摘要:

AbstractNon‐visual responsiveness to photic stimulation was investigated in pigeon embryos (days 11½–17½ of incubation) and neonates (6–24 hours posthatch). At all ages observed, these animals exhibited a marked overt response to light onset, a response which occurred even when the entire head was occluded from light, but which could be blocked (in hatchlings) by covering all of the body except the head. It was therefore concluded that retinal or direct brain mediation did not underlie the response, but rather, some form of dermal sensitivity would best account for it. Chicken embryos (day 19 of incubation) and Ring dove hatchlings (12–24 hours posthatch) were similarly investigated. Although there was evidence in both of these species for light‐contingent motility, their responsiveness was seemingly mediated by either visual or direct brain stimulation, since occlusion of the head eliminated the effect. Thus, of the three species tested, only the pigeon appeared to possess the non‐visual dermal light sensitivity. Possible significance of this responsiveness for this species

ISSN:0022-104X    

DOI:10.1002/jez.1401880302

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

年代:1974

数据来源: WILEY

摘要:

AbstractA surgical approach to the cetacean (Tursiops truncatusandLagenorhynchus obliquidens) ear represented a unique problem. The first obstacle was the development of a safe and humane anesthesia procedure and techniques of long‐term physiological maintenance of the animal during surgery. The surgical anatomy was a challenge especially because of the extensive venous plexuses that invest the entire ear and adnexa. Thecorpus cavernosum carotidisand other small arterial networks course through this venous mass.Sodium pentothal‐halothane anesthesia and careful physiological monitoring were determined to be adequate for long‐term maintenance during surgery and cochlear recording experiments. A specially designed surgical tank held the animal during the procedure. Immersion in water relieved the lungs of external pressure that ordinarily occurs, when the animal is out of the water, due to the flexible thorax. Thermoregulation was provided for by regulating the water temperature in response to the dolphin's core temperature. This arrangement also provided for underwater auditory stimulation and easy manipulation of the animal since dolphins with their lungs inflated are close to neutral buoyancy.It was necessary to ligate the external and internal carotid arteries, neither of which supplies blood to the ear or brain. Hemostasis in the massive venous plexus could be achieved only by partial removal and subsquent application of oxycel and surgical cement to effectively dam off the area of the round window and other ear structures for electrical potential recording and experimental manipulations.With this technique the round window of the cochlea was exposed. Fully anesthetized animals were maintained for periods up to 24 hours while electrophysiological measurements were being made. Some of the auditory measurements required further surgical manipulation of the auditory meatus, bulla, ossicular chain and other middle‐ear str

ISSN:0022-104X    

DOI:10.1002/jez.1401880303

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe parotid, sublingual and submaxillary buds of the embryonic rat can undergo typical morphogenesis in response to capsular mesenchyme from either the parotid or submaxillary‐sublingual rudiment. The submaxillary epithelium can be induced by embryonic bronchial mesenchyme to undergo limited morphogenesis, while the sublingual epithelium exhibits more extensive morphogenesis in response to the same stimulus. Pancreatic mesenchyme and jaw mesenchyme are essentially inactive in inducing the submaxillary epithelium, but can consistently stimulate morphogenesis of the sublingual rudiment at a relatively low level of complexity. Thus, the sublingual rudiment shows a less‐stringent mesenchymal requirement than does the submaxillary, and with both rudiments, lung mesenchyme is more effective than pancreas or jaw mesenchyme in supporting morphogene

ISSN:0022-104X    

DOI:10.1002/jez.1401880304

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe in vitro incorporation of3H‐amino acids into purified lipovitellin by cultured crustacean ovaries can be demonstrated using either density gradient centrifugation or preparative electrophoresis as a final purification step. In addition3H‐glycerol is incorporated into the phosphatidyl choline moiety of the lipovitellin. This evidence strongly suggests that the ovary is capable of synthesizing both the lipid and the protein components of the lipovitellin and therefore may not incorporate such moieties intact from the circulating hemoly

ISSN:0022-104X    

DOI:10.1002/jez.1401880305

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

年代:1974

数据来源: WILEY

摘要:

AbstractAnalysis of the determinants of oxygen exchange inCeriantheopsis americanus, a tubicolous anthozoan, indicates that in the natural habitat the site of oxygen entry is restricted to the tentacular crown. Predicted rates of oxygen diffusion solely across the marginal tentacles are sufficient to account for observed uptake rates in intact animals. The anatomical restriction of the site of exchange is, in part, a result of the absence of active irrigation of the tube. This pattern of gas exchange is more like that in epifaunal anemones than in a previously studied burrowing anemone.Gradual decline in ambient pO2leads to a gradual decrease in oxygen consumption rate. Although the partial pressure differential across the exchange surface drops with declining ambient pO2, this decrease is not sufficient in itself to explain the relationship between oxygen consumption rate and ambient pO2. We suggest that differential oxygen sensitivities of the epidermis and gastrodermis and changes in surface area and diffusion distance during expsure to lowered pO2may modify the oxygen consumption response.

ISSN:0022-104X    

DOI:10.1002/jez.1401880306

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

年代:1974

数据来源: WILEY

摘要:

AbstractPreimplantation embryos from matings between mice heterozygous for the yellow allele (Ay) of the agouti locus were cultured in vitro and their development was compared with embryos from control matings (Ay/a × a/a). No morphological abnormalities were consistently observed at the eightcell stage, but after 24 hours of culture there were abnormalities in 16.8% of embryos from Ay/a × Ay/a matings. The abnormalities, which consisted primarily of arrest of several blastomeres and their exclusion from the embryo, were also present in 23.9% of embryos removed from the uterus as morulae and blastocysts. Those embryos that became abnormal during preimplantation stages were presumed to be the Ay/Ayhomozygotes because their frequency approximated the Mendelian expectation of 25% in Ay/a × Ay/a matings but not in control matings. The morphological abnormalities indicated an effect of the Ayallele as early as the fourth cleavage division.Presumed Ay/Ayearly blastocysts collapsed and died without hatching when cultured for five days under conditions that allowed normal embryos to hatch and grow out on the substrate. If the zona pellucida was removed from these blastocysts before culture, limited trophoblastic outgrowth occurred, but the outgrown cells were few and small and the inner cell mass disintegrated entirely.The Ayallele in the homozygous condition thus appears to be a cell lethal that allows growth up to the early blastocyst stage but prevents the normal postblastocyst growth and differentiation of either trophoblast or inner cell ma

ISSN:0022-104X    

DOI:10.1002/jez.1401880307

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

年代:1974

数据来源: WILEY

摘要:

AbstractMicrotubules of isolated crayfish ventral nerve cords rapidly dissociate at 40°C and upon reincubation at ambient temperatures part of the microtubule population transiently reforms. Colchicine had little effect on the structure or number of intact microtubules of unwarmed nerve connectives, but vinblastine caused a decrease in microtubular numbers and led to the formation of typical paracrystalline arrays. After warming, both colchicine and vinblastine treatment prevented microtubule reassembly, presumably by interacting with the heat‐induced microtubular dissociation products, and led to the formation of axoplasmic inclusions. The inclusions seen in vinblastine‐treated prewarmed connectives were identical to the paracrystalline arrays produced in unwarmed preparations but the inclusions seen following colchicine treatment of warmed connectives have a unique appearance and are ultrastructurally distinct from vinblastine‐induced

ISSN:0022-104X    

DOI:10.1002/jez.1401880308

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe process of pair formation by sexual strains ofTetrahymena pyriformisis an inducible pathway interrupting the cellular activities of vegetative growth. A specific series of events leading from vegetatively growing cells to mating pairs is described. The sequence is composed of two separate stages: initiation and co‐stimulation. Initiation is the response to certain starvation conditions, is sensitive to tonicity, is independent of mating types, and takes about two hours at 30°C. Co‐stimulation is a reaction between already initiated cells of different mating types, requires specific cell‐cell interactions, takes about one hour at 30°C, and results in stimulated cells which are able to form pairs. An understanding of the sequence leading to the programmed developmental activities of conjugation makes possible efficient mating techniques and facilitates a search for genetic and physiological constituents of the entire

ISSN:0022-104X    

DOI:10.1002/jez.1401880309

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe anuran tadpole tail is capable of regenerating in the absence of the spinal cord. This is in contrast to urodeles and lizards that require the spinal cord for normal tail regeneration. Quantitation of peripheral nerves in theRana clamitanstadpole tail reveals an average of 6.9 nerve fibers per unit area of soft tissue. This value falls short of the threshold nerve requirement established for regeneration of theTrituruslimb. However, when nerve fiber size is taken into consideration, we find that the axoplasm area per unit area of soft tissue exceeds the threshold requirement for limb regeneration inTriturus.When judged against this standard, regeneration of the tadpole tail in the absence of the spinal cord can be explained on the basis of a sufficient neurotrophic contribution made by the peripheral nerves alone.

ISSN:0022-104X    

DOI:10.1002/jez.1401880310

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

年代:1974

数据来源: WILEY

摘要:

AbstractSelective food pecking by young domestic chiks to parental calls from different individual hens was demonstrated. Previous experience with a parental call paired with visual movement can decrease the number of food pecks to novel calls in testing as compared to the responses of chicks which have received either the parental call or visual movement alone in training. Selective food pecking to parental calls appears to assist in the maintenance of the family unit.

ISSN:0022-104X    

DOI:10.1002/jez.1401880311

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

年代:1974

数据来源: WILEY