Sequential V(A)/Q distributions in the normal rabbit by micropore membrane inlet mass spectrometry.
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We developed micropore membrane inlet mass spectrometer (MMIMS) probes to rapidly measure inert-gas partial pressures in small blood samples. The mass spectrometer output was linearly related to inert-gas partial pressure (r(2) of 0.996-1.000) and was nearly independent of large variations in inert-gas solubility in liquid samples. We infused six inert gases into five pentobarbital-anesthetized New Zealand rabbits and used the MMIMS system to measure inert-gas partial pressures in systemic and pulmonary arterial blood and in mixed expired gas samples. The retention and excretion data were transformed into distributions of ventilation-to-perfusion ratios (V(A)/Q) with the use of linear regression techniques. Distributions of V(A)/Q were unimodal and broad, consistent with prior reports in the normal rabbit. Total blood sample volume for each VA/Q distribution was 4 ml, and analysis time was 8 min. MMIMS provides a convenient method to perform the multiple inert-gas elimination technique rapidly and with small blood sample volumes. (+info)
Production and characteristics of 125Xe: a new noble gas for in vivo studies.
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Radionuclides of the noble gases are extensively used to assess ventilation and blood flow in clinical and investigative studies. Xenon-133 is most commonly used but is not optimal for these in vivo studies. Xenon-125 has better physical characteristics and can be produced with a cyclotron by a 127I(p,3n)125Xe reaction; this reaction results in a maximum of 25 mCi/gm/cm2/muA-hr for 31-MeV protons. Under actual production conditions, 11 mCi/muA-hr were collected. Xenon-125 decays by electron capture with a 17.2-hr half-life and contributes less radiation per dose of radioactivity than 133Xe. The radiation dose to the lungs from 133Xe and 125Xe is 5.0 and 1.8 mrads/mCi-min, respectively. The radiation dose per usable photon for 125Xe is only 0.3 of 133Xe. The principal photons of 125Xe, 188 keV (55%) and 243 keV (29%), are more intense and are in an energy range that is more advantageous for imaging than the 81 keV (35%) of 133Xe. These physical properties of 125Xe result in better spatial resolution at the same information density and with less radioactivity administered to the patient. Phantom studies showed that 12.7-, 9.5-, and 6.4-mm lead bars were resolved with 125Xe using a 410- keV diverging collimator wheras only the 12.7- and 9.k-mm lead bars were resolved using 133Xe and either a 410-keV or 140keV diverging collimator. (+info)
Comparison of 85krypton and 133xenon cerebral blood flow measurements before, during, and following focal, incomplete ischemia in the squirrel monkey.
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A comparison of regional cerebral blood flow measurements made with beta- and gamma-emitting isotopes revealed good correspondence in areas of normal perfusion and reactive hyperemia but poor correspondence in areas of focal ischemia. After middle cerebral artery occlusion at normocapnia, there was a 65% reduction in regional cerebral blood flow from 1.40 plus or minus 0.27 ml/g min--1 to 0.49 plus or minus 0.10 ml/g min--1 in monkeys studied with 85Kr but only a 27% reduction in regional cerebral blood flow from 0.84 plus or minus 0.09 ml/g min--1 to 0.61 plus or minus 0.08 ml/g min--1 in monkeys studied with 133Xe. The lack of correlation within areas of focal, incomplete ischemia was attributed to an impairment of isotope delivery to the area of ischemia coupled with the inherent lack of spatial resolution of determinations made with 133Xe. This finding may partly explain the numerous discrepancies in experimental and clinical studies of the effects of alterations in the arterial partial pressure of CO2 on regional cerebral blood flow in areas of ischemia; it may also explain the failure of such studies to reflect the true severity of focal ischemia. (+info)
Variations in right and left coronary blood flow in man with and without occlusive coronary disease.
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The relation of angiographically recognized coronary occlusion to regional myocardial blood flow has not been studied adequately in spite of its clinical significance. This is particularly important, as revascularization procedures, based on angiographic studies, are being performed with increasing frequency. To compare the severity of reduction in flow to the severity of coronary occlusion, regional myocardial blood flow (85-Kr washout) was measured in 34 patients. Selective coronary anteriograms were obtained using the Sones technique, and occlusions were graded as a percentage of luminal diameter. Of 26 right coronary arteries for which satisfactory arteriograms and coronary blood flow measurements were obtained, 16 were normal and 10 had significant stenosis (greater than 50%). Dominant right coronary arteries appeared to have high flows (67 plus or minus 6 ml min-minus1 per 100 g muscle) and a greater incidence of occlusion (10 of 20) than nondominant arteries, which had less flow (41 plus or minus 2 ml min-minus1 per 100 g muscle) and a lower incidence of occlusion (1 of 8). Coronary blood flow in 16 normal left coronary arteries was 84 plus or minus 5 ml min-minus1 per 100 g muscle and in 15 with 50 per cent or greater occlusion, 68 plus or minus 3 ml min-minus1 per 100 g muscle. Though coronary blood flow appeared reduced when lesions of both the right and left coronary arteries were present, a critical reduction was seen only when occlusion was greater than 90 per cent. (+info)
Factors affecting the cerebrovascular response to noradrenaline in the dog.
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1 Noradrenaline infused into the internal carotid artery of the dog (0.01-1 mug kg(-1) min(-1)) constricts the blood vessels of the cortex. This constriction is mediated by the action of noradrenaline on alpha-adrenoceptors of the cerebral arteries.2 Intravenous (1 mug kg(-1) min(-1)) or intra common carotid arterial (0.01-1 mug kg(-1) min(-1)) infusions of noradrenaline cause an increase in cortical blood flow that can be dissociated from changes in blood pressure.3 The effect of intravenous noradrenaline on the cortical blood vessels and metabolism is blocked by high PaCO(2) levels, or by the prior administration of (+/-)-propranolol. (+)-Propranolol is without such effect.4 Following section of both vagi and both sinus nerves, intravenous noradrenaline fails to cause an increase in cortical blood flow.5 In another series of animals the area of the carotid bifurcation was vascularly isolated and perfused with blood from a second dog. Chemoreceptor and baroreceptor activity was shown to be intact.6 Administration of 5% CO(2) to the donor dog caused an increase in cerebral blood flow in the recipient dog.7 Administration of intravenous noradrenaline (1.0 mug kg(-1) min(-1)) to the donor animal caused an increase in cerebral blood flow, cerebral O(2) and glucose utilization of the recipient.8 Administration of 5% CO(2) and intravenous (-)-noradrenaline (1.0 mug kg(-1) min(-1)) caused a further increase in flow and metabolism.9 This evidence suggests that the cerebrovasodilatation observed following intravenous noradrenaline is reflex and is triggered by chemoreceptor activity.10 The evidence also suggests that the antagonism of the cortical dilatory effects of intravenous noradrenaline by raised PaCO(2) in the intact animal must be at a site different from the peripheral chemoreceptors. (+info)
Assessment of regional ventilation by continuous inhalation of radioactive krypton-81m.
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A simple technique is described for producing high-quality functional images of regional ventilation during physiological tidal breathing of the inert gas 81mKr. These images are quickly obtained on a gamma-camera without the need of computerized systems for data acquisition and display and are directly comparable with those of perfusion obtained with 99mTc-labelled macroaggregates. The short time required for the procedure, its simplicity, and the extremely low absorbed-radiation dose enable serial images of ventilation to be obtained in multiple views. (+info)
Brain-blood partition coefficients of 85Krypton at 37 C and 29.5 C.
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To permit utilization of the Kety-Schmidt technique for measuring cerebral blood flow during hypothermia, the brain-blood partition coefficients for 85krypton at 37 C and 29.5 C were determined in a series of cats. At 37 C the partition coefficient for 85krypton was 1.092 +/- 0.009; it was 0.931 +/- 0.007 (SE) at 29.5 C. These values were significantly different from each other (P less than .001). (+info)
Analysis of violet-excited fluorochromes by flow cytometry using a violet laser diode.
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BACKGROUND: Low power violet laser diodes (VLDs) have been evaluated as potential replacements for water-cooled argon-ion and krypton-ion ultraviolet and violet lasers for DNA content analysis using the Hoechst dyes and 4,6-diamidino-2-phenylindole (Shapiro HMN, Perlmutter NG: Cytometry 44:133-136, 2001). In this study, we used a VLD to excite a variety of violet-excited fluorescent molecules important in biomedical analysis, including the fluorochromes Cascade Blue and Pacific Blue, the expressible fluorescent protein cyan fluorescent protein (CFP), and the fluorogenic alkaline phosphatase (AP) substrate 2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazoline (ELF-97; for endogenous AP detection and cell surface labeling with AP-conjugated antibodies). METHODS: Comparisons were made between VLD excitation and a krypton-ion laser emitting at 407 nm (both at higher power levels and with the beam attenuated at levels approximating the VLD) on the same FACSVantage SE stream-in-air flow cytometer. We evaluated a Power Technology 408-nm VLD (30 mW) equipped with circularization optics (18 mW maximum output, set to 15 mW) and a Coherent I-302C krypton-ion laser emitting at power levels ranging from 15 to 75 mW. RESULTS: Cascade Blue, Pacific Blue, and CFP showed comparable signal-to-noise ratios and levels of sensitivity with VLD excitation versus the krypton-ion laser at high and VLD-matched power outputs. Multicolor fluorescent protein analysis with 488-nm excitation of green fluorescent protein and DsRed and VLD excitation of CFP was therefore feasible and was demonstrated. Similar levels of excitation efficiency between krypton-ion and VLD sources also were observed for ELF-97 detection. CONCLUSIONS: These evaluations confirmed that VLDs may be cost- and maintenance-effective replacements for water-cooled gas lasers for applications requiring violet excitation in addition to DNA binding dyes. (+info)