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Biomedical subjects

X Ma

Publications and source records attributed to X Ma.

At least 181 records · Page 10Linked to original sources
PubMed1999

Ursodeoxycholic acid prevents cytochrome c release in apoptosis by inhibiting mitochondrial membrane depolarization and channel formation.

The hydrophilic bile salt ursodeoxycholic acid (UDCA) is a potent inhibitor of apoptosis. In this paper, we further characterize the mechanism by which UDCA inhibits apoptosis induced by deoxycholic acid, okadaic acid and transforming growth factor beta1 in primary rat hepatocytes. Our data indicate that coincubation of cells with UDCA and each of the apoptosis-inducing agents was associated with an approximately 80% inhibition of nuclear fragmentation (P<0.001). Moreover, UDCA prevented mitochondrial release of cytochrome c into the cytoplasm by 70 - 75% (P<0.001), thereby, inhibiting subsequent activation of DEVD-specific caspases and cleavage of poly(ADP-ribose) polymerase. Each of the apoptosis-inducing agents decreased mitochondrial transmembrane potential and increased mitochondrial-associated Bax protein levels. Coincubation with UDCA was associated with significant inhibition of these mitochondrial membrane alterations. The results suggest that the mechanism by which UDCA inhibits apoptosis involves an interplay of events in which both depolarization and channel-forming activity of the mitochondrial membrane are inhibited.

Animals↗
PubMed1999

Differential effects of traumatic brain injury on vesicular acetylcholine transporter and M2 muscarinic receptor mRNA and protein in rat.

Experimental traumatic brain injury (TBI) produces cholinergic neurotransmission deficits that may contribute to chronic spatial memory deficits. Cholinergic neurotransmission deficits may result from presynaptic alterations in the storage and release of acetylcholine (ACh) or from changes in the receptors for ACh. The vesicular ACh transporter (VAChT) mediates accumulation of ACh into secretory vesicles, and the M2 muscarinic receptor subtype can modulate cholinergic neurotransmission via a presynaptic inhibitory feedback mechanism. We examined the effects of controlled cortical impact (CCI) injury on hippocampal VAChT and M2 muscarinic receptor subtype protein and medial septal mRNA levels at 4 weeks following injury. Rats were anesthetized and surgically prepared for CCI injury (4 m/sec, 2.5 to 2.9 mm in depth) and sham surgery. Animals were sacrificed, and coronal sections (35 microm thick) were cut through the dorsal hippocampus for VAChT and M2 immunohistochemistry. Semiquantitative measurements of VAChT and M2 protein in hippocampal homogenates from injured and sham rats were assessed with Western blot analysis. Changes in VAChT and M2 mRNA levels were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). At 4 weeks after injury, both immunohistochemical and Western blot methods demonstrated an increase in hippocampal VAChT protein. An increase in VAChT mRNA was also observed. Immunohistochemistry demonstrated a loss of M2; however, there was no significant change in M2 mRNA levels in comparison with sham controls. These changes may represent a compensatory response of cholinergic neurons to increase the efficiency of ACh neurotransmission chronically after TBI through differential transcriptional regulation.

Acetylcholine↗
PubMed1999

Recognition of multiple patterns of DNA sites by Drosophila homeodomain protein Bicoid.

Our previous studies demonstrated that the Drosophila homeodomain protein, Bicoid (Bcd), binds DNA cooperatively. In this study, we determined the patterns of adjacent DNA sites required for cooperative recognition by Bcd. Our in vitro selection and biochemical experiments demonstrated that Bcd binds preferentially to both head-to-head and tail-to-tail symmetric sites that are separated by short spacing. An increase in the spacing reduces the strict requirement of symmetric patterns of adjacent sites, permitting Bcd to recognize tandem repeat sites cooperatively. Our further experiments in vivo showed that the only pair of optimally spaced symmetric Bcd sites in a hunchback (hb) enhancer element contributes the most to transcriptional activation by Bcd, demonstrating the biological importance of the binding site patterns revealed by our in vitro selection studies.

Animals↗
PubMed1999

Differential regulation of prostaglandin EP and FP receptors in pregnant sheep myometrium and endometrium during spontaneous term labor.

In the present study, we characterized the mRNA abundance of prostaglandin E(2) receptor subtypes (EP1 and EP3, which stimulate excitatory responses; EP2 and EP4, which stimulate inhibitory responses) and the FP receptor in pregnant sheep myometrium and endometrium in relation to parturition. Myometrial and endometrial poly(A) RNA was extracted from control ewes at 143-147 days gestational age (dGA, n = 6) and from ewes in spontaneous term labor at 145-147 dGA (n = 6), and was subjected to Northern blot analysis for FP, EP1, EP2, EP3, and EP4 mRNA. Myometrial EP3, EP4, and FP mRNA abundance increased during labor (P<0.05); EP2 mRNA did not change. EP1 mRNA was not detectable in the myometrium. Endometrial EP2 and EP4 mRNA remained unchanged during labor. EP3 mRNA was expressed at a very low level, and EP1 and FP mRNA were not detected in endometrium in any animals studied. In conclusion, there is differential expression in myometrium and endometrium of EP subtypes and FP receptor in relation to labor. Increases in EP3 and FP, together with increased prostaglandin production from intrauterine tissues, may lead to the switch in the myometrial contraction pattern that occurs during labor. These differences within and between myometrium and endometrium may result from different anatomical location, such as longitudinal or circular layers of myometrium, or vascular location.

Animals↗
PubMed1999

Monte Carlo simulations of liquid spreading on a solid surface: effect of end-group functionality.

The spreading of liquid droplets composed of molecules with or without reactive end groups over a solid surface has been studied using Monte Carlo simulations. For molecules without reactive end groups, a molecular layering in the spreading profiles is predicted, depending on the ratio of the magnitude of intermolecular interactions to thermal energy. As intermolecular interactions become smaller than thermal energy, the layered structure vanishes. For molecules with reactive end groups, interactions between end groups and between end groups and the surface complicate the situation. By assuming an end-to-end interaction between molecules and the pinning of end groups to the surface, a complex layered structure is obtained. Our simulation predicts spreading profiles that accurately describe the broad spectrum of data obtained from scanning microellipsometry for perfluoropolyalkylethers with and without reactive end groups.

Journal Article↗
PubMed1999

Genetic and functional analyses of the conserved C-terminal core domain of Escherichia coli FtsZ.

In Escherichia coli, FtsZ is required for the recruitment of the essential cell division proteins FtsA and ZipA to the septal ring. Several C-terminal deletions of E. coli FtsZ, including one of only 12 amino acids that removes the highly conserved C-terminal core domain, failed to complement chromosomal ftsZ mutants when expressed on a plasmid. To identify key individual residues within the core domain, six highly conserved residues were replaced with alanines. All but one of these mutants (D373A) failed to complement an ftsZ chromosomal mutant. Immunoblot analysis demonstrated that whereas I374A and F377A proteins were unstable in the cell, L372A, D373A, P375A, and L378A proteins were synthesized at normal levels, suggesting that they were specifically defective in some aspect of FtsZ function. In addition, all four of the stable mutant proteins were able to localize and form rings at potential division sites in chromosomal ftsZ mutants, implying a defect in a function other than localization and multimerization. Because another proposed function of FtsZ is the recruitment of FtsA and ZipA, we tested whether the C-terminal core domain was important for interactions with these proteins. Using two different in vivo assays, we found that the 12-amino-acid truncation of FtsZ was defective in binding to FtsA. Furthermore, two point mutants in this region (L372A and P375A) showed weakened binding to FtsA. In contrast, ZipA was capable of binding to all four stable point mutants in the FtsZ C-terminal core but not to the 12-amino-acid deletion.

Bacterial Proteins↗
PubMed1999

PAF binding to a single receptor in corneal epithelium plasma membrane.

PURPOSE: To study the binding characteristics and the expression of platelet-activating factor receptors (PAF-R) in corneal epithelium to elucidate the site of action of PAF. METHODS: Binding of [3H]PAF was investigated in subcellular fractions of the epithelia of bovine corneas and in membranes from cultured rabbit corneal epithelial cells. Dose-response inhibition curves of [3H]PAF-specific binding were generated using increasing concentrations of several PAF-R antagonists. RNA from rabbit corneal epithelial cells was probed for PAF-R expression by reverse transcription-polymerase chain reaction (RT-PCR) with specifically designed degenerated primers. RESULTS: Scatchard analysis showed a high-affinity binding site in bovine and rabbit corneal epithelium. The dissociation constant (Kd) and the maximum binding sites (Bmax) in a bovine membrane preparation and similar rabbit fraction were 0.77+/-0.03 nM and 180+/-21 femtomoles/mg protein and 4.3 nM and 1.3 picomoles/mg protein, respectively. Specific PAF-binding sites were found in bovine preparations enriched in plasma membranes with a Kd = 69.6 pM and Bmax = 80 femtomoles/mg protein; no specific binding was found in nuclei or microsomal fractions. RT-PCR of rabbit corneal epithelium generated a single product of the predicted size (478 bp). The deduced amino acid sequence of the purified PCR product was 87% homologous to human PAF-R. The hetrazepines BN 50727 and BN 50730 and the PAF structural analogues CV 3988 and CV 6209 competitively inhibited [3H]PAF binding to corneal epithelium with similar potency. WEB 2086 BS was two orders of magnitude less active in antagonizing PAF binding. CONCLUSIONS: Corneal epithelium contains a single population of receptors localized in the plasma membrane. PAF antagonists exert their actions by blocking this PAF-R. The partial sequence deduced in rabbit corneal PAF-R show a higher homology to the human PAF-R.

Amino Acid Sequence↗
PubMed1999

New buccinator myomucosal island flap: anatomic study and clinical application.

The authors studied the vascular anatomy of the buccinator muscle by dissecting fresh cadavers. The anatomy of the buccal branches of the facial artery consistently confirmed the existence of a posterior buccal branch, a few inferior buccal branches, and anterior buccal branches to the posterior, inferior, and anterior portions of the buccinator. The buccal artery and posterior buccal branch anastomose to each other and ramify over the muscle. Several veins originate from the lateral aspect of the muscle, converge into the buccal venous plexus, and drain into the facial vein (from two to four tributaries) or into the pterygoid plexus and the internal maxillary vein (from the buccal vein). These vessels and nerves enter the posterior half of the buccinator posterolaterally. The facial artery and vein are located at variable distances from each other around the oral commissure and the nasal base. Two patterns of buccinator musculomucosal island flaps supplied by these buccal arterial branches are proposed in this article. The buccal musculomucosal neurovascular island flap (posteriorly based), supplied by the buccal artery, its posterior buccal branch, and the long buccal nerve, can be passed through a tunnel under the pterygomandibular ligament for closure of mucosal defects in the palate, pharyngeal sites, the alveolus, and the floor of the mouth. The buccal musculomucosal reversed-flow arterial island flap (superiorly based), supplied by the distal portion of the facial artery through the anterior buccal branches, can be used to close mucosal defects in the anterior hard palate, alveolus, maxillary antrum, nasal floor and septum, lip, and orbit. The authors have used the flaps in 12 patients. There has been no flap necrosis, and results have been satisfactory, both aesthetically and functionally.

Adult↗
PubMed1999

[A prevalence study on injuries among 2,553 children 7-16 years old].

OBJECTIVE: In order to find out the present situation and cause of injuries among children. METHODS: A cluster sampling study on the conditions of injuries was conducted among 2,553 children 7-16 years old during the period of October 1996 to September 1997 in Shantou City, Guangdong Province. RESULTS: There was a trend that the incidence of injuries increased with age among children. The overall incidence of injuries was 37.96% with schoolboys higher than schoolgirls (P < 0.05). There were 38.1% children who had more than two episodes. Falls took the leading type of incidence among both sexes and all age groups. Among the causes of injuries, playing, motion, riding and walking ranked the consecutive leading 4 places. The places where injuries occurred were mainly at home and then on campus. Self injured was mostly seen followed with hurt by others (classmate, sibling, et al). Medium and serious injuries took up 8% with a disability rate of 121.4/100,000. CONCLUSION: Some preventive measures were preliminarily suggested.

Adolescent↗
PubMed1999

Baculovirus expression of the major surface antigen of Toxoplasma gondii and the immune response of mice injected with the recombinant P30.

The major surface antigen (P30) of the Toxoplasma gondii was expressed by an insect cell culture system infected with recombinant baculovirus. About 750 microg of purified (95% purity) P30 was obtained from a culture of 10(8) insect Sf21 cells. The recombinant P30 was used to immunize mice to induce immune response. Mice injected with the recombinant protein produced specific humoral and cellular immune responses. Immunization with P30 also prolonged the period of survival of mice infected by Toxoplasma. The average survival time of control group is 13.25+/-1.16 days, but are 16.13+/-2.1 days, 19.50+/-3.21 days, 20.38+/-3.38 days in different immunized groups, respectively.

Animals↗
PubMed1999

[Prevention and treatment of eyelid retraction and ectropion following lower eyelid blepharoplasty with tarsal tuck procedure].

OBJECTIVE: To prevent or decrease eyelid retraction and ectropion following lower eyelid blepharoplasty. METHODS: The tarsal tuck procedure was performed during lower eyelid blepharoplasty to tighten the lower eyelid. This method had been used since 1991. RESULTS: After the operation, the lower eyelid was tensional and steady. The complications of eyelid retraction and ectropion were diminished. CONCLUSION: The pathologic basis of the eyelid bag is that the supporting tissues become lax so that the lower eyelid and lateral canthus move downwards. The exact aim of the tarsal tuck procedure is to correct these pathologic changes.

Blepharoplasty↗
PubMed1999

[A historical review of the study of electrical activity of heart and origination of electrocardiography].

This paper has an overall review of the historical process of electrocardiographic development and the origination of modern electrocardiography in retrospect and also has an analysis of the scientific background, the important events and the historical effect of outstanding figures throughout the development. The experience and laws contained in the historical development are briefly summerized in this paper. At the same time the authors point out that the establishment of modern electrocardiography and the related technical development are crystallization of the wisdom and the result of the hard work of many scientists including the figures who should have been awarded Nobel Prizes.

Biophysics↗
PubMed1999

[The relationship between IgA nephropathy and HBV infection].

OBJECTIVE: To clarify the correlation between hepatitis B virus (HBV) infection and the pathogenesis of IgA nephropathy. METHODS: Ninety-one cases of primary IgA nephropathy were investigated by using in situ hybridization(HBV DNA), immunohistochemistry (HBAg) and HBV DNA-HBAg double staining techniques. In some of the cases, Southern blot analysis and serologic HBV infectious markers were detected also. RESULTS: The positive rate of HBAg in renal tissue detected by immunohistochemistry was 69% (63/91) and that of the HBV DNA detected by in situ hybridization was 43% (39/91). Eighteen of 27 cases showed HBV DNA positive in Southern blot analysis, and all of the positive cases were identified to be the integrated form. Among them, 17 cases were HBAg detectable in renal tissue by immunohistochemistry and 16 cases were HBV DNA detectable by in situ hybridization simultaneously. The positive rate of the expression of HBcAg [77% (30/39)] and HBsAg [72% (28/39)] of the tubular epithelial cells with HBV DNA signals in nuclears by in situ hybridization was significantly higher than that of the cells without HBV DNA signals(10%, 21%). The double staining showed that most of the HBV DNA positive tubular epithelial cells coexpressed HBsAg and(or) HBcAg. CONCLUSION: The renal tissue of some of IgA nephropathy infected with HBV directly and express HBAg in situ.

Adult↗
PubMed1999

[Sodium arsenite selectively inducing apoptosis of G2 + M phase NB4 cells].

OBJECTIVE: To explore the mechanism of sodium arsenite inducing apoptosis of NB4 cells. METHODS: The apoptosis of NB4 cells was studied by flow cytometry, DNA gel electrophoresis and Western blot analysis. RESULTS: 1. Sodium arsenite induced apoptosis of NB4 cells while the cells were arrested in G2 + M phase; 2. dUTP-FITC specifically labeled NB4 cells in G2 + M phase after the cells were treated with sodium arsenite; 3. After the treatment the expressions of cyclin A, E, D1, D2 and D3 of the NB4 cells did not change significantly, while the expression of cyclin B1 was up-regulated with prolongation of the treatment; 4. Some of S phase NB4 cells expressed high level cyclin B1 during the early period of treatment (16 h), but most of NB4 cells expressing high level of cyclin B1 were in G2 + M phase. CONCLUSION: Sodium arsenite selectively induced apoptosis of G2 + M phase NB4 cells, accompanied by upregulation of cyclin B1.

Apoptosis↗
PubMed1999

[Pathologic study on synovial fluid after intra-articular corticosteroid therapy in temporomandibular joint disorders].

OBJECTIVE: To study what happens after intra-articular injection of corticosteroid. METHODS: Synovial fluid after intra-articular corticosteroid therapy in temporomandibular joint disorders (TMD) was studied by hematoxylin-eosin, PAS, and Atcian blue staining. RESULTS: The results were that broken synovial membrane and articular cartilage, lots of synovial lining cells, macrophagocytes, inflammatory cells and free cartilage matrix could be found in the lavage fluid. CONCLUSION: The results suggest that drug synovectomy may be one mechanism about intra-articular corticosteroid therapy in TMD, and this therapy could lead to progressive degradation and destruction of the articular cartilage. Arthrocentesis and lavage are needed three to five days after this therapy.

Adolescent↗
PubMed1999

[Experimental study on three-dimensional adjustable condyle prosthesis for reconstruction of temporomandibular joint].

OBJECTIVE: To study the possibility of reconstructing TMJ with a modified three-dimensional adjustable condylar prosthesis (TDACP). METHODS: The modified TDACP was placed immediately after resection of the mandibular ramus and condyle in 3 adult rhesus monkeys. The results were evaluated by radiography, histological and anatomical examinations, as well as chewing function at 3, 6, and 14 months after surgery. RESULTS: Through adjustment the condyle prosthesis could fit exactly, the functions were good, every part of the prosthesis was firm, the screws were osteointegrated, there was no adverse soft tissue reactions and no pathological changes in the TMJ of non-operated opposite condyle. Problems were: the distribution of fixation stress of screws was somewhat unreasonable, the downward sliding of the condyle was limited, there was erosion of the posterior slope of the glenoid fossa, and the articular disc could not keep its in situ place and function. CONCLUSION: The results suggests that the prosthesis needs further improvement.

Animals↗
PubMed1999

[Improved method of obtaining medial plantar cutaneous graft and its clinical application].

OBJECTIVE: To introduce a skin flap containing the middle cutaneous branch of the medial plantar artery. METHODS: Microanatomic study was performed on 8 fresh cadaveric feet, the arteries were dissected and infused with methylene blue to observe their vascular distribution and the skin area supplied by the middle cutaneous branch. Furthermore, the clinical application was reported. A local pedicled flap containing the middle cutaneous branch was used to repair the soft tissue defects of the foot in 7 patients, and free cutaneous graft was used to repair the skin defects of the fingers in 6 patients. RESULTS: The results showed that the medical plantar artery gave off 3 cutaneous branches to supply the medial aspect of the foot, among which the middle branch was the largest one and anastomosed with the other two branches. The skin flaps used clinically were all survived completely. CONCLUSION: Medial plantar cutaneous graft had a reliable blood supply, and it's one of the best choice in repairing small to middle sized skin defects of the foot and the fingers.

Adolescent↗