ISSN:0022-104X    

DOI:10.1002/jez.1402370102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractShort‐circuited recta of the lubber grasshopper show an initial rapid decline in the short‐circuit current (Isc) over the first 60–90 min in vitro. This is followed by a pseudo steady state during which Iscdeclines slowly and steadily until a true steady state is reached after 4 h. Isccan be stimulated 4–6 fold by the addition of homogenates of corpora cardiaca (CC) or cAMP to the hemocoel‐side of the preparations. This increase in Iscis accompanied by an increase in transepithelial electropotential difference and a large drop in transepithelial resistance. Tracer studies reveal that the initial decline in Iscand its subsequent restoration to high levels is almost entirely due to changes in the active uptake of chloride from the lumen‐side (J LCl→H). Recta maintained in vitro show a graded response to increasing doses of CC homogenates with the threshold occurring near 0.002 gland pair. In all respects these results are qualitatively and quantitatively comparable to those previously reported for the desert locust,Schistocerca gregaria. This represents the first unequivocal demonstration of hormonally‐stimulated chloride transport in an insect other thanSchistocerca, and suggests that this may represent a widespread mechanism for ionic homeostasis in insects. These experiments further lay the groundwork for attempts to purify both the hormone and the chlo

ISSN:0022-104X    

DOI:10.1002/jez.1402370103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIon‐binding ligands and the conformations of some of the acidic matrix macromolecules present in the shells of a gastroped, a bivalve, and a cephalopod, are investigated in vitro by Fourier transform infrared spectroscopy. The complex assemblage of matrix constituents present in the EDTA‐soluble fraction is first separated into two quite different classes of macromolecules by a reversed‐phase chromatographic procedure. Infrared spectra indicate that the constituents of one class, which are proteins rich in aspartic acid, adopt the β‐sheet conformation upon binding calcium to the protein carboxylate groups. The second class of matrix constituents contains proteins rich in serine that appear to be associated with relatively large amounts of polysaccharide. They also bind calcium and upon doing so undergo a conformationa

ISSN:0022-104X    

DOI:10.1002/jez.1402370104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractHuman spermatozoa freed from seminal plasma using a discontinuous Percoll gradient procedure were incubated overnight in modified Tyrode's media containing either CaCl2(CA medium) or with SrCl2instead of CaCl2(SR medium). The following morning these spermatozoa were washed by centrifugation, resuspended in fresh CA medium and incubated for either 2 or 3 h with zona‐free hamster eggs to test their fertilizing ability. Penetration rates were higher after 3 h of sperm‐egg contact than after 2 h, and the spermatozoa preincubated in SR medium penetrated significantly more hamster oocytes than those preincubated in CA med

ISSN:0022-104X    

DOI:10.1002/jez.1402370105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe osmoregulatory responses to warmer temperatures and hormone treatment in cold‐adapted (5° C)Rana catesbeianatadpoles and newly metamorphosed frogs were examined. Tadpoles transferred to 11° C and 18° C and left for 5 days lost 7% and 10% of their body weight. Plasma [Na+] was elevated 28% and 21%, respectively. Control (5° C) animals maintained their body weight and plasma [Na+] constant. Daily treatment with either ovine prolactin (oPRL) or ovine growth hormone (oGH) prevented the weight loss and the increase in extracellular [Na+] that occurred when tadpoles were transferred to 18° C. Neither propylthiouracil (PTU) nor arginine vasotocin (AVT) were effective in countering temperature‐induced weight loss in tadpoles. Newly metamorphosed frogs transferred to 18° C also lost weight; this was not prevented by daily treatment with saline, oPRL, oGH or PTU. However, in frogs treated daily with AVT, initial BW was regained by day 6. When warm‐adapted (18° C) tadpoles were treated daily for 18 days with saline, bPRL, bGH, thyroxine (T4), ergocornine, cortisol, or cortisol + T4, bPRL was most effective in retarding weight loss and maintaining body water content, whereas T4+ cortisol caused the greatest loss of weight and body water. By day 20, the correlations between weight loss and both body water content and hematocrit were highly significant. These data suggest that reported increases in plasma solute concentrations in larval amphibians may actually reflect decreases in extracellular fluid volume, rather than increased amounts of sol

ISSN:0022-104X    

DOI:10.1002/jez.1402370106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractPieces of coverslip glass, polycarbonate filters, or coverslip plastic, coated with fibrinogen or type I collagen, were implanted under one edge of a fresh skin wound on adult newt hind limbs so that the implant served as wound bed for migrating epidermal cells as they attempted to form a wound epithelium. Migratory events were then analyzed by phase contrast and electron microscopy. Phase‐contrast microscopy revealed two types of lamellipodia on leading edge cells: one which was attached broadly to the cell body and one attached by a long, thin stalk. Stalkless forms were by far the most common type and we believe they provide the motive force for cell movement. Stalked forms often moved at distinct angles to the direction of sheet movement, suggesting that they may be sensory appendages. Phase photographs of the leading edge of migrating sheet 4 hours and 8 hours after implantation showed that all cells that were on the leading edge at 4 hours continued to advance for the next 4 hours, demonstrating clearly that under these circumstances the distalmost cells do not become immobile upon contact with the substrate as others have suggested. TEM revealed that migrating sheets were modified monolayers and that regardless of proximodistal location in the sheet, and even in the intact skin adjoining a wound, each epidermal cell adjacent to the substrate puts forth a lamellipodium which underlaps the cell in front. This and the behavior of sheets as they were teased or pulled from the implant suggest strongly that all basal cells contribute to movement of the sheet by interacting with the substrate. Based on TEM, this interaction may be by either focal or close contact

ISSN:0022-104X    

DOI:10.1002/jez.1402370107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe isometric contraction kinetics, ultrastructure, and growth of locust flight muscle that is derived from body wall muscle (metathoracic dorsal longitudinal muscle) and from limb muscle (second metathoracic tergocoxal muscle) were studied during the last three nymphal instars and in the adult 2 weeks past the terminal molt. Two distinct developmental patterns were found that correlated with use during nymphal life. The second tergocoxal muscle (TC2) is used from the time of hatching as a coxal remoter. As such, its contraction kinetics and ultrastructure are characteristic of fast, phasic muscle, which predisposes it to use in the adult as a wing levator. In contrast, the dorsal longitudinal muscle (DLM) is nonfunctional during nymphal life; contraction kinetics and ultrastructure characteristic of fast, phasic muscle develop gradually in late nymphal life until the adult kinetics are attained 2 weeks past the terminal molt. Although growth in both of these muscles occurs as the result of increases in fiber number and cross‐sectional area, there are differences in the manner in which this growth is achieved. In the TC2, there is a continuous increase in fiber number through the last three nymphal instars. In contrast, in the DLM, the increase in fiber number is nearly complete by two molts before adulthoo

ISSN:0022-104X    

DOI:10.1002/jez.1402370108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of retinoids on forelimb regeneration in the leopard frog,Rana pipiens, was examined by the topical application of a concentrated solution of vitamin A palmitate to the amputated left limb stumps of 30 froglets. This treatment resulted in the enhancement of regeneration; regenerative outgrowths of experimental frogs were more frequent, larger in size, and had improved morphology compared to their untreated control counterparts. We conclude that vitamin A palmitate, topically administered in concentrated dosages, exerts a positive effect on the regenerative capacity ofRana pipiens.

ISSN:0022-104X    

DOI:10.1002/jez.1402370109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractTunic in 46‐hr‐oldAscidia callosalarvae reared from dechorionated neurulae is either markedly reduced in thickness or absent altogether. The epidermis is fragile and cuticular fins fail to develop. Dechorionated neurulae treated with tunichrome and other reducing compounds (e.g., glutathione, ascorbate) show an enhancement in tunic formation and rudimentary fin development. UV absorbance spectra of extracts from unfertilized eggs, late tail‐bud embryos, and tadpole larvae indicate that tunichrome may be present in all developmental stages. Experiments with neurulae in which the chorion was punctured with tungsten needles but not removed signify that the test cells are the most likely source of tunichrome. Results are consistent with the hypothesis that tunichrome is involved in the natural processes of tunic morphogenesis in ascidian em

ISSN:0022-104X    

DOI:10.1002/jez.1402370110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractWhenX. laeviseggs developed with their animal‐vegetal axis oriented normally, the mitochondria of the germ plasm in eight‐cell embryos were frequently found to adhere to each other forming branching chains, and also the aggregates of germinal granules were physically associated with adjacent mitochondria. In embryos of the same stage developing from eggs inverted by 180°, these two components were arranged more loosely, so that the whole region of the germ plasm was less compact in appearance. In these embryos, the average number of intermitochondrial adhesions was reduced to approximately one‐third of that in the controls, while the average distance from the edge of an aggregate of germinal granules to the nearest mitochondrion was almost three times the control value. The morphology of the aggregates of germinal granules was also altered: they were much less compact, often with a large central space, and the individual granular components appeared as rings organised into chains. Absence of these associations between the two main constituents of the germ plasm in inverted eggs may correlate with the reduced numbers of primordial germ cells that enter the genital ridges, i.e., the function of the germ plasm as a determinant of primordial germ cells may depend on these associ

ISSN:0022-104X    

DOI:10.1002/jez.1402370111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY