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Biomedical subjects

L W Wang

Publications and source records attributed to L W Wang.

48 records · Page 3Linked to original sources
PubMed1986

Temperature sensitivity of a nifA-like gene in Enterobacter cloacae.

Nitrogen fixation (nif) genes of Enterobacter cloacae, a rhizosphere diazotroph of rice plants, were identified by using cloned Klebsiella pneumoniae nif gene fragments as probes for molecular hybridization. The product of a nifA-like gene of E. cloacae appeared less temperature sensitive than the K. pneumoniae nifA gene product. This result correlates with the fact that E. cloacae can fix nitrogen at 39 degrees C, while K. pneumoniae cannot.

Bacterial Proteins↗
PubMed1983

Effect of nifA product on suppression of Nif- phenotype of gln mutation and constitutive synthesis of nitrogenase in Klebsiella pneumoniae.

This paper describes the role of nifA product on the ammonia regulation of nitrogen fixation in K. pneumoniae. A plasmid carrying nifA gene under the promoter of tetracycline resistance gene was constructed. When this nifA carrying plasmid was introduced into a glnAG mutant, the Nif- phenotype of this gln mutant was suppressed. Furthermore, when the plasmid was introduced into the wild type and glnAG mutant, derepression of nitrogenase synthesis in ammonia occurred in both strains and the products of nif genes can be detected by two-dimensional gel electrophoresis in the extracts of these ammonia-grown bacterial cells. The constitutive synthesis of nitrogenase in NH4+ was also demonstrated in free living nitrogen-fixing bacteria, Enterobacter cloacae, when the bacteria received the plasmid carrying nifA gene from K. pneumoniae.

Ammonia↗
PubMed1982

Fecal mutagens in two Japanese populations with different colon cancer risks.

Human feces from 223 Japanese in Hawaii at high risk for colon cancer and feces from 166 Japanese of northern rural Japan at low risk for colon cancer were shown to contain mutagenic activity under five different test conditions. The first assay, using the Ames TA98 and TA100 Salmonella test, detected ether-soluble mutagens in the presence and absence of rat liver microsomes. Of these, the TA98 direct-acting mutagens are present more frequently in the feces of the high-risk population than the low-risk population at a high level of statistical significance (p less than 0.01). TA98 mutagens activated by rat liver microsomes also occur significantly more frequently in the feces of the Japanese from Hawaii (p less than 0.05). Mutagens detected by TA100 in the presence and absence of rat liver microsomes are not commonly found in either Japanese population. The second bacterial test system used to detect fecal mutagens uses Escherichia coli rec-. This system detects water-soluble fecal mutagens which are also present more frequently in the high-risk population than in the low-risk population (p less than 0.05).

Age Factors↗
PubMed1977

Identification and determination of ionic surface active agents.

A general colorimetric method has been developed to analyze either anionic or cationic surfactants in fresh water. An appropriate dye will react with ionic surfactant to form a chloroform-soluble, colored complex in the presence of chloroform. The color intensity of the vigorously rocked and subsequently settled chloroform layer is proportional to the concentration of the "dye-ionic surfactant complex", and can then be measured by making spectrophotometric readings of the chloroform solution at the optimum wavelength of the instrument used. When cationic surfactants are to be analyzed, methyl orange shall be used as a dye; when anionic surfactants are to be analyzed, azure A or methylene blue shall be used as a dye; Other chemical reagents, apparatus and spectrophotometers, however, can be nearly identical for either cationic surfactant or anionic surfactant measurement. The new analytical method is stoichiometric, and can be easily performed by a laboratory technician within a very short period of time.

Chemical Phenomena↗
PubMedDate not supplied

Refractory fetal supraventricular tachycardia with hydrops: report of one case.

Fetal tachycardia sometimes is quite difficult to treat, especially when the fetus has congestive heart failure. Sustained supraventricular tachycardia and hydrops had been diagnosed in a fetus as early as the 27th week of gestational age. A variety of antiarrhythmic agents, including digoxin, digoxin in combination with quinidine or propranolol or verapamil, have been prescribed for the mother, always in a vain effort of conversion of the tachycardia. A baby was born via vaginal delivery at 35 weeks' gestation because of premature labor. The tachycardia disappeared immediately after birth, but several episodes of tachycardia occurred during the neonatal period, and were converted only by electric cardioversion or intravenous amiodarone. Oral amiodarone was then prescribed for three months to prevent recurrence. The baby has lived well without attacks during a one-and-a-half-year follow-up.

Adult↗
PubMedDate not supplied

Systemic fungal infection in very low-birth-weight infants.

This retrospective study was designed to investigate the related factors and outcome of systemic fungal infection in very low-birth-weight (VLBW) infants. Medical records of infants admitted to the neonatal intensive care unit of National Cheng Kung University Hospital between January 1990 and June 1994 were reviewed. Of the 262 VLBW infants, 15 (5.7%) had fungemia (14 Candida 1 Cryptococcus) during the study period. Among the fungemic infants, 60% also had urinary tract infection; 18% had central nervous system infection. Their mean birth weight was 1079 +/- 78 g (504-1474 g), and the gestational age was 28.6 +/- 0.6 weeks (23-32 weeks). Thirteen of them (87%) had respiratory distress syndrome and patent ductus arteriosus, while 60% had chronic lung disease. The percentage of antibiotic usage, parenteral hyperalimentation, endotracheal intubation, placement of central venous line and steroid therapy were 100%, 100%, 73%, 67% and 36% respectively. The mean age at diagnosis of fungemia was 40.5 +/- 4.8 days (10-76 days). Common clinical manifestations were respiratory deterioration (93%), poor feeding (58%) and fever (53%). The frequency of side effects of amphotericin B in decreasing order were: hypokalemia (54%), hyponatremia (31%) and decreased urine amount (23%). The mortality rate was 40%. It was concluded that systemic fungal infection in VLBW infants might result in high mortality and the side effects were high in the treated infants.

Amphotericin B↗
PubMedDate not supplied

Radiosurgery as a treatment alternative for dural arteriovenous fistulas of the cavernous sinus.

PURPOSE: Radiosurgery is an effective treatment for cerebral arteriovenous malformations. We conducted the present study to investigate the feasibility and efficacy of gamma knife radiosurgery for dural arteriovenous fistulas (DAVFs) of the cavernous sinus. METHODS: Eighteen patients (12 women and six men; 29-75 years old [mean age, 55 years]) with DAVFs of the cavernous sinus (Barrow's type B:1, C:7, and D:10) treated by gamma knife radiosurgery were enrolled in the study. DAVFs were bilateral in six patients and unilateral in 12. Stereotactic X-ray angiography and MR imaging were performed for targeting the radiosurgery. Areas of arteriovenous communication targeted for irradiation were first outlined on the X-ray angiograms. The target regions were then transferred to and displayed on the MR images. Dose planning was based on findings on the integrated images. Prescribed maximum target doses were 22 to 38 Gy (mean, 28 Gy). The targets were covered by 50% to 90% isodose levels. Radiation doses to the surrounding optic apparatus were kept to less than 8 Gy. The patients were followed up with color Doppler sonography and MR imaging. When noninvasive imaging suggested obliteration, X-ray angiography was performed to verify the results. RESULTS: The DAVFs were totally obliterated in 12 (80%) of the 15 patients. In the other three, one was almost completely obliterated at 14 months and two were partially obliterated at 19 and 27 months, respectively, after radiosurgery. No complications or symptom worsening occurred during the follow-up period. CONCLUSION: Gamma knife radiosurgery is a feasible, effective, and safe treatment for DAVFs of the cavernous sinus. Integration of stereotactic X-ray angiography and MR imaging not only aids treatment efficacy but also protects the relevant vital structures, especially the optic apparatus, from the hazards of radiation.

Adult↗