Nitric oxide mediates activity-dependent synaptic suppression at developing neuromuscular synapses

Temporal correlation between pre- and postsynaptic activities is an important mechanism that regulates synaptic connectivity during development and synaptic plasticity in the adult. In developing neuromuscular junctions, postsynaptic activity is critical in functional suppression and, ultimately, elimination of the synapses. Although repetitive postsynaptic firing asynchronous to the presynaptic activity results in a persistent synaptic suppression, the underlying molecular mechanism remains unknown. Here we provide evidence that nitric oxide (NO), a free radical implicated in several forms of synaptic plasticity, may serve as a retrograde signal for activity-dependent suppression in the neuromuscular synapse. NO donors and activators of the cyclic GMP pathway suppressed spontaneous and evoked synaptic currents. Moreover, the synaptic suppression induced by repetitive postsynaptic depolarization was prevented by the NO-binding protein haemoglobin and by inhibitors of NO synthase. Thus, synaptic suppression may be triggered by NO released from a postsynaptic myocyte that fires asynchronously to the presynaptic terminal.

[Theory of similarity between close relative species of toxic medicinal herbs in toxicity and poisoning action]

The article puts forward an opinion that there are identical or similar toxic components and poisoning action among close relative species of toxic medicinal herbs. These components, however, may vary in contents with different species. Many scientific examples are enough to prove that we can take treating, curing and preventative measures effectively only if we hold the conception that "Toxicity and poisoning action to each other may exist in close relative species of toxic medicinal herbs".

Different oxidant sensitivities of the alpha 1 and alpha 2 isoforms of Na+/K(+)-ATPase expressed in baculovirus-infected insect cells

Inhibition of Na+/K(+)-ATPase by partially reduced oxygen metabolites is an early event in the course of cell injury caused by oxidative stress. We showed before that isoforms of the enzyme obtained from different sources have different oxidant sensitivities. To evaluate the role of tissue-specific impurities in this difference, cDNAs of alpha 1 and alpha 2 isoforms were expressed in Sf-9 insect cells, and the effects of H2O2 on the resulting isolated enzymes were studied. The expressed alpha 2 was significantly more sensitive than alpha 1 to H2O2. These findings, together with our previous data showing different oxidant sensitivities of alpha 1 and alpha 3 in a cardiac enzyme preparation, indicate that differential oxidant sensitivities of Na+/K(+)-ATPase isoforms of various tissues are dictated by the primary sequences of alpha 1, alpha 2, and alpha 3 subunits.

Molecular cloning of two rat Na+/Pi cotransporters: evidence for differential tissue expression of transcripts

Recently, Na+/Pi cotransport activity has been demonstrated in rat liver hepatocytes. Here, we report the isolation of two Na+/Pi cotransporter cDNAs (RNaPi-1a and RNaPi-1b) from a rat liver cDNA library. The two cDNAs have the same coding but different 5'-untranslated regions. The rat cDNAs encode a polypeptide of 465 amino acids, having 62% and 66% identity with the rabbit NaPi-1 and human kidney Na+/Pi cotransporter, respectively. Northern blot analysis showed that a RNaPi-1a--specific probe detected two major transcripts (2.3 and 1.8 kb), whereas a RNaPi-1b--specific probe hybridized with one transcript (1.8 kb) in rat kidney, liver, and hepatocytes in primary culture. Rat liver expressed much higher levels of RNaPi-1a than RNaPi-1b, whereas the converse was true for rat kidney. Low levels of RNaPi-1 mRNAs were also detected in rat heart, brain, and skeletal muscle. These findings indicate that there are at least two isoforms of RNaPi-1 transcripts expressed in liver and kidney and that the levels of expression of the RNaPi-1a and RNaPi-1b may be controlled by tissue-specific factors.

A pathway for the biosynthesis of straight and branched, odd- and even-length, medium-chain fatty acids in plants

Pathways and enzymes of fatty acid synthase-mediated, long-even-chain (generally C16-C20) fatty acid synthesis are well studied, and general metabolism involved in short-chain (C4-C7) fatty acid biosynthesis is also understood. In contrast, mechanisms of medium-chain (C8-C14) fatty acid synthesis are unclear. Recent work suggests involvement of chain-elongation-terminating thioesterases in medium-chain fatty acid formation in oilseeds and animals. We have shown that iso- and anteiso-branched and straight, odd- and even-length, short-chain fatty acids esterified in plant-trichome-gland-produced sucrose esters are synthesized by using carbon skeletons provided by modified branched-chain amino acid metabolism/catabolism. The principal enzymes involved are those catalyzing leucine biosynthesis in all organisms and those leading to short-chain alcohols in mutant yeasts and alkyl acids in Clostridium species (products often serving as mammalian pheromones). Here we provide evidence that C10-C12 straight medium-chain and C10-C12 branched medium-chain acyl acids of tomato, C6-C8 straight-chain acyl acids of Petunia, and C6 and C8 branched acyl acids of Nicotiana glutinosa are formed by alpha-ketoacid elongation without participation of fatty acid synthase-mediated reactions or -independent thioesterases. This different metabolism suggests greater integration of amino acid and fatty acid metabolism than previously considered and provides other avenues to study and manipulate not only straight even-length but also odd- and even-length straight and branched medium-chain fatty acid biosynthesis.

Liposome-induced activation of the classical complement pathway does not require immunoglobulin

We have investigated the contribution of immunoglobulin to the liposome-induced activation of complement in human serum. Liposomes containing the negatively charged phospholipids cardiolipin, phosphatidylglycerol or phosphatidylinositol, in addition to phosphatidylcholine and cholesterol, were used to activate complement in a whole serum system. The contribution of immunoglobulin was studied by comparing normal human serum (NHS) to serum depleted of IgG and IgM (DDS). Using hemolytic assays of complement function, greater concentrations of phospholipids were required to activate complement in the absence of immunoglobulins. Activation of the classical pathway was confirmed using a C1q ELISA which showed that activation was dependent on the presence of C1q and confirmed that greater concentrations of phospholipids were required to activate complement in the absence of immunoglobulins. Complement activation was also assessed using crossed immunoelectrophoresis of C3 activation fragments. Using immunoblot analysis, iC3b was detected on the surface of liposomes exposed to NHS or DDS. These studies demonstrate that when liposomes, containing anionic phospholipids at an equivalent charge to cardiolipin 20 mol%, are exposed to immunoglobulin depleted serum they become opsonized by complement proteins.

Contraction and depolarization induced by fetal bovine serum in airway smooth muscle

We investigated the effects of fetal bovine serum (FBS) on the resting membrane potential and muscle tone of canine airway smooth muscles using tension recording and microelectrode methods. At concentrations > 0.1%, FBS induced a sustained increase in muscle tone. At concentrations > 1%, FBS depolarized the resting membrane potential of dog trachea in a dose-dependent manner. When FBS was dialyzed, it failed to induce a sustained increase in muscle tone or to depolarize the membrane, indicating that FBS contained factor(s) that induced contraction of dog airway smooth muscles. When FBS was dialyzed against distilled water, the outer solution which was freeze dried and then reconstituted (> 1% in original vol) induced a sustained increase in muscle tone, indicating that FBS contained dialyzable factor(s) that increased muscle tone and depolarized the resting membrane potential of dog airway smooth muscles. Methysergide (10(-6) M) or cyproheptadine (10(-6) M), nonspecific antagonists to serotonin receptors, 5-hydroxytryptamines (5-HT1 and 5-HT2), markedly reduced the FBS-induced increase in the muscle tone to approximately 20% of the original value but did not abolish the response. On the other hand, methysergide (10(-6) M) completely suppressed the increase in the muscle tone evoked by peak fractions obtained by application of the dialysate of FBS or 5-HT to a C18 reverse-phase column, indicating the peak fractions contained only 5-HT. These observations indicate that FBS contained 5-HT and an unknown factor(s) responsible for increase in the muscle tone of the airway smooth muscle induced by FBS.

Effects of epithelial cell supernatant on membrane potential and contraction of dog airway smooth muscles

We investigated the effects of cultured epithelial cells and supernatants on resting membrane potential and excitatory neuroeffector transmission in smooth muscle cells of dog trachea and bronchioles. The mean resting membrane potential of the mucosa-free tracheal smooth muscle cells was -59.5 +/- 1.5 mV (+/- SD). Application of cultured epithelial cells (> 2.5 x 10(5) cells/ml) hyperpolarized the membrane, resulting in a potential of -64.5 +/- 1.7 mV. The supernatant of the cultured epithelial cells also increased the resting membrane potential of the mucosa-free tracheal smooth muscle cells by 4 to 9 mV. These hyperpolarizing actions were not modified by indomethacin (10(-5) M), l-NG-nitroarginine (10(-5) M), or oxyhemoglobin (10(-5) M), but were inhibited by glibenclamide (10(-6) M). The supernatants of the cultured epithelial cells completely or partially suppressed the contractile response of epithelium-denuded bronchioles to electrical field stimulations and suppressed the amplitude of excitatory junction potentials of the trachealis evoked by electrical field stimulations. Indomethacin prevented the inhibitory effect of supernatants on the amplitude of twitch contractions and excitatory junction potentials and markedly suppressed supernatant-associated inhibition of the excitatory neuroeffector transmission. Furthermore, indomethacin with AA861, a lipoxygenase inhibitor, completely suppressed this effect. Our findings suggest that cultured airway epithelial cells spontaneously release at least two factors. One factor selectively modulates the resting membrane potential, and the other inhibits the excitatory neuroeffector transmission.

Closely Approaching the Silylium Ion (R3Si+)

The crystal structure of the tri-isopropyl silyl species, i-Pr(3)Si(Br(6)-CB(11)H(6)), where the brominated carborane Br(6)-CB(11) H(6)(-) is perhaps the least nucleophilic anion presently known, has revealed the highest degree of silylium cation character (R(3)Si(+)) yet observed. The average C-Si-C angle is 117 degrees , only 3 degrees short of the planarity expected of a pure silylium ion(120 degrees ). This value compares to 114 degrees recently reported for a toluene-solvated silyl cation, [Et(3)Si(toluene)](+) by Lambert and co-workers. The greater silylium ion character of i-Pr(3)Si(Br(6)-CB(11)H(6)) versus [i-Pr(3)Si(toluene)](+) is also reflected in the larger downfield shift of the silicon-29 nuclear magnetic resonance, 109.8 versus </=94.0 parts per million. The unusual bonding of toluene to R(3)Si(+) in Lambert's compound is reinterpreted as a significant covalent pi interaction.

Induction of hippocampal long-term potentiation by alpha-tocopherol

Long-term potentiation (LTP) of synaptic transmission in the hippocampus is thought to be one of the cellular mechanisms underlying learning and memory. Recent evidence in literature suggests the involvement of free radicals in impeding LTP maintenance. In the present study, the effects of alpha-tocopherol, a major lipid-soluble antioxidant which could prevent lipid peroxidation, were examined on the excitatory post-synaptic potentials (EPSPs) of CA1 neurons in guinea pig hippocampal slices. alpha-Tocopherol phosphate disodium salt (0.2 mM applied for 5 min) induced a slowly developing long-lasting increase of the EPSP, without significantly changing the membrane potential, the input resistance and the ability to generate action potentials. No significant changes in the fast and the slow inhibitory post-synaptic potentials (IPSPs) were observed during the alpha-tocopherol-induced LTP of the EPSP. 2-Amino-5-phosphonovalerate (APV) did not block the induction of this LTP. L-Ascorbic acid (Na salt, 3-10 mM), a water-soluble antioxidant, failed to produce any significant enhancement in the EPSP. These results indicate that alpha-tocopherol can induce LTP of the EPSP in guinea pig hippocampal CA1 neurons. The activation of N-methyl-D-aspartate (NMDA) receptors does not appear to be necessary for this action of alpha-tocopherol. Whether the LTP-inducing action of this agent is related to its antioxidant property is unclear.

Major causes of the regional difference in fertility rate: factor analysis of 72 counties and county-level cities in Anhui Province

The author compares fertility rates among 72 counties and county-level cities in Anhui Province, China. "The many causes of fertility difference...may be categorized into two major groups: social, economic and cultural factors; and population control (mainly birth control) factors.... This paper uses modern statistical methods and techniques, proposes necessary hypotheses and, through factor analysis, transforms the myriad of indexes related to economy, culture and population control in the 72 counties and cities into two indices.... Following the factor analysis, the counties and cities are then categorized into groups and types according to the values of these two indices."

Effects of PAF on excitatory neuro-effector transmission in dog airways

1. Effects of PAF on excitatory neuro-effector transmission in smooth muscle cells of mucosa-free trachea and epithelium-intact bronchiole of the dog were investigated, by isometric tension recording, microelectrode and double sucrose-gap methods. 2. PAF (10(-11)-10(-7) M) dose-dependently enhanced the amplitude of contraction evoked by repetitive field stimulations (10 stimuli at 20 Hz) in both tracheal and bronchiolar tissues. At higher concentrations PAF (> 10(-8) M) increased the amplitude of contraction to a greater extent in the bronchiole than in the trachea. 3. In both muscle tissues, in parallel to the amplitude of contraction, PAF markedly enhanced the amplitude of excitatory junction potentials (e.j.ps) evoked by a single field stimulation in a dose-dependent manner, with no change in the resting membrane potential or input membrane resistance of the smooth muscle cells. PAF (5 x 10(-7) M) enhanced the amplitude of e.j.p. to a greater extent in the bronchiole than in the trachealis. In contrast, lyso-PAF (10(-10)-10(-7) M) showed no effect on e.j.p. amplitude in bronchiolar tissues. At a high concentration (10(-7) M) lyso-PAF slightly enhanced the e.j.p. amplitude in tracheal tissue, however the lyso-PAF induced stimulation of e.j.p. amplitude in the trachea was small compared to that of PAF. 4. PAF (10(-7) M) had no effect on the membrane depolarization induced by acetylcholine (ACh, 10(-9)-10(-5) M) and carbachol (10(-9)-10(-5) M) in tracheal smooth muscle cells. 5. The PAF-antagonists CV3988 (5 x i0-7 M) or WEB2086 (5 x 10-7 M) significantly enhanced the e.j.p. amplitude themselves, PAF (5 x 10-8 M) further enhanced the ej.p. amplitude in the presence of WEB2086 (5 x l0-7 M) but not CV3988 (5 x 10-7 M). In contrast, the new PAF-antagonist, E 6123(5 x l0-8 M), did not affect the ej.p. amplitude itself, and completely inhibited the increase in ej.p. amplitude caused by 5 x 10-8 M PAF. On the other hand, in the presence of the Hi-antagonist,mepyramine, PAF (5 X 10-8 M) further enhanced the ej.p. amplitude.6. The leukotriene synthesis inhibitor AA-861 (10-6 M) or leukotriene antagonist ONO1078 (10-7 M)inhibited the increase in ej.p. amplitude caused by 5 X 10-8 M PAF, respectively.7. In the presence of AA-861 (10-6 M), leukotriene B4 (LTB4, 10-' M) or LTD4 (10-8 M) slightly, and LTC4 (10- M) markedly enhanced the ej.p. amplitude. In contrast, LTE4 (10-8 M) significantly suppressed the e.j.p. amplitude.8. PAF (5 x 10-8 M) attenuated the depression phenomena of ej.ps observed during double stimulus experiments at different time intervals (5-10 s), but had no effect on the summation of ej.ps during repetitive field stimulation at a high frequency (20 Hz) in the trachealis.9. These results indicate that PAF potentiates excitatory neuro-effector transmission mainly through stimulating the release of lipoxygenase products, mainly LTC4 in the dog airway smooth muscle tissues.

Simulation of maternal immunity by inoculation of immune yolk preparations into the yolk sac of 1-day-old chickens

Yolk harvested from eggs laid by hens hyperimmunized with killed Newcastle disease virus (NDV) was inoculated into the yolk sac of 1-day-old specific-pathogen-free (SPF) chickens. Serum hemagglutination-inhibition antibody titers reached maximum levels 1 to 4 days after yolk inoculation and declined at a rate similar to that reported for naturally acquired maternal antibody. Expected levels of immune interference were observed when yolk-inoculated chickens were vaccinated with a conventional oil-emulsion NDV vaccine. These results show that yolk-sac inoculation with yolk antibody is a suitable approach for producing maternally immune chickens for laboratory studies.

Anxiolytic-like effects of the noncompetitive NMDA antagonist MK 801

The present study examined the effects of the noncompetitive NMDA antagonist, MK 801 (dizocilpine), on behavior in the conditioned suppression of drinking (CSD) punished drinking paradigm, a repeated-measures conflict task. In daily 10- or 15-min sessions, water-restricted rats drank from a tube that was occasionally electrified (0.25- or 0.5-mA shocks signaled by a tone). Trained subjects (4 weeks of CSD testing) exhibited stable baselines for both punished (approximately 40 or 100 shocks received/session at the 0.5- and 0.25-mA shock intensities, respectively) and unpunished (approximately 15 ml/session water intake at either shock intensity) responding. Over a wide range of doses, (+) MK 801 did not increase punished responding when administered using a 10-min, 4-h, or 48-h pretreatment. However, at a 24-h pretreatment (+) MK 801 (0.04-0.4 mg/kg, IP) produced a dramatic and dose-dependent increase in punished responding. The "inactive" (-) isomer of MK 801 did not produce a significant anxiolytic-like effect in the CSD paradigm at doses up to 2 mg/kg when tested using a 24-h pretreatment. These data suggest that the anticonvulsant agent (+) MK 801 also may exert antianxiety effects in humans.

Actions of somatostatin on GABA-ergic synaptic transmission in the CA1 area of the hippocampus

Somatostatin and gamma-aminobutyric acid (GABA) are co-localized in some neurons in the CA1 area of the hippocampus. Since it is possible that the peptide and the amino acid are co-released, the interactions between the actions of somatostatin and GABA-ergic inhibitory post-synaptic potentials (IPSPs) in the CA1 pyramidal neurons of guinea pig hippocampal slices have been investigated. Somatostatin (2 microM) induced a hyperpolarization of the CA1 neurons associated with a reduction in the input resistance of the cells. These effects were not blocked by picrotoxinin (20 microM) or phaclofen (1 mM). Chelation of intracellular Ca2+ (Ca2+i) with BAPTA or the inhibition of protein kinase C (PKC) with sphingosine (30 microM) had no significant effects on the hyperpolarizing actions of somatostatin. The peptide suppressed the GABAA receptor-mediated fast IPSPs and the GABAB receptor-mediated slow IPSPs, but had no significant effect on the excitatory post-synaptic potentials (EPSPs). Somatostatin-induced depression of the IPSPs was not due to the hyperpolarization of the neurons. Baclofen (20 microM) suppressed the EPSP, as well as the fast and the slow IPSPs. The hyperpolarization of the CA1 neurons caused by somatostatin was greatly reduced in the presence of baclofen, an effect that was not due to the hyperpolarization of the cell by baclofen. The presence of QX-314 in the CA1 neurons, which suppressed the Na+ spikes and the slow IPSPs, prevented the hyperpolarization of the neurons by somatostatin and baclofen.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway epithelial cells regulate membrane potential, neurotransmission and muscle tone of the dog airway smooth muscle

1. The effects of epithelial cells were investigated on resting membrane potential and neuro-effector transmission in smooth muscle cells of the dog tracheal and bronchiolar tissues. 2. The mean value of the resting membrane potential of the epithelium-intact bronchiolar smooth muscle cells of the dog was--70.0 +/- 1.1 mV (+/- S.D., n = 40) and mechanical denudation of the epithelial layer depolarized the membrane to -57.0 +/- 2.5 mV (+/- S.D., n = 40). Application of isolated and dispersed epithelial cells (greater than 2 x 10(5) cells/ml) to the perfusing solution repolarized the membrane of epithelium-denuded bronchiolar smooth muscle cells to -67.0 +/- 2.7 mV (+/- S.D., n = 20). The mean resting membrane potential of the mucosa-free tracheal smooth muscle cells was -59.1 +/- 1.4 mV (+/- S.D., n = 50), and application of isolated and dispersed cells (greater than 2 x 10(5) cells/ml) hyperpolarized the membrane to -67.2 +/- 1.8 mV (+/- S.D., n = 50). These repolarizing actions were not modified by indomethacin (10(-5) M). 3. In the epithelium-denuded bronchioles, ACh (greater than 10(-9) M) dose-dependently depolarized the smooth muscle cells, while in the epithelium-intact bronchioles, ACh (10(-11) - 10(-8) M) did not affect the resting membrane potential. At a concentration of 10(-7) M, ACh significantly depolarized the membrane. 4. Electrical field stimulation (EFS; 50 microseconds in duration and about 10-20 V in strength) applied to ring preparations of the bronchioles evoked twitch-like contractions (hereafter referred as twitch contraction), and size of the twitch contractions gradually and continuously decreased in the presence or absence of indomethacin (10(-5) M) and guanethidine (10(-6) M). When similar experiments were performed using epithelium-denuded bronchiolar ring preparations, in no case was there a prominent reduction in the amplitude of the twitch contractions in the presence of indomethacin and guanethidine. 5. The decremental response of the twitch contraction observed in the epithelium-intact bronchioles was overcome by application of the leukotriene synthesis inhibitor AA861 (10(-6) M) and the leukotriene antagonist ONO1078 (10(-5) M). 6. Leukotrienes C4 and D4 (LTC4 and LTD4, greater than 10(-8) M) evoked muscle contraction with a steady increase in muscle tone, up to a certain level. However, at 10(-9) M, LTC4 increased and LTD4 decreased the amplitude of the twitch contractions evoked by EFS in the epithelium-intact bronchioles.(ABSTRACT TRUNCATED AT 400 WORDS)

Blockade of hippocampal long-term potentiation by saccharin

Population spikes, population excitatory postsynaptic potentials and intracellular excitatory postsynaptic potentials were recorded in the CA1 area of guinea-pig hippocampal slices in response to low frequency stimulation of the stratum radiatum. Tetanic stimulation of the same afferents during an application of saccharin (10 mM, 10 min) failed to induced a long-term potentiation of the population spike, population excitatory postsynaptic potential and intracellularly recorded excitatory postsynaptic potential. A post-tetanic application of saccharin did not prevent long-term potentiation of the population spike from developing. Saccharin did not change the input resistance, the membrane potential or the ability to induce action potentials in the CA1 neurons. The slope of the intracellular excitatory postsynaptic potentials recorded in normal medium, in normal medium containing 2-amino-5-phosphonovalerate, or in Mg(2+)-free medium containing 6-cyano-7-nitroquinoxaline-2,3-dione was not significantly altered by saccharin. The depolarizations of CAI neurons produced by superfusion of N-methyl-D-aspartate or during a brief tetanic stimulation of the stratum radiation were also not altered by the drug. It therefore appears that saccharin blocks the induction of long-term potentiation by a mechanism that does not involve a blockade of N-methyl-D-aspartate receptors. Application of fluid samples collected from rabbit neocortical surface during a tetanic stimulation of the neocortex caused neurite growth in PC-12 cells, suggesting that growth-related substances were present in the collected samples. If these samples were superfused onto hippocampal slices, long-term potentiation developed. If however, the samples were co-applied with saccharin, neither neurite growth in PC-12 cells nor long-term potentiation in hippocampal slices was observed, raising the possibility that growth-related substances are involved in long-term potentiation.

[Hepatitis B virus infection in hemodialysis patients]

Hepatitis B virus infection in 199 patients undergone hemodialysis was compared with that in patients with chronic kidney diseases, patients received blood-transfusion and general medical patients. Of 199 hemodialysis patients, 60 were followed up for over one years. It was found the prevalence of HBV markers (previous and current infection) in these patients was 78.4%, that in the blood-transfused patients 76.5%, in the non-transfused general medical patients, 60.0% and in the patients with chronic kidney diseases 62.2%. The HBV prevalence in 60 followed up hemodialysis patients was increasing with the duration of hemodialysis. Analysis indicates that blood-transfusion is the main cause of HBV infection in the hemodialysis patients.

Personal characteristics of Chinese children and their discrepancies: a report on children's development in Anhui (I)

The authors report on a 1990 survey on the characteristics of children in China which included 1,000 primary school pupils in Anhui Province. The focus is on differences between only children and those with brothers or sisters. The results suggest that "the development of temperaments, moral character, behavior and basic ability of primary school pupils in Anhui is generally healthy despite certain discrepancies among different types of children."