Biomedical subjects

S Huang

Publications and source records attributed to S Huang.

At least 325 records · Page 18Linked to original sources

PubMed1998

[Quantitative analysis on platelets cytosolic free calcium concentration and ulcerous tissue calcium in patients with recurrent aphthous ulceration].

To study the relationship between the abnormal behavior of calcium (Ca2+) and the pathogenesis of recurrent aphthous ulceration (RAU) by measuring quantitatively the concentration of platelets' cytosolic free calcium ions ([Ca2+]i) and tissue calcium (Wca2+), the patients with RAU (n = 50) and the healthy volunteers (n = 30) were chosen randomly. Then platelets [Ca2+]i was determined in calcium fluorescent indicator Fura-2/AM loaded washed platelets by spectrofluorophotometer and tissue Wca2+ was measured quantitatively by OCPC autoanalyzer method. The results showed that the concentration levels of platelets [Ca2+]i in patients with RAU in attack stage and attack-free stage were significantly higher than that of the control group (P < 0.01, P < 0.05), and the concentration level of the ulcerous tissue Wca2+ was also obviously higher than that of the normal control group (P < 0.001). There was a significantly positive correlation between the platelets [Ca2+]i and the ulcerous tissue Wca2+ (P < 0.01). The results suggested that the influx disorder and overload of Ca2+ might play an important role in the pathogenesis of RAU.

Adolescent↗

PubMed1998

[Hepatitis B virus antigen-induced specific TCR V beta gene subfamily amplifications and their diversity].

The human immune system confronts various antigens, then the recognitive structures of T lymphocytes must be diverse. In this study, we analyzed the TCR V beta 1-20 gene repertoire by reverse transcription-polymerase chain reaction (RT-PCR) in peripheral blood lymphocytes (PBLs) from individuals vaccinated with recombinant hepatitis B vaccine and PBLs from healthy donors stimulated by supernatants of the HepG2 2215 cell line transfected by HBV-DNA. The specific amplifications of V beta 6, 14, V beta 6, 15 were observed in PBLs after vaccination and stimulation by HepG2 2215 cell line respectively. The results suggest that the V beta segments may be the specific recognitive units for these antigens and involved in restriction and cytotoxicity.

Cells, Cultured↗

PubMed1998

[Study on chemical components of Momordica charantia].

The paper deals with the study of chemical constituents of the unmatured fruits of Chinese traditional medicine Momordica charantia L. which is usually used as green-stuff. There are two parts of the extracts obtained by ethanol precipitation, and four compounds obtained from the further isolation. They are identified as Vincine, Mycose, Momordicoside A and Momordicoside B.

Drugs, Chinese Herbal↗

PubMed1998

[Studies on the chemical components of Brucea javanica].

Three active components were isolated from treated dry-fruits of Brucea javanica (L.) Merr by chromatographic methods, and they were identified as Brusatol (I), Bruceine D (II), Bruceosidae A (III) by means of UV, IR, 1H-NMR, 13C-NMR spectroscopic analysis methods.

Brucea↗

PubMed1998

[Management of very complicated retinal detachment].

PURPOSE: To evaluate the management for a group of complicated retinal detachment in very severe conditions including(A) rhegmatogenous retinal detachment associated with severe posterior and anterior PVR, (B) giant retinal tear (GRT) retinal detachment with severe PVR, (C) severe perforating eye injury with tractional retinal detachment. METHODS: A total number of 31 eyes from 31 patients was included, in which 14 eyes were in group A, 8 eyes were group B and 9 eyes group C. Procedures including scleral buckling, encircling, cryotherapy, total vitrectomy, epiretinal membrane peeling/excision, relaxing retinectomy, use of perfluorocarbon liquid and silicone oil were applied to all patients. Patients were followed up for three to 16 months. RESULTS: Retinas of 21 out of 31 eyes(67.7%) were completely reattached and 5 eyes (16.1%) were partially reattached, 5 eyes were failed(16.1%). Postoperative vision was significantly improved in 25 eyes. The visual acuity of 19 eyes was better than 0.02, while before operation only two eyes were better than 0.02. PVR and GRT patients had better results. CONCLUSION: The results showed that a big part of very complicated retinal detachment which was called as hopeless cases could still be successfully treated with comprehensive procedures, more than half of them may have useful vision which may obviously improve their life quality.

Adolescent↗

PubMed1998

11q13 allelic loss in pituitary tumors in patients with multiple endocrine neoplasia syndrome type 1.

Pituitary adenomas may develop sporadically or as part of the multiple endocrine neoplasia type 1 (MEN 1) syndrome. The gene responsible for MEN 1 syndrome was recently identified and cloned. Low rates of MEN 1 gene mutations and deletions have been reported in sporadic pituitary adenomas. To elucidate the role of the MEN 1 gene in the pathogenesis of MEN 1-associated pituitary tumors, we examined pituitary adenomas from 11 MEN 1 patients for the presence of 11q13 allelic loss. Ten of the 11 pituitary tumors were informative by PCR-based loss of heterozygosity analysis. Using a combination of family pedigree analysis and restriction analysis directed at the mutated allele in 8 of the 10 informative cases, it was demonstrated in all 8 cases that it is the wild-type allele that undergoes deletion. All 11 tumors, 4 of which were growth hormone secreting, were additionally analyzed for mutation in the Gs alpha subunit (gsp) gene. None of the tumors (0 of 11 tumors) revealed a gsp gene mutation. Therefore, genetic alterations of the MEN 1 gene seem to play a dominant role in MEN 1-associated pituitary tumorigenesis, whereas gsp gene mutations do not seem to be a frequent event in either growth hormone-secreting or other types of MEN 1-associated pituitary tumors. These results suggest that MEN 1-associated pituitary tumors develop via genetic pathways that differ from those of most sporadic pituitary tumors.

Adenoma↗

PubMed1998

[Application of chromosome painting to analysis of structural aberration in five cases].

OBJECTIVE: This article reports that competitive hybridization using entire chromosome specific libraries as probe and human genomic DNA as the competitor allows intense and specific fluorescent staining of human chromosome in metaphase. This general approach is called "chromosome painting". METHODS: The probes comprising chromosomes 2, 5, 6, 7, 13, 14, X specific libraries were used to analyse five cases which had been suspected of subtle translocation and deletion in karyotype analysis by G-banding of metaphase cells. The authors selected entire chromosome-specific DNA libraries hybridizing with the five cases. Unlabeled human genomic DNA was used to inhibit the hybridization of sequences in the library that bind to multiple chromosome. RESULTS: The target chromosome was made at least 20 times brighter parunit length than the others. Translocations and deletions were detected clearly in metaphase and were consistent with G-banding. However, the result was clearer and the detection easier, compared with G-banding. CONCLUSION: Chromosome painting is very powerful for identification of chromosome structural aberrations. Translocation and deletion involving these chromosomes can be strikingly visualized. The hybridization intensity and specificity are such that even very small portions of the involved chromosome can be detected. This technique is especially useful in settings where high-quality banding is difficult.

Adult↗

PubMed1998

[Detection of the mutant phenylalanine hydroxylase gene by dideoxy fingerprinting].

OBJECTIVE: To establish a method with high efficiency in detecting phenylalanine hydroxylase (PHA) gene mutations and hence to rapidly diagnose prenatal fetals with phenylketonuria. METHODS: Dideoxy fingerprinting (ddF) was used. It is a hybrid method of dideoxy sequencing and single strand conformation polymorphism (SSCP); it can effectively detect the presence of mutant genes and would not be limited by the length of the amplified products, by ddF, the mutant genes Y165X, Y204C and Q355H of PAH genes were detected. RESULTS: Many bands showed altered migration, compared with the controls. Abnormal band migration in Y165X and Q355H was also detected by SSCP, but it was not detected in Y204C which had large amplified products. CONCLUSION: Compared with SSCP, ddF is a more sensitive method detecting gene mutations in large fragments, ddF is a practicable method for detecting gene mutations.

DNA Fingerprinting↗

PubMed1998

Candidate hematopoietic stem cells from fetal tissues, umbilical cord blood vs. adult bone marrow and mobilized peripheral blood.

As part of our ongoing effort to identify a rich source of pluripotent progenitor cells for transplantation and gene therapy, we cultured single-sorted CD34+ subpopulations from different human hematopoietic tissues to assess the relationship between immunophenotype expression and functional characteristics. In combination with index sorting, single cell culture permits precise assessment of the colony efficiency (CE), growth characteristics, and replating potential (RP) of each individual phenotype without interference from other cell types. CD34+ cells from fetal liver (FL), fetal bone marrow (FBM), umbilical cord blood (UCB), adult BM (ABM), and mobilized peripheral blood (MPB) were sorted and cultured as single cells according to the coexpression of CD38. With the exception of FL, higher CEs were found among CD34+/CD38+ cells vs. CD34+/CD38- cells from the same cell source. However, colonies with dispersed growth pattern (DGP) and mixed growth pattern (MGP) were found predominantly in the CD34+/CD38- subsets. We next examined the functional characteristics of CD34+ subsets defined by three-color analysis and coexpression of CD38 and HLA-DR or CD38 and CDw90 (Thy-1). Using the combination CD34, CD38, and HLA-DR, the highest CEs, the highest percentages of colonies with DGP/MGP and the maximum RP were found in the CD34+/CD38-/HLA-DR+ subset among samples from FL, FBM, and UCB. The CEs and percentages of colonies with DGP/MGP of single-sorted CD34+/CD38-/HLA-DR+ cells were 72.7+/-11.8% (mean +/- standard deviation) and 20.1+/-10.4%, respectively, in FL; 60.9+/-11.1% and 11.5+/-5.4% in FBM; 57.0+/-16.5% and 24.1+/-7.3% in UCB; 27.2+/-12.8% and 9.0+/-4.9% in MPB, and 9.6+/-7.8% and 4.6+/-3.2% in ABM. Using the combination CD34, CD38, and CDw90(Thy-1), the subset with the highest CEs and highest percentages of colonies with DGP/MGP was found to be CD34+/CD38-/CDw90- in FL and FBM, but colonies with high RP were distributed evenly among CDw90+ and CDw90- subsets derived from FL, FBM, UCB, or MPB. We conclude that the CD34+/CD38-/HLA-DR+ subset contained the highest number of candidate stem cells among the various immunophenotypes, and that FL contained the highest concentration of CD34+ cells (11.4+/-7.5%) and the highest level of CD34+/CD38-/HLA-DR+ subsets (34.7+/-8.2%) among cells from various ontogenic age. Our estimate of candidate stem cells using single cell suspension culture correlated with that obtained by single cell long-term culture-initiating cells. CD34+/CD38-/HLA-DR+ cells from FL appear to represent the best targets for ex vivo stem cell expansion and genetic manipulation.

ADP-ribosyl Cyclase↗

PubMed1998

Which workers smoke?

OBJECTIVES: This article examines differences by occupation in daily cigarette smoking prevalence and intensity among full-time workers, and how these differences are associated with smoking restrictions at work. DATA SOURCES: Most of the data are from a Health Canada-sponsored Supplement to the 1994/95 National Population Health Survey (NPHS). The analysis is based on 5,674 respondents aged 15 to 64 who were full-time workers at the time of their interview. Comparable information is presented from the 1978/79 Canada Health Survey and the 1986 Labour Force Survey Smoking Supplement. MAIN RESULTS: In 1994/95, 28% of full-time workers were daily smokers, and about a third of them smoked 25 or more cigarettes a day. Smoking prevalence and intensity were lowest among white-collar workers and highest among blue-collar workers. Since 1978/79, there has been an overall decline in smoking prevalence, and since 1986, a decline in smoking intensity among all workers except those in outdoor blue-collar occupations. About 6 in 10 full-time workers who smoked daily encountered restrictions at work.

Adolescent↗

PubMed1997

Mutations of the MEN1 tumor suppressor gene in pituitary tumors.

Although pituitary adenomas are monoclonal proliferations, somatic mutations involving genes that govern cell proliferation or hormone production have been difficult to identify. The genetic etiology of most pituitary tumors, therefore, remains unknown. Pituitary adenomas can develop sporadically or as a part of multiple endocrine neoplasia type 1 (MEN1). Recently, the gene responsible for MEN1 was cloned. To elucidate the potential etiological role of the MEN1 gene in pituitary tumorigenesis, 39 sporadic pituitary adenomas from 38 patients and 1 pituitary adenoma from a familial MEN1 patient were examined for MEN1 gene mutations and allelic deletions. Four of 39 sporadic pituitary adenomas showed a deletion of one copy of the MEN1 gene, and a specific MEN1 gene mutation in the remaining gene copy was detected in 2 of these tumors. The corresponding germ-line sequence was normal in all sporadic cases. A specific MEN1 mutation was detected in a pituitary adenoma and corresponding germ-line DNA in a patient with familial MEN1. An allelic deletion of the remaining copy of the MEN1 gene was also found in the patient's tumor. Genetic alterations of the MEN1 gene represent a candidate pathogenetic mechanism of pituitary tumorigenesis. The data suggest that somatic MEN1 gene mutations and deletions play a causative role in the development of a subgroup of sporadic pituitary adenomas.

Adenoma↗

PubMed1997

Identification and characterization of a catalytic base in bacterial luciferase by chemical rescue of a dark mutant.

Mutation of the His44 residue of the alpha subunit of Vibrio harveyi luciferase to an alanine was known to reduce the enzyme bioluminescence activity by five orders of magnitude [Xin, X., Xi, L., and Tu, S.-C. (1991) Biochemistry 30, 11255-11262]. We found that the residual activity of the alpha H44A luciferase was markedly enhanced by exogenously added imidazole and other simple amines. The peak luminescence intensity in nonturnover assays was linearly proportional to levels of alpha H44A and the rescue agent, indicating a lack of significant binding under our experimental conditions. The rescue effect of imidazole was pH dependent and quantitatively correlated well with the amount of imidazole base. The rescue efficiencies of imidazole and amines were found to be regulated by both their molecular volume and pKa. A Brønsted analysis revealed a beta value of 0.8 +/- 0.1. The enhancement of alpha H44A activity by imidazole took place after the formation of the flavin 4a-hydroperoxide intermediate. The predominant form of the flavin 4a-hydroperoxide intermediate generated by alpha H44A was inactive in bioluminescence, but was reactive with the aldehyde substrate for bioluminescence in the presence of imidazole. These findings, taken together, provide evidence for assigning a role for the alpha His44 imidazole as a catalytic base in the luciferase reaction. This study provides the first characterization of a catalytic residue for bacterial luciferase and the first demonstration of the rescue of a histidine-mutated enzyme by exogenous imidazole and amines.

Amines↗

PubMed1997

The RNA binding domain of ribosomal protein L11: three-dimensional structure of the RNA-bound form of the protein and its interaction with 23 S rRNA.

The three-dimensional solution structure has been determined by NMR spectroscopy of the 75 residue C-terminal domain of ribosomal protein L11 (L11-C76) in its RNA-bound state. L11-C76 recognizes and binds tightly to a highly conserved 58 nucleotide domain of 23 S ribosomal RNA, whose secondary structure consists of three helical stems and a central junction loop. The NMR data reveal that the conserved structural core of the protein, which consists of a bundle of three alpha-helices and a two-stranded parallel beta-sheet four residues in length, is nearly the same as the solution structure determined for the non-liganded form of the protein. There are however, substantial chemical shift perturbations which accompany RNA binding, the largest of which map onto an extended loop which bridges the C-terminal end of alpha-helix 1 and the first strand of parallel beta-sheet. Substantial shift perturbations are also observed in the N-terminal end of alpha-helix 1, the intervening loop that bridges helices 2 and 3, and alpha-helix 3. The four contact regions identified by the shift perturbation data also displayed protein-RNA NOEs, as identified by isotope-filtered three-dimensional NOE spectroscopy. The shift perturbation and NOE data not only implicate helix 3 as playing an important role in RNA binding, but also indicate that regions flanking helix 3 are involved as well. Loop 1 is of particular interest as it was found to be flexible and disordered for L11-C76 free in solution, but not in the RNA-bound form of the protein, where it appears rigid and adopts a specific conformation as a result of its direct contact to RNA.

Amino Acid Sequence↗

PubMed1997

Somatic mutations of the MEN1 tumor suppressor gene in sporadic gastrinomas and insulinomas.

Gastrinomas and insulinomas are frequent in multiple endocrine neoplasia type 1 (MEN1). The MEN1 tumor suppressor gene was recently identified. To elucidate the etiological role of the MEN1 gene in sporadic enteropancreatic endocrine tumorigenesis, we analyzed tumors (28 gastrinomas and 12 insulinomas) from 40 patients for MEN1 gene mutations and allelic deletions. One copy of the MEN1 gene was found to be deleted in 25 of 27 (93%) sporadic gastrinomas and in 6 of 12 (50%) sporadic insulinomas. MEN1 gene mutations were identified in 9 of 27 (33%) sporadic gastrinomas and 2 of 12 (17%) insulinomas and were not seen in corresponding germ-line DNA sequence. A specific MEN1 mutation was detected in one gastrinoma and in the corresponding germ-line DNA of a patient who had no family history of MEN1. Somatic MEN1 gene mutations and deletions play a critical role in the tumorigenesis of sporadic gastrinomas and may also contribute to the development of a subgroup of insulinomas.

Adolescent↗

PubMed1997

A comparison of functional and structural consequences of the tyrosine B10 and glutamine E7 motifs in two invertebrate hemoglobins (Ascaris suum and Lucina pectinata).

The architecture of the distal heme pocket in hemoglobins and myoglobins can play an important role in controlling ligand binding dynamics. The size and polarity of the residues occupying the distal pocket may contribute steric and dielectric effects. In vertebrate systems, the distal pocket typically contains a "distal" histidine at position E7 and a leucine at position B10. There are several invertebrate organisms that have hemoglobins or myoglobins that display a pattern in which residues E7 and B10 are a glutamine and tyrosine, respectively. These proteins often have very high oxygen affinities stemming from very slow ligand off rates. In this study, two such hemoglobins, one from the nematode Ascaris suum and the other from the sulfide-fixing clam Lucina pectinata, are compared with respect to conformational and functional properties. Ultraviolet resonance Raman spectroscopy and visible resonance Raman spectroscopy are used to probe, respectively, the ligand-dependent hydrogen bonding pattern of the tyrosine residues and the proximal heme pocket interactions. Fourier transform infrared absorption spectroscopy is used to probe the dielectric properties of the distal heme pocket through the stretching frequency of carbon monoxide bound to the heme. Functionality is probed through the geminate rebinding of both CO and O2. The findings reveal two very different patterns indicative of two different mechanisms for achieving low oxygen off rates. In Hb Ascaris, a hydrogen bonding network that includes the E7 Gln, B10 Tyr, and oxygen bound to the heme results in a tight cage for the oxygen. Dissociation of the O2 requires a large amplitude conformational fluctuation that results both in a spontaneous dissociation of the oxygen through the loss of hydrogen bond stabilization and in an enhanced probability for ligand escape though the transient disruption and opening of the tight distal cage. In the case of the Hb from Lucina, there is no evidence for a tight cage. Instead the data support a model in which the hydrogen bonding network is far more tenuous and the equilibrium state of distal pocket is far more open and accessible than is the case in Ascaris. The results explain why Hb Ascaris has one of the highest oxygen affinities known (P50 approximately 10(-)3 Torr) while Hb Lucina II has an oxygen affinity comparable to that of Mb (P50 = 0.13 Torr) even though both of these Hbs contain the B10 Tyr and E7 Gln motif and display very low oxygen off rates. The roles of water and proximal strain are discussed.

Amino Acid Substitution↗

PubMed1997

Transcriptional repression mediated by the PR domain zinc finger gene RIZ.

The RIZ (G3B or MTB-Zf) zinc finger gene is structurally related to the myeloid leukemia gene, MDS1-EVI1, and the transcription repressor/differentiation factor, PRDI-BF1/BLIMP1, through a conserved amino-terminal motif, the PR domain. Similar to MDS1-EVI1, RIZ gene normally produces two protein products that differ by the PR domain. The smaller protein RIZ2 lacks the PR domain of RIZ1 but is otherwise identical to RIZ1. Here we show that RIZ proteins bind to GC-rich or Sp-1-binding elements and repress transcription. Both RIZ1 and RIZ2 repressed the herpes simplex virus thymidine kinase (HSV-TK) promoter, one of the best characterized eukaryotic promoters. Recombinant RIZ1 proteins were able to bind to HSV-TK promoter. This binding was mediated by the GC-rich Sp-1 elements of the promoter and the first three zinc finger motifs of RIZ1. RIZ also encodes a repressor domain that was mapped to the central region of the protein. Fusion of this region to the GAL4 DNA-binding domain generated GAL4 site-dependent transcriptional repressors. We also show that RIZ1 protein can efficiently repress the simian virus 40 (SV40) early promoter, which primarily consists of Sp-1 sites; RIZ2, however, only weakly repressed this promoter, suggesting a role for PR in modulating RIZ protein function. The data have implications for a role of RIZ proteins in the regulation of cellular gene promoters, many of which are characterized by GC-rich elements.

3T3 Cells↗

PubMed1997

Three types of serotonin-containing amacrine cells in tadpole retina have distinct clonal origins.

In the Xenopus tadpole there are three different serotonin-containing amacrine cells: large, brightly fluorescent (LB), and small, dimly fluorescent (SD) cells in the inner nuclear layer and displaced (DIS) cells in the ganglion cell layer. To reveal the potential roles of regional cues and lineage factors in their determination, quantitative maps were made of the spatial distribution and blastomere origin of each cell type. LB and SD cells were evenly distributed across the four retinal quadrants, arguing against a hypothesis that these cells are induced differentially by quadrant-specific cues. Blastomere progenitors of the 32-cell embryo are biased to produce only subsets of serotonin amacrine cells: 1) all nine progenitors of one retina produced some SD cells, but only eight produced LB, and only five produced DIS cells; and 2) there are overlapping but distinct subsets of blastomere progenitors for each serotonin subtype. This bias is not simply a reflection of the size of a clone in the retina; significant quantitative differences were observed between the proportion of serotonin progeny and the proportion of the entire retina produced by six of the nine retinal progenitors. This bias also is not simply a reflection of the spatial distribution of a blastomere clone in the retina; the number of LB descendants in each retinal quadrant was statistically different from its progenitor's total contribution to the quadrant. These results indicate that the development of the three different serotonin-containing amacrine cells in the retina is biased by membership in specific blastomere clones.

Animals↗

PubMed1997

High concentrations of phosphatidylinositol-4,5-bisphosphate may promote actin filament growth by three potential mechanisms: inhibiting capping by neutrophil lysates, severing actin filaments and removing capping protein-beta2 from barbed ends.

Cell locomotion requires rapid growth of cortical actin filaments whose barbed ends are capped in the resting cell. Phosphatidylinositol-4,5-bisphosphate (PIP2) may play a critical role as an intracellular messenger in cytoskeletal rearrangement after stimulation. We have examined the effects of PIP2 micelles on the Ca2+-independent actin filament capping activity in high speed supernatants of neutrophil lysates which we had previously demonstrated to be almost entirely due to capping protein-beta2, a homologue of cap Z. High concentrations of PIP2 totally prevented the capping of exogenous spectrin-F-actin seeds by dilute supernatants of neutrophil extracts. Capping could also be inhibited, albeit less effectively, by PIP and PI, but not by other phospholipids. When incubated with filaments in the absence of supernatant, PIP2 increased the number of growing ends. PIP2 also uncapped previously capped actin filaments, as demonstrated by incubating supernatant-capped and uncapped seeds with and without PIP2 and then comparing the initial elongation rates after addition of pyrenyl-G-actin. Incubation of capped seeds with high concentrations of PIP2 increased the number of free barbed ends to a level comparable to that of the uncapped seeds exposed to PIP2. PIP2 caused uncapping to occur too quickly to be explained simply by the off-rate of capping protein-beta2, implying that PIP2 interacted directly with capping protein on the filament ends. In fact, PIP2 transiently uncapped capped seeds in the presence of excess free capping protein. From our data, we estimate that millimolar concentrations of PIP2 (almost 100-fold higher than the amount predicted from the effective concentration in purified systems) would be required to inhibit all the capping protein-beta2 in the cytosol. This discrepancy probably results, in large part, from sequestration of PIP2 by other PIP2-binding proteins in the cytoplasm. If PIP2 mediates differential cytoskeletal growth after chemoattractant stimulation in vivo, very high concentrations may be required subjacent to the plasma membrane for regional severing and uncapping of actin filaments to occur quickly near the perturbed membrane.

Actin Depolymerizing Factors↗