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Biomedical subjects

R Xu

Publications and source records attributed to R Xu.

At least 307 records · Page 17Linked to original sources
PubMed1993

The presence of mast cells in the human endometrium pre- and post-insertion of intrauterine devices.

A study of the density of mast cells in the human endometrium was carried out on biopsy specimens prepared for light microscopy in 87 cases with three types of IUDs (stainless steel ring SS-type, copper Cu-T 220 and LNG-IUD levonorgestrel-releasing device) pre- and post-insertion. The results revealed that, in general, there was an increase of mast cells after 3 to 24 months' use of IUD, independent of type (p < 0.01 when compared with the pre-insertion value). The increase in number of mast cells was most prominent in women having used the Cu-T220 IUD for 24 months (p < 0.05 when compared with the SS-IUD and p < 0.01 when compared with the LNG-IUD). The difference between the SS-IUD and the LNG-IUD as to the number of mast cells was not significant. No significant difference was found between the "bleeders" and "non-bleeders" in any of the three types of IUDs. It is noteworthy that patients using the Cu-T220-IUD had the highest percentage of patients with abnormal bleeding (> 50%) and that this group also had the highest density of mast cells per mm2 after 24 months' use. Although no significant difference with regard to the density of mast cells could be found between the "bleeders" and the "non-bleeders" in the present study, the number of "bleeders" of the three study groups is usually small and sometimes this number does not allow an adequate statistical analysis for comparison. Further investigations, involving larger number of IUD users, may yield a better understanding with regard to the potential relationship between the number of bleeding episodes and the density of mast cells in the human endometrium.

Adult↗
PubMed1993

White sturgeon tissue fatty acid compositions are affected by dietary lipids.

Juvenile white sturgeon (Acipenser transmontanus) were fed eight isonitrogenous and isoenergetic purified diets for 9 wk to study their ability to utilize different dietary lipids. Each diet contained 15% of control oil mixture (corn oil-cold liver oil-lard, 1:1:1), corn oil, cod liver oil, lard, linseed oil, soybean oil, safflower oil or canola oil. No significant (P > 0.05) differences in percentage of body weight increase, feed efficiency or body composition were observed among sturgeon fed the different lipids. Tissue fatty acid compositions most sensitive to dietary lipids were those of muscle and liver, whereas brain fatty acid composition was the least sensitive. Results of this study indicate that it is possible to increase the levels of (n-3) polyunsaturated and highly unsaturated fatty acids in sturgeon muscle by feeding the fish lipids high in these fatty acids for 9 wk.

Animals↗
PubMed1993

The cardiac troponin T alternative exon contains a novel purine-rich positive splicing element.

We have characterized a novel positive-acting splicing element within the developmentally regulated alternative exon (exon 5) of the cardiac troponin T (cTNT) gene. The exon splicing element (ESE) is internal to the exon portions of the splice sites and is required for splicing to the 3' splice site but not the 5' splice site flanking the exon. Sequence comparisons between cTNT exon 5 and other exons that contain regions required for splicing reveal a common purine-rich motif. Sequence within cTNT exon 5 or a synthetic purine-rich motif facilitates splicing of heterologous alternative and constitutive splice sites in vivo. Interestingly, the ESE is not required for the preferential inclusion of cTNT exon 5 observed in primary skeletal muscle cultures. Our results strongly suggest that the purine-rich ESE serves as a general splicing element that is recognized by the constitutive splicing machinery.

Alternative Splicing↗
PubMed1993

Loss of cancellous bone mass and connectivity in ovariectomized rats can be restored by combined treatment with parathyroid hormone and estradiol.

To evaluate the potential use of a combination of antiresorption and bone formation-promoting agents as a treatment for postmenopausal osteoporosis, we examined the effects of combined and separate administration of estrogen (17 beta-estradiol, 30 micrograms/kg per d, s.c.) and parathyroid hormone (rPTH [1-34], 40 micrograms/kg per d, s.c.) on the proximal tibia of ovariectomized (Ovx) rats. The treatments lasted for 4 wk and were initiated 1, 3, and 5 wk after surgery. Ovx resulted in rapid loss of cancellous bone volume (Cn-BV/TV) as well as trabecular connectivity, as determined by two dimensional strut analysis. When administered in a preventive mode, treatment beginning 1 wk post-Ovx, estrogen or PTH treatment alone preserved Cn-BV/TV and trabecular connectivity, and combined estrogen and PTH treatment caused a 40% increment in Cn-BV/TV while maintaining comparable trabecular connectivity with that seen in the Sham-operated animals. When administered in a curative mode to rats with established osteoporosis, treatments beginning 3 or 5 wk post-Ovx, estrogen or PTH treatment alone prevented further loss of connectivity and Cn-BV/TV, whereas the combined treatment resulted in as much as a 300% improvement in one of the parameters of trabecular connectivity, node to node strut length, and a 106% increase in Cn-BV/TV, with respect to the bone status at the initiation of treatment. The beneficial effects of this combined treatment derive from estrogen's ability to prevent accelerated bone resorption and, simultaneously, PTH's promotion of bone formation. These data demonstrate, in an animal model, that therapies can be devised to cure the skeletal defects associated with established osteoporosis.

Animals↗
PubMed1993

[Influence of capsaicin treating sciatic nerve on the pain threshold and the effect of acupuncture analgesia of rats].

The model of local application of 1.5% Capsaicin (Cap) on the right sciatic nerve and control of Vehicle (Veh) on the left were used. The influence of Cap on pain threshold, electroacupuncture (EA) analgesia and Fluoride-resistant acid phosphatase (FRAP) activity in the dorsal horn of spinal cord were observed. The results showed, the pain threshold of Cap treatment side rose significantly compared with the control side, FRAP in dorsal horn of spinal cord vanished, and the analgesic effect of EA at "Huantiao" of the Cap treatment side markedly decreased, compared with not only that EA at the control side but also that EA before Cap treatment. It is indicated that the C fibers of the primary afferent participate in the input of pain and EA analgesic information.

Acid Phosphatase↗
PubMed1993

Degradation of two AChR populations at rat neuromuscular junctions: regulation in vivo by electrical stimulation.

The effect of electrical stimulation on the stability of junctional ACh receptors (AChR) on soleus muscles of Wistar rats was compared to that of denervation and reinnervation. Denervation causes the degradation rate of the slowly degrading AChRs (Rs) at the neuromuscular junction to accelerate and be replaced by rapidly degrading AChRs (Rr), while reinnervation restabilizes the accelerated Rs. Electrical stimulation initiated at the time of denervation prevented the acceleration of the Rs. It could not, however, reverse the effect of denervation if initiated after the AChRs became destabilized, nor could it slow the degradation rate of the Rr. We conclude that electrical stimulation of denervated muscle downregulates the expression of the Rr and prevents the destabilization of Rs.

Animals↗
PubMed1992

Differences in unwinding of supercoiled DNA induced by the two enantiomers of anti-benzo[a]pyrene diol epoxide.

The unwinding of supercoiled phi X174 RFI DNA induced by the tumorigenic (+) and non-tumorigenic (-) enantiomers of trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) has been investigated by agarose slab-gel and ethidium titration tube gel electrophoresis. The differences in adduct conformations were verified by flow linear dichroism techniques. Both enantiomers cause a reversible unwinding by the formation of noncovalent intercalative complexes. The effects of covalently bound BPDE residues on the electrophoretic mobilities of the RF I DNA form in agarose gels were investigated in detail in the range of binding ratios rb approximately 0.0-0.06 (covalently bound BPDE residues/nucleotide). In this range of rb values, there is a striking difference in the mobilities of (+)-BPDE- and (-)-BPDE-adducted phi X174 DNA in agarose slab-gels, the covalently bound (+)-BPDE residues causing a significantly greater retardation than (-)-BPDE residues. Increasing the level of covalent adducts beyond rb approximately 0.06 in the case of the (+)-BPDE enantiomer, leads to further unwinding and a minimum in the mobilities (corresponding to comigration of the nicked form and the covalently closed relaxed modified form) at rb 0.10 +/- 0.01; at still higher rb values, rewinding of the modified DNA in the opposite sense is observed. From the minimum in the mobility, a mean unwinding angle (per BPDE residue) of theta = 12 +/- 1.5 degrees is determined, which is in good agreement the value of theta = 11 +/- 1.8 degrees obtained by the tube gel titration method. Using this latter method, values of theta = 6.8 +/- 1.7 degrees for (-)-BPDE-phi X174 adducts are observed. It is concluded that agarose slab gel techniques are not suitable for determining unwinding angles for (-)-BPDE-modified phi X174 DNA because the alterations in the tertiary structures for rb < 0.06 are too small to cause sufficiently large changes in the electrophoretic mobilities. The major trans (+)-BPDE-N2-guanosine covalent adduct is situated at external binding sites and the mechanisms of unwinding are therefore different from those relevant to noncovalent intercalative BPDE-DNA complexes or to classical intercalating drug molecules; a flexible hinge joint and a widening of the minor groove at the site of the lesion may account for the observed unwinding effects. The more heterogeneous (-)-BPDE-nucleoside adducts (involving cis and trans N2-guanosine, and adenosine adducts) are less effective in causing unwinding of supercoiled DNA for reasons which remain to be elucidated.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1992

Acid pH-induced conformational changes in bovine liver rhodanese.

The enzyme rhodanese is greatly stabilized in the range pH 4-6, and samples at pH 5 are fully active after several days at 23 degrees C. This is very different from results at pH greater than 7, where there is significant loss of activity within 1 h. A pH-dependent conformational change occurs below pH 4 in a transition centered around pH 3.25 that leads slowly to inactive rhodanese at pH 3 (t 1/2 = 22 min at pH3). The inactive rhodanese can be reactivated by incubation under conditions required for detergent-assisted refolding of denatured rhodanese. The inactive enzyme at pH 3 has the maximum of its intrinsic fluorescence spectrum shifted to 345 nm from 335 nm, which is characteristic of native rhodanese at pH greater than 4. At pH 3, rhodanese shows increased exposure of organized hydrophobic surfaces as measured by 1,1'-bis(4-anilino)naphthalene-5,5'-disulfonic acid binding. The secondary structure is maintained over the entire pH range studied (pH 2-7). Fluorescence anisotropy measurements of the intrinsic fluorescence provide evidence suggesting that the pH transition produces a state that does not display greatly increased average flexibility at tryptophan residues. Pepsin digestibility of rhodanese follows the pH dependence of conformational changes reported by activity and physical methods. Rhodanese is resistant to proteolysis above pH 4 but becomes increasingly susceptible as the pH is lowered. The form of the enzyme at pH 3 is cleaved at discrete sites to produce a few large fragments. It appears that pepsin initially cleaves close to one end of the protein and then clips at additional sites to produce species of a size expected for the individual domains into which rhodanese is folded. Overall, it appears that in the pH range between pH 3 and 4, titration of groups on rhodanese leads to opening of the structure to produce a conformation resembling, but more rigid than, the molten globule state that is observed as an intermediate during reversible unfolding of rhodanese.

Animals↗
PubMed1992

[Activation of delta-opiate receptor simultaneously stimulates ACTH beta-endorphin and prolactin release].

To evaluate a possible physiological and pathological role of brain delta-opiate receptor and endogenous ligands in the control of ACTH, beta-endorphin (beta-EP) and prolactin (PRL) release, a specific agonist of the delta-opiate receptor--[D-Pen2, D-Pen5]-enkephalin (DPDPE) was microinjected into the third cerebral ventricle (1 microgram or 3 micrograms/3 microliters/rat) in conscious freely-moving male rats. Plasma ACTH, beta-EP and PRL concentrations were measured by radioimmunoassay (RIA). Our results clearly indicate that third ventricular injection of DPDPE significantly elevates plasma ACTH, beta-EP and PRL levels in comparison with control values, and that the stimulatory effects of DPDPE on the release of the three hormones are dose-related at 1 and 3 micrograms. The data suggest that activation of the delta-opiate receptor may be a mechanism behind the concomitant release of ACTH, beta-EP and PRL during stress and certain pathologic conditions.

Adrenocorticotropic Hormone↗
PubMed1992

[Mechanisms of protective action of radix Salviae miltiorrhizae (RSM) against experimental hepatic injury in rats].

The results indicated that RSM could significantly inhibit the lipid peroxidation of normal livers and cultured hepatocytes of rats, induce liver microsomal cytochrome P450 in normal rats, increase nucleic acids, proteins, urea and cerolloplasmin of damaged cultured hepatocytes of rats, relieve ultrastructural damage of cultured hepatocytes induced by CCl4. The pharmacological actions mentioned above should be considered as important mechanisms of RSM against liver injury.

Animals↗
PubMed1992

[Antioxidative effect of Chinese drugs].

The antioxidative effect of more than 50 ethanol extracts of Chinese drugs were studied on the air oxidation of linoleic acid. Several ethanol extracts such as Glycyrrhiza uralensis, Magnolia officinalis and Zingiber officinale etc., were found having stronger antioxidative effect.

Antioxidants↗
PubMed1992

Clinical and experimental studies on tong yu ling in the treatment of diabetic hyperlipemia.

72 diabetes mellitus patients (70 cases non-insulin-dependent) were treated routinely with D860. After one month, cases with persisting hyperglycemia and hyperlipemia were randomly divided into Group A to be treated with D860 plus Tong Yu Ling (TYL), and Group B to continue treatment with D860 alone, while Group C, comprising cases with persisting hyperlipemia only, were treated with TYL alone. Therapeutic results showed that of the total 50 cases of Group A and C, 26 were markedly improved, 14 improved, and 10 cases ineffective. The antihyperlipemic effect was pronounced in Group A, where the blood cholesterol, beta-lipoprotein and triglyceride showed remarkable decline, less pronounced in Group C, and insignificant in Group B. Experiments in rat models of non-insulin-dependent diabetes demonstrated that TYL was markedly effective in treating hyperlipemia.

Adult↗
PubMed1992

Graft-specific MHC class II gene expression in response to allogeneic stimulus in heterotopic murine cardiac allografts.

Although, major histocompatibility complex (MHC) class II antigen expression in allografts is thoroughly studied, regulation of the genes for these antigens is not fully understood. The graft-specific MHC class II genes are potentially important in determining the immunogenicity of graft but their detection in a mixed-cell population such as in the allograft would require unambiguous differentiation of graft-specific class II expression from those in host lymphoid cells. With an oligonucleotide probe that specifically hybridizes to I-Ab mRNA from H-2k haplotype mice, we have studied I-A gene expression in cardiac allografts heterotopically transplanted from B10.Br (H-2k) to B10.D2 (H-2d) mice. Normal B10.Br hearts do not have appreciable I-Ab transcripts as determined with this probe, but 4 days after allografting, a substantial increase in I-Abk messenger RNA (mRNA) content was noted in the allografted hearts which persisted for the next 2 days and then decreased concomitant with destruction of the heart. The increase in I-Abk mRNA preceded the expression of surface Iak antigens on dendritic and endothelial cells in the allograft. These data indicate increased transcription of the I-Ab gene in cells of graft origin suggesting that transcriptional regulation is the initial mechanism for expression of class II genes in allografts. The sustained rise in graft-specific class II mRNA also seen in these allografts suggests that increased mRNA stability may be another mechanism for the increased density of class II antigens in allografts undergoing rejection.

Animals↗