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Y M Li

Publications and source records attributed to Y M Li.

122 records · Page 7Linked to original sources
PubMed1980

Observations on Baiji (Lipotes vexillifer) and finless porpoise (Neophocaena asiaeorientalis) in the lower reaches of the Chang Jiang.

Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April. The Finless porpoises are usually seen in groups of five or six individuals. The blow of Lipotes lasts 0.2-0.6 sec and that of Neophocaena 0.2-0.5 sec. In Lipotes, a short dive would take 10-20 sec and a long dive up to 1-2 min (average value being 31 sec). In Neophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec. Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eye muscles and nerves and the position of the eyes in the head correspond with the physical conditions of the environments, so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direction under water. With the Baiji this would occasionally cause fatal injuries by the propeller of the ship. Such a case seems much less often with Neophocaena. The population of Lipotes is at present very small. In the stretch of the river (between Nanjing and Taiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. The cause for its scarcity is mostly due to accidents or wounds caused by propellers.

Adaptation, Physiological↗
PubMedDate not supplied

Endothall thioanhydride: structural aspects of unusually high mouse toxicity and specific binding site in liver.

The thioanhydride of the herbicide endothall is highly toxic to mice on intraperitoneal (ip) administration, with an LD50 of 0.31 mg/kg compared to 4.0 and 14 mg/kg for the corresponding anhydride and dicarboxylic acid, respectively. This unusually high toxicity of the thioanhydride relative to the anhydride and dicarboxylic acid is observed also for the 5,6-dehydro analogue and less so for the 2-methyl and 5-endo-(cyanomethyl) analogues but not for five related series of 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acids, anhydrides, and thioanhydrides with various 2-, 3-, 5- and 6-substituents. Synthesis of [exo,exo-5,6-3H]endothall thioanhydride ([3H]ETA) allowed radioligand binding studies with mouse liver cytosol, which was found to have a high-affinity binding site (apparent dissociation constant 32 nM, maximum number of binding sites 2.8 pmol/mg of protein, greater than 95% specific binding). The potency of 18 endothall analogues as dicarboxylic acids and anhydrides for inhibiting [3H]ETA binding in vitro is a very good predictor of their mouse toxicity (r = 0.95, n = 16; two related compounds are of low activity in both assays) in a similar manner to earlier studies with [3H]-2,3-dimethylendothall anhydride (cantharidin) (r = 0.83, n = 15). This correlation does not extend to most of the thioanhydrides, particularly the 2,3-dimethyl and 2,3-trimethylene compounds, which are the most stable to hydrolytic cleavage. The [3H]ETA binding site of liver cytosol is inhibited 75-80% by LD50 doses of 2,3-dimethylendothall anhydride and thioanhydride but only 24% by an LD50 dose of endothall thioanhydride, with assays 30 min after ip treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Anhydrides↗