Biomedical subjects

Z Mao

Publications and source records attributed to Z Mao.

At least 37 records · Page 2Linked to original sources

PubMed2000

Cloning and functional characterization of the 5'-flanking region of human methionine adenosyltransferase 1A gene.

Methionine adenosyltransferase (MAT) is an essential cellular enzyme which catalyses the formation of S-adenosylmethionine, the principal methyl donor and precursor for polyamines. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT respectively. We previously described a switch in the MAT expression from MAT1A to MAT2A in human liver cancer, which offered the cancerous cell a growth advantage. Loss of MAT1A expression was due to lack of gene transcription. To study regulation of the MAT1A gene, we have cloned and characterized a 1.9 kb 5'-flanking region of the human MAT1A gene. One transcriptional start site, located 25 nt downstream from a consensus TATA box, was identified by primer extension and RNase protection assays. The promoter contains several consensus binding sites for CAAT enhancer binding protein (C/EBP) and hepatocyte-enriched nuclear factor (HNF), transcriptional factors important in liver-specific gene expression. The human MAT1A promoter was able to efficiently drive luciferase expression in Chang cells, a human liver cell line, but not in HeLa cells. Sequential deletion analysis of the promoter revealed two DNA regions upstream of the translational start site, -705 to -839 bp and -1111 to -1483 bp, which are involved in positive and negative gene regulation, respectively. Specific protein binding to these regions was confirmed by electrophoretic-mobility-shift and DNase I footprinting assays. Similar to the situation with the rat MAT1A, glucocorticoid treatment also increased human MAT1A expression and promoter activity in a dose- and time-dependent manner.

5' Untranslated Regions↗

PubMed2000

Expression of p53 and p21 protein in transitional mucosa adjacent to rectal carcinoma and its clinical implication.

To study the biopathological characteristics of the transitional mucosa adjacent to rectal carcinoma, 34 cases were subjected to mucin histochemical and immunohistochemical study to observe the expression of p53 and p21 protein in distal mucosa adjacent to rectal carcinoma and its relationship to the mucin change. The expression of p53 protein was found in 29.4% (10/34) of distal transitional mucosa in the cytoplasm of goblet cells, and its positive staining was within 4 cm from carcinoma margin. All p53 positive mucosa was transitional mucosa. Overexpression of p21 protein was found in 26.5% (9/34) of distal transitional mucosa in cytoplasm of crypt cells, and its positive staining was within 2 cm from carcinoma margin. There was no relationship between the expression of p53 and p21 protein in carcinoma and that in transitional mucosa (P > 0.05). These findings indicated that there was aberrant alteration of p53 and p21 genes in transitional mucosa adjacent to colorectal carcinoma, which provided further evidence that transitional mucosa was an unstable pre-cancerous change. The aberrant mucin change and genetic alteration in distal mucosa of rectal cancer is within 4 cm.

Adenocarcinoma↗

PubMed2000

Nanosecond electron microscopes

Combining electron optics, fast electronics and pulsed lasers, a transmission and a photoelectron emission microscope were built, which visualize events in thin films and on surfaces with a time resolution of several nanoseconds. The high-speed electron microscopy is capable to track fast laser-induced processes in metals below the ablation threshold, which are difficult to detect by other imaging techniques. The material response to nano- and femtosecond laser pulses was found to be very different. It was dominated by thermo/chemocapillary flow and chemical reactions in the case of nanosecond pulses, and by mechanical deformations and non-thermal electron emission after a femtosecond pulse.

Journal Article↗

PubMed2000

[A study on relationship between plasma heat stress protein 70 and cytokine in patients with heat apoplexy].

OBJECTIVE: To study the change of levels of plasma heat stress protein 70 (HSP70) and cytokine and their interrelationship in pathogenicity of heat apoplexy. METHODS: Plasma HSP70 was determined with Western blot, and plasma interleukin-2 (IL-2), soluble interleukin-2 receptor (sIL-2R) and interleukin-6 (IL-6) were determined with enzyme-linked immunosorbent assay (ELISA). RESULTS: Plasma level of HSP70 was 4 211.2 +/- 1,286.2 (integral optical density) in average in the patients of heat apoplexy group, 4,137.8 +/- 1, 207.5 in those of severe heat apoplexy group, and 6,043.5 +/- 1,354.8 in control group, with very significant difference (P < 0.01). Plasma IL-2 level was (64.3 +/- 32.3) pg/ml and (200.0 +/- 50.0) pg/ml and sIL-2R (54.9 +/- 33.3) U/ml and (167.5 +/- 89.0) U/ml in the patients with heat apoplexy and in controls, respectively, with very significant difference. But, there was no significant difference in IL-6 between varied groups. CONCLUSIONS: The above-mentioned results suggest that establishment of heat acclimatization correlates to the interaction of network of neuroendocrine-cytokine-HSP, in which decrease in plasma IL-2 was one of the important factors causing reduction of HSP70 expression. Balance of network regulation was broken by pathological factors, finally resulting in heat apoplexy.

Adolescent↗

PubMed2000

[The expression of connexin 43 and desmin in viral myocarditis].

OBJECTIVE: To study the cytobiological basis of constriction dysfunction and arrhythmia in cardiac muscle cells with viral myocarditis. METHODS: The expression of connexin 43 and desmin in cardiac muscle cells of mice with experimental viral myocarditis was determined by immunohistochemistry. RESULTS: In normal mice, connexin 43 and desmin are located in the intercalated disks of cardiac muscle, and the latter also revealed a positive immunoreactivity in the cross striations of sarcomeres. In viral myocarditis, the expression of both became much weakened, can even become negative. CONCLUSION: In myocarditis, expression of connexin 43 and desmin in the involved cardiac muscle cells was inhibited, resulting in dysfunction of gap junctional communication and arrhythmia.

Animals↗

PubMed2000

[A study on the association of telomere length with the experimental carcinogenesis of oral cavity].

OBJECTIVE: The life cycle of cell can be effected by the length of telomere. Loss of telomeric DNA during cell proliferation may play a role in chromosome instability, cellular apoptosis and cancer. The purpose of the study is to measure the dynamic changes of telomere length in experimental oral cavity cancer during golden hamster cheek pouch carcinogenesis induced by DMBA. METHODS: First, 52 golden hamsters were divided into 2 groups. Four of them were not done any treatment and were killed after 3 days. The others were covered with DMBA on the surface of cheek pouch on one side in order to induce carcinogenesis, the other side of cheek pouch was treated as the control. Then, the 48 golden hamsters were divided into 4 groups and were killed in 7, 10, 14, 20 weeks. Light microscope was used to observe the pathologic changes. Southern hybridization was used to analysis the dynamic development of the length of telomeric repeat. In different periods, the reduction rate of telomere length was calculated. RESULTS: 1. The cheek pouch mucosa uncovered with DMBA had no abnormal pathologic changes, while that covered with DMBA was observed pathologic changes of different degrees. 4 cases of hyperplasia lesions and 8 cases of dysplasia lesions were observed in the 7-week group, 7 cases of dysplasia lesions and 5 cases of mucosa carcinoma in situ in the 10-week group, 5 cases of mucosa carcinoma in situ, 4 cases of squamous cell carcinomas and 3 cases of death in the 14-week group, and 7 cases of squamous cell carcinomas and 5 cases of death in the 20-week group. 2. The telomere length of the normal mucosa was reduced with the hamsters age increasing, but the telomere length was significantly shorter than that of the normal control during the mucosa carcinogenesis of cheek pouch. The average shortened length was about 0.225 kb (the normal mucosa was 0.17 kb). 3. The highest reduction rate (0.3985) was in a later premalignant period. CONCLUSION: Age is one of the factors that can short telomere length. However, the speed that telomere length is shorted is faster than ever while telomere is abnormal. There is an obvious relationship between the abnormal degree of telomere length and the malignant degree of carcinoma. So the abnormal shorting of telomere length is an early molecular evidence of the oral carcinogenesis.

Animals↗

PubMed2000

[Identification of telomerase activity in the experimental carcinogenesis of oral cavity].

OBJECTIVE: Telomerase is a ribonucleoprotein enzyme which synthesizes telomere DNA repeat sequences and maintain stably telomere length. The activity of telomerase may be necessary for the growth of immortalized cells overcoming cellular senescence. The researches have shown that telomerase activities are associated with most cancers. The purpose of the study is to detect the development of telomerase activity during golden hamster cheek pouch carcinogenesis induced by DMBA. METHODS: First, 52 golden hamsters were divided into 2 groups. Four of them were not done any special treatment and were killed after 3 days. The others were covered with DMBA on the surface of cheek pouch on one side in order to induce carcinogenesis, the other side of cheek pouch was treated as the control. Then, the 48 golden hamsters were divided into 4 groups and were killed in 7, 10, 14 and 20 weeks. The telomeric repeat amplification protocol (TRAP) based on PCR and ELISA was used to analysis the activity of telomerase. RESULTS: 1. The expression of telomerase activity existed in normal cheek pouch mucosa of golden hamsters, which meant that telomerase played an important role on controlling cell proliferation. 2. The level of telomerase activity gradually increased while hyperplasia and dysplasia was observed in the cheek pouch mucosa covered with DMBA. It reached its top at a later premalignant period and gradually decreased after that. 3. There was negative correlation between the degree the telomere length was shortened and the activity of telomerase (r = -0.9654), and there was positive correlation between the reduced rate of telomere length and the activity of telomerase (r = 0.9471). CONCLUSION: The activity of telomerase is one of important factors that can effect the stability of telomere length and plays a crucial role in the progression of oral cancer. So the activity of telomerase is an early molecular marker of carcinogenesis.

Animals↗

PubMed2000

[Establishment of rat submandibular gland squamous cell carcinoma induced by DMBA].

OBJECTIVE: To study carcinogenesis and development of salivary gland tumor and establish an animal model of submandibular gland (SMG) tumor. METHODS: Histopathological study during carcinogenesis in rat SMGs using (9,10-dimethyl-1,2-benzanthracene (DMBA) was evaluated. A total of 50 male and female Sprague-Dawley (SD) rats of 8 weeks old and 180-200 g weight were obtained from the Animal Center of Henan Medical University. Under pentobarbital sodium anesthesia, the left SMGs were exposed by surgical procedure. A sponge pellet (1.0 mm x 1.0 mm x 1.0 mm, made by authors) was used as the carrier of the carcinogen. The sponge containing 2% DMBA (Fluka, Switzerland)/acetone solution was implanted into the glandular tissue of the left SMGs. Four rats (2 males and 2 females) were killed after every 2 weeks of the DMBA/sponge implantation. The same method of sponge implantation without DMBA was used at the right side of SMG as a control. All rats left were killed after 20 weeks. The SMGs were fixed in 10% formalin buffer solution for 24 hours, and embedded in paraffin, then 4 microns-thick sections were made for histopathological study. RESULTS: The earliest tumor occurred after 4 weeks of implantation of sponge, a total of 21 lateral tumors were induced (10 females, 11 males). There was no tumor found in the controlled SMG. The peak time of tumor genesis was after 8-12 weeks of implantation, all tumors induced were squamous cell carcinomas(SCCs). The induced tumors grew slowly below the mandibles of rats, which were present as nodular masses without capsules, and the borders were not clear. They were slightly hard when palpated. The process of carcinogenesis can be described as following: squamous metaplasia of cyst-like structures occurred, then SCCs were induced and invaded surrounding tissues. No metastasis was observed in regional lymph nodes and other organs. CONCLUSION: SCCs of SMG can be induced by implantation of DMBA. The present study supports the conclusion that all duct segments undergo squamous metaplasia, and therefore may participate in the genesis of neoplasia during experimental carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2000

[Pharmacognostical identification of one Rhizoma Drynariae habitually used species from Yunnan].

The species recorded on the "Rhizoma Drynariae" item of Chinese Pharmacopeia is the dry rhizoma of Drynaria fortunei from Polypodiacae. But in Yunnan province, many plants (including D. delavayi) are habitually used as Rhizoma Drynariae. In this article the authors identified D. delavayi on Chinese medinal materials discriptions, microscopic characters and TLC. This proved evidences for the utilization and identification of D. delavayi in some extent.

Chromatography, Thin Layer↗

PubMed2000

Clinical observation of 126 cases of sutureless phacoemulsification with PMMA intraocular lens implantation.

OBJECTIVE: To observe the safety and effect of sutureless phacoemulsification with PMMA intraocular lens (IOL) implantation. METHODS: One-hundred and twenty-six cases (126 eyes) of sutureless phacoemulsification with PMMA intraocular lens (IOL) implantation were retrospectived and evaluated. The surgeries were performed through a limbal tunnel incision. PMMA IOLs with 5.5 mm or 6.0 mm in diameter were implanted. RESULTS: The follow-up was 3-20 months. Visual acuity of 0.5 or better was obtained in 120 cases (95.2%), and that of 1.0 or better was obtained in 89 cases (70.6%). Intra-operative complications included posterior capsule rupture in 9 cases (7.1%) and iris injury in 7 cases (5.6%). Postoperative complications included early corneal edema in 96 cases (76.2%), transient intraocular pressure elevation in 5 cases (4.3%), remnant of cortex in 1 case and leakage of incision in 1 case. All were properly managed with good results. CONCLUSION: Sutureless phacoemulsification with PMMA IOL implantation is safe even in grass-root hospitals where cataracts are harder.

Aged↗

PubMed1999

Calcineurin enhances MEF2 DNA binding activity in calcium-dependent survival of cerebellar granule neurons.

Myocyte enhancer factor 2 (MEF2) has been shown recently to be necessary for mediating activity-dependent neuronal survival. In this study, we show that calcium signals regulate MEF2 activity through a serine/threonine phosphatase calcineurin. In cultured primary cerebellar granule neurons, the electrophoretic mobility of MEF2A protein was sensitive to the level of extracellular potassium chloride (KCl) and depolarizing concentrations of KCl led to hypophosphorylation of the protein. The specific inhibitors of calcineurin cyclosporin A (CsA) and FK506 could overcome KCl-dependent MEF2A hypophosphorylation. The effects of CsA and FK506 were KCl specific as they had little effect on MEF2A phosphorylation when granule neurons were cultured in the presence of full media. Hyperphosphorylation of MEF2A led to the loss of its DNA binding activity as determined by DNA mobility shift assay. Consistent with this, CsA/FK506 also inhibited MEF2-dependent reporter gene expression. These findings demonstrate that regulation of MEF2A by calcium signals requires the action of protein phosphatase calcineurin. By maintaining MEF2A in a hypophosphorylated state, calcineurin enhances the DNA binding activity of MEF2A and therefore maximizes its transactivation capability. The identification of MEF2 as a novel target of calcineurin may provide in part a biochemical explanation for the therapeutic and toxic effects of immunosuppressants CsA and FK506.

Animals↗

PubMed1999

Neuronal activity-dependent cell survival mediated by transcription factor MEF2.

During mammalian development, electrical activity promotes the calcium-dependent survival of neurons that have made appropriate synaptic connections. However, the mechanisms by which calcium mediates neuronal survival during development are not well characterized. A transcription-dependent mechanism was identified by which calcium influx into neurons promoted cell survival. The transcription factor MEF2 was selectively expressed in newly generated postmitotic neurons and was required for the survival of these neurons. Calcium influx into cerebellar granule neurons led to activation of p38 mitogen-activated protein kinase-dependent phosphorylation and activation of MEF2. Once activated, MEF2 regulated neuronal survival by stimulating MEF2-dependent gene transcription. These findings demonstrate that MEF2 is a calcium-regulated transcription factor and define a function for MEF2 during nervous system development that is distinct from previously well-characterized functions of MEF2 during muscle differentiation.

Animals↗

PubMed1999

[Effect of hypertonic saline/dextran 70 on delayed resuscitation of dogs with burn shock].

OBJECTIVE: To investigate the effect of hypertonic saline/dextran 70 on delayed resuscitation of burn shock. METHODS: Eighteen mongrel dogs with 35% TBSA, third-degree burn were used in this study. Lactated Ringer's (LR) or 7.5% NaCl+ 6% dextran 70 (HSD) was given for resuscitation 6 h postburn. The volumes and rates of fluid infusion were controlled basically on the urinary output of 1.0 ml.kg-1.h-1 and cardiac output (CO) of 70%-80% of preburn values. The volume load, +dp/dtmax, -dp/dtmax, CI,DO2 and VO2 were obtained to evaluate the effect of HSD resuscitation. RESULTS: The resuscitated volume of HSD was 30.56% less during first 24 h postburn and 59.50% less at 4 h after resuscitation than LR's. The +dp/dtmax, CI,DO2 and VO2 were increased significantly with HSD infusion at 2 h, 1 h and 0.5 h after resuscitation compared with LR's. CONCLUSION: HSD could expand plasma volume significantly with small quantity. The cardiac contractility was enhanced and the oxygen delivery, oxygen consumption were increased in delayed resuscitation of burn shock.

Animals↗

PubMed1999

[Clinical study of advanced nasopharyngeal carcinoma treated with radiotherapy combined with DDP and vindesine].

OBJECTIVE: To evaluate the result of radiotherapy combined with chemotherapy for advanced nasopharyngeal carcinoma (NPC). METHODS: From August 1996 to October 1997, 64 cases of advanced NPC (stage N2-N3) patients were randomized to receive radiotherapy (RT) alone or RT combined with 2 cycles of chemeotherapy (CT) (cisplatin, vindesine). Thirty two patients were assigned to CT + RT, and 32 to RT alone. RESULTS: At 40 Gy of RT the response rate was 28.1% in RT group and 43.8% in CT + RT group. The response rate at 3 months after RT was 75.0% in RT group and 84.4% in CT + RT group (P < 0.05). The major toxic effects were gastrointestinal reaction, myelosuppession and alopecia. CONCLUSION: Chemotherapy with cisplatin and vindesine before and after radiotherapy increases the response rate of advanced NPC with lymph node metastases.

Adult↗

PubMed1999

[Neural network approach to medical grading of rheumatoid arthritis].

A grading system based on neural network has been developed and used int he medical grading diagnosis of a case group of Rheumatoid Arthritis presenting Cold syndrome intermingled with Heat syndrome. The possibility of using neural network in TCM diagnosis is preliminarily explored in this paper.

Algorithms↗

PubMed1999

[Determination of Pb, Cu and Sn in ancient bronze coins using X-ray fluorescence theoretical alpha coefficient method].

In this paper, the theoretical alpha coefficients of L-T equation were applied to the analysis of Pb, Cu and Sn in ancient bronze coins by X-ray fluorescence spectrometry. The results obtained in this way are in agreement with those by the fundamental parameter method and the simulant standard samples method, because this method and the simulant standard samples method were both developed from the fundamental parameter method, and the standard samples are the same. The calculation of element concentration is simple and rapid, but the precision of the results depends relatively largely on the concentration range of the standard samples by this method.

English Abstract↗

PubMed1998

Cloning and functional characterization of the 5'-flanking region of human methionine adenosyltransferase 2A gene.

Methionine adenosyltransferase (MAT) is a critical cellular enzyme which catalyzes the formation of S-adenosylmethionine, the principal methyl donor. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT, respectively. We have cloned and characterized a 1.4-kb 5'-flanking region of the human MAT2A (GenBank Accession No. AF039088). Two major transcriptional start sites were identified by primer extension and S1 nuclease protection analysis; one was within 10 nucleotides downstream and the other was located at 158 nucleotides upstream from the consensus TATA box, respectively. The promoter is highly GC rich (75%) in the first 300 base pairs and contains several Sp-1 binding sites, a C/EBP, a HSF2, a STATx, a c-Myb, several v-Myb, and numerous GATA consensus binding sites. The human MAT2A promoter was able to efficiently drive luciferase expression in both Jurkat and 293 cells, but sequential deletion analysis of the promoter revealed that different regions of the promoter are important for cell-specific MAT2A expression.

Base Sequence↗

PubMed1998

Differential expression of methionine adenosyltransferase genes influences the rate of growth of human hepatocellular carcinoma cells.

Methionine adenosyltransferase (MAT) catalyzes the formation of S-adenosylmethionine (SAM), the principal methyl donor, and is essential to normal cell function. The two forms of MAT, liver specific and non-liver specific, are products of two genes, MAT1A and MAT2A, respectively. We have reported a switch from MAT1A to MAT2A gene expression in human liver cancer cells. In the current work, we examined whether the type of MAT expressed by the cell influences cell growth. HuH-7 cells were stably transfected with MAT1A and were subsequently treated with antisense oligonucleotides directed against MAT2A. MAT2A antisense treatment reduced the amount of MAT2A mRNA by 99% but had no effect on MAT1A mRNA. Cell growth and DNA synthesis rates were reduced by approximately 20-25% after transfection with MAT1A and by an additional 30-40% after MAT2A antisense treatment. SAM level and SAM:S-adenosylhomocysteine (SAH) ratio increased by 50-75% after MAT1A transfection and by an additional 60-80% after MAT2A antisense treatment. DNA methylation changed in parallel to changes in SAM level and SAM:SAH ratio. Supplementing untransfected HuH-7 cells with SAM in the culture medium increased SAM level, SAM:SAH ratio, and DNA methylation and decreased cell growth and DNA synthesis. In conclusion, cell growth is influenced by the type of MAT expressed. The mechanism likely involves changes in SAM:SAH ratio and DNA methylation.

Carcinoma, Hepatocellular↗