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Brain edema is suggested to be the principal mechanism underlying the symptoms in acute hyponatremia. Identification of the mechanisms responsible for global and regional cerebral water homeostasis during hyponatremia is, therefore, of utmost importance. To examine the osmotic behavior of different brain regions and muscles, in vivo-determined water content (WC) was related to plasma sodium concentration ([Na+]) and brain/muscle electrolyte content. Acute hyponatremia was induced with desmopressin acetate and infusion of a 2.5% glucose solution in anesthetized pigs. WC in different brain regions and skeletal muscle was estimated in vivo from T1 maps determined by magnetic resonance imaging (MRI). WC, expressed in gram water per 100 g dry weight, increased significantly in slices of the whole brain [342(SD = 14) to 363(SD = 21)] (6%), thalamus [277(SD = 13) to 311(SD = 24)] (12%) and white matter [219(SD = 7) to 225(SD = 5)] (3%). However, the WC increase in the whole brain and white mater WC was less than expected from perfect osmotic behavior, whereas in the thalamus, the water increase was as expected. Brain sodium content was significantly reduced. Muscle WC changed passively with plasma [Na+]. WC determined with deuterium dilution and tissue lyophilzation correlated well with MRI-determined WC. In conclusion, acute hyponatremia induces brain and muscle edema. In the brain as a whole and in the thalamus, regulatory volume decrease (RVD) is unlikely to occur. However, RVD may, in part, explain the observed lower WC in white matter. This may play a potential role in osmotic demyelination.

Udgivelsesdato: 2010-Feb Meditation is an ancient spiritual practice, which aims to still the fluctuations of the mind. We investigated meditation with fMRI in order to identify and characterise both the "neural switch" mechanism used in the voluntary shift from normal consciousness to meditation and the "threshold regulation mechanism" sustaining the meditative state. Thirty-one individuals with 1.5-25 years experience in meditation were scanned using a blocked on-off design with 45 s alternating epochs during the onset of respectively meditation and normal relaxation. Additionally, 21 subjects were scanned during 14.5 min of sustained meditation. The data were analysed with SPM and ICA. During the onset of meditation, activations were found bilaterally in the putamen and the supplementary motor cortex, while deactivations were found predominately in the right hemisphere, the precuneus, the posterior cingulum and the parieto-temporal area. During sustained meditation, SPM analysis revealed activation in the head of nucleus caudatus. Extensive deactivations were observed in white matter in the right hemisphere, i.e. mainly in the posterior occipito-parieto-temporal area and in the frontal lobes. ICA identified 38 components including known baseline-resting state components, one of which not only overlaps with the activated area revealed in the SPM analysis but extends further into frontal, temporal, parietal and limbic areas, and might presumably constitute a combination of frontoparietal and cinguloopercular task control systems. The identified component processes display varying degrees of correlation. We hypothesise that a proper characterisation of brain processes during meditation will require an operational definition of brain dynamics matching a stable state of mind.

Udgivelsesdato: 2010-Mar-8 BACKGROUND: Several lines of evidence suggest hippocampal dysfunction in major depression, but the prevalence and nature of specific dysfunctions during the long-term course of major depression is yet to be assessed. A 3D virtual environment navigation task and measurements of hippocampal volume were assessed in remitted former inpatients with moderate to severe depression after an 8year follow-up period to evaluate whether functional and structural differences existed in the hippocampus beyond depression. METHODS: Performance on a right hippocampus-dependent 3D virtual reality navigation task, memory tests and right and left hippocampal volumes were assessed in 31 remitted depressed (unipolar) patients and 37 healthy subjects. RESULTS: Remitted depressed patients did not differ significantly from healthy subjects in terms of either neuropsychological performance or hippocampal volume. LIMITATIONS: The sample consisted of remitted inpatients that had been treated with psychotropic drugs during the 8-year follow-up period. Moreover, 11 of the 42 patients included in the original study were excluded from the follow-up study due to persisting depressive illness and suicide. CONCLUSIONS: The study of visuospatial navigation ability and hippocampal volume in remitted depressed patients offers a specific way of assessing dysfunction in the hippocampus in major depression. Our findings do not support the notion that hippocampal impairment of visuospatial function exists beyond the depressive state, thus indicating that hippocampus-related cognitive dysfunction and previously reported reduced hippocampal volume might represent a state and not a permanent trait of the illness. Moreover, our study suggests that intensive drug treatment of the depressive episodes might prevent the deterioration of the hippocampus.

Computer-based analysis of textures in magnetic resonance images provides a higher sensitivity to textural changes that cannot be recognized by the naked human eye. Thus, there is a better potential for identifying pathophysiological processes at an earlier stage or of a different character than even a trained radiologist can find. In the present study, the potential of texture analysis for in vivo identification of the administering effect of an anti-inflammatory drug in cerebral stroke in rats was evaluated. Twenty-seven Wistar rats underwent middle cerebral artery occlusion resulting in local ischemic brain infarct. One group of rats received alpha-melanocyte stimulating hormone (alpha-MSH) and a control group received saline only. T2-weighted images, apparent diffusion maps, and T2 maps were recorded by MR. Texture features were calculated in the T2-weighted images and correlated to the apparent diffusion coefficient (ADC) and the T2 values. From an array of tested texture features three independent features were tested further. Two of which were found to provide a significant discriminative classification between the control and the alpha-MSH groups. Furthermore, the same two texture features were significantly correlated to the ADCs. Thus, quantification of texture features can be helpful in detecting the effects of stroke therapy.

Objective: To investigate signal changes in transverse relaxation (T2) from porcine articular cartilages after the trypsin digestion in vitro. Methods: T2 relaxation times were measured from porcine patellar cartilages. The samples (n=20) were assigned to 2 groups. Group A of right patellar samples (n=10) were immersed in PBS and served as self-control group. The left patellar samples (n=10) were immersed in PBS with trypsin for 4 h and served as treated group (B). T2-images were collected with a spin-echo Sequence on a 7.0T scanner. Using a home-built analysis program, T2-maps were obtained and the cartilage from each sample was manually segmented by drawing regions-of-interest. This segmentation separated the patellar cartilage into four layers (superficial, middle, deep and calcified), which represented the superficial, transitional, radial, calcified zones respectively, to investigate regional differences of T2 in patellar cartilage. Results: T2 relaxation in full, superficial and middle layers (P

Udgivelsesdato: 2008-null PURPOSE: To evaluate the effect of the vascular disrupting drugs combretastatin A-4 disodium phosphate (CA4DP) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) on the intra/extracellular volume fraction of water and blood perfusion in tumours using MRI. METHODS AND MATERIALS: Mice with C3H mammary carcinomas underwent repeated MRI T2-weighted imaging, water-diffusion and perfusion measurements before and up to 6-hours following CA4DP and DMXAA treatment. RESULTS: CA4DP treatment caused an increase in water diffusion in those tumour areas that presented the lowest blood perfusion, however this appeared only after five hours. The blood perfusion in highly perfused tumour regions decreased immediately after administration of CA4DP. DMXAA treatment caused an early decrease in water diffusion in the low-perfused tumour segments and followed by a subsequent decrease in the remaining part of the tumour. The blood perfusion decreased early in all parts of the tumour. CONCLUSION: The effect of CA4DP and DMXAA on tumour blood flow was comparable. The reduction in regional blood flow caused by CA4DP in the whole tumour segment occurred early, however, changes in ADC after DMXAA appeared more extended and earlier than after CA4DP treatment, especially in tumour areas already suffering from a low blood perfusion.

The intestines of Grauballe Man, who is a 2400-old late Iron Age body found in a raised bog in the central part of Jutland, Denmark, was examined by microscopy and magnetic resonance imaging. Plant roots found in the tissue were radiocarbon dated by AMS. Magnetic resonance imaging (MRI) showed a uniform structure of the tissue, without any recognizable individual layers. Low signal areas with a diameter of less than 1 mm in diameter appeared with individual distances of 3-10 mm. Microscopy revealed that only the connective tissue layer just under the intestinal mucous membrane was left. The low signal spots observed by MRI turned out to be formed by plant roots penetrating the tissue. AMS 14C-dating of these indicated that penetration appeared not more than 200 years after the body was laid in the bog.

We report a highly significant regional increase of the BOLD response in the caudate nucleus in a group of Danish Christians while performing silent religious prayers. The effect was found in a main-effect analysis of high-structured and low-structured religious recitals relative to comparable secular recitals and to a non-narrative baseline. This supports the hypothesis that religious prayer as a form of frequently recurring behavior is capable of stimulating the dopaminergic reward system in practicing individuals. It extends recent research which demonstrates a relation between interpersonal trust and activation in the dopaminergic system to also encompass relations to abstract entities.

Udgivelsesdato: 2008-Nov-11 STUDY DESIGN.: Prospective and randomized experimental study with anterior lumbar interbody fusion in a porcine model. OBJECTIVE.: To assess the early time-course of spinal fusion with equine bone protein extract (COLLOSS E), recombinant human bone morphogenetic protein-2 (rhBMP-2), and autograft using quantitative methods of positron emission tomography (PET)/computed tomography and magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA.: Different growth and differentiation factors are currently being used for inducing bone formation in spinal fusion. However, the mechanisms and time-course of bone formation using these graft substitutes remain less known. METHODS.: Eighteen female Danish landrace pigs underwent a 3-level anterior lumbar interbody fusion procedure from L3-L6. A PEEK cage, packed with COLLOSS E, rhBMP-2, or autograft, was randomly placed. Each group of 6 pigs was observed for 2, 4, or 8 weeks, respectively. F PET/computed tomography and MRI examinations were performed, and data were correlated with histomorphometry. PET data were analyzed using a Gjedde-Patlak plot. K-values from the plot correspond to the metabolic rate. T2-values were calculated by T2 mapping. RESULTS.: rhBMP-2 presented the highest bone formation on histologic sections at 25.6% at 4 weeks after surgery. Eight weeks after surgery, autograft had the highest bone formation with 37.3%, which was significantly higher than rhBMP-2 at 30.5% (P < 0.05), and higher than COLLOSS E at 27.0% (P = 0.06). COLLOSS E and rhBMP-2 had significantly higher K-values than autograft (P < 0.05) at 2 weeks after surgery. There were no differences in K-values between COLLOSS E and autograft at 4 and 8 weeks. However, rhBMP-2 was significantly higher at 4 weeks and lower at 8 weeks than these 2 (P < 0.05). Linear correlation, R = 0.8275, was observed for intertrabecular volume/total volume and T2-values. CONCLUSION.: PET and MRI are valid tools for monitoring the process of interbody fusion in vivo. Osteogenic mechanisms using COLLOSS E resembles that of autograft by the process of endochondral ossification. rhBMP-2 deposits osteoid directly on the collagen network.

The impact of fasting on IHL (intrahepatic lipid) content in human subjects has not been investigated previously, but results indicate that it may change rapidly in response to metabolic cues. The aim of the present study was to measure IHL content after fasting and to correlate this with circulating lipid intermediates. A total of eight healthy non-obese young males were studied before and after 12 or 36 h of fasting. IHL content was assessed by 1H-magnetic resonance spectroscopy, and blood samples were drawn after the fasting period. IHL content increased significantly after the 36 h fasting period [median increase 156% (range, 4–252%); P

Udgivelsesdato: 2008-null INTRODUCTION: Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) allows in vivo characterization of tumour vasculature. As such, it is applicable for monitoring the effects of treatments targeting vasculature. The aims of this study were to evaluate the properties of tumour areas segmented-out by DCE-MRI parameters and to evaluate the changes induced by the vascular disrupting agent (VDA) combretastatin A-4 disodium phosphate (CA4DP), a leading VDA in clinical trials, in these areas. MATERIAL AND METHODS: Two tumour models previously shown to respond differently to CA4DP were chosen. The C3H mammary carcinoma and the KHT sarcoma were grown in the right rear foot of CDF(1) and C3H/km mice, respectively, and treated when at 200 or 800 mm(3) in size. DCE-MRI, using the contrast agent Gd-DTPA, was performed on a 7 T spectroscopy/imaging system before and 3 hours after i.p. CA4DP administration at a dose of 100 mg/kg. From the voxel concentration-time curves, the semiquantitative parameter of initial area under the curve (IAUC), the model parameters transfer constant K(trans), interstitial volume v(e), and blood plasma volume v(p), were calculated. Tumour images were segmented into three groups based on the DCE-MRI model parameters using the K-means algorithm, and the groups were ranked by IAUC. RESULTS: The resulting voxels of the tumour segments were mainly spatially connected structures. Initial DCE-MRI parameter values showed different dependencies on tumour model and size in the regions. For all regions in all tumour groups, the treatment reduced IAUC by 36-51%, whereas the model parameters showed more dependencies on tumour model and size. DISCUSSION: This segmentation technique identifies tumour regions with different microenvironmental characteristics responding differently to CA4DP and may be valuable in the optimization of combined VDA with radiotherapy or chemotherapy. The method may also prove useful for optimization and monitoring of local treatment such as radiotherapy.

Udgivelsesdato: 2008

Background/Aims: To investigate the effects of long-term epidermal growth factor (EGF) treatment on kidney growth, renal blood flow (RBF), AQP2 expression and urine output in newborn rats with partial unilateral ureteral obstruction (PUUO). Methods: PUUO (n = 29) and sham-operated control (CON) (n = 26) was created in 2-day-old rats. Fifteen PUUO and 14 CON rats were treated with EGF beginning from the second day after operation to 8 weeks of age. Total kidney volume (TKV) and RBF were measured by MRI at weeks 4 and 8, respectively. Urine volume and osmolality, plasma osmolality, and free water clearance were measured. Renal AQP2 expression was determined using semiquantitative immunoblotting. Results: PUUO induced a severe hydronephrosis and RBF reduction in the obstructed kidney which was attenuated in EGF-treated rats. Body weight, urine output and free water clearance increased, osmolality and the osmolar clearance decreased significantly in EGF-treated rats, despite unchanged AQP2 levels. Conclusions: Long-term EGF treatment attenuated the obstruction- induced RBF reduction. Body weight, urine output increased, and urine osmolality decreased in both control and PUUO rats treated with EGF. Solute-free water clearance increased in PUUO rats which seem to be independent of AQP2 expression.

The present study was designed to evaluate the short-term effects of intravenous administration of furosemide on key functions in the kidney cortex and the outer and inner medulla of rats by using magnetic resonance imaging (MRI). Renal tissue water content, renal tissue oxygenation (in relation to the magnetic resonance spin-spin relaxation rate), the apparent diffusion coefficient (ADC) of water, and volume of renal blood flow were measured. Furosemide administration resulted in an increased water content in all regions of the kidney. In parallel with this, we found a significant reduction in ADC in the cortex (2.7 ± 0.1 × 10−3 to 2.3 ± 0.1 × 10−3 mm2/s; P < 0.01) and in the outer medulla (2.3 ± 0.1 × 10−3 to 2.0 ± 0.1 × 10−3 mm2/s; P < 0.01), indicating that the intra- to extracellular volume fraction of water increased in response to furosemide administration. Furosemide also decreased the blood oxygenation in the cortex (49.1 ± 2.9 to 40.9 ± 2.0 s−1; P < 0.01), outer medulla (41.9 ± 2.8 to 33.2 ± 1.6 s−1; P < 0.01) and in the inner medulla (37.1 ± 2.9 to 26.7 ± 1.8 s−1; P < 0.01), indicating an increased amount of oxygenated Hb in the renal tissue. Moreover, renal blood flow decreased in response to furosemide (6.9 ± 0.2 to 4.4 ± 0.2 ml/min; P < 0.001). In conclusion, furosemide administration was associated with increased renal water content, an increase in the intra- to extracellular volume fraction of water, an increased oxygen tension, and a decrease in the renal blood flow. Thus MRI provides an integrated evaluation of changes in renal function, leading to decreased renal water and solute reabsorption in response to furosemide, and, in addition, MRI provides an alternative tool to monitor noninvasively changes at the cellular level.

A general hindrance to progress in adoptive cellular therapy is the lack of detailed knowledge of the fate of transferred cells in the body of the recipient. In this study, we present a novel technique for tracking of 124 I-labeled cells in situ, which combines the high spatial resolution of magnetic resonance imaging with the high sensitivity and spatial accuracy of positron emission tomography. We have used this technique, together with determination of tissue radioactivity, flow cytometry, and microscopy, to characterize and quantitate the specific accumulation of transferred CD8 + T cells in tumor tissue in a mouse model. Transgenic CD8 + T cells, specific for the ovalbumin peptide SIINFEKL, were adoptively transferred to recipients carrying a subcutaneous tumor of the ovalbumin-expressing malignant melanoma cell line B16-OVA. The number of SIINFEKL-specific CD8 cells in the tumor tissue was determined by flow cytometry each day for 8 consecutive days after adoptive transfer. From low levels 1 day after injection, their number gradually increased until day 5 when an average of 3.3 × 10 6 SIINFEKL-specific cells per gram tumor tissue was found. By applying the combined positron emission tomography/magnetic resonance imaging technique we were able to determine the position of the transferred, 124 I-labeled SIINFEKL-specific T cells in 3 dimensions in recipient mice, and could demonstrate a highly significant accumulation of the 124 I label in and around the subcutaneous B16-OVA tumors compared with normal tissue. Accumulation of 124 I was significantly higher in B16-OVA than in B16 tumors not expressing the OVA antigen.

Udgivelsesdato: Sep

In the metabolism of acetate several enzymes are involved, which play an important role in free fatty acid oxidation. Fatty acid metabolism is altered in diabetes patients and therefore acetate might serve as a marker for pathological changes in the fuel selection of cells, as these changes occur in diabetes patients. Acetylcarnitine is a metabolic product of acetate, which enables its transport into the mitochondria for energy production. This study investigates whether the ratio of acetylcarnitine to acetate, measured by noninvasive hyperpolarized [1-(13)C]acetate magnetic resonance spectroscopy, could serve as a marker for myocardial, hepatic, and renal metabolic changes in rats with Streptozotocin (STZ)-induced diabetes in vivo. We demonstrate that the conversion of acetate to acetylcarnitine could be detected and quantified in all three organs of interest. More interestingly, we found that the hyperpolarized acetylcarnitine to acetate ratio was independent of blood glucose levels and prolonged hyperglycemia following diabetes induction in a type-1 diabetes model.

The origin of electrical burns under gel-type surface electrodes is a controversial topic that is not well understood. To investigate the phenomenon, we have developed an excised porcine skin-gel model, and used low-frequency current density imaging (LFCDI) to determine the current density (CD) distribution through the skin before and after burns were induced by application of electrical current (200 Hz, 70% duty cycle, 20-35 mA monophasic square waveform applied to the electrodes for 30-135 min). The regions of increased CD correlate well with the gross morphological changes (burns) observed. The measurement is sensitive enough to show regions of high current densities in the pre-burn skin, that correlate with areas were burn welts were produced, thus predicting areas where burns are likely to occur. Statistics performed on 28 skin patches revealed a charge dependency of the burn areas and a relatively uniform distribution. The results do not support a thermal origin of the burns but rather electro-chemical mechanisms. We found a statistically significant difference between burn area coverage during anodic and cathodic experiments.

Texture analysis can be used to identify and discriminate between objects in an image and has already been used for the characterization of diseases. The present study evaluated the potential of texture analysis for monitoring tumor cell viability during treatment with an anti-vascular drug.Texture analysis of T2-weighted magnetic resonance images of C3H mammary carcinomas in mice was used to study tumor cell viability during treatment with the anti-vascular drug combretastatin A-4 disodium phosphate (CA4DP). Texture analysis was done by MaZda, and boot strap statistics were used to analyze the results.The results revealed significant differences in the textures of T2-weighted images when non-tumor tissue and tumor tissue were compared. Furthermore, selected texture parameters were significantly different when image data from before and after CA4DP administration were analyzed.Texture analysis is helpful in the diagnosis of different types of tissues, especially when these tissues can not be recognized by human observers. Some functional changes, such as perfusion changes in the tumor, can also be detected by texture analysis.

MRI measurements of water diffusion and blood perfusion are increasingly used for the evaluation of organ functionality and tissue viability (e.g., in tumors). While diffusion-weighted imaging is performed without contrast agents, measurement of blood perfusion is normally performed based on the administration of paramagnetic substances such as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Simultaneous measurements of these two parameters are often preferred. However, it may be argued that Gd-DTPA causes constriction of small blood vessels or alters hemodynamic parameters such as blood viscosity, thereby corrupting subsequent measurements of the apparent diffusion constant (ADC). The objective of the current study was to investigate the possible changes in the ADC in tumors following intravenous administration of 0.2 and 0.4 mmol/kg of Gd-DTPA in mice. The study was conducted with C3H mouse mammary carcinomas inoculated in the right foot of the animal subjects. The results were compared with findings in a sham group, demonstrating that Gd-DTPA had no significant impact on the ADC as measured in a 7-T animal system.

A method for precise and sensitive organ specific quantification of 124 I ( 124 IdUR) activities in small animals has been developed. The method is based upon high precision co-registration between PET and MR imagery, utilizing an innovative mouse fixation system with external point sources visible in bo th modalities. The methodology is generic, and thus can easily be extended to other types of small animal studies. The methodology comprises PET/MR rigid co-registration util ising external fiducial markers, measurement of activities within small 3D volumes manua lly drawn in MR data and extracted from the co-aligned PET data, and subsequently corrected for Partial Volume Effect. Keywords: Small animal imaging, image registration, PET, MRI, cell labelling 1. INTRODUCTION Today it is widely recognized that a variety of imaging technologies can provide valuable information for biology research and diagnosis of clinical patients. In clinical environments, techniques like x-ray computed tomography (CT), magnetic resonance imaging (MR) and ultrasound are used routinely to generate high resolution (~1 mm) images of human anatomy and pathology. In addition, highly sensitive molecular techniques using radio-labelled tracers are used for imaging specific physiological processes like perfusi on, metabolism, receptor binding, and enzyme activity. The classical technique for in-vivo physiological imaging is single-photon emission computed tomography (SPECT), however, more recently positron emission tomography (PET) has become increasingly popular due to better sensitivity and spatial resolution (~5 mm). Also, PET allows studying the distribution and localization of the tracer over time with time resolution down to a few seconds. In many cases, the radioisotope imaging techniques produce im ages with very specific ac cumulation of the tracer in a few selected organs or targets. The absence of general anatomical information complicates interpretation of radioisotope images, both in terms of precise localization of the signal, and separation of specific and non-specific accumulation. Consequently, the need for combining different imaging techniques with complementary information has been recognized, and algorithms for retrospective image registration have been developed (Hill; 2001). A recent

A first-pass upslope approach was used to estimate differential renal blood flow (DRBF) and a Patlak-Rutland approach was used to estimate differential renal function (DRF) using Gd-DTPA-BMA-enhanced MRI. DRBF and DRF were estimated in rat kidneys under three different experimental conditions: 1) transient renal artery occlusion (TRAO); 2) partial unilateral ureteric obstruction (PUO); and 3) sham-operated control rats (SHAM). A bolus of Gd-DTPA-BMA was given intravenously during a dynamic single slice T1-weighted gradient echo sequence, which allowed calculation of concentration from signal intensity values. Calculations based on the raw signal intensity showed that DRBF was decreased in both PUO (44 +/- 1%; P0.05) and in TRAO (38 +/- 1%; P0.05) compared with SHAM (52 +/- 1%). Converting the signal intensity into a measure of Gd-DTPA-BMA concentration did not substantially alter these findings (PUO: 40 +/- 3%, P0.05; TRAO: 35 +/- 2%, P0.05; SHAM 49 +/- 1%). Likewise, DRF decreased in both PUO (43 +/- 4%; P0.05) and TRAO (39 +/- 3%; P0.05) compared with SHAM (48 +/- 2%). Converting the signal intensity into measurements of Gd-DTPA-BMA concentration revealed similar findings (PUO: 41 +/- 5%, P0.05; TRAO: 34 +/- 5%, P0.05; SHAM: 49 +/- 2%). Our results suggest that renal damage in rats may be demonstrated by an observed reduction of DRBF and DRF as estimated from single-slice Gd-DTPA-BMA enhanced signal intensity using time-activity curves with and without quantitation of Gd-concentration.

The incidence of congenital hydronephrosis is ∼1% and is often associated with renal insufficiency. It is unknown whether early release is essential to prevent deterioration of renal function. Rats were subjected to partial unilateral ureteral obstruction (PUUO) on postnatal day 2. The obstruction was left in place or released after 1 or 4 wk. Renal blood flow (RBF) and kidney size were measured sequentially over 24 wk using MRI. In rats in which the obstruction was left in place, RBF of the obstructed kidney was progressively reduced to 0.92 ± 0.17 vs. 1.79 ± 0.12 ml·min−1·100 g body wt−1( P < 0.05) after 24 wk. Similarly, glomerular filtration rate of the obstructed kidney was severely reduced at 24 wk: 172 ± 36 vs. 306 ± 42 μl·min−1·100 g body wt−1( P < 0.05). These changes were preceded by development of severe hydronephrosis and obstructive nephropathy with a reduction in total protein content: 45 ± 3 vs. 58 ± 4 mg/kidney. Moreover, nonreleased PUUO caused a marked natriuresis (0.32 ± 0.07 vs. 0.11 ± 0.02 μmol·min−1·100 g body wt−1, P < 0.05) and impaired solute free water reabsorption (0.47 ± 0.16 vs. 2.71 ± 0.67 μl·min−1·100 g body wt−1, P < 0.05), consistent with a significant downregulation of Na-K-ATPase to 62 ± 7%, aquaporin-1 to 53 ± 3%, and aquaporin-3 to 53 ± 7% of sham levels. Release after 1 wk completely prevented development of hydronephrosis, reduction in RBF and glomerular filtration rate, and downregulation of renal transport proteins, whereas release after 4 wk had no effect. These results suggest that early release of neonatal obstruction provides dramatically better protection of renal function than release of obstruction after the maturation process is completed.

The objective of this study was to examine the effect of unilateral ureteral obstruction on the apparent diffusion coefficient (ADC) in pig kidney. Changes in ADC is suggested to reflect changes in the ratio of extracellular to intracellular volume. Thirteen pigs were allocated into three groups: 1) pigs subjected to acute unilateral ureteral obstruction (AUO) (n = 3), 2) pigs subjected to chronic partial unilateral obstruction (CPUO) (n = 3), and 3) control pigs (n = 7). The extra- to intracellular volume ratio was indirectly measured in both the ipsilateral obstructed kidney and contralateral non-obstructed kidney by the ADC of the renal tissue using diffusion-weighted echo-planar magnetic resonance imaging. ADC was 2.07 +/- 0.27 x 10(-3) mm2/s in the cortex and 2.10 +/- 0.24 x 10(-3) mm2/s in the medulla of normal control kidneys. In the obstructed kidney from the AUO group the ADC of the medulla was significantly reduced 24 hours after occlusion of the ureter (1.65 +/- 0.05 x 10(-3) mm2/s vs 2.10 +/- 0.24 x 10(-3) mm2/s; p0.05). Similarly ADC decreased slightly in the cortex of the ipsilateral kidney. In contrast, ADC of the ipsilateral kidney of CPUO pigs was increased both in the renal medulla (3.13 +/- 0.21 x 10(-3) mm2/s vs. 2.10 +/- 0.24 x 10(-3) mm2/s; p0.05) and cortex (3.09 +/- 0.14 x 10(-3) mm2/s vs. 2.07 x 10(-3) mm2/s, p0.05). In conclusion, the results of the present study suggest that diffusion weighted imaging (ADC) may be a useful parameter to incorporate when identifying whether a ureteric obstruction is acute or chronic.

The purpose of this study was to create a 3D visualization of the urinary tract by a novel virtual reality approach, and to evaluate the usefulness of this method for papillary classification as compared with 2D urogram obtained by maximum intensity projection (MIP).In one healthy pig, magnetic resonance urography was performed using a T1-weighted 3D gradient echo pulse sequence. Post-processing was performed by means of an MIP algorithm and by using 3D virtual reality modelling, followed by manual classification of papillae as being either simple or compound.The 2D MIP urogram demonstrated 6 simple and 6 compound papillae, whereas the 3D urogram demonstrated 5 simple and 7 compound papillae. In both urograms, some papillae were unsuccessfully classified.The possibility of using virtual reality devices allowed 3D rotation and offered additional diagnostic information. However, further studies should reveal its feasibility in diseased kidneys.

Objective. To examine the potential of gadolinium (Gd)-enhanced dynamic MRI in the detection of early femoral head ischemia. Furthermore, to apply a three-compartment model to achieve a clinically applicable MR index for femoral head perfusion during the steady state and arterial hip joint tamponade. Design and materials. In a porcine model femoral head perfusion was measured by radioactive tracer microspheres and by using a dynamic Gd-enhanced MRI protocol. Femoral head perfusion measurements and MRI tests were performed unilaterally before, during and after the experimentally induced ischemia of one of the hip joints. Ischemia was induced by increasing intra-articular pressure to 250 mmHg. Results. All pigs showed ischemia of the femoral head epiphysis under hip joint tamponade followed by reperfusion to the same level as before joint tamponade. In two cases perfusion after removal of tamponade continued to be low. In dynamic MRI measurements increases in signal intensity were seen after intravenous infusion of Gd-DTPA, followed by a slow decrease in signal intensity. The signal-intensity curve during femoral head ischemia had a minor increase. Also the coefficient determined was a helpful indicator of femoral head ischemia. Conclusions. Femoral head blood flow as measured by microspheres fell significantly under joint tamponade. Early detection of this disturbed regional blood flow was possible using a dynamic MRI procedure. A biomathematical model resulted from the evaluation of the intervals of signal intensity over time which allows detection of bone blood flow changes at a very early stage. Using this new method earlier detection of femoral head necrosis may be possible.

Cerebral water accumulation was studied during induction of brain edema in dystrophin-null transgenic mice ( mdx- β geo ) and control mice. Immunofluorescence and immunoelectron microscopic analyses of dystrophin-null brains revealed a dramatic reduction of AQP4 (aquaporin-4) in astroglial end-feet surrounding capillaries (blood–brain barrier) and at the glia limitans (cerebrospinal fluid–brain interface). The AQP4 protein is mislocalized, because immunoblotting showed that the total AQP4 protein abundance was unaltered. Brain edema was induced by i.p. injection of distilled water and 8-deamino-arginine vasopressin. Changes in cerebral water compartments were assessed by diffusion-weighted MRI with determination of the apparent diffusion coefficient (ADC). In dystrophin-null mice and control mice, ADC gradually decreased by 5–6% from baseline levels during the first 35 min, indicating the initial phase of intracellular water accumulation is similar in the two groups. At this point, the control mice sustained an abrupt, rapid decline in ADC to 58% ± 2.2% of the baseline at 52.5 min, and all of the animals were dead by 56 min. After a consistent delay, the dystrophin-null mice sustained a similar decline in ADC to 55% ± 3.4% at 66.5 min, when all of the mice were dead. These results demonstrate that dystrophin is necessary for polarized distribution of AQP4 protein in brain where facilitated movements of water occur across the blood–brain barrier and cerebrospinal fluid–brain interface. Moreover, these results predict that interference with the subcellular localization of AQP4 may have therapeutic potential for delaying the onset of impending brain edema.

The human ability to detect, interpret, assess and report visual stimuli is employed for qualitative and quantitative image analysis. Cross-sectional T1weighted MR images were acquired from a series of intact potatoes. Descriptive sensory image analysis was performed on the images. The sensory results were compared to conventional computer-assisted grey tone intensity histogram descriptors. A total of 60 tubers (2 varieties×2 storage times×15 replicate tubers) were submitted to MR-imaging. A trained panel of 9 assessors used 16 sensory descriptors to assess the images. These descriptors were developed by the panel during preliminary training sessions, and consisted in definitions of various biological compartments inside the tubers. The results from the sensory and the computer-assisted image analyses of the shape and interior structure of the tubers were related to the experimental design and to the dry matter content of the individual tubers, by partial least-squares regression (PLSR). Finally, predictive modelling of sensory image description from computer-assisted image analysis was attempted. The results showed that both the sensory and the computer-assisted image analyses were able to detect differences between varieties as well as storage times. The sensory image analysis gave better discrimination between varieties than the computer-assisted image analysis presently employed, and was easier to interpret. Some sensory descriptors could be predicted from the computer-assisted image analysis. The present results offer new information about using sensory analysis of MR-images not only for food science but also for medical applications for analysing MR and X-ray images and for training of personnel, such as radiologists and radiographers.