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Biomedical subjects

R Fenwick

Publications and source records attributed to R Fenwick.

11 recordsLinked to original sources
PubMed1999

A 6-year experience demonstrates the utility of screening for both cytogenetic and FMR-1 abnormalities in patients with mental retardation.

Cytogenetic abnormalities were found in 81 of 2,757 cases (2.93%) screened for both cytogenetic and FMR-1 mutations because of mental retardation from 1992 to 1997. Of these, 38 (46.9%) were unbalanced autosomal abnormalities, 23 (28.4%) sex chromosomal abnormalities, and 20 (24.7%) balanced autosomal rearrangements. Five subtle deletions were found, of which three involved the long arm of chromosome 7 (7q22-q31.1). Although a high-resolution banding method was used for screening, we concluded that a banding level of 450-550, generally achieved in routine analysis, was sufficient to detect all of these abnormalities. Fragile-X DNA studies revealed CGG expansion mutations in 72 other cases (2.61%). Of the abnormals, 36 (50%) were males and 8 (11.1%) females with full mutations, and 12 (16.7%) were males and 16 (22.2%) females with premutations. Together, our cytogenetic and DNA screening gave 5.5% abnormal results. In this report, these findings are compared with similar surveys of 3,940 subjects from five previous studies. From the combined data of 6,697 cases, this testing approach should reveal nearly equal numbers of cytogenetic and fragile X abnormalities in approximately 6-7% of subjects. It is productive, cost-effective, and consistent with American College of Medical Genetics (ACMG) guidelines for screening of mentally handicapped individuals.

Blotting, Southern↗
PubMed1999

Recession and well-being.

In this paper we address two related questions: how much do economic recessions affect the aggregate well-being of a population, and by what means? Using data from the 1973-77 Quality of Employment Panel of full-time workers who experienced the 1974-75 recession (N = 830), we answer these questions by using an analytic procedure that allows us to determine the percentage of total aggregate (mean) change in well-being attributable to various changes in sociodemographic statuses, labor market positions, and job characteristics. Results from this procedure showed significant increases in the mean levels of distress and dissatisfaction for this sample and that the largest percentages of change were accounted for by changes in job characteristics: about 20 percent of the total change in distress and 47 percent of the total change for dissatisfaction. In particular, increased job demands and increasingly inadequate pay made substantial contributions, with the latter alone accounting for a quarter of the total change in dissatisfaction. Unemployment experiences also contributed substantial, but smaller, percentages to the change in distress (10 percent).

Adult↗
PubMed1996

A preliminary study on the effect of germination on saponin content and composition of lentils and chick peas.

Two cultivars of chick peas (Cicer arietinum) and one cultivar of lentils (Lens culinaris) were subjected to germination in the dark for 6 days at 20 degrees C. Soyasaponin VI, also known as soyasaponin beta g, a DDMP- (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one-) conjugated form of soyasaponin I, was the only saponin detected in both the unprocessed and germinated seed. No significant changes in saponin content were observed for chick peas or lentils after a 6-day germination.

Carbohydrate Sequence↗
PubMed1994

The macroeconomic context of job stress.

Using data from the 1973-1977 Quality of Employment Panel Study, we test a model that conceptually links research on macroeconomic causes of stress with research on job structure causes of stress among employed workers. Results from LISREL 7 (Jöreskog and Sörbom 1989) indicate that, while both macroeconomic and job structure variables have significant cross-sectional and longitudinal effects on stress, the macroeconomic effects are almost entirely indirect in their effect on job structures. In particular, higher occupational unemployment rates increased stress and lowered life satisfaction indirectly through reduced decision latitude and increased job demands. Overall, results suggest that macroeconomic changes, such as recessions, can affect individual stress because they lead to changes in routine job structures that represent increased and continued exposure to stressful conditions.

Adolescent↗
PubMed1992

Physical and genetic characterization of the distal segment of the myotonic dystrophy area on 19q.

The mutation involved in myotonic dystrophy (DM) has been mapped to the region between the ERCC1 DNA repair gene and the anonymous D19S51 locus on 19q13.3. Starting at locus D19S112 (probe pX75b), which served as a novel entry site for this chromosome region, we have established a cosmid contig of approximately 200 kb. In the contig, a gene expressed in the brain and a highly informative, 12-allele (TG)n variable simple sequence motif (VSSM) were identified. With this marker, designated X75b-VSSM, a highly characteristic size distribution of alleles linked with DM, which differed significantly from that on normal chromosomes, was observed. Combining our physical mapping and genetic data, we show that the X75b-VSSM marker is the closest distal to DM, thus excluding the DM mutation from the entire telomeric portion of the ERCC1-D19S51 region.

Base Sequence↗
PubMed1992

An intact cysteine-rich domain is required for dystrophin function.

The carboxyl terminus of dystrophin is encoded by a highly conserved, alternatively spliced region of the gene. The few rare mutations reported in this region are of interest in unraveling the function of the dystrophin molecule. An unusual case of infantile onset Duchenne muscular dystrophy (DMD) with an internal 3' genomic deletion, and a membrane localized non-functional dystrophin protein, was used to explore the functional activity of this region. The patient's cDNA sequence showed an intragenic 1824-bp deletion precisely excising the cysteine rich and alternatively spliced COOH-terminal domains of dystrophin. The unaltered final 2.7 kb of the patients transcript was defined as a single exon localized to two genomic fragments, with the 5.9 kb HindIII fragment containing the stop codon. To understand the significance of deletions in this important region of the dystrophin gene, we mapped the order and cDNA coordinates for the 3' genomic HindIII fragments encoding the cysteine rich and alternative splicing domains. This 3' gene map was used to compare the clinical phenotype of the other reported COOH-terminal deletions in the literature. Our analysis concludes that the cysteine-rich domain confers an important function for the dystrophin protein.

Amino Acid Sequence↗
PubMed1991

Is the carboxyl-terminus of dystrophin required for membrane association? A novel, severe case of Duchenne muscular dystrophy.

Duchenne muscular dystrophy is a lethal X-linked recessive disorder caused by the deficiency of a component of the muscle fiber membrane cytoskeleton called dystrophin. Becker muscular dystrophy, a clinically milder disorder, results from dystrophin abnormalities rather than deficiency. We identified the first patient who is clearly an exception to these established clinical and biochemical correlates. The patient described clinically had particularly severe Duchenne dystrophy. Biochemically, his muscle contained substantial amounts of abnormal dystrophin (Becker-like). Characterization of the dystrophin protein and gene revealed a unique intragenic gene deletion resulting in a dystrophin protein missing the carboxyl-terminal domain. This patient's dystrophin seemed to have a deleterious "dominant" effect on his muscle: The presence of this abnormal protein was more damaging to the myofibers than the absence of dystrophin would have been. This patient challenges the current hypothesis that dystrophin associates with the plasma membrane solely via its carboxyl-terminus, yet supports the hypothesis that an intact carboxyl-terminus is crucial for correct dystrophin function.

Chromosome Deletion↗
PubMed1984

Gene amplification as a mechanism of reversion at the HPRT locus in V79 Chinese hamster cells.

Spontaneous phenotypic revertants of hypoxanthine phosphoribosyl-transferase (HPRT) temperature-sensitive V79 Chinese hamster cells were selected by plating a temperature-sensitive mutant in HAT medium at 39 degrees C. The incidence of such revertants was approximately 2 X 10(-4) per cell. The majority of the revertants examined had increases of between three- and tenfold in their specific activity of the enzyme, and they were able to grow continuously in the presence of HAT medium at 39 degrees C. When the revertants were cultivated in the absence of HAT, they recovered their HAT-sensitive phenotype and their lowered level of HPRT. Three of the revertants were examined for their temperature inactivation profiles, and all were found to have profiles identical to the ts parent, and quite different from the V79 wild type. The kinetic properties of the cell lines were studied: the Km for both PRPP and hypoxanthine was significantly different in the temperature-sensitive cells but was not significantly altered in the revertants with respect to the ts mutants. A specific antibody to Chinese hamster brain HPRT was employed in immunoprecipitation experiments. By measuring the point at which the immunoprecipitation of the antibody to HPRT was overcome by increasing concentrations of cell supernatant, it was possible to estimate the relative amount of enzyme molecules in the cell lines. From these data, it could be concluded that the revertants overproduced an enzyme with the same immunological properties as the ts line. Southern blots of the Hind III restricted DNA from the ts mutant and two revertant cell lines were examined with an HPRT cDNA probe. This established that the HPRT gene was amplified twofold in one of the revertants, and threefold in the other. However, if the revertants were reintroduced into nonselective medium, the gene copy number declined to one. Finally, northern blots of RNA extracted from the various cell lines demonstrated that the HPRT mRNA was augmented 1.5-fold in one revertant and 1.4-fold in the other. Reintroduction into non-selective medium resulted in a decline in mRNA level for the second mutant, whereas the first mutant appeared to be stabilized. We conclude that gene amplification and concomitant amplification of messenger RNA and enzyme levels are mechanisms of phenotypic reversion at the HPRT locus in Chinese hamster cells.

Animals↗