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1.
The systematic position ofthe Ebenaceae, Sapotaceae, Styracaceae, Ochnaceae, Stachyuraceae, Dipterocarpaceae, Clusiaceae and Hypericaceae has been investigated using serological comparisons of sets of antigenic determinants. The results show that the Sytracaceae and Sapotaceae are undoubtedly more closely associated with the Actinidiaeceae and Theaceae, respectively, than with each other. We found no corresponding determinants betnween antigen systems from the Ebenaceae and systems from any other family whose relations to this family have been proposed. As discovered previously, investigations of antigen systems from the Ochnaceae, Dipterocarpaceae, Stachyuraceae, Clusiaceae and Hypericaceae are against the idea of a natural order “Theales” in which these families, or at least some of them, are combined with the Theaceae and Actinidiaceae. This paper completes our previous investigations which largely support a superorder Ericanae sensu Ehrendorfer and Takhtajan. We propose to include the Actinidiaceae and Theaceae in this superorder, assigning them a central position laong with the Sapotaceae and Sytracaeae on one side and the Primulales and Ericales on the other. Another most interesting finding is that there are corresponding determinants between antigen systems from the members of the Ericanae and representatives of the Polemoniaceae and Loasaceae. 相似文献
2.
Several different models of the linker histone (LH)–nucleosome complex have been proposed, but none of them has unambiguously revealed the position and binding sites of the LH on the nucleosome. Using Brownian dynamics-based docking together with normal mode analysis of the nucleosome to account for the flexibility of two flanking 10 bp long linker DNAs (L-DNA), we identified binding modes of the H5-LH globular domain (GH5) to the nucleosome. For a wide range of nucleosomal conformations with the L-DNA ends less than 65 Å apart, one dominant binding mode was identified for GH5 and found to be consistent with fluorescence recovery after photobleaching (FRAP) experiments. GH5 binds asymmetrically with respect to the nucleosomal dyad axis, fitting between the nucleosomal DNA and one of the L-DNAs. For greater distances between L-DNA ends, docking of GH5 to the L-DNA that is more restrained and less open becomes favored. These results suggest a selection mechanism by which GH5 preferentially binds one of the L-DNAs and thereby affects DNA dynamics and accessibility and contributes to formation of a particular chromatin fiber structure. The two binding modes identified would, respectively, favor a tight zigzag chromatin structure or a loose solenoid chromatin fiber. 相似文献
3.
Interpreting channel behavior in patches requires an understanding of patch structure and dynamics, especially in studies of mechanosensitive channels. High resolution optical studies show that patch formation occurs via blebbing that disrupts normal membrane structure and redistributes in situ components including ion channels. There is a 1-2 μm region of the seal below the patch where proteins are excluded and this may consist of extracted lipids that form the gigaseal. Patch domes often have complex geometries with inhomogeneous stresses due to the membrane-glass adhesion energy (Ea), cytoskeletal forces, and possible lipid subdomains. The resting tension in the patch dome ranges from 1-4 mN/m, a significant fraction of the lytic tension of a bilayer (∼10 mN/m). Thus, all patch experiments are conducted under substantial, and uneven, resting tension that may alter the kinetics of many channels. Ea seems dominated by van der Waals attraction overlaid with a normally repulsive Coulombic force. High ionic strength pipette saline increased Ea and, surprisingly, increased cytoskeletal rigidity in cell-attached patches. Low pH pipette saline also increased Ea and reduced the seal selectivity for cations, presumably by neutralizing the membrane surface charge. The seal is a negatively charged, cation selective, space with a resistance of ∼7 gigohm/μm in 100 mM KCl, and the high resistivity of the space may result from the presence of high viscosity glycoproteins. Patches creep up the pipette over time with voltage independent and voltage dependent components. Voltage-independent creep is expected from the capillary attraction of Ea and the flow of fresh lipids from the cell. Voltage-dependent creep seems to arise from electroosmosis in the seal. Neutralization of negative charges on the seal membrane with low pH decreased the creep rate and reversed the direction of creep at positive pipette potentials. 相似文献
4.
Epigenetics and aging: the targets and the marks 总被引:14,自引:0,他引:14
'Aging epigenetics' is an emerging field that promises exciting revelations in the near future. Here we focus on the functional and biological significance of the epigenetic alterations that accumulate during aging and are important in tumorigenesis. Paradigmatic examples are provided by the global loss of DNA methylation in aging and cancer and by the promoter hypermethylation of genes with a dual role in tumor suppression and progeria, such as the Werner syndrome (WRN) and lamin A/C genes. Another twist is provided by sirtuins, a family of NAD-dependent deacetylases that act on Lys16 of histone H4, which are emerging as a link between cellular transformation and lifespan. 相似文献
5.
Metamorphosis in the Cirripedia Rhizocephala and the homology of the kentrogon and trichogon 总被引:2,自引:0,他引:2
The Rhizocephala are considered to be monophyletic due to several synapomorphies in the ontogeny of the cndoparasitic phase. The various types of metamorphosis described in the Rhizocephala are discussed and compared to metamorphosis in the Cirripedia Thoracica and Acrothoracica. In males and females of the suborder Kentrogonida. the cyprid settles and metamorphoses into a new instar, in males the trichogen and in females the infective kentrogon. The kentrogon goes through yet another. incomplete moult associated with the development of the stylet. Within the three kentrogonidan families. the Iernaeodiscid-peltogastrid type of kentrogon differs from the sacculinid type in the mode of attachment to the host. in the complexity of internal anatomy. in the position and penetration of the stylet, and in whether or not the cyprid carapace must be shed prior to penetration of the stylet. In the Akentrogonida metamorphosis never results in a new instar. Where observed (Clistosaccidae and Thompsoniidae). both male and female cyprids settle and penetrate into their substrate (female parasite or new host) with one of the antennules. Using the antennule as a syringe. male cyprids inject spermatogonia while female cyprids injects embryonic cells developing into an endoparasite. By comparison with metamorphosis in the Cirripedia Thoracica and Acrothoracica it is concluded that the presence of a metamorphic moult leading to a post-cyprid instar is plesiomorphic and that the trichogon and kentrogon are homologous with the first metamorphosed juvenile in these outgroups. The abbreviated ontogeny in the Akentrogonida without metamorphic moult and post-cyprid larval instars is considered apomorphic. This contradicts the long-held supposition that the Akentrogonida are the most‘primitive’Rhizocephala and dovetails with new information that this suborder contains many advanced traits. Within the Kentrogonida. the lernacodiseid-peltogastrid type of kentrogon is considered more plesiomorphic than the sacculinid type, which resembles the clistosaccidthompsoniid type in having the antennules involved in the penetration process. The homologization of the kentrogon with a juvenile barnacle indicates that presence of a kentrogon is plesiomorphic within the Rhizocephala and that the Kentrogonida is paraphyletic. 相似文献
6.
A I L'vovich 《Arkhiv anatomii, gistologii i émbriologii》1978,74(5):35-41
In 16 adult cats with electrolytically destructed external and internal parts of the globus pallidus and in 8 cats with destructed putamen direct strio-pallido-hypothalamic and strio-pallido-subthalamic pathways have been studied. Degeneration of the axonal preterminals and terminals have been examined in preparations treated after Nauta--Gygax, Nauta--Laidlow, Finck--Heimer with simultaneous additional staining of the nuclei with cresyl violet after Kawamura--Niimi. Direct pallido- and putamen-hypothalamic pathways to nuclei of the grey tubercle, posterior and lateral nuclei of the hypothalamus were stated. Direct pathways from the putamen to the subthalamic nucleus have been revealed, however, these pathways are represented in less degree than those of pallido-subthalamic connections. Direct pathways from the external portion of the globus pallidus and putamen to the subthalamic nucleus are more pronounced and represented by greater numbers of projections than those of strio-pallido-hypothalamic origin. 相似文献
7.
Baculoviruses and apoptosis: the good, the bad, and the ugly 总被引:8,自引:0,他引:8
Clem RJ 《Cell death and differentiation》2001,8(2):137-143
Since 1991, when a baculovirus was first shown to inhibit apoptosis of its host insect cells, considerable contributions to our knowledge of apoptosis have arisen from the study of these viruses and the anti-apoptotic genes they encode. Baculovirus anti-apoptotic genes include p35, which encodes the most broadly acting caspase inhibitor protein known, and iap (inhibitor of apoptosis) genes, which were the first members of an evolutionarily conserved gene family involved in regulation of apoptosis and cytokinesis in organisms ranging from yeast to humans. Baculoviruses also provide an ideal system to study the effects of an apoptotic response on viral pathogenesis in an animal host. In this review, I discuss a number of interesting recent developments in the areas of apoptotic regulation by baculoviruses and the effects of apoptosis on baculovirus replication and pathogenesis. 相似文献
8.
Nazarova AF Alkhutov SM 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》2008,66(1):51-66
The electrophoretical polymorphisms of some blood proteins were studied in the Talysh population of Pirasora situated in South-East Azerbaidjan. We calculated the gene frequencies of these polymorphisms and determined the genetic distances between the Talyshes and some Iranian populations of North, Central and South Iran, Afghans, and three populations of Azerbaijan. The Talyshes are very close to Iranians of Shiraz, whereas they are distant from the Azerbaijanians. Anthropological investigations showed that the Caucasoids and Mongoloids lived in the Aragvi Basin since the Eneolithic period. This was stated by Alexeev (1974), who emphasized the mixture of the Caucasus populations from ancient times on. We calculated the genetic distances between the Caucasus populations and numerous populations of other geographic regions, considering 28 alleles of 12 loci of blood group, serum protein and red cell enzyme polymorphisms and constructed the dendrogram of these populations. The position of the Caucasus populations in the dendrogram corresponds on principle to the earlier anthropological observations. The clustering of the Caucasoid populations corresponds completely with anthropological and historical data, and supports our earlier hypothesis (Nazarova 1999) concerning the differentiation of Caucasoids, Northern Mongoloids and Amerinds from the populations, which inhabitated Asia in palaeolithic times. 相似文献
9.
There is strong evidence that magnitudes in different dimensions can interfere. A majority of previous studies on the interaction of temporal magnitudes on numerosity showed no interfering effect, while many studies have reported the interference of numerosity on judgement of temporal magnitudes. We speculated that this one-way interference is confounded by the magnitudes used in the studies. We used a methodology that allowed us to study this interaction reciprocally. Moreover, we selected magnitudes for two dimensions that enabled us to detect their interfering effects. Participants had to either judge which of two successive sets of items was more numerous (numerosity judgement task), or which set of items was presented longer (duration judgement task). We hypothesised that a longer presentation of a set will be judged as being more numerous, and vice versa, a more numerous set will be judged as being presented longer. Results confirmed our hypothesis. A positive correlation between duration of presentation and judged numerosity as well as a positive correlation between the number of items and judged duration of presentation was found. This observation supports the idea that duration and numerosity judgements are not completely independent and implies the existence of (partly) generalised and abstract components in the magnitude representations. 相似文献
10.
11.
Joris F. Geys 《Pal?ontologische Zeitschrift》1980,54(3-4):199-224
Phymosomatoid echinoids from the Campanian and the Maastrichtian of Belgium and the Netherlands are systematically revised. Ten species, belonging to four genera are identified and described. One new species is introduced:Gauthieria?mosae sp. nov. 相似文献
12.
Segal MB 《Cellular and molecular neurobiology》2000,20(2):183-196
1. The fluid homeostasis of the brain depends both on the endothelial blood–brain barrier and on the epithelial blood–cerebrospinal fluid (CSF) barrier located at the choroid plexuses and the outer arachnoid membrane.2. The brain has two fluid environments: the brain interstitial fluid, which surrounds the neurons and glia, and the CSF, which fills the ventricles and external surfaces of the central nervous system.3. CSF acts as a fluid cushion for the brain and as a drainage route for the waste products of cerebral metabolism.4. Recent findings suggest that CSF may also act as a third circulation conveying substances secreted into the CSF rapidly to many brain regions. 相似文献
13.
Gastrulation movements: the logic and the nuts and bolts 总被引:1,自引:0,他引:1
Leptin M 《Developmental cell》2005,8(3):305-320
14.
《Saudi Journal of Biological Sciences》2019,26(8):1991-1994
ObjectiveTo investigate the efficacy of ropivacaine and bupivacaine in caesarean section and vital signs and the hemodynamics of the lying-in women.MethodsA total of 480 lying-in women who were admitted to this hospital for treatment between December 2017 and June 2018 were enrolled into this study as the subjects, which were divided into the experiment group and the control group, with 240 subjects in each group. In the experiment group, subjects received the local anesthesia by infusion of 1.5 mL ropivacaine (0.75%), while those in the control group also took the local anesthesia by infusion of 1.5 mL bupivacaine (0.75%). Thereafter, we observed the differences in the anesthetic efficiency, vital signs and hemodynamics of the lying-in women between two groups.ResultsThe excellent and good rates of the anesthesia in two groups were 92.1% and 87.9%, showing no obvious difference; in the experiment group, the average arterial pressures and systolic pressures at 5 min and 10 min after combined spinal and epidural analgesia (CSEA) were all elevated when comparing to the control group (all P < 0.05); in the experiment group, the onset time was obviously extended, while duration of sensory and motor block and the duration of motor block were all shorter than those in the control group (all P < 0.05). During anesthesia, the incidence rate of the adverse reactions in the control group was 2.50%, significantly higher than 0.83% in the experiment group (P < 0.05).ConclusionDespite that ropivacaine and bupivacaine are efficient in anesthesia in the CSEA in the caesarean section, ropivacaine is more recommended for little influence on the hemodynamics, shorter duration of sensory block and motor block and low incidence rate of adverse reactions, which are conducive to the recovery and also safe to the patients. 相似文献
15.
Jonathan Grose 《Biology & philosophy》2011,26(5):677-696
The story of the fall and rise of Zahavi??s handicap principle is one of a battle between models. Early attempts at formal modeling produced negative results and, unsurprisingly, scepticism about the principle. A major change came in 1990 with Grafen??s production of coherent models of a handicap mechanism of honest signalling. This paper??s first claim is that acceptance of the principle, and its dissemination into other disciplines, has been driven principally by that, and subsequent modeling, rather than by empirical results. Secondly, there is a vast literature on biological signalling but few studies that make all of the observations necessary to diagnose the handicap mechanism. My final claim is that many of the applications of ??costly signalling theory?? in other disciplines are conceptually confused. Misinterpretations of what is meant by ??costly signalling?? are common. Demonstrating that a signal is costly is insufficient and is not always necessary in order to prove that, and explain why, a signal is honest. In addition to the biological modelling of signals, there is an economic literature on the same subject. The two run in parallel in the sense that they have had little mutual interaction. Additionally, it is the biological modelling that has been picked up, and often misapplied, by other disciplines. 相似文献
16.
This study was undertaken to examine further the behavior of the Hre gene and its interaction with the growth and reproduction complex genes (grc) in the (Hre x BN)F2, Hre x (Hre x BN)F1 and (BIL/1 x Hre) F2 crosses. The blaze characteristic of rats carrying the Hre gene was linked to testicular weight but not to the body weight or to the major histocompatibility complex (MHC). The Hre defect was genetically unrelated to the testicular defect caused by the grc. The Hre gene had a variable effect on the testes of the rats in different crosses, and it could be categorized into three distinct stages of progressively greater severity. In the cross in which the parents carried the Hre/+ and grc/grc genes, respectively, there was a decreased litter size, an increased male:female ratio in the offspring and poor reproductive performance when compared to a similar cross in which the Hre/+ gene alone was segregating. There was, however, no effect on the severity of the testicular defect. Thus, the grc can interact with the Hre gene to cause embryonic death, which appears to be selective for females, but not to influence the severity of the testicular defect. 相似文献
17.
U Motro 《Journal of theoretical biology》1991,151(2):145-154
If food is patchily dispersed, food clumps being very rich, but rare and hard to find, each individual in a foraging flock then faces an evident dilemma: whether to co-operate and participate in the search, thus enhancing the rate by which rich patches are discovered, or to defect and let others do the searching, thus avoiding any possible expenditures and risks involved in the search (but enjoying the abundant resources once a rich patch is discovered). This conflict (and its possible solution) is treated as an example in the analysis of the synergistic n-player game presented in this paper. After deriving conditions for the existence of a mixed ESS in such games, the evolutionary stability of the mixed strategy against invasions by pure strategists, in particular against invasions by recognizable defectors, is analyzed. Whereas in any "degenerating" mixed-strategy model a recognizable defector can invade and spread, a "non-degenerating" model can sometimes yield a mixed ESS which is immune to such invasions. 相似文献
18.
pRb and the cdks in apoptosis and the cell cycle 总被引:3,自引:0,他引:3
Apoptosis is a fundamental biological process present in metazoan cells. Linking apoptosis to the cell cycle machinery provides a mechanism to maintain proper control of cell proliferation in a multicellular organism. pRb and the cyclin-dependent kinases may have dual roles as integral components of the cell cycle and regulators of apoptosis. In many instances manipulation of the cell cycle through these molecules can induce or inhibit apoptosis. Recent studies also identify pRb as a substrate for an apoptotic protease; however, other cell cycle components are not known substrates. While it is clear that many common molecules can affect cell proliferation and cell death, the universality of any one cell cycle molecule in apoptosis has yet to be determined. 相似文献
19.
David Holyoak 《Bird Study》2013,60(4):215-227
Analysis of Nest Record Cards reveals altitudinal and habitat differencesbetween these two species. The resident or partially migratory Stonechat has a longer breeding season (with a potential for rearing three broods) than the Whinchat which is a trans-Saharan migrant and arrives later. It is suggested that the greater productivity of the Stonechat might counterbalance a higher winter mortality. 相似文献
20.
F K Fuss 《Gegenbaurs morphologisches Jahrbuch》1990,136(1):37-68
In order to analyze the complicated movements of the mandible as the open-closing movement and the protrusio are, it is useful to evaluate the basic kinematic principles and reduce them to simple technical constructions. Both the open-closing movement and the protrusio could be reduced to 4-bar links, which were used to simulate the movements with help of a computer. Besides, the polodes and the curves of points in the muscular attachments could be constructed. The 2 entirely different 4-bar links have 3 things in common: The resting system - cranium, the moving system - mandibula, and 1 of the 2 arms connecting these 2 systems - the ligamentum laterale. As this ligament is taut during movements it can be considered a "guiding ligament" representing 1 of the 3 determining components of the mandibular movements. The other of the 2 arms has no anatomical equivalent; this arm, however, is "replaced" by the 2 other determining components of the mandibular movements: the joint and the muscles. The curves, which the Caput mandibulae describes, are practically identical for the open-closing movement and the protrusio despite of the different 4-bar links and these curves exactly correspond to the Discus articularis, taut by the upper part of the M. pterygoideus lateralis. The muscles do not only just move the mandibula, but they are also the component, which can choose between the different mandibular movements. By means of the curves, which points in the muscular attachments describe, the function of the masticatory muscles could be analyzed exactly. 相似文献