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H Iida

Publications and source records attributed to H Iida.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Clinical laboratory data and reference intervals standardized in Fukuoka].

In Fukuoka whose population is approximately five million inhabitants, surveys on the accuracy of laboratory data have been performed by the Fukuoka Prefecture Medical Association for the last 30 years. We have been attempting to evaluate the data for routine use since 1988, and it has become possible to share laboratory data between all institutions in Fukuoka prefectures. As a result, reference intervals for 23 clinical chemistry analytes were established in 1995, to which were added in 1996 five serum protein constituents that have been utilized for clinical examinations. Methods for documentations and monitorings the data obtained in the prefecture were also established, standardization of the above analytes extended to 97% of the institutions in the prefecture. Results for 14 of the 23 clinical chemistry analytes have become highly reliable and clinically useful as differences between institutions in terms of results have narrowed. Standardization of other analytes is now in progress.

Aged↗
PubMed2000

yam8(+), a Schizosaccharomyces pombe gene, is a potential homologue of the Saccharomyces cerevisiae MID1 gene encoding a stretch-activated Ca(2+)-permeable channel.

The Saccharomyces cerevisiae MID1 gene encodes a stretch-activated Ca(2+)-permeable channel. In a protein database, we found a Schizosaccharomyces pombe gene whose predicted protein shows 26% identical and 62% similar to the Mid1 channel in amino acid sequence. cDNA derived from this gene, designated yam8(+), was isolated by reverse transcription-polymerase chain reaction (RT-PCR). Further analysis showed that the Yam8 protein consists of 486 amino acids and has 6 hydrophobic segments. The yam8(+) cDNA, placed under the S. cerevisiae TDH3 promoter, partially complemented the mating pheromone-induced death (mid) phenotype of the S. cerevisiae mid1 mutant. The expression of the yam8(+) cDNA in the mid1 mutant cells partially remediated the mid phenotype and resulted in a slight increase in Ca(2+) uptake activity. These findings suggest that Yam8 is a potential homologue of Mid1.

Amino Acid Sequence↗
PubMed2000

Evaluation of bioactive bone cement in canine total hip arthroplasty.

Total hip arthroplasties (THAs) were performed in beagle dogs using a bioactive bone cement (BABC) consisting of a silane-treated apatite- and wollastonite-containing glass-ceramic (AW glass-ceramic) powder and a silica glass powder as the filling particles and a bisphenol-A-glycidyl dimethacrylate-based resin (Bis-GMA-based resin) as the organic matrix. The outcomes were compared with the results of polymethylmethacrylate (PMMA) bone cement. The mechanical properties of the BABC were stronger than those of PMMA bone cement. The bonding strength of the BABC to bone in the dogs' femora increased with time and reached 3.7 MPa at 24 months after implantation whereas that of PMMA bone cement was 2.0 MPa (p < 0.05). Histological examination showed direct bonding between the BABC and the femoral bone for up to 24 months after implantation. However, with PMMA bone cement an intervening soft-tissue layer consistently was observed at the bone-cement interface. Direct bonding at the interface between the BABC and the bone through a calcium phosphorous layer 30 microm-thick was revealed by scanning electron microscopy. Femoral bone resorption was observed at 24 months after implantation in the BABC group, but it was not observed in the PMMA bone cement group. Direct bonding between BABC and the bone may have accelerated femoral bone resorption. Cement fractures of the BABC were observed on the acetabular side 24 months after implantation. Weak bonding between the BABC and an acetabular component made of ultrahigh molecular weight polyethylene (UHMWPE), relatively high elastic characteristics of BABC, and weakness of the calcium phosphorous layer formed on the surface of this cement seemed to lead to failure at 24 months on the acetabular side.

Animals↗
PubMed2000

Localization of a syntaxin isoform, syntaxin 2, to the acrosomal region of rodent spermatozoa.

The acrosome reaction includes a membrane fusion event that is a prerequisite for sperm penetration through the zona pellucida and subsequent fertilization. Since SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins have been shown to be key players in membrane fusion during regulated exocytosis in nerve terminals and secretory cells, and since the acrosome reaction has some features in common with regulated exocytosis, we hypothesized that SNARE proteins might also regulate acrosomal exocytosis. RT-PCR analysis demonstrated the expression of SNARE proteins, three isoforms of syntaxin 2 (2A, 2B, and 2C) and syntaxin 4A, in rat testes. Immunoblot analysis with anti-syntaxin 2 antibody showed that the protein was expressed in rodent spermatozoa, and that it was associated with membrane components of spermatozoa prepared by sucrose density gradient centrifugation. Confocal laser scanning microscopy with double immunolabeling revealed that syntaxin 2 was colocalized with acrin 1, a 90 kDa acrosomal protein, over the acrosomal region of spermatozoa but was not associated with the posterior half of head or tail. Localization of syntaxin 2 over the acrosomal region was supported by the finding that it was shed from sperm heads during an acrosome reaction induced by calcium ionophore A23187 in vitro. In view of the putative role of syntaxin proteins in other membrane fusion systems, these data suggest that syntaxin 2 may be involved in regulating the acrosomal reaction in rodent spermatozoa.

Acrosome↗
PubMed2000

Patient anxiety scores after low-dose ketamine or fentanyl for epidural catheter placement.

PURPOSE: To compare the effect of low-dose ketamine with that of low-dose fentanyl on patient anxiety during the identification of the epidural space and catheterization. METHODS: Sixty patients were randomly assigned to one of three groups: saline group (n=20), saline 2 ml; ketamine group (n=20), 5 mg ketamine; or fentanyl group (n=20), 50 microg fentanyl. Each drug was administered intravenously (iv) five to ten minutes before the epidural procedures began. After epidural catheter placement had been accomplished, anxiety and pain were rated using a visual analog scale. RESULTS: The anxiety scores given for ketamine(20.2 +/- 18.5, mean +/- SD) and fentanyl (24.6 +/- 20.3) were similar, and both were lower than that for saline (44.1 +/- 32.7) (P=0.0034 and 0.0153 vs saline group, respectively). Pain scores were similar for all three groups. A decrease in hemoglobin oxygen saturation during the procedure was only observed in the fentanyl group, and two patients in fentanyl group had SpO2 <90%. CONCLUSION: Ketamine, 5 mg iv, is as effective as 50 microg fentanyl, iv, in alleviating patient anxiety and in providing adequate sedation during the procedures necessary for epidural catheter placement, without inducing severe complications.

Adult↗
PubMed2000

Quantitative assessment of regional myocardial blood flow using oxygen-15-labelled water and positron emission tomography: a multicentre evaluation in Japan.

Recently, a method has been proposed for the quantitative measurement of regional myocardial blood flow (MBF) using oxygen-15-labelled water and positron emission tomography (PET). A multicentre project was organized with the intention of evaluating the accuracy of this method, particularly as a multicentre clinical investigative tool. Each of seven institutions performed PET studies on more than five normal volunteers following a specified protocol. The PET study included a transmission scan, a 15O-carbon monoxide static scan and a 15O-water dynamic scan, thereby yielding MBF values which should have been independent of the spatial resolution of the PET scanner employed. Fifty-three subjects (aged 20-63 years, mean+/-SD 36+/-12 years) were studied at rest, and 31 of these subjects were also studied after dipyridamole in five institutions. Inter-institution consistency and intra-subject variation in MBF values were then evaluated. MBF averaged for all subjects was 0.93+/-0.34 ml min(-1) g(-1) at rest and 3.40+/-1.73 ml min(-1) g(-1) after the administration of dipyridamole, and the flow reserve (defined as the ratio of the two MBF values) was 3.82+/-2.12; these values are consistent with previous reports. Resting MBF values were significantly correlated with the heart rate-blood pressure product (RPP) (y=0.31+6.56E-5x, P<0.010), and RPP was in resting MBF observed in all institutions was well explained by the age-dependent RPP. No significant difference was observed in resting MBF among the institutions. Except in one institution, no significant difference was seen in dipyridamole MBF or myocardial flow reserve. No significant difference was found among the myocardial segments. Regional variation was reasonably small in five institutions, but was not acceptable in two institutions, which was attributed to the scanner performance. These observations suggest that the 15O-water PET technique is useful for a multicentre clinical study if the PET scanner can provide time-activity data with good count statistics.

Coronary Circulation↗
PubMed2000

Prognostic significance of the cell cycle inhibitor p27Kip1 in acute myeloid leukemia.

There are few molecular biologic determinants that are prognostic for patients with acute myeloid leukemia (AML). Hence, we examined whether cellular levels of the cyclin-dependent kinase inhibitor p27Kip1 in acute myeloid leukemia could be used to predict clinical outcome in AML. Using immunoblot analysis, levels of p27 were assessed in blast cells from 72 AML patients who were registered and treated by the identical chemotherapy protocol. AML cases were classified into three groups on the basis of the percentage of the expression level of p27 compared to a control cell line. AML cases exhibiting p27 expression at low, moderate, and high levels were 43, 9, and 20 cases, respectively. No significant differences in the rates of complete remission (CR) were observed among the three groups. Although the level of p27 expression was not correlated with any other possible prognostic markers, such as age, white blood cell count, chromosome abnormalities, and FAB subclasses, patients with high p27 expression had a significantly increased disease-free survival (DFS) (78% vs 19%, P = 0.004). We further examined the expression of cyclin E at the protein level in all 72 AML cases. We observed a statistically significant correlation between a high cyclin E level and a high p27 level (P < 0.005). However, we failed to find any correlation between the rates of CR or DFS and cyclin E expression. The present study reveals that levels of p27 expression can be one of the useful prognostic molecular markers for AML. Leukemia (2000) 14, 28-33.

Acute Disease↗
PubMed2000

Myocardial efficiency during levosimendan infusion in congestive heart failure.

AIMS: Levosimendan, a novel calcium-dependent calcium sensitizer of the myocardial contractile proteins, also enhances diastolic relaxation and induces peripheral vasodilation by opening potassium channels. To assess the combined energetical effects of levosimendan infusion in vivo, we performed positron emission tomography in patients with decompensated chronic heart failure. METHODS AND RESULTS: Eight hospitalized patients with New York Heart Association functional class III or IV heart failure received levosimendan or placebo intravenously in a randomized double-blind cross-over study. During steady-state, dynamic positron emission tomography with [11C]acetate was used to assess myocardial oxygen consumption and [15O]H2O to measure myocardial blood flow. Cardiac performance and dimensions were assessed by pulmonary artery catheterization and echocardiography. Compared with healthy volunteers, myocardial oxygen consumption during placebo was elevated in the right ventricle but comparable in the left ventricle. During administration of levosimendan, cardiac output increased by 32% (P = .002) mainly because of higher stroke volume. Coronary, pulmonary, and systemic vascular resistance values were significantly reduced. Mean myocardial blood flow increased from 0.76 to 1.02 mL/min/g (P = .033). Levosimendan was neutral on myocardial oxygen consumption and left ventricular efficiency, but it improved right ventricular mechanical efficiency by 24% (P = .012). CONCLUSIONS: Levosimendan has an energetically favorable short-term profile in the treatment of congestive heart failure. It enhances cardiac output without oxygen wasting, particularly by improving efficiency in the right ventricle.

Cardiotonic Agents↗
PubMed2000

Profile of a nonylphenol-degrading microflora and its potential for bioremedial applications.

Nonylphenol (NP) is an important intermediate in the production of various commercial and industrial materials, but is also known as a ubiquitous pollutant in urban aquatic environments. We recently studied the NP-degrading activities of microflora in several aquatic environments, and found a notable degrading activity for wastewater from a sewage treatment plant in Tokyo. This result led us to isolate NP-degrading microbes and identify biodegradation products. Using conventional plate culture techniques and molecular biological methods, Pseudomonas and Sphingomonas species, which are known for their degradation activities of many aromatic compounds, have been isolated. But it has also been found that Sphingomonas sp. (S-strain) is necessary and sufficient for the degradation of NP. Although the role of Pseudomonas sp. (P-strain) remains unclear, P-strain seems to provide some co-nutrients for the growth of S-strain. The degradation products were analyzed by GC/MS and NMR. More than 95% of NP was degraded within 10 days and aromatic compounds other than NP were not found, suggesting that the phenolic part of NP was completely degraded. We also examined the potential of S-strain for bioremedial applications. S-strain cells immobilized on chitosan or alginate beads retain their NP-degrading activity in flask-scale experiments. Furthermore, the chitosan-bound cells in a lab-scale bioreactor have been found to be persistent for repeated use, suggesting that S-strain is applicable to the treatment of NP-contaminated wastewater.

Base Sequence↗
PubMed2000

Antinociception by epidural and systemic alpha(2)-adrenoceptor agonists and their binding affinity in rat spinal cord and brain.

UNLABELLED: This study was designed primarily to relate the antinociceptive and hemodynamic effects of clinically available alpha(2)-adrenoceptor agonists to their binding affinity for alpha(2)-adrenoceptors in the spinal cord and brain. In rats with chronic indwelling epidural catheters, the percentage maximal possible effect on tail-flick latency was measured after epidural or IM dexmedetomidine (DXM), clonidine (CL), or tizanidine (TZ) administration. To examine their binding affinities, isolated spinal cord and brain membranes with an alpha(2) agonist were incubated with (3)H-UK14304, a selective alpha(2) agonist, and the radioactivity in the reaction mixtures was measured by liquid scintillation spectrometry. Epidural DXM (0.5-10 microg), CL (10-500 microg), and TZ (5-500 microg) all produced dose-dependent antinociceptive effects; the rank order of potencies was DXM > CL > TZ, the same as for their systemic administration. The antinociceptive effects were blocked by epidural yohimbine. The receptor binding affinities expressed as the concentration that inhibits 50% for spinal cord and brain, respectively, were 0.25 and 1.3 nM (DXM), 10.8 and 12.5 nM (CL), and 48.2 and 96.8 nM (TZ). The changes in arterial blood pressure and heart rate evoked by antinociceptive doses did not correlate with the rank order of antinociceptive potencies. The relative antinociceptive potencies of epidural alpha(2) agonists may depend on their binding affinities to alpha(2)-adrenoceptors in the spinal cord, but their cardiovascular effects may result from actions both inside and outside the central nervous system. IMPLICATIONS: Spinal antinociception caused by the epidural administration of alpha(2) agonists is well correlated with their binding affinity to spinal alpha(2)-adrenoceptors.

Adrenergic alpha-2 Receptor Agonists↗
PubMed2000

Antinociceptive action of epidural K+(ATP) channel openers via interaction with morphine and an alpha(2)- adrenergic agonist in rats.

Potassium (K(+)) channels may play some role in the analgesic actions of mu-opioid agonists and alpha(2)-adrenergic agonists (alpha(2) agonists). We examined whether the adenosine triphosphate-sensitive K(+)(K(+)(ATP)) channel openers, levcromakalim and nicorandil, (given epidurally), might have antinociceptive effects in a tail flick test in adult male Sprague-Dawley rats implanted with a lumbar epidural catheter. The interactions with morphine and an alpha(2) agonist were also examined. The epidural administration of levcromakalim (10 microg, 100 microg) or nicorandil (10 microg, 100 microg) alone did not produce antinociception, but 100 microg levcromakalim or nicorandil did potentiate the antinociceptive effect induced by epidural morphine. Epidural glibenclamide (10 microg), a K(+)(ATP) channel blocker, or naloxone (10 microg) antagonized this potentiation. Systemic administration of levcromakalim or nicorandil (at the same dose as that given into the epidural space) did not potentiate the epidural morphine-induced analgesia. A combination of epidural dexmedetomidine (1 microg) and morphine (1 microg) (each at a subantinociceptive dose) had a significant antinociceptive effect, and epidural glibenclamide (10 microg) partly antagonized this antinociception. These data suggest that levcromakalim and nicorandil potentiate the analgesic action of both morphine and dexmedetomidine, probably via an activation of K(+)(ATP) channels at the spinal cord level.

Adenosine Triphosphate↗
PubMed2000

Characteristics of ropivacaine block of Na+ channels in rat dorsal root ganglion neurons.

UNLABELLED: When used for epidural anesthesia, ropivacaine can produce a satisfactory sensory block with a minor motor block. We investigated its effect on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) currents in rat dorsal root ganglion (DRG) neurons to elucidate the mechanisms underlying the above effects. Whole-cell patch-clamp recordings were made from enzymatically dissociated neurons from rat DRG. A TTX-S Na(+) current was recorded preferentially from large DRG neurons and a TTX-R Na(+) current preferentially from small ones. Ropivacaine shifted the activation curve for the TTX-R Na(+) channel in the depolarizing direction and the inactivation curve for both types of Na(+) channel in the hyperpolarizing direction. Ropivacaine blocked TTX-S and TTX-R Na(+) currents, but its half-maximum inhibitory concentration (IC(50)) was significantly lower for the latter current (116 +/- 35 vs 54 +/- 14 microM; P: < 0.01); similar IC(50) values were obtained with the (R)-isomer of ropivacaine. Ropivacaine produced a use-dependent block of both types of Na(+) channels. Ropivacaine preferentially blocks TTX-R Na(+) channels over TTX-S Na(+) channels. We conclude that because TTX-R Na(+) channels exist mainly in small DRG neurons (which are responsible for nociceptive sensation), such selective action of ropivacaine could underlie the differential block observed during epidural anesthesia with this drug. IMPLICATIONS: Whole-cell patch-clamp recordings of tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neurons showed ropivacaine preferentially blocked tetrodotoxin-resistant Na(+) channels over tetrodotoxin-sensitive Na(+) channels. This could provide a desirable differential sensory blockade during epidural anesthesia using ropivacaine.

Amides↗
PubMed2000

Intrathecal dexmedetomidine attenuates hypercapnic but not hypoxic cerebral vasodilation in anesthetized rabbits.

BACKGROUND: Systemic dexmedetomidine (DXM) attenuates the cerebral vasodilation induced by hypercapnia and decreases the cerebral blood flow response to hypoxia. We determined whether lumbar intrathecal DXM affected the cerebrovascular reactivity to hypercapnia and hypoxia. METHODS: Rabbits (n = 55) anesthetized with pentobarbital were prepared for measurement of pial vessel diameters using a closed cranial window preparation. The first study evaluated the response to hypercapnia after intrathecal administration of DXM (2 microg/kg; n = 7) or normal saline (n = 8). The second evaluated the response to hypercapnia after intrathecal DXM in the presence of yohimbine (20 microg/kg followed by DXM 2 microg/kg; n = 7). The third evaluated the response to mild or moderate hypoxia after intrathecal DXM (2 microg/kg; n = 7) or normal saline (n = 7). The hypercapnic responses were also examined in the presence of systemic DXM (2, 10 microg/kg; n = 6), topical DXM (10-8 m, 10-6 m; n = 6) and of intrathecal clonidine (2 microg/kg; n = 7). RESULTS: The pial arteriolar dilator response to hypercapnia was significantly attenuated after intrathecal administration of DXM. Pretreatment with yohimbine completely blocked the decreased reactivity to hypercapnia. Intrathecal clonidine, although less than DXM, also attenuate the hypercapnic response. Intrathecal DXM did not affect the vasodilation of pial arterioles induced by mild or moderate hypoxia. The systemic DXM 10 microg/kg and topical DXM 10-6 m, but not systemic 2 microg/kg and topical 10-8 m, attenuated hypercapnic vasodilation of pial arterioles. CONCLUSIONS: The presence of alpha2-adrenoceptor agonist administered intrathecally into the lumbar spinal region attenuates hypercapnic but not hypoxic cerebral vasodilation, probably via a stimulation of central alpha2-adrenergic receptors of the central nervous system.

Adjuvants, Anesthesia↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: I. Theory, error analysis, and stereologic comparison.

Limited spatial resolution of positron emission tomography (PET) can cause significant underestimation in the observed regional radioactivity concentration (so-called partial volume effect or PVE) resulting in systematic errors in estimating quantitative physiologic parameters. The authors have formulated four mathematical models that describe the dynamic behavior of a freely diffusible tracer (H215O) in a region of interest (ROI) incorporating estimates of regional tissue flow that are independent of PVE. The current study was intended to evaluate the feasibility of these models and to establish a methodology to accurately quantify regional cerebral blood flow (CBF) corrected for PVE in cortical gray matter regions. Five monkeys were studied with PET after IV H2(15)O two times (n = 3) or three times (n = 2) in a row. Two ROIs were drawn on structural magnetic resonance imaging (MRI) scans and projected onto the PET images in which regional CBF values and the water perfusable tissue fraction for the cortical gray matter tissue (hence the volume of gray matter) were estimated. After the PET study, the animals were killed and stereologic analysis was performed to assess the gray matter mass in the corresponding ROIs. Reproducibility of the estimated parameters and sensitivity to various error sources were also evaluated. All models tested in the current study yielded PVE-corrected regional CBF values (approximately 0.8 mL x min(-1) x g(-1) for models with a term for gray matter tissue and 0.5 mL x min(-1) x g(-1) for models with a term for a mixture of gray matter and white matter tissues). These values were greater than those obtained from ROIs tracing the gray matter cortex using conventional H2(15)O autoradiography (approximately 0.40 mL x min(-1) x g(-1)). Among the four models, configurations that included two parallel tissue compartments demonstrated better results with regards to the agreement of tissue time-activity curve and the Akaike's Information Criteria. Error sensitivity analysis suggested the model that fits three parameters of the gray matter CBF, the gray matter fraction, and the white matter fraction with fixed white matter CBF as the most reliable and suitable for estimating the gray matter CBF. Reproducibility with this model was 11% for estimating the gray matter CBF. The volume of gray matter tissue can also be estimated using this model and was significantly correlated with the results from the stereologic analysis. However, values were significantly smaller compared with those measured by stereologic analysis by 40%, which can not be explained by the methodologic errors. In conclusion, the partial volume correction was essential in quantitation of regional CBF. The method presented in this article provided the PVE-corrected regional CBF in the cortical gray matter tissue. This study also suggests that further studies are required before using MRI derived anatomic information for PVE correction in PET.

Animals↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: II. Normal values and gray matter blood flow response to visual activation.

One of the most limiting factors for the accurate quantification of physiologic parameters with positron emission tomography (PET) is the partial volume effect (PVE). To assess the magnitude of this contribution to the measurement of regional cerebral blood flow (rCBF), the authors have formulated four kinetic models each including a parameter defining the perfusable tissue fraction (PTF). The four kinetic models used were 2 one-tissue compartment models with (Model A) and without (Model B) a vascular term and 2 two-tissue compartment models with fixed (Model C) or variable (Model D) white matter flow. Furthermore, rCBF based on the autoradiographic method was measured. The goals of the study were to determine the following in normal humans: (1) the optimal model, (2) the optimal length of fit, (3) the model parameters and their reproducibility, and (4) the effects of data acquisition (2D or 3D). Furthermore, the authors wanted to measure the activation response in the occipital gray matter compartment, and in doing so test the stability of the PTF, during perturbations of rCBF induced by visual stimulation. Eight dynamic PET scans were acquired per subject (n = 8), each for a duration of 6 minutes after IV bolus injection of H2(15)O. Four of these scans were performed using 2D and four using 3D acquisition. Visual stimulation was presented in four scans, and four scans were during rest. Model C was found optimal based on Akaike's Information Criteria (AIC) and had the smallest coefficient of variance after a 6-minute length of fit. Using this model the average PVE corrected rCBF during rest in gray matter was 1.07 mL x min(-1) x g(-1) (0.11 SD), with an average coefficient of variance of 6%. Acquisition mode did not affect the estimated parameters, with the exception of a significant increase in the white matter rCBF using the autoradiographic method (2D: 0.17 mL x min(-1) x g(-1) (0.02 SD); 3D: 0.21 mL x min(-1) x g(-1) (0.02 SD)). At a 6-minute fit the average gray matter CBF using Models C and D were increased by 100% to 150% compared with Models A and B and the autoradiographic method. There were no significant changes in the perfusable tissue fraction by the activation induced rCBF increases. The largest activation response was found using Model C (median = 39.1%). The current study clearly demonstrates the importance of PVE correction in the quantitation of rCBF in normal humans. The potential use of this method is to cost-effectively deliver PVE corrected measures of rCBF and tissue volumes without reference to imaging modalities other than PET.

Adult↗
PubMed2000

Regional differences in cerebral vascular response to PaCO2 changes in humans measured by positron emission tomography.

Hypercapnia and hypocapnia produce cerebral vasodilation and vasoconstriction, respectively. However, regional differences in the vascular response to changes in Paco2 in the human brain are not pronounced. In the current study, these regional differences were evaluated. In each of the 11 healthy subjects, cerebral blood flow (CBF) was measured using 15O-water and positron emission tomography at rest and during hypercapnia and hypocapnia. All CBF images were globally normalized for CBF and transformed into the standard brain anatomy. t values between rest and hypercapnia or hypocapnia conditions were calculated on a pixel-by-pixel basis. In the pons, cerebellum, thalamus, and putamen, significant relative hyperperfusion during hypercapnia was observed, indicating a large capacity for vasodilatation. In the pons and putamen, a significant relative hypoperfusion during hypocapnia, that is, a large capacity for vasoconstriction, was also observed, indicating marked vascular responsiveness. In the temporal, temporo-occipital, and occipital cortices, significant relative hypoperfusion during hypercapnia and significant relative hypoperfusion during hypocapnia were observed, indicating that cerebral vascular tone at rest might incline toward vasodilatation. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve by hypercapnia and in the correction of CBF measurements for variations in subjects' resting Paco2.

Aged↗