Cytoskeletal changes during neurogenesis in cultures of avain neural crest cells

Neural crest cells are motile and mitotic, whereas their neuronal derivatives are terminally post-mitotic and consist of stationary cell body from which processes grow. The present study documents changes in the cytoskeleton that occur during neurogenesis in cultures of avain neural crest cells. The undifferentiated neural crest cells contain dense bundles of actin filaments throughout their cytoplasm, and a splayed array of microtubules attached to the centrosome. In newly differentiating neurons, the actin bundles are disrupted and most of the remaining actin filaments are reorganized into a cortical layer underlying the plasma membrane of the cell body and processes. Microtubules are more abundant in newly-differentiating neurons than in the undifferentiated cells, and individual microtubules can be seen dissociated from the centrosome. Neuron-specific beta-III tubulin appears in some crest cells prior to cessation of motility and cell division, and expression increases with total microtubule levels during neurogenesis. To investigate how these early cytoskeletal changes might contribute to alterations in morphology during neurogenesis, we have disrupted the cytoskeleton with pharmacologic agents. Microfilament disruption by cytochalasin immediately arrests the movement of neural crest cells and causes them to round-up, but does not significantly change the morphology of the immature neurons. Microtubule depolymerization by nocodazole slows the movement of undifferentiated cells and causes retraction of processes extended by the immature neurons. These results suggest that changes in the actin and microtubule arrays within neural crest cells govern distinct aspects of their morphogenesis into neurons.     

Efficacy of monensin for the prevention of subclinical ketosis in lactating dairy cows

A total of 1010 dry cows and pregnant heifers was randomly selected from 25 dairy farms near Guelph, Ontario, Canada to receive either a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving. Serum samples were obtained at the time of treatment administration, and both serum and milk samples were collected at wk 1, 2, 3, 6, and 9 postcalving. The threshold used to define subclinical ketosis was selected a priori at a concentration of > or = 1200 mumol/L of beta-hydroxybutyrate. Using this threshold, the prevalence and incidence of subclinical ketosis were significantly reduced (50%) by monensin treatment. The duration of subclinical ketosis for cows that had been treated with monensin was also shorter than that for cows treated with the placebo. Monensin treatment significantly reduced the incidence of subclinical ketosis when the threshold was defined using higher concentrations of serum beta-hydroxybutyrate (1400 and 2000 mumol/L). In addition, monensin significantly reduced the prevalence of positive milk ketone tests.     

Chronic hepatitis in children after liver transplantation: role of hepatitis C virus and hepatitis G virus infections

BACKGROUND/AIMS: Chronic graft hepatitis occurs in 20-30% adults after liver transplantation but the prevalence and causes in children are not known. In adults, hepatitis C virus infection is prevalent prior to transplantation and recurrent infection is a frequent cause of graft dysfunction. The significance of the recently described hepatitis G virus infection remains unproven. The aim of this study was to examine the role of hepatitis C virus and hepatitis G virus infection in chronic graft hepatitis after paediatric liver transplantation. METHODS: The prevalence of graft hepatitis and the role of hepatitis C virus and hepatitis G virus infections in 80 children after liver transplantation have been studied, with a median follow up of 4.4 years (range 0.4 to 10.7), and the persistence of hepatitis G infection in the presence of immunosuppression has been determined. RESULTS: Chronic graft hepatitis was diagnosed in 19/80 (24%) children and was most frequently seen in children transplanted for cryptogenic cirrhosis (71%). There was no significant difference in the prevalence of chronic hepatitis in those transplanted before or after donor anti-HCV screening. Hepatitis C infection occurred in three children transplanted prior to donor screening but in only one was associated with chronic hepatitis. Hepatitis G infection was found in 22/79 (28%) transplant recipients but was not associated with graft hepatitis. In 17/21 children hepatitis G infection persisted for a median of 5.2 years after transplantation. CONCLUSION: Chronic hepatitis occurred in 24% of children after liver transplantation, a similar prevalence to that in adults. Cryptogenic liver disease predisposed to graft hepatitis, but neither hepatitis C nor hepatitis G infection was associated. Hepatitis G virus caused a frequent and usually persistent infection after transplantation.     

Analysis of vitamin formulations by electrokinetic chromatography utilizing tetradecylammonium ions as the pseudostationary phase

A recently proposed method for the separation of fat-soluble vitamins by electrokinetic chromatography was further developed and investigated in the present study. The separation medium consisted of acetonitrile-water (80:20 v/v) and contained 80 mM tetradecylammonium bromide (TDA+); the content of acetonitrile served to maintain the hydrophobic vitamins dissolved during electrophoresis, while the TDA+ ions served as the pseudostationary phase. With the cathode placed at the outlet of the capillary, the fat-soluble vitamins were separated based on different hydrophobic interactions to the TDA+ ions and migrated in order of decreasing hydrophobicity prior to the electroosmotic flow. Migration time stability was significantly enhanced by the addition of 4 mM borate to the separation medium. The separation system was validated for the determination of vitamin E acetate in commercial tablets; quantitative results deviated by less than 3.5% from specified values, varying by less than 2.5% relative standard deviation (RSD) for within-day experiments, and by less than 6.5% RSD during between-day experiments. The separation system was compatible with injection solvents ranging in polarity from water to tetrahydrofuran, and was even capable of separating the water-soluble vitamins B1, B2, B12, and nicotinamide.     

10MeV中子引起的~（238）U，~（209）Bi，Fe和~9Be的次级中子

１０ＭｅＶ中子引起的￣（２３８）Ｕ，￣（２０９）Ｂｉ，Ｆｅ和￣９Ｂｅ的次级中子双微分截面测量祁步嘉，唐洪庆，周祖英，周陈维，沈冠仁，柯尊建，孙振强，夏海鸿（中国原子能科学研究院核物理所，北京２７５－４６信箱，１０２４１３）次级中子双微分截面是核工程设...     

Oral administration of rapamycin and cyclosporine differentially alter intestinal function in rabbits

The immunosuppressive drugs rapamycin (Rap) and cyclosporine A (CsA) are used clinically to modify or abolish immune-mediated functions. This study examined the effect of orally administered regimens of Rap, CsA, and a combination of Rap/CsA on intestinal function in male New Zealand white rabbits. Animals received oral doses of CsA (15 mg/kg/body weight/day), low-dose (LD) and high-dose (HD) Rap (0.25 or 1 mg/kg/body wt/day, respectively), or Rap/CsA (0.25 and 5 mg/kg/body wt/day, or 0.5 and 5 mg/kg/body wt/day, respectively) for 20 days. We measured in vitro uptake of nutrients and permeability, and morphometric measurements in the jejunum and ileum were made. Animals receiving HD-Rap or HD-Rap/CsA had decreased food intake, body weight, and intestinal weight, when compared with LD-Rap, LD-Rap/CsA, CsA, or controls. The maximal transport rate (Vmax) for the active jejunal uptake of D-glucose was increased in HD-Rap and CsA, but not in the HD-Rap/CsA-treated animals. The jejunal Vmax of D-glucose in the LD-Rap- or -Rap/CsA-treated animals was no different from controls. In the HD-Rap- and HD-Rap/ CsA-treated animals, jejunal rates of uptake of stearic, linoleic, and linolenic acids were reduced when compared with controls. Jejunal and ileal permeability (as assessed by the passive uptake of L-glucose, tissue conductance, and mucosal-to-serosal flux of [3H]inulin) was increased in animals treated with HD-Rap or HD-Rap/CsA, when compared with CsA or controls. These parameters of permeability were no different at lower doses of Rap or Rap/CsA. The jejunal and ileal villous surface area was increased in CsA, but decreased in HD-Rap or HD-Rap/CsA animals. Thus, HD-Rap given alone or in combination with CsA reduced body weight gain, in part due to reduced food intake and malabsorption of lipids, which was due at least in part to reduced intestinal surface area. The relevance of these findings to patients undergoing chronic immunosuppressive drug therapy needs to be established.     

Influence of Neotyphodium coenophialum on copper concentration in tall fescue

Poor performance of livestock that graze tall fescue (Festuca arundinacea Schreb.) has been associated with the endophyte fungus Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Recent evidence suggests lowered Cu status and a depression of Cu-related immune function in steers that graze endophyte-infected (E+) tall fescue. Greenhouse and field studies investigated relationships between the endophyte and Cu concentrations in tall fescue. Seventeen infected 'Kenhy' clones were divided, and one plant of each pair was treated three times with Benomyl to remove the endophyte (E-). Plants were watered with nutrient solution in a greenhouse for 6 mo before sampling. Copper concentrations were greater (P < .001) in E- than in E+ clones (3.4 vs 2.8 microg/g; SE, .06). In the second greenhouse experiment, genetically similar E+ and E- 'Kentucky'-31 (KY-31) and 'Georgia Jessup' were grown from seed and fertilized with nutrient solution to produce mature plants. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (8.6 vs 7.6 microg/g; SE, .3). In a field plot experiment in Texas, E+ and E- KY-31 were grown with 0, 50, and 100% replacement of potential evapotranspiration. By September, Cu concentrations were higher (P < .05) in E- than in E+ tall fescue (7.3 vs 6.6 microg/g; SE, .2). In pasture experiments, KY-31 E+ (> 70% infection level) and E- (< 5% infection level) tall fescue were grown in Virginia at two locations with three rates of N fertilizer. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (4.8 vs 4.5 microg/g; SE, .1) and increased (P < .01) linearly in response to N. Our data demonstrate that the presence of the endophyte is associated with lower Cu concentrations in tall fescue, which may contribute to lowered Cu status in animals and thus contribute to the etiology of fescue toxicity.     

Expression of beta 2-integrins and L-selectin on polymorphonuclear leukocytes in septic patients

Adhesion molecules on polymorphonuclear leukocytes (PMNL) play an important role in nonspecific defense mechanisms directed at invading microorganisms. When local infection, however, cannot be controlled, a systemic inflammatory response syndrome (SIRS) ensues which may progress to septic shock and multiple organ failure, these being major determinants of the patient's outcome. In the present study, the expression of beta 2-integrins and L-selectin on blood PMNL was measured on subsequent days in patients with sepsis (n = 17) and in healthy volunteers (n = 15). beta 2-Integrins and L-selectin molecules were detected by flow cytometry, using the monoclonal antibodies IB4 (anti-CD18) and Dreg200 (anti-CD62L), respectively. Adhesion molecules were determined at baseline immediately after blood collection and also 45 min after incubation of cells in vitro at body temperature to allow for spontaneous regulation. In addition, PMNL were activated by receptor-dependent and receptor-independent stimuli to characterize stimulus-specific adhesion molecule expression. In parallel with the measurement of adhesion molecules, severity of sepsis was assessed by the Elebute score. The results demonstrate significant differences in the basal, spontaneous and stimulus-induced expression of adhesion molecules between healthy volunteers, survivors (n = 11) and nonsurvivors (n = 6). Moreover, when survivors and nonsurvivors with severe sepsis (Elebute score > 12) were compared, basal expressions of both beta 2-integrins and L-selectin were significantly lower in patients who did not survive. Thus, measurement of adhesion molecules on circulating PMNL may be useful to identify septic patients at high risk for lethal outcome.     

设计沟通中的噪音——从传播学角度看设计沟通中的困难

文章从传播学的角度探讨设计沟通过程中的困难。设计沟通是贯穿于整个设计管理活动的重要环节,是传达信息的主要途径,但在实践过程中却经常遇到困难,导致设计活动无法顺利进行。文章通过引入噪音的概念,分析设计沟通的困难产生的原因,并利用传播学的理论提出通过冗余调节噪音的想法,以解决设计沟通中的问题。