Regional distribution and characterization of nitric oxide synthase activity in the brain of the common marmoset

Influence of post-mortem delay and storage temperature on the immunohistochemical detection of antigens in the CNS of mice

The aim of this work was to compare the results of histochemical and immunohistochemical methods using mouse brains which were fixed with various post-mortem delays and storage temperatures (at a constant 4 degrees C or 22 degrees C, or at gradually decreasing post-mortem temperatures, mimicking conditions of human corpse). We studied the effects of post-mortem delay on glial fibrillary acidic protein, extracellular matrix components to which Wisteria floribunda agglutinin binds, non-phosphorylated neurofilament H, synaptophysin, calbindin and nitric oxide synthase isoenzymes. At the light microscopic level first signs of post-mortem changes were detectable after 6 h. Glial fibrillary acidic protein was most affected by post-mortem delay since its immunoreactivity increased dramatically with increasing post-mortem delay. N-acetylgalactosamines-beta1 labeled lectin binding sites, calbindin and intraneuronal non-phosphorylated neurofilament H seemed to be stable up to 12 h post-mortem. Storage temperature influenced the NADPH-d activity and the content of synaptophysin immunoreactivity to higher degree than all of the other parameters. We found only marginal differences of alterations comparing neocortex, hippocampus and corpus callosum. Our results indicate that different antigens are affected differently by the ongoing catabolic processes during post-mortem delay.

The level of nitric oxide in the cortex correlates well with brain lateralization

The correlation between nitric oxide (NO) levels in the cortices and brain lateralization was investigated via the paw preference test in which three groups of mice (left-pawed, ambidextrous and right pawed) were selected. Results showed that the right cortices had higher NO levels than the left cortices for both normal and lipopolysaccharide-treated mice. There were significant differences in NO levels in the right/left cortices depending on the behavioral lateralization as expressed by paw preference. Finally, individual levels of NO in the right/left cortices correlated well with individual paw preference scores. The relationship was parabolic. The results suggest a strong relationship between NO asymmetries as well as the direction and the intensity of behavioral lateralization.

Regional distribution of nitric oxide synthase and NADPH-diaphorase activities in the central nervous system of teleosts

Neuronal nitric oxide synthase (nNOS) and NADPH-diaphorase activities were investigated in discrete areas of the central nervous system of goldfish and brown trout. Both species showed a similar distribution pattern of nNOS activity with regional differences in all examined areas. Telencephalon and hypothalamus showed the highest nNOS values, while in the goldfish cerebellum and its valvula nNOS was not detectable. In both species, NADPH-diaphorase activity showed a lower regional variability, compared to nNOS. The highest activity was measured in the olfactory bulbs where, conversely, low levels of nNOS activity were present. The non close correspondence between NOS and NADPH-diaphorase activities confirms the discrepancies indicated by morphological data. Western blot analysis revealed the presence of a nNOS isoform of about 150 kDa mol. wt. corresponding to that of mammals. The pattern of nNOS expression in the considered brain regions of the goldfish and trout was comparable to the levels of the nNOS activity.

Differential and constitutive expression of neuronal, inducible, and endothelial nitric oxide synthase mRNAs and proteins in pathologically normal human tissues

Nitric oxide (NO) is produced by NO synthases (nNOS, iNOS, and eNOS) expressed in various human tissues and depending on the amount of NO produced in each tissue, the physiological function of NO is determined. However, due to the difficulty in obtaining normal human tissues, little is known about the basal levels of each of the three NOS mRNAsand proteins expressed constitutively in various human tissues. Results of the present study indicate that the basal levels of each of the three NOS mRNAs and proteins expressed in various regions of brain and peripheral tissues are different both in their sizes and in their contents. In Northern blot analysis, two different-sized mRNAs were found for each NOS isozymes: for the nNOS, approximately 12 and <12 kb mRNAs; for the iNOS, 4.2 and 4.5 kb mRNAs; for the eNOS, 4.2 and 4.4 kb mRNAs. In the Western blot, several different-sized NOS proteins were detected ( approximately 160, approximately 140, and approximately 130 kDa for nNOS; approximately 130 kDa for iNOS and eNOS) with tissue-specific expression patterns. These differential expression patterns of NOS mRNAs and proteins were caused by alternative splicing in the open-reading frame, and 5'- and/or 3'-untranslated regions of NOS mRNAs. These results suggest that regulation for differential expression of the three NOS genes in various human tissues may occur by alternative splicing of the NOS mRNAs in tissue-specific patterns.

Partial cloning of constitutive and inducible nitric oxide synthases and detailed neuronal expression of NOS mRNA in the cerebellum and optic tectum of adult Atlantic salmon (Salmo salar)

Studies of different species have implicated nitric oxide (NO) synthase (NOS) in various physiological and pathological events. Three major NOS isoforms are present in the brain of mammals; endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS). Little is known about the significance of the presence of these proteins in the brain. We report the first investigation into the presence of nNOS and iNOS isoforms in a teleost, adult Atlantic salmon (Salmo salar). Complementary DNA was synthesized from cerebellum and thymus mRNA using RT-PCR techniques with primers against conserved regions of NOS. Cloning and sequencing revealed a partial gene sequence of 560 bp corresponding to mammalian nNOS from cerebellum cDNA. The predicted protein sequence of identified salmon nNOS possessed 85% identity to that of mammalian nNOS. Northern blot analysis of different tissues revealed expression in brain and heart, and indicated expression of three different nNOS mRNAs in the brain. In addition, a 389 bp sequence corresponding to iNOS was identified in thymus cDNA. Salmon iNOS is almost identical to rainbow trout iNOS (95%), but shows much less amino acid identity to goldfish (65%) and mammalian (52%) iNOS. Phylogenetically, all vertebrate nNOS and iNOS homologues are clustered separately. Expression studies by means of in situ hybridization revealed abundant nNOS mRNA transcripts in distinct neuronal populations throughout the Purkinje cell layer of the corpus cerebellum and the periventricular layer of the optic tectum. Our data show that adult Atlantic salmon possess a gene encoding an nNOS isoform and putative alternatively spliced forms, which are expressed in distinct neuronal populations in the cerebellum and optic tectum, and in yet unidentified cell types in the heart. The data suggest that the arising of different vertebrate NOS isoforms is an evolutionary old event. The well conserved sequences present in salmon and mammalian nNOS may reflect their importance in protein function, whereas interspecies distributional differences in cellular expression of nNOS and sequence differences of iNOS may reflect variations and specializations in routes of NO action in the vertebrate phylogeny.

Characterization and regional distribution of nitric oxide synthase in the human brain during normal ageing

Nitric oxide (NO) is a highly diffusible cellular mediator generated from L-arginine by the enzyme nitric oxide synthase (NOS). As little is known about the regional distribution of NOS in the human brain, we examined the distribution pattern of nitric oxide synthase activity in 28 regions of the human brain using the [(3)H]L-citrulline formation assay. To elucidate which isoforms contribute to the total NOS activity we performed Western blot analysis of neuronal, inducible and endothelial NOS. We further determined brain levels of arginine and citrulline as a potential index of NOS activity pre mortem. NOS activity appears to remain unaltered during ageing and is independent of post mortem delay, gender or sample storage time. We identified a regional pattern of NOS distribution with highest levels of NOS activity in the substantia innominata, cerebellar cortex, nucleus accumbens and subthalamicus, whereas lowest levels were measured in the corpus callosum, thalamus, occipital cortex, and dentate nucleus. nNOS was measured throughout the brain, in contrast iNOS and eNOS were not detectable. We therefore conclude that primarily nNOS is responsible for NOS activity in the human brain. Levels of citrulline were higher than those of arginine, but did not correlate with the enzyme activity, suggesting that these parameters are unsuitable for testing NOS activity premortem. The characterization and topographical pattern of NOS in the human brain during normal ageing may assist our understanding of the physiological role of NO and its relevance in Parkinson's and Alzheimer's disease, alcoholism, schizophrenia and AIDS.