The blood-brain barrier of the chick glycogen body (corpus gelatinosum) and its functional implications

Abstract

Among recent vertebrates only birds possess a glycogen body (corpus gelatinosum), located in the rhomboidal sinus of the lumbosacral region of the spinal cord and separated from the neural tissue proper. Because of the specific topographical situation of this circumventricular organ, the structure of its vascular system is of special interest with respect to the still unsolved functional problems. The existence of a blood-brain barrier is demonstrated by the exclusion of intravascularly injected tracer (horseradish peroxidase), and immunocytochemical demonstration of glucose transporter-1 as a functional marker and of neurothelin, occludin and ZO-1 as structural markers. Alkaline phosphatase and gamma-glutamyltransferase activities, two enzyme reactions frequently used for demonstration of an established blood-brain barrier in vitro, were localized histochemically on the plasmalemma of glycogen body cells and were absent from the endothelium. In addition, local enlargements of the intercellular space were observed by transmission and scanning electron microscopy. In accordance with the concept of a third circulation the cerebrospinal fluid may be the vehicle for distributing substances originating in the glycogen body to the CNS, while the vascular endothelium maintains the internal milieu by virtue of its dynamic barrier functions.

A comparative assessment of aging-related NADPH diaphorase positivity in the spinal cord and medullary oblongata between pigeon and murine

“…With regard to the spinal cord of a bird, a specialization of pigeon spinal cord is semicircular canal-like structures in the coronal transverse section through the glycogen body (Matulionis, 1972; Necker, 1999; Moller and Kummer, 2003; Imagawa et al, 2006). Research suggests the correlation of function of the blood-brain barrier with the glycogen body (Moller and Kummer, 2003). In addition, other studies suggest that the lumbosacral specialization of the vertebral canal with the spinal cord as a whole system is thought to function as balance sensation (Necker, 1999).…”

“…The other segments of the spinal cord are still important. The avian spinal cord shows some particularity in the lumbosacral region that discloses dorsally to form a rhomboid sinus occupied by the glycogen body (Matulionis, 1972; Necker, 1999; Moller and Kummer, 2003; Imagawa et al, 2006). Specialized semicircular canal-like structures (lumbosacral canals) is noted the coronal sections at the rhomboid sinus (Necker, 1999).…”

Fluoride concentrations in the pineal gland, brain and bone of goosander (Mergus merganser) and its prey in Odra River estuary in Poland

“…This type of research has not been conducted on birds, but it is known that birds maintain higher plasma glucose than other vertebrates of similar body mass and, in most cases, appear to store comparatively very little glucose intracellularly as glycogen, and instead store it a bird-specific structure located in the spinal cord (the corpus gelatinosum) and in astrocytes (Moller and Kummer 2003 ; Braun and Sweazea 2008 ). The avian nervous system utilizes glucose as a metabolic substrate, but little is known about the metabolism of glycogen in the avian brain, including those diving species at risk of oxygen deficiency (Brown and Ransom 2007 ; Braun and Sweazea 2008 ).…”

Form and Function of the Vertebrate and Invertebrate Blood-Brain Barriers

“…For example, one notable difference between birds and mammals is the existence of the glycogen body (corpus gelatinosum) in birds. The glycogen body is located in the rhomboidal sinus of the lumbosacral region of the spinal cord, and is surrounded by a functional BBB, which has been proposed to maintain homeostatic balance of the glycogen body [97,98]. Although the exact function of the glycogen body is not known, it has been hypothesized that it plays a role in insulin handling, glucose homeostasis, and osmoregulation [97][98][99].…”

“…The glycogen body is located in the rhomboidal sinus of the lumbosacral region of the spinal cord, and is surrounded by a functional BBB, which has been proposed to maintain homeostatic balance of the glycogen body [97,98]. Although the exact function of the glycogen body is not known, it has been hypothesized that it plays a role in insulin handling, glucose homeostasis, and osmoregulation [97][98][99]. This suggests a unique role of the BBB in metabolic control in birds.…”