The Experts below are selected from a list of 60 Experts worldwide ranked by ideXlab platform

William J Pearce - One of the best experts on this subject based on the ideXlab platform.

  • maturation modulates serotonin and potassium induced Calcium 45 uptake in ovine carotid and cerebral arteries
    Pediatric Research, 1995
    Co-Authors: Shelley D Zurcher, William J Pearce
    Abstract:

    Neonatal vulnerability to intracranial hemorrhage is often attributed to a relative inability of immature cerebral arteries to contract. Because this depressed contractility may involve age-related differences in cerebrovascular Calcium handling, the present study examined age-related differences in cerebral artery contractility and its dependence on extracellular Calcium from 24 newborn lambs and 36 adult sheep. Contractile tensions and 45 Ca uptakes were measured under baseline conditions and as a function of time during stimulation by both receptor-dependent (100 μM serotonin) and receptor-independent (122 mM K + ) mechanisms of contraction in endothelium denuded newborn (N) and adult (A) ovine middle cerebral (MCA) and common carotid (COM) arteries. Maximum contractile responses to potassium averaged 4.5 ± 0.2 (N-COM), 5.8 ± 0.9 (A-COM), 3.0 ± 1.1 (N-MCA), and 3.1 ± 0.6 (A-MCA) g. Corresponding averages for responses to serotonin were 7.2 ± 0.8, 7.3 ± 1.1, 3.6 ± 0.1, and 3.6 ± 0.2 ; except for COM responses to potassium, contractile responses were little affected by maturation in either artery type. At baseline, uptakes averaged 0.39 ± 0.04 (N-MCA), 0.33 ± 0.04 (A-MCA), 0.25 ± 0.03 (N-COM), and 0.14 ± 0.01 (A-COM) μmol Ca/g dry weight/min. Maximum increases in Calcium uptake produced by potassium depolarization averaged 231 ± 19% (N-MCA), 152 ± 13% (A-MCA), 156 ± 11% (N-COM), and 140 ± 14% (A-COM) above baseline. Corresponding increases produced by 100 μM serotonin averaged 201 ± 15% (N-MCA), 129 ± 23% (A-MCA), 143 ± 20% (N-COM), and 145 ± 18% (A-COM). Under all conditions examined, Calcium uptakes were uniformly greater in newborn than adult arteries, and were greater in MCA than COM segments of the same age. For equivalent contractile tensions, newborn arteries required greater Calcium uptakes than corresponding adult arteries. We attribute these differences largely to age-related variations in the activation of Calcium entry through voltage-sensitive and receptor-operated membrane Calcium channels.

David A Hovda - One of the best experts on this subject based on the ideXlab platform.

  • effects of an n type Calcium channel antagonist snx 111 ziconotide on Calcium 45 accumulation following fluid percussion injury
    Journal of Neurotrauma, 1999
    Co-Authors: Amir Samii, Hedieh Badie, Robert R Luther, David A Hovda
    Abstract:

    ABSTRACT Accumulation of Calcium following experimental traumatic brain injury (TBI) has been demonstrated to be a prominent pathophysiological component that can compromise mitochondrial functioning and threaten cell survival. The omega-conopeptide SNX-111, also known as Ziconotide, is a potent antagonist of the voltage-gated N-type Calcium channel and has demonstrated significant neuroprotective effects against ischemia-induced neuronal injury. To determine whether this compound would be effective in reducing Calcium accumulation associated with TBI, SNX-111 was administered intravenously to rats 1 hour following a moderate (2.2 to 2.75 atm) lateral fluid-percussion injury (or sham) at doses of 1 (n = 30), 3 (n = 31), or 5 (n = 30) mg/kg; another group received 0.9% saline solution (n = 35). Brains were processed for Calcium 45 (45Ca) autoradiography at 6, 12, 24, 48, and 96 hours following insult. Optical density measurements of 20 cortical and subcortical regions were analyzed. Injured animals adminis...

Shelley D Zurcher - One of the best experts on this subject based on the ideXlab platform.

  • maturation modulates serotonin and potassium induced Calcium 45 uptake in ovine carotid and cerebral arteries
    Pediatric Research, 1995
    Co-Authors: Shelley D Zurcher, William J Pearce
    Abstract:

    Neonatal vulnerability to intracranial hemorrhage is often attributed to a relative inability of immature cerebral arteries to contract. Because this depressed contractility may involve age-related differences in cerebrovascular Calcium handling, the present study examined age-related differences in cerebral artery contractility and its dependence on extracellular Calcium from 24 newborn lambs and 36 adult sheep. Contractile tensions and 45 Ca uptakes were measured under baseline conditions and as a function of time during stimulation by both receptor-dependent (100 μM serotonin) and receptor-independent (122 mM K + ) mechanisms of contraction in endothelium denuded newborn (N) and adult (A) ovine middle cerebral (MCA) and common carotid (COM) arteries. Maximum contractile responses to potassium averaged 4.5 ± 0.2 (N-COM), 5.8 ± 0.9 (A-COM), 3.0 ± 1.1 (N-MCA), and 3.1 ± 0.6 (A-MCA) g. Corresponding averages for responses to serotonin were 7.2 ± 0.8, 7.3 ± 1.1, 3.6 ± 0.1, and 3.6 ± 0.2 ; except for COM responses to potassium, contractile responses were little affected by maturation in either artery type. At baseline, uptakes averaged 0.39 ± 0.04 (N-MCA), 0.33 ± 0.04 (A-MCA), 0.25 ± 0.03 (N-COM), and 0.14 ± 0.01 (A-COM) μmol Ca/g dry weight/min. Maximum increases in Calcium uptake produced by potassium depolarization averaged 231 ± 19% (N-MCA), 152 ± 13% (A-MCA), 156 ± 11% (N-COM), and 140 ± 14% (A-COM) above baseline. Corresponding increases produced by 100 μM serotonin averaged 201 ± 15% (N-MCA), 129 ± 23% (A-MCA), 143 ± 20% (N-COM), and 145 ± 18% (A-COM). Under all conditions examined, Calcium uptakes were uniformly greater in newborn than adult arteries, and were greater in MCA than COM segments of the same age. For equivalent contractile tensions, newborn arteries required greater Calcium uptakes than corresponding adult arteries. We attribute these differences largely to age-related variations in the activation of Calcium entry through voltage-sensitive and receptor-operated membrane Calcium channels.

Amir Samii - One of the best experts on this subject based on the ideXlab platform.

  • effects of an n type Calcium channel antagonist snx 111 ziconotide on Calcium 45 accumulation following fluid percussion injury
    Journal of Neurotrauma, 1999
    Co-Authors: Amir Samii, Hedieh Badie, Robert R Luther, David A Hovda
    Abstract:

    ABSTRACT Accumulation of Calcium following experimental traumatic brain injury (TBI) has been demonstrated to be a prominent pathophysiological component that can compromise mitochondrial functioning and threaten cell survival. The omega-conopeptide SNX-111, also known as Ziconotide, is a potent antagonist of the voltage-gated N-type Calcium channel and has demonstrated significant neuroprotective effects against ischemia-induced neuronal injury. To determine whether this compound would be effective in reducing Calcium accumulation associated with TBI, SNX-111 was administered intravenously to rats 1 hour following a moderate (2.2 to 2.75 atm) lateral fluid-percussion injury (or sham) at doses of 1 (n = 30), 3 (n = 31), or 5 (n = 30) mg/kg; another group received 0.9% saline solution (n = 35). Brains were processed for Calcium 45 (45Ca) autoradiography at 6, 12, 24, 48, and 96 hours following insult. Optical density measurements of 20 cortical and subcortical regions were analyzed. Injured animals adminis...

Tang Chao Shu - One of the best experts on this subject based on the ideXlab platform.

  • changes in amount of adm mrna and ramp2 mrna in calcified vascular smooth muscle cells
    Peptides, 2003
    Co-Authors: Shu Heng Wang, Baohong Zhang, Tang Chao Shu
    Abstract:

    This work was aimed to explore the changes and significance of adrenomedullin (ADM) mRNA and receptor activity modifying protein 2 (RAMP2) mRNA in calcified vascular smooth muscle cells (VSMCs). Calcification of cultured rat VSMCs was produced by incubation with beta-glycerophosphate. Content of ADM released by VSMCs was measured by radioimmunoassay (RIA). The amount of ADM mRNA and RAMP2 mRNA was determined by competitive quantitative RT-PCR. The intracellular Calcium content, alkaline phosphatases activity and cellular (45)Ca(2+)-uptake were determined. The results showed that the content of Calcium, (45)Ca(2+)-uptake and alkaline phosphatases activity in calcified VSMCs were increased by 118%, 174% and seven-fold (all P<0.01), respectively, compared with control VSMCs. Content of ADM in medium was increased by 99% (P<0.01). Furthermore, it was found that the amount of ADM mRNA and RAMP2 mRNA in calcified cells was elevated by 78 and 56% (all P<0.05), respectively, compared with control. The elevated levels of RAMP2 mRNA were in positive correlation with ADM mRNA (r=0.76, P<0.05) in calcified VSMCs. In conclusion, calcified VSMCs generated an increased amount of ADM, and up-regulated gene expressions of ADM and RAMP2.