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Biomedical subjects

W S Yu

Publications and source records attributed to W S Yu.

At least 19 recordsLinked to original sources
PubMed2004

Electron-impact ionization of CCl4 and CCl2F2.

Absolute partial and total cross sections for electron-impact ionization of CCl4 and CCl2F2 are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ion species are collected with equal efficiency irrespective of their initial kinetic energies. Data are presented for production of CCl3(+), CCl2(+), CCl+, C+, Cl2(+), and CCl3(2+) from CCl4; and for production of CCl(2)F+, CClF2(+), CClF(+), (CCl+ + CF2(+)), Cl+, CF+, F+, and C+ from CCl2F2. Data are also reported for formation of (CCl2(+),Cl+) and (CCl+, Cl+) ion pairs from CCl4. The total cross section for each target is obtained as the sum of the partial cross sections. The overall uncertainty in the absolute cross sections for most of the singly charged ions is +/- 5-7 %. The present partial cross sections for lighter fragment ions are found to be considerably greater than had been previously reported but the most recent total cross section measurements agree well with those reported here. Neither the binary-encounter-Bethe theory nor the Deutsch-Mark theory reproduces the experimental cross sections correctly for both targets.

Journal Article↗
PubMed2000

Expression of heat shock protein 72 in rat cochlea with cisplatin-induced acute ototoxicity.

Cisplatin ototoxicity is known to involve mainly the organ of Corti. Outer hair cells (OHCs). especially in the basal turn, are preferentially involved. One possible mechanism of ototoxicity might be alteration of the antioxidant system causing an increase in free radicals. It has been demonstrated that heat shock proteins (HSPs), which are believed to protect cells by dissolving and refolding misfolded or denatured protein are induced by various form of stress. HSP is also demonstrated to be induced by free radicals. The purpose of this study was to evaluate HSP 72 induction in cochlea following cisplatin injection in the animal model. Sprague-Dawley (SD) rats were injected intraperitoneally with normal saline as control or cisplatin at a dose of 5, 10 or 20 mg/kg. Cochleae were harvested 1, 3, 6 and 12 h after injection and compared with those of controls. Immunocytochemical study with surface preparation and Western blotting were performed to investigate the expression of HSP 72. Auditory brainstem response (ABR) was also recorded to assess functional change according to the dosage of cisplatin and duration after injection. In the 5 and 10 mg/kg groups, immunostaining for HSP 72 in the OHCs reached a plateau level at 3 h, which was maintained until 12 h after injection. The amount of immunoreactive OHCs in the 20 mg/kg group was smaller than those in 5 and 10 mg/kg groups and declined after 6 h. The bands for HSP 72 became less intense as the cisplatin dosage increased from 5 to 10 and 20 mg/kg in Western blotting. The change in ABR threshold was small in the 5 and 10 mg/kg groups and a marked change in threshold was observed in the 20 mg/kg group. Detection of HSP 72 after cisplatin injection could confirm the OHCs as one of the major injured cells in the cochlea. With a lethal dosage of cisplatin (20 mg/kg), HSP 72 expression was less prominent and declined after 6 h.

Animals↗
PubMed1995

The effects of experimentally increased perilymphatic pressure on click-evoked otoacoustic emissions in guinea pigs.

We used the IL088 Otodynamic Analyzer system to study click-evoked otoacoustic emissions (CEOAEs) in 30 healthy guinea pigs. The animals were anesthetized and patterns of the CEOAEs were evaluated before manipution, after the tympanic bulla was opened, and after formation of a microfistula on the basal turn of the cochlea. The animals then were divided into three pressure loading groups (10, 20, and 30 cm H2O). CEOAEs were recorded with a capillary manometer at pretest, 5, 10, 20, 30, 45, and 60 min after perilymphatic pressure loading to the basal turn of cochlea, and 10 and 20 min after pressure unloading. As perilymphatic pressure increased, all three pressure groups showed maximum decreases in both echo response and reproducibility 5 min after pressure loading. In the 10 cm H2O pressure group, emissions recovered 10 min after pressure loading, and this tendency continued. However, in the 20 and 30 cm H2O pressure groups, no recovery of emissions was seen throughout the 60 min observation period, except for emissions after pressure unloading. The results suggest that the echo response and reproducibility may be sensitive indicators of cochlear function and perilymphatic pressure regulation capacity.

Acoustic Stimulation↗
PubMed1994

Contribution of neurons born during embryonic, juvenile, and adult life to the brain of adult canaries: regional specificity and delayed birth of neurons in the song-control nuclei.

Neurogenesis occurs in adult song birds, which suggests that neurons born after hatching may contribute to histogenesis and plasticity of the avian brain. However, little is known about the overall contribution to the mature brain of neurons born in juveniles and adults, and how this process affects different regions of the avian brain. In fact, studies of the histogenesis of the avian forebrain have made the classical assumption that neuronal birth ends before hatching. Here we determined the contribution of neurons born before and after hatching to different regions throughout the adult canary brain. Male canaries were injected with [3H]-thymidine at different times during embryonic, juvenile, and adult life. The position of labeled neurons was mapped in parasagittal brain sections. Because all birds were killed as adults, results indicate the time of birth of neurons that survived to adulthood in different structures of the avian brain. Injection at embryonic day (E) 5 or E9 resulted in labeled neurons in all regions of the neuroaxis. The vast majority of neurons outside of the telencephalon were born before E9. One exception was a discrete region in the dorsal thalamus, a part of the song-control circuit, where neurons continued to be born after E9. Most regions of the telencephalon had a high proportion of its neurons labeled by the embryonic injections. In particular, archistriatum, anterior neostriatum, and the hippocampus had most of their neurons labeled before hatching. This indicates that many of the telencephalic neurons born in the embryo are long lived and are not replaced by other neurons that continue to be added to the telencephalon after hatching. Neurons labeled by [3H]-thymidine injections after hatching were restricted to the telencephalon and contributed importantly to many regions. In particular, the avian striatum (lobus parolfactorius, LPO) received a large number of its neurons during the first 20 days of life, but continued to incorporate new neurons throughout juvenile and adult life. Neurons continued to be added to the telencephalon of adults (even in 4-year-old birds). The distribution of labeled neurons after [3H]-thymidine injections in adults was similar to that observed in latter stages of juvenile development. The contribution of neurons born at different ages from embryonic development to adulthood varied among different anatomical subdivisions of the canary brain. this could, in part, explain differences in the cytoarchitecture and plasticity between brain regions. Neurogenesis after hatching may allow the modification of selected brain circuits as the bird matures and ages.

Animals↗
PubMed1993

Polyphenols from Rhodiola crenulata.

A novel gallotannin, crenulatin ( 7), has been isolated from RHODIOLA CRENULATA. The structure was elucidated by spectral analyses (including 2D-NMR spectral measurements) and chemical methods. Also six known polyphenols have been isolated and identified.

Journal Article↗
PubMed1990

Cyst fluid proteases.

The precise origin of breast cyst fluid remains obscure. Molina has presented evidence that type II cysts (high Na/K ratio) may be transudative, that is, partly derived from plasma elements which enter through gap junctions, while Type I cysts (high K/Na ratio) are primarily secretory. In transudative cysts, plasma protease inhibitors may be present, but the balance between protease and its inhibitors may fluctuate as a result of as yet undetermined circumstances. An imbalance between the protease activity of cyst fluid and its inhibitors may be involved in the pathogenesis of breast gross cystic disease. Accumulation of protein fragments with resistant bonds would produce an elevated oncotic pressure causing a shift of fluid into the cyst capsule. Albumin is a good substrate for the protease, which may account for its low concentration in cyst fluid. The major protease fraction closely corresponds to the progesterone binding protein (GCDFP-24) described by Haagensen. Affinity columns containing aprotinin or benzamidine ligands retain the protease which can then be eluted with 0.5 M NaCl. The HD1 protease and progesterone binding protein are either tightly complexed or are the same protein. Cyst fluid is a complex mixture of biomolecules. If the progesterone binding protein is a protease, many questions must be answered concerning the influence of cyst fluid steroids, lipids, anions, and cations on enzyme action. Determination of the amino acid sequence of HD1 may help elucidate the source of the enzyme and its relationship to other tissue proteases. Human plasma contains inhibitors of this protease activity. When pooled, dialyzed plasma was mixed with pooled, dialyzed cyst fluid, the ratio of plasma/cyst fluid at which all activity was inhibited was 6/1. A comparison of the rate of cleavage of three 14C-protein substrates shows that cyst fluid proteases cleave in a characteristic manner, distinct from either trypsin or calpain. A simple method for semiquantitative estimation of protease activity in cyst fluid is described which utilizes prestained Coomassie blue-albumin containing agarose gel plates. All cyst fluids tested had protease activity but showed variability in their ability to cleave 14C-albumin by a factor of 4. There is much direct and indirect evidence that proteases are involved in the cancer process. In view of the higher than normal incidence of breast cancer in women who have had gross cystic breast disease, the possibility exists that an imbalance between these proteases and their inhibitors is somehow involved.

Exudates and Transudates↗
PubMed1988

Proteases in cyst fluid from human gross cyst breast disease.

Cyst fluid from women with gross cystic breast disease was found to contain protease activity when assayed against [14C]albumin. At least six different proteases were detected when the fluid was fractionated by a combination of S-300 Sephacel, hydroxylapatite, and DEAE-Sephacel chromatographic techniques. The distribution of the proteases appeared to be related to the ionic composition of the fluids. A major protease component, found in both high Na and high K fluids, was isolated. It showed chymotryptic cleavage characteristics against the beta-chain of insulin. It was partially inhibited by alpha 2-macroglobulin, N-tosyl-L-phenylalanine chloromethyl ketone, and benzamidine but not by leupeptin, pepstatin, N-tosyl-L-lysine chloromethyl ketone, or alpha 1-protease inhibitor. The protease has an apparent molecular weight of 110,000 with Mr 24,000 subunits. This protease may be identical or closely associated with Haagensen's GCDFP-24 progesterone binding protein which was isolated in a similar manner. An imbalance between protease and protease inhibitors in cyst fluid may account for gross cyst formation and may be involved in the tumorigenic process. The accumulation of poorly diffusible peptide fragments, as a result of protease activity, would increase the oncotic pressure leading to enlargement of the cyst cavity as water enters to reestablish osmotic equilibrium.

Female↗
PubMed1985

Bladder carcinoma. Experience with radical and preoperative radiotherapy in 421 patients.

Four hundred twenty-one patients with bladder carcinoma were treated with radical intent between 1968 and 1981: 356 were treated with irradiation alone with megavoltage tumor doses of 60-66 Gy delivered over a period of 6 to 7 weeks. Actuarial 5- and 10-year survival was 66% and 58% for Stage A (58 patients), 42% and 35% for Stage B1 (62 patients), 35% and 28% for Stage B2 (120 patients), and 23% and 19% for Stage C (75 patients), respectively. Five-year survival after salvage cystectomy (47 patients) was 51% from the time of surgery, with 4 operative mortalities and a major complication rate of 30%. Sixty-five patients were entered into an integrated preradical cystectomy irradiation program. Fifty-three patients in stages B2-C-D1 received high-dose preoperative radiotherapy (40-50 Gy) before a planned, delayed radical cystectomy. The actuarial 5-year survival was 66% for 65 patients, and 64% for the 53 patients in the high-dose precystectomy program; major complications were encountered in 34% and there were 2 mortalities. Five-year actuarial survival for Stage B2-C was 30% but fell to 24% when patients with salvage cystectomy were excluded. Distant metastasis was found in 30% of patients in Stage B2-C-D1, and also in the high-dose precystectomy program patients. Two-thirds of patients with distant metastasis in the radiation alone group were never considered for salvage cystectomy as they had distant metastasis alone, persistent disease with metastasis within 6 months after initiation of irradiation, or local recurrence and distant metastasis simultaneously. Early local recurrence may be salvaged in 50% to 60% of patients without a significant increase in mortality or major complications. Accordingly, a program of radical irradiation with salvage cystectomy may avoid loss of the bladder in 45% of patients in Stage B2-C-D1 without compromising overall survival.

Adult↗
PubMed1984

External-beam irradiation of carcinoma of the penis.

Twenty-four patients with biopsy-proved squamous-cell carcinoma of the penis underwent external-beam radiation therapy between 1966 and 1980. Fifteen were treated for the primary tumor and 9 for metastatic inguinal lymphadenopathy; no patient received prophylactic nodal irradiation. Doses ranged from 4,500 rad (45 Gy)/15 fractions/3 wk. to 6,400 rad (64 Gy)/32 fractions/6 1/2 wk. Seven out of 9 tumors in stage I, 2/3 in stage II, and 1/3 in stage IV were controlled for three years. Control of fixed, inoperable groin nodes was poor, and none of these patients survived beyond 1 1/2 years.

Adult↗
PubMed1982

The changing role of external-beam irradiation in the management of malignant tumors of the major salivary glands.

Postoperative irradiation reduces the local recurrence rate for malignant salivary gland tumors. Less extensive surgery followed by immediate radiotherapy is possible without decreasing local control; moreover, cosmetic appearance and physiological function are preserved. Local tumor control was achieved in 16 out of 17 patients without gross tumor using a dose of 6,000 rad/6 wk. Combined photon and electron beams give better cosmetic and functional results than either modality alone. Irradiation with greater than or equal to 7,000 rad should be employed in unresectable cases and may effect tumor control.

Adult↗
PubMed1980

External irradiation for malignant thyroid tumors.

Thirty-eight patients with residual or recurrent primary thyroid cancers which did not take up 1-131 were treated with external beam irradiation. Excluding 5 patients with malignant lymphoma, there were 23 patients with local disease and 10 with distant metastases. Doses ranged from 3,500 to 7,000 rads (35-70 Gy) among the 23 with local disease; local tumor control was achieved in 8. Six are alive and well 2-11 years later. External beam irradiation should be considered in locally advanced, incompletely resected, recurrent and metastatic thyroid malignancies of all histological types without 1-131 uptake. Reviewed are the age and sex distribution, histology, stage, extent of surgery, and dose and radiotherapy technique as they affect survival and patterns of failure.

Adenocarcinoma↗