Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epileptogenic foci were created by topical application of penicillin to the cerebral cortex in 40 paralyzed and artificially ventilated cats receiving halothane anesthesia. The animals were divided into two equal groups to compare primary and secondary foci. The following variables were recorded at normocapnia, hypocapnia, and hypercapnia prior to and during seizure activity: cerebral blood flow (CBF), determined by clearance of xenon 133; cortical redox states, measured by the fluorescence of reduced pyridine nucleotides (PN); brain pH, measured using a lipid-soluble, pH-sensitive fluorescent indicator; and electroencephalograms (EEG). Mean arterial blood pressure, arterial pH, arterial carbon dioxide tension (PaCO2), and arterial oxygen tension (PaO2) were monitored in each animal. All animals had a normal PaCO2-CBF response prior to the creation of a seizure focus, assuring the presence of autoregulation and normal metabolic function. CBF increased equally with seizures in the primary and secondary hemispheres. The relative increase was related to the PaCO2 but approximated 68% at normocapnia. There was an alteration in the PaCO2-CBF response with seizures, but the ability of the cerebral vasculature to constrict and dilate with hypocapnia and hypercapnia was retained. There was no significant difference in the reduced PN signal with variations in PaCO2 prior to seizures, but there was an apparent 10 to 15% fall with seizures. The "equivalent" intracellular pH fell to 6.94 at normocapnia in the primary focus but remained essentially unchanged from the control value of 7.10 in the secondary focus. These differences in pH were consistent with the greater degree of seizure activity observed in the primary focus. We conclude that a nonhypoxic acidosis existed in the primary focus and that changes in CBF were not related to it because the CBF changed equally in both hemispheres.
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PMID:Correlation of intracellular redox states and pH with blood flow in primary and secondary seizure foci. 678 36

Bright-field and dark-field illumination techniques for in vivo measurements of reduced pyridine nucleotide fluorescence were compared in 15 rats during periods of normocapnia, hypocapnia, hypercapnia, and anoxia. Parameters investigated included fluorescence, cortical reflectance, cortical blood flow, and electroencephalograms. In normal brain, with preserved autoregulation, reduced pyridine nucleotide fluorescence was constant through a wide range in Pa(CO2), cortical blood flow, and cerebral blood volume in animals studied using vertical illumination (bright-field) techniques. There was a marked increase in reduced pyridine nucleotide fluorescence at death from anoxia. Artifacts were reduced by monochromators for excitation, emission, and reflected light; low-intensity vertical excitation energy and high-sensitivity recording instrumentation; and a small avascular (123 microns) field. Potential sources of error include photodecomposition, hemoglobin interference from absorption and reflectance, and light scattering. Vertical excitation techniques using a small field appeared to give more reliable and reproducible results than circumferential techniques using a larger field of observation.
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PMID:Comparison of dark-field and bright-field incident illumination for in vivo measurements of reduced pyridine nucleotides. 976 36