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71.
This report describes the responses of an experienced gorilla mother to inappropriate maternal behavior displayed by her young adult daughter toward a newborn baby and repeated acts of baby-transfer between these two females in a captive social group of lowland gorillas (Gorilla g. gorilla). The quality of infant care by the young adult daughter clearly improved during the first 4 days after birth, and this improvement was at least partly based on her mothers encouragement. Thus, the mothers activities can be considered scaffolding for her daughter with regard to maternal infant care. 相似文献
72.
73.
Serum-free cryopreservation of porcine hepatocytes 总被引:2,自引:0,他引:2
Müller P Aurich H Wenkel R Schäffner I Wolff I Walldorf J Fleig WE Christ B 《Cell and tissue research》2004,317(1):45-56
The use of porcine hepatocytes in xenotransplantation, bioartificial liver support or pharmacological approaches demands serum-free cryopreservation protocols yielding high quality, viable, functional hepatocytes. Here, primary porcine hepatocytes were frozen without serum in liquid nitrogen by the use of a computer-assisted freezing device. After thawing, more than 90% of the initial hepatocytes were lost, in part because of damage to genomic DNA. When cryoprotectants were used, the loss was lowered to 70% of the initial cell number; 90% of the remaining cells excluded trypan blue indicating a high degree of viability. Cells were seeded serum-free onto collagen-coated plastic dishes to determine proliferation and retainment of specific functions representing prominent features of hepatocytes in vivo. Whereas no cells adhered to the substratum effectively in conventional culture medium, the addition of conditioned medium derived from hepatic non-parenchymal cells improved attachment. Cells proliferated, retained hepatocyte-specific functions, such as urea production and cytochrome P450 activity, and expressed liver-specific genes to levels observed in non-cryopreserved hepatocytes. Thus, serum-free cryopreserved primary porcine hepatocytes may serve as a valid source of cells for downstream applications. The cells seem to function adequately when an appropriate environment is chosen for recovery after cryopreservation, an ultimate demand for the clinical application of human hepatocytes. 相似文献
74.
Synthesis and antiviral activity of P1' arylsulfonamide azacyclic urea HIV protease inhibitors 总被引:2,自引:0,他引:2
Huang PP Randolph JT Klein LL Vasavanonda S Dekhtyar T Stoll VS Kempf DJ 《Bioorganic & medicinal chemistry letters》2004,14(15):4075-4078
A series of novel azacyclic urea HIV protease inhibitors bearing a benzenesulfonamide group at P1' were synthesized utilizing a parallel synthesis method. Structural studies of early analogs bound in the enzyme active site were used to design more potent inhibitors. The effects of substituting the P1' benzenesulfonyl group on antiviral activity and protein binding are described. 相似文献
75.
Chazaud B Sonnet C Lafuste P Bassez G Rimaniol AC Poron F Authier FJ Dreyfus PA Gherardi RK 《The Journal of cell biology》2003,163(5):1133-1143
Once escaped from the quiescence niche, precursor cells interact with stromal components that support their survival, proliferation, and differentiation. We examined interplays between human myogenic precursor cells (mpc) and monocyte/macrophages (MP), the main stromal cell type observed at site of muscle regeneration. mpc selectively and specifically attracted monocytes in vitro after their release from quiescence, chemotaxis declining with differentiation. A DNA macroarray-based strategy identified five chemotactic factors accounting for 77% of chemotaxis: MP-derived chemokine, monocyte chemoattractant protein-1, fractalkine, VEGF, and the urokinase system. MP showed lower constitutive chemotactic activity than mpc, but attracted monocytes much strongly than mpc upon cross-stimulation, suggesting mpc-induced and predominantly MP-supported amplification of monocyte recruitment. Determination of [3H]thymidine incorporation, oligosomal DNA levels and annexin-V binding showed that MP stimulate mpc proliferation by soluble factors, and rescue mpc from apoptosis by direct contacts. We conclude that once activated, mpc, which are located close by capillaries, initiate monocyte recruitment and interplay with MP to amplify chemotaxis and enhance muscle growth. 相似文献
76.
Letort C Nardi M Garault P Monnet V Juillard V 《Applied and environmental microbiology》2002,68(6):3162-3165
In milk, Streptococcus thermophilus displays two distinct exponential growth phases, separated by a nonexponential one, during which proteinase synthesis was initiated. During the second exponential phase, utilization of caseins as the source of amino acids resulted in a decrease in growth rate, presumably caused by a limiting peptide transport activity. 相似文献
77.
Astrocytes,cells involved in neuro-immune interactions in the central nervous system 总被引:2,自引:0,他引:2
Giraudon P Malcus C Chalon A Vincent P Khuth S Bernard A Belin MF 《Journal de la Société de Biologie》2003,197(2):103-112
The astrocyte, the major glial cell in the central nervous system, may influence many aspects of inflammation and immune reactivity within the brain. We have established a model of chronically activated T lymphocytes, interacting with neural cells of diverse origin to study the complex immune regulatory system suspected to lead to neuroinflammatory diseases. We show that human astrocytes became reactive following T cell contact, secreting proinflammatory cytokines, matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinase (TIMP). The altered MMP/TIMP system was shown to be involved in deleterious effects displayed by activated T cells towards human multipotent neural precursers by controlling their sensitivity to T cell-induced Fas-mediated apoptosis. MMP/TIMP was suspected to stabilize Fas at the cell membrane. In a model of mixed rat glial cells in primary culture (astrocytes, oligodendrocytes), activated T lymphocytes induced the collapse of processes and the death of immature oligodendrocytes. These effects were associated with upregulation of Fas at the cell surface of oligodendrocytes and secretion of MMP and TIMP by astrocytes. By amplifying the expression of inflammatory molecules including the MMP/TIMP system, astrocytes appear to be a crucial relay in the deleterious molecular cascade triggered by activated T lymphocytes. Detection of altered MMP/TIMP in patients suffering from myelopathy associated with retroviral infection (HTLV-1) strongly suggests its involvement in the physiopathological process of the disease. 相似文献
78.
Extreme population fluctuations, or outbreaks, are driven by interacting processes that are often more complex than isolated changes in consumer or resource control. Blooms of the macroalga Caulerpa sertularioides in the eastern tropical Pacific overgrew and killed reef-building corals, with blooms onto reefs corresponding to cool La Niña phases of inter-decadal fluctuations of the El Niño–Southern Oscillation. We quantified factors responsible for the maintenance of C. sertularioides patches in off-reef areas, namely an associational mutualism with an epiphytic cyanobacteria (Lyngbya majuscula), coupled with spatial refuges at the scales of individual thalli and habitat. Maintenance of near reef algal populations with a strong response to nutrient addition showed that these populations were primed to bloom onto reefs in response to enhanced nutrient delivery, such as those potentially associated with La Niña conditions. However, our experiments demonstrated that no single factor related to consumer or resource control was likely to stimulate bloom formation in isolation. Rather, we propose a novel model of reef bloom formation where off-reef blooms are sustained by processes reducing consumer control, and then bloom onto reefs through an interaction between increased allochthonous nutrient input and an uncoupling of consumer control by an association with epiphytic cyanobacteria. 相似文献
79.
We investigated the ability of Enteromorpha intestinalis (L.) Link to take up pulses of different species of nitrogen simultaneously, as this would be an important mechanism to enhance bloom ability in estuaries. Uptake rates and preference for NH4+ or NO3− following 1, 3, 6, 9, 12 or 24 h of exposure to either 15NH4NO3 or NH415NO3 were determined by disappearance of N from the medium. Differences in assimilation rates for NH4+ or NO3− were quantified by the accumulation of NH4+, NO3−, and atom % 15N in the algal tissue. NH4+ concentration was reduced more quickly than water NO3− concentration. Water column NH4+ concentration after the longest time interval was reduced from 300 to 50 μM. Water NO3− was reduced from 300 to 150 μM. The presence of 15N or 14N had no effect on uptake of either NH4+ or NO3−. 15N was removed from the water at an almost identical rate and magnitude as 14N. Differences in accumulation of 15NH4+ and 15NO3− in the tissue reflected disappearance from the water; 15N from NH4+ accumulated faster and reached an atom % twice that of 15N from NO3−. This outcome suggested that when NH4+ and NO3− were supplied in equal concentrations, more NH4+ was taken up and assimilated. The ability to take up high concentrations of NH4+, and NO3− simultaneously is important for bloom-forming species of estuarine macroalgae subject to multiple nutrient species from various sources. 相似文献
80.
Jung CJ Iyengar S Blahnik KR Jiang JX Tahimic C Torok NJ de vere White RW Farnham PJ Zern M 《Molecular cancer research : MCR》2012,10(7):979-991
The self-renewal capacity ascribed to embryonic stem cells (ESC) is reminiscent of cancer cell proliferation, raising speculation that a common network of genes may regulate these traits. A search for general regulators of these traits yielded a set of microRNAs for which expression is highly enriched in human ESCs and liver cancer cells (HCC) but attenuated in differentiated quiescent hepatocytes. Here, we show that these microRNAs promote hESC self-renewal, as well as HCC proliferation, and when overexpressed in normally quiescent hepatocytes, induce proliferation and activate cancer signaling pathways. Proliferation in hepatocytes is mediated through translational repression of Pten, Tgfbr2, Klf11, and Cdkn1a, which collectively dysregulates the PI3K/AKT/mTOR and TGFβ tumor suppressor signaling pathways. Furthermore, aberrant expression of these miRNAs is observed in human liver tumor tissues and induces epithelial-mesenchymal transition in hepatocytes. These findings suggest that microRNAs that are essential in normal development as promoters of ESC self-renewal are frequently upregulated in human liver tumors and harbor neoplastic transformation potential when they escape silencing in quiescent human hepatocytes. 相似文献