The involvement of muscarinic, β-adrenergic and metabotropic glutamate receptors in long-term potentiation in the fimbria-CA3 pathway of the hippocampus

Possible modulatory actions of endogenous neurotransmitters on long-term potentiation (LTP) were investigated in the fimbria-CA3 pathway of rat hippocampal slices. Bath application of atropine (10 microM), but neither timolol (10 microM) nor D,L-2-amino-3-phosphonopropionate (AP3, 100 microM), significantly attenuated LTP induced by 20 pulses of 50 Hz stimulation. When stronger stimulation (3 trains of 100 Hz, 100 pulses) was used for the induction of LTP, timolol significantly attenuated LTP, but atropine and AP3 did not. These results suggest that, under specified conditions, endogenous acetylcholine through muscarinic receptors, and noradrenaline through beta-adrenergic receptors may modulate the generation of LTP in the fimbria-CA3 pathway. Metabotropic glutamate receptors may be involved not in the generation of LTP but in low-frequency synaptic transmission, since 300-1,000 microM AP3 greatly reduced, or abolished synaptic transmission in this pathway.

Possible physiological roles of aspartase, NAD- and NADP-requiring glutamate dehydrogenases of Pseudomonas fluorescens

The levels of aspartase, NADP- and NAD-requiring glutamate dehydrogenases (GDHs) in Pseudomonas fluorescens grown under various nutritional conditions were determined. NADP-GDH showed the highest value on glucose-ammonium sulfate medium and markedly lower values on amino-acid and casamino-acids media, while the reverse was found for the NAD-GDH, as in the case of other microorganisms with two GDHs. Aspartase did not show a marked variation between the media examined. Glucose nutritionally induced NADP-GDH but suppressed NAD-GDH; and it had no effect on aspartase, which was slightly induced by casamino acids. Transfer of the cells grown on glucose-ammonium sulfate medium to casamino-acids medium clearly increased the levels of NAD-GDH and aspartase, while addition of chloramphenicol to the media abolished the increases, suggesting that the increases were due to de novo synthesis of the enzyme proteins. These results indicate that the aspartase of this microorganism has a different function from those in others, including Escherichia coli.

Involvement of postsynaptic G proteins in hippocampal long-term potentiation

The possible involvement of postsynaptic guanosine 5-triphosphate (GTP)-binding proteins (G proteins) in long-term potentiation (LTP) was studied in rat hippocampal slices, using whole-cell recording techniques. The inclusion of guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) in the recording pipette significantly reduced or abolished the baclofen-induced hyperpolarization of pyramidal neurons, which indicates uncoupling of the signal transduction from G protein-coupled receptors by these compounds. Both GDP beta S and GTP gamma S significantly attenuated the magnitude of LTP in the fimbria-CA3 synapses, but not in the mossy fiber-CA3 synapses. GTP gamma S did not attenuate LTP in the Schaffer-CA1 synapses. The effects of guanine nucleotide analogs on fimbrial LTP were reversed by postsynaptic depolarization during high frequency stimulation. These results suggest that postsynaptic G proteins may be involved in the generation of LTP in the fimbrial synapses, possibly by affecting membrane depolarization during high frequency afferent activation.

YM-14673, a new thyrotropin-releasing hormone analog, augments long-term potentiation in the mossy fiber-CA3 system of guinea pig hippocampal slices

Effects of a new thyrotropin-releasing hormone (TRH) analog, N alpha-[[(S)-4-oxo-2-azetidinyl]carbonyl]L-histidyl-L-prolinamide dihydrate (YM-14673), which improves experimentally induced memory dysfunction, on long-term potentiation (LTP) in the mossy fiber-CA3 system, were investigated using guinea pig hippocampal slices. At concentrations of 10(-7) M and 10(-6) M, YM-14673 significantly augmented LTP in a concentration dependent manner. The magnitude of effect of 10(-6) M YM-14673 was similar to that of 10(-6) M TRH. As LTP in the hippocampus is regarded as an elementary process of memory and learning, the augmenting effect of YM-14673 on LTP in the present study may contribute to this drug's ability to remedy memory dysfunction.

Separate mechanisms of long-term potentiation in two input systems to CA3 pyramidal neurons of rat hippocampal slices as revealed by the whole-cell patch-clamp technique

Excitatory synaptic transmission from two input systems to hippocampal CA3 pyramidal neurons was investigated by the whole-cell patch-clamp technique for thin slice preparation, with special reference to long-term potentiation (LTP) in these systems. Excitatory postsynaptic currents (EPSCs) evoked by fimbrial stimulation consisted of two components; one was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the other was persistent at depolarized membrane potentials and blocked by D-2-amino-5-phosphonovalerate (D-AP5). The contribution of the D-AP5-sensitive component to EPSCs evoked by stimulation of mossy fibers was much less than that to fimbrial EPSCs. High-frequency stimulation of afferent fibers, under current-clamp conditions, elicited LTP. Bath application of D-AP5 blocked the induction of LTP in the fimbrial but not in the mossy fiber synapses. Induction of fimbrial LTP was completely blocked by 10 mM BAPTA applied intracellularly. In contrast, mossy fiber LTP was not blocked by 10 mM BAPTA. Furthermore, mossy fiber LTP, but not fimbrial LTP, was elicited by high-frequency stimulation under voltage-clamp (-80 mV) conditions. These results suggest that activation of NMDA receptors, increase in postsynaptic [Ca2+]i, and postsynaptic membrane depolarization are required for the induction of fimbrial but not for mossy fiber LTP.

Effects of thyrotropin-releasing hormone and a related analog, CNK-602A, on long-term potentiation in the mossy fiber-CA3 pathway of guinea pig hippocampal slices

The effects of thyrotropin-releasing hormone (TRH) and a related analog, CNK-602A, that induces the release of catecholamines, on long-term potentiation (LTP) of the population spike in mossy fiber-CA3 pathways were investigated in guinea pig hippocampal slices. TRH augmented LTP of the population spike at concentrations of 10(-6)-10(-5) M. CNK-602A also augmented LTP at concentrations of 10(-6)-10(-5) M in a dose-dependent manner. LTP in slices of the hippocampus obtained from animals given 6-hydroxydopamine (6-OHDA) intraventricularly was significantly lower than that in non-treated animals. However, both TRH and CNK-602A (10(-6) M) augmented LTP in slices from 6-OHDA-treated animals. These findings suggest that TRH and CNK-602A augment LTP in the mossy fiber-CA3 pathway without activating noradrenergic and/or dopaminergic fibers.

Smoking and health: a review prepared by the Smoking and Health Subcommittee of the Tobacco Industries Council, a council formed by the Minister of Finance of Japan

Any definition of health is inevitably broad and contains various elements that may differ from one individual to another. Recent studies on the effects of smoking on physical and mental health have progressed remarkably and have great value in the fields of epidemiology, pathology, clinical medicine, and psychiatry. This report concludes that while smoking may have beneficial psychological effects on smokers, it may pose a risk to physical health.

Age-related deterioration of long-term potentiation in the CA3 and CA1 regions of hippocampal slices from the senescence-accelerated mouse

Long-term potentiation (LTP) is one candidate for the mechanism underlying memory storage. In the present study, we carried out electrophysiological studies on hippocampal slices prepared from the senescence-accelerated mouse (SAM-P/8), a strain which shows accelerated senescence and failure of certain types of learning in behavioral tests. The findings were compared with those noted in the SAM-R/1 substrain without severe symptoms of senescence. No significant differences were found between SAM-R/1 and SAM-P/8 of the same ages in responses in the absence of tetanic stimulation, and in LTP after tetanic stimulation. However, there were marked decreases in the degree of potentiation with aging in both strains.

Interleukin-1 beta inhibits long-term potentiation in the CA3 region of mouse hippocampal slices

The effect of recombinant human interleukin 1-beta (IL-1 beta) on long-term potentiation (LTP) in the mossy fiber-CA3 pathway of mouse hippocampal slice preparations was investigated. IL-1 beta significantly inhibited LTP in concentrations as low as 2.9 pM (50 pg/ml). This effect of IL-1 beta was blocked by concurrent application of 100 nM Lys-D-Pro-Thr, a tripeptide analogue of IL-1 beta. This is the first evidence that IL-1 beta can regulate LTP of synaptic transmission in the hippocampus.

Different drug-susceptibilities of long-term potentiation in three input systems to the CA3 region of the guinea pig hippocampus in vitro

The susceptibilities to several drugs of long-term potentiations in the three input systems (mossy, commissural/associational and fimbrial fibres) to CA3 pyramidal neurones were investigated in hippocampal slices from the guinea pig. D-2-Amino-5-phosphonovalerate (D-APV), a selective antagonist at N-methyl-D-aspartate (NMDA) receptors, blocked the long-term potentiations in the commissural/associational fibre- and fimbrial fibre-CA3 systems, but did not significantly affect that in the mossy fibre-CA3 system. The latter was suppressed by kynurenate, a non-selective glutamate receptor antagonist. On the other hand, naloxone, an opioid antagonist, inhibited and bifemelane, which improves metabolism in brain and has an anti-amnesic action, augmented long-term potentiation in mossy fibre-CA3 system but did not influence those in commissural/associational fibre- and fimbrial fibre-CA3 systems. These findings suggest that the mechanisms, relevant to production of long-term potentiation in the mossy fibre-CA3 system, are different from those in the commissural/associational fibre- and fimbrial fibre-CA3 systems. N-Methyl-D-aspartate receptors are involved in the latter systems, while non-NMDA receptors for L-glutamate and opioid receptors are involved in the former. Further, the mossy fibre-CA3 system is more susceptible to a drug, having an anti-amnesic action, than are the other two systems.

Indeloxazine augments long-term potentiation in the mossy fiber-CA3 system of guinea pig hippocampal slices

The effects of indeloxazine and piracetam, which reportedly prevent experimental impairments of memory and learning, on long-term potentiation (LTP) of the population spike in the mossy fiber-CA3 system were studied in vitro using the guinea pig hippocampal slices. Indeloxazine (10(-6) M) or piracetam (10(-4) M) significantly augmented the LTP and the effect of indeloxazine on the LTP was approximately 100 times as potent as that of piracetam.

Isolation and characterization of an Escherichia coli mutant having temperature-sensitive farnesyl diphosphate synthase

The screening of a collection of highly mutagenized strains of Escherichia coli for defects in isoprenoid synthesis led to the isolation of a mutant that had temperature-sensitive farnesyl diphosphate synthase. The defective gene, named ispA, was mapped at about min 10 on the E. coli chromosome, and the gene order was shown to be tsx-ispA-lon. The mutant ispA gene was transferred to the E. coli strain with a defined genetic background by P1 transduction for investigation of its function. The in vitro activity of farnesyl diphosphate synthase of the mutant was 21% of that of the wild-type strain at 30 degrees C and 5% of that at 40 degrees C. At 42 degrees C the ubiquinone level was lower (66% of normal) in the mutant than in the wild-type strain, whereas at 30 degrees C the level in the mutant was almost equal to that in the wild-type strain. The polyprenyl phosphate level was slightly higher in the mutant than in the wild-type strain at 30 degrees C and almost the same in both strains at 42 degrees C. The mutant had no obvious phenotype regarding its growth properties.

Idebenone and vinpocetine augment long-term potentiation in hippocampal slices in the guinea pig

The effects of idebenone and vinpocetine which reportedly prevent impairment of learning and memory were studied in vitro, on the long-term potentiation of the population spike in the pyramidal layer of CA3 region of slices of hippocampus in the guinea pig. Idebenone (10(-9) M-10(-6) M) or vinpocetine (10(-7) M-10(-6) M) significantly augmented long-term potentiation in the mossy fibre-CA3 pyramidal cell system, without any significant changes in population spikes in the absence of tetanic stimulation. These results suggest that both drugs have direct actions on the hippocampal neurones to augment long-term potentiation at fairly small concentrations. Further, when the two drugs were applied together, the augmenting effects were additive.

Different susceptibilities of long-term potentiations in CA3 and CA1 regions of guinea pig hippocampal slices to nootropic drugs

Effects of the nootropic drugs, piracetam and bifemelane, on long-term potentiation (LTP) of population spikes in the CA3 and CA1 regions of guinea pig hippocampal slices were investigated. Piracetam (10(-6) to 10(-4) M) and bifemelane (10(-8) to 10(-6) M) significantly augmented the LTP in the CA3 region. The effects of these drugs were inhibited by scopolamine (10(-6) M). However, the LTP in the CA1 region was not affected by piracetam and bifemelane even at highly effective concentrations (10(-5) and 10(-6) M, respectively). Thus, the LTP in the CA3 is more susceptible to nootropic drugs than in the CA1.

Further analysis of cDNA clones for maize phosphoenolpyruvate carboxylase involved in C4 photosynthesis. Nucleotide sequence of entire open reading frame and evidence for polyadenylation of mRNA at multiple sites in vivo

Four clones of cDNA for phosphoenolpyruvate carboxylase [EC 4.1.1.31] were obtained from a maize green leaf cDNA library by colony hybridization. The largest cDNA was of full-length (3335 nucleotides), being 243 nucleotides longer than the cDNA cloned previously [(1986) Nucleic Acids Res. 14, 1615-1628]. Alignment of the sequence for the N-terminal coding region found in two of the four clones with the sequence reported previously, established the sequence of the entire coding region for the enzyme. The sequencing of 3'-untranslated region of the clones revealed that the poly(A) tract is attached at multiple sites in vivo.

Preparation and characterization of monoclonal antibodies against phosphoenolpyruvate carboxylase of Escherichia coli

Twelve hybridoma clones which secrete monoclonal antibodies (mAb) against purified phosphoenolpyruvate carboxylase [EC 4.1.1.31] from Escherichia coli K-12 were obtained. These 12 mAb were prepared from the ascites fluids of mice. Six among the 12 mAb formed precipitin lines with the enzyme on immunodiffusion. Four mAb inhibited the activity of the enzyme and 2 mAb enhanced it. Four mAb altered the sensitivity of the enzyme to allosteric effectors. Competitive enzyme-binding experiments among the 12 different mAb were also performed. The results showed that the 12 mAb can be classified into at least 8 groups.

Isolation and characterization of an altered cytochrome P-450 from a yeast mutant defective in lanosterol 14 alpha-demethylation

A cytochrome P-450 (P-450SG1) was purified from a lanosterol 14 alpha-demethylase (P-450(14DM)) defective mutant of Saccharomyces cerevisiae, strain SG1, by a method similar to that used in the purification of the wild type enzyme (Yoshida, Y., and Aoyama, Y. (1984) J. Biol. Chem. 259, 1655-1660). P-450SG1 had the same apparent Mr as and was immunochemically identical to P-450(14DM). Peptide maps of P-450SG1 made by limited proteolysis with Staphylococcus aureus V8 proteinase, chymotrypsin, or papain followed by gel electrophoresis were identical to corresponding peptide maps of P-450(14DM). However, P-450SG1 showed no lanosterol 14 alpha-demethylase activity and its mode of interaction with diniconazole [(E)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-y1)-1- penten-3- o1], a specific inhibitor of P-450(14DM), was fundamentally different from that of P-450(14DM). The absorption spectrum of ferric P-450SG1 was unusual for a native low-spin cytochrome P-450 and was superimposable on that of 1-methylimidazole complex of P-450(14DM), indicating that P-450SG1 has a histidine 6th ligand trans to the thiolate 5th ligand, while the 6th ligand of other ferric low-spin cytochrome P-450s is a water molecule or a hydroxyl group of an oxyamino acid. It is concluded that P-450SG1 is an altered P-450(14DM). Difference in the primary structure between P-450SG1 and P-450(14DM) may be slight and was not detected by peptide mapping. However, the alteration caused significant change in the substrate site and heme environments of the cytochrome. P-450SG1 is the first example of a cytochrome P-450 having a histidine axial ligand trans to thiolate and of a genetically altered cytochrome P-450 isolated in a homogeneous state.

Adsorbed behavior of spin-labeled silane coupling agent on colloidal silica studied by electron spin resonance

The adsorption mechanism of silane coupling agent on the colloidal silica surface is studied with spin-labeled silane coupling agent using ESR method. The density of the adsorbed silane molecules was determined to be approximately 1.5-2 molecules per 100 A2 of the silica surface in 95% ethanol solution. In addition, ESR signal of spin-labeled agent adsorbed on the colloidal silica surface was composed of two components; slow component attributable to the agents adsorbed directly on the Si--OH groups of the silica surface through hydrogen bond formation and rapid one attributable to the agents interacted with such adsorbed silane molecules.

Physiological roles of two enzymes with fumarase activity in two Pseudomonads

Effects of Fe2+ ions on the levels of two enzymes (fumarase and mesaconase) with fumarase activity in two Pseudomonads grown under various nutritional conditions were investigated. Fe2+ ions decreased fumarase but increased mesaconase. A high level of mesaconase was found in Ps. arvilla which was unable to metabolize itaconate. The level of mesaconase in the itaconate-grown cells of Ps. fluorescens was almost the same as that in the glucose-grown cells. This suggests that mesaconase is not an enzyme involved in the metabolism of C5-branched-chain dicarboxylates but presumably, taking the place of fumarase, plays a role in the operation of the tricarboxylic acid cycle in the cells grown in the medium containing Fe2+ ions more than 10 nmol/ml.

Characterization of nystatin-resistant mutants of Saccharomyces cerevisiae and preparation of sterol intermediates using the mutants

Analysis of sterols of Saccharomyces cerevisiae mutants N3, N15, N26, and N3H, defective in sterol biosynthesis, was performed. Strains N3, N15, and N26 were isolated from their mother strain, M10, by screening with nystatin (Nagai et al. (1980) Mie Med. J. 30, 215-224), and strain N3H was isolated from N3 as a doubly-mutated strain. The main sterols of N3, N15, N26, and N3H were ergosta-7,22-dienol, ergost-8-enol, cholesta-5,7,24-trienol, and ergosta-7,22,24(28)-trienol, respectively. The former three strains were characterized as defective in delta 5-desaturation, delta 8--delta 7 isomerization, and C-24 transmethylation. Strain N3H was found to be defective in delta 5-desaturation as well as in delta 24(28)-reduction. However, the defect of N26 and N3H was suggested to be leaky, since small amounts of ergosterol and ergosta-7,22-dienol were found in these mutants, respectively. In N15, an accumulation (2% in total sterols) of the compound likely to be hydroxylated sterol was found. By aerobic adaptation of these strains, the accumulation of these strains, the accumulations of ergosta-7,22-dienol (22 mg/g dry cells), ergosta-7,22,24(28)-trienol (24 mg), ergosta-8,24(28)-dienol (18 mg), and cholesta-8,24-dienol (22 mg) reached a maximum in N3, N3H, N15, and N26 after 20, 20, 30, and 30 h, respectively. These strains appear to be useful for making 14C-labeled and non-labeled preparations of the above sterols.

Phosphoenolpyruvate carboxylase of Escherichia coli K-12. N- and C-terminal sequences and tentative assignment of the catalytically essential cysteine residue

The N- and C-terminal amino acid sequences of phosphoenolpyruvate carboxylase [EC 4.1.1.31] from Escherichia coli K-12 were determined to establish the primary structure deduced from the nucleotide sequence of the cloned gene for the enzyme (Fujita, N., Miwa, T., Ishijima, S., Izui, K., & Katsuki, H. (1984) J. Biochem. 95, 909-916). As predicted from the nucleotide sequence, two polypeptides were produced upon treatment with hydroxylamine, which specifically cleaves the Asn-Gly bond, and their amino acid compositions were also in accordance with those predicted. The tryptic peptides which contained cysteine residues labeled with a fluorescent reagent, N-[7-(dimethylamino)-4-methylcoumarinyl]maleimide, were isolated by high-performance liquid chromatography and partially sequenced. All of them could be assigned on the deduced primary structure. The modified cysteine residues were Cys-157, Cys-385, Cys-458, Cys-568, Cys-665, and Cys-754. Furthermore, the essential cysteine residue which is presumably located at or near the active site was tentatively identified as Cys-568, since it was consistently protected against the modification by 2-phospholactate, a substrate analog.

Isoprenoid synthesis in Escherichia coli. Separation and partial purification of four enzymes involved in the synthesis

Isopentenyl pyrophosphate (IPP) isomerase, farnesyl pyrophosphate (FPP) synthetase, octaprenyl pyrophosphate (OPP) synthetase and undecaprenyl pyrophosphate (UPP) synthetase were partially purified from Escherichia coli by DEAE-Toyopearl chromatography. FPP synthetase catalyzed the condensation of IPP with dimethylallyl pyrophosphate (DPP) as well as with geranyl pyrophosphate (GPP) to yield FPP as final product. OPP synthetase and UPP synthetase catalyzed the condensation of IPP with FPP to yield OPP and cis,trans-polyprenyl pyrophosphates (the C45-, C50, and C55-compound), respectively. Neither DPP nor GPP acted as a priming substrate for either enzyme. These four enzymes required Mg2+ or Mn2+ for their activities. UPP synthetase required also Triton X-100 for its activity. The addition of Triton X-100 enhanced OPP synthetase, but it did not affect IPP isomerase and FPP synthetase. It seems possible that the combination of the four enzymes ensures the in vivo synthesis of long-chain isoprenoids in E. coli.