Opening angles and residual strains in normal rat trachea

The no-load state and zero-stress state o1 the normal rat trachea were analyzed. It was found that there exist compressive residual strains in the inner wall region of the rat trachea and tensile residual strains in the outer wall region. The fact that the opening angle of the rat trachea cut at the cartilaginous region is significantly larger than that cut at the muscular portion shows that residual strains exist mainly in the muscular region in the rat trachea. It was also indicated that the opening angles and residual strains expressed by cutting at the muscular portion are basically identical along longitudinal location and those expressed by cutting in the cartilaginous region tend to increase in the longitudinal direction in the normal rat, and that there exists quantitatively positive correlation between the opening angles and residual strains in rat trachea. The results will help to further understand the opening angles and residual strains in the trachea and study tracheal remodeling in response     

A Preliminary Study of the Noninvasive Remote Control System for Rat Bio-Robot

<正> A system is described here that can noninvasively control the navigation of freely behaving rat via ultrasonic,epidermaland LED photic stimulators on the back.The system receives commands from a remote host computer to deliver specifiedelectrical stimulations to the hearing,pain and visual senses of the rat respectively.The results demonstrate that the three stimuliwork in groups for the rat navigation.We can control the rat to proceed and make right and left turns with great efficiency.Thisexperiment verified that the rat was able to reach a setting destination in the way of cable with the help of a person through theappropriate coordination of the three stimulators.The telemetry video camera mounted on the head of the rat also achieveddistant image acquisition and helped to adjust its navigation path over a distance of 300 m.In a word,the non-invasive motioncontrol navigation system is a good,stable and reliable bio-robot.     

Characterisation of the low affinity interaction between rat cell adhesion molecules CD2 and CD48 by analytical ultracentrifugation

CD2 is a cell adhesion molecule found on the plasma membrane of T-lymphocytes. Its counter-receptor in rat is the structurally related CD48. This interaction is believed to contribute to the adhesion of T-cells to other cells such as cytotoxic targets and antigen presenting cells. Cell-cell adhesion involves the formation of multiple cell adhesion molecule complexes at the cell surface and if cell-cell de-adhesion is to occur, these complexes need to be disrupted. The affinities of cell adhesion molecule interactions are suggested to be relatively weak to allow this de-adhesion of cell-cell interactions. The CD2/CD48 interaction has been studied using recombinant extracellular proteins and the affinity of the interaction of soluble recombinant rat CD2–CD48 has been determined (at 37°C) using surface plasmon resonance (and shown to be weak), with the dissociation constant K_d=60–90 μm. The values determined by surface plasmon resonance results could be affected by the immobilisation of the ligand on the chip and any self-association on the chip. We used three different analytical ultracentrifuge procedures which each allowed the interaction to be studied in free solution without the need for an immobilisation medium. Both sedimentation equilibrium (using direct analysis of the concentration distribution and also modelling of molecular weight versus concentration data) and sedimentation velocity at 5°C yielded dissociation constants in the range of 20– 110 μm, supporting the surface plasmon resonance findings showing that binding between these cell adhesion molecules is relatively weak. These studies also ruled out the presence of any significant self-association of the reactants which could lead to systematic error in the surface plasmon resonance results. Accepted: 19 November 1996     

Phenolsulfonphthalein (phenol red) metabolism in primary monolayer cultures of adult rat hepatocytes

Summary The sulfonic acid dye, phenolsulfonphthalein (PSP or phenol red), has been incorporated as a pH indicator in many tissue culture media formulations since the emergence of tissue culture methodologies. The present study was designed to examine the pathway, time course, and degree of metabolism of this anionic dye in monolayer cultures of adult rat hepatocytes. Thin layer chromatographic studies coupled with β-glucuronidase studies show that glucuronidation is the major metabolic pathway for PSP in vitro. About 20% of the dye is metabolized in the first 24 h, but this functional activity is decreased by approximately half at 48 h, and even further at 72 h of culture. This metabolic activity was not affected by continuous exposure to the dye. The effect of PSP concentration on its rate of metabolism by the adult rat hepatocyte in culture seemed to be biphasic, and at concentrations of less than 100μM there was indication of a saturable process. Although PSP seemed not to be toxic to hepatocyte cultures, it is partially metabolized by these cells (as opposed to no observed metabolism in human fibroblasts or HeLa cells). Therefore, its incorporation into tissue culture media formulations for use in hepatocyte cultures should be avoided, especially when studying the mechanism(s) of glucuronidation or metabolic pathways thought to be affected by this anionic dye. This study was supported in part by NIH Grants HL-11945-11 and 1 R01 AM 26520-01A1.     

Proteome analysis of hepatic non-parenchymal cells of immune liver fibrosis rats

Elucidation of the mechanisms of liver fibrogenesis is important to treat liver fibrosis.In this study,we established rat models of liver fibrosis with stages from 0–1,2,and 3–4 to 4 at 2,4,6,and 8 weeks,respectively,by injection of pig serum.Liver fibrogenesis was detected by Masson’s trichrome staining.Rat non-parenchymal cells(NPCs)were enriched 4-fold by Percoll density gradient centrifugation.Protein extracts from NPCs were prepared at 4 and 8 weeks,separated by two-dimensional electrophoresis,and then stained with Coomassie Blue G-250.At 4 weeks,we identified 18 non-redundant differentially expressed proteins of which protein disulfide-isomerase associated protein 3(PDIA3)and NDUV showed consistent expression at protein and mRNA levels from 4 to 8 weeks.PDIA3 was found to be down-regulated by Western blotting in the rat model and immunohistochemically in human liver.Our results revealed important aspects of the pathogenesis/progression of liver fibrosis and demonstrated important changes in protein expression levels of NPCs at various stages of liver fibrosis.     

Studies on the mitogenic effect of transferrin by membrane signal transduction

One of the earliest events leading to cell activation and growth is the hydrolysis of inositol phospholipids producing various membrane signals induced by an interaction between growth factors or hormones with their respective receptors on the cell membrane [1].To demonstrate the mitogenic action of transferrin,our results show that an addition of transferrin to “serum-deprived” rat hepatoma cells produced a rapid but transient rise in inositol 1,4,5-trisphosphate(IP3) level,and at the same time,an increased intracellular Ca^2 activity and a cytoplasmic alkalinization were observed.These signal transductions further lend support to the mitogenic nature of transferrin.In addition,a possible link between the receptor-mediated endocytosis of transferrin with the generation of intracellular signals is discussed herewith.     

Recording of calcium transient and analysis of calcium removal mechanisms in cardiac myocytes from rats and ground squirrels

With confocal microscopy, we recorded calcium transients and analyzed calcium removal rate at different temperatures in cardiac myocytes from the rat, a non-hibernator, and the ground squirrel, a hibernator. The results showed a remarkable increase of the diastolic level of calcium transients in the rat but no detectable change in the ground squirrel. Calcium transient of the ground squirrel, compared with that of the rat at the same temperature, had a shorter duration and showed a faster calcium removal. As indicated by the pharmacological effect of cyclopiazonic acid, calcium uptake by sarcoplasmic reticulum (SR) was the major mechanism of calcium removal, and was faster in the ground squirrel than in the rat. Our results confirmed the essential role of SR in hypothermia-tolerant adaptation, and negated the importance of Na-Ca exchange. We postulated the possibility to improve hypothermia-tolerance of the cardiac tissue of non-hibernating mammals.     

Cloning, structural organization and chromosomal mapping of rat costimulatory molecule 4-1BBL

4-1BBL （TNFSF9） is a member of the tumor necrosis factor （TNF） ligand superfamily, which is expressed on some activated antigen presenting cells and B cells. We isolated a rat cDNA clone encoding the rat homologue of the human 4-1BBL （GenBank accession No. AY259541）. The deduced rat 4-1BBL protein, consisting of 308 amino acids with a molecular weight of 33,469 Da, was a typical type II transmembrane glycoprotein, the same as human and murine 4-1BBL. “SDAA” in the cytoplasmic domain of rat 4-1BBL was deduced to act as the phosphorylation site for casein kinase I （“SXXS” motif）, which is present in the cytoplasmic domains of human and murine 4-1BBL, and all other TNF ligand family members known to utilize reverse signaling. The two introns of 4-1BBL were also cloned （GenBank accession No. AY332409）. Rat 4-1BBL is much more homologous with murine 4-1BBL than with human 4-1BBL, in both nucleotide and amino acid sequences. Rat 4-1BBL was expressed in all tested tissues： brain, lung, colon, liver, thymus, testicle, kidney, adrenal, stomach, spleen and heart. The chromosomal location of rat 4-1BBL was first identified by bioinformatics, then by fluorescence in situ hybridization at 9q11 （GenBank accession UniGene No. Rn.46783）. Rat, murine and human 4-1BBL genes are evolved from a common gene. The identification and characterization of the rat counterpart of human 4-1BBL will facilitate studies of the biological function of this molecule.     

The presence of ANP in rat peritoneal mast cells

Atrial natriuretic peptide （ANP） is an important component of the natriuretic peptide system. A great role in many regulatory systems is played by mast cells. Meanwhile involvement of these cells in ANP activity is poorly studied. In this work, we have shown the presence of ANP in rat peritoneal mast cells. Pure fraction of mast cells was obtained by separation of rat peritoneal cells on a Percoll density gradient. By Westem blotting, two ANP-immunoreactive proteins of molecular masses of 2.5 kDa and 16.9 kDa were detected in lysates from these mast cells. Electron microscope immunogold labeling has revealed the presence of ANP-immunoreactive material in storage, secreting and released granules of mast cells. Our findings indicate the rat peritoneal mast cells to contain both ANP prohormone and ANP. These both peptides are located in mast cell secretory granules and released by mechanism of degranulation. It is discussed that many mast cell functions might be due to production of natriuretic peptides by these cells.     

Human augmenter of liver regeneration: molecular cloning, biological activity and roles in liver regeneration

The complete amino acid sequence of human augmenter of liver regeneration (hALR) was reported by deduction from nucleotide sequence of its complementary DNA . The cDNA for hALR was isolated by screening a human fetal liver cDNA library and the sequencing of this insert revealed an open reading frame encoding a protein with 125aa and highly homologous (87% ) with rat ALR encoding sequence. The recombinant hALR expressed from its cDNA in transient expression experiments in cos-7 cells could stimulate DNA synthesis of HTC hepatoma cell in the dose-dependent and heat-resistant way. Northern blot analysis with rat ALR cDNA as probe confirmed that ALR mRNA was expressed in the normal rat liver at low level and that dramatically increased in the regenerating liver after partial hepatectomied rat. This size of hALR mRNA is 1.4 kb long and expressed in human fetal liver, kidney and testis. These findings indicated that liver itself may be the resource of ALR and suggested that ALR seems to be an im-portant parac     

Retake the center stage--new development of rat genetics

The rat is a powerful model for the study of human physiology and diseases,and is preferred by physiologists,neuroscientists and toxicologists.However,the lack of robust genetic modification tools has severely limited the generation of rat genetic models over the last two decades.In the last few years,several gene-targeting strategies have been developed in rats using N-ethyl-N-nitrosourea(ENU), transposons,zinc-finger nucleases(ZFNs),bacterial artificial chromosome(BAC) mediated transgenesis,and recently established rat embryonic stem(ES) cells.The development and improvement of these approaches to genetic manipulation have created a bright future for the use of genetic rat models in investigations of gene function and human diseases.Here,we summarize the strategies used for rat genetic manipulation in current research.We also discuss BAC transgenesis as a potential tool in rat transgenic models.     

The effects of cell density, attachment substratum and dexamethasone on spontaneous apoptosis of rat hepatocytes in primary culture

Summary The rates of spontaneous cell detachment, cell viability, and apoptosis in primary cultures of rat hepatocytes plated at high and low density were compared. Apoptosis was frequent in detached cells, and the rates of cell detachment and apoptosis were greater in high-density than in low-density cultures. Among attached cells, more cells had condensed or fragmented nuclei in high-density than in low-density cultures. Further, ladder-like DNA fragmentation was not seen in low-cell-density cultures but was clearly evident in high-density cultures. Bax was more highly expressed in cells cultured at high density, and on collagen vs. matrigel, whereas changes of Bcl-2 and Fas expression observed in culture appeared unrelated to the rate of apoptosis. The rate of hepatocyte apoptosis appeared to be identical in low-density cultures on collagen 1 and matrigel, but when cells were cultured at high density, matrigel suppressed apoptosis by more than 50% at 36 h. In hepatocytes cultured on collagen 1, dexamethasone (0.1 μM) suppressed apoptosis in both low- and high-density cultures; higher doses had no further effects. In high density cultures, aurintricarboxylic acid (10 μM) suppressed apoptosis and this improved cell attachment at 48 h. It is concluded that cell viability in primary cultures of rat hepatocytes grown on collagen I is dependent on optimal culture density and that the cell population is regulated, at least in part, by apoptosis. Corticosteroids suppress spontaneous apoptosis of cultured hepatocytes in a non-dose-dependent manner, whereas matrigel abolishes apoptosis induced by increasing cell density. Bax may be an important protein in the cell density and cell matrix-dependent regulation of apoptosis in cultured hepatocytes.     

Construction of a small-caliber tissue-engineered blood vessel using icariin-loaded β-cyclodextrin sulfate for in situ anticoagulation and endothelialization

The rapid endothelialization of tissue-engineered blood vessels(TEBVs) can effectively prevent thrombosis and inhibit intimal hyperplasia. The traditional Chinese medicine ingredient icariin is highly promising for the treatment of cardiovascular diseases.β-cyclodextrin sulfate is a type of hollow molecule that has good biocompatibility and anticoagulation properties and exhibits a sustained release of icariin. We studied whether icariin-loaded β-cyclodextrin sulfate can promote the endothelialization of TEBVs. The experimental results showed that icariin could significantly promote the proliferation and migration of endothelial progenitor cells; at the same time, icariin could promote the migration of rat vascular endothelial cells(RAVECs). Subsequently,we used an electrostatic force to modify the surface of the TEBVs with icariin-loaded β-cyclodextrin sulfate, and these vessels were implanted into the rat common carotid artery. After 3 months, micro-CT results showed that the TEBVs modified using icariin-loaded β-cyclodextrin sulfate had a greater patency rate. Scanning electron microscopy(SEM) and CD31 immunofluorescence results showed a better degree of endothelialization. Taken together, icariin-loaded β-cyclodextrin sulfate can achieve anticoagulation and rapid endothelialization of TEBVs to ensure their long-term patency.     

The cloning and expression characterization of the centrosome protein genes family (centrin genes) in rat testis

Centrins are members of the centrosome protein family, which is highly conserved during revolution. The homologous genes of centrin in many organisms had been cloned, but the sequences of the rat centrin genes were not reported yet in GenBank. We cloned the cDNA fragments of centrin-1, -2 and -3 from the rat testis by RT-PCR, and analyzed the homology of the deduced amino acid sequences. The expression characterization of centrin genes in rat spermato-genesis was carried out by semi-quantitative RT-PCR. The results show that the homology of the corresponding centrin proteins in human, mouse and rat is high. The expression of centrin-1 is testis-specific, spermatogenic cell-specific and developmental stage-related. Centrin-1 begins to be transcribed when the meiosis occurs, and its mRNA level reaches the peak in round spermatids. Centrin-2 and centrin-3 are highly expressed in spermatogonia and their mRNA level decreases markedly when meiosis occurs. These results suggest that centrin-1 may play roles in     

Fluid Dynamics of Flapping Insect Wing in Ground Effect

The fluid dynamics of flapping insect wing in ground effect is investigated numerically in this study. To model the insect wing cross-section in forward-flight mode, the laminar flow over a NACA0012 airfoil animated by a combination of harmonic plunge and pitch rotation is considered. To implement the simulation, the proposed immersed boundary-lattice Boltzmann method is employed. By fixing the Reynolds number and the amplitude of motion, we systematically examine the influences of the distance between the foil and the ground and the flapping frequency on the flow behaviors. As compared to the situation out of ground effect, the forces for foil placed in close proximity to the ground show some differences. The mean drag coefficient is increased at low frequency and decreased at high frequency. Meanwhile, the mean lift coefficient is increased at both low and high frequencies and decreased at middle frequency. Moreover, an interesting phenomenon with oblate vortices due to vortex interaction with the ground is observed.     

Selenomethionine induces polyamine biosynthesis in regenerating rat liver tissue

Summary. Our study was undertaken to elucidate the effects of selenomethionine (SeMet) on polyamine metabolism in regenerating rat liver tissue, as useful model of rapidly growing normal tissue. We have examined the levels of spermine, spermidine and putrescine in liver tissue. At the same time we have evaluated the activities of polyamine oxidase (PAO) and diamine oxidase (DAO), the catabolic enzymes of polyamine metabolism. The obtained results suggest that polyamine levels in regenerating liver tissue, at 7^th day after two-thirds partial hepatectomy, were higher in comparison with control group. The administration of selenomethionine to hepatectomized animals during seven days, in a single daily dose of 2.5 μg/100 g body weight, increases the amount of spermine and spermidine; the level of putrescine does not change under the influence of SeMet in regenerating rat liver tissue. PAO activity is lower in regenerating hepatic tissue than in control group. Supplementation of hepatectomized animals with SeMet significantly decreases the activity of this enzyme. DAO activity was significantly higher in hepatectomized and in operated animals treated with SeMet compared to the sham-operated and control ones. The differential sensitivity observed in our model of highly proliferating normal tissue to SeMet, compared with the reported anticancer activity of this molecule is discussed.