摘要:

We have used visual screening for a mutationally induced uncoordinated phenotype, coupled with subsequent enzymatic assay, to isolate 19 new mutations producing acetylcholinesterase (AChE) deficiencies in the nematodeCaenorhabditis elegans. At least 13 of these are independent, and all fall within two genes,ace-1 Xandace-2 I, previously shown to control respectively two kinetically distinct major AChE classes, A and B. Three of the 4 newace-1alleles and one of the 15 newace-2alleles are apparently leaky; the rest are probably null. For the 3 leakyace-1alleles, qualitative changes in the residual class A AChE strongly support the contention thatace-1is a structural gene. Inace-2;ace-1mutants, marked reduction in class A and B AChE reveals a third, minor, previously unrecognized AChE class, designated C.

ISSN:0167-7063    

DOI:10.3109/01677068509100144

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Inace-2;ace-1double mutants of the nematodeC. elegans, where the major acetylcholinesterase (AChE) classes A and B have been eliminated by mutation, the animals are viable and residual AChE activity remains. This residual activity differs markedly from AChE classes A and B; itsKmfor acetylcholine is 1000-5000-fold lower, its resistance to eserine is 3000-260,000-fold higher, it is markedly more thermo-labile, and it can be separated from classes A and B by ion exchange chromatography. It has been designated class C AChE. Class C AChE of indistinguishable properties is also present in wild type C.elegans, at levels approximating those seen inace-2;ace-1double mutants, suggesting that it is controlled by a third, as yet unidentified, gene. Amongst other sources examined, class C-like AChE has been detected in another nematode species,Stepkanurus dentatus, but not inDrosophila melanogaster, Torpedo californica, orRattus rattus.

ISSN:0167-7063    

DOI:10.3109/01677068509100145

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

A direct assay has been developed for succinic semialdehyde dehydrogenase in sonicates of human lymphocytes and Epstein-Barr Virus transformed cultured lymphoblasts. Enzyme activity was quantified by incubating cell extracts with uniformly labeled [14C]succinic semialdehyde and monitoring the conversion to [14C] succinic acid. Radiolabeled products were separated by liquid partition chromatography on hydrated silicic acid. Kinetic properties and requirements of succinic semialdehyde dehydrogenase in lymphoblast sonicates were investigated in order to determine optimal conditions for the direct assay. Enzyme activity was stimulated by dithiothreitol, ammonium and potassium ions and 0.1% Triton X-100. The concentrations for half maximal activation by ammonium and potassium were 5.2 and 13.7 mM respectively. The mean activity of succinic semialdehyde dehydrogenase in assays in which equimolar NADP+had been substituted for NAD+was 19 % of the activity of assays which contained NAD+. Substrate Michaelis constants were 21 and 30μM for NAD+and 26, 42 and 70μM for succinic semialdehyde. The enzyme displayed a pH optimum between 8 and 9 and demonstrated a slight temperature activation between 37°and 45°C. A deficiency of succinic semialdehyde dehydrogenase activity was documented in cultured lymphoblasts derived from a patient withγ-hydroxybutyric aciduria.

ISSN:0167-7063    

DOI:10.3109/01677068509100146

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

A boy with the Dandy-Walker syndrome associated with multiple congenital abnormalities is described. Chromosomal analyses revealed an abnormal chromosome 21, inherited from his father who had a balanced translocation involving chromosomes 12 and 21: rcp(12;21)(q24.1;q22.1). The clinical features of this patient are compared with published descriptions for duplication 12q24→qter and a review of the literature pertaining to chromosomal anomalies found in other patients with the Dandy-Walker syndrome is presented.

ISSN:0167-7063    

DOI:10.3109/01677068509100147

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

ISSN:0167-7063    

DOI:10.3109/01677068509100148

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor