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N K Smith

Publications and source records attributed to N K Smith.

At least 55 records · Page 3Linked to original sources
PubMed1984

Intraventricular 6-hydroxydopamine increases the adrenal cortex mitotic activity in rats.

Effects of intraventricular injections of 6-hydroxydopamine (6-OHDA) on adrenocortical cell proliferation in rats have been investigated by means of the colchicine metaphase-arrest technique. In the group of animals receiving 6-OHDA alone, an increase of mean mitotic activity rate (MMAR) was observed at 96 h and 144 h after injection. This rise of MMAR was completely inhibited by pretreatment of animals with desmethylimipramine (DMI) - a blocker of norepinephrine uptake. It is concluded that enhancement of ACTH secretion is responsible for the above mentioned increase of mitotic activity after 6-OHDA administration. This phenomenon is related to abolition of the inhibitory noradrenergic effect on ACTH secretion by 6-OHDA treatment. Additionally, the results suggest little or no involvement of dopaminergic neurons in early changes of ACTH secretion after intraventricular 6-OHDA.

Adrenal Cortex↗
PubMed1984

The subcellular concentration of ions and elements in thin cryosections of onion root meristem cells. An electron-probe EDS study.

Quantitative electron-probe energy dispersive X-ray microanalysis has, for the first time, been accomplished at a subcellular level in plant tissue using cryofixed and thin freeze-dried cryosections. The subcellular concentrations of Na+, Cl-, K+, P, S, Mg2+ and Ca2+ were measured in mol/kg dry weight in two types of root meristematic cells of the onion, Allium cepa. The cell wall of the meristematic cells had much higher concentrations of K+ and Ca2+ than was found in the intracellular compartments. Storage granules in the protoderm cells were about 6-12 times lower in P and were about four times higher in S as compared to other intracellular compartments. Comparison between the concentrations of ions and other elements in meristematic plant cells and in mouse cardiac myocytes confirms that major differences in cytoplasmic Na+ and Cl- concentrations do indeed exist between these cell types.

Animals↗
PubMed1984

Nuclear-cytoplasmic distribution of ions in the hepatocyte.

To determine if nuclear/cytoplasmic (N/C) gradients of ions exist in mammalian hepatocytes, as has been shown to exist in the amphibian oocyte, small pieces of mouse liver were cryofixed for energy dispersive X-ray microanalysis of Na, K and Cl in thin freeze-dried cryosections. Expressing the data on a dry weight basis showed small but significant N/C gradients for Na and K but not for Cl. When the data were expressed on a wet weight basis no significant N/C gradients of Na, K or Cl were revealed. Questions of data interpretation are discussed.

Animals↗
PubMed1983

Effect of experimental hyperthyroidism on the elemental content of rat hepatocytes.

X-ray microanalysis has been used to determine elemental content in the cytoplasm of hepatocytes of hyperthyroid rats in comparison with euthyroid controls. No significant differences were found for any examined element (sodium, phosphorus, sulfur, chlorine, potassium, magnesium and calcium). In contrast to earlier reports from another laboratory, these data indicate that thyroid hormones do not substantially affect elemental content in rat hepatocytes.

Animals↗
PubMed1983

X-ray microanalysis of cardiocytes in the Snell dwarf mouse.

X-ray microanalysis has been used to determine elemental content in the nucleus, myofibrillar cytoplasm and mitochondrially enriched cytoplasm of cardiocytes in Snell dwarf mice in comparison with phenotypically normal mice from the same strain. It was found that there was significantly lower chlorine concentration in all three subcellular locations and significantly lower sodium concentration in the nucleus of dwarf mouse cardiocytes. In both normal and dwarf mice, statistically significant subcellular compartmentalization was found for phosphorus, sulfur, and potassium.

Animals↗
PubMed1983

Intracellular elemental content of cardiac and skeletal muscle of normal and dystrophic hamsters.

To test the hypothesis that the genetic lesion causing muscular dystrophy might be reflected in an abnormal intracellular elemental content, the elemental content of individual cardiac and skeletal muscle fibers in 50-day-old male control and cardiomyopathic BIO 53.58 hamsters was determined. The technique of electron probe x-ray microanalysis of freeze-dried tissue was employed. No electrolyte content differences were found between control and diseased animals for nuclei, myofibrillar cytoplasm, or mitochondrially-enriched cytoplasm of cardiac myocytes. Sulfur was elevated in dystrophic cardiac myocytes and was the only element significantly different in heart tissue of control and cardiomyopathic animals. Sulfur was also elevated in dystrophic soleus muscle fibers. The pattern of electrolyte content of these cells reflected a mixture of normal cells and damaged cells with altered electrolyte content. In this hamster model, alteration of electrolyte content of myocytes appears to be a result of the disease process and not an inherent characteristic of muscular dystrophy. The elevated sulfur in dystrophic hamster myocytes reflects a biochemical lesion which deserves further study.

Animals↗
PubMed1983

Inclusion bodies in pinealocytes of the cotton rat (Sigmodon hispidus). An ultrastructural study and X-ray microanalysis.

Pinealocytes of the cotton rat (Sigmodon hispidus) often contain large (2-6 micron diameter) intracytoplasmic inclusions, the function of which is not known. These inclusions may represent nucleolus-like bodies, mineral deposits, secretory products or viral inclusions. In this study these inclusions were classified as type A, B or C inclusions based on the amount of electron-dense material interspersed within the finely granular material comprising the bulk of these inclusions. Each type of inclusion was analyzed by X-ray microanalysis and enzymatic proteinaceous digestion. X-ray microanalysis of these inclusions differed both quantitatively and semiquantitatively from that of human or gerbil pineal concretions, the latter two of which are extracellular deposits. Pronase, a proteolytic enzyme, digested the electron-dense material only after longer times of tissue exposure to this enzyme in contrast to the easily digested, finely granular matrix-like material of these inclusions. Such intrapinealocytic inclusions have only been observed in the cotton rat. Their functional significance remains unknown.

Animals↗
PubMed1983

Compensatory thyroid hyperplasia in hemithyroidectomized Snell dwarf mice.

The effect of hemithyroidectomy (HEMITX) on the proliferation of follicular cells in the remaining thyroid lobe in Snell dwarf mice (dw/dw) and in phenotypically normal mice from the same strain (?/+) was examined by means of the colchicine metaphase-arrest technique. In both the normal and dwarf mice, the mean mitotic activity rate of the thyroid lobe 48 h after contralateral HEMITX was significantly higher than that in the animals with intact contralateral lobe (P less than 0.001), indicating the existence of compensatory thyroid hyperplasia (CTH). Since in Snell dwarfs not only GH and PRL but also TSH is lacking, it is concluded that extrapituitary factors, most probably neural pathways, are involved in CTH in these animals.

Animals↗
PubMed1983

X-ray microanalysis of hepatocytes in thyroidectomized rats.

Thyroid hormones are assumed to be a factor which influences elemental distribution in animal tissues, including liver, by their action on the passive Na-K permeability of cell membrane (Folke and Sestoft, 1977) and/or by stimulation of the Na-K pump (Ismail-Beigi and Edelman, 1970), as well as by the enhancement of tubular reabsorption of Na and Cl in kidneys (Discala and Kinney, 1971). We have shown previously that thyroxine administration does not significantly change intracellular ion concentrations in rat hepatocytes (Smith et al., 1983). In the present study we have used X-ray microanalysis to examine the effect of thyroidectomy on the elemental content of rat hepatocytes.

Animals↗
PubMed1983

Effects of amiloride on tumor growth and intracellular element content of tumor cells in vivo.

The effects of amiloride, a reported inhibitor of serum-stimulated sodium influx, were tested on tumor growth, tumor cell proliferation, and intracellular element content of cancer cells in vivo. We have shown previously that cancer cells have high intranuclear levels of sodium compared to those of their normal counterpart cells and have postulated that such a high level of sodium may be involved in the cancer state. We now report that amiloride, when given in a series of injections, inhibited both H6 hepatoma and DMA/J mammary adenocarcinoma growth in vivo in a dose-dependent fashion and that 3 injections of amiloride at a dose of 1.0 microgram/g body weight into mice bearing H6 hepatomas resulted in a significant decrease in the intranuclear content of sodium but not the content of magnesium, phosphorus, sulfur, chlorine, or potassium as measured by electron probe X-ray microanalysis in the H6 hepatoma cells. Amiloride at dosages as low as 1.0 microgram/g body weight per injection also inhibited tumor cell proliferation as measured by the tritated thymidine autoradiography labeling index. Amiloride caused no changes in the mean profile diameters of metaphase or interphase H6 hepatoma or DMA/J mammary adenocarcinoma cells, suggesting that the action of amiloride on tumor growth was not due to cell volume changes. These data show that amiloride both inhibited tumor growth and decreased the proliferation of the tumor cells in the H6 hepatomas which was correlated with a decreased intranuclear sodium content.

Adenocarcinoma↗
PubMed1982

Cell cycle-fluctuations in concentration of various elements in cytoplasm and in nucleus/chromatin of Physarum polycephalum.

The concentrations of Na, Mg, P, Cl, S, K, and Ca (m mol/kg dry wt) were measured during the cell cycle of P. polycephalum using electron-probe X-ray microanalysis. Significant cell cycle-associated fluctuations in the concentrations of all of these elements occurs in both the cytoplasm and the nucleus. In most cases the levels of each element were elevated during mitosis but greatly reduced during the S phase. Phosphorus and sulphur were concentrated in the nucleus/chromatin at metaphase. Ultrastructural analysis of these cells reveals a phase dependent variation in the density of the cytoplasmic ground substance which is most pronounced at mitosis. The changes seen in the cytoplasm occur not only in conjunction with the increased concentration of elements in the nucleus but also with the cessation of protoplasmic migration.

Cell Cycle↗
PubMed1981

Elemental content in the nucleus and in yolk and yolk-free cytoplasm of developing Rana pipiens oocytes: an x-ray microanalysis study.

Energy dispersive x-ray microanalysis measured the Na, K, Cl, P, Mg, S, and Ca contents (mM/kg dry weight) in the nucleus, yolk-free cytoplasm, and yolk platelets of Rana pipiens oocytes quick frozen in the ovary. The data revealed that significant content changes occur in frog oocytes during intraovarian growth. All elements but Ca changed in content in the nucleus and cytoplasm, while in the yolk platelet only Na content did not change. A nucleus to cytoplasm K gradient develops and increases in magnitude during oocyte growth. The data from this and previous reports lead to the hypothesis that intra-oocytic water and elements undergo changes in state during oocyte growth and that three subcellular Na compartments exist.

Animals↗
PubMed1981

Observations on electron probe x-ray microanalysis compared to other methods for measuring intracellular elemental concentration.

Electron probe X-ray microanalysis provides the capability of accurately measuring the concentration of a number of elements at the subcellular level in tissues which are appropriately prepared using cryofixative procedures. This preview compares quantitative data obtained by the authors, using X-ray microanalysis, with quantitative data obtained in other laboratories using routine chemical procedures such as flame photometry, atomic absorption spectrophotometry, titrimetry, and ion-selective electrodes. Results are compared for cells in whole tissue, for cells in suspension (erythrocytes), and for subcellular analysis. Subcellular elemental data obtained after cell fractionation and isolation and after cryomicrodissection are considered. Agreements and differences between the results obtained by the different methods of analysis as compared to microprobe are discussed and the sources of the differences are explored. The biological significance of microprobe concentration data itself is limited without additional information regarding the state of the elements, such as oxidation state, ionic activity, degree of binding, etc. In this regard, the supplementation of subcellular elemental concentration with ionic activity and flux data for the large amphibian oocyte is presented as an example of how measurement of multiple parameters can be used to explain the maintenance of subcellular concentration gradients.

Animals↗
PubMed1981

X-ray microanalysis of electrolyte content of normal, preneoplastic, and neoplastic mouse mammary tissue.

Intracellular sodium, chlorine, and potassium concentrations (mmol/kg dry weight) were determined by electron probe X-ray microanalysis of individual epithelial cells in freeze-dried 2-micrometer sections of mouse mammary tissue which were cut at -30 degrees. A model system was utilized in order to compare elemental content of cells from normal pregnant mammary tissue and preneoplastic and neoplastic mammary tissues from female BALB/cCrlMed mice. Animals were killed by cervical dislocation, and tissue was rapidly frozen in liquid propane. Normal mammary glands were obtained from primiparous mice at 16 to 17 days of gestation. Tissue from the hyperplastic alveolar nodule line D1 was removed from donor mice 12 to 16 weeks after transplantation into the cleared mammary fat pad. All mammary adenocarcinomas, D1T, were primary tumors which developed in mice with transplants of nodule line D1. Data were collected from five animals (10 cells/animal) in each of the three groups. It was found that the electrolyte content of cells of preneoplastic tissue was the same as that of the normal mammary tissue but was significantly elevated in neoplastic tissue (162, 130, and 48% increases for sodium, chlorine, and potassium, respectively). Thus, an increase in electrolyte content seems to be associated with the transformation to a neoplastic state and not associated with conversion to the preneoplastic state.

Adenocarcinoma↗
PubMed1980

Intracellular concentration of elements in normal and dystrophic skeletal muscles of the chicken.

In this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X-ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 +/- 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 +/- 16.5 in normal controls. The concentration of chlorine was 90.5 +/- 27.5 and 54.1 +/- 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.

Animals↗
PubMed1980

Intracellular concentration of potassium and other elements in vaginal epithelial cells stimulated by estradiol administration.

Electron probe x-ray microanalysis was used to measure cytoplasmic elemental content (in mmoles/kg dry weight) of the basal layer of cells of the vaginal epithelium of ovariectomized rats. Measurements were made both before estradiol injection and at 2 hr, 17 hr, and 24 hr after estradiol administration. Mitotic figures first appeared in the basal cell layer at 24 hr. During the course of the study significant time-dependent differences were seen in the content of all elements mesured. A pattern of change in cytoplasmic content was seen for Na, P, S, and Cl; all of which decrease significantly by 17 hr and then return to approximately the nonstimulated concentration by 24 hr. On the other hand K, and to a lesser extent Mg, show an early and continued increase in cytoplasmic content after estadiol injection. Thus, the marked increase in the intracytoplasmic content of K in the estradiol treated cells suggests that K, or the ratio of Na to K, may be directly or indirectly involved in growth stimulation.

Animals↗