Search PubMed⌕ Search

Biomedical subjects

A F Moorman

Publications and source records attributed to A F Moorman.

At least 145 records · Page 8Linked to original sources
PubMed1991

Spatial distribution of connexin43, the major cardiac gap junction protein, in the developing and adult rat heart.

The developmental appearance and spatial distribution pattern of gap junctions were studied in prenatal and adult rat hearts. Gap junctions were visualized immunohistochemically with an antibody raised against a unique cytoplasmic epitope of connexin43, and the spatial distribution pattern was determined by three-dimensional reconstruction. The results demonstrate that from embryonic day 13 onward, connexin43 becomes detectable immunohistochemically in the myocardium of atria and ventricles. No expression is initially detectable in the myocardium of the sinus venosus, the sinoatrial node, the posterior wall of the atrium and pulmonary veins, the interatrial septum, the atrioventricular canal, including atrioventricular node and bundle, the interventricular septum, and the outflow tract. The developmental increase in the density of gap junctions in atria and ventricles of prenatal hearts correlates well with the reported developmental increase in conduction velocity. Whereas connexin43 becomes expressed in the derivatives of the sinus venosus (except for the sinoatrial node) and in the subepicardial layer of the ventricular free wall shortly before birth, it remains undetectable in the atrioventricular node and bundle and the proximal part of the ventricular conduction tissue, even in the adult heart. The apparent absence of an abundant expression of connexin43 at a location with a supposedly high conduction velocity (i.e., the atrioventricular bundle and bundle branches) is unexpected. These observations were confirmed in studies of the adult mouse heart, which showed, in addition, that connexin32 is not expressed in any part of the heart.

Aging↗
PubMed1991

Detection of CAIII mRNA in rat skeletal muscle and liver by in situ hybridization.

We carried out a variety of in situ methods of hybridization on rat liver and rat skeletal muscle using 35S-labeled or biotin-labeled rat carbonic anhydrase III (CAIII) cDNA clone. The methods were compared and evaluated. Use of the biotin system produced defined but nonspecific results which were shown not to be due to the biotinylated cDNA probe binding to the mRNA in the muscle sections. This artifact was shown to persist despite various attempts to eliminate it. Alternatively, using 35S-labeled cDNA gave reproducible results which were shown to be consistent with probe binding specifically to mRNA in the muscle section.

Adenosine Triphosphatases↗
PubMed1990

Metabolic effects of developmental, tissue-, and cell-specific expression of a chimeric phosphoenolpyruvate carboxykinase (GTP)/bovine growth hormone gene in transgenic mice.

Transgenic mice were used to investigate sequences within the promoter of the gene for the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) from the rat (EC 4.1.1.32) (PEPCK) which are involved in tissue-specific and developmental regulation of gene expression. Segments of the PEPCK promoter between -2000 and -109 were linked to the structural gene for bovine growth hormone (bGH) and introduced into the germ line of mice by microinjection. Bovine growth hormone mRNA was found in tissues that express the endogenous PEPCK gene, mainly in the liver but to a lesser extent in the kidney, adipose tissue, small intestine, and mammary gland. In the liver the chimeric PEPCK/bGH(460) gene was expressed in periportal cells, which is consistent with the zonation of endogenous PEPCK. The PEPCK/bGH gene was not transcribed in the livers of fetal mice until immediately before birth; at birth the concentration of bGH mRNA increased 200-fold. Our results indicate that the region of the PEPCK promoter from -460 to +73 base pairs contains regulatory sequences required for tissue-specific and developmental regulation of PEPCK gene expression. Mice transgenic for PEPCK/bGH(460) were not hyperglycemic or hyperinsulinemic in response to elevated bGH, as were transgenic mice with the MT/bGH gene. The number of insulin receptors in skeletal muscle was no different in mice transgenic for MT/bGH when compared with mice transgenic for PEPCK/bGH(460) and control animals. However, mRNA abundance for the insulin-sensitive glucose transporter in skeletal muscle was decreased in mice transgenic for the MT/bGH gene. The differences in glucose homeostasis noted with the two types of transgenic mice may be the result of the relative site of expression, the different developmental pattern, or hormonal regulation of expression of the bGH gene.

Animals↗
PubMed1990

Diet- and hormone-induced reversal of the carbamoylphosphate synthetase mRNA gradient in the rat liver lobulus.

A hybridocytochemical analysis of adult liver from normal control and from hormonally and dietary-treated rats was carried out, using radioactively-labelled probes for the mRNAs of glutamine synthetase (GS), carbamoylphosphate synthetase (CPS) and phosphoenolpyruvate carboxykinase (PEPCK). In line with previous findings, GS mRNA is exclusively expressed in a small pericentral compartment, CPS mRNA exclusively in a contiguous large periportal compartment and PEPCK mRNA across the entire porto-central distance. The density of labelling in CPS and PEPCK mRNA-positive hepatocytes decreases in a porto-central direction. Starvation resulted in a reversal of the gradient of CPS mRNA within its periportal compartment; glucose refeeding counteracted this effect. Livers of glucocorticosteroid-treated, starved or diabetic rats also revealed a reversal of the normal gradient of CPS mRNA, but now across the entire porto-central distance. The patterns of expression of GS and PEPCK mRNA remained essentially unchanged, notwithstanding substantial changes in the levels of expression. It is concluded that blood-borne factors constitute the major determinants for the expression patterns of CPS mRNA within the context of the architecture of the liver lobulus.

Animals↗
PubMed1990

Zonal distribution of peroxisomal 3-oxoacyl-CoA thiolase mRNA in liver from rats treated with di-(2-ethylhexyl)phthalate.

Treatment of rats with di-(2-ethylhexyl)phthalate leads to a dramatic increase in peroxisomal 3-oxoacyl-CoA thiolase RNA, the concentration being higher in the pericentral than in periportal hepatocytes. These findings indicate that the production of peroxisomal thiolase and the zonal distribution of the enzyme are regulated at a pretranslational level.

Acetyl-CoA C-Acyltransferase↗
PubMed1990

Monoclonal antibody evidence for structural similarities between the central rod regions of actinin and dystrophin.

A monoclonal antibody, MANDYS141, binds to both dystrophin and actinin on Western blots (SDS-denatured), but only to actinin in frozen sections of human muscle (native conformation). It differs from a polyclonal cross-reacting antiserum in that it binds to several muscle isoforms of actinin (smooth, fast and slow) from man, mouse and chicken and recognises a quite different part of the proposed triple-helical region of dystrophin (amino acids 1750-2248). The results suggest that structural homologies between actinin and dystrophin occur more than once in their central helical regions and provide experimental support for an actinin-like central rod model for dystrophin.

Actinin↗
PubMed1990

Isolation and characterization of the rat glutamine synthetase-encoding gene.

From a rat genomic library in phage lambda Charon4A, a complete glutamine synthetase-encoding gene was isolated. The gene is 9.5-10 kb long, consists of seven exons, and codes for two mRNA species of 1375 nucleotides (nt) and 2787 nt, respectively. For both mRNAs, full-length cDNAs containing a short poly(A) tract were identified. The sequences of the entire mRNA and of the exon-intron transitions were determined. The smaller mRNA is identical to the 5' 1375 nt of the long mRNA and contains the entire protein-coding region. The position of the transcription start point was mapped. Within the first 118 bp of promoter sequence, a (T)ATAA-box, a CCAAT-box and an SP1-binding site were identified.

Animals↗
PubMed1990

Isomyosin expression pattern during formation of the tubular chicken heart: a three-dimensional immunohistochemical analysis.

Three-dimensional (3-D) distribution of atrial and ventricular isomyosins is analysed immunohistochemically during the formation of the tubular chicken heart (stage 7 to 12 [H/H]) using antibodies specific for adult chicken atrial and ventricular myosin heavy chains, respectively. This analysis revealed that both types of isomyosins can be first detected at stage 8 (H/H, possessing four pairs of somites), i.e., when the heart primordium still exists as two separate cardiogenic plates. The ventricular type of isomyosin is initially expressed in those areas of cardiogenic plates in the vicinity of the anterior intestinal portal. The atrial type of isomyosin is initially expressed in zones caudal and lateral to the areas of ventricular isomyosin expression. Medial to the atrial isomyosin-expressing areas, cardiogenic plate areas exist that initially lack myosin expression. Those parts of the cardiogenic plates that fuse in front of the anterior intestinal portal, thereby forming the heart tube, are characterized by the expression of both isomyosins; however, the caudolateral parts of the heart primordium maintain their single atrial isomyosin expression during further development. Cardiac contractions are therefore first observed at stage 10 (H/H, possessing ten pairs of somites) in myocardium that coexpresses both isomyosins.

Animals↗
PubMed1990

Spatial distribution of "tissue-specific" antigens in the developing human heart and skeletal muscle. I. An immunohistochemical analysis of creatine kinase isoenzyme expression patterns.

Using monoclonal antibodies against the M and B subunit isoforms of creatine kinase (CK) we have investigated their distribution in developing human skeletal and cardiac muscle immunohistochemically. It is demonstrated that in skeletal muscle, a switch from CK-B to CK-M takes place around the week 8 of development, whereas in the developing heart, CK-M is the predominant isoform from the earliest stage examined onward (i.e., 4 1/2 weeks of development). In all hearts examined, local differences in concentration of the CK isoforms are observed. The CK-M expression in the developing outflow tract (OFT) and conduction system is described in detail. Between the weeks 5 and 7 of development, the distal portion of the OFT is characterized by low CK-M expression, whereas around the week 8-10 of development the myocardium around the developing semilunar valves in the OFT expresses a very high level of CK-M. At all stages examined, a relatively low CK-M level is observed in those regions in which the "slow" components of the conduction system do develop (e.g., the sinoatrial junction and atrioventricular junction), whereas a relatively high concentration of CK-M is observed in those areas that are destined to become the "fast" components, i.e., the subendocardial myocardium of the ventricles. The high expression of CK-M in the developing "fast components" of the conduction system contrasts with the relatively low expression of CK-M in the force-producing myocardium of the interventricular septum and free ventricular wall.

Creatine Kinase↗
PubMed1990

Distribution pattern of acetylcholinesterase in early embryonic chicken hearts.

To study the developmental appearance of acetylcholinesterase in early embryonic hearts, an enzyme-histochemical study was carried out in chicken embryos ranging from cardiogenic plate to late tubular stages. Initially acetylcholinesterase is present in all cells of the (future) myocardium. When 13-14 pairs of somites have developed, i.e., shortly before blood propulsion starts, acetylcholinesterase selectively disappears from the ventral and lateral wall of the developing ventricle. Slightly later, when 18-19 pairs of somites have developed, acetylcholinesterase also disappears from the dorsal and anterior wall of the atrium. High concentrations of acetylcholinesterase remain present in the outflow tract and lower concentrations in a continuous tract along the lesser curvature of the heart, the atrial side of the atrioventricular canal, and the left wall of the atrium. In late tubular stages of heart development, acetylcholinesterase is reexpressed in the inner myocardial layer of the ventricle, i.e., in the developing trabeculae and the ventricular side of the atrioventricular canal, where it is continuous with the acetylcholinesterase-expressing cells of the atrial side of the atrioventricular canal. The expression pattern of acetylcholinesterase in early embryonic chick hearts coincides with that of areas that control the conduction of the impulse and may reveal a cholinergic signal transduction system that is responsible for a coordinated contraction pattern of the myocardium prior to the development of the definitive conductive system.

Acetylcholinesterase↗
PubMed1990

Hepatocytes explanted in the spleen preferentially express carbamoylphosphate synthetase rather than glutamine synthetase.

Urea cycle enzymes and glutamine synthetase are essential for NH3 detoxification and systemic pH homeostasis in mammals. Carbamoylphosphate synthetase, the first and flux-determining enzyme of the cycle, is found only in a large periportal compartment, and glutamine synthetase is found only in a small, complementary pericentral compartment. Because it is not possible to manipulate experimentally the intrahepatic distribution of carbamoylphosphate synthetase and glutamine synthetase, we looked for conditions in which explanted hepatocytes would exhibit either the carbamoylphosphate synthetase phenotype or glutamine synthetase phenotype. In the spleen hepatocytes either settle as individual cells or in small agglomerates. The dispersed cells only express the carbamoylphosphate synthetase phenotype. Within the agglomerates, sinusoids that drain on venules develop. Hepatocytes surrounding the venules stain only weakly for carbamoylphosphate synthetase but are strongly positive for glutamine synthetase. These observations were made for explanted embryonic hepatocytes (no prior expression of either carbamoylphosphate synthetase or glutamine synthetase), neonatal hepatocytes (compartments of gene expression not yet established) and adult periportal and pericentral hepatocytes.

Age Factors↗
PubMed1990

Detection of truncated dystrophin in fetal DMD myotubes.

An immunohistochemical study was carried out on a twelve-week old fetus, aborted for high risk of Duchenne muscular dystrophy. Southern and FIGE analysis showed an intragenic duplication in the DMD gene, which had previously resulted in a severe Duchenne phenotype in three relatives. Polyclonal antibodies directed against the NH2-terminal half of dystrophin showed a positive reaction an a similar distribution of dystrophin in the skeletal myotubes of a twelve-week old normal fetus and the affected fetus. In contrast, a polyclonal antibody directed against the COOH-terminus of dystrophin, i.e., distal to the mutation in this family, did only react with the myotubes of the normal fetus and not with those of the affected fetus. This indicates the presence of a truncated dystrophin in the affected fetus. Apparently at this stage, before binding of dystrophin to the sarcolemma, no distinction is made yet between normal and abnormal dystrophins. This implies that the potential to bind to the sarcolemma could be a major point of discrimination between normal and defective dystrophins. The truncated dystrophin will probably be degraded in a later stage during fetal development. So it appears that the use of dystrophin immunostaining to confirm high Duchenne risk abortions requires great caution. To prevent false-positive results, the combined use of NH2- and COOH-terminal antibodies is mandatory.

Dystrophin↗
PubMed1990

Creatine kinase isozyme expression in prenatal rat heart.

The distribution pattern of creatine kinase (E.C 2.7.3.2) isozymes in prenatal rat heart and skeletal muscle was studied by immunohistochemistry. Between embryonic day (ED) 12-18, creatine kinase M (CK-M) is heterogeneously expressed in the heart: a pronounced staining of CK-M is first observed in the outflow tract and the trabeculae of the right ventricle (ED12-14), and subsequently in the venous valves, the interatrial septum and the sinoatrial node. From ED18 onwards, a homogeneous expression of CK-M is observed due to an increase in isozyme concentration in the remaining part of the myocardium. By contrast, the developmental appearance of creatine kinase B (CK-B) occurs almost homogeneously throughout the heart between ED11-14. Thereafter, a decrease of the CK-B is first observed in the inflow tract (in particular in the sinoatrial node), in the inner part of those atrial walls that are adjacent to the atrioventricular junction, and temporarily in a band in the upper part of the interventricular septum. From ED18, a selective disappearance of CK-B is found in the papillary muscle of the left ventricle. At birth, a considerable amount of CK-B remains present in the ventricular walls. Although some of the stage-dependent regional differences in expression of the creatine kinase isozymes, in particular those of the M-subunit, are shared by other mammalian and avian species, their significance for the developmental changes in the physiology of the heart is speculative at present.

Animals↗