bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of the primordial pool size of the mouse liver using a histochemically demonstrable X-linked enzyme in the adult female mouse
Authors: Wareham Kathryn A. , Williams E. D. 
Published: April 2021

ABSTRACT
We have used a histochemical technique to study cellular mosaicism in the livers of female mice heterozygous for an abnormal form of the X-linked enzyme ornithine carbamoyltransferase. The proportion of cells expressing the normal enzyme was found to be consistent within a liver lobe, but discordant between lobes, with as few as 4 % or as many as 91 % of cells being enzyme positive. Systematic observation of variation of the proportion of positive cells in different lobes of 12 mice was used to calculate the primordial pool size for each lobe and for the liver as a whole. Although confidence limits for this small study are wide, the data suggest that the liver pool is about 15 cells, and that it enlarges to at least 50 cells before subdividing into six lobe pools ranging in size from a minimum of 4 to a maximum of at least 14 cells.
The cellular origin of fibronectin in the basement membrane zone of developing tooth
Authors: Hurmerinta Kirsti , Kuusela Pentti , Thesleff Irma 
Published: April 2021

ABSTRACT
The cellular source of fibronectin in the dental epitheliomesenchymal interface was studied in interspecies combinations of mouse and quail tissue. Species-specific fibronectin antibodies were produced by immunizing rabbits with purified mouse or chicken fibronectin and by absorbing both antisera with purified heterologous fibronectin and insoluble tissue extract. The absorbed antisera to mouse and chicken fibronectin showed fluorescent staining only in mouse and chicken tissue sections, respectively, but not vice versa. When the mouse mesenchymal dental papilla was combined and cultured either with the mouse enamel organ or with the quail pharyngeal epithelium, mesenchymal cell differentiation was initiated and typical alignment of mesenchymal cells along the basement membrane was seen. Examination with transmission electron microscope revealed a typical bilaminar basal lamina with adherent fibrillar matrix on its mesenchymal aspect. Immunofluorescent localization of fibronectin with the mouse-specific fibronectin antiserum showed a brilliant staining in the mesenchymal tissue and in the basement membrane zone. When the chicken-specific fibronectin antiserum was used, no staining was detected in either tissue recombinations. We have suggested earlier that fibronectin in the dental basement membrane plays an important role during the differentiation of mesenchymal cells into odontoblasts. The present study demonstrates that fibronectin in the basement membrane of the developing tooth is produced exclusively by the differentiating mesenchymal cells.
Selforganization of ependyma in regenerating teleost spinal cord: evidence from serial section reconstructions
Authors: Anderson Marilyn J. , Choy Chi Y. , Waxman Stephen G. 
Published: April 2021

ABSTRACT
Multiple ependymal structures have been observed in regenerating spinal cord of the teleost Apteronotus albifrons. Evidence is presented for two modes of formation of the secondary ependymas: budding off from the primary ependyma, and de novo origin of a tube-like ependymal structure within a group of undifferentiated cells. Serial sections of regenerated cord provide evidence that undifferentiated cells not in immediate contact with the main ependymal layer can organize and differentiate into an ependymal structure in the regenerating spinal cord. These findings suggest that a significant amount of morphological organization can take place independent of the normal developmental sequence and environment.
Cell distribution during mouse secondary palate closure
Authors: Brinkley Linda L. , Bookstein Fred L. 
Published: April 2021

ABSTRACT
The patterns of distribution of both total mesenchymal cells and the ratios of [3H] thymidine-labelled to total cells were mapped during secondary palatal shelf reorientation in vivo and in vitro. Smoothed spatial averaging, a computer-assisted method which takes into account the positions of all cells across an entire histological section of the shelf, was employed. Changes in shelf cross-sectional area and cell size were also measured. Three shelf regions, anterior and posterior presumptive hard and presumptive soft palate, were studied at developmental stages which were 30, 24 and 18 h prior to expected in vivo elevation, after in vivo reorientation and during the course of in vitro reorientation. Region-specific patterns of cell distribution change with shelf reorientation. These changes were observable within 6h. Increases in cell number by cell division may enhance some high local cell densities, but cannot account for decreases in cell density. Increase in cell size is not a factor in decreasing cell density, nor is cell death. Displacement of cells by expansion of the extracellular matrix may be involved.
The histogenetic potential of neural plate cells of early-somite-stage mouse embryos
Authors: Chan W. Y. , Tam P. P. L. 
Published: April 2021

ABSTRACT
The mesencephalic neural plate of early-somite-stage mouse embryos differentiated underneath the renal capsule to form mostly neural tissues together with other tissues some of which were probably of neural crest cell origin. The capacity to form non-neural tissues such as skeletal tissues and melanocytes was lost at about the 5-somite stage. The lateral areas of the plate tended to form non-neural tissues more than the medial areas. The cephalic neural plate of presomite head-fold-stage embryos differentiated extensively to form both ectodermal and mesodermal tissues. However, upon completion of neurulation, the mesencephalic neuro-epithelium of forelimb-bud-stage embryos gave rise to neural tissues only. Therefore there is a progressive restriction in the histogenetic capacity of the mesencephalic neural plate during neurulation and this could be attributed to the cellular commitment for neural differentiation and the loss of the neural crest cells.
Disruption of segmentation in a short germ insect embryo
Authors: Mee Jane E. , French Vernon 
Published: April 2021

ABSTRACT
A heat shock (of 15 min at 48°C) given to early embryos of the locust, Schistocerca gregaria, results in localized abnormalities in the segment pattern subsequently formed. Most defects involve two consecutive segments of the thorax or abdomen, and these are analysed in detail. The abdominal defects fall into three main classes each of which involves the absence of a particular region of the segment pair and, in one class, duplication of the region which remains. The thoracic defects similarly involve absence of parts of the segments and the formation of a single limb base from which one, two, or three limbs develop.
Heat shock may result in the absence of parts of segments in two distinct ways. It may interfere with the process of segmentation or it may delete parts of already formed segment primordia. These possibilities are discussed although, at present, neither can be excluded.
The duplication observed in some abdominal disruptions and the formation of triple limbs indicates that the absence of parts of embryonic segments is followed by pattern regulation similar to that occurring in regeneration studies on larval segments and appendages of other insects. Two out of the three classes of abnormality can be explained in terms of intercalary regeneration restoring pattern continuity, but it is possible that discontinuities persist in the remaining class.
Genetic activity at the albino locus in Cattanach’s insertion in the mouse
Authors: Deol M. S. , Truslove Gillian M. , McLaren Anne 
Published: April 2021

ABSTRACT
Cattanach’s insertion (Is(In7;X)lCt or XCt) includes the normal allele at the albino locus (c+), which is subject to inactivation of the X chromosome carrying it, so that XCtX; cc mice have albino and pigmented patches. The X-autosome translocation T(X;16)16H or XT16H leads to preferential inactivation of the other X chromosome in female cells, so that XCtXT16H; cc mice are almost entirely white. However, they grow darker with age, as if reversal of inactivation of the c+ allele were taking place in increasing numbers of melanocytes. To test whether this is dependent only on age or whether it is related to the number of times the animal has moulted, hair was repeatedly plucked from selected areas at the early telogen stage when the follicles are also removed, assuming that the melanocytes or melanoblasts in that region of the skin would be forced to undergo further divisions to colonize the new follicles. The plucked areas grew darker at the same rate as the rest of the coat, suggesting that the progressive reversal of inactivation is dependent only on age.
As direct examination of melanocytes in the follicles is difficult, they were examined in the choroid and the retinal pigment epithelium (RPE) of the eye. The frequency of the pigmented cells was lower in the choroid than in the RPE. Since the melanocytes in these structures are different in origin as well as in physical characteristics, it appears that cell type influences either reversal of inactivation, or the frequency with which the influence of the X chromosome extends to the albino locus.
Ciliary band formation in the doliolaria larva of Florometra
Authors: Lacalli T. C. , West J. E. 
Published: April 2021

ABSTRACT
The development of ciliary band pattern in the doliolaria larva of Florometra serratissima is described based on scanning and transmission electron microscopy. The uniformly ciliated epithelium of the post-hatching larva develops four regularly spaced bands over a period of approx. 20 h generating an epithelial pattern that is, essentially, a series of stripes. The first visible events of pattern formation progress over the larval surface in a posterior-to-anterior and dorsal-to-ventral sequence, but the initial pattern is not, in fact, striped. It instead consists of a close-packed array of oval interband domains separated and surrounded by belts of band cells. Secondarily the interband domains expand laterally and coalesce to form continuous, broad stripes, while the bands remain as narrow stripes between them. Two possible explanations for this unusual sequence of events are discussed: (1) that it can be understood in evolutionary terms with reference to band pattern in other echinoderm larvae, and (2) that it is a morphogenetic necessity because limitations inherent in the patterning mechanism prevent the direct formation of regular stripes.
The control of pigment cell pattern formation in the California newt, Taricha torosa
Authors: Tucker R. P. , Erickson C. A. 
Published: April 2021

ABSTRACT
Neural crest-derived pigment cells form species-specific patterns of pigmentation in amphibian embryos. We have characterized the appearance and changes in pigment cell distribution in the embryos of the California newt, Taricha torosa. Black melanophores first appear scattered over the surface of the somites intermingled with yellow xanthophores in stage 34/35 embryos. The melanophores then migrate either dorsally to form a dorsal stripe at the apex of the somites or ventrally along the intersomitic furrows to form a midbody stripe at the somite-lateral plate mesoderm border. Xanthophores remain between the two melanophore stripes and are also found in the dorsal fin and head. The formation of the dorsal stripe coincides with a change in melanophore tissue affinity from the surface of the somites to the subectodermal extracellular matrix (ECM). The latter substratum is the location of the cue used to organize the dorsal stripe. In addition, melanophores become elongate and highly arborized, which would allow them to extend to the region where the dorsal stripe forms. In contrast, xanthophores do not form long processes in vitro. This suggests that the ability of melanophores but not xanthophores to search for a cue at the apex of the somites may account in part for the segregation of these cells types. Melanophores and xanthophores are trapped to form the midbody stripe by the pronephric duct, which is located just beneath the ectoderm at the bases of the intersomitic furrows. Ablation of the duct prevents formation of the midbody stripe, although melanophores and xanthophores still fail to migrate ventrally over the lateral plate mesoderm. Melanophores grafted to the ventral midline fail to leave the confines of the donor tissue. This suggests that a factor in the lateral plate mesoderm in addition to the pronephric duct is inhibiting further ventral migration. There is no gross morphological difference in the organization of the subectodermal ECM dorsal and ventral to the pronephric duct as revealed by alcian blue, ruthenium red and staining with antibodies to fibronectin. We also conclude that the directed dispersal of the neural crest into the space between the somites and ectoderm is due to contact inhibition of cell movement, since T. torosa neural crest cells demonstrate contact inhibition in vitro and there are enough cells in the lateral migratory spaces to make contact events likely during dispersal.
Distribution, expression and germ line transmission of exogenous DNA sequences following microinjection into Xenopus laevis eggs
Authors: Etkin Laurence D. , Pearman Bradley 
Published: April 2021

ABSTRACT
We analysed the fate, expression and germ line transmission of exogenous DNA which was microinjected into fertilized eggs of Xenopus laevis. DNA was injected into fertilized eggs within 1h following fertilization. The injected DNA was dispersed around the site of injection and became localized to cleavage nuclei by stage 6. Injected DNA persisted in the tissues of 6-to 8-month-old frogs and exhibited a mosaic pattern of distribution with regard to the presence or absence and copy number between different tissues. We detected the exogenous DNA sequences in 60 % of injected frogs. Restriction digestion analysis of this DNA suggested that it is not rearranged and was organized as head-to-tail multimers. The copy number varied from 2 to 30 copies/cell in various tissues of the same frog. Plasmid pSV2CAT which contains the prokaryotic gene coding for chloramphenicol acetyl transferase (CAT) enzyme linked to the SV40 early gene promoter was expressed in 50 % of the animals containing the gene. The pattern of expression, however, varied between different animals and could not be correlated with copy number. We also showed that the exogenous DNA sequences were transmitted through the male germ line and that each offspring contained the gene integrated into a different region of the genome.
Cell- and tissue-specific monoclonal antibodies in eggs and embryos of the ascidianHalocynthia roretzi*
Authors: Mita-Miyazawa Izumi , Nishikata Takahito , Satoh Noriyuki 
Published: April 2021

ABSTRACTTo obtain specific immunological probes for studying molecular mechanisms involved in the early embryonic development of ascidians, we have produced monoclonal antibodies directed against a homogenate of larvae of the ascidian Halocynthia roretzi. Among these, we have screened monoclonal antibodies that specifically recognize cells and/or tissues of the embryo. Characterization of six epidermis-specific monoclonal antibodies (including larval tunic-specific and larval fin-specific), three muscle-specific antibodies, two endoderm-specific antibodies, one notochord-specific antibody and two monoclonal antibodies that specifically recognize trunk-lateral cells suggests that these monoclonal antibodies may be useful as markers for analysing molecular mechanisms involved in specification of these cells. Seven monoclonal antibodies characteristically stain intercellular materials of the developing embryo and may therefore be valid for studying cellular construction of the embryo. Furthermore, monoclonal antibodies that recognize components of follicle cells, perivitelline space and sperm have also been established.
Muscle cell differentiation in ascidian embryos analysed with a tissue specific monoclonal antibody
Authors: Nishikata Takahito , Mita-Miyazawa Izumi , Deno Takuya , Satoh Nori Yuki 
Published: April 2021

ABSTRACTUtilizing a muscle-specific monoclonal antibody (Mu-2) as a probe, we analysed developmental mechanisms involved in muscle cell differentiation in ascidian embryos. The antigen recognized by Mu-2 was a single polypeptide with a relative molecular mass of about 220 ×103. It first appeared at the early tailbud stage and continued to be expressed until the swimming larva stage. There were distinct and separate puromycin and actinomycin D sensitivity periods during the occurrence of the antigen, suggesting the new synthesis of the polypeptide by developing muscle cells. Embryos that had been permanently arrested with aphidicolin in the early cleavage stages up to the 32-cell stage did not express the antigen. DNA replications may be required for the antigen expression.Embryos that had been arrested with cytochalasin B in the 8-cell and later stages developed the antigen, and the number and position of the arrested blastomeres exhibiting the differentiation marker almost corresponded to those of the B4.1-line muscle lineage. Furthermore, in quarter embryos developed from each blastomere pair isolated from the 8-cell embryo, all the B4.1 as well as a part of b4.2 partial embryos expressed the antigen, while the a4.2 and A4.1 partial embryos did not show the antigen expression. These results may provide further support for the existence of cytoplasmic determinants for muscle cell differentiation in this mosaic egg.
Ethanol-induced inhibition of pinocytosis and proteolysis in rat yolk sacin vitro
Authors: Steventon G. B. , Williams K. E. 
Published: April 2021

ABSTRACTPinocytic capture of 12SI-labelled polyvinylpyrrolidone and of formaldehyde-denatured l25I-labelled bovine serum albumin by 17 · 5-day rat visceral yolk sacs incubated in vitro was rapidly and strongly inhibited by low concentrations (0 · 01 and 0 · 05%, v/v) of ethanol. The induced inhibition of pinocytosis was readily reversible, but a marked lag was observed before ethanol-exposed tissue regained its full proteolytic capacity towards the exogenous protein.These observations suggest that the acute administration of ethanol to a pregnant rat may give rise to concentrations of ethanol in the maternal blood and/or uterine fluid that induce dysfunction of the yolk sac. In late gestation such inhibition of yolk-sac function may interfere with the transfer of passive immunity across the yolk sac. If similar dysfunction is induced earlier in gestation, in the period before the chorioallantoic placenta is functional, this could cause a transient period of inhibition of histiotrophic nutrition that may be important to the pathogenic mechanism of action of ethanol as a teratogen.
Ciliary band formation in the doliolaria larva ofFlorometra: II. Development of anterior and posterior half-embryos and the role of the mesentoderm
Authors: Lacalli T. C. , West J. E. 
Published: April 2021

ABSTRACTWe report the results of cutting experiments on embryos of the crinoid Florometra serradísima, which produce, in the doliolaria stage, a striped pattern of ciliary bands. Embryos at gastrula and post-hatching elongation stages were divided into anterior and posterior fragments. Complementary fragments express parts of the total pattern without adding extra pattern elements, i.e. the pattern is a mosaic. Some fragments elongate which, from an examination of internal structures, we interpret as due to the elongation and displacement of the mesenteric sac. The number of pattern elements expressed correlates with degree of elongation and internal landmarks correlate with certain external pattern features. This suggests that the pattern mosaic may reside in the internal tissues, i.e. in the mesentoderm, but we are as yet unable to prove this. The results are discussed with reference to the roles of tissues of different germ layer origin in related embryos, including vertebrates, in which the mesentoderm has a significant instructive role.
Behavioral responses of streamer F mutants of Dictyostelium discoideum: Effects of cyclic GMP on cell motility
Authors: Segall Jeffrey E. 
Published: April 2021

ABSTRACT
Streamer F (stmF) mutants have a prolonged increase in intracellular cGMP in response to addition of the chemoattractant cAMP. The speed of movement and area of stmF cells were quantitated as the cells were stimulated with a rapid, uniform increase in extracellular cAMP. The speed of stmF cells rapidly drops as does that of the wild-type, but then requires about 300 seconds to recover. In contrast, the speed of the parental strain, XP55, recovers within 60-70 seconds. This prolonged drop in speed correlates with the time during which intracellular cGMP remains high, suggesting that intracellular cGMP induces this prolonged reduction in speed. Mutants from other streamer complementation groups do not show this altered response. Area measurements indicate that stmF cells do not cringe or round up as XP55 does, but spread with the same kinetics as XP55. Chemotactic orientation of the stmF cells in stable spatial gradients is similar to or slightly greater than that of the wild-type. Tracking of cells moving during aggregation indicates that the stmF cells show large drops in speed between pulses, resulting in the banding pattern seen in streams. The cells can still respond to new pulses, resulting in an aggregation time that is similar to that of XP55.
Tumour infiltrating macrophages are capable of bone resorption
Authors: Quinn J. M. W. , Athanasou N. A. 
Published: April 2021

ABSTRACTThe cell types responsible for osteolysis associated with skeletal metastasis of solid malignancies are unclear. Tumour infiltrating macrophages (TIMs) isolated from primary mammary carcinomas of C3H/Avy mice were cultured on bone slices to assess their ability to resorb bone. After 14 days in co-culture with murine marrow stromal cell line ST2 and added 1,25-dihydroxyvitamin D3 and dexamethasone, TIMs showed increased tartrate-resistant acid phosphatase activity and formed numerous lacunar resorption pits. In the absence of ST2 cells, TIMs did not form lacunar resorption pits but produced roughening of the bone surface with exposure of mineralized collagen fibres. Normal alveolar macrophages, in both the presence and absence of ST2 cells similarly produced only surface resorption. TIMs are thus capable of both low-grade (surface) and high-grade (lacunar) pathological bone resorption, a specific interaction with stromal cells being necessary for the latter to occur. TIM-mediated bone resorption could account for different clinical and pathological patterns of tumour osteolysis.
Stretch-activated Ca2+ and Ca2+-activated K+ channels in the hyphal tip plasma membrane of the oomycete Saprolegnia ferax
Authors: Garrill Ashley , Lew Roger R. , Heath I. Brent 
Published: April 2021

ABSTRACT
We have used the patch clamp technique to study ion channels involved in hyphal tip growth in the oomycete Saprolegnia ferax. The development of a technique in which protoplasts are produced in distinct linear arrays has permitted the study of transport proteins in protoplasts derived from different regions of the hypha. Using the cell-attached mode we find two K+ channels of different amplitudes, both of which are activated by Ca2+, as shown by the addition of the Ca2+ ionophore A23187. In nearly all the recordings (95%) there was a characteristic but variable oscillatory nature to the activity of these channels. K+ fluxes through these channels are inward and are of a sufficient magnitude to have a significant impact on cell turgor. Hyphal tip, but rarely distal protoplasts, also contain two stretch-activated channels, one displaying larger amplitudes and permeable to both Ca2+ and K+ and a smaller channel permeable to Mg2+. Stretch-activated ion channels permeable to calcium are of particular interest in relation to tip growth and their concentration at the hyphal tip supports a direct role in the tip growth process. This represents a significant advance toward understanding the mechanisms of regulation of this mode of cellular growth.