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R K Lee

Publications and source records attributed to R K Lee.

At least 55 records · Page 3Linked to original sources
PubMed1996

Metabotropic glutamate receptors regulate APP processing in hippocampal neurons and cortical astrocytes derived from fetal rats.

It has previously been shown that stimulation of muscarinic m1 or m3 receptors can, by generating diacylglycerol (DAG) and activating protein kinase C (PKC), accelerate the breakdown of the amyloid precursor protein (APP) to form soluble, non-amyloidogenic peptides (APPs). This relationship has been demonstrated in human glioma and neuroblastoma cells as well as in transfected human embryonic kidney (HEK) cells and PC12 cells. We now provide evidence that stimulation of metabotropic glutamate receptors (mGluRs), which also are coupled to DAG and PKC, similarly accelerates processing of APP into non-amyloidogenic APPs in hippocampal neurons and cortical astrocytes derived from normal fetal rats. The mGluR antagonist, L(+)-2-amino-3-phosphonopropionic acid (L-AP3), and GF 109203X, an inhibitor of PKC, both blocked the release of APPs from hippocampal neurons and astrocytes evoked by glutamate receptor stimulation. Inasmuch as glutamatergic neurons in cortex and hippocampus are known to be damaged in Alzheimer's disease, our findings suggest that amyloid formation may be enhanced by the resulting glutamate deficiency and that selective mGluR agonists may be useful in facilitating synaptic efficacy and treating the disease.

Amyloid beta-Protein Precursor↗
PubMed1996

Structure and expression of murine CD30 and its role in cytokine production.

Murine CD30 cDNA predicts a protein of 498 amino acids with homology to the TNF receptor family of proteins characterized by repeated cysteine-rich motifs in the extracellular domain. Murine CD30, although homologous to human CD30, has a 90 amino acid gap in an extracellular region that appears to be duplicated in human CD30. Murine CD30 cDNA was shown to be functional through the production of a soluble murine Ig fusion protein (CD30-Ig) that was active in binding to cells that expressed CD30 ligand. CD30-Ig also served as an immunogen for the production of hamster anti-mouse CD30 mAbs, which recognized both CD30 expressed by murine lymphocytes and CD30 expressed by cells transfected with murine CD30 cDNA. CD30 mRNA is highly expressed in the thymus and in activated spleen cells, but not in other tissues tested. In anti-CD3-activated spleen cells, CD30 ligand is expressed primarily by CD4+ T cells, with peak expression at days 1 and 2, whereas CD30 is expressed primarily by CD8+ T cells, with peak expression on days 4 and 5. Stimulation of CD30 by plate-bound anti-CD30 directly signaled for IL-5 but not IFN-gamma production by CD30+ CTL lines. These studies demonstrate that CD30 directs cytokine secretion and suggest that CD30 signaling may be pivotal in the pattern of cytokine production by T cells.

3T3 Cells↗
PubMed1996

Bcl-2 protects against Fas-based but not perforin-based T cell-mediated cytolysis.

Fas ligand and perforin are the two key effector mechanisms in T cell-mediated cytotoxicity. These molecules mediate cytolysis of target cells by membrane damage and apoptosis. bcl-2 is known to protect cells against apoptosis induced by many stimuli including growth factor removal. However bcl-2's effect on Fas ligand and perforin-induced lysis has not been studied extensively. We investigated the effect of overexpression of bcl-2 alone, Fas alone or their combined overexpression on lysis of a commonly used target, P815, by perforin-sufficient, Fas ligand-sufficient and perforin-deficient or Fas ligand-deficient, allospecific cytotoxic T lymphocytes (CTL). Wild-type P815 are susceptible to lysis by perforin-sufficient CTL, regardless of the presence or absence (gld) of Fas ligand, but are poorly lysed by perforin-deficient CTL. Fas transfection of P815 makes target cells highly susceptible to lysis by both perforin-sufficient and -deficient CTL, indicating the presence of the Fas ligand-mediated cytotoxicity on both types of CTL. Co-transfection of P815-fas with bcl-2 abolishes their increased susceptibility to Fas-mediated lysis, even in the face of Fas overexpression on the cell membrane. The protective effect of bcl-2 against cell lysis is evident with perforin-deficient CTL as effector cells or when perforin activity is eliminated by the absence of extracellular calcium in perforin-sufficient CTL. bcl-2 overexpression by P815, however, does not protect against CTL lysis by the perforin pathway, regardless of Fas overexpression, as demonstrated by fas ligand mutated gld and wild-type perforin-sufficient CTL. Therefore bcl-2 can protect P815 target cells against Fas-mediated lysis when triggered by the Fas ligand on CTL, but not against perforin-mediated lysis.

Animals↗
PubMed1995

Amyloid precursor protein processing is stimulated by metabotropic glutamate receptors.

Stimulation of muscarinic m1 or m3 receptors can, by generating diacylglycerol and activating protein kinase C, accelerate the breakdown of the amyloid precursor protein (APP) to form soluble, nonamyloidogenic derivatives (APPs), as previously shown. This relationship has been demonstrated in human glioma and neuroblastoma cells, as well as in transfected human embryonic kidney 293 cells and PC-12 cells. We now provide evidence that stimulation of metabotropic glutamate receptors (mGluRs), which also are coupled to phosphatidylinositol 4,5-bisphosphate hydrolysis, similarly accelerates processing of APP into nonamyloidogenic APPs. This process is demonstrated both in hippocampal neurons derived from fetal rats and in human embryonic kidney 293 cells transfected with cDNA expression constructs encoding the mGluR 1 alpha subtype. In hippocampal neurons, both an mGluR antagonist, L-(+)-2-amino-3-phosphonopropionic acid, and an inhibitor of protein kinase C, GF 109203X, blocked the APPs release evoked by glutamate receptor stimulation. Ionotropic glutamate agonists, N-methyl-D-aspartate or S(-)-5-fluorowillardiine, failed to affect APPs release. These data show that selective mGluR agonists that initiate signal-transduction events can regulate APP processing in bona fide primary neurons and transfected cells. As glutamatergic neurons in the cortex and hippocampus are damaged in Alzheimer disease, amyloid production in these regions may be enhanced by deficits in glutamatergic neurotransmission.

Alanine↗
PubMed1995

Treatment of HIV-related hairy leukoplakia with podophyllum resin 25% solution.

Ten HIV-infected patients who had bilateral hairy leukoplakia on the tongue were treated with topical podophyllum resin 25% solution. Only one side of the bilateral lesion was treated and the other side served as the control and was not treated. The lesions on both the treatment and control sides were evaluated at day 2, 7, and 30 by an investigator who had not been involved in the initial treatment and had no knowledge of which side had been treated. Therefore the treatment side is compared with the control side in a single-subject design, single-blind control setting. The lesions were judged by the degree of resolution and assigned a number of 0 to 4 with 4 indicating the highest degree of resolution and 0 indicating no resolution or worsening of the condition. The results were analyzed by Student's t test. Significant resolution of hairy leukoplakia was noted on the treatment side compared with the control side at the 2-, 7-, and 30-day levels; the 2-day results were the most significant. Furthermore, the patients reported minimal side effects, which included burning sensation, bad or altered taste, and pain, that were of mild intensity and short duration. The side effects were reported to occur immediately after the topical application. Patient tolerance and acceptance were found to be very favorable. No systemic side effect was reported. We conclude that single topical application of podophyllum resin 25% solution is efficacious in producing significant short-term resolution of HIV-related oral hairy leukoplakia. We also conclude that it is a safe topical regimen with minimal side effects.

Administration, Topical↗
PubMed1995

In-vitro activity of oxazolidinones against Mycobacterium avium complex.

Options for treating disseminated Mycobacterium avium complex (MAC) disease have improved. However, efficacy is not always certain, resistance is common and rapidly bactericidal agents would improve efficacy and prevent resistance. Certain oxazolidinones were tested against MAC strains and inhibited growth at expected serum concentrations or lower. Activity correlated with hydrophobicity and one agent was bactericidal at concentrations two to five times greater than the MIC.

Amikacin↗
PubMed1995

Violence research: an overview.

This article discusses the problem of violence in America and presents an overview of pertinent research studies. It considers data sources on violence and the categorization of injuries. The article next focuses on the specific problems of family violence: child abuse, spouse abuse, and elder abuse. The second part of the article considers the nursing discipline's specific contribution to violence research by reviewing nursing studies on abuse during pregnancy, female partner abuse, elder abuse, and child abuse. Nursing research, which is grounded in the clinical concerns of the discipline, is presented as having an advocacy orientation that avoids the victim blaming and emphasis on pathology often characteristic of other disciplines' research. The paper discusses how nurses can participate in prevention approaches to reduce violence-related injuries, and it concludes by offering policy recommendations for nursing organizations.

Domestic Violence↗
PubMed1994

Prevention of vertebrate neuronal death by the crmA gene.

Interleukin-1 beta converting enzyme (ICE) is a mammalian homolog of CED-3, a protein required for programmed cell death in the nematode Caenorhabditis elegans. The activity of ICE can be specifically inhibited by the product of crmA, a cytokine response modifier gene encoded by cowpox virus. Microinjection of the crmA gene into chicken dorsal root ganglion neurons was found to prevent cell death induced by deprivation of nerve growth factor. Thus, ICE is likely to participate in neuronal death in vertebrates.

Animals↗
PubMed1994

Cardiovascular development in the zebrafish. II. Endocardial progenitors are sequestered within the heart field.

We have examined the zebrafish embryo to ascertain the location of endocardial and myocardial progenitors prior to gastrulation, in an attempt to define the earliest stages of cardiac patterning. Currently there is uncertainty as to the spatial and lineage relationship of the progenitors for these two phenotypically distinct cell types that form the two concentric layers of the primitive heart tube. By single-cell injection and tracking, we distinguish a region in the early and midblastula which has the properties of a heart field, in that it defines a zone of cardiac progenitors within which there is a spatial gradient of propensity to generate heart cells, and which regulates, in the sense of adapting to the transplantation of pluripotential cells. This zone extends from the future ventral axis dorsally along the margin, with cardiogenic propensity tapering off laterally and dorsally. Myocardial progenitors are spread throughout this region, but endocardial precursors are restricted to the ventral marginal region. The cardiovascular progeny of the ventral cells include, in addition to endocardium and myocardium, cells in the endothelium and blood.

Animals↗
PubMed1993

GABAergic innervation of the Mauthner cell and other reticulospinal neurons in the goldfish.

The Mauthner cells are pair of identifiable hindbrain neurons that participate in the escape response of fishes. Membrane excitability in these cells is regulated by inhibitory neurons that use glycine as a transmitter. We examined the possibility that the inhibitory transmitter gamma-amino butyric acid (GABA) may also act on the Mauthner cells. We used immunocytochemical methods involving an antibody against glutamic acid decarboxylase (GAD), the synthesizing enzyme for GABA. Our study revealed dense GAD immunoreactive terminals surrounding the Mauthner cells. Puncta counts showed that the distribution of GAD immunoreactivity was densest at the distal lateral dendrite of the Mauthner cells; the distribution of puncta tapers gradually in regions closer to the soma. The axon cap was devoid of GABAergic immunoreactivity. We also performed unilateral lesions of the octaval nuclei to evaluate the origin of the GAD immunoreactive terminals. Following the lesions, we found marked decreases in GAD immunoreactive terminals on the proximal lateral dendrite, soma, and proximal ventral dendrite of both Mauthner cells. These results suggest that the octaval region contributes to bilateral inhibition of the Mauthner cells. The distal lateral dendrite of the ipsilateral Mauthner cell also showed a reduction in GAD immunoreactive terminals. This suggests that GABA mediates remote dendritic inhibition of this cell. GAD immunoreactive puncta also surrounded other large reticulospinal neurons, some of which are serially reiterated along the anterior-posterior axis of the hindbrain. Thus, GABA may also exert an influence not only on the Mauthner cells, but also on other reticulospinal neurons.

Afferent Pathways↗
PubMed1993

Segmental arrangement of reticulospinal neurons in the goldfish hindbrain.

The hindbrain is evolutionarily conserved among diverse vertebrate phyla. In vertebrate embryos, the hindbrain is segmentally organized as a series of overt swellings known as rhombomeres. In the larval zebrafish Brachydanio rerio, conspicuous and identifiable reticulospinal neurons are positioned in the center of rhombomeres. Segmentally homologous reticulospinal neurons that share a range of morphological, developmental, and biochemical features occupy adjacent rhombomeres. We have recently shown that reticulospinal neurons of the zebrafish survive ontogeny without considerable morphological modification and we suggested that homologous neurons may share similar functions at different stages of development (Lee and Eaton: Journal of Comparative Neurology 304:34-52, 1991). The goldfish Carassius auratus, a related cyprinid, is especially suited for neurophysiological and behavioral studies. However, it is not yet known if the various reticulospinal neurons of zebrafish are generalizable to other species such as the goldfish. Therefore, we sought to examine the extent to which reticulospinal neurons of the zebrafish are also present in the adult goldfish. Analysis of 45 brains retrogradely labeled with horseradish peroxidase (HRP) from the spinal cord showed that reticulospinal neurons are arranged as a series of seven segments within the hindbrain; a regular interval of approximately 200 microns separates adjacent segments. Although the goldfish reticulospinal system has more neurons than the zebrafish, many reticulospinal neuron types continue to be identifiable. Moreover, comparisons of dendritic arborizations and axon paths between the two species showed that the morphology between various neuron types is virtually identical. The cross-taxonomic similarities between the reticulospinal systems of these related cyprinids make it possible to pursue functional considerations of segmentally homologous neurons in the goldfish hindbrain.

Animals↗
PubMed1993

Compartmentalization of acetylcholinesterase mRNA and enzyme at the vertebrate neuromuscular junction.

Acetylcholinesterase (AChE) is concentrated at the vertebrate neuromuscular synapse. To determine whether increased transcript levels could underlie this selective accumulation, we employed a quantitative reverse transcription polymerase chain reaction-based assay to determine mRNA copy number in samples as small as single neuromuscular junctions (NMJs) and a microassay to measure AChE enzyme activity at single synapses. Our results show that AChE mRNA is an intermediate transcript at NMJs, whereas in noninnervated regions of muscle fibers, AChE transcripts are either undetectable or rare. In contrast, alpha-actin transcript levels in the same samples are similar in junctional and extrajunctional regions. However, compared with AChE enzyme activity and alpha-actin mRNA levels, the levels of AChE transcripts at NMJs are highly variable. These results indicate that AChE mRNA and protein expression are compartmentalized at the vertebrate NMJ and provide a direct approach toward dissecting the molecular events leading from synaptic activation to plastic changes in gene expression at single vertebrate synapses.

Acetylcholinesterase↗
PubMed1993

Cardiovascular development in the zebrafish. I. Myocardial fate map and heart tube formation.

We have analyzed the origin of cardiac progenitors in the zebrafish embryo by injection of single blastomeres with a lineage tracer dye, and examined the formation of the zebrafish heart tube by serial sectioning of immunostained embryos. At the 512-cell stage (early blastula), most cardiac progenitors lie in a marginal zone that extends from 90 degrees longitude (midway between the future dorsal and ventral axis) through 180 degrees longitude (the future ventral axis) to 270 degrees longitude. By focusing on myocardial progenitors located at 90 degrees (and 270 degrees) longitude, we found that a single cell injected in the early blastula can contribute progeny to both the atrium and ventricle. A cell injected in the midblastula contributes progeny to either the atrium or ventricle, but not both. This analysis suggests that, at least for these myocardial progenitors, the atrial and ventricular lineages separate in the midblastula. Precardiac cells involute early during gastrulation and turn towards the animal pole with other early involuting cells. These cardiogenic cells reach the embryonic axis around the 8-somite stage, and there they coalesce to form a pair of myocardial tubular primordia on either side of the midline. By the 21-somite stage, the tropomyosin-immunoreactive myocardial tubes have moved closer to each other, and a distinct group of cells, the endocardial progenitor cells, sits medially between them. The myocardial tubes then fuse to enclose the endocardial cells and form the definitive heart tube. By 22 hours postfertilization (26-somite stage), the heart tube is clearly beating. The regionalization of cardiac myosin heavy chain expression distinguishes the cardiac chambers at this stage, although they are not morphologically delineated until 36 hours. This work shows that cardiogenic regions can be identified in the early blastula, and that chamber restriction seems to arise in the midblastula. Additionally, it provides the basis for embryological perturbation at the single cell level, as well as for the genetic analysis of heart tube formation in the zebrafish.

Animals↗
PubMed1991

Incidence rates of firearm injuries in Galveston, Texas, 1979-1981.

Firearm injury mortality rates have been characterized in various settings, but little is known of the total magnitude of firearm injury, including morbidity. The authors determined population-based incidence rates of firearm injury among residents of Galveston, Texas, from 1979-1981 by using police, emergency department, hospital, emergency medical services, medical examiner, and vital records to identify 239 firearm injury cases. Vital records, medical examiner, and police records each identified more than 95% of the fatalities, but police records (sensitivity = 98%) were better than emergency department or hospital records (sensitivity = 82% and 28%, respectively) for identifying all nonfatal cases. The annual age-adjusted incidence rate of firearm injury was 128 per 100,000 persons. Black males, with the highest firearm injury rate (459 per 100,000 persons), were injured at 46 times the rate of white females (10 per 100,000 persons). The overall case fatality rate was 30%, including 25% of the assaults/homicides, 81% of the parasuicides/suicides, and 0% of the unintentional injuries. On the basis of the case fatality rates, an estimated 140,000 firearm injuries occur in the United States annually. The case fatality rate for penetrating head injuries was 80% versus 48% for chest injuries and 6% for all other parts of the body. The results are discussed with respect to policy recommendations for reducing firearm injuries.

Adolescent↗
PubMed1991

Identifiable reticulospinal neurons of the adult zebrafish, Brachydanio rerio.

Reticulospinal neurons of the larval zebrafish Brachydanio rerio have been categorized into 27 different types (Kimmel et al.: Journal of Comparative Neurology 205:112-127, 1982; Metcalfe et al.: Journal of Comparative Neurology 251:147-159, 1986). Nineteen of these occur as bilateral pairs which are individually identifiable. Since considerable remolding of brain structures (e.g., cell death and modifications of neuronal architecture) occurs during development, we ask if these cells are preserved in the adult zebrafish and the extent to which neuronal morphology of the larva is conserved during ontogeny. In our analysis, we studied reticular neurons from 84 brains retrogradely labelled from the spinal cord with HRP. We show that all reticulospinal types of the larva are retained without considerable change in morphology in the adult. Many neurons, including the Mauthner cell and two of its serial homologues, MiD2cm and MiD3cm, can be individually and unambiguously identified. In addition, the appearance of later developing (tertiary) neurons leads to an increase in the numbers of some neuron types. Although tertiary neurons are often isomorphic with neighboring cells, they can have unique morphologies of their own and, therefore, are also individually identifiable. We suggest that the appearance of tertiary neurons may serve to extend the behavioural repertoire of the embryo. Moreover, morphological repetitions in adjacent segments of the otic region (level of VIIIth nerve entry) may represent the replication of a functional motif, perhaps involving the C-type escape response which is known to involve the Mauthner cell.

Age Factors↗
PubMed1991

Detection of rubella virus gene sequences by enzymatic amplification and direct sequencing of amplified DNA.

We developed a rapid and sensitive polymerase chain reaction (PCR) assay for detecting and identifying rubella virus (RV). A segment of the RV gene which encodes the E1 membrane glycoprotein of RV was selected as a target for PCR amplification. Single-stranded viral RNA, extracted from infected cells or released from virions, was used as a template for reverse transcription followed by PCR amplification with two different sets of primer pairs, one nested within the other. The amplified E1 gene sequences were detected in ethidium bromide-stained agarose minigels, and their identities were verified by restriction enzyme digestion and hybridization to a probe directed at a site within the PCR target. Single-stranded DNA generated by asymmetric amplification of the target was directly sequenced by using fluorescent dideoxy-terminators and an automated procedure in order to confirm the target sequence. This PCR assay provides a rapid confirmatory test for the detection of RV by cell culture and appears to have considerable potential for the direct detection of RV in clinical specimens. The strategy used in the development of this PCR assay should be useful for developing other diagnostic PCR assays for viruses.

Animals↗