The migration of melanoblasts in the extra-epidermal structures of the Silver Campine fowl.

The sequence of time and tracking of melanoblast migration has been worked out for Silver Campine fowl. The routes of entry and modes of dispersal of melanoblasts into different tissues have been described. The time and condition of pigment cell differentiation in extra-epidermal tissues is fully accounted.     

Patterns of amino acid enzyme in domestic fowl breast and leg muscle during development

Activities of alanine and aspartate transaminases, glutamine synthetase, adenylate deaminase, glutamate and xanthine dehydrogenases and lactate dehydrogenase were measured in leg and breast muscles of developing chicks from day 10 in ovo to day 5 of free life, and compared with measurements for adult hens. Xanthine dehydrogenase activity was low in both muscles with adult levels attained on day 15 in ovo. Glutamine synthetase for chicks was maintained higher during development than for adults in both muscles. Minor differences were observed between both muscles in all enzymes tested up to day 18. With low embryonic values and important rises before hatching, the differences were initiated in the posthatching period. Important differences were observed between adult levels of activity. Leg muscle revealed higher enzyme values except for lactate dehydrogenase and indistinguishable levels for adenylate deaminase and xanthine dehydrogenase in both muscles. Alanine, instead of glutamine, is postulated as the main nitrogen transport between muscle and liver in the domestic fowl.     

Acetylcholine compartments in skeletal muscle

I studied acetylcholine compartments in skeletal muscle with the aim to find their anatomical origin, and, in addition, their correlation with functional compartments, i.e. the pools in which synthesis, storage and release take place.     

Establishment of compartments in the developing leg imaginal discs ofDrosophila melanogaster

Summary By X-irradiation ofM/M ⁺ embryos and larvae to induce mitotic recombination, clones ofM ⁺/M⁺ genotype were obtained (Fig. 1). Since such cells grow faster than the surroundingM/M ⁺-cells they can fill large areas within the compartments of an imaginal disc.The present studies concentrated mainly on the three leg discs. Clones were induced by doses of 1000 r at ages ranging from 3±0.5 h after oviposition to 144 h.All clones induced later than the blastoderm stage were absolutely restricted to either the anterior or the posterior compartment of a disc. The border between the anterior and posterior compartment runs as a straight line along the entire leg and at the distal end separates the two claws (Figs. 5, 6, 7). A further subdivision of the anterior compartment is indicated by clones initiated in the second larval instar (Fig. 11). A parallel subdivision could not be detected in the posterior compartment. Irradiation in the early third instar led to clones which were restricted to single longitudinal bristle rows and leg segments. But no clear-cut compartment borders could be found; in particular a proximo-distal separation appears to be absent.Among the 318 clones induced at the blastoderm stage eleven extended from the wing into the second leg (Fig. 8), or from the haltere into the third leg.With the exception of 3 clones that apparently occupied the anterior as well as the posterior compartment of a wing or a leg, all clones remained confined to either the anterior or the posterior compartment.Frequently clones overlapped left and right forelegs (Fig. 9). Intersegmental overlaps were not observed.The results show that the earliest compartment borders appear in all thoracic discs. This suggests that compartmentalization is a fundamental process common to all discs.Supported bySchweizerischer Nationalfonds Gesuch Nr. 3.480-0.75     

Ca2+ compartments in saponin-skinned cultured vascular smooth muscle cells

A method for saponin skinning of primary cultured rat aortic smooth muscle cells was established. The saponin-treated cells could be stained with trypan blue and incorporated more 45Ca2+ than the nontreated cells under the same conditions. At low free Ca2+ concentration, greater than 85% of 45Ca2+ uptake into the skinned cells was dependent on the extracellularly supplied MgATP. In the intact cells, both caffeine and norepinephrine increased 45Ca2+ efflux. In the skinned cells, caffeine increased 45Ca2+ efflux, whereas norepinephrine did not. The caffeine-releasable 45Ca2+ uptake fraction in the skinned cells appeared at 3 X 10(-7) M Ca2+, increased gradually with the increase in free Ca2+ concentration, and reached a plateau at 1 X 10(-5) M Ca2+. The 45Ca2+ uptake fraction, which was significantly suppressed by sodium azide, appeared at 1 X 10(-5) M Ca2+ and increased monotonically with increasing free Ca2+ concentration. The results suggest that the caffeine-sensitive Ca2+ store, presumably the sarcoplasmic reticulum, plays a physiological role by releasing Ca2+ in response to norepinephrine or caffeine and by buffering excessive Ca2+. The 45Ca2+ uptake by mitochondria appears too insensitive to be important under physiological conditions.     

The electric charge of pigment granules in pigment cells

Black pigment cells called melanophores change colour in response to environmental changes and have lately been studied as promising biosensors. To further elucidate the intracellular processes involved in the colour changes of these cells, and to find optimal biosensing principles, the electric charge of intracellular pigment granules, melanosomes, has been determined in vitro by electrophoresis. Melanosomes from the two extreme states in the cell colour change (aggregated and dispersed melanosomes) were measured. The charge was found to be -1.5 x 10(-16) and -1.7 x 10(-16) C, aggregated and dispersed melanosomes, respectively, without significant difference between the two conditions. This charge is of the same order of magnitude as the one of 1000 electrons. The origin of the melanosome charge, and the use of these findings in new biosensor principles, is discussed.     

Leptofibrils in intrafusal muscle fibres of muscle spindles in the domestic fowl

Summary Leptofibrils consisting of narrow dark and wide light bands at regular periods are commonly found in intrafusal muscle fibres of chicken muscle spindles. They are particularly abundant in intrafusal muscle fibres with the loose type of myofilaments. They occur either at the periphery of intrafusal muscle fibres or in deeper regions, or even close to sensory nerve terminals. Dark bands of some peripheral leptofibrils vary considerably in size and appear less regular in configuration. Lateral extensions from the dark bands may occur with or without interconnections. Lateral attachments to myofilaments at the immediate neighbourhood may also occur.     

C pigment locus mutants of the fowl produce enzymatically inactive tyrosinase-like molecules

Three albino mutants of the fowl were tested for tyrosinase activity. Two of these mutants (c and ca) are alleles at the autosomal C locus, while the third mutant (sal) is sex-linked. Both the standard type, E, and sal are tyrosinase positive whereas the two C mutants are tyrosinase negative. Anti-chicken tyrosinase mouse serum was produced and all four genotypes were found to have cross-reacting material to this antiserum. Tyrosinase from the standard type was isolated and its location on denaturing two-dimensional gels determined. A co-migrating series of spots was found within the protein pattern of both the standard type and the tyrosinase positive albino, sal. The same pattern of spots was also observed for c and ca with no apparent change in either the pI or the molecular weight. Transmembrane blots also showed spots that reacted with anti-tyrosinase serum in all four genotypes and that migrated to the same location as that of standard tyrosinase. It is proposed that both c and ca are CRM+ mutants which produce tyrosinase-like molecules that are inactive due to a change that is electrophoretically and antigenically "silent".     

The effects of steroids on the granulosa cells in the domestic fowl

Summary The fine structure of granulosa cells of the domestic fowl as seen after administration of steroids is described. Diaethylstilboestrol, estradiol and hydroxy-progesterone were given as intramuscular injections for a 28-days period. The main cytoplasmic changes of the granulosa cells were an increase in the number of mitochondria and dense bodies. The Golgi apparatus became enlarged, and occupied a large portion of the cell. The nucleus was found located adjacent to the oocyte, and there was an increase in number of the annular desmosomes. The investigation has demonstrated that even if steroids in high dosages induce atrophic alterations of the ovary, they stimulated proliferation of the granulosa cells of the small follicles. Apparently the small follicles with the granulosa cells retain the ability to regain development, which may be to some importance when steroids are used therapeutically (gynecologic disorders, contra-ception).     

Complementation and noncomplementation in heterokaryons of three unlinked pigment mutants of the fowl.

This study shows that melanocyte heterokaryons formed between cells of the blue and recessive white genotypes complement one another to produce normal pigmentation, while heterokaryons of the blue and pinkeye genotypes fail to complement. The simplest interpretation of these findings is that the blue and recessive white mutations affect different aspects of pigment synthesis so that when both kinds of nuclei exist in the same cytoplasm, they can correct (complement) each other's defect. On the other hand, the blue and pinkeye mutations, although unlinked, apparently affect the same aspect of pigment synthesis so that when both kinds of nuclei are in a common cytoplasm, they cannot correct each other's defect. This suggests that one of these two loci exerts some kind of control, or "regulation," over the other. It has previously been shown that recessive white--pinkeye heterokaryons can complement. Thus, only two heterokaryon complementation groups are evident within the three mutants examined.