Variability of ventricular premature complexes and mortality risk

A method using a parameter from the field of nonlinear dynamics to quantify the variability of ventricular premature complexes (VPCs) is presented. One hundred patients with coronary artery disease and > or = 10 VPCs/hour were included in the study. The RR intervals were plotted in a three-dimensional artificial phase space, and the structures in phase space were quantified by the local scaling indices, alpha. In the frequency distribution histogram, n(alpha), for each patient, the maximum of the ventricular ectopies alpha VPC, adjusted to the VPC frequency, was assessed; alpha VPC was used as the risk indicator. Endpoints were total mortality and sudden cardiac death. During follow-up (mean 3.1 years), 28 out of 100 patients died, 16 suddenly; alpha VPC had a significant prognostic impact and was independent from other risk indicators, such as left ventricular ejection fraction (LVEF). Patients who died during follow-up were characterized by a high alpha VPC. The optimal discrimination of high risk patients and low risk patients occurred at alpha VPC = 3.0. After 4 years, the survival rate of patients with a alpha VPC > 3.0 was 59%, in contrast to 97% in patients with alpha VPC < or = 0.3. As to the sudden death mortality, the survival rates were 74% and 97%, respectively. The difference between the groups were significant for both endpoints. Patients with an increased VPC variability (i.e., alpha VPC > 3.0) were at enhanced risk of sudden death and total mortality risk; alpha VPC was independent from other risk indicators such as the LVEF or heart rate variability parameters.

Intravenous immunoglobulin therapy in systemic onset juvenile rheumatoid arthritis: a followup study

OBJECTIVE

To report the short and longterm effect of intravenous immunoglobulin (IVIG) in patients with systemic onset juvenile rheumatoid arthritis (SOJRA).

METHODS

A retrospective chart review of 27 patients with SOJRA treated with IVIG and followed for 37.1 +/- 18.2 months was undertaken. Indications for treatment were fever, arthritis, or steroid dependency.

RESULTS

We treated 27 patients with SOJRA with IVIG monthly for 3-54 months. Six months after IVIG therapy, 20 patients had a least a 50% decrease in at least one of the following: the number of days of fever; prednisone dose; or the number of active joints. Five patients failed to respond to IVIG, and 2 dropped out after 3 and 4 months. At last followup visit (mean 37.6 +/- 18 months), 11 of the initial 20 responder group patients were in remission, while 3 had significantly improved but still had active arthritis, and 6 were now unresponsive. Of the initial 5 patients in the nonresponder group, 4 had nonresponsive arthritis and 1 had improved at last followup. Three patients in the responder group subsequently developed other diseases.

CONCLUSION

The main benefit of IVIG therapy to most of our patients was a significant improvement in the systemic features, with resolution of fever and a significant reduction in the steroid dose. The efficacy of IVIG in altering the course of arthritis was less predictable. We suggest that IVIG has a role in the management of SOJRA, but it should be limited to patients with severe SOJRA in whom prolonged unresponsiveness to standard therapy is present.

Accelerated nodulosis during methotrexate therapy for juvenile rheumatoid arthritis

We describe two patients with rheumatoid factor-positive, polyarticular-onset juvenile rheumatoid arthritis in whom accelerated nodulosis developed during methotrexate therapy. Although they had only a few nodules at diagnosis, the nodules increased in number and size 3 to 4 months after the start of methotrexate therapy in both patients. The nodules regressed after withdrawal of methotrexate therapy in one patient and were arrested with the addition of hydroxychloroquine in the other. Physicians treating patients with methotrexate for juvenile rheumatoid arthritis must be aware of this extraarticular side effect.

Effects of nimodipine and other calcium channel antagonists in alcohol-preferring AA rats

Several lines of evidence suggest that L-type calcium (CA2+) channels play a role in excessive ethanol (EtOH) intake. In accordance with this, a considerable amount of antagonists for these ion channels has been found to suppress EtOH intake and preference in various animal models of alcoholism. The aim of the present study was to examine antialcohol effects of L-type Ca2+ channel antagonists in alcohol-preferring AA rats. These rats, a Wistar line selectively bred for a high 10% v/v EtOH preference in a free-choice situation, have thus far not been subjected to systematic investigations with Ca2+ channel antagonists. Therefore, effects on EtOH preference and intake, as well as on food and total fluid intake, were evaluated for the 1,4-dihydropyridine (DHP) derivatives nimodipine, felodipine, isradipine, nicardipine, nifedipine, and nitrendipine, as well as for the phenylalkylamine verapamil and the benzothiazepine diltiazem, utilizing a limited access, free-choice procedure. All DHPs were found to be highly effective in reducing both EtOH intake and preference, without affecting total fluid intake. Irrespective of route of application (IP or PO), the effective dose ranges were found to be very similar across compounds (10-30 mg/kg). Nevertheless, because food intake was also reduced, the effects were not completely selective. For nimodipine, the (-)-enantiomer seemed to be more effective as its (+)-enantiomer, possibly reflecting stereoselectivity at central binding sites. Compared to the DHPs, verapamil produced a similar profile of activity, but diltiazem was found to be ineffective. These results confirm and extend previous findings with L-type Ca2+ channel antagonists obtained in other models of alcoholism and suggest that this class of compounds offers an interesting approach for the pharmacotherapy of alcoholism.

Characterization of detergent-solubilized beef liver mitochondrial NAD+ glycohydrolase and its truncated hydrosoluble form

Membrane-bound beef liver mitochondrial NAD+ glycohydrolase (NADase) was partially purified after its solubilization by either detergent or crude pancreatic lipase, steapsin. Solubilization by steapsin yielded a homogeneous water-soluble enzyme. A fluorescence assay was developed that allowed visualization of NADase activity directly within the gel after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular masses of the detergent- and steapsin-solubilized forms were estimated to be about 30,000 and 28,000, respectively. The small part that was cleaved by steapsin represents presumably the membrane anchor of the mitochondrial NADase, as its removal converted the enzyme from a highly hydrophobic to a hydrosoluble protein. The fluorescence staining for activity was also successfully applied to other NADases. Kinetic analyses of the two forms of solubilized mitochondrial NADase revealed that the catalytic properties were unaffected after the steapsin treatment. Neither the binding affinity of the substrate analog 1, N6-etheno-NAD+ nor the inhibition by nicotinamide differed significantly between these two forms of the enzyme. Moreover, the dependence of the enzyme activity on temperature, pH, or ionic strength was also similar for both preparations. However, activity of the detergent-solubilized but not of the truncated steapsin-solubilized enzyme was strongly dependent on the presence of bivalent metal ions such as ZN2+. These results suggest that the membrane part of the mitochondrial NAD+ glycohydrolase is not required for catalysis. It appears, however, to be of importance for the regulation of the enzyme.

Ethanol intake-reducing effects of ipsapirone in rats are not due to simple stimulus substitution

The present series of experiments was conducted to investigate whether the previously reported ethanol intake reducing effects of the 5-HT1A receptor agonist ipsapirone could be based on possible stimulus similarities between both compounds. Rats were trained to discriminate ethanol (12.5% w/v, 1000 mg/kg, IP) from saline in a two-lever food-reinforced drug discrimination (DD) procedure. Discrimination criterion was reached after a mean number of training sessions of 42. In subsequent generalization sessions, a dose-response curve was established for ethanol (125-1000 mg/kg, IP, ED50 value: 355 mg/kg). In additional cross-generalization tests with ipsapirone (1-30 mg/kg, IP), stimulus substitution for the ethanol cue was not noted (maximal degree of generalization: 33%, at 10 and 30 mg/kg). To confirm the DD findings that ipsapirone does not substitute for ethanol, an alternative cross-familiarization conditioned taste aversion paradigm (CF-CTA) was utilized. In rats, 1000 mg/kg IP ethanol was used as the reference drug producing a conditioned taste aversion (CTA). It was found that preexposure to ethanol (500-1500 mg/kg, IP) dose-dependently attenuates the CTA produced by this same drug. Full familiarization was noted with 1000 and 1500 mg/kg. In contrast with this, ipsapirone (1-30 mg/kg, IP) failed to abolish ethanol-induced CTA, suggesting again that the ipsapirone stimulus complex is dissimilar to that produced by ethanol. Because the present findings indicate that, in rats, ipsapirone does not substitute for ethanol, it is suggested that the reported ethanol intake-reducing effects of ipsapirone in animal models of alcoholism are not due to simple stimulus substitution.

The human immunodeficiency virus type 1 transmembrane gp41 protein is a calcium-binding protein and interacts with the putative second-receptor molecules in a calcium-dependent manner

Fusion is a crucial event in the life cycle of the human immunodeficiency virus (HIV); is is initiated by the high-affinity binding between gp120, the external surface glycoprotein of HIV-1, and the differentiation antigen CD4 and finally results in the insertion of the hydrophobic amino terminus of the gp41 envelope glycoprotein into the plasma membrane of the target cell. Recent results suggest that this process is dependent upon calcium ions, but the mechanism or the proteins involved are not understood. Computer-assisted sequence analysis revealed a putative calcium-binding site within the extracellular part of gp41 that was highly reminiscent of the calcium-binding EF-hand structure. To test this hypothesis, calcium-binding experiments were performed. Binding of a recombinant soluble form of the transmembrane protein (rsgp41) to its putative second-receptor molecules in equilibrium was dependent upon calcium. The affinity was not influenced by calcium, but the maximum binding was increased in a dose-dependent manner. Radioactive calcium bound to rsgp41 covalently attached to Sepharose but not to bovine serum albumin. Binding was inhibited by the addition of nonradioactive calcium, indicating that binding was specific. Neither magnesium nor manganese inhibited the binding of labeled calcium to rsgp41. Binding was dependent on the oxidative state of the rsgp41 molecule, suggesting the functional importance of the correctly folded structure of the rsgp41 protein. In this report, we demonstrate that the HIV-1 transmembrane protein gp41 is a calcium-binding protein and interacts with the putative second-receptor molecules in a calcium-dependent manner.

Metals used to fabricate removable partial denture frameworks

This article will help the dental technician choose from among the many alloys available for fabricating dental prostheses. It will explain terminology and compare and explain inherent properties and characteristics of alloys. Although all of the materials discussed produce a clinically acceptable removable partial denture framework, the predominantly base alloys dominate the market because of the low cost of the metal, case of casting, high yield strength and modulus of elasticity.

Cloning of human ubiquitin-conjugating enzymes UbcH6 and UbcH7 (E2-F1) and characterization of their interaction with E6-AP and RSP5

E6-AP, a 100-kDa cellular protein, was originally identified through its interaction with the E6 protein of the oncogenic human papillomavirus types 16 and 18. The complex of E6-AP and E6 specifically interacts with p53 and mediates ubiquitination of p53 in concert with the E1 ubiquitin-activating enzyme and the E2 ubiquitin-conjugating enzyme UbcH5. Recent results suggest that E6-AP is representative of a family of putative ubiquitin-protein ligases. Members of this family are characterized by a conserved C-terminal region, termed hect domain. In this paper, we describe the isolation of two human E2s, designated as UbcH6 and UbcH7, that in addition to UbcH5 can interact with E6-AP. UbcH6 is a novel member of an evolutionally conserved subfamily of E2s that includes UbcH5 and Saccharomyces cerevisiae UBC4. Although UbcH7 does not appear to be a member of this subfamily, UbcH7 efficiently substitutes for UbcH5 in E6-AP-dependent ubiquitination. Surprisingly, UbcH6 was only weakly active in this particular assay. In addition, UbcH5 but not UbcH6 or UbcH7 efficiently interacts with the heet protein RSP5. These results indicate that E6-AP can interact with at least two species of E2 and that different hect proteins may interact with different E2s.

A randomized controlled trial of salmon calcitonin to prevent bone loss in corticosteroid-treated temporal arteritis and polymyalgia rheumatica

Patients treated with high-dose or long-term corticosteroids are at risk of accelerated osteoporosis and spontaneous vertebral and traumatic fractures. To assess the efficacy of salmon calcitonin in preventing corticosteroid- induced osteoporosis, 48 patients with newly diagnosed polymyalgia rheumatica, temporal arteritis, and other vasculitides were enrolled in a 2-year, double-blind, randomized, controlled trial. Patients were randomized to receive subcutaneous injections t.i.w. of either 100 IU of salmon calcitonin (25 patients) or placebo (23 patients). After 2 years, 19 and 21 patients, respectively, were evaluable. All patients also received supplemental calcium carbonate (1500 mg daily in divided doses) and vitamin D3 (400 IU daily). Baseline and serial radiologic assessments included dual-energy X-ray absorptiometry (DXA) of the lumbar spine and hip, and spine radiographs to detect vertebral fractures. There were no significant baseline differences between the two study groups. The mean within-subject percentage change in DXA lumbar spine density in the two groups over the 2-year period of the study was only -0.1% (calcitonin plus calcium) versus -0.2% (placebo plus calcium) a nonsignificant difference despite the high mean cumulative corticosteroid doses of 5371 mg and 4680 mg, respectively (NS). The incidence of vertebral fracture was 12.5% (calcitonin plus calcium: 11%, versus placebo plus calcium: 14%, NS), with four fractures in the first year and one fracture in the second year. Higher cumulative cortico-steroid dose was associated with a greater loss in bone density. In rheumatic disease patients starting high-dose, long-term corticosteroids, salmon calcitonin with calcium and vitamin D3 provided no greater bone preservation than that observed with calcium and vitamin D3 alone.

RNase of classical swine fever virus: biochemical characterization and inhibition by virus-neutralizing monoclonal antibodies

The structural glycoprotein E0 of classical swine fever virus (CSFV) possesses an intrinsic RNase activity. Here we present the first comprehensive biochemical characterization of E0, using a recombinant glycoprotein expressed in insect cells. We were able to show that the presence of neither carbohydrate moieties nor disulfide bonds is a prerequisite for RNase activity. In addition, virus-neutralizing and nonneutralizing anti-E0 monoclonal antibodies were tested for their ability to influence RNase activity. In these experiments, the antibodies which effectively blocked the infection of STE cells also exerted a high degree of E0 RNase inhibition. This correlation suggests that the RNase activity of CSFV E0 plays a role in the viral life cycle.

The HSSP database of protein structure-sequence alignments

HSSP is a derived database merging structural three dimensional (3-D) and sequence one dimensional(1-D) information. For each protein of known 3-D structure from the Protein Data Bank (PDB), the database has a multiple sequence alignment of all available homologues and a sequence profile characteristic of the family. The list of homologues is the result of a database search in Swissprot using a position-weighted dynamic programming method for sequence profile alignment (MaxHom). The database is updated frequently. The listed homologues are very likely to have the same 3-D structure as the PDB protein to which they have been aligned. As a result, the database is not only a database of aligned sequence families, but also a database of implied secondary and tertiary structures covering 27% of all Swissprot-stored sequences.

Identification and purification of a bovine liver mitochondrial NAD(+)-glycohydrolase

Nonenzymatic ADP-ribosylation of mitochondrial proteins is thought to play a role in the regulation of Ca2+ efflux from mitochondria. It has been shown that intramitochondrial ADP-ribose is generated by a specific NAD(+)glycohydrolase, which catalizes hydrolysis of NAD+ to ADP-ribose and nicotinamide. We purified this enzyme from bovine liver mitochondrial membranes. The final preparation had a 1660-fold purified enzyme activity and contained a main protein band with an apparent molar mass of 32,000 in a SDS-polyacrylamide gel. The identity of this protein band with NAD(+)-glycohydrolase was verified by renaturation of its enzymatic activity. Partial amino acid sequence information was obtained from two enzyme fragments after proteolytic cleavage of the protein band in the SDS-polyacrylamide gel. Searches in protein databases revealed that an arginine ADP-ribosyl hydrolase harbours two stretches of amino acids that are highly similar to the partial NAD(+)-glycohydrolase sequences.

Characterization of functionally independent domains in the human ubiquitin conjugating enzyme UbcH2

UbcH2 encodes a human ubiquitin conjugating enzyme (E2) able to conjugate ubiquitin to histone H2A in an E3 independent manner in vitro, which indicates that UbcH2 directly interacts with its substrates. To identify parts of the enzyme that are capable of binding H2A, we expressed several deletion mutants of UbcH2 in E. coli and tested the ability of the affinity purified mutant proteins to ubiquitinate H2A in the presence of bacterial expressed E1 and ubiquitin. With this in vitro assay we identified a C-terminal part of UbcH2 to be important for the interaction with H2A. Transfer of this C-terminal domain to another human E2, which is unable to catalyze ubiquitination of histones, leads to a fully active hybrid human ubiquitin conjugating enzyme capable of H2A ubiquitination. These results demonstrate that UbcH2 consists of two functionally independent domains. A N-terminal core domain with ubiquitin conjugating activity, and a C-terminal domain which interacts with substrate proteins.

Different respiratory-defective phenotypes of Neurospora crassa and Saccharomyces cerevisiae after inactivation of the gene encoding the mitochondrial acyl carrier protein

The nuclear genes (acp-1, ACP1) encoding the mitochondrial acyl carrier protein were disrupted in Neurospora crassa and Saccharomyces cerevisiae. In n. crassa acp-1 is a peripheral subunit of the respiratory NADH : ubiquinone oxidoreductase (complex I). S. cerevisiae lacks complex I and its ACP1 appears to be located in the mitochondrial matrix. The loss of acp-1 in N. crassa causes two biochemical lesions. Firstly, the peripheral part of complex I is not assembled, and the membrane part is not properly assembled. The respiratory ubiquinol : cytochrome c oxidoreductase (complex III) and cytochrome c oxidase (complex IV) are made in normal amounts. Secondly, the lysophospholipid content of mitochondrial membranes is increased four-fold. In S. cerevisiae, the loss of ACP1 leads to a pleiotropic respiratory deficient phenotype.

Nerve growth factor binding site on TrkA mapped to a single 24-amino acid leucine-rich motif

The extracellular domains of the TrkA nerve growth factor (NGF) receptor and its homologs harbor a modular mosaic of potential ligand binding motifs, namely two immunoglobulin (Ig)-like modules and an LRM3 cassette consisting of a tandem array of three leucine-rich motifs (LRMs) flanked by cysteine-rich clusters (Schneider, R., and Schweiger, M. (1991) Oncogene 6, 1807-1811). Identification of a structural motif capable of specifically recognizing the various neurotrophins was achieved by assessing their affinities to isolated recombinant modules of TrkA and TrkB. In both receptors the LRM3 cassette alone could mediate the respective neurotrophin selectivities and affinities. Further tracking down of this NGF-binding site in TrkA strikingly revealed that a single LRM of 24 amino acids could bind NGF selectively with nanomolar affinity. Since this is the first example of a single LRM with a highly specific, well defined function, it might serve as a valuable tool to elucidate the general structural requirements of substrate recognition and high affinity binding in the large superfamily of LRM-containing proteins.

Positive and negative inotropic effects of DL-sotalol and D-sotalol in failing and nonfailing human myocardium under physiological experimental conditions

BACKGROUND

DL-Sotalol has class III antiarrhythmic activity through prolongation of the repolarization phase of the action potential as well as beta-adrenoceptor-blocking properties. Although the former effect was found to exert positive inotropic effects in animal experimental studies, the latter may be detrimental in heart failure due to negative inotropism. In contrast to DL-sotalol, D-sotalol is suggested to exert only positive inotropic effects, which were never tested in isolated human myocardium.

METHODS AND RESULTS

Therefore, we investigated the effects of racemic DL-sotalol and its enantiomer D-sotalol in human right atrial muscle strip preparations and in left ventricular muscle strip preparations from nonfailing and end-stage failing human hearts. DL-sotalol and D-sotalol significantly (P < .01) increased peak developed force in atrial preparations by 14.0 +/- 3.4% and 16.7 +/- 3.8%, respectively, but had no effect in ventricular myocardium. In nonfailing ventricular myocardium, both DL-sotalol and D-sotalol shifted the dose-response curve for isoproterenol to higher concentrations (P < .01); however, DL-sotalol was 100-fold more effective than D-sotalol. In non-failing myocardium, a positive force-frequency relation was found between 30 and 120 beats per minute, but isoproterenol was much more powerful in its inotropic effects. In failing myocardium, reduction in stimulation rate from 120 to 30 beats per minute increased peak developed force more pronounced than did the application of isoproterenol.

CONCLUSIONS

(1) D-Sotalol has no relevant beta-adrenoceptor-blocking activity compared with DL-sotalol. (2) Neither DL-sotalol nor D-sotalol exhibit positive inotropic effects in human left ventricular myocardium. (3) Heart rate reduction increases contractile force in end-stage failing human myocardium due to an inverse force-frequency relation and thereby counteracts the potential negative inotropic properties of beta-blockade.

Specific neurotrophin binding to leucine-rich motif peptides of TrkA and TrkB

The extracellular domains of the TrkA and TrkB neurotrophin receptors contain defined structural modules such as immunoglobulin-like domains and leucine-rich motifs (LRMs) [Schneider and Schweiger, Oncogene 6 (1991) 1807-1811]. Recently, the second LRM of TrkA was identified as a functional nerve growth factor (NGF) binding site [Windisch et al, J. Biol. chem. (1995) in press]. A peptide corresponding to this region effectively bound NGF and blocked binding of NGF to the recombinant extracellular domain of TrkA. The corresponding TrkB peptide exhibited the same effects with respect to brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4), indicating that all three TrkB ligands utilize this same binding site. Isolated LRMs therefore embody independent functional entities.

Characterization of a cDNA clone encoding E2-20K, a murine ubiquitin-conjugating enzyme

The 20-kDa ubiquitin-conjugating enzyme E2-20K is induced specifically during a late stage of erythroid differentiation. Here we report the sequence of a murine cDNA encoding E2-20K. Northern blot analysis identified polyadenylated transcripts of 3.5 and 6.5 kb which are present at comparable levels in many nonerythroid tissues.

Characterization of the chemical bonding in inner layers of composite materials

The efficiency of near edge structure investigations in electron energy loss spectroscopy (EELS) is discussed for characterizing the chemical bonding of elements present in the interfacial zone in fibre/matrix composites at nanometre resolution. Two different examples of corresponding analyses are given for a SiC-fibre reinforced borosilicate glass. In particular, the chemical bonding between silicon and carbon or oxygen (e.g. SiC, SiO(2) and SiO(x)C(y)), respectively, is characterized. The results have been attained in a fingerprint manner by comparing the fine structure measured from a material of unknown stoichiometry to that of a standard specimen. In addition, a possibility is demonstrated to image the chemical bonding by energy-filtered microscopy using energy loss near edge structures (ELNES).

Brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4 bind to a single leucine-rich motif of TrkB

TrkB is a member of the Trk family of neurotrophin receptors. Its extracellular domain exhibits the same modular structure found in its homologs, TrkA and TrkC, consisting of an N-terminal LRM3 cassette and two immunoglobulin-like modules (Ig2 domain) adjacent to the membrane. The LRM3 cassette comprises two cysteine-rich clusters framing a tandem array of three leucine-rich motifs (LRMs). On the basis of the recent identification of a nerve growth factor (NGF) binding site within TrkA, the ability of the different structural entities within the extracellular domain of TrkB to bind the various neurotrophins was determined by using a recombinant receptor approach. Brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) bound to the LRM3 cassette of TrkB, whereas NGF did not. These binding characteristics evidently reflect in vivo specificities. A more precise mapping of the region(s) responsible for binding BDNF, NT-3, and NT-4 identified the second leucine-rich motif of TrkB as a functional unit capable of binding all three neurotrophins. The affinities and kinetics that this short stretch of amino acids exhibited with respect to the different neurotrophins were clearly akin to those observed for cells ectopically expressing TrkB receptors. With 24 amino acids determining the affinities and kinetics of the interactions with three different partners, the leucine-rich motif is strongly established as one of the most potent and flexible protein--protein interaction motifs.