Effect of colchicine and vincristine on DNA synthesis in regenerating rat liver

The increases in the activities of hepatic thymidylate synthetase and thymidine kinase were significantly suppressed at 24 h after 70% partial hepatectomy in rats which had been administered a microtubule disrupter, colchicine or vincristine. The decrease of these enzymic activities was accompanied by a reduction of DNA content in 24 h regenerating liver. The immunoblotting assay showed that the depression of the thymidylate synthetase activity by the injection of colchicine or vincristine was due to the decrease of the enzyme protein. These results indicate that colchicine and vincristine inhibit the DNA synthesis during liver regeneration by inhibiting the induction of the key enzyme in DNA synthesis.     

Isolation and identification of prostaglandin I 2 stimulating factor from human plasma

To isolate and identify the plasma factor which stimulates prostaglandin I 2 production by rat aortic ring, a human plasma fraction which showed a major stimulating activity on prostaglandin I 2 production was purified by ultrafiltrate, Sephadex G-10 gel filtration and QAE-Sephadex column chromatography. The purified plasma factor was identified as acid by its ultraviolet and infrared absorption spectroscopy, and ¹H nmr and ¹³C nmr spectroscopy. The stimulating activity of the purified plasma factor and that of authentic uric acid coincided with each other. The stimulating potency of uric acid at its physiological concentration in human plasma (about 50 μg/ml) was half of the deproteinized human plasma, and was about 30 fold stronger than that of L-tryptophan, a cofactor of prostaglandin hyperoxidase.     

An immunodominant domain in adenovirus type 2 early region 1A proteins.

Six independent rat hybridoma cell lines producing monoclonal antibodies to human subgroup C adenovirus early region 1A (E1A) proteins were isolated. Competition binding experiments revealed that each of the monoclonal antibodies was directed against the same epitope or overlapping cluster of epitopes on the E1A proteins. Viral E1A deletion mutants and deleted forms of E1A proteins expressed in Escherichia coli were used to localize the antibody recognition sites to sequences between amino acids 23 and 120, encoded within the first exon of the E1A gene. Similarly, polyclonal antisera raised against the trpE-E1A fusion protein, as well as against the native, biologically active E1A protein, were also directed primarily against this immunodominant region.     

Inhibin activity and secretion of gonadotropin during the period of follicular maturation

To evaluate the relative contributions of the ovarian inhibin and estradiol-17 beta (E) on the regulation of FSH secretion, inhibin and E in ovarian venous plasma (OVP) and FSH and LH in peripheral plasma were simultaneously measured using superovulating rats with special reference to follicular maturation. By the transplantation of a pituitary gland from adult male rats under the kidney capsule between 1100 and 1200 hr on diestrus-1 in cyclic rats, superovulation was successfully induced on the morning of the next estrus without any additional treatment with human chorionic gonadotropin (hCG). The number of maturing follicles capable of ovulating in response to hCG significantly increased at 12 hours after the grafting as compared with sham-operated controls and further increases occurred until the afternoon of proestrus. In the superovulating rat, first and second surges of FSH were completely blocked and an LH surge was also partially suppressed during the periovulatory period when surges of FSH and LH were normally observed in controls. Contents of FSH as well as LH in the animal's own pituitary gland were suppressed significantly after the grafting as compared with controls. A marked increase in inhibin activity in OVP of rats with a pituitary transplant occurred concomitantly with an increase in the number of follicles capable of ovulating whereas E levels in OVP did not so. Inhibin activity in OVP at each point was much higher in the pituitary grafted rats than in controls but this was not true for E levels. These results suggest that ovarian inhibin derived from the maturing follicles rather than E may be a primary factor for regulation of FSH secretion, and high levels of endogenous inhibin can suppress synthesis of LH as well as FSH in the pituitary gland of the female rat.     

Typing of Verotoxins by DNA Colony Hybridization with Poly- and Oligonucleotide Probes,a Bead-Enzyme-Linked Immunosorbent Assay,and Polymerase Chain Reaction

To identify the type of Verotoxins (VT) produced by Verocytotoxin-producing Escherichia coli (VTEC), a sensitive bead-enzyme-linked immunosorbent assay and polymerase chain reaction with common and specific primers to various VTs (VT1, VT2, VT2vha, VT2vhb, and VT2vp1) were developed. Together with colony hybridization tests with oligo- and polynucleotide probes, these methods were applied to VTEC isolates to type the VT produced. The toxin types of 26 of 37 strains were identified, but the reaction profiles in assays of the remaining 11 strains suggested the existence of new VT2 variants. The application of these identification procedures may be useful as a tool for clinical and epidemiological studies of VTEC infection.