scholarly journals Replenishment of LH stores of gonadotrophs in relation to gene expression, synthesis and secretion of LH after the preovulatory phase of the sheep oestrous cycle

2000 ◽  
Vol 167 (3) ◽  
pp. 453-463 ◽  
Author(s):  
JL Crawford ◽  
RJ Currie ◽  
AS McNeilly
Keyword(s):  
Electron Microscopy ◽  
Secretory Granule ◽  
Secretory Granules ◽  
Secretory Activity ◽  
Ultrastructural Level ◽  
Lh Surge ◽  
Pulsatile Secretion ◽  
Molecular Biological Analysis ◽  
Prostaglandin F ◽  
Buserelin Treatment

The pattern of replenishment of LH secretory granule stores in sheep pituitary gonadotrophs, after an induced LH surge, was determined by immunogold localisation at the ultrastructural level by electron microscopy. Twenty-four Welsh Mountain ewes were initially synchronised with progestagen devices for 14 days before luteolysis was induced by a prostaglandin F(2 alpha) analogue, cloprostenol. A further 24 h later, a preovulatory LH surge was induced by intravenous injection of a GnRH agonist, buserelin. Animals were divided into four groups (n=6) and blood sampled at 2 h intervals from 4 h prior, to 18 h after, buserelin administration and then at infrequent intervals (1 to 8 h) thereafter until death. Pulse profiles of LH were also obtained by an additional collection of blood samples within a 6 h window directly preceding death. Groups of animals were killed at 24, 48, 72 or 96 h after buserelin treatment. Pituitaries were dissected and processed for transmission electron microscopy and frozen for later molecular biological analysis. A characteristic preovulatory surge of LH was observed in all animals. The cytoplasm of gonadotrophs, in animals killed 24 h after buserelin treatment, was completely empty of secretory granules. This was associated with diminutive pituitary LH content, low pituitary GnRH binding levels and an almost complete absence (one pulse in one animal) of LH pulsatile secretion. Despite the lack of apparent secretory activity, clusters of exposed LH beta label present within the cytoplasm at this time and constant LHbeta mRNA expression levels irrespective of tissue collection time, suggest that the cell is actively synthesising LHbeta. The formation of sparse numbers of small LH beta immuno-labelled electron-dense secretory granules was apparent at 48 h after buserelin treatment, and replenishment of LH beta immuno-labelled granule stores continued until total granule numbers had increased two-fold (P<0.01) by 96 h post-treatment. Affiliated with granule replenishment was a significant increase in pituitary LH content (P<0.01), pituitary GnRH binding levels (P<0.01) and the restoration of LH pulsatile secretion. Despite the replenishment of granule stores with time, cytoplasmic area did not vary. These results suggest that restoration of pulsatile LH secretion after a preovulatory LH surge is related to replenishment of LH beta secretory granule stores and an increase in GnRH binding levels.

Mobilization of LH secretory granules in gonadotrophs in relation to gene expression, synthesis and secretion of LH during the preovulatory phase of the sheep oestrous cycle

1995 ◽  
Vol 147 (2) ◽  
pp. 259-270 ◽  
Author(s):  
R J W Currie ◽  
A S McNeilly
Keyword(s):  
Electron Microscopy ◽  
Luteal Phase ◽  
Secretory Granules ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Single Type ◽  
Maximum Diameter ◽  
Northern Analysis ◽  
Mrna Levels ◽  
Lh Surge

Abstract Changes in LH secretory granules in pituitary gonadotrophs throughout the sheep oestrous cycle were determined by immunogold localisation of LH at ultrastructural level by electron microscopy. Oestrous cycles in Welsh Mountain ewes were initially synchronised with progestagen sponges and studies carried out in the subsequent cycle. Animals were allocated at random to six groups each of five animals, one killed on day 12 of the luteal phase and the other groups after prostaglandin (PG)-induced luteal regression at PG plus 18 h (early follicular phase), oestrus (PG plus 33·6±1·0 h), oestrus plus 9 h just before the preovulatory LH surge, 1 h after GnRH agonist-induced LH surge at PG plus 48 h (mid-LH surge) and oestrus plus 24 h, after the preovulatory LH surge. Blood samples collected throughout confirmed the pulsatile secretion of LH before and the timing in relation to the preovulatory LH surge. Pituitaries were dissected and processed for transmission electron microscopy and frozen for later extraction of mRNA. Only a single type of LH cell was present in the sheep pituitary. In the luteal phase, LHimmunopositive secretory granules were distributed throughout the cytoplasm in 80% of cells while in 20% of cells granules were polarised to the region of the cell next to a vascular sinusoid. The percentage of polarised cells increased during the follicular phase to 45% at oestrus, 75% at oestrus plus 9 h just before the LH surge and 90% in mid-LH surge. Cell size increased in parallel with polarisation. Gonadotrophs after the LH surge were almost totally devoid of LH granules but prominent LHβ immunoreactivity was observed in the rough endoplasmic reticulum. Analysis of granule diameters revealed a single class of granules with a maximum diameter of 300 nm. Polarised cells had significantly fewer 130–150 nm granules than non-polarised cells, suggesting preferential exocytosis of LH-containing granules of this size from polarised cells. Northern analysis showed that LHβ mRNA levels decreased from luteal through the follicular phase. These results suggest that the preovulatory LH surge in sheep is not related to a change in synthesis of LH but to a progressive recruitment of gonadotrophs into a releasing state, priming, as indicated by polarisation of secretory granules to the region of the cell next to the vascular system. Journal of Endocrinology (1995) 147, 259–270

scholarly journals Alimentary Canal of the Adult Blow Fly,Chrysomya megacephala(F.) (Diptera: Calliphoridae)—Part I: Ultrastructure of Salivary Glands

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Worachote Boonsriwong ◽  
Kabkaew L. Sukontason ◽  
Tarinee Chaiwong ◽  
Urai Chaisri ◽  
Roy C. Vogtsberger ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Salivary Gland ◽  
Salivary Glands ◽  
Basal Lamina ◽  
Secretory Granules ◽  
Gross Anatomy ◽  
Ultrastructural Level ◽  
Blow Fly ◽  
Chrysomya Megacephala ◽  
Sem Image

The salivary gland ultrastructure of the adult male blow fly,Chrysomya megacephala(F.) (Diptera: Calliphoridae), was investigated at the ultrastructural level using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The salivary glands are paired structures composed of a single median deferent duct bifurcated into two long, narrow efferent ducts connected to the coiled tubular glands. The SEM image of the gland surface revealed that the basal lamina is relatively smooth in general, but the whole surface appeared as a trace of rough swollen insertion by intense tracheal ramification. Ultrastructurally, the salivary gland is enclosed within the basal lamina, and interdigitation cytoplasmic extensions were apparent between the adjacent gland cells. The basement membrane appeared infoldings that is similar to the complex of the labyrinth channel. The cytoplasm characteristic of the gland revealed high activity, based on the abundance of noticeable secretory granules, either singly or in an aggregated reservoir. In addition, mitochondria were found to intersperse among rich parallel of arrays rough endoplasmic reticulum. Thick cuticle, which was well-delineated and electron dense, apically lined the gland compartments, with discontinuity of the double-layer cuticle revealing a trace of secretion discharged into the lumen. Gross anatomy of the adult salivary gland was markedly different from that of the third instar of the same species, and structural dissimilarity is discussed briefly.

scholarly journals Electron Microscopic Evidence Suggesting Secretory Granule Formation within the Golgi Apparatus

1957 ◽  
Vol 3 (2) ◽  
pp. 319-322 ◽  
Author(s):  
Marilyn G. Farquhar ◽  
S. Robert Wellings
Keyword(s):  
Golgi Apparatus ◽  
Secretory Granule ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Secretory Activity ◽  
Pancreatic Acinar Cells ◽  
Electron Microscopic ◽  
Granule Formation ◽  
Golgi Bodies ◽  
Rat Pituitary

Secretory granules have been seen within components of the Golgi bodies of rat pituitary acidophils and mouse pancreatic acinar cells. The fact that secretory granules are much more frequently encountered within Golgi components under conditions of increased secretory activity suggests that granule formation may occur within the Golgi apparatus in these two types of cells.

scholarly journals Determination of secretory granule maturation times in pancreatic islet beta-cells by serial block face scanning electron microscopy

2019 ◽  
Author(s):  
A. Rao ◽  
E.L. McBride ◽  
G. Zhang ◽  
H. Xu ◽  
T. Cai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Beta Cell ◽  
Pancreatic Islets ◽  
Beta Cells ◽  
Secretory Granule ◽  
Secretory Granules ◽  
Pancreatic Islets Of Langerhans ◽  
Beta Cell Volume ◽  
Block Face ◽  
Electron Lucent

AbstractIt is shown how serial block-face electron microscopy (SBEM) of insulin-secreting beta cells in wild-type mouse pancreatic islets of Langerhans can be used to determine maturation times of secretory granules. Although SBEM captures the beta cell structure at a snapshot in time, the observed ultrastructure can be considered representative of a dynamic equilibrium state of the cells since the pancreatic islets are maintained in culture in approximate homeostasis. It is found that 7.2±1.2% (±st. dev.) of the beta cell volume is composed of secretory granule dense-cores exhibiting angular shapes surrounded by wide (typically ≳100 nm) electron-lucent halos. These organelles are identified as mature granules that store insulin for regulated release through the plasma membrane, with a release time of 96±12 hours, as previously obtained from pulsed 35S-radiolabeling of cysteine and methionine. Analysis of beta cell 3D volumes reveals a subpopulation of secretory organelles without electron-lucent halos, identified as immature secretory granules. Another subpopulation of secretory granules is found with thin (typically ≲30 nm) electron-lucent halos, which are attributed to immature granules that are transforming from proinsulin to insulin by action of prohormone convertases. From the volume ratio of proinsulin in the immature granules to insulin in the mature granules, we estimate that the newly formed immature granules remain in morphologically-defined immature states for an average time of 135±14 minutes, and the immature transforming granules for an average time of 130±17 minutes.

Ultrastructural Aspects of Golgi Complex Function in Parathyroid Cells of Winter Frogs

1973 ◽  
Vol 31 ◽  
pp. 680-681
Author(s):  
William J. Dougherty
Keyword(s):  
Golgi Complex ◽  
Secretory Granules ◽  
Complex Function ◽  
Secretory Activity ◽  
Secretory Proteins ◽  
Perivascular Spaces ◽  
Pituitary Cells ◽  
Electron Microscopic ◽  
Ca Ions ◽  
Regulation Of Secretion

The regulation of secretion in exocrine and endocrine cells has long been of interest. Electron microscopic and other studies have demonstrated that secretory proteins synthesized on ribosomes are transported by the rough ER to the Golgi complex where they are concentrated into secretory granules. During active secretion, secretory granules fuse with the cell membrane, liberating and discharging their contents into the perivascular spaces. When secretory activity is suppressed in anterior pituitary cells, undischarged secretory granules may be degraded by lysosomes. In the parathyroid gland, evidence indicates that the level of blood Ca ions regulates both the production and release of parathormone. Thus, when serum Ca is low, synthesis and release of parathormone are both stimulated; when serum Ca is elevated, these processes are inhibited.

Permeability of Endometrial Blood Vessels to Exogenous Horse Radish Peroxidase in Mice. Electron Microscope Study

1973 ◽  
Vol 31 ◽  
pp. 562-563
Author(s):  
M.C. Castillo-Jessen ◽  
A. González-Angulo
Keyword(s):  
Electron Microscopy ◽  
Blood Vessels ◽  
Electron Microscope Study ◽  
Ultrastructural Level ◽  
Low Molecular Weight ◽  
Horse Radish Peroxidase ◽  
Intravascular Injection ◽  
Normal Morphology ◽  
Functional Implications ◽  
Low Molecular Weight Proteins

Information regarding the normal morphology of uterine blood vessels at ultrastructural level in mammals is scarce Electron microscopy studies dealing with endometrial vasculature despite the functional implications due to hormone priming are not available. Light microscopy observations with combined injection of dyes and microradiography along with histochemical studies does not enable us to know the detailed fine structure of the possible various types of blood vessels in this tissue. The present work has been designed to characterize the blood vessels of endometrium of mice as well as the behavior of the endothelium to injection of low molecular weight proteins during the normal estrous cycle in this animal. One hundred and forty female albino mice were sacrificed after intravascular injection of horse radish peroxidase (HRP) at 30 seconds, 5, 15, 30 and 60 minutes.

Immunocytochemistry. A Review of Methodology for Electron Microscopic Applicaiton

1974 ◽  
Vol 32 ◽  
pp. 328-329
Author(s):  
Joseph E. Mazurkiewicz
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Ultrastructural Level ◽  
Electron Microscopic ◽  
Biological Interest ◽  
Investigative Approach ◽  
Immunologic Activity ◽  
Dense Label

Immunocytochemistry is a powerful investigative approach in which one of the most exacting examples of specificity, that of the reaction of an antibody with its antigen, isused to localize tissue and cell specific molecules in situ. Following the introduction of fluorescent labeled antibodies in T950, a large number of molecules of biological interest had been studied with light microscopy, especially antigens involved in the pathogenesis of some diseases. However, with advances in electron microscopy, newer methods were needed which could reveal these reactions at the ultrastructural level. An electron dense label that could be coupled to an antibody without the loss of immunologic activity was desired.

Erythrophagocytosis by Entamoeba histolytica.- Ultrastructural Study

1972 ◽  
Vol 30 ◽  
pp. 156-157 ◽  
Author(s):  
Norberto Treviño ◽  
Alfredo Feria-Velasco ◽  
I. Ruiz de Chávez
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Entamoeba Histolytica ◽  
Ultrastructural Study ◽  
Saline Solution ◽  
Physiological Saline ◽  
Ultrastructural Level ◽  
Hot Plate ◽  
Physiological Saline Solution ◽  
Axenic Conditions

Although erythrophagocytosis by various species of Entamoeba is a well known phenomenon this has not yet been studied in detail at the ultrastructural level. The present work deals with the description of the incorporation process of erythrocytes by trophozoites of E. histolytica. For this study, trophozoites of E. histolytica, HK-9:NIH strain cultured in axenic conditions and washed human erythrocytes were placed on a hot plate at 37°C in physiological saline solution. After 5 minutes, 2.5% glutarldehyde was added and the samples were processed according to conventional techniques for electron microscopy.Based upon light microscopy studies on living trophozoites in contact with erythrocytes, it seems that erythrophagocytosis only takes place in one pole of the parasite.

The Ultrastructure of Lymphocytic Hypophysitis

1981 ◽  
Vol 39 ◽  
pp. 466-467
Author(s):  
S.L. Asa ◽  
K. Kovacs ◽  
J. M. Bilbao ◽  
R. G. Josse ◽  
K. Kreines
Keyword(s):  
Electron Microscopy ◽  
Plasma Cells ◽  
Secretory Granules ◽  
Sella Turcica ◽  
Uranyl Acetate ◽  
Lymphocytic Hypophysitis ◽  
Pituitary Cells ◽  
Transmission Electron ◽  
Ultrathin Sections ◽  
Mass Lesions

Seven cases of lymphocytic hypophysitis in women have been reported previously in association with various degrees of hypopituitarism. We report two pregnant patients who presented with mass lesions of the sella turcica, clinically mimicking pituitary adenoma. However, pathologic examination revealed extensive infiltration of the anterior pituitary by lymphocytes and plasma cells with destruction of the gland. To our knowledge, the ultrastructural features of lymphocytic hypophysitis have not been studied so far.For transmission electron microscopy, tissue from surgical specimens was fixed in glutaraldehyde, postfixed in OsO4, dehydrated and embedded in epoxy-resin. Ultrathin sections were stained with uranyl acetate and lead citrate and examined with a Philips 300 electron microscope.Electron microscopy revealed adenohypophysial cells of all types exhibiting varying degrees of injury. In the areas of most dense inflammatory cell infiltration pituitary cells contained large lysosomal bodies fusing with secretory granules (Fig. 1), as well as increased numbers of swollen mitochondria, indicating oncocytic transformation (Fig. 2).

Ultrastructural studies of the relationship between actin filaments and secretory granules

1990 ◽  
Vol 48 (3) ◽  
pp. 458-459
Author(s):  
Ellen Holm Nielsen
Keyword(s):  
Electron Microscopy ◽  
Colloidal Gold ◽  
Actin Filaments ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Granule Membrane ◽  
Ultrathin Sections ◽  
Lowicryl K4m

In secretory cells a dense and complex network of actin filaments is seen in the subplasmalemmal space attached to the cell membrane. During exocytosis this network is undergoing a rearrangement facilitating access of granules to plasma membrane in order that fusion of the membranes can take place. A filamentous network related to secretory granules has been reported, but its structural organization and composition have not been examined, although this network may be important for exocytosis.Samples of peritoneal mast cells were frozen at -70°C and thawed at 4°C in order to rupture the cells in such a gentle way that the granule membrane is still intact. Unruptured and ruptured cells were fixed in 2% paraformaldehyde and 0.075% glutaraldehyde, dehydrated in ethanol. For TEM (transmission electron microscopy) cells were embedded in Lowicryl K4M at -35°C and for SEM (scanning electron microscopy) they were placed on copper blocks, critical point dried and coated. For immunoelectron microscopy ultrathin sections were incubated with monoclonal anti-actin and colloidal gold labelled IgM. Ruptured cells were also placed on cover glasses, prefixed, and incubated with anti-actin and colloidal gold labelled IgM.

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