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Biomedical subjects

L Ying

Publications and source records attributed to L Ying.

At least 37 records · Page 2Linked to original sources
PubMed1998

Structure-activity relationship and classification of flavonoids as inhibitors of xanthine oxidase and superoxide scavengers.

The structure-activity relationship of flavonoids as inhibitors of xanthine oxidase and as scavengers of the superoxide radical, produced by the action of the enzyme xanthine oxidase, was investigated. The hydroxyl groups at C-5 and C-7 and the double bond between C-2 and C-3 were essential for a high inhibitory activity on xanthine oxidase. Flavones showed slightly higher inhibitory activity than flavonols. All flavonoid derivatives except isorhamnetin (30) were less active than the original compounds. For a high superoxide scavenging activity on the other hand, a hydroxyl group at C-3' in ring B and at C-3 were essential. According to their effect on xanthine oxidase and as superoxide scavengers, the flavonoids could be classified into six groups: superoxide scavengers without inhibitory activity on xanthine oxidase (category A), xanthine oxidase inhibitors without any additional superoxide scavenging activity (category B), xanthine oxidase inhibitors with an additional superoxide scavenging activity (category C), xanthine oxidase inhibitors with an additional pro-oxidant effect on the production of superoxide (category D), flavonoids with a marginal effect on xanthine oxidase but with a prooxidant effect on the production of superoxide (category E), and finally, flavonoids with no effect on xanthine oxidase or superoxide (category F).

Enzyme Inhibitors↗
PubMed1998

Characterization and comparison of the human and mouse GLC1A glaucoma genes.

The GLC1A gene (which encodes the protein myocilin) has been associated with the development of primary open angle glaucoma. Bacterial artificial chromosomes containing the human GLC1A gene and its mouse ortholog were subcloned and sequenced to reveal the genomic structure of the genes. Comparison of the coding sequences of the human and mouse GLC1A genes revealed a high degree of amino acid homology (82%) and the presence of several conserved motifs in the predicted GLC1A proteins. The expression of GLC1A was examined by Northern blot analysis of RNA from adult human tissues. GLC1A expression was observed in 17 of 23 tissues tested, suggesting a wider range of expression than was recognized previously. The comparison of the human and mouse GLC1A genes suggests that the mouse may be a useful model organism in studying the molecular pathophysiology of glaucoma.

Amino Acid Sequence↗
PubMed1998

[The choice of intraocular lens before cataract extraction for cases with high myopia].

OBJECTIVE: To study the choice of diopter and size of optical portion of intraocular lens (IOL) before cataract extraction for cases with high myopia. METHODS: Extracapsular cataract extraction (ECCE) or phacoemulsification with IOL implantation was performed on 60 cases (94 eyes) with high myopia (axial length > 26mm). The posterior chamber IOL selected and inserted was the one with the diopter and size of the optical portion suitable for the recipient to have a postoperative low myopia and easy to be examined with an ophthalmoscope. RESULTS: The postoperative eyes were of low myopia, -2.07 +/- 1.95 D. The larger size of optical portion was more suitable for ocular fundus examination. Great care was taken for phacoemulsification for cataractous nucleus below III grade. CONCLUSIONS: For patients with axial myopia, the IOL implanted should create low myopia postoperatively. Larger optic size is better for fundus examination. Phacoemulsification can produce less astigmatism and damage, but the indication must be controlled strictly.

Adolescent↗
PubMed1997

Transactivation of the human renin promoter by the cyclic AMP/protein kinase A pathway is mediated by both cAMP-responsive element binding protein-1 (CREB)-dependent and CREB-independent mechanisms in Calu-6 cells.

We examined the DNA sequence and transcription factor requirements for cAMP-induced transactivation of the human renin promoter using Calu-6 cells that express human renin mRNA endogenously. A series of constructs containing 896 base pairs of human renin 5'-flanking DNA fused to the luciferase gene and containing either the native, a consensus, or a nonfunctional cAMP response element (CRE) were used to assess DNA sequence requirements mediating the cAMP response. Expression vectors encoding the CREB-1 transcription factor, a dominant negative mutant form of CREB-1, and the catalytic subunit of protein kinase A (PKA) were used to assess transcription factor requirements mediating the cAMP response. Forskolin treatment alone only caused a 2-3-fold activation of the HREN promoter in Calu-6 cells, but nearly a 10-fold activation in JEG-3 cells, which do not express renin but are highly responsive to cAMP. Gel shift assays revealed the binding of five specific DNA-protein complexes consisting of the ATF-1 and CREB-1 transcription factors, one of which was an ATF-1.CREB-1 heterodimer suggesting the potential for regulation of CREB-1 activity by ATF-1. However, over-expression of CREB-1 did not significantly enhance forskolin-induced human renin transcriptional activity. Transfection of both Calu-6 and JEG-3 cells with a PKA expression vector resulted in a 10-fold induction of human renin transcriptional activity in constructs containing the native or consensus CRE and 5-fold activation in a construct containing a nonfunctional CRE. We confirmed that the PKA response has both a CREB-dependent and CREB-independent component by demonstrating that the PKA response was abolished by co-transfection of a dominant negative mutant form of CREB-1 into cells containing the native or consensus CRE construct but not in cells containing the nonfunctional CRE construct. We therefore conclude that the human renin promoter can be transcriptionally activated in a renin expressing cell line through the cAMP-PKA pathway and is mediated by both a CREB-dependent and CREB-independent mechanism.

Activating Transcription Factor 1↗
PubMed1997

Expression of acidic fibroblast growth factor in Barrett's esophagus and associated esophageal adenocarcinoma.

OBJECTIVE: Adenocarcinoma of the esophagus is generally attributed to the neoplastic transformation of intestinal metaplastic lesions (Barrett's esophagus). On the basis of our preliminary data that showed significant acidic fibroblast growth factor mRNA and protein expression in adenocarcinoma of the esophagus, we studied expression of fibroblast growth factor in esophageal adenocarcinoma and its precursor lesions, intestinal metaplasia, low-grade dysplasia, and high-grade dysplasia. Fibroblast growth factor belongs to a family of polypeptides that are involved in differentiation and cellular proliferation. METHODS: We examined 30 esophagectomy specimens that were resected for adenocarcinoma (n = 27) and high-grade dysplasia (n = 3). After confirmation of the diagnosis by routine light microscopy, the index lesions (invasive carcinomas) and adjoining Barrett's mucosa were evaluated with a monoclonal antibody against human acidic fibroblast growth factor. The results are expressed with the use of an immunoreactive score that allows distinction between weak, moderate, and strong immunoreactivity. RESULTS: Adenocarcinoma demonstrated a moderate-to-strong mean immunoreactive score of 8. In contrast, high-grade dysplasia demonstrated a weak-to-moderate mean score of 4.5, which was significantly different (p < 0.05). Intestinal metaplasia and low-grade dysplasia displayed even weaker expression of fibroblast growth factor, with a negligible immunoreactive score less than 1 (p < 0.005). Seventy-five percent of evaluable cases demonstrated an increasing degree of fibroblast growth factor expression in the spectrum of lesions ranging from metaplasia to dysplasia and carcinoma. CONCLUSIONS: These data indicate that in patients with adenocarcinoma arising in association with Barrett's esophagus, fibroblast growth factor is generally sequentially accumulated in the progression from metaplasia to neoplasia. This progression may affect future investigation into the role of fibroblast growth factors in tumorigenesis and, possibly, the application of fibroblast growth factor immunohistochemistry to diagnosis.

Adenocarcinoma↗
PubMed1997

Characterization of integrin expression in a well differentiated endometrial adenocarcinoma cell line (Ishikawa).

The pattern of constitutive and cycle-dependent integrins in normal endometrium has recently been established, suggesting a role for cell adhesion molecules in endometrial receptivity and implantation. Currently few, if any, models exist for the study of human endometrial integrins and their role in establishment of the receptive endometrial phenotype. The Ishikawa cell line maintains functional estrogen receptors and progesterone receptors. The progesterone receptors in these cells are inducible by priming with estradiol and down-regulated by treatment with progesterone. In the present study the pattern of integrin expression in this well differentiated endometrial cell line is compared to that in normal endometrial epithelium using immunohistochemistry and flow cytometry and is confirmed by immunoprecipitation, Western immunoblot, and PCR. Like normal endometrial epithelium, Ishikawa cells maintain constitutive expression of alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 4. PCR demonstrates the expected size fragments of each, although evidence for alternatively spliced forms of the alpha 2-subunit was noted. Progesterone treatment of estradiol-primed cells resulted in increased expression of the alpha 1 beta 1 collagen-laminin receptor and suppression of the alpha v beta 3 vitronectin receptor, two of the cycle-dependent integrins expressed by normal endometrial epithelium. These data support the use of Ishikawa cells as an excellent model to study the regulation endometrial integrins and advance our understanding of hormonally mediated events surrounding implantation.

Adenocarcinoma↗
PubMed1995

Morphometry of rat germ cells during spermatogenesis.

BACKGROUND: There has never been a study of the components of germ cells as they progress through spermatogenesis. METHODS: The structural changes taking place in rat germ cells, from spermatogonia to late spermatids, were studied utilizing morphometric techniques conducted largely at the ultrastructural level. RESULTS: Volume and surface area parameters for virtually all cellular and subcellular features were obtained for nine periods during the spermatogenic cycle. Virtually all germ cell components show dynamic properties associated with specific phases of their development. CONCLUSIONS: The data provided can be used in an objective way to characterize structural changes taking place during spermatogenesis and to relate those structural changes to functional properties of germ cells.

Acrosome↗
PubMed1995

Effectiveness of Norplant implants through seven years: a large-scale study in China.

The effectiveness of Norplant implants over a seven year period of continuous use was studied in a multicenter trial. Pregnancy rates were 0.4 per 100 in both year six and year seven. More than 3,600 women completed 6 years and more than 2,400 women completed 7 years. Pregnancy rates increased with weight (p < .05) and decreased with age, but in years 6 and 7 combined, the pregnancy rate neither reached nor exceeded 1 per 100 woman years in any 5 year age group or in any 10 kg weight group.

Adult↗
PubMed1994

Insertional mutation that causes acrosomal hypo-development: its relationship to sperm head shaping.

A family of transgenic mice (OVE 219) was generated by microinjection of a tyrosinase minigene (Ty811C). The transgenic mice demonstrate an atypical and variable coat color pattern and the homozygous males show abnormalities of spermatogenesis that are variably expressed from animal to animal. Heterozygous mice proved to have normal spermatogenesis and along with non-transgenic mice were used as controls to study the abnormalities in spermatogenesis in OVE 219 homozygous males. These abnormalities shed light on the features controlling normal spermatogenesis. In some homozygous males early spermiogenesis was disrupted as the flagellar microtubules became disorganized within the flagellar process. What appeared to be crystalline tubulin was noted within some of the rounded flagellar processes. Sperm with this defect did not develop a flagellum. In other homozygous males defects were apparent by step 6 or 7 of spermiogenesis when the acrosome did not grow and spread over the nucleus as noted in control animals. The modified nuclear envelope underlying the acrosome continued to develop and spread well beyond one margin of the acrosome. Since the modified nuclear envelope grew independently of the acrosome, the acrosome was not the controlling factor in determining the spread of the modified nuclear envelope. Micrographs revealed that Sertoli ectoplasmic specialization failed to form over most regions of the spermatid head lacking a normal acrosome. In homozygous males, the manchette took origin (proximally) in close relation to the modified nuclear envelope and never in relation to the edge of the spreading acrosome, a feature indicating that manchette placement was influenced by the position of the modified nuclear envelope and not the edge of the acrosome. Thus the modification in the nuclear envelope may be the primary event to signal acrosomal spread and manchette development. In spermatids where the manchette developed from an ectopic site, the result was abnormal caudal head shaping. In some spermatids a portion of the manchette was lacking. When this occurred the caudal head was rounded in the region of the missing manchette. In a minority of spermatids there was no evidence for a manchette. The entire caudal head was gently rounded. These data support the growing body of evidence that the caudal sperm head is shaped, in part, by the manchette. The OVE 219 family of mice provides a useful model to understand the processes involved in periods of spermiogenesis that are critical to development of a normally shaped sperm head.

Acrosome↗
PubMed1994

Iron-induced conformational change in human lactoferrin: demonstration by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analysis of effects of iron binding to the N and C lobes of the molecule.

Analysis of Fe-saturated- and apo-lactoferrin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) without heating the samples prior to application revealed a substantial difference in mobility. The mobility shift was fully reversible on repetitive removal and readdition of Fe. Binding of a single Fe to the N-lobe binding site was sufficient to cause the gel shift; binding of a second Fe to the C-lobe site did not further alter mobility. Removal of Fe from the N lobe of Fe2 lactoferrin did not restore mobility to the position of apolactoferrin. No change in mobility with Fe binding was detected in N and C lobes isolated from intact lactoferrin by controlled trypsin digestion. The data indicate that a conformational change induced by Fe binding to a single site on lactoferrin is detectable by SDS-PAGE and that this change requires an intact molecule, possibly due to the need for interactions between the two homologous lobes of the molecule.

Apoproteins↗
PubMed1994

The urethral glands of male mice in relation to depletion of secretory granules upon mating.

The present study describes the effects of mating on urethral gland acinar cells in male mice. Histological and morphometric analysis demonstrated that there was a depletion of secretory granules in the urethral glands during mating. However, no change occurred in the rough endoplasmic reticulum containing tubular elements. The results indicate that the urethral glands are functional during mating. The timing of their granule depletion suggests that urethral gland secretions may contribute to the formation of semen or the copulation plug.

Animals↗
PubMed1994

The influence of age and location of arterial lesion on the pathogenesis and development of early atherosclerotic lesions in youth.

From 1986 to 1989, 324 aortae from accidental death aged 15-39 were collected from two locations, one of higher prevalence (Beijing in North China), and the other of lower prevalence (Nanning in South China) of atherosclerosis (AS) and coronary heart disease (CHD). Morphometry and biochemical analyses, were used in the study with emphasis on the changes of smooth muscle cells (SMC) in the aortic intima and on the aortic proteoglycans (PGs) of specimens from both locations to elucidate their relationship with the pathogenesis and development of AS and to find ways, if any, for the prevention and control of AS. The results showed that the densities, especially the area density of the cell nuclei of aortic SMC were significantly higher in specimens from the North than those from the South (P < 0.01). Nuclear densities of SMC negatively correlated with alcian blue-positive substances; both total PGs and Heparin sulfate PG (HSPG, inhibitory to SMC proliferation) of the aortic intima and media were lower in specimens from the North than those from the South (P < 0.01). The percentage of sudanophilic lesion (SL) in the total intimal area, showing the extent of fatty infiltration of aortae from the two locations, was similar except that of the male abdominal aortae which was higher in the North (P < 0.01). The above findings showed that decreased content of HSPG which is inhibitory to SMC proliferation might be one of the causes of the augmentation of aortic SMC proliferation in Beijing specimens; and also the increased serum cholesterol concentration of the population in Nanning was reflected in the SL of the aortic intima.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Iron binding to human lactoferrin alters reactivity of the protein with plant lectins.

Binding of Fe by human apolactoferrin results in altered reactivity of the glycoprotein with plant lectins. Reaction with wheat germ agglutinin (WGA) and peanut agglutinin (PNA) was abolished with Fe binding. Reaction with the lectins from Datura stramonium (DSA) and Aleuria aurantia (AAA) was significantly reduced but not fully abolished on Fe binding, while reaction with the Artocarpus integrifolia lectin (Jacalin) and Sambucus nigrabark (SNA) was not changed at all. Loss of WGA reactivity occurred when only one of two Fe binding sites on the molecule was saturated. The results demonstrate conformational changes that are associated with high-avidity binding of Fe by lactoferrin.

Antibodies, Monoclonal↗
PubMed1993

Sertoli cell cycle: a re-examination of the structural changes during the cycle of the seminiferous epithelium of the rat.

Seminiferous tubules in mammals are composed of cell associations that show a cyclic pattern of renewal and development. The cyclic nature of germ cell development suggests that the cells supporting the spermatogenic process, the Sertoli cells, might also differ structurally during the spermatogenic cycle in terms of the quantity of their constituents. In the present study, cyclic differences in volumes, and surface areas were determined using a sampling technique at the electron microscope level that proportionally samples the Sertoli cell within the seminiferous tubule. Among the many parameters studied, only the surface area of the cell, the volume of lipid, and the volume and surface area of the rough endoplasm reticulum were shown by statistical analysis to vary cyclically. Regarding rough endoplasm reticulum, the volume and surface area of this organelle peaked at mid-cycle and its low was recorded near the end of the cycle, exhibiting an approximate 15-fold difference between extremes. The rough endoplasm reticulum parameters generally correlated with known patterns of protein secretion within the tubule and with the secretion of specific proteins as well as the factors important in controlling protein secretion. Many Sertoli cell structural parameters suggested to be influenced cyclically in the rat in other studies could not be confirmed by the present study. Methodological differences in the present study and past studies are discussed as potential sources of error for these discrepancies.

Animals↗
PubMed1992

Is the establishing of tolerance to self obligatorily MHC restricted?

The prevailing paradigm used to interpret how T cells recognize antigen treats antigen processing as obligatory because the T cell antigen receptor complex can only detect antigen located in a "groove" found on MHC-encoded restricting elements. The vast majority of experimental systems used to analyze how T cells recognize antigen depend on induced T cells executing their effector functions, and it is agreed without exception that this event is MHC restricted. However, to date, the extrapolation of the obligatory MHC restriction of effector function to the level of the antigen-responsive T cell that makes the tolerance induction decision, depends not on experiment, but on theoretical constructs. The few experiments designed to test whether tolerance is MHC restricted are open to several interpretations, only one of which is consistent with the view that all antigen recognition events must be MHC restricted. If it can be shown that tolerance is not obligatorily MHC restricted, then the pillar of the prevailing paradigm will have fallen. The experiments described here throw into serious doubt the evidence that has been used to conclude that tolerance is obligatorily MHC restricted.

Animals↗
PubMed1987

Communication between two globular domains of calmodulin in the presence of mastoparan or caldesmon fragment. Ca2+ binding and 1H NMR.

Ca2+ binding to calmodulin was measured in the presence of mastoparan or caldesmon fragment. Mastoparan and caldesmon fragment were used as model compounds of enzymes and cytoskeleton proteins, respectively, working as the target of calmodulin. Although the Ca2+ bindings of the two globular domains of calmodulin occur independently in the absence of the target peptide (or proteins), mastoparan and caldesmon fragment increased the affinity of Ca2+ and, at the same time, produced the positive cooperative Ca2+ bindings between the two domains. The result of Ca2+ binding was compared with 1H NMR spectra of calmodulin in the presence of equimolar concentration of mastoparan. It is known that a conformation change of the C-terminal half-region (C-domain) occurs by the Ca2+ binding to C-domain. A further change in conformation of C-domain was demonstrated by the Ca2+ binding to the N-terminal half-region (N-domain) in the presence of mastoparan. It indicates that the two domains of calmodulin get into communication with each other in the associated state with the target, and we concluded that the Ca2+ binding to the N-domain is responsive to the development of calmodulin function.

Animals↗
PubMed1987

Oral and maxillofacial surgery in China.

The primary author is a 41-year-old oral and maxillofacial surgeon on the attending staff of the Stomatology Hospital of Nanjing Medical University in Nanjing, China. He is currently a visiting scholar at the University of Michigan and has a wide variety of experience in medicine and dentistry, including 11 years of general surgery, plastic surgery, and tumor surgery training in addition to his stomatology education. His experiences during the past 20 years have prompted his American colleagues to encourage him to present his views with respect to oral and maxillofacial surgery in China today. The purpose of this article is to promote understanding among colleagues in China and in the West.

China↗