scholarly journals Rapid activation of the medullary bone osteoclast cell surface by parathyroid hormone.

1978 ◽  
Vol 76 (3) ◽  
pp. 615-618 ◽  
Author(s):  
S C Miller
Keyword(s):  
Electron Microscope ◽  
Parathyroid Hormone ◽  
Calcium Metabolism ◽  
De Novo ◽  
Plasma Calcium ◽  
Medullary Bone ◽  
Transmission Electron ◽  
Egg Shell ◽  
Rapid Activation

Quantitative transmission electron microscope methods were used to determine the response of functionally inactive avian medullary bone osteoclasts to parathyroid hormone (PTH). Egg-lying Japanese quail were used during a period of the egg cycle when medullary bone was not being resorbed for egg shell calcification and when medullary bone osteoclasts were functionally inactive. Ruffled borders adjacent to bone surfaces were rarely, if ever, found on these cells. 20 min after the administration of PTH, over 70% of the osteoclast profiles had ruffled borders adjacent to bone surfaces. These ruffled borders were bounded by filamentous-rich "clear zones" and resembled ruffled borders found on functionally active cells. There was also a marked increase in plasma calcium levels after PTH administration. This study demonstrates that PTH stimulates the de novo generation of ruffled borders on osteoclasts in vivo and suggests that osteoclasts may be involved in the acute regulation of calcium metabolism by exogenous PTH.

scholarly journals Cell-substratum interaction of cultured avian osteoclasts is mediated by specific adhesion structures.

1984 ◽  
Vol 99 (5) ◽  
pp. 1696-1705 ◽  
Author(s):  
P C Marchisio ◽  
D Cirillo ◽  
L Naldini ◽  
M V Primavera ◽  
A Teti ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Intermediate Filaments ◽  
Immunofluorescence Microscopy ◽  
Laying Hens ◽  
Cell Types ◽  
Medullary Bone ◽  
Transformed Cell ◽  
The Core ◽  
Low Calcium Diet

The cell-substratum interaction was studied in cultures of osteoclasts isolated from the medullary bone of laying hens kept on low calcium diet. In fully spread osteoclasts, cell-substratum adhesion mostly occurred within a continuous paramarginal area that corresponded also to the location of a thick network of intermediate filaments of the vimentin type. In this area, regular rows of short protrusions contacting the substratum and often forming a cup-shaped adhesion area were observed in the electron microscope. These short protrusions showed a core of F-actin-containing material presumably organized as a network of microfilaments and surrounded by a rosette-like structure in which vinculin and alpha-actinin were found by immunofluorescence microscopy. Rosettes were superposable to dark circles in interference-reflection microscopy and thus represented circular forms of close cell-substratum contact. The core of ventral protrusions also contained, beside F-actin, fimbrin and alpha-actinin. Villin was absent. This form of cell-substratum contact occurring at the tip of a short ventral protrusion differed from other forms of cell-substratum contact and represented an osteoclast-specific adhesion device that might also be present in in vivo osteoclasts as well as in other normal and transformed cell types.

scholarly journals NEW MEMBRANE FORMATION DURING CYTOKINESIS IN NORMAL AND CYTOCHALASIN B-TREATED EGGS OF XENOPUS LAEVIS

1973 ◽  
Vol 59 (1) ◽  
pp. 89-108 ◽  
Author(s):  
John G. Bluemink ◽  
Siegfried W. de Laat
Keyword(s):  
Electron Microscope ◽  
Cytochalasin B ◽  
De Novo ◽  
Binding Capacity ◽  
Ruthenium Red ◽  
Cytoplasmic Inclusions ◽  
Transmission Electron ◽  
Carbohydrate Complex ◽  
Electrophysiological Measurements ◽  
Surface Marking

A method is described for measuring and calculating the preexisting surface in uncleaved Xenopus eggs and the rate of surface growth in cleaving eggs. Surface-marking experiments with cytochalasin B-treated eggs show that the unpigmented surface grows by de novo formation and not by expansion of preexisting pigmented surface. The onset of new surface formation during first cleavage was studied by using transmission electron microscope and scanning electron microscope techniques. At 3–4 min and at 7–8 min after the onset of cleavage the eggs were fixed in the presence of ruthenium red (RR). Evidence is presented that unpigmented surface representing new membrane comes into appearance between four and eight min. This surface has a selective binding capacity for RR. Concomitantly with the appearance of new membrane, endoplasmic reticulum (ER) cisternae are in continuity with, and dense cytoplasmic inclusions coalesce with, the membrane along the furrow. The latter give rise to liposome-like bodies. The possibility is discussed that the ER cisternae transport a surface exudate (a carbohydrate complex), that the dense cytoplasmic inclusions represent pools of membrane precursor, and that membranogenesis takes place by direct insertion of pooled precursors into the cell surface. In a second paper, these findings will be correlated with electrophysiological measurements.

scholarly journals In Vivo Distribution of Poly(ethylene glycol) Functionalized Iron Oxide Nanoclusters: An Ultrastructural Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2184
Author(s):  
Maria Suciu ◽  
Claudiu Mirescu ◽  
Izabell Crăciunescu ◽  
Sergiu Gabriel Macavei ◽  
Cristian Leoștean ◽  
...  
Keyword(s):  
Iron Oxide ◽  
De Novo ◽  
Superparamagnetic Iron Oxide ◽  
In Vivo Distribution ◽  
Transmission Electron ◽  
Blood And Urine Samples ◽  
Poly Ethylene ◽  
Exposure Evaluation

The in vivo distribution of 50 nm clusters of polyethylene glycol-conjugated superparamagnetic iron oxide nanoparticles (SPIONs-PEG) was conducted in this study. SPIONs-PEG were synthesized de novo, and their structure and paramagnetic behaviors were analyzed by specific methods (TEM, DLS, XRD, VSM). Wistar rats were treated with 10 mg Fe/kg body weight SPIONs-PEG and their organs and blood were examined at two intervals for short-term (15, 30, 60, 180 min) and long-term (6, 12, 24 h) exposure evaluation. Most exposed organs were investigated through light and transmission electron microscopy, and blood and urine samples were examined through fluorescence spectrophotometry. SPIONs-PEG clusters entered the bloodstream after intraperitoneal and intravenous administrations and ended up in the urine, with the highest clearance at 12 h. The skin and spleen were within normal histological parameters, while the liver, kidney, brain, and lungs showed signs of transient local anoxia or other transient pathological affections. This study shows that once internalized, the synthesized SPIONs-PEG disperse well through the bloodstream with minor to nil induced tissue damage, are biocompatible, have good clearance, and are suited for biomedical applications.

Effects of parathyroid hormone and the synthetic 1–34 amino-terminal fragment in rats and dogs

1983 ◽  
Vol 97 (1) ◽  
pp. 21-30
Author(s):  
R. W. Stevenson ◽  
J. A. Parsons
Keyword(s):  
Parathyroid Hormone ◽  
Infusion Rate ◽  
Calcium Absorption ◽  
Biological Activities ◽  
Direct Action ◽  
Plasma Calcium ◽  
Biologically Active ◽  
Amino Terminal ◽  
Active Fragments

Since the structural requirements for all known biological activities of parathyroid hormone (PTH(1–84)) are virtually satisfied by the amino-terminal 34 amino acid fragment, PTH(1–34), we investigated whether this fragment could elaborate the overall actions of the intact hormone in the whole animal by comparing the effects of equimolar infusions of each peptide to dogs and rats. Infusion of bovine PTH(1–84) (bPTH(1–84)) at 17 pmol/kg per h for 20 h to three dogs or at 100 and 200 pmol/kg per h to groups of six rats for 5 days produced greater hypercalcaemia (3·02±0·03, 2·52±0·07 and 3·24±0·11 mmol/l respectively) than equimolar infusions of human PTH(1–34) (hPTH(1–34)) (2·61±0·03, 2·46 ± 0·05 and 2·71 ±0·09 mmol/l respectively). A significant calcium rise was not observed in dogs until after 4 h of PTH infusion. No rise in plasma calcium was apparent in rats, however, until the third day of PTH infusion. Only in parathyroidectomized rats was there a rise in plasma calcium within 24 h of starting an infusion of PTH. The hypercalciuria and plasma phosphate responses in dogs during equimolar infusions of hPTH(1–34) and bPTH(1–84) were not significantly different. However, by day 5 of infusion in rats greater hypercalciuria was produced by bPTH(1–84). Although infusion of hPTH(1–34) and bPTH(1–84) caused rises in urinary cyclic AMP excretion (measured only in the dog) of immediate onset and equal magnitude, bPTH(1–84) tended to produce greater phosphaturia than hPTH(1–34) in both species. If the assumption is correct that the half-lives of hPTH(1–34) and bPTH(1–84) in the circulation are similar and provided that hPTH does not inherently have less biological activity than bPTH, then during equimolar infusions of these peptides into dogs and rats, the greater responses observed with bPTH(1–84) suggest that intact PTH may have a direct action of its own in vivo before being metabolized into smaller biologically active fragments. In additional experiments using parathyroidectomized rats, the infusion rate of bPTH(1–84) required to restore normocalcaemia was 26 pmol/kg per h. Although near-normal calcaemia and intestinal calcium absorption could still be maintained when the infusion rate was increased to 39 pmol/kg per h, hypercalciuria and phosphaturia became apparent.

Normal plasma calcium, phosphate, and parathyroid hormone levels during 1,25(OH)2D3 infusions in rats

1992 ◽  
Vol 262 (1) ◽  
pp. E126-E129 ◽  
Author(s):  
J. Fox ◽  
U. Kollenkirchen
Keyword(s):  
Vitamin D ◽  
Parathyroid Hormone ◽  
Calcium Phosphate ◽  
Cell Function ◽  
Plasma Calcium ◽  
Dihydroxyvitamin D3 ◽  
Subcutaneous Infusion ◽  
Cellular Effects ◽  
Precise Role

The changes in plasma calcium, phosphate, and parathyroid hormone (PTH) levels that accompany 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] administration to experimental animals represent major obstacles to determining the precise role that 1,25(OH)2D3 plays in cell function in vivo. These difficulties arise because calcium, phosphate, and PTH have major cellular effects independent of 1,25(OH)2D3. To circumvent this obstacle, we have developed an animal model in which plasma 1,25(OH)2D3 levels were raised from 20 +/- 3 to 96 +/- 19, 240 +/- 49, and 459 +/- 66 pg/ml in vitamin D-deficient rats without influencing plasma ionized calcium, total calcium, phosphate, or NH2-terminal immunoreactive PTH (irPTH) levels. The elevated 1,25(OH)2D3 levels were achieved by constant subcutaneous infusion of 1,25(OH)2D3 using osmotic minipumps. Progressive reduction in the calcium and phosphorus content of the diet as the 1,25(OH)2D3 infusion rate was increased prevented concomitant changes in plasma calcium, phosphate, and irPTH levels. This experimental model, in conjunction with our previously developed normocalcemic rat model of vitamin D deficiency, provides a powerful experimental tool for the investigation of 1,25(OH)2D3 effects in vivo in the absence of concomitant changes in other parameters of calcium homeostasis.

A DECREASED RESPONSE TO PARATHYROID HORMONE IN MAGNESIUM DEFICIENCY

1971 ◽  
Vol 49 (2) ◽  
pp. 253-258 ◽  
Author(s):  
J. MacMANUS ◽  
F. W. HEATON ◽  
P. W. LUCAS
Keyword(s):  
Parathyroid Hormone ◽  
Incubation Medium ◽  
Inorganic Phosphate ◽  
Magnesium Deficiency ◽  
Plasma Calcium ◽  
Target Organs ◽  
Calcium And Magnesium

SUMMARY The effect of magnesium deficiency on the response to parathyroid hormone has been investigated in vitro and in vivo. Parathyroid hormone increased the release of calcium, inorganic phosphate and hydroxyproline from rat femora into the incubation medium, but had a lesser effect on bones from magnesium-deficient animals than on femora from control rats. Similarly, injection of the hormone into thyro-parathyroidectomized rats produced smaller rises in plasma calcium and magnesium concentrations in magnesium-deficient rats than in control animals. It is concluded that magnesium deficiency inhibits the action of parathyroid hormone on its target organs.

scholarly journals Use of RNA Arbitrarily Primed-PCR Fingerprinting To Identify Vibrio cholerae Genes Differentially Expressed in the Host following Infection

2000 ◽  
Vol 68 (7) ◽  
pp. 3878-3887 ◽  
Author(s):  
Amit Chakrabortty ◽  
Soumita Das ◽  
Sabita Majumdar ◽  
Kanchan Mukhopadhyay ◽  
Susanta Roychoudhury ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Vibrio Cholerae ◽  
Transmission Electron Microscope ◽  
Differentially Expressed ◽  
Loop Model ◽  
Pcr Fingerprinting ◽  
Transmission Electron ◽  
Ultrathin Sections

ABSTRACT Evidence suggests that a repertoire of Vibrio cholerae genes are differentially expressed in vivo, and regulation of virulence factors in vivo may follow a different pathway. Our work was aimed at characterization of in vivo-grown bacteria and identification of genes that are differentially expressed following infection by RNA arbitrarily primed (RAP)-PCR fingerprinting. The ligated rabbit ileal loop model was used. The motility of in vivo-grown bacteria increased by 350% over that of in vitro-grown bacteria. Also, the in vivo-grown cells were more resistant to killing by human serum. By using the RAP-PCR strategy, five differentially expressed transcripts were identified. Two in vitro-induced transcripts encoded polypeptides for the leucine tRNA synthatase and the 50S ribosomal protein, and the three in vivo-induced transcripts encoded the SucA and MurE proteins and a polypeptide of unknown function. MurE is a protein involved in the peptidoglycan biosynthetic pathway. The lytic profiles of in vivo- and in vitro-grown cells suspended in distilled water were compared; the former was found to be slightly less sensitive to lysis. Ultrathin sections of both cells observed under the transmission electron microscope revealed that in contrast to the usual wavy discontinuous membrane structure of the in vitro-grown cells, in vivo-grown cells had a more rigid, clearly visible double-layered structure. The V. cholerae murE gene was cloned and sequenced. The sequence contained an open reading frame of 1,488 nucleotides with its own ribosome-binding site. A plasmid containing the murE gene of V. cholerae was transformed into V. cholerae 569B, and a transformed strain, 569BME, containing the plasmid was obtained. Ultrathin sections of 569BME viewed under a transmission electron microscope revealed a slightly more rigid cell wall than that of wild-type 569B. When V. cholerae 569B and 569BME cells were injected separately into ligated rabbit ileal loops, the transformed cells had a preference for growth in the ileal loops versus laboratory conditions.

Conversion of Octacalcium Phosphate into Hydroxyapatite and Bone Regeneration

2007 ◽  
Vol 361-363 ◽  
pp. 993-996 ◽  
Author(s):  
Osamu Suzuki ◽  
Shinji Kamakura ◽  
Takahisa Anada
Keyword(s):  
Bone Regeneration ◽  
De Novo ◽  
Acrylic Resin ◽  
Ultrastructural Level ◽  
Octacalcium Phosphate ◽  
Nano Particles ◽  
Apatite Formation ◽  
Calvarial Bone ◽  
Transmission Electron

The present study was designed to investigate the mechanism of in vivo conversion from synthetic octacalcium phosphate (OCP) into hydroxyapatite (HA) at ultrastructural level, where the implanted OCP is enhancing bone regeneration in mouse calvarial bone defect. OCP granules were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for 3 weeks. Transmission electron microscopy of undecalcified frontal sections, obtained from the acrylic resin-embedded skull specimens showed that the bone crystals in newly formed bone directly bonded to the OCP particles implanted. The morphological characteristic of original plate-like OCP particles was remained unchanged even after the implantation, whereas a number of de novo nano-particles were also directly formed onto the plate-like OCP particles. Some of OCP particles were linked with other OCP particles through these nano-particles. The results suggest that the OCP-apatite conversion, involving the enhanced bone regeneration, advances via topotaxial conversion without changing the original OCP morphology, accompanied by solution-mediated de novo nano-apatite formation, in the vicinity of the implanted OCP particles.

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