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Biomedical subjects

X H Yang

Publications and source records attributed to X H Yang.

At least 19 recordsLinked to original sources
PubMed2006

A time-temperature rheological study of konjac glucomannan hydrocolloid.

Konjac glucomannan (KGM) is one of the most versatile soluble biomaterials having wide-ranging applications. The shear storage, G', and loss, G", moduli of this hydrocolloid were recorded as functions of angular frequency varying from 0.1 to 100.0 rad/s and temperature from 5 to 50 degrees C. It was found that both G' and G" mainly increase with angular frequency in the range from 0.1 to 100 rad/s. As the temperature increases from 5 to 95 degrees C, the values of G' and G" decrease. A novel criterion for the thermorheologically simple material, and a procedure to calculate the shift factor from the angular frequency sweep and temperature ramp data were presented. By these methods, the KGM hydrocolloid is found to obey the TTS principle as log G" and log G' are less than 1.529 and 1.436, respectively. The Williams-Landel-Ferry equation can describe the shift factor of the KGM hydrocolloid.

Colloids↗
PubMed2001

Tumor formation and inactivation of RIZ1, an Rb-binding member of a nuclear protein-methyltransferase superfamily.

The retinoblastoma protein-interacting zinc finger gene RIZ (PRDM2) is a member, by sequence homology, of a nuclear protein-methyltransferase (MTase) superfamily involved in chromatin-mediated gene expression. The gene produces two protein products, RIZ1 that contains a conserved MTase domain and RIZ2 that lacks the domain. RIZ1 gene expression is frequently silenced in human cancers, and the gene is also a common target of frameshift mutation in microsatellite-unstable cancers. We now report studies of mice with a targeted mutation in the RIZ1 locus. The mutation inactivates RIZ1 but not RIZ2. These RIZ1 mutant mice were viable and fertile but showed a high incidence of diffuse large B-cell lymphomas (DLBL) and a broad spectrum of unusual tumors. RIZ1 deficiency also accelerated tumorigenesis in p53 heterozygous mutant mice. Finally, several missense mutations of RIZ1 were found in human tumor tissues and cell lines; one of these was particularly common in human DLBL tumors. These missense mutations, as well as the previously described frameshift mutation, all mapped to the MTase functional domains. All abolished the capacity of RIZ1 to enhance estrogen receptor activation of transcription. These data suggest a direct link between tumor formation and the MTase domain of RIZ1 and describe for the first time a tumor susceptibility gene among methyltransferases.

Alleles↗
PubMed2001

Reconstitution of caspase 3 sensitizes MCF-7 breast cancer cells to doxorubicin- and etoposide-induced apoptosis.

MCF-7, a breast cancer-derived cell line, is deficient of caspase 3 and relatively insensitive to many chemotherapeutic agents. To study the association of caspase 3 deficiency and chemotherapeutic resistance, we reconstituted caspase 3 in MCF-7 cells and characterized their apoptotic response to doxorubicin and etoposide. Western blots demonstrated that caspase 3 was constitutively expressed in the reconstituted MCF-7 cells. Both morphological observation and survival assays showed that caspase 3 reconstitution significantly sensitized MCF-7 cells to both drugs. Remarkably increased activation of caspases 3, 6, and 7, cleavage of cellular death substrates, and DNA fragmentation were detected in the reconstituted MCF-7 cells after drug treatment. Together, these data demonstrated a specific role for caspase 3 in chemotherapy-induced apoptosis and in activation of caspases 6 and 7. Our results also suggest that caspase 3 deficiency may contribute to chemotherapeutic resistance in breast cancer.

Antibiotics, Antineoplastic↗
PubMed2000

[Clinical study on nosocomial infection in patients with burns].

OBJECTIVE: To study clinical characters and related factors of nosocomial infection in patients with burns. METHODS: To study 782 cases of burns as a group hospitalized in our department for more than 48 h, from January, 1993 to December, 1996. Prospective and retrospective investigation of infection locations, infection rates, pathogen and drug sensibility was carried out. RESULTS: The infection most often found in blood and wound, less often in respiratory system. Nosocomial infection rates in patients with burns were closely related to the severe degree, diagnosis and therapy of these patients and hospital surroundings. Infection bacteria species: Gram-positive bacterium accounted for 43.82%, and mainly were staphylococcus aureus and anaerobic peptococcus. Gram-negative bacterium accounted for 52.81%, of which pseudomonas aeruginosa and nitrate-negative bacillus constituted the majority. CONCLUSION: According to these characters and related factors of nosocomial infection in patients with burns, effective measures of preventing and controlling infection should be taken, so that the incidence of nosocomial infection in these patients will drop.

Adolescent↗
PubMed2000

Determination of low-level mercury based on a renewable-drops sensing technique.

The design and characteristics of a novel drop-based fluorescence-detection technique for the determination of mercury(II) are described. The method, using a flow injection technique, is based on the renewable-drops of 3,3',5,5'-tetramethylbenzidine(TMB), which are formed at the bottom tip of a silica capillary tube connected to the end of the flow system. An excitation beam from a high-pressure Hg lamp directly illuminates the drops, the fluorescence emission is conducted to a photodiode (PD) to convert the photocurrent into a voltage signal (mV). Optimum analytical conditions for Hg(II) assays have been established. In NaAc/HAc buffer at pH 3.09 this assay has a wide linear range for Hg(II) from 8.0 x 10(-8) to 2.0 x 10(-5) mol/L with a detection limit of 2.0 x 10(-8) mol/L. The use of renewable drops allowing a fresh reaction surface for each sample is of particular value to solving the problems of irreversible reactions. Besides its high sensitivity, the method permits a simple, fast, and inexpensive measurement with only micro-quantities of reagent consumption. The technique described provides a simple and sensitive way to fabricate sensors of feasible prospects and commercial advantages.

Benzidines↗
PubMed2000

[A new flavonoid glycoside from Allium cepa L. var agrogatum Don].

AIM: To investigate the chemical constituents from the bulb stems of the Chinese medicinal plant Allium cepa L. var. agrogatum Don. METHODS: The crude extracts of the bulb stem were purified by Sephadex LH-20 chromatography. IR, UV, MS, 1H, 13CNMR, 1H-1H COSY, 1H-13C COSY and HMBC spectra were used to determine the structure of the isolated constituents. RESULTS: A new compound named quercetin 3'-methoxy-4'-O-beta-D-glucopyranoside(I), together with three known compounds kaempferol(II), quercetin 4'-O-beta-D-glucopyranoside(III) and quercetin 3,4'-di-O-beta-D-glucopyranoside(IV) were isolated. CONCLUSION: Quercetin 3'-methoxy-4'-O-beta-D-glucopyranoside(I) is a new compound, compounds II-IV were isolated from this plant for the first time.

Allium↗
PubMed2000

[Treatment of diseased middle turbinate in endoscopic sinus surgery].

OBJECTIVE: To study the clinical significance of reservation of the middle turbinate in functional endoscopic sinus surgery (FESS) for sinusitis and/or nasal polyps. METHOD: According to anatomic criteria of the middle turbinate surgery in adult, 32 cases who had sinusitis and/or nasal polyps were treated and followed up. The recovery of middle turbinate contour, postoperative ethmoid cavity and the rate of patency of the maxillary sinus ostium were observed postoperatively. RESULT: 1. After 6 months, the form of middle turbinate returned to normal in 24 cases (75%), adhesions occurred in 8 cases (25%), including the closure of ethmoid sinus cavity in 2 cases. 2. The patency of maxillary sinuses ostium maintained well in 25 cases (78.1%), stenosed in 6 cases (18.8%) and closed in 1 case (3.1%). The diseased middle turbinate can recover to normal contour in most cases, often plastics in FESS. CONCLUSION: Reservation of middle turbinate plays an important role in promoting the clinical cure rate.

Adolescent↗
PubMed1999

PFM1 (PRDM4), a new member of the PR-domain family, maps to a tumor suppressor locus on human chromosome 12q23-q24.1.

The PR domain, first noted as the PRDI-BF1 (HGMW-approved symbol PRDM1) and RIZ (HGMW-approved symbol PRDM2) homologous region, defines a small family of transcription factors involved in cell differentiation and tumorigenesis. The shared role of this family in human cancer raises considerable interest in identifying novel members of this family as candidate cancer genes. This paper describes a new human PR family member, designated PFM1 (HGMW-approved symbol PRDM4). A full-length PFM1 cDNA of 3902 nucleotides has been isolated based on its homology to the PR domain. It encodes an open reading frame of 796 amino acids and contains a PR domain in the middle region and six zinc finger motifs at the carboxyl-terminus. Several PFM1 mRNA species of different lengths were detected by Northern blot analysis, one species of which lacked the amino-terminal region of PFM1 and part of the PR domain. The major PFM1 mRNA species of approximately 4.6 kb was widely expressed but more abundant in ovary, testis, pancreas, brain, heart, and prostate. PFM1 mRNA levels were highly elevated in PC12 cells treated with NGF, suggesting a role for PFM1 in the NGF signal transduction pathway. STS marker and radiation hybrid analyses mapped PFM1 to human chromosome 12q23-q24.1, a region thought to harbor tumor suppressor genes for ovarian, gastric, and pancreatic cancers. These results suggest a role for PFM1 in cell differentiation and tumor suppression, remarkably consistent with the known functions of the PR-domain family.

Amino Acid Sequence↗
PubMed1998

Telomerase activation in nasopharyngeal carcinomas.

Nasopharyngeal carcinomas (NPC) are common in Hong Kong and southern China but rare in Western countries. Telomerase activation is common in human cancers but has not been reported previously in NPC. Telomerase activation in NPC was determined using the sensitive TRAP (telomerase rapid amplification protocol) assay in 45 nasopharyngeal biopsies (36 NPC, nine normal nasopharyngeal mucosae) in four xenografted NPC tumours established in nude mice and in five in vitro NPC cell lines. Telomerase activation is common in NPC and can be detected at high frequencies (85% in primary tumours and 100% in recurrent tumours). The frequency of telomerase activation was lowest in NPC biopsies without lymph node involvement (60%) compared with those with positive lymph node involvement (100%), and the difference is statistically significant (P < 0.05; Fisher exact test). All the xenografted NPC tumours and in vitro NPC cell lines were strongly positive for telomerase activity. Our results suggest that telomerase activation is common in NPC and it may be useful as a diagnostic marker in the detection of tumour cells in nasopharyngeal biopsies. The high frequency of telomerase activation in stage I NPC (80% positive) suggests that it is an early event in tumour progression.

Adolescent↗
PubMed1997

Novel phosphorylated forms of E2F-1 transcription factor bind to the retinoblastoma protein in cells overexpressing an E2F-1 cDNA.

In cells overexpressing an exogenous cDNA encoding the E2F-1 transcription factor, as many as eight closely-migrating protein bands were detected after denaturing protein gel electrophoresis and immunoblotting with an E2F-1-specific antibody. Control cells, not overexpressing an E2F-1 cDNA, contained only four E2F-1 specific bands. Pretreatment of protein extracts, from both control and E2F-1 overexpressing cells, with lambda-phosphatase eliminated all E2F-1-specific bands except the single band migrating most rapidly on the gels. These data demonstrated that the multiple protein bands were differentially-phosphorylated forms of E2F-1 protein and showed that novel, more highly phosphorylated E2F-1 forms were present in cells overexpressing the E2F-1 protein. In addition, immunoprecipitation of the retinoblastoma (pRb) protein from cells overexpressing the E2F-1 cDNA showed that the novel, highly phosphorylated E2F-1 forms were preferentially coimmunoprecipitated, indicating that pRb bound preferentially to these E2F-1 forms.

3T3 Cells↗
PubMed1996

[Mechanism of intracellular calcium homeostasis in heat-exposed cardiomyocytes of rats].

The activity of Ca(2+)-ATPase and calcium content were measured in sarcoplasmic reticulum (SR) and mitochrondria of myocardium from 40 adult female Wistar rats after exposure to 37 degrees C, 39 degrees C, 41 degrees C and 43 degrees C for 40 min respectively in vitro. The 45Ca uptake, intracellular free Ca2+ concentration ([Ca2+]i) and the relatively active calmodulin content were also observed in cultured cardiomyocytes from 120 neonatal Wistar rats under the same condition of heat exposure. The results showed that (1) the activity of Ca(2+)-ATPase of SR and mitochrondria of myocardium decreased after heat exposure, (2) the calcium content of SR and mitochrondria also showed a tendency of decrease with increase of exposure temperature, (3) the 45Ca uptake and mean [Ca2+]i increased, whereas the calmodulin content decreased. It is suggested that disturbances of intracellular calcium homeostasis may be responsible for cardiac functional disorder after heat exposure.

Animals↗
PubMed1995

Platelet-derived growth factor B-chain comprises the major part of enhanced released mitogen from aortic endothelial cells of stroke-prone spontaneously hypertensive rats.

1. The present study was conducted to analyse the release and production of mitogen in cultured aortic endothelial cells of stroke-prone spontaneously hypertensive rats (SHRSP), for the further understanding of the role of arterial endothelial cells in the genesis of vascular lesions in hypertension. 2. The cultured aortic endothelial cells derived from SHRSP increased released mitogens were compared with those from control Wistar-Kyoto rats (WKY) with respect to cultured vascular medial smooth muscle cells and fibroblasts. 3. Biochemical analyses determined that the major part of mitogen released from aortic endothelial cells of both SHRSP and controls was the platelet-derived growth factor B-chain. 4. Further northern analyses revealed that the transcripts of PDGF B-chain were constitutively accumulated three- to four-fold in quiescent aortic endothelial cells from SHRSP, compared with those from WKY through passages 2 to 5. 5. However, the half-lives of the transcripts after actinomycin D treatment were 1.12 h (s.d. = 0.14, n = 4) and 1.28 h (s.d. = 0.08, n = 3), in SHRSP and in WKY, respectively, showing no significant difference. 6. These suggest that the increased accumulated transcripts of PDGF B-chain in SHRSP are due to an enhanced transcriptional rate. These enhanced release and production of PDGF-B chain in arterial endothelial cells, which may be induced under chronic hypertensive conditions, is suggested to contribute to the genesis of vascular lesion in hypertension, through the stimulation of vascular smooth muscle cell proliferation and hypertrophy.

Animals↗
PubMed1995

Overexpression of the E2F-1 transcription factor gene mediates cell transformation.

The E2F transcription factor can regulate expression of numerous cellular genes controlling proliferation, including proto-oncogenes and genes regulating cell cycle progression. Therefore, genes comprising the E2F gene family could potentially contribute to carcinogenesis. To test the potential of E2F to act as a transforming gene, a cDNA encoding E2F-1 was constitutively overexpressed in established rodent cells using a retroviral vector. Overexpressed E2F-1 was functional, as shown by stimulation of a transfected adenovirus E2 promoter driving a chloramphenicol acetyltransferase reporter gene in E2F-1 overexpressing cells. This stimulation was dependent on functional E2F binding sites in the promoter. Examination of phenotype showed that E2F-1 overexpression mediated cell transformation as measured by the ability of cells to form colonies in soft agar medium. In addition, overexpressed E2F-1 shortened the duration of the G1 cell cycle phase in proliferating cells, a property characteristic of other transforming genes. These data provide direct evidence that E2F-1 can act as a transforming gene and a critical regulator of cell cycle progression and suggest the possibility of E2F involvement in carcinogenesis.

3T3 Cells↗
PubMed1994

alpha-Tocopherol protects against radical-induced injury in cultured neurons.

The effect of alpha-tocopherol on neurons in protecting against radical-induced injuries caused by cumene hydroperoxide was assessed using a culture system. Structural and biochemical deteriorations in both clonal neuroblastoma cells and primary cultured neurons were induced by cumene hydroperoxide. These deteriorative changes were prevented prevented by pretreatment of alpha-tocopherol. Since simultaneous supplementation of alpha-tocopherol and cumene hydroperoxide had limited protective effects, prophylactic administration of alpha-tocopherol for risk patients with brain diseases concerned with damages induced by free radical is recommended to hamper the progression of neuronal impairment after attacks.

Animals↗
PubMed1994

Immunoglobulin A antibodies directed against Campylobacter jejuni flagellin present in breast-milk.

We studied the relationship between IgA anti-campylobacter flagellin antibodies in breast milk samples and protection of breastfed infants living in a rural Mexican village from campylobacter infection. There were fewer episodes of campylobacter infection (symptomatic and asymptomatic combined) in infants breastfed with milk containing specific anti-flagellin antibodies (1.2/child/year, 95% CI 0.6-1.8) versus non-breastfed children (3.3/child/year, 95% CI 1.8-4.8; P < 0.01). Infants breastfed with milk that was anti-flagellin antibody negative by ELISA also had fewer episodes of infection compared with non-breastfed children, but the difference did not reach statistical significance (1.8/child/year, 95% CI 0.7-3.0 versus 3.3/child/year, 95% CI 1.8-4.8, P > 0.05). Breastfeeding has a protective effect against campylobacter infection and is associated with the presence of specific antibodies directed against campylobacter flagellin.

Analysis of Variance↗
PubMed1994

[Effects of vocalization and respiration and fiber connections on hyperstriatum ventrale pars caudale in Fringilla montifringilla].

In urethane-anesthetized Fringilla montifringilla, effects of electrically stimulating the hyperstriatum ventrale pars caudale (HVc) on vocalization and respiration were observed. Central connections of HVc were investigated by means of injecting CB-HRP into HVc. The results were as follows: (1) Electrical stimulation of HVc caused vocal response. (2) Long train electrical pulses stimulation of HVc elicited significant respiratory facilitating effects, that is, increase of respiratory rate and depth. (3) Short train stimulation administered in HVc during inspiratory phase terminated switching-off of inspiration, and during expiratory phases produced the prolongation of expiratory phase so to coordinate vocalization and then increasing the respiratory rate and depth. (4) CB-HRP traces revealed that HVc projected to robust nucleus of the archistriatum, and atea X of lobus parolfactorius. HVc received projections from medial nucleus magnocellularis of the anterior neostriatum, nucleus interfacialis of midneostriatum, telencephalic auditory nucleus-field L, nucleus uvaeformis of the thalamus, and locus ceruleus of the pons. These results showed that, besides vocal control, HVc may be involved in neural regulations of respiratory facilitation, the effect on respiration seeming specific. It is suggested that HVc may play an important role in coordinating singing and respiration.

Animals↗