A fatal case of sclerosing mesenteritis

A 22-year-old patient was admitted because of abdominal pain and vomiting. Computed tomography diagnosed small intestinal malignancy. Ileal resection was performed, and the histological findings were consistent with sclerosing mesenteritis. The patient was treated with enteral nutrition, corticosteroids, azathioprine and methotrexate, but died 2 years later.

Structure of beta-ketoacyl-[acyl carrier protein] reductase from Escherichia coli: negative cooperativity and its structural basis

The structure of beta-ketoacyl-[acyl carrier protein] reductase (FabG) from Escherichia coli was determined via the multiwavelength anomalous diffraction technique using a selenomethionine-labeled crystal containing 88 selenium sites in the asymmetric unit. The comparison of the E. coli FabG structure with the homologous Brassica napus FabG.NADP(+) binary complex reveals that cofactor binding causes a substantial conformational change in the protein. This conformational change puts all three active-site residues (Ser 138, Tyr 151, and Lys 155) into their active configurations and provides a structural mechanism for allosteric communication between the active sites in the homotetramer. FabG exhibits negative cooperative binding of NADPH, and this effect is enhanced by the presence of acyl carrier protein (ACP). NADPH binding also increases the affinity and decreases the maximum binding of ACP to FabG. Thus, unlike other members of the short-chain dehydrogenase/reductase superfamily, FabG undergoes a substantial conformational change upon cofactor binding that organizes the active-site triad and alters the affinity of the other substrate-binding sites in the tetrameric enzyme.

Beclomethasone dipropionate: absolute bioavailability, pharmacokinetics and metabolism following intravenous, oral, intranasal and inhaled administration in man

AIMS

To assess the absolute bioavailability, pharmacokinetics and metabolism of beclomethasone dipropionate (BDP) in man following intravenous, oral, intranasal and inhaled administration.

METHODS

Twelve healthy subjects participated in this seven-way cross-over study where BDP was administered via the following routes: intravenous infusion (1000 microg), oral (4000 microg, aqueous suspension), intranasal (1344 microg, aqueous nasal spray) and inhaled (1000 microg ex-valve, metered dose inhaler). The contribution of the lung, nose and gut to the systemic exposure was assessed by repeating the inhaled, intranasal and oral dosing arms together with activated charcoal, to block oral absorption. Blood samples were collected for 24 h postdose for the measurement of BDP, beclomethasone-17-monopropionate (B-17-MP) and beclomethasone (BOH) in plasma by liquid chromatography tandem mass spectrometry.

RESULTS

Intravenous administration of BDP (mean CL 150 l h-1, Vss 20 l, t(1/2) 0.5 h) was associated with rapid conversion to B-17-MP which was eliminated more slowly (t1/2 2.7 h). In estimating the parameters for B-17-MP (mean CL 120 l h-1, Vss 424 l) complete conversion of BDP to B-17-MP was assumed. The resultant plasma concentrations of BOH were low and transient. BDP was not detected in plasma following oral or intranasal dosing. The mean absolute bioavailability (%F, 90% CI; nominal doses) of inhaled BDP was 2% (1-4%) and not reduced by coadministration of charcoal. The mean percentage F of the active metabolite B-17-MP was 41% (31-54%), 44% (34-58%) and 62% (47-82%) for oral, intranasal and inhaled dosing without charcoal, respectively. The corresponding estimates of nasal and lung absorption, based on the coadministration of charcoal, were < 1% and 36% (27-47%), respectively.

CONCLUSIONS

Unchanged BDP has negligible oral and intranasal bioavailability with limited absorption following inhaled dosing due to extensive (95%) presystemic conversion of BDP to B-17-MP in the lung. The oral and intranasal bioavailabilities of the active metabolite B-17-MP were high and similar, but direct absorption in the nose was insignificant. The total inhaled bioavailability of B-17-MP (lung + oral) was also high (62%) and approximately 36% of this was due to pulmonary absorption. Estimates of oral bioavailability and pulmonary deposition based on total BOH were approximately half those found for B-17-MP.

Identification and analysis of the acyl carrier protein (ACP) docking site on beta-ketoacyl-ACP synthase III

The molecular details that govern the specific interactions between acyl carrier protein (ACP) and the enzymes of fatty acid biosynthesis are unknown. We investigated the mechanism of ACP-protein interactions using a computational analysis to dock the NMR structure of ACP with the crystal structure of beta-ketoacyl-ACP synthase III (FabH) and experimentally tested the model by the biochemical analysis of FabH mutants. The activities of the mutants were assessed using both an ACP-dependent and an ACP-independent assay. The ACP interaction surface was defined by mutations that compromised FabH activity in the ACP-dependent assay but had no effect in the ACP-independent assay. ACP docked to a positively charged/hydrophobic patch adjacent to the active site tunnel on FabH, which included a conserved arginine (Arg-249) that was required for ACP docking. Kinetic analysis and direct binding studies between FabH and ACP confirmed the identification of Arg-249 as critical for FabH-ACP interaction. Our experiments reveal the significance of the positively charged/hydrophobic patch located adjacent to the active site cavities of the fatty acid biosynthesis enzymes and the high degree of sequence conservation in helix II of ACP across species.

Inhibition of beta-ketoacyl-acyl carrier protein synthases by thiolactomycin and cerulenin. Structure and mechanism

The beta-ketoacyl-acyl carrier protein (ACP) synthases are key regulators of type II fatty acid synthesis and are the targets for two natural products, thiolactomycin (TLM) and cerulenin. The high resolution structures of the FabB-TLM and FabB-cerulenin binary complexes were determined. TLM mimics malonyl-ACP in the FabB active site. It forms strong hydrogen bond interactions with the two catalytic histidines, and the unsaturated alkyl side chain interaction with a small hydrophobic pocket is stabilized by pi stacking interactions. Cerulenin binding mimics the condensation transition state. The subtle differences between the FabB-cerulenin and FabF-cerulenin (Moche, M., Schneider, G., Edwards, P., Dehesh, K., and Lindqvist, Y. (1999) J. Biol. Chem. 244, 6031-6034) structures explain the differences in the sensitivity of the two enzymes to the antibiotic and may reflect the distinct substrate specificities that differentiate the two enzymes. The FabB[H333N] protein was prepared to convert the FabB His-His-Cys active site triad into the FabH His-Asn-Cys configuration to test the importance of the two His residues in TLM and cerulenin binding. FabB[H333N] was significantly more resistant to both antibiotics than FabB and had an affinity for TLM an order of magnitude less than the wild-type enzyme, illustrating that the two-histidine active site architecture is critical to protein-antibiotic interaction. These data provide a structural framework for understanding antibiotic sensitivity within this group of enzymes.

Neuronal death in newborn striatum after hypoxia-ischemia is necrosis and evolves with oxidative stress

The mechanisms for neurodegeneration after hypoxia-ischemia (HI) in newborns are not understood. We tested the hypothesis that striatal neuron death is necrosis and evolves with oxidative stress and selective organelle damage. Piglets ( approximately 1 week old) were used in a model of hypoxia-asphyxia and survived for 3, 6, 12, or 24 h. Neuronal death was progressive over 3-24 h recovery, with approximately 80% of putaminal neurons dead at 24 h. Striatal DNA was digested randomly at 6-12 h. Ultrastructurally, dying neurons were necrotic. Damage to the Golgi apparatus and rough endoplasmic reticulum occurred at 3-12 h, while most mitochondria appeared intact until 12 h. Mitochondria showed early suppression of activity, then a transient burst of activity at 6 h, followed by mitochondrial failure (determined by cytochrome c oxidase assay). Cytochrome c was depleted at 6 h after HI and thereafter. Damage to lysosomes occurred within 3-6 h. By 3 h recovery, glutathione levels were reduced, and peroxynitrite-mediated oxidative damage to membrane proteins, determined by immunoblots for nitrotyrosine, occurred at 3-12 h. The Golgi apparatus and cytoskeleton were early targets for extensive tyrosine nitration. Striatal neurons also sustained hydroxyl radical damage to DNA and RNA within 6 h after HI. We conclude that early glutathione depletion and oxidative stress between 3 and 6 h reperfusion promote damage to membrane and cytoskeletal proteins, DNA and RNA, as well as damage to most organelles, thereby causing neuronal necrosis in the striatum of newborns after HI.

Mechanisms for neuronal degeneration in amyotrophic lateral sclerosis and in models of motor neuron death (Review)

Amyotrophic lateral sclerosis (ALS), also referred to as motor neurone disease, is a fatal neurological disease that is characterized clinically by progressive muscle weakness, muscle atrophy, and eventual paralysis. The neuropathology of ALS is primary degeneration of upper (motor cortical) and lower (brainstem and spinal) motor neurons. The amyotrophy refers to the neurogenic atrophy of affected muscle groups, and the lateral sclerosis refers to the hardening of the lateral white matter funiculus in spinal cord (corresponding to degeneration of the corticospinal tract) found at autopsy. Because the mechanisms for the motor neuron degeneration in ALS are not understood, this disease has no precisely known causes and no effective treatments. Very recent studies have identified that the degeneration of motor neurons in ALS is a form of apoptotic cell death that may occur by an abnormal programmed cell death (PCD) mechanism. In order to treat ALS effectively, we need to understand the mechanisms for motor neuron apoptosis more completely. Future studies need to further identify the signals for PCD activation in neurons as they relate to the pathogenesis of ALS and to clarify the molecular pathways leading to motor neuron apoptosis in animal and cell culture model systems. These studies should lead to a better understanding of motor neuron death and to the design of new therapeutic experiments critical for the future treatment of ALS.

Motor neuron degeneration after sciatic nerve avulsion in adult rat evolves with oxidative stress and is apoptosis

The mechanisms for motor neuron degeneration and regeneration in adult spinal cord following axotomy and target deprivation are not fully understood. We used a unilateral sciatic nerve avulsion model in adult rats to test the hypothesis that retrograde degeneration of motor neurons resembles apoptosis. By 21 days postlesion, the number of large motor neurons in lumbar spinal cord was reduced by approximately 30%. The death of motor neurons was confirmed using the terminal transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling method for detecting fragmentation of nuclear DNA. Motor neuron degeneration was characterized by aberrant accumulation of perikaryal phosphorylated neurofilaments. Structurally, motor neuron death was apoptosis. Apoptotic motor neurons undergo chromatolysis followed by progressive cytoplasmic and nuclear condensation with chromatin compaction into uniformly large round clumps. Prior to apoptosis, functionally active mitochondria accumulate within chromatolytic motor neurons, as determined by cytochrome c oxidase activity. These dying motor neurons sustain oxidative damage to proteins and nucleic acids within the first 7 days after injury during the progression of apoptosis, as identified by immunodetection of nitrotyrosine and hydroxyl-modified deoxyguanosine and guanosine. We conclude that the retrograde death of motor neurons in the adult spinal cord after sciatic nerve avulsion is apoptosis. Accumulation of active mitochondria within the perikaryon and oxidative damage to nucleic acids and proteins may contribute to the mechanisms for apoptosis of motor neurons in the adult spinal cord.

Phase III multicenter trial of high-dose gadoteridol in MR evaluation of brain metastases

PURPOSE

To assess the efficacy and safety profile of high-dose (0.3 mmol/kg cumulative dose) gadoteridol in patients with suspected central nervous system metastatic disease.

METHODS

We studied 67 patients using an incremental-dose technique. Patient monitoring included a medical history, physical examination, vital signs, and extensive laboratory tests within 24 hours before and after the MR examination. Precontrast T1- and T2-weighted spin-echo studies were performed, followed by intravenous injection of 0.1 mmol/kg of gadoteridol. T1-weighted images were acquired immediately after and at 10 and 20 minutes after injection. At 30 minutes an additional 0.2 mmol/kg of gadoteridol was administered (0.3-mmol/kg cumulative dose), and T1-weighted images were acquired. Cases demonstrating abnormal MR findings were assessed for efficacy by unblinded and blinded reviewers and were analyzed quantitatively.

RESULTS

Three adverse effects in two patients were considered to be related to gadoteridol administration. No adverse effects were serious; all self-resolved. Forty-nine cases showed abnormal MR findings and were included in the efficacy analysis. A significantly greater number of lesions was seen on the high-dose as opposed to the standard-dose images. Blinded and unblinded readers identified 5 and 8 patients, respectively, with solitary lesions on standard-dose examination and multiple lesions on high-dose examination. Two patients who had normal standard-dose findings had lesions identified on high-dose studies. Quantitative analysis of 133 lesions in 45 patients demonstrated significant increases in lesion signal intensity on high-dose studies when compared with standard-dose studies.

CONCLUSION

Gadoteridol can be safely administered up to a cumulative dose of 0.3 mmol/kg. High-dose contrast studies provide improved lesion detectability and additional diagnostic information over studies performed in the same patients with a 0.1-mmol/kg dose and aid in patient diagnosis and treatment. High-dose gadoteridol study may facilitate the care of patients with suspected central nervous system metastasis.

High-dose gadoteridol in MR imaging of intracranial neoplasms

Twelve patients with a high suspicion of brain metastases by previous clinical or radiologic examinations were studied in a phase III investigation with magnetic resonance (MR) imaging at 1.5 T after a bolus intravenous injection of 0.1 mmol/kg gadoteridol followed at 30 minutes by a second bolus injection of 0.2 mmol/kg gadoteridol. All lesions were best demonstrated (showed greatest enhancement) at the 0.3-mmol/kg (cumulative) dose, with image analysis confirming signal intensity enhancement in the majority of cases after the second gadoteridol injection. More lesions were detected with the 0.3-mmol/kg dose than with the 0.1-mmol/kg dose, and more lesions were detected with the 0.1-mmol/kg dose than on precontrast images. In this limited clinical trial, high-dose gadoteridol injection (0.3-mmol/kg cumulative dose) provided improved lesion detection on MR images specifically in intracranial metastatic disease.

The prospective evaluation of Gd-DTPA in 225 consecutive cranial cases: adverse reactions and diagnostic value

This prospective study evaluates two facets of gadopentetate dimeglumine (Gd-DTPA) enhanced MR imaging in 225 consecutive cranial cases in patients greater than 18 years of age: (i) patient and physician perception of adverse reactions, (ii) diagnostic value of the Gd-DTPA enhanced exam. The 225 cases included 173 head cases, 27 IAC cases, and 25 sella cases. Forty-six percent of the cases were abnormal excluding cases of mild atrophy and ischemic white matter disease judged to be related to aging and not pertinent to the patient's presenting complaint. Concerning adverse reactions, 83% of patients had no complaints. Five percent of the patients had reactions that were judged by the physician to be related to Gd-DTPA. All reactions were minor and required no therapy. In a subset of exams (115) that were blindly and independently interpreted by two board-certified, fellowship-trained radiologists, the Gd-DTPA-enhanced exam resulted in a change in diagnosis in 5%-8% of cases. Additionally, a major benefit of Gd-DTPA administration was the increased diagnostic confidence afforded by the addition of a contrast enhanced exam due to improved lesion characterization and exclusion of additional significant intracranial pathology. In 52%-69% of the abnormal cases, Gd-DTPA provided additional diagnostic information and in 26%-39% the absence of enhancement aided in interpretation. The Gd-DTPA-enhanced exam aids in the diagnosis and characterization of neoplastic disease, acoustic neuroma, subacute infarction, inflammatory disease (meningeal and parenchymal), and certain vascular abnormalities.

Remyelination in the human central nervous system

Remyelination, albeit incomplete, has been demonstrated in human central nervous system (CNS). However, information about the initial stage and the final extent of such remyelination is not available. We describe the morphologic findings of a demyelinating lesion with evidence of early remyelination in a biopsy obtained from a 15-year-old boy about two weeks after the onset of neurologic symptoms. The demyelinated area appeared hypercellular with a relatively large number of oligodendrocytes frequently seen in the process of new myelin formation. In addition to the usual reactive changes, the astrocytes were often seen to contain otherwise normal-looking oligodendrocytes within their cytoplasm. In the ensuing months, the patient made apparently total functional recovery accompanied by nearly complete resolution of the white matter lesions demonstrated by the subsequent magnetic resonance studies. These observations suggested that the initial remyelination seen in the biopsy eventually succeeded in producing extensive remyelination in the lesion. Although the exact nature of the demyelinating disorder in our patient remains undetermined, this study indicates that clinically significant remyelination is possible in human CNS. Also, our findings appeared strikingly similar to those described in certain experimental animal models in which widespread remyelination is known to occur.

Gd DTPA. Clinical efficacy

Both the diagnostic accuracy and sensitivity of the MRI diagnosis of central nervous system neoplasms appear to be improved by the administration of a paramagnetic contrast agent, Gd DTPA.

Gd DTPA. Future applications with advanced imaging techniques

In this admittedly preliminary view of the future, the authors present a number of new concepts in MR imaging and consider their possible advantages and limitations.

Craniopharyngioma: CT and MR imaging in nine cases

Magnetic resonance (MR) imaging and CT examinations were performed in nine patients with surgically proven craniopharyngioma. Computed tomography was found to be superior to MR in detection of calcification and cyst formation. Extent of involvement of adjacent structures (e.g., optic chiasm, third ventricle, and intracavernous carotid artery) was more clearly delineated by MR. Craniopharyngioma fluid collections were found to be uniformly bright on T2-weighted sequences. However, on T1-weighted sequences, the signal intensity of the fluid ranged from hypointense to hyperintense, reflecting the heterogeneous contents of cysts in these tumors. Since calcification and cyst formation are hallmarks of craniopharyngiomas, we believe that CT is more specific than MR in diagnosis of craniopharyngiomas. Magnetic resonance, however, offers a more accurate assessment of the tumor extent.

Primary glioma: diagnosis with magnetic resonance imaging

Seventeen patients with surgically documented primary glial-origin brain tumors were evaluated by magnetic resonance imaging and high-resolution computed tomography. The exclusion of CT ring-enhancing lesions directed the focus of this study toward lower grade tumors that were more difficult to diagnose. The computed tomography abnormalities were often subtle and included areas of low attenuation, mass effect, and focal enhancement. Spin-echo sequences with both heavy T1 and T2 weighting were utilized. Prolonged T1 and T2 values were observed in all tumors. The T2-weighted spin-echo 1000/120 sequence was the most sensitive in tumor detection and was positive in all cases. Magnetic resonance imaging was superior to computed tomography in tumor detection, tumor localization, assessment of tumor extent, and determination of associated changes, ie, brain stem encroachment. All the magnetic resonance sequences used showed an increase in severity of imaging changes with increasing tumor grade. The T2-weighted sequence showed progressive margin irregularity, whereas the T1-weighted (inversion recovery) sequence showed increasing severity of internal tissue changes. The superior resolution of these changes by magnetic resonance imaging may have implications for better assessment of tumor grade in the future than is currently possible with computed tomography.

Early changes in experimental hydrocephalus

In acute obstruction of the cerebral spinal fluid (CSF) absorption pathways, fluid is produced more rapidly than it is absorbed, and the ventricles enlarge proximal to the obstructions. Communicating hydrocephalus results from a difference between the rates of production and absorption of cerebrospinal fluid. In animals with chronic communicating hydrocephalus, the initial pathologic changes appear to involve the periventricular tissue near the angles of the lateral ventricles. The present investigation was designed to identify the various changes associated with the production of communicating hydrocephalus in acutely hydrocephalic preparations and to relate these findings to those found in experimental animals with chronic communicating hydrocephalus. The results of this study seem to confirm that the changes noted in the chronically hydrocephalic animals occur as early as 12 hours after the restriction of the normal flow of CSF.

Contrast enhanced MRI. Evaluation of a canine model of osmotic blood-brain barrier disruption

An osmotic model of blood-brain barrier (BBB) disruption was studied by magnetic resonance (MR) imaging (0.5 T) in 17 canines. The animals were killed after imaging and the lesions confirmed on gross pathology by the presence of Evans blue dye. No accompanying cerebral edema was demonstrated on histologic examination. The disrupted BBB could be identified in only one of five control animals on unenhanced MRI, despite the use of calculated T1 and T2 images. In a second group of five animals, the area of abnormal vascular permeability was consistently demonstrated after IV injection of 0.25 mmol/kg Gd DTPA. The time course of enhancement was evaluated in four additional animals. The brain tissue concentration of the gadolinium ion responsible for the observed enhancement was determined by ion coupled plasma analysis in the last three canines. In a study of pulse techniques, spin echo sequences with both short TRs and TEs (ie, SE 500/30) and inversion recovery techniques proved to be most efficacious for the detection of contrast enhancement. However, contrast could be demonstrated on more T2 weighted sequences.

Magnetic resonance imaging and other techniques in the diagnosis of multiple sclerosis

We evaluated 35 patients with multiple sclerosis (MS) by magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, evoked potential testing, and computed tomographic (CT) scanning. As classified by the McAlpine et al and McDonald and Halliday criteria, 27 patients had definite MS, three had probable MS, and five had possible MS. All of the patients had multiple white matter lesions detectable by MRI that were evident predominantly in the periventricular areas but also in the cerebral or cerebellar white matter. The severity of the MRI abnormality, as judged by the number and size of the lesions, correlated with the likelihood of a positive CT scan but not with the duration of disease, the degree of disability, or positive CSF oligoclonal banding. Magnetic resonance imaging successfully demonstrated brain-stem lesions in 15 patients (none were seen on CT scans). Magnetic resonance imaging seems to be a sensitive indicator of MS lesions, but clinical assessment will continue to be crucial to the diagnosis of MS.

The use of Gd DTPA as a perfusion agent and marker of blood-brain barrier disruption

To provide contrast enhancement in magnetic resonance imaging, a new class of compounds has been developed, the paramagnetic metal ion chelates. Gadolinium (Gd) DTPA, a prototype of this class, shows a sufficiently high in vivo stability and low toxicity for use in initial clinical trials. This type of agent, designed for rapid clearance by glomerular filtration, allows the assessment on MRI of renal function, alterations in tissue perfusion, myocardial ischemia, and perhaps most significantly disruption of the blood-brain barrier (BBB). Research at Vanderbilt has demonstrated these applications, with particular emphasis in three areas. Tissue perfusion changes, such as those produced by ligation of the arterial blood supply to portions of the spleen and kidney, cannot easily be detected on unenhanced MRI. These acute tissue infarcts can be readily identified following the administration of Gd DTPA. The question of field strength dependence of Gd DTPA has been addressed by experimentation at 0.15, 0.5, and 1.5 tesla. Furthermore, the ability to detect an alteration of the BBB, when present without associated edema, has been demonstrated with the application of control enhancement. The use of contrast agents in MRI will enhance both the sensitivity and specificity of magnetic resonance imaging.

Diagnosis of spinal arteriovenous malformation in a pregnant patient by MR imaging

An intraspinal arteriovenous malformation (AVM) was diagnosed by magnetic resonance imaging in a pregnant patient. Serpentine areas of low signal intensity surrounded by cerebrospinal fluid were considered diagnostic of this surgically verified abnormality. In addition, T2 weighted images helped to determine the extent of the spinal canal occupied by the AVM.

Dyke Award. Evaluation of contrast-enhanced MR imaging in a brain-abscess model

An alpha-streptococcus brain abscess was produced in five dogs and studied with magnetic resonance (MR) imaging (0.5 T) and computed tomography (CT). Non-contrast- and contrast-enhanced CT scans were obtained using gadolinium diethylenetriamine-pentaacetic acid (Gd DTPA) for MR imaging and meglumine iothalamate for CT scanning. Each animal was evaluated in the early and later cerebritis stages of abscess evolution. On MR, the area of cerebritis enhanced after administration of Gd DTPA in a manner similar to that observed with contrast-enhanced CT. However, contrast enhancement was greater on the MR examination. Early lesions in two animals were detected only with contrast-enhanced MR imaging. This experience suggests that intravenously administered agents such as Gd DTPA should increase the diagnostic potential of MR imaging in neurologic diseases, especially those altering the blood-brain barrier.

Magnetic resonance imaging of multiple sclerosis: a study of pulse-technique efficacy

Forty-two patients with the clinical diagnosis of multiple sclerosis were examined by proton magnetic resonance imaging (MRI) at 0.5 T. An extensive protocol was used to facilitate a comparison of the efficacy of different pulse techniques. Results were also compared in 39 cases with high-resolution x-ray computed tomography (CT). MRI revealed characteristic abnormalities in each case, whereas CT was positive in only 15 of 33 patients. Milder grades 1 and 2 disease were usually undetected by CT, and in all cases, the abnormalities noted on MRI were much more extensive than on CT. Cerebral abnormalities were best shown with the T2-weighted spin-echo sequence (TE/TR = 120/1000); brainstem lesions were best defined on the inversion-recovery sequence (TE/TI/TR = 30/400/1250). Increasing TE to 120 msec and TR to 2000 msec heightened the contrast between normal and abnormal white matter. However, the signal intensity of cerebrospinal fluid with this pulse technique obscured some abnormalities.

Intravascular contrast agents suitable for magnetic resonance imaging

Two paramagnetic chelates, chromium EDTA and gadolinium DTPA, were evaluated as potential intravenous contrast agents for magnetic resonance imaging (MR) using a 0.5-T superconducting scanner. After evaluating both agents in vitro, in vivo studies were conducted in dogs to document changes in renal appearance produced by contrast injection. Acute splenic and renal infarction were diagnosed with contrast-enhanced MR and confirmed by gamma camera imaging following administration of Tc-99m-labeled DMSA and sulfur colloid. The authors conclude that intravenous paramagnetic contrast agents presently offer the best mechanism for assessment of tissue function and changes in perfusion with MR.

Intervertebral disk-space infection: CT changes. Work in progress

Seven patients who had spinal interspace infections underwent clinical, laboratory, and radiographic examinations, and findings are reported. Lytic fragmentation of adjacent vertebral bodies is a characteristic appearance on CT scans. Sagittal-coronal reformations confirm the end-plate irregularity and establish the diagnosis. Since the changes of diskitis are delayed and often obscured by accompanying degenerative disease on plain radiographs, CT appears to offer a diagnostic modality that shortens the usual delay from onset of symptoms to diagnosis.

Neuroradiologic applications of intraarterial digital subtraction angiography

In the neuroradiologic evaluation of 118 patients using intraarterial digital subtraction angiography definite advantages and disadvantages were defined. Advantages include reduction of contrast medium volume, catheter time, and patient risk and discomfort. It also aids in angiographic planning. The paramount disadvantage is less spatial resolution compared with conventional film angiography.

Therapeutic embolization of juvenile angiofibroma

Therapeutic embolization of juvenile angiofibromas was performed in 15 boys, aged 12--18 years, 11 of whom subsequently underwent surgery. Intraoperative blood loss was reduced from an average of 2,400 ml in nonembolized patients to 800 ml after embolization. Angiography is of value to confirm the diagnosis prior to excision and to delineate the extent of the tumor. Embolization may be performed at the same sitting as a presurgical adjunct or possibly as a definitive or palliative therapeutic method. The embolization procedure is discussed in detail, emphasizing techniques and potential hazards of such procedures.

Aortic dysplasia in infancy simulating anomalous origin of the left coronary artery

A case is reported of an infant believed to have had anomalous origin of the left coronary artery. Clinical evaluation and angiography appeared to support the diagnosis. At necropsy, however, the left coronary was seen to arise from the aorta but was totally occluded by dysplastic changes which resulted in myocardial infarction and death of the patient. There was minimal aortic deformity produced by these changes, and no aortic gradient was present. Thus, this very rare case of minimal supravalvular aortic stenosis with left coronary artery occlusion was not recognizable clinically nor angiographically.

Schizophrenic thought process: analysis of the WAIS

Differences in performance on the WAIS for schizophrenics classified as active or in remission are described.