摘要:

AbstractThe dart apparatus, used during courtship in some groups of hermaphroditic land snails, has long been assumed to have a “stimulatory” effect on the mating partner, though how stimulation occurs and exactly what function it serves has never been determined. In this study, extracts of the mucous glands of the dart apparatus of the land snailHelix aspersawere injected into conspecifics and into a related snail,Cepaea nemoralis, in order to test the hypothesis that the dart is used to achieve inflow of bioactive mucous gland secretions into the darted snail.Helix aspersainjected with the extract responded by everting their terminal genitals; eversion normally takes place during courtship and mating. Boiling the extract increased the bioactivity. Pronase‐treated extract lost bioactivity, and gel filtration of the boiled extract indicated that the active substance has a molecular weight of about 5,000. The active substance may be a polypeptide.Cepaea nemoralisalso everted their genitals when injected with the boiledHelixextract. The active substance appears to be a contact sex pheromone, the second such pheromone in a pulmonate land snail for which experimental evidence has been obt

ISSN:0022-104X    

DOI:10.1002/jez.1402380202

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

年代:1986

数据来源: WILEY

摘要:

AbstractChloride secretion (Isc) by the opercular epithelium of the teleost,Fundulus heteroclitus, is stimulated by elevations in intracellular cyclic AMP (cAMP) elicited by β‐adrenergic agonists, such as isoproterenol, and is accompanied by a small but significant increase in the transepithelial conductance (Gt). Cupric ions (Cu2+) have been shown to block the apical membrane CI−channels in this epithelium, leading to a reduction in both the Isc and Gt (Degnan, '85). In the present studies, the effects of Cu2+on cAMP‐elevated and cAMP‐depleted epithelia were observed to define the actions of cAMP in this stimulatory process. At a concentration of 5 × 10−4M in the mucosal solution, Cu2+inhibited the Isc 79.8% and reduced the Gt 39.2%. Isoproterenol produced an attenuated stimulation of the Isc in these tissues compared to untreated controls, but had no effect on the Gt. In tissues bathed bilaterally with Cl−‐free Ringer, the Isc was virtually abolished and the Gt was reduced 37.0%; neither Cu2+nor isoproterenol had any effects on the Isc or Gt under this condition. Simultaneous22Na and36Cl unidirectional flux determinations indicated that the only effects of both isoproterenol and Cu2+were on the active Cl‐ secretory flux. An inhibitor of adenylate cyclase, 2′,5′ dideoxyadenosine (DDA), reduced the Isc and Gt 39.8% and 20.8% respectively. This inhibitor had no additional effects in Cu2+‐treated tissues and the action of Cu2+on the Gt was reduced in DDA‐treated tissues. The results indicate that cAMP stimulation of Cl−secretion involves only the active transcellular Cl−pathway and is accomplished in part by an increase in a Cl−‐dependent, mucosal Cu2+‐inhibitable increase in the Gt, which is most likely localized to the a

ISSN:0022-104X    

DOI:10.1002/jez.1402380203

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

年代:1986

数据来源: WILEY

摘要:

AbstractRecent work in our laboratory indicated that the liver of rats and pigeons secretes a prolactin synergist (synlactin) in vitro. We have investigated the secretion of this activity by the liver of nine species of ectothermic vertebrates. Liver from three teleosts (goby, salmon, and tilapia), four amphibians (Ambystoma,Necturus, bullfrog, and grass frog) and two reptiles (turtle and anole) was diced, washed, and incubated for 3 hr in isotonic medium. After dialysis, the liver incubation media (LIM) were tested with and without prolactin (PRL) in the local pigeon crop‐sac bioassay. The LIM for turtle, larval bullfrog, freshwater salmon, and 5% seawater‐adapted goby significantly augmented the local crop‐sac response to PRL, but the LIM from anole, adult bullfrog, grass frog, fasted larvalAmbystoma,Necturus, 100% seawater‐adapted goby, and tilapia did not contain synergizing activity. We conclude that synlactin is secreted by the liver of several species representing three of the major ectothermic classes of vertebrates. It is significant that in two cases, larval bullfrog and 5% seawater‐adapted goby, the presence of synlactin occurs in physiological states in which PRL is active. In the opposite cases (adult frog and 100% seawater‐adapted goby) the activity was not detectable. We also found that the liver of larval and adult bullfrogs and tilapia released a factor in vitro that had proliferative activity in the crop‐sac. This activity appears to be distinct f

ISSN:0022-104X    

DOI:10.1002/jez.1402380204

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

年代:1986

数据来源: WILEY

摘要:

AbstractDorsal aortic and cardinal venous blood pressures, dorsal aortic blood flow, and heart rate were measured in different combinations in conscious unrestrained eels (Anguilla australis). One group of animals was treated with either bretylium (10 mg.kg−1) or saline vehicle and dorsal aortic blood pressure and heart rate were monitored for the next 6 days. Two other groups were treated with phentolamine (5 mg.kg−1) and either dorsal aortic blood pressure and heart rate, or dorsal aortic blood flow and venous pressure monitored for 6 hr. In vivo treatment with either bretylium of phentolamine produced effective blockade of the α‐adrenoceptor‐mediated vasoconstriction of stimulated saline‐perfused trunk preparations; however, neither drug had no lasting effects on arterial blood pressure. In addition, phentolamine had no lasting effects on venous blood pressures or dorsal aortic blood flow. It is concluded that, in the resting eel, systemic vascular resistance is not normally under adrenerg

ISSN:0022-104X    

DOI:10.1002/jez.1402380205

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

年代:1986

数据来源: WILEY

摘要:

AbstractAmerican bullfrogs,Rana catesbeianarespond to prostaglandins with changes in heart rate and blood pressure. These studies compare responses of warm (22°C) and cold acclimated (5°C) bullfrogs to prostaglandins. Gas chromatographic analysis determined equivalent fatty acid profiles in total lipids of heart and artery tissue from warm and cold acclimated animals. Arachidonic acid was the fatty acid precursor found in greatest abundance in both groups. For cardiovascular experiments, bullfrogs were cannulated by using a T‐cannula implanted in the right sciatic artery. In warm acclimated bullfrogs, preinfusion systemic arterial pressure (SAP) was 14.7 ± 0.5 mm Hg, and heart rate was 33.0 ± 1.7 beats/min. Cold acclimated bullfrogs had SAP values of 8.0 ± 0.8 mm Hg, and heart rate was 6.9 ± 0.3 beats/min. Arachidonic and eicosapentaenoic 3‐acid infusions (2,000 μg/kg body weight [bw]) were hypertensive in cold acclimated and hypotensive in warm acclimated animals. These effects were blocked by indomethacin (4 mg/kg bw). In both warm and cold acclimated bullfrogs, prostaglandin F2α(3–100 μg/kg bw) was hypertensive, while prostaglandin I2(0.03‐3 μg/kg bw) was hypotensive, with both prostaglandins stimulating a greater absolute response in warm acclimated animals. In addition, both prostaglandins increased heart rate in warm but not in cold acclimated bullfrogs. The results suggest diminished cardiovascular sensitivity to prostaglandins at low environme

ISSN:0022-104X    

DOI:10.1002/jez.1402380206

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe time lag in the appearance of the first feather papillae (rate of feather regeneration) was studied after monthly depluming of the redheaded bunting (Emberiza bruniceps). Results indicate that the rate of feather regeneration varies over an annual time scale. When a comparison was made between monthly changes in levels of plasma thyroid hormones (thyroxine‐T4and triiodothyronine‐T3) in redheaded buntings (Pathak and Chandola, '82a) and the rate of feather regeneration, the rate of regeneration showed a distinct correlation with levels of circulating T4. The rate of feather regeneration was faster during December and June when endogenous T4levels were high and slower during July/August and March/April when levels of circulating T4were relatively low. Such a relationship was, however, not observed with T3. Results of administration of T4and T3separately, in normal as well as in thyroidectomized birds; in different doses; and during different phases of the annual cycle, indicate a strikingly greater influence of T4on the rate of feather regeneration and on the number of regenerated papillae than T3. Injection of propylthiouracil (PTU—an effective inhibitor of peripheral conversion of T4to T3in the redheaded bunting) in thyroidectomized birds that were also receiving T4, resulted in even faster rates of feather regeneration. Thyroidectomized birds receiving saline had no feather regeneration. Castration led to a slow rate of feather regeneration during May/June only. During this period thyroid activity of the redheaded bunting is known to be significantly influenced by gonadal hormones; this influence is not apparent during January/February or August. Injections of testosterone neutralized the effects of castration. It is concluded that T4is more important than T3for feather regeneration in redheaded buntings and that the effects of castration are due to alterations in thyroid fun

ISSN:0022-104X    

DOI:10.1002/jez.1402380207

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe activity of the enzyme 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase, E.C.3.1.4.37) has been studied in the retina of three vertebrate species. Activity was highest in the goldfish, followed byXenopus laevisandRana pipiens. Also, high activity levels were found in goldfish retinal pigment epithelium and choroid, but not in the other two species. When added to in vitro culture systems, 2′,3′‐cyclic nucleotides were found to have no effect on goldfish cone retinomotor movement, but caused a marked inhibition ofRana pipiensrod outer segment disc membrane shedding. It is suggested that CNPase may play a role in cellular processes requiring membrane structural

ISSN:0022-104X    

DOI:10.1002/jez.1402380208

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

年代:1986

数据来源: WILEY

摘要:

AbstractTwenty‐two stages of the life cycle of the laboratory‐reared frogLimnodynastes tasmaniensis, from the fertilised egg to the adult frog, have been subjected to acute irradiation from cobalt‐60 (60Co) gamma rays to determine the lethal dose (LD50) values. The period of observation was 40–160 days, depending on the stage irradiated. The most sensitive stage was the fertilised egg, with an LD50/40of 0.6 Gy. Thereafter, radioresistance increased in an uneven pattern, with periods of relatively rapid increase alternating with periods of little change. The most resistant stages of the life cycle were medium to large tadpoles at limb bud and toe development stages (LD50/60∼ 25 Gy). At metamorphosis, resistance decreased significantly to an LD50/160of 18.3 Gy, with a very similar result, 18.7 Gy, for young adult frogs. The latter figure, when compared with LD50values for other frogs, is found to be in good agreement with other results obtained using gamma rays. Preliminary experiment on chronic caesium‐137 (137Cs) gamma irradiation ar

ISSN:0022-104X    

DOI:10.1002/jez.1402380209

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

年代:1986

数据来源: WILEY

摘要:

AbstractDuring metamorphosis of the anuran tadpole, dorsal skin of the larva develops into adult back‐skin, whereas tail‐skin disappears simultaneously with resorption of the tail. Although it has been shown by transplantation experiments that the regional specificity is intrinsically determined in the respective skin, survival of a tail‐skin graft to the body has also been reported. In order to resolve the contradiction, developmental changes of back‐and tail‐skin grafts transplanted to the same tadpole were examined using an electron microscope. Back‐skin transplanted to the tail developed into adult‐type back‐skin, regardless of degeneration of the surrounding tail tissue. When tail‐skin was transplanted to the back region, collagen layers of the dermis degenerated during the early stage of metamorphosis. As metamorphosis progressed, however, fibroblasts derived from the adjacent back region formed collagen fibers in the subepidermis and the new dermis slowly replaced the regressive graft dermis. Epidermis of this tail‐skin graft remained intact, transforming into flattened epithelium and some epidermal cells clearly proliferated during metamorphosis. Furthermore, the epidermis formed secretory glands that are characteristic of adult back‐skin and survived even after metamorphosis. These results suggest that the tail‐epidermis is able to survive if the tissue is translocated under appropriate conditions prior to the begin

ISSN:0022-104X    

DOI:10.1002/jez.1402380210

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

年代:1986

数据来源: WILEY

摘要:

AbstractPieces of dorsal neural tube (stages 22–23) or late neural crest tissue (stages 24–26) ofXenopus laeviswere cultured. Migratory cells moved out of explants to form an outgrowth of multipolar melanophores on the substratum. Treatment with β‐galactosidase (0.1–0.4 U/ml) to remove cell surface galactose was correlated with detahment of melanophores. In the presence of lower concentrations of this enzyme the shapes of these cells were converted to arborized, spidery morphologies and cell movement was inhibited. Unpigmented cells were affected more slowly. Neuraminidase treatment, to remove cell surface sialic acid and expose more galactose, only affected melanophores. These became increasingly spread on the substratum and cell overlap was observed. These results suggest that the relative amounts of galactose and sialic acid at the cell surface become increasingly important in controlling cell adhesion asX. laevisneural crest cells migrate and differentiate into mela

ISSN:0022-104X    

DOI:10.1002/jez.1402380211

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

年代:1986

数据来源: WILEY