Search PubMed⌕ Search

Biomedical subjects

J D Engel

Publications and source records attributed to J D Engel.

At least 145 records · Page 8Linked to original sources
PubMed1981

A 200 base pair region at the 5' end of the chicken adult beta-globin gene is accessible to nuclease digestion.

A DNA segment close to the 5' end of the chicken adult beta-globin gene contains a hypersensitive site for nuclease action. Using a variety of endonucleases, we show that this hypersensitive site is in fact an accessible region, which extends from approximately 60 to approximately 260 base pairs 5' from the start of mRNA transcription. The presence of this hypersensitive region is correlated with gene activity; it is observed in nuclei isolated from the definitive erythrocytes of 14-day chicken embryos, but is not observed in nuclei isolated from the primitive erythrocytes of 5-day embryos (which do not express this gene) or in brain nuclei or purified DNA. The close spacing of accessible digestion sites on this DNA segment is not consistent with the presence of a normal nucleosome. Furthermore, a 115 base pair DNA fragment contained within this nuclease-sensitive region can be excised by Msp I digestion and released from nuclei, in at least 50% yield. Approximately one third of the released fragments behave as protein-free DNA.

Animals↗
PubMed1981

Adult chicken alpha-globin genes alpha A and alpha D: no anemic shock alpha-globin exists in domestic chickens.

Three alpha-type globin genes have been identified in the alpha-globin linkage group of chickens. No other alpha-type genes hae been directly shown to be within 10 kilobase pairs of any of these three closely linked genes. These three genes have been conclusively identified by DNA sequence analysis. The gene at the 5' end of the linkage group is an embryonic alpha-type globin gene, pi or pi', and the central gene corresponds to the minor adult alpha- globin, alpha D. The 3'-terminal gene sequence corresponds to the sequence of cDNA clones previously described as "alpha S", presumed anemic shock-induced alpha-globin gene [Salser, W. A., Cummings, I., Liu, A., Strommer, J., Padayatty, J. & Clarke, P. (1979) in Cellular and Molecular Regulation of Hemoglobin Switching, eds. Stamatoyannopoulos, G. & Nienheis, A. (Grune and Stratton, New York), pp. 621-643; Richards, R. I. & Wells, J. R. E. (1980) J. Biol. Chem. 255, 9306-9311]. Several groups of workers have isolated alpha S-type cDNA clones but no one has identified a cDNA clone corresponding to the published amino acid sequence of the major chicken alpha-globin, alpha A. We have identified the alpha S-type sequence as the only abundant alpha-like globin sequence in cDNA clones made from reticulocyte mRNA isolated from nonanemic chickens. Therefore, we suggest that the alpha S-type sequence corresponds to the true alpha A-globin species.

Amino Acid Sequence↗
PubMed1981

Histone genes are clustered but not tandemly repeated in the chicken genome.

The recombinant chicken DNA library was screened for histone genes by using pSp17, a recombinant sea urchin DNA probe containing the H2a and H3 genes of Strongylocentrotus purpuratus. Three of the isolated lambda recombinants have been analyzed by restriction enzyme mapping and Southern blotting; one histone H3 gene-encoding recombinant was further analyzed by DNA sequence determination. These studies reveal that the chicken histone genes are not tandemly reiterated, but that, at the least, several histone genes are physically closely linked in a nonrepetitive arrangement within the chicken genome. The evolutionary implications of this arrangement versus that seen in Drosophila and sea urchins is discussed.

Amino Acid Sequence↗
PubMed1981

Research approaches in health professions education: problems and prospects.

Research in health professions education has been dominated by a research paradigm emphasizing controlled experimentation. Widespread criticism has been voiced by leaders in the research community concerning the adequacy of the paradigm to deal with complex human behavior occurring in complex social environments. This article is concerned with exploring the implications of controlled studies for health professions education and proposing an alternative research strategy.

Health Occupations↗
PubMed1980

Analysis of the closely linked adult chicken alpha-globin genes in recombinant DNAs.

Recombinant bacteriophage (from a library of chicken chromosomal DNA fragments inserted into lambda Charon 4A) have been isolated which contain the coding information for both of the adult chicken alpha-globin genes, alpha A and alpha D. One of these recombinant phage also contains an as yet unidentified embryonic alpha-like globin gene sequence. The two adult genes are encoded on the same DNA strand and are separated by approximately 2.4 kilobase pairs, with the arrangement of the genes relative to the direction of transcription being 5'-alpha D-alpha A-3'. Electron microscopic R-loop visualization experiments demonstrate that both alpha-globin genes contain two intervening sequences of similar size in a manner analogous to the structure observed in the mouse alpha-globin gene. The linkage of the two highly divergent chicken adult alpha-globin genes further underscores the principle that chromosomal clustering of families of developmentally related genes may be a general phenomenon in higher eukaryotic gene sequence arrangement.

Animals↗
PubMed1979

Isolation of the chicken beta-globin gene and a linked embryonic beta-like globin gene from a chicken DNA recombinant library.

A library of random chicken DNA fragments, 15-22 kb long, has been prepared in the vector lambda Charon 4A. This library was screened with combined adult and embryonic globin cDNA, and several independent globin gene-containing recombinants were isolated. One of these recombinants, lambda Chicken beta-globin 1 (lambda C beta G1), contains the adult chicken beta-globin gene and a closely linked embryonic beta-like globin gene. Both genes are transcribed in the same direction with the adult gene located 5' to the embryonic gene. Electron microscopic visualization of R loop structures generated by hybridization of globin RNA to lambda C beta G1 demonstrates that both globin genes contain major intervening sequences about 800 bp long, similar to those present in mammalian beta-globin genes. The adult beta-globin gene also contains a minor (approximately 100 bp long) intervening sequence analogous to the one observed in mammalian beta-globin genes. Restriction enzyme analysis of the adult beta-globin gene on lambda C beta G1 is consistent with the hypothesis that its two intervening sequences occur in the same positions with respect to the beta-globin amino acid sequence as do the corresponding mammalian intervening sequences.

Animals↗
PubMed1979

Gene localization by chromosome fractionation: globin genes are on at least two chromosomes and three estrogen-inducible genes are on three chromosomes.

Chicken metaphase chromosomes were partially purified by rate zonal centrifugation, and DNA was prepared from each of the fractions of the sucrose gradient. The DNA was digested with various restriction enzymes and subjected to electrophoresis in agarose gels. The DNA was transferred to nitrocellulose filters (as described by Southern), and the filters were hybridized with cDNA probes. Four globin genes alpha A, alpha D, beta, and rho or epsilon are located on at least two chromosomes, and three of the estrogen-inducible genes of the hen oviduct--ovalbumin, ovomucoid, and transferrin--are on three different chromosomes. These experiments also confirm our earlier assignment of the endogenous viral sequence related to Rous-associated virus-0 to a separate (and larger) chromosome than the cellular sequence related to the transforming gene of avian sarcoma virus (cellular sarc), although it now appears that cellular sarc is on a small macrochromosome, rather than on a microchromosome.

Animals↗
PubMed1978

Analysis of the adult and embryonic chicken globin genes in chromosomal DNA.

Globin-specific mRNA has been purified from the red blood cells of anemic adult hens and from those of 5-day and 7-day chick embryos. These RNA preparations were used to synthesize labeled cDNA for solution and filter hybridization (Southern blotting) experiments. Hybridization of cDNAs prepared with separated adult alpha- and beta-mRNAs and of rabbit globin-specific probes to restriction enzyme-digested, filter-bound chicken chromosomal DNA has shown that the adult globin genes of the chicken exist within EcoRI-cleaved chromosomal DNA fragments which are 4.3, 6.0, and 12.5 kilobase pairs (kbp) in size. These fragments contain the majority or entirety of the adult alpha D, beta, and alpha A genes, respectively. Furthermore, we present evidence that the predominant chicken embryonic globins are contained within EcoRI fragments 9.4 and 15 kbp in size. Evidence is also presented that the same globin organization exists in several different breeds of chickens and in several chicken culture cell types. Finally, it is demonstrated that the pattern of globin-specific hybridization to reticulocyte chromosomal DNA digested with several restriction enzymes is unchanged during erythropoietic development.

Animals↗
PubMed1978

Addition of poly(adenylic acid) to RNA using polynucleotide phosphorylase: an improved method for electron microscopic visualization of RNA-DNA hybrids.

We have observed that the enzyme polynucleotide phosphorylas from M. luteus or from E. coli will polymerize adenosine (A) from adenosine diphosphate onto 3' ends of RNA molecules. For gene mapping, the poly(A)-tailed RNA is hybridized to its complementary sequence on a longer DNA strand. The position of the poly(A)tail, and thus the position of the 3' end of the RNA on the DNA strand, can then be observed by electron microscopy. Our preferred mapping technique involves the synthesis of a poly(A)-specific label by polymerization of a poly(dBrU) tail onto one or both ends of a linear duplex DNA of defined length (a restriction fragment) and hybridization of this label to the poly(A) tail. In test experiments with a plasmid containing a Drosophila DNA sequence coding for 5S rRNA genes, overall labeling efficiencies of 70--80% were achieved.

Animals↗
PubMed1978

Progress toward development of a general model for competence definition in health professions.

For the past three years a team of educational evaluators and health professionals has worked on development of (1) definitions of competence in occupational therapy, clinical dietetics and medical technology, and (2) associated prototype assessment instruments. This study has also involved an effort to develop a research methodology for pursuing similar investigations in other fields. That methodology, the Professional Performance Situation Model, proved appropriate for occupational therapy. A second application with clinical dietetics brough a number of significant modifications which support the view that PPSM is a valid special model for direct patient contact health professions. The third application, with medical technology, is intended to extend PPSM as a general model for competence definition in health professions. This article concentrates on the application of PPSM in clinical dietetics. It is argued that evidence for the feasibility and validity of PPSM is sufficient to justify confidence in the methodology. Completion of the next phase of development promises to support the authors' contention that they have developed a general paradigm for competence definition and assessment in all health professions.

Clinical Competence↗
PubMed1977

A comparison of diagnostic and certifying examinations.

Testing and measurement represent a critical component of an educational system since they provide the essential information for making fundamental educational decisions. The type of information required in a particular situation determines how one should conceive, develop, and evaluate the measurement device. This paper compares certifying exams used to determine a person's overall level of competence, and diagnostic exams used to determine a profile of a person's strengths and weaknesses in a particular area. These two types of exams are discussed in terms of their associated educational problem, types of decisions required, optimal test development procedures, and appropriate forms of reliability and validity.

Allied Health Personnel↗