Biomedical subjects
Publications and source records attributed to T F Tsao.
Color Doppler twinkling artifact is known as a rapidly changing mixture of red and blue behind certain strongly reflecting structures. This artifact has been described behind calcifications in various tissues. We describe a case of twinkling artifact related to chronic pancreatitis with parenchymal calcification.
The effects of electrosurgery, retraction cord, and the rotary gingival curettage technique were tested clinically and histologically in dogs. Postoperative periods analyzed ranged from 6 hours to 14 days. All methods induced some kind of minor damage. Recession of clinical magnitude was induced only by rotary gingival curettage. Apical migration of the junctional epithelium was not seen.
The facial marginal alveolar bone of dogs was exposed with a full-thickness flap and touched by an activated electrosurgery electrode for periods of 0, 1, 5 and 10 seconds. Microscopic results were evaluated after periods ranging from 0 hours to 28 days. Various electrode exposure times produced similar changes in bone and periodontal ligament. The extent of the destruction was greater than that found in surgical areas not exposed to electrosurgery; healing and remodeling phases were also delayed in the electrosurgical sites.
The susceptibility of selected oral bacteria, including suspected periodontopathogens, to a commonly employed Chinese herbal medicine Huang-chin (HC, Scutellaria baicalensis) was tested in vitro. The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) were determined. HC was also compared with tetracycline, alexidine, and stannous fluoride. HC decoction, at a concentration of 2%, was bacteriostatic in eight of 11 bacteria tested, but a concentration of 3.13% or greater was required for bactericidal effect. Among the tested bacteria, Bacteroides melaninogenicus ss intermedius was the most sensitive (MIC = 1.57%, MBC = 2%); Actinomyces viscosus was the least sensitive (MIC = 6.25%, MBC = 12.5%). Tetracycline, alexidine, and SnF2 were bactericidal in vitro in all bacteria tested at concentrations lower than those used clinically.
Two dentists--an American who has visited China three times in the past two years and a Chinese who is on a two-year teaching exchange program in the United States--provide their American colleagues with an introduction to dentistry in the People's Republic of China.
Neurospora crassa can utilize various purine bases such as xanthine or uric acid and their catabolic products as a nitrogen source. The early purine catabolic enzymes in this organism are regulated by induction and by ammonium repression. Studies were undertaken to investigate purine base transport and its regulation in Neurospora. The results of competition experiments with uric acid and xanthine transport strongly suggest that uric acid and xanthine share a common transport system. It was also shown that the common transport system for uric acid and xanthine is distinct from a second transport system shared by hypoxanthine, adenine and guanine, and apparently also distinct from the transport system(s) for adenosine, cytosine and uracil. Regulation of the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system was studied. The results reveal that the uric acid-xanthine transport system is regulated by ammonium repression, but does not require uric acid induction. Neither ammonium repression nor uric acid induction controls the hypoxanthine-adenine-guanine transport system. A gene, designated amr, which is believed to be a positive regulatory gene for nitrogen metabolism of Neurospora crassa, was found to dramatically affect both the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system. A model for the action of the amr locus as a positive regulatory gene and for the interaction between the amr gene product and its recognition sites will be discussed.