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A T Burns

Publications and source records attributed to A T Burns.

11 recordsLinked to original sources
PubMed1998

Apoptosis in ischemia/reperfusion injury of human renal allografts.

BACKGROUND: Ischemia/reperfusion injury of human renal allografts has a number of clinically significant consequences. A number of mechanisms of ischemia/ reperfusion injury have been elucidated, and there is evidence that apoptosis may be a contributing factor. METHODS: To examine immediate posttransplant events, fixed tissue sections from paraffin-embedded wedge biopsy specimens taken before and after reperfusion of human renal allografts were stained using terminal deoxytransferase-mediated dUTP nick-end labeling to detect the DNA fragmentation characteristic of apoptosis. Thirty-six pairs of pre- and postreperfusion biopsy specimens were examined, 11 from living-related donor renal transplants and 25 from cadaveric donor transplants. RESULTS: Quantitation of the terminal deoxytransferase-mediated dUTP nick-end labeling signal showed that significantly more apoptosis occurred in postreperfusion compared with prereperfusion biopsy specimens from cadaveric donor transplants, but a similar difference was not observed in living-related donor renal transplants. Furthermore, significantly more apoptosis was observed in postreperfusion biopsy specimens from cadaveric compared with living-related renal transplants. Postreperfusion biopsy specimens from kidneys that were cold preserved longer than 30 hr had a higher mean apoptosis score than those stored for less than 24 hr, but the result was not statistically significant. CONCLUSIONS: Thus, apoptosis occurs predominantly as a result of reperfusion after cold preservation of cadaveric donor renal allografts and provides additional information regarding the extent of ischemia/ reperfusion injury in an organ. The clinical value of this information remains to be determined.

Adolescent↗
PubMed1980

Complicated organization of a single repeated DNA sequence in the chicken genome is revealed by cloning.

The structural organization of a family of repeated DNA sequences in the chicken genome has been determined by hybridization of a cloned repeated DNA sequence to Southern blots of total DNA. The length of the cloned DNA fragment is 3600 nucleotide pairs. This fragment consists principally, if not entirely, of a single repeated DNA sequence occurring only once within the cloned fragment. In the chicken genome, the family of repeated DNA sequences homologous to the cloned sequence has a limited number of alternative forms. Some of the restriction fragments of total DNA to which the cloned sequence hybridizes correspond to those expected from the location of restriction endonuclease cleavage sites within the cloned sequence. There are also a limited number of other genomic restriction fragments, each present in multiple copies, to which the cloned sequence hybridizes but which do not relate in any obvious way to the length of the cloned sequence. These various restriction fragments differ from one another in that they appear to be present in unequal amounts in total DNA, and many of them do not contain the entire cloned sequence. This study provides some new information about the structure of repeated DNA sequences in the chicken genome. The copies of a repeated DNA sequence may differ from one another both by minor variations in nucleotide sequence (divergence) and in more substantial ways as would be expected to arise from processes such as insertion, deletion, and translocation. In addition to this description of a single cloned repeated DNA sequence from the chicken genome, this paper reports the cloning of more than 100 different restriction fragments of chicken DNA, each of which contains one or more repeated DNA sequences.

Animals↗
PubMed1978

Cloning of a double-stranded cDNA that codes for a portion of chicken preproalbumin. A general method for isolating a specific DNA sequence from partially purified mRNA.

A scheme is presented for cloning a double-stranded cDNA molecule that codes for a portion of chicken preproalbumin. This method, which does not require pure mRNA or cDNA, has widespread applicability. Chicken preproalbumin was identified as a Mr = 72,000 polypeptide by immunoprecipitation of proteins synehesized in a wheat germ cell-free translation system from total, guanidine.HCl-extracted, rooster liver RNA. After removal of the bulk of the ribosomal RNA by poly(U)-Sephadex G-10 chromatography, albumin mRNA was enriched approximately 2-fold by centrifugation through low salt, isokinetic sucrose gradients, until it represented about 30% of the mRNA sequences present. Double-stranded cDNA prepared from this mRNA was then inserted into the Pst 1 site of the plasmid PBR322 by the "G-C tailing" technique and the recombinant DNA was used to transform Echerichia coli stran X1776. Transformants containing putative albumin DNA sequences were identified by colony hybridization with a cDNA probe that was highly enriched for albumin cDNA sequences. This probe was isolated by hybridizing the partially purified RNA preparation to its cDNA, under conditions of RNA excess, to a R0t value such that only the most abundant cDNA sequences had hybridized. Unhybridized, less abundant, sequences were destroyed by subsequent S1 nuclease digestion. The identity of clones that hybridized to this abundant class cDNA was established by DNA-mRNA hybrid-arrested cell-free translation. Hybridization of nick-translated, albumin-containing, plasmid DNA to total liver poly(A)+ RNA, that had been separated on methyl mercury agarose gels and transferred to diazobenzyloxymethyl paper, established that avian albumin mRNA has a molecular weight of 850,000. This molecular weight corresponds to approximately 2,600 nucleotides, or 600 nucleotides longer than the size required to code for the preproalbumin polypeptide.

Animals↗
PubMed1978

Primary induction of vitellogenin mRNA in the rooster by 17beta-estradiol.

We have studied the kinetics of vitellogenin mRNA accumulation in rooster liver after a primary injection of 17beta-estradiol. The levels of vitellogenin mRNA have been determined both by hybridization of total cellular RNA to vitellogenin cDNA and by translation of vitellogenin mRNA in a wheat germ cell-free system. The results obtained by both methods of analysis are in good agreement and indicate that vitellogenin mRNA is present in the liver of normal roosters at a level of 0-5 molecules per liver cell and increases in amount during the 3 days following injection of estrogen, reaching a level of almost 6000 molecules per cell at the peak of the response. The level of vitellogenin mRNA declined exponentially during the next 14 days with a half-life of 29 hr, reaching a level of less than 10 molecules per cell at 17 days after injection of the hormone. The levels of vitellogenin mRNA after stimulation with estrogen have been correlated with the in vivo rate of synthesis of the vitellogenin polypeptide. The results indicate that the rate of vitellogenin synthesis is closely correlated with the level of vitellogenin mRNA. On the basis of these findings, we conclude that vitellogenin mRNA does not exist in the liver in an untranslated form after withdrawal from estrogen.

Animals↗
PubMed1977

Kinetics of avian vitellogenin messenger RNA induction. Comparison between primary and secondary response to estrogen.

Following either primary or secondary stimulation of cockerels with 17beta-estradiol, vitellogenin mRNA begins to accumulate in the liver after about 30 min, reaches a maximum in 3 days, and decays thereafter with a half-life of 30 h. During primary induction, accumulation of vitellogenin mRNA begins at a low rate (50 nucleotides/s/nuclear equivalent of DNA) and after 4 h, shifts to a higher rate (340 nucleotides/s/nuclear equivalent of DNA). In contrast, during secondary induction (administration of estrogen several weeks after the primary response has ceased), accumulation of vitellogenin mRNA begins at the rate of 350 nucleotides/s/nuclear equivalent of DNA and subsequently increases by about 40%. These accumulation rates result in a maximal level of vitellogenin mRNA that is approximately 1.5 times higher during secondary stimulation than that found during primary stimulation. This difference is sufficient to explain the anamnestic response to secondary hormonal stimulation that results in higher levels of circulating vitellogenin in the plasma of the rooster.

Animals↗
PubMed1977

In vitro translation of avian vitellogenin messenger RNA.

Administration of 17beta-estradiol to roosters induced the synthesis of vitellogenin in the liver. The mRNA that specifies this protein has been purified from the livers of estrogen-treated roosters and has been shown to have a molecular weight of 2.3 X 10(6) (Deeley, R.G., Gordon, J.I., Burns, A.T.H., Mullinix, K.P., Bina-Stein, M., and Goldberger R.F. (1977) J. Biol. Chem. 252, 8310-8319). In order to rigorously establish the identity of the polypeptide specified by this mRNA, we used a staphylococcal nuclease-treated, mRNA-dependent wheat germ cell-free translation system capable of synthesizing polypeptides as large as vitellogenin (monomer Mr = 240,000). Vitellogenin mRNA directs the in vitro synthesis of a polypeptide with the following features: (a) it co-migrates with authentic vitellogenin in SDS-polyacrylamide gels; (b) it is highly enriched for serine but is not phosphorylated; (c) it is immunoprecipitated by purified, monospecific, anti-vitellogenin antibody; and (d) it has an unusual cyanogen bromide cleavage pattern characteristic of vitellogenin. The most striking characteristic of the cyanogen bromide cleavage products is an extremely large polypeptide (Mr = 90,000) that contains two phosvitins. The kinetics of incorporation of serine and methionine into vitellogenin synthesized in the wheat germ cell-free translation system indicates that the phosvitins are located near the COOH-terminal portion of the molecule.

Animals↗