NMDA receptors and voltage-dependent calcium channels mediate different aspects of acquisition and retention of a spatial memory task.

Activity dependent calcium entry into neurons can initiate a form of synaptic plasticity called long-term potentiation (LTP). This phenomenon is considered by many to be one possible cellular mechanism underlying learning and memory. The calcium entry that induces this phenomenon can occur when N-methyl-D-aspartate receptors (NMDARs) and/or voltage-dependent calcium channels (VDCCs) are activated. While much is known about synaptic plasticity and the mechanisms that are triggered by activation of these two Ca(2+) channels, it is unclear what roles they play in learning. To better understand the role activation of these channels may play in learning we systemically administered pharmacological antagonists to block NMDARs, VDCCs, or both during training trials and retention tests in a radial arm maze task. Wistar rats injected with the NMDAR antagonist MK-801 (0.1mg/kg) were impaired in the acquisition of this task. In contrast, rats injected with verapamil (10mg/kg), an antagonist to VDCCs, acquired the task at the same rate as control animals, but were impaired on a 10-day retention test. A group of animals injected with both antagonists were unable to learn the task. The results suggest that each of the calcium channels and the processes they trigger are involved in a different stage of memory formation or expression.

Combined slurry and solid-phase bioremediation of diesel contaminated soils.

This work investigates, at a laboratory and pilot-scale, the influence of various operating parameters on the combined slurry and solid-phase bioremediation technique for a diesel contaminated soil. For slurry-phase bioreactors (SPB), it has been found that, as far as famine conditions are attained at the end of the react cycle, a low hydraulic retention time and a low slurry recycle ratio allows for a better utilization of the reactor volume. A 7-day slurry-phase bioreactor treatment has been shown to provide enough contaminant removal allowing the soil drawn from the slurry-phase bioreactors to be fed effectively to the solid-phase bioreactors (SoPB) for completing the soil cleanup. However, an important improvement of the solid-phase bioreactor performance has been found using soil additives, namely sand and surfactants. While the first soil additive improves pile porosity and consequently oxygen diffusion, the latter increases contaminant bioavailability.

Role of voltage-dependent calcium channel long-term potentiation (LTP) and NMDA LTP in spatial memory.

This experiment explores the role of two forms of long-term potentiation (LTP) in behavioral memory. NMDA and/or voltage-dependent calcium channels (VDCCs) were antagonized pharmacologically at levels that block nmdaLTP and vdccLTP, respectively, in rats learning an eight-arm radial maze task. Animals were trained twice a day for 11 d under the systemic influence of MK-801, verapamil, both drugs, or saline. During acquisition, the mixed drug group displayed significantly more working memory errors and reference memory errors than all other groups. The mixed drug group was markedly impaired on the first daily trial but improved dramatically on their second daily trial. After a 7 d delay, saline and MK-801 animals maintained their predelay level of performance. The performance of the verapamil groups declined significantly over the delay. These results demonstrate that: (1) vdccLTP is necessary for the retention of information over a 7 d period, (2) the blockade of both forms of LTP prevents the retention of information over a 21 hr period, and (3) blockade of both forms of LTP does not prevent the storing of information over a short period of time (3 hr).

Brain-derived neurotrophic factor immunoreactivity in the limbic system of rats after acute seizures and during spontaneous convulsions: temporal evolution of changes as compared to neuropeptide Y.

Seizures increase the synthesis of brain-derived neurotrophic factor in forebrain areas, suggesting this neurotrophin has biological actions in epileptic tissue. The understanding of these actions requires information on the sites and extent of brain-derived neurotrophic factor production in areas involved in seizures onset and their spread. In this study, we investigated by immunocytochemistry the changes in brain-derived neurotrophic factor in the hippocampus, entorhinal and perirhinal cortices of rats at increasing times after acute seizures eventually leading to spontaneous convulsions. We also tested the hypothesis that seizure-induced changes in brain-derived neurotrophic factor induce later modifications in neuropeptide Y expression by comparing, in each instance, their immunoreactive patterns. As early as 100 min after seizure induction, brain-derived neurotrophic factor immunoreactivity increased in CA1 pyramidal and granule neurons and in cells of layers II-III of the entorhinal cortex. At later times, immunoreactivity progressively decreased in somata while increasing in fibres in the hippocampus, the subicular complex and in specific layers of the entorhinal and perirhinal cortices. Changes in neuropeptide Y immunoreactivity were superimposed upon and closely followed those of brain-derived neurotrophic factor. One week after seizure induction, brain-derived neurotrophic factor and neuropeptide Y immunoreactivities were similar to controls in 50% of rats. In rats experiencing spontaneous convulsions, brain-derived neurotrophic factor and neuropeptide Y immunoreactivity was strongly enhanced in fibres in the hippocampus/parahippocampal gyrus and in the temporal cortex. In the dentate gyrus, changes in immunoreactivity depended on sprouting of mossy fibres as assessed by growth-associated protein-43-immunoreactivity. These modifications were inhibited by repeated anticonvulsant treatment with phenobarbital. The dynamic and temporally-linked alterations in brain-derived neurotrophic factor and neuropeptide Y in brain regions critically involved in epileptogenesis suggest a functional link between these two substances in the regulation of network excitability.

alpha-Difluoromethylornithine decreases inhibitory transmission in hippocampal slices independently of its inhibitory effect on ornithine decarboxylase.

We tested the effect of DL-alpha-(difluoromethyl)ornithine (DFMO), a specific inhibitor of ornithine decarboxylase (ODC), on recordings in area CA1 of rat hippocampal slices. In the concentration range in which it is used as an ODC inhibitor, DFMO increased neuronal excitability and blocked paired-pulse inhibition. The effect of DFMO was reversed by perfusing the slice with normal bathing solution. These effects were not attenuated by the simultaneous addition of putrescine; thus the activity of DFMO was not related to a decrease in putrescine caused by the inhibition of ODC. Mediation by the N-methyl-D-aspartate (NMDA) receptor was ruled out because DL-2-amino-5-phosphonovalerate (APV), an NMDA antagonist, did not block the effect of DFMO. Intracellular and extracellular recordings of pharmacologically isolated IPSPs supported the notion that DFMO depressed GABAergic transmission. DFMO has frequently been used as a tool to study the role of the ODC-polyamine system in neural preparations. This report suggests that the results from such studies must be interpreted with caution. In addition, our findings raise questions about the proposed use of DFMO as a neuroprotective agent against excitotoxicity.

Hyperpolarizing and depolarizing GABAA receptor-mediated dendritic inhibition in area CA1 of the rat hippocampus.

1. gamma-Aminobutyric acidA (GABAA) receptor-mediated inhibition of pyramidal neuron dendrites was studied in area CA1 of the rat hippocampal slice preparation with the use of intracellular and extracellular recording and one-dimensional current source-density (CSD) analysis. 2. Electrical stimulation of Schaffer collateral/commissural fibers evoked monosynaptic excitatory postsynaptic potentials (EPSPs) and population EPSPs, which were followed by biphasic inhibitory postsynaptic potentials (IPSPs). In the presence of the excitatory amino acid receptor antagonists 6,7-dinitroquinoxaline-2,3-dione (DNQX) and D,L-2-amino-5-phosphonovalerate (APV), stimulation in stratum radiatum evoked monosynaptic fast, GABAA and late, GABAB receptor-mediated IPSPs and fast and late positive field potentials recorded in s. radiatum. 3. Fast monosynaptic IPSPs and fast positive field potentials evoked in the presence of DNQX and APV were reversibly abolished by the GABAA receptor antagonist bicuculline methiodide (BMI; 30 microM) and were not changed by the GABAB receptor antagonist P-[3-aminopropyl]-P-diethoxymethylphosphinic acid (CGP 35,348; 0.1-1.0 mM). CGP 35,348 (0.1 mM) reversibly blocked late monosynaptic IPSPs and late positive field potentials. These results suggest that fast field potentials are GABAA receptor-mediated population IPSPs (GABAA, fast pIPSPs) and that late field potentials are GABAB receptor-mediated population IPSPs (GABAB, late pIPSPs). 4. Fast pIPSPs were reversibly abolished when the extracellular Cl- concentration [( Cl-]o) was reduced from 132 to 26 mM in parallel with a depolarizing shift in the reversal potential of fast IPSPs. Paired or repetitive stimulation in s. radiatum reversibly depressed fast pIPSPs and fast IPSPs. Paired-pulse depression of fast pIPSPs was reversibly antagonized by CGP 35,348 (0.4-0.8 mM). 5. Laminar analysis of s. radiatum-evoked fast pIPSPs and one-dimensional CSD analysis revealed active current sources in s. radiatum and passive current sinks in s. oriens and s. lacunosum moleculare. S. radiatum sources were abolished by pressure application of BMI in s. radiatum but not in s. oriens. Stimulation in s. oriens, s. pyramidale, or s. lacunosum moleculare evoked GABAA current sources horizontal to the stimulation site. Changes in the dendritic location of inhibitory current with changes in stimulus location paralleled changes in the distribution of excitatory current. 6. In the presence of 4-aminopyridine (50-100 microM), DNQX and APV long-lasting depolarizing GABAA receptor-mediated responses (LLDs) occurred spontaneously or could be evoked. Current sinks associated with s. radiatum-evoked LLDs were located in the same dendritic area as sources associated with hyperpolarizing fast IPSPs.(ABSTRACT TRUNCATED AT 400 WORDS)

Methods for studying the conductance changes associated with synaptic activation of forebrain slices: the interpretation of field potentials using CSD profiles.

In this report the cortical slice preparation and an array electrode that instantaneously records laminar field potentials are used to evaluate issues related to the interpretation of cortical CSD profiles. The major issues are: (1) what cell types are responsible for producing the source/sink pairs seen in CSD profiles; (2) what neurotransmitters are responsible for producing the sinks/sources seen in the CSD profile and do the sinks/sources reflect activation of receptors that produce inward currents, outward currents, or both; (3) can active and passive currents be distinguished; (4) do action potentials contribute to the CSD profile; and (5) can synaptic population with different kinetics and onset latencies be distinguished? Methods for analyzing neuronal circuits and analyzing CSDs quantitatively are discussed.

An integrated multielectrode electrophysiology system.

An integrated system for recording and analyzing electrophysiological data from multiple channels is described. The system uses an MS-DOS microcomputer, a 16-channel amplifier, and multiple-tipped electrode arrays designed for use in intact and slice preparations. The system is designed for applications where the collection and analysis of multiple-channel electrophysiological data is desirable, including the construction of current source density (CSD) profiles from field potential data. The software incorporates on-line averaging, CSD and freeze-frame capabilities to guide the experiment in progress. Additional off-line analyses include multiple unit activity, power spectra, and automatic scans of data files for peak amplitude, area, latency, and slope within user-defined latency windows. All data and analyses can be exported to commercial statistical/graphical programs for the creation of publication-ready figures.

[Isoenzymes of creatine kinase and prostate-specific antigen in the monitoring of prostatic carcinoma]. / Isoenzimi della creatin-chinasi (CKMM-CKBB) e antigene prostatico specifico (PSA) nel monitoraggio del carcinoma prostatico.

We have valued serum levels of the prostatic specific antigen and of the creatine-kinase isoenzymes (MM-BB) in 30 patients with prostatic carcinoma at C and D stage. Our results demonstrate that these markers are useful for monitoring and for checking of metastasis. But the isoenzymes seem to us predictive in the monitoring of metastasis. The isoenzymes' determination was executed by electrophoretic method (Helena) which is sensitive, specific and swift.

[Isoenzymes of lactate dehydrogenase, alkaline phosphatase, creatine kinase. Possible use as tumor markers]. / Isoenzimi della lattato deidrogenasi, fosfatasi alcalina, creatin-chinasi. Possibilità di impiego come markers tumorali.

The electrophoresis of serum isoenzymes in cancer pathology at different stages has enabled us to recognise for LDH4 and LDH5, characteristics of sensitivity in all stages, with positivity greater than 60% in the advanced and multiply metastasized stages or with interference from other pathologies; to reveal portions pathologically heavy like FAST (46%); to reveal atypical bands (BB and MIT), as well as the values for normal or really low enzymatic activity. Through the elevated sensitivity and the high percentage of positivity, the isoenzymes LDH4 and LDH5 can be considered tumour markers and superior in validity to the conventional markers.

Effects of camera cuts and music on selective attention and verbal and motor imitation by mentally retarded adults.

Effects of experimentally manipulating camera cuts (high vs. low frequency) and music (present vs. absent) on total and selective visual attention to and imitation of prosocial TV programs were examined. Subjects were 96 adults (mean IQ = 46). Within programs, selective viewing of content features (dialogue, distress, helping, and reinforcement) and media features (music, cuts, zooms, and scene changes) were examined. Subjects selectively attended to cuts and zooms and all four content features. High-cuts frequencies in a program reduced selective attention and subsequent verbal imitation. There were no significant effects for music.