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Biomedical subjects

N Burton

Publications and source records attributed to N Burton.

8 recordsLinked to original sources
PubMed1991

Evidence for a factor required for transcriptional stimulation by the chimeric acidic activator GAL-VP16 in HeLa cell extracts.

We provide biochemical evidence for the existence of a transcriptional intermediary factor (TIF) in HeLa whole-cell extracts (WCE) that is distinct from the basic transcription factors and that is required for transcriptional stimulation by the chimeric acidic activator GAL-VP16. We have fractionated HeLa WCE by heparin-agarose chromatography. Of transcriptionally active fractions eluting in a step between 0.24 and 0.6 M KCl, the initial fractions are refractory to GAL-VP16 stimulation, whereas subsequent fractions are strongly stimulated by the activator. Aliquots of GAL-VP16-responsive fractions efficiently complement refractory fractions for transcriptional stimulation. Aliquots of responsive fractions are also far more efficient than those of refractory fractions in overcoming transcriptional inhibition that is brought about by high concentrations of GAL-VP16. Experiments performed with heat-treated WCE support the idea that HeLa cells contain a TIF that is essential for GAL-VP16 stimulation, but that is not required for basal transcription. Addition of recombinant yeast or human transcription factor TFIID (rTFIIDY and rTFIIDH, respectively) to a WCE heated at 48 degrees C for 15 min restores basal transcription, but in neither case is the reconstituted system activated by GAL-VP16. However, a 45 degrees C heat-treated WCE reconstituted with either rTFIIDH or rTFIIDY is stimulated by GAL-VP16, suggesting that a HeLa TIF can be selectively inactivated by heating at 48 degrees C, but not at 45 degrees C. Interestingly, a TFIID fraction partially purified from HeLa cell extracts, but not rTFIIDH, efficiently relieves transcriptional inhibition by GAL-VP16, suggesting that there may be an association between TIF(s) and TFIID and, moreover, that TIF(s) may be the direct target of the acidic domain of GAL-VP16. In summary, our results support the existence of a TIF that is not essential for basal transcription but that is required to mediate the stimulatory activity of the acidic activator GAL-VP16.

Biological Factors↗
PubMed1990

New developments in affinity chromatography.

The design, synthesis and chromatographic operation of a new range of stable and selective immobilized dye affinity adsorbents for potential application in the purification of pharmaceutical proteins is described. Computer aided molecular design has been exploited to design novel dye ligands which show a predictable selectivity for the target protein and which, when coupled to stable perfluoropolymer supports, yield high capacity, low leakage adsorbents for affinity chromatography. It is anticipated that these new materials will withstand the rigorous conditions required for sanitization and cleaning in situ of industrial scale processes.

Biotechnology↗
PubMed1979

Cardiac allograft survival in rhesus primates treated with combined total lymphoid irradiation and rabbit antithymocyte globulin.

Eighteen abdominal heterotopic cardiac allografts were performed in outbred rhesus primates. For immunosuppression seven animals received six 100-rad/day total lymphoid irradiation (TLI) doses the week preceding transplant and three 3-mg/kg i.m. rabbit antithymocyte globulin (RATG) doses on postoperative days -1, 0, and +1; five animals were given this RATG dose but no irradiation; three were given TLI alone; and three were given no immunosuppressive therapy. Circulating T lymphocyte counts were monitored in all animals (rosettes). Graft survival in the combined TLI-RATG therapy group (169 +/- 15 days) was significantly greater than in untreated (11 +/- 1 days), RATG alone (22 +/- 12 days), or TLI alone (38 +/- 6 days) treated animals (P less than 0.001, 0.0001, and 0.001, respectively). The animals receiving combined TLI-RATG therapy also achieved significantly greater and more prolonged T lymphopenia than that obtained in the other three groups. Six of seven cardiac allografts placed in animals receiving TLI-RATG therapy were removed electively before cessation of electrical activity; however, in four of these rejection pathology was noted. Thus, it seems that combined TLI-RATG therapy may be of benefit in the management of transplant recipients, but its use will probably not abolish these patients' requirements for immunosuppressive maintenance measures.

Animals↗
PubMed1975

Prostaglandin F2alpha (PGF2alpha) and prolactin secretion in rats.

Plasma prolactin and F-prostaglandins (PGF) were measured anesthetized male Sprague-Dawley rats before and at 15, 30, 45 and 60 minutes following i.v. injection of either PGF2alpha (4 mg/kg), chlorpromazine, 1 mg/kg or chlorpormazine (1 mg/kg) after pretreatment with i.p. indomethacin (2 mg/kg). Following PGF2alpha administration, plasma prolactin levels increased significantly only at 15 and 30 minutes in spite of extremely high PGF levels throughout 60 minutes. Besides the expected rise in plasma prolactin, chlorpromazine caused a transient but statistically significant increase in PGF. Indomethacin blocked the chlorpormazine-induced PGF rise but not prolactin increase. Animals stressed with ether anesthesia showed elevation of plasma prolactin, which was not blocked by indomethacin although PGF concentration fell. Theese results indicate that PGF2alpha can stimulate prolactin release. This effect does not appear to be physiologic since very high PGF levels are required. Furthermore, blockade of prostaglandin synthesis by indomethacin does not prevent the release of prolactin in response to chlorpormazine or stress. Our findings do not support a possible role of PGFs as intermediaries in prolactin release. However, it is possible that PGFs may work through other mechanisms not investigated in our study.

Animals↗
PubMedDate not supplied

Expression in Escherichia coli: purification and properties of the yeast general transcription factor TFIID.

A T7 RNA polymerase expression system has been used for the efficient expression of the yeast RNA polymerase general transcription factor TFIID (TFIIDY), the TATA-box factor (previously called BTF1) in Escherichia coli. Expression of the gene was performed at 25 degrees C instead of 37 degrees C to increase the total amount of soluble TFIIDY. Soluble TFIIDY was purified in three chromatographic steps and was eluted from the final column, a heparin-5PW HPLC column, in two peaks at 0.38 M (peak I) and 0.42 M (peak II) KCl in which this protein was 52% and greater than 95% pure, respectively. The protein in both peaks was active in an in vitro transcription assay. However, while TFIIDY from peak II was essentially indistinguishable from the material isolated from yeast, the protein of peak I differed in a number of biochemical characteristics, having a lower specific activity in an in vitro transcription assay and displaying an altered pattern of bands in a DNA band shift assay. Despite these differences, the proteins in both peaks have identical molecular weights on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, have indistinguishable N-terminal amino acid sequences, and apparently exist as monomers under the conditions used for the heparin-5PW chromatography.

Amino Acid Sequence↗
PubMedDate not supplied

Vanguard family planning acceptors in Senegal.

This study examines contraceptive use among clients at the three clinics providing family planning services in Dakar, Senegal in early 1983. Most clients first became interested in family planning following the birth of a child, and most are interested in spacing future pregnancies, although one-third state that they want no more children. The clinic itself was found to be an important determinant of the type of contraceptive used, with only the government-operated clinic providing a balance between IUDs, oral contraceptives, and barrier methods. Nearly half of the clients interviewed said that a lack of knowledge about contraception is the reason for the low contraceptive prevalence rates among Senegalese women; another frequently cited reason was the opposition of the husband. Most clients reported the broadcast media to be the best means of providing family planning information to potential acceptors.

Contraceptive Devices, Male↗