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Biomedical subjects

Z F Liu

Publications and source records attributed to Z F Liu.

At least 19 recordsLinked to original sources
PubMed2006

Activated carbon with excellent chromium(VI) adsorption performance prepared by acid-base surface modification.

In the present work, activated carbon (AC) with excellent Cr(VI) adsorption performance especially at low concentrations was prepared by an acid-base surface modification method. Raw activated carbon (AC(0)) was first oxidized in boiling HNO(3) (AC(1)), then treated with a mixture of NaOH and NaCl (AC(2)). Batch equilibrium and continuous column adsorption were conducted to evaluate the adsorption performance. Boehm titration, elemental analysis, and N(2)/77K adsorption isotherm methods were used to characterize the surface properties and pore structure of modified ACs. The results revealed that the modified AC exhibited excellent Cr(VI) adsorption performance in terms of adsorption capacity and adsorption rate: AC(2)>AC(1)>AC(0). Modification caused S(BET) to decrease and the total number of surface oxygen acidic groups to increase. HNO(3) oxidization produced positive acid groups, and subsequently NaOH treatment replaced H(+) of surface acid groups by Na(+), and the acidity of AC decreased. The main cause of higher Cr(VI) adsorption capacity and rate for AC(2) was the presence of more oxygen surface acidic groups and suitable surface acidity. HNO(3)-NaOH modification shows potential for the preparation of high quality AC for the effective removal of low concentrations of Cr(VI).

Adsorption↗
PubMed2005

Adsorption of triplet O(2) on Si(100): the crucial step in the initial oxidation of a silicon surface.

It has long been understood that a precursor mediated chemisorption is a significant part of the dynamics for the adsorption of O(2) on Si(100), which is a much studied model system of surface reaction with considerable technological relevance. However, theoretical studies on the interaction between O(2) and Si(100) have been focused on the excited singlet state of O2 and unable to explain the observations in surface scattering experiments. We demonstrate by first principles calculations that such a focus is misplaced. In reality, triplet O(2) can also react with Si(100), after overcoming small barriers, and its reaction paths provide a full account for experiments. Our results highlight the important role played by triplet O(2) in surface oxidation.

Journal Article↗
PubMed2004

Ab initio study on structural and electronic properties of BanOm clusters.

Density-functional calculation within local density approximation, shows that the electronic property of a barium oxide cluster is strongly correlated with its equilibrium structure. The ground-state structures of BanOm (4 < or = n < or = 9,m < or = n) clusters can be classified into four categories: (a) compact, (b) dangling state, (c) F-center, and (d) stoichiometric. The compact cluster is metallic, almost no energy gap exists between the highest occupied and the lowest unoccupied molecular orbitals. The energy gap for the dangling state cluster is larger than that for the F-center cluster, while the stoichiometric cluster has the largest energy gap.

Journal Article↗
PubMed2001

Chemisorption of hydrogen molecules on carbon nanotubes under high pressure.

Based on first principles calculations, we propose a mechanism for the dissociative chemisorption of H2 on carbon nanotubes. The breaking of the H--H bond is concerted with the formation of two C--H bonds on two adjacent carbon nanotubes in solid phase, facilitated by the application of high pressure which shortens the interstitial distance between nanotubes. The process is reversible upon the release of external pressure and could make an important contribution to the observed hydrogen storage capacity of carbon nanotubes. The previously unexplained experimental observations of the direct hydrogenation of fullerenes under high pressure lend further support for such a mechanism.

Journal Article↗
PubMed2001

The role of phosphorylation/dephosphorylation in agonist-induced desensitization of D1 dopamine receptor function: evidence for a novel pathway for receptor dephosphorylation.

Exposure of D1 dopamine receptors to agonists results in rapid desensitization of the receptor-stimulated accumulation of cAMP. It is believed that agonist-induced phosphorylation of the receptor plays a critical role in the processes that underlie this phenomenon. To investigate the role of agonist-induced receptor phosphorylation, a FLAG epitope was added to the amino terminus of the rat D1 dopamine receptor and this construct was stably expressed in C6 glioma cells. It was found that the D1 receptor was stoichiometrically phosphorylated under basal conditions and that its phosphorylation state was increased by 2- to 3-fold upon exposure of the cells to dopamine for 10 min. The dopamine-induced receptor phosphorylation could be blocked by D1-selective antagonists but was unaffected by inhibitors of either protein kinase A or protein kinase C. The incorporation of phosphate into the receptor was rapid but transient, despite the continued presence of dopamine. A comparison of the rates of receptor phosphorylation approximately ion (t(1/2) < 1 min) and dopamine-induced desensitization (t(1/2) approximately 7 min) revealed that receptor phosphorylation was not the rate limiting step for receptor desensitization. Upon removal of dopamine, the receptor was rapidly dephosphorylated (t(1/2) approximately 10 min) and this was not blocked by agents (i.e., concanavalin A or hypertonic sucrose) that inhibit D1 receptor internalization. Using specific inhibitors, the phosphatase involved in D1 receptor dephosphorylation was shown not to correlate with the recently identified "G protein-coupled receptor phosphatase" (Proc Natl Acad Sci USA 92:8343-8347, 1995). These results suggest that the phosphorylated D(1) receptor is processed through a novel recovery pathway and that internalization is not required for receptor dephosphorylation.

Animals↗
PubMed2000

Cutaneous blood vessels in scent pigs.

The purpose of this study was to systematically provide anatomic data for flap research in plastic surgery on the cutaneous blood vessels. Seven scent pigs used in this study were killed anesthetically, and their carotid vessels were intubated and injected with a black liquid rubber. Twenty-four hours later, the integument of the scent pig was removed, and the perforating points of the cutaneous vessels were recorded. The different-sized pieces of integument became transparent. Part of this transparent skin tissue was cut into cross-sectional strips. There were three types of the cutaneous vascular source, the same as in humans. Six division levels of vessels in the skin were identified, which formed five vascular plexuses and two systems (the perforating vessel system and the cutaneous vessel system). There were two sets of vein systems: the concomitant vein and the oscillating vein; the latter can be divided into regular and irregular types. The structures of the perforating vessel system and the cutaneous vessel system were the morphological basis for choosing flaps. Two anatomic points have been emphasized: the preserved vascular plexus in thin flaps (not the subcutaneous vascular network reported previously) and the dependency of vascular structure on its location. Otherwise, this study has also provided two new kinds of flaps used in experimental study: the arterial loop flap and the intermuscular septal perforator flap. Although there were differences as well as similarities in skin vasculature between humans and the scent pig, the scent pig is still suitable for flap research.

Animals↗
PubMed2000

Effect of anti-digoxin antiserum on endoxin and membrane ATPase activity in hypoxia-reoxygenation induced myocardial injury.

AIM: To evaluate the protective effect of anti-digoxin antiserum on hypoxia-reoxygenation induced injured myocardium and its mechanism. METHODS: Anti-digoxin antiserum of different concentrations was used, its effect on endoxin and ATPase activity in cell membrane in hypoxia-reoxygenation myocardium model was observed. RESULTS: The level of endoxin was remarkably higher, ATPase activities in cell membrane were remarkably lower in hypoxic group and hypoxia-reoxygenation injury group than those of normal group; anti-digoxin antiserum could resume ATPase activity in a concentration-dependent manner. CONCLUSION: Rise of endoxin was the molecular biological basis of myocardial damage during myocardial hypoxia-reoxygenation. Anti-digoxin antiserum had lessened myocardial injury and had a protective effect on hypoxia-reoxygenation myocardium by antagonizing effect of endoxin.

Animals↗
PubMed1999

109 cases of blepharoptosis treated by forked frontalis muscle aponeurosis procedure with long term follow-up.

109 cases of severe or recurrent blepharoptosis have been treated with the forked frontalis muscle aponeurosis (FFMA) technique since 1989. In comparison with other frontalis muscle flap (FMF) protocols, this technique has three advantages: (i) no skin incision in the lower rim of the eyebrow; (ii) no incision in the frontalis muscle; and (iii) no dissection under the frontalis muscle. The FFMA is formed at the junction of the frontalis and orbicularis muscles. The 9-year follow-up shows that this is a highly effective procedure. The postoperative function of the frontalis muscle is good and the lack of damage has been confirmed by EMG. There are a few complications such as the sluggishness of the upper eyelid on downward gaze and the possibility of asymmetrical brow height in unilateral blepharoptosis. However, this technique may serve as the best choice in the treatment of severe or recurrent blepharoptosis.

Adolescent↗
PubMed1999

GABAA receptor subunit mRNAs in rat superior cervical ganglia.

gamma-Aminobutyric acid (GABA), one of the most important neurotransmitters in the brain, is also found in the periphery. GABAA receptors are chloride channels opened by GABA whose presence in the rat superior cervical ganglion has been indicated by functional and binding measurements. We describe the first molecular data on the possible subunit composition of these receptors, detecting mRNAs for 12 subunits (alpha1-5, beta1-3, gamma1-3, delta) by reverse-transcriptase polymerase chain reaction. Preliminary quantitation gave highest levels (in descending order) for the gamma2 (both short and long forms), beta3, gamma3, and alpha1 subunits.

Animals↗
PubMed1998

A synthetic standard for competitive RT-PCR quantitation of 13 GABA receptor type A subunit mRNAs in rats and mice.

We describe a synthetic 769-bp DNA internal standard, GABARQuant 1, for measuring mRNAs of 13 GABA(A) receptor subunits by reverse transcriptase-polymerase chain reaction (RT-PCR). When it is transcribed into cRNA, added in known amounts to target mRNAs in extracts from rat or mouse tissue. competitively reverse transcribed into cDNA, and amplified by the polymerase chain reaction (PCR), the relative intensities of the amplified, stained target and standard DNA bands enable measurement of small amounts of mRNAs for GABA(A) receptor subunits alpha1-6, beta1-3, gamma1-3 and delta and the three cellular markers beta-actin, light neurofilament protein, and glutamine synthetase. For the subunits, most standard products (263-504 bp) differ in size from target products (398-564 bp) by 10-20%. Primer pairs span at least one intron, to prevent interference by genomic DNA, and at least one rat versus mouse restriction fragment length polymorphism (RFLP), to enable rat products to be distinguished from mouse products.

Animals↗
PubMed1998

The alpha5 subunit of the murine type A GABA receptor.

GABA[A] receptors in the brain convert binding of GABA (gamma-aminobutyric acid) to inhibition by chloride currents. Several important classes of drugs, including benzodiazepines and alcohol, modulate these receptors, which have also been implicated in epilepsy. We describe the alpha5 subunit of GABAA receptors in mice, comparing inbred DBA/2J mice, prone to juvenile audiogenic seizures, with seizure resistant C57BL/6J mice. We find no sequence differences between the strains, although there are several interesting amino acid differences from the rat. We also compare the expression of the alpha5 subunit in whole brains of DBA/2J mice to that in C57BL/6J mice at 21 days, the peak of the former's seizure susceptibility, again finding no significant difference. We further describe the pattern of expression of alpha5 mRNA during mouse brain development, with a peak at 3 days after birth, and among five brain regions in the adult mouse, with the highest levels in the hippocampus. Finally, we present preliminary evidence for rare alternative splicing of this subunit's message, in the N-terminal extracellular domain, to give a form not translatable into a functional protein.

Alternative Splicing↗
PubMed1998

The GABA(A) receptor gamma1-subunit in seizure prone (DBA/2) and resistant (C57BL/6) mice.

Gamma-aminobutyric acid (GABA)A receptors are the sites of action for many antiepileptic drugs such as benzodiazepines and barbiturates. We report the results of molecular cloning of the gamma1-subunit from seizure prone DBA/2J and resistant C57BL/6J inbred mice, and analyses of nucleotide sequences and expression of the gamma1-subunit messenger RNA (mRNA) in DBA/2 and C57BL/6 inbred mice. The mouse gamma1-subunit complementary DNA (cDNA) shares 98% similarity with that of the rat at the level of amino acid sequence. Northern blot hybridization indicates that the gamma1-subunit mRNA is expressed predominantly in areas other than the cerebral cortex and cerebellum and shows little change with postnatal development. No differences have been found for the subunit between DBA/2 and C57BL/6 mice either for nucleotide sequence or for level of expression of the subunit's mRNA in whole brain by Northern blots at 3 weeks of age.

Acoustic Stimulation↗
PubMed1998

GABA(A) receptor alpha4 subunit in DBA/2J and C57BL/6J mice.

GABA(A) receptors are chloride channels in the brain activated by binding of gamma-aminobutyric acid (GABA). Several important classes of drugs, including alcohol and certain antiepileptic drugs, modulate the actions of GABA. We report the sequence and expression of alpha4 subunits of GABA(A) receptors in two inbred strains of mice, DBA/2J and C57BL/6J, which differ in susceptibility to seizures and to behavioral effects of alcohol. We find no differences between the two strains in cDNA sequence, or in levels of alpha4 mRNA in whole brains of the two strains at 21 days of age, when DBA/2J are most susceptible to audiogenic seizures. We also describe the pattern of developmental expression and brain regional distribution of this subunit in mice, finding the highest developmental expression at about 14 days of age in whole brains, and the highest regional levels in hippocampus and basal forebrain (including thalamus) in adults.

Age Factors↗
PubMed1996

[Absorption, tissue distribution, and excretion of zinc acexamate in rats].

UNLABELLED: beta = 11.6 h. The bioavailability was about 52.8%. After ig [3H]ZA (4.44 MBq.kg-1), higher radioactivities were observed in kidney, liver, and gastrointestinal tract but lower in brain, fat, and femur. CONCLUSION: ZA given i.g. in rats was absorbed rapidly and distributed widely to most of the organs and tissues.

Aminocaproates↗
PubMed1994

Allelic loss of chromosome 18q and prognosis in colorectal cancer.

BACKGROUND: Colorectal cancer occurs in approximately 150,000 people each year in the United States. Prognostic assessment influences the treatment of patients with colorectal cancer, including decisions about adjuvant therapy. We evaluated chromosome 18q allelic loss, a genetic event associated with tumor progression, as a prognostic marker for this disease. METHODS: We developed procedures to examine the status of chromosome 18q with microsatellite markers and DNA from formalin-fixed, paraffin-embedded tumors. Allelic loss of chromosome 18q was assessed in 145 consecutively resected stage II or III colorectal carcinomas. RESULTS: Among patients with stage II disease, the five-year survival rate was 93 percent in those whose tumor had no evidence of allelic loss of chromosome 18q and 54 percent in those with allelic loss; among patients with stage III disease, survival was 52 and 38 percent, respectively. The overall estimated hazard ratio for death in patients whose tumor had chromosome 18q allelic loss was 2.83 (P = 0.008) according to univariate analysis. Furthermore, chromosome 18q allelic loss remained a strong predictive factor (hazard ratio for death, 2.46; 95 percent confidence interval, 1.06 to 5.71; P = 0.036) after adjustment for all other evaluated factors, including tumor differentiation, vein invasion, and TNM stage. CONCLUSIONS: The status of chromosome 18q has strong prognostic value in patients with stage II colorectal cancer. The prognosis in patients with stage II cancer and chromosome 18q allelic loss is similar to that in patients with stage III cancer, who are thought to benefit from adjuvant therapy. In contrast, patients with stage II disease who do not have chromosome 18q allelic loss in their tumor have a survival rate similar to that of patients with stage I disease and may not require additional therapy.

Aged↗
PubMed1993

[SC6 antigen for the diagnosis of pancreatic cancer before operation].

SC6 antigen, defined by monoclonal antibody SC6 purified by our laboratory, was measured with a sandwich immunoradiometric assay. Its normal upper limit was considered 41 U/ml. Levels of serum SC6 antigen, a new tumor marker for pancreatic cancer, were assayed in 42 patients who were diagnosed as having pancreatic cancer before operation, acute pancreatitis in 16, and chronic pancreatitis in 7, involving 40 healthy controls. The concentration of SC6 antigen of 19 from the 42 patients was higher than normal upper limit. 15 of the 19 patients was last diagnosed as having pancreatic cancer by operation and pathology. The sensitivity, specificity and predictive value of this assay for pancreatic cancer was 76.2% (15/21), 94% and 75%. The levels of SC6 antigen in 4 patients with pancreatic cancer were observed in different times. The false positive rate of serum SC6 antigen was lower than that of CA19-9. The results show that the antigen is significant for diagnosis, prognosis and observation of the change of serum SC6 antigen for pancreatic cancer. It may be of help to find early pancreatic cancer.

Adult↗