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Biomedical subjects

R Xu

Publications and source records attributed to R Xu.

At least 253 records · Page 14Linked to original sources
PubMed1996

Saponins from Mussaenda pubescens.

Two new triterpenoid saponins, named mussaendosides G and K, were isolated from aerial parts of Mussaenda pubescens by normal and reverse phase chromatography. On the basis of chemical and spectroscopic methods, their structures have been elucidated as heinsiagenin A 3-O-{alpha-L-rhamnopyranosyl(1-->2)-[beta-D-glucopyranosyl (1-->6)]-beta-D-glucopyranosyl(1-->2)}-alpha-L -rhamnopyranosyl(1-->4)-O-beta-D-glucopyranoside and 3 beta,19 alpha-dihydroxyl-olean-12-en-24, 28-dioic acid-24,28-di-O-beta-D-glucopyranoside, respectively.

Carbohydrate Conformation↗
PubMed1996

Human acute myeloid leukemias may be etiologically associated with new human retroviral infection.

The etiology of human acute myeloid leukemias (AML) remains uncertain. In order to examine the possibility of retroviral etiology in AML, we determined retroviral antigens related to HTLV-I in leukemic cell samples from 32 AML cases and peripheral blood mononuclear cells (PBMNCs) from 20 healthy donors by D-IGSS with high sensitivity and specificity, reverse transcriptase (RT) activity by a simple and sensitive non-radioisotopic RT assay, and retroviral particles by electron microscopy. The HTLV-I-related antigens were detected in 50.0% (16/32) of fresh leukemic cell samples and 87.5% (28/32) of cultured leukemic cell samples. The HTLV-I-related antigen-positive cells in fresh and cultured leukemic samples were 10.2% and 52.8%, respectively. Both frequency and level of HTLV-I-related antigens in cultured samples were much higher than in fresh samples. In contrast, no HTLV-I-related antigens were found in normal hematopoietic cells from 20 healthy donors. Further study results show that RT activity was detected not only in HTLV-I-related antigen-positive samples, but was also well correlated with the level of HTLV-I-related antigens in these samples, and preferred Mn+2 to Mg+2 as a cation. Moreover, typical retroviral particles were localized in most cultured HTLV-I-related antigen-positive samples by immunoelectron microscope. These data suggest that human acute myeloid leukemias may be etiologically associated with new human retroviral infection.

Acute Disease↗
PubMed1996

Expression and distribution of the receptors for coxsackievirus B3 during fetal development of the Balb/c mouse and of their brain cells in culture.

This study was designed mainly to determine the relationships between the expression and distribution of the cellular receptor proteins for coxsackievirus B3 (CVB3) and susceptibility of mouse brain cells during fetal development of Balb/c mice. Immunoblot analysis of fetal extracts demonstrated that the CVB3 receptor proteins were first expressed at day 14 of the fetal stage, and that maximal expression of the cellular receptor occurred at near term or newborn stage. Results also suggested that newborn mouse brain tissue expressed much larger quantities of viral receptor proteins, compared to other tissues. In vitro studies showed that both mouse neurons and astrocytes could be infected by two CVB3 strains, pantropic CVB3 Nancy strain (CVB3N) and myocardiotropic CVB3 Woodruff strain (CVB3W). CVB3N, however, replicated and grew to high titer in primary astrocyte cultures and in primary neuron cultures, whereas, primary astrocyte cultures were relatively resistant to CVB3W. Virus binding assays revealed that CVB3N bound faster and in greater amounts to mouse brain cells than CVBW. These two virus strains, however, were found to share the same receptor specificity by virus competition assays. The number of virus binding sites for CVB3 on newborn mouse brain cells was approximately 1.8 x 10(4) per cell. The data suggested that preferential expression of the cellular receptors on newborn mouse brain cells may be related to their high susceptibilities to CVB3 infection.

Animals↗
PubMed1996

Site-specific adducts derived from the binding of anti-5-methylchrysene diol epoxide enantiomers to DNA: synthesis and characteristics.

The direct synthesis and characterization of site-specific adducts derived from the binding of (+)-1R,2S-dihydroxy-3S,4R-epoxide-1,2,3,4-tetrahydro-5-methylchrysene and the (-)-1S,2R,3R,4S-enantiomer [(+)- and (-)-5-MeCDE, respectively], to the N2-guanine residues in the oligonucleotide d(CCATCGCTACC) are described. The spectroscopic characteristics of the 5-MeCDE-modified oligonucleotides are discussed, and it is shown that their CD characteristics can be used to distinguish between the trans-addition products of the binding of the (+)- and (-)-enantiomers of 5-MeCDE (C4 position). The 11-mer duplexes with the normal complementary strands are destabilized by the site-specific, covalently bound 5-MeCDE residues: the melting points, Tm, are 5-10 degrees lower than in the case of the unmodified duplex. Stereoselective exonuclease enzyme digestion patterns of the single-stranded (+)- and (-)-trans-5-MeCDE-modified oligonucleotides (Mao et al, 1993, Biochemistry, 32, 11785-11793) were used to probe the orientations of the covalently bound 5-MeCDE residues relative to the modified guanine and the 5'-3' strand polarity; the aromatic residues are positioned either on the 5'-side [(+)-5-MeCDE], or the 3'-side [(-)-5-MeCDE adduct] of the modified guanine residues. The electrophoretic mobilities of the (+)-5-MeCDE-modified 11-mer duplexes in native polyacrylamide gels are slower than those of unmodified and modified duplexes containing the stereoisomeric (-)-5-MeCDE-N2-dG lesions. This indicates that the lesions derived from the tumorigenic (+)-5-MeCDE induce greater degrees of bending or local flexibility than the non-tumorigenic (-)-5- MeCDE enantiomer. These differences in the orientational and structural characteristics are similar to those observed with analogous DNA adducts derived from the tumorigenic (+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and the non-tumorigenic 7S,8R,9R,10S-enantiomer, respectively. The adducts derived from BPDE and 5-MeCDE enantiomers thus display similar characteristics that depend primarily on the PAH diol epoxide enantiomer stereochemistry. This direct synthesis approach can be used to generate milligram quantities of site-specific 5-MeCDE-modified oligonucleotides that are suitable for NMR studies (Cosman, et al., 1995, Biochemistry, 34, 6247-6260).

Base Sequence↗
PubMed1996

Optimal technique of screw placement in the ischial tuberosity for posterior acetabular fractures.

Thirty dry adult bony specimens and eight embalmed cadavers were used to report on the morphological data of the ischial tuberosity and to determine the most optimal technique for ischial tuberosity screw placement for open reduction and internal fixation of posterior acetabular fractures. The average width, height, and depth of the ischial tuberosity were 27.0 mm, 32.2 mm, and 32.4 mm, respectively. The average angles between the posterior and medial aspects and between the posterior and lateral aspects of the ischial tuberosities were 79.5 degrees, and 111.5 degrees, respectively. The risk to the internal pudendal neurovascular bundle increases with either a more medially placed screw or a laterally placed screw that is angled medially. The tendinous origin of the hamstrings becomes quite substantial (7-10 mm thick) at a point 2 cm distal to the inferior acetabular margin. The exposure of the ischial tuberosity should therefore be restricted to this level. The entry point of the screws should be 5 mm or 10 mm medial to the lateral margin of the ischial tuberosity, and the screws should be directed 35-40 degrees, 45-50 degrees, and 50-55 degrees caudally at the level of the inferior acetabular margin and 1 cm and 2 cm below it, respectively, to obtain the most favorable bony purchase.

Acetabulum↗
PubMed1996

Anatomic considerations of plate-screw fixation of the anterior column of the acetabulum.

Fifteen cadaveric adult bony hemipelvis specimens and 30 adult dry bone specimens were obtained to evaluate the configuration of the anterior column of the acetabulum and to develop a safe path for screw placement into it. Each cadaveric specimen was sectioned at 1-cm intervals, beginning at the level of the inferior border of the acetabulum (junction between the anteroinferior edge of the acetabulum and the most anterolateral edge of the superior ramus of the pubic bone). The plane of the cross-section was perpendicular to the anterior column. The projection of the medial acetabular boundary on the anterior column was determined by analysis of each cross-section. Results showed that the average width of the anterior column at 1.0, 2.0, and 3.0 cm superior to the inferior acetabular boundary is 31.0 +/- 4.7, 34.2 +/- 5.1, and 39.4 +/- 6.2 mm, respectively. At 1.0 cm superior to the inferior margin of the acetabulum, the average medial angulation for 0.5-, 1.0-, and 1.5-cm entry points lateral to the pelvic brim were 24.9 +/- 4.4 degrees, 35.5 +/- 5.2 degrees, and 44.4 +/- 6.6 degrees, respectively. At 2.0 cm superior to the inferior acetabular margin, the corresponding average medial angulation for 0.5-, 1.0-, 1.5-cm entry points were determined to be 29.2 +/- 5.5 degrees, 38.6 +/- 5.9 degrees, and 48.1 +/- 5.7 degrees, respectively. At 3.0 cm superior to the inferior acetabular margin, these angles were found to be 20.7 +/- 4.3 degrees, 29.4 +/- 6.0 degrees, and 39.3 +/- 5.9 degrees, respectively. All of the above mentioned angles are with respect to the perpendicular of the longitudinal axis of the anterior column without violation of the hip joint. Screws placed 1.0 cm lateral to the pelvic brim at the levels of 1.0, 2.0, 3.0, and 4.0 cm superior to the inferior acetabular margin and directed perpendicular to the anterior column penetrated the hip joint.

Acetabulum↗
PubMed1996

[Osteoblast-like cells cultured in vitro].

OBJECTIVE: To identify the relationship of osteogenesis and osteoblast-like cells from different tissues, and the shape and functional changes of these cells in their different growing stages. METHODS: Three types of osteoblast-like cells, long spindle-shaped, spherical, and squamous cells were obtained from the fetal calvaria of SD rats or Leghorn chickens cultured in vitro. RESULTS: The long spindle-shaped and the spherical cells developed into the squamous cells. They had the same developing tendency and the same results of development. Three types of cells in their different growing stages displayed separately their functional status. They secreted acid mucopolysaccharide, collagen, calcium salt, alkaline phosphatase, etc. The secreted substances heaped up to form new bone tissues. At the same time there were positive acid phosphatase-staining cells around the new bone tissues. CONCLUSIONS: The cells isolated from the fetal calvaria contained two lines of bone cells, carrying out both bone formation and bone resorption.

Animals↗
PubMed1996

The quantitative anatomy of the iliac vessels and their relation to anterior lumbosacral approach.

Forty embalmed cadavers (24 men and 16 women) were obtained to evaluate the anatomic features of iliac vessels with respect to the anterior approach to the lumbosacral junction. Through a midline longitudinal incision over the linea aspera and retraction of the intraperitoneal contents, exposure of the abdominal aorta, inferior vena cava, and common iliac vessels was done. Direct measurements regarding the relations of these greater vessels to the sacral promontory were then performed. The results showed the average width of the trigone, measured between the medial edges of the left common iliac vein and the right common iliac artery, was 55.9 mm for male and 55.3 mm for female subjects, respectively. The average height of the trigone, measured from its apex to the sacral promontory, was 36.9 mm for male and 35.2 mm for female subjects separately. The width of the uncovered left common iliac vein averaged 7.2 mm for male and 6.3 mm for female subjects, respectively, with a range of 3-11 mm for both male and female specimens. One should be always aware of the medially placed left common iliac vein and an approach medial to the right common iliac artery to the L5-S1 disk is recommended if anterior surgery is desired.

Aged↗
PubMed1996

Radiological evaluation of S1 dorsal screw placement.

Twelve bony pelves were used in this study. S1 dorsal screws were inserted in the anteromedial, anterior, anterolateral, and anteroinferior directions. When the screws were inserted within 5-10 mm beyond the anterior sacral cortex, radiographs were obtained in the anteroposterior, modified inlet, modified outlet, and lateral projections to evaluate the position of the screws and penetration of the anterior cortex. In addition, 30 dried sacral were obtained for anatomic evaluation focused on the anterior and superior aspect of the sacral alae and its relationship to the anterior aspect of the sacrum. The results showed that a screw penetration of the anterior cortex of the S1 vertebral body or ala is best detected in the modified inlet view. A misdirected screw into the S1 anterior foramen is best seen in the modified outlet view. The lateral view also is useful in determining the extraosseous penetration. The average distance from the anteriormost limit of the ala to the anterior sacral cortex was approximately 11 mm. The average sagittal angle between the superior surface of the ala and S1 dorsal aspect was approximately 51 degrees. This study suggested that the modified inlet and lateral radiograph views are most useful for detecting screw penetration of the anterior cortex of the sacrum. The modified outlet projection is the best for determination of a screw violating the S1 anterior foramen. Also, the modified inlet projection will show the screw orientation relative to the mediolateral plane (the sacral canal and sacroiliac joint), and the lateral view will show the screw direction relative to the superoinferior plane.

Adult↗
PubMed1996

[Gastric devascularization for acute gastric mucosal lesion and bleeding].

Thirteen patients with acute gastric mucosal lesion and bleeding were treated with gastric devascularization. Of all, 11 apparently stopped bleeding, two failed to respond to the procedure, one rebled, and three died. Clinical analysis of the patients suggested that low blood pressure, damage of liver function, serious infection, acidosis and uremia were precipitating factors of the disease and for AGML in portal hypertension, the effect of this procedure was poor. Meanwhile, the etiology and pathological mechanism of AGML, the selection of operation types for the disease, and the anatomical and physiological bases of gastric devascularization were also discussed.

Adult↗
PubMed1996

[Influence of electroacupuncture and capsaicin treatment on AChE activity and [3H]-QNB binding sites in the spinal dorsal horn].

1.5% Capsaicin (Cap) or Vehicle was respectively used to treat the right or left sciatic nerve in 20 Sprague-Dawley rats. On the seventh day, the 20 rats were at random divided into electroacupuncture (EA) group and non-EA group, the spinal cord corresponding to the afferent segments of sciatic nerve was taken out for observing the changes of acetylcholinesterase (AChE) activity and [3H]-quinuelidinylbenzylate (QNB) binding sites in the spinal dorsal horn (SDH). The results were as follows: (1) EA "Huantiao" could enhance AChE activity in the SDH and decrease [3H]-QNB binding sites; (2) Cap treating sciatice nerve could weaken AChE activity in the SDH and merease [3H]-QNB binding sites; (3) Cap treatment could inhibit or partially inhibit the actions of EA as above. The results indicated that ACh participated in the primary afferent of acupuncture information and might exist in Cap-sensitive neurons.

Acetylcholinesterase↗
PubMed1996

[Electroacupuncture along meridians activating subcutaneous primary afferents in acupoints--CB-HRP tracing study].

The experiment was performed to observe the segmental distribution of sensory afferent nerves in acupoints and the influence of electroacupuncture (EA) along meridians on it. 1% CB-HRP solution (5 microliters) was injected subcutaneously at unilateral "Zusanli" or "Ruzhong" acupoint of rats. The HRP labeled cells were counted in the related spinal dorsal root ganglia (DRG). The results were as follows: the sensory nerve terminals of "Zusanli" acupoint mainly projected to the neurons of L4 and L5 DRG and that of "Ruzhong" acupoint projected to the neurons of T4, T5 and T6 DRG; sensory nerve terminals of "Zusanli" or "Ruzhong" acupoint were activated by the EA stimulation along meridians, their ability of uptaking HRP was enhanced, so the HRP labeled cells increased in the related DRG, the HRP labeled DRG segments spread. This study provides a new morphological evidence for the mechanism's explanation of propagated sensation along the meridians.

Acupuncture Points↗
PubMed1996

[Quantitative analysis of organochlorine pesticide residues in Chinese drugs].

This paper reports the GC determination of 20 organochlorine pesticides in Chinese drugs Flos Ionicerae and Moluodan etc by the present method of Japan for determinaing pesticide residues. The results suggest that except Folium Isatidis, Radix Codonopsis and Sanqi Pian all accord with the for provisions pesticide residues in Japanese foodstuffs.

Chromatography, Gas↗
PubMed1995

E-cadherin expression is silenced by DNA hypermethylation in human breast and prostate carcinomas.

Expression of the Ca(2+)-dependent, homotypic cell:cell adhesion molecule, E-cadherin (E-cad), suppresses tumor cell invasion and metastasis in experimental tumor models. Decreased E-cad expression is common in poorly differentiated, advanced-stage carcinomas. These data implicate E-cad as an "invasion suppressor" gene. The mechanism by which E-cad is silenced in advanced stage carcinomas is unclear. In this report, we show that: (a) the 5' CpG island of E-cad is densely methylated in E-cad-negative breast and prostate carcinoma cell lines and primary breast carcinoma tissue but is unmethylated in normal breast tissue; (b) treatment with the demethylating agent, 5-aza-2'-deoxycytidine, partially restores E-cad RNA and protein levels in E-cad-negative breast and prostate carcinoma cell lines; and (c) and E-cad promoter/CAT construct is expressed in both E-cad-positive and -negative breast and prostate carcinoma cell lines, indicating that these cells have the active transcriptional machinery necessary for E-cad expression. Our data demonstrate that frequent loss of E-cad expression in human breast and prostate carcinomas results from hypermethylation of the E-cad promoter region.

Base Sequence↗