bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of thyroxine on the normal development of the pancreas in Rana pipiens larvae
Authors: Race James , Robinson C. , Terry Robert J.
Published: June 2005

Comparative studies were made of the exocrine pancreas in normal, thyroidectomized, and thyroxine treated Rana pipiens tadpoles during various stages of development. The weight of the pancreas as milligram per cent body weight (mg% B.W.) is greatly reduced during both artificially induced and natural metamorphosis. During natural metamorphosis the reduction in mg% B.W. of the pancreas begins in the early larval stages and continues in a consistently decreasing pattern through the final stages with the maximum reduction (69%) occurring by the mid‐larval stages (XVI‐XX).

In thyroxine treated tadpoles, reduction in mg% B.W. of the pancreas is directly proportional to hormone concentration and the relative weight of the gland is significantly less than that observed in any of the controls of equivalent limb stages even though the absolute weight of the gland has increased over that of the earliest stages (I–V). The pancreas of the thyroidectomized tadpoles showed no significant difference in mg% B. W. when compared to that of a normal control of equivalent limb stage range. Histological investigation of the pancreas revealed no evidence of widespread cellular necrosis of the exocrine elements. Some acinus disorganization, typified by large spaces in the connective tissues and a syncytial nature of the acinar cell cytoplasm, can be seen in the later stages. A discussion of the possible role of thyroid hormone in the normal development of the pancreas is presented. It is concluded that reduction in the mg% B.W. of the pancreas is a naturally occurring phenomenon during metamorphosis resulting from intestinal evacuation and water loss. The water loss may be influenced and regulated indirectly by thyroxine through an effect on cellular and subcellular membrane permeability.
X‐irradiation of lateral‐line primordia in Amblystoma
Authors: Piatt Jean
Published: June 2005

Embryos of Amblystoma punctatum were x‐irradiated with 500 r to 2,000 r at stages 28–30. A rectangle of ectoderm including postauditory placodal material was transplanted orthotopically from the right side of irradiated embryos to nonirradiated hosts of the same age. Controls consisted of the same operation between non‐irradiated embryos. Animals were studied at stage 46 to determine the effects of irradiation upon development of lateral‐line migratory primordia, nerves and ganglion.

The dorsal lateral‐line was most affected by irradiation, averaging approximately 90% less organs and 85% less nerve fibers than normal. Midbody lateral‐line averaged approximately 65% less organs and 55% less nerve fibers. There was no reduction in number of ventral lateral‐line organs and scarcely any in number of nerve fibers. Number of lateralis ganglion cells averaged approximately 62% less than normal. Control animals developed normal numbers of organs and nerve fibers in all three lateral‐lines and showed no appreciable reduction of ganglion cells on the operated side.

X‐irradiation affects the migration of lateral‐line primordia as well as the proliferation or maturation of Xth lateralis nerve cells. Normality of the ventral lateral‐line in these experiments requires further investigation.
Effects of hormones on adult frog (Rana pipiens) testes in organ culture
Authors: Basu S. L. , Nandi Jean , Nandi S.
Published: June 2005

Testes from adult Rana pipiens were maintained for five days in organ culture in a chemically defined medium consisting of CulturSTAT 199 organics dissolved in amphibian Ringer's solution. Various steroid hormones and vitamins, when added individually to testicular organ cultures, were found to be toxic. Toxicity of these substances was reduced or abolished by the simultaneous addition of protein hormones. Most combinations of protein hormones resulted in improved maintenance of cultured testes over that obtained in hormone‐free media. The combinations FSH + LH, and FSH + LH + insulin + testosterone, resulted in almost complete testicular maintenance in vitro and, in some circumstances, even stimulation of spermatogenesis. However, in no case were secondary spermatocytes maintained in these organ cultures, and spermatogenesis could be stimulated only through the first meiotic division.

Testosterone, previously demonstrated in vivo to inhibit spermatogenesis at the secondary spermatogonial level, exerted no such inhibitory action in vitro. At the dose level used, testosterone appeared to have a slightly deleterious, but nonspecific, effect on testicular maintenance.

Seasonal variations in the sensitivity of the testis to hormones and other conditions in vitro were noted. Testicular maintenance was relatively poor, even in hormone‐supplemented media, during the period of active spermatogenesis (summer). In contrast, gonadotropin‐induced stimulation of spermatogenesis in vitro occurred only in testes taken from winter frogs, at a time when the testicular epithelium is presumed to be maximally sensitive to gonadotropic action.
An electrophoretic study of proteins in chick embryonic fluids
Authors: Geelhoed Sally E. , Conklin James L.
Published: June 2005

The protein fractions of 7–18 day chick serum, allantoic and amniotic fluid and egg white were demonstrated by acrylamide gel electrophoresis.

The similarity in protein fractions suggests that most of the amniotic fluid proteins are derived from egg white while serum contributes most of the allantoic fluid proteins.

Several protein fractions which are unique to the respective fluids may be produced by components of the extraembryonic membranes.

The nature of the proteins found in both serum and allantoic fluid suggests a selective transfer of protein between the two fluids.
Effect of tetracycline on osteogenesis in vitro
Authors: Saxén Lauri
Published: June 2005

The effect of tetracycline on developing bones was explored in organotypic tissue culture. Such culture conditions proved to be suitable for certain experiments dealing with the “teratogenic” effect of drugs, and the first part of the paper examines the possibilities, limitations and fallacies of this technique.

Embryonic mouse bones cultivated in vitro show rapid incorporation of tetracycline, and after 30 minutes of cultivation a definite fluorescence is seen. The drug is incorporated at least into two fractions: one which is rapidly released after the withdrawal of tetracycline and one which remains in the calcium‐containing zones of the bone.

Tetracycline in concentrations of the order of 5 μg/ml completely inhibits the elongation of the calcified zone of the bone rudiments and the increase of their total calcium. However, experiments with labeled calcium still show an incorporation in the presence of tetracycline although no cumulative uptake is seen. The results thus indicate the existence of a rapidly incorporated calcium fraction which is independent of tetracycline.

The inhibition of calcification is reversible up to some five days of treatment, whereafter a transfer to normal medium does not lead to a recovery, and the mineralization seems to be irreversibly blocked.

It is concluded that the results speak in favor of the theory of a direct action of tetracycline on the formations of the bone salts, rather than interference with enzymatic activity dependent on divalent cations.
The intra‐embryonic and extra‐embryonic distribution of hydroxyproline in the hen's egg
Authors: Mottet N. Karle , Hall Harold E.
Published: June 2005

Recent modifications in the biochemical method for determining hydroxyproline have improved its accuracy. The increasing use of fibroblasts from chick embryos for production of collagen necessitates the reinvestigation of hydroxyproline production in chick embryos. The levels of proline and free and bound hydroxyproline were determined in embryonated hen eggs by the method of Prockop and Udenfriend. Determinations on the yolk, white, and embryo were done separately. Analysis of specimens taken from the onset of incubation to the thirteenth day of incubation revealed the presence of 20 to 80 μMoles of proline in each compartment throughout the period of study. Free hydroxyproline was present in the yolk and white at a constant low level of less than 1 μMole per egg. Hydroxyproline (total: bound and free) was first detected in five day embryos. By nine days the level was 0.5 μMoles; at 11 days, 1.5 μMoles, and at 13 days, 4.25 μMoles. The increase in hydroxyproline when calculated per milligram of wet weight of embryo approximated a straight line.
The genetic control of sea urchin development: A chromatographic study of protein synthesis in the Arbacia punctulata Embryo
Authors: Ellis Charles H.
Published: June 2005

An analysis of the problem of embryonic differentiation in terms of protein synthesis was carried out in the embryo of Arbacia punctulata. The problem was approached with the technique of ion‐exchange chromatography of the embryonic proteins soluble in 0.5 M sodium chloride. Synthetic activity was measured as the incorporation of radioactive amino acids into protein fractions. It was seen that the complexity of the embryo's protein‐synthetic repertoire increases during early development indicating that differentiation at this level can be detected during early development.

The antibiotic Actinomycin‐D was found to inhibit most of the specific protein syntheses during late development, while inhibiting fewer in early development. This indicates that most of the differential changes in early protein‐synthetic profiles occur under control of the readout of the embryo's stable messenger RNA. However, most differential changes associated with later development seem to be under control exerted at the gene level. Both translation‐level and transcription‐level control mechanisms appear to be active simultaneously at the stages of development analyzed.

The inhibition of DNA‐dependent RNA synthesis, and of further differentiation beyond blastula, was found to be reversible, even after developmental arrest had occurred. The inhibition of protein synthesis was also reversible on removing embryos from the presence of the antibiotic. Since normal development and normal protein‐synthetic profiles are seen following this release of inhibition, it is concluded that there is no stringent requirement for the gene‐directed synthesis of any specific protein during the first 18 hours of development, in order for normal larval development to occur.
Effect of metopiron (SU‐4885) on luteinizing hormone and corticosteroid‐induced ovulation and spawning in hypophysectomized catfish, Heteropneustes fossilis (Bloch)
Authors: Sundararaj Bangalore I. , Goswami Shashi V.
Published: June 2005

Experiments were performed to evaluate the effect of metopiron on luteinizing hormone and corticosteroid‐induced ovulation and spawning in three‐day hypophysectomized gravid catfish, Heteropneustes fossilis. Pretreatment of hypophysectomized gravid females with metopiron greatly attenuates the ovulatory capacity of LH, whereas desoxycorticosterone acetate and hydrocortisone acetate induce ovulation and/or spawning regardless of pretreatment. These findings indicate that LH may not act directly on the ovary but via the interrenal. The possible mechanisms involved are discussed.
An analysis of the chemical control of polarized form in hydra
Authors: Lesh Georgia E. , Burnett Allison L.
Published: June 2005

Development and maintenance of polarized form in Hydra is controlled chemically by a diffusible factor, concentrated in, and probably produced by nerves in the hypostomal region of the animal. This polarizing (or inductive) factor may be isolated from tissue homogenates of Hydra. It is recovered from the supernatant fraction after centrifugating the homogenate at 25,000 × G for 50 minutes. Concentrated amounts of the extracted substance induce “heteropolarity” in regenerating annuli of Hydra pirardi. Heteropolarity is expressed through the development of supernumerary tentacles and “head” regions. Over 40 tentacles may be induced in heteropolar individuals, compared to the normal number of eight. The polarizing effect of this material is not species specific; H. viridis, H. littoralis, and H. pirardi contain extractable amounts of the active factor. Heterogeneous invertebrate tissue such as Dugesia extract does not induce heteropolarity. Because the active material is both dialyzable and can be digested by trypsin, it is suggested that it may be a peptide.

Although the mechanism of action of the polarizing component has not been fully determined, the active material probably is bound by the tissues of the assay animal during the incubation period. It appears to act by directing the differentiation of interstitial cells. Interstitial cells in the annulus tested probably bind excessive amounts of the inducer and differentiate into nerve cells. Secretion of additional inducer from these nerve centers initiates the heteropolar state. The fact that heteropolar animals possess more extractable material per animal than do normal unipolarized hydra substantiates this conclusion, and suggests that a single inductive substance, varying quantitatively apico‐basally, controls the direction of differentiation of neoblast cells in Hydra.
Studies on the mechanisms of ammonia tolerance of the guano bat
Authors: Studier Eugene H.
Published: June 2005

The ammonia concentrations in many day‐roosts occupied by the guano bat, Tadarida brasiliensis, are frequently high enough to produce respiratory discomfort and distress and sometimes reach levels lethal to humans. Investigations were begun in an attempt to elucidate some of the mechanisms of ammonia tolerance of the guano bat. Initial findings show that the blood pH of the guano bat is 7.66 and remains constant during extended exposure to a high concentration of atmospheric ammonia. The efficiency of respiratory filtration of ammonia was measured by noting the increase above normal in total blood nitrogen and non‐protein nitrogen after exposing the blood in vivo and in vitro to highly ammoniated air. From the difference in these two values the amount of ammonia filtered by the respiratory tract was obtained. At ammonia levels of 3,000 parts per million in the air, the bat removes 30–35% of this noxious gas; thus, the existence of an efficient ammonia filtering system is indicated. The filtering mechanism is probably dependent upon the mucous of the respiratory tract, and the filtering efficiency is a function of its rate of production and chemical nature. The observed in vivo increase in blood non‐protein nitrogen resulting from exposure to highly ammoniated air may be attributed to ammonium ions. Ammonia is exhaled by the guano bat upon its return from highly ammoniated to normal air. Renal excretion of fixed base is probably not an adaptive feature contributing to the high degree of ammonia tolerance exhibited by T. brasiliensis.
Some aspects of sexual polymorphism in Chlorohydra viridissima
Authors: Stagni Anna
Published: June 2005

Protracted observations on a wild population of Chlorohydra viridissima revealed a sexual polymorphism, expressed by the occurrence all together of male, female and hermaphrodite specimens. The hermaphrodites were either simultaneous or protandrous or protogynous. Careful culturing of several clones under strictly identical environmental conditions strongly indicated a genetic basis of such differences and suggested a polyfactorial sex‐determining system. Andro‐, medio‐ and gyno‐hermaphrodite clones, which more or less tended to shift towards pure male or pure female sex conditions, were detectable. Andro‐ and gyno‐hermaphrodite clones showed less tendency to become sexual. Such a condition is typical of an “unbalanced hermaphroditism” which serves to maintain the species in a mainly hermaphrodite state.
The role of interstitial cells in the maintenance of hydra. IV. Migration of interstitial cells in homografts and heterografts
Authors: Diehl Fred A. , Burnett Allison L.
Published: June 2005

Normal and mustard‐treated halves of Hydra pseudoligactis and Hydra pirardi were grafted in distal‐proximal combinations. In all cases H. pseudoligactis grafted more readily than H. pirardi. Mustard‐treated H. pseudoligactis were grafted to normal H. pseudoligactis after various intervals from the time of treatment. Interstitial cells migrated from the normal portions into treated portions lacking them and within 5 to 10 days the animals appeared normal.

Normal portions of H. pseudoligactis and H. pirardi were grafted together and in some cases they remained attached for 60 days. Large numbers of interstitial cells accumulated in each portion, near the graft junction. After 15 days, some of these interstitial cells differentiated into cnidoblasts. Interstitial cells migrated from a normal portion of H. pirardi into a mustard‐treated portion of H. pseudoligactis. Differentiation of interstitial cells into cnidoblasts was observed in the host tissue. In heterografts between normal H. pseudoligactis and mustard‐treated H. pirardi there was no exchange of interstitial cells. There was, however, an accumulation of interstitial cells near the graft junction.

In both species successful homografts were made between mustard‐treated portions, indicating that interstitial cells are not required for acceptance of grafts. Grafts between mustard‐treated H. pirardi and mustard‐treated H. pseudoligactis showed less initial acceptance than any of the other groups. The rate of detachment was very high in this group. It was suggested that mustard treatment may inhibit production of substances required for adherence of cells.

The results are discussed in terms of possible mechanisms controlling interstitial cell migration, division and differentiation.
Unidirectional mating type changes in individual cells from selfing cultures of Paramecium aurelia
Authors: Taub Stephan R.
Published: June 2005

Individual cells participating in mating reactions in selfing cultures of syngen 7, P. aurelia, were isolated and tested to ascertain the mating type they were expressing at the time of isolation and the mating type they were expressing several hours later. In this way a number of cases were discovered in which cells initially expressing mating type XIII had changed to type XIV A transient, hermaphrotypic stage may be involved in this change. The possible significance of these observations is discussed with regard to the process of mating type expression.
Influence of monovalent cations on the growth of Hydra littoralis
Authors: Lenhoff Howard M.
Published: June 2005

Li+, Cs+, Rb+, and K+ inhibit the clonal growth rate of Hydra littoralis and, depending upon conditions, can be toxic to the animals. These effects are counteracted by increasing the concentration of Na+ in the environment. In contrast to its inhibitory effect, K+, when in the presence of high concentrations of Na+, increases the growth rate of hydra significantly. Choline and histidine also increase the growth rate, but to a lesser extent. Various combinations of the monovalent ions lead to specific structural and behavioral changes in the animals.
Nutritional requirements for the realization of regulative (repair) capacities of young chick blastoderms
Authors: Spratt Nelson T. , Haas H.
Published: June 2005

Studies of the regulative (repair) capacities of young chick blastoderms in ovo and explanted in vitro on culture media varying in their growth promoting properties clearly indicate that these capacities are realized fully only under the most optimal nutrient conditions. Thus the ability of an explanted part of a young blastoderm to form a bilaterally symmetrical embryo body depends not only on the region of the blastoderm isolated, on its intrinsic growth potentiality and on its size (cell number) but also on the growth promoting properties of the culture medium. Realization of regulative potentiality goes hand‐in‐hand with realization of growth (or other synthetic) potentiality.
Differentiation of pulsating regions in genital imaginal discs after culture in Vivo (Drosophila melanogaster)
Authors: Nöthiger Rolf , Oberlander Herbert
Published: June 2005

After male genital discs of Drosophila melanogaster had been cultured for 8 to 19 days in the abdomens of adult female flies a number of them contained rhythmically pulsating regions. The percentage of discs which pulsated was dependent on the age of the donor larvae, the length of culture time, the presence or absence of ring glands and on the age of the host. The best conditions for the differentiation of pulsating discs were an old disc in a young host to which a ring gland from a mature larva was added.

In normal development the genital disc after metamorphosis gives rise to the genital apparatus with morphologically differentiated ejaculatory duct, sperm pump and paragonia (soft parts) which contract rhythmically. In the cultured discs, however, the contractions are not accompanied by morphogenesis.

The prospective fate of the pulsating region of a disc is mostly contracting soft parts of the genital apparatus, whereas the non‐contracting area forms mostly chitinous parts (anal plates, claspers, lateral plates). Other discs, e.g. leg discs and wing discs, which in normal development do not form involuntary muscles also do not contract after culture in vivo.

It is concluded that the formation of pulsating regions represents a phase in the normal differention of genital discs. Some of the conditions which lead to pulsation are established early in the third instar within the cells which form the pulsating regions. Their full differentiation is influenced by hormones secreted by the ring gland.
Temperature‐induced alterations in hepatocyte structure of rainbow trout (Salmo gairdneri)
Authors: Berlin J. D. , Dean John Mark
Published: June 2005

Electron microscopic examination showed that hepatocytes from rainbow trout (Salmo gairdneri) possess abundant amounts of rough endoplasmic reticulum. Particulate materials, presumably synthesized in the endoplasmic reticulum and transported to the Golgi apparatus, were more numerous in hepatocyte Golgi complexes of trout acclimated at 5° C compared to fish acclimated at 18° C. This temperature‐induced structural modification is thought to reflect an increased secretory activity on the part of the hepatic cell as a result of the organism's adaptation to low temperature.
The Source and identity of a regeneration‐inhibiting factor in hydroid polyps
Authors: Davis Lary V.
Published: June 2005

It has been found that cell‐free homogenates of tentacles and hydranths, but not of stems, are capable of inhibiting distal regeneration in Corymorpha palma. The results of several experiments on this species, and on Chlorohydra viridissima, Hydra littoralis, and H. pirardi have indicated that the observed inhibition was caused mainly by a nematocyst toxin, tetramethylammonium.

This conclusion is supported by three independent lines of evidence: (1) direct counts of the nematocysts contained in tentacle, hydranth, and stem homogenates has shown that the amount of inhibitory activity is correlated with the number of nematocysts present; (2) tetramethylammonium was found to inhibit distal regeneration in transected polyps; and (3) paper chromatography of acetone extracts has demonstrated the presence of this quaternary ammonium compound in all species examined.
Diploid and haploid hybridization of different populations of the Rana pipiens complex. I. Experiments with females from Mexico
Authors: Moore John A.
Published: June 2005

Diploid and androgenetic haploid hybrids have been made with eggs of Rana pipiens from the Mexican locality Oaxaca and sperm from individuals of the pipiens‐complex from nine localities in Mexico and the United States. The diploid hybrids are normal or nearly so when the males are from localities as distant as Florida, Vermont, or Wisconsin. They are very abnormal when the males are from a locality in the nearby Gulf Coast lowlands, San Andres Tuxtla. Haploid hybrids on the other hand are almost always very abnormal. This suggests that there has been considerable evolutionary divergence in the local populations of the pipiens‐complex and that androgenetic hybridization is a useful technique for detecting this divergence. A few experiments with eggs with another Mexican locality, Zamora, are also reported.
Cleavage of sand dollar eggs with altered patterns of new surface formation
Authors: Rappaport R. , Ratner J. H.
Published: June 2005

The normal pattern by which new surface is formed in cleaving echinoderm eggs is incorporated as an intrinsic part of several general theories of cytokinesis. The purpose of this investigation was to determine whether the normal pattern is necessary for cleavage in sand dollar eggs. Denuded Echinarachnius parma eggs become sticky in citrated, calcium‐free synthetic sea water. When such eggs are pressed against clean glass or plastic, the surfaces adhere tightly. Cells were stuck to flat, cylindrical and hemispherical concave surfaces. Cleavage took place despite bilateral constraint of large portions of the surface. Constraint of the polar and subpolar surfaces begun before or at the beginning of division did not prevent cleavage. Only when the surface next to the furrow was held was division slowed or stopped. Normal, extensive polar and subpolar expansion is not a prerequisite for cleavage. An egg can cleave if its furrow can exert sufficient force to overcome the resistance to deformation of the surface outside the furrow. No preliminary step in which local areas are induced to weaken or relax appears necessary.
Analysis of the effects of neutron radiation on developing Triturus embryos
Authors: Suzuki Akio
Published: June 2005

Triturus pyrrhogaster embryos at various stages of development were exposed to neutron radiation, and the effects were studied externally and microscopically. For an analysis of the abnormality in the nervous system produced by the irradiation, the difference in neutron‐sensitivity between the presumptive neural ectoderm and the chordamesoderm was also investigated in vitro.

Neutron‐sensitivity descreased from the cleavage stage to the tail‐bud stage; in the latter no effect was observed. Rather high frequency of abnormality was observed in mid‐blastula and early gastrula stages. The abnormalities consisted of microcephalia, acephalia, cyclopia, axial distortion, and edema. The nervous system in particular was very sensitive to neutron radiation.

The irradiated presumptive neural ectoderm wrapping non‐irradiated chordamesoderm underwent cytoloysis in vitro and no differentiation occurred in it, while the irradiated chordamesoderm wrapped in the non‐irradiated ectoderm was never affected and retained its inducing and self‐differentiation ability. The results suggest that the irradiated and damaged cells release a cytotoxic agent.
Shedding of the zona pellucida by the rat blastocyst
Authors: Dickmann Z.
Published: June 2005

It is known that rat blastocysts shed their zonae pellucidae during the afternoon of day 5 of pregnancy. The aim of the present study was to determine whether one can detect any morphological changes in the zonae before, during, and after shedding. From 74 rats killed between 11:00 and 19:30 hours on day 5 pregnancy, 711 blastocysts were recovered: 407 were zona‐encased, 293 were zonafree, and 11 were half‐way out of the zona. Preshedding changes were observed in the zonae of 34 of the zona encased blastocysts. The changes were confined to the regions of the embryonic and abembryonic poles. It was concluded that the blastocyst can escape from its zona by way of either the embryonic or the abembryonic pole. The entire process of zona shedding seems to be very rapid, since only 45 blastocysts (i.e., 34 exhibiting preshedding changes and 11 being half‐way out of the zona), out of the 711 recovered, were observed during the process of shedding. Theoretically, for every zona‐free blastocyst, an empty zona should have been recovered. However, the 293 zona‐free blastocysts recovered were matched by only seven empty zonae. The reason for the rapid disappearance of the zona after shedding was not determined.
Nature of induced persistent vaginal cornification in mice. II. Effect of estradiol and testosterone on vaginal epithelium of mice of different ages
Authors: Kimura T. , Nandi S. , Deome K. B.
Published: June 2005

Immature female mice of the BALB/c strain were treated with 25 m̈g/day of estradiol or testosterone for five days, beginning at various ages. Ovary‐independent persistent vaginal cornification was obtained only when the treatment was started within 24 hours after birth, although some irreversible hyperplasia of the epithelium was observed in mice treated with estradiol beginning at three days of age. Ovary‐dependent persistent vaginal estrus occurred when treatment was begun at ten days or earlier with estradiol, and at seven days or earlier with testosterone.

Vaginae of one‐day and three‐week‐old BALB/c mice were transplanted into one‐day‐old and into three‐week‐old syngeneic hosts. Hosts were treated with various doses of estradiol. Irrespective of the age of the hosts, ovary‐independent hyperplasia or cornification occurred in transplants from one‐day‐old donors. Transplants from three‐week‐old donors showed only ovary‐dependent cornification. The results suggest, however, that both vaginal tissue age and host age play some role in determining the nature and occurrence of steroid‐induced persistent vaginal changes.
RNA synthesis in relation to DNA replication in synchronized Chinese hamster cell cultures
Authors: Klevecz Robert R. , Stubblefield Elton
Published: June 2005

Selection and reversal of Colcemid‐blocked mitotic cells yielded synchronous populations of 90% purity, representing 10% of the original culture. This system gave sufficient material to allow the isolation of RNA, pulse‐labelled with tritiated uridine, in various stages of the cell cycle. Sucrose gradient sedimentation of such isolations showed that incorporation of the isotope into the most rapidly sedimentating RNA fractions was greater in S and G2 than it was in G1. In addition, the total amount of labelled RNA in a given pulse was greater following the initiation of DNA synthesis. The rate of RNA synthesis increased following mitosis and reached an initial plateau after one hour. A second increase in rate was observed three hours later, or about one hour after the beginning of DNA synthesis. Several peaks in synthetic rate seemed to be superimposed on the overall increase. Short pulse times appeared to accentuate the discontinuous nature of the rate curve, while longer pulse times made the cyclic peaks more obvious. Inhibition of DNA synthesis with 1 mM thymidine prevented the change in RNA synthetic rate from occurring.

The doubling in RNA synthetic rate is interpreted to be the result of replication of the functional DNA templates. The periodic fluctuations in rate suggest that, although the potential for RNA synthesis is doubled with DNA replication, the rate at any instant is not totally determined by the gene dosage.
Activity of aminopeptidases (amino naphthylamidases) during early limb bud differentiation in the chick embryo
Authors: Karle N. Mottet
Published: June 2005

The morphologic changes in the differentiation of chick embryo limb buds from Hamburger‐Hamilton stages 19 through 34 were correlated with biochemical measurements of hydroxyproline biosynthesis and aminopeptidase enzyme activity. The distribution and quantitative approximations of collagen, mucopolysaccharides and aminopeptidase activity were observed by histochemical methods. Aminopeptidase enzyme activity increased after four days of incubation (stages 24‐25) concomitantly with the formation of precartilage masses (development of lakes of intercellular mucopolysaccharides). Histochemical preparations revealed the mesodermal cells in the precartilage masses to have an increased aminopeptidase enzyme activity. It was also noted that the enzyme activity in the ectodermal ridge was in excess of that found in the subjacent mesodermal cells or adjacent epithelium. Wet weights of limb buds revealed a constant rapid rate of growth throughout the period of study. However, aminopeptidase enzyme activity was not biochemically detectable until the onset of increased mucopolysaccharide synthesis, when cartilaginous differentiation begins. At five days (stage 26), hydroxyproline was first detectable biochemically and collagen histochemically. This was concomitant with the onset of hydroxyproline production in the embryo in toto, reported previously. The curve of acceleration of hydroxyproline production per milligram of bud mesoderm was less than the acceleration of aminopeptidase activity. The aminopeptidase enzyme activity in the premuscle masses and ectodermal‐mesodermal interface, where histochemically detectable collagen was located, was at the same level as the intervening tissues. After stage 19, limb bud mesoderm was cultured in vitro for seven days. Hydroxyproline production was not biochemically detectable and collagen not stainable, though mucopolysaccharide production was extensive. No muscle differentiation occurred and cell proliferation was minimal. Aminopeptidase enzyme activity had increased 20‐fold. It is suggested that at least part of the aminopeptidase enzyme activity of limb buds is associated with mucopolysaccharide synthesis. There was no evidence that it was associated with mesodermal cell proliferation, muscle differentiation, or hydroxyproline production.
Glucose metabolism and chick neurogenesis. II. 6‐phosphofructokinase and aldolase activity in the embryonic brachial spinal cord
Authors: Burt Alvin M.
Published: June 2005

Microquantitative procedures were employed for the assay of 6‐phosphofructokinase (6‐PFK) and aldolase activity in the brachial spinal cord of chick embryos from four and one‐half to 21 days' incubation. Activity of 6‐phosphofructokinase increased 9.2‐fold from stage 25 to stage 46. The ontogenetic pattern was characterized by two periods of rapid increase in enzymatic activity, from stage 25 (4 1/2 days) to stage 29 (6 days) and from stage 36 (10 days) to stage 42 (16 days). Aldolase activity increased 1.7‐fold from stage 25 to stage 46. The ontogenetic pattern showed a 50% increase in enzymatic activity during the 48‐hour period from stage 36 to stage 38. Several transient changes in level of activity for both 6‐phosphofructokinase and aldolase are described. The temporal patterns of both enzymes are discussed in relation to glucose‐6‐phosphate dehydrogenase activity, glucose metabolism and functional differentiation. The results of the present study suggest that glycolysis is relatively low during the early phases of neurogenesis, increasing just prior to a rapid decline in pentose cycle activity, and that glycolytic metabolism then increaases during the period of functional maturation.
The cell cycle during lens regeneration
Authors: Zalik Sara Eisenberg , Yamada Tuneo
Published: June 2005

The cell cycle in the proliferating zone of the lens regenerate of the adult newt, Triturus viridescens, was investigated by autoradiography using H3‐thymidine as the labeled precursor. For estimation of the DNA synthetic period (S period), we followed the changes in frequency of labeled mitoses after injection of the labeled precursor in 15‐day regenerates. The synthetic index of regenerates (number of labeled cells/number of cells in proliferation zone) was measured at 5, 8, 11, 15, 20, 25, and 30 days after lens removal.

For 15‐day regenerates, the DNA synthetic period was estimated to be ca. 19 hours, the G‐2 period ca. 2 hours, the G‐1 period ca. 40 hours, and the cell generation time ca. 65 hours. The synthetic index increased with the progress of regeneration. Using the DNA synthetic period found for 15‐day regenerates, we calculated the average generation time for each stage of regeneration. It decreases from 11 days at stage I to 2.5 days at stages X and XI.
The course of mauthner axons in Janus‐headed Xenopus embryos
Authors: Swisher John E. , Hibbard Emerson
Published: June 2005

Several studies have demonstrated that rotated segments of the embryonic hindbrain will repolarize to conform with the host gradients, and that the developing Mauthner (M‐) axons reorient accordingly, tending to follow a normal course. To investigate the response of these axons to an irreversibly antagonistic polarity, we prepared Janus‐headed telobionts in which initially descending M‐fibers would begin to ascend upon entering the opposite head. About one‐third of the fibers became disoriented within the graft region, evidently as a result of inadequate healing. The remaining two‐thirds traversed the graft and continued to ascend the opposite head past the medulla and into the midbrain and forebrain. The apparent ease with which these M‐axons made their way upgradient may have been enhanced by (1) inability of growth cones to respond to head‐on gradients; (2) selective fasciculation; (3) weakening of the rostrocaudal (longitudinal) gradients as a result of birostral telobiosis; and (4) growth through intact tissue.

Most of these M‐axons negotiated a rostrocaudal polar inversion in much the same way as commissural fibers normally do in passing from lateral to medial, then from medial to lateral. We suggest that crossing fibers may be impeded by their encounter with the contralateral antagonistic gradient, and that for this reason the rostrocaudal directional tendencies of decussating axons are expressed only after the midline has been crossed. This hypothesis does not require assumptions of right‐left specificity or intricately coordinated timing of developmental events to explain decussation.
Nature of induced persistent vaginal cornification in mice. III. effects of estradiol and testosterone on vaginal epithelium in vitro
Authors: Kimura T. , Basu S. L. , Nandi S.
Published: June 2005

Vaginae of newborn BALB/c mice were cultured in vitro with or without 1 μg/ml of estradiol for 1‐3 days, and then transplanted into 4‐day‐old syngeneic hosts. Intermittent or persistent estrus was indicated by smears from many of these transplanted vaginae which had previously been cultured with estradiol, even after ovariectomy of the hosts. Those transplants which had been cultured for 2‐3 days with estradiol had thickened epithelium (hyperplasia), and cornification was observed histologically in some. In contrast, where estradiol was not used in the cultures, transplanted vaginae (controls) showed no cornification after host ovariectomy. Histologically, the epithelium of these controls was thin and in most cases slightly mucified. Vaginae of 3‐week‐old BALB/c mice, cultured with or without estradiol, resembled the controls, derived from newborn donors.

When vaginae from newborn donors were cultured with 0.01‐ 5 μg/ml of estradiol for three days, and then transplanted into 4‐day‐old syngeneic hosts, ovary‐independent hyperplasia and cornification were observed in a number of the transplants. When vaginae from newborn donors were cultured in 0.001 μg/ml of estradiol, or in 0.001‐5 μg/ml of testosterone, neither persistent cornification nor hyperplasia was observed subsequent to transplantation. These results suggest that the mechanism of induction of persistent vaginal estrus in vivo by estradiol and by testosterone may be different. Whereas estradiol may act directly on the vaginal epithelium of newborn mice, the effect of testosterone would appear to be indirectly mediated.
Differentiation of black‐red melanin in the fowl: Interaction of pattern genes and feather follicle milieu
Authors: Brumbaugh J. A.
Published: June 2005

The multiple‐allelic E pattern series in the fowl is the major controller of black‐red melanin distribution. Embryonic grafting experiments showed that the melanoblasts of each pattern are autonomous. However, fasting and thyroxine‐feeding experiments with the normal (e+) adult changed the melanin distribution and showed that other factors also influence differentiation. It is suggested that the interaction between these genetic and environmental factors takes place in the zone of differentiation of the growing feather. The action of this zone upon the normal melanoblst is probably a function of time, and related to feather growth. Rapid movement of melanoblasts through this zone favors eumelanin synthesis, hence black bars appeared on red feathers when stimulated by thyroxine. Slow movement through this zone favors phaeomelanin synthesis, hence, with fasting, red bars appeared. In contrast to normal melanoblasts, the melanoblasts of the other E alleles differ in sensitivity to the action of the milieu in the feather follicle. The insensitive E/E melanoblasts become exclusively eumelanin‐producing melanocytes, while the hypersensitive ey/ey melanoblasts become mostly phaeomelanin‐producing melanocytes. The remaining alleles fall in between these two types in their response.
Effects of hormones on the renal response to unilateral nephrectomy in hypophysectomized rats
Authors: McCreight Charles E. , Reiter Russel J.
Published: June 2005

The roles of selected hormones in restoring the capacity of the remaining kidney following uninephrectomy of hypophysectomized rats to respond by tubular hyperplasia were explored. Autoradiography, using tritiated thymidine, was employed for identifying cells synthesizing new deoxyribonucleic acid within a standard period, a valid measure of mitotic activity. For animals with intact pituitary glands, both cortex and medulla of kidneys remaining three days after uninephrectomy exhibited a 3½‐fold increase in numbers of labeled cells over control levels. The amount of mitotic activity in either region of bilaterally intact kidneys of hypophysectomized animals was not significantly different from that for animals with intact pituitaries, but the compensatory renal hyperplastic response to uninephrectomy was reduced to one‐third. Either a small amount of growth hormone or a much larger amount of anterior pituitary extract, administered subcutaneously twice daily for several days, restored the compensatory response to uninephrectomy to levels obtained in rats with intact hypophyses. Adrenocorticotropic hormone depressed mitosis markedly in control kidneys of hypophysectomized animals and to an even lower level in remaining kidneys. Growth hormone would appear to be a necessary and effective component of the pituitary secretion in permitting compensatory renal hyperplasia to take place. Since prior studies have shown adrenalectomy to promote cellular division in renal tubules, it was assumed that the presently reported depression of renal mitosis by excess adrenocorticotropic hormone was mediated by an overactivity of the adrenal glands.
Studies of frog oviducal jelly secretion. II. Cytology of secretory cycle
Authors: Lee Peter A.
Published: June 2005

Electron microscopy reveals that the secretory glandular cells of the oviduct of Rana pipiens contain granules which may develop from small vesicles with smooth membranes. The latter may represent dispersed Golgi elements, although cytochemical reactions fail to reveal a localized Golgi complex within these cells. Individual granules enlarge throughout the growing season without fusing with other granules. The mature cell is packed with granules, each of which possesses uniquely an interior electron‐dense (dense) part and an electron‐lucid shell enclosed by a smooth membrane. The dense part first appears as a condensed body. As growth proceeds, the dense component branches to form a net‐like pattern within the granule. When the granule has attained its mature size, the dense component appears to revert to a condensed pattern again. Cytoplasmic granules which are observable by light microscopy after staining with toluidine blue at pH 4.0 apparently correspond to the dense component seen in the electron microscope.
Excretory pathways of ammonia and urea in the earthworm Lumbricus terrestris L.
Authors: Tillinghast Edward K.
Published: June 2005

The earthworm Lumbricus terrestris voids ammonia principally via the gut, while urea is voided via the nephridia.

The possible significance of these separate pathways for nitrogenous wastes is discussed.
Behavioral studies of inhibition and integration in the mosquito Culiseta inornata (Williston)
Authors: Owen William B.
Published: June 2005

A study was made of the interaction in the central nervous system of sensory input arising from the simulatneous application of opposing stimuli to receptors on the tarsi and labella of the mosquito. Stimulating chemosensory hairs on the tarsi with 5 M NaCl failed to inhibit the labeller response to sucrose at concentrations above 0.125 M. At lower sucrose concentrations there was a decrease in the number of mosquitoes responding. The application of 5 M NaCl to the tarsal receptors elevated the labellar threshold for sucrose in all subjects tested. This influence of the salt was expressed whether acting on the tarsi in an ipsilateral or contralateral manner. Stimulating the tarsal hairs with 2 M sucrose resulted in a labellar response to NaCl at concentrations of 0.50 M and lower. Ordinarily NaCl is rejected at all concentrations by this mosquito. Evidence was obtained which indicated that the labellar response to NaCl was mediated by the water receptor rather than by the salt receptor.
The osmotic behavior of digestive cells of Chlorohydra viridissima
Authors: Koblick Daniel C. , Yu‐Tu Lorna
Published: June 2005

Digestive cells of Chlorohydra viridissima undergo reversible volume changes when suspended in varying concentrations of sucrose. The cells are isotonic to 50 mM sucrose. At sucrose concentrations higher than 200 mM volume changes are ideal, and correspond to an osmotically inactive volume of 0.71. Below 200 mM, deviations from ideal behavior occur; these indicate the development of an intracellular hydrostatic pressure, which reaches a maximum at about 50 mM. Below this concentration, the pressure remains constant. When suspended in culture medium these cells assume a prolate spheroid shape with axial ratio 0.75 ± 0.07.

In sucrose solutions, the axial ratio undergoes systematic changes; as the sucrose concentration is reduced, the axial ratio slowly increases to a maximum value between 50 and 70 mM. On further dilution of the culture medium it drops rapidly. These shape changes are discussed in terms of the osmotic volume changes observed.
Nucleic acid and protein synthesis in melanocytes of Amphiuma liver: A radioautographic study
Authors: Prasad Kedar N.
Published: June 2005

Nucleic acid and protein synthesis was studied in the melanocytes and hepatocytes of the liver of Amphiuma with H3 thymidine, H3 cytidine and H3 leucine. In this organism, the hepatic melanocytes are highly pigmented (containing an abundance of melanin‐containing organelles, polymelanosomes), have only a small area of non‐pigmented cytoplasm (containing smooth endoplasmic reticulum and no polymelanosomes). The presence of polysomes in both pigmented and non‐pigmented areas could not be demonstrated.

Only an occasional melanocyte and 2% of the hepatocytes were labeled with H3 thymidine. Rate of RNA metabolism in melanocytes was slower than in hepatocytes. Actinomycin D had no significant effect on nuclear incorporation of H3 cytidine in melanocytes, but it inhibited nuclear uptake in hepatocytes by 86% of controls. Cytoplasmic incorporation of H3 cytidine in both cell types was insensitive to actinomycin D treatment.

Protein synthesis, as based on H3 leucine uptake, was less in the pigmented areas than in non‐pigmented ones. Although protein synthesis on the basis of grain count/cell appeared greater in hepatocytes than in melanocytes, the density of grain count was equal after correction for differences in cell size. The incorporation of H3 leucine was not reduced in the melanocytes or the hepatocytes 96 hours after actinomycin D treatment.