Behavior of major and trace elements in a transient surface water/groundwater system following removal of a long-term wastewater treatment facility source

In many aquatic environments, municipal wastewater treatment facility (WWTF) effluent discharges influence local hydrologic and chemical connectivity between the surface-water and adjacent alluvial shallow-groundwater systems. Fourmile Creek located in Polk County, Iowa received effluent from the Ankeny WWTF for nearly forty years before it was shut down in November 2013. The decommissioning of the municipal WWTF provided a unique opportunity to characterize the recovery from impacts of treated wastewater discharge on water quality at the surface-water/groundwater interface in a shallow, unconfined alluvial aquifer. Dissolved major element and trace element concentrations in Fourmile Creek surface water, hyporheic-zone water, and shallow, unconfined groundwater were monitored upstream and downstream from the WWTF discharge before and after the shutdown. Multivariate statistical techniques including principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) were used to differentiate source-water contributions, characterize elemental components, and describe surface-water/groundwater interaction dynamics. During the post-closure assessment, there was subsurface attenuation of wastewater constituents including Al, B, Cu, Gd, K, Mo, Na, P, Pb, Sb, and Zn. During the same time, groundwater concentrations increased for As, Ba, Ca, Fe, Mg, Mn, SiO₂, Sr, and U and represented a profile characteristic of the shallow alluvial aquifer. Hydrologic conditions transitioned from predominantly wastewater infiltration and hyporheic exchange before the WWTF shutdown, to predominantly discharge of native groundwater. Precipitation-driven streamflow events created fluctuations in the groundwater water-table elevations, resulting in variable contact between the saturated and unsaturated zones within the unconfined, alluvial aquifer and intermittent exposure to constituents stored in the sediments. The inorganic fingerprint of municipal wastewater was flushed relatively quickly (≤19 weeks) from the hyporheic zone indicating that processes like diffusion or sorption/desorption that might extend recovery may not be important for many trace elements in this system.

Mercury and methylmercury stream concentrations in a Coastal Plain watershed: a multi-scale simulation analysis

Mercury is a ubiquitous global environmental toxicant responsible for most US fish advisories. Processes governing mercury concentrations in rivers and streams are not well understood, particularly at multiple spatial scales. We investigate how insights gained from reach-scale mercury data and model simulations can be applied at broader watershed scales using a spatially and temporally explicit watershed hydrology and biogeochemical cycling model, VELMA. We simulate fate and transport using reach-scale (0.1 km(2)) study data and evaluate applications to multiple watershed scales. Reach-scale VELMA parameterization was applied to two nested sub-watersheds (28 km(2) and 25 km(2)) and the encompassing watershed (79 km(2)). Results demonstrate that simulated flow and total mercury concentrations compare reasonably to observations at different scales, but simulated methylmercury concentrations are out-of-phase with observations. These findings suggest that intricacies of methylmercury biogeochemical cycling and transport are under-represented in VELMA and underscore the complexity of simulating mercury fate and transport.

Care delivery and self-management strategies for adults with epilepsy

BACKGROUND

Epilepsy care has been criticised for its lack of impact. Various service models and strategies have been developed in response to perceived inadequacies in care provision.

OBJECTIVES

To compare the effectiveness of any specialised or dedicated intervention for the care of adults with epilepsy to the effectiveness of usual care.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2006), MEDLINE (1966 to May 2006), EMBASE (1988 to May 2006), PsychINFO (1806 to May 2006) and CINAHL (1982 to May 2006).

SELECTION CRITERIA

Randomised controlled trials, controlled or matched trials, cohort studies or other prospective studies with a control group, or time series studies.

DATA COLLECTION AND ANALYSIS

Each review author independently selected studies, extracted data and assessed the quality of included studies.

MAIN RESULTS

There are 13 trials and 16 reports included in this review. Seven distinct groups of interventions were identified: seven papers reported on five trials of specialist epilepsy nurses. Of the 13 trials, at least three (four reports) have methodological weaknesses, and some of the results from other analyses within studies need to be interpreted with caution because of limiting factors in the studies. Consequently, there is currently limited evidence for the effectiveness of interventions to improve the health and life quality of people with epilepsy. It was not possible to combine study results in a meta-analysis because of the heterogeneity of outcomes, study populations, interventions, and time scales across the studies.

AUTHORS' CONCLUSIONS

Two intervention types, the specialist epilepsy nurse and self-management education, have some evidence of benefit. However, we did not find clear evidence that other service models substantially improve outcomes for adults with epilepsy. It is also possible that benefits are situation specific and may not generalise to other settings. These studies included only a small number of service providers whose individual competence or expertise may have had a significant impact on outcomes. At present it is not possible to advocate any single model of service provision.

Chloroethene biodegradation in sediments at 4 degrees C

Microbial reductive dechlorination of [1,2-14C]trichloroethene to [14C]cis-dichloroethene and [14C]vinyl chloride was observed at 4 degrees C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-14C]cis-dichloroethene and [1,2-14C]vinyl chloride to 14CO2 also was observed under these conditions.

Spinal cord plasticity in response to unilateral inhibition of the rat motor cortex during development: changes to gene expression, muscle afferents and the ipsilateral corticospinal projection

In developing Wistar albino rats, ventral horn muscle afferent boutons are lost following corticospinal innervation. Motor cortex lesions rescue a proportion of these boutons and perturb activity dependent expression of cJun and parvalbumin (PV) in the spinal cord. Therefore, we tested whether activity-dependent competition between corticospinal and proprioreceptive afferents determines the balance of these inputs to motor output pathways by delivering the inhibitory GABA agonist muscimol unilaterally to the forelimb motor cortex using slow release polymer implants from postnatal day 7 (P7) coincident with corticospinal synaptogenesis. Controls received saline. Inhibition of immature cortical neurons by muscimol was confirmed with separate in vitro electrophysiological recordings. After P28, spinal cord sections were immunostained for PV, cJun and muscle afferents transganglionically labelled with cholera toxin-B (CTB). Unilateral inhibition reduced contralaterally the number of PV positive spinal cord neurons and muscle afferent boutons in the dorsolateral ventral horn, compared to controls, and significantly altered the distribution of motoneuronal cJun expression. Separately, descending tracts were retrogradely traced with CTB from the cervical hemicord contralateral to implants. Forelimb sensorimotor cortex sections were immunostained for either CTB or PV. In muscimol treated animals, significantly fewer neurons expressed PV in the inhibited hemicortex, but as many CTB labelled corticospinal neurons were present as in controls, along with an equally large corticospinal projection from contralateral to the implant, significantly greater than in controls. Unexpectedly, unilateral inhibition of the motor cortical input did not lead to an expanded muscle afferent input. Instead, this was reduced coincident with development of a bilateral corticospinal innervation.

Post-synaptic GABAB receptors—possible controllers of coincidence detection?

Post-synaptic GABA(B) responses (slow, late hyperpolarisations which can be eliminated by perfusion with phaclofen) can be recorded in vitro from many, but not all, neurones in the intermediate medial hyperstriatum ventrale (IMHV). The IMHV is an area of the chick forebrain which is remarkable for its plasticity, and for its essential role in two specific types of early learning-imprinting, and a form of one-trial passive-avoidance learning. Post-synaptic GABA(B) responses are strongly statistically associated with other properties (such as high membrane resistance) which are, themselves, dependent on a bird's past history. There is also evidence that their incidence changes with prior training in vivo and with age. GABA(B) hyperpolarisations are always offset to a varying extent by excitatory NMDA components. These two components follow a very similar time-course, so that the duration and (to a lesser extent), the magnitude of a response is controlled by the balance between the two systems. The evidence suggests that this balance fluctuates, and that its fluctuations determine the extent to which any neurone can function as a coincidence detector.

Effect of redox conditions on MTBE biodegradation in surface water sediments

Microbial degradation of methyl tert-butyl ether (MTBE) was observed in surface water-sediment microcosms under anaerobic conditions. The efficiency and products of anaerobic MTBE biodegradation were dependent on the predominant terminal electron-accepting conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, tert-butyl alcohol (TBA). In the absence of significant methanogenic activity, accumulation of [14C]TBA generally decreased, and mineralization of [U-14C]MTBE to 14CO2 generally increased as the oxidative potential of the predominant terminal electron acceptor increased in the order of SO4, Fe(III), Mn(IV) < NO3 < O2. Microbial mineralization of MTBE to CO2 under Mn(IV)-or SO4-reducing conditions has not been reported previously. The results of this study indicate that microorganisms inhabiting the sediments of streams and lakes can degrade MTBE effectively under a range of anaerobic terminal electron-accepting conditions. Thus, anaerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States.

Low-threshold N-methyl-D-aspartate receptor function correlates negatively with learning

The intermediate, medial hyperstriatum ventrale (IMHV) is an area of the forebrain of the domestic chick which exhibits great plasticity. Moreover, there is a strong link between plasticity in the IMHV and specific changes in behaviour. The IMHV in vitro is still plastic, and many of its physiological properties are age-dependent, peaking in slices taken from 3- or 4-day-old birds. This 'window' coincides with an important transitional period in a chick's normal behavioural development. It has also been claimed that reversal training is at its most effective in 3- and 4-day-old birds - a proposition which was confirmed by the experiments reported here. A combination of in vivo training followed by in vitro electrophysiology also revealed that the function of low-threshold N-methyl-D-aspartate receptors (one of the age-related variables) is negatively related to the effectiveness of reversal training, when age is held constant.

Methyl t-butyl ether mineralization in surface-water sediment microcosms under denitrifying conditions

Mineralization of [U-(14)C]methyl t-butyl ether (MTBE) to (14)CO(2) without accumulation of t-butyl alcohol (TBA) was observed in surface-water sediment microcosms under denitrifying conditions. Methanogenic activity and limited transformation of MTBE to TBA were observed in the absence of denitrification. Results indicate that bed sediment microorganisms can effectively degrade MTBE to nontoxic products under denitrifying conditions.

Methyl tert-butyl ether biodegradation by indigenous aquifer microorganisms under natural and artificial oxic conditions

Microbial communities indigenous to a shallow groundwater system near Beaufort, SC, degraded milligram per liter concentrations of methyl tert-butyl ether (MTBE) under natural and artificial oxic conditions. Significant MTBE biodegradation was observed where anoxic, MTBE-contaminated groundwater discharged to a concrete-lined ditch. In the anoxic groundwater adjacent to the ditch, concentrations of MTBE were > 1 mg/L. Where groundwater discharge occurs, dissolved oxygen (DO) concentrations beneath the ditch exceeded 1.0 mg/Lto a depth of 1.5 m, and MTBE concentrations decreased to <1 microg/L prior to discharge. MTBE mass flux calculations indicate that 96% of MTBE mass loss occurs in the relatively small oxic zone prior to discharge. Samples of a natural microbial biofilm present in the oxic zone beneath the ditch completely degraded [U-14C]MTBE to [14C]CO2 in laboratory liquid culture studies, with no accumulation of intermediate compounds. Upgradient of the ditch in the anoxic, MTBE- and BTEX-contaminated aquifer, addition of a soluble oxygen release compound resulted in oxic conditions and rapid MTBE biodegradation by indigenous microorganisms. In an observation well located closest to the oxygen addition area, DO concentrations increased from 0.4 to 12 mg/L in <60 days and MTBE concentrations decreased from 20 to 3 mg/L. In the same time period at a downgradient observation well, DO increased from <0.2 to 2 mg/L and MTBE concentrations decreased from 30 to <5 mg/L. These results indicate that microorganisms indigenous to the groundwater system at this site can degrade milligram per liter concentrations of MTBE under natural and artificial oxic conditions.

Excited-state properties of Rh(2)(O(2)CCH(3))(4)(L)(2) (L = CH(3)OH, THF, PPh(3), py)

The photophysical properties of Rh(2)(O(2)CCH(3))(4)(L)(2) (L = CH(3)OH, THF = tetrahydrofuran, PPh(3) = triphenylphosphine, py = pyridine) were explored upon excitation with visible light. Time-resolved absorption shows that all the complexes possess a long-lived transient (3.5-5.0 micros) assigned as an electronic excited state of the molecules, and they exhibit an optical transition at approximately 760 nm whose position is independent of axial ligand. No emission from the Rh(2)(O(2)CCH(3))(4)(L)(2) (L = CH(3)OH, THF, PPh(3), py) systems was detected, but energy transfer from Rh(2)(O(2)CCH(3))(4)(PPh(3))(2) to the (3)pipi excited state of perylene is observed. Electron transfer from Rh(2)(O(2)CCH(3))(4)(PPh(3))(2) to 4,4'-dimethyl viologen (MV(2+)) and chloro-p-benzoquinone (Cl-BQ) takes place with quenching rate constants (k(q)) of 8.0 x 10(6) and 1.2 x 10(6) M(-1) s(-1) in methanol, respectively. A k(q) value of 2 x 10(8) M(-1) s(-1) was measured for the quenching of the excited state of Rh(2)(O(2)CCH(3))(4)(PPh(3))(2) by O(2) in methanol. The observations are consistent with the production of an excited state with excited-state energy, E(00), between 1.34 and 1.77 eV.

Widespread potential for microbial MTBE degradation in surface-water sediments

Microorganisms indigenous to stream and lake bed sediments, collected from 11 sites throughout the United States, demonstrated significant mineralization of the fuel oxygenate, methyl-tert-butyl ether (MTBE). Mineralization of [U-14C]MTBE to 14CO2 ranged from 15 to 66% over 50 days and did not differ significantly between sediments collected from MTBE contaminated sites and from sites with no history of MTBE exposure. This result suggests that even the microbial communities indigenous to newly contaminated surface water systems will exhibit some innate ability to attenuate MTBE under aerobic conditions. The magnitude of MTBE mineralization was related to the sediment grain size distribution. A pronounced, inverse correlation (p < 0.001; r2 = 0.73) was observed between the final recovery of 14CO2 and the percentage content of silt and clay sized grains (grain diameter < 0.125 mm). The results of this study indicate that the microorganisms that inhabit the bed sediments of streams and lakes can degrade MTBE efficiently and that this capability is widespread in the environment. Thus aerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States and may contribute to the reported transience of MTBE in some surface waters.

Effect of anti-tuberculosis treatment on the tuberculin interferon-gamma response in tuberculin skin test (TST) positive health care workers and patients with tuberculosis

SETTING

Public hospital, Victoria, Australia.

OBJECTIVE

To evaluate the effect of multidrug treatment and isoniazid (INH) chemoprophylaxis on the tuberculin interferon-y assay (QIFN) in 19 patients with culture-confirmed Mycobacterium tuberculosis and 119 health care workers (HCWs) with tuberculin skin tests (TST) > or =15 mm.

DESIGN

Patients with M. tuberculosis were treated with standard medication and tested with QIFN at diagnosis and at regular intervals over a 12-month period. All HCWs, 59 (50%) of whom were prescribed INH chemoprophylaxis, were tested with QIFN at baseline, 2, 4, 6 and 12 months.

RESULTS

QIFN results in patients with tuberculosis were consistent and reproducible. At the initial time point QIFN assays were positive for M. tuberculosis in 67%, and once positive, the QIFN assay remained so over the 12-month period. In the HCWS, initial QIFN assays were positive in 73 (61%). During the 12-month study, 91 HCWs had a QIFN assay on at least two occasions. The overall reproducibility between tests was fair (kappa statistic = 0.45), and was little affected by administration of INH.

CONCLUSION

These data suggest that although the QIFN assay is generally positive in patients with proven tuberculosis, it does not provide clinically useful information during the first 12 months of treatment with multidrug chemotherapy or INH chemoprophylaxis.

Effects of nitric oxide release in an area of the chick forebrain which is essential for early learning

Extracellular recording techniques were used to study the effects of the nitric oxide releasing agents diethylamine-NO (DEA-NO) and S-nitroso-N-acetyl-penicillamine (SNAP) on synaptic transmission in the intermediate and medial part of the hyperstriatum ventrale (IMHV), a part of the domestic chick forebrain that is essential for some forms of early learning. The field response evoked by local electrical stimulation was recorded in the IMHV in an in vitro slice preparation. DEA-NO (100-200 mgr) significantly depressed the field response in a concentration dependent and reversible manner. However, the depression produced by perfusion with 400 mgr DEA-NO, was not reversed following washout of the drug. With 400 mgr DEA-NO, NO reaches a maximum concentration of 10 mgr at 2 min of perfusion, and then declines slowly. SNAP (400 mgr) produced an effect similar to 400 mgr DEA-NO. Neither the immediate nor the longer-term depressive effect of NO is mediated by activation of guanylyl cyclase because in the presence of both low and high doses of ODQ, a potent and selective inhibitor of NO-stimulated guanylyl cyclase, NO produced the same depression of the field response. There is evidence however that the IMHV possesses c-GMP responsive elements since direct perfusion of 8-Br-cGMP (1 mM) produced a long-term but not an immediate depression. The long-term depression produced by 400 mgr DEA-NO was eliminated in the presence of either a selective adenosine A(1) receptor antagonist or an ADP-ribosyltransferase inhibitor. It was also possible to prevent the long-term effect in the presence of tetraethyl ammonium a K(+)-channel blocker. These results suggest that the NO may be acting presynaptically in a synergistic fashion with the adenosine A(1) receptor to depress transmitter release.

Humic acids as electron acceptors for anaerobic microbial oxidation of vinyl chloride and dichloroethene

Anaerobic oxidation of [1,2-14C]vinyl chloride and [1, 2-14C]dichloroethene to 14CO2 under humic acid-reducing conditions was demonstrated. The results indicate that waterborne contaminants can be oxidized by using humic acid compounds as electron acceptors and suggest that natural aquatic systems have a much larger capacity for contaminant oxidation than previously thought.

Anaerobic Oxidation of [1,2- 14 C]Dichloroethene under Mn(IV)-Reducing Conditions

Anaerobic oxidation of [1,2- 14 C]dichloroethene to 14 CO 2 under Mn(IV)-reducing conditions was demonstrated. The results indicate that oxidative degradation of partially chlorinated solvents like dichloroethene can be significant even under anoxic conditions and demonstrate the potential importance of Mn(IV) reduction for remediation of chlorinated groundwater contaminants.

Microbial Mineralization of VC and DCE Under Different Terminal Electron Accepting Conditions

Production of 14CO2 from [1,2-14C] dichloroethene (DCE) or [1,2-14C] vinyl chloride (VC) was quantified in aquifer and stream-bed sediment microcosms to evaluate the potential for microbial mineralization as a pathway for DCE and VC biodegradation under aerobic, Fe(III)-reducing, SO4-reducing, and methanogenic conditions. Mineralization of [1,2-14C] DCE and [1,2-14C] VC to 14CO2 decreased under increasingly reducing conditions, but significant mineralization was observed for both sediments even under anaerobic conditions. VC mineralization decreased in the order of aerobic > Fe(III)-reducing > SO4-reducing > methanogenic conditions. For both sediments, VC mineralization was greater than DCE mineralization under all electron-accepting conditions examined. For both sediments, DCE mineralization was at least two times greater under aerobic conditions than under anaerobic conditions. Although significant microbial mineralization of DCE was observed under anaerobic conditions, recovery of 14CO2 did not differ substantially between anaerobic treatments.

Improved detection of weak, clinically significant antibodies by supplementation of polyethylene glycol with a low-ionic solution

A comparative study of 164 serum samples was carried out to determine the specificity and sensitivity of the indirect antiglobulin test (IAGT) in three different formulations: physiologic saline, low-ionic solution (RAM), and RAM supplemented with polyethylene glycol (PEG). Serum samples containing mostly weak antibodies (anti-D, -C, -E, -c, -Jka, -Fya, -K, -S, -Lea, -Lua, -M, -Cob, -P1, -I, and -Kna) were used in a 10-minute IAGT in which PEG-IAGTs were compared with saline- IAGTs and RAM-IAGTs. With the exception of anti-P1, anti-I, and an anti-Lea, PEG-IAGTs detected all the antibodies tested compared with 72.3% and 77.4% for saline-IAGTs and RAM-IAGTs, respectively. The end-point titers of at least 82% of antibodies detected by PEG-IAGTs were 1-3 dilutions higher than those by saline- and RAM-IAGTs. When specificity of PEG-IAGTs was tested using 268 randomly selected, fresh (< 1 day old) blood samples, PEG-IAGT detected 11 out of 268 samples as positive compared with 7 out of 268 by both saline-IAGTs and RAM-IAGTs. The four antibodies that were not detected were identified as anti-D, anti-E, anti-Bga, and an autoantibody known previously to be only reactive with papain-pretreated red cells. No nonspecific reactions were detected by PEG-IAGTs and no hemolysis was evident in any of the IAGTs. PEG-IAGTs were more sensitive than saline- and RAM-IAGTs. PEG-IAGTs detected all weak, clinically significant antibodies as well as four antibodies that were otherwise undetected by saline-IAGT or RAM-IAGT. The overall sensitivity of the PEGIAGT was 96.3% compared with 84.1% and 73.2% for the RAM- and saline-IAGT, respectively.

Morphological and electrophysiological properties of neurons in an area of the chick brain involved in learning

The intermediate, medial part of the hyperstriatum ventrale (IMHV) is an area of the avian forebrain which is essential for two forms of early learning in the domestic chick. We have developed an in vitro slice preparation which contains part of the IMHV and have found that the electrophysiological properties of the area show a considerable degree of plasticity. In particular, age and prior learning appear to modify the properties of single neurons recorded intracellularly. We have used the in vitro slice preparation to make intracellular recordings from 38 single neurons in the IMHV and have then dye-injected each cell to find out whether there is any relationship between electrophysiological and morphological characteristics. The basic membrane properties of each neuron were measured. Responses to standard electrical stimuli, delivered extracellularly, were also recorded, and each neuron was classified on this basis. Finally, the presence or absence of spontaneously occurring bursts of EPSPs was noted. At the end of recording biocytin was injected into the cell. After the tissue had been processed, each cell was drawn. The area of the cell body was measured, the number of dendrites was counted, and dendritic extent and branching were estimated. Each cell was also classified as 'spiny' or 'non-spiny'. We found that neurons displaying one particular type of response to external stimulation possessed a well defined set of morphological and electrical properties. In addition, three parameters--electrical resistance, somatic area, and the presence or absence of dendritic spines--were related to specific subsets of anatomical and physiological characteristics. The possible relevance of these findings to the plasticity of the IMHV is discussed.

Electrophysiological correlates of prior training: an in vitro study of an area of the avian brain which is essential for early learning

Day-old domestic chicks will peck at any small, distinct object, such as a metal bead. One-trial passive avoidance learning can be established by coating the metal bead with methyl anthranilate (MeA) and allowing the birds to peck it once, after which they conspicuously avoid it. We have used birds successfully trained not to peck metal beads, and a control set of chicks where the training beads were innocuously dipped in water. Brain slices were prepared from both groups, containing the left, intermediate, medial part of the hyperstriatum ventrale (IMHV)--a region essential for this form of early learning. The electrophysiological properties of neurones in the IMHV were examined in vitro. Neurones recorded intracellularly in slices taken from MeA-trained birds had higher membrane resistances than did cells from water-trained controls. MeA training was also associated with an increased incidence of spontaneous, large EPSPs. Field responses to local electrical stimulation appeared to be somewhat greater in MeA-trained birds than in water-trained controls. In contrast, field potentials proved harder to potentiate with a burst of relatively high frequency stimulation in MeA-trained birds: the change in amplitude was less in MeA-trained birds, and there was less variability than in slices from water-trained controls.

Age and the effects of 2-D,L-amino-5-phosphonovalerate in an area of the chick forebrain which is essential for early learning

The intermediate, medial part of the hyperstriatum ventrale (IMHV) is a region of the avian forebrain which is known to be essential for early learning in the domestic chick. The IMHV in an in vitro slice preparation displays two forms of synaptic plasticity. The incidence of both varies with age and is maximal between 3 and 5 days post-hatch. Since NMDA receptors are critical for at least one of these plasticities, we have investigated the relationship between age and the contribution of NMDA receptors to the field response evoked by local, low-frequency stimulation and have found that the magnitude of the NMDA-dependent component of the response varies with age peaking between 3 and 5 days post-hatch. Spontaneous neural activity, recorded intracellularly, can be completely and reversibly silenced by NMDA receptor blockade and the incidence of spontaneous activity also varies with age, peaking between 3 and 5 days. These results suggest that the IMHV contains NMDA receptors which can be activated near resting membrane potential. Either the efficiency or the numbers of these receptors is maximal at a specific point in development and their peak activity coincides with a peak in synaptic plasticity. These characteristics are similar to those reported for young mammals.

Noradrenaline and potentiation in the chick brain slice

The role of the noradrenergic system as a modulator of neurotransmission in the chick forebrain was investigated in brain slices containing the medial hyperstriatum ventrale, an area known to be involved in learning and memory. The alpha 2-agonist clonidine (20 microM) decreased the post-synaptic response to local stimulation at 0.1 Hz, while activation of beta 2 receptors increased this response. Induction of persistent potentiation following stimulation at 5 Hz was blocked by drugs (20 microM ICI 118,551; 20 microM propranolol) which showed preferential antagonistic activity at the beta 2 receptor but not by the beta 1-preferential antagonist timolol. This effect may be due to an interaction with the NMDA receptor system.

Effects of light hatching on synapse number and size in the intermediate and medial part of the hyperstriatum ventrale of the domestic chick

The effects of pre-hatch light exposure on synaptic development in the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the chick brain were investigated. Quantitative electron microscopical techniques were used to determine the size and numerical density of synapses and it was seen that in light hatched chicks there was a significant increase in the density of synapses in the left IMHV but that the size of synapses in these birds was decreased. These results provide a link between synaptic development and plasticity.

Microbial Transformation of Nitroaromatics in Surface Soils and Aquifer Materials

Microorganisms indigenous to surface soils and aquifer materials collected at a munitions-contaminated site transformed 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to amino-nitro intermediates within 20 to 70 days. Carbon mineralization studies with both unlabeled (TNT, 2,4-DNT, and 2,6-DNT) and radiolabeled ([ 14 C]TNT) substrates indicated that a significant fraction of these source compounds was degraded to CO 2 .

NMDA-receptors and potentiation in an area of avian brain essential for learning

The intermediate medial part of the hyperstriatum ventrale (IMHV), part of the avian forebrain, is essential for early learning in the domestic chick. Persistent potentiation (PP) can sometimes be induced in the IMHV in vitro. One can predict success from events which occur during the stimulation (1 min at 5 Hz) which is used for induction: the original response must be transiently replaced by a later, slower response (the LPSR). The LPSR has a comparatively high threshold of activation, its rate of development is inversely related to magnesium concentration and it can be eliminated by NMDA antagonists, as can the induction of PP. PP in the IMHV is therefore dependent upon NMDA receptors and the LPSR represents the activation of these receptors.

Protein kinase activity and synaptic plasticity in a chick brain slice

In an in vitro slice preparation of the chick brain it is possible to record responses to single electrical stimuli from within the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region known to be involved in learning. The amplitude of such responses is significantly increased by superfusion of the slice with 10 microM 4 beta-phorbol 12,13 diacetate (PDAc), a phorbol ester which stimulates protein kinase activity. The ability of PDAc to induce potentiation is greatest in chicks less than 6 days old. Administration of the kinase antagonist H7 prevents the induction of persistent potentiation and in fact produces a long lasting depression of response amplitude. H7 also produces a short term increase in excitability within the IMHV and results in increased expression of N-methyl-D-aspartate receptor activity.

Morphological correlates of protein kinase C induced potentiation in the chick brain slice

Continuous perfusion of a chick brain slice with 10 microM 4 beta phorbol 12,13 diacetate (PDAc) produces a significant increase in the amplitude of the response to electrical stimulation at 0.1 Hz recorded within the intermediate and medial part of the hyperstriatum ventrale (IMHV). This PDAc-induced potentiation and that induced by tetanising stimulation appear to share similar mechanisms. Quantitative electron microscopy of synapses within the IMHV from slices in which a PDAc induced potentiation had been produced 30 minutes earlier showed that compared with control slices there was a significant increase in the size of the postsynaptic density of spine synapses. The change was greater in magnitude than that observed in spine synapses following tetanically induced potentiation. No other synaptic parameters were affected.

Morphological correlates of persistent potentiation in the chick brain slice

In an in-vitro slice preparation of the chick brain it is possible to induce persistent potentiation of responses to single electrical stimuli by giving two bursts of 300 stimuli at 5 Hz separated by ten minutes of control stimulation at 0.1 Hz. We investigated the morphological correlates of this potentiation in a group of 2 day old chicks using quantitative electron microscopical techniques. It was found that in slices which showed a clearly potentiated response there was a significant increase in the size of the postsynaptic densities of synapses on spines in the left hyperstriatum ventrale (IMHV). No such increases were seen in a control group nor in slices which failed to potentiate. These results provide further evidence for the lability of synapses in the IMHV.

Potentiation of synaptic responses in slices from the chick forebrain

Coronal slices, containing part of the medial hyperstriatum ventrale (MHV), were cut from the left forebrains of domestic chicks and maintained in vitro. Records were made of the field responses evoked in the MHV by local electrical stimuli provided at 0.1 Hz. Two 1 min periods of stimulation at 5 Hz, separated by 10 min, were used in attempts to induce a persistent increase in the size of the postsynaptic response to test stimulation at 0.1 Hz. This procedure produced a potentiation which usually lasted longer than 2 h. The probability of inducing this persistent potentiation of the response (PPR) is not distributed evenly over the whole anteroposterior length of the MHV but is higher in slices that also contain the septo-mesencephalic tract ventrally. These are the slices that contain the intermediate part of the medial hyperstriatum ventrale (IMHV); an area that is essential for early behavioural learning. At this level PPR is not confined to the IMHV. It can also be produced in the lateral neostriatum in response to similar local stimulation at 5 Hz. No PPR was observed in either the caudal ectostriatum, or the paleostriatum.

The effects of age and visual experience on potentiation of responses in slices from the chick forebrain

A single coronal slice, containing the intermediate part of the medial hyperstriatum ventrale (IMHV) was cut from the left forebrain of a series of domestic chicks and maintained in vitro. Records were made of field responses evoked in the IMHV by local electrical stimuli. Two 1-min periods of 5 Hz stimulation, separated by 10 min, were used in attempts to induce persistent potentiation of the responses (PPR) to test stimulation at 0.1 Hz. In dark-hatched chicks the probability of producing PPR is much higher in slices from chicks aged 2-5 days post-hatch than in those from either younger or older birds. As an independent measure of plasticity in dark-hatched chicks, the probability of eliciting unit responses to repeated stimulation of remote sites in the slice at 3.3 Hz was analysed. This probability was greater in slices from chicks aged 2-5 days than in those from either younger or older birds. In light-hatched chicks the probability of inducing PPR is significantly higher during the first day post-hatch, than in dark-hatched chicks of this age. The probability of producing PPR in slices from light-hatched chicks aged 2-3 days is less than that in slices from either younger or older birds. It is clear that both the age and past experience of the domestic chick affect the neurophysiological properties of slices of brain, tested in vitro.

The influence of salinity on the kinetics of NH inf4sup+ uptake in Spartina alterniflora

The effects of short- and long-term exposure to a range in concentration of sea salts on the kinetics of NH _inf4^sup+ uptake by Spartina alterniflora were examined in a laboratory culture experiment. Long-term exposure to increasing salinity up to 50 g/L resulted in a progressive increase in the apparent K_m but did not significantly affect V_max (mean V_max=4.23±1.97 μmole·g^-1·h^-1). The apparent K_m increased in a nonlinear fashion from a mean of 2.66±1.10 μmole/L at a salinity of 5 g/L to a mean of 17.56±4.10 μmole/L at a salinity of 50 g/L. These results suggest that the long-term effect of exposure to total salt concentrations within the range 5-50 g/L was a competitive inhibition of NH _inf4^sup+ uptake in S. alterniflora. No significant NH _inf4^sup+ uptake was observed in S. alterniflora exposed to 65 g/L sea salts. Short-term exposure to rapid changes in salinity significantly affected both V_max and K_m. Reduction of solution salinity from 35 to 5 g/L did not change V_max but reduced K_m by 71%. However, exposing plants grown at 5 g/L salinity to 35 resulted in an decrease in V_max of approximately 50%. Exposure of plants grown at 35 g/L to a total sea salt concentration of 50 g/L for 48h completely inhibited uptake of NH _inf4^sup+ . For both experiments, increasing salinity led to an increase in the apparent K_m similar to that found in response to long-term exposure. Our data are consistent with a conceptual model of changes in the productivity of S. alterniflora in the salt marsh as a function of environmental modification of NH _inf4^sup+ uptake kinetics.

Aerobic biodegradation potential of subsurface microorganisms from a jet fuel-contaminated aquifer

In 1975, a leak of 83,000 gallons (314,189 liters) of jet fuel (JP-4) contaminated a shallow water-table aquifer near North Charleston, S.C. Laboratory experiments were conducted with contaminated sediments to assess the aerobic biodegradation potential of the in situ microbial community. Sediments were incubated with 14C-labeled organic compounds, and the evolution of 14CO2 was measured over time. Gas chromatographic analyses were used to monitor CO2 production and O2 consumption under aerobic conditions. Results indicated that the microbes from contaminated sediments remained active despite the potentially toxic effects of JP-4. 14CO2 was measured from [14C]glucose respiration in unamended and nitrate-amended samples after 1 day of incubation. Total [14C]glucose metabolism was greater in 1 mM nitrate-amended than in unamended samples because of increased cellular incorporation of 14C label. [14C]benzene and [14C]toluene were not significantly respired after 3 months of incubation. With the addition of 1 mM NO3, CO2 production measured by gas chromatographic analysis increased linearly during 2 months of incubation at a rate of 0.099 mumol g-1 (dry weight) day-1 while oxygen concentration decreased at a rate of 0.124 mumol g-1 (dry weight) day-1. With no added nitrate, CO2 production was not different from that in metabolically inhibited control vials. From the examination of selected components of JP-4, the n-alkane hexane appeared to be degraded as opposed to the branched alkanes of similar molecular weight. The results suggest that the in situ microbial community is active despite the JP-4 jet fuel contamination and that biodegradation may be compound specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Connections of the IMHV in the domestic chick Gallus domesticus

The responses to single electrical stimuli have been recorded from neurons in the brains of domestic chicks, by using an in vitro preparation consisting of a coronal slice taken from the forebrain. All slices were cut so that they contained the intermediate part of the medial hyperstriatum ventrale (IMHV). When such a slice is bathed in standard Krebs' solution there is no evidence that the excitation produced by a single stimulus can be transmitted more than 1 mm either towards or away from the IMHV. The addition of bicuculline methiodide (more than 3 x 10(-6) M) to Krebs' solution allows the excitation produced by a single stimulus to spread in all directions throughout the dorsal half of a coronal slice. At points remote (more than 1.5 mm) from the stimulated point, the magnitude of the spreading wave of excitation bears an all-or-nothing relation to the strength of stimulus used to excite it. This wave of excitation spreads from the excited point in all directions without attenuation at 0.9 +/- 0.017 (s.d.) m s-1 and consists of a prolonged burst of activity of the invaded neurons. The properties of coronal slices described above are also true of brain slices cut in a parasagittal plane. The spreading response to a single stimulus given in the presence of bicuculline, can be reduced in magnitude by the addition of AP-5 but it still spreads throughout the dorsal part of the slice at the same velocity. The response can be eliminated by the addition of kynurenic acid. The addition of curare to the bathing medium produces similar responses that spread in a similar fashion to those seen under bicuculline. These results suggest that the dorsal part of the forebrain of the domestic chick (in fact, the part derived from the embryological alar plate) contains a network of reciprocally connected local circuits. Transmission throughout the network is normally prevented by active inhibition.

Local circuitry in the IMHV of the domestic chick (Gallus domesticus)

The responses to local stimulation have been recorded from neurons in the intermediate part of the medial hyperstriatum ventrale (IMHV) of the domestic chick, by using an in vitro slice preparation. When the slice is bathed in gassed Krebs' solution, a single stimulus evokes a short-lasting diphasic response. The first phase is negative and lasts some 3 ms, whereas the second, positive phase is often of lower amplitude and usually persists for about 15 ms. The first phase is little altered by perfusion with either Ca2(+)-free Krebs' solution or Krebs' solution containing a high concentration of Mg2+. In contrast, the second phase is abolished by these procedures. The post-synaptic phase is positive when it is recorded anywhere between 0.1-1.25 mm from the stimulated point; however, in the immediate vicinity (0.0-0.1 mm) of the stimulating electrodes, the post-synaptic response is strongly negative. A pair of stimuli has to be separated by at least 10 s to guarantee complete recovery of excitability of the post-synaptic response. The recovery curve for this response shows a refractory period of some 5 ms, a peak of excitability at an interval of about 20 ms, and then a sharp trough of relative inexcitability at about 200 ms. The post-synaptic response is considerably reduced in magnitude and duration by the addition of AP-5 to the perfusion fluid; the remaining post-synaptic response is completely abolished by kynurenic acid. The addition of bicuculline methiodide in concentrations of at least 1 x 10(-6) M increases both the magnitude and duration of the second, positive phase of the response to single stimuli. This extended positive response (which may last from 500-800 ms) is abolished by perfusion with bicuculline dissolved in Ca2(+)-free Krebs' solution. For the entire duration of the extended post-synaptic positive response produced by bicuculline, the irregular discharge of single neurons can be recorded. Like the post-synaptic positive response in Krebs' solution, the much larger response produced by bicuculline shows a very localized negativity beneath the stimulating electrodes and displays an almost identical time-course for the recovery of excitability following a single stimulus. The bicuculline induced positive response is also considerably reduced by the presence of AP-5; the addition of kynurenic acid abolishes the remaining post-synaptic response completely. A post-synaptic response, similar to that produced under bicuculline, can be produced by the addition of a maximally effective dose of d-tubocurarine.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of dark-rearing on dendritic development in two regions of the forebrain of the domestic chick

The effects of dark-rearing on dendritic development were studied in domestic chicks aged 72 h. Two areas of the forebrain were investigated, the hyperstriatum accessorium (HA) and the intermediate part of the medial hyperstriatum ventrale (IMHV). Dark-rearing significantly reduced spine density on the dendrites of large multipolar neurones in both left and right HA. In the IMHV there was a significant decrease in spine density in the left hemisphere in chicks reared in the light. No other parameters of dendritic development were affected. These results reinforce the conclusion that in the young domestic chick the left IMHV is a particularly labile region.

Anisomycin and amnesia in the chick: state-dependent effects are not present with intracranial injections

It has recently been suggested that intraperitoneal (IP) injection of anisomycin (ANI) in the chick produces amnesia for a one-trial passive avoidance task in a state-dependent manner. We have examined the behavioral and biochemical effects of IP and intracranial (IC) injections of ANI in chicks trained on a one-trial passive avoidance task. IC injection of ANI produced 35% brain protein synthesis inhibition whereas IP injection produced only negligible amounts of protein synthesis inhibition in the brain. IC injection of ANI produced amnesia and was not state-dependent. Patterns of behavior consistent with state-dependent effects were produced by IP injection of ANI. These experiments indicate that there are differences in the pattern of results produced by IP and IC injection of ANI and support the hypothesis that the expression of long-term memory in chicks is associated with protein synthesis.

Response characteristics of neurons in chick forebrain slices

Coronal sections were taken from the forebrains of domestic chicks, aged 1-20 days, and maintained in vitro. Extracellular recordings of neural activity were made from the intermediate part of the medial hyperstriatum ventrale (IMHV). Spontaneous activity was rarely recorded, but neuronal responses could be evoked by stimulation of various sites. Each recording point was surrounded by an arc of sites which, when stimulated, typically elicited a short-latency field potential. These 'local responses' could be recorded in slices from chicks of any age. Stimulation of more distant sites failed to evoke field potentials from the IMHV. Instead, trains of large, unit action potentials appeared on an undisturbed baseline. Such 'unit' responses could only be evoked by stimuli delivered at specific frequencies. They required facilitation, were of variable latency, and often finally decayed. The number of sites capable of evoking a 'unit' response from the IMHV fell dramatically in slices taken from chicks older than 4 days.

State-dependent recall can be induced by protein synthesis inhibition: behavioural and morphological observations

The possibility that the amnesia induced by protein synthesis inhibition is state dependent was investigated. Chicks injected with the protein synthesis inhibitor anisomycin and then trained in a single-trial passive avoidance learning task showed no recall for the task when tested 6 h later in the absence of the drug. If, however, the same chicks were subsequently retested 30 min after a second administration of the drug they demonstrated clear recall for the task. Control groups showed that this effect was not the result of the administration of anisomycin per se but was due to state-dependent recall. Quantitative morphological characterisation of synapses in a region of the chick forebrain (the intermediate part of the medial hyperstriatum ventrale (IMHV) previously shown to be involved in passive avoidance learning was performed. The characteristic increase in the length of the postsynaptic density in the left IMHV was only evident in chicks killed after the behavioural test in which they had demonstrated recall. No synaptic changes were observed in chicks in which state-dependent recall had been demonstrated in a previous test but which were killed after a test in which they appeared amnestic. These results suggest that a memory trace may be established even in the absence of protein synthesis but that this trace may not normally be accessible. It is also suggested that the synaptic changes observed following learning may be dependent on some aspect of the recall phenomenon.

The effects of protein synthesis inhibition on structural changes associated with learning in the chick

The effect of the protein synthesis inhibitor anisomycin on the structural changes associated with passive avoidance learning in the chick was investigated. Chicks were trained when they were 24 h old by allowing them to peck at a shiny bead coated with either water or the aversive-tasting substance methylanthranilate (MeA). Chicks which peck the MeA-coated bead will on subsequent testing avoid pecking a similar, but water-coated bead. Behavioural testing was carried out 12 h after training and immediately afterwards the chicks were killed and their brains prepared for electron microscopy. A specific region of the forebrain, the intermediate and medial part of the hyperstriatum ventrale (IMHV) was investigated. When the IMHV of the MeA trained chicks was compared with that of water-trained controls structural changes of the synapse were detected. These changes involved a significant increase in the mean length of the postsynaptic density (LPSD) of symmetrical synapses in the left IMHV. Chicks injected with 0.8 mg of anisomycin 30 min before training with a MeA-coated bead showed aversion for the shiny bead when tested 12 h later. Electron microscopic analysis of the IMHV from these amnestic chicks showed no evidence for the change in LPSD demonstrated in the water-injected controls. These results are discussed in relation to the nature of the memory trace induced by training on a passive avoidance task.

The application of network analysis to the study of branching patterns of large dendritic fields

Network analysis of dendritic fields not only defines the topology and connectivity of segments of an arborescence, but offers a means of discovering how networks grow. An important theory has recently been formulated29 suggesting that dendritic branching patterns may be established by synaptogenic interaction of dendritic growth cones with growing axons. This thesis may be verified through network analysis since the theory predicts that growth at pendant vertices will predominate in dendritic networks, that dendritic growth will be directed into areas of maximal synaptogenic activity and that arc lengths will be inversely related, and the order of branching at vertices directly related, to the magnitude of the synaptogenic activity operating about growing dendritic terminals. The possibility of a preponderance of terminal growth may be detected by comparing the topologies in an observed dendritic network with those of a series of hypothetical growth models. This paper provides the frequency table for models grown by monochotomous, dichotomous and trichotomous branching on random pendant vertices and random arcs for large networks in which 'set theory' contingencies are included. The paper also describes a method of calculating branching probabilities from the measurement of segment lengths, which is a means of testing the last mentioned prediction of the synaptogenic theory of denddritic growth. The method of network analysis is then discussed in relation to probable dendritic growth patterns, the constancy of segment lengths and the interaction of extrinsic and intrinsic factors in determining branching probabilities.