11 resultados para CALCIUM STONE FORMERS
em Brock University, Canada
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The concrete wall gets its exterior finished in stone.
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Through this descriptive exploratory study, the ways that wilderness recreation leaders experience nature are illuminated, deconstructing the assumed environmental benefits of and practices used in outdoor recreation (Haluza-Delay, 2001). This study also offers a foundation for advancing an environmental ethic among wilderness recreation leaders, participants, and organizations. With the continued degradation of and threats to natural environments, and the rising popularity of outdoor recreation participation, the outdoor recreation professional can be a leader in promoting human reconnections to the Earth (Henderson, 1999). Leaders of outdoor recreation experiences play an important role in encouraging these revived relationships to natural settings and can contribute to the necessary environmental consciousness shift needed within Western society (Hanna, 1995; Jordan, 1996). The purpose of this research was to describe the lived-experience in nature of wilderness recreation leaders. Specifically, a phenomenological method of inquiry was used to describe the meaning of nature, the connections and relationships to nature, and the behaviours and emotions experienced in nature by a group of wilderness canoe trip leaders employed by a residential summer camp. In addition to the implications of this research, achieving this outcome provides a rich descriptive understanding of wilderness leaders' experiences—a basis from which to extend future research endeavours and programmatic practices that promote effective environmental outcomes of outdoor recreation participation. Each of the five study participants was employed in the summer of 2003 by an Ontario residential summer camp organization that sponsors extended wilderness river canoe trips for youth. Two in-depth and semi-structured interviews were performed with each participant, asking them to reflect on the canoe trip that they led for the summer camp organization during 2003. Phenomenological data was analyzed according to Colaizzi's (1978) thematic analysis process. Consistent with van Manen's (1997) emphasis on phenomenological writing, the final result presents the essence of the nature experiences of wilderness recreation leaders in the format of a narrative description. This narrative piece is the culmination of this research effort. Throughout the journey, however, various foundations within the outdoor recreation field, such as minimum impact principles, environmentally responsible behaviours, anthropocentric and ecocentric worldviews, and effective leadership are deconstructed and discussed.
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The relationship between photoperiod, plasma concentration of ionic calcium and the histology of the prolactin-secreting cells of the rostral pars distalis of the pituitary gland, the Corpuscles of Stannius and the Ultimobranchial gland were investigated. Neither the plasma concentration of ionic calcium nor histologically apparent prolactin cell activity could be correlated with photoperiod. Some evidence of a photoperiodic effect on both the Corpuscles of Stannius and the Ultimobranchial gland was obtained. The expected reciprocal relationship between the activity of these glands was not obvious at the histological level . Quantitative and qualitative analysis at the light microscope level revealed, however, that the hormone prolactin-secreting eta cells of the rostral pars distalis and the hypocalcin-secreting cells of the Corpuscles of Stannius may be arranged in a lamellar pattern comprized of synchronous bands of cells in like-phase of a secretory cycle consisting of four stages - synthesis, storage, release and reorganization. Such synchronized cell cycles in these glands have not heretofore been described in literature. It is suggested that the maintenance of at least 255? of the cells in any one phase of the cycle ensures a supply of the required hormone at all times.
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Increasing the impulse activity of neurons in vivo over 3 or more days causes a reduction in transmitter release that persists for days or weeks (eg. Mercier and Atwood, 1989). This effect is usually accompanied by decreased synaptic fatigue. These two changes involve presynaptic mechanisms and indicate "long-term adaptation" (LTA) of nerve terminals. Previous experiments have shown that LTA requires extracellular calcium and protein synthesis (eg. Hong and Lnenicka, Soc. Neurosci. Abstr. 17:1322) and appears to involve communication between the cell body and the nerve terminals. The present study examines the possibility that the reduction in transmitter release is caused by an -increase in the calcium buffering ability within the nerve terminals. It examines the responses of adapted and control nerve terminals to exogenously applied calcium buffer, BAPTA-AM, which decreases transmitter release (Robitialle and Charlton, 1992). If LTA increases intrinsic Ca2+-buffering, the membrane permeant form of BAPTA should have less effect on adapted nerve terminals than on controls. Experiments are performed on the phasic abdominal extensor motor neurons of the crayfish, Procambarns clarkii. BAPTA-AM decreases excitatory postsynaptic potentials (EPSP's) of the phasic extensor muscles in a dosedependent manner between 5 and 50 JLM. LTA is elicited by in vivo stimulation at 2.5 Hz for 2-4 h per day over 3 days, which reduces EPSP's by over 50%. Experiments indicate that BAPTA-AM produces no significant change in EPSP reduction in adapted neurons when compared to controls. These results do not support the hypothesis that increased daily activity alters rapid intrinsic calcium buffers, that are able to reduce transmitter output in the same manner as BAPTA.
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Numerous investigations have demonstrated large increases in y-amino butyrate (GABA) levels in response to a variety of stresses such as touch or cold shock (Wallace et ale 1984) Circumstantial evidence indicating a role of Ca2 + in these increases includes elevated Ca2+ levels in response to touch and cold shock (Knight et ale 1991), and the demonstration of a calmodulin binding domain on glutamate decarboxylase (GAD), the enzyme responsible for GABA synthesis (Baum et al 1993) In the present study the possible role of Ca2+ and calmodulin in stimulation of GAD and subsequent GABA accumulation was examined using asparagus mesophyll cells. Images of cells loaded with the Ca2+ indicator Fluo-3 revealed a rapid and transient increase in cytosolic Ca2+ in response to cold shock. GABA levels increased by 106% within 15 min. of cold shock. This increase was inhibited 70% by the calmodulin antagonist W7, and 42% by the Ca2+ channel blocker La3+.. Artificial elevation of intracellular Ca2+ by the Ca2+ionophore A23187 resulted in an 61% increase in GABA levels. Stimulation of GABA synthesis by ABA resulted in an 83% increase in GABA levels which was inhibited 55% by W7. These results support the hypothesis that cold shock stimulates Ca2+ entry into the cytosol of the cells which results in Ca2+/calmodulin mediated activation of GAD and consequent GABA synthesis.
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Sarco(endo)plasmic reticulum calcium ATPase (SERCA) is a transmembrane protein whose function is regulated by its immediate lipid environment (annulus). The composition of the annulus is currently unknown or it’s susceptibility to a high saturated fat diet (HSFD). Furthermore it is uncertain if HSFD can protect SERCA from thermal stress. The purpose of the study was to determine SERCA annular lipid composition, resulting impact of a HSFD, and in turn, influence on SERCA activity with and without thermal stress. The major findings were annular lipids were shorter and more saturated compared to whole homogenate and HSFD had no effect on annular lipid composition or SERCA activity with and without thermal stress. Both average chain length and unsaturation index were positively correlated with SERCA activity with and without thermal stress. These findings suggest that annular lipid composition is different than whole homogenate and its composition appears to be related to SERCA function.
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Receipt to S.D. Woodruff from Harnden Co. Stone for charges on the level, 1846.
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Certificate of exportation to S.D. Woodruff from Harnden Co. Stone for items sent to Lewiston from Buffalo. This is a handwritten 1 page document, Jan. 1, 1846[7].
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Letter to S.D. Woodruff from the Clough Stone Co. acknowledging the payment made for stone shipped to B. Allen, July 24, 1876.
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Receipt from J.D. Hibbard for brick and stone work, Dec. 14, 1876.
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Printed blank sent to Mr. B. Allen from the Clough Stone Co. of North Amherst, Ohio, Miners and Manufacturers of Grindstones and Building Stone regarding shipping. This is signed by Mr. Davis, July 19, 1876.