Miklós Emri

Hypo-osmotic shock induces an osmolality-dependent permeabilization and structural changes in the membrane of carp sperm

We carried out spectrofluorimetric and flow cytometric measurements to investigate the effect of hypo-osmotic shock on cell membranes of common carp sperm. The time course of the permeability of the sperm cell membrane, as monitored by DNA-related propidium iodide (PI) fluorescence, was followed for 30 min after dilution of semen in hypo-osmotic environments of different ionic strengths. Spectrofluorimetric measurements indicated a continuous increase in the total PI emission intensity of a sperm suspension. Cell-by-cell flow cytometric measurements suggested that the permeability changes were of the all-or-none type. The permeabilized fraction of cells in the individual samples was time and osmolality dependent. The number and percentage of cells in which DNA was stained by PI increased gradually over time and reached a steady-state plateau value after 5-15 min. This equilibrium fraction of cells with a PI-permeable cytoplasmic membrane displayed an inverse relationship with the osmolality of the diluent, having a near 100% value for fresh water and distilled water. Dilution of sperm in hypo-osmotic medium brought about a fast decrease in the forward light-scattering signal on a short time scale compared to the pre-steady-state time of the permeabilization. With the addition of extracellular Ca2+ (1.8 mM), restoration of the light scattering signal was observed. Permeabilization of the membrane and restoration of light scattering were not coincident in time. We propose a two-dimensional reorganization of the lipid structure as the underlying mechanism of the latter process.

Flow cytometric determination of absolute membrane potential of cells.

Membrane potential measurements using fluorescent membrane potential indicator dyes report on relative changes but usually do not result in an absolute value of the measured parameter. The method developed in this paper is based on the assumption that the negatively charged bis-oxonol distributes across the cytoplasmic membrane according to the Nernst equation. It is further supposed that the fluorescence intensity measured from a given stained cell is a single-value function of the intracellular dye concentration. The protocol suggested incorporates the construction of a calibration curve (fluorescence intensity measured from stained cells vs. extracellular dye concentration). This allows the evaluation of the membrane potential in millivolts using fluorescence readings of the cells both in the depolarized state and in the state of interest. Good agreement was found between absolute membrane potential data of human peripheral blood lymphocytes by our method and results of parallel patch clamp measurements.

Effects of vinpocetine on the redistribution of cerebral blood flow and glucose metabolism in chronic ischemic stroke patients: a PET study ☆

The pharmacological effects of the neuroprotective drug vinpocetine, administered intravenously in a 14-day long treatment regime, on the cerebral blood flow and cerebral glucose metabolism in chronic ischemic stroke patients (n=13) were studied with positron emission tomography in a double-blind design. The regional and global cerebral metabolic rates of glucose (CMRglc) and cerebral blood flow (CBF) as well as vital physiological parameters, clinical performance scales, and transcranial Doppler parameters were measured before and after the treatment period in patient groups treated with daily intravenous infusion with or without vinpocetine. While the global CMRglc values did not change markedly as a result of the infusion treatment with (n=6) or without (n=7) vinpocetine, the global CBF increased and regional CMRglc and CBF values showed marked changes in several brain structures in both cases, with more accentuated changes when the infusion contained vinpocetine. In the latter case the highest rCBF changes were observed in those structures in which the highest regional uptake of labelled vinpocetine was measured in other PET studies (thalamus and caudate nucleus: increases amounting to 36% and 37%, respectively). The findings indicate that a 2-week long intravenous vinpocetine treatment can contribute effectively to the redistribution of rCBF in chronic ischemic stroke patients. The effects are most pronounced in those brain regions with the highest uptake of the drug.

Glioma grade assessment by using histogram analysis of diffusion tensor imaging-derived maps

IntroductionCurrent endeavors in neuro-oncology include morphological validation of imaging methods by histology, including molecular and immunohistochemical techniques. Diffusion tensor imaging (DTI) is an up-to-date methodology of intracranial diagnostics that has gained importance in studies of neoplasia. Our aim was to assess the feasibility of discriminant analysis applied to histograms of preoperative diffusion tensor imaging-derived images for the prediction of glioma grade validated by histomorphology.MethodsTumors of 40 consecutive patients included 13 grade II astrocytomas, seven oligoastrocytomas, six grade II oligodendrogliomas, three grade III oligoastrocytomas, and 11 glioblastoma multiformes. Preoperative DTI data comprised: unweighted (B0) images, fractional anisotropy, longitudinal and radial diffusivity maps, directionally averaged diffusion-weighted imaging, and trace images. Sampling consisted of generating histograms for gross tumor volumes; 25 histogram bins per scalar map were calculated. The histogram bins that allowed the most precise determination of low-grade (LG) or high-grade (HG) classification were selected by multivariate discriminant analysis. Accuracy of the model was defined by the success rate of the leave-one-out cross-validation.ResultsStatistical descriptors of voxel value distribution did not differ between LG and HG tumors and did not allow classification. The histogram model had 88.5% specificity and 85.7% sensitivity in the separation of LG and HG gliomas; specificity was improved when cases with oligodendroglial components were omitted.ConclusionConstructing histograms of preoperative radiological images over the tumor volume allows representation of the grade and enables discrimination of LG and HG gliomas which has been confirmed by histopathology.

Radiation myelopathy with partial functional recovery: PET evidence of long-term increased metabolic activity of the spinal cord

Postoperative telecobalt irradiation was performed with a biologically effective extrapolated response dose of 165 Gy2 delivered to the spinal cord of a papillary thyroid cancer patient. Incomplete cervical transection developed, followed by a gradual functional improvement, which is still continuing 8 years after radiotherapy. Between the 6th and 8th years of the clinical course, positron emission tomography investigations demonstrated an increased 18F-deoxyglucose accumulation and (15)O-butanol perfusion, but negligible 11C-methionine uptake in the irradiated spinal cord segment. We suggest that the increased metabolism and perfusion, and the lack of detectable protein synthesis may be related to the increased energy demands of action potential conduction, due to the higher than normal density of sodium channels along demyelinated axons displaying restored conduction.

Converging evidences on language impairment in Landau–Kleffner Syndrome revealed by behavioral and brain activity measures: A case study

OBJECTIVE To assess the linguistic abilities of a boy having Landau-Kleffner Syndrome, and relate the focal disturbance of brain activity due to epilepsy to the cognitive and linguistic deficits. METHODS Several kinds of assessments were carried out, including epileptic source analysis using electronic source localization methods and PET, neuropsychological assessment of cognitive functions, and assessment of speech perception skills (discrimination of phonetic and stress cues) using ERPs. RESULTS The source of epileptic activity was localized in the left superior temporal lobe. The neuropsychological assessment showed dissociation between verbal and nonverbal functions, and the performance in former was bellow the normal range. ERPs obtained to the processing of phonetic and stress speech cues indicated that the two cues were processed asymmetrically: the mismatch negativity component (MMN) was obtained for the phoneme difference, but not for the stress pattern difference. CONCLUSIONS Our data converged as it showed that the patient presented a selective impairment of the language system, and the verbal working memory system appeared to be especially defective. It is suggested that the language deficit is at least partly due to the focal disturbance of those neural networks that underlie the functioning of the working memory system. SIGNIFICANCE LKS is a childhood language disorder that might serve as a model in studying what happens to the language system if, in the course of development, the essential neural circuits are severely disturbed.

Development of an FPGA-based data acquisition module for small animal PET

We report on the design of a data acquisition (DAQ) module for a small animal PET camera developed at our institutes. During the design an important guideline was to develop a system which is built up from strictly identical DAQ modules, and which has no built-in hardware limitation on the maximum number of modules. The developed DAQ module comprises of an LSO scintillator crystal block, a position sensitive PMT, analog signal conditioning circuits, a digitizer, an field programmable gate array (FPGA) for digital signal processing, and a communication module through which the collected data are sent to a cluster of computers for postprocessing and storage. Instead of implementing hardware coincidence detection between the modules, we attach a precise time stamp to each event in our design, and the coincidence is determined by the data collecting computers during postprocessing. The digital CFD algorithm implemented in the FPGA gives a time resolution of 2 ns FWHM for real detector signals

Autistic traits in neurotypical adults: correlates of graph theoretical functional network topology and white matter anisotropy patterns.

Attempts to explicate the neural abnormalities behind autism spectrum disorders frequently revealed impaired brain connectivity, yet our knowledge is limited about the alterations linked with autistic traits in the non-clinical population. In our study, we aimed at exploring the neural correlates of dimensional autistic traits using a dual approach of diffusion tensor imaging (DTI) and graph theoretical analysis of resting state functional MRI data. Subjects were sampled from a public neuroimaging dataset of healthy volunteers. Inclusion criteria were adult age (age: 18–65), availability of DTI and resting state functional acquisitions and psychological evaluation including the Social Responsiveness Scale (SRS) and Autistic Spectrum Screening Questionnaire (ASSQ). The final subject cohort consisted of 127 neurotypicals. Global brain network structure was described by graph theoretical parameters: global and average local efficiency. Regional topology was characterized by degree and efficiency. We provided measurements for diffusion anisotropy. The association between autistic traits and the neuroimaging findings was studied using a general linear model analysis, controlling for the effects of age, gender and IQ profile. Significant negative correlation was found between the degree and efficiency of the right posterior cingulate cortex and autistic traits, measured by the combination of ASSQ and SRS scores. Autistic phenotype was associated with the decrease of whole-brain local efficiency. Reduction of diffusion anisotropy was found bilaterally in the temporal fusiform and parahippocampal gyri. Numerous models describe the autistic brain connectome to be dominated by reduced long-range connections and excessive short-range fibers. Our finding of decreased efficiency supports this hypothesis although the only prominent effect was seen in the posterior limbic lobe, which is known to act as a connector hub. The neural correlates of the autistic trait in neurotypicals showed only limited similarities to the reported findings in clinical populations with low functioning autism.

PET identifies transitional metabolic change in the spinal cord following a subthreshold dose of irradiation.

Positron emission tomographic (PET) investigations were performed to obtainin vivo information on symptomless radiation-induced pathological changes in the human spinal cord. PET investigations were carried out prior to radiotherapy and during the regular follow-up in an early hypopharyngeal cancer patient (the spinal cord was irradiated with a biologically effective dose of 80 Gy2), with [18F]fluorodeoxyglucose (FDG), [11C]methionine and [15O]butanol as tracers; radiosensitivity and electroneuronographic (ENG) studies were also performed. A very low background FDG accumulation (mean standardized uptake values, i.e. SUV: 0.84) was observed in the spinal cord before the initiation of radiotherapy. An increased FDG uptake was measured 2 months after the completion of radiotherapy (mean SUV: 1.69), followed by a fall-off, as measured 7 months later (mean SUV: 1.21). By 44 months after completion of irradiation, the FDG accumulation in the irradiated segments of the spinal cord had decreased to a level very close to the initial value (mean SUV: 1.11). The simultaneous [15O]butanol uptake results demonstrated a set of perfusion changes similar to those observed in connection with the FDG accumulation. The patient exhibited an extremely low [11C]methionine uptake within the irradiated and the nonirradiated spinal cord during the clinical course. She has not had any neurological symptoms, and the results of central ENG measurements before radiotherapy and 2 months following its completion proved normal. Radiobiological investigations did not reveal unequivocal signs of an increased radiosensitivity. A transitory increased spinal cord FDG uptake following radiotherapy may be related to the posttherapeutic mild inflammatory and regenerative processes. The normal [11C]methionine accumulation observed is strong evidence against intensive cell proliferation. The high degree of normalization of the temporarily increased FDG uptake of the irradiated spinal cord segments by 44 months is in good agreement with the results of monkey studies, which demonstrated a nearly complete recovery from radiation-induced spinal cord injury.

Temperature adaptation changes ion concentrations in spermatozoa and seminal plasma of common carp without affecting sperm motility

Abstract Cold or warm adaptation usually results in changes of the cellular parameters of poikilothermic animals. However, no data are available about the changes in cellular parameters of sperm samples from cold or warm adapted animals. Here the effects of warm and cold adaptation on the spermation of common carp ( Cyprinus carpio L.) and the changes in the characteristics of the individual sperm cells are described. Measurements were carried out on semen samples from 10 warm adapted and 10 cold adapted animals. The sperm cells from the cold adapted animals had a higher intracellular pH (7.4±0.1) than those from the warm adapted ones (7.1±0.1). The pH of the seminal plasma of the cold adapted animals (8.6±0.2) was also higher than that of the warm adapted animals (8.3±0.1). The concentration of spermatozoa in the semen of cold adapted animals was about half that for the warm adapted animals (0.7±0.1×10 10 vs. 1.4±0.2×10 10 cells/ml). The Na + concentration of the seminal plasma of the cold adapted animals (83±12 mM) was higher, while the K + concentration in these samples (64±11 mM) was lower than the corresponding data for the warm adapted animals (63±10 mM and 87±16 mM, respectively). All of these differences proved to be significant at 5% level of significance using the Students t -test. In contrast, there was no significant difference between the intracellular free K + concentrations in the spermatozoa from cold and warm adapted animals (58±8 mM vs. 60±7 mM). The ion compositions and concentrations of the blood sera of cold and warm adapted animals were similar. Also, the motile fraction and duration of motility of the spermatozoa from cold and warm adapted animals were identical. An increase by 0.2 pH unit occurred in the intracellular pH during hypoosmotic shock induced motility of sperm cells from the cold and warm adapted animals. This pH increase could be blocked by the Na + /H + exchange inhibitor amiloride in a concentration of 100 μM. Based on the kinetics of the processes involved and on additional experimental evidence it is suggested that the hypoosmotic shock induced immediate hyperpolarization of the sperm under usual spawning conditions. Thus, it may be a regulatory step in the motility activation of common carp sperm but not in the relatively slowly occurring intracellular alkalinization.