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Biomedical subjects

W H Yong

Publications and source records attributed to W H Yong.

12 recordsLinked to original sources
PubMed2003

June 2003: 33-year-old male with a frontal lobe mass.

The June 2003 COM. A 33-year-old male with a history of seizures was found to have an intra- and extra-axial frontal lobe mass. The histology of the resected tumor showed a meningioma with underlying meningioangiomatosis. Meningioangiomatosis (MA) is a benign intracortical plaque-like proliferation of meningothelial cells, microvasculature and fibroblast-like cells probably of hamartomatous origin. Very rarely, MA is associated with an overlying meningioma as in this case. When MA is accompanied by a meningioma, it is generally not associated with clinical evidence of neurofibromatosis. It is important to distinguish MA from an invasive meningioma, because of its favorable prognosis after resection.

Adult↗
PubMed2002

A rare symptomatic presentation of ecchordosis physaliphora and unique endoscope-assisted surgical management.

We report on the presentation, diagnosis, and surgical management of a rare symptomatic case of ecchordosis physaliphora, including the use of endoscopy as a valuable imaging device in its operative management. A 49-year-old male presented with a intradural extra-axial mass located to the left of the basilar artery in the prepontine space. The tumor was exposed via a transmaxillary transclival approach and resected under binocular microscopic visualization. Prior to and following resection, endoscopes were introduced into the surgical field to conduct anatomic surveys of the region and to assess the completeness of tumor removal. Ecchordosis physaliphora is an uncommon benign lesion originating from embryonic notochordal remnants. It rarely causes clinical symptoms due to its slow growth patterns. Although similarities between EP of the spheno-occiput and chordomas of the clivus make distinction obscure, differentiation is important. Differences in these lesions impact upon patient prognosis as well as therapeutic strategies. The use of endoscopy in the resection of this mass marks an innovative approach to intraoperative imaging of the clival region; improved visualization of the prepontine area allows for more accurate defintion of the surgical anatomy of the tumor and for thorough assessment of the completeness of tumor removal.

Brain↗
PubMed2001

Overexpression of alpha4 chain-containing laminins in human glial tumors identified by gene microarray analysis.

Differential gene expression in tumors often involves growth factors and extracellular matrix/basement membrane components. Here, 11,000- gene microarray was used to identify gene expression profiles in brain tumors including high-grade gliomas [glioblastoma multiforme (GBM) and anaplastic astrocytoma], low-grade astrocytomas, or benign extra-axial brain tumors (meningioma) in comparison with normal brain tissue. Histologically normal tissues adjacent to GBMs were also studied. All GBMs studied overexpressed 14 known genes compared with normal human brain tissue. Overexpressed genes belonged to two broad groups: (a) growth factor-related genes; and (b) structural/extracellular matrix-related genes. For most of these 14 genes, expression levels were lower in low-grade astrocytoma than in GBM and were barely detectable in normal brain. Despite normal-appearing histology, gene expression patterns of tissues immediately adjacent to GBM were similar to those of their respective primary GBMs. Two genes were consistently up-regulated in both high-grade and low-grade gliomas, as well as in histologically normal tissues adjacent to GBMs. These genes coded for the epidermal growth factor receptor (previously reported to be overexpressed in gliomas) and for the alpha4 chain of laminin, a major blood vessel basement membrane component. Changes in expression of this laminin chain have not been previously associated with malignant tumors. Overexpression of laminin alpha4 chain in GBM and astrocytoma grade II by gene microarray analysis was confirmed by semiquantitive reverse transcription-PCR and immunohistochemistry. Importantly, an alpha4 chain-containing laminin isoform, laminin-8 (alpha4beta1gamma1), was expressed mainly in blood vessel walls of GBMs and histologically normal tissues adjacent to GBMs, whereas another alpha4 chain-containing laminin isoform, laminin-9 (alpha4beta2gamma1), was expressed mainly in blood vessel walls of low-grade tumors and normal brain. GBMs that overexpressed laminin-8 had a shorter mean time to tumor recurrence (4.3 months) than GBMs with overexpression of laminin-9 (9.7 months, P = 0.0007). Up-regulation of alpha4 chain-containing laminins could be important for the development of glioma-induced neovascularization and glial tumor progression. Overexpression of laminin-8 may be predictive of glioma recurrence.

Adult↗
PubMed2001

Vaccination of malignant glioma patients with peptide-pulsed dendritic cells elicits systemic cytotoxicity and intracranial T-cell infiltration.

In this Phase I trial, patients' peripheral blood dendritic cells were pulsed with peptides eluted from the surface of autologous glioma cells. Three biweekly intradermal vaccinations of peptide-pulsed dendritic cells were administered to seven patients with glioblastoma multiforme and two patients with anaplastic astrocytoma. Dendritic cell vaccination elicited systemic cytotoxicity in four of seven tested patients. Robust intratumoral cytotoxic and memory T-cell infiltration was detected in two of four patients who underwent reoperation after vaccination. This Phase I study demonstrated the feasibility, safety, and bioactivity of an autologous peptide-pulsed dendritic cell vaccine for patients with malignant glioma.

Adult↗
PubMed2000

Glioblastoma induction after radiosurgery for meningioma.

A 70-year-old woman developed a glioblastoma in the irradiated field 7 years after stereotactic radiosurgery for meningioma. Glioma induction has been previously reported after external beam radiation for leukaemia, pituitary adenoma, tinea capitus, and meningioma. This radiosurgery-induced malignancy may portend further reports of tumour induction. The theoretical risk of tumour induction by low doses of radiation to normal neural tissue after radiosurgery is now confirmed. Reports of additional cases of radiosurgery-induced tumours might temper the use of this increasingly used technique for benign surgically accessible lesions.

Aged↗
PubMed1995

Cloning of a highly conserved human protein serine-threonine phosphatase gene from the glioma candidate region on chromosome 19q13.3.

Allelic loss studies have suggested that a glioma tumor suppressor gene resides in a 425-kb region of chromosome 19q, telomeric to D19S219 and centromeric to D19S112. Exon amplification of a cosmid contig spanning this region yielded four exons with high homology to a rat protein serine-threonine phosphatase from a cosmid approximately 100 kb telomeric to D19S219. Isolation of a near full-length cDNA from a human fetal brain cDNA library revealed a protein serine-threonine phosphatase with a tetratricopeptide motif, almost identical to human PPP5C (PP5) and highly homologous to rat PPT. Northern blotting demonstrated expression in most tissues, including brain. Primary and cultured gliomas were studied for genetic alterations in this gene using pulsed-field gel electrophoresis, routine Southern blots, and genomic DNA-and RNA-based single-strand conformation polymorphism analysis. Genomic alterations were were not detected in any of the gliomas, and all studied gliomas expressed the gene, suggesting that this phosphatase is not the putative chromosome 19q glioma tumor suppressor gene.

Amino Acid Sequence↗
PubMed1995

Chromosome 19q deletions in human gliomas overlap telomeric to D19S219 and may target a 425 kb region centromeric to D19S112.

Chromosome 19q harbors a tumor suppressor gene that is involved in astrocytoma, oligodendroglioma and mixed glioma tumorigenesis. We had previously mapped this gene to an approximately 5 megabase region of chromosome 19q13.2-13.3 between APOC2 and HRC. To narrow the location of this tumor suppressor further, we studied 138 gliomas for loss of allelic heterozygosity at six microsatellite polymorphisms between APOC2 and HRC, including a newly described polymorphism in the ERCC2 gene. Allelic loss occurred in 48 gliomas (35%), including 25 of 41 oligodendroglial tumors (61%). Four cases had proximal breakpoints within the APOC2-HRC region, two telomeric to ERCC2 and two telomeric to D19S219. In addition, one of the latter tumors had an interstitial deletion between D19S219 and D19S112, a distance of only 425 kilobases surrounding the DM (myotonic dystrophy) gene. These findings suggest that the glioma tumor suppressor on chromosome 19q maps to 19q13.3, telomeric to D19S219 and perhaps centromeric to D19S112. The data exclude a number of candidate genes from 19q13.2-13.3, including a putative phosphatase gene and the DNA repair/metabolism genes ERCC1, ERCC2 and probably LIG1.

Base Sequence↗
PubMed1995

Cyst fluid NB/70K concentration and leukocyte esterase: two new markers for differentiating pancreatic serous tumors from pseudocysts.

Cystic lesions of the pancreas include inflammatory pseudocysts, serous cystadenomas, and mucinous tumors, some of which are malignant. Preoperative clinical and radiological parameters are unreliable and may result in incorrect diagnosis and inappropriate treatment. Cyst fluid analysis for cytology, viscosity, carcino-embryonic antigen, CA 72-4, and CA 15-3 will distinguish mucinous from nonmucinous lesions and usually help in determining malignancy. Currently, there is no reliable method to differentiate inflammatory pseudocysts from serous cystadenomas. This distinction is important because the treatment of these two lesions is different; pseudocysts are either observed or drained, whereas serous tumors are usually resected. The tumor marker NB/70K was measured in aspirated cyst fluid from 13 inflammatory pseudocysts and 11 serous cystadenomas by a commercial immunoassay. Leukocyte esterase was measured using Chemstrip SG urine test strips and amylase and lipase on a routine chemistry analyzer. The cyst fluid NB/70K concentration was significantly higher in pseudocysts (mean, 555 U/ml; range, 42-1,926 U/ml) than in serous cystadenomas (mean, 12 U/ml; range 0-130 U/ml) and this difference was significant (p < 0.0002). Leukocyte esterase was detected in 7 of 11 pseudocysts but was absent in 10 of 10 serous tumors (p = 0.002). Amylase and lipase values were generally higher in pseudocysts but these markers were unreliable due to marked outliers. Cyst fluid NB/70K and leukocyte esterase are promising markers to help differentiate pseudocysts from serous tumors on percutaneous aspirates. When combined with previously reported cyst fluid parameters (amylase, lipase, cytology, and amylase isoenzymes), these two cystic lesions can be reliably distinguished.

Antigens, Neoplasm↗
PubMed1994

Comparison of fecal lactoferrin latex agglutination assay and methylene blue microscopy for detection of fecal leukocytes in Clostridium difficile-associated disease.

The fecal lactoferrin assay was more sensitive (75%) than methylene blue microscopy (40%) for the detection of leukocytes in Clostridium difficile toxin-positive fecal samples. Although limited sensitivity and specificity precludes its use as a laboratory screening test, it may be a more useful initial test in an algorithm for clinically suspected C. difficile-associated disease.

Bacterial Proteins↗
PubMed1992

Cerebral hemorrhage with biopsy-proved amyloid angiopathy.

Clinical, radiological, and immunohistochemical findings in brain biopsy specimens from six patients with cerebral amyloid angiopathy-associated intracerebral hemorrhage were reviewed. Acute clinical presentations included headache, nausea and vomiting, loss of consciousness, and focal neurological deficits such as hemiplegia and blindness. Transient ischemic attacks experienced by one patient and referable to one hemisphere did not indicate impending hemorrhage in that region. Computed tomographic scans revealed acute, irregular, superficial, lobar hemorrhage with occasional ring enhancement. Immunohistochemical studies were performed on biopsy specimens using primary antibodies against portions of the Alzheimer A4 (beta-) peptide or gamma-trace peptide (the vascular amyloid protein in patients with hereditary cerebral hemorrhage with amyloidosis-Icelandic type). In all patients, anti-A4 and anti-gamma-trace labeled cerebral microvessels. Immunoreactive senile plaques were few compared with the numbers of stained microvessels. Reactive astrocytes in some patients were labeled by both antiserum samples, suggesting uptake or production of these proteins by the astrocytes. This study demonstrates the heterogeneous clinical and radiological features of cerebral amyloid angiopathy-related brain hemorrhage and the value of anti-A4 and anti-gamma-trace immunohistochemical study of biopsy material from patients with suspected cerebral amyloid angiopathy-related intraparenchymal bleeding.

Aged↗
PubMed1990

Optimal conditions for synthesizing complementary DNA in the HIV-1 endogenous reverse transcriptase reaction.

Concentration of monovalent and divalent cations, anionic detergent, reducing agent and nucleotides, as well as pH, temperature, and incubation time were optimized for high levels of HIV-1 endogenous reverse transcriptase activity. In addition, mellitin, a peptide substitute for anionic detergent, and oligo(dT)12-18 were found to stimulate nucleic acid synthesis. This HIV-1 endogenous reaction demonstrated RNA- and DNA-dependent DNA polymerase activities. Nucleic acid intermediates and final products included RNA:DNA hybrids as well as single- and double-stranded DNA. The complementary DNA products formed were representative of all regions of the HIV-1 genome.

Cations↗