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Biomedical subjects

T Y Chou

Publications and source records attributed to T Y Chou.

At least 37 records · Page 2Linked to original sources
PubMed1996

Retinal detachment in U.S. Air Force flyers.

Retinal detachment is a serious ocular condition, even though 85% can be repaired permanently. Long-term complications include decreased or loss of vision, redetachment, visual field changes, and proliferative vitreoretinpathy. To assess the effect of retinal detachment on flying careers, we reviewed the records of all aviators with a rhegmatogenous retinal detachment who were examined by the Ophthalmology Branch of the Aerospace Medicine Directorate at the Armstrong Laboratory (formerly the USAF School of Aerospace Medicine) from 1967-1986. Of the 19 flyers, 12 were returned to flying duties; only 2 were disqualified for ocular reasons alone. In 10 flyers, the detachments were previously undiagnosed. Associated vitreoretinal pathology was common in both eyes (42%). All received some type of treatment. Redetachment occurred in 4 flyers, but the overall final reattachment rate was 95%. Final posttreatment visual acuities were 20/20 or better in 16 flyers. Treatment-induced myopia was common. Many flyers enjoyed long flying careers after detachment repairs.

Adult↗
PubMed1995

c-Myc is glycosylated at threonine 58, a known phosphorylation site and a mutational hot spot in lymphomas.

c-Myc is a helix-loop leucine zipper phosphoprotein that heterodimerizes with Max and regulates gene transcription in cell proliferation, cell differentiation, and programmed cell death. Previously, we demonstrated that c-Myc is modified by O-linked N-acetylglucosamine (O-GlcNAc) within or nearby the N-terminal transcriptional activation domain (Chou, T.-Y., Dang, C.V., and Hart, G.W. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 4417-4421). In this paper, we identified the O-GlcNAc attachment site(s) on c-Myc. c-Myc purified from sf9 insect cells was trypsinized, and its GlcNAc moieties were enzymically labeled with [3H]galactose. The [3H]galactose-labeled glycopeptides were isolated by reverse phase high performance liquid chromatography and then subjected to gas-phase sequencing, manual Edman degradation, and laser desorption/ionization mass spectrometry. These analyses show that threonine 58, an in vivo phosphorylation site in the transactivation domain, is the major O-GlcNAc glycosylation site of c-Myc. Mutation of threonine 58, frequently found in retroviral v-Myc proteins and in human Burkitt and AIDS-related lymphomas, is associated with enhanced transforming activity and tumorigenicity. The reciprocal glycosylation and phosphorylation at this biologically significant amino acid residue may play an important role in the regulation of the functions of c-Myc.

Amino Acid Sequence↗
PubMed1995

Glycosylation of the c-Myc transactivation domain.

O-linked N-acetylglucosamine (O-GlcNAc) is an abundant and dynamic posttranslational modification composed of a single monosaccharide, GlcNAc, glycosidically composed of a single monosaccharide, GlcNAc, glycosidically linked to the side-chain hydroxyl of serine or threonine residues. Although O-GlcNAc occurs on a myriad of nuclear and cytoplasmic proteins, only a few have thus far been identified. These O-GlcNAc-bearing proteins are also modified by phosphorylation and form reversible multimeric complexes. Here we present evidence for O-GlcNAc glycosylation of the oncoprotein c-Myc, a helix-loop-helix/leucine zipper phosphoprotein that heterodimerizes with Max and participates in the regulation of gene transcription in normal and neoplastic cells. O-GlcNAc modification of c-Myc is shown by three different methods: (i) demonstration of lectin binding to in vitro translated protein using a protein-protein interaction mobility-shift assay; (ii) glycosidase or glycosyltransferase treatment of in vitro translated protein analyzed by lectin affinity chromatography; and (iii) direct characterization of the sugar moieties on purified recombinant protein overexpressed in either insect cells or Chinese hamster ovary cells. Analyses of serial deletion mutants of c-Myc further suggest that the O-GlcNAc site(s) are located within or near the N-terminal transcription activation/malignant transformation domain, a region where mutations of c-Myc that are frequently found in Burkitt and AIDS-related lymphomas cluster.

Acetylglucosamine↗
PubMed1995

A link between increased transforming activity of lymphoma-derived MYC mutant alleles, their defective regulation by p107, and altered phosphorylation of the c-Myc transactivation domain.

The c-Myc protein is a transcription factor with an N-terminal transcriptional regulatory domain and C-terminal oligomerization and DNA-binding motifs. Previous studies have demonstrated that p107, a protein related to the retinoblastoma protein, binds to the c-Myc transcriptional activation domain and suppresses its activity. We sought to characterize the transforming activity and transcriptional properties of lymphoma-derived mutant MYC alleles. Alleles encoding c-Myc proteins with missense mutations in the transcriptional regulatory domain were more potent than wild-type c-Myc in transforming rodent fibroblasts. Although the mutant c-Myc proteins retained their binding to p107 in in vitro and in vivo assays, p107 failed to suppress their transcriptional activation activities. Many of the lymphoma-derived MYC alleles contain missense mutations that result in substitution for the threonine at codon 58 or affect sequences flanking this amino acid. We observed that in vivo phosphorylation of Thr-58 was absent in a lymphoma cell line with a mutant MYC allele containing a missense mutation flanking codon 58. Our in vitro studies suggest that phosphorylation of Thr-58 in wild-type c-Myc was dependent on cyclin A and required prior phosphorylation of Ser-62 by a p107-cyclin A-CDK complex. In contrast, Thr-58 remained unphosphorylated in two representative mutant c-Myc transactivation domains in vitro. Our studies suggest that missense mutations in MYC may be selected for during lymphomagenesis, because the mutant MYC proteins have altered functional interactions with p107 protein complexes and fail to be phosphorylated at Thr-58.

Alleles↗
PubMed1995

MR of the cerebral operculum: topographic identification and measurement of interopercular distances in healthy infants and children.

PURPOSE: To evaluate the role of axial, coronal, and sagittal MR in identification of surface landmarks of the cerebral operculum and to determine the reference values of interopercular distances of each hemisphere in healthy infants and children on MR images. METHODS: Two hundred fourteen cerebral opercula of 35 healthy infants and 72 healthy children were retrospectively evaluated from 107 routine MR brain examinations. The surface landmarks of the operculum and interopercular distances of each hemisphere, which were subjectively divided into anterior interopercular distance (anterior sylvian width) and posterior interopercular distance (posterior sylvian width), were recorded from axial, coronal, and sagittal MR images, respectively. The mean value of anterior interopercular distance of each hemisphere was obtained by averaging two linear measurements of the anterior sylvian width from lateral, sagittal, and axial planes of the same side. Likewise, the posterior interopercular distance of each side of the brain was obtained from averaging of two measurements on lateral, sagittal, and coronal planes. RESULTS: The landmarks of the operculum were best identified by sagittal MR, followed by axial and coronal images. The average values of left anterior interopercular distance, right anterior interopercular distance, left posterior interopercular distance, and right posterior interopercular distance in infants were 1.9 +/- 1.3, 1.6 +/- 1.1, 0.4 +/- 0.7, and 0.2 +/- 0.4 mm, and in children, 0.9 +/- 1.3, 1.0 +/- 1.4, 0.03 +/- 0.23, and 0.01 +/- 0.07 mm, respectively. Infants showed significantly wider interopercular distances than children. Left anterior interopercular distance was significantly wider than right in infants, but not in children. Male children displayed a more significant increase in anterior interopercular distance than did female children. There was no statistic difference in measurements of anterior interopercular distance and posterior interopercular distance between female and male infants. CONCLUSIONS: The operculum should be evaluated with MR in three planes. Infants may show conspicuous sylvian fissures that should not exceed 4.5 mm (mean + 2 SD) anteriorly on axial and sagittal planes and 1.8 mm posteriorly on sagittal and coronal planes. Healthy children who have fully developed opercula should have an anterior interopercular distance of no more than 3.5 mm and a posterior interopercular distance of 0.5 mm.

Adolescent↗
PubMed1994

Bilophila wadsworthia isolated from clinical specimens in Taiwan.

Bilophila wadsworthia, a newly discovered anaerobic gram-negative species, has been found in such various clinical specimens as bile, pus, blood et cetera, in addition to appendicitis specimens. The formation of black center colonies in bacteroides bile esculin (BBE) agar is one of the important characteristics of the species.

Culture Media↗
PubMed1992

Traumatic tension pneumocephalus--intracerebral pneumatocele: a case report.

An 18-year-old Chinese man, suffering from head injury in a motorcycle accident, with right traumatic frontal intracerebral hemorrhage and frontal bone fractures, underwent emergency craniotomy with evacuation of hematoma at a local out-patient clinic and three months later, he suffered from CSF rhinorrhea. Headache, nausea and vomiting developed a week prior to admission. Tension pneumocephalus was diagnosed by computed tomography (CT) scan and plain skull X-ray. The fistula tract of the ethmoid sinus was investigated by radioisotope albumin (RISA) cisternography. The patient subsequently underwent emergency craniotomy for decompression. During the operation, we found that the intracerebral pneumatocele in the right frontal lobe communicated with the ipsilateral ethmoidal sinus, through which extracranial air ingressed and CSF egressed. This pneumatocele was unroofed and the fistula was temponaded by pericranial muscles and the Gelfomas sealed by tissue glue. Finally duraplasty was performed. Follow-up CT scan revealed that pneumocephalus subsided and the patient was cured of CSF rhinorrhea on discharge. As a surgical emergency, tension pneumocephalus can be successfully treated only by early diagnosis and early treatment.

Adolescent↗
PubMed1991

[Castleman's disease: 6 cases report].

The authors present six cases of Castleman's disease. One was located in the left middle lung near the lung root, one in the right posterior mediastinum, one in the gallbladder fossa, one in the left perinephric space, and the last two in the mesenteric region. All the hyaline-vascular type showed good enhancement after contrast medium injection. The only one case of plasma cell type located in mesentery was not enhanced after contrast injection. Ultrasound of abdomen was performed in one of the six patients, which showed homogeneous and hypoechoic in echo-pattern.

Adolescent↗
PubMed1991

Soft tissue chondroma: case report.

Soft tissue chondromas are relatively rare benign tumors, while as osseous chondromas are more commonly found. Although these tumors resemble many other soft tissue lesions, they can usually be differentiated. A review of literature is presented, and clinical manifestations and roentgenographic features are also discussed. An important point to note is that this tumor is benign and spares the patient unnecessary radical therapy.

Adolescent↗
PubMed1989

Polymeric activated ester reagents for off-line and on-line derivatizations of amine nucleophiles in high-performance liquid chromatography with ultraviolet and fluorescence detection.

A novel polymeric activated ester reagent has been developed that improves final detectability and chromatographic performance in high-performance liquid chromatography (HPLC) for virtually all primary and secondary amines or amine analogues. This has involved the synthesis, characterization of final reagent, optimization of derivatization and separation conditions, and determination of analytical figures of merit. The polymeric reagent contained an activated ester linkage to the 9-fluorenyl group, which imparted ultraviolet (UV) and fluorescence (FL) detector properties to the final derivatives. Kinetic studies of these solid-phase (heterogeneous) reactions have been conducted, and specific rate constants were compared with those of the analogous solution reaction for the same substrates. Percent derivatizations have reached 90% and 70% for primary and secondary amines, respectively, under optimized conditions. High reaction reproducibility has been obtained by using the on-line approach, for more than 50 separate injections of the same amine substrate with a single solid-phase reactor. These solid-phase derivatizations have led to detection limits for typical amines in the low-parts-per-billion range. The final, overall methods can provide rapid, automatable, accurate, and precise detection and quantitation of primary/secondary amines and amine-like compounds in real-world sample matrices. As an illustrative example, amphetamine spiked in urine has been derivatized off-line and on-line, with minimum sample preparation, and detected via HPLC-UV/FL with acceptable accuracy and precision.

Amines↗
PubMed1989

Chiral polymeric reagents for off-line and on-line derivatizations of enantiomers in high-performance liquid chromatography with ultraviolet and fluorescence detection: an enantiomer recognition approach.

Optically active and detector-sensitive polymeric reagents have been synthesized, loadings determined, derivatizations/separations/detection optimized, and applications to simple amines and amino alcohols described. Such reagents have been designed to contain different chiral centers, usually amino acids, leashed via an activated ester attachment to an insoluble, structurally rigid, organic polymer backbone. 9-Fluorenylmethyl (FMOC) moieties chemically bonded to the amino acids were used as ultraviolet (UV) and fluorescence (FL) sensitive detector probes to the final diastereomers of enantiomer substrates. Such diastereomers can be readily separated by isocratic or gradient elution normal-phase methods. The kinetics for diastereomer formation have been determined, and final UV/FL responses for known mixtures of enantiomers have been compared to demonstrate overall validity of the method. Minimum detection limits, linearity of calibration plots, dual detector responses, and linear diode array spectra and absorbance ratios have also been demonstrated. In some cases, authentic standards have been prepared to calculate absolute percent derivatizations for specific enantiomer pairs. The overall approach permits, for the very first time, off-line or on-line precolumn derivatization for the formation of diastereomers having unique detector properties. It has been proven that the rates and rate constants for such formations are identical for at least those pairs of enantiomers studied. Separations are base-line or near-base-line, permitting accurate and precise quantitative determinations, by both UV and FL, of enantiomer/optical purity and chemical purity.

Chemical Phenomena↗
PubMed1989

Clear cell sarcoma of tendons and aponeuroses (malignant melanoma of soft parts): report of 2 cases.

Clear cell sarcoma of tendons and aponeuroses (CCSTA, malignant melanoma of soft parts), first described by Enzinger in 1965, is a rare and slow-growing soft tissue tumor mainly affecting the extremities of young adults. The tumor is believed to be a tumor of melanocyte, although its histogenesis is not definitely established. Here we report 2 cases of CCSTA with typical clinical and pathological features. A tumor grew from the right ankle of a 32-year-old man (case 1) and from the left foot of an 18-year-old woman (case 2). The tumors were deep seated and intimately bound to tendons or aponeuroses without involvement of the overlying skin. Grossly, they were greyish white, variegated with brown or black patches. Histologically, the tumor cells were arranged in nests or fascicles and composed of fusiform or polygonal cells with clear cytoplasm. Ultrastructurally, they consisted of closely apposed cells with intracytoplasmic melanosomes. Case 1 was found to have distant metastases within 6 months and died 1 year later. Case 2 received postoperative radiotherapy and was free of recurrence or metastasis 14 months after operation. The treatment of CCSTA should include radical excision, radiotherapy, and chemotherapy. The prognosis is poor.

Adolescent↗
PubMed1988

Polymeric benzotriazole reagent for the off-line high-performance liquid chromatographic derivatization of polyamines and related nucleophiles in biological fluids.

A polymeric benzotriazole reagent containing a 9-fluorenylmethyleneoxycarbonyl (FMOC) group has been synthesized, characterized, and its derivatizations, off-line, for three polyamines, have been optimized with regard to solvent, time, and temperature. An authentic FMOC derivative of cadaverine has been prepared, characterized, and used as the external standard for quantitation of off-line derivatizations and identification of final derivatives. Actual percent derivatizations have been determined, rather than just percent disappearance of starting material. The polyamines in urine or other biological fluids can be derivatized without organic solvent or solid phase extraction, but rather in situ by the simple addition of the polymeric reagent to the fluid, incubation for a few minutes at room or elevated temperature, filtration and direct injection. Derivatizations could also be performed by transferring a small volume of the hydrolyzed and filtered biological fluid to a disposable pipette containing the polymeric reagent. Derivatization was then followed by elution, filtration, and direct injection onto the high-performance liquid chromatographic (HPLC) system. Automation of the overall polymeric derivatization, filtration, HPLC injection, separation, detection, quantitation, and data acquisition-interpretation is suggested. The polymeric reagent has been utilized for the qualitative and quantitative determination of cadaverine and putrescine, normally occurring polyamines, in human urine. These levels were compared with the corresponding literature values for healthy human subjects, and the values were found to be in excellent agreement. This novel derivatization approach, though off-line, provides for a much simpler, more rapid, and more efficient conversion of these and related polyamines or nucleophiles to derivatives having vastly improved chromatographic detection properties in HPLC. The final derivatives contain the FMOC group, making them extremely chromophoric and fluorophoric, and providing trace detection at ppb (microgram/l) and sub-ppb levels. The overall approach is recommended for these and other biologically occurring polyamines, in fluids and tissues, as well as related bioorganic and biologically active nucleophiles, including drugs and their metabolites.

Cadaverine↗
PubMed1988

New polymeric benzotriazole reagents for off-line derivatizations of amines and polyamines in HPLC.

New polymeric reagents are synthesized, based on a polystyrene-bound benzotriazole containing an o-acetylsalicyl or 9-fluorenyl labelling moiety. This is used in an off-line mode, prior to high performance liquid chromatography (HPLC), for derivatizations of trace primary and secondary amines, polyamines, and related compounds in connection with HPLC. Standards are prepared, characterized by physical and spectral properties, and then used as external standards to determine percent derivatizations. The polymeric reagents are characterized by elemental analyses and loading determinations. The feasibility and applicability of this reagent for derivatization of nucleophiles is confirmed with a number of amines under optimized conditions. The activated labelling moiety, bonded to the polymeric support, makes the derivatization reactions extremely rapid and efficient under mild reaction conditions. This alone provides significant advantages over the analogous solution derivatizations for the same amines. A comparison of solution and solid phase derivatization reactions is reported. The limits of detection are 1 to 2 pmol for polyamines, such as cadaverine, putrescine, and 1,7-diaminoheptane, using the benzotriazole fluorenyl reagent followed by fluorescence detection.

Amines↗
PubMed1987

Replacement of aromatic fluorine by a methoxy group during reaction with methyl iodide in N,N-dimethylformamide solvent.

The DNA base uracil was derivatized with pentafluorobenzoyl chloride, followed by methylation with methyl iodide in the presence of N,N-dimethylformamide (DMF). In addition to a 3-pentafluorobenzoyl-1-methyl derivative of uracil, GC/MS analysis of the reaction mixture revealed the formation of an unusual product, whose molecular weight was 12 U higher than that of the prior derivative. This unexpected product has been identified as the 3-(para-methoxytetrafluorobenzoyl)-1-methyl derivative of uracil. Isotopic labeling and related experiments have revealed that the DMF solvent contributes the oxygen atom of the methoxy group that replaces the para fluorine atom. This work allowed a single derivative to be obtained for the methylation reaction by changing the solvent to acetonitrile.

Acylation↗