A quantitative study of inhibitory interneurons in laminae I-III of the mouse spinal dorsal horn

Laminae I-III of the spinal dorsal horn contain many inhibitory interneurons that use GABA and/or glycine as a neurotransmitter. Distinct neurochemical populations can be recognised among these cells, and these populations are likely to have differing roles in inhibiting pain or itch. Quantitative studies in rat have shown that inhibitory interneurons account for 25-40% of all neurons in this region. The sst2A receptor is expressed by around half the inhibitory interneurons in laminae I-II, and is associated with particular neurochemically-defined populations. Although much of the work on spinal pain mechanisms has been performed on rat, the mouse is now increasingly used as a model, due to the availability of genetically altered lines. However, quantitative information on the arrangement of interneurons is lacking in the mouse, and it is possible that there are significant species differences in neuronal organisation. In this study, we show that as in the rat, nearly all neurons in laminae I-III that are enriched with glycine also contain GABA, which suggests that GABA-immunoreactivity can be used to identify inhibitory interneurons in this region. These cells account for 26% of the neurons in laminae I-II and 38% of those in lamina III. As in the rat, the sst2A receptor is only expressed by inhibitory interneurons in laminae I-II, and is present on just over half (54%) of these cells. Antibody against the neurokinin 1 receptor was used to define lamina I, and we found that although the receptor was concentrated in this lamina, it was expressed by many fewer cells than in the rat. By estimating the total numbers of neurons in each of these laminae in the L4 segment of the mouse, we show that there are around half as many neurons in each lamina as are present in the corresponding segment of the rat

Abnormal motoneuron migration, differentiation, and axon outgrowth in spinal muscular atrophy

The role of heterotopic (migratory) motoneurons (HMN) in the pathogenesis of spinal muscular atrophy (SMA) is still controversial. We examined the occurrence and amount of HMN in spinal cord tissue from eight children with SMA (six with SMA-I and two with SMA-II). All affected subjects were carrying a homozygous deletion of exon 7 in the SMN1 gene. Unlike controls, virtually free from HMN, all SMA subjects showed a significant number of HMN at all levels of the spinal cord. Heterotopic neurons were hyperchromatic, located mostly in the ventral white matter and had no axon or dendrites. More than half of the HMN were very undifferentiated, as judged from their lack of immunoreactivity for NeuN and MAP2 proteins. Small numbers of more differentiated heterotopic neurons were also found in the dorsal and lateral white matter region. As confirmed by ultrastructural analysis, in situ end labeling (ISEL) and CD68 immunoreactivity, HMN in the ventral outflow were found to have no synapses, to activate microglial cells, and to eventually die by necrosis. An unbiased quantitative analysis showed a significant negative correlation between age of SMA subjects (a reflection of the clinical severity) and the number of HMN. Subjects who died at older ages had increased number of GFAP-positive astrocytes. Complementing our previous report on motoneuron apoptosis within the ventral horns in SMA, we now propose that abnormal migration, differentiation, and lack of axonal outgrowth may induce motoneuron apoptosis predominantly during early stages, whereas a slower necrosis-like cell death of displaced motoneurons which "escaped" apoptosis characterizes later stages of SMA

A stereological study of the effects of mercury inhalation on the cerebellum

Mercury in the environment that arises from organic and inorganic sources can cause irreversible damage to the nervous system. Toxicity may be direct or may arise from interactions with other metals in the environment. We evaluated the possible effects of mercury vapor on rat cerebellum. Twelve adult female rats were divided into control and experimental groups. The rats in the experimental group were exposed to mercury vapor for 9 h/day for 45 days. Cerebellar tissue samples were evaluated using stereology and for histopathology. The total number of Purkinje cells was estimated using a physical disector method. We found that in the experimental group, overall volume decreased and the number of Purkinje cells was reduced. We also found cellular damage including pycnotic nuclei, eosinophilic cytoplasm and vacuolization; these features were absent in the control group. We found that chronic exposure to inorganic mercury vapor is toxic to the cerebellum

The expansion of 300 CTG repeats in myotonic dystrophy transgenic mice does not induce sensory or motor neuropathy

Summary: Although many studies have been carried out to verify the involvement of the peripheral nervous system (PNS) in dystrophia myotonica (DM1) patients, the results remain controversial. The generation of DM1 transgenic mice displaying the human DM1 phenotype provides a useful tool to investigate the type and incidence of structural abnormalities in the PNS. In the present study, the morphological and morphometric analysis of semi-thin sections of sciatic and sural nerves, lumbar dorsal root ganglia (DRG) and lumbar spinal cords revealed that in DM1 transgenic mice carrying 300 CTG repeats, there is no change in the number and diameter of myelinated axons compared to wild type. Only a non-significant reduction in the percentage of thin myelinated axons was detected in electron micrographs of ultra-thin sciatic nerve sections. Analysis of the number of neurons did not reveal a loss in number of either sensory neurons in the lumbar DRG or motor neurons in the lumbar spinal cord in these DM1 mice. Furthermore, in hind limb muscle sections, stained with a neurofilament antibody and α-bungarotoxin, the intramuscular axon arborization appeared normal in DM1 mice and undistinguishable from that in wild-type mice. Moreover, in DM1 mice, there was no irregularity in the structure or an increase in the endplate area. Also statistical analysis did not show an increase in endplate density or in the concentration of acetylcholine receptors. Altogether, these results suggest that 300 CTG repeats are not sufficient to induce axonopathy, demyelination or neuronopathies in this transgenic mouse mode

Utilidad de un sistema de seguimiento óptico de instrumental en cirugía laparoscópica para evaluación de destrezas motoras

En este trabajo se estudia la utilidad de un sistema de evaluación de destrezas quirúrgicas basado en el análisis de los movimientos del instrumental laparoscópico. Método: El sistema consta de un simulador físico laparoscópico y un sistema de seguimiento y evaluación de habilidades técnicas quirúrgicas. En el estudio han participado 6 cirujanos con experiencia intermedia (entre 1 y 50 intervenciones laparoscópicas) y 5 cirujanos expertos (más de 50 intervenciones laparoscópicas), todos ellos con la mano derecha como dominante. Cada sujeto realizó 3 repeticiones de una tarea de corte con la mano derecha en tejido sintético, una disección de la serosa gástrica y una sutura en la disección realizada. Para cada ejercicio se analizaron los parámetros de tiempo, distancia recorrida, velocidad, aceleración y suavidad de movimientos para los instrumentos de ambas manos. Resultados: En la tarea de corte, los cirujanos expertos muestran menor aceleración (p = 0,014) y mayor suavidad en los movimientos (p = 0,023) en el uso de la tijera. Respecto a la actividad de disección, los cirujanos expertos requieren menos tiempo (p = 0,006) y recorren menos distancia con ambos instrumentos (p = 0,006 para disector y p = 0,01 para tijera). En la tarea de sutura, los cirujanos expertos presentan menor tiempo de ejecución que los cirujanos de nivel intermedio (p = 0,037) y recorren menos distancia con el disector (p = 0,041). Conclusiones: El sistema de evaluación se mostró útil en las tareas de corte, disección y sutura, y constituye un progreso en el desarrollo de sistemas avanzados de entrenamiento y evaluación de destrezas quirúrgicas laparoscópicas

Automated identification of Fos expression

The concentration of Fos, a protein encoded by the immediate-early gene c-fos, provides a measure of synaptic activity that may not parallel the electrical activity of neurons. Such a measure is important for the difficult problem of identifying dynamic properties of neuronal circuitries activated by a variety of stimuli and behaviours. We employ two-stage statistical pattern recognition to identify cellular nuclei that express Fos in two-dimensional sections of rat forebrain after administration of antipsychotic drugs. In stage one, we distinguish dark-stained candidate nuclei from image background by a thresholding algorithm and record size and shape measurements of these objects. In stage two, we compare performance of linear and quadratic discriminants, nearest-neighbour and artificial neural network classifiers that employ functions of these measurements to label candidate objects as either Fos nuclei, two touching Fos nuclei or irrelevant background material. New images of neighbouring brain tissue serve as test sets to assess generalizability of the best derived classification rule, as determined by lowest cross-validation misclassification rate. Three experts, two internal and one external, compare manual and automated results for accuracy assessment. Analyses of a subset of images on two separate occasions provide quantitative measures of inter- and intra-expert consistency. We conclude that our automated procedure yields results that compare favourably with those of the experts and thus has potential to remove much of the tedium, subjectivity and irreproducibility of current Fos identification methods in digital microscopy

APOL1 risk alleles are associated with exaggerated age-related changes in glomerular number and volume in African-American adults: an autopsy study

APOL1 genetic variants contribute to kidney disease in African Americans. We assessed correlations between APOL1 profiles and renal histological features in subjects without renal disease. Glomerular number (N-glom,) and mean glomerular volume (V-glom,) were measured by the dissector/fractionator method in kidneys of African-American and non-African-American adults without renal disease, undergoing autopsies in Jackson, Mississippi. APOL1 risk alleles were genotyped and the kidney findings were evaluated in the context of those profiles. The proportions of African Americans with none, one, and two APOL1 risk alleles were 38%, 43%, and 19%, respectively; 38% of African Americans had G1 allele variants and 31% of African Americans had G2 allele variants. Only APOL1-positive African Americans had significant reductions in N-glom and increases in V-glom with increasing age. Regression analysis predicted an annual average loss of 8834 (P=0.03, sex adjusted) glomeruli per single kidney over the first 38 years of adult life in African Americans with two risk alleles. Body mass index above the group medians, but below the obesity definition of >= 30 kg/m(2), enhanced the expression of age-related changes in N-glom in African Americans with either one or two APOL1 risk alleles. These findings indicate that APOL1 risk alleles are associated with exaggerated age-related nephron loss, probably decaying from a larger pool of smaller glomeruli in early adult life, along with enlargement of the remaining glomeruli. These phenomena might mark mechanisms of accentuated susceptibility to kidney disease in APOL1-positive African Americans

Sun tracker with rotatable plane-parallel plate and two photocells Patent

Sun tracker with rotatable plane-parallel plate and two photocell

Effect of mercury vapor inhalation on rat ovary: stereology and histopathology

AimMercury, an environmental contaminant, is a risk factor for health in whole living organisms. In this study, we investigated whether mercury vapor (HgO) inhalation has an effect on rat ovary. MethodsTwelve Wistar albino rats were divided equally into experimental (Hg) and control groups (n = 6). Animals in the Hg group were exposed to HgO for 45 days at a dose 1 mg/m(3)/day, after which, histological and stereological assessment were carried out. ResultsOvaries exposed to HgO had histo-morphometric alterations. HgO inhalation resulted in reduction of the total number of primordial, primary and Graaf follicles. Also, mean volume of ovary, medulla and cortex, corpus luteum (c.luteum) and Graaf follicles was decreased in the Hg group. Moreover, there was a significant increase in total volume of the atretic follicles. On light microscopy, thickening of tunica albuginea, increase of fibrils within the connective tissue, congestion of the capillaries and venous vessels, thinned walls and fibrin deposition in some large blood vessels, and edema were seen. Also, irregular follicle and oocyte borders, and hydropic degeneration in follicular granulosa cells were detected. ConclusionStructural alterations could be attributed to the toxic influence of HgO on rat ovary. The use of Hg should therefore be more controlled to minimize its toxic effect

Effect of voluntary exercise on number and volume of cardiomyocytes and their mitochondria in the mouse left ventricle

Voluntary exercise (VE) has a beneficial influence on the heart and mean lifespan. The present study evaluates structural adaptations of cardiomyocytes and their mitochondria due to VE by new, unbiased stereological methods. Female, 7-9-week-old mice were randomly assigned to a control (CG, n=7) or VE group (EG, n=7). EG animals were housed in cages with free access to a running wheel and had a mean running distance of 6.7 (1.8)km per day. After 4weeks, the hearts of all mice were processed for light and electron microscopy. We estimated the number and volume of cardiomyocytes by the disector method and the number and volume of mitochondria by estimation of the Euler number. In comparison to CG, VE did not have an effect on the myocardial volume of the left ventricle (CG: 93 (10), EG: 103 (17) (mm3)), the number of cardiomyocytes (CG: 2.81 (0.27), EG: 2.82 (0.43) (×106)) and their number-weighted mean volume. However, the composition of the cardiomyocytes changed due to VE. The total volume of mitochondria (CG: 21.8 (4.9), EG: 32.2 (4.3) (mm3), P<0.01) and the total number (CG: 3.76 (0.44), EG: 7.02 (1.13) (×1010), P<0.001) were significantly higher in EG than in CG. The mean number-weighted mitochondrial volume was smaller in EG than in CG (P<0.05). In summary, VE does not alter ventricular volume nor cardiomyocyte volume or number but the oxidative capacity of cardiomyocytes by an increased mitochondrial number and total volume in the left ventricle. These structural changes may participate in the beneficial effects of V