Human red cell NADP-dependent xylitol dehydrogenase: kinetic and genetic studies

A Thesis submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, for the Degree of Doctor of Philosophy.A deficiency of the enzyme NADP dependent xylitol dehydrogenase (L-xylulose reductase) has previously been found to be the cause of chronic essential pentosuria. Essential pentosuria is a recessively inherited condition which is marked by the continual excretion of relatively large amounts of the enzymes substrate, L-xylulose. The major objective of the study described was to find a simple method for the identification of individuals who are heterozygous for the "pentosuria" and normal alleles. The pentosuria allele could then be used as a gene marker in linkage studies aimed at mapping the L-xylulose reductase locus. A L-xylulose reductase assay suitable for the identification of carriers of essential pentosuria was developed and tested on members of a South African Lebanese family in which the inheritance of pentosuria had previously been suggested to be dominant. It was found that family members could, on the basis of their L-xylulose reductase activities, be classified as either normal, heterozygous or homozygous for the pentosuria allele. Measurements of serum L-xylulose concentrations revealed that pentosuria is, contrary to the previous report, . recessively inherited in this family. A sample of the local Ashkenazi Jewish population was screened for pentosuria carriers. Six out of the 237 individuals screened were found (on the basis of their L-xylulose reductase activities and from the results of a loading test), to carry the pentosuria allele. The frequency of the pentosuria allele in this population was estimated from the apparent heterozygote frequency to be 0.0127. Linkage analyses were carried out on the families of the identified heterozygotes and on members of the Lebanese family mentioned above. No evidence of tight linkage was found between the pentosuria allele's locus and those coding for various red cell antigens, red cell enzymes and serum proteins. Kinetic, chromatographic and electrophoretic studies revealed that the red cells of normal individuals contain two distinct L-xylulose reductases, a minor and a major isozyme. Pentosurics lack the major isozyme but appear to have approximately normal amounts of the minor isozyme. The minor isozyme is e1ectrophoretica 1 1 y distinct from the major isozyme, has markedly higher Michael is constants for the substrates L-xylulose and xylitol and shows a lower pH optimum when catalysing the oxidation of xylitol. Electrophoresis also revealed that liver tissue contains two L-xylulose reductases which occur in similar proportions to those of red cells but which migrate at slightly different rates.WHSLYP201

Spherical Categories

This paper is a study of monoidal categories with duals where the tensor product need not be commutative. The motivating examples are categories of representations of Hopf algebras and the motivating application is the definition of 6j-symbols as used in topological field theories. We introduce the new notion of a spherical category. In the first section we prove a coherence theorem for a monoidal category with duals following MacLane (1963). In the second section we give the definition of a spherical category, and construct a natural quotient which is also spherical. In the third section we define spherical Hopf algebras so that the category of representations is spherical. Examples of spherical Hopf algebras are involutory Hopf algebras and ribbon Hopf algebras. Finally we study the natural quotient in these cases and show it is semisimple.Comment: 16 pages. Minor correction

Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs

Cryptophyte and chlorarachniophyte algae are transitional forms in the widespread secondary endosymbiotic acquisition of photosynthesis by engulfment of eukaryotic algae. Unlike most secondary plastid-bearing algae, miniaturized versions of the endosymbiont nuclei (nucleomorphs) persist in cryptophytes and chlorarachniophytes. To determine why, and to address other fundamental questions about eukaryote–eukaryote endosymbiosis, we sequenced the nuclear genomes of the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. Both genomes have \u3e21,000 protein genes and are intron rich, and B. natans exhibits unprecedented alternative splicing for a single-celled organism. Phylogenomic analyses and subcellular targeting predictions reveal extensive genetic and biochemical mosaicism, with both host- and endosymbiont-derived genes servicing the mitochondrion, the host cell cytosol, the plastid and the remnant endosymbiont cytosol of both algae. Mitochondrion-to-nucleus gene transfer still occurs in both organisms but plastid-to-nucleus and nucleomorph-to-nucleus transfers do not, which explains why a small residue of essential genes remains locked in each nucleomorph

Some discriminative properties of syntactic structures

SummaryForty scripts were prepared that contained the same 36 kernel sentences with one of four syntactic structures: declarative, negative, passive, or query. The relative frequency of the structures in each script was varied systematically. Tape recordings of the scripts, read by 40 speakers, were presented to listeners who sorted a (different) set of 144 sentences according to their estimate of which speaker was most likely to have said each sentence. The distribution of syntactic structures in the stimulus scripts was compared with the corresponding distribution arrived at by the listener.When a particular syntactic structure predominated in a speaker's corpus, the listeners tended to assign all the sentences of the dominant form exclusively to that speaker. When the relative frequencies of the syntactic structures in a corpus were more nearly equal, the listeners tended to assign structures at random. Most of the confusions in discrimination, that is, assignment of a structure to a speaker much more often than it was uttered, were associated with the declarative and passive sentence structures. These syntactic forms generalized most often with each other and more often with the remaining syntactic forms than either negative or interrogative sentences.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32180/1/0000236.pd

Aquilegia, Vol. 22 No. 4, July-August 1998: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1085/thumbnail.jp

Exchangeable Urn Processes

1 online resource (PDF, 14 pages

A Strong Law for Some Generalized Urn Processes Hill

1 online resource (PDF, 24 pages