Bergmann Glial S100B Activates Myo-inositol Monophosphatase 1 and Co-localizes to Purkinje Cell Vacuoles in SCA1 Transgenic Mice

Spinocerebellar ataxia-1 (SCA1) is a late onset neurodegenerative disease caused by the expansion of a polyglutamine repeat within ataxin-1 protein. The toxic effects triggered by mutant ataxin-1 result in degeneration of the neurons in cerebellum, brain stem and spinocerebellar tracts. The targeted overexpression of mutant ataxin-1 in cerebellar Purkinje cells (PCs) of the SCA1 transgenic mice results in the formation of cytoplasmic vacuoles in PCs. These vacuoles appear early on before the onset of behavioral abnormalities. Interestingly, we found that vacoules contain S100B and vimentin proteins, which normally localize to neighboring Bergmann glia (BG). Further, immunohistochemical and specialized silver stain analysis revealed that vacuolar formation is associated with alterations in the morphology of dendritic spines of PCs. To gain insights into the mechanisms of vacuolar formation, we investigated if vacuoles in SCA1 PCs have an autophagic origin or are a consequence of some other event. We examined the expression levels (by Western blotting) of microtubule-associated protein light chain 3 (LC3)-I and LC3-II, and the degradation levels of p62 (a LC3 partner) in the cerebellar fractions prepared from pre-symptomatic SCA1 and age-matched wild-type mice. No p62 degradation was observed; however, LC3-II/(LC3-I + LC3-II) ratios were significantly altered in SCA1 mice indicating changes in the autophagic flux. In addition, LC3 localized to PC vacuoles. Further, we observed a co-localization of myo-inositol monophosphatase 1 (IMPA1) with S100B in PC vacuoles. IMPA1 is present in PC spines and has been implicated in autophagy. In vitro studies using purified IMPA1 and S100B demonstrated that S100B interacted with and activated IMPA1. Both apo and Ca²⁺-bound S100B were found to activate IMPA1, depending on substrate concentration. IMPA1 is regulated by another calcium-binding protein calbindin-D28k (CaB), since we reported earlier that the CaB levels are reduced in SCA1 PCs, the activation of IMPA1 by S100B may modulate CaB-dependent inositol signaling. This may cause BG–PC interface to degenerate resulting in vacuolar formation. In sum, these data indicate that vacuoles appearing early in SCA1 PCs could be developing through some unknown autophagic mechanism.     

Methylmercury impairs motor function in early development and induces oxidative stress in cerebellar granule cells

Environmental toxicants such as methylmercury play a critical role in the pathogenesis of many neurodevelopmental disorders. Environmental exposure to methylmercury frequently occurs at low doses, most frequently through fish consumption. Although the general population is at risk for exposure, pregnant women and young children are the most vulnerable. A common symptom of perinatal exposure to methylmercury is increased sensory (visual) deficits, motor impairment, and an overall cognitive decline. Research has indicated that the developing cerebellum, specifically the cerebellar granular layer, is particularly vulnerable to methylmercury neurotoxicity. This review examines the effects of low-level methylmercury exposure on motor coordination. We specifically focus on the role of cerebellar granule cells in methylmercury neurotoxicity. We suggest that methylmercury induces oxidative stress in cerebellar granule cells, which subsequently results in apoptotic cell death. Understanding the mechanism by which methylmercury induces toxicity within the developing brain will allow for enhanced treatments and potential reversal of the detrimental effects.     

A novel cost-effective approach to post-vasectomy semen analysis

Study Type – Diagnostic (cost minimisation analysis)
Level of Evidence 3b

OBJECTIVE

• ? To examine compliance, clearance rates and cost‐effectiveness of a novel approach to managing men following vasectomy based on the testing of sperm viability.

PATIENTS AND METHODS

• ? Between January 2003 and March 2005, 832 men undergoing vasectomy were followed prospectively for a minimum of 12 months.
• ? Post‐vasectomy semen analysis (PVSA) was carried out at 16 weeks with repeat at 20 weeks only if sperm were detected on initial PVSA i.e. a single clear PVSA on simple microscopy was deemed sufficient for declaring vasectomy successful.
• ? In men with persistent non‐motile sperm (PNMS) in the second specimen, comprehensive analysis of number and viability of sperm using a fluorescent probe was carried out on a fresh semen specimen taken in accordance with British Andrology Society (BAS) guidelines.

RESULTS

• ? Overall compliance with the PVSA protocol was 81.3% (95% CI 78.5 to 83.8). No sperm were seen in 540 (78.8%) and 70 (10.3%) at the initial and 2^nd PVSA respectively.
• ? Persistent spermatozoa at 20 weeks were present in 66 (9.8%, 7.8 to 12.2) cases with 58 (8.6%, 6.7 to 11.0) having PNMS and 8 (1.2%, 0.6 to 2.3) having motile sperm.
• ? Fluorescent viability testing in 53 of the 58 with PNMS showed viable sperm in 2 (3.8%, 1.0 to 12.8). The failure rate of vasectomy defined by PVSA (8 with motile sperm on 2^nd PVSA and 2 with viable non‐motile sperm on fluorescent testing) was 1.2% (0.7 to 2.2).
• ? Average cost per vasectomy of PVSA using this protocol was £10.77 (US$ 16.67) compared with a minimum likely average cost using BAS guidelines of £18.10 (US$ 28).

CONCLUSION

• ? Demonstrating absence of sperm on simple light microscopy in a single specimen of semen at 16 or 20 weeks post‐vasectomy and reserving comprehensive testing of sperm viability for only the higher risk group with PNMS improves compliance and represents a cost‐effective strategy for declaring surgical success. This reduces the costs of PVSA by least 40% compared with adherence with BAS guidelines without compromising success in determining outcome after vasectomy.

     

Methotrexate-induced Leukoencephalopathy

Methotrexate, a folic acid antagonist, is commonly administered intrathecally or intravenously as part of treatment of acute lymphoblastic leukemia, brain tumor, or childhood osteosarcoma. It is well documented that intrathecal administration of methotrexate combined with radiation therapy causes leukoencephalopathy; however, there are no reports on the effects of methotrexate administered intravenously without radiation. A child with acute lymphoblastic leukemia was given intravenous methotrexate and subsequently developed clinical signs and magnetic resonance imaging findings consistent with leukoencephalopathy.     

Temporal artery biopsy… Who needs one?

Objective

To review a 10 year period of temporal artery biopsies, using the American College of Rheumatology (ACR) 1990 criteria: a five point scoring system for the diagnosis of giant cell arteritis (GCA).

Design

Population based, retrospective cohort analysis.

Setting

One district general hospital in the United Kingdom, over one decade.

Participants

All patients who underwent temporal artery biopsy from July 1994 to June 2004.

Main outcome measures

ACR score and temporal artery biopsy result.

Results

During the 10 year period 111 patients were identified. The median (range) age at presentation was 71 (29–85) years. Seventy five patients had an initial ACR score of three or four at presentation. There were 20 positive biopsy specimens. In 19 of these cases at least three of the other criteria were positive so there was already sufficient clinical information for a confident diagnosis. In only one case did the positive result influence the diagnosis by changing the ACR score from two to three. In our series, corticosteroid treatment before biopsy did not significantly reduce the yield of the biopsy.

Conclusions

The ACR score of three or more has a sensitivity of 93.5% and specificity of 91.2% for the diagnosis of GCA. Using these criteria, 68% of patients had sufficient clinical features when referred to make a confident diagnosis of GCA. Temporal artery biopsy was therefore unnecessary in this group. In the remaining group (ACR score ⩽2) there was one positive biopsy. The biopsy only changed the diagnosis in this one case—less than 3% of the uncertain cases and less than 1% of the total cases. Using the ACR criteria and restricting biopsy to those cases in which it might change the diagnosis will reduce the number of biopsies by two thirds without jeopardising diagnostic accuracy.