摘要:

AbstractGluconeogenesis from lactate in hepatocytes from rainbow trout is activated by glucagon and inhibited by insulin in a dose‐dependent fashion. The maximal responses to both hormones occur within their probable physiological concentration ranges. Gluconeogenic activation by glucagon is accompanied by a profound inhibition of pyruvate kinase activity. This is reflected in increases in both the S0.5and nHfor phosphoenolpyruvate and increased sensitivity to inhibition by MgATP compared to the enzyme isolated from cells not treated with hormone (control). Gluconeogenic inhibition by insulin is accompanied by activation of pyruvate kinase activity. This is observed as decreases in both the S0.5and nHfor phosphoenolpyruvate and a decreased sensitivity to inhibition by MgATP compared to enzyme isolated from control cells. These results indicate that insulin and glucagon are involved in the regulation of hepatic gluconeogenesis in trout and that their effects are mediated, at least partly, through the control of pyruvate kinase activit

ISSN:0022-104X    

DOI:10.1002/jez.1402430202

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

年代:1987

数据来源: WILEY

摘要:

AbstractGlutamine synthetase was shown to be mitochondrial in liver tissue and cytosolic in brain tissue of the holocephalanHydrolagus colliei.The liver mitochondrial form has an Mrapproximately 1,500 larger than the brain cytosolic form, so the two represent compartmental isozymes. Similar isozymes have been shown to be present in elasmobranchs, and their occurrence in holocephalans suggests the two groups share a common ancestry.

ISSN:0022-104X    

DOI:10.1002/jez.1402430203

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

年代:1987

数据来源: WILEY

摘要:

AbstractThese studies were performed in order to investigate the roles of GnRH and GtH in the regulation of reproductive function in male brown bullhead catfish,Ictalurus nebulosus.Adult catfish were given intravenous injections of salmon GtH (SG‐G100) or salmon GnRH (sGnRH), and plasma testosterone, 11‐ketotestosterone, and estradiol‐17β levels were measured. SGG100 elicited parallel increases in testosterone and 11‐ketotestosterone, with peak levels between 8–12 hr after treatment. The effects of SG‐G100 on plasma testosterone were dose‐dependent, whereas increased 11‐ketotestosterone was only seen with the two highest doses. Treatment with sGnRH elicited increased testosterone at 4 hr, and 11‐ketotestosterone between 4–24 hr posttreatment. No clear dose‐response to sGnRH was observed. The effects of SG‐G100 and sGnRH varied with the annual reproductive cycle. During early testicular recrudescence in May, both the pituitary and testis were sensitive to trophic stimulation, with 2‐ to 4‐fold increases in plasma androgens following sGnRH and SG‐G100. Neither treatment was effective in mature animals trapped in July. In November, despite low basal androgen levels, SG‐G100 and sGnRH elicited 2‐fold increases in plasma androgen levels. The stimulatory effects of sGnRH, but not SG‐G100, were abolished in hypophysectomized fish. These results indicate a functional hypothalamic‐pituitary‐testicular axis in this species, the components of which vary in sensitivity during the annual reproductive cycle in a manner consistent with the observed

ISSN:0022-104X    

DOI:10.1002/jez.1402430204

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

年代:1987

数据来源: WILEY

摘要:

AbstractMechanical properties of mineralized and sclerotized puparial cuticles of the face fly,Musca autumnalis, and the house fly,M. domestica, respectively, were determined. The thickness of mineralized cuticle is 55% greater than that of sclerotized cuticle (thickness = 41.7 and 26.8 μm, respectively) from puparia of similar diameter (2.4 to 2.8 mm). Nonetheless, breaking forces for both types of puparial cuticle are similar (load ultimate strength = 9.3–10.9 g). However, the mineralized puparia are considerably stiffer than sclerotized puparia (elastic modulus = 346.4 kg mm−1and 711.5 kg mm−1, respectively) and exhibit fracture at relatively lower load values (percentage total deformation at fracture = 3.5% and 11.0%, respectively). Differences in mechanical properties of puparial cuticle are probably due to the kinds and quantities of cuticular components: The mineralized puparia contain appreciably more inorganic components such as calcium, phosphorus and magnesium, while the sclerotized puparia consist of relatively more organic components such as proteins and phenolics. The evolutionary and functional significance of mineralization and sclerotization as mechanisms for puparial cuticle stabilization is dis

ISSN:0022-104X    

DOI:10.1002/jez.1402430205

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

年代:1987

数据来源: WILEY

摘要:

AbstractTen frogs (Xenopus laevis) were injected with mixed bacteria to produce a septic peritonitis. Peritoneal inflammatory cells of eight animals were studied for monohydroxyeicosanoid and leukotriene production from exogenous arachidonic acid. Large amounts of 12‐hydroxyeicosatetraenoic acid were produced; smaller amounts of 5‐ and 15‐hydroxyeicosatetraenoic and leukotriene B4were produced. Identifications were confirmed by retention times on HPLC, ultraviolet spectroscopy on all products, and gas chromatograph/mass spectrometry in the case of 12‐hydroxyeicosatetraeno

ISSN:0022-104X    

DOI:10.1002/jez.1402430206

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

年代:1987

数据来源: WILEY

摘要:

AbstractA series of chimeric rats was used to investigate the histogenesis of the adrenal cortex. These animals were produced by amalgamating preimplantation embryos of two congenic strains which express different alloantigens of the major histocompatibility system. The manner in which cells assort themselves during embryogenesis and organ renewal is amenable to analysis by using radiolabeled antibodies directed to the class I antigens. Mosaic pattern analysis of the adrenal cortex of these rats revealed that a clonal pattern of division was maintained across all three histogenic zones of the organ, even in highly unbalanced chimeric combinations. No apparent relationship existed between the proportion of cell types and the area of contiguously similar lineage (patch size). In the series examined, the percentage of cells derived from the PVG‐RT1alineage varied from 5 to 85%. The number of parallel cords varied from 6 to 28. The pattern analysis of informative corners of cross sections of the gland supports the thesis that organ maintenance is the result of cell division from the outside of the cortex toward the inside medullary surfac

ISSN:0022-104X    

DOI:10.1002/jez.1402430207

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

年代:1987

数据来源: WILEY

摘要:

AbstractPrenauplius larvae of the brine shrimpArtemiaemerged abnormally from their survival cysts in certain substitutes for seawater unless the concentration of metabolising cysts exceeded about 1 mg/ml. Emergence was normal in natural seawater. The abnormality was manifest as the release of prenauplii trapped within an additional membrane surrounding the hatching membrane, preventing normal development. It was shown to be caused by a failure of the cyst inner cuticular membrane to rupture when the remainder of the cuticle and the external tertiary envelope ruptured. The biochemical basis of the abnormal emergence was found to be a deficiency of bicarbonate ion, and a requirement for this ion for normal emergence was demonstrated. In the model of the normal emergence mechanism, bicarbonate is now implicated as an additional component in the energy‐requiring process for the generation of the osmotic potential necessary for successful expulsion of the prenaupliu

ISSN:0022-104X    

DOI:10.1002/jez.1402430208

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

年代:1987

数据来源: WILEY

摘要:

AbstractRemoval of the ocular lens in adult newts (Notophthalmus viridescens) is followed by a series of cellular events leading to regeneration of a new lens by cell type conversion of pigmented iris epithelial cells at the dorsal pupillary margin (Yamada, Curr. Top. Dev. Biol.2:247–283, 1967). Following depigmentation and five to seven cell divisions, iris epithelial cells redifferentiate into lens fiber cells and synthesize crystallin proteins (Yamada, Curr. Top. Dev. Biol.2:247–283, 1967). This process is dependent upon neural retina in vivo (Stone, Anat. Rec.131:151–172, 1958; Reyer, Dev. Biol.14:214–225, 1966) and in vitro (Yamada et al., Differentiation1:65–82, 1973). Acting on the hypothesis that the role of the neural retina is to promote passage of iris epithelial cells through the requisite number of cell cycles which will then allow them to redifferentiate as lens fiber cells (Yamada, in: Cell Biology of the Eye. Academic Press, New York, 1982), we undertook testing of the effects of eye‐derived mitogenic substances, as well as other mitogens, on regeneration of lens from iris in organ culture. We have previously defined a critical period for the retinal influence in vivo and in vitro, and have shown that crude extracts of retina can enhance regeneration of lenses in culture (Connelly et al., J. Exp. Zool.,240:343–351, 1986). In this paper, we report on the lens regeneration enhancing activity (LRA) of more highly purified fractions of the retinal extracts. Heparin‐sepharose chromatography of the crude retinal extract yields three fractions (Courty et al., Biochemie67:265–269, 1985) called EDGF I, II, and III. EDGF I and II have affinity for heparin, while EDGF III does not. In our bioassay, LRA appears only in the EDGF III fraction. Dialysis of EDGF III against 0.1 N acetic acid yields a fraction which has affinity for cibacron blue sepharose (eluting at 2.15 M salt) and also has significant LRA. Because insulin at high doses has a marginal effect on lens regeneration in culture (Williams and McGlinn, Am. Zool.19:923, 1979; Connelly, Differentiation16:85–91, 1980), we tested IGF‐I. Because of the putative neurotrophic effects of transferrin (Tf) (Mescher and Munaim, J. Exp. Zool.,230:485–490, 1986), we tested Tf for its ability to enhance regeneration of the lens in culture. IGF‐I seems to have an enhancing effect on lens

ISSN:0022-104X    

DOI:10.1002/jez.1402430209

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe have studied the ability of fertilized eggs ofIlyanassa obsoletato undergo polar lobe formation and cytokinesis in the presence of Ca2+antagonists (Ca2+channel blockers, Ca2+uptake inhibitors). Earlier work had suggested little need for exogenous Ca2+during these cellular shape changes. Again it appears that exogenous Ca2+probably is not required, based on cell ability to undergo the shape changes with no, or only minor, delay in the presence of 50 mM La3+at pH 6.5, 10 mM concentrations of Ni2+or Co2+, 1 mM Cd2+, and 100 μM concentrations of Mn2+, papaverine, verapamil, D600, or diltiazem. In nominally Ca2+‐free seawater (containing ∼ 10 μM Ca2+) (CFSW), there still is no effect of Cd2+(up to 100 μM), Ni2+, Co2+, Mn2+, or diltiazem; however, papaverine, verapamil, and D600 in CFSW cause longer delays in the shape changes than they do in the presence of normal levels of Ca2+(SW). In 10–50 μM nifedipine, shape changes are progressively delayed to the same extent in both SW and CFSW, but more so in CFSW at concentrations above 50 μM nifedipine.Among calmodulin antagonists, trifluoperazine up to 100 μM was without effect, but chlorpromazine at 25–100 μM and calmidazolium at 50–100 μM caused substantial, concentration‐dependent delays in the starting times for the shape changes. Methylxanthines caused a substantialspeed‐upin the starting times for both polar lobe formation and cytokinesis. The most effective of these, caffeine, at optimal concentrations of 0.7–10 mM in SW or CFSW caused shape changes to occur 12–15 minearlierthan in controls undergoing a normal 50‐min cycle. Caffeine is known to cause release of Ca2+from muscle sarcoplasmic reticulum. A putative antagonist of intracellular Ca2+mobilization, TMB‐8, significantly inhibited the shape changes of theIlyanassacells, whereas a variety of inhibitors of exogenous Ca2+uptake noted above did not inhibit. We conclude that Ca2+may be necessary for polar lobe formation and cytokinesis inIlyanassacells, but that it may be released from intracellular, sequestered stores rather than d

ISSN:0022-104X    

DOI:10.1002/jez.1402430210

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

年代:1987

数据来源: WILEY

摘要:

AbstractMorphological studies on the gametes and entry of the spermatozoan into the egg of the zebra danio,Brachydanio rerio, were conducted primarily with scanning electron microscopy. The spermatozoan showed a spherical head, which lacked an acrosome, a midpiece containing several mitochondria, and a flagellum. Observations of the unfertilized egg confirmed and extended prior studies showing a distinct cluster of microvilli on the plasma membrane, identified as the sperm entry site, beneath the inner micropylar aperture (Hart and Donovan, '83). The fertilizing spermatozoan attached to the sperm entry site within 5 seconds of the mixing of a gamete suspension. Binding to the egg microvilli appeared restricted to the equatorial surface of the spermatozoan. Fusion between the plasma membranes of the interacting gametes was followed by the formation of a distinct, nipple‐shaped fertilization cone. The sperm head was partially incorporated into the fertilization cone cytoplasm by 60 seconds postinsemination. The incorporation of the entire sperm head, midpiece, and a portion of the flagellum occurred between 1 and 2 minutes. During this time, the fertilization cone shortened and was transformed into a massive, blister‐like cytoplasmic swelling. Concurrently, upward movements of the ooplasm resulted in the gradual disappearance of the original depression in the egg surface containing the sperm entry site. The second polar body, fully developed by 10 minutes postinsemination, formed approximately 10–15 μm from the site of sperm penetration. Development of the fertilization cone, formation of the second polar body and exocytosis of cortical granules at the sperm entry site readily occurred in parthenogenetically activated eggs, indicating that these surface rearrangements do not require sperm binding and/or

ISSN:0022-104X    

DOI:10.1002/jez.1402430211

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

年代:1987

数据来源: WILEY