Temperature dependent 15N NMR study of nitric oxide.

For the first time, 15N NMR data are obtained for a sample of nitric oxide at various temperatures. Spectra have been obtained in the liquid and solid state. In the former, the chemical shift as well as the spin-lattice relaxation time is characterized by the dynamic equilibrium of the dimerization reaction. Only the signal of the (NO)2 dimer is observed, while the paramagnetic NO has strong influences on the NMR parameter. From T1 relaxation and linewidth analysis a range for the correlation time of the exchange between monomer and dimer is obtained. SQUID measurements corroborate the NMR analysis.

"Hydration Shells" of CH2 Groups of ω-Amino Acids as Studied by Deuteron NMR Relaxation.

Hydration phenomena play a very important role in various processes, in particular in biological systems. Water molecules in aqueous solutions of organic compounds can be distributed among the following substructures: (i) hydration shells of hydrophilic functional groups of molecules, (ii) water in the environment of nonpolar moieties, and (iii) bulk water. Up to now, the values of hydration parameters suggested for the description of various solutions of organic compounds were not thoroughly analyzed in the aspect of the consideration of the total molecular composition. The temperature and concentration dependences of relaxation rates of water deuterons were studied in a wide range of concentration and temperature in aqueous (D2O) solutions of a set of ω-amino acids. Assuming the coordination number of the CH2 group equal to 7, which was determined from quantum-chemical calculations, it was found that the rotational correlation times of water molecules near the methylene group is 1.5-2 times greater than one for pure water. The average rotational mobility of water molecules in the hydration shells of hydrophilic groups of ω-amino acids is a bit slower than that in pure solvent at temperatures higher that 60 °C, but at lower temperatures, it is 0.8-1.0 of values of correlation times for bulk water. The technique suggested provides the basis for the characterization of different hydrophobic and hydrophilic species in the convenient terms of the rotational correlation times for the nearest water molecules.

Investigation of the spin-lattice relaxation of 13CO and 13CO2 adsorbed in the metal-organic frameworks Cu3(btc)2 and Cu(3-x)Zn(x)(btc)2.

The (13)C nuclear spin-lattice relaxation time of (13)CO and (13)CO2 molecules adsorbed in the metal-organic frameworks (MOFs) Cu2.97Zn0.03(btc)2 and Cu3(btc)2 is investigated over a wide range of temperatures at resonance frequencies of 75.468 and 188.62 MHz. In all cases a mono-exponential relaxation is observed, and the (13)C spin-lattice relaxation times (T1) reveal minima within the temperature range of the measurements and both frequencies. This allows us to carry out a more detailed analysis of the (13)C spin relaxation data and to consider the influence due to the spectral functions of the thermal motion. In a model-free discussion of the temperature dependence of the ratios T1 (T)∕T1,min we observe a motional mechanism that can be described by a single correlation time. In relation to the discussion of the relaxation mechanisms this can be understood in terms of dominating translational motion with mean jump distance being larger than the minimum distances between neighboring adsorption sites in the MOFs. A more detailed discussion of the jump-like motion observed here might be carried out on the basis of self-diffusion coefficients. From the present spin relaxation measurements activation energies for the local motion of the adsorbed molecules in the MOFs can be estimated to be 3.3 kJ∕mol and 2.2 kJ∕mol, for CO and CO2 molecules, respectively. Finally, our findings are compared with our recent results derived from the (13)C line shape analysis.

Slow motion of confined molecules: NMR and broadband dielectric spectroscopy investigations.

Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopy are used to investigate the dynamics of small glass-forming molecules confined to restricted geometries. Ethylene glycol molecules are embedded in the supercages of NaX zeolites. The combined application of NMR and broadband dielectric spectroscopy advances the understanding of the slowing down of the motion near the glass transition temperature of these confined molecules. In combination with nuclear spin relaxation and nuclear magnetic resonance spectroscopy, dielectric relaxation studies on glass forming molecules allow conclusions on the character of the motion. High resolution 1H magic angle spinning (MAS) NMR measurements not only enable a characterisation of the state of the adsorbed molecules via a chemical shift analysis. By means of an analysis of MAS spinning sidebands we may also estimate a correlation time the meaning of which will be discussed in comparison to the results of longitudinal proton spin relaxation measurements. In addition to broadband dielectric spectroscopy slow molecular motions of partially deuterated ethylene glycol adsorbed in NaX are studied by means of 2H NMR line-shape analysis.

Dielectric spectroscopy of nano BaTiO3 confined in MCM-41 mesoporous molecular sieve materials.

Dielectric properties of barium titanate (BaTiO3) particles, synthesized directly in the pores of MCM-41 materials, have been investigated in the frequency range from 20 Hz to 1 MHz for temperature intervals from 100 K to 500 K. The dielectric spectra of BaTiO3 confined in these molecular sieves were compared with the results obtained from the investigation of pure MCM-41 materials. Obtained results confirmed successful incorporation of BaTiO3 into porous matrix, but no phase transition from paraelectric to ferroelectric phase was observed due to the particle size being smaller than the critical size. Also, the overall dielectric response of investigated materials is strongly influenced by adsorbed water molecules.

Paragliding accidents with spinal cord injury: 10 years' experience at a single institution.

STUDY DESIGN: A retrospective analysis of 41 patients with spinal cord injury (SCI) after paragliding accidents. OBJECTIVE: To determine the lesioned pattern and prognostic radiologic factors for rehabilitation potential. SUMMARY OF BACKGROUND DATA: Paragliding accidents with SCI present a new injury pattern, dealt with in the current literature from a purely orthopedic, sports medicine, or insurance point of view. Few combinations of orthopedic and neurologic data are available. METHODS: Over a 10-year period, the case records of 41 patients with SCI caused by paragliding accidents were analyzed with regard to vertebral and other skeletal fractures, neurologic recovery (American Spine Injury Association score), and professional reintegration. RESULTS: Vertebral fractures peaked in the thoracolumbar region, with L1 most frequently (30%) affected. The levels of vertebral lesion and neurologic deficit differed in 32% of patients. Combination with lower-limb fractures was characteristic for paragliding SCI (P < 0.001); 93% of patients with initial bony occlusion of the spinal canal of <70% left the clinic ambulatory. CONCLUSION: Paragliding accidents with SCI show a characteristic injury pattern associated with a high recovery potential if the initial bony spinal canal occlusion is <70%. Half the patients will reintegrate in their former profession and place of employment.

1H MAS NMR investigations of ethylene glycol adsorbed in NaX.

The application of 1H MAS NMR allows a detailed study of the behavior of ethylene glycol adsorbed in NaX zeolites which may be used to understand the effect of confinement. Typical changes in the chemical shift values for the CH2 and OH groups were found which are very sensitive to interactions between the molecules and the internal surfaces. This allows clear differentiation between molecules within the zeolite cages and those adsorbed at the outer surface of the zeolite grains and also allows study of the dynamics of the different species. Selective 1H T1 measurements were carried out for various pore-filling degrees where large differences were found in the thermal mobility. It is shown that for the molecules inside the supercages, a dynamic heterogeneity occurs which may be related to the competing influences of molecule-internal surface interactions and molecule-molecule interactions within a network of intermolecular hydrogen bonds.

Prevention of bone loss in paraplegics over 2 years with alendronate.

UNLABELLED: To assess the effects of long-term treatment of bone loss with alendronate in a group of paraplegic men, 55 patients were evaluated in a prospective randomized controlled open label study that was 2 years in duration comparing alendronate and calcium with calcium alone. Bone loss was stopped at all cortical and trabecular infralesional sites (distal tibial epiphysis, tibial diaphysis, total hip) with alendronate 10 mg daily. INTRODUCTION: Bone loss after spinal cord injury (SCI) leads to increased fracture risk in the lower limbs of paraplegics. The aim of this study was to document long-term treatment of bone loss with alendronate in a group of paraplegic men with complete motor lesion after SCI. MATERIALS AND METHODS: Sixty-five men with complete motor post-traumatic medullary lesion between T1 and L2 with total motor and sensory loss (Frankel classification, stage A) or with total motor and partial sensory loss (Frankel classification, stage B) after SCI were included in this prospective randomized controlled open label study that was 2 years in duration. The patients were randomized to either the treatment group with alendronate 10 mg daily and elemental calcium 500 mg daily or to the control group with elemental calcium 500 mg daily alone. The primary endpoint was defined as the effect over 24 months of alendronate and calcium compared with calcium alone on the BMD values at the distal tibial epiphysis (as a surrogate for trabecular bone in the paralyzed zone). The secondary endpoints were changes in BMD at supra- and infralesional sites of measurement. Biochemical markers of bone turnover were assessed. RESULTS: Fifty-five subjects, 0.1-29.5 years post-SCI, completed the study over 24 months. BMD at the distal tibial epiphysis significantly decreased from baseline in the calcium group (-10.8 +/- 2.7% at 24 months, p < 0.001), whereas it remained stable in the alendronate plus calcium group (-2.0 +/- 2.9% at 24 months, p = not significant versus baseline), leading to a significant intergroup difference over time (p = 0.017). At the tibial diaphysis, similar significant results were observed. At the ultradistal radius and the radial shaft, BMD did not change significantly from baseline in either treatment group. At the total hip, BMD decreased significantly in the calcium group (-4.1 +/- 1.6%, p = 0.038) but remained stable in the alendronate plus calcium group (+0.43 +/- 1.2%), with a significant intergroup difference (p = 0.037). At the lumbar spine, BMD increased significantly (p < 0.0001) from baseline in both groups. Biochemical markers of bone resorption were significantly decreased with alendronate versus baseline and control. Alendronate and calcium were generally safe and well tolerated. CONCLUSIONS: In paraplegic men, SCI bone loss was stopped at all measured cortical and trabecular infralesional sites over 24 months with alendronate 10 mg daily.

Long-term changes in bone metabolism, bone mineral density, quantitative ultrasound parameters, and fracture incidence after spinal cord injury: a cross-sectional observational study in 100 paraplegic men.

To study the time course of demineralization and fracture incidence after spinal cord injury (SCI), 100 paraplegic men with complete motor loss were investigated in a cross-sectional study 3 months to 30 years after their traumatic SCI. Fracture history was assessed and verified using patients' files and X-rays. BMD of the lumbar spine (LS), femoral neck (FN), distal forearm (ultradistal part = UDR, 1/3 distal part = 1/3R), distal tibial diaphysis (TDIA), and distal tibial epiphysis (TEPI) was measured using DXA. Stiffness of the calcaneus (QUI.CALC), speed of sound of the tibia (SOS.TIB), and amplitude-dependent SOS across the proximal phalanges (adSOS.PHAL) were measured using QUS. Z-Scores of BMD and quantitative ultrasound (QUS) were plotted against time-since-injury and compared among four groups of paraplegics stratified according to time-since-injury (<1 year, stratum I; 1-9 years, stratum II; 10-19 years, stratum III; 20-29 years, stratum IV). Biochemical markers of bone turnover (deoxypyridinoline/creatinine (D-pyr/Cr), osteocalcin, alkaline phosphatase) and the main parameters of calcium phosphate metabolism were measured. Fifteen out of 98 paraplegics had sustained a total of 39 fragility fractures within 1,010 years of observation. All recorded fractures were fractures of the lower limbs, mean time to first fracture being 8.9 +/- 1.4 years. Fracture incidence increased with time-after-SCI, from 1% in the first 12 months to 4.6%/year in paraplegics since >20 years ( p<.01). The overall fracture incidence was 2.2%/year. Compared with nonfractured paraplegics, those with a fracture history had been injured for a longer time ( p<.01). Furthermore, they had lower Z-scores at FN, TEPI, and TDIA ( p<.01 to <.0001), the largest difference being observed at TDIA, compared with the nonfractured. At the lower limbs, BMD decreased with time at all sites ( r=.49 to.78, all p<.0001). At FN and TEPI, bone loss followed a log curve which leveled off between 1 to 3 years after injury. In contrast, Z-scores of TDIA continuously decreased even beyond 10 years after injury. LS BMD Z-score increased with time-since-SCI ( p<.05). Similarly to DXA, QUS allowed differentiation of early and rapid trabecular bone loss (QUI.CALC) vs slow and continuous cortical bone loss (SOS.TIB). Biochemical markers reflected a disproportion between highly elevated bone resorption and almost normal bone formation early after injury. Turnover declined following a log curve with time-after-SCI, however, D-pyr/Cr remained elevated in 30% of paraplegics injured >10 years. In paraplegic men early (trabecular) and persistent (cortical) bone loss occurs at the lower limbs and leads to an increasing fracture incidence with time-after-SCI.

Nontraumatic pancreatitis in spinal cord injury.

STUDY DESIGN: A retrospective analysis of 10 patients with pancreatitis after traumatic spinal cord injury. OBJECTIVES: To determine the conditions leading to nontraumatic pancreatitis in spinal cord injury. SUMMARY OF BACKGROUND DATA: Little is known in the literature about pancreatitis after spinal cord injury. A few authors suggest a multifactorial pathogenesis. METHODS: Over a 4-year period the case reports of 338 patients with traumatically caused SCI were reviewed concerning p-amylase and/or lipase elevations. Acute pancreatitis was defined as an elevation of p-amylase and/or lipase of more than three times the upper normal limit. RESULTS: Ten of 338 patients had p-amylase and/or lipase elevations three times higher than the upper normal limit. All 10 were male with a mean age of 40.4 years. The average onset time of acute pancreatitis was 16 +/- 5.5 days after trauma. The usual etiologic factors of acute pancreatitis such as obstructive, toxic, or traumatic events were excluded. CONCLUSION: The clinical recognition of acute pancreatitis in paraplegic and quadriplegic patients is hampered by diminished or lost visceral sensitivity and therefore is based on laboratory investigations. The current authors therefore hypothesize that acute pancreatitis in the setting of high-level spinal cord injury may result from a combination of locally mediated sphincter of Oddi dysfunction and vagal dominant innervation of the pancreatic gland in autonomic failure.