A comparison of enalapril with hydralazine-isosorbide dinitrate in the treatment of chronic congestive heart failure

BACKGROUND

To define better the efficacy of vasodilator therapy in the treatment of chronic congestive heart failure, we compared the effects of hydralazine and isosorbide dinitrate with those of enalapril in 804 men receiving digoxin and diuretic therapy for heart failure. The patients were randomly assigned in a double-blind manner to receive 20 mg of enalapril daily or 300 mg of hydralazine plus 160 mg of isosorbide dinitrate daily. The latter regimen was identical to that used with a similar patient population in the effective-treatment arm of our previous Vasodilator-Heart Failure Trial.

RESULTS

Mortality after two years was significantly lower in the enalapril arm (18 percent) than in the hydralazine-isosorbide dinitrate arm (25 percent) (P = 0.016; reduction in mortality, 28.0 percent), and overall mortality tended to be lower (P = 0.08). The lower mortality in the enalapril arm was attributable to a reduction in the incidence of sudden death, and this beneficial effect was more prominent in patients with less severe symptoms (New York Heart Association class I or II). In contrast, body oxygen consumption at peak exercise was increased only by hydralazine-isosorbide dinitrate treatment (P less than 0.05), and left ventricular ejection fraction, which increased with both regimens during the 2 years after randomization, increased more (P less than 0.05) during the first 13 weeks in the hydralazine-isosorbide dinitrate group.

CONCLUSIONS

The similar two-year mortality in the hydralazine-isosorbide dinitrate arms in our previous Vasodilator-Heart Failure Trial (26 percent) and in the present trial (25 percent), as compared with that in the placebo arm in the previous trial, (34 percent) and the further survival benefit with enalapril in the present trial (18 percent) strengthen the conclusion that vasodilator therapy should be included in the standard treatment for heart failure. The different effects of the two regimens (enalapril and hydralazine-isosorbide dinitrate) on mortality and physiologic end points suggest that the profile of effects might be enhanced if the regimens were used in combination.

HK-2: an immortalized proximal tubule epithelial cell line from normal adult human kidney

Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.

Epstein-Barr virus-coded BHRF1 protein, a viral homologue of Bcl-2, protects human B cells from programmed cell death

Epstein-Barr virus, a human herpesvirus that persists within the B-lymphoid system, can enhance the survival potential of latently infected B cells in vitro through up-regulation of the cellular survival protein Bcl-2. The possibility that an analogous effect is operative in lytically infected cells was suggested by the observation of distant sequence homology between an Epstein-Barr virus-coded early lytic cycle protein, BHRF1, and Bcl-2. Here we show by gene transfer that BHRF1 resembles Bcl-2 both in its subcellular localization and in its capacity to enhance B-cell survival. Thus confocal microscopic analysis of cells acutely cotransfected with BHRF1 and Bcl-2 expression vectors revealed substantial colocalization of the two proteins in the cytoplasm. In subsequent experiments, stable BHRF1 gene transfectants of Burkitt lymphoma cells paralleled Bcl-2 transfectants in their enhanced survival under conditions that induce cell death by apoptosis. Despite their limited sequence conservation, therefore, the two proteins appear to be functionally homologous. We suggest that BHRF1 provides an alternative, Bcl-2-independent, means of enhancing B-cell survival that may operate during the virus lytic cycle.

The regulation of anoikis: MEKK-1 activation requires cleavage by caspases

Certain cell types undergo apoptosis when they lose integrin-mediated contacts with the extracellular matrix ("anoikis"). The Jun N-terminal kinase (JNK) pathway is activated in and promotes anoikis. This activation requires caspase activity. We presently report that a DEVD motif-specific caspase that cleaves MEKK-1 specifically is activated when cells lose matrix contact. This cleavage is required for the activation of the kinase activity. When overexpressed, the MEKK-1 cleavage product stimulates apoptosis; the wild-type, full-length MEKK-1 sensitizes cells to anoikis; and a cleavage-resistant mutant of MEKK-1 partially protects cells against anoikis. The cleavage-resistant or kinase-inactive mutants also prevent caspase-7 from being activated completely. Thus, caspases can induce apoptosis by activating MEKK-1, which in turn activates more caspase activity, comprising a positive feedback loop.

Glial neoplasms: dynamic contrast-enhanced T2*-weighted MR imaging

PURPOSE

To evaluate the role of T2*-weighted echo-planar perfusion imaging by using a first-pass gadopentetate dimeglumine technique to determine the association of magnetic resonance (MR) imaging-derived cerebral blood volume (CBV) maps with histopathologic grading of astrocytomas and to improve the accuracy of targeting of stereotactic biopsy.

MATERIALS AND METHODS

MR imaging was performed in 29 patients by using a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence followed by conventional imaging. The perfusion data were processed to obtain a color map of relative regional CBV. This information formed the basis for targeting the stereotactic biopsy. Relative CBV values were computed with a nondiffusible tracer model. The relative CBV of lesions was expressed as a percentage of the relative CBV of normal white matter. The maximum relative CBV of each lesion was correlated with the histopathologic grading of astrocytomas obtained from samples from stereotactic biopsy or volumetric resection.

RESULTS

The maximum relative CBV in high-grade astrocytomas (n = 26) varied from 1.73 to 13.7, with a mean of 5.07 +/- 2.79 (+/- SD), and in the low-grade cohort (n = 3) varied from 0.92 to 2.19, with a mean of 1.44 +/- 0.68. This difference in relative CBV was statistically significant (P < .001; Student t test).

CONCLUSION

Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy.

Racial differences in response to therapy for heart failure: analysis of the vasodilator-heart failure trials. Vasodilator-Heart Failure Trial Study Group

BACKGROUND

Heart failure in blacks has been associated with a poorer prognosis than in whites. In such diseases as hypertension, blacks show pathophysiological differences and respond differently to some therapies than whites. The aim of this study is to evaluate the clinical characteristics and response to therapy of black compared with white patients with heart failure.

METHODS AND RESULTS

In the first Vasodilator-Heart Failure Trial (V-HeFT I), 180 black male patients were compared with 450 white male patients for baseline characteristics, prognosis, and response to therapy. In V-HeFT II, the same comparisons were made for 215 black and 574 white male patients, including an analysis stratified by the presence or absence of a history of hypertension. In both trials, black patients had a lower incidence of coronary artery disease, greater incidence of previous hypertension, and a greater cardiothoracic ratio (P < .05) than white patients. In V-HeFT II, plasma norepinephrine levels were significantly less in blacks; plasma renin activity was less only in blacks with a history of hypertension. Overall mortality or hospitalization for congestive heart failure did not differ between blacks and whites in the placebo group in V-HeFT I. However, the mortality of black patients receiving hydralazine plus isosorbide dinitrate (H-I) was reduced (P = .04) in V-HeFT I, whereas white patients showed no difference from placebo. In V-HeFT II, only white patients showed a mortality reduction from enalapril therapy compared with H-I therapy (P = .02). Whites also showed evidence of greater blood pressure reduction and enhanced regression of cardiac size in response to enalapril. When stratified by history of hypertension in V-HeFT II, only whites with a history of hypertension, who had greater renin levels, showed significant mortality reduction with enalapril compared with H-I therapy. Hospitalization rates did not differ between treatment groups in either study.

CONCLUSION

Whites and blacks showed differences in cause, neurohormonal stimulation, and pharmacological response in heart failure. This retrospective analysis suggests angiotensin-converting enzyme inhibitors are particularly effective in whites, and the H-I combination can be equally effective in blacks. Prospective trials involving large numbers of black patients are needed to further clarify their response to therapy.

Germinal center cells express bcl-2 protein after activation by signals which prevent their entry into apoptosis

B cells undergo selection within germinal centers on the basis of their capacity to be activated by antigen held on follicular dendritic cells. Isolated germinal center B cells in culture kill themselves by apoptosis but this is prevented if their receptors for antigen are cross-linked. In this study it is confirmed that almost all germinal center B cells, unlike other B cells, do not express the 25-kDa protein encoded by the bcl-2 oncogene. Cross-linking the surface Ig of isolated germinal center cells causes them to express bcl-2 protein. Two other stimuli which inhibit the entry of germinal center cells to apoptosis result in the expression of bcl-2 protein. These stimuli are: (a) CD40 antibody and (b) recombinant 25-kDa fragment of the CD23 protein plus recombinant interleukin 1 alpha. Respectively, these induce germinal center cells to differentiate to resting B cells or plasmablasts. Dual-fluorescence studies on small lymphocytes confirm the presence of bcl-2 protein in mitochondria but show that this is also present in other extra-nuclear areas. Burkitt lymphoma cells have a phenotype which indicates that they are neoplastic cells of germinal center origin. The expression of bcl-2 protein by Burkitt lymphoma lines was also studied. Burkitt lines which retain the phenotype of fresh Burkitt lymphoma cells can be induced to enter apoptosis on culture with the Ca2+ ionophore ionomycin. These cells were found not to express bcl-2 protein. By contrast, Burkitt lines which have drifted towards a lymphoblastoid cell line phenotype and are resistant to the induction of apoptosis express high levels of the bcl-2 protein. The findings support the concept that the susceptibility of germinal center cells to entering apoptosis is associated with their lack of expression of bcl-2 protein. Aberrant expression of bcl-2 protein by some neoplastic germinal center cells may allow survival in situations where their normal counterparts die.

The cardinal manifestations of Bardet-Biedl syndrome, a form of Laurence-Moon-Biedl syndrome

To determine the interfamilial and intrafamilial variation in the expression of the Bardet-Biedl syndrome (a form of Laurence-Moon-Biedl syndrome), we looked for the five recognized features of the disorder (retinal dystrophy, obesity, polydactyly, mental retardation, and hypogonadism), plus possible renal manifestations, in some or all of 32 patients with this disorder. All 28 patients examined had severe retinal dystrophy, but only 2 had typical retinitis pigmentosa. Polydactyly was present in 18 of 31 patients, but syndactyly, brachydactyly, or both were present in all. Obesity was present in all but 1 of 25 patients. Only 13 of 32 patients were considered mentally retarded. Scores on verbal subtests of intelligence were usually lower than scores on performance tasks. Seven of eight men had small testes and genitalia, which was not due to hypogonadotropism. All 12 women studied had menstrual irregularities, and 3 had low serum estrogen levels (1 of these had hypogonadotropism, and 2 had primary gonadal failure). The remaining women who were of reproductive age had endocrinologic evidence of reproductive dysfunction. Diabetes mellitus was present in 9 of 20 patients. Renal structural or functional abnormalities were universal (n = 21), and three patients had end-stage renal failure. We conclude that the characteristic features of Bardet-Biedl syndrome are severe retinal dystrophy, dysmorphic extremities, obesity, renal abnormalities, and (in male patients only) hypogenitalism. Mental retardation, polydactyly, and hypogonadism in female patients are not necessarily present.

AMP-activated protein kinase is activated by low glucose in cell lines derived from pancreatic beta cells, and may regulate insulin release

The role of the AMP-activated protein kinase (AMPK) cascade in the glucose-sensitive pancreatic beta cell lines HIT-T15 and INS-1 was addressed. In both cell types, removal of glucose leads to a >5-fold activation of AMPK activity. Activation of AMPK was due to phosphorylation, since the effect was reversed by protein phosphatase treatment of the extracts, and was restored by re-addition of MgATP and the purified upstream kinase. When the effects of different concentrations of medium glucose were examined, insulin secretion and AMPK activity were inversely related, and varied over the same concentration range. The activation in response to glucose removal appeared to be due to changes in the concentration of the known regulators of the cascade, i.e. AMP and ATP, since AMPK activation was associated with a large increase in the cellular AMP/ATP ratio, and the two parameters varied over the same range of glucose concentrations. In late-passage HIT-T15 cells that had lost the glucose-dependent insulin secretion response, both AMPK activity and the AMP/ATP ratio also became insensitive to the extracellular glucose concentration. Treatment of INS-1 cells, but not HIT-T15 cells, with AICA riboside (5-aminoimidazole-4-carboxamide riboside) results in accumulation of the ribotide, ZMP (AICA riboside monophosphate), and activation of AMPK. AICA riboside treatment of INS-1 cells, and of isolated rat islets, had both inhibitory and stimulatory effects on insulin secretion. These results show that in beta cell lines the AMP-activated protein kinase, like its yeast homologue the SNF1 complex, can respond to the level of glucose in the medium, and may be involved in regulating insulin release.

Germinal centres in T-cell-dependent antibody responses

For more than a century follicles have been recognized as a site of intense cell proliferation and cell death. At last the significance of this activity is beginning to emerge: antigen-driven B-cell proliferation, somatic mutation, positive and negative selection, and memory and plasma cell development all appear to take place within the follicle.

Fat suppression in MR imaging: techniques and pitfalls

Fat suppression is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue. Fat suppression can be achieved with three methods: fat saturation, inversion-recovery imaging, and opposed-phase imaging. Selection of a fat suppression technique should depend on the purpose of the fat suppression (contrast enhancement vs tissue characterization) and the amount of fat in the tissue being studied. Fat saturation is recommended for suppression of signal from large amounts of fat and reliable acquisition of contrast material-enhanced images. The main drawbacks of this technique are sensitivity to magnetic field nonuniformity, misregistration artifacts, and unreliability when used with low-field-strength magnets. Inversion-recovery imaging allows homogeneous and global fat suppression and can be used with low-field-strength magnets. However, this technique is not specific for fat, and the signal intensity of tissue with a long T1 and tissue with a short T1 may be ambiguous. Opposed-phase imaging is a fast and readily available technique. This method is recommended for demonstration of lesions that contain small amounts of fat. The main drawback of opposed-phase imaging is unreliability in the detection of small tumors embedded in fatty tissue.

Time course of endothelial dysfunction and myocardial injury during myocardial ischemia and reperfusion in the cat

Myocardial ischemia and reperfusion have been shown to impair coronary vasorelaxation to endothelium-dependent vasodilators. To examine the time course of this dysfunction, occlusion of the left anterior descending (LAD) coronary artery (90 minutes) was followed by reperfusion for 0, 2.5, 5, 20, 180, or 270 minutes. Coronary arterial rings from the ischemic LAD and control left circumflex (LCx) arteries were tested for responsiveness to the endothelium-dependent receptor-mediated vasodilator, acetylcholine (ACh), and the endothelium-dependent nonreceptor-mediated vasodilator, A23187, as well as the endothelium-independent vasodilator, NaNO2. ACh relaxation was not impaired after 90 minutes of ischemia without reperfusion. However, 2.5 minutes of reperfusion resulted in depressed ACh responses (36 +/- 10% of control) that was further reduced to 16 +/- 6% at 20 minutes, and remained comparably depressed at every time thereafter. A23187 vasodilator responses were also attenuated after reperfusion, although the reduced response occurred later (that is, at 20 minutes). There was no significant decrease in response to NaNO2 in the LAD at any time or to any vasodilator in LCx control rings. Treatment with recombinant human superoxide dismutase (hSOD, 5 mg/kg/hr, that is, 15,545 SOD units/kg/hr), starting 10 minutes before reperfusion, preserved the vasodilator response to ACh (82 +/- 6%) and A23187, but treatment with the hydroxyl ion scavenger N-(2-mercapto proprionyl)-glycine (MPG) (8 mg/kg/hr) only protected the A23187 response. No damage to the surface of the endothelium was observed by scanning electron microscopy at any time point. Myocardial cell damage increased with time of reperfusion as assessed by increasing plasma CK activities and amounts of necrotic tissue indexed to area at risk. Significant myocardial injury occurred at 3 hours after reperfusion. These findings suggest that endothelial dysfunction resulting in reduced endothelium-derived relaxing factor release occurs before the development of myocardial cell necrosis and may be due to oxygen-derived free radicals produced rapidly on reperfusion.

The role of NMR imaging in the assessment of multiple sclerosis and isolated neurological lesions. A quantitative study

The form and distribution of MRI abnormalities in 114 patients with clinically definite multiple sclerosis (MS) have been compared with observations on 53 apparently healthy individuals, 129 patients with isolated focal neurological lesions with which MS often presents (51 patients with optic neuritis, 44 with isolated brainstem lesions and 34 with isolated spinal cord syndromes) and 105 patients with disorders which may be confused clinically or radiologically with MS. The latter comprised 55 patients with cerebral vascular disease (including 7 cases of dementia with diffuse white matter disease), 24 with degenerative ataxic disorders, 8 with cerebellar tonsillar ectopia, 7 with sarcoidosis and 11 with a variety of other disorders. Periventricular abnormalities were found in all but 2 patients with MS and discrete white matter lesions in all but 12. Characteristically the periventricular changes in MS were irregular in outline. Periventricular abnormalities which were often milder and of smooth outline were seen in 37/55 patients with cerebral vascular disease, 9/24 with cerebellar degeneration, 5/7 with sarcoidosis and in 2/3 apparently healthy individuals over the age of 60. The appearances in the 7 cases of dementia resembled those with advanced MS. Cerebellar and/or brainstem atrophy characteristic of the cerebellar degenerations, in the absence of white matter abnormalities, was helpful in making the distinction from MS. Congenital anomalies and tumours in the region of the brainstem and foramen magnum were readily shown. More than half the patients with symptoms attributable to isolated focal neurological lesions had additional lesions at presentation. MS cannot be diagnosed in these cases at presentation, but repeat scans after 5 to 20 months in 25 patients with optic neuritis and 10 with clinically isolated brainstem lesions have shown new lesions in 7 (20%). The patients with new lesions fulfil the criteria for clinically probable MS (Poser et al., 1983). Measurements of T1 and T2 in vivo permitted the distinction of acute from chronic brainstem lesions. There were quantitative differences in T1 and T2 between the normal appearing white matter in MS and normal brain. Studies of postmortem brains provided convincing evidence that the MRI abnormalities in MS correspond with plaques. Evidence is adduced to support the view that an important source of the abnormal NMR signals in acute lesions is oedema, and in chronic lesions is gliosis; demyelination per se is unlikely to make an important contribution.

Targeting acute ischemic stroke with a calcium-sensitive opener of maxi-K potassium channels

During ischemic stroke, neurons at risk are exposed to pathologically high levels of intracellular calcium (Ca++), initiating a fatal biochemical cascade. To protect these neurons, we have developed openers of large-conductance, Ca++-activated (maxi-K or BK) potassium channels, thereby augmenting an endogenous mechanism for regulating Ca++ entry and membrane potential. The novel fluoro-oxindoles BMS-204352 and racemic compound 1 are potent, effective and uniquely Ca++-sensitive openers of maxi-K channels. In rat models of permanent large-vessel stroke, BMS-204352 provided significant levels of cortical neuroprotection when administered two hours after the onset of occlusion, but had no effects on blood pressure or cerebral blood flow. This novel approach may restrict Ca++ entry in neurons at risk while having minimal side effects.

Serial gadolinium enhanced magnetic resonance imaging in multiple sclerosis

Serial gadolinium-DTPA (Gd-DTPA) enhanced magnetic resonance imaging (MRI) was performed in 9 patients with multiple sclerosis (MS). On the first scan enhancing lesions were seen in 7 patients, all of whom were in acute relapse. Most enhancing lesions were asymptomatic. On the second scan (3 to 5 weeks later), persisting enhancement was seen in only 12/54 lesions which enhanced on the first scan. No lesion showed persisting enhancement on the third scan (after 6 months). Enhancement occurred in all 12 new lesion areas seen on the unenhanced second scan and in 8 of 15 new lesions seen on the third scan. Enhancement was also seen in 4 older lesions which had been nonenhancing on earlier scans. Relaxation time measurements demonstrated a high water content in some nonenhancing lesions, which could be due to a subtle blood-brain barrier disturbance not detected with Gd-DTPA. The results show that blood-brain barrier impairment is a consistent finding in new MS lesions detected with MRI. Gd-DTPA is a useful marker of new and biologically active lesions and should prove of value in monitoring therapeutic trials in MS.

Length distribution of CDRH3 in antibodies

Sequences of the third complementarity determining region of antibody heavy chains (CDRH3s) are listed according to their length. Human sequences vary from 2 to 26 amino acids residues, but less extensively in other species. When combined with the other five complementarity determining regions, this enormous length variation of CDRH3, together with amino acid substitutions in their sequences, can provide a very large number of antibody specificities and can influence the shape of antibody combining sites.

Development of a measure of the burden of pain due to herpes zoster and postherpetic neuralgia for prevention trials: adaptation of the brief pain inventory

In preparation for clinical trials of a vaccine against herpes zoster (HZ), we conducted a prospective, observational study to evaluate (1) the Zoster Brief Pain Inventory (ZBPI), an HZ-specific questionnaire to quantify HZ pain and discomfort, (2) an operational definition of postherpetic neuralgia (PHN), and (3) a severity-duration measure of the burden of illness caused by HZ. HZ patients aged 60 years or older (n = 121) were enrolled within 14 days of rash onset and completed ZBPI, McGill Pain Questionnaire Present Pain Intensity (PPI), quality of life (QoL), and activities of daily living (ADL) questionnaires on a predetermined schedule. Reliability, measured by intraclass correlation coefficients within 14 days of rash onset, ranged between 0.63 and 0.78. ZBPI pain scores were strongly correlated with other pain measures, interference with ADL, and worsening QoL. The operational definition of PHN, a ZBPI pain score of 3 or greater occurring 90 or more days after rash onset, had high agreement with pain worse than mild on the PPI (kappa = 0.72). The ZBPI pain severity-duration measure had high correlations with severity-duration measures of ADL interference, worsening QoL, and other pain scales. These findings support the validity and utility of the ZBPI, the definition of PHN, and the severity-duration measure of the burden of HZ illness.

PERSPECTIVE

Herpes zoster pain, as measured by the ZBPI severity-duration measure, is associated with impairment in daily living activities and quality of life. The ZBPI measure appears useful for quantifying herpes zoster pain, postherpetic neuralgia, and impairment in daily living activities for clinical trials of herpes zoster prevention.

The balance between isoforms of the prickle LIM domain protein is critical for planar polarity in Drosophila imaginal discs

The tissue polarity mutants in Drosophila include a set of conserved gene products that appear to be involved in the control of cytoskeletal architecture. Here we show that the tissue polarity gene prickle (pk) encodes a protein with a triple LIM domain and a novel domain that is present in human, murine, and Caenorhabditis elegans homologs which we designate PET. Three transcripts have been identified, pk, pkM, and sple, encoding 93-, 100-, and 129-kD conceptual proteins, respectively. The three transcripts span 70 kb and share 6 exons that contain the conserved domains. The pk and sple transcripts are expressed with similar tissue-specific patterns but have qualitatively different activities. The phenotypes of pk mutants, and transgenic flies in which the different isoforms are overexpressed show that the balance between Pk and Sple is critical for the specification of planar polarity. In addition, these phenotypes suggest a tessellation model in which the alignment of wing hairs is dependent on cell shape and need not reflect fine-grained positional information. Lack of both pk and sple transcripts gives a phenotype affecting the whole body surface that is similar to those of dishevelled and frizzled (fz) suggesting a functional relationship between pk and fz signaling.

The peripheral anionic site of acetylcholinesterase: structure, functions and potential role in rational drug design

The peripheral anionic site of acetylcholinesterase lies at the entrance to the active site gorge. It is composed of five residues (Tyr 70, Asp 72, Tyr 121, Trp 279 and Tyr 334; Torpedo numbering); associated with it are a number of surface loops, conferring a high degree of conformational flexibility on the area. The site is involved in the allosteric modulation of catalysis at the active centre and is the target of various anti-cholinesterases. It is also implicated in a number of non-classical functions, in particular, amyloid deposition, cell adhesion and neurite outgrowth. A number of peptide and protein ligands for the site have been identified. In this review, the structure and multiple functions of the peripheral anionic site are discussed, together with its potential as a target in rational drug design for the development of novel and improved inhibitors and of therapeutics for the treatment of neural cancers, nerve regeneration and neurodegenerative disorders such as Alzheimer's disease.

Implantable transvenous cardioverter-defibrillators

BACKGROUND

Implantable transvenous cardioverter-defibrillators offer a significant opportunity to decrease procedural morbidity and medical costs in the care of patients with life-threatening ventricular arrhythmias who otherwise would have required a sternotomy or thoracotomy for device insertion. The purpose of this study was to examine prospectively the safety, efficacy, and limitations associated with the use of a transvenously implanted, tiered-therapy cardioverter-defibrillator with antitachycardia pacing function in a consecutive population of 84 ventricular fibrillation (VF) and sustained ventricular tachycardia (VT) survivors.

METHODS AND RESULTS

The index arrhythmia promoting transvenous cardioverter-defibrillator implantation was VF in 41 patients, VT in 27, and both VF and VT in 16. In each patient, transvenous defibrillation via a coronary sinus, a right ventricular, a superior vena caval, and/or a subcutaneous chest patch lead system was attempted. The pulsing methods used include two-electrode single-pathway pulsing or three-electrode dual-pathway simultaneous or sequential pulsing. A transvenous cardioverter-defibrillator was inserted if the defibrillation threshold (DFT) was < or = 20 J. Successful implantation of a transvenous cardioverter-defibrillator was possible in 80 of 84 (95%) patients. The mean implant DFT was 10.9 +/- 4.8 J. After cardioverter-defibrillator implantation, all patients were extubated in the operating room and sent to a standard telemetry ward for monitoring. No patient suffered a postoperative pulmonary complication or perioperative flurry of cardiac arrhythmias. Postoperative complications included lead dislodgments in eight, transient long thoracic nerve injury in one, asymptomatic left subclavian vein occlusion in two, asymptomatic small pericardial effusion in one, subcutaneous patch pocket hematomas in four, pulse generator pocket infection in one, and lead fracture in one. As experience was gained with the procedure, it was routine to discharge patients 3 days after surgery. The mean hospital stay was 6.0 +/- 2.4 days. Upon discharge, all patients returned to their prehospital activities including those with complications except for the patient with a pocket infection, who required intravenous antibiotic therapy. Patient survival using an intention-to-treat analysis was 98% over an 11 +/- 7-month follow-up period. During this time period, 31 of the 80 patients (39%) with transvenous lead systems were successfully treated by their device for sustained VT or VF. Antitachycardia pacing was used in 424 episodes of monomorphic VT and was successful in 371 (88%). All episodes of VF were aborted by the device. Antiarrhythmic drugs were used after device implantation in only eight of 80 patients (10%).

CONCLUSIONS

Transvenous cardioverter-defibrillator implantation is practical in most candidates. Implant DFTs are usually low, surgical morbidity and postoperative complications are modest, therapy of VT and VF is efficient, and survival is excellent.

A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans

Biphasic waveforms have been suggested as a superior waveform for ventricular defibrillation. To test this premise, a prospective randomized intraoperative evaluation of defibrillation efficacy of monophasic and biphasic waveform pulses was performed in 22 survivors of out of hospital ventricular fibrillation who were undergoing cardiac surgery for implantation of an automatic defibrillator. The initial waveform used in a patient for defibrillation testing, either monophasic or biphasic, was randomly selected. Subsequently, each patient served as his or her own control for defibrillation testing of the other waveform. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate ventricular fibrillation with a single discharge delivered 10 s after initiation of an episode of ventricular fibrillation induced with alternating current. Each defibrillation pulse was recorded oscilloscopically, and defibrillation pulse voltage, current, resistance and stored energy were measured. Fifteen (68%) of the 22 patients had a lower defibrillation threshold with the biphasic pulse, 3 (14%) had a lower threshold with the monophasic pulse and 4 (18%) had equal defibrillation thresholds (within 1.0 J) regardless of waveform. The mean leading edge defibrillation threshold voltage was 317 +/- 105 V when the monophasic pulse was used and 267 +/- 102 V (16% less) when the biphasic pulse was used (p = 0.008). Mean leading edge defibrillation threshold current was 7.9 +/- 3.7 A when the monophasic pulse was used and 6.8 +/- 3.8 A (14% less) when the biphasic pulse was used (p = 0.051).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain tissue sodium concentration in multiple sclerosis: a sodium imaging study at 3 tesla

Neuro-axonal degeneration occurs progressively from the onset of multiple sclerosis and is thought to be a significant cause of increasing clinical disability. Several histopathological studies of multiple sclerosis and experimental autoimmune encephalomyelitis have shown that the accumulation of sodium in axons can promote reverse action of the sodium/calcium exchanger that, in turn, leads to a lethal overload in intra-axonal calcium. We hypothesized that sodium magnetic resonance imaging would provide an indicator of cellular and metabolic integrity and ion homeostasis in patients with multiple sclerosis. Using a three-dimensional radial gradient-echo sequence with short echo time, we performed sodium magnetic resonance imaging at 3 T in 17 patients with relapsing-remitting multiple sclerosis and in 13 normal subjects. The absolute total tissue sodium concentration was measured in lesions and in several areas of normal-appearing white and grey matter in patients, and corresponding areas of white and grey matter in controls. A mixed model analysis of covariance was performed to compare regional tissue sodium concentration levels in patients and controls. Spearman correlations were used to determine the association of regional tissue sodium concentration levels in T(2)- and T(1)-weighted lesions with measures of normalized whole brain and grey and white matter volumes, and with expanded disability status scale scores. In patients, tissue sodium concentration levels were found to be elevated in acute and chronic lesions compared to areas of normal-appearing white matter (P < 0.0001). The tissue sodium concentration levels in areas of normal-appearing white matter were significantly higher than those in corresponding white matter regions in healthy controls (P < 0.0001). The tissue sodium concentration value averaged over lesions and over regions of normal-appearing white and grey matter was positively associated with T(2)-weighted (P < or = 0.001 for all) and T(1)-weighted (P < or = 0.006 for all) lesion volumes. In patients, only the tissue sodium concentration value averaged over regions of normal-appearing grey matter was negatively associated with the normalized grey matter volume (P = 0.0009). Finally, the expanded disability status scale score showed a mild, positive association with the mean tissue sodium concentration value in chronic lesions (P = 0.002), in regions of normal-appearing white matter (P = 0.004) and normal-appearing grey matter (P = 0.002). This study shows the feasibility of using in vivo sodium magnetic resonance imaging at 3 T in patients with multiple sclerosis. Our findings suggest that the abnormal values of the tissue sodium concentration in patients with relapsing-remitting multiple sclerosis might reflect changes in cellular composition of the lesions and/or changes in cellular and metabolic integrity. Sodium magnetic resonance imaging has the potential to provide insight into the pathophysiological mechanisms of tissue injury when correlation with histopathology becomes available.