Study of experimental cataract produced by sugar alcohols in the organ-cultured mammalian ocular lens

Freshly isolated rabbit lenses were cultured in isosmolar TC-199 medium or hyperosmolar medium containing 180 mM sorbitol or mannitol. These experiments were performed to investigate the probable effects of hyperosmolar media on lens clarity and the ability of lens fiber cells to synthesize membrane intrinsic protein, MP-26. The data from these experiments show that incubation in hyperosmolar medium causes depressed MP-26 synthesis, whereas the presence of sugar alcohols in the culture medium induced anterior and posterior subcapsular opacities. The cation levels of lenses incubated in iso- and hyperosmolar medium were also measured. Data from these experiments revealed that although the experimental lenses display prominent opacities, their cation levels are generally similar to those of control lenses. It is proposed that the observed lens opacities are due to the presence of sugar alcohols in the culture medium and not to hyperosmolar shock.     

Measurement of the normal optic chiasm on coronal MR images.

PURPOSETo develop an objective method for measuring the optic chiasm and to document its normal range in size.METHODSMeasurements of the height and area of the optic chiasm, made on coronal T1-weighted MR images with the use of commercially available region-of-interest software, were obtained in 114 healthy subjects who had a total of 123 MR studies. A normal range and standard deviation were calculated, and the information was broken down by age and sex.RESULTSThe mean area of the optic chiasm was 43.7 mm2, with a standard deviation of 5.21. The mean width was 14.0 mm, with a standard deviation of 1.68.CONCLUSIONThe area and width of the optic chiasm can be measured with the use of commercially available software, which allows an objective estimate of the chiasm''s size. Knowledge of the normal size range of the optic chiasm can be helpful in the early detection of some disorders.     

Characterization of Pseudomonas aeruginosa adherence to mouse corneas in organ culture.

The present study was designed to obtain further information on the nature of the corneal macromolecule(s) to which Pseudomonas aeruginosa adheres and how adherence might be prevented. Scarified adult mouse corneas in organ culture were treated with trypsin or lipase to determine whether the receptor molecule(s) was protein or lipid in nature. Trypsin (20 micrograms/ml) treatment of the cornea for 5 min had no significant effect on bacterial adherence, and longer periods of enzyme exposure resulted in extensive surface cell lysis. In contrast, lipase treatment (50,000 U/ml) for 1 h caused little visible cell lysis and significantly reduced bacterial adherence. To test further the lipid nature of the receptor, a highly purified monosialoganglioside (GM1) preparation (500 micrograms/ml) was used to preincubate (1 h) the cornea prior to bacterial application, and this also inhibited bacterial adherence. Similar corneal treatment with gangliotetraosylceramide (asialo GM1) (500 micrograms/ml) had little effect on ocular bacterial binding. Premixing of the bacterial inoculum with GM1 prior to corneal application had no significant effect on inhibiting bacterial binding, but similarly premixing the bacterial inoculum with asialo GM1 transiently decreased adherence. Lastly, premixing of the bacterial inoculum or preincubation of corneas with fibronectin (500 micrograms/ml for 1 h) both decreased bacterial adherence. These findings provide evidence that the receptor-adhesin interactions of P. aeruginosa at the ocular surface in organ culture are complex, involve a glycolipid moiety, and may be blocked by a ganglioside containing at least one sialosyl residue or by fibronectin, which may bind to membrane-associated gangliosides.     

Microscopic characterization of ocular damage produced by Pseudomonas aeruginosa toxin A.

The ocular damage in young adult mice produced by purified Pseudomonas aeruginosa exotoxin A was microscopically characterized at 1 and 5 h and at 1, 3, 5, 7, 10, 14, and 21 days after toxin A challenge, using light, transmission, and scanning electron microscopic techniques. Similarly to previously described infection with viable organisms, toxin A killed both epithelial and endothelial cells and induced stromal cell swelling within 5 to 24 h after application onto the nonpenetrating wounded corneal surface. Other toxin-induced damage similar to the damage produced by infection with the viable bacteria was production of electron-dense particles within the corneal stroma, dispersal of undamaged collagen fibrils, and apparent loss of stromal proteoglycan ground substance. Toxin A damage differed from infection with the viable bacteria in essentially two ways. First, more purulent exudate and more polymorphonuclear neutrophilic leukocyte (PMN) infiltration of the corneal stroma were produced by infection with the viable organisms than by the toxin. Additionally, PMN did not appear within the toxin-treated corneas until 3 days after treatment, whereas in corneas infected with the viable organisms, PMN were numerous by 18 h. Secondly, toxin A produced cataract of the ocular lens, whereas infection with the viable organisms did not.     

Substance P regulates natural killer cell interferon-gamma production and resistance to Pseudomonas aeruginosa infection

Studies have shown that after Pseudomonas aeruginosa (P. aeruginosa) corneal infection, BALB/c mice that are capable of resolving the disease, locally produce IFN-gamma. As T cells are not detected in the infected cornea of these mice, antibody depletion was used to test whether NK cells produce the cytokine. After depletion, decreased corneal IFN-gamma mRNA and increased disease severity, bacterial load, and PMN infiltrate resulted. Further work determined if substance P (SP), a pro-inflammatory neuropeptide, participated in regulation of this response. To this end, mice were treated with the SP antagonist, spantide I that blocks SP interaction with neurokinin-1, its major receptor. The treatment significantly decreased corneal IFN-gamma and IL-18 protein levels and corneal perforation resulted. In vitro experiments using isolated splenic NK cells confirmed their ability to respond to IL-18 and SP and to secrete IFN-gamma protein. We conclude: that for development of the BALB/c resistance response, NK cells are required to produce IFN-gamma; that the cells express the neurokinin-1 receptor; and that SP directly regulates IFN-gamma production through this receptor. The data suggest a unique link between the nervous system and development of innate immunity in the cornea.     

The role of apolipoprotein AI domains in lipid binding

Apolipoprotein AI (apoAI) is the principal protein constituent of high density lipoproteins and it plays a key role in human cholesterol homeostasis; however, the structure of apoAI is not clearly understood. To test the hypothesis that apoAI is organized into domains, three deletion mutants of human apoAI expressed in Escherichia coli were studied in solution and in reconstituted high density lipoprotein particles. Each mutant lacked one of three specific regions that together encompass almost the entire 243 aa sequence of native apoAI (apoAI Δ44-126, apoAI Δ139-170, and apoAI Δ190-243). Circular dichroism spectroscopy showed that the α-helical content of lipid-free apoAI Δ44-126 was 27% while the other mutants and native apoAI averaged 55 ± 2%, suggesting that the missing N-terminal portion contains most of the α-helical structure of lipid-free apoAI. ApoAI Δ44-126 exhibited the largest increase in α-helix upon lipid binding (125% increase versus an average of 25% for the others), confirming the importance of the C-terminal half of apoAI in lipid binding. Denaturation studies showed that the N-terminal half of apoAI is primarily responsible for α-helix stability in the lipid-free state, whereas the C terminus is required for α-helix stability when lipid-bound. We conclude that the N-terminal half (aa 44–126) of apoAI is responsible for most of the α-helical structure and the marginal stability of lipid-free apoAI while the C terminus (aa 139–243) is less organized. The increase in α-helical content observed when native apoAI binds lipid results from the formation of α-helix primarily in the C-terminal half of the molecule.     

Distributional Properties and Criterion Validity of a Shortened Version of the Social Responsiveness Scale: Results from the ECHO Program and Implications for Social Communication Research

Prior work proposed a shortened version of the Social Responsiveness Scale (SRS), a commonly used quantitative measure of social communication traits. We used data from 3031 participants (including 190 ASD cases) from the Environmental Influences on Child Health Outcomes (ECHO) Program to compare distributional properties and criterion validity of 16-item “short” to 65-item “full” SRS scores. Results demonstrated highly overlapping distributions of short and full scores. Both scores separated case from non-case individuals by approximately two standard deviations. ASD prediction was nearly identical for short and full scores (area under the curve values of 0.87, 0.86 respectively). Findings support comparability of shortened and full scores, suggesting opportunities to increase efficiency. Future work should confirm additional psychometric properties of short scores.