Evidence of a diverse T cell receptor repertoire for acetylcholine receptor,the autoantigen of myasthenia gravis

We utilized two methods to look for T cell clonal expansions in myasthenia gravis (MG). We analyzed TCRBV CDR3 length polymorphism (spectratyping) to look for evidence of clonal expansion of CD4 or CD8 T cells directly from peripheral blood of MG patients. No statistically significant differences were found between the diversity of TCR repertoires in MG patients compared to normal control individuals when analyzed as groups. Rare oligoclonal expansions were detected in some individual MG patients but the significance of these findings is unclear. Next, we analyzed a panel of T cell hybridomas from acetylcholine receptor (AChR) immunized, MG-susceptible HLA-DR3 transgenic mice. The epitope specificity, TCRBV gene usage and CDR3 sequences of these hybridomas were highly diverse. We conclude there is only limited evidence for restricted TCR repertoire usage in human MG and suggest this may be due to the inability of HLA-DR molecules to select for restricted TCR recognition of AChR epitopes.     

Eye tracking as an objective measure of hyperphagia in children with Prader‐Willi syndrome

This study examined sensitivity of eye tracking measures to hyperphagia severity in Prader‐Willi syndrome (PWS). Gaze data were collected in 57 children with PWS, age 3–11 years, and 47 typically developing peers at two study sites during free visual exploration of complex stimulus arrays that included images of food, animals, and household objects. Analysis of the number and duration of fixations as well as gaze perseverations revealed that food items are not exceptionally salient for children with PWS. Instead, increased attention to food in the context of other high‐interest items (e.g., animals) was associated with caregiver reports of more severe hyperphagia and more advanced nutritional phase. The study also provided preliminary evidence of possible genetic subtype and sex differences as well as demonstrated that multiple investigators in a wide range of settings can effectively implement the eye tracking protocol. The results indicate that gaze characteristics derived from eye tracking may be a promising objective marker of hyperphagia in PWS for use in research and clinical trials.     

Localization of a novel X-linked congenital stationary night blindness locus: close linkage to the RP3 type retinitis pigmentosa gene region

X-linked congenital stationary night blindness (CSNBX) is anon-progressive retinal disorder characterized by decreasedvisual acuity and loss of night vision. CSNBX Is clinicallyheterogeneous with respect to the involvement of retinal rodsand/or cones in the disease. in this study, we localize a newlocus for CSNBX to Xp21.1, thus providing evidence that CSNBXis also genetically heterogeneous. A clear correlation betweendifferent genotypes and phenotypes cannot be found yet. Thenew CSNBX gene described here is closely linked to the X-linkedretinitis pigmentosa type 3 gene region, which supports thehypothesis that there may be a functional relationship betweencongenital stationary night blindness and retinitis pigmentosa.     

The impact of testing accommodations on MCAT scores: descriptive results.

PURPOSE: Medical College Admission Test (MCAT) examinees with disabilities who receive accommodations receive flagged scores indicating nonstandard administration. This report compares MCAT examinees who received accommodations and their performances with standard examinees. METHOD: Aggregate history records of all 1994-2000 MCAT examinees were identified as flagged (2,401) or standard (297,880), then further sorted by race/ethnicity (broadly identified as underrepresented minority and non-URM, at the time of testing) and gender. Those with flagged scores were also classified by disability (LD = learning disability, ADHD = attention deficit hyperactivity disorder, LD/ADHD = learning disability and attention deficit hyperactivity disorder, and Other = other disability) and type of accommodation. Mean MCAT scores were calculated for all groups. A group of 866 examinees took the MCAT first as a standard administration and subsequently with accommodations. In a separate analysis, their two sets of scores were compared. RESULTS: Less than 1% of examinees (2,401) had accommodations; of these, 55% were LD, 17% ADHD, 5% LD/ADHD, and 23% Other. Extended time was the most frequently provided accommodation. Mean flagged scores slightly exceeded mean standard scores on all MCAT sections. Examinees who retook the MCAT with accommodations after a standard administration increased their scores by six points, quadrupling the average gain Standard-Standard retest cohort from another study. CONCLUSION: The small but statistically significant different higher flagged scores may reflect either appropriate compensation or overly generous accommodations. Extended time had a positive impact on the scores of those who retested with this accommodation. The validity the flagged MCAT in predicting success in medical school is not known, and further investigation is underway.     

Attempts to isolate virus from human trigeminal and facial ganglions

Herpes virus hominis type 1 was isolated from the trigeminal ganglion (ganglion semilunare, gasservian) in three out of 20 randomly selected autopsies. Two of the three patients had been treated with immunosuppressive or cytostatic agents. Clinical signs of herpes infection were not observed during the previous 6 months. No virus was isolated from the facial ganglion (geniculate ganglion) in the same 20 cases. The findings are discussed in relation to the viral etiology of acute peripheral facial palsy.     

CATs and HATs: the SLC7 family of amino acid transporters

The SLC7 family is divided into two subgroups, the cationic amino acid transporters (the CAT family, SLC7A1–4) and the glycoprotein-associated amino acid transporters (the gpaAT family, SLC7A5–11), also called light chains or catalytic chains of the hetero(di)meric amino acid transporters (HAT). The associated glycoproteins (heavy chains) 4F2hc (CD98) or rBAT (D2, NBAT) form the SLC3 family. Members of the CAT family transport essentially cationic amino acids by facilitated diffusion with differential trans-stimulation by intracellular substrates. In some cells, they may regulate the rate of NO synthesis by controlling the uptake of l-arginine as the substrate for nitric oxide synthase (NOS). The heterodimeric amino acid transporters are, in contrast, quite diverse in terms of substrate selectivity and function (mostly) as obligatory exchangers. Their selectivity ranges from large neutral amino acids (system L) to small neutral amino acids (ala, ser, cys-preferring, system asc), negatively charged amino acid (system x_c^–) and cationic amino acids plus neutral amino acids (system y⁺L and b^0,+-like). Cotransport of Na⁺ is observed only for the y⁺L transporters when they carry neutral amino acids. Mutations in b^0,+-like and y⁺L transporters lead to the hereditary diseases cystinuria and lysinuric protein intolerance (LPI), respectively.