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R G Kirk

Publications and source records attributed to R G Kirk.

At least 37 records · Page 2Linked to original sources
PubMed1983

The correlation of composition and morphology during the high to low potassium transition in single erythropoietic cells.

The change from high potassium dog erythroid cells to low potassium red blood cells during erythropoiesis was investigated by X-ray microanalysis of single cells. A correlation of morphology and composition, using freeze-dried cryosectioned preparations, showed that during normal erythropoiesis in dog bone marrow the switch from high potassium to low potassium occurs during the change from early to late nucleated erythroid cells, and in synchrony with the beginning of iron accumulation. In contrast, during rapid erythropoiesis in dogs with phenylhydrazine-induced anemia, the most prominent change in cation composition as well as the accumulation of iron occurs during the reticulocyte stage in the peripheral blood. The determination of the absolute amounts of sodium and potassium per cell in stress reticulocytes of peripheral blood indicated that the changeover from high potassium to low potassium actually occurs by the loss of cellular potassium during volume reduction, with little change in the amount of cellular sodium. This suggests that maturation may involve a selective change in potassium permeability. Lastly, it was observed that not all cells followed the predominant pathway with respect to change in morphology, membrane permeability and hemoglobin synthesis. One particular subpopulation appeared to follow a sequence which expressed the complete HK to LK transition before the accumulation of any iron; this implies the possibility of completing protein synthesis in a low potassium intracellular milieu.

Anemia↗
PubMed1983

The distribution of intracellular ions in the avian salt gland.

To investigate the mechanism of salt secretion in the avian salt gland, we used quantitative electron probe microanalysis to measure the intracellular elemental concentrations in dry cryosections of unspecialized and partially specialized secretory epithelial cells from fresh water- and salt water-adapted ducklings, respectively. In conjunction with this, human and duckling erythrocytes were also analyzed, since these provided the experimental basis for using in situ erythrocytes as standards for determining the local water content of epithelia from the analysis of dried cryosections. The microprobe results from both types of erythrocytes compared favorably with chemical determinations of elemental concentrations. The nucleated avian erythrocytes, whose wet-weight elemental concentrations were determined by a compartmental analysis that required neither a peripheral standard nor a measure of the local mass, revealed a marked accumulation of P and K in the nucleus (388 and 190 mmol/kg wet wt, respectively) relative to the cytoplasm (67 and 85 mmol/kg wet wt). In both developmental states of the epithelial cells, the nucleus and apical cytoplasm had essentially similar and unremarkable concentrations of Na (76 and 83 mmol/kg dry wt, respectively, in the adapted cells vs. 72 and 81 mmol/kg dry wt in the control cells) and K (602 and 423 mmol/kg dry wt vs. 451 and 442 mmol/kg dry wt). Chloride, however, which was in general rather high, was significantly depressed in the apical cytoplasm of adapted cells only (164 and 124 mmol/kg dry wt in the nucleus and cytoplasm, respectively, of adapted cells (P less than 0.05) vs. 138 and 157 mmol/kg dry wt for control cells (P less than 0.05). Cation concentrations (Na + K) were elevated approximately 15% in the basal regions of adapted cells as compared with apical cytoplasm. When tissue water variations are accounted for, the results suggest that: (a) an active, energy-requiring process is responsible for chloride accumulation in this cell; (b) the apical membrane is a regulatory site for secretion; and (c) there are regional distinctions in the distribution of ions and water, particularly in the salt water-adapted cell. These conclusions are consistent with active chloride transport as the basis for salt secretion in this tissue.

Animals↗
PubMed1983

Influence of acute potassium loading on renal phosphate transport in the rat kidney.

UNLABELLED: This study examined 1) whether potassium-induced depression of phosphate excretion is a parathyroid hormone-dependent phenomenon, and 2) whether such stimulation of tubular phosphate reabsorption capacity involves increased phosphate reabsorption in the distal tubule. Potassium was infused into intact rats (25 mumol X min-1 X kg-1) during stepwise addition of phosphate to the infusion and led to a significant drop in phosphate excretion; this effect was abolished in thyroparathyroidectomized (TPTX) animals. In intact rats the maximal tubular Pi reabsorption per milliliter of glomerular filtrate (max TRPi/ml GF) was significantly higher in the potassium group (2.54 +/- 0.06 mumol/ml GF) compared with the control group (2.31 +/- 0.06 mumol/ml GF) (means +/- SE). In TPTX rats no difference in max TRPi/ml GF was observed: 3.44 +/- 0.07 and 3.49 +/- 0.07 mumol/ml GF during potassium and sodium infusion, respectively. Free-flow micropuncture was carried out on superficial distal tubules of intact rats and fluid samples were analyzed for [3H]inulin and phosphorus (electron microprobe). Phosphorus delivery into the distal tubule was similar in control and potassium-loaded rats. Whereas net phosphorus reabsorption along the distal tubule was absent in the control group, intravenous potassium administration stimulated distal phosphorus reabsorption. CONCLUSION: potassium stimulates renal phosphate reabsorption capacity, an effect that is abolished after TPTX. The potassium effect on phosphate occurs along the distal tubule.

Animals↗
PubMed1983

An X-ray microanalysis study of cation changes during development in erythropoietic cells.

The change from high potassium (HK) stem cells to low potassium (LK) red blood cells which occurs during erythropoiesis in the dog has been investigated by electron probe x-ray microanalysis of single cells. The intracellular elemental concentrations of potassium, sodium and iron were determined: 1) in the reticulocytes of peripheral blood from dogs with experimentally and naturally accelerated erythropoiesis, using wavelength-dispersive spectrometry of intact single cells; and 2) in the various erythropoietic cells of normal, adult dog marrow, using energy-dispersive spectroscopy of quench-frozen cryosections. The former experiments demonstrated that the switch from HK to LK cell type, which occurs during or slightly before denucleation of the orthochromatophilic erythroblast, is clearly correlated with a decrease in potassium concentration and also with the bulk of hemoglobin synthesis. The studies using cryosectioned preparations of normal dog confirmed a similar, negative correlation between sodium and potassium, although in this case only the onset of iron accumulation could be detected in the nucleated cells. When combined with the morphological information available from cryosections, it is concluded that the most immature erythroid cells are HK cells (CK greater than 80 mmols/kg wet-wt.), whereas a majority of the later erythroid cells were of the LK variety (CK less than 10 mmols/kg). This indicates that in normal dogs, the switch from HK to LK type occurs mainly in the basophilic erythroblasts.

Animals↗
PubMed1982

Study of maturation of membrane transport function in red blood cells by X-ray microanalysis.

Red blood cells of certain species of animals, such as dogs and cats contain low potassium and high sodium, whereas the erythropoietic stem cells giving rise to these cells are of high potassium type. This paper examines the sequence of membrane transport changes during erythropoiesis by analyzing the K, Na and Fe in single bone marrow cells, reticulocytes and mature red blood cells with X-ray microanalysis. The relationship between K/Na ratios and Fe/(K + Na), which is analogous to hemoglobin concentration, gives an index of maturation stage. The relationships between K/Na and Fe/(K + Na) in the marrow cells of normal adult dog and those of a phenylhydrazine-injected dog with accelerated erythropoiesis show that the modification of cation composition occurs after the initiation of hemoglobin synthesis but before its completion. Similar relationships in the reticulocytes obtained from phenylhydrazine-injected dogs as well as from newborn dogs show a consistent decrease in K/Na with increased Hb, indicating a drastic change in cation composition during the maturation of the reticulocytes. Therefore the modification in membrane transport function must have occurred before or during the formation of reticulocytes.

Aging↗
PubMed1978

Quantitative electron probe microanalysis of biological thin sections: the use of stem for measurement of local mass thickness.

A method for performing quantitative electron probe microanalysis on ultrathin (less than 30 microgram/cm2) biological samples is described and evaluated. The technique is based on a measurement of the characteristic peak count rate and the degree of beam attenuation as the primary electron beam passes through the sample. Using this method it is possible to measure the concentration of a given element such as sodium in sections ranging in mass-thickness from several microgram/cm2 up to 30 microgram/cm2 with an accuracy of better than 10%. For sections having a mass thickness of approximately 11 microgram/cm2 the minimum detectable concentration for sodium was found to be 20 mmolar or 4 X 10(-2) wt.%. The interaction of the electron beam with the sample is also discussed with emphasis on characterizing the variation in sample mass with radiation dose.

Electron Probe Microanalysis↗
PubMed1978

Electron probe microanalysis of red blood cells. I. Methods and evaluation.

The concentrations of potassium, sodium, and iron in human and sheep red blood cells were measured with an electron probe. Cells were prepared for analysis by spraying them on pyrolytic graphite supports. The results obtained with this spray technique agreed well with values measured on similar cells that were prepared for analysis by freezing, sectioning, and freeze-drying. Higher Na concentrations and lower K concentrations were found to be associated with lower cell volumes in human and high-potassium sheep cells. In low-potassium sheep cells the reverse was found, lower Na and higher K concentrations were associated with lower cell volumes. However, the amounts of iron were found to remain relatively constant in all human cells.

Cell Membrane Permeability↗
PubMed1978

Electron probe microanalysis of red blood cells. II. Cation changes during maturation.

To understand the sequence of maturation of membrane transport and hemoglobin production during erythropoiesis, we have measured the K, Na, and Fe content in single mature red blood cells and bone marrow cells of dog using electron probe microanalysis (EPMA). Mature red blood cells of dog are low in potassium (LK) and high in sodium. These cells are derived from erythroblastic stem cells, which are high in potassium (HK) and low in sodium. This change from HK stem cells to LK red cells occurs in the marrow. The ratio of K/Na was found to be less than 0.2 independent of Fe/(K + Na) in circulating red cells. However, a significant number of marrow cells had both low K/Na and low Fe/(K + Na). We conclude that the changes in cation transport properties responsible for the conversion of HK to LK cells occur before the synthesis of hemoglobin in at least some marrow cells.

Animals↗
PubMed1978

X-ray microanalysis of cation and hemoglobin contents in red blood cells.

From the results presented, it is clear that X-ray microanalysis can be used to determine the K and Na content in single red blood cells. With a simultaneous determination of Fe content and cation content, it is possible to deduce the sequence of events in the maturation of membrane transport function in relation to hemoglobin synthesis. This kind of deduction can only be made from a cell by cell analysis of the elemental contents. In addition, X-ray microanalysis can be used to measure other elements such as phosphate, which would permit a better understanding of the role of phosphate compound in volume regulation and metabolism of single red cells. Kinetic studies of active transport in single red cells are also possible by measuring the uptake of rubidium which is normally absent in the cell. Rubidium behaves like potassium in its transport characteristics in most red cells. The technique described here can be used to study the normal and the pathological state of single red cells and can also be applied to other single cells such as white cells, bacteria, and dispersed cells in tissue culture.

Animals↗
PubMed1977

Potassium transport and lipid composition in mammalian red blood cell membranes.

Potassium influxes in red cells from eight species have been found to follow exponential relationship with membrane phosphatidylcholine and sphingomyelin content. This relationship with membrane phosphatidylcholine and sphingomyelin content. This relationship with membrane phospholipid patterns was found to exist with both ouabain sensitive and insensitive fraction of potassium transport. When published values of chloride and phosphate permeabilities were compared with potassium permeabilities, correlations were found in seven out of nine of the species studied. On the basis of these findings it appears that potassium, phosphate, and chloride permeabilities in red blood cells of most species are related to the membrane phosphatidylcholine and sphingomyelin content; that is, membrane permeabilities increase with increasing amounts of phosphatidylcholine and decrease with increasing amounts of sphingomyelin. These results indicate that the membrane lipid is an important factor in transport processes in mammalian red blood cells.

Animals↗
PubMed1977

Electron probe microanalysis of chemical elemental content of single human red cells.

Sodium, potassium, iron and sulfur contents of single human red cells were measured using electron microprobe microanalysis. Three preparative procedures were compared, and the most reliable technique was found to be spraying of cells onto polished pyrolytic graphite by atomization. Primary standards were prepared by adjusting the intracellular electrolyte content of red cells, eliminating the need to correct for X-ray absorption. Samples were stable under the electron beam during analysis, and could be stored for long periods of time. Strong correlations were found between the X-ray intensities of iron and sulfur and between potassium and sodium. X-ray intensities of potassium and sodium were found to be directly proportional to internal ionic content. Large populations of single cells could be analyzed and the distribution of their elemental content studied.

Electron Probe Microanalysis↗
PubMed1977

Hyposmotic fluid formation in Hydra.

A detailed model for hyposmotic fluid formation in Hydra is presented. We propose that enteron fluid formation occurs in two steps: (1) segregation of an isosmotic fluid in large intercellular vacuoles with (2) subsequent reabsorption of solute in the intercellular channels to form the hyposmotic fluid of the enteron. Intercellular spaces in Hydra have been studied by light microscopy and thin-section electron microscopy, as well as by electrophysiological methods. These spaces are of two types: (1) large vacuoles which are located in the cells of both the epidermis and gastrodermis, being more numerous in the epidermis; and (2) lateral intercellular channels which run from the intercellular vacuoles, leading eventually to the enteron. These vacuoles and channels are highly convoluted, forming a complex three-dimensional network. We suggest that the network is involved in the water balance of Hydra.

Animals↗
PubMed1976

Anion transport and membrane morphology.

Freeze-fracture electronmicroscopy has been used to examine the membrane ultrastructure of human red blood cells in the presence of inhibitors of chloride exchange. The extent of inhibition was correlated with a decrease of intramembrane particle density on the B-fracture face. Dimethylsulfoxide (DMSO) and glycerol, which markedly and reversibly reduced the intramembrane particle density, were shown to drastically and reversibly inhibit chloride self-exchange. DMSO was shown to be a noncompetitive inhibitor of chloride flux.

Biological Transport↗