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Biomedical subjects

X Dai

Publications and source records attributed to X Dai.

At least 109 records · Page 6Linked to original sources
PubMed1996

E. coli SSB activates N4 virion RNA polymerase promoters by stabilizing a DNA hairpin required for promoter recognition.

Bacteriophage N4 virion RNA polymerase transcription of double-stranded promoter-containing DNAs requires supercoiled template and E. coli single-stranded DNA-binding protein (EcoSSB); other single-stranded DNA-binding proteins cannot substitute. The DNA determinants of virion RNA polymerase binding at the promoter comprise a small template-strand hairpin. The requirement for EcoSSB is surprising, since single-stranded DNA-binding proteins destabilize hairpin structures. DNA footprinting of EcoSSB on wild-type and mutant promoters indicates that EcoSSB stabilizes the template-strand hairpin owing to the hairpin-loop sequences. Other single-stranded DNA-binding proteins destabilize the promoter hairpin, explaining the specificity of EcoSSB activation. We conclude that EcoSSB activates transcription by providing the appropriate DNA structure for polymerase binding. The existence of small hairpins stable to single-stranded protein binding suggests a novel mechanism that provides structural determinants for specific recognition in single-stranded DNA transactions by an otherwise nonspecific DNA-binding protein.

Base Sequence↗
PubMed1996

Conformational flexibility and crystallization of tandemly linked type III modules of human fibronectin.

Fibronectin is a large cell adhesion molecule that is composed of several functional domains. The cell-binding domain that binds to cell surface integrins consists of repeated homologous type III modules. In this study, recombinant fragments from the cell-binding domain of human fibronectin that participate in a newly characterized fibronectin-fibronectin interaction with FNIII1 were crystallized. In each case, the crystals had more than one fibronectin fragment in the asymmetric unit. Crystals of FNIII10-11 grew in the space group C2 with a = 117.1 A, b = 38.6 A, c = 80.6 A, beta = 97.2 degrees, and two molecules in the asymmetric unit. These crystals diffracted to 2.5 A resolution. Fragment FNIII8-11 and a shorter fragment, FNIII8-10, crystallized in hexagonal space groups with large unit cells and two to four molecules per asymmetric unit. Even very large crystals of these fragments did not diffract beyond 4 A. The crystal packing for this collection of fibronectin fragments suggests conformational flexibility between linked type III modules. The functional relevance of this flexibility for elongated versus compact models of the cell-binding domain of fibronectin is discussed.

Ammonium Sulfate↗
PubMed1996

Analysis of the N-glycosylation of the serum glycoproteins defined by Con A, PHA-E, RCA1 and WGA in Chinese patients with gastrointestinal diseases.

Glycoproteins from tumor cells isolated by Con A, PHA-E and RCA1, were coupled to horse radish peroxidase and then used as reporters to evaluate the oligosaccharides change on serum glycoproteins in digestive tract diseases and individual healthy persons. A value 2 standard deviation above the mean of the healthy person group was considered positive. The results indicated that the positive rates of the oligosaccharides bound with Con A, PHA-E and RCA1 were 51% (61/119), 70.6% (84/119), and 76.4% (91/119) in patients with gastric cancer; 53.3% (16/30), 46.7% (14/30) and 66.7% (20/30) in esophageal cancers; 28.5% (15/49), 49.0% (24/49) and 46.9% (23/49) in colorectal cancer; 78.1% (25/32), 81.3% (26/32) and 31.3% (10/32) in gallbladder tumors; 60.4% (29/48), 54.1% (26/48) and 39.5% (19/48) in hepatocellular cancer. The positive rates among the patients with benign diseases were also found to be 12.7% (16/126), 15.5% (20/126) and 26.2% (33/126). However, the expression of the oligosaccharide moieties recognized by WGA on the glycoprotein bound with Con A, was significantly lower in the serum of patients with tumors than in those with benign disease and in healthy individuals (P < 0.01, P < 0.01).

Adult↗
PubMed1996

[Expression of CDKN2 gene product in human bronchogenic carcinoma].

OBJECTIVE: To examine the expression of P16 protein in bronchogenic carcinoma and normal tissue adjacent to carcinoma and to determine the relationship between the gene and bronchogenic carcinoma. METHOD: Using a rabbit polyclonal antibody against P16 (N-20), the expression of P16 protein was studied immunohistochemically on formalin fixed, paraffin embedded sections. RESULTS: The cytoplasmic P16 protein was mainly present in normal bronchial epithelium (93.8%), serous gland (92.6%) and alveolar epithelium (71.4%), the expression levels of P16 were significantly lower in carcinoma tissues (61.9%) when compared to levels in their normal counterparts (P < 0.01). Among tumors, squamous cell carcinomas and small cell carcinomas exhibited lower P16 expression levels compared with adenocarcinomas (P < 0.01). The expression levels of P16 were lower in poorly-differentiated adenocarcinomas compared with those in well-differentiated adenocarcinomas (P < 0.05). CONCLUSIONS: The results suggested that CDKN2 gene was a tumor suppressor gene, the inactivation of which were involved in the carcinogenesis of bronchogenic carcinoma and implicated in tumor differentiation.

Adenocarcinoma↗
PubMed1996

[Effect of xiaopiling granules on the treatment of gastric precancerous changes as detected by image analyzer and electronic microscope].

Therapeutic effect of Xiaopiling Granules on gastric precancerous changes was observed, using image analyzer and electronic microscope. The result indicated that the Granules could efficiently eliminate gastric mucositis, nourish gastric mucosa, soften or restrain dysplasia, ameliorate structure atypism and cell atypism of dysplasia, promote elimination of dysplasia and efficiently ameliorate the ultrastructure of gastric precancerous changes.

Adult↗
PubMed1995

Cleavage of an amide bond by a ribozyme.

A variant form of a group I ribozyme, optimized by in vitro evolution for its ability to catalyze magnesium-dependent phosphoester transfer reactions involving DNA substrates, also catalyzes the cleavage of an unactivated alkyl amide when that linkage is presented in the context of an oligodeoxynucleotide analog. Substrates containing an amide bond that joins either two DNA oligos, or a DNA oligo and a short peptide, are cleaved in a magnesium-dependent fashion to generate the expected products. The first-order rate constant, kcat, is 0.1 x 10(-5) min-1 to 1 x 10(-5) min-1 for the DNA-flanked substrates, which corresponds to a rate acceleration of more than 10(3) as compared with the uncatalyzed reaction.

Amides↗
PubMed1995

Intracellular calcium reaches different levels of elevation in hyperactivated and acrosome-reacted hamster sperm.

Calcium plays a role in sperm motility hyperactivation and the acrosome reaction, but the relationship between cytoplasmic calcium (Ca2+in) levels in the two states was heretofore unknown. The Ca2+ indicator indo-1 was used to detect Ca2+in in moving hamster sperm in two sets of experiments. In the first experiment, activated, hyperactivated, and zona pellucida-induced acrosome-reacted/hyperactivated sperm were analyzed at the time of peak of activity for each state. In the second experiment, sperm in all states were analyzed at one time point. In both sets, mean Ca2+in in the acrosomal region, postacrosomal region, and flagellar midpiece was greater in hyperactivated sperm than in activated sperm, and in acrosome-reacted/hyperactivated sperm than in unreacted/hyperactivated sperm (P < 0.001). Ca2+in had increased to a greater extent in the midpiece than in the head in hyperactivated sperm, while the reverse was true for acrosome-reacted sperm. Oscillations at the frequency of the flagellar beat cycle were detected chiefly in the proximal flagellar midpiece of acrosome-reacted sperm, as they had been previously reported to occur in activated and hyperactivated sperm. Thus, Ca2+in may be maintained at two different elevated levels in sperm, and continues to oscillate after the acrosome reaction.

Acrosome↗
PubMed1995

Development of an ELISA to detect MX virus, a human calicivirus in the snow Mountain agent genogroup.

MX virus is a Snow Mountain agent (SMA) genogroup human calicivirus (HuCV) identified in a Mexican child with diarrhoea. An ELISA using hyperimmune antisera to the recombinant MX virus (rMX) capsid was developed to detect SMA genogroup HuCVs in stool specimens. The rMX ELISA detected the prototype MX virus, SMA, and Hawaii agent (HA), but not Norwalk virus (NV) or Sapporo virus. Twenty-three diarrhoea stool specimens from children attending day care centres in Norfolk, Virginia, were positive by the rMX ELISA and results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR). Eight of 20 diarrhoea stool specimens from children in the United Kingdom previously shown to contain small round structured viruses (SRSVs) or HuCVs by electron microscopy were also positive by the rMX ELISA and RT-PCR. Sequence analysis of the RT-PCR products showed that all the rMX ELISA-positive viruses belong to the SMA genogroup. These data also showed that the SMA genogroup can be further divided into two subgroups: subgroup 1 includes prototypes SMA and HA, and subgroup 2 includes MX virus, minireovirus, Oth-25 and Bristol virus.

Animals↗
PubMed1995

[Effect of xiaopiling granules on muscular histochemistry of gastric precancerous changes in rats].

The effect of Xiaopiling Granules on muscular histochemistry of gastric precancerous changes in rats was observed quantitatively. The activity of SDH and M-ATPase as well as the content of muscular glycogen in model groups were found significantly lower than those of the normal groups (p < 0.01), and in this decrease Xiaopiling Granules had markedly played a preventive and therapeutic role.

Animals↗
PubMed1995

[Effects of 3 kinds of decoction on serum gastrin, gastrin cell density and the content of PGE2 of gastric antral mucosa in experimental chronic gastritis in rats].

Experimental chronic gastritis (ECG) models were established in rats by inserting a spring into pyloric canal as well as feeding sodium deoxycholate. An experiment was undertaken to observe the therapeutic effects of three formulas of traditional Chinese medicine "Shipitong" (SPT), "Ganpingyangwei" (GPYW) and "Weile" (WL). The experimental results show that all of the three decoctions can make serum gastrin, gastrin cell density and amount of antral mucosal PGE2 of the ECG rats return to normal levels.

Animals↗
PubMed1995

Field potential mapping of neurons in the lumbar spinal cord activated following stimulation of the mesencephalic locomotor region.

The spinal neurons involved in the control of locomotion in mammals have not been identified, and a major step that is necessary for this purpose is to determine where these cells are likely to be located. The principal objective of this study was to localize lumbar spinal interneurons activated by stimulation of the mesencephalic locomotor region (MLR) of the cat. For this purpose, extracellular recordings of MLR-evoked cord dorsum and intraspinal field potentials were obtained from the lumbosacral enlargement during fictive locomotion in the precollicular-postmammillary decerebrate cat preparation. Potentials recorded from the dorsal surface of the cord between the third lumbar (L3) and first sacral (S1) segments typically showed four short-latency positive waves (P1-P4). These P-waves were largest between the L4-L6 segments. The amplitude of the P2-4 waves increased with the appearance of locomotion and displayed rhythmic modulation during the locomotor step cycle. Microelectrode recordings from the L4-L7 spinal segments during fictive locomotion revealed the presence of both positive and negative short-latency MLR-evoked intraspinal field potentials, and were used to construct isopotential maps of the evoked potentials. Positive field potentials were observed throughout the dorsal horn of the L4-L7 spinal segments with the largest amplitude potentials occurring in laminae III-VI. Negative field potentials were found in laminae VI-X of the lumbar cord. The shortest latency negative field potentials were observed in lamina VII and at the border between laminae VI and VII and were considered to be evoked monosynaptically from the arrival of the descending volley. Short-latency mono- and disynaptic negative field potentials were also observed in lamina VIII. Longer latency, tri- and polysynaptic field potentials were observed in laminae VII and VIII. Many of the longer latency negative waves observed in laminae VII and VIII followed shorter latency negative potentials recorded from the same location. Laminae VII and VIII negative field potentials were largest in the L5-6 and L4-5 spinal segments, respectively. Negative field potentials were also evoked in the motor nuclei of the L4-7 spinal segments. The segmental latencies for these potentials indicate that they were evoked di- and trisynaptically.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1995

[Effects of three kinds of decoction on histopathology of gastric mucosa, gastric pH and the content of bile acid in experimental chronic gastritis in rats].

Experimental chronic gastritis (ECG) models were established in rats by inserting a spring into pyloric canal as well as feeding sodium deoxycholate. An experiment was undertaken to observe the therapeutic effects of three formulas of traditional Chinese medicine "Shipitong", "Ganpingyangwei" and "Weile". The experimental results show that all of the three decoctions can reduce gastric pH and bile acid of the ECG rats and make gastric mucosal histomorphology of these rats change markedly.

Animals↗
PubMed1995

[Expression of oncogene and anti-oncogene in mouse lung cancer induced by coal-burning smoke].

Previous epidemiology studies have shown association between coal burning and human lung cancer. To confirm relationship of coal burning to lung cancer formation and progression the expression of p53 and c-myc in 13 mouse lung cancer induced by coal-burning smoke and 5 mouse lung tissue control was studied by DNA-RNA in situ hybridization (ISH). Nine of 13 specimens showed c-myc overexpression but it occurred only 1 in 9 in the adjacent tissue. There was overexpression of p53 mRNA in all 13 lung cancer and 5 adjacent tissues. None in the controls was expression of p53 and c-myc detected. When compared to controls, there was significant higher expression of c-myc gene (P = 0.002) and p53 gene (P = 0.0001). The results confirm that overexpression of p53 and c-myc are common molecular events of lung cancer by coal-burning smoke and provide further evidence that smoke from coal burning is a causative agent of lung cancer.

Adenocarcinoma↗
PubMed1995

[T antigen test of sputum--a new simple method for the screening of lung cancer].

The sputum specimens from 116 healthy persons and 216 cases of benign and malignant lung diseases were detected for T antigen using a strip test by enzyme galactose oxidase-Schiff sequence. The result shows that 165 cases of the 182 patients with lung cancer, confirmed by cytology and histology, had positive results, whereas 22/116 (19.0%) of healthy controls were positive. So the sensitivity was 90.7% and the specificity was 81.0%. In 28 cases of patients whose cytology of sputa showed various degrees of dysplasia, 21 were found T antigen positive, of which 15 patients were identified to be lung cancer in the follow-up study. In addition, three cases of early lung cancer in this study were also positive, suggesting that T antigen was expressed at an earlier stage in the malignant process. The study has indicated that T antigen test of sputum is a sensitive method for the diagnosis of lung cancer. It may also be a promising approach for the massive screening of lung cancer in terms of its rapidity, economy and simplicity.

Adenocarcinoma↗
PubMed1995

[Promoter activity detection and transcription initiation site determination of the D-xylose isomerase gene of Streptomyces diastaticus strain No.7 M1033].

The DNA segment of the Streptomyces diastaticus strain No.7 M1033 D-xylose Isomerase gene, from -192 to +581 bp according to the translation start site (tss), was cloned in Streptomyces promoter-probe plasmid pIJ4083 from recombination plasmid pUB1 and its M13 subclone S1 respectively. The protoplasts of S. lividans TK24 were transformed with the recombinant, and then detected the promoter activity by measuring the catethol dioxygenase expression. Results of S1 mapping of total RNA of S. di. M1033 indicatedthat: the transcription initiation site of D-XI gene was 40bp upstream the coding region; there was another gene encoded on the antisense strand upstream D-XI gene, with a 114-nucleotide sequence separating their coding regions. According to its DNA sequence, we believed it was the xylulose kinase gene. Data from quantitive S1 mapping also suggested that transcription of the two genes was induced by D-xylose and repressed by glucose.

Aldose-Ketose Isomerases↗