Effect of cilobradine in cats with a first episode of congestive heart failure due to primary cardiomyopathy.

INTRODUCTION: Heart rate (HR) is often elevated in cats with cardiomyopathies (CMPs). Pharmacologic modulation of HR may reduce cardiac morbidity and mortality. OBJECTIVES: To investigate the effects of cilobradine vs. placebo, regarding time to cardiac mortality or morbidity in cats with first episode of congestive heart failure (CHF) due to primary CMP. ANIMALS: Three hundred and sixty-seven client-owned cats with primary CMP that had presented with a first episode of CHF at 50 centers in Europe. Per-protocol population comprised 193 cats (n = 89 cilobradine, n = 104 placebo). An interim analysis for futility was planned. METHODS: Prospective, randomized, placebo-controlled, double-blinded, multicenter clinical trial. Primary outcome variable was the time to a composite of cardiac mortality or cardiac morbidity. RESULTS: Median time to primary outcome was 84 days (95% confidence interval [CI]: 63-219 days) in the cilobradine group (CG) and 203 days in the placebo group (95% CI: 145-377 days) with observed hazard ratio of 1.44, indicating a higher hazard for the CG (P = 0.057). Mean HR was 28 beats per minute (bpm) lower at Day 7 (P < 0.0001) and remained 29 bpm lower at Day 360 (P = 0.026) in the CG than that in the placebo group. Although the number of adverse events did not differ, there were more serious adverse events in the CG. CONCLUSIONS: Heart rate reduction by cilobradine in cats with a first episode of CHF due to primary CMP did not reduce cardiac mortality and morbidity.

A randomized, double-blind placebo-controlled trial of iron in restless legs syndrome.

BACKGROUND: Previous open-label trials have shown iron to be efficacious in the treatment of restless legs syndrome. We performed a randomized, double-blind, placebo-controlled trial of iron sulfate. METHODS: Twenty-eight patients were randomized to receive either ferrous sulfate 325 mg b.i.d. or placebo for 12 weeks. The primary outcome measure was the dichotomous variable of improvement or no improvement in average quality of sleep as recorded by a visual analog scale nightly over a 2-week period, comparing a pretreatment 2-week baseline to weeks 13-14. Secondary outcome measures included a comparison of the quality of sleep as measured by a visual analog scale, effect of restless legs syndrome on life as a whole as measured by a different visual analog scale, and the percentage of nights patients were symptomatic. RESULTS: No significant differences were noted between iron and placebo groups for both primary and secondary outcome measures. Responders taking iron did have a significant increase in their iron saturation compared to nonresponders taking iron. CONCLUSIONS: Iron sulfate does not appear to be an effective empiric treatment for restless legs syndrome.

Curvature of dinucleotide poised for formation of trinucleotide in transcription with Escherichia coli RNA polymerase.

A frequently used schematic model of transcriptional elongation shows an RNA polymerase molecule moving along a linear DNA. This model is of course highly idealized and not compatible with promoter sequences [Gralla, J. D. (1991) Cell 66, 415-418; Schleif, R. (1992) Annu. Rev. Biochem. 61, 199-223] and regulatory proteins [Koleske, A. J., and Young, R. A. (1995) Trends Biochem. Sci. 20, 113-116; Dunaway, M., and Dröge, P. (1989) Nature 341, 657-659; Müller, H. P., Sogo, J. M., and Schaffner, W. (1989) Cell 58, 767-777] located some distance away from the point of transcription initiation [Karsten, R., von Hippel, P. H., and Langowski, J. (1995) Trends Biochem. Sci. 20, 500-506]. These circumstances lead to the expectation of curvature along the DNA strand and require looping between sometimes distant points. We have now shown curvature in a dinucleotide formed at the very onset of transcription when it is poised for reaction with a mononucleotide to form a trinucleotide. The curvature became evident from the demonstration that a metal ion bound with a mononucleotide in the i+1 (elongation) site is approximately equidistant from bases at the 5' end (i-1 site) and 3' end (i site) of the dinucleotide. Similar results were obtained with three different dinucleotides and four mononucleotides. Curvature of the RNA initiate may reflect curvature of the DNA to which it is bound. These studies show curvature to be a significant feature in the interaction between DNA template and RNA elongate even at the very beginning of transcription.

Specificity of an Escherichia coli RNA polymerase-associated NTPase.

Standard preparations of Escherichia coli RNA polymerase harbor a 70 kDa protein with NTPase (beta-gamma cleavage) activity that is not a recognized polymerase subunit. The NTPase activity of this component, before and after separation from the polymerase, is strongly dependent on the presence of DNA; single-stranded polydeoxynucleotides are more effective than double-stranded. ATP and GTP are cleaved, the latter much less readily. The NTPase as it occurs with the polymerase displays cleavage preference for NTPs that are not complementary to the DNA, a fact that has led to proposals for involvement of the NTPase in transcriptional error prevention [Volloch, V. Z., Rits, L. & Tumerman, L. (1979) Nucleic Acids Res. 6, 1535-1546; Libby, R. T., Nelson, J. L., Calvo, J. M., & Gallant, J. A. (1989) EMBO J. 8, 3253-3158]. We find, however, that the lesser cleavage in the presence of complementary DNA results from competition for the NTP between the processes of incorporation by the polymerase and of cleavage by the NTPase, operating on the same substrate pool. The greater cleavage with noncomplementary DNA occurs because of the lack of incorporation by the polymerase, which then does not compete with the NTPase for the substrate pool. Thus, these findings indicate that the cleavage preference of the NTPase for noncomplementary NTPs is not part of a mechanism for error prevention during transcription.

Study on the suitability of sow colostrum for the serological diagnosis of porcine reproductive and respiratory syndrome (PRRS).

Serum and colostrum from 73 sows were collected. The serum samples were tested by Immuno. Peroxidase Monolayer Assay (IPMA) and the corresponding colostrum samples with the indirect Immuno fluorescent Antibody (IFA) technique. All serum positive sows were colostrum positive and all colostrum negative were serum negative. Eight sows only reacted positively in the colostral testing. Compared to the serum standard test the specificity was 82.6% and the sensitivity 100%. The observed agreement between both tests was 89.2%. In addition all serum samples were also tested with the IF test (IFT). Of the eight sows which were negative in the IPMA serum test and positive in the IFA colostrum test, three were found positive when the serum was tested with IFA. Consequently, the observed agreement was higher at 93.2%. After the suitability of colostrum for porcine reproductive and respiratory syndrome (PRRS) diagnosis was demonstrated, 1915 colostrum samples collected from 135 different farms were tested in a comparative study with the IPMA and IFA techniques. Of the 1915 colostrum samples 139 were positive with both IPMA and IFA. With IPMA only, 43 samples were positive compared with 192 samples found positive with the IFA technique. A total of 1541 samples were negative in both tests. The observed agreement between both tests was 87.5%. The quotient of the observed agreement minus chance agreement and the maximum possible agreement beyond chance level (Kappa Quotient) was 0.49. In 90% of the farms that tested IFA positive there was a seroconversion of more than 50% of all colostrum tested. By comparison only 29% of the IPMA positive farms were positive with more than 50%. Based on the epidemiological findings on PRRS it was concluded that the IFA technique indicates a higher sensitivity for the detection of PRRS virus antibodies in sow colostrum. Finally the possible advantages and disadvantages of sow colostrum testing and serum testing are discussed.

Iodixanol vs iopamidol in intravenous DSA of the abdominal aorta and lower extremity arteries: a comparative phase-III trial.

Iodixanol (Visipaque, 320 mgI/ml) was compared with iopamidol (Solutrast, 370 mgI/ml) in a double-blind, randomized, parallel group, intravenous DSA phase-III trial for evaluation of safety and efficacy. A total of 117 patients received iodixanol (n = 60) or iopamidol (n = 57). Diagnostic efficacy was evaluated using categoric and visual analogue scales. Discomfort and adverse events were recorded. A total of 39 patients collected urine up to 72 h after the examination for analysis. Diagnostic efficacy and radiographic density were similar in both groups. Discomfort was milder with iodixanol. The difference between the frequency of adverse events between both groups (iodixanol = 7, iopamidol = 2) was without statistical significance. Creatinine clearance was slightly more affected by iodixanol, whereas the increase in renal excretion of N-acetyl-beta-glucosaminidase (NAG) in the first 24-h collection period after the examination was significantly higher (p < 0.01) with iopamidol. Iodixanol was of equal diagnostic efficacy compared with iopamidol despite its reduced iodine content. Both contrast media are well suited for IV DSA.

A simple probe for DNA accessibility in chromatin.

When DNA is treated with Cu(II) and then heated, the melting temperature (Tm) of the DNA is dramatically decreased (8). The Cu(II) binds to the DNA in such a way as to destabilize the double helix and help to break the hydrogen bonds between the bases. When soluble chromatin is similarly treated with Cu(II) and heated, the Tm is unaffected. Apparently the Cu(II) cannot penetrate the chromatin structure and thus cannot initiate the DNA destabilization process. However, when H-1 histone is removed from the chromatin by affinity chromatography, subsequent treatment with Cu(II) does lead to a lowered Tm when the chromatin is heated. This Tm lowering is also achieved by two less drastic techniques that do not remove histone H-1, but decrease the affinity of the H-1 to the DNA: (1) a mild acetylation procedure that specifically modifies either 2 or 4 epsilon-amino groups of lysines on the H-1 histone, and (2) reaction with phosphate-binding divalent metal ions, e.g., Mg(II), Mn(II), or Co(II). Apparently, removal of H-1 or decreased affinity of H-1 for DNA increases the accessibility of the DNA to the Cu(II). This phenomenon suggests a very simple qualitative probe for the degree of structural change in chromatin produced by a change in the stability of the DNA-H-1 interaction.

A structural model for fidelity in transcription.

Distances between the metal ions bound to the product terminus i site and the substrate i + 1 site of Escherichia coli RNA polymerase range from 5.0 to 5.6 A when the substrate is complementary to a template base and from 6.5 to 7.0 A for a noncomplementary relationship. The metal bound to the substrate at the i + 1 site exhibits a constant distance to the three phosphates on the substrate regardless of complementarity, but the distance to base and ribose protons changes. The differences in these geometric parameters are explained by the ability of the enzyme to assume two conformations, one to place correct nucleotide substrates in optimal position for bond formation and the other to prevent incorrect nucleotides from assuming such a position. In this scheme a metal-triphosphate complex can move toward or away from the terminal 3' OH group of the growing RNA chain, to assure fidelity of transcription.

Is there any relationship between aluminum and Alzheimer's disease?

The controversial role of aluminum in Alzheimer's disease (AD) is reviewed. While current data would suggest the lack of a causative role, alterations in the brain and other organ systems caused by AD might increase the penetration of aluminum as well as other metals into the brain and lead to their contribution to such pathological features as neurofibrillar tangles (NFTs).

Selectivity of Escherichia coli RNA polymerase for template conformation.

Escherichia coli RNA polymerase (RNAP) exhibits a strong selectivity for the secondary structure of its template DNA, as shown by the influence both of the DNA conformation on the transcription cycle and of the enzyme on the DNA conformation itself. Binding, chain initiation and elongation characteristics of RNAP, and DNA conformational characteristics were examined by use of the alternating copolymer poly(dGdm5C).poly(dGdm5C) as template. Transcription is impeded when the DNA is in the Z conformation as compared with the B; the initial conformation is determined by the concentration of the conformational effectors of Mg2+ and [Co(NH3)6]3+. RNAP binds to both Z and B conformers; the total binding is moderately greater when the template is in the B conformation than when it is strongly stabilized in the Z, by [Co(NH3)6]3+ concentrations much higher than those required for B-Z transition. However, the Z conformer is much more easily displaced competitively from the bulk of its complexes with RNAP than is the B, indicating a specific binding preference for the B conformer. When the template is in the B conformation, or is moderately stabilized in the Z by Mg2+ concentrations such that the polynucleotide is just fully converted from B to Z, elongation is predicted well by chain initiation, indicating that on the Z conformer RNAP is effectively inhibited at the chain initiation or at an earlier stage. The average chain growth rates for polymeric product synthesized on B and on moderately stabilized Z are similar, even though overall RNA synthesis is considerably lowered on the Z form, again indicating that the limiting events precede elongation. When the Z conformer is strongly stabilized, chain initiation and elongation are further inhibited. Elongation is still roughly correlated with chain initiation, but some additional inhibition of elongation takes place independently. Circular dichroism analysis shows that RNAP-DNA binding affects the B-Z conformational equilibrium, leading to reformation of the B conformer from Z and interference with conversion of B to Z, under conditions that would otherwise favor the Z conformer. Thus, there is an RNAP concentration dependent shift of the B-Z transition to higher concentrations of Z-inducing cation, and there is an RNAP concentration dependent decrease in the rate of B to Z conversion. These effects were observed for poly(dGdm5C).poly(dGdm5C), with Z stabilized by [Co(NH3)6]3+ or Mg2+. (They were observed as well for the unmethylated copolymer poly(dGdC).poly(dGdC), with Z stabilized by [Co(NH3)6]3+.) Perturbation of the Z conformer was detectable by circular dichroism at an RNAP:polynucleotide ratio down to a practical limit of approximately 1 RNAP:500 bp.(ABSTRACT TRUNCATED AT 400 WORDS)

Photomultiplier for optically probing Comet Halley.

A low mass eight-color channel photopolarimeter was developed for the Giotto spacecraft. Utilizing the spin of the spacecraft, a multichannel plate photomultiplier, and a unique optical design, the instrument required no moving parts to measure color and linear polarization. The photopolarimeter collected data as the spacecraft passed through the coma of Comet Halley on 13 and 14 Mar. 1986. This instrument's design, calibration, and reduction are discussed and some final results are presented.

Structural studies on the active site of Escherichia coli RNA polymerase. 2. Geometrical relationship of the interacting substrates.

Since a major function of RNA polymerase must be to bring together substrates in the optimal configuration for internucleotide bond formation, studies have been undertaken to understand the geometrical relationship of the two substrates. A model has been constructed for the geometry of interaction of two ATP molecules poised on the active site of the Escherichia coli enzyme for the formation of the first bond in RNA synthesis. The model is based primarily on the distance, measured by EPR, between the two metals in the i and i + 1 subsites, as well as distances, measured by NMR, from each metal to points on the substrate in the same subsite, in the presence of a poly(dAdT).poly(dAdT) template. Both the Zn(II) in the i site and the Mg(II) in i + 1 are displaced by Mn(II). The nucleotide bases are not parallel to each other, in line with the reaction of the ATP molecules with DNA within the transcription bubble. The metal in the i site appears too far removed from substrate to participate in catalysis, but the metal in i + 1 is in position to bind to the beta- and gamma-phosphate groups and probably is involved in cleavage of the triphosphate, as has been previously suggested.

Structural studies on the active site of Escherichia coli RNA polymerase. 1. Interaction of metals on the i and i + 1 sites.

The two substrates between which an internucleotide bond is formed in RNA synthesis occupy two subsites, i and i + 1, on the active site of Escherichia coli RNA polymerase, and each subsite is associated with a metal ion. These ions are therefore useful as probes of substrate interaction during RNA synthesis. We have studied interactions between the metals by EPR spectroscopy. The Zn(II) in the i site and the Mg(II) in the i + 1 site were substituted separately or jointly by Mn(II). The proximity of the metals was established by EPR monitoring of the titration at 5.5 K of the enzyme containing Mn(II) in i with Mn(II) going into the i + 1 site, and the 1:1 ratio of the metals in the two sites was confirmed in this way. The distance between the two metals was determined by EPR titration at room temperature of both the enzyme containing Zn(II) in i and Mn(II) in i with Mn(II) going into the i + 1 site, making use of the fact that EPR spectra are affected by dipolar interactions between the metals. The distances calculated in the presence of enzyme alone, in the presence of enzyme and two ATP substrates, and when poly(dAdT).poly(dAdT) was added to the latter system ranged from 5.2 to 6.7 A.

Polynucleotide cross-linking by aluminum.

The observations that there was an increased concentration of Al in the brains of Alzheimer's, Guam-Parkinson, and amyotrophic lateral sclerosis disease patients and that there was an apparent localization of the Al in chromatin led to a study of the interaction of Al(III) with DNA. We have previously shown that Al cross-links calf thymus DNA at low pH (S. J. Karlik, G. L. Eichhorn, P. N. Lewis, and D. R. Crapper, Biochemistry 19, 5991 [1980]). Extended studies indicate that cross-linking occurs in DNAs of all base ratios, including polydAdT and polydGdC. Since Al cross-links prevent renaturation in polydAdT, the decrease in the amount of polymer renatured in the presence of Al becomes a quantitative appraisal of the extent of cross-linking. Saturation of cross-linking occurs at a 0.4 ratio of Al to nucleotide phosphate, indicating that potentially 80% of the base pairs are Al bound. Cross-links are broken at elevated pH and by EDTA.

[Psychosocial problems of elderly patients with cardiovascular diseases]. / Psychosoziale Probleme von Patienten im höheren Lebensalter mit Herz-Kreislauf-Krankheiten.

Based on a survey of different age theories, the complex character of the aging process is demonstrated in the experience of the individual as well as in its social connections (DORNER, 1988). On this basis the peculiarities of experiencing the disease and of mastering the disease by older patients with coronary heart disease are shown, taking various test results into account. Depending on experiencing the disease, but also depending on learned forms of mastering stress situations, different mastering mechanisms could be found with patients with angiocardiopathies which may be of decisive importance to the further rehabilitative success. Recommendations for the behaviour of the physician towards the old-aged patient with coronary heart disease are concluded.

Reversible toroidal compaction of DNA by aluminum.

Electron microscopy has been used to characterize the products of the reactions of aluminum with DNA under three different conditions, one of which, pH 5 and Al (III)/DNA(P) ratio of 0.4, has been previously shown to produce reversible interstrand crosslinking in double-stranded DNA molecules. Under this condition, aluminum produced macromolecular aggregates of DNA upon heating, with a distinctive ultrastructure reversible to double-stranded DNA after removal of the aluminum. These structures were toroidal in configuration and exhibited mean widths of 4.9 +/- 1.8 nm and were 18.6 +/- .4 nm in diameter with a toroidal internal diameter of 7.4 +/- 4.7 nm. Previous results have shown that these structures contain Al(III) - crosslinked DNA, the present data suggests that this intermolecular crosslinking is associated with the production of compacted structures.