摘要:

AbstractTemperature effects on the cochlear alternating potentials are described in lizards of the Eublepharidae (4 spp. and subspp.), Diplodactylinae (2 spp.), Gekkoninae (7 spp. and subspp.) and Sphaerodactylidae (1 sp.). Pure tones (50–15,000 Hz) were applied to the anaesthetized gecko's external ear. Sound intensity needed for a standard response was plotted (db versus frequency). A total of 249 such sensitivity functions were obtained from 50 animals, at temperatures of 15–40°.For each species, an optimal sensitivity function is definable by its extreme sensitivity and relative smoothness. This is obtained throughout a specific optimal temperature range. At lower temperatures, the function is less sensitive and its best sensitivity is at a lower frequency. The specific optimal cochlear temperature range resembles the specific ecological temperature preferendum where known. Both are broader in gekkonoid than in iguanid lizards.The temperature effects on the sensitivity function occur even with aerial or mechanical stimulation at the oval window after middle ear extirpation. Hence they arise in the inner ear. Their magnitude (db/°C) is half that known from auditory nerve potentials.When accurate auditory data are desired, the specific optimal temperature and its possible seasonal variation require consideration. This increases the need for proper identification of subjects by name and origin, and for monitoring experimental thermal parameters, including pre‐experimental accl

ISSN:0022-104X    

DOI:10.1002/jez.1401950302

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe developing arms of axolotl larvae from the 2‐digit stage onward and the aneurogenic arms of surgically denervated larvae maintained in parabiosis are able to regenerate after amputation. Such regeneration is uniformly inhibited by local irradiation of the arm, whether innervated or not. This demonstration refutes a recent hypothesis that X‐rays interfere with a special activity of nerves required for regeneration, and supports the earlier concept that X‐rays act directly on those cells which must proliferate to form the regenerated ti

ISSN:0022-104X    

DOI:10.1002/jez.1401950303

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

年代:1976

数据来源: WILEY

摘要:

AbstractPhenoloxidase was extracted fromModiolus demissusmantles and periostraca with the detergent sodium dodecyl sulfate. Partial purification of the periostracal enzyme was achieved by gel filtration and polyacrylamide gel electrophoresis. The enzyme, present in the mantle in latent or proenzyme form, can be chymotryptically activated. Molecular weights of the proenzyme and active enzyme as determined by SDS gel electrophoresis were 80,000 and 70,000 daltons, respectively. A considerable portion of phenoloxidase activity in the periostracum is associated with a large macromolecule that cannot be reduced into smaller subunits, suggesting enzyme covalently immobilized by quinones. Optimal pH of 8.0–8.5 was found for the active enzyme (MW 70,000). Activity was diminished by adding copper chelators or by reducing disulfide bonds. In the former case, activity was restored by titrating the inhibitor with divalent copper. A hydrophobic active site on the enzyme is suggested by low Kmand high reaction velocities for substrates with high partition coefficients in 2‐octanol:water such as 4‐methylcatechol and 4‐butylc

ISSN:0022-104X    

DOI:10.1002/jez.1401950304

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

年代:1976

数据来源: WILEY

摘要:

AbstractDrosophilaembryos were damaged by microcautery at the cellular blastoderm stage at the sites of presumptive histoblasts, identified from fate maps. The resulting adults were analyzed for abnormal abdominal structures in one series, and in two further series the pupal cases of the defective adults which hatched were also checked for irregularities in segmentation of the larva, both dorsally and ventrally. The relationships between the larval segmentation and adult pattern are described. A sample of pupal cases of morphologically normal flies hatching from microcautery were checked and showed that regulation only rarely occurred, i.e., abnormal larvae sometimes produced normal adults.Both tergite and sternite defects occurred, and duplications of parts of these structures were observed in both cases. In general, abnormal fusions, missing hemi‐segments, and partial deletions were associated with larval defects and were therefore probably the result of damage to larval cells, or both larval cells and histoblasts. Duplications and partial segment deficiencies also resulted from apparantly normal pupal cases and were therefore probably the result of directly damaging the presumptive histoblast cells of the blastoderm. It is suggested that the various nests of histoblasts in each segment act as one morphogenetic field, with larval cells within the fiel

ISSN:0022-104X    

DOI:10.1002/jez.1401950305

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe light microscopic characteristics of spermatogenic stages of the germ cell line in the anuran,Xenopus laevis, have been described as they appear in both nuclear squash preparations and plastic embedded thick sections of intact testes. Tritiated thymidine autoradiography was employed to unequivocally identify stages. Using this methodology, it was determined that the premeiotic DNA synthetic period occurs in a cell which is morphologically indistinguishable from a late secondary spermatogonial cell. In addition, kinetic studies with tritiated thymidine were employed to determine the duration of meiotic prophase and spermiogenesis inXenopus. Results indicate that at 18°C, the most rapidly maturing cells in the testis spend four days in leptotene, six days in zygotene, twelve days in pachytene, one day in diplotene, one day in meiotic division, and twelve days in spermiogenesis. An estimate for the duration of the premeiotic S stage was indirectly calculated from combined data to yield a value of six to seven days. Pooled spermatocyte counts measuring the frequency of occurrence of individual stages produced results which correlated closely with estimates obtained by tritiated thymidine labelling. Individual counts, however, show wide variations between testes from single animals and between testes from different animals, whether sacrificed together or at different times of the year. Nevertheless, in all cases, both morphology and labelling patterns indicate that spermatogenesis is continuously active. The variation observed in individual testes appears to be the result of waves of non‐random entry of spermatogonial stem cells into the population of cells irreversibly committed to differentiati

ISSN:0022-104X    

DOI:10.1002/jez.1401950306

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

年代:1976

数据来源: WILEY

摘要:

AbstractRabbit antiserum against hamster ovary was examined on agargel diffusion plates against several hamster tissues, and also against rat and mouse ovarian extracts. Unabsorbed anti‐hamster ovary antiserum showed eight to nine precipitin bands for hamster ovary and four to eight bands for other tissue extracts, but no bands against sperm antigens. Anti‐hamster ovary antiserum also showed three to four bands for rat and one to two bands for mouse ovarian extracts.The present experiments confirmed previous reports for the hamster and mouse that treatment of eggs with anti‐ovary antiserum blocked in vitro fertilization and that the extent of the inhibition was related to the formation of a precipitate on the zona pellucida.A single injection of anti‐hamster ovary antiserum inhibited fertilizationinmice but notinrats. In vitro fertilization of mouse eggs was also inhibited in the presence of such an

ISSN:0022-104X    

DOI:10.1002/jez.1401950307

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

年代:1976

数据来源: WILEY

摘要:

AbstractStudies on the distribution of67Ga in pregnant rabbits showed a marked concentration of the isotope in uterine tissue and flushings of 5‐day pregnant rabbits 24 hours after isotope injection. The isotope no longer localized throughout the uterine tissues and flushings on injection of 7‐ to 8‐day pregnant rabbits but was specifically associated with the blastocysts and sites of implantation. As the gestation time progressed67Ga increasingly concentrated in placental and mammary tissue while the concentration in serum and thymus tissue decreased. The marked concentration in placental tissue was readily discernible on total‐body scans of pregnant rabbits.Column chromatography of uterine washings and placental extracts from pregnant rabbits and thymus extracts from estrous rabbits showed most of the isotope associated with moieties ⩾ 200,000 MW whereas the isotope in “milk” and extracts of mammary tissue was bound to components of 25,000–35,000 MW. Extracts of thymus from pregnant rats showed a marked, selective loss of67Ga binding in two peaks of approximately 50,000 and 120,000 MW compared to the chromatographic profile of extracts from no

ISSN:0022-104X    

DOI:10.1002/jez.1401950308

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

年代:1976

数据来源: WILEY

摘要:

AbstractThermal acclimation of rainbow trout (Salmo gairdneri) taken from 20°C to 7°C resulted in adaptation of mitochondrial function, as evidenced by increases in the specific activities of NADH‐ and succinate‐cytochrome c reductase of 1.93‐ and 2.7‐fold respectively. Mitochondria from both gill and liver obeyed the Boyle‐van't Hoff relationship in the range from 400 to 60 mosM. Thermal acclimation had no effect on the osmotic properties of liver mitochondria, whereas gill mitochondria from cold‐acclimated trout were more sensitive to osmotic swelling than mitochondria from warm‐acclimated individuals. The non‐electrolyte permeability of liver mitochondria was assessed by optically monitoring mitochondrial swelling rates in isosmotic solutions of urea, glycerol, mannitol and glucose. Two parameters of mitochondrial swelling were determined: (a) initial swelling rates, d(1/A)dt, and (b) swelling constants, ks, derived from the time required to swell a fixed volume. Regardless of the assay temperature or the permeant employed, liver mitochondria from cold‐acclimated trout exhibited greater initial swelling rates than mitochondria from warm‐acclimated trout, indicating properties of temperature‐compensated permeability. The apparent ranking of nonelectrolyte permeabilities was urea>glycerol>mannitol>glucose. ksvalues for urea and glycerol from cold‐acclimated trout were greater than values typical of warm‐acclimated populations; however ksvalues for glucose and mannitol were not influenced by thermal acclimation. Regardless of the permeant considered, activation energies for ksvalues were 3‐ to 5‐fold greater than those for initial swelling rates. The time course of mitochondrial swelling consists of two components, an initial rapid swelling phase characterized by a half life of 3–12 seconds, and a slower swelling phase characterized by a half life of 1–6 minutes. Initial swelling rates, which approximate the rapid swelling component, are considered to be the least ambiguous index of permeability, whereas ksvalues are more complex and strongly influenc

ISSN:0022-104X    

DOI:10.1002/jez.1401950309

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

年代:1976

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1401950310

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

年代:1976

数据来源: WILEY