Adolfo Toledano

Chronic nicotine administration increases NGF-like immunoreactivity in frontoparietal cerebral cortex

Nicotine/nicotine agonists, which have been proposed as therapeutic agents for the treatment of Alzheimers disease and other neurodegenerative disorders, produce a wide variety of effects on the nervous system. Some mechanisms involved remain poorly understood. In this work, immunohistochemical techniques were used to determine the effect of nicotine on nerve growth factor (NGF) in the frontoparietal (motor, somatosensory) brain cortex of the albino rat. Nicotine was chronically administered intraperitoneally using osmotic pumps (0.35 mg nicotine base/kg body weight/day for 14 days). An increase in the number and the immunoreaction intensity of NGF‐like positive pyramidal and nonpyramidal neurons of these cortical areas was observed after treatment. Immunopositive astroglial cells were always seen in sections of treated animals but not in controls. The neuropil of control animals was, in general, devoid of reaction, but in treated animals, immunopositive prolongations were located randomly, some in close association with capillaries. At the electron microscopic level, these prolongations were demonstrated as belonging to neurons (dendrites and axons) and astroglial cells. Nicotinic activation of selected neurons and glial cells seems to trigger NGF/neurotrophic mechanisms, suggesting their use may be of benefit in prevention and treatment of neurodegenerative diseases.

FTIR microspectroscopic analysis of the effects of certain drugs on oxidative stress and brain protein structure

This study reports the changes in lipids and proteins of different brain areas of nicotine, D(+)‐amphetamine, and nicotine and D(+)‐amphetamine treated rats by monitoring lipid peroxidation and protein β‐sheet formation using infrared microspectroscopy. Compared with the untreated brain samples, the peroxide level is relatively higher in the amphetamine‐treated brain sections, both in the cortex and hippocampus area. However, this peroxide increase is attenuated when administering amphetamine plus nicotine. Analogous drug‐dependent trends for protein β‐sheet content are observed, which suggests a connection between lipid oxidation involved in oxidative stress and β‐sheet protein structure generally present in neurodegenerative diseases. The above property of nicotine is of interest, in the sense that it might reduce the production of β‐amyloid proteins in Alzheimers disease.

Discrimination Analysis of Blood Plasma Associated with Alzheimer's Disease Using Vibrational Spectroscopy

In this study we have determined whether Raman and infrared spectroscopy of blood plasma differentiates Alzheimers disease (AD) from normal aging of healthy controls. Spectroscopic analysis was conducted on blood plasma samples from 8 mild AD, 16 moderate AD, 11 severe AD, and 12 normal elderly control persons using Fourier transform spectrometers and a near-infrared laser beam as excitation source for Raman spectroscopy. Spectra were processed employing discriminant analysis to determine whether band areas and frequency-intensity relationships might reveal biochemical differences associated with AD. Seven spectral biomarkers were identified in the Raman regions of 1700-1600 cm-1 (protein secondary structure), 980-910 cm-1 (protein α-helices), 790-730 cm-1 (protein tertiary structure), and 440-390 cm-1 (protein backbone) and in the infrared regions of 1700-1600 cm-1 (protein secondary structure) and 1150-1000 cm-1 (oxidative stress). This discriminant analysis model differentiated AD from normal aging of elderly control persons with a sensitivity of 89% and specificity of 92%. Moreover, specificity increases to 100% for the detection of mild AD. In summary, our results open the possibility of using this spectroscopic approach as a non-invasive, rapid, and relatively inexpensive procedure for early accurate diagnosis of AD.

Diversity and variability of the effects of nicotine on different cortical regions of the brain. Therapeutic and toxicological implications

Nicotine/nicotine agonists or allosteric modulators of nicotine receptors have been suggested as the most important therapeutic agents in the prevention and clinical control of cognitive impairment which characterize neuropsychiatric and neurodegenerative disorders such as schizophrenia, attention deficit/hyperactivity disorder and Alzheimers disease. Both clinical studies and animal experiments support the important role of the nicotinic systems in learning, different kind of memory and cognition. For development of nicotinic treatments we have a well characterized lead compound, nicotine. However, the neural nicotinic mechanisms underlying cognitive functions are not well known because the side effects of nicotine overdose have hindered the development of this therapeutical line. The new development of non-toxic, brain specific nicotine drugs need a full knowledge of these mechanism and a reevaluation of the nicotine effects. This review aims to analyze the different kind of effects of nicotine on the Central Nervous System (CNS), especially on the cortex and hippocampus. Nicotine effects are, theoretically and/or practically, of variable character depending on daily dose and time of treatment; on the subtype and density of the different nicotinic receptors existing in the distinct brain regions; on the processes of desensitization and tolerance of nicotinic receptors and on other neuronal factors. Nicotine produces the above mentioned activation of the cognitive functions acting directly or indirectly on cortical neurons. In some experiments, high doses of nicotine can impair memory. This substance induces increases in the glycolytic pathway and Krebs cycle of neurons, as well as brain blood flow. Nicotine also produces an increase in NGF immunoreactivity in frontoparietal cortex. All these neuronal changes may cause different positive effects such as neuroprotection, neuroplasticity and better performance of synaptic circuits. The benefit of other neuronal changes can be matter of discussion such as some modifications in synaptic transmission, the COX-2 increase in frontoparietal cortex and hippocampus or the changes in the antioxidant systems. Finally, other neuronal changes can be of negative effect such as the induction of apoptosis and oxidative stress (DNA damage, ROS and lipid peroxide increase). All these described effects explain both the beneficial and neurotoxic consequences of the activation of the nicotinic receptors. The diversity and variability of the nicotinic effects should take into account when nicotine agonists will be used as a possible cognitive treatment.

Astroglial cell subtypes in the cerebella of normal adults, elderly adults, and patients with Alzheimer's disease: A histological and immunohistochemical comparison

Objectives and experimental design Cerebella of young adults, elderly adults, and patients with Alzheimers disease (AD) (with and without cerebellar amyloid deposits) were studied by Golgi staining and glial fibrillary acid protein (GFAP) immunocytochemical methods. Observations Three subtypes of Golgi epithelial cells and nine subtypes of stellate neuroglia (both normal and hypertrophic) were defined by their morphology, their GFAP‐reactivity, their specific location in the cortical layers, and their responses in senility and AD. The GFAP immunoreaction was subtype specific. In aged and AD cerebella, different morphological and GFAP‐immunoreactive subtype‐specific changes were observed: in the white matter, the subtypes were always GFAP‐immunopositive, but in the grey matter some astroglial subtypes showed a variable or no increase in GFAP staining. The astrocytes at the limits of the granule cell layer showed more and longer processes. Variations were seen in one or more folia, involving one or more subtypes and affecting different numbers of cells of each subtype. No clear differences were seen in glial reactivity between beta‐amyloid positive and β‐amyloid (Aβ) negative AD cerebella. No important relationships were found between Aβ deposits. In aged and AD cerebella, different subtypes expressed new proteins (APP, calretinin). Conclusions The existence of different glial subtypes in different locations suggests they have different functions. General and local variations in these subtypes suggest that both general and local induction factors must also exist. The responses of glial cells to as‐yet undefined stimuli might lead to general or local neuronal changes important in senility and the pathogenic course of AD. GLIA 2015;63:287–312

Infrared spectroscopic analysis of mononuclear leukocytes in peripheral blood from Alzheimer's disease patients

Peripheral mononuclear leukocytes from Alzheimer’s disease (AD) patients were analyzed by infrared spectroscopy and their spectroscopic properties were compared with those from age-matched healthy controls. Two-dimensional correlation analysis of mean spectra measured at various disease stages shows that the protein secondary structure from AD patients involves β-sheet enrichment and carbonyl intensity increase relative to healthy controls. The area percentages of β-sheets, which were obtained by using a peak ratio second-derivative spectral treatment, were used for receiver operating characteristic (ROC) analysis to distinguish between patients with AD and age-matched healthy controls. The critical concentration and area under the curve (AUC) were determined by this curve analysis which showed a good performance for this quantitative assay. The results were 90% sensitivity and 90.5% specificity for determinations involving mild and moderate AD patients, and 82.1% sensitivity and 90.5% specificity for determinations involving patients at the three AD stages (mild, moderate, and severe). The AUC was greater than 0.85 in both scenarios. Taken together these results show that healthy controls are distinguished from mild and moderate AD patients better than from patients with severe disease and suggest that this infrared analysis is a promising strategy for AD diagnostics.

Histochemical study of acute and chronic intraperitoneal nicotine effects on several glycolytic and krebs cycle dehydrogenase activities in the frontoparietal cortex and subcortical nuclei of the rat brain

The effects of nicotine on the activity of different dehydrogenases in frontoparietal regions and subcortical nuclei of the rat brain have been studied using histochemical methods. Nicotine sulphate was intraperitoneally administered in acute (4 mg/kg/day × 3 days) or chronic (ALZET osmotic pump providing 2 mg/kg/day × 15 days) doses. The enzymes analyzed were glyceraldehyde‐3‐phosphate, lactate, malate and succinate dehydrogenases (gly3PDH, LDH, MDH, and SDH, respectively). The results demonstrate that chronic as well as acute administration of nicotine produced strong increases in all these enzymatic activities in the superior layers (I, II and III) of the frontoparietal cortex (cingulate, motor and somatosensory regions); but high increases were not seen in the deeper layers of the cortex or in the subcortical nuclei (substantia nigra, caudate‐putamen, nucleus accumbens or nucleus basalis magnocellularis). These hyperactivities were produced in brain regions with normally low enzymatic activity (cortex), but not in those with great intensity (subcortical nuclei). The results are in rough agreement with previous reports on nicotine‐induced increases in glucose utilization, gly3PDH genic expression and neuronal hyperactivity in the brain cortex; but significant discrepancies between the cortical enzymatic maps and those obtained both in these studies and others on nicotine(N)‐receptor localization have been appreciated. The results support the hypothesis that nicotinic cholinergic drugs can have metabolic, long‐lasting stimulant effects on cortical neurons at specific points (probably layer III pyramidal cells and structures with α7‐N‐receptors) of the cortical circuits that could be of great interest in improving altered cognitive functions that are present in Alzheimer disease, as well as in other less severe mental disturbances. Mitochondrial hyperfunction should also be evaluated as a possible side‐effect (as an oxidative stress inductor) of these kinds of drugs. J. Neurosci. Res. 64:626–635, 2001.

Pyritinol facilitates the recovery of cortical cholinergic deficits caused by nucleus basalis lesions

SummaryThe effect of a nootropic, Pyritinol, on the recovery of cortical cholinergic deficits induced by injury of the nucleus basalis has been tested on two groups of unilateral quisqualic acid nbM-lesioned rats. The first group had a 30 nmol lesion producing a cortical cholinergic impairment at 21 days, with a spontaneous recovery at 45 days. The second group had a 50 nmol lesion that produced a deeper cholinergic deficit, which did not recover at 45 days. Pyritinol enhanced the recovery in the 30 nmol group of animals on the 21st day after surgery. The recovery was measured as an increase in the activities of acetylcholinesterase (AChE), choline acetyltransferase (ChAT) and the high affinity choline uptake system, and the histochemical densities of the cortical AChE network and the M2 receptor. Histochemical analysis of the nbM enabled cortical recovery to be related to the number of surviving neurons and also to their hypertrophy and AChE-ChAT hyperactivity. Pyritinol enhanced recovery in 30 nmol lesioned animals but in the other group, with a lower number of surviving neurons and a lower ability of the cells to become hypertrophic, the drug was unable to promote cortical recovery.

Histochemical study of mucopolysaccharides in the subthalamic region of rats

Histological sections of the Subthalamic region of rats were treated with solutions of: Toluidin Blue, Thionin, Alcian Blue and Colloidal Iron. The microscopic observation of the histological sections treated with those histochemic reactions showed the existence in the Subthalamic region of three neuronal types, differentiated between them because of the morphologic and histochemic points of view. In the LUYs Subthalamic nucleus was observed only one neuronal type, while in the nucleus of the FORELs field and in the Zona incerta were found two very special types of neurons (alpha and beta) differentiated between them because of their reaction before the Collidal Iron. It is suggested the possibility that those different types of neurons have different functional characteristics.

Calretinin-immunopositive Cells and Fibers in the Cerebellar Cortex of Normal Sheep

Calretinin (CR)-immunopositive cells and fibers in the cerebellar cortex (vermal archicerebellum—lobules X and IX—and neocerebellum—lobules VIIb and VIII) of two and 4-year-old Manchega and Rasa Aragonesa sheep were studied. CR-immunoreactivity was seen in subsets of all neurons and afferent fibers described in the cerebellar cortex. Generally, immunopositive cells were seen in very high densities in lobules X and IX, and in low density in lobule VIIb. Apparently, all unipolar brush cells were CR-immunopositive and showed a greater variety of shape than had been reported in other species. CR-immunoreactivity of Purkinje cells was either absent or varied from low to medium intensity. Few granule cell perikarya were immunostained (<5%) but a large number of their axons were CR-immunopositive. Subsets of stellate and basket cells were CR-immunoreactive—quite different to what is seen in most of mammalian species. Strongly CR-immunopositive mossy and climbing fibers, isolated or grouped, were observed in all lobules. Although we found neither a difference in CR-immunoreactivity between the two breds of sheep, nor between the two ages examined, we observed important differences in CR-immunoreactivity between sheep and other mammalian species. Our observation of neuronal clusters and groups of fibers with very high CR-immunopositivity supports the idea of a heterogeneous species-specific functional organization for the cerebellar cortex within an apparent homogeneous histological structure maintained throughout mammalian evolution. The results also suggest that the varied levels of CR expression may be related to the specific functions of these immunopositive neurons and fibers rather than to a general neuroprotective role played by calretinin in the cerebellar cortex.