Biomedical subjects

Di Wu

Publications and source records attributed to Di Wu.

At least 73 records · Page 4Linked to original sources

PubMed2005

p63 and p73 do not contribute to p53-mediated lymphoma suppressor activity in vivo.

p53 is one of the most important tumor suppressor genes in human cancer, but the roles of its homologues p63 and p73 in tumor suppression, alone or in collaboration with p53, remains controversial. Both p63 and p73 can be deregulated after DNA damage, and induce cell cycle arrest and apoptosis, but mice carrying inactive alleles of these genes do not develop spontaneous tumors. Since heterozygous loss of p53 confers strong sensitization to radiation-induced lymphoma development, we investigated the possibility that radiation exposure may reveal previously undetected tumor suppressor properties in p63 or p73, alone or in combination with p53. Animals heterozygous for p63 or p73, as well as both double heterozygous p53/p63 or p53/p73 mice, showed no significant differences in tumor latency, spectrum or frequency after gamma-radiation, compared to their control counterparts. Deletions were found near the p63 locus on chromosome 16 in radiation-induced tumors, but these frequently included the knockout allele. No deletions or LOH involving the p73 gene were detected, and expression of both genes was maintained in the tumors. We conclude that p53 homologues do not contribute to p53 tumor suppressor activity in lymphoma development.

Animals↗

PubMed2005

The structure and the large nonlinear optical properties of Li@calix[4]pyrrole.

A new compound with electride characteristics, Li@calix[4]pyrrole, is designed in theory. The Li atom in Li@calix[4]pyrrole is ionized to form a cation and an excess electron anion. Its structure with C(4v) symmetry resembles a cup-like shape. It may be a stable organic electride at room temperature. The first hyperpolarizability of the cup-like electride molecule is first investigated by the DFT (B3LYP) method. The result shows that this electride molecule has a considerably large first hyperpolarizability with beta(0) = 7326 au (63.3 x 10(-30) esu), while the beta(0) value of the related calix[4]pyrrole system is only 390 au. Obviously, the Li atom doped in calix[4]pyrrole brings a dramatic change to the electronic structure, so that the first hyperpolarizability of Li@calix[4]pyrrole is almost 20 times larger than that of calix[4]pyrrole. We find that the excess electron from the Li atom plays an important role in the large first hyperpolarizability of Li@calix[4]pyrrole. The present investigation reveals a new idea and different means for designing and synthesizing high-performance NLO materials.

Journal Article↗

PubMed2005

Phase-space overlap measures. I. Fail-safe bias detection in free energies calculated by molecular simulation.

We consider ways to quantify the overlap of the parts of phase space important to two systems, labeled A and B. Of interest is how much of the A-important phase space lies in that important to B, and how much of B lies in A. Two measures are proposed. The first considers four total-energy distributions, formed from all combinations made by tabulating either the A-system or the B-system energy when sampling either the A or B system. Measures for A in B and B in A are given by two overlap integrals defined on pairs of these distributions. The second measure is based on information theory, and defines two relative entropies which are conveniently expressed in terms of the dissipated work for free-energy perturbation (FEP) calculations in the A-->B and B-->A directions, respectively. Phase-space overlap is an important consideration in the performance of free-energy calculations. To demonstrate this connection, we examine bias in FEP calculations applied to a system of independent particles in a harmonic potential. Systems are selected to represent a range of overlap situations, including extreme subset, subset, partial overlap, and nonoverlap. The magnitude and symmetry of the bias (A-->B vs B-->A) are shown to correlate well with the overlap, and consequently with the overlap measures. The relative entropies are used to scale the amount of sampling to obtain a universal bias curve. This result leads to develop a simple heuristic that can be applied to determine whether a work-based free-energy measurement is free of bias. The heuristic is based in part on the measured free energy, but we argue that it is fail-safe inasmuch as any bias in the measurement will not promote a false indication of accuracy.

Algorithms↗

PubMed2005

Co-expression of radial glial marker in macrophages/microglia in rat spinal cord contusion injury model.

Macrophages/microglia are implicated in spinal cord injury but their precise role in the process is not clear. Our previous studies have reported that radial glia (RG) possess properties of neural stem cells and remerged after central nervous system (CNS) injury which may play an important role in neural repair and regeneration. In the present study, we examined the expression of ED1 (a specific marker for activated macrophages/microglia) and RG in a spinal cord injury (SCI) model and detected the activation at 1, 4, 8, and 12 weeks in both dorsal funiculus and ventral white matter after SCI. For both ED1-positive cells and RG cells, there was a gradual increase in density and in number from 1 to 4 weeks followed by down-regulation up to 12 weeks after injury. The morphologies of macrophages and radial glia were different. However, some ED1-positive cells were also stained by RG marker. These results suggest that macrophages may have some lineage to radial glial cells.

Animals↗

PubMed2005

[Experimental study on preparation of decellularized artery vascular graft matrix and explantation of carotid artery allografts].

OBJECTIVE: To set up a new process to access the preparation of decellularized artery grafts. And to evaluate the feasibility of decellularized artery allografts was evaluated. METHODS: This study compared the effects of four extraction chemicals [1% t-octyl-phenoxypolyethoxyethanol (Triton X-100), 1% tri (n-butyl) phosphate (TnBP), and 1% sodium dodecyl sulfate (SDS) and trypsin (0.125, 0.25%) on thoracic artery vascular for 24 h (except trypsin for 2 h). At the base of it, a four-step process, including hypotonic, hypertonic solutions and combining with 1% Triton X-100 and 1% SDS detergents, were performed in rabbit thoracic artery vascular. Histological examination, tensile tests and expanding-burst tests were done on the samples. The decellularized carotid artery allografts were transplanted in other rabbits. RESULTS: Treatment with 1% SDS or 1% Triton X-100 for 24 h could remove most cells with retention of near normal structure. A four-step process could remove all cells with the extracellular matrix well conserved. The pulling mechanical properties and burst pressure of decellularized carotid artery were similar to the control. The decellularized carotid artery allografts (diameter of 2 mm) were patent at explanting up to 2 months. CONCLUSIONS: The acellular artery vascular graft matrix is well prepared with four-step process including detergents, such as TritonX-100, SDS without compromising the graft structure or mechanical properties significantly. The carotid artery allografts (diameter of 2 mm) decellularized by the process are patent at explanting up to 2 months.

Animals↗

PubMed2005

The para substituent of S-3-(phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamides is a major structural determinant of in vivo disposition and activity of selective androgen receptor modulators.

Selective androgen receptor modulators (SARMs) have many potential therapeutic applications, including male hypogonadism, osteoporosis, muscle-wasting diseases, sexual libido, and contraception. A series of S-3-(phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamides bearing a four-halogen substituent in the B-ring that displayed in vivo activity were identified in our previous study. Interestingly, in vivo pharmacological activity was not correlated with in vitro androgen receptor (AR) binding affinity. In this study, analysis of the area under the concentration-time curve-response relationship demonstrated that the discrepancy between in vitro and in vivo pharmacological activity of these halogen-substituted SARMs was due to differences in systemic exposure rather than intrinsic pharmacological activity. Studies also suggested that two simple criteria (i.e., Ki < 10 nM and lower in vivo clearance) could be used to identify efficacious and potent SARMs. We tested this hypothesis using a series of four compounds incorporating either a nitro or cyano substituent at the para-position of the A- and B-aromatic rings. The S-3-(4-nitrophenoxy) and S-3-(4-cyanophenoxy) 2-hydroxy-2-methyl-N-(4-nitro-3-trifluromethylphenyl) propionamides (S-19 and S-20, respectively) and S-3-(4-nitrophenoxy) and S-3-(4-cyanophenoxy) 2-hydroxy-2-methyl-N-(4-cyano-3-trifluromethylphenyl) propionamides (S-21 and S-22, respectively) demonstrated high AR binding affinity, with Ki values ranging from 2.0 to 3.8 nM. Pharmacokinetic studies of selected compounds showed that the in vivo clearance of S-22 was the slowest followed sequentially by S-20, S-21, and S-19. The dose-response relationships for S-22 showed that S-22 exerted efficacious and selective activity in anabolic tissues at dose rates as low as 0.03 mg/day, indicative of the high potency of this compound in anabolic tissue (relative potency 4.41) and its potential for clinical use in androgen deficiency-related disorders.

Amides↗

PubMed2005

Expression of tissue inhibitor of matrix metalloproteinases-1 during aging in rat liver.

AIM: To investigate the expression and role of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) during natural aging in rat liver and to detect the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9. METHODS: The rats were divided into 3-mo-old group (n = 5), 10-mo-old group (n = 5) and 24-mo-old group (n = 5). Histopathologic changes of liver were observed with HE and Masson stain. The location and protein expressions of TIMP-1 were determined by immunohistochemistry and Western blot; message RNA (mRNA) levels were measured in livers from rats of various ages by semi-quantitative reverse transcriptional polymerase chain reaction (RT-PCR). In addition, the expression of MMP-2 and MMP-9 was assessed by RT-PCR and Western blot. RESULTS: Histologic examination showed that the aging liver had excessive fatty degeneration and collagen deposition. Immunohistochemical staining showed that TIMP-1 related antigen in livers was located in cytoplasm. The protein expression of TIMP-1 was significantly higher in the oldest animals and the mRNA expression was increased significantly in the 24-mo-old rats (t = 4.61, P = 0.002<0.05, 24-vs 10-mo-old rats; t = 4.31, P = 0.003<0.05, 24- vs 3-mo-old rats). The expression of MMP-2 and MMP-9 had no change during aging; the ratios TIMP-1/MMP-2 and TIMP-1/MMP-9 in aging liver were significantly higher than those in maturation and young livers. CONCLUSION: TIMP-1 may play an important role in the process of liver aging.

Aging↗

PubMed2005

An optimized protocol for detection of E. coli beta-galactosidase in lung tissue following gene transfer.

Staining by 5-bromo-4-chloro-3-indolyl-beta-D: -galactopyranoside (X-gal) typically detects activity of E. coli beta-galactosidase (beta-gal) in transduced tissues that express the LacZ reporter gene. In lung tissue from mice that received beta-galactosidase-expressing adeno-associated virus (AAV) vectors via intranasal inhalation, we observed only a low frequency of positive cells after X-gal staining in contrast to other reporter genes, such as alkaline phosphatase or green fluorescent protein. In this study, we systematically tested a number of parameters to improve the sensitivity of X-gal staining in lungs transduced with beta-galactosidase-expressing AAV2/5 vectors. We observed that the use of nuclear-targeted LacZ instead of cytoplasmic LacZ as the reporter gene substantially increases the number of positive cells after X-gal staining. The pH of the staining solution determines staining sensitivity and background staining with pH 7.0 resulting in high sensitivity and no background levels. Glutaraldehyde at 0.2% or 0.5% in PBS as fixative provides optimal results for X-gal staining. The alternative substrate, Bluo-gal, showed no improvement compared with X-gal but instead caused nonspecific background staining. We further stained intact fixed lungs with X-gal and processed them for paraffin embedding or cryosectioning, resulting in equal staining intensities. However, en bloc staining of intact tissues resulted in the absence of positive cells within deeper-located lung areas.

Adenoviridae↗

PubMed2005

Rosenbluth-sampled nonequilibrium work method for calculation of free energies in molecular simulation.

We present methods that introduce concepts from Rosenbluth sampling [M. N. Rosenbluth and A. W. Rosenbluth, J. Chem. Phys. 23, 356 (1955)] into the Jarzynski nonequilibrium work (NEW) free-energy calculation technique [C. Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)]. The proposed hybrid modifies the way steps are taken in the NEW process. With it, each step is selected from a range of alternatives, with bias given to steps that contribute the least work. The definition of the work average is modified to account for the bias. We introduce two variants of this method, lambda-bias sampling and configuration-bias sampling, respectively; a combined lambda- and configuration-bias method is also considered. By reducing the likelihood that large nonequilibrated work values enter the ensemble average, the Rosenbluth sampling aids in remedying problems of inaccuracy of the calculation. We demonstrate the performance of the proposed methods through a model system of N independent harmonic oscillators. This model captures the difficulties involved in calculating free energies in real systems while retaining many tractable features that are helpful to the study. We examine four variants of this model that differ qualitatively in the nature of their phase-space overlap. Results indicate that the lambda-bias sampling method is most useful for systems with entropic sampling barriers, while the configuration-bias methods are best for systems with energetic sampling barriers. The Rosenbluth-sampling schemes yield much more accurate results than the unbiased nonequilibrium work method. Typically the accuracy can be improved by about an order of magnitude for a given amount of sampling; this improvement translates into two or more orders of magnitude less sampling required to obtain a given level of accuracy, owing to the generally slow convergence of the NEW calculation when the inaccuracy is large.

Algorithms↗

PubMed2005

Generation of mouse anti-human urate anion exchanger antibody by genetic immunization and its identification.

BACKGROUND: Human urate anion exchanger (hURAT1) as a major urate transporter expressed on renal tubular epithelial cells regulates blood urate level by reabsorbing uric acid. Antibody is an important tool to study hURAT1. This study aimed, by genetic immunization, to produce mouse anti-hURAT1 polyclonal antibody with high throughput and high specificity and to detect the location of hURAT1 in human kidney. METHODS: Human renal total RNA was isolated and the entire cDNA of hURAT1 was amplified by RT-PCR. The sequence of intracellular high antigenicity fragment (A280 to R349) was chosen by prediction software of protein antigenicity, and its cDNA was amplified from cDNA of hURAT1, and then cloned into pBQAP-TT vector to construct recombinant plasmid pBQAP-TT-hURAT1-210 for genetic immunization. Mice were inoculated with this recombinant plasmid and two other adjuvant plasmids, pCMVi-GMCSF and pCMVi-Flt3L, which helped to enhance the antibody's generation. After four weeks, the mice were sacrificed to obtain the anti-hURAT1 antibody from serum. The antibody was identified by western blot analysis and immunohistochemistry. At the same time, rabbit anti-hURAT1 antibody was produced by protein immunization. The specificity and efficiency between the rabbit and mouse anti-hURAT1 antibody were compared by western blot analysis and immunohistochemistry. RESULTS: The entire cDNA of hURAT1 and cDNA of its intracellular high immunogenic fragment were amplified successfully. Recombinant plasmid pBQAP-TT-hURAT1-210 for genetic immunization was confirmed by restriction digestion and sequencing. Both the mouse anti-hURAT1 antibody and rabbit anti-hURAT1 antibody recognized 58 kD hURAT1 and 64 kD glycosylated hURAT1 protein bands in western blot. Immunohistochemically, hURAT1 was located at the brush border membrane of renal proximal tubular cells. In addition, the throughput and specificity of the mouse anti-hURAT1 antibody were higher than those of the rabbit anti-hURAT1 antibody. CONCLUSION: Genetic immunization can generate anti-hURAT1 polyclonal antibody of high throughput and specificity.

Animals↗

PubMed2005

Covalent assembly of shortened multiwall carbon nanotubes on polyelectrolyte films and relevant electrochemistry study.

A significant and versatile approach was developed for perpendicularly aligning multiwall carbon nanotubes on diverse substrates suitable for layer-by-layer self-assembly. The multiwall carbon nanotubes (s-MWNTs) used were shortened with oxidation under ultrasonic and functionalized with acyl chloride in thionyl chloride (SOCl2). The monolayer of s-MWNTs perpendicularly grafted to the substrate was obtained by dipping the polyelectrolyte modifying substrate into a tetrahydrofuran suspension of the functionalized s-MWNTs. The interaction proved to be stable and not liable to be affected by the ambience. Transmission electron microscopy and atomic force microscopy were used to examine the morphology of the MWNTs and s-MWNTs grafted on the substrates. Raman spectroscopy was applied to verify the existence of s-MWNTs for assembly, and Fourier transform infrared absorption spectra were used to investigate the interaction pattern between s-MWNTs and polyelectrolyte. The electrochemistry properties of the monolayer of s-MWNTs when the substrate was indium-tin oxide were studied.

Journal Article↗

PubMed2005

Inverse sodium hydride: density functional theory study of the large nonlinear optical properties.

"Inverse sodium hydride" (AdzH(+)Na-) is an alkalide compound synthesized in recent experiments containing the unusual charge distribution H+ and Na- (inverse charge state). The new class of compounds interests scientists to investigate their especial structures and properties. In this paper, the structures of three alkalides compounds, (Me)3NH(+)Na-, AdzH(+)Na-, and AdzLi(+)Na-, have been obtained in theory. Especially, the structure of AdzLi(+)Na- is still researched by experimental scientists. We investigated the NLO properties of the alkalides complexes for the first time and found that inverse sodium hydride AdzH(+)Na- has a considerably large NLO response beta0 = 5.7675 x 10(4) au by density functional theory (DFT). To understand the essential features of the large NLO properties, four related systems have been also calculated. Their first hyperpolarizabilities are beta0 = 7.357 x 10(3) au for (Me)3NH(+)Na-, beta0 = 3.9 au for (Me)3NH+, beta0 = 1.10 x 10(2) au for (Me)3NH(+)Cl-, and beta0 = 6.20681 x 10(5) au for AdzLi(+)Na-, respectively. By comparing, we found that, first, the Na- anion plays a crucial role in the considerably large first hyperpolarizability of inverse sodium hydride and, second, the first hyperpolarizability of inverse sodium hydride increases with the charge value of the sodium anion. The above results are useful for designing potential NLO materials.

Journal Article↗

PubMed2005

Study of pi halogen bonds in complexes C2H(4-n)Fn-ClF (n = 0-2).

The pi-halogen bond may be considered, in a broad sense, essentially a pi-hydrogen bond. Using the counterpoise-corrected potential energy surface method (interaction energy optimization), the stationary structures of the C2H(4-n)Fn-ClF (n = 0-2) complexes with all real frequencies have been obtained at the MP2/aug-cc-pVDZ level. For C2H(4-n)Fn-ClF (n = 0-2), the pi-halogen bond has a long distance and is elongated by the F substituent effect. The pi-halogen bond length order is 2.661 A for C2H4-ClF < 2.745 A for C2H3F-ClF < 2.766 A for g-C2H2F2-ClF < 2.8076 A for trans-C2H2F2-ClF < 2.8079 A for cis-C2H2F2-ClF. For three complexes C2H3F-ClF, g-C2H2F2-ClF, and cis-C2H2F2-ClF, the pi-halogen bonds are further shifted and sloped by the F substituent effect. The F substituent effect reduces also the interaction energy of the pi-halogen bond. The interaction energies are respectively -3.7 for C2H4-ClF, -2.8 for C2H3F-ClF, -2.3 for g-C2H2F2-ClF, -1.9 for cis-C2H2F2-ClF, and -1.8 kcal/mol for trans-C2H2F2-ClF, at the CCSD(T)/aug-cc-pVDZ level. The electron correlation contribution of the interaction energy is large for C2H(4-n)Fn-ClF (n = 0-2), which shows that the stabilities of the pi-halogen bond systems results primarily from the dispersion interaction. In the double F substituent systems, the interaction energy of the pi-halogen bond structure with a longer interaction distance is larger than that of the corresponding pi-hydrogen bond structure with a shorter interaction distance. This may be because there are the large electron correlation contributions of the interaction energy, and a secondary interaction between lone pairs of Cl atom and some atoms (H, C) with positive charges in the pi-halogen bond structure.

Chlorides↗

PubMed2005

Use of chimeric adenoviral vectors to assess capsid neutralization determinants.

In order to elucidate the relative importance of neutralizing determinants on each of the three major adenoviral capsid components, we have generated chimeric vectors where the hexon protein, or the fiber protein, or both hexon and fiber proteins of one serotype (Simian Adenovirus 24/Pan 7) have been replaced by those of another (Simian Adenovirus 23/Pan 6). The effect of each replacement was evaluated by neutralization assays and by attempted vector re-administration into mice. Both hexon and fiber were found to harbor neutralization epitopes although in vivo transduction was more severely affected by anti-hexon antibodies.

Adenoviruses, Simian↗

PubMed2005

Structural analysis of sterol distributions in the plasma membrane of living cells.

Although plasma membrane (PM) cholesterol-rich and -poor domains have been isolated by subcellular fractionation, the real-time arrangement of cholesterol in such domains in living cells is still unclear. Therefore, dehydroergosterol (DHE), a naturally occurring fluorescent sterol, was incorporated into cultured L-cell fibroblasts. Two PM markers, the enhanced cyan fluorescent protein (ECFP-Mem) and 3'-dioctadecyloxacarbocyanine perchlorate [DiOC(18)(3)], were used to distinguish DHE localized at the PM of living cells. Spatial enrichment of DHE in the PM of living cells was visualized in real time by multiphoton laser scanning microscopy (MPLSM). Quantitative models and image-processing techniques were developed for statistical analysis of the distribution of DHE within the PM. The PM was resolved from the cytoplasm in a two-step process, and a smooth trajectory reference of the PM was refined by statistical regression and moments-based techniques. Thus, DHE intensities over the PM were measured following the major DHE intensity distributions. Spatial distributions of DHE within the PM were examined by a statistical inference technique, complete spatial randomness (CSR). For PM regions densely populated with DHE, the distributions of DHE exhibited statistical arrangements that were not spatial random (i.e., homogeneous Poisson process) or regular but, instead, exhibited strong cluster patterns. In effect, real-time MPLSM imaging data for the first time demonstrated that sterol enrichment occurred in clustered regions in the PM, consistent with the existence of cholesterol-rich domains in the plasma membrane of living cells.

Animals↗

PubMed2005

Characteristics and risk factors of intrarenal arterial lesions in patients with IgA nephropathy.

BACKGROUND: Although the clinical importance of immunoglobulin-A nephropathy (IgAN) is widely recognized, the characteristics of intrarenal arterial lesions in this disease and the main factors associated with them have not been studied extensively, and a large-scale analysis of intrarenal arterial lesions in IgAN has not been performed. METHODS: To clarify these issues, we investigated the prevalence, underlying factors and significance of intrarenal arterial lesions in 1005 patients with IgAN. We distinguished different degrees of severity of small artery and arteriolar lesions (mild, moderate and severe), using a semi-quantitative scoring system. We compared the arterial lesions of IgAN patients with those of 627 non-IgAN patients, who had mesangial proliferating glomerulonephritis without IgA deposits, and of 221 patients with membranous nephropathy (MN). RESULTS: The IgAN patients with arterial lesions were significantly younger than the non-IgAN and MN patients (mean ages 34.6 vs 40.4 and 47.7 years, respectively). The prevalence of intrarenal small artery and arteriolar lesions was 54.6% in IgAN patients, compared with 26.6 and 47.1% in non-IgAN and MN patients, respectively; the percentages of moderate/severe arterial lesions were 37.0 vs 21.6 and 23.1%, respectively; and the percentages of hyaline changes were 43.7 vs 16.8 and 21.2%, respectively. The differences in the prevalence of lesions between IgAN patients and the two other groups were statistically significant for all three parameters. Our search for possible relationships between arterial-arteriolar lesions and various indirect outcome markers disclosed significant associations with hypertension, higher serum creatinine and uric acid, high urinary protein excretion, glomerulosclerosis, tubular atrophy and interstitial fibrosis. Furthermore, these parameters were changed more markedly in IgAN patients with moderate/severe arterial lesions and hyaline changes than in IgAN patients who had mild arterial lesions and wall thickening alone. CONCLUSIONS: The prevalence of small intrarenal arterial-arteriolar lesions was higher in IgAN patients than in non-IgAN and MN patients; moreover, the lesions in IgAN patients were associated with younger age, were more severe and exhibited a higher degree of hyaline changes. Finally, the severity of small arterial- arteriolar lesions was linked to several markers of adverse outcome.

Adult↗

PubMed2005

Proton transfer of NH3-HCl catalyzed by only one molecule.

The proton transfer in NH(3)-HCl by only one molecule of catalyst was studied by using the MP2 method with the large 6-311++G(2d,2p) basis set. The 18 structures are obtained for the smallest units, NH(3)-HCl-A trimers, for which the proton transfer maybe occurred. The final results show that the proton transfers have occurred in the 15 cyclic shape structures for A = H(2)SO(4), H(2)SO(3), HCOOH (a), HF, H(2)O(2), HNO(3), HNO(2) (a), CH(3)OH, HCl, HNC, H(2)O, HNO(2) (b), NH(3), HCOOH (b), and HCHO, and not occurred in another 3 trimer structures for A = HCN, H(2)S, and PH(3). These results show that the proton transfer occurs from HCl to NH(3) when catalyst molecule A (acidic, neutral, or basic) not only as a proton donor strongly donates the proton to the Cl atom but as an acceptor strongly accepts the proton from the NH(3) molecule in the cyclic H-bond structure. In this work, a proton circumfluence model is proposed to explain the mechanism of the proton transfer. We find that, for the trimer, when the sum of two hydrogen bond lengths (R = R(1) + R(2)) is shorter than 5.0 A, molecule A has the ability to catalyze the proton transfer. In addition, we also find that the interaction energy E(int) between NH(3)-HCl and A is nearly related to the extent (R(H1)(-)(Cl)) of proton transfer, that is, the interaction energy E(int) increases with the proton transfer.

Ammonia↗

PubMed2005

Knockdown of fibronectin induces mitochondria-dependent apoptosis in rat mesangial cells.

Extracellular matrix (ECM) expansion and mesangial cell (MC) proliferation are prominent features of most types of glomerulosclerosis. A delicate balance between the ECM and MC regulates cell survival. Increasing evidence shows that a loss of ECM components can cause mitochondrial dysfunction and induce cell apoptosis. It is proposed that directly blocking the synthesis of ECM components could lighten ECM accumulation and suppress cell overproliferation status. Fibronectin, one of the predominant adhesive glycoproteins of the mesangial ECM, provides the survival signal for cells. Its accumulation can be observed in most types of glomerulosclerosis. In this study, angiotensin II-induced fibronectin was suppressed by an RNA interference technique. It is interesting that MC slowly underwent apoptosis after infection with a retrovirus that continuously suppressed fibronectin synthesis. It was found that MC apoptosis occurred in a mitochondria-dependent manner mainly as a result of cytochrome c release and downstream caspase-3 and -9 activation. Furthermore, it was demonstrated that fibronectin knockdown affected mitochondrial handling of Ca(2+) release from the endoplasmic reticulum. Importantly, blocking the inositol 1,4,5-triphosphate receptor with, 3,4,5-trimethoxybenzoate or decreasing Ca(2+) in the ECM with EGTA partially saved the cells from apoptosis. These studies, which explored a new method for simultaneously inhibiting MC proliferation and ECM accumulation, may represent a novel therapeutic approach to glomerulosclerosis.

Animals↗