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Biomedical subjects

X J Liu

Publications and source records attributed to X J Liu.

At least 19 recordsLinked to original sources
PubMed2003

Cell differentiation and colony alteration of an edible terrestrial cyanobacterium Nostoc flagelliforme, in liquid suspension cultures.

Morphological characteristics of an edible terrestrial cyanobacterium Nostoc flagelliforme in liquid suspension cultures under photoautotrophic conditions are presented. Different cell forms alternated in a regular manner during the experimentation period (30 d). N. flagelliforme exhibited a very complex life cycle in terms of colony morphology, including mainly 4 different colony morphological forms, viz. hormogonia, filaments, seriate colonies and aseriate colonies. Under laboratory conditions it formed spherical colonies on solid media but not threadlike colonies as it did under natural conditions. The overall life span of the alga was not altered by the existence of different nitrogen sources in the media despite the depression of some cell forms or colony morphologies. Compared with growth on the medium with urea and ammonium as nitrogen sources, the alga on standard medium had a short period of hormogonia and aseriate colony, suggesting that both ammonium and urea could stimulate the formation of hormogonia, at the same time inhibiting the formation of heterocystous cells. The new information on the growth and morphology of N. flagelliforme could be potentially used for the scale-up or field cultivation.

Agar↗
PubMed2002

Formation of immiscible alloy powders with egg-type microstructure.

The egg-type core microstructure where one alloy encases another has previously been obtained during experiments in space. Working with copper-iron base alloys prepared by conventional gas atomization, we were able to obtain this microstructure under gravity conditions. The minor liquid phase always formed the core of the egg, and it sometimes also formed a shell layer. The origin of the formation of this core microstructure can be explained by Marangoni motion on the basis of the temperature dependence of the interfacial energy, which shows that this type of powder can be formed even if the cooling rate is very high.

Journal Article↗
PubMed2002

Enhanced release of adenosine in rat hind paw following spinal nerve ligation: involvement of capsaicin-sensitive sensory afferents.

Modulation of endogenous adenosine levels by inhibition of adenosine metabolism produces a peripheral antinociceptive effect in a neuropathic pain model. The present study used microdialysis to investigate the neuronal mechanisms modulating extracellular adenosine levels in the rat hind paw following tight ligation of the L5 and L6 spinal nerves. Subcutaneous injection of 50 microl saline into the nerve-injured paw induced a rapid and short-lasting increase in extracellular adenosine levels in the subcutaneous tissues of the rat hind paw ipsilateral to the nerve injury. Saline injection did not increase adenosine levels in sham-operated rats or non-treated rats. The adenosine kinase inhibitor 5'-amino-5'-deoxyadenosine and the adenosine deaminase inhibitor 2'-deoxycoformycin, at doses producing a peripheral antinociceptive effect, did not further enhance subcutaneous adenosine levels in the nerve-injured paw. Systemic pretreatment with capsaicin, a neurotoxin selective for small-diameter sensory afferents, markedly reduced the saline-evoked release of adenosine in rat hind paw following spinal nerve ligation. Systemic pretreatment with 6-hydroxydopamine, a neurotoxin selective for sympathetic afferent nerves, did not affect release. These results suggest that following nerve injury, peripheral capsaicin-sensitive primary sensory afferent nerve terminals are hypersensitive, and are able to release adenosine following a stimulus that does not normally evoke release in sham-operated or intact rats. Sympathetic postganglionic afferents do not appear to be involved in such release. The lack of effect on such release by the inhibitors of adenosine metabolism suggests an altered peripheral adenosine system following spinal nerve ligation.

Adenosine↗
PubMed2001

Discovery of a series of nonpeptide small molecules that inhibit the binding of insulin-like growth factor (IGF) to IGF-binding proteins.

Insulin-like growth factors (IGF-I and II) play an important role in metabolic and mitogenic activities through stimulation of the IGF-I receptor on the cell surface. Although the concentration of IGF in blood and cerebrospinal fluid is quite high (>100 nM), this large pool of IGF is biologically inactive because of its association with six distinct binding proteins, which form high-affinity complexes with IGF. Thus, inhibitors of IGF-binding proteins (IGFBPs), especially IGFBP-3, could potentially alter the distribution between the "free" and "bound" forms of IGF and thereby elevate biologically active IGF-I to exert a beneficial effect on those patients with diseases that respond to the application of exogenous IGF-I. Whereas IGF-I peptide variants, which bind to IGFBPs but not the IGF-I receptor, have been shown to be potent IGF/IGFBP inhibitors, small molecule nonpeptide IGF/IGFBP inhibitors have the potential advantages of oral bioavailability and flexible dosing regimen. Here we report the discovery of several isoquinoline analogues, exemplified by 1 and 2, which bind IGFBP-3 as well as other IGFBPs at low nanomolar concentrations. More importantly, both compounds were shown to be able to release biologically active IGF-I from the IGF-I/IGFBP-3 complex. These results point to the feasibility of developing orally active therapeutics to treat IGF-responsive diseases by optimization of the lead molecules 1 and 2.

3T3 Cells↗
PubMed2001

Involvement of primary sensory afferents, postganglionic sympathetic nerves and mast cells in the formalin-evoked peripheral release of adenosine.

Injection of formalin into the rat hind paw produces a dose-dependent local peripheral release of adenosine. Low doses of formalin (0.5-2.5%) evoke release during the first 10 min following injection, while a high dose of formalin (5%) evokes release lasting for 60 min. The current study was designed to determine the possible origin of release produced by two doses of formalin (1.5% and 5%). Microdialysis probes were implanted into the subcutaneous tissue under the glabrous skin of the hind paw of anaesthetized rats, and adenosine was determined by high performance liquid chromatography. Pretreatment with capsaicin, a neurotoxin selective for unmyelinated small diameter primary afferent nerves, markedly reduced the adenosine released by 1.5% formalin and the early phase of release by 5% formalin. Acute injection of 1% capsaicin to the hind paw of untreated rats also induced adenosine release. Pretreatment with 6-hydroxydopamine, a neurotoxin selective for sympathetic postganglionic nerve terminals, had no effect on release evoked by 1.5% formalin, but significantly reduced adenosine release during the late phase of release induced by 5% formalin. Pretreatment with compound 48/80, which degranulates mast cells, had no effect on adenosine release evoked by either concentration of formalin. We conclude that the origin of the adenosine released peripherally by formalin depends on the formalin concentration. At the lower concentration (1.5%), release is predominantly from unmyelinated sensory afferent nerve terminals, while at the higher concentration (5%), unmyelinated afferent nerve terminals are involved in the early phase, while sympathetic postganglionic nerve terminals are involved in the later phase. Mast cells do not contribute to release of adenosine evoked by either concentration of formalin.

Adenosine↗
PubMed2001

Significance of cadmium concentrations in blood and hair as an indicator of dose 15 years after the reduction of environmental exposure to cadmium.

To evaluate the significance of cadmium (Cd) concentrations in blood (B-Cd) and hair (H-Cd) as an indicator of dose, a cross-sectional study was performed on 40 residents in a Cd-polluted area, Nagasaki Prefecture, Japan, in 1996. In the study area, soil replacement of Cd-polluted rice fields ended in 1981. B-Cd and H-Cd were significantly higher in the study population than in the control subjects. B-Cd was positively correlated with urinary Cd (U-Cd) (Spearman r=0.50, P=0.06 for males and r=0.72, P=0.0001 for females), while H-Cd was weakly or moderately correlated with U-Cd. After adjustment for gender using logistic regression analysis, log(B-Cd) and log(U-Cd), but not log(H-Cd), were significantly associated with the prevalence of increased urinary beta2-microglobulin (P for trend <0.05). These findings suggest that B-Cd is a good indicator of cumulative dose many years after the reduction of environmental exposure to Cd. H-Cd may be weakly or moderately correlated with body burden.

Adult↗
PubMed2001

Identification of a nonpeptide ligand that releases bioactive insulin-like growth factor-I from its binding protein complex.

Insulin-like growth factor-I (IGF-I) has both metabolic and mitogenic activities mediated through interaction with the type 1 IGF receptor. The circulation of IGF-I in blood and interstitial fluid is not free but bound mostly to a family of six high affinity IGF-binding proteins, which form stable complexes with IGF and neutralize its bioactivity. Therefore, displacement of this large pool of endogenous IGF from the binding proteins could elevate "free" IGF levels to elicit beneficial effects in diabetes and other IGF-responsive diseases comparable with those produced by administration of exogenous IGF-I. We report here the identification of a nonpeptide ligand NBI-31772, which displaces IGF-I from all six IGF-binding proteins at low nanomolar concentrations from screening of the in-house chemical libraries. Furthermore, the released free IGF-I was shown to be biologically active in an in vitro bioassay. Thus, NBI-31772 could serve as a valuable lead molecule for the design of novel therapeutics to treat diabetes and other IGF-responsive diseases.

Animals↗
PubMed2001

Fragmented condensate ground state of trapped weakly interacting bosons in two dimensions.

The ground state and its structure for a rotating, harmonically trapped N-boson system with a weak repulsive contact interaction are studied as the angular momentum L increases up to 3N. We show that the ground state is generally a fragmented condensate due to angular momentum conservation. In response to an (arbitrarily weak) asymmetric perturbation of the trap, however, the fragmented ground state can be transformed into a single condensate state. We manifest this intrinsic instability by calculating the conditional probability distributions, which show patterns analogous to the boson density distributions predicted by mean-field theory.

Journal Article↗
PubMed2001

Support vector machines for predicting protein structural class.

BACKGROUND: We apply a new machine learning method, the so-called Support Vector Machine method, to predict the protein structural class. Support Vector Machine method is performed based on the database derived from SCOP, in which protein domains are classified based on known structures and the evolutionary relationships and the principles that govern their 3-D structure. RESULTS: High rates of both self-consistency and jackknife tests are obtained. The good results indicate that the structural class of a protein is considerably correlated with its amino acid composition. CONCLUSIONS: It is expected that the Support Vector Machine method and the elegant component-coupled method, also named as the covariant discrimination algorithm, if complemented with each other, can provide a powerful computational tool for predicting the structural classes of proteins.

Algorithms↗
PubMed2001

Regulation of Xenopus oocyte meiosis arrest by G protein betagamma subunits.

BACKGROUND: Progesterone induces the resumption of meiosis (maturation) in Xenopus oocytes through a nongenomic mechanism involving inhibition of an oocyte adenylyl cyclase and reduction of intracellular cAMP. However, progesterone action in Xenopus oocytes is not blocked by pertussis toxin, and this finding indicates that the inhibition of the oocyte adenylyl cyclase is not mediated by the alpha subunits of classical G(i)-type G proteins. RESULTS: To investigate the possibility that G protein betagamma subunits, rather than alpha subunits, play a key role in regulating oocyte maturation, we have employed two structurally distinct G protein betagamma scavengers (G(t)alpha and betaARK-C(CAAX)) to sequester free Gbetagamma dimers. We demonstrated that the injection of mRNA encoding either of these Gbetagamma scavengers induced oocyte maturation. The Gbetagamma scavengers bound an endogenous, membrane-associated Gbeta subunit, indistinguishable from Xenopus Gbeta1 derived from mRNA injection. The injection of Xenopus Gbeta1 mRNA, together with bovine Ggamma2 mRNA, elevated oocyte cAMP levels and inhibited progesterone-induced oocyte maturation. CONCLUSION: An endogenous G protein betagamma dimer, likely including Xenopus Gbeta1, is responsible for maintaining oocyte meiosis arrest. Resumption of meiosis is induced by Gbetagamma scavengers in vitro or, naturally, by progesterone via a mechanism that suppresses the release of Gbetagamma.

Animals↗
PubMed2001

Mortality and cancer incidence among a population previously exposed to environmental cadmium.

OBJECTIVES: This paper evaluates the associations of previous exposure to environmental cadmium (Cd) and renal function with total mortality and cancer incidence. METHODS: The study population comprised 275 residents (aged 40-92 years at baseline) in a Cd-polluted area located on Tsushima Island, Nagasaki, Japan. In the study area, the dietary intake of Cd decreased because the soil of the Cd-polluted rice fields was replaced with new soil between 1980 and 1983. The mortality rate from 1982 to 1997 and cancer incidence from 1985 to 1996 were investigated. Standardized mortality and incidence ratios (SMR and SIR) were calculated by using regional reference rates. The associations of renal function and urinary Cd levels with total mortality and cancer incidence were evaluated with Cox regression models. RESULTS: The SMR for all subjects, and those with a urinary beta2-microglobulin (U-beta2M) concentration > or = 1,000 microg/g creatinine (Cr) and < 1,000 microg/g Cr was estimated at 90 [95% confidence interval (CI) 73-109], 138 (95% CI 101-183) and 66 (95% CI 49-87), respectively. After adjustment for age and other potential confounders, in men, serum beta2M (S-beta2M) (> or = 2.3 mg/l) and in women, serum Cr (> or = 21.2 mg/ 100 ml), relative clearance of beta2M (> or = 21%) and U-beta2M (> or = 1,000 microg/g Cr), were associated with a significantly increased risk of mortality, with hazard ratios exceeding 2.0. After further adjustment for log(U-beta2M), the rate ratio of deaths associated with, in men, increased S-beta2M was 2.53 (95% CI 0.97-6.65) and, in women, increased serum Cr (S-Cr) concentrations was 2.75 (95% CI 1.24-6.14). Urinary Cd concentrations (> or = 10 microg/g Cr) were not significantly associated with mortality. The overall SIR of all malignant neoplasms was 71 (95% CI 44-107). CONCLUSIONS: These findings suggest that renal tubule dysfunction and a reduced glomerular filtration rate are predictors of mortality among persons previously exposed to environmental Cd. However, the results also suggest that overall mortality rates in Cd-polluted areas are not necessarily increased, because of the low mortality among those with no, or only slight, signs of low-molecular weight proteinuria. Overall cancer incidence may not be increased among residents in Cd-polluted areas.

Adult↗
PubMed2001

Artificial neural network model for predicting membrane protein types.

Membrane proteins can be classified among the following five types: (1) type I membrane protein. (2) type II membrane protein. (3) multipass transmembrane proteins. (4) lipid chain-anchored membrane proteins, and (5) GPI-anchored membrane proteins. T. Kohonen's self-organization model which is a typical neural network is applied for predicting the type of a given membrane protein based on its amino acid composition. As a result, the high rates of self-consistency (94.80%) and cross-validation (77.76%), and stronger fault-tolerant ability were obtained.

Algorithms↗
PubMed2001

Mononuclear phagocyte differentiation, activation, and viral infection regulate matrix metalloproteinase expression: implications for human immunodeficiency virus type 1-associated dementia.

The pathogenesis of human immunodeficiency virus type 1 (HIV-1)-associated dementia (HAD) is mediated mainly by mononuclear phagocyte (MP) secretory products and their interactions with neural cells. Viral infection and MP immune activation may affect leukocyte entry into the brain. One factor that influences central nervous system (CNS) monocyte migration is matrix metalloproteinases (MMPs). In the CNS, MMPs are synthesized by resident glial cells and affect the integrity of the neuropil extracellular matrix (ECM). To ascertain how MMPs influence HAD pathogenesis, we studied their secretion following MP differentiation, viral infection, and cellular activation. HIV-1-infected and/or immune-activated monocyte-derived macrophages (MDM) and human fetal microglia were examined for production of MMP-1, -2, -3, and -9. MMP expression increased significantly with MP differentiation. Microglia secreted high levels of MMPs de novo that were further elevated following CD40 ligand-mediated cell activation. Surprisingly, HIV-1 infection of MDM led to the down-regulation of MMP-9. In encephalitic brain tissue, MMPs were expressed within perivascular and parenchymal MP, multinucleated giant cells, and microglial nodules. These data suggest that MMP production in MP is dependent on cell type, differentiation, activation, and/or viral infection. Regulation of MMP expression by these factors may contribute to neuropil ECM degradation and leukocyte migration during HAD.

AIDS Dementia Complex↗
PubMed2001

Clinical outcome of patients with previous myocardial infarction and left ventricular dysfunction assessed with myocardial (99m)Tc-MIBI SPECT and (18)F-FDG PET.

UNLABELLED: Myocardial viability was assessed by (99m)Tc-methoxyisobutylisonitrile (MIBI) SPECT and (18)F-FDG PET to evaluate the prognosis and treatment strategy of patients with myocardial infarction (MI) and left ventricular (LV) dysfunction. METHODS: One hundred twenty-three consecutive patients with previous MI and LV dysfunction (LV ejection fraction [EF], 35% +/- 6% [mean +/- SD]) who underwent (99m)Tc-MIBI SPECT and FDG PET were followed-up for 26 +/- 10 mo (mean +/- SD). Distributions of the 2 radiotracers in myocardial segments were classified into 2 patterns: myocardial perfusion-metabolism mismatch (MM) and match (M). LV EF and LV end-diastolic diameter (EDD) were measured by echocardiography at baseline, 3 mo (Pos1), and 6 mo (Pos2) after revascularization. Cardiac death, acute MI, unstable angina, and late revascularization (>3 mo) experienced by the patients during follow-up were defined as cardiac events. RESULTS: Sixty-seven patients underwent revascularization and 56 patients were treated medically. Of the 72 patients with > or =2 MM segments, 42 underwent revascularization (group A1) and 30 were treated medically (group A2). Of the 51 patients with <2 MM segments, 25 underwent revascularization (group B1) and 26 were treated medically (group B2). The 4 groups had similar baseline characteristics and rest LV EF. After revascularization, EF (mean +/- SD) increased in group A1 from 36% +/- 5% to 44% +/- 8% (P < 0.0001) in Pos1 and to 51% +/- 9% (P < 0.0001) in Pos2. EDD (mean +/- SD) decreased from 62 +/- 8 mm to 56 +/- 5 mm (P < 0.001) in Pos1 and to 55 +/- 5 mm (P < 0.001) in Pos2. However, EF and EDD were unchanged in group B1 (P > 0.05). During the follow-up, 22 patients (17.9%) suffered from cardiac events, including 11 cardiac deaths, 4 acute MI, 6 late coronary artery bypass grafting, and 1 unstable angina pectoris. The cardiac event rate in group A2 (50%) was significantly higher than that of groups A1 (2.4%; chi(2) = 23.08; P < 0.0001), B1 (12%; chi(2) = 8.94; P = 0.003), and B2 (11.5%; chi(2) = 9.45; P = 0.002). CONCLUSION: Assessment of myocardial viability using hybrid (99m)Tc-MIBI SPECT and FDG PET can predict the clinical outcome and is helpful to decision making in the treatment strategy of patients with MI and LV dysfunction. Revascularization can improve the LV function and clinical outcome of patients with >2 viable myocardial segments.

Aged↗
PubMed2001

Naltrexone microspheres: in vitro release and effect on morphine analgesia in mice.

AIM: To study in vitro release and in vivo effect of four different types of sustained-release naltrexone microspheres on morphine analgesia. METHODS: Release of naltrexone from four types of biodegradable microspheres was investigated by HPLC. Their antagonist effects on morphine analgesia were observed using mouse hot-plate procedure. RESULTS: Poly latide-co-glycolide (PLGA) composition had a remarkable effect on naltrexone release from microspheres and its antagonism towards morphine analgesia. Two formulations of PLGA 50:50 formulation released more than 80 % of total naltrexone and lost their antagonism by 8 d. The PLGA 75:25 formulation with 20 % and 30 % drug loadings did not release 95 % of total drug and lose antagonism until 40 d and 30 d, respectively. Increasing the drug loading enhanced naltrexone release from microspheres and seemed to shorten the analgesic antagonistic effect of naltrexone. CONCLUSION: Antagonism by naltrexone microspheres towards morphine analgesia correlates well with the drug release in vitro.

Analgesia↗
PubMed2001

[Distribution of MICA microsatellite in 13 population groups of China].

The genetic data of MICA microsatellite were obtained by genotyping 577 samples in 13 population groups of China, which are Han-YN, Han-GD, Han-SD, Bai, Dai, Lahu, Li, Naxi, Sala, She, Tu, Wa and Zang-YN, with genescan. Five alleles have been observed in the population groups, which are A4, A5, A5.1, A6 and A9. A5 allele is the most frequent in all population groups except Lahu and Li, while the most frequent allele for Lahu and Li is A5. 1 and A4 respectively. The second most frequent allele is the A5.1 in Han-YN, Han-SD, Dai, Naxi, Sala, She, and Wa. The lest frequent allele for Han-YN, Han-GD, Lahu, Naxi, She, Wa is the A6 which is not observed in Li. A4 allele is the lest frequent in Han-SD, Bai, Dai, Sala, Tu, Zang-YN. The results show that the distribution of MICA microsatellite is different in these population groups, and the polymorphism information contents (PIC) of this microsatellite is high. It is a potential useful marker in the study of human origin and migration, personal identification, gene mapping and location, and disease diagnosis.

China↗
PubMed2001

[Study on application of CODIS loci to excluding paternity].

OBJECTIVE: The study was carried out on application of CODIS loci (FGA, vWA, CSF1PO, TH01, TPOX, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51 and D21S11) in 100 cases of excluding paternity. METHODS: The PCR amplified products of Profiler Plus and Cofiler amplification kit were injected into a capillary on the ABI PRISM 310 Genetic Analyzer. GeneScan software analyzed the collected data, which can then be imported into Genotyper software for genotyping of alleles. RESULTS: In the group of Mother-Child-Alleged Father, more than 3 STR loci incompatibilities between alleged father and child were found in all observed cases, the mean incompatibility was 6.63; In the group of Alleged Father-Child, 94.0% of all cases observed was found more than 3 STR loci incompatibilities, the mean incompatibility was 5.01. CONCLUSION: The results showed that CODIS loci had good application to excluding paternity, and the choice of hyperpolymorphic markers in investigation, which were valued by DP, H and PE, had direct relation with the augmentation of incompatibilities in excluding paternity.

Adult↗