Contribution of voltage-gated sodium channels to the b-wave of the mammalian flash electroretinogram

Voltage-gated sodium channels (Na(v) channels) in retinal neurons are known to contribute to the mammalian flash electroretinogram (ERG) via activity of third-order retinal neurons, i.e. amacrine and ganglion cells. This study investigated the effects of tetrodotoxin (TTX) blockade of Na(v) channels on the b-wave, an ERG wave that originates mainly from activity of second-order retinal neurons. ERGs were recorded from anaesthetized Brown Norway rats in response to brief full-field flashes presented over a range of stimulus energies, under dark-adapted conditions and in the presence of steady mesopic and photopic backgrounds. Recordings were made before and after intravitreal injection of TTX (approximately 3 microm) alone, 3-6 weeks after optic nerve transection (ONTx) to induce ganglion cell degeneration, or in combination with an ionotropic glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 200 microm) to block light-evoked activity of inner retinal, horizontal and OFF bipolar cells, or with the glutamate agonist N-methyl-D-aspartate (NMDA, 100-200 microm) to reduce light-evoked inner retinal activity. TTX reduced ERG amplitudes measured at fixed times corresponding to b-wave time to peak. Effects of TTX were seen under all background conditions, but were greatest for mesopic backgrounds. In dark-adapted retina, b-wave amplitudes were reduced only when very low stimulus energies affecting the inner retina, or very high stimulus energies were used. Loss of ganglion cells following ONTx did not affect b-wave amplitudes, and injection of TTX in eyes with ONTx reduced b-wave amplitudes by the same amount for each background condition as occurred when ganglion cells were intact, thereby eliminating a ganglion cell role in the TTX effects. Isolation of cone-driven responses by presenting test flashes after cessation of a rod-saturating conditioning flash indicated that the TTX effects were primarily on cone circuits contributing to the mixed rod-cone ERG. NMDA significantly reduced only the additional effects of TTX on the mixed rod-cone ERG observed under mesopic conditions, implicating inner retinal involvement in those effects. After pharmacological blockade with CNQX, TTX still reduced b-wave amplitudes in cone-isolated ERGs indicating Na(v) channels in ON cone bipolar cells themselves augment b-wave amplitude and sensitivity. This augmentation was largest under dark-adapted conditions, and decreased with increasing background illumination, indicating effects of background illumination on Na(v) channel function. These findings indicate that activation of Na(v) channels in ON cone bipolar cells affects the b-wave of the rat ERG and must be considered when analysing results of ERG studies of retinal function.     

Identification of appropriate primitive polynomials to avoid cross-contamination in multifocal electroretinogram responses

The basis of the multifocal/electroretinogram is the use of a decimated m-sequence for simultaneous and independent stimulation of many areas of the visual pathway. The purpose of this study was to investigate the effects of cross-contamination from higher orders of the response. A series of primitive polynomials were found by construction of finite fields. The first-order ERG response was formed by cross-correlation of m-sequence with the physiological response. A second-order response was formed by investigation of particular flash sequences of the stimulation sequence and cross-correlation of a second-order m-sequence with the physiological response. Zech logarithms were used to identify cross-contamination between the various first and second-order sequences. Tables of good and bad primitive polynomials were constructed for degrees 12–16, and the effects of window length and decimation length were examined. When the sequence was decimated into 128 areas, and a window of length 16 was examined, cross-contamination occurred in all sequences generated from primitive polynomials of degree less than or equal to 12, but in only 26% of degree 14, and 5.6% of degree 16. A photodiode (artificial eye) was used in an experiment to construct trace arrays showing responses from 61 individual areas. Additional waveforms were present on the trace array when the experiment was carried out with a bad primitive polynomial. The use of finite field theory to generate primitive polynomials and Zech logarithm analysis allowed prediction of which primitive polynomials were suitable for m-sequence generation for multifocal electroretinography. Practical investigations supported the theoretical analysis. This has important implications for developers of multifocal electrophysiology systems.     

Clonality analysis of multifocal carcinoid tumours of the small intestine by X-chromosome inactivation analysis

The clonality of intestinal carcinoids and the relationship between different tumour deposits of multiple intestinal carcinoids were investigated in this study. Six cases of multiple ileal carcinoids were selected for analysis and three independent carcinoid lesions from each case were microdissected. Clonality of the lesions was determined by polymerase chain reaction (PCR)-based X-chromosome inactivation of the human androgen receptor gene. Four out of six cases were heterozygous for microsatellite repeats within the androgen receptor gene and thus informative for the study. The results showed that all 12 lesions analysed had non-random X-chromosome inactivation (monoclonal) patterns, compared with the background normal intestinal mucosal tissues. This finding proves for the first time the monoclonal origin of human intestinal carcinoids, by X-chromosome inactivation analysis. More interestingly, identical X-chromosome inactivation patterns were found in different carcinoid lesions from each individual case. This evidence strongly indicates that multiple carcinoids of the small intestine were generated by metastasis of a primary tumour to different locations in the intestine, rather than being of multiple origin. This study provides an important insight into the carcinogenesis of intestinal carcinoids.     

Application of wavelet-based similarity analysis to epileptic seizures prediction

Epileptic seizures prediction is an interesting issue in epileptology, since it can promise a novel approach to control seizures and understand the mechanism of epileptic seizures. In this paper, we describe a new method, called wavelet-based nonlinear similarity index (WNSI), to predict epileptic seizures using EEG recordings in real time. This method combines wavelet techniques and nonlinear dynamics. The test results of EEG recordings of rats and humans show that WNSI can track the hidden dynamical changes of brain electrical activity. Particularly, we found that it can obtain the best performance of seizure prediction at the beta (10-30 Hz) frequency band of EEG signals. A possible reason is suggested from the functional connectivity of the brain. In terms of this study, it is recommended that wavelet technique is very useful to improve the performance of epileptic seizures prediction.     

Improved early stroke detection: wavelet-based perception enhancement of computerized tomography exams

Nonenhanced computerized tomography (CT) exams were used to detect acute stroke by notification of hypodense area. Infarction perception improvement by data denoising and local contrast enhancement in multi-scale domain was proposed. The wavelet-based image processing method enhanced the subtlest signs of hypodensity, which were often invisible in standard CT scan review. Thus improved detection efficiency of perceptual ischemic changes was investigated. Data processing became more effective by initial segmentation of brain tissue and extraction of regions susceptible to tissue density changes. The new method was experimentally verified. Sensitivity of stroke diagnosis increased to 56.3% in comparison to 12.5% of standard CT scan preview.     

膀胱肿瘤细胞克隆分析及意义

一、膀胱上皮细胞的克隆性增生与膀胱肿瘤膀胱上皮性肿瘤 常常同时或先后发生于同一患膀胱之不同部位,不同病灶可显示相同或不同的组织学特征。对于此特征,不同学具有不同的观点。多数学认为多发性肿瘤起源于同一克隆,即所有肿瘤均由肿瘤性转化的同一祖先细胞增生而来,经腔道内种植或经上皮内游走而形成多数肿瘤病灶。另有学认为,多发性肿瘤是由于致瘤因素同时作用于膀胱不同部位而导致多数部位的细胞同时或先后发生肿瘤性转化,进而形成多发的,遗传学上互不相关的多数癌灶。[第一段]     

Clonality analysis of multifocal papillary thyroid carcinoma by using genetic profiles

Papillary thyroid carcinoma (PTC) is the most common adult thyroid malignancy and often presents with multiple anatomically distinct foci within the thyroid, known as multifocal papillary thyroid carcinoma (MPTC). The widespread application of the next‐generation sequencing technologies in cancer genomics research provides novel insights into determining the clonal relationship between multiple tumours within the same thyroid gland. For eight MPTC patients, we performed whole‐exome sequencing and targeted region sequencing to identify the non‐synonymous point mutations and gene rearrangements of distinct and spatially separated tumour foci. Among these eight MPTCs, completely discordant mutational spectra were observed in the distinct cancerous nodules of patients MPTC1 and 5, suggesting that these nodules originated from independent precursors. In another three cases (MPTC2, 6, and 8), the distinct MPTC foci of these patients had no other shared mutations except BRAF V600E, also indicating likely independent origins. Two patients (MPTC3 and 4) shared almost identical mutational spectra amongst their separate tumour nodules, suggesting a common clonal origin. MPTC patient 7 had seven cancer foci, of which two foci shared 66.7% of mutations, while the remaining cancer foci displayed no common non‐synonymous mutations, indicating that MPTC7 has multiple independent origins accompanied by intraglandular disease dissemination. In this study, we found that 75% of MPTC cases arose as independent tumours, which supports the field cancerization hypothesis describing multiple malignant lesions. MPTC may also arise from intrathyroidal metastases from a single malignant clone, as well as multiple independent origins accompanied by intrathyroidal metastasis. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Quantitative analysis of the insulating effect of silicone oil on the electroretinogram

A model of the ERG focusing on the insulation effect of silicone oil replacing the vitreous was used to quantify the ERG. The electrical properties of the structures of the eye, the frequency content of the ERG and the percentage of the silicone oil along with the remaining vitreous were incorporated in the model. The result was that it was not until at least 50 per cent of the vitreous was replaced with silicone oil that there was a small reduction in the ERG. As more silicone oil was put into the vitreous cavity the ERG became smaller. If the replacement were large leaving a layer of vitreous 0·24 mm thick, little ERG would be measured even if the retina were functional.     

Papovavirus detection by electron microscopy in the brain of an elderly patient without overt progressive multifocal leukoencephalopathy

Virions resembling papovavirus were demonstrated in glial cells in the brain of an aged patient without overt progressive multifocal leukoencephalopathy. The patient was not in a severely immunocompromised state. On histological examination, only a few tiny incomplete necrotic foci were found in the subcortical area. These foci were widely dispersed. Rare, swollen oligodendroglial cells and astrocytes in which papovavirus capsid protein (VP-1) was demonstrated immunohistochemically were present around the foci. The two typical types of virus particles i.e. 35 to 40 nm round particles and elongated particles, were observed in the nuclei of the swollen glial cells. The latter were in the minority. Distinct crystals were also found in the nuclei. The centre-to-centre distance of the particles in the crystals, about 40 nm, and the electron-opaque spots of the round-shaped virions and of the elongated particles, were indicative of structural subunits of papovavirus capsids. This case provides further evidence that papovavirus, possibly JC virus, may be reactivated in the brains of aged patients who are not in an immunocompromised state.     

Molecular analysis of multifocal prostate cancer lesions

To analyse the origin of multifocal prostate cancer lesions, radical prostatectomy specimens from 17 patients were examined. As a marker of genetic lineage, the allelotype based on 33 microsatellite loci was compared between the different tumours present in a given case. Some results provide evidence suggestive of a clonal origin of multiple tumours in a subset of the prostates. In five cases, for example, comparison of multifocal tumour lesions within a given case revealed at least two concordant changes in allelic imbalance (AI) sequence dosages at different loci. In addition, considerable heterogeneity of allelotype was found within and among tumour foci of a given case. In five of the six tumours analysed for intratumour heterogeneity, for example, more than five discordant AI changes were found in one tumour region but not in the other. Conclusions regarding the clonality of such heterogeneous lesions are difficult to draw. A high frequency of AI changes in four lesions exhibiting prostatic intraepithelial neoplasia (mean 6·5 changes per lesion, range 3–6) was found, compared with eight primary tumours present in the same cases (mean 5·8 changes per lesion, range 3–6). The interpretation of AI associated with clinically detected prostate cancer remains a highly complex issue. The fact that no clear evidence was obtained for either a clonal or a non-clonal origin of multiple lesions in a given prostate indicates that several different mechanisms are likely to operate in establishing the allelotype and that additional evidence from unique mutations or selective gene inactivation may be necessary to obtain definitive results. Copyright © 1999 John Wiley & Sons, Ltd.     

Evaluating the entrainment of the alpha rhythm during stroboscopic flash stimulation by means of coherence analysis

Two major conflicting hypotheses propose that alpha rhythm activity should be either the output of a linear filter having a white noise as input or reflect the output of a nonlinear oscillator. External stimulation can be employed to test for nonlinearity in alpha genesis, since an entrainment of such rhythmic activity (shift in the alpha peak) could only be explained by nonlinear relationships. Flash photic stimulation has been used to investigate such entrainment. Nevertheless, only entrainments due to the second harmonic of the stimulation could be suitably measured. Aiming at overcoming this limitation, a coherence-based technique is proposed for evaluating the strength of responses due to rhythmic stimulation. It was applied to the occipital EEG derivations of 12 normal subjects during stroboscopic stimulation. Entrainment of alpha rhythm by the second harmonic of the stimulation occurred in 75% of the subjects, whilst no spectral shifts were observed for the remained that exhibited broadband alpha peak at rest. However, stimulating with fundamental frequency close to that peak led to entrainment in all subjects. These differences in the degree of synchronization due to stimulation at the first and second harmonics should reflect complex nonlinear mechanisms in alpha genesis.     

Specific features of the electroretinogram of vertebrates induced by X-rays

The net electroretinograms of dark-adapted retinas of the common frog in situ were investigated on an automated experimental system with programmed control and electronic differentiation of biopotentials with respect to the first and second derivatives. It was demonstrated that X-rays elicit an electroretinogram consisting of two components, provisionally called the first and second X-ray reactions (X-1 and X-2), which differ with respect to their parameters from electroretinograms elicited under the same conditions by red and blue light. The administration of sodium azide, sodium nitrate, monoiodoacetate and other substances alter the X-1 and X-2 as well as the photo-induced ERGs in different ways; this indicates their relative independance and different mechanisms of the occurrence and passing of excitation across the structures of the retina, and makes it possible to partially isolate these for individual study. Thus, the assertion of a number of investigators regarding the absence of specific features in the X-ray induced electroretinograms becomes problematical. The discovery of X-ray-specific reactions in the retina makes it possible to hope that the radiological phosphene (the X-ray phosphene) may serve as a test for the determination of the individual radiational excitability of the central nervous system.Translated from Fiziologicheskii, Zhurnal, Vol. 77, No. 8. pp. 99–106, August, 1991.     

The electroretinogram evoked by the excitation of human foveal cones

1. A 2° test stimulus foveally fixed and viewed against a blue background (40° in extent and producing 2·0 × 10⁴ scotopic td of retinal illuminance) evokes a small voltage which can be recorded from the human eye with a conventional contact lens electrode if the test stimulus is flashed at a rate of 15 c/s, and the responses to at least several hundred flashes are averaged.

2. The action spectrum of the response obtained in this way agrees reasonably well with the observer's psychophysical foveal luminosity curve.

3. For the peripheral retina, the action spectrum is similar to that of the fovea when allowance is made for differences in screening macular pigment.

4. Such responses diminish when the test stimulus is focused on to the peripheral retina and disappear when the test light is focused on the blind spot.

5. Therefore, the response to the test light fixated centrally is the result of the excitation only of cones mainly, if not exclusively, in the fovea.

6. When the intensity of the background is reduced by a factor of 10, the action spectrum shows evidence of the effect of excitation of rods in the blue part of the spectrum and of cones in the red. These red and blue responses add linearly when combined together, provided they are adjusted to coincide in phase.

     

Progressive multifocal leucoencephalopathy: detection of papovavirus JC in kidney tissue

Cellular DNA of the kidney from a patient with PML was analyzed by reassociation kinetics for the presence of JC virus DNA. Various amounts of viral DNA sequences were detected in different areas of the kidney. The highest concentration (175 genome equivalents/cell) was found in the renal medulla and there were almost none in the renal cortex. Differentiation from the closely related BK virus was carried out by reassociation kinetics and restriction enzyme cleavage with subsequent Southern blot analysis. The enzyme Hind II, which does not cleave within the BK virus genome, generated four restriction enzyme fragments in the cellular DNA from the kidney, thus documenting the presence of JC virus DNA. By examination of the renal DNA with the "no-cut" restriction enzyme XHO I and the "one-cut" enzymes Eco RI and BAM HI it was possible to show that free and not integrated viral DNA was present in these cells. Nonhomogeneous defective DNA bands were not detectable. By in situ hybridization the epithelial cells lining the collecting tubules were found as predominant site of the viral infection in the kidney.