In fish, the pectoral appendage is adjacent to the head, but during vertebrate evolution a long neck region emerged via caudal relocation of the pectoral appendage. The pectoral appendage is comprised of endochondral portions, such as the humerus and the scapula, and a dermal portion, such as the clavicle, that contributes to the shoulder girdle. In the search for clues to the mechanism of the caudal relocation of the pectoral appendage, the cell lineage of the rostral lateral plate mesoderm was analyzed in chickens. It was found that, despite the long neck region in chickens, the origin of the clavicle attached to the head mesoderm ranged between 1 and 14 somite levels. Because the pectoral limb bud and the endochondral pectoral appendage developed on 15-20 and 15-24 somite levels, respectively, the clavicle-forming region corresponds to the embryonic neck, which suggests that the relocation would have been executed by the expansion of the source of the clavicle. The rostral portion of the clavicle-forming region overlaps the source of the cucullaris muscle, embraces the pharyngeal arches caudally, and can be experimentally replaced with the head mesoderm to form the cucullaris muscle, which implies that the mesodermal portion could have been the head mesoderm and that the clavicle would have developed at the head/trunk boundary. The link between the head mesoderm and the presumptive clavicle appears to have been the developmental constraint needed to create the evolutionarily conserved musculoskeletal connectivities characterizing the gnathostome neck. In this sense, the dermal girdle of the ganathostomes would represent the wall of the branchial chamber into which the endochondral pectoral appendage appears to have attached since its appearance in evolution.

o f s i n u s o i d a l s p a c e s . W e t h e r e f o r e c o n s i d e r t h a t hematopoiesis is important for liver regeneration with a normal structure. Transplantation of the liver in the chorioallantoic membrane could be also useful for research into liver regeneration.

Peripheral targets regulate the development and survival of the nerve centers that serve them, because the elimination of the target normally results in massive death of the developing neurons that innervate it. This widely accepted theory appears to be well supported by developing limbs and their innervation in tetrapods, but it is unclear whether this concept applies to primitive vertebrates that have paired appendages. In this study, we examined the development of spinal motor neurons following pectoral fin bud removal (FBR) in medaka fish. After FBR, motor axons initially extended to the plexus region in a morphologically normal pattern. During the period of fin innervation, motor axons in the FBR‐medaka failed to form the normal brachial plexus and elongated ventrally toward the abdominal region. In the ventral horn that would normally innervate the pectoral fin, however, neurons did not undergo cell death following FBR. There were no differences in the numbers of axons in the ventral roots between the FBR and control sides. Motor neuron markers, RALDH2 and FOXP1, that are expressed in limb‐innervating motor neurons in the lateral motor column in tetrapods, were also expressed in the ventral horns of both the control and FBR sides in medaka fish. These results suggest that, although both tetrapod and medaka motor neurons share the same molecular characteristics for innervating paired appendages, the fates of neurons differ following the removal of their peripheral target. Therefore, the relationship between the peripheral target and its nerve center may be altered among vertebrates.

There have been many reports that osmotic fragility (OF) in red blood cells (RBCs) is a valuable tool for assessing the actions of various chemicals on the cell membrane in vitro. We determined the effects of benzoic acid and its derivatives on OF in sheep RBCs in vitro. Isolated sheep RBCs were exposed to these substances at 0-100 mM in a buffer solution for 1 h, and the 50% hemolysis was then determined by soaking in 0.1-0.8% NaCl solution. OF was determined as the NaCl concentration inducing 50% hemolysis which was colorimetrically measured by the released hemoglobin concentration. Benzoic acid decreased OF in a dose-dependent manner. Heptanoic acid and cyclohexanecarboxylic acid, both of which have 6 carbons in their saturated hydrocarbon structure, did not change OF. Replacement of the COOH bound to the benzene ring with PO(OH) 2 or SO 2 OH abolished the OF response obtained by benzoic acid. Replacement with OH did not affect OF up to 25 mM, but did induce hemolysis at 50 and 100 mM. Replacement with CONH 2 decreased OF, with the degree of the OF-lowering effect being greater than that of benzoic acid. Most derivatives possessing other groups (OH, CH 3 or NH 3) or halogens (Cl or Br) decreased or tended to decreased OF, with the degree of change in OF dependent on the position of the group introduced onto the benzene ring. 4-Methylbenzoic acid, and 3-,4-and 4-, 5-dichlorobenzoic acids demonstrated a biphasic effect on OF in sheep RBCs; lowering OF up to 50 mM followed by a lytic effect at 100 mM. The results of a regression analysis using the values of all substances tested revealed no significant correlations between the partition coefficient of the substances and their effects on OF response. However, some groups of substances at concentrations of 10-50 mM showed a negative and statistically significant correlation. For substances sharing very close chemical structures, partition coefficients can probably be used as an indicator for evaluating the effect on OF within an appropriate range of concentrations.