Ultrastructural changes and a second mode of flagellar degeneration during ageing of Phytophthora palmivora sporangia

1975 ◽  
Vol 19 (3) ◽  
pp. 563-577
Author(s):  
D.E. Hemmes ◽  
H.R. Hohl
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Close Correlation ◽  
Phytophthora Palmivora ◽  
Ultrastructural Changes ◽  
Wall Lining ◽  
Second Mode ◽  
Germ Tubes ◽  
Sporangial Wall

Ageing of sporangia in Phytophthora palmivora is accompanied by a gradual breakdown of flagella, a transformation of the ‘fingerprint’ vacuoles, extensive vacuolization of the cytoplasm, accumulation of bundles of microtubules (mastigonemes)contained within cisternae of the rough endoplasmic reticulum, formation of a germination wall lining the inside of the sporangial wall and production of secondary sporangia. The mechanism of flagellar degeneration differs from that observed in directly germinating sporangia. In ageing sporangia and in sporangia induced to germinate directly with germ tubes, there is a close correlation between loss of competence for zoosporogenesis and breakdown of the flagella.

Ultrastructural changes in posterior midgut cells associated with blood feeding in adult female Rhodnius prolixus Stal (Hemiptera: Reduviidae)

1983 ◽  
Vol 61 (11) ◽  
pp. 2574-2586 ◽  
Author(s):  
P. F. Billingsley ◽  
A. E. R. Downe
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Blood Meal ◽  
Apical Cell ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
Ultrastructural Changes ◽  
Dense Matrix ◽  
Apical Surface ◽  
Posterior Midgut

Modifications of posterior midgut cells of Rhodnius prolixus following a meal of rabbit blood are described. Prominent stacks and whorls of rough endoplasmic reticulum become redistributed following a blood meal but later reform during the postfeeding period. Lysosomes undergo internal structural changes and apparent fluctuations in their number per cell as a result of blood meal ingestion. Before blood feeding, the apical surface of the midgut cells show a typical arrangement of a plasma membrane covered on the lumenal surface by a glycocalyx. After a blood meal, a more complex organisation appears, consisting of two plasma membranes separated by an electron-dense matrix. The lumenal apical membrane proliferates during the digestion period to form loosely organised extracellular membrane layers which may function as a peritrophic membrane. Changes in the rough endoplasmic reticulum and lysosomes and modifications to the apical cell surface appear to coincide with previously described proteinase activity cycles in the posterior midgut of R. prolixus. The implications of these results are discussed and are compared with similar ultrastructural events from haematophagous Diptera.

scholarly journals The disulphide-bonded nature of procollagen and the role of the extension peptides in the assembly of the molecule

1977 ◽  
Vol 161 (2) ◽  
pp. 405-418 ◽  
Author(s):  
R Harwood ◽  
A H Merry ◽  
D E Woolley ◽  
M E Grant ◽  
D S Jackson
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Gel Filtration ◽  
Close Correlation ◽  
Helical Conformation ◽  
Composite Gels ◽  
Tendon Cells ◽  
Cartilage Cells ◽  
And Cartilage

1. The molecular weights of chick tendon and cartilage procollagens, and their constituent polypeptides, were determined by gel filtration and gel electrophoresis. The values obtained are in good agreement and indicate that the mol.wts. of the secreted procollagens (types I and II) and their individual pro-alpha-chains are of the order of 405 000-445 000 and 137 000-145 000 respectively.2. Digestion of tendon procollagen with human rheumatoid synovial collagenase gave products consistent with the presence of large non-helical peptide extensions at both N-and C-termini. Electrophoretic analysis gave apparent mol.wts. of 17 500 and 36 000 for the respective N- and C-terminal extensions of pro-alpha1(I)-and pro-alpha2-chains, and inter-chain disulphide bonds were restricted to the C-terminal location. 3. During the biosynthesis of procollagen by tendon and cartilage cells a close correlation was observed between the extent of inter-chain disulphide bonding and the proportion of procollagen polypeptides having a triple-helical conformation. These processes appeared to commence in the rough endoplasmic reticulum and be completed in the smooth endoplasmic reticulum, but the rate at which they occur in cartilage cells is markedly slower than that found in tendon cells. 4. When the intracellular [14C]procollagen polypeptides present in the rough-endoplasmic-reticulum fractions of tendon and cartilage cells were analysed under non-reducing conditions on agarose/polyacrylamide composite gels, no significant pools of dimeric intermediates were detected. 5. In both cell types, inter-chain disulphide-bond formation occurred even when hydroxylation, and hence triple-helix formation, was inhibited. The presence of pro-alpha1- and pro-alpha2-components in a ratio of 2:1 in the disulphide-linked unhydroxylated procollagen isolated from tendon cells demonstrated that correct chain association occurs in the absence of hydroxylation. This observation is consistent with a model for the assembly of pro-gamma112-chains in which the recognition and selection of pro-alpha1-and pro-alpha2-chains in a 2:1 ratio are directed by the non-helical C-terminal extension peptides of tendon procollagen.

Ultrastructural Changes in Rough Endoplasmic Reticulum of Renal Proximal Tubule Cells in Tetraethyllead Poisoning

1980 ◽  
Vol 38 ◽  
pp. 440-441
Author(s):  
P. R. Wade ◽  
L. W. Chang ◽  
V. L. Wade
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Renal Damage ◽  
Ultrastructural Changes ◽  
Pathogenetic Mechanism ◽  
Proximal Tubule Cells ◽  
Toxic Impact ◽  
Methylmercury Poisoning ◽  
Renal Proximal Tubule Cells ◽  
Ultrastructural Findings

Tetraethyllead (TEL), a gasoline antiknock additive, poses an occupational and environmental risk to human health. Renal damage is a prominent finding in human TEL intoxication. Levels of urinary and erythrocyte ALA-D are altered. Histological examination of the renal parenchyma reveals degenerative changes in the proximal tubules. Experimental TEL studies also demonstrate kidney damage in mice, rats, rabbits, and dogs by various investigators. The basic pathogenetic mechanism of TEL poisoning is unknown. However, in view of the disruption of rough endoplasmic reticulum (RER) and protein synthesis which constitutes the pathogenetic mechanism of methylmercury poisoning, alteration of the RER may also underl ie the toxic impact of organolead in the cells. This report presents unique ultrastructural findings of such an investigation.

Morphologic Changes in Contralateral Superior Vestibulo-Ocular Neurons following Labyrinthectomy in the Cat

1996 ◽  
Vol 105 (10) ◽  
pp. 791-794 ◽  
Author(s):  
Richard R. Gacek ◽  
Joanne Schoonmaker ◽  
Michael Lyon
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Synaptic Vesicles ◽  
Ultrastructural Changes ◽  
Vestibular Ganglion ◽  
Unilateral Labyrinthectomy ◽  
Morphologic Changes

Ultrastructural changes were measured in 22 contralateral superior vestibulo-ocular neurons (SVONs) from four cats painlessly sacrificed at 8 weeks and 25 contralateral SVONs from four cats sacrificed at 1 year following unilateral labyrinthectomy. The SVONs at 8 weeks showed a 43% decrease in somal size, a 34% loss in rough endoplasmic reticulum (RER), a 48% loss of ribosomes, and a 47% decrease in the number of synaptic profiles (SPs) contacting the soma. At 1 year the SVONs had a 31 % decrease in size, a 43% decrease in RER, a 50% loss of ribosomes, and a 71 % decrease in SPs. Synaptic vesicles (SVs) in both groups of SVONs showed no change in size or shape compared to control SVs. These findings resemble the contralateral SVON changes that occur following excision of the vestibular ganglion.

Modifications of pars intermedia cells of ovariectomized rats by oestrogen and progesterone

1986 ◽  
Vol 111 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Adriana Beatriz Ferreira ◽  
Maria Ester Celis
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Secretory Activity ◽  
Ovariectomized Rats ◽  
Ultrastructural Changes ◽  
Synthetic Activity ◽  
Pars Intermedia ◽  
Cytological Features ◽  
Electron Lucent

Abstract. The effects of the ovarian steroids, oestradiol benzoate (EB), and progesterone (P) on the cells of pars intermedia (PI) from chronically ovariectomized rats (CHR-OVX) were analyzed by qualitative and quantitative electron microscopy (EM) at different intervals after steroid injection. The PI cells of CHR-OVX are rich in secretory granules but poor in organelles related to hormonal synthesis. Twenty-four h after EB administration the cells exhibited cytological features indicative of an increased synthetic activity. These included hypertrophy of rough endoplasmic reticulum, cisternae, a moderately developed Golgi complex, and newly formed granules. These features were also observed in PI cells 48 h after EB administration. Thirty-two and 56 h after the treatment, the PI cells showed signs of both increased synthetic and secretory activity. Thus, it was possible to observe a well-developed rough endoplasmic reticulum, and Golgi apparatus, numerous electron-lucent vesicles, and secretory granules in contact with the cell membrane. However, no exocytotic figures were observed. Progesterone administration resulted in considerable modifications of the ultrastructural features of PI cells also indicative of increased synthetic and secretory activity. The greatest modifications were observed in the mornings with changes that were 12 h out of phase with respect to those observed with EB. Quantitative estimations of the variation in the content of secretory granules of PI cells fully confirmed the qualitative observations described above. The serum α-MSH concentrations in ovariectomized rats was found to be incresed 24 h after administration of a single dose of EB and thereafter serum MSH exhibited high levels in the afternoon, whereas the values in the morming were lower. In spayed rats, progesterone injection also resulted in an increase of the serum MSH concentration, but with high levels in the mornings and low levels in the afternoons. In conclusion, EB and P induce modifications in the levels of α-MSH as well as in the ultrastructural changes of the PI cells.

scholarly journals Ultrastructural Changes in the Posterior Gut of Atlantic Herring, Clupea harengus L. Larvae Exposed to Mercury

2005 ◽  
Vol 18 (2) ◽  
Author(s):  
H. A. JASTANIA ◽  
A. R. ABBASI
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Volume Ratio ◽  
Relative Volume ◽  
Clupea Harengus ◽  
Ultrastructural Changes ◽  
Atlantic Herring ◽  
Cellular Changes ◽  
Columnar Cells

Cellular changes attributed to mercury solutions (0.02, 0.05, 0.1 µg·l-1) were observed in columnar cells in the posterior gut of Atlantic herring, Clupea harengus L. larvae. Significant changes occurred in the specimens exposed to 0.05 and 0.1 µg·l-1mercury. These changes were (a) cytoplasm contained vacuoles and few ribosomes (b) increase in the relative volume of the mitochondria (c) reduction in the surface-to-volume ratio of the mitochondria cristae (d) swelling of smooth and rough endoplasmic reticulum (e) decrease in the number of microvilli at the lumen surface. The morphology of the columnar cells from control specimens is discussed.

QUANTIFICATION OF ULTRASTRUCTURAL CHANGES IN THE 'MELANOCYTE-STIMULATING HORMONE CELL' OF THE PARS INTERMEDIA OF THE PITUITARY OF XENOPUS LAEVIS, PRODUCED BY CHANGE OF BACKGROUND COLOUR

1972 ◽  
Vol 53 (2) ◽  
pp. 303-NP ◽  
Author(s):  
B. WEATHERHEAD ◽  
P. WHUR
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Ultrastructural Level ◽  
Ultrastructural Changes ◽  
White Background ◽  
Pars Intermedia ◽  
Black And White ◽  
Melanocyte Stimulating Hormone ◽  
Black Background ◽  
Stimulating Hormone

SUMMARY The fact that the transfer of amphibians between black and white backgrounds causes the 'melanocyte-stimulating hormone (MSH) cells' of the pars intermedia of the pituitary to undergo considerable morphological change has been established for some time. The application of morphometric techniques to the 'MSH cells' of Xenopus has permitted the quantitative analysis of these changes at the ultrastructural level. Of the nine classes of organelle selected for analysis in these cells, three, namely nucleus, plasma membrane and dense bodies, showed no statistically significant changes. The remaining classes of organelle all showed significant changes in the percentage of the total cell volume that they occupied, although not all the organelles changed at the same rate. Transfer of animals from a white to a black background for up to 12 days was associated with increase in the percent volume of rough endoplasmic reticulum, Golgi membranes, Golgi granules and mitochondria and with a decrease in the percent volume of the fibrous granules. Return of animals to a white background after 6 days on a black background produced a reversal of the above changes with return to, or close to, white background (control) levels. This quantitative ultrastructural approach also highlights discrepancies in both the rate and magnitude of the changes in some of the organelles and related non-morphological parameters previously reported, e.g. the size of the rough endoplasmic reticulum and the rate of incorporation of labelled amino acid into protein; or the numbers of fibrous granules and the levels of detectable pituitary MSH. Some possible interpretations of these discrepancies are discussed.

Ultrastructural changes in the rough endoplasmic reticulum and its contents following Brefeldin A treatment of human chondrocytes in vitro

1991 ◽  
Vol 49 ◽  
pp. 256-257
Author(s):  
H. E. Gruber
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Brefeldin A ◽  
Ultrastructural Level ◽  
Human Chondrocytes ◽  
Ultrastructural Changes ◽  
Ultrastructural Studies

The rough endoplasmic reticulum (rER) is now recognized as a major organelle responsible for ensuring that only structurally correct and properly folded proteins are allowed to enter the cellular secretory pathway. We are especially interested in the behavior of the chondrocyte rER since ultrastructural studies of many skeletal dysplasias have revealed that electron dense material accumulates or is not degraded within the rER of chondrocytes from patients. Remodelling of the rER in chick chondrocytes has also been evaluated at the ultrastructural level and the rER found to play a role in procollagen export from the cell. We have utilized normal human chondrocytes grown in culture to investigate the role of brefeldin A, an antiviral antibiotic, which has been shown to primarily block protein transport from the ER to the Golgi complex.

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