Biomedical subjects

C Zhou

Publications and source records attributed to C Zhou.

At least 163 records · Page 9Linked to original sources

PubMed1998

[The types and distributive features of gene mutation on beta-thalassemia in three districts in northwest China].

OBJECTIVE: To sum up the results of gene analyses on beta-Thalassemia in three districts in northwest China and discuss the types and distributive features of the mutation. METHODS: Polymerase china reaction in combination with dot-blot hybridization of allele-specific oligonucleutide probes(PCR-ASO). RESULTS: In the gene analysis carried out in 85 probands with beta-Thalassemia, twelve types of gene mutation were identified from five nationalities. CD8(-AA), CDs8-9(+G), CDs27-28(+C) heterozygote and [-28(A-->uG). CD17(A-->uT)/N] double heterozygote were firstly assayed in these districts besides the common types in Chinese, of which, [-28(A-->uG). CD17(A-->uT)/N] as double gene mutation in the same chromosome is rare. CONCLUSION: There are significant differences in the distribution and nationality features of gene mutation types for beta-Thalassemia in the three districts, so the three districts as a whole is an area with special distributive features of the disease.

Adolescent↗

PubMed1997

Short-chain phosphatidylinositol conformation and its relevance to phosphatidylinositol-specific phospholipase C.

The solution conformation of chiral diheptanoylphosphatidylinositol (D- and L-inositol isomers) has been characterized by NMR spectroscopy. A positive NOE between the inositol C2 proton and an sn-3 glycerol CH2 proton has been observed in the D- but not in the L-inositol isomer of diheptanoylphosphatidylinositol (PI). Computer modeling using QUANTA constrained by this NOE and ring coupling constants suggests that the inositol ring is nearly parallel to the chain packing direction, leaving the phosphate ester accessible to attack by phosphatidylinositol-specific phospholipase C enzymes. In this model, the hydroxyl groups in the 2- and 6-positions of inositol form hydrogen bonds with the pro-R and ester oxygens, respectively. Chemical shifts and 13C spin-lattice relaxation times were also used to assess conformation and lipid dynamics in monomer and micelle states. The 13C T1's of inositol C2 and C6 in monomeric phosphatidylinositol were markedly less than for other inositol ring carbons. These results are consistent with the hydrogen bonds to the phosphate constraining the motions of C2 and C6. Diheptanoylphosphatidyl-2-O-methylinositol is a good inhibitor of PI-specific phospholipase C because it blocks the initial phosphotransferase step in PI hydrolysis. Introduction of the methyl group on the C-2 hydroxyl group lowers the CMC of the derivative compared to diheptanoylphosphatidylinositol. However, an NOE between an sn-3 glycerol proton and the inositol C2 proton constrains the orientation of the inositol ring with respect to the glycerol backbone in a conformation similar to diheptanoylphosphatidylinositol. Modeling of the 2-O-methylinositol derivative suggests that the methyl group blocks one side of the phosphate, consistent with the observation that nonspecific phospholipase C enzymes which are able to hydrolyze PI, albeit poorly, are unable to hydrolyze diheptanoylphosphatidyl-2-O-methylinositol.

Bacillus thuringiensis↗

PubMed1997

Diacylglycerol partitioning and mixing in detergent micelles: relevance to enzyme kinetics.

For many of the enzymes that utilize or produce diacylglycerols, detergent mixed micelles are often used in assay systems to solubilize the lipophilic substrates or products. The assumption is often made that the diacylglycerol (DAG) is solubilized and well mixed throughout the population of micelles during the time course of the assay. In the present work the partitioning and exchange dynamics of diacylglycerols (from dihexanoyl-DAG to didecanoyl-DAG) in a variety of detergent micelles have been studied by NMR and fluorescence methods. In all detergents, the longer the DAG chain lengths, the more detergent is required for solubilization. However, efficiency of solubilization varies tremendously with Triton X-100 the most efficient (i.e. the least detergent is required), and deoxycholate the least efficient in solubilizing DAG. The mixing and exchange dynamics of pyrene-labeled DAG molecules in these micelles (measured by stopped-flow fluorescence) were fastest for Triton X-100 and slowest with charged bile salt micelles. Of the detergent systems characterized, Triton X-100 appears to be the optimal detergent for use in assays of enzymes that interact with DAG (beta-octylglucoside and diheptanoylphosphatidylcholine have good exchange dynamics, but higher amounts of these detergents are needed to solubilize DAG). Bile salt micelles provide the least solubilization and the slowest exchange kinetics (so slow that this could be a significant problem in some enzyme assays). This information on DAG behavior in micelles is discussed with respect to assays of an enzyme that generates DAG as product (phospholipase C) and one that uses DAG as substrate (DAG kinase). Although slow exchange of DAG occurs in some micelle systems, this does not appear to be a rate-limiting step in the kinetics for either of these enzymes.

Bacillus cereus↗

PubMed1997

Allosteric activation of phosphatidylinositol-specific phospholipase C: specific phospholipid binding anchors the enzyme to the interface.

Phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis exhibits 'interfacial activation' toward the water-soluble substrate myo-inositol 1,2-(cyclic)phosphate [Zhou et al. (1997) Biochemistry 36, 347-355]. The activation of PI-PLC enzyme is optimal with PC or PE interfaces. NMR experiments (TRNOE and 31P line width analyses) were carried out to investigate the interaction of PI-PLC with activator amphiphiles. These studies showed that the enzyme had high affinity for phosphatidylcholine (or PE) molecules with dissociation constants of 0.5 and 0.3 mM for diC6PC and diC7PC, respectively. TRNOE cross-peaks of bound PC were confirmed to represent intramolecular relaxation pathways using partially perdeuterated PC molecules consistent with a single molecule binding tightly. The large activation by a PC interface can be explained by a single PC molecule binding specifically to PI-PLC and anchoring the enzyme-lipid complex to the interface. Other interfaces, such as micellar diC8PS, can activate PI-PLC about 2-3-fold; however, the monomers of these detergents showed little affinity for the enzyme as measured by TRNOE or 31P NMR line widths. The 3.6-fold activation produced by polymerized vesicles of 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphocholine (compared to the 15-fold activation generated by nonpolymerized PC vesicles) was comparable to the nonspecific activation of other detergents. This confirmed that single-PC molecule binding was allosteric and anchored the enzyme in the interface. The conformation of interfacially activated enzyme is discussed in term of the stabilization of a critical surface loop and helix B observed with weak intensity in the X-ray crystal structure.

Allosteric Regulation↗

PubMed1997

Cytologic features of papillary serous adenocarcinoma of the uterine cervix.

BACKGROUND: The cytologic features of papillary serous carcinoma of the cervix (PSCC) have not been described in detail previously. In this study the cytologic features of primary, pure PSCC are described and correlated with the histology. Comparison is made with papillary serous ovarian carcinoma metastatic to the cervix. METHODS: Seven cases of primary pure PSCC and five cases of ovarian PSCC metastatic to the cervix were retrieved from the pathology files. The cytology records and slides, and clinical charts were traced and examined retrospectively. RESULTS: Five of the 7 patients with PSCC were younger than 40 years. The smears of PSCC contained many groups of atypical glandular cells. Monolayered sheets of mildly atypical glandular cells with papillary branches were observed only in the cases of primary PSCC. All cases contained multilayered sheets of mildly to moderately pleomorphic glandular cells, pseudopapillary fragments, and tight balls of cells resembling endometrial glandular cells. Squamoid cells with abundant densely staining cytoplasm were also encountered. Free-lying dissociated atypical cells were also present, some of which were markedly atypical. A marked tumor diathesis of inflammatory cells, cell debris, and blood was encountered with primary PSCC but was scanty in cases of papillary serous ovarian carcinoma metastatic to the cervix. CONCLUSIONS: PSCC has a relatively characteristic cytologic appearance which usually differs from other endocervical adenocarcinomas and from metastatic papillary serous carcinoma. However, some features may lead to underdiagnosis or confusion with other entities such as squamous carcinoma or endometrial carcinoma.

Adult↗

PubMed1997

Characterization of the Rep78/adeno-associated virus complex.

Adeno-associated virus (AAV) replication proteins Rep78 and Rep68 play major roles in the life cycle of AAV. We have recently provided in vivo evidence for the existence of a covalent association between Rep78 and virion single-stranded (ss) AAV DNA (K. M. R. Prasad and J.P. Trempe(1995) Virology 214, 360-370). In this work we have further characterized the Rep78 protein-AAV DNA covalent linkage. Exonuclease and primer extension analyses revealed that in the majority of isolated ssDNA, Rep78 protein is covalently linked to one of the 5' terminal thymidines. Pulse-chase experiments with radiolabeled methionine suggest that Rep protein remains associated with the virus particle for up to 8 hr after labeling in infected cells. Quantitative immunoprecipitation indicated that approximately 30% of the ssDNA remains associated with the Rep protein after cell fractionation and partial purification. When cells are infected with Rep-associated AAV particles, a significant proportion of viral DNA remains attached to Rep after entry into the nucleus. However, the linkage does not persist after nuclear entry. These observations suggest that covalently linked Rep78 protein may play a key role during wild-type AAV infections and AAV vector transductions.

Base Sequence↗

PubMed1997

Molecular cloning of ERp29, a novel and widely expressed resident of the endoplasmic reticulum.

We have isolated a full-length cDNA clone for a novel 29 kDa protein that is highly expressed in rat enamel cells. The clone encodes a 259-residue protein, here named ERp29, with structural features (signal peptide and a variant endoplasmic reticulum-retention motif, KEEL) that indicate it is a reticuloplasmin. ERp29 has limited homology with protein disulfide isomerase and its cognates, but lacks their characteristic thioredoxin-like catalytic moiety and calcium-binding motifs. ERp29 mRNA was expressed in all rat tissues tested, and a homologous transcript was detected in other animal livers (primate, ruminant, marsupial). In human hepatoma cells, ERp29 mRNA expression was not increased by stresses (tunicamycin, calcium ionophore) that induced other reticuloplasmins. We conclude that ERp29 is a new, highly conserved member of the reticuloplasmin family which is widely expressed. The apparent lack of both calcium binding properties and stress responsiveness distinguish ERp29 from all major reticuloplasmins characterised to dates.

Amino Acid Sequence↗

PubMed1997

Activation of phosphatidylinositol-specific phospholipase C toward inositol 1,2-(cyclic)-phosphate.

Phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis catalyzes the hydrolysis of phosphatidylinositol (PI) in discrete steps: (i) an intramolecular phosphotransferase reaction to form inositol 1,2-(cyclic)-phosphate (cIP), followed by (ii) a cyclic phosphodiesterase activity that converts cIP to inositol 1-phosphate. Water-soluble cIP was used as the substrate to study the cyclic phosphodiesterase activity and interfacial behavior of PI-PLC. Different detergent micelles and phospholipid vesicles were used to examine if "interfacial activation" of the enzyme could occur toward a soluble substrate. Almost all detergents examined activated the enzyme at least 2-fold, with PC species yielding the largest increases in PI-PLC specific activity. Kinetic parameters were measured in the absence and presence of several representative detergents (e.g., Triton X-100 and diheptanoylphosphatidylcholine (diC7PC)). Gel filtration experiments showed that, under these conditions, the cIP did not partition to any measurable extent with these detergent micelles. The concentration at which half the maximum activation was observed occurred near the detergent CMC. Both Km and Vmax were altered by the presence of a surface: Km decreased to different degrees depending on the detergent, while Vmax increased substantially. The Km for cIP was 90 mM without detergent and decreased to 29 mM with diC7PC micelles added; Vmax increased almost 7-fold in the presence of diC7PC micelles. The enzyme efficiency (Vmax/Km) in the presence of diC7PC increased more than 21-fold, but it was still 20-fold lower than initial phosphotransferase activity for monomeric dihexanoylphosphatidylinositol. The poor efficiency of the cyclic phosphodiesterase activity is largely due to substrate binding affinity. The dependence of rate on substrate concentration exhibits cooperative behavior, especially without detergent. This cooperativity is discussed in terms of protein aggregation and ligand binding sites on the enzyme.

Bacillus subtilis↗

PubMed1997

Stereocontrolled syntheses of water-soluble inhibitors of phosphatidylinositol-specific phospholipase C: inhibition enhanced by an interface.

Three inositol 1,2-(cyclic)-phosphate analogs, inositol cyclic phosphonates with different stereochemistry at the C-2 position of the inositol ring, have been synthesized as water-soluble inhibitors of phosphatidylinositol-specific phospholipase C (PI-PLC). Their inhibition of both phosphotransferase and cyclic phosphodiesterase activities has been studied in the absence and presence of an interface. Key results include the following. (i) Only the analog with the same stereochemistry at the C-2 position of the inositol ring as the natural substrate, myo-inositol 1,2-(cyclic)-phosphate (cIP), exhibits effective inhibition of PI-PLC. (ii) The inhibition of the PI-PLC cyclic phosphodiesterase activity by this cIP analog is enhanced by the presence of an interface (Triton X-100 or diC7PC micelles). This is the first observation of detergent enhancing the effectiveness of a water-soluble inhibitor competing with a water-soluble substrate. (iii) For the cyclic phosphodiesterase activity measured in the presence of 8 mM of the best (e.g., most activating) interface, diC7PC, myo-inositol 1,2-(cyclic)-2-methylenephosphonate (cICH2P) was shown to be a competitive inhibitor with a Ki of 12.3 mM. (iv) The IC50 obtained for the same compound inhibiting the PI-PLC hydrolysis of PI dispersed in DiC7PC micelles was consistent with a Ki approximately 10 mM for the phosphotransferase activity. The similarity of Ki for both PI and cIP processing by PI-PLC suggests both reactions occur at the same site on the enzyme.

Bacillus subtilis↗

PubMed1997

Inducible expression of Na+/myo-inositol cotransporter mRNA in anterior epithelium of bovine lens: affiliation with hypertonicity and cell proliferation.

Bovine lenses were pretreated with physiological (314 +/- 6 mosm) or hypertonic medium (> 450 mosm) for 20 hours prior to introduction of the lenses into modified Ussing chambers (providing a leakproof seal at the lens equator). The anterior (epithelial-containing) and posterior (cell-free) aspects of the mounted intact lens could thus be independently bathed with myo-[3H]inositol. Myo-inositol uptake as a function of concentration across the anterior aspect was indicative of an active carrier-mediated component and at high concentration, significant myo-inositol influx due to passive diffusion. Myo-inositol uptake was markedly stimulated across the anterior aspect and inhibitable by ouabain but not stimulated across the posterior aspect, when lenses were exposed to hyperosmotic medium by the addition of raffinose or sodium chloride. Myo-inositol rapidly desaturates across both aspects of the lens consistent with its efflux being largely a function of passive diffusional leakout from the extracellular space. In order to corroborate the apparent hypertonic-induced upregulation of gene expression inferred by kinetic analysts, the level of Na+/myo-inositol cotransporter mRNA was determined by reverse transcription and quantitative PCR using harvested anterior epithelial cells from intact lenses exposed to physiologic or hypertonic medium for 20 hours. RNA samples were microextracted from both the central and equatorial regions of the lenticular epithelium of the anterior lens capsule. The abundance of Na+/myo-inositol cotransporter mRNA was similar from epithelium of the central zone irrespective of medium tonicity but was markedly elevated from the equatorial zone of osmotically-stressed lenses. While both the quiescent epithelial cells of the central region and actively dividing epithelial cells of the equatorial zone of the intact lens express Na+/myo-inositol contransporter mRNA, only the equatorial epithelium responds to hypertonic insult with enhanced uptake of myo-inositol due to increased transcription of the Na+/myo-inositol cotransporter gene, suggesting a possible role for the state of cell proliferation.

Animals↗

PubMed1997

Cloning the bovine Na+/myo-inositol cotransporter gene and characterization of an osmotic responsive promoter.

Hyperosmotic-induced enhancement of myo-inositol accumulation in cultured bovine lens epithelial cells stems from increased uptake activity due to upregulation of Na+/myo-inositol cotransporter mRNA and de novo synthesis in myo-inositol carrier protein. The molecular mechanism of osmoregulation of Na+/myo-inositol cotransporter gene transcription was further investigated. The effect of hypertonicity on transcription initiation of the Na+/myo-inositol cotransporter gene was examined by use of the rapid amplification of cDNA ends (RACE) technique. 5"-RACE analysis revealed that one hypertonic and two isotonic (i.e. physiologic) transcription start sites are present in the Na+/myo-inositol cotransporter gene of cultured bovine lens epithelial cells. Moreover, the bovine Na+/myo-inositol cotransporter gene was cloned and its promoters were characterized by transient transfection assay using luciferase reporter constructs of various fragments of the 5"-flanking regions upstream of the individual transcription start sites. Among its promoters, only one was osmotically responsive and showed approximately a 3-fold induction of activity subsequent to hypertonic insult. Transient transfection assays revealed that the region between -398 and -331 bp, upstream of this hypertonic transcription start site, contains the putative osmotic response element. Preferential utilization of this osmotically responsive promoter contributes to the elevation of Na+/MI cotransporter mRNA abundance and increased myo-inositol uptake activity as initiated by osmotic stress.

Animals↗

PubMed1997

Postnatal development of Schwann cells at neuromuscular junctions, with special reference to synapse elimination.

The neuromuscular junctions (NMJs) of postnatal rat soleus muscles were examined by immunohistochemical staining for S100, a marker of Schwann cells (SCs), and for protein gene product 9.5, a neuronal marker, to elucidate the involvement of SCs in synapse elimination. The morphological maturation of S100-immunoreactive terminal SCs at NMJs proceeded with the gradual increase in their number. The number of terminal SCs per NMJ was one or two at postnatal day (P) 7, reaching the adult number at P28, when it became three or four. Confocal laser scanning microscopic analysis of multi-innervated NMJs, whose number decreased between P7 and P14, revealed a change in the ratio between terminal SCs and axons with age. At P7, the ratio between axons and terminal SCs per NMJ was > or = 2:1, which was exactly the reverse of that in adults, while at P14 this had changed to 2:2. A structural change appeared to occur at the same time at the preterminal region, this being prior to the establishment of a 1:1 relationship between axon and SC sheath which was detected at P14, with the > or = 2:1 relationship seeming to occur at P7. Thus, synapse elimination seems to proceed, at least for one week, with the gradual loss of axons which are at different stages of maturation with respect to their spatial relationship with SCs. From our results it seems unlikely that SCs play an active role in selecting a single axon to survive.

Animals↗

PubMed1997

[An investigation of precipitation of airborne fungi particles in the rooms of university library].

Precipitation of airborne fungi particles in the rooms of an University library and the influencing factors were studied in May 1994 with the fallen plate method. The total average precipitation of airborne fungi particles was 11.68 per dish in 5 minutes. The differences were significant from different room patterns, floors and times, so were the humidity assayed. The book-store rooms and reading rooms had an average precipitation of 15.01 and 8.35 per dish in 5 minutes respectively (P < 0.05), and humidity of 41.7 and 11.4 percent respectively (P < 0.01). The influencing factors were: different floors and room patterns, the people's activity, the different time, humidity, ventilation and book pollution.

Air Microbiology↗

PubMed1997

[Evaluation of reproducibilty of the hinge-axis and it's positional relation to condyles].

The aim of this paper was to study the reproducibility of the positions of hinge-axis of mandibular retruded small open-closed movements, and the positional relationship between the hinge-axis and condyles. Fourteen normal students were tested by a six degrees of freedom mandibular movement recorder MT1602 (Germany). The result showed that: the hinge-axis could not be exactly repeated and movable instantaneous centers of rotation (ICR) were recorded. These rotation centers distributed almost evenly around the condyles, the mean distance from these rotation centers to condyle centers was about 8.83 +/- 5.65 mm.

Adult↗

PubMed1997

[Investigation of the infectious route of peritonsillar abscess].

One hundred and thirty-one cases of peritonsillar abscess were studied to investigate the pathogenesis and the infectious route. The involved tonsils were resected in 83 patients. The surface of the resected tonsils was smooth and intact, neither ulceration nor pustular sinus was found on the surface of the upper part of these tonsils. There were some inflammatory and/or fibrotic minor salivary glands (Weber's glands) on the top of the quinsy tonsils. The glands adjacent to the tonsils of non-quinsy patients had normal appearance. It suggests that the origin of peritonsillar infection might be the Weber's glands rather than extension from acutely inflamed tonsil.

Adolescent↗

PubMed1997

[Correlativity among biological characteristics of Gardenia jasminoides Eills].

The relationship among certain biological characteristics, fruit yield and quality of G. jasminoides was studied, and the special features, closely correlateied with fruit production and quality, as well as with the steadiness of heredity were found out. According to these features the G. jasminoides produced in Sichuan province has been divided into 6 types.

Iridoids↗

PubMed1997

[Deletion of MTS1/p16 gene in endometrial carcinoma].

OBJECTIVE: To investigate the possible relationship between deletion of MTS1/p16 gene and progression of endometrial carcinoma. METHODS: Thirty two primary endometrial carcinoma, 7 tumor-adjacent endometrial tissue and 10 normal endometrial tissue specimens were examined for homozygous deletion of MTS1/p16 gene by polymerase chain reaction-based analysis. RESULTS: Of 32 endometrial cancer specimens, 6(18.8%) showed homozygous deletion of MTS1/p16 gene. No deletion was detected in the tumor-adjacent and normal endometrial tussues. Nor was it detected in well differentiated endometrial carcinoma. CONCLUSIONS: Deletion of MTS1/p16 gene might contribute to the progression of endometrial carcinoma and could be served as indicator for predicting prognosis.

Adenocarcinoma↗

PubMed1997

[The study and manufacture of spinning counter for experimental animals].

The single-chip microcomputer technique is used in the present study of spinning counter, which has 4 observation tunnels, the spinning behave of four experiment animals can be recorded at same time. The function of this instrument has four selections according to different experiment, and the recording data can be compute processed.

Animals↗