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Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 523 records · Page 29Linked to original sources
PubMed2000

[Characterization of the insecticidal crystal protein genes of Bacillus thuringiensis YBT-1520].

The insecticidal crystal protein genes of highly toxic Bacillus thuringiensis YBT-1520 were analyzed. Southern hybridization and PCR analysis indicated that this strain bears cry1Aa, cry1Ab, cry1Ac and cry2 genes. The copy number of three cry1A genes is different and cry1Ac gene (here named cry218) is the highest. The restriction location of three genes is different from that in typical strains, such as HD-1 and HD-73 strains. 4190 bp nucleotide sequence of cry218 gene was determined and this gene was named cry1Ac10 in the recently published gene nomenclature.

Bacillus thuringiensis↗
PubMed2000

[A procedure for developing selective isolation of Pseudonocardiacetes from soil samples].

Pseudonocardiacetes are a group of rare-actinomyces with type IV cell walls and without mycolic acids. Five different selective isolation media S1, S2, S3, S4 and S5 were devised and practiced to improve their selective isolation efficiency. The media were detected by 33 type strains of Pseudonocardiaceae, 4 strains of Saccharothrix and 15 type strains of Streptomyces cultured on them. Soil samples were examined on media S1 ad S2 compared with glucose-asparagine agar. It shows that media S1 and S2 are effective for growth and isolation of Amycolata, Pseudonocardia, Saccharomonospora and other genera of Pseudonocardiaceae.

Actinomycetales↗
PubMed2000

[PCR-RFLP analysis of the genus Saccharomonospora].

PCR-RFLP, a molecular method of polyphasic taxonomy of the genus Saccharomonospora was introduced. The feasibility of the application of this method at the species level in the taxonomy and identification of Saccharomonospora were discussed. The results showed that PCR-RFLP analysis is valuable for the determination of taxonomic position in the genus of some Saccharomonospora strains.

Actinomycetales↗
PubMed2000

The study on the expression of keratin proteins in pterygial epithelium.

PURPOSE: To evaluate the expression patterns of several keratin proteins in pterygial epithelium. METHODS: The proteins of K8, K10, K14, K16 and AE3 in the epithelium of 8 pterygia and 4 normal conjunctiva were detected using immunofluorescent staining. RESULTS: In pterygial epithelium, the staining patterns of 5 keratin proteins were different with normal conjunctiva. No staining of K8, K10 and K16 was detected in normal conjunctival epithelium, but in pterygial epithelium, K8 and K16 were present in full thickness and K10 was present in superficial cells. In normal conjunctiva, only base layer of epithelium showed positive staining with antibody of K14 and AE3 proteins, but they were present in the full thickness in pterygial epithelium and the antibody of AE3 protein stained the superficial cells heavily comparing with base cells. CONCLUSION: The abnormal expression of keratin proteins (K8, K10, K14, K16 and AE3) in pterygia indicates that the epithelial cells in pterygia are in the state of hyperproliferation and keratinization, which may be the cause of the abnormal tear function in patients with pterygia.

Adult↗
PubMed2000

[mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs].

OBJECTIVE: To detect the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs. METHODS: After consulting gene bank, we analyzed conservative sequence of hyaluronan synthases in different species, detected the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs with oligonucleotide probe by hybridization in situ. RESULTS: mRNA of hyaluronan synthase was strongly expressed in some epithelial cells of endolymphatic sac, coupled with negative expression in negative control groups. CONCLUSION: It confirms that endolymphatic sac cells can synthesize hyaluronan.

Animals↗
PubMed2000

[Re-evaluation of an embolic material for aneurysm cellulose acetate polymer].

OBJECTIVE: To re-evaluate the safety, effect, and pathological reactions of cellulose acetate polymer (CAP). METHODS: 30 right carotid arteries of rats were embolized and got two embolized vessels for histological study in each of the seven stages within four months. Fifteen canine aneurysmal models were created by transplantation of venous pouches. Twelve of them were occluded with CAP. Digital Subtraction Angiography (DSA) follow-ups of occluded aneurysmal models were carried out 1, 2 and 8 weeks after occlusion. One animal was sacrificed randomly at each stage for pathological study. RESULTS: Only five of the 12 aneurysmal models were completely or partially occluded within the patency of parent arteries within two months of observation after embolization with CAP. Stenosis of one branch of aneurysmal parent artery was occurred. The residual cavity of one partially occluded model artery was enlarged. Two models ruptured on four and five days after embolization. Three embolized models and their parent arteries were all occluded. PATHOLOGICAL FINDINGS: acute pathological reaction occurred within vessels embolized with CAP. Endothelial cell and basal membrane were damaged and vanished. Elastic lamina was exposed to arterial lumen and attached by thrombus layer. Fibrous cells and smooth muscle cells showed obvious degeneration. CAP and thrombus were gradually organized in two months after thrombosis. The orifices of aneurysmal models were covered with newly developed fibrous tissue and endothelial cells in two months after thrombosis. CONCLUSIONS: We think that acute chemical erosive effect of CAP was evident. A strong effect could lead to rupture of some of the CAP thrombosed aneurysmal models. Besides, stenosis or occlusion of the parent arteries could be induced in some cases after embolization with CAP. For the above shortcomings and limitations, it should be improved carefully before it is applied in clinic.

Aneurysm↗
PubMed2000

Complications in laparoscopic gynecologic surgery.

OBJECTIVE: To investigate retrospectively the complications and associated factors of gynecolgical laparoscopies. METHODS: 1 769 laparoscopic surgeries were carried out from January 1994 to October 1999 at our department. The procedures included 1421 surgeries of ovary and tube, 52 myomectomies and 296 cases of laproscopic-assisted vaginal hysterectomy (LAVH). A total of 312 patients had a history of prior laparotomy (17.6%). RESULTS: Complications occured in 34 cases, the overall complication rate was 1.92%. Unintended laparotomies occured in 6 cases (0.34%). 12 complications were associated with insertion of Veresse needle or trocar and creation of pneumoperitoneum, including 5 severe emphysema and 7 vascular injuries, this figure represents 35.3% of all complications of this series. Five intraoperative complications (14.7%) occured during the laparoscopic surgery (3 severe bleedings, one bladder injury and one skin burn of leg caused by damaged electrode plate), laparotomy was required in four of these cases. Seventeen complications occured during postoperative stage: 2 intraperitoneal hemorrhages needing laparotomy, 2 bowel injuries, 4 nerve paresis and 9 febrile morbidities. CONCLUSIONS: Operative gynecologic laparoscopy is associated with acceptable morbidity rate, but can not be overlooked. Complication rate seems to be higher in advanced procedures such as LAVH.

Female↗
PubMed2000

[Study on green upconversion luminescence of fluoride glasses doped with Nd3+].

In this paper, we report the upconversion luminescence of Nd: fluoride glasses pumped with 858 nm diode laser. Among the observed upconversion spectra, the green emission concerning with three photon process has overwhelming superiority in intensity, when the doping concentration of Nd3+ is enhanced, the green upconversion emission increases more drastically than that of other upconverted emissions. The experiment results indicate that fluoride glasses doped with Nd3+ posssess possibility of being green emitting upconversion materials. When the upconversion mechanism is discussed, the green luminescence concerning with three-photon is ascribed to three-ion cooperative upconversion.

English Abstract↗
PubMed2000

[Study on the photoinduced-color changing about novel azobenzocrown ether derivatives 16ABC-OH and 16ABC-NH2 in water solution and Langmuir-Blodgett film].

Two kinds of azobenzocrown ether derivation 16ABC-OH and 16ABC-NH2 have been synthesized, and their photoinduced color changing phenomena has been investigated in water solution, the reaction of 16ABC-OH is the photochemical Cis-trans-isomerization, and it is a first-order reaction, but the reaction of 16ABC-NH2 photochemical Cis-trans-isomeriation is very complex; and it is not a first-order reaction. In Langmuir-Blodgett film of 16ABC-OH, there is not molecular self-assembly phenomenon, the part of Cis-16ABC-OH become to iso-16ABC-NH2, but in the film, 16ABC-NH2 form H-Polymer by self-assembly, and the photochromic Cis-trans-isomerization is forbidded.

English Abstract↗
PubMed2000

[Binding ability of fluoride-resistant strains of S. mutans and S. sobrinus in vitro].

OBJECTIVE: To investigate the binding ability of S.mutans and S.sobrinus after their fluoride-resistant mutation. METHODS: The binding amount and binding percentage of S.mutans, S.sobrinus and their F-resistant strains to saliva-coated hydroxyapatite(SHA)were measured and compared by(3)H-labeled binding assay. RESULTS: The binding percentages of F-resistant and their parent strains had few difference(P>0.05) whereas the binding percentage of S.sobrinus was significantly lower than S.mutans (P<0.01). CONCLUSION: The data showed that the binding ability to SHA between F-resistant and F-sensitive S.mutans had no significant difference which indicated that the emerge of F-resistant strains could not reduce the cariogenicity of S.mutans and S.sobrinus.

English Abstract↗
PubMed2000

[An analysis of metablic organic acid of anaerobes by gas chromatography].

OBJECTIVE: The purpose of this study was to test the reliability of measurement of metablic organic acid of anaerobic bacteria by gas chromatography for the identification of anaerobes. METHODS: The metablic organic acid of 60 strains of 6 species of oral residential anaerobes were tested by gas chromatography qualitatively and quantitatively. RESULTS: It was found that the types and quantities of metablic organic acid of all anaerobes but two strains of lactobacillus were coincident with the standard of identification of anaerobes,and the total coincidence was 97.67%. CONCLUSION: The anaerobes could be identified accurately and quickly by gas chromatography.

English Abstract↗
PubMed2000

[In vitro study of Streptococcus mutans in the plaque on the surface of amalgam fillings on the conversion of inorganic mercury to organic mercury].

OBJECTIVE: To study the Streptococcus mutans in the plaque on the surface of amalgam fillings on the conversion of inorganic mercury to organic mercury. METHODS: Plaque was sampled from the amalgam restorations after amalgam filling regularly, serving the unfilled tooth as control. Streptococcus mutans was identified and inoculated to 10 ml TSB. After incubated 24 hours, mercury in water was added to the concentration of 100 ng/ml, incubated 24 hours again, the concentration of inorganic and organic mercury was determined. RESULTS: It was found that the difference of organic mercury and organic mercury between the baseline and the times after amalgam filling in test group and control was significant, while the difference between the times after amalgam filling was not significant, and the difference between the test group and the control was not significant, either. CONCLUSION: Streptococcus mutans can convert inorganic mercury to organic mercury in some way, and the mercury of amalgam plays some role in it.

English Abstract↗
PubMed1999

Structural and functional analysis of the 5' untranslated region of coxsackievirus B3 RNA: In vivo translational and infectivity studies of full-length mutants.

The lengthy 5' untranslated region (5'UTR) of coxsackievirus B3 (CVB3) forms a highly ordered secondary structure, which plays an important role in controlling viral transcription and translation. Our previous work has delineated the internal ribosome entry site (IRES) by mutation of mono- and bicistronic plasmids containing the 5'UTR and subsequent cell- free translation in rabbit reticular lysate (D. Yang, J. E. Wilson, D. R. Anderson, L. Bohunek, C. Cordeiro, R. Kandolf, and B. M. McManus. (1997). Virology 228, 63-73). To further identify the sequence elements responsible for viral translation and infectivity in tissue culture cells, >30 full-length mutants of CVB3 were constructed by mutations of the IRES and its flanking regions. Viral RNAs were transcribed from these constructs and transfected into HeLa cells. When the stem-loops G and H in the putative IRES were deleted, viral infectivity was abolished and viral protein translation was also undetectable by immunoblot analysis. However, when stem-loops A and B were deleted or stem-loop E was partially deleted, viral protein translation could be detected although cytopathic effect could not be observed. The data suggest that the crucial sequence of the IRES is located at stem-loops G and H. Further serial deletion mapping up and down stream of the crucial sequence defined more accurately the 5' and 3' boundaries of the IRES, located at nucleotides (nts) 309-432 and 639-670, respectively. These results indicate that the core sequence of the IRES should be located at nts 432-639. This IRES segment is much shorter and located closer to the initiation codon than that of poliovirus. To further define critical nucleotides within the IRES core, site-directed mutagenesis was conducted at the IRES core sequence by PCR. A 46-nt deletion in the pyrimidine-rich tract of stem-loop G abolished viral translation and infectivity. Interestingly, five single-nt substitutions in the pyrimidine-rich tract aimed at destabilizing the base pairing between the viral IRES and host 18S rRNA did not abolish CVB3 infectivity although viral protein translation was significantly reduced. This finding suggests that ribosomal internal initiation of translation and viral infectivity not only may require RNA secondary structure but also may need tertiary structure and perhaps the assistance of host protein factors.

5' Untranslated Regions↗
PubMed1999

A sequence in the Escherichia coli fdhF "selenocysteine insertion Sequence" (SECIS) operates in the absence of selenium.

The UGA codon context of the Escherichia coli fdhF mRNA includes an element called the selenocysteine insertion sequence (SECIS) that is responsible for the UGA-directed incorporation of the amino acid selenocysteine into a protein. Here, we describe an extended fdhF SECIS that includes the information for an additional function: the prevention of UGA readthrough under conditions of selenium deficiency. This information is contained in a short mRNA region consisting of a single C residue adjacent to the UGA on its downstream side, and an additional segment consisting of the six nucleotides immediately upstream from it. These two regions act independently and additively, and probably through different mechanisms. The single C residue acts as itself; the upstream region acts at the level of the two amino acids, arginine and valine, for which it codes. These two codons at the 5' side of the UGA correspond to the ribosomal E and P sites. Here, we present a model for the E. coli fdhF SECIS as a multifunctional RNA structure containing three functional elements. Depending on the availability of selenium, the SECIS enables one of two alternatives for the translational machinery: either selenocysteine incorporation into a polypeptide or termination of the polypeptide chain.

Arginine↗
PubMed1999

The three-dimensional structure of the HRDC domain and implications for the Werner and Bloom syndrome proteins.

BACKGROUND: The HRDC (helicase and RNaseD C-terminal) domain is found at the C terminus of many RecQ helicases, including the human Werner and Bloom syndrome proteins. RecQ helicases have been shown to unwind DNA in an ATP-dependent manner. However, the specific functional roles of these proteins in DNA recombination and replication are not known. An HRDC domain exists in both of the human RecQ homologues that are implicated in human disease and may have an important role in their function. RESULTS: We have determined the three-dimensional structure of the HRDC domain in the Saccharomyces cerevisiae RecQ helicase Sgs1p by nuclear magnetic resonance (NMR) spectroscopy. The structure resembles auxiliary domains in bacterial DNA helicases and other proteins that interact with nucleic acids. We show that a positively charged region on the surface of the Sgs1p HRDC domain can interact with DNA. Structural similarities to bacterial DNA helicases suggest that the HRDC domain functions as an auxiliary domain in RecQ helicases. Homology models of the Werner and Bloom HRDC domains show different surface properties when compared with Sgs1p. CONCLUSIONS: The HRDC domain represents a structural scaffold that resembles auxiliary domains in proteins that are involved in nucleic acid metabolism. In Sgs1p, the HRDC domain could modulate the helicase function via auxiliary contacts to DNA. However, in the Werner and Bloom syndrome helicases the HRDC domain may have a role in their functional differences by mediating diverse molecular interactions.

Adenosine Triphosphatases↗
PubMed1999

T suppressor lymphocytes inhibit NF-kappa B-mediated transcription of CD86 gene in APC.

CD8+CD28- human T suppressor cells (Ts) act on APC, inhibiting their ability to elicit Th activation and proliferation. This effect is due to inhibition of the CD40 pathway which normally leads to CD80 and CD86 up-regulation. To determine whether Ts inhibit expression of B7 molecules by blocking transcription, we cloned and characterized the CD86 promoter. Mutational analysis revealed that Ts inhibit transcription driven by the CD86 promoter. The NF-kappa B binding site, at -612 of the CD86 promoter, is essential for Th-induced transcription. In cultures containing Th and Ts, Ts inhibit Th-induced NF-kappa B activation in APC. Together, these findings indicate that Ts inhibition of NF-kappa B activation in APC is a means by which they regulate the activation and proliferation of Th.

Antigen-Presenting Cells↗
PubMed1999

Perceptual learning in motion discrimination that generalizes across motion directions.

When human subjects discriminate motion directions of two visual stimuli, their discrimination improves with practice. This improved performance has been found to be specific to the practiced directions and does not transfer to new motion directions. Indeed, such stimulus-specific learning has become a trademark finding in almost all perceptual learning studies and has been used to infer the loci of learning in the brain. For example, learning in motion discrimination has been inferred to occur in the visual area MT (medial temporal cortex) of primates, where neurons are selectively tuned to motion directions. However, such motion discrimination task is extremely difficult, as is typical of most perceptual learning tasks. When the difficulty is moderately reduced, learning transfers to new motion directions. This result challenges the idea of using simple visual stimuli to infer the locus of learning in low-level visual processes and suggests that higher-level processing is essential even in "simple" perceptual learning tasks.

Humans↗