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Biomedical subjects

J S Liang

Publications and source records attributed to J S Liang.

26 records · Page 2Linked to original sources
PubMed1979

Isolation and partial synthesis of a new metabolite of medroxyrogesterone acetate.

3 alpha-Hydroxy-17-acetoxy-6 alpha-methyl-5 beta-pregnan-20-one (IIIa) has been isolated from urine of patients receiving medroxyprogesterone acetate (MPA). It was characterized by partial synthesis from MPA by catalytic reduction with palladium-charcoal to 17-acetoxy-6 alpha-methyl-5 beta-pregnan-3,20-dione (IV) and reduction of the latter with sodium borohydride. The isolation of 6 beta, 17,21-trihydroxy-6 alpha-methyl-pregn-4-ene-3,20-dione (IIc) is reported for the first time. The 17- and 21-monoacetates of this compound have been isolated and characterized earlier by other investigators. 7 alpha-3H-Medroxyprogesterone acetate was administered to 4 subjects by intravenous and intramuscular injections and by mouth. The ring A saturated metabolite IIIa was excreted in 0.1% to 4.0% of the administered dose; the highest excretion was after the intravenous dose and lowest after oral ingestion. 6 beta, 17,21-Trihydroxy-6 alpha-methylpregn-4-ene-3,20-dione (IIc) and its 17- and 21-monoacetates were excreted in about 5% of the doses in all subjects. No increase in 6 beta-hydroxylation was observed in the patient treated with o,p'-DDD,2,2-bis(2-chlorophenyl, 4'-chlorophenyl)-l,1-dichloroethane.

Adult↗
PubMedDate not supplied

Anti-muscarinic toxins from Dendroaspis angusticeps.

Toxins from the venom of the African green mamba, Dendroaspis angusticeps, fulfill a major need for selective ligands for some of the five genetically defined subtypes of muscarinic acetylcholine receptors (m1-m5). Two toxins have been found that are highly selective antagonists for m1 and m4 receptors (m1-toxin and m4-toxin, respectively). Two other toxins (MT1 and MT2) bind with high affinity to both m1 and m4 receptors, and are agonists. Components of the venom also modify the binding of radiolabeled antagonists to m2 receptors, but an m2-selective toxin has not yet been isolated, m1-Toxin can bind to m1 receptors at the same time as typical competitive antagonists, suggesting that this toxin binds to the N-terminal and outer loops of m1 receptor molecules, rather than within the receptor pocket where typical agonists and antagonists bind. The binding of toxins to the outer parts of receptor molecules probably accounts for their much higher specificity for individual receptor subtypes than is seen with smaller ligands. Toxins are useful for identifying, counting, localizing, activating and blocking m1 and m4 receptors with high specificity.

Allosteric Regulation↗
PubMedDate not supplied

Congenital diaphragmatic hernia misdiagnosed as pneumothorax in a newborn.

Congenital diaphragmatic hernia (CDH) is usually left sided and has a large defect allowing abdominal viscera herniated into thoracic cavity. The chest films usually show air-filled stomach and/or loops of bowel in the ipsilateral hemithorax with mediastinal shift. We report a newborn with CDH, presenting as hyperlucent hemithorax, right-shifted mediastinum, apparently normal pattern of abdominal bowel gas, with the tip of nasogastric tube below the left hemidiaphragm on the radiograph. It was initially misdiagnosed as pneumothorax, and the acute respiratory distress was temporarily relieved by needle aspiration. Hyperlucent hemithorax due to intrathoracic gastric dilatation alone is an unusual presentation of CDH in neonatal period. Absence of stomach bubble in the left upper quadrant of the abdomen, in both radiography and abdominal sonography, is an important clue to make diagnosis of CDH in this misleading condition.

Diagnostic Errors↗