Hemodynamic flow improves rat hepatocyte morphology, function, and metabolic activity in vitro.

In vitro primary hepatocyte systems typically elicit drug induction and toxicity responses at concentrations much higher than corresponding in vivo or clinical plasma C(max) levels, contributing to poor in vitro-in vivo correlations. This may be partly due to the absence of physiological parameters that maintain metabolic phenotype in vivo. We hypothesized that restoring hemodynamics and media transport would improve hepatocyte architecture and metabolic function in vitro compared with nonflow cultures. Rat hepatocytes were cultured for 2 wk either in nonflow collagen gel sandwiches with 48-h media changes or under controlled hemodynamics mimicking sinusoidal circulation within a perfused Transwell device. Phenotypic, functional, and metabolic parameters were assessed at multiple times. Hepatocytes in the devices exhibited polarized morphology, retention of differentiation markers [E-cadherin and hepatocyte nuclear factor-4α (HNF-4α)], the canalicular transporter [multidrug-resistant protein-2 (Mrp-2)], and significantly higher levels of liver function compared with nonflow cultures over 2 wk (albumin ~4-fold and urea ~5-fold). Gene expression of cytochrome P450 (CYP) enzymes was significantly higher (fold increase over nonflow: CYP1A1: 53.5 ± 10.3; CYP1A2: 64.0 ± 15.1; CYP2B1: 15.2 ± 2.9; CYP2B2: 2.7 ± 0.8; CYP3A2: 4.0 ± 1.4) and translated to significantly higher basal enzyme activity (device vs. nonflow: CYP1A: 6.26 ± 2.41 vs. 0.42 ± 0.015; CYP1B: 3.47 ± 1.66 vs. 0.4 ± 0.09; CYP3A: 11.65 ± 4.70 vs. 2.43 ± 0.56) while retaining inducibility by 3-methylcholanthrene and dexamethasone (fold increase over DMSO: CYP1A = 27.33 and CYP3A = 4.94). These responses were observed at concentrations closer to plasma levels documented in vivo in rats. The retention of in vivo-like hepatocyte phenotype and metabolic function coupled with drug response at more physiological concentrations emphasizes the importance of restoring in vivo physiological transport parameters in vitro.

Periocular injection of an adenoviral vector encoding pigment epithelium-derived factor inhibits choroidal neovascularization.

Gene transfer provides an exciting new approach for the treatment of retinal and choroidal diseases. Two areas of concern are the potential for vector-related toxicity and uncertainties associated with prolonged transgene expression. One way to address these concerns for transfer of genes encoding secreted proteins is to transduce cells on the outside of the eye, provided the gene product can gain access to the eye and have the desired effect. In this study, we investigated the feasibility of this approach. Periocular injection of an adenoviral vector encoding beta-galactosidase (AdLacZ.10) resulted in LacZ-stained cells throughout the orbit and around the eye. Compared to periocular injection of 5 x 10(9) particles of control vector, periocular injection of 5 x 10(9) or 1 x 10(9) particles of an adenoviral vector expressing pigment epithelium-derived factor (PEDF) regulated by a CMV promoter (AdPEDF.11) resulted in significantly elevated intraocular levels of PEDF and suppression of choroidal neovascularization. Periocularly injected recombinant PEDF was also found to diffuse through the sclera into the eye. Although similar experiments are needed in an animal with a human-sized eye, these data suggest that periocular gene transfer deserves consideration for the treatment of choroidal diseases.

Multicenter study of principles-based waveforms for external defibrillation.

STUDY OBJECTIVE: The efficacy of a shock waveform for external defibrillation depends on the waveform characteristics. Recently, design principles based on cardiac electrophysiology have been developed to determine optimal waveform characteristics. The objective of this clinical trial was to evaluate the efficacy of principles-based monophasic and biphasic waveforms for external defibrillation. METHODS: A prospective, randomized, blinded, multicenter study of 118 patients undergoing electrophysiologic testing or receiving an implantable defibrillator was conducted. Ventricular fibrillation was induced, and defibrillation was attempted in each patient with a biphasic and a monophasic waveform. Patients were randomly placed into 2 groups: group 1 received shocks of escalating energy, and group 2 received only high-energy shocks. RESULTS: The biphasic waveform achieved a first-shock success rate of 100% in group 1 (95% confidence interval [CI] 95.1% to 100%) and group 2 (95% CI 94.6% to 100%), with average delivered energies of 201+/-17 J and 295+/-28 J, respectively. The monophasic waveform demonstrated a 96.7% (95% CI 89.1% to 100%) first-shock success rate and average delivered energy of 215+/-12 J for group 1 and a 98.2% (95% CI 91.7% to 100%) first-shock success rate and average delivered energy of 352+/-13 J for group 2. CONCLUSION: Using principles of electrophysiology, it is possible to design both biphasic and monophasic waveforms for external defibrillation that achieve a high first-shock efficacy.

Maintenance of sinus rhythm with oral d,l-sotalol therapy in patients with symptomatic atrial fibrillation and/or atrial flutter. d,l-Sotalol Atrial Fibrillation/Flutter Study Group.

Currently d,l-sotalol is widely used to prevent recurrence of atrial fibrillation and/or atrial flutter, although a randomized dose-response study has not previously been conducted to guide therapy for this indication. This study summarizes findings of a double-blind, placebo-controlled, multicenter, randomized trial evaluating the efficacy, safety, and dose-response relation of 3 fixed doses of d,l-sotalol (80, 120, and 160 mg twice daily) for the maintenance of sinus rhythm in 253 patients with atrial fibrillation and/or atrial flutter. All patients were in sinus rhythm at randomization. Treatment (69 patients on placebo, 59 on 80 mg, 63 on 120 mg, and 62 on 160 mg given twice daily) was continued for 12 months or until documented recurrence of symptomatic atrial fibrillation and/or flutter. Transtelephonic electrocardiographic monitoring was used to detect symptomatic recurrences. Demographic characteristics were not different in the 4 groups. Structural heart disease was present in 57% of patients. Patients with a history of heart failure were excluded. The time from randomization to symptomatic arrhythmia recurrence was significantly longer in the 2 higher d,l-sotalol dose groups than in the placebo group. The median times to recurrence were 27, 106, 229, and 175 days for the placebo, 80, 120, and 160 mg groups, respectively. There were no deaths or cases of torsade de pointes, sustained ventricular tachycardia, or ventricular fibrillation reported. Thus, d,l-sotalol appeared to be both safe and effective in maintaining sinus rhythm in patients with symptomatic atrial fibrillation and/or flutter. Further, the 120-mg twice daily dose appeared to provide the most favorable benefit and/or risk.

Separation of ventricular tachycardia from sinus rhythm using a practical, real-time template matching computer system.

Template matching morphology analysis of the intraventricular electrogram (IVEG) has been proposed for inclusion in implantable cardioverter defibrillators (ICDs) to reduce the number of false ventricular tachyarrhythmia detections caused by rate overlap between ventricular tachycardia (VT) and sinus tachycardia and/or supraventricular tachycardia. Template matching techniques have been developed that reduce the computational complexity while preserving the perceived important aspects of electrogram amplitude and baseline independence found in such computationally unsolved methods as correlation waveform analysis (CWA). These methods have been shown to work as well as CWA for separation of VT, however, they have not been proven in real-time on a system that incorporates many of the constraints of present day ICDs. The present study was undertaken with two purposes: (1) to determine if real-time IVEG template matching analysis on an ICD sensing emulator was accurate in separating VT from sinus rhythm (SR) electrograms; and (2) to compare amplitude normalized area of difference (NAD) with signature analysis (SIG), a new, computationally less expensive technique that normalizes for amplitude variation within the expected physiological level of variability. In this study, IVEGs, obtained from 16 patients who underwent electrophysiological study (EPS) for evaluation of sustained ventricular arrhythmia, were digitized to 250 Hz with 6-bit quantization after filtering (16-44 Hz) and differentiation. After an SR template was selected and periodically updated, it was compared to subsequent IVEGs using NAD and SIG. In general, SIG calculates the fraction of samples occurring outside template window boundaries. Eleven-beat running medians from beat-by-beat NAD and SIG results were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Mexiletine: pharmacology and therapeutic use.

Mexiletine is a Class IB antiarrhythmic which has basic and clinical electrophysiologic properties similar to lidocaine. Like other Class I antiarrhythmic agents, mexiletine blocks the rapid inward sodium current responsible for phase 0 of the action potential. It has been noted in the clinical electrophysiology laboratory to have minimal effect on sinus node function and AV nodal and His-Purkinje system conduction. Pharmacokinetic studies have shown that oral absorption is rapid with bioavailability of 80-90%. Mexiletine is predominantly metabolized by the liver with elimination half-life of 9 to 12 hours. The antiarrhythmic effects of the primary drug's metabolites remain to be defined. Hemodynamic studies have shown mexiletine to have a lesser negative inotropic effect than procainamide or disopyramide. Although mexiletine as a single agent successfully suppresses 60 to 80% of spontaneous ventricular arrhythmias, it has lower efficacy in suppression of induced ventricular arrhythmias. Multiple studies have shown that as monotherapy mexiletine is effective in preventing the induction of ventricular tachycardia in approximately 20% of patients. When used in combination with a Class IA antiarrhythmic drug for suppression of induced ventricular arrhythmias, multiple investigators have reported greater efficacy. Neurological side effects (tremor, dizziness, memory loss) occur in approximately 10% of patients while gastrointestinal side effects (nausea, anorexia, gastric irritation) occur in up to 40% of patients. Proarrhythmia or other serious toxicity from the drug is uncommon.

External cardiac programmed stimulation for noninvasive termination of sustained supraventricular and ventricular tachycardia.

To examine the feasibility of using a noninvasive temporary pacemaker for termination of well-tolerated supraventricular (SVT) and ventricular tachycardia (VT), a standard external demand pacemaker was modified to allow stimulation with single or multiple extrastimuli and overdrive pacing. To evaluate the efficacy, safety and tolerance of external cardiac programmed stimulation, a standard arrhythmia termination protocol was used in 223 tachycardias in 22 patients. The technique of external cardiac programmed stimulation was used in 209 episodes of SVT in 13 patients. It terminated 95% of the episodes with success in 19 of 20 episodes of atrioventricular nodal reentrant tachycardia and 179 of 189 episodes of atrioventricular reciprocating tachycardia. Of 198 episodes of SVT terminated by the technique 168 (85%) were terminated by a single extrastimulus and 28 (14%) by double extrastimuli. Only 2 episodes of SVT required overdrive pacing for termination. External cardiac programmed stimulation did not result in atrial fibrillation or arrhythmia acceleration. Of 14 episodes of sustained monomorphic VT 5 were terminated by external cardiac programmed stimulation. One tachycardia was terminated by a single extrastimulus, 1 by double extrastimuli and 3 by overdrive pacing. Arrhythmia acceleration occurred once and was terminated by endocardial pacing. On 27 separate occasions patient evaluation of maximal discomfort included 4 ratings of mild, 10 of moderate, 11 of severe and 2 of intolerable discomfort. External cardiac programmed stimulation is effective and safe in patients with well-tolerated sustained supraventricular or ventricular arrhythmias.

Sensitivity and specificity of programmed atrial stimulation for induction of supraventricular tachycardias.

The sensitivity and specificity of two programmed atrial stimulation protocols were studied in 92 consecutive patients undergoing electrophysiologic studies both with (35 patients) and without (57 patients) clinical supraventricular arrhythmias. Protocol I (P I) consisted of incremental atrial pacing to 2:1 atrioventricular (AV) block and a single atrial extrastimulus scanned by 10 ms decrements through diastole to the atrial effective refractory period at a single drive-cycle length. Protocol II (P II) included a second atrial extrastimulus scanned by 10 ms decrements through diastole at a single drive-cycle length with the first extrastimulus set 20 ms from the atrial effective refractory period. Rapid atrial pacing at cycle lengths of 350, 300, and 250 ms was then performed with P II. P I was employed in all patients while P II was studied in the final 48 patients only. Of the 35 patients with clinical atrial arrhythmias, 26 (74%) of their arrhythmias were induced with either P I (18/35; sensitivity = 51%) and/or P II (12/17; sensitivity = 71%). Of the 57 patients without clinical atrial arrhythmias (control group), atrial arrhythmias were induced in 11 (19%), 3 with P I (specificity 95%, 54/57) and 8 with P II (specificity 74%, 23/31). The sensitivity of P II was higher (71%), but its specificity was lower (74%) than P I (51% and 95%, respectively; p less than 0.05). The positive predictive value of P II was lower (60%) than that of P I (86%) (p less than 0.05), but the negative predictive value (82%) and predictive accuracy (73%) were comparable to those of P I (76% and 78%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitivity and specificity of the echocardiographic features of cardiac amyloidosis.

Thirty-one patients with documented cardiac amyloidosis were compared to 39 control subjects with left ventricular hypertrophy to determine specific 2-dimensional echocardiographic features of amyloid. In 16 patients, increased myocardial echogenicity was present when a single short-axis view was examined, and had a sensitivity of 63% and a specificity of 74% for the diagnosis of amyloidosis. When complete echocardiograms were reviewed (15 patients), an improved sensitivity of 87% and specificity of 81% based on increased echogenicity was seen. Increased atrial septal thickness was present in 60% of amyloid patients and no controls. The combination of increased myocardial echogenicity and increased atrial thickness was 60% sensitive and 100% specific for the diagnosis of amyloidosis. The ratio of electrocardiographic voltage (S in V1 + R in V5 or V6) to left ventricular cross-sectional area also was examined. A ratio of less than 1.5 was 82% sensitive and 83% specific for amyloid (excluding the 2 patients with left bundle branch block), but added little to the diagnosis as determined from the 2-dimensional echocardiogram.

The efficacy of full-lung tomography in the detection of early metastatic disease from melanoma.

In a prospective study, 62 patients with proved melanoma and negative chest radiographs underwent full-lung tomography. Of 109 examinations performed, 12 patients had positive findings on tomography; nine were false-positive and three were true-positive. Of the true-positive examinations, two patients already had widespread metastatic disease and one had an advanced local lesion. Clinical staging and therapy were changed in only one patient as a result of information provided by full-lung tomography. It appears from these results that full-lung tomography is of limited use in detection of metastases from melanoma in the presence of a negative chest radiograph.

Fate of oral neutralizing antacid and its effect on postprandial gastric secretion and emptying.

The fate and neutralizing efficiency of oral antacids (aluminum and magnesium hydroxides) as well as their effect on postprandial gastric function were quantified in 6 patients with duodenal ulcer disease. We employed a double-marker technique for measurement of gastric secretion and emptying and combined this with back-titration of the gastric samples and analysis of aluminum to trace the fate of antacid in the stomach and duodenum. These studies show that: (a) antacid therapy with aluminum and magnesium hydroxides significantly increases gastric secretion; (b) intragastric neutralization of gastric acid produces a significant and substantial decrease in net acid output (acid secreted minus acid neutralized), but the beneficial effects of neutralization are partially offset by incomplete intragastric formation of aluminum trichloride; (c) most but not all of the ingested antacid is utilized in acid neutralization in the stomach (average 78.6% in our 6 patients); and (d) antacid therapy does not modify the absolute rate of postprandial gastric emptying, but increases dilution of gastric contents, expanding the intragastric volume. Thus, the fractional gastric emptying rate declines, and this, in turn, should enhance antacid utilization by delaying its emptying.

Gastric secretion and emptying after ordinary meals in duodenal ulcer.

We have studied the gastric response to an ordinary solid-liquid meal in 12 patients with active duodenal ulcer and 8 healthy volunteers. Our method employs gastric and duodenal markers to quantify acid, pepsin, and volume outputs in response to the meal, without manipulating intragastric pH. Intragastric volume, rate of gastric emptying, delivery of acid into the duodenum, and serum gastrin response were also measured simultaneously. On a separate day, peak acid output in response to betazole (1.5 mg per kg subcutaneously) was determined. Our results indicate an inappropriately prolonged gastric secretory response to meals in duodenal ulcer disease, without a concomitant increase in peak postprandial secretory rates or an increase in serum immunoreactive gastrin levels. Further, the stomach in duodenal ulcer disease did not "retain" the additional acid secreted in the later postprandial period, and abnormally high rates of acid delivery into the duodenum occurred. Our data are consistent with a dual defect in the duodenal mechanisms regulating both acid secretion and acid delivery into the duodenum.

Comparison of an H2 receptor antagonist and a neutralizing antacid on postprandial acid delivery into the duodenum in patients with duodenal ulcer.

Measurement of the postprandial rate of acid delivery into the duodenum directly assessed the efficacy of two radically different acid-reducing therapies for duodenal ulcer disease. Cimetidine, 400 mg, with an ordinary solid meal decreased the 4-hr delivery of titratable acid and hydrogen ion into the duodenum by 63 and 86%, respectively (P less than 0.01 versus control). Liquid Maalox, 30 ml, 1 and 3 hr after an identical meal reduced 4-hr delivery of acid by 47 and 74%, respectively (P less than 0.01 versus control). During the study period, the H2 receptor antagonist effected a continuous reduction in gastric acidity and the delivery of acid into the duodenum. The liquid neutralizing antacid produced a more fluctuating decrease in these parameters. However, given in these dosages, the magnitude and duration of the acid-reducing effect were similar for both treatments.

Effect of D-penicillamine on copper retention in patients with primary billiary cirrhosis.

As part of a double blind, randomized trial evaluating D-penicillamine in primary biliary cirrhosis, we monitored urinary copper excretion and hepatic copper concentration during the 1st year of therapy in 46 patients with this disease. The retention of copper in primary biliary cirrhosis was confirmed by finding abnormally high levels of standard copper measurements in almost all patients before treatment. The hepatic copper was elevated in 43 of 45 patients, the urinary copper in 42 of 46, and the ceruloplasmin in 46 of 46. Urinary copper excretion correlated with the hepatic copper concentration (r = 0.68, P less than or equal to 0.001). No significant correlation occurred between hepatic copper and ceruloplasmin. Hepatic copper concentrations greater than 400 microng per g of dry weight were found almost exclusively in patients with advanced histological disease (P less than or equal to 0.01). Therapy with D-penicillamine and a low copper diet sustained increased urinary copper excretion for 1 year in almost all patients (P less than or equal to 0.001). Among patients taking placebo, the median hepatic copper concentration increased 13 microng per g of dry weight after 1 year. In contrast, among the patients taking D-penicillamine, the median hepatic copper concentration decreased 99 microng per g of dry weight (P less than or equal to 0.02). Continued observation of this therapeutic trial may help to clarify the relationship of copper retention and liver injury in primary biliary cirrhosis.