NADPH-diaphorase activity in area 17 of the squirrel monkey visual cortex: neuropil pattern, cell morphology and laminar distribution

We studied the distribution of NADPH-diaphorase activity in the visual cortex of normal adult New World monkeys (Saimiri sciureus) using the malic enzyme "indirect" method. NADPH-diaphorase neuropil activity had a heterogeneous distribution. In coronal sections, it had a clear laminar pattern that was coincident with Nissl-stained layers. In tangential sections, we observed blobs in supragranular layers of V1 and stripes throughout the entire V2. We quantified and compared the tangential distribution of NADPH-diaphorase and cytochrome oxidase blobs in adjacent sections of the supragranular layers of V1. Although their spatial distributions were rather similar, the two enzymes did not always overlap. The histochemical reaction also revealed two different types of stained cells: a slightly stained subpopulation and a subgroup of deeply stained neurons resembling a Golgi impregnation. These neurons were sparsely spined non-pyramidal cells. Their dendritic arbors were very well stained but their axons were not always evident. In the gray matter, heavily stained neurons showed different dendritic arbor morphologies. However, most of the strongly reactive cells lay in the subjacent white matter, where they presented a more homogenous morphology. Our results demonstrate that the pattern of NADPH-diaphorase activity is similar to that previously described in Old World monkeys.

Horizontal projections of area 17 in Cebus monkeys: metric features, and modular and laminar distribution

Metric features and modular and laminar distributions of intrinsic projections of area 17 were studied in Cebus apella. Anterogradely and retrogradely labeled cell appendages were obtained using both saturated pellets and iontophoretic injections of biocytin into the operculum. Laminar and modular distributions of the labeled processes were analyzed using Nissl counterstaining, and/or cytochrome oxidase and/or NADPH-diaphorase histochemistry. We distinguished three labeled cell types: pyramidal, star pyramidal and stellate cells located in supragranular cortical layers (principally in layers IIIa, IIIb α, IIIb ß and IIIc). Three distinct axon terminal morphologies were found, i.e., Ia, Ib and II located in granular and supragranular layers. Both complete and partial segregation of group I axon terminals relative to the limits of the blobs of V1 were found. The results are compatible with recent evidence of incomplete segregation of visual information flow in V1 of Old and New World primates.

Methylmercury intoxication and histochemical demonstration of NADPH-diaphorase activity in the striate cortex of adult cats

The effects of methylmercury (MeHg) on histochemical demonstration of the NADPH-diaphorase (NADPH-d) activity in the striate cortex were studied in 4 adult cats. Two animals were used as control. The contaminated animals received 50 ml milk containing 0.42 µg MeHg and 100 g fish containing 0.03 µg MeHg daily for 2 months. The level of MeHg in area 17 of intoxicated animals was 3.2 µg/g wet weight brain tissue. Two cats were perfused 24 h after the last dose (group 1) and the other animals were perfused 6 months later (group 2). After microtomy, sections were processed for NADPHd histochemistry procedures using the malic enzyme method. Dendritic branch counts were performed from camera lucida drawings for control and intoxicated animals (N = 80). Average, standard deviation and Student t-test were calculated for each data group. The concentrations of mercury (Hg) in milk, fish and brain tissue were measured by acid digestion of samples, followed by reduction of total Hg in the digested sample to metallic Hg using stannous chloride followed by atomic fluorescence analysis. Only group 2 revealed a reduction of the neuropil enzyme activity and morphometric analysis showed a reduction in dendritic field area and in the number of distal dendrite branches of the NADPHd neurons in the white matter (P<0.05). These results suggest that NADPHd neurons in the white matter are more vulnerable to the long-term effects of MeHg than NADPHd neurons in the gray matter.

Distribuição das enzimas NADPH-Diaforase e Tirosina Hidroxilase na substância negra de camundongos infectados pelo Toxoplasma gondii

O Toxoplasma gondii é um protozoário parasita intracelular obrigatório de prevalência mundial e importante causador de doenças em humanos e animais domésticos. No Brasil, até 80% da população pode estar infectada, dependendo da região. Os pacientes infectados agudamente geralmente apresentam infecção assintomática com posterior desenvolvimento de cistos teciduais, que são mais comumente encontrados nos músculos estriados, retina e cérebro. A infecção latente pode alterar o comportamento dos animais hospedeiros e provocar sintomas psicóticos em humanos. Estudos sugerem que esta infecção pode contribuir para a ocorrência de desordens neurológicas e psiquiátricas, como por exemplo, a doença de Parkinson e esquizofrenia, que são associadas com anormalidades do sistema dopaminérgico. Neste estudo, avaliou-se a imunoreatividade contra a enzima tirosina hidroxilase (TH) e a atividade da NADPH-diaforase na substância negra do cérebro de camundongos infectados. Camundongos machos da linhagem Swiss Webster (Mus musculus) receberam por gavagem 10 cistos contendo bradizoítos da cepa Me-49 do Toxoplasma gondii. Os cérebros destes camundongos foram removidos após eutanásia por decapitação após os períodos de 30 e 60 dias de inoculação. A análise das secções mostrou uma reduzida marcação histoquímica para NADPHdiaforase na substância negra dos animais infectados quando comparados com os animais controle. Esta redução foi observada também na imunoreatividade contra a enzima TH na substância negra. Estes resultados indicam que a presença do T. gondii modifica o metabolismo na região da substância negra, modulando os níveis de óxido nítrico (NO) e dopamina, o que pode ser responsável pelas alterações comportamentais presentes nos hospedeiros intermediários infectados.