Association between over-indebtedness and antidepressant use: A cross-sectional analysis

Background

Burden of disease caused by depression and its association with socioeconomic status is well documented. However, research on over-indebtedness is scarce although millions of European citizens in all socioeconomic positions are over-indebted. Prior studies suggested that over-indebtedness is associated with poor physical and mental health.

Aims

Investigate the association between over-indebtedness and antidepressant use in Germany.

Method

A cross-sectional survey among debt advice agencies’ clients was conducted in North Rhine-Westphalia, Germany, in 2017 (OID). Data were merged with the first wave of the German Health Interview and Examination Survey for Adults (DEGS1). Descriptive statistics and logistic regression analysis were used to examine antidepressant use in the previous 7 days (OID: n = 699; DEGS1: n = 7115).

Results

Prevalence of antidepressant use was higher in the over-indebted (12.3%) than the general population (5.0%). The over-indebted were significantly more likely to use antidepressants than the general population even after controlling for other socioeconomic, demographic and health factors (adjusted odds ratio 1.83; 95% confidence interval 1.35–2.48).

Conclusions

Stakeholders in health care, debt counselling, research and social policy should consider the link between over-indebtedness and mental illness to advance the understanding of health inequalities and to help those who have mental health and debt problems.

Patient-physician communication about financial problems: A cross-sectional study among over-indebted individuals

Background

About every tenth household across Europe is unable to meet payment obligations and living expenses on an ongoing basis and is thus considered over-indebted. Previous research suggests that over-indebtedness reflects a potential cause and consequence of psychosomatic health problems and limited access to care. However, it is unclear whether those affected discuss their financial problems with general practitioners. Therefore, this study examined patient-physician communication about financial problems in general practice among over-indebted individuals.

Methods

We conducted a cross-sectional survey among clients of 70 debt advice agencies in North Rhine-Westphalia, Germany, in 2017. We assessed the prevalence of patient-physician communication about financial problems and its association with patient characteristics using descriptive statistics and logistic regression analysis. Of 699 individuals who returned the questionnaire (response rate:50.2%), we included 598 respondents enrolled in statutory health insurance with complete outcome data in the analyses.

Results

Conversations about financial problems with general practitioners were reported by 22.6% (n = 135) of respondents. Individuals with a high educational level were less likely to report such conversations than those with medium educational level (aOR 0.11; 95%CI 0.01–0.83) after adjustment for other sociodemographic characteristics, health status and measures of financial distress. Those without a migrant background(aOR 2.09; 95%CI 1.32–3.32), the chronically ill(aOR 1.90; 95%CI 1.16–3.13) and individuals who reported high financial distress(aOR 2.15; 95%CI 1.22–3.78) and cutting on necessities to pay for medications(aOR 1.86; 95%CI 1.12–3.09) were more likely to discuss financial problems than their counterparts.

Conclusions

Few over-indebted individuals discussed financial problems with their general practitioner. Patients’ health status, coping strategies and perception of financial distress might contribute to variations in disclosure of financial problems. Thus, enhancing communication and screening by routine assessment of financial problems in clinical practice can help to identify vulnerable patients and promote access to health care and social services and well-being for all.

Cost-related medication nonadherence among over-indebted individuals enrolled in statutory health insurance in Germany: a cross-sectional population study

Background

Millions of citizens in high-income countries face over-indebtedness that implies being unable to cover payment obligations with available income and assets on an ongoing basis. Studies have shown an association between over-indebtedness and health outcomes, independent of standard socioeconomic status measures. Patterns of cost-related medication nonadherence (CRN) among over-indebted individuals are yet unclear. The aim of this study was to examine the frequency of nonadherence to prescribed medications due to cost, and to identify risk factors for CRN among over-indebted individuals in Germany.

Methods

In 2017, we conducted a cross-sectional survey among over-indebted individuals recruited in 70 debt advice agencies in North Rhine-Westphalia, Germany. Data on CRN in the last 12 months (i.e. not filling prescriptions, skipping or decreasing doses of prescribed medication due to financial problems) were collected by a survey using a self-administered written questionnaire that was returned by 699 individuals with a response rate of 50.2%. Prevalence of CRN was assessed using descriptive statistics. Multiple logistic regression analysis was performed to examine risk factors of CRN, including participants enrolled in statutory health insurance with complete data (n = 521).

Results

The prevalence of CRN was 33.6%. The chronically ill had significantly greater odds of cost-related medication nonadherence (aOR 1.96; 95% CI 1.27–3.03) than individuals without a chronic illness. CRN was more likely to occur in individuals who had discussed financial problems with their general practitioner (aOR 1.58; 95% CI 1.01–2.47). There was no association between CRN and other sociodemographic factors or socioeconomic status.

Conclusions

Medication nonadherence due to financial pressures is common among over-indebted citizens enrolled in statutory health insurance in Germany. Stakeholders in social policy, research and health care need to address over-indebtedness to develop strategies to safeguard access to relevant medications, especially among those with high morbidity.

Trial registration

Arzneimittelkonsum, insbesondere Selbstmedikation bei überschuldeten Bürgerinnen und Bürgern in Nordrhein-Westfalen (ArSemü), (engl. ‘Medication use, particularly self-medication among over-indebted citizens in North Rhine-Westphalia’), German Clinical Trials Register: DRKS00013100. Date of registration: 23.10.2017. Date of enrolment of the first participant: 18.07.2017, retrospectively registered.

Antidepressant use in over-indebted individuals compared to the general population in Germany

Background

About ten percent of European households across all socioeconomic groups are considered over-indebted due to ongoing difficulties meeting financial commitments and living expenses. Studies found an association between over-indebtedness and physical and mental health such as depression independent of standard socioeconomic status measures. However, antidepressant use in the over-indebted population has been understudied. In view of the substantial economic and social burden of mental illness in Europe, the aim of this study was to examine the association between over-indebtedness and antidepressant use in Germany to advance the understanding of socioeconomic inequalities in mental health.

Methods

We conducted a cross-sectional survey among clients of 70 debt advice agencies in North Rhine-Westphalia, Germany, in 2017 (OID), and merged data with the first wave of the German Health Interview and Examination Survey (DEGS1) representative of the general population. We used descriptive statistics and multiple logistic regression analysis to examine antidepressant use in the previous 7 days (OID: n = 699; DEGS1: n = 7115).

Results

Antidepressant use was more frequent in the over-indebted (12.3%) compared to the general population sample (5.0%). After adjustment for age, sex, education, employment, marital status and chronic disease, over-indebted respondents were more likely to use antidepressants than the general population sample (aOR 1.83; 95% CI 1.35-2.48).

Conclusions

Prevalence of antidepressant use was higher in the over-indebted compared to the general population. The association between over-indebtedness and antidepressant use cannot be fully explained by standard socioeconomic measures. Over-indebtedness reflects a relevant public health issue that needs to be addressed in health care, social policy and research. There is an urgent need to develop public health activities that specifically target those at risk of mental illness and over-indebtedness.

Key messages

Over-indebtedness is associated with antidepressant use. Public health interventions are needed to prevent adverse health effects of over-indebtedness and safeguard access to care according to need.

Non-invasive imaging demonstrates clinical features of ankylosing spondylitis in a rat adjuvant model: a case study

Main features of ankylosing spondylitis like inflammatory erosive osteopenia and bony overgrowth are recapitulated in rats challenged with complete Freund’s adjuvant. In vivo changes induced in the rat spine were followed longitudinally by magnetic resonance imaging (MRI) and assessed terminally by micro-computerized tomography (micro-CT) and histology. Signals reflecting inflammation were detected by MRI at levels L5-L6 throughout the experiment, peaking at day 27 after adjuvant. Bone erosion and formation occurred from this time point onward, as confirmed by micro-CT. Histology confirmed the inflammation and bone remodeling. The present study demonstrates the potential of imaging for longitudinal assessments of spinal changes in this animal model and the excellent correlation between in vivo images and histology underlines its fundamental role in the validation of non-invasive imaging.

[Functional Electrical Stimulation in a Case of Drop Foot and Atactic Gait: Expert Assessment of Contested Medical Aids]

Expert medical opinions are necessary in pretrial cases and other legal matters. They act as means of evidence for administrative bodies and courts. It may be necessary to adapt the method of evaluation depending upon the issue or subject matter to be evaluated. We report on a social court case, which needed to answer the question of the medical necessity of a functional electrical stimulation orthosis prescribed to improve the function of a drop foot accompanied by an atactic gait disorder. The claimant suffered from a stroke, which had occurred several years before. Her aids were an ankle-foot-orthosis for foot lift and a wheeled walker. The current treatment was to be augmented by the disputed device. The statutory health insurance declined to meet the costs. They failed to find relevant benefits after analysis of video tapes of the patient's gait while using an electrical stimulation orthosis. The social court requested an expert opinion to answer the question as to whether or not there was a relevant functional benefit to using functional electrical stimulation over the existing orthosis or to an alternative treatment. Video documentation was desired by the court. We used the clinic's gait analysis laboratory, which is equipped with a gait course and the claimed video documentation. Standardised video documentation offers substantial advantages for answering forensic questions such as these. It assures reproducibility and comparability of all tested scenarios, with objectification of the individual advantages or limitations. This gain in both validity and reliability fulfills the scientific requirements placed upon an expert assessment.

ENaC-mediated effects assessed by MRI in a rat model of hypertonic saline-induced lung hydration

BACKGROUND AND PURPOSE

The epithelial sodium channel (ENaC) regulates airway mucosal hydration and mucus clearance. The lack of such regulation in cystic fibrosis patients leads to desiccation of the airway lumen, resulting in mucostasis that establishes the environment for infections. Osmotic agents and negative ENaC regulators can be used to restore mucosal hydration. We aimed to assess whether: (i) osmotically driven fluid flux into the rat lung could be quantified in vivo by magnetic resonance imaging (MRI); and (ii) the MRI signals could be modulated through the regulation of ENaC function.

EXPERIMENTAL APPROACH

Lung images from spontaneously breathing rats were acquired following intra-tracheal (i.t.) administration of physiological or hypertonic saline (HS). Compounds known to modulate the ENaC function were given i.t. prior to saline. Volumes of fluid signals were quantified on the images.

KEY RESULTS

A tonicity-dependent increase in lung fluid was demonstrated following HS administration. Pretreatment with the ENaC blockers, amiloride or 552-02, resulted in an enhancement of HS-induced lung fluid signals, which were detectable for up to 4 h, consistent with a role for ENaC in fluid clearance. Aprotinin, a serine protease inhibitor that attenuates ENaC function, likewise enhanced the HS-induced increase in lung fluid signal, while alpha(1)-anti-trypsin was without significant effect.

CONCLUSIONS AND IMPLICATIONS

Proton MRI provides a non-invasive technique for studying modulators of lung fluid hydration in rat lung in vivo. The pharmacological sensitivity of MRI-detected fluid signals is consistent with ENaC-mediated fluid reabsorption after HS. This target-related readout may be used to characterize new ENaC modulators.

Activation of the lung S1P(1) receptor reduces allergen-induced plasma leakage in mice

BACKGROUND AND PURPOSE

It has been suggested that intratracheal administration of the immunomodulator, FTY720, could have anti-inflammatory effects without causing a decrease in blood lymphocyte counts. However, the receptor responsible for this effect has not been defined.

EXPERIMENTAL APPROACH

We have described, in a mouse model of allergen-induced inflammation, the use of proton magnetic resonance imaging to non-invasively assess lung fluid accumulation and inflammation. Here, we used this model to investigate the sphingosine-1-phosphate (S1P) receptor responsible for the anti-inflammatory effect of FTY720.

KEY RESULTS

When given intranasally, FTY720 (3 and 10 microg.kg(-1)) inhibited by approximately 50% the allergen-induced accumulation of fluid in the lung detected by magnetic resonance imaging, but had no effect on the cellular inflammation in the airway space or on circulating blood lymphocytes. Inhibition of the infiltration of inflammatory cells into the airways was only observed at a dose of FTY720 that induced lymphopenia (100 microg.kg(-1)). Similar results were observed in S1P(3)-deficient mice. The effect of FTY720 was mimicked by intranasal treatment of wild-type mice with a S1P(1)-specific agonist, AUY954.

CONCLUSIONS AND IMPLICATIONS

Thus, in contrast to previously published work, our results suggest that systemic exposure of FTY720 is necessary to obtain an airway anti-inflammatory effect. On the contrary, inhibition of the allergen-induced accumulation of fluid in the lung, via activation of the S1P(1) receptor, is obtainable without systemic effects.

Magnetic resonance methods and applications in pharmaceutical research

This review presents an overview of some recent magnetic resonance (MR) techniques for pharmaceutical research. MR is noninvasive, and does not expose subjects to ionizing radiation. Some methods that have been used in pharmaceutical research MR include magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods, among them, diffusion-weighted MRI, perfusion-weighted MRI, functional MRI, molecular imaging and contrast-enhance MRI. Some applications of MR in pharmaceutical research include MR in metabonomics, in vivo MRS, studies in cerebral ischemia and infarction, degenerative joint diseases, oncology, cardiovascular disorders, respiratory diseases and skin diseases. Some of these techniques, such as cardiac and joint imaging, or brain fMRI are standard, and are providing relevant data routinely. Skin MR and hyperpolarized gas lung MRI are still experimental. In conclusion, considering the importance of finding and characterizing biomarkers for improved drug evaluation, it can be expected that the use of MR techniques in pharmaceutical research is going to increase in the near future.

Capsaicin-induced mucus secretion in rat airways assessed in vivo and non-invasively by magnetic resonance imaging

BACKGROUND AND PURPOSE

An up-regulation of the sensory neural pathways in the lung has been implicated in asthma and chronic obstructive pulmonary disease (COPD) and is thought to contribute to mucus hypersecretion, an essential feature of both diseases. The aim of this study was to assess non-invasively the acute effects (up to 60 min) of sensory nerve stimulation by capsaicin in the lung, using magnetic resonance imaging (MRI).

EXPERIMENTAL APPROACH

Male Brown Norway rats were imaged prior to and 10, 30 and 60 min after intra-tracheal challenge with capsaicin (30 microg kg(-1)) or vehicle (0.5% ethanol solution). In subsequent studies, pre-treatment with the transient receptor potential vanilloid (TRPV)-1 antagonist, capsazepine; the dual neurokinin (NK) 1 and NK2 receptor antagonist, DNK333 and the mast cell stabilizer, di-sodium cromoglycate (DSCG) was used to modulate the effects of capsaicin.

KEY RESULTS

Diffuse fluid signals were detected by MRI in the lung as early as 10 min after capsaicin, remaining constant 30 and 60 min after treatment. Broncho-alveolar lavage (BAL) fluid analysis performed 60 min after capsaicin revealed increased mucin concentration. Capsazepine (3.5 mg kg(-1)), DNK333 (10 mg kg(-1)) but not DSCG (10 mg kg(-1)) administered prophylactically were able to block the effect of capsaicin in the airways.

CONCLUSIONS AND IMPLICATIONS

These observations suggest that the fluid signals detected by MRI after capsaicin administration reflected predominantly the release of mucus following activation of sensory nerves. They point to the opportunity of non-invasively assessing with MRI the influence of neuronal mechanisms in animal models of asthma and COPD.

Macrophage labeling by SPIO as an early marker of allograft chronic rejection in a rat model of kidney transplantation

Anatomical and functional information (renography, perfusion) was obtained by MRI in a life-supporting transplantation model, in which Lewis rats received kidneys from Fisher 344 donors. Renography and perfusion analyses were carried out with Gd-DOTA and small particles of iron oxide (SPIO), respectively. Starting 12 weeks posttransplantation, images from grafts of untreated recipients exhibited distinctive signal attenuation in the cortex. Animals treated with cyclosporin (Sandimmune Neoral; Novartis Pharma, Basel, Switzerland) to prevent acute rejection showed a signal attenuation in the cortex at 33 weeks posttransplantation, while kidneys from rats treated additionally with everolimus (Certican; Novartis), a rapamycin derivative, had no changes in anatomical appearance. A significant negative correlation was found between the MRI cortical signal intensity and the histologically determined iron content in macrophages located in the cortex. Renography revealed a significantly reduced functionality of the kidneys of untreated controls 33 weeks after transplantation, while no significant changes in perfusion were observed in any group of rats. These results suggest the feasibility, by labeling macrophages with SPIO, of detecting signs of graft rejection significantly earlier than when changes in function occur. Monitoring early changes associated with chronic rejection can have an impact in preclinical studies by shortening the duration of the experimental period and by facilitating the investigation of novel immunomodulatory therapies for transplantation.

MRI of lung parenchyma in rats and mice using a gradient-echo sequence

Signal of lung parenchymal tissue from the living rat and mouse lung was detected at 4.7 T with a good signal-to-noise ratio and motion-suppressed artifacts using a short TE gradient-echo sequence. Neither cardiac nor respiratory gating were applied, and animals respired freely during data collection. Mean T(2)* relaxation times of parenchyma in the anterior, middle and posterior regions of both lungs ranged between 403 and 657 micros and 397 and 751 micros, respectively for the rat and mouse. For the rat in the prone position, there was a gradient in T(2)* values, from the posterior to the anterior regions of both lungs. In the supine position, however, T(2)* values were larger in the posterior and in the anterior portions. For the mouse in both prone and supine positions, there was a tendential gradient in T(2)* from the anterior to the posterior portions. The robustness of the approach renders it well suited for routine applications, e.g. in pharmacological studies concerning asthma models in small rodents. The method was applied to lung inflammation models involving challenge with ovalbumin or lipopolysaccharide.

Current awareness

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of NMR in biomedicine. Each bibliography is divided into 9 sections: 1 Books, Reviews ' Symposia; 2 General; 3 Technology; 4 Brain and Nerves; 5 Neuropathology; 6 Cancer; 7 Cardiac, Vascular and Respiratory Systems; 8 Liver, Kidney and Other Organs; 9 Muscle and Orthopaedic. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.

Non-invasive, quantitative assessment of the anatomical phenotype of corticotropin-releasing factor-overexpressing mice by MRI

High resolution magnetic resonance imaging (MRI) was applied to quantify alterations in thymus and adrenal volumes, as well as body fat in genetically engineered corticotropin-releasing factor (CRF)-overexpressing mice. When compared to the organs in age-matched wild-type animals, the adrenals in CRF-overexpressing male mice were significantly enlarged and the thymus volume in females was significantly smaller. The fat content was significantly larger in CRF-overexpressing mice. The anatomical alterations observed in the MRI studies were in perfect line with post-mortem data (weights of organs). Furthermore, the observed interstrain differences are in agreement with recently published data on (i) the effect of continuous, intraventricular infusion of CRF in rats and (ii) the presence of atrophic adrenals in CRF-knockout mice. The present studies demonstrate that MRI can provide reliable measures of relatively small structures such as the adrenal glands and the thymus in mice. This makes MRI an attractive, non-terminal tool to monitor in laboratory animals, including transgenic mice, the consequence of continuous stress on relevant organs.

From anatomy to the target: contributions of magnetic resonance imaging to preclinical pharmaceutical research

In recent years, in vivo magnetic resonance (MR) methods have become established tools in the drug discovery and development process. In this article, the role of MR imaging (MRI) in the preclinical evaluation of drugs in animal models of diseases is illustrated on the basis of selected examples. The individual sections are devoted to applications of anatomic, physiologic, and "molecular" imaging providing, respectively, structural-morphological, functional, and target-specific information. The impact of these developments upon clinical drug evaluation is also briefly addressed. The main advantages of MRI are versatility, allowing a comprehensive characterization of a disease state and of the corresponding drug intervention; high spatial resolution; and noninvasiveness, enabling repeated measurements. Successful applications in drug discovery exploit one or several of these aspects. Additionally, MRI is contributing to strengthen the link between preclinical and clinical drug research.

MRI and ultrasonographic detection of morphologic and hemodynamic changes in chronic renal allograft rejection in the rat

PURPOSE

The purpose of this study is to describe the sonographic, MRI, and histopathologic findings in a rat model of chronic renal allograft rejection.

MATERIALS AND METHODS

Allogeneic renal grafts (male DA kidney into male Lewis rat with unilateral nephrectomy, N = 27) and syngeneic renal grafts (male Lewis kidney into male Lewis rat, N = 19) were examined serially with ultrasound, MRI, and histology.

RESULTS

Nonparametric Spearman rank correlation showed significance between the histologic score and the following parameters: the MRI score (r(s) = 0.91, P < 0.01, N = 46), the ultrasound score (r(s) = 0.9, P < 0.01, N = 46), the power Doppler score (r(s) = 0.86, P < 0.01, N = 46), and the MRI perfusion (r(s) = -0.80, P < 0.01, N = 45). Positive correlations were also found between the MRI volume estimations (graft r(s) = 0.49, P < 0.01, N = 46; native r(s) = 0.59, P < 0.01, N = 46), and the ultrasound volume estimations (graft r(s) = 0.39, P < 0.01, N = 45; native r(s) = 0.64, P < 0.01, N = 46) as well as with actual graft weight.

CONCLUSIONS

This study shows that both MRI and ultrasound can provide complementary, accurate information compared to histology in regard to the alterations in anatomy and hemodynamic changes associated with chronic allograft nephropathy.

Pulmonary edema induced by allergen challenge in the rat: noninvasive assessment by magnetic resonance imaging

The course of pulmonary edema formation after an intratracheal (i.t.) instillation of ovalbumin was followed noninvasively by magnetic resonance imaging (MRI) in actively sensitized Brown Norway (BN) rats. Changes in edema volume assessed by MRI mimicked the results from the analysis of the number and activation of inflammatory cells recovered from the broncho-alveolar lavage (BAL) fluid. Rats treated with budesonide did not develop edema following challenge with ovalbumin, and these animals showed a significant decrease in BAL fluid inflammatory cell numbers and eosinophil peroxidase and myeloperoxidase activities. Thus, following lung edema formation by MRI provides a reliable means of assessing pulmonary inflammation after allergen challenge. Unlike BAL fluid analysis, which requires killing animals at each time point, this method is noninvasive. MRI could be of importance for the noninvasive profiling of anti-inflammatory drugs in animal models of asthma and in the clinic. Magn Reson Med 45:88-95, 2001.

The role of magnetic resonance imaging and spectroscopy in transplantation: from animal models to man

Critical success factors in solid organ and vascular transplantation are the assessment of graft status/viability as well as stringent monitoring of transplant recipients, preferentially using noninvasive techniques. This review addresses the application of magnetic resonance imaging (MRI) and spectroscopy (MRS) in the field of transplantation. The first section is devoted to the description of the main MR techniques used for monitoring the status of the graft noninvasively. Subsequently, the role of MRI/MRS in the analysis of the viability of organs for transplantation is discussed. Since chronic rejection remains a major difficulty, development of new therapies is still ongoing. Thus, the third part is devoted to the use of MRI/MRS for monitoring graft rejection in animal models of transplantation. This is followed by a discussion of clinical studies of transplantation involving MRI/MRS. Finally, a general appraisal is made on available imaging techniques for the non-invasive characterization of grafts in situ, highlighting the role of MR methods in the field of transplantation.

High resolution magnetic resonance angiography non-invasively reveals mouse strain differences in the cerebrovascular anatomy in vivo

High resolution magnetic resonance angiography (MRA) revealed highly variable arterial cerebrovascular structures in mice from different strains and within the same strain. C57Black/6 mice presented small unilateral anastomoses between the posterior cerebral and the superior cerebellar arteries. Well developed, either unilateral or bilateral, posterior communicating arteries (PcomA) were detected on CBA mice. The arterial structure of CD1 mice ranged from no detectable anastomoses to well developed, unilateral PcomAs. SV-129 mice showed significantly shorter middle cerebral arteries compared to the other strains, and clear bilateral anastomoses between the posterior cerebral and the superior cerebellar arteries. Because of its non-invasiveness, MRA may be of importance in murine stroke studies by enabling the selection of animals and/or the side for performing the surgical intervention, and the verification of its success. Magn Reson Med 44:252-258, 2000.

High-resolution magnetic resonance angiography of the mouse brain: application to murine focal cerebral ischemia models

Three-dimensional time-of-flight high-resolution magnetic resonance angiography was applied to visualize the cerebral vasculature of the mouse brain. In normal mice, angiograms of good quality, showing the essential details of the arterial cerebrovascular anatomy, could be obtained in only 2.5 min without the use of contrast agents. Signals from slowly flowing blood, e.g., in veins, could also be detected after administration of a blood pool contrast agent. The technique was applied to mouse models of permanent and transient brain ischemia, involving the occlusion of the middle cerebral artery. High-resolution magnetic resonance angiography proved to be a very useful tool for verifying the success of the occlusion in these models.

Magnetic resonance angiography of the rat cerebrovascular system without the use of contrast agents

We describe and discuss the application of three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) to visualize non-invasively the cerebral vasculature of the rat. MR angiograms of healthy spontaneously hypertensive rats were obtained without the use of contrast agents. Total imaging time ranged from 1 to 50 min for a 3D data set. The influences of the data matrix and the inflow delay on the image quality and the total imaging time are assessed and discussed. Varying the inflow delay yielded in addition semiquantitative information on hemodynamics. The method was applied to obtain angiograms in rat models of permanent and temporal middle cerebral artery occlusion. Occlusion and reopening of the vessel could easily be verified by MRA. However, after reperfusion a slight reduction in blood flow was observed.

In vivo magnetic resonance methods in pharmaceutical research: current status and perspectives

In the last decade, in vivo MR methods have become established tools in the drug discovery and development process. In this review, several successful and potential applications of MRI and MRS in stroke, rheumatoid and osteo-arthritis, oncology and cardiovascular disorders are dealt with in detail. The versatility of the MR approach, allowing the study of various pathophysiological aspects in these disorders, is emphasized. New indication areas, for the characterization of which MR methods have hardly been used up to now, such as respiratory, gastro-intestinal and skin diseases, are outlined in a subsequent section. A strength of MRI, being a non-invasive imaging modality, is the ability to provide functional, i.e. physiological, readouts. Functional MRI examples discussed are the analysis of heart wall motion, perfusion MRI, tracer uptake and clearance studies, and neuronal activation studies. Functional information may also be derived from experiments using target-specific contrast agents, which will become important tools in future MRI applications. Finally the role of MRI and MRS for characterization of transgenic and knock-out animals, which have become a key technology in modern pharmaceutical research, is discussed. The advantages of MRI and MRS are versatility, allowing a comprehensive characterization of a diseased state and of the drug intervention, and non-invasiveness, which is of relevance from a statistical, economical and animal welfare point of view. Successful applications in drug discovery exploit one or several of these aspects. In addition, the link between preclinical and clinical studies makes in vivo MR methods highly attractive methods for pharmaceutical research.

High-resolution three-dimensional magnetic resonance imaging for the investigation of knee joint damage during the time course of antigen-induced arthritis in rabbits

OBJECTIVE

To investigate the efficacy of high-resolution 3-dimensional magnetic resonance imaging (3-D MRI) with gadolinium contrast agent enhancement in monitoring soft tissue and hard tissue changes during the course of antigen-induced arthritis in rabbits, comparing the images with the final histologic outcome.

METHODS

Arthritis was induced by intraarticular injection of methylated bovine serum albumin into rabbits that had been presensitized to the same antigen. MRI was carried out before and on predetermined days after the onset of inflammatory arthritis, up to day 60. At each time point, 3-D gradient-echo images were acquired. At the end of the study, the knee joints were processed for histologic study.

RESULTS

Time-related inflammatory changes, such as soft tissue swelling, were seen initially, followed by a reduction in the acute swelling and a progression to hard tissue damage at later time points. The final 3-D data sets were then used to compare MR images with the histologic sections. The knee joints were sectioned in the sagittal, coronal, or transverse direction. Comparison of final images and histologic features at day 60 enabled a more complete interpretation of the MR images, allowing direct correlation of joint damage observed using the MRI technique with that seen in the final histologic analysis.

CONCLUSION

Qualitative information derived from MR images correlated extremely well with histologic findings. These results indicate the great potential of MRI for noninvasive investigation of drug effects in this model of arthritis.

Effects of Sandimmune neoral on collagen-induced arthritis in DA rats: characterization by high resolution three-dimensional magnetic resonance imaging and by histology

In the present work the time course of collagen-induced arthritis and the effect of Sandimmune Neoral in this model of arthritis were followed in the rat over an extended period of time (70 days) using high resolution three-dimensional (3D) magnetic resonance imaging (MRI). High resolution 3D gradient-echo (TR = 100 ms; TE = 3.8 ms) images with a voxel size of 94 x 81 x 60 micron3 were acquired from the hind paw of DA rats (n = 21) at various time points after injection of type II bovine collagen into the tail. Eleven rats were treated with Neoral (15 mg/kg/day p.o. together with vehicle) for 42 days starting at day 14 after collagen injection. The remaining controls received vehicle. Pathomorphological changes associated with the collagen-induced arthritic process, e.g., increase of joint space and cartilage and bone erosion, could be observed in vivo in the control group. In contrast, no changes in the joint architecture were detected in Neoral-treated animals. Indeed, Neoral showed strong anti-inflammatory effects and marked protection against cartilage and bone destruction in this model. Qualitative information derived from the MR images correlated significantly with histological findings.

Signal changes in the spinal cord of the rat after injection of formalin into the hindpaw: characterization using functional magnetic resonance imaging

Changes in metabolism and local circulation occur in the spinal cord during peripheral noxious stimulation. Evidence is presented that this stimulation also causes signal intensity alterations in functional magnetic resonance images of the spinal cord during formalin-induced pain. These results indicate the potential of functional magnetic resonance imaging in assessing noninvasively the extent and intensity of spinal cord excitation in this well characterized pain model. Therefore, the aim of this study was to establish functional magnetic resonance imaging as a noninvasive method to characterize temporal changes in the spinal cord after a single injection of 50 microl of formalin subcutaneously into the hindpaw of the anesthetized rat. This challenge produced a biphasic licking activity in the freely moving conscious animal. Images of the spinal cord were acquired within 2 min, enabling monitoring of the site and the temporal evolution of the signal changes during the development of formalin-induced hyperalgesia without the need of any surgical procedure. The time course of changes in the spinal cord functional image in the isoflurane-anesthetized animal was similar to that obtained from behavioral experiments. Also, comparable physiological data, control experiments, and the inhibition of a response through application of the local anesthetic agent lidocaine indicate that the signal changes observed after formalin injection were specifically related to excitability changes in the relevant segments of the lumbar spinal cord. This approach could be useful to characterize different models of pain and hyperalgesia and, more importantly, to evaluate effects of analgesic drugs.

Analysis of tracer transit in rat brain after carotid artery and femoral vein administrations using linear system theory

Determination of tissue perfusion rates by MRI bolus tracking methods relies on the central volume principle which states that tissue blood flow is given by the tissue blood volume divided by the mean tracer transit time (MTT). Accurate determination of the MTT requires knowledge of the arterial input function which in MRI experiments is usually not known, especially when using small animals. The problem of unknown arterial input can be circumvented in animal experiments by directly injecting the contrast agent into a feeding artery of the tissue of interest. In the present article the passage of magnetite nanoparticles through the rat cerebral cortex is analyzed after injection into the internal carotid artery. The results are discussed in the framework of linear system theory using a one-compartment model for brain tissue and by using the well characterized gamma-variate function to describe the tissue concentration profile of the contrast agent. The results obtained from the intra-arterial tracer administration experiments are then compared with the commonly used intra-venous injection of the contrast agent in order to estimate the contribution of the peripheral circulation to the MTT values in the latter case. The experiments were analyzed using a two-compartment model and the gamma-variate function. As an application perfusion rates in normal and ischemic cerebral cortex of hypertensive rats were estimated in a model of focal cerebral ischemia. The results indicate that peripheral circulation has a significant influence on the MTT values and thus on the perfusion rates, which cannot be neglected.

Magnetic resonance imaging for the evaluation of rejection of a kidney allograft in the rat

Orthotopic DA (RT1a) into Lewis (RT1l) rat kidney allografts and control Lewis-into-Lewis grafts were assessed by magnetic resonance imaging (MRI) and perfusion measurement after intravenous injection of a superparamagnetic contrast agent. MRI anatomical scores (range 1-6) and perfusion rates were compared with graft histology (rank of rejection score 1-6). Not only acute rejection, but also chronic events were monitored after acute rejection was prevented by daily cyclosporine (Sandimmune) treatment during the first 2 weeks after transplantation. In acute allograft rejection (n = 11), MRI scores reached the maximum value of 6 and perfusion rates were severely reduced within 5 days after transplantation; histology showed severe acute rejection (histologic score 5-6). In the chronic phase (100-130 days after transplantation), allografts (n = 5) manifested rejection (in histology cellular rejection and vessel changes), accompanied by MRI scores of around 2-3 and reduced perfusion rates. Both in the acute and chronic phases, the MRI anatomical score correlated significantly with the histological score (Spearman rank correlation coefficient rs 0.89, n = 30, P < 0.01), and perfusion rates correlated significantly with the MRI score or histological score (rs values between -0.60 and -0.87, n = 23, P < 0.01). It is concluded that MRI represents an interesting tool for assessing the anatomical and hemodynamical status of a kidney allograft in the acute and chronic phases after transplantation.

Absolute quantification of the hepatic glycogen content in a patient with glycogen storage disease by 13C magnetic resonance spectroscopy

Using natural-abundance 13C magnetic resonance spectroscopy (MRS) on a conventional whole-body system operating at 1.5 T, the absolute hepatic glycogen concentration was noninvasively determined in a patient with type Ia glycogen storage disease. Furthermore, to assess the reliability of glycogen determination, hepatic glycogen content was assessed after an overnight fasting period in 35 healthy volunteers divided into two groups, one with a carbohydrate-rich diet, the other without any particular dietary preparation. In the patient, the glycogen concentration was found to be 458 mM. In the healthy subjects, average glycogen concentrations were 229 +/- 34 mM (mean +/- standard deviation) and 257 +/- 31 mM for the group without and with dietary preparation, respectively. The 13C-MRS results are in agreement with those obtained by conventional liver biopsy. 13C MRS in natural abundance may thus serve as a straightforward, fast, and noninvasive tool for quantification of the liver glycogen content in patients.

Early glycogenolysis and late glycogenesis in human liver after intravenous administration of galactose

Galactose is incorporated by a different metabolic pathway than glucose. Its contribution to glycogen synthesis has not been studied in humans. We administered galactose (0.5 g/kg iv) to overnight-fasted normal human volunteers and examined its effects on hepatic glycogen synthesis and hepatic glucose output (HGO). Hepatic glycogenesis was assessed noninvasively, determining glycogen concentration by 13C magnetic resonance spectroscopy (MRS) and liver volume by magnetic resonance imaging. HGO was determined by [6,6-2H2]glucose and gluconeogenesis calculated by adding the amount of hepatic glycogenesis to the HGO. After galactose administration, liver glycogen concentration (baseline 254 +/- 11 mmol/l) decreased in the first 45 min to 207 +/- 15 mmol/l (P < 0.05) and increased thereafter to 313 +/- 7 mmol/l (P < 0.01). Net hepatic glycogenesis was 101 +/- 12 mmol over 150 min. HGO (baseline 14.3 +/- 1.9 mumol.kg-1.min-1) increased threefold in the first 15 min and then returned to baseline. The average rate of gluconeogenesis was 12.3 mumol.kg-1.min-1. Intravenous galactose leads to an increase in hepatic glycogen and hepatic glucose output in normal humans. Competitive inhibition of UDP-glucose pyrophosphorylase by UDP-galactose could explain the apparent glycogenolysis observed early after galactose administration. 13C MRS in combination with a stable isotope tracer is a noninvasive and safe method to study hepatic carbohydrate metabolism in humans.

Noninvasive 3D MR microscopy as a tool in pharmacological research: application to a model of rheumatoid arthritis

Magnetic resonance microscopy (MRM) was applied to noninvasively image skeletal structures in the hindpaw of the live rat to characterize the progression of a heterologous type II collagen-induced arthritic process. Using a resonator, with optimized filling factor, three-dimensional (3D) gradient-echo images with voxel dimensions of 94 x 81 x 60 micron3 were acquired in 54.6 min. Three-dimensional MRM reduces the slice positioning problem, which is critical in longitudinal studies. Moreover, due to the much smaller slice thickness of images derived from 3D data sets, partial volume effects are less pronounced than in corresponding 2D images. Distinct pathomorphological changes associated with the collagen-induced arthritic process (e.g., increase of metatarsophalangeal joint space, and bone and cartilage erosion) could thus be analyzed under in vivo conditions.

Noninvasive observation of hepatic glycogen formation in man by 13C MRS after oral and intravenous glucose administration

The formation of glycogen in the liver of normal volunteers was followed noninvasively with 13C magnetic resonance spectroscopy (MRS) under two different conditions: a) intravenous infusion of [1-13C]glucose under hyperglycemic and hyperinsulinemic clamp conditions, and b) oral intake of glucose in the form of a bolus. For the intravenous infusion, [1-13C]glucose with an enrichment level of 99% was employed. The C1 signals of alpha- and beta-glucose could be detected in the human liver already after an infusion period of 8 min. However, an increase in the glycogen signal was observed only after a prolonged infusion of about 60 min. Changes in the glycogen signal correlated well with the time course of insulin and glucagon during the measurement. Experiments showed also that liver glycogen formation in man can be followed noninvasively by 13C-MRS using nonlabeled glucose or [1-13C]glucose with a low level of enrichment (6.6%). The use of nonlabeled glucose may therefore simplify the quantitation of net liver glycogen synthesis since it can be based directly on changes in the natural abundance 13C MRS glycogen signal, avoiding label dilution through the various metabolic pathways of glucose. The glucose uptake, estimated from the increase in the glycogen signal, was consistent with findings from more complex and invasive studies of glucose uptake in the liver. The average liver glycogen concentration in 12 h overnight fasted volunteers (n = 18) without any special dietary preparation was assessed to be 229 +/- 34 mM (minimum = 160 mM; maximum = 274 mM).

Relationship between the degree of unsaturation of dietary fatty acids and adipose tissue fatty acids assessed by natural-abundance 13C magnetic resonance spectroscopy in man

Natural-abundance 13C magnetic resonance spectroscopy was used for determining noninvasively the relative concentration of mono- and polyunsaturated fatty acids of adipose tissue in two groups of volunteers. The first consisted of subjects who had followed a fat-reduced diet for at least half a year before the 13C measurements. The second were control subjects who were on a usual high-fat diet. The ratio of unsaturated to total fatty acids in adipose tissue determined by 13C MRS correlated significantly with the same ratio in fat of the diet composition estimated by a dietician according to food records. The results indicate that 13C MRS is capable of assessing the degree of unsaturation of dietary fatty acids consumed during the preceding months.

13C NMR for the assessment of human brain glucose metabolism in vivo

Proton-decoupled 13C NMR spectra of the human head were obtained during hyperglycemic glucose clamping using intravenous infusions of [1-13C]glucose in normal volunteers. In addition to 13C signals of mobile lipids, a variety of new metabolite resonances could be resolved for the first time in the human brain. At an enrichment level of 20% [1-13C]glucose, the signals of alpha- and beta-glucose at 92.7 and 96.6 ppm, respectively, could be detected in the human brain after only an infusion period of 15 min. The spatial localization of the different regions of interest was confirmed by 13C NMR spectroscopic imaging with a time resolution of 9 min. Increasing the enrichment level to 99% [1-13C]glucose not only improved the time resolution but allowed the detection of metabolic breakdown products of [1-13C]glucose. The time course of 13C label incorporation into the C2, C3, and C4 resonances of glutamate/glutamine and into lactate could be recorded in the human brain. These results suggest the possibility of obtaining time-resolved, spatially selective, and chemically specific information on the human body.

Analysis of glycogen storage disease by in vivo 13C NMR: comparison of normal volunteers with a patient

Broadband proton-decoupled natural abundance 13C spectra of the human calf, liver, and head were obtained from normal volunteers and a patient with glycogen type IIIA storage disease. Two concentric and coplanar surface coils of diameters 8.0 cm and 13.0 cm were used for 13C (at 16.0 MHz) and 1H (at 63.6 MHz), respectively. A WALTZ-8 sequence lead to homogeneous decoupling over a large volume. In addition to lipid resonances a variety of other metabolite resonances could be resolved. The glycogen concentration in the muscle and the liver of normal volunteers varied considerably depending on dietary preparation and physical exercise. The glycogen level in the liver and the calf of a patient with glycogen type IIIA storage disease was increased by a factor of 2-3 compared to normal, well-trained volunteers. Proton-decoupled 13C spectra of human head are reported for the first time. The spectra are dominated by lipid resonances but an additional resonance at 54.0 ppm is clearly visible. The proton-decoupled 13C head spectrum of a patient with glycogen type IIIA storage disease revealed additional resonances between 71.0 and 85.0 ppm.

13C spectroscopic imaging. A simple approach to in vivo 13C investigations

13C spectroscopic imaging (SI) is implemented and tested on a Siemens whole-body MR instrument for in vivo localized 13C spectroscopy. The method provides spectroscopic maps of extended regions of interest. It is found that 13C SI is an ideal field of application for the spectroscopic imaging technique since most other localization methods suffer from chemical-shift or offset artifacts for this nucleus. Applications of 13C SI with a single 13C rf channel as well as in combination with polarization transfer experiments and heteronuclear broadband decoupling are shown.

Comparison of the signal-to-noise ratio at 1.5 and 2.0 T using a whole-body system

Signal-to-noise ratios for 1H, 31P, and 13C signals at 1.5 and 2.0 T were compared using a whole-body system with a fast rampable magnet. Results indicate that SNR lies within the predicted values of linear and 7/4th power dependency with the applied magnetic field, for lossy and lossless samples, respectively.