Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1-3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10-18.

Sunitinib (Sutent®): A novel agent for the treatment of metastatic renal cell carcinoma

Objective. To provide a review of the clinical data supporting the use of sunitinib (Sutent®), a multitargeted, small molecule, tyrosine kinase inhibitor, with focus on its approved indication for the treatment of advanced renal cell carcinoma in patients with metastatic disease requiring drug therapy.Data sources. A MEDLINE search of the medical literature was conducted using the terms ‘sunitinib’ and ‘SU11248’. References from the articles were reviewed and relevant sources were included. Data summary. The introduction of dual tyrosine kinase receptor inhibitors is a novel approach to treating advanced metastatic renal cell carcinoma (mRCC) by preventing angiogenesis and tumor growth. Based on its ability to inhibit several targets involved in angiogenesis and endothelial cell proliferation, sunitinib offers patients with mRCC an alternative for treatment. A recent Phase III study evaluating sunitinib as first-line therapy showed a significant difference when compared to interferonalfa (IFN-α) for a progression-free survival of 11 months in the sunitinib arm and 5 months in the IFN-α arm (hazard ratio 0.42; 95% CI 0.32–0.54; P50.001). Two Phase II trials determined sunitinib was effective as second-line therapy in mRCC patients who failed previous cytokine treatment. Partial response rates were 40% (95% CI 28%–53%) and 34% (95% CI 25%–44%). Multiple ongoing trials are currently underway to evaluate sunitinib for first-line therapy in mRCC. J Oncol Pharm Practice (2007) 13: 5–16.

Comprehensive, Integrative Genomic Analysis of Diffuse Lower-Grade Gliomas

BACKGROUND

Diffuse low-grade and intermediate-grade gliomas (which together make up the lower-grade gliomas, World Health Organization grades II and III) have highly variable clinical behavior that is not adequately predicted on the basis of histologic class. Some are indolent; others quickly progress to glioblastoma. The uncertainty is compounded by interobserver variability in histologic diagnosis. Mutations in IDH, TP53, and ATRX and codeletion of chromosome arms 1p and 19q (1p/19q codeletion) have been implicated as clinically relevant markers of lower-grade gliomas.

METHODS

We performed genomewide analyses of 293 lower-grade gliomas from adults, incorporating exome sequence, DNA copy number, DNA methylation, messenger RNA expression, microRNA expression, and targeted protein expression. These data were integrated and tested for correlation with clinical outcomes.

RESULTS

Unsupervised clustering of mutations and data from RNA, DNA-copy-number, and DNA-methylation platforms uncovered concordant classification of three robust, nonoverlapping, prognostically significant subtypes of lower-grade glioma that were captured more accurately by IDH, 1p/19q, and TP53 status than by histologic class. Patients who had lower-grade gliomas with an IDH mutation and 1p/19q codeletion had the most favorable clinical outcomes. Their gliomas harbored mutations in CIC, FUBP1, NOTCH1, and the TERT promoter. Nearly all lower-grade gliomas with IDH mutations and no 1p/19q codeletion had mutations in TP53 (94%) and ATRX inactivation (86%). The large majority of lower-grade gliomas without an IDH mutation had genomic aberrations and clinical behavior strikingly similar to those found in primary glioblastoma.

CONCLUSIONS

The integration of genomewide data from multiple platforms delineated three molecular classes of lower-grade gliomas that were more concordant with IDH, 1p/19q, and TP53 status than with histologic class. Lower-grade gliomas with an IDH mutation either had 1p/19q codeletion or carried a TP53 mutation. Most lower-grade gliomas without an IDH mutation were molecularly and clinically similar to glioblastoma. (Funded by the National Institutes of Health.).

Susceptibility-weighted imaging in patients with pyogenic brain abscesses at 1.5T: characteristics of the abscess capsule

BACKGROUND AND PURPOSE

SWI is a high-resolution 3D, fully velocity-compensated gradient-echo sequence that uses both magnitude and phase data. The purpose of this study was to investigate the phase behavior of the capsule of pyogenic brain abscesses with noncontrast SWI.

MATERIALS AND METHODS

Fourteen patients with pyogenic brain abscesses were studied at 1.5T. In all of the patients, SWI images were obtained and reviewed in addition to conventional MR images. Phase values within the abscess capsule were measured and compared with those from the abscess cavities and contralateral normal white matter using 1-way repeated measures ANOVA with post hoc Bonferroni analysis.

RESULTS

SWI phase images showed mild hypointesity in 6 patients, isointensity in 3 patients, and mixed iso- to mild hypointensity in 5 patients. The means of phase in the cavity, rim of abscesses, and contralateral normal white matter were -7.552 × 10(-3) ± 0.024, -0.105 ± 0.080, and +0.029 ± 0.011 radians, respectively. Post hoc comparisons showed significant differences between any pair of the 3 regions (abscess cavity, rim capsule, and normal white matter) in SWI (all Ps < .005).

CONCLUSIONS

SWI phase imaging shows evidence of paramagnetic substances in agreement with the presence of free radicals from phagocytosis. SWI may provide additional information valuable in the characterization of pyogenic brain abscesses.

In vivo differentiation of aerobic brain abscesses and necrotic glioblastomas multiforme using proton MR spectroscopic imaging

BACKGROUND AND PURPOSE

Abscesses caused by aerobic bacteria (aerobic abscesses) can simulate intracranial glioblastomas multiforme (GBMs) in MR imaging appearance and single voxel (SV) proton MR spectroscopy of the central cavity. The purpose of our study was to determine whether MR spectroscopic imaging (SI) can be used to differentiate aerobic abscesses from GBMs. Our hypothesis was that metabolite levels of choline (Cho) are decreased in the ring-enhancing portion of abscesses compared with GBMs.

MATERIALS AND METHODS

Fifteen patients with aerobic abscesses were studied on a 1.5T MR scanner using an SV method and an SI method. Proton MR spectra of 15 GBMs with similar conventional MR imaging appearances were used for comparison. The resonance peaks in the cavity, including lactate, cytosolic amino acids, acetate, succinate, and lipids, were analyzed by both SV MR spectroscopy and MRSI. In the contrast-enhancing rim of each lesion, peak areas of N-acetylaspartate (NAA), choline (Cho), lipid and lactate (LL), and creatine (Cr) were measured by MRSI. The peak areas of NAA-n, Cho-n, and Cr-n in the corresponding contralateral normal-appearing (-n) brain were also measured. Maximum Cho/Cr, Cho/NAA, LL/Cr-n, and Cho/Cho-n and minimum Cr/Cr-n and NAA/NAA-n ratios in abscesses and GBMs were compared using the Wilcoxon rank sum test. After receiver operating characteristic curve analysis, diagnostic accuracy was compared.

RESULTS

Cytosolic amino acid peaks were found in the cavity in 7 of 15 patients with aerobic abscesses. Means and SDs of maximum Cho/Cr, Cho/NAA, LL/Cr-n, and Cho/Cho-n and minimum Cr/Cr-n and NAA/NAA-n ratios were 3.38 +/- 1.09, 3.88 +/- 2.13, 2.72 +/- 1.45, 1.98 +/- 0.53, 0.53 +/- 0.16, and 0.44 +/- 0.09, respectively, in the GBMs, and 1.77 +/- 0.49, 1.48 +/- 0.51, 2.11 +/- 0.67, 0.81 +/- 0.21, 0.48 +/- 0.2, and 0.5 +/- 0.15, respectively, in the abscesses. Significant differences were found in the maximum Cho/Cr (P = .001), Cho/NAA (P = .006), and Cho/Cho-n ratios (P < .001) between abscesses and GBMs. Diagnostic accuracy was higher by Cho/Cho-n ratio than Cho/Cr and Cho/NAA ratios (93.3% versus 86.7% and 76.7%).

CONCLUSION

Metabolite ratios and maximum Cho/Cho-n, Cho/Cr, and Cho/NAA ratios of the contrast-enhancing rim were significantly different and useful in differentiating aerobic abscesses from GBMs by MRSI.

Do-not-resuscitate decision: the attitudes of medical and non-medical students

OBJECTIVES

To study the attitudes of both medical and non-medical students towards the do-not-resuscitate (DNR) decision in a university in Hong Kong, and the factors affecting their attitudes.

METHODS

A questionnaire-based survey conducted in the campus of a university in Hong Kong. Preferences and priorities of participants on cardiopulmonary resuscitation in various situations and case scenarios, experience of death and dying, prior knowledge of DNR and basic demographic data were evaluated.

RESULTS

A total of 766 students participated in the study. There were statistically significant differences in their DNR decisions in various situations between medical and non-medical students, clinical and preclinical students, and between students who had previously experienced death and dying and those who had not. A prior knowledge of DNR significantly affected DNR decision, although 66.4% of non-medical students and 18.7% of medical students had never heard of DNR. 74% of participants from both medical and non-medical fields considered the patient's own wish as the most important factor that the healthcare team should consider when making DNR decisions. Family wishes might not be decisive on the choice of DNR.

CONCLUSIONS

Students in medical and non-medical fields held different views on DNR. A majority of participants considered the patient's own wish as most important in DNR decisions. Family wishes were considered less important than the patient's own wishes.

A preliminary report of brain edema in patients with uremia at first hemodialysis: evaluation by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE

The dynamics of brain-water content associated with hemodialysis in patients with severe azotemia remains obscure. To investigate whether either interstitial or cytotoxic edema is responsible for dialysis disequilibrium syndrome (DDS), we used diffusion-weighted MR imaging (DWI) to measure the apparent diffusion coefficient (ADC), which is sensitive for detecting tissue water dynamics.

METHODS

Eight consecutive patients with end stage renal disease (ESRD) and blood urea nitrogen level of more than 100 mg/dL (160.9 +/- 53.1 mg/dL) were recruited. Conventional MR images, DWI, and clinical manifestations were obtained before and after the 1st hemodialysis. The ADC values were determined for regions of normal-appearing gray and white matter and for regions of hyperintensity of white matter on T2-weighted MR imaging.

RESULTS

Foci of bright areas of white matter were found in all patients on T2-weighted images. The ADC values of the patients with ESRD, in white matter and gray matter before and after hemodialysis, were greater than those of the healthy controls (P < .005). Regarding the impact of hemodialysis, the ADC of frontal lobe white matter increased significantly after hemodialysis (1.09 +/- 0.11 versus 1.03 +/- 0.11, P = .036). We did not find the specific area of brain edema reported in posterior leukoencephalopathy and the osmotic demyelination syndrome.

CONCLUSIONS

These results suggest that severe azotemia in end stage renal disease leads to interstitial brain edema reflected as increased ADC, and the further increased ADC reflects that edema associated with 1st hemodialysis is interstitial rather than cytotoxic in nature.

Upregulation of endothelial heme oxygenase-1 expression through the activation of the JNK pathway by sublethal concentrations of acrolein

Acrolein is a highly electrophilic alpha,beta-unsaturated aldehyde that is present in cigarette smoke. Heme oxygenase-1 (HO-1) is a cytoprotective enzyme activated by various such electrophilic compounds. In this study, the regulatory effects of acrolein upon the expression of HO-1 were investigated in endothelial cells (ECs). We demonstrate that acrolein induces the elevation of HO-1 protein levels, and subsequent enzyme activity, at non-cytotoxic concentrations. An additional alpha,beta-unsaturated aldehyde, cinnamaldehyde, was also found to increase HO-1 expression and have less cytotoxicity than acrolein. Moreover, acrolein-mediated HO-1 induction is abrogated in the presence of actinomycin D and cycloheximide. Nrf2 is a transcription factor involved in the induction of HO-1 through an antioxidant response element (ARE) in the promoter region of the HO-1 gene. We show that acrolein induces Nrf2 translocation and ARE-luciferase reporter activity. Acrolein was also found to induce the production of both superoxide and H2O2 at levels greater than 100 microM. However, with the exception of NAC, no antioxidant generated any effect upon acrolein-dependent HO-1 expression in ECs. Our present findings suggest that reactive oxygen species (ROS) may not be a major modulator for HO-1 induction. Using buthionine sulfoximine to deplete the intracellular GSH levels further enhanced the effects of acrolein. We also found that cellular GSH level was rapidly reduced after both 10 and 100 microM acrolein treatment. However, after 6 h of exposure to ECs, only 10 microM acrolein treatment increases GSH level. In addition, only the JNK inhibitor SP600125 and tyrosine kinase inhibitor genistein had any significant inhibitory impact upon the upregulation of HO-1 by acrolein. Pretreatment with a range of other PI3 kinase inhibitors, including wortmannin and LY294002, showed no effects. Hence, we show in our current experiments that a sublethal concentration of acrolein is in fact a novel HO-1 inducer, and we further identify the principal underlying mechanisms involved in this process.

Multidetector CT angiography in diagnosing type I and type IVA spinal vascular malformations

Multidetector CT (MDCT) angiography is an imaging technique that can provide high-resolution and high-contrast images; however, published reports of MDCT angiography in the evaluation of spinal vascular malformations are limited. We present 2 cases in which MDCT angiography led to diagnosis of a type I (spinal dural arteriovenous fistula) in one and type IVA (perimedullary spinal cord simple arteriovenous fistula fed by a single arterial feeder) spinal vascular malformation, both confirmed by conventional angiography. MDCT angiography can localize the feeding vessel and the fistula, thus greatly reducing the amount of time required for conventional angiography.

Upregulation of heme oxygenase-1 by Epigallocatechin-3-gallate via the phosphatidylinositol 3-kinase/Akt and ERK pathways

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme activated by various phytochemicals and we examined the ability of Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, to upregulate HO-1 expression in endothelial cells (ECs). We demonstrate that EGCG induces HO-1 expression in a concentration- and time-dependent manner. Furthermore, EGCG-mediated HO-1 induction was abrogated in the presence of actinomycin D and cycloheximide, indicating that this upregulation of HO-1 occurred at the transcriptional level. EGCG also upregulates Nrf2 levels in nuclear extracts and increases ARE-luciferase activity. Furthermore, EGCG is the most potent inducer of HO-1 expression of the different green tea constituents that we analyzed, but had no detectable cytotoxic effects over the 25-100 microM dosage range. The inhibition of intracellular ROS production by N-acetylcysteine (NAC), glutathione (GSH), superoxide dismutase (SOD), catalase and the mitochondrial complex I inhibitor, rotenone, results in a decrease in EGCG-dependent HO-1 expression. In addition, we determined that tyrosine kinase is involved in EGCG induction of HO-1 as this is abrogated by genistein. ECs treated with EGCG exhibit activation of Akt and ERK1/2. In addition, pharmacological inhibitors of phosphatidylinositol 3-kinase and MEK1/2, which are upstream of Akt and ERK1/2, respectively, attenuate EGCG-induced HO-1 expression. On the other hand, pretreatment of these cells with EGCG exerts significant cytoprotective effects against H2O2, suggesting that the induction of HO-1 is an important component in the protection against oxidative stress. Hence, EGCG is a novel phytochemical inducer of HO-1 expression and we further identify the principal underlying mechanisms involved in this process.

Neuromuscular hamartoma arising in the brachial plexus

We report a case brachial plexus neuromuscular hamartoma (choristoma) in a 28-year-old man who complained of numbness of the left hand and forearm for several years. MRI revealed a circumscribed, rounded mass in the left brachial plexus. The patient is well 2 years after surgery, with no neurological deficit.

Intramedullary spinal cryptococcoma: a case report

Intramedullary spinal cryptococcosis is very rare. We describe a case of intramedullary spinal cryptococcoma at the T12 level in a 60-year-old man who presented with a 3-month history of progressive bilateral lower limb weakness and no obvious immunocompromise. Magnetic resonance (MR) imaging revealed a 1.2 cm diameter mass within the spinal cord at T12 with intermediate signal intensity on T1-weighted images, a slight degree of homogeneous low signal intensity on T2-weighted images, and intense enhancement after infusion of gadopentetate dimeglumine. These findings led to a preoperative diagnosis of intramedullary tumor. After 2 months of postoperative antifungal treatment, the patient's clinical condition had markedly improved. Cryptococcoma should be considered when an enhancing lesion of the spinal cord is found on MR imaging, even in apparently immunocompetent patients. A careful lumbar puncture for cerebrospinal fluid analysis to diagnose cryptococcosis of the central nervous system should be made promptly, as early treatment is associated with a good prognosis.

Automated nasopharyngeal carcinoma detection with dynamic gadolinium-enhanced MR imaging

OBJECTIVES

The purpose of this research is to develop an automatic medical diagnosis for segmenting nasopharyngeal carcinoma (NPC) with dynamic gadolinium-enhanced MR imaging.

METHODS

This system is a multistage process, involving motion correction, head mask generation, dynamic MR data quantitative evaluation, rough segmentation, and rough segmentation refinement. Two approaches, a relative signal increase method and a slope method, are proposed for the quantitative evaluation of dynamic MR data.

RESULTS

The NPC detection results obtained using the proposed methods had a rating of 85% in match percent compared with these lesions identified by an experienced radiologist. The match percent for the two proposed methods did not have significant differences. However, the computation cost for the slope method was about twelve times faster than the relative signal increase method.

CONCLUSIONS

The proposed methods can identify the NPC regions quickly and effectively. This system can enhance the performance of clinical diagnosis.

In vivo proton MR spectroscopy of chorea-ballismus in diabetes mellitus

The most common cause of chorea-ballismus (CB) is a vascular lesion; it is also associated with nonketotic hyperglycaemia in diabetes mellitus (DM) and may be the first manifestation of this disorder. We describe the CT, MRI and proton MR spectroscopy (1H-MRS) of CB in eight patients. Six had hemichorea-hemiballismus (HC-HB) and two bilateral CB. Single-voxel (SV) 1H-MRS was performed using point-resolved spectroscopy (PRESS). Voxels were positioned in the basal ganglia of the patients and control subjects. PRESS was also used to obtain spectroscopic imaging (1H-MRSI) of the slice of interest in two patients. CT showed a slightly dense striatum in all the patients with CB, and T1-weighted images revealed high signal. The CB correlated well with the neuroimaging findings. SV 1H-MRS showed the mean (+/- SD) N-acetylaspartate (NAA)/ creatine (Cr) ratio to be 1.45 +/- 0.19 in HC-HB and 1.82 +/- 0.06 on the opposite normal side (P = 0.01). The choline (Cho)/ Cr ratio was 1.3 +/- 0.12 in HC-HB and 1.11 +/- 0.13 on the opposite normal side (P = 0.005). A lactate peak was seen in seven patients. The NAA/Cr ratio was 1.44 +/- 0.15 in bilateral CB and 1.74 +/- 0.16 in the controls (P = 0.017); the Cho/Cr ratios were 1.36 +/- 0.1 and 1.19 +/- 0.07 (P = 0.015). The low NAA/Cr suggests neuronal loss or damage and the high Cho/Cr probably indicates gliosis. The presence of lactate may suggest mild ischaemia due to acute vascular events during hyperglycaemia and underlying chronic focal cerebrovascular diseases in DM.

Sensitivity of diffusion-weighted magnetic resonance imaging in the diagnosis of acute lacunar infarcts

BACKGROUND AND PURPOSE

Heightened interest in the early diagnosis and treatment of acute stroke challenges neuroimaging specialists to optimize available modalities and to develop new techniques for the evaluation of cerebrovascular disease. The purpose of this study was to evaluate the sensitivity of diffusion-weighted (DW) magnetic resonance (MR) imaging in detecting early small infarcts and in differentiating acute from nonacute small infarcts when conventional MR imaging demonstrates multiple small infarcts.

METHODS

Thirty-eight consecutive patients with a clinical diagnosis of lacunar infarcts (20 men and 18 women, aged 50-79 yr) who underwent DW MR imaging within 3 days of symptom onset were enrolled in this study. All patients underwent both conventional fast spin-echo (FSE) MR imaging and DW MR imaging. Apparent diffusion coefficient (ADC) maps were also acquired. All patients had at least one of the following classic lacunar syndromes: pure motor hemiparesis, ataxic hemiparesis, dysarthria-clumsy hand, pure sensory stroke, and sensorimotor stroke.

RESULTS

Thirty-six patients (40 acute lesions) had focal areas of high intensity on DW MR imaging associated with their clinical symptoms. Acute lacunar infarcts were seen on DW MR imaging as bright areas of decreased ADC ratio (range 0.31-0.85, mean 0.64). Lesion conspicuity with DW MR imaging was superior to that with FSE in 33 acute lesions. In four patients with small hyperacute (within 6 hours) infarcts, DW MR imaging was particularly sensitive for infarcts that were not visible on FSE sequences. The sensitivity of DW MR imaging and ADC map for acute lacunar infarcts was 95%, specificity 94%, positive predictive value 97%, negative predictive value 90%, and accuracy 95%. In 15 patients with both acute and nonacute old small infarcts, DW MR imaging and ADC map could easily distinguish the new infarct from adjacent old ones, although this distinction was difficult to make with FSE.

CONCLUSIONS

DW MR imaging accompanied by ADC map is a sensitive diagnostic modality for hyperacute and acute lacunar infarcts. It is also sensitive in distinguishing fresh small infarcts from adjacent multiple old infarcts.

A major kinetic trap for the oxidative folding of human epidermal growth factor

The folding pathway of human epidermal growth factor (EGF) has been characterized by structural and kinetic analysis of the acid-trapped folding intermediates. Oxidative folding of the fully reduced EGF proceeds through 1-disulfide intermediates and accumulates rapidly as a single stable 2-disulfide intermediate (designated as EGF-II), which represents up to more than 85% of the total protein along the folding pathway. Among the five 1-disulfide intermediates that have been structurally characterized, only one is native, and nearly all of them are bridges by neighboring cysteines. Extensive accumulation of EGF-II indicates that it accounts for the major kinetic trap of EGF folding. EGF-II contains two of the three native disulfide bonds of EGF, Cys(14)-Cys(31) and Cys(33)-Cys(42). However, formation of the third native disulfide (Cys(6)-Cys(20)) for EGF-II is slow and does not occur directly. Kinetic analysis reveals that an important route for EGF-II to reach the native structure is via rearrangement pathway through 3-disulfide scrambled isomers. The pathway of EGF-II to attain the native structure differs from that of three major 2-disulfide intermediates of bovine pancreatic trypsin inhibitor (BPTI). The dissimilarities of folding mechanism(s) between EGF, BPTI, and hirudin are discussed in this paper.

Cerebral vasculitis in Henoch-Schönlein purpura: a case report with sequential magnetic resonance imaging changes and treated with plasmapheresis alone

Neurological complications are rare during the course of Henoch-Schönlein purpura (HSP). We report a 7-year-old girl with HSP who presented with seizures, loss of vision and disturbance of consciousness. Magnetic resonance imaging (MRI) showed high signal intensity in the gray and white matter over the left parietal and both occipital lobes, compatible with MRI findings of cerebral vasculitis. The eye fundi revealed multiple branches of retinal artery occlusion. Intravenous pulse methylprednisolone (MTP) followed by oral steroid therapy was initially administered for HSP nephritis. Cerebral vasculitis developed 10 days post-MTP treatment, with progressive worsening of consciousness. Oral steroid was discontinued and plasmapheresis was performed alone. Her level of consciousness dramatically improved after plasmapheresis. The brain MRI and eye fundi findings were consistent with her clinical improvement. To the best of our knowledge, this is the first description of MRI abnormalities and multiple retinal artery branch occlusion of cerebral vasculitis in a patient with HSP that was successfully treated by plasmapheresis alone. In conclusion, we propose that plasmapheresis may be used as a first-line therapy or rescue therapy for cerebral vasculitis in HSP.

Carpal tunnel syndrome caused by tophaceous gout: CT and MR imaging features in 20 patients

OBJECTIVE

The objective of this study is to describe the CT and MR imaging findings of gouty tophi in the wrist and present this entity as a cause of carpal tunnel syndrome.

MATERIALS AND METHODS

Retrospective review of the CT (n = 18) and MR imaging (n = 20) studies of the wrist in patients with a documented diagnosis of gout who presented with gout-related carpal tunnel syndrome was performed; images of 24 wrists were collected over a 5-year period. Patient population included 20 men, who ranged in age from 35 to 76 years. All images were reviewed by two musculoskeletal radiologists who reached a consensus opinion. Surgical correlation was available in 12 patients.

RESULTS

Tophi were found in the floor of the carpal tunnel (n = 18), carpal bones (n = 17), radiocarpal joint (n = 17), and extensor tendons or tendon sheaths (n = 16) of the wrist. All tophi showed similar signal characteristics (from low to intermediate signal intensity on T1-weighted images with heterogeneous signal intensity on T2-weighted images) with the exception of tophi in the floor of the carpal tunnel (low signal intensity on T2-weighted images). Varying degrees of calcification were noted on CT and MR imaging studies. Gadolinium-enhanced MR studies showed heterogeneous enhancement.

CONCLUSION

Gouty tophi should be entertained as a cause of carpal tunnel syndrome in the appropriate patient population. Familiarity with this entity and its imaging characteristics may prove helpful in diagnosis and preoperative planning.

Postanoxic parkinsonism: clinical, radiologic, and pathologic correlation

The authors report a 72-year-old patient who presented with parkinsonism after hypoxic-ischemic insult. T1-weighted MRI revealed high signal intensity lesions in the basal ganglia. Pathologic study of the brain disclosed multiple foci of old infarcts with gliosis and lipid-laden and hemosiderin-laden macrophages, indicating a previous minor hemorrhage after infarction. This observation provided pathologic correlation with the patient's clinical symptoms and MRI.

Unusual signs for dural arteriovenous fistulas with diffuse basal ganglia and cerebral calcification

We present a case of multiple dural arteriovenous fistulas (AVFs) in a 60-year-old man with the chief complaint of worsening headache, altered mental status and progressively unsteady gait over the course of one year. Computerized tomography revealed diffuse, symmetric calcification in the bilateral basal ganglia and bilateral periventricular and subcortical white matter. Magnetic resonance imaging revealed multiple, enhanced, punctate and linear vessels. These images were due to reflux into the parenchymal veins in the dural AVF of the superior sagittal sinus within the basal ganglia and deep white matter of both cerebral hemispheres. Cerebral angiography disclosed multiple dural AVFs. The exact mechanism of basal ganglia and subcortical calcification is proposed to be an arterial steal phenomenon or persistent venous congestion, with calcification occurring in a chronic hypoperfused state or with dystrophic changes in the walls of congested veins.

Small hepatocellular carcinoma: safety and efficacy of single high-dose percutaneous acetic acid injection for treatment

PURPOSE

To evaluate the safety and efficacy of single high-dose percutaneous acetic acid injection (PAI) for treatment of small (<3-cm-diameter) hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Eighteen patients with HCC (22 nodules; diameter range, 1.5-3.0 cm) underwent single PAI. With ultrasonographic or computed tomographic (CT) guidance, 4-11 mL of 50% acetic acid was slowly injected into the center of the nodule through a skinny multiple-side-hole needle. Follow-up was performed with helical contrast material-enhanced CT. Complications of high-dose PAI were recorded.

RESULTS

Seventeen nodules showed no local recurrence (follow-up, 6-29 months) after single PAI. At a mean follow-up of 15.6 months, mean tumor diameter was 2.1 cm and mean injected volume was 6.4 mL. Four nodules showed residual tumor (mean tumor diameter, 2.6 cm; mean injected volume, 5.8 mL). The mean ratio of injected to estimated volume of acetic acid was 1.21 in cases of successful single PAI and 0.72 in cases of local recurrence (P < .001). One patient with preexistent right portal venous thrombosis died of hepatic failure 37 days after PAI. Other complications included severe pain (11%), high fever (4%), and segmental wedge infarction (4%).

CONCLUSION

Single high-dose PAI is safe and effective for treatment of small HCC.

Detection and assessment of circle of Willis aneurysms in acute subarachnoid hemorrhage with three-dimensional computed tomographic angiography: correlation with digital substraction angiography findings

In this retrospective study, we examined the usefulness of computed tomographic angiography (CTA) for the detection and assessment of circle of Willis aneurysms in patients with acute nontraumatic subarachnoid hemorrhage (SAH), using selective digital substraction angiography (DSA) as the gold standard. Thirty-five patients who presented with acute, nontraumatic SAH, diagnosed on the basis of unenhanced computed tomography or lumbar puncture findings or both, underwent both CTA and DSA. The CTA images were interpreted for the presence, location, size, and shape of the aneurysm, presence of a neck, and relationship of the aneurysm to adjacent arterial branches. The CTA and DSA images were then compared, with the latter images serving as the gold standard. DSA revealed 37 aneurysms in 32 patients and ruled out intracranial aneurysms in the remaining three. The sensitivity and specificity of CTA for aneurysm detection were 97% and 100%, respectively. The size of the smallest aneurysm shown was 4 mm, and the largest aneurysm was 21 mm. The size and lobularity of the aneurysms estimated from CTA images corresponded well with those estimated from DSA images. In addition, CTA provided a three-dimensional representation of the aneurysmal lesion, which was considered useful for surgical planning. Our results confirm the accuracy of CTA in comparison with DSA. Because of its reliability, minimal invasiveness, and rapidity, CTA may become the technique of choice for neuroradiologic work-up of SAH patients. DSA then would be used to diagnose intracranial aneurysms only in selected, questionable cases.

Recurrent inverted papilloma: diagnosis with pharmacokinetic dynamic gadolinium-enhanced MR imaging

BACKGROUND AND PURPOSE

Dynamic gadolinium-enhanced MR imaging has been used successfully to identify post-treatment recurrence or postoperative changes in rectal and cervical carcinoma. Our purpose was to evaluate the usefulness of dynamic gadolinium-enhanced MR imaging for distinguishing recurrent inverted papilloma (IP) from postoperative changes.

METHODS

Fifteen patients with 20 pathologically proved lesions (recurrent IP, 12; fibrosis or granulation tissue, eight) were enrolled in the study. Three observers, blinded to pathologic results, independently evaluated conventional MR images, including T1-weighted (unenhanced and postcontrast), proton-density-weighted, and T2-weighted spin-echo images. Results then were determined by consensus. Dynamic images were obtained using fast spin-echo sequences at 5, 30, 60, 90, 120, 150, 180, and 300 seconds after the injection of gadolinium-diethylene-triamine penta-acetic acid. Time-signal intensity curves of suspected lesions were analyzed by a pharmacokinetic model. The calculated amplitude and tissue distribution time were used to characterize tissue, and their values were displayed as a color-coded overlay.

RESULTS

T2-weighted images yielded a sensitivity of 67%, a specificity of 75%, and an accuracy of 70% in the diagnosis of recurrent IP. Contrast-enhanced T1-weighted images yielded a sensitivity of 75%, a specificity of 50%, and an accuracy of 65%. Pharmacokinetic analysis showed that recurrent IP had faster (distribution time, 41 versus 88 seconds) and higher (amplitude, 2.4 versus 1.2 arbitrary units) enhancement than did fibrosis or granulation tissue. A cut-off of 65 seconds for distribution time and 1.6 units for amplitude yielded a sensitivity of 100% and a specificity of 100% for diagnosing recurrent IP.

CONCLUSION

Dynamic MR imaging can differentiate accurately recurrent IP from postoperative changes and seems to be a valuable diagnostic tool.

Imaging diagnosis of insufficiency fracture of the sacrum

BACKGROUND

Insufficiency fracture of the sacrum has been recognized as a major cause of lower back pain, especially in elderly osteoporotic patients with or without underlying malignancy and/or prior pelvic radiotherapy. Its diagnosis cannot be readily made from its nonspecific clinical features. Consequently some cases may be mistaken for bone metastases, causing patients to receive inappropriate diagnostic measures and management. Recognition of the spectrum of imaging features is the basis of correct diagnosis and treatment.

METHODS

The imaging studies of 14 cases (12 women and 2 men; age range, 60-84 years; mean age, 70 years) of sacral insufficiency fracture were reviewed retrospectively. These included 14 radiographs, six bone scintigraphs, eight computerized tomography (CT) scans and 12 magnetic resonance (MR) imaging studies. Six patients had a history of malignancy. Diagnosis was made by characteristic imaging findings, and clinical and radiographic follow-up for one to 3.5 years.

RESULTS

Five cases of sacral insufficiency fracture were suspected based on radiographic findings of fracture lines (2 cases) and focal sclerosis (3 cases). Seven cases were diagnosed by CT findings of linear fractures (7 cases) and focal sclerosis (2 cases). Nine MR examinations demonstrated characteristic vertical bands of marrow edema. A hypointense fracture line was identified in eight cases. The remaining two MR imaging studies disclosed nonspecific focal marrow edema. An early case, which appeared normal on CT scan, showed marrow edema on MR imaging. The positive and diagnostic rates were both 36% for plain radiographs, 88% for CT scans, and 100% and 83%, respectively, for MR images.

CONCLUSIONS

Plain radiographs are often unrewarding. Although MR imaging is the most sensitive tool, fracture lines are best demonstrated and diagnosed using CT. Due to the better diagnostic rate, popularity and cost effectiveness, CT is recommended as the definitive modality for confirming diagnosis of insufficiency fracture of the sacrum.

Analysis of the extent of unfolding of denatured insulin-like growth factor

Insulin-like growth factor (IGF-1) contains three disulfide bonds. In the presence of denaturant and thiol catalyst, IGF-1 shuffles its native disulfide bonds and denatures to form a mixture of scrambled isomers. The composition of scrambled IGF varies under different denaturing conditions. Among the 14 possible scrambled IGF isomers, the yield of the beads-form isomer is shown to be directly proportional to the strength of the denaturing condition. This paper demonstrates a new approach to quantify the extent of unfolding of the denatured protein.

Hypertrophic cranial pachymeningitis and lymphocytic hypophysitis in Sjögren's syndrome

The authors describe a patient with primary Sjögren's syndrome who developed pachymeningitis, hypopituitarism, and central diabetes insipidus. The patient improved with corticosteroid pulse therapy.

Intracranial acute arterial ischemia of the anterior circulation: evaluation with three-dimensional time-of-flight magnetic resonance angiography

BACKGROUND

Stroke has been the second most common cause of death, after cancer, in Taiwan since 1983. The cost of stroke to society in terms of morbidity, mortality and economics is profound. Heightened interest in the early diagnosis and treatment of acute stroke challenges neuroimagers to optimize available modalities and to develop new techniques for the evaluation of cerebrovascular disease. The aim of this study was to investigate the effectiveness of magnetic resonance angiography (MRA) in conjunction with spin-echo imaging in patients with acute brain infarction of the anterior circulation.

METHODS

Magnetic resonance imaging and three-dimensional Fourier transformed time-of-flight MRA studies, performed on 50 patients within one week after the onset of cerebral ischemia, were retrospectively reviewed and correlated with clinical records. Five of the 50 MRAs were considered nondiagnostic and excluded because of poor patient cooperation.

RESULTS

In 41 of the 45 cases, the area of infarct corresponding to the clinical deficit at the time of study was identified on T2-weighted spin-echo images. Arterial occlusions or severe stenoses that corresponded to ischemic manifestations were identified with MRA in 37 of the 45 patients. A focal discontinuity with decreased arterial caliber corresponded to stenosis and nonvisualization of distal branches represented arterial occlusion. MRA provided information for 23 cases not obtained from the MR images.

CONCLUSIONS

Vascular lesions demonstrated on intracranial MRA show a high correlation with infarct distribution. MRA, which provides information adjunctive to conventional MR imaging in a majority of cases, is concluded to be an important component of the complete evaluation of brain infarction.

Intracranial cystic cavernous angioma: a case report

We present a case of cystic cavernous angioma in an 18-year-old woman with the chief complaint of acute onset of seizures. Computed tomography (CT) and magnetic resonance (MR) imaging revealed a tumor with a slightly enhanced solid calcified portion and a large cystic portion. The patient was well without recurrence 6 months after surgery. The importance of MR imaging in the differential diagnoses is emphasized.

Primary intracranial leiomyoma: case report

We present a case of intracranial parenchymal leiomyoma in a 20-year-old woman with a chief complaint of numbness and a painful sensation over the right limbs for several years. CT and MRI revealed an intensely enhancing calcified mass. The patient was well, without recurrence, 2 years after surgery.

Putaminal petechial haemorrhage as the cause of chorea: a neuroimaging study

OBJECTIVES

A hyperintense putamen on either CT or MRI as a finding associated with chorea has occasionally been described and is almost always associated with non-ketotic hyperglycaemia. The cause of the hyperintensity of the striatum in these images is still controversial. Some reports have found that calcification was responsible whereas others have advocated petechial haemorrhage as the cause. The purpose of this study was to determine whether hyperintense striata are caused by petechial haemorrhage or calcification, with the sequential imaging changes.

SUBJECTS AND METHODS

Five patients presenting with an acute onset of either hemichorea or generalised chorea and showed either unilateral or bilateral hyperdense striatum on the initial CT were assessed. Neuroimaging studies including sequential CT and MRI examinations and detailed biochemical tests were performed.

RESULTS

Three patients had pronounced hyperglycaemia and the other two patients had no biochemical abnormalities. In all patients, the first CT scans, performed within two weeks of the onset of chorea, showed a high density over the striatum contralateral to the chorea, which diminished or disappeared two months later. T1 weighted imaging disclosed hypersignal intensities over the striatum contralateral to the chorea on admission which diminished two months later. T2 weighted imaging at two months showed hyposignal intensity changes corresponding to the area with hypersignal changes on T1 weighted images, implying haemosiderin deposition.

CONCLUSION

Based on the evolution of clinical manifestations and the findings of neuroimaging, putaminal petechial haemorrhage might be a new entity causing either hemichorea or generalised chorea.

Disseminated miliary cerebral candidiasis

We present a case of disseminated intracranial infection by Candida albicans in a 5-year-old girl who had fever and a change of consciousness after surgery for complex congenital heart malformation. MR imaging revealed multiple small ring-enhancing hemorrhagic abscesses. One year after antifungal treatment, the abscesses and ventriculomegaly were almost completely resolved. The patient was discharged in a stable but vegetative condition.

Traumatic dissection of the vertebral artery: a case report

This report concerns a patient suffering from a severe neck pain on the third day after a traffic accident. This condition was followed by a lateral medullary infarction on the next day. One week later, he was transferred to this hospital and dissection of the vertebral artery was disclosed. It should be emphasized that in case of acute cervical spine injury or severe neck pain after a major trauma, vertebral artery dissection should be considered, as its early diagnosis may have crucial therapeutic implications. In addition, the advantages of the combination of magnetic resonance imaging and magnetic resonance angiography as diagnostic tools-of-choice are emphasized.

Single-voxel proton brain spectroscopy exam (PROBE/SV) in patients with primary brain tumors

OBJECTIVE

The Single-Voxel Proton Brain Exam (PROBE/SV) is an automated MR spectroscopic technique. The purpose of this study was to investigate the use of PROBE/SV as a diagnostic tool in patients with primary brain tumors and to compare our findings with the known information obtained from conventional nonautomated MR spectroscopic techniques.

SUBJECTS AND METHODS

We used PROBE/SV to image 10 normal adults and 46 patients with primary brain tumors: 29 glioblastoma multiformes (GBMs), five anaplastic astrocytomas, and 12 low-grade astrocytomas. All studied were performed on a 1.5-T Signa unit. Average voxel sizes were 6-8 cm3. A corresponding point-resolved spectroscopy spectrum was obtained from normal-appearing brain parenchyma in each patient for comparison with the spectra from known areas of pathology.

RESULTS

In patients with low-grade gliomas (grades 1 and 2), we observed decreased N-acetylaspartate (12 of 12) and slightly increased choline (11 of 12) when we compared these metabolites with those in the spectra of patients' normal brains. This comparison in patients with GBM yielded markedly decreased N-acetylaspartate (29 of 29) and prominently increased choline (27 of 29). In the short TE spectra, we frequently saw lipid signal in high-grade tumors, especially in GBMs (12 of 20). We identified lactate peaks in high-grade tumors (anaplastic astrocytoma and GBM, 29 of 34) and also in low-grade tumors (four of 12). The creatine signal in all gliomas was slightly less than that of healthy brain tissue. The lowest N-acetylaspartate, choline, and creatinine levels in conjunction with the highest lactate levels were usually found in necrotic portions of high-grade tumors.

CONCLUSION

PROBE/SV is a simplified MR spectroscopy technique that reduces setup time and provides automatic on-line data processing and display. The voxel location can be selected to focus on the area of interest and to minimize voxel contamination from unwanted tissue. The results from our experimentation with PROBE/SV in patients with brain tumors generally concur with published reports of tumor spectra obtained by conventional MR spectroscopic techniques. The ease and accuracy of this new technique make it a useful clinical tool in differentiating human brain tumor grades.

Chorea-ballismus with nonketotic hyperglycemia in primary diabetes mellitus

PURPOSE

To describe the neuroimaging (Ct, MR, and single-photon emission CT [SPECT]) findings in a series of patients with chorea-ballismus associated with nonketotic hyperglycemia in primary diabetes mellitus and to correlate the imaging findings with the clinical presentation.

METHODS

The neuroimaging and clinical data from 10 patients with chorea-ballismus associated with nonketotic hyperglycemia in primary diabetes mellitus were evaluated. Family and drug histories, as well as other causes of chorea, were excluded. All 10 patients had CT, 5 also had MR imaging, and 3 had SPECT examinations. Three had follow-up CT and MR imaging studies, and MR findings were correlated with CT findings in 5 cases. Two experienced neuroradiologists, aware of the diagnosis but blinded to the clinical status of the patients, evaluated all images and reached a consensus as to the final interpretation.

RESULTS

CT studies in 9 of 10 patients showed a hyperdense putamen and/or caudate nucleus; in 1, the CT findings were normal. T1-weighted MR images in all 5 patients who had MR imaging (including the patient with a normal CT study) showed hyperintense lesions without significant T2 signal alternation at the basal ganglia. In all 3 of the patients who had SPECT studies of the brain, the scans revealed hypoperfusion at corresponding areas. All 3 follow-up studies depicted resolution of the lesions in the abnormal basal ganglia. Increased hypointensity on T2-weighted and gradient-echo T2*-weighted images was also observed in the sequential MR images. In all patients, the initial side of involvement correlated well with the neuroimaging findings. The chorea resolved within 2 days after treatment of the hyperglycemia in 9 patients.

CONCLUSION

In patients with chorea-ballismus associated with nonketotic hyperglycemia in primary diabetes mellitus, CT and T1-weighted MR images show unilateral or bilateral lesions of the putamen and/or caudate. SPECT scans show hypoperfusion. These findings may be related to petechial hemorrhage and/or myelin destruction. Early recognition of these imaging characteristics may facilitate diagnosis of primary diabetes mellitus with hyperglycemia and prompt appropriate therapy.

Carcinosarcoma of the salivary gland on CT

Three cases of carcinosarcoma of the salivary gland, two in the submandibular gland, and one in the parotid, were investigated with CT and exhibited a variety of findings. The density of the tumors was lower than that of normal submandibular tissue. A calcification was found in one case. One case showed extensive lymphadenopathy. The parotid lesion had low central density with an enhancing margin.

Resting tremor only: a variant of Parkinson's disease or of essential tremor

Resting tremor is one of the characteristic features of Parkinson's disease. However, there are a number of patients who typically have resting tremor alone for at least 5 years without development of other parkinsonian signs or symptoms. The etiology of an isolated resting tremor is still obscure. Recently, positron emission tomography was used to study these patients with isolated resting tremor, and demonstrated a markedly decreased striatal uptake of fluoro-dopa to the range of Parkinson's disease. These findings suggested the existence of a separate subtype, namely, tremulous Parkinson's disease with a manifestation of resting tremor alone. In order to confirm the existence of this subgroup of tremulous Parkinson's disease and further investigate its morphological changes and the usefulness of magnetic resonance imaging, we collected 5 patients who typically have resting tremor for at least 8 years in the absence of other features of Parkinson's disease. MRI was performed and the results of the images showed typical findings of Parkinson's disease with smudging or decreased distance between substantia nigra and red nucleus. Quantitative analysis also demonstrated a significant decrease of the above-noted distance when the resting tremor group was compared to the essential tremor group. Therefore, patients with an isolated resting tremor can have morphological abnormalities in addition to functional disturbances shown by positron emission tomography. To our knowledge, this is the first paper to report that resting tremor is a variant of Parkinson's disease rather than essential tremor, by using a double-blind method, with magnetic resonance imaging to support.

The disulfide folding pathway of human epidermal growth factor

Human epidermal growth factor (EGF) contains three disulfides and 53 amino acids. Reduced/denatured EGF refolds spontaneously in vitro to acquire its native structure. The mechanism of this folding process has been elucidated by structural analysis of both acid and iodoacetate trapped intermediates. The results reveal that the folding is accompanied by a sequential flow of unfolded EGF (0-disulfide) through three groups of folding intermediates, namely 1-disulfide, 2-disulfide, and 3-disulfide (scrambled) EGF isomers, to reach the native structure. Equilibrium occurs among isomers of each class of disulfide species, and the composition of intermediates appears to be highly heterogeneous. Together, at least 27 fractions of folding intermediates have been identified, but there exist only limited numbers of well populated species which constitute more than 80% of the total intermediates found during EGF folding. Six species of such well populated intermediates have been isolated, which included two 1-S-S, two 2-S-S, and two 3-S-S scrambled species. Their disulfide structures have been identified here. Both 1-S-S isomers are found to contain non-native disulfides. One of the 2-S-S species consists of two non-native disulfides and the other admits two native disulfides. Among the six disulfides of the two scrambled species, only one is native. Together, native disulfides constitute 25% of the total disulfides found in these six well populated intermediates. These results contrast sharply to those observed with bovine pancreatic trypsin inhibitor, which has shown that well populated folding intermediates consist of exclusively native disulfides (Weissman, J. S., and Kim, P. S. (1991) Science 253, 1386-1393). We propose that well populated folding intermediates, regardless of whether they contain native or non-native disulfides, do not necessarily represent the productive species and specify the folding pathway. Furthermore, conditions influencing the efficiency of EGF folding have been investigated. It is demonstrated here that under optimized compositions of redox agents, including the use of cysteine/cystine and protein disulfide isomerase, the in vitro folding of EGF could be achieved quantitatively within 1 min.

CT of gastritis cystica polyposa

Gastritis cystica polyposa (GCP) is an uncommon lesion that usually occurs at the gastroenterostomy site, although occasionally it can be found in an unoperated stomach. We present a rare case of GCP which presented as a large polypoid mass in the gastric fundus and contained cystic components demonstrable on preoperative computed tomography.

The effect of C-terminal processing on the activity of human interferon-gamma

Homogeneous recombinant human interferon-gamma (IFN-gamma) obtained from Escherichia coli (E. coli) was treated with a protease-containing fraction prepared from mechanically lysed E. coli cells. Polyacrylamide gel electrophoresis of the resulting product revealed two major components of molecular weight less than that of intact IFN-gamma. These were purified by ion exchange chromatography in the presence of 7 M urea and shown to have intact IFN-gamma N-terminal sequences, suggesting that they resulted via C-terminal cleavages of IFN-gamma. Amino acid analysis indicated that 4 C-terminal residues of IFN-gamma were lacking in one, and 15 in the other. The species lacking 4 C-terminal residues had activities virtually indistinguishable from those of IFN-gamma in antiviral and growth inhibitory assays using Encepharomyocarditis-treated HeLa or T98G cells and in a macrophage activation assay using macrophage-like U937 cells. The species lacking 15 C-terminal residues had markedly decreased activities in each of these assays, and had decreased binding affinity for IFN-gamma cell surface receptors. These observations define the C-terminal residues important for IFN-gamma's biological activity--information which should be useful in designing analogs of IFN-gamma with enhanced or altered biological activities.

Disulfide and secondary structures of recombinant human granulocyte colony stimulating factor

Molecular characteristics and secondary structures of recombinant methionyl human granulocyte colony stimulating factor produced by genetically engineered Escherichia coli are described. Limited radiolabeling of the protein with tritiated iodoacetate and determination of the labeled residue revealed that this recombinant protein contains only one free cysteine at position 17 which is not essential for activity. The free cysteine is inaccessible to modification unless the molecule is unfolded under denaturing conditions. The molecule forms two disulfide bridges which were assigned as Cys(36)-Cys(42) and Cys(64)-Cys(74) based on the results of isolation and characterization of disulfide-containing peptides obtained from a subtilisin digest of the intact protein. CD analyses and secondary structure prediction suggest that the molecule is abundant in alpha-helical structures.

Structural characterization of recombinant consensus interferon-alpha

Recombinant consensus interferon-alpha is derived from genetically modified Escherichia coli containing a synthetic gene constructed from a consensus of interferon sequences. The purified and biologically active protein has been subjected to detailed structural characterization including sequence determination and peptide isolation and identification. The homogeneous consensus interferon-alpha preparation contains two chromatographically indistinguishable homologous polypeptides with one containing an extra methionyl residue at the amino terminus. The delineated amino acid sequence of the protein is identical to that expected from the coding sequence of the gene. Correct oxidation of the molecule has been confirmed with two intramolecular disulfide linkages observed at Cys(1)-Cys(99) and Cys(29)-Cys(139).

Control of misincorporation of de novo synthesized norleucine into recombinant interleukin-2 in E. coli

Interleukin-2 produced from a recombinant E. coli was found to contain as much as 19% norleucine in place of methionine in a minimal medium fermentation. Medium supplementation experiments and use of a leucine-requiring mutant host strain indicated the origin of norleucine to be de novo biosynthesis by reactions involving the enzymes of the leucine biosynthetic pathway. The misincorporation was highly suppressed by addition of either L-leucine or L-methionine to the fermentation and completely suppressed by adding both amino acids.

Identification of unusual replacement of methionine by norleucine in recombinant interleukin-2 produced by E. coli

Moderate amounts of norleucine incorporation into recombinant interleukin-2 (IL-2) produced in E. coli have been detected. Incorporation of norleucine occurs both at the amino terminal and internal methionines as confirmed by the isolation of norleucine-containing tryptic peptides which eluted later than the respective methionine-containing peptides by reverse-phase HPLC. The occurrence of norleucine in intact protein and modified peptides was determined by amino acid analysis and amino acid sequencing including Edman degradation and fast atom bombardment mass spectrometry. In the subsequent paper, we determined that norleucine incorporation is caused by the endogenous synthesis of norleucine in E. coli.