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1.
The effects of physiological and excessive levels of growth hormone (GH) on reproductive functions are poorly understood, and impairment of fertility is frequently observed in transgenic animals overexpressing GH genes. The present study was undertaken to determine the effects of chronic exposure to heterologous bovine GH (bGH) on the testes and accessory reproductive glands in transgenic mice. Endocrine function of the testes was evaluated by measuring the activities of two steroidogenic enzymes, 5-3-hydroxysteroid dehydrogenase (5-3-HSD) and 17-hydroxysteroid dehydrogenase (17-HSD). The activities of acid phosphatase, alkaline phosphatase and -glucuronidase, important hydrolytic enzymes of lysosomal origin, were measured in testes, seminal vesicles and ventral prostates in normal and transgenic mice. Testicular 5-3-HSD activity was higher in transgenic than in normal mice, while testicular 17-HSD activity in transgenic mice was not altered. Acid phosphatase activity was elevated in both seminal vesicles and ventral prostates of transgenic mice, while alkaline phosphatase activity was increased only in the prostate. The activity of -glucuronidase was elevated in the testes, seminal vesicles and ventral prostate gland of transgenic mice. These results suggest that chronic exposure to bGH is associated with significant stimulation of some hydrolytic enzymes in the testes and in the accessory reproductive glands of transgenic mice.  相似文献   

2.
Petitpierre E  Garnería I 《Genetica》2003,119(2):193-199
The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xyp male meioformula, three have 2n=40 and 19+Xyp and one 2n=46 and 22+Xyp. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.  相似文献   

3.
Zusammenfassung In 2 Versuchsserien wurden Kohlmeisen(Parus major) und japanische Möwchen(Lonchura striata var.domestica) einzeln und schallisoliert gehalten. In der ersten Versuchsserie, in der alle Vögel einen dunklen Schlafkasten hatten, wurde der Einfluß der Beleuchtungsstärke auf die Periode () der Hüpfaktivität und auf das Verhältnis von Aktivitätszeit zu Ruhezeit ( : -Verhältnis) untersucht. Sowhol Kohlmeisen als auch japanische Möwchen folgen der Regel, daß mit wachsender Beleuchtungsstärke die Periode kürzer und das : -Verhältnis größer wird.In der 2. Serie wurde der Einfluß Ruhe im dunklen Schlafkasten auf die Periodenlänge und auf das : -Verhältnis untersucht. Es wurden die Messungen aus Bedingung 1 (der Vogel hat einen dunklen Schlafkasten zur Verfügung) mit den Messungen aus Bedingung 2 (der Vogel hat keinen oder einen hellen Schlafkasten zur Verfügung) verglichen. Das Ergebnis bei Kohlmeisen entspricht den Befunden bei konstantem Licht verschiedener Intensität. Unter Bedingung 1 ist länger und das : -Verhältnis kleiner als in Bedingung 2. Das Ausmaß der Änderung von nach Fortnahme des dunklen Kastens ist unabhängig von der Periodenlänge in Bedingung 1. Das Ausmaß der änderung von : ist unabhängig von a : in Bedingung 1, jedoch schwach negativ korreliert mit der Periodenlänge in Bedingung 1.Bei japanischen Möwchen entsprechen die Ergebnisse dieser Versuchsserie nicht der Regel für tagaktive Vögel. Mit Benützen des dunklen Schlafkastens ist kürzer als ohne den Schlafkasten. Ohne den Schlafkasten ist etwa 24 Std. Das : -Verhältnis ist in Bedingung 1 unter bestimmten Voraussetzungen kleiner als in Bedingung 2. Das Ausmaß der Änderung von nach Fortnahme des Kastens ist mit der dazugehörigen Periode in Bedingung 1 hochsignifikant korreliert (Regressionskoeffizient b=-1.01, Korrelationskoeffizient r=0.89). Ebenfalls ist das Ausmaß der Änderung von : nach Fortnahme des Kastens mit : aus Bedingung 1 korreliert; es scheint, als würde ein bevorzugtes : -Verhältnis von etwa 2.0 eingeregelt.Die Ergebnisse werden im Hinblick auf 4 Punkte diskutiert: 1) Das circadiane System arbeitet innerhalb eines engen Bereiches von - und : -Werten optimal. 2) Der Optimalbereich wird bevorzugt unter ungünstigen Bedingungen angestrebt. 3) Der Entzug des dunklen Schlafkastens belastet japanische Möwchen mehr als Kohlmeisen. 4) Bei japanischen Möwchen wird in Bedingung 1 durch fortplfanzungsphysiologischen Einfluß verkürzt.
Circadian activity rhythms of birds with and without a dark nest box
Summary Perch-hopping activity of Great tits(Parus major) and Bengales finches(Lonchura striata domestica), housed individually in soundproof boxes, was studied in two series of experiments. In the first series all birds had access to a dark nest box, in which they retired during their subjective night. In this experiment the effect of light intensity on the freerunning circadian activity rhythm was investigated. Both Great tits and Bengalese finches obey the circadian rule by responding to an increase in light intensity with shortening the circadian period () and with an increase of the ratio of activity time and rest time ( : ).In the second series of experiments the influence of sleeping in the dark nest box on both circadian period and : -ratio was studied. The results of two experimental conditions — without and with access to a dark nest box — were compared. In the Great tits, the results are in agreement with the effect of light intensity: when a dark nestbox is available, is longer and the : -ratio is smaller than in the absence of a nest box. The magnitude of the change in free-running period after removal of the nest box is independent of the original value of ; the amount of change : -ratio is likewise independent of the original : -ratio, but is weakly correlated to the original .InLonchura striata var. domestica, removal of the dark nest box leads to a lenghtening of the free-running period to about 24 hours; the : -ratio is smaller in the presence of a dark nestbox, if certain other conditions are fulfilled. The magnitude of the change in after removal of the nest box is highly correlated to the original free-running period (r=-0.89) in such a way that, without nest box, the period approaches a value of 24 hours. Also, the amount of change in : -ratio due to nest box removal is negatively correlated to the original : -ratio. A probably preferred : -ratio of 2.0 is adopted.These results are discussed in the view of 4 points: 1) The circadian system operates at its optimum within a narrow range of - and : -values. 2) This optimal range is especially adopted when conditions become adverse. 3) Removal of the dark nest box results in a more stressful situation for Bengalese finches than for Great tits. 4) In the Bengalese finches, is shortened in the presence of a nest box due to effects on reproductive physiology.


Herrn Prof. Dr. JürgenAschoff zum 60. Geburtstag gewidemt.  相似文献   

4.
P. Bucheli  M. Dürr  A. J. Buchala  H. Meier 《Planta》1985,166(4):530-536
Cotton fibres possess several -glucanase activities which appear to be associated with the cell wall, but which can be partially solubilised in buffers. The main activity detected was that of an exo-(13)--d-glucanase (EC 3.2.1.58) but which also had the characteristics of a -glucosidase (EC 3.2.1.21). Endo-(13)--d-glucanase activity (EC 3.2.1.39) and much lower levels of (14)--d-glucanase activity were also detected. The exo-(13)--glucanase showed a maximum late on (40 days post-anthesis) in the development of the fibres, whereas the endo-(13)--glucanase activity remained constant throughout fibre development. The -glucanase complex associated with the cotton-fibre cell wall also functions as a transglucosylase introducing, inter alia, (16)--glucosyl linkages into the disaccharide cellobiose to give the trisaccharide 4-O--gentiobiosylglucose.Abbreviations CMC carboxymethylcellulose - ONPG o-nitrophenyl--d-glucopyranoside - TLC thin-layer chromatography Presented at the Third Cell Wall Meeting held in Fribourg in 1984  相似文献   

5.
Plasticity and relationships between individual ATPases linked to energy-utilizing systems of hippocampus, a very sensitive functional area to both age and ischemia, were studied during ageing on synaptic plasma membranes of 1-year-old adult and 2-year-old aged rats after 15 min of complete cerebral ischemia and different reperfusion times (01, 24, 48, 72, and 96 h). Activities of Na+, K+, Mg2+-ATPase, Mg2+-ATPase ouabain insensitive, Na+,K+-ATPase, direct or basal Mg2+-ATPase, and acetylcholinesterase (AChE) were evaluated in synaptic plasma membranes, where they play the major role in the regulation of presynaptic nerve ending homeostasis. This in vivo study of recovery time-course from 15 mins of cerebral ischemia indicated specific biochemical assessments of functional meaning: (a) Na+K+-ATPase of synaptic plasma membranes in adult and aged animals is stimulated by ischemia; (b) this hyperactivity is more markedly related to adult than to aged animals; (c) these abnormalities still persist after 72 and 96 h during the recirculation times, indicating the delayed postischemic suffering of the brain; (d) specific Mg2+-ATPase enzyme system possess a lower catalytic power in aged animals than in adult ones, but remained unaltered in adult animals by ischemia and reperfusion; (e) Mg2+-ATPase is stimulated in aged animals by ischemia, further increasing during reperfusion up to 72–96 h, indicating the delayed hyperactivity of hippocampus; (f) the increased metabolic activity of hippocampus is indicated by the increased activity of cholinergic system; (g) integrity of synaptic plasma membranes seems not to be altered by 15 min ischemia to a critical extent to compromise their catalytic functionality during reperfusion; (h) AChE activity increases in both adult and aged at some survival times. There are logical reasons for the hypothesis that the modifications in ATPase's catalytic activities in synaptic plasma membranes, which have been modified by ischemia in presynaptic terminals, may play important functional role during recovery time in cerebral tissue in vivo, especially as regards its responsiveness to noxious stimuli, particularly during the recirculation period from acute (or chronic) brain injury.  相似文献   

6.
Summary The ultrastructural localization of glucose-6-phosphate dehydrogenase (NADP-linked) has been attempted in steroid-secreting cells. Rat adrenocortical cells and newt testicular glandular cells were fixed in an ice-cold mixture of 1% methanol-free formaldehyde and 0.25% glutaraldehyde. Potassium ferricyanide was used as the final electron acceptor.After incubation, the final copper ferrocyanide precipitate is exclusively observed in the hyaloplasm of these cells, provided that an electron carrier (1.0 mM PMS) has been added to the medium in order to by-pass the tissue diaphorase (NADPH-ferricyanide reductase) reaction. No precipitate appears in the absence of glucose-6-phosphate (substrate). Incubation in a medium devoid of PMS results in an exclusively mitochondrial reaction; the latter is that of the diaphorase, which in these cells is mitochondrial. These results prove the importance of utilizing exogenous electron carriers (such as PMS) in coenzyme-linked dehydrogenase cytochemistry.Although polyvinyl alcohol was included in the washing and incubation media, in order to increase their viscosity, problems still exist concerning ultracytochemical localization of this soluble enzyme; these problems are discussed in the paper.  相似文献   

7.
ATP synthase (F0F1) is driven by an electrochemical potential of H+ (H+). F0F1 is composed of an ion-conducting portion (F0) and a catalytic portion (F1). The subunit composition of F1 is 33. The active 33 oligomer, characterized by X-ray crystallography, has been obtained only from thermnophilic F1 (TF1). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the DELSEED sequence via -F0. In fact, cross-linking of DELSEED to stopped the ATP-driven rotation of in the center of 33. The torque of the rotation is estimated to be 420 pN·å from the H+ and H+-current through F0F1. The angular velocity () of is the rate-limiting step, because H+ increased theV max of H+ current through F0, but not theK m (ATP). The rotational unit of F0 (=ab2c10) is /5, while that in 33 is 2/3. This difference is overcome by an analog-digital conversion via elasticity around DELSEED with a threshold to release ATP. The distance at the C site is about 9.6 å (2,8-diN3-ATP), and tight Mg-ATP binding in 33 was shown by ESR. The rotational relaxation of TF1 is too rapid (=100 nsec), but the rate of AT(D)P-induced conformational change of 33 measured with a synchrotron is close to . The ATP bound between the P-loop and E188 is released by the shift of DELSEED from RGL. Considering the viscosity resistance and inertia of the free rotor (-c), there may be a stator containing OSCP (= of TF1) and F0-d to hold free rotation of 33.  相似文献   

8.
Poly-N-acetyllactosamines provide backbone structures for functional modifications such as sialyl Lewis X. To understand how the biosynthesis of poly-N-acetyllactosamines is regulated, two branched oligosaccharides of the structure Gal1,4GlcNAc1, 6(Gal1,4GlcNAc1,2)-Man1,6Man-octyl 1 and 2 were synthesized in which one of the terminal galactose units was selectively radiolabeled. Hexasaccharides 1 and 2 were assembled from the chemically synthesized pentasaccharide precursors GlcNAc1,6(Gal1,4GlcNAc1,2)-Man1,6Man-octyl3 and Gal1,4GlcNAc1,6(GlcNAc1, 2) - Man1,6 Man-octyl 4 respectively, through treatment with UDP-1-[3H]-Gal and 1,4 galactosyltransferase. Compounds 1 and 2 were subsequently incubated with UDP-GlcNAc and the UDP-GlcNAc: Gal1-4Glc(NAc)1,3-N-acetylglucosaminyltransferase (i-GlcNAc transferase) resulting in a partial conversion to a mixture of heptasaccharides which were purified by HPLC. The branch selectivity of the addition of N-acetylglucosamine to compounds 1 and 2 was then characterized by endo--galactosidase digestion of the heptasaccharides, followed by isolation of the resultant pentasaccharides on C18 reverse-phase silica cartridges. Comparison of the amount of radiolabel to a control reaction lacking endo--galactosidase indicated the favored site of GlcNAc addition to be the lower 1,2-branch over the 1,6-branch by a 3:1 ratio.  相似文献   

9.
To test the hypothesis that the T-cell receptor (Tcr) gene encodes a natural killer (NK) cell receptor molecule, three human NK clones and fresh peripheral blood lymphocytes with NK activity from two patients with a CD16+ lymphocytosis were analyzed for rearrangements and expression of the human Tcr , , and genes. Two of the clones displayed distinct rearrangements of their Tcr and genes and expressed mature Tcr , , and l RNA. However, one of the clones and both patient samples displayed marked NK activity but failed to rearrange or express any of their Tcr genes. These findings demonstrate that human natural killer activity is not dependent on Tcr gene rearrangement and expression. In addition, they confirm previous findings concerning the lack of Tcr and gene expression in some natural killer cells. Thus, they suggest the existence of additional NK-specific recognition molecules.  相似文献   

10.
Summary Four types of striated muscle fibers with distinctive ultrastructure were defined in the Atlantic hagfish (Myxine glutinosa, L.): white, intermediate, and red fibers of m. parietalis, and red fibers of m. craniovelaris.White fibers are thick, contain very few mitochondria and fat vacuoles, and possess distinct and separate myofibrils with thin Z-disks and distinct M-lines. Intermediate fibers are thinner, possess largely similar myofibrils that often are even better separated due to a higher content of fat vacuoles and especially mitochondria and glycogen granules. Red fibers of m. parietalis contain large amounts of mitochondria, fat vacuoles, and glycogen granules. Their myofibrils possess M-lines, and although branching more, the myofibrils of red fibers conform with a Fibrillenstruktur pattern like those of white and intermediate fibers. Red fibers of m. craniovelaris are very thin, possess many smaller fat vacuoles, and large amounts of mitochondria and glycogen granules. The myofibrils are significantly thinner than in m. parietalis fibers, run as quite independent well separated units, possess thicker Z-disks, and lack M-lines. Large amounts of myosatellite cells are associated with these red fibers.Triads are located near A/I-junctions in all four fiber types and occur irregularly, the density of triads being different in the various fiber types.We are indebted to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supply of hagfishes, and we also wish to thank Dr. Jan K. S. Jansen, Institute of Physiology, University of Oslo, for valuable suggestions during this study.  相似文献   

11.
Summary Ethidium bromide (EB) and ultraviolet light (UV) in combination are known to produce a synergistic induction of petite mutants in yeast. Two other agents were combined with EB, 3-Carbethoxypsoralene (3 CPs) activated by 365 nm light or rays. EB in combination with 3 CPs also resulted in an enhanced production of petite mutants. After the photoaddition of 3 CPs in exponential phase cells, recovery of the petite mutation during dark liquid holding was inhibited by the presence of EB producing an enhanced number of petite mutants. The behavior of mitochondrial antibiotic resistance markers after individual and combined treatments with EB and 3 CPs indicates a random loss of markers after EB and a preferential loss of a certain region for the 3 CPs photoaddition. The combination of the two agents leads to an additivity of total drug marker losses rather than a synergistic loss. The combination of EB with rays produced no enhancement in petite induction. A combination of UV and 3 CPs showed a synergistic interaction for petite induction. These results indicate that the three agents, EB, UV and 3 CPs photoaddition may share a common repair step for mitochondrial lesions.  相似文献   

12.
The present study was undertaken to determine the effects of AT1 receptor blockade which occurred in response to losartan, on the extracellular matrix (ECM) degradation process in the Bio 14.6 (n = 12) and Bio 53.58 (n = 12) strains which are referred as models of hypertrophic and dilated cardiomyopathy, respectively. The administration of losartan (30 mg/kg/day) in hamsters from 10–20 weeks of age reduced the accumulation of the left ventricular collagen matrix in both of the Bio 14.6 and the Bio 53.58 strains. According to the RTPCR, the levels of mRNA for matrix metalloproteinase (MMP) and the tissue inhibitor of MMP (TIMP) were examined. MMP1, 2, 3, and 9 were more enhanced in both myopathic strains than in the control F1 strains. With losartan, the levels of MMP1, 2, 9, TIMP1 and 2 decreased in the both strains but those for MMP3 did not in Bio 14.6 strains. TIMP3 and 4 mRNA levels did not change in any of the experimental hamsters, whether treated or untreated with losartan. The Western blots also showed similar observations in the both strains as seen in mRNA expressions although MMP2 in the Bio 53.58 strains did not differ between treated and untreated with losartan. Although losartan has an inhibitory effect on collagen accumulation in the development of cardiomyopathy, MMPs (1, 2, 9) and TIMPs (1, 2) seem to be susceptible to responding to losartan in Bio cardiomyopathic hamsters.  相似文献   

13.
Zusammenfassung Harzkonservierte Fossilien ermöglichen bei Anwendung adäquater Methoden die morphologische Analyse der Feinmerkmale bis zur Auflösungsgrenze des Lichtmikroskops, Beobachtung in verschiedenen Ebenen und Richtungen, und somit konkrete Rückschlüsse auf die Wirkung und Bedeutung der Einzelelemente und des Gesamtgefüges.Eine so eingehende funktionsmorphologische Analyse mit Berücksichtigung der Positionsvariation (graduell verschiedene Gestaltung in gesetzmäßiger Abhängigkeit von der Lage innerhalb der Gesamtfeder) der Einzelelemente wie Abzweigungs-, Knick-, Neigungswinkel, Krümmung, Länge, Dicke, Querschnitt, Dichte, Differenzierungsgrad der verschiedenen Abschnitte von Rhachis, Rami, Radii inklusive Häkchen und Cirren wird erstmals für fossile Vogelfedern geliefert (hier als Abriß zu einer dokumentarisch und thematisch ausführlicheren Darstellung in Stuttgarter Beiträge zur Naturkunde).Diese Federn entstammen der untersten Unterkreide und sind damit nur relativ wenig jünger alsArchaeopteryx. Sie weisen extrem differenzierten Aufbau auf, der auf hohe flugtechnische und wärmeisolierende Leistungsfähigkeit schließen läßt.Die hier vorgelegten funktionsmorphologischen Ermittlungen an fossilen Körperkonturfedern mögen auch zu einer intensiveren Analyse der bis jetzt stark vernachlässigten Untersuchung ganz normaler Körperfedern rezenter Vögel anregen. Erst dann, nach umfassender Kenntnis ihrer Ausgestaltung innerhalb der verschiedensten rezenten Vogelgruppen, läßt sich überzeugend begründen, ob und wieweit die hier vorgelegten Federn dieses Unterkreide-Vogels noch ursprüngliche Elemente (Plesiomorphien) oder ihnen eigene Sonderbildungen (Autapomorphien) aufweisen; das gilt sowohl für morphologische wie für funktionelle Elemente der Gesamtstruktur.
Resin-preserved fossil bird's feathers from the Lowermost Cretaceous
Summary Parts of some feathers, originating from a single bird, were discovered in our collections of Lower Cretaceous amber from the Lebanon mountains — which, in general, contains the oldest terrestrial microfossils preserved with all morphological details.These contour feathers of the trunk, which are nearly as old as Archaeopteryx (Lowermost Cretaceous: Neocomian/Uppermost Jurassic: Kimmeridigian) were studied with magnifications of 500–900 in several levels by a special technique. (In normal fossils, i.e., impressions, the granulation of the sediment and the fossil's bulky carbon remainders cause a blurred image even at a magnification of merely 100).Special emphasis was laid on the study of the individual elements' gradual variation, depending on the respective position within the total feather (position variation). Where appropriate, an analysis of lengths, quantity, degree of differentiation, angle of inclination, break, and branching, cross-sectional view, curvature, etc. of the rhachis, rami, distal and proximal radii, barbicles, hooklets, etc. were undertaken. [Through measurements of the depth of details the effects caused by a sloping position (apparent variation) may be precisely separated from the real variation.]On the basis of such a detailed knowledge of structure and relative position a thorough functional analysis of the single elements as well as the total system is given.Principal features: The production of plain stability in the feather's center, and of flexibility in its apical and lateral rims; dispersion of forces in case of pressure or a pulling load; function of the hooklets (which donot serve as an interlocking mechanism while the feather is in the normal resting position, but function with increasing braking action only when a neighboring ramus diverges to a precisely defined extent from its resting position) including the mechanism of their unhooking; devices for the avoidance of harmful hooking into contacted parts of other feathers; production of maximal stability by minimal air resistance, and of minute chambers (<0,00001 mm3) with still air for optimal heat isolation.Apart from this abstract, further information, accompanied by numerous figures, will be given in a later paper in Stuttgarter Beiträge zur Naturkunde.


Veränderte Fassung eines am 11. 10. 1971 gehaltenen Vortrages auf der 83. Jahresversammlung der Deutschen Ornithologengesellschaft in Bonn.  相似文献   

14.
The age, growth, feeding habits and reproductive biology of Leuciscus svallize in artificial lake Kremasta (Greece), are described. There is a considerable similarity in the feeding and reproductive characteristics between L. svallize and L. cephalus and also a similarity in the life span, growth patterns and age of maturation between L. svallize and some southern L. cephalus populations, which may suggest similar responses of closely related taxa to similar conditions.  相似文献   

15.
We investigated the influence of the combined use of sizofiran, a-1,3-glucan and a recombinant interferon- (rIFN-) upon biological activities of peritoneal macrophages (M). The number of peritoneal M and the production of cytokines (interleukin-1, interferon- and tumor necrosis factor) was increased by the combined treatment. Fully activated peritoneal M based on the increased number of elongated pseudopods were observed by electromicroscope. Sizofiran seems to assure a sufficient supply of M to kill tumor cells in the peritoneal cavity and co-administered rIFN- seems to directly stimulate the accumulated M in addition to its direct cytotoxicity against tumor cells. This combination therapy may be a step to the prevention of the recurrence of gynecological malignancies including ovarian cancer, after a negative second-look laparotomy.Abbreviations rIFN- recombinant interferon- - IL-1 interleukin-1 - TNF tumor necrosis factor - SLL second look laparotomy  相似文献   

16.
Summary White and intermediate parietal muscle fibers of Myxine are innervated focally at one end. Most synaptic vesicles are empty. These terminals also contain 1–2% large 800–1.100 Å dense-core vesicles. Red fibers of parietal and craniovelar muscle are innervated in a distributed fashion, and the presynaptic profiles contain a higher number of large dense-core vesicles (averaging 9% and 15%, respectively; up to 37%). For all terminals the synaptic gap is 450–600 Å wide, and postsynaptic folds are absent.Empty synaptic vesicles exist as round or elongated profiles. The proportion of elongated profiles increases by formation from round ones when increasing the molarity of the buffer in the aldehyde fixative. Furthermore, the proportion of elongated vesicle profiles in terminals on Myxine white fibers at different buffer molarities, is identical with that in mammalian motor terminals at similar molarities. On this basis the significance and mode of formation of elongated vesicle profiles is discussed. The conclusion is made that the susceptibility of flattening depends on the osmotic pressure of the vesicle contents once the aldehyde has influenced the vesicle membrane.The different vesicle populations in terminals on different types of muscle fibers are significant. Terminals on red fibers probably contain serotonin (5-HT) either as sole transmitter or in addition to acetylcholine.The author is indebted to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supply of hagfishes, and to Mrs. Jorunn Line Vaaland for expert technical assistance.  相似文献   

17.
Silver staining the chromosome scaffold   总被引:5,自引:0,他引:5  
Cytological silver-staining procedures reveal the presence of a core running along the chromatid axes of isolated HeLa mitotic chromosomes. In this communication we examine the relationship between this core and the nonhistone chromosome scaffolding, isolated and characterized in previous publications from this laboratory. When chromosomes on coverslips were subjected to the steps used for scaffold isolation in vitro and subsequently stained with silver, the characteristic core staining was unaffected. Control experiments suggested that the core does not contain large amounts of DNA. When scaffolds were isolated in vitro, centrifuged onto electron microscope grids, and stained with silver, they were found to stain selectively under conditions where specific core staining was observed in intact chromosomes. These results suggest that the nonhistone scaffolding is the principal target of the silver stain in chromosomes.  相似文献   

18.
19.
The twelve Cys and eight of the non-Cys residues are invariant in the glycoprotein hormone subunits from a variety of mammalian species. -Gin-54 of human lutropin (hLH) and choriogonadotropin (hCG) is one of these invariant amino acid residues. A single AG mutation in the LH gene of a patient presenting with hypogonadism resulted in the replacement of Gin-54 with Arg [1]. The authors also reported that an expressed mutant of hLH, with Arg replacing Gin-54, associated with the subunit, but there was no demonstrable binding of the mutant hormone to receptor. We have replaced Gin-54 in hCG with Glu and with Lys using site-directed mutagenesis. The expression plasmids pRSV-hCG (wild-type and mutants) were transiently transfected into CHO cells containing a stably integrated gene for bovine , and the media were analyzed for holoproteins, which were characterizedin vitro using competitive binding and steroidogenic assays with MA-10 cells. hCG(Glu-54) bound to almost as well as hCG wild-type, and the resulting heterodimer competed with [125l]hCG binding to the LH/CG receptor and stimulated progesterone production to the same extent as the wild-type control. However, the apparent potencies, as judged by ED50s, were less than those of the wild-type control, the effect being more pronounced in binding than in steroidogenesis. In contrast, hCG(Lys-54) associated very poorly with . Our results suggest that while Gin-54 in hCG participates in receptor binding, its major function appears to involve binding. Such dual functionality leads to interesting models for holoprotein formation and receptor binding.  相似文献   

20.
Based on the concept of pairs of basic functional states the evolution of the first chemiosmotic mechanism of energy conversion is discussed in terms of point mutations, gene duplications and of the neutral theory of evolution. A model for estimating the overall probability of the evolutionary step in question is presented, both for the selectionist and neutralist position. It is concluded that, concerning the present stage of knowledge, the evolution of transmembrane electron transport is an unsolved problem in evolutionary biology.  相似文献   

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