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A Feller

Publications and source records attributed to A Feller.

51 records · Page 3Linked to original sources
PubMed1983

Control-mechanisms acting at the transcriptional and post-transcriptional levels are involved in the synthesis of the arginine pathway carbamoylphosphate synthase of yeast.

In Saccharomyces cerevisiae, the synthesis of the arginine pathway enzyme carbamoylphosphate synthase (CPSase A) is subject to two control mechanisms. One mechanism, the general control of amino acid biosynthesis, influences the expression of both CPA1 and CPA2 genes, the structural genes for the two subunits of the enzyme. The second mechanism, the specific control of arginine biosynthesis, only affects the expression of CPA1. To study these mechanisms in more detail, we have cloned the CPA1 and CPA2 genes and used their DNA to measure the CPA1 and CPA2 mRNA content of cells grown under various conditions. A close coordination was observed in the variation of the levels of CPA1 and CPA2 mRNAs and polypeptide products under conditions where the general control of amino acid biosynthesis operates. In contrast, little correlation was found between the levels of CPA1 mRNA and the corresponding protein for conditions affecting repression by arginine: the total amplitude of variation was 6-fold higher for the CPA1 protein than for the CPA1 messenger transcript. Such findings are consistent with the conclusion that the general control operates at the transcriptional level and that the specific arginine control acts primarily at a post-transcriptional level.

Arginine↗
PubMed1982

Promoter mapping and selection of operator mutants by using insertion of bacteriophage Mu in the argECBH divergent operon of Escherichia coli K-12.

The analysis of a large number of Arg mutants obtained by inserting phage Mu in the argECBH cluster of genes confirmed the "facing" arrangement proposed earlier for the promoters of argE (argEp) and argCBH (argCBHp) and clarified remaining ambiguities regarding the localization of argEp. Casadaban and Cohen's Mu d lac phages (M. Casadaban and S. N. Cohen, Proc. Natl. Acad. Sci. U.S.A. 76:4530-4533, 1979) were used to construct strains where either an intact or a truncated lacZ gene was fused to argC or argB. Several operator-constitutive mutations could be selected for in such strains; the mutations affected both arms of the cluster, thereby defining one common operator region for both directions of transcription.

Bacteriophage lambda↗
PubMed1981

Hydrometrocolpos, postaxial polydactyly, congenital heart disease, and anomalies of the gastrointestinal and genitourinary tracts: a rare autosomal recessive syndrome.

Nine cases with the hydrometrocolpospolydactyly syndrome (4 males, 5 females) from four unrelated families are presented. Leading symptoms of this rare disorder were hydrocolpos and postaxial polydactyly. Three affected girls had urinary hydrocolpos without vaginal septum or imperforate hymen, one had partial vaginal atresia, and one had no hydrometrocolpos. Glandular hypospadias and prominent scrotal raphe are added to the spectrum of malformations in this disorder in males. The literature is reviewed and problems in genetic counseling in this autosomal recessive disorder are discussed.

Abnormalities, Multiple↗
PubMed1980

Patterns of polarity in the Escherichia coli car AB gene cluster.

The direction of transcription of the carAB gene cluster, which codes for Escherichia coli carbamoylphosphate synthase, was deduced from the effects of phage Mu-1 insertions in each of the two genes and from the results of ribonucleic acid-deoxyribonucleic acid hybridization experiments relating the quantity of car messenger ribonucleic acid to the location of various car mutations. The car locus appears to constitute an operon polarized from carA to carB. The levels of carA and carB products were determined in a large number of car mutants by using in vitro and in vivo complementation assays. The results obtained display strong anomalies, which are discussed in light of the conclusions described above.

Bacteriophage mu↗
PubMed1979

Dual regulation of the synthesis of the arginine pathway carbamoylphosphate synthase of Saccharomyces cerevisiae by specific and general controls of amino acid biosynthesis.

The synthesis of the arginine pathway carbamoylphosphate synthase (CPSase A) of Saccharomyces cerevisiae is subject to two control mechanisms. One mechanism is specific for CPSase A and is exerted by arginine; it probably involves a repressor-operator type of interaction. This "specific" mechanism regulates the expression of gene cpaI coding for the small "glutaminase" subunit of CPSase A but has little influence on the production of the large subunit of the enzyme, a product of gene cpaII. This large component, which alone has no biological significance, accumulates freely under conditions of arginine repression. The second mechanism is general: it controls enzyme synthesis in a number of amino acid biosynthetic pathways in addition to the arginine sequence. Two types of evidence that this "general" mechanism participates in the control of CPSase A synthesis are presented: (1) Derepression upon starvation for any amino acid of which the synthesis is subject to this general control; and (2) repression during growth in amino acid-rich medium. In contrast to the specific mechanism, the "general" mechanism regulates the expression of both the cpaI and cpaII genes.

Arginine↗
PubMedDate not supplied

Postprandial systolic blood pressure and subsyndromal depression.

Changes in systolic blood pressure following the consumption of a standard meal were measured. We hypothesized that larger postprandial drops in systolic blood pressure would be associated with elevated subsyndromal depressive symptomatology. Following an overnight fast, individuals consumed a liquid meal. Blood pressure and pulse were measured preprandially and during the 90-min postprandial period. Several days later, individuals completed a test for depression. Men and women, patients and caregivers, aged 51 to 82 years, were recruited at an outpatient geriatric day care center. Measurements included systolic and diastolic blood pressures, pulse, and Zung Self-Rating Depression Scale. Results showed that the larger the drop in systolic blood pressure, the higher level of somatic depressive symptomatology. This is the first study to identify depressive symptomatology associated with postprandial systolic blood pressure. These results parallel those reported by Perlmuter and Greenberg (Experimental Aging Research, 22, 325-341, 1996) showing that orthostatic changes in systolic blood pressure were associated with elevated subsyndromal depression.

Aged↗
PubMedDate not supplied

Survival after percutaneous endoscopic gastrostomy: the role of dementia.

BACKGROUND: Percutaneous Endoscopic Gastrostomy (PEG) is a widely used technique for enteral feeding in nursing home patients. Several factors including malnutrition, hypoalbuminemia, older age, number of co-morbidities and cognitive impairment adversely affect survival. OBJECTIVE: This study evaluated the relative impact of age, serum albumin, number of co-morbid illnesses and dementia on survival in male nursing home patients who had undergone percutaneous endoscopic gastrostomy (PEG). DESIGN: In a retrospective study the hospital records of all North Chicago Veterans Affair (VA) male nursing home residents (n=88) who had PEG placed between 1990 through 2000 were reviewed. Of the 88 charts reviewed, 17 were eliminated from analysis due to incomplete data. Following data was examined: Age, serum albumin, number of co-morbid illnesses, presence of dementia, survival in years following PEG placement. RESULTS: Advancing age was associated with increasing probability of dementia and increased number of co-morbidities. Post PEG survival decreased with increasing age, with lower serum albumin, and increased number of co-morbidities. Age and serum albumin were strong predictors of survival in PEG recipients without the diagnosis of dementia. However, in PEG recipients with a diagnosis of dementia, age and serum albumin no longer predicted survival. Dementia appears to attenuate the effects of age and serum albumin on survival following PEG placement. CONCLUSION: In the presence of dementia, none of the usual predictors of survival in PEG recipients remain significant.

Age Factors↗