A CRM1-mediated nuclear export signal governs cytoplasmic localization of BRCA2 and is essential for centrosomal localization of BRCA2

Germ-line mutations of the BRCA2 gene cause inherited susceptibility to breast and ovarian cancers. BRCA2 contains two nuclear localization signals, predominantly localizes in the nucleus and plays significant roles in DNA double-strand break repair. Recently, we reported that BRCA2 localizes to the centrosomes during the S and early M phases of the cell cycle. In this study, for the first time, we identified a functional nuclear export sequence (NES1; (1383)DLSDLTFLEVA(1393)) in BRCA2. The green fluorescent protein (GFP)-NES1 fusion protein was localized in the cytoplasm and could be blocked by the chromosomal region maintenance 1-specific export inhibitor leptomycin B. Mutation of a leucine residue in the NES1 motif to alanine (L1384A) resulted in both cytoplasmic and nuclear localization of the GFP-NES1 fusion protein and a nuclear accumulation of ectopic full-length BRCA2-FLAG. Moreover, treatment of cells with leptomycin B decreased centrosomal localization of BRCA2. Finally, by microinjection of an anti-BRCA2 antibody into the cytoplasm of HeLa S3 cells, we found that depletion of normal BRCA2 proteins in the cytoplasm leads to centrosome amplification and binucleated cells. Our results suggest that disruption of the NES function by genetic changes results in deregulation of BRCA2 export, which ultimately leads to centrosome disorder.

T1 signal intensity and height of the anterior pituitary in neonates: correlation with postnatal time

BACKGROUND AND PURPOSE

The anterior pituitary of a term neonate is usually hyperintense on T1-weighted MR images, which may represent histologic changes of the gland due to the effect of high estrogen levels during the fetal period; however, MR findings of a preterm neonate have not been fully evaluated. The purpose of this study was to investigate whether intensity and size of the neonatal anterior pituitary on MR images obtained near term of corrected age correlates with the gestational age at birth or postnatal time.

MATERIALS AND METHODS

Data of 88 consecutive neonates (gestational age, 24-41 weeks; mean, 31.5 weeks) were analyzed. All of the neonates underwent MR imaging at a corrected age of 0 months +/- 4 weeks. Relative signal intensity of the anterior pituitary compared with that of the pons on T1-weighted sagittal images was calculated. Height of the pituitary was also measured. Stepwise regression analysis was performed to evaluate the effects of gestational age at birth and postnatal time on the relative signal intensity and on the pituitary height.

RESULTS

The relative signal intensity significantly negatively correlated with postnatal time (P = .001) but not with gestational age at birth (P = .42). Pituitary height significantly negatively correlated with postnatal time (P = .049) but not with gestational age at birth (P = .071).

CONCLUSION

A significant negative correlation exists between postnatal time and signal intensity on T1-weighted MR images of the anterior pituitary obtained near term. A nonhyperintense anterior pituitary is a normal MR finding of preterm neonates when imaged near term.

Aberrant midsagittal fiber tracts in patients with hemimegalencephaly

BACKGROUND AND PURPOSE

In hemimegalencephaly, MR imaging often reveals midsagittal bandlike structures between the 2 lateral ventricles. To determine whether these structures are aberrant midsagittal fibers, we retrospectively reviewed them on conventional MR imaging and prospectively examined them by diffusion tensor MR and fiber tract (FT) reconstruction imaging.

MATERIALS AND METHODS

We retrospectively reviewed conventional MR images of 26 consecutive patients with hemimegalencephaly by 2 neuroradiologists, focusing on abnormal midsagittal structures. The distance between the 2 anterior horns and widths of midsagittal bandlike structures were measured. Prospective analysis was performed in 7 consecutive patients with hemimegalencephaly examined for midsagittal aberrant fibers by diffusion tensor imaging, and cortical distribution areas of the fibers were observed.

RESULTS

The distance between the 2 anterior horns was wide (>4 mm) due to white matter-intensity structures in 20 of 26 patients (76.9%). Mid-sagittal bandlike structures were observed in 15 patients (57.7%). Asymmetry of the fornices was detected in 7 patients (26.9%), and both fornices were thickened in 7 (26.9%) patients. On FT reconstruction, images showed that 4 of 7 patients with hemimegalencephaly had aberrant midsagittal fibers connecting frontal, occipital, or parietal lobes, bilaterally (n = 3) or ipsilaterally (n = 1). All 4 patients had increased width between the 2 anterior horns, and 3 of them exhibited midsagittal bandlike structures on conventional MR imaging. On the other hand, these MR imaging findings were not noted in 3 patients who did not have aberrant midsagittal fibers on diffusion tensor imaging.

CONCLUSIONS

Aberrant midsagittal FTs running intra- or interhemispherically do not infrequently exist in patients with hemimegalencephaly.

Diffusion tensor fiber tractography for arteriovenous malformations: quantitative analyses to evaluate the corticospinal tract and optic radiation

BACKGROUND AND PURPOSE

We hypothesized that diffusion tensor fiber tractography would be affected by intracranial arteriovenous malformation (AVM). The purpose of the present study was to evaluate the influence of intracranial AVM on corticospinal tract and optic radiation tractography.

MATERIALS AND METHODS

The subject group comprised 34 patients with untreated intracranial AVM. Hemorrhage was present in 13 patients and absent in 21 patients. Perinidal fractional anisotropy (FA) and number of voxels along the reconstructed corticospinal and optic radiation tracts were measured, and left-to-right asymmetry indices (AIs) for those values were quantified. Patients were assigned to 1 of 3 groups: tracts distant from nidus, tracts close to nidus without neurologic symptoms, and tracts close to nidus associated with neurologic symptoms. One-way analysis of variance was used to compare differences in AI between groups. Hemorrhagic and nonhemorrhagic groups were assessed separately.

RESULTS

In patients without hemorrhage, AI of optic radiation volume (P<.0001), AI of perinidal FA along corticospinal tract (P=.006), and optic radiation (P=.01) differed significantly between groups. In patients associated with hemorrhage, AI of corticospinal tract volume (P=.01), AI of perinidal FA along corticospinal tract (P=.04), and optic radiation (P=.004) differed significantly between groups.

CONCLUSIONS

Corticospinal tract and optic radiation tractography were visualized in patients with AVM. In patients with both hemorrhagic and nonhemorrhagic AVM, the 2 fiber tracts close to the nidus were less visualized in the affected hemisphere than those distant from the nidus. Tracts were less visualized in patients with neurologic symptoms than in asymptomatic patients.

Hemimegalencephaly: a study of abnormalities occurring outside the involved hemisphere

BACKGROUND AND PURPOSE

Hemimegalencephaly is a rare but well-known congenital malformation with ipsilateral enlargement of the hemicerebrum. However, very little is known about changes in structures outside the involved hemisphere in patients with this condition. We investigated morphologic abnormalities occurring outside the affected hemisphere by MR imaging in a large series of patients with hemimegalencephaly.

MATERIALS AND METHODS

MR imaging findings for 30 patients with hemimegalencephaly were retrospectively reviewed and evaluated for structures outside the involved hemisphere on routine MR images, such as cranial nerves (I, II, V), brain vessels, subdural and subarachnoid spaces, brain stem, and cerebellum, on both the ipsilateral and contralateral sides.

RESULTS

The ipsilateral olfactory and optic nerves were enlarged in 8 (26.7%) and 1 (3.3%) of the 30 patients, respectively, without enlargement on the contralateral side. No asymmetry was noted in the trigeminal nerves. Asymmetric vascular dilations in the ipsilateral cerebral hemisphere were observed in 12 of the 30 patients (40%), in deep cerebral vessels in 11 patients (36.7%), and in superficial cerebral vessels in 8 patients (26.7%). Ipsilateral brain stem and hemicerebellar asymmetric enlargement was detected in 2 patients (6.7%) and 14 patients (46.7%), respectively. Abnormal cerebellar folia were observed on the ipsilateral side in 6 patients (20%) and on the contralateral side in 3 patients (10%).

CONCLUSION

Ipsilateral olfactory nerve enlargement, cerebral vascular dilations, cerebellar enlargement, and bilateral or ipsilateral abnormal architecture of the cerebellar folia are often associated with hemimegalencephaly.

Frequent reduced expression of alpha-1B-adrenergic receptor caused by aberrant promoter methylation in gastric cancers

Recent studies have suggested that epigenetic inactivation of tumour-related genes by promoter methylation participates in the development of gastric cancer. We newly identified the frequently aberrant promoter methylation of alpha-1B-adrenergic receptor (ADRA1B) in colorectal cancer by methylation-sensitive representational difference analysis (MS-RDA) and examined the methylation status of the ADRA1B promoter in 34 paired samples of colorectal cancer and surrounding epithelial tissue, and 34 paired samples of gastric cancer and surrounding epithelial tissue. In colorectal cancers, only four of 34 (11.8%) tumours showed ADRA1B promoter methylation. In contrast, ADRA1B promoter methylation was detected in 24 of 34 (70.6%) gastric cancers and in 14 of 34 (41.2%) surrounding epithelial tissues. The frequency of ADRA1B promoter methylation was higher in gastric epithelial tissues with intestinal metaplasia (41.6%) than in those without intestinal metaplasia (25.0%). Reverse transcription–PCR detected reduced ADRA1B expression in 12 of 18 (66.7%) gastric cancers, and its promoter methylation was detected in 11 of these 12 (91.7%) gastric cancers with reduced ADRA1B expression. Thus, ADRA1B promoter is frequently methylated in gastric cancer. Our results suggest that the ADRA1B gene is an important tumour-related gene frequently involved in the development and progression of gastric cancer.

Subinsular vascular lesions: an analysis of 119 consecutive autopsied brains

The insula of Reil constitutes a functionally intriguing complex of the brain related to multifunctional activities. We examined the subinsular region in 119 consecutively autopsied patients, as T2 hyperintense lesions are frequently observed in magnetic resonance diagnosis of this region. The patients were admitted in neurology wards and were diagnosed as having cerebrovascular disease in 55 patients (46%), other neurological diseases in 57 patients (48%) and non-neurological diseases in seven patients (6%). Demyelination of the white matter was semi-quantified as a fiber density score (percent stained area/total area) with computer-assisted image analysis on Klüver-Barrera-stained sections. Astrogliosis was assessed by immunohistochemistry for glial fibrillary acidic protein. The lesion analysis showed a dilated perivascular space in 29 patients (24%), demyelination (fiber density score less than the mean - 1 SD) in 27 patients (23%), slit-shaped lesion in six patients (5%), lacunar infarction in one patient (1%) and cerebral hemorrhage in one patient (1%). A histologic-radiologic comparison in two patients with subcortical ischemic vascular dementia showed correspondence between subinsular hyperintensities, and demyelination, gliosis and a dilated perivascular space. These results indicate that subinsular lesions rarely signifies focal vascular lesions, and are consisted of demyelination, gliosis and a dilated perivascular space.

Diffusion tensor fiber tractography of the optic radiation: analysis with 6-, 12-, 40-, and 81-directional motion-probing gradients, a preliminary study

BACKGROUND AND PURPOSE

Knowing the exact location of the optic radiation preoperatively is important for surgery of the temporal lobe. We hypothesized that a greater number of motion-probing gradients (MPGs) would provide better results of diffusion tensor (DT) fiber tractography of the optic radiation. To test this hypothesis, this study evaluated differences in DT fiber tractography of the optic radiation under different MPG settings.

METHODS

DT images were obtained in 12 healthy volunteers (7 men, 5 women) with a mean age of 32 years (range, 22-45 years) by using a 3T MR imaging scanner with single-shot echo-planar imaging with parallel acquisition (reduction factor = 2). MPG was applied in 6, 12, 40, and 81 independent directions. The first region of interest (ROI) was placed in the occipital lobe, and the second ROI was placed in the lateral geniculate body. Fibers penetrating both ROIs were considered as the optic radiation. Anteroposterior distance between the tip of the Meyer loop and the lateral geniculate body on an axial section was defined as a loop index. Numbers of fibers and loop indices in both cerebral hemispheres were evaluated statistically.

RESULTS

The optic radiation was well visualized in full length by DT fiber tractography in 20 of 24 hemispheres (83%). No significant differences were noted in number of fibers and loop indices among different MPG settings.

CONCLUSION

DT fiber tractography can frequently depict almost the entire optic radiation. MPG number does not exert any significant effect on visualization of the optic radiation, and 6-directional MPG is thus sufficient for this purpose.

Frequent involvement of ras-signalling pathways in both polypoid-type and flat-type early-stage colorectal cancers

The development of colorectal neoplasms proceeds mainly via the adenoma-carcinoma sequence. BRAF and RASSF1A are members of Ras-signaling pathways, but the roles of their aberrations in colorectal carcinogenesis remain unclear. The authors studied mutations of the BRAF and K-ras genes, RASSF1A promoter methylation, and p53 overexpression in 43 polypoid-type and 30 flat-type early-stage colorectal cancers. No tumor simultaneously showed any combination of K-ras mutations, BRAF mutations, and RASSF1A promoter methylation. Three of the 73 tumors (4.1%) had BRAF mutations. All BRAF mutation-positive tumors were flat-type cancers, not associated with coexisting adenoma or p53 overexpression. RASSF1A promoter methylation was detected in 12 out of 73 tumors (16.4%), and the proportion of positive cases was similar in polypoid-type and flat-type cancers. BRAF mutations, K-ras mutations, and RASSF1A promoter methylation independently participate in early-stage colorectal carcinogenesis. BRAF mutations are involved only in flat-type cancers, whereas RASSF1A promoter methylation is involved in both polypoid-type and flat-type cancers. Thus, BRAF mutations most likely participate in de novo colorectal carcinogenesis, K-ras mutations in the adenoma-carcinoma sequence of colorectal carcinogenesis, and RASSF1A promoter methylation in both cascades.

Peroxisome proliferator-activated receptor gamma in human breast carcinoma: a modulator of estrogenic actions

It has been reported that agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) inhibit proliferation of breast carcinoma cells, but the biological significance of PPARgamma remains undetermined in human breast carcinomas. Therefore, we immunolocalized PPARgamma in 238 human breast carcinoma tissues. PPARgamma immunoreactivity was detected in 42% of carcinomas, and was significantly associated with the status of estrogen receptor (ER) alpha, ERbeta, progesterone receptor, retinoic X receptors, p21 or p27, and negatively correlated with histological grade or cyclooxygenase-2 status. PPARgamma immunoreactivity was significantly associated with an improved clinical outcome of breast carcinoma patients by univariate analysis, and multivariate analysis demonstrated that PPARgamma immunoreactivity was an independent prognostic factor for overall survival in ERalpha-positive patients. We then examined possible mechanisms of modulation by PPARgamma on estrogenic actions in MCF-7 breast carcinoma cells. A PPARgamma activator, 15-deoxy-Delta(12,14)- prostaglandin J(2) (15d-PGJ(2)), significantly inhibited estrogen-responsive element-dependent transactivation by estradiol in MCF-7 cells, which was blocked by addition of a PPARgamma antagonist GW9662. Subsequent study, employing a custom-made microarray focused on estrogen-responsive genes, revealed that mRNA expression was significantly regulated by estradiol in 49 genes, but this significance vanished on addition of 15d-PGJ(2) in 16 out of 49 (33%) genes. These findings were confirmed by real-time PCR in 11 genes. 15d-PGJ(2) significantly inhibited estrogen-mediated proliferation of MCF-7 cells, and caused accumulation of p21 and p27 protein. These results suggest that PPARgamma is mainly expressed in well-differentiated and ER-positive breast carcinomas, and modulates estrogenic actions.

Ictal monoparesis associated with lesions in the primary somatosensory area

Reported are three patients with ictal monoparesis of an arm. In the hemisphere contralateral to the monoparesis, ictal and interictal epileptiform discharges were observed in the centroparietal area, and a well-circumscribed lesion was commonly present in the primary arm somatosensory area (SI). In the presence of an SI lesion, the epileptic activity at the sensorimotor area could lead to selective or predominant activation of the inhibitory motor system.

A brainstem variant of reversible posterior leukoencephalopathy syndrome

Reversible posterior leukoencephalopathy syndrome (RPLS) is caused by various heterogeneous factors, the commonest being hypertension, followed by nonhypertensive causes such as eclampsia, renal diseases and immunosuppressive therapy. Patients with RPLS exhibit bilateral white and gray matter abnormalities in the posterior aspects of the cerebral hemispheres. However, this syndrome may affect the brainstem predominantly, and these cases are designated as hypertensive brainstem encephalopathy. We present here two patients with reversible brainstem encephalopathy: one with hypertension and the other without hypertension. These patients presented with swelling and diffuse hyperintensities of the brainstem in fluid-attenuated inversion-recovery (FLAIR) and T2-weighted MRI, but with relatively mild clinical symptoms. They recovered without major neurological deficits, but had residual lacunar lesions in the pons. Reversible brainstem encephalopathy with characteristic MRI features was found in both hypertensive and nonhypertensive patients. These patients were diagnosed with a brainstem variant of RPLS, which is potentially fully reversible after an adequate treatment, and therefore should be carefully differentiated from other brainstem disease conditions.

Comparison of computer-assisted instruction (CAI) versus traditional textbook methods for training in abdominal examination (Japanese experience)

PURPOSE

This study aimed to compare the effects of computer-assisted, text-based and computer-and-text learning conditions on the performances of 3 groups of medical students in the pre-clinical years of their programme, taking into account their academic achievement to date. A fourth group of students served as a control (no-study) group.

METHOD

Participants were recruited from the pre-clinical years of the training programmes in 2 medical schools in Japan, Jichi Medical School near Tokyo and Kochi Medical School near Osaka. Participants were randomly assigned to 4 learning conditions and tested before and after the study on their knowledge of and skill in performing an abdominal examination, in a multiple-choice test and an objective structured clinical examination (OSCE), respectively. Information about performance in the programme was collected from school records and students were classified as average, good or excellent. Student and faculty evaluations of their experience in the study were explored by means of a short evaluation survey.

RESULTS

Compared to the control group, all 3 study groups exhibited significant gains in performance on knowledge and performance measures. For the knowledge measure, the gains of the computer-assisted and computer-assisted plus text-based learning groups were significantly greater than the gains of the text-based learning group. The performances of the 3 groups did not differ on the OSCE measure. Analyses of gains by performance level revealed that high achieving students' learning was independent of study method. Lower achieving students performed better after using computer-based learning methods.

CONCLUSION

The results suggest that computer-assisted learning methods will be of greater help to students who do not find the traditional methods effective. Explorations of the factors behind this are a matter for future research.

Genotyping of single nucleotide polymorphism using model-based clustering

MOTIVATION

Single nucleotide polymorphisms have been investigated as biological markers and the representative high-throughput genotyping method is a combination of the Invader assay and a statistical clustering method. A typical statistical clustering method is the k-means method, but it often fails because of the lack of flexibility. An alternative fast and reliable method is therefore desirable.

RESULTS

This paper proposes a model-based clustering method using a normal mixture model and a well-conceived penalized likelihood. The proposed method can judge unclear genotypings to be re-examined and also work well even when the number of clusters is unknown. Some results are illustrated and then satisfactory genotypings are shown. Even when the conventional maximum likelihood method and the typical k-means clustering method failed, the proposed method succeeded.

The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes (JSGIT): initial aims and impact of the family history of type 1 diabetes mellitus in Japanese children

The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes (JSGIT) was established in July 1994 with the chief aim to improve the quality of therapy for type 1 diabetes in children, an entity far less common in Japan than in Europe. We proposed four initial research topics: (i) to determine the current status of medical care and glycemic control in Japanese children with type 1 diabetes mellitus; (ii) to standardize the measurement of hemoglobin A1c; (iii) to establish a registry of a large cohort of patients in order to enable prospective studies to improve the quality of therapy for children with type 1 diabetes in Japan; and (iv) to enable participants of the JSGIT to hold a workshop twice annually. We registered a total of 736 patients from 45 hospitals throughout Japan. Intervention via insulin treatment was instituted after 2 yr for those patients whose hemoglobin A1c level was more than 8.1%. The proportion of patients receiving multiple insulin injections increased after intervention; however, average hemoglobin A1c in females remained significantly higher than in males. We identified two forms of diabetes in Japanese children: a rapidly progressive form and a more slowly progressive form. There was a significantly higher prevalence of a family history of diabetes in first-degree relatives in the slowly progressive form. These preliminary findings are the result of the first collaborative study of childhood diabetes in Japan.

New thiocholine ester substrates for the assay of human serum cholinesterase

BACKGROUND

Several thiocholine alkanoyl esters were newly synthesized and explored as substrates for the assay of human serum cholinesterase after being subjected to the Ellman reaction (Arch Biochem Biophys 1958;74:443-50 and Arch Biochem Biophys 1959;82:70-7).

METHODS

We synthesized thiocholine ester iodides by the method of Renshow et al. (J Am Chem Soc 1938;60:1765-70). We examined solubility in H(2)O, substrate specificity serum for cholinesterase, (spontaneous) self-hydrolysis, storage stability, and reaction conditions for measurement of the activity of the enzyme.

RESULTS

Isobutyryl and cyclohexane-carboxyl esters showed the best efficiency for the specific and stable assay of human serum cholinesterase. Aqueous solubility of each was >10 mmol/L, and the reactivity with acetylcholinesterase was negligible. For isobutyryl and cyclohexane-carboxyl esters, respectively, spontaneous hydrolysis in the aqueous phase was approximately 1/25 and approximately 1/175 slower than the enzymatic hydrolysis, and assays with these substrates were linear to 1800 and 3000 U/L, respectively. The K(m) values of these acylthiocholines with human cholinesterase were almost equivalent (6.9 x 10(-3) mmol/L). The substrates were stable in aqueous solution and in the solid state as the iodides for at least 5 years at 5 degrees C.

CONCLUSIONS

The isobutyrate and cyclohexane-carboxylate of thiocholine are suitable for the specific assay of human serum cholinesterase.