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Biomedical subjects

X Feng

Publications and source records attributed to X Feng.

At least 91 records · Page 5Linked to original sources
PubMed2000

Inducible nitric oxide synthetase is expressed in adult but not fetal pig pancreatic islets.

Cytokine-induced expression of inducible nitric oxide synthetase (iNOS) and production of nitric oxide (NO) by pancreatic islet cells has been suggested as one potential mechanism for beta cell destruction. In this study, we investigated the role of iNOS and NO in islet primary non-function. Islets were assessed for their function, viability and expression of iNOS. Adult rat and pig islets isolated by collagenase digestion and fetal pig pancreas (FPP) grafts isolated by collagenase digestion or high oxygen culture were transplanted into C57BL6 mice and nude mice. iNOS protein was detected by immunohistochemistry. iNOS protein was found in normal rat and pig pancreas and adult rat and pig islets that were isolated by collagenase digestion and transplanted into either C57BL6 mice or nude mice. iNOS was not detected in fetal pig islet grafts, regardless of whether collagenase was used in the isolation process. In adult pig islet grafts, the presence of iNOS protein correlated with high levels of islet cell apoptosis and primary non-function. Despite the persistent presence of iNOS in rat islets, there was no evidence that it had a deleterious effect on rat islet viability, or function. Therefore, in isolated adult pig islets, there was a correlation between iNOS expression and apoptosis, suggesting that iNOS activation may be deleterious to the adult pig islets. However, other factors such as the fragility of the islet capsule may be equally important. By contrast, fetal pig islets did not express iNOS and this may be an important reason for their enhanced viability when compared with adult islet tissue.

Animals↗
PubMed2000

Angiogenesis in wound healing.

During wound healing, angiogenic capillary sprouts invade the fibrin/fibronectin-rich wound clot and within a few days organize into a microvascular network throughout the granulation tissue. As collagen accumulates in the granulation tissue to produce scar, the density of blood vessels diminishes. A dynamic interaction occurs among endothelial cells, angiogenic cytokines, such as FGF, VEGF, TGF-beta, angiopoietin, and mast cell tryptase, and the extracellular matrix (ECM) environment. Specific endothelial cell ECM receptors are critical for these morphogenetic changes in blood vessels during wound repair. In particular, alpha(v)beta3, the integrin receptor for fibrin and fibronectin, appears to be required for wound angiogenesis: alpha(v)beta3 is expressed on the tips of angiogenic capillary sprouts invading the wound clot, and functional inhibitors of alpha(v)beta3 transiently inhibit granulation tissue formation. Recent investigations have shown that the wound ECM can regulate angiogenesis in part by modulating integrin receptor expression. mRNA levels of alpha(v)beta3 in human dermal microvascular endothelial cells either plated on fibronectin or overlaid by fibrin gel were higher than in cells plated on collagen or overlaid by collagen gel. Wound angiogenesis also appears to be regulated by endothelial cell interaction with the specific three-dimensional ECM environment in the wound space. In an in vitro model of human sprout angiogenesis, three-dimensional fibrin gel, simulating early wound clot, but not collagen gel, simulating late granulation tissue, supported capillary sprout formation. Understanding the molecular mechanisms that regulate wound angiogenesis, particularly how ECM modulates ECM receptor and angiogenic factor requirements, may provide new approaches for treating chronic wounds.

Animals↗
PubMed2000

Phenylpropanes from Acorus tatarinowii.

In addition to a number of known compounds, four new phenylpropanes isoacoramone, (cis) epoxyasarone, (threo) 1',2'-dihydroxyasarone and (erythro) 1',2'-dihydroxyasarone were obtained from the roots of Acorus tatarinowii ("Shi-Chang-Pu" in Chinese). The later two isomers were obtained as a mixture. However, all the chemical shifts of the protons and carbons for these two components were assigned by 1D- and 2D-NMR techniques.

Magnetic Resonance Spectroscopy↗
PubMed2000

Triterpenoids, p-coumaric acid esters and flavonoids from Artemisia igniaria.

Twenty-eight components were detected from the extract of Artemisia igniaria, which included four triterpenoids, eight p-coumaric acid long chain alkyl esters, seven flavonoids and nine common plant constituents. Their structures were determined by spectroscopic methods. This is the first recorded instance of beta-glutinanol and cis-p-coumaric acid eicosanyl ester occurring in nature.

Artemisia↗
PubMed2000

Glutathione oxidation and mitochondrial depolarization as mechanisms of nordihydroguaiaretic acid-induced apoptosis in lipoxygenase-deficient FL5.12 cells.

Nordihydroguaiaretic acid (NDGA) induces apoptosis in a variety of cell lines. The mechanism(s) of this effect is not known, although the focus has been on the ability of NDGA to inhibit lipoxygenase (LOX) activities. In the present study, NDGA-induced apoptosis was studied in a murine hematopoietic cell line, FL5.12. Although this cell line lacks detectable LOX protein or activities, NDGA (10 microM) was able to induce apoptosis. There was a massive loss of mitochondrial membrane potential by 4 h after the addition of NDGA, suggesting that this organelle might be targeted by NDGA. A pro-oxidant NDGA effect has been suggested as playing a role in apoptosis. This was supported by the findings that glutathione disulfide levels were increased by 4 h following treatment with 10 microM NDGA, that pretreatment with N-acetylcysteine completely blocked the NDGA-induced loss of membrane potential and apoptosis, and that lipid peroxidation was enhanced in cells treated with NDGA. However, no evidence of increased levels of reactive oxygen could be seen in NDGA-treated cells loaded with dichlorofluorescin diacetate or dihydrorhodamine and analyzed by flow cytometry. Bcl-X(L) protein levels were unaffected by NDGA treatment. Caspase-3 was rapidly activated with a peak at 8 h after FL5.12 cells were treated with NDGA. Ac-DEVD-CHO (25 microM) and boc-asp-FMK (20 microM) both inhibited caspase-3 enzyme activity by 97% 8 h after NDGA treatment. Boc-asp-FMK, a more general caspase inhibitor, delayed NDGA-induced apoptosis while Ac-DEVD-CHO, a more specific inhibitor of caspase-3, had no effect. These results suggest that NDGA-induced apoptosis happens through reactions that depolarize mitochondria, oxidize glutathione and lipids, but do not generate significant amounts of free reactive oxygen species.

Acetylcysteine↗
PubMed2000

Extensive polymorphism in Cryptosporidium parvum identified by multilocus microsatellite analysis.

Restriction fragment length polymorphism and DNA sequence analysis discern two main types of Cryptosporidium parvum. We present a survey of length polymorphism at several microsatellite loci for type 1 and type 2 isolates. A total of 14 microsatellite loci were identified from C. parvum DNA sequences deposited in public databases. All repeats were mono-, di-, and trinucleotide repeats of A, AT, and AAT, reflecting the high AT content of the C. parvum genome. Several of these loci showed significant length polymorphism, with as many as seven alleles identified for a single locus. Differences between alleles ranged from 1 to 27 bp. Karyotype analysis using probes flanking three microsatellites localized each marker to an individual chromosomal band, suggesting that these markers are single copy. In a sample of 19 isolates for which at least three microsatellites were typed, a majority of isolates displayed a unique multilocus fingerprint. Microsatellite analysis of isolates passaged between different host species identified genotypic changes consistent with changes in parasite populations.

Animals↗
PubMed2000

Dual control of muscle cell survival by distinct growth factor-regulated signaling pathways.

In addition to their ability to stimulate cell proliferation, polypeptide growth factors are able to maintain cell survival under conditions that otherwise lead to apoptotic death. Growth factors control cell viability through regulation of critical intracellular signal transduction pathways. We previously characterized C2 muscle cell lines that lacked endogenous expression of insulin-like growth factor II (IGF-II). These cells did not differentiate but underwent apoptotic death in low-serum differentiation medium. Death could be prevented by IGF analogues that activated the IGF-I receptor or by unrelated growth factors such as platelet-derived growth factor BB (PDGF-BB). Here we analyze the signaling pathways involved in growth factor-mediated myoblast survival. PDGF treatment caused sustained activation of extracellular-regulated kinases 1 and 2 (ERK1 and -2), while IGF-I only transiently induced these enzymes. Transient transfection of a constitutively active Mek1, a specific upstream activator of ERKs, maintained myoblast viability in the absence of growth factors, while inhibition of Mek1 by the drug UO126 blocked PDGF-mediated but not IGF-stimulated survival. Although both growth factors activated phosphatidylinositol 3-kinase (PI3-kinase) to similar extents, only IGF-I treatment led to sustained stimulation of its downstream kinase, Akt. Transient transfection of a constitutively active PI3-kinase or an inducible Akt promoted myoblast viability in the absence of growth factors, while inhibition of PI3-kinase activity by the drug LY294002 selectively blocked IGF- but not PDGF-mediated muscle cell survival. In aggregate, these observations demonstrate that distinct growth factor-regulated signaling pathways independently control myoblast survival. Since IGF action also stimulates muscle differentiation, these results suggest a means to regulate myogenesis through selective manipulation of different signal transduction pathways.

Animals↗
PubMed2000

Mice lacking beta3 integrins are osteosclerotic because of dysfunctional osteoclasts.

Osteoclasts express the alphavbeta3 integrin, an adhesion receptor that has been implicated in bone resorption and that is therefore a potential therapeutic target. To assess the role of this heterodimer in skeletal development in vivo, we engineered mice in which the gene for the beta3 integrin subunit was deleted. Bone marrow macrophages derived from these mutants differentiate in vitro into numerous osteoclasts, thus establishing that alphavbeta3 is not necessary for osteoclast recruitment. Furthermore, the closely related integrin, alphavbeta5, does not substitute for alphavbeta3 during cytokine stimulation or authentic osteoclastogenesis. beta3 knockout mice, but not their heterozygous littermates, develop histologically and radiographically evident osteosclerosis with age. Despite their increased bone mass, beta3-null mice contain 3.5-fold more osteoclasts than do heterozygotes. These mutant osteoclasts are, however, dysfunctional, as evidenced by their reduced ability to resorb whale dentin in vitro and the significant hypocalcemia seen in the knockout mice. The resorptive defect in beta3-deficient osteoclasts may reflect absence of matrix-derived intracellular signals, since their cytoskeleton is distinctly abnormal and they fail to spread in vitro, to form actin rings ex vivo, or to form normal ruffled membranes in vivo. Thus, although it is not required for osteoclastogenesis, the integrin alphavbeta3 is essential for normal osteoclast function.

Animals↗
PubMed2000

Thyroid hormone regulation of hepatic genes in vivo detected by complementary DNA microarray.

The liver is an important target organ of thyroid hormone. However, only a limited number of hepatic target genes have been identified, and little is known about the pattern of their regulation by thyroid hormone. We used a quantitative fluorescent cDNA microarray to identify novel hepatic genes regulated by thyroid hormone. Fluorescent-labeled cDNA prepared from hepatic RNA of T3-treated and hypothyroid mice was hybridized to a cDNA microarray, representing 2225 different mouse genes, followed by computer analysis to compare relative changes in gene expression. Fifty five genes, 45 not previously known to be thyroid hormone-responsive genes, were found to be regulated by thyroid hormone. Among them, 14 were positively regulated by thyroid hormone, and unexpectedly, 41 were negatively regulated. The expression of 8 of these genes was confirmed by Northern blot analyses. Thyroid hormone affected gene expression for a diverse range of cellular pathways and functions, including gluconeogenesis, lipogenesis, insulin signaling, adenylate cyclase signaling, cell proliferation, and apoptosis. This is the first application of the microarray technique to study hormonal regulation of gene expression in vivo and should prove to be a powerful tool for future studies of hormone and drug action.

Adenylyl Cyclases↗
PubMed2000

Relationship between hypertensive left ventricular hypertrophy and levels of endothelin and nitric oxide.

To investigate the relationship between hypertensive left ventricular hypertrophy (LVH) and levels of endothelin (ET) and nitric oxide (NO), and to provide an experimental basis for prevention and treatment of hypertensive LVH. Fifty eight hypertensive patients and 14 healthy controls were studied. All patients were examined by echocardiography. Left ventricular mass (LVM) and left ventricular mass index (LVMI) were calculated using Devereux RB formula. Hypertensive patients were divided into a LVH (+) group (n= 21) and a LVH (-) group (n=37), and the levels of endothelin and nitric oxide in the peripheral venous blood were measured. The mean ET level was significantly higher in the LVH (+) group than in LVH (-) group (p < 0.05), but the NO level was significantly lower in the LVH (+) group. The ET/NO ratio was significantly higher in the LVH (+) group than in LVH (-) group (p< 0.01). For the stepwise multiple regression analysis, the LVMI of hypertensive patients served as a dependent variable, and age, sex, BMI, MAP, ET, NO, and ET/NO served as independent variables. Only MAP, ET, and NO were found to have significant correlation to hypertensive LVH. ET had a significant positive correlation, and NO a significant negative relation to LVMI, but ET/NO showed no correlation to hypertensive LVH. ET and NO are involved in hypertensive LVH; the independent action of ET and NO in the pathogenesis of hypertensive LVH may weaken the relation between ET/NO and hypertensive LVH.

Adult↗
PubMed2000

The application of CD71 and Hoechst33258 to staining method for sorting fetal nucleated red blood cells in the peripheral blood of pregnant women.

OBJECTIVE: To compare mononuclear cells labeled by CD71 single-staining method with CD71 and Hoechst33258(HO258) double-staining one, and sort nucleated red blood cells (NRBCs) in peripheral blood in pregnant women by use of the latter method. METHODS: Mononuclear cells in umbilical blood and peripheral blood in normal pregnant women and patients with mild or moderate pregnant hypertension syndrome were labeled by erythrocyte specific antibody CD71 and nuclear dye HO258. Furthermore, NRBCs were sorted in combination with the use of flow cytometry. RESULTS: Labeled by CD71 and Hoechst33258 double-staining method, the positive labeling rate of mononuclear cells in umbilical blood and peripheral blood in normal pregnant women and patients with pregnant hypertension syndrome was remarkably lower than that labeled by CD71 single-staining method (t-test, P<0.01). Meanwhile, CD71 and Hoechst33258 double-staining method was successfully used in sorting NRBCs in peripheral blood in pregnant women by flow cytometry. CONCLUSION: CD71 and HO258 double-staining method could exclude mature erythrocytes, thrombocytes and reticulocytes and this improve NRBCs' specific label and sorting purity.

Antigens, CD↗
PubMed2000

[The application of meshed acellular dermis xenograft (pigskin) with split thickness skin autograft in 23 patients].

OBJECTIVE: An effective and inexpensive coverage, which can prevent scar formation and fill up scar tissue depression for full thickness skin burns in 23 patients was presented. METHODS: A deepithelized and acellular basement membranes of dermis from freshly harvested pigskin was obtained as meshed acellular dermis xenograft. The patients were treated in one or two stages. Two stages, 7 day postoperative the meshed acellular xenograft, a split thickness skin autograft was applied. One stage, the meshed acellular xenograft and split thickness skin autograft were applied at same time. RESULTS: The take rate of two staged treatment was (87.0 +/- 25.4)% and one stage was (60.3 +/- 3.4)%. All grafts showed in pink or near normal skin color and felt soft and smooth. CONCLUSIONS: The combination of meshed acellular dermis xenograft and split thickness skin autograft demonstrated an ideal way for the coverage of full thickness skin burn, which is effective and inexpensive.

Adolescent↗
PubMed2000

[Research progress on PGPR/AMF interactions].

As one of the rhizospheric microorganisms PGPR(Plant Growth Promoting Rhizobacteria) and AMF(Arbuscular Mycorrhizal Fungi) play an important role in promoting plant growth. It is of significance to further study and elucidate the interactions between them to utilize and regulate the interactions among rhizospheric microorganisms, and promote and protecte plant growth. Many research results show that on one hand, there exists synergism between PGPR and AMF. AMF can transfer PGPR or act as a media in the process of spread of PGPR along roots, where PGPR create many beneficial conditions for the infection of AMF. Both of them can indirectly enhance the other side's colonization or infection ability through their own promoting role on plant growth. On the other hand, they compete with each other for nutrients and niches, and probably produce some secondary metabolites which cause detrimental effects on the other. However, whether these interactions are synergistic or competitive depends upon the AM fungal or PGPR species involved. So far, the research work is extensive, even in molecular level in some aspects, but not systematic and deep. It is believed however, with the development of techniques in molecular biology and the increasing application of advanced testing methods, the new breakthroughs will be gained in the study and understanding on the interactions.

Bacterial Physiological Phenomena↗
PubMed2000

Diagnostic potential of mitochondrial DNA assessment in patients with optic neuropathy.

OBJECTIVE: To study the primary mutations of mitochondrial DNA (mtDNA) associated with Leber's hereditary optic neuropathy (LHON) in patients with optic neuropathy. METHODS: Seventy-nine patients with a variety of bilateral optic neuropathies were examined. Mutations at np3460, np11,778 and np14,484 of mtDNA were tested by PCR-restriction detection in peripheral blood DNA from 16 cases of clinically probable LHON, 44 cases of possible LHON, 2 cases of alcohol amblyopia, 4 cases of multiple sclerosis, 5 cases of autosomal dominant optic atrophy, 4 cases of primary open-angle glaucoma, 3 cases of spinocerebellar degeneration, and 1 case of ethambutol-induced optic neuropathy. RESULTS: The mutation at np11778 was identified in 31 cases (39.2%) to establish LHON, which consisted of: all 16 of clinically probable LHON cases, 13 cases (29.5%) of possible LHON, and 2 cases of alcohol amblyopia. The remaining 48 cases were negative for mtDNA mutations at np3460, np11 778, and np14,484. CONCLUSION: Assessment of mtDNA provides a useful diagnostic aid in the definition and exclusion of LHON, in particular family history-negative, otherwise undefined bilateral optic nerve inflammatory disease.

Adolescent↗
PubMed2000

[A study of sensory pathway in central nervous system of experimental tooth movement in rats].

OBJECTIVE: To investigate whether ventral posteromedial thalamus nucleus (VPM) receive the stimulation from experimental tooth movement in rats through the conduction of spinal trigeminal caudal nucleus (Vc), thus to study the central sensory pathway of tooth movement. METHODS: 2% fluorogold (FG) was injected into rat's VPM using microinjector through retrograde tracing technique. After 4-6 days, the experimental tooth movement was conducted in contra-side against FG injection. 2 hours later, animals were sacrificed and FOS protein immunocytochemical reaction was conducted. The sections were observed under Olympus fluorescence microscope. RESULTS: FOS immunocytochemical-positive neurons were densely distributed in epilateral superfacial layer of Vc, being belt-like with more in dorsolateral 2 hours after experimental tooth movement; FG-labeled neurons were found in Vc and principle trigeminal nucleus complex, especially within the whole length of Vc, with more in layer I and the junction of layers I and II. There were both FOS immunocytochemically positive and FG-labeled neurons, approximately 5% of the whole FG-labeled neurons. CONCLUSION: As a special oro-facial stimulation, there are corresponding parts in the central nervous system according to tooth movement. The stimulating message integrated in Vc and Vc has projective neurons to VPM, and VPM might be a relay station of the stimulating message of experimental tooth movement in rats.

Afferent Pathways↗
PubMed2000

[Interaction between biofilm formed by Pseudomonas aeruginosa and antibacterial agents].

UNLABELLED: We hypothesized that bacterial biofilm formation could be an important factor that make some infection intractable. Interaction of P. aeruginosa biofilm with antibactial agents was examined in vitro. METHODS: P. aeruginosa incubated for 6 days in a saline-teflon system formed biofilm on the surfaces of the teflon piece. The biofilm were characteried by dense colonization of bacteria and thick membranous structure that covered the colonies, it was observed with a scanning electron microscopy. CPFX, CAM, ROX and Herba Andrographitis were added to the biofilm bacteria. RESULTS: The rate of survial of the floating bacteria decreased to 0.02% after 4 hours of contact with 2MIC of Ciprofloxacin (CPFX), but that of biofilms was 41% When 10 micrograms/mL of Clarithromycin (CAM per mL was combined with CPFX, the survial rate for the biofilm bacteria decreased to 0.2%. When 12 micrograms/mL of Roxithromycin (ROX) was combined with CPFX, the survial rate for the biofilm bacteria decreased to 0.5%. When 0.05 g of Burm. f. per mL was combined with CPFX the survial rate for the biofilm bacteria decreased to 2.7%. CONCLUSION: We conclude that biofilm bacteria are much more resistant to CPFX than the floating bacteria. The combination of CPFX and CAM, ROX HA were more effective in decreasing the biofilm bacteria survial rate than CPFX alone. The results suggest that the combination of CPFX and CAM, ROX, HA can be one of the therapeutic manauvers against biofilm bacteria.

Anti-Bacterial Agents↗
PubMed2000

[The experience with endoscopic natural ostiotomy].

OBJECTIVE: To improve the operative technique of endoscopic middle metal antrostomy. METHODS: One hundred and thirty-five patients with chronic sinusitis were divided into two groups(first stage and second stage groups). All of them had been followed up for more than 6 months. RESULTS: Middle metal antrostomy was performed for 79 patients (158 sides) in the first group. The diameter of middle meatal window ranged from 1.0 cm (anterior-posterior diameter) to 1.5 cm(superior-inferior diameter). Improved middle meatal antrostomy was performed for 56 patients (112 sides) in the second group. The anterior-posterior diameter of the middle meatal window was over 1.0 cm, and superior-inferior diameter was over 1.5 cm. In the first group, the patency rate in the first stage was 78.48% (124/158), and satisfactory patency rate was 43.0% (68/158). The patency rate was 85.4% (135/158), and satisfactory patency rate was 45.0%(71/158). In the second group, the patency rate was 92.9%(104/112) in the first stage, and 94.6%(106/112) in the second stage. The satisfactory patency rate in both stages was 79.5%(89/112). There was significant difference between two groups(P < 0.05). CONCLUSION: The patency rate and satisfactory patency rate of middle meatal antrostomy are increased by improved technique.

Adolescent↗