Biomedical subjects

J Liu

Publications and source records attributed to J Liu.

At least 361 records · Page 20Linked to original sources

PubMed2001

Studies on the frequencies of vitamin D receptor gene polymorphism in postmenopausal women of Han and Kazak nationality in China.

Polymorphyism of the vitamin D receptor (VDR) gene is reported to play a major role in variations of the genetic regulation of bone mass. The role of VDR polymorphisms within various ethnic populations is also undetermined. The purpose of the present study was to determine the frequencies of VDR genotypes in the Han and Kazak nationalities in China. We analyzed the polymorphism defined by the Bsm1 restriction enzyme using polymerase chain reaction-restriction fragment length polymorphism in 179 healthy postmenopausal Han women and 63 healthy postmenopausal Kazak women. The genotype frequencies of the VDR were calculated later using the Hardy-Weinberg equilibrium formula. The results showed that for women of Han nationality, the bb, Bb, and BB genotypes accounted for 90.5%, 9.5%, and 0%, respectively. In Kazak women, the respective frequencies were 38.1%, 55.56%, and 6.35%. We found that there was a significant difference between women of Han and Kazak nationality in terms of the frequency of distribution of VDR genotype (P < 0.001). There was a similar distribution of VDR genotypes in Kazak women to that seen for the Caucasian population of the USA. The results of the present study provide further evidence on the different pathogeny of osteoporosis in various ethnic groups.

Bone Density↗

PubMed2001

Self-monitoring of blood glucose levels and glycemic control: the Northern California Kaiser Permanente Diabetes registry.

PURPOSE: We sought to evaluate the effectiveness of self-monitoring blood glucose levels to improve glycemic control. SUBJECTS AND METHODS: A cohort design was used to assess the relation between self-monitoring frequency (1996 average daily glucometer strip utilization) and the first glycosylated hemoglobin (HbA1c) level measured in 1997. The study sample included 24,312 adult patients with diabetes who were members of a large, group model, managed care organization. We estimated the difference between HbA1c levels in patients who self-monitored at frequencies recommended by the American Diabetes Association compared with those who monitored less frequently or not at all. Models were adjusted for age, sex, race, education, occupation, income, duration of diabetes, medication refill adherence, clinic appointment "no show" rate, annual eye exam attendance, use of nonpharmacological (diet and exercise) diabetes therapy, smoking, alcohol consumption, hospitalization and emergency room visits, and the number of daily insulin injections. RESULTS: Self-monitoring among patients with type 1 diabetes (> or = 3 times daily) and pharmacologically treated type 2 diabetes (at least daily) was associated with lower HbA1c levels (1.0 percentage points lower in type 1 diabetes and 0.6 points lower in type 2 diabetes) than was less frequent monitoring (P < 0.0001). Although there are no specific recommendations for patients with nonpharmacologically treated type 2 diabetes, those who practiced self-monitoring (at any frequency) had a 0.4 point lower HbA1c level than those not practicing at all (P < 0.0001). CONCLUSION: More frequent self-monitoring of blood glucose levels was associated with clinically and statistically better glycemic control regardless of diabetes type or therapy. These findings support the clinical recommendations suggested by the American Diabetes Association.

Adult↗

PubMed2001

Uncertainty analysis for temperature prediction of biological bodies subject to randomly spatial heating.

An analytical solution to the Pennes bioheat transfer equation in three-dimensional geometry with practical hyperthermia boundary conditions and random heating was obtained in this paper. Uncertainties for the predicted temperatures of tissues due to approximate parameters were studied based on analyzing one-dimensional heat transfer in the biological bodies subject to a spatially decay heating. Contributions from each of the thermal parameters such as heat conductivity, blood perfusion rate, and metabolic rate of the tissues, the scattering coefficient and the surface power flux of the heating apparatus were compared and the uncertainty limit for temperature distribution in this case was estimated. The results are useful in a variety of clinical hyperthermia and biological thermal parameter measurement.

Body Temperature↗

PubMed2001

Testing cognitive models of visual attention with fMRI and MEG.

Neuroimaging techniques can be used not only to identify the neural substrates of attention, but also to test cognitive theories of attention. Here we consider four classic questions in the psychology of visual attention: (i) Are some 'special' classes of stimuli (e.g. faces) immune to attentional modulation?; (ii) What are the information units on which attention operates?; (iii) How early in stimulus processing are attentional effects observed?; and (iv) Are common mechanisms involved in different modes of attentional selection (e.g. spatial and non-spatial selection)? We describe studies from our laboratory that illustrate the ways in which fMRI and MEG can provide key evidence in answering these questions. A central methodological theme in many of our fMRI studies is the use of analyses in which the activity in certain functionally-defined regions of interest (ROIs) is used to test specific cognitive hypotheses. An analogous sensor-of-interest (SOI) approach is applied to MEG. Our results include: evidence for the modulation of face representations by attention; confirmation of the independent contributions of object-based and location-based selection; evidence for modulation of face representations by non-spatial selection within the first 170 ms of processing; and implication of the intraparietal sulcus in functions general to spatial and non-spatial visual selection.

Attention↗

PubMed2001

Age-related effects of chlorpyrifos on acetylcholine release in rat brain.

Chlorpyrifos (CPF) is an organophosphorus insecticide that elicits toxicity through inhibition of acetylcholinesterase (AChE). Young animals are markedly more sensitive than adults to the acute toxicity of CPF. We evaluated acetylcholine (ACh) release and its muscarinic receptor-mediated regulation (i.e. muscarinic autoreceptor function, MAF) during maturation as a possible contributing factor to age-related differences in sensitivity. Cortical and striatal slices were prelabeled with [3H]choline chloride, superfused in the presence or absence of the anticholinesterase physostigmine (PHY, 20 microM) and stimulated twice (S1 and S2) with a high concentration of potassium chloride (20 mM). Depolarization-stimulated ACh release (DSAR) was lowest in neonatal, intermediate in juvenile and markedly higher in adult tissues. MAF was not detectable in tissues from neonatal rats but was present in juvenile and adult tissues. ACh release and MAF were studied at 4, 24 and 96 h following oral exposure to CPF (0, 0.5 or 1 x LD10). In general, 40-60% and 80-90% maximal AChE inhibition followed exposure to the respective 0.5 and 1 x LD10 dosages. DSAR was decreased in neonatal cortex 1 day after LD10 exposure but increased in juvenile striatum 1 day after LD10 treatment. In adults, DSAR was reduced at 4 and 24 h after exposure, but increased 96 h after CPF exposure. In juveniles, MAF was reduced in both brain regions at 24 h after 0.5LD10 exposure and at 24 and 96 h after LD10 exposure in cortex. A later reduction in MAF was noted in adult tissues (i.e. only at 96 h after LD10 treatment). Together, the results suggest that ACh release dynamics in brain vary markedly during postnatal maturation and that acute CPF exposure can alter ACh release in an age-related manner. The functional status of presynaptic processes regulating neurotransmitter release may contribute to age-related neurotoxicity elicited by high-dose exposures to chlorpyrifos.

Acetylcholine↗

PubMed2001

DNA-binding and photocleavage studies of cobalt(III) mixed-polypyridyl complexes containing 2-(2-chloro-5-nitrophenyl)imidazo [4,5-f][1,10]phenanthroline.

The ligand 2-(2-chloro-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline(CNOIP) and its complexes [Co(bpy)(2)(CNOIP)](3+) (1) and [Co(phen)(2)(CNOIP)](3+) (2) (bpy=2,2'-bipyridine; phen=1,10-phenanthroline) have been synthesized and characterized. Binding of the two complexes with calf thymus DNA has been investigated by spectroscopic methods, cyclic voltammetry, viscosity, and electrophoresis measurements. The experimental results indicate that both complexes bind to DNA through an intercalative mode. In comparison with their parent complexes containing PIP ligand (PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline), the introduction of NO(2) and Cl groups to the PIP ligand decreased the binding affinity of complexes 1 and 2 to CT DNA. Both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA, the hydroxyl radical (OH*) is suggested to be the reactive species responsible for the cleavage.

Cobalt↗

PubMed2001

Neurotransmitter dopamine applied in electrochemical determination of aluminum in drinking waters and biological samples.

It was demonstrated that the decrease of the differential pulse voltammetric (DPV) anodic peak current of dopamine (3,4-dihydroxyphenylethylamine, DA) was linear with the increase of aluminum (Al) concentration. Under optimum experimental conditions (pH 4.6, 1.2 x 10(-3) M DA, and 0.04 M NaAc-HAc buffer solution), the linear range is 4.0 x 10(-7)-8.0 x 10(-5) M, the detection limit is 1.4 x 10(-7) M, and the relative standard deviation for 4 x 10(-5) M Al(III) is 3.5% (n=8). Many foreign species, especially some low-molecule-weight biological molecules, were chosen for interference testing. The proposed method was applied to the determination of Al in biological samples such as synthetic renal dialysate, Ringer's solution, human blood, cerebrospinal fluid of a patient, and urine of a diabetic patient. The corresponding recoveries were generally between 95 and 105%. The basic principle of the method was determined by examining Al complexed with DA. This results in the blockage of the electroactive sites on DA, followed eventually by the reduction of the electrochemical response of DA. This result was verified by examining the behavior of DA, both in the presence and absence of Al, using electrochemical, UV-Vis, Raman, and (13)C NMR spectroscopic methods.

Aluminum↗

PubMed2001

Prevention of brick tea fluorosis in rats with low-fluoride brick tea on laboratory observation.

To test whether low-fluoride brick tea can prevent the occurrence of fluorosis, rats had access only to a specially prepared low-fluoride brick tea for 1 year. The daily fluoride intake, fluoride metabolism, tissue distribution and development of tooth fluorosis were observed at 4-monthly intervals, at the end of months 4, 8 and 12, respectively. Rats drinking ordinary brick tea (F- 503.5 mg/kg) served as control. The daily intake of fluoride in the ordinary brick tea group was 0.3 mg, and this group developed dental fluorosis characterized as brown and white horizontal marks at the end of month 8, and white chalky dental fluorosis developed at the end of month 12. The total incidence was 75%. In contrast, the daily fluoride intake of the low-fluoride brick tea (F- 210 mg/kg) group was 0.19 mg, and this group did not develop any signs of dental fluorosis. Fluoride distribution was mainly retained in the bone tissue, and about half of the absorbed fluoride was excreted via urine and feces. The results suggest that this low-fluoride brick tea did not induce fluorosis in rats and can be used as an effective control measure for humans.

Age Factors↗

PubMed2001

Follicular growth in fresh and cryopreserved human ovarian cortical grafts transplanted to immunodeficient mice.

OBJECTIVE: To investigate follicle growth in fresh and cryopreserved human ovarian cortical grafts transplanted to immunodeficient mice. STUDY DESIGN: Fresh or frozen-thawed human ovarian cortex was grafted subcutaneously or under the kidney capsule of 43 mice (35 nude mice and eight SCID mice), 14 of which were non-stimulated controls, 21 injected intra-peritoneally with gonadotrophins during 2 weeks and eight injected during 3 months. Follicle count was compared by Chi-square. RESULTS: Proportions of primordial follicles were significantly lower in grafts than in the tissue before transplantation in gonadotrophin-stimulated mice (37% versus 79%), but not in non-stimulated mice (51% versus 74%). Proportions of primary and secondary follicles were increased after transplantation indicating early follicular growth. One antral follicle was observed in a graft in a mouse stimulated for 3 months. CONCLUSION: Primordial follicles in fresh or frozen-thawed human ovarian cortex transplanted under the kidney capsule or subcutaneously can grow and are responsive to hormonal stimulation. CONDENSATION: Primordial follicles in fresh and cryopreserved human ovarian cortical grafts can initiate growth after transplantation to immunodeficient mice

Adult↗

PubMed2001

Characterization of AC mode scanning ion-conductance microscopy.

A scanning ion-conductance microscope (SICM) with a vibrating probe has been recently developed (vSICM). In this system, the amplitude of the AC ionic current is detected by using a lock-in amplifier locked to the vibration frequency of the probe. Such a scheme allows for a better control of the tip position because the AC ionic current is more sensitive to the probe-surface distance than the DC ionic current used previously. In this paper, we demonstrate the utility of this technique to the imaging of topographically rough specimens and high-resolution imaging over selected small areas. We also show that it is possible to record the DC ionic current simultaneously during the scan, which can reveal additional information not apparent in the images obtained with the AC ionic current.

Electric Conductivity↗

PubMed2001

Heterogeneous nuclear ribonucleoprotein-H plays a suppressive role in visceral myogenesis.

Mouse embryonic mesenchymal cells undergo spontaneous smooth muscle (SM) differentiation upon spreading/elongation in culture (Relan et al., J. Cell Biol. 147 (1999) 1341; Yang et al., Development 125 (1998) 2621; Yang et al., Development 126 (1999) 3027). Using these cells we generated a subtracted cDNA library to identify potential suppressors of SM myogenesis. One of the differentially expressed genes was heterogeneous nuclear ribonucleoprotein-H (hnRNP-H), which is involved in pre-mRNA alternative splicing. hnRNP-H was highly expressed in mesenchymal cells prior to the onset of SM differentiation, but its expression rapidly decreased in mesenchymal cells undergoing SM myogenesis. In vivo, the drop in hnRNP-H expression was restricted to visceral SM cells. Antisense oligodeoxynucleotide and antisense RNA were used to inhibit hnRNP-H synthesis in SM-differentiating mesenchymal cells and in embryonic lung explants. A decrease in hnRNP-H levels resulted in upregulation of SM-specific gene expression and increased bronchial SM development in lung explants. hnRNP-H overexpression in cell cultures had the opposite effect. These studies, therefore, indicate a novel role for hnRNP-H in the control of visceral myogenesis.

Alternative Splicing↗

PubMed2001

Properties of lipophilic matrix tablets containing phenylpropanolamine hydrochloride prepared by hot-melt extrusion.

The objective of the present study was to investigate the influence of formulation factors on the physical properties of hot-melt extruded granules and compressed tablets containing wax as a thermal binder/retarding agent, and to compare the properties of granules and tablets with those prepared by a high-shear melt granulation (MG) method. Powder blends containing phenylpropanolamine hydrochloride, Precirol and various excipients were extruded in a single-screw extruder at open-end discharge conditions. The extrudates were then passed through a 14-mesh screen to form granules. The extrusion conditions and the optimum amount of wax to function as the thermal binder were dependent on the properties of the filler excipients. At the same wax level, drug release from tablets decreased in the order of using microcrystalline cellulose (MCC), lactose and Emcompress as the filler excipient. The observed differences in the dissolution properties of the tablets were due to the differences in the solubility, swellability and density of the filler excipients. Replacing Precirol with Sterotex K, a higher melting point wax, resulted in slightly increased dissolution rates, when the extrusion was performed at the same temperature conditions. Hot-melt extruded granules were observed to be less spherical than high-shear melt granules and showed lower values of bulk/tap densities. However, tablets containing MCC or lactose granules prepared by hot-melt extrusion (HME) exhibited higher hardness values. Slower drug release rates were found for tablets containing MCC by HME compared with MG. Analysis of the hot-melt extruded granules showed better drug content uniformity among granules of different size ranges compared with high-shear melt granules, resulting in a more reproducible drug release from the corresponding tablets.

Adrenergic alpha-Agonists↗

PubMed2001

Hexosaminidase inhibitors as new drug candidates for the therapy of osteoarthritis.

BACKGROUND: Articular cartilage from patients with osteoarthritis is characterized by a decreased concentration and reduced size of glycosaminoglycans. Degeneration of the cartilage matrix is a multifactorial process, which is due in part to accelerated glycosaminoglycan catabolism. Recently, we have demonstrated that hexosaminidase represents the dominant glycosaminoglycan-degrading glycosidase released by chondrocytes into the extracellular compartment and is the dominant glycosidase in synovial fluid from patients with osteoarthritis. Inhibition of hexosaminidase activity may represent a novel approach to the prevention of cartilage matrix glycosaminoglycan degradation and a potentially new strategy to treat osteoarthritis. RESULTS: We have synthesized and investigated a series of iminocyclitols designed as transition-state analog inhibitors of human hexosaminidase, and demonstrated that the five-membered iminocyclitol 4 expresses the strongest inhibitory activity with K(i)=24 nM. Inhibition of hexosaminidase activity in human cultured articular chondrocytes and human chondrosarcoma cells with iminocyclitol 4 resulted in accumulation of hyaluronic acid and sulfated glycosaminoglycans in the cell-associated fraction. Similarly, incubation of human cartilage tissue with iminocyclitol 4 resulted in an accumulation of glycosaminoglycans in the pericellular compartment. CONCLUSIONS: Inhibition of hexosaminidase activity represents a new strategy for preventing or even reversing cartilage degradation in patients with osteoarthritis.

Cartilage, Articular↗

PubMed2001

Enhanced CD4+ T cell proliferation and Th2 cytokine production in DR6-deficient mice.

We have found that DR6, a member of the TNF receptor family, is highly expressed in resting T cells and downregulated in activated T cells. DR6-targeted mutant mice were generated and showed normal development. However, DR6(-/-) CD4(+) T cells hyperproliferated in response to TCR-mediated stimulation and protein antigen challenge. Activated DR6(-/-) CD4(+) T cells exhibited upregulated CD25 expression and enhanced proliferation in response to exogenous IL-2 stimulation. In addition, increased CD28 and reduced CTLA-4 expression were observed in these cells. Enhanced Th2 cytokine production by activated DR6(-/-) CD4(+) T cells was associated with the increased transcription factor NF-ATc in nuclei. DR6, therefore, functions as a regulatory receptor for mediating CD4(+) T cell activation and maintaining proper immune responses.

Abatacept↗

PubMed2001

Cold adaptive thermogenesis in small mammals from different geographical zones of China.

The mechanisms of thermogenesis and thermoregulation were studied in the tree shrew (Tupaia belangeri) and greater vole (Eothenomys miletus) of the subtropical region, and Brandt's vole (Microtus brandti), Mongolian gerbil (Meriones unguiculatus), Daurian ground squirrel (Spermophilus dauricus) and plateau pika (Ochotona curzoniae) of the northern temperate zone. Resting metabolic rate (RMR) and non-shivering thermogenesis (NST) increased significantly in T. belangeri, E. miletus, M. brandti and M. unguiculatus after cold acclimation (4 degrees C) for 4 weeks. In T. belangeri, the increase in RMR and thermogenesis at liver cellular level were responsible for enhancing the capacity of enduring cold stress, and homeothermia was simultaneously extended. Stable body temperature in M. brandti, E. miletus, M. unguiculatus and O. curzoniae was maintained mainly through increase in NST, brown adipose tissue (BAT) mass and its mitochondrial protein content, and the upregulation of uncoupling protein (UCP1) mRNA, as well as enhancement of the activity of cytochrome C oxidase, alpha-glycerophosphate oxidase and T(4) 5'-deiodinase in BAT mitochondria. The RMR in O. curzoniae and euthermic S. dauricus was not changed, while NST significantly increased during cold exposure; the former maintained their stable body temperature and mass, while body temperature in the latter declined by 4.8 degrees C. The serum T(3) concentration or ratio of T(3)/T(4) in all the species was enhanced after cold acclimation. Results indicated that: (1) the adaptive mechanisms of T. belangeri residing in the subtropical region to cold are primarily by increasing RMR and secondly by increasing NST, and the mechanisms of thermogenesis are similar to those in tropical mammals; (2) in small mammals residing in northern regions, the adaptation to cold is chiefly to increase NST; (3) the mechanism of cold-induced thermogenesis in E. miletus residing in subtropical and high mountain regions is similar to that in the north; (4) a low RMR in warm environments and peak RMR and NST in cold environments enabled M. unguiculatus to tolerate a semi-desert climate; (5) O. curzoniae has unusually high RMR and high NST, acting mainly via increasing NST to adapt to extreme cold of the Qinghai-Tibet Plateau; (6) the adaptation of euthermic S. dauricus to cold is due to an increase in NST and a relaxed homeothermia; and lastly (7) the thyroid hormone is involved in the regulation of cold adaptive thermogenesis in all the species studied.

Adaptation, Physiological↗

PubMed2001

Siah-1 mediates a novel beta-catenin degradation pathway linking p53 to the adenomatous polyposis coli protein.

The adenomatous polyposis coli (APC) tumor-suppressor protein, together with Axin and GSK3beta, forms a Wnt-regulated signaling complex that mediates phosphorylation-dependent degradation of beta-catenin by the proteasome. Siah-1, the human homolog of Drosophila seven in absentia, is a p53-inducible mediator of cell cycle arrest, tumor suppression, and apoptosis. We have now found that Siah-1 interacts with the carboxyl terminus of APC and promotes degradation of beta-catenin in mammalian cells. The ability of Siah-1 to downregulate beta-catenin signaling was also demonstrated by hypodorsalization of Xenopus embryos. Unexpectedly, degradation of beta-catenin by Siah-1 was independent of GSK3beta-mediated phosphorylation and did not require the F box protein beta-TrCP. These results indicate that APC and Siah-1 mediate a novel beta-catenin degradation pathway linking p53 activation to cell cycle control.

Adenomatous Polyposis Coli Protein↗

PubMed2001

Cellular localization of BM88 mRNA in paraffin-embedded rat brain sections by combined immunohistochemistry and non-radioactive in situ hybridization.

With the advent of gene cloning and sequencing, it has become increasingly common to identify novel genes for which no antibody is available. The best approach to study the expression and the distribution of these new genes is by in situ hybridization. One of the challenges with this method is to define the exact cellular subtype where the gene of interest is expressed. Conventional isotopic in situ hybridization methods lack precision for cellular identification because radioactive probes often result in a scattered signal. To identify the exact cellular subtype expressing BM88, we established a rapid colocalization method using non-isotopic in situ hybridization followed by chromogenic immunohistochemistry on the same tissue section. We demonstrated that BM88, which was identified from subtractive hybridization experiments between normal and ischemic tolerant brain tissue, was expressed exclusively in neurons in normal adult rat brain. Paraffin-embedded tissue was used as it resulted in better preservation of tissue and cellular morphology, thus allowing for more accurate histological localization of gene expression. It also allowed for retrospective studies on a number of archived tissue samples.

Animals↗

PubMed2001

Spectroscopy study on the photochromism of Schiff bases N,N'-bis(salicylidene)-1,2-diaminoethane and N,N'-bis(salicylidene)-1,6-hexanediamine.

The photochromism of Schiff bases N,N'-bis(salicylidene)-1,2-diaminoethane (BSE) and N,N'-bis(salicylidene)-1,6-cyclohexanediamine (BSH) was studied by steady-state and time-dependent fluorescence, UV Vis absorption spectroscopy and theoretical chemistry calculations. The experimental results show that BSH can perform the photochromism easier than BSE, may be due to the molecular topology difference.

Ethylenediamines↗