Proton nuclear magnetic resonance studies on water structure in peritumoral edematous brain tissue

Comparative intermolecular cross-relaxation studies of human hemoglobin in red blood cells and bovine serum albumin in solution

Intermolecular cross-relaxation rate (CR) spectra [1/T(IS) (HDO) or 1/T(IS) (H(2) O) vs f(2) (ppm) profiles] for bovine serum albumin [BSA; molecular weight (MW), 66 kDa] solution, partially hydrolyzed BSA gel (BSA*gel) and packed human red blood cells (RBCs) with normal or unstable hemoglobin (Hb; MW, 65 kDa) were studied using f(2) irradiation ranging from - 100 to 100 ppm at γH(2) /2π of 250 Hz. The CR spectra for BSA*gel (pD 4.01, 0.10 M NaCl, 4.83 and 14.39%) exhibited different features in the off-resonance region (below - 2.00 and above 12.0 ppm) relative to that for BSA solution (pD 7.14, 0.10 M NaCl, 14.39%), indicating the association of BSA* molecules in the gel state. The CR spectrum for packed RBCs was compared with those for BSA*gel and BSA solution (14.39%) by correcting for differences in protein concentration. The corrected CR spectrum for packed normal RBCs in the off-resonance region was similar to that for BSA solution, indicating that the physical characteristics of Hb in normal RBCs may be in a solution-like state. Our results on normal RBCs were approximately consistent with the previously reported thermodynamic and hydrodynamic findings that Hb in RBCs and/or in concentrated solution seems to be in a suspension of hard scaled particles.

Comparative 1H NMR studies of saturation transfer in copolymer gels and mouse lenses

Saturation transfer in cross-linked copolymer gels and excised intact and perforating trauma-induced cataract mouse lenses (4- or 8-week-old) were studied using intermolecular cross-relaxation rates (1/T(IS)(H(2)O); 1/T(IS)), monitored with f(2)-irradiation at -8.79, -4.00, and 7.13 ppm (gammaH(2)/2pi approximately 69 Hz). [1] The 1/T(IS)(7.13 ppm) vs dry weight [W (%)] profiles for hydrophilic copolymer gels were far steeper than those for hydrophobic copolymer gels, indicating the participation of an amount of bound water and a number of copolymer hydroxyl groups in the saturation transfer process. In contrast, the 1/T(IS)(-8.79 ppm) vs W (%) profiles exhibited little difference between the hydrophilic and hydrophobic copolymer gels, indicating the major participation of molecular rigidity, i.e. W (%) in the saturation transfer process. [2] The 1/T(IS)(7.13 ppm) values for cataractous mouse lenses were larger than those for intact lenses, indicating the formation of large, immobile lens protein associates or aggregates containing a sufficient amount of bound water for the saturation transfer. [3] The 1/T(IS)(7.13 ppm) vs W (%) profiles for the hydrophilic copolymer gels exhibited similar characteristics to the intact and cataractous mouse lenses with regard to the saturation transfer process.

Saturation transfer in human red blood cells with normal and unstable hemoglobin

Saturation transfer phenomena from irradiated protein protons to observed water protons in packed human red blood cells (RBCs) with normal or unstable hemoglobin (Hb), i.e. Hb Yokohama and Hb Koeln, were studied using intermolecular cross-relaxation rates [CR; 1/T(IS)(H(2)O)], action spectra [[1-(I(infinity)/I(0))] vs f(2) (ppm), where I(0) and I(infinity) are the longitudinal magnetization of observed water protons before and after long-time f(2)-irradiation, respectively], CR spectra [CR vs f(2) (ppm)] and CR ratio vs f(2) (ppm) with f(2)-irradiation from -100 to 100 ppm at gammaH(2)/2pi of 69 or 250 Hz. RBCs (Hb Yokohama) exhibited many large Heinz bodies and strongly impaired filterability, while RBCs (Hb Koeln) showed few microscopically typical Heinz bodies and virtually normal filterability. However, increases in CR values for RBCs (Hb Koeln) and RBCs (Hb Yokohama), monitored by f(2)-irradiation below approximately -6 and above approximately 14 ppm, clearly indicated marked increases in association or aggregation of unstable Hb in RBCs compared with those in normal RBCs. CR values, monitored between approximately 0 and approximately 10 ppm, were related to not only association or aggregation of unstable Hb but also amounts of water in RBCs. Aggregation or association of unstable Hb exhibited greater effects on CR values compared with those of methemoglobin formation.

1H-NMR and raman studies on perforating trauma-induced cataract formation in a mouse lens

In order to provide new insight into the molecular mechanism of perforating trauma-induced cataract formation in an 8-week-old ddY mouse lens, we performed an in situ investigation into changes in the water-protein and/or protein-protein interactions by using 500 MHz (1)H-NMR spectroscopy, and into structural alterations in lens proteins by using Raman spectroscopy. Cross-relaxation times of water protons in the perforated opaque lens were considerably shorter than those in the intact transparent lens, whereas there was no significant difference in water content, suggesting a drastic change in water-protein and protein-protein interactions in the perforated lens. In addition, there was no significant difference in the intensity ratios of several key Raman bands between intact and perforated lenses, indicating that no significant local and overall conformational changes in lens protein itself occur in the perforated lens. The present (1)H-NMR and Raman results lead us to the conclusion that changes leading to lens opacification in the perforating trauma-induced cataract appear to involve the rapid formation of immobile large lens protein aggregates without formation of intra- and intermolecular disulfide linkages, and rapid increase in a fraction of bound water associated with large protein aggregates.

Effect of a gadodiamide contrast agent on the reliability of brain tissue T1 measurements

To determine whether brain spin-lattice relaxation time (T1) can routinely be measured after contrast-agent injection, we measured T1 by a precise and accurate inversion-recovery (PAIR) method in five brain tumor patients, before and again after contrast-agent injection. The T1 in at least 20 regions of interest (ROIs) was measured in each patient, avoiding areas of contrast enhancement visible by conventional MR imaging. Contrast-agent injection reduced T1 in 51 regions of interest in white matter by less than 1% (not significant), and in 50 regions of interest in gray matter by less than 2% (p = 0.001). Pixel-by-pixel plots demonstrate that T1 is reduced substantially in extra-parenchymal tissues, but not in brain tissues. Therefore, T1 mapping with the precise and accurate inversion-recovery method can routinely be done after contrast injection. Our results suggest that the precise and accurate inversion-recovery method is not sensitive to the T1 of blood in the presence of an intact blood-brain barrier, although a substantial T1 reduction does occur in the absence of a blood-brain barrier.

Magnetization transfer imaging of bone marrow with and without fat suppression

RATIONALE AND OBJECTIVES

To assess magnetization transfer (MT) ratios of bone marrow at magnetic resonance (MR) imaging performed with and without fat suppression.

MATERIALS AND METHODS

The authors performed MR imaging in 30 regions of normal bone marrow in 10 subjects by using four types of gradient-echo sequences: a combination of MT and fat-suppression techniques, only the fat-suppression technique, only the MT technique, and without MT or fat-suppression techniques. MT ratios of marrow obtained with and without the fat-suppression technique were quantitatively compared.

RESULTS

The average MT ratio of marrow with fat suppression was significantly higher than that without fat suppression (P < .01).

CONCLUSION

Because bone marrow includes both water and fat, the MT ratio of marrow was underestimated when MT imaging was performed without fat suppression. A fat-suppression technique should be used.

Methodological considerations of intracerebral microdialysis in pharmacokinetic studies on drug transport across the blood-brain barrier

For the study of the pharmacokinetics of drugs in the brain a number of in vivo techniques is available, including autoradiography, imaging techniques, cerebrospinal fluid sampling and in vivo voltammetry, which all have their specific advantages and limitations. Intracerebral microdialysis is a relatively new in vivo technique. It permits monitoring of local concentrations of drugs and metabolites at specific sites in the brain which makes it an attractive tool for pharmacokinetic research. In the use of this technique a number of factors should be considered. These include: type of probe, surgical trauma, post-surgery interval, perfusion flow rate, as well as composition and temperature of the perfusion medium. In particular in studies on drug transport across the blood-brain barrier (BBB), effects of insertion of the probe on BBB functionality is important. It appears that BBB functionality is not significantly affected if surgical and experimental conditions are well-controlled. The relationship between dialysate concentrations and those in the extracellular fluid of the periprobe tissue, the recovery of the drug, depends on periprobe processes governing the actual concentration of the drug at that site. These include extracellular-microvascular exchange, metabolism, and diffusion of the drug. Several methods have been proposed to determine recovery values. In particular the no net flux method and the extended no net flux method are useful in practice. Several microdialysis studies on BBB transport of drugs are presented showing that intracerebral microdialysis is capable to assess local BBB transport profiles. Compared with other in vivo techniques, intracerebral microdialysis is the only (affordable) technique that offers the possibility to monitor local BBB transport of drugs in unanaesthetized animals, under physiological and pathological conditions.

Comparative 1H-NMR studies on the physical state of water in soft contact lens and mouse lens

The physical state of water in mouse lenses (2-, 4- or 8-wk-old) and soft contact lenses (SCLs, water content from 18.4 to 79.2%) were studied by measuring spin-lattice relaxation times (T1) and apparent intermolecular cross-relaxation times (TIS) from irradiated protein or polymer protons to water protons, using 360 MHz 1H-NMR spectrometer at 25 degrees C. (1) 1/T1 values of SCLs increased gradually with increasing dry weight (W(%)). 1/TIS values of SCLs were approximately zero at W of 20.8 and 26.8%, increased gradually from 26.8% and then steeply above approximately 50%. (2) A plot of 1/T1 vs. W(%) of mouse lenses was almost equal to that of SCLs. However, a plot of 1/TIS vs. W(%) was an approximately straight line with the intercept at W of 23% and with the slope which is almost equal to that of SCLs above W of approximately 50%. The plot of 1/TIS vs. W(%) of mouse lenses might indicate the significant change in the physical state of water and/or protein-water interactions above W of 23%.

Successful extracorporeal membrane oxygenation (ECMO) support for fulminant community-acquired pneumococcal pneumonia

A case is described of fulminant community-acquired pneumococcal pneumonia in a 16 year old girl with no previous history of respiratory disease or any predisposing factors. She required extracorporeal membrane oxygenation (ECMO) until the diagnosis could be made and appropriate antibiotic therapy established.

In vivo tissue characterization of human brain by chisquares parameter maps: multiparameter proton T2-relaxation analysis

The heterogeneous proton MR relaxation decay process in human brain has been investigated by performing region-of-interest and pixel-by-pixel calculations on the multiecho MR images with different repetition times (TR) of human brains using a clinical 1.5-T whole-body superconducting MR scanner. Based on the monoexponential, biexponential, and continuous gaussian distribution relaxation models, first-order proton relaxation parameters (proton density, T1 and T2) and higher-order transverse proton relaxation parameters (T2-long, T2-short, T2-long fraction, T2-average, and T2-distribution width) were calculated. On the basis of an F test (p < .01), the statistical significance of the higher-order (biexponential and distribution) fits over the monoexponential fit was evaluated. Here, a significant improvement in the biexponential fit was found for some of the regions containing the ventricular cerebrospinal fluid (CSF) (T2-long = 2780 +/- 570 ms; T2-short = 159 +/- 42 ms; T2-long fraction = 0.51 +/- 0.08 ms) due to the partial volume effect but not for most of the white matter (WM). On the other hand, an improvement of fit to WM was obtained when distribution (T2-average = 80 +/- 8 ms; T2-distribution half-width = 21 +/- 4 ms) as opposed to monoexponential (T2 = 89 +/- 10 ms) fit was used. As internal controls, tubes of CuSO4 solution (T2 = 1293 +/- 128 ms) and agarose gel (T2 = 111 +/- 10 ms) which have similar T2 values as the CSF and WM of the brain, respectively, were attached to the human head and imaged concomitantly. No significance improvements in either the biexponential or distribution fits over the monoexponential fit were found for all the controls. In addition to the first-order and higher-order relaxation parameter maps, the monoexponential chisquares, as well as the chisquares ratio (chisquares of the monoexponential fit divided by that of the higher-order fit), maps were also generated. Unlike the higher-order T2-relaxation parameter maps, the chisquares parameter maps required no selection of any predetermined statistical confidence level. Therefore, these chisquares parameter maps provided a somewhat nonsubjective spatial profile of the heterogeneous transverse relaxation process in the brain. Our results led us to propose that the use of chisquares parameter maps, together with the first-and higher-order relaxation parameter maps, may further improve the in vivo tissue characterization capability of MRI in future clinical diagnosis and staging of intracranial diseases.

MRI and MRS studies on the time course of rat brain lesions and the effect of drug treatment: volume quantification and characterization of tissue heterogeneity by parameter selection

Magnetic resonance imaging has been used to follow the time course of lesions induced in the rat brain as an animal model for characterization of the volume of the lesion. The dispersion in spin-spin relaxation has been used to characterize the nature of the brain lesion. Parameter selective estimation of T2, quantitative determination of the lesion size and volume selective in vivo proton spectroscopy have been employed for the purpose. The work has been carried out on rats which were subject to lesioning by ibotenic acid as a model for excitotoxicity and also on rats which received doses of ibotenic acid and subsequent doses of the NMDA antagonist drug MK 801 (dizocilpine). The time course of the progress of the lesions in untreated animals and the effect of neuroprotection by MK 801 was continuously monitored in all test animals. Further, a relatively new inhalation anesthetic agent, isoflurane, has been employed. A more logical and semiquantitative T2 bandwidth demarkation useful in distinguishing different degrees of lesioning from the onset and up to the 'edema' stage through penumbra (mild lesion), medium degree lesion and severe lesion has been proposed.

Cerebral oedema associated with WHO-I, WHO-II, and WHO-III-meningiomas: correlation of clinical, computed tomographic, operative and histological findings

Meningiomas were studied in 60 patients retrospectively. Clinical, operative and histological findings were correlated with the occurrence and extension of peritumoural oedema as measured by computerized tomography. A relationship was found between both oedema and seizures and between oedema and tumour location. No relationship between tumour size, arachnoid breaching, WHO-grade or tumour vascularity and oedema was detected. In four patients with severe pre-operative oedema, cerebral signs and symptoms persisted despite uncomplicated tumour removal. The present study shows that peritumoural oedema is not only epileptogenic but that it can also cause irreversible cerebral damage as well. Since this study purports to demonstrate that meningiomas with intact leptomeninges can show severe peritumoural oedema, the blood barrier breakdown theory cannot be considered as the only aetiological factor.

Quantitation of non-Einstein diffusion behavior of water in biological tissues by proton MR diffusion imaging: synthetic image calculations

The non-Einstein diffusion behavior of water in a model biological tissue system, intact duck embryos, has been investigated by the use of an in vivo proton pulsed-gradient spin-echo (PGSE) MR imaging technique. Multiple-frame MR images of the intact duck embryos and control solution (0.5 mM CuSO4 doped water) were acquired systematically at different diffusion times and strengths of the diffusion-sensitizing magnetic field gradients of the PGSE sequence. These raw images were then used to generate various dynamic (self-diffusion coefficient) and structural (fractal, residual attenuation, and compartment fraction) diffusion parameter maps of water in the imaging objects on the basis of different Einstein and higher order (non-Brownian, Residual, and 2-compartment) diffusion models. The self-diffusion coefficients of the body tissues of the embryos obtained from all diffusion models were significantly lower than those of the surrounding embryonic fluid. The structural diffusion parameter maps obtained from the higher order diffusion models revealed that water molecules exhibited either non-Brownian, restricted, or compartmentalized diffusion behavior in the embryonic tissues, but Einstein or Brownian diffusion behavior in the embryonic fluid and control solution. The diffusion parameter maps, both dynamic and structural, were found to provide much better contrasts than the conventional relaxation time (T1, T2, and biexponential T2) maps in separating the tissues from the surrounding embryonic fluid in the duck embryos. The mathematical models and procedures for generating the dynamic and structural diffusion parameter maps are also presented in this paper.