PICking out progressive PIC alterations in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that causes motoneuron death. Alterations to motoneuron excitability in ALS are suspected to contribute to motoneuron degeneration. Therefore, mechanisms underlying changes in motoneuron excitability are being thoroughly investigated. A recent publication from Trajano et al. (Trajano GS, Orssatto LB, McCombe PA, Rivlin W, Tang L, Henderson RD. J Physiol 601: 4723-4735, 2023) examined temporal changes to persistent inward currents (PICs) in ALS patients. They show that delta frequency (ΔF, an estimate of PICs) has opposite temporal trends in stronger and weaker muscles of ALS patients. This study is very important to aid in the understanding of disease mechanisms. This Neuro Forum article explores some important considerations for interpreting the results of this study, including treatment effects, potential sex differences, and a lack of comparison to healthy individuals.

Structure of chondroitin sulfate on aggrecan isolated from bovine tibial and costochondral growth plates

The structure of chondroitin sulfate on aggrecan isolated from the rib and proximal tibial growth plates of bovine fetuses was investigated, and the previously reported increase in the hydrodynamic size of chondroitin sulfate chains between the reserve and hypertrophic zones of the rib was confirmed in the tibial growth plate. Superose 6 gel chromatography, calibrated for chondroitin sulfate chain length by monosaccharide analysis, showed that the average molecular mass of chondroitin sulfate in the reserve and maturing zones of both growth plates was 21,600 and 30,400, respectively. Determination by capillary zone electrophoresis of the disaccharide composition of chains following chondroitinase digestion showed that delta Di-0S, delta Di-4S, and delta Di-6S together accounted for more than 98% of the disaccharides in the digests from all zones of both growth plates; delta disulfated and delta trisulfated disaccharides were not detected. Furthermore, this analysis revealed a gradient in chondroitin sulfate composition from the reserve to the hypertrophic zone, characterized by a marked increase in the content of delta Di-6S (from about 32% to about 52%) and a marked decrease in the content of delta Di-4S (from about 53% to about 35%). Moreover, this altered pattern of sulfation was detected on chains of all sizes in the hypertrophic zone, suggesting that a proportion of the reserve zone aggrecan might be removed and replaced with aggrecan rich in chondroitin-6-sulfate synthesized during the proliferative and maturation stages of the resident chondrocytes. These data are discussed in relation to the biosynthetic mechanisms that control chondroitin sulfate chain length and sulfation on aggrecan and their modification during chondrocyte proliferation, maturation, and hypertrophy in the growth plate.

Immune complex-like disease in 23 persons following a booster dose of rabies human diploid cell vaccine

Following a routine 0.1 ml booster dose of Merieux rabies human diploid cell vaccine (HDCV), administered intradermally, 23(10.2%) of 226 persons had signs and symptoms compatible with an immune complex-like disease. The disease had its onset from 3-13 days after the injection, lasted 1-5 days, and consisted primarily of urticaria (78.3%), macular rash (65.2%), angiooedema (39.1%), and arthralgia (17.4%). None of the cases were considered severe, and all recovered with no sequelae. There were significant differences in attack rates between men (78.3% of all cases) and women, and between those receiving vaccinations on different days. Similar reactions have been reported following intramuscular booster doses of HDCV. Since the Merieux HDCV is used worldwide, physicians administering HDCV must be aware of these adverse reactions and warn patients. Appropriate therapy should be instituted as warranted by severity of reactions.

Rapid Rotation of the Solar Interior

A model proposed for the sun apparently can account for the maintenance of photospheric rotation against deceleration by the solar wind. The rotational period is about half a day near the top of the radiative mass, and 1.6 times shorter at the center.