Biomedical subjects

P Vainio

Publications and source records attributed to P Vainio.

At least 19 recordsLinked to original sources

PubMed2003

Three-dimensional respiratory-gated coronary MR angiography with reference to X-ray coronary angiography.

PURPOSE: To assess the clinical value of three-dimensional coronary MR angiography (CMRA) in the detection of significant coronary artery stenosis using conventional X-ray angiography as the standard reference. MATERIAL AND METHODS: Sixty-nine patients underwent X-ray coronary angiography and CMRA because of suspected or previously diagnosed coronary artery disease. MRI was performed with a 1.5-T whole body imaging system using ECG-triggered 3D gradient echo sequence with retrospective navigator echo respiratory gating and fat suppression. RESULTS: A total of 276 coronary artery segments were analyzed. The X-ray coronary angiography was normal in 22 patients. Significant proximal stenoses (exceeding 50%) or occlusions were present in 102 coronary artery segments. In all, 120 stenoses or occlusions were identified in CMRA. Sixteen percent of the coronary artery segments had to be excluded because of poor image quality. The overall sensitivity and specificity for MRA for identification of significant stenosis were 75% and 62%, respectively. CMRA correctly detected 89% of patients with at least one vessel disease, but 6 patients with coronary artery disease would have been missed. CONCLUSIONS: Because of the high data exclusion and false- negative case rate, CMRA with retrospective navigator echo triggering is at present not suitable as a clinical screening method in coronary artery disease.

Adult↗

PubMed2001

Diffusion and perfusion MR imaging in acute ischemic stroke: a comparison to SPECT.

Diffusion (DWI) and perfusion (PWI) magnetic resonance imaging are relatively new methods of clinical imaging that probably can detect infarcted (DWI) and hypoperfused but still salvageable tissue (PWI) in acute human stroke. Forty-six acute stroke patients were imaged within 24 h of ictus, on the second day and after a week. SPECT was also performed on 23 patients in the acute phase (first or second day). On the first day, mean volume of hypoperfused tissue was significantly greater (P<0.001) than the infarcted tissue. The initial hypoperfusion volume correlated significantly with the final infarct size (P<0.001). The initial perfusion-diffusion mismatch correlated significantly with the infarct growth (P< or =0.001). The hypoperfusion volumes measured from PWI and SPECT correlated significantly (P<0.001). In conclusion, combined DWI and PWI is a powerful tool in evaluating the hemodynamics of acute ischemic stroke and can predict the infarct growth during 1 week.

Aged↗

PubMed2001

Transthoracic three-dimensional echocardiography is as good as magnetic resonance imaging in measuring dynamic changes in left ventricular volume during the heart cycle in children.

AIMS: The purpose of the study was to assess the dynamic changes in left ventricular (LV) volume by transthoracic three-dimensional echocardiography (3DE) and to compare the results with those obtained by magnetic resonance imaging (MRI). METHODS AND RESULTS: Thirty healthy children were studied by digitized 3DE and Doppler, and by MRI. Three-dimensional echocardiography of LV was performed by using rotational acquisition from the transthoracic apical view with ECG gating and without respiratory gating. The acquisition of 3DE data took 10-15s. Three-dimensional echocardiography gave similar values to MRI for EDV, ESV and LVM measurements, and the results correlated well. Peak emptying rates by 3DE and MRI were -236.6 and -169.6ml/s and peak filling rates were 215.0 and 215.9ml/s, respectively. Dynamic changes of LV volumes during the heart cycle were detectable with both methods. CONCLUSION: Digitized 3DE performed in the outpatient clinic and MRI were both useful methods for studying the physiological volume changes in left ventricle in children. These methods may be used for further study of the systolic and diastolic function of the left ventricle in various clinical conditions.

Adolescent↗

PubMed2001

MR urography in evaluation of acute flank pain: T2-weighted sequences and gadolinium-enhanced three-dimensional FLASH compared with urography. Fast low-angle shot.

OBJECTIVE: The aim of this study was to compare the usefulness of breath-hold heavily T2-weighted sequences with gadolinium-enhanced three-dimensional fast low-angle shot (3D FLASH) MR urography in the evaluation of patients with acute flank pain. SUBJECTS AND METHODS: Forty consecutive patients with symptoms of acute flank pain underwent MR urography followed immediately by excretory urography. Heavily T2-weighted (combined thin-slice half-Fourier acquisition single-shot turbo spin-echo [HASTE] and thick-slab single-shot turbo spin-echo) and 3D FLASH sequences were evaluated separately and independently by two experienced radiologists for the presence, cause, level, and degree of obstruction. Interobserver agreement was calculated using the kappa statistic. Excretory urography and the final clinical diagnosis were used as reference. RESULTS: Twenty-six patients were found to have unilateral obstruction caused by ureteral stones. Both MR urography methods were excellent for detecting obstruction. In the detection of stones 3D FLASH was superior, with a sensitivity of 96.2% and 100% and specificity of 100% and 100% for observers A and B, respectively, compared with a sensitivity of 57.7% and 53.8% and a specificity of 100% and 100%, respectively, for T2-weighted sequences. The best degree of obstruction was seen with 3D FLASH, and the interobserver agreement was excellent for stone detection (kappa = 0.97). CONCLUSION: T2-weighted sequences alone are not sufficient for examining patients with acute flank pain. However, the combined use of both T2-weighted and 3D FLASH sequences will ensure better confidence in the evaluation of acute suspected renal colic. MR urography can replace conventional excretory urography when the latter is contraindicated or undesirable.

Acute Disease↗

PubMed2001

MR volumetry of the entorhinal, perirhinal, and temporopolar cortices in drug-refractory temporal lobe epilepsy.

BACKGROUND AND PURPOSE: The occurrence of damage in the entorhinal, perirhinal, and temporopolar cortices in unilateral drug-refractory temporal lobe epilepsy (TLE) was investigated with quantitative MR imaging. METHODS: Volumes of the entorhinal, perirhinal, and temporopolar cortices were measured in 27 patients with unilateral drug-refractory TLE, 10 patients with extratemporal partial epilepsy, and 20 healthy control subjects. All patients with TLE were evaluated for epilepsy surgery and underwent operations. RESULTS: In left TLE, the mean volume of the ipsilateral entorhinal cortex was reduced by 17% (P <.001 compared with control subjects) and that of the ipsilateral temporopolar cortex by 17% (P <.05). In right TLE, the mean ipsilateral entorhinal volume was reduced by 13% (P < or =.01), but only in patients with hippocampal atrophy. Asymmetry ratios also indicated ipsilateral cortical atrophy. When each patient was analyzed individually, the volume of the ipsilateral hippocampus was reduced (> or = 2 SD from the mean of controls) in 63% and that of the entorhinal cortex in 52% of patients with TLE. Furthermore, ipsilateral entorhinal (left: r = 0.625, P <.001; right: r = 0.524, P < or =.01), perirhinal (left: r = 0.471, P <.05), and temporopolar (right: r = 0.556, P <.01) volumes correlated with ipsilateral hippocampal volumes. There was no association, however, with clinically or pathologically identified causes of epilepsy, duration of epilepsy, or age at onset of epilepsy. Mean cortical volumes were unaffected in extratemporal partial epilepsy. CONCLUSION: Subpopulations of patients with unilateral TLE have ipsilateral damage in the entorhinal and temporopolar cortices. The damage is associated with hippocampal damage.

Adolescent↗

PubMed2000

[11 C]Flumazenil binding in the medial temporal lobe in patients with temporal lobe epilepsy: correlation with hippocampal MR volumetry, T2 relaxometry, and neuropathology.

OBJECTIVE: To detect reduced [11C]flumazenil in patients with temporal lobe epilepsy (TLE) and to relate binding to histopathology. METHODS: The authors studied 16 patients who underwent epilepsy surgery because of drug-resistant TLE using [11C]flumazenil PET and quantitative MRI. In 12 patients, resected hippocampus was available for histologic analysis. [11C]Flumazenil binding potential (fitted BP) was assessed with the simplified reference tissue model. RESULTS: [11C]Flumazenil fitted BP in the medial temporal lobe was reduced in all patients with abnormal hippocampal volumetry or T2 relaxometry on MRI. Fitted BP was also reduced in 46% of the patients with hippocampal volume within the normal range and in 38% of patients with less than 2 SD T2 prolongation. In all MRI-negative/PET-positive patients, the histologic analysis verified hippocampal damage. Also, [11C]flumazenil fitted BP correlated with the severity of reduced hippocampal volume, T2 prolongation, and histologically assessed neuronal loss and astrogliosis. CONCLUSION: [11C]Flumazenil PET provides a useful tool for investigating the hippocampal damage in vivo even in patients with no remarkable hippocampal abnormalities on quantitative MRI.

Adolescent↗

PubMed2000

Interrelations of T(1) and diffusion of water in acute cerebral ischemia of the rat.

Interrelation of T(1) and diffusion of water was studied in rat models of acute global and focal cerebral ischemia. Cortical T(1), as quantified with an inversion recovery method, increased by 4-7% within a few minutes of global ischemia at 4.7 and 9.4 T, but a significantly smaller change was detected at 1.5 T. The initial T(1) change occurred within seconds of cardiac arrest, much earlier than the extensive diffusion drop after 1-2 min. Thus, the initial increase in T(1) upon acute cerebral ischemia is directly caused by cessation of blood flow. In transient middle cerebral artery occlusion (MCAO), prolonged T(1) relaxation was detected within 10 min, with a subsequent increase during the course of ischemia. Spin density did not change during the first hour, showing that T(1) increase was not caused by net accumulation of water. Interestingly, partial recovery of T(1) upon release of MCAO, occurring independent of long-term tissue outcome, was observed only in concert with diffusion recovery.

Acute Disease↗

PubMed2000

Quantitative MRI of the hippocampus and amygdala in severe depression.

BACKGROUND: There is little evidence to support possible structural changes in the amygdala and hippocampus of patients with severe depression. METHODS: Quantitative MRI of the amygdala and hippocampus, as well as proton spectroscopy (MRS) of mesial temporal structures were studied in 34 drug-resistant in-patients with major depression and compared with 17 age-matched controls. Volumetric MRI data were normalized for brain size. RESULTS: The volume of the left hippocampus was significantly smaller in the patients compared with the controls. Both groups exhibited similar significant hippocampal asymmetry (left smaller than right). The patients, but not the controls, had significant asymmetry of the amygdalar volumes (right smaller than left). No differences were observed between the patients and controls in the T2 relaxation times for the hippocampus and amygdala. Mesial temporal lobe MRS revealed a significantly elevated choline/creatine ratio in the patients compared with the controls. CONCLUSIONS: This quantitative MRI study provides support for a possible association between structural and biochemical substrates and severe drug-resistant major depression.

Adult↗

PubMed2000

Herpes simplex virus thymidine kinase gene therapy in experimental rat BT4C glioma model: effect of the percentage of thymidine kinase-positive glioma cells on treatment effect, survival time, and tissue reactions.

Herpes simplex virus thymidine kinase (HSV-tk) gene transfer and ganciclovir (GCV) administration have been suggested for the treatment of malignant gliomas. To understand tissue responses and possible ways to improve the treatment effect, we studied tumor growth, tissue reactions, and survival time after HSV-tk/GCV treatment in a syngeneic BT4C rat glioma model by mixing various ratios of stably transfected HSV-tk-expressing BT4C-tk glioma cells with wild-type BT4C glioma cells (percentage of BT4C-tk cells: 0%, 1%, 10%, 30%, 50%, and 100%), followed by injection into BDIX rat brains (n = 79). With the exception of some animals with end-stage tumors, very little astroglia or microglia reactivity was detected in the wild-type tumors as analyzed by immunocytochemistry using glial fibrillary acid protein (GFAP)-, vimentin-, human histocompatibility leukocyte antigen-DR-, OX-42-, and CD68-specific monoclonal antibodies. After 14 days of GCV treatment, tumors induced with > or = 10% BT4C-tk cells showed a significant reduction in tumor size (P < .05) and prolonged survival time (P < .01). Astrogliosis, as indicated by a strong GFAP and vimentin immunoreactivity, was seen in the tumor scar area. GFAP and vimentin reactivity was already present after the GCV treatment in tumors induced with 1% BT4C-tk cells. Much less human histocompatibility leukocyte antigen-DR-positive microglia was seen in the treated animals, indicating low microglia reactivity and immunoactivation against the tumor. However, GCV-treated tumors were positive for apoptosis, indicating that apoptosis is an important mechanism for cell death in the BT4C-tk glioma model. Our results suggest that > or = 10% transfection efficiency is required for a successful reduction in BT4C glioma tumor size with HSV-tk/GCV treatment in vivo. Tissue reactions after 14 days of GCV treatment are characterized by astrogliosis and apoptosis, whereas microglia response and immunoactivation of the brain cells appear to play a minor role. Stimulation of the microglia response by gene transfer or other means might improve the efficacy of the HSV-tk/GCV treatment in vivo.

Animals↗

PubMed2000

Left atrial volume assessed by transthoracic three dimensional echocardiography and magnetic resonance imaging: dynamic changes during the heart cycle in children.

OBJECTIVE: To assess the dynamic changes in left atrial volume by transthoracic three dimensional echocardiography and compare the results with those obtained by magnetic resonance imaging (MRI). DESIGN AND PATIENTS: 30 healthy children (15 boys and 15 girls, aged 8 to 13 years) underwent examination by three dimensional echocardiography and MRI. METHODS: Three dimensional echocardiography of the left atrium was performed using rotational acquisition of planes at 18 degrees intervals from the parasternal window with ECG gating and without respiratory gating. Volume estimation by MRI was performed with a slice thickness of 4-8 mm and ECG triggering during breath holding in deep inspiration. A left atrial time-volume curve was reconstructed in each child. RESULTS: Left atrial maximum and minimum volumes averaged 24.0 ml/m(2) and 7. 6 ml/m(2) by three dimensional echocardiography, and 22.1 ml/m(2) and 11.9 ml/m(2) by MRI. The greater left atrial minimum volume in the latter was at least in part a result of breath holding. Dynamic changes in left atrial volume during the heart cycle were detectable by both methods. The higher temporal resolution of three dimensional echocardiography allowed a more precise evaluation of different phases. CONCLUSIONS: Three dimensional echocardiography and MRI were both useful methods for studying the physiological volume changes in the left atrium in children. These methods may be used for further study of the systolic and diastolic function of the heart.

Adolescent↗

PubMed2000

Midazolam 12 mg is moderately counteracted by 250 mg caffeine in man.

OBJECTIVE: Caffeine (Caf) counteracts various effects of benzodiazepines (BZDs). Since the effects of zolpidem, a short-acting atypical GABA(A)-BZD agonist, were not antagonized by Caf, we studied an interaction between Caf and midazolam (Mid) in healthy volunteers. SUBJECTS, MATERIALS AND METHODS: In Study 1, 108 healthy students divided to 6 parallel groups were given Mid 12 mg (capsule) and Caf 125 and 250 mg (in decaffeinated coffee), alone and in combinations in the double-blind placebo-controlled manner. Objective and subjective tests were done before and at 45 and 90 min after intake. Ranked delta-values (changes from baseline) were analyzed by one-way contrast ANOVA and Scheffe's tests. In Study 2, six healthy subjects took Mid 15 mg (tablet) with and without Caf 300 mg. The dynamic effects were analyzed as in Study 1 and the plasma concentrations were assayed. RESULTS: In Study 1, learn effects after placebo (ad + 15%) were seen for letter cancellation and digit symbol substitution tests. Midazolam alone significantly (p < 0.05 vs. delta-placebo) reduced letter cancellation and digit symbol substitution, lowered flicker fusion, impaired digit learning and caused subjective calmness on VAS. Caffeine alone did not differ from placebo objectively, yet improved quick-wittedness and contentedness on VAS. In the combinations, Mid + Caf 125 mg differed from placebo objectively as Mid alone, whereas Mid + Caf 250 mg did not. Mid + Caf 250 mg differed from Mid on digit substitution, but did not differ from Mid+Caf 150 mg in impairing memory and causing subjective sedation. In Study 2, Mid 15 mg caused sedation and Caf 300 mg increased plasma Mid at 45 min. Mid + Caf did not differ from Mid alone objectively, but did so subjectively on VAS (p > 0.05). CONCLUSION: In conclusion, in a parallel group study, sedative effects of Mid 12 mg were only moderately antagonized by Caf 250 mg but not by Caf 125 mg. In a cross-over study, a weak interaction was found subjectively but not in objective measures.

Adult↗

PubMed1999

Redox modulation of intracellular free calcium concentration in thyroid FRTL-5 cells: evidence for an enhanced extrusion of calcium.

Redox modulation is involved in the regulation of the intracellular free calcium concentration ([Ca2+]i) in several cell types. In thyroid cells, including thyroid FRTL-5 cells, changes in [Ca2+]i regulate important functions. In the present study we investigated the effects of the oxidizing compounds thimerosal and t-butyl hydroperoxide on [Ca2+]i in thyroid FRTL-5 cells. Thimerosal mobilized sequestered calcium, and evoked modest store-dependent calcium entry. Both compounds potently attenuated the increase in [Ca2+]i when store-operated calcium entry was evoked with thapsigargin. The entry of barium was not attenuated. Experiments performed with high extracellular pH, in sodium-free buffer and in the presence of vanadate suggested that thimerosal decreased [Ca2+]i by activating a calcium extrusion mechanism, probably a plasma membrane Ca2+-ATPase. All the observed effects were abrogated by the reducing agent beta-mercaptoethanol. The mechanism of action was apparently mediated via activation of protein kinase C, as thimerosal potently stimulated binding of [3H]phorbol 12, 13-dibutyrate, and was without effect on store-operated calcium entry in cells treated with staurosporine or in cells with down-regulated protein kinase C. Thimerosal did not depolarize the membrane potential, as evaluated using patch-clamp in the whole-cell mode. In immunoprecipitates obtained with an antibody against plasma membrane Ca2+-ATPase, we observed several phosphorylated bands in cells stimulated with thimerosal. In conclusion, we have shown that thimerosal attenuates an increase in [Ca2+]i, probably by activating a plasma membrane Ca2+-ATPase.

Animals↗

PubMed1999

Low efficacy of gene therapy for rat BT4C malignant glioma using intra-tumoural transduction with thymidine kinase retrovirus packaging cell injections and ganciclovir treatment.

BACKGROUND: The purpose of this study was to test the use of Herpes Simplex virus thymidine kinase (HSVtk) retrovirus packaging cell injections in the treatment of malignant brain tumours. METHODS: Therapeutic effect and tissue responses were examined in vivo in a syngeneic BT4C rat glioma model after HSVtk-producing PA317 packaging cell injections and intraperitoneal ganciclovir (GCV) medication. MRI was used to visualise the tumours before and after the treatment. Immunohistochemical stainings were performed to study astroglia and microglia responses and apoptosis-mediated cell death. RESULTS: The results suggest that only a limited treatment effect can be achieved with HSVtk packaging cell injections with no prolonged survival rates. Histological examination showed a strong astroglia response but only a modest microglia response after the treatment. HSVtk and GCV-induced cell death was at least partially mediated by apoptosis. It is concluded that HSVtk packaging cell injections and GCV treatment do not lead to eradication of malignant cells in a syngeneic BT4C rat glioma model. The lack of efficacy is most likely due to low gene transfer efficiency and limited life span of the injected packaging cell inside the tumours. CONCLUSIONS: Improvements in gene transfer efficiency, and stimulation of immunoresponse against tumour cells might lead to a more effective therapeutic response in vivo.

Animals↗

PubMed1999

Stent placement versus percutaneous transluminal angioplasty of human carotid arteries in cadavers in situ: distal embolization and findings at intravascular US, MR imaging and histopathologic analysis.

PURPOSE: To compare endovascular stent placement with percutaneous transluminal angioplasty (PTA) of carotid arteries with respect to distal embolization and findings at intravascular ultrasonography (US), magnetic resonance (MR) imaging, and histopathologic analysis. MATERIALS AND METHODS: PTA was performed in situ in one carotid artery, and stent placement was performed in the other, in ten cadavers (age range, 57-82 years; mean age, 68 years) with severe atherosclerosis by using fluoroscopic and intravascular US guidance. The carotid artery was connected to a pressurized tubing system in which a pulsatile pump circulated water. The effluent water was collected during the interventions, and after filtration and staining, the embolic material was analyzed histologically. After the interventions, the arteries were excised and 1.5-T spin-echo MR imaging was performed. RESULTS: No difference in severity of distal embolization during stent placement versus during PTA was found. The embolic particles were composed mainly of intimal strips and cellular constituents of the atherosclerotic plaques. MR imaging accurately depicted postinterventional changes, and the findings correlated closely with those of intravascular US and histopathologic analysis. CONCLUSION: Although stent placement and PTA were associated with equal distal embolization, the smooth surface and fully patent arterial lumen depicted at intravascular US and MR imaging postinterventionally may indicate that stent placement is preferable to PTA.

Aged↗

PubMed1999

Mild carotid artery atherosclerosis: assessment by 3-dimensional time-of-flight magnetic resonance angiography, with reference to intravascular ultrasound imaging and contrast angiography.

BACKGROUND AND PURPOSE: Our aim was to evaluate the usefulness of 3-dimensional time-of-flight magnetic resonance angiography (3-D TOF MRA) in detection and quantification of mild atherosclerotic changes of carotid arteries with reference to intravascular ultrasound (IVUS) and contrast angiography. METHODS: TOF MRA at 1.5 T, IVUS, and selective digital subtraction angiography were performed on 31 extracranial carotid arteries of 27 patients (mean age, 52 years; age range, 17 to 75 years) undergoing neuroendovascular interventions. The atherosclerotic lesions were registered, and quantitative measurements of plaque thickness, luminal diameters, and diameter stenosis were independently performed for the imaging modalities. RESULTS: Among 170 arterial segments analyzed, IVUS revealed a total of 48 atherosclerotic lesions (mean diameter stenosis, 17%; range, 4% to 40%), only 25 of which were depicted on digital subtraction angiography. Analysis of the axial source images of TOF MRA resulted in sensitivity of 77% to 83% and specificity of 71% to 80% in lesion depiction for the 2 readers with reference to IVUS. The values of diameter stenosis measured from MRA and IVUS were closely interrelated (r=0.53 to 0.61, P<0.001). CONCLUSIONS: Three-dimensional TOF MRA is feasible and moderately accurate for evaluation of mild atherosclerotic changes of carotid arteries.

Adolescent↗

PubMed1998

MRI does not change fetal cardiotocographic parameters.

The aim of this study was to determine whether magnetic resonance imaging (MRI) has any effect on fetal cardiotocographic (CTG) parameters or movement incidence. Sixteen mothers were examined during the last trimester at 28-39 weeks (mean 33 weeks; SD 4) of gestation due to a suspected fetal anomaly found in antenatal ultrasonography (US). MR imaging was performed using Siemens Magnetom Vision 1.5 T equipment with a 25 mT/m peak gradient amplitude. T2-weighted images were produced with HASTE and TRUE-FISP sequences and T1-weighted images with a 2D FLASH sequence. A four-element phase-array coil was used as the receiver. Before and after MRI-examination, a computerized analysis of the fetal heart rate (FHR) was produced. Basal FHR, short-term variation (STV) and fetal movements were calculated. The mean basal FHR was 136 beats/min (SD 11.6) before, and 133 beats/min (SD 8.9) after (P = 0.158). Short-term variation was in the normal range for both CTG-tracings: mean 9.7 ms (SD 2.7) and 8.8 ms (SD 2.8) (P = 0.196). The median for fetal movements before MRI was 48/h, and after MRI 24.5/h (P = 0.98). MRI at high field strength with powerful gradients did not affect fetal heart activity or movement incidence.

Cardiotocography↗

PubMed1998

Zolpidem 10 mg given at daytime is not antagonized by 300 mg caffeine in man.

OBJECTIVE: Caffeine counteracts various effects of traditional benzodiazepines (BZDs). As zolpidem, a short-acting hypnotic, is an atypical GABAA-BZD agonist, we investigated when caffeine would counteract the effects of zolpidem as well. METHODS: In daytime study I, zolpidem 10 mg (capsule) and caffeine 150 or 300 mg (in decaffeinated coffee) were given, alone and in combinations, to parallel groups (n = 15-17) of healthy students in double-blind and placebo-controlled manner. Objective and subjective tests were done before and 45 min and 90 min after intake. Ranked delta values (changes from baseline) were analysed by one-way contrast ANOVA and Scheffe's tests. In daytime study II, four healthy subjects took zolpidem 10 mg alone, and together with blinded caffeine 250 mg or (at -45 min) erythromycin 750 mg. Objective and subjective effects were measured and plasma zolpidem concentrations assayed at baseline and 45 min and 90 min after zolpidem intake. RESULTS: In study I, practice effects after placebo (ad + 30%) were seen for letter cancellation and digit symbol substitution but not for flicker fusion tests. Zolpidem alone significantly impaired (P < 0.05 vs delta placebo) letter cancellation and digit symbol substitution at 45 min and 90 min, lowered the flicker fusion threshold at 45 min, and caused subjective drowsiness, mental slowness, clumsiness and feeling of poor performance. Caffeine alone showed a non-significant trend to improve objective performance. The combined effects of zolpidem and either dose of caffeine matched those measured after zolpidem alone. Zolpidem + caffeine 300 mg was not stronger than zolpidem + caffeine 150 mg in impairing immediate memory and causing subjective sedation. In study II, zolpidem caused objective and subjective sedation; neither caffeine nor erythromycin modulated the effects of zolpidem or plasma zolpidem concentrations. CONCLUSION: The sedative effects of 10 mg of zolpidem are not antagonized by 150-300 mg of caffeine in pharmacodynamic or pharmacokinetic terms.

Adult↗

PubMed1998

Intravascular ultrasound and magnetic resonance imaging in the assessment of atherosclerotic lesions in rabbit aorta. Correlation to histopathologic findings.

RATIONALE AND OBJECTIVES: The authors compare the usefulness of intravascular ultrasound (IVUS) and magnetic resonance imaging (MRI) for quantitation of atherosclerosis in hyperlipidemic rabbits, correlated with histopathology. METHODS: Magnetic resonance imaging with T1- and T2-weighted spin echo sequences and three-dimensional time-of-flight MR angiography of the abdominal aorta was performed on seven rabbits using a 1.5 T MR imager and a standard head coil. X-ray angiography and IVUS examination (3.5 F/30 MHz imaging catheter) was performed via carotid artery access. RESULTS: Time-of-flight MR angiography source images provided the best resolution and plaque-lumen contrast in visual comparison between the different MRI sequences. Intra- and interobserver reproducibilities of the lesion thickness and area measurements were similar in IVUS and MRI (Pearson correlations 0.52-0.97; P < 0.01). The measurements from IVUS and MRI correlated closely with each other as well as with those made from histopathologic specimens (Pearson correlations 0.50-0.79; P < 0.001). The measurements from IVUS were somewhat more accurate than those made from MRI. CONCLUSIONS: Both MRI and IVUS with clinically available imaging equipments are feasible and accurate for the quantitation of experimental atherosclerosis of rabbit aorta.

Animals↗