Mutations for the autosomal recessive and autosomal dominant forms of polycystic kidney disease are not allelic

Summary The autosomal dominant form of polycystic kidney disease (ADPKD) has been linked to the -globin gene locus on 16p. Linkage studies between the autosomal recessive type (ARPKD) and the 3 HVR of the -globin gene cluster showed that the ARPKD and ADPKD are not allelic.     

Rioarribasaurus,a new name for a Late Triassic dinosaur from New Mexico (USA)

The Late-Triassic-dinosaur generic nameCoelophysis Cope 1889 (type species C.bauri [Cope 1887]) is a nomen dubium because the lectotype of C.bauri, AMNH 2722, is four sacral vertebrae and a pubic process of the ilium that are not diagnostic. Dinosaur specimens from the famous Whitaker (“Coelophysis”) quarry in the Rock Point Member of the Chinle Formation at Ghost Ranch, New Mexico thus lack a valid name. We create a new genus and species name,Rioarribasaurus colberti, for these specimens.     

Studies on the biosynthesis of tropane alkaloids in Datura stramonium L. transformed root cultures

The relative contributions made by the l-arginine/agmatine/N-carbamoylputrescine/putrescine and the l-ornithine/putrescine pathways to hyoscyamine formation have been investigated in a transformed root culture of Datura stramonium. The activity of either arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17) was suppressed in vivo by using the specific irreversible inhibitors of these activities, dl--difluoromethylarginine or dl--difluoromethylornithine, respectively. It was found that suppression of arginine decarboxylase resulted in a severe decrease in free and conjugated putrescine and in the putrescine-derived intermediates of hyoscyamine biosynthesis. In contrast, the suppression of ornithine decarboxylase activity stimulated an elevation of arginine decarboxylase and minimal loss of metabolites from the amine and alkaloid pools. The stimulation of arginine decarboxylase was not, however, sufficient to maintain the same potential rate of putrescine biosynthesis as in control tissue. It is concluded that (i) in Datura the two routes by which putrescine may be formed do not act in isolation from one another, (ii) arginine decarboxylase is the more important activity for hyoscyamine formation, and (iii) the formation of polyamines is favoured over the biosynthesis of tropane alkaloids. An interaction between putrescine metabolism and other amines is also indicated from a stimulation of tyramine accumulation seen at high levels of dl--difluoromethylornithine.Abbreviations ADC arginine decarboxylase - DFMA dl--dif-luoromethylarginine - DFMO dl--difluoromethylornithine - MPO N-methylputrescine oxidase - ODC ornithine decarboxylase - PMT putrescine N-methyltransferase We are indebted to Dr. E.W.H. Bohme of Merrell Dow Research Laboratories (Cincinnati, Ohio, USA) for kind gifts of DFMO and DFMA and to Dr. M.J.C. Rhodes for helpful advice and discussion.     

Rapid acquisition of three-dimensional triple-resonance experiments using pulsed field gradient techniques

Summary A rapid method for recording three-dimensional triple-resonance experiments utilising pulsed field gradient techniques is proposed, and applied to the HNCO experiment. In order to optimise the sensitivity of the method, a short phase cycle is used in conjunction with the pulsed field gradients to select the desired coherence transfer pathway. The method is demonstrated for the HU protein.     

Isolation of brush-border membranes from rat and rabbit colonocytes: Is alkaline phosphatase a marker enzyme?

Summary A method for the isolation of brush-border membranes of large intestinal epithelial cells was developed, which is based on the purification of intact brush-border caps by Percoll^® density-gradient centrifugation followed by separation of the vesiculated brush-border membranes on sucrose gradients. The procedure has two major advantages in comparison to known methods: 1) its first step does not depend on the determination of marker enzymes and 2) the method is applicable to rats as well as rabbits without major modifications. Due to the lack of an accepted marker for the colonic brush-border membrane the validity of the isolation procedure was tested by its application to the small intestine. Rat small intestinal brush-border membranes were enriched 21-fold when compared to the homogenate. The method was used to evaluate alkaline phosphatase as a marker enzyme for the colonic brush-border membrane. The results suggest that alkaline phosphatase is not exclusively localized in the brush-border membrane since this enzyme was also associated with membranes having different physical properties.     

Evolution and expression of the transplantation antigen gene family

We have cloned 26 different class I genes that are located in the major histocompatibility complex of the C57BL/10 mouse. Two of the three class I genes found in the H-2 complex encode the H-2Kb and H-2Db antigens; the other 23 class I genes map to the adjacent Tla complex. We have grouped the cosmids containing these genes into three clusters: one cluster links the H-2K and I-A regions, one cluster links the H-2D and Qa-2 regions, and the final cluster maps to the TL region. The class I gene organizations in the Qa-2 and TL regions of the C57BL/10 and BALB/c mice are generally similar, but there are several polymorphic segments. The Qa-2 region of both mice seems to have evolved by the duplication of gene pairs; furthermore, the H-2K region may have been generated by the translocation of a gene pair from the Qa-2 region. We have evidence that several of the genes in the Qa-2 region are expressed.