摘要:

AbstractThe kinematics of the paddling stroke of ducklings swimming in formation were analyzed to detect differences in relation to swimming effort and position in the formation. Paddling motions of the feet were filmed as ducklings swam in a constant 0.3 m/s water current behind a decoy which could be in the water or suspended above the water. Ducklings were tested in clutches of one, two, and four ducklings at ages of 3, 7, and 14 days of age. Ducklings swam in organized formations with the lead duckling 0.25 body length posterior of the decoy and with an average inter‐duckling distance of 0.1 body length. Stroke frequency was constant within any age and decreased with age. Age, decoy position, and clutch size affected the length of the arc traversed by the foot through the power stroke for the most posterior duckling in the formation. Trailing ducklings had an arc length 16.9% less than leading ducklings, and ducklings swimming in formation had an arc length as much as 29.8% less than a solitary duckling. These results suggest that mechanical energy is conserved when formation swimming is employed. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402730102

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, we investigated the influence of food availability and lactation upon seasonality in red deer. This was examined by testing the hypothesis that advancing the timing of breeding and autumn moult using the hormone melatonin will be prevented when the food availability of lactating hinds is severely restricted. This hypothesis was rejected. Implanting 1 g of melatonin between June 22 and November 30 resulted in advances in the timing of the onset of ovarian activity and winter coat growth of 18 and 35 days, respectively. Whilst the onset of ovarian activity was unaffected by lactation and restricted food availability, these factors significantly delayed the winter coat growth by 20 days. The date of onset of winter primary fibre growth was negatively correlated to plasma concentrations of the hormone prolactin in July. We suggest that seasonal changes in the growth of primary hair fibres are modified by two mechanisms: the increasing duration of melatonin secretion, as day lengths decline, which depresses prolactin secretion, and low nutrition, which elevates prolactin secretion in lactating deer.To conclude, we have demonstrated that the sensitivity of red deer to photoperiodic influences is preserved in lactating animals at low levels of nutrition, and that the timing of the onset of the breeding season and winter coat growth differ detectably in their sensitivity to nutrition and lactation. © 1995 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402730103

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

年代:1995

数据来源: WILEY

摘要:

AbstractFifty‐three fertilizedXenopus laevisembryos at early tail bud stage were launched into orbit aboard a Biocosmos satellite and remained in microgravity for 11.5 days. During this period, the embryos hatched and continued to develop as free‐living larvae. Forty‐eight individuals survived the mission. Upon recovery these tadpoles had smaller heads/bodies and proportionately longer tails than ground controls. Almost all the flight animals had caudal lordosis and consequently swam in backward somersaults. Compared to ground‐based controls, their notochords were significantly larger in cross‐sectional area and were deformed. Caudal muscle fibers were less dense and involuted in a fashion indicative of degeneration. In contrast, cranial muscles associated with buccal pumping did not differ between the flight and control animals.Upon landing, the flight larvae were found to be negatively buoyant and lay on the bottom when they were not swimming. They had significantly smaller lungs than controls, suggesting that they had failed to inflate their lungs in microgravity. Additionally, the branchial baskets, gill filters and thymuses all showed signs of retarded development or degeneration.The caudal deformity that we observed in the flightX. laevishas been independently observed in three other space flight experiments where embryos were launched then hatched in space. In contrast,Xenopuslarvae from another orbital experiment that were raised from fertilization through hatching in space did not exhibit any caudal abnormalities. These divergent results suggest that either features of the launch itself (i.e., high acceleration and vibration) or an abrupt decrease in gravity during the tail bud stage detrimentally affects musculoskeletal development in anurans. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402730104

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

年代:1995

数据来源: WILEY

摘要:

AbstractMorphology and histological structure of antlers grown after castration (performed on March 25) were studied in six young fallow bucks. In the year after castration, antlerogenesis occurred during the species‐specific time span, and the shape of the antlers, which remained permanently in velvet, was normal. During a cold period in December/January, the distal parts of the antlers suffered from frostbite and were subsequently detached. The process of sequestration was similar to that leading to normal antler casting. The sequestration sites were soon covered with skin, but (limited) regrowth of antler tissue from the stumps was not observed before late April/early May, i.e., the time of normal antler regeneration. Simultaneously, growth of knobby protuberances started on the surface of the antlers. Histological analysis of biopsies taken on December 20 in the year after castration revealed that the central parts of the antlers consisted of cancellous lamellar bone with mainly secondary osteons. Peripheral to this, the bone tissue (forming the protuberances) was of a more immature nature and exhibited larger intertrabecular spaces. The outermost layer consisted of woven bone formed by intramembranous ossification from the periosteum and was undergoing active growth and remodeling at the time of biopsy. Thus, bone formation at these sites occurred during a period when no antler growth is observed in normal fallow bucks. The velvet covering the bony protuberances was of normal appearance. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402730105

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

年代:1995

数据来源: WILEY

摘要:

AbstractTo investigate developmental responses to chronic hypoxia, we incubated alligator eggs at 17% O2and 21% O2for the entire course of embryonic development and for 5 months post‐hatching. Hypoxic‐incubated alligators hatched later and at a smaller size. Hematocrit was significantly higher in hypoxic‐incubated animals immediately post‐hatch. Allosteric modification of hemoglobin oxygen affinity did not appear to play a role in the adaptation to hypoxia, given equal nucleotide triphosphate‐to‐hemoglobin ratios in the hypoxic and normoxic groups. When acutely exposed to 21% O2, hypoxic‐incubated alligators maintained oxygen consumption relative to their normoxic siblings despite their lower mass. © 1995 W

ISSN:0022-104X    

DOI:10.1002/jez.1402730106

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe male germ cell cytodifferentiative process of the moleTalpa occidentalisis described. Cytochemical procedures were used 1) to follow acrosome formation and spermatid differentiation, dividing the seminiferous epithelium cycle into ten stages, each characterized by typical germ cell‐to‐cell associations, and recognizing 13 steps in spermatid differentiation; 2) to monitor, in situ, histones replacement by protamines at step 11 of the spermiogenic process.The seminiferous epithelium cycle of the mole has the basic histological features present in all mammals and appears rather similar to that of the common shrew (Sorex araneus), the only one so far known among Insectivora. The metabolism of the DNA‐associated proteins reveals that protamines replace histones during the late steps (11–13) of spermiogenesis, mRNA for protamines having been synthesized at an earlier step (assuming that in the mole this occurs at the first spermiogenic steps, as in the house mouse).In addition the genome size (5.0 pg) and the AT/GC ratio (1.3) were evaluated. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402730107

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

年代:1995

数据来源: WILEY

摘要:

AbstractTwo native forms of vitellogenin (EIP1 and EIP2) were identified in the plasma ofOreochromis niloticus. They were present in females and were estrogen‐inducible in males. Both were phosphoglycolipoproteins and both immunoreacted with the antiserum raised against egg proteins. Two prominent bands (EIpp1 and EIpp2; corresponding to 185 and 120 kDa, respectively), observed on sodium dodecyl sulfate‐polyacrylamide gels, were induced by estradiol treatment of males and immunoreacted with the antiserum against egg proteins. EIP1 and EIP2 were isolated by precipitation with Mg2+ions and ethylenediamine tetraacetic acid, preparative polyacrylamide gel electrophoresis, and electroelution. During purification the fractions containing EIP1 and EIP2 also retained EIpp2 and EIpp1, respectively. Immunoblot analyses using affinity‐purified antibodies against EIP1, EIP2, EIpp1, and EIpp2 confirmed that EIP1 and EIP2 were at least composed of EIpp2 and EIpp1, respectively. These results suggest that at least two immunochemically different proteins are induced and are secreted into the blood to serve as vitellogenin and to provide a source of nutrient for the developing embryo ofOreochromis niloticus. © 1995 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402730108

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe present study was conducted to investigate the direct action of hypoxanthine, which has been reported to be present in pig follicular fluid, on spontaneous meiotic resumption of pig denuded oocytes in vitro. No oocytes, which were surrounded by a cumulus and some membrana granulosa cells directly adjacent to it from healthy antral follicles, underwent germinal vesicle breakdown (GVBD) when they were cultured in serum‐supplemented 199 with or without 4 mM hypoxanthine. On the other hand, 81% of denuded oocytes prepared from such cumulus‐oocyte‐granulosa cell complexes showed GVBD after 24 h of culture. Hypoxanthine inhibited significantly this spontaneous resumption of meiosis in denuded oocytes. The inhibitory action of hypoxanthine was dose dependent at concentrations of 1–6 mM and was reversible following subsequent culture of the oocytes in hypoxanthine‐free medium. However, premature chromosome condensation was observed in oocytes cultured in hypoxanthine‐supplemented medium, and the oocytes released from the influence of hypoxanthine completed GVBD and reached the second metaphase slightly faster than those freshly isolated from the follicle. These results suggest that hypoxanthine inhibits spontaneous meiotic resumption of pig oocytes in vitro. However, the inhibitory action of hypoxanthine does not prevent all events involved in GVBD from occurring. © 1995 Wil

ISSN:0022-104X    

DOI:10.1002/jez.1402730109

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn domestic roosters, which were originally seasonal breeders and that are now kept under unnatural and unchanging conditions throughout the year, fertility peaks at 32 weeks of age (96%) but it subsequently declines rapidly to only 5% at 110 weeks despite the fact that roosters can live for about 10 years. Roosters exhibiting this low‐fertility syndrome have reduced levels of spermatozoa in the ejaculate. Concomitantly, however, superabundant but apparently normal spermatozoa are found attached to Sertoli cells and, in addition, the seminiferous epithelium fails to show evidence of the regression or atrophy that characterizes both aging non‐seasonal breeders and true seasonal breeders during non‐reproductive periods. This syndrome of premature low fertility appears to stem from impaired spermiation with resultant retention of spermatozoa by Sertoli cells. To examine this problem, we compared intratesticular incorporation of3H‐thymidine between high‐fertility (32‐week‐old) and low‐fertility (82‐week‐old) roosters. Radioactivity associated with spermatozoa, 33 days post‐injection, was almost 50% higher in the low‐fertility roosters than in the high‐fertility ones. By contrast, both groups showed similar characteristics with respect to a) intratesticular incorporation of3H‐thymidine, b) dynamics of spermatogenesis, c) intratesticular level of radioactivity just before the initiation of spermiation, and d) the duration of both spermatogenesis and the time required for sperm to pass through the genital tract. Our results confirm that intratesticular retention of sperm occurs in roosters with premature low‐fertility syndrome and suggest new possibilities for the study of the complex relationship between Sertoli cells and spermatozoa and the effects of this relationship on fert

ISSN:0022-104X    

DOI:10.1002/jez.1402730110

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

年代:1995

数据来源: WILEY

摘要:

AbstractCalcium, sulfur, and zinc content in normal and arthritic equine cartilage have been studied by synchrotron radiation‐induced X‐ray emission (SRIXE). Ranging from the superficial to the columnar zone of the normal tissue, calcium and zinc concentrations are increasingly higher, whereas sulfur is at its highest concentration in the transitional zone. In the arthritic tissue, calcium concentration is at its maximum in the transitional zone, whereas zinc and sulfur distributions are relatively homogeneous. Sulfur concentration in arthritic cartilage is reduced to about one‐third with respect to that in normal tissue. The possibility that zinc concentration reflects the distribution of the zinc‐containing enzyme alkaline phosphatase is presented. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402730111

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

年代:1995

数据来源: WILEY