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D Burstein

Publications and source records attributed to D Burstein.

45 records · Page 3Linked to original sources
PubMed1987

Intracellular sodium and lithium NMR relaxation times in the perfused frog heart.

We have used a combination of a shift reagent and mathematical filtering or presaturation of the extracellular sodium resonance for the quantitative investigation of the intracellular sodium and lithium relaxation times in the perfused frog heart. While the T1 of the intracellular sodium was found to consist of a single-exponential time constant (approximately 23 ms), the T2 was better fit as a double-exponential decay with time constants of approximately 2 and 17 ms. However, the relative amplitudes of the two time constants in the T2 decay were found to be inconsistent with those which would be expected from a homogeneous pool of nuclei undergoing quadrupolar interactions. The relaxation times were not changed by a fivefold increase in the intracellular sodium level (due to perfusion with a ouabain-containing buffer). The T1 and T2 of the intracellular lithium (after perfusion with lithium-containing buffer) were both well fit by single exponentials (700- and 31-ms time constants, respectively).

Animals↗
PubMed1987

Nuclear magnetic resonance studies of intracellular ions in perfused frog heart.

Intracellular sodium, potassium, and lithium were observed in a perfused frog heart by nuclear magnetic resonance (NMR) spectroscopy. A perfusate buffer containing the shift reagent, dysprosium tripolyphosphate, was used in combination with mathematical filtering or presaturation of the extracellular resonance to separate the intra- and extracellular sodium NMR signals. Addition of 10 microM ouabain to the perfusate, perfusion with a zero potassium, low-calcium buffer, and replacement of 66% of the perfusate sodium with lithium resulted in the following percent changes in the intracellular sodium levels (mean +/- SD): ouabain + 460 +/- 60% (n = 6), zero potassium + 300 +/- 30% (n = 3), and lithium - 51 +/- 6% (n = 3). An increase of 45% in the intracellular sodium was observed when changing the pacing rate from 0 to 60 beats/min (with proportional changes for intermediate pacing rates). The ratio of intracellular potassium to sodium concentration was determined to be 2.3 by NMR, indicating that a substantial amount of the intracellular potassium is undetectable with these NMR methods. In addition, intracellular lithium was observed during perfusion with a lithium-containing perfusate.

Animals↗
PubMed1987

Effect of interleukin-2 on diabetes in the BB/Wor rat.

Young diabetes prone BB/Wor rats were treated for 4-7 weeks with low dose (1,000 units/week) or high dose (75,000 units/week) recombinant human interleukin-2 (IL-2) and observed through 150 days of age for the development of spontaneous diabetes mellitus. Comparing treated rats with controls, it was found that IL-2 did not affect the cumulative incidence of diabetes, the age at onset of the disease, or peripheral lymphocyte subset numbers. High dose IL-2 administered to diabetes resistant BB/Wor rats also failed to induce the disease.

Animals↗
PubMed1983

Resolution of the diadenosine 5',5"'-P1,P4-tetraphosphate binding subunit from a multiprotein form of HeLa cell DNA polymerase alpha.

A diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) binding subunit has been resolved from a high molecular weight (640,000) multiprotein form of DNA polymerase alpha [deoxynucleoside triphosphate:DNA nucleotidyltransferase (DNA-directed), EC 2.7.7.7] from HeLa cells [DNA polymerase alpha 2 of Lamothe, P., Baril, B., Chi, A., Lee, L. & Baril, E. (1981) Proc. Natl. Acad. Sci. USA 78, 4723-4727]. The Ap4A binding activity copurifies with the DNA polymerizing activity during the course of purification. Hydrophobic chromatography on butylagarose resolves the Ap4A binding activity from the DNA polymerase. The Ap4A binding activity is protein in nature since the binding of Ap4A is abolished by treatment of the isolated binding activity with proteinase K but is insensitive to treatment with DNase or RNase. The molecular weight of the Ap4A binding protein, as determined by polyacrylamide gel electrophoresis under nondenaturing conditions or by NaDodSO4/polyacrylamide gel electrophoresis after photoaffinity labeling of the protein with [32P]Ap4A is 92,000 or 47,000. The binding activity of this protein is highly specific for Ap4A.

Adenine Nucleotides↗
PubMed1982

A naturalistic assessment of partial-hospital treatment.

Three hundred fifty-eight consecutive admissions to 13 partial hospitals were evaluated over an 8-month period. The design of the study focused on an unobstrusive measurement process involving clinical judgment of outcome. Analyses revealed that the clinical judgment process generated data which were both reliable and valid. The results of the study indicate that partial-hospital treatment is most effective for chronic and acute schizophrenic conditions, paranoid schizophrenia, and affective disorders and least so far patients diagnosed as adjustment disorders. Patients in the organic and neurotic diagnostic categories tended to remain stable. As in previous research, the pretreatment levels of the dependent variables were the best predictors of improvement, but the present study also reveals that progressive amounts of partial-hospital treatment lead to a greater improvement in patient functioning.

Analysis of Variance↗
PubMedDate not supplied

MR imaging of coronary artery flow in isolated and in vivo hearts.

Methods for imaging flow in coronary arteries with magnetic resonance (MR) imaging techniques are demonstrated in isolated heart preparations and live animal models. Coronary artery flow was first imaged with a flow-compensated gradient-echo pulse sequence in isovolumic and working perfused rat hearts and then in vivo. A bolus tracking technique was used to measure flow velocity in the coronary arteries. Ultrafast gradient-echo imaging techniques were then applied, with high resolution obtained by combining the information from several cardiac cycles. A stimulated-echo pulse sequence was demonstrated as a method for performing coronary angiography by flow tagging in isovolumic perfused hearts. This report describes the results of coronary flow MR imaging in isolated rat hearts and live mice and rats. The general approach has proved useful in evaluating new methods for coronary MR angiography and should permit well-controlled studies of pathologic conditions. This ability to image coronary flow in isolated hearts and in small animals should permit integrated MR studies of coronary flow, myocardial perfusion, myocardial metabolism, and cellular ionic status.

Animals↗
PubMedDate not supplied

Water diffusion and exchange as they influence contrast enhancement.

The contrast-enhanced magnetic resonance imaging (MRI) signal is rarely a direct measure of contrast concentration; rather it depends on the effect that the contrast agent has on the tissue water magnetization. To correctly interpret such studies, an understanding of the effects of water movement on the magnetic resonance (MR) signal is critical. In this review, we discuss how water diffusion within biological compartments and water exchange between these compartments affect MR signal enhancement and therefore our ability to extract physiologic information. The two primary ways by which contrast agents affect water magnetization are discussed: (1) direct relaxivity and (2) indirect susceptibility effects. For relaxivity agents, for which T1 effects usually dominate, the theory of relaxation enhancement is presented, along with a review of the relevant physiologic time constants for water movement affecting this relaxation enhancement. Experimental issues that impact accurate measurement of the relaxation enhancement are discussed. Finally, the impact of these effects on extracting physiologic information is presented. Susceptibility effects depend on the size and shape of the contrast agent, the size and shape of the compartment in which it resides, as well as the characteristics of the water movement through the resulting magnetic field inhomogeneity. Therefore, modeling of this effect is complex and is the subject of active study. However, since susceptibility effects can be much stronger than relaxivity effects in certain situations, they may be useful even without full quantitation.

Animals↗
PubMedDate not supplied

Multibolus stimulated echo imaging of coronary artery flow.

One limitation of traditional bolus tagging techniques for MR angiography is the small amount of blood labeled by one tagging, resulting in a limited filling of the downstream vessels. We describe a multiple bolus technique using stimulated echoes (STE) for imaging coronary flow. A series of radiofrequency (RF) pairs are given with each pair selective at the region of tagging, thus tagging consecutive volumes of blood, and a final nonselective pulse is given to "read out" all of the tagged spins. In this way, multiple boluses of tagged blood are imaged at one time.

Animals↗