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C C Bell

Publications and source records attributed to C C Bell.

At least 19 recordsLinked to original sources
PubMed2001

Myelinated dendrites in the mormyrid electrosensory lobe.

This is the third paper in a series on the morphology, immunohistochemistry, and synaptology of the mormyrid electrosensory lateral line lobe (ELL). The ELL is a highly laminated, cerebellum-like structure in the rhombencephalon that subserves an active electric sense: Objects in the nearby environment are detected on the basis of changes in the reafferent electrosensory signals that are generated by the animal's own electric organ discharge. This paper concentrates on the intermediate (cell and fiber) layer of the medial zone of the ELL and pays particular attention to the large multipolar neurons of this layer (LMI cells). LMI cells are gamma-aminobutyric acid (GABA)ergic and have one axon and three to seven proximal dendrites that all become myelinated after their last proximal branching point. The axon projects to the contralateral homotopic region and has ipsilateral collaterals. Both ipsilaterally and contralaterally, it terminates in the deep and superficial granular layers. The myelinated dendrites end in the deep granular layer, where they most likely do not make postsynaptic specializations, but do make presynaptic specializations, similar to those of the LMI axons. Because it is not possible to distinguish between axonal and dendritic LMI terminals in the granular layer, the authors refer to both as LMI terminals. These are densely filled with small, flattened vesicles and form large appositions with ELL granular cell somata and dendrites with symmetric synaptic membrane specializations. LMI cells do not receive direct electrosensory input on their somata, but electrophysiological recordings suggest that they nevertheless respond strongly to electrosensory signals (Bell [1990] J. Neurophysiol. 63:303-318). Consequently, the authors speculate that the myelinated dendrites of LMI cells are excited ephaptically (i.e., by electric field effects) by granular cells, which, in turn, are excited via mixed synapses by mormyromast primary afferents. The authors suggest that this ephaptic activation of the GABAergic presynaptic terminals of the myelinated dendrites may trigger immediate synaptic release of GABA and, thus, may provide a very fast local feedback inhibition of the excited granular cells in the center of the electrosensory receptive field. Subsequent propagation of the dendritic excitation down the myelinated dendrites to the somata and axon hillocks of LMI cells probably generates somatic action potentials, resulting in the spread of inhibition through axonal terminals to a wide region around the receptive field center and in the contralateral ELL. Similar presynaptic myelinated dendrites that subserve feedback inhibition, until now, have not been described elsewhere in the brain of vertebrates.

Animals↗
PubMed2001

Clinician safety: assessing and managing the violent patient.

Many clinicians deny the possibility of violence occurring in their practices, and this denial has its roots in fear of violence or overconfidence in safety. To appropriately address the issue of violence, clinicians must engage in proactive behaviors and attitudes that will ensure their safety.

Facility Design and Construction↗
PubMed2001

Memory-based expectations in electrosensory systems.

Adaptive processing of electrosensory information occurs in the cerebellum-like structures of three distinct groups of fish. Associations within each of these structures result in the generation of negative images of predictable features of the sensory inflow. Addition of these negative images to the actual inflow removes the predictable features, allowing the unpredictable, information-rich sensory signals to stand out. Evidence from all three groups of fish indicates that the negative images are mediated by plasticity at parallel fiber synapses.

Animals↗
PubMed2001

Cultivating resiliency in youth.

This paper highlights characteristics of resiliency and the importance of strengthening resiliency and how to build it. The neuropsychiatry of traumatic stress is underscored and more esoteric resiliency-building activities are discussed.

Adaptation, Psychological↗
PubMed2000

Activity of adenosine deaminase in the sleep regulatory areas of the rat CNS.

There are data to support the notion that adenosine (ADO), a neuromodulator in the CNS, is an important regulator of sleep homeostasis. It has been demonstrated that ADO agonists and antagonists strongly impact upon sleep. In addition, the level of adenosine varies across the sleep/wake cycle and increases following sleep deprivation. Adenosine deaminase (ADA) is a key enzyme involved in the metabolism of ADO. We questioned, therefore, whether there are differences in adenosine deaminase activity in brain regions relevant to sleep regulation. We found that ADA exhibits a characteristic spatial pattern of activity in the rat CNS with the lowest activity in the parietal cortex and highest in the region of the tuberomammillary nucleus (15.0+/-4.8 and 63.4+/-28.0 nmoles/mg protein/15 min, mean+/-S.D., respectively). There were significant differences among the brain regions by one-way ANOVA (F=31.33, df=6, 123, P=0.0001). The regional differences in ADA activity correlate with variations in the level of its mRNA. This suggests that spatial differences in ADA activity are the result of changes in the expression of the ADA gene. We postulate that adenosine deaminase plays an important role in the mechanism that controls regional concentration of adenosine in the brain and thus, it is a part of the sleep-wake regulatory mechanism.

Adenosine Deaminase↗
PubMed2000

Clinician safety: assessing and managing the violent patient.

Many clinicians deny the possibility of violence occurring in their practices, and this denial has its roots in fear of violence or overconfidence in safety. To appropriately address the issue of violence, clinicians must engage in proactive behaviors and attitudes that will ensure their safety.

Attitude of Health Personnel↗
PubMed2000

Prevention of violence.

Rebuilding the village, increasing access to health, improving bonding and attachment dynamics, providing opportunities to increase self-esteem and social skills enhancing the adult protective shield, and minimizing the impact of trauma are presented as basic principles to change health behavior. The intent of putting these principles into practice is to strengthen the two key support systems of children, the family and the school, so that they can provide primary prevention of violence.

Adolescent↗
PubMed2000

Reversible associative depression and nonassociative potentiation at a parallel fiber synapse.

The electrosensory lobe (ELL) of mormyrid electric fish is one of several cerebellum-like sensory structures in fish that remove predictable features of the sensory inflow. This adaptive process obeys anti-Hebbian rules and appears to be mediated by associative depression at the synapses between parallel fibers and Purkinje-like cells of ELL. We show here that there is also a nonassociative potentiation at this synapse that depends only on the repeated occurrence of the EPSP. The depression can be reversed by the potentiation and vice versa. Finally, we show that the associative depression requires NMDA receptor activation, changes in postsynaptic calcium, and the occurrence of a postsynaptic dendritic spike within a few milliseconds following EPSP onset.

2-Amino-5-phosphonovalerate↗
PubMed2000

Rapid activation of GABAergic interneurons and possible calcium independent GABA release in the mormyrid electrosensory lobe.

The primary afferent fibers from the electroreceptors of mormyrid electric fish terminate centrally in the granular layer of the electrosensory lobe (ELL). This study examines the excitatory and inhibitory processes that take place in this layer using an in vitro slice preparation and field potentials evoked by stimulation of primary afferent fibers in the deep fiber layer of ELL. The postsynaptic response to stimulation of the afferent fibers was still present after blocking chemical transmission in three different ways: by adding glutamate receptor antagonists to the medium, by substituting a nominally calcium-free medium for normal medium, and by blocking calcium channels with cadmium. Blockade of chemical transmission was demonstrated by disappearance of control responses to parallel fiber stimulation. The continued presence of a postsynaptic response in the absence of chemical excitation is consistent with previous anatomic and physiological evidence for electrical synapses between afferent fibers and granular cells in ELL. Granular cell activation by primary afferent fibers was followed by a powerful, short-latency inhibition mediated by GABA and GABA(A) receptors, as indicated by a large increase in the postsynaptic response to afferent fiber stimulation following application of the GABA(A) receptor antagonist, bicuculline. Bicuculline caused a marked increase of the postsynaptic response even after chemical synaptic excitation had been blocked by glutamate receptor antagonists, by a calcium-free medium, or by cadmium. Thus activation of the inhibitory interneurons responsible for GABA release did not require chemical excitation. Nonchemical excitation of the inhibitory interneurons could be mediated either by electrical synapses between afferent fibers and inhibitory interneurons, or by nonsynaptic activation of the large GABAergic terminals that are known to be present on granular cells. The marked increase of the postsynaptic response caused by bicuculline in a calcium-free medium or in the presence of cadmium suggests that the release of GABA by inhibitory terminals was not entirely dependent on calcium influx. This effect of bicuculline on the postsynaptic response in a calcium-free medium or in the presence of cadmium was markedly reduced by prior addition of the GABA transporter antagonist, nipecotic acid. Thus calcium-independent release of GABA may occur in ELL and may be partly dependent on reversal of a GABA transporter. Rapid and powerful inhibition at the first stage in the processing of electrosensory information could serve to enhance the small differences in latency among afferent fibers that appear to encode small differences in stimulus intensity.

Animals↗
PubMed2000

Assessment and management of the violent patient.

This article provides guidance on how to manage the unavoidable challenge of aggression in psychiatric relationships. Accordingly, this article addresses issues of personal safety and how to manage potentially violent patients, defuse situations that threaten imminent violence, and manage emergent violence. In addition, a useful chart is highlighted that differentiates different types of violence.

Guidelines as Topic↗
PubMed2000

Basic research and community collaboration: necessary ingredients for the development of a family-based HIV prevention program.

This article describes the development of a family-based, longitudinal HIV prevention program targeting urban, African American fourth- and fifth-grade children and their families living in areas with high rates of HIV infection. The intervention is based on the research findings of the Chicago HIV Prevention and Adolescent Mental Health Family Study, a longitudinal study of 315 urban, African American families with preadolescent children (Paikoff, 1997). Results from this study informed the development of a 12-week, family-based preventive intervention-the Chicago HIV-Prevention and Adolescent Mental Health Project (CHAMP) Family Program. The development and implementation of the program also was guided by a collaborative partnership between university researchers and community members (parents and school staff). A description of the process by which collaboration influenced the development of the intervention is provided. This article is meant to serve as a model for the integration of empirical findings and community collaboration into the development of HIV prevention programs.

Adult↗
PubMed1999

Mormyrid electrosensory lobe in vitro: morphology of cells and circuits.

The electrosensory lobe (ELL) of mormyrid electric fish is a cerebellum-like brainstem structure that receives the primary afferent fibers from electroreceptors in the skin. The ELL and similar sensory structures in other fish receive extensive input from other central sources in addition to the peripheral input. The responses to some of these central inputs are adaptive and serve to minimize the effects of predictable sensory inputs. Understanding the interaction between peripheral and central inputs to the mormyrid ELL requires knowledge of its functional circuitry, and this paper examines this circuitry in the in vitro slice preparation and describes the axonal and dendritic morphology of major ELL cell types based on intracellular labeling with biocytin. The cells described include medium ganglion cells, large ganglion cells, large fusiform cells, thick-smooth dendrite cells, small fusiform cells, granule cells, and primary afferent fibers. The medium ganglion cells are Purkinje-like interneurons that terminate on the two types of efferent cells, i.e., large ganglion and large fusiform cells, as well as on each other. These medium ganglion cells fall into two morphologically distinct types based on the distributions of basal dendrites and axons. These distributions suggest hypotheses about the basic circuit of the ELL that have important functional consequences, such as enhancement of contrast between "on" elements that are excited by increased afferent activity and "off" elements that are inhibited.

Animals↗
PubMed1999

Issues in the psychiatric treatment of African Americans.

African Americans constitute about 12 percent of the United States population. Sixty percent of African Americans live in urban areas, and 25 percent have incomes below the poverty level. Issues in the psychiatric assessment and evaluation of African-American patients include diagnostic bias that has resulted in overdiagnosis of schizophrenia. Use of screening instruments can help standardize assessment, but appropriate screening instruments that have been evaluated and found reliable in this population must be used. Issues in treatment and outcome for African Americans include challenges in establishing rapport in interethnic situations, racial identity as a focus in psychotherapy, and awareness of biological characteristics that affect response to medications. Many African Americans live in high-crime areas where high rates of drug abuse and violence create chronic stresses. Patients with dual diagnoses of chronic mental illness and substance use or abuse need targeted interventions. Strategies for prevention and treatment of the effects of having experienced or witnessed violence have been proposed. Additional research is needed to clarify the true prevalence of specific mental disorders among African Americans and to determine the most effective combinations of treatment strategies for various disorders.

Adolescent↗
PubMed1999

Physiology of electrosensory lateral line lobe neurons in Gnathonemus petersii.

In mormyrid electric fish, sensory signals from electroreceptors are relayed to secondary sensory neurons in a cerebellum-like structure known as the electrosensory lateral line lobe (ELL). Efferent neurons and interneurons of the ELL also receive inputs of central origin, including electric organ corollary discharge signals, via parallel fibers and via fibers from the juxtalobar nucleus. To understand the cellular mechanisms of the integration of sensory inputs and central inputs in the ELL, the intracellular activity and ionic properties of the efferent projection neurons and interneurons were examined in an in vitro slice preparation.We focus here on the electrophysiological properties of the efferent neurons of the ELL network, the large fusiform cells and large ganglion cells, and on a class of gamma-aminobutyric acid (GABA)-ergic interneurons known as medium ganglion (MG) cells. In response to current injection through a recording pipette, both types of efferent neuron fire a large narrow spike followed by a large hyperpolarizing afterpotential. The MG cells fire a complex spike which consists of small narrow spikes and a large broad spike. Although the forms of the action potentials in efferent neurons and in MG cells are different, all spikes are mediated by tetrodotoxin (TTX)-sensitive Na+ conductances and spike repolarization is mediated by tetraethylammonium (TEA+)-sensitive K+ conductances. In the presence of TEA+, substitution of Ba2+ for Ca2+ in the bath revealed the presence of a high-voltage-activated Ca2+ conductance. Stimulation of parallel fibers conveying descending input to the ELL molecular layer in vitro evokes an excitatory postsynaptic potential (EPSP), generally followed by an inhibitory postsynaptic potential (IPSP), in the efferent neurons. In MG cells, the same stimulation evokes an EPSP, often followed by a small IPSP. Synaptic transmission at parallel fiber synapses is glutamatergic and is mediated via both N-methyl-d-aspartate (NMDA)- and (AMPA)-type glutamate receptors. The inhibitory component of the parallel fiber response is GABAergic. It is probably mediated via the stellate neurons and the MG cells, which are themselves GABAergic interneurons intrinsic to the ELL network.A hypothetical neural circuit of the intrinsic connections of the ELL, based on the known morphology of projection neurons and medium ganglion interneurons, is presented. This circuit includes an excitatory and an inhibitory submodule. The excitatory submodule is centered on a large fusiform cell and appears to relay the sensory input as a positive 'ON' image of an object. The inhibitory submodule is centered on a large ganglion cell and relays a negative 'OFF' image to the next higher level. We suggest that MG cells exert an inhibitory bias on efferent neuron types and that the ELL network output is modulated by the dynamically plastic integration of central descending signals with sensory input.

Animals↗
PubMed1999

Synaptic plasticity in the mormyrid electrosensory lobe.

The mormyrid electrosensory lateral line lobe (ELL) is one of several different sensory structures in fish that behave as adaptive sensory processors. These structures generate negative images of predictable features in the sensory inflow which are added to the actual inflow to minimize the effects of predictable sensory features. The negative images are generated through a process of association between centrally originating predictive signals and sensory inputs from the periphery. In vitro studies in the mormyrid ELL show that pairing of parallel fiber input with Na+ spikes in postsynaptic cells results in synaptic depression at the parallel fiber synapses. The synaptic plasticity observed at the cellular level and the associative process of generating negative images of predicted sensory input at the systems level share a number of properties. Both are rapidly established, anti-Hebbian, reversible, input-specific and tightly restricted in time. These common properties argue strongly that associative depression at the parallel fiber synapse contributes to the adaptive generation of negative images in the mormyrid ELL.

Animals↗
PubMed1999

A critical approach to stress-related disorders in African Americans.

This article outlines an integrative, dynamic approach to stress and is, in part, a response to emergent debates within social science research and practice that suggest that African Americans are currently experiencing the reverberating psychological effects of slavery and oppression. It is the product of the work of an African-American mental health think tank situated at the Community Mental Health Council, Chicago, Illinois. We suggest the need to attend to biopsychosocial, environmental, and cultural factors that inform both exposure and responses to stress. Finally, consideration is given to matters of resiliency.

Black or African American↗
PubMed1998

The mormyrid electrosensory lobe in vitro: physiology and pharmacology of cells and circuits.

This paper is concerned with the electrosensory lobe (ELL) of mormyrid electric fish as examined in in vitro slices. Intracellular recordings from morphologically identified cells and field potential recordings were used to characterize the physiology and pharmacology of ELL cells. Most intracellular recordings were from the Purkinje-like interneurons that are known as medium ganglion cells and from the two types of efferent neurons, large ganglion and large fusiform cells. Stimulation of primary afferent fibers elicits both excitatory and inhibitory effects in these cells, with the excitatory effects being mediated by both the AMPA and NMDA types of glutamate receptors and the inhibitory effects being mediated by both GABAA and glycine receptors. Parallel-fiber stimulation evokes an EPSP-IPSP sequence, with the EPSPs being mediated by both AMPA and NMDA receptors and the IPSPs being mediated by GABAA receptors only. The parallel fiber-evoked EPSPs and IPSPs show marked paired-pulse facilitation. A large and unusually broad spike is recorded inside medium ganglion cells, and field potential responses suggest that this spike is propagated into the apical dendrites. The results provide essential information for understanding how peripheral and central inputs are integrated in ELL.

Animals↗
PubMed1998

Adolescent suicide.

This article reviews the origin of youth suicide. Theoretic suicide risk factors and empirically observed suicide risk factors are discussed along with proposed resiliency factors that prevent suicide. Finally, suicide prevention and intervention strategies are covered, and a call for better studies on suicide prevention is heralded.

Adolescent↗