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Biomedical subjects

S Huang

Publications and source records attributed to S Huang.

At least 613 records · Page 34Linked to original sources
PubMed1991

Efficient transformation and regeneration of rice small cell groups.

Transgenic plants have been regenerated from small cell groups of rice using a simpler, faster, and more efficient method than used previously (e.g., protoplast transformation and regeneration methods). Small cell groups of 50-100 cells were prepared from established suspension cultures of rice cell lines. Transformation of small cell groups with intact cell walls was carried out with a plasmid harboring the beta-glucuronidase gene and was mediated by polyethylene glycol. Assay of beta-glucuronidase activity indicated that the frequency of transformation was about 7%. beta-Glucuronidase activity was detected in the roots and leaves of plants regenerated from transformed calli. One or two copies of the beta-glucuronidase gene per cell were determined to be integrated into the rice chromosomal DNA isolated from transformed calli. This method of transformation and regeneration is widely applicable to both dicotyledonous and monocotyledonous plants, especially those varieties that are resistant to regeneration from protoplasts.

Journal Article↗
PubMed1991

Differential induction of cytochromes P450 and cytochrome P450-dependent arachidonic acid metabolism by 3,4,5,3',4'-pentachlorobiphenyl in the rat and the guinea pig.

Differential induction of hepatic cytochromes P450 by 3,4,5,3',4'-pentachlorobiphenyl (PENCB) has been observed in the rat and the guinea pig: (1) in rat and guinea pig, treatment with the chosen dose levels resulted in significant induction of total, carbon monoxide-discernible cytochrome P450 content; the absorption maximum of the CO-adduct of the dithionite-reduced microsomes from PENCB-induced rat liver was shifted from 450 to 448 nm, whereas its counterpart in the guinea pig did not; (2) PENCB treatment significantly increased EROD activity in rat liver microsomes (up to 60-fold), but the increase in the guinea pig was less than fivefold; (3) PENCB-induced rat liver microsomes significantly induced the omega-1 hydroxylation of arachidonic acid (AA); however, omega-1 hydroxylation of AA was hardly affected by PENCB treatment in the guinea pig. Instead, omega-hydroxylation was significantly increased in this latter species. In addition to omega-1 hydroxylation in the rat or omega-hydroxylation in the guinea pig, an additional AA metabolite (designated peak III) was significantly induced by PENCB in both rat and guinea pig; (4) Western blot and ELISA analyses with polyclonal anti-P450 IA1/IA2 and IVA1 antibodies demonstrated that P450 IA1 was significantly induced in the rat but only slightly induced in the guinea pig, whereas P450 IVA1 was significantly suppressed in the rat but significantly induced in the guinea pig by PENCB treatment. The induction of the third arachidonic acid metabolite peak, Peak III, in both rat and guinea pig, particularly in the guinea pig, is obviously neither mediated by P450 IA1 nor by P450 IV A1. At present, it is still unclear which form(s) of cytochrome P450 isoenzymes is responsible for this latter hydroxylation of arachidonic acid.

Animals↗
PubMed1991

Sequential generations of hematopoietic colonies derived from single nonlineage-committed CD34+CD38- progenitor cells.

Multiparameter flow cytometry was applied on normal human bone marrow (BM) cells to study the lineage commitment of progenitor cells ie, CD34+ cells. Lineage commitment of the CD34+ cells into the erythroid lineage was assessed by the coexpression of high levels of the CD71 antigen, the myeloid lineage by coexpression of the CD33 antigen and the B-lymphoid lineage by the CD10 antigen. Three color immunofluorescence experiments showed that all CD34+ BM cells that expressed the CD71, CD33, and CD10 antigens, concurrently stained brightly with anti-CD38 monoclonal antibodies (MoAbs). In addition, the CD38 antigen was brightly expressed on early T lymphocytes in human thymus, characterized by CD34, CD5, and CD7 expression. Only 1% of the CD34+ cells, 0.01% of nucleated cells in normal BM, did not express the CD38 antigen. The CD34+, CD38- cell population lacked differentiation markers and were homogeneous primitive blast cells by morphology. In contrast the CD34+, CD38 bright cell populations were heterogeneous in morphology and contained myeloblasts and erythroblasts, as well as lymphoblasts. These features are in agreement with properties expected from putative pluripotent hematopoietic stem cells; indeed, the CD34 antigen density decreased concurrently with increasing CD38 antigen density suggesting an upregulation of the CD38 antigen on differentiation of the CD34+ cells. Further evidence for a strong enrichment of early hematopoietic precursors in the CD34+, CD38- cell fraction was obtained from culture experiments in which CD34+ cell fractions with increasing density of the CD38 antigen were sorted singularly and assayed for blast colony formation. On day 14 of incubation, interleukin-3 (IL-3), IL-6, and GM-CSF, G-CSF, and erythropoietin (Epo) were added in each well. Twenty-five percent of the single sorted cells that expressed CD34 but lacked CD38 antigen gave rise to primitive colonies 28 to 34 days after cell sorting. The ability to form primitive colonies decreased rapidly with increasing density of the CD38 antigen. During 120 days of culture, up to five sequential generations of colonies were obtained after replating of the first-generation primitive colonies. This study provides direct evidence for the existence of a single class of progenitors with extensive proliferative capacity in human BM and provides an experimental approach for their purification, manipulation, and further characterization.

ADP-ribosyl Cyclase↗
PubMed1991

A cellular protein that competes with SV40 T antigen for binding to the retinoblastoma gene product.

Tumour-suppressor genes, such as the human retinoblastoma susceptibility gene (Rb), are widely recognized as being vital in the control of cell growth and tumour formation. This role is indicated, in part, by the suppression of tumorigenicity of human tumour cells after retrovirus-mediated Rb replacement. How Rb acts to bring about this suppression is not clear but one clue is that the Rb protein forms complexes with the transforming oncoproteins of several DNA tumour viruses, and that two regions of Rb essential for such binding frequently contain mutations in tumour cells. These observations suggest that endogenous cellular proteins might exist that bind to the same regions of Rb and thereby mediate its function. We report here the identification of one such human cellular Rb-associated protein of relative molecular mass 46,000 (46K) (RbAP46). Two lines of evidence support the notion that RbAP46 and simian virus 40 T antigen have homologous Rb-binding properties: first, several mutated Rb proteins that failed to bind to T also did not associate with RbAP46; and second, both T antigen and T peptide (amino acids 101-118) were able to compete with RbAP46 for binding to Rb. The apparent targeting of the RbAP46-Rb interaction by oncoproteins of DNA tumour viruses strongly suggests that formation of this complex is functionally important.

Amino Acid Sequence↗
PubMed1991

Risk factors for penile cancer: results from a case-control study in China.

An epidemiologic study of penile cancer involving 141 cases and 150 community controls was undertaken in a high-risk area in China. Personal interviews, as well as physical examinations among the prospectively ascertained subjects, enabled evaluation of a variety of potential risk factors. Strongly related to risk were conditions restricting the motility of the foreskin, including phimosis or paraphimosis, particularly when so severe that circumcision was used for treatment. Poor hygiene practices also appeared to increase risk, particularly as evidenced by detection of smegma on physical examination, although it was difficult to decipher whether this association was etiologic or merely a consequence of disease. A sexual relationship outside of marriage was associated with a RR of 1.7, and appeared to be a more important discriminator than number of lifetime sexual partners. Risk was increased among subjects reporting previous genital conditions, particularly sexually transmitted diseases, and physical examinations revealed the appearance of genital warts among 13 cases vs. I control. Interviews with wives of study subjects failed to provide evidence of a "female factor" in the etiology of penile cancer. This study supports the need for further evaluation of the role of hygiene and sexually transmitted agents in the etiology of penile cancer.

Adolescent↗
PubMed1991

Gas chromatographic-mass spectrometric characterisation of some novel hydroxyeicosatetraenoic acids formed on incubation of arachidonic acid with microsomes from induced rat livers.

The biotransformation of arachidonic acid by rat liver microsomes from both control animals and animals pretreated with known inducers of cytochrome P-450 isoenzymes has been studied using a combination of reversed- and normal-phase high-performance liquid chromatography and combined gas chromatography-electron-impact mass spectrometry. The metabolite profiles observed were found to be dependent upon the inducing agent. Five metabolites were identified, namely 16-, 17-, 18-, 19- and 20-hydroxylated arachidonic acids. Of these the 16- and 17-isomers have not been reported as products of arachidonic acid metabolism by any biological system and the 18-isomer has not been reported as a product of liver metabolism.

Animals↗
PubMed1991

Nascent pre-mRNA transcripts are associated with nuclear regions enriched in splicing factors.

We have used in situ hybridization and immunocytochemistry to compare the nuclear localization of a specific nascent pre-mRNA and the essential non-snRNP splicing factor SC-35. Nascent c-fos transcripts were detected in serum-induced mouse fibroblasts by in situ hybridization with genomic c-fos probes. Prior to serum induction no c-fos RNA is detected, but these transcripts localize to two dots in the interphase nucleus after induction. The time course of appearance of the dots correlates with the previously determined time course of transcriptional activation of the gene. Upon further analysis by confocal laser scanning microscopy, we have determined that the dots extend through the depth of the nucleus, forming paths. By using high-voltage electron microscopy, we have found that the c-fos path extends out and comes into direct contact with the nuclear envelope. We have also compared the localization of c-fos transcripts with the speckled nuclear regions that are enriched in snRNPs and the non-snRNP splicing factor SC-35. Direct observations of three-dimensional rotations have revealed a close association between the c-fos transcripts and the nuclear speckles. This study demonstrates a direct link between specific nascent RNA transcripts and nuclear speckles that are enriched in pre-mRNA splicing factors.

3T3 Cells↗
PubMed1991

Strain differences in mouse brain weight gain and spatial-location scores during postnatal development.

Brain weight and performance on a spatial-location test were measured from birth to weaning on mouse strains CD1, Balb/c, and their F1 cross. For CD1, onsets of both the last rapid-brain-growth stage and nonzero scores on the spatial-location test were around age 17 days; asymptotes of both were reached about age 23 days. Balb/c and F1 had at least 5- to 6-day delays of both onsets and asymptotes. For the strains studied, onset of nonzero performance on the spatial-location test may be a provisional indicator of onset of significant and rapid brain growth after age 15 days. The delayed F1 brain growth stage could indicate that control of brain growth about age 20 days resides in an inhibitory factor present in Balb/c but not in CD1.

Animals↗
PubMed1991

[An observation on growth hormone levels in patients with chronic renal failure].

Serum levels of growth hormone (GH) in the fasting and postprandial state were observed in 27 patients with chronic renal failure (CRF) [and in 27 normal controls. The results showed that serum levels of GH were significantly higher in CRF patients than in normal controls. Most patients exhibited a "paradoxical rise" of GH following an oral glucose load. There was no difference between GH concentrations in those with impaired glucose tolerance (IGT) and those with normal glucose tolerance (NGT) in the CRF cases. Elevation of GH could be returned to normal by kidney transplantation with the disappearance of the "paradoxical rise" of GH. The mechanism of these abnormalities and the relationship between abnormalities of GH and IGT were discussed.

Adult↗
PubMed1991

On the size of apical foramen in anterior teeth, bicuspids and molars.

The present authors have used a replica method to obtain area size measurements for the apical foramen in 4,613 human permanent teeth, and have obtained the following results: 1. The morphology of the apical foramen is rich in variety which make it difficult to express its accurate size using foramen diameter measurement. It is therefore more appropriate to determine its size as an area measurement. 2. Much variation was observed in the size of the apical foramen even for teeth of the same type. It was, however, also observed that the foramen is smaller in smaller types of teeth and larger in larger types of teeth. It was also observed that, in teeth of the same type, those with a greater number of roots have smaller foramen than those with a smaller number of roots.

Bicuspid↗
PubMed1991

[The color vision in patients with optic neuritis and chronic open-angle glaucoma].

Twenty eight cases (50 eyes) of chronic open-angle glaucoma and 21 cases (27 eyes) of optic neuritis were investigated with FM 100-hue test and panel D-15 test. In patients with optic neuritis, 70.37% and 85.19% of the affected eyes appeared abnormal in Panel D-15 test and FM 100-hue test respectively. The main defects were tritan-like in both of the tests. In patients with chronic open-angle glaucoma, 20% and 32% of the affected eyes had abnormal results in Panel D-15 test and FM 100-hue test respectively. The main defects were also tritan-like color vision defect. The total error scores of FM 100-hue test in patients with chronic open-angle glaucoma had no relation with the cup disc ratio and the area of peripheral visual field but had relation with the area of central visual field.

Adolescent↗
PubMed1991

Altered post-translational processing of p21ras oncoprotein in a transformation-suppressed cell line.

We have isolated a transformation-suppressed cell line, R35, which is altered in the maturation of p21ras. It was obtained from the transformed cell line NIH3T3(rasEJ) as a revertant with flat morphology and anchorage dependent growth. Immunoprecipitation of steady state labeled ras proteins reveals that the revertant produces p21ras, and in addition, accumulates a protein that migrates as 23kD. Fusion of revertant cells with nontransformed rat2 cells yields cell hybrids which are retransformed and do not accumulate p23, suggesting that accumulation of p23 and suppression of transformation may be related. The accumulated p23 appears to be a precursor to p21 because (1) pulse labeling and cell fractionation of revertant cells shows that label chases from cytoplasmic p23 to membrane-associated p21, although at a slower rate, and (2) the p23 of revertant cells is indistinguishable from the p23 precursor of p21 in parent cells by partial V8 protease digestion and two dimensional electrophoresis. R35 cells are slower than their transformed parent in palmitylation and polyisoprenylation, but not in methylation of ras proteins. These results suggest that the transformation-suppressed cell line R35 is defective in the rate at which it posttranslationally processes ras proteins, possibly because it is slower in polyisoprenylation of the cytoplasmic p23 precursor protein.

Animals↗
PubMed1990

Role of lysine-54 in determining cofactor specificity and binding in human dihydrofolate reductase.

Lysine-54 of human dihydrofolate reductase (hDHFR) appears to be involved in the interaction with the 2'-phosphate of NADPH and is conserved as a basic residue in other species. Studies have suggested that in Lactobacillus casei dihydrofolate reductase Arg-43, the homologous residue at this position, plays an important role in the binding of NADPH and in the differentiation of Km values for NADPH and NADH. A Lys-54 to Gln-54 mutant (K54Q) of hDHFR has been constructed by oligodeoxynucleotide-directed mutagenesis in order to study the role of Lys-54 in differentiating Km and Kcat values for NADPH and NADH as well as in other functions of hDHFR. The purpose of this paper is to delineate in quantitative terms the magnitude of the effect of the Lys-54 to Gln-54 replacement on the various kinetic parameters of hDHFR. Such quantitative effects cannot be predicted solely on the basis of X-ray structures. The Km for NADPH for the K54Q mutant enzyme is 58-fold higher, while the Km for NADH for K54Q is only 3.9-fold higher than that of the wild type, indicating that the substitution of Lys-54 with Gln-54 decreases the apparent affinity of the enzyme for NADPH dramatically, but has a lesser effect on the apparent affinity for NADH.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗