摘要:

AbstractPrevious in vivo clearance studies (Schrock et al., '82) have revealed that taurine is secreted by marine fish kidneys. In the present study taurine secretion by the flounder (Pseudopleuronectes americanus) renal tubule was investigated by assaying the transport of14C‐taurine in vitro. Collections from isolated fluid‐secreting flounder tubules confirmed the presence of a tubular mechanism for taurine secretion. The flounder renal tubule concentrated taurine in the lumen at a lumen/bath ratio of 25, with the movement across the peritubular membrane identified as the concentrating step of taurine transport. Studies with teased flounder renal tubules identified transport as Na+and Cl−dependent. Taurine transport was inhibited by β alanine, γ‐aminobutyric acid, and hypotaurine. In a study of the hormonal control of taurine transport, only the adrenal steroid dexamethasone stimulated taurine uptake by the flounder renal tubules. Transport was not affected by the second messengers adenosine 3′5′‐ cyclic monophosphate, guanosine 3′5′‐cyclic monophosphate, adenosine, or C

ISSN:0022-104X    

DOI:10.1002/jez.1402230202

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

年代:1982

数据来源: WILEY

摘要:

AbstractSubsequent to excision and explantation of the limb blastema into culture medium, there is an abrupt reduction in mitotic index lasting several hours. Coincident with the disappearance of mitosis, abnormal mitotic figures (AMFs), lacking the condensed chromosomal nature of normal figures, are seen. These persist until normal levels of mitotic activity are restored approximately 6 hr later. The transient loss of mitotic activity is observed in both ganglionated and nonganglionated explants. The large number of prophase figures observed at time zero were sharply reduced within minutes, without concomitant increases in the later phases. The possibility that some cells, without completing mitosis, become temporarily indistinguishable as mitotic figures, is discussed in terms of chromosomal decondensation and recondensation.

ISSN:0022-104X    

DOI:10.1002/jez.1402230203

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

年代:1982

数据来源: WILEY

摘要:

AbstractEnzyme activities and DNA content have been measured in axolotl liver during the metamorphic period (4–8 months after spawning). Three different types of enzyme activity profiles were observed. In the type I profile (carbamoyl‐phosphate synthase, arginase, ornithine transcarbamoylase, and glutamate dehydrogenase) enzyme activity is high in the youngest animals studied, and shows a minimum at 5 months followed by a maximum at 8 months of age. Thereafter activities do not change or slightly decrease. In the type II profile (tyrosine aminotransferase, glucose–6–phosphatase) enzyme activity shows a peak at 5 months of age and is low thereafter. Hexokinase, the enzyme with a type III profile, shows high activity throughout the metamorphic period. DNA content remains high throughout the metamorphic period but decreases 50% between 9 and 12 months of age, probably due to an increase in the size of the hepatocytes. No glucokinase activity was detected. High activities of cluster II enzymes represent early metamorphic events, while the rising part of cluster I is associated with late metamorphic events.The apparent molecular specific activity increases during natural development between 5 and 9 months of age, or precociously, upon thyroid hormone treatment. This change in apparent molecular specific activity is correlated to the advent of ure

ISSN:0022-104X    

DOI:10.1002/jez.1402230204

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

年代:1982

数据来源: WILEY

摘要:

AbstractA method has been developed to establish the degree of cross‐reactivity of an antiserum raised against purified carbamoyl‐phosphate synthase (ammonia) from adult rat liver, toward a homologous enzyme from another species without purification of the latter enzyme. For that purpose the ratio between enzyme activity and enzyme protein, i.e., the molecular specific activity in crude liver extracts, was determined by two independent methods.When the molecular specific activity was determined by means of radioimmunoassay using a specific antiserum raised against rat liver carbamoyl‐phosphate synthase this ratio was a factor four higher for the axolotl than for the rat.Both axolotl and rat liver carbamoyl‐phosphate synthase appear as a very prominent band with an apparant molecular weight of 165,000 after sodium dodecyl sulphate‐polyacrylamide gelelectrophoresis. Therefore, the amount of enzyme protein could be determined by means of densitometry of this band using purified rat liver carbamoyl‐phosphate synthase as a standard. The ratio between enzyme activity and enzyme protein calculated from this method appeared to be the same for axolotl and rat.From these results it can be deduced that the degree of cross‐reactivity between rat and axolotl liver carbamoyl‐phosphate synthase is approximately 25% when using the antiserum raised against the ra

ISSN:0022-104X    

DOI:10.1002/jez.1402230205

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

年代:1982

数据来源: WILEY

摘要:

AbstractThroughout the process of vitamin A (V‐A)‐induced mucous metaplasia of the scale epidermis of a 12‐day chick embryo, changes in the activities of cell proliferation were investigated in reference to morphological changes. In both the control and V‐A cultures after 5 days, a dynamic steady state was established among the stratified layers which differentiated into keratinizing epidermis during the first 7 days.In the control, cell proliferates within only the basal layer and the cell cycle time, except Tg2, increased during 30 days of culture. In the V‐A culture, this tendency was reversed in each parameter between day 10 and day 13, when symptoms of mucous metaplasia became morphologically prominent. On day 13 in the V‐A culture, superficial cornified cell layers were sloughed off as whole sheets and concurrently DNA synthesis was reactivated throughout the entire cell layers of the epithelium.The correlation between two of five cell cycle times (Tgc, Tg1, Ts, Tg2, Tm) was statistically treated as linear regression lines and gave highly significant coefficients in every case. The regression coefficients between Tsand Tgcand Ts and Tglin V‐A culture are significantly (P<0.01) smaller than those in the control. It was found that V‐A induced sequential alterations in mucous metaplasia with respect both to morphology and proliferation activity in the epidermis of t

ISSN:0022-104X    

DOI:10.1002/jez.1402230206

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

年代:1982

数据来源: WILEY

摘要:

AbstractStarvation of penultimate stage brachyuran larvae within 15 hours after ecdysis results in the suspension of the molt cycle in the early premolt stages. This suspension can be maintained for up to 7 days. Using this as a tool to extend the duration of the penultimate zoeal stage, it was possible to demonstrate that crustacean morphogenesis is at least partially regulated by a time‐dependent process which is independent of the number of larval instar

ISSN:0022-104X    

DOI:10.1002/jez.1402230207

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe gonadal differentiation of anurans,Rana japonicaandR. brevipoda, was examined in animals raised from eggs which had been irradiated at the vegetal hemisphere with UV (9300 erg/mm2) at the 2‐cell stage. InR. japonicaabout 70% of the larvae at stage I from the pressed and UV‐irradiated eggs were germ cell free, but at a stage immediately after metamorphosis all animals had at least some germ cells, although their gonads often were extremely small and poorly differentiated. When male animals matured sexually, many of them had abnormal gonads. However, all of them were shown by artificial means to be capable of fertilization. In the nonpressed and irradiated group, no larvae were germ cell free and the animals immediately after metamorphosis showed nearly normal gonadal differentiation except for the presence of a few degenerate oocytes in the ovaries. The results inR. brevipodawere basically similar to those inR. japonica. In both species, sex ratios were determined at two stages, the first immediately after metamorphosis and the other when the animals matured, as based on gonad morphology and histology and on external sexually dimorphic characters as well. Sex ratios at these two stages in frogs from the pressed and irradiated eggs differed markedly inR. brevipoda. The ratio was normal at metamorphosis but high M/F ratios occurred when animals became mature. That sex reversal took place in this species as well as inR. japonica(in which sex‐ratio deviation was not statistically significant) was supported by the sex ratios of the progenies of these supernumerary

ISSN:0022-104X    

DOI:10.1002/jez.1402230208

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

年代:1982

数据来源: WILEY

摘要:

AbstractGynogenetic rainbow trout lines can be produced easily with the simple UV sperm irradiation technique detailed in this study. The dose effect on embryonic survival rate is called a pseudo “Hertwig effect” because of major differences with results of gamma irradiation: Some mixing of various karyotypes (from diploid to haploid number) were obtained with mean doses, probably because of the weak penetrating power of the ultraviolet rays. Irradiations lasting 4 minutes or more are required to produce homogeneous haploid progeny; heat shock applied to such fertilized eggs results in diploid fry of the maternal phenot

ISSN:0022-104X    

DOI:10.1002/jez.1402230209

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

年代:1982

数据来源: WILEY

摘要:

AbstractBHC‐induced molt inhibition in the crab,Oziotelphusa senex senexFabricius, apparently by triggering the release of molt inhibition hormone (MIH

ISSN:0022-104X    

DOI:10.1002/jez.1402230210

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

年代:1982

数据来源: WILEY

摘要:

AbstractAutoradiographic demonstration of beta adrenergic receptors was achieved light microscopically in melanophores of isolated scales of a teleost fish,Oryzias latipes. [3H]hydroxybenzylisoproterenol, a beta adrenergic agonist, and [3H]propranolol, a beta adrenergic antagonist, were used as radioligands. In the autoradiograms, photographic grains of considerably high density were found to be distributed evenly over all parts of the surface of melanophores. Since the density of the grains was observed to decrease significantly in the presence of excess amounts of nonlabeled ligands, the results indicate the actual existence of beta adrenergic receptors in the present melanophores. This substantiates the findings obtained by other physiological and pharmacological methods that beta‐adrenergic receptors may exist and be involved in melanosome‐dispersion response of fish melanopho

ISSN:0022-104X    

DOI:10.1002/jez.1402230211

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

年代:1982

数据来源: WILEY