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Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 271 records · Page 15Linked to original sources
PubMed2000

Postnatal development of differential projections from the caudal and rostral motor cortex subregions.

The primary motor cortex of cats, monkeys, and humans has distinct rostral and caudal subregions. In the cat, projections from the caudal subregion terminate predominantly in laminae 4-6 and, from the rostral subregion, in laminae 6-8. The purpose of this study was to determine if these distinctive termination patterns are present during early postnatal development, when corticospinal axons are establishing connections with spinal neurons, or if there was postnatal refinement of the distribution of terminations. We used the anterograde tracer biotinylated dextran amine (BDA) to label selectively projections from the two subregions in immature (postnatal days 25, 35 at time of analysis) and mature animals. We compared the distribution of spinal gray matter labeling from caudal and rostral motor cortex. In immature animals, substantial bilateral terminations were present after tracer injection into either subregion. Partial axon reconstructions revealed that individual axons terminated bilaterally. The dorso-ventral laminar distribution of contralateral labeling after caudal motor cortex injections was significantly more extensive for immature than mature animals. In immature animals, most of the labeling was present in laminae 5-7 (dorsal portion). with lesser amounts in laminae 1-4 and 7 (ventral portion), 8, and 9. In mature animals, there were significant reductions in the amount of label in laminae 7-9, resulting in contraction of the labeled territory. The distribution of dorsal horn-ventral horn labeling shifted from 41% and 59% in immature animals to 77% and 23% in maturity. The distribution of contralateral labeling after rostral motor cortex injections also was different in immature and mature animals, but the changes were less extensive than for the caudal motor cortex. In immature animals, the distribution of labeling was similar to that after caudal motor cortex injections in animals of the same age. In mature animals, there was a significant reduction in the amount of labeling in laminae 1-4 and a smaller reduction in 7 (ventral)-9. The overall dorsal horn-ventral horn distribution, however, remained largely unchanged, from 40% and 60% in immature animals to 44% and 56% in maturity. In immature animals after rostral motor cortex injection, corticospinal terminations were present within the lateral motor nuclei. Thus, the distinctive spinal termination patterns of caudal and rostral motor cortex in maturity each reflected postnatal refinement of the distribution of axon terminations. It is plausible that the dorso-ventral refinement of corticospinal terminations relies on activity-dependent competition between caudal and rostral motor cortex, similar to activity-dependent refinement of the laterality of terminations. Our results, however, suggest that the developmental program for achieving corticospinal connectional specificity by the two subregions is different because there was large-scale refinement of the terminations of caudal motor cortex but only local refinement of rostral motor cortex terminations.

Age Factors↗
PubMed2000

Effect of retinoic acid and its complexes with transition metals on human bladder cancer cell line EJ in vitro.

The aim of this study was to investigate the effect of retinoic acid (RA) and its complexes with transition metals on the bladder cancer cell line EJ. Retinoic acid complexes with transition metals Cu, Co, Zn, and Ni were prepared. Cell proliferation was tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in the presence of RA or its complexes with transition metals Cu, Co, Zn, and Ni ¿Cu(RA)2.3H2O, Co(RA)2.3H2O, Zn(RA)2.4H2O, and Ni(RA)2.3H2O¿. Colony formation in soft agar culture, A agglutination reaction, and lactic acid dehydrogenase isoenzyme assay were performed in the cells treated with these drugs to estimate the induced differentiation. p53 or c-Ha-ras expression in drug-treated cells was assayed by ABC immunocytochemistry technique. The results demonstrate that EJ cells treated with the drugs become less confluent and tend to exhibit normal characteristics. Although RA and its complexes showed inhibition to proliferation of EJ cells at the concentrations of 10(-6) mmol/l, the inhibition induced by Ni(RA)2.3H2O was much more marked than that by RA. EJ cells were growth inhibited by RA or Ni(RA)2.3H2O from 48 to 96 h at the concentration of 10(-8) mol/l. The levels of LDH4 and LDH5 in the cells were greatly increased by RA. Nevertheless, Ni(RA)2.3H2O did not affect LDH isoenzyme in EJ cells. The number of colony formations of EJ cells in soft agar culture was decreased by RA or Ni(RA)2.3H2O. The percentage of colony formation in soft agar culture was much lower in EJ cells treated with Ni(RA)2.3H2O than with RA. The required concentration of A agglutination reaction was more increased for EJ cells treated with RA or Ni(RA)2.3H2O than for the control and was further increased in cells treated with Ni(RA)2.3H2O. Mutant p53 expression was more decreased in the EJ cells treated with RA or Ni(RA)2.3H2O than in the control. Although RA at the concentration of 10(-6) mmol/l caused lower p21 expression, Ni(RA)2.3H2O did not affect p21 expression in EJ cells. Therefore, RA and its transition metal complexes have a potential use in the treatment of bladder cancer.

Agar↗
PubMed2000

The role of apoptosis in the early corneal wound healing after excimer laser keratectomy in the rat.

BACKGROUND: The potential role of apoptosis in corneal wound healing after excimer laser keratectomy was investigated in a rat model. METHODS: Lewis rats underwent laser keratectomy using a 193-nm excimer laser. The central corneas were ablated in three depths: group A, epithelium; group B, superficial stroma; group C, deep stroma. Eyes were collected at 1, 12, 24, and 36 h and 1 week. Cellular markers associated with apoptosis--Fas, Fas ligand (FasL), Bcl-2, and Bax were examined by immunohistochemistry. Keratocyte depletion and endothelial changes were evaluated histologically. In situ end labeling of double-stranded DNA breaks was used to demonstrate apoptosis in corneal sections. RESULTS: Keratocyte depletion was observed in 6 (50%) of 12 rats (total from groups A, B, and C) at 12 h, 11 (73%) of 15 at 24 h, 3 (20%) of 15 at 36 h, and 2 (15%) of 13 at 1 week after laser surgery. Corneal endothelial edema was observed in the ablation zone. Expression of Fas, FasL, Bcl-2, and Bax in corneal cells showed dynamics similar to that of keratocyte depletion and endothelial changes. There was less expression of apoptotic molecules in newly generated epithelial cells and more in endothelial cells of the stromal ablation groups. CONCLUSIONS: Excimer laser keratectomy triggered apoptosis of corneal keratocytes and endothelial cells. More endothelial edema was observed in the stromal ablation than in the epithelial ablation group. The expression of apoptotic molecules coincided with the period of keratocyte depletion and regeneration and of endothelial recovery, suggesting that apoptosis is a dynamic part of corneal wound healing and remodeling after excimer laser keratectomy.

Animals↗
PubMed2000

Investigating the role of Ca2+-binding site IV in barnacle troponin C.

Two genetically engineered, recombinant versions of native barnacle troponin C (TnC) (BTnC,) were created from the bacterially expressed, recombinant, wild-type BTnC (BTnCWT) to investigate the role of the Ca(2+)-specific sites in force regulation. The mutant BTnC4- contains a single amino acid mutation in site IV which results in the inactivation of site IV Ca2+ binding; the mutant BTnCTrunc lacks the last II amino acids of the C-terminal, and hence most of site IV. Both mutant proteins, which retain an active site II, bind to native TnC-depleted myofibrillar bundles and restore approximately 40% of the tension-generating capacity, about half that seen with purified native BTnC1 or BTnC2. This observation implies that the Mg(2+)-dependent interaction with troponin I (TnI) is at a location on TnC other than the C-terminal Ca(2+)-binding sites of BTnC2. Replacement with BTnCTrunc increases the sensitivity of the myofibrillar bundle to changes in ionic strength. Decreasing the ionic strength from 0.15 to 0.075 M increased force by 34%, a value much greater that the 8% increase seen in control bundles or bundles substituted with BTnC4-. These findings implicate TnC in determining this fibre characteristic, although this cannot be simply due to the alteration in the numbers of Ca2+ ions bound by the troponin complex since both BTnC4- and BTnCTrunc bind only 1 mol Ca2+/mol protein.

Amino Acid Sequence↗
PubMed2000

Herpes simplex virus DNA identification from aqueous fluid in Fuchs heterochromic iridocyclitis.

PURPOSE: To report the presence of herpes simplex virus DNA in the aqueous humor of an eye with Fuchs heterochromic iridocyclitis. METHODS: In an eye with a clinical diagnosis of Fuchs heterochromic iridocyclitis, samples of aqueous humor and anterior capsule of the lens were obtained during cataract surgery. Polymerase chain reaction was performed on the samples to detect the presence of viral DNA including herpes simplex virus, varicella-zoster virus, and cytomegalovirus. Serologic analysis was also performed for antiviral immunoglobulins. RESULTS: Herpes simplex virus DNA was identified in the aqueous humor but not in the anterior capsule. Serum immunoglobulin G was positive for herpes simplex virus, varicella-zoster virus, and cytomegalovirus. CONCLUSIONS: The presence of herpes simplex virus DNA in the aqueous humor of an eye with Fuchs heterochromic iridocyclitis suggests that herpes simplex virus infection may play a role in the pathogenesis of Fuchs heterochromic iridocyclitis.

Adult↗
PubMed2000

On the protein residues that control the yield and kinetics of O(630) in the photocycle of bacteriorhodopsin.

The effects of pH on the yield (phi(r)), and on the apparent rise and decay constants (k(r), k(d)), of the O(630) intermediate are important features of the bacteriorhodopsin (bR) photocycle. The effects are associated with three titration-like transitions: 1) A drop in k(r), k(d), and phi(r) at high pH [pK(a)(1) approximately 8]; 2) A rise in phi(r) at low pH [pK(a)(2) approximately 4.5]; and 3) A drop in k(r) and k(d) at low pH [pK(a)(3) approximately 4. 5]. (pK(a) values are for native bR in 100 mM NaCl). Clarification of these effects is approached by studying the pH dependence of phi(r), k(r), and k(d) in native and acetylated bR, and in its D96N and R82Q mutants. The D96N experiments were carried out in the presence of small amounts of the weak acids, azide, nitrite, and thiocyanate. Analysis of the mutant's data leads to the identification of the protein residue (R(1)) whose state of protonation controls the magnitude of phi(r), k(r), and k(d) at high pH, as Asp-96. Acetylation of bR modifies the Lys-129 residue, which is known to affect the pK(a) of the group (XH), which releases the proton to the membrane exterior during the photocycle. The effects of acetylation on the O(630) parameters reveal that the low-pH titrations should be ascribed to two additional protein residues R(2) and R(3). R(2) affects the rise of phi(r) at low pH, whereas the state of protonation of R(3) affects both k(r) and k(d). Our data confirm a previous suggestion that R(3) should be identified as the proton release moiety (XH). A clear identification of R(2), including its possible identity with R(3), remains open.

Amino Acid Substitution↗
PubMed2000

Thyroid hormone receptor, v-ErbA, and chromatin.

The thyroid hormone receptor and the highly related viral oncoprotein v-erbA are found exclusively in the nucleus as stable constituents of chromatin. Unlike most transcriptional regulators, the thyroid hormone receptor binds with comparable affinity to naked and nucleosomal DNA. In vitro reconstitution experiments and in vivo genomic footprinting have delineated the chromatin structural features that facilitate association with the receptor. Chromatin bound thyroid hormone receptor and v-erbA generate Dnase I hypersensitive sites independent of ligand. The unliganded thyroid hormone receptor and v-erbA associate with a corepressor complex containing NCoR, SIN3, and histone deacetylase. The enzymatic activity of the deacetylase and a chromatin environment are essential for the dominant repression of transcription by both the unliganded thyroid hormone receptor and v-erbA. In the presence of ligand, the thyroid hormone receptor undergoes a conformational change that weakens interactions with the corepressor complex while facilitating the recruitment of transcriptional coactivators such as p300 and PCAF possessing histone acetyltransferase activity. The ligand-bound thyroid hormone receptor directs chromatin disruption events in addition to histone acetylation. Thus, the thyroid hormone receptor and v-erbA make very effective use of their stable association with chromatin and their capacity to alter the chromatin environment as a major component of the transcription regulation process. This system provides an exceptionally useful paradigm for investigating the structural and functional consequences of targeted chromatin modification.

Animals↗
PubMed2000

Qualitative and quantitative characterization of Fas (CD95) expression and its role in primary human acute leukemia cells.

Fas antigen, a cell surface molecule, directly mediates apoptosis, and is expressed on a limited number of human tissues. Blood or bone marrow samples from patients with acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL) and mixed leukemia were examined qualitatively and quantitatively for the expression of Fas as well as its function using flow cytometry and the annexin V staining method. Fas expression was flow cytometrically unimodal with heterogeneous density, and showed quantitatively characteristic features in different diseases: undetectable in mixed leukemia, faint to weak in ALL, low in M0 and M1, and variable (low to strong) in M2, M3, M4, and M5. Both the full-length and the alternatively spliced truncated mRNAs were detected constitutively even in acute leukemia cells with qualitatively negative and quantitatively faint Fas, and the band density of the former transcripts detected by RT-PCR was correlated with the level of expression of the Fas protein. Short-term culturing of freshly isolated leukemia cells gave rise to an increase of Fas density. In acute leukemia cells, the apoptosis induced by anti-Fas MoAb was compared with that induced by etoposide (a topoisomerase II inhibitor). We found that fresh ALL and AML cells were resistant to the anti-Fas IgM antibody, while etoposide could trigger apoptosis in all types of leukemia tested. The combined effects of the anti-Fas MoAb and etoposide were not always synergistic. These results suggest that Fas is a biological marker for characterizing ALL and AML cells, and provide insight into creating a new therapeutic modality using cytotoxic drugs and cytokines together with modulation of Fas.

Acute Disease↗
PubMed2000

Dual functions of thyroid hormone receptors during Xenopus development.

Thyroid hormone (TH) plays a causative role in anuran metamorphosis. This effect is presumed to be manifested through the regulation of gene expression by TH receptors (TRs). TRs can act as both activators and repressors of a TH-inducible gene depending upon the presence and absence of TH, respectively. We have been investigating the roles of TRs during Xenopus laevis development, including premetamorphic and metamorphosing stages. In this review, we summarize some of the studies on the TRs by others and us. These studies reveal that TRs have dual functions in frog development as reflected in the following two aspects. First, TRs function initially as repressors of TH-inducible genes in premetamorphic tadpoles to prevent precocious metamorphosis, thus ensuring a proper period of tadpole growth, and later as activators of these genes to activate the metamorphic process. Second, TRs can promote both cell proliferation and apoptosis during metamorphosis, depending upon the cell type in which they are expressed.

Animals↗
PubMed2000

The yeast polyadenylate-binding protein (PAB1) gene acts as a disease lesion mimic gene when expressed in plants.

We have expressed the gene (PAB1) encoding the yeast polyadenylate-binding protein (Pab1p) in tobacco. Plants that accumulate the Pab1p display a range of abnormalities, ranging from a characteristic chlorosis in leaves to a necrosis and large inhibition of growth. The severity of these abnormalities reflects the levels of yeast Pab1p expression in the transgenic plants. In contrast, no obvious differences could be seen in callus cultures between the transgene and vector control. Plants that display PAB-associated abnormalities were resistant to a range of plant pathogens, and had elevated levels of expression of a pathogenesis-related gene. These two properties--impairment of growth and induction of defense responses--indicate that the yeast PAB1 gene can act as a disease lesion mimic gene in plants.

Cell Division↗
PubMed2000

Immunotherapy of tumors with xenogeneic endothelial cells as a vaccine.

The breaking of immune tolerance against autologous angiogenic endothelial cells should be a useful approach for cancer therapy. Here we show that immunotherapy of tumors using fixed xenogeneic whole endothelial cells as a vaccine was effective in affording protection from tumor growth, inducing regression of established tumors and prolonging survival of tumor-bearing mice. Furthermore, autoreactive immunity targeting to microvessels in solid tumors was induced and was probably responsible for the anti-tumor activity. These observations may provide a new vaccine strategy for cancer therapy through the induction of an autoimmune response against the tumor endothelium in a cross-reaction.

Amino Acid Sequence↗
PubMed2000

Umbilical cord blood transplantation from unrelated HLA-matched donor in an adult with severe aplastic anemia.

A 23-year-old male suffering from severe aplastic anemia (SAA) weighing 60 kg was successfully treated by unrelated allo-CBSCT (cord blood stem cell transplantation). A six-loci HLA-identical umbilical cord blood (UCB) was infused after conditioning with low-dose cyclophosphamide (CTX) and antilymphocyte globulin (ALG). The prophylaxis of GVHD consisted of CsA and MTX. The infused cord blood provided 1.89 x 10(7) nucleated cells per kg, CD34-positive cells: 0.89%. Neutrophils >0.5 x 10(9)/l were reached 10 days after transplant, and platelets greater than 50.0 x 10(9)/l at day 26. RBC and platelet transfusion independence were reached on days 15 and 18. The patient developed grade 1 skin GVHD 10 months after engraftment of the donor cells. Microsatellite DNA fingerprinting indicated a stable and persistent donor-recipient mixed chimerism, whilst the circulating red cells remain of host origin.

Adult↗
PubMed2000

The high-sensitivity determination of protein concentrations by the enhancement of Rayleigh light scattering of Arsenazo-DBN.

A new Rayleigh light scattering (RLS) assay of protein is presented in this paper. At the optimum pH 4.10, the weak RLS of Arsenazo-DBN can be greatly enhanced by the addition of proteins due to the interaction between protein and Arsenazo-DBN. Based on this, the reactions of Arsenazo-DBN and proteins, including bovine serum albumin, human serum album, gamma-globulin, egg albumin, lysozyme and trypsin, were studied. A new quantitative determination method for proteins has been developed. The linear range for human serum albumin, for example, is 0.085-34.62 micrograms mL-1 with a detection limit of 44.8 ng mL-1. Besides high sensitivity, the method is characterized by good reproducibility, rapidity of reaction, good stability, and few interfering substances. The determination of the proteins in human serum and urine samples by this method give results very close to those obtained using Coomassie Brilliant Blue G-250 colorimetry, with relative standard deviations of 0.7-2.5%.

Arsenazo III↗
PubMed2000

Indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper.

A new method for the indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper in the presence of ascorbic acid is described. A small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) is precipitated with SCN-. In the course of phase separation of ethanol from water, the precipitated CuSCN stays in the interface of ethanol and water. A good linear relationship is observed between the flotation yield of Cu(II) and the amount of SCN-. Using 1.0 ml of 1 x 10(-3) M ascorbic acid solution, 50 micrograms of Cu(II), 3.5 g of (NH4)2SO4 and 3.0 ml of ethanol with a total volume of 10 ml, the concentration of thiocyanate could then be determined by determining the flotation yield of Cu(II). The detection limit for thiocyanate is 5 x 10(-5) M. Every parameter was optimized and the reaction mechanism was studied. The method is simple and rapid and it was successfully applied to the determination of thiocyanate in urine and saliva of smokers and non-smokers and in venous blood of patients infused with sodium nitroprusside.

Ammonium Sulfate↗
PubMed2000

Photoelectrochemistry as a novel strategy for DNA hybridization detection.

The special properties of ssDNA and dsDNA molecules in structure and electric behavior, may offer us some new ideas for the fabrication of genosensors and DNA-chips. In this work, the photoelectrochemical method was firstly employed to characterize the photoelectric behavior of a ssDNA probe electrode, which was prepared with the self-assembly technique, and its resulting dsDNA electrode. The obvious decrease in the photocurrent of the dsDNA modified electrode at open potential or a bias voltage indicated that photoelectrochemistry was another useful method for DNA hybridization detection. Using the special design of ssDNA probes, we attempt to discuss further the relationship between the properties of DNA molecules and their photoelectric behaviors. In addition, the electrochemical impedance method was employed to verify the occurrence of some modifications over the electrode interface before and after the hybridization event.

DNA↗
PubMed2000

Chromatographic methods for the determination of the logL16 solute descriptor.

A squalane packed column and two open-tubular columns coated with an immobilized stationary phase film of poly(dimethylsiloxane) or poly(methyloctylsiloxane) are evaluated as surrogate chromatographic systems for the determination of the logL16 solute descriptor by gas chromatography. Retention on the squalane column is dominated by gas-liquid partitioning with a significant temperature-dependent contribution from interfacial adsorption at the liquid-solid interface. Using the gas-liquid partition coefficient as the dependent model variable allows logL16 to be estimated to +/- 0.026 log units over the temperature range 60-120 degrees C. Without correction for interfacial adsorption a single column estimation of logL16 with phase loadings of 8 to 20% (m/m) over the temperature range 80-120 degrees C is possible for compounds with moderate hydrogen-bond basicity. The poly(dimethylsiloxane) stationary phase is both dipolar and hydrogen-bond basic and less suitable than the poly(methyloctylsiloxane) stationary phase, which is less cohesive and has similar dipolarity but no hydrogen-bond basicity. The determination of logL16 on the poly(methyloctylsiloxane) column requires prior knowledge of the solute dipolarity/polarizability descriptor to avoid significant errors in the measurement of logL16 for polar compounds. In such circumstances a single column estimation of logL16 over the temperature range 60-140 degrees C with an error of +/- 0.05-0.09 log units is possible.

Journal Article↗
PubMed2000

Study of the electrochemical behavior of mitoxantrone and its determination at a Co-C modified ultramicroelectrode.

In 0.005 mol dm-3 Tris-0.05 mol dm-3 NaCl buffer solution (pH 7.10), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Co-carbon fiber ion implantation modified ultramicroelectrode. A sensitive reduction peak was obtained. The peak potential was -0.798 V (vs. SCE), the peak current was proportional to the concentration of mitoxantrone over the range of 2.0 x 10(-7)-6.0 x 10(6) mol dm-3 and the detection limit was 4.2 x 10(-8) mol dm-3. This method was applied to the direct determination of mitoxantrone in urine. Recoveries were in the range 95.4-105.8%. The reduction process was quasi-reversible with absorptive characteristics at a Co-C ultramicroelectrode. According to Laviron's theory, the electrode reaction rate constant ks and the electron transfer alpha of mitoxantrone were 4.4 s-1 and 0.48, respectively. The composition and depth distribution of elements on the surface of the Co-C ultramicroelectrode were determined by Auger electron spectroscopy. The experiments showed that Co was implanted into the surface of the carbon fiber, and the Co-C ultramicroelectrode had good stability and reproducibility.

Journal Article↗