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.
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   

2.
Summary The temporal muscles of the guinea pig show a sexual differentiation reflected in their histochemical enzyme pattern. Using histochemical methods for mitochondrial (SDH, -GPDH), and glycolytic enzymes (phosphorylase, LDH) it could be shown, that in adult animals the male muscle is a white muscle with marked activity of glycolytic enzymes, the female muscle a red muscle displaying high activity of mitochondrial enzymes. This differential enzyme pattern can be converted by the application of testosterone to the female type during the postnatal development. The male sex hormone thus affects the histochemical enzyme pattern of the muscle, converting the red, female into a white, male muscle in the female guinea pig.  相似文献   

3.
A contextualizing image (CI) is a powerful central image of a dream which appears to contextualize (provide a picture-context for) the dreamer's emotion. For instance, dreamers who have experienced any serious traumatic event sometimes dream, I was overwhelmed by a tidal wave. This appears to picture their feeling of terror and/or vulnerability.A scoring system for CIs is examined here and is applied to dreams and daydreams supplied by 40 students. Two raters scoring dreams on a blind basis showed good inter-rater reliability. Recent dreams were shown to have more as well as more intense CIs than recent daydreams; likewise, dreams that stand out had more intense CIs than daydreams that stand out. Students with thin boundaries had more and more intense CIs than students with thick boundaries in their recent dreams and nightmare, but not so clearly in dreams and nightmares that stand out. The emotions judged as contextualized by the powerful images tended towards fear/terror and helplessness/vulnerability in dreams (especially in dreams that stand out) whereas emotions contextualized by images in daydreams showed a wide range with no clusters.  相似文献   

4.
Summary Two intracapillary (IC) media feed protocols termed media rich and media lean were examined in an effort to understand the effect of this variable on hollow fiber cell cultures. The media rich protocol emphasized a high volume IC media per day (5 liters) containing no serum and a normal amount of extracapillary (EC) media serum (10% v/v). Alternatively, the media lean protocol used up to 1.0 liter of IC media per day containing 5% v/v serum and increased EC media serum (20% v/v). Both protocols produced substantial amounts of antibody in 25 days using HFN7.1 hybridoma cells (ATCC CRL 1606), however the media rich protocol produced twice as much antibody as the media lean protocol. The metabolism of the cells was dramatically different as measured by glucose uptake rate (GUR) with media lean cells having a six-fold lower GUR. Our results indicate that the media rich protocol is useful for producing larger amounts of antibody in a short time frame. The media lean protocol may be considered when the production costs of antibody, particularly media and serum, is the overriding concern.  相似文献   

5.
The paper characterizes Darwin's theory, providing a synthesis of recent historical investigations in this area. Darwin's reading of Malthus led him to appreciate the importance of population pressures, and subsequently of natural selection, with the help of the wedge metaphor. But, in itself, natural selection did not furnish an adequate account of the origin of species, for which a principle of divergence was needed. Initially, Darwin attributed this to geographical isolation, but later, following his work on barnacles which underscored the significance of variation, and arising from his work on botanical arithmetic, he supposed that diversity allowed more places to be occupied in a given region. So isolation was not regarded as essential. Large regions with intense competition, and with ample variation spread by blending, would facilitate speciation. The notion of place was different from niche, and it is questioned whether Darwin's views on ecology were as modern as is commonly supposed. Two notions of struggle are found in Darwin's theory; and three notions of variation. Criticisms of his theory led him to emphasize the importance of variation over a range of forms. Hence the theory was populational rather than typological. The theory required a Lamarckian notion of inheritable changes initiated by the environment as a source of variation. Also, Darwin deployed a use/habit theory; and the notion of sexual selection. Selection normally acted at the level of the individual, though kin selection was possible. Group selection was hinted at for man. Darwin's thinking (and also the exposition of his theory) was generally guided by the domestic-organism analogy, which satisfied his methodological requirement of a vera causa principle.  相似文献   

6.
Summary Motor nerve terminals on white and intermediate muscle fibers of the Atlantic hagfish (Myxine glutinosa, L.) contain translucent synpatic vesicles and about 1–2% dense-core vesicles. Terminals on red muscle fibers contain up to 40% dense-core vesicles with diameter 800–1100 Å. Examinations for formaldehyde-induced fluorescence indicate yellow fluorescence (5-HT ?) apparently corresponding with terminal axons on red muscle fibers in craniovelar muscles. Possibly red muscle fibers of Myxine receive monoaminergic innervation.The author is indebted to Dr. Finn Walvig, Biological station, University of Oslo, Drøbak, for supply of hagfishes.  相似文献   

7.
F. Kozár 《Oecologia》1987,73(1):99-104
Summary A large scale survey, covering some 25 million km2 of Eastern-Europe, provided distributional data, and a more detailed picture on factors determining species composition and abundance of scale-insects colonizing deciduous orchard trees. No interspecific competition or competitive situations were detected among the 21 scale insect species, when taking into consideration the whole geographic area surveyed. Of all cases, 3.2% showed significant spatial separation in smaller geographic regions. However, no evidence for competition was found between species with overlapping distributions. In the case of introduced species, the role of past competition can also be excluded. Separation was thought to be determined by differences in ecological requirements. There is some probability of competition in the transitional zone (significant separation in 0.8% of cases), and somewhat more (2.4%) in the Southern zone. There was potential competition between species classified as Mediterranean and invader subguilds (7.1% of frequent species pairs), as well as between the Southern and invader (2.4% of frequent species pairs) subguilds. Its probability was very low between the species of the endemic (0.8% of frequent species pairs) and invader (1.6% of frequent species pairs) subguilds.  相似文献   

8.
Summary Using techniques for enhanced microtubular preservation, including albumin pretreatment (Gray, 1975), occipital cortex of rats was studied electron microscopically at various ages of development. A close structural relationship was seen between microtubules, sacs of SER and the postsynaptic thickening in primordial spines and with the dense plate material of spine apparatuses. Stereoscopic preparations in addition show a more complicated substructure than previously described for the plate. Microtubules may contribute to the formation of the plate of the spine apparatus which in turn is associated with the postsynaptic thickening of the mature spine. Possible functional correlates are discussed.Dr. L.E. Westrum is an affiliate of the CDMRC at the University of Washington and a recipient of a Burroughs-Wellcome (USA) — Wellcome Trust (U.K.) Research Travel Grant. The research was also supported in part by NIH Grants NS 09678, NS 04053 (NINCDS) and DE 04942 (NIDR), DHHS  相似文献   

9.
    
Zusammenfassung Es wird über Laboratoriums-Versuche mit 3 verschiedenen Typen von Bacillus thuringiensis-Präparaten an Honigbienen berichtet: (a) mit dem Sporen- Endotoxin-Komplex, (b) mit vegetativen Zellen und (c) mit von diesen produziertem wasserlöslichem thermostabilem Exotoxin. Während Sporen-Endotoxin-Präparate (geprüft an 5 Varietäten) in den für die Bekämpfung von Lepidopteren-Raupen benutzten Dosierungen ungefährlich sind, wirken hohe Dosen toxisch, wenn sie im Futtersaft adulten Bienen appliziert werden. Ein durch vegetative Zellen bedingter nachteiliger Einfluß auf Bienen wurde nicht beobachtet. Das Exotoxin welches von bestimmten Varietäten (z.B. var. thuringiensis) in die Kulturflüssigkeit abgegeben wird, wirkt auf Bienen giftig, wenn es im Futtersaft und als Konzentrat verfüttert wird.
Summary In laboratory trials the effects of three types of preparations of Bacillus thuringiensis were tested on adult honey bees (Apis mellifera L.): (a) the spore-endotoxin-complex, (b) vegetative cells, and (c) the exotoxin. Though spore-endotoxin-preparations (of 5 varieties) were harmless to bees in dosage used for biological control, higher dosages applied in sugar solution were toxic. By using a medium concentration of vegetative cells no disease symptoms could be observed on bees. But the water-soluble thermostable factor, the so-called exotoxin, which is produced by the vegetative cells of several varieties (for example var. thuringiensis), was toxic to bees after feeding. The consequences of these observations are discussed.
  相似文献   

10.
Summary Genetic evidence for a dimeric structure of dihydropteridine reductase in man and in the fish species Cheirodon axelrodi and Salmo irideus is presented. A single locus in man and two loci in the fishes examined encode this enzyme. Zymograms revealed two alleles for the locus in man and two alleles for each locus in the fish Cheirodon axelrodi. The liver homogenate of a patient with dihydropteridine reductase deficiency showed no detectable activity in the gel, while his parents showed the normal electrophoretic phenotype.  相似文献   

11.
Summary The mitochondrial ATPase from a PHO 1 mutant (OLI 2, PHO 1, OLI 4 region on mit DNA of S. cerevisiae) was further examined. A new purification method using Lysolecithin instead of Triton allowed us to solubilize and separate a heterogeneous ATPase population from PHO 1-mitochondria: the major abnormal fraction had extremely low oligomycin-sensitivity (but normal specific immunological reactivity), while a minor normal fraction (representing about 20% of the initial mitochondrial ATPase activity) had high sensitivity and affinity for oligomycin.Moderate urea treatment of PHO 1-mitochondria leads to partial loss of ATPase activity and a concomitant increase of oligomycin-sensitivity, suggesting that a heterogeneous ATPase population exists in situ in the mitochondrial membrane: part of the major abnormal ATPase fraction is selectively inactivated by urea, producing a concomitant enrichment in the initially minor normal ATPase fraction.If the minor normal ATPase fraction is the only one capable of in vivo ATP synthesis, the deficient but oligomycin-sensitive cell growth and oxidative phosphorylation in vitro are readily explained.Further structural studies are under way to ascertain whether the minor normal ATPase fraction is strictly identical to the wild type, in which case PHO 1 is a regulatory gene, or not, in which case PHO 1 is a structural gene.  相似文献   

12.
E. F. Abel 《Oecologia》1970,4(2):133-142
Zusammenfassung Die Tentakel der Edelkoralle vermögen sich an den Spitzen bis über die dreifache Länge der Normtentakel fadenartig zu verlängern (Fadententakel). Diese Tentakelfäden wickeln sich bei Berührung eines Nahrungsobjekts korkzieherartig auf und nähern dieses durch Kontraktion der Mundöffnung.Damit koordiniert führen die zugehörigen Basalabschnitte (Normtentakel) durch S-förmige Biegungen und eventuelle Verkürzungen die Stelle der gereizten Tentakelfadens präzise zum Mund.Werden die Normtentakel allein gereizt, so antworten sie mit raschem Einschlag zur Mundöffnung. Bei gleichzeitiger Reaktion aller Tentakel wird dadurch eine Tentakel-Faust oder ein Fangkorb gebildet. Bei schwachen Reizen antwortet der Normtentakel anstelle der schlagenden Reaktionen mit langsamen Krümmungen, die das Objekt zur Mundöffnung dirigieren. Unabhängig von der Reaktionsart der Tentakeln wird die Beute vor der Aufnahme stets geprüft und häufig abgelehnt. Ist der Polyp in Freßstimmung, so wird die Nahrung rasch durch das glockenartig erweiterte Schlundrohr geschleust und verschwindet nach wenigen Minuten im Coelenteron.
The tentacle apparatus of the red coral (Corallium rubrum L.) and its role in feeding behaviour
Summary The tentacles of the octocoral Corallium rubrum may become extremely elongated (threadlike-tentacle) the apical part of the norm-tentacle becoming stretched more than three times as much as the base.The threadlike parts of the tentacles contract corcscrew-like when touched by food particles.The stimulated part of the tentacle is brought close to the mouth by coordinated movements of its basal portion. Very often both threadlike-tentacle and norm-tentacle shorten in order to carry the particle to the pharynx.When the norm-tentacles only are touched, they react with quick strokes towards the oral disc. This behaviour, when shown by all tentacles at the same time results in the formation of either a tentacle-fist or a basketlike structure. At slight irritations the norm-tentacle will respond with slow bending movements, which lead the particle towards the mouth. Independent of the type of tentacle reactions the prey is always checked before entering the pharynx, and very often refused.If the polyp decides to accept, food is transported quickly through the elongated pharynx and within a few minutes will have disappeared in the coelenteron.
  相似文献   

13.
It is shown that the utility of usual circular line source models is highly questionable. A line source model related to arbitrary cross-sections is given and essential differences between the source strength of the circular and non-circular model are found in the case of fairly flat elliptic fibers.  相似文献   

14.
Summary Clothed men at rest were exposed to two conditioning indoor environments (British, coolmoist; American, warm dry) for 45 minutes, and then to a cold environment (36°F) at moderate and high relative humidity (50% and 85%). The following measurements were taken: Temperature—skin, rectum and clothing gradients; nude body weight change and metabolism; subjective data. An attempt was made to measure clothing humidity gradients. The results showed that warm conditioning kept the clothing and skin at a higher temperature for a matter of 1 1/2 hours or more during cold exposure. The physiological value of such conditioning may be less marked under field conditions. No physiological objective or subjective differences of practical importance were found between the effects of still air at 36°F at moderate or high humidity, except for the finding of a slightly warmer skin of the chest at the high humidity. These results agree fairly well with those of other workers for nude men.From the date obtained there is no clear evidence that sorption heat of wool is an important factor in keeping the body warm at resting conditions. Under field conditions, sorption heat might be of still less value. There is no basis for the supposition that moist air is either a better thermal conductor or a more efficient heat convector than dry air. The physiological difference between dry cold and damp cold is not due to properties of humid air, but to the associated weather or climatic differences (solar radiation, cloud cover, wind, barometric pressure, etc.) and, to some extent, to the mode of living indoors. Data from physical models and from physiological experiments in climatic chambers cannot be directly transposed into the realities of weather and climate out of doors.With statistical design and analysis by J. Draper  相似文献   

15.
Zusammenfassung Das Zetern der Amseln wurde von 1969 bis 1972 in einem sehr regelmäßig besetzten Revier automatisch registriert. Sowohl das Zetern sämtlicher registrierter Amseln, als auch das Zetern bestimmter Individuen gehorchen den meisten Aschoff'schen Regeln. Zwischen Individuen sind die Zeteranfänge äußerst unterschiedlich, die Zeterenden dagegen nicht. Die individuellen Zeteranfänge reichen in der Vergleichszeit von ca. 50 min bis 20 min vor Sonnenaufgang (Mittelwerte für 1/3 Monat).
The alarm-call activity of the Blackbird
Summary In a very regulary occupied district the alarm-call (Zetern) of blackbirds was automatically recorded from 1969 till 1972. The Zetern of all recorded blackbirds as well as the Zetern of single individuals obey to most of Aschoff's rules. Among the individuals the beginnings of the Zetern are extremly different, but not the endings of the Zetern.The interindividual beginnings of Zetern in the comparable time reach from about 50 min. to about 20 min. before sunrise (mean values for 1/3 of a month).
  相似文献   

16.
Summary The slow reassociating fraction of mouse DNA (unique DNA), when allowed to reassociate in 0.14 m sodium phosphate buffer at 50 °C showed a biphasic melting curve with a transition at 78–80 °C. On the basis of this feature, the slow reassociating DNA was separated preparatively into two fractions: unique DNA I and II. Their duplexes showed differences with respect to thermal stability, S1 nuclease resistance and rate of reassociation. About one third of the sequences in each fraction were fraction-specific. The conclusion was drawn that for unique DNA I these should be the low repetitive or single copy related sequences (multigene families) and for unique DNA II—the unrelated single copy sequences or recent families of low repetitive not yet diverged sequences.  相似文献   

17.
In many kinds of permeabilized cells, the restriction of metabolite diffusion by a mitochondrial porin closed state has been shown to control the respiration rate. However, since in isolated mitochondria the porin appears to be always open, the physiological relevance of a putative regulation via this channel status is now a subject of discussion. In Saccharomyces cerevisiae, in which some of the NADH dehydrogenase active sites are facing the intermembrane space, this regulatory mechanism might play an important role for the regulation of the cytosolic redox status. Using permeabilized spheroplasts from wild-type and porin-deficient mutant, we show that the NADH produced in the cytosol is channeled to the mitochondrial NADH dehydrogenases through a metabolic network involving the porin channel. Thus, the control exerted by the porin (i.e., open or closed state) seems to be determined through its participation or not in organized metabolic networks.  相似文献   

18.
Within evolutionary biology a distinction is frequently made between proximate and ultimate causes. One apparently plausible interpretation of this dichotomy is that proximate causes concern processes occurring during the life of an organism while ultimate causes refer to those processes (particularly natural selection) that shaped its genome. But ultimate causes are not sought through historical investigations of an organisms lineage. Rather, explanations referring to ultimate causes typically emerge from functional analyses. But these functional analyses do not identify causes of any kind, much less ultimate ones. So-called ultimate explanations are not about causes in any sense resembling those of proximate explanations. The attitude, implicit in the term ultimate cause, that these functional analyses are somehow superordinate to those involving proximate causes is unfounded. Ultimate causes are neither ultimate nor causes.  相似文献   

19.
The immune system furnishes the organism with the utmost effective defence mechanisms against foreign and changes in self without doing self-harm. However, optimized efficacy in the defence against the immense variety of foreign antigens generates a higher risk for inadvertent self challenge. Such inherent short-comings are the inevitable burden traded for the benefits of an optimally organized defence system. The central molecules involved in specific immune reactions include antigen receptors of B and T lymphocytes, and antigen-presenting proteins encoded by the major histocompatibility complex (MHC; in man HLA). The genetics and evolution of these multigene families is discussed here with respect to their potential contributions to disturbances of self recognition. Simple molecular biological tools and procedures for efficiently screening the immunologically relevant genes are described.Dedicated to Professor Dr. U. Wolf on the occasion of his 60th birthday  相似文献   

20.
Summary The cycle of the seminiferous epithelium of the nine-banded armadillo can be divided into ten stages. As in most mammals, only one stage is observed per tubular cross-section. The process of spermiogenesis can be divided into thirteen steps according to the development of the acrosomal system and the flagellum. Four generations of spermatogonia are observed in the germinal epithelium: 1) stem cells, 2) type A, 3) intermediate, and 4) type B spermatogonia. The stem cell is characterized by a highly irregular nucleus and the presence of glycogen in its cytoplasm. The type A spermatogonium contains an oblong nucleus with one or two shallow infoldings of the nuclear membrane. The intermediate spermatogonium contains an ovoid nucleus characterized by one or two nuclei and heterochromatin scattered in the nucleoplasm. The nucleus of the type B spermatogonium is more spherically shaped with a centrally placed nucleolus and heterochromatin associated with the nuclear envelope.The author wishes to acknowledge the technical assistance of Teri Lane  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