Bilirubin binding to polypeptides and chiral amines. Induced circular dichroism and fluorescence studies

Induced Cotton effects have been observed in the visible region on interaction of bilirubin with chiral mono- and diamines and poly-l -lysine. At alkaline pH distinct CD spectra are observed for bilirubin bound to the α-helical and β-sheet conformation of poly-l -lysine, which differ from that observed for the pigment bound to human serum albumin. The CD pattern observed on binding to N-acetyl-Lys-N¹-methylamide in CH₂Cl₂ and dioxane is different from that observed in the presence of l -Ala-NH-(CH₂)₆-NH-l -Ala in dioxane. The latter case resembles the spectrum observed in the presence of human serum albumin. Binding to the helical polypeptide melittin and the antiparallel β-sheet peptide, gramicidin S, in aqueous solutions results in opposite signs of the bilirubin CD bands. The quenching of tryptophan fluorescence in melittin, in aqueous solution and enhancement of bilirubin fluorescence in dioxane on binding to gramicidin S have been used to monitor pigment-peptide interactions. The results suggest the utility of bilirubin as a conformational probe.     

DNA AMPLIFICATION OF A REPETITIVE SEQUENCE - IS 6110 IN THE EARLY DIAGNOSIS OF EXTRA PULMONARY TUBERCULOSIS

DNA amplification by Polymerase Chain Reaction (PCR) of a repetitive sequence specific for Mycobacterium tuberculosis, from clinical samples of extra pulmonary origin were evaluated. The 123 base pair fragment of the insertion element IS 6110 in Mycobacterium tuberculosis was amplified. A total of 50 samples were analysed by PCR and compared with culture on Lowenstein-Jensen medium (LJ) and the clinical findings of the patient. Out of the total 26 samples were positive by PCR, while only seven grew the bacilli in culture. 24 samples were negative by PCR and culture. All the seven samples that grew the bacilli on culture were positive by PCR. In remaining 19 cases that were positive by PCR but did not grow the bacilli clinical features, radiological findings and Mantoux test were strongly suggestive of M. tuberculosis. All the amplification negative cases had no positive evidence of tuberculosis but were being followed up. When correlated with culture and clinical history the sensitivity of PCR for the diagnosis of active tuberculosis was 100%. However, the specifity was only 55.8% as culture on LJ (Gold Standard) was positive in only 7 samples out of 26 samples that were positive by PCR.KEY WORDS: DNA Amplification, IS 6110, Mycobacterium tuberculosis.     

Efficacy of once daily bisoprolol in stable angina pectoris: an objective comparison with atenolol and long term follow-up

Bisoprolol is a new cardioselective beta-blocker with a longhalf-life. The efficacy of once daily bisoprolol (10 mg) andatenolol (100 mg) was assessed in 20 patients with stable anginausing a placebo controlled double-blind randomized crossoverprotocol. Efficacy was assessed by computer assisted treadmillexercise testing with monitoring of leads CMS and CC5, carriedout 22–24 h after the last dose. The mean±SEM exercisetime on placebo was 6.5±0.4 min increasing to 7.8±0.5min on bisoprolol (P<0.001) and 8.6±0.6 mins on atenolol(P<0.001). The time to 1 mm ST depession in CM5 and CC5 wasalso prolonged significantly with both drugs. The mean basalresting heart rate of 84±4 bpm decreased to 63±2bpm on bisoprolol ( P<0.001 )and 64±3 bpm on atenolol(P<0.001), with a significant decrease in the peak exerciseheart rate seen with both drugs (P<0.001). The peak rate-pressureproduct was 175±8 after placebo, 146±7 (P<0.001)with bisoprolol and 149±5 (P<0.001) after atenolol.One patient was withdrawn because he suffered a myocardial infarction.Eighteen patients were prescribed bisoprolol 10 mg once a dayfor 6 weeks and an exercise test was performed at the end ofthis period. Bisoprolol retained its efficacy at the end ofthis period and was well tolerated. This data suggests thatbisoprolol is an effective anti-anginal agent, comparable inefficacy and duration of action with atenolol, which is suitablefor once-daily administration.     

Comparison of radionuclide ventriculography and 2D echocardiography for the measurement of left ventricular ejection fraction following acute myocardial infarction

To compare the measurement of left ventricular ejection fractionobtained by two-dimensional echocardiography and by radionuclideventriculography in patients following acute myocardial infarction,49 consecutive patients with acute myocardial infarction underwentechocardiography and radionuclide ventriculography on the sameday, pre-discharge. Left ventricular ejection fraction was assessedby two blinded observers for each method and reproducibilitywas also assessed for each technique. The limits of agreementfor the differences in ejection fraction (%) between the twomethods was –11.4, 12.2; the mean difference 0.4 was notsignificantly different from zero. The limits of agreement forthe intra- and inter-observer differences in ejection fractionby radionuclide ventriculography were –9.4, 7.6 and –86,11.0, respectively; the mean differences –0.9 and 1.2were not significantly different from zero. The limits of agreementfor the intra- and inter-observer differences by echocardiographywere –5.8, 6.6 and –8.9, 9.5 respectively; the meandifferences 0.4 and 0.3 were not significantly different fromzero. Thus, two-dimensional echocardiography compares well withradionuclide ventriculography for the assessment of ejectionfraction without the disadvantage of radiation.