摘要:

AbstractThe time structure of a biological system is at least as intricate as its spatial structure. Whereas we have detailed information about the latter, our understanding of the former is still rudimentary. As techniques for monitoring intracellular processes continuously in single cells become more refined, it becomes increasingly evident that periodic behaviour abounds in all time domains. Timekeeping is essential for synchronization and coordination of intracellular processes. The presence of a temperature‐compensated oscillator provides such a timer. The coupled outputs (epigenetic oscillations) of this ultradian clock constitute a special class of ultradian rhythm. These are undamped and endogenously driven by a device which shows biochemical properties characteristic of transcriptional and translational elements. Energy‐yielding processes, protein turnover, motility, and the timing of the cell division cycle processes, are all controlled by the ultradian clock. Different periods 30 min‐4h characterize different sp

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1037

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA human breast cancer cell line (MCF‐7), when sealed on confluent bovine pulmonary aortic endothelial cell (CPAE) monolayers, induced morphological changes (retraction) in CPAE cells. The area of retraction depended on the incubation time and the number of MCF‐7 cells, suggesting that MCF‐7 cells had the capacity to retract CPAE cells. This capacity was reduced by 60% by pretreatment of MCF‐7 cells with 17β‐estradiol (E) and progesterone (Pg). The extent of retraction was not affected by the addition of various protease inhibitors. CPAE retraction was induced also by adding conditioned medium (CM) from the culture of MCF‐7 cells. Considerably less activity was detected in the CM obtained from MCF‐7 cells cultured in the presence of E and Pg. The retraction was reversed in 24 h by culturing the monolayer in fresh medium without CM and was not induced by trypsin treat

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1038

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIt is known that insulin treatment increases the rate of protein synthesis in many cells and tissues and that it causes changes in the distribution of ribosomes between free (FP), cytoskeletal‐bound (CBP) and membrane‐bound polysome (MBP) populations. This paper concerns an analysis of the pattern of proteins in high‐salt extracts of FP, CBP and MBP isolated from Krebs II ascites and MPC‐11 cells. A combined detergent/salt extraction procedure was used to isolate the three fractions of polysomes from control cells and from cells following short‐term stimulation with insulin. There were differences in the protein patterns in the individual fractions and changes occurred after insulin st

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1039

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTaxol, a microtubule stabilizing agent, has been used to study changes in spindle microtubule organization during mitosis. PtK1cells have been treated with 5 μg/ml taxol for brief periods to determine its effect on spindle architecture. During prophase taxol induces microtubules to aggregate, particularly evident in the region between the nucleus and cell periphery. Taxol induces astral microtubule formation in prometaphase and metaphase cells concomitant with a reduction in spindle length. At anaphase taxol induces an increase in length in astral microtubules and reduces microtubule length in the interzone. Taxol‐treated telophase cells show a reduction in the rate of furrowing and astral microtubules lack a discrete focus and are arranged more diffusely on the surface of the nuclear envelope. In summary, taxol treatment of cells prior to anaphase produces an increase in astral microtubules, a reduction in kinetochore microtubules and a decrease in spindle length. Brief taxol treatments during anaphase through early G1promotes stabilization of microtubules, an increase in the length of astral microtubules and a delayed rate of cytokines

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1040

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe aim of the present study was to investigate the effect of maternal nicotine exposure (1 mg nicotine/kg body mass/day) on neonatal lung alveolar epithelial cells. Rats (Wistar descendants) were used. The data illustrate that maternal nicotine exposure during pregnancy and lactation resulted in alveolar fenestrations, blebbing and rupturing of the blood‐air barrier. The type I pneumocyte appears to be more sensitive to the effect of nicotine than the type II pneumocyte

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1041

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWhen ethidium bromide (EB) is combined with poly r(A‐U) at an EB/ribonucleotide ratio of 1/4, the antiviral activity of the EB increases 22‐fold. The increased antiviral activity is not due to increased interferon induction, direct viral inactivation or host cell cytotoxicity. Phase contrast, confocal and fluorescence microscopic observations reveal an increase in the nucleolar accumulation of the EB and/or the poly r(A‐U) in the EB/poly r(A‐U)‐treated fibroblasts. Ultrastructure of negatively stained and replica preparations demonstrated that EB‐induced condensation of poly r(A‐U). These results suggest the elevated antiviral activity may be related to the altered uptake and subcellular distribution of the EB/poly r

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1042

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn Na+‐ and K+‐free solution, an inward‐directed current can be detected in Xenopus oocytes, which is inhibited by cardic glycosides and activated by ATP. Therefore, it is assumed to be generated by the Na+, K+pump. At negative membrane potentials, the pump current increases with more negative potentials and with increasing [H+] in the external medium. This current is not observed when Mg2+instead of Ba2+is the only divalent cation present in the bath medium, and it does not depend on whether Na+or K+is present internally. At 5 to 10 mM Na+externally, maximum pump‐generated current is obtained while no current can be detected in presence of physiological [Na+]. It is suggested that in low‐Na+and K+‐free medium the Na+, K+pump molecule can either form a conductive pathway that is permeable to Ba2+or protons or operate in its conventional transport mode accepting Ba2+as a K+congener. A reversed pump mode or an electrogenic uncoupled Na+‐efflux mod

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1043

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1044

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1045

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1065-6995    

DOI:10.1006/cbir.1993.1046

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY