Human hybrid immunoglobulin M containing immunoglobulin A

Summary Some hybridoma clones made by fusion of a human lymphoblastoid cell line, HO323 with human B lymphocytes, secreted not only IgA but also IgM-like immunoglobulin molecules. The IgM-like immunoglobulin had a molecular size of 900 K which corresponded to that of IgM. Immunochemical analyses revealed that the IgM-like immunoglobulin contained two monomeric IgA and three monomeric IgM molecules. In the IgA moieties, half of original light chains were replaced withx chains derived from the IgM, and vice versa.     

Mechanism of the stimulatory effect of cyclodextrins on lankacidin-producing Streptomyces

Summary Gel-filtration analysis of a mixture of cyclodextrin (CyD) and lankacidin C showed that -CyD had strong, -CyD weak and -CyD no affinity for lankacidin C. Lankacidin C production activity, which was assayed by measuring the incorporation of l-[methyl-¹⁴C-]methionine into the lankacidin molecule, was the greatest with cells grown in the presence of -CyD, less with -CyD and the least with -CyD. Lankamycin and T-2636M, which are by-products in lankacidin C fermentation, were not included by -CyD and their production was not stimulated by -CyD. It was apparent that the stimulatory effect of CyD was closely related to the formation of an inclusion complex between CyD and the antibiotic. Lankacidin C biosynthesis was repressed by preincubating cells with lankacidin C, while the repressive effect of lankacidin C was abrogated by the inclusion by -CyD. Thus, abrogation of feed-back repression seems to be a main mechanism of the effect of CyD. However, -CyD, which had no affinity for lankacidin C, stimulated the production to the least extent and exhibited a complementary effect on the stimulation by -CyD or -CyD. -CyD also caused a change in cell morphology and cell-surface hydrophobicity. It was assumed that the modification of the cell surface is a secondary mechanism of the effect of CyD.The second report of the stimulatory effect of cyclodextrins on lankacidin fermentationOffprint requests to: H. Sawada     

Aspergillus taichungensis,a new species from Taiwan

Aspergillus taichungensis isolated from a soil sample collected in Taiwan is described as a new species. The new species is characterized by its restricted growth on Czapek's and malt extract agars and its white to light yellow colonies, radiate conidial heads, smooth and often diminutive conidiophores, hemispherical to elongate vesicles with biseriate aspergilla (conidiogenous cells), globose, micro-verrucose conidia and dark brown sclerotia. The species somewhat resemblesA. versicolor, A. terreus andA. flavipes, but differs in cultural and morphological details, and is considered to represent an interface species in the subgenusNidulantes.     

Materials for the fungus flora of Japan (49)

Two interesting microfungi are described as new to Japan:Talaromyces galapagensis (anam.Penicillium galapagense), isolated from soil in Shizuoka; andPenicillium megasporum, isolated from marine sludge in Nagasaki. Some observations are recorded, particularly on ascomatal initials ofT. galapagensis, which are similar to those described forTalaromyces flavus.(48): Kaneko, S., Mycoscience 36: 359–360, 1995.     

Adaptation of mouse-human hybridomas to a protein free medium

Summary Five mouse-human hybridoma cell lines secreting human IgM class monoclonal antibodies were examined for possible adaptation to a protein free medium. Four were successfully adapted to the medium. The adapted cell lines could be cultured for more than two months without any changes in their cell growth abilities.     

Talaromyces lagunensis,a new species from Philippine soil

A new species ofTalaromyces (Ascomycetes; Trichocomaceae) with aPenicillium anamorph,T. lagunensis, is described and illustrated. This fungus is characterized by its extremely restricted growh on Czapek-yeast extract agar, light yellow to light orange ascomata with a telaperidium, catenate, pyriform or ellipsoidal asci, ellipsoidal or subglobose ascospores with a microtuberculate wall, short conidiophores with an irregular, mostly monoverticillate to biverticillate penicillus, and subglobose to ovoid conidia. The holotype was isolated from forest soil in the Philippines.     

Fast polyspermy block and activation potential : Correlated changes during oocyte maturation of a starfish

Sperm entry into the oocyte of the starfish, Asterina pectinifera, was prevented when the membrane potential of the oocyte was held more positive than −10 to −5 mV, and multiple sperm entries were induced when the potential was held more negative. Based on this potential-dependent fertilization block mechanism, it was demonstrated that an activation potential (AVP) which is induced immediately after the attachment of the first sperm to the egg surface plays the role of a fast polyspermy block. The AVP-mediated polyspermy block mechanism develops as the oocyte matures and deteriorates as it ages. AVPs of mature oocytes exceeded −5 mV (the critical potential level for fertilization block) within 1 sec, and the potential stayed at +12 mV even after the initiation of fertilization membrane elevation. Consequently, the entry of a second sperm is prevented. In contrast, AVPs of overripe oocytes took about 15 sec to attain −5 mV, or they did not attain −5 mV at all. In overripe oocytes multiple sperm entries were associated with “step depolarization(s)” in the rising phase of the AVPs before membrane elevation took place. Immature oocytes generated AVPs associated with sperm entries, but without membrane elevation. AVPs in immature oocytes were characterized by the step depolarization(s) in the rising phase, and an AVP could be evoked again by a second insemination 20 min after the first insemination. These findings indicate that immature oocytes lack both fast and slow polyspermy block mechanisms.     

Tertiary structure of bacterial selenocysteine tRNA

Selenocysteine (Sec) is translationally incorporated into proteins in response to the UGA codon. The tRNA specific to Sec (tRNA^Sec) is first ligated with serine by seryl-tRNA synthetase (SerRS). In the present study, we determined the 3.1 Å crystal structure of the tRNA^Sec from the bacterium Aquifex aeolicus, in complex with the heterologous SerRS from the archaeon Methanopyrus kandleri. The bacterial tRNA^Sec assumes the L-shaped structure, from which the long extra arm protrudes. Although the D-arm conformation and the extra-arm orientation are similar to those of eukaryal/archaeal tRNA^Secs, A. aeolicus tRNA^Sec has unique base triples, G14:C21:U8 and C15:G20a:G48, which occupy the positions corresponding to the U8:A14 and R15:Y48 tertiary base pairs of canonical tRNAs. Methanopyrus kandleri SerRS exhibited serine ligation activity toward A. aeolicus tRNA^Sec in vitro. The SerRS N-terminal domain interacts with the extra-arm stem and the outer corner of tRNA^Sec. Similar interactions exist in the reported tRNA^Ser and SerRS complex structure from the bacterium Thermus thermophilus. Although the catalytic C-terminal domain of M. kandleri SerRS lacks interactions with A. aeolicus tRNA^Sec in the present complex structure, the conformational flexibility of SerRS is likely to allow the CCA terminal region of tRNA^Sec to enter the SerRS catalytic site.     

Thermal stability of oligodeoxynucleotide duplexes containing l-deoxynucleotide at termini

The effects of substituting l-deoxynucleotide for d-deoxynucleotide at duplex termini were evaluated and the terminal substitutions were found to show much less effects on duplex destabilization and to show a similar tendency in base pairing selectivity, compared with internal chiral substitutions.     

Production of Pentameric Hybrid Immunoglobulins Consisting of IgA and IgM

The amylomaltase from Escherichia coli IFO 3806 was purified to homogeneity seen by SDS- polyacrylamide gel electrophoresis after DEAE-Sephadex, Ultrogel AcA 44, hydroxylapatite, and 1,6- hexane-diamine-Sepharose 4B column chromatographies. The molecular weight of the purified enzyme was 93,000 by SDS-polyacrylamide gel electrophoresis. The enzyme was most active at pH 6.5 and at 35°C, and stable up to 45°C at pH 7.0 and from pH 6.0 —7.3 at 40°C on 30min incubation. The enzyme acted on maltotetraitol, maltopentaitol, and maltosylsucrose besides maltooligosaccharides, but did not act on maltitol, maltotriitol, glucosylsucrose, isomaltose, panose, isopanose, or isomaltosyl- maltose. This enzyme did not catalyze hydrolytic action on maltotetraitol, maltopentaitol, or maltosylsucrose.