POS1444 FLT1 AND EPHB2 ARE NOVEL GENETIC MARKERS ASSOCIATED WITH PANCREATITIS IN PATIENTS TAKING AZATHIOPRINE FOR IMMUNE-MEDIATED CONDITIONS: INTEGRATING GENOME- AND TRANSCRIPTOME-WIDE ASSOCIATION STUDIES

Background

Azathioprine (AZA) is a thiopurine immunosuppressant medication used to treat a variety of immune-mediated diseases. Unfortunately, its use is limited by adverse effects. Pancreatitis, a potentially severe, life-threatening side effect is independent of dose and necessitates AZA discontinuation given the high risk of recurrent pancreatitis with continued use or re-challenge. The mechanisms driving pancreatitis are unclear. While classic thiopurine-induced acute pancreatitis (TIAP) has been associated with HLA haplotypes, most patients taking AZA and presenting with pancreatitis do not fulfill the stringent criteria for TIAP.

Objectives

To identify genetic risk factors for pancreatitis in patients taking azathioprine for immune-mediated conditions.

Methods

Using a biobank linked to electronic health records (EHR) from a tertiary center, we identified new users of AZA. Patients were excluded if the primary indication for AZA was organ transplant or if there was a history of pancreatitis prior to AZA use. The analysis was restricted to patients with EHR-reported race as White due to insufficient case counts for the non-White group. We then identified patients with amylase or lipase values that exceeded twice the upper limit of normal (“>2x ULN”) or with ICD-9/ICD-10 codes for acute pancreatitis. Each record was manually reviewed to confirm the timing of AZA use in relation to laboratory derangements or ICD coding, as well as to further classify patients into three increasingly strict, but not exclusive categories: 1) pancreatic injury (amylase or lipase >2x ULN); 2) acute pancreatitis1, or 3) TIAP2. We completed genotyping with Illumina Infinium Expanded Multi-Ethnic Genotyping Array plus custom content data, employed Michigan Imputation servers for genetic imputation, and used PrediXcan (GTEx v8) to impute gene expression. We then conducted genome-wide association and transcriptome-wide association studies (GWAS, TWAS). Acknowledging the relatively small overall cohort, and possible imbalance of cases vs controls, we used the Firth logistic regression method, which is a penalized likelihood-based method.

Results

We studied 2127 AZA users (35.4% male; mean 44.5+/-17.2 years). The median AZA dose was 100mg/day (IQR: 50-125mg/day). Rheumatologic conditions (56.9%) and inflammatory bowel disease (40.4%) comprised the most common primary indications for AZA. Pancreatic injury, pancreatitis, and TIAP were diagnosed in 42 (2.0%), 16 (0.8%), and 9 (0.4%) patients, respectively. GWAS identified several significantly associated genes, many with overlapping TWAS findings in the pancreas and liver (Figure 1). From these, the two protein-encoding genes Fms Related Receptor Tyrosine Kinase-1 (FLT1) and Ephrin type-B receptor-2 (EPHB2) overlapped in two or more pancreatitis phenotypes in the TWAS and GWAS, respectively. EPHB2 was associated with a 8.6-fold (P=1.84 x 10-8) and a 31.4-fold (P=2.87x 10-8) higher likelihood of pancreatic injury and TIAP, respectively.

Figure 1.

Conclusion

FLT1—a gene that encodes a receptor tyrosine kinase and is a member of the vascular endothelial growth factor receptor (VEGFR) family—and EPHB2—a gene that encodes a member of the Eph receptor family, which is the largest subgroup of the receptor tyrosine kinase family—are novel genetic markers associated with pancreatitis in patients taking AZA. VEGF can potentiate inflammation and the pancreas microenvironment is known to promote VEGF expression, which has been linked to pancreatic cancer development; anti-VEGF treatments have been investigated both for mitigating inflammation and also anti-pancreatic cancer treatment. Future studies validating our findings in AZA-induced pancreatitis are warranted.

References

[1]Crockett et al. Gastroenterology (2018). 154(4):1096-1101.

[2]Heap et al. Nature Genetics (2014). 46:1131-1134

Disclosure of Interests

Shailja Shah Consultant of: ad hoc consultant for Phathom pharmaceuticals, Tyler Reese: None declared, Jacy Zanussi: None declared, Alyson Dickson: None declared, Laura Daniel: None declared, Ran Tao: None declared, Tyne Miller-Fleming: None declared, Peter Straub: None declared, Adriana Hung: None declared, Puran Nepal: None declared, Wei-Qi Wei: None declared, Elizabeth Phillips: None declared, Nancy Cox: None declared, Charles M. Stein: None declared, QiPeng Feng: None declared, Cecilia P. Chung: None declared

Surface enhanced Raman scattering specificity for detection and identification of dried bloodstains

Surface enhanced Raman spectroscopy (SERS) provides highly specific vibrational signatures identifying dried blood for a variety of forensic applications. SERS spectra on Au nanoparticle substrates excited at 785 nm are found to identify dried stains of human and nonhuman blood from seven animals, and distinguish stains due to menstrual and peripheral blood. In addition, the unique SERS bloodstain spectrum is distinct from the SERS spectra of thirty red-brown stains of potential household substances that could be visually mistaken for bloodstains and from food stains that have been shown to give positive results with presumptive colorimetric blood tests. Finally, a SERS swab procedure has been developed and demonstrates that the substrates that a blood sample dried on does not offer any Raman or fluorescence interference for the SERS identification of dried blood. Such bloodstains on porous and nonporous materials are all identical and exclusively due to the heme moiety of hemoglobin. Optimized selection of the extraction solvent is found to control the chemical composition of molecular components appearing in the SERS spectrum of complex, multicomponent biological mixtures, such as body fluids.

Increased blood pressure visit-to-visit variability in patients with systemic lupus erythematosus: association with inflammation and comorbidity burden

BACKGROUND

Blood pressure visit-to-visit variability is a novel risk factor for deleterious long-term cardiac and renal outcomes in the general population. We hypothesized that patients with systemic lupus erythematosus (SLE) have greater blood pressure visit-to-visit variability than control subjects and that blood pressure visit-to-visit variability is associated with a higher comorbidity burden.

METHODS

We studied 899 patients with SLE and 4172 matched controls using de-identified electronic health records from an academic medical center. We compared blood pressure visit-to-visit variability measures in patients with SLE and control subjects and examined the association between blood pressure visit-to-visit variability and patients' characteristics.

RESULTS

Patients with SLE had higher systolic blood pressure visit-to-visit variability 9.7% (7.8-11.8%) than the control group 9.2% (7.4-11.2%), P < 0.001 by coefficient of variation. Additional measures of systolic blood pressure visit-to-visit variability (i.e. standard deviation, average real variation, successive variation and maximum measure-to-measure change) were also significantly higher in patients with SLE than in control subjects. In patients with SLE, blood pressure visit-to-visit variability correlated significantly with age, creatinine, CRP, triglyceride concentrations and the Charlson comorbidity score (all P < 0.05). Hydroxychloroquine use was associated with reduced blood pressure visit-to-visit variability (P < 0.001), whereas the use of antihypertensives, cyclophosphamide, mycophenolate mofetil and corticosteroids was associated with increased blood pressure visit-to-visit variability (P < 0.05).

CONCLUSION

Patients with SLE had higher blood pressure visit-to-visit variability than controls, and this increased blood pressure visit-to-visit variability was associated with greater Charlson comorbidity scores, several clinical characteristics and immunosuppressant medications. In particular, hydroxychloroquine prescription was associated with lower blood pressure visit-to-visit variability.

Targeted diagnostic magnetic nanoparticles for medical imaging of pancreatic cancer

Highly aggressive cancer types such as pancreatic cancer possess a mortality rate of up to 80% within the first 6months after diagnosis. To reduce this high mortality rate, more sensitive diagnostic tools allowing an early stage medical imaging of even very small tumours are needed. For this purpose, magnetic, biodegradable nanoparticles prepared using recombinant human serum albumin (rHSA) and incorporated iron oxide (maghemite, γ-Fe2O3) nanoparticles were developed. Galectin-1 has been chosen as target receptor as this protein is upregulated in pancreatic cancer and its precursor lesions but not in healthy pancreatic tissue nor in pancreatitis. Tissue plasminogen activator derived peptides (t-PA-ligands), that have a high affinity to galectin-1 have been chosen as target moieties and were covalently attached onto the nanoparticle surface. Improved targeting and imaging properties were shown in mice using single photon emission computed tomography-computer tomography (SPECT-CT), a handheld gamma camera, and magnetic resonance imaging (MRI).

[What does the general and abdominal surgeon need to know about radiotherapy? - aspects of radiotherapy in general and abdominal surgery]

Radiooncological therapies are an integral part of the multimodal oncological treatment concepts in general and abdominal surgery. These include therapeutic approaches with a curative intention such as the neoadjuvant (pre-operative) radiotherapy of locoregionally advanced and/or N+ oesophageal and rectal cancer, definitive combined chemoradiotherapy of locally advanced, unresectable oesophageal cancer or oesophageal tumour lesions of the upper third, definitive radiotherapy of anal cancer (sphincter sparing) and pre- or post-operative radiotherapy of soft tissue sarcoma on the one hand. A yT0 stage achieved as characteristic of a curative effect by radiation in oesophageal and rectal cancer (omitting subsequent surgical intervention, naturally under clinical and imaging-based controls within short-term follow-up intervals) can be considered as a very interesting set-up with regard to its reasonable integration in daily clinical practice, which needs to be further and critically discussed. By integrating radiotherapy in interdisciplinary therapy concepts, improved tumour control and survival rates with clinically acceptable toxicity can be achieved. On the other hand, non-invasive, locally ablative radiooncological therapies such as extracranial stereotactic body radiotherapy constitute an effective and feasible treatment method for liver metastases in oligometastatic colorectal cancer or other tumour entities according to the decisions by the institutional tumour board, offering high local tumour control rates which can be part of multistep, multimodal procedures with curative intention. This review aims at providing an overview for the general and abdominal surgeon, outlining relevant radiooncological treatment aspects in the multimodal cancer therapy with a focus on the treatment of rectal, oesophageal and anal cancer as well as soft tissue sarcoma and hepatic metastases in oligometastatic colorectal cancer.

Nonrigid PET motion compensation in the lower abdomen using simultaneous tagged-MRI and PET imaging

PURPOSE

We propose a novel approach for PET respiratory motion correction using tagged-MRI and simultaneous PET-MRI acquisitions.

METHODS

We use a tagged-MRI acquisition followed by motion tracking in the phase domain to estimate the nonrigid deformation of biological tissues during breathing. In order to accurately estimate motion even in the presence of noise and susceptibility artifacts, we regularize the traditional HARP tracking strategy using a quadratic roughness penalty on neighboring displacement vectors (R-HARP). We then incorporate the motion fields estimated with R-HARP in the system matrix of an MLEM PET reconstruction algorithm formulated both for sinogram and list-mode data representations. This approach allows reconstruction of all detected coincidences in a single image while modeling the effect of motion both in the emission and the attenuation maps. At present, tagged-MRI does not allow estimation of motion in the lungs and our approach is therefore limited to motion correction in soft tissues. Since it is difficult to assess the accuracy of motion correction approaches in vivo, we evaluated the proposed approach in numerical simulations of simultaneous PET-MRI acquisitions using the NCAT phantom. We also assessed its practical feasibility in PET-MRI acquisitions of a small deformable phantom that mimics the complex deformation pattern of a lung that we imaged on a combined PET-MRI brain scanner.

RESULTS

Simulations showed that the R-HARP tracking strategy accurately estimated realistic respiratory motion fields for different levels of noise in the tagged-MRI simulation. In simulations of tumors exhibiting increased uptake, contrast estimation was 20% more accurate with motion correction than without. Signal-to-noise ratio (SNR) was more than 100% greater when performing motion-corrected reconstruction which included all counts, compared to when reconstructing only coincidences detected in the first of eight gated frames. These results were confirmed in our proof-of-principle PET-MRI acquisitions, indicating that our motion correction strategy is accurate, practically feasible, and is therefore ready to be tested in vivo.

CONCLUSIONS

This work shows that PET motion correction using motion fields measured with tagged-MRI in simultaneous PET-MRI acquisitions can be made practical for clinical application and that doing so has the potential to remove motion blur in whole-body PET studies of the torso.

Phase I/II study of cetuximab, capecitabine and oxaliplatin (CAPOX) combined with standard radiotherapy (RTX) as neoadjuvant treatment of advanced rectal cancer (RC)

3574

Background: CAPOX given concurrently to neoadjuvant RTX in RC is well tolerated and yielded high rates of pathologic complete responses in phase II trials. Cetuximab, a monoclonal antibody targeted against the EGF receptor, is active in metastatic colorectal cancer. Furthermore, synergy of cetuximab with RTX was shown in improved survival vs. RTX alone in head and neck cancer. This trial was to evaluate maximal tolerated dose (MTD), feasibility and efficacy of CAPOX + RTX with cetuximab in RC. Method: Patients (pts) had to have unpretreated T3–4 and/or N+ disease, with distant metastases allowed. During a conventionally fractionated RTX (1.8 Gy for 28 days [d]), cetuximab was given in standard dosage (400mg/m2 on d-7, then 6 weekly doses of 250 mg/m2, to d35). CAPOX was given on the basis of a previously examined schedule with oxaliplatin (50 mg/m2 d 1,8,22 and 29) in combination with capecitabine (d1–14 and d22–35) at 3 dose levels: 1000, 1300 and 1650mg/m2 bid. In phase I, a standard 3+3 design was used, allowing for dose escalation in 0/3 or 1/6 pt with dose-limiting toxicity (DLT). Results: 13 pts were enrolled: Median age 58 [35–75] yrs., m/f 7/6 pts. T3 85%, T4 15%; N+ 92%, M1 46%; G2 92%, G3 8%. As on dose level 1 one DLT (diarrhea grade 3) occurred, it was extended to 7 pts. No further DLT was observed as it was on levels 2 and 3 with 3 pts each. Full RTX course was administered in all pts, while CAPOX-cetuximab was stopped in the DLT case and cetuximab in 1 pt with hypersensitivity reaction. Toxicities are displayed in the table . Conclusion: CAPOX can safely be combined with cetuximab without requiring chemotherapy dose reduction. The multicenter phase II part of the trial with 31 pts. included so far is ongoing and updated results (including resectability) will be presented.

[Table: see text]

[Table: see text]

Concurrent pharmacological MRI and in situ microdialysis of cocaine reveal a complex relationship between the central hemodynamic response and local dopamine concentration

The mechanisms underlying the signal changes observed with pharmacological magnetic resonance imaging (phMRI) remain to be fully elucidated. In this study, we obtained microdialysis samples in situ at 5-min intervals during phMRI experiments using a blood pool contrast agent to correlate relative cerebral blood volume (rCBV) changes with changes in dopamine and cocaine concentrations following acute cocaine challenge (0.5 mg/kg iv) in the rat over a duration of 30 min. Three brain areas were investigated: the dorsal striatum (n = 8), the medial prefrontal cortex (mPFC; n = 5), and the primary motor cortex (n = 8). In the striatum and mPFC groups, cocaine and dopamine temporal profiles were tightly correlated, peaking during the first 5-min period postinjection, then rapidly decreasing. However, the local rCBV changes were uncorrelated and exhibited broader temporal profiles than those of cocaine and dopamine, attaining maximal response 5-10 min later. This demonstrates that direct vasoactivity of dopamine is not the dominant component of the hemodynamic response in these regions. In the motor cortex group, microdialysis revealed no local change in dopamine in any of the animals, despite large local cocaine increase and strong rCBV response, indicating that the central hemodynamic response following acute iv cocaine challenge is not driven directly by local dopamine changes in the motor cortex. The combination of phMRI and in situ microdialysis promises to be of great value in elucidating the relationship between the phMRI response to psychoactive drugs and underlying neurochemical changes.

Functional recovery after brain lesion--contralateral neuromodulation: an fMRI study

Behavioral recovery takes place even after permanent damage to the entire brain region normally controlling sensorimotor hind limb function in the rat. In our study, 2 weeks after full behavioral recovery from an experimental unilateral permanent brain damage, the topographic representation of the previous paretic hindlimb was investigated by fMRI. The analysis showed that during electrical stimulation of the previously paretic hindlimb, two normally inactive brain regions were now being activated. One region was the non-damaged contralateral sensori-motor cortex and the other region was located lateral to the lesion. These results suggest that behavioral recovery can be explained by functional reorganization and neuromodulation of the brain.

Cytoprotection does not preserve brain functionality in rats during the acute post-stroke phase despite evidence of non-infarction provided by MRI

In animal models of stroke the promise of a therapy is commonly judged from infarct size measurements, assuming that a reduction in infarct size results in reduction of the functional deficits. We have evaluated the validity of the concept that structural integrity translates into functional integrity during the acute post-stroke period (24 h). Unilateral permanent middle cerebral artery occlusion (pMCAO) in Fischer F344 rats leads to infarcts comprising the ipsilateral striatum and cortical structures, including the somatosensory cortex. Infarct volumes were assessed using magnetic resonance imaging (MRI) methods (T(2), diffusion, perfusion MRI). The functional integrity of the somatosensory cortex was assessed by functional MRI (fMRI) measuring changes in local cerebral blood volume, and by assessing the forelimb grip strength and the beam-walking performance of the animals. Treatment with the calcium antagonist isradipine (2.5 mg/kg injected s.c. immediately after pMCAO) reduced the total infarct size by more than 40% compared to vehicle-injected controls. In particular, the ipsilateral somatosensory cortex appeared normal in diffusion- and T(2)-weighted MRI images. In sham-operated rats simultaneous electrical stimulation of both forepaws led to similar activation of both somatosensory cortices, while in pMCAO animals given vehicle only the contralateral cortex showed an fMRI response. Similarly, in pMCAO rats treated with isradipine, functional activation following bilateral electrical stimulation was only detected in the contralateral somatosensory cortex despite the normal appearance of the ipsilateral cortex in MRI images. Furthermore, fMRI responses to pharmacological stimulation with bicuculline were virtually absent in the ipsilateral somatosensory cortices both in vehicle- and isradipine-treated rats. Finally there was no significant difference between vehicle- and isradipine-treated animals upon the performance of beam-walking test or in forelimb grip strength. It is concluded that during the acute (24 h) post-occlusion period, structural integrity in the somatosensory cortex revealed by MRI does not translate into preservation of function.

Intermittent use of amifostine during postoperative radiochemotherapy and acute toxicity in rectal cancer patients

PURPOSE

Amifostine has been shown to be able to reduce acute radiation toxicity if administered daily prior to radiation during a course of a conventionally fractionated radiotherapy. A disadvantage is the necessity of daily intravenous injection. We have used amifostin in patients undergoing adjuvant radiochemotherapy for rectal cancer. Amifostine was administered only in the first and fifth week of radiotherapy together with 5-FU chemotherapy. The objective was to determine whether the intermittent use of amifostine may be effective in reducing acute radiation toxicity.

PATIENTS AND METHODS

From September 1997 through October 1998, 30 patients with stage II/III rectal cancer underwent postoperative radiochemotherapy at our department. All patients had undergone curative (R0) resection and received 50.4 Gy to the pelvis with a 3-field technique using a belly board followed by a boost of 5.4 Gy to the presacral space in conventional fractionation with 1.8 Gy per fraction. 5-FU chemotherapy was administered as 120-hours continuous infusion in the first and fifth radiation week via a central venous catheter in a daily dosage of 1,000 mg/m2. All patients were offered to participate in a phase-II study using additional amifostine. Fifteen patients participated and received 500 mg amifostine daily on chemotherapy days (days 1 to 5 and 29 to 33) immediately prior to the daily radiation fraction. Fifteen patients did not participate and served as non-randomized control. The study was approved by the ethical committee of the Martin-Luther-University and informed consent was obtained from all patients.

RESULTS

The distribution of patients' characteristics and prognostic parameters was comparable in both groups. Side effects of amifostine were mild and included hypotension (53% grade I, 7% grade II) and nausea (47% grade I, 13% grade II). Antiemetics were not routinely used. All patients completed radiochemotherapy plus amifostine without unplanned breaks or dose reductions. One patient developed a cerebral infarction which was considered to be not related to the use of amifostine. As compared to the non-randomized control group, patients with additional amifostine had less acute skin and bowel toxicity (maximum erythema score 1.47 +/- 0.64 without vs 0.87 +/- 0.52 with amifostine, p = 0.009 and maximum diarrhea score 1.07 +/- 1.03 vs 0.40 +/- 0.63, p = 0.044). Oral 5-FU-related mucositis and hematological toxicity were not significantly different.

CONCLUSIONS

In this phase-II study, amifostine significantly reduced acute skin and bowel toxicity of adjuvant chemoradiation in patients with rectal cancer even if the drug was administered only intermittently and not during the whole course of radiotherapy. This finding might be important with regard to intense combined regimes and should be further investigated.

Immunohistochemical determination of HER-2/neu expression in invasive breast carcinoma

Numerous methods exist for HER-2/neu assessment; however, technical and interpretive standardization is virtually absent. We evaluated 2 commercially available antibodies on routinely fixed paraffin-embedded tissue sections to establish our own guidelines. Thirty-three cases of infiltrating breast carcinoma were evaluated simultaneously with monoclonal and polyclonal antibodies. Only membranous staining, no matter how focal, was considered positive. An additional 32 tumors were studied subsequently using only the polyclonal antibody. Of all carcinomas, 13.0% showed immunohistochemical evidence of HER-2/neu overexpression. High-grade tumors were more often positive. There was no HER-2/neu gene expression in the benign epithelium that generally was present in the tissue section or in any of the well-differentiated tumors tested. The polyclonal antibody proved more sensitive than the monoclonal antibody. While true cytoplasmic staining was present occasionally, it did not create substantial difficulty in interpretation. The polyclonal antibody cost substantially less than the monoclonal antibody. Fluorescence in situ hybridization assay for HER-2/neu gene amplification performed on 32 of 65 cases showed concordant results in 31 cases. The immunohistochemical assay for HER-2/neu gene overexpression, using our methods, is accurate, economic, and easily integrated into the laboratory.

Regional brain activation by bicuculline visualized by functional magnetic resonance imaging. Time-resolved assessment of bicuculline-induced changes in local cerebral blood volume using an intravascular contrast agent

Functional magnetic resonance imaging (fMRI) has been applied to study rat focal brain activation induced by intravenous administration of the GABA(A) antagonist bicuculline. Using magnetite nanoparticles as a blood pool contrast agent, local changes in cerebral blood volume (CBV) were assessed with high temporal (10 s) and spatial (0.35 x 0.6 mm(2)) resolutions. Upon infusion of the bicuculline region-specific increases in CBV have been observed, suggesting CBV to reflect brain activity. During the first 2 min, the signal increases were predominant in the cortex, followed by increases in other brain areas, such as the caudate putamen, thalamus and cerebellum. Ten minutes after the start of infusion, a dominant response was observed in the thalamus, while in the caudate putamen a biphasic response pattern was seen. The magnitude of the signal responses in all brain regions was dependent on the dose of bicuculline and, in general, matched the known distribution of GABA(A) binding sites. This study suggests that pharmacological fMRI, displaying brain function at the highly specific level of drug-receptor interaction, should foster our understanding of normal and pathological brain function.

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.

In situ measurements of creatine kinase flux by NMR. The lessons from bioengineered mice

P-31 nuclear magnetic resonance (NMR) is uniquely suited to measure the kinetics of the phosphoryl-exchange reaction catalyzed by creatine kinase in intact mammalian tissue, especially striated muscle. Recently developed transgenic mouse models of the creatine kinase iso-enzyme system open novel opportunities to assess the functional importance of the individual iso-enzymes and their relative contribution to the total in situ flux through the CK reaction. This chapter reviews the most recent findings from NMR flux measurements on such genetic models of CK function. Findings in intact mouse skeletal and cardiac muscle in vivo are compared to data from purified mitochondrial and cytosolic creatine kinase in vitro. The relevance of findings in transgenic animals for the function of CK in wild-type tissue is described and the perspectives of transgenic techniques in future quantitative studies on the creatine kinase iso-enzyme system are indicated.

Fluxes through cytosolic and mitochondrial creatine kinase, measured by P-31 NMR

The kinetic properties of the cytoplasmic and the mitochondrial iso-enzymes of creatine kinase from striated muscle were studied in vitro and in vivo. The creatine kinase (CK) iso-enzyme family has a multi-faceted role in cellular energy metabolism and is characterized by a complex pattern of tissue-specific expression and subcellular distribution. In mammalian tissues, there is always co-expression of at least two different CK isoforms. As a result, previous studies into the role of CK in energy metabolism have not been able to directly differentiate between the individual CK species. Here, we describe experiments which were directed at achieving this goal. First, we studied the kinetic properties of the muscle-specific cytoplasmic and mitochondrial CK isoforms in purified form under in vitro conditions, using a combination of P-31 NMR and spectrophotometry. Secondly, P-31 NMR measurements of the flux through the CK reaction were carried out on intact skeletal and heart muscle from wild-type mice and from transgenic mice, homozygous for a complete deficiency of the muscle-type cytoplasmic CK isoform. Skeletal muscle and heart were compared because they differ strongly in the relative abundance of the CK isoforms. The present data indicate that the kinetic properties of cytoplasmic and mitochondrial CK are substantially different, both in vitro and in vivo. This finding particularly has implications for the interpretation of in vivo studies with P-31 NMR.

Dynamic changes in water ADC, energy metabolism, extracellular space volume, and tortuosity in neonatal rat brain during global ischemia

To obtain a better understanding of the mechanisms underlying early changes in the brain water apparent diffusion coefficient (ADC) observed in cerebral ischemia, dynamic changes in the ADC of water and in the energy status were measured at postnatal day 8 or 9 in neonatal rat brains after cardiac arrest using 1H MRS/MRI and 31P MRS, respectively. The time courses of the MR parameters were compared with changes in the extracellular space (ECS) volume fraction (alpha) and tortuosity (lambda), determined from concentration-time profiles of tetramethylammonium applied by iontophoresis. The data show a decrease of the ADC of tissue water after induction of global ischemia of which the time course strongly correlates with the time course of the decrease in the ECS volume fraction and the increase in ECS tortuosity. This indicates that cell swelling is an important cause for the ADC decrease of water.

A fast method for in vivo lactate imaging

A robust method for fast lactate imaging is presented using a combination of a lactate editing sequence and a one-shot imaging experiment. The lactate editing method is based on manipulation of the phase of the lactate CH3 signal via J-modulation. This is applied as a preparation experiment to the U-FLARE imaging sequence. Phantom experiments are presented in which the quality of water and lipid suppression is established. Edited lactate images with a spatial resolution of 3 microL and total measuring time of 15.8 min are shown. These were obtained from a hemispherical ischemia in the gerbil brain. The images are compared with diffusion-weighted water images.

On the application of ultra-fast RARE experiments

The ultra-fast application of the RARE experiment is described in detail, with special emphasis on its multifarious applications with preparation experiments that produce transverse magnetization. The factors affecting the temporal evolution of the magnetization during the experiment are described, and the implications for the slice profile when using a Gaussian refocusing pulse are experimentally examined. The choice of phase-encoding scheme for use with preparation experiments is discussed, as is the use of various phase-encoding schemes to reduce line broadening in the phase-encoding direction if a number of averages are acquired. An explanation for the decomposition of the echo are into two components if the read gradient is imbalanced is given, and the experimental conditions necessary for the coherent addition of these two echo groups are described. An alternative sequence that removes one of these groups from the acquisition window is proposed. The sensitivity of the sequence to flow and motion is investigated, and the drastic loss of signal in this situation explained. The in vivo and in vitro application of preparation experiments leading to the accurate measurement of T1, T2, diffusion constant, and magnetization transfer characteristics is presented. The implementation of zoom-imaging using spin- and stimulated-echo preparation is described, and 3D in vivo spin-echo zoom images are presented. Simple phantom experiments demonstrating the feasibility of chemical-shift selective and spectroscopic imaging are also given.

Correlation of minimum coronary lumen diameter with left ventricular functional impairment induced by atrial pacing

To understand whether quantitative measurement of minimal coronary luminal diameter is a better method than percent diameter narrowing for assessing the functional impairment of myocardial contractility produced by coronary artery stenoses, measurements were made from 37 stenotic segments in 27 patients with coronary artery disease and from corresponding segments in 10 subjects without coronary artery narrowing. An assessment of the reliability of the 2 types of measurements was made by correlating them with the physiologic parameters of both segmental wall motion and global ejection fraction response induced by atrial pacing. Digitally acquired coronary angiograms were used to facilitate quantitative analysis. Measurements by edge detection and videodensitometry correlated closely (r = 0.94). Percent diameter narrowing correlated moderately with the change in ejection fraction (r = -0.41) or with the change in segmental wall motion (r = -0.44). The measurement of minimal lumen diameter correlated with the change in global ejection fraction (r = 0.61) and did so even better with the change in segmental wall motion (r = 0.78, p less than 0.05). A minimal lumen diameter of less than or equal to 1.5 mm identified patients likely to have a functional impairment during atrial pacing as assessed by either global ejection fraction or segmental wall motion defects. We conclude that minimal coronary luminal diameter provides a better method than percent diameter narrowing calculations to measure the anatomic severity of coronary artery narrowing.

Movements of vesicles on microtubules

Many cytoplasmic vesicles are observed to move along microtubules. Often, bidirectional movement of particles is observed on a single microtubule. We have isolated one cytoplasmic motor, kinesin, and defined another, the axoplasmic retrograde factor, which are capable of powering anionic latex beads toward the plus and minus ends of microtubules, respectively. Observations of vesicle movements show that vesicles have a defined direction of movement and that vesicles copurify with a kinesin motor activity. Current evidence suggests the hypothesis that kinesin and the retrograde motors power vesicle movements in vivo by attachment to the appropriate vesicle.

Videodensitometric determination of minimum coronary artery luminal diameter before and after angioplasty

Quantitative measurements of coronary stenoses were made from digital coronary angiograms in 19 patients before and after percutaneous transluminal coronary angioplasty (PTCA). Two methods of measurement were compared. Mean stenosis before PTCA was 67 +/- 10% by the edge detection method and 67 +/- 12% by videodensitometry (difference not significant). After PTCA, the mean stenosis was 32 +/- 14% by edge detection and 30 +/- 13% by videodensitometry (difference not significant). In addition, a new method was developed to rapidly calculate the absolute minimum luminal area and diameter by videodensitometry. The minimum luminal diameter before PTCA was 1.0 +/- 0.5 mm and after PTCA increased to 2.4 +/- 0.5 mm (p less than 0.001). The validity of the videodensitometric method was analyzed in a series of Lucite phantom studies, which suggested that when there is an irregular angiographic appearance, the densitometric method may be more accurate than standard edge detection methods. Digital acquisition of coronary angiograms provides a means for rapid application of quantitative analysis during coronary interventional procedures.

Vesicle movements and microtubule-based motors

The movements of many cytoplasmic vesicles follow the paths of microtubules, some moving in one direction and others moving in the opposite direction on the same microtubule. Recently we have isolated one cytoplasmic motor, kinesin, and defined another, the axoplasmic retrograde factor, both of which are capable of powering anionic latex beads in both directions along polar microtubule arrays. Evidence summarized here supports but does not prove the hypothesis that kinesin and the retrograde motors are indeed responsible for powering vesicle movements.

Spontaneous perforation of the colon in a hemodialysis patient

Spontaneous perforation of the colon by a barium stereoraceous fecaloma occurred two weeks after an upper gastrointestinal x-ray without intervening constipation or symptoms of intestinal obstruction. This patient is chronically uremic as have been a high percentage of the few previously reported similar cases. Renal failure and the associated factors in the management of uremia such as antacids, barium examinations, inactivity, changes in diet and finally abnormalities of the colonic mucosa due to uremia may all predispose these patients to an increased risk for this unusual serious complication.