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L Bolinger

Publications and source records attributed to L Bolinger.

33 records · Page 2Linked to original sources
PubMed1992

Structural determinants of Cys2His2 zinc fingers.

Two mutants of the zinc finger peptide Xfin-31 (Ac-YKCGLCERSFVEKSALSRHQRVHKN-CONH2) containing alterations to the conserved hydrophobic core have been constructed and their zinc-bound structures investigated by 1H NMR techniques. In the first (Xfin-31B) a double mutation R8F/F10G places the conserved core aromatic residue at position 8 rather than position 10. In the second (Xfin-31C), Phe-10 is replaced by Leu. A qualitative analysis of 1H chemical shifts, NOE connectivities and coupling constants indicates that the global folds of both mutants are similar to that of the wild-type protein. However, amide exchange rates suggest that the F10L mutant is much less stable than either the wild-type or the R8F/F10G mutant.

Amino Acid Sequence↗
PubMed1991

Metabolic heterogeneity in human calf muscle during maximal exercise.

Human skeletal muscle is composed of various muscle fiber types. We hypothesized that differences in metabolism between fiber types could be detected noninvasively with 31P nuclear magnetic resonance spectroscopy during maximal exercise. This assumes that during maximal exercise all fiber types are recruited and all vary in the amount of acidosis. The calf muscles of seven subjects were studied. Two different coils were applied: an 11-cm-diameter surface coil and a five-segment meander coil. The meander coil was used to localize the 31P signal to either the medial or the lateral gastrocnemius. Maximal exercise, consisting of rapid plantar flexions, resulted in an 83.7% +/- 7.8% decrease of the phosphocreatine pool and an 8-fold increase of the inorganic phosphate (Pi) pool. At rest the Pi pool was observed as a single resonance (pH 7.0). Toward the end of the first minute of exercise, three subjects showed three distinct Pi peaks. During the second minute of exercise the pH values stabilized at 7.12 +/- 0.12, 6.63 +/- 0.15, and 6.27 +/- 0.23. The same pattern was seen when the signal was collected from the medial or lateral gastrocnemius. In four subjects only two distinct Pi peaks were observed. The Pi peaks had differing relative areas in different subjects, but they were reproducible in each individual. This method allowed us to study the appearance and disappearance of the different Pi peaks, together with the changes in pH. Because multiple Pi peaks were seen in single muscles they most likely identify different muscle fiber types.

Adenine Nucleotides↗
PubMed1989

The use of finite impulse response filters in pulse design.

We develop a new way of synthesizing pulse sequences with desirable frequency characteristics. By combining our previous results with techniques from the theory of finite impulse response filters, we can specify (1) the total duration of the pulse sequence, (2) the frequency ranges it is desired to perturb, (3) the desired perturbation, and (4) the frequency range it is desired not to perturb. We can then synthesize a hard pulse sequence which will yield that desired perturbation with the minimal possible error. The minimum error is global, in the sense that no pulse sequence can do better at achieving the specifications, and is not just a local minimum, around the pulse sequences close to the derived pulse.

Algorithms↗
PubMed1989

The synthesis of soft pulses with a specified frequency response.

We propose a new approach to synthesizing shaped pulses, by first synthesizing a hard pulse sequence and then converting it to a soft pulse. In previous papers, we developed a new approach to synthesizing hard pulse sequences by exactly inverting the Bloch equation, which yields the optimal frequency response. These results can now be applied to shaped pulses. Specifically, one can specify (1) the total duration of the pulse, (2) the frequency range it is desired to perturb, (3) the perturbation desired and, (4) the frequency range it is desired not to perturb. One can then synthesize a shaped pulse which has the desired effect with the least possible error. This enables us to obtain very sharp inversion and pi/2 pulses.

Algorithms↗
PubMed1987

Cardiac transfer function relating energy metabolism to workload in different species as studied with 31P NMR.

Cardiac metabolism was studied with 31P NMR in 7 dogs and 4 cats to determine whether animals adapted for different life-styles (stalk and sprint vs endurance running) respond to increased work loads (heart rate X blood pressure product) with different high-energy phosphate kinetics. Hearts were exposed via a left lateral thoracotomy under Nembutal anesthesia (40 mg/kg). Two-turned solenoid surface coils were placed on the left ventricles; pacing wires were sutured into the left ventricular apices. The femoral artery and vein were cannulated for blood pressure and arterial blood gas monitoring and fluid and drug infusion, respectively. Animals were placed in a plexiglass holder into a 2.1-T, 31-cm-bore, superconducting magnet. 31P spectra were obtained from the heart using respiratory and electrocardiogram gating. Cardiac work loads were changed by pacing the heart at 4, 4.5, and 5 Hz. Heart rate X blood pressure product "work" was correlated with Pi/PCr ratios. Dog hearts were more resistant than those of cats to changes in Pi/PCr with increasing work load. It is possible that animals adapted to different life-styles may have cardiovascular systems which are metabolically and mechanically adapted for different forms of stress. These differences may be elicited and effectively delineated using in vivo NMR techniques during various physiological interventions, such as pacing. The basis for these differences may be related to cardiac microvasculature or to intrinsic differences in enzyme kinetics. Delineation of these mechanisms may be helpful in the understanding of the physiological basis of cardiac function in health and disease.

Adaptation, Physiological↗
PubMed1987

Forms of a self associating autoantibody complex between a monoclonal human IgG1 and human serum albumin.

The mode of association of an unusual human autoantibody complex, composed of a monoclonal immunoglobulin, Tu IgG, and human serum albumin was investigated. A crystalline complex forms from these components in the cold and we have shown that it consists of IgG and albumin in a 1:2 molar ratio [Jentoft et al., Biochemistry 21, 289-294 (1982)]. The crystalline complex was analyzed by electron microscopy and the soluble natural complexes (formed by dissolving the crystals at 20 degrees C) were studied by sedimentation velocity. The sedimentation studies demonstrated that the soluble Tu IgG-albumin complexes are in equilibrium with free Tu IgG and albumin molecules and that the major soluble sedimenting species has a S20,w value of 12.5S. At a constant concn of complex, the size of the sedimenting complex can be reduced by lowering the pH, increasing the ionic strength, or adding CaCl2, citrate, ascorbate or urea. These intermediate, soluble forms have S20,w values that are consistent with 1:1 and 1:2 Tu IgG-albumin complexes. Parameters of repeat distances and angles that were obtained from electron micrographs of the crystalline form of the Tu IgG-albumin complex were used to propose a model for the 12.5S species and were also incorporated into a three-dimensional model for the complex. The 12.5S complex is proposed to form by dimerization of the 1:2 Tu IgG-albumin complex via interactions of albumin with the Fc region of the antibody. The 12.5S dimer may be the nucleating species for subsequent rapid associations that lead to spontaneous formation of crystals. In the proposed model for the Tu IgG-albumin crystals, the angle between the Fab arms of each Tu IgG molecule is 90 degrees, the antigenic determinant on the albumin is located near one end of the long axis of the cylindrical molecule, the site of interaction with Fc is located at the other end of the cylinder, and the CH3 domain of the IgG contains the binding site for albumin that is responsible for the formation of the dimeric 12.5S species. A series of sedimentation velocity experiments suggest that the association between the CH3 domain of IgG and albumin requires the prior formation of the antibody-antigen complex.

Antibodies, Monoclonal↗
PubMed1987

Multinuclear MR imaging: a technique for combined anatomic and physiologic studies.

With the use of specially designed multiple-tuned probes for magnetic resonance (MR) imaging, data collection schemes can be developed for obtaining images of different nuclei simultaneously. Both phantom and in vivo MR images of two nuclei (either hydrogen-1, phosphorus-31, lithium-7, or fluorine-19) were obtained in the time span necessary to collect the image of the less sensitive nuclei. This technique offers a means by which physiologic and anatomic information can be gathered in a highly efficient fashion.

Animals↗
PubMed1986

Myocardial high energy phosphate metabolism in closed chest dog: creation of an animal model.

A chronic closed chest dog model was developed to study myocardial metabolism with NMR spectroscopy. Cardiac windows were surgically created in 10 dogs by removal of two ribs and accompanying skeletal muscle. Marlex mesh was sewn between the two exposed ribs, and fascia and skin were closed. 31P spectra were obtained using a surface coil placed into the surgically created pouch and using routine NMR pulsing techniques.

Adenosine Triphosphate↗
PubMed1986

Relaxation and imaging of lithium in vivo.

It has recently been demonstrated that NMR imaging can be used to record the distribution of lithium. We now report on the parameters pertinent to this imaging. Specifically, the relaxation of Li in aqueous solution, in agarose gel, and in vivo has been investigated. In the latter case, both the longitudinal and transverse relaxations were biexponential, consistent with the behavior expected for a spin 3/2 quadrupole relaxed nucleus. The overall relaxation rate was quite slow in vivo with T'1 = 3.5 sec and T''1 = 6.6 sec.

Animals↗
PubMed1984

Phosphorylethanolamine--the major constituent of the phosphomonoester peak observed by 31P-NMR on developing dog brain.

31P-NMR spectra of newborn dog brains exhibit a prominent phosphomonoester (PME) peak (6.78 +/- SD 0.05 ppm from phosphocreatine peak), similar to those of human neonates. Studies were undertaken to identify the chemical constituents of this peak. Brains of puppies were funnel frozen for methanol-HCl-perchloric acid extraction after in vivo 31P-NMR spectra were taken. The pK of the major component of the PME region in the NMR spectrum of extract was 5.4, corresponding to that of phosphorylethanolamine (PEt). Addition of PEt increased the major peak on the PME region over a wide range of pH, while addition of phosphorylcholine or ribose 5-phosphate yielded distinct peaks. We suggest that the major constituent of phosphomonoester peak of 31P-NMR spectra of newborn dog brain is phosphorylethanolamine. Biochemical mechanisms relevant to changes of phosphorylethanolamine during brain development are discussed.

Animals↗
PubMed1984

Turnover of succinyl-CoA:3-oxoacid CoA-transferase in glioma and neuroblastoma cells. Specific influence of acetoacetate in neuroblastoma cells.

The specific activity of succinyl-CoA:3-oxo-acid CoA-transferase (3-oxoacid CoA-transferase, EC 2.8.3.5) increases significantly during growth in culture in both mouse neuroblastoma N2a and rat glioma C6 cells. To investigate the mechanism(s) responsible for this, antibody specific for rat brain 3-oxoacid CoA-transferase was raised in rabbits. Immunotitrations of 3-oxoacid CoA-transferase from neuroblastoma and glioma cells on days 3 and 7 of growth after subculture showed that the ratio of 3-oxoacid CoA-transferase activity to immunoprecipitable enzyme protein remained constant, indicating that differences in specific activity of the enzyme at these times in both cell types reflect differences in concentration of enzyme protein. In glioma cells, the relative rate of 3-oxoacid CoA-transferase synthesis was about 0.04-0.05% throughout 9 days in culture. In contrast, the relative rate of synthesis of 3-oxo-acid CoA-transferase in neuroblastoma cells was about 0.07-0.08% on days 3, 5 and 7 after subculture, but fell to 0.052% on day 9. The degradation rates of total cellular protein (t1/2 = 28 h) and 3-oxoacid CoA-transferase (t1/2 = 46-50 h) were similar in both cell lines. The rise in specific activity of the enzyme in both cell lines from days 3 to 7 without a significant increase in the relative rate of synthesis reflects a slow approach to steady-state conditions for the enzyme secondary to its slow degradation. Differences in 3-oxoacid CoA-transferase specific activity between the two cell lines are apparently due to a difference of about 60% in relative rates of enzyme synthesis. The presence of 0.5 mM-acetoacetate in the medium significantly increased the specific activity of 3-oxoacid CoA-transferase in neuroblastoma cells during the early exponential growth phase. This treatment increased the relative rate of synthesis of 3-oxoacid CoA-transferase by 23% (P less than 0.025) in these cells on day 3, suggesting that substrate-mediated induction of enzyme synthesis is a mechanism of regulation of 3-oxoacid CoA-transferase.

3-Hydroxybutyric Acid↗
PubMedDate not supplied

Aortic aneurysm following subclavian flap repair: diagnosis by magnetic resonance imaging.

Aortic aneurysm following subclavian flap repair of coarctation of the aorta is thought to occur infrequently. We present a case in which aneurysm of the subclavian flap was found 10 years after the original surgery. The location and extent of the aneurysm was clearly defined using cardiac magnetic resonance imaging (MRI). This report adds further support to recent recommendations to make cardiac MRI a routine imaging study for all postoperative patients from coarctation of the aorta repair.

Aortic Aneurysm, Thoracic↗