Spatial distribution of turtle barnacles on the green sea turtle, Chelonia mydas

Distribution patterns of epibiotic barnacles on green sea turtles were investigated in waters neighboring Okinawa, Japan. A number of barnacle species were found to coexist on the turtles and were classified into three genera: Chelonibia, Platylepas and Stomatolepas. Attachment sites on the turtles varied among the barnacle species, suggesting that there is niche partitioning with respect to their microhabitat selection. Turtle bodies offer a “patchy” environment for barnacles, so we also analyzed coexistence patterns in the context of an aggregation model. Within each genus, individual barnacles showed a clumped distribution. The different genera do not have mutually exclusive distribution patterns, but instead occur on the same turtle to various degrees. However, when turtles were divided into two size classes, both the level of aggregation and the degree of interspecific overlap among the barnacles was significantly lower on large turtles. We suggest that obtaining basic information on turtle epibionts will shed light on the biology of wild turtles, which is still largely unknown.     

3 beta-hydroxyandrost-4-en-6-one derivatives as aromatase inhibitors

The 3-formate (II), 3-acetate (III), 3-bromoacetate (IV), 3-propionate (V), 3-methyl ether (VI), and 3-deoxy-derivative (VII) of 3 beta-hydroxyandrost-4-ene-6,17-dione (I) were synthesized and tested in human placental microsomes for their ability to inhibit aromatase. II, III, and VII of this series were potent inhibitors of aromatase with the IC50's (1.7 and 3.3 microM) of the latter two comparable to that (1.2 microM) of 4-hydroxyandrostenedione. Kinetic studies showed that the three steroids are competitive inhibitors of the enzyme with Ki's of 16.0, 5.5, and 0.61 microM for II, III, and VII. Furthermore, II showed a time-dependent, pseudo-first order rate of inactivation of aromatase with Ki of 20.5 microM and kinact of 1.54 x 10(-2) min-1, while III gave a time-dependent, biphasic loss of the enzyme activity. NADPH and oxygen were required for the time-dependent inactivation and the substrate, androstenedione, prevented it.     

Characterization of mouse integrin alpha3 subunit gene.

Integrin alpha3beta1 (VLA-3) is an adhesion receptor for extracellular matrix proteins including various isoforms of laminin. We have isolated mouse genomic clones encoding the integrin alpha3 subunit and deduced the exon/intron organization. The mouse integrin alpha3 subunit gene is encoded by 26 exons spanning 40 kb. The exon/intron structure of the integrin alpha3 subunit gene resembles that of the integrin alpha6 subunit gene, but differs somewhat from those of other members of the integrin family. We have demonstrated that the cytoplasmic domain splicing variants of the alpha3 subunits (alpha3A and alpha3B) are generated by alternative exon usage. We also cloned the 5'-flanking region and performed a preliminary analysis of its promoter activity in various tumor cell lines with different degrees of integrin alpha3 expression. Following transfection, activity in the luciferase assay was found to be roughly correlated with the expression level of integrin alpha3 as measured by flow cytometry. Furthermore, the luciferase assay was performed with normal and SV-40- or polyoma virus-transformed fibroblasts. In mouse, human, and hamster fibroblasts, higher levels of luciferase expression were observed in transformed cells than in normal cells. This result is consistent with our previous finding that integrin alpha3 expression at both the protein and mRNA levels is enhanced upon oncogenic transformation of fibroblasts by tumor viruses.     

Bioluminescence of the Ca-binding photoprotein, aequorin, after histidine modification

Modification studies of the 5 histidine residues in aequorin employing site-directed mutagenesis and diethyl pyrocarbonate suggested that His¹⁶⁹ may be the site of binding of molecular oxygen in aequorin. The modification of this residue led to complete loss of activity, whereas modification of the remaining 4 histidine residues yielded mutant aequorins with varying bioluminescence activities.     

Microassay of proteins on membrane filter in the nanogram range using cycloheptaamylase-dansyl chloride complex.

A protein assay is described in which the sample is spotted on a Sartorius membrane filter and dansylated with cycloheptaamylose-dansyl chloride complex dissolved in aqueous urea solution. The fluorescence intensity of the spot on the membrane was directly measured by a scanning fluorometer. This assay is rapid, simple, highly reproducible, and linear from 0.05 to 4 μg of protein. Very dilute solutions of protein can also be determined by filtering off the sample on the membrane filter in the presence of 0.1 m MgCl₂ and dansylating the protein collected on the membrane. There is no interference either by commonly used reagents such as Tris, citrate, guanidine, and glycine, or by naturally occurring amines and amino acids.