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排序方式: 共有107条查询结果,搜索用时 734 毫秒
1.
H. -D. Pfannenstiel 《Helgoland Marine Research》1985,39(1):49-53
The dye Lucifer yellow CH was iontophoresed into recently fertilized eggs and early blastomeres ofHydractinia echinata. Iontophoresis was carried out on the stage of an inverted microscope in order to follow filling of the injected cells by short pulses of epifluorescent illumination. Lucifer yellow proved to be nontoxic and development in embryos with injected blastomeres proceeded normally. When zygotes were injected all the cells of the forming embryo contained dye. When one of the first two blastomeres was injected all the progeny of the injected cell also contained dye. Dye-coupling between injected and uninjected blastomeres did not occur in two-cell embryos nor between descendants of either line. Development of Lucifer-yellow-filled blastomeres or zygotes could be stopped by blue light irradiation. In a number of injected cells, the dye tended to accumulate forming brightly shining spots. The dye did not penetrate the nuclear envelope of injected cells. 相似文献
2.
Michael J. Huether Paula J. Fedorka-Cray Mary Ann Pfannenstiel Gary A. Anderson 《FEMS microbiology letters》1987,48(1-2):179-182
Abstract This paper describes the plasmid profiles obtained for 73 of 96 field isolates of Haemophilus pleuropneumoniae serotypes 1, 3, 5, and 7. We also characterized the antibiotic susceptibilities of these 96 isolates. Because of the high proportion of isolates resistant to some of the antibiotics, no conclusions can be drawn as to the role of plasmids in antibiotic resistance. 相似文献
3.
High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans 总被引:1,自引:0,他引:1
We compared male-reproductive-tract polypeptides of Drosophila melanogaster
and D. simulans by using two-dimensional gel electrophoresis. Approximately
64% of male-reproductive-tract polypeptides were identical between two
randomly chosen isofemale lines from these two species, compared with 83%
identity for third-instar imaginal wing-disc polypeptides. Qualitatively
similar differences were found between reproductive tracts and imaginal
discs when D. sechellia was compared with D. melanogaster and with D.
simulans. When genic polymorphism was taken into account, approximately 10%
of male- reproductive-tract polypeptides were apparently fixed for
different alleles between D. melanogaster and D. simulans; this proportion
is the same as that found for soluble enzymes by one-dimensional gel
electrophoresis. Strikingly, approximately 20% of male-reproductive- tract
polypeptides of either D. melanogaster or D. simulans had no detectable
homologue in the other species. We propose that proteins of the Drosophila
male reproductive tract may have diverged more extensively between species
than have other types of proteins and that much of this divergence may
involve large changes in levels of polypeptide expression.
相似文献
4.
Stability of the larvicidal activity of Bacillus thuringiensis subsp. israelensis: amino acid modification and denaturants. 总被引:10,自引:7,他引:3 下载免费PDF全文
The Bacillus thuringiensis subsp. israelensis mosquito larvicidal toxin is not a sulfhydryl-activated toxin. The protein disulfide bonds were cleaved and blocked without loss of toxicity. In contrast, modification of the lysine side chains eliminated toxicity. Additionally, the toxin was resistant to high concentrations of salt (8 M NaBr), organic solvents (40% methanol), denaturants (4 M urea), and neutral detergents (10% Triton X-100). However, it was inactivated by both positively and negatively charged detergents and by guanidine hydrochloride. 相似文献
5.
Gabriele Schulz Klaus Peter Ulbrich Carl Hauenschild Hans-Dieter Pfannenstiel 《Development genes and evolution》1989,198(1):29-33
Summary In most nereids sexual maturation is accompanied by a dramatic reorganization of the body that enables swarming of the formerly benthic worms. However, a border exists between unchanged anterior (atokous) and metamorphosed posterior (epitokous) segments. The site of this atokous-epitokous border (a/e border) is different in sexually mature males and females of Platynereis dumerilii. There is no correlation between the total number of setigerous segments of a specimen and the location of the a/e border. The location of the a/e border and sexual development are affected neither by cutting off caudal segments of juveniles (including the prospective a/e border) nor by transecting the ventral nerve cord. When parapodia are transplanted from prospective epitokous regions to prospective atokous regions and vice versa, they maintain their original character during metamorphosis. The results presented here suggest that prospective atokous as well as epitokous characters are determined at or only very shortly after formation of the respective segments. Thus the a/e border is established well in advance of the onset of epitokous metamorphosis. 相似文献
6.
The details of spermatogenesis and spermiogenesis are described forOphryotrocha puerilis. The ultrastructure of mature sperm is shown forO. puerilis, O. hartmanni, O. gracilis, O. diadema, O. labronica, andO. notoglandulata. Clusters of sixteen cells each are proliferated by two stem cells in each setigerous segment ofO. puerilis representing the very early stages of both oogenesis and spermatogenesis. In each spermatocyte-I cluster, the cells are interconnected
by cytoplasmic bridges. Early, clusters are enveloped by peritoneal sheath cells. These transient gonad walls break down prior
to meiosis. The meiotic processes may start in the clusters with the cells still interconnected, or during breakdown of the
original cluster, giving rise to smaller subclusters of both spermatocytes I and spermatocytes II with various numbers of
cells. Finally, spermatid tetrads are present. As spermiogenesis progresses, the tetrads disintegrate. Golgi vesicles in both
spermatocytes and spermatids contain electron-dense material, presumably preacrosomal. The acrosome is formed by such vesicles.
In the six species studied here, the acrosomes appear to be of a similar overall structure but are of different shape. Centrioles
are usually located beneath the acrosome. The distal centriole forms the basal body of a flagellum-like cytoplasmic process.
The microtubules of these flagellar equivalents do not show a normal ciliar arrangement. The flagellar equivalent appears
to be non-motile. InO. hartmanni and inO. notoglandulata, a flagellar equivalent is missing. Microtubules originating from the proximal end of the distal centriole stretch to the
nuclear envelope. This feature appears to be especially conspicuous inO. puerilis and inO. labronica. InO. labronica and inO. notoglandulata, bundles of microtubules paralleling the cell perimeter appear to stabilise the sperm. Various numbers of mitochondria are
either randomly distributed around the nucleus or accumulate on one side, often directly under the acrosome.
Parts of the present paper were presented at the 2nd International Polychaete Conference, Copenhagen 1986 and at the 3rd International Polychaete Conference, Long Beach, Ca. 1989. 相似文献
7.
RS Fisher 《The Journal of general physiology》1977,69(5):571-604
When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport. 相似文献
8.
Summary As revealed by glyoxylic acid induced fluorescence, the protandric polychaeteOphryotrocha puerilis possesses different types of catecholaminergic primary bipolar sensory cells, the perikarya of which are located beneath the epidermis. About 20 of such receptors are situated in each segment but they are mostly found on antennae, palps, urites and parapodial cirri. The dendrites of these sensory neurones run to the cuticle and dilate to form receptive endings. Three different types of dendritic endings could be distinguished: (1) multiciliary receptors with 4–8 cilia and ciliary rootlets, (2) monociliary receptors with microvilli arranged like a funnel and electron-dense cuffs and (3) monociliary receptors of the collar-type with, constantly, ten microvilli surrounding one single central cilium. The latter type is also characterized by rootlet fragments. Dendrites and dilated receptive endings of all three types contain clear (putative secretory) vesicles, multivesicular bodies and mitochondria. Pharmacological treatment (dopamine, reserpine) does not affect the number of secretory vesicles of the receptor neurones. Extra vesicular storage of catecholamines is discussed. Secretory cells of unknown function containing large numbers of electron-dense vesicles are usually found in close association with sensory cells.Abbreviations
CA
catecholamines
-
DA
dopamine
-
RE
reserpine 相似文献
9.
Rosa I. Gallagher Joseph M. Patt Robert S. Pfannenstiel 《Journal of Insect Behavior》2013,26(1):79-88
Cheiracanthium inclusum (Hentz), a hunting spider, feeds on eggs of Helicoverpa zea (Boddie) and other moths. This study investigated whether C. inclusum can use chemical compounds present in H. zea scales and egg residues as kairomones to find these non-motile prey items. In a series of no- choice tests, spiders were presented with a piece of florist paper containing scales alone, scales + egg residues, or untreated controls. Next, spiders were presented with solvent extracts of either scales or eggs. Polar and non-polar solvents were used in the extractions. Contact with scales alone, scales + egg residues, and non-polar solvent extracts of both scales and eggs resulted in retention and/or induction of local searching behavior. Extracts made with polar solvents induced no apparent response, indicating that the chemostimulatory compounds are lipophilic. These results show that C. inclusum responds to kairomones left by ovipositing H. zea and use these chemical cues to detect and locate H. zea eggs. 相似文献
10.
Paula H Suss Luiz Guilherme A Capriglione Fabiane Barchiki Lye Miyague Danielle Jackowski Letícia Fracaro Andressa V Schittini Alexandra C Senegaglia Carmen LK Rebelatto Márcia Olandoski Alejandro Correa Paulo RS Brofman 《Experimental biology and medicine (Maywood, N.J.)》2015,240(7):969-978
The development of new therapeutic strategies is necessary to reduce the worldwide social and economic impact of cardiovascular disease, which produces high rates of morbidity and mortality. A therapeutic option that has emerged in the last decade is cell therapy. The aim of this study was to compare the effect of transplanting human umbilical cord-derived stromal cells (UCSCs), human umbilical cord blood-derived endothelial cells (UCBECs) or a combination of these two cell types for the treatment of ischemic cardiomyopathy (IC) in a Wistar rat model. IC was induced by left coronary artery ligation, and baseline echocardiography was performed seven days later. Animals with a left ventricular ejection fraction (LVEF) of ≤40% were selected for the study. On the ninth day after IC was induced, the animals were randomized into the following experimental groups: UCSCs, UCBECs, UCSCs plus UCBECs, or vehicle (control). Thirty days after treatment, an echocardiographic analysis was performed, followed by euthanasia. The animals in all of the cell therapy groups, regardless of the cell type transplanted, had less collagen deposition in their heart tissue and demonstrated a significant improvement in myocardial function after IC. Furthermore, there was a trend of increasing numbers of blood vessels in the infarcted area. The median value of LVEF increased by 7.19% to 11.77%, whereas the control group decreased by 0.24%. These results suggest that UCSCs and UCBECs are promising cells for cellular cardiomyoplasty and can be an effective therapy for improving cardiac function following IC. 相似文献