摘要:

AbstractAnchoring villi from the first trimester, early second trimester, and term were examined with the electron microscope. It was found that the small anchoring villi of the third and fourth month were particularly informative, since at this stage the cytotrophoblast is still proliferating, yet these cells form a compact discoidal region at the surface of the basal plate. Transitions from relatively undifferentiated cytotrophoblast cells adjacent to the stroma of the villus to large isolated cells surrounded by fibrinoid could readily be followed. These highly differentiated cytotrophoblast cells were found to have extensive regions of fine filaments, in addition to their pronounced endoplasmic reticulum, and were designated fibrous cytotrophoblast cells. The nature of the frequently incomplete epithelium covering anchoring villi at term was described, and some of the functions of the cytotrophoblast are discussed in relation to the observations of their fine structure.

ISSN:0002-9106    

DOI:10.1002/aja.1001220302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThe definitive chorio‐allantoic placenta of the bat is hemodichorial, since the cytotrophoblast layer persists to term. The syncytium contains intrasyncytial lacunae in which there is a continuous lamina interrupted only where portions of the syncytium communicate with the thin ectoplasmic layer at the surface of the maternal blood spaces.The future cytotrophoblast and syncytial trophoblast layers can be distinguished shortly after implantation. The future syncytial layer is not syncytial until after it invests most of the anastomotic vessels of the vascular tuft. The resulting labyrinth is converted from the vaso‐chorial to the hemodichorial condition as processes of syncytium pass through the basement membrane of the maternal vessels and spread out under the endothelial cells. The basement membrane is then included within the syncytium as the intrasyncytial lamina, and the maternal endothelial cells are lost. The numerous communications of the maternal vessels with the labyrinth seen early in gestation are reduced through occlusion of many of the efferent channels, which process also contributes areas of necrosis to the decidua basalis. The peculiarity of a maternal extracellular membrane being incorporated into the fetal portion of the placenta is discus

ISSN:0002-9106    

DOI:10.1002/aja.1001220303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractA study comprising both descriptive and experimental data was undertaken. The descriptive portion utilizes transverse, sagittal, and frontal serial sections of 10 through 20 day old rat embryos.As development proceeds, the somites lengthen along their dorsoventral dimension, and epithelial‐lined “buds” (ventral somite buds) extend into the lateral plate somatopleure. Concomitantly epithelium lining the somite “body” is converted to a loosely associated mass of mesenchyme, beginning at the deep medial border and extending around the cephalic and caudal faces of the somite to involve the superficial surface. Lastly, this process transforms the epithelium covering the ventral somite buds into a mesenchymal aggregation. Anlagen of the abdominal ventrolateral muscles arise in the precise position of the mesenchymal aggregation derived from the ventral somite buds.The experimental section tests the development capacities of isolated portions of the trunk body wall when implanted in the anterior chamber of the eye. Grafts of somite material are highly proficient in forming striated muscle, while grafts of somite‐free somatopleure have little ability to form striated muscle. Grafts of ventral body wall become more proficient in forming striated muscle with age. The increase in muscle‐forming ability correlates directly with the invasion of material from the ventral somite buds into the ventral body wall. It is concluded that the ventrolateral (abdominal) musculature is of s

ISSN:0002-9106    

DOI:10.1002/aja.1001220304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThe fine structure of the portion of the parietal yolk sac which extends across the fetal surface of the rat placenta (which is the only portion of the parietal yolk sac which persists after the sixteenth day of pregnancy) was examined sequentially on the even numbered days during the second half of gestation. The placental parietal yolk sac was seen to consist of two cellular layers, trophoblast and endodermal epithelium, which were separated by a thick, amorphous membrane (of Reichert). The trophoblast attenuated with increasing gestational age and, on day 18, became perforated by fenestrations which were closed by diaphragmata. By day 22, the attenuated trophoblast was patently perforate, and maternal blood was exposed to Reichert's membrane. Since throughout gestation, the cells of the parietal endoderm formed a discontinuous layer, at all stages Reichert's membrane was exposed to the vitelline cavity. When ferritin and thorotrast were injected i.v., both separately and together, the former passed readily from maternal blood through Reichert's membrane and was phagocytosed by cells of the parietal endoderm. Thorotrast, however, did not cross Reichert's membrane. Since the rodent yolk‐sac complex is known to serve as a placental route, selective permeability of Reichert's membrane may help regulate maternofetal exchang

ISSN:0002-9106    

DOI:10.1002/aja.1001220305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractCardiac nerves arising from the cervical and thoracic sympathetic chain, the vagi, and the recurrent laryngeal nerves of the dog were described. The findings are correlated with the nomenclature of the NA ('66) and proposals of the NAV ('67), and additional suggestions are made when appropriate. Although individual cardiac nerves were followed to specific areas of the heart, additional supplies to these areas were noted from the cardiac plexus. Sympathetic cardiac innervation arose primarily from the vertebral ganglion. Cranial vagal cardiac nerves on the left and caudal vagal cardiac nerves on the right contributed the majority of the parasympathetic cardiac innervation. Right cardiac nerves ramified primarily along the right coronary artery, left descending branch of the left coronary artery, circumflex branch of the left coronary artery on the left surface of the heart, and onto the right atrium. Left heart nerves, in addition to their direct contributions to all but the last area, proceeded along the circumflex branch of the left coronary artery on the caudal and right surfaces of the heart. Right nerves contributed more in the area of the S.A node, while left nerves formed a network in the area of the coronary sinus and A.V. node. Both sympathetic and parasympathetic nerves were followed to each area. It was noted that pulmonary innervation via the cardiac plexus would be disturbed by the technique of cardiac denervation referred to as regional neural ablations.

ISSN:0002-9106    

DOI:10.1002/aja.1001220306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractDetailed morphological studies of the cardiac innervation of the cat were reported. Sympathetic cardiac nerves arose from the thoracic, cervicothoracic, vertebral, and intermediate ganglia. Parasympathetic cardiac nerves arose from the vagi, both cranial and caudal to the origin of the recurrent laryngeal nerves, and from the right recurrent laryngeal nerve. Left cardiac nerves passed primarily to the caudal and right surfaces of the left chambers while right ones ramified on the right chambers and left portion of the left chambers. Left cardiac nerves are more prominent around the coronary sinus and atrioventricular node, while right ones contribute more to the area of the sinoatrial node. Both sympathetic and parasympathetic nerves were followed to each chamber. Interconnections through the cardiac plexus facilitated overlapping of nerve distributions.

ISSN:0002-9106    

DOI:10.1002/aja.1001220307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractBetween 0 and 266 days of age the weight of the pectoral and gastrocnemius muscles of chickens increased 300–600‐ and 40–90‐fold respectively depending on the breed and sex. In both muscles the mean cross‐sectional area of the fibres and the total number of nuclei (estimated from DNA determination) maintained a constant ratio during growth. This suggests that for individual fibres the cross‐sectional area increased in proportion to the number of nuclei. This phenomenon is discussed in relation to current knowledge concerning the mode of growth and multinucleation of skeletal muscle fibres.In the pectoral muscle, between 0 and 266 days, the cross‐sectional area of the fibres increased in proportion to the two‐thirds power of the muscle weight, which suggests that the length and diameter of the fibres maintained a constant ratio. The same relationship existed for the gastrocnemius for two months, after which the fibre cross‐sectional area increased in proportion to the muscle weight, which suggests that the fibre length

ISSN:0002-9106    

DOI:10.1002/aja.1001220308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractDuring unrestricted growth of the pectoral muscle of chickens, the mean cross‐sectional area of the fibres increased in proporiton to the total number of nuclei and in proportion to the two thirds power of the weight of the muscle. Continuous restricted feeding from 0 day, which limited the weight of the muscle at 16 days to 44% or 69% of that of chickens fedad libitum, did not affect these relationships.A sudden restriction of feed from eight days of age retarded growth of the muscle to approximately 70% of the weight of the controls at 16 days. It did not affect the relationship between the number of nuclei and the fibre cross‐sectional area, both of which were also limited to about 70% of those of the controls; but it did disrupt the relationship of these two variates to the weight of the muscle. Subsequentad libitumfeeding caused compensatory growth and restored the relationship.Starvation or severe undernutrition for a few days, which reduced weight of the muscle and the fibre cross‐sectional area by approximately 25%, caused no loss of nuclei, thereby disrupting both relationships. Subsequentad libitumfeeding initially caused an increase of muscle weight and fibre cross‐sectional area but no increase in the number of nuclei. This restored the relationships, which were then maintained during subsequent compensatory

ISSN:0002-9106    

DOI:10.1002/aja.1001220309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractLipopolysaccharide fromS. typhosa, injected intraperitoneally into Swiss albino mice, produced acute thymic involution—maximal at 48 hours after injection, followed by regeneration that was complete within 5 to 7 days. Using tissues fixed and embedded for electron microscopy, cell counts were made with the light microscope and cytological details were examined in electron micrographs. The cellular events of involution and regeneration were similar to those produced by injection of adrenal glucocorticoids, but it remains to be determined whether or not endotoxin acts on the thymus by inciting adrenal cortical secretion.Involution appeared to be the result of both the death of small lymphocytes and reduced lymphopoiesis in the thymus. Within 48 hours, macrophages had cleared away the cellular debris and medullary epithelial cells showed signs of hypertrophy and increased putative secretory activity. Subsequently, large lymphocytes proliferated at an accelerated rate in the subcapsular cortex, the cortex grew in width by the accumulation of small lymphocytes, and regeneration ceased when the thymus had reached its former size.These observations provide circumstantial evidence for the hypothesis that in regeneration, medullary epithelial cells increase their production of a lymphopoietic hormone which stimulates mitotic proliferaton of cortical lymphocyte

ISSN:0002-9106    

DOI:10.1002/aja.1001220310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractIt is shown in this study that cells of the mesometrial triangle proliferate at a high rate in the early formative period of the metrial gland. This, plus observations of sequential apperance of specific cell types during growth of this tissue, indicate that the metrial cells are formedin situ.Support for the hypothesis ofin situformation of metrial gland tissue also was obtained by observation of apparent differentiation of metrial cells from a precursor cell type. The precursor cells appear to arise from fibroblast‐like cells located in the mesometrial triangle throughout the formative period of the metrial gland. Quantitative autoradiographic studies indicate that the precursor cells accumulate glycogen, undergo division, and subsequently produce diastase‐resistant, PAS‐positive granules that are characteristic of metrial cells. These cells, which contain specific granules and glycogen, are an individual cell type and are referred to as mononucleate metrial cells. The experiments suggest that the mononucleate metrial cells undergo karyokinesis without cytokinesis resulting in typical binucleate metrial cells. Binucleate metrial cells synthesize DNA and appear to become polyploid rather than forming multinucleated cells or binucleate daughter cells. Some nuclei apparently attain a high ploidy, but the majority of binucleates are not highly poly

ISSN:0002-9106    

DOI:10.1002/aja.1001220311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY