Effects of breed type and sex on the fatty acid composition of subcutaneous neutral lipid and intramuscular neutral and phospholipids of longissimus lumborum muscle were investigated using 145 steers and 82 heifers that consisted of pure Japanese Black and Holstein and crossbreds among Japanese Black, Holstein, Japanese Brown, and Charolais. Steers and heifers were reared on a high plane of nutrition and were fed the same concentrate diet and rice straw. All animals were slaughtered serially and carcass composition was determined by dissection of the left side of the carcass. Breed type and sex differences of fatty acid percentages of carcass lipids were compared by adjusting the percentages to mean carcass fat percentages. Heifers had higher contents of 18:1 and total monounsaturated fatty acids in subcutaneous and intramuscular neutral lipids than steers (P < .05). The fatty acid composition of intramuscular phospholipids differed between sexes for 16:0, 20:1, and 20:5, but the differences were small. Breed differences were significant (P < .05) in steers for 16:0, 16:1, 18:1, and total saturated and monounsaturated fatty acids in both subcutaneous and intramuscular neutral lipids, and iso-16:0, 16:0, and total saturated fatty acids in phospholipids, respectively. However, in heifers, fewer fatty acids differed (P < .05) among breed types in the neutral lipids. It is suggested that the Japanese Black has a genetic predisposition for producing carcass lipids containing higher concentrations of monounsaturated fatty acids than Holstein, Japanese Brown, or Charolais.

15-Deoxy-D 12,14 -prostaglandin J 2 (15d-PGJ 2 ) has been identified as a natural ligand for peroxisome proliferatoractivated receptor (PPAR) c to promote adipogenesis. However, it remains elusive about the ability of PPARc-expressing adipocytes to produce PGJ 2 series and the role in the life cycle of adipocytes. Here, we developed an enzyme-linked immunosorbent assay specific for 15d-PGJ 2 . The analysis using this method revealed the increase in the endogenous synthesis of immunoreactive 15d-PGJ 2 in cultured adipocytes during the maturation phase. Further studies using cyclooxygenase inhibitors clarified the contribution of endogeous 15d-PGJ 2 produced by mature adipocytes to upregulation of fat storage in an autocrine manner.

No abstract

The formation of primitive adipose tissue is the initial process in adipose tissue development followed by the migration of preadipocytes into adipocyte clusters. Comparatively little is known about the molecular mechanism controlling preadipocyte migration. Here, we show that cytohesin-2, the guaninenucleotide exchange factor for the Arf family GTP-binding proteins, regulates migration of mouse preadipocyte 3T3-L1 cells through Arf6. SecinH3, a specific inhibitor of the cytohesin family, markedly inhibits migration of 3T3-L1 cells. 3T3-L1 cells express cytohesin-2 and cytohesin-3, and knockdown of cytohesin-2 with its small interfering RNA effectively decreases cell migration. Cytohesin-2 preferentially acts upstream of Arf6 in this signaling pathway. Furthermore, we find that the focal adhesion protein paxillin forms a complex with cytohesin-2. Paxillin colocalizes with cytohesin-2 at the leading edges of migrating cells. This interaction is mediated by the LIM2 domain of paxillin and the isolated polybasic region of cytohesin-2. Importantly, migration is inhibited by expression of the constructs containing these regions. These results suggest that cytohesin-2, through a previously unexplored complex formation with paxillin, regulates preadipocyte migration and that paxillin plays a previously unknown role as a scaffold protein of Arf guanine-nucleotide exchange factor.

Anterograde vesicle transport from the endoplasmic reticulum to the Golgi apparatus is the start of protein transport through the secretory pathway, in which the transport is mediated by coat protein complex II (COPII)-coated vesicles. Therefore, most proteins synthesized on the endoplasmic reticulum are loaded as cargo into COPII vesicles. The COPII is composed of the small GTPase Sar1 and two types of protein complexes (Sec23/24 and Sec13/31). Of these five COPII components, Sec24 is thought to recognize cargo that is incorporated into COPII vesicles by directly interacting with the cargo. The Arabidopsis genome encodes three types of Sec24 homologs (AtSec24A, AtSec24B, and AtSec24C). The subcellular dynamics and function of AtSec24A have been characterized. The intracellular distributions and functions of other AtSec24 proteins are not known, and the functional differences among the three AtSec24s remain unclear. Here, we found that all three AtSec24s were expressed in similar parts of the plant body and showed the same subcellular localization pattern. AtSec24B knockout plant, but not AtSec24C knockdown plant, showed mild male sterility with reduction of pollen germination. Significant decrease of AtSec24B and AtSec24C expression affected male and female gametogenesis in Arabidopsis thaliana. Our results suggested that the redundant function of AtSec24B and AtSec24C is crucial for the development of plant reproductive cells. We propose that the COPII transport is involved in male and female gametogenesis in planta.