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Biomedical subjects

M E Walker

Publications and source records attributed to M E Walker.

At least 37 records · Page 2Linked to original sources
PubMed1991

Isolation of a yeast mutant deficient in pyruvate carboxylase activity.

To improve our understanding of the catalytic mechanism and regulatory properties of pyruvate carboxylase (EC 6.4.1.1), an important biotin-dependent enzyme, we have sought to isolate mutants in Saccharomyces cerevisiae which are defective in pyruvate carboxylase activity. One mutant was isolated which was unable to grow on glucose minimal medium unless supplemented with aspartate. Although the enzyme had only 25% of the wild type pyruvate carboxylase activity, Western analysis and RNase protection analysis demonstrated that the mutant gene was expressed at approximately 70% of the wild type level. On the basis of genetic crosses and complementation tests, we have attributed the defect to mutations in the PYC gene encoding pyruvate carboxylase.

Base Sequence↗
PubMed1990

Transport of the yeast ATP synthase beta-subunit into mitochondria. Effects of amino acid substitutions on targeting.

We have isolated the yeast ATP2 gene encoding the beta-subunit of mitochondrial ATP synthase and determined its nucleotide sequence. A fusion between the N-terminal 15 amino acid residues of beta-subunit and the mouse cytosolic protein dihydrofolate reductase (DHFR) was transcribed and translated in vitro and found to be transported into isolated yeast mitochondria. A fusion with the first 35 amino acid residues of beta-subunit attached to DHFR was not only transported but also proteolytically processed by a mitochondrial protease. Amino acid substitutions were introduced into the N-terminal presequence of the beta-subunit by bisulphite mutagenesis of the corresponding DNA. The effects of these mutations on mitochondrial targeting were assessed by transport experiments in vitro using DHFR fusion proteins. All of the mutants, harbourin from one to six amino acid substitutions in the first 14 residues of the presequence, were transported into mitochondria, though at least one of them (I8) was transported and proteolytically processed at a much reduced rate. The I8 mutant beta-subunit also exhibited poor transport and processing in vivo, and expression of this mutant polypeptide failed to complement the glycerol- phenotype of a yeast ATP2 mutant. More remarkably, the expression of I8 beta-subunit induced a more general growth defect in yeast, possibly due to interference with the transport of other, essential, mitochondrial proteins.

Amino Acid Sequence↗
PubMed1989

An analysis of auditory alphabet confusions.

The present study, using the nonhierarchical overlapping clustering algorithm MAPCLUS to fit the Shepard-Arabie (1979) ADCLUS model, attempted to derive a set of features that would accurately describe the auditory alphabet confusions present in the data matrices of Conrad (1964) and Hull (1973). Separate nine-cluster solutions accounted for 80% and 89% of the variance in the matrices, respectively. The clusters revealed that the most frequently confused letter names contained common vowels and phonetically similar consonants. Further analyses using INDCLUS, an individual differences extension of the MAPCLUS algorithm and ADCLUS model, indicated that while the patterns of errors in the two matrices were remarkably similar, some differences were also apparent. These differences reflected the differing amounts of background noise present in the two studies.

Adult↗
PubMed1986

Serology for automated cytotoxicity testing. II. Routine reading of HLA-typing using the Contrast Fluorescence Test.

We have previously reported on the "Contrast Fluorescence Test" (CFT), a method for the fluorimetric of living vs dead lymphocytes and have proposed its use in automated HLA typing. In this report, we present data obtained with the CFT in the evaluation of an automated system built around the Zonax instrument (Zeiss America, Inc.). 13,664 individual CFT results were read by the machine and compared with manual readings; assignment of HLA specificity was done independently but using the same logic by hand and by machine. Excellent correlation of the instrumented and manual serological readings and identical antigen assignments were observed.

Cell Survival↗
PubMed1986

When children die: death in current children's literature and its use in a library.

Death and dying are dealt with realistically and sympathetically in current children's literature. Books can play an important role in helping children suffering from catastrophic illness by showing how other children have coped with similar situations; they can also form a basis for bibliotherapy with patients. This paper examines current trends in children's literature and describes how these books have been incorporated into a patient library at St. Jude Children's Research Hospital.

Bibliotherapy↗
PubMed1982

The HLA system in congenital rubella patients with and without diabetes.

The HLA antigens of 173 patients with the congenital rubella syndrome (CR) are reported. Twenty-one of these patients are also clinically diabetic, and among them the frequencies of the HLA antigens DR2 and DR3 are significantly lower and higher, respectively, than in CR patients without diabetes or in controls. These data suggest that the genes that control susceptibility to type I or insulin-dependent diabetes mellitus are necessary for the development of glucose intolerance in CR patients.

Adolescent↗
PubMed1977

Biochemical genetics of MN.

Quantitative hemagglutination studies of the MN-hemizygous (M/-) patient and his family reported by German et al. are given together with data on the electrophoretic mobility of their red cells. These results, and those obtained on the cells of a donor of the MU phenotype (MU=M+N-S-s-U+); Mu=M+N-S-s-U), demonstrate a series of shortcomings in the current 'precursor transferase' theory of the biochemical genetics of MN antigens. Another theory is proposed, according to which the effects of the MN genes take place exclusively in the protein part of the glycopeptide. The MN proteins would carry acceptor sites for the antigenic oligosaccharides which are put together by enzymes genetically independent of MN. In M glycoproteins, the acceptor sites are close to each other, in doublets, while in N they are all separate. This model is shown to apply successfully to several difficult problems in MN.

Electrophoresis↗
PubMed1976

Linkage of gene for C2 deficiency and the major histocompatibility complex MHC in man. Family study of a further case.

Close linkage between HL-A and C2 deficiency was first reported by FU and co-workers in 1974. We present here a pedigree of a 31-year-old C2-deficient individual with clinical manifestations of Hodgkins disease. The following markers were tested: C2 levels, factor B polymorphism, blood groups, and enzyme typing. In addition to close linkage between HL-A and C2 deficiency, both parents were heterozygous for Bf (HL-A linked, electrophoretic variation of B). The two HL-A haplotypes closely linked to C2 deficiency are different: 2, W18 and W24, W18. They share, however, the SD2 antigen W18 and the LD type 7a.

Adult↗
PubMed1976

Rhmod, a second kindred (Craig).

Three Rhmod siblings were found to have identical Rh: w1, w2, -3, -4, w5 (see article) phenotypes. All had stomatocytic hemolytic anemia. On quantitative hemagglutination studies, as well as on hand tests, all Rh antigens were not equally depressed. Rh17 (Hr0, 'not D') and Rh29 (RH, 'total Rh') were both normal. Rh5 (hr", e) was only slightly depressed. Rh25 (LW) had 50% of the expression expected in normal Rh:-1 cells. Rh1 (Rh0, D), Rh13 (RhA), Rh14 (RhB), Rh15 (RhC), and Rh16 (RhD), were severely depressed. Rh2 (rh', C) was depressed, while Rh7 (rhi, Ce) was absent. Both Rh19 (hrS) and Rh31 (hrB) were depressed. Rh12 (rhG, G) was distinctly depressed, scoring considerably less than rGrG red cells. The unrelated parents, the child of the proposita, and some siblings of each parent showed lessened depression of Rh antigens without displaying the consistent pattern that might be expected from a presumed single suppressor gene. Absence of a consistent pattern may have resulted from differing Rh genotypes, but a frequently observed depression involved Rh14, Rh15, and Rh16 (RhB, RhC, and RhD) without an effect on either Rh1 (RH3 or D) or Rh13 (RhA).

Female↗
PubMed1969

Epilepsy and oral contraception.

A controlled cross-over trial in 20 epileptic women, receiving regular anticonvulsant therapy showed that an oral contraceptive with a low oestrogen/ progestogen content had no significant effect on the average frequency of fits compared with identical dummy tablets.

Adolescent↗