Biomedical subjects

Fan Chen

Publications and source records attributed to Fan Chen.

26 records · Page 2Linked to original sources

PubMed2003

[Exploratory study of factors related sexual dysfunction among cancer patients].

OBJECTIVE: To investigate the factors related to the sexual dysfunction among cancer patients and make preparation for its prevention and treatment to improve the quality of life of cancer patients. METHODS: Self-designed questionnaires about sexual function were used and 130 patients in their rehabilitation period interviewed. These patients were suffering from different kinds of cancer. RESULTS: Age of patients and their perception of sex are two important factors resulting in significant difference of suffering rate of sexual dysfunction among these cancer patients. The total suffering rate of sexual dysfunction among patients suffering from reproductive cancer is significantly higher than that of patients suffering from cancer in other systems. Of all the factors we analyzed in the research, we found that stage of cancer; physical strength and perception of sex had significant correlation with newly emerging sexual dysfunction. From the patient's point of view, those newly suffering from sexual dysfunction after their cases were diagnosed as cancer thought that cancer treatment had negative effect on their sexual function. CONCLUSION: Stage of cancer, physical strength and perception of sex had significant correlation with sexual dysfunction of cancer patients who have received cancer treatment. This suggests that, intervention in patients' wrong perception of sex is the first aspect we should pay attention to in treating and preventing sexual dysfunction among cancer patients.

Adult↗

PubMed2003

Aerobic denitrification of Pseudomonas aeruginosa monitored by online NAD(P)H fluorescence.

Continuous cultures of Pseudomonas aeruginosa (ATCC 9027) maintained at different dissolved oxygen concentrations (DO) were studied for the effects of DO on various culture properties, especially aerobic respiration and denitrification. The DO was varied from 0 mg/liter (completely anoxic conditions) to 1.3 mg/liter and measured with optical sensors that could accurately determine very low DO based on oxygen-quenched luminescence. The strain was found to perform aerobic denitrification; while the specific rate decreased with increasing DO, denitrification persisted at approximately 1/8 of the maximum rate (1.7 mmol/g of cells/h) even at relatively high DO (1 to 1.3 mg/liter). In the presence of nitrate, the culture's Monod half-rate saturation constant for O(2) was very small, <0.1 mg/liter. Aerobic denitrification appeared to function as an electron-accepting mechanism supplementary to or competitive with aerobic respiration. The shift of the culture's respiratory mechanism was also clearly detected with a fluorometer targeting intracellular NAD(P)H, i.e., the reduced forms of the NAD(P) coenzymes. Comparatively, the NAD(P)H fluorescence under the anoxic, denitrifying conditions (NFU(DN)) was highest, that under fully aerobic conditions (NFU(OX)) was lowest, and that under conditions in which both denitrification and aerobic respiration occurred (NFU) was intermediate. Representing a quantitative measure of the culture's "fractional approach" to the fully denitrifying state, the normalized fraction (NFU - NFU(OX))/(NFU(DN) - NFU(OX)) was correlated with DO and the calculated fraction of electrons accepted by denitrification. The NFU fraction decreased with increasing DO, following an empirical exponential relationship. The fraction of denitrification-accepted electrons increased with the NFU fraction: the increase was gradual and approximately linear at DO of >/==" BORDER="0">0.1 mg/liter but much sharper at lower DO. Online NAD(P)H fluorescence was demonstrated as a feasible technique for effective monitoring and quantitative description of the microaerobic state of microorganisms.

Aerobiosis↗

PubMed2002

Comparison of three DNA marker systems for assessing genetic diversity in Asian arowana (Scleropages formosus).

Three DNA marker systems -- random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP) and microsatellites -- were used to estimate the genetic diversity in Asian arowana (Scleropages formosus) by genotyping fish individuals from three different sources. Parallel application of the three DNA marker systems allowed us to compare their utility for the analysis of genetic diversity. Microsatellites displayed the highest expected heterozygosity, whereas the values obtained by RAPD and AFLP were much lower. Multiplex ratio and marker index were higher for AFLP than for RAPD or microsatellites. Weak correlation was detected between genetic similarity estimated from data obtained with the three DNA marker systems: estimates from RAPD and AFLP data turned out to be higher than those from microsatellites. On the other hand genetic similarity was higher in the red variety than in the green one, especially when tested with microsatellites. Based on the genetic distance matrices calculated from microsatellite analysis, all red individuals were clustered into one group, whereas only a subset of them was clustered when either RAPD or AFLP was used. This indicated that the microsatellite system detected population subdivision more efficiently than either RAPD or AFLP.

Animals↗

PubMed2002

Genetic diversity within and among feral populations and domesticated strains of the guppy (Poecilia reticulata) in Singapore.

Genetic variability within and among feral populations and cultured strains of the guppy (Poecilia reticulata) was investigated by random amplification of polymorphic DNA (RAPD) fingerprinting. Feral guppies were collected from 6 isolated populations (BT, Bukit Timah; NS, Nee Soon; TS, Tuas; MF, Mount Faber; KR, Kranji; LI, laboratory-inbred feral line), while the Tuxedo and Green Variegated strains were sampled from 2 guppy farms in Singapore. Pairwise genetic distances analyzed by unweighted pair-group method with arithmetic means revealed distinct clustering of guppy individuals into their respective populations and strains. Percentage polymorphic loci ranged from 54.96% (TS) to 68.70% (KR), while average heterozygosity ranged from 0.220 (GV) to 0.271 (KR). In contrast, TS guppies had the highest (0.850) intrapopulation genetic similarity (S), whereas KR had the lowest (0.781). Among populations and strains, S ranged from 0.703 (between GV and LI) to 0.809 (between NS and MB). The GV strain S was closer to TX (0.784) than to the feral guppies. Bootstrapped genetic distance trees depicted 3 major nodes comprising BT-TS, NS-MF, and TX-GV. Principal coordinate analysis also differentiated the 6 feral populations from the 2 cultured strains.

Journal Article↗

PubMedDate not supplied

Genetic linkage maps of the guppy ( Poecilia reticulata): assignment of RAPD markers to multipoint linkage groups.

Genetic linkage maps of the guppy ( Poecilia reticulata) were constructed from independent crosses between the Tuxedo strain and a feral line (Wildtype). Segregation patterns of random amplified polymorphic DNA (RAPD) markers and phenotypic markers were investigated in F(2) offspring of Tuxedo male symbol male symbol x Wildtype female symbol female symbol and Wildtype male symbol male symbol x Tuxedo female symbol female symbol crosses. Among the 300 and 276 RAPD markers scored for the respective crosses, linkages were identified for 230 and 212, respectively. The Tuxedo male symbol male symbol x Wildtype female symbol female symbol and Wildtype male symbol male symbol x Tuxedo female symbol female symbol maps spanned 2100 Kosambi centiMorgans (cM(K)) and 1900 cM(K), respectively, in 28 linkage groups. Average marker resolution was 10 cM(K). Genome length was estimated at 4410 cM(K) and 4060 cM(K) for the respective crosses, with an average physical distance of 166 kbp/cM(K). Several RAPD markers were closely linked to or mapped onto the loci for the sex-determining region (SdR), and the sex-linked black caudal-peduncle ( Bcp) and red tail ( Rdt) genes. These primary linkage maps are the initial step toward the construction of a composite high-density map to facilitate map-based cloning and marker-assisted selection of quantitative trait loci that are essential for the development of comprehensive breeding programs for the guppy.

Animals↗

PubMedDate not supplied

Correlation of denitrification-accepted fraction of electrons with NAD(P)H fluorescence for Pseudomonas aeruginosa performing simultaneous denitrification and respiration at extremely low dissolved oxygen conditions.

In cystic fibrosis airway infection, Pseudomonas aeruginosa forms a microaerobic biofilm and undergoes significant physiological changes. It is important to understand the bacterium's metabolism at microaerobic conditions. In this work, the culture properties and two indicators (the denitrification-accepted e- fraction and an NAD(P)H fluorescence fraction) for the culture's "fractional approach" to a fully anaerobic denitrifying state were examined in continuous cultures with practically zero DO but different aeration rates. With decreasing aeration, specific OUR decreased while specific NAR and NIR increased and kept Y(ATP/S) relatively constant. P. aeruginosa thus appeared to effectively compensate for energy generation at microaerobic conditions with denitrification. At the studied dilution rate of 0.06 h(-1), the maximum specific OUR was 2.8 mmol O2/g cells-h and the Monod constant for DO, in the presence of nitrate, was extremely low (<0.001 mg/L). The cell yield Y(X/S) increased significantly (from 0.24 to 0.34) with increasing aeration, attributed to a roughly opposite trend of Y(ATP/X) (ATP generation required for cell growth). As for the denitrification-accepted e- fraction and the fluorescence fraction, both decreased with increasing aeration as expected. The two fractions, however, were not directly proportional. The fluorescence fraction changed more rapidly than the e- fraction at very low aeration rates, whereas the opposite was true at higher aeration. The results demonstrated the feasibility of using online NAD(P)H fluorescence to monitor sensitive changes of cellular physiology and provided insights to the shift of e- -accepting mechanisms of P. aeruginosa under microaerobic conditions.

Aerobiosis↗

PubMedDate not supplied

Modeling rhl quorum-sensing regulation on rhamnolipid production by Pseudomonas aeruginosa.

The effect of autoinducer PAI2 on rhamnolipid (RL) production by Pseudomonas aeruginosa was evaluated using an rhlI null mutant of PAO1 added with PAI2 at various concentrations. A model has also been developed to describe the production kinetics regulated by the rhl quorum-sensing system in three steps: First, PAI2 combines with RhlR protein. Second, the activated complex RhlR:PAI2 triggers the transcription (and expression) of the rhlAB operon that encodes for rhamnosyltransferase. Finally, the enzyme catalyzes the RL synthesis. The model describes fairly well the experimental results/profiles from three different studies (this and two others reported in the literature). The overall picture predicted by the model is as follows: The induced enzyme synthesis proceeds at the highest rate following PAI2 addition. The rate decreases with time as the autoinducer is degraded. The enzyme concentration nonetheless continues to increase until reaching the plateau at the exhaustion of autoinducer. Higher added PAI2 concentrations thus give not only higher initial enzyme synthesis rates but also longer induced synthesis. As the enzyme concentration increases with time, the RL production rate also increases, resulting in an accelerated rise in RL concentrations initially. The increase in RL concentrations becomes linear at the exhaustion of PAI2. The best-fit model parameters obtained also provided important insights. To complex half of the intracellular RhlR proteins would require 1.61 microM PAI2, about half of the PAI2 concentration obtained in the stationary-phase culture of wild-type PAO1. On the other hand, to activate the rhamnosyltransferase synthesis at half of its maximum rate would require the binding of 39% of RhlR with PAI2. The maximum RL production rate of the culture was found to be 0.042 g/L.h, and the fully induced culture would require at least 1.61 h to synthesize the enzyme to the necessary level for producing RL at half of the maximum rate.

Aldose-Ketose Isomerases↗

PubMedDate not supplied

Intrathoracic ectopic lobe of liver presenting as pulmonary sequestration.

Intrathoracic ectopic lobe of the liver in the presence of a normal intact diaphragm is extremely rare. We report a case of a 13-month-old male initially diagnosed with pneumonia and pulmonary sequestration who was found to have an intrathoracic liver lobe and intact diaphragm. The presence of this condition suggests an event preceding closure of the diaphragm and illustrates the unique potential of pediatric pathology to shed light on human embryology.

Bronchopulmonary Sequestration↗