摘要:

AbstractThe tolerance of the mudskipper,Boleophthalmus boddaerti, to cyanide is higher than those of other fishes reported elsewhere. The 24 h, 48 h, and 96 h LC50forB. boddaertiwere 0.37 mg HCN/liter, 0.34 mg HCN/liter, and 0.29 mg HCN/liter, respectively. The tolerance ofB. boddaertito cyanide does not involve a reduction of metabolic rate or an enhanced anaerobic metabolism, or a cyanide‐insensitive respiratory pathway. Instead, it is a result of the presence of a surplus of cytochrome oxidase and inducible cyanide‐detoxifying mechanisms in this mudskipper. Although cytochrome oxidase activities in the various tissues of the fish exposed to 0.23 mg HCN/liter were inhibited by more than 50%, no reduction in the O2consumption rate was observed.B. boddaerticould detoxify cyanide to thiocyanate. The activity of rhodanese in the liver extract of fish exposed to cyanide increased significantly compared to that of the control. The activities of cysteine amino‐transferase (CAT) and 3‐mercaptopyruvate sulfurtransferase (MPST) in the extracts from the liver and the muscle ofB. boddaertiexposed to cyanide also increased significantly compared to those of the control fish. Glutamate formed in the reaction catalyzed by CAT could undergo transamination leading to the accumulation of aspartate in the muscle of the fish exposed to

ISSN:0022-104X    

DOI:10.1002/jez.1402610102

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of hypercapnia on the acid‐base balance and acid‐equivalent transfers has been measured in the dogfishSqualus acanthias. Previous reports onSqualusare not in agreement as to the role played by compensatory acid‐base transfers between the animal and the water during hypercapnia.Cannulated animals were maintained in a closed circuit, seawater recirculation system. Plasma pH, Cco2(from which Pco2and [HCO3−] were calculated), and transfers of NH4+and HCO3−‐equivalent ions between the fish and the water, were measured during 24 hours of hypercapnic exposure (Pco2: 8–10 torr) and a subsequent 8–24 hour normocapnic recovery period.Respiratory acidosis resulted in a plasma pH depression, which was then almost completely compensated (within ˜ 0.1 pH unit) over 24 hours by a ˜ 20 mM increase in plasma [HCO3]. In contrast to previous studies on elasmobranch acid‐base regulation, hypercapnia induced a rapid 3 × increase in not only HCO3−‐equivalent uptake but also branchial ammonia (NH4+) excretion. These transfers combined for a net Δ H+loss to the water of 5.5 mmol kg−1. During the normocapnic period, net Δ H+was reversed to −6.9 mmol kg−1, nearly completely due to HCO3‐efflux.Several lines of evidence point to the contribution of gill Na+/NH4+exchange to the total ammonia excreted during hypercapnia, whereas NH3diffusion predominates during the recovery period. Likewise, Cl−/HCO3−or Cl−/OH−exchange may enh

ISSN:0022-104X    

DOI:10.1002/jez.1402610103

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe examined relationships between healing observed during embryonicXenopusretinal and optic nerve regeneration and resultant visuotectal pattern formation. Dorsal (D) and nasoventral (NV) 1/3 sized eye fragments were surgically created in stage 32Xenopus laevisembryos. Gross anatomical healing modes of these fragments were examined 2 days post‐surgery (stage 43). Healing was categorized according to the degree of cell movements observed. Animals were reared through metamorphosis and electrophysiologic mapping techniques were employed on those animals whose eyes regenerated. All D 1/3 fragments showed normal (non‐duplicated) projections to the tectum; most (80%) of the healing observed showed little cell movements (the remaining 20% showed substantial cell movements, yet failed to show duplicated projections). Most NV 1/3 fragments (73%) formed two mirror image projections to the contralateral midbrain optic tectum (pattern duplication). Most (88%) of the healing observed among these animals showed massive cell movements in the ventral retinal region (the remaining 12% showed moderate cell movements). The remaining NV 1/3 fragments (27%) showed moderate cell displacement and failed to show duplicated projections). These data are compatible with a cell‐movement:intercalary cell division hypothesis in which duplication is dependent upon specific positional confrontation and subsequent cell division.In additional studies, in adult animals, the optic nerves of eyes with duplicated projections were crushed and allowed to regenerate for 1 year. Duplicated projections were restored, indicating that developmental and maturational factors are probably not responsible for duplicative pattern formation; rather, information intrinsic to the eye, possibly created during healing interactions and/or fiber ingrowth to the tectum, underlies duplicate innervation of the t

ISSN:0022-104X    

DOI:10.1002/jez.1402610104

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe Siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in circulating prolactin levels. Pinealectomy prevented the decrease in serum prolactin and molt to the winter pelage displayed by castrated males housed under a short‐day photoperiod. A dopaminergic antagonist, pimozide, enhanced prolactin levels in both pinealectomized and shamoperated animals under both long and short photoperiods. In the short‐day animals, this effect of pimozide was associated with a prevention of the development of winter pelage. These results indicate that seasonal prolactin levels and related pelage changes are dependent upon the integrity of the pineal gland. However, basal prolactin levels under different photoperiod conditions appear to be only partly regulated by the actions of the dopaminergic sys

ISSN:0022-104X    

DOI:10.1002/jez.1402610105

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe effects of vertebrate gonadotropin‐releasing hormone (GnRH) variants on plasma and testicular androgen level in intact and hypophysectomized (PDX) male frogs,Rana esculenta, have been investigated. In intact animals, mammalian (m)‐GnRH, m‐GnRH analog (buserelin), salmon (s)‐GnRH, chicken (c) I‐GnRH, cII‐GnRH, D‐Arg6‐cII‐GnRH (cII‐GnRHA), and lamprey (l)‐GnRH (1.5μg and 6μg, total dose given on alternate days for 5 days) were able to enhance androgen production showing that specificity of pituitary responsiveness to GnRH variants appears to be low. Chicken II‐GnRH was more effective than s‐GnRH in eliciting testicular and circulatory androgen level increase. Moreover, in animals treated with 6μg of cII‐GnRH and s‐GnRH in combination, androgens decreased as compared with animal treated with cII‐GnRH only, suggesting that GnRH receptors bind preferentially the s‐GnRH form. In PDX animals, buserelin (1.5 and 6μg), cII‐GnRH, and its analog (6μg) were able to increase plasma androgen levels whereas testis androgen concentrations were increased by cII‐GnRH (1.5 and 6μg), D‐Arg6‐cII‐GnRHA, and buserelin (6μg). Since androgen production in PDX animals is influenced especially by peptides sharing cII‐GnRH structure, it is suggested that a testicular cII‐GnRH‐like material play a role as

ISSN:0022-104X    

DOI:10.1002/jez.1402610106

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

年代:1992

数据来源: WILEY

摘要:

AbstractMainly because of its transparency, theFundulusgastrula constitutes ideal material for direct study of morphogenetic cell movements in vivo. Marking studies show that deep cells of the germ ring converge toward and enter the embryonic shield, where they undergo extension. Those close to the shield move faster. Analysis of videotapes reveals thatalldeep cells of the dorsal germ ring move toward the shield. But none moves in a direct line. All meander considerably. Germ ring cells nearer the shield move toward it at a higher net rate than those farther away because they meander less. This suggests that exogenous factors promote their directionality. Cells in the prospective yolk sac adjacent to the germ ring also show net convergence, but they meander more. Directional forces are apparently stronger in the germ ring.Converging deep cells move both by filolamellipodia and, less frequently, by blebs. However, there is very little individual cell movement; all cells are almost always in adhesive contact with other cells in moving cell clusters. Clusters vary constantly in size, continually aggregating with other cells and other clusters and splitting. Filolamellipodial cells show contact inhibition of cell movement. Nevertheless, they move and do so directionally, presumably in part because, as members of cell clusters, much of their movement is passive. They also show intercalation or invasive activity, but, consistent with their contact‐inhibiting properties, only when neighboring cells separate and provide free space. Cells moving by blebbing locomotion are non‐contact inhibiting and intercalate readily. Cell division continues during convergence. Although this temporarily arrests their movement, the daughter cells soon join in the mass convergent movem

ISSN:0022-104X    

DOI:10.1002/jez.1402610107

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe regenerative ability of the pectoral fins of 14 species from 6 euteleostean families was tested. Blastema formation and distal outgrowth was observed in all species, indicating the initiation of regeneration in all species tested. Interspecific variation exists with respect to the frequency of malformations and the patterns produced by heteromorphic regeneration. Taking into account published reports on pectoral fin regeneration, the systematic distribution of homo‐ and heteromorphic regeneration leads to the following conclusions: 1) regenerative ability of pectoral fins is a property inherited from the common ancestor of euteleosteans. Whether it is also the ancestral condition for the whole teleostean group cannot be determined, because reports on more primitive teleosteans like the herring and the osteoglossimorphs are missing. 2) A propensity to produce high frequencies of heteromorphic regenerates originated independently at least three times in Cypriniformes, Scorpaeniformes, and Perciformes. 3) Impaired regeneration is most commonly found in bottom fishes, although not all ground fish groups show heteromorphic regeneration. This suggests that impaired regeneration is not directly related to bottom dwelling, but most probably originated as a side effect of other adaptive changes. Hence, neither the presence nor the loss of faithful regeneration can be associated with particular adaptive scenarios in this group, since regeneration seems to be ancestral to all major euteleost groups and its loss has no clear adaptive significance. Whether there are adaptive reasons to maintain regenerative capability or whether there are cases of reestablishment of regeneration after it was lost cannot be decided on the basis of recent evidence. More observations on phylogenetically closely related species with variable regenerative capability are necessary to assess adaptive explanations of regeneratio

ISSN:0022-104X    

DOI:10.1002/jez.1402610108

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn total, 196 two‐ to 32‐cell bovine embryo and 104 blastocysts were obtained by the in vitro fertilization of follicular oocytes matured in vitro, and 15 blastocysts fertilized in vivo were used. Chromosomal anomalies in these embryos and the inner cell mass (ICM) separated immunologically were investigated. Chromosomal anomalies were observed in 12.1% (5/41) of 2‐cell embryos, 20.0–36.4% of 4‐ to 16‐cell embryos, 7.1% (1/14) of 17‐ to 32‐cell embryos, 44.2% (15/34) of blastocysts, and 18.6% (13/70) of ICM cells derived from in vitro fertilization. These anomalies were mainly 3N and 4N at 2‐cell stage, 1N and 1N/2N at 4‐ to 32‐cell stages, and 2N/4N in blastocysts and in their ICM cells. Chromosomal anomalies of blastocysts from in vivo fertilization and their ICM were observed in 20.0% (1/5) of blastocysts and 33.3% (3/9) of ICM cells and these compositions were mainly 2N/4N. These results indicate that the abnormalities at early and blastocyst stages of embryos derived from in vitro fertilization were caused by abnormal fertilization in vitro and abnormal cleavage, respectively. Furthermore, a definite location of the chromosomal anomalies was observed in the trophectoderm of blastocysts derived from i

ISSN:0022-104X    

DOI:10.1002/jez.1402610109

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

年代:1992

数据来源: WILEY

摘要:

AbstractEyestalk ablation in Crustacea eliminates the inhibitory hormonal effects exerted by the eyestalk neuroendocrine center on ovarian growth. Planning to use crab eggs throughout the year as a model for physiological cell research, we performed a preliminary study to examine the characteristics of eggs that originated from eyestalk‐ablated females. Here we discuss the data that deal with the characteristics of eggs at fertilization and during the first 40 h of embryonic development. We found that eyestalk ablation in female crabs did not modify the resumption of egg meiosis that is stimulated by sea water, nor did it affect the electrical and cortical responses of eggs to fertilization. We also found that eyestalk ablation in females did not result in any changes in the nature of the two major ecdysteroids that are usually found in crabs' eggs (ponasterone A and 20‐hydroxyecdysone) or in their respective precursors (25‐deoxyecdysone and ecdysone) in eggs tested from 0 to 40 h post‐spawning. The respective variations in the concentrations of the four ecdysteroids were the same during this period as in control eggs. However, eyestalk ablation in females induced a striking decrease in the concentration of ponasterone A (60%) in eggs 30 to 40 h post‐spawning. Furthermore, eyestalk ablation in females promoted an increase in the titer of ponasterone A in the ovaries of about 2‐ and 20‐fold, at egg‐laying and 40 hours afterwards. This difference is discussed in terms of possible perturbations in either the synthesis of ponasterone A at the ovarian level, or its metabolism

ISSN:0022-104X    

DOI:10.1002/jez.1402610110

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe investigated the steroid biosynthetic capabilities of ovarian granulosa and thecal elements of the viviparous dogfish,Squalus acanthias. In this report we present evidence that granulosa cells secrete quantitatively important amounts of progesterone (P), testosterone (T) and estradiol‐17β (E), while theca has a more limited capacity to synthesize T and E. Ovarian granulosa cells were obtained from animals at each stage of gestation. After collagenase dispersion, an aliquot of 250,000 cells was incubated at 18°C in basal medium, containing Eagle's salts, glutamine, penicillin, streptomycin and adjusted with 136 mM sodium chloride and 350 mM urea. After a 4 hour incubation, the content of P, T, and E in medium was determined by radioimmunoassay. P was not detectable at any time, while E was present throughout the cycle, being maximal when gestation is three quarters complete (Stage C). T gradually increased from Stage B toward late pregnancy. In Stage C granulosa cells, E production increased in the presence of graded doses of T substrate. Also, a homologous pituitary extract (1/25 equivalents) and the calcium ionophore A23187 stimulated production of all 3 steroids. Using radioisotopes, granulosa cells showed a wide range of synthetic capacities. In Stage C thecal tissue, E production also increased in the presence of graded doses of T substrate, while pituitary extract only increased T. When granulosa and theca were recombined, in the presence of pituitary extract, P levels decreased with a corresponding increase in T, when compared to granulosa alone. These data suggest a possible interaction between granulosa and theca for steroid biosynthesis. They further indicate that granulosa cells alone have the capacity to synthesize P, T, and E, without any input from th

ISSN:0022-104X    

DOI:10.1002/jez.1402610111

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

年代:1992

数据来源: WILEY