Reappraisal of Schaubcylindrichnus: A probable dwelling/feeding structure of a solitary funnel feeder

The ichnogenus Schaubcylindrichnus has been considered as a cluster of multiple J-shaped tubes, all of which show congruency. Based on such a reconstruction, the trace fossil has commonly been regarded as dwelling tubes of gregarious, head-down deposit-feeding animals.

Well-preserved specimens of Schaubcylindrichnus are found in Miocene and Pleistocene strata of Japan. The trace fossil consists of a bundle of closely spaced, thickly lined tubes, each of which shows a gentle bow-like bend curving downward in a vertical to oblique plane. As individual tubes in a single bundle frequently show size-gradation of diameter, branching and/or cross-cutting, it is probable that the bundle was formed through successive burrowing by a solitary producer. In a longitudinal section of well-preserved specimens, a funnel-like, sediment-filled structure, which is attached to an upper end of a limb of the bow-shaped bundle, is observed. At the other end of the limb, there is a mound-like structure of sediment that is piled up from the bedding surface. The trace fossil was probably a burrow system of a solitary funnel-feeding animal, like an enteropneust.

According to comparisons with type specimens of the ichnospecies of Schaubcylindrichnus, namely, topotypes of Schaubcylindrichnus coronus and holotype and paratypes of S. freyi, S. freyi can be regarded as a junior synonym of S. coronus. As the topotype specimens of S. coronus have many common features with the traces in Japan, the latter should be included in the former. S. coronus therefore is concluded as the burrow system of a solitary funnel feeder.     

Nuclear fragmentation and DNA degradation during programmed cell death in petals of morning glory (Ipomoea nil)

We studied DNA degradation and nuclear fragmentation during programmed cell death (PCD) in petals of Ipomoea nil (L.) Roth flowers. The DNA degradation, as observed on agarose gels, showed a large increase. Using DAPI, which stains DNA, and flow cytometry for DAPI fluorescence, we found that the number of DNA masses per petal at least doubled. This indicated chromatin fragmentation, either inside or outside the nucleus. Staining with the cationic lipophilic fluoroprobe DiOC₆ indicated that each DNA mass had an external membrane. Fluorescence microscopy of the nuclei and DNA masses revealed an initial decrease in diameter together with chromatin condensation. The diameters of these condensed nuclei were about 70% of original. Two populations of nuclear diameter, one with an average diameter about half of the other, were observed at initial stages of nuclear fragmentation. The diameter of the DNA masses then gradually decreased further. The smallest observed DNA masses had a diameter less than 10% of that of the original nucleus. Cycloheximide treatment arrested the cytometrically determined changes in DNA fluorescence, indicating protein synthesis requirement. Ethylene inhibitors (AVG and 1-MCP) had no effect on the cytometrically determined DNA changes, suggesting that these processes are not controlled by endogenous ethylene.     

Apoptosis as a mechanism of skin renewal: Ley-antigen expression is involved in an early event of a cell's commitment to apoptosis

Skin renewal is a typical example of the active participation of a cell in its own death process. Cells arising from mitotic activity in the stratum germinativum of the epidermis continuously migrate upwards to the stratum corneum, where dead cells are eventually desquamated. Recent studies have suggested that apoptosis is involved in the dynamic process of skin renewal. However, this still remains to be further elucidated. In this paper, we investigated the involvement of apoptosis in the skin renewal process. Changes in the morphology of cells in different epidermal layers were compared with histochemical analyses of the extent of DNA fragmentation, as determined by nick end-labelling, and of the reactivities to a monoclonal antibody directed to Le^y-antigen, difucosylated type 2 chain determinant, which has a close association with apoptosis, and to a monoclonal antibody directed to the proliferating cell nuclear antigen. The results show that apoptosis proceeds concomitantly with cell movement in the epidermis. It seems likely that commitment of a cell to death by apoptosis occurs in the epidermal tissue immediately after completion of cell proliferation, and that Le^y-antigen expression may be involved in the entire apoptotic process including this early event.     

Cyanogenic glycosides in leaves of Perilla frutescens var. acuta

Besides 7-(2-O-β-D-glucuronyl-β-D-glucuronyloxy)-5,3′,4′-trihydroxyflavone, scutellarin, rosmarinic acid and caffeic acid, two cyanogenic glycosides have been isolated from the dried leaves of Perilla frutescens var. acuta. One of them is prunasin and the other is (R)-2-(2-O-β-D-glucopyranosyl-β-D-glucopyranosyloxy)-phenylacetonitrile, a new isomer of amygdalin.     

Role of cyclic AMP and ammonia in induction and maintenance of post-aggregative differentiation in a suspension culture of Dictyostelium discoideum

The effects of ammonia and cAMP on prespore and prestalk differentiation of Dictyostelium discoideum were investigated by monitoring eight developmentally regulated proteins as differentiation markers under the shake culture conditions in glucose/albumin medium. In the medium containing cAMP, cells form small agglomerates and undergo prespore differentiation [19]. Under the conditions where agglomeration was prevented, ammonia induced four marker proteins out of eight tested in the presence of cAMP, which included not only a prespore specific enzyme but also cell-type non-specific proteins. No inhibitory effect of ammonia was observed in presumptive cell differentiation. These results suggest that ammonia is an inducer of differentiation at the protein level as well as the mRNA level as found previously [24]. The effects of cAMP were examined with special attention to the difference between induction of differentiation and maintenance of differentiated state in this specific medium. The induction of differentiation from early aggregative cells was cAMP-dependent with all the marker proteins tested. This agrees with the observations so far obtained in other culture systems. However, when already differentiated cell masses (slugs) were dissociated and shaken in this specific medium, only two enzymes required cAMP to maintain the activity while five out of eight kinds of the proteins continued to be expressed as in undisturbed slugs even without cAMP. This suggests that for the maintenance of the differentiated state after slug disaggregation cAMP may not be required with respect to the majority of proteins, if cells are provided with some favorable conditions such as glucose/albumin medium.     

Increased expression of hepatitis B virus surface antigen gene in Escherichia coli by IS1 insertion

Summary We selected faster growing colonies of Escherichia coli harbouring an expression plasmid for hepatitis B virus surface antigen (HBsAg) gene after mutagenesis. Among these colonies, three were found to produce an increased level of HBsAg as a consequence of alteration of the plasmid. Analysis of this plasmid showed that an insertion sequence, IS1, was inserted into a middle region of the HBsAg gene (codon for Pro 127) to generate a termination codon 20 bp downstream from the junction site between the HBsAg gene and the left end of IS1. Insertion of a chemically synthesized termination codon into the same region of the HBsAg gene also increased the expression of the HBsAg gene. These results suggest that HBsAg lacking the COOH-terminal region is produced at a high level because it does not inhibit the growth of the host.     

SURVIVING PROTOPLASTS IN VITRO AND THEIR DEVELOPMENT IN BRYOPSIS1

In the coenocytic marine alga Bryopsis plumosa, extracellular protoplasts synthesize new cell walls in vitro and can develop into normal pinnate plants in the same way of the zygote of this species.     

MORPHOGENESIS OF MONOSTROMA OXYSPERMUM (KÜTZ.) DOTY (CHLOROPHYCEAE) IN AXENIC CULTURE,ESPECIALLY IN BIALGAL CULTURE1

The typical morphology of Monostroma oxyspermum (Kütz.) Doty is lost in axenic culture. In synthetic media of the ASP type, it grows as a colony-like mass composed of round cells with numerous rhizoids. Such a mass is a fragile structure which falls apart upon shaking, or slight touch, into small cell-groups and single cells or cells with a long rhizoid. Only temporary saccate or monostromatic fronds appear and reach 1–2 mm in length when grown in enriched seawater media, but disintegrate and become a colony-like mass. The typical morphology is easily restored by adding at specific intervals filtrates of bacterial cultures and supernatant medium from axenic brown and red algal cultures to the basal medium (ASP7), or by reinfecting the Monostroma with an appropriate bacterial flora. Furthermore, the typical morphology in also maintained by bialgal cultures between Monostroma and other axenic strains of various species of seaweeds except the species belonging to the Chlorophyceae. Monostroma thus appears to utilize some substances released by most species of brown and red algae for its typical growth. Active substances released by bacteria, brown and red algae have not yet been identified and purified. However, it is demonstrated that in axenic cultures many species of seaweeds produce active extracellular substances which play an important role in growth and Morphogenesis of other species of seaweeds.     

Insertion of muntjac gene segment into hamster cells by cell fusion

Indian muntjac diploid cells that have only three pairs of easily discernible large chromosomes were fused with hamster cells deficient in hypoxanthine guanine phosphoribosyltransferase (HGPRT) using polyethylene glycol. Cells that survived in hypoxanthine-aminopterine-thymidine (HAT)-oubaine medium were analyzed. Hybrid cells containing both muntjac and hamster chromosomes in a given cell were not found. Instead, the cells had the same chromosomal sets as those of either parental muntjac or hamster cells. A clonal isolate that had the same chromosomal sets as those of parental hamster cells was analyzed in detail and showed the following characteristics: (1) portions of the survival curve in various concentrations of HAT medium were intermediate between those of parental cells; (2) expressions of both muntjac and hamster antigen(s) were detected by immunofluorescence staining; (3) the mobility of the enzyme HGPRT in gel electrophoresis differed from that of parental hamster or muntjac cells. These results indicate that the clonal isolate (AD202h) is a somatic cell hybrid of hamster and muntjac that contains chromosomal sets of hamster with an inserted segment of the muntjac genome, including HGPRT. The formation of such an unusal hybrid and a possible explanation of transfer of some gene segments in the hybrid cell in this system are discussed.