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Biomedical subjects

S Lee

Publications and source records attributed to S Lee.

At least 199 records · Page 11Linked to original sources
PubMed2001

Bystander activation involving T lymphocytes in herpetic stromal keratitis.

Herpes simplex virus infection of mouse corneas can lead to the development of an immunopathological lesion, termed herpetic stromal keratitis (HSK). Such lesions also occur in TCR-transgenic mice backcrossed to SCID (TgSCID) that are unable to mount detectable HSV-specific immune responses. The present study demonstrates that lesion expression in such mice depends on continuous viral replication, whereas in immunocompetent mice, lesions occurred even if virus replication was terminated at 4 days after infection. The continuous replication in TgSCID mice was considered necessary to produce an activating stimulus to CD4(+) T cells that invade the cornea. Lesions in TgSCID were resistant to control by cyclosporin A, but were inhibited by treatment with rapamycin. This result was interpreted to indicate that T cell activation involved a non-TCR-mediated cytokine-driven bystander mechanism. Bystander activation was also shown to play a role in HSK lesions in immunocompetent mice. Accordingly, in immunocompetent DO11.10 mice, lesions were dominated by KJ1.26(+) OVA-specific CD4(+) T cells that were unreactive with HSV. In addition, KJ1.26(+) HSV nonimmune cells parked in ocularly infected BALB/c mice were demonstrable in HSK lesions. These results provide insight for the choice of new strategies to manage HSK, an important cause of human blindness.

Adoptive Transfer↗
PubMed2001

Lignification induced by pseudomonads harboring avirulent genes on Arabidopsis.

The responses of Arabidopsis thaliana ecotypes to the bacterial pathogen Pseudomonas syringae pv. maculicola 4326 (Psm4326) harboring cloned avirulence genes avrB and avrRpt2 from P. syringae pv. glycinea were examined. Psm4326 containing avirulent genes, avrB and avrRpt2 induced lignification and peroxidase activities in the bacteria infiltrated leaves of Col-O only and not in Mt-O, Bla-2 and Po-1. However, Arabidopsis ecotypes infiltrated with Psm4326 harboring with and without avirulent genes all showed differential induction of mRNA for peroxidase gene and lignin accumulation up to 24 h after infiltration. Only avrB gene in Col-O showed strong corelationship between peroxidase mRNA expression as well as lignification gradually up to 36 h after infiltration. These results extend previous observations that avirulence genes from pathogens of one host plant can be recognized by non-host plants and provide the genetic framework for analysis of the plant-specific response to the bacterial avirulent gene products in A. thaliana.

Arabidopsis↗
PubMed2001

Classification of CD and absorption spectra in the Soret band of H(2)TMPyP bound to various synthetic polynucleotides.

The binding mode of porphyrins, namely meso-tetrakis(N-methyl pyridinium-4-yl)porphyrin (H(2)TMPyP), was classified in this work by absorption and circular dichroism(CD) spectroscopy. The three binding modes of intercalation, minor groove binding and external stacking exhibit their own characteristic absorption and CD spectra. Intercalation occurs for this porphyrin when bound to GC-rich polynucleotides at a low mixing ratio, as expected. This binding mode produces hypochromism and a red shift in the absorption band and a negative CD band in the Soret absorption region. When it is complexed with AT-rich polynucleotides at a low mixing ratio, hypochromism and a red shift in the absorption band and a positive CD peak is apparent, and this species can easily be assigned to the minor groove-binding mode. For both AT- and GC-rich polynucleotides at a high binding ratio, an excitonic CD was apparent. The sign of excitonic CD depends on the order of the DNA bases; the CD spectra of H(2)TMPyP complexed with non-alternating homopolymer (disregarding the nature of base pairs, i.e. AT or GC) are characterized by a positive band at short wavelengths followed by a negative band at long wavelengths. In contrast, those complexed with alternating polynucleotide were opposite to those of non-alternating homopolymers.

Chemical Phenomena↗
PubMed2001

The X-ray structure of Aspergillus aculeatus polygalacturonase and a modeled structure of the polygalacturonase-octagalacturonate complex.

Polygalacturonases hydrolyze the alpha-(1-4) glycosidic bonds of de-esterified pectate in the smooth region of the plant cell wall. Crystal structures of polygalacturonase from Aspergillus aculeatus were determined at pH 4.5 and 8.5 both to 2.0 A resolution. A. aculeatus polygalacturonase is a glycoprotein with one N and ten O-glycosylation sites and folds into a right-handed parallel beta-helix. The structures of the three independent molecules are essentially the same, showing no dependency on pH or crystal packing, and are very similar to that of Aspergillus niger polygalacturonase. However, the structures of the long T1 loop containing a catalytic tyrosine residue are significantly different in the two proteins. A three-dimensional model showing the substrate binding mode for a family 28 hydrolase was obtained by a combined approach of flexible docking, molecular dynamics simulations, and energy minimization. The octagalacturonate substrate was modeled as an unbent irregular helix with the -1 ring in a half-chair ((4)H(3)) form that approaches the transition state conformation. A comparative modeling of the three polygalacturonases with known structure shows that six subsites ranging from -4 to +2 are clearly defined but subsites -5 and +3 may or may not be shaped depending on the nearby amino acid residues. Both distal subsites are mostly exposed to the solvent region and have weak binding affinity even if they exist. The complex model provides a clear explanation for the functions, either in catalysis or in substrate binding, of all conserved amino acid residues in the polygalacturonase family of proteins. Modeling suggests that the role of the conserved Asn157 and Tyr270, which had previously been unidentified, may be in transition state stabilization. In A. niger polygalacturonase, the long T1 loop may have to undergo conformational change upon binding of the substrate to bring the tyrosine residue close to subsite -1.

Amino Acid Sequence↗
PubMed2001

Investigation of inclusion complexation of paclitaxel by cyclohenicosakis-(1-->2)-(beta-D-glucopyranosyl), by cyclic-(1-->2)-beta-D-glucans (cyclosophoraoses), and by cyclomaltoheptaoses (beta-cyclodextrins).

Inclusion complexation of the poorly soluble drug, paclitaxel, was investigated with various host cyclooligosaccharides such as a family of isolated neutral cyclohenicosakis-(1-->2)-(beta-D-glucopyranosyl) (cyclic-(1-->2)-beta-D-glucans, cyclosophoraoses), dimethyl cyclomaltoheptaose (cyclodextrins, DM-beta-CD) and hydroxypropyl cyclomaltoheptaose (cyclodextrins, HP-beta-CD). Quantitative analysis with high-performance liquid chromatography (HPLC) indicated that all three cyclic oligosaccharides could increase the solubility of paclitaxel, where DM-beta-CD gave the best results and a family of cyclosophoraoses and HP-beta-CD, both gave similar results. Complexation of host molecules with paclitaxel was studied by NMR and fluorescence spectroscopic analyses. NMR spectroscopic analysis showed that the aromatic regions of paclitaxel experienced noticeable changes of the chemical shifts or peak shapes upon interaction with host molecules. The relatively bulky cyclosophoraoses allowed favorable accessibility to either the B-ring or A-ring of paclitaxel, while DM-beta-CD and HP-beta-CD allowed accessibility to all the aromatic rings including the C ring. The interaction of DM-beta-CD with paclitaxel greatly increased the fluorescence intensity compared with other host molecules, suggesting the more effective partitioning of a moderate fluorophore into a hydrophobic cluster adjacent to the C-ring of paclitaxel.

Cyclodextrins↗
PubMed2001

Palladium-catalyzed synthesis of arylamines from aryl halides and lithium bis(trimethylsilyl)amide as an ammonia equivalent.

[reaction: see text]. A simple, palladium-catalyzed method to convert aryl halides to the parent anilines using lithium bis(trimethylsilyl)amide (LiN(SiMe3)2) is reported. The reaction is catalyzed by Pd(dba)2 and P(t-Bu)3 and can be run with as little as 0.2 mol % of catalyst. The reaction is faster than competing generation of benzyne intermediates and, therefore, provides the aniline products regiospecifically.

Amines↗
PubMed2001

Effect of mutations in Pneumocystis carinii dihydropteroate synthase gene on outcome of P carinii pneumonia in patients with HIV-1: a prospective study.

BACKGROUND: Investigators have reported that patients infected with Pneumocystis carinii containing mutations in the DHPS (dihydropteroate synthase) gene have a worse outcome than those infected with P carinii containing wild-type DHPS. We investigated patients with HIV-1 infection and P carinii pneumonia to determine if DHPS mutations were associated with poor outcomes in these patients. METHODS: We compared presence of mutations at the DHPS locus with survival and response of patients to co-trimoxazole or other drugs. FINDINGS: For patients initially given co-trimoxazole, nine (14%) of 66 with DHPS mutant died, compared with nine (25%) of 36 with wild type (risk ratio50.55 [95% CI=0.24-1.25]; p=0.15). Ten (15%) of 66 patients with a DHPS mutant did not respond to treatment, compared with 13 (36%) of 36 patients with the wild type (0.42 [0.20-0.86]; p=0.02). For patients aged 40 years or older, four (14%) of 29 with the mutant and nine (56%) of 16 with the wild type died (0.25 [0.09-0.67]; p=0.005). INTERPRETATION: These results, by contrast with those of previous studies, suggest that patients with wild-type P carinii do not have a better outcome than patients with the mutant when given co-trimoxazole. Our results suggest that presence of a DHPS mutation should be only one of several criteria guiding the choice of initial drug treatment of P carinii pneumonia in patients with HIV-1 infection.

AIDS-Related Opportunistic Infections↗
PubMed2001

Diffractively produced charm final states in 800-GeV/c pp collisions.

We report the first observation of diffractively produced open charm in 800-GeV/c pp collisions of the type pp-->pD*X. We measure cross sections of sigma(diff)(D*+) = (0.185+/-0.044+/-0.054) (mu)b and sigma(diff)(D(*-)) = (0.174+/-0.034+/-0.029) (mu)b. Our measurements are based on 4.3x10(9) events recorded by FNAL E690 in the fixed-target run of 1991. We compare our results with previous fixed-target charm experiments.

Journal Article↗
PubMed2001

An Alu cassette in the human epithelial sodium channel.

Here, we report the presence of two splice variants of the human epithelial sodium channel alpha subunit (h alpha ENaC) containing Alu cassette, namely h alpha ENaC+22 and h alpha ENaC+Alu, in various tissues. Functional expression of these splice variants with hENaC beta and gamma subunits produced loss-of-channel activity in the Xenopus oocyte expression system. Interestingly, coexpression of h alpha ENaC+22 or h alpha ENaC+Alu, respectively, with wild type hENaC alpha, beta, and gamma subunits enhanced the expression of amiloride-sensitive current in oocytes. The presence of Alu sequences in the 3'-untranslated region of h gamma ENaC was also identified.

Alternative Splicing↗
PubMed2001

Recombinant human macrophage colony-stimulating factor augments pulmonary host defences against Aspergillus fumigatus.

The in vivo and ex vivo effects of macrophage colony-stimulating factor (M-CSF) were studied in a profoundly neutropenic rabbit model in order to determine its potential to augment pulmonary host defence against Aspergillus. M-CSF (100-600 microg/kg/d) was administered prophylactically to neutropenic rabbits with pulmonary aspergillosis starting three days pre-inoculation and then throughout neutropenia. Rabbits receiving M-CSF had significantly increased survival (P=0.01) and decreased pulmonary injury, as measured by decreased pulmonary infarction (P=0.004), when compared with untreated controls. Microscopic studies demonstrated greater numbers of activated pulmonary alveolar macrophages (PAMs) in lung tissue of rabbits receiving M-CSF, in comparison to controls (P<0.001). PAMs harvested from rabbits treated with M-CSF had a significantly greater percent phagocytosis of Aspergillus fumigatus conidia than did PAMs from controls (P=0.04). These data indicate that prophylactic administration of M-CSF augments pulmonary host defence against A. fumigatus and suggest a potential role for this cytokine as adjunctive therapy in the treatment of pulmonary aspergillosis in the setting of profound neutropenia.

Animals↗
PubMed2001

Down modulation of IL-18 expression by human papillomavirus type 16 E6 oncogene via binding to IL-18.

To understand modulation of a novel immune-related cytokine, interleukin-18, by human papillomavirus type (HPV) 16 oncogenes, HaCaT, normal keratinocyte cell line, and C-33A, HPV-negative cervical cancer cell line, were prepared to establish stable cell lines expressing E6, E6 mutant (E6m), E6E7, or E7 constitutively. Expressions of various HPV oncogene transcripts were identified by RT-PCR. Expression of HPV oncogene E6 was reversely correlated to the expression of interleukin-18, a novel pro-inflammatory cytokine. The expression of E6 in C-33A, independent of E6 splicing, resulted in decreased IL-18 expression and that of IL-18 was also significantly reduced in HaCaT cells expressing E6. The level of p53 was reduced in C-33A cells expressing E6 whereas not altered in HaCaT cells expressing E6, suggesting that E6 downregulated IL-18 expression via an independent pathway of p53 degradation in HaCaT cells which have a mutated p53 form. However, E7 did not affect IL-18 expression significantly in both C-33A and HaCaT cells. Cotransfection experiments showed that E6 oncogene did not inhibit the activities of IL-18 promoter P1 and P2, suggesting that E6 oncogene indirectly inhibited IL-18 expression. Taken together, E6, E6m and E6/E7 inhibited IL-18 expression with some variation, assuming that cells expressing E6 oncogene can evade immune surveillance by downregulating the expression of immune stimulating cytokine gene, IL-18, and inhibiting the cascade of downstream effects that follow activation of the IL-18 receptor.

Binding, Competitive↗
PubMed2001

Hepatitis B virus X protein differentially activates RAS-RAF-MAPK and JNK pathways in X-transforming versus non-transforming AML12 hepatocytes.

The hepatitis B virus (HBV) X protein (pX) is implicated in hepatocarcinogenesis of chronic HBV patients by an unknown mechanism. Activities of pX likely relevant to hepatocyte transformation include activation of the mitogenic RAS-RAF-MAPK and JNK pathways. To assess the importance of mitogenic pathway activation by pX in transformation, we employed a cellular model system composed of two tetracycline-regulated, pX-expressing cell lines, constructed in AML12-immortalized hepatocytes. This system includes the differentiated 3pX-1 and the de-differentiated 4pX-1 hepatocytes. Our studies have demonstrated that conditional pX expression transforms only 3pX-1 cells. Here, comparative in vitro kinase assays and various in vivo analyses demonstrate that pX affects an inverse activation of RAS-RAF-MAPK and JNK pathways in 3pX-1 versus 4pX-1 cells. Sustained pX-dependent RAS-RAF-MAPK pathway activation is observed in pX-transforming 3pX-1 cells, whereas sustained pX-dependent JNK pathway activation is observed in pX non-transforming 4pX-1 cells. This differential, pX-dependent mitogenic pathway activation affects differential activation of cAMP-response element-binding protein and c-Jun and determines the proliferative response of 3pX-1 and 4pX-1 cells. Furthermore, tetracycline-regulated, pX-NLS-expressing cell lines demonstrate that expression of the nuclear pX-NLS variant minimally activates the RAS-RAF-MAPK pathway and results in markedly reduced transformation. These results link sustained, pX-mediated activation of RAS-RAF-MAPK pathway to hepatocyte transformation.

Cell Division↗
PubMed2001

Neural recognition molecule NB-2 of the contactin/F3 subgroup in rat: Specificity in neurite outgrowth-promoting activity and restricted expression in the brain regions.

NB-2, a neural cell recognition molecule of the contactin/F3 subgroup, promoted neurite outgrowth of the cerebral cortical neurons but not the hippocampal neurons. NB-2 in rat became apparent after birth at protein level, reaching a maximum at postnatal day 14 in the cerebrum and postnatal day 3 in the cerebellum. NB-2 in the cerebellum declined abruptly thereafter. In situ hybridization demonstrated that NB-2 mRNA was highly expressed in regions implicated in the central auditory pathway, including the cochlear nuclei, superior olive, inferior colliculi, medial geniculate nuclei, and auditory cortex. In addition, a high level of NB-2 expression was observed in the accessory olfactory bulb, thalamic nuclei, facial nucleus, and inferior olive. By immunohistochemistry, intense immunoreactivity against NB-2 was also detected in the auditory pathway. Thus, NB-2 is expressed in highly restricted brain regions, including the auditory system, suggesting that it plays specific roles in the development and/or maturation of the regions.

Aging↗
PubMed2001

Membrane rejection of nitrogen compounds.

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

Membranes, Artificial↗
PubMed2001

Tracking the estrogen receptor in neurons: implications for estrogen-induced synapse formation.

Estrogens (E) and progestins regulate synaptogenesis in the CA1 region of the dorsal hippocampus during the estrous cycle of the female rat, and the functional consequences include changes in neurotransmission and memory. Synapse formation has been demonstrated by using the Golgi technique, dye filling of cells, electron microscopy, and radioimmunocytochemistry. N-methyl-d-aspartate (NMDA) receptor activation is required, and inhibitory interneurons play a pivotal role as they express nuclear estrogen receptor alpha (ERalpha) and show E-induced decreases of GABAergic activity. Although global decreases in inhibitory tone may be important, a more local role for E in CA1 neurons seems likely. The rat hippocampus expresses both ERalpha and ERbeta mRNA. At the light microscopic level, autoradiography shows cell nuclear [3H]estrogen and [125I]estrogen uptake according to a distribution that primarily reflects the localization of ERalpha-immunoreactive interneurons in the hippocampus. However, recent ultrastructural studies have revealed extranuclear ERalpha immunoreactivity (IR) within select dendritic spines on hippocampal principal cells, axon terminals, and glial processes, localizations that would not be detectable by using standard light microscopic methods. Based on recent studies showing that both types of ER are expressed in a form that activates second messenger systems, these findings support a testable model in which local, non-genomic regulation by estrogen participates along with genomic actions of estrogens in the regulation of synapse formation.

Animals↗
PubMed2001

Energy isosbestic points in third-row transition metal alloys.

The total electronic energies of the six electrons per atom (e per atom) alloys W, TaRe, HfOs, and YIr and the seven electrons per atom alloys Re, WOs, TaIr, HfPt, and YAu have been calculated in the local density approximation of density functional theory. When one considers common alloy structures such as atomically ordered variants of the body-centered cubic, face-centered cubic, or hexagonally closest packed structures and plots the total electronic energy as a function of the unit cell parameter, one finds for both the six and seven electrons per atom series energetic isosbestic points. An energetic isosbestic point corresponds to a critical value of the size parameter for which all members of the 6 or 7 e per atom series of compounds have nearly identical total electronic energy. Just as in spectroscopy, where the existence of such isosbestic points is the hallmark of two compounds present in the mixture, an energy isosbestic point implies there are just two separate energy curves. For both series it is found that the total electronic energy can be viewed as the weighted sum of a purely covalent term and a purely ionic term. Two semi-quantitative models are proposed to account for these two separate energies. In the first model the total energy is viewed as the sum of the elemental structural energy plus an ionic energy based on the Born-Mayer ionic model. In the second model one considers within the confines of mu2-Hückel theory the evolution of the total electronic energy as the Coulombic Hii integrals change in value.

Journal Article↗
PubMed2001

The significance of granzyme B expression in patients with angiocentric lymphoma of the head and neck.

BACKGROUND: The objectives of this study were to establish a correlation between granzyme B expression and the clinicopathologic characteristics of patients with angiocentric lymphomas of the head and neck and to determine whether the expression of granzyme B had any influence on the treatment outcomes of such patients. METHODS: Fifty-seven patients with angiocentric lymphoma of the head and neck who were treated between 1987 and 1996 were divided into two groups according to whether their tumors were immunoreactive for granzyme B: the granzyme B negative group (n = 22 patients) and the granzyme B positive group (n = 35 patients). The clinicopathologic features, immunohistochemical findings, patterns of disease failure, and survival data for the granzyme B positive group were compared with those for the granzyme B negative group. RESULTS: Greater than 60% of patients with angiocentric lymphoma of the head and neck were shown to have granzyme B positive tumors. All tumors that expressed granzyme B also consistently coexpressed CD56, indicating that they probably are the neoplastic equivalent of either natural killer (NK) cells or activated cytotoxic T cells. Although there were no significant differences in histopathologic features or expression of CD45RO and polyclonal CD3-epsilon between the groups, the Epstein-Barr virus genomes were detected more frequently in the granzyme B positive group compared with the granzyme B negative group. Despite a similar rate of complete remission after initial treatment, the locoregional recurrence rate of patients in the granzyme B positive group was much higher compared with patients in the granzyme B negative group. In addition, compared with patients in the granzyme B negative group, patients in the granzyme B positive group also had an increased risk of systemic disease recurrence and a decreased overall survival rate. CONCLUSIONS: The data indicate that the cytotoxic granule-associated protein, granzyme B, may be used as an additional marker for identifying NK/T-cell lymphoma and as a prognostic indicator for risk assessment in patients with angiocentric lymphoma of the head and neck.

Adult↗