bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in responsiveness of preimplantation mouse embryos to serum
Authors: Fishel Simon B. , Surani M. Azim H. 
Published: April 2021

ABSTRACT
Changes in uptake of radioactive uridine and its incorporation into RNA were determined in preimplantation mouse embryos, from the 2-cell to the blastocyst stage, as a measure of their responsiveness to extracellular conditions. Two media were tested, one contained serum and the other contained bovine serum albumen as a control. An increase in the acid-soluble pool occurred at the 8-cell stage and a marked increase in RNA synthesis occurred at the early blastocyst stage when the embryos were incubated with serum.
Gastrulation in the mouse: assessment of cell populations in the epiblast of tw18/tw18 embryos
Authors: Snow M. H. L. , Bennett D. 
Published: April 2021

ABSTRACT
The appearance of the primitive streak at the onset of gastrulation in the mouse heralds a 24 h period of extremely rapid growth (Snow, 1976). During that time, from 6·5 to 7·5 days post coitum, at least in the random bred Q strain of mice, the epiblast, an apparently uniform population of about 600 cells, generates the ectoderm and mesoderm of the pre-somite embryo which total about 15000 cells. The definitive endoderm, which in the foetus replaces the primary endoderm (Gardner & Papaioannou, 1975), has not yet been identified at this stage.
Transfilter induction of kidney tubules as a function of the extent and duration of intercellular contacts
Authors: Saxén Lauri , Lehtonen Eero 
Published: April 2021

ABSTRACTThe kinetics of kidney tubule induction were examined in transfilter experiments by varying the time of transfilter apposition, the porosity and pore size of the filters, and the culture conditions. Transfilter contact between the interacting cells is established within an hour when cytoplasmic processes emerge through the interposed filter; then a further 16–24 h are needed for completion of induction. This lag is a function of thickness and pore size of the filter, and is not reduced by precultivation of the inductor on the filter. Material that accumulates on the far side of the filter during such cultivation displays no morphogenetic activity.The intensity of the mesenchymal response was roughly quantified and shown to be a function of pore size, pore density and duration of transfilter contact.
Investigation of the potency of cells from the postimplantation mouse embryo by blastocyst injection: a preliminary report
Authors: Rossant J. , Gardner R. L. , Alexandre H. L. 
Published: April 2021

ABSTRACTChimaeric conceptuses have been produced by injection of and day extra-embryonic ectoderm and day embryonic and extra-embryonic endoderm into day mouse blastocysts. Extra-embryonic ectoderm cells contributed only to the ectoplacental cone and/or trophoblast giant cell fractions, reflecting the probable trophectoderm origin of these cells. Proximal (visceral) endoderm cells overlying both the embryonic and extra-embryonic ectoderm contributed cells only to the endoderm of the visceral yolk sac, indicating that the definitive embryonic endoderm has not formed by days p.c.
Features of cell lineage in preimplantation mouse development
Authors: Graham C. F. , Deussen Z. A. 
Published: April 2021

ABSTRACTThe cell lineage of the mouse was studied from the 2-cell stage to the blastocyst. Lineage to the 8-cell stage was followed under the microscope. Each cell from the 2-cell stage divided to form two daughter cells which remained attached. Subsequently, these two daughters each produced two descendants; one of these descendants regularly lay deep in the structure of the embryo while the other was peripheral. Lineage to the blastocyst was followed by injecting oil drops into cells at the 8-cell stage, and then following the segregation of these drops into the inner cell mass and trophectoderm. Between the 8-cell stage and the blastocyst, the deep cells contributed more frequently to the inner cell mass than did the peripheral cells.
Fluctuations of adenylate cyclase activity during anterior regeneration in Owenia fusiformis (Polychaete Annelid)
Authors: Coulon Josiane , Marilley Monique 
Published: April 2021

ABSTRACT
Biochemical assays of adenylate cyclase activity were performed during the early phases of regeneration in Owenia fusiformis (Polychaete Annelid).
The results indicate the existence of a strong stimulation in an early phase following trauma. This stimulation is then followed by periodic fluctuations exhibiting a diurnal rhythm correlated with the cell cycle. Adenylate cyclase activity is also shown to be neuro-transmitter-dependent.
In this paper it is proposed that neurotransmitters might participate in the regulation of cyclic AMP formation, by means of adenylate cyclase acting on target blastema cells, undergoing the cell cycle.
A mutant ofTetrahymena thermophilawith a partial mirror-image duplication of cell surface pattern
Authors: Frankel Joseph , Jenkins Leslie M. 
Published: April 2021

ABSTRACTThe CU-127 clone of Tetrahymena thermophila, which manifests an unusually high number of ciliary rows plus a second set of abnormal oral structures and of contractile vacuole pores with partial mirror-image reversal of asymmetry (Jerka-Dziadosz & Frankel, 1979), has been subjected to breeding analysis. The progeny ratios obtained in various crosses indicate that the abnormalities of cell-surface asymmetry are brought to expression as a result of the action of a recessive allele at a single gene locus, here named janus. When previously normal cells were made homozygous for the jan allele, the cortical pattern characteristic of the CU-127 clone came rapidly to expression, often without associated change in number of ciliary meridians. Conversely, when cells previously expressing jan re-acquired the wild-type (jan+) allele, they returned to the normal pattern of a single normal oral structure and a single nor-mally located set of contractile vacuole pores while still retaining the high ciliary meridian number characteristic of the original CU-127 clone. The capacity for manifestation of the unique asymmetry pattern depends solely on homozygous expression of the janus allele, whereas the stable number of ciliary meridians in janus clones and the degree of expression of secondary OAs is modulated by other factors, probably at least in part genic. These results, taken together with those of the preceding paper, indicate that the janus allele promotes the propagation and/or expression of a condition of reversed asymmetry in a precisely located cell region, and further indicates that the propagation and expression of this condition are largely independent of the number and asymmetry of ciliary meridians.
The Behaviour of Basophil Cytoplasmic Substances during Neural Induction in the Chick
Authors: Lavarack J. O. 
Published: April 2021

ABSTRACT
Basophil cytoplasmic substance of the cells concerned in neural induction in the chick was investigated by methyl green-pyronin staining and the action of ribonuclease. Comparison of a number of stages indicated that changes in both distribution and concentration occur. Most of the basophil substance was in the dorsal zone of the cytoplasm in presumptive neural and presumptive mesodermal epiblast. In the subsequent differentiation of neural epithelium and chorda-mesoderm its concentration throughout the cytoplasm of both cell-groups increased considerably. The highest concentrations observed developed in a sharply localized zone at the ventral poles of the cells of the neural groove in its early stages and in some somite cells. The time relationships of concentration changes in adjacent cells did not indicate whether concentration of the substance at the base of the neural epithelium depends on transfer from other cells.
The Effects on Foetal Development of Freezing Pregnant Hamsters(Mesocricetus auratus)
Authors: Smith A. U. 
Published: April 2021

ABSTRACTGolden hamsters at different stages of pregnancy were cooled until breathing and heart-beats stopped and until they froze with deep body temperatures below 0° C. They were subsequently resuscitated. Animals frozen for 30 min. at days or at days had normal numbers of well-developed foetuses when killed at days of gestation. Others frozen for 30 min. at these times gave birth to litters and reared young. Freezing for 45 min. at days of gestation was also harmless as judged by the number and appearance of foetuses at days. By contrast, freezing for 45 min. at days of gestation arrested development or caused malformation of most of the foetuses. The abnormalities included hydrocephalus, anencephaly, herniation of the brain, absence of one or both eyes, hare-lip, cleft palate, and deformities of the feet. There was a critical period of pregnancy between and days when uterine haemorrhage and foetal resorption resulted whether the hamsters were allowed to re-warm from body temperatures of 15 – 17° C. or whether they had been chilled below zero and frozen for 30 – 45 min.
Further Studies in Tissue Homotransplantation in Cattle
Authors: Billingham R. E. , Lampkin G. H. 
Published: April 2021

ABSTRACT
The present contribution presents a sequel to our previous investigations into problems which arose when attempts were made to use skin grafting to differentiate between monozygotic and dizygotic twins in cattle. In each of three trials grafts from a dam elicited similar reactions when transplanted to each of her one-egg twin offspring. On the basis of this finding the asymmetry of response which the majority of two-egg twins show towards grafts from their dam may be taken as evidence of their dizygotic origin.It has been shown that mutual graft exchange between unlike-sexed twins can be used as a reliable method for distinguishing reproductively normal females from freemartins. The complete success of this method provides strong evidence that homograft tolerance and the freemartin condition have a common anatomical origin.Grafts from a dam to her tetrazygotic offspring lived for upwards of 70 days, whereas grafts from a dam to her offspring of single birth rarely live for as long as 14 days. It is argued that this great prolongation in the life of their grafts is the outcome of the quadruplets having previously exchanged cells in foetal life through anastomoses of their circulations. Each must be incapable of reacting against a very wide spectrum of antigens since it will accept grafts from all its brothers and sisters.Evidence is presented which suggests that cells from her foetus not infrequently gain access to a dam and sensitize her to subsequent grafts of her offspring’s skin. A first pregnancy may be sufficient to elicit this sensitization. On the other hand, if maternal cells gain access to the foetus, this must occur very rarely for in none of seventeen calves tested with grafts of their dam’s skin was there the slightest evidence that they were tolerant.New-born calves react as vigorously as adult cattle against homografts, even when they have not received colostrum. Since new-born calves possess no serum globulins, including antibodies, this provides strong evidence that immune globulins play no essential part in the homograft reaction.
A Comparative Study of the Desoxyribonuclease Activity in Adult and Embryonic Tissue
Authors: Blumenthal Gertrude 
Published: April 2021

ABSTRACT
Determinations have been made of the desoxyribonuclease (DNase) activity of various embryonic stages and adult tissues of a sea-urchin, a frog, and the domestic fowl. Special attention has been paid to the pH optimum and the magnesium requirement of the enzymes. Of the three species investigated only the sea-urchin exhibited DNase activity during early embryonic development. This activity was essentially the same as that of crystalline bovine pancreatic DNase, although it is doubtful that the two enzymes are identical. The possible correlation of this enzyme with the amount of preformed desoxyribonucleotides in the egg is discussed. At later stages of development, all three species contain an enzyme which is similar to DNase II of mammalian origin. The possibility that the difference in enzyme activity between embryonic and mature tissue is due to the presence of inhibitors has been ruled out. The data obtained in this study and that of other workers suggests that the adult DNase may play a role in the processes of cell destruction and cell turnover in adult metazoans.
Neuroglial Development and Myelination in the Spinal Cord of the Chick Embryo
Authors: Bensted J. P. M. , Dobbing J. , Morgan R. S. , Reid R. T. W. , Wright G. Payling 
Published: April 2021

ABSTRACT
The widespread occurrence of the demyelinating diseases of the central nervous system makes the study of the events that accompany normal myelin formation one of major significance in neuropathology. In the latter part of the last century the earlier stages in the development of the nervous system in embryos were studied in detail by many investigators, but since then, in spite of its evident importance, this aspect of embryogenesis has attracted little attention from embryologists and neurohistologists. In view of the advances now being made in the chemistry of the nervous system, the time seems opportune to return to the problem of myelinogenesis with the hope of bringing together some of the many important relevant observations in neural morphology and biochemistry.
The utilization of an inhibitor of spermidine and spermine synthesis as a tool for the study of the determination of cavitation in the preimplantation mouse embryo
Authors: Alexandre H. 
Published: April 2021

ABSTRACTThe inhibition of spermidine and spermine synthesis by methylglyoxal-Bis(guanylhydrazone) (MeGAG) at concentrations of 5, 10 and 20μM, induces a reversible metabolic quiescence of mouse embryos, cultured in vitro from the 2-cell stage, at an average of 10·2, 8·5 and 6·9 cell stages respectively. In contrast, the inhibition of putrescine synthesis by a-methylornithine (α-MeOrn) at concentrations up to 10 mM fails to inhibit blastocyst formation, as shown previously.Complete reversibility of this induced arrest of development is observed for treatments up to 31 h with MeGAG at 10μM. In agreement with the biological clock theory of Smith & MacLaren’s hypothesis, the delay in cavitation is proportional to the length of treatment.However, the average cell numbers of the ‘delayed nascent blastocysts’ of all treated embryos (21·8–24·2) are consistently lower than that of control embryos (33·6) irrespective of the duration of treatment. It seems therefore that under some experimental conditions, DNA and chromosome replication on the one hand and cytoplasmic maturation on the other may be desynchronized. This suggests a role for a cytoplasmic factor in the induction of cavitation.
Evidence for differential cellular adhesion as the mechanism of sorting-out of various cellular slime mold species
Authors: Sternfeld John 
Published: April 2021

ABSTRACTVarious authors have shown previously that if the amoebae of two species of slime molds are mixed they have the ability to sort themselves out. In the work reported here, the sortingout of cells of several slime mold species was examined in clumps of cells in suspension.Cells of four species, Dictyostelium discoideum (Dd), D. mucoroides (Dm), D. purpureum (Dp), and Polysphondylium violaceum (Pv), were mixed in pairs in suspension and clumps of cells formed. Dd and Pv cells sorted out completely and formed separate clumps, each of single species. Both Dd and Dm, when mixed separately with Dp, formed clumps containing both species. Sorting-out took place in these clumps such that the cells of Dd and Dm partially enveloped the Dp cells. Finally, in the Dd–Dm mixtures, the Dm cells always sorted out such that they surrounded the Dd cells. When mixed in a 1:2 ratio (Dd:Dm) the Dm cells formed a complete shell around a sphere of Dd cells.Sorting-out of cells in clumps in suspension can occur by either of two possible mechanisms: response of cells to a chemotactic gradient or differences in cell surface strengths of adhesion (Steinberg, 1964). Mixing of two species in a clump of cells and observing the process of sorting-out permits one to distinguish between these two mechanisms (Steinberg, 1964). By such an analysis it was found that the sorting-out observed in mixtures of Dd and Dm is consistent with the mechanism of differential cellular adhesion. The major reasons for this are (1) when the adhesive properties of the cells are known to change the Dd cells began to move inside the clumps, (2) the Dd cells coalesced into islands rather than streaming inward independently, and (3) the Dd cells and cell masses did not lie at the center of the clumps but rather lay randomly within the clumps. The partial envelopment observed in the Dd–Dp and Dm–Dp mixtures and the separate clumps formed by the Dd–Pv mixtures are also consistent with differential cellular adhesion. They represent cases in which the interspecific strengths of adhesion are low (Dd–Dp and Dm–Dp) and near zero (Dd–Pv).
Changes in collagen ultrastructure, macroscopic properties and chemical composition of chick embryo cartilage induced by administration of aβ-D-xyloside
Authors: Hjelle J. T. , Gibson K. D. 
Published: April 2021

ABSTRACTNine-day chick embryos were injected with a β-xyloside and their sternal cartilage was examined 3 days and a week later. Sterna from 16-day embryos showed a reduction in size as compared to controls, with little or no change in the fraction of extracellular space, and a significant decrease in tensile strength. At the ultrastructural level, collagen fibrils in control sterna were dispersed evenly in the interstitial space, with few contacts between adjacent fibrils. In sterna from treated embryos, almost all collagen fibrils were aggregated into clumps and arrays throughout the interstitial space, with fibril-free areas in between. No abnormalities could be detected in the morphology of individual fibrils or in the ultrastructure of the chondrocytes. The changes in spatial distribution of collagen were fully evident 3 days after drug administration.The hydroxyproline/DNA ratio was the same in control and treated sterna, and no change was observed in the type of collagen. The uronic acid/DNA ratio was reduced by 14% 3 days after drug administration and by 40% after a week. The degree of sulfation of chondroitin sulfate was reduced from 80% in control sterna to 40% in treated sterna; almost all of this chondroitin sulfate was attached to peptide and the sedimentation pattern of the proteo-glycan resembled that of normal cartilage proteoglycan.The function of chondroitin sulfate in embryonic cartilage is discussed in terms of our results and others. It is suggested that a major physiological role of the proteoglycan is to control the spatial distribution of collagen fibrils as they assemble to form a cross-linked gel.
Phosphatase activity and ion levels associated with normal and abnormal skeletogenesis in the fetal rat
Authors: Brummett Elaine S. , Johnson E. Marshall 
Published: April 2021

ABSTRACTLimbs from rat fetuses exposed to the alkylating agent chlorambucil on day 14 of gestation undergo abnormal skeletogenesis (Brummett & Johnson, 1979). The abnormal developmental sequences are manifest as marked disruption of chondrogenesis and ossification. The present study examines some of the biochemical factors normally related to initial mineralization and their possible alteration during teratogenesis.The specific activities of the acid, alkaline and pyro-phosphatases were determined for normal and abnormal (drug-treated) fetal rat limbs during days 15–17 of gestation, the period of cartilage-model calcification. This was done to determine if altered enzymatic activity leading either to depressed localized phosphate levels or hydroxyapatite crystal growth inhibition would account for the decreased calcification. The level of alkaline phosphatase increased dramatically (sixfold in 3 days), in association with normal cartilage formation. In the abnormal limbs, this rise was only half as great. Pyrophosphatase and acid phosphatase activity in both normal and abnormal limbs did not change over the 3-day period.The normal concentrations of ions critical to calcification, i.e. phosphate, calcium and magnesium, were determined for maternal serum, amniotic fluid, whole fetuses and fetal limbs. Mean phosphate and calcium levels increased slightly in the limbs with increasing gestational age. The ion levels in drug-treated fetuses were within normal limits except in amniotic fluid where phosphate was increased significantly on day 17. Also the protein concentration in the fluid was elevated on day 16 and 17.
Replacement of posterior by anterior structures in theDrosophilawing caused by the mutationapterous-blot
Authors: Whittle J. Robert S. 
Published: April 2021

ABSTRACTThe recessive mutation apterous-blot in Drosophila melanogaster causes replacement of posterior wing structures by anterior ones, with variable penetrance and expressivity. Extreme transformations resemble mirror-image duplicate anterior wings as in the mutant engrailed. Anterior structures in the posterior wing only appear on the dorsal surface. Duplications solely of posterior structures are also seen.Clonal analysis shows that extra cell proliferation occurs in the posterior area but is complete by 108 h after egg deposition. Lineage analysis is consistent with a clonal perpetuation of the transformation. Genetic mosaics to test the cell-autonomy of apterous-blot show that it is not autonomously expressed in clones.The results of lineage analysis, the phenotypes of combinations of apterous-blot with other apterous alleles including a deletion for the locus and with various other homoeotic mutations, are together used to distinguish three alternative modes of action of this mutation. It is concluded that apterous-blot is unlikely to be a selector gene mutation but instead may cause the transformation by an event like transdetermination following a local failure in cell function in the wing disc.
Crinkly-tail, a mild skeletal mutant in the mouse
Authors: Johnson D. R. , Wallace Margaret E. 
Published: April 2021

ABSTRACT
Crinkly-tail, cy, is a new recessive mutant with imperfect penetrance, in chromosome 4 of the mouse. The only abnormality is in the shape of the vertebrae for one, more rarely two, lengths of the region C9 to C14. This is expressed briefly in the 11-day-old embryo as a duplicated tail gut. None of the mechanisms operating in most of the 20 known tail mutants in the mouse operates in crinkly-tail. The defect is probably due to misallocation of the tissue derived from the primitive streak.