Identification and biological activity of dihydroleukotriene B4: a prominent metabolite of leukotriene B4 in the human lung

Exogenous [3H]leukotriene B4 (LTB4) was converted into several polar and non-polar metabolites in the chopped human lung. One of the major metabolites was identified as 5(S),12-dihydroxy-6,8,14-eicosatrienoic acid (10,11-dihydro-LTB4) by means of co-chromatography with authentic standards, ultraviolet spectrometry and gas chromatography-mass spectrometry. Analysis of chiral straight phase HPLC revealed the presence of both the 12(S) and 12(R) epimers of dihydro-LTB4. Dihydro-LTB4 was also formed from endogenously generated LTB4 in ionophore A23187 stimulated incubations. The dihydro metabolites were approximately 100 times less potent than LTB4 in causing guinea pig lung strip contraction and leukocyte-dependent inflammation in the hamster cheek pouch in vivo.     

Nucleotide sequence of 4.5S RNA (C8 or hY5) from HeLa cells

The nucleotide sequence of C8 RNA, one of the 4.5S RNAs of HeLa cells, was determined. C8 RNA consists of 83 or 84 nucleotide residues containing pppA at its 5′-terminus and oligo U at its 3′-terminus. This RNA is rich in uridylate residues (about 38%) and does not have any modified nucleosides. C8 RNA is present mainly in the cytoplasm, with some in the nucleus and the C8 RNAs from the nucleus and cytoplasm have the same sequence.     

Preliminary X-ray studies on Pseudomonas isoamylase

Single crystals of Pseudomonas isoamylase (M_r 95,000) belong to space group P2₁2₁2₁ with unit cell dimensions of $\text{a = 137.9}\text{A}\text{?}\text{, b = 52.9}\text{A}\text{?}\text{, c = 151.2}\text{A}\text{?}$. A Guinier plot of the X-ray small-angle scattering of the protein solution gave the radius of gyration of the molecule as 27.5 Å.     

The effect of spermine on the disaccharidase activities in suckling rats of different age.

The influence of the age of the rat on the maturation of disaccharidase activities induced by spermine was studied. Three-day- and 9-day-old rats were used in the experiment. Spermine was administered orally or directly into the stomach using thin tubing daily for 3 days, and disaccharidase activities in the jejunum were measured. While spermine caused maturation of not only lactase activity but also maltase and sucrase activities in 9-day-old rats, it only caused maturation of lactase activity in 3-day-old rats. Histological studies showed no significant changes in the jejunum of 3-day-old rats treated with spermine.     

Critical Role of Heparin Binding Domains of Ameloblastin for Dental Epithelium Cell Adhesion and Ameloblastoma Proliferation

AMBN (ameloblastin) is an enamel matrix protein that regulates cell adhesion, proliferation, and differentiation of ameloblasts. In AMBN-deficient mice, ameloblasts are detached from the enamel matrix, continue to proliferate, and form a multiple cell layer; often, odontogenic tumors develop in the maxilla with age. However, the mechanism of AMBN functions in these biological processes remains unclear. By using recombinant AMBN proteins, we found that AMBN had heparin binding domains at the C-terminal half and that these domains were critical for AMBN binding to dental epithelial cells. Overexpression of full-length AMBN protein inhibited proliferation of human ameloblastoma AM-1 cells, but overexpression of heparin binding domain-deficient AMBN protein had no inhibitory effect. In full-length AMBN-overexpressing AM-1 cells, the expression of Msx2, which is involved in the dental epithelial progenitor phenotype, was decreased, whereas the expression of cell proliferation inhibitors p21 and p27 was increased. We also found that the expression of enamelin, a marker of differentiated ameloblasts, was induced, suggesting that AMBN promotes odontogenic tumor differentiation. Thus, our results suggest that AMBN promotes cell binding through the heparin binding sites and plays an important role in preventing odontogenic tumor development by suppressing cell proliferation and maintaining differentiation phenotype through Msx2, p21, and p27.The extracellular matrix provides structural support for cells and regulates cell proliferation, migration, differentiation, and apoptosis for tissue development and homeostasis (1). The extracellular matrix also plays a crucial role in pathological processes and diseases, such as wound healing, tumorigenesis, and cancer development (2, 3). AMBN (ameloblastin), also known as amelin and sheathlin, is a tooth-specific extracellular matrix and the most abundant non-amelogenin enamel matrix protein (4–6). AMBN is expressed primarily by ameloblasts, which are differentiated from the oral ectoderm and form a polarized single cell layer underlying the enamel matrix. In a previous study, we created Ambn-null mice and demonstrated that AMBN is required for cell attachment and polarization and for maintaining the differentiation state of ameloblasts and is essential for enamel formation (3). Overexpression of Ambn in transgenic mice causes abnormal enamel crystallite formation and enamel rod morphology (7). These results suggest that enamel formation and rod morphology are influenced by temporal and spatial expressions of AMBN and imply that the AMBN gene locus may be involved in the etiology of a number of cases of undiagnosed hereditary amelogenesis imperfecta (8). Further, it was reported that recombinant AMBN enhances pulpal wound healing and reparative dentine formation following pulpotomy procedures, suggesting that it functions as a signal molecule in epithelial-mesenchymal interactions (9).We previously reported that about 20% of Ambn-null mice developed an odontogenic tumor of dental epithelium origin in the buccal vestibule of the maxilla (3). The epithelial cells of odontogenic tumors express enamel matrix proteins, including AMEL (amelogenin), ENAM (enamelin), and TUFT (tuftelin), but not AMBN, indicating that AMBN deficiency is probably the primary cause of tumorigenesis seen in those mice. An ameloblastoma appearing in the jaw is the most frequently encountered odontogenic tumor and is characterized by benign but locally invasive behavior with a high rate of recurrence. Since abnormal proliferation and growth of ameloblastoma cells easily destroys surrounding bony tissues, wide excision is required to treat this disorder. It is also reported that ameloblastomas rarely metastasize to other parts of the body, such as the lungs and regional lymph nodes (10, 11). Associations of AMBN mutations were reported in ameloblastomas, adenomatoid odontogenic tumors, and squamous odontogenic tumors (12). These results suggest that AMBN regulates odontogenic tumor formation.In the present study, we investigated the mechanism of AMBN in dental epithelial cell adhesion and ameloblastoma proliferation. We found that AMBN has heparin binding domains, which are essential for AMBN binding to dental epithelial cells. We demonstrate that overexpression of recombinant AMBN inhibits proliferation of human ameloblastoma cells. This inhibition requires the heparin binding sites of AMBN and is accompanied by dysregulation of Msx2, p21, and p27. These results suggest that AMBN suppresses ameloblastoma cell proliferation by regulating cellular signaling through the heparin binding domains.     

Population genetic studies on aldehyde dehydrogenase isozyme deficiency and alcohol sensitivity

Population genetic studies on aldehyde dehydrogenase polymorphism using hair-root samples were performed on Europeans, Liberians, Sudanese, Egyptians, Kenyans, Vietnamese, Japanese, Indonesians, Chinese, Thais, and South American Indians. A possible correlation between ALDH I deficiency and sensitivity to alcohol in Oriental populations is discussed.     

Large Scale Synthesis of the Cap Part in Messenger RNA Using a New Type of Bifunctional Phosphorylating Reagent

Abstract

Bifunctional phosphorylating reagents 1 and 2 were employed for the synthesis of the cap part, m⁷G⁷ pppG, from guanosine 5′-phosphates on a large scale without any protecting groups.