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Biomedical subjects

S W Chen

Publications and source records attributed to S W Chen.

At least 55 records · Page 3Linked to original sources
PubMed1993

Transient, localized accumulation of alpha-spectrin during sea urchin morphogenesis.

The mRNA and protein of alpha-spectrin in the sea urchin embryo is shown here to be transiently overexpressed in cells initiating certain morphogenetic changes. This expression was detected by use of a 4.5-kb cDNA clone that encodes alpha-spectrin isolated from a Lytechinus variegatus cDNA library. DNA sequence analysis demonstrated 80% similarity of this cDNA to human nonerythroid alpha-spectrin. Sea urchin alpha-spectrin RNA accumulated to a uniform basal level in all cells of the embryo with a marked, transient increased accumulation in the primary mesenchyme cells of the vegetal plate just prior to gastrulation. Cells of the endoderm also express increased levels of spectrin during gastrulation and these levels remained high in the myoepithelial cells of the sphincter constrictions that separates the gut into foregut, midgut, and hindgut domains. Antibodies made to recombinant sea urchin spectrin synthesized in Escherichia coli were used to localize the protein in situ. These experiments showed that all cells of the embryo accumulated alpha-spectrin protein confined to the cortical regions of cell-cell contact. In epithelial cells, this localization showed a distinct honeycomb pattern. Primary mesenchyme cells and the myoepithelial cells of the gut sphincters showed significantly enhanced spectrin signal corresponding to the pronounced RNA localization pattern seen by in situ RNA hybridization. These data demonstrated that alpha-spectrin from the sea urchin is a highly conserved member of the spectrin superfamily of proteins and that its elevated expression in specific cell types anticipates overt morphogenesis.

Animals↗
PubMed1993

Effect of concentration of mixed-function oxidase on concentration of estrogen, rate of egg lay, eggshell thickness, and plasma calcium in laying hens.

The objective of this study was to investigate the effect of induction or depression of mixed-function oxidases (MFO) by xenobiotics on the peripheral concentration of estrogens, plasma Ca, rate of egg lay, and eggshell thickness in laying hens. In Exp. 1, 100 mg of phenobarbital (PB) administered orally each day for 3 or 7 d reduced concentrations of estrone and estradiol (E2) in serum. In Exp. 2, 25, 50, or 100 mg of PB was administered orally to laying hens for 3 or 7 d. Treatment with 100 mg of PB for 3 d or with 25, 50, or 100 mg for 7 d significantly increased liver:body weight ratios. Microsomal protein increased after 7 d of 50 or 100 mg of PB administration. Feeding PB decreased concentration of E2 and total plasma Ca in a dose- and period-dependent manner. Concentration of E2 was reduced to 10% of control, whereas hepatic cytochrome P-450 increased significantly with dose. The correlation between concentration of E2 and P-450 was negative and significant. Total Ca in the plasma was highly, positively correlated with concentration of E2. Eggshells were thinner from hens treated with 100 mg of PB for both 3 or 7 d than those from control hens. Rate of egg lay was reduced by 100 mg of PB for 7 d. In Exp. 3, .5 mL of CCl4 given orally for 1 d decreased P-450 and increased E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Lysosomal enzyme activity of cultured fetal cells in Chinese and its clinical application].

Lysosomal storage diseases (LSD) are caused by deficient activity of specific lysosomal enzymes. Early diagnosis and selective termination is still the trend of therapy. The purpose of this study was to establish an assay system and investigate the reference range of lysosomal enzyme activity of cultured fetal cells in the Chinese population. Seventy amniotic fluid and 9 chorionic villi samples were collected and cultured in this study. Enzyme activity assay was done by synthesized 4-Mu-binded substrates. The activity was expressed as nmol/mg protein/hour. In cultured amniotic cells, the results showed 14-138 of alpha-glucosidase, 8-133 of alpha-galactosidase, 32-470 of alpha-mannosidase, 101-1121 of alpha-fucosidase, 106-1321 of beta-galactosidase, 15-268 of beta-glucosidase, 11-279 of beta-glucuronidase, 101-1193 of Hexosaminidase A, and 886-6204 of N-acetyl-alpha-glucosaminidase. In cultured chorionic villi samples, it showed 22-335 of alpha-glucosidase, 31-230 of alpha-galactosidase, 47-250 of alpha-mannosidase, 35-218 of alpha-fucosidase, 49-934 of beta-galactosidase, 34-329, of beta-glucosidase, 57-379 of beta-glucuronidase, and 328-3412 of Hexosaminidase A. The enzyme activity was not correlated with the gestation age when sample was obtained. Furthermore, there was no statistical significance among the range of amniotic cells, chorionic villi samples, skin fibroblasts and peripheral leukocytes for each enzyme studied. It is suggested that the synthesis of lysosomal enzymes has been mature since the early fetal state, and the samples obtained as early as 8 weeks of gestation age can be used for early diagnosis of lysosomal storage diseases.

Cells, Cultured↗
PubMed1992

Isolation, cDNA cloning, and characterization of an 18-kDa hemagglutinin and amebocyte aggregation factor from Limulus polyphemus.

An 18-kDa hemagglutinin which possesses the property of inducing both aggregation of amebocytes and agglutination of erythrocytes has been isolated from Limulus polyphemus amebocytes and purified by ion exchange chromatography. This nonglycosylated, single chain polypeptide with an M(r) of 18,506 and isoelectric point of 8.3 is stored exclusively in the large secretory granules of amebocytes. Based on the partial N-terminal amino acid sequence of 63 residues, DNA probes have been synthesized for screening a pBR322 cDNA library constructed from Limulus amebocytes. The cDNA coding for this protein reveals the presence of a 19-residue signal peptide preceding the 153-residue open reading frame. Northern blot analysis indicates the presence of a single mRNA species. The primary structure derived from the corresponding cDNA sequence reveals an internal homology consisting of two consensus sequences, Val-Asn-Asp/Ser-Trp-Asp and Glu-Asp-Arg-Arg-Trp. The formation of 5 disulfide bonds between 10 half-cysteines divides the molecule into three looped domains each containing the Glu-Asp-Arg-Arg-Trp repeating unit. One of the novel features of this protein is that it shares 37% identity with a 22-kDa mammalian extracellular matrix protein isolated from fetal bovine skin (Neame, P.J., Choi, H.U., and Rosenberg, L.C. (1989) J. Biol. Chem. 264, 5474-5479). The two proteins exhibit a similar pattern of looped domains, each domain containing a homologous consensus sequence (i.e. Glu-Asp-Arg-Arg-Trp). The overall structure of both proteins seems to be highly related, with the exception of an N-terminal tyrosine-rich region present only in the mammalian extracellular matrix protein. The functional properties of the two proteins are similar in that the Limulus 18-kDa protein agglutinates horse erythrocytes and aggregates Limulus amebocytes, and the mammalian 22-kDa protein is an effective adhesion promoter for dermal fibroblasts. On the basis of these unique properties, the newly characterized hemagglutinin has been termed Limulus 18K agglutination-aggregation factor (18K-LAF).

Amino Acid Sequence↗
PubMed1992

Primary structure of an inactive mutant of phospholipase A2 in the venom of Bungarus fasciatus (banded krait).

From the acidic components of Bungarus fasciatus venom, a very small amount (0.16%) of a novel phospholipase A2 was obtained. Both neurotoxicity and enzyme activity were found to be lacking. Amino acid sequence study showed that it has a normal backbone of group I snake venom phospholipase A2 with 118 amino acid residues. The lack of enzyme activity was attributed to its mutation of the indispensable Asp residue to an Ala residue, i.e., the usual His-Asp47 turned out to be His-Ala47. This is the eighth isoform of phospholipase A2 found from the venom of Bungarus fasciatus. Examination of structural homology with three other isoforms revealed 66% similarity at most.

Amino Acid Sequence↗
PubMed1991

Purification and characterization of a trypsin inhibitor from mouse seminal vesicle secretion.

A Kazal-type trypsin inhibitor in mouse seminal vesicle secretion was purified to homogeneity via a series of purification steps including ammonium sulfate fractionation, affinity chromatography on a trypsin Affi-Gel 10 column, and HPLC on a reverse phase C4 column. It was shown to be a weak basic protein with an isoelectric point of 8.7 and to contain no carbohydrate. The protein had a specific activity of 184 U/mg protein in the inhibitory effect on the trypsin digestion of N-benzoyl-Pro-Phe-Arg-p-nitroanilide. Analysis of the kinetic data for the trypsin digestion of N-benzoyl-Phe-Val-Arg 7-amido-4-methylcoumarin revealed that the protein was a competitive inhibitor with an inhibitory constant (Ki) of 0.15 nM. The molecular mass of the protein was determined to be 7 kDa by both gel chromatography and electrophoresis. Results of direct amino acid determinations indicated that this protein corresponded to the reading frame of MP12 cDNA identified from mouse prostate. We found that cleavage only at the reactive site of this protein (Arg19-Ile20) resulted in its denaturation.

Amino Acid Sequence↗
PubMed1991

The amino acid sequence and properties of an edema-inducing Lys-49 phospholipase A2 homolog from the venom of Trimeresurus mucrosquamatus.

Three phospholipase A2 enzymes or homologs were purified from the venom of Trimeresurus mucrosquamatus (Taiwan habu). The most abundant one was found to be a phospholipase homolog without enzyme activity, and its complete amino acid sequence was determined using oligopeptide fragments derived from digestion by endopeptidases Glu-C, Asp-N, Lys-C and alpha-chymotrypsin, and by means of gas-phase sequencing. The sequence revealed that the protein belonged to the Lys-49 family of snake venom phospholipase A2. This protein's function was characterized as edema-inducing. The Lys-49 protein has the potential to bind membrane phospholipid and Ca2+ (Kd = 1.6 x 10(-4) M) as shown by ultraviolet difference spectra; however, the catalytic site appeared to be inactive and the edematous response was independent of the protein's hydrolytic activity. Mast cells and platelets were shown to be subject to activation by the Lys-49 protein.

Amino Acid Sequence↗
PubMed1991

Comparison of elemental concentrations in the acinar cells of the human labial salivary gland.

Two types of acinar cells were observed in human labial glands by conventional and analytical electron microscopic and light microscopic techniques. The predominant type contained large and prominent secretory granules that were strongly mucicarmine and PAS (with and without diastase) positive. The second type contained small, lacy, secretory granules, and these cells were faintly positive with these stains. The elemental contents of the two types of granules were measured by analytical electron microscopy using digital mapping and spot analysis applied to freeze-dried cryosections prepared from gland slices incubated in vitro under non-stimulated conditions. The large secretory granules had significantly higher Ca, S and Mg concentrations and significantly lower Cl and K concentrations than the small granules. The difference in elemental contents probably reflects differences in the content of secretory macromolecules. Specifically, the S content is thought to reflect the anionic properties of the secretory macromolecules, while the levels of divalent cations are thought to be determined by electroneutrality requirements for macromolecular folding and storage. No differences were found in nuclear or cytoplasmic elemental concentrations between the two cell types.

Adult↗
PubMed1991

Triflavin, an antiplatelet Arg-Gly-Asp-containing peptide, is a specific antagonist of platelet membrane glycoprotein IIb-IIIa complex.

Triflavin, an antiplatelet peptide containing Arg-Gly-Asp, purified from Trimeresurus flavoviridis venom, inhibits aggregation of human platelets stimulated by a variety of agonists. It blocks aggregation through interference with fibrinogen binding to its specific receptor on the platelet surface membrane in a competitive manner, but it has no apparent effect on intracellular events, such as thromboxane B2 formation, phosphoinositides breakdown and intracellular Ca2+ mobilization of thrombin-activated platelets. In this study, we determined the complete sequence of triflavin, which is composed of a single polypeptide chain of 70 amino acids. Its sequence is rich in cysteine and contains Arg-Gly-Asp at residues 49-51 in the carboxy-terminal domain. Triflavin shows about 68% identity of amino acid sequence with trigramin, which is a specific antagonist of the fibrinogen receptor associated with glycoprotein IIb/IIIa complex. [125I]Triflavin binds to unstimulated and ADP-stimulated platelets in a saturable manner and its Kd values are estimated to be 76 and 74 nM, respectively; the corresponding numbers of binding sites are 31,029 and 34,863 per platelet, respectively. [125I]Triflavin binding is blocked by Gly-Arg-Gly-Asp-Ser in a competitive manner. EDTA, the Arg-Gly-Asp-containing peptides (including naturally occurring polypeptides, trigramin and rhodostomin), and monoclonal antibody, 7E3, raised against GP IIb/IIIa complex, inhibit [125I]triflavin binding to unstimulated and ADP-stimulated human platelets. In conclusion, triflavin specifically binds to fibrinogen receptor associated with GP IIb/IIIa complex and its binding site is located at or near GP IIb/IIIa complex, overlapping with those of 7E3 and another Arg-Gly-Asp-containing polypeptide, rhodostomin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Comparison of the gamma-crystallins isolated from eye lenses of shark and carp. Unique secondary and tertiary structure of shark gamma-crystallin.

gamma-Crystallin isolated from the shark of cartilaginous fishes was compared with the cognate gamma-crystallin from the carp of bony fishes. Distinct differences in amino acid compositions, primary, secondary and tertiary structures were found. The most salient features of shark gamma-crystallin lie in the fact that this crystallin possessed a significant alpha-helical structure in the peptide backbone as revealed by circular dichroism study, in contrast to those orthologous gamma-crystallins from other vertebrate species including bony fishes which all show a predominant beta-sheet secondary structure. The tertiary structure as reflected in the intrinsic microenvironments of various aromatic amino acids in the native crystallins also shows unambiguous differences between these two classes of gamma-crystallins. N-Terminal sequence analysis corroborates the structural differences between shark and carp gamma-crystallins. gamma-Crystallin from the more primitive shark seems to be more in line with the main evolutionary phylogeny leading to the modern mammalian gamma-crystallin.

Amino Acid Sequence↗
PubMed1990

Revised amino acid sequences of the three major phospholipases A2 from Bungarus fasciatus (banded krait) venom.

The structures of three cardiotoxin-like proteins obtained from the venom of Bungarus fasciatus (banded krait) were elucidated previously (Lu and Lo, 1980, 1981). Since their molecular sizes are similar to that of phospholipase A2 and since they show weak phospholipase A2 activities (Chang et al., 1983), a further study of their primary structures was carried out. Fractions Va, Vb-2 and VI, corresponding to the former V-2, V-3 and VI were determined to be typical phospholipases A2. Among 118 amino acid residues, they all have in common a Pro29 between Gly28 and Gly30, the latter two residues being implicated in Ca2+ binding together with Tyr26 and Asp47.

Amino Acid Sequence↗
PubMed1990

[Preparation of toxoid from Taiwan cobra (Naja naja atra) venom].

Potency of sixty antitoxic unit was reached after two immunizations in 2-week intervals of rabbits and horses with 10-25 mg Taiwan cobra (Naja naja atra) venom which was detoxified by 0.125% glutaraldehyde. Now this procedure has become a routine antivenine-producing method by which snake bivalent neurotropic antivenine is produced. The stability test showed that Taiwan cobra toxoid kept at 37 degrees C for 40 days, the antigenicity increased by 24% and toxicity decreased by 10% as compared to the toxoid maintained at 4 degrees C.

Animals↗
PubMed1989

Purification and Characterization of Pectinmethylesterase from Ficus awkeotsang Makino Achenes.

Pectinmethylesterase from the pericarp of jelly fig (Ficus awkeotsang) achenes was extracted and purified to a specific activity of 289 micromole proton produced per minute per milligram protein. Pectinmethylesterase, a major protein with high specific activity in the crude extract, was monomeric with a molecular weight of 38,000. The enzyme preparation was stable in distilled water at 4 degrees C for at least 6 months, and at 60 degrees C for at least 10 minutes. This enzyme functioned optimally at pH 6.5 to 7.5 when the assay mixture contained no NaCl or at low NaCl concentration. The pH optimum shifted to lower pH as the NaCl concentration was increased. The K(m) value for pectin was 0.75 milligram per milliliter pectin, corresponding to a V(max) value of 310 micromoles per minute per milligram protein. Inhibition studies with antibodies indicated that jelly fig achene pectinmethylesterase and the two other pectinmethylesterases from orange and tomato were similar in their active site conformation; however, the surface determinants may be very different because no precipitation between anti-jelly fig pectinmethylesterase immune serum and the pectin methylesterase from orange and tomato could be observed in the double immunodiffusion analysis. Specific antisera raised against jelly fig achene pectinmethylesterase in a Western blot experiment also showed low similarity between jelly fig pectinmethylesterase with that from orange and tomato. This observation was also supported by the very low isoelectric point (pH 3.5) of jelly fig pectinmethylesterase, compared with high isoelectric points reported for most of the pectinmethylesterases. Amino acid composition and N-terminal sequence have been obtained. High homology of the N-terminal amino acid residues between jelly fig and tomato pectinmethylesterase (O Markovic, H Jornvall [1986] Eur J Biochem 158: 455-462) was observed. Pectinmethylesterase activity causes the release of protons from the deesterification of pectin such that a low pH environment is created, and this may be related to the cell growth. Pectinmethylesterase is not needed for jelly fig seed germination, however the gel formed from pectin and pectinmethylesterase may insure a water source for the germinating jelly fig seeds.

Journal Article↗
PubMed1989

Amino acid sequence of a neutral phospholipase A2 (III) in the venom of Bungarus fasciatus.

Two phospholipases were found in the venom of Bungarus fasciatus, one in fraction III, the other in fraction X of the chromatographic separation. A neutral PLA2(III) purified from fraction III was subjected to amino acid sequencing by means of an automated sequenator applied to the intact RCM-PLA2 (III) and the individual peptides obtained from HPLC separation of the three types of enzymatic peptides. PLA(III) was shown to consist of 118 amino acid residues with 14 half-cystines. It is 65% homologous to the basic PLA2 obtained from fraction X.

Amino Acid Sequence↗
PubMed1989

[Morphologic studies on the adulterant sharen in Alpinia].

In this paper, morphological studies on adulterant Sharen including eighteen fruits in Alpinia are reported. The morphological differences between genuine Sharen and its adulterants are distinct on their fruits, seeds and embryos. In addition, the distinguished characters for identification of the eighteen fruits and seeds are described with drawings and compared in a table.

Drug Contamination↗
PubMed1989

[Mucus histochemical study of bilirubin cholangiolithiasis in rabbit model].

Sulfated mucopolysaccharides have an important role in pigment gallstone formation. In this experiment, the animal model of bilirubin cholangiolithiasis was made with Japanese hybrid big-ear white rabbits. The source, nature, quantity and distribution of sulfated mucopolysaccharides in the cause of bilirubin cholangiolithiasis were observed by means of mucous histochemical study. There were three characteristic pathologic changes observed in this experiment: 1. In normal condition, the sulfated mucopolysaccharides were secreted by epithelium of biliary tracts and the quantity was minimum. When bacterial infection was present in the biliary tracts, they were secreted mainly by the proliferative glands in submucosa of the bile duct; 2. In 26 rabbits where the bilirubin cholangiolithiasis developed, there were many proliferative glands in submucosa of the bile duct. Most of the glands produced sulfonated acid mucin. In 5 rabbits where the gallstones did not develop in the stone growing stage, the proliferative glands were not present in the bile duct. It was suggested that there was a close relationship between the proliferative glands and the formation of bilirubin cholangiolithiasis, and 3. The glands in submucosa of the biliary tract provided the refuge where the bacteria could not be cleaned out easily and so it was difficult to control the infection of the biliary tract.

Animals↗
PubMed1989

[Studies on the histology and essential oils of the adulterant sharen in Alpinia].

Morphological studies on eighteen adulterants of Sharen in Alpinia had been carried out previously. In this paper, a report on the histology and essential oil of their seeds is presented. According to our TLC analysis and microscopical examination, the differences between genuine Sharen and its adulterants are distinct in histological characters and constituents of the essential oil. A description of identification of these eighteen seeds is given together with line drawings, chromatograms and a table for comparison.

Chromatography, Thin Layer↗