Search

Hypothermic machine perfusion (HMP) is widely used to preserve kidneys for transplantation with improved results over cold storage (CS). To date, successful transplantation of livers preserved with HMP has been reported only in animal models. In this, the first prospective liver HMP study, 20 adults received HMP preserved livers and were compared to a matched group transplanted with CS livers. HMP was performed for 3–7 h using centrifugal perfusion with Vasosol solution at 4–6◦C. There were no cases of primary non function in either group. Early allograft dysfunction rates were 5%in the HMP group versus 25% in controls (p = 0.08). At 12months, there were two deaths in each group, all unrelated to preservation or graft function. There were no vascular complications in HMP livers. Two biliary complications were observed in HMP livers compared with four in the CS group. Serum injury markers were significantly lower in the HMP group. Mean hospital stay was shorter in the HMP group (10.9} 4.7 days vs. 15.3 } 4.9 days in the CS group, p = 0.006). HMP of donor livers provided safe and reliable preservation in this pilot case-controlled series. Further multicenter HMP trials are now warranted.

The effect of Sb addition on microstructure, intermetallic compound (IMC) and mechanical properties of Sn-Ag solder joints is investigated. The compositions of selected solders are Sn2.58Ag, Sn2.82Ag1.75Sb, Sn2.87Ag4.75Sb and Sn2.7Ag8.78Sb. Experimental results show that most of the added Sb are solved in -Sn matrix, and the rest react with the Ag3Sn to form Ag3(Sb,Sn) phase, which contributes to suppress the coarsening of Ag3Sn phase. SbSn phase can be observed in β-Sn matrix as the Sb addition exceeds 4.75% and remains stable during the thermal storage test. The solder microhardness increases with increasing Sb. And the growth rate of interfacial IMC layer decreases as Sb addition increases. EPMA analysis indicates there are some Sb diffusing into the interfacial IMC layer. Shear strength of solder joints are raised by adding Sb. The shear strength by as-soldered condition are 27.8MPa (0%Sb), 29MPa (1.75%Sb), 30.4MPa (4.75%Sb) and 43.4MPa (8.78%Sb) respectively

AbstractIschemic preconditioning protects the kidney from subsequent ischemic injury but the signal transduction pathways involved are unknown. Human proximal tubular (HK-2) cells were protected from injury with 2.5 mM H2O2 by preconditioning with a single 15-min exposure to 500 μM H2O2 followed by 16 h of recovery (oxidant preconditioning). To identify the signaling pathways involved in oxidant preconditioning, we utilized inhibitors of several signaling intermediates (MAPK/ERK kinase I, p38 mitogen-activated protein kinase (MAPK), protein kinase C and tyrosine kinase). A rapid but transient increase in p38 MAPK was observed following oxidant preconditioning and an inhibitor of p38 MAPK (SB203580) abolished the protection provided by oxidant preconditioning. Oxidant preconditioning was also associated with heat shock protein-27 phosphorylation (by p38 MAPK) and an increased synthesis of heme oxygenease-1 (HO-1). Stimulation or inhibition of HO-1 with hemin or Zn(II) protoporphyrin IX, respectively, mimicked or abolished oxidant preconditioning-mediated cytoprotection. Inhibitors of new protein synthesis (cycloheximide) and gene transcription (actinomycin D) also blocked the cytoprotection by oxidant preconditioning. We conclude that oxidant preconditioning protects HK-2 cells against more severe oxidant injury via activation of signaling pathways that include p38 MAPK and increased synthesis of HO-1.Copyright © 2003 S. Karger AG, Basel

The object of the present work is to research the dissimilar welding of nickel based 690 alloy and SUS 304L stainless steel using two alternative Inconel filler metals, namely, 82 (I–82) and 52 (I–52). Gas tungsten arc welding with identical parameters and procedures was used to carry out single V groove butt welding with six passes in four layers on nickel based alloy 690 and 304L stainless steel. Mechanical and corrosion resistance tests were performed. Metallographical, fractographical, and compositional analysis were used to study filler metal dissimilarities. Mechanical tests show that the I–82 weldment, owing to its denser dendrites and formation of abundant niobium enriched precipitates, has a higher strength and hardness than the I–52 weldment. Rupture occurred in the alloy 690 base metal. In comparison, the I–52 weldment, with coarse dendrites and no niobium enriched precipitates, exhibits superior corrosion resistance to the I–82 weldment but has a lower tensile strength and ruptured in the fusion zone. Microstructural investigation reveals that I–52 is a mixture of cellular dendrites and columnar dendrites whereas I–82 is mainly columnar dendrites with niobium enriched precipitates.

The present work investigates the effects of adding different quantities of Nb (0·1, 1·03, 2·49, and 3·35 wt-%) to the flux of electrodes used in welding Inconel alloy 690 on the microstructure, mechanical properties, and corrosion behaviour of the resulting weldments. Inconel filler metal I–52 coated with flux was used as the welding electrode. Weldments were butt welded using a manual shielded metal arc welding process. The experimental results indicated that the subgrain structure of the fusion zone was primarily dendritic. Niobium was depleted at the dendritic cores and enriched in the interdendritic regions. A small heat affected zone with typical coarse grains, which subsequently formed ghost grain boundaries, was present. With increasing Nb, the welds tended to show a finer subgrain structure and smaller dendritic spacing. Niobium rich segregants in the form of small particles formed in interdendritic spaces, providing the sites for microvoid formation by rupture. Correspondingly, the tensile strength and microhardness of the fusion zone appeared to increase slightly whereas the ductility decreased significantly. However, corrosion tended to initiate on the interdendritic sites, and was worse with increasing Nb. With increasing Nb, the tensile rupture mode changed from slant (ductile) to flat (brittle) fracture.

This work investigated the weldability and mechanical properties of weldments made with Inconel filler metals I-52 and I-82 in the welding of Inconel alloy 690. Gas tungsten arc welding was used with different multipass sequences. The microstructures of the fusion and heat affected zones were examined and weldment properties were compared by tensile, hardness, and impact tests. Fracture surfaces were examined by scanning electron microscopy. Experimental results indicate that the subgrain structure near the fusion zone centreline was dominated by equiaxed dendrites in I-82 weldments but by columnar dendrites in I-52 weldments. In addition, the I-82 weldments had a finer subgrain structure near the fusion zone centreline and smaller cellular spacing near the fusion line than I-52 weldments. Mechanical test results demonstrate that the I-82 weldments had higher tensile strength (622–630 MPa) with rupture occurring in the base metal. In comparison, the I-52 weldments had lower tensile strength (568–578 MPa) and rupture occurred in the fusion zone. Filler metal I-52 showed better welding performance and greater impact toughness with only slight sensitivity to the number of passes. However, a gradual increase in the hardness of the weld was observed as the number of passes increased.

The syntheses and biological activities of a series of novel sulfonamide tetrazole derivatives are reported. The ability of these compounds to inhibit ACAT is described. Such agents may decrease the absorption of dietary cholesterol in the intestine and/or the secretion of VLDL by the liver and therefore provide a therapy for the treatment of hypercholesterolemia and atherosclerosis in man.

Prolonged tissue ischemia and subsequent reperfusion results in significant tissue injury due to the ischemic-reperfusion (IR) syndrome. Ischemic preconditioning (IPC) or adenosine (ADO) pretreatment are known to protect IR injury in cardiac muscle. Our aim was to determine whether IPC or ADO pretreatment attenuates and protects against ischemic tissue reperfusion injury in skeletal muscle. Rats were anesthetized and global hindlimb ischemia was induced by 60 min of suprarenal aortic clamping followed by 30 min of reperfusion period. The degree of skeletal muscle dysfunction was determined by decreases in maximum contractile force, and adenosine triphosphate (ATP) and creatine phosphate (CP) levels of extensor digitorum longus (EDL) muscle. The distal tendon of the EDL was attached to a force transducer for maximum isometric force measurement. Samples were taken from the EDL for measurement of ATP and CP levels. The following were protective protocols prior to the IR challenge: (1) four consecutive 5-min periods of ischemia separated by 5-min reperfusion periods (PC/I) or (2) i.v. adenosine infusion (350 μg/kg/min × 10 min, PC/A). Our data suggest that pretreatment with brief periods of ischemia or systemic ADO infusion attenuates ischemic tissue reperfusion injury in skeletal muscle [Table]

The pattern of expression for the entire α-amylase gene family in rice vegetative tissues during the developmental growth stages has been studied. We were surprised that the size of rice α-amylase mRNAs in the young roots, shoots, and different tissues from adult plant was shorter by approximately 250 bases than that in immature or mature embryos and aleurone layers of seed. Interestingly, the difference in the size of the α-amylase mRNAs of rice seed and vegetative tissues is due to the variation in the length of the 3′-poly(A) tracts. In addition, if without glycogen-precipitated treatment for alpha-amylase purification, no α-amylases can be detected in vegetative tissues by Western blot analysis. Furthermore, in vitro translation assay revealed that α-amylase mRNAs receiving shortened poly(A) tracts in vegetative tissues become translationally repressed. These results indicate that the 3′-poly(A) tract of eukaryotic mRNAs plays an important role in controlling mRNA translatability.

A rice (Oryza sativaL.) gene for α-amylase, αAmy3, was strongly and rapidly induced by treatment of suspension-cultured cells with okadaic acid (OA), a potent and specific inhibitor of protein serine/threonine phosphatases 1 and 2A. The massive accumulation of αAmy3 mRNB in response to OA treatment was due to the stimulation of gene transcription and a partial stabilization of this mRNA. This induction of αAmy3 message by OA occurred even though cellular protein synthesis was inhibited. Simultaneous treatment of cultured cells with OA and anisomycin synergistically induced αAmy3 expression. In addition, the inhibition of protein synthesis stabilized OA-induced αAmy3 mRNA. In the presence of protein kinase inhibitors H7, W7, and H8, αAmy3 mRNA accumulation induced by OA was unaffected. These results indicate that OA-dependent αAmy3 induction is regulated transcriptionally by a signal transduction pathway involving protein phosphorylation, but independent of both protein kinase C and Ca2+/calmodulin- or Ca2+-dependent protein kinases. Furthermore, an AMP-activated protein kinase may be required for this induction of αAmY3 expression.

Pluripotent stem cells have been generated from two embryonic sources: ES cells generated from ICM of blastocyst stage embryos, and embryonic germ (EG) cells generated from primordial germ cells (PGCs). Both ES and EG cells are pluripotent and exhibit important characteristics such as high alkaline phosphatase (AP) activity, multicellular colony formation, normal and stable karyotype, continuous passaging ability, and capacity to differentiate into three embryonic germ layers. This study was performed to establish the culture system for mouse EG cells derived from mouse PGCs. PGCs collected from the genital ridge of Day 11.5, 12.5, and 13.5 mouse embryos (C57BL/6 DBA/2) were cultured and subsequently passaged on mitotically inactivated STO feeder cell layer. Cells were grown in Dulbecco's modified eagle medium (DMEM) supplemented with 15% fetal bovine serum (FBS), 0.1 mM nonessential amino acids, 0.1 mM 2-mercaptoethanol, 2 mM glutamine, 100 IU/mL of penicillin, 100 ?g/mL of streptomycin, 1,000 units/mL of leukemia inhibiting factor (LIF), 6 ng/mL of SCF, and 10 ng/mL of bFGF at culture conditions of 5% CO2 in air, 95% relative humidity, 37C temperature. Cells were routinely passaged every 3?4 days. Over a period of 7?10 days in primary culture, PGCs proliferated to form small, densely packed, multicellular colonies consisting of AP-positive cells that morphologically resembled undifferentiated ES cells. RT-PCR analysis confirmed mRNA expression of transcription factors Oct-4 and Nanog in these cells. Cultured cells could be maintained on the feeder cell layer for at least 10 passages and still retain normal karyotype. These results suggest that cell lines derived from mouse primordial germ cells are presumably EG cell lines and could be useful for transgenic animal production and ES cell study.

Pluripotent stem cells have been generated from two embryonic sources: ES cells generated from ICM of blastocyst stage embryos, and embryonic germ (EG) cells generated from primordial germ cells (PGCs). Both ES and EG cells are pluripotent and exhibit important characteristics such as high alkaline phosphatase (AP) activity, multicellular colony formation, normal and stable karyotype, continuous passaging ability, and capacity to differentiate into three embryonic germ layers. This study was performed to establish the culture system for mouse EG cells derived from mouse PGCs. PGCs collected from the genital ridge of Day 11.5, 12.5, and 13.5 mouse embryos (C57BL/6 DBA/2) were cultured and subsequently passaged on mitotically inactivated STO feeder cell layer. Cells were grown in Dulbecco's modified eagle medium (DMEM) supplemented with 15% fetal bovine serum (FBS), 0.1 mM nonessential amino acids, 0.1 mM 2-mercaptoethanol, 2 mM glutamine, 100 IU/mL of penicillin, 100 ?g/mL of streptomycin, 1,000 units/mL of leukemia inhibiting factor (LIF), 6 ng/mL of SCF, and 10 ng/mL of bFGF at culture conditions of 5% CO2 in air, 95% relative humidity, 37C temperature. Cells were routinely passaged every 3?4 days. Over a period of 7?10 days in primary culture, PGCs proliferated to form small, densely packed, multicellular colonies consisting of AP-positive cells that morphologically resembled undifferentiated ES cells. RT-PCR analysis confirmed mRNA expression of transcription factors Oct-4 and Nanog in these cells. Cultured cells could be maintained on the feeder cell layer for at least 10 passages and still retain normal karyotype. These results suggest that cell lines derived from mouse primordial germ cells are presumably EG cell lines and could be useful for transgenic animal production and ES cell study.

A switch architecture is proposed for alleviating the HOL blocking by employing even/odd dual FIFO queues at each input and even/odd dual switching planes dedicated to each even/odd queue. Under random traffic, it gives 76.4% throughput without output expansion and 100% with output expansion r = 2, with the same amount of crosspoints as for the ordinary output expansion scheme.

Two head of line (HOL) packet arbitration mechanisms in an input buffered gigabit packet switch are proposed. These mechanisms have significant advantages in simple implementation while their performances still remain at acceptable levels.

The cryopreservation of sperm has contributed greatly to animal breeding and reproduction. This study was designed to examine the effect of raffinose, sucrose, and trehalose as cryoprotectants for freezing of mouse sperm. The cryoprotectant solution (CPA) consisting of 3% skim milk (Skim Milk dehydrated, Bacto, Difco, Seoul, Korea) as buffer or extender was prepared and supplemented with 0.3 M raffinose (D[+]raffinose pentahydrate, Sigma) or sucrose or trehalose as non-permeating cryoprotectants. Sperm samples for cryopreservation were collected from caudae epididymides and vas deferens of males of four mouse strains (ICR, FVB, C57BL/6, and CBA). Sperm samples from individual males were aliquoted in cryotubes, placed immediately in the vapor phase of a liquid nitrogen storage container for 10 min, and then plunged directly in liquid nitrogen. For thawing, frozen cryotubes were removed from liquid nitrogen and placed directly into a water bath kept at 37C for approximately 2 min until the ice melted. Survival of mouse sperm was measured by vital staining. Survival rates of spermatozoa frozen and thawed in freezing solution supplemented with raffinose were higher (ICR: 51.0%, FVB: 27.6%, C57BL/6: 25.7%, and CBA: 23.3%) than those supplemented with sucrose (35.8, 19.6, 12.3, and 19.7%) or trehalose (16.0, 25.4, 25.3, and 24.7%), all respectively. Furthermore, in vitro fertilization of mouse oocytes with sperm frozen in raffinose gave cleavage rates of 61.1 (FVB: 217/355 eggs), 59.4 (C57BL/6: 165/278 eggs), and 57.1% (CBA: 144/252 eggs), respectively. These cleaved embryos (FVB: 163, C57BL/6: 137, and CBA: 134) were transferred to 7, 5, and 6 pseudopregnant females, respectively. A total of 4, 3, and 4 females in the respective strains became pregnant and delivered 17 (10.4%), 17 (12.4%), and 18 (13.4%) offspring, respectively. Our results suggest that raffinose is a good cryoprotectant for freezing of sperm for production of inbred mice.

The cryopreservation of sperm has contributed greatly to animal breeding and reproduction. This study was designed to examine the effect of raffinose, sucrose, and trehalose as cryoprotectants for freezing of mouse sperm. The cryoprotectant solution (CPA) consisting of 3% skim milk (Skim Milk dehydrated, Bacto, Difco, Seoul, Korea) as buffer or extender was prepared and supplemented with 0.3 M raffinose (D[+]raffinose pentahydrate, Sigma) or sucrose or trehalose as non-permeating cryoprotectants. Sperm samples for cryopreservation were collected from caudae epididymides and vas deferens of males of four mouse strains (ICR, FVB, C57BL/6, and CBA). Sperm samples from individual males were aliquoted in cryotubes, placed immediately in the vapor phase of a liquid nitrogen storage container for 10 min, and then plunged directly in liquid nitrogen. For thawing, frozen cryotubes were removed from liquid nitrogen and placed directly into a water bath kept at 37C for approximately 2 min until the ice melted. Survival of mouse sperm was measured by vital staining. Survival rates of spermatozoa frozen and thawed in freezing solution supplemented with raffinose were higher (ICR: 51.0%, FVB: 27.6%, C57BL/6: 25.7%, and CBA: 23.3%) than those supplemented with sucrose (35.8, 19.6, 12.3, and 19.7%) or trehalose (16.0, 25.4, 25.3, and 24.7%), all respectively. Furthermore, in vitro fertilization of mouse oocytes with sperm frozen in raffinose gave cleavage rates of 61.1 (FVB: 217/355 eggs), 59.4 (C57BL/6: 165/278 eggs), and 57.1% (CBA: 144/252 eggs), respectively. These cleaved embryos (FVB: 163, C57BL/6: 137, and CBA: 134) were transferred to 7, 5, and 6 pseudopregnant females, respectively. A total of 4, 3, and 4 females in the respective strains became pregnant and delivered 17 (10.4%), 17 (12.4%), and 18 (13.4%) offspring, respectively. Our results suggest that raffinose is a good cryoprotectant for freezing of sperm for production of inbred mice.