Distribution and partial characterisation of IgG Fc binding protein in various mucin producing cells and body fluids

BACKGROUND AND AIMS

Mucus released from goblet cells is important in intestinal mucosal defence, and mucin glycoproteins are thought to be major components of mucus. Recently, we identified and cloned another component of human colonic mucus, IgG Fc binding protein (Fc gamma BP). Fc gamma BP is immunologically distinct from known Fc gamma receptors and its structure contains repeated cysteine rich unit sequences resembling those present in mucins. In this work, we assessed the tissue distribution of Fc gamma BP, its binding activity in various body fluids, and its ability to inhibit complement mediated haemolysis.

METHODS

Immunohistochemical localisation of Fc gamma BP, using monoclonal antibodies against Fc gamma BP (K9 or K17) and labelled IgG, was conducted in various mucin producing tissues: colon, small intestine, stomach, gall bladder, cystic duct, choledochus, bronchus, submandibular gland, conjunctiva, and cervix uteri. The binding activity of Fc gamma BP in mucus extracted from colon, gastric juice, bile, nasal discharges, saliva, sputum, and tears was also examined by immunodotblot and immunoprecipitation using these monoclonal antibodies. Inhibition of complement mediated haemolysis by Fc gamma BP was investigated using sheep red blood cells (SRBC) and anti-SRBC IgG.

RESULTS

The immunohistochemical study revealed that mucin secreting cells in the colon, small intestine, gall bladder, cystic duct, choledochus, bronchus, submandibular gland, and cervix uteri contained Fc gamma BP, and immunodotblot and immunoprecipitation analysis using IgG and monoclonal antibodies demonstrated that the fluids secreted by these cells were capable of binding IgG. Mucin producing cells of the conjunctiva did not express Fc gamma BP molecules or bind to IgG. The surface mucus cells in the stomach were variably positive for Fc gamma BP. Perhaps because of proteolytic degradation, Fc gamma BP in gut lavage fluid did not have IgG binding activity, although this activity was present in the mucus covering the colon. Fc gamma BP suppressed complement mediated haemolysis of SRBC.

CONCLUSIONS

Fc gamma BP is widely expressed on mucosal surfaces and in external secretions. It is functionally intact in several fluids. These findings lend support to the concept that Fc gamma BP is an important component of mucosal immunological defences.

[Esophageal rupture just after the graft replacement of thoracoabdominal aorta for chronic aortic dissection]

A 51-year-old man with thoracoabdominal aortic aneurysm (DeBakey IIIb type chronic aortic dissection) first underwent the graft replacement of thoracic aorta with elephant trunk technique. Postoperatively, the residual false lumen just distal to the inserted graft as an elephant trunk enlarged in a short period, and it compressed the esophagus. He underwent the second graft replacement of thoracoabdominal aorta 2 months after the first surgery. Just after the second surgery, he had the esophageal rupture probably because of direct damage due to the enlarged aneurysm and loss of the arterial blood supply due to the graft replacement. He died of bleeding from the distal anastomosis because of the uncontrolled graft infection. It may have to be kept in mind that the esophageal rupture after the graft replacement could be one of the reason of the graft infection when the aortic aneurysm severely compressed the esophagus preoperatively.

NK cell activity and subsets in women with a history of spontaneous abortion. Cause, number of abortions, and subsequent pregnancy outcome

OBJECTIVE

The aim of this study was to assess the role of NK cells in nonpregnant women with a history of spontaneous abortion.

STUDY DESIGN

113 nonpregnant women with a history of spontaneous abortion were assessed for peripheral NK cell activity and percentage of NK cell subsets, in relation to the cause of abortions, the number of spontaneous abortions, and subsequent pregnancy outcome (n = 56).

RESULTS

Neither NK cell activity nor subsets showed a significant difference in relation to the cause or number of spontaneous abortions. NK cell activity in nonpregnant women who later experienced subsequent abortion with normal chromosomes (n = 10) (mean +/- SD: 42.8 +/- 15.8%) was relatively higher than that in women with subsequent live birth (control, n = 39) (32.1 +/- 13.7%) (p = 0.099). NK cell activity in women who later experienced subsequent abortion with abnormal chromosomes (n = 7) (28.7 +/- 21.4%) was the same as the level in the control.

CONCLUSION

Peripheral NK cell activity or subsets during nonpregnant status were not related to the cause or number of previous spontaneous abortions. A relation between preconceptional NK cell activity and later experiencing abortion with normal chromosomes should be further studied.

Differentiation between high-grade glioma and metastatic brain tumor using single-voxel proton MR spectroscopy

The purpose of this study was to clarify the efficacy of single-voxel proton magnetic resonance spectroscopy (MRS) in differentiating high-grade glioma from metastasis. Thirty-one high-grade gliomas (11 anaplastic gliomas and 20 glioblastomas) and 25 metastases were studied. Proton MRS was performed using point-resolved spectroscopy with echo times (TEs) of both 136 and 30 ms. The peaks for lipid were evaluated at short TE, and those for N-acetyl-aspartate (NAA), creatine (Cr), and choline-containing compounds (Cho) were assessed at long TE. All the tumors exhibited a strong Cho peak at long TE. Twenty-one of 25 metastases showed no definite Cr peak. The remaining 4 metastases showed NAA and Cr peaks; however, the presence of NAA and relatively high NAA/Cr ratio (1.58+/-0.56) indicated normal brain contamination. All the gliomas, except for a single glioblastoma, showed a Cr peak with (n=16) or without (n=14) NAA. At short TE all metastases and glioblastomas showed definite lipid or lipid/lactate mixture, but anaplastic gliomas showed no definite lipid signal. Intratumoral Cr suggests glioma. Absence of Cr indicates metastasis. Definite lipid signal indicates cellular necrosis in glioblastoma and metastasis, and no lipid signal may exclude metastases.

Local thrombolysis for acute ischemic stroke based on findings of diffusion and perfusion MRI

SUMMARY

Cerebral per fusion and cerebral tissue integrity were studied in 13 patients with acute embolic stroke in the territory of the internal carotid artery by diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) within six hours after onset. PWI/DWI mismatch lesion was depicted in six patients. MCA was occluded in five of six patients, who underwent local thrombolytic therapy. In three cases, complete restoration of the cerebral circulation was obtained and enlargement of irreversible brain damage compared to initial DWI lesion was prevented. Seven patients without PWI/DWI mismatch did not undergo thrombolytic therapy. Spontaneous reopening of occluded MCA was verified with subsequent cerebral angiography in one of seven patients. CT depicted symptomatic intracerebral hemorrhage in this patient. It is concluded that DWI and PWI in combination are useful in selection of patients for thrombolytic therapy.

Detection of Fcgamma binding protein antigen in human sera and its relation with autoimmune diseases

Intestinal goblet cells of patients with ulcerative colitis and Crohn's disease highly express a binding protein of the Fc portion of IgG (FcgammaBP), which is entirely different from the Fcgamma receptors I,II, and III on neutrophils and macrophages. In this study, we proved the qualitative existence of FcgammaBP antigen in the sera of patients with rheumatoid arthritis and systemic lupus erythematosus, and, further, established a highly sensitive and quantitatively reproducible assay for FcgammaBP antigen in order to prevent the cross-reactivity of FcgammaBP with von Willebrand factor which has about 30% homology. This assay revealed a higher level of FcgammaBP antigen in the blood stream of patients with autoimmune diseases, especially progressive systemic sclerosis. This would suggest that abnormal production of autoantibodies reflects increased generation of FcgammaBP in goblet cells and its secretion into the circulation by an unknown mechanism.

Massive intravenous immunoglobulin treatment in women with four or more recurrent spontaneous abortions of unexplained etiology: down-regulation of NK cell activity and subsets

PROBLEM

The aims of this study were to investigate the efficacy of massive intravenous immunoglobulin (MIVIg) treatment for women with recurrent spontaneous abortion (RSA) of unexplained etiology, and to investigate changes in peripheral natural killer (NK) cell activity and subsets.

METHOD OF STUDY

MIVIg treatment was performed in 18 pregnancies from 15 women with 4 or more consecutive RSA of unexplained etiology. NK cell activity and subsets were assessed in 8 of the pregnancies.

RESULTS

14 pregnancies resulted in live births and 4 resulted in abortions with chromosome abnormality. The pre-infusion NK cell activity (mean + SD. 40.9 + 17.0%) at 4.4 +/- 0.5 weeks of gestation (GW) decreased to 15.0 +/- 7.90% at post-infusion status (5.4 +/- 0.5 GW). Pre-infusion percentages of CD56+ CD16- cells (3.5 +/- 2.1%) and CD56+ CD16- cells (16.8 +/- 8.8%) decreased to 3.0 +/- 2.2% and 11.1 +/- 6.9%, respectively, after MIVIg treatment.

CONCLUSIONS

MIVIg treatment was effective in all 14 pregnancies from RSA women of unexplained etiology, excluding 4 abortions with chromosome abnormality. Peripheral NK cell activity and subsets were suppressed by MIVIg treatment.

Heat labile ribonuclease HI from a psychrotrophic bacterium: gene cloning, characterization and site-directed mutagenesis

The rnhA gene encoding RNase HI from a psychrotrophic bacterium, Shewanella sp. SIB1, was cloned, sequenced and overexpressed in an rnh mutant strain of Escherichia coli. SIB1 RNase HI is composed of 157 amino acid residues and shows 63% amino acid sequence identity to E.coli RNase HI. Upon induction, the recombinant protein accumulated in the cells in an insoluble form. This protein was solubilized and purified in the presence of 7 M urea and refolded by removing urea. Determination of the enzymatic activity using M13 DNA-RNA hybrid as a substrate revealed that the enzymatic properties of SIB1 RNase HI, such as divalent cation requirement, pH optimum and cleavage mode of a substrate, are similar to those of E.coli RNase HI. However, SIB1 RNase HI was much less stable than E.coli RNase HI and the temperature (T(1/2)) at which the enzyme loses half of its activity upon incubation for 10 min was approximately 25 degrees C for SIB1 RNase HI and approximately 60 degrees C for E.coli RNase HI. The optimum temperature for the SIB1 RNase HI activity was also shifted downward by 20 degrees C compared with that of E.coli RNase HI. Nevertheless, SIB1 RNase HI was less active than E.coli RNase HI even at low temperatures. The specific activity determined at 10 degrees C was 0.29 units/mg for SIB1 RNase HI and 1.3 units/mg for E.coli RNase HI. Site-directed mutagenesis studies suggest that the amino acid substitution in the middle of the alphaI-helix (Pro52 for SIB1 RNase HI and Ala52 for E.coli RNase HI) partly accounts for the difference in the stability and activity between SIB1 and E.coli RNases HI.

Upper respiratory infection in acute pediatric care in internal conflict, Kosovo, 1999

Only a few reports focus on health issues among pediatric populations in internal conflicts including care for internally displaced persons (IDPs). This report examined the risk factors for pediatric upper respiratory infection (URI) during the internal conflict in Kosovo that presented at an acute care clinic before the aerial bombardment campaign by the North Atlantic Treaty Organization (NATO) in March 1999. The pediatric clinic was organized and managed by Kinderberg, one of the German humanitarian non-governmental organizations (NGOs) in the town of Vucitrn, 20 km north of the capital of Kosovo in mid-February 1999 at the height of internal conflicts and massive population migration in the area. This report discusses the results of a risk factor analysis for URI including overcrowding, malnutrition, and presence of smokers. A comparison of anthropometric measurements among IDPs and non-IDPs in our clinic populations was conducted to evaluate the state of nutrition in these two groups. There were no significant differences among IDPs and non-IDPs in anthropometric measurements. Smoking and having less than three meals per day were statistically associated with the increased risk of URI. Even during emergency medical interventions, prevention programs, such as smoking cessation and food security, may decrease URI in this pediatric population.

Ca(2+)-induced folding of a family I.3 lipase with repetitive Ca(2+) binding motifs at the C-terminus

In order to understand a role of the Ca(2+) ion on the structure and function of a Ca(2+)-dependent family I.3 lipase from Pseudomonas sp. MIS38, apo-PML, holo-PML, holo-PML*, and the N-terminal domain alone (N-fragment) were prepared and biochemically characterized. Apo-PML and holo-PML represent refolded proteins in the absence and presence of the Ca(2+) ion, respectively. Holo-PML* represents a holo-PML dialyzed against 20 mM Tris-HCl (pH 7.5). The results suggest that the C-terminal domain of PML is almost fully unfolded in the apo-form and its folding is induced by Ca(2+) binding. The folding of this C-terminal domain may be required to make a conformation of the N-terminal catalytic domain functional.

Repair of double-chambered right ventricle: surgical results and long-term follow-up

BACKGROUND

We reviewed the outcomes of double-chambered right ventricle repair.

METHODS

Between 1969 and 1998, 40 patients underwent surgical repair of a double-chamber right ventricle. The patients ranged in age from 3 months to 52 years (mean, 12.8 +/- 11.6 years). Right ventricular outflow tract pressure gradients were from 20 to 170 mm Hg (mean, 65.0 +/- 38.5 mm Hg) An associated ventricular septal defect was present in 27 patients (67.5%). Four patients were older than 30 years of age.

RESULTS

There were no hospital or late deaths. Mean postsurgical follow-up was 16.5 +/- 8.9 years (range, 2.5 to 31 years). No patient required further surgery to relieve obstruction of right ventricular outflow tract.

CONCLUSIONS

Surgical repair of a double-chambered right ventricle yields excellent hemodynamic and functional results over both the short and long term.

Origin of scaling structure and non-Gaussian velocity distribution in a self-gravitating ring model

Fractal structures and non-Gaussian velocity distributions are characteristic properties commonly observed in virialized self-gravitating systems, such as galaxies and interstellar molecular clouds. We study the origin of these properties using a one-dimensional ring model that we propose in this paper. In this simple model, N particles are moving, on a circular ring fixed in three-dimensional space, with mutual interaction of gravity. This model is suitable for the accurate symplectic integration method by which we argue the phase transition in this system. Especially, in between the extended phase and the collapsed phase, we find an interesting phase (halo phase) that has negative specific heat at the intermediate energy scale. Moreover, in this phase, there appear scaling properties and nonthermal and non-Gaussian velocity distributions. In contrast, these peculiar properties are never observed in other gas and core phases. Particles in each phase have a typical time scale of motions determined by the cutoff length xi, the ring radius R, and the total energy E. Thus all relaxation patterns of the system are determined by these three time scales.

Active subtilisin-like protease from a hyperthermophilic archaeon in a form with a putative prosequence

The gene encoding subtilisin-like protease T. kodakaraensis subtilisin was cloned from a hyperthermophilic archaeon Thermococcus kodakaraensis KOD1. T. kodakaraensis subtilisin is a member of the subtilisin family and composed of 422 amino acid residues with a molecular weight of 43,783. It consists of a putative presequence, prosequence, and catalytic domain. Like bacterial subtilisins, T. kodakaraensis subtilisin was overproduced in Escherichia coli in a form with a putative prosequence in inclusion bodies, solubilized in the presence of 8 M urea, and refolded and converted to an active molecule. However, unlike bacterial subtilisins, in which the prosequence was removed from the catalytic domain by autoprocessing upon refolding, T. kodakaraensis subtilisin was refolded in a form with a putative prosequence. This refolded protein of recombinant T. kodakaraensis subtilisin which is composed of 398 amino acid residues (Gly(-82) to Gly(316)), was purified to give a single band on a sodium dodecyl sulfate (SDS)-polyacrylamide gel and characterized for biochemical and enzymatic properties. The good agreement of the molecular weights estimated by SDS-polyacrylamide gel electrophoresis (44,000) and gel filtration (40,000) suggests that T. kodakaraensis subtilisin exists in a monomeric form. T. kodakaraensis subtilisin hydrolyzed the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide only in the presence of the Ca(2+) ion with an optimal pH and temperature of pH 9.5 and 80 degrees C. Like bacterial subtilisins, it showed a broad substrate specificity, with a preference for aromatic or large nonpolar P1 substrate residues. However, it was much more stable than bacterial subtilisins against heat inactivation and lost activity with half-lives of >60 min at 80 degrees C, 20 min at 90 degrees C, and 7 min at 100 degrees C.

Management of pregnancy with congenital antithrombin III deficiency: two case reports and a review of the literature

Women with antithrombin (AT) III deficiency are prone to pregnancy-associated venous thromboembolism. We report 2 cases with genetically confirmed ATIII deficiency, one with a mutation in exon 3A and the other with an exon 4 deletion, in whom the pregnancies were successfully managed with prophylactic therapies for thrombosis. A 35-year-old pregnant woman was treated with intravenous infusions of ATIII concentrate alone, and the other 22-year-old pregnant woman was mainly treated with subcutaneous injections of heparin and oral low-dose aspirin therapy. Both pregnancies resulted in vaginal deliveries of healthy neonates. The literature concerning prophylactic therapies for thrombosis in ATIII deficiency-complicated pregnancy is reviewed, and the clinical problems, including the adverse effects of the therapies, are discussed.

High NK cell activity in early pregnancy correlates with subsequent abortion with normal chromosomes in women with recurrent abortion

PROBLEM

The aim of this study was to assess the role of natural killer (NK) cells in pregnant women with a history of recurrent spontaneous abortion (RSA).

METHOD OF STUDY

Consecutive 66 pregnant women with a history of RSA were prospectively assessed for peripheral NK cell activity, percentage of the NK cell subsets, and subsequent pregnancy outcome.

RESULTS

NK cell activity in women with subsequent live birth (group I) at 4-5 gestational weeks (GW) (mean +/- SD, 32.5 +/- 12.31%) significantly decreased at 6-7 GW (28.1 +/- 12.1%) and at 8 9 GW (28.0 +/- 11.8%). NK cell activity in women with subsequent abortion with normal chromosomes (group II) at 6 7 GW (41.2 +/- 19.0%) was significantly higher than that in group I women, while NK cell activity at 6-7 GW in women with subsequent abortion with abnormal chromosomes (group III) was the same as the level in group I women.

CONCLUSIONS

High NK cell activity at 6-7 GW correlates with subsequent abortion with normal chromosomes.

A tentorial dural arteriovenous fistula successfully treated with interruption of leptomeningeal venous drainage using microvascular Doppler sonography: case report

BACKGROUND

Complete interruption of a dural arteriovenous fistula (DAVF) has been confirmed intraoperatively by visual inspection and intraoperative angiography. To confirm complete interruption of the shunt flow during the surgical treatment of a tentorial DAVF, we used intraoperative microvascular doppler monitoring.

CASE DESCRIPTION

A 71-year-old man suffered from severe subarachnoid hemorrhage. Angiography showed a tentorial DAVF with pure leptomeningeal drainage associated with a venous pouch. After the patient's neurologic condition had improved, he underwent interruption of the draining vein via a right suboccipital approach. An arterialized drainage vein was easily identified by applying the microvascular doppler probe to the shunting vessels and was completely obliterated by clipping. There were no complications associated with use of the microvascular doppler. The postoperative course was uneventful and follow-up angiography showed complete obliteration of the DAVF.

CONCLUSION

Intraoperative microvascular doppler monitoring is a useful technique not only for evaluating arterialized leptomeningeal drainage veins but also for confirming the complete obliteration of these vessels.

[Long-term results of Rygg's monocusp ventricular outflow patch for the reconstruction of right ventricular outflow tract in tetralogy of Fallot]

Thirty surviving patients after corrective surgery for tetralogy of Fallot with right ventricular outflow tract reconstruction (RVOTR) using monocusp ventricular outflow patch (MVOP) were reviewed retrospectively to determine the long-term results. The age at operation ranged from 2 to 55 years with a mean of 19 years, and follow-up extended to 18.2 years (cumulative: 345.4 patient-year). There were 4 late deaths (1.2% per patient-year), and the cumulative survival rate was 85.3% at 18 years after the corrective surgery. Eight patients (2.3% per patient-year) required intracardiac reoperations mostly resulted from problems after RVOTR with MVOP, such as recurrent stenosis of right ventricular outflow tract (3 cases) or pulmonary valvular incompetence (4 cases). In addition, one patient underwent balloon angioplasty for the recurrent stenosis located in the distal end of MVOP. Freedom from surgical or catheter reintervention for the MVOP-related complication was 60.6% at 18 years after the corrective surgery. MVOP caused compression of the pulmonary artery at the distal end of the anastomosis and reoperation in a younger patients quite early after the corrective surgery. Like other transannular patches, tissue failure and degeneration of MVOP were inevitable, and resulted in severe pulmonary valvular incompetence that required the valve replacement in 4 patients (1.3% per patient-year). Freedom from pulmonary valve replacement was 71.2% at 18 years after the corrective surgery. As long-term results, our experiences emphasize the need for an innovative transannular patch that possesses significantly better long-term durability.

Prolonged inhibition of obliterative airway disease in murine tracheal allografts by brief treatment with anti-leukocyte function-associated antigen-1 (CD11a) monoclonal antibody

BACKGROUND

We have previously shown that anti-leukocyte function-associated antigen (LFA)-1 (CD11a) monoclonal antibody (mAb) prevents acute rejection and produces donor-specific unresponsiveness in murine recipients of heterotopic heart allografts. Here, we investigate the ability of this mAb to prevent the development of obliterative airway disease (OAD) in murine recipients of tracheal allografts.

METHODS AND RESULTS

BALB/c tracheae were heterotopically transplanted into C3H mice. OAD developed by day 28 after transplantation and was characterized histologically by a loss of epithelial cell coverage and luminal obliteration of the tracheal allograft with a proliferation of fibrogenic mesenchymal cells, which is a lesion comparable to obliterative bronchiolitis in human lung transplant recipients. Monotherapy with anti-LFA-1 mAb preserved graft epithelium, prevented the development of OAD, and maintained unresponsiveness to donor antigen for more than 42 days after the final mAb administration.

CONCLUSION

These findings suggest the potential for anti-LFA-1 mAb therapy to suppress both acute and chronic rejection in clinical lung transplantation.

Isolation and characterization of psychotrophic bacteria from oil-reservoir water and oil sands

Four psychrotrophic strains, which grew at 4 degrees C but not at 37 degrees C, were isolated from Japanese oil-reservoir water (strains SIB1, SIC1, SIS1) and Canadian oil sands (strain CAB1). Strains SIB1, SIS1, and CAB1 had a maximum growth rate at 20 degrees C and grew to the highest cell densities at the cultivation temperature of 0-4 degrees C. Strain SIS1 was capable of growing even at -5 degrees C. The growth profile of strain SIC1 was rather similar to that of a mesophilic bacterium. Strains SIB1, SIC1, and SIS1 were identified as members of the genus Shewanella, and strain CAB1 was a member of the genus Arthrobacter. All these strains exhibited weak degradation ability against catechol, a hydroxylated aromatic hydrocarbon, and tributyrin. These strains are expected to be of potential use in the in situ bioremediation technology of hazardous hydrocarbons and esters under low-temperature conditions.

Interaction of TIP26 from a hyperthermophilic archaeon with TFB/TBP/DNA ternary complex

Interactions of TBP-interacting protein (TIP26), TBP, and TFB from a hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 with TATA-DNA were examined by electrophoretic mobility shift assay. Tk-TFB formed a ternary complex with Tk-TBP and TATA-DNA. Tk-TIP26 did not inhibit the formation of this ternary complex, but interacted with it to form a TIP26/TFB/TBP/DNA quaternary complex. This interaction is rather weak, and a large excess of Tk-TIP26 over Tk-TBP is required to fully convert the TFB/TBP/DNA ternary complex to the quaternary complex. However, determination of the concentration of Tk-TIP26 and Tk-TBP in KOD1 cells by Western blotting analysis indicated that the concentration of Tk-TIP26 is approximately ten times that of Tk-TBP, suggesting that the quaternary complex might also form in vivo.

Strong nucleic acid binding to the Escherichia coli RNase HI mutant with two arginine residues at the active site

The biochemical properties of the mutant protein D10R/E48R of Escherichia coli RNase HI, in which Asp(10) and Glu(48) are both replaced by Arg, were characterized. This mutant protein has been reported to have metal-independent RNase H activity at acidic pH [Casareno et al. (1995) J. Am. Chem. Soc. 117, 11011-11012]. The far- and near-UV CD spectra of this mutant protein were similar to those of the wild-type protein, suggesting that the protein conformation is not markedly changed by these mutations. Nevertheless, we found that this mutant protein did not show any RNase H activity in vitro. Instead, it showed high-nucleic-acid-binding affinity. Protein footprinting analyses suggest that DNA/RNA hybrid binds to or around the presumed substrate-binding site of the protein. In addition, this mutant protein did not complement the temperature-sensitive growth phenotype of the rnhA mutant strain, E. coli MIC3001, even at pH 6.0, suggesting that it does not show RNase H activity in vivo as well. These results are consistent with a current model for the catalytic mechanism of the enzyme, in which Glu(48) is not responsible for Mg(2+) binding but is involved in the catalytic function.

Diagnostic potential of short echo time MR spectroscopy of gliomas with single-voxel and point-resolved spatially localised proton spectroscopy of brain

Accurate neuroimaging grading of gliomas is useful for management, but techniques such as MRI and CT are not sufficiently reliable. Necrosis is a consistent, decisive prognostic factor and the key diagnostic criterion for glioblastoma multiforme. MR spectroscopy (MRS) allows noninvasive measurement of metabolites in brain tumours and mobile lipids reflect necrosis. However, short echo-time (TE) spectroscopy has been required for reliable assessment of lipids, since their relaxation times are very short. Recent advances have made it possible to perform short-TE MRS. We attempted to evaluate the significance of short TE spectroscopy as part of routine imaging for diagnosis and grading of gliomas. We performed TE 30 ms MRS in 25 patients with gliomas (grade II six; grade III three; grade IV, 16) and in 19 areas of healthy white matter using proton brain examination/single voxel (PROBE/SV) and point-resolved spatially localised spectroscopy (PRESS). With short-TE spectroscopy, lipid signals were detected in all 16 tumours of grade IV, one grade II (P = 0.0002) and none of grade III (P = 0.001). TE 136 ms MRS, carried out in 20 of these cases, showed lipid signals in only four of 14 grade IV tumours and in none of the other six. N-acetylaspartate/choline (NAA/Cho) ratios were always more than 1.0 in healthy tissues and less than 1.0 in all but one of the gliomas. The mean creatine (Cr)/Cho ratio in each tumour grade was significantly lower than in the healthy tissues. The mean Cr/Cho ratio was also significantly lower in grade IV than in grade II tumours (P < .0005). Considerable overlap in Cr/Cho ratio was observed between grade II and grades III and IV gliomas at long but less so at short-TE MRS. We conclude that short-TE MRS with PROBE/SV and PRESS is of value in grading gliomas.

Elevated plasma homocysteine levels and risk of silent brain infarction in elderly people

BACKGROUND AND PURPOSE

Silent brain infarction (SBI) on MRI is common in elderly people, and recent studies have demonstrated that SBI increases the risk of progression to clinically apparent stroke and cognitive decline. Therefore, an early and accurate detection of SBI and a search for potential treatable risk factors may have a significant impact on public health.

METHODS

Community-dwelling elderly people aged >/=66 years who participated in the present study (n=153) underwent brain MRI and standardized physical and neuropsychological examinations as well as blood biochemistry determinations, including total plasma homocysteine (pHcy), renal function, vitamin status, and polymorphisms of the methylenetetrahydrofolate reductase gene.

RESULTS

SBI was found in 24.8% of the participants. In the univariate analysis, the pHcy levels in subjects with SBI (13.6+/-4.1 micromol/L) were significantly higher (P=0.0004) than those in subjects without SBI (11.0+/-3.3 micromol/L). When pHcy levels were stratified into high (>/=15.1 mmol/L), moderate (11.6 to 15.0 mmol/L), and low (</=11.5 mmol/L) groups, age (P<0.0001), male sex (P<0.0001), the habits of cigarette smoking (P<0.0001) and of alcohol consumption (P=0.0002), and folate levels (P=0.01) were significantly associated with an elevation of pHcy levels. The elevated pHcy levels were significantly associated with SBI after individual adjustment for age, sex, hypertension, renal function, and the habits of smoking and alcohol consumption.

CONCLUSIONS

pHcy level is associated with age and nutritional and other lifestyle factors, and it contributes to a risk for SBI.