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Biomedical subjects

K Dai

Publications and source records attributed to K Dai.

At least 19 recordsLinked to original sources
PubMed2001

The Sma I polymorphism in the von Willebrand factor gene associated with acute ischemic stroke.

The von Willebrand factor (vWF) is a highly multimerized glycoprotein that promotes platelet adhesion and aggregation at a high shear rate, and also acts as a carrier of coagulation factor VIII. vWF has been identified as a risk factor for recurrent myocardial infarction in the general population. It has been reported that two polymorphisms of vWF gene promoter and the Thr789Ala polymorphism in vWF gene are associated with arterial thrombosis. The Sma I polymorphism is located in intron 2 of vWF gene. The relevance of this polymorphism to thrombotic disease was investigated by genotypic identification in two case-control studies: 107 patients with acute ischemic stroke, 49 patients with acute myocardial infarction (AMI), and 113 health controls age- and race-matched for each patient. Twenty-eight (26.2%) of the 107 patients with acute ischemic stroke, 8 (16.3%) of 49 patients with AMI, and 11 (9.7%) of 113 controls were found to be homozygous for CC genotype, respectively. The prevalence of the CC genotype in acute ischemic stroke was significantly higher than that of the normal controls (odds ratio [OR]=3.29, 95% confidence interval [CI]=1.54-7.01,.01>P>.001). However, the prevalence of the CC genotype in AMI was not significantly different from that of the normal controls (OR=1.81, 95% CI=0.68-4.82,.30>P>.20). Plasma vWF:Ag was also determined by enzyme-linked immunosorbent assay (ELISA) on the frozen plasma of 122 subjects. The mean plasma vWF:Ag levels of the controls, patients with acute ischemic stroke, and AMI were 0.468, 0.584, and 0.783 U/ml, respectively. The mean level of plasma vWF:Ag did not differ significantly between controls and patients with acute ischemic stroke (P=.195), but had significantly difference between controls and patients with AMI (P=.001). No association was found between the Sma I polymorphism and vWF plasma levels in controls, patients with acute ischemic stroke, or the AMI group (one-way ANOVA, P=.323, P=.315, P=.96). Results show that the Sma I polymorphism is strongly associated with increased risk of acute ischemic stroke, however, no association was observed between this polymorphism and AMI. This polymorphism of vWF may represent a newly identified risk factor for acute ischemic stroke in Chinese. Whether it is the real functional variant associated with acute ischemic stroke remains to be elucidated.

Acute Disease↗
PubMed2001

Identification and characterization of a melanin-concentrating hormone receptor.

Melanin-concentrating hormone (MCH), a neuropeptide expressed in central and peripheral nervous systems, plays an important role in the control of feeding behaviors and energy metabolism. An orphan G protein-coupled receptor (SLC-1/GPR24) has recently been identified as a receptor for MCH (MCHR1). We report here the identification and characterization of a G protein-coupled receptor as the MCH receptor subtype 2 (MCHR2). MCHR2 has higher protein sequence homology to MCHR1 than any other G protein-coupled receptor. The expression of MCHR2 has been detected in many regions of the brain. In contrast to MCHR1, which is intronless in the coding region and is located at the chromosomal locus 22q13.3, the MCHR2 gene has multiple exons and is mapped to locus 6q21. MCHR2 is specifically activated by nanomolar concentrations of MCH, binds to MCH with high affinity, and signals through Gq protein. This discovery is important for a full understanding of MCH biology and the development of potential therapeutics for diseases involving MCH, including obesity.

Alternative Splicing↗
PubMed2001

[The computer-aided measurement of medullary canal in proximal femur].

This study was conducted to search the law of the parameters of medullary canal section shape in proximal femur. The methods of image-processing and taper-curve-fit mathematics were adopted in the acquisition of data and parameters. Computer-aided method and manual method were employed to measure 10 samples of section shape in proximal femur. The results showed that no significant difference was seen between the computer-aided method and manual method(P> 0.05). This approach could reduce man-made errors and process mass samples automatically by computer.

Adult↗
PubMed2001

[Application of computer image process to the research on the contact characteristics of subtalar joint].

With the use of computer image processing technology, a new method was proposed for studying the contact characteristics of the subtalar joint. The results showed the total subtalar articulation area was 9.52 +/- 0.40 cm2. On neutral position and under 600 N load, the contact area of the subtalar joint was 2.00 +/- 0.11 cm2. The contact area of the posterior articulation was significantly larger than that of the anterior and medial articulation (p < 0.01). The average contact pressure was 19.3 +/- 1.38 N, the force transmitted by the subtalar was 389.16 +/- 28.75 N, which accounted for about 64.86% of the applied shank load (600 N), and 69.39% of the force was transmitted by the posterior articulation. The posterior articulation plays an important role in the load. The fracture line of the calcaneus often appears in this area.

Adult↗
PubMed2001

A histomorphometric and molecular study on stress adaptability of freeze-dried bone allograft.

OBJECTIVE: To Investigate stress adaptability of freeze-dried bone allograft. METHODS: Cortical and cancellous allograft were transplanted to each side of the midshaft diaphyseal ulna in two groups of 28 animals. The left transplanted allograft was free from fixation and bore a normal physiological load, while the right transplanted allograft was protected from loading by a simple external fixator and bore less load. Animals were sacrificed at the 2nd, 4th, 8th, 16th week after transplantation and specimens were taken out for bone histomorphometry studies and analysis of collagen gene expression by in situ cDNA-mRNA hybridization. RESULTS: Labeled surface(LS) and bone mineral apposition rate(MAR) of the normally loaded graft-host bone interface were significantly higher than that of the less loaded side at the 4th, 8th, 16th week after transplantation. Parameters reflecting the internal repair process of the allograft, such as LS in cortical and cancellous bone or MAR in cortical bone of the normally loaded side were significantly higher than those of the less loaded side at the 16th week after transplantation. The result of in situ hybridization indicated that more osteoblast-like cells expressing the type I collagen gene were found in the interface or interior of normally loaded grafts. CONCLUSION: The stimulus of physiologic load can accelerate the early union of allograft-host bone interface and later new bone creep substitution to the necrotic allograft.

Adaptation, Physiological↗
PubMed2001

[The Rsa I and Sma I polymorphisms in the von Willebrand factor gene discrimination by hybridization with oligonucleotide arrays].

OBJECTIVE: To develop a new assay for the Rsa I and Sma I polymorphisms (single nucleotide polymorphism, SNP) in the von Willebrand factor gene detection that utilizes oligonucleotide arrays (DNA chips) on glass supports. Expoloring the association of the RsaI and SmaI polymorphisms in the von Willebrand factor gene with thrombosis in Chinese. METHODS: Allele-specific oligonucleotides are covalently immobilized on glutaradehyde derivatized glass slides in arrays. Single strand PCR product of PCR-amplified genomic DNA is fluorescently labeled by assymetric PCR with fluorescently tagged dUTP and hybridized to the support-bound oligonucleotide array. The hybridization pattern is detected by fluorescence scenning. The effect of hybridization conditions were evaluated and optimized. The method was validated by the discrimination of blinded DNA samples identified by restriction enzymes. 50 patients with thrombosis were examined by this method. RESULTS: The genotypes scored by oligonucleotide arrays assay were in 100% agreement with restriction enzymes results. The genotype distributions GG, GA, AA and CC, CT, TT of RsaI and SmaI polymorphisms of patients or controls were 4.0%, 12.0%, 84.0% and 24.0%, 44.0%, 32.0% or 1.4%, 11.8%, 86.8% and 8.8%, 57.4%, 33.8%. The allele frequencies G, A and C, T were 10.0%, 90.0% and 46.0%, 54.0% or 7.4%, 92.6% and 37.5%, 62.5%. No statistical difference in genotype distribution and allele frequencies was observed between patients with thrombosis and the control groups (all P > 0.05). CONCLUSION: A rapid and accurate method for the RsaI and SmaI polymorphisms in the von Willebrand factor gene detection, or for the analysis of single nucleotide polymorphism (SNP) has been developed using oligonucleotide arrays on glass supports. No association was observed between the Rsa I and Sma I polymorphisms in the vWF gene and thrombotic disease.

Alleles↗
PubMed2001

[The development and application of computer-aided bone histomorphometry system].

The aim of this study is to develop a Computer-aided Bone Histomorphometry System. The method is based on the Micro-graphical Digital System composed of microscope, digital camera, computer and related programs. The methodology was developed to measure the basic data on each image of visual field of hard bone tissue with computer-assistance. Following this, the parameters of bone volume, bone structure and bone metabolism were calculated based on the standardization of bone histomorphometry. Such method has been used in the experimental and clinical studies of osteoporosis to predict the fracture risk and evaluate the drug effect.

Bone Density↗
PubMed2001

Effects of recombinant human growth hormone (r-hGH) on experimental osteoporotic fracture healing.

OBJECTIVE: To observe the effect of recombinant human growth hormone (r-hGH) on osteoporotic fracture healing in rats, and to provide an effective therapy for osteoporotic fracture. METHODS: Thirty-six female 8-month-old SD rats were randomized into two groups: therapy group and control group. After the experimental model of osteoporotic fracture was established, the therapy group was treated with r-hGH of 2.7 mg/kg body weigh/day (1 mg=3 IU) for 10 days continuously by daily subcutaneous injection; whereas the control group was treated with equivalent saline. Plasma insulin-like growth factor I concentration was detected and bone mineral density (BMD) as well as biomechanical strength of callus were measured at 2, 4, 8 weeks. RESULTS: Plasma insulin-like growth factor I concentration in the therapy group was higher than that in the control group (P<0.005) at 2nd week and began to decline at 4th week. At 8th week, there was no significant difference between the two groups. At 4th week, callus area and BMD in therapy group were higher than those in the control group, but at 8th week, they were lower and BMD had a significant difference between the two groups (P<0.001). Biomechanical testing of callus showed that torsional strength of the therapy group was higher than that of the control group at 4th or 8th week, meanwhile maximum torsional angle had a significant difference between the two groups (P<0.005). CONCLUSIONS: The results show that exogenous r-hGH can stimulate osteoporotic fracture healing in rats.

Animals↗
PubMed2000

Three mRNA transcripts of the proopiomelanocortin gene in human placenta at term.

The proopiomelanocortin (POMC) gene whose normal pituitary specific mRNA product is 1200 bases (b) is also expressed in placenta and its peptide derivatives such as ACTH and beta-endorphin may play an important role in the initiation of labor. So far, two mRNA transcripts, one small (800b) and one large (1380b) have been reported in placenta by Northern blot analysis, similar to other endocrine tissues and various extrapituitary tumors; however, it is questionable whether both of these transcripts are effectively translated to a functional protein. We examined by Northern blot analysis the size and the differential expression of placental POMC gene transcripts in pregnant women with different modes of delivery. Placental tissues were collected from two groups of pregnant women, six with vaginal delivery (VD) and five with cesarean section (CS). In both groups of placentae three POMC gene transcripts were detected of 800, 1200 and 1380 bases; the 1200b pituitary specific species often predominated and was always present. The 800b transcript was also always present, while the large transcript (1380b) was expressed in 3/6 VD and 2/5 CS placental tissues. No differences in the relative levels of any of these mRNA species showing effect of the mode of delivery were observed. We conclude that POMC gene transcription in placental tissue at term gives rise to three mRNA transcripts, thus resembling extrapituitary tumors. The reported changes in the levels of the derivative peptides according to the mode of delivery do not reflect changes in POMC mRNA levels and could be attributed to a post-translational effect.

Blotting, Northern↗
PubMed2000

Stress-relaxation plates and the remodeling of callus and cortex under the plate in rabbits.

OBJECTIVE: To study the influence of a stress-relaxation plate on the remodeling of callus and cortex under the plate. METHODS: The bilateral tibia diaphysis of New Zealand rabbit were osteotomized and fixed with stress-relaxation plate (SRP) and rigid plate (RP), respectively. Polarized light microscopy and transmission electron microscopy (TEM) were used to study the remodeling of callus and the cortex under the plate from 4 to 24 weeks postoperatively. RESULTS: Polarized light microscopy: the structural changes of callus and cortex beneath the plate are similar in the SRP and RP groups at the early postoperative stage, manifesting an alignment disorder of collagen fibers with a weak birefringence in the callus and absorption cavities in the cortex under the plate. After the twelfth postoperative week, the SRP group showed callus starting to transform to lamellar bone and absorption cavities in the cortex under the plate becoming smaller. By contrast in the RP group the absorption cavities in the callus and cortex under the plate became larger and the whole layer of cortex was cancellated. TEM: the active osteoclasts appeared in both SRP and RP groups in the period from 4 to 8 weeks postoperatively. In the SRP group, many functionally active osteoblasts could be seen on the surface of the bone, while in the RP group, the osteoblasts were not very active. By 24 weeks postoperatively, the shape of osteocytes were normal but the number of the osteoclasts were small in the SRP group. In the RP group, the osteoclasts became more active and osteocytic osteolysis was manifested. CONCLUSIONS: Fixation with SRP not only enhanced callus remodeling, but also abated the degree of osteoporosis in the cortex under the plate. This approach may lead to an improved osteosynthetic apparatus.

Animals↗
PubMed2000

[Effects of recombinant human growth hormone on cortical bone of ovariectomized rats].

OBJECTIVE: To study the effects of recombinant human growth hormone on cortical bone of middle femur and vertebra of variectomized rats. METHODS: Forty 6 month-old SD rats received low or high dose of growth hormone subcutaneously 3 months after ovariectomy for 8 weeks. Bone density and biomechanical strength of the femur were measured, and the thickness of cortical bone of the middle femur and L(2) vertebra was observed. The results were compared with those in estrogen group. RESULTS: Growth hormone increased the thickness of cortical bone and biomechanical strength and bone density. Estrogen therapy showed no effects on bone density and biomechanical strength of cortical bone. CONCLUSION: Recombinant human growth hormone can prevent bone loss from cortical bone of ovariectomized rat.

Animals↗
PubMed1998

p53-independent role of MDM2 in TGF-beta1 resistance.

Transforming growth factor-beta (TGF-beta) inhibits cell proliferation, and acquisition of TGF-beta resistance has been linked to tumorigenesis. A genetic screen was performed to identify complementary DNAs that abrogated TGF-beta sensitivity in mink lung epithelial cells. Ectopic expression of murine double minute 2 rescued TGF-beta-induced growth arrest in a p53-independent manner by interference with retinoblastoma susceptibility gene product (Rb)/E2F function. In human breast tumor cells, increased MDM2 expression levels correlated with TGF-beta resistance. Thus, MDM2 may confer TGF-beta resistance in a subset of tumors and may promote tumorigenesis by interference with two independent tumor suppressors, p53 and Rb.

Animals↗
PubMed1998

[Incorporation of cortical allograft: a biomechanical study].

OBJECTIVE: To explore the changes of biomechanical properties of cortical allograft in different mechanical environments. METHOD: Cortical allograft was transplanted to each side of the midshaft diaphyseal ulnar of 40 rabbits. The left transplanted allograft underwent normal physiological load, while the right underwent lower load. Animals were killed and specimens taken for examination of bone mineral density, bone porosity and maximal three-point-bend breaking load. RESULT: The union strength of allograft-host bone junction increased constantly, while the internal creeping substitution led to an initial greater weakening of the cortical allograft itself and the later recovery of its strength. In comparison, the union strength of the normally loaded graft-host surface was significantly higher than that of the lower loaded side at eight and sixteen weeks after transplantation. At the sixteenth week, there was greater bone strength in normally loaded graft than that in less loaded graft. CONCLUSION: The internal repair would lead to initial greater weakening of cortical allograft and the later gradual recovery of its strength. The effect of physiological load can accelerate the improvement of the biomechanical properties of allograft.

Animals↗
PubMed1998

[The curvature design on artificial femoral stem in Chinese population].

Based on A-P view geometory and lateral view geometory X-ray Photograph, the upper geometric curves of intermedulla were measured from each bone in 84 femur specimens in Chinese population. All curves were parameterized by lest mean square method. A statistical analysis on parameterized data was made for finding out the growth law of femur in Chinese population. The shape of the femur is classified into 7 types. This results of the research is for the the design of Chinese-Type artificial femur.

Adult↗
PubMed1997

Anal anomalies: an uncommon feature of velocardiofacial (Shprintzen) syndrome?

We report three cases of velocardiofacial syndrome (VCFS) with anal anomalies who have deletions of the 22q11 region and a further case where the proband has VCFS clinically and her father has an anal anomaly. It is important to consider VCFS in the differential diagnosis of children with anal anomalies and to look for other features of the syndrome, such as asymmetrical crying facies, submucous cleft of the palate, developmental delay, cardiac anomalies, and hypoparathyroidism.

Abnormalities, Multiple↗
PubMed1997

[The structural changes of cortical bone beneath plate after rigid platefixation and removal].

We investigated the structural changes of bone under the plate after plate fixation and removal. Twenty-four New Zealand white rabbits were plated on their intact left tibiae with stainless steel plates and 4 animals served as controls. The plates were removed 2 months after implantation in 20 plated animals, of which, 4 were sacrificed immediately after plate removal and the other were killed in successive groups of 4 each at 1, 2, 3 and 4 months after plate removal respectively. The remaining 4 plated animals were killed at 6 months after implantation. Bone samples were harvested and prepared for scanning microscopic observation. Internal fixation with a rigid plate may lead not only to osteopenia of the cortex under the plate, but also to disorganization of the cortex, in which the mineral column and collagen fibers were oriented in a randomized pattern. The regional osteoporosis could recover gradually after removal of the rigid plate. However, the restoration of normal bone structure occurred later than that of the bone mass. Delayed restoration of bone structure might be one of the potential causes of refracture of the plated bone.

Animals↗