Brain lipids of a case of juvenile Niemann-Pick disease

—Lipids of frontal lobe grey and white matter were examined in parallel from a normal and a diseased child (M. Niemann-Pick), both nine years of age. In the grey matter of the pathological case the following changes, although small, were found: a slight increase in all phospholipids and decreased values for nervonic acid in cerebrosides and for hydroxy fatty acids in sulphatides. White matter seemed much more affected by the disease: water content was about 6 per cent higher which corresponds to an approx. 20 per cent loss of dry substance compared with the normal brain. Further increases were observed in ‘ganglioside’ fraction and in all phosphatides. Cerebroside and sulphatide levels appeared decreased owing to destruction of myelin. In all of the glycerophosphatides oleic acid portions were lowered whereas in sphingolipids mainly nervonic acid values were reduced. Aldehyde content of both tissues seemed lowered in the disease, however, changes in composition were observed only in white matter, where the stearaldehyde portion of ethanolamine glycerophospholipid increased at the expense of palmitaldehyde and oleinaldehyde.     

A simple vertebrate collagenase assay using soluble radioactive collagen substrate

A highly sensitive assay for vertebrate collagenase has been developed using [14C]proline- or [3H]proline-labeled collagen as soluble substrate. The substrate was easy to prepare, gave high specific activity (1.4 X 10(6) cpm/mg collagen), and was stable at -20 degrees C for a long period. The digestion reaction for the assay was done at 21 degrees C to minimize the cleavage of collagen by proteases other than collagenase and to protect the 3/4 and 1/4 cleavage fragments of collagen from being further attacked by proteases. The cleaved products were denatured and then separated from undigested native collagen by precipitation with 1 M NaCl at pH 3.5. The conditions selected for denaturation and separation gave better discrimination between the cleaved products and uncleaved substrate than did conditions used in some other assays. The digestion products can be examined further by gel electrophoresis at the end of the assay to confirm the activity of vertebrate collagenase. This assay can also be adapted to assess telopeptidase activity independently of collagenase activity.     

Verification of a virtual fields method to extract the mechanical properties of human optic nerve head tissues in vivo

We aimed to verify a custom virtual fields method (VFM) to estimate the patient-specific biomechanical properties of human optic nerve head (ONH) tissues, given their full-field deformations induced by intraocular pressure (IOP). To verify the accuracy of VFM, we first generated ‘artificial’ ONH displacements from predetermined (known) ONH tissue biomechanical properties using finite element analysis. Using such deformations, if we are able to match back the known biomechanical properties, it would indicate that our VFM technique is accurate. The peripapillary sclera was assumed anisotropic hyperelastic, while all other ONH tissues were considered isotropic. The simulated ONH displacements were fed into the VFM algorithm to extract back the biomechanical properties. The robustness of VFM was also tested against rigid body motions and noise added to the simulated displacements. Then, the computational speed of VFM was compared to that of a gold-standard stiffness measurement method (inverse finite element method or IFEM). Finally, as proof of principle, VFM was applied to IOP-induced ONH deformation data (obtained from one subject’s eye imaged with OCT), and the biomechanical properties of the prelamina and lamina cribrosa (LC) were extracted. From given ONH displacements, VFM successfully matched back the biomechanical properties of ONH tissues with high accuracy and efficiency. For all parameters, the percentage errors were less than 0.05%. Our method was insensitive to rigid body motions and was also able to recover the material parameters in the presence of noise. VFM was also found 125 times faster than the gold-standard IFEM. Finally, the estimated shear modulus for the prelamina and the LC of the studied subject’s eye were 33.7 and 63.5 kPa, respectively. VFM may be capable of measuring the biomechanical properties of ONH tissues with high speed and accuracy. It has potential in identifying patient-specific ONH biomechanical properties in the clinic if combined with optical coherence tomography.     

Regionally-Specified Second Trimester Fetal Neural Stem Cells Reveals Differential Neurogenic Programming

Neural stem/progenitor cells (NSC) have the potential for treatment of a wide range of neurological diseases such as Parkinson Disease and multiple sclerosis. Currently, NSC have been isolated only from hippocampus and subventricular zone (SVZ) of the adult brain. It is not known whether NSC can be found in all parts of the developing mid-trimester central nervous system (CNS) when the brain undergoes massive transformation and growth. Multipotent NSC from the mid-trimester cerebra, thalamus, SVZ, hippocampus, thalamus, cerebellum, brain stem and spinal cord can be derived and propagated as clonal neurospheres with increasing frequencies with increasing gestations. These NSC can undergo multi-lineage differentiation both in vitro and in vivo, and engraft in a developmental murine model. Regionally-derived NSC are phenotypically distinct, with hippocampal NSC having a significantly higher neurogenic potential (53.6%) over other sources (range of 0%–27.5%, p<0.004). Whole genome expression analysis showed differential gene expression between these regionally-derived NSC, which involved the Notch, epidermal growth factor as well as interleukin pathways. We have shown the presence of phenotypically-distinct regionally-derived NSC from the mid-trimester CNS, which may reflect the ontological differences occurring within the CNS. Aside from informing on the role of such cells during fetal growth, they may be useful for different cellular therapy applications.     

Studies on lysine:N6-hydroxylation by cell-free systems of Aerobacter aerogenes 62-1

Electron microscopic examination has revealed the vesicular nature of the membrane component, of the cell-free system of Aerobacter aerogenes 62-1, which catalyses lysine: N6-hydroxylation. Regardless of the orientation of the vesicles, N-hydroxylation process is still stimulated by pyruvate. Both pyruvate oxidation and lysine: N6-hydroxylation were inhibited by protonophores and Gramicidin S.     

Numerical study of entrainment of the human circadian system and recovery by light treatment

Background

While the effects of light as a zeitgeber are well known, the way the effects are modulated by features of the sleep-wake system still remains to be studied in detail.

Methods

A mathematical model for disturbance and recovery of the human circadian system is presented. The model combines a circadian oscillator and a sleep-wake switch that includes the effects of orexin. By means of simulations, we characterize the period-locking zone of the model, where a stable 24-hour circadian rhythm exists, and the occurrence of circadian disruption due to both insufficient light and imbalance in orexin. We also investigate how daily bright light treatments of short duration can recover the normal circadian rhythm.

Results

It is found that the system exhibits continuous phase advance/delay at lower/higher orexin levels. Bright light treatment simulations disclose two optimal time windows, corresponding to morning and evening light treatments. Among the two, the morning light treatment is found effective in a wider range of parameter values, with shorter recovery time.

Conclusions

This approach offers a systematic way to determine the conditions under which circadian disruption occurs, and to evaluate the effects of light treatment. In particular, it could potentially offer a way to optimize light treatments for patients with circadian disruption, e.g., sleep and mood disorders, in clinical settings.