Search Results - (Author, Cooperation:H. K. Ng)

2014-06-05

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Adult ; Brain Neoplasms/*genetics/pathology ; Child ; Female ; Germ-Line Mutation/*genetics ; Humans ; Japan ; Male ; Mutation/*genetics ; Neoplasms, Germ Cell and Embryonal/*genetics/pathology ; Oncogene Protein v-akt/genetics ; Proto-Oncogene Proteins c-kit/genetics ; Reproducibility of Results ; Signal Transduction/genetics ; TOR Serine-Threonine Kinases/genetics ; Young Adult ; ras Proteins/genetics

1433-0350

Intraventricular neoplasm ; Central neurocytoma ; Oligodendroglioma

Springer Online Journal Archives 1860-2000

Medicine

Abstract Two patients with intraventricular tumours are presented. Both had similar features on light microscopic examination. On the basis of the specific immunohistochemical staining patterns and the ultrastructural findings, one was diagnosed as a central neurocytoma while the other was diagnosed as an intraventricular oligodendroglioma. The possibility of central neurocytoma should be considered in all young patients including children presenting with an intraventricular lesion. Definitive diagnosis requires electron microscopic and immunohistochemical studies.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Magneto-optical experiments have been performed on free and bound electrons in GaN films and GaN/AlGaN heterojunctions. Cyclotron resonance of two dimensional electron gas in GaN/ AlxGa1−xN heterojunctions has yielded m* = 0.23 m0, x-dependent scattering times consistent with values from transport measurements, and an apparent unexplained level crossing at 70 cm−1. Infrared absorption of doped GaN films has shown that the binding energy of Si donors, 29.0 meV, is much smaller than that of residual donors, in agreement with transport measurements, thus suggesting donor spectroscopy as a useful technique for defect/impurity qualitative analysis. Zeeman effect of the donor spectra has been used to determine the GaN low frequency dielectric constant, ε0 = 10.4. © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report on the frequency dependent conductivity of the modified Huesler alloy UNiSn in the antiferromagnetic state and in the presence of a magnetic field. UNiSn is paramagnetic above 43 K and has a semiconducting gap of about 65 meV. Below 43 K, the compound is in an itinerant antiferromagnetic state. The reflectance of UNiSn is measured from 4 meV to 0.4 eV and in fields up to 16 Tesla. At 5 K, there is a shift in spectral weight from the gap region to lower frequencies as the applied magnetic field is increased. This shift in spectral weight gives rise to increase conductivity with applied field in the metallic state. However, the gap value is unaffected by the field. No field dependence is observed for the isostructural compound, ThNiSn, which does not undergo an antiferromagnetic transition. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The fabrication by molecular-beam epitaxy of modulation-doped magnetic semiconductor heterostructures results in the creation of novel "magnetic" two-dimensional electron gases (2DEGs) with unusual transport properties. We report on the measurements of cyclotron resonance (CR) and effective mass in magnetic 2DEGs formed in modulation-doped ZnSe/Zn1−x−yCdxMnySe single quantum wells. Far-infrared absorption measurements are carried out at a nominal temperature of 4.2 K and in fields up to 30 T on these magnetic samples, as well as on corresponding nonmagnetic samples (ZnSe/Zn1−xCdxSe single quantum wells). The samples have carrier densities ranging from 1 to 4×1011 cm−2 and mobilities as high as 42 000 cm2/V s for the nonmagnetic samples. For the magnetic samples, the magnetic field dependence of the CR frequency shows marked oscillatory deviations from linearity in the vicinity of integer filling factors ν=2 and ν=1. For instance, compared to the nonmagnetic samples, the amplitude of the oscillations in the effective mass of the magnetic samples changes by 15% at half-filling factor. This is significantly larger than similar oscillatory effective mass behavior observed in standard semiconductor 2DEGS (e.g., GaAs/GaAlAs), suggesting a qualitatively different physical origin for this phenomenon in these magnetic systems. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report low-temperature (4.2 K) cyclotron resonance measurements on high-mobility, two-dimensional electron gases in modulation-doped ZnSe/Zn1−xCdxSe (x=0.06, 0.12, and 0.24) single quantum wells, as well as in a modulation-doped ZnTe/CdSe single quantum well. These experiments carried out in magnetic fields ranging up to 17 T yield reliable measurements of the effective mass m* of conduction-band electrons in Zn1−xCdxSe alloys, including the measurement of m* in cubic CdSe. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report a new technique of preparing unsupported thin films of YBa2Cu3Ox. These films are about 6×6 mm2 and less than half a micron thick. They were prepared via laser ablation on thin carbon films typically of order 50 μg/cm2 (∼2500 A(ring)). When the film was annealed, the carbon oxidized leaving behind a free-standing film. The film has a superconducting orthorhombic phase and an onset temperature of (approximately-equal-to)85 K.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Antisera to α1-antichymotrypsin, α1-antitrypsin and lysozyme were reacted with 20 cases of glioblastoma multiforme, seven anaplastic astrocytomas, eight astrocytomas, six oligodendrogliomas, four ependymomas and the cerebral cortex from six normal autopsy brains. In addition, two pleomorphic xantho-astrocytomas and two heavily lipidized malignant gliomas were similarly examined. All astrocytic lesions were confirmed with anti-GFAP antisera. Thirty astrocytic tumours (77%), four oligodendrogliomas (67%) and three ependymomas (75%) reacted positively with anti-α1-antichymotrypsin; 25 astrocytic tumours (64%), three oligodendrogliomas (50%) and three ependymomas (75%) showed positive staining for α1-antitrypsin. The pattern of staining with either of these two markers did not correlate with tumour grading. None of the gliomas examined stained positively with anti-lysozyme. Non-neoplastic glial elements did not react with any of the three antisera. The results of this study suggest that staining for α1-antichymotrypsin and α1-antitrypsin is of little value in the differential diagnosis of neuroepithelial or mesenchymal lesions in the brain.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Two cases of olfactory neuroblastoma which presented clinically as intracranial lesions are described. Prominent features of epithelial differentiation were present, which led to initial diagnoses of poorly differentiated carcinoma. The true nature of the lesions was only established subsequently by careful histological examination, immunohistochemistry and electron microscopy. The potential towards epithelial differentiation in such tumours was emphasized and certain new histological features were described, including a biphasic epithelial and stromal pattern, papillae formation and positive staining for cytokeratin. These two cases underline the importance of exhaustive examination of poorly differentiated epithelial-like lesions of the frontal lobes by conventional histology, immunohistochemistry and electron microscopy.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Nine cases of microcystic meningiomas, a distinct morphological variant of meningiomas, are reported. They are characterized by a vacuolated and myxomatous histological appearance with multiple cystic spaces lined by stellate-shaped tumour cells. Immunohistochemically, they shared a similar pattern of positive staining for epithelial membrane antigen and vimentin with other meningiomas. Their unusual histological features might lead to problems in differential diagnosis from other intracranial tumours, including schwannomas, chordomas, astrocytomas and angioblastic meningiomas.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Monoclonal antibodies (AE1/3, CAM 5.2 and PKK-1) and polyclonal antisera against the cytokeratin proteins were reacted with a range of astrocytic tumours, oligodendrogliomas and ependymomas. Seven of 12 cases (58%) of glioblastoma multiforme, five of eight (63%) anaplastic astrocytomas and two of five (40%) well-differentiated astrocytomas were immunoreactive with AE1/3 but not with the other anti-cytokeratin antibodies. In oligodendrogliomas, AEl/3 stained isolated astrocyte-like cells as well as scattered neoplastic oligodendrocytes in four of eight cases (50%) cases. Four ependymomas were negative for all cytokeratin markers examined. The immunostaining of astrocytomas and oligodendrogliomas with AE1/3 might represent co-expression of cytokeratin with glial fibrillary acidic protein by gliomas and calls for caution in the use of these antibodies in the differential diagnosis between gliomas and carcinomas.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

This report describes two cases of alveolar rhabdomyosarcoma of the nasal cavity with unusual histological appearances mimicking clear cell carcinoma. The closely packed tumour cells were polygonal and arranged in sheets and packets. They had an appreciable amount of clear cytoplasm due to accumulation of glycogen. The diagnosis of rhabdomyosarcoma was confirmed by positive staining for desmin and myoglobin. Rhabdomyosarcoma should be included in the differential diagnosis of nasal clear cell tumours, particularly in young adults. A correct diagnosis is important, because chemotherapy is indicated even for apparently localized disease.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A case of undifferentiated carcinoma of the salivary gland occurring in the parotid gland of a southern Chinese was reported. Tumour cells showed immunofluorescence for Epstein-Barr virus (EBV)-associated nuclear antigen, and DNA hybridization demonstrated the presence of EBV-DNA in tumour tissue. The findings in this case, together with previous reports, suggest a causal relationship between EBV and salivary gland carcinoma. The relationships between EBV and undifferentiated epithelial tumours of the salivary glands, nasopharynx and thymus are also discussed.

Electronic Resource

1365-2222

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Sixty-six Chinese patients with rhinitis, with or without asthma, were randomly allocated to a course of injections either with D. pteronyssinus extract or placebo. The course consisted of 18–22 weekly injections, followed by monthly maintenance injections with the highest concentration for 1 year.Progress was evaluated by a patient's daily diary and monthly assessments by the physician, by comparisons of skin and nasal challenge tests and by the specific serum IgE concentration, before treatment, at the end of the weekly course, and once during the maintenance course.No improvement was detected at the end of the weekly course, but during maintenance there was a consistent benefit to the patients receiving the D. pteronyssinus extract both in the diary and the physician's assessment, especially the former. There was no consistent change in the skin or nasal challenge tests and there was a trivial fall in the serum IgE levels in the patients on the extract. Adverse reactions were much more common in the patients on the extract, but most were trivial.The different methods of assessment used and the role of hyposensitization with D. pteronyssinus are discussed.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

AimsCentral neurocytoma is a rare central nervous system tumour typically found in the lateral ventricles and at the septum pellucidum. Histologically, it resembles oligodendrogliomas and yet ultrastructurally, it shows neuronal differentiation. Its molecular oncogenesis is not known. The aim of this study was to examine whether major genetic events found in oligodendrogliomas and neuronal tumours, namely allelic deletions of chromosomes 1p and 19q and N-myc amplification, can be found in central neurocytomas. As there was one report describing gain of chromosome 7 in central neurocytomas, we also examined epidermal growth factor receptor (EGFR) amplification, as the EGFR gene is located at chromosome 7p.Methods and resultsNine central neurocytomas and matched blood samples were examined for loss of heterozygosity (LOH) of 1p and 19q13.2–13.4 with 23 finely mapped microsatellite markers. N-myc amplification was studied by fluorescence in-situ hybridization using paraffin-embedded sections. EGFR amplification was tested for by differential PCR. Six of nine (67%) tumours showed LOH at one or more loci at 1p and 5/9 (56%) of cases showed LOH at 19q. However, common regions of deletion cannot be identified. The majority of informative markers are retained at 1p (84%) and 19q (86%). Only one tumour showed amplification of N-myc and none of the cases showed amplification of EGFR.ConclusionCentral neurocytomas are genetically distinct from oligodendrogliomas, and chromosomes 1p and 19q probably do not play an important role in their pathogenesis. N-myc and EGFR amplification are rare.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Aims: While it is well known that pilocytic astrocytomas are clinically distinct from diffuse astrocytomas, few comprehensive studies have focused on their genetic differences. The aim of this study was to examine pilocytic astrocytomas for genetic alterations that are commonly seen in diffuse astrocytomas.Methods and results:By using molecular genetic and immunohistochemical techniques, we evaluated p16, p53, CDK4 and PTEN genes in 29 pilocytic astrocytomas. Mutation screening of p53 and PTEN was performed by single strand conformation polymorphism analysis followed by direct sequencing. Loss of heterozygosity (LOH) of p53, p16 and 10q23–25 loci was performed with microsatellite markers and genomic microsatellite instability (MSI) was also screened. Protein expression of p16, p53, CDK4 and PTEN was examined by immunohistochemistry. Five tumours were found to have single genetic alterations, which included a p53 mutation, a PTEN mutation, MSI at a single microsatellite marker of the p16 locus, and one single LOH at each p16 and 10q23 loci. Protein expressions of p16, CDK4 and PTEN were detected in 73%, 61% and 38% of tumours, respectively. Significantly and in sharp contrast to diffuse astrocytomas, no pilocytic astrocytoma in our series stained for p53 protein.Conclusion:Pilocytic astrocytomas have neither MSI phenotype nor recurrent alterations of the p53 and p16 genes. However, altered expression of PTEN may be important in the genesis of pilocytic astrocytomas. We conclude that pilocytic astrocytomas are genetically distinct from diffuse astrocytomas. Lack of p53 mutation/immunostaining may serve as a diagnostic adjunct for differentiating pilocytic astrocytomas from diffuse astrocytomas in small neurosurgical biopsies.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Oligodendroglial tumours follow genetic pathways different from but overlapping with those of astrocytic tumours. The aim of this study was to examine whether major genetic events such as loss of chromosome 10 and p53 mutation found in astrocytic gliomas are also involved in the development and anaplastic transformation of non-astrocytic gliomas and to correlate the findings with histopathological subtypes of these tumours.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and resultsSixty-one formalin-fixed, paraffin-embedded oligodendroglial and ependymal tumours (16 oligodendrogliomas, 12 anaplastic oligodendrogliomas, seven oligoastrocytomas, 24 ependymomas and two anaplastic ependymomas) were examined for allelic deletions on chromosome 10q23 and 10q25–26 regions, mutations of PTEN/MMAC1 and p53, MDM2 gene amplification and apoptosis. The frequencies of allelic deletions at marker D10S2491 (which mapped within PTEN/MMAC1) and between markers D10S209 and D10S587 (where DMBT1 was located) were found to be 〈 30% in both types of non-astrocytic gliomas. High frequency of allelic deletions was detected at marker D10S215 (80%) at the proximal 10q23 region in both oligodendroglial and ependymal tumours and between markers D10S216 (42%) and D10S169 (67%) at distal 10q25–26 region in oligodendroglial tumours. No mutations of PTEN/MMAC1 were found. p53 mutations were detected in three oligoastrocytomas and one ependymoma; three out of five mutations were found in exon 4. MDM2 gene amplification was found in one ependymoma harbouring wild-type p53. The apoptotic index was lower in p53-mutated tumours than in tumours with wild-type p53.〈section xml:id="abs1-3"〉〈title type="main"〉ConclusionThe telomeric end of chromosome 10q could be involved in the development and anaplastic transformation of oligodendroglial tumours. Mutations of PTEN/MMAC1 and p53, amplification of the MDM2 gene and allelic loss on chromosome 10q do not play a major part in the pathogenesis or anaplastic transformation of oligodendrogliomas and ependymal tumours.

Electronic Resource

1437-9813

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource