Nanoscale assembly of amine functionalized colloidal iron oxide

We demonstrate a single-step facile approach for highly water stable assembly of amine-functionalized Fe(3)O(4) nanoparticles using thermal decomposition of Fe-chloride precursors in ethylene glycol medium in the presence of ethylenediamine. The average size of nanoassemblies is 40±1 nm, wherein the individual nanoparticles are about 6 nm. Amine functionalized properties are evident from FTIR, thermal and elemental analysis. The saturation magnetization and spin-echo r(2) of the nanoassemblies were measured to be 64.3 emu/g and 314.6 mM(-1)s(-1), respectively. The higher value of relaxivity ratio (r(2)/r(1)=143) indicates that nanoassemblies are a promising high efficiency T2 contrast agent platform.

Blood oxygen level-dependent MR imaging of the kidneys

Oxygenation status plays a major role in renal physiology and pathophysiology, and thus has attracted considerable attention in recent years. While much of the early work and a significant amount of present work is based on invasive methods or ex vivo analysis, and is therefore restricted to animal models, blood oxygen level-dependent (BOLD) MR imaging has been shown to extend these findings to human beings. BOLD MR imaging is most useful in monitoring effects of physiologic or pharmacologic maneuvers. Several teams around the world have demonstrated reproducible data and have illustrated several useful applications. Studies supporting the use of renal BOLD MR imaging in characterizing disease with prognostic value have also been reported. This article provides an overview of current state-of-the art of renal BOLD MR imaging.

Change in regional cartilage morphology and joint space width in osteoarthritis participants versus healthy controls: a multicentre study using 3.0 Tesla MRI and Lyon–Schuss radiography

Objective:

Cartilage morphology displays sensitivity to change in osteoarthritis (OA) with quantitative MRI (qMRI). However, (sub)regional cartilage thickness change at 3.0 Tesla (T) has not been directly compared with radiographic progression of joint space narrowing in OA participants and non-arthritic controls.

Methods:

A total of 145 women were imaged at 7 clinical centres: 86 were non-obese and asymptomatic without radiographic OA and 55 were obese with symptomatic and radiographic OA (27 Kellgren–Lawrence grade (KLG)2 and 28 KLG3). Lyon–Schuss (LS) and fixed flexion (FF) radiographs were obtained at baseline, 12 and 24 months, and coronal spoiled gradient echo MRI sequences at 3.0 T at baseline, 6, 12 and 24 months. (Sub)regional, femorotibial cartilage thickness and minimum joint space width (mJSW) in the medial femorotibial compartment were measured and the standardised response means (SRMs) determined.

Results:

At 6 months, qMRI demonstrated a −3.7% “annualised” change in cartilage thickness (SRM −0.33) in the central medial femorotibial compartment (cMFTC) of KLG3 subjects, but no change in KLG2 subjects. The SRM for mJSW in 12-month LS/FF radiographs of KLG3 participants was −0.68/−0.13 and at 24 months was −0.62/−0.20. The SRM for cMFTC changes measured with qMRI was −0.32 (12 months; −2.0%) and −0.48 (24 months; −2.2%), respectively.

Conclusions:

qMRI and LS radiography detected significant change in KLG3 participants at high risk of progression, but not in KLG2 participants, and only small changes in controls. At 12 and 24 months, LS displayed greater, and FF less, sensitivity to change in KLG3 participants than qMRI.

Accuracy of T1 measurement with 3-D Look-Locker technique for dGEMRIC

PURPOSE

To validate the accuracy of T1 measurement by three-dimensional Look-Locker method (3D LL) for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of human subjects with and without osteoarthritis (OA), as compared with two-dimensional inversion recovery fast spin-echo (2D IR-FSE) technique.

MATERIALS AND METHODS

MR sagittal images of the knees were acquired for T1 mapping in 29 subjects with standard 2D IR-FSE and 3D LL sequences 90-135 min following administration of 0.2 mmol/kg Gd-DTPA(2-). T1 maps of femoral and tibial cartilage were generated using custom software. Comparisons in T1 values between the two techniques were performed using regression analysis.

RESULTS

Good agreement in T1 values between 2D IR-FSE and 3D LL was observed (R values of 0.90, and 0.85, and 0.86 for all, OA, and control subjects, respectively) when acquired within 15 min.

CONCLUSION

The 3D LL sequence provides accurate T1 estimates of articular cartilage with advantages of entire joint coverage, shorter acquisition time, and a wide range of inversion times sampled within a single acquisition.

Precision of 3.0 Tesla quantitative magnetic resonance imaging of cartilage morphology in a multicentre clinical trial

OBJECTIVE

Quantitative MRI (qMRI) of cartilage morphology is a promising tool for disease-modifying osteoarthritis drug (DMOAD) development. Recent studies at single sites have indicated that measurements at 3.0 Tesla (T) are more reproducible (precise) than those at 1.5 T. Precision errors and stability in multicentre studies with imaging equipment from various vendors have, however, not yet been evaluated.

METHODS

A total of 158 female participants (97 Kellgren and Lawrence grade (KLG) 0, 31 KLG 2 and 30 KLG 3) were imaged at 7 clinical centres using Siemens Magnetom Trio and GE Signa Excite magnets. Double oblique coronal acquisitions were obtained at baseline and at 3 months, using water excitation spoiled gradient echo sequences (1.0x0.31x0.31 mm3 resolution). Segmentation of femorotibial cartilage morphology was performed using proprietary software (Chondrometrics GmbH, Ainring, Germany).

RESULTS

The precision error (root mean square coefficient of variation (RMS CV)%) for cartilage thickness/volume measurements ranged from 2.1%/2.4% (medial tibia) to 2.9%/3.3% (lateral weight-bearing femoral condyle) across all participants. No significant differences in precision errors were observed between KLGs, imaging sites, or scanner manufacturers/types. Mean differences between baseline and 3 months ranged from <0.1% (non-significant) in the medial to 0.94% (p<0.01) in the lateral femorotibial compartment, and were 0.33% (p<0.02) for the total femorotibial subchondral bone area.

CONCLUSIONS

qMRI performed at 3.0 T provides highly reproducible measurements of cartilage morphology in multicentre clinical trials with equipment from different vendors. The technology thus appears sufficiently robust to be recommended for large-scale multicentre trials.

Serial diffusion tensor imaging detects white matter changes that correlate with motor outcome in premature infants

The objective of the study was to assess predictive value of serial diffusion tensor MRI (DTI) for the white matter injury and neurodevelopmental outcome in a cohort of premature infants. Twenty-four infants less than 32 weeks' gestation were stratified to a control group (n = 11), mild brain injury with grades 1-2 of intraventricular hemorrhage (n = 6) and severe brain injury with grades 3-4 intraventricular hemorrhage (n = 4). Serial DTI studies were performed at around 30 and 36 weeks' gestation. Fractional anisotropy (FA) and apparent diffusion coefficient were calculated. Twelve infants were followed up for developmental outcome. Developmental testing was performed with the Bayley Scales of Infant Development to obtain psychomotor index (Performance Developmental Index). Apparent diffusion coefficient was higher in the severe injury group at the second MRI in the central and occipital white matter, and corona radiata; FA was lower in optic radiation compared to controls. Performance Developmental Index score correlated with FA on the scan taken at the 30th week and inversely with the change of FA between scans in internal capsule and occipital white matter. A low value of FA at 30 weeks and a higher change of FA predicted less favorable motor outcome at 2 years and suggests that early subtle white matter injury can be detected in premature infants even without obvious signs of injury.

Renal Artery Stenosis in Swine: Feasibility of MR Assessment of Renal Function during Percutaneous Transluminal Angioplasty

PURPOSE

To prospectively test--in a swine model of renal artery stenosis (RAS)--the hypothesis that magnetic resonance (MR) imaging can reveal changes in renal function at the time of percutaneous transluminal angioplasty (PTA).

MATERIALS AND METHODS

In this animal care and use committee-approved study, high-grade unilateral RAS was surgically induced in six pigs. MR imaging at 3.0 T was used for intraprocedural assessment of the anatomic and physiologic changes induced by x-ray-guided PTA. With use of MR imaging, changes in single-kidney glomerular filtration rate, extraction fraction, and renal blood flow were assessed during PTA. The arterial diameter of stenosis before and after PTA was assessed by using conventional digital subtraction angiography. Mean changes in functional and anatomic parameters were compared by using the Wilcoxon signed rank test (alpha = .05).

RESULTS

At digital subtraction angiography, the mean percentage of stenosis was 69% +/- 10 (standard deviation) before PTA and 26% +/- 10 after PTA (P<.03). Mean pre- and post-PTA extraction fraction values were 0.11 +/- 0.03 and 0.19 +/- 0.06, respectively (P<.03). The mean single-kidney glomerular filtration rate before PTA, 19 mL/min +/- 13, increased to 41 mL/min +/- 33 after PTA (P<.03). There was no significant change in mean renal blood flow after PTA (P=.44).

CONCLUSION

In swine, MR imaging can reveal changes in renal function after x-ray-guided PTA for unilateral RAS.

Fetal brain magnetic resonance imaging response acutely to hypoxia-ischemia predicts postnatal outcome

OBJECTIVE

Cerebral palsy (CP) is caused by either hypoxia-ischemia (H-I) or long-standing causative factors such as inflammation or genetics. Multiple pathophysiological events over time are thought to contribute eventually to cerebral palsy. Our objective was to examine whether the immediate response of the fetus to an acute H-I event determined the motor deficits associated with cerebral palsy.

METHODS

Serial diffusion-weighted imaging were performed on 79% gestation New Zealand white rabbits using a 3-Tesla magnetic resonance scanner during 40 minutes of uterine ischemia, 20 minutes of reperfusion, and at 4, 24, and 72 hours. Individual fetuses were tracked to near term, and the delivered kits were divided into hypertonic H-I (n = 18), nonhypertonic H-I (n = 9), stillbirth H-I (n = 4), and control groups (n = 16).

RESULTS

The hypertonia group had significantly less of a nadir in apparent diffusion coefficient (ADC) during H-I (71.6 +/- 23.8% vs 84.5 +/- 9.3% baseline) and slower and incomplete recovery of ADC during reperfusion compared with the nonhypertonic group. All fetuses in the hypertonic and stillbirth groups had an ADC nadir of less than 0.83 microm(2)/msec (70.3% decrease from baseline), whereas 94% of control animals had an ADC nadir greater than this value. The difference between outcome groups was the largest at 4 hours reperfusion and persisted for 24 hours.

INTERPRETATION

Serial fetal brain scans indicate that the immediate response of a fetus to H-I is crucial to the development of hypertonia. If the fetal brain can be scanned at the time of insult, ADC changes can predict which fetuses will have an unfavorable outcome.

Full-limb and knee radiography assessments of varus-valgus alignment and their relationship to osteoarthritis disease features by magnetic resonance imaging

OBJECTIVE

To examine the correlation between hip-knee-ankle and femur-tibia radiograph angles, calculate the offset of the femur-tibia angle with respect to the hip-knee-ankle angle, calculate the sensitivity and specificity and area under the receiver operating characteristic (ROC) curve of the femur-tibia angle, and examine the relationship of malalignment by each approach with osteoarthritis (OA) tissue pathology in the mechanically stressed compartment using magnetic resonance imaging (MRI).

METHODS

Individuals with knee OA underwent full-limb and knee radiographs and knee MRI. Linear regression was used to determine if the 2 angles differed systematically and to identify the cutoff. Alignment means for MRI grades were compared using Dunnett's t-test.

RESULTS

In the 146 participants (109 women, mean age 70 years, body mass index 30.6 kg/m(2)), femur-tibia and hip-knee-ankle angles correlated (r = 0.86; 95% confidence interval [95% CI] 0.81, 0.90). On average, the femur-tibia angle was 3.4 degrees more valgus (3.0 degrees in women and 4.7 degrees in men); after correction, its sensitivity and specificity (to predict the hip-knee-ankle angle) were 0.84 and 0.84 for identifying varus and 0.98 and 0.73 for valgus, respectively. The area under the ROC curve (95% CI) was 0.91 (0.86, 0.96) for varus and 0.94 (0.89, 0.99) for valgus. Varus severity worsened comparably with each alignment measure as medial lesion score on MRI worsened. Laterally, as lesion score worsened, comparably worse valgus was seen with either assessment approach.

CONCLUSION

In knee OA, the knee radiograph femur-tibia and full-limb radiograph hip-knee-ankle angles were correlated. The femur-tibia angle, corrected for mean offset, was sensitive, specific, and had excellent discriminative ability for identifying varus and valgus alignment evidenced by area under the ROC curve. The relationship between alignment and specific OA MRI features was comparable with the 2 approaches. Use of the femur-tibia angle, corrected for offset, should be considered in research and clinical settings.

Three-dimensional delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) at 1.5T and 3.0T

PURPOSE

To implement and validate a three-dimensional (3D) T1 measurement technique that is suitable for delayed gadolinium (Gd)-enhanced MRI of cartilage (dGEMRIC) and can be easily implemented with clinically available pulse sequences at 1.5T and 3.0T.

MATERIALS AND METHODS

A 3D inversion-recovery prepared spoiled gradient-echo (IR-SPGR) imaging pulse sequence with variable TR was used to implement a 3D T1 measurement protocol. The 3D T1 measurements were validated against a gold-standard single-slice 2D IR T1 measurement protocol in both phantoms and in vivo, in both asymptomatic volunteers and volunteers with osteoarthritis (OA).

RESULTS

T1 measurements in phantoms showed a statistically significant correlation between the 2D and 3D measurements at 1.5T (R2=0.993, P<0.001) and 3.0T (R2=0.996, P<0.001). In vivo application demonstrated the feasibility of using this 3D IR-SPGR sequence to evaluate the molecular status of articular cartilage throughout the knee joint with 0.63x0.63x3.0 mm spatial resolution within a 20-minute acquisition, even with the measurement parameters set for the higher T1(Gd) of cartilage at 3T (range=400-900 msec mean T1 within a region of interest (ROI) in cartilage, compared to 200-600 msec mean T1 at 1.5T).

CONCLUSION

This 3D T1 measurement protocol may prove useful for the evaluation and follow-up of cartilage dGEMRIC indices in clinical studies of OA.

Evaluation of intrarenal oxygenation in mice by BOLD MRI on a 3.0T human whole-body scanner

PURPOSE

To extend observations on intra-renal oxygenation with blood oxygen level-dependent (BOLD) MRI in human and rats to mouse kidneys imaged with a human whole-body scanner.

MATERIALS AND METHODS

Renal BOLD MRI studies were performed on a 3.0T scanner using a multiple gradient-echo (mGRE) sequence with a custom-designed 2.0-cm surface coil to acquire six T(2)*-weighted images in mice (N = 8) at an in-plane resolution of 156 x 156 mum(2). BOLD MRI data were obtained before and after administration of furosemide (10 mg/kg intravenously [i.v.]).

RESULTS

The mean weight of eight mice was 24.6 +/- 1.0 g. The baseline renal R(2)* (mean +/- standard error [SE]) was 28.6 +/- 2.1 seconds(-1) in the renal cortex (CO), 35.4 +/- 2.2 in the outer medulla (OM), and 21.2 +/- 2.1 seconds(-1) in the inner medulla (IM). The BOLD response to furosemide (DeltaR(2)*) was 4.1 +/- 1.4 in the CO, 10.1 +/- 2.1 seconds(-1) in the OM, and 3.4 +/- 0.8 seconds(-1) in the IM in mice.

CONCLUSION

Intrarenal BOLD MR images with sufficiently high resolution can be obtained on a human whole-body scanner when combined with a small receiver coil to allow studies in mice. Both baseline R(2)* and DeltaR(2)* values following administration of furosemide were consistent with previous experience in humans and rats.

dGEMRIC as a function of BMI

OBJECTIVE

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) reflects cartilage glycosaminoglycan (GAG) distribution. The technique assumes that the plasma levels of the contrast agent Gd-DTPA(2-) are the same across individuals after intravenous (IV) injection, when dosing by weight. However, adipose tissue has lower extracellular water (ECW) than lean tissue. The aims of this study were to measure (1) plasma Gd-DTPA(2-) levels vs body mass index (BMI), and (2) dGEMRIC vs BMI after correcting for the dose-BMI effect.

METHOD

(1) Plasma Gd-DTPA(2-) levels were analyzed at 3-90 min after IV injection per body weight in 24 individuals with BMI between 21.5 and 46.5. (2) dGEMRIC was compared with BMI in 19 asymptomatic volunteers and 23 with osteoarthritis (OA).

RESULTS

(1) Plasma Gd-DTPA(2-) kinetics were similar in obese and non-obese groups, however, overall concentration was higher in the obese group. A very obese subject (BMI 45) would have 1.4 times higher Gd-DTPA(2-) concentration than a lean subject (BMI 20), which translates into a bias in dGEMRIC of up to 20%. (2) With dose bias taken into account, dGEMRIC showed no correlation with BMI in asymptomatic knees. In OA knees, unnarrowed femoral compartments demonstrated a negative correlation between dGEMRIC and BMI (R=0.57, P=0.004). No correlation was seen in radiographically narrowed compartments.

CONCLUSION

BMI can be a source of dosing bias in dGEMRIC and a correction factor should be considered in cross-sectional studies with a large range of BMI. There is no correlation between dGEMRIC and BMI in asymptomatic knees, but a negative correlation in OA knees.

Functional MRI of the kidney: tools for translational studies of pathophysiology of renal disease

Magnetic resonance imaging (MRI) provides exquisite anatomic detail of various organs and is capable of providing additional functional information. This combination allows for comprehensive diagnostic evaluation of pathologies such as ischemic renal disease. Noninvasive MRI techniques could facilitate translation of many studies performed in controlled animal models using technologies that are invasive to humans. Such a translation is being recognized as essential because many proposed interventions and drugs that prove efficacious in animal models fail to do so in humans. In this article, we review the state-of-the-art functional MRI technique as applied to the kidneys.

Magnetic resonance imaging of myocardial infarction using a manganese-based contrast agent (EVP 1001-1): preliminary results in a dog model

PURPOSE

To investigate the MRI characteristics of an intracellular manganese-based contrast agent, EVP 1001-1 (Eagle Vision Pharmaceutical Corp.), in a canine model of myocardial infarction.

MATERIALS AND METHODS

Three dogs were imaged 14-37 days following permanent ligation of the left anterior descending coronary artery (LAD). Measurements of the longitudinal relaxation rate R(1) were made prior to EVP 1001-1 administration (20 micromol/kg i.v.) and for one hour thereafter. Triphenyl tetrazolium chloride (TTC) staining was used to document infarction.

RESULTS

In normal myocardium, EVP 1001-1 produced a substantial increase in the longitudinal relaxation rate, which remained fairly constant over the postcontrast imaging period (DeltaR1= 1.47 +/- 0.58 sec(-1) (mean +/- SD) at 35 minutes, P < 0.05). In the infarct, the response to EVP 1001-1 was small or negligible (DeltaR1= 0.27 +/- 0.28 sec(-1)). This resulted in a significant postcontrast difference in relaxation rate between normal and infarcted tissue (R1(normal) - R1(infarct) = 1.08 +/- 0.26 sec(-1), P < 0.05). The infarct remained clearly delineated in all animals throughout the steady-state imaging period, and qualitatively matched TTC results.

CONCLUSION

The persistent enhancement pattern revealed by MRI following EVP 1001-1 administration may be beneficial for identifying and characterizing myocardial infarction.

Evaluation of intra-renal oxygenation during water diuresis: a time-resolved study using BOLD MRI

Hypoxia of the renal medulla is a possible precursor to the onset of acute renal failure in humans and therefore an understanding of the factors influencing the oxygenation status within the renal medulla is very important. Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has been shown to non-invasively evaluate intra-renal oxygenation levels of the renal medulla in humans. A newly implemented three-dimensional (3-D) multiple gradient-recalled echo sequence, which permits examination of temporal responses to physiological or pharmacological stimuli, was used to monitor changes in intra-renal oxygenation status during water diuresis. Five healthy, young subjects (22+/-1.2 years) took part in the study. BOLD MRI data were acquired before and after water loading. Studies were repeated on a separate day after the subjects were pretreated with naproxen. Water diuresis significantly improved renal medullary oxygenation levels in all subjects (pre-waterload=30.3 1/s vs post-waterload 22.8 1/s); however, the temporal response was found to be subject dependent. In the presence of cyclooxygenase (COX) inhibition by naproxen, the improvement in oxygenation during water diuresis was completely abolished (pre-waterload=27.5 1/s vs post-waterload 28.5 1/s). Monitoring of temporal responses for the first time during water loading allowed for an appreciation of subject dependence. Comparison of the temporal response in terms of slopes demonstrated a significant difference between the waterload studies with and without naproxen (with naproxen=0.056 1/(s min) vs without naproxen=0.25 1/(s min)). The observed effects of naproxen were consistent with previous findings with COX inhibition.

Evaluation of Intra-Renal Oxygenation by BOLD MRI

This is a review of blood oxygenation level-dependent (BOLD) MRI as applied to the kidney. It has been shown that BOLD MRI measurements reflect changes in renal oxygenation, especially in the medulla. Renal medulla functions in a hypoxic milieu and is extremely sensitive to further decrease in blood flow or increase in oxygen consumption. Availability of a non-invasive technique such as BOLD MRI should allow for better understanding of the factors involved in the maintenance of renal oxygenation status, not only in animal models, but also in humans.

Evaluation of Intrarenal Oxygenation at 3.0 T Using 3-Dimensional Multiple Gradient-Recalled Echo Sequence

OBJECTIVE

The objective of this study was to validate quantitation of R2* and DeltaR2* measurements obtained with a 3-dimensional (3-D) multiple gradient-recalled echo (mGRE) sequence for evaluating intrarenal oxygenation in humans.

MATERIALS AND METHODS

Validation was accomplished (1) by comparing R2* values with previously established 2-D techniques (n = 5, mean age = 33.6 years) and (2) by measuring change in DeltaR2* after furosemide (20 mg intravenously) administration (n = 5, mean age = 22 years). Additional pre- and postfurosemide scans were done at 1.5 T for comparison purposes.

RESULTS

R2* measurements with the 3-D technique showed good agreement with the 2-D techniques. The baseline medullary R2* at 3.0 T was about twice the value found at 1.5 T. Furosemide-induced change in R2* was observed within 5 minutes after administration.

CONCLUSIONS

R2* measurements with 3-D mGRE were comparable with those reported using 2-D techniques. The 3-D implementation facilitates observation of temporal changes in the medullary oxygenation without compromising spatial coverage.

Functional Magnetic Resonance Imaging of the Kidney

In addition to exquisite anatomical detail, magnetic resonance imaging (MRI) provides a variety of avenues to study functional status of tissue. These functional parameters could either provide additional information, in terms of pathophysiology, or may improve the specificity of the diagnosis. This chapter reviews some current state-of-the-art functional MRI (fMRI) methods as applied to the kidney. Three parameters, renal perfusion, filtration or excretory function, and oxygenation are reviewed in depth. Illustrative examples are provided and advantages discussed.

Feasibility of Blood Oxygenation Level–dependent MR Imaging to Monitor Hepatic Transcatheter Arterial Embolization in Rabbits

Blood oxygenation level-dependent (BOLD) magnetic resonance (MR) imaging is a noninvasive method to assess changes in oxygen delivery to tissues. It was hypothesized that BOLD MR imaging can detect changes in rabbit VX2 liver tumor oxygenation after hepatic artery embolization with polyvinyl alcohol particles. In four discrete VX2 liver tumors, a statistically significant mean reduction in apparent transverse relaxation time was shown, from 55 milliseconds before embolization to 41 milliseconds after embolization (P < .01). This reduction corresponded to a decrease in hepatic tumor oxygenation. The use of BOLD MR imaging to monitor changes in hepatic tumor oxygenation after embolization is feasible. These functional MR imaging measurements of hypoxia may be targeted as an endpoint for therapy in future studies.

Hydrogen peroxide modulates meiotic cell cycle and induces morphological features characteristic of apoptosis in rat oocytes cultured in vitro

Hydrogen peroxide (H2O2) is known to induce cell cycle arrest and apoptosis in various somatic cell types cultured in vitro. We hypothesize that this reactive oxygen species (ROS) could modulate cell cycle and induce morphological features characteristics of apoptosis in oocytes cultured in vitro. To test this hypothesis, immature and mature oocytes were cultured in medium containing various doses of H2O2 with or without caspase-3 inhibitor for various times. The treatment of H2O2 induced germinal vesicle break down (GVBD) in all immature oocytes followed by initiation of shrinkage. Some of immature oocytes (but not mature oocytes) also showed membrane blebbing. On the other hand, H2O2 treatment inhibited first polar body emission in mature oocytes just prior to initiation of shrinkage. The cytoplasmic granulation and fragmentation into apoptotic bodies were observed in mature oocytes during later stages of H2O2 treatment. The shrinkage was induced by H2O2 in a dose- and time-dependent manner in both immature and mature oocytes. Although, H2O2-induced degeneration was observed in both immature and mature oocytes after 2.0 hrs of treatment, immature oocytes were more susceptible to undergo quick shrinkage, membrane blebbing and degeneration. Co-addition of caspase-3 inhibitor prevented shrinkage and degeneration of both immature and mature oocytes except membrane blebbing that was observed at higher doses of H2O2 after 1.0 hr of culture. Treatment of H2O2 induced bax protein expression (3 times), DNA fragmentation and caspase-3 activity (2.5 times) in oocytes undergoing morphological apoptotic changes. These findings clearly suggest that H2O2 induced GVBD in immature oocytes, inhibited first polar body extrusion in mature oocytes prior to initiation of morphological changes characteristic of apoptosis such as shrinkage, membrane blebbing and cytoplasmic fragmentation prior to degeneration.

Evaluation of intrarenal oxygenation by BOLD MRI at 3.0 T

PURPOSE

To examine the benefit of using higher field strengths for BOLD MRI to detect changes in renal medullary oxygenation following pharmacological maneuvers.

MATERIALS AND METHODS

Renal BOLD MRI, primarily at 1.5 T, has been shown to be useful for monitoring changes in medullary oxygenation status. We performed the present studies on a 3.0 T scanner using a multiple gradient-echo (mGRE) sequence with a multicoil array to acquire 16 T2*-weighted images within a single breath-hold. Data were obtained before and after administration of furosemide (20 mg iv).

RESULTS

The baseline renal R2* (mean +/- SE) at 3.0 T was 37.4+/-1.2 Hz in the medulla, and 21.8 +/- 1.2 Hz in the cortex. The BOLD response to furosemide (DeltaR2*) at 3.0 T was 11.8 +/- 1.1 Hz in the medulla, and 3.0 +/- 0.5 Hz in the cortex.

CONCLUSION

Higher magnetic field strength is beneficial for renal BOLD MRI studies. The cortico-medullary contrast on the R2* map was significantly improved at 3.0 T, with no evidence of increased bulk susceptibility artifacts. Baseline R2* and DeltaR2* in the renal medulla at 3.0 T were both significantly higher compared to our previously reported data obtained at 1.5 T.

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in knee osteoarthritis: Findings at different radiographic stages of disease and relationship to malalignment

OBJECTIVE

Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to examine the distribution of glycosaminoglycan in cartilage. This study sought to characterize dGEMRIC in the evaluation of knee osteoarthritis (OA) according to various radiographically determined disease parameters, and to examine the relationship between alignment of the knee joint and the lateral:medial dGEMRIC ratio.

METHODS

Thirty-one patients with knee OA underwent MRI with a dGEMRIC protocol at 1.5T. Semiflexed knee radiographs and full-limb radiographs were also obtained for assessment of alignment.

RESULTS

Compartments of the knee joint without joint space narrowing had a higher dGEMRIC index than those with any level of narrowing (mean 408 msec versus 365 msec; P = 0.001). In knees with 1 unnarrowed (spared) and 1 narrowed (diseased) compartment, the dGEMRIC index was greater in the spared versus the diseased compartment (mean 395 msec versus 369 msec; P = 0.001). In spared compartments, there was a trend toward a lower dGEMRIC index with increasing Kellgren/Lawrence (K/L) radiographic severity grade; the spared compartments of knees with a K/L grade 2 had a higher dGEMRIC index than those of knees with a K/L grade 4 (mean 425 msec versus 371 msec; P < 0.05). There was a range of dGEMRIC values in the spared compartments within a given K/L grade, demonstrating biochemical differentiation of disease in radiographically comparable compartments. Almost all compartments with narrowing had dGEMRIC indices of <400 msec. Valgus-aligned knees tended to have lower dGEMRIC values laterally, and varus-aligned knees tended to have lower dGEMRIC values medially; as a continuous variable, alignment correlated with the lateral:medial dGEMRIC ratio (Pearson's R = 0.43, P = 0.02).

CONCLUSION

The biochemical information provided by dGEMRIC scans may augment radiography by improving the differentiation of disease status within a given radiographic grade, especially in early OA.

Dark Flow Artifacts with Steady-State Free Precession Cine MR Technique: Causes and Implications for Cardiac MR Imaging

Steady-state free precession cine images from cardiac magnetic resonance imaging studies of 24 patients were reviewed retrospectively to identify dark flow artifacts. The cause and features of the artifacts were studied in flow phantom experiments. Dark flow artifacts were recognized in eight of the 24 cases and were characterized by low or inhomogeneous signal intensity in blood pools with little change in adjacent tissues. The artifacts could be mimicked in flow phantom experiments by deliberately deshimming the gradients and appeared periodically during imaging with off-centered frequencies. These artifacts appeared to be caused by spins moving within an inhomogeneous magnetic field.

First-pass contrast-enhanced magnetic resonance angiography in humans using ferumoxytol, a novel ultrasmall superparamagnetic iron oxide (USPIO)-based blood pool agent

PURPOSE

To evaluate the feasibility of first-pass contrast-enhanced magnetic resonance angiography (MRA) using ferumoxytol in humans.

MATERIALS AND METHODS

First-pass and equilibrium phase MRA were performed using ferumoxytol in one healthy volunteer and 11 patients with a fast three-dimensional spoiled gradient recalled (SPGR) pulse sequence. The examined vessels included carotid arteries, thoracic aorta, abdominal aorta, and peripheral arteries. A dose of either 71.6 micromol Fe/kg (n = 9), or 35.8 micromol Fe/kg (n = 3) was used. Based on a phantom study, the agent with initial concentration of 537.2 micromol Fe/mL was diluted by either four-fold (134.3 micromol Fe/mL) or eight-fold (67.1 micromol Fe/mL) for first-pass MRA.

RESULTS

All subjects completed their studies without adverse events. First-pass MRA showed selective arterial enhancement, with both arterial and venous enhancement on delayed acquisitions. Selective venous enhancement could be obtained by subtraction of arterial phase images from equilibrium phase images. The findings in ferumoxytol MRA were consistent with the results of original vascular tests.

CONCLUSION

Our preliminary experience supports the feasibility of first-pass MRA with ferumoxytol. Satisfactory arterial enhancement during first-pass imaging is obtained with injection of diluted contrast agent. With ferumoxytol, arteries and veins can be selectively depicted in a single exam.

Myocardial delayed enhancement imaging using inversion recovery single-shot steady-state free precession: Initial experience

PURPOSE

To evaluate the feasibility of using an inversion recovery single-shot steady-state free precession (SS_SSFP) sequence for myocardial delayed enhancement (MDE) imaging, and to compare SS_SSFP with the conventional inversion recovery segmented fast gradient echo (IR_FGRE) technique.

MATERIALS AND METHODS

Ten subjects (four volunteers and six patients with suspected or known coronary disease) were included in this study. All subjects were scanned with both IR_FGRE and SS_SSFP sequences 15-25 minutes after gadopentetate dimeglumine injection. Overall image quality, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) between the two techniques were compared.

RESULTS

Compared to IR_FGRE, SS_SSFP exhibited adequate image quality (average scores = 3.8 for IR_FGRE and 3.9 for SS_SSFP) with much shorter acquisition time (14.4 seconds for IR_FGRE and 1.3 seconds for SS_SSFP). SS_SSFP images showed higher SNRs (P < 0.05) and less motion artifact from breathing. Enhanced myocardium was detected by both techniques in three patients, but the image sharpness is compromised in SS_SSFP images.

CONCLUSION

SS_SSFP provides adequate image quality compared to IR_FGRE, while requiring a much shorter acquisition time. It is feasible to use SS_SSFP as an alternative method for MDE imaging, especially in patients who have difficulty with holding their breath.

Preliminary Evaluation of EVP 1001-1

RATIONALE AND OBJECTIVES

To investigate the potential of a novel manganese-based magnetic resonance (MR) contrast agent, EVP 1001-1 for the evaluation of myocardial ischemia.

METHODS

MR imaging with EVP 1001-1 was performed on 6 Yorkshire pigs, and T1 relaxation times were calculated. One animal served as a control, 2 were subjected to an acute coronary artery occlusion and 3 provided a model of chronic ischemia.

RESULTS

Administration of the agent in the control and acute coronary occlusion model demonstrated a short plasma half-life (approximately 1.5 minutes) and rapid myocardial uptake in nonoccluded regions, with long retention times in the myocardium (>1 hour) and no evidence of redistribution. In the chronic ischemia model, differential enhancement was observed between normal and ischemic tissue, particularly under dobutamine-induced stress.

CONCLUSIONS

These properties suggest the use of EVP 1001-1 for steady-state imaging of myocardial perfusion. Contrast administration could be performed under stress conditions outside the scanner, with high-resolution MR images reflecting the stress condition acquired after the stress has subsided.

Simultaneous magnetic resonance gadolinium-enhanced 2D perfusion and 3D angiographic imaging

A method was implemented and tested that allows the simultaneous acquisition of magnetic resonance 2D slice selective perfusion and 3D angiographic data during a single bolus injection of a contrast agent. High quality contrast-enhanced perfusion images and angiograms of the lung, kidney and heart were obtained in healthy volunteers. Combined perfusion and angiography provided additional information with an acceptable increase in acquisition time. No image artifacts were attributed to the technique. The combined information may be useful in detecting, as well as characterizing, vascular abnormalities.

Computing oxygen-enhanced ventilation maps using correlation analysis

Correlation maps of oxygen-enhanced ventilation were obtained in nine healthy volunteers using complete and selected image series. The complete series included all images acquired with the subjects alternately inhaling room air and 100% oxygen. The selected series were the subsets of the complete series and included only co-registered images that showed matched diaphragmatic position at maximal expiration. Cross-correlation was computed between the time response function of each pixel and the input function representing the alternation between periods of room air and 100% oxygen inhalation. The confidence level for the correlation analysis was set to 0.01. Pulmonary parenchymal anatomy was consistently reproduced throughout the lung, even in anterior slices where published data have reported correlation problems. The overall average correlation coefficient was 0.66 +/- 0.07 for the complete series and 0.75 +/- 0.08 for the selected series. It was concluded that correlation analysis could be used to reconstruct qualitative oxygen-enhanced ventilation maps.

Band artifacts due to bulk motion

Band artifacts due to bulk motion were investigated in images acquired with fast gradient echo sequences. A simple analytical calculation shows that the width of the artifacts has a square-root dependence on the velocity of the imaged object, the time taken to acquire each line of k-space and the field of view in the phase-encoding direction. The theory furthermore predicts that the artifact width can be reduced using parallel imaging by a factor equal to the square root of the acceleration parameter. The analysis and results are presented for motion in the phase- and frequency-encoding directions and comparisons are made between sequential and centric ordering. The theory is validated in phantom experiments, in which bulk motion is simulated in a controlled and reproducible manner by rocking the scan table back and forth along the bore axis. Preliminary cardiac studies in healthy human volunteers show that dark bands may be observed in the endocardium in images acquired with nonsegmented fast gradient echo sequences. The fact that the position of the bands changes with the phase-encoding direction suggests that they may be artifacts due to motion of the heart walls during the image acquisition period.

T1 efficacy of EVP-ABD: a potential manganese-based MR contrast agent for hepatic vascular and tissue phase imaging

PURPOSE

To evaluate the T1 efficacy of EVP-ABD, a new manganese (Mn)-based contrast agent, for vascular and liver tissue enhancement in comparison with currently approved agents.

MATERIALS AND METHODS

Ten Yorkshire pigs (body weight, 26 -46 kg) were used for the efficacy evaluation, nine for kinetic T1 evaluation (three each agent) and one for post EVP-ABD imaging. With a fast imaging scheme to monitor T1 values of blood and liver, 10 micromol/kg EVP-ABD was injected intravenously and compared with gadopentetate dimeglumine (Magnevist, GdDTPA) and mangafodipir trisodium (Teslascan, mangafodipir trisodium) at routine clinical dosages. All were imaged with 3D T1 Gradient Recalled Echo (GRE) sequence (TR/TE/alpha = 3.8/1.6/25 degrees ) prior to and 10 minutes post injection using a 1.5-T whole-body scanner. Additional high-resolution 2D liver images (TR/TE/alpha = 50/4.6/40 degrees ) and arterial phase images of the upper aorta were acquired from the pig for post EVP-ABD imaging.

RESULTS

At 10 micromol/kg, EVP-ABD provided a dramatic decline in blood T1, comparable to 0.1 mmol/kg GdDTPA, followed by a rapid return to blood baseline T1 values. In addition to the blood enhancement phase, EVP-ABD achieved a 70% reduction in liver T1 within 2 minutes postadministration, with an imaging window of at least 2 hours. A substantially improved signal-to-noise ratio (SNR) was observed in both the 2D and 3D liver images postcontrast.

CONCLUSION

EVP-ABD demonstrated peak vascular enhancement similar to GdDTPA and prolonged specific liver enhancement exceeding mangafodipir trisodium. EVP-ABD has favorable T1 enhancing characteristics with the potential to allow for a comprehensive liver evaluation.

MR assessment of left ventricular function: quantitative comparison of fast imaging employing steady-state acquisition (FIESTA) with fast gradient echo cine technique

PURPOSE

To evaluate the agreement of fast imaging employing steady-state acquisition (FIESTA) cine technique with segmented k-space fast gradient echo (GRE) cine technique when using them for assessment of cardiac function.

MATERIALS AND METHODS

Eleven MR cine studies were performed on six healthy volunteers and five patients, using FIESTA and fast GRE techniques. The quantitative measurements of ventricular function obtained from the two techniques were compared. The data analysis was performed by two observers independently.

RESULTS

Compared to fast GRE cine technique, FIESTA cine technique consistently resulted in higher end-diastolic volume (10.2%) and end-systolic volume (21.6%), but lower myocardial mass of left ventricle (19.2%) and ejection fraction (9.9%). The stroke volume obtained from the two techniques was very close. The primary explanation for this variability is that the two techniques have different mechanisms on establishing signal contrast.

CONCLUSION

Compared to fast GRE technique, FIESTA provides significantly different results when using it for assessment of left ventricular function. It is important to consider this difference in the assessment of cardiac function.

Effect of diabetes on renal medullary oxygenation during water diuresis

OBJECTIVES

To study the effect of water diuresis on renal medullary and cortical oxygenation in patients with diabetes using blood oxygenation level--dependent magnetic resonance imaging (BOLD MRI).

RESEARCH DESIGN AND METHODS

Nine mild diabetic subjects (48 +/- 2.7 years of age, six women) and nine nondiabetic subjects of similar age and sex, all without known vascular or renal disease, were studied noninvasively by MRI before and during water diuresis.

RESULTS

Water diuresis induced an increase in medullary oxygenation in control subjects, producing a decrease in R2* (apparent spin-spin relaxation time) of 1.89 +/- 0.27 (P < 0.01), but no significant change in the group of diabetic subjects.

CONCLUSIONS

These findings in middle-aged diabetic subjects, which resembled those previously described in elderly subjects >65 years of age, suggest early impairment of adaptive vasodilatation within the renal medulla in diabetes.

MR ventilation-perfusion imaging of human lung using oxygen-enhanced and arterial spin labeling techniques

Magnetic resonance ventilation-perfusion (V/Q) imaging has been demonstrated using oxygen and arterial spin labeling techniques. Inhaled oxygen is used as a paramagnetic contrast agent in ventilation imaging using a multiple inversion recovery (MIR) approach. Pulmonary perfusion imaging is conducted using a flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER) technique. A half Fourier single-short turbo spin echo (HASTE) sequence is used for data acquisition in both techniques. V/Q imaging was performed in ten of the twenty volunteers, while either ventilation or perfusion was imaged in the other ten. This V/Q imaging scheme is completely noninvasive, does not involve ionized radiation, and shows promising potential for clinical use in the diagnosis of lung diseases such as pulmonary embolism.

Malignant syphilis (leus maligna) in a HIV infected patient

A 40-year-old promiscuous man presented with nodulo ulcerative lesions all over the body and a healing genital ulcer. Blood VDRL was reactive in 64 dilutions and HIV (Elisa) was positive. Patient was diagnosed to have malignant syphilis (leus maligna) and was given appropriate treatment. Lesions healed with hypopigmented macules suggestive of 'Icukoderma colli'.

JWARA (fever)- a medico historical perspective

"JWARA" is important and critical among all the diseases, because it affects each and every living being. Hence, it has been given first place in the classical texts of Ayurveda. Atharvaveda (AV) has also referred Jwara with the name Takman (son of God Varuna) and drugs like Kustha, Jangida and Anjana have been prescribed for its management. References with regard to Jwara are also found in other non-medical literature Viz., Mahābhārata, Purānas etc. Acārya Suśruta has mentioned that, man comes to this world with Jwara and departs with it. Jwara affects the whole body, the organs of senses and also the mind. According to mythology, Jwara was originated from the hot and destructive breath of Lord Siva, which was produced from his nostrils during the paroxysms of grief and rage on the death of his wife, Durga. It attacks all persons of all ages and in all conditions. Jwara is the king of all diseases, destroyer of all creatures and severe hence a physician should be practically cautious in treating it. All these medico-historical aspects of Jwara have been presented in this article.

Changes in intrarenal oxygenation as evaluated by BOLD MRI in a rat kidney model for radiocontrast nephropathy

The pathogenesis of radiocontrast nephropathy is poorly understood. In an animal model, inhibition of the synthesis of nitric oxide and prostaglandins appears to predispose rats to severe renal injury following the administration of radiocontrast. Here we have investigated whether administration of radiocontrast, as well as changes in renal medullary oxygenation following pharmacologic inhibition of nitric oxide and prostaglandin synthesis, might be evaluated by blood oxygenation level-dependent (BOLD) MRI. Nineteen anesthetized (Inactin 100 mg/kg) rats were studied. BOLD MRI measurements were performed following administration of L-NAME (N-nitro-L-arginine methyl ester, 10 mg/kg), Indomethacin (10 mg/kg), and a radiocontrast agent (sodium iothalamate 60%, 6 mL/kg). Marked sequential changes in medullary R(*)(2), presumably reflecting decline in medullary pO(2), were noted after each of the pharmacological interventions employed. These results, obtained by noninvasive MRI, are consistent with prior direct recordings of pO(2) and doppler flow in the rat renal medulla after administration of L-NAME, Indomethacin and iothalamate. Medullary oxygenation in rats was reduced by inhibition of the synthesis of prostaglandins and nitric oxide, as well as by intravenous injection of radiocontrast agents. BOLD MRI can noninvasively evaluate changes in medullary oxygenation in rats that appear to predispose acute renal failure. J. Magn. Reson. Imaging 2001;13:744-747.

A study of dapsone syndrome at a rural teaching hospital in South India

Dapsone syndrome or sulphone syndrome was noticed within four to six weeks of starting treatment in 10 out of 604 patients (1.6%) on MDT for leprosy treated at Rajah Muthiah Medical College Hospital, South Arcot District, Tamil Nadu State during the period 1995-1998. Patients developed either maculo papular rash or exfoliation along with fever and lymphadenopathy. Abnormal liver function tests were noticed in 50%. The patients with dapsone syndrome were treated with corticosteriods after withdrawing dapsone. There was complete resolution of skin lesions and other symptoms.

Pulmonary ventilation: dynamic MRI with inhalation of molecular oxygen

We have recently demonstrated a non-invasive technique to visualize pulmonary ventilation in humans with inhalation of molecular oxygen as a paramagnetic contrast agent. In the current study, T1 shortening of lung tissue by inhalation of oxygen was observed (P<0.001). The T1 values of lung tissue were also correlated with arterial blood oxygen pressure (PaO(2)) in a pig, resulting in excellent correlation (r(2)=0.997). Dynamic wash-in and wash-out MR ventilation images as well as dynamic wash-in wash-out signal intensity versus time curves were obtained. The mean wash-in decay constants were 26.8+/-10.5 s in the right lung, and 26.3+/-9.5 s in the left lung. The mean wash-out decay constants were 23.3+/-11.3 s in the right lung, and 20.8+/-10.5 s in the left lung. Dynamic assessment of pulmonary ventilation is feasible using oxygen-enhanced MR imaging, which could provide dynamic MR ventilation-perfusion imaging in combination with recently developed MR perfusion imaging technique, and thus a robust tool for the study of pulmonary physiology and pathophysiology.

Magnetic resonance imaging in endourology

Historically, the utilization of magnetic resonance imaging (MRI) in endourology has been limited. The availability of faster and stronger gradient systems has given rise to a number of data acquisition strategies that have significantly broadened the scope of MRI applications. These methods have led to the evaluation of anatomy and function using a single modality, and we describe our experience with MRI for comprehensive evaluation of the obstructed ureteropelvic junction. We also utilize these new imaging sequences in the investigation of alterated renal hemodynamics after extracorporeal shockwave lithotripsy and present our preliminary data on the application of MR perfusion imaging as a noninvasive technique for the evaluation of renal blood flow.

Semiquantitative assessment of uterine perfusion using first pass dynamic contrast-enhanced MR imaging for patients treated with uterine fibroid embolization

The feasibility of using first pass dynamic contrast-enhanced MRI to monitor semiquantitatively the perfusion changes of the uterus after uterine arterial embolization is demonstrated. Ten women, who underwent uterine arterial embolization for fibroid treatment, were included in this study. To derive a perfusion index, an additional axial slice through the abdominal aorta was obtained simultaneously when acquiring MR perfusion data. This technique may prove valuable in monitoring the outcome of uterine arterial embolization and documentation of preserved uterine perfusion after this procedure. J. Magn. Reson. Imaging 2000;12:1004-1008.

Captopril MR renography in a swine model: toward a comprehensive evaluation of renal arterial stenosis

PURPOSE

To test the feasibility of captopril magnetic resonance (MR) renography and to validate the technique in an animal model of renal arterial stenosis.

MATERIALS AND METHODS

Seven pigs with induced renal arterial stenosis were studied. MR renography was performed with a T1-weighted approach by using three-dimensional fast imaging with steady-state precession, or FISP, sequences after administration of a bolus of 0.1 mmol of gadopentetate dimeglumine per kilogram of body weight. Captopril was administered to improve the specificity.

RESULTS

The results demonstrate that differences in renographic curves and indices are observed only if an anatomically substantial stenosis, typically a diameter reduction of more than 70%, is present and captopril is administered.

CONCLUSION

In this preliminary experience in an animal model, captopril MR renography provided data consistent with expectations based on conventional renographic results.

Noninvasive pulmonary perfusion imaging by STAR-HASTE sequence

The STAR-HASTE sequence has been shown to be useful for perfusion imaging in areas that are plagued by magnetic susceptibility artifacts. Pulmonary perfusion imaging with this technique was attempted in this study. Quantitative analysis was also conducted, using an appropriate kinetic model in one subject. In six healthy subjects, gradual enhancement was observed in pulmonary artery to distal lung parenchyma when inflow time was increased. Our initial results suggest that noninvasive evaluation of pulmonary perfusion by magnetic resonance imaging without administration of an exogenous agent is possible.

Atharvaveda and its materia medica

Atharvaveda is the fourth and last Veda of Hindu literature. Its oldest name was 'ATHARVANGIRASAH', because it was contributed by two sages, ATHARVAN and ANGIRA. It is also known as 'Bhaishajjvaveda'. Atharvaveda gives information regarding plants, minerals and animal products with their usage for medical purposes. For example, 'Apamarga', a plant is useful for cough, piles, itching and abdominal pain, wherea 'Lavana' is useful for pimples; 'Shankha' useful to protect from diseases and 'Mriga Shringa' is useful for pulmonary consumption and other chronic diseases etc.

Effects of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.)

Groundnuts (Arachis hypogaea L.) are an important crop of the semi-arid tropics where they are often exposed to maximum temperatures of > 40 degrees C for short periods during the growing season. The objectives of this study were to determine: (i) the effects of short periods of exposure to high temperature on flower production (FN), the proportion of flowers forming fruits (fruit-set) and the number of pegs and pods per plant (RNt); (ii) whether fruit-set is affected by high temperature during different periods of daylight in each diurnal cycle; and (iii) whether responses to temperature were qualitative or quantitative. Plants of cv. ICGV 86015 were grown in controlled environments at a day/night temperature of 28/22 degrees C from sowing until 9 d after flowering (DAF). Then, cohorts of plants were: (a) exposed to day temperature of 28, 34, 42 or 48 degrees C for 2, 4 or 6 d; or were (b) exposed to 34, 42 or 48 degrees C for 6 d either throughout a 12 h day (08.00 to 20.00 h, WD), or only during the first 6 h (AM) or second 6 h (PM) of the day. Values of RNt were significantly reduced by high temperature, by duration of exposure, and by timing of exposure. Variation in FN was quantitatively related to floral bud temperatures during the day over the range 28-43 degrees C. In contrast, only floral bud temperatures > 36 degrees C during AM and WD significantly reduced fruit-set and hence RNt, whereas high PM temperature had no effect on fruit-set. These findings indicate that the response of RNt to day temperature is quantitative and can be modelled by combining the responses of FN and fruit-set to temperature.

Effects of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.)

Groundnuts (Arachis hypogaea L.) are an important crop of the semi-arid tropics where they are often exposed to maximum temperatures of > 40 degrees C for short periods during the growing season. The objectives of this study were to determine: (i) the effects of short periods of exposure to high temperature on flower production (FN), the proportion of flowers forming fruits (fruit-set) and the number of pegs and pods per plant (RNt); (ii) whether fruit-set is affected by high temperature during different periods of daylight in each diurnal cycle; and (iii) whether responses to temperature were qualitative or quantitative. Plants of cv. ICGV 86015 were grown in controlled environments at a day/night temperature of 28/22 degrees C from sowing until 9 d after flowering (DAF). Then, cohorts of plants were: (a) exposed to day temperature of 28, 34, 42 or 48 degrees C for 2, 4 or 6 d; or were (b) exposed to 34, 42 or 48 degrees C for 6 d either throughout a 12 h day (08.00 to 20.00 h, WD), or only during the first 6 h (AM) or second 6 h (PM) of the day. Values of RNt were significantly reduced by high temperature, by duration of exposure, and by timing of exposure. Variation in FN was quantitatively related to floral bud temperatures during the day over the range 28-43 degrees C. In contrast, only floral bud temperatures > 36 degrees C during AM and WD significantly reduced fruit-set and hence RNt, whereas high PM temperature had no effect on fruit-set. These findings indicate that the response of RNt to day temperature is quantitative and can be modelled by combining the responses of FN and fruit-set to temperature.

Effect of hyperbaric oxygen treatment on nitric oxide and oxygen free radicals in rat brain

Oxygen (O(2)) at high pressures acts as a neurotoxic agent leading to convulsions. The mechanism of this neurotoxicity is not known; however, oxygen free radicals and nitric oxide (NO) have been suggested as contributors. This study was designed to follow the formation of oxygen free radicals and NO in the rat brain under hyperbaric oxygen (HBO) conditions using in vivo microdialysis. Male Sprague-Dawley rats were exposed to 100% O(2) at a pressure of 3 atm absolute for 2 h. The formation of 2,3-dihydroxybenzoic acid (2, 3-DHBA) as a result of perfusing sodium salicylate was followed as an indicator for the formation of hydroxyl radicals. 2,3-DHBA levels in hippocampal and striatal dialysates of animals exposed to HBO conditions were not significantly different from controls. However, rats treated under the same conditions showed a six- and fourfold increase in nitrite/nitrate, break down products of NO decomposition, in hippocampal and striatal dialysates, respectively. This increase was completely blocked by the nitric oxide synthase (NOS) inhibitor L-nitroarginine methyl ester (L-NAME). Using neuronal NOS, we determined the NOS O(2) K(m) to be 158 +/- 28 (SD) mmHg, a value which suggests that production of NO by NOS would increase approximately four- to fivefold under hyperbaric O(2) conditions, closely matching the measured increase in vivo. The increase in NO levels may be partially responsible for some of the detrimental effects of HBO conditions.

Protective effect of aminophylline on renal perfusion changes induced by high-energy shockwaves identified by Gd-DTPA-enhanced first-pass perfusion MRI

PURPOSE

The purpose of this study was to evaluate regional renal hemodynamics in a noninvasive manner using gadolinium-DPTA magnetic resonance imaging (MRI) before and after extracorporeal shockwave lithotripsy (SWL). In addition, the renoprotective effect of intravenous aminophylline was evaluated on the perfusion on kidneys undergoing SWL.

PATIENTS AND METHODS

Ten randomly selected patients were evaluated for regional renal blood flow in the cortex and medulla with Gd-DTPA MRI studies within 2 weeks before and 4 hours after SWL. Five of these patients were treated with 500 mg of intravenous aminophylline 45 minutes prior to SWL. Renal hemodynamics were assessed utilizing relative perfusion indices (PI) calculated from signal intensity-v-time curves obtained from regions of interest (ROI). The ROI choice was based on the contrast-enhanced MRI images. Relative PIs of pre-SWL and post-SWL studies were compared in the first group of patients. Relative PIs of the treated kidney were compared with those of the contralateral kidney in the second group of patients, who received aminophylline.

RESULTS

In the group not treated with aminophylline, there was no significant difference in cortical perfusion before SWL (average PI -7+/-3%). However, after lithotripsy, there was a reduction of cortical flow (average PI 31+/-12%) in the treated kidney. In the group treated with aminophylline, renal hemodynamics study after SWL revealed no significant difference in relative perfusion (average PI -8+/-6%). Relative PIs of the medulla were small for all patients, but standard errors were large, indicating a wide range of values.

CONCLUSIONS

This study helps to establish reduced cortical flow after SWL and demonstrates that aminophylline attenuated this response in the kidneys subjected to lithotripsy. It appears that aminophylline administration causes no alteration in medullary blood flow.

Dynamic three-dimensional magnetic resonance abdominal angiography and perfusion: implementation and preliminary experience

Implementation of and preliminary experience with an ultra-fast partial-Fourier radiofrequency (RF) spoiled gradient-echo sequence for gadolinium-enhanced imaging are presented. Three-dimensional angiograms can be acquired in less than 6 seconds. Repetition of the acquisition allows the three-dimensional visualization of several distinct vascular phases. Feasibility is demonstrated in three healthy volunteers. The trade-offs among spatial resolution, temporal resolution, and spatial coverage as well as the technical aspects of gadolinium-enhanced pulse sequences are discussed.