首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Peter Schopfer 《Planta》1967,72(4):297-305
Zusammenfassung Die positiven Photomorphosen Öffnung des Hypokotylhakens und Entfaltung der Kotyledonen können ganz ähnlich wie die phytochrominduzierte Anthocyansynthese und andere positive Photomorphosen durch Actinomycin D und Puromycin gehemmt werden. Man kann daraus schließen, daß diese beiden photomorphogenetischen Reaktionen des Senfkeimlings ebenfalls durch eine von P730 über eine Signalkette ausgelöste Aktivierung von potentiell aktiven Genen veranlaßt werden.
The inhibition of phytochrome-mediated photomorphogenesis (positive photoresponses) by actinomycin D and puromycin in the mustard seedling (Sinapis alba L.)
Summary The many photochrome-mediated photoresponses of a seedling (Sinapis alba L., white seeded mustard) can be divided into 3 categories: positive, negative, and complex photoresponses. Positive photoresponses are those which are characterized by an initiation or a promotion of biosynthetic or growth processes (Mohr, 1966b). Phytochrome-mediated anthocyanin synthesis is the prototype of a positive photoresponse. It has been shown in previous papers (e.g. Lange and Mohr, 1965; Mohr et al., 1965) that positive photoresponses can be specifically inhibited by actinomycin D and puromycin. It has been concluded that in the case of positive photoresponses P730 (the active phytochrome) exerts its function through differential gene activation.—In the present paper it has been demonstrated that phytochrome-mediated positive photoresponses of the mustard seedling like opening of the hypocotylar hook and unfolding of the cotyledons can be inhibited by relatively low doses of actinomycin D and puromycin in very much the same way as anthocyanin synthesis or cotyledon enlargement is inhibited. It has been concluded that in these cases too the action of P730 must be attributed to an activation of potentially active genes in the manner postulated on the basis of the data on anthocyanin synthesis.


Die Arbeit wurde durch Sachbeihilfen der Deutschen Forschungsgemeinschaft und der Stiftung Volkswagenwerk (an Prof. Mohr) ermöglicht.  相似文献   

2.
Summary The seven possible primary trisomics of Petunia (2 n= 14) located in the progenies of triploid, hypertriploid and hypotriploid plants were distinguished from one another and from diploid on the basis of cytological and morphological criteria. They were provisionally named as Oval, Semi, Slender, Pseudonormal, Arrow, Narrow and Giant. In three of the trisomics, the extra chromosome was identified for the first time at pachytene stage. Postpachytene studies revealed no precise relationship between the length of extra chromosome and the frequency of multiple association.  相似文献   

3.
The most commonly quoted mechanism of the coupling between the electrochemical proton gradient and the formation of ATP from ADP and Pi assumes that all states of the F1 portion of the ATP synthase have subunits in tight, loose, and open conformations. Models based on this assumption are inconsistent with some of the available experimental evidence. A mechanism that includes an additional subunit conformation, closed, observed in the rat liver structure overcomes these difficulties.  相似文献   

4.
A model of associative memory for time varying spatial patterns is proposed and simulated on a digital computer. This is a network composed of many neuron-like elements, and shows an ability for associative memory similar to that of the brain.Suppose a number of sequences of spatial patterns are presented to this network, for example, 12345, ABC, and so on. Then, these patterns are memorized in the network. After that, if any part of one of these sequences, say 23, is presented to the circuit, the rest of the sequence, 45, is recalled following to it. It resembles to such a situation — if we hear a part of a melody which we have memorized in the past, the rest of the melody is recalled even after it is stopped half-way. Although the recalled patterns are not always 100% correct, they are not completely destroyed even if the presented patterns are imperfect.  相似文献   

5.
This study provides a critical historical review and analysis of the variety of human expressions which have been erroneously labeled under the grandiose category mass hysteria. It is argued that Western science reductionist approaches to the classification of mass hysteria treat it as an entity to be discovered transculturally, and in their self-fulfilling search for universals systematically exclude what does not fit within the autonomous parameters of its Western-biased culture model, exemplifying what Kleinman (1977) terms a category fallacy. As a result of objectivist methodologies, the etiology of actions labeled as mass hysteria is typically viewed as deviant, irrational or abnormal behavior resulting from a malfunctioning proper social order. However, what constitutes the correct social order is a function of a researcher's historical sociocultural and/or scientific milieu. This study reviews the problem, advocating Geertz's (1973) culturally relativistic approach to understanding various cross-cultural behavior that is sensitive to and tolerant of the unique context and milieu of participants. Mass or epidemic hysteria is viewed as an invention of Western psychiatry and should be abandoned and replaced with the term collective exaggerated emotions. Instead of attempting to discover a neatly packaged, unitary external disease entity, the focus of a meaning-oriented approach emphasizes the deciphering of foreign realities, semantic networks and symbol systems.  相似文献   

6.
Conclusion Even a cursory look at the ethnographic literature on other Northwest Coast societies reveals some striking similarities with the Tlingit way of conceptualizing aristocrats as special persons. Thus the Kwakiutl referred to their chiefs as real or complete people, who were heavier than commoners. The Coast Tsimshian called their highest aristocrats real or ripe persons, in contrast to the low-ranking ones, who were described as unhealed or green. The Coast Tshimshian also referred to their chiefs as strong, heavy, and solid like a rock. The neighboring Gitksan contrasted the chiefs, described as people who were good and clean and stayed put, with the commoners, who were said to be dirty, ignorant, and always moving around. Because spirits of the dead liked to return to persons who were clean and showed respect by giving away wealth and feasts, there was considerable moral and practical pressure on the aristocrats to remain pure, train knowledgeable and clean heirs, and continue potlatching. Finally, among the Haida, rank was tied to a wider system of symbolic classification, associating aspects of food, space, clothing, ritual pollution and the ethic of industry with attributes of seniority.While some of the symbolic associations of aristocratic status are culture specific, others are present in several, if not all, of the NWC cultures. What we need is a comparative symbology of aristocratic status, which would combine the reanalysis of the existing ethnographic data with the introduction of some new materials that can still be obtained in the field. Such work would be the best tribute to Irving Goldman himself and to our common illustrious ancestors—Franz Boas and Marcel Mauss.Sergei Kan is Professor of Anthropology at Dartmouth College.  相似文献   

7.
Summary Secretory activities of bicellular microhairs from grasses belonging to the subfamilies Chloridoideae, Arundinoideae, Panicoideae, and Bambusoideae, and including the chloridoid, panicoid and Enneapogon microhair morphological types, have been investigated. Light microscopic histochemistry indicated that all microhairs studied secrete polysaccharide and protein (or glycoprotein), including those which also secrete salt. Localization of polysaccharide at ultrastructural level using periodic acid-thiocarbohydrazidesilver proteinate staining revealed that in panicoid type microhairs dictyosomes are involved in polysaccharide secretion, whereas in the chloridoid and Enneapogon types partitioning membranes seem to be involved instead.Abbreviations Ag silver precipitates representing localization of polysaccharide - BC basal cell - C cuticle - CC cap cell - CH cuticular chamber - CN system of membrane bound channels and vesicles - CP chloroplast - CW cell wall - D dictyosomes - M mitochondria - N nucleus - PTM partitioning membranes - RER rough endoplasmic reticulum - S secretory material - St starch grain - US unstained dictyosome cisternae - V vesicle  相似文献   

8.
At the transition from early reptilian ancestors to primordial mammals, the areas of sensory cortex that process topographic modalities acquire the laminar structure of isocortex. A prominent step in lamination is granulation, whereby the formerly unique principal layer of pyramidal cells is split by the insertion of a new layer of excitatory, but intrinsic, granule cells, layer IV. I consider the hypothesis that granulation, and the differentiation between supra- and infra-granular pyramidal layers, may be advantageous to support fine topography in their sensory maps. Fine topography implies a generic distinction between where information, explicitly mapped on the cortical sheet, and what information, represented in a distributed fashion as a distinct firing pattern across neurons. These patterns can be stored on recurrent collaterals in the cortex, and such memory can help substantially in the analysis of current sensory input. The simulation of a simplified network model demonstrates that a non-laminated patch of cortex must compromise between transmitting where information or retrieving what information. The simulation of a modified model including differentiation of a granular layer shows a modest but significant quantitative advantage, expressed as a less severe trade-off between what and where. The further connectivity differentiation between infra-granular and supra-granular pyramidal layers is shown to match the mix of what and where information optimal for their respective target structures.  相似文献   

9.
Soluble proteins from leaves of Nicotiana glauca Grah., N. langsdorffii Weinm., their reciprocal hybrids and amphiploid hybrid (N. glaucaxN. langsdorffii) were resolved by two-dimensional gel electrophoresis. Among a group of well-resolved polypeptides, in the isoelectric-point range of 5–5.5 and relative-molecular-mass (Mr) range of 18–23 kilodaltons (kDa), species-specific variation was observed. Polypeptides designated L and l are specific to N. langsdorffii, and G and g to N. glauca, while C is common to both species. Polypeptides L, G and C are localized in the chloroplasts and associated with thylakoid membranes. Polypeptide L is more acidic than polypeptide G, and both polypeptides have an Mr of 23 kDa. They were isolated from two-dimensional gels and their first 13 N-terminal amino-acid sequences were determined. These were found to be identical to the 13N-terminal amino acids of the photosystem II (PSII) 23-kDa polypeptide from spinach (T. Jansen et al. (1987) FEBS Lett. 216, 234–240) and, except for one change, to those from pea (R. Wales et al. (1989) Plant Molec. Biol., in press). Polypeptides G and L cross-react with antiserum against the PSII 23-kDa polypeptide from pea. Therefore, polypeptides G and L are extrinsic PSII 23-kDa polypeptides. They appear jointly and in equal amounts in the reciprocal hybrids. Since chloroplasts in Nicotiana are maternally inherited, these results demonstrate that polypeptides G and L are encoded by nuclear genes, are polymorphic variants of the PSII 23-kDa polypeptide, and are inherited in a Mendelian manner.Abbreviations kDa kilodalton - LS large subunit of Rubisco - Mr relative molecular mass - NEPHGE non-equilibrium pH gradient gel electrophoresis - PSII photosystem II - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - SS small subunit of Rubisco  相似文献   

10.
Paddy levees form networks of narrow linear habitats and play various roles in cultural landscapes. Traditional landscapes on the west side of Lake Biwa consist of paddy field terraces and both stone and soil levees that have been maintained by paddy field management using local resources. Paddy levees in this study site are principally classified into five different types. Our study points out how differences in paddy levee structure as well as in management practices influence the plant species. Seventeen paddy levee transects were split into four habitat types based on their species components by TWINSPAN. Spatial characteristics and physical structures of paddy levees depended on natural conditions and human activities. The species–area curves of each levee type showed a clear distinction: the soil, stone and abandoned curves were steep, while the concrete and consolidated ones were gentle. The vegetation on consolidated levees was utterly different from the vegetation on traditional levee types from the aspect of species richness and species components. Soil type levees contained various woody plant species and included more diverse and indigenous plant species than abandoned type levees.  相似文献   

11.
Zusammenfassung In zunehmendem Maße werden anisoploideBeta-Rübensorten angebaut, deren zytologische Kontrolle zwecks Feststellung der Genomstufenprozentanteile recht arbeitszeitaufwendig ist. Übereinstimmend mit polnischen Autoren wurde festgestellt, daß die Hypokotylfarbe ein geeigneter Markierungsfaktor für die einzelnen Genomstufen darstellt. Kreuzt man tetraploide Pflanzen, die ein grünes Hypokotyl besitzen, mit diploiden Pflanzen, die ein rosa Hypokotyl aufweisen, so erhält man von dem tetraploiden Partner tetraploide grüne und triploide hellbraune, von dem diploiden Partner diploide rosa und triploide hellbraune Nachkommenschaften. Die in bezug auf die Hypokotylfarbe heterozygoten Pflanzen kann man demnach von den homozygot grünen und homozygot rosa Individuen unterscheiden. Die Kreuzung diploid grünxtetraploid rosa ist für diese Zwecke nicht brauchbar, da sich die triploiden Heterozygoten mit einem grünen und zwei rosa Allelen in der Hypokotylfarbe nicht deutlich von den homozygoten rosa Pflanzen abheben. Auf die Bedeutung dieser Markierungsmöglichkeit für bestimmte Forschungsprobleme, die Züchtung und die Saatgutkontrolle wird hingewiesen.  相似文献   

12.
Summary The histochemical activities of succinic dehydrogenase (SDH), myofibrillar Adenosine triphosphatase (ATPase) and alpha glycerophosphate dehydrogenase were studied in serial sections of rat vastus lateralis (red) (RVL), gastrocnemius and diaphragm muscles. Three main fibre-types were distinguished. The Type I fibres of RVL and gastrocnemius muscles fell into two distinct groups: one category-Type IA showed very low ATPase activity. The second category of Type IB fibres displayed moderate ATPase reaction. The Type IA fibres were divisible into two sub-groups when tested for SDH reaction. Type IA1 fibres possessed a homogenous distribution of diformazan·granules throughout the fibre: Type IA2 fibres displayed characteristic moth-eaten pattern of diformazan localization. The diaphragm muscle did not show either Type IB or Type IA2 varieties. The great majority of Type I fibres were sub-type IA1 in the three fast muscles studied. It is also demonstrated here that an inherent heterogeneity exists between Type I fibres of diaphragm and leg muscles in regard to -GPD localization. This histochemical data emphasizes the fact that subdivision of Type I striated muscle fibres of mammalian animals into two sub-types is only approximate and that a further subcategorization is possible.  相似文献   

13.
Biology cannot accommodate all aspects of culture. Aspects of culture that a biological approach can take into account can be covered by the biological categories of phenotype and environment. There is no need to treat culture as a separate category. Attempts to elaborate biological explanations of cultural variation will meet with success only if biologists expand theories of development, and integrate them in evolutionary biology. The alternative — elaborating the idea of so-called cultural inheritance — makes little sense from a biological point of view.  相似文献   

14.
In the ascophoran bryozoanCryptosula pallasiana (Moll) many examples of regenerative growth and of abnormal zooids have been observed. Most of the different forms of monsters are caused by fusion of zooids or zooid buds respectively. Zooids may often fuse laterally but in a few cases also distally. Some monster zooids have two polypides and combined opercula caused by various degrees of fusion of the apertures. Lack of sufficient space may lead to the formation of dwarf zooids or remainder cystids.  相似文献   

15.
Thirty-two West African dwarf goats were exposed to temperature treatments: 20, 25, 30, 35, 35, 35, 30, 25, 20°C each lasting three days.Sixteen goats were kept in individual pens (I), the others in two group pens (G). Heat production (HP) and activity were recorded during 48 hours in each temperature treatment.Mean HP and ME intake were similar for G and I animals, but I animals had lower values than G animals at low chamber temperatures and higher values than G animals at high temperatures. Upper critical temperature was between 25°C and 30°C under an increasing T and between 30 and 35°C under a decreasing T. Adaptation of heat production and ME intake to a change in temperature of 5°C required at least six and possibly more than nine days.Diurnal variation in HP was large, up to 44% between extremes. This was largely due to variation in activity.  相似文献   

16.
R. H. Post 《Human genetics》1971,13(4):253-284
Summary Genetic traits which are disadvantageous or deleterious in primitive cultures, of hunters and food gatherers, have very low frequencies in almost all cases. There are a few special exceptions, such as the sickle cell trait. Some deleterious traits under genetic control are rare in primitive populations but have fairly high frequencies in populations with long histories or prehistories of civilization, such as Chinese, Japanese or European populations. The Darwinist might suggest that these traits have less selective disadvantage, that is, lower rates of selective elimination, in civilized habitats; i.e. that the various changes in habitat accompanying civilization have caused the rigor of natural selection to relax, in part or perhaps completely.Several cases are discussed of traits under genetic control or genetic influence which demonstrate this phenomenal contrast, between low frequencies among primitive populations and high frequencies among civilized populations. Population data are presented for 4 such cases: colorblindness, myopia, abnormality of the nasal septum and abnormally small external opening of the tear duct.
Zusammenfassung Mit einigen bekannten Ausnahmen, z. B. Sichelzellanämie, kommen genetische Merkmale, die bei den Urvölkern von Jägern und Sammlern ungünstig oder sogar schädlich wirkten, mit niedriger Häufigkeit vor. Genetisch bedingte schädliche Merkmale, die selten unter Urvölkern gefunden werden, kommen jedoch häufiger vor bei Bevölkerungen, die eine lange Geschichte bzw. Vorgeschichte der Zivilisation besitzen, wie z. B. in China, Japan oder Europa. Ein Darwinist würde behaupten, daß bei zivilisierten Wohnorten solche Merkmale selektiv weniger nachteilig wirken, d. h., daß die selektive Ausscheidung langsamer vorgeht. Anders gesagt: der mit der Zivilisation verbundene Wechsel des Wohnortes bildet einen Grund für eine Milderung der Strenge der natürlichen Auslese.Es werden einige genetisch bestimmte oder genetisch beeinflußte Merkmale besprochen, die den Unterschied zwischen den Häufigkeiten (niedrig bei Urvölkern, hoch bei zivilisierten Völkern) aufzeigen,. Für 4 solcher Fälle: Farbensinnstörungen, Kurzsichtigkeit, Nasenscheidenwand-Deformitäten und anomale kleine Außenöffnungen der Tränenwege werden die Befunde aus den Bevölkerungen dargestellt.
  相似文献   

17.
Various philosophers and evolutionary biologists have recently defended the thesis that species are individuals rather than sets. A decade of debates, however, did not suffice to settle the matter. Conceptual analysis shows that many of the key terms involved (individuation, evolutionary species, spatiotemporal restrictedness, individual) are ambiguous. Current disagreements should dissolve once this is recognized. Explication of the concepts involved leads to new programs for philosophical research. It could also help biology by showing how extant controversies concerning evolution may have conceptual rather than factual roots.  相似文献   

18.
Summary Myotendinous junctions in the myotomal tail muscles of the tadpole of Rana rugosa were examined by electron microscopy. At the site of the myotendinous junction, the sarcolemma is covered on its sarcoplasmic aspect by the connecting filament layer and the attachment layer, and on the extracellular aspect by the intermediary layer and the external lamina, with associated collagen fibrils. The intermediary layer consists of filamentous structures which closely resemble microfibrils (Hanak and Böck, 1971), spine-like or thread-like profiles (Korneliussen, 1973) and intermediary layer (Nakao, 1975a, b) in the myotendinous junctions of other vertebrate skeletal muscles.Particularly interesting is the fact that all the coverings and linings of the sarcolemma, including the external lamina, are completely absent in the terminal segment of the finger-like sarcolemmal invagination characteristic of the myotendinous junction. Furthermore, special types of coupling between a sac of sarcoplasmic reticulum and a part of the sarcolemmal invagination are frequently observed. These couplings always occur along the region of the sarcolemma where the external lamina is absent. The couplings show features similar to those of the triad, such as SR feet , scalloped SR membranes and granular content of the SR sac, suggesting that they are analogous and functionally similar to the triad and other equivalent structures.  相似文献   

19.
Summary In the present study, synaptic ribbons were studied morphologically and quantitatively in hamster pineal gland. The number of ribbons and spherules of hamster pinealocytes was counted over a 24-h period. The 24-h variations in the quantity of synaptic ribbons were found to parallel fluctuations in pineal melatonin concentrations. No significant circadian changes were observed for synaptic spherules, indicating different roles for these two structures.  相似文献   

20.
We have used restriction fragment length polymorphism (RFLP) analysis and DNA sequencing to characterize two distinct DRB1 alleles expressed on DRw52 and DQw7-associated haplotypes but not readily defined by conventional DR serology. These two haplotypes, designated HLA-D HAG and PEV, react variably with DRw13(w6), DRw14(w6), and the more broad DR 3+6 antisera. Analysis of RFLP revealed that HLA-D HAG and PEV are associated with different DRw52 variants, and that HAG is indistinguishable from DRw18(3) haplotypes. Sequencing of the HAG and PEV DRB1 genes showed each to represent novel alleles. Nevertheless, these sequences show similarities with the other alleles of the DR5, w6, and w8 family. HAG (DRB1*1303) appears to have arisen either from two recombinational events involving at least three DRB1 sequences (DRB1*1101, DRB1*0803, DRB1*0401) or from a single recombinational event together with multiple point mutational events. PEV appears to represent a DRB1*1301-1302/DRB1*1101 recombinant allele, with recombination having occured in the region of bases 175 – 198. The results of this study suggest that the DRw52 family haplotypes is derived from a relatively restricted number of ancestral sequences, with diversity among DRB1 alleles within this family arising through gene conversion or recombination events.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号