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Biomedical subjects

J R Li

Publications and source records attributed to J R Li.

At least 19 recordsLinked to original sources
PubMed2006

Genetic dissection of ethanol tolerance in the budding yeast Saccharomyces cerevisiae.

Uncovering genetic control of variation in ethanol tolerance in natural populations of yeast Saccharomyces cerevisiae is essential for understanding the evolution of fermentation, the dominant lifestyle of the species, and for improving efficiency of selection for strains with high ethanol tolerance, a character of great economic value for the brewing and biofuel industries. To date, as many as 251 genes have been predicted to be involved in influencing this character. Candidacy of these genes was determined from a tested phenotypic effect following gene knockout, from an induced change in gene function under an ethanol stress condition, or by mutagenesis. This article represents the first genomics approach for dissecting genetic variation in ethanol tolerance between two yeast strains with a highly divergent trait phenotype. We developed a simple but reliable experimental protocol for scoring the phenotype and a set of STR/SNP markers evenly covering the whole genome. We created a mapping population comprising 319 segregants from crossing the parental strains. On the basis of the data sets, we find that the tolerance trait has a high heritability and that additive genetic variance dominates genetic variation of the trait. Segregation at five QTL detected has explained approximately 50% of phenotypic variation; in particular, the major QTL mapped on yeast chromosome 9 has accounted for a quarter of the phenotypic variation. We integrated the QTL analysis with the predicted candidacy of ethanol resistance genes and found that only a few of these candidates fall in the QTL regions.

Chromosome Mapping↗
PubMed2002

Intracellular ribozyme applications.

The exquisite target selectivity of trans -acting ribozymes has fostered their use as potential therapeutic agents and tools for down-regulating cellular transcripts. In living cells, free diffusion of RNAs is extremely limited, if it exists at all. Thus, getting ribozymes to base-pair with their cognate targets requires co-localizing the ribozyme transcript with the target RNA. In addition, not all sites along a given target RNA are equally accessible to ribozyme base pairing. Cellular proteins greatly influence the trafficking and structure of RNA, and therefore making ribozymes work effectively in cells a significant challenge. This article addresses the problems of getting engineered ribozymes to effectively pair with and cleave targets in cells. The work described here illuminates methods for target-site selection on native mRNAs, methods for ribozyme expression, and strategies for obtaining a discrete intracellular localization of ribozymes.

Blotting, Northern↗
PubMed2002

Circulating levels of vascular endothelial growth factor in patients with oral squamous cell carcinoma.

Angiogenesis is a crucial step in tumour growth, progression, and metastasis. Recently, many angiogenic factors have been identified. Vascular endothelial growth factor (VEGF) is thought to be one such angiogenic factor and is also thought to be a selective mitogen for vascular endothelial cells. The present study was designed to determine the circulating levels of VEGF in human oral squamous cell carcinoma (OSCC) and to investigate its correlation with the clinicopathologic features and prognosis. The study consisted of 10 healthy volunteers and 31 patients with OSCC. A quantitative sandwich enzyme immunoassay technique was used to measure the concentrations of VEGF in the sera. The data obtained from the experiment were analysed with independent-samples t-test. The mean concentrations of serum VEGF were 148.80 +/- 64.17 pg x ml(-1) (range, 59-231 pg x ml(-1)) in normal controls and 567.97 +/- 338.17 pg x ml(-1) (range, 136-1,892 pg x ml(-1)) in OSCC group. Statistical analysis showed that the mean VEGF level in sera of OSCC patients was significantly higher than that in healthy controls (P<0.001). The serum VEGF levels of OSCC patients correlated with condition of nodal metastasis (P<0.05) and clinical stage (P<0.05) but not with sex (P>0.05) and degree of differentiation (P>0.05). Our study showed that OSCC was associated with significantly elevated serum VEGF concentration. Higher level of serum VEGF also correlated with lymph node metastasis and clinical stage of OSCC. Determination of serum VEGF concentration may be helpful to distinguish OSCC patients from the normal individuals.

Adult↗
PubMed2001

Effects of random potential on transport.

The effects of random potential on the transport of two systems, which are the motion of motor proteins along a biopolymer and the thermally assisted vortex diffusion in layered high-Tc superconductors, are investigated, respectively. It is found that the effects of the random potential on the transport process as the amplitude of random potential increased are much more remarkable than those as the correlation length of random potential increased. The amplitude and the correlation length of random potential play opposing roles in the transport of the systems.

Biophysical Phenomena↗
PubMed2001

Variations of dose and electrode spacing for rat breast cancer electrochemical treatment.

Electrochemical treatment (EChT) with direct current delivered through implanted electrodes has been used for local control of solid tumors in humans. This study tested the hypothesis that rat breast cancer responses to EChT are dependent on electrode spacing and dose, and explored suitable parameters for treating breast cancers with EChT. Rat breast cancers were initiated by injecting 1 x 10(6) MTF-7 cells to the right mammary gland fat pad of Fisher 344 female rats. The rats were randomly divided into designated experimental groups when the tumors grew to approximately 2 x 2 x 2 cm. One hundred and thirty rats were used for a survival study and 129 for a pathology study. A 4-channel EChT machine was used to administer coulometric doses. The survival study indicated that local tumor control rate is less than 40% in the 40 coulomb (C) and 60 C groups and more than 70% in the 80 and 100 C groups. Sixty six rats died of primary tumors, including all 10 rats in the control group. Once a rat's primary tumor was controlled, no recurrence was found. The main reason for terminating the primary tumor-free rats (51) was lymph node metastasis. Thirteen tumor-free rats survived for more than 6 months. The pathology study showed a significant dose effect on EChT induced tumor necrosis. At 10, 20, 40, and 80 C, the fraction showing necrosis were 39.7, 52.3, 62, and 77.7%, respectively (P </= 0.001). Electrodes spacing was not an important factor within a given range. At 5, 10, and 15 mm spacing, the fraction showing the necrosis were 54.1, 60.4, and 59.2%, respectively (P = 0.552). The overlap rate of necroses was similar in the 5 and 10 mm groups (82.5 and 85%) and lower in the 15 mm group (65%). We conclude that the tumor responses to EChT, local control, survival rates, and necrosis percentages were significantly increased with increasing dose. The changes in electrode spacing (3, 5, and 10 mm) did not significantly affect the tumor responses to EChT within the same dose. For a diameter of 2.0-2.5 cm rat breast cancer, EChT should be applied with 5-10 mm spacing and a minimum dosage of 80 C.

Animals↗
PubMed2001

Papain immobilization on a nitrilon fibre carrier containing primary amine groups.

A carrier containing primary amine groups was synthesized by the reaction between nitrilon fibre and diethylenetriamine, and papain was immobilized on this kind of carrier by using glutaraldehyde as a coupling agent. The factors involved with the activity recovery of the immobilized papain and the enzymic properties of the resulting immobilized papain were studied in comparison with free papain, for which casein was chosen as a substrate. The results show that the activity recovery of immobilized papain can reach 47.3%, and that the immobilized papain exhibits better environmental adaptability and reusability than free papain.

Amines↗
PubMed2001

[Enhanced immunogenicity of plasmid encoding polyprotein gene of infectious bursal disease virus by co-administration of chicken interleukin 2 (IL-2)].

Chicken interleukin 2 (IL-2) is one of important nonmammalian cytokines isolated recently. The influencing of IL-2 on immunogenicity of DNA vaccine was examined using infectious bursal disease virus as a model. The IL-2 cDNA of Xiaoshan chicken and the polyprotein gene of IBDV-ZJ2000 were amplified by RT-PCR, cloned, sequenced and inserted into the control of CMV promoter and enhancer of pCI vector. 14-day-old chickens were vaccinated intramuscularly with DNA vaccine, two weeks later, they were boosted with DNA, and two weeks post boost, they were challenged with virulent IBDV. The results showed that protective responses and neutralization antibody responses of DNA vaccine co-administrated with chicken IL-2 were much higher than those of injected with DNA vaccine alone. Furthermore, the T lymphocyte proliferation response of peripheral blood, thymus and spleen, and the B lymphocyte proliferation response of bursa induced by DNA vaccine can be significantly enhanced by chicken IL-2. These results obviously indicated that chicken IL-2 was a strong adjuvant which can significantly enhance the immunogenicity of IBDV DNA vaccine.

Animals↗
PubMed2001

Cloning and Phylogenetic Analysis of Interleukin-2 Gene in Xiaoshan Chicken, A Chinese Local Chicken Breed.

Chicken interleukin 2 (cIL-2) is one of important nonmammalian cytokines isolated recently. In this paper, optimum condition for production of chicken IL-2 in vitro was developed. Isolation of spleen lymphocytes from Xiaoshan chicken, activation by ConA, followed by RT-PCR in a single step, resulted in the synthesis of chicken IL-2 cDNA. The full-length chicken IL-2 cDNA was 737 bp, encoding a 143 amino acids precursor. Only 1--5 amino acid difference were found compared with other three published chicken IL-2s. This IL-2 shared 69.4% homology with turkey IL-2 and shared 21.2%--9.4% homology with mammalian IL-2. The predicted protein had a leader sequence composed of 22 amino acids, and four conversed cysteines allowing the formation of two intrachain disulfide bonds. There were four regions of heptad repeats, with hydrophobic amino acids at positions 1 and 4, were presumably forming amphipathic alpha-helices. These regions were equivalent to mammalian helices A, B, C and D. The amino acids at positions 40(D), 65(Y), 82(E), 108(N) and 142(Q) might play roles in binding to receptors of chicken IL-2. Phylogenetic tree analysis indicated that the chicken IL-2 may have evolutionary relationship with mammalian IL-2 they showed however species difference in function because of selective pressure of immune systems.

Journal Article↗
PubMed2000

Structures and magnetism of two novel heptanuclear lanthanide-centered trigonal prismatic clusters: [LnCu6(mu 3-OH)3(HL)2(L)4](ClO4)2.25H2O (Ln = La, Tb; H2L = iminodiacetic acid).

The new heteronuclear iminodiacetic acid (H2L) complexes [LnCu6(mu 3-OH)3(HL)2(L)4](ClO4)(2).25H2O with Ln = La (1) and Tb (2) have been prepared in aqueous solution and characterized by single-crystal X-ray diffraction to be isomorphous (crystallographic data for 1 and 2: hexagonal, P63/m; a = b = 12.6425(14) A, c = 24.541(5) A, Z = 2 (1); a = b = 12.5802(9) A, c = 24.285(4) A, Z = 2 (2)). Ln3+ was found to be located in the center of the trigonal prismatic cage formed by six Cu2+ ions, with a tricapped trigonal prismatic coordination environment of nine O atoms. The magnetic properties of complexes 1 and 2 have been studied. The results indicate the presence of ferromagnetic couplings between Tb3+ and Cu2+ in compound 2.

Journal Article↗
PubMed1999

Electrochemical treatment of human KB cells in vitro.

Electrochemical treatment (ECT) of cancer is a promising new method by which direct current is delivered into tumor tissue to induce tumor regression. The purpose of this study is to evaluate the effectiveness of ECT on human cancer cells and to investigate the factors that affect ECT. The biological mechanisms of ECT in cancer treatment were also explored. Using human KB cells, ECT was found to delay cell growth by using 0.3 coulombs (C)/ml (1.5 C in 5 ml of culture medium; 3 V, 400 microA for 62.5 min). From the results of a colony-forming assay, it was clearly demonstrated that increasing the ECT dose decreases tumor cell survival. A cytotoxicity study, in which a methylene blue assay was used, determined that, for 2.5 x 10(5) cells in culture, the 1D50 was 0.68 C/ml. For a fixed dose of 0.6 C/ml (3 C in 5 ml), using higher current and shorter treatment time resulted in better cell survival. Time, therefore, is an important factor. When cell concentration was altered, the survival was higher for increased cell concentrations. A thymidine incorporation assay indicated that the amount of [3H]thymidine incorporated into DNA decreased as the ECT dose increased. After treatment with 1 C/ml (5 C in 5 ml; 3 V, 400 microA for 208.4 min), pH at the anode decreased to 4.53 and at the cathode increased to 10.46. These results indicate that ECT is effective for killing human KB cells in vitro and that the toxicity effect is related to charge, current, and treatment time. The effect of pH alteration on cells is one of the mechanisms of ECT.

Cell Division↗
PubMed1999

TP53 tumor suppressor protein in normal human fibroblasts does not respond to 837 MHz microwave exposure.

The TP53 tumor suppressor protein (formerly known as p53) responds to a wide variety of environmental insults. To evaluate the safety of cellular telephones, TP53 responses in human fibroblast cells were studied after exposure to 837 MHz microwaves. Cells were exposed in a temperature-controlled transverse electromagnetic (TEM) chamber to a specific absorption rate (SAR) of 0.9 or 9.0 W/kg at 837 MHz continuous-wave (CW) microwave irradiation for 2 h. The TP53 protein levels were measured by Western blot at 2, 8, 24 and 48 h after treatment. The TP53 protein levels in microwave-treated cells, sham-treated cells, and untreated cells remained unchanged relative to each other at all times tested (Fisher test and Student-Newman-Keuls test, P > 0.05). No morphological alterations were observed in microwave-treated cells compared to sham-treated cells. We conclude that TP53 protein expression levels in cultured human fibroblast cells do not change significantly during a 48-h period after exposure to 837 MHz continuous microwaves for 2 h at SAR levels of 0.9 or 9.0 W/kg.

Cells, Cultured↗
PubMed1999

The influence of exogenous nerve growth factor on inferior alveolar nerve regeneration in silicone tubes.

OBJECTIVE: To explore the effects of exogenous nerve growth factor (NGF) in the regeneration of adult white rabbit inferior alveolar nerves within silicone tubes. METHODS: Twenty-four adult white rabbits were selected. Bilateral 8 mm inferior alveolar nerve gaps were created, and the proximal and distal stumps were inserted into a 12 mm silicone tube. The right side silicone tube was filled with exogenous NGF (experimental group) and the contralateral side was filled with saline (control group). Regeneration of the nerves was assessed by histological and nerve eletrophysiological observation. Total number of the regenerated myelinated fibers, conduction velocity of the nerves, thickness of myelin sheaths, and cross-section area of myelinated nerve fibers between the experimental and control groups were compared. RESULTS: The results show that NGF significantly increased the number of myelinated fibers. The experimental group demonstrated more myelinated fibers than the controls at 12 and 18 weeks. At the same time following surgery, the myelin sheath thickness and the cross-section area of myelinated fibers in the experimental group were significantly greater than those in the controls. At 12 and 18 weeks, the conduction velocity of regenerated nerves in the experimental group were greater than those of the control. CONCLUSION: This study suggests that exogenous NGF can enhance regeneration of the inferior alveolar nerves and recovery of their sensory function.

Animals↗
PubMed1998

A new step to the mechanism of the enhancement effect of gold nanoparticles on glucose oxidase.

Quantum size effect was strongly supported by the experiment on correlation between size of gold nanoparticles (below 10 nm) and activity of glucose oxidase attached to them. The attractive enhancement effect of gold nanoparticles on the activity of glucose oxidase was then satisfactorily explained. In this experiment, 2 nm and 6 nm (average diameter) particles were obtained on monolayer matrix. The 2 nm particles proved to be much more able to increase the activity of glucose oxidase.

Adsorption↗
PubMed1998

Evaluation of the effectiveness of preoperative embolization in surgery for nasopharyngeal angiofibroma.

We retrospectively analyzed the clinical data of 21 patients (22 procedures) with histologically proven nasopharyngeal angiofibromas. Eleven patients underwent preoperative intra-arterial digital subtraction angiography (IADSA) and embolization with Gelfoam. Embolization reduced the intraoperative blood loss from an average of 1136 ml in the non-embolized patients to 677 ml in the embolized cases (P < 0.05) and transfusions from an average of 836 ml to 400 ml (P < 0.01). Results again show that preoperative embolization is effective in reducing intraoperative blood loss.

Adolescent↗
PubMed1995

Oral administration of dihydroartemisinin and ferrous sulfate retarded implanted fibrosarcoma growth in the rat.

In the presence of iron, dihydroartemisinin forms free radicals and causes cell death. Since most cancer cells have high rates of iron intake, dihydroartemisinin would have selective cytotoxic effect on cancer cells. The present experiment was designed to study the effect of dihydroartemisinin and ferrous sulfate on the growth of implanted fibrosarcoma in the rat. We found that the growth rate of the tumor was significantly retarded by daily oral administration of ferrous sulfate followed by dihydroartemisinin. No significant tumor growth retardation effect was observed in rats treated with either dihydroartemisinin or ferrous sulfate alone. The drug treatment did not significantly affect body weight compared with untreated tumor-implanted animals and no apparent toxic effect was observed after drug treatment. An artemisinin analog-ferrous salt combination may provide a novel approach for cancer therapy.

Administration, Oral↗
PubMed1993

Classification of pulse waveform of cerebral spinal fluid during intracranial pressure monitoring.

Cerebral spinal fluid (CSF) pulse waveform basing on 899 records was classified. Eleven types of CSF pulse waveform were further classified according to the harmonic wave relation and the configuration of the pulse waveform. The characteristic features of various types of CSF pulse waveform were considered to reflect certain intracranial pathophysiological conditions including cerebral compliance, cerebral vasomotor reactivity and intracranial elastance.

Brain Injuries↗