Identification of abscess formation in native-valve infective endocarditis using transesophageal echocardiography: implications for surgical treatment

The object of the study was to follow patients with endocarditis-associated abscesses in order to evaluate the clinical outcome with and without surgical intervention. Transesophageal echocardiography successfully displayed the location and extent of abscess cavities in 14 patients (group A) with aortic valve endocarditis. The infective process was limited to the perivalvular tissue in two, extended into the ascending aorta in six, and included the interventricular septum, the right ventricular outflow tract, interatrial septum, and/or mitral valve annulus in six patients. The complication rate was significantly higher in group A than in group B, which consisted of 27 patients with proven signs of endocarditis but without endocarditis-associated abscesses. The complication rates were embolic events 64.3% in group A vs 29.6% in group B, need for surgery in 64.3% vs 18.5%, and death in 50.0% vs 3.7%, respectively. The duration of fever--as a marker of an active infective process--before diagnosis and the onset of adequate treatment was significantly higher in group A than in group B (46.7 +/- 8.4 days vs 7.7 +/- 2.6 days). Organisms were isolated in 71.4% in group A and in all patients of group B. Streptococcal infections were noted in A in 54.5% vs 44.4% in B., staphylococcal in 27.3% vs 40.7%. Initial surgical repair in 9 of 14 patients in A (64.3%) included nine aortic valve and one mitral valve prosthesis implantations, two aortic valve-annulus reconstructive procedures, one dacron patch closure, and three partial resections of the aorta ascendens with end-to-end anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Behavior of ventricular late potentials following catheter ablation of ventricular tachycardia]

In 10 patients non-invasively recorded signal-averaged electrocardiograms were obtained before and after direct-current ablation of ventricular tachycardia (right ventricular origin n = 5; left ventricular origin n = 5). The algorithms proposed by Simson and Karbenn et al. were used (modified Frank leads, high-pass filter cut-off frequency 25 Hz). No differences were observed between the mean values of the duration of the QRS-complex, the mean voltage during the last 40 ms of the QRS-complex, the duration of the late potentials and the number of patients having late potentials before and after ablation, respectively. The success of ablation could not be predicted by the signal-averaged ECG. There was no difference between the averaging parameters of those patients without recurrences of ventricular tachycardia during the follow-up period and those with (n = 3). Thus, the signal-averaged ECG did not prove helpful in predicting a successful outcome of direct-current catheter ablation of ventricular tachycardia.

Findings with cis-Z-clopenthixol in the treatment of acute mania and schizophrenia

The authors report the results of an open clinical trial with Cis(Z)-Clopenthixol (Cisordinol), the isolated Cis-isomer of the Clopenthixol racemate (Sordinol). The drug was applied to 18 patients with severe forms of manic or schizophrenic disease, diagnosed according to ICD 9. The compound was applied intravenously or orally, daily doses ranging from 10-160 mg. For the duration of the study (6 weeks) the patients were repeatedly rated with the CGI, BPRS or IMPS (abbreviated version), and several hematological and enzyme patterns, cardiac, renal function and electrolytes were monitored, as was the FFA. Due to the relatively small number of patients in relatively heterogeneous diagnostic composition, a number of items rated failed to reach statistical significance. The CGI showed a good therapeutic effect with a minimal incidence or severity of side effects. BPRS and IMPS documented an impressive decline in formal thought-disorders, agitation, logorrhea and tenseness. The sedative effects of the drug were slight and of short duration, anti-Parkinson medication was necessary in more than 50% of the patients studied. The results of the study show a good efficacy of the drug in manic and schizophrenic disorders, Cisordinol being well tolerated intravenously. The range of doses administered is approximately 50% of the dose-range of the parent-drug (Sordinol).

Influence of cofactor pyridoxal 5'-phosphate on reversible high-pressure denaturation of isolated beta 2 dimer of tryptophan synthase bienzyme complex from Escherichia coli

High hydrostatic pressure has been shown to cause reversible dissociation of the isolated apo beta 2 dimer of tryptophan synthase from Escherichia coli into enzymatically inactive monomers [Seifert, T., Bartholmes, P., & Jaenicke, R. (1982) Biophys. Chem. 15, 1-8]. Addition of the coenzyme pyridoxal 5'-phosphate affects the structural stability, as well as the kinetics of dissociation and deactivation. The apo beta 2 dimer is deactivated faster than the holoenzyme by a factor of 10. The midpoints of the corresponding equilibrium transition curves are observed at 690 and 870 bar, respectively. As shown by hybridization of native and chemically modified beta chains, the loss of enzymatic activity is accompanied by subunit dissociation. An additional deactivating effect is produced by the pressure-induced release of the cofactor from the holoenzyme. Renaturation after decompression has been monitored by circular dichroism and intrinsic fluorescence emission. Alterations of the dichroic absorption at 222 nm reflect the recovery of the native secondary structure, while tryptophan fluorescence represents a specific probe for the native tertiary structure in the immediate neighborhood of the active center of the enzyme. By application of both methods to monitor the reconstitution of the apo beta 2 dimer, two first-order processes may be separated along the time scale. The faster phase (k1 = 1.2 X 10(-2) s-1) yields a "structured monomer" with 85% native secondary structure and the tryptophan side chain buried in its native hydrophobic environment. As indicated by sodium borohydride reduction, this intermediate is able to interact with the coenzyme pyridoxal 5'-phosphate in the correct way; however, it does not show enzymatic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

High pressure dissociation of lactate dehydrogenase from Bacillus stearothermophilus and reconstitution of the enzyme after denaturation in 6 M guanidine hydrochloride

Tetrameric lactate dehydrogenase from Bacillus stearothermophilus exhibits unusual stability towards high hydrostatic pressure: In contrast to the mesophilic enzyme, incubation at pressures up to 2.8 kbar does not cause irreversible denaturation. Hybridization under these conditions suggests partial dissociation to the dimer, indicating that reassociation occurs within the dead-time after pressure release (less than 20 s at less than or equal to 40 micrograms/ml, 20 degrees C). Incubation at P less than 2.8 kbar affects neither the native quaternary structure nor the catalytic function of the enzyme. Reconstitution of the unfolded and dissociated subunits after denaturation, e.g., in 6 M guanidine . HC1, is characterized by fast association favouring the native assembled structure. Evidence from spectroscopic measurements shows that reconstitution starts with a fast refolding reaction generating a native-like conformation. The subsequent rate-determining transconformation of the "structured monomers" governs the kinetics of reactivation and reassociation as one single first-order process. Chemical crosslinking with glutaraldehyde proves that the "structured monomers" undergo fast association to form the tetrameric final state of reconstitution, with significant amounts of dimeric intermediates being detectable. The renatured enzyme is indistinguishable from the native enzyme regarding its physicochemical and enzymological properties (e.g., activation by fructose-1,6-bisphosphate, and susceptibility towards proteolytic digestion).

Binding of the fluorescent dye 8-anilinonaphthalene 1-sulfonic acid to the native and pressure dissociated beta 2-dimer of tryptophan synthase from Escherichia coli

The beta 2-dimer of tryptophan synthase from Escherichia coli exhibits weak binding of 8-anilinonaphthalene-1-sulfonic acid (ANS). Titrating the dye at 0.2 mM concentration with the apo-beta 2-dimer at atmospheric pressure causes increased fluorescence emission at 480 nm (lambda exc = 380 nm), corresponding to unspecific binding of the ligand to hydrophobic residues. Increasing hydrostatic pressure affects ANS binding. Up to 700 bar, a sigmoidal increase of ANS fluorescence reflects an increase in hydrophobic surface area, probably caused by subunit dissociation. At approximately 1 kbar, a maximum is reached; beyond this value, pressure competes with ligand binding causing fluorescence emission to be decreased again. Pressure release leads to a drastic fluorescence enhancement, ascribed to ANS binding to the partially and reversibly denatured enzyme. Plotting the total fluorescence enhancement vs. pressure yields a profile which parallels the pressure dependent dimer in equilibrium monomer transition monitored by subunit hybridization (T. Seifert, P. Bartholmes, and R. Jaenicke, Biochemistry, in press).

High-pressure dissociation of the beta 2-dimer of tryptophan synthase from Escherichia coli monitored by sucrose gradient centrifugation

The isolated beta 2-dimer of Escherichia coli tryptophan synthase exhibits reversible high-pressure deactivation and hybridization with an equilibrium transition at 690 and 870 bar for the apoenzyme and holoenzyme, respectively. To investigate the hypothetical dissociation mechanism ultracentrifugal analysis has been applied. In a conventional swing-out rotor (r(max) = 16 cm, fill-height 9 cm) a pressure gradient of 1 less than p less than 1840 bar is formed at maximum speed (40 000 rpm). Using a sucrose gradient to stabilize the particle distribution, pressure-dependent alterations of the state of association of oligomeric systems may be determined. In the present experiments ovalbumin (with a molecular mass close to the beta-monomer) has been used as a reference. The radial sedimentation velocity of the beta 2-dimer (in 5-20% sucrose, 10 degrees C) is found to decrease significantly at p approximately equal to 850 bar. From the slopes in an r-r(degrees) vs t plot the limiting values for the particle weight at the meniscus and the bottom of the tube are found to be the beta 2-dimer (M(r) = 85 800) and the beta-monomer (M(r) = 42 900), thus proving pressure-dependent dissociation. Since sucrose stabilizes the native quaternary structure, the beta 2 leads to 2 beta transition is shifted towards higher pressures compared to the dissociation in standard buffer. Conventional quench experiments in high-pressure cells in the presence of 13% (w/v) sucrose confirm the result of the sucrose gradient centrifugation with respect to the critical pressure where deactivation (and dissociation) occur.

Reconstitution of the isolated beta2-subunit of tryptophan synthase from Escherichia coli after dissociation induced by high hydrostatic pressure. Equilibrium and kinetic studies

The isolated beta2-subunit of Escherichia coli tryptophan synthase can be reversibly dissociated into enzymically inactive monomers under high hydrostatic pressure. Deactivation at 1.5 kbar which shows a half-time of 11 min (rate constant k=10 (-3) s (-1) is paralleled by dissociation with a small lag phase of about 5 min. Pressure release leads to 95 +/- 5% recovery of specific activity and complete restoration of the hydrodynamic and spectral properties which specify the native dimer. Over the concentration range 1-100 micrograms/ml (0.02-2.3 micrograms M) the kinetics of reactivation can be fitted by one apparent first-order rate constant (k=6.5 +/- 0.6 X 10 (-4) s (-1), half-time = 17.5 min). The reconstitution of catalytic activity is paralleled by alterations in tryptophan fluorescence at 327 nm, thus presenting direct evidence for conformational changes in the direct vicinity of the active center (k1 = 1.9 X 10 (-3) s(-1), k2 = 6.5 +/- 0.6 X 10(-4) s (-1) ). On the other hand, a definite mechanism of reactivation requires the association of the refolding monomers to be included. The kinetics of dimerization have been followed via hybridization between native and chemically modified beta-chains, yielding an apparent first-order rate constant of 6.3 +/- 0.6 X 10 (-4) s (-1). As a consequence, we propose a sequential uni-uni-bimolecular mechanism, which is characterized by a minimum of two conformational changes in substantially structured monomers followed by a fast dimerization reaction to yield the active beta2-subunit.