bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell lineage in the dorsal mesothoracic disc of Drosophila
Authors: Murphy Collin , Tokunaga Chiyoko
Published: June 2005

Problems 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

An 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

Developing 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

Mouse 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

A 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

Presumptive 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

Female, 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

Two 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

Cleavage 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

The 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

Many 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

The 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

Techniques 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

The 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.
Structural and contractile properties of lobster leg‐muscle Fibers
Authors: Jahromi S. S. , Atwood H. L.
Published: June 2005

Three leg muscles of the American lobster, namely, the extensor muscle of the carpopodite in the walking legs, the closer muscle of the “cutter” claw, and the closer muscle of the “crusher” claw, were examined to see what types of muscle fiber they contain. In all three muscles, slow and fast fibers, as well as intermediate types, were present. Contraction rates of both types increased with the amplitude of the applied depolarization; slow fibers showed more lability in this respect, but they did not contract as rapidly as the fast fibers even when strongly stimulated. Membrane potential threshold for contraction was positively correlated with resting membrane potential in both types of fiber. Slow fibers differed from fast fibers structurally in having longer sarcomeres and A‐bands, smaller numbers of diads per unit length of muscle fiber, larger thin:thick filament ratios, and more connective tissue and sarcolemmal elements. The two claw closer muscles differed markedly in their proportions of slow and fast fibers, the “cutter” claw having a preponderance of short‐sarcomere, fast fibers. This finding helps to explain the difference in contraction speed of these two claw muscles.
Studies on the transition to ureotelism in the earthworm Lumbricus terrestris L.
Authors: Tillinghast Edward K. , Janson Colette H.
Published: June 2005

The hypothesis that anatomically distinct endocrine centers control the production of urea and ammonia in the earthworm has been examined.

This hypothesis is not supported by the present data.

Ammonia output is markedly increased by a high protein diet, while the urea output is reduced by digestible carbohydrates.
Transneuronal effects on amphibian limb regeneration
Authors: Tweedle Charles
Published: June 2005

This investigation has demonstrated that in both the newt and axolotl the simultaneous removal of a second limb brings about a significantly slower linear regeneration rate, but only if the second limb removed is directly contralateral to the first one removed. Both morphologic and autoradiographic data point to a more prolonged chromatolysis in the brachial neurons following contralateral forelimb removal. This is thought to bring about the slower regeneration rate seen. Further evidence for this contention is the fact that just the severance of the brachial nerves of one forelimb of an animal will bring about a significantly slower regeneration rate of the contralateral forelimb. In salamanders without intervening nervous connections or CNS tissue between the limbs, i. e., the aneurogenic larvae, no effect on regeneration rate is seen following contralateral double limb removal. Autoradiographs using 3H thymidine as a precursor point to an early effect on growth as being the means that contralateral denervation or limb removal brings about a slower regeneration rate. This is thought to be due to a decrease in the trophic ability of the brachial innervation following the more profound disruption of the brachial neurons that accompanies double limb removal.
DNA content, ribosomal gene multiplicity, and cell size in fish
Authors: Pedersen Roger A.
Published: June 2005

The diploid nuclear DNA contents in eight species of fish have been found to differ over a 178‐fold range. Among these, lungfish have the highest values, and teleosts have the lowest. Shark and coelacanth have intermediate values, which are close to the highest teleost values. Such great variation in DNA contents among vertebrates indicates that fundamental differences in chromosome structure and DNA function have arisen during evolution.

In order to gain insight into the organization of genes in organisms with different DNA contents, the relative proportion of the genome coding for ribosomal RNA was determined for five species, winter flounder, goldfish, rainbow trout, dogfish shark, and Australian lungfish. The proportion of ribosomal DNA (r‐DNA) was found to vary over a six‐fold range from flounder to lungfish. In general, species with higher DNA contents have lower proportions of r‐DNA. The r‐DNA proportion of trout is consistent with the view that salmonids are recent tetraploids. If the goldfish is also considered a tetraploid, then its r‐DNA proportion indicates a loss of ribosomal genes subsequent to polyploidization. Measurement of the ribosomal genes in fish DNA's was based on hybridization with yeast ribosomal RNA, which was assumed to be equally homologous with the r‐DNA of all species studied.

The activity of multiple copies of genes was studied by measuring the volumes of blood cells in five species. It was found that erythrocyte volume correlated both with ribosomal gene multiplicity and with total DNA content. The size of goldfish and trout erythrocytes suggests that cell volume in these tetraploids has declined to the ancestral diploid level.

It is concluded that the multiplicity of specific repetitive genes varies out of proportion with the DNA content, contrary to expectation based on simple polyteny. This variation in the proportions of specific genes and the large variations in total DNA content among fish are thought to be due to a combination of tetraploidy and extensive linear replication of specific chromosomal regions during evolution.
Control of mitotic activity in Wolffian lens regeneration
Authors: Yamada Tuneo , Roesel Marion
Published: June 2005

The total numbers of mitotic cells in the iris epithelium, ciliary epithelium, and ora serrata were counted at various time intervals after lentectomy of adult newts, Notophthalmus (Triturus) viridescens, in bleached serial sections. In some cases colchicine was injected for the purpose of accumulating mitotic figures.

In the iris epithelium, which normally shows no mitotic cells, a wave of mitoses is induced by lentectomy. The wave starts on day 4 and has its peak period during days 7 to 15, when a portion of the iris epithelial cells depigment and form the lens vesicle. In the iris epithelium the wave subsides after formation of the regenerated lens and is gone by day 30. On the other hand, in the regenerated lens the mitotic activity is retained in the lens epithelium. The colchicine treatment has revealed an extremely small number of iris epithelial cells going into mitoses within one day after lentectomy. However, the same treatment failed to demonstrate any mitotic cells on days 0, 2, and 3.

Mitotic activity is also induced in the ciliary epithelium, which does not take part in formation of the lens regenerate. This induction is much lower in intensity than that in the iris epithelium.

The ora serrata area has a low level of mitotic activity in the normal condition, which is elevated to a high level after day 20. Significance of these observations for the mechanism of lens regeneration is discussed.

Estimation of the total cell number of iris and ciliary epithelia during the first 15 days after lentectomy indicated an increase in the iris epithelium, which can be accounted for by the number of mitoses counted during the corresponding period in the same tissue.

Some data on mitosis in the normal and regenerated lenses are also presented.
Hormonal influences on the glycogen content of normal and delayed implanting mouse blastocysts
Authors: Ozias C. Blake , Weitlauf Harry M.
Published: June 2005

The proportion of delayed implanting mouse blastocysts capable of normal development following transfer to pseudopregnant recipients is influenced by the length of the delay period. Thus, approximately one‐third develop normally when transferred on days 5, 9 or 15 (day 1, day of vaginal plug), while only 3% do so when transferred on day 30 (Weitlauf and Greenwald, '68a). In the present experiments, the amount of glycogen in normal and delayed implanting mouse blastocysts was estimated enzymatically to determine whether it plays a limiting role in embryonic survival.

Normal blastocysts and delayed implanting blastocysts (i. e., in mice ovariectomized on day 4) contained a similar amount of glycogen on day 5. However, by day 10 the amount of glycogen in the delayed implanting blastocysts dropped to about half that found on day 5 but showed no further decrease between day 10 and day 30. Therefore, the amount of glycogen in delayed implanting mouse blastocysts does not appear to be the limiting factor in embryonic survival.

It was further shown that ovarian hormones influenced the amount of glycogen in the blastocysts. Administration of estrogen to ovariectomized mice caused an increase, while progesterone reduced the levels of glycogen.
Physico‐chemical properties of an agent that induces parthenogenesis in Rana pipiens eggs
Authors: Fraser Lynn R.
Published: June 2005

All previous work on artificial parthenogenesis in frog eggs, where parthenogenesis is identified by cleavage and subsequent embryonic development, has involved the introduction of some cellular element. Earlier workers have shown that the cleavage initiating agent (CIA) is found primarily in the particulate fractions of various tissues, whereas this investigation indicates that the active molecules sediment only in the 10,000 g precipitable fraction. Since dialysis against EDTA does not remove activity, non‐specific adsorption to particles would appear to be excluded although the failure of distilled water treatment to remove activity may indicate that the CIA is associated with membranes. The CIA is trypsin‐sensitive, but DNase and RNase resistant, indicating that the molecules are protein in nature. Activity is also removed by incubation with a number of depolymerizing agents, including KI, KCl, and Sarkosyl, indicating that the CIA may be a polymer which must be polymerized to retain activity. The mechanism of action of this protein polymer appears to be that of a trigger since a wide range of concentrations will initiate cleavage. Colchicine gradually removes activity from a preparation while D2O increases activity. Both of these molecules are known to act on the polymerized form of microtubule protein with colchicine decreasing and D2O increasing polymerization. Electrophoresis of protein from five CIA‐containing frog tissues reveals a component common to all of them which migrates with an Rf similar to that of microtubule protein. The 10,000 g pellet from frog brain has significant 3H‐colchicine‐binding activity, and to date only microtubule protein has been shown to bind colchicine. Electron micrographs of 10,000 g pellet material from frog brain show the presence of pieces of microtubules enclosed in membranous vesicles. It is therefore possible that the CIA is microtubular in nature, with short pieces of microtubules perhaps acting as a “seed” for further polymerization. The unfertilized frog egg contains much unpolymerized microtubule protein but apparently lacks the proper template or catalyst to trigger the necessary centriole replication and spindle formation for cleavage; the CIA may fill this role.
Growth and differentiation of the testes in the large milkweed bug, Oncopeltus fasciatus (Dallas)
Authors: Economopoulos A. P. , Gordon H. T.
Published: June 2005

During the fourth instar there is a five‐fold increase in testis volume, caused by mitotic proliferation of spermatogonia that leads to accumulation of many layers of cysts of resting spermatocytes. At the beginning of the fifth instar the basal cysts undergo meiotic division, and a wave of meiosis followed by spermateleosis progreses apically. There is little or no spermatogonial multiplication; the three‐fold increase in testis size involves primarily spermatocyte differentiation. The wave of differentiation continues at a slower rate in the young adult; most of the spermatocyte cysts are transformed into about 250,000 spermatozoa by the twelfth day. Multinucleate apical cells that stain deeply with Feulgen reagent are present in the early fourth instar, enlarge in the fifth, and persist in the adult testis.

Spermatocyte differentiation is not affected by treatment of nymphs with a synthetic juvenile hormone to analog during the fourth or fifth instar, although the treatment causes moderate to high juvenilization at the metamorphic molt. Since late fourth‐instar testes transplanted into mature male or female adults also undergo extensive transformation of spermatocytes into spermatozoa, molting is not required for differentiation. Treatment of late fourth or early fifth instar nymphs with the chemosterilant tretamine causes high mortality at the metamorphic molt, but the wave of spermatocyte differentiation during the fifth instar proceeds normally, although there is evidence of severe chromosome damage.

Comparisons with development in the female of Oncopeltus and in other insect species suggest that there is a profound change in the biochemical milieu at the molt from fourth to fifth instar, many processes preceding this molt tending to be larval in character and to diminish or disappear afterward while processes normally occurring after the molt tend to be adultoid.
Sucrase activity in the intestine of the chick: Normal development and influence of hydrocortisone, actinomycin D, cycloheximide, and puromycin
Authors: Brown Kathren Mortenson
Published: June 2005

Sucrase activity in the intestine of the chick embryo increases to a pre‐hatching maximum at 19 days. A significant decrease in activity occurs by 20 days, followed by rapid increases in the jejunum and the ileum after hatching, while duodenal activity continues to decrease. The injection of hydrocortisone resulted in significant increases in sucrase activity. The decrease in activity that normally occurred after 19 days was delayed until after 20 days. The hydrocortisone‐induced increases were completely abolished when cycloheximide was administered two or three days after the hormone injection.

When actinomycin D was administered at 16 days, there were significant increases in sucrase activity at 18 days, and the maximum activity was produced at 19 days. High activities were obtained when actinomycin D was injected at 17 days. The administration of cycloheximide at 14 or 16 days did not change the sucrase activity through 19 days, but the 20‐day decrease was prevented. Large increases in activity were observed at 20 days when the antibiotic was injected at 17 days. Histological preparations revealed that these two antibiotics did not produce abnormalities in the epithelial cells of the tissues. Puromycin injection inhibited the normal decrease at 20 days. Actinomycin D and cycloheximide were injected simultaneously at 16 days. Cycloheximide did not prevent the elevation of sucrase activity caused by actinomycin D. It is suggested that the development of sucrase activity in the chick intestine may consist of a phase of activation followed by a phase of inhibition. In the first phase, de novo synthesis can apparently be evoked by hydrocortisone.
The effects of complete darkness and vitamin C supplement on the killifish, Fundulus heteroclitus, adapted to sea water. I. Calcium metabolism and gonadal maturation
Authors: Pang Peter K. T.
Published: June 2005

Adaptation to complete darkness for eight months had no effect on calcium metabolism in adult male Fundulus heteroclitus in sea water. However, scoliosis and hypocalcemia were evident in juvenile killifish kept in complete darkness for six and a half months. Hypocalcemia was also seen in juveniles after three and a half months in complete darkness but this fall in serum calcium level was prevented by vitamin C supplement in the diet. Complete darkness also induced a delay in testicular maturation in both adults and juveniles but this defect was not corrected by vitamin C supplement.
3,5,3′‐triiodo‐L‐thyronine uptake and development of metamorphic competence by Xenopus laevis embryonic tissues
Authors: Knutson Thomas L. , Prahlad Kadaba V.
Published: June 2005

The purpose of this investigation was to determine whether or not larval tissues of Xenopus laevis are capable of responding to a very short exposure of 3,5,3′‐triiodo‐L‐thyronine (T3), very early in their ontogeny. Ten dejellied embryos were immersed in 15 ml of aged tap water containing 30 μg of T3 per ml of medium. Exactly at the end of 24 hours all of the embryos were removed, rinsed thoroughly in fresh tap water and placed in aged tap water in a larger container. Both gross morphological and histological observations were carried out on embryos and larvae at an interval of 12 hours beginning at the termination of hormone treatment to the end of about 11 days.

The following changes were clearly observed in experimental animals (numbers in parenthesis indicate days after fertilization): (a) degenerative changes in adhesive gland (3.5); (b) more extensive development of nasal sac (5.0); (c) a visible and ventrally protruding hyoid arch (6.5); (d) a larger hind limb bud (5.0). In addition to the above, other obvious changes which were seen in experimental animals were a protruding lower jaw due to an extensive and well developed Meckel's cartilage, and a less extensive gut. The head was cone shaped in T3 treated animals. There was no change in tail to body length ratios.

The facts mentioned above appear to indicate a differential ontogenetic competence of embryonic and larval tissues of Xenopus in their response to T3.
Daily variations in the fattening response to prolactin in Fundulus grandis held on different photoperiods
Authors: Joseph M. M. , Meier Albert H.
Published: June 2005

Gulf killifish were placed on three different photoperiods (8L:16D; 12L:12D; 16L:8D) and injected daily for six days with prolactin at one of several times during the day. Gains in fat stores resulted from prolactin injections given eight hours after the onset of light regardless of the length of the photoperiod. Prolactin injections at other times of the day did not stimulate fattening. These results suggest that the endogenous system controlling the daily fattening response to prolactin is phased by the onset of light.
Thyrocalcitonin and its role in calcium regulation in mammals
Authors: Hirsch Philip F.
Published: June 2005

The discovery of thyrocalcitonin, the hypocalcemic, hypophosphatemic hormone secreted by the mammalian thyroid gland, and its current status with respect to cell of origin, chemistry, site and mode of action, and control of its secretion are reviewed. The physiological function of thyrocalcitonin has yet to be established with certainty.

Evidence that secretion of thyrocalcitonin prevents postprandial hypercalcemia is presented. Small amounts of calcium administered orally caused hypercalcemia in acutely thyroidectomized but not in intact rats. In the pig, a direct relationship has been established between thyrocalcitonin secretion and levels of blood calcium during hypercalcemia. However, in other studies in which calcium was given orally, thyrocalcitonin secretion rose even without a detectable increase in the concentration of blood calcium. These observations in rats and pigs raised questions regarding the stimulus to the thyroid gland for thyrocalcitonin secretion. Is a small and undetectable rise in the blood calcium after oral calcium a sufficient signal to the thyroid gland or are other factors involved? The recent finding that pentagastrin administered i.v. at low doses increased thyrocalcitonin secretion in pigs suggests that release of gastrin or a related gastrointestinal hormone after oral calcium may thereby aid in regulation of calcium metabolism.

The possibility also remains that the principal physiological function of thyrocalcitonin may be unrelated to calcium homeostasis. Attention has been focused on calcium partly because of the nature of the experiments leading to the discovery of thyrocalcitonin. Perhaps the correct pathway to elucidate the true role of this hormone in the body economy has not yet been followed.
Thyroxine induced metamorphosis in Aurelia
Authors: Spangenberg Dorothy Breslin
Published: June 2005

The functional activity of thyroxine in strobilation initiation in Aurelia is explored. Low temperature preconditioned jellyfish polyps are consistently induced to metamorphose by administration of triiodothyronine, diiodotyrosine, monoiodotyrosine, and thyroglobulin, as well as by previously reported iodide and thyroxine (Spangenberg, ′67). Jellyfish synthesize three protein‐bound iodocompounds during strobilation and excrete one protein‐bound compound into the medium. The culture medium containing the iodocompound induced strobilation in the absence of iodide. The protein‐bound compound found in the culture medium and in the polyps is tentatively identified as thyroxine since it consistently was co‐chromatographed with thyroxine in five different solvent systems.

No localized site of intense concentration of 131NaI or of 125I‐T4 was found in the polyps during initiation of strobilation. Both substances were present in greater amounts at the distal, differentiating end of the organisms than at the base, particularly during the early pre‐segmentation strobilation period. Distribution of these two substances between the tissue layers during strobilation indicates that thyroxine may be ingested orally and iodide taken up across the epidermis.

The strobilation system of Aurelia represents the simplest system in which thyroxine is functional and is probably synthesized. This system, therefore, offers new opportunities for the study of the action of thyroid hormone under less complicated developmental conditions than are found in higher organisms.
A study of the effects of ethidium bromide on the ultrastructure of sea urchin embryos
Authors: Geuskens M.
Published: June 2005

This study describes the ultrastructural changes which result from treatment of sea urchin embryos (Paracentrotus lividus) with ethidium bromide, particularly in: the chromatin (formation of a network of materials of various densities or clumping), the nucleoli (no typical granular region), the mitochondria (swelling, reduction in the number of cristae, appearance of numerous dense granules or a dense mass in the matrix) and the heavy bodies (enlargement and prolonged existence).

The experimental conditions were as follows:

Treatment with different doses from ten minutes before fertilization continued for 90 minutes afterwards.

Treatment with a high dose (100 μg/ml) for three hours at the young blastula stage.

Treatment with a low dose (15 μg/ml) for 48 hours from fertilization onwards.

Active nucleo‐cytoplasmic exchange visibly occurs across the nuclear membrane of control embryos throughout development: emission of multivesicular ergastoplasmic sacs into the cytoplasm up to the blastula stage and formation of ergastoplasmic diverticulae by its outer leaflet from the gastrula stage onwards. These signs of nuclear membrane activity are also observed in embryos treated with ethidium bromide.
Studies on the sterility phenotype of the pleiotropic mutant fused of Drosophila melanogaster
Authors: Fausto‐Sterling Anne
Published: June 2005

A further description of the sterility phenotype for three different alleles of the female‐sterile mutant fused of Drosophila melanogaster is reported. It was found that:

No more than 35% of the eggs laid by females homozygous for fu, fu57a, and fu59 when mated to Oregon R males are capable of hatching into larvae. This percentage is unaffected by the presence of a Y chromosome in the mother. The data indicate that the mechanism of control in the activation of the wild type allele of fused in an embryo from a homozygous fused mother is imprecise.

Homozygous fu, fu57a, and fu59 females show apparently allelic differences in the number of eggs they are capable of laying.

Heterozygous fu59 females have a somewhat reduced egg laying capacity when compared to Oregon R females if they are the daughters of either homozygous or heterozygous fu59 mothers but show no such difference if they are the daughters of Oregon R mothers. These data are consistent with the idea that fused is hypomorphic.
Behavioral thermoregulation by the white rat at high ambient temperatures
Authors: Clark Richard V.
Published: June 2005

At ambient temperatures greater than 40°C, rats must spread salvia on themselves to prevent lethal hyperthermia. This study examined the effect of other behavioral parameters on a rat's ability to thermoregulate. The animals were exposed to 42°C in a cylindrical wire cage; records of time spent saliva spreading and moving about the cage were made; and body temperatures were measured with thermocouples implanted in the animals' abdominal cavities. Very little time spent saliva spreading was necessary for an animal to become thoroughly wetted on its ventral surface. Once wetted, an animal's thermoregulatory ability depended on its amount of locomotion. Animals which spent a considerable amount of time climbing about the cage were unable to stabilize their body temperatures and suffered increasing hyperthermia. Those which had low levels of locomotion were able to hold a constant body temperature for an hour or more. Several of the animals were given seven successive exposures to 40°C, followed by a second exposure to 42°C. Most of these animals showed greatly improved thermoregulatory abilities in the second exposure at 42°C as compared with the first, and this improvement was associated with markedly decreased locomotion. Several animals showed increased saliva spreading, but this change was not well correlated with improved thermoregulatory ability. It was concluded that low levels of locomotion are essential for evaporative cooling by saliva spreading to be adequate, and that repeated exposures to heat can modify an animal's behavior to the type associated with prolonged thermoregulation.