PubMed Health⌕ Search

Biomedical subjects

H Zhou

Publications and source records attributed to H Zhou.

At least 613 records · Page 34Linked to original sources
PubMed1994

Elderly women in northern New England exhibit seasonal changes in bone mineral density and calciotropic hormones.

A seasonal component to bone loss has been reported in some postmenopausal women. We hypothesized that elderly women in northern New England would be at high risk for bone loss during winter because of their age, diet and lack of sunlight. Eighteen elderly but healthy women (mean age 77 years) started a 2-year observational study in a remote area of northwestern Maine (Greenville: 45.5 degrees N latitude). Fifteen women completed the study. Bone mineral density of the spine (L-BMD) and hip (F-BMD) and biochemical markers of bone turnover were measured biannually. In vitro photo-conversion of provitamin D3 to previtamin D3 was determined in the winter and spring. Initial calcium and vitamin D intake averaged 700 +/- 72 mg/day and 6.2 +/- 1.2 micrograms/day, respectively. During the first year L-BMD dropped 4.2% (P = 0.002) while F-BMD dropped 2.4% (P = 0.09), primarily because of steep declines during the fall and winter (August to February: L-BMD: 3.6%, P = 0.001; F-BMD: 3.0%, P = 0.04). In that 6-month period, serum 25 hydroxyvitamin D (25(OH)D) fell 13 +/- 6% (P = 0.06) and PTH rose 27 +/- 11% (P = 0.01). Additionally, there was no detectable in vitro conversion of provitamin D to previtamin D over 8 h of one sunny winter day. In the summer, PTH and 25(OH)D reverted to basal levels and significant in vitro photoconversion of provitamin D to previtamin D was detected. In the 2nd year of the study, vitamin D consumption increased (+2.0 +/- 1.2 micrograms/day, P = 0.03 vs. baseline), L-BMD increased slightly (+1.8%, P = 0.05) and F-BMD did not change (+0.5%, P = NS). Again, changes in BMD and vitamin D were seasonal: L-BMD and F-BMD were constant during fall and winter but both sites showed increases during summer (L-BMD: +1.7%, P = 0.04, F-BMD: +1.6%, P = 0.25). In the second winter, serum 25(OH)D fell nearly 20% and PTH rose 17%. Increased dietary consumption of vitamin D was positively correlated with changes in F-BMD at 18 months (r = 0.61, P = 0.02) and resulted in slightly greater serum 25(OH)D concentrations during the second winter than the first. The difference in serum 25(OH)D between the first and second winter was the strongest predictor of lumbar bone accretion during the second year of the study (r = 0.59, P = 0.04). In this 24-month observational study, significant seasonal changes in BMD, 25(OH)D and PTH were reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Primary structure and functional properties of an epithelial K channel.

Expression cloning in Xenopus oocytes was used to identify a clone for a renal K channel. The clone, named ROMK2, was obtained from a cDNA library constructed in the plasmid vector pSPORT using size-selected poly(A)+ RNA from whole rat kidney. ROMK2 consists of 1,837 nucleotides, with an open reading frame of 1,116 bases predicted to code for a 372-amino acid peptide. The clone appears to be a splice variant of a recently reported K channel (ROMK1) from rat renal outer medulla (Ho, K.H., C.G. Nichols, W.J. Lederer, J. Lytton, P.M. Vassilev, M.V. Kanazirska, and S.C. Hebert. Nature Lond. 362: 31-37, 1993). Northern blot analysis indicates that ROMK2 is expressed in renal cortex, medulla, and papilla. Expression in other tissues appears to be much lower. The functional properties of the channel as measured in Xenopus oocytes indicate its close relationship to ROMK1 and more distant relationship to the inward rectifier K channel (IRK1) (Kubo, Y, T.J. Baldwin, Y. N. Jan, and L. Y. Jan. Nature Lond. 362: 127-133, 1993). The inward conductance of the channel is a saturable function of external K, with a half-maximal conductance at <5 mM. The selectivity sequence for ion permeability based on reversal potential measurements was K > Rb > NH4 > Na, Li. The conductance to Rb was only one-half that to K. Extracellular Ba2+ and Cs+ blocked the channel in a voltage-dependent manner. The high sensitivity of Cs+ block to voltage is consistent with the channel's operating as a multi-ion pore. The channel was blocked by high concentrations (100 microM) of glibenclamide. It did not appear to be blocked by extracellular Na+ or tetraethyl-ammonium ion. Patch-clamp measurements indicated a single-channel conductance of 30 pS in the presence of 110 mM K and high open probability that was weakly dependent on voltage. This channel may be involved in maintaining the membrane potential of renal cells and/or mediating renal K secretion.

Amino Acid Sequence↗
PubMed1994

In vitro and in vivo association of dentin phosphophoryn with alpha1CB6 peptide of type I collagen.

A small number of molecules of phosphophoryns, dentin phosphoproteins, are associated to collagen tightly with the maturation of dentin. As an in vitro model of the process, we examined non-covalent association of phosphophoryns and collagen CNBr peptides. Cyanogen bromide peptides of type I collagen were separated with electrophoresis and transferred to a membrane, which was probed with labeled phosphophoryns. Phosphophoryns were bound preferentially to alpha1CB6 peptide. Another experiment using a cleavable crosslinking agent also demonstrated the affinity between phosphophoryns and the alpha1CB6 region of collagen. The matrix-bound fraction of phosphophoryns was solubilized by CNBr digestion of bovine dentin, and was partially purified. Compositional analysis revealed that the fraction was composed of association products of phosphophoryns and collagen at the ratio of 2:3. Considering the high molecular weight of the fraction, one phosphophoryn molecule should be associated with several collagen peptides. The fraction reacted with the antibody against alphalCB6 peptide. When the fraction was digested with lysyl endopeptidase, several peptides that coincided with peptides from alpha1CB6 were released. One of the peptides was sequenced and identified to be a peptide with Asp 975 of the alpha1(I) chain as an amino terminal residue. The alpha1CB6 peptide may be involved in the matrix-bound fraction, although involvement of other collagen peptides cannot be ruled out. Phosphophoryns may associate with collagen at the alpha1CB6 region at first, and then be immobilized on it, possibly by covalent crosslinking, with maturation of dentin. Binding of several alpha1CB6 peptides to a single phosphophoryn molecule is possible in current 3-dimensional models of collagen packing in mineralized tissue, which allows alignment of several hole zones in register.

Amino Acid Sequence↗
PubMed1994

[Semiquantitative detection and application about the expression of nitric oxide synthase gene].

Using the Reverse Transcription (RT)-Polymerase Chain Reaction (PCR) method of Martin (1993) for semiquantitation determinating of NOS gene, it was found that NOS mRNA is not only existed in brain, but also distributed extensively in heart, kidney, lung and liver. Among of them, NOS mRNA levels were highest in the brain, followed in descending order by kidney, heart. In addition to endothelial cell, NOS gene was also highly expressed in smooth muscle cells, suggesting that they may be an important site of NOS in organism. Furthermore, NOS mRNA levels were found to decrease significantly in brain, kidney, liver and smooth muscle cell in spontaneous hypertensive rat. These data suggest that pathogeny of hypertension may be related to low expression of NOS gene in these tissues.

Amino Acid Oxidoreductases↗
PubMed1994

High density cultivation of a recombinant CD-1 cell line producing prourokinase using a Biosilon microcarrier culture system.

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.

Animals↗
PubMed1994

Electro-oculogram of retinal vein occlusion.

Twenty five cases, including 26 eyes with retinal vein occlusion (RVO) were examined by means of the electro-oculogram. The results showed that 23 of the 26 eyes suffering from RVO exhibited abnormalities of the electro-oculogram (EOG). The potential difference and Arden ratio in the RVO eyes were lower than those in the normal eyes (P < 0.01). The more the visual acuity of ill eyes was decreased, the higher the abnormal rate of EOG in ill eyes was. 14 eyes had the visual acuity less than 0.1, whose EOGs were abnormal. Six eyes had the visual acuity from 0.2 to 0.4, in which the EOGs of 5 eyes were abnormal. Six eyes had the visual acuity more than 0.5, among which the EOGs of 4 eyes were abnormal. Based on the above observations, it may be considered that the circulatory disturbance resulting from RVO damages not only the internal layer but also the external layer of the retina. We suggest that EOG is a useful method for distinguishing lesions caused by RVO and may reflect the functional condition of the outer layer of the retina.

Adult↗
PubMed1994

The effect of two topoisomerase inhibitors on low-dose hypersensitivity and increased radioresistance in Chinese hamster V79 cells.

A preliminary investigation of the effect of topoisomerase inhibitors on the structure of the survival curve at low doses has been carried out in Chinese hamster V79 cells, where there is a deviation from the predicted response to radiation (Marples and Joiner, Radiat. Res. 113, 41-51, 1993). Cells were treated with one representative drug for each enzyme (topoisomerase I or II) prior to X irradiation in air and assessed for cell survival using automated microscopic location of cells. VP-16 causes little or no effect, while camptothecin has a measurable effect up to 2 Gy. The results are discussed in terms of the role of DNA damage and cell cycle in increased radioresistance, which encourage further investigation of the effects of this class of drugs at low doses.

Animals↗
PubMed1994

A preliminary investigation into the extent of increased radioresistance or hyper-radiosensitivity in cells of hamster cell lines known to be deficient in DNA repair.

The response to low doses of X rays was assessed in cells of three hamster cell lines which are defective in DNA repair and was compared with their parental lines. Cells of the V79-derived double-strand break repair-deficient line XR-V15B showed no radioresistance in the 0.5-Gy range compared with the V79B wild type, but instead showed an exponential response. Cells of the single-strand break repair-deficient line EM9 showed hyper-radiosensitivity and exhibited increased radioresistance. Most interestingly, cells of the UV-20 cell line appeared to respond exponentially, as a continuation of the hyper-radiosensitive portion of the curve, with no evidence of increased radioresistance. This line is defective in an incision step of excision repair and is sensitive to crosslinking agents. Further studies are warranted to address the possible role of single- and double-strand break repair and excision repair in hyper-radiosensitivity and increased radioresistance.

Animals↗
PubMed1994

The response of Chinese hamster V79-379A cells exposed to negative pi-mesons: evidence that increased radioresistance is dependent on linear energy transfer.

Chinese hamster V79-379A cells exhibit low-dose hypersensitivity to 250 kVp X rays followed by an increased radioresistant response over the dose range 0.5-1 Gy. This phenomenon is not seen with neutrons (Marples and Joiner, Radiat. Res. 133, 41-51, 1993). It was therefore postulated the induction of radioresistance might develop as a response to a cellular event(s) which predominates after low- and not high-LET radiation. To test this hypothesis, we measured the survival response of V79-379A cells exposed to pions. Clonogenic survival was assessed for cells irradiated in the Bragg peak (35 keV/microns) and plateau region (10-20 keV/microns) of the beam, using an automated microscope (DMIPS cell analyzer). As expected, peak pions were found to be more effective per unit of dose at killing cells than plateau pions. The survival curve for cells irradiated in the plateau of the pion beam was found to incorporate a region of low-dose hypersensitivity and increased radioresistance, the effective D0 was dose-dependent, ranging from 3.5-5. This was not seen with peak pions, where the effective D0 was, on average, constant reflecting a single-exponential survival curve. Fitting the data with an induced repair model indicates that the phenomenon of increased radioresistance is almost certainly dependent on LET.

Animals↗
PubMed1993

Adhesion to carcinoembryonic antigen by human colorectal carcinoma cells involves at least two epitopes.

Carcinoembryonic antigen (CEA) may be involved in both cell-cell and cell-substrate adhesion. Our purpose was to determine whether epitopes involved in the homophilic binding of human colorectal carcinoma cells to CEA participated in adhesion to basement membrane proteins. Three human colorectal adenocarcinoma cell lines and one CHO cell line transfected with CEA cDNA were tested in a solid-phase adhesion assay. The 2 CEA-expressing carcinoma cell lines (KM-12c and CCL 188) and the transfectant, but not the parental CHO line, bound to CEA. The CEA-non-producing carcinoma line (Clone A) did not bind to CEA. All colorectal carcinoma cell lines, the transfectant and the parental CHO line bound to laminin, while the colorectal carcinoma lines bound to type-IV collagen. MAbs to epitopes on CEA that cross-react with non-specific cross-reacting antigen (NCA) inhibited adhesion of CEA-expressing cells to CEA. MAbs to non-cross-reactive epitopes of CEA did not block adhesion to CEA. When the inhibitory anti-CEA antibodies were compared in a competitive radioimmunoassay, 2 distinct epitopes were identified. Epitope I is in the N-terminal domain and defined by MAbs MN3, T84.1 and C110, whereas epitope II is located in the repeating loop domains and is recognized by antibodies MN15, PR3B10 and NP1. None of the antibodies to epitope I or II blocked adhesion by KM-12c or CCL 188 cells to laminin or type-IV collagen. Thus, at least 2 different regions on CEA participate in adhesion to CEA but not to collagen or laminin by CEA-expressing human colorectal carcinoma cells.

Adenocarcinoma↗
PubMed1993

Specificity of anti-carcinoembryonic antigen monoclonal antibodies and their effects on CEA-mediated adhesion.

The carcinoembryonic antigen (CEA) domain specificities of a library of monoclonal anti-CEA antibodies were determined to investigate the mechanisms of homophilic binding involved in CEA-mediated intercellular adhesion. Using an indirect immunofluorescence cell surface staining technique, the reactivities of these antibodies were tested systematically on Chinese hamster ovary cells stably transfected with constructs of CEA gene family members CEA, nonspecific cross-reacting antigen, CGM6, and biliary glycoprotein, as well as on stable Chinese hamster ovary transfectants expressing truncated CEA and CEA/nerve cell adhesion molecule chimeric proteins. Epitopes for these antibodies were thus localized on the CEA molecule as follows: monoclonal antibody groups 1, 2, and 6 react with epitopes in the N-terminal domain of CEA, whereas groups 3, 5a, 5b, and 9 react with determinants found in the internal repeating domains located in the C-terminal part of the CEA molecule. Groups 4 and 8 appear to react with a repeating epitope in the internal domains of CEA and in all CEA subfamily members. Fab fragments of monoclonal antibody group 1 block aggregation of CEA transfectant cells, indicating that a region in the N domain is involved in CEA homophilic interaction. Fab fragments of monoclonal antibody group 9 recognize an epitope dependent on the B2 and A3 domains and stimulate aggregation. These results support the recently reported CEA-CEA homophilic reciprocal binding model in which anti-parallel molecules are bound by 2 bonds between the N domain of one molecule and the A3B3 domain of the interacting partner.

Animals↗
PubMed1993

[Primary hyperreninemia. An unusual cause of secondary arterial hypertension].

In 1975, scintigraphy revealed a 6.5 x 5 cm tumour in the region of the left adrenal in a 36-year-old man with known hypertension for 5 years (systolic pressure up to 250 mm Hg, diastolic up to 130 mm Hg). A laparotomy was performed for a suspected phaeochromocytoma. A tumour was located in the upper pole of the kidney and removed together with the kidney. The blood pressure quickly returned to normal after the operation: it remained stable for the following 17 years (between 130/80 to 150/90 mm Hg). Originally the tumour could not be clearly classified either clinically or histologically. But recently the paraffin-imbedded tumour specimen was re-examined by immunohistochemistry and in-situ hybridization. This identified a renin-producing tumour so that primary reninism was the cause of the arterial hypertension.

Adult↗
PubMed1993

Functional domains of transcription factor TFIIB.

Transcription factor TFIIB is an essential component of the RNA polymerase II initiation complex. TFIIB carries out at least two functions: it interacts directly with the TATA-binding protein (TBP) and helps to recruit RNA polymerase II into the initiation complex. The sequence of TFIIB reveals a potential zinc-binding domain and an imperfect duplication of approximately 70 amino acids. Mutagenesis of cysteine codons within the putative zinc finger results in mutant proteins that bind normally to TBP but are unable to recruit RNA polymerase II-TFIIF into the initiation complex. Changing the two most highly conserved amino acids in the TFIIB repeats reduces the ability of TFIIB to interact with TBP. Therefore, the two functions of TFIIB can be assigned to two separable functional domains of the protein.

Amino Acid Sequence↗
PubMed1993

Induction of metalloproteinase activity in human T-lymphocytes.

Matrix metalloproteinases are thought to play major roles in a wide array of normal and pathological processes. These proteinases are involved in the degradation of the extracellular matrix and are believed to facilitate the movement of cells from one site to another. In the current study, we examined the expression of the 92 kDa gelatinase activity (MMP-9) by the human T-lymphoma cell line, HSB. Proteinase activity was greatly elevated when cells were treated with TPA. This induction was initially observed at 6 h post-TPA treatment and continued to increase up to 48 h. Proteinase induction was inhibited by actinomycin D and cycloheximide, indicating that nascent RNA and protein synthesis were required. Staurosporine, an inhibitor of protein kinase C activity, suppressed the TPA-induction of gelatinase activity. Our results suggest that TPA induces the 92 kDa gelatinase activity by activating protein kinase C. TGF-beta also induced proteinase activity, although to a lesser extent than TPA. Several criteria indicate that this enzyme is a member of the family of matrix metalloproteinases: (1) this activity was inhibited by EDTA, 1,10-phenanthroline and TIMP; (2) this activity bound to a gelatin-agarose affinity resin; (3) it has a mass of approx. 92 kDa on SDS-polyacrylamide gels; (4) it cleaves gelatin and (5) the inducible proteinase cross reacts with antiserum to MMP-9.

Collagenases↗
PubMed1993

Differential effects of transforming growth factor-beta 1 and bone morphogenetic protein 4 on gene expression and differentiated function of preosteoblasts.

Transforming growth factor-beta (TGF-beta) and bone morphogenetic protein 4 (BMP 4) are both able, under certain circumstances, to induce endochondral bone formation in vivo. This study compared the effects of TGF-beta 1 and BMP 4 on the gene expression of a retinoic acid (RA) responsive rat clonal preosteoblast cell line, UMR 201, as well as the way in which these proteins interact with RA in these cells. Both similarities as well as differences between the effects and mechanism of action of TGF-beta 1 and BMP 4 were demonstrated. TGF-beta 1 (0.1 ng/ml) strongly induced matrix gla protein (MGP) mRNA and increased the steady state osteonectin (ON) mRNA level. Cotreatment with TGF-beta 1 and RA did not result in a further increase in MGP mRNA expression. In contrast, BMP 4 alone had no influence on MGP or ON mRNA expression but it significantly enhanced the RA induction of MGP mRNA. Pro-alpha 1(l) collagen mRNA was increased by TGF-beta 1 (1 ng/ml) and BMP 4 (50 ng/ml). The addition of either TGF-beta 1 or BMP 4 together with RA resulted in a further increase in pro-alpha 1 (l) collagen mRNA levels. Both RA and TGF-beta 1, but not BMP 4, increased the transcriptional rate of the pro-alpha 1 (l) collagen gene. TGF-beta 1 reduced the constitutive as well as RA-induced expression of osteopontin (OP) mRNA while BMP 4 reduced only the constitutive expression of OP mRNA. RA increased the transcriptional rate of the OP gene. Since the responses of UMR 201 cells to these structurally related factors were not identical, the results lend support to the concept that the coordinated expression of members of the TGF-beta 1 superfamily may be necessary to control the progression of specific cell types through their differentiation pathways.

Animals↗
PubMed1993

Protease activity and autodigestion (autolysis) assays using Coomassie blue dye binding.

A new proteolytic assay is described involving Coomassie blue. Under specified conditions, the amount of Coomassie-stained casein protein hydrolyzed by several proteases was proportional to the amount of protease. Coomassie dye reaction was used directly to determine the change in protein concentration of the substrate casein during proteolysis by three proteases: stem bromelain, papain, and trypsin. This method can be used with 0.1- to 0.5-micrograms quantities of protease. The dye reagent was used directly on the protease protein in order to obtain an assay of autodigestion. Autodigestion of bromelain at 50 and 25 degrees C was followed by measuring the amount of residual protease protein with time.

Autolysis↗