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 62 毫秒
1.
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   

2.
G. E. Marks 《Chromosoma》1965,16(6):681-692
Summary Phytophthora infestans has three kinds of somatic nuclei: an oval shaped nucleus (approx. 3.1×2.7 ) which stains diffusely except for a crescent shaped Feulgen positive cap which stains intensely; a granular nucleus whose contents are organized into a fairly constant number of stained bodies, and, a deeply staining condensed nucleus. The capped nucleus is thought to be metabolic or resting and the granular nucleus is thought to be dividing as it is most commonly found in hyphal tips. Attenuated forms of all three kinds of nuclei are found.Nuclear division is mitotic and intranuclear. Eight—ten chromosomes are seen at metaphase.Sporangia have a mean of 6.3 nuclei which is constant for age and strain of culture. Sporangia become multinucleate as a result of nuclear migration and not by division in the developing sporangium. Zoospores are usually uninucleate.The nuclear cap is persistent throughout nuclear division when it also divides. It is associated with flagella production and nuclear migration and has some of the properties of a blepharoplast.  相似文献   

3.
Summary Two-dimensional-electrophoretic analysis has been applied to non-neoplastic mammary epithelium from eight healthy women, tumor tissue from eight diploid mammary adenocarcinomas, and tumor tissue from eight aneuploid mammary adenocarcinomas. Compared with non-neoplastic mammary epithelium, a slight numerical net increase of the protein spots was detected in diploid tumors and a marked increase in aneuploid tumors. Two prominent spots were present in all 16 malignant tissues examined and absent in all eight non-neoplastic tissues (silver staining method).The results suggest that a difference in the composition of cellular proteins exists both between non-neoplastic mammary cells and malignant tumor cells, and between diploid and aneuploid tumors.In honour of Prof. P. von Duijn  相似文献   

4.
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   

5.
T. M. Butt  A. Beckett 《Protoplasma》1984,120(1-2):61-71
Summary A detailed account of the ultrastructure and behaviour of the spindle pole body (SPB) of the entomophthoraceous fungusErynia neoaphidis is presented for the first time.The SPB consists of extranuclear (ENC) and intranuclear (INC) components. The ENC is a saucepan-shaped structure which lies in a pocket of the nuclear envelope. It is composed of a forked, fibrillar handle and a shallow, cylindrical pan. The pan has a wall of two layers, both of which are thickened with a regular periodicity so that they appear to be beaded. It is postulated that the pan is formed from rough endoplasmic reticulum and that it synthesizes the amorphous, electron-dense material coating the ENC.The INC is a saucer-shaped, electron-dense plaque in which the ends of the spindle microtubules terminate. During metaphase, a clear zone separates the INC from the nuclear envelope and persists until telophase. The roles of the amorphous, electron-dense material and the clear zone as well as the method of SPB replication are discussed.  相似文献   

6.
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   

7.
    
Summary Ventral and dorsal aortic blood pressure, heart rate and plasma concentrations of adrenaline and noradrenaline have been measured in Atlantic cod before and after stress. The stress was induced by lowering the water level in the tank, which forced the animals to lie on their side struggling to regain the normal posture. The effects of stress were studied in fish in which the nerve supply to the head kidney was sectioned, using sham-operated animals as controls. In control animals, there was an increase in the ventral aortic blood pressure and plasma levels of both catecholamines as a result of stress while the dorsal aortic blood pressure remains constant and heart rate, if anything, decreases. The effect on the heart rate can be blocked by atropine, indicating a vagal reflex. In fish where catecholamine release from chromaffin tissue was strongly reduced by sectioning the nerve supply to the head kidney, the dorsal aortic blood pressure was lower before stress by comparison to controls, and decreased further following stress. No significant changes in ventral or dorsal aortic blood pressure and heart rate were observed in another group of fish where the sympathetic innervation of the gills had been sectioned, when compared to sham-operated controls before or after stress. It is concluded that circulating catecholamines released from the head kidney play a major role in the control of branchial vascular resistance after stress, counter-acting the effect of a non-adrenergic constrictory innervation of the gills. Circulating catecholamines may also be of importance in the control of systemic vascular resistance after stress.Abbreviations DAP mean dorsal aortic blood pressure - VAP mean ventral aortic blood pressure - HR heart rate - TBPD transbranchial pressure drop (VAP-DAP)  相似文献   

8.
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   

9.
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   

10.
A more precise taxonomic concept ofE. hirtella and its infraspecific synonymy is presented. Its diploid nature (2n = 22) is confirmed. Within the European area ofE. hirtella five different races may be recognised: typical, brandisii, capitulata, Rofan and Bretagne. Taxonomic rank is not yet attributed to these races. The heterogeneous taxonomic assembly E. drosocalyx is disentangled. The type refers to products of hybrid introgression ofE. rostkoviana-characters (long glandular hairs) intoE. minima.
Former contributions of this series areEhrendorfer & Vitek (1984) andGreilhuber & al. (1984).  相似文献   

11.
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   

12.
Summary Stationary phase cells of strain phr/MC 2 ofE. coli are not photoreactivable but the frequency of UV-induced mutations to low Streptomycine-resistance (S 3, 3/ml) is decreased strongly by illumination with light of fluorescence tubes (310 to 500 nm) after UV-irradiation. Also dark-reversion (DRM) of these mutations due to keeping UV-irradiated cells in saline is observed. Illumination before UV-irradiation decreases the frequency of the mutations (photoprotection against mutation=PPM) to the same extent as the combined action of photoreversion (PRM) and DRM. The lag-phase of cell division is prolonged strongly by illumination from 80 min without light to 150 min by the light-dose of highest activity. The additional lag is nearly the same if the illumination is done before, after or without UV-irradiation; this lag is about additive to the small lag caused by UV. Pre-illumination of the stationary-phase cells does not cause photoprotection against killing (PP), it even decreases the survival after high UV-doses. The observations support the hypothesis that PRM in this strain may be indirect, i.e. caused by the light-induced additional division lag which enhances the dark repair of UV-premutations. Also spontaneous premutations which are apparently present in the stationary-phase cells seem to be influenced by the light in this way.  相似文献   

13.
As a supporting component of the VALIMARproject, physicochemical investigations wereconducted monthly from 1995 to 1999 at theKrähenbach/Aich stream system (two samplingsites) and at the Körsch stream (sixsampling sites). Several physicochemicalparameters were analysed continuously bydataloggers during the entire sampling period.Moreover, a selection of the most importantmorphological parameters of the stream wererecorded in 1998.The results of these physicochemicalinvestigations demonstrated that theKrähenbach/Aich system could becharacterized as a natural rhithral submontanecarbonate stream system that is welloxygenated. Low temporal variations in pH,conductivity and chloride occurred at allsampling sites in the Krähenbach whichcoincided with the geological conditions atthis test stream. Because of relatively lowconcentrations of organic and inorganiccompounds during the entire study period thesites AB and AC in the Krähenbach/Aichsystem were classified as slightly polluted.The morphological assessment of the streamindicated a moderately affected status atboth of these streams.Physicochemical and morphologicalinvestigations along the Körsch streamsystem (KA to KE including the tributary streamSulzbach) indicated a highly affected rhithralsubmontane carbonate system characterized byhigh water velocity, flow rate and dissolvedoxygen. The Körsch, however, differssignificantly with respect to watertemperature, conductivity, pH, BOD5,nutrients, and chloride concentrations from theKrähenbach. As a result of differentanthropogenic inputs (e.g. several sewageplants, agriculture activities and waste waterdumping) the Körsch sites KA to KD wereclassified as critically to heavilypolluted. The morphological assessmentindicated a clearly affected to damagedstatus. The upstream site KE could becharacterized as slightly polluted and itsmorphological structure as moderatelyaffected.  相似文献   

14.
Summary The incidence of myosatellite cells associated with white and red muscle fibres of the parietal muscle and red fibres of the craniovelar muscle was estimated by quantitative electron microscopy in the Atlantic hagfish (Myxine glutinosa, L.). Myosatellite cell nuclei constitute 3, 11 and 23 % of the total number of nuclei inside the basal lamina of the three types of muscle fibres, respectively. However, the total number of nuclei is highest in white fibres, most of the nuclei belonging to striated muscle cells. Myosatellite cell profiles in transverse sections constitute 23, 41 and 61 % of the number of muscle fibre profiles of the three types, respectively. The intervals between adjacent myosatellite cells are 135 m in white fibres, 55 m in red parietal fibres, and only 25 m in craniovelar fibres. Since craniovelar fibres are also comparatively thin, myosatellite cells constitute a significant fraction of the volume inside the basal lamina in these fibres. The myosatellite cells are 30–50 m long and up to 5 m thick. Some myosatellite cells possess few organelles, whereas others appear to contain many free ribosomes, granular endoplasmic reticulum, prominent Golgi apparatus and lysosome-like bodies.This investigation was supported by the Norwegian Research Council for Science and the Humanities (NAVF grant No. C20.30–37). The authors are indebted to Jorunn Line Vaaland and Berit Branil for technical assistance, and to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supplying the hagfish  相似文献   

15.
Until the most recent times, products of nature were unpatentable, not as failing to qualify as a manufacture for which patent protection may be sought under 35 U.S.C. §101, but because they were mere isolates of natural products. Genetically engineered microorganisms (e.g., Chakrabarty's plasmid-injected oil eatingPseudomonas) and biologically pure cultures of wild strains (e.g., Bergy'sStreptomyces which produces the antibiotic lincomycin) open uncharted waters in patent law.  相似文献   

16.
Summary A new cytochemical technique is proposed for side by side localization of acetylcholine and of acetylcholinesterase activity of motor end-plate at ultrastructural level. The technique is based on the simultaneous ionic fixation of vesicular acetylcholine and of histochemical copper thiocholine precipitate with phosphomolybdic acid: the molybdic heteropolyanion forms insoluble salts with these two quaternary ammonium cations, providing in situ acetylcholine phosphomolybdate and copper thiocholine phosphomolybdate. Both of them are osmium resistant; the electron dense precipitates allow for a fine localization of acetylcholine and acetylcholinesterase activity at electron microscopic level.  相似文献   

17.
The lack of comparative reviews of the efficacy of EMG frontalis biofeedback versus alternative procedures for reduction of muscle tension prompted the present meta-analytic treatment of literature previously concluded to be equivocal. Twenty studies comparing EMG frontalis biofeedback with other tension-reduction procedures produced a total of 68 separate effect sizes suitable for meta-analysis. Differences between clinical and normal samples were nonsignificant, and data analyses revealed that EMG frontalis biofeedback was significantly superior to control (p<.05) but that alternative forms of muscle relaxation, while effective, did not reach statistical significance.  相似文献   

18.
Zusammenfassung Der Verlauf des Nahrungsflusses im Darmtrakt der Kleinzikade Euscelidius variegatus wird nach Verfütterung von farbstoffhaltiger Nährlösung ermittelt. Es wird der Beweis erbracht, daß die aufgenommene Nahrungsmenge in der Filterkammer geteilt wird und die beiden Anteile den Darmtrakt auf zwei verschiedenen Wegen in Richtung Rektalblase passieren. Ein Anteil der aufgenommenen Nährlösung wird über einen Kurzschlußweg in der Filterkammer sowohl über den Filterkammerdarm als auch über die Kryptonephridien direkt in den Enddarm gepumpt, während die in der Magentasche der Filterkammer verbleibenden Nahrungsanteile über einen langen Verdauungsweg zum After gelangen. Hierbei wird der Magentascheninhalt in den Magen gedrückt. Von dort aus passiert er den Mitteldarm und erreicht über den Enddarm den After. Der Kurzschlußweg und der Verdauungsweg können gleichzeitig benutzt werden. Der Kurzschlußweg wird von der Nahrung jedoch in viel kürzerer Zeit durchströmt als der längere Verdauungsweg.
The directions of the flow of food in the alimentary trad of the leafhopper Euscelidius variegatus KBM. (Jassidae)
Summary The leafhopper Euscelidius variegatus is fed with synthetic food, coloured with 1% Azorubin-S. Its flow in the alimentary tract has been studied. It has been found that the sucked-in food is divided into two parts in the filter chamber, each taking different way in the alimentary tract for its flow. One part of the food is pumped into the hindgut via the short circuit way going through the filter chamber once over the Filterkammerdarm and also over the kryptonephries. That part of the food, which remains in the pocket of the filter chamber takes the long digestion way to the anus over stomach, midgut and hindgut. Both the ways could be used at the same time. But the food takes much shorter time for its passage through the short circuit way as compared to the time needed for the long digestion way.
  相似文献   

19.
A presumed XY chromosome pair is described fromt estis squashes from the mesopelagic deep-sea fish Bathylagus wesethi, whose 2N chromosome number was determined as 34-XY. Although the metacentric X-chromosome is the largest in the entire compliment, the Y is the smallest and only acrocentric element. The positive heteropycnosis of the sex elements was not easily distinguishable in the nuclei of first meiotic prophase. Tetraploid nuclei were observed in peripheral supporting cells of the testis. Males of at least two other congeners have similar karyotypes.  相似文献   

20.
Summary Analysis of 62 mature Norway spruce (Picea abies provenance Viborg) trees growing in a Danish plantation was undertaken along with analysis of their nutrient contents (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Na), in each of the three youngest needle age classes, from branches of four exposure directions near the tree top. The aim was to investigate if one among the studied possible predisposing factors was also a triggering factor in the 1989 outbreak of the Red Norway spruce decline in Denmark. Neither nutrient imbalance or deficiency, nor excessive N-deposition or salt-stress were indicated as triggering factors in 1989. The Red syndrome, noticeable for the bright red colour of the current-year needles, was found to be an extension of the European type Novel Decline. Red syndrome is similar to previously reported phenomena of top-dying and sub top-dying, in that it had fewer needle age classes and significantly higher contents of mobile cations (and Ca) in the younger needle classes. Tree ring analysis suggested that the Red syndrome was initiated in the early 1980s, when the trees experienced adverse climatic conditions. Because of this long-term development of the Red Norway spruce decline syndrome, it is concluded that a triggering factor is of minor importance relative to the multitude of predisposing factors.  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