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M Peric

Publications and source records attributed to M Peric.

At least 19 recordsLinked to original sources
PubMed2001

Tension-free left ITA graft -- the pericardial strip technique.

Emphysematous lung occupying the whole dome of the left pleural cavity and expanding well over the midline may occasionally present a significant problem for positioning of the left internal thoracic artery, although the graft has been mobilized up to its origin. To avoid an undue tension on it, we combined a well known technique of the pericardial incision with the pericardial strip technique, enabling the lung to expand freely.

Humans↗
PubMed2000

Ab Initio Investigation of the ellipsis pi(2)(g) (X(3)Sigma(-)(g), 1(1)Delta(g), 1(1)Sigma(+)(g)) Electronic States of NCN. Study of the Renner-Teller Effect in the 1(1)Delta(g) State.

Large-scale CI calculations are carried out to obtain accurate potential energy surfaces for the ellipsis pi(2)(g) manifold (X(3)Sigma(-)(g), 1(1)Delta(g), 1(1)Sigma(+)(g)) of electronic states of NCN. Separation of the low-lying singlet states from the triplet ground state is computed in close agreement with the results of a recent photoelectron study by T. R. Taylor, R. T. Bise, K. R. Asmis, and D. M. Neumark [Chem. Phys. Lett. 301, 413-416 (1999)]. Vibronic coupling (Renner-Teller effect) in the 1(1)Delta(g) state is studied by means of a perturbative and a variational approach. Results of the present ab initio study confirm explicitly the rho(4) dependence postulated for the splitting of bending potential curves in Delta electronic states at small deviations from linearity. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Aziridinyl peptides as inhibitors of cysteine proteases: effect of a free carboxylic acid function on inhibition.

Peptides containing aziridine-2,3-dicarboxylate (Azi) as electrophilic building block are evaluated as inhibitors of the cysteine proteases papain, cathepsin B, cathepsin L and clostripain. The influence of a free carboxylic acid as functional group at different positions of the inhibitor molecule on inhibition is analyzed. Structure-activity relationships and binding mode hypotheses are discussed. In contrast to the bacterial enzyme clostripain, the papain like mammalian proteases (cathepsins) are irreversibly inactivated by aziridinyl peptides. N-Unsubstituted aziridines are much more potent inhibitors of papain and cathepsins if they contain the free carboxylic acid attached to the aziridine ring (HOAzi-Leu-ProOBzl). Two free carboxylic acid functions at the aziridine ring are necessary for good inhibition of these enzymes by N-acylated aziridinyl peptides (BOC-Phe-Azi(OH)2). Chimeric bispeptidyl derivatives are selective CB inhibitors if the free acid is located at the C-terminus of the peptide (BOC-Phe-(EtO)Azi-Leu-ProOH). Clostripain is only inhibited by aziridinyl peptide esters.

Aziridines↗
PubMed1999

Diminished aqueous microviscosity of tumors in murine models measured with in vivo radiofrequency electron paramagnetic resonance.

Using very low frequency in vivo electron paramagnetic resonance (EPR), we have compared, for the first time, the average microviscosity of the total aqueous compartment of murine fibrosarcomas and that of normal leg tissue in a living animal. EPR spectra from dissolved nitroxide spin probes report the solvent microviscosity. The tumor aqueous microviscosity, 1.8 +/- 0.1 centipoise, was significantly lower than that of the corresponding normal tissue, 2.9 +/- 0.3 centipoise, a difference of 38 +/- 7%. These results confirm the commonly observed increase in the water proton transverse relaxation times (T2) in magnetic resonance imaging of hyperproliferative states, for example, malignancy. The specificity of the localization of the EPR signal indicates a substantial portion of the T2 increase seen in magnetic resonance imaging derives from decreased bulk-water viscosity. The effect of this microviscosity differences may be the basis of several physiological differences between tumors and normal tissues which could confer a growth rate advantage to tumor tissue.

Animals↗
PubMed1999

Probing DMPG vesicle surface with a cationic aqueous soluble spin label.

A small, highly aqueous soluble, deuterated, cationic spin label, 4-trimethylammonium-2,2,6,6-tetramethylpiperidine-d17-1-oxyl iodide (dCAT1), was used to directly monitor the negatively charged DMPG vesicle surface in order to test a recent suggestion (Riske et al., Chem. Phys. Lipids, 89 (1997) 31-44) that alterations in the surface potential accompanied apparent phase transitions observed by light scattering. The temperature dependence of the label partition between the lipid surface and the aqueous medium indicated an increase in the surface potential at the gel to liquid-crystal transition, supporting the previous suggestion. Results at the phase transition occurring at a higher temperature were less definitive. Although some change in the dCAT1 ESR spectra was observed, the interpretation of the phenomena is still rather unclear. DMPG surface potentials were estimated from the dCAT1 partition ratios (surface label moles/total label moles), using a simple two-sites model, where the electrostatic potential is zero everywhere but at the vesicle surface, and the interaction between the spin label and the membrane surface is chiefly electrostatic. The Gouy-Chapman-Stern model predicts surface potentials similar to those observed, although the measured decrease in the surface potential with ionic strength is somewhat steeper than that predicted by the model.

Electron Spin Resonance Spectroscopy↗
PubMed1998

Contributions to the Gaussian line broadening of the proxyl spin probe EPR spectrum due to magnetic-field modulation and unresolved proton hyperfine structure.

A simple expression is derived to compute the total Gaussian linewidth of a Voigt line that is broadened by sinusoidal magnetic-field modulation as follows: delta HPPG(Hm)2 = delta HPPG(0)2 + kappa 2Hm2, where delta HPPG(Hm) is the Gaussian linewidth observed with an modulation amplitude Hm/2 and delta HPPG(0) is the Gaussian linewidth in the limit of zero modulation. The field modulation contributes an additional Gaussian broadening of kappa Hm, where kappa is a constant, which adds in quadrature to delta HPPG(0) to give the total Gaussian linewidth. Denoting the overall linewidth of the Voigt line in the absence of modulation broadening by delta HPP0(0), it is shown, both by analytical means and by spectral simulation, that the constant kappa is equal to 1/2 in the limit of Hm << = delta HPP0(0); however, using values of Hm as large as delta HPP0(0) leads to only minor departures from kappa = 1/2. The formulation is valid both for Lorentzian and Voigt lines and is tested for 2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-carboxylic acid (3-carboxy proxyl) in CCl4 and in aqueous buffer. This spin probe was studied because the proxyl group is the only major spin-probe moiety whose Gaussian linewidth had not been characterized in the literature. For 3-carboxy proxyl, it is found that delta HPPG(0) = 1.04 +/- 0.01 G independent of solvent polarity. Precision values of the 14N hyperfine coupling constant for 3-carboxy proxyl at 9.5 degrees C are as follows: 14.128 +/- 0.001 G in CCl4 and 16.230 +/- 0.002 G in aqueous buffer. The temperature dependence of delta HPPG(0) and the 14N hyperfine coupling constant are reported as empirical equations. Results of the present work taken together with previously published data permits accurate correction for the effects of inhomogeneous broadening due to unresolved hyperfine structure and modulation broadening for the majority of spin probes in common use.

Carbon Tetrachloride↗
PubMed1997

Ab Initio Study of the Electronic Spectrum of B2H2

The present paper represents the first part of an extensive theoretical study on the electronic spectrum of B2H2. The results of ab initio calculations of the vertical spectrum and the trans- and cis-bending potential curves for the low-lying triplet and singlet electronic states are reported. Special attention is paid to the study of the interaction between valence- and Rydberg-type electronic species. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Ab Initio Study of the Electronic Spectrum of B2H2

The results of ab initio calculations of the potential curves for the torsional motion, symmetric H-B stretching, and B-B stretching in low-lying valence- and Rydberg-character triplet and singlet electronic states of B2H2 are reported. Particularly, the dissociation process B2H2 --> BH + BH out of various electronic states of B2H2 is studied. The nature of binding in B2H2 is discussed in terms of the composition of the electronic wavefunctions. Copyright 1997Academic Press

Journal Article↗
PubMed1996

In vivo spin-label murine pharmacodynamics using low-frequency electron paramagnetic resonance imaging.

A novel, very-low-frequency electron paramagnetic resonance (EPR) technique is used to image the distribution of several nitroxides with distinct pharmacologic compartment affinities in the abdomens of living mice. Image acquisition is sufficiently rapid to allow a time sequence of the distribution for each compound. The spectra and concentrations of these nitroxides are imaged with the use of spectral-spatial imaging to distinguish a single spatial dimension. Liver and bladder of the mouse anatomy are distinguished by this technique. After an intraperitoneal injection of the spin-label probes, a shift in the distribution of the compounds from the upper abdomen (primarily liver) to the lower abdomen (primarily bladder) is observed. The time dependence of the shift in regional distribution depends on the structural properties of the side chain attached to the spin label. These results indicate that this application of in vivo electron paramagnetic resonance imaging will provide a new method of magnetic resonance imaging for determination of pharmacodynamics in the body of an intact animal.

Animals↗
PubMed1996

Measurement of differences in pO2 in response to perfluorocarbon/carbogen in FSa and NFSa murine fibrosarcomas with low-frequency electron paramagnetic resonance oximetry.

We have used very low-frequency electron paramagnetic resonance (EPR) oximetry to measure the change in oxygen concentration (delta pO2) due to change in breathing atmosphere in FSa and NFSa fibrosarcomas implanted in the legs of C3H mice infused with perfluoro-octylbromine (PFOB). Measurements in each tumor were made before and after the administration of the high-density (47% v/v) perfluorocarbon PFOB, perflubron (Alliance Pharmaceutical Corporation, San Diego, CA). Measurements in each tumor were also made, after the administration of the PFOB, both before (PFOB/air) and after the administration of carbogen (95% O2 + 5% CO2, PFOB/carbogen). Large changes (delta p02) relative to PFOB/air oxygenation were seen with the administration of PFOB/carbogen. No significant difference in oxygen concentration was seen between air-breathing mice with and without PFOB. The mean delta pO2 for FSa tumors was 13 +/- 6 torr, while the mean for NFSa fibrosarcomas was 28 +/- 7 torr. There were such large intertumor differences that the trend toward a smaller change in the more hypoxic FSa tumors was not significant (P = 0.13). This paper describes a novel method of measuring differences in oxygenation in tumor tissues. The results of such measurements indicate large differences in pO2 response to different breathing atmospheres in PFOB-infused tumors of similar histology. The intertumor delta pO2 differences may correlate with differences in radiation response.

Animals↗
PubMed1995

In situ detection, by spin trapping, of hydroxyl radical markers produced from ionizing radiation in the tumor of a living mouse.

Hydroxyl radicals are thought to be responsible for the toxicity associated with ionizing radiation in tissues. Measurements of hydroxyl radicals generated by ionizing radiation in cellular systems have failed thus far to elucidate higher-level homeostatic responses to this and other reactive oxygen species. Careful assessment of prior indirect hydroxyl radical assays in living tissues indicates that they are prone to a variety of artifacts, making all but the most qualitative relationships difficult to establish. This paper describes the detection of hydroxyl radicals produced during radiation in the leg tumor of a living mouse, where the free radicals evolve; detection uses low-frequency electron paramagnetic resonance in combination with in vivo spin trapping. To our knowledge, this is the first report of such a direct measurement of free radical production in the tissues of a living animals.

Animals↗
PubMed1995

Subaortic left ventricular pseudoaneurysm of obscure origin.

Subaortic pseudoaneurysms of the left ventricle are rare acquired cardiac defects. They are usually associated with previous valve surgery, trauma, or aortic valve endocarditis. We describe the appearance of subaortic pseudoaneurysm 10 years after left heart catheterization in a patient with both aortic stenosis and regurgitation. The differential diagnosis of such lesions is presented.

Aneurysm, False↗
PubMed1995

"Kissing-balloon" technique for abdominal aorta angioplasty. Initial results and long term outcome.

We evaluated results after angioplasty of the distal abdominal aorta using "kissing-balloon" technique. MATERIALS AND METHODS. From 1981 through 1993, 14 patients (12 women and 2 men, average age 52.4 years), underwent balloon angioplasty of the distal segment of the abdominal aorta. In 8 patients stenosis involved one or both iliac arteries as well. In all cases double balloon technique was used. Follow-up was based on clinical, angiographical and duplex scanning examinations. RESULTS. The initial success rate was 85% (12/14). In one case there was residual stenosis of 20% (redilated successfully 1 month later), and in one case there was acute thrombosis of the right iliac artery (successfully relieved surgically). Long-term follow-up (6-143 months) showed good patency of the dilated segment in all patients (including patients that initially failed). At follow-up, all patients were asymptomatic. CONCLUSION. Dilatation of the distal abdominal aorta using "kissing-balloon" technique is a safe and efficient modality of treatment, with acceptable initial and excellent long-term results.

Adult↗
PubMed1994

Oxymetry deep in tissues with low-frequency electron paramagnetic resonance.

We have measured the oxygen concentration in the body water of murine FSa and NFSa fibrosarcomas using a new method for quantitative oxygen concentration determination deep in the tissues of a living animal. The measurement uses unusually low-frequency electron paramagnetic spectroscopy sensitive to substrate 7 cm deep in tissue, partially deuterated spin probes (spin labels of molecular mass 195, approximating that of glucose) whose distribution compartment can be targeted with facile adduct substitution, and novel analytic techniques. We show that the water-compartment oxygen concentration of the tumors decreases as the tumor size increases and also shows a trend to decrease as radiobiologic hypoxia increases. An oxymetric spectral image of the tumor is presented. The technique will improve with larger human tissue samples. It provides the potential to quantitatively assess tissue hypoxia in ischemic or preischemic states in stroke and myocardial infarction. It will allow direct assessment of tumor hypoxia to determine the usefulness of radiation and chemotherapy adjuvants directed to hypoxic cell compartments.

Animals↗
PubMed1991

[Surgical treatment of diffuse coronary disease].

In order to obtain an idea on contemporary opportunities of surgical treatment of diffuse coronary disease the authors compared the results of surgery in 103 patients whose finding called for endarterectomy and bridging of at least one coronary artery (KEA) with the results in 220 patients where it was possible to overcome all significant changes by coronary bypasses only (KBP). Patients in group KEA had more infarctions before operation than patients in group KBP. Diffuse changes of the coronary arteries were found only in patients in group KEA. All patients were operated with extracorporeal circulation and local cooling of the myocardium. Surgery took longer in patients of group KEA than in group KBP. Early mortality was higher in group KEA--4.8% than in group KBP--0.9%. This difference was not statistically significant. Early morbidity in group KEA did not differ, from the morbidity in group KBP. Using effective peroperative protection of the myocardium by local cooling, the risk of KEA is only insignificantly higher than the risk of KBP. KEA makes safe and effective revascularization of the heart muscle in patients with diffuse coronary disease possible.

Coronary Angiography↗
PubMed1991

Use of a low-frequency ESR spectrometer: implications for spin-trapping free radicals, in situ.

We have adapted the low-frequency ESR spectrometer, designed and built by H.J. Halpern, to the physiologic needs of organ preparations operating at 250 MHz. Initial studies have allowed us to detect nitroxides in an isolated perfused heart. These in situ measurements were made with nitroxides specifically designed to mimic the lipophilic nature of 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and 2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxyl (DMPO-OH). These spin labels provided information about the influence of dynamic factors of the heart, such as flow rate, different cell populations and unequal distribution between compartments on our ability to conduct and interpret spin trapping experiments. They also clarified the sacrifice in sensitivity involved in operating at the lower frequencies. To deal with this later problem, we have increased the sensitivity of the spin trapping method by synthesizing a family of 15N- and deuterium-containing DMPO analogs and by determining their ability to spin trap free radicals generated by the model superoxide system of xanthine/xanthine oxidase. Finally, since activated neutrophils are one of the few cells known to generate free radicals as part of their physiologic function, we used these phagocytic cells, as a source of superoxide.

Animals↗