Biomedical subjects

X Jin

Publications and source records attributed to X Jin.

At least 37 records · Page 2Linked to original sources

PubMed2001

Requirement for tyrosine residues 315 and 319 within zeta chain-associated protein 70 for T cell development.

Engagement of the T cell antigen receptor (TCR) induces the transphosphorylation of the zeta chain-associated protein of 70,000 Mr (ZAP-70) protein tyrosine kinase (PTK) by the CD4/8 coreceptor associated Lck PTK. Phosphorylation of Tyr 493 within ZAP-70's activation loop results in the enzymatic activation of ZAP-70. Additional tyrosines (Tyrs) within ZAP-70 are phosphorylated that play both positive and negative regulatory roles in TCR function. Phosphorylation of Tyr residues (Tyrs 315 and 319) within the Interdomain B region of the ZAP-70 PTK plays important roles in the generation of second messengers after TCR engagement. Here, we demonstrate that phosphorylation of these two Tyr residues also play important roles in mediating the positive and negative selection of T cells in the thymus.

Animals↗

PubMed2001

Role of oxidative stress and antioxidant defense in 3,3',4,4',5-pentachlorobiphenyl-induced toxicity and species-differential sensitivity in chicken and duck embryos.

The role of oxidative stress and antioxidant defense in 3,3',4,4',5-pentachlorobiphenyl (PCB 126)-induced toxicity and species-specific sensitivity was examined in White Leghorn chicken (Gallus domesticus) and Pekin duck (Anas platyrhynchos) embryos. Eggs were injected into the air cell with 0.4-1.6 microgram PCB 126/kg egg in corn oil prior to incubation. Lipid peroxidation measured by thiobarbituric acid reactive substances (TBARS), the GSSG:GSH ratio, and glutathione peroxidase (GPox) activities were determined in liver and adipose tissue of day 19 chicken and day 26 duck embryos. In chicken embryos, PCB 126 increased mortality and the incidence of edema and liver lesions, decreased embryo size, increased eye and head malformations, and markedly reduced fat storage. In contrast, no effects on the endpoints were observed in duck embryos even at the highest dose used in chicken embryos. PCB 126 increased hepatic 7-ethoxyresorufin-O-deethylase (EROD) activity in a dose-dependent manner in chicken but not duck embryos. PCB 126 significantly increased TBARS levels in liver and to a greater degree in adipose tissue of chicken embryos, indicating that adipose tissue is a sensitive target for this compound. Increases in lipid peroxidation by PCB 126 were associated with significant decreases in GPox activity in these tissues. These biochemical changes support oxidative stress playing a role in PCB 126-induced embryo toxicity while antioxidant defenses provided protection against oxidative damage induced by this compound. Ducks, the less-sensitive species, showed higher basal levels of hepatic GPox than chickens, suggesting that this antioxidant enzyme may contribute to the differences in sensitivity to this compound between the two species.

Adipose Tissue↗

PubMed2001

Rapid kinetic and isotopic studies on dialkylglycine decarboxylase.

The two half-reactions of the pyridoxal 5'-phosphate (PLP)-dependent enzyme dialkylglycine decarboxylase (DGD) were studied individually by multiwavelength stopped-flow spectroscopy. Biphasic behavior was found for the reactions of DGD-PLP, consistent with two coexisting conformations observed in steady-state kinetics [Zhou, X., and Toney, M. D. (1998) Biochemistry 37, 5761--5769]. The half-reaction kinetic parameters depend on alkali metal ion size in a manner similar to that observed for steady-state kinetic parameters. The fast phase maximal rate constant for the 2-aminoisobutyrate (AIB) decarboxylation half-reaction with the potassium form of DGD-PLP is 25 s(-1), while that for the transamination half-reaction between DGD-PMP and pyruvate is 75 s(-1). The maximal rate constant for the transamination half-reaction of the potassium form of DGD-PLP with L-alanine is 24 s(-1). The spectral data indicate that external aldimine formation with either AIB or L-alanine and DGD-PLP is a rapid equilibrium process, as is ketimine formation from DGD-PMP and pyruvate. Absorption ascribable to the quinonoid intermediate is not observed in the AIB decarboxylation half-reaction, but is observed in the dead-time of the stopped-flow in the L-alanine transamination half-reaction. The [1-(13)C]AIB kinetic isotope effect (KIE) on k(cat) for the steady-state reaction is 1.043 +/- 0.003, while a value of 1.042 +/- 0.009 was measured for the AIB half-reaction. The secondary KIE measured for the AIB decarboxylation half-reaction with [C4'-(2)H]PLP is 0.92 +/- 0.02. The primary [2-(2)H]-L-alanine KIE on the transamination half-reaction is unity. Small but significant solvent KIEs are observed on k(cat) and k(cat)/K(M) for both substrates, and the proton inventories are linear in each case. NMR measurements of C2--H washout vs product formation give ratios of 105 and 14 with L-alanine and isopropylamine as substrates, respectively. These results support a rate-limiting, concerted C alpha-decarboxylation/C4'-protonation mechanism for the AIB decarboxylation reaction, and rapid equilibrium quinonoid formation followed by rate-limiting protonation to the ketimine intermediate for the L-alanine transamination half-reaction. Energy profiles for the two half-reactions are constructed.

Alanine↗

PubMed2001

Complexation of trivalent lanthanide cations by galactitol in the solid state. The crystal structure and an FT-IR study of 2NdCl3.galactitol.14H2O.

The crystal structure of 2NdCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: -1, with unit-cell dimensions: a = 9.736(2), b = 10.396, c = 8.027 A; alpha = 108.05(3), beta = 92.68(3), gamma = 88.44(3) degrees, V= 771.6(3) A3, Z = 2. Each Nd atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Nd-O distances from 2.461 to 2.552 A. The seventh water molecule is hydrogen-bonded by the hydroxyl hydrogen on O-1 (O-1-H-ll...O-10, 2.639 A). The FT-IR spectra of 2NdCl3.galactitol.14H2O and 2PrCl3.galactitol.14H2O are analogous, and show that Pr and Nd have the same coordination mode. The IR results are consistent with the crystal structures.

Carbohydrates↗

PubMed2001

Sugar interaction with metal ions. The crystal structure and Raman spectra study of SmCl3-galactitol complex.

The crystal structure of 2SmCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: P-1. The unit cell dimensions: a = 9.683(2) A, b = 10.341(2) A, c = 7.990(2) A; alpha = 108.01(3) degrees, beta = 92.71(3) degrees, gamma = 88.42(3) degrees. Each Sm atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Sm-O distance from 2.417 to 2.520 A. The seventh water molecule is hydrogen-bonded by the hydroxy hydrogen on O-3 (O(3)-H(13)...O(10), 2.635 A). After forming complexes the peaks have shifted and the relative intensities have changed in the IR and Raman spectra, which are corresponding to the changes in bond distances and bond angles of the structures. The IR and Raman spectra of Pr-, Nd- and Sm-galactitol complexes are similar, which show that the three metal ions have the same coordination mode.

Crystallography, X-Ray↗

PubMed2001

Differential functions of mPer1, mPer2, and mPer3 in the SCN circadian clock.

The role of mPer1 and mPer2 in regulating circadian rhythms was assessed by disrupting these genes. Mice homozygous for the targeted allele of either mPer1 or mPer2 had severely disrupted locomotor activity rhythms during extended exposure to constant darkness. Clock gene RNA rhythms were blunted in the suprachiasmatic nucleus of mPer2 mutant mice, but not of mPER1-deficient mice. Peak mPER and mCRY1 protein levels were reduced in both lines. Behavioral rhythms of mPer1/mPer3 and mPer2/mPer3 double-mutant mice resembled rhythms of mice with disruption of mPer1 or mPer2 alone, respectively, confirming the placement of mPer3 outside the core circadian clockwork. In contrast, mPer1/mPer2 double-mutant mice were immediately arrhythmic. Thus, mPER1 influences rhythmicity primarily through interaction with other clock proteins, while mPER2 positively regulates rhythmic gene expression, and there is partial compensation between products of these two genes.

Animals↗

PubMed2001

Studies of posttranslational modifications in spiny dogfish myelin basic protein.

The objective of this investigation was to determine whether nonmammalian myelin basic protein contained charge isomers resulting from extensive posttranslational modifications as seen in mammalian MBP. Four charge isomer components from dogfish MBP have been isolated. These forms arise by phosphorylation and deamidation modifications. Components C1, C2 and C3 have been characterized. We are currently characterizing component C8. Dogfish MBP is less cationic than mammalian MBP and has about 50% lower mobility on a basic pH gel electrophoresis relative to human and to bovine MBP. The mammalian component C1, which is unmodified, is modified in the dogfish by phosphorylation. The reduced electrophoretic mobility is largely attributable to the charge reduction resulting from phosphorylation in serine 72, 83, and 120 or 121 in C1, and C3. In component C2, two or three phosphate groups were distributed among residues 134, 138 and 139. It was found that dogfish amino acid residue 30 was a lysine residue and not a glutamate residue as reported in the literature.

Amino Acid Sequence↗

PubMed2001

Evaluation of endostatin antiangiogenesis gene therapy in vitro and in vivo.

Progressive growth and metastasis of solid tumors require angiogenesis, or the formation of new blood vessels. Endostatin is a 20-kDa carboxy-terminal fragment of collagen XVIII that has been shown to inhibit endothelial cell proliferation and tumor angiogenesis. Replication-deficient recombinant adenovirus (rAd) vectors were constructed, which encoded secreted forms of human and mouse endostatin (HECB and MECB, respectively), and, as a control, human alkaline phosphatase (APCB). Accumulation of endostatin was demonstrated in supernatants of cultured cells infected with the endostatin rAds. These supernatants disrupted tubule formation, inhibited migration and proliferation, and induced apoptosis in human dermal vascular endothelial cells or human vascular endothelial cells. Endostatin-containing supernatants had no effect on the proliferation of MidT2-1 mouse mammary tumor cells in vitro. A pharmacokinetic study of MECB in immunocompetent FVB mice demonstrated a 10-fold increase of serum endostatin concentrations 3 days after intravenous administration of 1x10(10) particles of this rAd (215-257 ng/mL compared to 12-38 ng/mL in control rAd-treated mice). Intravenous administration of MECB reduced b-FGF stimulated angiogenesis into Matrigel plugs by 38%. Intratumoral MECB inhibited growth of MidT2-1 syngeneic mammary tumors in FVB mice, but had minimal impact on the growth of MDA-MB-231 human breast tumors in SCID mice. Intravenous therapy with MECB also initially inhibited growth of MidT2-1 tumors, but this activity was subsequently blocked by induced anti-rAd antibodies. In summary, endostatin gene therapy effectively suppressed angiogenic processes in vitro and in vivo in several model systems.

Adenoviridae↗

PubMed2001

Methylcobalamin as antagonist to transient ototoxic action of gentamicin.

The objective of this study was to determine whether methylcobalamin inhibits the ototoxic action of gentamicin. Fourteen pigmented guinea pigs were randomly divided into experimental and control groups. Each animal in the experimental group was given a large single dose of gentamicin (125 mg/kg i.m.), followed by immediate administration of methylcobalamin (1 mg kg i.m.). In the control group, the animals received gentamicin only, at the same dose as the experimental group. The compound action potentials (CAPs) in the right ears of animals were measured using a signal processor before and 15, 30, 45, 60 and 75 min after injection of the drugs. The sound stimulus was presented by means of clicks and tone pips at 2, 4 and 8 kHz. Following the electro-physiological tests, the animal was sacrificed and prepared for scanning electron microscopic observation. There was prolongation of latency and diminution of amplitude of CAPs N1 and N2 15 min after injection of gentamicin. Although the N1-N2 intervals increased as the time after injection of gentamicin increased, the variations were still within normal ranges. In contrast, there was no prolongation of N1 latencies or N1-N2 intervals 30 min after injection in the experimental group. There were no marked changes in N1 or N2 amplitudes, compared with the results before injection, in the experimental group. The firing mechanism of the inner ear may be affected by a single dose of gentamicin. This suggests that the transient ototoxic action of gentamicin hardly affected the conductive function of the nerve fibres, even though the firing function of the inner ear was influenced. Methylcobalamin may inhibit the ototoxic side effects of gentamicin.

Action Potentials↗

PubMed2001

Vertical bias in dendritic trees of non-pyramidal neocortical neurons expressing GAD67-GFP in vitro.

The neocortical neuropil has a strong vertical (orthogonal to pia) orientation, constraining the intracortical flow of information and forming the basis for the functional parcellation of the cortex into semi-independent vertical columns or 'modules'. Apical dendrites of excitatory pyramidal neurons are a major component of this vertical neuropil, but the extent to which inhibitory, GABAergic neurons conform to this structural and functional design is less well documented. We used a gene gun to transfect organotypic slice cultures of mouse and rat neocortex with the enhanced green fluorescent protein (eGFP) gene driven by the promoter for glutamic acid decarboxylase 67 (GAD67), an enzyme expressed exclusively in GABAergic cells. Many GAD67-GFP expressing cells were highly fluorescent, and their dendritic morphologies and axonal patterns, revealed in minute detail, were characteristic of GABAergic neurons. We traced 150 GFP-expressing neurons from confocal image stacks, and estimated the degree of vertical bias in their dendritic trees using a novel computational metric. Over 70% of the neurons in our sample had dendritic trees with a highly significant vertical bias. We conclude that GABAergic neurons make an important contribution to the vertical neocortical neuropil, and are likely to integrate synaptic inputs from axons terminating within their own module.

Animals↗

PubMed2001

Characterization of one-dimensional capacitive micromachined ultrasonic immersion transducer arrays.

In this paper, we report on the characterization of 1-D arrays of capacitive micromachined ultrasonic transducers (cMUT). A 275- x 5600-micron 1-D CMUT array element is experimentally characterized, and the results are found to be in agreement with theoretical predictions. As a receiver, the transducer has a 0.28-fm/square root of Hz displacement sensitivity, and, as a transmitter, it produces 5 kPa/V of output pressure at the transducer surface at 3 MHz with a DC bias of 35 V. The transducer has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging. The radiation pattern of isolated single elements, as well as those of array elements are measured, and two major sources of acoustical cross talk are identified. A weakly dispersive non-leaky interface wave (Stoneley wave) is observed to be propagating at the silicon substrate-fluid interface at a speed close to the speed of sound in the fluid. This wave causes internal reflections, spurious resonance, and radiation from the edges of the silicon substrate. The large lateral component of the particle velocity generated by the membranes at the edge of the cMUT array elements is found to be the source of this interface wave. Lowest order Lamb waves in the silicon substrate are also found to contribute to the cross talk between elements. These waves are excited at the edges of individual vibrating membranes, where they are anchored to the substrate, and result in a narrowing of the beam profile of the array elements. Several methods, such as trench isolation and wafer thinning, are proposed and implemented to modify the acoustical cross coupling between array elements.

Journal Article↗

PubMed2001

DNA vaccination with the human immunodeficiency virus type 1 SF162DeltaV2 envelope elicits immune responses that offer partial protection from simian/human immunodeficiency virus infection to CD8(+) T-cell-depleted rhesus macaques.

DNA immunization of macaques with the SF162DeltaV2 envelope elicited lymphoproliferative responses and potent neutralizing antibodies. The animals were depleted of their CD8(+) T lymphocytes and then challenged intravenously with SHIV162P4. Compared to unvaccinated animals, the vaccinated macaques had lower peak viremia levels, rapidly cleared plasma virus, and showed delayed seroconversion.

AIDS Vaccines↗

PubMed2001

Role of oxidative stress and thiol antioxidant enzymes in nickel toxicity and resistance in strains of the green alga Scenedesmus acutus f. alternans.

Treatment with Ni(NO3)2 leads to the formation of reactive oxygen species (ROS) in the green alga Scenedesmus acutus f. alternans, causing lipid peroxidation. This effect was stronger in a Ni-sensitive strain, UTEX72, than in a Ni-resistant strain, B4. In the resistant strain, Ni induced an increased ratio of reduced to oxidized glutathione (GSH:GSSG), whereas it caused a lowered ratio in the sensitive strain. Enzymes involved in the control of ROS were studied in these strains as well as two others that have shown different degrees of nickel resistance. The resistant strain, B4, which grows while containing large amounts of internal Ni, had much higher levels of glutathione reductase and catalase than the other strains. The sensitive strain, UTEX72, had higher levels of glutathione peroxidase, superoxide dismutase, and glucose-6-phosphate dehydrogenase than did strain B4. The resistant strains, Ni-Tol and Cu-Tol, derived from strain UTEX72, which are partly able to exclude Ni, had enzyme profiles that resembled that of UTEX72 more closely than that of B4. Treatment with 10 and 100 microM Ni for 4 or 22 h had complex effects on enzyme levels in all four strains. Ni decreased glutathione reductase in B4, slightly increased it in Ni-Tol and Cu-Tol, and did not affect the low levels of this enzyme in UTEX72. Ni lowered glutathione peroxidase in B4 and either did not affect it or slightly raised it in the other strains. Ni lowered catalase in B4 and did not affect the other strains. Superoxide dismutase was raised in B4 and Ni-Tol and lowered in Cu-Tol and UTEX72, and glucose-6-phosphate dehydrogenase was lowered in all four strains. These results suggest that one major mechanism of Ni resistance, especially in strain B4, may be the ability to combat the formation of ROS when exposed to this metal, likely by maintaining a high GSH:GSSG ratio.

Antioxidants↗

PubMed2001

The hypocotyl chloroplast plays a role in phototropic bending of Arabidopsis seedlings: developmental and genetic evidence.

Chloroplasts of guard cells and coleoptiles have been implicated in the sensory transduction of blue light. The present study was aimed at establishing whether the chloroplast of the hypocotyl from Arabidopsis, another blue light-responding organ, has similar characteristics to that of sensory-transducing guard cell and coleoptile chloroplasts. Results showed that the phototropic curvature and arch length induced by blue light in Arabidopsis seedlings matched the distribution of mature chloroplasts in the bending hypocotyl. The bending arch consistently included the region of the hypocotyl containing mature chloroplasts, and never extended beyond that region. Manipulation of the extent of greening of dark-grown hypocotyls by varying red light pretreatments elicited blue light-stimulated curvatures and arch lengths that depended on the duration of the red light pretreatment and on the distribution of mature chloroplasts in the hypocotyl. Albino psd2 mutants of Arabidopsis, which lack mature chloroplasts, are devoid of phototropic sensitivity under conditions in which wild-type seedlings show large curvatures. The star mutant of Arabidopsis has a delayed greening and a delayed phototropic response as compared with wild type. Measurements of photosynthetic oxygen evolution and carbon fixation, dark respiration, and light-dependent zeaxanthin formation in the hypocotyl showed features similar to those of guard cells and coleoptiles, and distinctly different from those of mesophyll tissue. These results indicate that the hypocotyl chloroplast has characteristics similar to those associated with guard cell and coleoptile chloroplasts, and that phototropic bending of Arabidopsis hypocotyls appears to require mature chloroplasts.

Arabidopsis↗

PubMed2001

[GC-MS analysis of supercritical carbon dioxide extract from seeds of Zanthoxylum bungeanun Maxim].

The chemical components of supercritical carbon dioxide extracts from seeds of Zanthoxylum bungeanun Maxim. were studied by GC-MS-DS. Thirty-five compounds which account for 96.22% of the total area of the chromatographic peaks, were identified. The results showed that fatty acids and esters occupied 90.83% of total chromatographic efflux of the extracts. The main components of the extracts are oleic acid(38.91%), palmitic acid (29.45%), linoleic acid methyl ester(10.80%), linolenic acid methyl ester(8.64%), et al.

Carbon Dioxide↗

PubMed2001

[GC-MS analysis of supercritical carbon dioxide extraction products from pericarp of Zanthoxylum bungeanum].

The chemical constituents of supercritical carbon dioxide extraction products from pericarp of Zanthoxylum bungeanun Maxim. were studied by GC-MS-DS. Forty-five compounds which account for 86.76% of the area of the chromatographic peaks were identified. The results showed that the main components of the extracts are beta-pinene (10.33%), 1,8-terpinene (7.6%), cis-piperitol acetate (7.07%), oleic acid (5.46%), palmitic acid (5.41%) and 4-terpineol, (43.7%), et al.

Carbon Dioxide↗

PubMed2001

Analysis of hypermutation of the 5' noncoding region in the BCL-6 gene.

OBJECTIVE: To investigate BCL-6 gene mutations in Chinese populations with B-cell non-Hodgkin's lymphoma. METHODS: Polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and direct DNA sequencing were used to identify mutations in the 5' noncoding region of the BCL-6 gene in a total of 40 cases of diffuse large-cell lymphoma (DLCL) and follicular lymphoma (FL). RESULTS: Nine cases were found to have base substitutions. The incidence of BCL-6 gene mutation and the frequency of single-base changes were approximately 25.7% and (0.56-1.10) x 10(-2)/bp, respectively. CONCLUSIONS: The 5' regulatory region of the BCL-6 gene undergoes frequent somatic hypermutation during lymphomagenesis and the identification of BCL-6 gene hypermutations provides a molecular marker for confirmatory diagnosis of B-NHL.

5' Flanking Region↗

PubMed2001

A clinical investigation on 30 cases of senile benign renal arteriolosclerosis treated by huang qi gu jing yin.

Huang Qi Gu Jing Yin (HQGJY[symbol: see text]decoction of Astragalus root for Strengthening the Essence) was used in a controlled clinical trial for treatment of senile benign renal arteriolosclerosis. In the therapeutic group (n = 30), cure, marked effect and no effect were obtained respectively in 18 (60%), 9 (30%) and 3 (10%) cases with the total effective rate being 90%; the corresponding figures in the control group (n = 30) were 10 (33.3%), 9 (30%) and 11 (36.7%) with the total effective rate being 63.3%. The significant difference (P < 0.01) between the two groups demonstrated that HQGJY is an effective agent for treatment of the disease.

Aged↗