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Transient Rise (transient + rise)
Selected AbstractsTransient rise in intracellular calcium produces a long-lasting increase in plasma membrane calcium pump activity in rat sensory neuronsJOURNAL OF NEUROCHEMISTRY, Issue 4 2002William J. Pottorf II Abstract The plasma membrane Ca2+ ATPase (PMCA) plays a major role in clearing Ca2+ from the neuronal cytoplasm. Calmodulin stimulates PMCA activity and for some isoforms this activation persists following clearance of Ca2+ owing to the slow dissociation of calmodulin. We tested the hypothesis that PMCA-mediated Ca2+ efflux from rat dorsal root ganglion (DRG) neurons in culture would remain stimulated following increases in intracellular Ca2+ concentration ([Ca2+]i). PMCA-mediated Ca2+ extrusion was recorded following brief trains of action potentials using indo-1-based photometry in the presence of cyclopiazonic acid. A priming stimulus that increased [Ca2+]i to 506 ± 28 nm (>15 min) increased the rate constant for [Ca2+]i recovery by 47 ± 3%. Ca2+ clearance from subsequent test stimuli remained accelerated for up to an hour despite removal of the priming stimulus and a return to basal [Ca2+]i. The acceleration depended on the magnitude and duration of the priming [Ca2+]i increase, but was independent of the source of Ca2+. Increases in [Ca2+]i evoked by prolonged depolarization, sustained trains of action potentials or activation of vanilloid receptors all accelerated Ca2+ efflux. We conclude that PMCA-mediated Ca2+ efflux in DRG neurons is a dynamic process in which intense stimuli prime the pump for the next Ca2+ challenge. [source] Promotion of the fenton reaction by Cu2+ ions: Evidence for intermediatesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2006Mordechai L. Kremer The promotion of the Fenton reaction by Cu2+ ions has been investigated using a wide range of [Cu2+]. Both the disappearance of Fe2+ and the evolution of O2 were followed as a function of time by quenching the reaction mixture with o -phenanthroline or with excess Fe2 + ions, respectively. Two series of experiments were performed. In one series [H2O2] was 5 × 10,4 mol dm,3, and in the other [H2O2] was reduced to 5 × 10,5 mol dm ,3. By stopping the reaction with excess Fe2+ ions, significant differences in the measured absorbance in the two series were observed. In the higher [H2O2] range, the absorbance decreased monotonically in time, due to O2 formation during the reaction. In the lower range, an initial transient rise of the absorbance was observed, indicating the formation of spectroscopically distinct intermediates in the system. A mechanism involving the intermediates FeOCu4+ and FeOCu5+ has been set up. Rate constants of the mechanism have been determined. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 725,736, 2006 [source] The Effect of Leptin on Luteinizing Hormone Release Is Exerted in the Zona Incerta and Mediated by Melanin-Concentrating HormoneJOURNAL OF NEUROENDOCRINOLOGY, Issue 11 2000J. F. Murray Abstract The adipose hormone, leptin, not only restrains appetite, but also influences energy expenditure. One such influence is to promote sexual maturation and fertility. The neuromodulatory circuits that mediate this effect are not well known but the present study suggests that one mediator could be melanin-concentrating hormone (MCH). We show that the long-form receptor (Ob-Rb) is expressed in the zona incerta of the rat and that administration of leptin (both 0.5 µg and 1.0 µg/side) into this area of ovariectomized, oestrogen-primed rats stimulated the release of luteinizing hormone (LH) within 1 h, the effect enduring for a further 1 h. Injections of leptin into the arcuate nucleus induced a smaller, transient rise in LH while injections into the paraventricular and ventromedial nuclei were without effect. MCH neurones are present in the zona incerta and administration of this hormone into the medial preoptic area (mPOA) stimulates LH release, therefore we investigated the possibility that MCH might mediate this effect of leptin. An injection of MCH antiserum into mPOA prevented the rise in LH normally induced by leptin injected into the zona incerta. In addition, melanocortin receptor antagonists ([D-Arg8]ACTH(4-10) and [Ala6]ACTH(4-10)), previously shown to inhibit the stimulatory effect of MCH on LH release, also inhibited the effect of leptin. We propose that one route by which leptin may promote reproductive activity is by enhancing MCH release from fibres within the mPOA. Speculative mechanisms for the action of MCH include the following possibilities: MCH may be acting on the specific MCH receptor which in turn interacts with a melanocortin or melanocortin-like receptor; MCH may bind directly to one of the melanocortin receptors; or melanocortin antagonists may interact with the MCH receptor. [source] Effect of pamidronate on bone turnover and implant migration after total hip arthroplasty: A randomized trialJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2005J. Mark Wilkinson Abstract In this trial we studied the effect of pamidronate on periprosthetic bone turnover and pelvic implant migration over 2 years after hybrid total hip arthroplasty (THA). Twenty-two patients received 90 mg of pamidronate and 22 received placebo at randomization 5 days after surgery. Rapid periprosthetic bone loss occurred in the placebo group over the first 6 months and was accompanied by transient increases in biochemical markers of bone turnover. Partial recovery in bone mass occurred in most region after this period. No recovery of bone mass occurred at the femoral calcar or the medical wall of the acetabulum. Femoral calcar bone loss at 2 years was strongly predicted by acute biomarker changes at week 6. Pamidronate therapy reduced femoral bone loss in the region of the femoral calcar (P=0.01), but did not affect pelvic bone loss. Pamidronate therapy also inhibited the transient rise in biochemical markers of bone turnover during this period. Pamidronate therapy did not affect acetabular cup migration. Cup migration was inversely related to subject age, but unrelated to initial post-operative bone mineral density, or subsequent bone loss. In summary, early periprosthetic bone loss is associated with a transient expansion of the bone remodeling space. Bisphosphonate therapy reduces femoral calcar bone loss and bone turnover after THA, but did not influence cup migration in this study. Acute changes in biochemical markers predict femoral periprosthetic bone loss. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Effects of intra-abdominal CO2 -insufflation on normal and impaired myocardial function: an experimental studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2003C. A. Greim Background:, Intra-abdominal pressure (IAP) elevation during CO2 -pneumoperitoneum increases cardiac afterload and may enhance dysfunction of the already compromized heart. This study focused on the effects of acute IAP increases on left and right ventricular loadings and contractility in the heart with impaired global function. Methods:, Impairment of myocardial function (IMF) was pharmacologically induced in 16 pigs by administration of halothane and propranolol, while baseline arterial pressure was maintained by intravenous phenylephrine. Intra-abdominal pressure was gradually increased by 10 mmHg up to 30 mmHg in the supine position (IMF group 1, n = 8) or in a head-down tilted position (IMF group 2, n = 8). In two control groups with normal myocardial function, IAP was also increased in the supine position or the head-down tilted position. Cardiac function in all groups was assessed by epicardial echocardiography, intraventricular pressure measurements and pulmonary artery catheterization. Results:, The increase in IAP was accompanied by a transient rise in LV end-systolic wall stress and reduced cardiac output significantly by 16,24% in all groups. In the IMF groups, LV end-diastolic transmural pressure increased by 34,60% to peak values of 24 mmHg, while cross-sectional LV end-diastolic areas remained unchanged. Increases in right ventricular end-diastolic volume and decreases in right ventricular ejection fraction as well as in cardiac output were most pronounced at IAP 20 mmHg and significantly stronger in both IMF groups than in the control groups (P < 0.001). Conclusion:, Following the acute elevation of IAP, the right ventricular volume load shifted more extensively in the IMF groups than in the animals with normal myocardial function. Myocardial function in the impaired heart may worsen during IAP elevation due to right ventricular load alterations rather than a LV afterload increase. [source] Rapid Ca2+ flux through the transverse tubular membrane, activated by individual action potentials in mammalian skeletal muscleTHE JOURNAL OF PHYSIOLOGY, Issue 10 2009Bradley S. Launikonis Periods of low frequency stimulation are known to increase the net Ca2+ uptake in skeletal muscle but the mechanism responsible for this Ca2+ entry is not known. In this study a novel high-resolution fluorescence microscopy approach allowed the detection of an action potential-induced Ca2+ flux across the tubular (t-) system of rat extensor digitorum longus muscle fibres that appears to be responsible for the net uptake of Ca2+ in working muscle. Action potentials were triggered in the t-system of mechanically skinned fibres from rat by brief field stimulation and t-system [Ca2+] ([Ca2+]t-sys) and cytoplasmic [Ca2+] ([Ca2+]cyto) were simultaneously resolved on a confocal microscope. When initial [Ca2+]t-sys was , 0.2 mm a Ca2+ flux from t-system to the cytoplasm was observed following a single action potential. The action potential-induced Ca2+ flux and associated t-system Ca2+ permeability decayed exponentially and displayed inactivation characteristics such that further Ca2+ entry across the t-system could not be observed after 2,3 action potentials at 10 Hz stimulation rate. When [Ca2+]t-sys was closer to 0.1 mm, a transient rise in [Ca2+]t-sys was observed almost concurrently with the increase in [Ca2+]cyto following the action potential. The change in direction of Ca2+ flux was consistent with changes in the direction of the driving force for Ca2+. This is the first demonstration of a rapid t-system Ca2+ flux associated with a single action potential in mammalian skeletal muscle. The properties of this channel are inconsistent with a flux through the L-type Ca2+ channel suggesting that an as yet unidentified t-system protein is conducting this current. This action potential-activated Ca2+ flux provides an explanation for the previously described Ca2+ entry and accumulation observed with prolonged, intermittent muscle activity. [source] Early and Severe Hyperparathyroidism Associated with Hypercalcemia After Renal Transplant Treated with CinacalcetAMERICAN JOURNAL OF TRANSPLANTATION, Issue 10 2006N. Leca Bone disease is a common clinical problem following renal transplantation. In renal transplant recipients, multiple underlying factors determine the extent of bone loss and the subsequent risk of fractures. In addition to the well-recognized risk to bone disease posed by steroids, calcineurin inhibitors and pre-existing bone disease, persistent hyperparathyroidism (HPT) contributes to post-transplant bone loss. HPT is usually treated with vitamin D supplements combined with calcium. Patients whose HPT is associated with hypercalcemia pose a difficult therapeutic dilemma which often requires parathyroidectomy. Cinacalcet, a calcium mimetic agent, offers a unique pharmacologic approach to the treatment of patients with post-transplant hypercalcemia and HPT. In this paper, we describe the clinical course and biochemical changes in 10 renal transplant recipients with hypercalcemia and severe HPT early after renal transplantation treated with cinacalcet. Cinacalcet therapy corrected hypercalcemia and decreased parathyroid hormone (PTH) levels in all cases. A transient rise in the level of alkaline phosphatase was noted following initiation of cinacalcet therapy. In this patient population, correction of HPT was not permanent as discontinuing cinacalcet therapy led to a rapid rise in PTH level. [source] Mucosal Vascular Alterations in Isolated Small-Bowel Allografts: Relationship to Humoral SensitizationAMERICAN JOURNAL OF TRANSPLANTATION, Issue 1 2003Phillip Ruiz Acute vascular rejection (AVR) in human small-bowel transplantation is an inadequately characterized entity whose frequency and severity is not well understood. As compared to severe AVR, changes identifying early, mild or evolving AVR are not known. We created a scoring system to evaluate subtle mucosal vascular changes and examined 188 biopsies from 21 patients obtained in the first 3 months post transplant. A majority of patients had a transient rise in vascular injury, often within 30 days of transplant. Small-vessel congestion and erythrocyte extravasation were the most common alterations. The vascular injury score was not related to acute cellular rejection, HLA type or HLA antigen disparities. However, the patients with the vascular changes had significantly higher peak panel reactive antibodies (PRA) and a higher incidence of positive T-cell and B-cell crossmatch. Finally, graft survival was significantly lower in the patients demonstrating the early vascular lesions. These data suggest that the vascular injury is partially associated with humoral presensitization of the recipient and may be a form of acute vascular rejection. Since these vascular changes are frequent, we advocate early post-transplant monitoring to identify and manage potentially high-risk patients. [source] Photodynamic therapy with intravitreal application of triamcinolone acetonide in age-related macular degeneration: functional results in 54 patientsACTA OPHTHALMOLOGICA, Issue 2 2009Adjoa Frimpong-Boateng Abstract. Purpose:, This study aimed to investigate the functional results, efficacy and complications after photodynamic therapy (PDT) combined with intravitreal triamcinolone acetonide injection (IVTA) in patients with choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD). Methods:, A retrospective analysis of clinical data for 54 patients with CNV resulting from AMD was carried out. All patients had a follow-up of 12 months. The patients were treated with standardized PDT and IVTA (4 mg) as a first-line treatment or following PDT failure. Visual acuity (VA), greatest linear diameter (GLD) of the CNV and foveal thickness were evaluated. Results:, Mean VA at baseline was 0.8 logMAR (0.4,1.4). After 12 months VA improved (> 2 lines) in 20.4% of patients and stabilized (± 2 lines) in 64.8%. There was no statistical significance in VA outcome between patients undergoing first-line treatment and patients with PDT failure; however, fewer PDT treatments were required to stop CNV activity in patients undergoing first-line treatment. At 12 months, a reduction in foveal thickness was seen in 67.7% of patients and a reduction in CNV GLD in 32.7%. Complications occurred in 22% of patients and included a transient rise in intraocular pressure, cataract and sterile hypopyon. Conclusions:, Our analysis shows that fewer PDT treatments were required to stop CNV activity when triamcinolone was used as first-line treatment. We can thus conclude that PDT combines synergistically with IVTA and the combination may lead to a cost reduction compared with PDT therapy alone. The overall complication rate of 22% is high and must be compared with complication rates caused by new intravitreal anti-VEGF (vascular endothelial growth factor) drugs in combination with PDT. [source] | |||||||||||||