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Biomedical subjects

Y H Gao

Publications and source records attributed to Y H Gao.

At least 19 recordsLinked to original sources
PubMed2002

Synthesis and microstructural analysis of Si3N4 nanorods.

Alpha-Si3N4 nanorods with 20-80 nm width were synthesized by carbothermal reduction of SiO with amorphous activated carbon (AAC) as a reductant. Microstructural characterization of the synthesized nanorods was carried out by high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis. Many Si3N4 nanorods were found to be twisted. Each twisted nanorod contained several straight Si3N4 parts. The straight parts had the rod axes orientated along the (1010) direction, which is the closest packing direction of alpha-Si3N4. There were two kinds of joints between the two adjacent straight Si3N4 parts. Formation mechanism of the Si3N4 nanorods is discussed.

Charcoal↗
PubMed2001

Upper limb salvage with microvascular bone transfer for major long-bone segmental tumor resections.

A series of 14 young, active patients who underwent vascularized bone graft reconstructions of large (9-15 cm) segmental skeletal defects of the upper extremity resulting from resection of a variety of bony tumors is presented. Eight defects involved the proximal humerus and required shoulder joint reconstruction, two were mid humeral and four involved the distal radius. Surgical techniques for both distal radius reconstruction with vascularized iliac crest and vascularized fibular head and glenohumeral reconstruction using the vascularized fibula are described. Several cases are discussed in detail, including achievement of bony union, postoperative range of motion and pain, and each patient's ability to resume activities. The literature is reviewed, and other reconstructive options for large bony defects of the upper extremity after tumor resection are discussed: nonvascularized bone grafts, allograft transfer, and custom prosthetic devices. The authors think that vascularized bone grafting offers the most favorable method of upper extremity salvage with preservation of joint function, especially at the shoulder.

Adolescent↗
PubMed2000

Prolonged intake of fermented soybean (natto) diets containing vitamin K2 (menaquinone-7) prevents bone loss in ovariectomized rats.

The effect of the prolonged intake of dietary vitamin K2 (menaquinone-7, MK-7) on bone loss in ovariectomized (OVX) rats was investigated. OVX rats were freely given experimental diets containing the fermented soybean (natto; including 9.4 micrograms MK-7/100 g diet) without or with supplemental MK-7 (containing 14.1 or 18.8 micrograms of MK-7 as total per 100 g diet) for 150 days. Feeding produced a significant elevation of MK-7 concentration in the serum of OVX rats. In this case, the femoral MK-4 content was significantly increased, but MK-7 was not detected in the femoral tissues, indicating degradation of MK-7. Serum gamma-carboxylated osteocalcin concentration was significantly decreased by OVX. This decrease was significantly prevented by the feeding of the natto diets with supplemental MK-7 (18.8 micrograms/100 g diets). OVX caused a significant decrease in femoral dry weight, femoral calcium content, and mineral density. These decreases were significantly prevented by feeding with diets containing natto with MK-7 (total, 18.8 micrograms/100 g diets). This study demonstrates that the prolonged intake of natto dietary including MK-7 has a preventive effect on bone loss induced by OVX. Dietary MK-7 may be useful in the prevention of osteoporosis.

Animal Feed↗
PubMed2000

Synergistic effect of genistein and zinc on bone components in the femoral-metaphyseal tissues of female rats.

The effect of genistein and zinc on bone components in rats was investigated. Femoral-metaphyseal tissues obtained from female rats (4 weeks old) were cultured for 24 h in a medium containing either vehicle or genistein (10(-7)-10(-5) M) in the absence or presence of zinc sulfate (10(-6)-10(-4) M) in vitro. The presence of genistein (10(-6) and 10(-5) M) or zinc (10(-6) and 10(-5) M) caused a significant increase in alkaline phosphatase activity, deoxyribonucleic acid (DNA), and calcium content in the metaphyseal tissues. These increases were significantly enhanced by the combination of each compound. The synergistic effect on bone components was seen in the combination with genistein (10(-6) and 10(-5) M) plus zinc (10(-5) M). Such an effect was completely blocked by the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis. Moreover, the oral administration of genistein (100 and 300 micrograms/kg body weight) or zinc sulfate (1 and 5 mg Zn/kg) to rats for 3 days caused a significant elevation of alkaline phosphatase activity, DNA, and calcium content in the femoral-metaphyseal tissues. These increases were significantly enhanced by the combination of each compound. The synergistic effect was seen in the case of genistein (100 and 300 micrograms/kg) plus zinc (5 mg/kg). These results demonstrate that the anabolic effect of genistein on bone components is synergistically enhanced by zinc in vitro and in vivo. This study further supports the view that the combination of nutritional factors has a potent anabolic effect on bone metabolism.

Alkaline Phosphatase↗
PubMed2000

Radiation retards muscle differentiation but does not affect osteoblastic differentiation induced by bone morphogenetic protein-2 in C2C12 myoblasts.

PURPOSE: Effects of radiation on the differentiation of C2C12 myoblasts were studied using cell cultures in which the cells differentiated into either muscle cells or osteoblasts. MATERIALS AND METHODS: A mouse skeletal myoblast cell line, C2C12, was cultured and irradiated at confluence. Muscle differentiation was estimated by counting the number of myosin heavy chain (MHC)-positive multinucleated myotubes. Osteoblast differentiation was analysed by measuring alkaline phosphatase (ALP) activity and osteocalcin production in C2C12 cells treated with recombinant human bone morphogenetic protein-2 (rhBMP-2). RESULTS: Myotube formation in C2C12 cells was inhibited by 2 and 4 Gy irradiation, but recovered to non-irradiated control levels following further culture. In irradiated cultures, the number of MHC-positive mononucleated cells increased significantly. Irradiation did not, however, alter the induction of osteoblastic phenotypes induced by rhBMP-2 in C2C12. Irradiation also did not affect the expression of MyoD mRNA and myogenin mRNA in myogenic differentiation and induction of osteocalcin mRNA in osteoblastic differentiation. CONCLUSIONS: During differentiation of C2C12 cells, myotube formation was delayed after irradiation, while induction of osteoblasts with BMP-2 was unaffected.

Alkaline Phosphatase↗
PubMed2000

The microstructural analysis of SiC nanorods by high-resolution electron microscopy.

Beta-SiC nanorods have been synthesized by the reaction of SiO and carbon nano-capsules. For the synthesis of SiC nanorods, it was examined that the reaction temperature and the ratio of SiO to carbon nanocapsules are important and the most appropriate temperature and ratio are around 1380 degreesC and 5:2, respectively. The synthesized SiC nanorods were characterized by high-resolution electron microscopy. Most of the SiC nanorods are straight and have the diameter of 30-150 nm while the SiC tips of the SiC nanorods have the size 100-400 nm. The SiC nanorods have many stacking faults normal to the [111] direction. Each SiC nanorod has one kind of preferential axis direction, which is either parallel or normal to the [111] direction. Based on the microstructural analysis of the SiC nanorods, a possible growth mechanism of the SiC nanorods is proposed.

Journal Article↗
PubMed2000

Suppressive effect of genistein on rat bone osteoclasts: involvement of protein kinase inhibition and protein tyrosine phosphatase activation.

The suppressive effect of genistein on osteoclast-like multinucleated cells from rat femoral tissues was investigated. The bone cells isolated from rat femoral tissues were cultured for 48 h in an alpha-minimal essential medium (5% fetal bovine serum) containing either vehicle or genistein (10(-7)-10(-5) M). Osteoclasts were estimated by staining for tartrate-resistant acid phosphatase, a marker enzyme of osteoclasts. The presence of genistein caused a significant decrease in the number of osteoclasts. Such a decrease was also seen in the presence of calcium choride (10(-5) M). Magnesium chloride (10(-5)-10(-3) M), a blocker of Ca2+ channels, had no effect on the number of osteoclasts. The effect of genistein (10(-5) M) or calcium (10(-3) M) in decreasing osteoclasts was significantly prevented by the presence of magnesium (10-3 M). Vanadate (10(-6)-10(-4) M), an inhibitor of protein tyrosine phosphatase activity, did not have an effect on the number of osteoclasts. The genistein's effect was not altered by vanadate. When isolated osteoclasts were cultured for 24 h in the presence of genistein (10(-7)-10(-5) M), protein kinase activity in the 5500 g supernatant of homogenate of the cells was significantly decreased, while protein tyrosine phosphatase activity was significantly elevated. Such an effect was also seen by the addition of genistein (10(-7)-10(-5) in the enzyme reaction mixture in vitro. The present study suggests that the suppressive effect of genistein on rat bone osteoclasts is partly involved in the inhibition of protein kinase and the activation of protein tyrosine phosphatase in osteoclasts.

Animals↗
PubMed2000

Hydroxyurea induces a senescence-like change of K562 human erythroleukemia cell.

Hydroxyurea, a differentiation-inducing agent of human erythroleukemia K562 cells, is commonly used to treat some types of leukemia. However, the mechanism for its therapeutic effect is not clearly understood yet. In this study, we have observed an interesting effect of hydroxyurea on tumor cells: an induction of senescence-like changes. Human erythroleukemia K562 cells, when treated with hydroxyurea for 7 days or more, underwent a change into phenotypically senescent cells together with a reduction of hemoglobin generation, a differentiation marker. The hydroxyurea-treated cells showed positive senescence associated-beta-galactosidase staining, a senescence index, and the accumulation of cdk (cyclin dependent kinase) inhibitors, such as p16INK4a, p21Waf1, and p27Kip1, implicated in cellular senescence. Nonetheless, these changes were not accompanied by DNA fragmentation. Taken together, we summarize that the long-term treatment of cancer cells with hydroxyurea can induce cellular senescence different from differentiation or programmed cell death.

Antineoplastic Agents↗
PubMed1999

Combining serial analysis of gene expression and array technologies to identify genes differentially expressed in breast cancer.

Several methods have been used recently to determine gene expression profiles of cell populations. Here we demonstrate the strength of combining two approaches, serial analysis of gene expression (SAGE) and DNA arrays, to help elucidate pathways in breast cancer progression by finding genes consistently expressed at different levels in primary breast cancers, metastatic breast cancers, and normal mammary epithelial cells. SAGE profiles of 21PT and 21MT, two well-characterized breast tumor cell lines, were compared with SAGE profiles of normal breast epithelial cells to identify differentially expressed genes. A subset of these candidates was then placed on an array and screened with clinical breast tumor samples to find genes and expressed sequence tags that are consistently expressed at different levels in diseased and normal tissues. In addition to finding the predicted overexpression of known breast cancer markers HER-2/neu and MUC-1, the powerful coupling of SAGE and DNA arrays resulted in the identification of genes and potential pathways not implicated previously in breast cancer. Moreover, these techniques also generated information about the differences and similarities of expression profiles in primary and metastatic breast tumors. Thus, combining SAGE and custom array technology allowed for the rapid identification and validation of the clinical relevance of many genes potentially involved in breast cancer progression. These differentially expressed genes may be useful as tumor markers and prognostic indicators and may be suitable targets for various forms of therapeutic intervention.

Biomarkers, Tumor↗
PubMed1999

Inhibitory effect of genistein on osteoclast-like cell formation in mouse marrow cultures.

The effect of genistein on osteoclast-like cell formation in mouse marrow culture in vitro was investigated. The bone marrow cells were cultured for 7 days in alpha-minimal essential medium containing a well-known bone resorbing agent [parathyroid hormone (1-34) (PTH), prostaglandin E2 (PGE2), 1,25 dihydroxyvitamin D3 (VD3), or lipopolysaccharide (LPS)] with an effective concentration. Osteoclast-like cell formation was estimated by staining for tartrate-resistant acid phosphatase (TRACP), a marker enzyme of osteoclasts. The presence of PTH (10(-8) M), PGE2 (10(-6) M), VD3 (10(-8) M), or LPS (1 microg/mL) induced a remarkable increase in osteoclast-like multinucleated cells. These increases were inhibited significantly in the presence of genistein (10(-7) to 10(-5) M). The inhibitory effect of genistein (10(-5) M) was equal to that of 17 beta-estradiol (10(-8) M), calcitonin (10(-9) M), or zinc sulfate (10(-5) M). Genistein (10(-5) M) significantly inhibited dibutyryl cyclic adenosine monophosphate (10(-5) M)-induced osteoclast-like cell formation. However, genistein (10(-5) M) did not inhibit phorbol 12-myristate 13-acetate-induced osteoclast-like cell formation. The present study demonstrated that genistein has a potent inhibitory effect on osteoclast-like cell formation in mouse marrow culture. The inhibitory action of genistein may involve in cyclic AMP signaling.

Animals↗
PubMed1999

Effect of vitamin K2 (menaquinone-7) in fermented soybean (natto) on bone loss in ovariectomized rats.

The effect of dietary vitamin K2 (menaquinone-7) on bone loss in ovariectomized (OVX) rats was investigated. OVX rats were freely given experimental diets containing menaquinone-4 (MK-4; 12mg/100g diet) or menaquinone-7 (MK-7; 18.1mg/100g diet) for 24 days; MK-4 and MK-7 were equal in molar concentrations. This feeding caused a remarkable increase of MK-4 and MK-7 concentrations in the serum and femur of OVX rats. OVX-induced decrease in the femoral dry weight and femoral calcium content was prevented by the feeding of dietary MK-4 or NK-7. In separate experiments, OVX rats were freely given experimental diets containing the fermented soybean (natto; including 9.4 microg MK-7/100g diet) without or with added MK-7 (37.6 microg/100g diet) for 77 days. Feeding produced a significant elevation of MK-4 and MK-7 concentrations in the serum of OVX rats. In this case, a significant increase in the femoral MK-4 content was observed but MK-7 was not detected in the femoral tissues. OVX-induced decreases in the femoral dry weight and femoral calcium content were significantly prevented by the feeding of diets containing natto with MK-7 added (37.6 microg/100g diets). This study demonstrates that the intake of dietary MK-7 has a preventive effect on bone loss caused by OVX. This effect may be partly caused by MK-4, which is formed by degradation of MK-7.

Animals↗
PubMed1999

Anabolic effect of daidzein on cortical bone in tissue culture: comparison with genistein effect.

The effect of daidzein on cortical bone in vitro was investigated. Femoral-diaphyseal tissues obtained from elderly female rats were cultured for 24 h in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplementation with antibiotics and bovine serum albumin. The experimental cultures contained 10(-7) to 10(-5) M daidzein. The presence of daidzein (10(-6) and 10(-5) M) caused a significant increase of alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in bone tissues. This effect was equal to that of genistein (10(-6) and 10(-5) M). Daidzein (10(-5) M) or genistein (10(-5) M)-induced increase of calcium content and alkaline phosphatase activity in bone tissues was completely prevented by cycloheximide (10(-6) M), an inhibitor of protein synthesis. Anabolic effect of daidzein and genistein on bone components was equal to that of 17beta-estradiol (10(-8) M). The effect of isoflavohoids was not enhanced by the addition of 17beta-estradiol. The combination of daidzein and genistein did not have an additive effect. These findings indicate that daidzein has an anabolic effect on bone metabolism in tissue culture in vitro, and that this effect is equal to genistein effect. Isoflavonoids may stimulate bone formation and mineralization.

Alkaline Phosphatase↗
PubMed1999

Suppressive effect of genistein on rat bone osteoclasts: apoptosis is induced through Ca2+ signaling.

The effect of genistein on osteoclast-like multinucleated cells (MNCs) from rat femoral tissues was investigated. When rat marrow cells were cultured for 7 d in a medium containing either vehicle, parathyroid hormone (10(-8) M) or prostaglandine E2 (10(-6) M), the formation of tartrate-resistant acid phosphatase (TRACP)-positive MNCs was significantly increased. This increase was markedly weakened by the presence of genistein (10(-6) or 10(-5) M). The bone cells isolated from rat femoral tissues were cultured for 48 h in an alpha-minimal essential medium (5% fetal bovine serum) containing either vehicle or genistein (10(-8) to 10(-5) M). Osteoclasts were estimated by staining for TRACP, a marker enzyme of osteoclasts. The presence of genistein caused a significant decrease in the number of osteoclasts. Such a decrease was also seen in the presence of calcitonin (10(-10) to 10(-8) M), dibutyryl cyclic adenosine 5'-monophosphate (DcAMP; 10(-6) and 10(-5) M), calcium chloride (10(-4) and 10(-3) M) or daidzein (10(-7) to 10(-5) M). The suppressive effect of genistein (10(-5) M) was not further enhanced in the presence of calcitonin (10(-8) M), DcAMP (10(-5) M), or calcium chloride (10(-3) M), and was completely abolished by the presence of dibucaine (10(-6) M) or staurosporine (10(-7) M), both of which are inhibitors of Ca2+-dependent protein kinases. Ca2+ ionophore (A23187; 10(-6) M) induced a remarkable decrease in the number of osteoclasts in the absence or presence of genistein (10(-5) M) or calcium chloride (10(-3) M). The present study demonstrates that genistein has a direct suppressive effect on osteoclasts in vitro, suggesting that the isoflavone may induce apoptosis which is mediated through the pathway of intracellular Ca2+ signaling.

Animals↗
PubMed1998

Potential role of cbfa1, an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis: regulation of mRNA expression of osteoclast differentiation factor (ODF).

The role of Cbfa1 (core binding factor alpha1), an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis was investigated in vitro and in vivo using Cbfa1-deficient calvarial cells and mice. Co-cultures of calvarial cells isolated from embryos with three different Cbfa1 genotypes (Cbfa1+/+, Cbfa1+/- and Cbfa1-/-) and normal spleen cells generated TRAP-positive multinucleated osteoclast-like cells (OCLs) in response to 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and dexamethasone, but the number and bone-resorbing activity of OCLs formed in co-culture with Cbfa1-/- calvarial cells were significantly decreased in comparison with those formed in co-cultures with Cbfa1+/+ or Cbfa1+/- calvarial cells. The expression of osteoclast differentiation factor/osteoprotegerin ligand (ODF/OPGL) mRNA was increased by the treatment with 1alpha, 25(OH)2D3 and dexamethasone in calvarial cells from Cbfa1+/+ and Cbfa1+/- mouse embryos, but not from Cbfa1-/- embryos. In contrast, the expression of osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) mRNA was inhibited by 1alpha,25(OH)2D3 and dexamethasone similarly in all three types of calvarial cells. ODF/OPGL and OPG/OCIF mRNAs were highly expressed in the tibia and femur of Cbfa1+/+ and Cbfa1+/- embryos. In the tibia and femur of Cbfa1-/- embryos, however, ODF/OPGL mRNA was undetectable and the expression of OPG/OCIF mRNA was also decreased compared with those in Cbfa1+/+ and Cbfa1+/- embryos. These results suggested that Cbfa1 is somehow involved in osteoclastogenesis through regulation of ODF/OPGL.

Animals↗
PubMed1998

Inhibitory effect of genistein on bone resorption in tissue culture.

The effect of genistein on bone resorption in vitro was investigated. Femoral-metaphyseal tissues obtained from elderly female rats were cultured for 48 hr in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained 10(-7) to 10(-3) M genistein. The bone-resorbing factors parathyroid hormone (1-34) (PTH; 10(-7) M), prostaglandin E2 (PGE2; 10(-5) M), and lipopolysaccharide ( 10 microg/mL) caused a significant decrease in bone calcium content. The decrease in bone calcium content induced by bone-resorbing factors was inhibited completely by genistein (10(-7) to 10(-5) M). In addition, this isoflavonoid (10(-5) M) completely inhibited the PTH (10(-7) M)- or PGE2 (10(-5) M)-induced increase in medium glucose consumption and lactic acid production by bone tissues. Moreover, genistein (10(-5) M) blocked both PTH (10(-7) M)-increased acid phosphatase and -decreased alkaline phosphatase activities of bone tissues. The inhibitory effect of genistein (10(-5) M) on PTH (10(-7) M)-stimulated bone resorption was clearly prevented by the presence of 10(-6) M tamoxifen, an anti-estrogen reagent. Genistein (10(-5) M) did not further enhance the inhibitory effect of estrogen (10(-9) M) on PTH-stimulated bone resorption. These findings indicate that genistein has a direct inhibitory effect on bone resorption in tissue culture in vitro.

Acid Phosphatase↗
PubMed1998

Potent effect of zinc acexamate on bone components in the femoral-metaphyseal tissues of elderly female rats.

1. The effect of zinc compounds on bone components in the femoral-metaphyseal tissues from elderly female rats (50 weeks old) was investigated in vitro. Bone tissues were cultured for 24 hr in Dulbecco's modified Eagle medium containing either vehicle or zinc compounds (10[-7] to 10[-5] M). 2. Zinc content, alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in the metaphyseal tissues were significantly increased by the presence of zinc sulfate (10[-6] and 10[-5] M), beta-alanyl-L-histidinato zinc (AHZ; 10[-6] and 10[-5] M) and zinc acexamate (10[-7] to 10[-5] M). At 10[-5] M, the effect of zinc acexamate on the increase of bone components was more potent than that of zinc sulfate or AHZ. 3. The effect of zinc acexamate (10[-5] M) on the increase of alkaline phosphatase activity in the metaphyseal tissues was remarkable as compared with that of insulin (10[-8] M), estrogen (10[-9] M), insulin-like growth factor-I (10[-8] M), transforming growth factor-beta (10[-10] M), sodium fluoride (10[-3] M), dexamethasone (10[-7] M) and vitamin K2 (menaquinone-4; 10[-5] M) with an effective concentration. 4. The stimulatory effect of zinc acexamate (10[-5] M) on alkaline phosphatase activity and calcium content in the metaphyseal tissues was completely blocked by the presence of dipicolinate (10[-3] M), a chelator of zinc ion, and of cycloheximide (10[-6] M), an inhibitor of protein synthesis. 5. The present study demonstrates that zinc acexamate has a potent anabolic effect on bone components in the femoral-metaphyseal tissues from female elderly rats in vitro. The effect of zinc acexamate may be based in part on protein synthesis related to zinc ion in bone cells.

Alkaline Phosphatase↗
PubMed1998

Zinc enhancement of genistein's anabolic effect on bone components in elderly female rats.

1. The effect of genistein on the bone components in the femoral-metaphyseal and diaphyseal tissues of elderly female rats was investigated. 2. The oral administration of genistein (100 and 200 microg/kg body weight) for 3 days to rats caused a significant increase in alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in the femoral-metaphyseal and diaphyseal tissues. A dose of 50 microg genistein/kg appreciably increased alkaline phosphatase activity and DNA content in the metaphyseal but not the diaphyseal tissues. 3. Alkaline phosphatase activity, DNA and calcium contents in the femoral-metaphyseal and diaphyseal tissues were significantly elevated by the oral administration of zinc sulfate (5.5 mg Zn/kg) for 3 days. The effect of zinc on increasing bone DNA and calcium contents was synergistically enhanced by the simultaneous administration of genistein (100 microg/kg). 4. The stimulatory effect of zinc sulfate (10(-5) M) or genistein (10(-5) M) on bone calcium content was also seen in a culture system using the femoral-metaphyseal and diaphyseal tissues in vitro. This effect was completely prevented by the presence of cycloheximide (10(-6) M). 5. The present findings suggest that genistein has an anabolic effect on bone components and that the effect is enhanced by zinc, owing to its stimulating effect on bone protein synthesis.

Aging↗