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Biomedical subjects

L Lui

Publications and source records attributed to L Lui.

12 recordsLinked to original sources
PubMed2006

Association of higher levels of serum cartilage oligomeric matrix protein and N-telopeptide crosslinks with the development of radiographic hip osteoarthritis in elderly women.

OBJECTIVE: To examine the association of baseline concentrations of serum cartilage oligomeric matrix protein (COMP) and serum N-telopeptide crosslinks (NTX) with the development and progression of radiographic hip osteoarthritis (RHOA) in elderly women. METHODS: Pelvic radiographs were obtained a mean of 8.3 years apart from white women > or =65 years of age enrolled in the Study of Osteoporotic Fractures. Random sampling from a cohort of 5,928 subjects was performed, with subjects ( approximately 200 per group) assigned to nested case-control studies, one focusing on RHOA incidence and the other on RHOA progression. Baseline serum levels of COMP and NTX were measured by enzyme-linked immunosorbent assay in duplicate. Odds ratios (ORs) and 95% confidence intervals (95% CIs), indicating the likelihood of baseline serum COMP and NTX levels to be predictive of the development or progression of RHOA, were calculated using logistic regression analysis, with adjustment for potential covariates. RESULTS: At baseline, incident cases of RHOA were associated with higher serum levels of COMP and NTX (P < 0.05 for each) compared with the no RHOA control group. Higher baseline serum COMP and NTX levels were associated with an increased risk of incident RHOA compared with the no RHOA group, with an adjusted OR of 1.31 per SD increase in COMP (95% CI 1.02-1.68) and adjusted OR of 1.38 per SD increase in NTX (95% CI 1.07-1.79). In this community-based cohort, progression of RHOA was modest. However, there was a trend toward increased risk of RHOA progression with higher baseline COMP and NTX levels. CONCLUSION: These data suggest that serum levels of COMP and NTX are modest risk markers for the development of RHOA in a community-based cohort of elderly white women.

Aged↗
PubMed2006

Frizzled-related protein variants are risk factors for hip osteoarthritis.

OBJECTIVE: To examine the association of the Arg200Trp and Arg324Gly variants of FRZB with the risk and phenotype of radiographic osteoarthritis (OA) of the hip and serum levels of Frizzled-related protein (FRP) in a prospective cohort of elderly Caucasian women. METHODS: Radiographic hip OA status of patients was defined by the presence of severe joint space narrowing (JSN) (feature grade>or=3), a summary grade>or=3, or definite osteophytes (grade>or=2) and JSN (grade>or=2) in the same hip. Genotypes were obtained in 569 patients with radiographic OA of the hip and in 1,317 and 4,136 controls for the Arg200Trp and Arg324Gly variants, respectively. Serum FRP levels were measured by enzyme-linked immunosorbent assay. Multivariate logistic regression was performed. RESULTS: The minor allele frequency for the Arg200Trp polymorphism was 0.12 in the control group compared with 0.14 in the group with radiographic OA of the hip (P=0.12), and the minor allele frequency for the Arg324Gly variant was 0.083 in the control group compared with 0.088 in the group with radiographic OA of the hip (P=0.63). The multilocus genotypes available in 1,886 subjects suggested that inheritance of both minor alleles was a risk factor for developing OA characterized by JSN (P<0.01). Patients with radiographic OA of the hip who were homozygous for the Arg200Trp minor allele had higher serum FRP levels than controls who were homozygous for the major allele. CONCLUSION: Our data confirm findings of another study, that a rare haplotype with both Arg200Trp and Arg324Gly FRZB variants contributes to the genetic susceptibility to hip OA among Caucasian women, and that these polymorphisms may contribute to increased serum levels of proteins as biomarkers of OA.

Aged↗
PubMed2005

Type I collagen alpha1 Sp1 transcription factor binding site polymorphism is associated with reduced risk of hip osteoarthritis defined by severe joint space narrowing in elderly women.

OBJECTIVE: A common G/T substitution at an Sp1 binding site in intron 1 of the COL1A1 gene has been reported to be associated with reduced bone mineral density and increased risk of osteoporotic fracture. The purpose of this study was to examine whether there is an association between COL1A1 Sp1 polymorphism and radiographic osteoarthritis (OA) of the hip in elderly women in the Study of Osteoporotic Fractures. METHODS: Radiographic hip OA status of subjects was defined by the presence of 1 of the following criteria in either hip: a joint space narrowing (JSN) score of >/=3, a Croft summary grade of >/=3, or both definite (score >/=2) osteophytes and JSN in the same hip. Cases of radiographic OA of the hip were further subdivided into those with JSN score >/=3 and those with a femoral osteophyte score >/=2 and JSN score </=2. The COL1A1 Sp1 polymorphism was genotyped using allele-specific kinetic polymerase chain reaction in 4,746 women. Multivariate logistic regression was performed to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). RESULTS: Radiographic OA of the hip was present in 571 women (12%). Of these patients, 325 (57%) had severe JSN (score >/=3), and 131 (23%) had moderate or moderate-to-severe femoral osteophytosis (score >/=2). There was no association of the T/T genotype with either radiographic hip OA or radiographic hip OA characterized by osteophytosis. For radiographic OA of the hip characterized by moderate-to-severe JSN, the odds of disease were significantly reduced among subjects with the T/T compared with the G/G genotype (OR 0.30, 95% CI 0.11-0.81, P = 0.02) and did not change after adjustment for potential confounders (OR 0.36, 95% CI 0.13-0.99, P = 0.048). CONCLUSION: The T/T genotype of the COL1A1 Sp1 polymorphism was associated with a reduced risk of radiographic OA of the hip characterized by JSN. This association should be confirmed in other populations to determine if mechanistic studies are warranted.

Age Factors↗
PubMed2004

First- and second-order stimulus length selectivity in New World monkey striate cortex.

Motion is a powerful cue for figure-ground segregation, allowing the recognition of shapes even if the luminance and texture characteristics of the stimulus and background are matched. In order to investigate the neural processes underlying early stages of the cue-invariant processing of form, we compared the responses of neurons in the striate cortex (V1) of anaesthetized marmosets to two types of moving stimuli: bars defined by differences in luminance, and bars defined solely by the coherent motion of random patterns that matched the texture and temporal modulation of the background. A population of form-cue-invariant (FCI) neurons was identified, which demonstrated similar tuning to the length of contours defined by first- and second-order cues. FCI neurons were relatively common in the supragranular layers (where they corresponded to 28% of the recorded units), but were absent from layer 4. Most had complex receptive fields, which were significantly larger than those of other V1 neurons. The majority of FCI neurons demonstrated end-inhibition in response to long first- and second-order bars, and were strongly direction selective. Thus, even at the level of V1 there are cells whose variations in response level appear to be determined by the shape and motion of the entire second-order object, rather than by its parts (i.e. the individual textural components). These results are compatible with the existence of an output channel from V1 to the ventral stream of extrastriate areas, which already encodes the basic building blocks of the image in an invariant manner.

Action Potentials↗
PubMed2001

DNA hypomethylation of karyoplasts for bovine nuclear transplantation.

The objective of this research was to evaluate if DNA hypomethylation in cells used as karyoplasts would improve development of bovine nuclear transplantation (NT) embryos. DNA from serum-fed (SF), serum-starved (SS), and 1, or 5 microM 5-azacytidine (5-aza-CR) treated cells was digested with a methylation sensitive enzyme, and evaluated for DNA methylation. A significant reduction in DNA methylation was observed in cells cultured for 48 or 72 hr in SS medium as well as in cells cultured for 48 hr in the presence of 5 microM 5-aza-CR when compared to cells cultured in SF medium. All other comparisons contained no significant differences when compared to controls. When donor cells were cultured in 5-aza-CR, SF, or SS treatment media for 48 hr, no significant difference was observed (P = 0.06) in blastocyst development rates after NT. One embryo produced by donor cells treated with 5-aza-CR established a pregnancy. Four pregnancies resulted from embryos produced by SS donor cell NT and 3 resulted from embryos produced by SF donor cell NT. Supplementation of the donor cell culture medium with 5-aza-CR was not beneficial for increasing blastocyst rate or establishing pregnancy after NT.

Animals↗
PubMed2001

Reliability and reproducibility of a Chinese-language visual function assessment.

OBJECTIVE: The purpose of the study was to validate a Chinese-language visual function assessment within the context of a routine cataract surgery practice and to assess the contribution of the method of questionnaire administration. DESIGN: The visual function assessment (VFA) was translated into Chinese. Two groups of study subjects were recruited: Chinese who did not speak English and Chinese conversant in English. Consecutive preoperative cataract patients of Chinese ancestry presenting to an urban ophthalmology practice were recruited. The questionnaire was administered in person or by telephone interview. Pre-operative visual acuity was recorded. Visual function scores were analyzed to assess reliability and correlation with visual acuity. RESULTS: Among the 186 potential study subjects, 155 patients completed the study The Chinese-language visual function assessment had good internal consistency (Cronbach alpha = 0.97, inter-item correlations = 0.43 to 0.96) . Reliability (with regard to the English version) and test-retest reproducibility of the Chinese questionnaire were strong with intraclass correlation coefficients greater than 0.60. The method of administration contributed to the measures of reliability and reproducibility. CONCLUSION: These results show that a Chinese-language version of the VFA questionnaire is reliable and valid. In industrialized countries with large Chinese-speaking populations and newly developed countries of East and Southeast Asia, the visual function assessment may be helpful in assisting routine clinical patient evaluation and cross-cultural outcome assessment programmes. Our findings also suggest that self-administered visual function assessments may be more reliable and valid than interview-generated assessments.

Aged↗
PubMed1998

Absence of Gcn5 HAT activity defines a novel state in the opening of chromatin at the PHO5 promoter in yeast.

Histone acetyltransferase (HAT) activity has been demonstrated for several transcriptional activators, formally connecting chromatin modification with gene regulation. However, no effect on chromatin has been demonstrated. We have investigated the role of the HAT Gcn5 at the nucleosomally regulated PHO5 promoter. Under conditions of constitutive submaximal activation (i.e., in the absence of the negative regulator Pho80), deletion of Gcn5 determines a novel randomized nucleosomal organization across the promoter and leads to a dramatic reduction in activity. Furthermore, mutation of amino acids critical for Gcn5 HAT activity is sufficient to generate this structure. This intermediate state in chromatin opening gives way to the fully open structure upon maximal induction (phosphate starvation), even in the absence of Gcn5. Thus, Gcn5 is shown to affect directly the remodeling of chromatin in vivo.

Acetyltransferases↗
PubMed1994

The hypercoagulable state in cancer patients: evidence for impaired thrombin inhibitions.

Activation of prothrombin and the subsequent reactions of thrombin with its substrates and its major inhibitors, antithrombin III (AT III) and heparin cofactor II (HC II), likely reflect both intravascular and extravascular coagulation. Several studies have reported increased in vivo coagulation in cancer. Whether the increased thrombin production in malignancy is accompanied by a corresponding increase in thrombin inhibition is unknown. This study quantified prothrombin fragment 1 + 2 (F1 + 2), thrombin-AT III (TAT), thrombin-AT III-vitronectin (TAT.V), and thrombin-HC II-vitronectin (THCII.V) in the plasmas of healthy volunteers (n = 37); patients with localized solid tumours before treatment was initiated (n = 39); and five patients with non-Hodgkin's lymphoma, both before and during weekly chemotherapy. Two of the five non-Hodgkin's lymphoma patients developed deep venous thrombosis (DVT) during chemotherapy. In normal plasma, where the concentrations of the four parameters likely reflect haemostasis, the sum of TAT, TAT.V and THCII.V was 61% that of F1 + 2, compared with 30% in cancer plasmas. In addition, the mean +/- SEM of F1 + 2 in the plasmas of cancer patients (1.56 +/- 0.09 nM) was significantly elevated (P < 0.001) when compared with healthy volunteers (0.89 +/- 0.06 nM). Eight weeks of chemotherapy increased the F1 + 2 and the binary TAT in plasmas of the non-Hodgkin's lymphoma patients by approximately 1.5- and 2.9-fold, respectively. Thus, increased prothrombin activation in cancer patients, without corresponding increases in concentrations of thrombin-inhibitor complexes, raise the possibility that a significant portion of the thrombin generated in vivo escapes inhibition in cancer and contributes to the high risk of DVT in malignancy.

Adult↗
PubMed1993

[The responses of phrenic discharges to microinjection of morphine and naloxone into central nucleus amygdala in rabbits].

Experiments were done on 24 urethan anesthetized (20%, 1 g/kg), vagotomized and spontaneously breathing rabbits (2-3 kg). The effects on phrenic activity by microinjection of morphine and naloxone into central nucleus amygdala (ACE) were observed. The main results were as follows: (1) Injection of morphine resulted in two respiratory effects, firstly a marked increase in inspiratory time (Ti) and amplitude of phrenic activity (AMP) with little changes of respiratory frequency (RF), and secondly a significant decrease in AMP with little changes in Ti. (2) Injection of naloxone resulted in increases in RF, AMP and decreases in Ti with no marked changes in blood pressure. (3) Prolongation of inspiratory time by morphine can be blocked by previous injection of naloxone. The results suggested that endogenous morphine in ACE have different effects on respiration mediated by different receptor.

Amygdala↗
PubMed1983

Cysteine starvation, isoleucyl-tRNAIle, and the regulation of the ilvGEDA operon of Escherichia coli.

The involvement of undermodified tRNA in the regulation of the ilvGEDA operon has been investigated using Escherichia coli C6, a relA-, Cys-, Met- mutant. This strain accumulates thionucleotide-deficient or methyl-deficient tRNA when starved for cysteine or methionine, respectively. The levels of threonine deaminase, the ilvA gene product, and transaminase B, the ilvE gene product, were both lower in cysteine-starved cells, as compared with either growing or methionine-starved cultures. When cysteine was added to cysteine-starved cells, growth ensued promptly and both enzyme activities returned to control levels. Treatment of recovering cultures with valine limited growth by isoleucine limitation, but did not cause a derepression of the ilvGEDA operon. Valine treatment of nonstarved or methionine-starved cells led to the expected increase in threonine deaminase and transaminase B activities. Cysteine-starved cells slowly regained the ability to derepress the operon after 3 h of recovery in complete medium. In contrast, the induction of the lac operon was normal in cysteine-starved cultures, even in the presence of valine. The loss of derepressibility of the ilvGEDA operon was correlated with the presence of a kinetically and chromatographically altered tRNAIle in cysteine-starved cells. No changes in tRNAIle were observed after methionine starvation. Using the periodate method, we found that the charging of tRNAIle increased from the normal level of 60 to 80% or greater after starvation for cysteine. Under conditions where the ilvGEDA operon was fully derepressed in nonstarved cells, the charging of tRNAIle fell to 27%. Unexpectedly, nearly identical results were obtained with cysteine-starved cells after an identical derepression test. These results suggest that factors other than the aminoacylation state of tRNAIle may be important in the regulation of this operon. In particular, modifications to tRNA which involve cysteine may be necessary for controlling the expression of the ilvGEDA operon in E. coli.

Amino Acids↗