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Biomedical subjects

Y Y Huang

Publications and source records attributed to Y Y Huang.

At least 19 recordsLinked to original sources
PubMed1999

p73 is regulated by tyrosine kinase c-Abl in the apoptotic response to DNA damage.

The protein p73 is a structural and functional homologue of the p53 tumour-suppressor protein but, unlike p53, it is not induced in response to DNA damage. The tyrosine kinase c-Abl is activated by certain DNA-damaging agents and contributes to the induction of programmed cell death (apoptosis) by p53-dependent and p53-independent mechanisms. Here we show that c-Abl binds to p73 in cells, interacting through its SH3 domain with the carboxy-terminal homo-oligomerization domain of p73. c-Abl phosphorylates p73 on a tyrosine residue at position 99 both in vitro and in cells that have been exposed to ionizing radiation. Our results show that c-Abl stimulates p73-mediated transactivation and apoptosis. This regulation of p73 by c-Abl in response to DNA damage is also demonstrated by a failure of ionizing-radiation-induced apoptosis after disruption of the c-Abl-p73 interaction. These findings show that p73 is regulated by a c-Abl-dependent mechanism and that p73 participates in the apoptotic response to DNA damage.

Animals↗
PubMed1999

A method using biodegradable polylactides/polyethylene glycol for drug release with reduced initial burst.

Post-coating of biodegradable polylactides (PLA)/polyethylene glycol (PEG) microspheres with a gelatin film produced by dipping the microspheres into a gelatin solution to reduce the initial drug release burst was investigated. Biodegradable block PLA/PEG microspheres, prepared by w/o emulsion/solvent evaporation, showed that the hydrophilic segment PEG protruded to the sphere surface. However, these microspheres also showed a large burst release in the initial period. Post-coating of the PLA/PEG microspheres with a gelatin film by dipping the microspheres into a dilute gelatin solution effectively inhibited the initial burst release rate in the drug release tests. Post-coating of gelatin reduced 98% of the burst release. With thicker coatings, there were slower releasing rates, and the release rate can be simply related to the coating thickness.

Anti-Arrhythmia Agents↗
PubMed1999

Positive selection of NKT cells by CD1(+), CD11c(+) non-lymphoid cells residing in the extrathymic organs.

Previously, we found that NK1.1(+), TCRalpha beta(+) natural killer T (NKT) cells develop in cytokine-supplemented suspension cultures of fetal liver established from normal, but not from beta2 microglobulin-deficient [beta2m(- / -)] mice, and that recombination-deficient SCID fetal liver can reconstiute NKT cell development in beta2m(- / -) fetal liver cultures. We found here that cells of SCID adult liver, bone marrow, spleen and thymus were able to reconstitute NKT cell development in the former culture system with efficiency comparable to normal thymic cells. The reconstitution of NKT cells was also seen in the bone marrow chimeras that had been administered a combination of beta2m(- / -) and Rag-2(- / -) bone marrow cells. Development of NKT cells was hampered by depletion of CD11c(+) or CD11b(+) cells, but not by removal of B220(+) or Gr-1(+) cells from cultures of normal fetal liver cells. Furthermore CD11c(+), CD11b(+) and / or CD11c(+) CD11b(-) cells (both populations were CD1-dull positive) enriched from Rag-2-deficient fetal livers and pulsed with alpha-galactosylceramide, a possible antigen for NKT cells, were shown to reconstitute the NKT cell development in beta2m(- / -) fetal liver cultures. Collectively, our findings suggest that non-lymphoid cells, presumably CD11c(+), CD11b(+) and / or CD11c(+), CD11b(-) dendritic cells, are involved in the mechanism of positive selection of NKT cells in the thymus and extrathymic organs.

Animals↗
PubMed1999

Methodological considerations for the human platelet 5-HT2A receptor binding kinetic assay.

Analysis of an extensive database of human platelet 5-HT2A receptor binding assays has been conducted in order to identify factors that may affect the assay results. Despite anecdotal reports that storage of frozen platelet pellets may affect 5-HT2A binding affinity and capacity, no quantitative study has been reported in the literature. Analysis of binding data for 373 frozen samples with a storage time up to three years is presented in this paper. It is shown that prolonged storage significantly decreases binding. The loss of binding capacity begins in the first six month of storage. Bmax declines by half after 17 month. The impact of storage time on the binding affinity is much smaller. There is only about 20% increase in the value of affinity K(D) during the half-life of Bmax. Differences in sample storage time may partly explain discrepancies in results between different research groups. Nonspecific binding due to binding to filter material diminishes accuracy and reliability of the binding assays as a result of a decrease in the ratio of specific to nonspecific ratio. A data analysis based on our suggested mathematical model shows that this effect depends on tissue concentration in test tube and becomes pronounced when the concentration is below 0.1 mg protein/ml (at 0.2 nM of ligand). Above 0.1 mg protein/ml, percentage of specific to total binding exceeds 65%, which is an acceptable level for the ratio. The majority of the binding studies reported in the literature employed a tissue concentration more than 0.5 mg/ml, well above the minimal limit sufficient for a reliable assay. However, development of microassays to conserve precious tissue must take the limit into consideration.

Blood Platelets↗
PubMed1999

Relationship of psychopathology to the human serotonin1B genotype and receptor binding kinetics in postmortem brain tissue.

Knockout of the 5-HT1B gene in mice results in increased aggression, as well as alcohol and cocaine consumption. Given the clinical association of aggression, suicide, alcoholism, and substance abuse, we studied relationship of psychopathology to the human 5-HT1B receptor gene (N = 178) and postmortem human 5-HT1B receptor binding (N = 96) in the brain. The sample comprised: 71 suicide victims, 107 nonsuicides, 45 with a history of major depression and 79 without, 64 with a history of a alcoholism or substance abuse and 60 without, as well as 36 with a history of pathological aggression and 42 without. Single-strand conformational polymorphism (SSCP) analysis and DNA sequencing techniques were used to screen the coding region of the human 5-HT1B receptor gene in genomic DNA isolated from postmortem human brain tissue. Two common polymorphisms were identified in the 5-HT1B receptor gene, involving a silent C to T substitution at nucleotide 129 and a silent G to C substitution at nucleotide 861 of the coding region. These polymorphisms were found with the same frequency in the suicide and the nonsuicide groups and in those with and without a history of major depression, alcoholism, or pathological aggression. The binding indices (Bmax and KD of the 5-HT1B receptor in prefrontal cortex also did not differ in suicides and controls, major depression, alcoholism, and cases with a history of pathological aggression. The C129 or G861 allele had 20% fewer 5-HT1B receptor compared to the 129T or 861C allele. We did not identify a relationship between suicide, major depression, alcoholism, or pathological aggression with 5-HT1B receptor binding indices or genotype.

Accidents, Traffic↗
PubMed1999

Tissue-specific, hormonal, and developmental regulation of SCC-LacZ expression in transgenic mice leads to adrenocortical zone characterization.

We report here the study of the human CYP11A1 promoter in driving tissue-specific, developmentally and hormonally regulated reporter gene expression. A 4.4-kb fragment containing all known regulatory elements is more efficient than a short basal promoter fused to an upstream adrenal enhancer in driving reporter LacZ gene expression both in cell culture and in transgenic mice. The LacZ gene controlled by the 4.4- and 2.3-kb promoters was expressed in the adrenal cortex, testicular Leydig cells, ovarian corpora lutea, and granulosa cells. Transgene expression in the adrenals was stimulated by ACTH, indicating the presence of ACTH-responsive sequence. Beta-galactosidase activity was first detected in the adrenal primordia at 11.5 days postcoitum. Its expression continued throughout all stages of adrenal development in a pattern similar to that of the endogenous CYP11A1, which was expressed in all zones of the adrenal cortex, but was strongest in the X zone. The X zone grew before puberty but regressed afterward, as did the levels of CYP11A1 and LacZ gene expression in the X zone. Our study of the CYP11A1 promoter in transgenic mice led to characterization of the adrenocortical zones.

Adrenal Cortex↗
PubMed1999

PE-PEG/LEH can reduce its interactions with plasma expanders indexed through viscosity measurements.

To investigate whether PE-PEG coated LEH (PE-PEG/LEH) can reduce its interaction with different plasma expanders and possibly suspended in those expanders, we measured the viscosity of PE-PEG/LEH suspended in different plasma expanders as an index for the interactions. The results showed that lower viscosity values for PE-PEG/LEH were observed compared with LEH especially in low shear rate regions (e.g., 7.72 +/- 1.46 cp vs. 14.91 +/- 1.03 cp for gamma = 2.25 sec-1, respectively). Moreover, the viscosity values for PE-PEG/LEH suspended in fibrinogen suspensions were much less than those of LEH in the same media at low shear rate regions (e.g., 7.72 +/- 1.59 cp vs. 25.78 +/- 1.59 cp, gamma = 2.25 sec-1, respectively). Similar results were observed for PE-PEG/LEH suspended in 1.83% of oxypolygelatin (Gel) suspensions and 1.5% hydrooxyethyl starch (HES) compared to LEH in the same suspension media. On contrast, PE-PEG/LEH suspended in dextran (Dex) showed that dramatically increasing the viscosity values in low shear rates compared with LEH suspended in the same media (e.g., 78.87 +/- 0.56 cp vs. 51.08 +/- 3.52 cp, gamma = 2.25 sec-1, respectively) were observed. Since only minor interactions with Gel, HES or fibrinogen suspensions were observed, we suggest that PE-PEG/LEH suspended in those media but not in Dex can possibly serve for resuscitation oxygen-carrying fluids.

Animals↗
PubMed1999

Recurrent fetal thyrotoxicosis in a woman with Graves' disease: case report.

The thyroid stimulating immunoglobulins are generally believed to be the cause of hyperthyroidism in Graves' disease. Placental transfer of these antibodies from a mother with autoimmune thyroid disease can result in fetal thyroid disorders. We report the case of a 31-year-old woman who had a history of Graves' disease. She received thyroxine therapy for post thyroidectomy hypothyroidism. Two years after the thyroidectomy, she became pregnant. Unfortunately, intrauterine fetal death occurred in midgestation. One year later, she became pregnant again. In the 26th week of gestation, fetal thyrotoxicosis was diagnosed using clinical pictures, including fetal tachycardia and cardiomegaly, and a hormonal evaluation of a periumbilical blood sampling (T4: 18 micrograms/dl, T3: 65.3 ng/dl, TSH: < 0.03 microU/ml) was performed. Antimicrosomal antibodies were not detectable in either the maternal or fetal blood. In this case, high levels of TBII were detected during pregnancy and crossed the placenta to result in a thyrotoxic fetus in the second pregnancy. We recommend that both the regular monitoring of the thyrotropin receptor antibodies of pregnant women with a history of autoimmune thyroid disease, and routine measurements of the fetal heart rate and intrauterine growth during gestation be mandatory for the early detection of fetal thyroid disorders. Cordocentesis for measuring fetal thyroid function is helpful in reaching a definite diagnosis and for guiding therapy.

Adult↗
PubMed1998

Monoaminergic effects of high-dose corticotropin in corticotropin-responsive pediatric opsoclonus-myoclonus.

Children with the opsoclonus-myoclonus syndrome (OMS) usually respond to corticotropin (adrenocorticotrophic hormone, ACTH) treatment but the mechanism of benefit is unknown. We previously showed that both cerebrospinal fluid (CSF) homovanillic acid (HVA) and 5-hydroxyindole-acetic acid (5-HIAA) concentrations are low in pediatric OMS. In this study, we measured levels of CSF Dopa, catecholamines, deaminated metabolites of catecholamines, as well as HVA and 5-HIAA in eight patients before and during treatment with ACTH. All the children were ACTH-responsive with 50-70% improvement in multiple clinical features of OMS. ACTH treatment reduced the HVA concentration in every child by a mean of 21% (p < 0.001). Treatment with ACTH was associated with significant correlations between dopaminergic markers such as HVA, dihydroxyphenylacetic acid (DOPAC), and Dopa. There were no significant changes in the CSF concentrations of the noradrenergic markers norepinephrine (NE) and dihydroxyphenylglycol (DHPG), or the serotonergic marker 5-HIAA. The only child with a marked inflammatory pattern in CSF, which was reversed by ACTH, was atypical for a large increase in NE and decrease in 5-HIAA during ACTH treatment. Beneficial effects of ACTH in OMS are not associated with normalization of HVA or 5-HIAA levels. The pattern of decreased HVA and unchanged DOPAC levels could reflect decreased extraneuronal uptake of catecholamines (which steroids inhibit) or decreased 0-methylation of catecholamines in nonneuronal cells.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Postsynaptic induction and PKA-dependent expression of LTP in the lateral amygdala.

Whereas much is now known about the behavioral importance of the lateral nucleus of the amygdala for the storage of implicit memories of fear, little is known in molecular terms about the signal transduction pathways required for long-term potentiation (LTP) in this nucleus. Using brain slices containing the amygdala, we have studied LTP in the pathway from external capsule to the lateral nucleus, a pathway that mediates information from the auditory cortex important for fear conditioning. We found the induction of LTP is postsynaptic; it is dependent on postsynaptic depolarization, on the influx of Ca2+ into the postsynaptic cell and, at least in part, on the activation of N-methyl-D-aspartate (NMDA) receptors. The LTP is associated with a decrease of paired-pulse facilitation (PPF) and is blocked by bath application but not blocked by postsynaptic injection of inhibitors of the cyclic adenosine monophosphate-dependent (cAMP-dependent) protein kinase (PKA). Consistent with the possibility that the expression might involve PKA presynaptically, the adenylyl cyclase activator forskolin induced synaptic potentiation of this pathway that also was associated with a decrease of PPF, and this potentiation occluded the tetanus-induced LTP.

Amygdala↗
PubMed1998

Tissue plasminogen activator contributes to the late phase of LTP and to synaptic growth in the hippocampal mossy fiber pathway.

The expression of tissue plasminogen activator (tPA) is increased during activity-dependent forms of synaptic plasticity. We have found that inhibitors of tPA inhibit the late phase of long-term potentiation (L-LTP) induced by either forskolin or tetanic stimulation in the hippocampal mossy fiber and Schaffer collateral pathways. Moreover, application of tPA enhances L-LTP induced by a single tetanus. Exposure of granule cells in culture to forskolin results in secretion of tPA, elongation of mossy fiber axons, and formation of new, active presynaptic varicosities contiguous to dendritic clusters of the glutamate receptor R1. These structural changes are blocked by tPA inhibitors and induced by application of tPA. Thus, tPA may be critically involved in the production of L-LTP and specifically in synaptic growth.

Animals↗
PubMed1998

Study of Dengue virus infection in SCID mice engrafted with human K562 cells.

Here we report that severe combined immunodeficient (SCID) mice engrafted with human K562 cells (K562-SCID mice) can be used as an animal model to study dengue virus (DEN) infection. After intratumor injection into K562 cell masses of PL046, a Taiwanese DEN-2 human isolate, the K562-SCID mice showed neurological signs of paralysis and died at approximately 2 weeks postinfection. In addition to being detected in the tumor masses, high virus titers were detected in the peripheral blood and the brain tissues, indicating that DEN had replicated in the infected K562-SCID mice. In contrast, the SCID mice were resistant to DEN infection and the mock-infected K562-SCID mice survived for over 3 months. These data illustrate that DEN infection contributed directly to the deaths of the infected K562-SCID mice. Other serotypes of DEN were also used to infect the K562-SCID mice, and the mortality rates of the infected mice varied with different challenge strains, suggesting the existence of diverse degrees of virulence among DENs. To determine whether a neutralizing antibody against DEN in vitro was also protective in vivo, the K562-SCID mice were challenged with DEN-2 and received antibody administration at the same time or 1 day earlier. Our results revealed that the antibody-treated mice exhibited a reduction in mortality and a delay of paralysis onset after DEN infection. In contrast to K562-SCID, the persistently DEN-infected K562 cells generated in vitro invariably failed to be implanted in the mice. It seems that in the early stage of implantation, a gamma interferon activated, nitric oxide-mediated anti-DEN effect might play a role in the innate immunity against DEN-infected cells. The system described herein offers an opportunity to explore DEN replication in vivo and to test various antiviral protocols in infected hosts.

Animals↗
PubMed1997

Comparative analysis of the gp120-binding area of murine and human CD4 molecules.

The structural basis for the difference between human and murine CD4 molecules in binding to HIV envelope protein gp120 has been intensively studied. Eighteen mutant human CD4 molecules were produced by segmental replacement of beta strands and loops in the gp120-binding area of the molecule with corresponding murine sequences or by single amino acid substitutions. Examination of these mutant CD4 molecules for gp120 binding indicated that murine CD4 molecule does not bind gp120 for the following three reasons: (a) The loops flanking the C" strand are longer than their human counterparts, causing significant difference in local tertiary structure; (b) valin, rather than phenylalanine, which is the key amino acid for the binding occupies position 43; (c) amino acids at positions 45 and 46 are different, causing further decrease in binding affinity. Furthermore, the present study indicated that the aromatic ring of Phe43 and the negative charge of Arg59 play key roles in gp120 binding.

Amino Acid Sequence↗
PubMed1997

Effect of cisapride, a serotonin-4 receptor agonist, on aldosterone secretion: absence of age-related change.

Twenty healthy volunteers (age ranging from 19 to 72) were studied for their aldosterone response to oral administration of 10 mg cisapride, a serotonin-4 receptor agonist. The participants were studied after minimum of 4-hour ambulation (high basal renin) and a repeated test after overnight bed rest (low basal renin). Oral administration of cisapride caused a two-fold increase in the plasma aldosterone levels (182.6 +/- 28.0% in high renin state and 203.4 +/- 38.6% in low renin state; P = 0.659 between the means of two states) without affecting the plasma renin levels, Scatterplot of percentile aldosterone increment against age distribution demonstrated that the R-square were very low (0.039 for high renin and 0.009 for low renin state). Our data suggest that the age does not alter the serotonergic mediated effect on aldosterone secretion. The cisapride effect is also independent of the different basal renin states. Cisapride, as a single oral dose, could serve as a simple test to assess the functional capacity of aldosterone secretion.

Administration, Oral↗
PubMed1996

Functional trkB neurotrophin receptors are intrinsic components of the adult brain postsynaptic density.

Neurotrophins have long been thought to act as target-derived factors that regulate the survival and differentiation of afferent neurons. Recently, brain-derived neurotrophic factor (BDNF) was shown to elicit rapid increases in synaptic activity of cultured hippocampal neurons by enhancing responsiveness to excitatory input. These findings suggest a postsynaptic localization of neurotrophin receptors. In this study, we examined the expression of trkB, a high-affinity receptor for BDNF, in the postsynaptic density (PSD), a proteinaceous specialization of the postsynaptic membrane. Western blot analyses with antibodies to trkB revealed localization to the PSD in adult rat cerebral cortex and hippocampus. Only the full-length, active form of trkB was detected in PSD samples. BDNF treatment of the adult cortical PSD resulted in a 5-fold increase in trkB autophosphorylation, supporting the contention that the PSD contains functional trkB. Truncated trkB, which does not contain the tyrosine kinase signaling domain, though present in membrane fractions, was undetectable in the PSD. The presence of trkB in the PSD is consistent with a role for neurotrophins in the regulation of synaptic activity via direct postsynaptic mechanisms.

Animals↗
PubMed1996

Control of memory formation through regulated expression of a CaMKII transgene.

One of the major limitations in the use of genetically modified mice for studying cognitive functions is the lack of regional and temporal control of gene function. To overcome these limitations, a forebrain-specific promoter was combined with the tetracycline transactivator system to achieve both regional and temporal control of transgene expression. Expression of an activated calcium-independent form of calcium-calmodulin-dependent kinase II (CaMKII) resulted in a loss of hippocampal long-term potentiation in response to 10-hertz stimulation and a deficit in spatial memory, a form of explicit memory. Suppression of transgene expression reversed both the physiological and the memory deficit. When the transgene was expressed at high levels in the lateral amygdala and the striatum but not other forebrain structures, there was a deficit in fear conditioning, an implicit memory task, that also was reversible. Thus, the CaMKII signaling pathway is critical for both explicit and implicit memory storage, in a manner that is independent of its potential role in development.

Amygdala↗