摘要:

AbstractIn stages H18–H22 the neural tube was composed of a partially stratified epithelium, reflecting its origin from epidermal and sensory layers of ectoderm. Mitotic figures were distributed over the whole neural wall. Fifty‐four to 91% were peripheral to the luminal zone. There was no evidence of nuclear migration attending mitosis. After integration of epidermal and sensory cells into a single epithelium by stage H24, mitotic figures were mostly near the lumen and for some time prophase stages were distributed peripherally. During this period nuclear migration to and from the lumen accompanied mitosis as in higher vertebrates. By stage H46 nuclei of the neural epithelium were restricted to a narrow zone near the lumen. Most mitotic figures and all other phases of mitosis were in this zone. There was a consequent lack of appreciable nuclear migration. A few peripheral mitotic figures remained in neural cells through stage H46. Some were in epithelial cells whose nuclei did not migrate to the lumen. Others were in the mantle zone, perhaps in neuroblasts. These observations support the view that the neural epithelium, whatever its extent, is germinal. Neither a “germinal zone” nor a special strain of “germinal cells” could be distinguished a

ISSN:0003-276X    

DOI:10.1002/ar.1091540402

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

年代:1966

数据来源: WILEY

摘要:

AbstractOne hundred and seven female rabbits were divided into three groups and irradiated with 400 r from a radiocobalt source. The first group (71 animals) was irradiated before or 4–12 hours after mating and an ovulating injection of H.C.G. The second group (27 animals) were irradiated at about the same time after injection but inseminated after irradiation. The third group (9 animals) were inseminated with spermatozoa which had been irradiated in other females.The ova were recovered at various times for the determination of fertilization, cleavage, and blastocyst formation. Groups of animals were autopsied 14 or 29 days later for the determination of fetal development. The fertilization rate was not disturbed whether sperm, oocytes, or both were irradiated. The disturbance of nuclear material, the aberration of chromosomes, the retardation of cleavage, the fragmentation of cytoplasm, and the failure of blastocyst formation and embryonic development were observed especially whenever oocytes were irradiated. Irradiation of oocytes before mating and injection appeared to be less harmful but no differential effects were observed when irradiation was at 4, 6, 8, 10 or 12 hours after ovulating injection or when oocytes alone or both the oocytes and sperm were irradiated, probably due to the dosage being too high. Irradiation of sperm in the female tract was less harmful, normal blastocysts and apparently normal fetuses were obtained when nonirradiated ova were fertilized by such spermatozo

ISSN:0003-276X    

DOI:10.1002/ar.1091540403

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

年代:1966

数据来源: WILEY

摘要:

AbstractMast cells occurred along the internal cerebral veins in the brain of 55 female and 75 male Syrian hamsters, 35 to 844 days old. Observations on serial parasagittal sections stained with toluidin blue indicated that the largest aggregation of mast cells was in the arachnoid layer between the velum interpositum near the origin of the internal cerebral veins. Mast cells were aligned along short segments of thalamic veins usually near their entrances into the internal cerebral vein or along capillaries in the thalamus of 28 of 45 hamsters, 500 to 844 days old, but were absent in the thalamus of the 17 less than 200 days old. Mast cells and plasmacytes were present in the choroid plexuses of the lateral and third ventricles in 29 of 41, 521 to 844 days old, but were not found in the choroid plexuses of 42 hamsters, 35 to 381 days old, Plasmacytes but no mast cells occurred in the subfornical organ of 18 of 26, 500 to 775 days old and in only 1 of 13 less than a year old. Hibernation, binding of biogenic amines, and vasodilation are topics of discussion on the significance of heparin and histamine in mast cells.

ISSN:0003-276X    

DOI:10.1002/ar.1091540404

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

年代:1966

数据来源: WILEY

摘要:

AbstractLymphocytes with “atypical nuclei” have been shown to increase in lymph nodes during afferent drainage ('64). This report concerns the selective staining of these nuclei with the MBL technique (exposure of methylene blue stained sections to alcoholic Lugol's solution).Comparisons with other techniques, together with suitable extractive procedures, lead to the conclusion that chromatin throughout the hematogenous series of lymphocytes is subject to two general forms of selective response to the MBL technique during lymphatic drainage. These are distinguished by differences in: 1, time required for staining with the iodine solution; 2, morphology; and 3, ease of dedifferentiation.The first response (unpatterned, coarse, intranuclear granules) occurs in older hematogenous lymphocytes only, after brief exposures, and varies in ease of dedifferentiation.The second response (intranuclear, reticulated figures) occurs in hematogenous lymphocytes of any age, after long exposures to iodine, and is slow to dedifferentiate. The figures uniformly conform to the reticular patterns of inter‐ and prophase, and become condensed as cell volumes decrease.The findings show that fluctuant, dynamic relationships exist among hematogenous lymphocytes in nodes :‐ unidentified factors become associated with their chromatin and result in selective nuclear staining; the chromatin becomes restricted to reticular positions and mitoses cease; cell volumes shrink progressively; nucleo‐cytoplasmic ratios increase; and intranuclear structures become condensed. Yet evidences of degeneration are

ISSN:0003-276X    

DOI:10.1002/ar.1091540405

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

年代:1966

数据来源: WILEY

摘要:

AbstractPercentage change in water content and total solids was determined for the developing murine brain for both males and females from birth to 120 days.The central nervous system was divided into four components: (1) cerebrum (2) cerebellum (3) brain stem (4) spinal cord. The percentage of water was determined by dessication for groups of five animals at each day from birth to 20 days and then at five‐day increments to day 60 and at day 90 and day 120.Plots of the per cent solids (water content) against body weight showed a linear relationship for all parts except the cerebellum. No sex differences were noted. The cerebellum showed an early rapid water loss with a changing rate to a linear curve as the animal matured.Growth data were submitted to asymptotic regression using a computer to fit a curve y = α+βρxwhen y is the per cent solid at time × (in days) and α, β, ρ the constants to be determined. All of the central nervous system components gave constants of the same order of m

ISSN:0003-276X    

DOI:10.1002/ar.1091540406

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

年代:1966

数据来源: WILEY

摘要:

AbstractObservations were made on the pre‐ and postnatal development of the photoreceptors in the central region of the retina in the diurnal rhesus monkey. Histologic findings on the level of development of the retina at birth revealed a macula with the characteristic adult foveal depression. Observations on the ultrastructural development of the receptor inner and outer segments revealed that the photoreceptors were well differentiated even at birth. An evaluation of the prenatal morphogenesis of the photoreceptors indicated that the initial differentiation may take place as early as 100–125 days after conception. At 100 days after conception, the pigment epithelium consisted of a single layer of cuboidal cells with cytoplasmic content of smooth endoplasmic reticulum, but was only sparsely populated with mitochondria and rough endoplasmic reticulum. The photoreceptor inner segments contained vesiculation in the supranuclear region, while the incipient outer segments consisted of outbudding ciliary processes. By 125 days postconception, the pigment epithelium contained such cytoplasmic specializations as increases in rough endoplasmic reticulum and mitochondria, as well as greater organelle complexity. In the photoreceptor outer segments there were arrays of closed bimembranous discs, with vesiculation at the apical tip in the inner segments. A comparison of the pre‐ and postnatal ultrastructural changes in the choroid and the interstitial zone comprising the photoreceptor outer segments and the cell processes of the pigment epithelium suggested that the changes in these areas represent a critical aspect in the maturation of the r

ISSN:0003-276X    

DOI:10.1002/ar.1091540407

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe formation of the first blood cells which develop in the area vasculosa of the chick embryo have been examined to seven days of incubation. Angioblasts have been seen to arise from the mesoderm and to give origin to the first endothelium and intravascular blood islands. This occurs as the intercellular spaces enlarge and coalesce. The angioblasts and blood islands are not syncytial but are held in close relation by attachment areas and cytoplasmic processes. Two cell types arise concurrently from the blood islands, a stem cell and cells which have begun their differentiation into the primitive red cell series. The morphological events associated with this differentiation are similar to those in other hematopoietic organs. The definitive series of red blood cells arises from the stem cells at 4 to 5 days of incubation. The morphological differentiation of the definitive red cell is generally similar to that of the primitive series although the late and mature stages show structural differences. Nuclear structure, relation of interchromatin material to nuclear pores and the presence of marginal bands in the definitive series allow a differentiation between the two series.Granulocytes arise from extravascular stem cells at about five days of incubation but at seven days are not fully mature or abundant.Limited observations on the avian thrombocyte are reported.

ISSN:0003-276X    

DOI:10.1002/ar.1091540408

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe fine structure of the adrenal gland of the fetal armadillo was examined by electron microscopy to determine whether or not there were two cell types in the parenchyma of the fetal zone, as suggested by examination by light microscopy, and whether any of the cells of this zone had the cytological features associated with steroid production.Two cell types were found. One cell type is composed of large cells situated in clusters and containing a relative paucity of organelles. The other cell type is composed of smaller, eosinophilic, PAS positive cells, situated primarily in a reticular pattern around the blood vessels. This second cell type has numerous spherical mitochondria with tubular cristae and an extensive tubular agranular endoplasmic reticulum. It is concluded that this latter cell type is responsible for the steroid production reported by other authors. Both of the cell types of the fetal zone appear to be derived from the original mesenchymal blastema of the adrenal gland.

ISSN:0003-276X    

DOI:10.1002/ar.1091540409

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe tough, fibrous resilient, acellular capsule (chorion) of fish embryos has been characterized as protein‐keratin‐like in composition. It has resisted digestion by common proteinases, such as trypsin, chymotrypsin, pepsin, and papain. We have been able to remove the chorion with pronase, a commercially available (Calbiochem) proteolytic enzyme of bacterial origin with broad substrate specificity.The enzyme at concentrations of between 0.5 and 0.00625% was tested at room temperatures in several Ca++and Mg++‐free solutions including a weak salt solution (0.1% NaCl), Yamamoto solution (0.7% NaCl), and distilled water with either phosphate or Tris buffer at pH 6.0–11.5. The embryos were in their first day of development at the start of the treatment.It was found that the enzyme was most effective in Tris‐buffered water, less so in weak salt solution and least effective in Yamamoto solution. Phosphate buffer caused some precipitation of the enzyme. The chorion was thinned over a wide range of pH (7.0–11.0) and in concentrations of enzyme between 0.5–0.0125% within 21–36 hours. Although the embryos frequently escaped from the thinned chorion by rhythmical movements, many of the embryos could be removed easily with the aid of common forceps. Once removed from the chorion the embryos were placed in phosphate buffered weak salt solution (Rugh), where, with few exceptions, they developed normally.Considering least mortality and highest yield of embryos with maximally thinned chorions, Tris‐buffered distilled water at pH 9.5 or 10.0 in an enzyme concentration of 0.025% was found to be optimal. Under these conditions 78% of the total number of embryos treated had completely thinned chorion

ISSN:0003-276X    

DOI:10.1002/ar.1091540410

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe distribution of ascorbic acid in 17 tissues and organs of 20 human fetuses (10–23 weeks of age), was studied histochemically by means of the silver nitrate technic. The metallic silver precipitates which were formed by silver nitrate reduction by ascorbic acid could only be uniformly seen in tissues where quantitative biochemical studies indicated the concentration to be greater than 10 mg/100 gm of tissue. The human fetus derives its supply of ascorbic acid from maternal sources and there were no significant differences between the youngest (10 weeks) and oldest fetuses (23 weeks) studied. The concentration and uniformity of distribution of ascorbic acid throughout the organ was most conspicuous in the adrenal and thyroid gland, liver and the proximal convoluted tubules of the kidneys. In the pancreas no ascorbic acid was found in Islet cells but occasional alveolar cells were filled with precipitates. Fine granulation was observed in germ cells of the gonads and heavier accumulation in the follicular supporting cells and interstitial cells of Leydig. Muscle fibers did not reveal granulation but perivascular connective tissue cells in muscle and glands were occasionally heavily granulate

ISSN:0003-276X    

DOI:10.1002/ar.1091540411

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

年代:1966

数据来源: WILEY