Joaquin Garcia-Estrada

Dehydroepiandrosterone, pregnenolone and sex steroids down-regulate reactive astroglia in the male rat brain after a penetrating brain injury.

Astrocytes are a target for steroid hormones and for steroids produced by the nervoussystem (neurosteroids). The effect of gonadal hormones and several neurosteroids in theformation of gliotic tissue has been assessed in adult male rats after a penetrating wound of thecerebral cortex and the hippocampal formation. The hormones testosterone, 17β‐estradiol and progesterone and the neurosteroids dehydroepiandrosterone, pregnenolone andpregnenolone sulfate resulted in a significant decrease in the accumulation of astrocytes in theproximity of the wound and in a decreased bromodeoxyuridine incorporation in reactiveastrocytes. Of all steroids tested, dehydroepiandrosterone was the most potent inhibitor of gliotictissue formation. These findings suggest that neurosteroids and sex steroids may affect brainrepair by down‐regulating gliotic tissue.

Neurosteroids modulate the reaction of astroglia to high extracellular potassium levels

The extracellular concentration of potassium ([K+]0) in brain tissue is modified by neuronal activity and is increased under several pathological conditions. The influence of neurosteroids on the astroglia response to high [K+]0 was assessed on cultured slices from rat hippocampus. Exposure to [K+]0 above physiological (3 mM) levels resulted in the progressive appearance of cell processes immunoreactive for glial fibrillary acidic protein (GFAP). The maximal effect was observed at 50 mM [K+]0, and further increases of [K+]0 did not increase the extension of GFAP‐immunoreactive processes. The effect was observed as early as 10 min after increasing [K+]0, was independent of new protein synthesis, and was reversible, reaching control conditions by 15 h after resetting [K+]0 to physiological levels. Gonadal hormones and neurosteroids had prominent and variable effects on the stimulatory influence of high [K+]0 on astroglia morphology. At physiological [K+]0, 17β‐estradiol and pregnenolone, as well as its sulfate derivative, increased the extension of GFAP‐immunoreactive processes. However, at high [K+]0, testosterone, pregnenolone, and dehydroepiandrosterone and its sulfate derivative decreased the extension of GFAP‐immunoreactive processes. Effects of gonadal hormones and neurosteroids were blocked by the protein synthesis inhibitor cycloheximide. These results suggest that non‐genomic effects of high [K+]0 on glial cells interact with genomic effects of steroids to modulate astroglia morphology.

Deflazacort: a glucocorticoid with few metabolic adverse effects but important immunosuppressive activity.

Deflazacort (DFZ) is a synthetic glucocorticoid that has few adverse effects on glucose and calcium metabolism and fewer deleterious effects on the neuronal population. Therefore, it may have a crucial role in the treatment of patients with autoimmune disorders associated with central nervous system or metabolic affectations. To date, the pharmacologic safety profile of DFZ is considered similar to that of other glucocorticoids. Nevertheless, cumulative clinical and laboratory evidence suggests that DFZ has, in fact, greater immunosuppressive activity than was previously thought. Therefore, it is possible that DFZ increases the risk of acquiring opportunistic infection compared with other synthetic glucocorticoids. Additional pharmacologic studies are needed to fully establish the immunosuppressive potency of DFZ and, consequently, to determine the appropriate ratio of bioequivalence in humans.

Early-life exposure to noise reduces mPFC astrocyte numbers and T-maze alternation/discrimination task performance in adult male rats

In this experiment, we evaluated the long-term effects of noise by assessing both astrocyte changes in medial prefrontal cortex (mPFC) and mPFC-related alternation/discrimination tasks. Twenty-one-day-old male rats were exposed during a period of 15 days to a standardized rats′ audiogram-fitted adaptation of a human noisy environment. We measured serum corticosterone (CORT) levels at the end of the exposure and periodically registered body weight gain. In order to evaluate the long-term effects of this exposure, we assessed the rats′ performance on the T-maze apparatus 3 months later. Astrocyte numbers and proliferative changes in mPFC were also evaluated at this stage. We found that environmental noise (EN) exposure significantly increased serum CORT levels and negatively affected the body weight gain curve. Accordingly, enduring effects of noise were demonstrated on mPFC. The ability to solve alternation/discrimination tasks was reduced, as well as the number of astroglial cells. We also found reduced cytogenesis among the mPFC areas evaluated. Our results support the idea that early exposure to environmental stressors may have long-lasting consequences affecting complex cognitive processes. These results also suggest that glial changes may become an important element behind the cognitive and morphological alterations accompanying the PFC changes seen in some stress-related pathologies.

Ultrastructural alterations in caudate nucleus, cerebral cortex and hippocampus produced by morphine

1. Chronic morphine administration to rats produced diverse ultrastructural alterations in nerve cells and neuropile of caudate nucleus, cerebral cortex and hippocampus through a short term abstinence period. 2. All areas studied showed increasing damage related to time elapsed between the last morphine injection and animal sacrifice. 3. Intracytoplasmic neuronal membranous organelles mainly suffered severe swelling, membrane disarrangement and eventually cell disruption in all areas studied. 4. Hippocampus was the most affected area throughout the study, followed by caudate nucleus and cerebral cortex, where focal damage was seen. 5. Susceptibility to morphine cytotoxic effect in the three areas studied appears to be unrelated to their opiate receptor density. 6. Mitochondrial alterations produced by morphine could be related to interference of the intracellular energy production system and consequent unrestricted cell membrane permeability to water and solutes.

Structural changes in caudate nucleus, cerebral cortex and hippocampus induced by morphine. Light microscopy study

Intraperitoneal chronic morphine administration to rats produced structural alterations in nerve cells of caudate nucleus, cerebral cortex and hippocampus. All areas studied showed increased alterations related to time elapsed between last morphine injection and fixation of tissue samples. Lesions mainly consisted in vacuolar degeneration of nerve cells. The most extense and intense lesions were observed in hippocampus. Sensorimotor cortex and caudate nucleus showed focal damage. Neurocytotoxic effect of morphine appears to be unrelated to the opiate receptor density in brain areas, and the brain regions susceptible to that effect appears to be different from brain areas related to adaptation to morphine. Effect of morphine on integrity and function of nerve cells mitochondria, interfering with energy production could play an important role in the pathogenesis of neuronal lesions.

Glutamatergic Receptor Activation in the Commisural Nucleus Tractus Solitarii (cNTS) Mediates Brain Glucose Retention (BGR) Response to Anoxic Carotid Chemoreceptor (CChr) Stimulation in Rats.

Glutamate, released from central terminals of glossopharyngeal nerve, is a major excitatory neurotransmitter of commissural nucleus tractus solitarii (cNTS) afferent terminals, and brain derived neurotrophic factor (BDNF) has been shown to attenuate glutamatergic AMPA currents in NTS neurons. To test the hypothesis that AMPA contributes to glucose regulation in vivo modulating the hyperglycemic reflex with brain glucose retention (BGR), we microinjected AMPA and NBQX (AMPA antagonist) into the cNTS before carotid chemoreceptor stimulation in anesthetized normal Wistar rats, while hyperglycemic reflex an brain glucose retention (BGR) were analyzed. To investigate the underlying mechanisms, GluR2/3 receptor and c-Fos protein expressions in cNTS neurons were determined. We showed that AMPA in the cNTS before CChr stimulation inhibited BGR observed in aCSF group. In contrast, NBQX in similar conditions, did not modify the effects on glucose variables observed in aCSF control group. These experiments suggest that glutamatergic pathways, via AMPA receptors, in the cNTS may play a role in glucose homeostasis.

Combined approach for experimental Oto-neurosurgical procedures.

Background: Experimental procedures will continue to be a key element while going through the learning curve in the use of the endoscope and minimally invasive procedures. We describe the technical procedure of an experimental approach to middle ear in New Zealand rabbits through external auditory canal and its relevance as an ideal model to study graft materials and serve as a training tool for potential applications in otoneurology. Methods: A group of 28 adult New Zealand rabbits were subjected to an experimental myringoplasty, combining the transmeatal and retroauricular approach with endoscopic assistance and microsurgical technique. The different anatomical steps and systematization of the complete experimental procedure are described. Results: An experimental approach to middle ear live model and basic anatomic description was successfully used, standardizing the ideal technique. The eardrum could regenerate with no complications and with functional preservation in all the myringoplasty cases. This strategy involves a safe combined approach to the tympanic membrane and others neurosurgical as transcochlear and translaberyntic approaches and is useful as a test of other experimental procedures to evaluate biomaterials to repair the eardrum currently studied. This experimental myringoplasty model also facilitates functional tests such as impedanciometry and the endoscopic follow-up of the whole process. Conclusions: The method described to perform an experimental myringoplasty (type I tympanoplasty) in a New Zealand rabbit is an option to be used as a basic model to study the behavior of the graft in the tympanic membrane. Also, basic concepts for the use of combined instrumentation are established in the treatment of eardrum lesions, as a refinement of the technical training application in microsurgery and assisted endoscopy in the transcochlear and translaberintic approaches and otoneurology areas.

Iron binding to nutrients containing fiber and phenytoin

Ascorbate and citrate extracted more iron than EDTA from pig foodstuffs (P less than 0.001). Glucose-saline solution (GSS) and ascorbate were less capable than citrate of extracting iron from maize tortilla (P less than 0.001). GSS extracted 16-32% of the whole iron contained in the studied foodstuffs; 30, 40 and 42% of the remaining iron in maize bran, wheat bran and pig feed was released with 0.1 M HCl. 40% of the remaining iron in pigs feed was released with 5% pepsin-0.1 M HCl while the iron of cereals required an additional extraction with 1% ascorbate. 5% pepsin-0.1 M HCl solutions released more iron as the protein content in the foodstuffs increased (P less than 0.001). Iron-extracted maize fibers (Ftw/Fe) bound significantly more iron than Ftc/Fe, FDA and FDN correspondingly (P less than 0.001). Phenytoin bound significantly more iron than total maize fibers both, with and without previous iron extraction (P less than 0.001). Also, phenytoin combined with maize-fiber bound less iron than phenytoin alone in G.S.A.

Progesterone fate in rabbit cornea

Excised cornea from adult New Zealand rabbits were incubated with progesterone-4-14C in Eagles media for 96 hr. Samples were inactivated at intervals of 24 hr incubation periods. The following metabolites of progesterone were isolated: 20 alpha-Hydroxy-4-pregnen-3-one, 20-hydroxy-4-pregnen-3-one, 5 alpha-pregnane-3,20-dione; 5 beta-pregnane-3,20-dione and 6 beta-hydroxy-4-pregnen-3,20-dione. 20 alpha-Hydroxy-pregnen-3-one was the predominant metabolite of progesterone-4-14C. A linear increase was observed throughout 96 hr. The opposite was found for 5 alpha and 5 beta pregnane-3,20-dione. Compounds remaining at the origin of the paper chromatograms contained 6 beta-hydroxy-4-pregnen-3,20-dione and other still unidentified metabolites of progesterone-4-14C. Presence of 20 alpha and 20 beta-reductase; 5 alpha and 5 beta-reductase and 6 beta-hydroxylase enzyme systems are involved in corneal progesterone metabolism. No fungal neither bacterial enzymatic biotransformation occurred in the culture media.