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H Yeh

Publications and source records attributed to H Yeh.

At least 37 records · Page 2Linked to original sources
PubMed1993

Synthesis of di- to penta-saccharides related to the O-specific polysaccharide of Shigella dysenteriae type 1, and their nuclear magnetic resonance study.

The syntheses of oligosaccharide fragments of the O-specific polysaccharide of the lipopolysaccharide of Shigella dysenteriae type 1 are described, including disaccharides methyl O-alpha-D-mannopyranosyl-(1-->2)-alpha-D-galactopyranoside (1), and methyl O-(2-deoxy-2-propionamido-alpha-D-glucopyranosyl)-(1-->3)-alpha-L- rhamnopyranoside (2), trisaccharide methyl O-alpha-D-galactopyranosyl-(1-->3)-O-(2-acetamido-2-deoxy-alpha-D- glucopyranosyl)-(1-->3)-alpha-L-rhamnopyranoside (3), tetrasaccharide methyl O-alpha-L-rhamnopyranosyl-(1-->2)-O-alpha-D-galactopyranosyl-(1-->3)- O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-(1-->3)-alpha-L-rhamno -pyranoside (4), and pentasaccharide methyl O-alpha-L-rhamnopyranosyl-(1-->3)-O-alpha-L- rhamnopyranosyl-(1-->2)-O-alpha-D-galactopyranosyl- (1-->3)-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-(1-->3)-alpha-L- rhamnopyranoside (5). The following monosaccharide building blocks were used as starting compounds: methyl 6-O-tert-butyldiphenylsilyl-3,4-O-isopropylidene-alpha-D-galact opy ranoside (8), methyl 3,4,6-tri-O-benzyl-2-O-(4-methoxybenzyl)-1-thio-beta-D- galactopyranoside (11), methyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-1-thio-alpha- D-glucopyranoside (16), methyl 2-azido-4,6-O-benzylidene-2-deoxy-1-thio-alpha-D- glucopyranoside (18), methyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside (21), methyl 2,3,4-tri-O-benzoyl-1-thio-alpha-L-rhamnopyranoside (22), 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl bromide (23), and methyl 4-O-benzyl-alpha-L-rhamnopyranoside (24). Nuclear magnetic resonance data indicate that oligosaccharides 4 and 5 partially mimic the conformation of the O-specific polysaccharide of S. dys. type 1.

Antigens, Bacterial↗
PubMed1993

Cervical spine abnormalities in institutionalized adults with Down's syndrome.

The prevalence of increased anterior atlanto-odontoid distance (AAOD), a risk factor for spinal cord compression, and degenerative disease of the cervical spine (DDCS) in a population of institutionalized adults with Down's syndrome (DS) was determined and compared with age- and sex-matched 'normals' presenting to a hospital emergency department. Radiographs of the cervical spines of 99 adults with DS and 198 'normals' were compared using a standardized rating scale. The prevalence of an AAOD of 3 mm or greater, the threshold of risk from the literature, was 8% for DS cases and 2% for controls (P < 0.01). The mean AAOD for DS cases was 2.0 +/- 1 mm and for controls 1.5 +/- 0.5 mm (P < 0.01). There was a negative correlation between AAOD and age of DS cases. The prevalence of any degree of DDCS among the DS cases was 64%, the controls 39% (P < 0.001); for moderate or severe DDCS the prevalence among DS cases was 45%, controls 12% (P < 0.001). The prevalence of DDCS increased with age in both groups, but the severity of DDCS was significantly increased with age in both groups, but the severity of DDCS was significantly greater for DS individuals in all age groups. The levels of the cervical spine affected ranged from C2 to C6; the most commonly affected level was C5-C6. While DS adults are at increased theoretical risk for spinal cord compression due to increased AAOD, its clinical significance would appear to be small and to decline with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Analysis of gene expression in single live neurons.

We present here a method for broadly characterizing single cells at the molecular level beyond the more common morphological and transmitter/receptor classifications. The RNA from defined single cells is amplified by microinjecting primer, nucleotides, and enzyme into acutely dissociated cells from a defined region of rat brain. Further processing yields amplified antisense RNA. A second round of amplification results in greater than 10(6)-fold amplification of the original starting material, which is adequate for analysis--e.g., use as a probe, making of cDNA libraries, etc. We demonstrate this method by constructing expression profiles of single live cells from rat hippocampus. This profiling suggests that cells that appear to be morphologically similar may show marked differences in patterns of expression. In addition, we characterize several mRNAs from a single cell, some of which were previously undescribed, perhaps due to "rarity" when averaged over many cell types. Electrophysiological analysis coupled with molecular biology within the same cell will facilitate a better understanding of how changes at the molecular level are manifested in functional properties. This approach should be applicable to a wide variety of studies, including development, mutant models, aging, and neurodegenerative disease.

Animals↗
PubMed1991

Regulation of elastin gene expression.

Recent isolation and characterization of cDNAs encompassing the full length of chicken, cow, and human elastin mRNA have led to the elucidation of the primary structure of the respective tropoelastins. Comparison of the tropoelastin from the different species has revealed that large segments of the sequence are conserved, but considerable variation also exists, ranging in extent from relatively small alterations, such as conservative amino acid substitutions, to large-scale deletions and insertions. Several distinct approaches have yielded compelling evidence of a single elastin gene per haploid genome. Analysis of the bovine and human elastin genes revealed that functionally distinct hydrophobic and cross-link domains of the protein are encoded in separate exons which alternate in the genes. The human gene contains 34 exons, the intron/exon ratio is unusually large (20:1), and the introns contain large amounts of repetitive sequences that may predispose to genetic instability. Comparison of the cDNA and genomic sequences has demonstrated that the primary transcript of both species is subject to considerable alternative splicing, which can account for the presence of multiple tropoelastin isoforms. It is likely that the conformation of elastin is, at least in part, that of a random coil, and therefore it might be expected that the stringency for conservation of the amino acid sequence would be less than that for other proteins with unique conformations. This suggests that functional elastin molecules that vary in their sequence and fitness may exist in the human population and be compatible with a normal life. Potentially though, these variations could have profound consequences on the properties of vital tissues found in the cardiovascular and pulmonary systems over the lifetime of the individual. Consequently, analysis of the structure of the elastin gene and its variation in what is regarded as the normal human population, rather than in those individuals with clearly heritable diseases, assumes greater importance. The 5'-flanking region of the gene is G + C rich and contains several SP-1 and AP2 binding sites, as well as putative glucocorticoid, cAMP, and TPA responsive elements, but no consensus TATA box or functional CAAT box. Primer extension and S1 mapping of the elastin mRNA indicated that transcription was initiated at multiple sites. Transfection experiments using promoter elements/reporter gene constructs demonstrated that the basic promoter element was found within region -128 to -1. In addition, three distinct up-regulatory and two down-regulatory regions were delineated. Taken together, these findings suggest that the regulation of elastin gene expression is complex and takes place at several levels.

Amino Acid Sequence↗
PubMed1990

Fluorescent detection of lipopolysaccharide interactions with model membranes.

The critical importance of the lipid A moiety of LPS in resistance and pathogenesis in gram negative infections has led to the assumption that LPS interaction with target cells is due to hydrophobic interaction with plasma membranes. However, work from several laboratories, including our own, is consistent with the presence of a cell membrane structure with characteristics of a "receptor". We have proposed a two-step model for LPS-membrane interaction which resolves the two views, and have developed a model system to control the first step (binding to membrane protein) and study the second step (intercalation into lipid bilayer). We examined the interaction of LPS with small unilamellar phosphatidylcholine vesicles labeled in the hydrophobic portion of the bilayer with the fluorescent probe diphenylhexatrine (DPH) and detected changes in the physical properties of the bilayer by measuring DPH fluorescence anisotropy (delta r). We have found that purified, phenol-extracted S. typhimurium LPS interacts with the bilayer as measured by an increase in delta r and conclude that the LPS aggregate coalesced with the lipid bilayer. The greatest change in delta r was achieved with lipid A, Ra-Re glycolipids and diphosphoryl lipid A. Monophosphoryl lipid A and lipid X were less effective. Preparations of wild-type LPS fractionated according to the length of the O-antigen side chain and unfractionated LPS had least effect on delta r. Thus other factors such as serum components or membrane proteins may be necessary to enhance the interaction of LPS with target cells.

Carbohydrates↗
PubMed1989

Characterization of the complete human elastin gene. Delineation of unusual features in the 5'-flanking region.

Genomic clones encompassing the entire human elastin gene, including 11 kilobases flanking the ATG translation initiation codon, have been obtained and characterized by restriction enzyme analysis and extensive DNA sequencing. These analyses demonstrated that functionally distinct hydrophobic and cross-linking domains of the protein are segregated into separate exons throughout the gene. All exons are multiples of three nucleotides, and exon:intron borders always split codons in the same way which permits cassette-like alternative splicing. The 5'-flanking region lacks a canonical TATA sequence, is G + C-rich, and contains several SP1 binding sites and an AP2 binding site. Primer extension and S1 nuclease protection experiments indicate that transcription is initiated at multiple sites in the gene.

Amino Acid Sequence↗
PubMed1989

Structure of the bovine elastin gene and S1 nuclease analysis of alternative splicing of elastin mRNA in the bovine nuchal ligament.

Genomic clones encompassing all the translated sequences, the 3' untranslated sequence, and 1 kb flanking the ATG translation initiation codon of bovine tropoelastin have been obtained and characterized by restriction enzyme analysis and extensive DNA sequencing. These analyses demonstrated that functionally distinct hydrophobic and cross-linking domains of the protein are segregated into separate exons throughout the gene. The putative promoter region lacks a TATA box, has an extremely high G+C content, and contains several SP1 binding sites. Comprehensive S1 analyses using probes covering the entire mRNA and RNA isolated from the nuchal ligament of bovine fetuses of different ages, neonate calves, and adult cows demonstrated that while only a single exon is alternatively spliced at high frequency, many exons are alternatively spliced at limited, variable frequencies. The results also suggest that such limited splicing is increased in the adult tissue relative to fetal and neonate tissues.

Amino Acid Sequence↗
PubMed1989

Structure of the elastin gene and alternative splicing of elastin mRNA: implications for human disease.

The protein elastin is largely responsible for the elastic properties of vertebrate lungs, large blood vessels, and skin. The structure of the human, bovine, and chick elastin gene and protein monomer, tropoelastin, has recently been elucidated by using techniques of molecular biology. Extensive homology of amino acid sequence exists among the mammalian species and there is in addition strong conservation of nucleotide sequences in the 3' untranslated region of the gene. The translated exons are small and embedded in large expanses of introns. Sequences coding for the hydrophobic regions, responsible for the elastic properties of the molecule, and the alanine-lysine rich regions, responsible for crosslink formation between molecules, reside in separate exons and alternate for the most part in the elastin gene. S1 analyses and sequence analysis of cDNA and genomic clones have indicated that there is substantial alternative splicing of the primary elastin transcript. Variations in the structure of mRNAs resulting from alternative splicing could explain the existence of the multiple forms of tropoelastin observed electrophoretically in several species. Different kinds of splicing patterns could occur in human populations and may contribute to aging and pathological situations in the cardiovascular and pulmonary systems.

Aging↗
PubMed1989

Effect of insulin on acute experimental cerebral ischemia in gerbils.

We studied the effects of insulin with and without food deprivation on experimental cerebral ischemia in 197 gerbils. Ischemia was induced by unilateral common carotid artery occlusion for 4 hours. Gerbils were divided into four experimental groups and were studied for up to 1 week of survival: Group A (n = 50) was fed but received no insulin, Group B (n = 50) was deprived of food for 24 hours before surgery but received no insulin, Group C (n = 49) was fed and received daily injections of 0.1 IU lente insulin for 3 days before surgery, and Group D (n = 48) was deprived of food and received daily insulin injections. Insulin treatment was continued in Groups C and D after surgery. Blood glucose levels of all gerbils were determined before treatment (overall mean +/- SEM 88.0 +/- 12.4 mg/dl) and before carotid artery occlusion (Group A 92.2 +/- 18.3 mg/dl, Group B 81.4 +/- 11.7 mg/dl [p less than 0.05 different from before treatment], Group C 92.8 +/- 22.3 mg/dl, and Group D 66.1 +/- 24.0 mg/dl [p less than 0.001 different from before treatment]). Among the four groups, 52 gerbils died within 1 week. Neurologic deficits were scored and histologic evidence of the infarcts was graded in survivors at 1 week. Group C gerbils had the best stroke index scores. Histologic evaluation revealed that 35.9% of Group A, 21.1% of Group B, 13.9% of Group C (p less than 0.05 compared with Group A), and 28.1% of Group D survivors developed cerebral infarcts.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

Cloning of full-length elastin cDNAs from a human skin fibroblast recombinant cDNA library: further elucidation of alternative splicing utilizing exon-specific oligonucleotides.

A human cDNA library was constructed utilizing RNA isolated from cultured skin fibroblasts. Recombinant clones containing elastin sequences were identified by plaque hybridizations with previously characterized human placental elastin cDNAs. Seven positive recombinant clones with inserts of approximately 3.2-2.2 kb were isolated. Characterization of the clones by restriction endonuclease analysis and dot-blot hybridizations with exon-specific synthetic oligonucleotides demonstrated considerable variability in the primary nucleotide sequence. Dideoxy nucleotide sequencing confirmed this finding. The variability is most likely a result of alternative splicing of exons from the primary elastin transcripts. The two largest clones contained approximately 1 kb of 3' untranslated sequence and approximately 2.2 kb of translated sequence encoding 730 amino acids. Six amino acids, encoded by exon 12A, have not been previously noted in human elastin cDNAs. In addition, these human skin fibroblast clones contained a 49 bp 5' untranslated sequence. These results demonstrate that there is considerable variability in the processed nucleotide sequence of the elastin mRNAs. These transcripts may code for isoforms of tropoelastin with different biologic properties.

Amino Acid Sequence↗
PubMed1987

Sequence variation of bovine elastin mRNA due to alternative splicing.

Poly A+ RNA, isolated from a single 210 day fetal bovine nuchal ligament, was used to synthesize cDNA by the RNase H method, using AMV reverse transcriptase for first strand synthesis and DNA polymerase I for the second strand. The cDNA was inserted into lambda gt10 using EcoRI linkers, and recombinant phage containing elastin sequences were identified by hybridization with a 1.3 kb sheep elastin cDNA clone, pcSELI (Yoon, K. et al., Biochem. Biophys. Res. Comm. 118: 261-265, 1984). Three clones containing the largest inserts of 2.9, 2.8, and 2.6 kb were selected for further study. The complete sequence analysis of the 3 clones was correlated with the sequence of 10.2 kb of the bovine elastin gene. The analyses: (i) showed that the cDNA encompassed the great majority of the translated sequence, (ii) ordered the tryptic peptides of porcine tropoelastin, (iii) determined new amino acid sequences not previously found in the porcine peptides and (iv) demonstrated that alternative splicing of the primary transcript leads to significant variation in the sequence of the translated portion of the mRNA.

Amino Acid Sequence↗
PubMed1987

Persistent hypoglossal artery associated with basilar artery aneurysm.

A saccular aneurysm at the tip of the basilar artery in a patient with a persistent hypoglossal artery is reported. The persistent hypoglossal artery was arising from the left internal carotid artery. Both vertebral and posterior communicating arteries were absent bilaterally. The combination of a persistent hypoglossal artery and a basilar bifurcation aneurysm is a very rare occurrence. The anatomy of the cerebral circulation in this unique case is important for surgical planning.

Basilar Artery↗
PubMed1987

Alternative splicing of human elastin mRNA indicated by sequence analysis of cloned genomic and complementary DNA.

Poly(A)+ RNA, isolated from a single 7-mo fetal human aorta, was used to synthesize cDNA by the RNase H method, and the cDNA was inserted into lambda gt10. Recombinant phage containing elastin sequences were identified by hybridization with cloned, exon-containing fragments of the human elastin gene. Three clones containing inserts of 3.3, 2.7, and 2.3 kilobases were selected for further analysis. Three overlapping clones containing 17.8 kilobases of the human elastin gene were also isolated from genomic libraries. Complete sequence analysis of the six clones demonstrated that: the cDNA encompassed the entire translated portion of the mRNA encoding 786 amino acids, including several unusual hydrophilic amino acid sequences not previously identified in porcine tropoelastin, exons encoding either hydrophobic or crosslinking domains in the protein alternated in the gene, and a great abundance of Alu repetitive sequences occurred throughout the introns. The data also indicated substantial alternative splicing of the mRNA. These results suggest the potential for significant variation in the precise molecular structure of the elastic fiber in the human population.

Amino Acid Sequence↗
PubMed1985

Anterior interhemispheric approach to aneurysms of the anterior communicating artery.

A modified anterior interhemispheric approach for clipping aneurysms of the anterior communicating artery is described. This approach is preferred on anatomical grounds because the anterior circle of Willis can be fully visualized with minimal manipulation of the frontal lobes and anterior cerebral arteries. The advantages of this approach are minimal traction, reduced operative time, and preservation of the olfactory nerve.

Humans↗
PubMed1982

Arylhydroxamic acid bioactivation via acyl group transfer. Structural requirements for transacylating and electrophile-generating activity of N-(2-fluorenyl)hydroxamic acids and related compounds.

The synthesis of a series of 12 N-(2-fluorenyl)hydroxamic acids, N-(2-fluorenyl)-N-hydroxyureas, and N-(2-fluorenyl)-N-hydroxycarbamates is reported. The compounds were evaluated for their ability to serve as substrates for a partially purified hamster hepatic arylhydroxamic acid N,O-acyltransferase preparation. Transacylating activity was measured spectrophotometrically with 4-aminoazobenzene as the acyl group acceptor, and electrophile-generating activity was quantified by the N-acetylmethionine trapping assay. Only the N-acetyl, N-propionyl, and N-methoxyacetyl derivatives exhibited relatively high levels of activity as measured by either of the assay methods. These results are generally consistent with previously reported conclusions regarding the steric and electronic characteristics of acyl groups that are required for activation by this enzyme system. N,O-Acyltransferase inactivation by N-hydroxy-2-acetamidofluorene depressed the bioactivation of the N-acetyl compound to a greater extent than either the N-propionyl or N-methyloxyacetyl derivative.

Acetyltransferases↗