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Biomedical subjects

X Xu

Publications and source records attributed to X Xu.

At least 577 records · Page 32Linked to original sources
PubMed1998

Association of petrochemical exposure with spontaneous abortion.

OBJECTIVES: To assess the association between petrochemical exposure and spontaneous abortion, a retrospective epidemiological study in a large petrochemical complex in Beijing, China was conducted. METHODS: Plant employment records identified 3105 women who were married, were 20-44 years of age, and had never smoked. Of those, 3070 women (98.8%) reported at least one pregnancy. From this group, 2853 (93%) of the women participated in the study. According to their plant employment record, about 57% of these women workers reported occupational exposure to petrochemicals during the first trimester of their pregnancy. Trained interviewers administered a standardised questionnaire to this group of women and their husbands, collecting information on reproductive history, pregnancy outcomes, employment history, occupational exposure, smoking habits, alcohol consumption, indoor air pollution, and demographic variables. The results from the womens' first pregnancies were analysed. RESULTS: There was a significantly increased risk of spontaneous abortion for women working in all of the production plants with frequent exposure to petrochemicals (8.8%; range of 5.8%-9.8%) compared with those working in nonchemical plants (2.2%; range of 0.0%-7.1%). Also, when a comparison was made between exposed and non-exposed groups within each plant, exposure to petrochemicals was consistently associated with an increased risk of spontaneous abortion. The overall odds ratio (OR) was 2.7 (95% confidence interval (95% CI) 1.8 to 3.9) after adjusting for potential confounders. When the analysis was performed with the exposure information obtained from the women' interview responses for (self reported) exposures, the estimated OR for spontaneous abortions was 2.9 (95% CI 2.0 to 4.0). The analysis was repeated by excluding those 452 women who provided inconsistent reports between recalled exposure and work history, and a comparable risk of spontaneous abortion (OR 2.9; 95% CI 2.0 to 4.4) was found. In analyses for exposure to specific chemicals, an increased risk of spontaneous abortion was found with exposure to most chemicals, and the results for benzene (OR 2.5; 95% CI 1.7 to 3.7), gasoline (OR 1.8; 95% CI 1.1 to 2.9), and hydrogen sulphide (OR 2.3; 95% CI 1.2 to 4.4) were significant. CONCLUSION: An increased risk of spontaneous abortion was found associated with the exposure to petrochemicals, including benzene, gasoline, and hydrogen sulphide.

Abortion, Spontaneous↗
PubMed1998

Elevated growth hormone increases the Ca2+ sensitivity of slow- and fast-twitch skeletal muscle of female rats.

To determine the effect of plasma growth hormone (GH) on skeletal muscle function, we measured the free Ca2+ concentration-tension relationship of slow-twitch (soleus) and fast-twitch (peroneus longus) muscles isolated from rats undergoing acromegaly in response to implanted, GH-secreting tumors. Muscles from adult (9 mo) and aged rats (24 mo) were studied after the tumor-bearing rats weighted over 50% more than their age-matched controls. Ca(2+)-activated isometric tension was recorded from skinned muscle fibers. For soleus muscles, the free Ca2+ concentration producing 50% of maximal tension ([Ca2+]50) was 2.0 microM for rats with tumors and 3.4-3.6 microM for controls. For peroneus longus fibers, [Ca2+]50 shifted from 6.1-6.7 microM in controls to 3.5 microM after tumors were introduced into either adult or aged rats. Soleus muscle fibers from neonatal rats (14 days) were less sensitive to Ca2+ than those isolated from adult rats, having a [Ca2+]50 of 7.3 microM. The Ca2+ sensitivity of peroneus longus fibers did not change with age. We conclude that significant increases in myofibrillar Ca2+ sensitivity occur in skeletal muscles undergoing rapid growth induced by GH-secreting tumors.

Acromegaly↗
PubMed1998

Relationship between plasma NOx and cardiac and vascular dysfunction after LPS injection in anesthetized dogs.

The relationship between plasma nitrite, nitrate, and nitric oxide (NOx), cytokines, and cardiac and vascular dysfunction after lipopolysaccharide (LPS) was studied in chronically instrumented anesthetized dogs. LPS was administered (1 mg/kg i.v.), and hemodynamics were recorded at baseline, every 15 min for 1 h, and every hour for an additional 14 h. Dramatic reductions in mean arterial pressure (-48 +/- 6%), cardiac output (-40 +/- 8%), stroke volume (-42 +/- 9%), and first derivative of left ventricular pressure (LV dP/dt, -38 +/- 7%) were seen within 1 h after injection of endotoxin. Cardiac output was not different from control by 9 h, whereas mean arterial pressure (-19 +/- 7%), stroke volume (-32 +/- 8%), and LV dP/dt (-21 +/- 10%) remained significantly depressed from control. Total peripheral resistance was not significantly different from control. Therefore, the hypotension appears to be due to a reduction in cardiac function and not to vasodilation. Levels of plasma NOx were not different from control until 4 h after LPS reached levels 597 +/- 126% higher than control at 15 h. In vitro production of nitrite by coronary microvessels was also elevated, supporting our in vivo findings. In contrast, production of tumor necrosis factor-alpha and interleukin-6 occurred shortly after endotoxin injection, reaching peak levels at 45 and 150 min, respectively. Our data suggest that inducible nitric oxide synthase induction occurred after LPS injection. It is unlikely that nitric oxide contributed significantly to the hypotension and cardiac dysfunction early in our study, whereas cardiodepressive cytokines, particularly tumor necrosis factor-alpha, may be important. In contrast, the hemodynamic effects seen late after injection of endotoxin may be the result of an overproduction of nitric oxide, since there was a sixfold increase in plasma NOx levels at this time and a marked production of nitric oxide in isolated coronary microvessels in vitro.

Animals↗
PubMed1998

Regression of LV hypertrophy with captopril normalizes membrane currents in rabbits.

Recent studies indicate that regression of left ventricular hypertrophy (LVH) normalizes the in situ electrophysiological abnormalities of the left ventricle. This study was designed to determine whether regression of LVH also normalizes the abnormalities of individual membrane currents. LVH was induced in rabbits by renal artery banding. Single ventricular myocytes from rabbits with LVH at 3 mo after renal artery banding demonstrated increased cell membrane capacitance, prolonged action potential duration, decreased inward rectifier K+ current density, and increased transient outward K+ current density compared with myocytes from age-matched controls. Additional rabbits were randomized at 3 mo after banding to treatment with either vehicle or captopril for an additional 3 mo. Myocytes from LVH rabbits treated with vehicle showed persistent membrane current abnormalities. However, myocytes isolated from LVH rabbits treated with captopril had normal cell membrane capacitance, action potential duration, and membrane current densities. Captopril had no direct effect on membrane currents of either control or LVH myocytes. These data support the hypothesis that the action potential prolongation and membrane current abnormalities of LVH are reversed by regression. Normalization of membrane currents probably explains the reduced vulnerability to ventricular arrhythmia observed in this LVH model after treatment with captopril.

Action Potentials↗
PubMed1998

KGF increases SP-A and SP-D mRNA levels and secretion in cultured rat alveolar type II cells.

Studies of secretion of surfactant proteins by alveolar type II cells have been limited because the expression of the genes for these proteins decreases rapidly in primary culture. We developed a culture system to investigate the regulation of lipid and protein secretion by alveolar type II cells and the genes involved in these processes. Rat type II cells were plated on membrane inserts coated with rat-tail collagen in medium containing 10% fetal bovine serum (FBS) for 1 d before being changed to medium containing 5 ng/ml keratinocyte growth factor (KGF) and 2% serum for 3 d and to medium with 5% Engelbreth-Holm-Swarm tumor matrix (EHS) but without serum for 2 d. From this time forward, the cells were placed on a rocking platform and cultured with 0.4 ml medium on the apical surface at the air-liquid interface (A/L) in four different, serum-free media: basal Dulbecco's modified Eagle's medium (DMEM)/F12 medium (DF12), basal medium plus EHS (DF12/EHS), basal medium plus KGF (DF12/KGF), and basal medium plus EHS and KGF (DF12/EHS/KGF). Cells cultured in DF12 and DF12/EHS assumed an attenuated, flattened morphology, whereas those in DF12/KGF and DF12/EHS/KGF were more cuboidal, contained numerous lamellar bodies, and had apical microvilli. Cells cultured in DF12 and DF12/EHS produced a relatively weak signal for the surfactant protein mRNAs (surfactant proteins [SP]-A, SP-B, SP-C, and SP-D, respectively), and secretion of SP-A and SP-D remained low. In contrast, cells maintained for 3 d at A/L and cultured in the presence of KGF showed strong signals for SP-A, SP-B, and SP-D mRNAs, and secreted SP-A, SP-D, and lysozyme into the apical medium. The combination of 12-O-tetradecanoyl-phorbol-11-acetate (TPA) and terbutaline stimulated secretion of [3H]phosphatidylcholine ([3H]PC), SP-A, and lysozyme, but not SP-D. This primary culture system should prove useful for mechanistic studies of the secretion of SP-A, SP-D, and surfactant lipids.

Animals↗
PubMed1998

FGFR-3 and FGFR-4 function cooperatively to direct alveogenesis in the murine lung.

Mammalian lungs begin as an outpocket of the foregut, and depend on multiple stages of branching morphogenesis and alveogenesis to reach their final form. An examination of fgf receptor gene expression indicated that all four receptors (fgfr-1 to fgfr-4) are expressed in postnatal lungs at varying levels. We show that mice homozygous for a targeted mutation of fgfr-4 exhibited no overt abnormalities in the lungs or any other organ. However, mice doubly homozygous for disruptions of the fgfr-3 and fgfr-4 genes display novel phenotypes not present in either single mutant, which include pronounced dwarfism and lung abnormalities. Lungs of fgfr-3(-/-)fgfr-4(-/- )animals, which are normal at birth, are completely blocked in alveogenesis and do not form secondary septae to delimit alveoli. Consequently, air spaces in the lung are expanded and no alveoli can be seen. The mutant lungs failed to downregulate postnatal elastin deposition despite their normal levels of surfactant expression and cell proliferation. These data revealed a cooperative function of FGFR-3 and FGFR-4 to promote the formation of alveoli during postnatal lung development.

Animals↗
PubMed1998

Fibroblast growth factor receptor 2 (FGFR2)-mediated reciprocal regulation loop between FGF8 and FGF10 is essential for limb induction.

FGFR2 is a membrane-spanning tyrosine kinase that serves as a high affinity receptor for several members of the fibroblast growth factor (FGF) family. To explore functions of FGF/FGFR2 signals in development, we have mutated FGFR2 by deleting the entire immunoglobin-like domain III of the receptor. We showed that murine FGFR2 is essential for chorioallantoic fusion and placenta trophoblast cell proliferation. Fgfr2(DeltaIgIII/DeltaIgIII) embryos displayed two distinct defects that resulted in failures in formation of a functional placenta. About one third of the mutants failed to form the chorioallantoic fusion junction and the remaining mutants did not have the labyrinthine portion of the placenta. Consequently, all mutants died at 10-11 days of gestation. Interestingly, Fgfr2(DeltaIgIII/DeltaIgIII) embryos do not form limb buds. Consistent with this defect, the expression of Fgf8, an apical ectodermal factor, is absent in the mutant presumptive limb ectoderm, and the expression of Fgf10, a mesenchymally expressed limb bud initiator, is down regulated in the underlying mesoderm. These findings provide direct genetic evidence that FGF/FGFR2 signals are absolutely required for vertebrate limb induction and that an FGFR2 signal is essential for the reciprocal regulation loop between FGF8 and FGF10 during limb induction.

Animals↗
PubMed1998

Trehalose as osmoprotectant in Rhodobacter sphaeroides f. sp. denitrificans IL106.

The photosynthetic bacterium Rhodobacter sphaeroides f. sp. denitrificans IL106 can grow in high osmolarity. The accumulation of intracellular inorganic ions and organic solutes in cells grown in a synthetic medium containing different concentrations of NaCl was examined. Together with potassium ion, trehalose was the major organic osmoprotectant and its accumulation depended on the external salt concentration. Intracellular levels of glycine betaine and other osmoprotectants such as proline did not change when osmolarity increased.

Betaine↗
PubMed1998

Patterns of condom use among adolescents: the impact of mother-adolescent communication.

OBJECTIVES: The association between the timing of discussions about condoms between mother and adolescent and adolescents' condom use during their first and subsequent sexual encounters was examined. METHODS: Sexually active adolescents reported whether and when they discussed condoms with their mother and answered questions about their own condom use. RESULTS: Mother-adolescent discussions about condoms that occurred prior to sexual debut were strongly associated with greater condom use during first intercourse and most recent intercourse, along with greater lifetime regular condom use. CONCLUSIONS: Discussions about condoms prior to sexual debut are important in promoting condom use among adolescents.

Adolescent↗
PubMed1998

In vitro maturation and fertilization techniques for assessment of semen quality and boar fertility.

The reliability of using different in vitro-derived measures of sperm quality to predict boar fertility was examined. On three occasions during a 20-wk period of breeding, special collections of the first sperm-rich fraction of the ejaculate from six boars were carried out. After in vitro capacitation procedures, three dilutions (5 x 10(5), 1.25 x 10(5), and 3.125 x 10(4) sperm/mL) of these semen samples were used in a standardized in vitro fertilization (IVF) test with oocytes recovered from prepubertal slaughterhouse ovaries and matured in vitro. Routine assessments of sperm motility, concentration, and morphology were also carried out for all collections used for AI during the 20-wk period. Semen from the same ejaculate, processed according to normal commercial practice using the AndroHEP extender, was used to inseminate equal numbers of recently weaned sows with either 3 x 10(9) or 2 x 10(9) total sperm, three times during the estrous period. Data from a total of 444 sows were used to determine boar fertility; between 12 and 54 sows were bred with each semen dose across the six boars. All measures of sperm fertilizing ability in vitro were different among boars (all P < .05) and use of different semen dilutions for IVF allowed further discrimination of apparent sperm quality among boars. The laboratory evaluation of semen collected during the period of breeding indicated effects of boar on ejaculate volume, total number of sperm per ejaculate, motility, and the percentage of sperm with normal morphology (all P < .01). Sperm dose used in AI had no effect on farrowing rate (80.7 vs 81.5%), but the lower AI dose resulted in a reduction (P < .05) in total numbers born (10.8 vs 10.0). For all three semen dilutions, estimated potential embryo production rate accounted for up to 70% of the variation in litter size obtained with 3 x 10(9) sperm per AI dose, and the number of sperm attached per oocyte was a major factor accounting for variation in litter size obtained with 2 x 10(9) sperm per AI dose. These IVF variables may, therefore, be effective indicators of boar sperm quality for use in AI. With 2 x 10(9) sperm per AI dose, the percentage of sperm with normal morphology also explained a large part of the variance in litter size born (R2 = .59), indicating that morphological characteristics are a useful measure of semen quality.

Animals↗
PubMed1998

Microsurgical management of craniopharyngiomas--outcomes in 56 patients.

Fifty-six patients with craniopharyngiomas were operated by microsurgical techniques during a 20-year period. Of the 56 patients, 28 were males and 28 were females, with a mean age of 33 years (range 1 to 78 years). Twenty patients (35.7%) were less than 15 years of age. Remission was defined as clinical improvement with stable ophthalmological and neurological status, CT and/or MRI evidence of a decrease in tumor size or tumor disappearance when a patient was discharged from hospital. Ineffectiveness was defined as lack of change in the preoperative clinical status. The mean follow-up period in this study was 6.9 years, with 11 patients monitored. The most common presentation was visual dysfunction (69.6%). 33.9% of the patients presented with headache. The most frequent preoperative finding was a visual field defect, with 55.4% of the patients so affected; 39.5% of patients had preoperative hypothyroidism and 40% had hypoadrenalism. Diabetes insipidus was found preoperatively in 7.1%. Three female patients had amenorrhea. Hydrocephalus was uncommon, being present in only 10.7%. Unruptured aneurysms were found incidentally in 2 cases. A pterional approach was used in 29 patients (52%), a transcallosal approach in 13 (23%), a transcortical approach and a transsphenoidal approaches in 3 (5%), and a lamina terminalis approach in 1 patient. Multiple procedures were required in 8 patients in order to provide significant relief of compressive symptomatology. Overall, 12.5% of the tumors were completely resected. 92.9% of our patients were in remission, 2 had ineffectiveness result, and 2 died of postoperative complications. Except for the completely resected cases, all the other patients underwent radiotherapy postoperatively. The results of this series show that microsurgical management of craniopharyngiomas yields good operative results.

Adolescent↗
PubMed1998

A diagnostic polymerase chain reaction assay for species A and D of the Anopheles Dirus (Diptera: Culicidae) species complex based on ribosomal DNA second internal transcribed spacer sequence.

A polymerase chain reaction assay based on differences in the internal transcribed spacer regions of ribosomal DNA was developed for distinguishing 2 members of the Anopheles dirus sibling species complex. This assay distinguished An. dirus species A from species D by producing diagnostic bands, 374 base pairs (bp) in length for species A and 663 bp in length for species D. Both laboratory colonies and field collections from Hainan and Yunnan provinces of China were identified with 100% accuracy.

Amino Acid Sequence↗
PubMed1998

Transurethral prostate vaporization using an oval electrode in 82 cases of benign prostatic hyperplasia.

OBJECTIVE: To present our initial experience in transurethral vaporization of the prostate (TVP) using an oval electrode for the treatment of benign prostatic hyperplasia (BPH). METHODS: A total of 82 patients underwent TVP procedures with the oval electrode. The newly designed oval-shaped electrode can work with a High Frequency Electrosurgery Unit. Prostate gland tissue was vaporized through an Fr 24 percutaneous nephroscope transurethrally. The operation procedure was similar to transurethral resection of the prostate (TURP) or transurethral laser prostatectomy (TULP). Power setting ranged from 240 W to 320 W. Local vaporization temperature reached 120 degrees C. RESULTS: Urination was recovered in all 82 patients after TVP. Mean post-treatment International Prostate Symptom Score (I-PSS) reduced from 27.10 to 5.05; mean bladder residual urine volume dropped from 147.71 ml to 33.2 ml; and mean urine flow rate (MFR) increased from 4.45 ml/s to 14.57 ml/s (P < 0.01). The initial results of short-term follow-up were excellent. CONCLUSIONS: TVP with the oval electrode is easy to perform and causes less hemorrhage and few complications. It especially benefits elderly and/or critically-ill patients. We believe that TVP with our oval electrode is feasible with low risk.

Aged↗
PubMed1998

Preventive effect of artemether on schistosome infection.

OBJECTIVE: To study the preventive effect of artemether (Art) in protecting the people from schistosome infection during flood fighting in schistosomiasis endemic area of Poyang Lake, Jiangxi Province. METHODS: From mid July to mid August in 1996, the water level in Poyang Lake rose due to torrential rains and 2 embankments, Zhedi and Jiangtongdi, which appeared in dangerous situation and were selected as the pilot spots. After those who went to fight against flood arrived at the pilots their sera were collected within 48 hours and were examined with indirect hemagglutination test (IHA), enzyme-linked immunosorbent assay (ELISA) and McAb-ELISA. Individuals with negative outcome in the 3 tests were then selected as the study subjects and were allocated randomly to the Art or the control group. The first dose of Art given to the individuals contacted with the infested water within 11-15 days was 6 mg/kg. If the individual continually contacted the infested water, the same dose of Art was given once every 15 days. After the individuals withdrew from the pilot, one more dose of Art was administered 7-15 days later. Placebo (starch) was given to individuals in the control group at the same period as in artemether group. Stool examinations were made in both groups 40-50 days after the last medication for evaluation of the preventive effect of artemether. Double blind method was used in the administration of both artemether and placebo. RESULTS: In Zhedi pilot, the individuals fought against flood for about 1 month. In Art group, 99 individuals receiving 3 doses of the drug completed the stool examination with egg-positive rate of 4% and no acute schistosomiasis was seen. In the control group, among 110 people who completed the observation, 44 were egg-positive with an infection rate of 40%, and 29 were identified as having acute schistosomiasis. In Jiangtondi, the studied individuals contacted the infested water for only about 4 hours. But in the control group 4 out of 102 individuals were egg-positive, while none of the 103 individuals in Art group receiving 2 doses of the drug showed schistosome infection. No apparent side effect was seen in the people treated with artemether. CONCLUSION: After oral Art was given to the people fighting against flood in schistosomiasis endemic area of Poyang Lake, it was shown that the oral Art has a promising effect on controlling acute schistosomiasis and reducing the infection rate.

Adolescent↗
PubMed1998

New concepts and advances of immobilization of long bones.

OBJECTIVE: To present some new concepts in the treatment of fractures and bone defects of long bones with internal fixation. METHODS: Animal experiments, mechanical tests and clinical analyses were done. RESULTS AND CONCLUSIONS: Reduction of fracture should be perfect, bone defect can be reconstructed by intramedullary and extramedullary bone graft. Relatively rigid fixation at the early stage and elastic fixation at the later stage are beneficial not only for fracture healing, but also for bone remodeling. In order to avoid complications including non-union, immobilization syndrome of the bone and joint, and implant failure, radiographs should be taken periodically; if there is any bone resorption, weight-bearing should be restricted.

Animals↗
PubMed1998

Expression of calmodulin-binding domain of neuronal nitric synthase and its binding activity to calmodulin.

To facilitate the study of associations of nNOS functions with its calmodulin (CaM) binding domain and to prepare nNOS specific inhibiting peptides from phage peptide library, we have amplified the coding gene of nNOS CaM-binding domain (nNOS 2544-2988 bp) and expressed it in E.coli. The recombinant product in the size of 22 kDa was purified (over 90% in pure) by His.Tag-Sepharose column and its obvious CaM-binding activity was detected with CaM overlay assay. Since it possesses the sequence specificity and effective calmodulin-binding activity, the protein was considered an ideal target for screening nNOS specific peptides from peptide library and also an antigen for marking nNOS antibody.

Binding Sites↗