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Biomedical subjects

A Eblen-Zajjur

Publications and source records attributed to A Eblen-Zajjur.

12 recordsLinked to original sources
PubMed2004

Tridimensional animated brain mapping from conventional paper-ink EEG recordings.

One of the most powerful functional evaluations of the electrical activity of the brain is the EEG imaging, but wide clinical use is limited by its costs. It is also of clinical, academic and scientific interest to obtain brain electrical maps from old paper/ink, patient recordings. The aim of the present study was the development of a computer system designed to obtain bidimensional and tridimensional maps, continuous movie map display and mosaic presentation from conventional paper/ink EEG recordings. The wave amplitude was manually measured with a translucent template from conventional 8- to 16-channel EEG paper recordings using 10-20 monopolar montage for one or both hemispheres. The computer system allows the selection of the number and location of electrodes, input of amplitude values, and the map display mode. The electrical brain field was generated from amplitude measurements by a spherical splines interpolation algorithm on a conventional Pentium-based computer. The interpolated surface was represented on a semi-sphere modeled skull. The EEG maps displayed with pseudo-color or gray scales can be rotated, zoomed in or zoomed out and/or printed for clinical reports. Movie animation or mosaic display of space-temporal EEG voltage changes were generated by processing sequential amplitude measurements. This system represents a cost-effective method for EEG mapping from conventional paper/Ink EEG equipments.

Brain Mapping↗
PubMed2003

Inflammation induced increase of fluoride resistant acid phosphatase (FRAP) activity in the spinal dorsal horn in rats.

Fluoride-resistant acid phosphatase (FRAP) has been suggested as an enzymatic marker for nociceptive primary afferent terminals in the spinal dorsal horn, however there has not been demonstrated a direct functional relation between FRAP activity and an increased nociceptive transmission. For this purpose, we quantitated FRAP activity in the spinal dorsal horn of the rat in a heat-induced cutaneous inflammatory model. Male Sprague-Dawley rats anaesthetised with thiopental were separated in two groups where the left hindpaw was submerged during 60 s either in water at room temperature (control group) or in water at 60 degrees C (inflammation group) which induce in this group a progressive hindpaw inflammation. After 8 h, the lumbar enlargement of the spinal cord was extracted, cut in slices and 1 mm micropunch fragments were obtained from the right and left dorsal horn. The activity of FRAP was determined using the Gomori colorimetric method and corrected by the protein concentrations. FRAP activity in the left dorsal horn was statistically higher than right dorsal horn in the inflammation group (3.05+/-0.54 versus 1.91+/-0.23 u/g per l; P<0.05). Also, FRAP activity from the left dorsal horn of the control and inflammation groups show a significant increase in the last group (3.05+/-0.54 versus 2.17+/-0.23 u/g per l; P<0.05). This results demonstrate that FRAP is not only an enzymatic marker for neuronal and fibre integrity of nociceptive primary afferents but also it is associated to the nociceptive afferent activation.

Acid Phosphatase↗
PubMed2001

[Estimation of low density lipoprotein cholesterol concentration: regression analysis versus Friedewald's formula].

BACKGROUND: The Friedewald formula is used to estimate cholesterol of low density lipoprotein (LDL) from total cholesterol (CT), cholesterol of high density lipoprotein (HDL) and triglycerides (TG), but there are doubts about its precision. AIM: To compare Friedewald formula and regression analysis for the calculation of LDL cholesterol. MATERIAL AND METHODS: One hundred and fifty plasma samples from asymptomatic adults (aged 47.7 +/- 13 years, 50.6% male) were analyzed. CT, HDL, LDL and TG were determined by enzymatic methods. Friedewald formula (LDLc = CT-HDL-(TG/5)) and multiple regression analysis were applied to estimate LDL concentration. RESULTS: Mean total cholesterol was 175.3 +/- 39.7 mg/dl, HDL cholesterol was 35.57 +/- 0.8 mg/dl and TG was 128.4 +/- 65.4 mg/dl. Mean values for LDL cholesterol were significantly higher than those estimated by the Friedewald formula (136.4 +/- 37.9 mg/dl and 114.1 +/- 37.4 mg/dl respectively, p < 0.001) with a mean underestimation of 16.4 +/- 11.7%. LDL cholesterol values were directly proportional to TG concentration. Multiple regression analysis (LDLr = -14.376 + (age x 0.198) + (CT x 0.949) + (HDL x -0.474) + (TG x -0.064) showed no statistical differences with those obtained by the enzymatic method. CONCLUSIONS: These results confirm the underestimation of LDL concentration by the Friedewald formula despite normal range of TG concentration. A multiple regression analysis should be used to estimate LDL concentration with precision.

Adult↗
PubMed1999

A laboratory demonstration for learning about mast cell degranulation.

A simple experimental model of cell degranulation was implemented that exposed mast cells obtained from Sprague-Dawley rats to saponin. The model is flexible, asy, and low cost, is not very time-consuming to run, and needs a minimum of laboratory resources. It has been used for the last three years in our undergraduate medical physiology courses and has replaced the classic utilization of slides and drawings.

Animals↗
PubMed1999

[Reaction time to dichotic visual stimulation and its relationship to cerebral hemispheric specialization].

There is a renewed interest in the study of the cerebral hemispheric specialization given its physiological, physiopathological, clinical and educational relevancy. According to this, a stimulus is better processed in one of the cerebral hemispheres. The visual dichotic stimulation allows to present a stimulus selectively to one of the hemispheres, and this was used in the present study for the measurement of the reaction time (TR) and for the establishment of its correlation with an objective and validated measure of the cerebral hemispheric specialization. Ninety eight persons with an average age of 22.2 +/- 0.7 (X +/- EE) years were studied by means of the Oldfield protocol for the determination of the Cerebral Hemispheric Lateralization Index (IL). Additionally, the age, the sex and the date of last menstruation in the case of females, were registered. The dichotic stimulation and the determination of the visual TR was accomplished by computer with a time resolution of 100 microseconds. The stimulus consisted of the random presentation of a white square on a black background in a computer monitor, to which the subject had to respond by pressing a key with his best hand. The reaction time was registered 10 times in each visual field for a total of 20 records per eye. The IL of the sample was predominantly right (66.32 +/- 4.64), and significantly smaller in males than in females (p < 0.05). The TR to stimuli in the left visual field was significantly greater (p < 0.05) than in the right visual field for both eyes. When analyzing the global results of each cerebral hemisphere, a TR significantly smaller for the left hemisphere (304.33 +/- 4.1 ms) than for the right (312.35 +/- 4.5 ms, p < 0.05) was observed. These results suggest that the cerebral hemispheric specialization, expressed as a smaller response time, cannot alone be only the product of a better intrinsic hemispheric processing of the information, but also of the anatomical relationships of the proximity of the hemisphere that receives the stimulus and the center or area that will generate the response, as is the case of the motor center located in the left hemisphere in the immense majority of the right-handed subjects in the sample and in the general population.

Adolescent↗
PubMed1997

PAG-microinjected dipyrone (metamizol) inhibits responses of spinal dorsal horn neurons to natural noxious stimulation in rats.

In addition to their well-known peripheral and spinal effects, non-steroidal antiinflammatory drugs (NSAIDs) are believed to diminish nociceptive responses by acting supraspinally and activating descending modulatory systems. We have herein investigated whether this descending action involves a depression of spinal sensory neurons. In rats under barbiturate anesthesia, responses of lumbar wide-dynamic-range neurons to a noxious clamp in their receptive fields were depressed to 46% of baseline value by the microinjection of 100 microg dipyrone (metamizol) into the periaqueductal gray matter (PAG). These results show that PAG application of NSAIDs activates descending systems which depress the excitation of spinal sensory neurons by natural noxious stimuli.

Animals↗
PubMed1997

A simple analog of visual field retinal projection.

Basic biophysical principles of the eye, such as the retinal projection of the visual field, bidimensional image inversion, blind point determination, visual field and retinal quadrants, perimetric principles, and determination of scotoma, are seen on a working anatomic model of the eye and its visual field that can easily be constructed at very low cost and from easily obtained materials: an opaque glass globe, a styrofoam hemisphere, a wood screen, bulbs, sockets, wire, and switches. This model has been used for many years in our undergraduate medical physiology courses and has replaced the classical model of candle image inversion by a converging lens.

Audiovisual Aids↗
PubMed1996

Fractal analysis of spinal dorsal horn neuron discharges by means of sequential fractal dimension D.

The present study describes a new method for converting a typical point process, such as a train of neuronal action potentials (spikes), into a planar curve which is then processed by means of a fast algorithm to calculate and display the fractal dimension D values of each of a sequence of blocks having an equal and preselectable number of interspike intervals, hence the term sequential fractal dimension D (SFD). This method is fast, does not require special computing facilities, and provides a continuous, high temporal resolution display of the neuronal discharge complexity along the course of spontaneous activity or event relating changes. The method affords insight into short duration changes in neuronal behaviour in a way independent of its discharge rate. SFD analysis of spike trains from spinal dorsal horn neurons suggests that the neuronal response to a given stimulus can be expressed as changes in the discharge pattern complexity, thus revealing a novel sensory coding strategy.

Action Potentials↗
PubMed1995

Differential effects of spinalization on discharge patterns and discharge rates of simultaneously recorded nociceptive and non-nociceptive spinal dorsal horn neurons.

Recordings were made simultaneously from 2-5 neurons at the same site in the lumbar spinal dorsal horn of pentobarbital-anesthetized rats. Neurons were classified as low-threshold (LT) or multireceptive (MR) according to their responses to non-noxious mechanical or noxious radiant heat stimuli of the skin. At the same recording sites neurons could be encountered which belong to different classes and/or which had mechanoreceptive fields which did not overlap. Cold blocks of the upper or lower thoracic cord or transsections of the upper cervical cord were made to evaluate the effects of spinalization on both the rate and pattern of background activity and/or noxious heat-evoked responses of different dorsal horn neurons under identical experimental conditions. At 24 of 27 recording sites, spinalization had qualitatively or quantitatively different effects on the rate of background activity of simultaneously recorded neurons. Interspike interval (ISI) means of background activity were significantly reduced in 29 of 65 (44.6%) neurons, prolonged in 23 of 65 (35.4%) neurons, or unchanged in 13 of 65 (20%) neurons. MR neurons displayed a significantly higher incidence of decreased background activity 17 of 45 (37.8%) and a lower incidence of increased background activity (18 of 45, 40%) during spinalization than the LT neurons from which 1 of 12 (8.3%) decreased and 8 of 12 (66.6%) increased background activity. Almost all (95.4%) neurons changed their discharge patterns after spinalization. At 9 of 27 recording sites, the discharge patterns of simultaneously recorded neurons were affected differently by spinalization as revealed by the coefficient of dispersion of the interspike intervals (ISI), indicating changes in the tendency to discharge action potential in clusters (bursts). At the same recording sites the level of noxious heat-evoked responses of simultaneously recorded MR neurons was also differentially affected by spinalization. Nociceptive responses were significantly enhanced in 19 of 37 (51.4%) neurons (137.8 +/- 142.6% of control, mean +/- SD), reduced in 13 of 37 neurons (35.1%) (by 58.9 +/- 20.9%) and/or unchanged in 5 of 37 (13.5%) neurons. It is concluded that no general 'tone' of descending antinociception exists and that tonic descending excitatory and inhibitory systems may be active simultaneously modulating both the level and pattern of neuronal discharges.

Animals↗
PubMed1995

Analysis of single and multiple neuronal discharges as point processes: a computer program set.

The analysis of single or multiple neuron discharges as point processes has gained considerable importance for understanding the principles of information coding and processing in the central nervous system (CNS). Here, a set of programs written in BASIC language for microcomputers is described for the point process analysis of discharges of individual or multiple simultaneously recorded neurons as well as the mathematical basis of the methods implemented in these programs. The input data consist of one or more ASCII files with the spike or stimulus occurrence times generated by the spike sorting system used. Interspike interval histogram, autocorrelogram, autospectrum, cross-correlogram, joint impulse configuration scatter diagram, poststimulus time histogram and joint peristimulus time scatter diagram, together with other more conventional methods, are included in this package which provides graphical or alpha numeric results which can be printed or stored on disk for additional graphical or statistical analysis.

Action Potentials↗
PubMedDate not supplied

[Autoradiography of experimental blood brain barrier breakdown areas in the rat using pertechnetate as radiotracer].

INTRODUCTION: Absence of lipophility and other physical and chemical characteristics make the pertechnetate (99mTcO4 ) a potential autoradiographic radiotracer for the study of the blood brain and encephalic vasculature barrier integrity. PATHIENS and METHODS: Pertechnetate (99mTcO4Na) was i.v. injected (10 15 mCi) to 20 male Sprague Dawley rats. A hypervolemic hypertension was induced in the experimental group (n= 10) by i.v. Ringer infusion (333 mL/min up to 10 mL). Control group (n= 10) received normal hydration (16,6 mL/min). Rats were killed 60 min after 99mTcO4Na by a barbituric overdose and perfused with Ringer followed by formalin 4%. Coronal encephalic slides of 500 mm were located over odontological radiographic plates, allowed to dry for 12 14 hours and processed conventionally. Autoradiographic images were analysed by digital densitometry. RESULTS: Autoradiographies from control animals did not show activity images. Hypervolemic animals presented activity images located predominantly on putamen, caudate and hippocampus. The optical density of the autoradiographic images was correlated to the radioactivity of used standards (r= 0.98; p< 0.0005). Mean two points resolution obtained was 77.29+/-5.2 mm. CONCLUSION: The results suggest the utility of 99mTcO4Na as autoradiographic radiotracer in the experimental study of the blood brain barrier and encephalic vasculature integrity, showing a better two points resolution than that reported for [14C]2 deoxiglucose used for brain regional metabolism studies.

Animals↗