Biomedical subjects

Yi Xue

Publications and source records attributed to Yi Xue.

7 recordsLinked to original sources

PubMed2006

Protein side-chain dynamics observed by solution- and solid-state NMR: comparative analysis of methyl 2H relaxation data.

Rapid advances in solid-state MAS NMR made it possible to probe protein dynamics on a per-residue basis, similar to solution experiments. In this work we compare methyl 2H relaxation rates measured in the solid and liquid samples of alpha-spectrin SH3 domain. The solution data are treated using a model-free approach to separate the contributions from the overall molecular tumbling and fast internal motion. The latter part forms the basis for comparison with the solid-state data. Although the accuracy of solid-state measurements is limited by deuterium spin diffusion, the results suggest a significant similarity between methyl dynamics in the two samples. This is a potentially important observation, preparing the ground for combined analysis of the dynamics data by solid- and solution-state NMR.

Animals↗

PubMed2005

[Quantitative evaluation of the variation of aroma harmony in processed fruit and vegetable juices with gas chromatographic data].

To develop a quantitative evaluation model for the variation of aroma harmony in processed fruit and vegetable juices, gas chromatographic data from juice samples were summed up by mathematic modeling. Based on the original fruit and vegetable juices, the total change in volatile compounds expressed in term of percentage between the treated samples by various processes and the original juice, that is, the deviation of samples, are calculated. They were then used to describe the total change of aroma compounds in the fruit and vegetable juices before and after the processing. To compare the influences of different processes on aroma harmony in fruit and vegetable juices, the samples were analyzed by gas chromatography under the same conditions and the data were obtained by comparing the deviations of the samples. The lemon juices concentrated either by freeze-concentration or by vacuum evaporation were compared against the original lemon juices. The results showed that the freeze-concentration well retained not only the absolute contents of aroma compounds but also the aroma harmony of natural lemons.

Beverages↗

PubMed2004

In situ reduction of oxidative damage, increased cell turnover, and delay of mitochondrial injury by overexpression of manganese superoxide dismutase in a multistage skin carcinogenesis model.

To study early subcellular pathologic changes of tumorigenesis in mouse skin and possible modulation by overexpression of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD), skin keratinocytes from nontransgenic (Ntg) and transgenic (TgH) mice overexpressing MnSOD topically treated with one dose of 7,12-dimethylbenz(a)anthracene (DMBA) and a subsequent dose of 12-O-tetradecanoylphorbol 13-acetate (TPA) were analyzed in situ for levels of MnSOD and the oxidative damage product 4-hydroxy-2-nonenal (4HNE)-modified proteins using specific antibodies and immunogold electron microscopy. At all selected time points analyzed after TPA treatment, there was more MnSOD immunoreactive protein in mitochondria of keratinocytes of TgH mice than Ntg mice. Compared with untreated groups, there was a large increase in 4HNE-modified proteins at 6-24 h after TPA treatment, and this increase was larger in Ntg than TgH mice. Indices of mitosis and apoptosis of keratinocytes were greater in DMBA/TPA-treated TgH than Ntg mouse skin. Mitochondrial injury detected by transmission electron microscopy was delayed in keratinocytes of TgH compared with Ntg mice. The present study demonstrated that overexpression of MnSOD not only protected cells from oxidative damage, but also affected cell turnover kinetics. Thus, previously identified reduction in papilloma formation observed in TgH mice is correlated with mitochondrial events.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2004

Treponema putidum sp. nov., a medium-sized proteolytic spirochaete isolated from lesions of human periodontitis and acute necrotizing ulcerative gingivitis.

So far, little phenotypic heterogeneity has been detected in cultured oral treponemes with trypsin-like proteolytic activity, and all have been assigned to the species Treponema denticola. However, comparisons of protein patterns and antigen expression in our collection of proteolytic oral treponemes occasionally identified isolates with a unique phenotype; e.g. strain OMZ 830 (=ATCC 700768), which qualified as a 'pathogen-related oral spirochaete' due to the presence of a approximately 37 kDa protein reactive with the Treponema pallidum FlaA-specific mAb H9-2. In addition to such single isolates, a homogeneous group of seven independent strains is described that were highly motile, medium-sized, proteolytic but asaccharolytic spirochaetes and were cultured from human gingivitis, periodontitis and acute necrotizing ulcerative gingivitis in medium OMIZ-Pat supplemented with 1% human serum and antibiotics. Growth of these spirochaetes in OMIZ-Pat was not dependent on, but was stimulated by, human or bovine serum. Carbohydrates were neither required nor stimulatory for growth. The protein and antigen patterns of total cell extracts of these organisms separated by SDS-PAGE were distinct from those of all previously cultured spirochaetes, with highest similarity to T. denticola. The novel spirochaete has a 2 : 4 : 2 arrangement of the periplasmic flagella, similar to T. denticola. However, the flagellin pattern as detected by immunostaining or glycan staining of Western blots readily distinguished the novel group from T. denticola. Also, distinct from reference strains of T. denticola, none of the novel isolates displayed sialidase or dentilisin activities, both of which are expressed by most strains of T. denticola. Trypsin-like activity and other enzymes as detected by API ZYM test were similar to those of T. denticola. The status of a novel species is supported by the 16S rRNA gene sequence, with 98.5% similarity to its closest cultured relative, T. denticola. The name Treponema putidum sp. nov. is proposed (type strain OMZ 758T=ATCC 700334T=CIP 108088T).

Antigens, Bacterial↗

PubMed2004

Gingival crevice microbiota from Chinese patients with gingivitis or necrotizing ulcerative gingivitis.

The objective of this study was to quantitatively compare the bacterial population structure in plaque from the gingival margin of two groups of 21 Chinese patients with gingivitis or necrotizing ulcerative gingivitis (NUG). Subjects were recruited in four dental clinics in Eastern China. Samples were quantitatively assessed by immunofluorescence and fluorescent in situ hybridization for taxa known to be associated with periodontal diseases. The analyses showed that the fusiform taxa (Fusobacterium nucleatum/Fusobacterium periodonticum, Leptotrichia buccalis, Tannerella forsythensis, and Capnocytophaga sp.), Campylobacter rectus, Prevotella intermedia, Prevotella nigrescens, Selenomonas sputigena, and treponemes were present in both groups with high prevalence. Porphyromonas gingivalis and Actinomyces gerencseriae were much more prevalent in the NUG group. Quantitatively, most taxa, including P. gingivalis, F. nucleatum and the treponemes, accounted, on average, for < 3% of the total bacterial cell number. Only P. intermedia/P. nigrescens, P. gingivalis, S. sputigena, A. gerencseriae, and the sum of all monitored suspected periodontal pathogens were significantly increased in the NUG group. The present study demonstrates for both groups a highly diverse plaque composition and suggests that, etiologically, the overall concentration and the concerted effects of the entire group of opportunistic pathogens thriving in NUG-associated plaque are of prime importance.

Adult↗

PubMed2004

Synaptic release of dopamine in the subthalamic nucleus.

The direct modulation of subthalamic nucleus (STN) neurons by dopamine (DA) neurons of the substantia nigra (SN) is controversial owing to the thick caliber and low density of DA axons in the STN. The abnormal activity of the STN in Parkinson's disease (PD), which is central to the appearance of symptoms, is therefore thought to result from the loss of DA in the striatum. We carried out three experiments in rats to explore the function of DA in the STN: (i) light and electron microscopic analysis of tyrosine hydroxylase (TH)-, dopamine beta-hydroxylase (DbetaH)- and DA-immunoreactive structures to determine whether DA axons form synapses; (ii) fast-scan cyclic voltammetry (FCV) to determine whether DA axons release DA; and (iii) patch clamp recording to determine whether DA, at a concentration similar to that detected by FCV, can modulate activity and synaptic transmission/integration. TH- and DA-immunoreactive axons mostly formed symmetric synapses. Because DbetaH-immunoreactive axons were rare and formed asymmetric synapses, they comprised the minority of TH-immunoreactive synapses. Voltammetry demonstrated that DA release was sufficient for the activation of receptors and abolished by blockade of voltage-dependent Na+ channels or removal of extracellular Ca2+. The lifetime and concentration of extracellular DA was increased by blockade of the DA transporter. Dopamine application depolarized STN neurons, increased their frequency of activity and reduced the impact of gamma-aminobutyric acid (GABA)-ergic inputs. These findings suggest that SN DA neurons directly modulate the activity of STN neurons and their loss may contribute to the abnormal activity of STN neurons in PD.

Animals↗

PubMed2003

Molecular basis of metal-ion selectivity and zeptomolar sensitivity by CueR.

The earliest of a series of copper efflux genes in Escherichia coli are controlled by CueR, a member of the MerR family of transcriptional activators. Thermodynamic calibration of CueR reveals a zeptomolar (10(-21) molar) sensitivity to free Cu+, which is far less than one atom per cell. Atomic details of this extraordinary sensitivity and selectivity for +1transition-metal ions are revealed by comparing the crystal structures of CueR and a Zn2+-sensing homolog, ZntR. An unusual buried metal-receptor site in CueR restricts the metal to a linear, two-coordinate geometry and uses helix-dipole and hydrogen-bonding interactions to enhance metal binding. This binding mode is rare among metalloproteins but well suited for an ultrasensitive genetic switch.

Amino Acid Sequence↗