摘要:

AbstractAcid mucopolysaccharide levels in the Musculus complexus (hatching muscle) of the chick embryo progressively increase during the final 96 hours of incubation with the most marked increase occurring on the day of pipping. The significance of these changes in relation to the role this muscle plays in the hatching process remains obscure, but it is suggested that the mucopolysaccharides, together with the large amount of water simultaneously taken up by this tissue, form a spongy muscle mass which serves to cushion the skull when force is applied to the shell during pipping.

ISSN:0022-104X    

DOI:10.1002/jez.1401710302

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

年代:1969

数据来源: WILEY

摘要:

AbstractEach stage of preimplantation development in the mouse from the fertilized egg to the blastocyst stage (including the unfertilized egg) was studied cytologically and ultrastructurally. Observations were made on the appearance and elaboration of several cellular organelles, inclusions and cell surface specilizations. The fertilized egg exhibits many intranuclear annulate lamellae, an increase in cytoplasmic vesicle number when compared to the unfertilized egg, and small amounts of crystalloids; mitochondria are vacuolated and small. The 2‐cell stage is very similar to the fertilized egg but shows an increase in the number of cytoplasmic vesicles. The 4‐cell stage is characterized by many changes: functional nucleoli appear, vacuolated mitochondria enlarge, cytoplasmic vesicles continue to increase in number, rough endoplasmic reticulum appears (as mitochondria‐associated sacs), and some ribosomes are localized near the plasma membrane. At the 8‐cell stage, large numbers of free ribosomes are observed in the cytoplasm, but clusters (polysomes) predominate at the 16‐cell stage (morula). Morulae develop junctional complexes and exhibit differences in cytoplasmic basophilia between cells, which may be a prelude to differentiation. At the blastocyst stage, nucleoli change to an elongate form and differences in cytoplasmic background density can be observed ultrastructurally. Observations suggest that the contents of the blastocoel may be derived from the cytoplasmic vesicles, which increase in number and size subsequent to fertilization and discharge their contents into the intercellular spaces; the blastocoel arises as these fluid‐filled spaces become confluent

ISSN:0022-104X    

DOI:10.1002/jez.1401710303

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe causal mechanisms underlying the lethality of theeyDlethal homozygotes ofD. melanogasterwere studied. The phenocritical phase occurred at the onset of metamorphosis. Non‐pupating larvae remained in the third instar for periods of time ranging up to 120 hours after their normal sibs had pupated. By this time they had either died as arrested third instar larvae or else underwent a delayed pupation and then died. No “fourth instar” larvae were observed. Those lethals that did pupate died at a mean gonadal developmental age of 20–36 hours. A distinctive syndrome of morphological abnormalities, characteristic of an aphasic development, was found in the non‐eclosed pupae. Paraldehyde fuchsin staining of normal and lethal animals has indicated that the release of the neurosecretory substances in the lethals may be delayed for at least 36 hours following pupation. Injection of approximately 0.07 μg of α‐ecdysone enabled 94% of the non‐pupating larvae, arrested at the third instar for 72–84 hours after their normal sibs had pupated, to resume development and enter the prepupal or pupal stages. It is suggested that theeyDmutation most likely exerts its lethal effect by adversely affecting the ecdysone titer, thereby creating a hormonal imbalance with manifold effects on the deve

ISSN:0022-104X    

DOI:10.1002/jez.1401710304

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

年代:1969

数据来源: WILEY

摘要:

AbstractEggs and developmental stages of the sea urchinParacentrotus lividuswere incubated with radioactive (14C) amino acids. Incorporation of label into antigen was studied by means of rabbit antisera against sea urchin material. In an attempt to block genetic control of protein synthesis, eggs and embryos were treated with actinomycin D during different periods of development.During normal development the antigen‐labeling pattern, studied by immunoelectrophoresis and autoradiography, remained essentially unchanged until hatching. In the mesenchyme blastula, however, a new labeled antigen was detected, and one which earlier was unlabeled became heavily labeled. As seen in autoradiographs, during the same period, the intensity of labeling of other antigens also changed. When the embryos were exposed to actinomycin D (10–20 μg/ml) from hatching or some hours before, the development stopped at the mesenchyme blastula stage and these embryos never developed the labeling pattern characteristic of normal mesenchyme blastula.The results suggest that in contrast to the early development, gastrulation requires new production of templates. These templates seem to be essential for the changing pattern of antigen‐labeling. It is suggested that alterations in amino acid incorporation into antigens reflect changes in synthesis of proteins necessary for gastru

ISSN:0022-104X    

DOI:10.1002/jez.1401710305

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe study of the chameleon ear that began withChamaeleo senegalensisandChamaeleo quilensishas now been extended to two further species,Chamaeleo höhneliiandChameleo jacksoni, with results that are different in important respects. As measured in terms of cochlear potentials, the two species of the present study show definitely poorer sensitivity to aerial sounds. Also their responsiveness to these sounds is not made much worse by severing the columella, an observation that stands in contrast with the serious impairment that this operation produces inC. senegalensisandC. quilensis.The explanation lies in a difference between the sound receptive mechanisms in the two groups. In the species examined earlier a substitute tympanic membrane was found: beneath the surface at the side of the head is a diaphragm formed by a thin plate of the pterygoid bone and a membrane extending its surface to the border of the quadrate bone. In addition there is a branch process (anterior process) of the extracolumella that attaches to the middle of this pterygoid plate, and transmits the movements made by the plate in response to sounds to the stapedial footplate in the oval window. InC. höhneliiandC. jacksonithis anterior process is lacking, and the pterygoid plate cannot function as a sound receptive surfac

ISSN:0022-104X    

DOI:10.1002/jez.1401710306

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

年代:1969

数据来源: WILEY

摘要:

AbstractSeventy‐five per cent of a population of active copulators among Sprague‐Dawley male rats showed cyclic mating activity. This group of 84 animals had 6% 5‐day cyclers, 27% 4‐day cyclers, 45% 3‐day cyclers and 22% 2‐day cyclers. Observed copulatory sequences show that 82% of the time the copulation plug is dislodged from the female's vagina during the first three intromissions of a succeeding copulation. Most copulatory activity occurs between 3.5 and 5.5 hours after the start of the dark phase of the light cycle. Over 79% of the animals are sexually active for only one h

ISSN:0022-104X    

DOI:10.1002/jez.1401710307

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe amylases ofD. melanogasterwere characterized by several parameters. Starch‐iodine and 3,5‐dinitrosalicylic acid reduction methods were employed to determine activity. Conditions were defined under which activity, in crude aqueous extracts could be restricted to α‐amylase(s) of fly origin. Biochemical properties of the α‐amylases from eleven homozygousAmystrains were found to be very similar in temperature stability, pH optimum, substrate specificity and the effects of various activators and inhibitors. All were activated by chloride ions and showed a pH optimum of about 7.4. Relative efficiencies on several substrates were tested: soluble starch, amylopectin, β‐limit dextrins, glycogen and amylose. EDTA completely inhibited all extracts, presumably by the removal of calcium required for activation. The specific α‐amylase inhibitor from wheat grain also completely inhibited activity, as did reduced glutathione. PCMB had no discernible effects on activity.Eight of the 11 strains tested are known to produce different electrophoretic banding patterns for amylases. The total maximum activity of each strain may also be used to characterize it and, accordingly, three strains with amylases of the same electrophoretic mobility were distinguished by differences in their specific activities. Sexual dimorphism in amylase activity was defined, as well as activity in heterozygotes between strains. Aside from the distinctions between strains already noted, four strains differed in their relative susceptibility to heat and to α‐amylase inhibitor.Linkage experiments indicated that theAmyregion lies at 77.3 on the genetic map of the second chromosome and to the right, but near, section 52F on the saliv

ISSN:0022-104X    

DOI:10.1002/jez.1401710308

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

年代:1969

数据来源: WILEY

摘要:

AbstractInjection of teratogenic doses of trypan blue into pregnant mice resulted in depression of acid phosphatase activity in embryonic visceral yolk sac endoderm. In addition, the apical localization of this enzyme was lost, and enzyme active loci were dispersed throughout the cytoplasm. Perinuclear Golgi structures were prominent in yolk sac cells of control mice incubated for thiamine pyrophosphatase activity. In trypan blue treated animals the Golgi apparatus was attenuated and disrupted. Whereas yolk sacs of most trypan blue treated embryos showed depression of acid phosphatase activity and morphological alteration in Golgi, only 25% of such embryos exhibited gross malformations. Trypan blue treatment may cause malformations by altering nutritive and transport functions of the yolk sac placenta or the dye may exert a direct effect upon the cells of the embryo.

ISSN:0022-104X    

DOI:10.1002/jez.1401710309

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

年代:1969

数据来源: WILEY

摘要:

AbstractEarly lenses of mouse embryos were studied with the electron microscope to determine whether their cells contain organelles that can be causally related to the invagination of the lens placode. The cells of the placode and early lens cup are joined at their apical ends by junctional complexes. At the level of thezonula adhaerens, favorable sections show cytoplasmic filaments, 35 Å to 50 Å wide, arranged about the apex of a cell. Groups of filaments appear to originate on or near the plasma membrane and then to extend across the cytoplasm, parallel to the apical cell surface, to terminate on or near the plasma membrane some distance away. They are nearly always straight; in contrast, nearby lateral and apical cell membranes are twisted into irregular folds and projections.We present a model to explain lens invagination in which the filaments are considered to be contractile. On the basis of their location in the cells and their presumed function, these organelles are proposed to be a major component in the mechanism that leads to early morphogenesis of the len

ISSN:0022-104X    

DOI:10.1002/jez.1401710310

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

年代:1969

数据来源: WILEY

摘要:

AbstractMultiple forms of tyrosinase separable by acrylamide‐gel electrophoresis are demonstrable in extracts of hair bulbs prepared on the fifth (anagen IV) through the thirteenth days (anagen VI) of a hair growth cycle induced in C57BL/6J mice by plucking of quiescent hairs. The enzymic bands visualized by incubation of the gels in L‐DOPA have been designated as T1, T2and T3. Although T1has been observed through day 19, the T2and T3components disappear by day 15 of the hair growth cycle. Tyrosinase activity is not demonstrable in skin extracts prepared during telogen or on days 1–3 post‐plucking (anagen I–III). The slow development of a single DOPA‐melanin band in such samples has been demonstrated to represent non‐specific oxidation by hemoglobin that migrates at a slightly slower rate than the T3component. The precise state of tyrosinase within follicular melanocytes prior to day 5 of the hair growth cycle remains to be determined. The functional significance of the multiple forms of tyrosinase also is yet to b

ISSN:0022-104X    

DOI:10.1002/jez.1401710311

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

年代:1969

数据来源: WILEY