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Biomedical subjects

Y L Cheng

Publications and source records attributed to Y L Cheng.

47 records · Page 3Linked to original sources
PubMed1993

[The establishment of genomic DNA libraries for the human malaria parasite Plasmodium falciparum].

The DNA of Plasmodium falciparum has been purified and fragmented with restriction endonuclease BamHI. The fragments have been incorporated in vitro into derivatives of bacteriophage lambda EMBL4 digested with BamHI and Sal I. The recombinant mixture has been ligated and packaged in vitro. The recombinant phages have been identified in E. coli L95 host cell and the libraries have been established in which most of the parasite DNA is represented. The ligation proportion of vector to insert is 3:1. The recombinant phages of 4 x 10(5) have been obtained. By plaque hybridization, we have been able to recover from these libraries specific clones containing repetitive DNA sequences.

Animals↗
PubMed1993

Continuous epidermal growth factor delivery in corneal epithelial wound healing.

PURPOSE: To investigate the effects of a single prolonged exposure to recombinant epidermal growth factor on the healing of anterior keratotomy wounds in New Zealand white rabbits. METHODS: After wounding, eyes were perfused for 1, 2, 4, and 8 hours with either epidermal growth factor solution at a concentration of 50 micrograms/ml or balanced saline solution using a Morgan therapeutic lens (Mortan Inc, Missoula MT) and a syringe pump. Furthermore, concentration response was evaluated by perfusing with epidermal growth factor solutions at concentrations of 5, 50, 100 and 500 micrograms/ml for 4 hours. Wound healing rates were determined by quantitative morphometry of the wound area. The ratio of healing rates of eyes perfused with epidermal growth factor and control eyes provided a measure of the effect of epidermal growth factor on wound healing, and was defined as the epidermal growth factor enhancement factor. RESULTS: The enhancement factor was found to be 1.04 +/- 0.08, 1.17 +/- 0.07, 1.43 +/- 0.09, and 1.59 +/- 0.07 for perfusion times of 1, 2, 4, and 8 hours, respectively. The concentration response enhancement factors were 0.99 +/- 0.08, 1.43 +/- 0.09, 1.21 +/- 0.09, and 0.95 +/- 0.07 for the 5, 50, 100, and 500 micrograms/ml 4-hour perfusions, respectively. CONCLUSION: The results indicated that continuous epidermal growth factor exposures of as few as 2 hours produced a significant increase in healing rates (P < 0.05); increasing the time of exposure further increases the rate of wound healing. Results from the concentration response experiments showed that the optimum epidermal growth factor concentration for enhancing epithelial wound healing is approximately 50 micrograms/ml.

Animals↗
PubMed1993

Cloning of a DNA probe and its application in the detection of Plasmodium falciparum. A preliminary report.

The clones containing parasite DNA fragments were screened from a genomic DNA library of Plasmodium falciparum FCC1/HN isolate. A DNA probe derived from clone pBF4 consisting of 3 kilobase pairs hybridizes specifically with P. falciparum DNA but not with human DNA, P. cynomolgi DNA or P. berghei DNA. The nick translated radiolabelled probe can detect 10 pg purified P. falciparum DNA and a 0.001% parasitemia after 24 hours of film exposure. The probe reacts with all microscopically diagnosed P. falciparum samples and 3 of 41 P. vivax samples as well but not with any of 10 human DNA samples.

Adult↗
PubMed1990

[Fournier's gangrene: report of 3 cases].

Fournier's gangrene is defined classically as a fulminant, rapidly spreading infection of the scrotum that also involves the perineum, penis and abdominal wall. The pathologic findings are described as synergistic gangrene secondary to a polymicrobial flora with a poorly defined portal of entry. We report 3 cases of Fournier's gangrene. Case 1 was a 67 years old who was admitted with the chief complaint of scrotal swelling and necrosis. Case 2 was a 59 years old who was admitted with the problem of scrotal swelling and pain, he had sought other medical help without success, and was then transferred to our hospital. Case 3 was a 62 years old who was admitted with the chief complaint of scrotal swelling and pain for 2 days. These 3 patients were all found to have diabetes mellitus. All 3 patients required aggressive surgical debridement, broad-spectrum antibiotics and adjunctive measures. Blood cultures were usually negative and pus cultures were typically aerobic gram-negative rods and gram-positive cocci and anaerobic bacteria of various types, especially Bacteroids fragilis. Our pus cultures revealed Escherichia coli and Staphylococcus aureus in Case 1, Enterobacter cloacae in Case 2 and E. coli, B. fragilis and Pseudomonas aeruginosa in Case 3. This disease is no longer a disease of young men. After 1945, the average age in 119 reported cases was 51.3 years and the average age of our cases was 62.7 years. Before the era of antibiotics, scrotal gangrene was not a rarity. In these modern times, in spite of seeking medical attention early, patients still developed scrotal gangrene and the mortality rate is high.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Experimental study on topical antimicrobial agents in burns.

Numerous organic silver salts have been tested against a virulent strain of Pseudomonas aeruginosa which had been deliberately applied to the scalded tails of mice and deeper scald wounds on the backs of rabbits. Silver pipemidate was found to be more effective than silver sulphadiazine in treating these infected wounds.

Administration, Topical↗
PubMedDate not supplied

Finite element modeling of drug distribution in the vitreous humor of the rabbit eye.

Direct intravitreal injection of drug is a common method for treating diseases of the retina or vitreous. The stagnant nature of the vitreous humor and surrounding tissue barriers creates concentration gradients within the vitreous that must be accounted for when developing drug therapy. The objective of this research was to study drug distribution in the vitreous humor of the rabbit eye after an intravitreal injection, using a finite element model. Fluorescein and fluorescein glucuronide were selected as model compounds due to available experimental data. All required model parameters were known except for the permeability of these compounds through the retina, which was determined by fitting model predictions to experimental data. The location of the intravitreal injection in the experimental studies was not precisely known; therefore, several injection locations were considered, and best-fit retinal permeability was determined for each case. Retinal permeability of fluorescein and fluorescein glucuronide estimated by the model ranged from 1.94 x 10(-5) to 3.5 x 10(-5) cm s(-1) and from 0 to 7.62 x 10(-7) cm s(-1), respectively, depending on the assumed site of the injection. These permeability values were compared with values previously calculated from other models, and the limitations of the models are discussed. Intravitreal injection position was found to be an important variable that must be controlled in both experimental and clinical settings.

Algorithms↗
PubMedDate not supplied

Acid-base values of single pass, batch system, bicarbonate based hemodialysate.

The bicarbonate, calcium, and magnesium values of a single pass, batch system, bicarbonate based hemodialysate were found to be stable during a period of 5 hours, whether the solution was extensively covered by a floating polystyrene lid or not. The pH and PCO2 of the dialysate that had been covered with a floating lid remained stable during the 5 hours, whereas the corresponding values of the dialysate that had not been so covered did show changes that were secondary to the loss of carbon dioxide. The changes were not marked enough to preclude the clinical use of the latter uncovered dialysate.

Bicarbonates↗