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  • 1
    Electronic Resource
    Electronic Resource
    A morphometric study of the variations in subcellular structures of rat hepatocytes during 24 hours (1984)
    Springer
    Cell & tissue research 236 (1984), S. 305-315 
    Details
    ISSN: 1432-0878
    Keywords: Hepatocytes ; Rat ; Liver ; Circadian rhythm ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Subcellular structures of hepatocytes in periportal and perivenous zones were examined during 24 h. The volume, surface and numerical profile densities of cytoplasmic organelles were analysed morphometrically. Most subcellular structures in periportal and perivenous hepatocytes were subject to strong circadian variations. In hepatocytes from both zones, the volume densities of smooth endoplasmic reticulum (sER), mitochondria, lysosomes, peroxisomes, polysomes and lipid droplets demonstrated peak values at 16.00 h, 20.00 h or 00.00 h; trough values were at 04.00 h, 08.00 h, or 12.00 h, except for peroxisomes (16.00 h). However, the volume densities of glycogen granules and rough endoplasmic reticulum (rER) in periportal and perivenous hepatocytes exhibited maximal values at 04.00 h, 08.00 h or 12.00 h and minimal values at 20.00 h. The surface densities of sER, mitochondria, lysosomes and peroxisomes, and the numerical profile densities of mitochondria, lysosomes and peroxisomes in periportal and perivenous hepatocytes showed similar trends. These events suggest that membranes of the rER show a partial correlation with the sER, mitochondrial and lysosomal membranes during the 24-h span. This may involve the interaction between ribosomes and rER. Almost all cytoplasmic organelles examined displayed significant differences between periportal and perivenous hepatocytes, morphometrically and in fine structure, indicating that the morphofunctional variability of hepatocytes differs depending on the location in the liver acinus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214231
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  • 2
    Electronic Resource
    Electronic Resource
    A morphometric study of developing pancreatic acinar cells of rats during prenatal life (1984)
    Springer
    Cell & tissue research 237 (1984), S. 117-122 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas, exocrine (rat) ; Fine structure ; Membrane dynamics ; Development (ontogenetic) ; Morphometry ; Zymogen granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pancreatic acinar cells of rat embryos obtained at 15, 17, 19 and 21 days of gestation have been examined using fine-structural and morphometric techniques. Morphometric analysis demonstrates significant variations in the average volume of the cell, nucleus and cytoplasm, and the volume, surface and numerical densities of various cytoplasmic organelles during fetal life. In particular, the volume and surface densities of rER exhibit maximal values at 19 days of gestation, suggesting that secretory proteins are produced most actively at this time. Further-more, membrane continuity between the nuclear envelope and rER is frequently discernible in acinar cells, indicating that at this stage the rER is mainly derived from the nuclear envelope. Zymogen granules first appear at 17 days of gesstation. By 21 days, they occupy the greater part of the cytoplasm of the acinar cells, no polarity being seen in their distribution pattern. No direct evidence for the secretion of zymogen granules has been observed during fetal life. It therefore appears that membrane transport involved with intracellular movement of newly synthesized proteins from rER via the Golgi complex to zymogen granules occurs in one direction and lacks regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229206
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  • 3
    Electronic Resource
    Electronic Resource
    A morphometric study of the 24-hour variations in subcellular structures of rat pancreatic acinar cells during the periweaning period (1984)
    Springer
    Cell & tissue research 237 (1984), S. 131-138 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas, exocrine (rat) ; Circadian rhythm ; Morphometry ; Periweaning period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pancreatic acinar cells of rats obtained before (21 days of age) and after (31 and 42 days) weaning were morphometrically examined at six evenly spaced times during 24 h. Morphometric analysis demonstrated clear-cut variations in the average volume of the cell and nucleus, the incidence of binucleate acinar cells, and the volume and numerical densities of various cytoplasmic organelles during 24 h, at each stage. The daily mean values and variation of these parameters at 21 days clearly differed from those at 31 and 42 days. In particular, changes in the volume densities of rER and zymogen granules were bimodal at 21 days, whereas they were unimodal at 31 and 42 days. Moreoever, some parameters also differed between 31 and 42 days, the main difference being an 8 h time shift in the variation curves of the volume densities of rER and zymogen granules. These findings indicate that morphometric analysis of the subcellular structures of pancreatic acinar cells during 24 h can be used to determine their developmental stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229208
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  • 4
    Electronic Resource
    Electronic Resource
    Morphometric and fine-structural studies of rat pancreatic acinar cells during early postnatal life (1984)
    Springer
    Cell & tissue research 237 (1984), S. 123-129 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas, exocrine (rat) ; Ultrastructure ; Morphometry ; Development, ontogenetic ; Zymogen granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pancreatic acinar cells of rats obtained at 1,2, 3, 5, 7 and 14 days of age were examined using fine structural and morphometric techniques. From 5 days of age onwards, the acinar cells were analysed twice per day, at 20.00 h and 08.00 h. The present study demonstrates changes in the average volume of the cell, nucleus and cytoplasm, and volume densities of various cytoplasmic organelles during the first two weeks after birth. During early postnatal life, the volume density of rER increases, whereas that of zymogen granules decreases. From 5 days of age onwards, the volume densities of these two organelles differ significantly at 20.00 h and 08.00 h. During the first 2–3 days after birth, inclusion body-like structures appear in the cytoplasm of acinar cells; they contain aggregated zymogen granules and, sometimes, amorphous structures or cytoplasmic organelles. These structures also occur in interstitial cells and cells located in the intercalated region between acinar and ductal epithelial cells. Serum level of α-amylase activity is high at birth, compared with other stages during the first three weeks. Degenerating acinar cells and cell debris can be seen in the acinar and ductal lumina during these stages, a feature suggesting holocrine secretion. Cellular polarity appears to be incomplete during the first two or three days after birth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229207
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  • 5
    Electronic Resource
    Electronic Resource
    A histochemical study of variations in the localization of 5′-nucleotidase activity in the acinar cell of the rat exocrine pancreas over the twenty-four hour period (1983)
    Springer
    Cell & tissue research 230 (1983), S. 411-420 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas (rat) ; Acinar cells ; 5′-Nucleotidase ; Circadian variation ; Cytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The circadian variation of 5′-nucleotidase (AMPase) activity was studied in rat pancreatic exocrine cells. The localization of this enzyme, often associated with the plasmalemma, was studied by ultracytochemical methods at six time points over the 24-h period. The localization of AMPase activity exhibited a clear-cut circadian variation. During the light span strong activity was observed on the luminal plasmalemma, negative or weak activity on the baso-lateral plasmalemma and clearly visible activity on intracellular structures such as cytoplasmic vacuoles (fragmentation-like vesicles), dilated rims of the Golgi cisternae (or cisternal ends of the Golgi stacks), condensing vacuoles and lysosomal bodies. During the dark span the activity was detectable only on the baso-lateral plasmalemma. The fact that AMPase activity could not be found on the luminal plasmalemma during the dark span suggests that the luminal membranes may be replaced by the membranes of secretory granules, which do not display AMPase activity. The intracellular localization of AMPase activity during the light span, especially at 08.00 h, includes all cytoplasmic compartments which have hitherto been associated with the intracellular pathway for membrane retrieval from the plasmalemma. Moreover, the appearance of the activity in the dilated rims of the Golgi stack and condensing vacuoles indicates that these compartments may constitute a functional unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213814
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  • 6
    Electronic Resource
    Electronic Resource
    A morphometric study of 24-hour variations in subcellular structures of the rat pancreatic acinar cell (1982)
    Springer
    Cell & tissue research 226 (1982), S. 609-620 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas (rat) ; Circadian variations ; Acinar cells ; Zymogen granules ; Stereology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Subcellular structures of pancreatic acinar cells were examined at six evenly spaced time points in the 24-h period (light cycle: 06.00 h–18.00 h) in four Wistar male rats at each time point. At each sampling point, the area and circumference of acinar cell bodies and the area, number and circumference of their cytoplasmic organelles were measured using a semiautomatic computer system for morphometry and a point-counting method. The area, number and circumference-area ratio of the cytoplasmic organelles were subject to strong circadian variations, and the cellular area and circumference exhibited weak circadian variations. Variation pattern of the cytoplasmic organelles suggested an intracellular route for secretory proteins during a 24-h span. From the results it was possible to divide the 24-h period into three stages. 1. The resting or protein synthetic stage (00.00 h to 08.00h): the area of the rough surfaced endoplasmic reticulum (rER) was strongly increased, and that of zymogen granules was clearly decreased. 2. The granule accumulation stage (08.00h to 16.00h): the area of the rER was markedly decreased; that of zymogen granules was increased. 3. The secretion stage (16.00 h to 00.00): as a result of the release of zymogen granules from the acinar cell, the area of zymogen granules decreased, and that of the rER increased. The relationship between the area of the rER and zymogen granules varied in a reciprocal manner. Other cytoplasmic organelles, namely the Golgi complex, condensing vacuoles, mitochondria and lysosomes also varied prominently during the 24-h span, corresponding to variations in the rER and zymogen granules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214788
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  • 7
    Electronic Resource
    Electronic Resource
    Circadian alterations in tubular structures on the outer mitochondrial membrane of rat hepatocytes (1981)
    Springer
    Cell & tissue research 214 (1981), S. 519-527 
    Details
    ISSN: 1432-0878
    Keywords: Mitochondria ; Tubular structures ; Hepatocytes ; Circadian changes ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Subcellular structures of hepatocytes were examined at 11.00 h and 23.00h (light cycle: 06.00h–18.00h) in four adult male Wistar rats (AF/Han) per time period. 1. The volume density of mitochondria in the cytoplasm of hepatocytes obtained from peripheral parts of liver lobules shows a statistically significant difference between the two time periods examined. 2. Tubular structures arising from the outer mitochondrial membrane are clearly demonstrated. Their cisternae are continuous with the interspaces between outer and inner mitochondrial membranes. 3. These tubular structures often open directly into the cisternae of rough or smooth-surfaced endoplasmic reticulum (rER and sER) and form a “bridge” between the endoplasmic reticulum and mitochondria. 4. At 11.00 h, the rER connected with the tubular structures often possesses very few ribosomes; at 23.00 h, the amount of ribosomes on the rER is substantially greater. Furthermore, at 23.00h ribosomes are also occasionally found on the membranes of the tubular structures. 5. The incidence of tubular structures on the outer membrane of mitochondria varies significantly between the two time periods. 6. The changing pattern of the volume density of mitochondria in the cytoplasm parallels that of the incidence of the tubular structures, i.e., both are high during the active phase and low during the resting phase of the rat. 7. These results suggest that the tubular structures may play an important role in protein transport between the endoplasmic reticulum and mitochondria, and in the rearrangement of rER during a 24-h period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233492
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