The creation of diet-dependent cancer models using transgenesis in animals

We have created transgenic mice lines in which SV40 T and c-myc expression was controlled by the L-pyruvate kinase gene regulatory region which is responsible for hepatic and pancreatic expression specificity, and strong dependence of this expression upon the carbohydrate composition of the diet. Models of hepatoma and endocrine pancreatic tumors have been obtained. Both tumors were dependent upon the diet, since carbohydrates strongly increased frequency and precocity of both hepatic and pancreatic carcinomas.     

Mechanisms of the contractile effects of levosimendan in the mammalian heart

In spontaneously beating guinea pig right atria, levosimendan (LS, or R-[[-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)- phenyl]-hydrazono]propanedinitrile) exerted a positive chronotropic effect starting at 0.1 microM. In electrically driven guinea pig left atria, LS (0.1-10 microM) increased force of contraction without changing time parameters of contraction. In electrically driven right papillary muscles, LS (0.1-10 microM) enhanced force of contraction without affecting time parameters of contraction. The maximal effect on force of contraction at 10 microM amounted to 130 +/- 8.6% of predrug value. The positive inotropic effect of LS in papillary muscles was greatly diminished by additionally applied carbachol. In [32P]-labeled guinea pig ventricular cardiomyocytes, LS increased the phosphorylation state of phospholamban, the inhibitory subunit of troponin and C-protein. The maximal effect at 1 microM amounted to 134 +/- 8.6%, 124 +/- 4.2% and 121 +/- 8% of control for phospholamben, the inhibitory subunit of troponin and C-protein, respectively. LS (1 microM) increased cAMP content from 6.3 +/- 0.3 to 8.1 +/- 0.3 pmol/mg protein in guinea pig ventricular cardiomyocytes. Furthermore, whole-cell patch-clamp studies were performed in guinea pig ventricular cardiomyocytes. In this setup, 10 microM LS increased the amplitude of L-type Ca++ current to 402 +/- 86% of predrug value.     

Adenosine in the mammalian heart: nothing to get excited about

Until quite recently, the cardiodepressant actions of adenosine were widely accepted. A nucleoside that produces negative chronotropic and ionotropic effects, adenosine, has been used clinically as the drug of choice for terminating supraventricular (atrioventricular node) tachycardia and is likely to play an important part in regulating arrhythmogenic activity as an endogenous antiarrhythmic metabolite. Despite this, recent experimental data, particularly resulting from in vitro studies using animal models, have shown a paradoxical excitable action of adenosine in the heart. In this article, Amir Pelleg and Steven Kutalek present the reasons why they continue to believe that any excitatory actions of adenosine in the heart are clinically irrelevant.     

The origin of the avian germ line and transgenesis in birds

The origin of the germ cell lineage in vertebrates is a fundamental question that has preoccupied developmental biologists. Recent work on the origin of the avian germ line has extended and clarified our understanding of the temporal and spatial segregation of primordial germ cells (PGC) during prestreak stages of development. The germ cells first appear at Stage X (Eyal-Giladi and Kochav, 1976) in the ventral surface of the area pellucida in a scattered pattern among polyingressing cells. Subsequently, the PGC gradually translocate from the epiblast to the hypoblast. The entire process appears to be dependent upon the maintenance of an organized area pellucida. Little is known about the regulatory events governing germ cell emergence during this period; however, the culture of dispersed blastodermal cells on a mouse fibroblast feeder layer can compensate for a disorganized area pellucida and offers an in vitro system to examine the molecular basis of germ cell development. Such basic information is valuable for current approaches towards the production of transgenic poultry with targeted changes to the genome through the use of avian embryonic stem cells or primordial germ cells. Refinement of the culture of primordial germ cells or their precursors should allow academic and industrial research laboratories to answer significant biological questions and to improve the genetic potential of commercial poultry stocks. A better understanding of the biology of avian primordial germ cells during early embryo development can only enhance this process.     

Highly efficient lentiviral-mediated human cytokine transgenesis on the NOD/scid background

Human neo-organ formation from stem cells can only be assayed by in vivo xenotransplantation. The human nonobese diabetic-severe combined immunodeficient (HuNOD/scid) CD34+ cell transplantation is a model that allows examination of hematopoietic tissue formation, although human hematopoietic cell maturation is abortive. Conventional humanization of the cytokine microenvironment has depended on generation of human cytokine-transgenic mice in strains appropriate for conventional plasmid microinjection, followed by backcrossing, a costly and time-consuming approach. Lentiviral vector infection of single-cell embryos was recently reported to produce transgenic animals. Using this approach, we have generated direct human granulocyte-macrophage colony-stimulating factor (hGM-CSF) transgenic mice from lentivirus-microinjected NOD/scid embryos, with 68% efficiency and 100% penetrance; this allowed us to obtain NOD/scid transgenic mice with considerable savings of resources. This powerful technique should assist in producing novel mouse models for the study of human blood cell lineage development and other human neo-organs from stem cell xenotransplantation for which a similar "humanization" rationale may be required.     

电炉炉盖旋转及提升装置改造

针对宝钢电炉炉盖旋转及提升装置改进维修项目,分析了存在的问题及原因,提出改进设计方案并实施,获得了成功.     

Total artificial heart using neural and fuzzy controller

We investigated the effects of 10 phospholipids on the in vitro percutaneous penetration of prednisolone (PR) through the dorsal skin of guinea pigs. A marked enhancing effect of PR penetration was observed in the presence of phospholipids that have unsaturated acyl chains. A maximum of 68-fold enhancement was observed compared to that of control. On the contrary, phospholipids that have saturated acyl chains did not significantly increase the amount of PR passing to the receptor side. Attenuated total reflectance-Fourier transform infrared spectroscopy was used to monitor the outer several microns of stratum corneum (SC) surface. It was observed that phospholipids that have unsaturated acyl chains induced higher and broader absorbance shifts in the C-H bond stretching region while phospholipids that have saturated acyl chains induced lower and sharper absorbance shifts in the C-H bond stretching region. A significant parallel between the amount of PR penetrated and the lipid-chain fluidity of the SC was found. These results suggest that phospholipids may influence the percutaneous penetration of PR by changing the lipid-chain fluidity of the SC.     

Studies on the toxic effects of streptolysin ''O'': effect on the contractility of isolated and intact mammalian and amphibian heart

The effect of streptolysin O (a streptococcal exotoxin) on the myocardial contractility of isolated and intact mammalian and amphibian heart has been investigated. Streptolysin O caused marked reduction or complete cessation of myocardial contractility of mammalian and amphibian heart both in vivo and in vitro. The effect of submaximal doses of streptolysin O on isolated atria was reversible after repeated washings and the myocardial depressant effect of streptolysin O on isolated atria was reversible after repeated washings and the myocardial depressant effect of streptolysin O was not antagonised by atropine. These observations would suggest that streptolysin O is cardiotoxic and may be involved in the causation of myocardial failure associated with acute rheumatic fever in man.     

PASting together the mammalian clock

Over the past year, the first components of the mammalian clock have been identified; Clock, bmal1 and three homologs of Drosophila period have been cloned, all of which encode PAS proteins. Expression of the mammalian period gene oscillates in many tissues in vivo and in immortalized cell cultures in vitro. Now, can we say that every cell has a circadian clock?     

S112混砂机的技术改造

本文介绍了S112混砂机技术改造的方案，内容及其主要特征等。     

Mannose enters mammalian cells using a specific transporter that is insensitive to glucose

The concentration of D-mannose in serum is 20-50 micron, but its physiological significance for glycoprotein synthesis is unknown. Here, we show that the uptake of D-mannose by different mammalian cell lines involves a mannose-specific transporter(s) with a K(uptake) of about 30-70 micron and a V(max) which is probably sufficient to account for the bulk of mannose needed for glycoprotein synthesis. Mannose uptake appears to be through a facilitated transport process since it is not inhibited by cyanide. Phloretin completely inhibits mannose uptake, but phloridzin inhibits only 25-30%. Both of these inhibitors can block 2-deoxyglucose uptake in fibroblasts which occurs through the typical glucose transporters. None of 9 other sugars tested inhibited mannose transport. Most importantly, 5 mM D-glucose only inhibits mannose uptake by 50% showing that it is not an efficient competitor. These results suggest that this transporter(s) may use serum mannose for glycoprotein synthesis.     

Feedback regulation of mammalian ornithine decarboxylase. Studies using a transient expression system

Ornithine decarboxylase catalyzes the first step in the biosynthesis of polyamines in mammalian cells. The enzyme is subject to various control mechanisms to maintain adequate intracellular levels of polyamines. Polyamines exert a strong feedback control on ornithine decarboxylase. In a recent study [van Daalen Wetters, T., Macrae, M., Brabant, M., Sittler, A. & Coffino, P. (1989) Mol. Cell. Biol. 9, 5484-5490], it was concluded that feedback control of ornithine decarboxylase is mainly, if not exclusively, a posttranslational phenomenon. The existence of a fast-acting polyamine-stimulated component of ornithine decarboxylase degradation that acts on newly synthesized monomeric forms of the enzyme was postulated. In the present study we have used a transient expression system to test this hypothesis. The expression of ornithine decarboxylase in mock-transfected COS cells varied depending on the cellular supply of polyamines as has been found in other mammalian cells. Thus, supplementing the cells with exogenous spermidine resulted in a marked decrease in ornithine decarboxylase activity, whereas depletion of intracellular polyamines, using an ornithine decarboxylase inhibitor, gave a large increase in the cellular content of the enzyme. COS cells expressing an ornithine decarboxylase mRNA devoid of its 5' non-translated region did not exhibit any feedback control of the enzyme, neither in the presence of exogenous spermidine nor when the intracellular polyamine levels were depleted to the same extent as in the mock-transfected COS cells. The results strongly suggest that the feedback control of ornithine decarboxylase is not merely a posttranslational phenomenon.     

Initial experience using an intraluminal shunt during revascularization of the beating heart

BACKGROUND: For decades, surgeons have relied on extracorporeal circulation and induced cardiac asystole to provide a bloodless, motionless field in which to construct coronary bypass grafts. However, the technique of coronary grafting without heart-lung support is now being revitalized. The current resurgence of off-pump coronary artery bypass grafting and the advent of less invasive incisions make it imperative that technical advances be applied to maximize the safety of these procedures. METHODS: This report describes an inexpensive intraluminal shunt that maintains coronary perfusion, prevents ischemia, reduces backbleeding, and molds the suture line to prevent accidental missuturing of the posterior coronary wall. RESULTS: In 63 patients, saphenous grafts were placed to the left anterior descending (49), diagonal (9), and right coronary artery (27) without extracorporeal circulation using an intraluminal shunt. There were no deaths (0% mortality) and one perioperative infarction (1.5%). Complication and graft patency rates were comparable with those obtained by conventional techniques. CONCLUSIONS: Temporary intraluminal shunting greatly facilitates the surgeons' operative environment by permitting safe and precise construction of coronary artery grafts on the beating heart in a bloodless field. Intraluminal shunting may have future implications on the ability to perform safe and reproducible grafting on the beating heart through minimally invasive or endoscopic approaches.