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Biomedical subjects

Y Ji

Publications and source records attributed to Y Ji.

At least 91 records · Page 5Linked to original sources
PubMed1999

Regulated antisense RNA eliminates alpha-toxin virulence in Staphylococcus aureus infection.

The ability to selectively disrupt gene function remains a critical element in elucidating information regarding gene essentiality for bacterial growth and/or pathogenesis. In this study, we adapted a tet regulatory expression system for use in Staphylococcus aureus, with the goal of downregulating gene expression via induction of antisense RNA. We demonstrate that this system exhibits a 50- to 100-fold dose-dependent level of induction in bacterial cells grown in culture (i.e., in vitro) and also functions in mice (i.e., in vivo) following oral administration of inducer. To determine whether induced antisense RNA could interfere with chromosomally derived gene expression, we cloned a fragment of the S. aureus alpha-toxin gene (hla) in antisense orientation downstream of the tet promoter system and introduced the construct into S. aureus. Induced antisense hla RNA downregulated chromosomally derived hla gene expression in vitro approximately 14-fold. Similarly, induction of hla antisense RNA in vivo dramatically reduced alpha-toxin expression in two different murine models of S. aureus infection. Most importantly, this reduction completely eliminated the lethality of the infection. These results indicate that the tet regulatory system functions efficiently in S. aureus and induced antisense RNA can effectively downregulate chromosomal gene expression both in vitro and in vivo.

Animals↗
PubMed1999

SERCA1a can functionally substitute for SERCA2a in the heart.

We recently generated a transgenic (TG) mouse model in which the fast-twitch skeletal muscle sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA1a) is overexpressed in the heart. Ectopic overexpression of SERCA1a results in remodeling of the cardiac SR containing 80% SERCA1a and 20% endogenous SERCA2a with an approximately 2.5-fold increase in the total amount of SERCA protein (E. Loukianov et al. Circ. Res. 83: 889-897, 1998). We have analyzed the Ca2+ transport properties of membranes from SERCA1a TG hearts in comparison to control hearts. Our data show that the maximal velocity of SR Ca2+ transport was significantly increased ( approximately 1.9-fold) in TG hearts, whereas the apparent affinity of the SERCA pump for Ca2+ was not changed. Addition of phospholamban antibody in the Ca2+ uptake assays increased the apparent affinity for Ca2+ to the same extent in TG and non-TG (NTG) hearts, suggesting that phospholamban regulates the SERCA1a pump in TG hearts. Analysis of SERCA enzymatic properties in TG hearts revealed that the SERCA pump affinity for ATP, the Hill coefficient, the pH dependence of Ca2+ uptake, and the effect of acidic pH on Ca2+ transport were similar to those of NTG hearts. Interestingly, the rate constant of phosphoenzyme decay (turnover rate of SERCA enzyme) was also very similar between TG and NTG hearts. Together these findings suggest that 1) the SERCA1a pump can functionally substitute for SERCA2a and is regulated by endogenous phospholamban in the heart and 2) SERCA1a exhibits several enzymatic properties similar to those of SERCA2a when expressed in a cardiac setting.

Adenosine Triphosphate↗
PubMed1999

Physical assignment of microsatellite- containing BACs to bovine chromosomes.

Here we report the physical assignment of 40 microsatellite markers by fluorescence in situ hybridization to 13 different bovine chromosomes. This information will be valuable in providing physically anchored landmarks for the construction of contigs throughout the bovine genome. It also is useful for the purpose of integrating the linkage maps of these chromosomes to their physical maps and determining the physical coverage of these linkage groups.

Animals↗
PubMed1999

Targeted mutation of plasma phospholipid transfer protein gene markedly reduces high-density lipoprotein levels.

It has been proposed that the plasma phospholipid transfer protein (PLTP) facilitates the transfer of phospholipids and cholesterol from triglyceride-rich lipoproteins (TRL) into high-density lipoproteins (HDL). To evaluate the in vivo role of PLTP in lipoprotein metabolism, we used homologous recombination in embryonic stem cells and produced mice with no PLTP gene expression. Analysis of plasma of F2 homozygous PLTP-/- mice showed complete loss of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin, and partial loss of free cholesterol transfer activities. Moreover, the in vivo transfer of [3H]phosphatidylcholine ether from very-low-density proteins (VLDL) to HDL was abolished in PLTP-/- mice. On a chow diet, PLTP-/- mice showed marked decreases in HDL phospholipid (60%), cholesterol (65%), and apo AI (85%), but no significant change in non-HDL lipid or apo B levels, compared with wild-type littermates. On a high-fat diet, HDL levels were similarly decreased, but there was also an increase in VLDL and LDL phospholipids (210%), free cholesterol (60%), and cholesteryl ester (40%) without change in apo B levels, suggesting accumulation of surface components of TRL. Vesicular lipoproteins were shown by negative-stain electron microscopy of the free cholesterol- and phospholipid-enriched IDL/LDL fraction. Thus, PLTP is the major factor facilitating transfer of VLDL phospholipid into HDL. Reduced plasma PLTP activity causes markedly decreased HDL lipid and apoprotein, demonstrating the importance of transfer of surface components of TRL in the maintenance of HDL levels. Vesicular lipoproteins accumulating in PLTP-/- mice on a high-fat diet could influence the development of atherosclerosis.

Animals↗
PubMed1999

[Linkage analysis of chromosome 5 and asthma in a Chinese population].

OBJECTIVE: To investigate the linkage between asthma and 5q31-33 in a Chinese population. METHODS: The linkage between microsatellite markers in 5q and asthma and allergy was tested by lod score analysis. RESULTS: The linkage between asthma and 5q31-33 was not confirmed. CONCLUSION: The genes at 5q31-33 are not likely to contribute to inheritance of asthma in this Chinese population.

Asthma↗
PubMed1999

[The clinical application of triamcinolone to accelerate soft tissue expansion].

OBJECTIVE: To speed up the expansion procedure. METHODS: Triamcinolone was injected during tissue expansion in 26 cases. RESULTS: The study proved that triamcinolone shortened the injection interval to 32 +/- 6 hours. The mean time of full expansion was shortened to 20 +/- 5 days in the experimental group. The injection interval and mean time of full expansion were 6 +/- 2 days and 42 +/- 8 days respectively in the control group (P < 0.01). The immediate retraction ratios of expanded skin of the two groups were 17% and 26% respectively. CONCLUSION: This new method is feasible in clinical application.

Adolescent↗
PubMed1999

[Quantitative analysis of thirty-one elements in the stained dental fluorosis of enamel].

OBJECTIVE: To study the relationship between concentrations of thirty elements and fluorine element in teeth with stained dental fluorosis from high fluoride water area and teeth from normal fluoride area. METHODS: The concentration of thirty-one elements in 43 teeth was measured by plasmatron spectrographic analysis and fluoride selective electrode. RESULTS: 1. Content of F, P, Ca, Mn, As, Se, Al, Ti, Mo, B elements in enamel had a direct relationship to severity of enamel staining. 2. Content of Mn, As, Se, Sr, Nb, Ca, P elements were high positively related to content of fluorine in enamel (P < 0.05). CONCLUSION: Mn, As, Se, F content is closely related to the pigment formation in dental fluorosis of enamel.

Adolescent↗
PubMed1999

[Effect of Callicarpa herbs on antioxidation in vitro].

The concentration of half inhibition (IC50) of Callicarpa herbs, including Callicarpa kochiana(Ck), C. bodinieri (Cb) and its fruit (Cbf), C. japonica, C. macrophrlla, C. cathaarana, C. giraldi(Cg) on lipid peroxidation (LPO) of tissus homogenate incubated in 37 +/- 0.5 degrees C were tested. The result showed that all but Cg could inhibit lipid peroxidation. The IC50 of Cbf was minimum. IC50 of Cb, Cbf and Ck inhibiting red blood cell (RBC) LPO and hemolysis caused by hydroxyl free radical (.OH), inhibiting brain homogenate LPO induced by .OH and inhibiting or clean .OH formation by system of H2O2 and FeSO4 were also tested. It was found the IC50 were Cbf > Cb > Ck. These results suggested that the most strong inhibitor to automatic LPO reaction was Cbf, but to LPO caused by .OH was Ck.

Antioxidants↗
PubMed1998

Liver-specific overexpression of scavenger receptor BI decreases levels of very low density lipoprotein ApoB, low density lipoprotein ApoB, and high density lipoprotein in transgenic mice.

Scavenger receptor BI (SR-BI) is known to mediate the selective uptake of high density lipoprotein (HDL) cholesteryl ester (CE) in liver and steroidogenic tissues. To evaluate the role of SR-BI in plasma lipoprotein metabolism, we have generated transgenic mice with liver-specific overexpression of murine SR-BI. On a chow diet SR-BI transgenic (SR-BI Tg) mice have decreased HDL-CE, apoA-I, and apoA-II levels; plasma triglycerides, low density lipoprotein (LDL) cholesterol, and very low density lipoprotein (VLDL) and LDL apoB were also decreased, compared with control mice. Turnover studies using non-degradable CE and protein labels showed markedly increased total and selective uptake of HDL-CE in the liver and increased HDL protein catabolism in both liver and kidney. To evaluate the changes in apoB further, mice were challenged with high fat, high cholesterol diets. In SR-BI Tg mice plasma apoB levels were only 3-15% of control levels, and the dietary increase in VLDL and LDL apoB was virtually abolished. These studies show that steady state overexpression of hepatic SR-BI reduces HDL levels and increases reverse cholesterol transport. They also indicate that SR-BI can play a role in the metabolism of apoB-containing lipoproteins. The dual effects of increased reverse cholesterol transport and lowering of apoB-containing lipoproteins that result from hepatic SR-BI overexpression could have anti-atherogenic consequences.

Animals↗
PubMed1998

Enhanced myocardial contractility and increased Ca2+ transport function in transgenic hearts expressing the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+-ATPase.

In this study, we investigated whether the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ transport pump (SERCA1a) can functionally substitute the cardiac SERCA2a isoform and how its overexpression affects cardiac contractility. For this purpose, we generated transgenic (TG) mice that specifically overexpress SERCA1a in the heart, using the cardiac-specific alpha-myosin heavy chain promoter. Ectopic expression of SERCA1a resulted in a 2.5-fold increase in the amount of total SERCA protein. At the same time, the level of the endogenous SERCA2a protein was decreased by 50%, whereas the level of other muscle proteins, including calsequestrin, phospholamban, actin, and tropomyosin, remained unchanged. The steady-state level of SERCA phosphoenzyme intermediate was increased 2.5-fold, and the maximal velocity of Ca2+ uptake was increased 1.7-fold in TG hearts, demonstrating that the overexpressed protein is functional. Although the basal cytosolic calcium signal was decreased by 38% in TG cardiomyocytes, the amplitude of cytosolic calcium signal was increased by 71.8%. The rate of calcium resequestration was also increased in TG myocytes, which was reflected by a 51.6% decrease in the normalized time to 80% decay of calcium signal. This resulted in considerably increased peak rates of myocyte shortening and relengthening (50.0% and 66.6%, respectively). Cardiac functional analysis using isolated work-performing heart preparations revealed significantly faster rates of contraction and relaxation in TG hearts (41.9% and 39.5%, respectively). The time to peak pressure and the time to half-relaxation were shorter (29.1% and 32.7%, respectively). In conclusion, our study demonstrates that the SERCA1a pump can functionally substitute endogenous SERCA2a, and its overexpression significantly enhances Ca2+ transport and contractile function of the myocardium. These results also demonstrate that the SERCA pump level is a critical determinant of cardiac contractility.

Animals↗
PubMed1998

Sarco(endo)plasmic reticulum Ca2+ ATPase isoforms and their role in muscle physiology and pathology.

Recent studies suggest that SR Ca2+ transport function is altered in hypertrophied and failing myocardium. To understand whether alterations in SR Ca2+ ATPase levels affect myocardial contractility, we generated transgenic mice that specifically overexpress SERCA2a or SERCA1 pump in the mouse heart, using the cardiac alpha-MHC promoter. Analysis of SERCA2a transgenic mice show both an increase in mRNA and protein levels (120-150% of the wild type). Isolated work performing heart preparations revealed that SERCA2a mice have improved myocardial performance. On the other hand, SERCA1 overexpression in the heart resulted in isoform replacement without any change in total SERCA protein. Interestingly, SERCA1 transgenic hearts exhibited super contractility with a significant increase in rates of muscle contraction (+dp/dt) and relaxation (-dp/dT). The time to peak pressure and half-time to relaxation were significantly shorter.

Animals↗
PubMed1998

Protein S-thiolation and redox regulation of membrane-bound glutathione transferase.

Membrane-bound GST transferase (GSTm) occurs in hepatic microsomal and plasma membranes as well as in the outer mitochondrial membrane, and it is known to be activated by N-ethylmaleimide. We recently analysed the activation by GSSG in some detail. The approximately 5-fold stimulation is reversed upon reduction of GSSG by GSSG reductase. In steady-state experiments, the Kox value was determined to be 0.05, i.e. 20 times more GSSG than GSH produces half-maximal activation. Kox is independent of the total glutathione concentration, indicating that S-thiolation by mixed disulfide formation, rather than interchain or intrachain disulfide bridge formation, is responsible for activation. In Western blots, a 17.7 kDa band, in addition to the 17.3 kDa band, was detected upon treatment with GSSG or with GSH plus t-butyl hydroperoxide. We suggest that under oxidative stress, GSTm is activated through direct S-thiolation of the enzyme. Dethiolation occurs via thiol disulfide exchange governed by the cellular glutathione redox state.

Animals↗
PubMed1998

Opposing effects of intracerebroventricularly injected norepinephrine on oxytocin and vasopressin neurons in the paraventricular nucleus of the rat.

Our previous study shows that intracerebroventricularly (i.c.v.) injected norepinephrine (NE) had different effects on the discharge of different firing patterns of magnocellular neurons in the paraventricular nucleus (PVN). In the present study we further classified antidromically identified magnocellular neurons into two groups: vasopressin (VP) and oxytocin (OT) secreting neurons, and found that of all 48 cases of magnocellular neurons, NE had mainly excitatory effects on 36 cases of putatively OT-secreting neurons, and inhibitory effects on 12 cases of VP-secreting neurons. The third ventricular injected NE had almost the same effect on two types of neurons as that of lateral ventricular injection, partly ruling out the possibility that the lateral ventricularly injected NE may have acted indirectly on the magnocellular neurons in PVN. The results show that different mechanisms may be involved in mediating the effect of i.c.v. injected NE on VP- and OT-secreting neurons in the PVN.

Animals↗
PubMed1998

Scavenger receptor class B type I as a mediator of cellular cholesterol efflux to lipoproteins and phospholipid acceptors.

We recently reported that the rate of efflux of cholesterol from cells to high density lipoprotein (HDL) was related to the expression level of scavenger receptor class B type I (SR-BI). Moreover, the expression of this receptor in atheromatous arteries raises the possibility that SR-BI mediates cholesterol efflux in the arterial wall (Ji, Y., Jian, B., Wang, N., Sun, Y., de la Llera Moya, M., Phillips, M. C., Rothblat, G. H., Swaney, J. B., and Tall, A. R. (1997) J. Biol. Chem. 272, 20982-20985). In this paper we describe studies that suggest that the presence of phospholipid on acceptor particles plays an important role in modulating interaction with the SR-BI. Specifically, enrichment of serum with phospholipid resulted in marked stimulation of cholesterol efflux from cells that had higher levels of SR-BI expression, like Fu5AH or Y1-BS1 cells, and little or no stimulation in cells with low SR-BI levels, such as Y-1 cells. Stimulation of efflux by phospholipid enrichment was also a function of SR-BI levels in Chinese hamster ovary cells transfected with the SR-BI gene. Efflux to protein-free vesicles prepared with 1-palmitoyl-2-oleoylphosphatidyl-choline also correlated with SR-BI levels, suggesting that phospholipid, as well as protein, influences the interaction that results in cholesterol efflux. By contrast, cholesterol efflux from a non-cell donor showed no stimulation consequent to phospholipid enrichment of the serum acceptor. These results may help to explain observations in the literature that document an increased risk of atherosclerosis in patients with depressed levels of HDL phospholipid even in the face of normal HDL cholesterol levels.

Animals↗
PubMed1998

Macromolecular organization and genetic mapping of a rapidly evolving chromosome-specific tandem repeat family (B77) in cotton (Gossypium).

Isolation and characterization of the most prominent repetitive element families in the genome of tetraploid cotton (Gossypium barbadense L; [39]) revealed a small subset of families that showed very different properties in tetraploids than in their diploid progenitors, separated by 1-2 million years. One element, B77, was characterized in detail, and compared to the well-conserved 5S and 45S rRNA genes. The 572 bp B77 repeat was found to be concentrated in several discontinuous tandem arrays confined to a single 550 kb SalI fragment in tetraploid cotton. Genetic mapping based on the absence of the pentameric 'rung' in the G. barbadense 'ladder' showed that B77 maps to a D-subgenome chromosome. In situ hybridization supports the contention that the array is confined largely to a single chromosomal site in the D-subgenome. The B77 repeat has undergone a substantial increase in copy number since formation of tetraploid cotton from its diploid relatives. RFLPs observed among tetraploid cotton species suggest that amplification and/or rearrangement of the repeat may have continued after divergence of the five tetraploid cotton species. B77 contains many short direct repeats and shares significant DNA sequence homology with a Nicotiana alata retrotransposon Tna1-2 integrase motif. The recent amplification of B77 on linkage group D04 suggests that the D-subgenome of tetraploid cotton may be subject to different evolutionary constraints than the D-genome diploid chromosomes, which exhibit few genome-specific elements. Further, the abundance of B77 in G. gossypioides supports independent evidence that it may be the closest extant relative of the D-genome ancestor of cotton.

Base Sequence↗
PubMed1998

Impact of M49, Mrp, Enn, and C5a peptidase proteins on colonization of the mouse oral mucosa by Streptococcus pyogenes.

Resistance to phagocytosis is a hallmark of virulent Streptococcus pyogenes (group A streptococcus). Surface-bound C5a peptidase reduces recruitment of phagocytes to the site of infection, and hyaluronic acid capsules and/or the M protein limit the uptake of streptococci. In this study the relative impact of M and M-like proteins and the C5a peptidase on the virulence of a serotype M49 strain was assessed. The capacities of isogenic strains with an insertion mutation in emm49; with a deletion mutation in scpA49 (C5a peptidase gene); and with a deletion that removes all three M-like genes, mrp49, emm49, and enn49, to colonize mice and resist phagocytosis were compared. Experiments confirmed results obtained in an earlier study, which showed that the M49 protein was not required for in vitro resistance to phagocytosis, and also showed that the M protein was not required for colonization of mice. Failure to produce all three M-like proteins, M49, Mrp, and Enn49, significantly reduced the ability of these streptococci to resist phagocytosis in vitro but did not significantly alter the persistence of streptococci on the oral mucosa. In vitro experiments indicate that M+ streptococci are phagocytized by polymorphonuclear leukocytes that have been activated with phorbol-12-myristate 13-acetate or recombinant human C5a. This observation may explain the finding that expression of M49 protein is not essential for short-term colonization of the mouse oral mucosa.

Adhesins, Bacterial↗