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Biomedical subjects

A W Nienhuis

Publications and source records attributed to A W Nienhuis.

At least 19 recordsLinked to original sources
PubMed1979

Detection of early cardiac dysfunction in patients with severe beta-thalassemia and chronic iron overload.

To detect early left ventricular dysfunction, we used radionuclide cineangiography to determine left ventricular ejection fraction during exercise in 24 patients with transfusion-dependent, congenital anemias, 21 of whom had severe beta thalassemia. Ejection fraction at rest was normal in 21 patients (greater than 45 per cent) and in all patients was 53 +/- 2 per cent (mean +/- S.E.M.)--not significantly different from the value in normal subjects. However, ejection fraction during exercise was normal in only 11 patients (53 +/- 3 per cent in all patients, P less than 0.001 as compared with the normal value). All eight patients who had received fewer than 100 transfusions but only three of 16 (19 per cent, P less than 0.001) who had received 100 or more transfusions had normal responses during exercise. Whereas echocardiographic fractional shortening at rest was normal in 16 of 19 patients studied, eight patients with normal fractional shortening had abnormal ejection-fraction responses to exercise. Thus, radionuclide cineangiography during exercise is a highly sensitive technique for detecting preclinical myocardial dysfunction in patients with systemic iron overload.

Adolescent↗
PubMed1979

Hemoglobin switching in sheep. Synthesis, cloning, and characterization of DNA sequences coding for the beta B, beta C, and gamma-globin mRNAs.

Synthetic double-stranded DNAs (sDNAs) were prepared from sheep globin mRNA templates isolated from reticulocytes producing either hemoglobin B (HbB) (alpha 2 beta B2), HbC (alpha 2 beta C2), or HbF (alpha 2 gamma 2). These DNAs were inserted into the Eco RI site of plasmid pMB9 by the homopolymer tailing method and used to transform Escherichia coli X1776 to tetracycline resistance. Recombinant clones were identified by colony hybridization and further characterized by molecular hybridization and restriction endonuclease analysis. All plasmids analyzed thus far contained either beta- or gamma-globin DNA sequences. Moreover, sDNAs used for cloning yielded restriction endonuclease fragments consistent with the presence of predominantly beta- or gamma-sDNA, indicating that formation of double-stranded alpha-sDNA proceeds much less efficiently under our conditions than the formation of non-alpha-sDNAs. Three recombinant plasmids, pS beta B2, pS beta C69, and pS gamma 56, were selected for detailed study. These were shown to contain, respectively, beta B-, beta C-, and gamma-DNA sequences by molecular hybridization and by protection of the appropriate cDNAs from S1 nuclease digestion. Each contained all of the restriction endonuclease sites defined for the synthetic sDNAs and protected at least 90% of the sequence length of homologous cDNA. Restriction endonuclease maps of the beta B- and beta C-globin genes were identical at all 12 sites that were mapped, whereas four differences were identified in the gamma gene compared to the two others; three of these corresponded to differences in amino acid sequence of the globins. A method was developed to isolate the anti-mRNA strand of the insert for use as a specific molecular hybridization probe analogous to complementary DNA.

Animals↗
PubMed1979

Selective activation of human beta-but not gamma-globin gene in human fibroblast x mouse erythroleukaemia cell hybrids.

The human alpha- and beta-globin genes have been activated in MEL X human fibroblast cell hybrids. However, even though the human gamma- and beta-globin genes are closely linked and were shown in these hybrid clones to be present in approximately equal numbers, no human gamma-globin mRNA was produced. Thus, the human beta- and gamma-globin genes in these cells are differentially regulated apparently by a positive regulatory factor(s) specific for individual globin genes.

Animals↗
PubMed1979

Traumatic cardiac hemolytic anemia: a late complication of a Starr-Edwards mitral valve prosthesis.

Severe, traumatic, cardiac, hemolytic anemia developed in a patient nine years after mitral valve replacement with a Starr-Edwards model 6120 prosthesis. Cardiac catheterization failed to demonstrate a perivalvular leak or prosthetic malfunction. Transfusion on two occasions resulted in accelerated hemolysis and failed to maintain an appreciable elevation of the hemoglobin level. At operation, a perivalvular leak was found. Replacement of the valve led to complete resolution of the hemolytic problem. The case demonstrates that cardiac hemolysis may be a good indicator of valve dysfunction.

Anemia, Hemolytic↗
PubMed1978

Echocardiographic abnormalities in patients with transfusion-dependent anemia and secondary myocardial iron deposition.

The heart was evaluated by echocardiography in 56 patients at risk for myocardial iron deposition. Fifty-four had congenital anemia for which they required repeated transfusions, and two had primary hemochromatosis. The data, plotted according to one of three functions of the body surface area, were compared to values obtained in 105 normal subjects whose age spanned a similar range. Left ventricular wall thickness, transverse dimension and mass, as well as left atrial transverse dimension, were increased in the majority of patients with chronic iron overload despite the infrequent occurrence of cardiac enlargement on routine chest films (32 per cent) or electrocardiographic abnormality (16 per cent). Left ventricular ejection fraction was normal in all but four patients. These four patients died within a six month follow-up period suggesting that deterioration in systolic function is an indicator of poor prognosis. Our findings indicate that echocardiography provides a simple noninvasive means for assessing changes in cardiac structure and function that should prove useful in the serial evaluation of patients who are at risk for the development of myocardial iron deposition.

Adolescent↗
PubMed1978

Hemoglobin switching in sheep: only the gamma gene is in the active conformation in fetal liver but all the beta and gamma genes are in the active conformation in bone marrow.

Differential expression of the closely linked gamma, beta(A) (or beta(B)), and beta(C) globin genes in sheep results in the production of fetal hemoglobin (Hb F, alpha(2)gamma(2)) during gestation and the adult hemoglobins (Hb A, alpha(2)beta(2) (A), and Hb B, alpha(2)beta(2) (B)) after birth. Erythropoietic stress in certain animals leads to production of Hb C (alpha(2)beta(2) (C)). The molecular mechanism of differential expression of these genes in nuclei of fetal and adult erythroid cells has been investigated by analysis of their susceptibility to digestion by DNase I (genes that are in the conformation associated with active transcription are sensitive to this nuclease). The concentration of globin gene sequences in DNA from control and DNase I-digested nuclei was determined by annealing to synthetic DNAs and analogous cDNA probes derived from recombinant plasmids containing one of the sheep globin genes. In nuclei from sheep fetal liver erythroid cells, the gamma genes but not the beta genes were digested by DNase I; the gamma locus was open but the beta(A) or beta(C) loci was closed, consistent with synthesis of only Hb F by these cells. DNase I digestion of nuclei from bone marrow of anemic sheep making only Hb C or Hb B resulted in equivalent digestion of the beta and gamma gene sequences, although gamma mRNA was not detected in these cells. Digestion by DNase I did not decrease the globin gene sequence concentration in residual DNA of spleen nuclei. As a further control, DNA from digested bone marrow and spleen nuclei were shown to anneal equally well to a cDNA prepared from liver polysomal mRNA. Differential expression of the gamma and beta globin genes in sheep fetal erythroid cell appears to be based on differences in chromatin structure. The gamma globin gene remains in the active conformation in adult erythroid cells; failure of gamma mRNA to accumulate in these cells probably reflects transcriptional or post-transcriptional regulation.

Animals↗
PubMed1978

Cellular and molecular studies on globin gene expression.

Globin gene expression has been studied with the use of a combination of cell and molecular biology techniques. With a somatic cell hybrid between mouse erythroleukemia (MEL) and human erythroid cells, human and mouse globin genes can be coexpressed in the same hybrid cell. Somatic cell hybridization between MEL cells and nonerythroid cells (e.g., human fibroblasts) results in hybrid cells that cannot be induced to produce hemoglobin of any type. Molecular hybridization of cellular DNA and RNA with globin cDNA indicates that the globin genes are present but that no globin mRNA is in the nonexpressing hybrid cell. This finding demonstrates that the loss of globin gene expression in the hybrid cell occurs at the level of transcription or mRNA processing. The nucleus of the nonerythroid cell is not necessary for the extinction of globin gene expression, since cybrids formed from MEL cells with enucleated nonerythroid cells also result in cells which cannot be induced to synthesize hemoglobin even after 40 or more generations. These data suggest that the cytoplasm of cells contains diffusible regulatory molecules which influence globin gene expression. In our attempt to develop an intracellular assay to test for regulatory molecules, we studied the procedure microinjection with red blood cell (RBC) ghosts. Rabbit globin mRNA (with hemin) was loaded into RBC's and then, by Sendai virus-mediated fusion, into Chinese hamster ovary (CHO) cells growing in culture; these microinjected CHO cells synthesized hemoglobin. Since this microinjection procedure appears to be effective in inserting both proteins and nucleic acids into intact cells, it should be possible to develop modifications for inserting aliquots of fractionated cytoplasm into growing cells. The procedure might then be useful as an assay for putative genetic regulatory molecules.

Animals↗
PubMed1977

Regulation of hemoglobin synthesis during the development of the red cell (third of three parts).

In this article we have surveyed the current state of knowledge regarding the accumulation of globin mRNA and hemoglobin in red cells. We have attempted to examine the interplay of numerous processes that seem to be necessary to achieve this highly differentiated state. Finally, we have made an effort to formulate some of the mechanisms whereby individual red cells may come to contain varying proportions of specific hemoglobins. The past several years have been characterized by a veritable explosion of knowledge concerning the globin structure genes, and the structure, transcription, processing and function of globin mRNA in erythroid cells. It now seems possible to analyze the earlier stages of erythropoiesis by cultivation and examination of erythroid colonies in vitro. The primary differentiation events leading to the production of specific globins, especially for hemoglobin F production in man, are now experimentally accessible. There is good reason to hope that these advances will soon permit achievement of the long desired therapeutic goal of enhancing hemoglobin F synthesis in patients with severe beta-chain hemoglobinopathies. Our aim has been to review the scientific information that might provide the rationable for amelioration of the clinical phenotypes in patients inheriting abnormal globin genes.

Adult↗