Lesion-induced sprouting in the rat dentate gyrus is inhibited by repeated ethanol administration

The effect of ethanol on hippocampal axonal sprouiting was studied with a histochemical technique for identifying acetylcholinesterase. Unilateral lesion of the entorhinal cortex in adult rats produced an increase in the density of acetylcho-linesterase staining in the outer molecular layer and a concomitant increase in the width of the pale-staining commissural-associational zone of the dentate gyrus. Other rats were given ethanol (11.3 +/- 0.45 grams per kilogram) for 2 weeks before and 9 days after receiving the lesion. Ethanol abolished the expansion of the commissural-associational zone. The effect of ethanol on sprouting axons suggests that it may inhibit recovery of function after brain injury.     

Long-term potentiation in the motor cortex

Long-term potentiation (LTP) is a model for learning and memory processes. Tetanic stimulation of the sensory cortex produces LTP in motor cortical neurons, whereas tetanization of the ventrolateral nucleus of the thalamus, which also projects to the motor cortex, does not. However, after simultaneous high-frequency stimulation of both the sensory cortex and the ventrolateral nucleus of the thalamus, LTP of thalamic input to motor cortical neurons is induced. This associative LTP occurs only in neurons in the superficial layers of the motor cortex that receive monosynaptic input from both the sensory cortex and the ventrolateral nucleus of the thalamus. Associative LTP in the motor cortex may constitute a basis for the retention of motor skills.     

Pattern separation in the human hippocampal CA3 and dentate gyrus

Pattern separation, the process of transforming similar representations or memories into highly dissimilar, nonoverlapping representations, is a key component of many functions ascribed to the hippocampus. Computational models have stressed the role of the hippocampus and, in particular, the dentate gyrus and its projections into the CA3 subregion in pattern separation. We used high-resolution (1.5-millimeter isotropic voxels) functional magnetic resonance imaging to measure brain activity during incidental memory encoding. Although activity consistent with a bias toward pattern completion was observed in CA1, the subiculum, and the entorhinal and parahippocampal cortices, activity consistent with a strong bias toward pattern separation was observed in, and limited to, the CA3/dentate gyrus. These results provide compelling evidence of a key role of the human CA3/dentate gyrus in pattern separation.     

Pattern separation in the dentate gyrus and CA3 of the hippocampus

Theoretical models have long pointed to the dentate gyrus as a possible source of neuronal pattern separation. In agreement with predictions from these models, we show that minimal changes in the shape of the environment in which rats are exploring can substantially alter correlated activity patterns among place-modulated granule cells in the dentate gyrus. When the environments are made more different, new cell populations are recruited in CA3 but not in the dentate gyrus. These results imply a dual mechanism for pattern separation in which signals from the entorhinal cortex can be decorrelated both by changes in coincidence patterns in the dentate gyrus and by recruitment of nonoverlapping cell assemblies in CA3.     

Long-term synaptic potentiation in the superior cervical ganglion

Brief tetanic stimulation of the preganglionic nerves to the superior cervical ganglion enhances the postganglionic response to single preganglionic stimuli for 1 to 3 hours. This long-term potentiation of transmission through the ganglion is apparently not attributable to a persistent muscarinic action of the preganglionic neurotransmitter, acetylcholine, since neither the magnitude nor the time course of the phenomenon is reduced by atropine. The decay of long-term potentiation can be described by a first-order kinetic process with a mean time constant of 80 minutes. We conclude that long-term potentiation, once considered a unique property of the hippocampus, is in fact a more general feature of synaptic function. This form of synaptic memory may significantly influence information processing and control in other regions of the nervous system, including autonomic ganglia.     

Long-term potentiation of neuron-glia synapses mediated by Ca2+-permeable AMPA receptors

Interactions between neurons and glial cells in the brain may serve important functions in the development, maintenance, and plasticity of neural circuits. Fast neuron-glia synaptic transmission has been found between hippocampal neurons and NG2 cells, a distinct population of macroglia-like cells widely distributed in the brain. We report that these neuron-glia synapses undergo activity-dependent modifications analogous to long-term potentiation (LTP) at excitatory synapses, a hallmark of neuronal plasticity. However, unlike the induction of LTP at many neuron-neuron synapses, both induction and expression of LTP at neuron-NG2 synapses involve Ca2+-permeable AMPA receptors on NG2 cells.     

Associative induction of posttetanic and long-term potentiation in CA1 neurons of rat hippocampus

Electrical stimulation of fibers in the stratum radiatum causes an excitatory postsynaptic potential in CA1 neurons of the hippocampus. Other excitatory inputs to or direct depolarization of these CA1 neurons during stimulation of the stratum radiatum caused a subsequent increase in the excitatory postsynaptic potential. This enhancement was characterized as a brief potentiation (2 to 3 minutes, similar to posttetanic potentiation) and a long-term potentiation (presumed to be involved in learning and memory). These potentiations are probably induced by an interaction of the postsynaptic cell or other presynaptic terminals with the test presynaptic terminals.     

青春期双酚A暴露对老年CD-1小鼠海马 齿状回Synaptotagmin 1含量的影响

探讨青春期双酚A暴露对老年期齿状回Synaptotagmin 1（Syt 1）含量的影响。结果显示,18月龄CD-1小鼠齿状回Syt 1相对含量显著高于6月龄小鼠（Ps<0.05）;青春期双酚A暴露高剂量小鼠齿状回Syt 1表达量显著高于同年龄对照小鼠（Ps<0.05）,雌鼠更明显。这些结果进一步支持小鼠海马Syt 1呈年龄相关性增加的结论,青春期双酚A暴露可加剧这种增加。     

Inhibition of human acute lymphoblastic leukemia cells by immunotoxins: potentiation by chloroquine

Immunotoxins containing pokeweed antiviral protein and monoclonal antibodies against human T cells or human transferrin receptor efficiently killed acute lymphoblastic leukemia cells. Chloroquine specifically enhanced the rate of protein synthesis inhibition by immunotoxin. Depending on its concentration, chloroquine (10 to 100 micromolar) reduced by up to 65-fold the amount of immunotoxin required to inhibit protein synthesis in the target cells 50 percent.     

Diabetes mellitus: induction in mice by encephalomyocarditis virus

Hyperglycemia and lesions of the pancreatic islets of Langerhans developed in some, but not all, adult mice infected with a variant of the encephalomyocarditis virus. Large amounts of virus were recovered from the pancreas during acute stages of infection. At this time blood glucose concentrations were markedly elevated and the islets of Langerhans exhibited focal necrosis and degranulation of beta cells. Evidence of abnormal glucose metabolism persisted for varying periods after recovery from the infection. The islets of Langerhans of chronically hyperglycemic mice were distorted and decreased in size, and the beta cells were degranulated. Encephalomyocarditis virus appears to cause diabetes mellitus by reducing the mass of functional beta cells of the islets of Langerhans.     

Brain edema: induction in cortical slices by polyunsaturated fatty acids

The presence of polyunsaturated and saturated fatty acids in leukocytic membranes prompted study of their possible role in the induction of brain edema. Polyunsaturated fatty acids including sodium arachidonate, sodium linoleate, sodium linolenate, and docasahexaenoic acids induced edma in slices of rat brain cortex. This cellular edema was specific, since neither saturated fatty acids nor a fatty acid containing a single double bond had such effect.     

Delta-aminolevulinic acid synthetase: induction in embryonic chick liver by glucagon

Glucagon elicits a twofold increase in delta-aminolevulinic acid synthetase activity in the livers of 18-day-old chick embryos. This rise occurs when RNA synthesis is inhibited, but is prevented when protein synthesis is blocked. Cyclic adenosine monophosphate appears not to be involved.     

Induction of synaptic potentiation in hippocampus by patterned stimulation involves two events

Electrical stimulation of axons in the hippocampus with short high-frequency bursts that resemble in vivo activity patterns produces stable potentiation of postsynaptic responses when the bursts occur at intervals of 200 milliseconds but not 2 seconds. When a burst was applied to one input and a second burst applied to a different input to the same target neuron 200 milliseconds later, only the synapses activated by the second burst showed stable potentiation. This effect was observed even when the two inputs innervated completely different regions of the postsynaptic cells; but did not occur when the inputs were stimulated simultaneously or when the second burst was delayed by 2 seconds. Intracellular recordings indicated that the first burst extended the decay phase of excitatory postsynaptic potentials evoked 200 milliseconds later. These results suggest that a single burst of axonal stimulation produces a transient, spatially diffuse "priming" effect that prolongs responses to subsequent bursts, and that these altered responses trigger spatially restricted synaptic modifications. The similarity of the temporal parameters of the priming effect and the theta rhythm that dominates the hippocampal electroencephalogram (EEG) during learning episodes suggests that this priming may be involved in behaviorally induced synaptic plasticity.     

Breast cancer: induction of differentiation by embryonic tissue

A mouse mammary tumor, adenocarcinoma BW 10232, was maintained in vitro for 14 days, separated from embryonic mammary mesenchyme by a Millipore filter. Tubules developed in the tumor; deoxyibonucleic acid synthisis declined; and a presumptive acid mucopolysaccharide matrix, not evident in the controls, appeared.     

Mitosis: induction by cultures of human peripheral lymphocytes

Ribosomal RNA extracted from peripheral lymphocytes, which had been recently stimulated by specific antigens to which the donor was sensitized, is capable of promoting transformation and mitosis when added to cultures of autologous unstimulated lymphocytes.     

Communication between dolphins in separate tanks by way of an electronic acoustic link

Two isolated dolphins (Tursiops truncatus) were provided with an electronic acoustic link during alternate periods of approximately 2 minutes. The dolphins repeatedly communicated in a tight sequence when the acoustic link was connected. Their responses varied as the experiment progressed. Some information regarding possible meaning of the whistles was obtained.     

Hydra: induction of supernumerary heads by isolated neurosecretory granules

Neurosecretory granules of Hydra littoralis were isolated by differential centrifugation. Excised midsegments of hydra that were exposed to the fraction containing neurosecretory granules developed additional heads at any site, as they regenerated. Hence neurosecretory granules may contain a factot that regulates or stimulates growth in normal and regenerating hydra.     

Liver cancer: neonatal estrogen enhances induction by a carcinogen

A single injection of 100 micrograms of estradiol benzoate into newborn rats was followed after weaning by dietary treatment with one of two dosages of the carcinogen N-hydroxy-N-2-fluorenylacetamide. Autopsies 26 weeks later showed a higher incidence of liver cancer in male and, particularly, female rats injected with hormone than in controls. The weights of livers were greater but gonads were smaller in size in the estradiol groups. Endocrine and possibly centralnervous-system factors may play roles in formation of liver tumors.     

Indole-2-carboxylic acid: a competitive antagonist of potentiation by glycine at the NMDA receptor

The N-methyl-D-aspartate (NMDA) class of excitatory amino acid receptors regulates the strength and stability of excitatory synapses and appears to play a major role in excitotoxic neuronal death associated with stroke and epilepsy. The conductance increase gated by NMDA is potentiated by the amino acid glycine, which acts at an allosteric site tightly coupled to the NMDA receptor. Indole-2-carboxylic acid (I2CA) specifically and competitively inhibits the potentiation by glycine of NMDA-gated current. In solutions containing low levels of glycine, I2CA completely blocks the response to NMDA, suggesting that NMDA alone is not sufficient for channel activation. I2CA will be useful for defining the interaction of glycine with NMDA receptors and for determining the in vivo role of glycine in excitotoxicity and synapse stabilization.     

gamma-Glutamyl transpeptidase in isolated brain endothelial cells: induction by glial cells in vitro

The endothelia of microvessels isolated from mouse brain by mechanical means are rich in gamma-glutamyl transpeptidase; however, the enzyme often disappears when the cells migrate or proliferate from the microvessel isolates. In an endothelial cell line derived from similar isolates and negative for gamma-glutamyl transpeptidase, the enzyme could be induced in the endothelial cells when they were cocultured with glial cells. Thus there may be a requirement for continuous induction of gamma-glutamyl transpeptidase in brain microvessels by adjacent glial cells.