Effect of base substitutions in the colicin E1 gene on colicin E1 export and bacteriocin activity

Summary Base substitutions have been introduced into the segment of the colicin E1 gene corresponding to the polypeptide region between the 404th and the 502nd residues which was considered to participate in colicin E1 export and bacteriocin activity. The methods used were in vitro localized mutagenesis with sodium bisulphite and in vivo mutagenesis using either nitrosoguanidine or ethyl methane sulphonate. Cells carrying mutagenized plasmids were screened by their inability to form a clear zone on a lawn of colicin E1 sensitive cells. Mutation sites were determined from the nucleotide sequence analysis and the altered amino acid residues were reduced. The mutant proteins were analysed for their ability to be exported to the periplasmic space and for their bacteriocin activity. Out of eight mutants obtained, three had a single amino acid replacement. Mutant proteins that had Ser and Glu in place of Pro-462 and Gly-502, respectively, showed a decrease in both the export and the bacteriocin activity. A mutant protein having Arg in place of Gly-439 showed a decrease only in the bacteriocin activity. These results suggest that the target region of colicin E1 contributes to the export as well as the bacteriocin activity but the two functions are supported in part by different amino acid residues of the protein.     

Effects of Nutrient Limitation and {gamma}-Irradiation on Tracheary Element Differentiation and Cell Division in Single Mesophyll Cells of Zinnia elegans

The effects of nutrient limitation and -irradiation on trachearyelement differentiation and cell division were investigatedusing single cells isolated from the mesophyll of Zinnia elegans.When the phosphate concentration of the medium was reduced to10 µM (1/50 of Fukuda and Komamine's medium, 1980a), thefrequency of cell division during 4 days of culture decreased,while the frequency of tracheary element differentiation wasunaffected. -Irradiation with a dose of 92 Gy at 36 h of culturepreferentially and thoroughly suppressed cell division withoutreducing the number of tracheary elements formed. The appearanceof secondary cell wall thickenings was delayed by irradiation,but synchrony was maintained. Thus the Zinnia system previouslyreported [Fukuda and Komamine (1980a) Plant Physiol. 65: 57]was improved to give a more useful system for the study of cytodifferentiation,in which tracheary element formation occurred from single cellswithout cell division. ¹Present address: Biological Institute, Faculty of Science,Tohoku University, Sendai, Miyagi 980, Japan. (Received November 28, 1985; Accepted February 22, 1986)     

Basic studies of cryochemotherapy in a murine tumor system

The combined effect of cryosurgery and anticancer drugs (cryochemotherapy) was studied in an experimental B16 melanoma/BDF1 tumor system. Vascular volume and vascular permeability after cryosurgery of normal skin and the tumor were measured by using 51Cr-labeled red blood cells and 125I-labeled serum albumin. The vascular volume and vascular permeability of both the normal vessels and the tumor vessels greatly increased immediately after cryosurgery, and their vascular volume decreased to less than the normal level within a few hours. However, the tumor vessels showed less dilatation and increase in permeability than the vessels of normal tissue. There was a difference in functional characteristics in response to cryoinjury between the normal vessels and the tumor vessels. The anticancer drugs, peplomycin and adriamycin, were administered intraperitoneally in combination with cryosurgery. When peplomycin was administered 5 min, 1 hr, and 3 hr after cryosurgery, the drug concentration in the frozen tumor was higher than that in the untreated tumor. But when administered 1 hr before cryosurgery, peplomycin was not trapped in the tumor. Trapping of adriamycin was not observed after the same treatment. In cryochemotherapy, it is necessary to administer the appropriate drug at the appropriate time. However, the trapping of the anticancer drug results in a high concentration and lasts for a long time, so that cryochemotherapy is expected to be a new mode of cancer therapy, particularly as a multidisciplinary treatment for cancer.     

Changes in synthetic activity of cell walls during the cell cycle in a synchronous culture of Catharanthus roseus

The incorporation rates of [¹⁴C] glucose into various fractions of the cell walls and into the sugar constituent of each fraction were investigated in a synchronous culture of Catharanthus roseus (L.) G. Don in order to elucidate the synthetic aspects of the cell walls during the cell cycle. Changes in the incorporation of radioactivity were closely correlated with changes in the amount of each cell wall fraction as well as with those in sugar composition as reported previously (S. Amino et al. Physiol. Plant. 60: 326–332, 1984). The specific activity of galactose was higher than that of other sugars throughout the cell cycle, and a temporary increase in the incorporation of radioactivity into all cell wall fractions except cellulose was observed just before the increase in cell numbers. The synthetic activities may play key roles in the regulation of cell wall polysaccharide dynamics during the cell cycle.     

A Comparison of Tomato Fruit Chloroplast and Chromoplast DNAs as Analyzed with Restriction Endonucleases

Chromoplast DNA was isolated from ripe-red tomato fruits, andits structure compared with that of chloroplast DNAs from maturegreen fruits and leaves. There was a good correspondence betweenthe structures analyzed by BamHI or EcoRI digestion and by hybridizationwith a probe for the gene of the ribulose 1,5-bisphosphate carboxylase/oxygenaselarge subunit. ¹ Present address: Koryo International College, Nisshin, Aichi470-01, Japan. (Received November 5, 1984; Accepted February 6, 1985)     

The core molecule from type H proteoglycan. Release of mannose-containing oligosaccharides by digestion with N-oligosaccharide glycopeptidase.

Chick-embryo cartilage contains a unique set of proteoglycans. Type H proteoglycan (PG-H) is the most abundant, constituting over 90% of the total cartilage hexuronate. We previously showed that treatment of PG-H with chondroitinase ACII and keratanase yields a protein-enriched core molecule [PG(-CS,KS)] with enzymically modified linkage oligosaccharides of the chondroitin sulphate and keratan sulphate chains. We report here that further treatment of PG(-CS,KS) with pepsin and N-oligosaccharide glycopeptidase (almond glycopeptidase) released four distinct types of mannose-containing oligosaccharide. Two of them were shown to be: (Formula: see text). Of the mannose-containing glycopeptides formed by pepsin digestion, about 40% (as mannose) were resistant to N-oligosaccharide glycopeptidase. Since the resistant fraction was enriched in keratan sulphate remnants, it is suggest that the mannose-containing oligosaccharides in this fraction represent those located in a keratan sulphate-enriched region of PG-H.     

Triterpenes from Periandra dulcis roots

Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene.     

Length heterogeneity of the large spacer of Vicia faba rDNA is due to the differing number of a 325 bp repetitive sequence elements

Summary The DNA fragments including the whole large spacer region of Vicia faba rDNA were cloned in plasmid pBR325. Sixteen clones were classed into five groups which differed from each other in the lengths of the rDNA inserts. Physical maps of these length variants cloned were constructed using EcoRI, SalI, HpaI, MluI and AccI and evidence was obtained that the length heterogeneity was due mainly to the differing number of 325 base pairs (bp) subrepeating elements in the large spacer. Sequence analysis of this subrepeating element revealed that it consisted of a duplet of an approximately 155 bp sequence and a 14 bp unrelated sequence. This structure of the repetitive element is novel.     

Correlations in one-dimensional fully developed chaos

Correlations in the baker map and the tent map as examples of one-dimensional, fully developed chaos are considered. It is shown, utilizing symbolic dynamical systems derived from these maps, that the vanishing second-order correlation function is not sufficient to guarantee uncorrelatedness. Importance of the higher-order, especially third-order, correlation functions is emphasized for chaotic systems. In search of the quantities that grasp correlational behaviors as a whole in chaotic systems, it is proposed to use the fixed-separation correlation integral, which is a modified quantity of the usual correlation integral devised to calculate the fractal dimension of strange attractors, for these maps. It is shown that the new quantity contains all the even-number orders of autocorrelation function that are commonly considered.     

Responses of aerial ventilation to hypoxia and hypercapnia inChanna argus,an air-breathing fish

Summary The snake-head fish (Channa argus) is an obligate air-breather inhabiting fresh waters in the temperate zone of East Asia.Ventilation of the air-breathing organ and aerial gas exchange were measured in 1 to 2 kg specimens at 15 and 25°C. Additionally, the ventilatory responses to hypoxia and hypercapnia were studied. Aerial ventilation increased from 1.1 to 2.9 mlbtps·kg^–1·min^–1 when temperature rose from 15 to 25°C. Concomitantly, O₂-uptake through airbreathing increased from 0.1 mlstpd·kg^–1·min^–1 (15°C) to 0.28 mlstpd·kg^–1·min^–1 (25°C), whereas aerial gas exchange was less important for CO₂-climination as evident from low gas exchange ratios (0.16 at 15°C, 0.29 at 25°C).Ventilation increases only slightly in response to inspiration of hypercapnic gas mixtures or to hypoxic conditions in water. By contrast, inspiration of hypoxic gas mixtures caused marked increases of ventilation in particular at the higher temperature.Aerial ventilation inChanna is low compared to values for ectothermic pulmonary breathers. However, its ventilatory responses to hypoxia strikingly resemble those of reptiles: The most marked ventilatory response to hypoxia occurs at the higher temperature where the demands for O₂ are greatest.