摘要:

AbstractInitiation and development of the follicle population in mice were examined during embryonic and early postnatal life. The shape of the curve relating follicle density with age suggests that follicle intiation begins in the 14‐day‐old embryo and continues until about two days after birth. During the period of follicle intiation, groups of follicles are established in a regular and systematic way but at any particular age during this period, the stage of development of adjacent groups is not always synchronous so that when initiation ceases the composition and numerical size of different groups are highly variable. Although 75% of all groups contained three, four, or five follicles some were composed of only two and others as many as 11 folllices. In adult mice the most notable feature of the spatial distribution of follicles is often only the tendency for follicles to be arranged in rows. An examination of the follicle population about six days after birth showed that this feature is not incompatible with the earlier developmental grouping structure. A comparison of the proportions of different fiber types in the coat with the proportions of follicles occupying specific positions in the follicle groups was unable to establish any close relationship between follicle and fiber types. Evidently the type of fiber grown by a follicle is more dependent on the age when the follicle is initiated than on the position of the follicle in the follicle gr

ISSN:0003-276X    

DOI:10.1002/ar.1091540202

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

年代:1966

数据来源: WILEY

摘要:

AbstractRabbit eggs 11–18 hours after mating were incubated with tritiated thymidine for 30 minutes, fixed in osmium tetroxide and prepared for autoradiography. DNA synthesis in both pronuclei takes place between 3–6 hours after fertilization. The presynthetic and synthetic periods are short, followed by a long postsynthetic per

ISSN:0003-276X    

DOI:10.1002/ar.1091540203

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

年代:1966

数据来源: WILEY

摘要:

AbstractA histological study was made of the quantitative distribution of elastic elements in the aorta of the baboon,Papio doguera. Materials were obtained in East Africa from freshly sacrificed animals as well as from domestic stock, and represented all age groups from a fetus near term to 28 years. Verhoeff's elastic tissue stained sections were prepared from 4 zones from the arch to the bifurcation.All specimens showed an attenuation of the thickness of the aortic wall as well as a decrease in the number of layers of elastic membranes from the arch to the bifurcation. The attenuation was less prominent in the older and heavier animals. The reduction in the number of elastic membranes at the lower end indicates a reduced requirement for the storage of ventricular energy by the elastic constituents for blood propulsion. Gravitational forces may be instrumental in maintaining blood flow to the lower extremities without additional expenditure of energy of ventricular origin.

ISSN:0003-276X    

DOI:10.1002/ar.1091540204

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

年代:1966

数据来源: WILEY

摘要:

AbstractChick embryos, incubated at 38–39°C to stages 8–11 (Hamburger‐Hamilton staging), were injected (under the vitelline membrane) with ten MLD (mice) per 0.05 ml of tetanus toxin or with avian physiological saline solution. Seventeen hours after the injection the embryos were harvested and fixed in Bouin's solution. Selected control and experimental specimens were sectioned for histological study.Observations of gross specimens show that open neural folds of younger embryos are more susceptible than are the more extensively closed tubes of older embryos. The progressively more caudal restriction of toxin‐susceptible sites with increasing age is a manifestation of this correlation with the degree of closure at injection time.Study of serial sections establishes the concentration of lesions almost exclusively in neural tissue, especially in the alar region of the neuraxis. Tetanus‐induced lesions include encephaloschisis, myeloschisis and platyneury at various levels of the neural tube. These basic defects are comparable to those reported after treatment with many CNS teratogens.Suggestions are made concerning the possible effect of tetanus toxin on biochemical interactions that might lead to aberrations from the normal morphogenesis of the central nerv

ISSN:0003-276X    

DOI:10.1002/ar.1091540205

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

年代:1966

数据来源: WILEY

摘要:

AbstractAn accelerated method for the production of wax plate models from serial sections is described. Serial sections are projected on the back of 1 mm wax plates and the sharp image produced on the front of the plate is cut out directly with a knife. The construction of a simple projection apparatus which permits back‐lighted projection is described and illustrated. The apparatus is built of common‐size lumber and a small sheet of Plexiglas. It consists of a screen for the image and a wooden track on which a light source and microscope can be moved back and forth for different magnifications. Commercially available wax plates can be used. A method and the equipment needed to produce larger plates are described.The cut‐out images when piled up to form the model are welded together and strengthened by inserting heated straight pins. The exterior of the model is smoothed with an electrically heated glass instrument which provides constant heat of desired temperatures. The construction of the glass instrument is illust

ISSN:0003-276X    

DOI:10.1002/ar.1091540206

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

年代:1966

数据来源: WILEY

摘要:

AbstractMeasurements of nerve fiber size in the trochlear nerve indicate that many small nerve fibers are present which could serve as the small nerve motor supply for innervation of the slow muscle fibers in the superior oblique of the cat. Twitch and slow muscle fibers in the superior oblique muscle of the cat have been examined in the electron microscope. In twitch fibers, triads consisting of the transverse tubule and dilated sacs of the sarcoplasmic reticulum occur at the level of junction of A and I bands. In the slow fibers, the sarcoplasmic reticulum is reduced in amount and the transverse tubular system is completely absent. The junctional folds of the postsynaptic membrane of the muscle fiber under the nerve terminal of a twitch fiber are present, although not extensive; in slow fibers, these postjunctional sarcolemmal folds are essentially absent. Some physiological implications of these differences in fine structure of twitch and slow fibers and their respective nerve terminals are discussed.

ISSN:0003-276X    

DOI:10.1002/ar.1091540207

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe Gomori (metal‐salt) and azo‐dye techniques were used for the localization of alkaline and acid phosphatases in the metanephric kidneys from 13‐ to 22‐day‐old fetal rats. Alkaline phosphatase activity was localized first in the luminal (brush) border of the differentiated proximal tubule in the kidneys of 19‐day‐old fetuses. Acid phosphatase activity was first localized in the cytoplasm of all the morphologically differentiated cells of the nephron in the kidneys of 20‐day‐old fetuses as cytoplasmic “droplets.” The relationships of the localization of these to the morphological differentiation of the

ISSN:0003-276X    

DOI:10.1002/ar.1091540208

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe histology of the thymus of both germfree and conventional mice at days 0, 14, 50, and 168 supports the interpretation of the growth pattern of the thymus as a reflection of the lymphocyte population of the cortex and medulla. In general the conventional thymus has more small lymphocytes in the cortex and more lymphocytes migrating into the medulla than in its germfree counterpart. Hence it would seem that antigenic challenge stimulates lymphocyte production in the thymus cortex and initiates a chain of events that may eventually result in thymus lymphocytes populating the other lymphoid tissues of the body, or that may result in lymphocyte degeneration in the thymus and the subsequent releas of a humoral factor that may stimulate the other lymphoid tissue to lymphocytopoiesis.

ISSN:0003-276X    

DOI:10.1002/ar.1091540209

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

年代:1966

数据来源: WILEY

摘要:

AbstractWith the aid of the electron microscope, it has been possible to demonstrate that the configuration of keratohyalin in rat tongue epithelium is highly variable. The configurations described by others are seen, i.e., the globular or irregular granules made up of homogeneous electron‐opaque material. In addition to these, there are two other types of granules. One type is constituted heterogeneously of material similar in density to that usually described and another slightly less dense material. In the other type, keratohyalin is arranged as a dense rim around an electron‐translucent, amorphous center. In addition to the cytoplasmic keratohyalin granules, intranuclear dense granules were demonstrated. The morphology of these intranuclear granules is similar in some ways to cytoplasmic keratohya

ISSN:0003-276X    

DOI:10.1002/ar.1091540210

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe wide range of rotational movement found in the elongated foot ofGalago senegalensiscannot be accounted for by movement at the subtalar joint. A gross and microscopic study of the intertarsal joints of this animal have revealed a discrete calcaneonavicular articulation between the shafts of these bones together with a pivot joint at the calcaneocuboid articulation. It is suggested that little movement occurs at the subtalar joint and that most of the rotation found is produced by a movement of the navicular and distal tarsal bones about an axis which passes through the attachment of the plantar calcaneonavicular ligament to the calcaneus, the calcaneal portion of the calcaneonavicular joint and the pivot of the calcaneocuboid joint. A comparison is made with the foot ofTarsiusand with the rotational movements of the forearm.

ISSN:0003-276X    

DOI:10.1002/ar.1091540211

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

年代:1966

数据来源: WILEY