Search PubMed⌕ Search

Biomedical subjects

R Briggs

Publications and source records attributed to R Briggs.

69 records · Page 4Linked to original sources
PubMed1975

Experimental studies on a lethal gene (1) in the Mexican axolotl, Ambystoma mexicanum.

1. Gene ł is a recessive lethal factor found in the white strain of axolotls. Animals heterozygous for the gene are phenotypically normal. When mated with each other they give offspring 25% of which exhibit the lethal effects of the gene. 2. The ł/ł homozygotes develop normally to an advanced embryonic stage (Harrison stage 40) before the effects of the gene are first manifested. They then come to display a characteristic combination of abnormalities, including a disproportionately small head, small and poorly developed eyes, abnormal poorly developed gills, undifferentiated limb buds, and reduced overall growth rate. They may feed briefly, but soon stop and invariably die within a few weeks of the time of hatching. 3. The action of gene ł has been analyzed by parabiosing mutant and normal embryos, and by grafting various organ primordia reciprocally between mutant and normal embryos. Parabiosis to normal embryos fails to correct the abnormalities of the mutants, although their survival may be somewhat prolonged. Grafts of mutant organ primordia (eye, limb, gill, pronephros, gonad, head) also invariably fail to show improved development or to survive on normal hosts; normal organ primordia develop normally on mutant hosts so long as the mutant survives. These experiments indicate that gene ł is a recessive autonomous cell lethal affecting all of the organ systems during late embryonic and early larval development.

Ambystoma↗
PubMedDate not supplied

Renal hemodialysis and maternal serum triple analyte screening.

The obstetrical management of women with renal disease is complicated and associated with increased fetal and maternal morbidity. However, maternal serum screening is an integral part of obstetrical care and should be offered to all women. We found that maternal serum levels of a-fetoprotein and human chorionic gonadotropin did not significantly change as a result of hemodialysis, whereas levels of unconjugated estriol were markedly decreased following hemodialysis. Maternal serum screening should be limited to alpha-fetoprotein analysis in women undergoing hemodialysis until the effects of hemodialysis on all serum analytes are better delineated.

Adult↗
PubMedDate not supplied

Variations in the organization and expression of human histone genes in normal diploid and tumor cell lines.

The organization and expression of human histone genes were examined in W138 normal human diploid fibroblasts, SV40 transformed W138 cells, A549 epithelial lung carcinoma cells, two adeno-carcinoma cell lines (LOVO and HT29) and three leukemia cell lines (HL60, KG1 and K562). Analysis of the restriction enzyme digests of total genomic DNAs by hybridization with a series of cloned human histone sequences indicated polymorphic organization of at least a subset of the moderately reiterated human histone genes in these cells. Quantitative and qualitative differences were also observed in the representation of histone mRNAs by Northern blot analysis using cloned human histone genes as hybridization probes. However, there was no apparent correlation between variations in the representation of transcripts from various copies of the histone genes, variations in histone gene organization, and the extent of tumor progression.

Base Sequence↗
PubMedDate not supplied

A study of the effectiveness of an interactive computer classroom.

This study examined the use of an interactive computer classroom (ICC) compared with a traditional lecture/discussion format (LD) for a nursing management course taught from fall semester 1994 through fall semester 1996. The ICC was structured around a group systems support software, a tool previously used in business settings for group decision-making activities. Structured learning activities allowed all students to participate simultaneously and anonymously. Data were collected during the second and final semesters of the study. The outcomes included academic performance, measured by course exams; class participation, measured by direct observation; and attendance records. The control group was a concurrent management course taught with the same objectives and evaluated by identical examinations. The examination scores and the frequency of class participation of the ICC group were significantly higher than those measures of the LD group. There was no significant difference in class attendance. Evaluation forms with open-ended questions were completed by the ICC students and revealed that the students believed that the process enhanced application and understanding. The negative aspects of the ICC experience were the need for increased preparation time for faculty and the students' lack of tolerance when technical difficulties caused delays.

Computer-Assisted Instruction↗