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332 registered by a neutron monitor. This paper uses data from the “Spaceship Earth” network of neutron monitors to characterize the time evolution of cosmic rays during the event. We also investigate spectral evolution using multiplicity data from a specially instrumented mobile monitor that was located in McMurdo Sound at the time of the event. INJECTION AND TRANSPORT OF RELATIVISTIC SOLAR PROTONS ALONG BOTH LEGS OF A CLOSED INTERPLANETARY MAGNETIC FIELD LOOP (NO. 882) David Ruffolo 1 , Paisan Tooprakai 2 , Manit Juiwarodom 2 , Thiranee Khumlumlert 3 , Maneenate Wechakama 4 , John W. Biever 5 , Pau Evenson 5 , Roger Pyle 5 1 Department of Physics, Faculty of Science, Mahidol University, Bangkok, Thailand; 2 Department of Physics, Faculty of Science, Chuylalongkorn University, Bangkok, Thailand; 3 Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand; 4 Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.; 5 Bartol Research Institute, University of Delaware, Newark DE 19716, USA. Worldwide neutron monitor observations of relativistic solar protons on 1989 October 22 have proven puzzling, with an initial spike at some stations followed by a second peak, which is difficult to understand in terms of transport along a standard Archimedean spiral magnetic field or a second injection near the Sun. Here we analyze data form polar monitors, which measure the directional distribution of solar energetic particles (mainly protons) at rigidities of –1-3 GV. This event has the unusual properties that the particle density dips after the initial spike, followed by a hump with bidirectional flows and then a very slow decay. The density and anisotropy data are simultaneously fit by numerically solving the partial differential equation of particle transport for various magnetic field confirgurations and then performing numerical convolutions to determine the best-fit injection function near the Sun. The data are not well fit for an Archiedean spiral field, a magnetic bottleneck beyond Earth, or particle injection along one legs of a closed magnetic loop. A model with simultaneous injection along both legs of a closed loop proveds the best explanation: particles moving along the near leg make up the spike, those coming from the far leg make up the hump, and trapping the loop accounts for the slow decay of the particle density. The injection of particles near the Sun exhibits a short, strong peak, extended injection at a low level over = 100 minutes, and a sharp cutoff that is probably due to changing magnetic connection to the source. Refuined fits indicate a very low spectral index of turbulence q, a mean free path of 2.2 to 3.3 AU, a loop lengh of 4.1 to 4.6 AU, and escape of relativistic protons from the loop on a time scale of 3 hours. The weak scattering is consistent with reports of weak fluctuations in magnetic loops and other regions other regions of high Alfven speed, while the low q value may indicate a lower correlation length as well. LONG-TERM PROLACTIN EXPOSURE DIFFERENTIALLY STIMULATED THE TRANSCELLULAR AND SOLVENT DRAG- INDUCED CALCIUM TRANSPORT IN THE DUODENUM OF OVARIECTOMIZED RATS (NO. 883) Nateetip Krishnamra, Kukiat Tudpor, and Narattaphol Charoenphandhu Department of Physiology, Faculty of Science, Mahidol University E-mail: scnks@mahidol.ac.th, scnch@mahidol.ac.th Key words : calcium, duodenum, prolactin Faculty of Science Prolactin, having been shown to stimulate transcellular active and solvent drag-induced calcium transport in the duodenum of female rats, was postulated to improve duodenal calcium transport in estrogen-deficient rats. The present study therefore aimed to demonstrate effects of long-term prolactin exposure produced by anterior pituitary (AP) transplantation on the duodenal calcium transport in young (9-week-old) and adult (22-week-old) ovariectomized rats. We found that estrogen deficiency did not alter the transcellular active duodenal calcium transport in both young and adult rats fed with normal calcium diet (1.0% w/w Ca), but the same condition manifested a decrease in the solvent drag-induced duodenal calcium transport from 75.50±10.12 to 55.75±4.77 nmol•hr -1 •cm -2 (P < 0.05) only in adult rats. Long-term prolactin exposure stimulated the transcellular active calcium transport in duodenum of young and adult AP-grafted ovariectomized rats fed with normal calcium diet by more than two-fold from 7.56±0.79 to 16.54±2.05 (P < 0.001), and 9.78±0.72 to 15.99±1.75 (P < 0.001) nmol•hr -1 •cm -2 , respectively. However, only the solvent drag-induced duodenal calcium transport in young rats was enhanced by prolactin from 95.51±10.64 to 163.20±18.03 nmol•hr -1 •cm -2 (P < 0.001) while that in adult rats still showed a decreased flux from 75.50±10.12 to 47.77±5.42 nmol•hr -1 •cm -2 (P < 0.05). Because oral calcium supplement has been widely used to improve calcium balance in estrogen-deficient animals, the effect of high calcium diet (2.0% w/ w Ca) was also investigated. The results showed that stimulatory action of long-term prolactin on the transcellular active duodenal calcium transport in both young and adult rats was diminished after feeding high calcium diet. The same diet also abolished prolactinenhanced solvent drag-induced duodenal calcium transport in young, and further decreased that in adult AP-grafted ovariectomized rats. We concluded that solvent drag-induced duodenal calcium transport in adult rats was decreased after ovariectomy. Long-term prolactin exposure stimulated the transcellular active duodenal calcium transport in both young and adult rats, while enhanced solvent draginduced duodenal calcium transport only in young rats. Effects of prolactin were abolished by high calcium diet. (Supported by the National Center for Genetic Engineering and Biotechnology (BIOTEC, to Prof. Nateetip) and the Thailand Research Fund (TRF, to Prof. Nateetip). PDF created with FinePrint pdfFactory Pro trial version http://www.pdffactory.com
Mahidol University Annual Research Abstracts, Vol. 33 333 SIGNIFICANT EFFECTS OF ESTROGEN ON CARDIAC MYOFILAMENT ACTIVATION UNDER DIABETIC COMPLICATION (NO. 884) Ariyaporn Thawornkaiwong and Jonggonnee Wattanapermpool Department of Physiology, Faculty of Science, Mahidol University. E-mail: tejwt@mahidol.ac.th Key words: estrogen, insulin, diabetes Deficiency of either estrogen (E 2 ) or insulin (Ins) suppresses maximum myofibrillar ATPase activity to the same magnitude but only in ovariectomized (Ovx) hearts demonstrating myofilament Ca 2+ hypersensitivity. Surprisingly, no additive suppression in maximum myofibrillar ATPase activity was observed in diabetic-Ovx (Diab- Ovx) hearts in which the Ca 2+ hypersensitivity was still present. We therefore hypothesized that the two hormones play a similar regulatory mechanism in maximum myofibrillar ATPase activity but E 2 plays a dominant effect on myfilament Ca 2+ sensitivity. To investigate the potential regulatory pathway of the hormones on myofilament activation, relations of %?-myosin heavy chain (?- MHC) and maximum ATPase activity were then examined. Despite the same ratio of ATPase to % ?-MHC detected in Ovx and control groups, the ratio in Diab group was significantly increased. These results indicate an adaptive response of crossbridge interaction in Ins deficient heart which may be resulted from the presentation of E 2 . The same suppression of this ratio in Diab-Ovx hearts indicates beneficial effects of E 2 on cardiac adaptation in Diab rats. Concerning the proposed dominant role of E 2 in myofilament Ca 2+ hypersensitivity, the mobilization of intracellular Ca 2+ by sarcoplasmic reticulum (SR) was then focused. The SR Ca 2+ uptake activity and the expression of SR Ca 2+ ATPase (SERCA) were examined. Surprisingly, deficiency of both Ins and E 2 or of individual hormone caused reductions in both activity and expression of SERCA to the same degree. Thus, the induction in myofilament Ca 2+ hypersensitivity in E 2 deficient hearts may not be due to changes in intracellular Ca 2+ . Alterations in the myofilament apparatus could serve as a potential target for the hormonal regulation. Results from the present study clearly indicate an essential role of E 2 in cardiac myofilament activation especially under diabetic complication. (Supported by the Medical Scholar Program (MSP). CARDIO-PROTECTIVE EFFECTS OF EXERCISE TRAINING ON CHANGES IN SR Ca 2+ UPTAKE ACTIVITY IN OVARIECTOMIZED RATS (NO. 885) Jitanun Laosiripisan and Jonggonnee Wattanapermpool Department of Physiology, Faculty of Science, Mahidol University. E-mail: tejwt@mahidol.ac.th Key words : estrogen, exercise training, SR Ca 2+ uptake, SR Ca 2+ ATPase activity The use of hormone replacement therapy in postmenopausal women has been recently shown to induce many unfavorable effects, including cardiovascular defects, which then urges the studies of other preventive or therapeutic alternatives. In the present study, preventive effects of exercise training on changes in cardiac SR Ca 2+ uptake activity in 10-wk ovariectomized (OVX) rats were tested. A 9-wk running program on a motor-driven treadmill was introduced to the exercise groups one week after surgery. The SR Ca 2+ uptake and SR Ca 2+ -ATPase (SERCA2a) activities were measured using left ventricular homogenate and SR vesicles, respectively. Significant suppressions in both Ca 2+ uptake and SERCA2a activities but increases in Ca 2+ uptake sensitivity were demonstrated in OVX hearts. Immunoblot analysis shows the downregulation of SERCA2a protein in OVX hearts with no change in the expression level of its regulatory protein called phospholamban (PLB). It is the phosphorylation of PLB either at Ser-16 or Thr-17 residues that will release its inhibitory action on SERCA2a. The amounts of these phosphorylated forms of PLB were then analysed using Western blot probing with individual phosphorylated-PLB antibody. There was a significant reduction in phospho-Thr-17-PLB in OVX hearts, in which exercise training could also prevent the change. These results indicate the cardio-protective effects of exercise training on changes in cardiac SR Ca 2+ uptake activities in OVX rats via restoration of both the amount and activity of SERCA2a protein. (Supported by The Thailand Research Fund, Faculty of Science, and Mahidol University) SIGNIFICANCE OF ESTROGEN ON CARDIAC CONTRACTILE ACTIVITY & THE BENEFIT OF PHYTOESTROGENS (NO. 886) Jonggonnee Wattanapermpool Department of Physiology, Faculty of Science, Mahidol University. E-mail: tejwt@mahidol.ac.th Key words: estrogen, cardiac contractile activity, exercise training An important question related to the well recognizable sex difference in the incidence of cardiovascular diseases is the significance of sex hormones on the cardiovascular system especially on the cardiac contractile function. Although the receptors are present in the cardiac myocardium, the regulatory role of estrogen in the cardiac contractile activity is still unclear. A series of experimental studies using ovariectomized rats as a model of estrogen deficiency have demonstrated a significant role of estrogen in regulating the cardiac contractile activity. Changes in the intracellular Ca 2+ in signaling the contraction/relaxation cycle were largely contributed by alterations in Ca 2+ handling process of the cardiac myocytes. Besides hormone replacement therapy, exercise training and phytoestrogens could be other alternative modes for the cardio-protection. (Supported by The Thailand Research Fund, Faculty of Science, and Mahidol University) SECRETION OF CARNITINE IN THE DISTAL CAPUT EPIDIDYMIDIS OF RATS PERFUSED IN VITRO (NO. 887) Chumpol Pholpramool and Kanokporn Poungpong Department of Physiology, Faculty of Science, Mahidol University. E-mail: sccpp@mahidol.ac.th Key words : carnitine transporter, rat epididymis, carnitine PDF created with FinePrint pdfFactory Pro trial version http://www.pdffactory.com
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