Memory-related changes of nitric oxide synthase activity and nitrite level in rat brain

The changes of nitric oxide synthase (NOS) activity and nitrite level in rat brain regions after spatial learning were investigated. NOS activity was assayed by conversion of [3H]L-arginine to [3H]L-citrulline, and a sensitive fluorometric assay for quantification of nitrite was used. Compared with sham-trained rats, NOS activity and nitrite level in hippocampus and cortex, and also the nitrite level in cerebellum, was elevated significantly one day after rats had learnt a water-rewarded spatial alteration task. These results suggest a spatial memory-related changes of endogenous NO in rat brain, and support the idea that NO participates in learning and memory processes.

A population-based study of salivary lysozyme concentrations and candidal counts

The relationship between salivary lysozyme concentration and oral candida load was examined in 595 adults. Unstimulated whole saliva, and citrate-stimulated parotid and submandibular/sublingual saliva were collected from each participant. Candida colony-forming units (c.f.u.) in unstimulated whole saliva were determined. An enzyme-linked immunosorbent assay for lysozyme using commercially available antibodies was developed. This assay showed a linear relation of salivary lysozyme concentrations from 0.5 to 4.0 ng/ml. Significant negative relations were observed between lysozyme concentration and flow rate: r = -0.16 (p < 0.001) for stimulated parotid and r = -0.22 (p < 0.0001) for stimulated submandibular/sublingual saliva. The lysozyme concentration in stimulated submandibular/sublingual saliva was higher in males than in female, but no sex difference was observed for stimulated parotid saliva. The lysozyme concentration of stimulated parotid saliva was positively correlated with candida counts (r = 0.18: p < 0.005). Further study of groups according to their levels of candida in whole saliva revealed that lysozyme concentrations were higher in the high candida (> or = 1000 c.f.u./ml) group than in the zero and moderate candida categories in stimulated parotid saliva (p < 0.001): there were no concentration differences in stimulated submandibular/sublingual saliva. These results suggest that parotid lysozyme concentration increases as candida load increases.

Inhibition of lipid peroxidation

Lipid peroxy radicals (ROO.) were detected by electron spin resonance (ESR) at low temperature after formation by addition of H2O2 into a suspension of mice lymphocytes. If lymphocytes were treated with selenomethionine (Se-Met) prior to addition of H2O2, ROO. formation was inhibited in a fashion that was dependent on Se-Met concentration. Formation of ROO. in the spleen of mice was induced by 60Co irradiation. Animals that were supplemented with Na2SeO3 prior to irradiation exhibited a lower ROO. concentration than that of nontreated animals. Based on our experiments, we have concluded that Se has an oxygen-free radical scavenging effect. This should be a protective effect against lipid peroxy radical cellular attack.

Inhibitory effect of 764-3 on Ca2+ uptake in rat brain synaptosomes

In an attempt to examine the effect of 764-3, a purified component extracted from Radix Salviae Miltiorrhizae (RSM), on calcium channel, Ca2+ uptake in rat brain synaptosome stimulated by high-K+ and Glutamate (Glu) was investigated by using radioisotope labeled 45CaCl2. It was found that 764-3 could decrease the uptake of Ca2+ induced by high-K+ (60 mM) and 0.1 mM glutamate in a concentration-dependent manner. The maximum inhibiting rates were 45.22 +/- 4.88% and 37.58 +/- 4.52%, respectively. The results indicated that neuroprotective effect of RSM on cerebral ischemic injury may be related to its blocking effects on calcium channel.

[A legionella pneumophila strain serologically cross-reacting with thirteen serogroups of this species]

A bacterial strain, designated as Jin-1, was isolated from a water sample taken from the Jinyang Lake located in the suburbs of Taiyuan City, Shanxi Province. Its morphologic and tinctorial properties, nutritional requirements, growth characteristics, biochemical reactions, as well as results of DNA and peptide analysis overall met the criteria for identification of Legionella pneumophila. In serogrouping, extensive cross-reactions between Jin-1 and the type strains of L. pneumophila serogroup 1 through 14 were observed in both slide and tube agglutination tests mediated by the IgM antibodies. However, Jin-1 revealed the L. pneumophila serogroup 5 specificity in IFA, ELISA and dot-ELISA, all mediated by the IgG antibodies. Jin-1 was finally identified as a strain of L. pneumophila serogroup 5 with the more complex antigenic composition than the ATCC type strain of this serogroup. The taxonomic conclusion has been confirmed by CDC. A Legionella pneumophila strain which serologically cross-reacting with so many serogroups of this species has never been reported in the published articles. It is presumed that the cross-reacting antigen of Jin-1 belongs to the thymus-independent antigen by nature.

The splicing factor U2AF35 mediates critical protein-protein interactions in constitutive and enhancer-dependent splicing

The splicing factor U2AF (U2 snRNP auxiliary factor) is a heterodimer with subunits of 65 and 35 kD (U2AF65 and U2AF35). U2AF65 binds specifically to 3' splice sites, but previous studies failed to demonstrate a function for U2AF35. Here, we report that U2AF35 is required for constitutive splicing and also functions as a mediator of enhancer-dependent splicing. Nuclear extracts deficient in U2AF35 were inactive; however, both constitutive and enhancer-dependent splicing could be restored by the addition of purified recombinant U2AF35. In vitro protein-RNA interaction studies with pre-mRNAs containing either a constitutive or regulated splicing enhancer revealed that U2AF35 directly mediates interactions between U2AF65 and proteins bound to the enhancers. Thus, U2AF35 functions as a bridge between U2AF65 and the enhancer complex to recruit U2AF65 to the adjacent intron.

Effect of selenium in recovery of immunity damaged by H2O2 and 60Co radiation

Con A stimulated lymphocytes proliferation was measured as [3H]thymidine incorporation and IgG was quantified by single radial immunodiffusion to study recovering or protecting effect of selenium (Se) on immunity attacked by exogenous active oxygen species, H2O2 and 60Co-radiation, respectively. Lipid peroxidation was also determined to observe the relation between antioxidation ability and protecting ability of Se. It was found that H2O2 injured lymphocytes immunocompetence deeply and 60Co-radiation decreased immune response capacity greatly, but that administration of Se counteracts this damage. The antioxidative ability of Se was correlated with its protecting ability.

The mechanism for the effect of selenium supplementation on immunity

Lipid peroxide (LPO) in lymphocytes from mice was evaluated by measuring substances reactive to thiobarbituric acid (TBA). The product resulting from the reaction of TBA with lymphocytes was extracted with n-butyl and fluorescence intensity was determined. The degree of lipid peroxidation, expressed as fluorescence intensity f547, was assessed for stimulation of lymphocytes with concanavalin A (Con A), and was related to lymphocyte proliferation in response to Con A if Se was administered. The lymphocyte proliferation was determined by [3H]thymidine incorporation, expressed as cpm. The effect of superoxide dismutase (SOD), added to cell culture on lymphocyte proliferation was also evaluated. It was found that LPO in lymphocytes before Con A stimulation was significantly less than that after stimulation (p < 0.001), and that SOD promoted lymphocyte proliferation dose dependently. The addition of Na2Seo3 to lymphocyte culture or supplementation in drinking water to mice decreased the produced LPO in lymphocyte in response to Con A. In the presence of Se, there is an inverse correlation between the levels of LPO in lymphocyte and the stimulated proliferation (r = -0.8902, r = -0.9439). In conclusion, active oxygen species scavenging was proposed as one of the mechanisms for Se to promote immunity.

The human splicing factor ASF/SF2 can specifically recognize pre-mRNA 5' splice sites

ASF/SF2 is a human protein previously shown to function in in vitro pre-mRNA splicing as an essential factor necessary for all splices and also as an alternative splicing factor, capable of switching selection of 5' splice sites. To begin to study the protein's mechanism of action, we have investigated the RNA binding properties of purified recombinant ASF/SF2. Using UV crosslinking and gel shift assays, we demonstrate that the RNA binding region of ASF/SF2 can interact with RNA in a sequence-specific manner, recognizing the 5' splice site in each of two different pre-mRNAs. Point mutations in the 5' splice site consensus can reduce binding by as much as a factor of 100, with the largest effects observed in competition assays. These findings support a model in which ASF/SF2 aids in the recognition of pre-mRNA 5' splice sites.

Protein-protein interactions and 5'-splice-site recognition in mammalian mRNA precursors

Exactly how specific splice sites are recognized during the processing of complex precursor messenger RNAs is not clear. Small nuclear ribonucleoprotein particles (snRNPs) are involved, but are not sufficient by themselves to define splice sites. Now a human protein essential for splicing in vitro, called alternative splicing factor/splicing factor 2, is shown to cooperate with the U1 snRNP particle in binding pre-mRNA. This cooperation is probably achieved by specific interactions between the arginine/serine-rich domain of the splicing factor and a similar region in a U1 snRNP-specific protein.

Functional domains of the human splicing factor ASF/SF2

The human splicing factor ASF/SF2 displays two predominant activities in in vitro splicing assays: (i) it is an essential factor apparently required for all splices and (ii) it is able to switch utilization of alternative 5' splice sites in a concentration-dependent manner. ASF/SF2 is the prototype of a family of proteins typified by the presence of one or two RNP-type RNA binding domains (RBDs) and a region highly enriched in repeating arginine-serine dipeptides (RS regions). Here we describe a functional analysis of ASF/SF2, which defines several regions essential for one, or both, of its two principal activities, and provides insights into how this type of protein functions in splicing. Two isoforms of the protein, which arise from alternative splicing, are by themselves inactive, but each can block the activity of ASF/SF2, thereby functioning as splicing repressors. Some, but not all, mutations in the RS region prevent ASF/SF2 from functioning as an essential splicing factor. However, the entire RS region can be deleted without reducing splice site switching activity, indicating that it is not absolutely required for interaction with other splicing factors. Experiments with deletion and substitution mutants reveal that the protein contains two related, but highly diverged, RBDs, and that both are essential for activity. Each RBD by itself retains the ability to bind RNA, although optimal binding requires both domains.

Further evidence for multiple forms of an N-methyl-D-aspartate recognition domain in rat brain using membrane binding techniques

Pretreatment with sulfhydryl-reactive agents, such as N-ethylmaleimide and p-chloromercuriphenylsulfonic acid, invariably resulted in marked inhibition of the binding of DL-(E)-2-amino-4-[3H]propyl-5-phosphono-3-pentenoic acid ([3H]CGP 39653), a competitive antagonist at an N-methyl-D-aspartate (NMDA)-sensitive subclass of central excitatory amino acid receptors, in brain synaptic membranes extensively washed and treated with Triton X-100, but did not significantly affect the binding of L-[3H]-glutamic acid ([3H]Glu), an endogenous agonist. The pretreatment was effective in reducing the binding of [3H]-CGP 39653 at equilibrium, without altering the initial association rate, and decreased the affinity for the ligand. Pretreatment with sulfhydryl-reactive agents also enhanced the potencies of NMDA agonists to displace [3H]-CGP 39653 binding and attenuated those of NMDA antagonists, but had little effect on the potencies of the agonists and antagonists to displace [3H]Glu binding. The binding of both [3H]CGP 39653 and [3H]Glu was similarly sensitive to pretreatment with four different proteases in Triton-treated membranes, whereas pretreatment with phospholipase A2 or C markedly inhibited [3H]CGP 39653 binding without altering [3H]Glu binding. Moreover, both phospholipases not only induced enhancement of the abilities of NMDA agonists to displace the binding of [3H]CGP 39653 and [3H]Glu, but also caused diminution of those of NMDA antagonists. These results suggest that both sulfhydryl-reactive agents and phospholipases may predominantly interfere with radiolabeling of the NMDA recognition domain in a state favorable to an antagonist by [3H]CGP 39653, with concomitant facilitation of that in an antagonist-preferring form by [3H]Glu. The possible presence of multiple forms of the NMDA recognition domain is further supported by these data.

Identification of an snRNP-associated kinase activity that phosphorylates arginine/serine rich domains typical of splicing factors

The U1 snRNP-specific 70K protein is one of the few snRNP proteins from higher eukaryotic cells that is phosphorylated in vivo (1,2). Immunoaffinity purified spliceosomal snRNPs (U1, U2, U5, and U4/U6) were tested for their ability to phosphorylate in vitro the U1-specific 70K protein. An snRNP-associated kinase activity which phosphorylates all U1-70K isoelectric variants was identified. Like its in vivo counterpart, this snRNP-associated enzyme phosphorylates solely serine residues of the 70K protein, preferentially utilizing ATP as a phosphodonor. Tryptic phosphopeptide analysis revealed an overlapping set of at least four radiolabeled peptides in the in vivo and in vitro phosphorylated protein, suggesting that the snRNP-associated serine kinase is responsible, at least in part, for the 70K protein phosphorylation observed in vivo. Chymotryptic digestion of in vitro, 32P-labeled 70K protein and in vitro phosphorylation studies with a synthetic peptide, indicated that the multiple 70K phosphorylation sites are limited to a highly charged, C-terminal domain of the protein. In vitro phosphorylation studies with the splicing factor ASF/SF2 and several deletion mutants demonstrated that, similar to the U1-70K protein, the snRNP-associated serine kinase phosphorylates the carboxy terminal RS-rich domain of ASF/SF2. A potential general role for this enzyme in the phosphorylation of splicing factors and its consequences for pre-mRNA splicing regulation are discussed.

Comparative studies on binding of 3 different ligands to the N-methyl-D-aspartate recognition domain in brain synaptic membranes treated with Triton X-100

Treatment with a low concentration of Triton X-100 almost tripled the binding of [3H]D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid (CGP 39653), a novel competitive antagonist at an N-methyl-D-aspartate (NMDA)-sensitive subclass of brain excitatory amino acid receptors, in synaptic membranes of the rat brain. The binding linearly increased with increasing protein concentrations of up to 0.4 mg/ml and also increased in proportion to incubation time with a plateau within 60 min after the initiation of incubation at 2 degrees C in Triton-treated membranes. Elevation of incubation temperature from 2 degrees C to 30 degrees C resulted in a marked decrease in the binding at equilibrium by 80%, and a maximal level was obtained within 1 min after the initiation of incubation at 30 degrees C with a gradual decline of up to 10 min. Bound [3H]CGP 39653 was rapidly dissociated by the addition of excess unlabeled L-glutamic acid (Glu), and the time required to attain complete dissociation was 60 min at 2 degrees C and 1 min at 30 degrees C, respectively. Among several agonists and antagonists tested, Glu was the most potent displacer of [3H]CGP 39653 binding with progressively less potent displacement by D-2-amino-5-phosphonovaleric, (+-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic (CPP), D-2-amino-7-phosphonoheptanoic, N-methyl-D-aspartic and N-methyl-L-aspartic acids.(ABSTRACT TRUNCATED AT 250 WORDS)

The Drosophila RNA-binding protein RBP1 is localized to transcriptionally active sites of chromosomes and shows a functional similarity to human splicing factor ASF/SF2

An RNA-binding protein gene (rbp1) from Drosophila melanogaster, encoding an RNA recognition motif and an Arg-Ser rich (RS) domain, has been characterized. The predicted amino acid sequence of rbp1 is similar to those of the human splicing factor ASF/SF2, the Drosophila nuclear phosphoprotein SRp55, and the Drosophila puff-associated protein B52. Northern and immunohistochemical analyses showed that rbp1 is expressed at all stages in all tissues and that the RBP1 protein is localized to the nucleus. Consistent with a role in mRNA metabolism, indirect immunofluorescence reveals that the RBP1 protein colocalizes with RNA polymerase II on larval salivary gland polytene chromosomes. RBP1 protein made in Escherichia coli was tested for splicing activity using human cell extracts in which ASF has been shown previously both to activate splicing and to affect the choice of splice sites in alternatively spliced pre-mRNAs. In these assays, RBP1 protein, like ASF, is capable of both activating splicing and switching splice site selection. However, in each case, clear differences in the behavior of the two proteins were detected, suggesting that they have related but not identical functions. The general nuclear expression pattern, colocalization on chromosomes with RNA polymerase II, the similarity to ASF/SF2, SRp55, and B52, along with the effect on alternative splicing shown in vitro, suggest that rbp1 is involved in the processing of precursor mRNAs.

Study of experimental hypoparathyroidism in rats. III. Fluidity changes in brain synaptolemma

The changes of brain synaptolemma fluidity in experimental parathyroidectomized (PTX) rats were studied by using fluorescence polarization and differential scanning calorimetry (DSC) techniques. The results showed that microviscosity (eta) of the rat brain synaptolemma in the cerebral cortex, hippocampus, midbrain and striatum were decreased after a 2-month period of continuous hypocalcemia, and in the hippocampus and cerebral cortex it was decreased significantly as compared with control. These results suggest that the fluidity of the synaptolemma in the brains of hypocalcemic rats is increased. In addition, hypocalcemia also lowered the Tc of hippocampus synaptolemma lipid, which indicates that both fluidity and permeability had increased in these rats.

Metabolism in and function of the central dopamine system after transplanting adrenal medullary tissue into the rat brain

The unilateral nigrostriatal pathway of rats was destroyed by microinjecting 6-hydroxydopamine (6-OH-DA), and isogenous rat adrenal medullary tissue was then transplanted into the lesioned lateral caudate nucleus. After 2 months, rotational movement was almost abolished in 40% of the transplanted rats, and it was significantly reduced in the remaining 60%. Dopamine (DA) and its metabolites contents were significantly decreased in the lesioned side of the forebrain, while no changes of NA were found. After transplanting adrenal medullary tissue, the DA contents increased by 9% only, whereas the NA contents increased significantly. In addition, by examining synaptosomes in the brains of these rats, we found that on the lesioned side of nontransplanted rats, DA uptake and DA receptor binding were increased significantly, while no such changes were seen in the transplanted group.

Presence of the binding of a variety of ligands related to ionotropic excitatory amino acid receptors in rat retina

The binding of [3H]L-glutamic (Glu), [3H](+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic and [3H]D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acids was detected in rat retinal membranes extensively washed and treated with a low concentration of Triton X-100, in addition to the binding of both [3H]glycine (Gly) and [3H]5,7-dichlorokynurenic acid. Furthermore, retinal membranes exhibited the binding of [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne in the presence of Glu, Gly and spermidine irrespective of the incubation period employed. Rat retina also contained the binding of [3H]kainic acid as well as the binding of [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid which was sensitive to potentiation by potassium thiocyanate. In addition, the binding of both [3H](+)-3-(hydroxyphenyl)-N-(l-propyl)piperidine and [3H]1,3-di-o-tolyl-guanidine was found in rat retinal membranes extensively washed but not treated with Triton X-100. These results give support for the proposal that the rodent retina contains subclasses of ionotropic brain excitatory amino acid receptors including the N-methyl-D-aspartate receptor ionophore complex as well as sigma sites.

Primary structure of the human splicing factor ASF reveals similarities with Drosophila regulators

We described previously the purification of a human protein, called alternative splicing factor (ASF), that can switch utilization of alternative 5' splice sites in an SV40 early pre-mRNA. We now report the isolation of a cDNA, designated ASF-1, that encodes this protein. ASF-1 consists of 248 amino acid residues, including an 80 residue RNA-binding domain at its N-terminus and a 50 residue C-terminal region that is 80% serine plus arginine. ASF-1 produced in E. coli can activate splicing in vitro and switch 5' splice-site utilization, establishing that the recombinant protein is sufficient to supply these activities. Analysis of additional cDNAs revealed that ASF pre-mRNA can itself be alternatively spliced, surprisingly, by utilization of a shared 5' splice site and two closely spaced 3' splice sites. Use of the upstream site results in a second mRNA (ASF-2) in which translation of the downstream exon occurs extensively in an alternative reading frame distinct from ASF-1.

[Changes in neurotransmitters uptake and their receptors binding after transplanting adrenal medullary tissue into central striatum in rats]

Unilateral nigrostriatal pathway of rats was destroyed by using injection of 6-hydroxydopamine (6-OHDA), presenting the rotative movement model and transplanting isogenous rat adrenal medullary tissues into their lesioned lateral caudate nucleus. After 2 months, the rotative movement almost abolished by 34% out of the total transplanted rats, and it was significantly reduced by 57% of the same rats. Taking the above rats brain synaptosome, we found the lesioned side, the uptake of tyrosine, dopamine and choline increased significantly, nevertheless, in another group which transplanted with adrenal medullary tissue, the uptake of same neurotransmitters recover to the normal level. In addition, we also found that dopamine (DA2) receptor binding increased remarkably but muscarinic and GABAA receptors binding decreased significantly in lesioned side brain synaptic membrane, while the transplanted group didn't shown such changes.

Activation and repression of transcription by the gap proteins hunchback and Krüppel in cultured Drosophila cells

We have studied the ability of the Drosophila gap proteins Krüppel and hunchback to function as transcriptional regulators in cultured cells. Both proteins bind to specific sites in a 100-bp DNA fragment located upstream of the segment polarity gene engrailed, which also contains functional binding sites for a number of homeo box proteins. The hunchback protein is a strikingly concentration-dependent activator of transcription, capable of functioning both by itself and also synergistically with the pair-rule proteins fushi tarazu and paired. In contrast, Krüppel is a transcriptional repressor that can block transcription induced either by hunchback or by several different homeo box proteins. While repression of the homeo box protein activators requires a Krüppel-binding site on the DNA, repression of hunchback can occur efficiently in the absence of a Krüppel-binding site. We discuss the possible molecular mechanisms underlying these activities, as well as the potential significance of these results with respect to segmentation in Drosophila.

Structure in the precore region of hepatitis B core gene affecting its expression in E. coli

Restriction fragments of HBV-DNA, cleaved by endonuclease HhaI, containing HBcAg gene were trimmed by BAL-31 exonuclease to remove different lengths of the precore sequence. They were inserted into plasmid pUR222 at EcoRI site through synthetic linker ligation. Transformants in E. coli BMH7118 showing different levels of HBcAg gene expression were screened and analyzed for their nucleotide sequences in the junction region both by Maxam and Gilbert's chemical degradation method and by M13 chain termination method. Results of sequence analysis of different transformants revealed a partial palindromic (loop and stem) structure, at -7 to -35 nucleotide with regard to ATG of the HBcAg gene as position +1, which has dramatic effect on the level of expression of the inserted gene using the same promoter, SD sequence and identical N-terminus. The amount of HBcAg synthesized differed from 9% in the high expressing plasmid to less than 0.01% of the total cell proteins in the low expressing transformants. The findings were compared to results obtained by other workers in studies of HBcAg expression in procaryotes and their significance in the expression of eucaryotic genes in procaryotic cells were discussed.