摘要:

AbstractAn examination of serial sections of the ears of several specimens ofChamaeleo senegalensisandChamaeleo quilensisgives support to an earlier suggestion that these ears function by means of a substitute round window. The usual type of round window is absent, but there is a tortuous pathway leading from the scala tympani through the perilymphatic recess and then along the foramen of the glossopharyngeal nerve to the air cavity of the middle ear.This pathway makes possible a mobilization of the cochlear fluids in response to sound pressures exerted at the oval window by the columellar footplate. However, the mechanism is somewhat inefficient; the frictional resistance along the pathway reduces the amplitude of cochlear motion. The relatively poor sensitivity of these chameleon ears is thus largely accounted for.

ISSN:0022-104X    

DOI:10.1002/jez.1401710102

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe mesoglea ofHydraserves both as a skeleton and as a substratum for cell migration. These functions are made possible inHydra pseudoligactisby a system of fibers that run along the body column, parallel to the oral‐aboral axis, and perpendicular to the oral‐aboral axis. The fibers are either a mucoprotein or a close spatial arrangement of protein and polysaccharide. They are 0.3 μ in diameter and contain an elastin‐like and collagen‐like protein.Spaced along the fibers are acid mucopolysaccharide‐like particles, 0.7 μ in diameter, which appear to serve a structural or supportive function. Between the fibers are 2.4 μ diameter holes for extension of epithelial cell processes. The remainder of the mesoglea consists of an amorphous gel with a collagen matrix.The physical arrangement of the fibers allows the normal movements of hydra and could also control the direction of cell migration. The arrangement of fibers may be a dynamic system under the control

ISSN:0022-104X    

DOI:10.1002/jez.1401710103

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

年代:1969

数据来源: WILEY

摘要:

AbstractExamination of histological sections and isolated mesogleas inHydra pseudoligactisreveals that the mesoglea is not a uniform structure but changes in form in different body regions and during asexual reproduction. At the extremities of the body column, the rim of the mouth and aboral pore, the fiber system of the mesoglea is strongly developed and appears to occlude the cementing matrix which usually surrounds the fibers. Cells, on reaching these extremities, pass over the fiber mass and slough off the body column.The mesoglea of the gastric region is well‐developed but the fibers here are thinner than those in the peduncle. During budding the fiber system breaks down throughout the gastric and budding region while the fiber system in the peduncle persists. It is suggested that cells moving down the gastric column, because their basal processs can no longer attach to the fiber system, cannot readily enter the peduncle where attachment sites are already occupied. These cells will pass out into the budding tissue. It is suggested that the spindle orientation of dividing cells is probably perpendicular to the oral‐aboral axis of the parents in the area of the bud.The adhesiveness of the two cell layers in various body regions is discus

ISSN:0022-104X    

DOI:10.1002/jez.1401710104

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe fibers in the deep and superficial extensor muscles of the lobster abdomen differ in structural and physiological characteristics. The superficial extensor muscle fibers have relatively long (>6 μ) sarcomeres, in which thin and thick myofilaments overlap for about 3 μ per half‐sarcomere at rest length. The deep extensor muscle fibers have relatively short (<4 μ) sarcomeres, in which the region of overlap is about 1.5 μ per half‐sarcomere at rest length. The ratio of thin to thick filaments is 6:1 in the superficial muscle fibers and 3:1 in the deep muscle fibers. Contraction and relaxation are much more rapid in the deep muscle fibers. The superficial muscle fibers develop substantially more tension than the deep muscle fibers in high K+, in caffeine, in high K+plus caffeine, and during prolonged spikes in solutions containing tetraethylammonium chloride. The results are consistent with the predictions of the sliding filament hypothesis of muscle cont

ISSN:0022-104X    

DOI:10.1002/jez.1401710105

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

年代:1969

数据来源: WILEY

摘要:

AbstractFour groups of male starlings were exposed to stimulatory photoperiods. Two groups had 14 hours of light per day, the other two groups, 12 hours. One of the two groups treated with each photoperiod was in a cage including both male and female starlings; the other group was in a cage including only male starlings. Testis widths were measured via laporotomy every 15 days through a growth and regression cycle.Neither the rate of testis development, nor the maximum size reached, was significantly changed by the presence of the females in either photoperiod. Likewise, the chronology of testis involution in those treated with a 14 hour light per day photoperiod was not changed by the presence of females. But maintenance of spermatogenesis in birds treated with 12 hours of light daily was significantly longer in the group caged with females.

ISSN:0022-104X    

DOI:10.1002/jez.1401710106

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

年代:1969

数据来源: WILEY

摘要:

AbstractPreferred temperatures ofSceloporus undulatus, which were acclimated to 20°C under 12 hour and 6 hour photoperiods, were determined in a thigmothermal gradient. The longer photoperiod (12 hours light) increased the preferred temperature in lizards collected in May while the shorter photoperiod (6 hours light) decreased the preferred temperature in lizards collected in July. Response in the preferred temperature to photoperiod is suggested to be a physiological adaptation which facilitates the use of the mechanism of acclimation of the thermal tolerance to seasonal changes in environmental temperatures. Photoperiod differences did not alter the criitcal maximum or lethal maximum temperatures

ISSN:0022-104X    

DOI:10.1002/jez.1401710107

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

年代:1969

数据来源: WILEY

摘要:

AbstractPotassium contractures were recorded isometrically in locust extensor tibialis muscles. The graphs relating contracture tension to external potassium, and contractute tension to depolarization were of sigmoid shape. In normal circumstances, peak contracture tension was obtained with 100 mM/1 potassium saline at a depolarization level of about −10 mV. At a concentration of 2 mM/1, caffeine considerably lowered the mechanical threshold of the muscle fibres such that peak contracture tension was obtained with 40 mM/1 potassium saline, at a depolarization level of only −30 mV. Withdrawal of calcium ions from caffeine containing salines resulted in a loss of the contractile response to depolarization, and the lowering of the mechanical threshold was abolished. These results are consistent with the view that caffeine may activate musclein vivoby accelerating calcium release from the sarcoplasmic reticulum and by suppressing active calcium binding by the reticular calcium pump. Since caffeine can activate depolarized muscle it is suggested that caffeine short‐circuits the normal excitation‐contraction coupling channels to initiate a direct release of calcium ions from the sarcoplasmic reticulum without transient depolar

ISSN:0022-104X    

DOI:10.1002/jez.1401710108

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

年代:1969

数据来源: WILEY

摘要:

AbstractFlattened eggs of the sea urchinHemicentrotus pulcherrimuswere used in experiments designed to determine whether furrow establishment depends upon any particular geometrical relationship between the asters and the equatorial surface. In normal eggs at first cleavage the asters are 29.5 μ apart and the distance from the spindle center to the equatorial surface is 47.3 μ. In flattened eggs, the mitotic apparatus was pushed to an excentric position. The maximum spindle‐to‐surface distance that permitted furrowing was 62.5 μ. At second cleavage the spindle‐to‐surface distance is normally 36.2 μ but furrows develop when the distance is as great as 47.5 μ. The interastral distance and spindle‐to‐surface distance were varied simultaneously in flattened, dispermic eggs containing four asters. The activity of supernumary sperm asters was not detectably different from that of the mitotic apparatus. If the interastral distance was 32.5 μ furrows formed when the spindle‐to‐surface distance was between 32.5 μ and 47.5 μ. When the interastral distance is increased to 35 μ or more at the same spindle‐to‐surface distances, furrowing was rare. Very short spindle‐to‐surface distances were produced by perforating the flattened cells. They allowed study of combinations involving large interastral distances and short spindle‐to‐surface distances. Under this circumstance asters 35 μ or farther apart invariably elicited furrows when the spindle‐to‐surface distance was 20 μ or less. Decreasing the spindle‐to‐surface distance remedies a deficiency occasioned by abnormally great interastral distances. These results are considered to support the view that furrow establishment requires conjoint action of

ISSN:0022-104X    

DOI:10.1002/jez.1401710109

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

年代:1969

数据来源: WILEY

摘要:

AbstractTo determine the capacity of earthworms to reject tissue transplants, first‐set orthotopic allografts of body wall were exchanged between 280 adultLumbricus terrestris. In addition, 30 worms were autografted as controls. Both auto‐ and allogeneic tissue transplants healed in promptly; autografts survived permanently while allografts showed varying degrees of incompatibility. Intrapopulation allografts in worms from Canada showed 22% permanently surviving transplants while 95% were not destroyed in the Oregon group; the remaining allografts in both groups were completely destroyed after prolonged chronic periods or showed incomplete rejection after observations during eight and one‐half months. No intrapopulation Oregon transplants were rejected completely while only 1% were in the Canadian group. About 5.5% of interpopulation allografts were destroyed on Oregon hosts and 15.3% on Canadian recipients between 38 and 153 days after grafting. Therefore, recognition and rejection of tissue allo‐antigens are characteristic of the primitive immune response of anneli

ISSN:0022-104X    

DOI:10.1002/jez.1401710110

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

年代:1969

数据来源: WILEY

摘要:

AbstractRemoval of the pars distalis several days before the amputation of the tail inAnolis carolinensisdelays blastema formation and virtually abolishes tail regeneration. Hypophysectomy on, or several days after, tail amputation does not delay blastema formation but tail growth is largely abolished. If lizards are hypophysectomized after the blastema has formed and the tail has begun to elongate, the rate of tail regeneration is greatly reduced within a few days.Injection of a combination of adenohypophysial hormones (growth hormone, prolactin, gonadotropin, and thyrotropin) restored tail regeneration to near normal levels in hypophysectomized lizards.A quantitative relationship was evident between the amount of pars distalis removed and the rate of tail regeneration. However, there was no apparent relationship between the region of the gland removed and regeneration, indicating that tail regeneration is probably dependent on a combination of several pituitary hormones.

ISSN:0022-104X    

DOI:10.1002/jez.1401710111

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

年代:1969

数据来源: WILEY