Biomedical subjects

R W Storrs

Publications and source records attributed to R W Storrs.

6 recordsLinked to original sources

PubMed1997

Quantitative analysis of apoptotic cell death using proton nuclear magnetic resonance spectroscopy.

Quantification of apoptotic cell death in vivo has become an important area of investigation in patients with acute lymphoblastic leukemia (ALL). We have devised a noninvasive analytical method to estimate the percentage of apoptotic lymphoblasts in doxorubicin-treated Jurkat T-cell ALL cultures, using proton nuclear magnetic resonance spectroscopy (1H NMR). We have found that the ratio of the methylene (CH2) resonance (at 1.3 ppm) to the methyl (CH3) resonance (at 0.9 ppm) signal intensity, as observed by 1H NMR, is directly proportional to the percentage of apoptotic lymphoblasts in vitro. The correlation between the CH2/CH3 signal intensity ratio and the percentage of apoptotic lymphoblasts was optimal 24 to 28 hours after doxorubicin treatment (r2 = .947, N = 27 samples). There was also a direct temporal relationship between an increase in the CH2/CH3 signal intensity ratio and the onset of apoptosis as detected by nuclear morphologic analysis, fluorescein-annexin V flow cytometry, and DNA gel electrophoresis. Thin-layer chromatography confirmed that a dynamic and/or compositional change of the plasma membrane, rather than increases in lipase activity or fatty acid production, appears to account for the increase in the CH2/CH3 signal intensity ratio during apoptosis. 1H NMR may have clinical utility for the early noninvasive assessment of chemotherapeutic efficacy in patients with ALL.

Annexin A5↗

PubMed1996

Detection of apoptotic cell death by proton nuclear magnetic resonance spectroscopy.

Cells undergoing apoptosis (programmed cell death) display profound morphologic and biochemical changes in the nucleus, cytoplasm, and plasma membrane. We have shown a direct temporal relationship between the onset of apoptosis in Jurkat T-cell lymphoblast cultures and a greater than two-fold increase in the signal intensity of the methylene resonance (at 1.3 ppm) as observed by proton nuclear magnetic resonance spectroscopy (1H NMR). The increase in the methylene resonance intensity was seen when apoptosis was induced by serum deprivation, glucocorticoid, and doxorubicin treatment but not in necrotic (nonapoptotic) cell death. We have found similar changes in a variety of other cell lines undergoing apoptosis including the Hut 78 T-cell leukemia, JY natural killer T-cell leukemia, Daudi B-cell lymphoma, HeLa, and 3T3 fibroblast cell lines. Furthermore, this spectral change was diminished in Bcl-2 overexpressing HL-60 cell cultures treated with doxorubicin, which were relatively resistant to apoptosis, as compared to apoptotic HL-60 cultures. 1H NMR spectroscopy therefore may be useful in detecting apoptotic cell death in vivo.

3T3 Cells↗

PubMed1992

Helix propagation in trifluoroethanol solutions.

Helix propagation of the S-peptide sequence (residues 1-19 of ribonuclease A) in 2,2,2-trifluoroethanol (TFE) solutions has been investigated with CD and nmr Overhauser effect spectroscopies. In this study, the S-peptide helix is covalently initiated at the N-terminus through disulfide bonds to a helix scaffold derived from the N-terminal sequence of the bee venom peptide apamin. The entire S-peptide sequence of this hybrid sequence peptide becomes helical at high proportions of TFE. Residues 14-19 of the S-peptide are not helical in the free peptide in TFE, nor are they helical in ribonuclease A. The "helix stop" signal encoded by the S-peptide sequence near residue 13 does not persist at high TFE with this hybrid sequence peptide. The helix-stabilizing effects of TFE are due at least in part to facilitated propagation of an extant helix. This stabilizing effect appears to be a general solvation effect and not due to specific interaction of the helical peptide with TFE. Specifically these data support the idea that TFE destabilizes the coil state by less effective hydrogen bonding of the peptide amide to the solvent.

Amino Acid Sequence↗

PubMed1990

Folding and activity of hybrid sequence, disulfide-stabilized peptides.

Peptides have been synthesized that have hybrid sequences, partially derived from the bee venom peptide apamin and partially from the S peptide of ribonuclease A. The hybrid peptides were demonstrated by NMR spectroscopy to fold, forming the same disulfides and basic three-dimensional structure as native apamin, containing a beta-turn and an alpha-helix. These hybrids were active in complementing S protein, reactivating nuclease activity. In addition, the hybrid peptide was effective in inducing antibodies that cross-react with the RNase, without conjugation to a carrier protein. The stability of the folded structure of this peptide suggests that it should be possible to elicit antibodies that will react not only with a specific sequence, but also with a specific secondary structure. Hybrid sequence peptides also provide opportunities to study separately nucleation and propagation steps in formation of secondary structure. We show that in S peptide the alpha-helix does not end abruptly but rather terminates gradually over four or five residues. In general, these hybrid sequence peptides, which fold predictably because of disulfide bond formation, can provide opportunities for examining structure-function relationships for many biologically active sequences.

Amino Acid Sequence↗

PubMed1986

One- and two-dimensional NMR relaxation studies of dynamics and structure in bile salt-phosphatidylcholine mixed micelles.

A series of one- and two-dimensional 1H-NMR relaxation measurements has been conducted on simple and mixed micellar aggregates of taurocholate, diphenylvaleroylphosphatidylcholine (diPVPC) and egg yolk phosphatidylcholine (egg PC). The results are interpreted to provide structural and dynamic comparisons between micelles and vesicles, between phospholipids of varying chain length, and between different lipid components within the same micellar aggregate. Both chemical shift changes and two-dimensional nuclear Overhauser effect cross peaks suggest direct interaction of taurocholate and PC chemical sites, although the latter observations may also be accounted for by PC-PC interactions. These experiments demonstrate the promise of NMR relaxation techniques for investigations of molecular organization in model substrate for lipolytic enzymes.

Bile Acids and Salts↗

PubMedDate not supplied

Paramagnetic polymerized liposomes as new recirculating MR contrast agents.

We describe a well-tolerated blood pool contrast agent with extended recirculatory half-life based on paramagnetic polymerized liposomes (PPLs). PPLs were constructed from a new type of polymerizable lipid molecule that has a derivative of gadopentetate dimeglumine as the hydrophilic head group and diacetylene groups in the hydrophobic acyl chains, which cross-link when irradiated with ultraviolet (UV) light. Biodistribution, blood pool half-life, and MR image enhancement were determined for PPLs composed of 10% of the gadopentetate dimeglumine lipid and 90% of ditricosadiynoyl tricosadiynayl phosphatidylcholine (DAPC) at a dose of 0.015 mmol Gd+3/kg in rats. In T1-weighed MR images (TR/TE = 400/18 msec), an average signal enhancement of 34% in the kidneys and 20% in the liver was observed, which persisted for at least 90 minutes after administration of the PPLs. Biodistribution studies using radiolabeled PPLs confirmed that 80% of the injected dose remained in the blood pool after 2 hours. The half-life of elimination from the blood pool was 19 hours. The preparation was well tolerated in rats and produced similar MR contrast enhancement of the blood pool as produced by other liposome contrast agents. However, the half-life of PPL elimination from the blood pool was prolonged relative to other liposome systems.

Animals↗