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  • 1
    ISSN: 1432-0878
    Keywords: Peripolar cells ; Juxtaglomerular apparatus ; Cytoplasmic granules ; Exocytosis ; Electron microscopy ; Sheep, newborn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Scanning and transmission electron microscopy were used to study the ultrastructural characteristics and positions of granulated peripolar cells in newborn lamb kidney. Following tissue fixation by vascular perfusion in situ, the vascular pole region of the glomerulus was exposed for examination by scanning electron micoscopy following removal of the glomerular tuft. Peripolar cells were recognized by their surface morphology enabling their quantification and an assessment of the relationship of their position in the renal cortex. The prominent expression of peripolar cells in this species was confirmed. Almost every vascular pole examined revealed peripolar cells (405 out of 407; 99.5%) and thus, throughout the cortex, the distribution of peripolar cells was the same as the distribution of renal corpuscles. Larger, more protruding peripolar cells were observed in the outer cortical renal corpuscles. The numbers of peripolar cells encircling each vascular pole ranged from 1 to 10. There was no correlation between number of granulated peripolar cells at the vascular pole and the position of the renal corpuscle within the renal cortex. As viewed by transmission electron microscopy, organelles of protein synthesis were abundant in the cytoplasm of peripolar cells. Exocytosis of cytoplasmic granules was observed by both scanning and transmission electron microscopy implying that a process of regulative secretion occurs from these cells. The use of ultrastrural techniques has provided evidence supporting the concept that peripolar cells are prominent in the cuff region of each renal corpuscle of the newborn lamb and further-more that peripolar cells in this species most likely have a secretory function.
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  • 2
    ISSN: 1432-0878
    Keywords: Peripolar cells ; Juxtaglomerular apparatus ; Newborn sheep ; Dexamethasone ; Ultrastructure ; Cytoplasmic granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the renal juxtaglomerular region of newborn sheep, it was found that glomerular peripolar cells and their granules were very much larger than those found in fetal lambs or adult sheep. Similar peripolar cell hypertrophy was triggered in fetal lambs treated in utero with intraperitoneal injections of dexamethasone. Ultrastructurally, granules of peripolar cells from newborn lambs resembled closely the enlarged zymogen granules described in the pancreas of newborn rats. Such peripolar cell hypertrophy may reflect a functional adaptation of the kidney to immediate postnatal life.
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  • 3
    ISSN: 1432-0878
    Keywords: Peripolar cells ; Juxtaglomerular apparatus ; Kallikrein ; Ultrastructure ; Mammals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Peripolar cells are granulated glomerular epithelial cells that form a cuff around the vascular pole of the glomerulus. Quantitation of these cells in 17 species of mammals (including man, several laboratory animals and a variety of other species) indicated that they were detectable by light microscopy in all but one of the mammals that were examined (the Australian hopping mouse). In adult mammals with detectable peripolar cells, the “peripolar cell index” (the percentage of randomly sectioned glomeruli that displayed peripolar cells in histological sections of kidney) ranged from 0.15 (for echidna) to 11.86 (for sheep). Newborn lambs and rats showed strikingly high values (23.30 and 10.76, respectively) compared with their adult counterparts. Using electron microscopy, peripolar cells were observed in all species that were examined, including the Australian hopping mouse. Morphologically, peripolar cells were similar in all species although their size and granule population varied. They showed a predominantly outer cortical glomerular distribution and a close anatomical relationship with the renin-containing myoepithelioid cells. These findings indicate that peripolar cells are present in a wide variety of species and support the view that such cells may play a significant role in the regulation of normal renal function.
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  • 4
    ISSN: 1432-0878
    Keywords: Pregnancy ; Adrenal zona glomerulosa ; Juxtaglomerular apparatus ; Ultrastructure ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural changes in the adrenal zona glomerulosa and renal juxtaglomerular apparatus have been examined during normal pregnancy in sheep. As pregnancy progressed, increasing numbers of cells in the adrenal zona glomerulosa displayed mitochondria with straight tubular “rod-like” structures replacing their normal lamelliform cristae; groups of cells showing these mitochondrial changes were predominantly located in the middle and superficial regions of the zona glomerulosa, but at all stages remained interspersed with cells with apparently normal mitochondria. In the same animals, the renal juxtaglomerular index was raised, reflecting an increase in renin storage, and juxtaglomerular myoepithelioid cells showed increased numbers of cytoplasmic granules, but no apparent increase in granular endoplasmic reticulum and Golgi profiles; there were no distinguishing morphological changes in juxtaglomerular peripolar cells. These findings provide morphologic evidence of stimulation of the adrenal zona glomerulosa in association with increased juxtaglomerular renin storage during pregnancy. The mitochondrial changes observed in an increasing proportion of cells in the zona glomerulosa closely resemble those seen in sodium-depleted animals, and may reflect the altered steroidogenic capacity of the adrenal gland in pregnant sheep. The finding of groups of cells displaying altered mitochondria lying next to cells with normal mitochondria suggests the presence of cells with different sensitivities to stimuli for aldosterone production or may indicate the presence of different cell types in the zona glomerulosa responding to different stimuli.
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  • 5
    ISSN: 1432-0878
    Keywords: Adrenal zona glomerulosa ; Ultrastructure ; Sodium depletion ; Sodium loading ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of alterations in sodium status upon the morphology of the adrenal zona glomerulosa in sheep have been examined qualitatively and quantitatively, using lightand electron microscopy, and correlated with functionally related biochemical data. With severe sodium depletion induced by parotid-cannula drainage, there was mitotic activity throughout the zona glomerulosa, and glandular cells showed striking ultrastructural changes. These changes particularly affected mitochondria, which were enlarged, rounded and showed replacement of their normal lamelliform cristae by thin elongated cristal elements and bundles of tubular “rod-like” structures. Quantitative morphometric studies showed an increase in the volumes of zona glomerulosa cells, nuclei, mitochondria, smooth and granular endoplasmic reticulum, and Golgi profiles. In contrast, with dietary sodium loading, zona glomerulosa cells appeared shrunken and showed cytoplasmic lipid accumulation; mitochondria and other organelles were not significantly altered. The correlation of the ultrastructural cytological alterations in zona glomerulosa cells in sodium-depleted sheep with raised blood aldosterone levels suggests that such morphologic changes reflect a heightened capacity of these cells for aldosterone biosynthesis and secretion. These changes may also account for the increased sensitivity of the zona glomerulosa to aldosterone-producing stimuli during sodium deficiency.
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  • 6
    ISSN: 0003-276X
    Keywords: Development ; Immunohistochemistry ; Renin-containing cells ; Sheep ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: Renin-containing (RC) cells in small ruminant kidneys have been known to be widely distributed along the blood vessels. In the present study, RC cells in developing sheep kidneys were studied to investigate not only the appearance but distribution with the potential physiological significance using immunohistochemical and histophanimetrical techniques.Methods: Seven fetal, 12 newborn, and 3 adult metanephric kidneys were used and immunostained by anti-renin antiserum. In the histoplanimetrical analysis, the numerical values of RC cells existing at the walls of 3 major arterial types in the kidneys were calculated.Results: At day 44 of gestation, RC cells were already demonstrated in the walls of renal, interlobar, and afferent vessels, located in the deep cortex and the medulla. In intermediate gestational periods, RC cells were detected throughout the intrarenal arterial trees. In late gestational periods, RC cells expressed in the walls of interlobar/arcuate and interlobular arteries tended to decrease or disappear gradually, while they were distributed predominantly in the afferent glomerular vessels. In newborn lambs, especially days 1 to 3 after birth, increased numbers of RC cells were demonstrated throughout the arterial trees in the kidneys. In older lambs, RC cells located in the interlobar/arcuate arteries and the proximal region of the interlobular arteries decreased in number and gradually disappeared. Some RC cells were still distributed in the distal portion of the interlobular artery even in the adult sheep.Conclusions: These results suggest that the wide distribution of RC cells in sheep kidney is formed in perinatal life, and that the neuronal regulation is associated with the maintenance of this distribution. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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