摘要:

AbstractBeating of cilia and flagellae allows movement of the fluid surrounding isolated cells (for example: protists) or epithelia (bronchial tissue) but is also responsible for the movement of unicellular organisms in this medium (such as spermatozoa or protists). This paper aims to describe: (1) the biochemical and structural elements of the ‘9 +2’ structure called the axoneme; (2) the mechanisms of wave generation and propagation along the axoneme of cilia and flagellae are then described, stating that in most models of wave propagation, a clear distinction is made between the dynein‐dependent microtubule sliding which represents the oscillatory motor and the bending mechanism which regulates wave propagation. In current models, the bending propagation is supported by a bind /relax cyclic mechanism which propagates in register, but frame‐shifted, with the powering action of the dynein motor along the axoneme. While a large amount of knowledge was accumulated about the motor, little is known about the resisting elements regulating the bending. (3) The present study also puts forward ideas as to how these organelles have been highly conserved throughout eucaryotic evolution, and concludes with suggestions for further fields of investigation into this unique mechanical device used for cell m

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0012

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAn investigation into the development of the Vervet monkey endocrine pancreas revealed a sequence of occurrence of pancreatic peptides that differed from previous reports in mice, dog and human with PP and somatostatin occurring before glucagon and insulin. All four pancreatic peptides were identified, immunohistochemically, in only one of the pancreatic primordial buds, before fusion of the two buds to form the pancreas. This questions the hypothesis that the heterogeneous endocrine cell distribution seen in the adult pancreas is due to the contribution of only PP cells by the ventral bud and non‐PP cells by the dorsal bud. Co‐localization of glucagon and PP was observed extensively in the developing pancreas and the predominant expression of one over the other in an apparently organized non‐random manner accounted for the glucagon‐ and PP‐rich areas seen in the developing pancreas. A small number of cells immunoreactive to glucagon and PP were also observed in the adult. Reports of plasticity of differentiation of other pancreatic cells led us to investigate regeneration potential of the adult monkey pancreas. Partial obstruction of the Vervet monkey main pancreatic duct, by cellophane wrapping, resulted in duct cell proliferation and differentiation to form new endocrine tissue in a way that mimics normal organogenesis. Focal areas of hepatocytes were found in the regenerated pancreas of one monkey, illustrating further the latent developmental capabilities of adult pancreas cells. These findings could lead to interesting new therapies for pancreas and live

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0013

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractElectron probe X‐ray microanalysis has been used for the last 25 years by biologists to obtain information about the distribution of elements at the cell and tissue level. During this period, progress has mainly been made through the development of more adequate techniques for specimen preparation (mainly low temperature techniques) and quantitative analysis, so that accurate analysis of the physiologically important cellular ions can be carried out. Use ofin vitrosystems and cell cultures may further increase the number of problems to which X‐ray microanalysis can be applied. Among the numerous applications of X‐ray microanalysis in cell biology and cell pathology, applications in the areas of epithelial ion transport, the role of calcium in secretory and contractile cells, and the role of ions in cell proliferation and cancer are discussed in more d

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0014

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe importance of the dendritic cell for the capture of antigens and initiating an immune response is now well recognized. Whereas much is known about their structure and function, their lineage is still not clear. Studiesin vitrohave demonstrated that the regulated maturation of function that occurs in culture explains many of thein vivoevents relating to antigen capture and presentation. The control over maturation and migration of these cells to the immune system is decisive as to whether an immune response is mounted or not. ‘Danger ’ signals provided by conserved bacterial products or by microenvironmental cytokines are important regulators. Dendritic cells have been clearly involved in the development of respiratory disease and our understanding of their involvement will have an impact on our future therapeutic strateg

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0015

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractGap junctional communication plays a vital role in embryogenesis, cell differentiation and the co‐ordination of tissue responses. Gap junctions are formed by a family of closely‐related proteins called connexins which show tissue‐specific patterns of expression. The role of gap junctions in the mammary gland remains unclear. The lumena of mammary gland ducts are lined by luminal cells with an outer layer of basal cells. In rodents, the luminal cells express connexin26 only during pregnancy and lactation and the basal cells, in some reports, express connexin43. In the normal human breast the basal cells express connexin43, although human mammary epithelial cellsin vitrohave been reported to express both connexin26 and connexin43. Analysis of connexin expression at the molecular level is now bringing new insights into the structure and function of gap junctions in a range of normal and pathological cell sy

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0016

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractIf the plasma membrane and its associated transport proteins are solely responsible for maintenance of the asymmetric solute distribution then disruption of the plasma membrane would quickly lead to the symmetric distribution of all unattached inorganic ions between the cell and the extracellular environment. To test this hypothesis fresh pig lenses were incubated in Hanks ’ balanced salt solution in either absence or presence of non‐ionic detergents (0.2 % Triton X‐100 or 0.2 % Brij 58). Both detergents caused permeabilization of every lens fiber cell as shown by electron microscopy. The flux kinetics of K+, Mg2 +, Na+, Ca2 +, water and protein out of and into the permeabilized lens fiber cells was measured. Triton X‐100 caused a faster flux rate of all solutes than did Brij 58. The Triton X‐100 induced flux of solutes and water was associated with a decrease in lens ATP. Incubation of untreated lenses in solutions of different osmotic pressures at 0 °C demonstrated that the major fraction of lens water was osmotically unresponsive. Thus the asymmetric distribution of solutes in lens fiber cells is dependent on an intact plasma membrane and on a co‐operative ATP‐dependent association between K+, Mg2 +, water and cytom

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0017

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractDespite significant advances in our understanding of the roles of the cytoskeleton and matrix receptors in cell locomotion, derived largely fromin vitrostudies on the movement of epithelial cell sheets and isolated cells, the mechanism of epithelial cell migration in the adult intestine remains an enigma. The primary function of the epithelial cell cytoskeleton seems to be in the maintenance of the apical region of the epithelium facing the gut lumen. There we find the brush border, with its associated enzymes, and the intercellular adhesion complexes that give the epithelium its cohesiveness and its barrier function. Curiously, there is little in the way of an organized cytoskeleton in the basal region of the epithelium adjacent to the basement membrane on which the epithelium is presumed to migrate. In this short review, I focus on what is known about epithelial migration from our understanding of the structure of the epithelium and from studies on wound healing, and indicate some avenues for future study.

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0018

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe negative and positive enantiomers of 7‐hydroxy‐ Δ6‐tetrahydrocannabinol‐dimethylheptyl (designated HU‐210 and HU‐211 respectively) differentially affect undifferentiated and differentiating cultured pheochromocytoma cells (PC‐12 cells). In general, cell viability and cell proliferation were suppressed to a much greater extent with HU‐210 than with HU‐211 in differentiating cells. The effects of these synthetic cannabinoids on the cytoskeleton of PC‐12 cells were examined by epifluorescence and confocal microscopy. In both undifferentiated and differentiating PC‐12 cells, HU‐211 has little effect on the cytoarchitecture whereas HU‐210 disrupts the distribution of microtubules and microfilaments. Vacuoles (2–4 μm) were evident in the cytoplasm of HU‐210‐treated cells but not in the cytoplasm of HU‐211‐treated cells or in vehicle controls. Tubulin and actin mRNA levels were reduced to 5 and 40 %, respectively (relative to untreated controls) in 10 μmHU‐210‐treated cells whereas the same concentration of HU‐211 reduced tubulin and actin mRNA levels to 90 and 95 %, respectively. A comparison of the effects of the paired enantiomers and Δ1‐THC on the cellular parameters studied reveals that in differentiating cells the action of Δ1‐THC is intermediate between that of HU‐210 and HU‐211. This study demonstrates that compared to HU‐210 and Δ1‐THC

ISSN:1065-6995    

DOI:10.1006/cbir.1996.0019

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY