摘要:

AbstractAn electron microscopic study of the small intestine of rats from birth to 15 days of age has demonstrated a gradient of both structure and function along the length of the small intestine. During this period of development, only the ileum was found to absorb intact exogenous ferritin or colostral proteins. In newborn rats ferritin particles or milk proteins are incorporated by ileal absorptive cells into tubular invaginations of the apical plasmalemma which connect with vacuoles or cisternae in the apical cytoplasm. The ferritin particles are then transported by another vacuolar system to the supranuclear region where several such vacuoles coalesce to form a single supranuclear vacucle. After the first feeding the supranuclear vacuole is established in the ileal cells so that additional ingested proteins, whether ferritin or from milk, are transported from the cisternae directly to the supranuclear vacuole. There was no evidence in the present study to indicate that ferritin is transmitted from the ileal cell to the circulation. The subject of protein transport by the intestinal epithelium is reviewed briefly.

ISSN:0002-9106    

DOI:10.1002/aja.1001230202

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe maturation of brown adipose cells, derived at various time intervals from interscapular brown fat pads of neonatal rats, has been investigated electron microscopically. The major changes inin vivobrown adipose cells are related to lipid accumulation. In older animals, fat droplets are separated by a membrane complex, and membranous fragments are seen within large lipid inclusions. The ultrastructural characteristics of monolayer cultures of brown fat cells, isolated from neonatal brown fat pads by tryptic dissociation, and maintained for one to six days on a reconstituted collagen matrix, have also been investigated. Adipose cellsin vitroare morphologically similar to control brown fat cells, and lipid accumulation closely parallels that seenin vivo. In vitrolipid droplet coalescence, impossible to visualizein vivo, has been documented by time‐lapse cinematography, and membrane complexes similar to those observedin vivoare seen. Major changes in cultivated fat cells, compared toin vivocells, involve extensive glycogen deposition and breakdown of cytoplasmic ribosomal rosettes. Older cultures contain adipose cells exhibiting characteristics of white fat cells. Effects of tissue culture environment upon the brown fat cells, and the possible conversion of the brown fat cell into a white fat cell are discusse

ISSN:0002-9106    

DOI:10.1002/aja.1001230203

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the crevicular epithelium of clinically healthy cat gingiva was similar to that of other non‐keratinizing oral epithelia. However, it differed in that the intercellular spaces were wide and extended as a continuous network from the basal lamina to the epithelial surface. Basal cells contained numerous mitochondria, Golgi apparatus, free ribosomes and a fine feltwork of evenly distributed tonofilaments. Hemidesmosomes were present in relation to the basal lamina. Cells in the intermediate layers showed a decrease in the number of organelles and an increase in concentration of tonofilaments, Superficial cells were further flattened and the remaining organelles commonly showed degenerative changes. Epithelial cells showed prominent microvilli extending into the intercellular spaces. Some of these formed desmosomes with similar processes of adjacent cells. Occasional randomly distributed tight junctions were also observed. Inactive basal melanocytes, more superficial Langerhans cells and leucocytes were seen between epithelial cells. The great majority of leucocytes were neutrophils and many of these ruptured as they approached the epithelial surface scattering their specific granules into the intercellular spaces. These findings are discussed in relation to the peculiar permeability of the gingival crevicular region of the oral mucosa to tissue fluid and leucocyte

ISSN:0002-9106    

DOI:10.1002/aja.1001230204

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe adrenal cortex of the 13‐lined ground squirrel was examined by means of phase contrast and electron microscopy. At the most, two cell types were observed. One of these two types was observed in three morphologically different stages of activity. They had some common characteristics, although they were very different in general appearance. The findings substantiate Symington's (′60, ′61) statements that the zona reticularis contains the active cells and the zona fasciculata contains the inactive cells of the deep adrenal cortex. The cell types do not stay within the bounds of the three classical zones, and it is suggested these be used for general topography only. A number of modifications and derivations of mitochondria are described, one of which lends strength to Lever's ('55) suggestion that mitochondria might be converted into lipoidal m

ISSN:0002-9106    

DOI:10.1002/aja.1001230205

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe nerve pattern of the bone marrow of the monkey, rabbit, rat and mouse was studied in serial sections specially stained to demonstrate myelinated and nonmyelinated nerve fibers. Features that are common to the different species studied were found in the bone marrow of the femur of the rat in a simple arrangement.A scheme is proposed based on thirteen photomicrographs demonstrating the nerve pattern of the bone marrow and the relation of the nerve fibers with the arterial tree, the sinusoids and the blood forming cells. This scheme shows that the necessary anatomical conditions exist permitting a direct influence of the nervous system on the function of the bone marrow. These conditions are the presence of myelinated nerve fibers traversing the parenchyma of the marrow, and the existence of nonmyelinated fibers ending in sphincterlike structures at the origin of the arterioles.Single myelinated nerve fibers and small bundles of both myelinated and nonmyelinated fibers lie in close contact with the endothelial wall of the sinuses during long trajects. Only the very thin endothelium of the sinuses separates the newly formed blood and the nerve fibers. An interaction between both elements is possible along these areas of contact.

ISSN:0002-9106    

DOI:10.1002/aja.1001230206

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

年代:1968

数据来源: WILEY

摘要:

AbstractSpermatozoa have been observed with the electron microscope at various stages of their approach to and penetration of the rabbit ovum. No significant change in fine structure is observed in uterine sperm, or in many of the sperm at the periphery of the granulosa investment around the ovum. By contrast, a majority of sperm lying between the granulosa cells or on the surface of the zona pellucida display various stages of the “acrosome reaction”; this involves fusion and vesicle formation between the plasma membrane and the outer membrane of the acrosome. Loss of these vesicular elements, and content of the acrosome cap, takes place before sperm begin to penetrate the substance of the zona. The constricted posterior “equatorial” segment of the acrosome cap does not take part in the acrosome reaction and remains with its content intact during penetration of the zona; neither does the content of the apical sub‐acrosomal region (perforatorium) or post‐acrosomal region appear to change in traversing the zona. The hypothetical zona lysin is thus presumed to be closely associated with the persistent inner membrane of the acrosome, which now becomes the limiting membrane around the anterior part of the sperm nucleus.No “penetration filament” has been observed, but sperm within the zona pellucida of ageing eggs are often preceded by a straight or curved fissure in the substance of the zona. The possible nature of capacitation and its relation to the acrosome reaction and to the process of penetration, are di

ISSN:0002-9106    

DOI:10.1002/aja.1001230207

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

年代:1968

数据来源: WILEY

摘要:

AbstractResults of autoradiographic investigations utilizing tritiated proline reveal an intricate mechanism of rat calvarial growth and reshaping from age two days through 75 days. Generalized intramembranous bone growth dominates the growth process from two through eight days; however, this simple bony enlargement is terminated early. At eight days a differential apposition‐resorption process begins dorsally in the calvarium and progresses rostrally within a ten day period. This process includes differential apposition on the ectocranial and endocranial periosteal surfaces accompanied by a differential apposition‐resorption pattern on the endosteal surfaces. The wave‐like process begins in the occipital bone and progresses ventrally to the frontal bone resulting in a flattening of the bony components. At 35 days bone accretion is again generalized on most calvarial surfacse. However, at 40 days another change in the growth process evolves on the occipital and frontal bones. These bones are now seemingly displaced in a superior direction as bone apposition continues on their superior surfaces, namely, the ectocranial periosteal and endocranial endosteal surfaces and resorption progresses on the two inferior surfaces. The magnitude and duration of the process described in this paper is sufficient to account for calvarial flattening in the absence of bony spatial reorientation due to bending at sutures. The findings described here when compared to proposed in vitro studies can help put the importance of the so‐called “functional matrix” related to bone growth into its proper

ISSN:0002-9106    

DOI:10.1002/aja.1001230208

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe fine structure of smooth muscle cells of the rat uterus was studied at 6, 12, 24, 48, 72 and 96 hours after a single subcutaneous injection of estradiol dipropionate (10 μg). The control rats were ovariectomized, but did not receive hormone treatment. Changes in the ultrastructure of the muscle cells occurred soon after estrogen stimulation. An increase in the number of ribosomes on the outer nuclear membrane and evagination of the membrane into the surrounding cytoplasm was noted at six hours. The amount and dilatation of the granular endoplasmic reticulum (GER) increased gradually from 6 to 96 hours. At 24 and 48 hours the mitochondria appeared to increase in number and at later time intervals they increased in size. The Golgi complex was more prominent at 72 and 96 hours than at the earlier time intervals. An increase in free ribosomes was observed at 6 and 12 hours, but a marked accumulation of them occurred at 24 hours and continued to 96 hours. The glycogen granules were very pronounced at 24 and 48 hours with a reduction at 72 and 96 hours. Many pinocytotic vesicles and dense bodies were present in the controls and at 6 and 12 hours. A decrease in number occurred in both at the later time intervals. Organelles accumulated at the nuclear poles beginning at 24 hours and extending to 96 hours. The observations made provide additional information on the fine structure of uterine smooth muscle cells following estrogen stimulation and support previous biochemical studies on glycogen concentration and RNA synthesis in the rat uterus

ISSN:0002-9106    

DOI:10.1002/aja.1001230209

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

年代:1968

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001230201

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

年代:1968

数据来源: WILEY