Zinc deficiency induces enhanced depression-like behaviour and altered limbic activation reversed by antidepressant treatment in mice.

A relationship between zinc (Zn)-deficiency and mood disorders has been suspected. Here we examined for the first time whether experimentally-induced Zn-deficiency in mice would alter depression- and anxiety-related behaviour assessed in established tests and whether these alterations would be sensitive to antidepressant treatment. Mice receiving a Zn-deficient diet (40% of daily requirement) had similar homecage and open field activity compared to normally fed mice, but displayed enhanced depression-like behaviour in both the forced swim and tail suspension tests which was reversed by chronic desipramine treatment. An anxiogenic effect of Zn-deficiency prevented by chronic desipramine and Hypericum perforatum treatment was observed in the novelty suppressed feeding test, but not in other anxiety tests performed. Zn-deficient mice showed exaggerated stress-evoked immediate-early gene expression in the amygdala which was normalised following DMI treatment. Taken together these data support the link between low Zn levels and depression-like behaviour and suggest experimentally-induced Zn deficiency as a putative model of depression in mice.

Hippocampal levels of gamma-enolase, C-1-tetrahydrofolate synthase and serotransferrin fluctuate over the estrous cycle in the rat.

Hippocampal functions vary across the estrous cycle but metabolic changes at the protein level have not been systematically studied so far. It was therefore the aim of the study to screen expression of metabolic proteins mainly represented by metabolic enzymes in the hippocampus over the estrous cycle and in males. Female and male OFA Sprague-Dawley rats were used and female estrous phases were determined by vaginal smears, according to which females were separated into groups of proestrous, estrous, early and late metestrous and diestrous. Proteins were extracted from hippocampal tissue and separated on two-dimensional gel electrophoresis followed by identification with mass spectrometry methods (MALDI-TOF-TOF and nano-LC-ESI-MS/MS). Comparative analysis of protein levels was carried out by quantifying protein spot volumes by means of specific software. Levels of one expression form of gamma-enolase were different between diestrous and early metestrous; C-1-tetrahydrofolate synthase levels were elevated in proestrous as compared with estrous and serotransferrin levels were increased in diestrous as compared with proestrous, estrous, metestrous and in males. The outcome of estrous cycle- and gender-dependent protein fluctuations is relevant for the interpretation of previous and future work as well as for the design of further studies at the protein level in the hippocampus.

Protein expression of BACE1, BACE2 and APP in Down syndrome brains.

Down syndrome (DS) is the most common human chromosomal abnormality caused by an extra copy of chromosome 21. The phenotype of DS is thought to result from overexpression of a gene or genes located on the triplicated chromosome or chromosome region. Several reports have shown that the neuropathology of DS comprises developmental abnormalities and Alzheimer-like lesions such as senile plaques. A key component of senile plaques is amyloid beta-peptide which is generated from the amyloid precursor protein (APP) by sequential action of beta-secretases (BACE1 and BACE2) and gamma-secretase. While BACE1 maps to chromosome 11, APP and BACE2 are located on chromosome 21. To challenge the gene dosage effect and gain insight into the expressional relation between beta-secretases and APP in DS brain, we evaluated protein expression levels of BACE1, BACE2 and APP in fetal and adult DS brain compared to controls. In fetal brain, protein expression levels of BACE2 and APP were comparable between DS and controls. BACE1 was increased, but did not reach statistical significance. In adult brain, BACE1 and BACE2 were comparable between DS and controls, but APP was significantly increased. We conclude that APP overexpression seems to be absent during the development of DS brain up to 18-19 weeks of gestational age. However, its overexpression in adult DS brain could lead to disturbance of normal function of APP contributing to neurodegeneration. Comparable expression of BACE1 and BACE2 speaks against the hypothesis that increased beta-secretase results in (or even underlies) increased production of amyloidogenic A beta fragments. Furthermore, current data indicate that the DS phenotype cannot be fully explained by simple gene dosage effect.

Strain-dependent effects of cognitive enhancers in the mouse.

A series of cognitive enhancers (CEs) have been reported to increase spatial memory in rodents, information on behavioral effects, however, is limited. The aim of the study was therefore to examine the behavioral effects of three CEs in two well-documented inbred mouse strains. C57BL/6J and DBA/2 mice were administered intraperitonial. D-cycloserine (DCS; NMDA receptor agonist), 1-(4-Amino-5-chloro-2-methoxyphenyl)-3-[1-butyl-4-piperidinyl]-1-propanone hydrochloride (RS67333; 5HT4-receptor agonist), and (R)-4-{[2-(1-methyl-2-pyrrolidinyl)ethyl]thio}phenol hydrochloride (SIB-1553A; beta-4-nicotinic receptor agonist) and tested in the open field (OF), elevated plus maze (EPM), neurological observational battery and rota-rod. Cognitive performance was tested in the Morris water maze. All compounds modified behavioral performance in the OF, DCS showed an anxiolytic effect in the EPM, and differences in the observational battery were observed i.e. vestibular drop was decreased by SIB-1553A and RS67333 treatment in C57BL/6J and increased with DCS treatment in DBA/2 mice. In the rota rod SIB-1553A improved motor performance. DCS effects on learning and memory was comparable to controls whereas the other compounds impaired performance in the Morris water maze. In conclusion, behavioral testing of CEs in the mouse revealed significant changes that may have to be taken into account for evaluation of CEs, interpretation of cognitive studies and warrant further neurotoxicological studies. Moreover, strain-dependent differences were observed that in turn may confound results obtained from behavioral and cognitive testing.

Mass spectrometrical analysis of the processed metastasis-inducing anterior gradient protein 2 homolog reveals 100% sequence coverage.

Anterior gradient protein 2 homolog is a metastasis-inducing protein in a rat model of rat breast cancer and prognostic for outcome in hormonally treated breast cancer patients. Carrying out protein profiling in several mammalian cells and tissues, we detected this protein (synonym: secreted cement gland protein XAG-2 homolog) that was originally described in toad skin, in human bronchial epithelia. Tissues obtained from biopsies were homogenised and extracted proteins were run on two-dimensional gel electrophoresis. Following in-gel digestion with proteases trypsin, AspN, LysC and chymotrypsin, mass spectrometrical analysis was carried out by MALDI-TOF/TOF. The use of MS following multi-enzyme digestion of the protein resulted into 100% sequence coverage. MS/MS analysis enabled sequencing of 87% of the protein structure. This percentage does not include the signal peptide that was not observed in our protein due to processing. No posttranslational modifications were detectable and no sequence conflicts were observed. Complete analysis, unambiguous identification and characterisation of this biologically important protein could be shown, which is relevant for the definition of a marker protein that has been described so far by immunochemical methods only. Complete analysis is of importance as it forms the basis for all future work on this protein and, moreover, may serve as an analytical tool for further studies.

Identification and characterisation of arsenite (+3 Oxidation State) methyltransferase (AS3MT) in mouse neuroblastoma cell line N1E-115.

Handling and detoxification of metals by enzymes is a major issue that is not in the focus of current biomedical research concepts. The finding of the presence of arsenic (+3 Oxidation State) methyltransferase (AS3MT) in neuroblastoma cells NE-115 as a high abundance protein made us investigate primary structure of AS3MT reflecting an example of metal-handling in eucaryotes. Proteins extracted from NE-115 cells were run on 2-DE followed by two different mass spectrometrical methods. High sequence coverage was obtained by multiple protease digestion and a sequence conflict was solved at arginine 335. These findings are important when future studies on this enzyme are designed at the protein level and in particular, when antibodies against this protein will be generated.

Tuberin activates the proapoptotic molecule BAD.

TSC1, encoding hamartin, and TSC2, encoding tuberin, are tumor suppressor genes responsible for the autosomal dominantly inherited disease tuberous sclerosis (TSC). TSC affects approximately 1 in 6000 individuals and is characterized by the development of tumors, named hamartomas, in different organs. Hamartin and tuberin form a complex, of which tuberin is assumed to be the functional component. The TSC proteins have been implicated in the control of cell cycle and cell size. In addition to enhanced growth, reduced death rates can lead to tumor development. Therefore, defects in the apoptosis-inducing pathways contribute to neoplastic cell expansion. Here, we show that tuberin triggers apoptosis, accompanied by downregulation of p70S6K activity and of phosphorylation of BAD on residue Ser136, and by upregulation of the interaction of BAD/BCL-2 and BAD/BCL-XL. AKT phosphorylation negatively regulates tuberin's potential to trigger apoptosis. Experiments with BAD-/- cells demonstrate BAD to be a mediator of tuberin's effects on the regulation of apoptosis. Tuberin interferes with insulin-like growth factor-1-induced BAD Ser136 phosphorylation and cell survival. Our work proposes a model in which tuberin-mediated inhibition of p70S6K activates BAD to heterodimerize with BCL-2 and BCL-XL to promote apoptosis. A mutation of TSC2--as it occurs in TSC patients--attenuates this proapoptotic potential, underscoring the relevance of our findings for human pathophysiology.

Start-to-end processing of two-dimensional gel electrophoretic images.

Gel electrophoresis serves as a basic analytical tool in the proteomic studies. However, processing of gel electrophoretic images is still the main bottleneck of data analysis, and there is an increasing need for the fully automated approaches. The proposed start-to-end strategy of analyzing the gel images consists of chemometric tools, which allow their effective preprocessing, automatic warping, and data modeling. The image preprocessing techniques: denoising in the wavelet domain and the penalized asymmetric least squares approach for the background estimation are proposed. Matching of images is based on fuzzy warping of features, extracted from the gel images. For the classification or calibration purpose, multivariate approaches such, as partial least squares (PLS) or kernel-PLS methods are used. Performance of the proposed strategy is demonstrated on the real set of the two-dimensional gel images.

Strain-dependent regulation of neurotransmission and actin-remodelling proteins in the mouse hippocampus.

Individual mouse strains differ significantly in terms of behaviour, cognitive function and long-term potentiation. Hippocampal gene expression profiling of eight different mouse strains points towards strain-specific regulation of genes involved in neuronal information storage. Protein expression with regard to strain- dependent expression of structures related to neuronal information storage has not been investigated yet. Herein, a proteomic approach based on two-dimensional gel electrophoresis coupled with mass spectrometry (MALDI-TOF/TOF) has been chosen to address this question by determining strain-dependent expression of proteins involved in neurotransmission and activity-induced actin remodelling in hippocampal tissue of five mouse strains. Of 31 spots representing 16 different gene products analysed and quantified, N-ethylmaleimide-sensitive fusion protein, N-ethylmaleimide-sensitive factor attachment protein-alpha, actin-like protein 3, profilin and cofilin were expressed in a strain-dependent manner. By treating protein expression as a phenotype, we have shown significant genetic variation in brain protein expression. Further experiments in this direction may provide an indication of the genetic elements that contribute to the phenotypic differences between the selected strains through the expressional level of the translated protein. In view of this, we propose that proteomic analysis enabling to concomitantly survey the expression of a large number of proteins could serve as a valuable tool for genetic and physiological studies of central nervous system function.

Mass-spectrometrical analysis of proteins encoded on chromosome 21 in human fetal brain.

Overexpression of chromosome 21 genes is directly or indirectly responsible for the Down syndrome phenotype. In order to analyse chromosome 21 gene products (Chr21Ps), we extracted proteins from fetal human brain cortex and applied an ultracentrifugal and chromatographic prefractionation principle followed by two-dimensional gel electrophoresis (2-DE) and mass-spectrometrical analysis using high-throughput automated MALDI-TOF/TOF. Nine Chr21Ps were identified: pyridoxal kinase; superoxide dismutase [Cu/Zn] 1; carbonyl reductase 1; ES1 protein homolog, mitochondrial [Precursor]; cystathionine-beta-synthetase; T-complex protein 1, theta subunit; cystatin B; 6-phosphofructokinase; glycinamide ribonucleotide synthetase. Mass-spectrometric characterisation of Chr21Ps following separation in 2-DE gels is a useful tool for the analysis of these structures in brain, independent of antibody availability and specificity.

Brain G protein-dependent signaling pathways in Down syndrome and Alzheimer's disease.

Premature aging and neuropathological features of Alzheimer's disease (AD) are commonly observed in Down syndrome (DS). Based on previous findings in a DS mouse model, the function of signaling pathways associated with adenylyl cyclase (AC) and phospholipase C (PLC) was assessed in cerebral cortex and cerebellum of age-matched adults with DS, AD, and controls. Basal production of cAMP was reduced in DS but not in AD cortex, and in both, DS and AD cerebellum. Responses to GTPgammaS, noradrenaline, SKF 38393 and forskolin were more depressed in DS than in AD cortex and cerebellum. Although no differences in PLC activity among control, DS and AD cortex were observed under basal and GTPgammaS- or Ca-stimulated conditions, the response of DS cortex to serotonergic and cholinergic stimulation was depressed, and that of AD was only impaired at cholinergic stimulation. No differences were documented in cerebellum. Our results demonstrate that PLC and AC were severely disturbed in the aged DS and AD brains, but the alterations in DS were more severe, and differed to some extent from those observed in AD.

Repeated application of Modafinil and Levodopa reveals a drug-independent precise timing of spatial working memory modulation.

Cognition enhancing drugs often target the dopaminergic system, which is involved in learning and memory, including working memory that in turn involves mainly the prefrontal cortex and the hippocampus. In most animal models for modulations of working memory animals are pre-trained to a certain criterion and treated then acutely to test drugs effects on working memory. Thus, little is known regarding subchronic or chronic application of cognition enhancing drugs and working memory performance. Therefore we trained male rats over six days in a rewarded alternation test in a T-maze. Rats received daily injections of either modafinil or Levodopa (L-Dopa) at a lower and a higher dose 30min before training. Levodopa but not modafinil increased working memory performance during early training significantly at day 3 when compared to vehicle controls. Both drugs induced dose dependent differences in working memory with significantly better performance at low doses compared to high doses for modafinil, in contrast to L-Dopa where high dose treated rats performed better than low dose rats. Strikingly, these effects appeared only at day 3 for both drugs, followed by a decline in behavioral performance. Thus, a critical drug independent time window for dopaminergic effects upon working memory could be revealed. Evaluating the underlying mechanisms contributes to the understanding of temporal effects of dopamine on working memory performance.

Proteomic analysis of the TerC interactome: Novel links to tellurite resistance and pathogenicity.

The tellurite resistance gene operon (ter) is widely spread among bacterial species, particularly pathogenic species. The ter operon has been implicated in tellurite resistance, phage inhibition, colicine resistance, and pathogenicity. The TerC protein represents one of the key proteins in tellurite resistance and shows no significant homology to any protein of known function. So far, there is no experimental evidence for TerC interaction partners. In this study, proteomic-based methods, including blue native electrophoresis and co-immunoprecipitation combined with LC-MS/MS, have been used to identify TerC interaction partners and thus providing indirect evidence for tentative functions of TerC in Escherichia coli. An interactome has been constructed and robust physical interaction of integral membrane protein TerC with TerB, DctA, PspA, HslU, and RplK has been shown. The TerC-TerB complex appears to act as a central unit that may link different functional modules with biochemical activities of C4-dicarboxylate transport, inner membrane stress response (phage shock protein regulatory complex), ATPase/chaperone activity, and proteosynthesis. In previous reports, it was hypothesized that a transmembrane unit formed by TerC protein may interact with the TerD family, but herein neither TerD nor TerE proteins were identified as TerC complex components. We propose that TerD/TerE participates in tellurite resistance through TerC-independent action.

Neonatal islet cell adenoma: a distinct type of islet cell tumor?

An encapsulated, compact-type islet cell adenoma of the pancreas, found in a newborn infant with hyperinsulinemic hypoglycemia, was investigated by conventional histology and immunofluorescence. Although the histologic structure of the tumor was indistinguishable from that of most islet cell tumors of adults, immunofluorescence revealed that the four islet cell hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) were all present in the tumor. They were stored in different cells that showed the same spatial distribution usually seen in normal islets. We conclude that neonatal islet cell adenoma can be distinguished from those of adults on the basis of the content and topographic distribution of their constituent endocrine cells.

Decreased brain levels of 2',3'-cyclic nucleotide-3'-phosphodiesterase in Down syndrome and Alzheimer's disease.

In Down syndrome (DS) as well as in Alzheimer's disease (AD) oligodendroglial and myelin alterations have been reported. 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) and carbonic anhydrase II (CA II) are widely accepted as markers for oligodendroglia and myelin. However, only data on CNPase activity have been available in AD and DS brains so far. In our study we determined the protein levels of CNPase and CA II in DS, AD and in control post mortem brain samples in order to assess oligodendroglia and myelin alterations in both diseases. We used two dimensional electrophoresis to separate brain proteins that were subsequently identified by matrix assisted laser desorption and ionization mass-spectroscopy (MALDI-MS). Seven brain areas were investigated (frontal, temporal, occipital and parietal cortex, cerebellum, thalamus and caudate nucleus). In comparison to control brains we detected significantly decreased CNPase protein levels in frontal and temporal cortex of DS patients. The level of CA II protein in DS was unchanged in comparison to controls. In AD brains levels of CNPase were decreased in frontal cortex only. The level of CA II in all brain areas in AD group was comparable to controls. Changes of CNPase protein levels in DS and AD are in agreement with the previous finding of decreased CNPase activity in DS and AD brain. They probably reflect decreased oligodendroglial density and/or reduced myelination. These can be secondary to disturbances in axon/oligodendroglial communication due to neuronal loss present in both diseases. Alternatively, reduced CNPase levels in DS brains may be caused by impairment of glucose metabolism and/or alterations of thyroid functions.

L-Arginine reduces lipid peroxidation in patients with diabetes mellitus.

A current concept for the development of diabetic long-term complications is the involvement of oxidative stress, as, e.g., lipid peroxidation, in the diabetic state. Data published recently show also oxidative damage to DNA, which might be one factor for accelerated aging and diabetic microangiopathy. In our study we tested the hypothesis that L-arginine can reduce lipid peroxidation in patients with diabetes. We performed a blind placebo controlled study with crossing over two treatment periods for 3 months. Thirty patients with diabetes mellitus were randomly assigned to treatment group A (first treatment then placebo) and B (first placebo then treatment). Treatment consisted of two daily dosages of 1 g L-arginine free base. Lipid peroxidation as reflected by malondialdehyde was evaluated in urine using a standard HPLC assay. After 3 months of treatment there was a significant reduction in malondialdehyde levels in group A (p < .0032), whereas there was no difference compared to the baseline values after three months of placebo treatment in group B (p < .97). After crossing over, there was a significant reduction in malondialdehyde levels in group B (p < .0002). Group A showed a significant increase in malondialdehyde levels (p < .0063) returning to baseline values. L-Arginine treatment was able to reduce the lipid peroxidation product malondialdehyde. This provides evidence that treatment with L-arginine may counteract lipid peroxidation and thus reduce microangiopathic long-term complications in diabetes mellitus.

Aromatic hydroxylation in nasal lavage fluid following ambient ozone exposure.

Ozone at ambient concentrations affects lung function and initiates an inflammatory response of the airways. However, the underlying mechanisms are poorly understood. In vitro studies have shown that ozone reacts with water to give reactive hydroxyl radicals capable of oxidizing a wide range of biomolecules. We conducted a study to determine if in vivo hydroxyl radical attack on human airways occurs under natural exposure to ozone. The relation of orthotyrosine to para-tyrosine as a measure of hydroxyl radical attack was analyzed in nasal lavage samples of 44 primary school children in an epidemiologic study. Repeated nasal lavages were performed between May and October 1991 both following "low" (daily half-hour maximum < 140 micrograms/m3, approximately 70 ppb) and "high" (daily half-hour maximum > 180 micrograms/m3, approximately 90 ppb) ozone exposure. Concomitantly, lung function tests were performed. On average, 11.6 (6-16) nasal lavages were performed for each of 24 study days (10 days following "low" ozone exposure and 14 days following "high" ozone exposure). Average ortho-tyrosine (median; 5-95% percentile) for each child was 0.037 mumol/L (0.016-0.064 mumol/L) and average para-tyrosine was 15.7 mumol/L (9.8-24.1 mumol/L). Ortho-tyrosine (as percentage of tyrosine) was significantly higher following days with "high" ozone exposure (0.18%) vs. days following "low" ozone exposure (0.02%; p = .0001). Ortho-tyrosine showed an inverse relationship with forced vital capacity (p = .01) but was not related to inflammation of the upper airways as assessed by cell counts of polymorphonuclear neutrophils. Hydroxyl radical attack subsequent to ambient ozone occurs in the upper airways of healthy children and is related to lung function decrements.

Aberrant protein expression in cerebral cortex of fetus with Down syndrome.

Down syndrome is the most common birth defect associated with mental retardation. Identifying proteins that are aberrantly expressed therefore helps to understand how chromosomal imbalance leads to subnormal intelligence in Down syndrome. In the present study, we generated a fetal brain map with the use of an analytical method based on two-dimensional electrophoresis coupled with mass spectrometry and searched the proteome for differential protein expression. Among 49 proteins analyzed in seven control and nine Down syndrome fetuses, we found 11 proteins that have been deregulated in cerebral cortex of fetal Down syndrome. While double-strand break repair protein rad 21 homologue, eukaryotic translation initiation factor 3 subunit 5, mixed lineage leukemia septin-like fusion protein-B and heat shock protein 75 were increased; beta-amyloid precursor-like protein 1, tropomyosin 4-anaplastic lymphoma kinase fusion oncoprotein type 2, Nck adaptor protein 2, Src homology domain growth factor receptor bound 2-like endophilin B2, beta tubulin, septin 7 and hematopoietic stem/progenitor cells 140 were decreased. The current data suggest that misexpression of proteins that have functions ranging from signaling to cellular structural organization could contribute to or reflect brain dysgenesis in Down syndrome.

Neurocircuitries of the basal ganglia studied in organotypic cultures: focus on tyrosine hydroxylase, nitric oxide synthase and neuropeptide immunocytochemistry.

The nigrostriatal and mesolimbic systems of the rat were reconstructed using an organotypic culture model, whereby neonatal brain tissue was grown in vitro for approximately one month. The nigrostriatal system comprised of tissue from the substantia nigra, the dorsal striatum and the frontoparietal cortex, while the mesolimbic system included the ventral tegmental area, ventral striatum (including the fundus striati, accumbens nucleus, olfactory tubercle, lateral septum, ventral pallidum and piriform cortex) and cingulate cortex. These regions were also cultured alone or in pairs. The cultures were monitored in vitro, and after one month fixed in a formalin-picric acid solution, and processed for immunohistochemistry using antibodies raised against tyrosine hydroxylase, nitric oxide synthase, preprocholecystokinin, glutamate decarboxylase, neuropeptide Y, dopamine- and cyclic AMP-regulated phosphoprotein-32 and glial fibrillary acidic protein. The tissue survived in single, double or triple cultures, although differences were found depending upon the source and combination of cultured region. Neurons had localization and shape as in vivo. Local networks were especially prominent in the mesencephalon, where both tyrosine hydroxylase-positive axons spread from the "substantia nigra" to the rest of the tissue, and where nitric oxide synthase-positive networks also surrounded tyrosine hydroxylase-positive neurons. Glutamate decarboxylase-positive nerve terminals formed dense networks around tyrosine hydroxylase-positive neurons. In the striatum, nitric oxide synthase and dopamine- and cyclic AMP-regulated phosphoprotein-32 neurons were surrounded by tyrosine hydroxylase-positive nerve terminals. The nigral and ventral tegmental area dopamine neurons projected to striatal and cortical structures, but the projection from the ventral tegmental area to the cingulate cortex was more prominent. With regard to co-existence, preprochole-cystokinin-like immunoreactivities was found in many tyrosine hydroxylase-positive neurons and neuropeptide Y- and nitric oxide synthase-like immunoreactivity co-existed in striatal and cortical tissues. In general terms, the chemical neuroanatomy in the cultures was similar to that described earlier in vivo. Nitric oxide synthase staining was particularly intense. Taken together, the organotypic model captures many of the morphological and neurochemical features seen in vivo, providing a valuable model for studying neurocircuitries of the brain in detail, where 'normal' and 'pathological' conditions can be simulated.

Nitric oxide and nitric oxide synthase in the early phase of perinatal asphyxia of the rat.

The role of nitric oxide, a compound involved in neurotransmission and regulation of cerebral blood flow, in cerebral ischemia is still not fully elucidated yet. Although well studied in adult systems of cerebral ischemia/hypoxia, information on nitric oxide in perinatal asphyxia is limited and, in particular, no direct evidence for its generation has been provided. We therefore decided to study nitric oxide generation in brain of asphyctic rat pups by biophysical and biochemical methods. We used a simple, non-invasive rat model resembling the clinical situation in perinatal asphyxia: rat pups delivered by Caesarean section were placed into a water bath at 37 degrees C still in patent membranes for various asphyctic periods (up to 20 min). Brain pH, cerebral blood flow, neuronal nitrix oxide synthase messenger RNA (by northern and dot blot analysis), immunoreactive protein (by western blot analysis) and nitric oxide synthase activity were determined; generation of nitric oxide was evaluated directly by electron paramagnetic resonance spectroscopy. Neuronal nitric oxide synthase messenger RNA activity and nitric oxide generation were unaffected, whereas neuronal nitric oxide synthase-immunoreactive protein of 150,000 mol. wt was decreased and of 136,000 mol. wt was increased with the length of the asphyctic period. This is the first report on direct evidence for the generation of nitric oxide in perinatal asphyxia and we demonstrate that nitric oxide production remains unaffected even by 20 min of asphyxia, at a time-point when cerebral blood flow was increased four-fold and severe acidosis was present. However, it was found that levels of immunoreactive neuronal nitric oxide synthase of 136,000 mol. wt were increased paralleling the length of asphyxia. Levels of the 150,000 mol. wt immunoreactive neuronal nitric oxide synthase protein decreased, suggesting a different regulation pattern. Thus, the present biochemical and biophysical results form the basis for further investigations on nitric oxide in perinatal asphyxia.