Showing papers on "Apical cytoplasm published in 1973"

Pinocytotic activity of the uterus of the rat

Abstract: With both scanning and transmission electron microscopy, large ectoplasmic projections are found intruding into the lumen from the epithelial cells of the rat uterus. These projections, which are abundant both prior to implantation and during delayed implantation, communicate with the underlying cytoplasm only by a small pedicel as though in the process of pinching off. However, introduction of tracer material into the uterine lumen demonstrates the pinocytotic nature of these projections. Within three minutes after introduction of tracer the projections, termed pinopods, contain numerous vacuoles filled with tracer. Within ten minutes large vacuoles containing tracer are present in the apical cytoplasm subjacent to the individual pinopods. The varied images observed in the experimental and control materials suggest that there is a continual turnover of pinopods. Initially a simple ectoplasmic projection, the pinopod apparently develops rapidly into a mass of ectoplasm 2–3 μ in diameter with multiple folds and pockets at its surface and numerous internal vacuoles. Following a period of active endocytosis of fluid, the pinopod becomes more spherical and, together with contained material, is withdrawn into the apical cytoplasm. It is suggested that pinocytosis might play a role in producing apposition of the blastocyst to the luminal epithelium, in passing information from the blastocyst to the stroma, and in diminishing the molecular contents of the uterine lumen during specific times in the reproductive process.

The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat epididymis.

Abstract: The ultrastructure of the principal cells and intraepithelial leucocytes in the initial segment of the rat caput epididymidis was examined with the electron microscope. Specializations of the principal cells associated with absorption include numerous endocytic invaginations of the cell surface, numerous coated vesicles and multivesicular bodies in the apical cytoplasm. It was demonstrated that particulate tracers are taken into the cells and sequestered in secondary lysosomes and multivesicular bodies. Morphological features consistent with secretory activity are also found in the principal cells and include numerous cisternae of rough endoplasmic reticulum with a flocculent grey content and an extremely well-developed Golgi apparatus. The speculation that the principal cells are actively secretory despite the absence of secretory granules formed in the Golgi and of a visible mechanism for release of the product at the cell surface is discussed. The “halo cells” in the epididymal epithelium were also examined and it is shown that many of these cells are not typical migratory lymphocytes. Chief among the differences are their granule-containing multivesicular bodies and more abundant endoplasmic reticulum. Nonetheless, it is conceivable that the halo cells are lymphocytes and that the conditions they encounter as they leave the circulation and enter the epididymal epithelium may stimulate morphological changes. The possible immunological significance of these observations is discussed.

Polarized intercellular bridges in ovarian follicles of the cecropia moth

Abstract: Fluorescein-labeled rabbit serum globulin was injected into vitellogenic oocytes of the cecropia moth. Though the label spread throughout the ooplasm in less than 30 min, it was unable even after 2 h to cross the complex of intercellular bridges connecting the oocyte to its seven nurse cells. After injection into a single nurse cell, fluorescence was detected in the oocyte adjacent to the bridge complex within 3 min and had spread throughout the ooplasm in 30 min. Here also, the cell bodies of the six uninjected nurse cells remained nonfluorescent. Four of the nurse cells are not bridged directly to the oocyte but only through the apical ends of their siblings. Unidirectional movement must therefore occur in the apical cytoplasm of the nurse cells, as well as in the intercellular bridges. The nurse cells of healthy follicles had an intracellular electrical potential -40 mV relative to blood or dissecting solution, while oocytes measured -30 mV. A mV difference was also detected by direct comparison between a ground electrode in one cell and a recording electrode in the other. Three conditions were found in which the 10 mV difference was reduced or reversed in polarity. In all three cases fluorescent globulin was able in some degree to cross the bridges from the oocyte to the nurse cells.

Absorption of protein macromolecules by the enterocytes of the carp (Cyprinus carpio L.). Ultrastructural and cytochemical study.

Abstract: In the adult carp, the ultrastructure of the enterocytes of the distal segment of the medium intestine is similar to that of the intestinal cells of certain mammals during the neonatal period. Frequent aspects of pinocytosis are visible at the base of a plateau of already developed microvillosities. The apical cytoplasm shows the presence of a dense tubulo-vesicular network. The vacuoles which separate off run together to form a voluminous supranuclear body. Their P.A.S. positive and orthochromatic contents are rich in alkaline phosphatases. The permeability of this epithelium to macromolecules is demonstrated by the administration of “Horseradish Peroxidase” (HRP). This protein penetrates by pinocytosis into the apical tubulo-vesicular system and reaches the blood circulation via the extra-cellular spaces. The presence of certain structures involved in protein transport following a period of experimental fasting of six months reflects their independence with regard to exogenous supplies.

Cell membrane resorption in the rat exocrine pancreas cell after in vivo stimulation of the secretion, as studied by in vitro incubation with extracellular space markers

Abstract: Pancreatic secretion in the rat was stimulated in vivo by pilocarpine injection causing 90% of the storage granules to be discharged within 2 h. Incubation in vitro with [14C]sorbitol indicated that maximal ingestion of this extracellular space marker occurred 3 h after secretogogue injection. Morphological cell membrane measurements on cells with stimulated secretion revealed a simultaneous decrease in amount of membrane bordering the microvilli at the cell apex, lamellar processes, and infoldings present at the latero-basal face of these cells. In 3-h stimulated cells, having the average zymogen granule content characteristic for that phase of secretion, ferritin treatment in vitro showed that the infoldings and related fragmentation vesicles had ingested ferritin and could consequently be considered as being transport vehicles for redundant cell membrane. During stimulated secretion numerous vesicles and vacuoles appeared in the apical cytoplasm. Part of these structures were postulated to be related to the Golgi complex and were discussed in relation to secretory protein transport. Another part of these structures was assumed to have an endocytotic nature, although they never contained ferritin.

Development and Maintenance of the Oviductal Epithelium during the Estrous Cycle in the Bitch

Abstract: The epithelium of the ampulla of the bitch oviduct was studied by light and electron microscopy during representative stages of the normal estrous cycle. Anestrus and early proestrus cells were characteristically low cuboidal and of uniform staining density. The disappearance of large patches of condensed chromatin from the nucleus and the enlargement of the nucleolus during midproestrus was the first evidence of differentiation in the parenchyma. Hypertrophy and ciliation of about 60% of the cells were characteristic of late proestrus. The apical cytoplasm of the ciliated cells contained a row of basal bodies, numerous mitochondria, and a complex network of fine filaments. Maximum secretory cell differentiation was not reached until midestrus at which time these cells were characterized by dilated cisternae of rough endoplasmic reticulum (RER), enlarged Golgi apparatus, and apical secretory granules. During metestrus there was an atrophy of the secretory cells, a loss of cilia, and an increase in the nucleocytoplasnaic ratio. This marked the onset of a sequence of regressive events leading back to the anestrus state where low cuboidal basal cells are predominant. The results are correlated with ovarian steroid plasma levels. The differentiation sequence observed during proestrus and early estrus in the oviductal epithelium of the bitch is directly correlated with, and appears to be the result of, an estrogen surge which occurs at the onset of proestrus. The dedifferentiation sequence observed throughout metestrus is correlated with, and may be the result of, a progesterone surge which occurs during midestrus and reaches a peak early in metestrus. In addition, hormonal and morphological events are so timed that when the ova are released during early estrus, ciliation and secretion are at a maximum for ova/zygote transport and maintenance. To date, no fine structural study of the

Fine structure of the gastric epithelium of the ascidian Botryllus schlosseri. Vacuolated and zymogenic cells.

Abstract: Vacuolated and zymogenic cells, which are two of five cell types identified by electron microscopy in gastric epithelium of B. schlosseri, are described in detail. The vacuolated cells are characterized by one, or a few, supranuclear vacuoles containing myelin figures. A peculiar Golgi apparatus is consistently found at the base of the vacuoles; it consists of cisternae frequently containing small vesicles and tubules of constant diameter and/or a strong electron-opaque material. A variety of vesicles and multivesicular bodies are visible in the apical cytoplasm below long ribbon-like microvilli. The se findings suggest that the vacuolated cells are involved in absorptive and perhaps secretory activity. The zymogenic cells are characterized by a highly developed RER, numerous apical secretory granules and a well developed supranuclear Golgi apparatus. At the apical end, autophagosomes are frequently encountered, some of which contain also zymogen granules. Both cell types contain numerous lipid droplets, which are interpreted as an energy reserve available for the cells and for the entire colony during the change of generation. Correlation between structure and function in both cell types is discussed by taking into account the peculiar life cycle of B. schlosseri, as well as previously reported data on similar cells in other ascidians.

Histogenesis of the yolk sac in the chick.

Abstract: The histogenesis of the chick yolk sac was studied from incubation day 3 to posthatching day 8. During incubation the epithelial lining forms complex folds which penetrate into the yolk mass. Hemopoiesis is at a maximum between incubation days 11 and 13. The mesoderm is a thin layer during early incubation but thickens in the later stages to form a covering serosa, an intermediate connective tissue layer, and an inner vascularized layer which forms lymphatic tissue after hatching. Involution includes the processes of autolysis and phagocytosis. Protein assimilation, by pinocytosis and phagocytosis, reaches a peak at incubation day 13. Glycogen is present in peak amounts between incubation days 7 and 9. Endodermal alkaline phosphatase activity is localized in the apical cytoplasm between days 7 and 13 and in the basal cytoplasm during the latter incubation stages. Acid phosphatase activity increases throughout incubation to peak levels at day 2 posthatching. Maximum lipid absorption occurs during the latte...

Electron microscopic study on the thyroid gland of the salamander Hynobius nebulosus in the breeding season

Abstract: The effect of thyrotropic hormone (TSH) on the salamander thyroid gland was studied by electron microscopy. The following sequence of changes in the follicular cells was observed: (1) 1–1.5 hrs after a single administration of 1 i.u. of TSH, many large colloid droplets appear in the apical cytoplasm; (2) within about 2 hrs hereafter, most of them are replaced by large vacuolar bodies, and cytosomes are remarkably decreased; (3) 2.5–3 hrs after two administrations of 1 i.u. of TSH at an interval of 20 hrs, large vacuolar bodies with or without filaments are frequently observed but cytosomes are hardly encountered; (4) in the group placed at room temperature for 10 days after a single administration of TSH, large vacuolar bodies almost disappear; (5) in the group placed in the ice room for 10 days after the same treatment, large vacuolar bodies with or without filaments frequently appear but cytosomes almost disappear; and (6) in some of large vacuolar bodies with filaments the different stages of crystalloid formation are discernible. From these findings, it is suggested that large colloid droplets are changed into large vacuolar bodies and that crystalloid originates from large vacuolar bodies with filaments, probably as a result of interrupted hydrolysis caused by a deficiency of cytosomes.