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91.
92.
Effect of Macromolecular Synthesis on the Coordinate Morphogenesis of Polar Surface Structures in Caulobacter crescentus 下载免费PDF全文
The Caulobacter polar surface structures (flagella, pili, and the deoxyribonucleic acid phage phiCbK receptors), which are expressed at proximal sites of swarmer cells in a coordinate manner (Shapiro, Annu. Rev. Microbiol., 30:377-407, 1976) could be blocked by a single mutation. The mutant C. crescentus CB13 ple-801 did not form these surface structures when grown at 35 degrees C. Upon shift down to 25 degrees C, the mutant cells initiated the formation of the surface structures. When mitomycin C was added to the mutant culture upon shift down from 35 to 25 degrees C, phiCbK receptor formation was inhibited to a minimal level. Rifampin and chloramphenicol completely inhibited phiCbK receptor formation when added to the mutant culture upon shift down. Deoxyribonucleic acid as well as ribonucleic acid and protein synthesis seem to be required for the formation of phiCbK receptors. Penicillin V also inhibited phiCbK receptor formation, indicating the involvement of cell wall synthesis. When the mutant CB13 ple-801 cells were shifted down briefly from 35 to 25 degrees C and then shifted up to 35 degrees C, flagella and phiCbK receptors were formed even at 35 degrees C to different extents depending on how long the cells were incubated at 25 degrees C. This formation of the surface structures at 35 degrees C was inhibited by rifampin. From these results, it appears that translation, assembly, or localization processes for the formation of the surface structures are not temperature sensitive at 35 degrees C in the pleiotropic mutant CB13 ple-801. The syntheses of deoxyribonucleic acid and the cell wall do not appear to be temperature sensitive either, since the mutant grows normally at 35 degrees C. It is suggested that there exists a regulatory step that commits the cells to initiate the synthesis of requisite ribonucleic acid for the formation of the polar surface structures. 相似文献
93.
94.
Analysis of population changes by measurement of body weight in the Koshima troop of Japanese monkeys 总被引:5,自引:0,他引:5
Akio Mori 《Primates; journal of primatology》1979,20(3):371-397
Measurements of the body weight of monkeys in the Japanese monkey troop on Koshima islet in southern Japan have been made
since 1970. Population changes in the troop have been recorded since 1952. The population changes were further analyzed on
the basis of the body weight changes of the troop members. The recent history of the Koshima troop can be divided into three
periods differing according to conditions of artificial feeding: (1) a semi-wild period (SW Period, 1952–63); (2) an artificial
feeding period (AF Period, 1964–71); (3) and a restricted artificial feeding period (Non-AF Period, 1972–77). The AF Period
represented a period of population growth, whereas the Non-AF Period was a declining one when the population density of the
troop was roughly ten times that of most wild troops. These population changes, i.e., changes in population parameters especially
in the population declining phase, could be fairly well understood from the general features of the body weight changes of
the troop members, the slow body weight growth, elevation of age at first birth, and small size of adult females. Reproduction
and survival were affected by seasonal and yearly changes in body weight. The pattern of changes in body weight displayed
seasonal peaks in the autumn and spring. Of these, the former suggests that fruit eating in the autumn is an important factor
in the reproduction and growth of the monkeys. 相似文献
95.
A sulfite-dependent ATPase [EC 3.6.1.3
[EC]
] of Thiobacillus thiooxidanswas activated and solubilized by treatment with trypsin [EC3.4.4.4
[EC]
], and purified 84-fold with a 32% recovery. It requiredboth Mg2+ and SO32 for full activity, and its optimumpH was found at 7.58.0. Mn2+, Co2+, and Ca2+ could partiallysubstitute for Mg2+, while SeO32 and CrO42 couldpartially substitute for SO32. The enzyme hydrolyzed ATP and deoxy-ATP most rapidly and otherphosphate esters were poorer substrates. The apparent Km valuefor ATP was 0.33 mM. The enzyme activity was strongly inhibitedby 0.2 mM NaN3 and 10 mM NaF. (Received July 27, 1977; ) 相似文献
96.
97.
A small fraction (approximately 5%) of protein kinase C (PKC) in the adult rat brain synaptosomes is tightly associated with Triton X-100-insoluble components (most likely membrane-skeleton elements), and is solubilized only after denaturation with sodium dodecyl sulfate. The kinase domain of this PKC can be released as a soluble form after limited proteolysis with calpain, whereas the regulatory domain which binds phorbol ester remains insoluble. The PKC in this fraction was identified as the beta II-subspecies or its related molecule. Presumably, this enzyme subspecies is responsible for the phosphorylation of a major PKC substrate protein, growth-associated protein-43, which is located in nerve endings as well as in growth cones in association with the membrane-skeleton elements. 相似文献
98.
Large Inversion in Escherichia Coli K-12 1485in between Inversely Oriented Is3 Elements near Lac and Cdd 下载免费PDF全文
A companion study has shown that the inversion carried by strain 1485IN has one terminus between lac and proC and the other between his and cdd of the normal strain. Starting with this mapping data, we have done molecular work demonstrating that the inversion occurred by recombination between inversely oriented two IS3 elements, one present near lac and the other near the cdd locus; i.e., the inversion is IN(is3B-is3E). Evidence supporting this conclusion includes: (i) Normal and inversion strains share two short regions with identical restriction maps. One of these regions is near lac and the other near cdd. (ii) IS3 homology was detected in each of the terminus regions of both the normal and inversion strains. (iii) The sequence on one side of the original IS3 element near lac has been exchanged with the sequence on one side of the IS3 near cdd. Whether the inversion has occurred by one event of homologous recombination between the two IS3 elements or has been caused by involvement of IS3 elements on an F factor is discussed. Another rearrangement, probably related to inversion and deletion, was detected between the IS3 and cdd of the inversion strain. 相似文献
99.
Populations of the two-spotted spider mite, Tetranychus urticae Koch collected from various localities and from various host plants in Japan showed wide variations in diapause attribute. Diapause percentages at 18°C/9L15D varied from nearly 100% in the north to 0% in the south-west. At intermediate latitudes the mites showed wide inter-population variations. Populations on herbaceous hosts in vinyl- or glass-houses gave significantly lower incidence of diapause than those on roses and deciduous fruit trees. Presence of winter hosts and better host quality under protected environments seemed to favour non-diapausing mites. The temperature threshold for diapause expression also varied widely among local populations. Northern populations consistently had higher and less variable thresholds than populations at intermediate latitudes with thresholds between 15 and 18°C. Inbred lines derived from a population in Kyoto exhibited a wide variation in diapause percentage at 18°C. These results show that diapause in T. urticae is a quantitative threshold trait and that populations in central Japan consist of a variety of genotypes with different diapause traits. This might provide a genetic source for adaptation to local and temporal variations in environmental conditions. 相似文献
100.
Randi B. Silver Gustavo Frindt Lawrence G. Palmer 《The Journal of membrane biology》1992,125(1):13-24
Summary Changes in intracellular pH (pH
i
) were measured using the pH indicator, BCECF, in principal cells from split opened cortical collecting tubules (CCTs) derived from rabbits maintained on a normal diet. This monolayer preparation has the advantage of allowing us to visualize the morphological differences in the two major cell types in this nephron segment under transmitted light. The visual identification of the cell types was verified using emission measurements taken from single principal and intercalated cells in the opened tubule which had been exposed to fluorescein isothiocyanate (FITC)-labeled peanut lectin. We confirmed the existence of an amiloride-sensitive Na/H exchange process activated during intracellular acidosis in principal cells. In addition, the exchanger was active under basal conditions and over a wide range of pH
i
. Because the exchanger was active under basal conditions we tested the hypothesis that changes in intracellular Na (Na
i
) would alter pH
i
in a predictable way. Maneuvers designed to alter Na
i
were without significant effects within a 10-min time frame. Specifically, addition of 100 m ouabain to increase Na
i
or exposure of the tubules to 10–5
m amiloride to decrease luminal Na entry and reduce Na
i
did not have an effect on pH
i
. In some experiments we did observe however, after a 30-min exposure to ouabain, a small decrease in pH
i
. These results suggest that Na/H exchange is a major regulator of pH
i
in principal cells. However, regulation of Na transport by changes in pH
i
in principal cells of rabbit CCT via the activity of a Na/H exchanger do not seem to contribute to the feedback control of Na transport.This work was supported by U.S. Public Health Service grants DK27847 to L.G. Palmer and DK11489 to E.E. Windhager. 相似文献