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Biomedical subjects

H L Huang

Publications and source records attributed to H L Huang.

At least 19 recordsLinked to original sources
PubMed2006

Spontaneous rhythmic field potentials of isolated mouse hippocampal-subicular-entorhinal cortices in vitro.

The rodent hippocampal circuit is capable of exhibiting in vitro spontaneous rhythmic field potentials (SRFPs) of 1-4 Hz that originate from the CA3 area and spread to the CA1 area. These SRFPs are largely correlated with GABA-A IPSPs in pyramidal neurons and repetitive discharges in inhibitory interneurons. As such, their generation is thought to result from cooperative network activities involving both pyramidal neurons and GABAergic interneurons. Considering that the hippocampus, subiculum and entorhinal cortex function as an integrated system crucial for memory and cognition, it is of interest to know whether similar SRFPs occur in hippocampal output structures (that is, the subiculum and entorhinal cortex), and if so, to understand the cellular basis of these subicular and entorhinal SRFPs as well as their temporal relation to hippocampal SRFPs. We explored these issues in the present study using thick hippocampal-subicular-entorhinal cortical slices prepared from adult mice. SRFPs were found to spread from the CA1 area to the subicular and entorhinal cortical areas. Subicular and entorhinal cortical SRFPs were correlated with mixed IPSPs/EPSPs in local pyramidal neurons, and their generation was dependent upon the activities of GABA-A and AMPA glutamate receptors. In addition, the isolated subicular circuit could elicit SRFPs independent of CA3 inputs. We hypothesize that the SRFPs represent a basal oscillatory activity of the hippocampal-subicular-entorhinal cortices and that the subiculum functions as both a relay and an amplifier, spreading the SRFPs from the hippocampus to the entorhinal cortex.

Action Potentials↗
PubMed2005

Ca3 neuronal activities of dorsal and ventral hippocampus are differentially altered in rats after prolonged post-ischemic survival.

The aim of the present study is to explore the potential hyper-excitability of hippocampal CA3 neurons in rats after prolonged post-ischemic survival. We conducted 15-min four-vessel-occlusion ischemic episodes in rats, allowed these animals to survive for approximately 8 months and then examined the basic morphological features and population synaptic activities of CA3 neurons. In fixed tissue sections obtained from dorsal hippocampi of post-ischemic rats, we observed a complete loss of the CA1 neurons together with a shrunken CA1 sector. Extracellular recordings in slices revealed that the overall synaptic activities of dorsal hippocampal CA3 neurons were decreased in post-ischemic rats compared with sham-operated controls. Both sham control and post-ischemic ventral hippocampal neurons were capable of exhibiting intermittent spontaneous field potentials in slices. These spontaneous field potentials spread from the CA3 to the CA1 area and their generation relied on the activity of glutamate alpha-amino-3-hydroxy-5-methyl-4 isoxazole proprionic acid (AMPA) receptors. The propensity for displaying these spontaneous field potentials appeared to be greater in post-ischemic slices than sham control slices. Our data suggest that the hyper-excitability of the post-ischemic hippocampus, if it occurs, may preferentially take place in the ventral CA3 circuitry.

Action Potentials↗
PubMed2005

The transient appearance of collateral circulation during coronary spasm.

This article reports a case of transient augmentation of collateral circulation due to spontaneous coronary arterial spasm during angiography. The patient's electrocardiogram revealed ST-segment depression during vasospastic attack; this depression differs from the typical change of the ST-segment elevation in coronary spasm without collateral circulation.

Collateral Circulation↗
PubMed2002

Thermal contraction of au nanoparticles.

A fine Au powder, with a mean particle diameter of 4 nm, has been successfully fabricated. The crystalline structure of the 4 nm Au nanoparticles remains in fcc symmetry. No structural changes were found between 15 and 450 K. A crossover from a positive thermal expansion at low temperatures to a negative thermal expansion at high temperatures was observed in the fcc cell parameter at about 125 K. Anomalies associated with the crossover were also observed in the magnetic response and the heat capacity measurements. The observations can be reasonably well interpreted by accounting for the effects of the valence electron potential on the equilibrium lattice separations, with a weakly temperature dependent level spacing.

Journal Article↗
PubMed2001

Pulmonary veins and ligament of Marshall as sources of rapid activations in a canine model of sustained atrial fibrillation.

BACKGROUND: In dogs, chronic rapid pacing may result in sustained atrial fibrillation (AF). However, activation patterns in pacing-induced sustained AF are unclear. METHODS AND RESULTS: We induced sustained AF (>48 hours) in 6 dogs by rapid pacing for 139+/-84 days. We then performed computerized atrial epicardial mappings and recorded the activations in the ligament of Marshall (LOM) and the pulmonary veins (PVs). During AF, mean activation cycle length in the right atrial free wall (126+/-17 ms) was significantly longer than that in the left atrial free wall (96+/-5 ms, P:=0.006). In addition, mean activation cycle length in the left atrial free wall was significantly longer than that in the LOM (84+/-5 ms, P:<0.001), the left inferior PV (81+/-4 ms, P:=0.001), and the left superior PV (85+/-7 ms, P:=0.003). Similarly, the dominant frequency was highest in the LOM and the PVs (range 11.2 to 13.3 Hz), followed by the left and right atria (P:<0.001). In all dogs studied, rapid and complicated electrograms were consistently observed at the LOM and the PVs. During AF, both wandering wavelets and organized reentry were present. There were more wave fronts in the left atrium than in the right atrium (P:<0.001). CONCLUSIONS: In chronic pacing-induced sustained AF, the LOM and the PVs are the sources of rapid activations. The mechanism by which the left atrium activates faster and has more wave fronts than the right atrium may relate to the fact that the left atrium is closer to the sources of rapid activations.

Analysis of Variance↗
PubMed2001

Enhanced naphthalene solubility in the presence of sodium dodecyl sulfate: effect of critical micelle concentration.

Surfactants can increase the solubility of non-polar compounds, and have been applied in areas such as soil washing and treatment of non-aqueous phase liquids (NAPLs). This investigation explored the feasibility of removing vapor phase polycyclic aromatic hydrocarbon (PAH) from gases using an anionic surfactant. The solubility of vapor phase naphthalene was measured herein using gas chromatograph (GC) with a photon ionization detector (PID). The measurement results indicated that surfactant molecules were not favorable to micelle formation when temperatures increased from 25 degrees C to 50 degrees C. Regardless of whether solutions were quiescent or agitated, equilibrium naphthalene apparent solubility increased linearly with surfactant concentrations exceeding critical micelle concentration (CMC). The pH effects on naphthalene apparent solubility were small. Agitation increased naphthalene apparent solubility and lumped mass transfer coefficients. Furthermore, lumped mass transfer coefficients decreased with increasing surfactant concentration owing to increase in interfacial resistance and viscosity and decreased spherical micelle diffusion coefficients. Finally, the net absorption rate increased because the solubilization effects of micelles exceeded the reduction effects of mass transfer coefficient above the CMC. The enhanced naphthalene apparent solubility from the addition of surfactant can be expressed by an enrichment factor (EF). The EF value of naphthalene for the surfactant solution at 0.1 M with agitation at 270 rpm relative to quiescent water could reach 18.6. This work confirms that anionic surfactant can improve the removal efficiency of hydrophobic organic compound (HOC) from the gas phase.

Chromatography, Gas↗
PubMed2001

Conformational changes play a role in regulating the activity of the proline utilization pathway-specific regulator in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the ability to use proline as a nitrogen source requires the Put3p transcriptional regulator, which turns on the expression of the proline utilization genes, PUT1 and PUT2, in the presence of the inducer proline and in the absence of preferred nitrogen sources. Changes in target gene expression occur through an alteration in activity of the DNA-bound Put3p, a member of the Zn(II)2Cys6 binuclear cluster family of proteins. Here, we report that the 'on' conformation can be mimicked in the absence of proline by the insertion of an epitope tag in several different places in the protein, as well as by specific amino acid changes that suppress a put3 mutation leading to non-inducibility of the pathway. In addition, the presence of proline causes a conformational change in the Put3 protein detected by increased sensitivity to thrombin or V8 protease. These findings suggest that Put3p shifts from an inactive to an activate state via conformational changes.

Base Sequence↗
PubMed2001

Modulation of QT interval by cardiac sympathetic nerve sprouting and the mechanisms of ventricular arrhythmia in a canine model of sudden cardiac death.

INTRODUCTION: We previously reported that there is a high incidence of sudden cardiac death (SCD) in dogs with myocardial infarction (MI), complete AV block (CAVB), and nerve growth factor (NGF) infusion to the left stellate ganglion (LSG). Whether or not QT interval prolongation underlines the mechanism of SCD was unclear. METHODS AND RESULTS: We analyzed QT intervals in three groups of dogs. All dogs had CAVB and MI. The LSG group (n = 9) and right stellate ganglion (RSG) group (n = 6) received NGF infusion via the osmotic pumps over a 5-week period to LSG and RSG, respectively. The control group (n = 6) received no NGF. The dogs either died suddenly or were sacrificed within 2 to 3 months after MI. Heart rhythm and QT and RR intervals were monitored using implantable cardioverter defibrillator ECG recordings. There was a time-dependent increase of QTc intervals in the LSG group and a time-dependent decrease of QTc intervals in the RSG group. At the end of NGF infusion, QTc intervals in the LSG group (408 +/- 41 msec) were significantly longer than those in the control (350 +/- 41 msec; P < 0.05) and RSG groups (294 +/- 23 msec; P < 0.01). In the LSG group, 4 of 9 dogs died of SCD. There was no SCD in either the RSG or control group. Immunocytochemical staining showed NGF infusion to LSG and RSG resulted in left and right ventricular sympathetic nerve sprouting and hyperinnervation, respectively. CONCLUSION: NGF infusion to the LSG in dogs with MI and CAVB resulted in increased QT interval and incidence of ventricular tachycardia, ventricular fibrillation, and SCD, whereas NGF infusion to the RSG shortened QT interval and reduced the incidence of ventricular tachycardia. These findings indicate that QT interval prolongation is causally related to the occurrence of ventricular arrhythmia in dogs with nerve sprouting, MI, and CAVB.

Animals↗
PubMed2001

Simultaneous absorption of vapor phase polycyclic aromatic hydrocarbon and carbon dioxide in anionic surfactant solutions.

The goal of this work was to investigate whether the solubility of vapor phase polycyclic aromatic compounds (PAHs) and CO2 in water could be enhanced by adding anionic surfactant during the absorption process. Naphthalene was the PAH surrogate and sodium dodecyl sulfate (SDS) was the anionic surfactant. A series of batch experiments in an absorption cell were performed at 50 degrees C with the surfactant concentration both lower than and higher than the critical micelle concentration (CMC). The experimental findings indicate that the CMC was not a function of pH at values of 3, 5 and 7. Furthermore, at surfactant concentrations less than the CMC, naphthalene apparent solubility increased slightly. On the other hand, the equilibrium naphthalene or CO2 apparent solubility increased linearly, in proportion to the surfactant concentration at concentrations greater than the CMC. This is due to the solubilization effect of micelles, which were formed by the surfactant at concentrations above the CMC. During simultaneous absorption of the two, the presence of CO2 only slightly decreased naphthalene apparent solubility, while the apparent solubility of CO2 was drastically reduced in the presence of naphthalene. As the magnitude of the micelle solubilization effect was greater than the reduction of the mass transfer coefficient in the presence of the surfactant, the total gas absorption rate increased. When the surfactant concentration was 0.1 M, the enrichment factor (the ratio of the solubility in surfactant solution to that in water) values of naphthalene both with and without CO2 increased to 9.05 and 8.60, respectively. These experimental findings demonstrate that anionic surfactant may be applied to increase the removal efficiency of hydrophobic compounds and CO2 through either a spray or packed tower.

Absorption↗
PubMed2001

[Analysis of HLA-DQB1 polymorphism by PCR-SSO in Yichu of Yunnan Province].

HLA-DQB1 genes from 76 individuals of Yichu ethnic group in Yunnan Province were investigated, using PCR-SSO genotyping method. Of the 38 DQB1 alleles detected, DQB1 * 0301 (gene frequency: 36.18%-36.84%) was the most common gene. The frequencies of DQB1 * 0502(10.53%-11.18%), DQB1 * 0401 (9.21%), DQB1 * 0302(8.55%-9.21%), DQB1 * 0601(7.89%), DQB1 * 05031(6.58%), and DQB1 * 03032(5.92%-6.58%) are more than 5%. While DQB1 * 0504, DQB1 * 0604, DQB1 * 06052, DQB1 * 0606, DQB1 * 0607, DQB1 * 0608, DQB1 * 06112, DQB1 * 0613, DQB1 * 0615, DQB1 * 0203, DQB1 * 0305, DQB1 * 0306, DQB1 * 0307, and DQB1 * 0308 were not observed. Comparison of HLA-DQB1 allele frequencies of Yichu with those of 13 other Chinese ethnic groups showed some significant differences, suggesting Yichu is unique in the distribution of HLA alleles.

Alleles↗
PubMed2001

Effects of zinc deficiency on the vallate papillae and taste buds in rats.

BACKGROUND AND PURPOSE: Zinc deficiency is associated with multiple clinical complications, including taste disturbance, anorexia, growth retardation, skin changes, and hypogonadism. We investigated the zinc-deficiency-induced morphologic changes in the vallate taste buds of weanling and young adult male Wistar rats. METHODS: A total of 24 weanling and 30 young adult rats were used. Each age group was further divided into a control group fed a zinc-adequate (50 ppm) diet, a zinc-deficient (< 1 ppm) diet group, and a zinc-adequate pair-fed group who were fed the same amount of food as that taken by the zinc-deficient group. Weanling rats were fed for 4 weeks and young adult rats were fed for 6 weeks. The morphometry and morphologic changes of vallate taste buds were analyzed using light and transmission electron microscopy. RESULTS: Light microscopy revealed no significant difference in papilla size and morphology among the various groups. In both weanling and young adult rats in the zinc-deficient diet and pair-fed groups, the number of taste buds per papilla (per animal) and the average profile area of the taste bud were significantly smaller than those of the corresponding controls (p < 0.05). Ultrastructural changes were seen only in the taste buds of weanling rats fed the zinc-deficient diet, with derangement of the architecture of the taste bud and widening of the intercellular space between taste bud cells. The proportion of type I taste bud cells in the taste buds of weanling rats fed the zinc-deficient diet decreased from 59% to 39%, and that of type II taste bud cells decreased from 25% to 12%. No obvious changes in the ultrastructure of type III taste bud cells were observed. CONCLUSIONS: The main effects of zinc deficiency in weanling and young adult rats and in adequate diet pair-fed rats were changes in the number and size of taste buds, and fine structure changes in the taste bud cells, especially during the accelerated growth stage after weaning.

Aging↗
PubMed2001

[Advances in in vitro refolding of inclusion body proteins].

Overexpression of recombinant proteins in E. coli often results in formation of insoluble, inactive inclusion bodies. These inclusion bodies, which contain the recombinant proteins in a highly enriched form, can be isolated by solid/liquid separation. After solubilization, active proteins can be generated through an appropriate refolding process. Within the last decade, specific strategies and methods have been developed for preparing active recombinant proteins from inclusion bodies. Recent developments in renaturation procedure include the inhibition of aggregation during refolding by the application of low molecular weight additives and matrix-bound renaturation techniques.

Animals↗
PubMed2001

[Determination of active ingredients of 12 pesticides by capillary gas chromatography].

A method for the determination of the active ingredients of 12 pesticides, including procymidone and tebuconazole, with capillary gas chromatography has been developed. A wide bore capillary column(SE-30) and FID detector were employed. The internal standards were used for quantitative determination and GC/MS for qualitative determination. The average recoveries were 99.20%-102.44% while the relative standard deviations were within the range of 0.07% to 5.49%. The method is simple, practical and accurate for the determination of the active ingredients of individual pesticide, formulation or multi-pesticides as a whole.

Bridged Bicyclo Compounds↗
PubMed2001

[Gene cloning, construction and expression of single-chain Fv (scFv) against the membrane protein of Schistosoma japonicum].

OBJECTIVE: To construct single chain antibody specific to membrane protein of Schistosoma japonicum by genetic engineering technique. METHODS: The VH (heavy-chain variable region) and VL(light-chain variable region) genes were amplified by PCR from the genomic DNA of NP11-4 cell line, and sequenced by Sanger's method. The ScFv was constructed in pTHA90 vector using VH and VL genes, then expressed by IPTG. RESULTS: The VH and VL genes were obtained through PCR. The DNA sequences showed that VH and VL were new variable region genes of antibody. They were registered by GenBank. A ScFv gene with (Gly4Ser) 3 intralinker in the pTHA90 vector was successfully constructed. The ScFv was expressed as thioredoxin-fused proteins about 36.2 kDa. CONCLUSION: A specific ScFv against the membrane protein of Schistosoma japonicum was constructed and expressed.

Amino Acid Sequence↗
PubMed2000

Identification and characterization of a structural protein of hepatitis B virus: a polymerase and surface fusion protein encoded by a spliced RNA.

The hepatitis B virus (HBV) genome is known to contain four conserved and overlapped open reading frames (ORFs) encoding the viral core, polymerase (P), surface (S), and X proteins. Whether HBV encodes other proteins has long been a major interest in the field. Using (32)P-labeling of an introduced protein kinase A site attached to the N- or C-terminus of the HBV polymerase gene, a 43-kDa P-S fusion protein was detected in cell lysate, secreted virions, and 22-nm subviral particles. Immunobiochemical studies showed that the 43-kDa protein contains the epitopes of the N-terminus of polymerase and most parts of the surface proteins. This 43-kDa protein was shown to be a glycoprotein, similar to the surface protein. RT-PCR and sequence analyses identified a spliced mRNA which was derived from pregenomic RNA with a deletion of 454 nucleotides (nt) from nt 2447 to 2902. This splice event creates a P-S fusion ORF. This finding is consistent with the result obtained from an immunobiochemical study. Mutations at the splice donor or acceptor site on the HBV genome abrogated the production of the 43-kDa protein. These mutants had no effect on viral replication in transfected HuH-7 cells. However, this P-S fusion protein is able to substitute for the LS protein in virion maturation. On the basis of these results, we conclude that the 43-kDa protein is a polymerase-surface fusion protein encoded by a spliced RNA. Similar to the LS protein, the 43-kDa P-S fusion protein is a structural protein of HBV and might play a role in the HBV life cycle.

Aspartic Acid Endopeptidases↗