bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitrodevelopment of palatal tissues from embryonic mice:III. Interactions between palatal epithelium and heterotypic oral mesenchyme
Authors: Tyler Mary S. , Koch William E.
Published: April 2021

The epithelium of the secondary palate from embryonic mice (12-14 days of gestation) was enzymatically separated from the palatal mesenchyme and was cultured in association with mesenchyme from the embryonic tongue, incisor, and salivary gland. The histological differentiation of the epithelium in each type of heterotypic recombination was always palatal. Tongue mesenchyme supported full histodifferentiation of the palatal epithelium, whereas incisor mesenchyme supported only a limited histodifferentiation in the epithelium. Salivary gland mesenchyme in direct combination with palatal epithelium influenced the epithelium to become organized into a system of ducts and acini typical of glandular morphogenesis; histodifferentiation of the epithelium, however, was palatal. Salivary gland mesenchyme grown in isolation did not undergo glandular morphogenesis.

The results demonstrate that histodifferentiation of palatal epithelium may be supported by various types of mesenchyme. That a glandular morphogenesis can be induced in the epithelium without altering epithelial histogenesis indicates that histogenesis and morphogenesis are not necessarily interdependent parameters of epithelial differentiation. The ability of palatal epithelium to express its original histogenetic determination when separated from its mesenchyme as early as 12 days of gestation and recombined with heterotypic mesenchyme shows that the histogenetic program of the epithelium is relatively stable at an early stage in palatal development.
Karyotype analysis of teratocarcinomas and embryoid bodies of C3H mice
Authors: Iles S. A. , Evans E. P.
Published: April 2021

Karyotype and capacity for differentiation were determined in four transplantable teratomas, and their embryoid bodies, derived from C3H mouse embryos. An apparently normal karyotype was retained by one tumour and one subline that were able to differentiate into a wide range of tissues, but some chromosomal alterations were found in the two tumours and one subline that showed almost identical restrictions in their capacity for differentiation. Trisomy for chromosome 11 was shared by all three restricted tumours; two of the tumours had similar length changes in the same two chromosome (1 and 14) while the third was generally trisomic for four other chromosomes.
Modulation of alphafetoprotein synthesis in the early postimplantation mouse embryo
Authors: Dziadek M.
Published: April 2021

The visceral endoderm of mouse egg cylinders on the 7th and 8th days of gestation is divided into the visceral embryonic (VE) endoderm cell population which synthesizes alphafetoprotein (AFP), and the visceral extra-embryonic (VEX) endoderm population which does not synthesize AFP. Embryonic (E) and extra-embryonic (EX) ectoderm and visceral endoderm tissues were enzymically separated, reassociated in different combinations, and cultured in vitro for 48 h. The immunoperoxidase reaction on sections of cultured tissues showed that both VE and VEX endoderm cells synthesize high levels of AFP when cultured in isolation or in association with E ectoderm, but do not synthesize AFP when in close association with EX ectoderm. Both 7th and 8th day VEX endoderm cells synthesize detectable levels of AFP 12 h after isolation, and contain high levels by 24 h. It is concluded that both VE and VEX endoderm cells have the ability to synthesize AFP, but modulation of expression occurs through an inhibitory influence of the EX ectoderm.
Postembryonic development of the visual system of the locust, Schistocerca gregaria
Authors: Anderson Hilary
Published: April 2021

In the compound eye of the locust, Schistocerca gregaria, neurons from the retina project to the lamina in a precise topographical mapping.

The formation of this projection was investigated in grafting experiments which altered the spatial or temporal relationship between the retina and the lamina.

The results show that retina axons tend to grow along the paths of adjacent axons, with no indication of specificity for their normal termination sites.

It is suggested that the orderly sequence of retina differentiation during normal development plays a major role in imposing pattern both upon the developing projection and, through some form of inductive interaction between retina and lamina neurons, upon the lamina.
Studies on dwarf larvae developed from isolated blastomeres of the starfish,Asterina pectinifera
Authors: Dan-Sohkawa Marina , Satoh Noriyuki
Published: April 2021

Not only a whole denuded egg, but also blastomeres isolated from 2-, 4- and 8-cell starfish embryos developed into morphologically normal, but dwarf bipinnariae, the sizes of which were roughly proportionate to that of the respective original blastomeres. Some of the blastomeres isolated from the 16-cell stage were also capable of developing into the larval stage. All isolated blastomeres divided in good synchrony with the control embryos. Blastulae of all groups gastrulated within quite a short range of time, around 14·5 h after insemination at 20 ± 1 °C, although one-third of the 1/8-blastula missed this chance but gastrulated by 19-5 h. The number of constituent cells of the 1/8-gastrula was counted to be about 560, which corresponds roughly to one-half that of the 1/4-, one-fourth of the 1/2- and one-eighth of the 1/1-gastrula. This ratio also fitted roughly for the total cell volume.

The results are compared with those of other invertebrate species, as well as of some vertebrates, and are discussed in connexion not only with the concepts of ‘regulative’ and ‘mosaic’ eggs, but also with a criterion that does not fit into either of these; the developmental system of the mammals.
Cell adhesiveness and embryonic differentiation
Authors: Bellairs Ruth , Curtis A. S. G. , Sanders E. J.
Published: April 2021

The aim of the investigation was to decide whether changes in cell to cell adhesiveness took place during embryonic differentiation. The technique of Curtis (1969) was used to measure the adhesive behaviour of several types of ectodermal, neural and mesodermal cells of the chick embryo at stages 7 and 12 of differentiation. Cells dissected from segmented mesoderm were found to be more adhesive than cells from unsegmented mesoderm. Cells from the ectoderm were more adhesive than those from the neural tissue, at both stages 7 and 12. Cells from both ectoderm and neural tissue became more adhesive between stages 7 and 12. It is concluded that an increase in adhesiveness may play a role in somite segmentation, but not in neural tube formation.
Biochemical changes in developmentally retarded Xenopus laevis larvae
Authors: Doyle M. J. , Maclean N.
Published: April 2021

Premetamorphic tadpoles of Xenopus laevis reared in water containing 0·01 % propyl-thiouracil are developmentally retarded and metamorphosis is prevented. When uncrowded, they continue to grow to a giant size. Moderate crowding leads to a slower rate of growth. Thus morphologically premetamorphic tadpoles were produced with lens diameters appropriate to either normal premetamorphic, climactic or post-metamorphic animals. The lens crystallins of such tadpoles have been separated by immunoelectrophoresis and polyacryl-amide gel electrophoresis. The crystallin pattern was correlated with lens diameter rather than with body stage. Giant retarded larvae possessed crystallin patterns identical to those of normal adults. The thyroid antagonist propylthiouracil is therefore unable to prevent the lens crystallin transition, the beginning of which is normally temporally correlated with metamorphosis.
X-chromosome activity in preimplantation mouse embryos from XX and XO mothers
Authors: Monk Marilyn , Harper Mary
Published: April 2021

Embryos from XO female mice begin development with half the activity levels of an enzyme (HPRT) coded for by a gene on the X chromosome, compared with embryos from XX females. Groups of unfertilized eggs and individual embryos at the 8-cell, morula and blastocyst stages were assayed for HPRT activity. An autosomally coded enzyme (APRT) was assayed simultaneously in the same reaction mix as a control. There is a substantial increase in HPRT activity by the 8-cell stage. However, the mean activity of HPRT in embryos of XO mothers remains half that in embryos of XX mothers. This suggests a signifi- cant maternally inherited component of HPRT activity in 8-cell embryos. By the 9- to 16-cell morula stage the HPRT activities in the two groups of embryos become similar due, pre- sumably, to a transition to embryo-coded activity; HPRT activities in individual morulae from XX mothers show a bimodal distribution consistent with the hypothesis that both X- chromosomes are active in XX embryos at this stage.
The effects of some Robertsonian chromosome combinations on the seminiferous epithelium of the mouse
Authors: Redi C. A. , Garagna S. , Hilscher B. , Winking H.
Published: April 2021

In Mammals, structural rearrangements of the karyotype cause considerable trouble to the spermatogenic process. Making use of an experimental animal model of Robertsonian chromosomal variation in the house mouse (Gropp, Winking & Redi, 1982a) the effects of these chromosome structural rearrangements on the spermatogenic process were studied in fertile and chromosomally derived subfertile and sterile mice. Each karyotype condition was related to the cytological composition of the twelve stages of the seminiferous epithelium, studied in PAS-haematoxylin-stained testicular sections, with the following results: in subfertile males there is a depletion of spermatogonia in the regenerating compartment but their differentiation is not affected. In the sterile males there is degeneration of primary and secondary spermatocytes and massive spermatid degeneration.Spermatocyte development is retarded in nearly 50 % of the spermatocyte population in subfertile males. Moreover the ratio between primary spermatocytes and spermatids is reduced to about 1:2 in subfertile males, while the few spermatids produced in sterile males had degenerated during stages I to VIII.The number of Sertoli cells/100 μm throughout the cycle of spermatogenesis is the same in the three conditions studied. These data indicate that the spermatogenic process is affected by structural changes not only at the meiotic level (primary spermatocyte failure to follow the normal pattern of differentiation and occurrence of defective spermatids) but also at the premeiotic stage, when undifferentiated spermatogonia are regenerating.
Clonal analysis of intestinal crypt populations in mouse aggregation chimaeras
Authors: H. Schmidt Günter , Garbutt David J. , Wilkinson Maureen M. , Ponder Bruce A. J.
Published: April 2021

The epithelium of each individual intestinal crypt in adult mouse aggregation chimaeras is composed of cells of a single parental genotype (Ponder et al. 1985). Using a carbohydrate polymorphism recognized by Dolichos biflorus agglutinin as a strain-specific marker on entire sheets of intestinal mucosa, we have analysed the two-dimensional mosaic patterns of patches of the chimaeric intestinal crypt population. The relative proportions of each genotype varied greatly along the length of any one intestine. In chimaeras with highly unbalanced proportions, the minority component occurred as discrete patches. Patches of single or a few crypts were most frequent, but a smaller number of much larger patches was always present. The size frequency distribution of discrete patches was highly concave and departed significantly from a geometric distribution (a model for non-differential proliferation), but fitted the more skewed negative binomial model. The data are consistent with the interpretation that most progenitor crypts never or rarely divide, while a minority proliferate to a greater extent. We discuss ways in which our system could be analysed further to examine this interpretation. Our results also support Whitten’s (1978) conclusion from a computer simulation that the mean patch size, as it has previously been used in statistical analyses of chimaeric tissue, ‘is not a reliable statistic on which to judge mosaicism’.
Transcription of similar sets of rare maternal RNAs and rare nuclear RNAs in sea urchin blastulae and adult coelomocytes
Authors: Kleene Kenneth C. , Humphreys Tom
Published: April 2021

We studied the sequences transcribed in the rare class of hnRNA and the rare maternal RNA set in blastula embryos and a tissue of adult sea urchins, coelomocytes. About 26 % of labelled single-copy DNA formed hybrids which bound to hydroxyapatite after three cycles of hybridization with nuclear RNA from blastulae and coelomocytes. This corresponds to transcription of about 50 % of the single-copy genome by both cell populations. To compare the rare hnRNA sequences synthesized by blastulae and coelomocytes directly, labelled single-copy DNA was hybridized with blastula nuclear RNA to high RNA C0t, fractionated into sequences complementary and non-complementary to blastula nuclear RNA by chromotography on hydroxyapatite, and then each fraction was rehybridized with nuclear RNA from blastulae and coelomocytes. About 62 % of the labelled DNA complementary to blastula nuclear RNA and about 1·5 % of the labelled DNA non-complementary to blastula nuclear RNA hybridized with nuclear RNA from both cell populations. Thus, coelomocytes and blastula embryos transcribe essentially the same single-copy sequences in the rare hnRNA class. A probe for the rare maternal RNA set was isolated by hybridizing single-copy DNA with total egg RNA to high RNA C0t. 65–67 % of this probe hybridized with whole-cell RNA from eggs, blastulae, plutei and coelomocytes demonstrating that essentially all rare maternal RNAs are present, and presumably transcribed, in blastulae, plutei and coelomocytes.
Separation of wound healing from regeneration in the cockroach leg
Authors: Truby Paul R.
Published: April 2021

It has been shown that after a critical point in the moult cycle of a cockroach, wound healing can occur but regeneration of pattern does not take place until the following intermoult period. Leg removal after the critical point is used to separate the processes of wound healing and leg regeneration. This permits the study of patterns of cell division resulting from wound healing to be distinguished from those involved in leg regeneration.

During wound healing, cell division occurs in the epidermal cells of approximately the distal half of the trochanter. The cells then return to the resting state until after the next ecdysis. Regeneration starts with cell division occurring in the distal half of the trochanter, and then spreading to include cells of the proximal trochanter and distal coxa. This spread and the following patterns of growth and redifferentiation appear to be the same as for regeneration following leg removal prior to the critical point, with the more distal structures completing early stages of regeneration first.

Scanning electron micrographs of the cuticle of the trochanter after the ecdysis following leg removal support the evidence from the patterns of cell division in suggesting that the distal half of the trochanter is dedifferentiated during wound healing.
Synthesis of apolipoproteins, alphafoetoprotein, albumin, and transferrin by the human foetal yolk sack and other foetal organs
Authors: Shi W-K. , Hopkins B. , Thompson S. , Heath J. K. , Luke B. M. , Graham C. F.
Published: April 2021

Fragments of human foetal organs and blood at 5 –11 weeks of postfertilization development were cultured in radioactive protein precursors. The secreted products were characterized by immunoprecipitation, and by measuring the mobility of the immunoprecipitates on polyacrylamide gels. It was found that secondary human yolk sacks secreted apolipoproteins A1 and B. The work of previous authors on the synthesis of other serum products by this organ and by the foetal liver and by the foetal intestines was confirmed. Within the yolk sack, the endoderm, the blood cells, and the outside epithelium reacted with antibodies against apolipoprotein Al and transferrin. By metabolic labelling of umbilical cord blood, it was found that blood did not secrete apolipoproteins Al and B. Blood cells could therefore not be a source of these secreted products.
Cell surface changes during cleavage of newt eggs: scanning electron microscopic studies
Authors: Ohshima Hiromasa , Kubota Tomoyuki
Published: April 2021

Scanning electron microscopic studies were carried out on changes of the cell surface during the first cleavage of eggs of the newt, Cynopus (Triturus) pyrrhogaster. A dense population of elongated microvilli, which initially covered a double line indicating the initial furrow and stress marks running on each side of it, became located inside the pigmented area a little apart from its border with the unpigmented area when this borderline was established. This finding, together with data of carbon marking experiments, indicates that membrane growth occurs not only at the presumptive unpigmented surface, but also in a small portion of the presumptive pigmented area adjoining it. During cleavage within the vitelline membrane, a stable intercellular junction at the border of the pigmented and unpigmented surfaces was formed through the following successive processes: the appearance of individual lamellipodia on the borderline; contact of their apical filopodia with those of the opposite blastomere; contact of the lamellipodial bodies; and complete joining of the whole of the lamellipodia in contact. In cleavage of demembranated eggs, in which there is no chance of contact of lamellipodia of the two blastomeres, each lamellipodium persisted in an isolated state until the onset of the next division. In most cases, many strained or broken threads were seen across the space formed by opening of opposing blastomeres, at their peripheries. These threads were cytoplasmic in nature and showed cell contact. Similar threads were found stretched between blastomeres when the closed furrow was opened in medium containing EGTA.
The Development of Pandora inaequivalvis (Linné)
Authors: Allen J. A.
Published: April 2021

Artificial fertilization of the eggs of P. inaequivalvis has been carried out and the development followed to the dissoconch stage. The development is very rapid and metamorphosis occurs in less than 4 days. The veliger spends less than one day in the plankton and this is the first record of a short-lived planktotrophic lamellibranch larva. The speed of development is related to the relatively large (105– 125 μ diameter) size of the egg and its contained food reserves. There is minimal dispersal of the young from the very localized habitat of the adult. No protonephridia or larval eyes are developed and the gut follows a simple course in comparison with other lamellibranch larvae. The gills do not develop until after metamorphosis and the large palps and foot produce the ciliary currents connected with respiration, feeding, and cleansing between the loss of the velum and the development of the functional gill.
Cell Degeneration in the Larval Ventral Horn of Xenopus laevis (Daudin)
Authors: Hughes Arthur
Published: April 2021

Cell death accompanies a variety of developmental processes in many tissues and systems of organs. A comprehensive review by Glücksmann (1951) has revealed how widespread is the occurrence of degenerating cells in vertebrate embryos. Within the developing nervous system, the earliest descriptions of cellular degeneration are due to Barbieri (1905) in Amphibia, and to Collin (1906) in the chick embryo. Since that time, destruction of cells has been observed in the morphogenesis of the neural tube, most recently by Boyd (1955) and by Kallen (1955) in early mammalian embryos; in the establishment of regional differences between limb and non limb-levels in spinal ganglia of the chick (Hamburger & Levi-Montalcini, 1949), and also in the histogenesis of Anuran ventral horn cells (Xenopus,Hughes & Tschumi, 1958; Eleutherodactylus,Hughes, 1959).
Systemic Influence on Activity of Hair Follicles in Skin Homografts
Authors: Ebling F. J. , Johnson Elizabeth
Published: April 2021

Strips of skin from the flank were exchanged between rats aged 28 and 49 days respectively, so that their expected hair growth waves would be out of phase. Similarly sited autografts were used as controls. In the wave of growth immediately following grafting eruption of hairs on the homografts coincided with that on the donor’s autograft. In the older recipient this was significantly in advance and in the younger recipient significantly in retard of hair growth on their autografts. Thus, follicular activity has an inherent rhythm which continues for at least one cycle after homotopic grafting. In the succeeding waves of growth, when follicular activity in the recipient preceded that in the donor, the time of eruption of hair on the homograft was advanced, and by the third wave after grafting was completely in line with its host. When follicular activity in the recipient succeeded that in the donor the homografts tended to behave donor-wise. These results show clearly that both an inherent rhythm and a systemic stimulus are involved in follicular activity at a particular site.
Certain Aspects of Cell Lineage and Morphogenesis Studied in Embryos of Drosophila melanogaster with an Ultra-violet Micro-beam
Authors: Hathaway D. S. , Selman G. G.
Published: April 2021

A method is described for using a reflecting microscope to irradiate small precisely located areas of insect embryos with lethal micro-beams of ultraviolet light, so that cell lineages may be traced from histological studies of subsequent development. The gamete precursors in Drosophila melanogaster were shown to be those pole cells which are carried into the posterior mid-gut rudiment during gastrulation. The interblastodermal-migrating pole cells are not incorporated into the embryonic gonad but probably play a role in the formation of mid-gut epithelium. The mesodermal rudiment of the gonad is derived from the posterior half of the mid-ventral mesodermal invagination, and is formed independently of precursor gamete cells. Bilaterally and unilaterally castrated flies resulted after pole-cell irradiation. Support for certain parts of Poulson’s anlagen plan of the Drosophila egg was obtained from studies of development after irradiation of certain areas of blastema and blastoderm. The non-cellular blastema stage was more easily damaged by ultra-violet radiation than the blastoderm stage. Gastrulation was a critical stage, but the study supported Sonnenblick’s ideas concerning the morphogenic factors governing endodermal invagination. No departure from mosaicism was noticed, except that the results indicated some slight regulative capacity in the presumptive pole-cell area at the 1-hour stage.
Integrative genomic analysis of blood pressure and related phenotypes in rats
Authors: Takeuchi Fumihiko , Liang Yi-Qiang , Isono Masato , Tajima Michiko , Cui Zong Hu , Iizuka Yoko , Gotoda Takanari , Nabika Toru , Kato Norihiro
Published: April 2021

Despite remarkable progress made in human genome-wide association studies, there remains a substantial gap between statistical evidence for genetic associations and functional comprehension of the underlying mechanisms governing these associations. As a means of bridging this gap, we performed genomic analysis of blood pressure (BP) and related phenotypes in spontaneously hypertensive rats (SHR) and their substrain, stroke-prone SHR (SHRSP), both of which are unique genetic models of severe hypertension and cardiovascular complications. By integrating whole-genome sequencing, transcriptome profiling, genome-wide linkage scans (maximum n=1415), fine congenic mapping (maximum n=8704), pharmacological intervention and comparative analysis with transcriptome-wide association study (TWAS) datasets, we searched causal genes and causal pathways for the tested traits. The overall results validated the polygenic architecture of elevated BP compared with a non-hypertensive control strain, Wistar Kyoto rats (WKY); e.g. inter-strain BP differences between SHRSP and WKY could be largely explained by an aggregate of BP changes in seven SHRSP-derived consomic strains. We identified 26 potential target genes, including rat homologs of human TWAS loci, for the tested traits. In this study, we re-discovered 18 genes that had previously been determined to contribute to hypertension or cardiovascular phenotypes. Notably, five of these genes belong to the kallikrein–kinin/renin–angiotensin systems (KKS/RAS), in which the most prominent differential expression between hypertensive and non-hypertensive alleles could be detected in rat Klk1 paralogs. In combination with a pharmacological intervention, we provide in vivo experimental evidence supporting the presence of key disease pathways, such as KKS/RAS, in a rat polygenic hypertension model.
The liver metastatic niche: modelling the extracellular matrix in metastasis
Authors: Drew James , Machesky Laura M.
Published: April 2021

Dissemination of malignant cells from primary tumours to metastatic sites is a key step in cancer progression. Disseminated tumour cells preferentially settle in specific target organs, and the success of such metastases depends on dynamic interactions between cancer cells and the microenvironments they encounter at secondary sites. Two emerging concepts concerning the biology of metastasis are that organ-specific microenvironments influence the fate of disseminated cancer cells, and that cancer cell-extracellular matrix interactions have important roles at all stages of the metastatic cascade. The extracellular matrix is the complex and dynamic non-cellular component of tissues that provides a physical scaffold and conveys essential adhesive and paracrine signals for a tissue's function. Here, we focus on how extracellular matrix dynamics contribute to liver metastases – a common and deadly event. We discuss how matrix components of the healthy and premetastatic liver support early seeding of disseminated cancer cells, and how the matrix derived from both cancer and liver contributes to the changes in niche composition as metastasis progresses. We also highlight the technical developments that are providing new insights into the stochastic, dynamic and multifaceted roles of the liver extracellular matrix in permitting and sustaining metastasis. An understanding of the contribution of the extracellular matrix to different stages of metastasis may well pave the way to targeted and effective therapies against metastatic disease.
Synergic effect of atorvastatin and ambrisentan on sinusoidal and hemodynamic alterations in a rat model of NASH
Authors: Bravo Miren , Raurell Imma , Barberá Aurora , Hide Diana , Gil Mar , Estrella Federico , Salcedo María Teresa , Augustin Salvador , Genescà Joan , Martell María
Published: April 2021

In non-alcoholic steatohepatitis (NASH), decreased nitric oxide and increased endothelin-1 (ET-1, also known as EDN1) released by sinusoidal endothelial cells (LSEC) induce hepatic stellate cell (HSC) contraction and contribute to portal hypertension (PH). Statins improve LSEC function, and ambrisentan is a selective endothelin-receptor-A antagonist. We aimed to analyse the combined effects of atorvastatin and ambrisentan on liver histopathology and hemodynamics, together with assessing the underlying mechanism in a rat NASH model. Diet-induced NASH rats were treated with atorvastatin (10 mg/kg/day), ambrisentan (30 mg/kg/day or 2 mg/kg/day) or a combination of both for 2 weeks. Hemodynamic parameters were registered and liver histology and serum biochemical determinations analysed. Expression of proteins were studied by immunoblotting. Conditioned media experiments were performed with LSEC. HSCs were characterized by RT-PCR, and a collagen lattice contraction assay was performed. Atorvastatin and ambrisentan act synergistically in combination to completely normalize liver hemodynamics and reverse histological NASH by 75%. Atorvastatin reversed the sinusoidal contractile phenotype, thus improving endothelial function, whereas ambrisentan prevented the contractile response in HSCs by blocking ET-1 response. Additionally, ambrisentan also increased eNOS (also known as Nos3) phosphorylation levels in LSEC, via facilitating the stimulation of endothelin-receptor-B in these cells. Furthermore, the serum alanine aminotransferase of the combined treatment group decreased to normal levels, and this group exhibited a restoration of the HSC quiescent phenotype. The combination of atorvastatin and ambrisentan remarkably improves liver histology and PH in a diet-induced NASH model. By recovering LSEC function, together with inhibiting the activation and contraction of HSC, this combined treatment may be an effective treatment for NASH patients.
Regulation of mitosis: III. cytological effects of 2,4,5-trichloro-phenoxyacetic acid and of dioxin contaminants in 2,4,5-T formulations
Authors: Jackson W. T.
Published: April 2021

The conclusion of earlier studies that the pronounced cytological effects of 2,4,5-trichloro-phenoxyacetic acid (2,4,5-T) formulations are actually due to 2,4,5-T is unwarranted. Inhibition of mitosis and the development of cytological abnormalities are caused by a contaminant, 2>3,7>S-tetrachlorodibenzo-/>-dioxin. The appearance and behaviour of dividing endosperm cells of the African blood lily (Haemanthus katherinae Baker) subjected to a 10−4 M solution of highly purified 2,4,5-T, observed in vitro by phase-contrast microscopy for a 2-h treatment period, did not differ significantly from controls. Subjecting these cells to 0·2 or 10μg/l. dioxin, to 0 2 μg/1. dioxin plus 10−4 M 2,4,5-T (highly purified sample), or to 10−1 M 2,4,5-T containing dioxin as a contaminant caused a dramatic inhibition of mitosis. These preparations also induced formation of dicentric bridges, chromatin fusion with formation of multinuclei or a single large nucleus. Impairment of the functioning of the mitotic apparatus was evident; chromosomes ‘floated free ‘in the cytoplasm. Both quantitative and qualitative data substantiate these conclusions.

In view of the extreme toxicity of dioxins to man, of their demonstrated teratogenic effects in some animals under experimental conditions, of their effectiveness in producing cytological effects in dividing cells formerly ascribed to 2,4,5-T, of their presence as contaminants in 2.4.5-T, pentachlorophenol, and other polychlorophenols, and of the potential for widespread contamination of the environment with dioxins, investigation of all facets of this class of compounds should be given high priority. It is quite possible that contamination of the environment with dioxins from sources of polychlorophenols is far greater than that contributed by 2.4.5-T. Amplification of dioxin levels in food chains is, of course, of particular concern.
Cell electrophoresis of the cellular slime mould Dictyostelium Discoideum: I. characterization of some of the cell surface ionogenic groups
Authors: Lee K.-C.
Published: April 2021

The reduction in cell surface charge density during the early stages of differentiation of the cellular slime mould, Dictyostelium discoideum, has been studied by the technique of cell electrophoresis. Using specific chemical reagents, it was shown that the cell surface negative charge was probably due to side chain carboxyl groups of proteins. During differentiation, there was a decrease in the density of these groups, accompanied by an increase in that of amino groups. The significance of this finding is discussed in relation to cell surface structure and cell differentiation.
Dna synthesis in purified populations of avian erythroid cells
Authors: Williams A. F.
Published: April 2021

By the use of equilibrium density-gradient centrifugation erythroblasts and early polychromatic erythrocytes have been isolated from avian anaemic bone marrow. Cells from both the unfractionated and purified preparations have been characterized in terms of their histological type, size, haemoglobin content and ability to synthesize DNA. Erythroblasts were the only cells to synthesize DNA and it appeared that their progeny, the polychromatic erythrocyte, failed to enter a new S’ phase. The experimental system described allows biochemical characterization of earlier stages of avian erythropoiesis than has previously been possible.
Pronuclear membrane alterations during approximation of pronuclei and initiation of cleavage in the rabbit
Authors: Gondos B. , Bhiraleus P. , Conner L. A.
Published: April 2021

As the male and female pronuclei of flushed rabbit tubal ova approach each other, numerous projections appear on the proximal surfaces, resulting in a severely irregular appearance. Each pronuclear envelope consists of 2 parallel membranes separated by a distance of 40–60 nm; annular ‘pores ‘are conspicuous in regions of pronuclear approximation. Stacks of smoothsurfaced membranes form parallel annulate lamellae in the cytoplasm adjacent to the pronuclei. When the 2 pronuclei come to lie in direct apposition, the adjacent envelopes are flattened against one another, crowding out intervening cytoplasm and producing an arrangement of 4 equidistant membranes. Interspersed between segments of apposing membranes are small ‘cytoplasmic islets ‘. At several points along the approximating surfaces intemuclear channels form between adjacent projections. This results in partial pronuclear union, but not complete fusion. After disruption of the pronuclei and the appearance of chromosomal aggregates in the centre of the egg, segments of pronuclear membranes are still visible in the cytoplasm. The membrane fragments are associated with collections of smooth vesicles, the latter increasing greatly in number during cleavage.
Distribution of the intermediate elements operating in ER to Golgi transport
Authors: Saraste Jaakko , Svensson Kerstin
Published: April 2021

We have used a 58 kDa membrane protein (p58) as a marker to study the transport pathway between the rough endoplasmic reticulum (ER) and the Golgi apparatus. Immunolocalization of p58 in fibroblasts showed its presence in a single cisterna and in small tubular and vesicular elements at the cis side of the Golgi apparatus. In addition, the protein was detected in large (200–500 nm in diameter) tubulovesicular structures, clustered in the Golgi region but also found in peripheral locations. These represent intermediates in ER to Golgi transport since they contained newly synthesized viral glycoproteins, arrested in cells at I5°C. The peripheral structures accumulated at low temperature but reclustered rapidly to the Golgi region upon shift of cells back to 37°C. This movement involved long intracellular distances and was efficiently inhibited by nocodazole, indicating that it requires the integrity of microtubules. In contrast, reclustering was unaffected by brefeldin A (BFA), suggesting that this compound affects ER to Golgi transport prior to the temperature-sensitive step. In BFA-treated cells p58 was localized to scattered, tubular, smooth ER clusters, found in close association with rough ER cisternae. The cellular distribution of the intermediate elements indicates that the sites of protein exit are widely distributed within the rough ER network. We suggest that the smooth ER locations where p58 accumulates in BFA-treated cells could represent such peripheral exit sites.
Reorganization of cytoplasmic structures during cell fusion
Authors: Zheng Qiang , Chang Donald C.
Published: April 2021

In order to provide a better understanding of the dynamic process of cell fusion, we studied the reorganization of cytoplasmic structures in electrofused CV-1 cells. Using fluorescence microscopy and double staining methods, we examined correlations between the structural patterns of the major cytoskeletal proteins (microtubules, actin and vimentin intermediate filaments) and the distribution of various organelles (endoplasmic reticulum, mitochondria and nuclei) at different stages of cell fusion. Our results suggest that microtubules appear to play a primary role in the process of cytoplasmic reorganization. At the early stage of cell fusion, microtubules were observed to infiltrate rapidly into the newly formed cytoplasmic bridges and establish a connec tion between the cytoskeletal networks of fusing cells. The reorganization of microtubules was found to be correlated with the redistribution of endoplasmic reticulum (ER), vimentin intermediate filaments, mitochondria, and the aggregation of nuclei. The Factin system, on the other hand, appeared to be independent of the reorganization of the other cytoplasmic structures. The principal function of Factin during cell fusion is probably to widen the cytoplasmic bridges by lamellipodial extension.
Induction of vacuolar apical compartments in the Caco-2 intestinal epithelial cell line
Authors: Gilbert Thierry , Rodriguez-Boulan Enrique
Published: April 2021

Complete disruption of the microtubular network by colchicine or nocodazole in Caco-2 intestinal epithelial cells results in the appearance of basolateral microvilli and brush border-containing intracellular vacuoles (vacuolar apical compartment: VAC). These vacuoles are surrounded by a terminal web, express apical markers and exclude basolateral markers. The vacuoles do not originate from internalized apical or basolateral plasma membrane and their development is blocked by protein synthesis inhibitors, suggesting that they are newly synthesized. After removal of the microtubule inhibitors, VACs are usually degraded and/or released into the lateral intercellular space. Rarely was fusion with the apical membrane observed. These experiments support a role for microtubules in the biogenesis of the apical surface and indicate that, under some conditions, apical plasma membrane assembly may occur in the cytoplasm, as observed in some human pathological states.
Characterization of luminal and basal cells flow-sorted from the adult rat mammary parenchyma
Authors: Dundas S. R. , Ormerod M. G. , Gusterson B. A. , O’hare M. J.
Published: April 2021

Differentially expressed membrane antigens have been used to flow-sort viable luminal epithelial and myoepithelial cells from freshly disaggregated adult virgin rat mammary parenchyma. Resulting cultures and clones have been characterized morphologically and by a panel of antibodies that recognise cell-type-specific cytoskeletal antigens in the intact mammary gland. Five clonal phenotypes were recognisable by morphological criteria, three (types 1-3) exclusively associated with sorted luminal epithelial (25.5-positive) cells, and two (types 4 and 5) generated from the sorted myoepithelial (CALLA/neutral endopeptidase 24.11-positive) cells. All clones derived from myoepithelial cells continued to express a basal parenchymal marker in the form of the rat equivalent of human cytokeratin 14, while smooth muscle a-actin was expressed by the small slowly growing type 4 clones but was found in fewer cells in rapidly proliferating type 5 myoepithelially derived clones. Two of the luminal clone types, characterized by an attenuated appearance and slow growth (types 1/2), expressed only luminal-specific markers, including the equivalent of human cytokeratins 7/18/19. Type 3 clones, by contrast, consisted of rapidly proliferating cells, many of which either co-expressed CK14 and CK18 antigens (type 3a) or were composed of a mosaic of CK14+/CK18−, CK14+/CK18+ and CKI4−/ CK18+ cells (type 3b). The sorted myoepithelially derived clones grew faster than clones from sorted luminal cells as evidenced by the larger fraction of cells synthesizing DNA. All types of clone could be obtained from both isolated ducts and alveoli, when these were cloned separately, although there were some differences in their relative frequency. These results demonstrate a heterogeneity within both the luminal and the myoepithelial/basal compartments of the rat mammary parenchyma and provide the basis for studies of growth and differentiation of specific rodent mammary sub-populations in culture, and in vivo after transplantation.
Dictyostelium discoideumcontains two profilin isoforms that differ in structure and fuction
Authors: Haugwitz Michael , Noegel Angelika A. , Rieger Daniela , Lottspeich Friedrich , Schleicher Michael
Published: April 2021

Two profilin isoforms (profilins I and II) have been purified from Dictyostelium discoideum, using affinity chromatography on a poly(L-proline) matrix; the isoforms could be separated by cation-exchange chromatography on a FPLC system. The gene coding for profilin I was cloned from a Agtll cDNA library using a profilin I-specific monoclonal antibody. The profilin II cDNA was isolated by probing the cDNA library with an oligonucleotide deduced from the N-terminal amino acid sequence of profilin II, which has an open N terminus in contrast to profilin I. The deduced amino acid sequences of both genes show that profilin I in comparison to profilin II is slightly larger (13 064 Da vs 12 729 Da), has a more acidic isoelectric point (calc, pl 6.62 vs 7.26) and shares with profilin II 68 identical residues out of 126 amino acids. Although both profilins contain a conserved lysine residue in the putative actin-binding region and can be crosslinked covalently to G-actin, the crosslinking efficiency of profilin II to actin is substantially higher than that of profilin I. These data are in agreement with studies on the functional properties of the profilin isoforms. In most prep arations profilin II was more efficient in delaying the onset of elongation during the course of actin polymerization and caused a higher critical concentration for actin polymerization than profilin I, probably due to the slightly increased affinity of profilin II for D. discoideum G-actin (approx. Kd l.8×10-6M) as compared to that of profilin I (approx. Kd 5.l× 10-6M). This difference was not always so obvious and, we are trying to identify non-protein-aceous co-purifying inhibitors that can obscure the data obtained from in vitro assays. The messenger RNA of both profilin isoforms is present throughout development of D. discoideum. However, whereas the profilin I-specific mRNA accumulates after 6-9 h of starvation (aggregation stage), the profilin II-specific mRNA peaks at early stages and disappears during later development almost completely. This suggests differential functions for the profilin isoforms during D. discoideum development.
Postmitotic reassembly of the cell nucleus in whole cells: an electron-spectroscopic study
Authors: Stracke Sylvia , Martin Rainer
Published: April 2021

By electron-spectroscopic imaging it is possible to visualize selectively the distribution of phosphorusrich structures such as nucleosomes, ribosomes or other ribonucleoprotein particles. Using this method we re-examined assembly of the nucleus in telophase of dividing onion root cells and human HeLa cells. Our observations disagree considerably with conclusions drawn from work with cell-free systems. We consistently observed reassembly of nuclear envelope cisternae from vesicles in the cytoplasm without direct contact with chromatin. The preassembled envelope cisternae then enclosed the telophase chromosome mass, contacting the chromatin in some tracts, but also trapping cytoplasmic material such as ribosomes between chromosomes and envelope. Until a late stage in telophase the re-forming nuclear envelope left large gaps between the nuclear and the cytoplasmic compartments. Exclusion of cytoplasmic material from the re-assembling nucleus was facilitated by prenucleolar material, which accumulated in the deep furrows of the chromosomes and interchromosomal spaces. This material expanded considerably while the envelope was still open, in this way displacing cytoplasm non-selectively from the future nucleus. The model we propose for reassembly of the nucleus in whole cells does not postulate contact with and complete enclosure of chromosomes by the re-forming envelope, and suggests a decisive role for expanding prenucleolar material in the process of nucleocytoplasmic compartmentalization.
Pollen development in orchids. 5. A generative cell domain involved in spatial control of the hemispherical cell plate
Authors: Brown R. C. , Lemmon B. E.
Published: April 2021

The unequal first pollen mitosis in moth orchids (Phalaenopsis) is followed by an unusual form of cytokinesis that isolates a small lens-shaped generative cell from a large vegetative cell. No preprophase band of microtubules predicts the division plane and the new cell plate grows completely around the generative cell rather than fusing with the parental wall. Development of the phragmoplast cytoskeleton consisting of fusiform bundles of microtubules and F-actin occurs in three major stages: (1) the initial asymmetrical phragmoplast conforming to the shape of the interzonal region, which tapers from the broad mass of chromosomes at the generative pole to the rounded mass at the vegetative pole; (2) the symmetrical plate-like phragmoplast; and (3) the hemispherical phragmoplast, which curves around the generative nucleus. Microtubules of the generative half of the hemispherical phragmoplast are nuclearbased, while those on the vegetative side terminate in endoplasmic reticulum. The path of the phragmoplast appears to outline a cytoplasmic domain defined by a radial system of microtubules emanating from the generative nucleus.
The effects of dimethyl sulfoxide and retinoic acid on the cell growth and the phenotype of ovarian cancer cells
Authors: Grunt T. W. , Somay C. , Pavelka M. , Ellinger A. , Dittrich E. , Dittrich Ch.
Published: April 2021

We have compared the in vitro effects of the differentiation inducers dimethyl sulfoxide (DMSO) and retinoic acid (RA) on a polyclonal human ovarian cancer cell line (HOC-7). Density gradient fractionation of untreated cells reveals that a proportion of rapidly growing, polygonal cells with medium density is capable of spontaneous reversion into a slowly growing low-density phenotype with flattened morphology similar to non-transformed human ovarian surface epithelial cells. Clonal expansion of these low-density cells proves that the observed characteristics are stable for prolonged culture periods. Exposure of HOC-7 cells to DMSO and RA or removal of the serum from the medium is effective in enhancing the proportion of these low-density cells. Application of DMSO causes the cells to become flattened and elongated, and to develop rodlike protrusions. In these cytoplasmic extensions thick filament bundles are dominant. Immunofluorescence studies demonstrate that both untreated low-density subclones and DMSO-treated polyclonal cells are much more reactive for cytokeratin than medium-density subclones or untreated parental cells. Furthermore, immunocytochemistry and fixedcell ELISA reveal 2-to 5-fold greater amounts of desmoplakins I and II and of fibronectin in low-density subclones and in DMSO-treated cells as compared to medium-density subclones and control cultures. RA exerts weaker effects on the phenotype of the cells. Both inducers reduce DNA synthesis and inhibit the anchorage-dependent and the anchorageindependent cell growth in a dose- and time-dependent manner. The restoration of the original morphology and growth rate after removal of the differentiation-inducing agents proves that the observed changes are reversible; this indicates that the cells do not become terminally differentiated. The described phenotypic and growth kinetic reactions should prove useful for the future recognition of induced maturation of ovarian cancer cells.