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G Sato

Publications and source records attributed to G Sato.

At least 109 records · Page 6Linked to original sources
PubMed1980

Serum suppresses the expression of hormonally induced functions in cultured granulosa cells.

Growth and function of primary cultures of granulosa cells obtained from immature, hypophysectomized, estrogen-treated rats were compared in serum-containing and serum-free media. In serum-free medium (1:1 mixture of DMEM:F-12) supplemented with insulin, hydrocortisone, transferrin and fibronectin (4F medium), the cells remained healthy and steroidogenically responsive for at least 60 days in culture. The growth profile of the granulosa cells in 4F medium was similar to that obtained in serum-containing medium. In both media cell proliferation did not exceed more than one cell doubling. DMEM:F-12 alone did not support the cell viability. Upon FSH stimulation, the cells produced 25 fold more progestin and estrogen per cell in 4F medium than in medium supplemented with 5% serum. This effect was not directly related to serum proteins which mediate cell adhesion since cells cultured in dishes precoated with serum remained steroidogenically responsive to FSH. Cholera toxin and Bt2-cAMP readily stimulated progestin production in the presence of serum. The inhibitory effect of serum was not reversed by adding the four factors to serum-containing medium. The factors were essential for the FSH-induced steroidogenesis in serum-free medium. After four days of incubation in 4F medium, the cells showed a transient loss of their ability to produce progestin in response to FSH. In both 4F medium as well as in serum-containing medium, the cells regained their hormonal responsiveness after 35 days in culture. Since the loss of hormonal responsiveness occurred at the same time as growth was initiated in the cultures, it is suggested that the FSH-induced steroidogenesis is negatively controlled by growth-related processes.

Animals↗
PubMed1980

Genetical relationship between R plasmids derived from Salmonella and Escherichia coli obtained from a pig farm, and its epidemiological significance.

A total of 475 Salmonella strains belonging to 5 serovars, isolated from a pig farm which had been heavily contaminated with Salmonella for the past 2 years were tested for antibiotic susceptibility and detection of R plasmids. Thirty-three Escherichia coli isolates from the same farm were also examined in a similar way. Out of 475 strains 348 (73.2%) were resistant to one or more antibiotics such as tetracycline (Tc), streptomycin (Sm), sulfadimethoxine (Su), chloramphenicol (Cm) and kanamycin (Km), and 247 (85.2%) out of 290 strains belonging to 3 serovars examined harboured conjugative R plasmids. There was no change in the pattern of drug resistance during this survey nor any variation in the pattern of resistance of R plasmids, whatever the serovar. The antibiogram pattern Tc Sm Su, mainly S. typhimurium, was common among Salmonella strains. Among the transferred resistance patterns, the thermosensitive R plasmids conferring the Tc marker detected in this study were Fi-, and belonged to incompatibility group H1, whereas the R plasmids conferring Sm Su resistances which coexisted in the same host were Fi+, and compatible with the reference R plasmids tested. The I alpha plasmid conferring Cm resistance alone was isolated from S. anatum and the FII plasmid conferring Sm Km resistances was also isolated from S. typhimurium. In contrast, the 33 E. coli strains examined were resistant to three or five antibiotics and most of the resistance markers were located on conjugative R plasmids. I alpha plasmids conferring Cm resistance alone or FII plasmids conferring Cm or Km markers were common in the E. coli strains. H1 and H2 plasmids conferring multiple resistance markers were also found in them. The genetic properties of R plasmids derived from Salmonella or E. coli strains are compared, and the potential spread of R plasmids between strains of Salmonella and E. coli is discussed.

Animals↗
PubMed1980

Distribution of citrate utilization plasmids in Salmonella strains of bovine origin in Japan.

Attempts to detect transferable citrate-utilizing (Cit) ability in enterobacterial strains were carried out by conjugation experiments. Of 318 strains of Salmonella typhimurium and 1 strain of Salmonella bredeney isolated from cattle in Japan from 1970 to 1979, 107 (33.5%) strains contained transferable Cit characters. Most of the strains transferred the Cit characters to recipient Escherichia coli more efficiently at 28 degrees C than at 37 degrees C, indicating that their transfer of the Cit character is thermosensitive. Transferred Cit characters were found in association with drug resistance markers such as ampicillin, chloramphenicol, kanamycin, streptomycin, sulfonamides, and tetracycline or with mercury resistance, but Cit plasmids conferring Cit ability alone were also obtained. Of 221 conjugative Cit plasmids tested for fertility inhibition (Fi), all but 2 were Fi- and exhibited thermosensitive transfer; 2 Cit plasmids showing the Fi+ character were also isolated from 2 S. typhimurium strains. No transferable Cit character was detected from strains of Proteus, Serratia, Klebsiella, Enterobacter, and Citrobacter spp. isolated from humans or cows in the present study. The utilization of tricarboxylic acids by strains with plasmid-borne Cit ability was examined, and two different patterns of utilization were found in the Cit+ E. coli transconjugants.

Animals↗
PubMed1980

Spontaneous emergence of an Hfr strain with a cit plasmid from natural isolates of citrate-positive Escherichia coli bovine origin.

From citrate-utilizing (Cit+) Escherichia coli strain C53 of bovine origin, strains C53A and C53B were obtained. Upon mating with recA+ but not with recA mutant recipients of K-12, C53A produced chromosomal recombinants at quite high frequencies, leading to the following conclusions: (i) C53A is an Hfr strain; (ii) the site of integration of the Cit plasmid (IncH1) is between metA (89 min) and ara (1 min); (iii) the direction of chromosome transfer is clockwise; and (iv) the plasmid-associated determinants are transferred as the terminal markers. A transductant of a dnaA(Ts) strain, CRT46, which acquired Cit determinants from a recombinant, SG13, was also an Hfr strain similar to SG13, and thermoresistant due to suppressive integration. On the other hand, unstable C53B did not produce recombinants, but the frequency of RecA-independent transfer of the Cit plasmid was high, indicating that the Cit plasmid (IncH1) exists autonomously in C53B. Attempts to isolate an Hfr strain from C53B failed.

Animals↗
PubMed1980

Antibiotic resistance and genetic properties of R plasmids in Salmonella isolates of swine origin in Japan.

A total of 84 Salmonella isolates of ten serovars from swine in Japan were tested for antibiotic susceptibility and detection of R plasmids. Of these, 58 (69.0%) were resistant to one or more antibiotic(s) such as tetracycline, streptomycin, sulfadimethoxine, and chloramphenicol; and 38 (65.5%) of the 58 resistance isolates (mainly Salmonella typhimurium isolates) had conjugative R plasmids. Among the 38 conjugative R plasmids, 36 thermosensitive R plasmids carrying tetracycline resistance were Fi- (no fertility inhibition) and belonged to incompatibility group Hl, whereas the R plasmids carrying streptomycin and sulfadimethoxine resistances coexisted in the same host, were Fi+, and were also compatible with the reference R plasmids tested. The epidemiologic significance of R plasmids derived from Salmonella isolates from swine is discussed.

Animals↗
PubMed1980

Incompatibility of R plasmids derived from Salmonella and Escherichia coli strains isolated simultaneously from a bovine fecal sample.

Seven strains of Salmonella typhimurium were isolated from 2 fecal samples of calves, and the strains were resistant to ampicillin, chloramphenicol, kanamycin, nalidixic acid, streptomycin, sulfadimethoxine, and tetracycline. Also, 11 Escherichia coli strains were obtained from 1 of the 2 samples, and these strains possessed the identical drug resistance patterns as did the salmonellae. The thermosensitive R plasmids conferring sextuple drug resistance and mercury resistance from Salmonella strains were Fi- (no fertility inhibition) and belonged to incompatibility group H1, whereas conjugative 6 R plasmids isolated from 11 E coli strains were Fi+ (fertility inhibition) and belonged to incompatibility group FII. Thermosensitive R plasmids conferring sextuple drug (ampicillin, chloramphenicol, kanamycin, streptomycin, sulfadimethoxine, and tetracycline) have not been reported in Japan. Genetic relationship of R plasmids derived from the multiresistant strains of Salmonella and E coli was discussed on the basis of incompatibility properties of R plasmids.

Animals↗
PubMed1979

Fibronectin mediates cytokinesis and growth of rat follicular cells in serum-free medium.

In this study, the growth of rat follicular (RF-1) cells was severely depressed when the cells were subcultured by trypsinization directly into serum-free medium supplemented with insulin, transferrin and hydrocortisone, which are required for growth of these cells in vitro. Within 24 hr after plating, 50-65% of the cells became binucleated, indicating lack of cytokinesis. However, the addition of human plasma fibronectin (8 microgram/ml) to the serum-free medium eliminated cell binucleation and enhanced cell growth considerably. Fibronectin had the same effect when RF-1 cells were plated into tissue culture dishes on which fibronectin had been absorbed, and cells were inoculated into fibronectin-free medium. Cell binucleation and poor growth in serum-free medium occurred when the cells were subcultured by trypsinization, EGTA treatment or detachment of mitotic cells. Under some conditions, cells could be "rescued" if fibronectin was added soon after inoculation, indicating that fibronectin was needed mainly during a limited time when the subcultured cells were attaching to the tissue culture substratum. Our findings describe an adhesive activity for fibronectin which circumvents the serum preincubation usually needed after RF-1 cells are subcultured for growth in serum-free medium. They also indicate the importance of fibronectin-mediated adhesion for cytokinesis processes of these cells.

Animals↗
PubMed1979

The distribution of plasmids determining citrate utilization in citrate-positive variants of Escherichia coli from humans, domestic animals, feral birds and environments.

Sixty-seven isolates of citrate-positive variants of Escherichia coli were isolated from human, domestic animal, feral bird and environmental sources. With the exception of citrate utilization, all isolates were identified as typical E. coli by their biochemical reactions. The transmission of the ability to utilize citrate on Simmons' citrate agar was demonstrated in 53 (79.1%) out of the 67 citrate-positive E. coli variants obtained from various sources. Drug resistance determinants and citrate utilizing character were co-transmitted into E. coli K-12 by conjugation among citrate-positive E. coli isolates carrying R plasmids except for that isolated from horses. The other characters (haemolysin or colicin production, raffinose or sucrose fermentation) were not transmitted together with the citrate utilizing character. These facts suggested that the structural gene responsible for citrate utilizing ability in citrate-positive variants of E. coli was located on a conjugative plasmid.

Animals↗
PubMed1979

Growth of Madin-Darby canine kidney epithelial cell (MDCK) line in hormone-supplemented, serum-free medium.

Madin-Darby canine kidney (MDCK) cells can grow in synthetic medium supplemented with five factors--insulin, transferrin, prostaglandin E1, hydrocortisone, and triiodothyronine--as a serum substitute. These five factors permit growth for 1 month in the absence of serum and a growth rate equivalent to that observed in serum-supplemented medium. Dibutyryl adenosine 3',5'-cyclic monophosphate substitutes for prostaglandin E1 in the medium. Potential applications of the serum-free medium are discussed. The medium permits a defined analysis of the mechanisms regulating hemicyst formation by hormones and permits the growth of primary kidney epithelial cell cultures in the absence of fibroblast overgrowth.

Animals↗
PubMed1979

Plasmids in Escherichia coli controlling citrate-utilizing ability.

The citrate-utilizing ability of 19 out of 22 citrate-positive Escherichia coli strains isolated from pig sewage was transferred via conjugation to E. coli K-12. The conjugal transfer of citrate-utilizing (Cit) abilities was thermosensitive and concurrent with transfer of drug resistance. Weakly citrate-positive colonies were readily obtained in conjugation experiments. Their Cit characters could be transmitted to the other E. coli strains at a similar frequency in the retransfer experiments, and the transconjugants obtained still showed same characteristic growth on Simmons citrate agar plates. The 19 thermosensitive plasmids conferring citrate utilization and drug resistance were Fi-, and 16 of these plasmids belonged to incompatibility group H1. However, occasionally two conjugative plasmids (pOH3122-1 and pOH3124-1) carrying only the citrate utilization were also obtained in the conjugation experiments, and they were Fi+ and compatible with 19 reference R plasmids. In the two citrate-positive E. coli strains, it was suggested that the conjugative Cit plasmid showing Fi+ character and the more thermosensitive H1 plasmid conferring both the Cit character and drug resistance coexisted in the strain. The characterization of citrate utilization plasmids derived from pig farm sewage is discussed.

Animals↗