摘要:

AbstractWith the aim of understanding the organization of the nervous system in the Prosobranchia gastropodConcholepas concholepas, we studied the properties, specificity, sedimentation coefficient, and solubility of the cholinergic enzyme, acetylcholinesterase (AChE). It was found that 95% of the esterase was inhibited by BW284c51 dibromide but not by iso‐OMPA, which is consistent with the specificity of AChE. The calculated Km0.22 mm is eight to ten times higher than are the Kms for AChE of other invertebrates and similar to the values reported for fishes and vertebrates.The AChE shows a maximal activity around 22°C, has a glycoproteic character, and presents sedimentation coefficients of 6.5 S and 10.5 S. Most of this AChE activity is soluble under low ionic strength conditions; however, the enzyme aggregates in the absence of detergents.In conclusion, our evidence indicates the presence of a well‐recognized molecular marker that could be useful for the study of the development ofConcholepas conchol

ISSN:0022-104X    

DOI:10.1002/jez.1402550102

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

年代:1990

数据来源: WILEY

摘要:

AbstractDogfish shark heart mitochondria isolated fromSqualus acanthiaswere exposed to increasing concentrations of mannitol/sucrose, trimethylamine oxide (TMAO), betaine, and urea. For all but urea, respiratory control ratios (RCR) and rates of oxygen uptake (V̇O2) in the presence of malate/glutamate were low in basal medium (220 mOsm), increased with solute concerntration to about 420–870 mOsm, and declined in the highest concentrations (1,150 mOsm). Increasing urea concentration up to about 1,150 mOsm had relatively little effect on RCR or V̇O2. The results were not changed significantly by prolonged incubation in these media or by the addition of 0.3 M urea to either mannitol/sucrose or TMAO media. We conclude that, like mannitol/sucrose, betaine, and probably TMAO permeate shark heart mitochondria slowly or not at all, but that urea readily permeates the mitochondria and is thus osmotically inactive. The highest V̇O2values were obtained in media at 580 mOsm, hypoosmotic to shark blood (897 mOsm) and to local seawater (879 mOsm) but approximately isoosmotic to blood without the osmotic contribution of the permeant urea. We conclude that V̇O2is superior to RCR as a comparative measure of mitochondrial act

ISSN:0022-104X    

DOI:10.1002/jez.1402550103

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn early stages of avian development, respiratory gas exchange takes place mainly through the blood vessels of the yolk sac membrane. Therefore, a short distance between the yolk sac membrane and the eggshell is required to ensure a sufficient oxygen supply of the embryo. In freshly laid eggs the yolk sphere is located approximately in the center of the egg, but soon after the beginning of incubation it moves to the upper pole right beneath the eggshell. The cause for this displacement is not known. To quantify the forces acting on the yolk sphere of chicken eggs during incubation, we measured the densities of albumen, yolk and subembryonic fluid and the viscosity of the liquid albumen. We found that between day 0 and day 4 of incubation the calculated buoyancy due to density differences between the egg components increases only threefold. This is probably too small to overcome the yield stress of the gel‐like thick albumen that forms a capsule around the yolk sphere. A different process responsible for the yolk displacement is proposed. Under reduced gravity, the movements of the yolk are influenced substantially by the fluid properties of the thin albumen, especially yield stress. Furthermore, acceleration peaks present in a space laboratory will probably displace the yolk sphere away from the eggshell. This is strong evidence that an early chick embryo will not be able to survive in a space laboratory in ov

ISSN:0022-104X    

DOI:10.1002/jez.1402550104

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

年代:1990

数据来源: WILEY

摘要:

AbstractA passerine bird, the European StarlingSturnus vulgaris, demonstrated a seasonal ability to respond to odor cues. Cardiac conditioned responses were most evident when birds were in breeding condition. Once birds were in nonbreeding condition, responding to odors all but ceased. For birds in breeding condition, threshold sensitivity to the odor cyclohexanone was comparable to levels reported for nonpasserine birds (0.3% vapor saturation or 3.778 × 1014molecules/ml). In contrast, the threshold level during the postreproductive phase of the annual cycle was 10% vapor saturation (1.256 × 1016molecules/ml). a level high enough to implicate the trigeminal system as the modality mediating chemosensory perception. The strong cyclic responding pattern suggests links between photoperiodically controlled endocrine production, breeding behavior, and olfactory sensitivit

ISSN:0022-104X    

DOI:10.1002/jez.1402550105

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

年代:1990

数据来源: WILEY

摘要:

AbstractSixty‐six captive‐reared, juvenile alligators maintained in environmentally controlled chambers were randomly assigned to four treatments consisting of stocking densities of 0.35, 0.18, 0.12, and 0.09 m2/alligator. Alligators were maintained at these densities for 3.5 months. At approximately 4 week intervals the alligators were weighed, measured, and bled via cardiac puncture. Duplicate aliquots of plasma were assayed for corticosterone. All of the alligators continued to grow during the experiment, but alligators maintained at the lowest stocking density were significantly heavier and grew significantly faster (P<0.01) and had significantly lower plasma corticosterone (P<0.01) than alligators maintained at the highest stocking density. These results indicate that crowding (i.e., high‐density rearing) of juvenile alligators inhibits maximum growth and that the subsequent stress associated with this crowding results in chronically elevated plasma corticosterone. Plasma corticosterone showed a strong negative correlation with change in body weight; the faster the rate of growth, the lower the hormone levels. These results also show that a single blood sample taken at monthly intervals is sufficient to monitor chronically elevated plasma corticosterone in this sp

ISSN:0022-104X    

DOI:10.1002/jez.1402550106

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

年代:1990

数据来源: WILEY

摘要:

AbstractMitotic chromosomes of the European water frogsRana ridibundaandRana lessonae, the parental species ofRana esculenta, differ significantly in their centromeric regions: when C‐banded or when made fluorescent, the centromeres ofR. ridibunda(and of theridibundachromosomes inR. esculenta) are visible as a conspicuous dark granule or as a conspicuous fluorescent spot; the centromeres ofR. lessonae(and of thelessonaechromosomes inR. esculenta) are inconspicuous or not fluorescent. Lampbrush chromosomes of these three taxa are described in detail for the first time; those ofR. ridibundaandR. lessonaediffer significantly in morphostructural characters such as conspicuousness of centromeres and number, form, and location of giant loops as well as in chiasma frequency. Chromosomes of the two parental species can thus be distinguished when present in lampbrush complements of hybrids. Reproduction in both sexes of naturalR. esculentalineages is hemiclonal: only the unrecombined genome of one parental species, usuallyR. ridibunda, is transmitted to haploid gametes (hybridogenesis). In 18 hybrids from natural populations of Poland, somatic tissues had allodiploid complements with chromosomes from each parental species. In contrast, spermatocytes I of five males and oocytes I of seven of eight females (221 of 222 oocytes) were autodiploid and contained onlyR. ridibundachromosomes that formed n bivalents. These 12 hybrids thus were hybridogenetic. A single female hybrid had oocytes I (33 of 34) with genomes of both parental species; they showed various disturbances including tetraploidy, reduced number of chiasmata, and incomplete synapsis resulting in univalents. This individual thus was not hybridogenetic. The irregular lampbrush patterns indicate that such hybrids will have severely reduced fertility and most of their successful gametes will result in allotriploid progen

ISSN:0022-104X    

DOI:10.1002/jez.1402550107

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

年代:1990

数据来源: WILEY

摘要:

AbstractAlthough prostaglandins (PGs) have been shown to play an important role in gonadotropin‐induced ovulation in mammals, birds, and fishes, nothing is known about the role of PGs in reptilian ovulation. Females of the lizardAnolis carolinensis, each with a large vitellogenic ovarian follicle, were pretreated with an inert subcutaneous pellet or one containing indomethacin (an antiprostaglandin) at a delivery rate of 2.38 μg/lizard/day. Females in each pretreatment group were treated with subcutaneous injections, 7 h apart, of either vehicle alone or 25 μg porcine FSH. They then were sacrificed at 9, 12, and 24 h after the initial injection. After noting whether ovulation had occurred, ovaries from animals with an unovulated large (>5 mm diameter) follicle were incubated in 5 mlAnolisRinger's for 1 h. The follicles then were examined histologically, and levels of PGE in the incubation medium were determined by radioimmunoassay. FSH significantly induced ovulation in a majority of females by 12 h, and indomethacin significantly reduced the number of FSH‐induced ovulations at 12 h but not at 24 h. Thus, indomethacin delayed FSH‐induced ovulation. Indomethacin also inhibited the preovulatory changes in histology of the follicular wall seen after FSH treatment alone and lowered PGE secretion at all time periods. Secretion of PGE was not influenced by FSH. Thus, prostaglandins may mediate or permit, at the ovarian level, the ovulatory influence of gonadotropin in this

ISSN:0022-104X    

DOI:10.1002/jez.1402550108

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

年代:1990

数据来源: WILEY

摘要:

AbstractFull‐grownXenopus laevisoocytes resume meiosis from prophase arrest in response to progesterone stimulation. Recent studies have shown that the tumor promoter, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), a very potent activator of protein kinase C, can also induce the resumption of meiosis in amphibian oocytes. We have investigated the possibility that sn‐1,2‐diacylglycerol (DAG), the intracellular activator of protein kinase C, may be involved in the pathway normally used by progesterone. We have found that full‐grown oocytes arrested in meiotic prophase contain 48 ± 5 pmoles DAG/oocyte. This level increases within the first 5 minutes following the addition of progesterone and reaches a maximum of 75 ± 10 pmoles following 60 minutes of steroid stimulation. Progesterone induces the up‐regulation of a Na+/H+antiport in the plasma membrane of the oocyte causing an increase in pHifollowing 60 minutes of steroid stimulation. We have found that the addition of 200 μM DAG (1,2‐dioctanoylglycerol, diC8) to the culture medium can cause a partial up‐regulation of this Na+/H+pump in the absence of hormonal stimulation. These results suggest that DAG and protein kinase C may be involved in regulating certain aspects of meiotic maturation in progesterone‐

ISSN:0022-104X    

DOI:10.1002/jez.1402550109

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

年代:1990

数据来源: WILEY

摘要:

AbstractTestes of the Western spotted skunk enlarge and regress seasonally. The pineal hormone, melatonin, may be important in timing this seasonal reproductive activity. Likewise, the suprachiasmatic nuclei (SCN) have been implicated as possible neural regulators of pineal and reproductive events. These experiments were conducted to determine whether ablation of the SCN or constant administration of melatonin alters timing of the seasonal pattern of testicular regression and recrudescence. Male skunks (n = 24) were treated as follows: six received two empty Silastic capsules, six received two melatonin‐filled Silastic capsules, six received sham lesions to the SCN, and six received lesions to the SCN (SCNx). All skunks were exposed to a natural photoperiod and had regressed testes at the onset of the experiment. Four of six males from the SCNx group had an average of 94 ± 11.3% of these nuclei destroyed. Sham SCNx, animals with<40% of the SCN ablated, and males with empty capsules did not have fully enlarged testes until October. SCNx and melatonin‐treated skunks exhibited a hastening of testicular recrudescence with maximal testis size being reached in June. Skunks with lesions to the SCN maintained enlarged testes for 5 months while all other groups exhibited rapid regression after attaining maximal testis size. Testicular regression occurred from July through October in animals receiving continuous melatonin, while controls exhibited recrudescence during this same period. Our data suggest that the SCN, melatonin, and thus the pineal gland, play a role in regulating the seasonal testicular cycle of the spotted s

ISSN:0022-104X    

DOI:10.1002/jez.1402550110

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

年代:1990

数据来源: WILEY

摘要:

AbstractDuring the courtship ofHelix aspersa, the snails push calcareous darts into one another. To examine the importance f this unusual action for the normal expression of their sexual behaviour, one group ofHelix aspersawas prevented from exchanging darts by surgically removing their dart sacs. Another group ofHelix aspersahad their digitiform glands surgically removed. These glands secrete a mucus that coats the dart. Glandless snails were capable of exchanging darts, but the darts lacked their normal mucus coating. Both dartless and glandless pairs required more courtship time to reach copulation than did sham‐operated controls. Therefore, it appears that it is the mucus from the digitiform gland, not the mechanical action of the dart, which affects courtship duration.Injections of gland homogenate decreased the courtship duration of sexually receptive, dartless, and glandless snails. Gland homogenate also increased the size of the recipient's genital eversion, and retarded locomotion. The mucus was only effective if it entered the circulatory system of a sexually receptive snail at a specific stage of genital eversion.The active agent in the digitiform gland mucus fulfills the requirements for the substance to be classified as a pheromone. It enters the circulatory system of the conspecific via inoculation by the dar

ISSN:0022-104X    

DOI:10.1002/jez.1402550111

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

年代:1990

数据来源: WILEY