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T Peterson

Publications and source records attributed to T Peterson.

At least 73 records · Page 4Linked to original sources
PubMed1992

Insertional mutagenesis of the maize P gene by intragenic transposition of Ac.

The P-rr allele of the maize P gene regulates the synthesis of pigments derived from flavan-4-ol in the pericarp, cob glumes and other floral organs. We characterized 21 P alleles derived by intragenic transposition of Ac from three known positions. Ac transpositions can occur in either direction in the P gene, and with no apparent minimum distance: in one case Ac transposed just 6 bp from its original insertion site. However, the distribution of transposed Ac elements was markedly nonrandom: of 19 transposed Ac elements derived from a single Ac donor, 15 were inserted in a 1.1-kb region at the 5' end of P, while none had inserted in an adjacent 3.2-kb intronic region. All of the Ac insertions affect both pericarp and cob glume pigmentation, providing further evidence that the P-rr allele contains a single gene required for both pericarp and cob glume pigmentation. The distribution of the inserted Ac elements and the phenotype conditioned by each allele suggests a structure of P-rr which is similar to that previously determined molecularly. Possible explanations for the nonrandom distribution of transposed Ac elements are discussed.

Base Sequence↗
PubMed1992

[Traumatic aneurysm of the hand--a rare complication of a stab injury].

This is a case report of a 22-year-old male who suffered a stab injury to his right hand. Sixteen days after primary wound closure, he complained of pain from a pulsating mass in his right palm, with numbness along the ulnar side of the middle finger. At operation, a false aneurysm was found and resected, after ligation of the common digital artery proximal and distal to the aneurysm.

Adult↗
PubMed1991

Alternatively spliced products of the maize P gene encode proteins with homology to the DNA-binding domain of myb-like transcription factors.

The Zea mays P gene has been postulated to regulate the biosynthetic pathway of a flavonoid-derived pigment in certain floral tissues [Styles, E. D. & Ceska, O. (1977) Can. J. Genet. Cytol. 19, 289-302]. We have characterized two P transcripts that are alternatively spliced at their 3' ends. One message of 1802 nucleotides encodes a 43.7-kDa protein with an N-terminal region showing approximately 40% homology to the DNA-binding domain of several members of the myb family of protooncogene proteins. A second message of 945 nucleotides encodes a 17.3-kDa protein that contains most of the myb-homologous domain but differs from the first protein at the C terminus. The deduced P-encoded proteins show an even higher homology (70%) in the myb-homologous domain to the maize regulatory gene C1. Additionally, the P and C1 genes are structurally similar in the sizes and positions of the first and second exons and first intron. We show that P is required for accumulation in the pericarp of transcripts of two genes (A1 and C2) encoding enzymes for flavonoid biosynthesis--genes also regulated by C1 in the aleurone.

Amino Acid Sequence↗
PubMed1991

A possible hot spot for Ac insertion in the maize P gene.

We have analyzed the footprints left by a single Ac transposable element during its intragenic transposition to different positions in the maize P gene. One site appears to have been visited twice by transposons, indicating that it may be an insertion hot spot. Implications of this finding for the origin of the P-vv allele are discussed. Analysis of transposon footprints may prove generally useful for establishing pedigree relationships among gene alleles.

Alleles↗
PubMed1991

Potential role of PFOB enhanced sonography of the kidney. I. Detection of renal function and acute tubular necrosis.

Perfluorooctylbromide (PFOB) enhances the echogenicity of perfused tissues on sonography. Since PFOB is not filtered and is limited to the intravascular space, the particles are concentrated in the vasa rectae as they travel across the osmotic gradient. Because sonography has been unable to detect renal function, we aimed to determine whether sonography when aided by PFOB could detect and distinguish the normal from the abnormal osmotic gradient. The sonographer, unaware of rabbit assignment, imaged both kidneys in 17 rabbits before and 24 hours after the temporary occlusion of one of the renal arteries and then again after the infusion of up to 5 ml/kg of PFOB (N = 10) or saline (N = 7). Two normal rabbits were imaged before and after PFOB infusion and then again after i.v. furosemide. Without PFOB, the normal and impaired kidneys were indistinguishable. The echogenicity of the medulla which was darker than cortex in normal kidneys became brighter than cortex after PFOB (increased by 117% +/- 10%; P less than 0.01). PFOB, which was visible in the renal medulla on real-time sonography, produced an echogenic gradient that increased in brightness towards the papillary tip. Because the medulla of kidneys with ATN mildly increased in brightness after PFOB (increased by 40% +/- 7.8%; P less than 0.01), and because the echogenic gradient produced by PFOB was reversed (decreased in brightness towards the papillary tip), ATN kidneys were distinguished from normal kidneys in all 10 rabbits after 2.5 ml/kg PFOB. Medullary echogenicity produced by PFOB in normal kidneys was lost after furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ac induces homologous recombination at the maize P locus.

The maize P gene conditions red phlobaphene pigmentation to the pericarp and cob. Starting from two unstable P alleles which carry insertions of the transposable element Ac, we have derived 51 P null alleles; 47 of the 51 null alleles have a 17-kb deletion which removes the 4.5-kb Ac element and 12.5 kb of P sequences flanking both sides of Ac. The deletion endpoints lie within two 5.2-kb homologous direct repeats which flank the P gene. A P allele which contains the direct repeats, but does not have an Ac insertion between the direct repeats, shows very little sporophytic or gametophytic instability. The apparent frequency of sporophytic mutations was not increased when Ac was introduced in trans. Southern analysis of DNA prepared from the pericarp tissue demonstrates that the deletions can occur premeiotically, in the somatic cells during development of the pericarp. Evidence is presented that the deletions occurred by homologous recombination between the two direct repeats, and that the presence of an Ac element at the P locus is associated with the recombination/deletion. These results add another aspect to the spectrum of activities of Ac: the destabilization of flanking direct repeat sequences.

Alleles↗
PubMed1991

Release of nitrogen oxides from cultured bovine aortic endothelial cells is not impaired by calcium channel antagonists.

BACKGROUND: The endothelium-derived relaxing factor has been shown to be nitric oxide or a related nitroso compound, synthesized by the enzyme nitric oxide synthetase, which oxidizes the guanidono nitrogens of arginine. This enzyme is activated by increases in cytosolic calcium. The effect of the clinically used calcium channel antagonists on this process is controversial. The present study was performed to determine whether calcium channel blockade with these pharmacologic agents would alter the activity of nitric acid synthetase in intact endothelial cells. METHODS AND RESULTS: A specific and sensitive chemiluminescence assay was used to measure the release of nitrogen oxides (nitric oxide and one-electron oxidation products of nitric oxide) from bovine aortic endothelial cells grown in culture. Under basal conditions, the release of nitrogen oxides was about 0.2 nmol/100 micrograms protein/hr. Bradykinin doubled this response. Removal of extracellular calcium abolished basal and bradykinin-stimulated release of nitrogen oxides. Neither diltiazem, verapamil, nor nifedipine in concentrations that are encountered clinically altered the release of nitrogen oxides. CONCLUSIONS: These experiments show that although the production of nitrogen oxides is dependent on extracellular calcium, the clinically used calcium channel antagonists do not inhibit the release of the endothelium-derived relaxing factor.

Amino Acid Oxidoreductases↗
PubMed1991

Cardiac arrest outcome in a tiered response system.

The Emergency Medical Service system must provide prompt CPR, early defibrillation and full advanced cardiac life support (ACLS) within the time 'window of effectiveness.' Timely availability of these combined components determines the chance for survival.

Allied Health Personnel↗
PubMed1990

Intragenic transposition of Ac generates a new allele of the maize P gene.

The maize P gene is required for the production of red phlobaphene pigments in the pericarp and cob. The P-vv allele, which specifies variegated pericarp and cob, contains an insertion of the transposable element Ac in the P gene. A new P-ovov allele (orange variegated pericarp and cob) was obtained as a single event mutation from P-vv. In contrast to the progenitor P-vv allele, P-ovov provides substantial pericarp and cob pigmentation and produces significant amounts of normal-sized P transcripts. The Ac element is not detectably altered in the P-ovov allele, but it has transposed to a new position within P that is 161 bp distant and inserted in the opposite orientation. This example provides molecular confirmation for the hypothesis that changes in expression of genes bearing insertions of transposable elements can occur via movement of the element to new sites within the gene.

Alleles↗
PubMed1990

In vivo estimation of perfluorooctylbromide concentration in tissues.

Currently, the only available method to measure perfluorooctylbromide (PFOB) in tissues requires its extraction with a solvent followed by gas chromatography. Not only is this method invasive, but it cannot be validated because the amount of unextracted PFOB is unknown. Using a cylindrical CT phantom with eight wells in the wall filled with bromine (Br) standards, an in vivo method to measure PFOB tissue concentration was developed. Neutron activation analysis (NAA) was used to calibrate and validate the phantom since NAA allows the quantification of Br by making Br radioactive without the need for extraction. Once NAA was validated for PFOB, the phantom was calibrated using 80 rats and tested using 20 rats relative NAA. The phantom produced linear correlation between CT number and known PFOB concentrations with r = 0.998. After its calibration with NAA, the CT method produced a linear correlation between tissue PFOB concentration determined by CT and NAA near the line of identity with an r = 0.984, thus allowing the determination of PFOB tissue content in vivo noninvasively.

Animals↗
PubMed1990

AUR Memorial Award 1990. The physiologic basis of the radiodense renal medulla after the administration of blood pool contrast agent PFOB.

The hypothesis that the greater CT enhancement of the renal medulla relative to cortex after the administration of perfluorooctylbromide (PFOB) was due to the renal medullary osmotic gradient was tested in eight dogs infused with 10 g/kg PFOB. Urine osmolarity and CT attenuation of the cortex and medulla of each kidney under the full effect of antidiuretic hormone were measured before and after 40 mg of furosemide given intravenously, which is known to destroy the renal osmotic gradient. In an attempt to measure the fractional blood volume of the cortex and medulla, which could account for the observed difference on CT, 10 mCi of 99mTc-labeled erythrocytes were given and cortical and papillary tip tissue samples harvested within 1 minute of the animals' death. Cortical blood volume was eight times that of the medulla (21.6 +/- 5.1% vs 2.7 +/- 0.5%, P less than 0.01) and was not significantly affected by furosemide. Furosemide markedly decreased urine osmolarity (1473 +/- 176 mOsm to 454 +/- 45 mOsm, P less than 0.01), had a minor effect on cortical attenuation (decreased from 90.4 +/- 8.2 to 85.1 +/- 8.1 HU, P less than 0.01), and a marked effect on medullary attenuation (decreased from 140.9 +/- 12.4 to 85.9 +/- 8.9 HU, P less than 0.01) which resulted in total loss of corticomedullary contrast (decreased from 20.0 +/- 3.1% to 0.1 +/- 2.2%, P less than 0.01). Thus, the observed greater CT attenuation of the medulla than cortex following the administration of PFOB, a blood pool agent, is due to the osmotic gradient across the medulla which increases the concentration of the agent in the vasa rectae.

Animals↗
PubMed1989

Isolation and molecular analysis of the maize P locus.

The maize P locus is involved in the synthesis of a red flavonoid pigment in the pericarp, cob and other floral tissues. The tissue-specific pattern of expression of certain P alleles suggests that P may be a complex locus, with more than one functional unit. The P-VV allele, which specifies variegated pericarp and variegated cob, however, shows that insertion and excision of the transposable element Ac affects both pericarp and cob expression as though cob and pericarp pigmentation are controlled by a single gene. Using Ac as a transposon tag, we have isolated 34 kb of genomic DNA from the P-VV and P-RR allele. The cloned DNA contains two 5.8 kb cross-hybridizing regions, in direct orientation relative to each other, separated by 6.6 kb of intervening DNA. A sequence motif of 250 bp is repeated at three locations within the cloned region: once within each of the 5.8 kb repeats, and once outside the 5.8 kb repeats. DNA fragments flanking the Ac element detect five transcripts in RNA from wild type (P-RR) that are absent from mutant (P-VV) tissues. To localize the transcribed sequences, DNA probes spanning the 34 kb of cloned DNA were used in Northern analysis of RNA from mutant and wild-type kernels. The results suggest the presence of a single transcriptional unit located primarily within the DNA between the 5.8 kb repeats. The five RNAs transcribed from this region may be formed by alternative splicing. The size of the P gene derived from the length of the transcribed region seems much smaller than the gene size estimated from Ac-induced P-VV mutations.

Alleles↗
PubMed1989

Hemodynamic effects of intravenous lecithin-based perfluorocarbon emulsions in dogs.

We evaluated and compared the acute hemodynamic effects of perfluorooctylbromide-100% (PFOB), a fluorocarbon emulsified in lecithin without pluronic-F68 (F68), to those of a standard iodinated contrast agent, renografin-76% (R76), and Fluosol-DA 20% (Fluosol), a fluorocarbon emulsified in part by F68. Five open chest dogs were instrumented to evaluate hemodynamic changes after iv injection of PFOB (1 ml.1 g/kg) and R76 (1 ml.0.37 g of iodine/kg). Fluosol (1 ml.0.2 g/kg) was given to two of the five dogs at the end of their study. Fluosol caused transient hemodynamic collapse in both dogs. R76 caused the known transient effect of hypotension (-15.4 +/- 3.3%) followed by hypertension (6.5 +/- 2.7%) and an increase in aortic flow (29.3 +/- 3.9% at 30 sec). PFOB caused minimal, clinically insignificant decrease in aortic flow (4 +/- 1% at 10 sec).

Animals↗
PubMed1989

IV injection of air-filled human albumin microspheres to enhance arterial Doppler signal: a preliminary study in rabbits.

When air-filled human albumin microspheres are injected IV, they have been shown to traverse the pulmonary circulation and markedly influence the echogenicity of the left atrium and ventricle. We studied the possibility that the microspheres can be used to enhance the Doppler signal from systemic arteries and the portal vein. Doppler sonography of the aorta, renal artery, intrarenal branch, and portal vein was performed after the IV injection of saline or microspheres in doses of 1.0, 0.5, 0.3, and 0.1 ml in four rabbits. With appropriate blinding of the observers, subjective estimates of enhancement of the Doppler signal were made in each case. All injections of saline had no detectable effect. All four doses of microspheres enhanced the Doppler signal in the aorta in all rabbits. Signals from the renal artery enhanced in all rabbits after injections of 0.3 ml or greater, but in only two rabbits after 0.1 ml. Although the 1.0-ml dose enhanced the Doppler signal from the intrarenal arterial branch in all rabbits, the 0.5- and 0.3-ml doses enhanced signals in two and the 0.1-ml dose in one. The effect was typical for bolus IV injections. The mean time from injection to onset of enhancement was 5 sec and the effect lasted for 12 sec. Portal venous signals were evaluated in three rabbits. Ten injections were made, four at 1.0 ml and two at each of the lesser doses. Portal vein signals enhanced after all four injections of 1.0 ml of microspheres but after only one of the six injections of lower doses. Our results show that the IV injection of air-filled human albumin microspheres enhances the Doppler signal from systemic arteries and the portal vein and that the microspheres have the potential to serve as a contrast agent for Doppler sonography in humans.

Albumins↗
PubMed1988

Response of the left ventricular end-systolic pressure-volume relation in conscious dogs to a wide range of contractile states.

We assessed the linearity and slope of the left ventricular end-systolic pressure (PES)-volume (VES) relation over a wide range of contractile states in conscious dogs. The animals were instrumented to determine left ventricular volume from ultrasonic left ventricular internal dimensions and measure left ventricular pressure with a micromanometer. Studies were performed 1-2 weeks after instrumentation while the animals were conscious. Contractile state was increased by incremental infusion of dobutamine (0, 2, 4, 6, and 8 micrograms/kg/min i.v.) and decreased by verapamil (10 mg i.v.) given after autonomic blockade. The 44 +/- 11 mm Hg (mean +/- SD) portion of the PES-VES relation generated by bicaval occlusion demonstrated a slight but consistent nonlinearity, apparent as a concavity toward the volume axis. This nonlinearity, present at all inotropic states, did not prevent the PES-VES relation from being well approximated by a straight line (r = 0.984 +/- 0.020, SEE = 2.1 +/- 1.4 mm Hg); furthermore, the slope of the PES-VES line provided a sensitive index of contractile state, progressively increasing with incremental doses of dobutamine and decreasing in response to verapamil. The volume-axis intercept of the linear approximation of the PES-VES relation was 2.9 +/- 3.3 ml less (p less than 0.05) than the volume-axis intercept of the nonlinear quadratic fit. Thus, the linear PES-VES relation, whose slope is sensitive to a wide variety of inotropic states, is a reasonable and useful description of the left ventricle in the range of PES-VES points that can be produced by bicaval occlusion in the conscious dog. However, linear extrapolation of the relation beyond the range of data points may not be accurate.

Animals↗
PubMed1988

Cash management.

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Budgets↗