ISSN:0002-9106    

DOI:10.1002/aja.1001400202

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

年代:1974

数据来源: WILEY

摘要:

AbstractLight and electron microscope examination of gastro‐intestinal epithelia in the adult mouse revealed the widespread presence of a cell type characterized by deep surface invaginations or “caveolae” and, accordingly, called “caveolated cell.”The caveolated cells are scattered within the epithelia of stomach, small and large intestine; they have a narrow apex bordering the lumen and a wide base in contact with the basement membrane. In the light microscope, they display microvilli longer than in nearby cells; the cytoplasm is usually pale and contains an apical group of parallel fibrils, next to which are minute light spaces which may correspond to the caveolae. In the electron microscope, each fibril is found to be composed of a bundle of straight filaments, extending from the core of a microvillus down into the deeper portion of the supranuclear region; microtubules are often associated with these filaments. Filaments of a different type are arranged in bundles which go from desmosome to desmosome around the apical region of the cell. The caveolae are long and tortuous channels opening at the cell surface between the microvilli and extending deep into the cytoplasm. From the walls of caveolae, polyp‐like structures project into the lumen. The heads of the polyps are believed to be released into this lumen where they appear as small spheres. These in turn may come out of the caveolae to appear between and next to the microvilli.Caveolated cells are not numerous, e.g., they make up less than 1% of the epithelial cells in the crypts of descending colon. They may be found in the intestinal crypts among poorly differentiated cells, and at the surface of stomach and intestine among fully differentiated cells. They appear to undergo renewal, but since they have not been seen in mitosis, they probably arise from the differentiation of some other epith

ISSN:0002-9106    

DOI:10.1002/aja.1001400203

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

年代:1974

数据来源: WILEY

摘要:

AbstractMorphological changes in the acrosomic system and nuclei of developing spermatids were evaluated as a basis for classifying the stages of the cycle of the seminiferous epithelium in the bovine testis. Light microscopic examination of periodic acid‐Schiff‐stained testicular tissue permitted identification of 14 steps of spermatid development (spermiogenesis). The first 12 steps in this sequence were utilized as the major criterion to divide the cycle of the seminiferous epithelium into 12 distinct stages. Following this, the pattern of germ cell differentiation was investigated by counting the number of germ cells at each stage of the cycle. Based on cell counts, type A spermatogonia divided primarily during stages VII–VIII and IX–X of the cycle. Some type A cells divided again at the end of stage XII to produce intermediate spermatogonia, while others apparently remained “dormant” until the following cycle. At the end of stage IV, intermediate spermatogonia divided to produce type B1spermatogonia which in turn divided at the end of stage V to produce type B2spermatogonia. Primary spermatocytes appeared during stage VIII and divided late in stage XI of the following cycle to form secondary spermatocytes. These divided to form young spermatids at the end of stage XII. It was concluded that changes in the acrosomic system and nuclear morphology of developing spermatids provide useful criteria for dividing the cycle of the seminiferous epithelium into stages as well as investigating the pattern of germ cell development during spermatogenesis in the bo

ISSN:0002-9106    

DOI:10.1002/aja.1001400204

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

年代:1974

数据来源: WILEY

摘要:

AbstractIt is generally accepted that in the kidney insulin is metabolized in the proximal tubule, but whether in the convoluted segment, the straight segment, or both has not been established. By means of autoradiography counting of radioactivity, and interrupted flow techniques, the following observations have been made.131I‐labelled porcine insulin is metabolized exclusively in the convoluted segment of the proximal tubule. Although the glomerular filtrate is the major source of insulin supply to the renal epithelia, the peritubular capillary plexuses provide as much as 30% or more of the total insulin delivered to the renal epithelia. The epithelium of the convoluted segment is capable of sequestering131I‐insulin from the peritubular capillary plexuses, a phenomenon which has not been established previou

ISSN:0002-9106    

DOI:10.1002/aja.1001400205

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

年代:1974

数据来源: WILEY

摘要:

AbstractBronchiolar neuro‐epithelial bodies in neonatal mice were studied by light and electron microscopy. These bodies occurred in thickened areas of the epithelium, and consisted of groups of specialized, non‐ciliated columnar epithelial cells with many cytoplasmic granules. These cells were usually closely parallel to one another and had elongated nuclei containing conspicuous peripheral chromatin condensations. These cells were associated with intra‐epithelial axons.With electron microscopy, the non‐myelinated axon under the neuro‐epithelial body was observed to penetrate the basal lamina and enter the epithelial layer. After penetration, the intra‐epithelial axon containing numerous mitochondria lost its Schwann cell sheath, became enlarged, and ramified among the epithelial cells.These innervated neuro‐epithelial bodies probably function as sensory receptors in th

ISSN:0002-9106    

DOI:10.1002/aja.1001400206

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

年代:1974

数据来源: WILEY

摘要:

AbstractVinblastine sulfate was given to adult rats by two tail‐vein injections. After a total treatment time of five hours, kidney cortex was fixed and prepared for examination by routine transmission electron microscopy. Cells of proximal convoluted tubules from treated animals were found to contain focal aggregates of smooth endoplasmic reticulum. Such aggregates were not normally present in cells of control animals. The smooth membranes of these aggregates bear some resemblance to phenobarbital‐induced proliferations of smooth endoplasmic reticulum described in liver cells by many previous investigators, and the suggestion is made that the aggregates described here may reflect a vinblastine‐induced increase within proximal tubule cells of enzymes which function in drug metabolism. That molecules of vinblastine actually entered proximal tubule cells was evidenced by the fact that cytoplasmic microtubules were greatly reduced in number and paracrystals of microtubular protein were occasionally obs

ISSN:0002-9106    

DOI:10.1002/aja.1001400207

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

年代:1974

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was used to explore electron microscopically the uptake and transport of protein by the rat visceral yolk sac at 2 minutes, 6 hours, and 12 hours following a single intravenous injection into pregnant rats on day 12 and day 21.5 of gestation.On both days, the visceral endoderm absorbed peroxidase via micropinocytosis at 2 min postinjection, but not at the 6 and 12 hr intervals. At the latter two postinjection intervals on day 12, peroxidase was localized mainly at two sites, i.e., within intraepithelial supranuclear storage vacuoles, and within the vitelline endothelium deep to the visceral endoderm. On day 21.5 at 6 and 12 hr postinjection, peroxidase was localized in supranuclear storage vacuoles, though most of it was within tubular structures and small vacuoles in the paranuclear and infranuclear cytoplasm of the endoderm. Many dense vacuoles were in close anatomical relationship with the basal cell membrane. Deep to the endoderm a few macrophages were actively engulfing peroxidase, but reaction product was rarely found in the fenestrated vitelline endothelium.The results presented differ from the previous physiological and anatomical transport studies of the visceral yolk sac in that protein (peroxidase) transport was observed deep to the endoderm during both mid‐ and late gestatio

ISSN:0002-9106    

DOI:10.1002/aja.1001400208

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

年代:1974

数据来源: WILEY

摘要:

AbstractPerivertebral cervical connective tissue was taken from chick embryos of incubation ages from 72 hours through hatching and from 4, 8, 12, and 16 week old chicks. Preparations for electron microscopy were routine except for en bloc staining with 5% aqueous uranyl acetate. Collagenase digestions of thin sections confirmed the presence of tropocollagen in banded extracellular fibrils.Banding becomes demonstrable in fibrils at about seven days but repeating units cannot be measured. Close to connective tissue cells the banded material is present in wide sheets. Partially banded fibrils (250 Å wide) physically related to microfibrils are present in acellular regions. Growth in fibril diameter is slow through the second week (up to 300 Å) but increases nearly 200 Å on days 14 and 15. Fibrils larger than 500 Å resist uranium and lead staining following the period of accelerated growth. Smaller fibrils (<500 Å) continue to stain well. A basic banding pattern of measurable periodicity is established by the eighth day. This consists of a major doublet, two minor doublets, and two singlets. The intraperiod distance does not change significantly with growth (510 Å average). Additional bands near the first minor doublet and singlets of the basic pattern are first clearly demonstrable at 14 and 15 days. Ambiguities in banding and period length are believed to be due to plane of section, interference with detail by other fibrils and flaky amorphous material or possibly to differential shrinkage along the length of a single f

ISSN:0002-9106    

DOI:10.1002/aja.1001400209

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

年代:1974

数据来源: WILEY

摘要:

AbstractAdult male rats received 5 mg methotrexate daily and were sacrificed 1, 1.5, 2, 2.5 and 3 days after the beginning of the treatment. Other groups received 9,000 rads of abdominal x‐radiation and were sacrificed 1, 2 and 3 days later. Histological samples were taken from five regions of the small intestine and processed for light microscopic examination. Average area occupied by the crypts and the villi respectively, was measured per unit length of histological section. A few animals received3H‐thymidine an hour before the methotrexate treatment or irradiation; the histological samples were processed for radioautography.Significant mitotic activity was absent throughout the experiments. During the first 1.5 days, mainly the crypts diminished. Radioautography revealed that migration of crypt cells to the villi continued during this time. During the second and third days, the villi also showed marked diminution, and cell migration became irregular. In general, the histometric data were similar after methotrexate and irradiation. Epithelial denudation started in terminal ileum on the third day after methotrexate. The epithelium was much reduced but not yet denuding at this time in the irradiated animals.Methotrexate inhibition of DNA and RNA synthesis was assumed to be associated, respectively, with mitotic inhibition and with a decline of protein synthesis which manifested itself in villus diminution. Survival of epithelial cells varied presumably according to the amount of RNA pool and was longest in cells being in the S‐phase at the onset of the treatment. The similarity of the data after irradiation implied a similar sequence of e

ISSN:0002-9106    

DOI:10.1002/aja.1001400210

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

年代:1974

数据来源: WILEY

摘要:

AbstractElectron microscopy of superior cervical ganglia of the mouse shows both pre‐ and postganglionic elements impinging upon the soma of principal neurons. The preganglionic cholinergic axon terminals are estimated to cover about 0.7% of the total surface area of the neuronal soma and are characterized by dense packing of synaptic vesicles which remain unchanged after the administration of 5‐hydroxydopamine. Postganglionic elements are estimated to cover about 1.8% of the total surface of the neuronal soma. In many cases they contain small granular vesicles (with or without agranular reticulum), and are considered to be represented in part by vesiculated segments of the dendrite and in part by recurrent axon collaterals of the principal neuron. These postganglionic elements usually make puncta adhaerentes, but occasionally an efferent synapse, on the soma of principal neurons in the ganglion. Evidence is presented which suggests that the soma, in turn, is capable of influencing the perisomal, postganglionic elements through a somatic efferent syna

ISSN:0002-9106    

DOI:10.1002/aja.1001400211

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

年代:1974

数据来源: WILEY