Manduca sexta hemolymph protease-2 (HP2) activated by HP14 generates prophenoloxidase-activating protease-2 (PAP2) in wandering larvae and pupae

Melanization is a universal defense mechanism of insects against microbial infection. During this response, phenoloxidase (PO) is activated from its precursor by prophenoloxidase activating protease (PAP), the terminal enzyme of a serine protease (SP) cascade. In the tobacco hornworm Manduca sexta, hemolymph protease-14 (HP14) is autoactivated from proHP14 to initiate the protease cascade after host proteins recognize invading pathogens. HP14, HP21, proHP1*, HP6, HP8, PAP1-3, and non-catalytic serine protease homologs (SPH1 and SPH2) constitute a portion of the extracellular SP-SPH system to mediate melanization and other immune responses. Here we report the expression, purification, and functional characterization of M. sexta HP2. The HP2 precursor is synthesized in hemocytes, fat body, integument, nerve and trachea. Its mRNA level is low in fat body of 5th instar larvae before wandering stage; abundance of the protein in hemolymph displays a similar pattern. HP2 exists as an active enzyme in plasma of the wandering larvae and pupae in the absence of an infection. HP14 cleaves proHP2 to yield active HP2. After incubating active HP2 with larval hemolymph, we detected higher levels of PO activity, i.e. an enhancement of proPO activation. HP2 cleaved proPAP2 (but not proPAP3 or proPAP1) to yield active PAP2, responsible for a major increase in IEARpNA hydrolysis. PAP2 activates proPOs in the presence of a cofactor of SPH1 and SPH2. In summary, we have identified a new member of the proPO activation system and reconstituted a pathway of HP14-HP2-PAP2-PO. Since high levels of HP2 mRNA were present in integument and active HP2 in plasma of wandering larvae, HP2 likely plays a role in cuticle melanization during pupation and protects host from microbial infection in a soil environment.

Loss of β-carotene 15,15'-oxygenase in developing mouse tissues alters esterification of retinol, cholesterol and diacylglycerols

We provide novel insights into the function(s) of β-carotene-15,15'-oxygenase (CMOI) during embryogenesis. By performing in vivo and in vitro experiments, we showed that CMOI influences not only lecithin:retinol acyltransferase but also acyl CoA:retinol acyltransferase reaction in the developing tissues at mid-gestation. In addition, LC/MS lipidomics analysis of the CMOI-/- embryos showed reduced levels of four phosphatidylcholine and three phosphatidylethanolamine acyl chain species, and of eight triacylglycerol species with four or more unsaturations and fifty-two or more carbons in the acyl chains. Cholesteryl esters of arachidonate, palmitate, linoleate, and DHA were also reduced to less than 30% of control. Analysis of the fatty acyl CoA species ruled out a loss in fatty acyl CoA synthetase capability. Comparison of acyl species suggested significantly decreased 18:2, 18:3, 20:1, 20:4, or 22:6 acyl chains within the above lipids in CMOI-null embryos. Furthermore, LCAT, ACAT1 and DGAT2 mRNA levels were also downregulated in CMOI-/- embryos. These data strongly support the notion that, in addition to cleaving β-carotene to generate retinoids, CMOI serves an additional function(s) in retinoid and lipid metabolism and point to its role in the formation of specific lipids, possibly for use in nervous system tissue.

Localization of Na(+)/K(+)-ATPase in silkworm brain: a possible mechanism for protection of Na(+)/K(+)-ATPase from Ca(2+)

In mammalian blood, the Na(+) concentration is higher than the K(+) concentration, whereas in hemolymph of lepidopterous insects, the K(+) concentration is higher than the Na(+) concentration. Na(+)/K(+)-ATPase regulates Na(+) and K(+) concentrations in mammalian blood. Therefore, the absence of Na(+)/K(+)-ATPase in lepidopterous insects might be expected. However, we have observed that Na(+)/K(+)-ATPase is abundant in nerve tissues of larvae of silkworm, a lepidopterous insect. Furthermore, we found that silkworm Na(+)/K(+)-ATPase was completely inhibited by 3 mM Ca(2+)in vitro (Homareda, 2010), although the Ca(2+) concentration is very high (30-50 mM) in the hemolymph of silkworm larvae. To investigate the reason why silkworm Na(+)/K(+)-ATPase is not inhibited by Ca(2+)in vivo, we observed the localization of Na(+)/K(+)-ATPase in nerve tissues using immunohistochemical techniques. Na(+)/K(+)-ATPase was distributed in the cortex and neuropile but not in the perineurium of the silkworm brain, while plasma membrane Ca(2+)-ATPase appeared to distribute in the perineurium as well as in the cortex and neuropile. These results support a possibility that neuronal Na(+)/K(+)-ATPase is protected from a high Ca(2+) concentration by the blood-brain barrier consisting of perineurial glial cells with plasma membrane Ca(2+)-ATPase.

[Cholinesterase activity in tissues of some crab species from the Japan Sea]

The comparative study of the cholinesterase activity in some crab species was carried out for the first time with use of a set of thiocholine substrates. The substrate specificity was studied in stellar nerve, heart, and hemolymph of three crab species. The crab hemolymph was shown to be characterized by the highest enzyme activity. The enzyme from various crab organs has different structure o substrate specificity. Properties of crab enzymes was compared with acetylcholinesterase (AChE) of human blood erythrocytes, butyrylcholinesterase (BuChE) of horse blood serum, enzyme o squids and bivalve molluscs. The obtained data allow the conclusion to be made on differences in properties of enzymes both at the interspecies and at the tissue levels.

[Localization of acetylcholinesterase in the nervous system of Cotylophoron indicum]

The nervous system of Cotylophoron indicum was studied by using acetylcholine esterase histochemical staining techniques. Cranial ganglia and transverse commissure situate at dorso-lateral body between oral sucker and genital sucker. From the cranial ganglia four pairs of nerves proceed cephalad and connect with nerve network of the oral sucker. The posterior nerve cords from the cranial ganglia consist of 3 pairs and the ventral ones are the stoutest and longest nerves. A few branches from the 3 pairs of nerve cords connect to ventral sucker. There is a developed nerve network distributed in its genital sucker. The nerve fibers on body surface in pairs and parallel are diagonal and cross to form a nerve network on body surface. Three kinds of neurocytes distribute at the prosomal region. Results show that the nervous system structure of C. indicum is consistent with the essential features of Digenea, but more special and complicated around genital sucker.

Doñana National Park survey using crayfish (Procambarus clarkii) as bioindicator: Esterase inhibition and pollutant levels

Utility of carboxylesterase and acetylcholinesterase inhibition as pesticide exposure biomarker was studied at Doñana National Park (SW Spain) in crayfish (Procambarus clarkii). Activities were measured in animals from reference sites or potentially exposed to pesticides, and their reactivation studied after dilution or 2-PAM treatment. Crayfish from affected sites had significantly less carboxylesterase and acetylcholinesterase activity than reference ones. No significant differences were found after dilution or 2-PAM treatment, showing that inhibition was irreversible. High pesticide levels were found in water and/or soil at rice growing sites, and lower levels at other affected places. High metal levels existed at rice growing sites and lower at other affected and at both reference sites. A combined effect on esterase inhibition of pesticides and metals is proposed. This field study suggest that the rice growing areas near Guadiamar stream are most polluted, followed by strawberry and citrics growing zones near Partido and Rocina streams. However, no correlation exist between the pesticide concentration at different sites and the extent of esterase inhibition, indicating that other factors could affect esterase response of animals from polluted sites.

Separate development of nitric oxide synthase- and vasoactive intestinal polypeptide-immunoreactive nerves arising from the vertebral artery in the rat

Development of nitric oxide synthase (NOS)-and vasoactive intestinal polypeptide (VIP)-immunoreactive (-IR) nerves supplying the basilar and vertebral arteries (BA and VA) was investigated in White Wistar rats, using double immunohistochemistry. NOS-IR and VIP-IR nerves via the anterior circulation (AC), which mostly expressed NO(+)/VIP(+), extended to the BA during the second postnatal week, and usually reached as far as the rostral two third of the BA on PND 20. NOS-IR nerves were completely lack in the cBA and the VA on PND10, and often absent from these arterial regions even at PND 20. Nevertheless, a small number of VIP(+)/NOS(-) nerves were localized in the walls from the caudal BA (cBA) to the VA on PND 5. On PND 20, they frequently met with the descending NOS-IR and VIP-IR nerves via the AC around the lower portion of the middle BA. Fiber bundles containing NOS(+)/VIP(+) axons were first visualized on the caudal VA at PND 30 and observed frequently at PND 80, with a distinct increase in number of NOS-IR and VIP-IR nerves supplying the cBA and the VA. Thus, NOS-IR nerves coming from the VA develop through its own characteristic sequence that lags markedly behind the time of appearance for VIP-IR nerves from the same vascular route and for NOS-IR and VIP-IR nerves via the AC.

Neuronal function and alpha3 isoform of the Na/K-ATPase

The Na/K-ATPase is a complex of integral membrane proteins that carries out active transport of sodium and potassium across the cell plasma membrane, and maintains chemical gradients of these ions. The alpha subunit of the Na/K-ATPase has several isoforms that are expressed in a cell type- and tissue-dependent manner. In adult vertebrates, while kidney cells express mostly alpha1, muscle and glial cells -- alpha1 and alpha2, and sperm cells -- alpha1 and alpha4 isoforms of Na/K-ATPase, neurons may express alpha1, alpha2, alpha3 or any combination of these isoforms, and evidence suggests that neuronal type is the determining factor. The functional significance of multiple isoforms of the Na/K-ATPase and their non-uniform expression, and the link between neuron function and expression of a given isoform of the Na/K-ATPase in particular, remains unknown. Several hypotheses on this account were introduced, and in this work we will review the present status of these hypotheses, and their standing in application to recent data on the expression of isoforms of the Na/K-ATPase in the peripheral nervous system of vertebrate animals.

Matrix metalloproteinases-9 and -2 in secondary vasculitic neuropathies

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endoproteinases that play an important role in inflammation and tissue degradation. MMP-9 and MMP-2 are gelatinases that have been implicated in the degradation of the blood-brain or blood-nerve barrier. We present an immunohistochemical study on 11 nerve biopsy samples of inflammatory and non-inflammatory polyneuropathies. Perineurium and endothelium were positive for MMP-2 in all tissue sections. In addition, there was a specific up-regulation of MMP-2 in stromal cells of chronic inflammatory demyelinating polyneuropathy (CIDP) and even more in vasculitic neuropathies. MMP-9-positive cells were detected in vessel walls, infiltrates, epineurium and endoneurium of vasculitic neuropathies. In CIDP, MMP-9-positive cells were prominent in vessel walls. Only a few MMP-9-positive cells were detected in noninflammatory controls in blood vessels and adhering to vessel walls. Double staining indicated that the infiltrating cells were T cells and macrophages. Our findings suggest that MMP-9 plays an important role in inflammatory peripheral neuropathy probably as means for inflammatory cell invasion.

Dynamic expression of a glutamate decarboxylase gene in multiple non-neural tissues during mouse development

BACKGROUND

Glutamate decarboxylase (GAD) is the biosynthetic enzyme for the neurotransmitter gamma-aminobutyric acid (GABA). Mouse embryos lacking the 67-kDa isoform of GAD (encoded by the Gad1 gene) develop a complete cleft of the secondary palate. This phenotype suggests that this gene may be involved in the normal development of tissues outside of the CNS. Although Gad1 expression in adult non-CNS tissues has been noted previously, no systematic analysis of its embryonic expression outside of the nervous system has been performed. The objective of this study was to define additional structures outside of the central nervous system that express Gad1, indicating those structures that may require its function for normal development.

RESULTS

Our analysis detected the localized expression of Gad1 transcripts in several developing tissues in the mouse embryo from E9.0-E14.5. Tissues expressing Gad1 included the tail bud mesenchyme, the pharyngeal pouches and arches, the ectodermal placodes of the developing vibrissae, and the apical ectodermal ridge (AER), mesenchyme and ectoderm of the limb buds.

CONCLUSIONS

Some of the sites of Gad1 expression are tissues that emit signals required for patterning and differentiation (AER, vibrissal placodes). Other sites correspond to proliferating stem cell populations that give rise to multiple differentiated tissues (tail bud mesenchyme, pharyngeal endoderm and mesenchyme). The dynamic expression of Gad1 in such tissues suggests a wider role for GABA signaling in development than was previously appreciated.

Nerve tissue-specific (GLUD2) and housekeeping (GLUD1) human glutamate dehydrogenases are regulated by distinct allosteric mechanisms: implications for biologic function

Human glutamate dehydrogenase (GDH), an enzyme central to the metabolism of glutamate, is known to exist in housekeeping and nerve tissue-specific isoforms encoded by the GLUD1 and GLUD2 genes, respectively. As there is evidence that GDH function in vivo is regulated, and that regulatory mutations of human GDH are associated with metabolic abnormalities, we sought here to characterize further the functional properties of the two human isoenzymes. Each was obtained in recombinant form by expressing the corresponding cDNAs in Sf9 cells and studied with respect to its regulation by endogenous allosteric effectors, such as purine nucleotides and branched chain amino acids. Results showed that L-leucine, at 1.0 mM:, enhanced the activity of the nerve tissue-specific (GLUD2-derived) enzyme by approximately 1,600% and that of the GLUD1-derived GDH by approximately 75%. Concentrations of L-leucine similar to those present in human tissues ( approximately 0.1 mM:) had little effect on either isoenzyme. However, the presence of ADP (10-50 microM:) sensitized the two isoenzymes to L-leucine, permitting substantial enzyme activation at physiologically relevant concentrations of this amino acid. Nonactivated GLUD1 GDH was markedly inhibited by GTP (IC(50) = 0.20 microM:), whereas nonactivated GLUD2 GDH was totally insensitive to this compound (IC(50) > 5,000 microM:). In contrast, GLUD2 GDH activated by ADP and/or L-leucine was amenable to this inhibition, although at substantially higher GTP concentrations than the GLUD1 enzyme. ADP and L-leucine, acting synergistically, modified the cooperativity curves of the two isoenzymes. Kinetic studies revealed significant differences in the K:(m) values obtained for alpha-ketoglutarate and glutamate for the GLUD1- and the GLUD2-derived GDH, with the allosteric activators differentially altering these values. Hence, the activity of the two human GDH is regulated by distinct allosteric mechanisms, and these findings may have implications for the biologic functions of these isoenzymes.

Effect of active molluscicidal component of spices on different enzyme activities and biogenic amine levels in the nervous tissue of Lymnaea acuminata

In vivo exposure of Lymnaea acuminata to thymol and [6]-gingerol (active molluscicidal components of Trachyspermum ammi and Zingiber officinale, respectively) indicates that they significantly alter acetylcholinesterase, lactic dehydrogenase, succinic dehydrogenase and cyto-oxidase activity in the nervous -tissue of snails. In vitro exposure showed that, except for acetylcholinesterase and lactic dehydrogenase, no significant changes were observed in cyto-oxidase and succinic dehydrogenase activity in the nervous tissue of L. acuminata. Sublethal exposure to thymol and [6]-gingerol reduced the levels of 5-hydroxytryptamine (5-HT) and dopamine (DA) in the nervous tissue of L. acuminata. There was, however, no significant change in the level of 5-hydroxy indol acetic acid (5-HIAA). Thymol and [6]-gingerol thus affects all the known neurotransmission mechanisms in the snail either separately or through a complex interaction between the different neurotransmitters. This may account for their toxicity to snails.

Localization of [3H]octylphosphonyl-labeled neuropathy target esterase by chicken nervous tissue autoradiography

Neuropathy target esterase (NTE) undergoes phosphorylation and aging as the initial steps in organophosphorus (OP)-induced delayed neuropathy (OPIDN). Localization of NTE is an important step in characterizing the mechanism of OPIDN. Earlier histochemical immunoreactivity or esterase assays localized NTE in areas of the brain and spinal cord rich in neuronal cell bodies and in the dorsal root ganglion. We use a more direct and quantitative autoradiographic approach of forming phosphorylated and aged [3H]octylphosphonyl-NTE on treatment with the highly potent [octyl-3H]octyl-4H-1,3,2-benzodioxaphosphorin 2-oxide to determine NTE as the labeling site resistant to the non-neuropathic paraoxon and sensitive to the neuropathic mipafox. NTE is observed in the cerebral cortical layer, some layers of the optic tectum, the gray matter of the spinal cord and the sensory neurons of the dorsal root ganglion to a higher extent than in adjacent areas.

Glycolipid sialyltransferases are enhanced during neural differentiation of mouse embryonic carcinoma cells, P19

We have studied ganglioside alterations and their enzymatic basis during the course of neural differentiation of mouse embryonic carcinoma cell line P19. This cell line can differentiate into neurons and astrocytes on cell aggregation after treatment with retinoic acid (RA) or into muscle cells on dimethyl sulfoxide (DMSO) treatment. GD3, detected on immunostaining after thin-layer chromatography (TLC) with monoclonal antibody (MAb) R24, was markedly present in aggregates treated with RA. GM3 synthase (alpha 2,3-sialyltransferase, SAT-I) in neurons was found to exhibit the highest activity. GD3 synthase (alpha 2,8-sialyltransferase, SAT-II) and GD3 synthase mRNA, as analyzed by Northern blotting, were also markedly present in aggregates and neurons induced by RA. However, on treatment with DMSO, which induces muscle cells, there was no change in the level of GD3 synthase activity, and its transcript was hardly detected during the course of muscle differentiation. GT1b synthase (alpha 2,3-sialyltransferase, SAT-IV) was present at similar levels in undifferentiated cells and aggregates treated with RA, but a higher level was observed in neurons. On the other hand, the level of GQ1b synthase (alpha 2,8-sialyltransferase, SAT-V) in RA-induced aggregates was significantly higher than that in neurons. These results show that RA but not DMSO induces the expression of GM3, GD3, GT1b and GQ1b synthases, and particularly GD3 synthase mRNA, in the ganglioside biosynthetic pathway during the neural differentiation of embryonic carcinoma P19 cells.

Expression of glutamic acid decarboxylase in nervous tissue structures targeted by autoantibodies in patients with diabetic autonomic neuropathy

We have previously identified an association between symptomatic diabetic autonomic neuropathy (DAN) and autoantibodies to sympathetic and parasympathetic nervous structures. The antigens identified by these autoantibodies are not known, but glutamic acid decarboxylase (GAD) has been suggested as a candidate target, since anti-GAD autoantibodies are present in patients with long-term diabetes and GAD is expressed in a variety of cell types and structures in the nervous system. The aim of this study was to examine GAD expression in sympathetic ganglia and vagus nerve and to compare the distribution of GAD within these tissues with that of anti-sympathetic ganglia and anti-vagus nerve autoantibodies from patients with DAN, using single and double indirect immunofluorescence on tissue sections. The monoclonal antibody GAD-6, specific for GAD65, gave a granular, peripheral, cytoplasmic staining pattern in sympathetic ganglion cells. Dual immunofluorescence demonstrated that serum from a patient with anti-sympathetic ganglion autoantibodies stained the same cells, but homogeneously throughout the cytoplasm. In the vagus nerve, patient's serum stained the fibres only; GAD-6 stained the cytoplasm of parasympathetic ganglion cells but only occasional fibres. In addition, GAD enzymatic activity was detectable in both sympathetic ganglia and vagus nerve. Incubation of sera or GAD-6 overnight with a crude homogenate of human brain as an antigen source abolished staining of the nervous tissues by GAD-6, but not by patients' sera. The different localisation of GAD and the autoantigens targeted by patients' sera indicates that GAD is not the target of the autoantibodies characteristic of DAN. Moreover, absorption studies using human brain homogenate suggest that the targets of anti-sympathetic ganglion and anti-vagus nerve autoantibodies are absent or represented only at low levels in the central nervous system and may be confined to the periphery.

Nerve tissue-specific human glutamate dehydrogenase that is thermolabile and highly regulated by ADP

Glutamate dehydrogenase (GDH), an enzyme that is central to the metabolism of glutamate, is present at high levels in the mammalian brain. Studies on human leukocytes and rat brain suggested the presence of two GDH activities differing in thermal stability and allosteric regulation, but molecular biological investigations led to the cloning of two human GDH-specific genes encoding highly homologous polypeptides. The first gene, designated GLUD1, is expressed in all tissues (housekeeping GDH), whereas the second gene, designated GLUD2, is expressed specifically in neural and testicular tissues. In this study, we obtained both GDH isoenzymes in pure form by expressing a GLUD1 cDNA and a GLUD2 cDNA in Sf9 cells and studied their properties. The enzymes generated showed comparable catalytic properties when fully activated by 1 mM ADP. However, in the absence of ADP, the nerve tissue-specific GDH showed only 5% of its maximal activity, compared with approximately 40% showed by the housekeeping enzyme. Low physiological levels of ADP (0.05-0.25 mM) induced a concentration-dependent enhancement of enzyme activity that was proportionally greater for the nerve tissue GDH (by 550-1,300%) than of the housekeeping enzyme (by 120-150%). Magnesium chloride (1-2 mM) inhibited the nonactivated housekeeping GDH (by 45-64%); this inhibition was reversed almost completely by ADP. In contrast, Mg2+ did not affect the nonstimulated nerve tissue-specific GDH, although the cation prevented much of the allosteric activation of the enzyme at low ADP levels (0.05-0.25 mM). Heat-inactivation experiments revealed that the half-life of the housekeeping and nerve tissue-specific GDH was 3.5 and 0.5 h, respectively. Hence, the nerve tissue-specific GDH is relatively thermolabile and has evolved into a highly regulated enzyme. These allosteric properties may be of importance for regulating brain glutamate fluxes in vivo under changing energy demands.

Biochemical properties and cellular localization of the Drosophila DG1 cGMP-dependent protein kinase

The protein encoded by the Drosophila cGMP-dependent protein kinase gene, DG1, was expressed in Sf9 cells. cGMP (10 microM) stimulated histone H2B phosphorylation by the DG1 protein kinase 20-fold. Maximal activity was observed at 40-50 mM Mg2+. The concentrations of cGMP, cAMP, cIMP, 8-bromo-cGMP, and 8-bromo-cAMP that gave 50% activation were 0.19 +/- 0.06, 11.7 +/- 2.8, 5.3 +/- 1.5, 0.04 +/- 0. 01, and 0.62 +/- 0.06 microM, respectively. cGMP activation was cooperative with a Hill coefficient (nH) of 1.28 +/- 0.10, whereas activation by cAMP was not cooperative. DG1 kinase expressed in Sf9 cells was found to be a dimer with an amino-terminal dimerization domain. It also autophosphorylated in a reaction stimulated by cGMP and cAMP. Immunoadsorbed DG1 protein from fly extracts was also capable of autophosphorylation, and this assay was used to quantitate the DG1 kinase in extracts from heads and bodies of adults and whole embryos. Activity was highest in heads of either sex and male bodies, intermediate in female bodies, and lowest in embryos. These results were in accord with DG1 mRNA abundance. Tissue distribution of the DG1 kinase was investigated by immunohistochemistry. In embryos, specific immunoreactivity was observed in large cells scattered along the anterior-posterior axis at stage 13. Prominent staining of adult heads was restricted to the proximal level of the lamina cortex.

[A comparative analysis of monoamine oxidase activity in the tissues of the deep-sea squid (Berryteuthis magister) and the mouse under normal and elevated atmospheric pressure]

The monoamine oxidase (MAO) from the liver of Comandor squid inhabiting at depth of 800 m transformed histamine along with specific substrates (tyramine, serotonin, benzylamine). MAO from the squid nervous ganglia as well as from mouse liver and brain was inactive towards histamine. Under normal atmospheric pressure the activity of the enzyme prepared from the squid frozen tissues was an order of 10 lower than the enzymic activity revealed in fresh and previously frozen tissues of mouse brain and liver. Under 101 atm the squid tissue enzyme activity did not change whereas it decreased in mouse tissues. The distinctions in MAO sensitivity to high atmospheric pressure between land and deep-sea species is suggested to be due to both peculiar lipid composition of cell membranes and different structural features of the enzyme in the species investigated.

Implications of the subtilisin/kexin-like precursor convertases in the development and function of nervous tissues

Furin, PC1, PC2, and PC5 represent mammalian convertases (PCs) found in endocrine, central and peripheral nervous tissues, which cleave a number of precursors at basic residues normally processed in vivo. Typical bonds cleaved by PCs include the pairs Lys-Arg, Arg-Arg and Arg-X-Lys/Arg-Arg. These cleavage sites have been detected following coexpression of each convertase in cell lines together with different precursors as models, including proopiomelanocortin (POMC), proinsulin and proNGF and proBDNF. The presence of PCs and different precursors was revealed by in situ hybridization or immunocytochemistry in cultured AtT-20 cells, in the developing CNS, pituitary, and pancreatic islets. In an experimental model of epilepsy in which epileptiform activities were provoked by kainic acid administration, we observed a similar transient expression of furin and PC1 as compared to that of NGF and BDNF. In conclusion, it is proposed that under different stimuli various precursors are activated by a unique cocktail of convertases, each of which either alone or in combination with others acts to process inactive precursors, and thereby playing an important role in development and in the plasticity of the neuronal system.

Nitric oxide synthase-containing, peptide-containing, and acetylcholinesterase-positive nerves in the cat lower oesophagus

The innervation of the cat lower oesophagus, including the lower oesophageal sphincter, was studied by enzyme histochemistry, immunohistochemistry, and confocal microscopy. In the lower oesophageal sphincter, and at a level 2 cm above it, no apparent differences were seen in the nerve distribution pattern. Among the nerve populations studied, acetylcholinesterase (AChE)-positive nerves were the most abundant in both these regions. The density of AChE-positive nerves was particularly marked in the circular muscle layer. A rich supply of nitric oxide synthase (NOS)-containing nerves was identified by using an antiserum against neuronal NOS, or by enzyme histochemical staining for NADPH diaphorase activity. Vasoactive intestinal peptide (VIP)-immunoreactive nerves had a similar distribution pattern as NOS-immunoreactive nerves, and nerves displaying immunoreactivity for NOS and VIP often showed profiles coinciding with AChE-positive nerves. As judged by confocal microscopy, immunoreactivities for helospectin, pituitary adenylate cyclase-activating peptide (PACAP) and VIP, to a large extent were found in the same nerves. At a level 7 cm above the lower oesophageal sphincter, the total nerve supply was less than in the sphincter itself and 2 cm above it. Immunoreactivity towards VIP, PACAP and helospectin was also found to co-exist with NOS and neuropeptide Y within the same nerve structures. It is concluded that there is an intricate innervation pattern in the feline lower oesophagus reflecting the complexity in the regulation of its motility.

Mutual interaction between host and graft tissues in embryonic neural transplantation

The differentiation of AChE-positive cells in embryonic neural grafts from various brain regions into the hippocampus after fimbria-fornix transection was investigated. Rat fetal cell suspensions of basal forebrain, hippocampus, mesencephalon or cortex were prepared from fetuses of either embryonic day 14 (E14) or day 19 (E19) gestational age, and these were transplanted into the rat brain after unilateral fimbria-fornix transection. Dense acetylcholinesterase (AChE) positive fibres were observed in both E14 and E19 basal forebrain grafts. These fibres were also found in E14 hippocampal grafts. However E19 hippocampal grafts did not have any AChE-positive fibres. These results suggest that E14 hippocampal grafts might be affected by the host brain tissues and differentiate into cholinergic neurones.

A neural gene from Drosophila melanogaster with homology to vertebrate and invertebrate glutamate decarboxylases

Cross-species hybridization has been used to isolate a second Drosophila gene, with homology to a feline glutamate decarboxylase (Gad) cDNA. The gene differs in sequence, chromosomal location, and spatial expression from the previously reported Drosophila Gad gene, but both encode proteins of 58 kDa. The derived amino acid sequence reveals a typical pyridoxal phosphate binding site and sequence homology consistent with a glutamate decarboxylase function. The protein includes an amino-terminal polyasparagine sequence, and a beta-pleated sheet region, with regularly spaced glutamine and arginine residues, not found in other decarboxylases. Expression in the adult is limited to the neuropil of the first optic ganglion and to regions of the thoracic musculature that may correspond to the location of motor neuron axons. This is consistent with a glial localization for the transcript. There is no overlap with the reported expression of Drosophila Gad. Although the molecular evidence suggests that this gene encodes a pyridoxal phosphate-dependent decarboxylase, glutamate decarboxylase activity associated with this gene could not be demonstrated, and the in vivo substrate is unknown. It is possible that the protein encoded by this gene is novel, not only in sequence and spatial expression, but also in substrate specificity.

Type I calmodulin-sensitive adenylyl cyclase is neural specific

The distribution of type I calmodulin-sensitive adenylyl cyclase in bovine and rat tissues was examined by northern blot analysis and in situ hybridization. Northern blot analysis using poly(A)(+)-selected RNA from various bovine tissues indicated that mRNA for type I adenylyl cyclase was found only in brain, retina, and adrenal medulla, suggesting that this enzyme is neural specific. In situ hybridization studies using bovine, rabbit, and rat retina indicated that mRNA for type I adenylyl cyclase is found in all three nuclear layers of the neural retina and is particularly abundant in the inner segment of the photoreceptor cells. The neural-specific distribution of type I adenylyl cyclase mRNA and its restricted expression in areas of brain implicated in neuroplasticity are consistent with the proposal that this enzyme plays an important role in various neuronal functions including learning and memory.

Oxygen radicals and other toxic oxygen metabolites as key mediators of the central nervous system tissue injury

Free radicals are species containing one or more unpaired electrons, and for this reason they are highly reactive and can combine with a great variety of biomolecules, changing their physico-chemical characteristics. Oxygen free radicals are normally produced during cellular metabolism and aerobic cells are provided with antioxidant defense mechanisms able to counteract this physiological production. In conditions of increased production or decreased scavenging of free radicals, they can assume a fundamental importance in the pathogenesis of acute or chronic brain diseases.

Characterization and localization of nitric oxide synthase in non-adrenergic non-cholinergic nerves from bovine retractor penis muscles

1. Partially purified soluble nitric oxide (NO) synthase was isolated from the bovine retractor penis muscle (BRP), a tissue in which the inhibitory response to non-adrenergic non-cholinergic nerve (NANC) stimulation appears to be mediated by NO or NO-like material. 2. NO synthase from BRP used L-arginine as a substrate, required NADPH, tetrahydrobiopterin, and FAD as co-factors and was Ca2+/calmodulin-dependent. The activity of NO synthase was inhibited by NG-methyl-L-arginine and NG-nitro-L-arginine, and haemoglobin blocked the effect of NO formed by the enzyme. 3. On reducing SDS polyacrylamide gel electrophoresis the apparent molecular mass of NO synthase from BRP was 160 +/- 2 kDa, which is similar to that of the cerebellar NO synthase. Protein immunoblot and immunoprecipitation showed that NO synthase from BRP cross-reacted with the selective antiserum to neuronal NO synthase from rat cerebellum. 4. Immunohistochemistry using the same antiserum demonstrated that NO synthase in BRP was located exclusively within nerve fibres. Thus, autonomic nerves synthesizing the NANC neurotransmitter seem to contain an isoform of NO synthase which is similar to that from rat cerebellum.

[The role of transaminases in realizing the protective effect of L-aspartate in hypoxia]

Activation of aspartate aminotransferase and alanine aminotransferase of mitochondria introduced to the incubation medium of pyridoxal-5'-phosphate (40 microM) is approximately 2 times higher than that of the corresponding cytoplasmic forms. At hypoxia aspartate aminotransferase activity in mitochondria and postmitochondrial supernatant tends to an increase while that of alanine aminotransferase decreases (above 2 times). The protection from hypoxic damage when using L-aspartate (100 mg/kg subcutaneously 3-5 min before hypoxia) intensifies an adaptive increase of aspartate aminotransferase activity and removes a decrease of alanine aminotransferase activity. Under these conditions stimulating effect of pyridoxal-5'-phosphate on transaminases activity in vitro weakens. A simultaneous administration of vitamin-coenzyme complex (thiamine pyrophosphate, lipoate, sodium 4-phospho-pantothenate, flavin-mononucleotide, nicotinate) intensifies these metabolic shifts and protective action of L-aspartate.

[Changes in the esterase activity and isoenzyme spectrum following the transplantation of embryonic nerve tissue into the brain of adult rats]

Nervous tissue of 17-days old rat embryos was transplanted into lateral ventricle of the brain of adult rats. 15 days after transplantation esterase activity was analyzed from transplant tissue and flanking regions of cerebral cortex. Isoenzymes were shown to activate their activity after embryonic tissue transplantation either in transplants or flanking regions. These changes result obviously from the effect of substances, synthesized by transplant.

In vitro inhibition of Ca+2 ATPase by methylparathion in prawn: a kinetic approach

After in vitro addition of IC50 concentration of methylparathion on Ca+2 ATPase in nervous and hepato-pancreatic tissues of prawn were studied. The inhibitory pattern of Ca+2 ATPase elucidate the interaction of methylparathion with ATPase system. The significant decrease in maximal velocity (Vmax) without appreciable change in apparent Michaelis-Menten constant (Km) suggests that the impact of methylparathion on Ca+2 ATPase is independent of substrate and is of a classical non-competitive type.

Long-term survival of neural transplants to senescence in rats

A critical issue for clinical and research applications of transplant techniques is the long-term survival of transplanted tissue and its effect on the host brain. In this study, entorhinal cortices from donor embryos were transplanted into the lesioned angular bundle of juvenile male Sprague-Dawley rats. Animals were maintained for 2 years and then sacrificed for histological and histochemical examinations. The results indicate that entorhinal transplants survive to old age and that both the host and transplant tissues maintain morphological features consistent with those of short-term neural grafts. An unexpected finding of this experiment was the persistence in the transplanted tissue and adjacent host cortex of a pattern of AChE staining which is typical of early postnatal development.

[The effect of the x-ray irradiation of rats on the NAD-pyrophosphorylase and poly(ADP-ribose)polymerase activities of brain nuclei and on the NAD content in nerve tissue]

A study was made of the influence of X-irradiation of rats with various doses on NAD-pyrophosphorylase and poly(ADP-ribose) polymerase activity of brain nuclei. It was shown that X-radiation was ineffective with regard to NAD-pyrophosphorylase activity of nuclei and increased their poly(ADP-ribose) polymerase activity. Stimulation of poly(ADP-ribose) polymerase activity of nuclei was a function of radiation dose and correlated with the decrease in the NAD content of nervous tissue. It was found that mainly nonhistone proteins were ADP-ribosylated in nuclei of both irradiated and nonirradiated rats.

Immunodetection of Na,K-ATPase alpha 3-isoform in renal and nerve tissues

At least three types of mRNA of the catalytic subunit of Na,K-ATPase namely alpha-,alpha+- and alpha 3-isoforms are identified in different tissues. Only two of them alpha and alpha+ have well known structural and catalytic properties. Here we present immunochemical data indicating that the alpha 3 protein really exists in pig and human kidney, and human brain. Crude membrane fractions and purified membrane-bound Na,K-ATPases were immunoblotted with alpha 3-specific antibodies raised against the synthetic peptide corresponding to the unique sequence of this isoform. The mature alpha 3-subunit is shown to include the sequence GDKKDDKSSPK followed by the initiating methionine residue. Nephron collecting tubules are proposed to specifically contain Na,K-ATPase alpha 3-isoform.

[Changes in concentrations of nerve- and muscle-related proteins during reinnervation of slow and fast muscles]

The concentration of the nerve-related (gamma-enolase) and muscle-related (beta-enolase and creatine kinase of B type) proteins was measured in the rat sciatic nerve and the muscles; soleus (SOL), a typical slow-twitch muscle, and extensor digitorum longus (EDL), a typical fast-twitch muscle. The nerves and muscles were subjected to experimental manipulation of their innervation. 1. Nerve-related protein, gamma-enolase. The concentration of gamma-enolase in the distal part of the transected sciatic nerve was decreased in 2 weeks to about 10% of normal. When the sciatic nerve was sutured immediately after the transection, the concentration of gamma-enolase recovered in 34 weeks to a level of about 62.8% of normal. 2. Fast muscle-related protein, beta-enolase. The concentration of the beta-enolase in the SOL and the EDL was reduced after sciatic nerve transection. When the sciatic nerve was sutured immediately after complete transection, the concentration of beta-enolase of SOL and EDL became almost equal on the 34th week. After cross union of the nerves innervating the SOL and EDL muscles, the concentration of the beta-enolase were almost equal on the 20th post-operative week in the both muscles, and reversed on the 34th week. The beta-enolase concentrations in the SOL and EDL muscles innervated by the TTX-perfused sciatic nerve were reduced to 72.3% and 70.4%, respectively. Continuous electrical stimulation of the sciatic nerve reduced the beta-enolase concentration in the EDL to 51.8% of normal, but did not affect the SOL significantly. 3. Slow muscle-related protein, creatine kinase of B type (CK-B). After complete severance of the sciatic nerve the CK-B concentration showed a marked increase in the both muscles. When the sciatic nerve was sutured immediately after transection, the CK-B concentration on the 34th week was about 35.3% in the SOL and close to normal in the EDL. On the 34th week after cross union of the nerves innervating the SOL and EDL muscles, the CK-B concentration was reduced to about 41.1% in the SOL, while it was increased to about 111% in the EDL. On the 20th week after self re-union of the nerves innervating the SOL and EDL muscles, the CK-B concentration in the EDL recovered the normal level, but in the SOL muscle it was increased significantly. 4. It appears that the measurement of the concentration of gamma-enolase, beta-enolase and CK-B can provide valuable informations on the recovery course of skeletal muscles after nerve injury.

Enzyme replacement in nervous tissue after allogeneic bone-marrow transplantation for fucosidosis in dogs

Bone-marrow transplantation after total lymphoid irradiation in an alpha-L-fucosidase-deficient dog raised the enzyme activity in both visceral and neural tissues with consequent reduction in the severity of storage lesions. These results offer hope that early marrow transplantation may prevent the development of disease in neurovisceral storage disorders.

Effect of halothane on brain 2',3'-cyclic nucleotide 3'-phosphodiesterase during neurodevelopment in the rat

Chronic exposure to anesthetic concentrations of halothane during the prenatal and early postnatal periods inhibits the incorporation of the leucine into myelin subcellular fractions in the rat. The enzyme 2',3' - cyclic nucleotide 3' - phosphodiesterase (CNPase) has been widely used as a myelin marker. To determine the effect of halothane on the developmental profile of CNPase, two groups of pregnant Sprague Dawley rats were exposed to 500 p.p.m. or 250 p.p.m. halothane, eight hours per day, five days per week from the third day after conception through postnatal day ten. Control animals were exposed to air alone. CNPase activity was significantly decreased by 500 p.p.m. halothane (34%) and by 250 p.p.m. halothane (29%) at postnatal day 17. Brain and body weights in both halothane treated groups were also less than control animals throughout the measurement period. The data indicates that chronic pre- and postnatal halothane exposure at low levels delays myelination in the rat.

Enhanced graft survival in the hippocampus following selective denervation

The trophic effects of denervation on the survival of fetal cholinergic neuronal cell suspensions grafted to the hippocampal formation of the rat were assessed in the present study. Young adult female rats were injected with cell suspensions of neurons obtained from the fetal basal forebrain region into the hippocampal formation simultaneously with (or without) a fimbria-fornix transection, which removes the hippocampal cholinergic afferents. Four to six months later, one group of grafted animals was evaluated histochemically for: transplant volume; number of acetylcholinesterase-positive cells, and size of acetylcholinesterase-positive cells in the graft. A parallel study was conducted to determine the total number and size of the acetylcholinesterase-positive cells in the septal-diagonal band-substantia innominata complex of the adult rat, to match with the cell survival and growth in the grafts. A second group of grafted rats was taken in parallel for biochemical analysis of choline acetyltransferase activity in the grafted hippocampus. The transplant volume in the rats with fimbria-fornix transection was greater than twice the volume seen in animals without fimbria-fornix lesion. In addition, the number of acetylcholinesterase-positive cells in the transplant was twice as great in the denervated animals as in the non-denervated ones. However, the number of acetylcholinesterase-positive cells per mm3 of graft volume did not differ between the two groups, suggesting that the trophic effect of the denervation was not specific for the cholinergic neurons, but affected the entire grafted tissue. The hippocampal choline acetyltransferase activity of the animals that received the fimbria-fornix lesion simultaneously with transplantation was about three times higher than that of the rats that received grafts but no simultaneous fimbria-fornix transection. A control experiment with animals that received an aspirative lesion of the retrosplenial cortex, transecting the perforant path input, revealed no enhancing effect of hippocampal choline acetyltransferase activity over non-lesioned grafted animals. Thus, the denervation-enhancing effects of the fimbria-fornix lesion appear to be selective and not the result of a general wound-induced mechanism. These results strongly support the contention that neurotrophic factors are released as a result of denervation in the adult hippocampal formation, and that these neurotrophic factors can support survival and growth of central cholinergic neurons. However, the factors involved do not appear to be specific for the cholinergic neurons, but rather have their trophic effects on many types of cells.

Effect of insulin, proinsulin and pancreatic extract on myelination and remyelination in organotypic nerve tissue in culture

The effect of insulin, proinsulin and crude pancreatic extract was studied in organotypic nerve tissue cultures, principally in relation to the development of myelin. Cultures were exposed to media supplemented with these substances beginning on the first day of explantation. By 4 days in vitro, there was a good neuritic outgrowth from all the fragments. That from the insulin and pancreatic extract-fed were more profuse and extended further than from the control group. By 8-12 days in vitro it was also possible to observe more myelinated axons in these treated groups. The pattern of changes in the myelin associated enzyme activity, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) paralleled the differential increase in myelination. Insulin-fed cultures showed a more rapid increase in CNPase activity, which, after 21 days in vitro reached a plateau about 30-50% over that of the controls. Cultures treated with pancreatic extract showed a similar pattern of increased activity, while in proinsulin-treated explants the activity was only significantly higher after 21 days in vitro. To study the effect of these substances on remyelination, well myelinated cultures were completely demyelinated by exposure to anti-white matter antiserum and were subsequently exposed to the same normal control or supplemented media. The amount of myelin and concomitantly the CNPase activity increased rapidly and in the same proportion between the various groups as was observed previously during primary myelination. Insulin as well as crude pancreatic extract and, to some extent, proinsulin demonstrated a marked effect on the time of onset and principally on the total amount of myelin developed by treated cultures as compared to those maintained in normal nutrient medium.

Developmental changes in gamma-glutamyl transpeptidase activity in nervous tissues with reference to amino acid transmission processes

In homogenate supernatants of hippocampal formation and cerebellum of the rat, gamma-glutamyl transpeptidase (gamma-GTP) activities increased about 6 times from postnatal day 6 (0.178 +/- 0.02 and 0.187 +/- 0.007 U/g wet wt., respectively) to day 100. In dorsal root ganglia (0.183 +/- 0.003 U/g at day 6) and superior cervical ganglia (0.188 +/- 0.019 U/g at day 6) in which apparently amino acidergic transmission processes do not occur, enzyme activities were seen to go up 4 times and 2.4 times, respectively. Based on protein, enzyme activities in both brain material and dorsal root ganglia showed a similar pattern, whereas the activity increase in superior cervical ganglia was somewhat gradual (1.4 times from day 6 to day 100). Postnatal changes in gamma-GTP activities indicated a functional correlation with the maturation of amino acidergic structures. Kainic acid added to hippocampal extracts (0.45 and 5.0 mM) and, for comparison, to those of kidney (5.0 mM) did not yield any statistically significant effect on gamma-GTP activity.

Creatine phosphokinase in Rana pipiens: expression in embryos, early larvae and adult tissues

1. Creatine phosphokinase (CPK) isozymes found in Rana pipiens are similar to those found elsewhere; muscle-specific (MM-CPK), brain-specific (BB-CPK) and intermediate hybrid (MB-CPK) isozymes were identified. 2. Adult tissues exhibit CPK isozyme patterns similar to other vertebrates although variations are notable in nervous tissue, liver and kidney. 3. CPK isozyme patterns in ovarian eggs, ovulated eggs and selected stages of early development demonstrate a significant rise in CPK with neurulation. Most notable is a sharp increase in brain-specific BB-CPK. 4. MM-CPK purified from skeletal muscle is found to be similar, in properties studied, to the corresponding isozyme in other vertebrate species.

Distribution of acetylcholinesterase molecular forms in brain, nerve and muscle tissue of Torpedo marmorata

The distribution of multiple molecular esterase forms in brain, electromotor nerve, back muscle and a subcellular synaptosomal fraction from the electric organ of Torpedo marmorata was investigated. Each tissue was characterized by a specific pattern of distribution of esterase forms. Electric lobe exhibited a marked difference to the other brain tissues and electric organ, in that it contained predominantly fast sedimenting 17 S acetylcholinesterase. The solubilization properties indicated that the 17 S form is not exclusively associated with basal lamina. The results support the view that location and function of the various molecular esterase forms can vary from tissue and depend on the physiological demands of each system.

A study of the cholinesterases of the canine pancreatic sphincters and the relationship between reduced butyrylcholinesterase activity and pancreatic ductal hypertension

Previous work from this laboratory revealed in increased canine pancreatic intraductal pressure following cholinesterase inhibitor intoxication. The pressure was negatively correlated with serum butyrylcholinesterase (BChE) activity, suggesting that BChE activity mediated the pressure rise. This study uses a histochemical technique to investigate the tissue cholinesterase activity of the canine pancreatic sphincters and the effect of a cholinesterase inhibitor (ChEI) on tissue cholinesterase activity. In five control dogs, serial sections of the major and minor spincters were stained for acetylcholinesterase (AChE) and BChE activity. Four treated dogs were given the ChEI, O,O-diethyl-O- (2-isopropyl-6-methyl-4-pyrimidinyl) phosphoro-thioate, 25 mg/kg, one hour prior to excising the ampullae. In the control dogs, BChE activity is present in the periampullary nerves and the pancreatic smooth muscle sphincters. AChE activity is present in nerves but not in smooth muscle. In the treated group, following a dose of ChEI known to cause ductal hypertension, BChE activity was absent in the pancreatic sphincters but AChE activity was preserved in the periampullary nerves. These data suggest that the pancreatic ductal hypertension that occurs following ChEI administration is due to a selective reduction in pancreatic smooth muscle BChE activity.