MR Diffusion Anisotropy Imaging of Spinal Cord Mechanical Compression and Injury on the Rat Model. In Vivo.

The aim of this study was the application of magnetic resonance diffusion anisotropy imaging (MR DAI) for assessment of spinal cord compression (SCC) and injury (SCI) in rats depending on the time course from the moment of injury. Twenty rats were used, divided into three groups (five with no surgical operation, five with laminectomy only and ten with SCI produced using a dynamic weight - drop model). MR DAI was performed four times (1, 24, 48 and 168 hours after surgery) at 4.7 T with diffusion gradients applied parallel and perpendicular to the spine. Diffusion parameters (lADC, tADC and AI) were calculated for defined regions of white and gray matter. Epidural hematoma which appeared after laminectomy compressed spinal cord and caused a decrease of apparent diffusion coefficient (ADC) values in GM and WM. SCI in WM produced a decrease of lADC and increase in tADC. In GM an increase in both lADC and tADC values after SCI was observed. MR DAI will disclose dynamic changes in water diffusion during the first days after spinal cord contusion.

Brains with different degrees of dysplasia show different patterns of neurodegenerative changes following pilocarpine-induced seizures. Histologic evidence of tissue damage correlated with MRI data.

OBJECTIVE: Brain dysplasias produced by irradiation with gamma rays at various stages of prenatal development cause different post-natal susceptibility to seizures. To detect possible determinants of this difference, patterns of degenerative changes in the dysplastic brains following pilocarpine-induced epilepsy were analysed. METHODS: Pregnant Wistar rats were exposed to a 1.0 Gy dose of gamma rays on gestation days 15 (E15) or 17 (E17). On post-natal day 60, their offspring received pilocarpine injections to evoke status epilepticus. Motor manifestations of seizure activity were observed continuously for 6 hours and rated. Six days following the status epilepticus, the rats were anesthetized and T(2)-weighted magnetic resonance (MR) images were obtained. Frontal sections of the brains were immunostained for immunoglobulins G (IgGs) to detect blood-brain barrier damage and IgG cell uptake and glial fibrillary acidic protein (GFAP) or S-100-beta protein to visualize astrocytes. Bandeiraea simplicifolia isolectin-B4 (BSI-B4) isolectin histochemistry was also performed to detect microglia/macrophages. RESULTS: Tissue damages within epileptic brains as observed by light microscopy generally reflected changes in magnetic resonance imaging (MRI) at similar locations. Brains of rats irradiated on E15 or E17 and showing epileptic symptoms at comparable intensity also displayed different distribution of the pathologic changes. Among other post-epileptic changes, in rats irradiated on E17 as well as controls, the laterodorsal and ventrolateral thalamic nuclei showed signs of severe degeneration. In rats irradiated on E15, the nuclei were free of such changes. CONCLUSIONS: The obtained data point to important differences in the pattern of propagation of epileptic activity in the dysplastic brains suffering from neuronal loss in functionally different structures.

Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain.

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.

Determination of pethidine in rabbit plasma by capillary gas chromatography.

A simple and fast gas chromatographic method for the determination of pethidine hydrochloride in rabbit plasma is described and validated. This method is an improvement on the GC method which uses a glass column, and was described previously by Koska et al. [Anaesth. Analg. 60 (1981) 8]. The samples were analysed by a GC 5890 HP system using Rtx-5, fused-silica capillary column linked to a nitrogen-phosphorus ionization detector. Lidocaine hydrochloride was used as the internal standard. Calibration curves were linear within the range 5-200 ng/ml. The limit of quantification was about 5 ng using a 1-ml biological sample and no interference was observed in the blank plasma. The mean recovery of the drug from plasma samples was 95.71+/-2.82%. This procedure turned out to be sensitive and convenient enough for the use in pharmacokinetic studies of pethidine.

CD investigations on conformation of H-X-(Pro)n-Y-OH peptides (X = Trp, Tyr; Y = Tyr, Met); models for intramolecular long range electron transfer.

Conformations of three series of peptides: H-Trp-(Pro)n-Tyr-OH (n = 1-5), H-Trp-(Pro)n-Met-OH (n = 1-3) and H-Tyr-(Pro)n-Met-OH (n = 1-3), used as models in studies on long range electron transfer through protein matrix, were investigated by CD spectroscopy in aqueous solution at pH 5.2 in the temperature range of 10 degrees C-90 degrees C. CD spectra of their component N- and C-terminal dipeptide and oligoproline fragments were also measured under similar conditions. In interpretation of the spectra the cis<-->trans equilibrium about X-Pro bonds was taken into account and CD spectra of Trp-Pro and Tyr-Pro chromophores in trans and cis configuration of the peptide bond were evaluated. The spectra of n = 3-5 peptides from the first series and those with n = 2-3 from the other two series exhibit a strong negative band in the 202-207 nm region, the strength of which is proportional to the number of Pro residues in the (Pro)n bridge, and characterized by a large temperature decrement. In view of close similarity between characteristics of this band and the 206 nm band of aqueous oligoproline peptides (n > or = 3), known to attain a left handed helical conformation similar to that of 3(1) helix of the all-trans poly-L-proline II, this band was attributed to a conformation of the latter type. H-Trp-(Pro)2-Tyr-OH does not form this conformation due to sterical interaction between the two bulky aromatic side chains. Conclusions drawn from analysis of the CD spectra are supported by 1H and 13CNMR data reported elsewhere.