Detailed expression profile of the six Glypicans and their modifying enzyme, Notum during chick limb and feather development

The development of vertebrate appendages, especially the limb and feather buds are orchestrated by numerous secreted signalling molecules including Sonic Hedgehog, Bone Morphogenetic Proteins, Fibroblast Growth Factors and Wnts. These proteins coordinate the growth and patterning of ectodermal and mesenchymal cells. The influence of signalling molecules is affected over large distances by their concentration (morphogen activity) but also at local levels by the presence of proteins that either attenuate or promote their activity. Glypicans are cell surface molecules that regulate the activity of the major secreted signalling molecules expressed in the limb and feather bud. Here we investigated the expression of all Glypicans during chick limb and feather development. In addition we profiled the expression of Notum, an enzyme that regulates Glypican activity. We show that five of the six Glypicans and Notum are expressed in a dynamic manner during the development of limbs and feathers. We also investigated the expression of key Glypicans and show that they are controlled by signalling molecules highlighting the presence of feedback loops. Lastly we show that Glypicans and Notum are expressed in a tissue specific manner in adult chicken tissues. Our results strongly suggest that the Glypicans and Notum have many as yet undiscovered roles to play during the development of vertebrate appendages.

Detailed expression profile of all six Glypicans and their modifying enzyme Notum during chick embryogenesis and their role in dorsal-ventral patterning of the neural tube

Vertebrate development is orchestrated by secreted signalling molecules that regulate cell behaviour and cell fate decisions during early embryogenesis. The activity of key signalling molecules including members of Hedgehog, Bone Morphogenetic Proteins and Wnt families are regulated by Glypicans, a family of GPI linked polypeptides. Glypicans either promote or inhibit the action of signalling molecules and add a layer of complexity that needs to be understood in order to fully decipher the processes that regulate early vertebrate development. Here we present a detailed expression profile of all six Glypicans and their modifying enzyme Notum during chick embryogenesis. Our results strongly suggest that these proteins have many as yet undiscovered roles to play during early embryogenesis. Finally, we have taken an experimental approach to investigate their role during the patterning of a key embryonic structure - the neural tube. In particular, we show that over-expression of Notum leads to the dorsalisation of this structure.

Characterisation of Development and Electrophysiological Mechanisms Underlying Rhythmicity of the Avian Lymph Heart

Despite significant advances in tissue engineering such as the use of scaffolds, bioreactors and pluripotent stem cells, effective cardiac tissue engineering for therapeutic purposes has remained a largely intractable challenge. For this area to capitalise on such advances, a novel approach may be to unravel the physiological mechanisms underlying the development of tissues that exhibit rhythmic contraction yet do not originate from the cardiac lineage. Considerable attention has been focused on the physiology of the avian lymph heart, a discrete organ with skeletal muscle origins yet which displays pacemaker properties normally only found in the heart. A functional lymph heart is essential for avian survival and growth in ovo. The histological nature of the lymph heart is similar to skeletal muscle although molecular and bioelectrical characterisation during development to assess mechanisms that contribute towards lymph heart contractile rhythmicity have not been undertaken. A better understanding of these processes may provide exploitable insights for therapeutic rhythmically contractile tissue engineering approaches in this area of significant unmet clinical need. Here, using molecular and electrophysiological approaches, we describe the molecular development of the lymph heart to understand how this skeletal muscle becomes fully functional during discrete in ovo stages of development. Our results show that the lymph heart does not follow the normal transitional programme of myogenesis as documented in most skeletal muscle, but instead develops through a concurrent programme of precursor expansion, commitment to myogenesis and functional differentiation which offers a mechanistic explanation for its rapid development. Extracellular electrophysiological field potential recordings revealed that the peak-to-peak amplitude of electrically evoked local field potentials elicited from isolated lymph heart were significantly reduced by treatment with carbachol; an effect that could be fully reversed by atropine. Moreover, nifedipine and cyclopiazonic acid both significantly reduced peak-to-peak local field potential amplitude. Optical recordings of lymph heart showed that the organ’s rhythmicity can be blocked by the HCN channel blocker, ZD7288; an effect also associated with a significant reduction in peak-to-peak local field potential amplitude. Additionally, we also show that isoforms of HCN channels are expressed in avian lymph heart. These results demonstrate that cholinergic signalling and L-type Ca²⁺ channels are important in excitation and contraction coupling, while HCN channels contribute to maintenance of lymph heart rhythmicity.

Efficient myogenic reprogramming of adult white fat stem cells and bone marrow stem cells by freshly isolated skeletal muscle fibers

Stem cells that can be directed to differentiate into specific cell types offer the prospect of a renewable source of replacement cells to treat diseases. This study evaluates the reprogramming of 2 readily available stem cell populations into skeletal muscle. We show for the first time that freshly isolated muscle fibers reprogram bone marrow or white fat stem cells far more efficiently than muscle cell lines. In addition, we show that the ability of muscle fibers to reprogram stem cells can be almost doubled through the use of chromatin remodeling reagents such as trichostatin A. This novel approach permits the generation of myogenic cells that could be used to treat a range of muscle-wasting diseases.

Canonical Wnt signalling induces satellite-cell proliferation during adult skeletal muscle regeneration

Satellite cells represent the stem cell population of adult skeletal muscle. The molecular mechanisms that control the proliferation of satellite cells are not well understood. In this study, we show that in response to injury, myofibres activate Wnt ligand transcription and activate a reporter cell line that is sensitive to the canonical Wnt-signalling pathway. Activated satellite cells on isolated cultured myofibres show robust expression of activated-β-catenin (Act-β-Cat), a key downstream transcriptional coactivator of canonical Wnt signalling. We provide evidence that the Wnt family of secreted glycoproteins act on satellite cells in a ligand-specific manner. Overexpression of Wnt1, Wnt3a or Wnt5a protein causes a dramatic increase in satellite-cell proliferation. By contrast, exposure of satellite cells to Wnt4 or Wnt6 diminishes this process. Moreover, we show that the prolonged satellite-cell quiescence induced by inhibitory Wnt is reversible and exposing inhibited satellite cells to stimulatory Wnt signalling restores their proliferation rate. Stimulatory Wnt proteins induce premature satellite cell BrdU incorporation as well as nuclear translocation of Act-β-Cat. Finally, we provide evidence that the Act-β-Cat translocation observed in single fibres during in vitro culture also occurs in cases of acute and chronic skeletal muscle regeneration in rodents and humans. We propose that Wnt proteins may be key factors that regulate the rate of satellite-cell proliferation on adult muscle fibres during the wound-healing response.

Expression and regulation of Nkd-1, an intracellular component of Wnt signalling pathway in the chick embryo

The Wnt family of secreted signalling molecules control a wide range of developmental processes in all metazoans. The intracellular response to Wnt signalling depends on the choice of signalling cascade activated in the responding cell. Cells can activate either the canonical pathway that modulates gene expression to control cellular differentiation and proliferation, or the non-canonical pathway that controls cell polarity and movement. Recent work has identified the protein Naked Cuticle to act as an intracellular switch to promote the non-canonical pathway at the expense of the canonical pathway. We have cloned chick Naked Cuticle-1 (cNkd-1) and show that it is expressed in a dynamic manner during early embryogenesis. We show that it is expressed in the somites and in particular regions where cells are undergoing movement. Lastly, we show that the expression of cNkd-1 is regulated by Wnt expression originating from the neural tube. This study provides evidence that non-canonical Wnt signalling plays a part in somite development.

Magnetic dilution in the geometrically frustrated SrCr(9p)Ga(12-9p)O19 and the role of local dynamics: A muon spin relaxation study

We investigate the spin dynamics of SrCr(9p)Ga(12-9p)O19 for p below and above the percolation threshold p(c) using muon spin relaxation. Our major findings are as follows: (i) At T-->0 the relaxation rate is T independent and approximately p(3), (ii) the slowing down of spin fluctuation is activated with an energy U, which is also a linear function of p(3) and lim U as p-->0 = 8 K; this energy scale could stem only from a single ion anisotropy, and (iii) the p dependence of the dynamical properties is identical below and above p(c), indicating that they are controlled by local excitation.

Female chromosomes in cockerel ejaculates

We describe a polymerase chain reaction which amplifies part of the Eco RI repeat unit of the fowl W chromosome. The resulting 447 bp fragment enables DNA from female birds to be identified. The composition of this DNA is confirmed by a nested polymerase chain reaction which specifically amplifies a known internal 263 bp region in this fragment. Using this technique it is possible to follow the fate of female cells in male germline chimaeras. The polymerase chain reaction fragment can be traced in cells of the embryonic and hatchling gonad and in adult sperm implying that cells containing the W chromosome are capable of being processed through the avian testis.

The role of the renin-angiotensin system in the control of blood pressure and drinking in the European eel, Anguilla anguilla

The role of the renin-angiotensin system (RAS) in the control of blood pressure and drinking was investigated in fresh water (FW)- and seawater (SW)-adapted eels, Anguilla anguilla, by comparing the effects of pharmacological manipulation through the use of papaverine (stimulator) and captopril (inhibitor) on the endogenous system. In SW eels basal blood pressure levels were lower (23.3 +/- 0.8 mm Hg) with correspondingly higher basal drinking rates (0.51 +/- 0.07 ml/kg/hr) and plasma AII concentrations (32.89 +/- 4.19 fmol/ml) compared to FW eels (33.8 +/- 1.3 mm Hg, 0.06 +/- 0.02 ml/kg/hr, 9.72 +/- 0.60 fmol/ml, respectively). In FW eels papaverine caused immediate hypotension with full recovery, decrease in plasma osmolality, and increase in drinking rate and plasma AII concentration, but in SW eels, hypotension with full recovery and an increase in plasma osmolality, drinking rate, and plasma AII concentration occurred. In FW eels captopril had no effect on the parameters measured, but in SW eels it caused a sustained decrease in blood pressure and a decline in the basal drinking rate and plasma AII concentration. Papaverine was also administered 15 min after captopril. In FW eels this manipulation caused hypotension only after the papaverine injection, followed by a partial recovery. Osmolality was unaffected, the previously observed papaverine-induced dipsogenic response was blocked, and the rise in plasma AII concentrations was smaller than with papaverine only. In SW eels there was an immediate hypotension after captopril administration with full recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Manipulations of germ-cell populations in the gonad of the fowl

1. Embryos of the domestic fowl have been partially sterilised by injecting the drug busulphan into 24-h incubated eggs. 2. Some of these embryos were injected with primordial germ cells (PGCs) after 55 h of incubation to attempt to repopulate the gonads. 3. Primordial germ cells transfected with a defective retrovirus containing the reporter gene lac Z were shown to settle in these sterilised gonads. 4. Quantitative histology of 6-d embryos showed that busulphan produced 75% sterilisation but that PGCs could repopulate these gonads. 5. The technique of producing such germ line chimaeras is of value in studying cell kinetics, gonad differentiation and the production of transgenics.

Germ-line chimaeras can produce both strains of fowl with high efficiency after partial sterilization

The drug busulphan is known to be cytotoxic to migrating primordial germ cells (PGCs). A technique is described in which doses of 0, 25, 50 and 250 micrograms busulphan in 40 microliters sesame oil were injected into the yolk of White Leghorn eggs incubated for 0, 24, 48 and 72 h. The percentage survival values of these embryos showed that the older the embryo at the time of injection, the greater the survival. Increasing the dose of busulphan decreased the survival. The percentage of embryos showing abnormalities increased with higher doses of busulphan. The number of germ cells in histological sections from gonads of 16-day embryos was estimated and in embryos treated with 50 micrograms and 250 micrograms busulphan the number of germ cells was significantly less than in the controls. Eggs were injected with 50 micrograms busulphan at 24-30 h, and at 50-55 h the embryos received an intravascular injection of a germinal crescent cell suspension containing PGCs from Rhode Island Red embryos. Twenty hatchlings from these experiments were raised to sexual maturity. All these birds were fertile and half of the breeding groups producing offspring from the transferred germ cells at a rate of about 35% of the total. The technique would improve the efficiency of producing transgenic gametes.

Serum concentration of pregnancy specific and pregnancy-associated proteins in early gestation

PAPP-A, SP1, hCG and alpha 2-PAG were determined in the serum of 17 patients at weekly intervals between 3 and 12 weeks from the last menstrual period; progesterone and 17 beta-oestradiol concentrations were also measured in the same samples. SP1 and hCG concentrations were consistently found to rise steeply from the first time the proteins were detected. PAPP-A, though detectable in early samples from 9 of the patients, started to rise sharply in all cases between 6 and 10 weeks after LMP. Alpha 2-PAG, which was detected in all serum samples, showed no consistent behaviour with advancing pregnancy. In 3 patients, alpha 2-PAG was elevated as early as 3 weeks after LMP, while in others it remained at low levels during the entire interval observed. The correlation between these proteins (except between SP1 and hCG) is therefore poor; and their synthesis or secretion seems to be independently controlled.

Comparison of the concentration of schwangerschaftsprotein 1 (SP1) in the serum and urine of pregnant women

Schwangerschaftsprotein 1 (SP1) values in serum and urine were compared. The first appearance of the protein in urine happens 9-17 days after the first SP1-positive serum, i.e., about 9 days after the first missed period. Urinary SP1 values up to 6 weeks after LMP do not correlate with gestational age as do serum values, but towards the end of the first trimester this correlation becomes almost as good as the one obtained with serum. The urinary SP1 concentration of SP1 fluctuates around 2.3% of the serum concentration throughout pregnancy.