Abstract: A process is disclosed for preparing of aromatic polyester-polystyrene block copolymers which comprises subjecting preferentially styrene polymers (A) having terminal functional groups reactive with acid chloride groups and an excess of aromatic dicarboxylic acid dihalides (C) to condensation and then subjecting continuously the resultant mixture and aromatic dihydroxy compounds (B) to interfacial polymerization at the ratio (A)/[(B)+(C)] by weight of 5/95 to 80/20, without separating reaction products of styrene polymers (A) and aromatic dicarboxylic acid dihalides (C), and the block copolymers thus prepared contain a small amount of uncopolymerized styrene polymers, have long aromatic polyester segments, show low birefringence, good transparency, exceptionally low birefringence, low melt viscosity, and good mechanical strength, and are particularly useful as materials for optical instruments.

Abstract: The invention relates to a polyamide resin composition comprising(A) nylon 4.6,(B) an aliphatic polyamide having a CH.sub.2 /NHCO ratio of from 6 to 11 and(C) a non-crystalline polyamide having a glass transition temperature of at least 100.degree. C. The composition has a decreased water absorption while retaining high mechanical strength, heat stability and chemical resistance. Dimensional stability and mechanical properties after water absorption are unexpectedly good.

Abstract: A reagent for assaying .gamma.-glutamyltranspeptidase (.gamma.-GTP) which contains an amino acid dehydrogenase and a substrate specific to .gamma.-glutamyltranspeptidase activity. The reagent can be used to assay the .gamma.-GTP activity directly from the continuous course of reaction without using a standard substance with known activity. The procedure required is simple and easy, and the reagent is capable of determining .gamma.-GTP activity with good accuracy and without being affected by interfering substances, making it satisfactory for routine use in clinical laboratories.