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Biomedical subjects

G Lee

Publications and source records attributed to G Lee.

At least 55 records · Page 3Linked to original sources
PubMed2001

New reproductive anomalies in fruitless-mutant Drosophila males: extreme lengthening of mating durations and infertility correlated with defective serotonergic innervation of reproductive organs.

Several features of male reproductive behavior are under the neural control of fruitless (fru) in Drosophila melanogaster. This gene is known to influence courtship steps prior to mating, due to the absence of attempted copulation in the behavioral repertoire of most types of fru-mutant males. However, certain combinations of fru mutations allow for fertility. By analyzing such matings and their consequences, we uncovered two striking defects: mating times up to four times the normal average duration of copulation; and frequent infertility, regardless of the time of mating by a given transheterozygous fru-mutant male. The lengthened copulation times may be connected with fru-induced defects in the formation of a male-specific abdominal muscle. Production of sperm and certain seminal fluid proteins are normal in these fru mutants. However, analysis of postmating qualities of females that copulated with transheterozygous mutants strongly implied defects in the ability of these males to transfer sperm and seminal fluids. Such abnormalities may be associated with certain serotonergic neurons in the abdominal ganglion in which production of 5HT is regulated by fru. These cells send processes to contractile muscles of the male's internal sex organs; such projection patterns are aberrant in the semifertile fru mutants. Therefore, the reproductive functions regulated by fruitless are expanded in their scope, encompassing not only the earliest stages of courtship behavior along with almost all subsequent steps in the behavioral sequence, but also more than one component of the culminating events.

Animals↗
PubMed2001

Staging of neurofibrillary degeneration caused by human tau overexpression in a unique cellular model of human tauopathy.

The hyperphosphorylation of human tau and its aggregation into neurofibrillary tangles are central pathogenic events in familial tauopathies and Alzheimer's disease. However, the cellular consequences of neurofibrillary tangle formation in vivo have not been directly studied because cellular models of human neurofibrillary degeneration have been unavailable until recently. Incorporation of human tau into filaments in vivo and the association of filamentous tau with cytodegeneration were first demonstrated experimentally with the overexpression of human tau in identified neurons (anterior bulbar cells) in the lamprey central nervous system. In this system, filamentous tau deposits are associated with the loss of dendritic microtubules and synapses, plasma membrane degeneration, and eventually the formation of extracellular tau deposits and cell death. Here we show that human tau hyperphosphorylation in anterior bulbar cells is spatiotemporally correlated with a highly stereotyped sequence of degenerative stages closely resembling those seen in human neurofibrillary degeneration. Hyperphosphorylated tau deposits first appear in the distal dendrites and somata, together with degenerative changes that begin in distal dendrites and progress proximally over time. This sequence is independent of the tau isoform used, the presence of epitope tags and the method used to overexpress tau, and thus has important implications for the cytopathogenesis of human neurofibrillary disease.

Animals↗
PubMed2001

The Bifurcating Neuron network 1.

The Bifurcating Neuron (BN), a chaotic integrate-and-fire neuron, is a model of a neuron augmented by coherent modulation from its environment. The BN is mathematically equivalent to the sine-circle map, and this equivalence relationship allowed us to apply the mathematics of one-dimensional maps to the design of BN networks. The study of symmetry in the BN revealed that the BN can be configured to exhibit bistability that is controlled by attractor-merging crisis. Also, the symmetry of the bistability can be controlled by the introduction of a sinusoidal fluctuation to the threshold level of the BN. These two observations led us to the design of the BN Network 1 (BNN-1), a chaotic pulse-coupled neural network exhibiting associative memory. In numerical simulations, the BNN-1 showed a better performance than the continuous-time Hopfield network, as far as the spurious-minima problem is concerned and exhibited many biologically plausible characteristics.

Action Potentials↗
PubMed2001

Morphologic features of melanocytes, pigmented keratinocytes, and melanophages by in vivo confocal scanning laser microscopy.

Confocal scanning laser microscopy (CSLM) represents a novel imaging technique for in vivo microscopic analysis of skin lesions at a level of resolution that allows morphologic analysis of microanatomic structures. We investigated the feasibility of recognizing the cellular constituents of pigmented skin lesions, such as pigmented keratinocytes, melanocytes, and melanophages, by CSLM. Fifteen pigmented lesions (five pigmented seborrheic keratoses, and 10 compound melanocytic nevi) from 15 patients were studied, as well as normal skin. After the clinical lesions were imaged by CSLM, they were biopsied or excised for examination by conventional histology for comparison of the morphologic features. In images obtained by CSLM, pigmented keratinocytes were seen as polygonal cohesive cells with variably bright granular cytoplasm. Melanocytes appeared as bright round, oval, fusiform, or dendritic cells. The architectural growth pattern of melanocytes could be analyzed. Melanocytes were identified by their nested growth pattern as aggregates of bright round to oval structures at the dermoepidermal junction or in the superficial dermis. Melanocytes were also recognizable as single cells along the dermoepidermal junction, usually separated from each other by a variable number of keratinocytes. Melanophages appeared as large bright plump cells with ill-defined cytoplasmic borders, usually located around or near vessels of the superficial dermis. Our results demonstrate that the cellular constituents of pigmented lesions can be recognized by CSLM. This technique sets a new paradigm for noninvasive quasihistologic examination of pigmented lesions in vivo and merits further evaluation for diagnostic use.

Diagnosis, Differential↗
PubMed2001

Probiotic impact on microbial flora, inflammation and tumour development in IL-10 knockout mice.

BACKGROUND: The enteric bacterial flora has been implicated in the pathogenesis of enterocolitis and colon cancer in C57BL/6 IL-10 knockout mice. Probiotic Lactobacilli modify the enteric flora and are thought to have a beneficial effect on enterocolitis. We conducted a controlled feeding trial in IL-10 knockout mice using the probiotic Lactobacillus salivarius ssp. salivarius UCC118. AIM: To determine the effect of probiotic consumption on the gastrointestinal microflora, tumour development and colitis in IL-10 knockout mice. METHODS: Twenty IL-10 knockout mice were studied (10 consumed probiotic organisms in milk and 10 consumed unmodified milk) for 16 weeks. Faecal microbial analysis was performed weekly to enumerate excretion of the probiotic UCC118, total lactobacilli, Clostridium perfringens, bacteroides, coliforms, bifidobacteria and enterococci. At sacrifice, the small and large bowel were microbiologically and histologically assessed. RESULTS: L. salivarius UCC118 was detected in faeces from all mice in the probiotic fed group, but not the control group. Faecal coliform and enterococci levels were significantly reduced in probiotic fed animals compared to the controls (P < 0.05). At sacrifice, a significant reduction in C. perfringens numbers was observed in the test mice (P < 0.05). There were no fatalities in the test group compared to two deaths from fulminant colitis in the control group. Only one test mouse developed colonic adenocarcinoma compared to five in the control group. Test animal mucosal inflammation consistently scored lower than that of the control mice. CONCLUSION: In this placebo controlled trial, modification of enteric flora in IL-10 knockout mice by probiotic lactobacilli was associated with reduced prevalence of colon cancer and mucosal inflammatory activity.

Animals↗
PubMed2001

Characterization of the 5' flanking region of the rat D(3) dopamine receptor gene.

The D(3) dopamine receptor has a restricted regional distribution in brain and is regulated by dopaminergic agents. Additionally, the D(3) gene is implicated in the pathogenesis of several neuropsychiatric disorders or in their response to pharmacological agents. Elucidating its transcription control mechanisms is therefore of interest in order to explain these biological features of the D(3) gene. In this study, the 5' flanking region of the rat D(3) gene was characterized by isolating the 5' end of its cDNA as well as 4.6 kb of genomic sequence. Analysis of this region revealed the presence of two new exons 196-bp and 120-bp long, separated by an 855-bp intron, located several kilobases upstream of the previously published coding exons. Thus, current evidence indicates that the rat D(3) gene is organized into eight exons. Transcription initiation site was determined by primer extension analysis and repeated rounds of 5' RACE and was found to localize at a pyrimidine-rich consensus 'initiator' sequence, similar to the rat D(2) gene. The D(3) promoter lacks TATA or CAAT boxes but unlike that of other dopamine receptor genes has only 52% GC content. Functional analysis of D(3) promoter deletion mutants fused to a reporter gene in TE671 cells, which endogenously express this gene, revealed strong transcriptional activity localized within 36 nucleotides upstream of transcription start site, and a potent silencer between bases --37 and --537. The D(3) promoter is inactive in C6 and COS7 cells. We conclude that the D(3) gene, similar to the closely related D(2) gene, is transcribed from a tissue specific promoter which is under intense negative control.

5' Untranslated Regions↗
PubMed2001

Newly diagnosed pulmonary sarcoidosis in HIV-infected patients.

PURPOSE: To determine the radiologic and clinical features of newly diagnosed pulmonary sarcoidosis in human immunodeficiency virus (HIV)-infected patients. MATERIALS AND METHODS: Ten HIV-infected patients (seven women, three men; age range, 26-66 years; mean age, 37 years) with newly diagnosed sarcoidosis between 1989 and 1997 were retrospectively identified. Charts were reviewed for the interval between the two diagnoses, CD4 cell count, signs or symptoms, angiotensin-converting enzyme level, and initiation of highly active antiretroviral therapy (HAART). Chest radiographs (n = 10) and computed tomographic (CT) scans (n = 8) were assessed for lymphadenopathy, pulmonary nodules, focal consolidation, reticular or granular opacities (thickened interlobular septa and ground-glass opacities at CT), cysts or cavities, and fibrosis. RESULTS: Mean interval between the two diagnoses was 3 years. Mean CD4 cell count was 213 cells per cubic millimeter. When sarcoidosis was diagnosed, eight patients had pulmonary signs or symptoms. The angiotensin-converting enzyme level was elevated in five of six patients; two developed sarcoidosis after beginning HAART. Chest radiographs revealed lymphadenopathy, pulmonary nodules, focal consolidation, reticular opacities, granular opacities, and cysts or cavities. Chest CT scans revealed lymphadenopathy, nodules, thickened interlobular septa, focal consolidation, reticular opacities, ground-glass opacities, and cysts or cavities. There was no relationship between the radiographic findings of sarcoidosis and the CD4 cell count. CONCLUSION: The radiologic features of newly diagnosed sarcoidosis in HIV-infected patients resemble the findings of sarcoidosis in non-HIV-infected patients. In HIV-infected patients receiving HAART, sarcoidosis may be a manifestation of disease related to restoration of the immune system.

Adult↗
PubMed2001

Effects of taurine on cerulein-induced acute pancreatitis in the rat.

Taurine, or 2-aminoethane sulfonic acid, is an intracellular amino acid and has been suggested to have a function in protecting biological systems from oxidative tissue damage. The aim of this study was to determine the effect of taurine against cerulein-induced acute pancreatitis in rats. Acute pancreatitis was induced by administering three subcutaneous injections of cerulein (40 microg/kg body weight) at 1-hour intervals, while taurine was administered intravenously at graded doses (30, 100, or 300 mg/kg, respectively) following the first cerulein injection. The severities of pancreatitis and lung injury were determined by measuring biochemical parameters, tissue myeloperoxidase (MPO), and histological changes. To clarify the mechanism of taurine, serum IL-1beta and TNF-alpha levels and tissue concentrations of malondialdehyde (MDA) were evaluated. In cerulein-induced acute edematous pancreatitis, treatment with taurine significantly decreased hyperamylasemia, tissue MPO, pancreatic edema, and the extent of pancreatic and pulmonary injury. Taurine decreased MDA concentration in the pancreas and lung, but not the serum cytokine concentration. We would conclude that taurine has beneficial effects in cerulein-induced acute pancreatitis and lung injuries by preventing the production of oxygen free radicals.

Acute Disease↗
PubMed2001

Magnetic resonance imaging in a military setting: a utilization analysis.

A prospective study was conducted to evaluate the use of magnetic resonance imaging (MRI) by orthopedic surgeons and residents versus the use of MRI by non-orthopedically trained health care providers in diagnosing knee pathology. Fifty patients initially evaluated by members of one of these groups who underwent subsequent knee MRI evaluation were selected to participate. Two orthopedic examiners individually examined all patients, recording clinical diagnosis and the merit of MRI evaluation in each case. Clinical accuracy, sensitivity, and specificity were compared between groups based on MRI findings. Diagnostic accuracy was similar; however, the orthopedic group displayed greater sensitivity, suggesting better clinical assessment. The study examiners observed both groups using MRI equally inappropriately and found 62% of the imaging studies unjustified. We conclude that knee MRI is used inappropriately in the current military setting. An algorithm is proposed to guide the future use of MRI in the diagnosis and management of knee pathology.

Adult↗
PubMed2001

Cumulative pregnancy rates after four embryo transfers of either fresh or frozen embryos.

PURPOSE: To evaluate in the modern era of in vitro fertilization (IVF) cumulative probability of pregnancy for the first four embryo transfers (ET) irrespective of whether the embryos were fresh or frozen. METHODS: Retrospective review over a 2 1/2 year period. Cumulative probability of pregnancy for four consecutive cycles of either fresh or frozen ETs divided into four age groups. RESULTS: The cumulative clinical and viable pregnancy rates after four ETs were 92% and 88%; 87% and 82%; 83% and 69%; and 68% and 52% for age groups <30, 30-34, 35-39, and 40-44. The cumulative rates decline with age. CONCLUSIONS: Pregnancy rates per transfer for the first four ETs regardless of age are similar even in IVF centers that emphasize frozen ETs.

Adult↗
PubMed2001

Functional expression of P-glycoprotein in rat brain microglia.

In the central nervous system, the primary targets of the human immunodeficiency virus-1 (HIV-1) are microglia, resulting in a disorder called HIV-1 dementia. P-glycoprotein (P-gp), a membrane-associated ATP-dependent efflux transporter, limits entry into the brain of numerous xenobiotics, including anti-HIV drugs (i.e., protease inhibitors). This project investigates the functional expression of P-gp in the endogenous immune cells of the brain, a parenchymal compartment not previously studied. We used a cell line (MLS-9) derived from rat microglia to study the transport of digoxin, a known P-gp substrate. Reverse transcriptase-polymerase chain reaction analysis detected mRNA for only mdr1b in MLS-9 cells, whereas both mdr1a and mdr1b mRNA were expressed in primary cultured microglia from which they were derived. Western blot analysis with the C219 antibody detected a single band at ~170 to 180 kDa in MLS-9 cells, which is the size previously reported for P-gp. Immunocytochemical analysis with the monoclonal antibodies C219, MRK16, and MAB-448 labeled P-gp protein along the plasma membrane and nuclear envelope of MLS-9 cells. [3H]Digoxin accumulation by monolayers of MLS-9 cells was significantly enhanced in the presence of any of several P-gp inhibitors (verapamil, cyclosporin A, quinidine, PSC 833), protease inhibitors (i.e., saquinavir, indinavir, and ritonavir), and sodium azide, an ATPase inhibitor. These results provide the first evidence for the functional expression of P-gp in microglia and imply that entry of pharmacological agents, including protease inhibitors, may be prevented within the brain parenchyma, as well as at the blood-brain barrier.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Spectrum of cdk-9 inhibitor activity against HIV-1 replication among various models of chronic and latent infection.

The cellular transcription elongation factor, P-TEFb, and its kinase component, cdk-9, have been implicated in the regulation of HIV-1 transactivation and transcription. We tested a panel of demonstrated cdk-9 kinase inhibitors for the ability to block HIV-1 expression in a variety of cell models representing chronic and latent/inducible infection. These agents induced cellular toxicity, in accordance with their potency for cdk-9 inhibition, with more pronounced toxicity in cultures of T-cell lineage. These agents also inhibited HIV-1 expression, in accordance with their potency for cdk-9 inhibition, in several latent models tested (representing T-lymphocytic, promonocytic and promyelocytic lineages) and using various extracellular stimuli that activate HIV-1 expression via distinct intracellular pathways. Such was the case even though some of these cell models of latent/inducible HIV-1 infection harbour viral defects in the HIV-1 transactivation mechanism. Two additional cell models of latent/inducible HIV-1 infection, both derived from Jurkat T-lymphocytes, were relatively resistant to inhibition of viral expression by these agents. This apparent lack of effect was most likely due to the narrow therapeutic range of these agents in T-cell cultures. Inhibition of HIV-1 replication by these agents was also observed in two cell models representing constitutive viral expression in cells of T-lymphocytic and promyelocytic lineages. Overall, the observed pattern of viral inhibition with these compounds suggests that cdk-9 enzymatic activity is important for HIV-1 expression irrespective of cell lineage or cellular pathway of viral activation. However, because of the non-selective nature of these inhibitors, other cellular pathways must also be considered. Agents that target cellular components essential for HIV-1 expression may provide new therapeutic approaches to limit viral replication, especially when combined with potent antiretroviral regimens.

Cell Line↗
PubMed2001

Influence of IL-6 on MDR and MRP-mediated multidrug resistance in human hepatoma cells.

The objective of this study was to examine effects of interleukin-6 (IL-6) on the expression and activity of the drug resistance transporters (MDR1 and MRP) in human hepatoma cell lines. Expression and activity of MDR1 and MRP transporters were examined in IL-6-treated and control HuH 7 and HepG2 cells using semi-quantitative RT-PCR analysis and by rhodamine 123 and 5-carboxyfluorescin efflux assays. Results from RT-PCR demonstrated expression of MRP3, MRP6, and MDR1 in HuH 7 cells and expression of MRP1, MRP2, MRP3, MRP6, and MDR1 in HepG2 cells. Compared with controls, treatment of HuH 7 cells with IL-6 (10 ng/mL, 24 h) resulted in a 1.8-fold increase in MRP-mediated efflux of 5-CF with a corresponding 1.5-fold induction of MRP3 mRNA levels (p < 0.05). Similarly, in HepG2 cells, a 2-fold increase in MRP functional activity and a 1.8-fold induction of MRP1 mRNA levels were seen in the IL-6 treated cells (p < 0.05). Treatment of cells with IL-6 was also found to cause significant reductions in the expression and activity of MDR1 in HuH 7 cells, but not in HepG2 cells. Our data suggest that IL-6 induces MRP expression and activity in human hepatoma cell lines. Suppressive effects of IL-6 on MDR1 expression and activity were also observed in HuH 7 cells. This underscores the importance of examining the regulation of multiple drug resistance proteins as these proteins may have opposing regulatory mechanisms in malignant cells.

Blood Proteins↗
PubMed2001

Drug transporters in the central nervous system: brain barriers and brain parenchyma considerations.

Drug transport in the central nervous system is highly regulated not only by the blood-brain and the blood-cerebrospinal fluid barriers but also in brain parenchyma. The novel localization of drug transporters in brain parenchyma cells, such as microglia and astrocytes, suggest a reconsideration of the present conceptualization of brain barriers as it relates to drug transport. That is, the cellular membranes of parenchyma cells act as a second "barrier" to drug permeability and express transporters whose properties appear similar to those localized at the conventional brain barriers. This review will focus on the molecular characteristics, localization, and substrate specificities of several classes of well known membrane drug transporters (i.e., the organic cation, organic anion, nucleoside, P-glycoprotein, and multidrug resistance proteins) in the brain. Comparisons to similar transporters localized within the peripheral system and clinical implications of the functional expression of specific drug transport families will be discussed when appropriate. Nutrient and neurotransmitter transporters, whose characteristics have been reviewed extensively elsewhere, will not be considered in this review.

Animals↗
PubMed2000

ZIC2 and Sp3 repress Sp1-induced activation of the human D1A dopamine receptor gene.

The human D(1A) dopamine receptor is transcribed from a tissue-specific regulated gene under the control of two promoters. An activator region (AR1) located between nucleotides -1154 and -1136 (relative to the first ATG) enhances transcription from the upstream promoter that is active in the brain. In this investigation, we sought to identify the nuclear factors that regulate the D(1A) gene through their binding to AR1 using yeast one-hybrid screening. Sp3 and Zic2 were among the positive clones isolated. Although Sp1 was not isolated from this screening and purified Sp1 alone does not bind to AR1 in gel shift experiments, this general transcription factor binds to AR1 in the presence of D(1A) expressing NS20Y nuclear extract and activates the D(1A) promoter. Thus, Sp1 appears to require an unknown factor(s) or post-translational modification to interact with AR1. On the other hand, Zic2 and Sp3 inhibit Sp1-induced activation of the D(1A) gene in an AR1-dependent manner. Zic2 and D(1A) genes have reciprocal brain regional distributions; Zic2 is expressed primarily in the cerebellum, and D(1A) is highly expressed in corpus striatum. These observations collectively suggest that one of the physiologic functions of Zic2 is repression of D(1A) gene transcription and that the intracellular balance among Sp1, Sp3 and Zic2 is important for regulating the tissue-specific expression of this dopamine receptor.

Base Sequence↗
PubMed2000

A Stat3-interacting protein (StIP1) regulates cytokine signal transduction.

Genetic and biochemical studies have led to the identification of the Stat3-Interacting Protein StIP1. The preferential association of StIP1 with inactive (i.e., unphosphorylated) Stat3 suggests that it may contribute to the regulation of Stat3 activation. Consistent with this possibility, StIP1 also exhibits an affinity for members of the Janus kinase family. Overexpression of the Stat3-binding domain of StIP1 blocks Stat3 activation, nuclear translocation, and Stat3-dependent induction of a reporter gene. These studies indicate that StIP1 regulates the ligand-dependent activation of Stat3, potentially by serving as a scaffold protein that promotes the interaction between Janus kinases and their Stat3 substrate. The ability of StIP1 to associate with several additional members of the signal transducer and activator of transcription family suggests that StIP1 may serve a broader role in cytokine-signaling events.

3T3 Cells↗
PubMed2000

Epithelial cell-specific laminin 5 is required for survival of early thymocytes.

The gene LamC2 encoding the gamma2 chain of laminin 5, an epithelial cell-specific extracellular matrix protein, was identified in a PCR-based subtracted cDNA library from mouse thymic stromal cells. The mRNA existed in two alternative forms (5.1 and 2.4 kb). The full-length message was highly expressed in SCID thymus and in a nurse cell line, but not in other thymic epithelial cell lines, while the short form was more widely expressed. In situ hybridization and immunohistochemical staining revealed laminin 5 expression mostly in the subcapsular region of the adult thymus. Addition to fetal thymic organ cultures of a cell adhesion-blocking mAb to the alpha3 chain of laminin 5 interrupted T cell development. There was a 40% reduction in the total yield of thymocytes, and the most profound decrease (75-90%) was seen in the CD25+CD44+ and CD25+CD44-subsets of the CD4-CD8- double negative fraction. Most of the surviving double negative thymocytes expressed Sca-1, and there were significant increases in the number of cells with CD69 expression and in the fraction of annexin V-stained cells. None of these changes were observed with a nonblocking anti-laminin alpha3 chain mAb. These results suggest that the interaction between double negative thymoctyes and laminin 5 made by subcapsular epithelial cells is required for the survival and differentiation of mouse thymocytes.

Animals↗