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Biomedical subjects

C V Gay

Publications and source records attributed to C V Gay.

At least 73 records · Page 4Linked to original sources
PubMed1987

Role of epiphyseal cartilage in endochondral bone formation.

The avian epiphyseal growth plate plays an important role in skeletal development. Compared with the mammalian species, the avian growth plate contains more cells, is less well organized and appears more susceptible to malformation. Abnormal cartilage development is associated with chondrodystrophy, tibial dyschondroplasia and rickets. Many nutrient deficiencies result in chondrodystrophy, which is characterized by shortened, thickened bones and a narrowing of the epiphyseal growth plate. Manganese, the most extensively studied of these deficiencies, is necessary for proteoglycan biosynthesis. Tibial dyschondroplasia is a condition in which the prehypertrophic cells fail to hypertrophy and vascularization is aborted. This abnormality is found in genetically predisposed animals and its occurrence is altered by subtle changes in calcium, phosphorus and electrolyte content of the diet. Calcium and vitamin D deficiencies cause rickets, which is characterized by an increase in the width of the prehypertrophic zone of the epiphyseal growth plate. Most of the biochemical and histological changes can be related to the need for calcium for chondrocyte hypertrophy and maturation, although there is some evidence that chondrocytes require specific vitamin D metabolites. Phosphorus deficiency increases the zones of hypertrophy and metaphyseal primary spongiosa.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Ultracytochemical evidence for a proton-pump adenosine triphosphatase in chick osteoclasts.

The distribution of Mg++-ATPase in osteoclasts along the endosteal surface of the chick tibia was investigated by neutral and alkaline pH cytochemical methods at the electron-microscopic level. Reaction product was observed in mitochondria, cytoplasmic vesicles, and ruffled-border membrane. Levamisole, ouabain, and vanadate did not affect the enzymatic activity. Para-chloromercuribenzoic acid (PCMB) prevented staining of mitochondria, ruffled border, and most cytoplasmic vesicles. Tri-n-butyltin decreased the amount of reaction product in cytoplasmic vesicles and ruffled-border membrane, but did not inhibit reaction product formation within mitochondria. Duramycin, which is a potent inhibitor for proton-pump ATPase, blocked reaction-product formation along the ruffled-border membrane, in mitochondria, and in cytoplasmic vesicles at alkaline pH, but not at neutral pH. It is concluded that the alkaline pH method for Mg++-ATPase appears to demonstrate sites of proton-pump ATPase activity.

Animals↗
PubMed1985

Effects of parathyroid hormone and calcitonin on carbonic anhydrase location in osteoclasts of cultured embryonic chick bone.

The ultrastructural location of carbonic anhydrase has been examined in osteoclasts of cultured embryonic chick metatarsi. In untreated cultures and in those to which parathyroid hormone (PTH) was added, the enzyme was found in close association with the plasma membrane of the ruffled border. After brief calcitonin treatment (10 min) the ruffled border disappeared and the association of carbonic anhydrase with the plasma membrane was diminished. The results indicate that the hormones employed act directly on embryonic bone to alter osteoclast structure and the intracellular location of carbonic anhydrase.

Animals↗
PubMed1985

The effects of calcitonin, parathyroid hormone and prostaglandin E2 on cyclic AMP levels of isolated osteoclasts.

Cyclic AMP (cAMP) levels were measured in both isolated and attached osteoclasts. The level of cAMP was 0.1 pmol/10(5) osteoclasts. No change in cAMP level of osteoclasts could be detected following calcitonin treatment. Parathyroid hormone (PTH) and prostaglandin E2 (PGE2) treatment stimulated cAMP production in proportion to alkaline phosphatase levels and divergent to acid phosphatase levels. This indicates that osteoblasts, not osteoclasts, were responsive to PTH and PGE2.

Acid Phosphatase↗
PubMed1985

Vertical distribution of elements in cells and matrix of epiphyseal growth plate cartilage determined by quantitative electron probe analysis.

Quantitative electron probe analysis was performed on chick epiphyseal growth cartilage prepared by two anhydrous methods, ultrathin cryosections and freeze-dried epoxy-embedded tissue. Levels of Na, Mg, P, S, Cl, K, and Ca were determined in cytoplasm, mitochondria, extracellular matrix, matrix vesicles, and mineral nodules in four zones of the cartilage--proliferative, prehypertrophic, early hypertrophic, and early calcification. The exceptionally high levels of Na and K (up to 550 and 200 mmol/kg wet wt, respectively) found in the matrix are believed to be largely bound to fixed anions. Within cells, Na was higher than K (140 versus 20-34 mmol/kg wet wt), a condition that may reflect hypoxia. Ca and P were low in cells and unmineralized matrix. Ca and P were high in mitochondrial granules of the early hypertrophic zone and diminished in amount in the calcifying zone; the converse occurred in matrix vesicles. Mg was low to undetectable except in heavily mineralized structures (i.e., mitochondrial granules, matrix vesicles, and mineral nodules). S levels were high in matrix (approximately 400 mmol/kg wet wt) and increased slightly with maturation. The amount of S present greatly exceeds Ca levels and implies that sulfate, the predominant form of sulfur in proteoglycans, may serve as an ion-exchange mechanism for the passage of Ca through the matrix to sites where Ca and phosphate are precipitated.

Animals↗
PubMed1985

Ultrastructural localization of calcium-activated adenosine triphosphatase (Ca2+-ATPase) in growth-plate cartilage.

The electron-microscopic cytochemical localization of calcium-activated adenosine triphosphatase (Ca2+-ATPase) was determined in chick epiphyseal growth-plate cartilage. In the reserve zone, mitochondria and lysosomes contained substantial amounts of reaction product, while the plasma membrane and the Golgi complex showed very weak enzymatic activity, and matrix vesicle membranes did not exhibit the cytochemical reaction. As maturation proceeded, the plasma membrane, Golgi complex, and matrix vesicle membranes also stained and were most intense in the proliferative and early hypertrophic zones. From the hypertrophic to the calcifying zone, cytochemical staining decreased progressively in the plasma membrane, the Golgi complex, and lysosomes, while in some cases mitochondrial reaction product remained intense. Matrix vesicles lost their enzymatic activity at the same time that matrix vesicle calcification commenced. It is proposed that this event allows matrix vesicles to calcify, since efflux of calcium would no longer occur.

Adenosine Triphosphate↗
PubMed1985

Avian tibial dyschondroplasia. I. Ultrastructure.

Tibial dyschondroplasia is an abnormality of the growth cartilage that occurs in chickens and other rapidly growing animals. The disease is characterized by a mass of avascular opaque cartilage, which is continuous with the growth plate of the proximal tibia and extends into the metaphysis. In this study electron micrographs revealed that chondrocytes in the hypertrophic zone of the growth plate were normal in appearance with the exception that the cells did not undergo complete hypertrophy. In the proximal region of the lesion, cells began to undergo necrotic changes suggestive of an energy depletion. These changes included dilatation and vesiculation of the endoplasmic reticulum, enlargement of the paranuclear space, mitochondrial swelling with dilatation of the intracristal spaces and the appearance of electron-dense, flocculent material in the mitochondrial matrix, chromatin margination, and dilatation of the Golgi saccules. Chondrocytes also occurred with rarefied cytoplasm and atrophic Golgi saccules. A few cartilage cells in the proximal region of smaller lesions contained crescentic caps of condensed chromatin in the nuclei, which is indicative of apoptosis. These cells also exhibited dilated endoplasmic reticulum and lamellar bodies; and sometimes, in the proximal region of the lesion, they appeared to be condensed and convoluted. This process continued in the mid and distal regions. The condensed necrotic cells appeared as amorphous osmiophilic masses with karyorrhexic and pyknotic nuclei. Matrix vesicles were observed at all levels of the lesion, but calcified only at the distal edge of the lesion, where mineralization of both matrix and cells occurred. The resulting shell of mineral may act as a diffusion barrier.

Animals↗
PubMed1985

Avian tibial dyschondroplasia. II. Biochemical changes.

Biochemical parameters (dry matter, DNA, protein, cAMP, and calmodulin) were measured in tibial dyschondroplastic (TD) cartilage. This abnormal cartilage, which is a mass of unmineralized, unvascularized cartilage found in the proximal metaphysis of the tibiotarsus and tarsometatarsus, was compared with normal epiphyseal growth plate and hypertrophic cartilage obtained from day-old embryonic cone. The latter tissue is an example of cartilage which rapidly undergoes vascularization and mineralization. When compared with normal growth plate, tibial dyschondroplastic cartilage was found to contain lower amounts of dry matter, DNA, protein, cAMP, and calmodulin. This cartilage did not respond to factors in serum which stimulate 35S uptake. Although the above two types of cartilage contained similar amounts of ash, TD cartilage had less phosphorus and potassium and more sodium than the growth plate. The two types of cartilage had similar lysozyme activity and proteoglycan (hexosamine) content. In many of the parameters measured, day-old hypertrophic cartilage was similar to the normal growth plate. However, these tissues did differ in DNA, protein, ash, and lysozyme content. Substantially greater amounts of ash and lysozyme were found in the hypertrophic cartilage, which appeared to be related to events of mineralization and vascularization of this cartilage. These events did not occur in the abnormal cartilage cells found in the tibial dyschondroplastic lesion.

Animals↗
PubMed1985

Avian tibial dyschondroplasia. III. Electron probe analysis.

Tibial dyschondroplastic (TD) lesions and their associated growth plates, obtained from chickens, were prepared by freeze-drying and embedding in an anhydrous epoxy resin. Quantitative electron probe analysis was performed on dry, unstained sections. Levels of Na, Mg, P, S, Cl, K, and Ca were determined in cytoplasm (endoplasmic reticulum), mitochondria, and extracellular matrix of the proliferative, prehypertrophic, and early hypertrophic zones of the growth plate and in the proximal, mid, and distal regions of the lesion. A zone of calcification in the growth plate was absent. The concentration of elements in all regions of the TD growth plate was the same as found in an earlier study for normal growth plate. The cytoplasm of proximal lesion chondrocytes was similar to that of early hypertrophic chondrocytes. However, in the remainder of the lesion there was a progressive increase in cellular Na, S, Cl, and Ca and a progressive loss of P. In matrix, there was less S and K than expected in all regions of growth plate and lesion, except in the proliferating zone. Also, in matrix of the distal lesion there was less Na and Cl. The levels of Na, S, Cl, and K in matrix may have been lowered by their adsorption into the condensed masses of dead cells. Mitochondria acquire only half as much Ca and P as normal and release it earlier than usual (ie, early prehypertrophic cells, rather than chondrocytes of the lower hypertrophic zone). There were no granules in mitochondria of the cells at all levels of the lesion, even though anhydrous methods were used. The first sign of the disease appears in the matrix of the growth plate, where it seems that S and K are in abnormally low amounts. Although there are sufficient levels of Ca and P present, the matrix does not calcify. The cartilage remains avascular, and the cells appear to be dying. The event that triggers the chondrocytes of the growth plate to form an abnormal uncalcified matrix is not known.

Animals↗
PubMed1983

Lipoidal membranes stabilize isolated salmon and chicken carbonic anhydrase under conditions of increased temperature and pH.

1. Solutions of purified carbonic anhydrase from chicken and salmon erythrocytes were incubated in buffer for 1 hr at 5 degrees or 22 degrees C, at pH 7.3, 7.6, 7.9 or 8.2. 2. At 22 degrees C the enzymes lost up to 25% of their ability to catalyze the CO2 hydration reaction when compared to control solutions maintained in the cold. 3. Loss of enzyme activity (approximately 50%) also occurred as pH was increased from 7.3 to 8.2. 4. The presence of lecithin vesicles or microsomes completely protected the enzymes from denaturation caused by pH changes and afforded partial protection from changes due to increased temperature.

Animals↗
PubMed1983

Purification and properties of carbonic anhydrase from salmon erythrocytes.

Carbonic anhydrase (CA) from erythrocytes of the pink salmon, Onchorhyncus gorbushka, was purified using chloroform-ethanol extraction and Sephadex G-75 gel filtration. A single, high specific-activity CA isozyme having a molecular weight of 29,000 was found. The enzyme sedimented as a single boundary at a sedimentation velocity of 2.9S. Amino acid analysis revealed a composition similar to other submammalian CAs with the exception that the cysteine content was low (1 mol cysteine/mol enzyme). Like other submammalian CAs, the presence of a sulfhydryl reducing agent was required to maintain full activity and to prevent structural changes in the enzyme.

Amino Acids↗
PubMed1982

Ultrastructural immunocytochemical localization of carbonic anhydrase in normal and calcitonin-treated chick osteoclasts.

Carbonic anhydrase was localized in osteoclasts by light and electron microscopy using a preembedding peroxidase-antiperoxidase staining method. Osteoclasts on the endosteal surface of the metatarsi of calcitonin-treated and untreated (control) chicks were studied. A positive staining reaction was seen in the cytosol, in the Golgi apparatus, in and on vesicles, on the plasma membrane of the ruffled border, and on the bone surface beneath control osteoclasts. After calcitonin treatment, positive staining reactions were seen at the same sites except that staining was absent on the plasma membrane and endosteal bone surface. The morphology of osteoclasts from calcitonin-treated chicks was indicative of cell inactivity. The carbonic anhydrase which was bound to the plasma membrane of the ruffled border is appropriately arrayed for hydrogen ion secretion and subsequent mineral dissolution. The presence of the enzyme within lysosomelike vesicles and on the endosteal surface beneath active cells suggests that it may be released into the resorbing zone along with the lysosomal hydrolases. The function of the extracellular enzyme is also unknown.

Animals↗
PubMed1982

Carbonic anhydrase localization by light and electron microscopy: a comparison of methods.

The histochemical localization of carbonic anhydrase by Hansson's cobalt-salt method was compared with immunocytochemical localization in the proventriculus (glandular stomach), the chorioallantoic membrane, and in articular and growth-plate cartilages from the domestic hen. Numerous differences were observed. Staining was positive by Hansson's method and negative by immunocytochemistry for the submucosal glands of the proventriculus, articular cartilage cells, resting and proliferating cells of the growth plate, nuclei, and intercellular spaces. Red blood cells stained faintly and inconsistently by Hansson's method. Both methods were in agreement for the cytoplasm of the surface mucosal cells of the proventriculus, the cytoplasm of the villus cavity cells in the chorioallantoic membrane, and in hypertrophic cells of growth-plate cartilage. Acetazolamide usually inhibited the histochemical reaction, even in those sites that, according to other methods, did not contain enzyme. Consequently, acetazolamide inhibition appears to be an unreliable control for the histochemical reaction.

Animals↗
PubMed1982

Identification of carbonic anhydrase in chick growth-plate cartilage.

Carbonic anhydrase has been localized by immunocytochemistry in the cells and territorial matrix of the hypertrophic and calcifying zones of chick growth-plate cartilage. Adjacent epiphyseal and articular cartilage were not stained. By biochemical assay the activity levels were 61.3, 1.8, 34.7, and 703.3 units/g wet weight for growth plate, epiphyseal/articular cartilage, spongiosa, and blood, respectively. The role of the enzyme in growth plate is discussed.

Animals↗
PubMed1981

Sites of carbonic anhydrase in avian gastric mucosa identified by electron microscope autoradiography.

Carbonic anhydrase was localized at the ultrastructural level by autoradiography of [3H]acetazolamide in quail gastric mucosa. Grains were associated predominantly with mucin granules at the apical end of surface mucosal cells. Secreted mucin was also labeled. Oxynticopeptic cells of the multilobular glands were not labeled. The pH of fluid secreted by was 7.0-7.4 compared with a pH of 1.3-1.8 of freshly secreted fluid in the gastric lumen. The results of this study suggest that surface mucosal cells, which are strikingly similar in birds, amphibians, and mammals, are the site of acid secretion in the vertebrate stomach.

Acetazolamide↗
PubMed1981

Ultrastructural localization of carbonic anhydrase in the chorioallantoic membrane by immunocytochemistry.

Carbonic anhydrase was localized in the chick embryo chorionic ectoderm at the ultrastructural level by immuno-cytochemistry. Preembedding staining of whole tissue was performed. The enzyme was present in the cytoplasm, on the membranes of apical vesicles, and on the membranes of microvilli in villus cavity cells, cells that may be involved in acid secretion and subsequent dissolution of the egg shell. In sinus covering cells, the enzyme is solely in the cytoplasm. The location of the enzyme in the thin cytoplasmic arms of the sinus covering cells is consistent with the role in nonrespiratory CO2 release.

Allantois↗