Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor.

In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 µm to 5 µm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m(-1) K(-1) at room temperature.

Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows.

For almost two decades the properties of 'dwarf' galaxies have challenged the cold dark matter (CDM) model of galaxy formation. Most observed dwarf galaxies consist of a rotating stellar disk embedded in a massive dark-matter halo with a near-constant-density core. Models based on the dominance of CDM, however, invariably form galaxies with dense spheroidal stellar bulges and steep central dark-matter profiles, because low-angular-momentum baryons and dark matter sink to the centres of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present-day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different dark-matter particle candidate. Here we report hydrodynamical simulations (in a framework assuming the presence of CDM and a cosmological constant) in which the inhomogeneous interstellar medium is resolved. Strong outflows from supernovae remove low-angular-momentum gas, which inhibits the formation of bulges and decreases the dark-matter density to less than half of what it would otherwise be within the central kiloparsec. The analogues of dwarf galaxies-bulgeless and with shallow central dark-matter profiles-arise naturally in these simulations.

Reductive dechlorination of low concentration polychlorinated biphenyls as affected by a rhamnolipid biosurfactant.

We investigated whether the threshold concentration for polychlorinated biphenyl (PCB) dechlorination may be lower in biosurfactant-amended sediments compared with biosurfactant-free samples. At PCB concentrations of 40, 60, and 120 ppm, the surfactant amendment enhanced the PCB dechlorination rate at all concentrations and the rate was also faster at higher concentrations. On a congener group basis, dechlorination proceeded largely with group A (congeners with low threshold) in both surfactant-free and -amended sediments, accumulating mainly group C (residual products of dechlorination) congeners, and surfactant enhanced the dechlorination rate of group A congeners. Since the PCB threshold concentration for the inoculum in the experiment was lower than 40 ppm, we carried out another experiment using sediments with lower PCB concentrations, 10, 20, and 30 ppm. Sediments with 100 ppm were also performed to measure dechlorination at a PCB saturation concentration. Comparison between the plateaus exhibited that the extent of dechlorination below 40 ppm PCBs was much lower than that at a saturation concentration of 100 ppm. There was no significant difference in the extent of dechlorination between surfactant-free and -amended sediments. Moreover, surfactant did not change the congener specificity or broaden the congener spectrum for dechlorination at PCB concentrations below 40 ppm. Taken together, it seems that at a given PCB concentration, dechlorination characteristics of dechlorinating populations may be determined by not only the congener specificity of the microorganisms but also the affinity of dechlorinating enzyme(s) to individual PCB congeners.

Dechlorination of individual congeners in aroclor 1248 as enhanced by chlorobenzoates, chlorophenols, and chlorobenzenes.

Previous investigations showed that three classes of haloaromatic compounds (HACs; chlorobenzoates, chlorophenols, and chlorobenzenes) enhanced the reductive dechlorination of Aroclor 1248, judging from the overall extent of reduction in Cl atoms on the biphenyl. In the present study, we further investigated the kind of polychlorinated biphenyl (PCB) congeners involved in the enhanced dechlorination by four isomers belonging to each class (2,3-, 2,5-, 2,3,5-, and 2,4,6-chlorobenzoates; 2,3-, 3,4-, 2,5-, and 2,3,6-chlorophenols; and 1,2-, 1,2,3-, 1,2,4-, and penta-chlorobenzenes). Although the PCB congeners involved in the enhanced dechlorination varied with the HACs, the enhancement primarily involved paradechlorination of the same congeners (2,3,4'-, 2,3,4,2'- plus 2,3,6,4'-, 2,5,3',4'- plus 2,4,5,2',6'-, and 2,3,6,2',4'- chlorobiphenyls), regardless of the HACs. These congeners are known to have low threshold concentrations for dechlorination. To a lesser extent, the enhancement also involved meta dechlorination of certain congeners with high threshold concentrations. There was no or less accumulation of 2,4,4'- and 2,5,4'-chlorobiphenyls as final products under HAC amendment. Although the dechlorination products varied, the accumulation of orthosubstituted congeners, 2-, 2,2'-, and 2,6-chlorobiphenyls, was significantly higher with the HACs, indicating a more complete dechlorination of the highly chlorinated congeners. Therefore, the present results suggest that the enhanced dechlorination under HAC enrichment is carried out through multiple pathways, some of which may be universal, regardless of the kind of HACs, whereas others may be HAC-specific.

Developmental exposure to 3,4-methylenedioxymethamphetamine results in downregulation of neurogenesis in the adult mouse hippocampus.

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a powerful releaser of 5-HT and chronic use of this drug can cause depletion of monoamines. Recently, concerns about the risk of adult brain damage due to fetal exposure to MDMA have been raised. We investigated whether developmental MDMA exposure affected adult neurogenesis in C57 black/6 mice. MDMA (1.25 or 20 mg/kg, p.o.) or vehicle was administered daily to the mother from prenatal 6th day to postnatal 21st day. When the offspring were 11 weeks old, they were injected with 5-bromo-2'-deoxyuridine (BrdU) (120 mg/kg, i.p.) once a day for 4 days. After 24 h or 28 days, the animals were killed to count the BrdU-positive cells in the dentate gyrus. At 24 h after the last BrdU injection, the number of BrdU-positive cells in the offspring developmentally exposed to MDMA was significantly lower than that of the control group. At 28 days post-BrdU labeling, BrdU-positive cells in the dentate gyrus of female offspring with developmental exposure to high dose MDMA were significantly fewer compared with the control group. In addition, most BrdU-positive cells were co-labeled with the mature neuronal marker, neuronal nuclei, while a few BrdU-labeled cells were merged with an astrocyte marker. Our results suggest that developmental exposure to MDMA can result in decreases in the proliferation and survival of mature newborn cells in the adult dentate gyrus.

Effects of a rhamnolipid biosurfactant on the reductive dechlorination of polychlorinated biphenyls by St. Lawrence River (North America) microorganisms.

The effect of a rhamnolipid biosurfactant on the reductive dechlorination of polychlorinated biphenyls was investigated with the use of clean sediments spiked with Aroclor 1248. The surfactant was added to the contaminated sediments at four different concentrations (5, 10, 25, and 50 microg/g sediment [ppm] on a sediment dry wt basis), and dechlorination was followed over a 40-week period. The rate of overall dechlorination was enhanced at the three highest concentrations. Dechlorination at the lowest concentration (5 ppm) was not different from that in surfactant-free sediments. On a congener basis, enhanced dechlorination was mostly found in the congeners that have high threshold concentrations for dechlorination. These congeners are characterized by an initial increase in concentration before dechlorination starts. At the three highest biosurfactant concentrations, this initial concentration increase was absent or dramatically reduced. Therefore, the enhancement in dechlorination appears to be caused by an increase in bioavailability at high surfactant concentrations. The biosurfactant also reduced the lag time before dechlorination began in these congeners. Among those congeners that have low threshold concentrations, dechlorination enhancement was found only in two peaks. For these two, there was no lag period, either with or without the rhamnolipids. The maximum level of dechlorination and the congener pattern of final dechlorination products were identical, regardless of biosurfactant concentration.

Bioconcentration and redeposition of polychlorinated biphenyls by zebra mussels (Dreissena polymorpha) in the Hudson River.

The potential impact of zebra mussel infestation on the dynamics of polychlorinated biphenyls (PCBs) in the Hudson River was determined by investigating the biodeposition and bioconcentration of PCBs, using algal food contaminated with 2,5,2'- and 2,4,2',4'-chlorobiphenyls (CBPs) in the laboratory. Approximately 46-90% of the total food was ingested depending on the supply rate. The highest proportion of ingested congeners was found in biodeposits (64+/-11% for 2,5,2'-CBP, and 52+/-6% for 2,4,2',4'-CBP), followed by tissues (17+/-3% for 2,5,2'-CBP, and 23+/-5% for 2,4,2',4'-CBP), and the lowest in shells. The clearance rate decreased with increasing food concentration, but increased with dilution rate. On the other hand, ingestion rate (IR) increased with food concentration and dilution rate. IR also increased with food supply rate (food concentrationxdilution rate) following the same linear function whether the supply rate was varied through food concentration or dilution rate. Therefore, the dilution rate- or food concentration-dependent variation in IR was due to the change in the food supply rate. IR was independent of the kind of PCB congeners. The trend of bioaccumulation in mussel tissues from food ingestion was similar to that of IR; bioaccumulation increased linearly with food supply rate, whether the supply rate was varied through the dilution rate or the food concentration. The bioaccumulation of 2,4,2',4'-CBP was significantly higher than that of 2,5,2'-CBP (p<0.05). The bioaccumulation was linearly related to the IR or to the total amount of food ingested. Assimilation efficiency, PCB incorporated in the tissue per total ingested PCB, was higher for 2,4,2',4'-CBP than for 2,5,2'-CBP (p<0.05). The congener concentration in biodeposits increased with food supply rate. However, the concentration of 2,5,2'-CBP was significantly greater than that of 2,4,2',4'-CBP in a mirror image of bioaccumulation. These results indicate that zebra mussels may significantly alter PCB dynamics in the Hudson River through redeposition from the water column and through bioconcentration.

Reductive dechlorination of polychlorinated biphenyls: threshold concentration and dechlorination kinetics of individual congeners in Aroclor 1248.

Reductive dechlorination of individual PCB congeners in Aroclor 1248 was investigated using sediment microorganisms from the St. Lawrence River (NY). No dechlorination was observed at Aroclor concentrations below 40 ppm [137 nmol (g of sediment)(-1)]. Above this threshold, congeners could be divided into three categories: group A, congeners that dechlorinated above 40 ppm; group B, congeners that dechlorinated only at high concentrations above 60 ppm [206 nmol (g of sediment)(-1)]; and group C, lower chlorinated congeners that increased in concentration. The dechlorination rate of congeners in groups A and B was a linear function of their initial sediment concentration. For group A congeners, the concentration intercepts of this linear function were the same as their concentrations in the Aroclor at the threshold concentration, and these therefore represented the threshold values. However, the intercepts of group B congeners were significantly higher than their levels at the threshold Aroclor concentration and were equivalent to their concentrations in Aroclor 1248 at about 75 ppm [258 nmol (g of sediment)(-1)]. The final concentrations of group A and group B congeners at the end of dechlorination were the same, regardless of their initial concentrations. These final concentrations were significantly lower than their threshold values. The accumulation rate of group C congeners was a linear function of their initial concentrations, and the total accumulation was greater at higher Aroclor concentrations in sediments.

Kinetics of polychlorinated biphenyl dechlorination by Hudson River, New York, USA, sediment microorganisms.

The kinetics of polychlorinated biphenyl (PCB) dechlorination by Hudson River (New York, USA) sediment microorganisms were investigated using Aroclor 1242 at 10 concentrations ranging from 0 to 900 ppm (0-11.2 micromol Cl/g sediment). The time course of PCB dechlorination and population growth were determined by congener-specific analysis and the most-probable-number technique, respectively, over a 44-week incubation period. Dechlorination rate (nmol Cl removed/g sediment/d) was a linear function of PCB concentrations similar to the dechlorination of Aroclor 1248 by sediment microorganisms from the St. Lawrence River (New York, USA). However, the rate was much slower, with the linear slope being only 24% that of the St. Lawrence River. The threshold concentration below which no dechlorination occurs was (mean +/- standard deviation) 1.06 +/- 0.18 micromol Cl/g sediment (85 +/- 14 ppm), threefold higher than that for the dechlorination of Aroclor 1248. The maximum extent of dechlorination was greater at higher Aroclor concentrations. Dechlorinating microorganisms did not show any significant growth until late in the lag phase of dechlorination, and their maximum was greater at higher initial Aroclor 1242 concentrations. Although dechlorination rates were significantly lower with the Hudson River inoculum, when normalized to the maximum number of dechlorinating organisms, they were not significantly different from those for Aroclor 1248 by St. Lawrence River microorganisms. These results further support the idea that PCB dechlorination is tightly linked to the growth of dechlorinating microorganisms.

Enhancement of microbial PCB dechlorination by chlorobenzoates, chlorophenols and chlorobenzenes.

Abstract We investigated the effects of chlorobenzoates (3-, 2,3-, 2,4-, 2,5-, 2,3,5- and 2,4,6-chlorobenzoate), chlorophenols (2,3-, 3,4-, 2,5-, 2,3,6- and penta-chlorophenol), and chlorobenzenes (1,2-, 1,2,3-, 1,2,4- and penta-chlorobenzene) on polychlorinated biphenyl (PCB) dechlorination and on the enrichment of PCB-dechlorinating microorganisms. When the natural microbial populations eluted from St. Lawrence River sediments were enriched with each of the 15 haloaromatic compounds (HACs) in PCB-free sediments, PCB-dechlorinating microorganisms were found in all but pentachlorophenol-amended sediments. Similarly, dechlorinating microorganisms were also found in PCB-spiked sediments amended with all HACs, except for those with pentachlorophenol. In HAC-amended PCB sediments there was a long lag in PCB dechlorination until the HACs were reduced to a plateau level. Despite this lag, once PCB dechlorination started it was faster in the HAC-amended sediments compared to the unamended controls. The overall extent of PCB dechlorination was significantly enhanced by all HACs except pentachlorophenol and pentachlorobenzene, but the extent as well as the pattern of the enhancement varied. Of the 13 effective HACs, six (2,3-, 2,4- and 2,4,6-chlorobenzoates; 3,4- and 2,3,6-chlorophenols; and 1,2,3-chlorobenzene) enhanced only meta-dechlorination, whereas five (3-chlorobenzoate; 2,3- and 2,5-chlorophenols; and 1,2- and 1,2,4-chlorobenzenes) increased both meta- and para-dechlorination, and two (2,5- and 2,3,5-chlorobenzoates) promoted overall, substitution non-specific dechlorination. When the maximum extent of dechlorination was plotted against the highest number of PCB-dechlorinating microorganisms for each HAC, there was a linear relationship (P<0.01), suggesting that dechlorination enhancement was related to the increase in their population size. However, there was also evidence to suggest that different dechlorinating microorganisms were selected.

The effect of 2,5,2',5'-tetrachlorobiphenyl on growth and death of the cyanobacterium Anabaena flos-aquae.

The effect of 2,5,2',5'-tetrachlorobiphenyl (TcBP) on cell death was investigated in the cyanobacterium Anabaena flos-aquae (Lyngb.) Bréb grown in a P-limited, semicontinuous culture under N2-fixing conditions during a 17-d period. The TcBP was supplied daily to yield final concentrations of 1, 10, and 100 ppb (or ng/ml). At 1 and 10 ppb, the population size of live cells (sum of live vegetative cells and live heterocysts) was not different from that of the TcBP-free controls (p > 0.1, t test) and remained constant both in its absolute value (9.6 X 10(5) cells/ml) and as a percentage of the total population (98.6%). However, at 100 ppb, the population size of live cells declined significantly after the 11th day (8.2 x 10(5) cells/ml, or 96.6% of total population; p < 0.01, t test). The decrease in viable cells was mostly found in vegetative cells. Bioconcentration factor in the cell ([pg TcBP/g dry wt cells]/[pg TcBP/ml]) was 1.23 x 10(5).

Reductive dechlorination of polychlorinated biphenyls as affected by sediment characteristics.

The effect of sediment sources on the selection of polychlorinated biphenyl (PCB) dechlorinating competence was investigated using sediments from two different locations, the Grasse River and Owasco Lake. These two sediments had a similar organic carbon content but different particle size distribution. The two PCB-free sediments were spiked with Aroclor 1248 and inoculated with microorganisms from the Reynolds and General Motors sites in the St. Lawrence River, which exhibited different dechlorination patterns. When each inoculum was serially transferred into fresh sediments four times (every 8-10 weeks), they still maintained the initial dechlorination patterns regardless, the source of sediments and the number of transfers, and dechlorination patterns of the two inocula in the same sediments did not converge. In a parallel approach, when the acclimated microorganisms from the Reynolds site were inoculated into fresh sediments from both sources as well as sediments enriched with organic carbon (2%, w/v), the dechlorination pattern remained unchanged after a 40-week incubation. These results suggest that the sediment characteristics or organic carbon content did not play a role in the selection of dechlorinating populations.

Protective effects of acetylbergenin against carbon tetrachloride-induced hepatotoxicity in rats.

The present study was undertaken to investigate whether or not the hepatoprotective activity of acetylbergenin was superior to bergenin in carbon tetrachloride (CCl4)-intoxicated rat. Acetylbergenin was synthesized by acetylating bergenin, which was isolated from Mallotus japonicus. The hepatoprotective effects of acetylbergenin were examined against CCl4-induced liver damage in rats by means of serum and liver biochemical indices. Acetylbergenin was administered orally once daily for 7 successive days, then a 0.5 ml/kg mixture of CCl4 in olive oil (1:1) was intraperitoneally injected at 12 h and 36 h after the final administration of acetylbergenin. Pretreatment with acetylbergenin reduced the elevated serum enzymatic activities of alanine/aspartate aminotransferase, sorbitol dehydrogenase and gamma-glutamyltransferase in a dose dependent fashion. Acetylbergenin also prevented the elevation of hepatic malondialdehyde formation and depletion of glutathione content dose dependently in CCl4-intoxicated rats. In addition, the decreased activities of glutathione S-transferase and glutathione reductase were restored to almost normal levels. The results of this study strongly suggest that acetylbergenin has potent hepatoprotective activity against CCl4-induced hepatic damage in rats by glutathione-mediated detoxification as well as having free radical scavenging activity. In addition, acetylbergenin doses of 50 mg/kg showed almost the same levels of hepatoprotective activity as 100 mg/kg of bergenin, indicating that lipophilic acetylbergenin is more active against the antihepatotoxic effects of CCl4 than those of the much less lipophilic bergenin.

Kinetics of polychlorinated biphenyl dechlorination and growth of dechlorinating microorganisms.

The present study has investigated a correlation between the kinetics of polychlorinated biphenyl (PCB) dechlorination and the growth of dechlorinating microbial populations. Microorganisms were eluted from Aroclor 1248-contaminated St. Lawrence River (NY, USA) sediments and inoculated into clean sediments spiked with Aroclor 1248 at 10 concentrations ranging from 0 to 3.12 micromol/g sediment (0-900 ppm). The time course of PCB dechlorination and population growth were concurrently determined by congener-specific analysis and the most probable number technique, respectively. The specific growth rate was a saturation function of PCB concentrations above the threshold concentration (0.14 micromol/g sediment, or 40 ppm), below which no dechlorination or growth of dechlorinations were observed. The maximum growth rate was 0.20/d with a half-saturation constant of 1.23 micromol/g sediment. The yield of dechlorinating microorganisms showed a peak at 0.70 micromol/g sediment (200 ppm), with a value of 10.3 x 10(12) cells/mol Cl removed, and decreased below and above this concentration. The dechlorination rate (micromol Cl removed/g sediment/d) was a linear function of Aroclor concentration. Both the log of this rate and the maximum level of dechlorination were significantly correlated with growth rate. The biomass-normalized dechlorination rate (micromol Cl removed/g sediment/cell/d) was first order because of the exponential manner of the population growth. The first-order rate constant was a saturation function of Aroclor concentrations, with a maximum of 0.24/d (a half-life of 2.9 d) and a half-saturation constant of 1.18 micromol/g sediment, which are similar to the constants for growth. These results indicate that the dechlorination rate is tightly linked to the population growth of dechlorinating microorganisms.

Microbial PCB dechlorination in dredged sediments and the effect of moisture.

Evidence of reductive dechlorination of polychlorinated biphenyls (PCBs) in sediments was investigated in Hudson River sediments dredged and encapsulated in 1978 at Moreau, NY. The effect of different moisture contents in dredged sediments on dechlorination and dechlorinating microorganisms was also determined using PCB-spiked sediments in which the moisture level was adjusted by simulating a dewatering process. The congener pattern of PCBs indicated that the dechlorination in the dredged sediments was far less advanced than that in the river sediments collected from the general area of the dredged site (Ft. Edward site). Dechlorination in encapsulated sediments at the Moreau site appeared to have stopped soon after dredging. When microorganisms eluted from the encapsulated sediments were inoculated in clean sediments spiked with Aroclor 1242, an extensive dechlorination was observed, indicating that the encapsulated sediments still harbored dechlorinating microorganisms. However, the same inoculum failed to further dechlorinate residual congeners in the dredged sediments. On the other hand, an inoculum obtained in 1990 from the dredged site in the Hudson River dechlorinated the residual congeners further. In simulated dredged sediments, the maximum level of dechlorination was lower at reduced moisture contents. The population size of dechlorinating microorganisms, as determined by the most probable number (MPN) technique, was also smaller at the lower moisture levels. There was a significant correlation between the maximum extent of dechlorination and the specific death rate of dechlorinating populations. These results indicate that the underlying mechanism of the moisture-dependent maximum dechlorination is the moisture-dependence of the death rate of dechlorinating microorganisms.

Topical oleo-hydrogel preparation of ketoprofen with enhanced skin permeability.

In an attempt to improve the skin penetration of ketoprofen, various transdermal formulations were prepared, and their in vitro skin permeability and in vivo percutaneous absorption were evaluated. In vitro permeation studies were performed using a modified Franz cell diffusion system in which permeation parameters such as cumulative amount at 8 hr Q8hr, steady-state flux Jss, or lag time tL were determined. In the in vivo percutaneous absorption study using the hairless mouse, maximum concentration Cmax and area under the curve at 24 hr AUC24h were measured. The optimal transdermal formulation (oleo-hydrogel formulation) of ketoprofen showed a Q8hr value of 227.20 micrograms/cm2, a Jss value of 29.61 micrograms/cm2/hr, and a tL value of 0.46 hr. The Q8hr and Jss values were about 10-fold (p < .01) higher than those (Q8hr = 19.61 micrograms/cm2; Jss = 2.66 micrograms/cm2/hr) from the K-gel and about 3.5-fold (p < .01) than those (Q8hr = 60.00 micrograms/cm2; Jss = 7.99 micrograms/cm2/hr) of the K-plaster. In the in vivo percutaneous absorption, the Cmax (6.82 micrograms/ml) and AUC24h (55.74 micrograms.hr/ml) values of the optimal formulation were significantly (p < .01) higher than those of K-gel and K-plaster. The relative bioavailability of the oleo-hydrogel following transdermal administration in reference to oral administration was about 37%, and the Cmax value (4.73 micrograms/cm2) in the hypodermis following topical administration was much higher than those from the conventional products (Cmax of K-gel and K-plaster were 0.92 +/- 0.19 microgram/cm2 and 1.27 +/- 0.37 microgram/cm2, respectively). These data demonstrate that the oleo-hydrogel formulation of ketoprofen was more beneficial than conventional products (K-gel and K-plaster) in enhancing transdermal permeation and skin absorption of ketoprofen. Furthermore, there was a good correlation between in vitro permeation parameters and in vivo percutaneous absorption parameters.

NMDA receptor antagonists inhibit apomorphine-induced climbing behavior not only in intact mice but also in reserpine-treated mice.

The present study showed that the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists, MK-801 {(+)-5-methyl-10,11-dihydroxy-5H-dibenzo-[a,d]-cyclohepten-5,10-im ine hydrogen maleate}, ketamine, dextrorphan and dextromethorphan attenuated apomorphine-induced climbing behavior in reserpine-treated mice. In addition, the competitive NMDA receptor antagonists, D(-)-2-amino-5-phosphonopentanoic acid (AP-5) and D(-)-3-(2-carboxypipera-zine-4-yl)-propyl-1-phosphonic acid (CPP), also inhibited the apomorphine-induced climbing behavior in reserpine-treated mice as well as in intact mice. Previous work in our laboratory had shown that the noncompetitive NMDA receptor antagonists, MK-801, ketamine, dextrorphan and dextromethorphan cause a pronounced inhibition of apomorphine-induced cage climbing behavior in intact mice, suggesting the involvement of NMDA receptors in the glutamatergic modulation of dopaminergic function at the postsynaptic dopamine (DA) receptors. Therefore, the present results strongly support our previous conclusion that the NMDA receptors play important roles in the glutamatergic modulation of dopaminergic function at the postsynaptic DA receptors.

Effects of ginseng total saponin on morphine-induced hyperactivity and conditioned place preference in mice.

A single or repeated administration of morphine in mice produced hyperactivity, conditioned place preference (CPP) and postsynaptic dopamine (DA) receptor supersensitivity. The hyperactivity induced by morphine was evidenced by measuring the enhanced ambulatory activity using a tilting-type ambulometer. CPP effects were evaluated assessing the increased time spent by the mice to morphine and the inhibition of CPP by the decreased time spent by the mice in the white compartment. Postsynaptic DA receptor supersensitivity in mice displaying a morphine-induced CPP was evidenced by the enhanced response in ambulatory activity to the DA agonist, apomorphine (2 mg/kg, s.c.). The intraperitoneal injection of ginseng total saponin (GTS) from the root of Panax ginseng C.A. Meyer (Araliaceae), prior to and during the morphine treatment in mice inhibited morphine-induced hyperactivity and CPP. GTS inhibited the development of postsynaptic DA receptor supersensitivity. A single dose administration of GTS also inhibited apomorphine-induced climbing behavior, showing the antidopaminergic action of GTS at the postsynaptic DA receptor. These results suggest that the development of morphine-induced CPP may be associated with the enhanced DA receptor sensitivity and that GTS inhibition of the morphine-induced hyperactivity and CPP may be closely related with the inhibition of dopaminergic activation induced by morphine.

Population dynamics of polychlorinated biphenyl-dechlorinating microorganisms in contaminated sediments.

The growth dynamics of polychlorinated biphenyl (PCB)-dechlorinating microorganisms were determined for the first time, along with those of sulfate reducers and methanogens, by using the most-probable-number technique. The time course of Aroclor 1248 dechlorination mirrored the growth of dechlorinators; dechlorination ensued when the dechlorinating population increased by 2 orders of magnitude from 2.5 x 10(sup5) to 4.6 x 10(sup7) cells g of sediment(sup-1), at a specific growth rate of 6.7 day(sup-1) between 2 and 6 weeks. During this period, PCB-dechlorinating microorganisms dechlorinated Aroclor 1248 at a rate of 3.9 x 10(sup-8) mol of Cl g of sediment(sup-1) day(sup-1), reducing the average number of Cl molecules per biphenyl from 3.9 to 2.8. The growth yield was 4.2 x 10(sup13) cells mol of Cl dechlorinated(sup-1). Once dechlorination reached a plateau, after 6 weeks, the number of dechlorinators began to decrease. On the other hand, dechlorinators inoculated into PCB-free sediments decreased over time from their initial level, suggesting that PCBs are required for their selective enrichment. The numbers of sulfate reducers and methanogens increased in both PCB-free and contaminated sediments, showing little difference between them. The maximum population size of sulfate reducers was about an order of magnitude higher than that of dechlorinators, whereas that of methanogens was slightly less. Unlike those of dechlorinators, however, numbers of both sulfate reducers and methanogens remained high even when dechlorination ceased. The results of this study imply that PCB concentrations may have to exceed a certain threshold to maintain the growth of PCB dechlorinators.

Inhibition by noncompetitive NMDA receptor antagonists of apomorphine-induced climbing behavior in mice.

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptors is an important mediator of several forms of neural and behavioral plasticity. In the present study, we examined the potential role of NMDA receptors in the glutamatergic modulation of dopaminergic function at the postsynaptic dopamine receptor by determining the effects of NMDA antagonists on apomorphine-induced climbing behavior in mice. The noncompetitive NMDA receptor antagonists, MK-801, ketamine, dextrorphan, and dextromethorphan attenuated the apomorphine-induced climbing behavior at does well below those that produce untoward side effects. These results suggest that the NMDA receptors play important roles in the glutamatergic modulation of dopaminergic function at the postsynaptic dopamine receptors that mediate the apomorphine-induced climbing behavior in mice.