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Biomedical subjects

T A Peterson

Publications and source records attributed to T A Peterson.

At least 19 recordsLinked to original sources
PubMed2001

Quantitative assessment of myocardial perfusion during graded coronary artery stenoses by intravenous myocardial contrast echocardiography.

OBJECTIVES: The purpose of this study was to examine whether coronary stenoses of variable severity could be quantitatively assessed by analysis of myocardial perfusion as determined by intravenous (IV) myocardial contrast echocardiography. BACKGROUND: Recently, new contrast agents and imaging technology have been developed that may enable improved assessment of myocardial perfusion by IV contrast injection. METHODS: Variable obstruction of the left anterior descending (LAD) coronary artery in dogs was produced by a screw occluder. Coronary artery flow was measured with a transit time flowmeter during baseline, pharmacological vasodilation, a non-flow-limiting stenosis at rest in conjunction with vasodilation, a flow-limiting stenosis, and total occlusion. Myocardial contrast echocardiography was performed after IV injection of the contrast agent NC 100100. Time-intensity curves were obtained off-line for the LAD risk area and the adjacent left circumflex (LCx) territory, and peak background-subtracted video intensity was determined. Fluorescent microspheres were injected at each intervention for determination of regional myocardial blood flow. RESULTS: During non-flow-limiting stenosis, flow limiting stenosis and total occlusion, LAD/LCx ratios of peak myocardial videointensity and blood flow decreased proportionately. Both LAD/LCx ratios of video intensity and blood flow identified the non-flow-limiting and the flow-limiting stenoses as well as total occlusion of the LAD artery. A significant correlation between LAD/LCx video intensity and blood flow ratios was observed (r = 0.83, p < 0.0001). CONCLUSIONS: The degree of blood flow mismatch between ischemic and normal myocardial regions during graded coronary stenoses can be estimated in the dog by quantitative assessment of myocardial perfusion produced by IV myocardial contrast echocardiography.

Animals↗
PubMed1987

Nucleotide Metabolism in Salt-Stressed Zea mays L. Root Tips: I. Adenine and Uridine Nucleotides.

Corn plants (Zea mays L. cv Pioneer 3906) were grown in a glass house on control and saline nutrient solutions, in winter and summer. There were two saline treatments, both with osmotic potential = -0.4 megapascal but with different Ca(2+)/Na(+) ratios: 0.03 and 0.73. Root tips and shoot meristems (culm tissue) of 26 day-old plants were analyzed for nucleotides to ascertain if there were correlations between nucleotide pool size and the reduced growth on saline cultures. Several other cell components also were determined. Plants grown in winter were only half as large as those grown in summer mainly because of the lower light intensity and lower temperature. But the relative yield reduction on salt treatment compared to the control was similar in winter and summer. The two different salt treatments caused similar yield reductions. Neither salt treatment affected nucleotide pools in culm tissue, with the possible exception of UDPG in winter. In the case of root tips, salt treatment had little or no effect on nucleotide pool sizes in winter when many already seemed near a critical minimum, but in summer it reduced several pools including ATP, total adenine nucleotide, UTP, total uridine nucleotide, and UDP-glucose. The reductions were greatest on the salt treatment with low Ca(2+)/Na(+). There was no simple correlation between the effects of salt stress on growth and on nucleotide pool size. The nucleotide pools of culm tissue indicated that in some respects this tissue was effectively insulated from the salt stress. Roots that were in direct contact with the saline solution indicated significant reductions in nucleotide pools only in the summer whereas growth was reduced both summer and winter. It is possible that the nucleotide concentrations of root cells in winter were already near a critical minimum so that nucleotide synthesis and growth were tightly linked. Significant reductions in nucleotide pools that would be expected to affect growth were more evident in summer when pools were larger and growth was more rapid. But even where ATP and total adenine nucleotides were reduced, the ratio of ATP:ADP and the adenylate energy charge remained unchanged indicating an active adenylate kinase that had access to most of the adenine nucleotide pools, and possible catabolism of excess AMP.

Journal Article↗
PubMed1986

Nucleotide sequence of the yeast cell division cycle start genes CDC28, CDC36, CDC37, and CDC39, and a structural analysis of the predicted products.

The nucleotide sequences of the yeast cell division cycle start genes CDC36, CDC37, and CDC39 are presented. An open reading frame corresponding in size and mapped position to the mRNA for each gene was revealed. These sequences, as well as that of the CDC28 gene, were analyzed for the presence of consensus sequences postulated to be transcriptional or translational signals, or to be involved in mRNA processing. In addition, the predicted protein products of the four genes were subjected to a number of structural and statistical analyses including codon usage bias analysis, secondary structure analysis and hydropathicity analysis.

Amino Acid Sequence↗
PubMed1986

Cold potassium cardioplegia versus topical hypothermia and intermittent aortic occlusion for myocardial protection during coronary artery surgery: a randomized clinical study.

The effect of two different myocardial preservation techniques on perioperative myocardial necrosis during coronary artery bypass surgery was assessed by serial myocardial creatine kinase determinations in 100 consecutive patients operated on by the same surgeon. Topical hypothermia with cold potassium cardioplegia was used randomly in 50 patients (group 1), and topical hypothermia with local interruption of the coronary circulation was used in the other 50 patients (group 2). Myocardial creatine kinase was measured by column chromatography every 6 hours for 36 hours after surgery. There was no significant difference between the two groups in terms of age, sex, functional class, extent of coronary artery disease, number of bypassed arteries, ejection fraction, or cardiopulmonary bypass time. Myocardial creatine kinase release (mean +/- standard error of the mean) was 193 +/- 33 IU/L X hours in group 1 patients operated on with cardioplegia and 210 +/- 31 IU/L X hours in group 2 patients operated on with topical hypothermia (p greater than 0.5). Myocardial creatine kinase peaks were 9.2 +/- 1.9 IU/L and 10.0 +/- 1.6 IU/L, respectively (p greater than 0.5). Perioperative myocardial infarction, as defined by serum enzyme activity and electrocardiographic criteria, occurred in 4 patients in group 1 and 3 patients in group 2. Thus, the addition of cardioplegia to topical hypothermia, although perhaps offering technical advantages, does not appear to improve myocardial protection over topical hypothermia with local interruption of the coronary circulation during coronary artery bypass surgery.

Aorta, Thoracic↗
PubMed1986

Interactive roles of progesterone, prostaglandins, and collagenase in the ovulatory mechanism of the ewe.

Interrelationships between production of progesterone (P4), prostaglandin (PG) E2 and PGF2 alpha, and collagenase by periovulatory ovine follicles and their possible involvements in the ovulatory process were investigated. Follicles were isolated from ovaries at intervals (0 to 24 h) after the initiation of the preovulatory surge of luteinizing hormone (LH). Progesterone and PGs within follicles were determined by radioimmunoassay. Digestion of radioactive collagen during coincubation with tissue homogenates was used to assess the production of a bioactive follicular collagenase(s). Follicular accumulation of PGs and P4 increased at 12 and 16 h, respectively, after the onset of the surge of LH; PGE2 then decreased at 20 h. Collagenolytic activity of follicular tissue increased at 20 h and was maximal at 24 h (during the time of follicular rupture). An inhibitor of synthesis of P4 (isoxazol) or PGs (indomethacin) was injected into the follicular antrum at 8 h. Isoxazol did not prevent the initial rise in PGs, but inhibited synthesis of PGF2 alpha at 16 h and therafter. Isoxazol negated the decline in PGE2 and increase in collagenolysis. Indomethacin did not influence synthesis of P4; however, it suppressed collagenolytic activity of follicular tissue. Ovaries with treated follicles were left in situ and observed for an ovulation point at 30 h. Isoxazol or indomethacin was a potent inhibitor of ovulation. The blockade of ovulation by isoxazol was reversed by systemic administration of P4 or PGF2 alpha, but not by PGE2. Reversal of the blockade by indomethacin was accomplished with PGE2 or PGF2 alpha. Collagenolytic activity of follicular tissue was likewise restored by such treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstenols↗
PubMed1985

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

We have cloned CDC9, the structural gene for Saccharomyces cerevisiae DNA ligase, and investigated its transcriptional regulation both as a function of cell cycle stage and after UV irradiation. The steady-state level of DNA ligase mRNA increases at least fourfold in late G1, after the completion of start but before S phase. This high level of CDC9 mRNA then decays with an apparent half-life of ca. 20 min and remains at a low basal level throughout the rest of the cell cycle. The accumulation of CDC9 mRNA in late G1 is dependent upon the completion of start but not the CDC7 and CDC8 functions. Exposure of cells to UV light elicits an eightfold increase in DNA ligase mRNA levels.

Cell Cycle↗
PubMed1983

Isolation and transcriptional characterization of three genes which function at start, the controlling event of the Saccharomyces cerevisiae cell division cycle: CDC36, CDC37, and CDC39.

The genes CDC36, CDC37, and CDC39, thought to function in the cell division control process in Saccharomyces cerevisiae, were isolated from a recombinant plasmid library prepared by partial digestion of S. cerevisiae genomic DNA with Sau3A and insertion into the S. cerevisiae-Escherichia coli shuttle vector YRp7. In each case, S. cerevisiae DNA sequences were identified which could complement mutant alleles of the gene in question and which could direct integration of a plasmid at the chromosomal location known to correspond to that gene. Complementing DNA segments were subcloned to remove extraneous coding regions. The coding regions corresponding to CDC36, CDC37, and CDC39 were then identified and localized by R-loop analysis. The estimated sizes of the three coding regions were 615, 1,400, and 2,700 base pairs, respectively. Transcriptional orientation of the coding regions was established by using M13 vectors to prepare strand-specific probes followed by hybridization to blots of electrophoresed S. cerevisiae mRNA. The intracellular steady-state abundance of the mRNA species corresponding to the genes was estimated by comparing hybridization signals on RNA blots to that of a previously determined standard, the cell cycle start gene CDC28. The quantities calculated for the three mRNA species were low, ranging from 1.5 +/- 1 copies per haploid cell for the CDC36 mRNA to 3.1 +/- 1.5 and 4.6 +/- 2 copies per haploid cell for the CDC37 and CDC39 mRNAs, respectively. The CDC28 mRNA had been previously estimated at 7.0 +/- 2 copies per cell.

Cell Cycle↗
PubMed1981

Predictors of perioperative myocardial infarction in coronary artery operation.

Postoperative graft patency and thirteen perioperative variables were evaluated as potential risk factors for perioperative myocardial infarction (MI) in 102 consecutive patients undergoing coronary artery bypass grafting. Also, the incidence of perioperative MI and the amount of CK-MB released in the postoperative period were compared in three groups of patients selected according to the myocardial preservation technique employed: (1) topical hypothermia with and (2) without aortic cross-clamping and (3) cardioplegia. A perioperative MI as detected by electrocardiogram, enzymes, and myocardial scintigraphy with technetium 99 developed in 15 patients. Most important predictors of perioperative MI were found to be (1) left main and triple-vessel coronary artery disease, (2) a left ventricular end-diastolic pressure greater than or equal to 15 mm Hg, (3) a decreased ejection fraction (p < 0.05), and (4) cardiopulmonary bypass time > 120 minutes (p < 0.01). The incidence of perioperative MI was 50% in patients with three or more risk factors and 7% in those with less than three risk factors (p < 0.001). Graft patency was similar in patients with or without perioperative MI. Differing myocardial preservation techniques did not influence CK-MB release or the incidence of perioperative MI. Thus, the severity of ischemic heart disease and the length of the cardiopulmonary bypass time were important predictors of perioperative MI while graft patency and myocardial preservation technique did not appear to be related to its incidence in this study.

Aged↗