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Biomedical subjects

X L Zhou

Publications and source records attributed to X L Zhou.

At least 19 recordsLinked to original sources
PubMed2004

Functional luteinizing hormone/chorionic gonadotropin receptors in human adrenal cortical H295R cells.

Previous studies have suggested that activation of normal human adrenal and adrenal tumor luteinizing hormone (LH)/chorionic gonadotropin (hCG) receptors results in an increased secretion of steroid hormones. Since it is not feasible to test this suggestion on normal human adrenal cells, we used human adrenal cortical carcinoma H295R cells, which are similar in some respects to normal adrenal cortical cells. These cells contained LH/hCG receptor transcripts and receptor protein that can bind (125)I-hCG in a hormone-specific manner. Culturing the cells with highly purified hCG resulted in a time- and dose-dependent significant increase in dehydroepiandrosterone sulfate (DHEAS) secretion as compared with the controls. The DHEAS response was hormone as well as steroid specific. Since hCG treatment did not increase DHEA secretion, we suspected that the hCG might increase DHEA sulfotransferase (ST). Consistent with this possibility, hCG treatment increased steady-state DHEA-ST mRNA levels. The hCG effects require its receptors, as inhibition of their synthesis by treatment with antisense phosphorothioate oligodeoxynucleotides (ODN) made from the LH/hCG receptor sequence resulted in loss of DHEA-ST and DHEAS responses. The findings that 1) hCG treatment increased cAMP levels and activated protein kinase A (PKA), 2) 8-bromo cAMP mimicked hCG, and 3) blocking PKA activation prevented hCG as well as 8-bromo cAMP from increasing both DHEA-ST mRNA and DHEAS levels suggested that cAMP/PKA signaling was involved in the hCG actions. In conclusion, H295R cells contain LH/hCG receptors, which are coupled to increasing DHEAS secretion through upregulating the ST enzyme mRNA level. This action is mediated by the cAMP/PKA signaling pathway. These findings support the concept that adrenal function in normal and pathological conditions could be influenced by LH and hCG.

Adrenal Cortex↗
PubMed2003

Early expression of chicken gonadotropin-releasing hormone-1 in the developing chick.

Gonadotropin-releasing hormone (GnRH), which is essential for reproductive function, is made by neurones that migrate from the nasal region into the brain during early embryonic development. This migration begins in chick when the olfactory pit is formed. This is approximately the time that GnRH neurones can be detected immunocytochemically. The present study investigated (i). how early in development the GnRH gene is expressed and (ii). the sites of its expression. Accordingly, reverse transcriptase-polymerase chain reaction (PCR) and in situ hybridization were performed on chick embryos before gastrulation up until the stage by which GnRH neurones have begun to migrate into the central nervous system. Primers were made to the 5'- and 3'-UTR region of the message for cGnRH-I, the form of the peptide that is essential for reproductive function in the chicken. PCR product was found in all stages and the sequences of products from all stages were identical. Thus, the GnRH gene is expressed continuously throughout embryonic development. In situ hybridization with a digoxygenin labelled riboprobe revealed staining along the primitive streak immediately before gastrulation. In later stages, cGnRH-I gene expression was seen in association with the anterior neural ridge. The expression was subsequently restricted to a narrow, clearly defined region, which is associated with the presumptive nasal cavity and olfactory placode. Later, GnRH neurones could be seen in their migratory routes by both in situ hybridization and immunocytochemistry. Expression of the GnRH gene has been described in preimplantation stages in mammals and there is evidence that the neuropeptide plays a role in formation and maintenance of the placenta. What role (if any) it may play in early avian development remains unknown. The demonstration of sites of GnRH expression during the early period of neurulation suggests that GnRH neurones arise before olfactory placode formation.

Animals↗
PubMed2001

A TRP homolog in Saccharomyces cerevisiae forms an intracellular Ca(2+)-permeable channel in the yeast vacuolar membrane.

The molecular identification of ion channels in internal membranes has made scant progress compared with the study of plasma membrane ion channels. We investigated a prominent voltage-dependent, cation-selective, and calcium-activated vacuolar ion conductance of 320 pS (yeast vacuolar conductance, YVC1) in Saccharomyces cerevisiae. Here we report on a gene, the deduced product of which possesses significant homology to the ion channel of the transient receptor potential (TRP) family. By using a combination of gene deletion and re-expression with direct patch clamping of the yeast vacuolar membrane, we show that this yeast TRP-like gene is necessary for the YVC1 conductance. In physiological conditions, tens of micromolar cytoplasmic Ca(2+) activates the YVC1 current carried by cations including Ca(2+) across the vacuolar membrane. Immunodetection of a tagged YVC1 gene product indicates that YVC1 is primarily localized in the vacuole and not other intracellular membranes. Thus we have identified the YVC1 vacuolar/lysosomal cation-channel gene. This report has implications for the function of TRP channels in other organisms and the possible molecular identification of vacuolar/lysosomal ion channels in other eukaryotes.

Amino Acid Sequence↗
PubMed2001

Genetic modification of hematopoietic progenitor cells for combined resistance to 4-hydroperoxycyclophosphamide, vincristine, and daunorubicin.

AIM: To investigate whether human peripheral blood hematopoietic progenitor cells (PBPC) modified with human aldehyde dehydrogenase class-3 gene (ALDH-3) and multidrug resistance gene 1 (MDR1) would increase chemotherapy resistance to 4-hydroperoxycyclophosphamide (4-HC) and -glycoprotein effluxed drugs. METHODS: A bicistronic retroviral vector G1Na-ALDH3-IRES-MDR1 cDNA was constructed and used to transfect the packaging cell lines PA317 by electroporation. CD34+ PBPC were isolated with a high-gradient magnetic cell sorting system (MACS), and then were transfected with supernatant of retrovirus containing human ALDH-3 and MDR1 cDNA. PCR, RT-PCR, Southern blot, Northern blot, FACS, and MTT assay were used to evaluate the transfection and expression of the transgene in target cells. RESULTS: The bicistronic retroviral vector construction was verified by PCR and restriction endonuclease analysis. Dual drug resistance genes were integrated into the genomic DNA of CD34+ PBPC and expressed efficiently. The efficiency of gene transfection in CD34+ PBPC was tested to be 18 % on colonies. Nested PCR and Neor rescue assay indicated that no helper virus was present in this system. Compared with the untransduced cells, transgene recipient cells conferred 4.5-fold resistance to 4-HC, 6.6-fold and 7.8-fold resistance to P-glycoprotein effluxed drug, vincristine and daunorubicin, respectively. CONCLUSION: Efficient transduction of two different types of drug resistance genes into human peripheral blood hematopoietic progenitor cells and the co-expression may decrease cumulative myelosuppression of combination chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

[Studies on anamorph of Cordyceps sinensis (Berk) from Naqu Tibet].

OBJECTIVE: To isolate and determine the strain of anamorph of Cordyceps sinensis collected from Naqu Tibet. METHOD: Isolating the strains of anamorph of Cordyceps sinensis collected from Baqing Shuoxian, Biru Counties by means of the ascope, tissue, ossified larva and body liquid. RESULT: Same strain of anamorph of Cordyceps sinensis was obtained with 4 different methods. CONCLUSION: The strain of Hirsutella sinensis is the anamorph of C. sinensis from Naqu Tibet.

Animals↗
PubMed2001

[Application of digestion pot of HP hermetic seal in sample pretreatment in spectral analysis].

Atomic absorption spectrometry is a rapid and effective method for the quantitative determination of elements, but in complete dissolution of solid sample can greatly influence the analytical accuracy. The scale sample obtained from the power plant is hardly to digestion. In this paper, a method is proposed namely digestion pot of HP hermetic seal, it can digest the scale sample, and the digestion condition is obtained. After the sample is completely digested, the conventional elements in scale sample is determined by atomic absorption spectrometry.

Copper↗
PubMed2000

A Monte Carlo dosimetry-based evaluation of the 7Li(p,n)7Be reaction near threshold for accelerator boron neutron capture therapy.

Advanced methods of boron neutron capture therapy (BNCT) use an epithermal neutron beam in conjunction with tumor-targeting boron compounds for irradiation of glioblastomas and metastatic melanomas. A common neutron-producing reaction considered for accelerator-based BNCT is 7Li(p,n)7Be, whose cross section increases very rapidly within several tens of keV of the reaction threshold at 1.88 MeV. Operation in the proton energy region near threshold will have an appreciable thick target neutron yield, but the neutrons produced will have relatively low energies that require little moderation to reach the epithermal range desirable for BNCT. Because of its relatively low projected accelerator cost and the portability of the neutron source/target assembly, BNCT based on the near-threshold technique is considered an attractive candidate for widespread hospital use. A systematic Monte Carlo N-Particle (MCNP) investigation of the dosimetric properties of near-threshold neutron beams has been performed. Results of these studies indicate that accelerator proton energies between 1.93 and 1.99 MeV, using 5 cm of H2O moderator followed by thin 6Li and Pb shields, can provide therapeutically useful beams with treatment times less than one hour and accelerator currents less than 5 mA.

Beryllium↗
PubMed2000

[Analysis of a suppressor element of mouse Nodal gene in its 5' flanking sequences].

Nodal gene is a member of the TGF-beta superfamily. It is required for the formation of the primitive streak during mouse gastrulation. Mice without Nodal gene will die due to the lack of mesoderm formation. F9 cells were transiently transfected with a series of luciferase reporter constructs containing the subcones of Nodal 5' filanking sequences and their deletions. By analyzing the luciferase activity of these constructs, a suppressor element was determined at about 1 kb up stream the transcription initiation site, around an EcoR I site. Its central part was located at about 100 bp downstream of that EcoR I site. It could almost totally, suppress the Nodal gene promoter activity, though it had no effect on SV40 promoter. It behaved differently in different cell lines. In CHO cells, it had an activation activity.

Animals↗
PubMed2000

[Analysis of an inhancer element of mouse Nodal gene in its 5' flanking sequence].

Nodal, a member of TGF-beta superfamily, plays a very important role in the mesoderm formation during mouse early development. Mice without the Nodal gene will die due to the lack of mesoderm. The flanking sequences of Nodal were dissected. By using lucifirase as reporter gene, F9 cells were transfected with a series of reporter constructs containing the subclones of the flanking sequences and their nested deletions. The effect of these subclones and deletions-2 kb up stream the Nodal gene and its cell type specificity was determined.

Animals↗
PubMed1999

Treatment of human endometrial gland epithelial cells with chorionic gonadotropin/luteinizing hormone increases the expression of the cyclooxygenase-2 gene.

Endometrial glands contain higher levels of LH/hCG receptors than other cells in the human uterus. The present study investigated their functional importance. Northern and Western blotting and covalent receptor cross-linking demonstrated that human endometrial gland epithelial cells in culture contained multiple LH/hCG receptor transcripts and an 80-kDa receptor protein that can bind [125I]hCG in a hormone-specific manner. Culturing cells with highly purified hCG resulted in a time- and dose-dependent increase in steady state levels of cyclooxygenase-2 (COX-2) messenger ribonucleic acid and protein and the secretion of PGE2. Although human LH could mimic hCG, FSH, TSH, and alpha- or beta-subunits of hCG had no effect on COX-2 protein levels. Studies on signaling revealed that treatment of cells with hCG resulted in an increase in cAMP levels and protein kinase A (PKA) activity. Inhibition of PKA activity by cotreatment with isoquinoline-sulfonamide (H-89) prevented hCG from increasing COX-2 protein levels. Treatment with 8-bromo-cAMP mimicked the effect of hCG, and cotreatment with a selective inhibitor of type I PKA, 8-chloro-cAMP, prevented 8-bromo-cAMP and hCG from increasing COX-2 protein levels. The requirement of receptors for LH/hCG action was investigated by 24-h treatment of human endometrial gland epithelial cells with 21-mer phosphorothioate oligodeoxynucleotides (ODNs) synthesized from human receptor sequence. Treatment with 2 micromol/L antisense, but not sense, ODN resulted in a dramatic reduction in LH/hCG receptor protein levels. hCG was unable to increase COX-2 protein, PGE2, and cAMP levels in an antisense, but not in sense, ODN-treated cells. In summary, we conclude that hCG and LH treatment can increase expression of the COX-2 gene in human endometrial gland epithelial cells. The effect was time and dose dependent, hormone specific, and mediated by the cAMP/type I protein kinase A signaling pathway. The hCG actions require a normal complement of its receptors in cells. These hCG and LH effects may be another action of these hormones in human endometrium that is important for implantation of the blastocyst and continuation of pregnancy.

Adult↗
PubMed1999

[A cis-regulatory enhancer element of the nodal gene is present in its first intron].

The mouse nodal gene is expressed during early embryogenesis and plays an important role during gastrulation and the determination of the left-right body symmetry/axis formation. The embryonic stem (ES) cell line 413-d 3563 contains a single copy of a retrovirus insertion in the first inton of the nodal gene. Using a quantitative RNase protection assay, the level of the nodal gene expression in this cell line was compared to that of the parental CCE cell line. A 2.3 fold down regulation of the nodal transcript in the 3563 ES cell line suggested that the proviral insertion might decrease the nodal mRNA expression by disrupting the potential cis regulatory elements present at the insertion site in the first intron of the nodal gene. Luciferase reporter constructs containing the entire first intron fragment or part of it were tested by a transient transfection assay for their potential transcriptional regulatory activity. A 2.4 kb DNA fragment from the 5' end of the intron was sufficient to increase the expression level of the reporter gene 8 fold, suggesting that an important cis acting enhancer element for the nodal gene expression is localized within the first intron.

Animals↗
PubMed1999

[Delineation of the cis-regulatory sequences of the nodal gene].

In mouse embryo development, nodal is expressed in the node during the gastrulation. It is involved in mesoderm formation and left-right axis determination. The expression of the nodal gene has a restricted spatial and temporal specificity. Studies on the function of the nodal first intron in the gene expression regulation have shown that a 220 bp fragment at the 5' end of the first intron has an enhancer activity. Rather unexpectedly, the transient transfection assays in F9 cells indicate that this fragment also displayed a promoter activity when it is cloned upstream of basic luciferase reporter gene only in sense orientation. We present here the nucleotide sequence of this 220 bp fragment, and discuss its possible role in the nodal gene regulation.

Animals↗
PubMed1998

Cafeteria diet-induced obesity is associated with a low spontaneous growth hormone secretion and normal plasma insulin-like growth factor-I concentrations.

Pituitary growth hormone (GH) secretion has been shown to be blunted in human and animal obesity. With respect to human obesity, cafeteria diet-induced obesity might be an appropriate model to study spontaneous GH secretion. In 6 cafeteria diet-overfed obese male Wistar rats and 6 control rats with chronically implanted catheters, GH levels were measured every 15 min over 6 h by standard RIA. A significantly lower GH secretion, reflected by the integrated GH concentration, was found in the obese rats (median 16.46, [range 10.55-19.13] ng/ml x 6 h vs 35.63 [range 21.90-41.50] ng/ml x 6 h, P < 0.05). The GH secretion in the obese rats was significantly negatively correlated with the body fat percentage, assessed by dual X-ray absorptiometry (Rho = -0.95, P < 0.05). Median plasma insulin-like growth factor-I (IGF-I) concentration was comparable between the two groups, while the median insulin concentration was significantly higher in the obese group (1.95 [range 1.76-3.55] ng/ml vs 1.21 [range 0.86-2.13] ng/ml, P < 0.05). No significant correlation existed between GH secretion and the plasma insulin concentration. In conclusion, cafeteria diet-induced obesity is associated with a low spontaneous GH secretion and normal plasma IGF-I concentration. The hyperinsulinemia present in this model probably explains the normal IGF-I concentrations, but not the GH hyposecretion.

Animals↗
PubMed1997

Random mutagenesis reveals a region important for gating of the yeast K+ channel Ykc1.

YKC1 (TOK1, DUK1, YORK) encodes the outwardly rectifying K+ channel of the yeast plasma membrane. Non-targeted mutations of YKC1 were isolated by their ability to completely block proliferation when expressed in yeast. All such mutations examined occurred near the cytoplasmic ends of the transmembrane segments following either of the duplicated P loops, which we termed the 'post-P loop' (PP) regions. These PP mutations specifically caused marked defects in the 'C1' states, a set of interrelated closed states that Ykc1 enters and exits at rates of tens to hundreds of milliseconds. These results indicate that the Ykc1 PP region plays a role in determining closed state conformations and that non-targeted mutagenesis and microbial selection can be a valuable tool for probing structure-function relationships of ion channels.

Amino Acid Sequence↗
PubMed1996

[The influence of masking agent on adhesion of composite resin]

In this study we used light cured resin,opaque resin and composite resin/masking agent to bond 24 teeth in vitro and then we tested their bonding stress.We also used these three materials to treat 240 tetracycline stained teeth in clinic.After half a year,one year,two years follow-up we found:in vitro study,the highest stress of composite resin is 144.3kG/cm(2).There is no significant difference in statistics among these three materials if we used the masking agent or opaque resin or not.In clinical follow-up,there is no significant difference in shed,partial shed,margin stain,gingival inflammation,and unsatisfied rate in three groups.The author believed the masking agent or opaque resin has no influence on the stress of resin restoration.So when we treated tetracycline stained teeth,we could choose it to increase aesthetic feeling.

Journal Article↗
PubMed1995

YKC1 encodes the depolarization-activated K+ channel in the plasma membrane of yeast.

Our previous patch-clamp studies showed that depolarization activates a K(+)-specific current in the plasma membrane of the budding yeast, Saccharomyces cerevisiae [Gustin et al. (1986) Science 233, 1195-1197]. The Yeast Genome Sequencing Project has now uncovered on the left arm of chromosome X an open reading frame (ORF) that predicts a 77-kDa protein reminiscent of a shaker-like alpha subunit with 6 membrane spans followed by a subunit with 2 spans. We found that deleting this ORF removes the yeast K+ current. Furnishing the ORF from plasmids restores or even greatly amplifies this current. These manipulations have no effects on the 40-pS mechanosensitive conductance also native to this membrane. Thus, this ORF, named YKC1 here, likely encodes a structure for the K(+)-specific channel of the yeast plasma membrane. This and other K+ channel subunits are compared and the possible uses of this gene in research are discussed. YKC1 has recently been shown by others to induce in frog oocytes a K+ current. Its activation is coupled to EK+ and its outward rectification depends on external divalent cations. We found the YKC1 channel in its native membrane activates at low voltages largely independent of EK+ and it remains so despite removal of divalents by chelation.

Amino Acid Sequence↗
PubMed1995

Functional reconstitution of ion channels from Paramecium cortex into artificial liposomes.

Toward isolating channel proteins from Paramecium, we have explored the possibility of functionally reconstituting ion channels in an artificial system. Proteins from Paramecium cortex reconstituted with soybean azolectin retained several channels whose activities were readily registered under patch clamp. The most commonly encountered activities were three: (i) a 71-pS cation channel that opens at all voltages unless di- or trivalent cations were added to close them, (ii) a 40 pS monovalent cation channel, and (iii) a large-conductance channel that prefers anions and exhibits many subconductance states. These channels survived mild detergent treatments without observable functional alterations. The possible origin of these channels from internal membranes, the possible role of 71-pS channel in internal Ca2+ release, and the prospects of their purification are discussed.

Animals↗