Effect of ocular hypertension on the pattern of retinal ganglion cell subtype loss in a mouse model of early-onset glaucoma.

Glaucoma is a neurodegenerative disease with elevated intraocular pressure as one of the major risk factors. Glaucoma leads to irreversible loss of vision and its progression involves optic nerve head cupping, axonal degeneration, retinal ganglion cell (RGC) loss, and visual field defects. Despite its high global prevalence, glaucoma still remains a major neurodegenerative disease. Introduction of mouse models of experimental glaucoma has become integral to glaucoma research due to well-studied genetics as well as ease of manipulations. Many established inherent and inducible mouse models of glaucoma are used to study the molecular and physiological progression of the disease. One such model of spontaneous mutation is the nee model, which is caused by mutation of the Sh3pxd2b gene. In both humans and mice, mutations disrupting function of the SH3PXD2B adaptor protein cause a developmental syndrome including secondary congenital glaucoma. The purpose of this study was to characterize the early onset nee glaucoma phenotype on the C57BL/6J background and to evaluate the pattern of RGC loss and axonal degeneration in specific RGC subtypes. We found that the B6.Sh3pxd2bnee mutant animals exhibit glaucoma phenotypes of elevated intraocular pressure, RGC loss and axonal degeneration. Moreover, the non-image forming RGCs survived longer than the On-Off direction selective RGCs (DSGC), and the axonal death in these RGCs was independent of their respective RGC subtype. In conclusion, through this study we characterized an experimental model of early onset glaucoma on a C57BL/6J background exhibiting key glaucoma phenotypes. In addition, we describe that RGC death has subtype-specific sensitivities and follows a specific pattern of cell death under glaucomatous conditions.

Novel copy number variants in children with autism and additional developmental anomalies.

Autism is a neurodevelopmental disorder characterized by three core symptom domains: ritualistic-repetitive behaviors, impaired social interaction, and impaired communication and language development. Recent studies have highlighted etiologically relevant recurrent copy number changes in autism, such as 16p11.2 deletions and duplications, as well as a significant role for unique, novel variants. We used Affymetrix 250K GeneChip Microarray technology (either NspI or StyI) to detect microdeletions and duplications in a subset of children from the Autism Genetic Resource Exchange (AGRE). In order to enrich our sample for potentially pathogenic CNVs we selected children with autism who had additional features suggestive of chromosomal loss associated with developmental disturbance (positive criteria filter) but who had normal cytogenetic testing (negative criteria filter). We identified families with the following features: at least one child with autism who also had facial dysmorphology, limb or digit abnormalities, or ocular abnormalities. To detect changes in copy number we used a publicly available program, Copy Number Analyser for GeneChip® (CNAG) Ver. 2.0. We identified novel deletions and duplications on chromosomes 1q24.2, 3p26.2, 4q34.2, and 6q24.3. Several of these deletions and duplications include new and interesting candidate genes for autism such as syntaxin binding protein 5 (STXBP5 also known as tomosyn) and leucine rich repeat neuronal 1 (LRRN1 also known as NLRR1). Lastly, our data suggest that rare and potentially pathogenic microdeletions and duplications may have a substantially higher prevalence in children with autism and additional developmental anomalies than in children with autism alone.

Pax6 3' deletion results in aniridia, autism and mental retardation.

The PAX6 gene is a transcription factor expressed early in development, predominantly in the eye, brain and gut. It is well known that mutations in PAX6 may result in aniridia, Peter's anomaly and kertatisis. Here, we present mutation analysis of a patient with aniridia, autism and mental retardation. We identified and characterized a 1.3 Mb deletion that disrupts PAX6 transcriptional activity and deletes additional genes expressed in the brain. Our findings provide continued evidence for the role of PAX6 in neural phenotypes associated with aniridia.

Determining the source of fecal contamination in recreational waters.

Public health departments bear the responsibility for investigating recreational water-associated disease outbreaks. Tracking the source of the disease is often problematic, however, because routine monitoring of recreational waters (for bacterial counts) is not source specific. The intent of the project reported here was to monitor Escherichia coli levels in a small recreational lake in Iowa and to determine their source. The authors monitored water samples for E. coli and used phenotypic methods to analyze multiple samples of lake water, well water, and known fecal sources. Moderate to high levels of E. coli were found in lake water samples from the swimming area throughout the summer. The highest levels of E. coli were found after rainfall events in both lake water samples and samples taken from monitoring wells. Phenotypic analyses indicated that likely sources of E. coli in the lake included both human and wildlife (goose) fecal material. The authors also found that the phenotype used to characterize E. coli isolated from geese frequenting this lake could not be used to characterize E. coli isolated from geese in a neighboring watershed. Identifying the source of fecal material will help authorities implement the proper preventive measures to avoid fecal contamination of the lake in the future.

A quantitative study of ramped radio frequency, magnetization transfer, and slab thickness in three-dimensional time-of-flight magnetic resonance angiography in a patient population.

RATIONALE AND OBJECTIVES: The authors compare the effectiveness of various magnetic resonance (MR) angiography acquisition strategies in enhancing the visibility of small intracranial vessels. METHODS: Blood vessel contrast-to-noise ratio (CNR) in time-of-flight MR angiography was studied as a function of vessel size and several selectable imaging parameters. Contrast-to-noise measurements were made on 257 vessel segments ranging in size from 0.3 mm to 4.2 mm in patients who recently had undergone intraarterial cerebral angiography. Imaging parameters studied included magnetization transfer, spatially variable radio frequency (RF) pulse profile (ramped RF), and imaging slab thickness. RESULTS: The combination of thin slabs (16 slices/slab), ramped RF, and magnetization transfer resulted in the highest CNR for all but the smallest vessel sizes. The smallest vessels (< 0.5 mm) had the highest CNR, using the thick slab (64 slices/slab) with ramped RF and magnetization transfer. Magnetization transfer always improved vessel CNR, but the improvement diminished as the slab thickness was reduced. The CNR increased with a decrease in slab thickness for all but the smallest vessel sizes. CONCLUSIONS: Overall, the results provide a quantitative demonstration that inflow enhancement of blood is reduced for small vessels. Thus, whereas magnetization transfer is important at all vessel sizes, it becomes the primary factor in improving the visibility of the smallest vessels.

Dynamics of chromosome spreading.

Consistency of optimum chromosome spreading during harvest of cytogenetic specimens remains a major concern. We have tested the idea that a precise control of the drying rate (the time with which metaphase cells dry), as fixed cell suspension is placed on a slide or an in situ culture in last fixation, may be the answer. Amniocyte and lymphocyte cultures were allowed to dry at defined combinations of relative humidity (RH) and temperature (T) in a modified Thermotron environmental control unit. We were able to demonstrate, based on 2,250 amniocytes and 1,650 lymphocytes, that the metaphase area after drying was a function of RH and T for both in situ and non-in situ culture systems. As the RH and T increase, the metaphase area increases until a threshold is reached. Also, as RH increases, the slide drying time increases. Data obtained using a response surface regression, proportional hazards regression analysis and slide drying time studies are consistent with our model of chromosome spreading. Optimum metaphase areas can be achieved at various combinations of RH and T. We propose that the use of an environmental control unit is a practical way of achieving optimum chromosome spreading routinely and in a highly consistent manner.

Immune response factors in rheumatic heart disease: meta-analysis of HLA-DR associations and evaluation of additional class II alleles.

OBJECTIVES: This study used a meta-analysis to examine HLA-DR frequencies in rheumatic heart disease and prospectively examined other class II allelic disease associations. BACKGROUND: Studies of rheumatic heart disease have reported HLA class II allelic associations, but these are inconsistent. METHODS: A meta-analysis combined all known (n = 10) studies to determine disease risk associated with HLA-DR antigen expression. Meta-analysis of studies grouped by ethnic derivation of subjects was also performed. The present study also examined DQA, DQB and DPB allele frequencies by DNA-based strategies. RESULTS: Meta-analysis showed a significant negative disease association with DR5 (odds ratio [OR] 0.67, p < 0.00003) for all combined studies. Among black patients, DR1 was increased (OR 2.80, p < 0.004); DR6 was increased (OR, 2.03, p < 0.003); and DR 8 was decreased (OR 0.32, p < 0.02). Among Eastern Indian patients, DR3 was increased (OR 2.44, p < 0.00003), with decreased expression for DR2 (OR 0.31, p < 0.00001) and DR5 (OR 0.52, p < 0.05). DR4 was increased among American whites (OR 1.74, p < 0.03), although there was significant heterogeneity among studies of whites. DQA, DQB and DPB allele frequencies were similar for control subjects and patients. CONCLUSIONS: Our findings support an association between major histocompatibility complex class II alleles and risk for rheumatic heart disease. However, heterogeneity in associations was observed among different ethnic and racial groups; regional and temporal differences in streptococcal outbreaks may compound this heterogeneity. Further studies are necessary to elucidate the respective contributions of these variables.