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Biomedical subjects

F J Manasek

Publications and source records attributed to F J Manasek.

At least 19 recordsLinked to original sources
PubMed1992

Effects of injecting fibronectin and antifibronectin antibodies on cushion mesenchyme formation in the chick. An in vivo study.

During heart development in the chick some of the endocardial cells that cover the cushion areas leave the cushion endocardium, seed the underlying cardiac jelly, and are transformed into mesenchyme. Cushion mesenchymal (CM) cells migrate from the endocardium toward the myocardium using the cardiac jelly as substratum. Developing cushions have been microinjected with fibronectin (FN), antifibronectin antibodies (AbFN), and four synthetic peptide probes. Two of these peptides (P7 and P10) contained the sequence Arg-Gly-Asp-Ser (RGDS), while the other two (P15 and PColl) did not. Cushion area, individual cell area, cell density, cell orientation and a factor of form were evaluated in both experimental and control cushions. CM cell migration was inhibited by FN and AbFN, only partially inhibited by P10 and unaffected by P7. Cushions injected with P15 and PColl were unaffected. These results can be explained by steric modifications of the extracellular matrix, that may render cardiac jelly nonpermissive for CM cell migration, or by interaction of the substances injected at the endocardial cell surface. Migrating CM cells do not present any preferential orientation in any particular direction. CM cell migration seems to depend upon intrinsic migratory behaviour and the presence of FN at the CM cell surface. The enforcement of the direction of CM cell migration does not appear to rely upon matrix signals but be the result of randomly migrating cells becoming distributed more evenly in the matrix.

Amino Acid Sequence↗
PubMed1987

Transitions in cardiac isomyosin expression during differentiation of the embryonic chick heart.

The expression of different isoforms of the contractile protein myosin plays a major role in determining contractile characteristics in both cardiac and skeletal muscle in the adult. There is little evidence pertaining to putative changes in myosin phenotype during cardiac embryogenesis or if such changes could play a role in modulating the contractile characteristics of the developing heart. We examined isomyosin expression during cardiogenesis in the chick by indirect immunofluorescence microscopy with monoclonal antibodies to adult ventricular and atrial myosin heavy chains. Antibody specificity was characterized in the adult on the basis of immunofluorescence localization, ELISA, and protein blot immunoassay. Results show that the early embryonic chick heart has a different myosin phenotype than the later embryonic or adult heart. Both the embryonic ventricular and atrial myocardia initially expressed a myosin heavy chain that was recognized by antibody specific (in the adult) for ventricular myosin heavy chain. The ventricles remained reactive throughout life with the ventricular antibody, but reactivity of the atrial myocardium was confined to the initial 6 days of embryonic development. On the other hand, reactivity of the embryonic heart with multiple antibodies specific (in the adult) for atrial myosin was confined to the atrial myocardium throughout development. Thus, the distribution of myosin isoforms became similar to that of the adult myocardium by the time the embryonic heart achieved a 4-chambered configuration at 6 days in ovo.

Aging↗
PubMed1985

Ventricular trabeculations in the chick embryo heart and their contribution to ventricular and muscular septal development.

Sixty-two chick embryo hearts were studied at incremental stages of development (Hamburger-Hamilton stages 16 to 39) by scanning electron microscopy following 3% glutaraldehyde fixation and critical point drying. Early in cardiac development, the primitive ventricle becomes homogeneously trabeculated with highly organized sheets of myocytes lined by endocardial cells, with the trabeculae generally oriented in the dorsoventral direction. Coalescence of these trabecular sheets begins at stage 26, initially at the area of the bulboventricular flange, and later proceeding caudally toward the floor of the ventricle. The fusion process is finished by stage 30, resulting in a muscular ventricular septum that has now divided the primitive ventricle into right and left ventricles. Further growth of the ventricular septum is by continued fusion of the adjoining trabecular sheets. Remnants of the apposing trabecular sheets are found in the solidified muscular septum in the form of endocardial channels. We suggest that persistent patency of these channels results in muscular ventricular septal defects.

Animals↗
PubMed1985

Developmental aspects of cardiac contractile proteins.

The change in the isomyosin complement of avian and mammalian hearts was examined during the embryonic period in primary cultures of embryonic myocytes and in the cross-section of the adult ventricular wall. The type of myosin was determined by immunofluorescence using Abs specific for heavy chains of V1 and V3 isomyosins and by cytochemical staining for Ca2+ activated myosin ATPase. Our analysis indicates that the first isomyosin to appear in both chambers of avian heart is of the V3 type (HC beta). With advancing development, however, the atria initiate the expression of HC alpha and repress that of HC beta while the ventricle retains HC beta. In cultured myocytes derived from rat embryos cellular heterogeneity was detected in response to thyroid hormone. The cells are not synchronized in their response. Two populations are discernible with the minor one being thyroid hormone insensitive. Heterogeneity of the cellular populations was also seen in the left ventricle of adult rabbits. Myocytes with a similar isomyosin complement appear clustered with a predominance of V1 in the epicardium. Heterogeneous myocytes are, however, also frequently seen connected by an intercalated disc.

Aging↗
PubMed1984

An indirect immunofluorescence study of the distribution of fibronectin during the formation of the cushion tissue mesenchyme in the embryonic heart.

Indirect immunofluorescence studies have localized fibronectin (FN) within the trunco-conal ridges of the chick embryo heart during the formation of the cushion tissue mesenchyme. Prior to cell migration into the endocardial pads, fluorescence for FN is demonstrated almost entirely in association with the basal surfaces of endocardium and myocardium. Scattered spots and thin dotted-strands of fluorescent material can be demonstrated in the cardiac jelly. Cushion tissue (CT) cells migrating into the cardiac jelly have patches of fluorescent material associated with their surfaces. Filopodial processes always show intense fluorescence. The close association between the fluorescence and the surface of the CT cells suggests that FN may be implicated in the interaction of these cells with the matrical components of the cardiac jelly and, therefore, in the process of cell migration into the endocardial pads. The intensity and amount of FN staining decreased concomitantly with the progressive accumulation of cells in the cushion areas. After the completion of CT cell migration only reduced amounts of faint fluorescence remained in the endocardial pad areas. The possible significance of the changes observed in the distribution of FN during the formation of the cushion tissue mesenchyme is discussed.

Animals↗
PubMed1984

Immunofluorescence analysis of the primordial myosin detectable in embryonic striated muscle.

Immunofluorescence analysis showed that the earliest myosin detectable in both the embryonic chicken heart and somitic myotome, the precursor to skeletal muscle, was strongly reactive with two different monoclonal antibodies specific for the heavy chain of cardiac ventricular myosin, but it showed no reactivity with affinity-purified polyclonal antibodies specific for the heavy chains of either fast-twitch or slow-tonic skeletal myosins. The heart remained reactive exclusively with the antibodies to cardiac myosin throughout development, while late embryonic (day 20) skeletal muscles were strongly reactive only with their homologous skeletal myosin antibodies. Our findings suggest that the primordial myosin heavy chain detectable in both forms of embryonic chicken striated muscle, the myotome and the heart, is immunologically distinct from myosins expressed in later embryonic as well as adult skeletal muscles, but it contains antigenic determinants similar to those present in cardiac ventricular myosin.

Animals↗
PubMed1983

Control of early embryonic heart morphogenesis: a hypothesis.

The early events of looping (rotation and bending) of the embryonic vertebrate heart are deformations. The deformative forces and their regulation are intrinsic to the heart. A model of cardiac morphogenesis is described in this paper. It is proposed that synthesis of extracellular matrix by the myocardium generates an internal pressure. This pressure acts as a deforming force on the myocardium which controls strain by regulating compliance. This model provides an explanation of cardiac morphogenesis at the biochemical and biomechanical levels.

Animals↗
PubMed1983

Fibronectin distribution during early chick embryo heart development.

The distribution of fibronectin (FN) during early stages of chick embryo heart development has been studied by indirect immunofluorescence methods. The cardiac extracellular matrix (cardiac jelly) was almost devoid of FN-positive material throughout the period studied (stages 8-18). Intensely extracellular fluorescent material was only demonstrated at the heart midline and in the dorsal mesocardium. Fluorescence associated with the basal surface of the myocardium was demonstrated first at the time of fusion of the two heart tubes. While the heart remains attached to the embryonic trunk by the dorsal mesocardium, two different myocardial basal zones can be distinguished according to the intensity of fluorescence: an intensely stained dorsal zone and a much less fluorescent ventral zone. The endocardium did not present a strongly fluorescent basement membrane until stage 13. The intensity of fluorescence of the endocardial basal surface varied according to the rostrocaudal levels of the heart and also to the development stage of the embryo. The levels of fluorescence increased in myocardium and endocardium at the onset of trabeculation but decreased as trabeculation was completed. The quantitative and qualitative variations of FN distribution have been associated with a number of developmental events.

Animals↗
PubMed1981

Determinants of heart shape in early embryos.

The early embryonic vertebrate heart is a tubular organ that changes shape rapidly. It acquires a pronounced bulge, and bends and rotates to the right side in a process called looping. There has been to date no satisfactory explanation of the mechanisms regulating this morphogenetic sequence. Evidence is presented suggesting that this is a physical deformation rather than the result of differential growth. The control of heat deformation is discussed and possible regulatory mechanisms are explored. It is not yet possible to identify all the factors responsible but it appears that a number of independently regulated variables such as cytodifferentiation and matrix production interact to regulate expression of complex shapes.

Animals↗
PubMed1981

An experimental study of the relation of cardiac jelly to the shape of the early chick embryonic heart.

The structural roles of cardiac jelly components were examined in the early developing chick embryonic heart. Cardiac jelly matrix components were enzymically removed in situ by injecting nanogram quantities of enzymes directly into the cardiac jelly. Injection of ovine testicular hyaluronidase caused shrinkage and the heart became flaccid, but overall heart shape did not change. These responses were the result of enzymatic removal of glycosaminoglycan sugar moieties and were not due to lumenal collapse. Although purified collagenase did not cause any noticeable change, enzymes with non-specific proteolytic activity induced marked cardiac shape changes. In such hearts the dorsal mesocardium opened completely, and the myocardium as well as splanchnic mesoderm of foregut detached from their substrate and the entire heart region swelled. Consequently the shape of the heart was altered completely. The results suggested that in the normal condition the myocardial envelope was under an internal pressure due to the presence of glycosaminoglycans in the cardiac jelly space, and that some matrical non-collagenous protein components were essential to control the internal pressure. Therefore it is suggested that the internal pressure of cardiac jelly may be the direct driving force for the looping process and protein components of cardiac jelly may be important in directing the force for the morphogenetic process.

Animals↗
PubMed1981

Myocardial filopodia during early heart development.

We have compared the surface architecture of embryonic chick heart myocardial cells in two different grooves to see if any regional differences in surface features could be related to the developing anatomy of the myocardium. There was a qualitative difference in filopodia distribution. The developing interventricular sulcus completely lacked them whereas the ventral groove had numerous filopodia. The ventral groove is an anatomical landmark that remains after the precardiac anlage have fused. Thus, it is a post-fusion structure. This indentation "pops out" in later development and disappears. This region is therefore more compliant than the interventricular sulcus which doesn't pop out. Filopodia are therefore not associated with fusion or infolding per se but may be related to compliance.

Animals↗
PubMed1978

Experimental studies of the shape and structure of isolated cardiac jelly.

The properties of the early chick embryonic heart cardiac jelly were studied. The cells of the heart were removed by sequential treatments with calcium magnesium-free medium; the same medium containing 5 mM EDTA; and aqueous 0.1% deoxycholate. The transparent, naked cardiac jelly retained the original shape and size of the untreated original heart when immersed in physiological ionic strength medium. Its size and shape responded to changes in the ionic strength of the surrounding media. Alcian blue, cetylpyridinium chloride and testicular hyaluronidase abolished the ability of the jelly to respond to ionic strength changes. Electron microscope examination of the negatively stained spread cardiac jelly revealed an extensive network of collagenous fibrils and fine filaments with some amorphous adhering material. Treatment with testicular hyaluronidase removed much of the amorphous material and improved the details of the filaments. These results suggest that glycosaminoglycans play an important part in the hydration of the cardiac jelly and that the stability of the cardiac jelly shape is mainly due to the filamentous network and their possible interactions with macromolecules of the cardiac jelly matrix. It is suggested that the factors that control the depositon of the connective tissue macromolecules and the assembly of the filamentous network are significant factors which influence the morphogenesis of the early embryonic heart.

Animals↗
PubMed1977

Structural development of endocardial cushions.

Development of chick and rat endocardial cushions (cardiac mesenchyme) was studied histologically (using Nomarski differential interference optics on living and unfixed tissue), ultrastructurally (scanning and transmission electron microscopy), cytochemically (using acidified dialyzed iron as a visual probe for polyanionic material) and autoradiographically (using 35S) to elucidate the origin of the mesenchyme, the morphologic sequences leading to cushion formation and secretion of sulfated glycosaminoglycans, if any, by migrating mesenchymal cells. Cushion formation was similar for both species. Mesenchymal cells appeared initially, in 16- to 18-somite embryos, beneath the endothelium (which lacked a basal lamina) of the future atrioventricular canal and outflow tract. The cytoplasm of cushion mesenchymal cells was structurally similar to the ensothelium; probably these cells arose by proliferation of the endothelium. Mitotic figures among the "seeded" cells were also numerous. Cushion cells were initially attached to the endothelium by desmosomes but acquired motile apparatus (pseudopodia and filopodia containing microtubules and microfilamentous bundles). Serial sectioning of successively-aged embryos (20-44 somites) indicated a centrifugal migratory direction. Interaction of the cell processes with extracellular matrix suggested that the latter was used as a migratory substrate. Contact of the advancing wedge of cushion cells with the myocardium produced no alteration in cell structure or mitotic activity. Localization of hyaluronidase-sensitive, dialyzed iron (DI) precipitates in 250-nm Golgi vacuoles and hyaluronidase-sensitive 35S-endangendered silver grains over cushion cells indicated that this tissue contributed sulfated macromolecules to the matrix. Localization of hyaluronidase-labile, DI material in coated, endocytic-like vesicles and caveolae also suggested potential modification or conditioning of the matrix by migrating mesenchymal cells. Altogether, the study established loci in developing cushions where disruption where disruption of the developmental sequence could engender valvular or septal defects.

Animals↗
PubMed1977

Cardiac mutant salamanders: evidence for heart induction.

Homozygosity for gene c in Ambystoma mexicanum results in no detectable heartbeat in situ. Alteration of the cardiac environment through organ culture results in rapid initiation of spontaneous heartbeat, indicating that absence of cardiac function in situ is not the result of failure of embryonic induction.

Ambystoma↗