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Biomedical subjects

Andrew Tong

Publications and source records attributed to Andrew Tong.

6 recordsLinked to original sources
PubMed2006

D2-class dopamine receptor inhibition of NMDA currents in prefrontal cortical neurons is platelet-derived growth factor receptor-dependent.

NMDA receptor function is modulated by both G-protein-coupled receptors and receptor tyrosine kinases. In acutely isolated rat hippocampal neurons, direct activation of the platelet-derived growth factor (PDGF) receptor or transactivation of the PDGF receptor by D4 dopamine receptors inhibits NMDA-evoked currents in a phospholipase C (PLC)-dependent manner. We have investigated further the ability of D2-class dopamine receptors to modulate NMDA-evoked currents in isolated rat prefrontal cortex (PFC). We have demonstrated that, similar to isolated hippocampal neurons, the application of PDGF-BB or quinpirole to isolated PFC neurons induces a slow-onset and long-lasting inhibition of NMDA-evoked currents. However, in contrast to hippocampal neurons, the inhibition of NMDA-evoked currents by quinpirole in PFC neurons is dependent upon D2/3, rather than D4, dopamine receptors. In PFC slices, application of both PDGF-BB and quinpirole induced a phosphorylation of the PDGF receptor at the PLCgamma binding and activation site, Tyr1021. The PDGF receptor kinase inhibitor, tyrphostin A9, and the D2/3 dopamine receptor antagonist, raclopride, inhibited quinpirole-induced Tyr1021 phosphorylation. These finding suggest that quinpirole treatment inhibits NMDAR signaling via PDGF receptor transactivation in both the hippocampus and the PFC, and that the effects of quinpirole in these regions are mediated by D4 and D2/3 dopamine receptors, respectively.

Animals↗
PubMed2005

Allergic rhinitis and ear pain in flight.

BACKGROUND: Ear pain is the most common physiologic incident in hypobaric chamber training in the Japan Air Self-Defense Force, and the incidence of ear pain has been gradually increasing. There has been a concomitant increase in the incidence of allergic rhinitis in Japan. We hypothesized that the increased incidence of ear pain may be due to the increased incidence of eustachian tube dysfunction associated with allergic rhinitis. OBJECTIVE: To explore whether there is an association between allergic rhinitis and ear pain experienced in hypobaric chamber training. METHODS: We examined 9 years of training records and noted whether there was a seasonal influence on the occurrence of ear pain in 7047 trainees. In addition, we studied the prevalence of allergic rhinitis among trainees during a representative training year using a questionnaire method, noting association between allergic rhinitis and the occurrence of ear pain. RESULTS: Comprehensive review of training records showed 429 (6.1%) of 7047 trainees complained of ear pain. Ear pain occurred more often in spring than the other 3 seasons. The questionnaire data showed 202 (23.0%) of 878 trainees had allergic rhinitis. Trainees with allergic rhinitis complained of ear pain more often in the spring than trainees without allergic rhinitis. CONCLUSIONS: Active allergic rhinitis is closely associated with the occurrence of ear pain in hypobaric chamber training. A similar phenomenon might occur in an actual flight. Special attention should be paid to not only common cold but also allergic rhinitis in both hypobaric chamber training and actual flights.

Aerospace Medicine↗
PubMed2003

Cerebral infarction in a 24-year-old pilot.

Ischemic stroke is a rare event in young adults. We report on a 24-yr-old pilot with cerebral infarction of undetermined etiology, temporally associated with chain smoking. The patient exhibited dysphasia, stupor (confused consciousness), and right facial-nerve palsy. Computed-tomography revealed a low-density area in the left insular cortex. Cerebroangiography showed severe stenosis in a branch of the left middle cerebral artery. After admission, the patient made a rapid and uneventful recovery within 72 h. MRI showed an area of hyperintensity on T2-weighted images 2 mo after the attack. Based on the hyperintense area on FLAIR (fluid attenuated inversion recovery sequence) images obtained in MRI performed 10 mo after the attack, we diagnosed a cerebral infarction. In the Japan Air Self-Defense Force, cerebral infarction is an aeromedically disqualifying condition. However, in the evaluation 2 mo after the attack, differentiation from reversible ischemic neurological deficit was difficult. We discuss the criteria used for diagnosis and the risk factors for cerebral infarction in young adults, as well as the aeromedical disposition of young pilots.

Adult↗
PubMed2002

Physiological incidents during 39 years of hypobaric chamber training in Japan.

BACKGROUND: Hypobaric chamber training for military aircrew is very important for flight safety. Since we began hypobaric training in our laboratory in 1960, some trainees have suffered physiological incidents. This study will characterize the physiological incidents during hypobaric chamber training at the Japan Air Self-Defense Force (JASDF). METHODS: All available training records from 1960-1998 were reviewed and the frequency of physiological incidents counted and analyzed. RESULTS: There were 29,677 trainees and 58,454 exposures. Overall frequency of physiological incidents was 6.3%. Physiological incidents included ear pain, paranasal sinus pain, abdominal pain, hypoxia, hyperventilation, joint pain, and toothache. Decompression sickness (DCS-I, simple joint pain only) was rare. In cases of DCS-I, joint pain was easily relieved with controlled descent. During the last three decades, overall prevalence of physiological incidents has gradually increased from 5.3 to approximately 6.1% before 1991, to 6.8-9.9% after 1991. However, prevalence rate showed no change through out the period when ear pain was factored out. The increase in prevalence was entirely due to an increased frequency of ear pain: 3.6 to approximately 4.6% before 1991, and 5.4 to approximately 7.2% after 1991. CONCLUSIONS: DCS has not been a problem in the JASDF hypobaric chamber training experience. The majority of physiological incidents during hypobaric chamber training in JASDF have been ear pain, a minor but frequent obstacle to hypobaric training. The exact cause of the observed increase in frequency of Eustachian tube dysfunction currently remains unclear.

Adult↗
PubMed2002

Pilot cerebral oxygen status during air-to-air combat maneuvering.

BACKGROUND: Successful monitoring of in-flight cerebral oxygen status (COS; cerebral hemoglobin concentration changes and oxygenation changes under dynamic flight conditions) was recently achieved using near-infrared spectroscopy (NIRS). In this study, we examined the effects of air-to-air combat maneuvering on COS. METHOD: Six F-15 fighter pilots performed 2-vs.-1 air-to-air combat one to three times in each of eight sorties. We took continuous measurements of the pilots' in-flight COS using a commercial NIRS system. We measured the direct effects of G-forces on COS as evidenced by relative concentrations of oxy- and deoxy-hemoglobin. RESULTS: With respect to the G-levels reached during air combat maneuvering (Gz range of -0.4 to + 9.5), oxyhemoglobin concentration (O2Hb) and tissue oxygenation index (TOI, the ratio of oxygenated to total tissue hemoglobin) decreased with increasing G-forces during aerial combat maneuver (ACM). Maximum changes in relative O2Hb ranged from -4.2 to -26 micromol x L(-1). Subjects' experience as measured by total fighter time was an independent determinant of the magnitude of decrease in relative oxygenation. CONCLUSIONS: 1. Pilots' COS declined with dynamic G-forces experienced under aerial combat conditions. 2. Fighter pilots with more flying hours maintained a higher cerebral oxygen level at the same level of G-forces than pilots with less flying time. 3. NIRS technology in the form of the NIRO-300G has matured for continuous monitoring of in-flight cerebral oxygen status under vigorous field conditions.

Adult↗