Antonio Eblen-Zajjur

Sensory lateralization in pain subjective perception for noxious heat stimulus.

The aim of the present study was to identify and characterize hemispheric lateralization for pain intensity perception. A sample of 351 healthy volunteers was tested by the immersion of the right hand for 10 s followed by the same test for the left hand (RL group; n = 199) or in a random sequence (RND group; n = 152) into a water bath (48°C, 15 s). Pain intensity was self-reported by the Visual Analogue Scale (VAS). The motor hemispherical Lateralization Index (LI) was obtained by the Edinburgh Inventory. Gender, hand skin fold, interstimulus time and menstrual cycle data in case of female subjects were recorded. The sample, 60.7% females and 39.3% males, 20.4 - 0.18 (mean - SEM) years old, showed 92.1% right-handed subjects. Left hand VAS was significantly higher than right hand VAS for RL (7.24 - 1.31 vs 6.74 - 1.52; p < 0.01) and RND (7.24 - 0.82 vs 6.73 - 1.25; p < 0.01) both for right- and left-handed subjects. A low but significant correlation for VAS scores and LI was found ( r = 0.14; p < 0.05 or r = 0.18; p < 0.05, for left or right hand, respectively). Skin fold was statistically similar in both hands ( p > 0.05) being highly correlated with each other ( r = 0.68; p < 0.05). Pain subjective perception was not correlated to interstimulus time ( r = -0.01; p > 0.05). Females showed significantly higher values than males for both left and right hand VAS scores. Periovulatory phase VAS value was significantly higher than luteal phase VAS only for the right hand test (7.57 - 0.20 vs 6.47 - 0.33; p < 0.01). The results of the present study suggest a lateralization of pain intensity perception to the right hemisphere not correlated with the motor hemispheric lateralization.

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.

Normal expression and inflammation-induced changes of Na and Na/K ATPase activity in spinal dorsal horn of the rat.

We tested whether that peripheral inflammation induces changes in the spinal dorsal horn ATPase activity. Adult Sprague-Dawley rats were anesthetized (thiobarbital), the left hind paw (inflammation group; n = 15) was immersed in water at 60 degrees C for 60s, which induced a local inflammation. A control group (n = 12) was tested with water at room temperature. After 60 min of peripheral inflammation left (LDH) or right lumbar dorsal horn (RDH) were processed for total, Na/K, Na and remanent ATPase activities (nM P(i) (mgprotein)(-1) min(-1)). In control animals isoenzymatic activities were: Na (31.2%); Na/K (20.6%) and remanent (48.2%) from total ATPase activity. No LDH-RDH asymmetry was found. The inflammation group presented an ipsilateral increase of total ATPase activity in LDH (X+/-S.E.M.; 4798.9+/-601) over the RDH (3982.2+/-451; Delta+817; P<0.05). This is due to an increase in Na ATPase activity (1609.3+/-297) over RDH (1164.2+/-166; Delta+445; P<0.05). ATPase activities were increased in LDH from inflamed over the control group as follows: total (4798.9+/-601; Delta+840; P<0.05), Na/K (1298.1+/-301; Delta+483; P<0.05) and Na (1609.3+/-297; Delta+373; P<0.05). These increased ATPase activities, induced in a short time, can be considered a functional marker of nociceptive neuronal activity.

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.

Magnesium sulphate reduces cell volume in physiological conditions but not in the cytotoxic oedema during global brain ischemia

Primary objective: To establish the effect of MgSO4on brain cellular volume during physiological and global ischemia using impedanciometric method. Research design: Impedanciometric measure in the brain before and during global brain ischemia, with or without intravenous infusion of MgSO4. Methods and procedures: Male Sprague-Dawley rats were anaesthetized (thiobarbital, 60 mg kg−1 i.p.). Ringer solution (n = 9) or MgSO4(n = 8; 1 mmol Kg−1) where i.v. isovolumetrically administered. Sub-cortical impedance was recorded before and after the infusion of ringer or MgSO4and during global cerebral ischemia induced by a cardiopulmonary arrest. Main outcomes and results: In non-ischemic conditions, MgSO4infusion induced higher voltage values than those of ringer infusion (Wilcoxon, Z = 2.49; p = 0.01). During global cerebral ischemia, the MgSO4infused animals showed a fast drop of voltages (82%) in the first 5 minutes, 4-fold the values of ringer infused animals (p < 0.0001). In the following 15 minutes no differences were found between ringer and MgSO4infused animals. Conclusions: The results suggest that MgSO4significantly reduced brain cell volume in physiological conditions but not in global brain ischemia

INFLUENCE OF ACUTE HYPERGLYCAEMIA ON THE AMPLITUDE OF NOCICEPTIVE SPINAL EVOKED POTENTIALS IN HEALTHY RATS

To evaluate the effect of blood glucose level on the amplitude of nociceptive spinal evoked potentials in healthy rats, an acute hyperglycaemia state was induced in an experimental group of 12 rats, through the infusion of glucosade solution. A Ringer-lactate solution was administered equivolumetrically to the control group (5 rats) under the same experimental conditions. Nociceptive spinal evoked potentials were recorded every 2 min, before and during the induction of hyperglycaemia, from the left lumbar cord dorsum activated orthodromically by ipsilateral electrical stimulation of the hind paw (20 Volts, 0.5 ms, 0.2 Hertz). Acute hyperglycaemia induced an increase of amplitude in both N (+8.92%, p = .000006) and P (+10.46%, p = .000037) waves when comparing control and experimental groups or basal versus infusion values, in response to nociceptive stimuli. The present results show that acute hyperglycaemia could contribute to central nociceptive sensitization; it would be attributed to an increased synchronization of spinal dorsal horn neuronal discharges.

Nongenomic effect of levothyroxine on the synchronous electrical activity of the spinal dorsal horn in the rat

Abstract Levothyroxine (T4) has a well-known effect on the central nervous system (CNS). This effect requires hours of latency by genetic pathway. We tested for short latency nongenomic effects of T4 superfusion on the spinal dorsal horn (DH) evaluating lumbar somatosensory evoked potentials in rats. T4 increased N and P wave amplitudes and N wave area under the curve, but reduced P wave duration and N–P interval, suggesting that T4 exerts both excitatory and synchronizing effects on DH interneurons in less than 300 s, thus, providing evidence of nongenomic effects of T4 on DH.

Digital Morphometric Characterization of Lumbar Dorsal Root Ganglion Neurons in Rats

Abstract Because of contrasting morphometric reports about dorsal root ganglion (DRG) neurons in rats, the aim of this study was to precisely characterizate these cells by means of digital imaging processing (DIP) to establish the different cellular groups located in lumbar DRG and possible correlations between different cellular morphometric parameters. DRG were extirpated from 10 male Sprague-Dawley rats, fixed, and histologically processed. Digital photomicrographs were obtained for cytomorphometric analysis of cellular diameter, cytoplasmic density, and distance to the DRG capsule. A total of 266 DRG neurons were sampled: 60% of cells presented diameters between 25 and 55μm; 64% were dark and 14.6% clear. No correlation was found between cellular diameter and cytoplasmic density. Nuclear density showed a bimodal distribution with a high correlation to cytoplasmic density. The current study demonstrates that DRG neurons in rat consist of one predominant group of cells with a mean diameter of 30 μm; these cells may exhibit a dark or clear cytoplasm with nuclear density directly related to cytoplasm density. (The J Histotechnol 33(3):113–118, 2010) Submitted January 11 , 2009; accepted July 20, 2010.

EVALUACIÓN DE PARÁMETROS INFLAMATORIOS LOCALES Y SISTÉMICOS DE QUEMADURA PERIFÉRICA EN UN MODELO ANIMAL

To evaluate the edema volume and leukocyte, platelet, and fibrinogen count of peripheral burn in an animal model. The back left leg of Rattus norvegicus (experimental group) was placed in water at 60 °C for 60 seconds or at room temperature (control group). An analysis was carried out before and after the induced burn (at 4, 8, 12, and 24 h). The edema volume was determined by an orthogonal photo, the leukocyte and platelet counts were determined using automated equipment, and the fibrinogen count was determined using the gravimetric method. The maximum value of the edema was recorded at 4 h and leukocytes at 24 h. The platelet count did not vary at different post-edema time intervals. The fibrinogen level increased at 4 h and 24 h. In this animal model we induced systemic inflammation characterized by leukocytosis and elevated fibrinogen levels, combined with edema located at the induction area.

Evaluación in silico de una epidemia de influenza aviar AH5N1 con transmisión humano-humano: efecto de las medidas sanitarias en Valencia, Venezuela, 2012

BACKGROUND There is a risk for an avian influenza AH5N1 virus pandemia. AIM To estimate the magnitude and impact of an AH5N1 pandemic in areas of Latin-America in order to design interventions and to reduce morbidity-mortality. METHODS The InfluSim program was used to simulate a highly pathogenic AH5N1 aviar virus epidemic outbreak with human to human transmission in Valencia, Venezuela. We estimated the day of maximal number of cases, number of moderately and severely ill patients, exposed individuals, deaths and associated costs for 5 different interventions: absence of any intervention; implementation of antiviral treatment; reduction of 20% in population general contacts; closure of 20% of educational institutions; and reduction of 50% in massive public gatherings. Simulation parameters used were: population: 829.856 persons, infection risk 6-47%, contagiousness Index Rh o 2,5; relative contagiousness 90%, overall lethality 64,1% and, costs according to the official basic budget. RESULTS For an outbreak lasting 200 days direct and indirect deaths by intervention strategies would be: 29,907; 29,900; 9,701; 29,295 and 14,752. Costs would follow a similar trend. DISCUSSION Reduction of 20% in general population contacts results in a significant reduction of up to 68% of cases. The outbreak would collapse the health care system. Antiviral treatment would not be efficient during the outbreak. Interpersonal contact reduction proved to be the best sanitary measure to control an AH5N1 theoretical epidemic outbreak.