• The Korean Journal of Physiology
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• v.30 no.1
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• pp.105-116
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• 1996

Rendering the brain ischemic would evoke the cerebral ischemic reflex which is characterized by an arterial pressor response, apnea and bradycardia. Since the rostral ventrolateral medulla (RVLM) is known to play a key role in the maintenance of normal cardiopulmonary activity, during the cerebral ischemic reflex some cardiac related cells should be excited and respiration related cells inhibited. In this context, the responses of RVLM neurons to systemie and focal hypoxia were analyzed in the present study. Twenty-five adult cats of either sex were anesthetized with ${\alpha}-chloralose$ and the single neuronal activities were identified from RVLM area. For the induction of focal hypoxia in the recording site, sodium cyanide was applied iontophoretically and for systemic hypoxia the animal was ventilated with nitrogen gas for a twenty-second period. Cellular activities were analyzed in terms of their discharge pattern and responses to the hypoxia by using post-stimulus time and single-pass time histograms. Of eighteen cardiac related cells recorded from the RVLM area, twelve cells were excited by iontophoresed sodium cyanide and of twenty-five respiration related cells, fourteen cells were excited by iontophoresed sodium cyanide. Remaining cells were either inhibited or unaffected. Eight of fifteen cells tested with iontophoresed sodium lactate were excited and remaining seven cells were inhibited. Systemic hypoxia induced by nitrogen gas inhalation elevated the arterial blood pressure, but excited, inhibited or unaffected the single neuronal activities. Some cells showed initial excitation followed by inhibition during the systemic hypoxia. Bilateral vagotomy resulted in a decrease of arterial pressor response to the systemic hypoxia, and a slight decrease in the rhythmicity related to cardiac and/or respiratory rhythms. The single neuronal responses to either systemic or focal hypoxia were not affected qualitatively by vagotomy. From the above results, it was concluded that the majority of the cardiac- and respiration- related neurons in the rostral ventrolateral medulla be excited by hypoxia, not through the mediation of peripheral chemoreceptors, and along with the remaining inhibited cells, all these cells be involved in the mediation of cerebral ischemic reflex.

• Clinical and Experimental Pediatrics
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• v.51 no.1
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• pp.93-97
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• 2008

Pheochromocytoma is a rare tumor of childhood, arising from adrenal medullary and chromaffin tissue. Because chronic hypoxia may induce pheochromocytoma, there have been several reports of pheochromocytoma development in cyanotic patients after corrective or palliative cardiac surgery. The variable clinical presentation of pheochromocytoma is obscured by both underlying heart disease and medications. If sudden hypertension, aggravation of a heart condition, or unusual symptoms such as diabetes mellitus develops in a cyanotic patient with congenital heart disease, pheochromocytoma must be ruled out. We report two patients presenting with cyanotic single-ventricle heart disease with pheochromocytoma.

• Korean Journal of Radiology
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• v.20 no.5
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• pp.830-843
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• 2019

Objective: To examine the potential of intravoxel incoherent motion (IVIM) and blood oxygen level-dependent (BOLD) magnetic resonance imaging for detecting renal changes after iodinated contrast-induced acute kidney injury (CI-AKI) development in a diabetic rabbit model. Materials and Methods: Sixty-two rabbits were randomized into 2 groups: diabetic rabbits with the contrast agent (DCA) and healthy rabbits with the contrast agent (NCA). In each group, 6 rabbits underwent IVIM and BOLD imaging at 1 hour, 1 day, 2 days, 3 days, and 4 days after an iohexol injection while 5 rabbits were selected to undergo blood and histological examinations at these specific time points. Iohexol was administrated at a dose of 2.5 g I/kg of body weight. Further, the apparent transverse relaxation rate (R2^*), average pure molecular diffusion coefficient (D), pseudo-diffusion coefficient (D^*), perfusion fraction (f) were calculated. Results: The D and f values of the renal cortex (CO) and outer medulla (OM) were significantly decreased compared to baseline values in the 2 groups 1 day after the iohexol injection (p < 0.05). A marked reduction in the D^* values for both the CO and OM was also observed after 1 hour in each group (p < 0.05). In the OM, a persistent elevation of the R2^* was detected for 4 days in the DCA group (p < 0.05). Histopathological changes were prominent, and the pathological features of CI-AKI aggravated in the DCA group until day 4. The D, f, and R2^* values significantly correlated with the histological damage scores, hypoxia-inducible transcription factor-1α expression scores, and serum creatinine levels. Conclusion: A combination of IVIM and BOLD imaging may serve as a noninvasive method for detecting and monitoring CI-AKI in the early stages in the diabetic kidney.

• Investigative Magnetic Resonance Imaging
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• v.17 no.1
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• pp.19-25
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• 2013

Purpose : Renal blood oxygen level-dependent (BOLD) MRI has been used in the evaluation of renal oxygenation. We tried to provide the normal $R2^*$ value of the human kidney with 3.0 T, and evaluated the differences in $R2^*$ values according to gender and location. Materials and Methods: Twenty-four healthy volunteers underwent BOLD MRI at 3.0 T. Multi gradient echo-echo planar imaging sequence with seventeen echoes was used. After generation of the $T2^*$ map, the $R2^*$ was calculated. The statistical differences in $R2^*$ values between the cortex and medulla, males and females, and the right and left kidney were analyzed. The regional differences of $R2^*$ within the both kidneys were evaluated respectively. Results: BOLD MRI was successful in all participants. No gross artifact interfered with $R2^*$ measurement. The mean $R2^*$ at 3.0 T was $17.1{\pm}2.60s^{-1}$ in the cortex and $27.7{\pm}4.83s^{-1}$ in the medulla (p < 0.001). The $R2^*$ value in the medulla was significantly higher in the male than female volunteers (p = 0.025). There were no statistical differences of $R2^*$ according to the side and location in the kidney (p = 0.197). Conclusion: Renal BOLD MRI can be efficiently performed with 3.0 T MRI. Renal medullary hypoxia is present in normal volunteers. Our results may be used as reference values in the evaluation of pathologic conditions using BOLD MRI.