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Biomedical subjects

D Huang

Publications and source records attributed to D Huang.

At least 163 records · Page 9Linked to original sources
PubMed1996

The heme redox center of chloroplast cytochrome f is linked to a buried five-water chain.

The crystal structure of the 252-residue lumen-side domain of reduced cytochrome f, a subunit of the proton-pumping integral cytochrome b6f complex of oxygenic photosynthetic membranes, was determined to a resolution of 1.96 A from crystals cooled to -35 degrees. The model was refined to an R-factor of 15.8% with a 0.013-A RMS deviation of bond lengths from ideality. Compared to the structure of cytochrome f at 20 degrees, the structure at -35 degrees has a small change in relative orientation of the two folding domains and significantly lower isotropic temperature factors for protein atoms. The structure revealed an L-shaped array of five buried water molecules that extend in two directions from the N delta 1 of the heme ligand His 25. The longer branch extends 11 A within the large domain, toward Lys 66 in the prominent basic patch at the top of the large domain, which has been implicated in the interaction with the electron acceptor, plastocyanin. The water sites are highly occupied, and their temperature factors are comparable to those of protein atoms. Virtually all residues that form hydrogen bonds with the water chain are invariant among 13 known cytochrome f sequences. The water chain has many features that optimize it as a proton wire, including insulation from the protein medium. It is suggested that this chain may function as the lumen-side exit port for proton translocation by the cytochrome b6f complex.

Chloroplasts↗
PubMed1996

Effect of domestically-made levonorgestrel-releasing intrauterine device on the endocrine system and menstruation in monkeys.

Effect of domestically-made levonorgestrel-releasing intrauterine device (LNG, release rate, 6 micrograms/day) on the endocrine system and menstruation in monkeys was investigated. The results showed that the Estradiol (E2) and progesterone (P) levels were significantly decreased 2 ovulatory cycles after insertion of the devices as compared with those before insertion in 3 monkeys (P > 0.001), suggesting an evident ovulation-suppressing effect. In 1 monkey, the E2 and P levels were the same before and after insertion, and expulsion of device was found in the monkey later. The plasma LNG concentration in 3 animals was 493.69-454.60 pg/ml and plasma LNG was not detected in 1 monkey. The hormone level returned to normal level after removal of the devices.

Animals↗
PubMed1996

Expression of biglycan, decorin and fibromodulin in the hypertrophic phase of experimental osteoarthritis.

This study sought to assess the relative levels of the mRNAs of the core proteins of the small proteoglycans (PGs) biglycan, decorin and fibromodulin in the hypertrophic phase of the early osteoarthritis (OA) that follows joint injury. Experimental OA was induced in eight dogs by transection of the anterior cruciate ligament. Articular cartilage was harvested from each joint, the total RNA was extracted and the concentration of DNA in the cartilage was measured. The relative levels of mRNA for biglycan, decorin and fibromodulin were assessed by northern blot analyses. An increase in cartilage mass with no increase in DNA concentration confirmed that the joints were in the hypertrophic phase that follows joint injury. The total RNA per microgram of DNA was increased 2.5 times. Compared with control cartilage, the mRNA levels in osteoarthritic cartilage, when normalized to the concentration of DNA, were increased 3.9 times for biglycan, 1.2 times for decorin and 2.4 times for fibromodulin. Because these small PGs affect collagen fibrillogenesis in vitro, their discoordinate metabolism may contribute to the abnormal collagen formation and deposition that occurs in OA and to the ultimate failure of the articular cartilage.

Animals↗
PubMed1996

Genetic interactions between REG1/HEX2 and GLC7, the gene encoding the protein phosphatase type 1 catalytic subunit in Saccharomyces cerevisiae.

Mutations in GLC7, the gene encoding the type 1 protein phosphatase catalytic subunit, cause a variety of abberrant phenotypes in yeast, such as impaired glycogen synthesis and relief of glucose repression of the expression of some genes. Loss of function of the REG1/HEX2 gene, necessary for glucose repression of several genes, was found to suppress the glycogen-deficient phenotype of the glc7-1 allele. Deletion of REG1 in a wild-type background led to overaccumulation of glycogen as well as slow growth and an enlarged cell size. However, loss of REG1 did not suppress other phenotypes associated with GLC7 mutations, such as inability to sporulate or, in cells bearing the glc7Y-170 allele, lack of growth at 14 degrees. The effect of REG1 deletion on glycogen accumulation is not simply due to derepression of glucose-repressed genes, although it does require the presence of SNF1, which encodes a protein kinase essential for expression of glucose-repressed genes and for glycogen accumulation. We propose that REG1 has a role in controlling glycogen accumulation.

Base Sequence↗
PubMed1996

Attenuated Salmonella vaccine-induced suppression of murine spleen cell responses to mitogen is mediated by macrophage nitric oxide: quantitative aspects.

Previous reports from our laboratory have shown that 7 days after infection of C3HeB/FeJ mice with an attenuated strain of Salmonella typhimurium, there is profound suppression of responses to B- and T-cell mitogens and suppression of the capacity of spleen cells to mount a primary, in vitro plaque-forming-cell (PFC) response to sheep erythrocytes. Inhibition of the PFC response was shown to be mediated by nitric oxide (NO), as NG-monomethyl-L-arginine (NMMA) gave complete reversal of suppression. The experiments reported here examined the role of NO in suppression of the response to the mitogen concanavalin A (ConA). In contrast to the PFC system, it was found that addition of NMMA to ConA-stimulated immune spleen cells resulted in less than 20% reversal of suppression. However, addition to NMMA resulted in a 50% reversal of suppression in cocultures of immune and normal spleen cells at a ratio of 1:4. A complete restoration of ConA-induced responses was achieved in cocultures incubated in medium containing a reduced concentration of L-arginine plus 1.25 mM NMMA. Investigation of why NMMA alone was not 100% effective in reversing suppression showed that addition of ConA significantly augmented production of nitrite and gamma interferon (IFN-gamma) in cocultures containing immune cells. Addition of anti-IFN-gamma reduced nitrite levels in the cultures, although results with the combination of anti-IFN-gamma and NMMA were not significantly better than results with NMMA alone. These findings suggest that suppression in cultures stimulated with ConA is difficult to reverse completely with NMMA alone because of an overproduction of NO, which can be offset by either reducing the L-arginine concentration or blocking IFN-gamma. The quantitative relationship between nitrite levels and suppression in cocultures was examined. It was found that suppression did not correlate directly with the nitrite concentration but rather with the log10 of the nitrite concentration. Nitrite levels above 15 microM gave almost complete suppression, and levels between 1 and 10 microM gave a wide range of suppression. These results strongly support NO as the suppressor factor in Salmonella-induced immunosuppression of responses to ConA and, by inference, suppression of responses to mitogens induced by other microbes. The results show that involvement of NO cannot always be demonstrated by simple addition of NMMA to suppressed mitogen-stimulated spleen cell cultures.

Animals↗
PubMed1996

Pho85p, a cyclin-dependent protein kinase, and the Snf1p protein kinase act antagonistically to control glycogen accumulation in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, nutrient levels control multiple cellular processes. Cells lacking the SNF1 gene cannot express glucose-repressible genes and do not accumulate the storage polysaccharide glycogen. The impaired glycogen synthesis is due to maintenance of glycogen synthase in a hyperphosphorylated, inactive state. In a screen for second site suppressors of the glycogen storage defect of snf1 cells, we identified a mutant gene that restored glycogen accumulation and which was allelic with PHO85, which encodes a member of the cyclin-dependent kinase family. In cells with disrupted PHO85 genes, we observed hyperaccumulation of glycogen, activation of glycogen synthase, and impaired glycogen synthase kinase activity. In snf1 cells, glycogen synthase kinase activity was elevated. Partial purification of glycogen synthase kinase activity from yeast extracts resulted in the separation of two fractions by phenyl-Sepharose chromatography, both of which phosphorylated and inactivated glycogen synthase. The activity of one of these, GPK2, was inhibited by olomoucine, which potently inhibits cyclin-dependent protein kinases, and contained an approximately 36-kDa species that reacted with antibodies to Pho85p. Analysis of Ser-to-Ala mutations at the three potential Gsy2p phosphorylation sites in pho85 cells implicated Ser-654 and/or Thr-667 in PHO85 control of glycogen synthase. We propose that Pho85p is a physiological glycogen synthase kinase, possibly acting downstream of Snf1p.

Alleles↗
PubMed1996

[The clinical observations on 110 cases of adhesive otitis media].

The treatment of the adhesive otitis media (AOM) remains a challenge to the otologists. This paper analysed 110 cases of AOM (120 ears) collected during 25 years from 1967 to 1992. The clinical observation found that the lesions of AOM affected all parts of the middle ear, even the round and oval windows. There were various degrees of tympanic fibrous adhesions and atelectatic tympanum in these cases. After the tympanic adhesions were surgically separated and the lesions were removed, the silastic film or a slice of the homologous cartilages were put into the tympanum to prevent a new adhesion. It was showed that the silastic film was frequently enveloped in a capsule formed by the fibrous collagenous tissue and other extensive adhesions were existed around the capsule. But the cartilage slice caused the slighter pathological reactions. However, their hearing did not recovery to an available level. Therefore the further studies for the treatment of AOM are necessary.

Adolescent↗
PubMed1996

[Determination of copper and cadmium in water by continuous flow analysis].

A continuous flow analysis system for the preconcentration of Cu2+ and/or Cd2+ in water was developed. Trace copper or cadmium in water could be concentrated on activated carbon particles packed in micro column at pH > or = 9.0. The adsorbed analyte was eluted with 0.5 ml 2.5% nitric acid and determined by flame atomic absorption spectrometry. A sample size of 10-25 ml sufficed for the determination of copper2+ or cadmium at a level as low as microgram/L. The relative standard deviation of 6 parallel determinations was 4.3% for copper and 11% for cadmium. The proposed method was applied to the determination of copper and cadmium in natural water with a recovery of 84.4%-118%.

Cadmium↗
PubMed1996

[Failure in mastoidectomy with posterior canal wall preservation and tympanoplasty case analysis].

Preservation of the posterior canal wall in mastoidectomy is essential for rebuilding normal tympanum and conductive structures, and has been widely recommended. However, controversies remain about the technique due to its complications and diverse results reported. This paper analysed the causes of four failed cases in detail and proposed measure to reduce morbidities and promote success. The review includes case selection, operation staging, surgical techniques and lesion removal etc.

Adult↗
PubMed1996

[Histopathology of the temporal bone in adhesive otitis media].

To understand the histopathological changes of adhesive otitis media (AOM) in human, temporal bone sections processed with the celloidin-embedding technique were reviewed. In the 338 pairs of temporal bone specimens, 20 cases (26 ears) showed characteristics of AOM. The results showed that the lesions of AOM were extensive, involving all middle ear structures including tympanic muscles, round and oval windows. There were various pathological changes, in every stage of inflammation and tissue repair. According to the main pathological characteristics, histopathological changes of the 26 ears were staged as exudation, inflammatory grannlation formation, histocyte response and collegen proliferation. As the process progressed, the amount of inflammatory cells and exudate decreased with the increase of fibroblasts. Certain factors were speculated to play an important role in the process of fibrosis. The authors analysed the difficulties in the management of AOM and causes of the unsatisfactory therapeutic results. Possible measures to improve treatment results were proposed.

Adult↗
PubMed1995

Conformational compatibility as a basis of differential affinities of tachykinins for the neurokinin-1 receptor.

The neurokinin-1 receptor is characterized by sub-nanomolar affinity for substance P and 30-100 nM affinity for other substance P-related peptides, including neurokinin B and septide. We have characterized a neurokinin-1 receptor mutant containing a Y216A substitution in the fifth transmembrane segment. This receptor mutant binds substances P with sub-nanomolar affinity but loses much of its peptide discrimination capability, exhibiting 1-2 nM binding affinity for other tachykinins. Kinetic measurements of ligand binding indicate that the increased binding affinity of neurokinin B and septide for the Y216A mutant compared to the wild-type receptor is due to a 100-fold increase in the association rate constant without appreciable change in the dissociation rate constant. The substantially increased association rate constant for the Y216A mutant suggests that the mutant receptor is probably more flexible in accommodating the approaching peptide molecule. It is proposed that a major determinant of peptide specificity for the wild-type neurokinin-1 receptor is the overall conformational compatibility between the receptor and the ligand, rather than residue-specific interactions with the divergent N-terminal residues of different peptides. Furthermore, the highly conserved nature of Tyr-216 in the G protein coupled receptor family suggests that this residue may also play an important role in the receptor activation process in general.

Amino Acid Sequence↗
PubMed1995

Rapamycin selectively blocks interleukin-2-induced proliferating cell nuclear antigen gene expression in T lymphocyte. Evidence for inhibition of CREB/ATF binding activities.

The macrolide rapamycin arrests T lymphocytes stimulated by interleukin-2 (IL-2) at G1/S. We have recently found that IL-2 induced an increase in the binding of discrete transcription factors of the ATF/cAMP-responsive element binding factor (CREB) family at G1/S, and that this effect was inhibited by rapamycin (Feuerstein, N., Huang, D., Hinrichs, S. H., Orten, D. J., Aiyar, N., and Prystowsky, M. B. (1995) J. Immunol. 154, 68-79). We now show, by using high resolution two-dimensional gel electrophoresis, that rapamycin inhibited selectively the synthesis of three discrete IL-2-induced soluble proteins (35 kDa/pI approximately 5, 68 kDa/pI approximately 4, 110 kDa/pI approximately 4.3). Analysis of nuclear proteins demonstrated that rapamycin selectively blocked the expression of proliferating cell nuclear antigen (PCNA), an obligate cofactor of DNA polymerase-delta, an important component for DNA replication. Rapamycin inhibited the IL-2-induced PCNA mRNA, and the murine PCNA promoter activity in IL-2-stimulated cells. Inducible CRE-binding proteins were shown previously to be required for PCNA promoter activity in IL-2-stimulated T lymphocytes. Using DNA binding gel mobility shift assay we demonstrated that rapamycin potently inhibited the binding of CREB/ATF transcription factors to CRE elements in the murine proximal PCNA promoter. These results suggest that PCNA is a preferred target in a rapamycin-sensitive transduction pathway, and that the mechanism by which rampamycin inhibits PCNA gene expression may involve the inhibition of the interaction of CREB/ATF transcription factors with CRE elements in the proximal PCNA promoter.

Activating Transcription Factors↗
PubMed1995

Transcriptional regulation of the lactate dehydrogenase A subunit gene by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate.

Regulation of lactate dehydrogenase (LDH) (EC 1.1.1.27) isozymes occurs through a multitude of physiological signals. Here, we show that modulation of LDH A subunit occurs via the protein kinase C pathway. Activators of protein kinase C, such as tetradecanoylphorbol acetate (TPA) and dioctanoylglycerol (DG), caused a 3-4-fold accumulation of LDH A subunit mRNA in rat C6 glioma cells. The specific protein kinase C inhibitor bisindolylmaleimide GF 109203X prevented the TPA-induced increase of LDH A subunit mRNA. To analyze the molecular basis of these effects in more detail, the transcription-modulatory effects of TPA and DG were evaluated in transient transfection assays using plasmids which contain LDH A subunit promoter fragments fused to a chloramphenicol acetyltransferase reporter gene. Both effector agents caused a marked increase of the transcriptional activity of an LDH -830/+25 bp promoter/CAT construct. In contrast, a phorbol ester which fails to activate protein kinase C, phorbol 12 beta,13 alpha-didecanoate, had no effect on the LDH promoter activity. Transient transfection analysis of LDH promoter deletion/CAT constructs, DNA/protein binding assays, including footprint and gel shift analyses, identified a TRE/AP-1 enhancer module at position -294 bp which was the target for the protein kinase C-mediated signal transduction pathway. Thus, our data demonstrate an active role of the protein kinase C signal pathway in regulating LDH A subunit gene expression which may be significant in regulating LDH isozyme patterns under various physiologic conditions.

Animals↗