Biomedical subjects

H Yu

Publications and source records attributed to H Yu.

At least 379 records · Page 21Linked to original sources

PubMed1998

Expression of the mRNA for types I and II interleukin-1 receptors in dental tissues of mice during tooth development.

Interleukin-1 (IL-1) can exert its pleiotropic effects on nearly every tissue by binding to its cognate receptor. Two types of IL-1 receptors have been identified. A large number of cell types have been shown to possess IL-1 receptors in vitro and in vivo, but few studies have addressed the question of expression in dental tissues in vivo. Using in situ hybridization in normal newborn, young and adult mice, we have examined the cellular distribution of both types of IL-1 receptors in dental tissues. In the ameloblast layer of incisors and molars, the mRNA for the type I IL-1 receptor (IL-1RI) and the type II IL-1 receptor (IL-1RII) was detected at the presecretory stage. The expression level markedly increased and remained during amelogenesis at the secretory stage. At the maturation stage, however, the transcripts for both IL-1RI and -II mRNA disappeared. Expression of IL-1RI and -II mRNA was also observed in odontoblasts after crown morphogenesis had been completed, and continued in these cells during dentinogenesis. No transcripts were detected in stratum intermedium cells and other cells in dental follicle, stellate reticulum, dental papilla, or pulp. Additionally, both types of IL-1R mRNA were also detected in osteoclasts on surfaces of alveolar bone. These results demonstrated for the first time that enamel-secreting ameloblasts and dentine-secreting odontoblasts express IL-1RI and -II mRNA, suggesting that IL-1 plays a regulatory role in the function of ameloblasts and odontoblasts during tooth development of mice.

Age Factors↗

PubMed1998

Effects of a cationic and hydrophobic peptide, KL4, on model lung surfactant lipid monolayers.

We report on the surface behavior of a hydrophobic, cationic peptide, [lysine-(leucine)4]4-lysine (KL4), spread at the air/water interface at 25 degrees C and pH 7.2, and its effect at very low molar ratios on the surface properties of the zwitterionic phospholipid 1,2-dipalmitoylphosphatidylcholine (DPPC), and the anionic forms of 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) and palmitic acid (PA), in various combinations. Surface properties were evaluated by measuring equilibrium spreading pressures (pi(e)) and surface pressure-area isotherms (pi-A) with the Wilhelmy plate technique. Surface phase separation was observed with fluorescence microscopy. KL4 itself forms a single-phase monolayer, stable up to a surface pressure pi of 30 mN/m, and forms an immiscible monolayer mixture with DPPC. No strong interaction was detected between POPG and KL4 in the low pi region, whereas a stable monolayer of the PA/KL4 binary mixture forms, which is attributed to ionic interactions between oppositely charged PA and KL4. KL4 has significant effects on the DPPC/POPG mixture, in that it promotes surface phase separation while also increasing pi(e) and pi(max), and these effects are greatly enhanced in the presence of PA. In the model we have proposed, KL4 facilitates the separation of DPPC-rich and POPG/PA-rich phases to achieve surface refinement. It is these two phases that can fulfill the important lung surfactant functions of high surface pressure stability and efficient spreading.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1998

Cholesteryl esterase-treated LDL augments oxidized LDL-mediated cholesteryl ester deposition in mouse peritoneal macrophages.

Arterial unesterified cholesterol, phospholipid particles have been isolated from atherosclerotic lesions and characterized. However, the role of these 'liposomes' in macrophage foam cell formation is unclear. Recently, LDL, after trypsin and cholesteryl esterase treatment (T/CE LDL), was shown to have physical properties similar to the unesterified cholesterol, phospholipid particles isolated from atherosclerotic lesions. Yet, when mouse peritoneal macrophages were incubated with these model particles in culture medium (DMEM and 5% LPDS), only an insignificant accumulation of cellular cholesteryl esters was observed. Previously, we demonstrated that complex formation between unesterified cholesterol, phosphatidylcholine liposomes and cupric sulfate-oxidized LDL dramatically enhances the ability of the liposomes to augment cellular cholesterol accretion (Greenspan P, Yu H, Mao F, Gutman RL. J Lipid Res 1997;38:101-109). When T/CE LDL, another cholesterol-rich phospholipid particle, was substituted for unesterified cholesterol phosphatidylcholine liposomes in our complex, mouse peritoneal macrophages accumulated a significant amount of both cellular unesterifed cholesterol (61 microg/mg cell protein) and cholesteryl esters (76 microg/mg cell protein) after 48 h of incubation. These results demonstrate again that the interaction of two cholesterol-bearing particles (T/CE LDL and oxidized LDL), which individually can not promote significant cholesterol accumulation in cells, will, when combined, produce macrophage foam cells.

Animals↗

PubMed1998

Osteopontin expression in ovarian carcinomas and tumors of low malignant potential (LMP).

Expression of osteopontin (OPN) by ovarian tumors is not known. Neoplasms arising from the ovarian epithelium are distinguished in adenocarcinomas and borderline tumors (LMPs), which overall have a favorable prognosis even with omental implants. Tissues from primary ovarian tumors and their metastases from 30 patients (16 LMPs and 14 adenocarcinomas) were evaluated for OPN expression by immunohistochemistry, Western blotting, and in situ hybridization. OPN was weak or absent in 93% of ovarian adenocarcinomas or their metastases. In contrast, 81.5% of the LMPs and 50% of omental and lymph node implants were OPN positive (P < .028). Histological type, grade, or clinical stage did not correlate with OPN expression. Expression of OPN primarily by ovarian neoplasms with favorable prognosis is an intriguing new finding of potential importance in the pathogenesis of ovarian LMPs.

Adenocarcinoma↗

PubMed1998

Activation and suppression of natural cellular immune functions by Pneumocystis carinii.

The regulatory role of soluble cytokines in innate cellular immune responses induced by Pneumocystis carinii was assessed in vitro in direct comparison to induction by Listeria monocytogenes. This report shows that P. carinii organisms, as well as L. monocytogenes, stimulated in whole spleen cell cultures of SCID mice the release of IFN-gamma, TNF-alpha/beta, IL-10, IL-12, and iNO. This response was independent of functional T cells. Both macrophages (M phi) and natural killer (NK) cells were necessary for either microorganism to induce release of these cytokines. Cocultures of purified M phi--including alveolar M phi--and purified NK cells indicated that no other cell population was necessarily involved. Microbial induction of NK cell-derived IFN-gamma has been reported to be mediated by the combined effects of TNF-alpha and IL-12 released by M phi upon adequate microbial stimulation. Interestingly, only L. monocytogenes, but not P. carinii organisms could directly induce detectable amounts of TNF-alpha/beta, IL-12, or iNO in purified M phi cultures. In dose-response experiments, release of IFN-gamma, TNF-alpha/beta, and iNO was reduced at high relative concentrations of either microorganism. This high-dose suppression was at least partially controlled by M phi-produced IL-10. Our data show that, P. carinii potently induces activating and inhibitory innate cellular immune response mechanisms and indicate that the initial step of macrophage-mediated NK cell activation might also involve other pathways than those described to date.

Animals↗

PubMed1998

Mutant human presenilin 1 protects presenilin 1 null mouse against embryonic lethality and elevates Abeta1-42/43 expression.

Mutations in presenilin 1 (PS1) are linked to early onset of familial Alzheimer's disease (FAD) and are shown to foster production of Abeta1-42/43 in FAD patients and transgenic mice. PS1 null mice are embryonic lethal and exhibit axial skeleton malformation and CNS defects. We show that transgenic mouse lines expressing either the wild-type human PS1 protein or human PS1 with the A246E FAD mutation can rescue the PS1 knockout mouse from embryonic lethality to similar degrees, indicating that the mutation does not lead to loss of PS1 function during development. Furthermore, a 50% reduction of PS1 activity in PS1(+/-) mice does not lead to Abeta1-42/43 increase, whereas expression of human mutant PS1 on murine PS1 null background is sufficient to elevate Abeta1-42/43, supporting a gain-of-function activity as the result of the PS1 mutation.

Alzheimer Disease↗

PubMed1998

Interactions between HIV1 Nef and vacuolar ATPase facilitate the internalization of CD4.

CD4 is the primary receptor for the human immunodeficiency virus (HIV). Nef is an accessory protein of HIV that decreases the expression of CD4 on the surface of infected cells. In this study, we identified the Nef binding protein 1 (NBP1), which interacts specifically with Nef in vitro and in vivo. Since it shares sequence similarity with the catalytic subunit of the vacuolar ATPase (V-ATPase) and complements the loss of this VMA13 gene in yeast, NBP1 is the human homolog of Vma13p. Direct interactions between Nef and NBP1 were correlated with the ability of Nef to internalize CD4. The expression of the antisense NBP1 abrogated these effects. We conclude that NBP1 helps to connect Nef with the endocytic pathway.

Amino Acid Sequence↗

PubMed1998

Direct binding of CDC20 protein family members activates the anaphase-promoting complex in mitosis and G1.

Activation of the anaphase-promoting complex (APC) is required for anaphase initiation and for exit from mitosis. We show that APC is activated during mitosis and G1 by two regulatory factors, hCDC20 and hCDH1. These proteins directly bind to APC and activate its cyclin ubiquitination activity. hCDC20 confers a strict destruction-box (D-box) dependence on APC, while hCDH1 shows a much more relaxed specificity for the D-box. In HeLa cells, the protein levels of hCDC20 as well as its binding to APC peak in mitosis and decrease drastically at early G1. Thus, hCDC20 is the mitotic activator of APC and directs the degradation of substrates containing the D-box. The hCDH1 protein level remains constant during the cell cycle and may target specific substrates lacking the D-box in G1, such as polo-like kinase, for ubiquitination.

Anaphase-Promoting Complex-Cyclosome↗

PubMed1998

Evaluation of gene therapy for citrullinaemia using murine and bovine models.

Citrullinaemia is an autosomal recessive disorder caused by the deficiency of argininosuccinate synthase. The deficiency of this enzyme results in an interruption in the urea cycle and the inability to dispose of excess ammonia derived from the metabolism of protein. The only treatment for this disorder has been dietary restriction of protein and supplementation with medications allowing for alternative excretion of excess nitrogen. Gene therapy offers the possibility of a long-term cure for disorders like citrullinaemia by expressing the deficient gene in the target organ. We have explored the use of adenoviral vectors as a treatment modality for citrullinaemia in two animal models, a naturally occurring bovine model and a murine model created by molecular mutagenesis. Mice treated with adenoviral vectors expressing argininosuccinate synthase lived significantly longer than untreated animals (11 days vs 1 day; however, the animals did not exhibit normal weight gain during the experiment, indicating that the therapeutic effectiveness of the transducing virus was suboptimal. It is speculated that part of the failure to observe better clinical outcome might be due to the deficiency of arginine. In the bovine model, the use of adenoviral vectors did not result in any change in the clinical condition of the animals or in the level of plasma ammonia. However, the use of 15N isotopic ammonia allowed us to assess the flux of nitrogen through the urea cycle during the experiment. These studies revealed a significant increase in the flux through the urea cycle following administration of adenoviral vectors expressing argininosuccinate synthase. We conclude that the use of adenoviral vectors in the treatment of citrullinaemia is a viable approach to therapy but that it will be necessary to increase the level of transduction and to increase the level of enzyme produced from the recombinant viral vector. Future experiments will be designed to address these issues.

Adenoviruses, Human↗

PubMed1998

Prediction of beta-turns.

Kohonen's self-organization model, a neural network model, is applied to predict the beta-turns in proteins. There are 455 beta-turn tetrapeptides and 3807 non-beta-turn tetrapeptides in the training database. The rates of correct prediction for the 110 beta-turn tetrapeptides and 30,229 non-beta-turn tetrapeptides in the testing database are 81.8% and 90.7%, respectively. The high quality of prediction of neural network model implies that the residue-coupled effect along a polypeptide chain is important for the formation of reversal turns, such as beta-turns, during the process of protein folding.

Amino Acid Sequence↗

PubMed1998

Expression of Th1/Th2 cytokine mRNA in peritoneal exudative polymorphonuclear neutrophils and their effects on mononuclear cell Th1/Th2 cytokine production in MRL-lpr/lpr mice.

Peritoneal exudative polymorphonuclear neutrophils (PEC-PMN) and mononuclear cells (PEC-MNC) were obtained from normal BALB/c and from autoimmune MRL-lpr/lpr mice (lpr) with different disease severities. The spontaneous and mitogen-stimulated expression of T-helper lymphocyte type-1 (Th1) [represented by interferon-gamma (IFN-gamma) and interleukin (IL-2)] and T-helper lymphocyte type-2 (Th2) (represented by IL-4 and IL-10) cytokine mRNA in these cells was detected by reverse transcription-polymerase chain reaction (RT-PCR). The production of these cytokines was measured by enzyme-linked immunosorbent assay (ELISA). We found that the spontaneous expression of Th1/Th2 cytokine mRNA in PEC-PMN from autoimmune mice was progressively increased in parallel with disease severity but was not changed by lipopolysaccharide (LPS) stimulation. By contrast, spontaneous expression of Th1/Th2 cytokine mRNA in PEC-MNC from these mice was progressively decreased in parallel with disease severity but retained the responsiveness to phytohaemagglutinin (PHA) stimulation. To determine the effect of PEC-PMN on Th1/Th2 cytokine production by PEC-MNC, autologous PEC-PMN and PEC-MNC were co-cultured at MNC:PMN ratios of 5:0, 4:1, 3:2, 2:3, 1:4 and 0:5 with PHA stimulation for 24 hr. The production of cytokines at each ratio was compared with the expected value, by calculation. We found that PEC-PMN from autoimmune mice progressively suppressed the production of IL-4, IL-10 and IFN-gamma whereas the production of IL-2 was enhanced by autologous MNC in parallel with disease severity. These results suggest that a reciprocal relationship exists in the expression of Th1/Th2 cytokine mRNA between PEC-PMN and PEC-MNC in lpr mice in parallel with disease severity. Autoimmune PEC-PMN can exert significant modulatory effects on Th1/Th2 cytokine production by autologous MNC in stimulation.

Animals↗

PubMed1998

Catabolism dominates the first-pass intestinal metabolism of dietary essential amino acids in milk protein-fed piglets.

To investigate the extent of first-pass intestinal metabolism of dietary amino acids, seven female pigs (28 d old, 8.0 kg) were implanted with arterial, venous, portal and gastric catheters and with an ultrasonic portal blood flow probe. The pigs were fed a milk-based diet once hourly and infused intragastrically with [U-13C]algal protein. On average, 56% of the essential amino acid (EAA) intake appeared in the portal blood. However, the net portal balance of methionine (48% of intake) and threonine (38% of intake) tended (P = 0.08) to be lower than the mean of all EAA. The net portal balance (expressed as a percentage of intake) of alanine (205%), tyrosine (167%) and arginine (137%) exceeded their intake. Net portal outflow of ammonia accounted for 18% of total amino acid nitrogen intake. As a percentage of the enteral tracer input, there was substantial first-pass metabolism of lysine (35%), leucine (32%), phenylalanine (35%) and threonine (61%). However, only 18, 21, 18 and 12% of the total first-pass metabolism of lysine, leucine, phenylalanine and threonine, respectively, were recovered in mucosal protein. We conclude that roughly one third of dietary intake of EAA is consumed in first-pass metabolism by the intestine and that amino acid catabolism by the mucosal cells is quantitatively greater than amino acid incorporation into mucosal protein.

Amino Acids↗

PubMed1998

Dietary amino acids are the preferential source of hepatic protein synthesis in piglets.

To investigate the utilization of dietary amino acids for hepatic protein synthesis, seven female pigs ( 28 d old, 7.5 kg) were implanted with catheters in a carotid artery, the jugular and portal veins, and the stomach. A portal flow probe was also implanted. The pigs were fed a high protein diet once hourly and infused intragastrically with [U-13C]algal protein for 6 h. Amino acid labeling was measured in arterial and portal blood, in the hepatic free and protein-bound pools and in apolipoprotein B-100 (apoB-100), albumin and fibrinogen. The isotopic enrichments of apoB-100-bound [U-13C]threonine, leucine, lysine and phenylalanine were 33, 100, 194 and 230% higher than those of their respective hepatic free amino acid pools (P < 0.01). Using the labeling of apoB-100 to estimate that of the protein synthetic precursor, the fractional rate of hepatic protein synthesis was 42 +/- 2%/d. Between 5 and 8% of the dietary tracer amino acids was used for hepatic protein synthesis. In contrast to the small intestinal mucosa, in which the majority of the metabolized amino acids were apparently catabolized, protein synthesis utilized from 48% (threonine) to 90% (lysine) of the hepatic uptake of tracer amino acids. It appears that hepatic protein synthesis consumes nutritionally significant quantities of dietary essential amino acids in first pass and that extracellular, especially portal, essential amino acids are channeled to hepatic protein synthesis in the fed state.

Albumins↗

PubMed1998

Interferon-gamma-inducing factor elicits antitumor immunity in association with interferon-gamma production.

Interferon-gamma-inducing factor (IGIF) is a novel cytokine that stimulates T-cell proliferation, augments natural killer (NK) cell lytic activity, and induces interferon-gamma (IFN-gamma) production in established type 1 T-helper (Th1) cells in the presence of anti-CD3 antibody. The in vitro induction of IFN-gamma by recombinant murine IGIF in these cells was more potent than that induced by murine interleukin-12 (IL-12) and occurred apparently independent of murine IL-12. Here we report that subcutaneous injection into mice of tumor cells transfected with murine IGIF complementary DNA (cDNA) resulted in > or = 10-fold increase of mitogen-stimulated IFN-gamma production in cultured splenocytes. In addition, IGIF-transfected Renca and K1735 tumor cells can be rejected in vivo. The IGIF antitumor effect was abrogated in mice that were sublethally irradiated or depleted of both CD4+ and CD8+ T cells but not in mice depleted of either subpopulation alone. The antitumor effect mediated by IGIF appears to be dependent on IFN-gamma production, because in vivo neutralization of IFN-gamma was accompanied by growth of IGIF-transfected tumors in 100% of the animals. Taken together, our results show that murine IGIF can elicit T-cell-dependent antitumor immunity associated with IFN-gamma induction.

Animals↗

PubMed1998

Cosegregation of spontaneously hypertensive rat renin gene with elevated blood pressure in an F2 generation.

OBJECTIVE: To investigate the role of the renin gene in the hypertension of the spontaneously hypertensive rat (SHR) of the Okamoto strain. METHODS: We determined whether the SHR renin allele was cosegregated with high blood pressure in 137 F2 rats derived from inbred SHR and Wistar-Kyoto rats. Systolic blood pressure in conscious rats was measured by the tail-cuff method, whereas mean arterial pressure was determined from an indwelling catheter in the left carotid artery. Renin genotypes of F2 rats were determined using a SHR-specific Bg/II restriction fragment length polymorphism that we have previously described. RESULTS: The SHR renin allele was cosegregated significantly with higher systolic blood pressure in male F2 rats aged 8-24 weeks and in females aged 12-24 weeks. The greatest differences in blood pressure between SHR renin allele homozygotes and Wistar-Kyoto rat renin allele homozygotes were 35 mmHg for males and 17 mmHg for females aged 24 weeks. The SHR renin allele was also associated with a higher mean arterial pressure in rats aged 24 weeks and cosegregated with higher body weight of male F2 rats aged 12-24 weeks but not with that of the females. In contrast to the relationship with blood pressure, the SHR renin allele was segregated with lower plasma renin concentrations in rats aged 24 weeks. CONCLUSION: These results are consistent with the SHR renin gene being one of the loci determining high blood pressure in rats of this strain, possibly through action at some extra-renal site subserving control of blood pressure.

Animals↗

PubMed1998

Cesium effects on i(f) and i(K) in rabbit sinoatrial node myocytes: implications for SA node automaticity.

Cesium blocks the hyperpolarization-activated current i(f) but blocks neither the delayed-rectifier current i(K) nor the sinoatrial (SA) node discharge. It has been proposed that the failure of Cs+ to block SA discharge is either an incomplete block or a negative shift of i(f). However, an alternative possibility is that i(K) (rather than i(f)) has a predominant role in the SA-pacemaker potential. To investigate this point, the effects of Cs+ on both i(f) and i(K) in the pacemaker range of potentials were studied in the same single SA node cell at the same time by means of the perforated patch-clamp technique. Hyperpolarizing steps from a holding potential (Vh) of -35 mV into and past the pacemaker-potential range resulted in a progressively larger i(f) associated with an increasing slope conductance. Cs+ (2 mM) reversibly blocked both i(f) and the slope conductance increase, suggesting that the current activated was indeed predominantly i(f). Subsequently, hyperpolarizing steps to -50, -60, and -70 mV were applied in the absence (to activate only i(f)) and in the presence of a prior depolarizing step to +10 mV (to activate i(K) as well, as the action potential normally does). Cs+ almost abolished i(f) but only slightly decreased i(K). It is concluded that the failure of Cs+ to block the SA- node spontaneous discharge is not due to a shift of i(f) out of the pacemaker range (due to run-down) or an incomplete block of i(f). Instead, the resistance of i(K) to block by Cs+ is consistent with a predominant role of i(K) for the discharge of the SA node, although i(f) can contribute under normal or special circumstances. The reduction of i(K) by Cs+ raises the question whether the Cs+ slows the SA-node discharge not only by suppressing I(f), but also by reducing i(K).

Action Potentials↗

PubMed1998

Binding of salivary glycoprotein-secretory immunoglobulin A complex to the surface protein antigen of Streptococcus mutans.

The interaction between a surface protein antigen (PAc) of Streptococcus mutans and human salivary agglutinin was analyzed with a surface plasmon resonance biosensor. The major component sugars of the salivary agglutinin were galactose, fucose, mannose, N-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminic acid. Binding of salivary agglutinin to PAc was calcium dependent and heat labile and required a pH greater than 5. Binding was significantly inhibited by N-acetylneuraminic acid and alpha2,6-linked sialic acid-specific lectin derived from Sambucus sieboldiana in a dose-dependent manner. Pretreatment of the salivary agglutinin with sialidase reduced the binding activity of the agglutinin to the PAc molecule. The agglutinin was dissociated into high-molecular-mass glycoprotein and secretory immunoglobulin A (sIgA) components by electrophoretic fractionation in the presence of 1% sodium dodecyl sulfate and 1% 2-mercaptoethanol. Neither of the components separated by electrophoretic fractionation, high-molecular-mass glycoprotein or sIgA, bound to the PAc molecule. Furthermore, the high-molecular-mass glycoprotein strongly inhibited the binding of the native salivary complex to PAc. These results suggest that the complex formed by the high-molecular-mass salivary glycoprotein and sIgA is essential for the binding reaction and that the sialic acid residues of the complex play an important role in the interaction between the agglutinin and PAc of S. mutans.

Acetylgalactosamine↗

PubMed1998

Microbial pathogenesis in cystic fibrosis: pulmonary clearance of mucoid Pseudomonas aeruginosa and inflammation in a mouse model of repeated respiratory challenge.

Chronic endobronchiolitis compounded by recurring Pseudomonas aeruginosa infections is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). In this study, a mouse model of repeated respiratory exposure to P. aeruginosa was established to facilitate investigations of factors contributing to P. aeruginosa persistence and associated inflammatory processes in the lung. While a single exposure to P. aeruginosa aerosols resulted in only mild histopathological changes, repeated exposure caused significant lung pathology in C57BL/6J mice. The peak of histopathological changes and inflammation in C57BL/6J mice was characterized by subacute lymphohistiocytic bronchopneumonia and persistent elevation of tumor necrosis factor alpha and macrophage inflammatory protein 2 in the lung but not in the serum. When isogenic nonmucoid (mucA+) and mucoid (mucA22) P. aeruginosa strains were compared, the mucoid cells were cleared several-fold less efficiently than the parental nonmucoid strain during the initial stages of the aerosol exposure regimen. However, the microscopic pathology findings and proinflammatory cytokine levels were similar in mice exposed to nonmucoid and mucoid P. aeruginosa throughout the infection. We also tested lung histopathology and proinflammatory cytokines in interleukin 10 (IL-10)-deficient transgenic (IL-10T) mice. Significant mortality was seen in IL-10T mice on initial challenge with P. aeruginosa, although no histopathological differences could be observed in the lungs of C57BL/6J and surviving IL-10T mice after a single exposure. However, increased pathology was detected in IL-10T mice relative to C57BL/6J after repeated challenge with P. aeruginosa. This observation supports the proposals that anti-inflammatory cytokines may play a role in suppressing P. aeruginosa-induced tissue damage during chronic infection.

Animals↗