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Biomedical subjects

H Lee

Publications and source records attributed to H Lee.

At least 631 records · Page 35Linked to original sources
PubMed1993

Signal transduction through extracellular signal-regulated kinase-like pp57 blocked in differentiated cells having low protein kinase C beta activity.

pp57 is a cytoplasmic kinase which is related antigenically and functionally to the extracellular signal regulated kinase or the mitogen-activated kinase family of signal transduction proteins. Two undifferentiated colon carcinoma cell lines responded to the diacylglycerol diolein by growth and a rapid 3-4-fold increase in tyrosine phosphorylation of pp57, and smaller increases in threonine and serine phosphorylation. By enhancing tyrosine phosphorylation of pp57, diolein increased pp57 kinase activity on myelin basic protein. Two enterocytic differentiated colon carcinoma cell lines, when treated with diolein, exhibited neither increased pp57 tyrosine phosphorylation nor increased growth. Both enterocytic lines exhibited 30% of the total PKC activity, 10-20% of the abundance of PKC beta as detected by Western blotting with anti-peptide antisera, and 10-20% of the PKC beta activity, by immune complex kinase reactions, that was expressed in the undifferentiated cell lines. The abundance of three other PKC isozymes, alpha, epsilon, and zeta appeared unchanged in the undifferentiated and enterocytic lines, reflecting their common parental cell line origin. The association between loss of PKC beta activity and blocked signaling through pp57 in each of two cell lines suggests that PKC beta is part of a signal transduction system activating pp57.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1993

A generalized estimating equations approach to fitting major gene models in segregation analysis of continuous phenotypes.

This paper discusses the application of estimating equations methods based on a quadratic exponential model [Prentice and Zhao, 1991] as a potential competitor with full likelihood approaches to estimating the effect of major genes in a segregation analysis [Elston, 1981] of continuous phenotypes, in the single allele problem. We show that while the estimating equations methods based on the quadratic exponential family cannot be used by themselves to estimate all parameters of interest, an iterative two-stage approach can be used, in which the population allele frequency is first considered to be a known parameter, which permits the estimating equations method to estimate the remaining parameters. At the second stage a "pseudo-profile" loglikelihood based only on the founders is used to estimate the allele frequency. After each maximization of the pseudo-profile loglikelihood at the second stage, the parameters in the first stage are reestimated using a new value of the allele frequency, and a new value of the second stage pseudo-profile loglikelihood is obtained. We used simulated pedigree data for illustrations.

Alleles↗
PubMed1993

Use of generalized estimating equations in segregation analysis of continuous outcomes.

The use of generalized estimating equations (GEE) [Liang and Zeger, 1986] is explored as a potential alternative to maximum likelihood methods for segregation analysis of continuous phenotypes. We discuss the number of sample moments required by GEE to estimate parameters in simple major gene models, and the computational burden of the GEE methods applied to large pedigrees.

Humans↗
PubMed1993

Peptide vaccines incorporating a 'promiscuous' T-cell epitope bypass certain haplotype restricted immune responses and provide broad spectrum immunogenicity.

An ideal peptide vaccine should contain both B- and T-cell epitopes. Recognition of antigen by B cells is highly dependent on the three-dimensional conformation of the antigen whereas T cells recognize antigen only after it has been processed to release a peptide fragment which is bound to the major histocompatibility complex (MHC) class II molecule. However, T cells provide 'help' to B cells displaying the same processed, MHC-restricted form of the antigen, demonstrating that the T-cell response to a protein antigen is under genetic control. Thus, strategies for co-inclusion of T cell 'helper' epitopes with the B-cell determinant elicit immune responses that are in most cases genetically restricted to only one or a few alleles of the MHC with limited activity across divergent MHC class II haplotypes. This genetically restricted T cell stimulatory activity of peptides is a serious obstacle and consequently such constructs would be of limited practical value as a vaccine targeted to a majority of an outbred population. In the study described here, we have engineered two peptides to encompass the sequences from the universally immunogenic tetanus toxoid (TT) epitope and the contraceptive vaccine candidate lactate dehydrogenase C4 (LDH-C4). We demonstrate the feasibility of using 'promiscuous' T-cell epitopes colinearly constructed with a defined B-cell epitope to induce high titer antipeptide IgG antibodies specific for native protein antigen LDH-C4 in several inbred strains of mice, outbred mice and rabbits. There appears to be a strong correlation between the capacity for the hybrid peptides to be stimulatory for the corresponding T cells in C57BL/6 (H-2b) and C3H/HeJ (H-2k) mice and their ability to be immunogenic. This correlation, however, appears to break down in H-2d strains of mice since no antibodies were detected in BALB/c and barely detectable levels of antibodies in B10.D2 although activated T cells were detectable. Conversely, high titers of antipeptide antibodies are elicited in some strains (B10.BR (H-2k); C57BL/10 (H-2b) without detectable IL-2 responses. Finally, we show that a determinant which was previously restricted to H-2k can be rendered immunogenic in H-2b with the 'promiscuous' TT epitope. Thus, certain haplotype-restricted immune responses can be bypassed, setting forth the ground work for the design of a universal vaccine by broadening the effective response in a larger number of individuals typical of the genetically diverse outbred human population.

Amino Acid Sequence↗
PubMed1993

Detection of HTLV-I and HTLV-II infection in Africans using type-specific envelope peptides.

Antibodies to HTLV were determined in 4,630 black African individuals from Zaire, Ghana and South Africa; 185 (4%) were confirmed as seropositive. Seroprevalance was 0.2% in a group of South African women, 0.9% among Ghanaian refugees in Belgium and from less than 1% to over 15% in various sites and populations in Zaire. With the use of HTLV-I and HTLV-II type-specific envelope peptides, 93% of confirmed HTLV seropositives were classified as HTLV-I. Five persons from the Haut Zaire region had HTLV-II serological reactivities, suggesting the presence of HTLV-II or a related retrovirus in central Africa. A cluster of HTLV-I-like indeterminate western blot patterns lacking anti-p24 antibody was found in Bas Zaire.

Belgium↗
PubMed1993

Acrogranin, an acrosomal cysteine-rich glycoprotein, is the precursor of the growth-modulating peptides, granulins, and epithelins, and is expressed in somatic as well as male germ cells.

Spermatogenesis is a unique system of differentiation involving cellular remodeling and the biogenesis of sperm-specific organelles. To study the biogenesis of one such organelle, the acrosome, we have been examining the gene expression, biosynthesis, and targeting of specific acrosomal proteins during mammalian spermatogenesis. An acrosomal marker that we recently purified and began characterizing is acrogranin, a 67,000-molecular-weight glycoprotein originally isolated from guinea pig testes. This glycoprotein is detected in pachytene spermatocytes and is found later in the acrosomes of developing spermatids and sperm. Immunoblotting of several tissues and immunofluorescent localization in frozen sections of guinea pig testes suggested that acrogranin was a germ cell-specific glycoprotein that was expressed meiotically and post-meiotically. However, Northern blot analysis demonstrated that the mRNA for acrogranin was ubiquitously expressed in all guinea pig and mouse tissues examined. Furthermore, the primary structures of guinea pig and mouse acrogranins, deduced from the cDNA sequences, reveal that this glycoprotein is a cysteine-rich molecule with a motif that is tandemly repeated seven times, very similar to that of the human epithelin/granulin precursor. We conclude that guinea pig and mouse acrogranins are homologues of the precursor of the human and rat epithelin/granulin peptides previously demonstrated to have growth-modulating properties.

Acrosome↗
PubMed1993

Crystallization and preliminary X-ray crystallographic analysis of carboxylesterase from pseudomonas fluorescens.

Large crystals of carboxylesterase from Pseudomonas fluorescens have been grown in the presence of dioxane using ammonium sulfate and lithium sulfate as precipitant. They belong to the tetragonal space group P4(1)2(1)2 (or P4(3)2(1)2), with unit cell dimensions of a = 82.01 (+/-0.06) A and c = 145.44 (+/- 0.08) A. The presence of one carboxylesterase dimer in the asymmetric unit gives the crystal volume per protein mass (VM) of 2.56 A3/Da and solvent fraction of 52.0% by volume. The crystals diffract to at least 2.3 A Bragg spacing when exposed to CuK alpha X rays from a rotating anode generator. X-ray data (nearly complete to 2.6 A Bragg spacing) have been collected from a native crystal.

Carboxylic Ester Hydrolases↗
PubMed1993

Complete nucleotide sequence of HTLV-II isolate NRA: comparison of envelope sequence variation of HTLV-II isolates from U.S. blood donors and U.S. and Italian i.v. drug users.

The entire nucleotide sequence of human T-cell lymphotropic virus type II (HTLV-II) from a previously described isolate of patient NRA (HTLV-IINRA) was determined. Clones encoding the 5' LTR and gag, pol, env and tax/rex open reading frames were subcloned and sequenced on both strands. The provirus consisted of 8957 nucleotides and showed 95.2% homology with the HTLV-IIMo prototype at the nucleotide level. Less than 5% amino acid variation between HTLV-IINRA and HTLV-IIMo was observed for coding regions. Although isolate HTLV-IINRA had an additional 25 amino acids at the 3' end of tax/rex, this region was 96% homologous with the 5' end of HTLV-IIMo 3' LTR. To further investigate HTLV-II variability, a portion of the env gp46 gene derived from 9 HTLV-II infected persons was amplified by polymerase chain reaction and sequenced. Sequence was obtained for 320 nucleotides corresponding to HTLV-IIMo positions 5291 to 5610. Isolates similar to the HTLV-IIMo and HTLV-IINRA prototypes were identified, and sequences were highly conserved.

Amino Acid Sequence↗
PubMed1993

Interaction of pine cone extract fraction VI with mutagens.

Pine cone extract fraction VI (PC-VI) inhibited the mutagenicity of the promutagens tested: the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P) dose-dependently, and the aromatic amines 2-aminoanthracene (AA) and 2-acetylaminofluorene (AAF) at high concentrations. PC-VI had no effect on the mutagenicity of the direct-acting mutagens 2-(2-furyl)-3-(5-nitrofuryl)acrylamide (AF-2) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), but inhibited the mutagenicity of the direct-acting mutagen N-hydroxy 2-acetylaminofluorene (N-OH AAF, proximate mutagen of AAF). The addition of PC-VI to rat hepatic microsomes resulted in a decrease of their enzyme activities, especially NADPH-cytochrome c reductase. By gas-chromatographic analysis of B[a]P or AA contents after incubation of B[a]P or AA and PC-VI and S9 mix, the inhibition of hepatic metabolizing enzymes and the interaction between AA and PC-VI were confirmed. On the other hand, PC-VI had no effect on the DNA repair systems for B[a]P- or AA-induced mutagenesis. We conclude that PC-VI shows indirect antimutagenicity by interfering with cytochrome P-450-dependent bioactivation and by direct interaction with AA and the proximate mutagenic product of AAF.

2-Acetylaminofluorene↗
PubMed1993

PDGF-BB and TGF-alpha rescue gastrulation, spiculogenesis, and LpS1 expression in collagen-disrupted embryos of the sea urchin genus Lytechinus.

Development and LpS1 transcription in Lytechinus embryos are arrested at the mesenchyme blastula stage when collagen deposition is inhibited by the lathrytic agent beta-aminopropionitrile (BAPN) or by proline analogs. We found that human recombinant platelet derived growth factor-BB (PDGF-BB) and transforming growth factor-alpha (TGF-alpha) synergistically rescue collagen disrupted/developmentally arrested L. pictus and L. variegatus embryos so that development and RNA accumulation of LpS1 proceed. In addition, nonspecific antagonists of PDGF block gastrulation and LpS1 RNA accumulation. The embryos recover and LpS1 RNA accumulation resumes when the antagonists are removed. These data suggest that a growth factor mediated pathway, associated with the ECM, is required for sea urchin gastrulation, spiculogenesis, and LpS1 gene activation.

Animals↗
PubMed1993

Transfusion transmission of human T-lymphotropic virus types I and II: serologic and polymerase chain reaction results in recipients identified through look-back investigations.

To determine the transmissibility of human T-lymphotropic virus types I and II (HTLV-I and HTLV-II) via transfusion, persons who, from 1983 to 1989, received blood components donated by persons who subsequently tested anti-HTLV-I-positive were evaluated. It was found that 16 (30%) of 54 evaluable recipients of transfused cellular components became infected with one of the HTLVs: 8 had HTLV-I and 8 had HTLV-II. Forty percent of platelet recipients and 28 percent of red cell recipients acquired infection. The rate of transmission of HTLV-I and HTLV-II was significantly correlated with storage age of red cell units prior to transfusion: 47 percent for red cells stored < or = 14 days and 0 for red cells stored > 14 days (p < 0.01). Multiple confirmatory serologic tests performed in 46 anti-HTLV-I enzyme immunoassay-negative recipients revealed that HTLV infection could not be excluded in 3 recipients of blood components from HTLV-II-infected donors. Polymerase chain reaction established HTLV-II infection in one recipient, and the other two recipients could not be classified with respect to HTLV infection status. It appears that some HTLV-II-infected transfusion recipients will not be detected by existing HTLV-I antigen-based reagents. If it is deemed necessary to initiate or continue look-back programs to detect transfusion transmission of HTLV-II infection, it is suggested that the current testing algorithm be modified in selected cases.

Erythrocyte Transfusion↗
PubMed1993

Transfusion-associated transmission of human T-lymphotropic virus types I and II: experience of a regional blood center.

During a 22-month period, 78,000 blood donors were screened for human T-lymphotropic virus types I and II (HTLV-I/II) at Belle Bonfils Memorial Blood Center (Denver, Colorado). Positive donors and the living recipients of their previously donated blood components were evaluated for risk factors and symptoms related to HTLV-I infection, were screened by enzyme immunoassay, confirmed by Western blot for HTLV-I/II, and subsequently tested by polymerase chain reaction and peptide enzyme immunoassay to distinguish between HTLV-I and -II infection. Six seropositive blood donors (0.008%) were identified; four were typed as having HTLV-I infection and two as having HTLV-II. Of 18 living recipients of components from seropositive donors, none had risk factors for HTLV-I infection prior to transfusion and none had signs or symptoms of HTLV-I infection at follow-up. The mean time from transfusion to testing was 6.4 years. Seven recipients of HTLV-I-infected components were HTLV seropositive; all were typed as having HTLV-I. A possible case of posttransfusion HTLV-I-associated myelopathy was identified in one patient who died before complete evaluation. One possible case of transfusion-associated HTLV-II was identified. These data further support the continued screening of blood donors for HTLV-I/II.

Adult↗
PubMed1993

Mutation in Escherichia coli and mammalian cells induced by closely spaced 1-methylpyrene-deoxyadenosine adducts in opposite DNA strands.

Twenty-eight base complementary oligonucleotides were synthesized with deoxyadenosine residues modified at the N6 position with 1-methylpyrene (MP) specifically positioned 3 bp apart in opposite DNA strands. Doubly modified constructs as well as non-modified and singly modified constructs were ligated into M13mp19 and an SV40-based shuttle vector pSVL-lac for transfection into Escherichia coli and large T-antigen-expressing monkey kidney epithelial cells respectively. Repair of MP adducts was analyzed by direct nucleotide sequencing after selection of clones containing the 28mer construct. In E. coli, double MP adducts induced base substitutions at positions mainly adjacent to modified adenines, while single MP adducts were not mutagenic. Single base insertions were also induced proximal to modified adenines. The frequency of mutation induced by double MP adducts in E. coli was approximately 4% (eight mutations out of 196 analyzed). In monkey kidney cells, double MP adducts induced one and three base deletions and single base insertions. Base substitution was observed in constructs containing non-modified and singly modified adenine residues, indicative of a significant spontaneous mutation rate. The frequency of mutation induced by double MP adducts in monkey kidney cells was approximately 9% (six mutations out of 66 clones analyzed). Modification of adenine residues by MP caused termination of DNA replication by E. coli DNA polymerase I (Klenow fragment) in vitro at the position opposite the MP adduct and at the preceding base. The repair of closely spaced polycyclic aromatic hydrocarbon adducts in opposite DNA strands is discussed as it relates to mutagenesis and carcinogenesis in mammalian cells.

Animals↗
PubMed1993

A new method for computed tomography image compression using adjacent slice data.

RATIONALE AND OBJECTIVES: The authors developed and subjectively evaluated an interslice compression algorithm that explores the redundancy among adjacent slices of an x-ray computed tomography (CT) scan. This algorithm has been compared to an intraslice compression algorithm based on the two-dimensional discrete cosine transform. METHODS: Nine x-ray CT head images from three patients were compressed with this interslice method at compression ratios of 5:1, 10:1, and 15:1. The same images were also compressed with the intraslice method at the same ratios. Six radiologists judged quality of randomly selected compressed and decompressed images compared to that of the originals. The evaluation data were analyzed statistically with the analysis of variance and Tukey's multiple comparison. Kappa-like statistics (Williams index and O'Connell and Dobson indexes) were also calculated to measure the agreement among readers beyond the amount expected by chance. RESULTS: The interslice coding algorithm showed significantly better quality than the intraslice method at significance level 0.05, even though there was no difference in the objective distortion measure (signal-to-noise ratio). Also, the quality of 10:1 compressed images with the interslice coding algorithm was not significantly different from that of the originals at level 0.05. While large variations in agreement occurred among readers, the overall agreement was statistically significant. CONCLUSIONS: By using adjacent slice information in compressing x-ray CT images, significantly better quality in compressed and decompressed images was achieved. While 10:1 compressed images with the interslice algorithm were not significantly different from the originals in quality at level 0.05, effect on diagnostic accuracy remains to be investigated.

Algorithms↗
PubMed1993

Pseudomonas aeruginosa UG2 rhamnolipid biosurfactants: structural characterization and their use in removing hydrophobic compounds from soil.

The structure of two rhamnolipid biosurfactants produced by Pseudomonas aeruginosa UG2 was studied. Analyses by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy showed these two rhamnolipids to be alpha-L-rhamnopyranosyl-beta-hydroxydecanyol-beta-hydroxydecanoate and 2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyl-beta-hydroxydecan oyl-beta- hydroxydecanoate. The ability of UG2 rhamnolipid biosurfactants to enhance removal of naphthalene, anthracene, phenanthrene, fluorene, 2,2',5,5'-tetrachlorobiphenyl, and 3,3',4,4',5,5'-hexachlorobiphenyl into the aqueous phase was affected by soil type, hydrocarbon equilibration time, and biosurfactant adsorption to soil. Partially purified UG2 biosurfactants at a concentration of 5 g/L removed approximately 10% more hydrocarbon from a sandy loam soil than slit loam soil. High levels of UG2 rhamnolipids adsorbed to soil. In 18% (w/v) soil slurries 74, 49, 38, and 20% of 0.5, 1, 2, and 5 g UG2 rhamnolipids/L, respectively, were bound to the soil phase. Sodium dodecyl sulphate recovered lower levels and Witconol SN70 higher levels of phenanthrene and 2,2',5,5'-tetrachlorobiphenyl than UG2 biosurfactants.

Carbohydrate Sequence↗
PubMed1993

Distribution of Borrelia burgdorferi specific antibody among patients with juvenile rheumatoid arthritis in Korea.

Lyme disease, a multi-systemic infection occurring worldwide, has yet to be reported in Korea, although the spirochete B. burgdorferi, known as the causative organism of the disease, has recently been isolated from the vector tick Ixodes persulcatus in the region. To contribute to revealing whether Lyme disease exists in Korea or not, B. burgdorferi specific antibodies (IgG, IgM, and/or IgA) were measured by three individual enzyme-linked immunosorbent assays (ELISA) utilizing different antigens in 38 patients with juvenile rheumatoid arthritis (JRA) which shares a number of clinical features with Lyme arthritis. The antibody prevalence rates in patients with JRA were various depending on the antigens (21% of IgG and IgM antibodies to purified organisms, 0% for IgG antibody to purified native flagella, and 5% for IgG, IgM, and IgA antibodies to recombinant p39) and were not different compared to 39 controls (21%, 0%, and 0% respectively). The antibody prevalence rates compared in various subgroups of patients with JRA according to types of JRA, length of illness, age, and sex were not different. Comparing the three different antigens, the greatest number of positive responders were yielded by purified organisms followed by p39 and purified flagellin, however the possibility of nonspecificity with purified organisms remained. The data indicate that serologic tests using ELISA fail to illustrate Lyme disease among 38 patients with JRA in Korea.

Adolescent↗