Biomedical subjects

Y Mao

Publications and source records attributed to Y Mao.

At least 109 records · Page 6Linked to original sources

PubMed2001

[Recognizing of the transglottic carcinoma].

OBJECTIVE: A study was undergone about transglottic carcinoma(TGC) in eighty six cases from 1979 to 1998, so as to recognize the TGC. METHOD: Evaluating retrospectively the procedure of the disease, surgical operations, presence of cervical metastasis, gathering the data on histopathological discovery and following up and so on. RESULT: The TGC was different from T2, T3 supraglottic or glottic carcinoma of larynx. In 86 TGC, there were 63 cases which were operated with total laryngectomy, 9 cases subtotal laryngectomy and 14 cases frontolateral hemilaryngectomy, 47 cases with neck dissection. In TGC which size > 2 cm, there were 58% which extend to the framework of larynx, 46% with extension out of larynx, and 71% with neck metastasis. The result of following up shows that 5-year survival rate was 55.41%, 10-year was 29.72%, 15-year and more was 18.92%. CONCLUSION: There is an actual signification for TGC to be a special type of the laryngeal carcinoma. The characteristics of the precise topography of the the paraglottic space (PGS) can explain the reason of extension, spread of the TGC and cervical metastasis. Elective neck dissections and complemental radiotherapy postoperatively should be included during surgical resection.

Adult↗

PubMed2001

[Studies on regulation of glutamine synthetase activity from Streptomyces lincolnensis].

Glutamine synthetase in crude extracts from Streptomyces lincolnensis growing under different nitrogen sources were studied. The results showed that NH4+ in high concentration repressed the biosynthesis of the enzyme. To determine whether Streptomyces lincolnensis has undergone covalent modification, a comparison of the glutamine synthetase isolated from cells grown on different nitrogen sources was made. No significant difference was observed in specific activity, pH optima, divalent cation response, and ultraviolet absorption spectra. Glutamine synthetase activity was not influenced by ammonia shock or snake venom phosphodiesterase treatment. Under these conditions, the activity of glutamine synthetase from K. aerogenes was markedly changed. There was therefore no evidence for enzymatic adenylylation of glutamine synthetase from Streptomyces lincolnensis. Glutamine synthetase was subject to feedback inhibition by end products of glutamine metabolism. Cumulative feedback inhibition of the Mn(2+)-dependent glutamine synthetase activity was demonstrated. These results suggest that glutamine synthetase from Streptomyces lincolnensis is an allosteric enzyme.

Ammonia↗

PubMed2001

[Effects of isocarbophos on the integrity of epidermic cell membrane of human skin].

OBJECTIVE: To investigate the effects of isocarbophos, a new and highly effective organophosphorus pesticide on the membranes of keratinocytes. METHODS: The epidermic cells of human skin cultured in the medium were adopted as a biological material. The activity of lactate dehydrogenase (LDH) was used as an indicator. We tested the activities of LDH and alkaline phosphatase (ALP) in the medium in different isocarbophos dosage conditions. RESULTS: It was found that the activity of LDH in the medium decreased with the increase of isocarbophos dosage. The LDH activities of the dosage groups were statistically different from those of the positive and negative groups. The ALP activities were of no significant difference between the groups. CONCLUSION: The above findings reveal that isocarbophos does not damage the membranes of keratinocytes directly, however it inhibits the LDH of human skin keratinocytes; thus it is suggested that isocarbophos like most organophosphorus pesticides used widely can pass through the intact human skin and poison the body before the skin is damaged. Therefore, protection during work hours is of paramount importance.

Alkaline Phosphatase↗

PubMed2001

[Study on the chemosensitivity test of human gastric cancer using the MTT assay].

OBJECTIVE: This study was conducted to investigate the chemosensitivity of gastric carcinoma. METHODS: 112 cases of fresh human gastric cancer samples were obtained for drug sensitivity testing using MTT. RESULTS: The sensitivity sequence of antitumor agents was 5-Fu, DDP, MMC, etc. On the other hand, the sensitivity was relative to pathology and individual differences. CONCLUSION: The MTT assay is an accurate system for determination of the chemosensitivity of tumor cells.

Adenocarcinoma↗

PubMed2001

Clinical characteristics and basic research development of Peutz-Jeghers syndrome.

OBJECTIVE: To improve clinical knowledge of Peutz-Jeghers syndrome. METHODS: Eight patients with Peutz-Jeghers syndrome from 1984 to 1998 in our hospital were retrospectively reviewed and analyzed in the present study. RESULT: The result of this analysis showed that there were 4 patients appeared with family histories of Peutz-Jeghers syndrome. All of the included patients admitted to the hospital with various complications, and eventually received surgical interventions for these complications, among which, 6 of them had intestinal obstructions mostly (5/6) due to small bowel intussusception, and 2 of them suffered with hemafecia. Post-operative recoveries were generally satisfactory with zero mortality. CONCLUSION: Peutz-Jeghers syndrome is an uncommon digestive dominant hereditary disease. The diagnosis of it with history, symptoms, signs, and proper examinations usually is not difficult Surgical interventions are necessary once complications occur.

Adolescent↗

PubMed2001

Trends in colorectal cancer incidence and mortality.

OBJECTIVES: This article examines recent trends in the incidence of and mortality from colorectal cancer among Canadian men and women, then further analyzes trends by three subsites. DATA SOURCES: Incidence data for colorectal cancer were obtained from the National Cancer Incidence Reporting System and from the Canadian Cancer Registry. Mortality data were extracted from the Canadian Vital Statistics Database. Supplementary data on nutrition are from the National Population Health Survey. ANALYTICAL TECHNIQUES: Age-standardized incidence and mortality rates were calculated for men and women. Age-specific incidence and mortality rates were calculated by 10-year age groups. Joinpoint analysis was applied to detect statistically significant changes in linear trends. MAIN RESULTS: Since the mid-1980s, colorectal cancer incidence has been declining, with steeper rates of decrease among women. Decreasing rates of colorectal cancer are limited to tumours located in the distal colon and rectum; the incidence of cancers of the proximal colon has not changed over time.

Adult↗

PubMed2001

[Diagnosis and treatment of paragangliomas in the central nerve system].

OBJECTIVE: To explore the diagnosis and treatment of paragangliomas in the central nerve system. METHODS: 17 patients with paragangliomas in the central nerve system over a 20-year period (1976-1999) were analyzed retrospectively. They included 11 patients with glomus jugular tumors, 1 with carotid body tumor, 1 with supersellar paraganglioma, 2 with spinal involvement, and 2 with superficial hemisphere involvement. RESULTS: Neoplasm was completely resected in 11 patients, subtotally in 3, and partial in 3. The postoperative mortality was 1/17. One patient remained severe disability, yet the others had excellent long-time outcome. CONCLUSIONS: Both the characteristic clinical presentation and neuroradiological manifestation were useful for preoperative diagnosis. Total resection is ideal for paragangliomas. Preoperative embolization should be used routinely to control intraoperative bleeding, and postoperative radiation-therapy would be valuable to control the recurrence of the remaining tumor.

Adult↗

PubMed2000

Untwisting of a cholesteric elastomer by a mechanical field

A mechanical strain field applied to a monodomain cholesteric elastomer will unwind the helical director distribution. There are similarities with the classical problem of an electric field applied to a cholesteric liquid crystal but also differences. Frank elasticity is of minor importance unless the gel is very weak. The interplay is between the director being helically anchored to the rubber elastic matrix and the external mechanical field. Stretching perpendicular to the helix axis induces the uniform unwound state via the elimination of sharp, pinned twist walls above a critical strain. Unwinding through conical director states occurs when the elastomer is stretched along the helical axis.

Journal Article↗

PubMed2000

Locally resonant sonic materials

We have fabricated sonic crystals, based on the idea of localized resonant structures, that exhibit spectral gaps with a lattice constant two orders of magnitude smaller than the relevant wavelength. Disordered composites made from such localized resonant structures behave as a material with effective negative elastic constants and a total wave reflector within certain tunable sonic frequency ranges. A 2-centimeter slab of this composite material is shown to break the conventional mass-density law of sound transmission by one or more orders of magnitude at 400 hertz.

Journal Article↗

PubMed2000

SUMO-1 conjugation to human DNA topoisomerase II isozymes.

Topoisomerase I-mediated DNA damage induced by camptothecin has been shown to induce rapid small ubiquitin-related modifier (SUMO)-1 conjugation to topoisomerase I. In the current study, we show that topoisomerase II-mediated DNA damage induced by teniposide (VM-26) results in the formation of high molecular weight conjugates of both topoisomerase IIalpha and IIbeta isozymes in HeLa cells. Immunological characterization of these conjugates suggests that both topoisomerase IIalpha and IIbeta isozymes are conjugated to SUMO-1. The involvement of SUMO-1/UBC9 in the modification of topoisomerase II isozymes is also supported by the demonstration of physical interaction between topoisomerase II and SUMO-1/UBC9. Surprisingly, ICRF-193, which does not induce topoisomerase II-mediated DNA damage but traps topoisomerase II into a circular clamp conformation, is also shown to induce similar SUMO-1 conjugation to topoisomerase II isozymes. In addition, we show that both oxidative and heat shock stresses, which can cause protein damage, rapidly increase nuclear SUMO-1 conjugates. These studies raise the question on whether SUMO-1 conjugation to topoisomerases is an indirect result of a DNA damage response or a direct result because of protein conformational changes.

DNA Topoisomerases, Type II↗

PubMed2000

p53 dependence of topoisomerase I recruitment in vivo.

DNA damage is attended by rapid recruitment of endogenous type I topoisomerase (topo I) into covalent cleavage complexes with genomic DNA in vivo. In contrast, endogenous topoisomerase II alpha and beta are not stimulated by DNA damage. We show that topo I and p53 are able to associate at arrested topo I-genomic DNA covalent complexes in vivo, suggesting that p53 directly stimulates topo I activity and damage to the genome of the afflicted cell. Moreover, cells that express wild-type p53 are most proficient at recruiting topo I after DNA damage; however, the p53 dependence is conditional because topo I recruitment after DNA damage can be restored if p53 mutant cells (containing a single mutant allele) are artificially held in G1. In contrast, p53 null mutants do not recruit topo I after DNA damage under any conditions (although camptothecin-dependent topo I/DNA complexes readily form in the nulls). These results show that topo I activation after DNA damage depends on the p53 status of the cell. It also depends upon the cell cycle in a way that is very different from that observed with DNA replication-dependent, camptothecin-mediated DNA breaks. The data suggest a model where p53 activates topo I, which inflicts additional genomic damage after the initial UV damage events. Topoisomerases therefore contribute to the p53 commitment to apoptosis, and topo I might assist in elimination of DNA-damaged cells as part of the cellular proofreading function inherent in the p53 pathway.

Antigens, Neoplasm↗

PubMed2000

Application of the thermally tuned tandem column concept to the separation of several families of environmental toxicants.

Separations of several families of environmental toxicants were optimized by means of the thermally tuned tandem column (T3C) concept. We use a tandem combination of an octadecylsilane (ODS) and a carbon-coated zirconia (C-ZrO2) column; and tune the selectivity by independently adjusting the isothermal temperatures of the two columns. This results in the change in the contribution that each column makes to the overall retention and selectivity. The separation was optimized by locating the optimum pair of column temperatures which give the best separation of the critical solute pair. For both triazine herbicides and carbamate pesticides samples, dramatically different selectivities and different critical pairs were observed for the two types of phases. Although neither individual phase gave adequate separation, the T3C approach provided baseline separations using only four preliminary trial separations. We also showed that, for the triazine samples, the T3C approach gave a better separation than did conventional mobile phase optimization with an ODS column. The combination of superior selectivity of T3C and high flow rate allows the baseline separation of complex mixtures in just a few minutes.

Carbamates↗

PubMed2000

Theory of chiral imprinting

We present a continuum model for a nematic elastomer network formed in a chiral environment, for instance, in the presence of a chiral solvent. When this environment is removed, the network can retain some memory of its chiral genesis. We predict the residual chiral order for a number of possible scenarios, and examine the robustness (stability) of the imprinted chirality. We show that a twist-untwist transition can take place, which determines whether the imprinting has been successful. A transition is via a coarsening of the helical director pattern and a lengthening of its pitch. Finally, the effect due to a subsequent swelling by an achiral solvent, or by a solvent of differing chirality, is considered.

Journal Article↗

PubMed2000

SUMO-1 conjugation to topoisomerase I: A possible repair response to topoisomerase-mediated DNA damage.

Ubiquitin/26S proteasome-dependent degradation of topoisomerase I (TOP1) has been suggested to be a unique repair response to TOP1-mediated DNA damage. In the current study, we show that treatment of mammalian cells or yeast cells expressing human DNA TOP1 with camptothecin (CPT) induces covalent modification of the TOP1 by SUMO-1/Smt3p, a ubiquitin-like protein. This conclusion is based on the following observations: (i) Mammalian DNA TOP1 conjugates induced by CPT were cross-reactive with SUMO-1/Smt3p-specific antibodies both in yeast expressing human DNA TOP1 as well as mammalian cells. (ii) The formation of TOP1 conjugates was shown to be dependent on UBC9, the E2 enzyme for SUMO-1/Smt3p. (iii) TOP1 physically interacts with UBC9. (iv) Ubc9 mutant yeast cells expressing human DNA TOP1 was hypersensitive to CPT, suggesting that UBC9/SUMO-1 may be involved in the repair of TOP1-mediated DNA damage.

DNA Damage↗

PubMed2000

Crystal structure of the VHS and FYVE tandem domains of Hrs, a protein involved in membrane trafficking and signal transduction.

We have determined the 2 A X-ray structure of the 219-residue N-terminal VHS and FYVE tandem domain unit of Drosophila Hrs. The unit assumes a pyramidal structure in which the much larger VHS domain (residues 1-153) forms a rectangular base and the FYVE domain occupies the apical end. The VHS domain is comprised of an unusual "superhelix" of eight alpha helices, and the FYVE domain is mainly built of loops, two double-stranded antiparallel sheets, and a helix stabilized by two tetrahedrally coordinated zinc atoms. The two-domain structure forms an exact 2-fold-related homodimer through antiparallel association of mainly FYVE domains. Dimerization creates two identical pockets designed for binding ligands with multiple negative charges such as citrate or phosphatidylinositol 3-phosphate.

Amino Acid Sequence↗

PubMed2000

Adjusting selectivity in liquid chromatography by use of the thermally tuned tandem column concept.

In this study, we propose the novel "thermally tuned tandem column (T3C)" concept for the optimization of selectivity in LC by continuous adjustment of the stationary phase. Two columns with distinctly different chromatographic selectivities (e.g., polybutadiene- and carbon-coated zirconia) are serially coupled and independently temperature-controlled. Selectivity is "tuned" by adjusting the individual temperatures of the two columns. The effect of changing column temperature is quite analogous to changing the relative column lengths, thereby altering the relative and absolute contribution each column makes to the overall retention time in T3C. The distinct selectivity differences between polybutadiene- and carbon-coated zirconia as well as the extraordinary thermal stability of zirconia-based phases (thermally stable to 200 degrees C) allow us to tune the overall chromatographic selectivity over a very substantial range. We have developed a simplified useful model, which characterizes retention and selectivity for the T3C system as a function of the two column temperatures. The model is in good agreement with the experimental results. We also describe a simple computer-assisted optimization strategy based on the window diagram method, which facilitates the optimization of the T3C system with only four or five initial runs.

Chromatography, High Pressure Liquid↗

PubMed2000

Liquid chromatography/electrospray tandem mass spectrometry method for the quantitation of fosinoprilat in human serum using automated 96-well solid-phase extraction for sample preparation.

A sensitive, specific, accurate and reproducible liquid chromatography/electrospray tandem mass spectrometry method was developed and validated for the quantitation of fosinoprilat in 0.2 mL of human serum. The method employed acidification (with pH 4.0 sodium acetate buffer) of the serum samples to minimize the hydrolysis of the prodrug fosinopril to fosinoprilat prior to purification by automated 96-well solid-phase extraction. The required chromatographic separation of fosinoprilat and fosinopril was achieved isocratically on a Luna C8 analytical column (2 x 50 mm, 3 microm). The total run time was 2 min. The mobile phase contained methanol and water with 10 mM ammonium acetate. Detection was by positive ion electrospray tandem mass spectrometry. The standard curve, which ranged from 2.00 to 500 ng/mL, was fitted to a 1/x(2) weighted linear regression model. Fosinoprilat quality control (QC) samples used to determine the accuracy and precision of the method were prepared in human serum at concentrations of 5.00, 200, 400 and 1000 ng/mL. The assay accuracy was within 8% (dev). The intra- and inter-assay precisions were within 6 and 3% (RSD), respectively. Fosinopril QC samples used to gauge the rate of hydrolysis of fosinopril to fosinoprilat during the assay procedure were prepared in human serum at 500 ng/mL. The hydrolysis of fosinopril to fosinoprilat was </=1%. This degree of conversion would cause little error in the analysis of post-dose serum samples since such samples are known to contain low levels of the prodrug compared with the drug.

Analysis of Variance↗

PubMed2000

Factors affecting the severity of motor vehicle traffic crashes involving elderly drivers in Ontario.

A population-based cross-sectional study was conducted to examine factors affecting the severity of motor vehicle traffic crashes (MVTCs) involving elderly drivers in Ontario. The study population included drivers aged 65 and over involved in injury-producing MVTCs between 1988 and 1993 on Ontario public roads. Information was obtained from the Canadian Traffic Accident Information Databank (TRAID) compiled from police reports. The severity of MVTC was classified as fatal, major, minor or minimal. Comparisons between fatal-, major-, minor- and minimal-injury crashes were conducted. Percentage distributions of crashes at each level of severity involving elderly drivers were examined according to specific factors and tested using the X2 test. Multivariate unconditional logistic regression was used to calculate the estimated relative risk as odds ratios (ORs) while controlling for confounding factors. A number of factors were significantly related to the increased risk of fatal-injury in crashes compared with a reference category for each variable. These included age (OR = 1.4 for 70-79 and OR = 2.3 for 80 + ), sex (OR = 1.4 for males), failing to yield right-of-way/disobeying traffic signs (OR = 1.7), non-use of seat belts (OR = 4.0), ejection from vehicle (OR = 11.3), intersection without traffic controls (OR = 1.7), roads with higher speed limits (OR = 7.9 for 70-90 km/h; OR= 5.8 for 100 km/h), snowy weather (OR= 1.6), head-on collisions (OR=55.1), two-vehicle turning collisions (OR = 3.1 for left-turn, OR = 8.7 for right-turn), overtaking (OR = 5.6), and changing lanes (OR = 2.1). Adverse medical/physical conditions increased the risk of fatality by a factor of 5 for drivers 75-79 years of age and a factor of 3.5 for those 80 years and over. However, in the age group 65-74, medical/physical condition did not appear to be related to risk of fatality. Similar but weaker associations between these factors and risk of major- and minor-injury in crashes were also observed. To reduce the severity of crashes involving elderly drivers, strategies could target specific factors such as head-on collisions, single-vehicle collisions, and traffic controls at intersections. Driver conditions such as medical/physical conditions and driver actions such as failing to yield right-of-way/disobeying traffic signs should be examined further.

Accidents, Traffic↗