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Biomedical subjects

R W Li

Publications and source records attributed to R W Li.

13 recordsLinked to original sources
PubMed2001

Variation in vernier evoked cortical potential with age.

PURPOSE: To investigate the effects of age on transient vernier visual evoked potential (VEP) and vernier acuity estimated by extrapolation. METHODS: Transient vernier VEPs were examined in normal subjects aged 20 to 75 years. Vernier offsets were presented for the first 350 msec of the stimulus period, and the segments were then realigned in the following 400 msec. The six vernier offsets used were 20, 40, 60, 80, 100, and 140 seconds of arc. Averaging for each offset setting produced vernier VEP waveforms, for which amplitude and latency of visual evoked response and background electroencephalographic (EEG) noise level were determined. Extrapolation of the function relating signal-to-noise ratio and log vernier offset to a ratio of 1.0 resulted in an estimate of vernier acuity. RESULTS: Amplitude of vernier VEP waveforms was significantly reduced in subjects more than 60 years of age, and the latency to the first negative peak was progressively prolonged with increasing age. There was no statistically significant change in electroencephalographic (EEG) noise with advancing age. VEP vernier acuity was significantly degraded in the 61- to 75-year age group. These results are parallel to recent psychophysical findings that alignment performance is worse in older persons than in younger ones. CONCLUSIONS: The present findings provide the first electrophysiological evidence of age-related cortical degeneration associated with vernier processing. Reduced neural activity probably contributes to the loss of vernier acuity with advancing age. Also provided are the first normative data for subjects of different ages for vernier VEP and VEP vernier acuity. Moreover, the present study has demonstrated that vernier VEP is sensitive to neural changes and therefore may be applied in clinical situations to evaluate the integrity of the visual system.

Adult↗
PubMed2000

Variation in vernier acuity with age.

Many visual functions deteriorate with increasing age, vernier acuity apparently being an exception. We used an improved experimental protocol to investigate vernier thresholds in subjects in four age groups. Vernier threshold was found to increase with increasing age, and the difference in this, compared with previous findings is probably due to the smaller inter-pixel angle used. Vernier acuities in young subjects in other studies seem to have been underestimated. As vernier acuity did not vary with retinal illuminance and the sensitivity loss does not seem to be a learning effect, neural rather than optical changes are likely to account for the deterioration. Measurement of vernier acuity may have clinical application in the determination of visual function behind cataract, and it will be necessary to consider the effect of age on vernier acuity.

Adult↗
PubMed1999

Adhesive solutions: report of a case using multiple adhesive techniques in the management of enamel hypoplasia.

Enamel hypoplasia is a common condition that may present a severe aesthetic problem. Although the teeth affected may not be particularly susceptible to caries, patients may request cosmetic improvement. Adhesive techniques may be useful in such situations. This paper discusses the management of a patient with enamel hypoplasia using a combination of adhesive systems including enamel- and dentine-bonded veneers, dentine-bonded crowns, a cantilever resin-retained bridge, bonded amalgam restorations and chairside tin plating. Where adhesion was contraindicated, conventionally retained crowns were used.

Adult↗
PubMed1996

[The clinical analysis of oral squamous cell carcinoma under age of 40 years old]

44 cases of oral squamous cell carcinoma under 40 years old were analyzed retrospectively.The ratio of male to female was 1.93:1,the youngest was 3,and the majority were within 30-40 years old.The predict site was on the tongue,21 cases shown and accounting for 66.90%.Histologically,the most cases were highly differentiated,accounting for 81092%.About one half cases were present in the terminal clinical stage,and for tongue cancer,terminal stage cases were as high as 61.90%.The patients did not cooperate with treatment very well,only minority could fulfill combined therapy in strict meaning.The recurrence was high and might affected the prognosis.The results were discussed and literatures were reviewed.

Journal Article↗
PubMed1977

Passive immunotherapy for mouse leukemias with antisera of "directed" specificity: synergism with the action of cyclophosphamide.

Antileukemia sera with "directed" specificity are produced by immunization of rabbits with mouse leukemia cells admixed with normal antigen blocking (NAB) serum. Addition of NAB serum to the leukemia cells inhibits production of antibodies to normal cell components and directs specificity toward leukemia cell antigens. The resulting antileukemia serum (ALK-NABS) was not sufficiently potent to produce more than moderate therapy in the standard L1210 leukemia therapy assay. When given together with noncurative doses of cyclophosphamide (CTX), ALK-NABS acts synergistically. It is most effective when given early after injection of the leukemia cells and prior to injection of CTX. Daily repeated injections of a given dose are more effective than a single injection of that dose. Most important, small doses of ALK-NABS produce a significant prolongation of lifespan in conjunction with CTX. Results of therapy for BW-A leukemia with ALK-NABS in conjunction with CTX were negative.

Animals↗
PubMedDate not supplied

The specialty of family dentistry: a future for general dental practitioners?

A new Specialty in dentistry, Family Dentistry, has been established to provide a structured, co-ordinated training for general dental practitioners who are the major oral health service providers. The training emphasizes the importance of continuing and comprehensive care, the interface between primary and secondary care, the relationship between the patient and his/her family and the community, and a holistic approach in treatment planning and delivery.

Comprehensive Dental Care↗