摘要:

AbstractDeer were exposed for three years to photoperiods which increased or decreased two hours every four months, starting at 4L/20D or 20L/4D, respectively. Under both sets of conditions, antlers were repeatedly shed and replaced, usually in synchrony with every other time the day lengths were changed. On decreasing days, antler cycles were omitted as the photoperiod passed the equinox (12L/12D). On increasing days, the equinoctial photoperiod induced prolonged episodes of antler growth.The tendency for the antler replacement cycle to lock onto alternate changes in artificial photoperiods is consistent with the seasonal growth of antlers every other time the day lengths change in the natural environment. It is suggested that antler replacement is triggered neither by shortening nor lengthening days, but by the alternation of such changes irrespective of the direction of the shift in the photoperiod.

ISSN:0022-104X    

DOI:10.1002/jez.1401970302

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn vitro activity of the anaerobic enzymes phosphofructokinase and lactic dehydrogenase from axial muscle tissue ofColuber constrictor,Crotalus viridisandLichanura roseofuscawas shown to correlate with levels of lactate production during activity by these snakes. Additionally, gross and histological lung structure and axial muscle myoglobin concentration were investigated in these species.Coluberwas shown to have the most complex lung structure and highest muscle myoglobin content. These are interpreted to be correlated with high aerobic scope inColuber. Finally, the ophidian saccular lung is postulated to assist in maintanance of high tidal volume.

ISSN:0022-104X    

DOI:10.1002/jez.1401970303

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

年代:1976

数据来源: WILEY

摘要:

AbstractPhagocytosis of algal chloroplasts by digestive gland cells in the sacoglossan opisthobranchPlacida dendriticais described. It is suggested that engulfment of chloroplasts is accomplished by veils of cytoplasm which are derived from elongating microvilli.

ISSN:0022-104X    

DOI:10.1002/jez.1401970304

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

年代:1976

数据来源: WILEY

摘要:

Abstract1The frequency of column contractions inHydra littoralis(taken as a measure of the rate of water elimination) is maximal at about 5 × 10−4M Na+, and falls off markedly at higher and lower concentrations, even though total medium osmotic pressure is kept constant by replacement with K+.2Reduction in Ca++concentration causes a reduction in the frequency of column contractions. This reduction is half‐maximal at about 4.8 × 10−4M Ca++.3The significance of these findings in the light of the osmoregulatory mechanism inHydrais discussed, and it is suggested that Na+plays a regulatory role in the mechanism of extrusion of water and salts from the cells to the gastrovascular

ISSN:0022-104X    

DOI:10.1002/jez.1401970305

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

年代:1976

数据来源: WILEY

摘要:

AbstractBy autoradiography with tritiated thymidine, the rate of cell migration was studied for the groove population of epithelial cells lining the stomach ofStyela. After one hour, the tritiated thymidine is incorporated into undifferentiated, dividing cells. Labeled differentiated cells appear after three days, and the migration of labeled cells to the extrusion zone takes about 16 days (T= 19°C). Stomach growth is accomplished by an increase in both number and height of epithelial folds. The percentage rate of cell migration probably remains fairly constant throughout adult life. However, it is decreased by starvation and low temperatures

ISSN:0022-104X    

DOI:10.1002/jez.1401970306

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

年代:1976

数据来源: WILEY

摘要:

AbstractPrevious studies involving the end‐to‐end fusion of the forelimbs of the adult newt have demonstrated that new limbs can regenerate from the transected ends of proximo‐distally reversed limb segments. The limb regeneration could only have been initiated by nerve fibers of contralateral origin. The purpose of the present study is to describe histologically the manner in which nerve fibers of contralateral origin regenerate through the junction of fused limbs into the opposite limb. The first sign of nerve regeneration into the opposite limb was observed at eight days post fusion. The nerves crossed over into the opposite, originally denervated limb in a highly dispersed manner. These nerve fibers eventually aggregated, however, either under the skin or within persisting nerve trunks. By 19 days post fusion the nerve fibers had reached the elbow region of the originally denervated limb and by 25 days they were seen at the most proximal extent of the limb. The diameters of the axons seemed smaller than the diameters of regenerating axons observed in non‐fused newt fo

ISSN:0022-104X    

DOI:10.1002/jez.1401970307

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

年代:1976

数据来源: WILEY

摘要:

AbstractStarfish (Asterias forbesi) oocytes encased within their follicle cells mature spontaneusly during a portion of the normal reproductive period when released from the ovary into seawater. A previous report has shown that oocytes isolated in acidic seawater do not mature spontaneously but retain the capacity to do so when returned to normal seawater. The object of this study was to determine the mechanism by which acidic pH reversibly blocks spontaneous oocyte maturation in isolated follicles. Incidence of spontaneous oocyte maturation in follicles isolated in acidic seawater decreased as pH decreased from 7 to 4. Oocytes in which spontaneous maturation was inhibited (ASW at pH 4.7 to 5.4) underwent germinal vesicle breakdown with the addition of 1‐methyladenine. Oocytes isolated in acidic seawater (pH 4 or 5) with intact follicle cells matured spontaneously when transferred immediately to normal seawater (pH 8); after four hours, 60‐65% of the follicles incubated in seawater at pH 5 matured spontaneously when returned to normal seawater as compared to less than 10% of the follicles maintained at pH 4. Inhibition of spontaneous maturation was not reversible in the absence of the follicle cells. Oocytes isolated in acidic seawater with their follicle cells did not spontaneously mature when transferred to calcium‐free seawater at pH 8. The results obtained support the hypothesis that acidic seawater reversibly inhibits spontaneous oocyte maturation by interfering with the release of meiosis‐inducing substance from the follicl

ISSN:0022-104X    

DOI:10.1002/jez.1401970308

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

年代:1976

数据来源: WILEY

摘要:

AbstractA total of 130 female mice pregnant at 8 days were exposed singly to a 7.3 watt microwave waveguide at 2,450 MHz wave length while being monitored for total absorbed dose, the exposure being four minutes. Among the 1,328 offspring examined (327 of which were controls) those not anesthetized but irradiated showed greater fetal damage than those that were anesthetized and placed in one of the three positions with respect to the radiation beam. Immobilization with anesthesia and restraint in the broadside position provided the greatest protection to the fetus against any teratologic effects. Anesthesia reduces the body temperature to a degree equivalent to the rise in temperature expected from the radiation conditions used, hence the protection against the primary thermal effect of microwave irradiation.

ISSN:0022-104X    

DOI:10.1002/jez.1401970309

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

年代:1976

数据来源: WILEY

摘要:

AbstractFrozen mouse eggs were examined to determine the effects of low temperatures, concentration of cryoprotective agents and cooling rates on their survival, fertilizability in vitro and subsequent development. Dimethyl sulfoxide administered at 1.5 M concentration was found to be the most effective cryoprotective agent. Upon thawing, 51% and 56% of the eggs appeared to be normal after having been cooled at 0.33°C/min to − 30°C and −50°C, but only 18% of the eggs appeared to be normal after having been cooled at the same rate to − 75°C. When eggs were cooled at 0.33°C/min to −45°C and the cooling rate increased to 1°C/min from −45°C to −75°C, 44% and 72% appeared normal upon thawing. Of the normal eggs fertilized in vitro from C3H mice, 65% cleaved to the 2‐cell stage and 24% of the 2‐cell eggs developed into blastocysts. Following the transfer of 17 blastocysts into three recipient mice, one mouse deli

ISSN:0022-104X    

DOI:10.1002/jez.1401970310

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe ability of mesenchyme from the urogenital ridge to participate in the development of male and female urogenital organs was studied by preparing homo‐and heterotypic recombinants of epithelium and stroma from ductus deferens and uterus of neonatal mice. The recombinants as well as intact 14‐day old embryonic urogenital ridges (UGR) were grown for two to eight weeks in adult male and female hosts. The development of ductus deferens and seminal vesicle from female UGR's grafted into male hosts and uterus from male UGR's grafted into female hosts demonstrates that the mesenchyme of embryonic UGR's is capable of participating in the development of either male or female urogenital structures. During normal development of the female urogenital tract, the bisexual morphogenetic potentiality of UGR mesenchyme persists postnatally as demonstrated by the ability of uterine stroma to support normal differentiation of epithelium of ductus deferens in male hosts. Conversely, during the normal development of the male urogenital tract, the morphogenetic potentiality of mesenchyme of the urogenital ridge is restricted as stroma from the ductus deferens appears incapable of participating in uterine morphogenesis in male or female hosts. These differences in the developmental properties of UGR stroma may be attributed to differences in hormonal conditions in male and female fetu

ISSN:0022-104X    

DOI:10.1002/jez.1401970311

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

年代:1976

数据来源: WILEY