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31.
Cell kinetic studies in the epidermis of mouse. III. The percent labelled mitosis (PLM) technique 总被引:2,自引:0,他引:2
C S Potten H E Wichmann K Dobek J Birch T M Codd L Horrocks M Pedrick S P Tickle 《Cell and tissue kinetics》1985,18(1):59-70
Full PLM curves have been obtained for four sites in the mouse. The first peaks have been analysed by computer and the duration of the G2 + M and S phases determined together with their standard deviations. The full curves showed a general similarity for all four sites with no clear second peak. The data are compared with the published data for mouse and human epidermis using the in vivo PLM technique. The timing and shape of the first peak can vary considerably even for one site in mice. Hence, both G2 + M and S can vary in their durations. Cells labelled at one time of day exhibit different kinetic properties to those labelled at another time of day. The duration of G2 + M is shortest in dorsum labelled at 03.00 hours (3 X 2 hr) and longest in tail (up to 7 X 5 hr). The S-phase is shortest in dorsum (6 X 3-7 X 2 hr) and longest in tail or ear (13 X 3-14 X 1 hr). There is also a very large standard deviation in tail and foot. There is little general variability when the psoriatic human data are considered, which is surprising. The general variability amongst the data from experimental mice might also be expected amongst humans which might make comparisons between the cell kinetics of normal and diseased skin difficult. 相似文献
32.
M. Spassova I. R. Mellor A. G. Petrov K. A. Beattie G. A. Codd H. Vais P. N. R. Usherwood 《European biophysics journal : EBJ》1995,24(2):69-76
Nodularin (NODLN), a cyclic pentapeptide hepatotoxin from the cyanobacterium Nodularia spumigena, induces pores in bilayers of diphytanoyl lecithin (DPhL) and in locust muscle membrane. NODLN increases the surface pressure of a DPhL monolayer; except when the surface pressure of the monolayer is high when the toxin causes a reduction of this parameter. NODLN pores exhibit many open conductance states; the higher state probabilities increasing when the transmembrane pressure is increased. The results from these studies are discussed in terms of two models for a NODLN pore, a torroidal model and a barrel-stave model. The edge energy of the NODLN pore of 1.4× 10–12 J/m is determined.Abbreviations NODLN
Nodularin
- MCYST-LR
Microcystin-LR
- ADDA
3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid
- DPhL
diphytanoyl lecithin
Correspondence to: A. G. Petrov 相似文献
33.
Pyruvate and nitrogenase activity in cell-free extracts of the blue-green alga Anabaena cylindrica 总被引:1,自引:0,他引:1
G A Codd P Rowell W D Stewart 《Biochemical and biophysical research communications》1974,61(2):424-431
When extracts of are prepared in the absence of dithionite, they catalyze pyruvate-dependent acetylene reduction, a reaction not observable in assays containing dithionite. Ferredoxin and coenzyme-A, but not NADP and ferredoxin-NADP reductase, are required for maximal pyruvate-dependent activity. These acetylene-reducing extracts do not exhibit NADP-pyruvate dehydrogenase activity. However, pyruvate:ferredoxin oxidoreductase is present at levels of activity sufficient to support the rate of pyruvate-supported acetylene reduction. These data support earlier evidence that pyruvate:ferredoxin oxidoreductase transfers electrons from pyruvate to nitrogenase in . 相似文献
34.
35.
Ribulose 1,5-bisphosphate (RuBP) carboxylase-oxygenase fromthe cyanobacterium Anabaena cylindrica has been purified tohomogeneity by the criterion of polyacrylamide gel electrophoresisand shown to consist of two types of subunits of molecular weights51K (large) and 12K (small). The enzyme is of the higher planttype and probably consists of 8 large plus small subunits. Isoelectricfocusing of the S-carboxymethylated protein in 8 M urea revealeda profile of consisting of 3 major polypeptides plus 1 minorpolypeptide. Some characteristics of the carboxylase and oxygenasereactions were studied using simultaneous measurements of bothactivities. Pyridoxal 5'-phosphate inhibited both activitiesequally. Neither the carboxylase nor oxygenase reaction wasaffected by glutamate (5 mM), although 6-phosphogluconate andfructose 1,6-bisphosphate inhibited both reactions. RuBP oxygenasewas more sensitive to 6-phosphogluconate (0.5 and 1.0 mM) thanRuBP carboxylase. Marked changes in the oxygenase to carboxylaseactivity ratio of the purified enzyme were effected by homologousantiserum (which preferentially inhibited carboxylation).
1Present address: Institute of Applied Microbiology, Universityof Tokyo, Bunkyo-ku, Tokyo 113, Japan. (Received May 22, 1980; ) 相似文献
36.
Ribulose 1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) activity was approximately equally distributed between supernatant and pellet fractions produced by differential centrifugation of disrupted cells of Chlorogloeopsis fritschii. Low ionic strength buffer favoured the recovery of particulate RuBP carboxylase. Density gradient centrifugation of resuspended cell-free particulate material produced a single band of RuBP carboxylase activity, which was associated with the polyhedral body fraction, rather than with the thylakoids or other observable particles. Isolated polyhedral body stability was improved by density gradient centrifugation through gradients of Percoll plus sucrose in buffer, which yielded apparently intact polyhedral bodies. These were 100 to 150 nm in diameter and contained ring-shaped, 12 nm diameter particles. It is inferred that the C. fritschii polyhedral bodies are carboxysomes. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis of SDS-dissociated polyhedral bodies revealed 8 major polypeptides. The most abundant, with molecular weights of 52,000 and 13,000, correspond with the large and small subunits, respectively, of RuBP carboxylase.Abbreviations RuBP
ribulose 1,5-bisphosphate
- Ru5P
ribulose 5-phosphate
- SDS
sodium dodecyl sulphate
- PAGE
polyacrylamide gel electrophoresis
- EDTA
ethylenediamine tetraacetic acid
- Tris
tris (hydroxymethyl) methylamine
- IB
isolation buffer
- TCA
trichloroacetic acid 相似文献
37.
Rates and products of photosynthetic 14CO2 fixation by division synchronized cultures of Euglena gracilis strain Z were determined over the cycle. Rate of 14CO2 fixation doubled in a continuous manner throughout the light phase followed by a slight reduction of photosynthetic capacity in the dark phase. Greater 14C incorporation into the nucleic acid-polysaccharide fraction occurred with mature cells. Products of 14CO2 fixation varied markedly over the cycle: although with mature cells 14C-labeled sucrose was not detected, with dividing cells this was the main sugar labeled; in young cells 14C maltose was formed. Cells removed at end of dark phase accumulated 14C in glycolate, whereas at other stages over the cycle less 14C was present in glycolate, and this was accompanied by a rapid incorporation of 14C into glycine and serine. Glycerate was an early and major product of photosynthesis with cells at the mature stage of the cycle. 相似文献
38.
The functions of polymorphonuclear leukocytes from tobacco smokers are altered compared to those from nonsmokers. Since neutrophil chemotaxis and oxidative metabolism are mediated by surface receptors, we studied the association of the chemotactic peptide formyl Met-Leu-Phe with neutrophils from smokers and non-smokers. An apparently single class of binding sites was observed in neutrophils from all the non-smokers, whereas upwardly curving Scatchard plots were obtained for binding to smokers' cells. Thus changes at the receptor level may be responsible for the previously observed alterations in smoker neutrophil function. 相似文献
39.
Shared behavioural, morphological and physiological characteristics are indicative of the evolution of extant birds from nonavian maniraptoran dinosaurs. One such shared character is the presence of uncinate processes and respiratory structures in extant birds. Recent research has suggested a respiratory role for these processes found in oviraptorid and dromaeosaurid dinosaurs. By measuring the geometry of fossil rib cage morphology, we demonstrate that the mechanical advantage, conferred by uncinate processes, for movements of the ribs in the oviraptorid theropod dinosaur, Citipati osmolskae, basal avialan species Zhongjianornis yangi, Confuciusornis sanctus and the more derived ornithurine Yixianornis grabaui, is of the same magnitude as found in extant birds. These skeletal characteristics provide further evidence of a flow-through respiratory system in nonavian theropod dinosaurs and basal avialans, and indicate that uncinate processes are a key adaptation facilitating the ventilation of a lung air sac system that diverged earlier than extant birds. 相似文献
40.
Increased plasminogen activator inhibitor-1 (PAI-1) activity is associated with greater risk of myocardial infarction. PAI-1 expression is regulated by a 4G/5G promoter polymorphism. The 4G allele is associated with higher PAI-levels and greater circadian variation. Here we show that clock protein heterodimers BMAL/CLOCK cause greater activation (approximately 2-fold, P<0.05) of the 4G allele. Site-directed mutagenesis studies suggest that clock genes act on two canonical E-boxes to regulate PAI-1 promoter activity. These results identify a potential novel mechanism whereby allele-specific clock genes - mediated modulation of PAI-1 expression may contribute to circadian variation in cardiac risk. 相似文献