Nuclear and cellular size of myocytes in different segments of the developing rat heart

Knaapen, Michiel; Vrolijk, B.C.M.; Wenink, Arnold C. G.

doi:10.1002/(sici)1097-0185(199601)244:1<118::aid-ar12>3.3.co;2-3

Cited by 4 publications

(9 citation statements)

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“…It is possible that changes in cardiac GRP78 expression with increasing embryonic age are related to proportional changes in volumes of individual cardiac segments, as demonstrated in the rat (Knaapen et al 1995(Knaapen et al , 1996. However, the relatively constant level of GRP78 expression throughout early organogenesis, with decreases only in late organogenesis and fetal stages, argues against this interpretation.…”

Section: Discussionmentioning

confidence: 99%

Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

Barnes

Smoak

2000

Anatomy and Embryology

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This study investigates the distribution and heart levels of glucose regulated protein (GRP) 78 during normal development and in response to hypoglycemia in the mouse. Results demonstrate that GRP78 is strongly expressed with in the heart, neural tube, gut endoderm, somites, and surface ectoderm of mouse embryos during early organogenesis, and GRP78 staining remains prominent in the heart from gestational days 9.5 through 13.5. Cardiac myocytes are the primary site of GRP78 expression within the heart. GRP78 levels are highest in the heart during early organogenesis and levels decrease significantly by the fetal period. GRP78 expression is increased after 24 h of hypoglycemia in the early organogenesis-stage heart. Considering the tissue specific pattern of GRP expression and changes during development of the heart, GRPs may play significant roles in the normal differentiation and development of cardiac tissue. GRP induction may also be involved in hypoglycemia-induced cardiac dysmorphogenesis.

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Section: Discussionmentioning

confidence: 99%

Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

Barnes

Smoak

2000

Anatomy and Embryology

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“…The transitional zones, atrioventricular canal, and distal outlet segment do not increase their myocardial volume after day 15 , indicating their diminishing role as sphincters (Goerttler, 1955;Jaffee, 1965). However, after the time of septation, the segments destined to be the working atrial and ventricular myocardium show a rapid increase in myocardial mass, which is caused by hyperplasia (Knaapen et al, 1996). Because the ventricular pressure increases during development , as the heart rate does (Broekhuizen et al, 1993), the working myocardium needs to increase its contractile force.…”

Section: Discussionmentioning

confidence: 99%

“…Obviously, at this time of development, important physiological alterations take place in the embryonic heart, and the mass of the working myocardium increases rapidly. Even when the temporary decline of cellular myofibrils is accounted for, the increasing number of myocytes (Knaapen et al, 1996) still leads to a continuous increase of total ventricular myofibrillar mass. Myocyte division continues until 2 weeks after birth, and we have compared our data whith the data of investigators who have measured the cellular organelles in the postnatal period (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…SI is the number of estimated intercepts hitting the structure of interest, and SP is the number of points hitting the reference space. The data on the cellular volumes, presented previously (Knaapen et al, 1996), were used to calculate the absolute values of the ultrastructural parameters in this study.…”

Section: Stereologymentioning

confidence: 99%

“…The embryonic heart consists of eight different cardiac segments and intersegmental junctions that develop differently with respect to their individual myocardial volumes and to their number of myocytes (Knaapen et al, , 1996. Functionally, the intersegmental junctions, also described as transitional zones , are described as having specific tasks during early development before valves have developed (Goerttler, 1955;Jaffee, 1965).…”

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Ultrastructural changes of the myocardium in the embryonic rat heart

1997

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Background Ultrastuctural changes of the embryonic heart have been described, and quantitative studies have reported the changes of cellular organelles in late fetal and postnatal development. However, no specific data are available on the quantitative morphology of the individual segments and intersegmental junctions of the early embryonic heart, although these components must have different functions. Methods We measured the absolute volumes of glycogen, Golgi complex, myofibrils, mitochondria, and the surface areas of the rough endoplasmic reticulum and mitochondrial cristae in the different regions of the embryonic rat heart by using stereological tools. Results During embryonic development, the cardiac segments and intersegmental junctions increase their glycogen volume. The sinuatrial junction and primary fold show a more rapid increase than all the other cardiac regions, whereas the atrioventricular canal shows a high level of glycogen content throughout the period studied. The Golgi complex and rough endoplasmic reticulum show a conspicuous decrease from day 15 onward. The cellular content of myofibrils and mitochondria and the surface area of the mitochondrial cristae show a gradual increase from day 11 to day 17 of development, but full maturation apparently takes place in late fetal and early postnatal stages. At day 15 of development, the cellular volumes of myofibrils and mitochondria show a temporary decrease. Conclusions The glycogen content cannot be explained on the basis of metabolism alone. The storage of glycogen is hypothesized to serve mechanical cell stability and may also be related to a target mechanism for ingrowing nerves. Myofibrillar and mitochondrial contents of the myocytes indicate a relatively late differentiation of the venous pole of the heart. Uninterrupted maturation is only started at the time of septation. Anat Rec. 248:233‐241, 1997. © 1997 Wiley‐Liss, Inc.

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Developmental patterning of the myocardium

et al. 2000

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The heart in higher vertebrates develops from a simple tube into a complex organ with four chambers specialized for efficient pumping at pressure. During this period, there is a concomitant change in the level of myocardial organization. One important event is the emergence of trabeculations in the luminal layers of the ventricles, a feature which enables the myocardium to increase its mass in the absence of any discrete coronary circulation. In subsequent development, this trabecular layer becomes solidified in its deeper part, thus increasing the compact component of the ventricular myocardium. The remaining layer adjacent to the ventricular lumen retains its trabeculations, with patterns which are both ventricle- and species-specific. During ontogenesis, the compact layer is initially only a few cells thick, but gradually develops a multilayered spiral architecture. A similar process can be charted in the atrial myocardium, where the luminal trabeculations become the pectinate muscles. Their extent then provides the best guide for distinguishing intrinsically the morphologically right from the left atrium. We review the variations of these processes during the development of the human heart and hearts from commonly used laboratory species (chick, mouse, and rat). Comparison with hearts from lower vertebrates is also provided. Despite some variations, such as the final pattern of papillary or pectinate muscles, the hearts observe the same biomechanical rules, and thus share many common points. The functional importance of myocardial organization is demonstrated by lethality of mouse mutants with perturbed myocardial architecture. We conclude that experimental studies uncovering the rules of myocardial assembly are relevant for the full understanding of development of the human heart.

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Nuclear and cellular size of myocytes in different segments of the developing rat heart

Cited by 4 publications

References 10 publications

Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

Ultrastructural changes of the myocardium in the embryonic rat heart

Developmental patterning of the myocardium

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