Search PubMed⌕ Search

Biomedical subjects

C Li

Publications and source records attributed to C Li.

At least 37 records · Page 2Linked to original sources
PubMed2006

Search for novel gene markers of traumatic brain injury by time differential microarray analysis.

Neuronal and glial cell death caused by axonal injury sometimes contributes to whole brain pathology after traumatic brain injury (TBI). We show that neuroprotection by 2 types of immunosuppressants, cyclosporin A (CsA) and tacrolimus (FK506), in a cryogenic brain injury model results from inhibition of calcineurin and protection from mitochondrial damage caused by formation of a mitochondrial permeability transition pore induced by cyclophilin D (CyPD), one of the prolyl cis/trans isomerase family members. We evaluated why CsA is neuroprotective by microarray analysis of gene expression in the cryogenic brain injury rat model. Analyses of expression patterns demonstrated that expression of over 14,000 genes changed between the groups with and without CsA treatment, and about 350 genes among them were extracted showing a significant difference. We learned that the differential expression of several gene targets showed specific patterns in a time-dependent manner. These results may help elucidate the mechanisms of neuronal cell death after TBI and the neuroprotective effects of CsA after TBI.

Animals↗
PubMed2006

Improved mechanical properties of acrylic bone cement with short titanium fiber reinforcement.

Acrylic bone cements are widely used in total joint arthroplasties to grout the prosthesis to bone. The changes in the tensile properties and fracture toughness of polymethylmethacrylate (PMMA) bone cements obtained by the addition of control and heat treated short titanium fibers are studied. Heat treatment of titanium fibers is conducted to precipitate titania particles on the fiber surface to improve the biocompatibility of the metal. Control and heat treated short titanium fibers (250 micro long and 20 micro diameter) were used as reinforcements at 3 volume %. X-ray diffraction indicated the presence of a rutile form of titania due to the heat treatments. The tensile and fracture properties were improved by the addition of fibers. Bone cements reinforced with titanium fibers heated at 550 degrees C for 1 h followed by 800 degrees C for 30 minutes show the largest increase in fracture toughness along with the smallest changes in elastic modulus and needs to be further investigated.

Benzoyl Peroxide↗
PubMed2006

Improved mechanical properties of acrylic bone cement with short titanium fiber reinforcement.

Acrylic bone cements are widely used in total joint arthroplasties to grout the prosthesis to bone. The changes in the tensile properties and fracture toughness of polymethylmethacrylate (PMMA) bone cements obtained by the addition of control and heat treated short titanium fibers are studied. Heat treatment of titanium fibers is conducted to precipitate titania particles on the fiber surface, which may improve the biocompatibility of the metal. Control (non-heat treated) and heat treated short titanium fibers (250 microm long and 20microm diameter) were used as reinforcements at 3 volume %. X-ray diffraction indicated the presence of a rutile form of titania due to the heat treatments. Results indicate that the tensile and fracture properties of unfilled bone cement were improved by the addition of control and heat-treated fibers. The fracture properties of bone cements reinforced with control titanium fibers were at least 10% higher than those reinforced with heat treated titanium fibers. Therefore, we recommend further studies on the use of non-heat treated titanium fibers to reinforce acrylic bone cement.

Coated Materials, Biocompatible↗
PubMed2006

Exploratory analysis of the bacteriological status of post-irradiation wounds and its relationship to healing.

AIMS: To investigate the bacteriological status of post-irradiation wounds and its relationship to wound healing in patients with nasopharyngeal cancer. MATERIALS AND METHODS: One hundred and forty-six nasopharyngeal cancer patients with post-irradiation wounds on one or both sides of the neck were studied prospectively. Swabs were taken from the wounds at the initial study visit for bacteriological examination. A further swab for culture was taken when possible signs of infection developed. Wound healing was assessed on alternate days with respect to wound condition, the presence of clinical infection and healing time. RESULTS: The results showed that most of the post-irradiation wounds were colonised with bacteria. This was not associated with clinical signs of infection in any instance. There was no association between wound healing time and the presence of organisms, the identity of organisms, the number of species of organisms, or the use of antibiotics. CONCLUSIONS: The presence of bacteria in post-irradiation wounds, in the absence of clinical signs of wound infection, is not a barrier to wound healing. Oncology practitioners should recognise the unique features of radiation-induced wounds and skin reactions with confidence and provide appropriate treatment as needed.

Adult↗
PubMed2006

Endostatin therapy reveals a U-shaped curve for antitumor activity.

Developing continuous systemic delivery of endostatin has been a goal of many laboratories. We have employed a method of gene therapy utilizing different viral constructs. Here, we report that a new serotype of adeno-associated viruses, which incorporates canine endostatin, provides dose-dependent transgene expression in the circulation after intramuscular injection in mice. Elevated levels of endostatin remained stable in the circulation for at least 4 months. In vitro assays determined that the protein expressed was biologically active. Antitumor activities of the above construct demonstrated a U-shape curve, where the maximum activity was observed within a certain critical concentration range. These data suggest that an optimum dose range may be required to achieve therapeutic efficacy in large animal models.

Amino Acid Sequence↗
PubMed2006

Birth weight, puberty, and systolic blood pressure in children and adolescents: a longitudinal analysis.

We examined the association between birth weight and systolic blood pressure (SBP) from pre-puberty to late puberty in a cohort of American children. Ninety-eight children aged 4-12 years at baseline were followed annually for 2-6 years with at least two Tanner stages. Annual measures included SBP, age, gender, race, birth weight, Tanner stage, and body composition using dual-energy X-ray absorptiometry and computed tomography. Birth weight was inversely correlated with SBP in pre-pubertal children (r=-0.23, P<0.05), especially in white children. SBP persisted at a higher level from pre-puberty through late puberty among children with low birth weight (<2500 g). However, SBP significantly increased from pre-puberty to early or late puberty among children with high birth weight (>or=4000 g). After adjusting for visceral fat, one unit change of birth weight category was associated with a 2.6 mm Hg reduction in SBP (P<0.05), but this association was attenuated as puberty progressed. The changes in SBP across puberty followed different trajectories in children with low vs high birth weight. Attenuation in the association between birth weight and SBP from pre-puberty to late puberty may be influenced by sexual maturation.

Adolescent↗
PubMed2006

Aberrant termination triggers nonsense-mediated mRNA decay.

NMD (nonsense-mediated mRNA decay) is a cellular quality-control mechanism in which an otherwise stable mRNA is destabilized by the presence of a premature termination codon. We have defined the set of endogenous NMD substrates, demonstrated that they are available for NMD at every round of translation, and showed that premature termination and normal termination are not equivalent biochemical events. Premature termination is aberrant, and its NMD-stimulating defects can be reversed by the presence of tethered poly(A)-binding protein (Pab1p) or tethered eRF3 (eukaryotic release factor 3) (Sup35p). Thus NMD appears to be triggered by a ribosome's failure to terminate adjacent to a properly configured 3'-UTR (untranslated region), an event that may promote binding of the UPF/NMD factors to stimulate mRNA decapping.

3' Untranslated Regions↗
PubMed2006

Echocardiographic characteristics of chickens with ascites syndrome.

1. B- and M-mode echocardiography was used to compare cardiac function in broilers with spontaneous ascites syndrome with that of normal chickens. 2. Thirty ascitic chickens and 15 normal chickens aged three, 4, 5, and 6 weeks from the same flock (180 birds in total) were examined. They were restrained gently in a natural standing position, and echocardiographs were obtained from a 7.0-MHz linear transducer placed on the left pectoral apterium. Indices of cardiac structure and functioning were calculated from the echocardiographs, and some were normalised to body weight. Heart rate was also measured. 3. All cardiac structural indices in both ascitic and normal chickens increased with age. Compared with normal chickens, right ventricular diameter at the end of systole in ascitic chickens was greater at 4, 5 and 6 weeks of age. Ventricular septal thickness at the end of both systole and diastole was greater in ascitic chickens at 5 and 6 weeks. Left ventricular free wall thickness at the end of diastole was less in ascitic chickens at 3 weeks. However, all the structural indices decreased with age after normalisation with body weight. 4. The heart rate of ascitic chickens was lower at 4, 5 and 6 weeks. Normalised left ventricular fractional shortening was lower in ascitic chickens at 4, 5 and 6 weeks, as was normalised right ventricular fractional shortening. Incrassation of the ventricular septum (Delta T), which changed little in normal chickens, was less at 4, 5 and 6 weeks in ascitic chickens. Left ventricular fractional shortening, right ventricular fractional shortening and Delta T were all negatively correlated with ascites heart index at all ages. 5. Taken together the results suggest heart failure of both ventricle, but that right ventricular dysfunction is more extensive than left ventricular dysfunction. We suggest that secondary pulmonary hypertension would result in these ascitic chickens due to volume overload.

Animals↗
PubMed2006

Detection of prostate cancer by alpha-methylacyl CoA racemase (P504S) in needle biopsy specimens previously reported as negative for malignancy.

AIMS: To investigate the possibility of detecting small focal prostatic cancer by alpha-methylacyl CoA racemase (AMACR)/P504S immunohistochemistry on needle biopsy specimens that were previously interpreted as negative for carcinoma on routine haematoxylin and eosin (H&E)-stained sections. METHODS: Prostate needle biopsy specimens (n = 793) previously interpreted as benign prostatic tissue by conventional morphology from 239 patients with prostatic cancer diagnosed in other biopsy cores taken at the same biopsy session were stained with the P504S monoclonal antibody. If a biopsy specimen stained positively, two pathologists independently reviewed the original corresponding H&E-stained sections to establish the malignant diagnosis. RESULTS: Eighty-four of the 793 biopsy specimens showed AMACR immunoreactivity; nine of these (9/793, 1.1%) contained previously unrecognized small focal prostatic carcinoma (Gleason 6, N = 8; Gleason 8, N = 1). Six of nine (67%) carcinomas showed foamy/pseudohyperplastic (N = 3) or atrophic (N = 3) features. Additionally, five biopsy specimens (5/793, 0.6%) with positive AMACR staining that did not meet the criteria for prostatic cancer on the original H&E slides were considered to be atypia. CONCLUSIONS: In this study, we found a 1.1% false-negative rate for carcinoma on routine H&E-stained sections. AMACR immunohistochemical staining has shown the ability to improve detection of small focal prostatic carcinoma that could be missed by conventional histological examination.

Biopsy, Needle↗
PubMed2006

Transient appearance of hepatic natural killer cells with high cytotoxicity and unique phenotype in very young mice.

There were few natural killer (NK) cells in the liver in very young mice at the age of 1-2 weeks. This was because the cell yield from the liver of young mice was low. The percentage of NK cells in the liver of young mice, however, was almost comparable with that in the liver of adult mice. Lymphocytes were isolated from the liver and spleen of C57BL/6 (B6) mice, and NK cytotoxicity and phenotype were herein examined in this study. NK cytotoxicity was extremely high in the liver of very young mice. This phenomenon was seen in the liver of various normal mouse strains. In contrast, the appearance of high cytotoxicity was not seen in NK cells of the spleen, irrespective of mouse strains. The quality of NK cells in the liver of young mice was different from that in adult mice. NK cells in the liver of young mice were mainly CD69(+)Mac-1(-) Fas ligand(+), whereas those in the liver of adult mice were CD69(-)Mac-1(+) Fas ligand(-). These results revealed that the quality of hepatic NK cells changes in the process of ageing. Namely, liver NK cells in very young mice temporarily show the highest NK cytotoxicity and a unique activated phenotype. Physiological meaning of the present phenomenon was discussed.

Age Factors↗
PubMed2006

MMP-1 promoter gene polymorphism and susceptibility to chronic periodontitis in a Chinese population.

A single nucleotide polymorphism in the promoter region of -1607 bp of the human MMP-1 gene has been found to be associated with an increased risk of various inflammatory diseases and cancer metastasis. This study aimed to evaluate the association between the MMP-1 promoter gene polymorphism and chronic periodontitis susceptibility and/or severity in a Chinese population. Genomic DNA was obtained from whole blood samples in 60 Chinese subjects with chronic periodontitis and 50 periodontally healthy subjects as controls. MMP-1 promoter fragment was amplified by polymerase chain reaction, and the polymorphism was analyzed by restriction endonuclease cleavage. In the control subjects, the 2G allele was observed a frequency of 49%, while in severely diseased patients, the 2G allele was seen in 73.4%. The individuals with the 2G allele seem to be approximately three times at greater risk for developing the severe chronic periodontitis (chi(2) = 12.148, P = 0.000). The genotype of 2G/2G was found in 58.5% of the severe periodontitis and 24% of the control group (chi(2) = 11.779, P = 0.003). This study suggests that a single nucleotide polymorphism in the MMP-1 promoter region of -1607 bp may be associated with severe chronic periodontitis in a Chinese population.

Adult↗
PubMed2006

Fermentative hydrogen production in packed-bed and packing-free upflow reactors.

Fermentative hydrogen production from a synthetic wastewater containing 10 g/L of sucrose was studied in two upflow reactors at 26 degrees C for 400 days. One reactor was filled with packing rings (RP) and the other was packing free (RF). The effect of hydraulic retention time (HRT) from 2 h to 24 h was investigated. Results showed that, under steady state, the hydrogen production rate significantly increased from 0.63 L/L/d to 5.35 L/L/d in the RF when HRT decreased from 24 h to 2 h; the corresponding rates were 0.56 L/L/d to 6.17 L/L/d for the RP. In the RF, the hydrogen yield increased from 0.96 mol/mol-sucrose at 24 h of HRT to the maximum of 1.10 mol/mol-sucrose at 8 h of HRT, and then decreased to 0.68 mol/mol-sucrose at 2 h. In the RP, the yield increased from 0.86 mol/mol-sucrose at 24 h of HRT to the maximum of 1.22 mol/mol-sucrose at 14 h of HRT, and then decreased to 0.78 mol/mol-sucrose at 2 h. Overall, the reactor with packing was more effective than the one free of packing. In both reactors, sludge agglutinated into granules. The microbial community of granular sludge in RP was investigated using 16S rDNA based techniques. The distribution of bacterial cells and extracellular polysaccharides in hydrogen-producing granules was investigated by fluorescence-based techniques. Results indicated that most of the N-acetyl-galactosamine/galactose-containing extracellular polysaccharides were distributed on the outer layer of the granules with a filamentous structure.

Bioreactors↗
PubMed2006

Relationships of feedlot feed efficiency, performance, and feeding behavior with metabolic rate, methane production, and energy partitioning in beef cattle.

Residual feed intake (RFI) is the difference between the actual and expected feed intake of an animal based on its BW and growth rate over a specified period. The biological mechanisms underlying the variation in feed efficiency in animals with similar BW and growth rate are not well understood. This study determined the relationship of feedlot feed efficiency, performance, and feeding behavior with digestion and energy partitioning of 27 steers. The steers were selected from a total of 306 animals based on their RFI following feedlot tests at the University of Alberta Kinsella Research Station. Selected steers were ranked into high RFI (RFI > 0.5 SD above the mean, n = 11), medium RFI (RFI +/- 0.5 SD above and below the mean, n = 8), and low RFI (RFI < -0.5 SD below the mean, n = 8). The respective BW +/- SD for the RFI groups were 495.6 +/- 12.7, 529.1 +/- 18.6, and 501.2 +/- 15.5 kg. Digestibility and calorimetry trials were performed on a corn-or barley-based concentrate diet in yr 1 and 2, respectively, at 2.5 x maintenance requirements. Mean DMI (g/kg of BW(0.75)) during the measurements for high-, medium-, and low-RFI groups, respectively, were 82.7 +/- 2.0, 78.8 +/- 2.6, and 81.8 +/- 2.5 and did not differ (P > 0.10). Residual feed intake was correlated with daily methane production and energy lost as methane (r = 0.44; P < 0.05). Methane production was 28 and 24% less in low-RFI animals compared with high- and medium-RFI animals, respectively. Residual feed intake tended to be associated (P < 0.10) with apparent digestibilities of DM (r = -0.33) and CP (r = -0.34). The RFI of steers was correlated with DE (r = -0.41; P < 0.05), ME (r = -0.44; P < 0.05), heat production (HP; r = 0.68; P < 0.001), and retained energy (RE; r = -0.67; P < 0.001; energy values are expressed in kcal/kg of BW(0.75)). Feedlot partial efficiency of growth was correlated (P < 0.01) with methane production (r = -0.55), DE (r = 0.46), ME (r = 0.49), HP (r = -0.50), and RE (r = 0.62). With the exception of HP (r = 0.37; P < 0.05), feed conversion ratio was unrelated to the traits considered in the study. Feeding duration was correlated (P < 0.01) with apparent digestibility of DM (r = -0.55), CP (r = -0.47), methane production (r = 0.51), DE (r = -0.52), ME (r = -0.55), and RE (r = -0.60). These results have practical implications for the selection of animals that eat less at a similar BW and growth rate and for the environmental sustainability of beef production.

Animal Feed↗
PubMed2006

Test duration for growth, feed intake, and feed efficiency in beef cattle using the GrowSafe System.

This study was conducted to determine the optimum test duration and the effect of missing data on accuracy of measuring feed efficiency and its 4 related traits ADG, DMI, feed conversion ratio, and residual feed intake in beef cattle using data from 456 steers with 5,397 weekly averaged feed intakes and BW repeated measurements taken over 91 d. Data were collected using the GrowSafe System at the University of Alberta Kinsella Research Station. The changes and relative changes in phenotypic residual variances and correlations (Pearson and Spearman) among data from shortened test durations (7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, or 84 d) and a 91-d test were used to determine the optimum test duration for the 4 traits. The traits were fitted to a mixed model with repeated measures using SAS. Test durations for ADG, DMI, feed conversion ratio, and residual feed intake could be shortened to 63, 35, 42, and 63 d, respectively, without significantly reducing the accuracy of the tests when BW was measured weekly. The accuracy of the test was not compromised when up to 30% of the records were randomly removed after the first 35 d on test. These results have valuable and practical implications for performance and feed efficiency testing in beef cattle.

Animals↗
PubMed2006

Development of a recombinant fowlpox virus vector-based vaccine of H5N1 subtype avian influenza.

The genetic stability of the recombinant fowlpox virus (named rFPV-HA-NA) was confirmed by serial passage on chicken embryo fibroblast (CEF) cells. The immune efficacy, safety, the minimum immunising dose, the time of immunity induced and the immune duration of the vector-based vaccine was evaluated in specific-pathogen-free (SPF) chickens. The recombinant virus vaccine containing 100 plaque form units (PFU) could induce complete protection against challenge with H5N1 highly pathogenic avian influenza virus (HPAIV). The immune efficacy, protecting chickens from clinical signs and death after challenge, was obtained one week after the immunisation with this vaccine. Protective immunity could last for 40 weeks post-immunisation. So the recombinant fowlpox vaccine is a safe and highly effective gene engineering vaccine candidate, and will be used to prevent H5 subtype avian influenza in the future.

Animals↗
PubMed2005

Differential expression of NMDA and AMPA/KA receptor subunits in the inferior olive of postnatal rats.

We have employed immunohistochemistry to determine the expression patterns of receptor subunits of N-methyl-d-aspartate (NMDA-NR1 and NR2A/B) and alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid/kainic acid (AMPA/KA-GluR1, GluR2, GluR2/3, GluR4, and GluR5/6/7) in the inferior olive of postnatal rats up to adulthood. Immunoreactivity for distinct receptor subunits was predominantly localized in the soma and dendrites of neurons. Semi-quantification showed that the overall immunoreactivity in the inferior olive of adults was intense for GluR1, moderate for NR1 and NR2A/B, and low for GluR2, GluR2/3, GluR4, and GluR5/6/7. At P7, GluR1 was restricted to the dorsomedial cell column, subnucleus beta, principal nucleus and ventrolateral protrusion while the other subunits were found in all subnuclei of the inferior olive. The immunoreactivities for all glutamate receptor subunits ranged from low to moderate. As the rats matured, the immunoreactivity of GluR4 decreased after the second postnatal week, while those of the other subunits showed a general trend of increase, reaching adult level during the third postnatal week. Double immunofluorescence revealed that all NR1-containing neurons exhibited NR2A/B immunoreactivity, indicating that native NMDA receptors comprise of hetero-oligomeric combinations of NR1 and NR2A/B. Furthermore, co-localization of NMDA and AMPA/KA receptor subunits was demonstrated in individual neurons of the inferior olive. All NR1-containing neurons exhibited GluR1 immunoreactivity, and all NR2A/B-containing neurons showed GluR5/6/7 immunoreactivity. Our data suggest that NMDA and AMPA/KA receptors are involved in glutamate-mediated neurotransmission, contributing to synaptic plasticity and reorganization of circuitry in the inferior olive during postnatal development.

Aging↗