摘要:

AbstractDeveloping Xenopus oocytes removed from the ovary and divested of their outermost cellular layers (theca and surface epithelium) will incorporate protein continuously over a period of at least two to six days when culturedin vitro.The rate of protein incorporation depends upon:(a) the extent to which the donor has been stimulated by gonadotropin; (b) the size of the oocyte; and (c) the protein composition of the medium, since a mechanism exists to sequester selected protein. Protein uptake is negligible when oocytes are cultured either with all their cellular layers intact or with all their cellular layers removed. These results imply that the outer surface epithelium is relatively impermeable to protein and that the integrity of the investing follicular epithelium is essential for vigorous protein incorporation by the oocyte.

ISSN:0022-104X    

DOI:10.1002/jez.1401750302

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

年代:1970

数据来源: WILEY

摘要:

AbstractMouse eggs obtained from oviducts 14–16 hours after an injection of HCG were inseminatedin vitrowith fresh epididymal sperm in the presence of heated bovine follicular fluid. When examined one to eight hours later the proportion of sperm without acrosome increased, the proportion of eggs penetrated by sperm increased from 2 to 79%, and that of eggs undergoing fertilization increased from 13% at two hours to 67% at eight hours after insemination. Although the average number of sperm that had penetrated into each egg increased progressively until five hours after insemination, the number of sperm that had entered the vitellus did not increase during this time, showing the existence of a block mechanism in the vitelline membrane. When fresh epididymal sperm were pre‐incubated in the presence of bovine follicular fluid for three to four hours and used for insemination, sperm penetration occurred 20 minutes later and the proportion of eggs penetrated by sperm increased from 17% at 20 minutes to 90% at two hours after insemination, showing a requirement of capacitation of mouse sperm. When eggs were inseminated with pre‐incubated sperm, sperm penetration appeared to occur sooner and the proportion of polyspermic eggs was higher in the eggs without follicular cells (17–35%) than in the eggs with follicular cells

ISSN:0022-104X    

DOI:10.1002/jez.1401750303

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

年代:1970

数据来源: WILEY

摘要:

AbstractA maternal octanol dehydrogenase (ODH) isozyme pattern is observed in embryos of reciprocal crosses of A and B variants both in intraspecific hybrids ofD. pellewaeand ofD. metzii, respectively, and in interspecific hybrids ofD. metziicrossed with eitherD. pellewaeorD. leticiae.In addition, slowly migrating ODH isozymes not detectable in unfertilized eggs or single adult females can be seen in both intra‐ and interspecific hybrid embryos. In reciprocal intraspecific hybrids ofD. pellewae, the slowly migrating embryonic isozymes appear as early as two and one half hours after fertilization, before the gastrula stage. They are presumably synthesized by pregastrula embryos. The present work supports the idea that in intraspecific hybrids ofD. pellewae, maternally and paternally derived ODH genes become active at about the same time, producing a triplet isozyme pattern at positions 3, 4, 5 in late first instar larvae. The 3, 4, 5 pattern is maintained through second and third instar larvae and pupae. In adults isozymes at positions 6 and 7 often appear.The sequence of developmental changes normally observed in ODH isozyme patterns is retarded in interspecific hybrids, and aberrant patterns occur in some individuals. Sometimes early embryonic patterns persist in both B ♀/A ♂ and A ♀/B ♂ interspecific hybrids as late as the pupal stage. Either a paternally or maternally introduced ODH structural gene expected to contribute subunits to the 4 and 5 isozymes may fail to do so to a detectable degree. Other abnormalities seen in interspecific third instar larvae or pupae include a 3, 4 or 4, 5 pattern where a 3, 4, 5 triplet is expected. Gene action leading to the abnormal isozyme patterns is discussed on the basis of the tetramer hypothesis of ODH (Pip

ISSN:0022-104X    

DOI:10.1002/jez.1401750304

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

年代:1970

数据来源: WILEY

摘要:

AbstractForelimbs of larvalAmbystomawere amputated through the elbow. In many cases the humerus was partially or totally extripated. Homoplastic transplants, previously labeled with tritiated thymidine, were then inserted into the limb stump, which was re‐amputated through the graft.Experiments involving the addition of appendicular or visceral skeletal parts revealed fusion of the implant with the humerus and suggested interactions between skeletal components. The morphology of such regenerates was usually normal. The various skeletal elements exhibited a differential susceptibility to regression, Meckel's cartilage being particularly resistant. As a consequence, the distal blastema was often spatially removed from the proximal shoulder region. Nevertheless, reconstitution of the head of the humerus was always observed. The cellular origin of this portion of the regenerate was probably local connective tissue.Unlike Meckel's cartilage, the humerus released many cells to the accumulation blastema. These labeled cells may have divided at a higher rate than other blastemal cells, suggesting the possibility of tissue‐specific regeneration of cartilage.Transplanted muscle and connective tissue originating from either the jaw region or the limb behaved similarly to each other. Labeled connective tissue cells proximal to the amputation plane began dividing before the blastema was established, therefore the time of onset of cell division may vary according to the tissue involved and its location with respect to the blastema. A distinction between inductive phenomena and cell contributions was also m

ISSN:0022-104X    

DOI:10.1002/jez.1401750305

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

年代:1970

数据来源: WILEY

摘要:

AbstractPresumptive heart mesoderm from early neurulae of the newt,Taricha torosa, was combined in explants with endoderm from five different regions of the embryo to study the distribution in the endoderm of the capability to induce heart formation.The percentages of such cultures that ultimately formed beating heart tissue, and the average numbers of days in culture before doing so, are compared with control levels established by explanting presumptive heart mesoderm alone.The ability to induce hearts is found to be broadly distributed and to be strongest in anterior endoderm. The heart‐forming response is accelerated only by the endoderm normally underlying the presumptive heart mesoderm, and this endoderm retains its inductive capability into tailbud stages. Other anterior endoderm is a powerful heart inductor but acts more slowly. Posterior endoderm not only did not promote heart formation, but also increased the time in culture before the beginning of contraction in the few responding cases.Mesoderm immediately posterior to the presumptive heart mesoderm can also be induced to form beating tissue. However, compared to presumptive heart mesoderm, a much longer time elapses before contractions begin. Since endoderm near that which normally underlies the heart has substantial ability to induce heart, the mesoderm overlying these regions experiences some measure of heart induction. Normally these regions of affected mesoderm do not contribute to the heart, but under altered conditions they can. This extended mesodermal area of heart potential is the heart “field.” The existence and extent of the heart field appears to be a result of the distribution of heart‐inducing activity in the e

ISSN:0022-104X    

DOI:10.1002/jez.1401750306

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe anatomy of the middle ear is outlined for lizards in general and described in detail forCrotaphytus collaris(Iguanidae). By use of the alternating potentials of the cochlea, the general function of the middle ear in the reception of aerial sounds was determined by comparing the ear's sensitivity when the middle ear mechanism was intact with the sensitivity remaining when the columellar shaft was severed, thus eliminating the connection between the stapedial footplate and the more peripheral parts. This comparison was made under two conditions, with the sound applied in the usual way at the external auditory meatus and with the sound introduced through a tube sealed over the oval window. The loss of transmission observed under the first condition is complicated by the presence in the sound path of the nonfunctioning tympanic membrane and by an interaction of sound waves reaching both round and oval windows of the cochlea, but the second condition, in which these complications are avoided, reflects the true performance of the middle ear as a mechanical transformer. This transformer action was measured as 35 db on the average for tones between 300 and 4000 Hz, which is the region of best hearing for this lizard.Further analysis of the operation of the tympanic mechanism was carried out by measurements of sensitivity before and after severing the connection between the internal process and the quadrate bone. These observations showed that the internal process makes little or no contribution to the ear's sensitivity. Other experiments performed with mechanical stimulation showed that the columellar system acts as a reduction lever, and the measurements gave a general indication of the amount of this lever action.The pressure increase provided by the columellar lever, together with a still greater increase produced by the areal ratio between the effective surface of the tympanic membrane and the surface of the columellar footplate, can account in large part at least for the total transformer action. This action makes it possible for acoustic energy to be conveyed with great efficiency from the air to the relatively dense and stiff sensory elements of the cochlea. This problem of the matching of impedances between two media, and its solution by the use of a mechanical transformer, has long been studied in mammals, and especially in the cat, and the solution provided by the lizard's middle ear seems altogether as satisfactory as that provided by the structurally different ossicular mechanism of the mammals.

ISSN:0022-104X    

DOI:10.1002/jez.1401750307

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe tendon of the pigeon's biventer cervicis was sectioned, and the muscle examined histologically after varying post‐operative intervals. Tissues were prepared by routine histological procedures and stained in a number of ways. The results indicate that the fast fibers of the muscle have a faster onset of atrophy than do the slow fibers, but the slow fibers attain the same degree of atrophy in later stages. The onset of atrophic activity is characterized by a swelling of the nuclei and their migration away from the subsarcolemmal position in the twitch fibers. Slow fibers do not show any histological changes at this early stage (6 days). Vacuolization and lipomatosis begin at this stage, as well as some phagocytosis. These characteristics become more prominent as the tenotomy period increases, and connective tissue formation within the fibers can be seen, as well as ring fiber formation and other pathological conditions. The tenotomized muscles demonstrate conditions typical of various human muscle diseases, but differences are noted, and discusse

ISSN:0022-104X    

DOI:10.1002/jez.1401750308

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

年代:1970

数据来源: WILEY

摘要:

AbstractAggregates were prepared containing mouse and chick embryonic limb mesoblast cells. After 21 to 33 hours in culture, these aggregates showed prominent sorting out of the mouse cells from the chick cells. This sorting out was even more extensive after 46 to 54 hours. This sorting out is contrary to previous reports for mouse‐chick limb aggregates.After three to four days of culture, chondrification became quite prominent within the aggregates. Accompanying this event, the segregation of mouse and chick cells became less extensive within the chondrified zones. This rescrambling seems to be due at least in part to the interpenetration of neighboring chondrifying regions. Such interpenetration would be expected, due to the expansion which occurs within chondrifying areas. This reshuffling is the probable reason why sorting out was not observed in earlier experiments with mouse‐chick limb aggregates. In these earlier studies, the reports were limited to aggregates which had extensive matrix secretion.The finding that mouse and chick limb mesoblast cells sort out from each other, together with recent reports that similar sorting out occurs in mouse‐chick heart ventricle aggregates and in mouse‐chick mesonephric aggregates, invalidates the generalization that cell sorting properties for any one tissue are constant from species to species among warm‐blooded vertebrat

ISSN:0022-104X    

DOI:10.1002/jez.1401750309

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

年代:1970

数据来源: WILEY

摘要:

AbstractBeginning within 24 hours after birth, young mice were given daily subcutaneous injections of 5 μg estradiol‐17β in olive oil. The mice were sacrificed at varying times; six hours before death, they were given a subcutaneous injection of colchicine. The mitotic rate was studied in the epithelium in the uterine horns, uterine cervix, and müllerian vagina. Eighteen hours after the first estradiol injection, the mitotic rate was increased in the uterine epithelium, but decreased in the cervical and müllerian vaginal epithelium compared with the controls. At a continued treatment with estradiol, the mitotic rate values decreased to a level somewhat below the control level in the uterine horns; in the uterine cervix and müllerian vagina the mitotic rate decreased to very low values, significantly lower than in the corresponding regions in the controls. The mechanisms behind this mitotic rate inhibition as well as its consequences are dis

ISSN:0022-104X    

DOI:10.1002/jez.1401750310

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

年代:1970

数据来源: WILEY

摘要:

AbstractUptake into blood and incorporation into tissue protein of cystine‐35S were assayed in larvae of controls and of five heterozygous Minute mutants ofDrosophila melanogaster.The mutants studied were M(2)S‐10, M(2)12, M(2)z, M(3)y and M(3)w. In all mutants, the level of cystine in the blood was significantly higher than in controls and differences in concentration between these mutants were evident. All mutants incorporated cystine into protein, although the specific activities obtained were dependent on genotype. The fraction of the cystine in the blood pool which was incorporated into protein was directly correlated with viability and rate of growth. In contrast, the radioactivity of leucine‐1‐14C, both in blood and in tissue proteins, was not different in M(2)12and M(3)w heterozygotes as compared to controls, although in M(2)12the fraction of leucine in the blood pool incorporated into protein was lowered. It was concluded that these mutants possessed a common inability to withdraw cystine (or other sulfur‐containing compounds) from the blood into various metabolic pathways. Feeding activity, digestion and absorption of nutrients appeared normal in thes

ISSN:0022-104X    

DOI:10.1002/jez.1401750311

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

年代:1970

数据来源: WILEY