Experimental analysis of the extensive pigmentation in the Silkie fowl embryo: Evidence for an environmental regulatory process

Summary Heterospecific coelomic grafts, associated with the quail-chick marker system, showed that quail embryo melanoblasts exhibit the same invading behavior as Silkie fowl melanoblasts, when they came into contact with Silkie embryo organs. Thus the colonizationor noncolonization of the organs of the Silkie fowl embryo by melanoblasts seems to depend on environmental cues.     

Modeling melanoblast development

Melanoblasts are a particular type of cell that displays extensive cellular proliferation during development to contribute to the skin. There are only a few melanoblast founders, initially located just dorsal to the neural tube, and they sequentially colonize the dermis, epidermis, and hair follicles. In each compartment, melanoblasts are exposed to a wide variety of developmental cues that regulate their expansion. The colonization of the dermis and epidermis by melanoblasts involves substantial proliferation to generate thousands of cells or more from a few founders within a week of development. This review addresses the cellular and molecular events occurring during melanoblast development. We focus on intrinsic and extrinsic factors that control melanoblast proliferation. We also present a robust mathematical model for estimating the doubling-time of dermal and epidermal melanoblasts for all coat color phenotypes from black to white.     

Sur les interactions entre l'axe embryonnaire normal et les formations secondaires produites par la centrifugation de la blastula et de la gastrula chez les Amphibiens

Summary The complexes of organs induced by centrifugation of Amphibia blastulas or gastrulas interfere with the primary axis of the embryo: (a) explantates of centrifugated ectoblast are always poorer in differentiation than the same ectoblast leftin situ; (b) the complexes arising in the ventral part of the embryo have the tendency to elongate parallel to the main axis of the embryo and become connected with the head of the primary embryo; (c) grafts made on Axolotl eggs show that, when the reaction is poor, it cannot express itself except in cases of close contact with the normal organizer; (d) reciprocally, implants of strongly reacting centrifugated ectoblast placed on the ventral part of a normal gastrula of Pleurodeles induce modifications of the primary organs, viz. the transformation of the first somites into chorda.These facts lead to the conclusion that quantitative factors—and not qualitative—are effective in the differentiation of the embryo.     

The control of melanoblast differentiation in the periodic albino mutant ofXenopus

Summary Studies on the incidence of melanophores in older ventral trunk tissues and in isolated regions of periodic albino embryos ofXenopus suggest that melanin granule formation in mutant melanoblasts depends on an environmental contribution which arises at stage 43 in the endodermal tissues.     

Iridophore development in wild-type and periodic albinoXenopus larvae

Summary Light microscopic studies of iridophore preparations from a^p mutantXenopus larvae revealed abnormalities in the morphology and size distribution of reflecting platelets; purine synthesis is normal. A pleiotropic effect of the a^p gene on melanoblasts and iridoblasts is proposed.     

Advanced optical imaging in living embryos

Developmental biology investigations have evolved from static studies of embryo anatomy and into dynamic studies of the genetic and cellular mechanisms responsible for shaping the embryo anatomy. With the advancement of fluorescent protein fusions, the ability to visualize and comprehend how thousands to millions of cells interact with one another to form tissues and organs in three dimensions (xyz) over time (t) is just beginning to be realized and exploited. In this review, we explore recent advances utilizing confocal and multi-photon time-lapse microscopy to capture gene expression, cell behavior, and embryo development. From choosing the appropriate fluorophore, to labeling strategy, to experimental set-up, and data pipeline handling, this review covers the various aspects related to acquiring and analyzing multi-dimensional data sets. These innovative techniques in multi-dimensional imaging and analysis can be applied across a number of fields in time and space including protein dynamics to cell biology to morphogenesis.     

Effects of monosodium glutamate on circulating concentrations of luteinizing hormone and growth hormone in young growing domestic fowl (Gallus domesticus)

Summary The administration of monosodium glutamate (MSG) at a dose of 4 g/kg in 5-day-old fowl or 5 daily injections of MSG (total dose 20 g/kg) in 1- to 5-day-old fowl did not affect body growth in either male or female domestic fowl. Neither MSG treatment schedule affected either testis weight or the circulating concentration of luteinizing hormone (LH). A small, but significant decrease in the plasma concentration of growth hormone (GH) was observed in female chicks which had received daily MSG injections.Acknowledgments. Paper of Journal Series, New Jersey State Experiment Station, project No. 18141 and 18443, supported by State and Hatch Act funds and grants from the National Science Foundation (PCM 80227227) and the Upjohn Company.     

Autonomic control of renal portal blood flow in the domestic fowl

Summary Electrical stimulation of the intrinsic nerves of the renal portal valve of the domestic fowl demonstrated the presence of noradrenergic inhibitory, and cholinergic excitatory fibres. They may be involved in the control of venous return.     

The control of onset of melanoblast differentiation inXenopus larvae

Summary Studies on the time of first appearance of melanophores in uniformly-sized vesicles of hypomeric tissues containing different masses of neural crest tissues suggest that regional differences in the time of first appearance of trunk melanophores inXenopus are regulated by regional variation in the population density of melanoblasts.This work was supported by the Science Research Council and presented in a thesis, University of Glasgow.The author thanks Professor D. R. Newth for his interest and valuable criticisms.     

Autonomic control of renal portal blood flow in the domestic fowl.

Electrical stimulation of the intrinsic nerves of the renal portal valve of the domestic fowl demonstrated the presence of noradrenergic inhibitory, and cholinergic excitatory fibres. They may be involved in the control of venous return.     

A scanning electron microscopic study of the air and blood capillaries of the lung of the domestic fowl (Gallus domesticus)

Summary Air and blood capillaries of the lung of the domestic fowl constitute the functional gas exchange units. They anastomose profusely and interlace with each other in 3 dimensions. Air capillaries are not blind-ending tubules as has occasionally been suggested. I am most grateful to: Mr K. Veltkamp for aid with SEM, Dr M.A. Abdalla for help with injections, Prof. A.S. King for critical suggestions, Mr J. Geary for aid with photography.     

Granulationes leptomeningicae beiGallus domesticus

Summary Arachnoid granulations were found in the domestic fowl. They represent a protrusion of the welldeveloped arachnoid membrane which is covered with a neurothelium. The granulation resemble those described in mammals.     

Die frühe Differenzierung erster Melanocyten beim Entenembryo

Summary The first melanocytes in the duck (Khaki Campbell) appear after an incubation period of 88 h (about 40 somites) in the otic region. The melanoblasts of that region can be traced back to cells of the rhombencephalic neural crest of the 17-somites stage.

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Das Untersuchungsmaterial wurde während des Aufenthaltes am Hubrecht-Laboratorium in Utrecht anlässlich des Second International Teamwork gesammelt. Zur Durchführung der Untersuchungen standen Mittel der Deutschen Forschungsgemeinschaft zur Verfügung.     

Sur l'apparition d'organes variés dans l'ectoblaste, à la suite de la centrifugation de la blastula et de la gastrula chez les Amphibiens

Summary The centrifugation of the Amphibia blastula or gastrula produces in the ectoblastic area the appearance of complexes of ecto- and mesoblastic organs. Experiments of explantations and cultivationin vitro and also of grafts on a normal embryo demonstrate that those very abnormal secundary embryos are formed without any intervention of the normal organizer. The ectoblastic cells that undergo this increase of morphogenetic potential are characterized by a great concentration of ribonucleic acid in their cytoplasm (this part of work in collaboration withJ. Brachet). Those secundary embryos vary greatly in their frequence, their nature, and their location, depending on the stage in which the centrifugation was done. It is supposed that the nature of the organs formed is dependent on the degree of potency attained by the ectoblast at the time when the reaction arises that is produced by the cellular trauma.     

Somatostatin immunoneutralization overcomes the inhibitory effects of quipazine and pargyline on growth hormone secretion in domestic fowl

The inhibitory effects of pargyline and quipazine on chicken growth hormone secretion were overcome by passive immunoneutralization of endogenous somatostatin (SRIF)-14 or SRIF-28(1-14)-like immunoreactivity. Administration of the specific antisera to control birds pretreated with 0.9% NaCl elevated the basal plasma GH concentrations. These results suggest that peptides with SRIF-14 or SRIF-28(1-14)-like immunoreactivity tonically inhibit GH secretion and are at least partially responsible for the inhibitory effects of pargyline and quipazine on GH release in immature domestic fowl.     

Histochemical localization of carbonic anhydrase in fowl proventriculus

Summary The carbonic anhydrase activity in fowl proventriculus was studied by the histochemical method of Hansson. The activity was observed in the mucose membrane cells and in proventricular gland cells. These results, about which there is disagreement in the literature, are discussed in the text.     

Somatostatin immunoneutralization overcomes the inhibitory effects of quipazine and pargyline on growth hormone secretion in domestic fowl

Summary The inhibitory effects of pargyline and quipazine on chicken growth hormone secretion were overcome by passive immunoneutralization of endogenous somatostatin (SRIF)-14 or SRIF-28(1–14)-like immunoreactivity. Administration of the specific antisera to control birds pretreated with 0.9% NaCl elevated the basal plasma GH concentrations. These results suggest that peptides with SRIF-14 or SRIF-28(1–14)-like immunoreactivity tonically inhibit GH secretion and are at least partially responsible for the inhibitory effects of pargyline and quipazine on GH release in immature domestic fowl.     

Alpha-thioglycerol sensitive excitatory oxytocin receptors in fowl rectum

The selective antagonism of the excitatory responses of oxytocin by alpha-thioglycerol and its potentiation by Mg++ indicate the presence of specific oxytocin receptors in fowl rectum. In addition, the sensitivity of the rectum to very small doses of oxytocin suggests a possible facilitatory role of neurohypophyseal hormones in oviposition.     

Sensitivity of follicular melanoblasts in newborn mouse skin to tritiated thymidine: Evidence for a long term retention of label

Summary Injection of tritiated thymidine into newborn mice results in a progressive greying of hair that does not begin until after the first hair coat is grown. After a year the depigmentation is appreciable (about 60% of the hair are white). The effect cannot be simulated by external irradiation of newborn mice or by the administration of radioactive uridine or methionine. The effect can best be explained by a long-term retention of radioactivity in the DNA of melanocyte stem cells (melanoblasts) in spite of several rounds of cell division. This could be achieved by labelling the strands of DNA destined to act as templates throughout life by being selectively retained in the stem line as described in Cairns' hypothesis.Acknowledgments. This work was supported by grants from the Cancer Research Campaign. I am indebted to Joan Bullock for her careful, patient help with these experiments. CSP is a fellow of the Cancer Research Campaign.     

Peptide-stimulated release of prolactin from the fowl anterior pituitary gland

Summary Anterior pituitary glands from broiler fowl were preincubated for 24 h in either medium 199 only or medium containing estradiol 17, following which they were incubated in medium containing thyrotrophin releasing hormone (TRH), vasoactive intestinal polypeptide (VIP) or substance P (SP), alone or with the dopamine agonist, apomorphine. Estradiol priming stimulated release of prolactin and enhanced apomorphine-inhibition of prolactin release. TRH stimulated prolactin release, an effect reversed by apomorphine, and priming with estradiol potentiated both effects. VIP stimulated prolactin to a lesser degree and again this was inhibited by apomorphine and potentiated by estradiol. SP had little effect on the nonsteroid-primed pituitary, but stimulated release of prolactin after estradiol treatment, though less effectively than TRH or VIP.