bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Effects of Cold and of Hybridity on the Growth of Mice
Authors: Barnett S. A. , Scott Sybil G. 
Published: April 2021

ABSTRACT
Mice of strains A and A2G, born and reared at an environmental temperature of − 3°C, were lighter at the ages from 3 to 16 weeks than controls at 21°C. The body-weight of mice of strain C57BL was unaffected by the low temperature. F1 mice from the cross A × C57BL were heavier than those of the parent strains at both temperatures. Mice from the cross C57BL × A2G, and from the reciprocal cross, were intermediate in weight between the parent strains in the warm, but superior in the cold. The growth of F1 mice was not depressed by cold. Outbred mice, derived from crossing the above inbred strains and G FF, were selected for superior breeding performance in the cold environment. After twelve generations these mice were heavier than controls kept at 21 °C. A2G mice transferred from −3°C to 21 °C at 3 weeks were lighter at that age than controls kept at 21 °C and failed to make up the growth deficit. Their offspring, too, kept at 21 °C, were lighter than the controls. Outbred mice of the twelfth generation in the cold were transferred from − 3°C to 21 °C at 5 weeks. Their offspring, reared at 21 °C, were heavier than the controls which had been bred permanently in the warm; they were also heavier than the outbred mice kept in the cold. This was evidently a result of selection. In all strains the males were heavier than the females. Weights of kidneys, relative to body-weight, were observed in A2G, C57BL and outbred mice. In all three strains they were higher at -3°C. Of the same strains liver weights were raised in the cold in C57BL and outbred mice but not A2G. There was evidence that these two inbred strains had lighter gonads in the cold; but the outbred mice of the twelfth generation had heavier testes in the cold than in the warm. There was no evidence of an effect of heterozygosis on variance in bodyweight. There was some tendency for growth to be more uniform in the cold than in the warm environment.
Regional Organization of Pre-pacemaker Cells in the Cardiac Primordia of the Early Chick Embryo
Authors: Dehaan Robert L. 
Published: April 2021

ABSTRACT
The lateral cardiac primorida of the early chick embryo were cut into anterior, middle and posterior fragments. Each fragment was incubated at 37°C in culture medium, for 48 hours. At the middle and end of the incubation period each culture was examined for the presence of spontaneously beating heart tissue, and its intrinsic pulsation rate was determined. The posterior fragments, which in the intact embryo form atrial and sinus tissue, gain the capacity to produce spontaneously contractile heart vesicles earliest (stage 4+), and exhibit the highest level of heart-forming potency. The middle fragments are first able to form beating hearts at stage 5, but do so in a lower percentage of the cases. The cells in these fragments normally form ventricle. The anteriormost fragments, which represent the presumptive conus and cono-ventricular regions of the heart, are not able to form beating cardiac vesicles until stage 7, and then do so with very low frequency. Vesicles from all three fragments increase in spontaneous pulsation rate with age of the donor. The posterior fragments produce heart tissue which beats at from 90 to 135 beats/min., with a mean of 115 beats/min. Vesicles from the middle pieces range from 40 to 85 beats/min., averaging 65 beats/min. The anterior fragments increase from 10 to 40 beats/min., with an average rate of 36 beats/min. It may be concluded from these results that the various parts of the heart (sinus, atrium, ventricle and conus) are represented in specific, localized portions of the heart-forming regions in the early embryo (stages 5-9), and that each portion contains pre-pacemaker cells which develop an appropriate level of intrinsic rhythmicity. The antero-posterior rate gradient observed in the formed functional heart is already defined in the heart-forming regions of the head-process stage embryo. Whether this early regionalization of pacemaker activity is due to the distribution in the cardiac primordia of pre-pacemaker cells already determined as to their future pulsation rate, or is the result of a gradually emerging, epigenetic pattern of localized interactions between the pre-heart mesoderm and surrounding tissues, cannot be decided on the basis of the present experiments. A test of this question is suggested, and other points of relevance to these results are discussed.
Modification Expérimentale du Développement de l’Ovaire de Souris sous l’influence du Testicule Embryonnaire de Poulet
Authors: Salzgeber par Berthe 
Published: April 2021

ABSTRACT
Mouse ovaries from foetuses 12–21 days of gestation were explanted in vitro in association with gonads of 6–10 days chick embryos. After 2-6 days of culture, the expiants were grafted into the coelom of young chick embryos. Grafts were removed when hosts were 12–19 days old (Plate 1, Figs. 1 and 2). In associations of mouse and chick ovaries, the two organs fused together forming chimeric organs (Plate 1, Fig. 3). The mouse gonad, containing numerous oocytes and primary follicles, lay in the medullary part of the chick gonad (Plates 1 and 2, Figs. 3–7). In associations of mouse ovary with chick testis, the development of the mouse ovary was inhibited (Plates 2 and 3, Figs. 8–14). Cortical structures were very sensitive to the testicular influence; and oocytes degenerated or failed to develop. Follicles when present had an abnormal appearance (Plate 2, Fig. 9). The degree of inhibition depended on the type of association and the age of the gonad when transplanted (Plate 2, Figs. 9 and 10). Some ‘medullary’ structures persisted in these inhibited ovaries. The rete ovarii, which looks like winding cords, was well developed and penetrated into the chick tissue where it established direct connection with testicular tubules (Plate 3, Fig. 16). In some expiants, in the vicinity of the rete, cords of testicular aspect which sometimes contained oocytes or degenerating follicles were observed (Plate 3, Fig. 13). These results demonstrate that mouse ovary associated with chick ovary can develop when transplanted to chick embryos. Oogenesis takes place, the oocytes grow and primary follicles develop.
The Origin and Development of Smooth Muscle and Contractility in the Ductus Epididymidis of the Rat
Authors: Velde Robert L. Van De , Risley Paul L. 
Published: April 2021

ABSTRACT
The smooth muscles of the ductuli efferentes and ductus epididymidis develop from primitive mesonephric mesenchyme. In both ductuli efferentes and ductus epididymidis a proliferation and condensation of the mesenchyme occurs around the ductuli and epididymal duct. This appears in the ductuli efferentes of the 14- and 15-day rat embryo, and by birth it has extended to the cauda epididymidis. Subsequent to the condensation around the ducts, elongation of the mesenchymal cell nuclei beings, and the cytoplasm becomes aligned and extended. This appears first in the circular layer of the caput by the 16th day of gestation, and in the investing layer of the corpus epididymidis by the 20th day. Formation follows lastly in the region of the cauda epididymidis, occurring by parturition or very soon thereafter. After the smooth muscle cells are differentiated, delicate pulsations or contractions may be observed in the ductuli efferentes and ductus epididymidis. They can be seen first at 17 days of gestation in the region of the coni vasculosi, where they occur at intervals of 60 sec. This condition may not be representative of all 17-day embryos as contractions were seen in but three of thirty-three preparations studied. Rhythmic movements of the ductuli and upper and middle caput epididymidis take place with regularity, occurring approximately at 40-45 sec. intervals in the ductuli and upper caput and at 20-25 sec. in the middle caput epididymidis at birth. By the 10th day, a visible contractile wave commences in the region of the ductuli and passes to the upper corpus where it disappears. Inspection of contraction frequency data for the ductuli and upper segments of the epididymis indicates that the interval between successive rhythmic waves diminishes with age. An incidental examination of the Müllerian duct of female neonatal and post-natal animals demonstrated that rhythmic contractions are established by birth.
Production élective de la phocomélie sous l’influence d’ypérite azotée
Authors: Salzgeber par Berthe 
Published: April 2021

ABSTRACT
Chick embryos of to days of age (Stages 17-22 of Hamilton & Hamburger) were injected with nitrogen mustard (methyl-bis-chlorethylamine) dissolved in distilled water. Each embryo received a dose of from 0 · 6 to 1 · 6 μg. Most of the embryos (181 out of 199) showed serious malformations of the limbs of which the most characteristic was phocomelia. Embryos which died, or were sacrificed, before 10 days of age had very short limbs most of which in course of degenerating. Embryos taken at ages greater than 12 days showed various degrees of alterations of wings and legs. In the most severe cases the digits appeared to be inserted directly into the flank of the animal (type I). The least affected cases showed feet or wings shortened and deformed (type III). Between these two types are placed a group whose members approach the phocomélie type but in whom a short segment separates the distal parts of the limb from the body (type II). The digits were also malformed, and both fusions (syndactyly) and regression was observed. There were very few other malformations. There were many aberrations in the development of the skeletal elements. In the foot, the fibula was first to disappear. In the wing, the ulna or the radius was affected. The other elements were generally reduced in size or abnormally developed. Fusions and abnormal bends were seen. The femur and the humerus were generally altered less than the other intermediate pieces of the skeleton. This work brings evidence of a selective action of nitrogen mustard in the limb rudiments. Certain parts of these rudiments are more sensitive than others. Certain elements of the skeleton disappear in a constant order: fibula (foot), radius or ulna (wing), digit I of the foot. The most typical malformation obtained was phocomelia, seen in 65 out of 107 cases. The distal structures, the digits, are least affected. The hypothesis of a selective action upon mesodermal structures is put forward. Other malformations were rare, 26 out of 107 autopsied before the 12th day of incubation showed scoliosis of the neck. Among them, four showed a malformation of the eye.
Developmental Abnormalities in the Rat Induced by Heat Shock
Authors: Škreb N. , Frank Z. 
Published: April 2021

ABSTRACT
A simple method for applying heat shock directly to the uterus of pregnant rats is described. In an experimental series a temperature of 40–41 °C. was maintained for 40 min. A number of malformed foetuses were observed, and the resorption rate was high. In a control series animals were operated upon in the same manner as the experimental ones, but the temperature was kept at 37–38°C. No malformations were found. Deformities of the head and extremities were produced by the heat shock. These malformations are compared with those produced by other teratogens, and the differences are discussed.
Evidence for a Substance Responsible for the Spacing Pattern of Aggregation and Fruiting in the Cellular Slime Molds
Authors: Bonner John Tyler , Hoffman Mary E. 
Published: April 2021

ABSTRACT
In the cellular slime molds, after the individual amoebae have finished their growth and depleted their food supply, they aggregate into centers. Each center ultimately produces a small fruiting body (a spore mass supported by a slender stalk) that rises into the air. In a previous study (Bonner & Dodd, 1962a) it was shown that the size of the aggregation territories remained constant for any one species under a given set of environmental conditions even though the density of the amoebae in the culture dish might vary considerably. From this it was suggested that one of the possible hypotheses might be that a center-inhibiting substance is diffusing outward from the first formed centers and its effectiveness is independent of the number of cells within a territory. In another study (Bonner & Dodd, 1962b) evidence was brought forth to support the notion that as the fruiting body rises into the air it orients with respect to the environment by producing a gas to which it is sensitive and it orients away from regions of high concentration. In the discussion of this second paper we made the point that the adaptive significance of these two phenomena are one and the same; they both tend to space the fruiting bodies, first by keeping the centers separate during aggregation, and then by keeping the sorocarps separate as they rise into the air. Together they produce optimum conditions for effective spore dispersal.
The Development in vitro and in vivo of Fusion of the Palatal Processes of Rat Embryos
Authors: Moriarty Thomas M. , Weinstein Sam , Gibson R. D. 
Published: April 2021

ABSTRACT
The feasibility of employing organ culture and transplantation techniques for obtaining fusion of the lateral palatal processes of the rat embryo was investigated. The methods of obtaining live embryos and the operations upon these embryos to obtain palatal tissues were described. Nineteen organ cultures of the unfused palatal tissues of 15-day Sprague-Dawley rat embryos were made. Five of these palates achieved fusion. Twenty transplantations of the unfused palatal tissues of 15-day Sprague-Dawley rat embryos were carried out. Ten of the heterografted palates developed fusion. Four of the five homografts achieved fusion. The morphology of palatal process closure was observed and photographed at regular intervals in the in vitro and in vivo experiments. The morphology of closure of the secondary palate as found in the experimental tissues differs slightly from that of normal Sprague-Dawley embryos. The tongue appears to have a direct relationship with morphology and mode of closure. Removal of the tongue from between the lateral palatal processes of the experimental tissues immediately modifies process morphology and mode of closure. The abnormal environments of both explants and transplants cause cellular ‘regressions, in them. The histological progress of cellular fusion appears similar for the experimental and normal tissues.
Sur les Structures Différenciées par l’Ectoderme de Batracien après Irradiation aux Rayons X
Authors: Reyss-Brion par MME. M. 
Published: April 2021

ABSTRACT
L’ Ectoderme n’ est capable de réagir à l’ action des inducteurs que pendant un laps de temps assez court et bien déterminé. Waddington (1938) a dé-nommé ‘compétence’, cette réactivité de l’ ectoderme caractérisque d’ un stade du développement embryonnaire.
Mumps Virus Infection of the Pregnant Hamster
Authors: Ferm Vergil H. , Kilham Lawrence 
Published: April 2021

ABSTRACT
The objective of our present studies has been to follow the course of mumps virus when injected intravenously into pregnant hamsters during early stages of gestation, in order to determine possible relations to fetal disease and/or malformations. Several considerations prompted the selection of mumps virus for these investigations. One was that, while rubella (Gregg, 1941) and cyto-megalic inclusion body disease (Weller & Hanshaw, 1962) have been the only two viruses shown to have a definite cause-effect relation in the etiology of human congenital malformations, there has been a continuing suspicion that mumps virus may also act as a teratogenic agent in human pregnancy (Kaye & Reaney, 1962; Blattner & Heys, 1961; Hyatt, 1961). A second reason was that mumps virus has a natural pathogenicity for hamsters (Kilham & Overman, 1953). In addition, this agent is capable of infecting women at term, the strain used in present experiments having been obtained from human milk a few days post-partum (Kilham, 1951).
The Control of Growth of the Chick Embryo Liver Studied by the Method of Parabiosis
Authors: Chaytor Daniel E. B. 
Published: April 2021

ABSTRACT
Chicken embryos of 9 days’ incubation have been parabiosed with partners of 12 days’ incubation and the effects on liver growth during the subsequent 4 days studied. Control 9- and 12-day embryos were parabiosed with partners of their own age.
The younger embryo parabiosed with an older partner was found to show a diminished growth of liver when body weight was standardized.
The mitotic index in liver parenchymal cells of the younger embryo para-biosed to the older was about half that of controls. The liver mitotic index in the older partner did not differ from controls.
Parabiosis per se does not appear to have any adverse effect on the mitotic activity of the liver.
The results have been discussed in terms of a blood-borne liver growth in-hibitor produced by the liver and acting by a feed-back mechanism, of the kind that has been postulated in the adult mammal.
A Quantitative Study of Primordial Germ Cells in the Male Rat
Authors: Beaumont Heather M. , Mandl Anita M. 
Published: April 2021

ABSTRACT
A cytological and quantitative study was made of the testes of foetal and neonatal rats. The population of germ cells was estimated for a total of 111 specimens. A volumetric method (Beaumont & Mandl, 1962) was used for animals aged 14.5 days p.c. to 4.5 days p.p. Counts were made of the numbers of dividing germ cells in foetal testes. Numbers of normal, degenerating and dividing gonocytes, ‘transitional’ cells and spermatogonia type-A were estimated from differential counts made on specimens aged 3-6.5 days p.p. The primordial germ cells divide mitotically up to the age of about 18.5 days p.c. Thereafter they remain at interphase for a period of 6-8 days, during which they enlarge considerably. Although many gonocytes appear to undergo degeneration during this resting period, few ‘disappear’ from the testis until 2-4 days after birth. Differentiation of gonocytes into definitive germ cells sets in about 4 days p.p. The formation of spermatogonia type-A is preceded by the appearance of ‘transitional’ cells and a renewal of mitotic activity. The total population of primordial germ cells rises from about 20,000 at 14..5 days p.c. to.reach a plateau of 120,000-140,000 between 20 days p.c. and 2 days p.p. The number of gonocytes then declines to ca. 50,000 at 6-6.5 days after birth. This decrease is due to (a) the elimination of degenerating germ cells, and (b) the transformation of gonocytes into definitive germ cells. With the re-initiation of mitotic activity, which accompanies germinal differentiation, the total population of germ cells increases to ca. 200,000 at 6-6.5 days, of which spermatogonia type-A number between 50,000 and 90,000.
Ecdysone-dependent proteolysis of an apical surface glycoprotein may play a role in imaginal disc morphogenesis in Drosophila
Authors: Birr Cynthia A. , Fristrom Dianne , King David S. , Fristrom James W. 
Published: April 2021

Abstract
An apical surface glycoprotein, designated gp125 for its apparent molecular weight of 125 000, appears in Ca2+-free, ionic detergent extracts of imaginal discs of Drosophila melanogaster in response to the steroid hormone, 20-hydroxyecdysone (20-HE). Gpl25 is not synthesized in response to 20-HE, but results from modification of an existing macromolecule. Treatment of discs or larval epidermis with serine protease (e.g., trypsin) results in hormone-independent production of gp125. Antiserum raised to electrophoretically purified gp125 recognizes, in addition to gp125, two closely related glycoproteins with higher apparent molecular weights, gp200 and gp180. This family of glycoproteins is localized at the apical surface of imaginal disc cells and of the epidermal epithelium in embryos, larvae and prepupae. Ca2+ affects both the solubility and the proteolytic products of this family of glycoproteins. We discuss the possibility that gp125 is generated through the action of a hormonally controlled serine protease in a process that is necessary for disc morphogenesis.
Changes in mRNA length accompany translational regulation of the somatic and testis-specific cytochrome c genes during spermatogenesis in the mouse
Authors: Hake Laura E. , Alcivar Acacia A. , Hecht Norman B. 
Published: April 2021

Abstract
The mouse testis contains two isotypes of cytochrome c, which differ in 14 of 104 amino acids: cytochrome cs is present in all somatic tissues and cytochrome cT is testis specific. The regulation of cytochrome cS and cytochrome cT gene expression during spermatogenesis was examined by Northern blot analysis using specific cDNA probes. Total RNA was isolated from adult tissues, enriched germinal cell populations and polysomal gradients of total testis and isolated germinal cells. Three cytochrome CS mRNAs were detected averaging 1.3 kb, 1.1 kb and 0.7 kb in all tissues examined; an additional 1.7 kb mRNA was observed in testis. Isolated germinal cells through prepuberal pachytene spermatocytes contained only the three smaller mRNAs; the 1.7 kb mRNA was enriched in round spermatids. All three smaller cytochrome cs mRNAs were present on polysomes; the 1.7 kb mRNA was non-polysomal. Cytochrome cT mRNA of 0.6 – 0.9 kb was detected in testis; mRNA levels were low in early spermatogonia and peaked in prepuberal pachytene spermatocytes. In adult pachytene spermatocytes, a subset of the cytochrome cT mRNAs, 0.7 – 0.9kb, was present on polysomes; a shortened size class, 0.6 – 0.75 kb, was non-polysomal. A distinct, primarily non-polysomal, cytochrome cT 0.7 kb mRNA was present in round spermatids. These results indicate that (1) both cytochrome c.s and cytochrome cT mRNAs are present in early meiotic cells, (2) a 1.7 kb cytochrome cS mRNA is post-meiotically expressed and non-polysomal and (3) cytochrome cS and cytochrome cT mRNAs are each developmentally and translationally regulated during spermatogenesis.
Storage protein gene expression is localised to regions lacking mitotic activity in developing pea embryos. An analysis of seed development in Pisum sativum XIV
Authors: Hauxwell Angela J. , Corke Fiona M. K. , Hedley Cliff L. , Wang Trevor L. 
Published: April 2021

Abstract
Storage protein gene expression has been studied in relation to mitotic activity to ascertain whether these processes are linked during embryo development in pea. Sections from immature pea embryos were probed by in situ hybridisation to show the pattern of vicilin storage protein gene expression. In addition, the location of mitotic cells was identified using fluorescence microscopy. Vicilin mRNA was first localized in the parenchyma cells of the upper adaxial region of the cotyledons. As the embryos increased in fresh weight, gene expression spread from this region, in a wave-like manner, down and across the cotyledons. The gene was only expressed in those regions of the embryo that lacked mitotic activity.