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71.
The relevance of phenotype fluctuations among clones (i.e., organisms with identical genes) to evolution has recently been recognized both theoretically and experimentally. By considering the stability of the distributions of genetic variations and phenotype fluctuations, we derive a general inequality between the phenotype variance due to genetic differences and the intrinsic phenotype variance of clones. For a given mutation rate, an approximately linear relationship between the two is obtained which elucidates the consistency between the fundamental theorem of natural selection by Fisher and the evolutionary fluctuation-response relationship (fluctuation dissipation theorem) proposed recently. A general condition for the error catastrophe is also derived as the violation of the inequality, which sets up the limit to the speed of stable evolution. All of these theoretical results are confirmed by a numerical evolution experiment of a cell that consists of a catalytic reaction network. Based on the relationships proposed here, relevance of the phenotypic plasticity to evolution as well as the genetic assimilation is discussed. 相似文献
72.
73.
Abe C Kawada T Sugimachi M Morita H 《Journal of applied physiology (Bethesda, Md. : 1985)》2011,111(6):1614-1621
To examine a cooperative role for the baroreflex and the vestibular system in controlling arterial pressure (AP) during voluntary postural change, AP was measured in freely moving conscious rats, with or without sinoaortic baroreceptor denervation (SAD) and/or peripheral vestibular lesion (VL). Voluntary rear-up induced a slight decrease in AP (-5.6 ± 0.8 mmHg), which was significantly augmented by SAD (-14.7 ± 1.0 mmHg) and further augmented by a combination of VL and SAD (-21 ± 1.0 mmHg). Thus we hypothesized that the vestibular system sensitizes the baroreflex during postural change. To test this hypothesis, open-loop baroreflex analysis was conducted on anesthetized sham-treated and VL rats. The isolated carotid sinus pressure was increased stepwise from 60 to 180 mmHg while rats were placed horizontal prone or in a 60° head-up tilt (HUT) position. HUT shifted the carotid sinus pressure-sympathetic nerve activity (SNA) relationship (neural arc) to a higher SNA, shifted the SNA-AP relationship (peripheral arc) to a lower AP, and, consequently, moved the operating point to a higher SNA while maintaining AP (from 113 ± 5 to 114 ± 5 mmHg). The HUT-induced neural arc shift was completely abolished in VL rats, whereas the peripheral arc shifted to a lower AP and the operating point moved to a lower AP (from 116 ± 3 to 84 ± 5 mmHg). These results indicate that the vestibular system elicits sympathoexcitation, shifting the baroreflex neural arc to a higher SNA and maintaining AP during HUT. 相似文献
74.
Kim J Hirasawa T Saito M Furusawa C Shimizu H 《Applied microbiology and biotechnology》2011,91(1):143-151
Glutamate overproduction by Corynebacterium glutamicum is triggered by treatment with penicillin or Tween 40 and is accompanied by a decrease in 2-oxoglutarate dehydrogenase complex
(ODHC) activity. We have reported that de novo synthesis of OdhI, which inhibits ODHC activity by interacting specifically
with the E1o subunit of ODHC (OdhA), is induced by penicillin, and that odhI overexpression induces glutamate overproduction in the absence of any triggers for glutamate overproduction. In this study,
to determine the function of OdhI in glutamate overproduction by C. glutamicum, changes in OdhI levels and phosphorylation status during penicillin- and Tween 40-induced glutamate overproduction were
examined by western blot. The synthesis of both unphosphorylated and phosphorylated OdhI was increased by addition of Tween
40 or penicillin and the levels of unphosphorylated OdhI, which can inhibit ODHC activity, was significantly higher than those
of phosphorylated OdhI, which is unable to inhibit ODHC activity. Meanwhile, the OdhA levels were maintained throughout the
culture. These results indicate that OdhI synthesis is induced by additions of penicillin and Tween 40 and most synthesized
OdhI is unphosphorylated, resulting in the decrease in ODHC activity and glutamate overproduction. Similarly, in the odhI-overexpressing strain, both unphosphorylated and phosphorylated OdhI were synthesized, while the levels of OdhA were nearly
constant throughout culture. Our results suggest that high level of unphosphorylated OdhI regulates glutamate overproduction
by C. glutamicum. 相似文献
75.
76.
Tsuboi S Sutoh M Hatakeyama S Hiraoka N Habuchi T Horikawa Y Hashimoto Y Yoneyama T Mori K Koie T Nakamura T Saitoh H Yamaya K Funyu T Fukuda M Ohyama C 《The EMBO journal》2011,30(15):3173-3185
The O-glycan branching enzyme, core2 β-1,6-N-acetylglucosaminyltransferase (C2GnT), forms O-glycans containing an N-acetylglucosamine branch connected to N-acetylgalactosamine (core2 O-glycans) on cell-surface glycoproteins. Here, we report that upregulation of C2GnT is closely correlated with progression of bladder tumours and that C2GnT-expressing bladder tumours use a novel strategy to increase their metastatic potential. Our results showed that C2GnT-expressing bladder tumour cells are highly metastatic due to their high ability to evade NK cell immunity and revealed the molecular mechanism of the immune evasion by C2GnT expression. Engagement of an NK-activating receptor, NKG2D, by its tumour-associated ligand, Major histocompatibility complex class I-related chain A (MICA), is critical to tumour rejection by NK cells. In C2GnT-expressing bladder tumour cells, poly-N-acetyllactosamine was present on core2 O-glycans on MICA, and galectin-3 bound the NKG2D-binding site of MICA through this poly-N-acetyllactosamine. Galectin-3 reduced the affinity of MICA for NKG2D, thereby severely impairing NK cell activation and silencing the NK cells. This new mode of NK cell silencing promotes immune evasion of C2GnT-expressing bladder tumour cells, resulting in tumour metastasis. 相似文献
77.
Kiyoko Taniai Chikara Hirayama Kazuei Mita Kiyoshi Asaoka 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2014,184(7):827-834
Four glycine-rich protein (GRP) genes were identified from expressed sequence tags of the maxillary galea of the silkworm. All four genes were expressed in the maxillary pulp, antenna, labrum, and labium, but none of the genes were expressed in most internal organs. Expression of one of the genes, termed bmSIGRP, was further increased approximately fivefold in the mouth region (including the maxilla, antenna, labrum, labium, and mandible) after 24 h of starvation. bmSIGRP expression peaked at 24 h and gradually declined during the subsequent 2 days. When a synthetic diet not containing proteins was fed, bmSIGRP expression increased significantly in the mouth region to levels similar to that observed in starved larvae. Synthetic diets that lacked vitamins or salts but contained amino acids did not significantly affect bmSIGRP expression. These results suggest that amino acid depletion increases bmSIGRP expression. 相似文献
78.
79.
Ichiro Tamaki Katsushige Nomura Reiko Nomura Chieko Tate Chikara Watanabe Yoshihiro Miyakami Yumiko Yabe 《Landscape and Ecological Engineering》2018,14(2):269-276
Magnolia stellata is a rare subcanopy tree species that grows in secondary forests in warm temperate zones. It is now endangered due to habitat degradation by vegetation succession. In an attempt to improve the habitat, a 30 m?×?10 m plot (0.03 ha) was set up with all vegetation including M. stellata being clear-cut in January 2012. The number of sprouts increased for 1–2 years after clear-cutting and then gradually decreased or remained constant. Five years after clear-cutting, the numbers of individuals and stems, and the total basal area (BA), were 87.0, 165.5 and 3.2%, respectively, of the values before clear-cutting. BA was highest for Ilex pedunculosa, followed by M. stellata and Hydrangea paniculata. Some sprouted individuals of M. stellata produced flower buds in the second year after clear-cutting, and flowered and fruited in the spring and summer of the third year, respectively. The densities of potential canopy species were 18,533 ha?1 (height >?0.5 m) and 7,267 ha?1 (height >?1.2 m), vastly exceeding the value of the criterion for successful natural regeneration after clear-cutting of warm temperate forests in the region (3,000 ha?1). Based on this criterion, it is thus considered that the natural regeneration has reached completion. However, 45.1% (height >?0.5 m) and 95.5% (height >?1.2 m) of M. stellata individuals were regenerated by sprouting. Further research is needed into how individuals, regenerated from seedlings, develop and reach sexual maturity, and how successive generations change. 相似文献