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M C Cheng

Publications and source records attributed to M C Cheng.

66 records · Page 4Linked to original sources
PubMed1975

New aromatic diamidines with central alpha-oxyalkane or alpha, omega-dioxyalkane chains. Structure-activity relationships for the inhibition of trypsin, pancreatic kallikrein, and thrombin and for the inhibition of the overall coagulation process.

A series of omega-amidinophenylalkyl amidinophenyl ethers was synthesized and examined for inhibitory activity against trypsin, pancreatic kallikrein, and thrombin. Modifications of the compounds included lengthening of the alkane chain, variation in the position of the amidino groups, and substitution of halogen on the benzene rings. The compounds act as competitive reversible inhibitors, and many of them possess considerable potency. An outstanding trypsin inhibitor was found in 4-amidinophenylethyl 4 amidino-2-bromophenyl ether (compound 7) with a Ki value of 7.3 x 10(-8) M (pH 8.1, 37 degrees). A number of aromatic diamidines with a central dioxyalkane chain were similarly studied. Here, 1-(4-amidino-2-iodophenoxy)-5-(3-amidinophenoxy)pentane (compound 32) was a highly effective inhibitor of bovine thrombin (Ki = 1.1 x 10(-6) M), of human thrombin, and of the overall clotting process of human plasma.

Amidines↗
PubMedDate not supplied

N-acetylated endorphins in ovine anterior pituitary and neuro-intermediate lobe.

We have used an antiserum for immunohistochemistry and RIA/RP-HPLC which recognizes all fragments of N-acetylated endorphin (NacEP). In the rat neuro-intermediate lobe (N-IL), in addition to the N-acetylated forms of immunoreactive-beta-endorphin (ir-beta EP) already reported, we have demonstrated Nac beta EP as a minor component. In the sheep pituitary processing of beta EP is markedly different. In the anterior pituitary (AP), staining was indistinguishable with beta EP and NacEP antisera, in contrast with the rat where many fewer AP cells stained with the NacEP antiserum. Secondly, as in the rat, all N-IL cells stained with both antisera; on RP-HPLC, however, the major forms of NacEP in the sheep N-IL were Nac beta EP (approximately 40%), Nac beta EP (approximately 25%) and Nac beta EP (approximately 20%), with Nac beta EP (approximately 2%) as a minor component. A similar profile was seen on RP-HPLC of sheep AP. These data suggest that (1) patterns of processing in sheep AP are similar to those in N-IL, though the extent of acetylation is less and (2) in the sheep pituitary low molecular weight acetylated fragments predominate, in contrast with the rat.

Acetylation↗
PubMedDate not supplied

Classification, pathogenicity, and drug susceptibility of hemolytic gram-negative bacteria isolated from sick or dead chickens.

Fifteen hemolytic gram-negative bacteria were isolated from the respiratory tracts of sick birds suffering from a long-lasting respiratory syndrome or from the bone marrow of dead birds distributed in the southern part of Taiwan. These were classified as Pseudomonas aeruginosa (10 isolates), Pseudomonas fluorescens (2 isolates), Pseudomonas stutzeri (1 isolate), Pasteurella haemolytica (1 isolate), and Proteus morganii (1 isolate). Each isolate was inoculated intraperitoneally into one group of ten 4-week-old male white leghorn chickens. Mortality and lesions were scored daily for 1 week. Three of the 10 isolates of Pseudomonas aeruginosa caused 100% mortality. Six other isolates of Pseudomonas aeruginosa and the one isolate of Proteus morganii caused 50% mortality. The remaining isolates induced less than 30% mortality. The sole nonpathogenic sample was one isolate of Pseudomonas fluorescens. When therapeutic levels of 22 antibiotics or sulfa drugs were evaluated for their inhibitory activity against the 15 isolates, the most effective were apramycin (15/15), gentamicin (15/15), spectinomycin (13/15), oxytetracycline (8/15), and sulfachloropyrazine (7/15). The least effective were ampicillin, cloxacillin, and tiamulin, which were not effective against any of the isolates. The 14 other drugs were of very low (> 4/15) effectiveness. Most of the isolates studied were virulent for chickens and very resistant to currently used drugs.

Animals↗