bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ultrastructure of the compound eye of a mosquito Aedes aegypti L
Authors: Brammer J. D. 
Published: June 2005

AbstractEach ommatidium in the mosquito compound eye consists of a dioptric apparatus and layer of retinula cells. The dioptric apparatus includes a cuticular cornea, a biconvex lens, and four cone cells. The cone cells have processes which extend into the receptor layer and terminate below the rhabdom as pigment‐filled sacs. Two primary pigment cells and an undetermined number of secondary pigment cells surround the dioptric apparatus. In the receptor layer eight retinula cells are found in each ommatidium. Six are peripherally arranged around a central one, whereas the remaining retinula cell is sandwiched between and somewhat external to two of the peripheral retinula cells. Each of the eight retinula cells possesses a well developed rhabdomere, along with the usual array of other intracellular organelles characteristic of arthropod photoreceptor cells.
Cell lineage in the dorsal mesothoracic disc of Drosophila
Authors: Murphy Collin , Tokunaga Chiyoko 
Published: June 2005

AbstractProblems of cell lineage within the dorsal mesothorax of Drosophila are treated in a comprehensive way. The study utilizes both gynandromorphs and induced mosaics which have chaetae genetically “marked” at various developmental stages. It includes regions not previously studied due to lack of chaetae by inducing mosaics on a hairy background. It analyzes the distributions of spots by a combination of statistical techniques.Lineage relationships among the 11 mesonotal macrochaetae are traced by comparing correlation data from different samples. In general, the distances between pairs of macrochaetae are inversely proportional to phi correlation values. Related cells remain together and cell lineage pathways become gradually restricted during development.The dorsal suface of the mesonotum is divided into 63 different sections. Analysis of their interrelationships confirms results obtained by the study of macrochaetae, since distance between macrochaetae or sections does play a role in their lineage relationship and each section studied is significantly correlated with its surrounding and neighboring sections. Overall lineage relationships are defined by dividing the dorsal mesothorax into clusters of related sections by means of principal‐component analysis.In some sections which are intimately related by cell lineage, the role of distance is secondary because of differential growth patterns. In addition, there are regionally variable sensitivities of developing cells for the induction of somatic crossing over, which may imply differential mitotic rates.Cell lineage of the mesonotum is nonrandom, in that the spacial relationship among cells developing from the same line is preserved throughout ontogeny, with modifications by differential growth rates.
The distribution of glycosaminoglycans in the axial region of the developing chick embryo. II. Biochemical analysis
Authors: Kvist Tage N. , Finnegan Cyril V. 
Published: June 2005

AbstractAn investigation of the appearance of glycosaminoglycans in the axial region (dermatome, myotome, scleratome, neural tube and notochord) of the developing chick embryo during early somite differentiation (stages 17–28; 2.5 to 5.5 days of age) was conducted with biochemical methods for comparison with a previously conducted histochemical analysis (Kvist and Finnegan, '70). The biochemical analysis confirmed that the weakly acidic anionic glycosaminoglycan observed histochemically was hyaluronic acid and that the sulphated anionic glycosaminoglycan was mainly chondroitin‐4‐ and/or chondroitin‐6‐sulphate (chondroitin‐sulphate A and/or C). Trace amounts of dermatan‐sulphate (chondroitin‐sulphate B) were found and, since some glucosamine was present in the sulphated fractions, it is possible that a small amount of heparin was present. This latter observation could account for the polysulphated material seen with histochemical methods.Quantitatively, the hyaluronic acid concentration (uronic acid/gm dry weight of tissue) was at a peak between stages 21–25 and exceeded the chondroitin‐sulphate concentration in axial tissues until stage 25, after which time chondroitin‐sulphate concentration increased very rapidly, concomitant with perichordal cartilage formation, while hyaluronic acid concentration began slowly to decline. Thus, whereas hyaluronic acid concentration was 2.5 times that of chondroitin‐sulphate at stage 17, this ratio was nearly completely reversed by stage 28.The increase in sulphated anionic glycosaminoglycans would seem to be directly related to cartilage formation but the high level of hyaluronic acid content in stages 21–25, when myotube formation as well as sclerotome aggregation are occurring, and its subsequent decrase could indicate that it plays some developmental role in somitogenesis.
Protein incorporation by isolated amphibian oocytes. I. Preliminary studies
Authors: Wallace Robin A. , Jared Donald W. , Nelson Bettie L. 
Published: June 2005

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 cultured in 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.
Further investigation of capacitation of sperm and fertilization of mouse eggs in vitro
Authors: Iwamatsu T. , Chang M. C. 
Published: June 2005

AbstractMouse eggs obtained from oviducts 14–16 hours after an injection of HCG were inseminated in vitro with 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 (3–23%).
Aberrant octanol dehydrogenase isozyme patterns in interspecific Drosophila hybrids
Authors: Pipkin Sarah Bedichek , Bremner Theodore A. 
Published: June 2005

AbstractA maternal octanol dehydrogenase (ODH) isozyme pattern is observed in embryos of reciprocal crosses of A and B variants both in intraspecific hybrids of D. pellewae and of D. metzii, respectively, and in interspecific hybrids of D. metzii crossed with either D. pellewae or D. 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 of D. 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 of D. 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 (Pipkin, '69).
Heart induction: Distribution of active factors in newt endoderm
Authors: Fullilove Susan L. 
Published: June 2005

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 endoderm.
Effects of progesterone and estrogen on the electrical activity of the limbic system
Authors: Innes David L. , Michal E. Keith 
Published: June 2005

AbstractFemale, virgin rats studied to determine areas within the limbic system that respond to gonadal steroids. Under ether anesthesia bipolar electrodes were stereotaxically placed in the lateral septum, dorsal hippocampus, medial amygdala and parietal cortex. Following cutaneous injections of novacain, animals were injected with tubocurare and respirated artificially. Intraperitoneal (IP) injections of estradiol‐17B and progesterone in propylene glycol were given and the electrical activity of the limbic structures was recorded and a frequency analysis made. Those areas which responded to systemic treatment were implanted with the same gonadal steroids using a recording cannula‐electrode. The parietal cortex and medial amygdala showed no significant change in electrical activity that was consistent throughout the experiment. The dorsal hippocampus responded to IP injections of both estradiol‐17B and progesterone in diestrous and estrous rats, but did not respond to direct stimulation with the gonadal steroids. The electrical activity of the hippocampus increased within 30 minutes when the septum was stimulated directly with either progesterone or estradiol‐17B. The lateral septum responded to injections of both estradiol‐17B and progesterone in diestrous and estrous animals. Following direct implantation of either gonadal steroid into the lateral septum, there was an immediate increase in the activity of the septum. The lateral septum appears to be a site within the limbic system that is able to respond to both estrogen and progesterone.
Protein synthesis by blastocysts in the uteri and oviducts of intact and hypophysectomized mice
Authors: Weitlauf Harry M. 
Published: June 2005

AbstractTwo possible explanations for the stimulatory effect of estrogen and progesterone on protein synthesis by preimplantation mouse embryos are that the hormones: (1) stimulate the embryos directly; or (2) induce changes in the uterus that in turn affect the embryos.To determine which of these possibilities is correct, mouse blastocysts were retained in one oviduct by a ligature at the uterotubal junction; the mice were then either left intact or hypophysectomized. 35S methionine was injected and the tubal and uterine blastocysts were recovered and prepared for radioautography.Blastocysts in utero incorporate 35S methionine only if the pituitary is present. On the other hand, blastocysts in the oviducts incorporate 35S methionine regardless of the hormonal status of the mother. This suggests that estrogen and progesterone influence the level of protein synthesis in uterine blastocysts by inducing changes in the uterus rather than by stimulating the embryos directly.In addition, blastocysts were recovered from oviducts or uteri between day 5 and day 10 post coitum and transferred to pseudopregnant females to test their ability to develop into normal fetuses. Uterine blastocysts retained the ability to develop normally while the percentage of tubal blastocysts capable of development dropped sharply between day 5 and day 10. Therefore, it is suggested that the dormant condition of mouse blastocysts in utero during delayed implantation may serve to protect the embryos from damage.
Cleavage furrow formation in a telolecithal egg (Loligo pealii). II. Direct evidence for a contraction of the cleavage furrow base
Authors: Arnold John M. 
Published: June 2005

AbstractCleavage of the highly telolecithal egg of a squid is meroblastic and stops when the base of each furrow cuts through the cytoplasm of the blastodisc and contacts the yolk. The base of each furrow is composed of a band of 50 Å filaments which apparently are linked to the surface membrane. By cutting the base of the furrow or by flattening the blastodisc of the egg, it has been possible to demonstrate that this band contracts and remains in a state of tension. Analysis of the shape change of the cells in normal cleavage also supports this contraction‐tension hypothesis. Furrows which cross another furrow are linked to it at specific sites (anchor points). As the furrows extend, new linkages between the filamentous band and the surface membrane are formed. The amount of tension produced by contraction of a furrow is proportional to its length. It appears that the entire blastoderm is in a state of dynamic tension caused by balanced contraction of the filamentous band. These results and conclusions are in agreement with postulated mechanisms of cleavage furrow formation in many other types of animal cells.
Nucleic acid synthesis in preimplantation rabbit embryos. II. Delayed synthesis of ribosomal RNA
Authors: Manes Cole 
Published: June 2005

AbstractThe qualitative aspects of ribonucleic acid (RNA) synthesis in preimplantation rabbit embryos have been investigated by the electrophoretic separation of tritium‐labeled embryonic RNA on polyacrylamide gels. Labeling of an RNA species having migratory properties identical with those of transfer RNA can be detected from the 2‐cell stage onward. Labeling of RNA species having the migratory properties of 28S and 18S ribosomal RNA is first detectable at 72 hours post coitum, at the time of the morula‐to‐blastocyst transformation. Labeling of heterogeneous RNA migrating between the 4S and 18S markers is detectable at all stages. The sensitivity of this labeling to inhibition by Actinomycin D is consistent with DNA‐dependent synthesis. The findings demonstrate that cleavage of the rabbit ovum can be accomplished in the absence of significant ribosomal RNA synthesis, and provide evidence that at least one gene product sufficient to sustain early protein synthesis is supplied by the maternal genome prior to fertilization. The distinct temporal separation in the initiation of transfer and ribosomal RNA synthesis is consistent with their independent regulation in these embryos.
Reversal of chemical cleavage inhibition in echinoderm eggs
Authors: Rappaport R. 
Published: June 2005

AbstractMany agents will, in low concentrations, reversibly block cytokinesis without seriously affecting mitosis. Frequently such agents visibly reduce the size of the mitotic apparatus. The purpose of this investigation was to determine whether failure to divide as a result of this treatment is causally related to reduction in size of the mitotic apparatus. Ether and ethyl urethane were used as blocking agents. Hemicentrotus pulcherrimus eggs fail to cleave when placed in either 0.75% ether or 0.06M ethyl urethane in filtered sea water 30 minutes or more before cleavage time. Both agents reduce the asters. When eggs are constricted by partial removal of the fertilization membrane, the mitotic apparatus and surface are brought closer together. Constricted eggs developed furrows in concentrations of blocking agents that prevented cleavage in spherical eggs. Furrows were permanent when they coincided with the plane of artificial constriction. Cleavage in Echinarachnius parma eggs is blocked by 0.052 M ethyl urethane. The behavior of constricted, treated eggs is similar to that of H. pulcherrimus eggs. When the reduced mitotic apparatus of the treated cell is pushed to an excentric position, well‐developed but usually temporary furrows appear. Hexanediol augments the in vivo mitotic apparatus. When eggs are exposed to combined treatment of 0.25% hexanediol and 0.052 M ethyl urethane about half will, in favorable cases, develop furrows. About half the furrows are permanent. In otherwise normal eggs hexanediol treatment slightly increases the maximum spindle‐to‐surface distance that permits furrowing. It appears that the cleavage blocking effects of ethyl urethane and ether in these experiments were partially reversed by measures that restore a more nearly normal geometrical relationship between the reduced mitotic apparatus and the surface.
Mechanics of sound production in toads of the genus Bufo: Passive elements
Authors: Martin William F. 
Published: June 2005

AbstractThe vibration mechanics of the vocal tracts of over 40 species of toads (genus Bufo) were studied, using an apparatus to artificially activate the larynges of freshly killed animals. The effects of laryngeal ablations on the mating and release calls were studied. They confirmed the results obtained by artificial activation. The mating and release call dominant frequencies are determined primarily by the fundamental frequencies of vibration of the paired vocal cords. Vocal cord resonant frequencies are in turn largely determined by the activation air pressure and the masses of cartilagenous deposits in their lateral portions. In most species, fleshy folds within the larynx at the anterior extremities of the arytenoid cartilages cause these cartilages to vibrate during sound production, amplitude modulating the vocal cord output. In most species, the contraction pattern of the vocal musculature is reflected as a periodic pulsation. Frequency modulations of the mating call dominant (or carrier) frequency are described, partially explained, and deemphasized in importance with respect to toad acoustical communication. The findings of this investigation are made relevant to the overall problem of the structure and evolution of toad acoustical communication by use of an analogy with standard AM radio broadcast.
Studies on aging in a bdelloid rotifer. I. The effect of various culture systems on longevity and fecundity
Authors: Meadow Norman D. , Barrows Charles H. 
Published: June 2005

AbstractTechniques are described for the aseptic manifpulation of rotifers cultured in exposed containers. The elimination of bacterial contaminants resulted in much greater stability of mean life span than had been obtained from contaminated (synxenic) cultures. The aseptic procedures have also facilitated the development of a mass culture system which provides milligram quantities of animals of known ages. Comparisons of dry weight and enzymatic activities of animals grown in mass and isolation cultures have demonstrated unifromity of animals maintained in the two systems. A number of bacteria and algae were tested as food sources. Optimal reproductive rate and longevity were obtained when a mixture of Aerobacter aerogenes and a strain of Pseudomonas species designated N6 was used (a dixenic culture system). Mortality among dixenically cultured rotifers was low until after reproduction ended. The reproductive rate was reduced when the animals were grown monoxenically on either A. aerogenes, Chlorella vulgaris or Chlamydomonas reinhardi. A second species of Pseudomonas reduced longevity without any effect on reproduction. Dry weight of the rotifers increased throughout the entire life span, and fat, ash and protein content increased in proportion to the dry weight. RNA content remained constant. Both total and specific activity of lactate and malate dehydrogenase decreased in older animals. These patterns of enzyme activity are similar to those found in other organisms.
Fertilization of partially jellied and jellyless oocytes of the frog Rana pipiens
Authors: Elinson Richard P. 
Published: June 2005

AbstractThe oocyte of Rana pipiens is coated by three visible jelly layers designated V1, V2, and V3 from inner to outer. Oocytes with V1 were rarely fertilized, while oocytes with V1 and V2, V1 and V3, and V3 were fertilized. Oocytes with V1 and V3 lost their fertilizability more rapidly after being placed in 10% Ringer's than did oocytes with V1, V2, and V3.When jellied oocytes were dejellied with KCN, they were not fertilized on insemination. The addition of a water extract of jellied oocytes (egg‐water) insured fertilization of dejellied oocytes. The finding that the factors necessary for fertilization are diffusible decreases the importance of locating them in a given jelly layer. The activity of the egg‐water survived lyophilization and was heatlabile. Both a dialyzable and a non‐dialyzable fraction were required to insure a high frequency of fertilization. Egg‐water had to be present with the sperm and the oocytes in order for fertilization to occur. Sperm incubated in egg‐water lost their fertilizing ability with time.Mature body cavity oocytes, which had not been coated with jelly by the oviduct, were fertilized at a low frequency under the same conditions that resulted in a high frequency of fertilization of dejellied oocytes. Similarly, dejellied oocytes of the toad Bufo americanus were fertilized in toad or frog egg‐water, while body cavity toad oocytes were not fertilized.