Biomedical subjects

R Xu

Publications and source records attributed to R Xu.

At least 217 records · Page 12Linked to original sources

PubMed1997

Glycoprotein D of herpes simplex virus (HSV) binds directly to HVEM, a member of the tumor necrosis factor receptor superfamily and a mediator of HSV entry.

Glycoprotein D (gD) is a structural component of the herpes simplex virus (HSV) envelope which is essential for virus entry into host cells. Chinese hamster ovary (CHO-K1) cells are one of the few cell types which are nonpermissive for the entry of many HSV strains. However, when these cells are transformed with the gene for the herpesvirus entry mediator (HVEM), the resulting cells, CHO-HVEM12, are permissive for many HSV strains, such as HSV-1(KOS). By virtue of its four cysteine-rich pseudorepeats, HVEM is a member of the tumor necrosis factor receptor superfamily of proteins. Recombinant forms of gD and HVEM, gD-1(306t) and HVEM(200t), respectively, were used to demonstrate a specific physical interaction between these two proteins. This interaction was dependent on native gD conformation but independent of its N-linked oligosaccharides, as expected from previous structure-function studies. Recombinant forms of gD derived from HSV-1(KOS)rid1 and HSV-1(ANG) did not bind to HVEM(200t), explaining the inability of these viruses to infect CHO-HVEM12 cells. A variant gD protein, gD-1(delta290-299t), showed enhanced binding to HVEM(200t) relative to the binding of gD-1(306t). Competition studies showed that gD-1(delta290-299t) and gD-1(306t) bound to the same region of HVEM(200t), suggesting that the differences in binding to HVEM are due to differences in affinity. These differences were also reflected in the ability of gD-1(delta290-299t) but not gD-1(306t) to block HSV type 1 infection of CHO-HVEM12 cells. By gel filtration chromatography, the complex between gD-1(delta290-299t) and HVEM(200t) had a molecular mass of 113 kDa and a molar ratio of 1:2. We conclude that HVEM interacts directly with gD, suggesting that HVEM is a receptor for virion gD and that the interaction between these proteins is a step in HSV entry into HVEM-expressing cells.

Animals↗

PubMed1997

Clinical review 91: Female sex hormones and cardiovascular disease in women.

Cardiovascular disease is the leading cause of mortality in women, a fact that is underappreciated by women and physicians. Clinical and experimental data underscore the cardioprotective effects of female sex hormones, particularly estrogen. Indeed, the loss of female sex hormones after menopause contributes to the striking increase in the incidence of cardiovascular morbidity and mortality after menopause. Estrogen replacement therapy improved lipoprotein profiles in the postmenopausal women, but this accounts for less than half of the cardioprotective effects of estrogen replacement therapy. Addition of progestins to estrogen therapy in women appears not to significantly attenuate the cardioprotective effects of estrogen replacement therapy despite experimental data suggesting otherwise. This review addresses potential mechanisms, other than influences on lipoproteins, by which estrogen and progesterone exert their cardiovascular protective effects. Particular emphasis is directed to genomic and nongenomic effects of estrogen and progesterone that are exerted directly on cardiovascular tissue.

Blood Vessels↗

PubMed1997

Placement of screws in the uncemented acetabulum: anatomic analysis of the danger zone.

Six cadavers were used to define the projection of the external iliac artery on the inner table of the acetabulum, and to quantitatively determine bony dimensions of the danger zone with regard to screw placement. The results showed that the majority of projections of the external iliac arteries were located on the superior portion of the posterosuperior quadrant and extended to the mid-superior portion of the anterosuperior quadrant (danger zone). The inferior portion of the danger zone was relatively far from the external iliac artery. The greatest depths of bone were found in the inferior portion of the danger zone, and the depths of bone in the middle and superior portion of the danger zone were relatively thinner. This anatomic study showed that the real danger zone was found in the middle and superior portions of the anterosuperior quadrant of the acetabulum. The inferior portion of the anterosuperior quadrant was relatively safer. This area may be considered if transacetabular screw replacement in the anterosuperior quadrant is required.

Acetabulum↗

PubMed1997

[The effects of E2 and it's metabolites on the proliferation of rat anterior pituitary cells in vitro].

OBJECTIVE AND METHODS: The present work is determined to observe the effects of E2 (estradiol), 2-OHE1 (2-hydroxyestrone), 2-OHE2 (2-hydroxyestrodiol) on the proliferation of rat anterior pituitary cells (APC) in vitro by laser scanning confocal microscopy. RESULTS: 10(-6) mol/L E2 stimulated the growth of APC. After 2 days of incubation with E2, the DNA content of APC increased to 1.3 times of the control group (P < 0.01). 10(-6) mol/L 2-OHE2 (other than 2-OHE1) stimulated proliferative activity of APC and inhibited the inhibitory effect of peribidil (10(-5) mol/L), a dopamine receptor agonist, on the poliferative activity of rat APC.

Animals↗

PubMed1997

[Melatonin inhibits TRH-stimulating prolactin gene expression of anterior pituitary cells in newborn rat in vitro].

OBJECTIVE AND METHODS: This work was to investigate whether melatonin (MEL) plays a role in the gene expression of prolactin (PRL), by the Method of in situ hybridyzation. RESULTS: Our results indicated that, at a higher concentration, MEL not only inhibits TRH (thyrotropin releasing hormone) stimulating PRL gene expression of anterior pituitary cell in newborn rat, but also exerts a direct inhibitory effect on PRL gene expression in vitro. CONCLUSION: These results suggest that MEL may be a regulator of PRL synthesis and secreting in vivo.

Animals↗

PubMed1997

[A bio-electrochemical theory in pathogenesis of dental caries].

Since the Bio-electrochemical theory in pathogenesis of dental caries was suggested by Huang (1990), many experimental proofs have obtained in studies of dental bio-electrical potential and dielectric properties of the tooth. Recently, the model of the electrochemical artificial dental caries that have directly proved Huang's theory was developed successfully in laboratory. This paper make a systematic exposition of the bio-electrochemical theory in pathogenesis of dental caries.

Dental Caries↗

PubMed1997

[The different influences of splenectomy plus ligation of pericardial vein and shunt on portal hypertensive gastropathy].

A prospective and controlled study has been made to probe into the different influences of splenectomy plus ligation of pericardial vein (SPLPY) and shunt on portal hypertensive gastropathy (PHG). 26 patients with cirrhosis of liver and portal hypertension admitted from January 1994 to April 1996 were randomized into two groups. One group was treated with SPLPV (15 cases), and the other shunt (11 cases). Gastroscopy was made in all patients pre- and postoperatively to observe the changes of gastric mucosa. It has been shown that SPLPV exacerbate PHG (P < 0.05) and the shunt has an opposite effect (P < 0.05). We consider that it is necessary to modify SPLPV and reevaluate the clinical effects of the both.

Adult↗

PubMed1997

[The development of a multivision glare tester].

This paper presents a new kind of multivision glare tester. Its composition, function, hardware, software and application are introduced. The tester provides a practical tool for evaluating visual function change under glare-producing conditions.

Contrast Sensitivity↗

PubMed1997

[Determination of adenosine and thymidine in Fritillaria bulbs by ultraviolet spectrophotometry].

A convenient method for quantitative analysis of the nucleosides in Fritillaria bulbs has been developed by means of thin layer chromatography and ultraviolet spectrophotometry. The MeOH extracts from four species of Fritillaria were analyzed with this method. The results show that both adenosine and thymidine in the four species are quite disparate, suggesting that the nucleosides may be responsible for the anti-coagulative activity of Fritillaria.

Adenosine↗

PubMed1997

Effect of degeneration of the intervertebral disk on the process of diffusion.

PURPOSE: To test the hypothesis that diffusion of contrast medium into the intervertebral disk is affected by the integrity of the nucleus pulposus and annulus fibrosus. METHODS: In canine intervertebral disks, defects were made in the annulus fibrosus and nuclear material was removed from the disk with a nucleotome. MR imaging was performed with intravenous contrast medium at 15, 30, 60, and 90 days after the procedure. The diffusion of contrast medium in the intervertebral disk was studied by visual inspection and by measuring changes in signal intensity. The intervertebral disk were classified at each MR study as normal or abnormal on the basis of the signal intensity on T2-weighted images. RESULTS: In untreated disks after intravenous injection of contrast medium, a band of increased signal intensity was observed near the endplates that became wider with time and approached the center of the disk. In six of the 12 treated disks, the band of increased signal intensity was visibly diminished or less discrete compared with that in the control disks. Weeks later, these treated disks showed diminished signal intensity on T2-weighted images and bulging of the annulus fibrosus. CONCLUSIONS: Intervertebral disks with defects in the annulus fibrosus and reduced cartilage content were characterized by abnormal diffusion of contrast medium into the disk, and changes characteristic of early disk degeneration were detected subsequently.

Animals↗

PubMed1997

The effect of anterior translation of the vertebra on the canal size in the lower cervical spine: a computer-assisted anatomic study.

Eighteen adult dry-bone spine specimens were used in conjunction with computer analysis to determine the average axial spinal canal area at the levels of C6, C7, and T1 after different degrees of anterior translation of the cephalad vertebra. Simulating a distractive flexion injury, the cephalad vertebra was anteriorly displaced on the caudal vertebra at 1-mm intervals. After each displacement, the remaining axial spinal canal area of the caudal vertebra was calculated. The results showed that the average axial spinal canal areas for both male and female specimens were approximately 222 mm2 for C6, 217 mm2 for C7, and 210 mm2 for T1, respectively. After a 6-mm anterior translation of the cephalad vertebra (assuming 50% of anterior translation of the vertebral body), the average axial spinal canal area of the caudal vertebra for both sexes significantly decreased to 59% at C6, 51% at C7, and 56% at T1, respectively. This study suggests that the size of the axial spinal canal directly depends on the degree of anterior vertebral translation.

Adult↗

PubMed1997

Sacroiliac joint injection: a cadaveric study.

Eleven bony pelves were studied in an attempt to find an ideal approach for needle placement into the sacroiliac joint and to describe the unique anatomy of the sacroiliac joint relative to sacroiliac joint injection. A posterior approach starting 2 cm to 3 cm inferior to the posterior superior iliac spine, angled 20 degrees to 30 degrees laterally, relative to the sagittal plane, and 10 degrees to 20 degrees inferiorly, relative to the transverse plane, was found to be the best approach to the intra-articular portion of the sacroiliac joint.

Aged↗

PubMed1997

Anatomic considerations of anterior instrumentation of the thoracic spine.

Forty-seven dry thoracic specimens from T-3 to T-12 (470 thoracic vertebrae) were used to measure the dimensions of the vertebral body of the thoracic spine and to determine the relationship of the posterior angulation of screw placement to the spinal canal from different entrance points. Statistically significant differences in dimensions of male and female specimens were found in the anterior vertebral body height and all of the angular measurements. The average maximum posterior angle relative to the frontal plane from T-3 to T-12 for both sexes ranged from 11 degrees to 14 degrees at the initial point (the level of the most anterior edge of the upper costal facet), from 20 degrees to 23 degrees at the point of 5 mm anterior to the initial point, and from 30 degrees to 34 degrees at the point of 10 mm anterior to the initial point. This study suggests that there is considerable risk of violating the spinal canal if the screws are inadvertently angled posteriorly. The authors recommend insertion of screws in the anterior or middle part of the lateral aspect of the vertebral body. The screws should be directed perpendicular to the lateral plane of the vertebral body. A posteriorly placed screw should be directed anteriorly.

Adult↗

PubMed1997

Radiologic evaluation of the relation of the screw tip to the nerve root in the intervertebral foramen.

Eight cervical spines were used to evaluate the relation of the screw tip to the nerve root in the intervertebral foramen. The specimens were divided into two groups: (a) lateral placement without contact with the nerve root, and (b) lateral placement with penetration of the nerve root. Six screws were used for each specimen. After screw placement, oblique radiographs and axial computed tomography (CT) scans were taken. The results on oblique radiographs showed that 23 (95.8%) of 24 screws without contact with the nerve root were found in the upper zone or the junction between the upper and lower zones of the intervertebral foramen. Twenty (83.3%) of 24 screws with penetration of the nerve root were located in the junction between the lower zone of the intervertebral foramen and the pedicle zone. No definite diagnosis of screw penetration of the nerve root could be made on axial CT scans, although scans can show that the screw is violating the foramen. Whether or not a screw violating the intertransverse foramen and affects the nerve root depends on its position on the oblique radiograph. It may be not necessary to remove or change the screw immediately if a longer screw is found in the upper portion of the intervertebral foramen on the oblique view and angled laterally on axial CT scan in a patient without radicular symptoms.

Adult↗

PubMed1997

Location of the vertebral artery foramen on the anterior aspect of the lower cervical spine by computed tomography.

Axial computed tomography scans were performed on 14 cadaveric cervical spines to determine the location of the vertebral artery foramen on the anterior aspect of the lower cervical spine. The best scan through the vertebral artery foramen from each level at C3-C6 was selected. Measurements of the vertebral artery foramen included the foramen depth, foramen width, interforaminal distance, the distance from the anterior border of the transverse foramen to the anterior border of the transverse process, the distance from the posterior border of the transverse foramen to the posterior border of the lateral mass, and the distance from the medial border of the vertebral artery foramen to the lateral border of the vertebral body. The results show that the average transverse foramen width was 5.5 +/- 0.4 mm at C3, 5.7 +/- 1.0 mm at C4, 5.9 +/- 0.7 mm at C5, and 5.7 +/- 0.7 mm at C6. The average transverse foramen depth and average interforaminal distance gradually increased from C3 to C6. The distance from the anterior border of the vertebral artery foramen to the anterior border of the transverse process gradually increased from C3 (1.2 +/- 0.4 mm) to C6 (2.7 +/- 0.8 mm) as well. The average distance between the medial border of the transverse foramina and the lateral border of the vertebral body for C3-C6 ranged from 1.8 to 2.2 mm. The average distance between the anterior borders of the vertebral artery foramina and the anterior border of the vertebral body gradually decreased from C3 (8.4 +/- 1.4 mm) to C6 (7.0 +/- 1.6 mm). This study suggested that the lateral border of the vertebral body may be a reliable landmark during anterior cervical decompression. The vertebral artery foramen should be free of violation if vertebrectomy or subtotal vertebrectomy is performed medial to the lateral border of the vertebral body.

Aged↗

PubMed1997

Quantitative anatomy of the cervical facet and the posterior projection of its inferior facet.

For this study, 41 cervical spines from C3 to C7 were directly evaluated. Anatomic evaluation of the cervical superior and inferior facets included the facet height, width, and angulation relative to the coronal plane. The projection of the inferior facet on the posterior aspect of the lateral mass was constructed and measured, and the dimensions of the lateral mass were evaluated. In general, the male linear parameters were larger than the female parameters, but the male angular dimensions were smaller than those of females. The posterior projection height of the inferior facet was found to be 7.4-9.0 mm from C3 to C7 for both sexes and was approximately 2 mm larger than half the height of the lateral mass. C6 and C7 had relative larger superior and inferior facet angles. The lateral mass was thinner at the level of C6-7. This study indicated that there may be a risk of violating the inferior articular facet and the related superior articular facet of the most caudal facet joint if a screw starting at the midpoint or below the midpoint of the lateral mass is directed perpendicular to the posterior aspect of the lateral mass at the level of C3-7.

Aged↗

PubMed1997

Construction and identification of a recombinant adenovirus which expresses human interferon-gamma.

An E1-deleted adenoviral vector, pAdl2/RSV-IFN-bpA, harboring human IFN-gamma cDNA, and plasmid pJM17 were cotransfected into a human embryo kidney cell line 293 by the calcium-phosphate precipitation method. Six strains of recombinant adenovirus (rAd) were obtained after 11-day incubation. PCR analysis indicated that all six rAds contained human IFN-gamma cDNA. The biological activity of IFN-gamma was detected in the supernatant of the cultured 293 cells following rAd infection, and it could be blocked by the antibody against IFN-gamma. The B16F10 cells infected with the purified rAd (RSV/IFN-01) didn't show cytopathic effect (CPE), and more biological activity of IFN-gamma was detected in the supernatant of the infected B16F10 cells with increased MOI (multiple of infection) values. Therefore, the recombinant adenovirus constructed in this study can express and secrete human IFN-gamma.

Adenoviruses, Human↗

PubMed1996

Anatomic consideration of transpedicular screw placement in the cervical spine. An analysis of two approaches.

STUDY DESIGN: This study compared the effectiveness of two transpedicular screw placement techniques: blind screw placement versus screw placement after direct determination of the superior, medial, and inferior borders of the pedicle through the opening of a "window" by the partial laminectomy and tapping technique. OBJECTIVES: To determine if the incidence and severity of pedicle violations resulting from transpedicular screw placement could be reduced by direct determination of the superior, medial, and inferior borders of the pedicle through the opening of a "window" by partial laminectomy. SUMMARY OF BACKGROUND DATA: Several studies regarding transpedicular screw fixation for unstable cervical spine injuries have been reported, but none has addressed the effectiveness in lowering the incidence of pedicle violation by opening a "window" by partial laminectomy for direct determination of the superior, medial, and inferior borders of the pedicle and using the tapping technique before and in planning for screw placement. METHODS: Eight adult cadaveric cervical spines (40 vertebrae from C3 to C7) were used for this study. Two groups were formed according to screw placement techniques. The first group was composed of 38 blinded transpedicular screw placements. The second group was composed of 40 screw placements using the partial laminectomy and tapping technique. After transpedicular screw placement, all specimens were evaluated radiographically and visually for violation of the pedicle. RESULTS: A decrease in the incidence and severity of pedicle violation was seen in the second group with opening of the lamina and tapping technique compared with the blind screw placement group. However, the percentage of screws found to violate the pedicle with the opening of the lamina and tapping technique still was relatively high. CONCLUSIONS: Transpedicular screw placement in the cervical spine is difficult, and a high percentage of violations of the pedicle wall occur. This technique should not be used routinely.

Anatomy, Cross-Sectional↗