Biomedical subjects

Dingcai Cao

Publications and source records attributed to Dingcai Cao.

13 recordsLinked to original sources

PubMed2006

Efficacy of naltrexone in smoking cessation: a preliminary study and an examination of sex differences.

This double-blinded, placebo-controlled trial evaluated the efficacy of naltrexone as an adjunct to standard smoking cessation treatment. Participants (N = 110) were adult male and female nicotine-dependent smokers who expressed interest in quitting smoking. All subjects received six sessions of behavioral counseling (1 hr/session for 6 weeks), and 1 month of the nicotine patch (21 mg for the first 2 weeks, 14 mg the third week, 7 mg the fourth week). Subjects were randomly assigned to the naltrexone or placebo group. The naltrexone group started at 25 mg daily for 3 days prior to the quit date, and increased to 50 mg/day on the quit date and following 8 weeks. At the end of medication treatment, the naltrexone group had better quit rates versus the placebo group (48% quit on naltrexone vs. 41% on placebo), but this difference was not statistically significant. However, men and women differed on several measures: in the placebo group, women had significantly lower quit rates than men (39% vs. 67%, p<.05), but in the naltrexone group, women had quit rates comparable with those of men (58% vs. 62%, p = ns). Further examination revealed that naltrexone significantly reduced men's and women's cessation-related weight gain and selectively reduced women's urge to smoke to relieve negative affect and withdrawal. The results suggest continued examination of naltrexone as an adjunct in smoking cessation, particularly in female smokers, who have historically shown worse outcomes with traditional treatment methods.

Adult↗

PubMed2005

Chromatic assimilation measured by temporal nulling.

Chromatic assimilation is the shift in color appearance toward nearby light. Assimilation was measured using nearby light with time-varying chromaticity. This light induced time-varying assimilation within the test area. Assimilation was quantified by the amplitude of temporally varying test-area light--in counter-phase to the induced assimilation--required to null the assimilation. Unlike previous studies of assimilation, observers here judged only the steadiness of the test area, not its color. The inducing light was varied in luminance, temporal frequency and chromaticity. The measured assimilation could not be explained by only optical factors affecting receptoral quantal absorption. This implies a neural process contributes to assimilation. The nulling measurements showed also that assimilation was not induced independently within the L/M- and S-cone pathways.

Adult↗

PubMed2005

Associating color appearance with the cone chromaticity space.

A cone chromaticity space, a transform of a colorimetric specification system into coordinates that represent cone excitations, does not provide color appearance information. Boynton and Olson (Color Research and Application 12, 94-105, 1987) gathered color naming for the 424 Optical Society of America Uniform Color Scales (OSA-UCS) color samples. Here, a computational algorithm was developed that converts OSA-UCS sample values into L, M, S cone excitations based on the 1964 CIE 10 degrees Standard Observer. This makes it possible to plot the cone chromaticities associated with the eight color names used by Boynton and Olsen's observers to describe the non-dark appearing colors.

Algorithms↗

PubMed2005

Matching rod percepts with cone stimuli.

Traditional methods for studying the effects of rod activity on color vision make it hard to assess the underlying physiological mechanisms. In this study, rod-mediated changes in color appearance were assessed by matching them with cone-mediated color changes. A four-primary photostimulator allowed independent control of rod and cone stimulation and identification of the cone types that generate color sensations equivalent to rod color sensations. The results showed that increases in rod stimulation required matches with cone stimuli that excited M-cones more than L-cones for all conditions. Matches for low-luminance conditions also required some S-cone stimulation. A subsidiary experiment showed that increases in rod modulation of an inducing field produced chromatic contrast effects like those produced by the M-cone system. The data are consistent with a hypothesis of perceptual normalization of scotopic vision to the chromatic appearance of objects under photopic conditions.

Color Perception↗

PubMed2004

Chromatic assimilation: spread light or neural mechanism?

Chromatic assimilation is the shift in color appearance of a test field toward the appearance of nearby light. Possible explanations of chromatic assimilation include wavelength independent spread light, wavelength-dependent chromatic aberration and neural summation. This study evaluated these explanations by measuring chromatic assimilation from a concentric-ring pattern into an equal-energy-white background, as a function of the inducing rings' width, separation, chromaticity and luminance. The measurements showed, in the s direction, that assimilation was observed with different inducing-ring widths and separations when the inducing luminance was lower or higher than the test luminance. In general, the thinner the inducing rings and the smaller their separation, the stronger the assimilation in s. In the l direction, either assimilation or contrast was observed, depending on the ring width, separation and luminance. Overall, the measured assimilation could not be accounted for by the joint contributions from wavelength-independent spread light and wavelength-dependent chromatic aberration. Spatial averaging of neural signals explained the assimilation in s reasonably well, but there were clear deviations from neural spatial averaging for the l direction.

Adult↗

PubMed2004

Fetal loss associated with excess thyroid hormone exposure.

CONTEXT: Maternal hypothyroidism and hyperthyroidism have deleterious effects on the outcome of pregnancy. While the effects of thyroid hormone (TH) deprivation on the fetus, independently from that on the mother, can be studied in infants with congenital hypothyroidism, this is not the case in those with fetal thyrotoxicosis. OBJECTIVE: To study the effects of TH excess on fetuses carried by mothers with resistance to TH (RTH) who are euthyroid despite high TH levels but who may carry normal fetuses that are exposed to high maternal hormone levels. DESIGN, SETTING, AND PARTICIPANTS: Retrospective study of 167 members of an Azorean family with RTH. Affected individuals had the RTH phenotype (high serum concentration of free thyroxine and triiodothyronine without suppressed thyrotropin) confirmed by genotyping to identify the Arg243-->Gln mutation in the TH receptor beta gene. MAIN OUTCOME MEASURES: Pregnancy outcome of affected mothers vs that of unaffected mothers carrying fetuses conceived by affected fathers, as well as that of unaffected first-degree relatives and outcomes from the general island population. Comparison of birth weights and blood concentrations of thyrotropin (TSH) obtained during routine neonatal screening of infants born to these 3 groups. RESULTS: Thirty-six couples with complete information belonged to 1 of 3 groups: affected mothers (n = 9), affected fathers (n = 9), and unaffected relatives (n = 18). Mean miscarriage rates were 22.9%, 2.0%, and 4.4%, respectively (chi2 = 8.66, P =.01). Affected mothers had an increased rate of miscarriage (z = 3.10, P =.002, by Wilcoxon rank-sum test). They had marginally higher than expected numbers of affected offspring, ie, 20 affected and 11 unaffected children (P =.07), while affected fathers had 15 affected and 12 unaffected children (P =.35). Unaffected infants born to affected mothers were significantly smaller than affected infants, having a mean SD score for gestational age of -1.79 (SD, 0.86) vs -0.06 (SD, 1.11) to -0.22 (SD, 0.70) for all other groups (P<.001). Only unaffected infants born to affected mothers had undetectable blood levels of TSH. CONCLUSION: There was a higher rate of miscarriage in mothers affected by RTH that may have involved predominantly unaffected fetuses. The lower birth weight and suppressed levels of TSH in unaffected infants born to affected mothers indicates that the high maternal TH levels produce fetal thyrotoxicosis. These data indicate a direct toxic effect of TH excess on the fetus.

Abortion, Spontaneous↗

PubMed2004

A randomized Phase II trial of the antiangiogenic agent SU5416 in hormone-refractory prostate cancer.

PURPOSE: To assess the activity of the antiangiogenic agent and VEGFR2 inhibitor SU5416 in hormone-refractory prostate cancer. PATIENTS AND METHODS: Thirty-six chemotherapy naïve patients were randomized to treatment with SU5416 (145 mg/m(2)) and dexamethasone premedication or dexamethasone alone. Patients in the control arm could cross over to experimental therapy after progression. Prostate-specific antigen (PSA) was measured every 2 weeks, and radiological evaluation was performed every 8 weeks. In vitro assessment of SU5416 on PSA secretion was assessed in the LNCaP cell line. Baseline serum basic fibroblast growth factor and plasma vascular endothelial growth factor (VEGF) were explored as prognostic factors. RESULTS: VEGF receptor-2 expression is detectable in prostate cancer cell lines, and SU5416 inhibited in vitro PSA secretion. No effect of SU5416 on PSA secretion or time to progression is detectable in patients. VEGF and basic fibroblast growth factor were not prognostic. Headache and fatigue were the most common SU5416 toxicities, but hyperglycemia, hyponatremia, lymphopenia, infection, and adrenal suppression, all attributable to steroids and the required central line, were common. CONCLUSION: No disease modifying effects of SU5416 were detectable in this small study. Modest toxicity, an inconvenient administration schedule, and availability of other VEGFR-targeted agents support the decision to halt further evaluation of SU5416 in prostate cancer.

Aged↗

PubMed2004

Gender differences in the impact of comprehensive services in substance abuse treatment.

This study examines the impact of comprehensive services on treatment outcomes for women and men. The study uses data collected from 1992 to 1997 for the National Treatment Improvement Evaluation Study, a prospective, cohort study of substance abuse treatment programs and their clients. The analytic sample consists of 3,142 clients (1,123 women and 2,019 men) from 59 treatment facilities. The results show that substance abuse treatment benefits both women and men. Further, both women and men benefit from comprehensive services provided as part of substance abuse treatment: specifically, the receipt of educational, housing and income support services is related to reduced post-treatment substance abuse for both women and men. Gender differences are revealed by the fact that, overall, greater proportions of women receive services and, when individual, service, and treatment organizational characteristics are controlled, women show greater reductions in post-treatment substance use. Further, women and men differ in their responsiveness to organizational characteristics: the availability of on-site services and the frequency of counseling significantly predict reduced post-treatment substance use for men but not for women.

Adolescent↗

PubMed2004

Recovery from sleep deprivation occurs during propofol anesthesia.

BACKGROUND: Some neurophysiologic similarities between sleep and anesthesia suggest that an anesthetized state may reverse effects of sleep deprivation. The effect of anesthesia on sleep homeostasis, however, is unknown. To test the hypothesis that recovery from sleep deprivation occurs during anesthesia, the authors followed 24 h of sleep deprivation in the rat with a 6-h period of either ad libitum sleep or propofol anesthesia, and compared subsequent sleep characteristics. METHODS: With animal care committee approval, electroencephalographic/electromyographic electrodes and intrajugular cannulae were implanted in 32 rats. After a 7-day recovery and 24-h baseline electroencephalographic/electromyographic recording period, rats were sleep deprived for 24 h by the disk-over-water method. Rats then underwent 6 h of either propofol anesthesia (n = 16) or ad libitum sleep with intralipid administration (n = 16), followed by electroencephalographic/electromyographic monitoring for 72 h. RESULTS: In control rats, increases above baseline in non-rapid eye movement sleep, rapid eye movement sleep, and non-rapid eye movement delta power persisted for 12 h after 24 h of sleep deprivation. Recovery from sleep deprivation in anesthetized rats was similar in timing to that of controls. No delayed rebound effects were observed in either group for 72 h after deprivation. CONCLUSION: These data show that a recovery process similar to that occurring during naturally occurring sleep also takes place during anesthesia and suggest that sleep and anesthesia share common regulatory mechanisms. Such interactions between sleep and anesthesia may allow anesthesiologists to better understand a potentially important source of variability in anesthetic action and raise the possibility that anesthetics may facilitate sleep in environments where sleep deprivation is common.

Anesthesia Recovery Period↗

PubMed2004

Delayed radioprotection by NFkappaB-mediated induction of Sod2 (MnSOD) in SA-NH tumor cells after exposure to clinically used thiol-containing drugs.

The ability of thiol-containing reducing agents to activate transcription factors leading to changes in gene expression and enzyme activities provides an additional mechanism to potentially protect against radiation-induced cell killing. Manganese superoxide dismutase (Sod2) is one such gene whose expression levels have been shown to be elevated after exposure to the thiol compounds WR-1065 and N-acetyl-L-cysteine (NAC), resulting in an increase in radiation resistance. To further characterize this effect, SA-NH sarcoma cells, both wild-type and a clone stably transfected with a plasmid containing an IkappaBalpha gene mutated at serines 32 and 36, which prevents the inducible phosphorylation of these residues and the subsequent activation of NFkappaB (SA-NH+mIkappaBalpha1), were grown to confluence and then exposed to amifostine's free thiol WR-1065 at a concentration of 4 mM for 30 min. Effects of thiol exposure on NFKB activation in SA-NH+mIkappaBalpha1 cells were determined by a gel shift assay, and changes in Sod2 protein levels in these cells 24 h after exposure to 40 microM or 4 mM WR-1065 were measured by Western blot analysis and compared with wild-type cells exposed to the NFkappaB inhibitor BAY 11-7082. Changes in radiation response, measured immediately after thiol exposure or 24 h later, were determined using a colony-forming assay and were correlated with NFKB activation and Sod2 protein levels. The effects of captopril, mesna and NAC, each at a dose of 4 mM, on radiation response were also determined and contrasted with those of WR-1065. Only WR-1065 and captopril protected SA-NH cells when present during irradiation, i.e. 1.57 and 1.31 times increase in survival at 2 Gy, respectively. All four thiols were protective if irradiation with 2 Gy occurred 24 h later; i.e. increases in survival of 1.40, 1.22, 1.35, and 1.25 times were found for WR-1065, captopril, mesna and NAC, respectively. This delayed radioprotective effect correlated with elevated Sod2 protein levels in wild-type SA-NH tumor cells but was not observed in SA-NH+mIkappaBalpha1 cells, indicating that interference with thiol-induced NFKB activation abrogates this delayed radioprotective effect. Because the delayed radioprotective effect is readily demonstrable at a radiation dose of 2 Gy 24 h after exposure to clinically approved thiol-containing drugs such as amifostine, captopril, mesna and NAC, it suggests a new potential concern regarding the issue of tumor protection and the use of these agents in cancer therapy.

Acetylcysteine↗

PubMedDate not supplied

Chromatic assimilation unaffected by perceived depth of inducing light.

Chromatic assimilation is a shift toward the color of nearby light. Several studies conclude that a neural process contributes to assimilation but the neural locus remains in question. Some studies posit a peripheral process, such as retinal receptive-field organization, while others claim the neural mechanism follows depth perception, figure/ground segregation, or perceptual grouping. The experiments here tested whether assimilation depends on a neural process that follows stereoscopic depth perception. By introducing binocular disparity, the test field judged in color was made to appear in a different depth plane than the light that induced assimilation. The chromaticity and spatial frequency of the inducing light, and the chromaticity of the test light, were varied. Chromatic assimilation was found with all inducing-light sizes and chromaticities, but the magnitude of assimilation did not depend on the perceived relative depth planes of the test and inducing fields. We found no evidence to support the view that chromatic assimilation depends on a neural process that follows binocular combination of the two eyes' signals.

Calibration↗

PubMedDate not supplied

Dark-adapted rod suppression of cone flicker detection: Evaluation of receptoral and postreceptoral interactions.

Dark-adapted rods in the area surrounding a luminance-modulated field can suppress flicker detection. However, the characteristics of the interaction between rods and each of the cone types are unclear. To address this issue, the effect that dark-adapted rods have on specific classes of receptoral and postreceptoral signals was determined by measuring the critical fusion frequencies (CFF) for receptoral L-, M-, and S-cone and postreceptoral luminance ([L+M+S] and [L+M+S+Rod]) and chromatic ([L/(L+M)]) signals in the presence of different levels of surrounding rod activity. Stimuli were generated with a two-channel photostimulator that has four primaries for a central field and four primaries for the surround, allowing independent control of rod and cone excitation. Measurements were made either with adaptation to the stimulus field after dark adaptation or during a brief period following light adaptation. The results show that dark-adapted rods maximally suppressed the CFF by approximately 6 Hz for L-cone, M-cone, and luminance modulation. Dark-adapted rods, however, did not significantly alter the S-cone CFF. The [L/(L+M)] postreceptoral CFF was slightly suppressed at higher surround illuminances, that is, higher than surround luminances resulting in suppression for L-cone, M-cone, or luminance modulation. We conclude that rod-cone interactions in flicker detection occurred strongly in the magnocellular pathway.

Color Perception↗

PubMedDate not supplied

The color of night: Surface color perception under dim illuminations.

Several studies document rudimentary color vision under dim illumination. Here, hue perceptions of paper color samples were determined for a wide range of light levels, including very low light levels where rods alone mediate vision. The appearances of 24 paper color samples from the OSA Uniform Color Scales were gauged under successively dimmer illuminations from 10-0.0003 Lux. Triads of samples were chosen representing each of eight basic color categories; red, pink, orange, yellow, green, blue, purple, and gray. Samples within each triad varied in lightness. Observers sorted samples into groups that they could categorize with specific color names. Above 0.32 Lux, observers sorted the samples into the originally chosen color groups with few exceptions. For 0.1-0.01 Lux, the red and orange samples were usually correctly identified as either red or orange. The remaining samples tended to be grouped into two categories, associated with the scotopic sample reflectance. The lowest reflectance samples were below threshold and were named black. The higher reflectance group was named predominately as green or blue-green (three observers; the fourth observer used blue or achromatic). At the three dimmest levels (< or = 0.0032 Lux) there continued to be conspicuous color percepts. Color categories were reliably assigned based on relative sample scotopic lightness. Of the samples above threshold, those with lower reflectance were classified as red or orange (all observers) and the higher reflectance samples as green or blue-green (three observers) or achromatic or blue (the fourth observer). Rods and L-cones presumably mediated color percepts at the intermediate light levels used in the study. At the three lowest light levels there were distinct color appearances mediated exclusively by rods. We speculate that at these light levels the visual system estimates probable colors based on prior natural experience.

Color↗