A Critical Period of Ventricular Fibrillation More Susceptible to Defibrillation: Real-Time Waveform Analysis Using a Single ECG Lead

Previous studies have suggested that variations in the underlying ventricular fibrillation (VF) waveform may be one of the factors responsible for the probabilistic nature of defibrillation. The heart appeared to be more susceptible to defibrillation at higher absolute VF voltages (AVFV). This study investigated in an open-chest canine model (n = 8), a newly developed system that analyzed the VF waveform in real-time, instantaneously determined the time to shock, and immediately delivered a fixed low energy DC shock. A two parameter tracking technique using a running long-term and short-term AVFV average was devised to automatically identify a high voltage peak area of the VF waveform, which has been hypothesized to represent a critical period susceptible to defibrillation. Using a DC shock estimated at the 50% success level, the performance using this technique in 58 defibrillation trials was compared to the performance of the conventional method of shocking at a fixed time (random shock method) in 62 trials. Patch size, electrode location, and discharge voltage were kept constant while VF duration, transmyocardial resistance (TMR), energy delivered, and AVFV at the point of shock were measured. Shock energy and current, TMR, and VF duration were similar with both shock methods. A significantly higher AVFV was observed for trials performed with the peak shock method (0.66 ± 0.02 mV) as compared to trials performed with the random shock method (0.25 ± 0.09 mV) (P < 0.003). Using lead II as the only sensing lead, the success rate was increased in 6 of 8 dogs (75%) with the new method. One animal showed identical performance, and one animal a worse performance. The overall increase in success rate was 24% using a single ECG lead (range 0%-100%; P < 0.04). Our data document that using this algorithm a period of high VF voltage can be detected in realtime. The improved success in the majority of animals supports the hypothesis that a critical period susceptible to defibrillation exists during VF. However, the high AVFV detected using a single ECG lead did not translate to an improved success rate in all animals. This suggests that other factors in addition to the VF voltage measured on a single lead of the ECG are important in characterizing this critical period.     

Variability of the pattern electroretinogram

Conflicting results have been obtained concerning the parametric properties of the pattern electroretinogram. These discrepancies may be due to the large amount of variability inherent in recording amplitudes. We have found the variability within a single stimulus condition to be so large (ranging from 30% to 67% of the mean value) that it could mask any underlying spatial frequency tuning. Changing the stimulus conditions failed to significantly reduce the observed variability, although changing recording conditions produced some reduction. The use of a narrower rejection band, a greater number of sweeps, and placement of the reference electrode on the ipsilateral ear (as opposed to the ipsilateral temple) combined to decrease variability of the pattern electroretinogram within a single recording session; however, intersession variability remained high. Therefore one must be careful in evaluating data from this technique, and caution is advised in its clinical use.     

Monoclonal antibodies to intermediate filament proteins: Diagnostic specificity in orbital pathology

Intermediate filaments derived from different cell types are antigenically distinct. Monoclonal antibodies to human intermediate filament proteins can, therefore, be used as tissue-specific reagents capable of distinguishing cell type in poorly differentiated neoplasms. We report a case demonstrating the specificity of antiintermediate filament protein antibodies in establishing a difficult orbital diagnosis of esthesioneuroblastoma.     

Influence of individually estimated portion size on the assessment of nutritional risk in colorectal cancer in Portugal

We evaluated the influence of individually estimated portion sizes on the estimate of nutrient related risk of colorectal cancer, using data from a Portuguese hospital based case-control study on diet and colorectal cancer. A total of 100 patients with colorectal adenocarcinoma (aged 15-92 years) and 211 controls (aged 36-89 years) were included. Two data sets were created for nutrient analysis, the first one allowed estimates of food intake using data on portion size as collected with visual aids during the interview. The second estimate substituted respondents' estimate with a standard portion size, as used in the semi-quantitative (SQ) food frequency approach. The two analytic approaches yielded similar energy and nutrient intakes in cases and controls. The percent range of concordance is acceptable, in the same quartile varying from 44 to 82% (mean: 56%) and very good in the same or adjacent (+/-1) quartile (mean: 91%, range: 85-97%). The two estimates lead to a similar pattern of multivariate odd's ratio, however the SQ estimates resulted in more significant findings. We conclude that little extra information is gained by including individual portion size information when assessing diet-related risk of colorectal cancer.     

修饰电极技术在维生素K_1含量测定中的应用

日的:寻找一种测定溶液中维生素K,含量的新方法、方法:由修饰玻碳电极为工作电极的三电极体系,用锁相交流溶出伏安法进行测定。结果:峰电流(ip)与维生素K1的浓度(c)在7.21 X 10-7g/ml～8.11×l0-6 g/ml范围内呈现良好的线性关系,检出限为7.8×10-8g/ml。结论:该方法与其它方法相比,简便、快捷,结果令人满意     

Epidermolysis bullosa herpetiformis (Dowling-Meara type) exhibits ultrastructural derangement of tonofilaments and desmosomes

Ultrastructural and immunohistochemical studies of clinically intact skin obtained from three severe neonatal cases of epidermolysis bullosa herpetiformis (Dowling-Meara type) demonstrated disorders in the assembly of keratin intermediate filaments and desmosomes of the keratinocytes. During mitosis, K5- and K14-positive and K1- and K10-negative tonofilaments were disrupted and formed spherical bodies associated with intracytoplasmic desmosomes by invagination of the desmosomes and the adjacent plasma membrane. During the invagination process, destructive changes in the internalized membrane were noted. These were accompanied by gradual loss of reactivity with a monoclonal antibody ZK31, which detected plasma membrane adjacent to the attachment plaques of desmosomes. However, the reactivity of the attachment plaques of the internalized desmosomes for desmoplakins and desmoglein did not decline during the process of internalization. In the suprabasal layers of the epidermis, filamentous substructures and K1 and K10 appeared at the periphery of the spherical bodies. Simultaneously, the desmosomes that were sparsely located in the lower epidermis, increased in number as cell differentiation progressed. Thus, the keratinocytes attained an almost normal appearance with respect to tonofilaments and desmosomes by the time they reached the upper layer of the epidermis. These findings may be relevant to the mechanism responsible for the clinical appearance of the herpetiform blisters in epidermolysis bullosa herpetiformis, which are also characterized by spontaneous involution during childhood or when exposed to high ambient temperatures.Part of this work was presented at the annual meeting of the Japanese Society for Ultrastructural Cutaneous Biology, 12 May 1990, Tokushima, Japan, at the joint meeting of the Society for Cutaneous Ultrastructure Research and the Japanese Society for Ultrastructural Cutaneous Biology, 23–25 May 1991, Vienna, Austria, and at the sixth Conference on Disorders of Keratinization, 6 July 1991, Tokyo, Japan     

A Pilot Study: Defibrillation Thresholds in Dogs are Similar with Isoflurane, Halothane, and Pentobarbital

The objective of this pilot study was to determine if three common anesthetic drugs have differing effects on the measurement of defibrillation thresholds (DFT) in dogs. The drugs compared were pentobarbital, isoflurane, and halothane. We used six dogs, which were surgically instrumented, in a chronic study design. Each dog had two internal defibrillation patches placed on its heart, which were used to deliver the defibrillation energy. DFT was determined while each dog was anesthetized under each of the listed drugs in a crossover design. This pilot study suggests that differences in DFT due to the anesthetic drugs is not significant in studies with low numbers of animals (halothane 14.5 ± 1.0, isoflurane 14.2 ± 1.0, pentobarbital 12.8 ± 1.0;P = NS; mean ± SE). Tbe variation in DFT between individual animals is much larger than the difference in DFT due to the drugs.     

Alpha and gamma motoneurons in the peroneal nuclei of the cat spinal cord: an ultrastructural study.

The aim of the present study was to investigate whether ultrastructural features can be used as a guide to identify alpha- and gamma-motoneurons among the intermediate-size neurons of the peroneal motor nuclei. The peroneus brevis and peroneus tertius muscles of adult cats were injected with horseradish peroxidase, and motoneurons labeled by retrograde axonal transport were examined by electron microscopy. In both nuclei, the distributions of cell-body diameters, measured in the light microscope, were bimodal covering the range of 28-84 microns, with a trough around 50 microns. The sample of 25 motoneurons selected for the ultrastructural study included not only large (presumed alpha) and small (presumed gamma) neurons but also intermediate-size cell bodies with diameters in the 40-60 microns range. For each motoneuron, 2-5 profiles were reconstructed from ultrathin sections taken at 6-8 microns intervals. Synaptic boutons were counted and their lengths of apposition were measured. On the basis of three criteria, namely: (1) bouton types present on the membrane, (2) percentage of membrane length covered by synapses, and (3) the aspect of the nucleolus, all the examined motoneurons, including those with intermediate sizes, fell into one of two categories. Fourteen motoneurons, with cell-body diameters in a range of 55-84 microns, were contacted by all types of boutons (mainly S-type with spherical vesicles, F-type with flattened vesicles, and C-type with subsynaptic cistern); the synaptic covering of the somatic membrane was over 40% and the nucleus contained a vacuolated nucleolus. These were considered alpha-motoneurons. Eleven motoneurons, with only S and F boutons, a synaptic covering under 30%, a compact nucleolus and a cell-body diameter ranging between 28 and 50 microns, were considered gamma-motoneurons. No other combination of the three criteria was observed. These results show that unequivocal distinction of alpha- and gamma-motoneurons is possible in the peroneal nuclei, on the basis of morphological differences independent of cell-body size.     

Direct injections of calcitriol into enlarged parathyroid glands in chronic dialysis patients with severe parathyroid hyperfunction

Summary: Severe secondary hyperparathyroidism in chronic dialysis patients has been recently treated by supraphysiological concentration of calcitriol achieved through pulse therapy. However, there are many patients resistant to this therapy, who usually have larger parathyroid gland(s). to overcome this resistance, calcitriol was injected directly into the enlarged glands under ultrasonographic guidance. We injected 70–90% of the calculated gland volume of calcitriol solution (1 μg/mL) into the glands of 7 patients three times per week for 2 weeks. the parathyroid hormone (PTH) levels decreased significantly after 2 weeks of direct injections of calcitriol. Following a further 4 weeks of calcitriol pulse therapy, PTH levels remained suppressed and serum alkaline phosphatase activity and the volume of parathyroid glands also decreased. During the long-term follow up, five patients remained well controlled with calcitriol pulse therapy, while two patients needed ethanol injections to control hyperparathyroidism. Although we could not completely rule out a toxic effect of the vehicle, direct injection of calcitriol into parathyroid glands may be another treatment option for chronic dialysis patients. Our data further support the important role of resistance of parathyroid cells to calcitriol in the pathogenesis of parathyroid hyper function in uraemic patients.     

Optimization of self-reference thermometry using complex field estimation.

Referenceless, or self-reference, thermometry is a technique for mapping temperature differences in the region of interest (ROI) using the baseline phase estimated by extrapolating the field in the surrounding region for estimation (RFE) and subtracting the estimated baseline from the measured field. In the present work a self-reference technique based on complex field estimation using 2D polynomials comprising complex-valued coefficients was proposed and optimized. Numerical simulations with a Gaussian-profiled phase distribution demonstrated that the ROI radius had to be 2.3-2.5 times the standard deviation (SD) of the Gaussian function in order to keep the error below 8% of the peak phase change. The area ratio between the ROI and the RFE had to be larger than 2.0 to maintain the error level. Based on the simulations, and phantom and volunteer experiments, the complex-based method with independently optimized polynomial orders for the two spatial dimensions was compared with the phase-based method using the similar-order optimization strategy. The complex-based method appeared to be useful when phase unwrapping was not removed. Otherwise, the phase-based method yielded equivalent results with less polynomial orders.