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Biomedical subjects

C R Liu

Publications and source records attributed to C R Liu.

At least 19 recordsLinked to original sources
PubMed2002

Heritability of subclinical atherosclerosis in Latino families ascertained through a hypertensive parent.

Although clinical coronary heart disease and many cardiovascular risk factors are well known to aggregate within families, the heritability of carotid artery intima-media thickness (IMT) is less well documented. We report IMT heritability estimates in Mexican American, Salvadoran American, or Guatemalan American (all referred to as Latino) families ascertained through a hypertensive proband. IMT and cardiovascular risk factors (age, sex, blood pressure, body mass index, lipids, fasting glucose, and insulin sensitivity) were measured in 204 adult offspring of 69 hypertensive probands, along with 82 parents (54 probands and 28 spouses). In the offspring, variance component analysis revealed a heritability for IMT of 64% (P< 0.0001) after adjustment for significant cardiovascular risk factors. Genetic factors accounted for 50% of the total variation in IMT, whereas significant cardiovascular risk factors explained 22% (14% were due to age). For offspring and parents combined, adjusted IMT heritability was less, 34% (P=0.0005), with genetic factors accounting for 18% of the total IMT variation, whereas significant cardiovascular risk factors explained 46% (38% were due to age). We conclude that variation in common carotid artery IMT is heritable in Latino families with a hypertensive proband. Heritability is particularly evident in younger family members, suggesting that acquired factors contribute progressively to IMT variability with aging.

Adolescent↗
PubMed1999

Characterization of differentially expressed genes in purified Drosophila follicle cells: toward a general strategy for cell type-specific developmental analysis.

Axis formation in Drosophila depends on correct patterning of the follicular epithelium and on signaling between the germ line and soma during oogenesis. We describe a method for identifying genes expressed in the follicle cells with potential roles in axis formation. Follicle cells are purified from whole ovaries by enzymatic digestion, filtration, and fluorescence-activated cell sorting (FACS). Two strategies are used to obtain complementary cell groups. In the first strategy, spatially restricted subpopulations are marked for FACS selection using a green fluorescent protein (GFP) reporter. In the second, cells are purified from animals mutant for the epidermal growth factor receptor ligand gurken (grk) and from their wild-type siblings. cDNA from these samples of spatially restricted or genetically mutant follicle cells is used in differential expression screens employing PCR-based differential display or hybridization to a cDNA microarray. Positives are confirmed by in situ hybridization to whole mounts. These methods are found to be capable of identifying both spatially restricted and grk-dependent transcripts. Results from our pilot screens include (i) the identification of a homologue of the immunophilin FKBP-12 with dorsal anterior expression in egg chambers, (ii) the discovery that the ecdysone-inducible nuclear hormone receptor gene E78 is regulated by grk during oogenesis and is required for proper dorsal appendage formation, and (iii) the identification of a Drosophila homologue of the human SET-binding factor gene SBF1 with elevated transcription in grk mutant egg chambers.

Animals↗
PubMed1998

The role of carotid arterial intima-media thickness in predicting clinical coronary events.

BACKGROUND: Carotid arterial intima-media thickness is used as a noninvasive surrogate end point to measure progression of atherosclerosis, but its relation to coronary events has not been fully explored. OBJECTIVE: To determine whether carotid arterial intima-media thickness predicts coronary events. DESIGN: Long-term follow-up (average, 8.8 years) of a previously assembled cohort of persons who completed the 2-year Cholesterol Lowering Atherosclerosis Study, a randomized arterial imaging trial designed to study the effects of lipid lowering on progression of atherosclerosis. SETTING: University-based ultrasonography laboratory. PATIENTS: 146 men 40 to 59 years of age who had previously had coronary artery bypass graft surgery. MEASUREMENTS: Preintrusive atherosclerosis in the common carotid artery was evaluated every 6 months with B-mode ultrasonography, and intrusive atherosclerosis in the coronary arteries was evaluated at baseline and at 2 years with quantitative coronary angiography. After the trial, the incidences of coronary events (nonfatal acute myocardial infarction, coronary death, and coronary artery revascularization) were documented. RESULTS: For each 0.03-mm increase per year in carotid arterial intima-media thickness, the relative risk for nonfatal myocardial infarction or coronary death was 2.2 (95% CI, 1.4 to 3.6) and the relative risk for any coronary event was 3.1 (CI, 2.1 to 4.5) (P < 0.001). Absolute intima-media thickness was also related to risk for clinical coronary events (P < 0.02). Absolute thickness and progression in thickness predicted risk for coronary events beyond that predicted by coronary arterial measures of atherosclerosis and lipid measurements (P < 0.001). CONCLUSION: Noninvasive B-mode ultrasonographic measurement of progression of intima-media thickness in the distal common carotid artery is a useful surrogate end point for clinical coronary events.

Adult↗
PubMed1998

Photon beam skin dose analyses for different clinical setups.

A comprehensive set of data on skin dose for 8 MV and 18 MV photon beams from a medical linear accelerator was measured using a parallel-plate chamber to document the effect of field size, source-to-surface distance (SSD), off-axis distance, acrylic block tray, wedge (external standard wedge), Lipowitz's metal block, multileaf collimator (MLC), and dynamic wedge. The skin dose increased as field size increased from 5 X 5 cm2 to 40 X 40 cm2 (6% to 38% for 8 MV and 5% to 44% for 18 MV beam). With the use of an acrylic block tray, the skin dose increased for all field sizes (7% to 59% for 8 MV and 5% to 62% for 18 MV beam), but the increase was minimal for small fields. The skin dose with a wedge showed a much more complex trend. It was generally lower than the dose for an open field, but higher in the case of large fields and higher degree wedges. When both wedge and block tray were used, the tray was a major contributor to the skin dose because some of the contaminant electrons from the wedge assembly were absorbed by the block tray. Field-shaping blocks increased the skin dose, but, interestingly, the block tray reduced the skin dose for small blocked fields treated with a high-energy photon beam. The effect of an MLC on skin dose was very similar to that of a Lipowitz's metal block, but its magnitude was less. The skin dose was higher for dynamic wedge fields than it was for standard wedge fields. As SSD decreased, the skin dose increased, and this effect was dominant in larger field sizes. The SSD effect was enhanced in the presence of an acrylic block tray. The skin dose off-axis was the same as at the central axis, or smaller. A similar pattern of behavior of the skin dose is expected for photon beams from other linear accelerators.

Acrylic Resins↗
PubMed1997

Performance evaluation of a diode array for enhanced dynamic wedge dosimetry.

The performance of a diode array (Profiler) was evaluated by comparing its enhanced dynamic wedge (EDW) profiles measured at various depths with point measurements using a 0.03 cm3 ionization chamber on a commercial linear accelerator. The Profiler, which covers a 22.5 cm width, was used to measure larger field widths by concatenating three data sets into a larger field. An innovative wide-field calibration technique developed by the manufacturer of the device was used to calibrate the individual diode sensitivity, which can vary by more than 10%. Profiles of EDW measured with this device at several depths were used to construct isodose curves using the percentage depth dose curve measured by the ionization chamber. These isodose curves were used to check those generated by a commercial treatment planning system. The profiles measured with the diode array for both 8 and 18 MV photon beams agreed with those of the ionization chamber within a standard deviation of 0.4% in the field (defined as 80% of the field width) and within a maximum shift of less than 2 mm in the penumbra region. The percentage depth dose generally agreed to within 2% except in the buildup region. The Profiler was extremely useful as a quality assurance tool for EDW and as a dosimetry measurement device with tremendous savings in data acquisition time.

Humans↗
PubMed1997

[Studies on characteristics of proliferation and differentiation of hematopoietic stem cells in mice].

By using Y chromosome specific sex-determining region (Sry) as a new cytogenetic marker and PCR technique, the characteristics of proliferation and differentiation of hematopoietic stem cells in mice were studied. Bone marrow cells from male mice were injected into lethally-irradiated female mice, PCR results indicated that all of the CFU-S were originated from donor. It was found that CFU-S was able to proliferate and differentiate into various hematopoietic cells in vivo during its transplantation. Whereas the fibroblasts within donor CFU-S and the fibroblasts from bone marrow in recipient mouse reestablished by donor CFU-S were shown to be originated from the recipient. The above data demonstrated that CFC-S from bone marrow in mice possessed the characteristics of hematopoietic stem cells but was not prone to differentiate into fibroblasts.

Animals↗
PubMed1996

Effect of supplementary antioxidant vitamin intake on carotid arterial wall intima-media thickness in a controlled clinical trial of cholesterol lowering.

BACKGROUND: There is accumulating experimental, epidemiological, and clinical evidence of an association between anti-oxidant vitamin intake and reduced risk of coronary heart disease. Using data from the Cholesterol Lowering Atherosclerosis Study (CLAS), we explored the association of self-selected supplementary antioxidant vitamin intake on the rate of progression of early preintrusive atherosclerosis. METHODS AND RESULTS: CLAS was an arterial imaging trial in which nonsmoking 40- to 59-year-old men with previous coronary artery bypass graft surgery were randomized to colestipol/niacin plus diet or placebo plus diet. The rate of progression of early preintrusive atherosclerosis was determined in 146 subjects using high-resolution B-mode ultrasound quantification of the distal common carotid artery far wall intima-media thickness (IMT). From the nutritional supplement database, 22 subjects had an on-trial average supplementary vitamin E intake of > or = 100 IU per day (high users) and 29 subjects had an average on-trial supplementary vitamin C intake of > or = 250 mg per day (high users). Within the placebo group, less carotid IMT progression was found for high supplementary vitamin E users when compared with low vitamin E users (0.008 versus 0.023 mm/y, P = .03). No effect of vitamin E within the drug group was found. No effect of vitamin C within the drug or placebo group was found. CONCLUSIONS: Supplementary vitamin E intake appears to be effective in reducing the progression of atherosclerosis in subjects not treated with lipid-lowering drugs while the process is still confined to the arterial wall (early preintrusive atherosclerosis).

Adult↗
PubMed1994

Evaluation of computerized edge tracking for quantifying intima-media thickness of the common carotid artery from B-mode ultrasound images.

A new method to measure carotid intima-media thickness (IMT) from B-mode ultrasound images was developed that utilizes automatic tracking of the lumen-intima and media-adventitia echoes. Phantom studies and human replicate studies under typical clinical protocols for common carotid IMT measurement were carried out to assist in evaluation of the method. A lucite step wedge phantom was used to show that incorporation of sub-pixel interpolation to locate echo boundaries allowed detection of changes in the echo separation that were 5-10 times smaller than the axial resolution of the ultrasound transducer. For average IMT measured in the distal common carotid artery (CCA) wall in 24 subjects scanned twice within 60 days, mean absolute difference was 0.036 mm with a standard deviation of 0.045 mm. Replicate scans obtained 1 week apart of eight subjects by three sonographers showed the intersonographer variability was 5.4%. In another study of 12 subjects scanned every 4 months for 48 months, the root mean square deviation of the IMT measurements from a linear regression line was 0.030 mm. These data indicate that the method is equally precise over short intervals (60 days) and over long intervals (48 months). The new automated computerized edge tracking method presented in this paper represents an advance for image analysis of B-mode ultrasound images of common carotid IMT with measurement variability substantially reduced (2 to 4 times) compared with currently available manual methods.

Adult↗
PubMed1993

Beneficial effects of colestipol-niacin therapy on the common carotid artery. Two- and four-year reduction of intima-media thickness measured by ultrasound.

BACKGROUND: Controlled clinical trials have reported treatment effects evaluated with serial imaging in coronary and femoral but not cervical arteries. The Cholesterol Lowering Atherosclerosis Study, a coronary, cervical, and femoral angiographic trial of colestipol plus niacin, included a pilot study of standardized carotid ultrasound imaging. METHODS AND RESULTS: Seventy-eight subjects had ultrasound studies at baseline, 2, and 4 years. Twenty-four drug and 22 placebo subjects had carotid ultrasound images at baseline, 2, and 4 years with matching cervical angiograms. Computer image processing was applied to ultrasound images of common carotid (far wall) and cervical angiograms. Computer operators were blind to treatment group. Carotid ultrasound measurements were tested for treatment effects and compared with measurements of atherosclerosis in coronary and cervical angiograms. Drug subjects showed significant progressive reduction in carotid thickness at 2 (P = .0001) and 4 years (P = .0001); placebo subjects significantly increased wall thickness at 2 and 4 years. Reduced levels of apolipoprotein B and increased levels of high density lipoprotein cholesterol and apolipoprotein C-III were significant predictors of carotid wall thinning. Ultrasound-measured carotid intima-media thickness was correlated at baseline with visually read coronary angiographic stenosis and at 2 years with a robust computer measurement of mild carotid atherosclerosis. CONCLUSIONS: Common carotid intima-media thickening can be reduced by colestipol-niacin treatment. Two-year image-processed carotid ultrasound trials can provide adequate power with 50 subjects per group to test for this treatment effect.

Adult↗
PubMed1993

One-year reduction and longitudinal analysis of carotid intima-media thickness associated with colestipol/niacin therapy.

BACKGROUND AND PURPOSE: The Cholesterol Lowering Atherosclerosis Study has reported significant reduction of coronary artery disease and of carotid arterial intima-media thickness (IMT) at 2 and 4 years with colestipol/niacin therapy. We now report on treatment effects on carotid IMT at 6 months and 1 year. METHODS: One hundred eighty-eight nonsmoking men, aged 40 to 59 years, with prior coronary artery bypass graft surgery were randomized to colestipol/niacin plus diet therapy or placebo plus diet therapy. Computerized image processing of carotid ultrasound films was used to measure IMT in the right common carotid artery. Treatment group comparisons were made at 6 months and 1 year (46 and 33 subjects, respectively, with baseline and 6-month or 1-year ultrasound measures). The time course of the treatment effect on carotid IMT was estimated using the complete sample of 78 subjects with baseline and on-trial data. RESULTS: No significant treatment group differences on carotid IMT were found at 6 months. At 1 year, the treated group showed significant reduction of carotid IMT (P = .01 between groups). The placebo group showed continuing progression of IMT during the 4-year study period (estimated progression rate, 0.018 mm/y). The treated group showed reduction of IMT during the first 3 years and a plateau during the remainder of the study. CONCLUSIONS: Reduction of carotid IMT was found with aggressive lipid-lowering therapy. Ultrasound measures of IMT offer a noninvasive and precise measure of early carotid atherosclerosis that will decrease sample size requirements, potentially decrease dropout rates, and widen the study population of antiatherosclerotic clinical trials.

Adult↗
PubMed1991

Deleted HTLV-I provirus in blood and cutaneous lesions of patients with mycosis fungoides.

Mycosis fungoides, a rare form of cutaneous T cell leukemia/lymphoma, is suspected of having a viral etiology on the basis of certain similarities to adult T cell leukemia, which is associated with human T cell leukemia/lymphoma virus type I (HTLV-I) infection. Cell lines were established from peripheral blood mononuclear cells (PBMC) of an HTLV-I-seronegative patient with mycosis fungoides. DNA hybridization analysis revealed the presence of HTLV-I-related sequences with unusual restriction endonuclease sites. Sequence analysis of subcloned fragments demonstrated the presence of a monoclonally integrated provirus with a 5.5-kilobase deletion involving large regions of gag and env and all of pol. Additional evidence for the presence of deleted proviruses was found by polymerase chain reaction (PCR) amplification of DNA from cutaneous lesions of five other HTLV-I-seronegative patients. The findings suggest that HTLV-I infection may be involved in the etiology of at least certain cases of mycosis fungoides.

Base Sequence↗
PubMed1990

Very early aortic responses during atherosclerosis induction in rabbits: measurement by duplex ultrasound. I. Non-invasive study of aortic hyperresponsiveness to serotonin.

We report the use of a non-invasive ultrasound method to visualize and measure changes in serotonin reactivity of the abdominal aorta during the early stages of atherosclerosis development. Studies were performed at 0, 4, 8, and 14 weeks in New Zealand white rabbits fed a diet enriched with 0.5% cholesterol. Change in systolic vessel diameter at each examination was compared with changes in rabbits fed a control diet or rabbits on a diet enriched with cholesterol plus a concentrated marine lipid. After 4 weeks on the diets, the abdominal aortae of rabbit fed the cholesterol-rich diet displayed an enhanced vasoconstriction to serotonin (P less than 0.01). The enhanced vasoconstriction was observed prior to visible morphologic changes, and progressed when restudied at succeeding examinations. Morphologic abnormalities became evident at 8 weeks in cholesterol-fed animals. Dietary supplementation with marine lipid, rich in polyunsaturated fatty acids, diminished the effect of the atherogenic diet on aortic vasoconstriction.

Animals↗
PubMed1988

Clinical and serological features of human herpesvirus-6 infection in three adults.

3 adult patients with serological evidence of human herpesvirus-6 (HHV-6) infection had mild, afebrile illnesses with nonspecific symptoms. In each case, the characteristic clinical feature was the presence of enlarged, bilateral, non-tender, anterior and posterior cervical nodes early in the illness which persisted for up to 3 months. HHV-6 IgG antibody reciprocal titres of 160 to 2560 were found during acute infection, and decreased to a titre of 10 in 1 patient 3 years later. IgM responses were detected at low reciprocal titres (10) in 2 patients and disappeared after several months.

Acute Disease↗
PubMed1988

B-cell lymphoproliferation and lymphomagenesis are associated with clonotypic intracellular terminal regions of the Epstein-Barr virus.

We analyzed 17 B-cell lineages cloned from two patients with infectious mononucleosis and found that different B-cell lineages exhibited notable variation in the length of the fused Epstein-Barr virus (EBV) terminal region on intracellular EBV episomes. EBV termini in different B-cell clones from the same person differed by as many as 15 to 20 reiterations of the ca. 500-base-pair terminal repeat sequence. In contrast, analysis of seven B-cell lineages cloned from a patient with a fatal, oligoclonal lymphoma revealed that three of the cell clones had the same-sized EBV terminal region. These three clones had previously been shown, by immunoglobulin gene analysis, to be metastatic daughter cells descended from a common progenitor. Similarity of the EBV terminal regions in the three daughter clones suggested that EBV infected the progenitor cell before proliferation and metastasis. Individual, EBV-infected cells from a single individual showed sufficient heterogeneity in their EBV termini to allow use of terminal fragment size as a clonal marker in studies addressing the contribution of EBV to the clonal pathogenesis of tumors with which this virus has been associated.

B-Lymphocytes↗