The Digestive Diverticula in the Carnivorous Nudibranch, Melibe leonina, Do Not Contain Photosynthetic Symbionts.

A number of nudibranchs, including Melibe engeli and Melibe pilosa, harbor symbiotic photosynthetic zooxanthellae. Melibe leonina spends most of its adult life on seagrass or kelp, capturing planktonic organisms in the water column with a large, tentacle-lined oral hood that brings food to its mouth. M. leonina also has an extensive network of digestive diverticula, located just beneath its translucent integument, that are typically filled with pigmented material likely derived from ingested food. Therefore, the focus of this project was to test the hypothesis that M. leonina accumulates symbiotic photosynthetic dinoflagellates in these diverticula. First, we conducted experiments to determine if M. leonina exhibits a preference for light, which would allow chloroplasts that it might be harboring to carry out photosynthesis. We found that most M. leonina preferred shaded areas and spent less time in direct sunlight. Second, we examined the small green circular structures in cells lining the digestive diverticula. Like chlorophyll, they exhibited autofluorescence when illuminated at 480 nm, and they were also about the same size as chloroplasts and symbiotic zooxanthellae. However, subsequent electron microscopy found no evidence of chloroplasts in the digestive diverticula of M. leonina; the structures exhibiting autofluorescence at 480 nm were most likely heterolysosomes, consistent with normal molluscan digestion. Third, we did not find evidence of altered oxygen consumption or production in M. leonina housed in different light conditions, suggesting the lack of any significant photosynthetic activity in sunlight. Fourth, we examined the contents of the diverticula, using HPLC, thin layer chromatography, and spectroscopy. The results of these studies indicate that the diverticula did not contain any chlorophyll, but rather harbored other pigments, such as astaxanthin, which likely came from crustaceans in their diet. Together, all of these data suggest that M. leonina does sequester pigments from its diet, but not for the purpose of symbiosis with photosynthetic zooxanthellae. Considering the translucent skin of M. leonina, the pigmented diverticula may instead provide camouflage.

Varios nudibranquios, incluidos Melibe engeli y Melibe pilosa, albergan zooxantelas fotosintéticas simbióticas. Melibe leonina pasa la mayoría de su vida adulta en pastos marinos o quelpo, donde captura organismos planctónicos en la columna de agua con una gran capucha oral forrada por tentáculos que llevan comida a su boca. Melibe leonina también tiene una extensa red de divertículos digestivos, ubicados justo debajo de su tegumento translúcido, que generalmente están llenos de material pigmentado probablemente derivado de alimentos ingeridos. Por lo tanto, el objetivo de este proyecto fue evaluar la hipótesis de que M. leonina acumula dinoflagelados fotosintéticos simbióticos en estos divertículos. Primero, realizamos experimentos para determinar si M. leonina se orienta hacia la luz, lo cual permitiría a los cloroplastos que podría albergar el realizar la fotosíntesis. Descubrimos que la mayoría de M. leonina prefería las áreas sombreadas y pasaba menos tiempo bajo la luz solar directa. En segundo lugar, examinamos las pequeñas estructuras circulares verdes en las células que recubren los divertículos digestivos. Al igual que la clorofila, exhibieron autofluorescencia cuando se iluminaban a 480 nm, y también tenían aproximadamente el mismo tamaño que los cloroplastos y las zooxantelas simbióticas. No obstante, la microscopía electrónica no produjo evidencia de cloroplastos en los divertículos digestivos de M. leonina. Es probable que las estructuras que exhibieron autofluorescencia en 480 nm fuesen heterolisosomas, lo cual es consistente con la digestión normal de moluscos. En tercer lugar, no encontramos evidencia de un consumo o producción de oxígeno alterado en M. leonina alojadas varias condiciones lumínicas, lo cual sugiere la ausencia de actividad fotosintética significativa en la presencia de luz solar. En cuarto lugar, examinamos el contenido de los divertículos mediante HPLC, cromatografía en capa fina, y espectroscopia. Los resultados de estos estudios indican que los divertículos no contenían clorofila, pero si otros pigmentos como la astaxantina que probablemente provenía de crustáceos en su dieta. Nuestros datos sugieren que M. leonina secuestra pigmentos de su dieta, pero no con el propósito de la simbiosis con zooxantelas fotosintéticas. Teniendo en cuenta la piel translúcida de M. leonina, los divertículos pigmentados podrían quizás proporcionar camuflaje.

Pyroglutamate-modified Aß(3-42) affects aggregation kinetics of Aß(1-42) by accelerating primary and secondary pathways.

The aggregation into amyloid fibrils of amyloid-ß (Aß) peptides is a hallmark of Alzheimer's disease. A variety of Aß peptides have been discovered in vivo, with pyroglutamate-modified Aß (pEAß) forming a significant proportion. pEAß is mainly localized in the core of plaques, suggesting a possible role in inducing and facilitating Aß oligomerization and accumulation. Despite this potential importance, the aggregation mechanism of pEAß and its influence on the aggregation kinetics of other Aß variants have not yet been elucidated. Here we show that pEAß(3-42) forms fibrils much faster than Aß(1-42) and the critical concentration above which aggregation was observed was drastically decreased by one order of magnitude compared to Aß(1-42). We elucidated the co-aggregation mechanism of Aß(1-42) with pEAß(3-42). At concentrations at which both species do not aggregate as homofibrils, mixtures of pEAß(3-42) and Aß(1-42) aggregate, suggesting the formation of mixed nuclei. We show that the presence of pEAß(3-42) monomers increases the rate of primary nucleation of Aß(1-42) and that fibrils of pEAß(3-42) serve as highly efficient templates for elongation and catalytic surfaces for secondary nucleation of Aß(1-42). On the other hand, the addition of Aß(1-42) monomers drastically decelerates the primary and secondary nucleation of pEAß(3-42) while not altering the pEAß(3-42) elongation rate. In addition, even moderate concentrations of fibrillar Aß(1-42) prevent pEAß(3-42) aggregation, likely due to non-reactive binding of pEAß(3-42) monomers to the surfaces of Aß(1-42) fibrils. Thus, pEAß(3-42) accelerates aggregation of Aß(1-42) by affecting all individual reaction steps of the aggregation process while Aß(1-42) dramatically slows down the primary and secondary nucleation of pEAß(3-42).

Spatial propagation of protein polymerization.

We consider the spatial dependence of filamentous protein self-assembly. Through studying the cases where the spreading of aggregated material is dominated either by diffusion or by growth, we derive analytical results for the spatial evolution of filamentous protein aggregation, which we validate against Monte Carlo simulations. Moreover, we compare the predictions of our theory with experimental measurements of two systems for which we identify the propagation as either growth or diffusion controlled. Our results connect the macroscopic observables that characterize the spatial propagation of protein self-assembly with the underlying microscopic processes and provide physical limits on spatial propagation and prionlike behavior associated with protein aggregation.

The role of rehabilitation medicine in the management of chronic pain: description of a pain control program and longitudinal outcomes.

Longitudinal outcomes of 35 patients with chronic benign pain were studied following their participation in a 3-week multidisciplinary pain management program. Pretreatment status with respect to activity levels, health care utilization, medication use, and subjective pain intensity was compared statistically with post-treatment status at three follow-up assessments (discharge, 1.6 months, and 22.7 months post-discharge). Results suggest a positive impact of treatment on activity levels, health care utilization, and medication use post-discharge, with diminution of that impact over time. Pain management programs increasingly will need to demonstrate cost effectiveness, including finding ways to maximize program gains over time.

Skin complications other than pressure ulcers following spinal cord injury.

This study identifies skin and nail complications other than pressure ulcers after spinal cord injury and correlate these complications to the level of injury. A prospective study was performed at the time of 679 annual spinal cord injury clinic visits from 1988 to 1991 at which time the skin and nails were examined for changes or other lesions. Clinical skin thickening and nail hypertrophy were the most frequent findings. Skin thickening occurred in 57.9% of cervical injuries, 31.6% of higher thoracic injuries, 23.6% of lower thoracic injuries, and 16.0% of thoracolumbar injuries, p < .0001. Skin thickening was also seen more commonly with increasing time after injury, 20.3% at 1 year and 51.2% at 5 years, p < .0001. Nail hypertrophy occurred in the lower extremities and was not correlated with the level of injury. Denervation and autonomic dysfunction may be implicated in these changes.

Clinical skin thickening following spinal cord injury studied by histopathology.

Dermatohistopathologic studies were performed in persons with spinal cord injury to evaluate the clinical observation of skin thickening. Twenty subjects were included in a prospective acute study and 59 subjects in a chronic study. Skin biopsies of the lower lateral thigh were studied by routine histopathology. The most common histopathologic findings included dermal fibrosis and perivascular inflammatory infiltrate. Dermal fibrosis was already identified within two months after injury in the acute study. In chronic patients, dermal fibrosis was found in 65 percent of persons with tetraplegia compared to 25 percent with paraplegia (p = .0038). Perivascular inflammatory infiltrate was less frequent and its presence was not associated with the level of injury. Histopathologic findings were generally not as prominent as the clinical picture. This disparity may be explained by a combination of edema and dermal fibrosis. Loss of autonomic nervous system control or other neuroendocrine dysfunction is suspected as a causative factor in the pathogenesis of these findings.

Occurrence of ether-containing inositol phospholipids in bovine erythrocytes.

Several proteins including bovine erythrocyte acetylcholinesterase are anchored in the membrane through glycoinositol phospholipids containing an alkyl linkage at the sn-1 position of the glycerol. However, the existence of 1-alkyl-2-acyl-sn-glycero-3-phosphoinositol (alkylacyl-GPI) in biological systems has not been demonstrated. In this study, we identified the presence of alkylacyl-GPI in bovine erythrocytes by the following criteria: (1) TLC-Rf value, (2) radyllyso-GPI was produced after phospholipase A2 treatment of the diradyl-GPI, and (3) benzoate derivatives of alkylacylglycerols produced by phospholipase C hydrolysis of diradyl-GPI had the same retention time as that of authentic alkylacylglycerobenzoates on normal-phase HPLC. Diradyl-GPI consisted of 5-10% alkylacyl-GPI. Reverse-phase HPLC analysis of alkylacylglycerobenzoates derived from bovine erythrocyte alkylacyl-GPI showed a multiplicity of species with 18:0-20:4 (11.7%), 16:0-18:1 + 18:0-18:2 (34.9%), and 18:0-18:1 (19.4%) being the major components. Composition of alkyl chains of alkylacyl-GPI from bovine erythrocytes was similar to the reported value for alkylacylglycerols isolated from the glycoinositol phospholipid anchor of bovine erythrocyte acetylcholinesterase. Based on these results, we suggest that alkylacyl-GPI serves as a precursor for the glycoinositol phospholipid of the anchored proteins.