic heart failure are higher (risky for sudden cardiac death) after VPB with longer coupling intervals (50-100%, event. 67-100% of RR interval). The TS values are lower (risky for sudden cardiac death) after VPB with longer coupling interval, too. For evaluation of HRT we should use the VPBs with long coupling intervals.

[Analysis of the effect of circadian rhythm on the heart rate turbulence in patients without evidence of organic heart disease]. / Analýza vlivu cirkadiánního rytmu na turbulenci srdecní frekvence u pacientu bez prukazu organického onemocnení srdce.

Some studies have demonstrated circadian incidence of sudden cardiac death (SCD), ventricular ectopies, acute coronary syndromes and heart rate variability. One of new parameters applied in non-invasive stratification of sudden cardiac death is heart rate turbulence (HRT). Detection of circadian oscillations in HRT and optimised measurement of HRT can increase the positive predictive value of HRT as a sign of SCD risk. The set consisted of 48 patients in a sequence order aged 45 +/- 12 years (of which 23 men and 25 women), indicated for Holter monitoring ofventricular ectopies who had good left ventricular function with LV EF 0.53 +/- 0.11. HRT was measured in two-hour intervals within a 24 hour period, followed by an analysis of circadian dependence of HRT. A significant circadian oscillation in the TS (turbulence slope) parameter was recorded. No circadian signs were detected for the TO (turbulence onset) parameter. The project is supported by grant no. NR/8478-3.

[Analysis of circadian rhythm influence to heart rate turbulence in patients post myocardial infarction with left ventricular dysfunction]. / Analýza vlivu cirkadiánního rytmu na turbulenci srdecní frekvence u pacientu s poinfarktovou dysfunkcí levé srdecní komory.

BACKGROUND: Some study reported circadian occurence of sudden cardiac death, ventricle ectopic activity, acute coronary syndromes and heart rate variability. Heart rate turbulence (HRT) is one of a new markers of noninvasive stratification of sudden cardiac death. METHODS AND RESULTS: We have evaluated HRT in 120 consecutive patiens post myocardial infarction in mean age 62.7+/-12.4 years (90 M, 30 W), indicated for ecg Holter monitoring with LVEF 0.45+/-0.12 in 2hours interval during 24 hours. We have analysed circadian variation of the HRT. CONCLUSIONS: The statistically significant circadian patterns were found in turbulence slope parameter of HRT. No significant changes for turbulence onset parameter were described.

Impact of RYR1 genotype of Piétrain boars on litter traits of Czech Large White x Czech Landrace crossbred sows.

Piétrain boars of different ryanodine receptor (RYR1) genotypes (NN, Nn and nn, three boars each) were mated with approximately 10 Czech Large White x Czech Landrace sows (genotype NN) each to produce one litter per sow. The progeny of nn boars had a significantly higher individual weaning weight (7.31 kg versus 6.86 kg) and average daily gain from birth to weaning (252 g/day versus 240 g/day) than the progeny of NN boars. Furthermore, piglets from nn boars differed statistically significant also from piglets of boars with the Nn genotype for these two traits. The litters of the NN boars were greater by 0.5 piglets than the litters of the nn boars for the total number of piglets born, piglets born alive and piglets weaned, but the differences were not significant. The Nn genotype showed for all litter size traits and the number of stillborn piglets the best values. The difference between the genotypes Nn and nn was statistically significant at the 0.05 level for the number of piglets born alive and the number of piglets weaned.

Preparation of a monoclonal antibody specific for the class IV isotype of beta-tubulin. Purification and assembly of alpha beta II, alpha beta III, and alpha beta IV tubulin dimers from bovine brain.

Tubulin, the 100-kDa subunit protein of microtubules, is a heterodimer of two 50-kDa subunits, alpha and beta. Both alpha and beta subunits exist as numerous isotypic forms. There are four isotypes of beta-tubulin in bovine brain tubulin preparations; their designations and relative abundances in these preparations are as follows: beta I, 3%; beta II, 58%; beta III, 25%; and beta IV, 13%. We have previously reported the preparation of monoclonal antibodies specific for beta II and beta III (Banerjee, A., Roach, M. C., Wall, K. A., Lopata, M. A., Cleveland, D. W., and Luduena, R. F. (1988) J. Biol. Chem. 263, 3029-3034; Banerjee, A., Roach, M. C., Trcka, P., and Luduena, R. F. (1990) J. Biol. Chem. 265, 1794-1799). We here report the preparation of a monoclonal antibody specific for beta IV. By using this antibody together with those specific for beta II and beta III, we have prepared isotypically pure tubulin dimers with the composition alpha beta II, alpha beta III, and alpha beta IV. We have found that, in the presence of microtubule-associated proteins, all three dimers assemble into microtubules considerably faster and to a greater extent than does unfractionated tubulin. More assembly was noted with alpha beta II and alpha beta III than with alpha beta IV. When assembly is measured in the presence of taxol (10 microM), little difference is seen among the isotypically purified dimers or between them and unfractionated tubulin. These results indicate that the assembly properties of a tubulin preparation are influenced by its isotypic composition and raise the possibility that the structural differences among tubulin isotypes may have functional significance.

Increased microtubule assembly in bovine brain tubulin lacking the type III isotype of beta-tubulin.

Tubulin, the major constituent protein of microtubules, is a heterodimer of alpha and beta subunits. Both alpha and beta exist in multiple isotypic forms. It is not clear if different isotypes perform different functions. In order to approach this question, we have made a monoclonal antibody specific for the beta III isotype of tubulin. This particular isotype is neuron-specific and appears to be phosphorylated near the C terminus. We have used immunoaffinity depletion chromatography to prepare tubulin lacking the beta III subunit. We find that removal of the beta III isotype results in a tubulin mixture able to assemble much more rapidly than is unfractionated tubulin when reconstituted with either of the two microtubule-associated proteins (MAPs), tau or MAP 2. Our results suggest that the different isotypes of tubulin differ from each other in their ability to polymerize into microtubules. We have also found that the anti-beta III antibody can stimulate microtubule assembly when reconstituted with tubulin and either tau or MAP 2. When reconstituted with tubulin lacking the beta III isotype, the antibody causes the tubulin to polymerize into a polymer that is a microtubule in the presence of MAP 2 and a ribbon in the presence of tau.

The effects of 6-benzyl-1,3-benzodioxole derivatives on the alkylation of tubulin.

Derivatives of 6-benzyl-1,3-benzodioxole are known to bind to tubulin and inhibit tubulin polymerization. For a better understanding of the mechanism of action of the 6-benzyl-1,3-benzodioxole derivatives, we have examined their effect on the alkylation of tubulin sulfhydryls by iodo[14C]acetamide and N,N'-ethylene(bis)iodoacetamide. We have found that the 6-benzyl-1,3-benzodioxole derivatives with an intact dioxole ring affect alkylation to an extent proportional to their ability to inhibit tubulin polymerization. Those derivatives with the strongest resemblance to podophyllotoxin have the weakest effects. However, derivatives with a disrupted dioxole ring show little or no ability to inhibit polymerization, but their effect on alkylation is directly related to the degree of resemblance they bear to the trimethoxy ring of podophyllotoxin. It thus appears that the relatively simple approach of using alkylating agents can generate a significant amount of information on the mechanism by which various drugs interact with tubulin.

The effect of 2-(4-methyl-1-piperazinylmethyl) acrylophenone dihydrochloride on the alkylation of tubulin.

2-(4-Methyl-1-piperazinylmethyl) acrylophenone dihydrochloride (MPMAP) is a novel inhibitor of microtubule assembly in vitro and in vivo whose molecular mechanism of action has not been investigated (M. L. Mallevais, A. Delacourte, I. Lesieur, D. Lesieur, M. Cazin, C. Brunet, and M. Luyckx (1984) Biochimie 66, 477-482). We have examined the effect of MPMAP on the alkylation of tubulin by iodo[14C]acetamide and N,N'-ethylenebis(iodoacetamide) (EBI). MPMAP is a very potent inhibitor of tubulin alkylation by iodo[14C]acetamide. MPMAP gives half-maximal inhibition at a concentration of 15 microM. MPMAP also inhibits the alkylation of denatured tubulin and of aldolase, implying that it reacts strongly with sulfhydryl groups. MPMAP does not, however, interfere with formation by EBI of a crosslink between cysteines 239 and 354 in the beta subunit of tubulin, suggesting that these sulfhydryls are located in a cleft in the tubulin molecule.

beta 2-Tubulin, a form of chordate brain tubulin with lesser reactivity toward an assembly-inhibiting sulfhydryl-directed cross-linking reagent.

Beta 1 and beta 2 are the designations given to two forms of beta-tubulin that have different electrophoretic mobilities on discontinuous polyacrylamide gels in the presence of sodium dodecyl sulfate [Little, M. (1979) FEBS Lett. 108, 283-286]. Beta 1 and beta 2 constitute respectively 75% and 25% of the total beta-tubulin in bovine brain. Although beta 1 appears to be ubiquitous in animals, beta 2 has so far only been found in the brains of cows, pigs, deer, rats, chicks, and dogfish but not in squid brain. Beta 2 is not found in bovine kidneys, in porcine lungs, or in any nonchordate tubulin that has been examined. When tubulin is reacted with the sulfhydryl-directed reagent N,-N'-ethylenebis(iodoacetamide) (EBI), beta 1, but not beta 2, is converted to a faster moving form, beta. The yield of beta 2 in this reaction is not altered by the presence of drugs. When [14C]EBI is used as a probe, most of the label is incorporated into beta 1 rather than beta 2. Tubulin molecules that have reacted with EBI to form beta are much less likely to polymerize into microtubules than are molecules that have not formed beta. In view of the observation that only beta 1, and not beta 2, can form beta, it is possible that beta 1 represents a form of tubulin whose assembly may be regulated by a mechanism involving sulfhydryls. In contrast, beta 2 may represent a form of tubulin whose assembly is regulated by some other mechanism.