摘要:

AbstractSplitting the uterus longitudinally through implantation sites makes it possible to obtain access to blastocysts and implantation chambers during stages of implantation of the blastocyst in the rat. On the afternoon of day 5 of pregnancy, blastocysts lie in a shallow antimesometrial depression and tend to fall free of the uterus when the chamber is opened. On day 6, blastocysts are oriented in a mesometrial‐antimesometrial plane, occupy a distinct implantation chamber, and tend to adhere to one side or the other of the uterus, leaving an imprint on the contralateral side. After about noon of day 6, some of the blastocysts split in half laterally, and by day 7 all blastocysts which are exposed are split. In addition to demonstrating increased adhesion of blastocyst to uterine epithelium, the procedure clearly shows the progressive elongation of the implantation chamber. The embryonic cell mass is specifically oriented on day 6, and is clasped but not distorted, whereas the abembryonic trophoblast is slightly compressed and indented by the uterine epithelium. The microvilli of the uterine epithelium within the imprint become progressively flattened when compared to the microvilli of the implantation chamber outside of the imprint. The method provides a means of gaining direct access to the surface of uterine epithelium precisely where it has been in association with the blastocyst not only for scanning electron microscopy but also for studies of the properties of the surface constituent

ISSN:0003-276X    

DOI:10.1002/ar.1091820202

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

年代:1975

数据来源: WILEY

摘要:

AbstractNotochords were isolated from Hamburger‐Hamilton stages 13–15 chick embryos by trypsinization and microdissection. These were shown by electron microscopy to be completely devoid of extracellular materials or mesenchymal contaminants. Cultivation of notochordal isolates was carried out on a non‐collagenous (Falcon Plastic) substratum for 0 to 48 hours. At 12 hours of in vitro incubation, a discontinuous basal lamina could be demonstrated on the surface of notochordal cells. This was followed by the appearance of microfibrils of various sizes and other components of the extracellular matrix. By 48 hours of in vitro incubation, the same extracellular materials which surround the notochord in vivo (notochord sheath) could be demonstated in vitro.Autoradiographic studies show that tritiated proline is taken up by notochordal cells and secreted to the extracellular space where label is associated with basal lamina, microfibrils and ground substance. When cis‐hydroxyproline, a known collagen‐specific inhibitor is added to the system, tritiated proline label is located primarily intracellularly and fewer areas of active fibrillogenesis are noted. This suggests that ultrastructurally recognizable materials produced by notochordal cells in vitro may be at least partially collagenous. Significantly, these materials are produced in vivo at the same time (following stage 10) that notochordal tissues actively induce somite differentiation and cartilage formation. It seems reasonable that a biochemically or ultrastructurally identifiable component of the extracellular matrix may possibly mediate such

ISSN:0003-276X    

DOI:10.1002/ar.1091820203

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

年代:1975

数据来源: WILEY

摘要:

AbstractContraction of the conus arteriosus (conus) is visibly delayed in the tubular heart of the chick embryo, and since the electromechanical coupling interval of isolated conal segment is similar to other areas of the embryonic heart, the delayed contraction of the conus indicated an impedance in the spread of the depolarization wave across the ventriculo‐conal (VC) junction.A surface electrode placed on the conus of hearts obtained from the 72‐hour chick embryo records a deflection, termed the C wave, appearing between the QRS complex and the T wave. To establish that the C wave arose from below the atrioventricular sulcus, atria were removed from a series of hearts from 96‐hour embryos and the electrogram revealed a C wave without a P wave.The VC junction responds to digitoxin just as the atrioventricular tissue. Digitoxin prolongs the interval between the QRS and the C wave prior to a complete block in a manner analogous to the PR interval increase prior to the development of the Wenckebach phenomenon or complete atrioventricular block.As the embryonic heart developed after 96 hours, the C wave was no longer identifiable in th

ISSN:0003-276X    

DOI:10.1002/ar.1091820204

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe oocytes of types 2, 3, 4 and 5 follicles from the normal spiny mouse were examined with the electron microscope. Multiple juxtanuclear Golgi bodies, mitochondria associated with flattened granular endoplasmic reticulum, and large nucleus are the main features of the type 2 follicle oocyte. The numbers of mitochondria and Golgi apparati increase significantly at later stages. Small mitochondrial aggregates lacking “intermitochondrial cement” are seen in the ooplasm of types 3, 4 and 5 follicles. “Lamellar complexes” comprising two to six elongate flattened rough ER cisternae and intercisternal filaments begin to appear in the oocyte of the type 3 follicle. The intercisternal filaments may be observed as punctate‐, dashed‐, and solid‐lines in cross sections. In tangential sections the filaments display a paracrystalline structure. In the type 4 follicle oocytes, the “lamellar complex” becomes more extensive; polysomes and ribosomal fibrils are juxtaposed to the “lamellar complexes.” Bundles of ribosomal fibrils are abundant in the ooplasm of the type 5 follicle. The origin of ribosomal filaments and the functional significance of “lamellar c

ISSN:0003-276X    

DOI:10.1002/ar.1091820205

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

年代:1975

数据来源: WILEY

摘要:

AbstractDiuresis and natriuresis follow volume expansion by intravenous infusion of either blood or saline. However, the mechanisms underlying the renal responses seem different for the two types of expansion. It has been suggested that the response to saline expansion is due to changes in physical factors with alterations in the morphology of the lateral intercellular space (LIS). The present study examines the width of the LIS of the proximal tubule after a Ringer‐Locke (1%, 2.3%, or 7% body weight) or whole blood (2.3% body weight) infusion and in nonexpanded control. After Ringer‐Locke infusion, a significant widening of the LIS of the proximal tubule is seen at all levels of expansion. There is a linera relationship between the level of the Ringer‐Locke infusion and the degree of expansion of the LIS. In contrast, after blood volume expansion, the width of the LIS is the same as nonexpanded controls. These studies are consistent with the view that the renal response to saline expansion is mediated at least in part by physical factors affecting the proximal t

ISSN:0003-276X    

DOI:10.1002/ar.1091820206

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

年代:1975

数据来源: WILEY

摘要:

AbstractA culture system utilizing single skeletal muscle fibers from adult rats was developed to study the origin and behavior of mononucleated myoblasts during muscle regeneration. The single fibers are removed manually from the leg and thigh muscles of 300–400 gm rats and maintained in vitro embedded in a fibrin clot overlain with culture medium. Regenerative events were monitored by continuous observation of the cultured fibers. During the first few hours in vitro the fibers undergo degenerative changes including the formation of myofibrillar contraction clots and pyknosis of myonuclei. The endomysial tube (basement lamina) remains intact along the entire length of the fiber and forms transparent chambers bridging the contraction clots. Single fibers are free of endomysial cells and display no cellular outgrowth in culture, except at the cut ends. In contrast, a rich outgrowth of endomysial connective tissue cells is found with bundles consisting of two or more fibers. Isolated mononucleated cells, presumed to be muscle satellite cells, are present within the endomysial tube of single fibers at the onset of the culture period. There is no evidence that myonuclei contribute to the formation of mononucleated cells. The satellite cells enlarge and begin to proliferate during the second day in vitro to form clones of presumptive myoblasts within the endomysial tube. The early clones have a cell doubling time of about 22 hours and exhibit mitotic synchrony. After 5–7 days in vitro the satellite cell progeny begin to fuse to from multinucleated myotubes within the endomysial tube of the original fiber. The myotubes display spontaneous contractile activity and may extend throughout the length of the endomysial t

ISSN:0003-276X    

DOI:10.1002/ar.1091820207

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

年代:1975

数据来源: WILEY

摘要:

AbstractFemale reproductive tracts from 84 bats were examined by light and/or electron microscopy to observe early embryology and implantation inMacrotus. The earliest pregnancy was observed in October and by the end of October all bats were pregnant. Implantation had begun in most specimens from late October. In late November females were carrying implanted blastocysts in which differentiation of endoderm was noted. Reichert's membrane was first observed in November.In early December the trophoblast had begun to differentiate into cytotrophoblast and syncytiotrophoblast and by the end of January this differentiation was most evident. Reichert's membrane persisted until late January. Endoderm in the January sample completely surrounded the yolk sac cavity.By late February the embryos were at the embryonic disc stage and had differentiated mesoderm. The uterine‐fetal relationship was complex and an early placenta was recognized.In late March the embryos spanned a range of development from neural plate to limb‐bud stages. Parturition occurred in June.This lengthy gestation period is characterized by an embryonic diapause of approximately four and one‐half months. The roles of food supply and/or temperature in controlling this growth rate and the evolutionary implications of this development are disc

ISSN:0003-276X    

DOI:10.1002/ar.1091820208

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

年代:1975

数据来源: WILEY

摘要:

AbstractAdult and half grown healthy male and female cats were used in this study. The white and gray matter of the dorsolateral region in the upper lumbar levels of the spinal cord were examined by electron microscopy after fixation by aldehyde perfusion and commonly used methods of embedding, sectioning and staining. The report is limited to description and illustration of specialized junctions of astrocytes. In addition to previously described astrocyte‐astrocyte gap junctions, astrocytes are connected by gap junctions to oligodendroglia cells and to neurons. Astrocytes also are connected with each other and with neurons by junctions characterized by wide (250 Å) gaps containing opaque gap material and by dense material adhering to the inner surfaces of the plasma membranes. The results suggest a morphological basis for adhesion and intercommunication between all adult derivatives of the embryonic neural tu

ISSN:0003-276X    

DOI:10.1002/ar.1091820209

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

年代:1975

数据来源: WILEY

摘要:

AbstractA procedure for differential staining of decalcified bone with silver nitrate showed major histological features which appeared to correspond closely to microradiographic images. The extent to which this is actually the case was investigated directly by preparing microradiographs of ground sections of baboon and dog radii and then decalcifying and staining the same sections. The many detailed similarities indicate that this staining procedure is a useful adjunct to microradiography. Thus, poorly mineralized osteons or layers of circumferential lamellae are darker stained by silver nitrate, and the variably mineralized layers of circumferential lamellae are closely duplicated by light and dark bands in the stained sections. These similarities imply that there is a relationship between the mineral density of bone and some condition of the organic matrix which is probably related to maturation changes in the collagen.

ISSN:0003-276X    

DOI:10.1002/ar.1091820210

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

年代:1975

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091820201

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

年代:1975

数据来源: WILEY