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Biomedical subjects

E Y Yu

Publications and source records attributed to E Y Yu.

11 recordsLinked to original sources
PubMed2001

In situ observation of the generation of isothiocyanates from sinigrin in horseradish and wasabi.

Sulfur K-edge X-ray absorption spectroscopy has been used to determine the chemical identity of the sulfur-containing species in horseradish (Armoracia lapthifolia) and wasabi (Wasabia japonica) in situ, before and after cell disruption. The major sulfur-containing species in the intact root is sinigrin (1-thio-beta-D-glucopyranose 1-N-(sulfoxy)-3-buteneimidate) and related congeners. Disrupting the cells by applying local pressure allowed the conversion of the sulfur moieties in sinigrin to isothiocyanates and sulfate in approximately equimolar amounts. In contrast to previous suggestions, no detectable thiocyanates were formed, but an unusual thio intermediate may have been identified for the first time.

Brassica↗
PubMed2001

Analysis of sulfur biochemistry of sulfur bacteria using X-ray absorption spectroscopy.

Many sulfide-oxidizing organisms, including the photosynthetic sulfur bacteria, store sulfur in "sulfur globules" that are readily detected microscopically. The chemical form of sulfur in these globules is currently the focus of a debate, because they have been described as "liquid" by some observers, although no known allotrope of sulfur is liquid at physiological temperatures. In the present work we have used sulfur K-edge X-ray absorption spectroscopy to identify and quantify the chemical forms of sulfur in a variety of bacterial cells, including photosynthetic sulfur bacteria. We have also taken advantage of X-ray fluorescence self-absorption to derive estimates of the size and density of the sulfur globules in photosynthetic bacteria. We find that the form of sulfur that most resembles the globule sulfur is simply solid S(8), rather than more exotic forms previously proposed.

Chlorobi↗
PubMed2001

Comparative evaluation of the antitumor activity of antiangiogenic proteins delivered by gene transfer.

Although the systemic administration of a number of different gene products has been shown to result in the inhibition of angiogenesis and tumor growth in different animal tumor models, the relative potency of those gene products has not been studied rigorously. To address this issue, recombinant adenoviruses encoding angiostatin, endostatin, and the ligand-binding ectodomains of the vascular endothelial growth factor receptors Flk1, Flt1, and neuropilin were generated and used to systemically deliver the different gene products in several different preexisting murine tumor models. Single i.v. injections of viruses encoding soluble forms of Flk1 or Flt1 resulted in approximately 80% inhibition of preexisting tumor growth in murine models involving both murine (Lewis lung carcinoma, T241 fibrosarcoma) and human (BxPC3 pancreatic carcinoma) tumors. In contrast, adenoviruses encoding angiostatin, endostatin, or neuropilin were significantly less effective. A strong correlation was observed between the effects of the different viruses on tumor growth and the activity of the viruses in the inhibition of corneal micropocket angiogenesis. These data underscore the need for comparative analyses of different therapeutic approaches that target tumor angiogenesis and provide a rationale for the selection of specific antiangiogenic gene products as lead candidates for use in gene therapy approaches aimed at the treatment of malignant and ocular disorders.

Adenoviridae↗
PubMed2000

Sequence-specific DNA recognition by the Myb-like domain of plant telomeric protein RTBP1.

We have identified a rice gene encoding a DNA-binding protein that specifically recognizes the telomeric repeat sequence TTTAGGG found in plants. This gene, which we refer to as RTBP1 (rice telomere-binding protein 1), encodes a polypeptide with a predicted molecular mass of 70 kDa. RTBP1 is ubiquitously expressed in various organs and binds DNA with two or more duplex TTTAGGG repeats. The predicted protein sequence includes a single domain at the C terminus with extensive homology to Myb-like DNA binding motif. The Myb-like domain of RTBP1 is very closely related to that of other telomere-binding proteins, including TRF1, TRF2, Taz1p, and Tbf1p, indicating that DNA-binding domains of telomere-binding proteins are well conserved among evolutionarily distant species. To obtain precise information on the sequence of the DNA binding site recognized by RTBP1, we analyzed the sequence-specific binding properties of the isolated Myb-like domain of RTBP1. The isolated Myb-like domain was capable of sequence-specific DNA binding as a homodimer. Gel retardation analysis with a series of mutated telomere probes revealed that the internal GGGTTT sequence in the two-telomere repeats is critical for binding of Myb-like domain of RTBP1, which is consistent with the model of the TRF1.DNA complex showing that base-specific contacts are made within the sequence GGGTTA. To the best of our knowledge, RTBP1 is the first cloned gene in which the product is able to bind double-stranded telomeric DNA in plants. Because the Myb-like domain appears to be a significant motif for a large class of proteins that bind the duplex telomeric DNA, RTBP1 may play important roles in plant telomere function in vivo.

Amino Acid Sequence↗
PubMed2000

Effect of laser in situ keratomileusis on tear stability.

OBJECTIVE: Patients frequently experience dry eye symptoms after laser in situ keratomileusis (LASIK). The mechanisms that lead to these changes are not well understood. The purpose of this study was to investigate the effect of LASIK on tear function. DESIGN: Prospective, comparative, nonrandomized interventional trial. PARTICIPANTS: Fifty-eight consecutive patients (96 eyes) who underwent myopic LASIK treatment. METHODS: The prospective study involved 58 consecutive patients (96 eyes) who underwent sequential or bilateral LASIK for the correction of myopia. Dry eye symptoms, standardized Schirmer test values, basal tear secretion test, and tear break-up time were measured before surgery and 1 day, 1 week, and 1 month after surgery. MAIN OUTCOME MEASURES: Schirmer test value, basal tear secretion value, and tear break-up time. RESULTS: Before surgery, 15.6% of patients (15/96) had dry eye symptoms. After surgery, 94.8% of patients (91/96), 85.4% of patients (82/96), and 59.4% of patients (57/96) experienced dry eye symptoms at 1 day, 1 week, and 1 month, respectively. Schirmer test value (13.32 +/- 10. 67 mm) increased at 1 day (14.48 +/- 10.57 mm; P = 0.25) and subsequently decreased at 1 week (11.18 +/- 9.81 mm; P = 0.05) and at 1 month (10.83 +/- 10.02 mm; P = 0.03). Basal tear secretion test value (8.49 +/- 8.48 mm) decreased at 1 day (6.80 +/- 6.48 mm; P = 0.05), at 1 week (5.97 +/- 6.88 mm; P = 0.005), and at 1 month (5.89 +/- 6.24 mm; P = 0.007). Tear break-up time (5.32 +/- 2.35 seconds) decreased 1 day (4.14 +/- 1.90 seconds; P < 0.001) and 1 week (4.49 +/- 1.70 seconds; P = 0.004) after surgery and recovered by 1 month after surgery (5.09 +/- 3.03 seconds; P = 0.52). Poor preoperative tear functions with a Schirmer test value less than 10 mm was a significant risk factor (72% vs. 46%; relative risk, 1.58 [1.10-2.26]) for experiencing dry eye symptoms at 1 month after surgery. CONCLUSIONS: Dry eye symptoms are common after myopic LASIK surgery. Laser in situ keratomileusis significantly altered the tear break-up time, Schirmer test values, and basal tear secretion. Patients with preexisting tear flow abnormality as demonstrated by Schirmer test values less than 10 mm are especially at risk of experiencing dry eye symptoms.

Adult↗
PubMed2000

Structural basis of the antagonism between inorganic mercury and selenium in mammals.

Mercuric chloride toxicity in mammals can be overcome by co-administration of sodium selenite. We report a study of the mutual detoxification product in rabbit plasma, and of a Hg-Se-S-containing species synthesized by addition of equimolar mercuric chloride and sodium selenite to aqueous, buffered glutathione. Chromatographic purification of this Hg-Se-S species and subsequent structural analysis by Se and Hg extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of four-coordinate Se and Hg entities separated by 2.61 A. Hg and Se near-edge X-ray absorption spectroscopy of erythrocytes, plasma, and bile of rabbits that had been injected with solutions of sodium selenite and mercuric chloride showed that Hg and Se in plasma samples exhibited X-ray absorption spectra that were essentially identical to those of the synthetic Hg-Se-S species. Thus, the molecular detoxification product of sodium selenite and mercuric chloride in rabbits exhibits similarities to the synthetic Hg-Se-S species. The underlying molecular mechanism for the formation of the Hg-Se-S species is discussed.

Animals↗
PubMed1999

Recent advances in refractive surgery.

Refractive errors are some of the most common ophthalmic abnormalities world-wide and are associated with significant morbidity. Tremendous advances in treating refractive errors have occurred over the past 20 years. The arrival of the excimer laser has allowed a level of accuracy in modifying the cornea that was unattainable before. Although refractive surgery is generally safe and effective, it does carry some risks. Careful patient selection, meticulous surgical technique and frequent follow-up can avoid most complications. The experience of a surgical team can also affect the outcome and the incidence of complications. The future should bring continued improvement in outcomes, fewer complications and exciting new options for treating refractive errors.

Humans↗
PubMed1997

Histologic differences in benign prostate hyperplasia between Chinese and American men.

BACKGROUND: This investigation sought to determine morphologic differences between Chinese and Americans with symptomatic benign prostatic hyperplasia (BPH), in an admixture of stroma, epithelium, and luminal spaces. METHODS: Adjacent sections of simple prostatectomy specimens from China and the U.S. were stained to highlight the stroma and epithelium. Image analysis was performed on random fields. RESULTS: Chinese tissue had higher glandular densities (mean = 12.5 acini/mm2 vs. 6.2 acini/mm2; P < 0.0001), while American samples had higher percent stroma (mean = 66% vs. 51%; P = 0.0003). Mean luminal cell heights in the Chinese and American prostate acini were 11.7 and 19.0 microns, respectively (P < 0.0001). CONCLUSIONS: These data indicate significant histologic variation in BPH between Chinese and American men undergoing simple prostatectomy. These differences may provide a focus for investigating the epidemiological variation in clinical BPH and carcinoma between our two countries, and could have applications in clinical management of symptomatic BPH.

Aged↗
PubMed1997

The relation of p53 protein nuclear accumulation and angiogenesis in human prostatic carcinoma.

All neoplasms require angiogenesis and resulting neovascularity for growth beyond 1 mm(2). Quantitative microvessel density (MVD) has been shown to provide staging and prognostic significance in human prostate cancer (CaP). recently, it has been demonstrated that loss of the wild-type allele of the p53 tumour suppressor gene results in reduced expression of thrombospondin-1 (TSP-1), a potent inhibitor of angiogenesis. There is also an increased expression of vascular endothelial growth factor which promotes neovascularization. p53 gene mutation and MVD were investigated in men with prostate cancer. Sections from 103 radical prostatectomy cases were evaluated with immunohistochemistry to detect mutant p53 proteins. Quantitative MVD was performed on the cases exhibiting p53 positive staining and compared with negative fields of similar Gleason grade on the same histologic sections. Twenty of the 103 cases (19.4%) revealed positive p53 staining nuclei. In 19 of these 20 cases, the MVD in p53 positive areas was greater than corresponding control regions (overall P<0.0001). Extent of p53 abnormality, as well as MVD, correlated with pathologic stage. These data suggest that mutations of the p53 tumour suppressor gene may be associated with increased angiogenesis in CaP. In addition to providing staging and prognostic information, this relationship potentially has therapeutic implications.

Journal Article↗
PubMed1984

Use of surnames in ethnic research: the case of Kims in the Korean-American population.

This paper introduces a method for estimating the size of the Korean American population in communities in the United States. Since about 22 percent of Korean Americans have the surname Kim and the telephone subscription/listing rate for Korean Americans is extremely high, a fairly simple equation for such estimation can be constructed. The number of Kims listed in the published telephone directory for a community, the mean size of the Kim households, the residence telephone subscription/listing rate, and the proportion of Kims are the factors included in the equation. A specific value for each of the factors has been derived from various "unobtrusive" and nongovernmental sources. Only insignificant differences have been found between estimates made using this method and the enumeration figures from the 1980 census for the Korean American population in the New York metropolitan area and Los Angeles and Orange counties. It appears that the equation is effective in estimating the size of the Korean American population in a community and could be a useful instrument in evaluating the accuracy of the 1980 Census enumeration of Korean Americans. The paper also describes the potential utility of Kims listed in published telephone directories as a sampling frame of Korean Americans in the United States. The ideas and procedures presented here can be extended to other ethnic populations with unique surnames, such as Nguyen for the Vietnamese American population and those starting with "Yama" . . . for the Japanese American population.

Demography↗