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At least 559 records · Page 31Linked to original sources
PubMed1984

Post mortem changes in skeletal muscle proton spin-lattice relaxation times.

A previously published report indicated that there are early post mortem changes in the pulsed NMR proton spin-lattice relaxation time (T1) of skeletal muscle which must be taken into account in in vitro tissue analysis. We re-examined this subject. When T1 measurements were done by allowing the signal intensity to decay over two orders of magnitude from the original intensity, the T1 decay curves showed more than a single exponential relaxation time component as reported earlier. However, when T1 measurements were done by allowing signal intensity to decay to about one order of magnitude from the original intensity only a single exponential relaxation time component was found. We postulate that the latter method gives the average T1 value of the various macroscopic tissue components present and that this method gives a representative T1 value for the entire tissue. Using data obtained in this manner we could not find significant post mortem changes in the muscle T1 relaxation times during the first four hours but found change at a later time.

Animals↗
PubMed1997

Degeneration of the pyramidal tracts in patients with amyotrophic lateral sclerosis. A premortem and postmortem magnetic resonance imaging study.

To investigate focal hyperintensity in the internal capsule (IC) on magnetic resonance images (MRIs) and its clinical significance, 80 patients with amyotrophic lateral sclerosis (ALS) and 80 sex- and age-matched normal control subjects were studied. On T2-weighted images, hyperintense foci were found in the posterior part of the posterior limb (PL) of the IC in 41 (51%) of 80 control subjects. However, no subject showed increased signal intensities on proton density-weighted images. Hyperintense foci were also observed in the posterior part of the PL of the IC on T2-weighted images in 52 (65%) of 80 ALS patients and on proton density-weighted images in 26 (65%) of 40 ALS patients; the abnormally intense foci were seen at the same anatomical location in the IC as those in the normal control subjects. On postmortem MRI, the abnormally intense foci were found in the posterior part of the PL of the IC in the formalin-fixed brains from 9 ALS patients. Three normal control subjects did not show signal intensity changes on postmortem MRI. On histological examination of 9 ALS brains, distinct myelin pallor and gliosis were found in the posterior third of the PL of the IC. Proton density-weighted images appear to be useful to distinguish neuropathological changes in the corticospinal tract of ALS patients.

Adult↗
PubMed1997

Postmortem findings in suicide victims. Implications for in vivo imaging studies.

Alterations in serotonergic and noradrenergic receptor binding in membrane homogenates from the brain of suicide victims suggest a biological substrate for the vulnerability to commit suicide. We and others have employed high-resolution quantitative autoradiography of full coronal sections of the prefrontal cortex to map the locus of maximal change in receptor binding. We found alterations in binding to the serotonin transporter, the 5-HT1A, and the 5-HT2A receptors primarily in the ventral and ventrolateral prefrontal cortex of suicide victims. Importantly, these changes are often modest in magnitude and anatomically restricted to one or two Brodmann areas. Furthermore, we have found that care in case selection is essential, because sex, age, drugs, and comorbid diagnoses contribute to receptor binding. The implications for in vivo imaging are considerable, directing the focus of such studies toward the ventrolateral prefrontal cortex. However, because ligands are limited, as is the resolution of current methods, including PET, automated analyses that produce statistical images, rather than manual selection of individual slices, will likely lack the ability to detect the discrete receptor changes found postmortem. Alternatively, the advantages of examining large numbers of subjects, imaging the entire brain, obtaining detailed clinical information in the living patient, and magnifying the changes with neuropharmacological challenges present a promising outlook for making major advances into the identification of brain abnormalities associated with suicide risk.

Brain↗
PubMed1990

Morphology of the aging human lens. II. Ultrastructure of clear lenses.

Clear human post mortem lenses, varying in age between 23 and 82 years, were investigated using scanning and transmission electron microscopy. The lenses were obtained from the Corneabank Amsterdam. The post mortem delay ranged from 8-24 hours. Apart from some minor mitochondrial changes no hypoxic post mortem disturbances in epithelial cells and lens fibers were observed. In the lens fibers three main age-related fine structural alterations were found: i) membrane ruptures, ii) watervacuoles and iii) multilamellar bodies. The frequency of these alterations increased with age and they remained restricted to the superficial equatorial cortex. They were absent in the anterior and posterior cortex, supranuclear equatorial cortex and nucleus. The relevance of these observations in relation to the etiology and early pathogenesis of senile cataract is discussed. The membrane ruptures and watervacuoles are in morphological support of the view, based on biochemical evidence, that oxidative stress leads to destabilization and desintegration of membranes and consequently disturbs the waterbalance of fibers. It is postulated that the lamellar bodies are involved in the repair of ruptured membranes and breakdown of affected proteins thus explaining the late onset of senile cataractous changes.

Adult↗
PubMed1985

Central nicotine binding sites: a study of post-mortem stability.

The effect of post-mortem treatment on the binding of d, I-[3H]nicotine, to rat cerebrocortical membranes, has been evaluated. Neither freezing [-70 degrees C] and thawing, a four hour post-mortem period at room temperature, nor refrigeration for up to 96 hrs at 4 degrees C caused any significant changes in the density or properties of nicotine binding sites in cerebrocortical membranes. The results suggest that nicotine binding to membranes in brain is unlikely to be affected by the usual postmortem delays experienced before human necropsies.

Animals↗
PubMed2006

Quasi-static transfer function of the rabbit middle ear' measured with a heterodyne interferometer with high-resolution position decoder.

Due to changes in ambient pressure and to the gas-exchange processes in the middle ear (ME) cavity, the ear is subject to ultra-low-frequency pressure variations, which are many orders of magnitude larger than the loudest acoustic pressures. Little quantitative data exist on how ME mechanics deals with these large quasi-static pressure changes and because of this lack of data, only few efforts could be made to incorporate quasi-static behavior into computer models. When designing and modeling ossicle prostheses and implantable ME hearing aids, the effects of large ossicle movements caused by quasi-static pressures should be taken into account. We investigated the response of the ME to slowly varying pressures by measuring the displacement of the umbo and the stapes in rabbit with a heterodyne interferometer with position decoder. Displacement versus pressure curves were obtained at linear pressure change rates between 200 Pa/s and 1.5 kPa/s, with amplitude +/-2.5 kPa. The change in stapes position associated with a pressure change is independent of pressure change rate (34 microm peak-to-peak at +/-2.5 kPa). The stapes displacement versus pressure curves are highly nonlinear and level off for pressures beyond +/-1 kPa. Stapes motion shows no measurable hysteresis at 1.5 kPa/s, which demonstrates that the annular ligament has little viscoelasticity. Hysteresis increases strongly at the lowest pressure change rates. The stapes moves in phase with the umbo and with pressure, but the sense of rotation of the hysteresis loop of stapes is phase inversed. Stapes motion is not a simple lever ratio mimic of umbo motion, but is the consequence of complex changes in ossicle joints and ossicle position. The change in umbo position produced by a +/-2.5 kPa pressure change decreases with increasing rate from 165 microm at 200 Pa/s to 118 microm at 1.5 kPa/s. Umbo motion already shows significant hysteresis at 1.5 kPa/s, but hysteresis increases further as pressure change rate decreases. We conclude that in the quasi-static regime, ossicle movement is not only governed by viscoelasticity, but that other effects become dominant as pressure change rate decreases below 1 kPa/s. The increasing hysteresis can be caused by increasing friction as speed of movement decreases, and incorporating speed-dependent friction coefficients will be essential to generate realistic models of ossicle movements at slow pressure change rates.

Animals↗