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Biomedical subjects

Z Ren

Publications and source records attributed to Z Ren.

At least 55 records · Page 3Linked to original sources
PubMed1999

Clinical and experimental studies of large amplitude action potential of the suffered facial muscles in intratemporal facial nerve paralysis.

OBJECTIVE: To testify the phenomenon that large amplitude action potential appears at the early stage of facial paralysis, and to search for the mechanism through clinical and experimental studies. PATIENTS (ANIMALS) AND METHODS: The action potentials of the orbicular ocular and oral muscles were recorded in 34 normal persons by electromyogram instruments. The normal range of amplitude percentage was found out according to the normal distribution. One hundred patients with facial paralysis were also studied. The action potentials of facial muscles were recorded in 17 guinea pigs before and after the facial nerve was compressed and the facial nerve was examined under electromicroscope before and after the compression. RESULTS: The amplitude percentage of the suffered side to the healthy side was more than 153 percent in 6 of the 100 patients. Large amplitude action potential occured in 35 per cent guinea pigs which were performed the experiment of facial nerve compression. Electromicroscopic examination revealed separation of the lammae of the facial nerve's myelin sheath in the guinea pigs which exhibited large amplitude action potential. CONCLUSION: The facial nerve exhibited a temporary over-excitability at the early stage of facial nerve injury in some patients and guinea pigs. If the injury was limited in the myelin sheath, the prognosis was relatively good.

Action Potentials↗
PubMed1998

Crystal structure of the ribosomal RNA domain essential for binding elongation factors.

The structure of a 29-nucleotide RNA containing the sarcin/ricin loop (SRL) of rat 28 S rRNA has been determined at 2.1 A resolution. Recognition of the SRL by elongation factors and by the ribotoxins, sarcin and ricin, requires a nearly universal dodecamer sequence that folds into a G-bulged cross-strand A stack and a GAGA tetraloop. The juxtaposition of these two motifs forms a distorted hairpin structure that allows direct recognition of bases in both grooves as well as recognition of nonhelical backbone geometry and two 5'-unstacked purines. Comparisons with other RNA crystal structures establish the cross-strand A stack and the GNRA tetraloop as defined and modular RNA structural elements. The conserved region at the top is connected to the base of the domain by a region presumed to be flexible because of the sparsity of stabilizing contacts. Although the conformation of the SRL RNA previously determined by NMR spectroscopy is similar to the structure determined by x-ray crystallography, significant differences are observed in the "flexible" region and to a lesser extent in the G-bulged cross-strand A stack.

Animals↗
PubMed1998

Static Laue diffraction studies on acetylcholinesterase.

Acetylcholinesterase (AChE) is one of nature's fastest enzymes, despite the fact that its three-dimensional structure reveals its active site to be deeply sequestered within the molecule. This raises questions with respect to traffic of substrate to, and products from, the active site, which may be investigated by time-resolved crystallography. In order to address one aspect of the feasibility of performing time-resolved studies on AChE, a data set has been collected using the Laue technique on a trigonal crystal of Torpedo californica AChE soaked with the reversible inhibitor edrophonium, using a total X-ray exposure time of 24 ms. Electron-density maps obtained from the Laue data, which are of surprisingly good quality compared with similar maps from monochromatic data, show essentially the same features. They clearly reveal the bound ligand, as well as a structural change in the conformation of the active-site Ser200 induced upon binding.

Acetylcholine↗
PubMed1998

Phage T4 SOC and HOC display of biologically active, full-length proteins on the viral capsid.

The T4 phage capsid accessory protein genes soc and hoc have recently been developed for display of peptides and protein domains at high copy number (Ren et al., 1996. Protein Science 5, 1833-1843; Ren et al., 1997. Gene 195, 303-311). That biologically active and full-length foreign proteins can be displayed by fusion to SOC and HOC on the T4 capsid is demonstrated in this report. A 271-residue heavy and light chain fused IgG anti-EWL (egg white lysozyme) antibody was displayed in active form attached to the COOH-terminus of the SOC capsid protein, as demonstrated by lysozyme-agarose affinity chromatography (>100-fold increase in specific titer). HOC with NH2-terminal fused HIV-I CD4 receptor of 183 amino acids can be detected on the T4 outer capsid surface with human CD4 domain 1 and 2 monoclonal antibodies. The number of molecules of each protein (10-40) bound per phage and their activity suggest that proteins can fold to native conformation and be displayed by HOC and SOC to allow binding and protein-protein interactions on the capsid.

Bacteriophage T4↗
PubMed1998

Structure refinement against synchrotron Laue data: strategies for data collection and reduction.

The synchrotron Laue technique has been applied to high-resolution structure refinement of the ribotoxin, restrictocin [Yang & Moffat (1996). Structure, 4, 837-852]. By employing carefully designed data-collection strategies and the data-reduction algorithms incorporated in the software system LaueView [Ren & Moffat (1995a). J. Appl. Cryst. 28, 461-481; Ren & Moffat (1995b). J. Appl. Cryst. 28, 482-493], a set of high-resolution Laue data with a completeness and accuracy comparable to excellent monochromatic data was obtained. Through detailed comparison with the monochromatic data and electron-density maps derived from the Laue data, optimum data-collection and reduction strategies were identified and the application of Laue diffraction techniques to conventional crystallographic refinement was demonstrated.

Algorithms↗
PubMed1998

Energy transduction on the nanosecond time scale: early structural events in a xanthopsin photocycle.

Photoactive yellow protein (PYP) is a member of the xanthopsin family of eubacterial blue-light photoreceptors. On absorption of light, PYP enters a photocycle that ultimately transduces the energy contained in a light signal into an altered biological response. Nanosecond time-resolved x-ray crystallography was used to determine the structure of the short-lived, red-shifted, intermediate state denoted [pR], which develops within 1 nanosecond after photoelectronic excitation of the chromophore of PYP by absorption of light. The resulting structural model demonstrates that the [pR] state possesses the cis conformation of the 4-hydroxyl cinnamic thioester chromophore, and that the process of trans to cis isomerization is accompanied by the specific formation of new hydrogen bonds that replace those broken upon excitation of the chromophore. Regions of flexibility that compose the chromophore-binding pocket serve to lower the activation energy barrier between the dark state, denoted pG, and [pR], and help initiate entrance into the photocycle. Direct structural evidence is provided for the initial processes of transduction of light energy, which ultimately translate into a physiological signal.

Bacterial Proteins↗
PubMed1998

Modulation of small G protein isoprenylation by anticancer monoterpenes in in situ mammary gland epithelial cells.

Monoterpenes have been shown to both prevent and treat mammary cancer in animal models and are currently in clinical testing in advanced cancer patients. In this study, we investigated a biochemical modulation associated with the antitumor activity of monoterpenes, the inhibition of protein isoprenylation in monoterpene chemoprevention target tissue, i.e. the in situ mammary gland epithelial cells. We first developed a new methodology that for the first time permitted the study of protein isoprenylation and other products in the mevalonate pathway in in situ mammary cells. Using this approach, we found that chronically feeding rats with an anticancer dose of perillyl alcohol resulted in a 22% inhibition of coenzyme Q synthesis and a 19% inhibition of small G protein isoprenylation in mammary gland epithelial cells in situ. The greatest inhibition of small G protein isoprenylation observed was the 28% inhibition of isoprenylation of RhoA by type I geranylgeranyl protein transferase (GGPTase). Given that some substrates of type I GGPTase, such as RhoA and Rac1, have transforming properties, the possibility that the inhibition of type I GGPTase will change the cellular location and functionality of these proteins and thus contribute to the chemoprevention activity of monoterpenes, is discussed.

Animals↗
PubMed1998

hgpB, a gene encoding a second Haemophilus influenzae hemoglobin- and hemoglobin-haptoglobin-binding protein.

Haemophilus influenzae requires heme for growth and can utilize both hemoglobin and hemoglobin-haptoglobin as heme sources. We previously identified a hemoglobin- and hemoglobin-haptoglobin-binding protein, HgpA, in H. influenzae HI689. Mutation of hgpA did not affect binding or utilization of either heme source. The hgpA mutant exhibited loss of a 120-kDa protein and increased expression of a 115-kDa protein. These data suggested that at least one other gene product is involved in binding of these heme sources by H. influenzae. A 3.2-kbp PCR product derived from HI689 was cloned. The nucleotide sequence indicated a separate, distinct gene with high homology to hgpA, which would encode a 115-kDa protein. Primers were designed for directional cloning of the structural gene in the correct reading frame. Sonicates of induced Escherichia coli harboring the cloned open reading frame bound both hemoglobin and hemoglobin-haptoglobin. An insertion/deletion mutant of H. influenzae at the newly identified locus, designated hgpB, was constructed. The 115-kDa protein was not detected in the mutant after affinity purification using biotinylated hemoglobin. An hgpA hgpB double-mutant strain exhibited a reduced ability to utilize hemoglobin-haptoglobin, although it was unaltered in the ability to utilize hemoglobin. Affinity isolation of hemoglobin-binding proteins from the double mutant resulted in isolation of an approximately 120-kDa protein. Internal peptide sequencing revealed this protein to be a third distinct protein, highly homologous to HgpA and HgpB. In summary a second hemoglobin- and hemoglobin-haptoglobin-binding protein of H. influenzae has been identified and characterized, and the presence of an additional protein of similar function has been revealed.

Amino Acid Sequence↗
PubMed1998

[Histopathological study of local invasiveness of transglottic cancer].

OBJECTIVE: To explore the characteristics and relevant factors of transglottic cancer invading paraglottic space (PGS) and pre-epiglottic space (PES). METHODS: Whole-organ serial sections of 50 transglottic cancer specimens were studied histopathologically. RESULTS: Transglottic cancer invading PGS was observed in 39 of the 50 (78.0%) specimens. In 32 of the 39 specimens, the invasion outstripped PGS, involving elastic cone in 26(81.3%), thyroid cartilage in 24(75.0%) and cricothyroid membrane in 20(62.5%). Transglottic cancer invading PES was seen in 23 of the 50 specimens (46.0%). With the increase in tumor staging and tumor size, PGS and PES became increasingly invaded. There were two possible routes of invasion to PES: a) extending anteriorly and upward via PGS; b) extending upward via anterior commissure to destroy the stem of epiglottic cartilage. CONCLUSION: PGS is easily invaded by transglottic cancer. Partial laryngectomy is recommended in patients with T3, T4 transglottic cancer larger than 20 mm in diameter.

Adult↗
PubMed1998

[Clinical and experimental study on facial paralysis in temporal bone fracture].

To study the main prognostic factors and significance of facial nerve decompression of facial paralysis in temporal bone fracture, the main relative prognostic factors of 64 patients with facial paralysis were analyzed. Experimental model of facial paralysis was made. Expansion rate of facial nerve in facial canal opening group and non-opening group was measured and observed under electron microscope. The main factors affecting the prognosis were facial nerve decompression and selection of surgery time. Expansion rate of facial nerve in opening group was significantly higher than that of non-opening group. Injury degree of nerve fiber of non-opening group was severe. It is suggested that early facial nerve decompression is of beneficial to restoration of facial nerve function.

Adolescent↗
PubMed1998

[A new rat brain-glioma model].

OBJECTIVE: To build a new rat brain glioma model with LacZ as a reporter gene. METHODS: Plasmid BAG was transfected into C6 glioma cell. The cell cycle, cell proliferation, malignant infiltrative ability of wild and transfected glioma cell were observed. Rat glioma model was built using stereotaxic implantation. RESULTS: There was no difference between transfected and wild glioma cell in cell growth characteristics and tumorigenesis. CONCLUSIONS: It was easy to observe the infiltrative area on cellular level from the rat glioma model made by transfected tumor cell. The method is satisfactory for radiation and chemotherapeutic trials of glioma.

Animals↗
PubMed1997

Inhibition of type I and type II geranylgeranyl-protein transferases by the monoterpene perillyl alcohol in NIH3T3 cells.

The monoterpene perillyl alcohol has anticancer activities that include both prevention and treatment of a wide variety of cancers in animal models. In purified enzyme studies, perillyl alcohol inhibited farnesyl-protein transferase and type I geranylgeranyl-protein transferase. However, whether and which of the polyprenyl-protein transferases is inhibited by perillyl alcohol in vivo is not known. The previously reported monoterpene-induced inhibition of the incorporation of [14C]mevalonolactone into proteins in cultured cells could be due to an inhibition of one or several enzymes in the mevalonate pathway or to changes in the levels of protein substrates for isoprenylation. In the current study, we first analyzed the levels of individual phosphorylated isoprenoid intermediates between mevalonate and geranylgeranyl pyrophosphate in NIH3T3 cells labeled for 4 hr with [14C]mevalonolactone and found that perillyl alcohol did not inhibit the synthesis of these intermediates. Next, proteins including Ras, RhoA, and Rab6 were immunoprecipitated from NIH3T3 cells. Perillyl alcohol was found to inhibit the incorporation of [14C]mevalonolactone into RhoA and Rab6 but not Ras protein. The cellular levels of these three proteins were constant over the 4-hr treatment period. Finally, the distribution of Ras, Rap1, and Rab6 proteins between the aqueous and the detergent-enriched phases was measured. Rap1 and Rab6 but not Ras from perillyl alcohol-treated NIH3T3 cells accumulated in the aqueous phase. Thus, we conclude that perillyl alcohol can inhibit the in vivo prenylation of specific proteins by type I and type II geranylgeranyl-protein transferases but not farnesyl-protein transferase in NIH3T3 cells.

3T3 Cells↗
PubMed1997

Structure of a protein photocycle intermediate by millisecond time-resolved crystallography.

The blue-light photoreceptor photoactive yellow protein (PYP) undergoes a self-contained light cycle. The atomic structure of the bleached signaling intermediate in the light cycle of PYP was determined by millisecond time-resolved, multiwavelength Laue crystallography and simultaneous optical spectroscopy. Light-induced trans-to-cis isomerization of the 4-hydroxycinnamyl chromophore and coupled protein rearrangements produce a new set of active-site hydrogen bonds. An arginine gateway opens, allowing solvent exposure and protonation of the chromophore's phenolic oxygen. Resulting changes in shape, hydrogen bonding, and electrostatic potential at the protein surface form a likely basis for signal transduction. The structural results suggest a general framework for the interpretation of protein photocycles.

Bacterial Proteins↗
PubMed1997

Synchrotron radiation applications to macromolecular crystallography.

Progress has been rapid in the development and application of four different types of macromolecular crystallographic experiment at synchrotron hard X-ray sources: multiwavelength anomalous diffraction; studies of crystals with very large unit cell dimensions; structure determination at atomic or near-atomic resolution; and time-resolved studies. The results illustrate the interplay between the advanced technical capabilities available at new beamlines and more challenging scientific issues.

Crystallography, X-Ray↗
PubMed1997

[Expression of human papillomavirus 16, 18 E6 protein of cervical squamous cell carcinoma].

OBJECTIVE: To investigate the expression of human papillomavirus (HPV) 16, 18 E6 protein of cervical squamous cell carcinoma and to assess the practical value of HPV 16, 18 E6 antibody. METHODS: Immunohistochemistry SP method was used to examine HPV 16, 18 E6 protein expression in 40 cases of squamous cell carcinoma of uterine cerivx, 30 cases of chronic cervicitis and 30 cases of normal cervical epidermal tissue. RESULTS: 27/40 carcinoma cases and 1/30 chronic cervicitis showed positive staining. None of the normal epithelium specimens gave positive results. The difference between malignant and benign groups was significant. CONCLUSION: A close relation between high risk HPV 16, 18 E6 antibody could be a good indicator for HPV 16, 18 infection and early diagnosis of cervical carcinoma.

Carcinoma, Squamous Cell↗
PubMed1997

[Contrast analysis of clinical and pathological staging of supraglottic carcinomas].

To evaluate the accuracy of clinical staging of supraglottic carcinomas, a retrospective histopathological study of larynges from 53 patients who had undergone total laryngectomy was adopted. All larynges were processed as whole-organ serial sections in coronal plane. The results showed that clinical underestimation had been made in 24.5% of all laryngeal cancer cases. Clinical underestimation occured in 54.5%, 33.3% of T2, T3 laryngeal cancer cases, respectively. There was no overestimation in clinical staging. The important factors that affected clinical underestimation were invasion of the pre-epiglottic space and thyroid cartilage. It is suggested that the pre-epiglottic space should be resected in early supraglottic carcinoma. The thyroid cartilage involvement should be suspected in laryngeal cancer with extensive invasion of anterior commisure or extensive invasion of the paraglottic space accompanied by cartilage ossification.

Adult↗
PubMed1997

[Estrogen receptor expression and its relationship with biologic feature in hepatocellular carcinoma].

OBJECTIVE: For understanding the clinicopathologic significance of estrogen receptor (ER) in hepatocellular carcinoma (HCC) ER of the surgical resected species was detected and its relation to biologic feature was analysis. METHODS: ER was detected in 62 HCC species with Dextran coated charcoal method. Some pathologic characteristics were studied with gross and microscopic examination and proliferating cell nuclear antigen (PCNA) was determined with immunohistochemistry using monoclonal antibody PC-10. RESULTS: ER positive HCC had higher incidence of single nodule (83.3%) and complete encapsulation (58.3%) compared to ER negative HCC (42.1% and 21.0%). The difference was significant (P < 0.05). In small liver cancer ER positive rate was 62.5% which was higher than 30.4% in large liver cancer (P < 0.05). The PCNA labeled index was (26.2 +/- 18.7)% in ER positive HCC and (43.6 +/- 32.0)% in ER negative HCC. The difference was significant (P < 0.05). CONCLUSION: The results suggest that ER positive HCC has less malignant biologic behavior and better prognosis than ER negative HCC.

Adult↗