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G Xu

Publications and source records attributed to G Xu.

At least 433 records · Page 24Linked to original sources
PubMed1995

Comparing antimicrobial activity against resistant Pseudomonas aeruginosa using an index for the absence of cross-resistance.

We devised an index to estimate the degree cross-resistance between piperacillin, ceftazidime, sulbactam/cefoperazone, amikacin, tobramycin, carumonam and imipenem against 139 separate clinical isolates of Pseudomonas aeruginosa. A negative value of the index indicated the cross-resistance whereas a positive value suggested the converse making the device an index for the absence of cross resistance (ACR). Using the ACR index, we identified pairs of antibiotics exhibiting the least degree of cross-resistance and therefore the highest potential for treating infections due to P. aeruginosa.

Aminoglycosides↗
PubMed1995

Primary care and non-primary care physicians: a longitudinal study of their similarities, differences, and correlates before, during, and after medical school.

PURPOSE--To investigate similarities and differences between physicians in primary care and non-primary care specialties on performance measures prior to, during, and after medical school, and on demographic characteristics, professional plans and preferences in medical school, professional activities, career satisfaction, perceived problems and research activities, and to predict primary--non-primary care career choices from information obtained in medical school. A questionnaire was mailed to 1,076 physicians who graduated from Jefferson Medical College between 1982 and 1986. Of those who responded (62%), 232 were primary care and 406 were non-primary care physicians (29 physicians in mixed specialties were excluded). Data from the questionnaire concerning professional activities, satisfaction, problems, and research productivities were merged with the college's longitudinal study database. RESULTS--Comparisons of primary care--non-primary care physicians indicated no significant difference between them on performance measures before, during, and after medical school, with the exception that non-primary care physicians had higher scores on quantitative tests before medical school, and primary care physicians scored higher on a licensing examination of general clinical skills and patient management taken during residency training. Also, compared with non-primary care physicians, those in primary care were less likely to be employed full-time, were less likely to locate in metropolitan areas, had a lower rate of academic appointment, and had a higher rate of board certification. Other results showed differences between the groups in terms of age at entrance to medical school, proportion of women, estimates during medical school of anticipated income, career plans during medical school, satisfaction with career and income, and research and scientific activities. A logistic regression model could predict primary care--non-primary care status from specialty interest, professional plans and interests expressed in medical school.

Attitude of Health Personnel↗
PubMed1995

Gender comparisons of young physicians' perceptions of their medical education, professional life, and practice: a follow-up study of Jefferson Medical College graduates.

PURPOSE: To obtain information from a group of young physicians and compare men and women on their evaluations of selected areas of the medical school curriculum, their perceptions of issues related to medical practice and professional life, and their specialty choices, professional activities, and research productivity. METHOD: In 1992, a questionnaire was mailed to 1,076 physicians who had graduated from Jefferson Medical College between 1982 and 1986. The responses of men and women were compared using multivariate and univariate analyses of variance, t-tests, chi-square, and median test. RESULTS: Completed questionnaires were returned by 667 graduates (530 men and 137 women). The curriculum areas of interpersonal skills, disease prevention, medical ethics, and economics of health care were rated by both men and women as being the most important in medical training. Conversely, research methodology and statistics received the lowest ratings. Women, in general, valued psychosocial aspects of medical care higher than did men. Among the areas of perceived problems related to practice, lack of leisure time received the highest ratings (as being the greatest problem) and interpersonal interactions received the lowest ratings (as being the least problem) from both men and women. The men were more concerned than the women about the areas of patient chart and documentation, malpractice litigation, physician oversupply, peer review, and interaction with patients. These differences remained when specialties and numbers of hours worked per week were held constant. Generally, the physicians reported satisfaction with their professional lives, but the men tended to be more satisfied than the women about their decisions to become physicians and in their perceptions of medicine as a rewarding career. The proportion of men employed full-time (99.4%) was significantly higher than that for women (84%). Women were more likely to practice general pediatrics, while men were more likely to practice surgery and surgical subspecialties. Full-time--employed women worked fewer hours per week (57) than men (63), and men reported more research productivity than women. CONCLUSION: The implications of the findings of numerous gender differences are discussed regarding the issues of physician workforce, types of care rendered by men and women, and possible changes in the national health care system.

Analysis of Variance↗
PubMed1995

A national study of the factors influencing men and women physicians' choices of primary care specialties.

BACKGROUND: Despite a recent increase in the percentage of graduating U.S. medical students planning to pursue generalist careers, interest in primary care among students is still far below what it was in the early 1980s and falls well short of the stated goal of the Association of American Medical Colleges that half of all graduates should choose generalist careers. Also during the past decade, the number of women students and physicians has increased. Given the importance of concerns regarding the primary care work force, it is timely to examine the relationship between gender and other factors that influence the decision to enter primary care. METHOD: Totals of 1,038 (65%) men and 558 (35%) women primary care physicians selected from the 1983 and 1984 graduates of all allopathic U.S. medical schools were surveyed in early 1993. Gender comparisons were made on the 19 variables that influenced the physicians' decisions to enter primary care specialties and on the six factor scores derived from a factor analysis of these 19 variables. Also included in the gender comparisons were characteristics of practice, populations served, timing of making the decision to enter primary care, and personal demographic information. RESULTS: Men, more than women, were influenced to become primary care physicians by early role models. Women, more than men, were influenced by personal and family factors. Overall, medical school experience and personal values are two important factors that explained the largest variances of the 19 predictor variables influencing the physicians' choices of primary care disciplines. There was no gender difference in place of origin, family income as a child, timing of the decision to become a primary care physician, or the amount of debt upon graduation. CONCLUSION: This nationwide study of primary care physicians indicates that men and women physicians differ in their perceptions of the relative importances of factors influencing the choice of a primary care specialty. Gender-specific factors should receive more attention in the development of successful strategies to attract more medical students into primary care specialties.

Career Choice↗
PubMed1995

A comparison of flow cytometry and microcytotoxicity for the evaluation of alloimmune therapy in patients with recurrent spontaneous abortions.

PROBLEM: There is substantial data that support the efficacy of paternal leukocyte immunization (PLI) for the treatment of alloimmune mediated miscarriage; however, there is confusion regarding the laboratory test that should be performed to determine levels of maternal anti-paternal leukocyte antibodies (MAPLA). METHOD: Popular methodologies employed include: 1) microcytotoxicity (MCX), 2) mixed lymphocyte culture (MLC), and 3) cell flow cytometry crossmatch (FCXM). Cell flow cytometry crossmatch correlates well with the more difficult MLC assay although the former proves the more sensitive study. This work compares the MCX assays with FCXM. The study group consisted of ten women who had a history of three or more spontaneous abortions (SABs). All ten had very low levels (< 10%) of MAPLA as measured by FCXM. Following PLI all subjects demonstrated elevated levels (> 50%) of MAPLA by FCXM. At 12 weeks gestation, sera were simultaneously measured for MAPLA by MCX and FCXM. RESULTS: Although all ten patients had very high levels of MAPLA by FCXM during pregnancy, five of ten had antibodies to HLA Class I and two of ten had antibodies to HLA Class II paternal antigens by MCX. Furthermore, all patients who were positive by MCX to paternal Class I antigens were also positive to Class I antigens not seen in either parent. Both patients who were positive by MCX to paternal Class II antigens were also positive to maternal Class II antigens. Notable is that all ten women eventually delivered healthy infants. CONCLUSION: Based on this preliminary study, the MCX assay is neither sensitive or reliable enough to determine the need and/or to monitor the effectiveness of PLI. Flow cytometry should be the modality of choice when determining the need for alloimmunotherapy and to monitor the effectiveness of treatment.

Abortion, Habitual↗
PubMed1995

[Clinical utility of DNA fingerprinting by arbitrarily-primed polymerase chain reaction (AP-PCR) in nosocomial infection caused by methicillin-resistant Staphylococcus aureus].

Recently, nosocomial outbreaks of MRSA have become an serious social problem in Japan. To examine the routes of transmission of MRSA, the establishment of an accurate MRSA typing system is essential. Previously, we reported that the DNA fingerprinting by AP-PCR might be a useful method to differentiate MRSA strains. In this study, we tried to investigate the clinical usefulness of DNA fingerprinting by AP-PCR using clinically-isolated MRSA strains. Twenty-four MRSA strains (12 with coagulase type IV, and 12 with coagulase type II) isolated from patients in our department were used. Other typing methods (the sensitivity of antibiotics, pulsed-field gel electrophoresis, and plasmid analysis) were also performed. As a result, the typing pattern by AP-PCR correlated well with other typing methods. MRSA strains with coagulase type IV showed almost the same pattern, suggesting that these strains were nosocomially transmitted. On the other hand, MRSA strains with coagulase type II showed various patterns, suggesting these strains were not nosocomially transmitted. In conclusion, the typing by AP-PCR seemed to be a useful tool evaluate a nosocomial MRSA transmission.

Cross Infection↗
PubMed1995

[DNA fingerprinting by arbitrarily primed polymerase chain reaction (AP-PCR) for methicillin-resistant Staphylococcus aureus].

Recently, nosocomial outbreaks of MRSA have become an important social problem in Japan. To examine the routes of transmission of MRSA, the establishment of accurate MRSA typing system is essential. However, more recently, because MRSA strains with type II coagulase have been increasing, it is difficult to discriminate MRSA strains by the coagulase typing method. Under this background, our study was designed to evaluate the clinical significance of DNA fingerprinting by arbitrarily primed polymerase chain reaction (AP-PCR). Several MRSA strains isolated from patients in our department were used in this study. To optimize the condition of AP-PCR, the differences of amplified products by AP-PCR were evaluated according to the following conditions: extracting methods of DNA from MRSA strains, buffer conditions, the temperature of AP-PCR, cycles of AP-PCR, and several primers. As a result, the optimal conditions of AP-PCR were as follows: extracted DNA using the InstaGene kit, amplified DNA by two-step AP-PCR using a M13 reverse primer with a buffer condition of 3.5 mM of magnesium chloride, and a pH of 8.5. The results of AP-PCR correlated well with the results of pulsed-field gel electrophoresis. In conclusion, DNA fingerprinting by AP-PCR seems to be useful in examining the nosocomial MRSA outbreak.

Bacterial Typing Techniques↗
PubMed1995

[Effect of erythromycin on macrophage functions].

Recently, it has been suggested that macrolide antibiotics act as immunomodulators. In this study, we evaluated the effect of EM on macrophage function. We used the mouse macrophage cell line, J774.1. The following direct effects of EM on macrophage function were evaluated: chemotaxis to EM, chemokinetic effect by EM, and the effect of EM on macrophage growth. In order to examine the indirect effects of EM on macrophage functions, we preincubated macrophages with several concentrations of EM and then removed the EM. Thereafter, the phagocytosis of beads, cytocidal activity against Candida albicans, and chemotaxis to lipopolysaccharide were evaluated. EM (at the concentration between 0.04 and 0.2 microgram/ml) directly stimulated macrophage chemotaxis and chemokinesis. In addition, EM dose-dependently stimulated the growth of macrophages. EM pretreatment (for 4 hours at the contractions between 0.04 and 0.2 microgram/ml) stimulated macrophage phagocytosis, cytocidal activity against Candida albicans, and chemotaxis to lipopolysaccharide. These results suggest that EM has direct and indirect effects on macrophage functions.

Animals↗
PubMed1995

[Effect of clarithromycin on macrophage functions].

Recently, it has been suggested that macrolide antibiotics act as immunomodulators. In this study, we evaluated the effect of clarithromycin (CAM) on macrophage function. We used the mouse macrophage cell line, J774.1. The following direct effects of CAM on macrophage function were evaluated: chemotaxis to CAM, chemokinetic effect of CAM, and the effect of CAM on macrophage growth. In order to examine the indirect effects of CAM on macrophage functions, we preincubated macrophages with several concentrations of CAM and then removed the CAM. Thereafter, the phagocytosis of beads, cytocidal activity against Candida albicans, and chemotaxis to lipopolysaccharide were evaluated. In addition, the indirect effects of CAM on endoxan (4 mg/ml) treated macrophage phagocytosis, cytocidal activity, and chemotaxis were evaluated. CAM (at the concentration between 0.04 and 0.2 microgram/ml) directly stimulated macrophage chemotaxis and chemokinesis. In addition, CAM dose-dependently stimulated the growth of macrophages. CAM pretreatment (for 4 hours at the concentrations between 0.04 and 0.2 microgram/ml) stimulated macrophage phagocytosis, cytocidal activity against Candida albicans, and chemotaxis to lipopolysaccharide. In addition, CAM recovered macrophage phagocytosis, cytocidal activity, and chemotaxis which were decreased after endoxan exposure. These results suggest that CAM has direct and indirect effects on macrophage functions.

Animals↗
PubMed1995

Reproducing abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome by inhibiting the conversion of 7-dehydrocholesterol to cholesterol in rats.

The Smith-Lemli-Opitz syndrome is a recessive inherited disorder characterized by neurologic developmental defects and dysmorphic features in many organs. Recently, abnormal cholesterol biosynthesis with impaired conversion of 7-dehydrocholesterol to cholesterol has been discovered in homozygotes. To reproduce the biochemical abnormality, BM 15.766, a competitive inhibitor of 7-dehydrocholesterol-delta 7-reductase, the enzyme that catalyzes the conversion of 7-dehydrocholesterol into cholesterol was fed by gavage to rats. After 14 d, plasma cholesterol concentrations declined from 48 mg/dl to 16 mg/dl and 7-dehydro-cholesterol levels rose from trace to 17 mg/dl. Hepatocytes surrounding the central vein developed balloon necrosis. Stimulating cholesterol synthesis with cholestyramine followed by BM 15.766 produced an additional 40% decline (P < 0.05) in plasma cholesterol and 34% increase in 7-dehydrocholesterol levels compared to the inhibitor alone. Adding 2% cholesterol to the diet during the second week of BM 15.766 treatment increased plasma cholesterol threefold and decreased 7-dehydrocholesterol concentrations 55%. Hepatic 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase activity increased 73% with a 3.9-fold rise in mRNA levels but cholesterol 7 alpha-hydroxylase activity decreased slightly though mRNA levels increased 1.4 times with BM 15.766 treatment. These results demonstrate that BM 15.766 is a potent inhibitor of 7-dehydrocholesterol-delta 7-reductase. The model reproduces abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome and is useful to test different treatment strategies. Stimulating early steps of cholesterol synthesis worsens the biochemical abnormalities while feeding cholesterol inhibits abnormal synthesis, improves the biochemical abnormalities and prevents liver damage.

Abnormalities, Multiple↗
PubMed1995

Unexpected inhibition of cholesterol 7 alpha-hydroxylase by cholesterol in New Zealand white and Watanabe heritable hyperlipidemic rabbits.

We investigated the effect of cholesterol feeding on plasma cholesterol concentrations, hepatic activities and mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and hepatic LDL receptor function and mRNA levels in 23 New Zealand White (NZW) and 17 Watanabe heritable hyperlipidemic (WHHL) rabbits. Plasma cholesterol concentrations were 9.9 times greater in WHHL than NZW rabbits and rose significantly in both groups when cholesterol was fed. Baseline liver cholesterol levels were 50% higher but rose only 26% in WHHL as compared with 3.6-fold increase with the cholesterol diet in NZW rabbits. In both rabbit groups, hepatic total HMG-CoA reductase activity was similar and declined > 60% without changing enzyme mRNA levels after cholesterol was fed. In NZW rabbits, cholesterol feeding inhibited LDL receptor function but not mRNA levels. As expected, receptor-mediated LDL binding was reduced in WHHL rabbits. Hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels were 2.8 and 10.4 times greater in NZW than WHHL rabbits. Unexpectedly, cholesterol 7 alpha-hydroxylase activity was reduced 53% and mRNA levels were reduced 79% in NZW rabbits with 2% cholesterol feeding. These results demonstrate that WHHL as compared with NZW rabbits have markedly elevated plasma and higher liver cholesterol concentrations, less hepatic LDL receptor function, and very low hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels. Feeding cholesterol to NZW rabbits increased plasma and hepatic concentrations greatly, inhibited LDL receptor-mediated binding, and unexpectedly suppressed cholesterol 7 alpha-hydroxylase activity and mRNA to minimum levels similar to WHHL rabbits. Dietary cholesterol accumulates in the plasma of NZW rabbits, and WHHL rabbits are hypercholesterolemic because reduced LDL receptor function is combined with decreased catabolism of cholesterol to bile acids.

Alanine Transaminase↗
PubMed1995

Physicians' intention to stay in or leave primary care specialties and variables associated with such intention.

A national mail survey of primary care physicians was conducted in 1993 to examine the differences between those who planned to leave and those who planned to stay in primary care disciplines. The physicians who planned to stay in primary care were those who, at the time of choosing primary care specialties, were more influenced by factors such as personal social values, religion, and the presence of a role model prior to medical school. Physicians' race, sex, workload, debt, place where they grew up, family income as a child, and timing when they made the decision to enter primary care disciplines are not associated with their plans to stay in or leave primary care disciplines. Findings indicated that personal social values, religious beliefs, and the presence of a role model prior to medical school not only influenced physicians' choice of primary care, but had a lasting effect on their commitment to such choice.

Career Mobility↗
PubMed1995

Influence of formulation change on drug release kinetics from hydroxypropylmethylcellulose matrix tablets.

Examination was made of the release of indomethacin from hydroxypropylmethylcellulose (HPMC) matrices and the results were found to usually follow first order release kinetics. The release mechanism changed with formulation. HPMC content was the predominant controlling factor. As the HPMC content increased, drug release rate decreased, and the release mechanism gradually changed from Higuchi diffusion release to case II transport. Additives increased the release rate and enhanced Fickian diffusion. As drug content increased, release rate calculated from percent release data decreased while that calculated from mg release data increased. When indomethacin content was lower, drug release was diffusion controlled and when higher, non-Fickian transport or case II transport was apparent. Additive effects were also examined. Starch was found to most effectively maintain case II release. Complex additives containing starch were superior to any additive by itself. A multiple regression model was used to determine the relationship between response (release rate) and factors (content of HPMC and diluents), and on the basis of this model a formulation was established and found valid by agreement with data from the regression model.

Chemical Phenomena↗
PubMed1995

Measurements of plasma elastase alpha 1-proteinase inhibitor complexes in patients receiving cancer chemotherapy with granulocyte colony-stimulating factor.

We monitored the plasma elastase alpha 1-proteinase inhibitor complex levels in 21 patients with primary lung cancer who received combination chemotherapy with or without recombinant human granulocyte colony-stimulating factor (rhG-CSF), and 15 normal nonsmokers as controls. Of the 21 patients, 14 received combination chemotherapy without rhG-CSF (among them, 6 developed pneumonia) and 7 received combination chemotherapy with rhG-CSF (among them, 1 developed pneumonia). We measured peripheral WBC counts, C-reactive protein (CRP) levels, plasma elastase alpha 1-proteinase inhibitor complex (complex) levels, and complex/WBC values during cancer chemotherapy. In patients who received cancer chemotherapy without rhG-CSF and had no complications (n = 8), WBC values decreased after chemotherapy, and then gradually increased. Complex levels also decreased slightly after chemotherapy and gradually recovered. The value obtained from dividing the complex concentration by WBC count (complex/WBC value) remained stable during cancer chemotherapy. In patients who received cancer chemotherapy with rhG-CSF and had no complications (n = 6), WBC values decreased after chemotherapy, and then rapidly increased to abnormally high values. Complex levels also decreased slightly after chemotherapy and rapidly increased to abnormally high values together with the WBC counts. The complex/WBC values remained stable during cancer chemotherapy. In patients who developed pneumonia during cancer chemotherapy with or without rhG-CSF (n = 7), their complex levels, complex/WBC values, and CRP levels were elevated at the onset of pneumonia. The maximum complex levels (the highest levels during chemotherapy) were significantly higher in patients who received cancer chemotherapy with rhG-CSF and did not develop pneumonia (583.1 +/- 114.5 ng/mL) and in patients who developed pneumonia during cancer chemotherapy (516.7 +/- 113.2 ng/mL), compared with normal nonsmokers (130.2 +/- 5.5, p < 0.01) and patients who received cancer chemotherapy without rhG-CSF and did not develop complications (211.5 +/- 23.3, p < 0.01). The maximum complex/WBC values were not increased in patients who received cancer chemotherapy with rhG-CSF (0.08 +/- 0.01) and patients who received cancer chemotherapy without rhG-CSF (0.092 +/- 0.01, p < 0.01). The maximum complex/WBC values were significantly higher in patients with pneumonia (0.56 +/- 0.12) compared with normal nonsmokers (0.026 +/- 0.002, p < 0.01) and patients without complications. These findings suggest that although rhG-CSF increases total plasma elastase burden, increased release of neutrophil elastase from individual neutrophils does not take place in vivo in the absence of pneumonia.

Aged↗
PubMed1995

[Enhancing effects of the supernatant of pulmonary alveolar macrophages stimulated by BCG on proliferation on pulmonary fibroblasts].

The supernatant of pulmonary alveolar macrophages (PAM) stimulated by 7.5-60mg/L of BCG could significantly enhance proliferation of pulmonary fibroblasts (PFB), and the supernatant contained high level of TNF. This result indicated BCG could stimulate PAM to produce TNF in vitro. On the other hand, the supernatant of PAM stimulated by 50mg/L of SiO2 could also enhance proliferation of PFB, but the level of TNF in the supernatant was very low and it demonstrated the ingredient in the supernatant enhancing proliferation was not TNF. TNF showed synergistic effect with this ingredient for enhancing proliferation of PFB. Therefore, TNF produced by tuberculosis bacteria-stimulated PAM might be an important factor enhancing the development of fibrosis of silicotuberculosis.

Animals↗