Signed value of monophasic action potential duration difference. A useful measure in evaluation of dispersion of repolarization in patients with ventricular arrhythmias

AIMS: To evaluate the usefulness of the signed value of monophasic action potential duration difference in analysing the cause of dispersion of ventricular repolarization. METHODS AND RESULTS: Monophasic action potentials were simultaneously recorded from the right ventricular apex and outflow tract during programmed stimulation in 36 patients with ventricular arrhythmias. The time difference between the ends of repolarization on the two monophasic action potentials was used as a measure of the dispersion of ventricular repolarization, and the signed value of the monophasic action potential duration difference was used to specify the contributions of the activation time difference and the monophasic action potential duration difference to the dispersion of ventricular repolarization. During right ventricular pacing, single and double programmed stimulation and at the induction of ventricular arrhythmias, the dispersion of ventricular repolarization and the signed value of monophasic action potential duration difference were markedly greater in the 11 patients with polymorphic ventricular tachycardia/ventricular fibrillation induced than in the 13 patients with monomorphic ventricular tachycardia induced, and in the 10 patients with clinical polymorphic ventricular tachycardia/ventricular fibrillation/cardiac arrest than in the 12 patients with sustained monomorphic ventricular tachycardia. This disclosed that the increased dispersion of ventricular repolarization was caused by increases in both the activation time difference and the monophasic action potential duration difference in the former, but mainly by an increased activation time difference in the latter groups. CONCLUSION: The signed value of monophasic action potential duration difference can specify whether an increased dispersion of ventricular repolarization is caused by inhomogeneous repolarization, inhomogeneous conduction or both, and thereby it is useful in study of the mechanism of ventricular arrhythmias.     

Recovery of the human compound action potential following prior stimulation

The recovery from prior stimulation of the compound action potential (CAP) was measured using a forward masking stimulus paradigm in four normal-hearing, human subjects. The CAP was recorded using a wick electrode placed on the tympanic membrane. The effects of a 4000-Hz, 97-dB SPL conditioning stimulus on CAP amplitude in response to a 4000-Hz probe were measured as a function of conditioner-probe interval for three probe levels. The normalized probe response amplitude was completely recovered to the control values at an average conditioner-probe interval of 1359 ms, similar to that observed in chinchilla (Relkin, E.M., Doucet, J.R., Sterns, A., 1995. Recovery of the compound action potential following prior stimulation: evidence for a slow component that reflects recovery of low spontaneous-rate auditory neurons, Hear. Res. 83, 183-189). The present results are interpreted as a consequence of the slow recovery of low spontaneous-rate (SR), high threshold neurons from prior stimulation (Relkin, E.M., Doucet, J.R., 1991. Recovery from prior stimulation. I: Relationship to spontaneous firing rates of primary auditory neurons. Hear. Res. 55, 215-222) and may provide indirect physiological evidence for the existence of a class of low-SR auditory neurons in humans.     

Secondary structure of the DNA-binding domain of the c-Myb oncoprotein in solution. A multidimensional double and triple heteronuclear NMR study

Euglycemic hyperinsulinemia evokes both sympathetic activation and vasodilation in skeletal muscle, but the mechanism remains unknown. To determine whether insulin per se or insulin-induced stimulation of carbohydrate metabolism is the main excitatory stimulus, we performed, in six healthy lean subjects, simultaneous microneurographic recordings of muscle sympathetic nerve activity, plethysmographic measurements of calf blood flow, and calorimetric determinations of carbohydrate oxidation rate. Measurements were made during 2 h of: (a) insulin/glucose infusion (hyperinsulinemic [6 pmol/kg per min] euglycemic clamp), (b) exogenous glucose infusion at a rate matched to that attained during protocol a, and (c) exogenous fructose infusion at the same rate as for glucose infusion in protocol b. For a comparable rise in carbohydrate oxidation, insulin/glucose infusion that resulted in twofold greater increases in plasma insulin concentrations than did glucose infusion alone, evoked twofold greater increases in both muscle sympathetic nerve activity and calf blood flow. Fructose infusion, which increased carbohydrate oxidation comparably, but had only a minor effect on insulinemia, did not stimulate either muscle sympathetic nerve activity or calf blood flow. These observations suggest that in humans hyperinsulinemia per se, rather than insulin-induced stimulation of carbohydrate metabolism, is the main mechanism that triggers both sympathetic activation and vasodilation in skeletal muscle.     

Neonatal encephalopathy following fetal distress. A clinical and electroencephalographic study

Twenty-one neonates of over 36 weeks' gestation suffered perinatal asphyxia but not chronic hypoxia. Three clinical stages of postanoxic encephalopathy were distinguished. Stage 1 lasted less than 24 hours and was characterized by hyperalertness, uninhibited Moro and stretch reflexes, sympathetic effects, and a normal electroencephalogram. Stage 2 was marked by obtundation, hypotonia, strong distal flexion, and multifocal seizures. The EEG showed a periodic pattern sometimes preceded by continuous delta activity. Infants in stage 3 were stuporous, flaccid, and brain stem and autonomic functions were suppressed. The EEG was isopotential or had infrequent periodic discharges. Infants who did not enter stage 3 and who had signs of stage 2 for less than five days appeared normal in later infancy. Persistence of stage 2 for more than seven days or failure of the EEG to revert to normal was associated with later neurologic impairment or death.     

Mandibular fractures following third molar extraction. A retrospective clinical and radiological study

Health care workers (HCW) are at risk of occupationally acquiring Mycobacterium tuberculosis (TB) infection. The Centers for Disease Control and Prevention has published guidelines for health care facilities to protect HCW. One of the recommended elements is TB infection surveillance among HCW using purified protein derivative (PPD) skin testing and analysis of the data by occupational group and work location to determine areas of increased risk of infection. At the military medical center (MMC) we studied, occupational groups with statistically significant (p < 0.05) above-average PPD conversion risk (> 1.1%/year) included respiratory therapists (15.6%/year), nursing technicians (2.3%/year), and military personnel (1.6%/year). Maintenance and engineering workers (2.6%/year), food service workers (2.5%/year), laboratory workers (2.0%/year), custodial workers (1.8%/year), and practical nurses (1.7%/year) had above-average, but not statistically significant, risk. The fourth floor of the MMC had 39% (21/54) of the converters. The surveillance program also uncovered 235 individuals who had not completed adequate prophylactic therapy, and a case of active TB in a laboratory worker.     

Thrombosis following hip arthroplasty. A study using phlebography and 125I-fibrinogen test

The rate of incidence and morphology of metastases in 284 Fallopian tubes from 148 patients with primary uterine corpus cancer have been investigated. In 44 patients metastases were discovered in inner organs, of which in 17 (11.5% patients) in 23 oviducts. In 10 of these patients the Fallopian tubes were the only localization of metastases. Macroscopical alterations in the form of thickening and condensation, tumor nodules on the surface of the affected oviducts were discovered in 7 cases. In the remainder no macroscopical changes have been noted. There predominated lymphogenic metastases, in a smaller number of cases there were implantation and lymphogeno-implantation type metastases, localized mostly in the ampullary regions of the oviducts. More often, one could observe involvement by lymphogenic metastases of the subserosal layers together with muscular tissue, less frequently of mucosal layers, and total involvement of all layers of the wall of Fallopian tubes in the form of single or multicentric tumor nests, or diffuse tumor infiltration of tissues of the oviduct wall. Implantation metastases in the form of micronodules, multicellular agglomerates were discovered on the serosa more often than on the mucosa of Fallopian tubes. Secondary oviduct carcinomas differ from primary ones by their histological structure and character of growth. The Fallopian tubes play an essential role in the dissemination of metastases in the presence of primary uterine corpus carcinoma.     

Hysterical blindness: A case report and study using a modern psychophysical technique.

Investigated a 16-yr-old girl with constricted tubular visual fields and a presumptive diagnosis of hysterical blindness, to determine if she could see in the claimed blind field. Using a modified Goldmann perimeter and 2-alternative forced-choice procedure, evidence was obtained strongly suggesting sight where the S claimed she was blind. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of double and triple lesions of the cat's limbic system on subsequent learning behavior.

Investigated the effects of multiple lesions of the chain-linked subicular cortex, mamillary bodies, and anterior thalamus on the acquisition of a visual reversal and an active 2-way avoidance task by 45 cats. Compared with controls, Ss with lesions of the anterior thalamus and the mamillary bodies (Group AT/MM), of the anterior thalamus and the subiculum (Group AT/SUB), or of the mamillary bodies and the subiculum (Group MM/SUB) were strongly impaired in acquiring the reversal task; Ss with lesions of all 3 structures (Group AT/MM/SUB) were unimpaired. Similarly, in the active avoidance task, 2 of the 3 groups with double lesions (MM/SUB and AT/SUB) were impaired, but Groups AT/MM and AT/MM/SUB were not, compared with the control group. It is suggested that lesion-induced shifts possibly act on intact cortical and/or thalamic structures that, prior to massive limbic lesion, remained inhibited or otherwise suppressed. It is assumed that the influence of 1 of the 3 core regions of the modified Papez-circuit is sufficient for inhibiting the action of such structures, which, following a complete lesion of the system, may control essential parts of the behaviors tested. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A clinical study of hair removal using the long-pulsed ruby laser

BACKGROUND: Laser hair removal is rapidly becoming a widely used modality. Clinical studies are needed to assess these hair removal systems. The long-pulsed ruby laser is one such modality for the removal of unwanted hair. OBJECTIVES: To evaluate the efficacy of the long-pulsed ruby laser (694 nm, 3-msec pulsewidth, 7- or 10-mm spot size) in removing unwanted hair, and to provide treatment guidelines for the proper utilization of this laser system. METHODS: Forty-eight areas of unwanted facial and body hair from 25 patients with blonde, brown, or black hair were treated with the long-pulsed ruby laser at fluences between 10 and 40 J/cm2. Hair regrowth was measured at 4 weeks after the first treatment, 4 weeks after the second treatment, 4 weeks after the third treatment, and 16 weeks after the third treatment by counting the number of terminal hairs compared with baseline pretreatment values. All complications and treatment outcomes were documented. RESULTS: The mean percent of regrowth after the first treatment was 65.5%, 41% after the second treatment, and 34% after the third treatment. Overall, regardless of skin type or targeted body region, patients who underwent three treatment sessions demonstrated an average 35% regrowth in terminal hair count compared with baseline pretreatment values 6 months after initial therapy. CONCLUSION: Long-pulsed ruby laser treatment resulted in significant hair growth delay in most cases. Repeated laser treatments produced an increased number of vellus hairs, an increase in growth delay, and a decreased percentage of hair regrowth.     

The influence of subtalar and triple arthrodesis on the tibiotalar joint. A long-term follow-up study

From 1975 to 1990 we performed subtalar or triple arthrodesis on 54 patients; 48 of them were reviewed after a mean follow-up of 10 years (6 to 15). There were 17 subtalar fusions in 14 patients and 37 triple arthrodeses in 28 patients. We assessed tibiotalar ankle function using the criteria of Mazur which gives a points score of a maximum of 100. Radiological evidence of degenerative change was graded on a scale of 0 to 4. The mean Mazur score was 85 for the subtalar fusions and 78 for the triple arthrodeses. The radiological score showed no degenerative changes in 36 feet (24 triple and 12 subtalar arthrodeses) and an increase of one grade in 14 feet (10 triple and 4 subtalar), of two grades in three feet (all triple arthrodeses) and of three grades in one foot after a subtalar arthrodesis. We found no statistically significant difference in the radiological score in unilateral fusions between feet with subtalar and triple arthrodeses and the contralateral foot. In all four feet which showed an increase in degenerative changes of two or more grades, there was an abnormality of the tibiotalar joint before the fusion operation. Of the 14 feet which showed an increase of one grade, there was a similar increase on the contralateral side in nine. Our findings show that subtalar or triple arthrodesis has little adverse influence on the function of the tibiotalar joint, even after many years.     

Effects of sympathetic stimulation on microcirculatory dynamics in patients with essential acrocyanosis. A study using mental stress

Cytokines are central to the development of effective immunity against microbial pathogens and their beneficial effects in the control of a variety of infections of man and animals are well-documented. However, it appears that cytokines may also have detrimental effects in infections by actually enhancing microbial growth. These observations emphasise the fact that many successful pathogens possess mechanisms enabling them to evade the immune response and that caution needs to be exercised in using cytokines as therapeutic agents to control infections in various human diseases.     

Simulation of cardiac activity and the ECG using a heart model with a reaction-diffusion action potential

A computerized model of the heart for the simulation of the electrical cardiac activity is described. The cardiac cells are arranged in a three-dimensional cubic lattice and their action potential is governed by modified FitzHugh-Nagumo reaction-diffusion state equations system which exhibits properties such as oscillations, variable excitability and refractoriness. The modifications of the FitzHugh-Nagumo equations system account for asymmetric action potential regarding the fast depolarization and slow repolarization rate and for rotational anisotropic propagation. An isolated cell is tested for reproduction of the strength-duration curves and restitution. The structure basic unit cell is assigned with an individual set of control parameters that creates inhomogeneity and anisotropy to simulate the various cardiac components such as pacers, muscle cells and conduction fibers. The spatial resolution of the structure is 1 mm. The collective activity of the cells generates a realistic ECG waveform that scales the simulated temporal step unit to 0.2 msec. The effective diffusion coefficient ranges between 0.055 mm2/msec to 1 mm2/msec. The propagation velocity of the myocardial activation is calculated at normal direction to the wavefront surface and values obtained are 1.17 mm/msec at the muscle cells and 2.5 mm/msec at the main conduction fibers. An ischemia is induced to verify the capability of the model to account for abnormalities. The developed model can give an insight into the local and global complex dynamics of the heart's electrical activity in the transition from normal to abnormal myocardial activity and may help to estimate the effects of myocardial properties on the ECG rhythm.     

Immunosuppressive treatment of a spontaneous inhibitor hemophilia A using cyclophosphamide, vincristine and prednisone following prior Factor VIII stimulation

A 59-year-old patient who presented with hematuria and recurrent soft tissue bleeding was found to have a factor VIII inhibitor level of 52 Bethesda units (BU)/ml and acquired hemophilia was diagnosed. After treatment with immunoglobulins (0.4 g IgG/kg per day for one week) the factor VIII inhibitor titer decreased to 12 BU/ml. Because of another episode of retroperitoneal hemorrhage, the patient was put on an immunosuppressive combination therapy which was first described by Lian et al. (1988). Our patient was infused with a factor VIII concentrate followed by cyclophosphamide, vincristine and prednisone. This regimen was repeated every 3-4 weeks. After 6 courses a further decline in the factor VIII inhibitor concentration, but no complete eradication of the autoantibody, was achieved. The factor VIII inhibitor level has remained at 2.5 BU/ml for more than 7 weeks without further bleeding episodes. The pathophysiology and treatment of acquired hemophilia are discussed.     

Guided tissue regeneration for the treatment of intraosseous defects using a biabsorbable membrane. A controlled clinical study

The aim of this controlled, clinical study was to evaluate guided tissue regeneration using a bioabsorbable membrane in periodontal intraosseous defects. Forty patients, each contributing one defect > or =4 mm in depth participated. The control group (18 individuals) received conventional flap therapy, while the test group (22 individuals) was treated using the bioabsorbable membrane, Guidor. Clinical assessments were made by one examiner, blinded with respect to treatment group, at baseline, 6 and 12 months following surgery. Baseline probing pocket depths of 7.7+/-1.4 mm in the membrane group and 7.6+/-1.9 mm in the control group were measured. Twelve month results showed a significant clinical attachment level gain in both control (1.1+/-1.8 mm), and membrane group (1.3+/-2.1 mm). Probing pocket depth reduction of 2.6+/-1.9 mm and 2.7+/-1.9 mm was observed in the respective groups. Bone sounding showed a non-significant gain of 0.4+/-1.8 mm and 0.6+/-1.4 mm at membrane and control sites, respectively. Radiographic evaluation confirmed these results. There were no significant differences found between treatment groups for any of the tested variables. Smoking had a negative effect on healing in both groups. In conclusion, clinical and radiographic results indicate that guided tissue regeneration using a bioabsorbable membrane at intraosseous defects did not predictably achieve greater clinical attachment level gain nor bone gain when compared to conventional flap therapy.     

Radiographic stereoplotting. A new technique and its application to the study of the spine

Radiographic stereoplotting is a method for taking three-dimensional measurements from a pair of x-ray films. The x-ray technique is described, as is the stereoplotter. Using this machine it is possible to locate any point within the patient and measure the distance between that point and any other point. From this information it is possible to compute areas, volumes, and angles with great accuracy, which hitherto has been impossible using noninvasive techniques. It is planned to take measurements of the spinal canal in normal backs and in patients with nonspecific back pain, in order to try to define some of these syndromes on a structural basis. It is likely that stereoplotting has some useful application in most branches of clinical medicine, since the x-ray technology is available in any diagnostic x-ray department.