Microtubules (MT), composed of a protein tubulin (TN) α, β-heterodimer with concomitant other proteins, microtubule associated proteins (MAPs and τ), are known to be the main component of spindles in a mitotic apparatus of eucaryotic cells, and are also involved in many other basic and essential cell functions. There are a number of natural and synthetic compounds that interfere with MT function to cause the mitotic arrest of eucaryotic cells. Such antimitotic agents show a broad biological activity, and can be used for medicinal and agrochemical purposes. On the other hand, they are also important as the biochemical tools for understanding the dynamics of MT network. Most of such antimitotic agents, with a few exceptions, bind to β-TN. Among them, colchicine (CLC), vinblastine (VLB) and taxol have been of major importance in biochemical studies of MT and in studies of their intracellular functions. The former two both inhibit MT assembly but their binding sites on β-TN are different ; CLC-site and VLB-site, and many MT inhibitors bind to either sites. Taxol bind to TN at a site other than CLC-site and VLB-site, and promote MT assembly. We have worked on a variety of antimitotic agents that bind to CLC, VLB or taxol-site, in discoveries, structures, bilogical actions and/or interactions with TN. In this paper, I summarized the results of our studies on VLB-site ligands ; (1) rhizoxin (RZX), isolated as a phytotoxin produced by a plant pathogenic fungus, and its related compounds, (2) derivatives of ansamitocin P-3 (ASMP3) (maytansinoid : MAY), isolated as a cytotoxic metabolite of an Actinomycete, (3) phomopsin A (PMSA), isolated as a mycotoxin produced by a plant parasitic fungus, (4) dolastatin 10 (DLS10), isolated as a cytotoxic metabolite of a see animal, (5) ustiloxins (USL) A-F, isolated as a mycotoxin produced by a plant pathogenic fungus, (6) arenastatin A (ARSA), isolated as a cytotoxic metabolite of a sponge, and its synthetic analogs. From our studies on interactions of these VLB-site ligands with TN, we showed that the presence of a distinct RZX/MAY-binding site which only partially overlap with VLB-site, and that PMSA, DLS10, USLs and ARSA bind to the RZX/MAY site. RZX, ASMP3 and ARSA inhibit the growth of a variety of fungi, including Aspergillus nidulans. In order to obtain information as to the drug-TN interaction at the RZX/MAY site, RZX-resistant β-TN gene mutants, single amino acid (100th) alteration, asparagine-to-isoleucine, was observed. Sequence displacement experiments confirmed that this alteration conferred resistance to RZX and ASMP3, and also to ARSA. This resistance mechanism was further verified with yeasts Schizosaccharomyces pombe and Saccharomyces serevisiae. All the natural ligands mentioned above show potent cytotoxicity against human and murine tumor cells, but VLB, PMSA, DLS10 and USLA are inactive to both RZX-sensitive and -resistant fungal strains.
This report deals with adhesive properties and related phenomena of powdered materials including pharmaceuticals. The adhesive force between a powder particle and substrate as well as the tensile strength of a powder bed and tablet was measured. Various factors were found to affect powder adhesion. Physical properties such as the size, shape and surface roughness were examined. The adhesive force between a particle and substrate decreased remarkably in the presence of ultrafine particles, which is of interest since the addition of adequate amount of "glidant" causes an increase in powder fluidity. From a pharmaceutical point of view, temperature and humidity were essential to particle adhesion. For several organic substances, the adhesive force increased significantly at homologous temperatures more than ca. 0.7, suggesting the sintering mechanism to be operative. The adhesive force between polymer films and glass beads varied according to polymer and relative humidity. A close correlation of water sorbed by the polymer film with adhesive force was noted. In connection with powder fluidity, compaction properties were studied by the centrifugal and tapping methods. Apparent adhesion defined as the ratio of the adhesive force between two contacting particles to the external force acting on a particle was noted to be the primary determinant of the void fraction or the porosity of the powder bed, indicating that the probability of particle displacement essentially depended on apparent adhesion.
The pharmacokinetics of norephedrine enantiomers were determined after the independent i.v. administration of (±)-norephedrine (20 mg/kg), (-)-norephedrine (10 mg/kg), and (+)-norephedrine (10 mg/kg) to rats. Significant differences were observed in the pharmacokinetic parameters of each enantiomer when the enantiomers were administered singly and as a racemate. For example, the values of total body clearance (Cltot) and urinary excretion clearance (Clr) of (-)-norephedrine administered as a racemate were higher than those of the norephedrine enantiomer administered singly. The areas under the curve of concentration versus time (AUC) of (-)-norephedrine administered as a racemate had a tendency to increase. While Cltot of (+)-norephedrine administered as a racemate showed a lower value and AUC showed a higher value. The value of Clr of (+)-norephedrine administered as a racemate showed a tendency to decrease. There was no difference in the in vitro serum protein binding of (-)- and (+)-norephedrine. The data from this study reveal that pharmacokinetic interactions exist between the norephedrine enantiomers and also reveal that the serum protein binding is not concerned with those interactions. The differences in the pharmacological effects after the individual administration of (-)-norephedrine or (±)-norephedrine may be coused by the differences in their concentrations in the plasma.
The biological response modifier (BRM) activity of a preparation of heat killed cells of Lactococcus lactis 332 which can produce large amount of lactate in culture, was investigated in C3H/He and ICR mice. Intraperitoneal injection of Lactococcus lactis 332 caused an accumulation of neutrophils and macrophages in the peritoneal cavity of the mice, similarly to BRMs used clinically. As a parameter of the activation of macrophages, the effect of the Lactococcus lactis 332 preparation on the production of tumor necrosis factor (TNF) was examined. The Lactococcus lactis 332 preparation was revealed to have both priming and triggering activities for the production of TNF. The TNF level in the sera reached about 1000 IU/ml in mice 2 h after the triggering injection. This preparation also stimulated peritoneal macrophages to produce TNF in vitro. Intratumoral injection of the Lactococcus lactis 332 preparation regressed MM46 tumor cells in C3H/He mice. These results suggest that the Lactococcus lactis 332 preparation is a biological response modifier (BRM) with various activities on phagocytes similarly to a streptococcal antitumor agent, OK432, used clinically.