Distribution of collagens and fibronectin in the subepicardium during avian cardiac development

Summary The development of the layer of connective tissue between ventricular epicardium and myocardium was studied during chick morphogenesis using electron microscopy, light microscopy and immunohistochemical techniques. This layer, called the subepicardium, increases rapidly in volume from embryonic day 6 to 11 (E6–E11) during mesenchymal cell invasion. Fibrous, matrix components are initially apparent at E11 to E16, and as fibrous connective tissue structures accumulate, subepicardial volume decreases. Antibody labeling shows that fibronectin is an early, prominent constituent of the subepicardium, and by E8, the subepicardium is the cardiac site most enriched in fibronectin. Collagen type III is present in circumferentially-oriented fibers at E8. During subsequent cardiac growth, collagen type III fibers become broadly distributed in the subepicardium, with some fibers appearing to attach myocardium to epicardium. Collagen type I fibers are not apparent until E10. At E12 collagen type I fibers are distributed circumferentially around the heart in bundles crimped into waves of low amplitude. Other collagen type I fibers are oriented radially in the subepicardium. During late cardiac morphogenesis and in fully-differentiated hearts, fibronectin and collagen types I and III are more concentrated in the subepicardium than within the myocardium. These observations suggest that the composition and organization of the subepicardial connective tissue may make important contributions to cardiac mechanics from the latter half of embryonic development through adulthood.     

Developmental alterations in 5'-nucleotidase kinetics and lipid composition of rat heart sarcolemma

The objective of these studies was to examine the mechanism by which the specific activity of heart sarcolemma 5'-nucleotidase decreases as function of age. We examined the kinetic properties and the lipid composition of the sarcolemma from animals with different ages. The age groups used were 1 month, 6-8 months and 13-15 months. It was found that the Km of this enzyme increases as the animal develops from 1 month to 6-15 months. The opposite was true with 5'-nucleotidase Vmax. There was no significant difference between the middle age and the older age groups in those parameters. The results of these experiments suggest that the increase in Km in sarcolemma 5'-nucleotidase could be due to the reduction of the sarcolemmal polyunsaturated fatty acid concentration, the only lipid alteration observed.     

NCAM in developing mouse gonads and ducts

Summary The expression of theNeuralCell AdhesionMolecule, NCAM, in mouse gonads and ducts was studied from fetal life to maturity. The methods used were immunocytochemical staining and Western blotting. The immunocytochemical studies showed that the only structures that remain NCAM-positive throughout life were the mesonephric-derived rete ovarii and rete testis. Also in the fetal gonads some somatic cell lining the groups of differentiating germ cells were stained. In the immature as well as in the mature ovary the granulosa cells and oocytes of growing and large follicles — but not of small follicles — were stained. A particularly strong staining of the cytoplasm of the oocyte, healthy as well as atretic, was seen. All cells of the testis remained negative except for weakly stained residual bodies and late spermatids. At all ages the male ducts showed only weak staining, whereas in the female Müllerian duct the epithelium became strongly positive at puberty. The stroma of the Müllerian duct was positive during a transitory period around day 16 of fetal life in both sexes. One-dimensional gel immunoblotting of total protein from gonads, rete and ducts from immature and mature mice showed that only the two largest isoforms of NCAM (NCAM-A and NCAM-B) were present. The gonads and the rete of both sexes and the adult uterus expressed only NCAM-B, whereas NCAM-A was also detected in the adult epididymis. The present findings suggest that NCAM may be involved in the normal development and formation of both the gonads and ducts. In particular, NCAM may play a part in sustaining the integrity of the rete testis, thus ensuring the pathway for spermatozoa from the testis to the epididymis. Furthermore this cell adhesion molecule may also be important for follicular growth and differentiation.     

Calcineurin in the postnatal striatum of the rat: an immunohistochemical study

Summary This report concerns the postnatal expression of calcineurin (CaN) in rat striatum. For this purpose an immunohistochemical procedure was used. In neonatal striatum CaN immunoreactivity was found in discrete patches composed of many immature cells. With development there was an increase in staining intensity and in the proportion of positively reacting cells. CaN expression and localization in the striatum of 22–25 day old rats were similar to those of adult animals.     

Zur histogenese und cytogenese des tapetum lucidum cellulosum der katze

Zusammenfassung Die postnatale Entwicklung des Tapetum lucidum cellulosum der Katze wird mit licht- und elektronenmikroskopischen Methoden untersucht. Bereits am ersten postnatalen Tag sind im Bereich des prospektiven Tapetum zwei Zellarten voneinander zu unterscheiden: 1. mesenchymale Bindegewebszellen und 2. prospektive Tapetumzellen, die durch elektronendichte Tapetumstäbchen gekennzeichnet sind. Die Mesenchymzellen unterteilen als parallel zur Retinaoberfläche ausgebreitete Zellplatten in der Choriodea am hinteren Augenpol den weiten extracellulären Raum in 20–25 etwa 5 m hohe Schichten. Die Tapetumzellen liegen zwischen den Mesenchymzellplatten und wachsen im Verlaufe der ersten vier postnatalen Wochen innerhalb der Schichten in die Breite, bis sie den extracellulären Raum vollständig ausfüllen und als polygonale Zellen direkt aneinander grenzen. Im weiteren Verlauf der Entwicklung werden die Mesenchymzellplatten rückgebildet, so daß bei der adulten Katze die Tapetumzellschichten direkt übereinander liegen und nur von Netzen elastischer und kollagener Fasern getrennt sind.Die von einer Elementarmembran umgebenen Tapetumstäbchen enthalten einen elektronendichten, in den ersten postnatalen Wochen mit einer Periode von 100 Å quergestreiften Kern. Zunächst nehmen sie an Zahl und Länge zu und füllen am Ende der vierten postnatalen Woche, zu Bündeln von parallel verlaufenden Stäbchen geordnet, das Cytoplasma der Tapetumzellen. Dann nehmen die Tapetumstäbchen an Dicke zu, und ihre Querstreifung wird von einem elektronendichten Material überlagert. Die Entwicklung der Tapetumstäbchen hat eine starke Ähnlichkeit mit der in der Literatur beschriebenen Entwicklung von Melanosomen in Melanocyten. Das Tapetum lucidum cellulosum wird als ein dichter Verband hochdifferenzierter extrakutaner Melanocyten angesehen.

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Summary The postnatal development of the tapetum lucidum cellulosum of the cat was studied by light and electron microscopy. Already by the first postnatal day two cell types can be distinguished in the prospective tapeta area: 1. mesenchymal cells and 2. prospective tapetal cells, characterized by electron dense, membrane bound, rod-like inclusions. The flattened mesenchymal elements form 20–25 separate layers of cells, which are arranged parallel to the surface of the retina, subdividing the extracellular space of the chorioidea at the posterior pole of the eye into 5 m high compartments. These compartments contain the tapetal cells which enlarge (in their longitudinal axis) during the first four weeks post partum until they occupy the extracellular space almost completely. At this stage, the tapetal cells are polygonal in shape and closely attached to each other. During the subsequent period of development there is a gradual involution of the mesenchymal cell plates. Thus, in adult cats the individual layers of tapetal cells are only separated from each other by networks of collagen and elastic fibers.The tapetal rods are bound by unit membranes and contain an electron dense core which, during the early postnatal weeks, exhibits a periodic cross-striation (100 Å). The tapetal rods increase in number and length during the first four weeks post partum; by the end of the fourth week, they occupy the whole cytoplasm of the tapetal cells. Parallelly arranged rods are grouped into individual bundles coursing inside the cytoplasm in different directions. Thereafter, the tapetal rods increase in thickness and their cross-striation becomes obscured by an electron dense material. This development of the tapetal rods closely resembles that of melanosomes.Thus the tapetum lucidum cellulosum can be regarded as a compact tissue made up of modified extracutaneous melanocytes.

Auszugsweise vorgetragen auf der 69. Versammlung der Anatomischen Gesellschaft in Kiel, Juni 1974.     

鸡胚心脏外形变化及心外膜的发生

本研究用扫描电镜、透射电镜和光镜,观察了早期鸡胚心脏发生的外形变化及心外膜的发生。1.心脏发生经历2个阶段,首先是心脏的成襻过程,心管表面的一定部位出现沟,沟相应部位内面出现嵴。心襻的完成,标志着心脏各部原基的确立。第2个阶段是心脏各部原基的进一步分化,包括心腔内部的分隔及心脏各部位置的变化。心房与心锥的移位,可能是受左右心室移位的影响。2.心外膜片并非由心肌外层原位分化,而是由静脉窦处的间充质细胞增殖,并迁移覆盖在心肌层表面形成。     

Spatiotemporal changes of coxsackievirus and adenovirus receptor in rat hearts during postnatal development and in cultured cardiomyocytes of neonatal rat

Coxsackievirus B is the most common cause of viral myocarditis and is particularly virulent in neonates and children. Adenovirus is also a leading cause of the disease. The determinant of tropism for both viruses is considered to be the expression of coxsackievirus and adenovirus receptor (CAR) in target organs. However, developmental change and physiological localization of CAR in the heart are unknown. We examined expression levels of CAR in rat hearts by quantitative real-time polymerase chain reaction and Western blot analysis and found that CAR decreased gradually during postnatal development, although CAR was detectable, even in adults. Immunohistochemistry revealed CAR on the whole surface of cardiomyocytes in immature rat hearts. In contrast, CAR was detected predominantly on intercalated disks in the adult heart and was accumulated especially at the contact point between the cultured cardiomyocytes, even though they were prepared from the neonatal rat heart. In conclusion, CAR was expressed abundantly on the whole surface of cardiomyocytes in immature rat hearts. Both the expression level and the localization of CAR are possible determinants of the susceptibility to viral myocarditis of neonates and children.     

Expression of serotonin2A receptors in Purkinje cells of the developing rat cerebellum

Previous physiological and pharmacological studies have shown that the serotonin_2A (5-HT_2A) receptor is involved in cerebellar functions. However, the expression of 5-HT_2A receptors in the developing cerebellum has not been elucidated to date. In the present immunohistochemical study, we examined developmental changes of the distribution of 5-HT_2A receptors in Purkinje cells of the rat cerebellum from embryonic day 18 (E18) to postnatal day 21 (P21). The weak immunoreaction to 5-HT_2A receptors was found in the deep cerebellar nuclei on E19. In the cerebellar cortex of the hemisphere and the posterior vermis, somata of Purkinje cells became weakly immunoreactive on P0. With the dendritic elongation and arborization, the immunoreaction appeared in the proximal parts of Purkinje cell dendrites. Distal parts of the dendrites became immunoreactive after P12, and were strongly immunolabeled by P21. The present study may provide a structural basis to investigate the roles of 5-HT_2A receptors during the cerebellar development.     

Growth hormone as an early embryonic growth and differentiation factor

In this review we consider the evidence that growth hormone (GH) acts in the embryo as a local growth, differentiation, and cell survival factor. Because both GH and its receptors are present in the early embryo before the functional differentiation of pituitary somatotrophs and before the establishment of a functioning circulatory system, the conditions are such that GH may be a member of the large battery of autocrine/paracrine growth factors that control embryonic development. It has been clearly established that GH is able to exert direct effects, independent of insulin-like growth factor-I (IGF-I), on the differentiation, proliferation, and survival of cells in a wide variety of tissues in the embryo, fetus, and adult. The signaling pathways behind these effects of GH are now beginning to be determined, establishing early extrapituitary GH as a bona fide developmental growth factor.     

Some notes on uncertainty; Federal policy and innovation

The legislative background and current responsibilities of the new National Center for Health Care Technology (NCHCT) are discussed. The NCHCT's charge is to consider the stage of development, the actual or potential risks, costs and rate of use of health care technology. The role of Government in supporting new technologies, stimulating innovation and encouraging application of research products is considered. These issues are discussed in the context of the uncertainty inherent in planning and the formulation of public policy.