Carcinoembryonic Ag-related cell adhesion molecule 1 (CEACAM1), the primordial carcinoembryonic Ag gene family member, is a transmembrane cell adhesion molecule expressed in leukocytes, epithelia, and blood vessel endothelia in humans and rodents. As a result of differential splicing, CEACAM1 occurs as several isoforms, the two major ones being CEACAM1-L and CEACAM1-S, that have long (L) or short (S) cytoplasmic domains, respectively. The L:S expression ratios vary in different cells and tissues. In addition to CEACAM1, human but not rodent cells express GPI-linked CEACAM members (CEACAM5–CEACAM8). We compared the expression patterns of CEACAM1-L, CEACAM1-S, CEACAM6, and CEACAM8 in purified populations of neutrophilic granulocytes, B lymphocytes, and T lymphocytes from rats, mice, and humans. Human granulocytes expressed CEACAM1, CEACAM6, and CEACAM8, whereas human B lymphocytes and T lymphocytes expressed only CEACAM1 and CEACAM6. Whereas granulocytes, B cells, and T cells from mice and rats expressed both CEACAM1-L and CEACAM1-S in ratios of 2.2–2.9:1, CEACAM1-S expression was totally lacking in human granulocytes, B cells, and T cells. Human leukocytes only expressed the L isoforms of CEACAM1. This suggests that the GPI-linked CEACAM members have functionally replaced CEACAM1-S in human leukocytes. Support for the replacement hypothesis was obtained from experiments in which the extracellular signal-regulated kinases (Erk)1/2 were activated by anti-CEACAM Abs. Thus, Abs against CEACAM1 activated Erk1/2 in rat granulocytes, but not in human granulocytes. Erk1/2 in human granulocytes could, however, be activated by Abs against CEACAM8. We demonstrated that CEACAM1 and CEACAM8 are physically associated in human granulocytes. The CEACAM1/CEACAM8 complex in human cells might accordingly play a similar role as CEACAM1-L/CEACAM1-S dimers known to occur in rat cells.

The binding of phenolic ligands to the insulin hexamer occurs as a cooperative allosteric process. Investigations of the allosteric mechanism from this laboratory resulted in the postulation of a model consisting of a three-state conformational equilibrium and the derivation of a mathematical expression to describe the insulin system. The proposed mechanism involves allosteric transitions among two states of high symmetry, designated T3T3' (a low affinity state) and R3R3' (a high affinity state), and a third state of lower symmetry, designated T3oR3o (a state of mixed low and high affinities). To further characterize this mechanism, we present rapid kinetic fluorescence studies, equilibrium binding isotherms, and molecular modeling investigations for the Co(II)-substituted wild-type and E-B13Q mutant hexamers. These studies show that the measured on and off rates (kon and koff) for the binding of the allosteric ligands 2,6- and 2,7-dihydroxynaphthalene provide an independent measure of the dissociation constant for binding to the T3oR3o conformation (KRo). These constants are in agreement with the value obtained by computer fitting of the equilibrium binding isotherms to the quantitative allosteric mechanism. We analyze the structural differences between the T3oR3o and R6 phenolic binding sites and predict the structures of the T3oR3o-2,6-DHN and R6-2, 6-DHN complexes by 3-D molecular modeling. Assignment of H-bonding of the first hydroxyl group to CysA6 and CysA11 has been supported by stacking interactions analogous to phenol using 1H-NMR. H-bonding of the second hydroxyl group of 2,6-DHN to the GluB13 carboxylate side chains is predicted by molecular modeling and is supported by a reduction of affinity for Ca2+, which is postulated to bind to the GluB13 side chains.

Abstract. Fifty-eight formalin-fi xed par affin-embedd ed canine mammar y tum or s, 19 malignant and 39 benign, were used in th is stud y. T umors were ob tai ned fro m dogs sub mi tte d for surgica l resection of lesions at privat e veterinary pra ctices in Brussels or fro m the su rgery unit of the Fac ulty of Veterinary Med icine, University of Liege. Immunoh isto chem ical eva luation was performed , usin g mon oclon al anti bod ies directed against keratins 8-18 and 19, vime ntin, desmi n, and a -actin and polyclonal anti bod ies directed against high-molecular-weight keratins and S-I 00 protein. Th e main cell types, epithelial, myoepithelial, and connective, were identifi ed , and myoep ith elial cells represent ed the major com po nent of most tum ors, both benign and malignan t. Myoep ith elial cells had five patt ern s: resting and proliferati ve supra basa l cells, spindle and sta r-shaped inters titial cells, and cartilage. Reactivity to keratin 19, vimen tin, a -actin, and S-I00 prot ein suggested a prog ressi ve transformation from resting cells to cartilage. Epithelial cell reac tivities were lim ited to keratins; only keratinized cells were posit ive for polyclonal keratins. Myofibroblasts were positive for both vime ntin and a -actin, and connective tissue cells were posit ive for vi me ntin. Myoepithelial cells appeared to be th e major com po nent of carcino mas , j ustifying reeva luation and sim plification of histomorphologic class ifications, with a " pleomorphic carci no ma" gro up incl uding all carcinomas exce pt squa mo us, mucino us, and comedo carcino ma s. Imm unoh istochem ical evaluation, in add itio n to routine hem atoxylin and eos in histop ath ologic eval uation is recommended for precise classificati on of canine mammary tumors.Key words: Canine species; im m uno histoc hemis try; mamm ar y tum ors ; myoepithelial cells. After skin tumor s, mammary tumors ar e th e seco nd acteriza tio n and histogenesis. ", , · ' 5. ' 9.23,28 Epithe lial cells most frequent neoplasm in dogs ." Malignant tumors express cyto keratin filam ents, mesenchymal cells exocc ur sponta neously in elde rly animals->' or often de-press vimentin filam ents, and mu scle cells express desvelop on ben ign lesions. 2 -4.32 Canine mammary tumors min fila me nts. Ab out 20 d ifferent subtypes of kerat in s a re an exce llent mod el for th e study of human breast ha ve been describ ed acco rd ing to th eir molecular ca ncer. 8 , 16,25 They have sim ilar histol ogic origin and weight, and th ey are characteristically found in certa in comparable regional and systemi c metastasis, and th ey epi the lia. For example, in hum an mamma ry glands, appear in signi ficant number s at a sim ilar relati ve age." epithe lial cells ex press keratins 14 and 18.14 Markers However , freq uency o f th e vario us histologic types is othe r than interme d iate filaments can also be used to d ifferenL ' 7 ,22,26 ide ntify cell types, for exa m ple, a -actin m icrofil am ents Charac teris tica lly, canine mammary tum ors ha ve ...