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Guillermo Ortega Diego A. Golombek Dino Otero Lilia Romanelli Daniel P. Cardinali 《Chronobiology international》1992,9(2):137-147
The two-oscillator model of human circadian rhythmicity was analyzed when a zeitgeber relative intensity of 1, 0.5, or 0.1 was introduced into the equations. Fourier analysis was compared with dynamic analysis such as attractor reconstruction or Liapunov exponent calculation. After a 50 or 90% reduction in zeitgeber intensity, the dynamics of the system became equivalent and differed significantly from those of a system with maximal zeitgeber intensity. When 10% aleatory noise was added to the data, the analysis was still applicable, and the results obtained were essentially the same as in the absence of noise. Dynamic analysis could thus provide a distinct classification for periodic data, based on the type of analysis. 相似文献
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Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
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大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
7.
Mutational analysis of the ICP4 binding sites in the 5'' transcribed noncoding domains of the herpes simplex virus 1 UL 49.5 gamma 2 gene.
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A previous report (P. Mavromara-Nazos and B. Roizman, Proc. Natl. Acad. Sci. USA 86:4071-4075, 1989) demonstrated that substitution of sequences of the thymidine kinase (tk) gene, a beta gene, extending from -16 to +51 with sequences extending from -12 to +104 of the gamma 2 UL 49.5 gene in viral recombinant R3820 conferred upon the chimeric gene gamma 2 attributes in the context of the viral genome in a productive infection. The UL49.5 gene sequences extending from -179 to +104 contain four DNA binding sites for the major regulatory protein ICP4. Of these sites, two map between nucleotides +20 and +80 within the sequence which confers gamma 2 regulation upon the chimeric gene. To determine the role of these ICP4 binding sites in conferring the gamma 2 gene attributes, sequences comprising the two ICP4 binding sites were mutagenized and used to reconstruct the R3820 recombinant virus. In addition, a new recombinant virus (R8023) was constructed in which tk sequences extending from -240 to +51 were replaced with wild-type or mutated sequences contained between nucleotides -179 to +104 of the UL 49.5 gene. Vero cells infected with the recombinant viruses in the presence or absence of phosphonoacetate, a specific inhibitor of viral DNA synthesis, were then tested for accumulation of tk RNA by using an RNase protection assay. The results indicate that in the recombinant R3820, a mutation which destroyed one of the two UL49.5 ICP4 DNA binding sites significantly reduced the accumulation of tk RNA at both early and late times after infection. The effect of this mutation was less pronounced in cells infected with the R8023 virus, whose chimeric tk gene contains the two upstream UL49.5 ICP4 binding sites. None of the mutations affected the sensitivity of the chimeric genes to phosphonoacetate. The mutated site appears to be involved in the accumulation of RNA. 相似文献
8.
The fatty acid composition and content of phosphatidylinositol, phosphatidylserine and phosphatidic acid have been studied during the early development of toad embryos. Acidic phospholipids have been analyzed in whole oocytes and embryos and in the following subcellular fractions: yolk platelets, mitochondria and microsomes. Also cardiolipin, a mitochondrial phospholipid, has been analyzed. Gastrula stage embryos have shown, mainly in the mitochondrial fraction, an increase in the content of phosphatidic acid, phosphatidylserine and phosphatidylinositol with respect to unfertilized oocytes. Changes in the distribution of acyl groups of phosphatidic acid have been detected when different subcellular fractions are compared. On the other hand, the phosphatidylserine composition remains unmodified. Arachidonate and stearate are the principal components of phosphatidylinositol. Cardiolipin shows the same composition up to gastrulation and linoleate comprises about 50% of the total acyl groups. 相似文献
9.
Three thermophilic cellulolytic fungi, Chaetomium thermophile var. coprophile, Sporotrichum thermophile, and Thermoascus aurantiacus were studied to determine the conditions for a high rate of cellulose degradation. The range of temperature over which good growth occurred was determined first in a temperature gradient incubator; the optimum temperature was then established in shake flask cultures. T. aurantiacus had the highest optimum growth temperature range (46 to 51 C), whereas S. thermophile had the broadest range over which good growth occurred (36 to 43 C). Optimum temperatures for the three organisms, T. aurantiacus, S. Thermophile, and C. thermophile were 48, 40, and 40 C, respectively. It was found that the addition of an organic carbon and nitrogen source to a cellulose mineral solution medium markedly increased the rate of cellulose degradation. The surfactant, Tween 80, which has been reported to be of value in the production and recovery of the enzyme, cellulase, was shown to be detrimental to the degradation of cellulose in culture. In the medium used, S. thermophile gave the highest rate of substrate utilization; 56% of the cellulose was hydrolyzed in 72 h. The average degree of polymerization of cellulose decreased from 745 to 575. 相似文献
10.
M G Romanelli 《Bollettino della Società italiana di biologia sperimentale》1986,62(8):1005-1008