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Biomedical subjects

Y Yuan

Publications and source records attributed to Y Yuan.

283 records · Page 16Linked to original sources
PubMed1989

Students performance vs. hospital performance in the labor market for medical interns and residents. Do hospitals perform better due to asymmetry in information available to them relative to students?

This paper concerns the labor market for medical interns and residents in the U.S., and in particular, the question of whether the current matching mechanism between graduating medical students and hospitals is 'informationally inefficient'. It was found that overall students performed better than hospital programs in contrast to the common claim that hospitals are more likely to perform better due to seeming superiority in analyzing publicly available information or through access to non-publicly available information. We also conducted a similar analysis for the different specialty programs. In six specialty programs the students' performance was better than hospitals, in two specialty programs the hospitals performance was better than the students and in 14 specialty programs the difference in performance was not statistically different from zero. Thus, only in two cases the hypothesis that the specialty market is informationally inefficient cannot be rejected using the data available. It should be noted that this market is atypical (compared with other labor markets) in that we can test whether it is informationally inefficient by using a practical definition adopted from the field of finance.

Algorithms↗
PubMed1989

Nucleotide and deduced amino acid sequences for the four variable domains of the major outer membrane proteins of the 15 Chlamydia trachomatis serovars.

The amino acid sequences of major outer membrane proteins (MOMPs) from Chlamydia trachomatis serovars A, B, C, L1, and L2 are predominantly conserved but have four variable domains (VDs) in which major neutralizing and serotyping antigenic determinants are located. Because these MOMP VDs are primarily responsible for antigenic differences between serovars and are associated with important immunological and biological properties, we undertook studies focused on defining these sequences within the MOMPs of all 15 C. trachomatis serovars. We used oligonucleotide primer extension sequencing of MOMP mRNA to determine the nucleotide and deduced amino acid sequences of the four MOMP VDs of the 15 C. trachomatis serovars. Comparative amino acid sequence homologies of all four domains separated the serovars into three groups: group 1, serovars B, Ba, D, E, L1, and L2; group 2, serovars G and F; and group 3, serovars A, C, H, I, J, K, and L3. Hydrophilicity and charge values for each domain were determined. The MOMP VDs of given serovars with the greatest total hydrophilicity and charge values were found to be the location of antigenic determinants recognized by MOMP-specific monoclonal antibodies. These findings should be useful for predicting MOMP antigenic determinants and testing the antigenic properties of these VDs by using synthetic peptides corresponding to each MOMP VD. The potential usefulness of the VD sequence information is discussed in relation to the development of defined synthetic peptides and oligonucleotides that may be used to develop new serological and diagnostic assays for C. trachomatis infections.

Amino Acid Sequence↗
PubMed1988

Changes in the rate of haemolysis during the early stage after burns in the rabbit.

The kinetics of erythrocyte haemolysis in blood samples taken from normal and burned rabbits were investigated by nephelometry. The rate of haemolysis decreased significantly from 30 min to 2 h after severe burns, when many abnormal red cell forms were found in blood films; there was also an increase in osmotic fragility. The results confirm that the rate of haemolysis is strongly related to structural changes of the red cell membrane but do not parallel osmotic fragility. Differences in haemolysis rate and osmotic fragility between erythrocytes taken from burned animals and those heated in vitro suggest that erythrocyte changes following burning injury involve complex kinetic processes in which factors other than the direct effect of heat play important roles.

Animals↗
PubMed1987

Rapid purification of arrowhead proteinase inhibitors by high performance hydrophobic interaction chromatography on a PEG bonded phase column.

A new hydrophobic interaction HPLC column is used for the rapid purification of proteinase inhibitors isolated from arrowhead. The inhibitors, partially purified by DEAE-cellulose column chromatography, are resolved into three components with a mobile phase gradient of decreasing salt concentration from 1.1 M ammonium sulfate in 0.01 M phosphate buffer to phosphate buffer alone. This new HPLC column is found to be very useful for rapid, semipreparative purification of hydrophobic protein and sample loading of up to 1.6 mg of inhibitors can be fully resolved on an analytical column.

Amino Acids↗
PubMed1987

Distribution of red cell blood group systems in Yi, Tibetan and Manchu ethnic groups in China.

A survey on distribution of ten red cell blood group systems was carried out in 1985 in the Yi, Tibetan and Manchu nationalities in China. Significant differences were found in the distribution of Rh, MNSs, P and especially in the ABO system, while no significant difference was found for Diego, Duffy, Kell, Kidd and XG systems. The DI*a gene frequency was about 0.03, FY*a rather high (0.94), KEL*K extremely low (0.005) and JK*a was about 0.4. In the three nationalities under study, Yi is characterized by high frequencies of the alleles A, M and CDe and by the absence of CDE and Cde. Tibetans show a high frequency of O and a relatively high frequency of P*P1, while Manchus have the lowest frequency of M and in particular of MS.

Alleles↗
PubMedDate not supplied

Organization of spliceosomal U6 snRNA genes in the mouse genome.

U6 RNA is an abundant small nuclear RNA (snRNA) required for splicing of pre-mRNAs. In mammalian cells, the genes for U1 to U4 snRNAs consist of multigene families ranging from 10 to 100 copies of real genes per haploid genome, and are transcribed by RNA polymerase II. In contrast, results obtained in this study indicate that U6 RNA, which is transcribed by RNA polymerase II and III, may be coded for in mouse cells by only two genes. These two U6 genes are at least 9 kb apart from each other, and the flanking sequences are highly conserved, indicating that the organization of U6 genes is similar to that observed for other mammalian U-snRNA genes.

Animals↗
PubMedDate not supplied

Development of a central matching system for the allocation of cadaveric kidneys: a simulation of clinical effectiveness versus equity.

OBJECTIVES: 1) To develop a computer-based simulation to prospectively study the impacts of explicitly incorporating different equity criteria into the process of allocating kidneys to recipients, given the scarcity of this resource. 2) To assess the tradeoffs between systems that allocate kidneys based only on medical criteria, systems that allocate kidneys based only on equity criteria, and systems that consider both medical and equity criteria. METHODS: A computer-based simulation was developed that describes the flows of patients and kidneys. This model provides information at various time points about the number of patients in the system who are awaiting transplants, the number of kidneys available for transplantation, the number of transplantations performed for each matching algorithm, and the number of kidneys discarded (when applicable), as well as the means and standard deviations of the HLA-match scores, number of days from registration to transplantation, and number of days (from registration) of those who are still waiting for transplants. Five different matching algorithms were compared, ranging from determination of the allocation by a single medical criterion (i.e, HLA match) to determination by a single equity criterion (i.e., relative position in the waiting queue). The remaining algorithms represent different strategies of weighting these two considerations. Estimates regarding the main parameters of the model were derived utilizing data collected through the Multiple Organ Retrieval and Exchange Programme of Ontario, Canada. RESULTS: The simulation was set to run for a period of ten years. A tradeoff between graft survival (or improved HLA matching) and equal treatment of patients regardless of their likelihood to benefit was found. It is clear that an algorithm that allocates kidneys based only on temporal location of patient on the waiting list is likely to be unacceptable because of the very poor average HLA-match scores that it yields. Pool size was found to be a major determinant in the attainment of optimal matching from a medical perspective. CONCLUSIONS: 1) The final choice about any allocation algorithm to be used requires that a value judgment be made, i.e., how great a reduction in HLA-match score should be traded in order to improve equity score (or vice versa). 2) A computer-based simulation model is a feasible way to prospectively test the impact of any given allocation algorithm on any given system.

Algorithms↗
PubMedDate not supplied

A compound sensor for biomechanical analyses of buttock soft tissue in vivo.

A sensor for in vivo biomechanical characterization of buttock soft tissue has been developed and evaluated. The sensor measures interface pressure, applied force, tilt, and rotation angle of the sensor head, and the thicknesses of multiple soft tissue layers. A composite ultrasonic transducer using a 1-3 ceramic-polymer structure was developed for the sensor. The sensor can identify subcutaneous soft tissue interfaces 5 to 65 mm below the skin surface with a 0.26-mm axial resolution, pressure over the range of 0 to 68 kPa, and force over the range of 0 to 3.6 kg. Our purpose for developing the sensor was to study the biomechanical characteristics of buttock soft tissues. Successful identification of distinguishing characteristics in persons with a susceptibility to pressure ulcers may result in the development of a risk assessment tool based on tissue characterization.

Biomechanical Phenomena↗