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Y Yan

Publications and source records attributed to Y Yan.

At least 307 records · Page 17Linked to original sources
PubMed1995

[Cloning, sequencing and characterizing repetitive DNA of Glycine max].

One satellite DNA family, cloned from Glycine max, was sequenced and chracterized. The unit of the repetitive sequences was 91bp. They concentrated on the arms of chromosomes M2 and M11, and spreaded on whole chromosomes Sm7 and M12. Southern blot analysis with 18 acessions, belonged to subgenus Glycine and subgenus Soj a of genus Glycine, showed that the repetitive sequences were specific to subgenus Soj a. It was subgenus specific repetitive sequence. This result, from another aspact, supported the idea that the three species in subgenus Soj a should be considered as one species.

Base Sequence↗
PubMed1994

Renin gene promoter activity in GC cells is regulated by cAMP and thyroid hormone through Pit-1-dependent mechanisms.

Transcriptional activity of human renin gene (hREN) 5'-flanking DNA sequences in pituitary cells is highly dependent on binding of the pituitary-specific transcription factor Pit-1. Pit-1 has been implicated in cAMP regulation of a number of pituitary genes and has also been shown to interact with thyroid hormone (T3) receptors in mediating T3 responsiveness of the rat growth hormone gene. In the present study we examine the effects of forskolin and T3 on the expression of luciferase hybrid genes containing hREN 5'-flanking DNAs (hREN.luc) transiently transfected into the pituitary cell line GC. Basal activities of all hREN.luc constructs transfected into cells grown in media containing serum stripped of hormones were low. Addition of forskolin stimulated expression up to 48-fold, depending on the hREN sequences present. The hREN sequence -148 to +18 was sufficient for both maximal expression and maximal stimulation by forskolin. Mutagenesis of the Pit-1 site between -82 and -58 reduced forskolin induction 4-5-fold. In addition to the Pit-1 site, the sequence between -148 and -98 was also required for maximal activity and forskolin induction. T3 on its own had no effect on hREN promoter activity in GC cells, but suppressed the effects of forskolin. Gel mobility shift and Western blot analyses indicated that forskolin treatment had no effect on Pit-1 DNA binding or Pit-1 levels. However, T3 reduced Pit-1 levels which was reflected in lower DNA binding under the conditions employed. Taken together, these findings emphasize the importance of cAMP-dependent mechanisms in directing renin gene expression.

Animals↗
PubMed1994

Characterization of glycosylated and catalytically active recombinant human alpha-galactosidase A using a baculovirus vector.

Fabry disease is an X-linked inborn error of glycolipid metabolism caused by a deficiency of the lysosomal enzyme alpha-galactosidase A (GalA; EC 3.2.1.22). In order to obtain large quantities of this human enzyme for physical characterization and for the development of new approaches for enzyme therapy, we constructed derivatives of the Autographa californica nuclear polyhedrosis virus that produce the human enzyme. The recombinant GalA (re-GalA) is produced at high levels, and is active with both the artificial substrate, 4-methylumbelliferyl-alpha-D-galactopyranoside, and the natural in vivo substrate, trihexosylceramide. The purified re-GalA is glycosylated and is taken up by normal and Fabry fibroblasts in cell culture. Mass spectral analysis of total monosaccharides released by hydrazinolysis indicates that it contains fucose, galactose, mannose and N-acetylglucosamine. Amino-acid sequence analysis of six proteolytic peptides corresponded to sequences predicted by the cDNA. The molecular masses of the purified enzyme, estimated by electrospray mass spectroscopy and laser desorption time-of-flight analysis are 46.85 and 46.62 kDa, respectively, approx. 10% greater than the polypeptide portion predicted by the cDNA. The recombinant enzyme retains significant catalytic activity after modification with poly(ethylene glycol), a treatment which decreases the immunogenicity and increases the circulation life of many proteins used therapeutically.

Amidohydrolases↗
PubMed1994

Structure of murine polyomavirus complexed with an oligosaccharide receptor fragment.

The polyomaviruses are non-enveloped, icosahedrally symmetrical particles with circular double-stranded DNA genomes. The outer shell of the virion contains 360 copies of viral protein VP1 (M(r) approximately 42K) arranged in pentamers. We report here the structure at 3.65 A resolution of murine polyomavirus ('polyoma') complexed with an oligosaccharide receptor fragment. This structure has been determined using the previously described model of simian virus 40 (SV40). Although very similar in structure to SV40, polyoma has interesting biological differences. Cell-surface N-acetyl neuraminic acid (sialic acid) is required for polyoma infectivity, but not for SV40. Polyoma attaches to the surface of susceptible cells by stereospecific recognition of oligosaccharides terminating in (alpha 2,3)-linked sialic acid. Studies of pathogenicity show that the specificity of viral binding to such oligosaccharides is an important determinant of the virus' ability to establish a disseminated infection and to induce tumours in the natural host. The complex described here show how polyoma recognizes the receptor fragment and how strains with different receptor specificities can distinguish between alternative ligands. The results also suggest an explanation for the large disparity in pathogenicity exhibited by strains differing in only one amino-acid residue of VP1.

Capsid↗
PubMed1994

Engineering of betabellin 14D: disulfide-induced folding of a beta-sheet protein.

The betabellin target structure consists of 2 32-residue beta sheets packed against each other by hydrophobic interactions. We have designed, chemically synthesized, and biophysically characterized betabellin 14S, a single chain, and betabellin 14D, the disulfide-bridged double chain. The 32-residue nongenetic betabellin-14 chain (HSLTASIkaLTIHVQakTATCQVkaYTVHISE, a = D-Ala, k = D-Lys) has a palindromic pattern of polar (p), nonpolar (n), end (e), and beta-turn (t,r) residues (epnpnpnttnpnpnprrpnpnpnttnpnpnpe). Each half contains the same 14-residue palindromic pattern (underlined). Pairs of D-amino acid residues are used to favor formation of inverse-common (type-I') beta turns. In water at pH 6.5, the single chain of betabellin 14S is not folded, but the disulfide-linked betabellin 14D is folded into a stable beta-sheet structure. Thus, folding of the covalent dimer beta-bellin 14D is induced by formation of the single interchain disulfide bond. The binary pattern of alternating polar and nonpolar residues of its beta-sheets is not sufficient to induce folding. Betabellin 14D is a very water-soluble (10 mg/mL), small (64 residues), nongenetic (12 D residues) beta-sheet protein with properties (well-dispersed proton NMR resonances; Tm = 58 degrees C and delta Hm = 106 kcal/mol at pH 5.5) like those of a native protein structure.

Amino Acid Sequence↗
PubMed1994

Deuterium exchange of alpha-helices and beta-sheets as monitored by electrospray ionization mass spectrometry.

Deuterium exchange was monitored by electrospray ionization mass spectrometry (ESI-MS) to study the slowly exchanging (hydrogen bonded) peptide hydrogens of several alpha-helical peptides and beta-sheet proteins. Polypeptides were synthetically engineered to have mainly disordered, alpha-helical, or beta-sheet structure. For 3 isomeric 31-residue alpha-helical peptides, the number of slowly exchanging hydrogens as measured by ESI-MS in 50% CF3CD2OD (pD 9.5) provided estimates of their alpha-helicities (26%, 40%, 94%) that agreed well with the values (17%, 34%, 98%) measured by circular dichroic spectroscopy in the same nondeuterated solvent. For 3 betabellins containing a pair of beta-sheets and a related disordered peptide, their order of structural stability (12D > 12S > 14D > 14S) shown by their deuterium exchange rates in 10% CD3OD/0.5% CD3CO2D (pD 3.8) as measured by ESI-MS was the same as their order of structural stability to unfolding with increasing temperature or guanidinium chloride concentration as measured by circular dichroic spectroscopy in water. Compared to monitoring deuterium exchange by proton NMR spectrometry, monitoring deuterium exchange by ESI-MS requires much less sample (1-50 micrograms), much shorter analysis time (10-90 min), and no chemical quenching of the exchange reaction.

Amino Acid Sequence↗
PubMed1994

ICAM-1 (CD54) expression on B lymphocytes is associated with their costimulatory function and can be increased by coactivation with IL-1 and IL-7.

Recent studies have demonstrated that acute lymphoblastic leukemia-derived pre-B cell lines are deficient in their costimulatory function for T cell proliferation in response to the mitogen Con A and the superantigens TSST-1 and SEB. Stimulation of these pre-B cells with IL-7 increased their costimulatory function which involved the B7/CD28 pathway. In the present study, we stimulated T cells with Con A, TSST-1, and SEB in the presence of peripheral blood B lineage cells that do not constitutively express B7/BB1 on their surface and investigated whether their costimulatory function could also be enhanced by IL-7. We found that, in the presence of IL-1, stimulation with IL-7 increased the costimulatory function of B cells and their surface expression level of ICAM-1 (CD54). We then investigated whether costimulatory B cell function could be inhibited by blocking the ICAM-1/LFA-1 pathway. Addition of anti-ICAM-1 mAb to the coculture of T and B cells inhibited T cell proliferation by approximately 20%. In contrast, addition of anti-LFA-1 beta (CD18) mAb, directed against the T cell ligand of ICAM-1, inhibited T cell proliferation almost completely. To determine the role of ICAM-1 in costimulatory B cell function, we sorted B cells into ICAM-1low-and ICAM-1high-expressing populations. We found that B cells expressing high levels of surface ICAM-1 elicited significantly higher T cell responses than those with low levels, suggesting that the expression level of ICAM-1 on peripheral blood B cells correlates with their costimulatory function.

Antibodies, Monoclonal↗
PubMed1994

A Pit-1 binding site in the human renin gene promoter stimulates activity in pituitary, placental and juxtaglomerular cells.

One of the principal aims of our research is to determine the mechanisms which direct renin gene expression to different sites. We recently demonstrated that human renin (hRen) 5'-flanking DNA sequences -148 +/- 11 can drive the transient expression of a linked luciferase reporter gene transfected into pituitary GC cells. This activity was found to be dependent on the binding of Pit-1 to a site approximately 70 bp upstream from the transcription start site. Pit-1 is a pituitary-specific transcription factor which is involved in directing the cell-specific expression of growth hormone (GH) and prolactin (PRL) gene expression to somatotrope and lactotrope cells of the anterior pituitary. Thus, Pit-1 may be play a role in directing the expression of renin to primate lactotrope cells. Renin promoter-driven luciferase or CAT hybrid genes were found to be expressed following transfection into primary, or early passage cell cultures of placental chorionic membranes, and the renin-secreting renal tumor cell line As4.1. As with GC cells, deletion or mutagenesis of the Pit-1 site reduced activity several-fold in both placental and renal cells. These results suggest that members of the POU family of transcription factors, or some other closely related group such as the Hox proteins, participate in directing renin gene expression to placental and juxtaglomerular cells.

Binding Sites↗
PubMed1994

Dietary calcium reduces blood pressure, parathyroid hormone, and platelet cytosolic calcium responses in spontaneously hypertensive rats.

Dietary calcium effects on blood pressure, parathyroid hormone (PTH), and platelet cytosolic calcium concentrations were investigated. The dietary calcium (low, 0.2%; medium, 0.5%; and high, 2.0% wt/wt) was supplemented in spontaneously hypertensive rats from 6 through 22 weeks of age. Mean systolic blood pressure was decreased by age 12 weeks with calcium supplementation (low, 227 +/- 6 mm Hg; medium, 211 +/- 6 mm Hg; and high, 182 +/- 7 mm Hg; P < .001). By the 10th week of age, the low calcium group had significantly (P < .05) more elevated (44 +/- 2.3 pg/ml) plasma PTH compared with the high calcium-supplemented group (15 +/- 4.5 pg/mL). Regression analysis showed a significant (P < .001) positive correlation (r = 0.3) between systolic blood pressure and PTH. The platelet cytosolic calcium concentration was determined using the fura-2 method. The basal calcium was 134 +/- 5.5 nmol/L for the low calcium group and thrombin increased to 228 +/- 8 nmol/L (P < .0001; +70% change). The normal calcium group had 202 +/- 8 nmol/L; thrombin increased to 239 +/- 10 nmol/L (P < .0026; +19% change). The high calcium group had basal levels 145 +/- 7 nmol/L, with thrombin stimulating to 212 +/- 8 nmol/L (P < .0001; +46% change). Although thrombin increased platelet cytosolic calcium concentration in all groups, normal and high dietary calcium groups had smaller percentage increases (51% and 24% lesser, respectively) compared with the low dietary calcium group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Nucleotide sequence of polymerase chain reaction product amplified from Rickettsia japonica DNA using Rickettsia rickettsii 190-kilodalton surface antigen gene primers.

The PCR product amplified from Rickettsia japonica with the primer pair Rr 190.70p and Rr 190.602n of R. rickettsii 190-kDa antigen gene was cloned into M13mp19 RF DNA at the Eco RI site and sequenced by chemiluminescent DNA sequencing. The sequence revealed a molecular size of 533 base pairs (bp). The primer-flanking region of 491 bp, an open reading frame, was compared with the corresponding region of R. rickettsii, demonstrating 35 nucleotide substitutions in R. japonica. The sequence of primer portions in R. japonica DNA was also analyzed, revealing one nucleotide substitution in the Rr 190.70p and two in the Rr 190.602n portion. The homology in the overall sequence of PCR-amplified regions between R. japonica and R. rickettsii was 93% in nucleotide and 85% in putative amino acid structure. The sequence contains no cleavage site for the restriction endonuclease AfaI but two PstI sites giving three fragments of 121, 159, and 253 bp, which differentiated R. japonica from other spotted fever group rickettsiae in addition to R. rickettsii. The cleavage sites for endonucleases AluI, HinfI, and MunI that disappeared or appeared in the sequence by nucleotide substitution differentiated R. japonica from others, as did PstI. The estimation of molecular size of DNA fragments on polyacrylamide gel electrophoresis is discussed.

Antigens, Bacterial↗
PubMed1994

Pituitary-specific transcription factor (Pit-1) binding site in the human renin gene 5'-flanking DNA stimulates promoter activity in placental cell primary cultures and pituitary lactosomatotropic cell lines.

Renin gene expression is limited to a number of specific tissues, including the kidney, adrenal glands, reproductive organs (of particular relevance to this study, the placenta), and the pituitary gland. In the present study, we investigated the human renin (hRen) 5'-flanking DNA sequences required to drive the expression of a luciferase reporter gene in placental and pituitary cells and in two cell lines, 293 and JEG-3, which have been proposed as model systems with which to study transcriptional regulation of renin genes. The activities of specific sequences in the hRen 5'-flanking DNA sequences in human placental cell primary cultures were very similar to those that we previously reported in pituitary cells, suggesting the involvement of common promoter elements and related transcription factors. Accordingly, the binding site for the pituitary-specific transcription factor (Pit-1) was the major determinant of renin promoter activity in both pituitary and placental cells. Gel mobility shift analysis showed a placental nuclear factor with a gel mobility different from that of Pit-1. However, Northern blot analysis failed to demonstrate abundant Pit-1-related mRNAs in renin-expressing cultures of chorionic and decidual cells, suggesting that the placental factor is not closely related to Pit-1. Although a factor from 293 cells also bound to the Pit-1 site, it had gel mobility shift characteristics different from Pit-1 and the placental factor. Moreover, the low promoter activity in 293 cells was independent of this site or, indeed, of sequences upstream from the TATA box. In JEG-3 cells, renin 5'-flanking DNA sequences showed virtually no transcriptional activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1994

[Detection of P-glycoprotein expression in patients with acute leukaemia and clinical significance].

Anti-P-glycoprotein monoclonal antibody JSB-1 and alkaline phosphatase-anti-alkaline phosphatase (APAAP) immunocytochemical staining technique were used to study the relation between P-glycoprotein expression and clinical multidrug resistance (MDR) in 42 patients with acute leukaemia (23 ALL and 19 ANLL). 10 of 17 patients who were diagnosed as refractory or relapsed acute leukaemia were positive with P-glycoprotein expression, while only 3 of 14 newly diagnosed and 1 of 11 who were in complete remission were positive. The preliminary results indicated that there was a close association between the P-glycoprotein expression and the clinical resistance to chemotherapy in some patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

[Effect of GG on the occurrence of tongue retropulsion--an experimental observation of electromyography].

To evaluate the effect of GG activity on tongue backwardness during sleep, we conducted experiments on 16 rabbits. The electric activities of the muscles involved in tongue motion were recorded in different phases (wakefulness, presnoring and snoring) with unipolar electrodes inserted into the muscles under direct vision. The observations demonstrated that GG played a more active role in the occurrence of tongue backwardness during sleep.

Animals↗
PubMed1994

Role of collagen metabolism changes in the pathogenesis of pulmonary hypertension in rats and its reversibility.

Pulmonary arterial pressure (PAP) was increased obviously in rats after 3 days of normobaric hypoxic exposure and reached a maximum at 14 days of hypoxia. It remained at the same level during prolonged hypoxic exposure of up to 21 days. Right ventricular weight (RV/LV+S) and hydroxyproline (HP) content in the pulmonary artery began to increase at day 7. HP content had increased much faster than the relative rate of increase of PAP after 14 days, but HP content in the thoracic aorta showed no change. The relative proportion of type I to III collagen increased significantly, and compliance of the pulmonary vessels obviously decreased. All parameters returned to the normal range within 14 days after recovery from hypoxia, except for HP content as expressed per vessel. 764-3 treatment obviously attenuated most of the changes caused by hypoxia, though it had no effect on compliance of the pulmonary vessels. It is suggested that collagen, especially type I collagen, accumulation may play an important role in maintaining pulmonary hypertension. 764-3 has certain protective effects and may be useful in the treatment of early chronic obstructive pulmonary disease.

Animals↗
PubMed1994

[Long-term culture of normal and leukemia bone marrow cells].

Using long-term bone marrow culture (LTBMC), we studied the in vitro growth status of bone marrow nucleated cells from 5 normal subjects and 14 patients with acute leukemia. The results showed that LTBMC could support normal hematopoiesis selectively, and in the meantime, inhibit the leukemic progenitor growth. Our preliminary clinical application indicated that this culture system could be used to purge the autologous bone marrow graft in vitro for allogeneic bone marrow transplantation.

Bone Marrow↗
PubMed1994

Cloning and high level expression of gene encoding ES antigen from Trichinella spiralis muscle larvae.

The partial structure gene encoding ES antigen derived from Trichinella spiralis (TSP) muscle larvae was cloned, characterized, and expressed in E. coli. The target DNA (0.7 kb) was directly obtained from the TSP total RNA by using RNA PCR technique. Based on the analysis with the RE digestion, the fragment was cloned into the fusion expression vector pEX31C. It was shown that a kind of 37kDa fusion protein was expressed in E. coli containing the recombinant plasmid by SDS-PAGE electrophoresis. The expressed protein was over 22% of the total cell protein, and it was aggregated in the form of inclusion bodies in E. coli. The purified protein could be recognized in ELISA both by sera from swine-infected with TSP and by the monoclonal antibody against TSP. These findings suggest that the recombinant protein is a potentially valuable antigen both for immunodiagnosis and vaccine development of trichinellosis.

Animals↗
PubMed1994

[Determination of psoralens by gas chromatography].

A gas chromatography capillary column determination of a mixture of psoralens is proposed. The validation of quantitative analysis is detailed and used for the evaluation of psoralens extraction from pharmaceuticals. Moreover stability in acidic or basic media is studied by LC/MS as well as the proposed gas chromatographic methods. A gas chromatography capillary column determination of a mixture of psoralens is proposed.

Chromatography, High Pressure Liquid↗