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N K Smith

Publications and source records attributed to N K Smith.

At least 37 records · Page 2Linked to original sources
PubMed1988

Role of plasma membrane and of cytomatrix in maintenance of intracellular to extracellular ion gradients in chicken erythrocytes.

Ultrastructural observations in combination with electron probe X-ray microanalysis on detergent (Brij 58) permeabilized (disruption of the plasma membrane) nucleated chicken erythrocytes support the view that a large fraction of cytoplasmic and nuclear K+ is not freely diffusible and that adsorption of K+ on detergent released mobilizable proteins exists within the cell. The data also suggest that the detergent proteins are normally immobilized by a detergent-resistant cytoskeleton so that they are not immediately free to diffuse from the cell for several minutes after detergent disruption of the plasma membrane.

Animals↗
PubMed1988

Fluctuation in the intracellular concentration of Na+ and Cl- but not of K+ or Mg2+ at mitosis of the first cell cycle in fertilized sea urchin eggs.

This report concerns changes in the cytoplasmic concentration of Na+, Cl-, K+ and Mg2+ during the first cell cycle and into the second cell cycle of fertilized sea urchin eggs of Lytechinus variegatus. The results of electron probe x-ray microanalysis showed a significant equimolar decrease in Na+ and Cl- at the first cell division which was followed by a significant increase early in the second cell cycle. Neither K+ nor Mg2+ showed such significant changes. The loss of a large fraction of the Na+ ions from the egg at metaphase was not accompanied by a significant egg volume change. The observed pattern of ionic change was related to several previously reported chemical and metabolic changes at cell division in sea urchin eggs.

Animals↗
PubMed1988

Investigations of threonine requirements of broiler chicks fed diets based on grain sorghum and soybean meal.

Three trials were conducted to estimate the threonine (Thr) requirement of male broiler chicks. Chicks 7 days of age were fed a grain sorghum-soybean meal diet containing .59% Thr, supplemented with 0, .05, .09, .15, .22, .27, or .28% L-Thr. Levels of basal and supplemental amino acids were confirmed by ion-exchange chromatography. Diets were fed for 18 or 20 days, depending upon the trial. A corn-soybean meal diet analyzed to contain .90% Thr was used for comparison. Results of the three trials were pooled for determination of Thr requirements. A significant improvement in gain was observed when the basal grain sorghum-soybean meal diet was supplemented with .09% supplemental Thr (total .68% Thr). No further improvements in gain were observed at higher levels of Thr supplementation. Body weight gain of chicks fed the Thr-supplemented diets did not differ significantly from that of chicks fed the corn-soybean meal control diet. For maximum feed utilization, the Thr requirement was .79%, as estimated by regression analysis. This is in agreement with the .80% requirement suggested by the National Research Council in 1984. Feed utilization of chicks fed the corn-soybean meal diet was significantly better than that of chicks fed any of the grain sorghum-soybean meal diets regardless of the level of Thr supplementation.

Animal Feed↗
PubMed1988

Estimation of the tryptophan requirement of male broiler chickens.

Three experiments were conducted to determine the response of the male broiler chick to tryptophan (TRP) supplementation. Chicks were fed from 7 to 18 or 7 to 20 days posthatch either a grain sorghum-soybean meal diet containing .16% TRP, supplemented with 0, .02, .04, .06, .09, or .11% L-TRP, or a corn-soybean meal positive control diet containing .25% TRP. Levels of TRP in all diets were confirmed by ion-exchange chromatography using an alkaline hydrolysis. The test diet contained 15.34% CP (N x 6.25) from intact ingredients and 20% CP (N x 6.25) when supplemented with other amino acids to 110% of National Research Council recommendations in 1984. No improvement in gain or feed efficiency was observed with chicks fed the grain sorghum-soybean meal diet at any level of TRP supplementation. Feed utilization but not weight gain of the chicks fed the TRP-supplemented test diets was significantly poorer than that of chicks fed the corn-soybean meal positive control diets. These results suggest that the TRP requirement of the young (0 to 21-day-old) broiler chicken is no greater than .16% of a diet containing 3,200 kcal ME/kg.

Animals↗
PubMed1988

Influence of cytomatrix proteins on water and on ions in cells.

This review concerns the influence that cytomatrix proteins have on the motional properties of water and on the major inorganic ions in cells. The techniques we used for study of water in cells and on the cytomatrix proteins include: pulsed NMR of water protons, quench cooled ice crystal imprint size, and osmotic behavior. The technique for study of ions involved use of electron-probe X-ray microanalysis of thin cryosections of cells. The cytomatrix was found to play the major role in determining the extent of hydration water in cells. The amount of hydration water varied greatly between cell types (e.g., lens fiber cells have no detectable bulk water) and varied in the same cell type studied under different states (e.g., unfertilized and fertilized sea urchin eggs). Aggregation of cytomatrix proteins (actin in particular) is a determinant of the extent of hydration water in cells. Hydration water appears not to participate in the ideal osmotic equation of van't Hoff. The ionic content of cells does not accurately predict the chemical activity of the ions in cytoplasm. A major proportion of intracellular K+ and a substantial fraction of Cl- was found to be influenced by the cytomatrix such that their diffusion was impaired. The cytomatrix is responsible for the decreased motional properties of a substantial portion of cellular water and ions.

Animals↗
PubMed1987

The locations and amounts of endogenous ions and elements in the cap and elongating zone of horizontally oriented roots of Zea mays L.: an electron-probe EDS study.

We used quantitative electron-probe energy-dispersive x-ray microanalysis to localize endogenous Na, Cl, K, P, S, Mg and Ca in cryofixed and freeze-dried cryosections of the cap (i.e. the putative site of graviperception) and elongating zone (i.e. site of gravicurvature) of horizontally oriented roots of Zea mays. Ca, Na, Cl, K and Mg accumulate along the lower side of caps of horizontally oriented roots. The most dramatic asymmetries of these ions occur in the apoplast, especially the mucilage. We could not detect any significant differences in the concentrations of these ions in the central cytoplasm of columella cells along the upper and lower sides of caps of horizontally-oriented roots. However, the increased amounts of Na, Cl, K and Mg in the longitudinal walls of columella cells along the lower side of the cap suggest that these ions may move down through the columella tissue of horizontally-oriented roots. Ca also accumulates (largely in the mucilage) along the lower side of the elongating zone of horizontally-oriented roots, while Na, P, Cl and K tend to accumulate along the upper side of the elongating zone. Of these ions, only K increases in concentration in the cytoplasm and longitudinal walls of cortical cells in the upper vs lower sides of the elongating zone. These results indicate that (1) gravity-induced asymmetries of ions differ significantly in the cap and elongating zone of graviresponding roots, (2) Ca accumulates along the lower side of the cap and elongating zone of graviresponding roots, (3) increased growth of the upper side of the elongating zone of horizontally-oriented roots correlates positively with increased amounts of K in the cytoplasm and longitudinal walls of cortical cells, and (4) the apoplast (especially the mucilage) may be an important component of the pathway via which ions move in graviresponding rots of Zea mays. These results are discussed relative to mechanisms for graviperception and gravicurvature of roots.

Calcium↗
PubMed1986

Statoconia formation in molluscan statocysts.

The gravity sensors of all molluscs phylogenetically below the cephalopods are spherical organs called statocysts. The wall of the sphere contains mechanosensory cells whose sensory cilia project into the lumen of the cyst. The lumen is filled with fluid and dense "stones", the statoconia or statoliths, which sink under the influence of gravity to load, and stimulate, those receptor cells which are at the bottom. The statoconia of Aplysia californica are shown to be calcified about a lamellar arrangement of membranes. Similar lamellar membrane arrangements are seen within the receptor cells, and their possible role in the formation of the statoconia is discussed. SEM of unfixed statoconia reveals plate-like crystallization on their surface. Elemental analysis shows a relatively high Sr content, which is of interest, since others have recently reported that Sr is required in the culture medium of several laboratory reared molluscs in order for the statoconia to develop.

Animals↗
PubMed1986

Disruption of the plasma membrane leads to an influx of Na+ and Cl- but not an efflux of K+ in mouse hepatocytes and erythrocytes.

To determine what mechanisms might be involved in the maintenance of the known extra-/intracellular concentration gradients of Na+, Cl- and K+, small pieces of mouse liver and heparinized blood were appropriately cryofixed. The tissues were cryosectioned and cryosorbed at -100 degrees C or at -40 degrees C. The former temperature prevented diffusion of all ions as measured by electron probe x-ray microanalysis of the thin (0.1 micron) cryosorbed sections of the cells while the latter temperature allowed significant diffusion of Na+ and Cl- into the hepatocytes and erythrocytes but did not allow diffusion of K+ from the hepatocytes or the erythrocytes. These results indicate that the plasma membrane is involved in maintenance of the extra-/intracellular gradients of Na+ and Cl- but that intracellular association of K+ with macromolecules is the main mechanism responsible for maintenance of the extra-/intracellular K+ concentration gradient.

Animals↗
PubMed1985

Stimulus-permeability coupling in rat pulmonary macrophages challenged by Pseudomonas aeruginosa. An X-ray microanalysis study.

Electron probe X-ray microanalysis (XRMA) of freeze-dried ultrathin sections provides the capability of measuring intracellular elemental content. This methodology was used to investigate the stimulus-permeability coupling responses associated with phagocytosis of Pseudomonas aeruginosa by cultured pulmonary alveolar macrophages (PAMs) of rats. PAMs were challenged with P. aeruginosa suspended in Gey's buffer at a bacteria to PAM ratio of 50:1 for 1 h at 37 degrees C. A 1-mm3 pellet of the unchallenged control PAMs, challenged PAMs and P. aeruginosa alone was quench-frozen in nitrogen-cooled, liquid propane, and 0.1-micron cryosections were cut at -100 degrees C. X-ray spectra were collected for nucleus and cytoplasm of 39 control PAMs, 36 challenged PAMs and 40 P. aeruginosa. Concentrations (mmole/kg dry weight) were obtained for Na, Cl, K, Ca, Mg, P, S for each cell. In the control PAMs, the content was similar to other mammalian cells. Moreover, there were no differences in elemental content between nucleus an cytoplasm. In the challenged PAMs, Na concentration was 4 times that of control PAMs (p less than 0.001) whereas Cl was double (p less than 0.001), K was 29% lower (p less than 0.001), and Ca was 4 times higher (p less than 0.05). The elemental concentration profile in the P. aeruginosa was distinctly different from that of the PAMs: higher Na, Ca, Mg, but lower Cl and K values. These results demonstrated elemental content changes in cultured PAMs challenged with P. aeruginosa that indicate a stimulus-permeability response by membranes associated with the phagocytic process.

Animals↗
PubMed1985

Immunological tests and the diagnosis of dementia in elderly women.

Serum immunoglobulins and circulating antinuclear antibodies were assayed in 91 elderly female in-patients with dementia. Clinical criteria were used to distinguish a group with multi-infarct dementia from those with senile dementia of Alzheimer type and the results were compared with those of 19 age-matched controls. Dementia patients aged 85 and over had a higher prevalence of antinuclear antibodies (P less than 0.05) and those aged 90-95 had higher levels of IgA than younger age groups (P less than 0.025). IgG levels were higher than controls in the 'multi-infarct' group (P less than 0.025).

Aged↗
PubMed1985

The effects of increased levels of niacin supplementation on growth rate and carcass composition of broiler chickens.

Four experiments were conducted to examine the response of broiler chickens to different levels of niacin. Practical-type diets, calculated to contain from 20.7 to 23.7 mg niacin per kg from intact ingredients, were fortified with a complete vitamin mixture which provided 33 mg supplemental niacin per kg of diet, in excess of the National Research Council (1977) suggested requirement of 27 mg per kg through 6 weeks of age. A niacinamide supplement was used to provide additional levels of 0, 33, or 66 mg per kg. Diets differed in content of added fat and energy levels in two of the experiments and in the presence or absence of animal protein sources in two others. The addition of niacinamide at 33 and 66 mg per kg to a diet already supplemented with 33 mg per kg from a complete vitamin premix, calculated to exceed the present NRC suggested requirement, resulted in improved body weight gains with sex differences noted in some experiments. Feed utilization was improved in some studies. There was no effect on the amount of abdominal fat or carcass dressing percentage. The results of these studies indicate that the modern rapidly growing broiler chick may require niacin levels greater than those generally recommended by the National Research Council (1977), which are based largely on studies where performance was considerably lower than obtained with the modern strains of broilers.

Animal Feed↗
PubMed1984

Effects of intraventricular injections of 6-hydroxydopamine on anterior pituitary cell proliferation.

Effects of intraventricular injections of 6-hydroxydopamine (6-OHDA; 200 micrograms/20 microliter vehicle) on anterior pituitary cell proliferation in rats have been investigated by means of the colchicine metaphase-arrest technique. In those groups of animals receiving 6-OHDA alone or 6-OHDA plus desmethylimipramine (DMI, 25 mg/kg body weight i.p.), where the mean mitotic activity rates (MMARs) were initially low at 48 hours, an increase of MMARs was observed at 96 and 144 hours after the drug injections. At 144 hours after drug administration, the MMARs values in the 6-OHDA-injected group and in the 6-OHDA + DMI-treated group were significantly higher than those in the control groups. This increase of MMARs resulted from the enhancement of acidophilic and chromophobe cell proliferation. The low MMARs at 48 hours after 6-OHDA injection are probably a result of dopamine release from damaged nerve endings; the enhancement of MMARs (particularly evident in the 6-OHDA + DMI-treated group) at 96 and 144 hours after drug administration is presumably related to a deficiency of dopaminergic control of anterior pituitary cell proliferation.

Animals↗
PubMed1984

Further evidence of inactivity of hypothalamo-pituitary-thyroid axis in Snell dwarf mice.

The effects of hemithyroidectomy (hemiTX) and complete thyroidectomy (TX) on the cellular composition and the mitotic activity of the anterior pituitary gland were examined in genetically thyrotropin (TSH)-deficient female Snell dwarf mice (dw/dw) and in phenotypically normal female mice (?/+) from the same strain. In normal (nondwarf) mice, both hemiTX and TX reduced the percentage of acidophilic (orange G-positive) cells and increased the percentage of thyrotropic (aldehyde fuchsin [AF]-positive) cells, whereas the percentage of gonadotrophs (PAS-positive cells) and chromophobes (unstained cells) was not affected. Both interventions increased the mean mitotic activity rate (MMAR) of the anterior pituitary lobe. This effect was related to the enhancement of the MMAR of acidophilic cells and, particularly, thyrotropic cells. The MMAR of thyrotrophs in thyroidectomized normal mice was significantly higher than that in sham-TX controls or in hemithyroidectomized animals. In Snell dwarf mice, neither hemiTX nor TX affected the percentage of the various cell categories (PAS-positive, unstained, and extremely rare AF-positive cells) in the anterior pituitary lobe. Furthermore, neither hemiTX nor TX substantially influenced the MMAR of the gland. No mitotic figures were found in the AF-positive cells. Since the AF-positive cells in the anterior pituitary of dwarf mice completely failed to respond to hemiTX or TX, we believe they are not true thyrotropic cells. Using electron microscopy, we confirmed a lack of somatotrophs, mammotrophs, and normal thyrotrophs in the anterior pituitary of Snell dwarf mice. The results provide morphological evidence of inactivity of the hypothalamo-pituitary-thyroid axis in Snell dwarf mice.

Animals↗
PubMed1984

Calcium amelioration of cadmium-induced cytotoxicity in cultured rat hepatocytes.

Parenchymal hepatocytes from neonatal rats were isolated, cultured about 24 h, exposed to cadmium with or without calcium, and processed for scanning electron microscopy. To assess the severity of cadmium-induced changes, exposed hepatocytes were categorized based upon the extent of morphological damage. Differences in surface blebbing, alterations in microvilli, variations in the degree of swelling, and changes in cell shape were used to categorize the severity of cell damage. A double-blind morphometric analysis (a geometricostatistical processing of two-dimensional data for the collection of three-dimensional information) of cellular changes was conducted for each exposure time and for each concentration of cadmium in the presence or absence of calcium. Significant decreases occurred in the percent relative volume of normal, flattened cells present in cultures exposed for 30 min to 50 or 100 microM cadmium in the absence of calcium. In contrast, the percent relative volume of severely damaged spherical cells was significantly increased after exposure to solutions containing 50 or 100 microM cadmium and lacking calcium. Percent relative volume of intermediate cells (which were slightly swollen and showed changes in microvillar number) was significantly increased following a 30 min exposure to all cadmium concentrations in the absence of calcium. The examination of hepatocytes exposed for 60 min showed that the degree of cadmium-induced cytotoxicity was more severe in the absence of calcium than was the case for the hepatocyte cultures exposed for 30 min: approximately 30% more spherical cells and 30% fewer flattened cells were present if cultures were exposed in the absence of calcium for 60 min compared to those exposed for 30 min. The degree of blebbing was significantly greater at all cadmium concentrations in the absence of calcium. The presence of calcium, therefore, reduced cadmium-induced cytotoxicity in primary cultures of rat hepatocytes subjected to morphometric analysis after scanning electron microscopy.

Animals↗
PubMed1984

Inhibitory action of the pineal gland on the nuclear volume of thyroid follicular cells in male gerbils (Meriones unguiculatus).

Karyometric investigations of thyroid follicular cells were performed in four groups of adult male gerbils [I. sham-operated (Sham PX) + short photoperiod (SPP)-exposed; II. Sham PX + long photoperiod (LPP)-exposed; III. pinealectomized (PX) + SPP-exposed; IV. PX + LPP-exposed]. The mean nuclear volume (MNV) of thyroid follicular cells was significantly higher in both PX groups (III and IV) when compared to Sham PX controls (I and II). In Sham PX gerbils the maintenance of animals in SPP (10 h light: 14 h darkness) for 13 weeks resulted in significant decrease of MNV of thyroid follicular cells in comparison to that in Sham PX animals kept in LPP (14 h light: 10 h darkness). Lighting conditions did not significantly affect the MNV of thyroid follicular cells in PX gerbils. These data suggest that the pineal gland itself and not light deprivation is the most important factor depressing the activity of the thyroid in male gerbils. Lighting conditions seem to affect the function of thyroid follicular cells inasmuch as they activate or block the action of the pineal gland.

Animals↗