bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns of peanut agglutinin binding within the developing grasshopper central nervous system
Authors: Burt Richard , Anderson Hilary 
Published: April 2021

ABSTRACT
The location of peanut agglutinin (PNA) binding was investigated in the segmental ganglia of the developing grasshopper embryo. Neuronal processes were stained but cell bodies were not. The first appearance of PNA binding in development was associated with the first neurons to initiate axon outgrowth, the progeny of the MP2 cells. In the early stages of development the location of PNA binding was congruent with that of antibodies against horseradish peroxidase (HRP), which bind to neurons. In more advanced ganglia only a subpopulation of those neuronal processes that bound auti-HRP also bound PNA. The results suggest that PNA-binding sites are present only on those neuronal processes which are still developing and raise the possibility that these molecules may play a rôle in neurite outgrowth and navigation.
The role of glycosaminoglycans in anuran pigment cell migration
Authors: Tucker R. P. 
Published: April 2021

ABSTRACT
The migratory pathways of neural crest-derived pigment cells were examined in two anurans, Xenopus laevis and Discoglossus pictus, and correlated with the distribution of glycosaminoglycans (GAG) in the extracellular matrix (ECM) of these pathways. In Xenopus, melanophores in the trunk reach the dermis by initially migrating ventrally, between the neural tube and somites, and then by migrating through the somites to reach the subectodermal space. In Discoglossus, melanophores, iridophores, and xanthophores migrate laterally over the dorsal margin of the somites to reach the dermis. GAG was identified in the light microscope using alcian blue staining and in the electron microscope using ruthenium red staining. The ECM at the dorsal entrance to the lateral pathway in Xenopus and in young Discoglossus (at a stage prior to invasion by pigment cells) is filled with 25–50 nm chondroitin sulphate proteoglycan aggregates. When this ECM in Xenopus is digested in vivo with chondroitinase ABC, melanophores enter the lateral pathway. In older Discoglossus embryos, the migration of pigment cells into the lateral pathway is correlated with increases in the space between the ectoderm and somites and in the number of hyaluronate microfibrils. These observations suggest that chondroitin sulphate proteoglycan in the subectodermal ECM restricts the migration of pigment cells into the lateral pathway by limiting the amount of space for migration and possibly by acting as a less adhesive migratory substratum than the ventral pathway, and that in Discoglossus hyaluronate opens spaces permitting the migration of pigment cells directly over the dorsal margin of the somites.
Regulation of development in the fully grown mouse oocyte: chromosome-mediated temporal and spatial differentiation of the cytoplasm and plasma membrane
Authors: Blerkom Jonathan Van , Bell Hobart 
Published: April 2021

ABSTRACT
The relationship between nuclear maturation and the differentiation of the cytoplasm and plasma membrane during resumption of arrested meiosis was investigated by culture of GV- and Mil-stage mouse oocytes in the presence and absence of nocodazole. Culture in the presence of nocodazole was associated with dispersal of MI and Mil chromosomes throughout the sub-plasmalemmal cytoplasm. A progression of cortical (thickening of actin filaments) and plasma membrane changes (denudation of microvilli, reduction in cell surface glycoproteins, formation of chromosome-containing evaginations) that normally occurs in proximity to chromosomes associated with intact MI or Mil spindles took place only in those regions of the cortical cytoplasm containing the dispersed subplasmalemmal chromosomes. The dispersion and migration of the chromosomes occurred in an apparently random fashion. Fluorescent probe analysis of normal and treated oocytes indicated a stage-specific association between the spatial distribution of chromosomes and mitochondria. Transfer of individual bivalent chromosomes to untreated oocytes at different stages of maturation and to cytoplasts derived from oocytes anucleated prior to GVB demonstrated (1) the necessity of chromosomes for cytoplasmic and plasma membrane differentiation, and (2) that the capacity of the cytoplasm and plasma membrane to differentiate in response to the presence of a chromosome is acquired prior to GVB.
The formation of axonal projections of the mesencephalic trigeminal neurones in chick embryos
Authors: Hiscock Jennifer , Straznicky Charles 
Published: April 2021

ABSTRACT
Horseradish peroxidase-wheat germ agglutinin conjugate (HRP) was injected into masticatory and eye muscles of 6-to 15-day-old chick embryos and posthatched chicks to establish the timetable of axonal outgrowth and distribution of central and peripheral terminations of mesencephalic trigeminal neurones (MTN).
HRP-labelled MTN first appeared on the 10th day of incubation and by the 14th day most of MTN became labelled, indicating that axonic outgrowth to peripheral targets occurred between the 10th and 14th days of incubation. Peripheral targets included the pterygoideus lateralis and medialis, protractor quadratus, pseudotemporalis superficialis and profundus, and adductor mandibulae of jaw-closing muscles. HRP-filled central axonic processes of MTN were identified first on the 13th day of incubation and they terminated exclusively in the motor nucleus of the trigeminal nerve.
Between the 10th and 13th days of incubation, at the peak of naturally occurring cell death in the MTN pool, a consistently lower percentage of neurones could be labelled with HRP than in older embryos and in posthatched chicks. This finding suggests that many MTN die before establishing contact with peripheral targets.
Regeneration of mammary glands in vivo from isolated mammary ducts
Authors: Ormerod E. Jane , Rudland Philip S. 
Published: April 2021

ABSTRACT
Rat mammary ducts, free of buds, can alone regenerate complete mammary trees when transplanted into the interscapular fat pads of syngeneic host rats. All the main mammary cell types are identified within such outgrowths. Epithelial cells, which show the presence of milk fat globule membrane antigens and microvilli on their luminal surfaces, line the ducts. Basal cells surrounding the ducts show characteristic features of myoepithelial cells: immunoreactive actin and keratin within the cytoplasm, myofilaments, pinocytotic vesicles and hemidesmosomal attachments to the basement membrane. Cells within the end buds and lateral buds, however, show few if any cytoplasmic myofilaments and are relatively undifferentiated in appearance. Intermediate morphologies between these cells and myoepithelial cells are seen nearer the ducts. In this respect they exactly resemble the cap cells found in terminal end buds (TEBs) of normal mammary glands. Occasional epithelial cells within alveolar buds show the presence of immunoreactive casein, which is a product of secretory alveolar cells in the normal rat mammary gland. Dissected terminal end buds can regenerate similar ductal outgrowths. Thus, ductal tissue alone can generate all the major mammary cell types seen in the normal gland, including the cap cells.
Epithelial–mesenchymal tissue interactions guiding otic capsule formation: the role of the otocyst
Authors: McPhee Joseph R. , Van De Water Thomas R. 
Published: April 2021

ABSTRACT
The otocyst is the epithelial anlage of the membranous labyrinth which interacts with surrounding cephalic mesenchyme to form an otic capsule. A series of in vitro studies was performed to gain a better understanding of the epithelial–mesenchymal interactions involved in this process. Parallel series of otocyst/mesenchyme (0/M) and isolated periotic mesenchyme (M) explants provided morphological and biochemical data to define the role of the otocyst in organizing and directing formation of its cartilaginous otic capsule. Explants were made from mouse embryos ranging in age from 10 to 14 days of gestation, and organ cultured under identical conditions until the chronological equivalent of 16 days of gestation. Expression of chrondrogenesis was determined by both histology and biochemistry. The in vitro behaviour of periotic mesenchyme explanted either with or without an otocyst supports several hypotheses that explain aspects of otic capsule development. The results indicate that (a) prior to embryonic day 12 the otocyst alone is not sufficient to stimulate chondrogenesis of the otic capsule within O/M explants; (b) the otocyst acts as an inductor of capsule chondrogenesis within O/M explants between embryonic days 12 to 13; (c) isolated mesenchyme within M explants taken from 13-day-old embryos are capable of initiating in vitro chondrogenesis, but without expressing capsule morphology in the absence of the otocyst; and (d) the isolated mesenchyme of M explants obtained from 14-day-old embryos expresses both chondrogenesis and otic capsule morphology in the absence of the otocyst. These findings suggest that the otocyst acts as an inductor of chondrogenesis of periotic mesenchyme tissue between embryonic days 11 to 13, and controls capsular morphogenesis between embryonic days 13 to 14 in the mouse embryo.
Regulation of extraembryonic calcium mobilization by the developing chick embryo
Authors: Tuan Rocky S. , Ono Tamao 
Published: April 2021

ABSTRACT
During development, the chick embryo mobilizes the calcium it needs from two extra-embryonic sources, first the yolk and then the eggshell. Since previous studies have strongly suggested that vitamins D and K may regulate chick embryonic calcium metabolism, we have examined here how these vitamins might be involved in regulating the calcium mobilization processes. We used as our experimental system chick embryos which were maintained in longterm in vitro culture in the absence of the eggshell. Our results showed that exogenous vitamin D3, in the form of the active 1,25-dihydroxylated metabolite, was hypercalcaemic in both control embryos and the calcium-deficient, shell-less embryos. Since the eggshell was absent in the latter, the vitamin D-induced hypercalcaemia must involve mobilization of calcium from the yolk and, or, the embryonic skeleton. The latter was unlikely since concomitant hyper-phosphataemia was not observed. By radiolabelling the yolk with 45Ca2+ and subsequently monitoring its distribution, we showed that vitamin D3 stimulated yolk calcium mobilization. However, exogenous vitamin D3 did not appear to influence the calcium uptake activity of the chorioallantoic membrane (CAM), the tissue responsible for translocating eggshell calcium. On the other hand, when embryos were rendered vitamin K deficient by the administration of its antagonist, Warfarin, CAM calcium activity was significantly depressed, an effect which was remedied by vitamin K supplementation. We conclude that, during normal chick embryonic development, vitamin D is primarily involved in regulating yolk calcium mobilization whereas vitamin K is required for eggshell calcium translocation by the CAM.
Small eyes (Sey) : a homozygous lethal mutation on chromosome 2 which affects the differentiation of both lens and nasal placodes in the mouse
Authors: Hogan Brigid L. M. , Horsburgh Gwynn , Cohen James , Hetherington Colin M. , Fisher Graham , Lyon Mary F. 
Published: April 2021

ABSTRACT
Small eyes (Sey) is a semidominant, homozygous lethal mutation in the mouse (Roberts, 1967). It is allelic with SeyH, a radiation-induced homozygous prenatal lethal which has been mapped on chromosome 2. The effect of the Sey mutation is apparently limited to the growth and differentiation of the presumptive lens and nasal placodes. Homozygous Sey/Sey embryos can be distinguished as early as 10·5 days post coitum (p.c.f, the optic vesicles grow out, but the ectoderm does not give rise to a lens and nasal pits never form. Immunohistochemical studies show that the distribution of the extracellular matrix glycoprotein laminin is not significantly different in the cephalic region of Sey/Sey versus Sey/+ or +/+ embryos. Sey/Sey embryos develop to term but without eyes or nose, and die soon after birth. Further analysis of Sey/Sey embryos may throw light on the mechanisms underlying morphogenesis of craniofacial structures in mammals.
Development of erythroid colony-forming cells in rat fetal spleen: apparent lack of sensitivity to anin vivocorticosteroid excess as compared to fetal liver
Authors: Nagel M.-D. , Nagel J. 
Published: April 2021

ABSTRACTThe development of splenic erythroid colony-forming cells from rat embryos in the last 4 days of intrauterine life was examined after 2 and 7 days in a methylcellulose culture system. The number of 2- and 7-day erythroid colonies decreased sharply between, respectively, days 20 and 21 of gestation and days 19 and 20. Concomitantly, a maturation of proerythro-blasts and basophilic erythroblasts to mature erythroblasts was detected on smears of splenic cellular suspensions.The effect of a corticosteroid excess induced by a maternal laparotomy was tested on spleen and liver cultures from the same control or experimental fetuses. The ratio of the number of 2-day to the number of 7-day erythroid colonies did not differ in experimental and control splenic cultures, but in liver cultures was significantly lower at days 19 and 20 in experimental than in control cultures.
A method for determining the periodicity of a troponin component in isolated insect flight muscle thin filaments by gold/Fab labelling
Authors: Newman R. , Butcher G. W. , Bullard B. , Leonard K. R. 
Published: April 2021

ABSTRACT
Insect flight muscle has a large component (Tn-H) in the tropomyosin-troponin complex that is not present in vertebrate striated muscle thin filaments. Tn-H is shown by gold/Fab labelling to be present at regular intervals in insect flight muscle thin filaments. The Fab fragment of a monoclonal antibody to Tn-H was conjugated directly with colloidal gold and this probe used to label isolated thin filaments from the flight muscle of Lethocerus indicus (water bug). The distribution of gold particles seen in electron microscope images of negatively stained thin filaments was analysed to show that the probe bound to sites having a periodicity of approximately 40 nm, which is the expected value for the tropomyosintroponin repeat. Conjugates of Fab with colloidal gold particles of 3 nm diameter labelled almost all sites. Conjugates with gold particles of 5 nm and 10 nm diameter labelled less efficiently (70% and 30%, respectively) but analysis of the distribution of inter-particle intervals among a number of filaments again gave the same fundamental spacing of 40 nm. The error in the measurements (standard deviation approximately ±4.2 for 5 nm gold/Fab) is less than earlier estimates for the size of the gold/Fab complex. Measurements on gold/Fab in negative stain suggest that the bound Fab contributes a shell about 2 nm in thickness around the gold particle. The radius of the probe (about 4.5 nm for 5 nm gold/Fab) would then be consistent with the value of error found. The size of the probe suggests that the gold particle binds to the side of the Fab molecule, rather close to the antibody combining site. The potential resolution of the technique may thus be better than originally expected.
Mutants of the microtubule motor protein, nonclaret disjunctional, affect spindle structure and chromosome movement in meiosis and mitosis
Authors: Hatsumi Machiko , Endow Sharyn A. 
Published: April 2021

ABSTRACT
The Drosophila microtubule motor protein, nonclaret disjunctional (ned), is required for proper chromosome distribution in meiosis and mitosis. We have examined the meiotic and mitotic divisions in wild-type Drosophila oocytes and early embryos, and the effects of three ncdmutants (cand, ncd and ncdD) on spindle structure and chromosome movement. The ncdmutants cause abnormalities in spindle structure early in meiosis I, and abnormal chromosome configurations throughout meiosis I and n. Defective divisions continue in early embryos of the motor null mutant, cand, with abnormal early mitotic spindles. The effects of mutants on spindle structure suggest that ncdis required for proper meiotic spindle assembly, and may play a role in forming or maintaining spindle poles in meiosis. The disruption of normal meiotic and mitotic chromosome distribution by ncdmutants can be attributed to its role as a spindle motor, although a role for ncdas a chromosome-associated motor protein is not excluded. The ncd motor protein functions not only in meiosis, but also performs an active role in the early mitotic divisions of the embryo.
Screening and identification of a gene, PSE-1, that affects protein secretion in Saccharomyces cerevisiae
Authors: Chow Terry Y.-K. , Ash Josee J. , Dignard Daniel , Thomas David Y. 
Published: April 2021

ABSTRACT
Utilizing a screening method designed for the identification of genes involved with enhanced protein secretion in Saccharomyces cerevisiae we identified a gene, which we named PSE-1 (Protein Secretion Enhancer). Overexpression of PSE-1 in a multi-copy plasmid, as shown by Northern hybridization, gave a fourfold enhancement in total protein secretion. The repertoire of proteins that are found to be secreted in greater quantities include three known biologically active proteins: k 1 killer toxin, a-factor, and acid phosphatase. The PSE-1 gene is located on chromosome XII of the yeast genome and codes for a hydrophobic protein containing 1089 amino acids. Haploid yeast cells that contained a LEU2 insertion mutation in PSE-1 grow very poorly, a phenotype similar to other conditional SEC mutants at restrictive temperature.
The Bacillus thuringiensis Cry1Ac toxin-induced permeability change in Manduca sexta midgut brush border membrane vesicles proceeds by more than one mechanism
Authors: Carroll Joe , Wolfersberger Michael G. , Ellar David J. 
Published: April 2021

ABSTRACT
Aminopeptidase N purified from whole Manduca sexta midgut binds the Cry1Ac insecticidal toxin from Bacillus thuringiensis and this binding is inhibited by N-acetyl-galactosamine (GalNAc). We have examined the membrane permeabilising activity of the Cry1Ac toxin using brush border membrane vesicles (BBMV) prepared from the anterior (A-BBMV) and posterior (P-BBMV) subregions of the M. sexta midgut. A toxin mixing assay demonstrated a faster rate of toxin activity on P-BBMV than on A-BBMV. In the presence of GalNAc this rapid activity on P-BBMV was reduced to the rate seen with A-BBMV. GalNAc had no effect on the rate of A-BBMV permeabilisation by Cry1Ac. Aminopeptidase N assays of A- and P-BBMV demonstrated that this Cry1Ac binding protein is concentrated in the posterior midgut region of M. sexta. It therefore appears that there are two mechanisms by which Cry1Ac permeabilises the M. sexta midgut membrane: a GalNAc-sensitive mechanism restricted to the posterior midgut region, probably involving aminopeptidase N binding, and a previously undetected mechanism found in both the posterior and anterior regions.
Two kinds of BIR-containing protein - inhibitors of apoptosis, or required for mitosis
Authors: Silke John , Vaux David L. 
Published: April 2021

ABSTRACT
The baculoviral IAP repeat (BIR) is a zinc-binding fold. Some BIR-containing proteins (BIRCs), including several from insect viruses, insects and vertebrates, are inhibitors of cell death and act by binding to active caspases. Their ability to do so can be antagonized by pro-apoptotic insect proteins such as Grim, HID and Reaper, or the mammalian protein Diablo/Smac. Members of one structurally distinct subgroup of BIR-containing proteins, which are present in yeasts and Caenorhabditis elegans as well as insects and vertebrates, do not act as caspase inhibitors; instead, they are required for chromosome segregation and cytokinesis, and act in concert with inner centromere protein (INCENP) homologues and aurora kinase homologues.
The effect of inhalational anaesthetics on the swimming velocity of Tetrahymena pyriformis
Authors: Nunn J. F. , Sturrock Jean E. , J-Wills E. , Richmond Joan E. , Mcpherson C. K. 
Published: April 2021

ABSTRACT
The effect of 6 inhalational anaesthetics on speed of swimming (produced by ciliary movement) has been studied in Tetrahymena pyriformis. There was no evidence of stimulation at low dose levels and higher levels caused rapid, reversible, dose-dependent reduction in swimming velocity. The concentrations of anaesthetics which depressed motility by 50 % were of the same order as those required for anaesthesia in mammals, except in the case of cyclopropane, for which the required level was 4 times higher than the anaesthetic level. Correlation with lipid solubility was not as close as is the case for narcotic concentration. Oxygen consumption was reduced with increasing amounts of halothane in parallel with the reduction in swimming velocity. Halothane produced deciliation of Tetrahymena at about 10 times the anaesthetic dose for man; regrowth of cilia took place within 4 h of withdrawal of the drug. There were no changes in the ultrastructure of the cilia, basal bodies and associated microtubular systems at levels of halothane sufficient to stop cilial beat. At higher concentrations deciliation occurred immediately distal to the axosome and there was variable swelling of the mitochondria.
Erythrophagocytosis by the epithelial cells of the bladder
Authors: Wakefield J. ST J. , Hicks R. M. 
Published: April 2021

ABSTRACT
N-methyl-W-nitrosourea (MNU), methyl methane sulphonate (MMS), ethyl methane sulphonate (EMS) and cyclophosphamide (CP) are all cytotoxic to the transitional epithelium lining the urinary bladder, and also cause haemorrhage from the subepithelial blood capillaries. Erythrocytes enter the epithelium and are phagocytosed by the epithelial cells where they are subsequently digested. Two other compounds, dibutyl nitrosamine (DBN) and N-(4-(5-nitro-2-furyl)-2-thiazolyl)-formamide (NFTF) are only mildly cytotoxic but produce bladder epithelial tumours. Where haemorrhage occurs in these tumours, the erythrocytes are phago-cytosed and digested by the neoplastic epithelial cells.
The ingested red cells appear to lie free in the epithelial cell cytoplasm, surrounded by only a single unit membrane. Densitometrie tracings, however, show that this membrane is derived from the epithelial cells and that the red cells lie within a phagocytic vacuole. Careful inspection reveals the red cell membrane within the dense content of the vacuole, indicating that the permeability of the red cell membrane changes rapidly as soon as it is engulfed, so that haemoglobin is released into the phagocytic vacuole. The contents of the vacuole disintegrate and myelin figures and small amounts of residual dense material appear, but at no time was it possible to demonstrate acid phosphatase activity associated with the vacuole.