粗、细粒径花岗岩冻融损伤机理及其演化规律

通过粗、细两种颗粒花岗岩的冻融循环试验和岩石力学试验,研究了不同粒径岩石的冻融循环作用对岩石物理力学特性的影响.利用核磁共振技术对冻融循环前后的岩样进行检测,得到了横向弛豫时间谱的变化和岩样核磁共振成像,分析了岩样在冻融前后的孔隙度变化、空隙结构及分布的演化特性等.采用宏观唯象损伤理论和自洽理论对不同粒径花岗岩在冻融条件下的宏、细观损伤演化规律进行了分析.研究发现在冻融循环作用下,岩石内部的孔隙逐渐增多,不断造成岩石的强度损失;损伤模型的计算值与实际相符,但不同损伤理论对花岗岩损伤程度趋势变化的反应存在差异;细颗粒花岗岩呈现出较高冻融耐久性.     

Influence of macrophage-derived apolipoprotein E on plasma lipoprotein distribution of apolipoprotein A-I in apolipoprotein E-deficient mice

Two-dimensional multiple-quantum magic angle spinning (MQMAS) NMR and MAS NMR of 11B at various magnetic fields, were applied to elucidate the structure of vitreous (glassy) boron trioxide (v-B2O3), vitreous boron trisulfide (v-B2S3) and crystalline boron trisulfide (c-B2S3). These techniques, when combined with computer simulations of the resulting spectra, provide the isotropic chemical shifts and the quadrupole parameters, as well as a quantitative measure of the intensities of various boron resonances. The MAS NMR of v-B2O3 produced overlapping anisotropic lineshapes corresponding to the -1/2<-->1/2 transition in two distinct types of BO3 units with 3(+/-0.08):] intensity ratio. A combination of MAS and the multiple-quantum method resulted in a better resolved, isotropic 11B spectrum of v-B2O3. A remarkable enhancement of resolution of the MQMAS NMR proved instrumental in finding and identifying various impurities present in v-B2S3 and c-B2S3. In addition to the resonances from boron in two types of BS3 groups, four other structural units, BOS2, BO2S, BO3 and BS4, were elucidated from the spectra of vitreous and crystalline samples. The effects of various experimental parameters, such as the magnitude of the B0 and B1 fields, on the resolution of the MAS and MQMAS techniques are also shown.     

29Si CP/MAS NMR of phosphorus-bearing organosilicon compounds

While liquid-state 29Si NMR of phosphorus-bearing organosilicon compounds with more than one phosphorus per molecule can take advantage of the presence of J-coupling nJ(31P29Si) for purposes of structural assignment from J-coupling patterns, conventional 29Si CP/MAS spectra of such molecular solids do not reveal structural details in a straightforward manner. For such compounds it is necessary to obtain 29Si CP/MAS spectra under conditions of simultaneous 1H- and 31P-high power decoupling in order to derive reliable 29Si chemical shift information. 29Si CP/MAS NMR spectra, obtained with and without 31P high power decoupling during the acquisition time, of several organosilicon compounds containing SixPy (x = 1-10, y = 1-10) moieties are reported.     

Magic angle spinning NMR of the protonated retinylidene Schiff base nitrogen in rhodopsin: expression of 15N-lysine- and 13C-glycine-labeled opsin in a stable cell line

The apoprotein corresponding to the mammalian photoreceptor rhodopsin has been expressed by using suspension cultures of HEK293S cells in defined media that contained 6-15N-lysine and 2-13C-glycine. Typical yields were 1.5-1.8 mg/liter. Incorporation of 6-15N-lysine was quantitative, whereas that of 2-13C-glycine was about 60%. The rhodopsin pigment formed by binding of 11-cis retinal was spectrally indistinguishable from native bovine rhodopsin. Magic angle spinning (MAS) NMR spectra of labeled rhodopsin were obtained after its incorporation into liposomes. The 15N resonance corresponding to the protonated retinylidene Schiff base nitrogen was observed at 156.8 ppm in the MAS spectrum of 6-15N-lysine-labeled rhodopsin. This chemical shift corresponds to an effective Schiff base-counterion distance of greater than 4 A, consistent with structural water in the binding site hydrogen bonded with the Schiff base nitrogen and the Glu-113 counterion. The present study demonstrates that structural studies of rhodopsin and other G protein-coupled receptors by using MAS NMR are feasible.     

Altered presynaptic protein NACP is associated with plaque formation and neurodegeneration in Alzheimer''s disease

BACKGROUND: When perfused neonatal brain slices are studied ex vivo with nuclear magnetic resonance (NMR) spectroscopy, it is possible to use 31P detection to monitor levels of intracellular adenosine triphosphate (ATP), cytosolic pH, and other high-energy phosphates and 1H detection to monitor lactate and glutamate. Adult brain slices of high metabolic integrity are more difficult to obtain for such studies, because the adult cranium is thicker, and postdecapitation revival time is shorter. A common clinical anesthesia phenomenon--loss of temperature regulation during anesthesia, with surface cooling and deep hypothermia, was used to obtain high-quality adult rat cerebrocortical slices for NMR studies. METHODS: Spontaneously breathing adult rats (350 g), anesthetized with isoflurane in a chamber, were packed in ice and cooled until rectal temperatures decreased to approximately 30 degrees C. An intraaortic injection of heparinized saline at 4 degrees C further cooled the brain to approximately 18 degrees C. Slices were obtained and then recovered at 37 degrees C in oxygenated medium. Interleaved 31P/1H NMR spectra were acquired continually before, during, and after 20 min of no-flow hypoxia (PO2 approximately 0 mmHg). Histologic (Nissl stain) measurements were made from random slices removed at different times in the protocol. Three types of pretreatment were compared in no-flow hypoxia studies. The treatments were: (1) hyperoxia; (2) hypercapnia (50% CO2); and (3) hypoxia, which was accomplished by washing the slices with perfusate equilibrated with 100% N2 and maintaining a 100% N2 gas flow in the air space above the perfusate. RESULTS: During hyperoxia, 31P NMR metabolite ratios were identical to those seen in vivo in adult brains, except that, in vitro, the Pi peak was slightly larger than in vivo. A lactate peak was seen in in vitro 1H spectra of slices after metabolic recovery from decapitation, although lactate is barely detectable in vivo in healthy brains. The in vitro lactate peak was attributed to a small population of metabolically impaired cells in an injury layer at the cut edge. NMR spectral resolution from the solenoidal coil exceeded that obtained in vivo in surface coil experiments. Phosphocreatine and ATP became undetectable during oxygen deprivation, which also caused a three- to sixfold increase in the ratio of lactate to N-acetyl-aspartate. Within experimental error, all metabolite concentrations except pHi recovered to control values within 2 h after oxygen restoration. Nissl-stained sections suggested that pretreatment with hypercapnia protected neurons from cell swelling during the brief period of no-flow oxygen deprivation. CONCLUSIONS: Perfused, respiring adult brain slices having intact metabolic function can be obtained for NMR spectroscopy studies. Such studies have higher spectral resolution than can be obtained in vivo. During such NMR experiments, one can deliver drugs or molecular probes to brain cells and obtain brain tissue specimens for histologic and immunochemical measures of injury. Important ex vivo NMR spectroscopy studies that are difficult or impossible to perform in vivo are feasible in this model.     

High-resolution mono- and multidimensional magic angle spinning 1H nuclear magnetic resonance of membrane peptides in nondeuterated lipid membranes and H2O

High-speed (14 kHz) solid-state magic angle spinning (MAS) 1H NMR has been applied to several membrane peptides incorporated into nondeuterated dilauroyl or dimyristoylphosphatidylcholine membranes suspended in H2O. It is shown that solvent suppression methods derived from solution NMR, such as presaturation or jump-return, can be used to reduce water resonance, even at relatively high water content. In addition, regioselective excitation of 1H peptide resonances promotes an efficient suppression of lipid resonances, even in cases where these are initially two orders of magnitude more intense. As a consequence, 1H MAS spectra of the peptide low-field region are obtained without interference from water and lipid signals. These display resonances from amide and other exchangeable 1H as well as from aromatic nonexchangeable 1H. The spectral resolution depends on the specific types of resonance and membrane peptide. For small amphiphilic or hydrophobic oligopeptides, resolution of most individual amide resonance is achieved, whereas for the transmembrane peptide gramicidin A, an unresolved amide spectrum is obtained. Partial resolution of aromatic 1H occurs in all cases. Multidimensional 1H-MAS spectra of membrane peptides can also be obtained by using water suppression and regioselective excitation. For gramicidin A, F2-regioselective 2D nuclear Overhauser effect spectroscopy (NOESY) spectra are dominated by intermolecular through-space connectivities between peptide aromatic or formyl 1H and lipid 1H. These appear to be compatible with the known structure and topography of the gramicidin pore. On the other hand, for the amphiphilic peptide leucine-enkephalin, F2-regioselective NOESY spectra mostly display cross-peaks originating from though-space proximities of amide or aromatic 1H with themselves and with aliphatic 1H. F3-regioselective 3D NOESY-NOESY spectra can be used to obtain through-space correlations within aliphatic 1H. Such intrapeptide proximities should allow determination of the conformation of the peptide in membranes. It is suggested that high-speed MAS multidimensional 1H NMR of peptides in nondeuterated membranes and in H2O can be used for studies of both peptide structure and lipid-peptide interactions.     

1H/27Al TRAPDOR NMR studies on aluminum species in dealuminated zeolites

Aluminum species in several dealuminated zeolites (ultrastable HY, HZSM-5 and mordenite) were investigated in detail by means of the newly introduced 1H/27Al TRAPDOR method in combination with 27Al MAS NMR, and the quadrupole coupling constants (Q[CC]s) for aluminum atoms associated with these species were obtained. A signal at ca. 6.8 ppm, due to water molecules adsorbed on Lewis acid sites, was observed in the 1H MAS spectra for all the three zeolites. The TRAPDOR NMR provides direct evidence that there is a strong interaction between the adsorbed water molecules and the aluminum atoms of the Lewis-acid sites. The Q(CC) values for this aluminum species of 8.3, 6.7 and 11.3 MHz were determined from the TRAPDOR profiles for the ultrastable HY, HZSM-5 and mordenite zeolites, respectively. The Q(CC)s calculated from the TRAPDOR curves are usually larger than 10 MHz for both Bronsted-acid sites (SiOHAI) and non-framework aluminum species in the three zeolites. Three narrow peaks at 54, 30 and 0 ppm are separately superimposed on a broad hump in the 27Al MAS spectra of the three dehydrated zeolites, while the latter is associated with the 'NMR invisible' Al. The NMR experimental results suggest that the three kinds of aluminum species (non-framework aluminum species, Bronsted- and Lewis-acid sites) are all responsible for the resonance of the broad hump in dehydrated zeolites, which makes it difficult to explain the 27Al MAS spectra. Fortunately, the TRAPDOR NMR provides a direct method for individually studying different aluminum species with large Q(CC)s via their dipolar coupling to nearby proton nuclei.     

Classification of 1H MR spectra of biopsies from untreated and recurrent ovarian cancer using linear discriminant analysis

Proton (1H) magnetic resonance (MR) spectra of ex vivo biopsy samples of ovarian cancers provided biochemical information that was used to discriminate cancer from normal ovarian tissue. Possible differences present in intrinsically resistant tumors or changes in biochemistry after the induction of resistance were identified. Using multivariate techniques, in particular linear discriminant analysis (LDA), ovarian cancer was distinguished from normal ovarian tissue with a sensitivity of 100%, a specificity of 95% and an accuracy of 98%. Moreover, LDA was able to distinguish untreated ovarian cancer from recurrent ovarian cancer with a sensitivity of 92%, a specificity of 100%, and an accuracy of 97%; removal of the single "fuzzy" specimen increased the accuracy to 100%. Applications of this knowledge to in vivo measurements could lead to noninvasive diagnosis of ovarian cancer.     

Patterns of occurrence of second primary non-mammary malignancies in breast cancer patients: results from 1382 consecutive autopsies

In a previous study, we demonstrated the existence of a 3.2 +/- 0.2 ppm peak in the 1H NMR spectrum at 60 MHz from human pancreatic adenocarcinomas (Capan-1 cell) heterotransplanted into nude mice. This peak, which is not present in normal human pancreas, was attributed to enhanced membrane fluidity and/or or an increase in phospholipid turnover. The present study was designed to identify this signal by comparing the 1H NMR spectra recorded in vivo at 100 MHz from Capan-1 tumors, after suppression of the tissular water proton peak, to those recorded from normal pancreatic tissue, and to those recorded at 300 MHz from lipid extracts. The 1H NMR spectra at 100 MHz of the Capan-1 tumors in vivo exhibited three main peaks in the 3.2 +/- 0.2 ppm region: 1. A peak at 2.8 +/- 0.1 ppm from CH2 protons of the acyl chains of unsaturated phospholipids; 2. A peak at 3.2 +/- 0.1 ppm from the protons of the N(CH3)3 group of choline; and 3 A peak at 3.5 +/- 0.1 ppm attributed to GPC. The NMR 1H 300 MHz spectrum of phospholipid extracts of Capan-1 tumors displayed 12 principal resonances, of which only the N(CH3)3 peak of PC had a similar chemical shift to that observed at low resolution (3.2 +/- 0.2 ppm). This peak had a higher intensity in the xenografts than in normal human pancreatic tissue. HPLC analysis of the same lipid extracts from Capan-1 cells in culture, of tumors derived from these cells and from normal pancreas showed: 1. Identical concentrations of the different phospholipids from cancerous human pancreatic cells in vivo and in culture; and 2. A significantly higher level of PC in the extracts of normal human pancreatic tissue. The increase in intensity of the N(CH3)3 peak of PC in the Capan-1 tumors was not thought to be caused by an increase in PC concentration, but to a difference in conformation or mobility of the PC protons in the xenografts. The increase in relaxation time in cancerous tissue (from 60 to 125 ms) was also taken to be evidence in favor of a high mobility of protons.(ABSTRACT TRUNCATED AT 400 WORDS)     

Investigation on the cation location,structure and performances of rare earth-exchanged Y zeolite

A series of Y zeolites exchanged with different amount of cerium and lanthanum cations were investigated. Comprehensive routine analysis tools including X-ray photoelectron spectroscopy(XPS), X-ray fluorescence(XRF), X-ray diffraction(XRD) and Py-Fourier transform infrared spectroscopy(Py-FTIR) were used to identify the cation location, and the result was verified via XRD Rietveld study. The results revealed that almost all the RE cations in RE-4, most cations in RE-8 to RE-14 and part of cations in RE-16 were located in the sodalite cage. The Al~(IV)/(Al~V+Al~(VI)) values revealed by ~(27)Al MAS NMR spectra, the silicon aluminum ratio of the framework(SARF) values deduced from ~(29)Si MAS NMR spectra and XRD, and hydroxyl amount were reasonably in accordance with the location and content of rare earth cations. The hydrothermal stability derived from in situ XRD investigation and catalyst activity provided by micro-activity test manifested that samples RE-8 to RE-14 exhibited better performances than RE-4 and RE-16, among which RE-12 had the best properties. The phenomena were interpreted by the cation location and structural properties.     

1H MAS and 1H[23Na] double resonance NMR studies on the modification of surface hydroxyl groups of gamma-alumina by sodium

The modification of surface hydroxyl groups with sodium in a series of Na2CO3-gamma-Al2O3 catalysts was investigated as a function of both the Na2CO3 loading and the calcination temperature by means of 1H magic angle spinning (MAS) and 1H(23Na) spin-echo double resonance NMR techniques. The 1H NMR experiments revealed that sodium ions are homogeneously distributed over the alumina surface and closely coordinated with the surface hydroxyl groups. In the catalysts calcined at 250 degrees C, the acidic hydroxyl groups (with a chemical shift of 2.0 ppm) are preferentially associated with sodium ions at low Na2CO3 coverages (5 and 10%), while both the acidic and the basic (0 ppm) hydroxyl groups are accessible for sodium ions at high coverages (15 and 20%). The coordination causes a low-field shift of about 2 ppm in the 1H MAS spectra, and a broad signal at 4.5 ppm appears. It is interesting that the 4.5 ppm signal is completely suppressed in the 1H(23Na) MAS experiments, providing direct evidence that a strong interaction exists between adsorbed sodium ions and the surface hydroxyl groups. Increasing the calcination temperature to 450 degrees C results in preferential removal of the acidic hydroxyl groups, and only the most basic hydroxyl groups remain when the calcination temperature is raised to 600 degrees C. This is attributed to the formation of the coordinated species. [formula: see text] which enhances the acidity of the surface hydroxyl groups and prompts their dehydroxylation, especially at high calcination temperature. Correlation of the 1H MAS NMR results and catalytic activity measurements indicates that the basic hydroxyl groups are essential for the carbonyl sulfide hydrolysis reaction.     

A reproducible model of circulatory arrest and remote resuscitation in rats for NMR investigation

BACKGROUND AND PURPOSE: Because noninvasive physiological monitoring of cerebral blood flow, metabolic integrity, and brain ion and water homeostasis can now be accomplished with new, state-of-the-art MR spectroscopy and imaging techniques, it is appropriate to develop controllable and reproducible animal models that permit prolonged circulatory arrest and resuscitation in the magnet and also allow for studies of long-term survival and outcome. We have developed such a model in rats that involves minimal surgical preparations and can achieve resuscitation remotely within precisely controlled time. METHODS: Cardiac arrest was induced by asphyxiation, the duration of which ranged from 8 to 24 minutes. Resuscitation was achieved remotely by a slow, intra-aortic infusion of oxygenated blood (withdrawn either from the same rat before asphyxia or from a healthy donor rat) along with a resuscitation cocktail containing heparin (50 U/100 g), sodium bicarbonate (0.1 mEq/100 g), and epinephrine (4 micrograms/100 g). The body temperature was measured by a tympanic thermocouple probe and was controlled either by a heating pad (constant tympanic temperature = 37 degrees C) or by warm ambient air (constant air temperature = 37 degrees C). Interleaved 31P/1H nuclear magnetic resonance (NMR) spectroscopy was used in a selected group of rats to measure the cerebral metabolism before and during approximately 20 minutes of circulatory arrest and after resuscitation. RESULTS: The overall success rate of resuscitation, irrespective of the duration of cardiac arrest, was 82% (51 of 62). With a programmed infusion pump, the success rate was even higher (95%). The survival time for rats subjected to 15 and 19 minutes of asphyxia with core temperature tightly controlled was significantly lower than that with ambient temperature control (P < 0.001 and P < 0.04, respectively). High-quality NMR spectra can be obtained continuously without interference from the resuscitation effort. Final histological examinations taken 5 days after resuscitation showed typical neuronal damages, similar to those found in other global ischemia models. CONCLUSIONS: Because the no-flow time and resuscitation time can be precisely controlled, this outcome model is ideally suited for studies of ischemic and reperfusion injuries in the brain and possibly in other critical organs, permitting continuous assessment of long-term recovery and follow-up in the same animals.     

Iterative lineshape fitting of MAS NMR spectra: a tool to investigate homonuclear J coupling in isolated spin pairs

Possibilities and limitations of iterative lineshape fitting procedures of MAS NMR spectra of isolated homonuclear spin pairs, aiming at determination of magnitudes and orientations of the various interaction tensors, are explored. Requirements regarding experimental MAS NMR spectra as well as simulation and fitting procedures are discussed. Our examples chosen are the isolated 31P spin pairs in solid Na4P2O7. 10H2O, (1), and Cd(NO3)2. 2PPh3, (2). In both cases the two 31P chemical shielding tensors in the molecular unit are related by C2 symmetry, and determination of the orientations of these two tensors in the molecular frame is possible. In addition, aspects of homonuclear J coupling will be addressed. For 1, both magnitude and sign of 2Jiso(31P, 31P) (Jiso = -19.5 +/- 2.5 Hz) are obtained; for 2, (Jiso = +139 +/- 3 Hz) anisotropy of J with an orientation of the J-coupling tensor collinear, or nearly collinear, with the dipolar coupling tensor can be excluded, while absence or presence of anisotropy of J with any other relative orientation of the J-coupling tensor cannot be determined.     

Lactate turnover in rat glioma measured by in vivo nuclear magnetic resonance spectroscopy

Elevated tissue lactate concentrations typically found in tumors can be measured by in vivo nuclear magnetic resonance (NMR) spectroscopy. In this study, lactate turnover in rat C6 glioma was determined from in vivo 1H NMR measurements of [3-13C]lactate buildup during steady-state hyperglycemia with [1-13C]glucose. With this tumor model, a narrow range of values was observed for the first-order rate constant that describes lactate efflux, k2 = 0.043 +/- 0.007 (n = 12) SD min-1. For individual animals, the standard error in k2 was small (< 18%), which indicated that the NMR data fit the kinetic model well. Lactate measurements before and after infusing [1-13C]glucose showed that the majority of the tumor lactate pool was metabolically active. Signals from 13C-labeled glutamate in tumors were at least 10-fold smaller than the [3-13C]lactate signal, whereas spectra of the contralateral hemispheres revealed the expected labeling of [4-13C]glutamate, as well as [2-13C] and [3-13C]glutamate, which indicates that label cycled through the tricarboxylic acid cycle in the brain tissue. Lack of significant 13C labeling of glutamate was consistent with low respiratory metabolism in this glioma. It is concluded that lactate in rat C6 glioma is actively turning over and that the kinetics of lactate efflux can be quantified noninvasively by 1H NMR detection of 13C label. This noninvasive NMR approach may offer a valuable tool to help evaluate tumor growth and metabolic responsiveness to therapies.     

NMR-spectroscopic study of 207Pb in pure and barium diluted lead phosphate

31P and 207Pb MAS and static 207Pb NMR spectra of Pb3(PO4)2 and (Pb1-xBa(x))3(PO4)2 (x = 0.08, 0.12) are analysed. The resonances stemming from different cation sites are correlated with the corresponding local symmetry and their oxygen neighbours. The coordination sphere of Pb(1) consists of 12 oxygen atoms and shows characteristics of a near-axial arrangement with a comparatively low anisotropy. The tenfold coordinated Pb(2) atoms are located in a more anisotropically-coordinated site. In Pb-diluted lead phosphate crystals the Pb(2) positions appear to be preferentially substituted by barium. There are indications that the cation distributions in the diluted samples are inhomogeneous. Furthermore, 31P MAS NMR experiments indicate a single phosphorus position.     

Compartmental analysis of colonic transit reveals abnormalities in constipated patients with normal transit

Previous studies had concluded that the treadmill velocity-endurance time hyperbolic relationship for runs could be accuratly approached with a regression at condition that bouts of exercise duration were included between 2 and 12 min. This regression allows to calculate the critical speed (CS) defined as the slope of the regression of work (distance) on time to exhaustion, the anaerobic running capacity (ARC) being the intercept of this line (Monod & Scherrer, 1965). The purpose of this investigation was to give practical indication concerning the choice of the velocities in reference to the maximal aerobic speed (MAS i.e. the minimum speed which elicits VO2max). Subjects were fourteen elite male long-distance runners (27 +/- 3 years old; VO2max = 74.9 +/- 2.9 ml.kg-1.min-1, MAS = 22.4 +/- 0.8 km.h-1, CS = 19.3 +/- 0.7 km.h-1 and 86.2 +/- 1.5% MAS). tlim 100 values (321 +/- 83 s) were negatively correlated with MAS (r = -0.538, p < 0.05) and with CS (km.h-1) (r = -0.644, p < 0.01). tlim 90 (1015 +/- 266 s) was positively correlated with CS when expressed in % MAS (r = 0.645, p < 0.01) and not when expressed in km.h-1 (r = -0.095, P > 0.05). tlim 105 (176 +/- 40 s) only was correlated with ARC (r = 0.526, p < 0.05). These data demonstrate that running time to exhaustion at 100 and 105% of MAS in a homogeneous elite male long-distance runners group is inversely related to MAS. Moreover, tlim 90 is positively correlated with CS (%MAS) but neither with tlim 100 and 105 nor with maximal aerobic speed. So from a practical point of view, the velocities chosen to determine the critical speed, would be closed to the maximal aerobic speed (time to exhaustion around 6 min), taking into account that the tlim 105 is correlated with the anaerobic capacity, whereas tlim 90 is correlated with the critical speed.     

Lipoprotein lipase transport in plasma: role of muscle and adipose tissues in regulation of plasma lipoprotein lipase concentrations

Lipoprotein lipase (LPL) is synthesized in tissues involved in fatty acid metabolism such as muscle and adipose tissue. LPL is also found in the circulation, but is mostly lipolytically inactive. The proportion of active circulating LPL increases after a fatty meal. We investigated the release of active and inactive LPL from adipose tissue and muscle in the fasting and postprandial states. Arteriovenous concentration gradients of LPL across adipose tissue and forearm muscle were measured in male subjects before and after a fat-rich meal (n = 7) and before and during infusion of a triacylglycerol emulsion (Intralipid) (n = 6). Plasma LPL activity rose after the meal and more so during Intralipid infusion. Plasma LPL mass (>95% inactive LPL) increased after the meal but decreased after Intralipid infusion. In the fasting state (n = 13) muscle efflux of LPL activity was 0.263 +/- 0.098 mU/min per 100 ml of muscle tissue whereas there was an influx of LPL activity to adipose tissue of 0.085 +/- 0.100 mU/min per 100 g of adipose tissue (P < 0. 02 muscle vs. adipose tissue). Similarly in the postprandial state only muscle released LPL activity. Both tissues released LPL mass. In the fasting state efflux was 17.8 +/- 8.8 ng/min per 100 ml muscle and 55.2 +/- 21.3 ng/min per 100 g of adipose tissue (P < 0. 05 muscle vs. adipose tissue). Release of LPL, either active or inactive, was not correlated with levels of non-esterified fatty acids or plasma triacylglycerol. In conclusion, there is a substantial release of LPL from adipose tissue and muscle, most of which is inactive. A small proportion of active LPL seems to be redistributed from muscle to adipose tissue.     

Comparison of localized proton NMR signals of skeletal muscle and fat tissue in vivo: two lipid compartments in muscle tissue

In vivo 1H NMR spectra of small volumes-of-interest (VOI) were localized in human soleus muscle (8 ml) and compared with volume selective spectra of subcutaneous fat tissue and femoral yellow bone marrow (2 ml). All examinations were performed by the double spin echo (PRESS) localization technique. To provide comparability, spectra of different tissues were recorded using identical sequence timing. Clearly improved resolution of the lipid signals of muscle tissue was obtained using long echo times TE > 200 ms. The spectra of muscle tissue exhibit lipid signals that stem from two compartments with a difference of their resonance frequencies of about 0.2 ppm (Larmor frequency difference 12-13 Hz at 1.5 T). The existence of two fatty acid compartments is supported by measurements of the relaxation times and line shape analysis. Both compartments contain fatty acids or triglycerides with similar composition. Probably one compartment corresponds to fat cells within muscle tissue, the other compartment with lower Larmor frequency is located within muscle cells.     

Effects of storage and homogenization methods on the hepatic recovery of dextrans determined by size-exclusion chromatography

The effects of storage and homogenization methods on the analytical recovery of dextran macromolecules from rat livers were investigated using a high-performance size-exclusion chromatographic (HPSEC) method. Livers were collected from rats dosed with fluorescein-labeled dextrans with molecular weights of 150 or 70 kD. Subsequently, the livers were subjected to different methods to study the effects of the following parameters on the hepatic recovery of dextrans: storage method (freezing the livers before homogenization or freezing the homogenates); contents of the homogenization buffer (addition of 1% Triton X-100); and sample type (HPSEC analysis of the whole homogenate or the supernatant after centrifugation). It is shown that in the absence of Triton in the homogenization buffer, the hepatic recovery of dextrans is substantially affected by all the factors studied. However, in the presence of 1% Triton in the buffer, the hepatic recoveries were maximal and independent of the storage method or sample type. These studies suggest that for optimal recovery of dextran macromolecules from the liver, a sample preparation method capable of disrupting the subcellular membranes should be used.