The development of a functional tissue requires coordination of the amplification of progenitors and their differentiation into specific cell types. The molecular basis for this coordination during myotome ontogeny is not well understood. Dermomytome progenitors that colonize the myotome first acquire myocyte identity and subsequently proliferate as Pax7-expressing progenitors before undergoing...

Fossils preserving traces of soft anatomy are rare in the fossil record; even rarer is evidence bearing on the size and shape of sense organs that provide us with insights into mode of life. Here, we describe unique fossil preservation of an avian brain from the Volgograd region of European Russia. The brain of this Melovatka bird is similar in shape and morphology to those of known fossil orni...

Colonization of trunk neural crest derivatives in avians follows a ventral to dorsal order beginning with sympathetic ganglia, Schwann cells, sensory ganglia and finally melanocytes. Continuous crest emigration underlies this process, which is accounted for by a progressive ventral to dorsal relocation of neural tube progenitors prior to departure. This causes a gradual narrowing of FoxD3, Sox9...

Modern birds do not have teeth. Rather, they develop a specialized keratinized structure, called the rhamphotheca, that covers the mandible, maxillae, and premaxillae. Although recombination studies have shown that the avian epidermis can respond to tooth-inductive cues from mouse or lizard oral mesenchyme and participate in tooth formation, attempts to initiate tooth development de novo in bir...

In avians and mice, trunk neural crest migration is restricted to the anterior half of each somite. Sclerotome has been shown to play an essential role in this restriction; the potential role of other somite components in specifying neural crest migration is currently unclear. By contrast, in zebrafish trunk neural crest, migration on the medial pathway is restricted to the middle of the medial...

N-methyl-D-aspartate receptors (NMDA-Rs) are located at each synapse in the lower auditory pathway of mammals and avians. Characterized by a slow and long-lasting excitatory response upon glutamate activation, their existence in a sensory system biologically engineered for speed and precision seems counterintuitive. In this review we consider the diverse functions of NMDA-Rs. Their developmenta...

Ten-day-old chicks were exposed to a pure tone (1.5 kHz) or white noise at 125 dB SPL avg. RMS for 4 to 24 hours, and were sacrificed either 10, 30 or 60 days after exposure. The basilar papillae were embedded in plastic, sectioned, and hair cells were counted at 100-micrometer intervals throughout the length of the papilla. As sound exposure duration increased, both the maximum number of hair ...

Several types of cells, including blastoderm cells, primordial germ cells, and embryonic germ cells were injected into early-stage recipient embryos to produce chimera avians and to gain insights into cell development. However, a limited number of studies of avian adult stem cells have also been conducted. This study is, to the best of our knowledge, the first to evaluate chicken bone marrow ce...

A wide spectrum of human diseases can result from chlamydial infections. Psittacosis is an infectious disease of avians caused by Chlamydia psittaci that can manifest in severe systemic disease in humans.' Chlamydia trachornatis infections are the leading cause of sexually transmitted genital tract disease, the only cause of classic trachoma, and also result in perinatal infant pneumonia and co...

In avians, yolk synthesis is regulated by incorporation of portomicrons from the diet, transport of lipoproteins from the liver, and release of lipids from adipose tissue; however, the extent to which lipolysis in adipose tissue contributes to yolk synthesis and egg production has yet to be elucidated. G0/G1 switch gene 2 (G0S2) is known to bind and inhibit adipose triglyceride lipase (ATGL), t...