Biomedical subjects

Ying Q Chen

Publications and source records attributed to Ying Q Chen.

4 recordsLinked to original sources

PubMed2005

A non-stationary model for functional mapping of complex traits.

SUMMARY: Understanding the genetic control of growth is fundamental to agricultural, evolutionary and biomedical genetic research. In this article, we present a statistical model for mapping quantitative trait loci (QTL) that are responsible for genetic differences in growth trajectories during ontogenetic development. This model is derived within the maximum likelihood context, implemented with the expectation-maximization algorithm. We incorporate mathematical aspects of growth processes to model the mean vector and structured antedependence models to approximate time-dependent covariance matrices for longitudinal traits. Our model has been employed to map QTL that affect body mass growth trajectories in both male and female mice of an F2 population derived from the Large and Small mouse strains. The results from this model are compared with those from the autoregressive-based functional mapping approach. Based on results from computer simulation studies, we suggest that these two models are alternative to one another and should be used simultaneously for the same dataset.

Aging↗

PubMed2004

Studies relying on passive retrospective cohorts developed from health services data provide biased estimates of incidence of sexually transmitted infections.

OBJECTIVE: Passive retrospective cohorts composed of persons who have tested 2 or more times for a sexually transmitted infection (STI) of interest during clinical visits have been used to estimate STI incidence. We hypothesized that the analytic period of a passive cohort might affect the estimate of STI incidence, with shorter periods yielding higher estimates of incidences of infection. STUDY: We analyzed data collected from women, 12 to 24 years of age, tested for chlamydia 2 or more times at 6 sites in San Francisco between January 1997 and December 2000. Incidence was calculated for 10 different analytic periods. RESULTS: The calculated incidence of chlamydial infection during 1997 was 16.8 (95% confidence interval [CI], 10.9-24.0) per 1000 person-months of follow up. The calculated incidence dropped markedly as the analytic period lengthened, with the incidence estimated to be 9.7 (95% CI, 8.6-10.9) using a study period of 4 years (1997-2000). Estimates of incidence were similar when using the same analytic period, regardless of calendar year, and there was a similar decline in estimated incidence using longer analytic periods. CONCLUSIONS: Estimates of STI incidence based on passive cohort data may have limited epidemiologic value because incidence measures may be highly dependent on the analytic period.

Adolescent↗

PubMed2003

Soft contact lens extended wear affects corneal epithelial permeability: hypoxic or mechanical etiology?

Contact lens extended wear increases the permeability of epithelium to sodium fluorescein (P(dc)). The exact mechanism is not known. However, changes in P(dc) likely result from either corneal hypoxia or mechanical trauma, or both. We explored the effects of one-night continuous wear with either high- or low-Dk/t soft lenses on P(dc). The results show that corneal epithelial barrier function decreases significantly with both lens groups. We also observed that Asian eyes had higher P(dc) after overnight wear compared to non-Asian and that for both Asian and non-Asian eyes, the elimination of corneal hypoxia did not prevent changes in epithelial permeability.

Journal Article↗

PubMed2003

The effects of ocular and lens parameters on the postlens tear thickness.

PURPOSE: To assess the effects of soft contact lens base curve radius (BCR), sex, ethnicity, central corneal curvatures, and vertical palpebral aperture size (PAS) on the postlens tear thickness (PLTT). METHODS: The PLTT was measured using optical pachometry on 114 experienced lens wearers who were fitted with lathe-cut soft lenses (Alden 47, polymacon, 35.5% H2O, -2.00 diopter, and 14.0 mm). Each subject was randomly allocated to one lens group receiving a BCR of 7.9, 8.3, or 8.7 mm. Pachometry measurements were taken at 30 min after lens insertion. Vertical PAS and keratometry readings were measured for 94 of the 114 subjects. RESULTS: The mean (95% confidence interval) PLTT was 15.7 microm (13.2-18.0 microm), 12.8 microm (10.9-14.7 microm), and 12.1 microm (10.2-14.0 microm) for the 7.9-mm, 8.3-mm, and 8.7-mm BCR groups, respectively. The differences in PLTT among the three BCR groups was significant (analysis of variance F-test; P=0.039). Post hoc testing using the Tukey honestly significant difference statistic showed that only the two extreme BCR groups (7.9 mm and 8.7 mm) were significantly different. Sex had no effect on the PLTT; however, the PLTT was significantly thinner for the Asian compared with non-Asian eyes (P=0.0001). The Asian PLTT did not vary with different soft lens BCRs. The non-Asian PLTT was thicker with lenses of the steep BCR compared with the flat BCR. CONCLUSION: These results show that the base curve radius of a soft contact lens and several ocular characteristics can affect the thickness of the postlens tear film.

Adult↗