Effect on product formation in recombinant Saccharomyces cerevisiae strains expressing different levels of xylose metabolic genes

The XYL1 and XYL2 genes from Pichia stipitis encoding xylose reductase (XR) and xylilitol dehydrogenase (XDH), respectively, were transformed into Saccharomyces cerevisiae. These two genes were placed in different directions under the control of the alcohol dehydrogenase I (ADHI) and phosphoglycerate kinase (PGK) promoters and inserted into the E. coli-yeast shuttle plasmid YEp24. Different recombinant S. cerevisiae strains were constructed with different specific activities of XR and XDH. The highest XR or XDH activities were obtained when the expressed gene was controlled by the PGK promoter and located downstream after the ADHI promoter-gene-terminator sequence. The XR/XDH ratio (ratio of specific enzyme activities of XR and XDH) in these recombinant S. cerevisiae strains varied from 17.5 to 0.06. In order to enhance xylose utilization, in the XYL1, XYL2 containing S. cerevisiae strains, the native TKL1 gene encoding transketolase and the TALI gene encoding transaldolase were also overexpressed, which showed considerably good growth on the xylose plate. Fermentation of the recombinant S. cerevisiae strains containing XYL1, XYL2, TKL1, and TAL1 were studied with mixtures of glucose and xylose. The strain with XR/XDH ratio of 0.06 consumed 3.25 g/L xylose and formed no xylitol and less glycerol and acetic acid, but more ethanol compared with the strains with a higher XR/XDH ratio.

Zebrafish translation elongation factor EF1 alpha mRNA: sequence and secondary structures

We have determined the complete sequence of the translation elongation factor EF1 subunit alpha (EF1 alpha) mRNA of zebrafish, and the 3'-untranslated sequence of EF1 alpha mRNA of halibut. The 5'-untranslated leader sequence of the EF1 alpha mRNA starts with a polypyrimidine tract. This feature is shared with the mRNAs for ribosomal proteins, where it affects the utilization of mRNA by ribosomes. However, the secondary structures of these leader sequences may differ. 5'-Polypyrimidine tracts of vertebrate EF1 alpha mRNAs participate in the formation of stable stem-loop structures, whereas those of 15 randomly chosen mRNAs for ribosomal proteins do not. This difference may provide a basis for differential control of translation for the two classes of mRNA. The 3'-untranslated sequences of vertebrate EF1 alpha mRNA have diverged little during evolution. Analyses of sequence and putative secondary structures suggest that both sequence-specific interactions and secondary structures may have contributed to sequence conservation.

Inhibition of microsomal lipid peroxidation by baicalein: a possible formation of an iron-baicalein complex

Baicalein decreased the production of thiobarbituric acid reactive substances, the rate of oxygen consumption and iron reduction in the reaction system of ascorbic acid with FeCl3. Superoxide dismutase, catalase and hydroxyl radical scavengers had no significant effect. Iron-chelators had an inhibitory effect similar to that of baicalein. The production of thiobarbituric acid reactive substances of baicalein-treated microsomes obtained by centrifugation after incubation with baicalein was not observed in the reaction system, but was stimulated by adding iron with increases in concentration. The amount of bound iron to microsomal membranes increased by increasing both the concentration of baicalein and iron. The amount of baicalein bound to microsomal membranes increased with increasing concentration of added baicalein. These results suggest that baicalein bound to microsomal membranes inhibits lipid peroxidation by formating an iron-baicalein complex.

[Angioimmunoblastic lymphadenopathy and angioimmunoblastic T-cell lymphoma]

To investigate the clinicopathological changes of angioimmunoblastic lymphadenopathy (AILD) and angioimmunoblastic T-cell lymphoma (AITL), 5 cases of AILD and AITL were analyzed by using immunohistochemistry and Polymerase chain reaction (PCR) methods. The clinical manifestations included general lymphadenopathy, hepatosplenomegaly, fever and hematologic abnormalities. The diagnosis and differentiation of AILD and AITL were depended on the histopathologic features of lymphnodes biopsy. The presence of clusters of clear cells with variable atypia and positivity of T-cell marker were the most important diagnostic criterion for AITL. PCR analysis of TCR-beta rearrangement and EBV-genome was performed on 4 of 5 cases. All of the cases showed clonal rearrangement of TCR-beta and 3 of them were EBV-DNA positive. The results suggest that AILD might be a prelymphomatous lesion, related to EBV infection with a high incidence of developing to malignant lymphoma.

[Study on the interrelationship between human papilloma virus infection and Langerhans cell in carcinogenesis of esophagus]

In order to find out the interrelationship between human papilloma virus (HPV) infection and Langerhans cells (LCs) during the development of esophageal carcinoma, and the mechanism of carcinogenesis during HPV infection, digoxigenine labelled HPV DNA probes of HPV 6B/11, HPV 16/18 with in situ hybridization, and anti-S-100 protein antibody with immunohistochemical LSAB-assays were used respectively in order to investigate HPV infection and the distribution of LCs in 40 cases of esophageal squamous cell carcinoma (ESCC). The results showed that there were fewer LC infiltration in HPV-positive cases in comparison with that of the HPV-negative cases. There were also changes about the morphology and distribution of LCs in HPV infected epithelia adjacent to the tumor. The results indicated that HPV infection might inhibit the number of locally LCs infiltrated, destroy the immune surveillance system, and work simultaneously with other carcinogenic factors, in favor of the development of ESCC.

Chronic electrical stimulation of the ventralis intermedius nucleus of the thalamus as a treatment of movement disorders

Tremor was suppressed by test stimulation of the thalamic ventralis intermedius (VIM) nucleus at high frequency (130 Hz) during stereotaxy in nonanesthetized patients suffering from Parkinson's disease or essential tremor. Ventralis intermedius stimulation has since been used by the authors over the last 8 years as a treatment in 117 patients with movement disorders (80 cases of Parkinson's disease, 20 cases of essential tremor, and 17 cases of various dyskinesias and dystonias including four multiple sclerosis). Chronic electrodes were stereotactically implanted in the VIM and connected to a programmable stimulator. Results depend on the indication. In Parkinson's disease patients, tremor, but not bradykinesia and rigidity, was selectively suppressed for as long as 8 years. Administration of L-Dopa was decreased by more than 30% in 40 Parkinson's disease patients. In essential tremor patients, results were satisfactory but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their tremor. In other types of dyskinesias (except multiple sclerosis), results were much less favorable. Fifty-nine patients underwent bilateral implantation and 14 other patients received implantation contralateral to a previous thalamotomy. Thirty-seven patients (31.6%) experienced minor side effects, which were always well tolerated and immediately reversible. Three secondary scalp infections led to temporary removal of the implanted material. There was no permanent morbidity. This tremor suppression effect could be due to the inhibition or jamming of a retroactive loop. Chronic VIM stimulation, which is reversible, adaptable, and well tolerated even by patients undergoing bilateral surgery (74 of 117 patients) and by elderly patients, should replace thalamotomy in the regular surgical treatment of parkinsonian and essential tremors.

Osmotic separation of pancreatic exocrine cells from crude islet cell preparations

A novel approach is introduced here to selectively lyse exocrine cells in an islet preparation by hypo-osmotic treatment. Time to hypotonic cell lysis required for the islet cells was much longer than that for the exocrine cells, which permits a possibility of selectively killing the exocrine cells by hypotonic treatment. The first set of experiments was designed to select an appropriate osmolality for the hypotonic treatment. Kinetic changes in cell volume in response to extracellular anisosmolalities (30 to 90 mOsm/kg) were recorded using an electronic particle counter. The results indicated that, when exposed to a 30 mOsm/kg solution, islet cells swelled slowly to reach volumetric equilibrium in approximately 3 min. There was no significant hypotonic cell lysis observed even at the end of 4 min (n = 4). In contrast, pancreatic exocrine cells, when exposed to the same solution, expanded rapidly to the lytic volume and burst within 30 s. Significant exocrine cell lysis was invariably achieved within 30 s when cells were exposed to the osmolalities below 60 mOsm/kg. For osmolalities between 70 to 80 mOsm/kg, exocrine cell lysis was highly variable. When cells were exposed to 80 to 90 mOsm/kg, no significant cell lysis was observed. Thus, an osmolality of 50 mOsm/kg is recommended for hypotonic treatment, as it maximizes the lysis of exocrine cells without unnecessarily stressing (osmotically) the islet cells. The second set of experiments (time-course experiments, 20 to 120 s) was designed to determine the length of exposure time for which the exocrine cells were irreversibly damaged but the islet cells had only swollen to such a degree that cell function is restored upon returning to an isotonic condition. Viability of the hypotonic treated cells was evaluated at two different levels: membrane integrity, measured by combined fluorescent dye staining with propidium iodide (PI) and carboxyfluorescein diacetate (CFDA), and mitochondrial function, measured by colorimetric MTT assay. The results showed that hypotonic treatment in a 50 mOsm/kg solution for 30 s resulted in over 85% loss of the membrane integrity for the exocrine cells. About 90% of these membrane lysed cells lost mitochondrial function (n = 3). By contrast, under the same treatment, less than 15% of the islet cells lost membrane integrity and mitochondrial function (n = 3). In conclusion, hypotonic treatment with a 50 mOsm/kg solution for 20 to 30 s at room temperature is sufficient to lyse the majority of the contaminating exocrine cells in an islet cell preparation, while maintaining function in the islet cells.

Recovery from spinal cord injury mediated by antibodies to neurite growth inhibitors

There is little axonal growth after central nervous system (CNS) injury in adult mammals. The administration of antibodies (IN-1) to neutralize the myelin-associated neurite growth inhibitory proteins leads to long-distance regrowth of a proportion of CNS axons after injury. Our aim was: to determine if spinal cord lesion in adult rats, followed by treatment with antibodies to neurite growth inhibitors, can lead to regeneration and anatomical plasticity of other spinally projecting pathways; to determine if the anatomical projections persist at long survival intervals; and to determine whether this fibre growth is associated with recovery of function. We report here that brain stem-spinal as well as corticospinal axons undergo regeneration and anatomical plasticity after application of IN-1 antibodies. There is a recovery of specific reflex and locomotor functions after spinal cord injury in these adult rats. Removal of the sensorimotor cortex in IN-1-treated rats 2-3 months later abolished the recovered contact-placing responses, suggesting that the recovery was dependent upon the regrowth of these pathways.

APX-1 can substitute for its homolog LAG-2 to direct cell interactions throughout Caenorhabditis elegans development

The homologous LAG-2 and APX-1 membrane proteins are putative signaling ligands in the GLP-1/LIN-12 signal-transduction pathway in Caenorhabditis elegans. Normally, LAG-2 and APX-1 mediate distinct cell interactions. Here, we demonstrate that APX-1, which normally interacts with GLP-1 in the early embryo, can substitute for LAG-2 throughout development. When expressed under control of the lag-2 promoter, an apx-1 cDNA can completely rescue a lag-2 null mutant. To substitute for LAG-2, APX-1 must be able to interact with both GLP-1 and LIN-12 receptors and to mediate a variety of cell interactions during development. Therefore, APX-1 and LAG-2 are essentially equivalent in their ability to influence receptor activity. On the basis of this result, we suggest that the existence of multiple-signaling ligands in the LIN-12/GLP-1 signal transduction pathway does not reflect the evolution of functionally distinct proteins but rather the imposition of distinct controls of gene expression upon functionally similar proteins. Finally, we propose that the specification of distinct cell fates by the LIN-12/GLP-1 signal-transduction pathway relies on activities functioning downstream of the ligand and receptor, rather than on specific ligand-receptor interactions.

Protection by baicalein against ascorbic acid-induced lipid peroxidation of rat liver microsomes

The effect of baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a flavonoid isolated from Scutellaria baicalensis Georgi, on lipid peroxidation in rat liver microsomes was studied. Ascorbic acid-induced lipid peroxidation in microsomes obtained from baicalein-treated rats was inhibited by treatment on different days and at different doses. Iron release induced by ascorbic acid from microsomes of baicalein-treated rats was markedly lower than from microsomes of control rats. However, no statistical differences in total, nonheme and nonprotein-bound (free iron) iron contents could be detected in the two microsomes. The degradation of calf thymus DNA, an indicator of free iron existence, was observed in the reactions of microsomes obtained from control and baicalein-treated rats with ascorbic acid in the presence of bleomycin. These results suggest that baicalein can inhibit lipid peroxidation in microsomes induced by ascorbic acid by forming an inert complex of iron.

Water permeability and its activation energy for individual hamster pancreatic islet cells

Coupled with the rapid development of clinical pancreatic islet transplantation, there is an increasing requirement for cryopreservation of viable islets. Fundamental cryobiology requires determination of several cryobiophysical parameters to predict optimal cryopreservation procedures. These include water permeability or hydraulic conductivity (Lp) and its activation energy (Ea), the permeability of the cell plasma membrane to a cryoprotectant(s) (Ps) and its Ea, the osmotically inactive fraction of cell volume (Vb), and the intracellular ice formation temperature. For islet cells, these parameters have not previously been reported. In the present studies, the Lp, its Ea, and Vb were determined for isolated individual golden hamster pancreatic islet cells. The Lp and Vb parameters were also measured for corresponding exocrine cells. Both islet and the exocrine cells appeared to be ideal osmometers over the experimental range when examined by the Boyle Van't-Hoff relationship (linear regression, r = 0.99 for both types of cells). Extrapolation of these plots generated Vb values of 0.40 for the islet cells and 0.45 for the pancreatic exocrine cells. To determine the Lp, kinetic changes of cell volume over time (dv/dt) in response to anisoosmotic conditions (ranging from 145 mOsm/kg to 1.35 Osm/kg) were measured using an electronic particle counter. The experimental data were fitted to generate the Lp values by least-squares curve fitting to a differential equation describing osmotic water movement across the plasma membrane. For pancreatic islet cells, the Lp was determined to be 0.25 +/- 0.03 microns/min/atm (mean +/- SD, n = 14) at 22 degrees C, 0.54 +/- 0.07 (n = 10), 0.06 +/- 0.008 (n = 9), and 0.01 +/- 0.001 (n = 9) at 37, 8 and 0 degrees C, respectively. The Ea for Lp was calculated from the slope of the Arrhenius plot based upon the mean Lp values at the four different temperatures. The Ea was 16.21 Kcal/mol between 0 and 37 degrees C. Based upon these values, an optimal cooling rate for cryopreserving pancreatic islet cells is predicted to be approximately 0.5 degrees C min. The Lp for the individual exocrine cells was determined to be 3.73 +/- 1.75 microns/min/atm (n = 13) at 22 degrees C, which was approximately 10 times the Lp value of the corresponding islet cells.

High water permeability of human spermatozoa is mercury-resistant and not mediated by CHIP28

A novel integral membrane protein with an apparent molecular mass of 28 kDa (CHIP28) was first isolated from human erythrocytes and is now recognized as a water channel protein. The expression of this protein has been found in several other cell types that all require high water permeability for their functions. Recent studies have shown that the water permeability (Lp) of human spermatozoa is among the highest reported for mammalian cells. Together with the low activation energy of human spermatozoa for Lp, this suggests that CHIP28 water channel may be present in the plasma membrane of human spermatozoa. However, our current studies do not support this hypothesis. Results from Western blot analysis on human sperm plasma membrane proteins, performed through use of an antibody against human erythrocyte CHIP28 protein, indicated that human spermatozoa do not express CHIP28 protein on their cell surface (n = 10). Consistent with the Western blot finding, mercuric chloride (HgCl2), a known water channel blocker, failed to reduce the osmotic water permeability of human spermatozoa. The calculated Lp values were 1.30 +/- 0.29 micron/min/atm (n = 16; mean +/- SEM) for the control group and 1.31 +/- 0.29 (n = 9; mean +/- SEM), 1.04 +/- 0.27 (n = 11; mean +/- SEM), and 1.34 +/- 0.19 (n = 6; mean +/- SEM), respectively, for the 10 microM, 30 microM, and 50 microM HgCl2-treated groups. These Lp values are not different (p > 0.05). In contrast, the same concentration of HgCl2 significantly blocked the osmotic water transport across the membrane of human erythrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

lag-2 may encode a signaling ligand for the GLP-1 and LIN-12 receptors of C. elegans

The C. elegans lag-2 gene is required for several cell-cell interactions that rely on the receptors GLP-1 and LIN-12. In this paper, we report that lag-2 encodes a putative membrane protein with sequence similarity to Drosophila Delta, a proposed ligand for the Notch receptor. Furthermore, we show that the lag-2 promoter drives expression of a reporter protein in the signaling distal tip cell (DTC) of the DTC/germline interaction. By in situ hybridization, we have found that endogenous lag-2 mRNA is present in the DTC but not the germ line. One fusion protein, called LAG-2::beta-gal(intra), rescues a lag-2 null mutant and can be detected in both DTC and germ line. Taking these results together, we propose that lag-2 may encode a signaling ligand for GLP-1/LIN-12 and that the entire LAG-2 protein may be taken up into the receiving cell during induction by GLP-1 and lateral signaling by LIN-12.

Characterization of the synthesis and expression of the GTA-kinase from transformed and normal rodent cells

The murine transformed cell line YC-8 and beta-adrenergic receptor agonist (isoproternol) treated rat and mouse parotid gland acinar cells ectopically express cell surface beta 1-4 galactosyltransferase during active proliferation. This activity is dependent upon the expression of the GTA-kinase (p58) in these cells. Using total RNA, cDNA clones for the protein coding region of the kinase were isolated by reverse transcriptase-PCR cloning. DNA sequence analysis failed to show sequence differences with the normal homolog from mouse cells although Southern blot analysis of YC-8, and a second cell line KI81, indicated changes in the restriction enzyme digestion profile relative to murine cell lines which do not express cell surface galactosyltransferase. The rat cDNA clone from isoproterenol-treated salivary glands showed a high degree of protein and nucleic acid sequence homology to the GTA-kinase from both murine and human sources. Northern blot analysis of YC-8 and a control cell line LSTRA revealed the synthesis of a major 3.0 kb mRNA from both cell lines plus the unique expression of a 4.5 kb mRNA in the YC-8 cells. Reverse transcriptase-PCR of LSTRA and YC-8 confirmed the increased steady state levels of the GTA-kinase mRNA in YC-8. In the mouse, induction of cell proliferation by isoproterenol resulted in a 50-fold increase in steady state mRNA levels for the kinase over the low level of expression in quiescent cells. Expression of the rat 3' untranslated region in rat parotid cells in vitro led to an increased rate of DNA synthesis, cell number an ectopic expression of cell surface galactosyltransferase in the sense orientation. Antisense expression or vector alone did not alter growth characteristics of acinar cells. A polyclonal antibody monospecific to a murine amino terminal peptide sequence revealed a uniform distribution of GTA-kinase over the cytoplasm of acinar and duct cells of control mouse parotid glands. However, upon growth stimulation, kinase was detected primarily in a perinuclear and nuclear immunostaining pattern. Western blot analysis confirmed a translocation from a cytoplasmic localization in both LSTRA and quiescent salivary cells to a membrane-associated localization in YC-8 and proliferating salivary cells.

Parasexual crosses and hybrid selection with a near haploid variant of the epithelioma papulosum cyprini, cell line EPC: a tissue culture model for the analyses of dominance, recessiveness, and complementation of mutant phenotypes

We describe techniques for insertional mutagenesis of tissue-cultured piscine cells in which we use transfection with G418 and hygromycin B resistance-conferring plasmids, cell matings by electrofusion, and positive selections of fusion hybrids by dual challenge with the antibiotics G418 and hygromycin B. These techniques are designed to facilitate genetic and molecular analyses of tissue-cultured cells. The experiments were conducted with EPC-1, a new variant of the carp epithelioma cyprini cell line. EPC, with a near haploid number of chromosomes, EPC-1 retains cell morphology and growth characteristics of EPC, including anchorage independence, but shows a higher degree of contact inhibition. The number of metaphase chromosomes of EPC-1 is 53, as opposed to 96 reported for EPC.

[Cloning and expression of beta-glucosidase gene in Xanthomonas campestris XA5-5]

A beta-glucosidase gene from Xanthomonas campestris XA5-5 was cloned in Escherichia coli with the broad-host-range plasmid pRK404. The beta-glucosidase encoding plasmid designated pLZS1 contained a 1.1kb PstI DNA fragment deriving from XA5-5. The plasmid pLZS1 was transconjugated by filter mating into XA5-5 producing homologous clones XA5-5(pLZS1). Plasmid stability analysis revealed that pLZS1 was more stable in XA5-5 than in E. coli JM83. The level of beta-glucosidase expressed in XA5-5 (pLZS1) was much higher than in E. coli JM83 (pLZS1) using salicin as the substrate. From the results obtained, it seems that the gene product of this cloned DNA fragment has higher affinity to salicin substrate, and in some sense reduces the affinity between the enzyme and pNPG substrate in XA5-5.

Cryopreservation of human spermatozoa. IV. The effects of cooling rate and warming rate on the maintenance of motility, plasma membrane integrity, and mitochondrial function

OBJECTIVE

To test the hypotheses that there is a two-factor aspect of cellular damage during cryopreservation that occurs in human sperm (osmotic effects versus intracellular ice formation) and that there is a cooling rate by warming rate interaction related to this damage.

DESIGN

Ejaculates from healthy men were cooled at 0.1, 1.0, 10, 175, or 800 degrees C/min to -80 degrees C in a solution of 0.85 M glycerol and plunged into liquid nitrogen. Samples were warmed at 400 degrees C/min (experiment 1) or either 1 degrees C or 400 degrees C/min (experiment 2). After warming, sperm were assessed for survival using motility as the endpoint in experiment 1 and motility, plasma membrane integrity, and mitochondrial function in experiment 2.

RESULTS

In experiment 1, over the various cooling rates with a standard 400 degrees C/min warming rate, a plot of motility versus cooling rate produced a classical inverted U-shaped curve (n = 6) with maximum motility at the 10 degrees C/min cooling rate. In experiment 2, over the various cooling rates, both 1 and 400 degrees C/min warming rates produced similar but shifted plots of motility, plasma membrane integrity, and mitochondrial function versus cooling rate, which also produced inverted U-shaped patterns (n = 11). Maximal survival for each of the three endpoints occurred at 10 degrees C/min cooling rate for the rapidly warmed sperm and at 1 degree C/min for the slowly warmed sperm.

CONCLUSIONS

These data support the hypotheses that a two-factor hypothesis of cryodamage applies to human spermatozoa and that an interaction exists between cooling rate and warming rate. These data also suggest that motility, plasma membrane integrity, and mitochondrial function are not differently affected by cooling and warming during cryopreservation.

Recovery of function after spinal cord injury: mechanisms underlying transplant-mediated recovery of function differ after spinal cord injury in newborn and adult rats

Fetal spinal cord transplants placed into the site of spinal cord injury support axonal growth of host systems in both newborn and adult animals. The amount of axonal growth, however, is much more robust in the newborn animals. The current studies were designed to determine if the differences in the magnitude of the anatomical plasticity of host pathways in the presence of transplants is reflected in differences in recovery of function between the neonatal and adult operates. Newborn and adult rats received a midthoracic "overhemisection." Immediately following the hemisection embryonic (E14) spinal cord transplants were placed into the lesion site. All animals were trained and tested as adults, on a battery of qualitative and quantitative tests of motor function. Immunocytochemical methods were used to compare the extent of growth of descending (serotonergic and noradrenergic) and segmental (calcitonin gene-related peptide containing dorsal root axons) pathways in both groups. The growth of descending pathways into the transplants was substantially greater in density and spatial extent after lesions at birth than at maturity. The distribution of segmental dorsal root axons, in contrast, was similar in both groups. Fetal spinal cord transplants promoted recovery of motor function in both newborn and adult operates. The particular aspects of locomotor function which recover differ between the neonatal and adult operates, suggesting that the mechanisms underlying recovery of function must differ between the two groups.

Finite-element analysis of arterial anastomoses with vein, Dacron and PTFE grafts

A finite-element simulation of an end-to-end artery/graft anastomosis has been presented in this study to evaluate the distribution of compliance and stresses in the vicinity of the anastomosis due to any mismatch in compliance characteristics. The arterial wall was assumed to be made of linear isotropic elastic material in this simplified model and a static analysis was performed with a mean arterial pressure loading of the artery-graft model. Anastomoses to vein grafts and both Dacron and polytetrafluoroethylene (PTFE) grafts were studied. The results suggested the presence of a hypercompliant zone on the arterial side and a region of high tensile stresses in the wall on the graft side of the anastomosis. The presence of a hypercompliant zone has been reported from previous in vivo studies. The hypercompliance was larger with Dacron and PTFE grafts compared with that with the vein graft. However, larger tensile stresses were present in the wall of the vein graft compared with the synthetic grafts. The analysis further showed that increasing the diameter of the graft compared with the host artery to increase flow through the implant will result in a significant increase in the hypercompliance on the arterial side. Such simulation studies may prove valuable in studying the effects of compliance mismatch and suggest ways to improve the design of small diameter vascular grafts.

[Protection on experimental sinus node dysfunction in rabbits with ginsenosides]

This experiment was carried out to evaluate the effect of ginsenosides from stems and leaves (GSL) on the sinus node dysfunction (SND) by observing the changes of the electrophysiological parameters of sinus node in limited period. Anesthetized rabbits were randomly divided into 3 groups. In the acute experiment, GSL, 50 mg/kg, iv, was given to the GSL group (G), n = 12. Normal saline (NS), the same volume, to the control group (C), n = 12. After GSL was administered 30-50 mg/kg.d for 14 days, iv, another data were obtained from chronic experimental group (CE), n = 15. The results show that the parameters, spontaneous cycle length (SCL), maximal sinus node recovery time (SNRTmax), corrected sinus node recovery time (CSNRT) were shorter in G group and CE group than C group respectively (P less than 0.05, P less than 0.01). It was suggested that GSL exerted protective effects on the experimental sinus node dysfunction.