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1.
Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
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2.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:8,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
相似文献
3.
Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low. 相似文献
4.
The anabolic action of intermittent parathyroid hormone on cortical bone depends partly on its ability to induce nitric oxide‐mediated vasorelaxation in BALB/c mice 下载免费PDF全文
S Gohin A Carriero C Chenu AA Pitsillides TR Arnett M Marenzana 《Cell biochemistry and function》2016,34(2):52-62
There is strong evidence that vasodilatory nitric oxide (NO) donors have anabolic effects on bone in humans. Parathyroid hormone (PTH), the only osteoanabolic drug currently approved, is also a vasodilator. We investigated whether the NO synthase inhibitor L‐NAME might alter the effect of PTH on bone by blocking its vasodilatory effect. BALB/c mice received 28 daily injections of PTH[1–34] (80 µg/kg/day) or L‐NAME (30 mg/kg/day), alone or in combination. Hindlimb blood perfusion was measured by laser Doppler imaging. Bone architecture, turnover and mechanical properties in the femur were analysed respectively by micro‐CT, histomorphometry and three‐point bending. PTH increased hindlimb blood flow by >30% within 10 min of injection (P < 0.001). Co‐treatment with L‐NAME blocked the action of PTH on blood flow, whereas L‐NAME alone had no effect. PTH treatment increased femoral cortical bone volume and formation rate by 20% and 110%, respectively (P < 0.001). PTH had no effect on trabecular bone volume in the femoral metaphysis although trabecular thickness and number were increased and decreased by 25%, respectively. Co‐treatment with L‐NAME restricted the PTH‐stimulated increase in cortical bone formation but had no clear‐cut effects in trabecular bone. Co‐treatment with L‐NAME did not affect the mechanical strength in femurs induced by iPTH. These results suggest that NO‐mediated vasorelaxation plays partly a role in the anabolic action of PTH on cortical bone. © 2016 The Authors. Cell Biochemistry and Function published by John Wiley & Sons, Ltd. 相似文献
5.
AA Smith 《Biotechnic & histochemistry》2016,91(6):396-400
One can determine the best dilution of a primary antibody for immunohistochemistry that uses horseradish peroxidase conjugated to a secondary antibody by testing increasing concentrations sequentially on the same tissue section. When the same tissue section is incubated repeatedly with increasing concentrations of primary antibodies to epithelial membrane antigen, smooth muscle α-actin, or vimentin using alkaline phosphatase conjugated to a secondary antibody as the reporter, the best staining was obtained with a less concentrated primary antibody than was optimal for a single staining test. The best concentration of primary antibody for single run staining using an alkaline phosphatase reporting system is usually four times the best concentration for staining with multiple runs. The optimal concentration can be determined by denaturing the residual alkaline phosphatase and extracting residual stain by incubating the section in 4:1 diglyme:phosphate buffered saline for 20 min at 80o C between tests of primary antibody concentrations. I tested the method for four chromogens from one supplier and one chromogen from a different supplier. 相似文献
6.
Sara M Mohamed Emam A Abdel-Rahim Tahany AA Aly AbdelMoneim M Naguib Marwa S Khattab 《Experimental biology and medicine (Maywood, N.J.)》2022,247(5):385
Increased environmental pollution and unhealthy lifestyle are blamed for escalated chronic diseases. Exposure to aflatoxins was recently suggested to have a role in the increased incidence of type 2 diabetes mellitus. Diet modification and consumption of different functional food are now gaining attention, especially in diabetes management. This study investigates the effect of a diet containing barley microgreen against diabetes induced by streptozotocin with or without aflatoxin administration in rats. Barley microgreen was rich in 3′-Benzyloxy-5,6,7,4′-tetramethoxyflavone (48.8% of total) followed by 5β,7βH,10α-Eudesm-11-en-1α-ol (18.46%). Streptozotocin injection and/or aflatoxin administration significantly elevated glucose level, decreased insulin level, decreased β-cell function, deteriorated liver and kidney function parameters, and induced oxidative stress in the liver. Histopathology revealed irregular small-sized islets and decreased area % of insulin-positive beta cells in the pancreas, hepatic degeneration, nephropathy, and neuropathy in diabetic and/or aflatoxin administered rats compared to control. Barley microgreen diet fed to diabetic rats with or without aflatoxin alleviated all evaluated parameters. Barley microgreen diet also ameliorated the toxic effect of aflatoxin. In conclusion, exposure to aflatoxin aggravated diabetes and its complication. The incorporation of barley microgreen in the diet was able to control type 2 diabetes mellitus and the improved outcomes observed with barley microgreen treatments involved or occurred in conjunction with improved biomarkers of oxidative stress. 相似文献
7.
Supramolecular chromatin organization of the somatic nucleus (macronucleus--Ma) was studied in a free-living unicellular eukaryotic organism, the ciliate Bursaria ovata Beers 1952, at two late successive stages of its encystment (in the state of preparation to cryptobiosis). A modified Miller's method (Sergejeva et al., 1987) and the same technique in combination with high resolution DNA autoradiography were used. In chromatin spread preparations of Ma, not labeled by 3H-thymidine, numerous electron dense structures (rounded, stick-like and polygonal) were revealed, along with rarely occurring typical supramolecular chromatin structures, such as nucleosomic and not nucleosomic threads, nucleomeres, chromomeres, rosette-like looping chromatin, and electron dense chromonemes (Fig. 1). For DNA visualizing in the revealed polygonal structures, the vegetative cells (trophonts) of B. ovata were inoculated into the culture medium, containing 3H-thymidine and food (ciliates Paramecium caudatum). Here, the ciliates passed through 3-4 successive cell division cycles, thus progressively accumulating the radioactive DNA precursor in Ma. After washing the ciliates in 3H-thymidine-free culture medium, the process of their encystment was induced, and Ma were isolated by hand from the ciliates being at two late successive stages of encystment. Isolated Ma were dispersed in the low ionic solutions, as described elsewhere (Sergejeva et al., 1987). The carbon shadowed electron grids, that contained spread Ma preparations, were individually coated with photographic emulsion, according to the loop interference method (Angelier et al., 1976a; Bouteille, 1976). After a 6 month exposure at 4 degrees C, thymidine incorporation was revealed in fibril crowds, rosette-like structures (Fig. 2), and crystal-like plates of different size and morphology (Fig. 3). In all our experiments, non-specific localization of radioactive DNA precursor was not observed. The above data confirm undoubtedly our earlier assumption (Sergejeva et al., 1987; Sergejeva, Bobyleva, 1988) that the Ma chromatin of Bursaria may undergo crystallization during encystment, i.e. in the state of preparation to cryptobiosis. The present data enable us first to suggest that the looping rosette-like chromatin may be transformed into crystal-like structures ("exotic liquid crystal structures") by means of a peculiar loop packing within the limits of an individual resette (Fig. 2-4), these structural transformations taking place without any visible loop destruction. In this paper, we first describe new morphological types of polygonal plates, differing from those earlier reported elsewhere for the Ma of Bursaria (Sergejeva, Bobylova, 1988), and also from the plates earlier described in studies on liquid crystals both in vivo and in vitro (see: Gianonni et al., 1969; Lerman, 1974; Livolant, 1991: Leforestier et al., 1993, 1997, 1999). The technical approaches used in the present work enabled us to obtain, for the first time, a direct evidence of the presence of DNA in the crystallized structures of somatic nuclei of ciliates during their preparation to cryptobiosis, the DNA-containing polygonal structures being highly morphologically diverse. Further studies into the reasons of this diversity are needed. 相似文献
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10.
Condensin complexes are essential for chromosome condensation and segregation in mitosis, while condensin dysfunction, among
other pathways leading to chromosomal bridging in mitosis, may play a role in tumor genomic instability, including recently
discovered chromotripsis. To characterize potential double-strand breaks specifically occurring in late anaphase, human chromosomes
depleted of condensin were analyzed by γ-H2AX ChIP followed by high-throughput sequencing (ChIP-seq). In condensin-depleted
cells, the nonrepeated parts of the genome were shown to contain distinct γ-H2AX enrichment zones 75% of which overlapped
with known hemizygous deletions in cancers. Furthermore, some tandemly repeated DNA sequences, analyzed separately from the
rest of the genome, showed significant γ-H2AX enrichment in condensin-depleted anaphases. The most commonly occurring targets
of such enrichment included simple repeats, centromeric satellites, and rDNA. The two latter categories indicate that acrocentric
human chromosomes are especially susceptible to breaks upon condensin deficiency. The genomic regions that are specifically
destabilized upon condensin dysfunction may constitute a condensin-specific chromosome destabilization pattern. 相似文献