PubMed Health⌕ Search

Biomedical subjects

C Lin

Publications and source records attributed to C Lin.

At least 37 records · Page 2Linked to original sources
PubMed2002

The effect of glutamine-supplemented total parenteral nutrition on nitrogen economy depends on severity of diseases in surgical patients.

BACKGROUND: Gln is an important substrate for enterocyte and rapid proliferation cells. Studies have shown that parenteral supplementation of Gln maintains the intracellular Gln pool, improves nitrogen balance and shortens hospital stay. However, some studies showed Gln-supplemented TPN had no effect on restoring the Gln pool in critically ill patients. OBJECTIVE: To evaluate the effect of glutamine (Gln) dipeptide supplementation of total parenteral nutrition (TPN) on postoperative nitrogen balance and immune response of patients undergoing surgery. METHODS: This study is a prospective, randomized double-blind clinical trial. APACHE II score and TISS were used to evaluate the patients after admission. Forty-eight patients with major abdominal surgery were allocated to two groups to receive isonitrogenous (0.228 g nitrogen/kg/day) and isoenergetic (30 kcal/kg/day) TPN for 6 days. Two groups (Conv and Ala-Gln) were further divided to high (APACHE>or=6) and low (APACHE <6) groups. Control group (Conv) received 1.5 g amino acids/kg/day, whereas the Ala-Gln group received 0.972 g amino acids/kg/day and 0.417 g of L-alanyl-L-glutamine (Ala-Gln)/kg/day. Blood samples were collected on day 1 and day 6 after surgery for plasma amino acid and CD4, CD8 cell and T lymphocyte analysis. Cumulative nitrogen balance were also measured on day 2, 3, 4, 5 postoperatively. RESULTS: Although there was a tendency to have better cumulative nitrogen balance on the postoperative days in the Ala-Gln group, no significant difference was observed between two groups. However, a better significant cumulative nitrogen balance was observed on the 2nd, 3rd and 5th postoperative day in the Ala-Gln group than in the Conv group in patients with APACHE II <6, whereas no significant difference was noted in patients with APACHE II >or= 6. No difference in urine 3-methylhistidine excretion were observed between the 2 groups. Patients in the Ala-Gln group had significant higher T lymphocyte and CD4 cells than did those in the Conv group. CONCLUSION: TPN supplemented with Gln dipeptide had beneficial effect on enhancing the immune response. However, the effect of Ala-Gln administration on improving nitrogen economy was only observed in patients with low APACHE II scores. These results may indicate that Gln required for reversing the catabolic condition may depend on the characteristics and severity of the diseases.

APACHE↗
PubMed2002

Naphthalene-induced respiratory tract toxicity: metabolic mechanisms of toxicity.

The lung, which is in intimate contact with the external environment, is exposed to a number of toxicants both by virtue of its large surface area and because it receives 100% of the cardiac output. Lung diseases are a major disease entity in the U.S. population ranking third in terms of morbidity and mortality. Despite the importance of these diseases, key issues remain to be resolved regarding the interactions of chemicals with lung tissue and the factors that are critical determinants of chemical-induced lung injury. The importance of cytochrome P450 monooxygenase dependent metabolism in chemical-induced lung injury in animal models was established over 25 years ago with the furan, 4-ipomeanol. Since then, the significance of biotransformation and the reasons for the high degree of pulmonary selectivity for a myriad of different chemicals has been well documented, mainly in rodent models. However, with many of these chemicals there are substantial differences in the susceptibility of rats vs. mice. Even within the same species, varied levels of the respiratory tract respond differently. Thus, key pieces of data are still missing when evaluating the applicability of data generated in rodents to primates, and as a result of this, there are substantial uncertainties within the regulatory community with regards to assessing the risks to humans for exposure to some of these chemicals. For example, all of the available data suggest that the levels of cytochrome P450 monooxygenases in rodent lungs are 10-100 times greater than those measured in the lungs of nonhuman primates or in man. At first glance, this suggests that a significant margin of safety exists when evaluating the applicability of rodent studies in the human, but the issues are more complex. The intent of this review is to outline some of the work conducted on the site and species selective toxicity and metabolism of the volatile lung toxic aromatic hydrocarbon, naphthalene. We argue that a complete understanding of the cellular and biochemical mechanisms by which this and other lung toxic compounds generate their effects in rodent models with subsequent measurement of these cellular and biochemical events in primate and human tissues in vitro will provide a far better basis for judging whether the results of studies done in rodent models are applicable to humans.

Animals↗
PubMed2002

Leptin directly regulates bone cell function in vitro and reduces bone fragility in vivo.

Fat mass is an important determinant of bone density, but the mechanism of this relationship is uncertain. Leptin, as a circulating peptide of adipocyte origin, is a potential contributor to this relationship. Recently it was shown that intracerebroventricular administration of leptin is associated with bone loss, suggesting that obesity should be associated with low bone mass, the opposite of what is actually found. Since leptin originates in the periphery, an examination of its direct effects on bone is necessary to address this major discrepancy. Leptin (>10(-11) m) increased proliferation of isolated fetal rat osteoblasts comparably with IGF-I, and these cells expressed the signalling form of the leptin receptor. In mouse bone marrow cultures, leptin (>or=10(-11) m) inhibited osteoclastogenesis, but it had no effect on bone resorption in two assays of mature osteoclasts. Systemic administration of leptin to adult male mice (20 injections of 43 micro g/day over 4 weeks) reduced bone fragility (increased work to fracture by 27% and displacement to fracture by 21%, P<0.001). Changes in tibial histomorphometry were not statistically significant apart from an increase in growth plate thickness in animals receiving leptin. Leptin stimulated proliferation of isolated chondrocytes, and these cells also expressed the signalling form of the leptin receptor. It is concluded that the direct bone effects of leptin tend to reduce bone fragility and could contribute to the high bone mass and low fracture rates of obesity. When administered systemically, the direct actions of leptin outweigh its centrally mediated effects on bone, the latter possibly being mediated by leptin's regulation of insulin sensitivity.

Animals↗
PubMed2001

Neutral dodecanuclear supramolecular complexes containing dimetal units linked by the trimesate anion.

Two compounds having six metal-metal bonded Mo(2)(4+) and Rh(2)(4+) units, the midpoints of which occupy the vertexes of an octahedron, are described here. Each of the M(2)(4+) units is also bridged by two mutually cis formamidinate groups of the type DAniF = N,N'-di-p-anisylformamidinate. These units are linked to each other by four tricarboxylate anions from trimesic acid, the centers of which form a tetrahedron that is encapsulated by the octahedron of dimetal units. Each of the neutral cages has a clathrated solvent molecule, CH(2)Cl(2) when the metal M is Mo and CH(3)CN when it is Rh. For the latter, there are CH(3)CN molecules occupying (2)/(3) of the axial sites on the Rh(2) units in a way that reduces the symmetry. These symmetrical structures appear to persist in solution as shown by the (1)H NMR spectra. The compounds [M(2)(cis-DAniF)(2)](6)[1,3,5-C(6)H(3)(CO(2))(3)](4), 1 for M = Mo and 2 for M = Rh, were crystallized as 1.22.1CH(3)CN.2.3CH(2)Cl(2) and 2.13.9CH(3)CN, respectively. In 1 there are four crystallographically independent quadruply bonded Mo-Mo distances in the narrow range 2.098-2.104 A. For 2, the six independent singly bonded Rh-Rh distances are in the range 2.428-2.438 A.

Journal Article↗
PubMed2001

Controlling the dimensionality of metal-metal bonded Rrh(2)(4+) polymers by the length of the linker. A disciplined example of crystal engineering.

Reaction of the molecular loop [Rh(2)(cis-DAniF)(2)(CH(3)CN)](2)(malonato)(2), DAniF = N,N'-di-p-anisylformamidinate, with 2 equiv of 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldinitrile gives a linear tubular structure with Rh-Rh distances of 2.435(1) A. A comparison of the structures obtained with this molecular loop but employing other linkers support the idea that longer linkers favor one-dimensional structures while shorter linkers favor two-dimensional structures because of the increased clashing between the large p-anisyl groups. Crystallographic data at 213(2) K for [[Rh(2)(cis-DAniF)(2)](2)(O(2)CCH(2)CO(2))(2)(NCC(6)F(4)C(6)F(4)CN)(2)] x 6.8nCH(2)Cl(2) are: monoclinic, P2(1)/m, a = 11.802(1), b = 28.303(2), c = 18.820(2) A, beta = 95.673(2) degrees, and Z = 2.

Journal Article↗
PubMed2001

The involvement of a stress-activated pathway in equine influenza virus-mediated apoptosis.

We have shown elsewhere that equine-2 influenza virus (EIV; subtype H3N8) induced pronounced cell death in infected cells through apoptosis as demonstrated by DNA fragmentation assay and a combined TUNEL and immunostaining scheme. In this study, we investigated the mechanism of EIV-mediated cytotoxicity on a permissive mammalian epithelial cell line, Madin-Darby canine kidney (MDCK) cells. EIV infection increased the cellular levels of oxidative stress and c-Jun/AP-1 protein (which is known to be affected by oxidative stress), as well as its DNA binding activity. Increased production of TGF-beta1, an inducer of c-Jun N-terminal kinase or stress-activated protein kinase (JNK/SAPK) activation, was also detected in EIV-infected MDCK cells. It has been reported that TGF-beta may initiate a signaling cascade leading to JNK/SAPK activation. Addition of c-Jun antisense oligodeoxynucleotide, antioxidant N-acetyl-cysteine (NAC), JNK/SAPK inhibitor carvedilol, or TGF-beta-neutralizing antibody effectively blocked c-Jun/AP-1 upregulation and TGF-beta1 production mediated by EIV infection. These treatments also attenuated EIV-induced cytopathogenic effects (CPE) and apoptosis. Our results suggest that a stress-activated pathway is involved in apoptosis mediated by EIV infection. It is likely that EIV infection turns on the JNK/SAPK cascade, which modulates the activity of apoptosis-promoting regulatory factor c-Jun/AP-1 and epithelial growth inhibitory cytokine TGF-beta.

Animals↗
PubMed2001

Tbx19, a tissue-selective regulator of POMC gene expression.

Pituitary cell types arise in a temporally and spatially specific fashion, in response to combinatorial actions of transcription factors induced by transient signaling gradients. The critical transcriptional determinants of the two pituitary cell types that express the pro-opiomelanocortin (POMC) gene, the anterior lobe corticotropes, producing adrenocorticotropin, and the intermediate lobe melanotropes, producing melanocyte-stimulating hormone (MSH alpha), have remained unknown. Here, we report that a member of the T-box gene family, Tbx19, which is expressed only in the rostral ventral diencephalon and pituitary gland, commencing on e11.5, marks pituitary cells that will subsequently express the POMC gene and is capable of altering progression of ventral cell types and inducing adrenocorticotropin in rostral tip cells. It is suggested that Tbx19, depending on the presence of synergizing transcription factors, can activate POMC gene expression and repress the alpha glycoprotein subunit and thyroid-stimulating hormone beta promoters.

Amino Acid Sequence↗
PubMed2001

Permeability of lipophilic compounds in drug discovery using in-vitro human absorption model, Caco-2.

Highly lipophilic compounds are often encountered in the early stages of drug discovery. The apparent permeability (Papp) of these compounds in Caco-2 cell could be underestimated because of considerable retention by the Caco-2 monolayer and non-specific binding to transwell surface. We have utilized a general approach for the determination of permeability of these compounds, which includes the addition of 1-5% DMSO in the apical (AP) and 4% bovine serum albumin (BSA) in the basolateral (BA) side. Two highly lipophilic and highly protein bound Schering compounds, SCH-A and SCH-B, exhibited poor recovery and low Papp in the conventional Caco-2 system that included 1% DMSO in the AP and BA sides. In contrast, both compounds were well absorbed in cynomolgus monkeys. Inclusion of BSA (up to 4%) in the BA side provided necessary absorptive driving force similar to in vivo sink conditions improving both recovery and Papp of these compounds as well as progesterone, a model highly lipophilic and highly protein bound compound. Whereas, the recovery and Papp of mannitol (high recovery, low permeability) and propranolol (high recovery, high permeability) remained unaffected. The presence of 4% BSA increased Papp of SCH-A, SCH-B, and progesterone by five-, four-, and three-fold, respectively. We also compared this approach with a second, based on the disappearance of the compound from the AP side, which resulted in a reasonable estimate of the permeability (23.3x10(-6) cm/s) for SCH-A. The results demonstrated that the reliable estimates of permeability of highly lipophilic compounds that are subjected to considerable retention by the cell monolayer and exhibit non-specific binding are obtained by the addition of BSA to the BA side.

Caco-2 Cells↗
PubMed2001

Twist-averaged boundary conditions in continuum quantum Monte Carlo algorithms.

We develop and test Quantum Monte Carlo algorithms that use a"twist" or a phase in the wave function for fermions in periodic boundary conditions. For metallic systems, averaging over the twist results in faster convergence to the thermodynamic limit than periodic boundary conditions for properties involving the kinetic energy and has the same computational complexity. We determine exponents for the rate of convergence to the thermodynamic limit for the components of the energy of coulomb systems. We show results with twist averaged variational Monte Carlo on free particles, the Stoner model and the electron gas using Hartree-Fock, Slater-Jastrow, and three-body and backflow wave function. We also discuss the use of twist averaging in the grand canonical ensemble, and numerical methods to accomplish the twist averaging.

Journal Article↗
PubMed2001

[Experimental therapy of adenovirus-transferred antisense c-myc on hepatocellular cancer cell].

OBJECTIVE: To investigate the therapeutic effects of Adenovirus-transferred antisense c-myc (Ad-Asmyc) on hepatocellular cancer cells and its mechanism. METHODS: Human hepatocellular cancer cell line BEL-7402 and QSG-7701 were transfected with Ad-Asmyc. Cell growth curve and coloning formation were used to investigate the therapeutic effects of Ad-Asmyc in Vitro. The treating effects of Ad-Asmyc on transplanted tumor in nude mice was also studied. RT-PCR and Western blot were used to detect relating gene expression. Flowcytometry, DNA ladder and tunnel assay were used to study the cell cycle and apoptosis. RESULTS: The expression of c-myc in cancer cells was reduced after infected Ad-Asmyc. Ad-Asmyc had obviously inhibiting effects on the growth of two hepatocellular carcinoma cell lines in vitro and also in vivo. It can induced cell cycle arrest (G1 arrest) and apoptosis. CONCLUSION: Ad-Asmyc can inhibit HCC cell proliferation and induce apoptosis, so has obvious therapeutic effects on hepatocellular cancer cells.

Adenoviridae↗
PubMed2001

Vibrationally inelastic scattering of high- n Rydberg H atoms from N2 and O2.

The vibrationally inelastic scattering of Rydberg H atoms (n = 30-50) from N2 and O2 at E(coll) = 1.84 eV was studied as a function of laboratory deflection angle. On average, 4 times more vibrational excitation was observed in collisions with O2 than with N2. Vibrational excitation of O2 results largely from collisions in which an electron is briefly transferred from O2 to the proton core, while the Rydberg electron remains a spectator. This provides further evidence that the free electron model applies to low energy collisions involving the ionic core leading to substantial momentum transfer.

Journal Article↗
PubMed2001

Cloning and characterization of MST4, a novel Ste20-like kinase.

MST4, a novel member of the germinal center kinase subfamily of human Ste20-like kinases, was cloned and characterized. Composed of a C-terminal regulatory domain and an N-terminal kinase domain, MST4 is most closely related to mammalian Ste20 kinase family member MST3. Both the kinase and C-terminal regulatory domains of MST4 are required for full activation of the kinase. Northern blot analysis indicates that MST4 is ubiquitously distributed, and the MST4 gene is localized to chromosome Xq26, a disease-rich region, by fluorescence in situ hybridization. Although some members of the MST4 family function as upstream regulators of mitogen-activated protein kinase cascades, expression of MST4 in 293 cells was not sufficient to activate or potentiate extracellular signal-regulated kinase, c-Jun N-terminal kinase, or p38 kinase. An alternatively spliced isoform of MST4 (MST4a) was isolated by yeast two-hybrid interaction with the catalytic domain of Raf from a human fetal brain cDNA library and also found in a variety of human fetal and adult tissues. MST4a lacks an exon encoding kinase subdomains IX-XI that stabilizes substrate binding. The existence of both MST4 isoforms suggests that the MST4 kinase activity is highly regulated, and MST4a may function as a dominant-negative regulator of the MST4 kinase.

Amino Acid Sequence↗
PubMed2001

Desmoglein isoform distribution affects stratum corneum structure and function.

Desmogleins are desmosomal cadherins that mediate cell-cell adhesion. In stratified squamous epithelia there are two major isoforms of desmoglein, 1 and 3, with different distributions in epidermis and mucous membrane. Since either desmoglein isoform alone can mediate adhesion, the reason for their differential distribution is not known. To address this issue, we engineered transgenic mice with desmoglein 3 under the control of the involucrin promoter. These mice expressed desmoglein 3 with the same distribution in epidermis as found in normal oral mucous membranes, while expression of other major differentiation molecules was unchanged. Although the nucleated epidermis appeared normal, the epidermal stratum corneum was abnormal with gross scaling, and a lamellar histology resembling that of normal mucous membrane. The mice died shortly after birth with severe dehydration, suggesting excessive transepidermal water loss, which was confirmed by in vitro and in vivo measurement. Ultrastructure of the stratum corneum showed premature loss of cohesion of corneocytes. This dysadhesion of corneocytes and its contribution to increased transepidermal water loss was confirmed by tape stripping. These data demonstrate that differential expression of desmoglein isoforms affects the major function of epidermis, the permeability barrier, by altering the structure of the stratum corneum.

Animals↗
PubMed2001

Broussochalcone A, a potent antioxidant and effective suppressor of inducible nitric oxide synthase in lipopolysaccharide-activated macrophages.

The antioxidant properties of broussochalcone A (BCA) and its effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated macrophages were investigated in this study. BCA, isolated from Broussonetia papyrifera Vent., inhibited iron-induced lipid peroxidation in rat brain homogenate in a concentration-dependent manner with an IC(50) of 0.63 +/- 0.03 microM. It was as potent as butylated hydroxytoluene, a common antioxidant used for food preservation. In a diphenyl-2-picrylhydrazyl assay system, the radical-scavenging activity of BCA seemed to be more potent than that of alpha-tocopherol, its IC(0.200) being 7.6 +/- 0.8 microM. BCA could directly scavenge superoxide anion and hydroxyl radicals. These results indicated that BCA was a powerful antioxidant with versatile free radical-scavenging activity. On the other hand, we found that BCA suppressed NO production concentration-dependently, with an IC(50) of 11.3 microM in LPS-activated macrophages. This effect was not the consequence of a direct inhibitory action on the enzyme activity of inducible NO synthase (iNOS). Our results indicated that BCA exerts potent inhibitory effects on NO production, apparently mediated by its suppression of IkappaBalpha phosphorylation, IkappaBalpha degradation, nuclear factor-kappa B activation, and iNOS expression. Therefore, we conclude that the antioxidant activities of BCA and its inhibition of IkappaBalpha degradation and iNOS protein expression may have therapeutic potential, given that excessive free radicals and NO production have been associated with various inflammatory diseases.

Animals↗
PubMed2001

The simplest supramolecular complexes containing pairs of Mo(2)(formamidinate)(3) units linked with various dicarboxylates: preparative methods, structures, and electrochemistry.

Twelve compounds containing two quadruply bonded Mo(2)(DAniF)(3) (DAniF = N,N'-di-p-anisylformamidinate) units linked by dicarboxylate anions have been prepared in high purity and good yields. All of these compounds have been characterized by crystallography and NMR. The dinuclear pairs display electrochemical behavior which is controlled by the nature of the bridging dicarboxylate group. As described by the linkers, the compounds are oxalate, 1; acetylene dicarboxylate, 2; fumarate, 3; tetrafluorophthalate, 4; carborane dicarboxylate, 5; ferrocene dicarboxylate, 6; malonate, 7; succinate, 8; propane-1,3-dicarboxylate, 9; tetrafluorosuccinate, 10; bicyclo[1.1.1]pentane-1,3-dicarboxylate, 11; and trans-1,4-cyclohexanedicarboxylate, 12.

Acetylene↗
PubMed2001

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

Journal Article↗
PubMed2001

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Journal Article↗