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Biomedical subjects

R G Jones

Publications and source records attributed to R G Jones.

At least 109 records · Page 6Linked to original sources
PubMed1982

Calcium-containing lysosomes in the outer mantle epithelial cells of Amblema, a fresh-water mollusc.

The cells of the outer mantle epithelium contain numerous large pleomorphic electron dense bodies. In their fine structure they resemble lysosomes. Positive acid phosphatase histochemistry confirms that these supranuclear and subnuclear structures are lysosomes. A major portion of the intralysosomal material is resistant to high-temperature microincineration, indicative of an inorganic component. Subsequent microprobe analyses identified considerable calcium within these organelles. Such entities are similar in structure and ionic content to the lysosomes of avian intestinal absorbing cells, another calcium-transporting epithelium. These mantle lysosomes may function in transcellular calcium transport during shell formation, growth, and repair, especially since the mantle is the shell-forming organ in molluscs.

Animals↗
PubMed1982

Electron-microscopic and morphometric study of vesiculation in the epithelial cell layer of the toad urinary bladder. Effect of antidiuretic hormone.

Basolateral vesicles are apparent in mitochondria-rich, granular and basal cells of the epithelium of unstimulated toad urinary bladder. Such vesicles are smooth-walled rather than coated. Because of the number of these vesicles, we decided to investigate the effect of arginine vasopressin (AVP) on this vesicle population during the hydroosmotic response. Both glutaraldehyde and glutaraldehyde-osmium tetroxide fixation procedures, as well as electron-microscopic morphometric techniques were utilized. Fifteen min after the administration of AVP in the presence of an osmotic gradient, the intracellular area occupied by basolateral vesicles was increased approximately threefold when compared to unstimulated control hemibladders (0.92 +/- 0.15% vs: 2.67 +/- 0.39%). The intracellular nature of the majority of these vesicles was confirmed by experiments utilizing lanthanum as an electron-dense tracer. It is hypothesized that this vesicular activity may be involved in water movement across the tissue after hormone treatment.

Animals↗
PubMed1982

Lysosomal proliferation in rachitic avian intestinal absorptive cells following 1,25-dihydroxycholecalciferol.

Lysosomes in chick intestinal absorptive cells from rachitic (vitamin D-deficient) and vitamin D-replete animals were studied utilizing transmission electron microscopic histochemistry and ultrastructural morphometry. Absorptive cells from rachitic animals, serum calcium = 7.3 +/- 0.3 mg%, contained an average of 4.0 +/- 0.3 supranuclear lysosomes. In rachitic chicks sacrificed 9 hr post-injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D, the values for both serum calcium, 9.8 +/- 0.2 mg%, and the number of apical absorptive cell lysosomes, 12.9 +/- 0.6, were increased over non-injected or vehicle-only injected animals. Lysosomes in vitamin D-replete absorptive cells were characterized by their intense staining with pyroantimonate, indicative of their high calcium content. The same organelles also produced a positive reaction for acid phosphatase. Rachitic lysosomes, also acid phosphatase positive, were only lightly stained with pyroantimonate. The lysosomal proliferation apparently induced by 1,25-dihydroxycholecalciferol may be a further indication that these organelles play a role in intestinal calcium transport and/or intracellular calcium homeostasis within the absorptive cell.

Acid Phosphatase↗
PubMed1982

Cartilage calcification: an ultrastructural, histochemical, and analytical x-ray microprobe study of the zone of calcification in the normal avian epiphyseal growth plate.

Sections from the zone of calcification of ruthenium red-fixed normal avian epiphyseal growth plates were analyzed by various morphological (histochemical) and analytical techniques. Calcium and phosphorus were identified in the chondrocyte pericellular rim, the uncalcified extracellular (territorial) matrix, and in both the peripheral and central aspects of the calcified accumulations within extracellular matrix. Cartilage proteoglycan, as determined by ruthenium binding, positive staining with acidic phosphotungstic acid, and the X-ray spectroscopic detection of sulfur, was identified in the same four zones. Thus, it appears that proteoglycans, in some form, are indeed retained at sites of biological calcification. Additionally, these macromolecules, synthesized in chondrocytes, may be involved in extracellular calcium translocation.

Animals↗
PubMed1982

A histochemical and X-ray microanalysis study of calcium changes in insect flight muscle degeneration in Solenopsis, the queen fire ant.

Potassium pyroantimonate histochemistry, coupled with ethyleneglycoltetraacetic acid (EGTA)-chelation and X-ray microprobe analysis, was employed to localize intracellular calcium binding sites in the normal and degenerating flight musculature in queens of Solenopsis, the fire ant. In normal animals, calcium distribution was light to moderate within myofibrils and mitochondria. In the early contracture stages of the insemination-induced degeneration, both myofilament and mitochondrial calcium loading was markedly increased. In the terminal stages of myofibril breakdown, only Z-lines (isolated or in clusters) with an associated filamentous residue persisted. These complexes were also intensely calcium positive. This study further documents the presence of increased sarcoplasmic calcium during muscle necrosis. Surface membrane defects, mitochondrial calcium overload, and calcium-activated proteases may all be involved in this "normal" breakdown process.

Animals↗
PubMed1981

Calcium lysosomes in rachitic and vitamin D3 replete chick duodenal absorptive cells.

Calcium-containing lysomes were described in a previous communication in this series (Davis et al., 1979). Their potential role in intestinal calcium uptake and transcellular transports was hypothesized. To further this notion, the effects of a rachitogenic diet and vitamin D3 repletion were investigated. Intestinal absorptive cells from chicks maintained on a vitamin D deficient diet were characterized by decreased numbers of supranuclear calcium lysosomes. In contrast, intestinal cells from chicks given vitamin D3 (cholecalciferol) subsequent to the rachitogenic diet showed numerous large compound supranuclear calcium lysosomes. Since other steroid hormones are known to effect lysosomes, it is tempting to speculate that vitamin D, itself a steroid hormone, may activate lysosomes which themselves might be involved in calcium homeostatic mechanisms.

Animals↗
PubMed1981

Ultrastructural changes in the lysosomes of rachitic intestinal absorptive cells.

In chicks maintained on a rachitogenic (vitamin D deficient) diet, the number of intestinal absorptive cell calcium-lysosomes is markedly decreased in comparison to normal animals. In addition, the majority (better than 50%) of these rachitic calcium-lysosomes are atypical in their fine structure resembling the lamellar bodies seen in certain diseases (Tay-Sachs disease, Duchenne's muscular dystrophy). Such atypical organelles are characterized by their internal membranous swirls reminiscent of myelin figures. This information appears to be a further indication that lysosomes are normally involved in calcium homeostatic mechanisms and therefore sensitive to circulating vitamin D levels.

Animals↗
PubMed1981

Microperoxisomes in the epithelial cells of the amphibian urinary bladder: an electron microscopic demonstration of catalase and malate synthase.

All cells that comprise the epithelium of the toad urinary bladder were found to contain small ovoid to tubular membrane-bound bodies with a finely granular matrix. Such organelles were devoid of dense cores (nucleoids). These microperoxisomes reacted positively when incubated for the demonstration of catalase or malate synthase activity. In the toad liver, peroxisomes as well as microperoxisomes were seen. Histochemically, both demonstrated catalase activity; neither showed malate synthase activity. The presence of malate synthase, a glyoxylate cycle enzyme, in toad urinary bladder microperoxisomes may make these latter organelles unique among vertebrates, since malate synthase has been thought to be absent in higher animals.

Animals↗
PubMed1981

An electron microscopic histochemical and analytical X-ray microprobe study of calcification in Bruch's membrane from human eyes.

Transmission electron microscopy, electron microprobe analysis, high temperature microincineration, and electron microscopic histochemical procedures were used to study the electron-dense deposits characteristic of the macular aspect of aged human eyes. These inorganic deposits were rich in calcium and phosphorus and selectively removed by flotation on formic acid. The amorphous decalcified masses showed a significant sulfur peak and were readily stained with acidic phosphotungstic acid. The latter observations are indicative of the presence of organic matrical proteoglycan. Such data may be a further indication that proteoglycans are retained at sites of calcification.

Calcinosis↗
PubMed1980

A scanning electron microscopic study of the inorganic and organic matrices comprising the mature shell of Amblema, a fresh-water mollusc.

The scanning electron microscope has been used to describe the morphology of the mature shell in a fresh-water bivalve. The structure of the organic and inorganic components within the nacre, the myostracum, and the prismatic layer is described. A transitional or intermediate zone, interposed between the prismatic layer and the nacre, was identified. In demineralized samples, the organic component of the nacre was found to consist of parallel matricial sheets interconnected by irregular transverse bridges. The structure of the mineral component of the nacre was found to vary with the method of specimen preparation. With polished-etched samples, brick-like units were seen. When shells were simply broken and fixed in osmium, the layers of nacreous material consisted of fusing rhomboidal crystals of aragonite which demonstrated subconchoidal fractures. On the inner surface of the shell, the rhomboidal crystals showed an apparent spiral growth pattern. The myostracum was characterized by regions of modified nacreous structure consisting of enlarged aragonite crystals with a pyramidal morphology. The peripheral aspect of the muscle scars was characterized by rhomboidal crystals, the latter fusing to form the typical nacreous laminae. The uniqueness of the anterior adductor scar is exemplified by the presence of pores, each pore walled by pyramidal units, for the insertion of adductor fibres. In most regions of the shell, the prismatic layer consisted of one prism unit thickness with a height of approximately 225--250 micrometer. However, in two specialized regions of the shell, this layer was seen to consist of multiple layers of stacked prisms. The organic matrices of the prismatic layer are arranged in a honeycomb-like arrangement and packed with mineralized spherical subunits.

Animals↗
PubMed1980

Morphological studies on the calcification process in the fresh-water mussel Amblema.

Light microscopy, transmission electron microscopy, scanning electron microscopy, various histochemical procedures for the localization of mineral ions, and analytical electron microscopy have been used to investigate the mechanisms inherent at the mantle edge for shell formation and growth in Amblema plicata perplicata, Conrad. The multilayered periostracum, its component laminae formed from the epithelia lining either the periostracal groove or the outer mantle epithelium (of the periostracal cul de sac), appears to play the major regulatory and organizational role in the formation of the component mineralized layers of the shell. Thus, the inner layer of the periostracum traps and binds calcium and subsequently gives rise to matricial proteinaceous fibrils or lamellar extensions which serve as nucleation templates for the formation and orientation of the crystalline subunits (rhombs) in the forming nacreous layer. Simultaneously, the middle periostracal layer furnishes or provides the total ionic calcium pool and the matrical organization necessary for the production of the spherical subunits which pack the matrical 'bags' of the developing prismatic layer. The outer periostracal layer appears to be a supportive structure, possibly responsible for the mechanical deformations which occur in the other laminae of the periostracum. The functional differences in the various layers of the periostracum are related to peculiar morphological variables (foliations, vacuolizations, columns) inherent in the structure and course of this heterogeneous (morphologically and biochemically) unit. From this study, using the dynamic mantle edge as a morphological model system, we have been able to identify at least six interrelated events which culminate in the production of the mature mineralized shell layers (nacre, prisms) at the growing edge of this fresh-water mussel.

Animals↗
PubMed1980

Glyoxylate cycle in toad urinary bladder: possible stimulation by aldosterone.

A homogenate of the toad urinary bladder epithelial cell layer has the two enzymatic activities unique to the glyoxylate cycle--isocitrate lyase (threo-Ds-isocitrate glyoxylate-lyase, EC 4.1.3.1) and malate synthase [L-malate glyoxylate-lyase (CA-acetylating), EC 4.1.3.2]--as well as the capacity to carry out CN-insensitive palmitoyl-CoA oxidation. When tissue is incubated in the presence of a fatty acid substrate, tissue glycogen levels increase. Additionally, in the presence of aldosterone, glycogen levels are higher. These data demonstrate the presence of glyoxylate cycle enzymes in tissue of a higher animal and raise the possibility that such tissue can convert lipid to carbohydrate.

Aldosterone↗
PubMed1980

Drinking and vasopressin release during ventricular infusions of hypertonic solutions.

Six dogs were administered third ventricular infusions of artificial cerebrospinal fluid (CSF) (292 mosmol/l) alone or artificial CSF to which neither NaCl, sucrose, glucose, or urea was added to yield a final osmolar concentration of 500 mosmol/l. The volume of water drunk during 45 min of infusion was measured and blood was sampled for determination of plasma vasopressin concentration at 15-min intervals. Artificial CSF made hypertonic by addition of NaCl or sucrose stimulated water intakes of 9.0 +/- 3.2 ml/kg (mean +/- SE) and 7.3 +/- 3.7 ml/kg, respectively. There was no statistical difference in the amounts drunk and the latencies. In contrast, artificial CSF containing glucose, urea, or artificial CSF alone were without effect. Plasma vasopressin concentration increased significantly in response to intraventricular NaCl and sucrose but was not affected by glucose, urea, or artificial CSF alone. These data are compatible with an osmoreceptor mechanism mediating drinking and vasopressin release.

Animals↗
PubMed1979

Calcium containing lysosomes in the normal chick duodenum: a histochemical and analytical electron microscopic study.

Absorptive cells of the normal chick duodenum contain numerous supranuclear vesicular/vacuolar structures. By routine transmission electron microscopy, such structures are membrane bound and demonstrate a granular content. These vesicles appear to move laterally and eventually coalesce with the lateral plasma membrane (exocytosis). The granular contents are resistant to high temperature microincineration, thus revealing their mineral-containing nature. The granular vesicular matrix also stains intensely with osmium pyroantimonate EGTA chelation of pyroantimonate-stained vesicles selectively extracts the granules indicating a high concentration of calcium. X-ray microanalysis also demonstrates a significant intravesicular calcium localization. When tissues were incubated for the presence of acid phosphatase, the supranuclear vesicles were markedly positive for this lysosomal enzyme. A possible role for these calcium-containing lysosomes in the transcellular flux of calcium ions across the intestinal absorptive cell is discussed.

Acid Phosphatase↗
PubMed1979

Responses of Atriplex spongiosa and Suaeda monoica to Salinity.

The growth and tissue water, K(+), Na(+), Cl(-), proline and glycinebetaine contents of the shoots and roots of two Chenopodiaceae, Atriplex spongiosa and Suaeda monoica have been measured over a range of external NaCl salinities. Both species showed some fresh weight response to low salinity mainly due to increased succulence. S. monoica showed both a greater increase in succulence (at low salinities) and tolerance of high salinities than A. spongiosa. Both species had high affinities for Na(+) and maintained constant but low shoot K(+) contents with increasing salinity. These trends were more marked with S. monoica in which Na(+) stimulated the accumulation of K(+) in roots. An association between high leaf Na(+) accumulation, high osmotic pressure, succulence, and a positive growth response at low salinities was noted. Proline accumulation was observed in shoot tissues with suboptimal water contents. High glycinebetaine contents were found in the shoots of both species. These correlated closely with the sap osmotic pressure and it is suggested that glycinebetaine is the major cytoplasmic osmoticum (with K(+) salts) in these species at high salinities. Na(+) salts may be preferentially utilized as vacuolar osmotica.

Journal Article↗