Disorder-to-order transition of the amyloid-ß peptide upon lipid binding.

There is mounting evidence that Alzheimer's disease progression and severity are linked to neuronal membrane damage caused by aggregates of the amyloid-ß (Aß) peptide. However, the detailed mechanism behind the membrane damage is not well understood yet. Recently, the lipid-chaperone hypothesis has been put forward, based on which the formation of complexes between Aß and free lipids enables an easy insertion of Aß into membranes. In order to test this hypothesis, we performed numerous all-atom molecular dynamics simulations. We studied the complex formation between individual lipids, considering both POPC and DPPC, and Aß and examined whether the resulting complexes would be able to insert into lipid membranes. Complex formation at a one-to-one ratio was readily observed, yet with minimal effects on Aß's characteristics. Most importantly, the peptide remains largely disordered in 1:1 complexes, and the complex does not insert into the membrane; instead, it is adsorbed to the membrane surface. The results change considerably once Aß forms a complex with a POPC cluster composed of three lipid molecules. The hydrophobic interactions between Aß and the lipid tails cause the peptide to fold into either a helical or a ß-sheet structure. These observations provide atomic insight into the disorder-to-order transition that is needed for membrane insertion or amyloid aggregation to proceed.

Liver damage promotes pro-inflammatory T-cell responses against apolipoprotein B-100.

OBJECTIVES: Liver-derived apolipoprotein B-100 (ApoB100) is an autoantigen that is recognized by atherogenic CD4+ T cells in cardiovascular disease (CVD). CVD is a major mortality risk for patients with chronic inflammatory liver diseases. However, the impact of liver damage for ApoB100-specific T-cell responses is unknown. METHODS: We identified ApoB100-specific T cells in blood from healthy controls, nonalcoholic fatty liver disease (NAFLD) patients, and CVD patients by activation-induced marker expression and analyzed their differentiation pattern in correlation to the lipid profile and liver damage parameters in a cross-sectional study. To assess the induction of extrahepatic ApoB100-specific T cells upon transient liver damage in vivo, we performed hydrodynamic tail vein injections with diphtheria toxin A (DTA)-encoding plasmid in human ApoB100-transgenic mice. RESULTS: Utilizing immunodominant ApoB100-derived peptides, we found increased ApoB100-specific T-cell populations in NAFLD and CVD patients compared to healthy controls. In a peptide-specific manner, ApoB100 reactivity in healthy controls was accompanied by expression of the regulatory T (Treg)-cell transcription factor FOXP3. In contrast, FOXP3 expression decreased, whereas expression of pro-inflammatory cytokine interleukin (IL)-17A increased in ApoB100-specific T cells from NAFLD and CVD patients. Dyslipidemia and liver damage parameters in blood correlated with reduced FOXP3 expression and elevated IL-17A production in ApoB100-specific T-cell populations, respectively. Moreover, DTA-mediated transient liver damage in human ApoB100-transgenic mice accumulated IL-17a-expressing ApoB100-specific T cells in the periphery. CONCLUSION: Our results show that liver damage promotes pro-inflammatory ApoB100-specific T-cell populations, thereby providing a cellular mechanism for the increased CVD risk in liver disease patients.

The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness.

OBJECTIVE: Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness. METHODS: Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: Ra, Rsk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics KI test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone. RESULTS: G2 and G4 specimens showed very similar, and high Ra values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (KIC). Weibull's analysis showed G2 (SIE) tendency to exhibit higher KIC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens. SIGNIFICANCE: Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (KIC) values with higher KIC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups.

The microbiology of Lascaux Cave.

Lascaux Cave (Montignac, France) contains paintings from the Upper Paleolithic period. Shortly after its discovery in 1940, the cave was seriously disturbed by major destructive interventions. In 1963, the cave was closed due to algal growth on the walls. In 2001, the ceiling, walls and sediments were colonized by the fungus Fusarium solani. Later, black stains, probably of fungal origin, appeared on the walls. Biocide treatments, including quaternary ammonium derivatives, were extensively applied for a few years, and have been in use again since January 2008. The microbial communities in Lascaux Cave were shown to be composed of human-pathogenic bacteria and entomopathogenic fungi, the former as a result of the biocide selection. The data show that fungi play an important role in the cave, and arthropods contribute to the dispersion of conidia. A careful study on the fungal ecology is needed in order to complete the cave food web and to control the black stains threatening the Paleolithic paintings.

The impact of arthropods on fungal community structure in Lascaux Cave.

AIMS: To determine the major components of the fungal population present in Lascaux Cave, France. The ceiling, walls, sediments and soil were colonized by Fusarium solani in 2001 and later, in 2006, black stains appeared. However, the origin of the successive fungal invasions is unknown as well as the ecology of the cave. METHODS AND RESULTS: The primers nu-SSU-0817F and nu-SSU-1536R were used for the direct amplification of fungal 18S-rDNA sequences from 11 samples. A total of 607 clones were retrieved. Eight out of the ten most abundant phylotypes corresponded to fungi associated with arthropods and represented about 50% of the clones. CONCLUSIONS: Entomophilous fungi play an important role in the cave and arthropods contribute to the dispersion of spores and fungal development. SIGNIFICANCE AND IMPACT OF THE STUDY: Choosing appropriate targets for control of fungal dispersal is dependent on knowing the causes of fungal colonization. A control of the arthropod populations seems to be a need in order to protect the rock art paintings in Lascaux Cave.

Stem-loop structures II-IV of the 5' untranslated sequences are required for the expression of the full-length hepatitis C virus genome.

The 5' and 3' untranslated regions (UTR) of the hepatitis C virus (HCV) genome contain stem-loop structures, which are important in viral gene expression and replication. In this study, the functional roles of the predicted stem-loop structures of HCV 5' UTR and 3' UTR in viral gene expression were examined using a chimeric clone of full-length HCV genomic cDNA clone and the gene for green fluorescent protein (GFP). High level expression of the HCV-GFP chimera in Huh-7 cells was accomplished by using a replication defective adenovirus that expresses T7 RNA polymerase and transcription plasmid containing full-length HCV-GFP chimera under the control of a T7 promoter. The HCV-GFP clone, with deletion of stem-loop I, expressed proteins in transfected Huh-7 cells at comparable levels to the wild type HCV clone. Other mutations of the 5' UTR, which either deleted or altered the base pairing of stem-loops II to IV, completely abolished the expression of HCV-GFP chimera. In contrast, deletion of 3' UTR sequences had no effect on HCV protein expression. These findings suggest that the stem-loop structures II to IV of HCV 5' UTR are necessary for protein expression, but that stem loop I is dispensable for protein translation. The stem-loop structures of 3' UTR of HCV genome appear to have no direct role in viral gene expression.

Spiroplasma sp. 16S rDNA in Creutzfeldt-Jakob disease and scrapie as shown by PCR and DNA sequence analysis.

The pathogenesis of the transmissible spongiform encephalopathies (TSE), which include Creutzfeldt-Jakob disease (CJD) in humans and scrapie in sheep, remains an enigma. In this paper we present evidence for the association of Spiroplasma sp., a wall-less prokaryote, with TSE. We have shown PCR amplification of Spiroplasma 16S rDNA in TSE-infected brain tissues (13 of 13 CJD cases and 5 of 9 scrapie cases) and not in control brains (0 of 50). Direct sequencing of the amplified PCR products has confirmed the presence of Spiroplasma-like DNA in all 5 of the TSE brains tested. Our evidence is not necessarily in conflict with involvement of a PrPres--a protease-resistant host-derived protein referred to as the prion--in the pathogenesis of TSE, since there is evidence that another factor is involved. We propose a bacterium, namely Spiroplasma, as this associated factor although the role of Spiroplasma in TSE cannot be determined from these experiments. The presence of the nucleic acid sequence of this microbe in all cases of TSE in our laboratory and not in controls provides direct evidence of the association of Spiroplasma sp. with TSE.

Creutzfeldt-Jakob disease in a husband and wife.

A 53-year-old man died of sporadic Creutzfeldt-Jakob disease (CJD) after a 1.5-year clinical course. Four and a half years later, his then 55-year-old widow died from CJD after a 1-month illness. Both patients had typical clinical and neuropathologic features of the disease, and pathognomonic proteinase-resistant amyloid protein ("prion" protein, or PrP) was present in both brains. Neither patient had a family history of neurologic disease, and molecular genetic analysis of their PrP genes was normal. No medical, surgical, or dietary antecedent of CJD was identified; therefore, we are left with the unanswerable alternatives of human-to-human transmission or the chance occurrence of sporadic CJD in a husband and wife.

Gliosarcoma developing from an irradiated ependymoma.

A 17-year-old girl was operated for a cystic mass located deep within the left parieto-occipital white matter. Histologically the tumor was an ependymoma with a vascular stroma. In spite of irradiation the tumor recurred locally twice, 1 and 2 years respectively after the original operation. The ependymoma portion of the tumor remained unchanged, but the stroma showed increased vascular hyperplasia at the time of the second operation and transformation into a fibrosarcoma in the third operative specimen. Proliferating cell markers (MIB-1) were positive only in the ependymoma cell nuclei in the first two specimens, but were also extensively present in the nuclei of the fibrosarcoma in the third specimen. In the latter, the fibrosarcoma portion greatly overwhelmed the residual ependymoma islands, but remained sharply delineated from them. This is the first observed case of a gliosarcoma originating from an ependymoma. The histological pattern of this mixed tumor clearly indicates that the source of the sarcomatous portions was the neoplastically transformed fibrovascular stroma of the original tumor, rather than "desmoplastic" alterations of the neoplastic ependymal cells themselves.

Vein, silastic, and polyglycolic acid fine mesh: a comparative study in peripheral nerve repair.

We investigated three sheathing materials (autogenous vein, silastic, and polyglycolic acid fine mesh) using the rat model. Forty rats were divided into five groups of eight animals each. Group A animals underwent transection of the sciatic nerve but had no repair. In Group B, a standard epineural repair was performed. In Groups C, D, and E, the nerve was repaired as in Group B with the addition of autogenous vein, Silastic, and polyglycolic acid fine mesh sheaths, respectively. Nerve regeneration and function were assessed using sciatic functional index, nerve conduction studies, and light microscopy. Sheathing methods showed no statistically significant advantage to standard epineural repair without a sheath.

Primary angiosarcoma of the brain.

We have described a 32-year-old black woman who had a primary angiosarcoma of the right occipital lobe. All three previously reported cases have been fatal within 1 year. Our patient is doing well more than 3 1/2 years after surgery.

Nonfulminant herpes simplex encephalitis as a cause for mesial temporal sclerosis.

Although mesial temporal sclerosis has been recognized for more than 100 years, its etiology remains unknown. It is proposed that a common infectious agent, herpes simplex virus type-1, may cause this disorder by means of a nonfulminant infection of mesial temporal lobe structures, which is resolved by the immune system and becomes gliotic in the course of healing by the central nervous system. Brain sections from a long-term experiment in a model of herpes simplex encephalitis reveal such a scar, which shows a high concentration of glial fibrillary acidic protein, without any evidence of residual herpes antigen, by immunocytochemistry.

The small midline occipital encephalomeningocele: definition of a syndrome.

An unusual group of encephalomeningoceles is described. Two children were noted at birth to have a raised area of abnormal skin at the occipital midline. Both of these lesions were found to perforate the superior sagittal sinus and to end between the leaves of the falx cerebri, and to contain a small amount of abnormal cerebral tissue with no connection to either occipital lobe. Previous case reports are reviewed; these lesions are true encephalomeningoceles, rather than glial heterotopias. The embryology of such lesions is considered, and likely differs from the much more common occipital encephalocele arising from one or both occipital lobes.

Effect of trimethoprim/sulphamethoxazole and hyperbaric oxygen on experimental Spiroplasma mirum encephalitis.

This study was undertaken to determine the susceptibility of experimentally induced Spiroplasma mirum infection in the rat to trimethoprim/sulfamethoxazole (TMP/SMX) in combination with hyperbaric oxygen (HBO). One-day-old Fisher 344 rats were intracerebrally inoculated with the GT-48 strain of S. mirum and were exposed to regimens employed combined antibiotic and HBO treatments. The exclusive use of TMP/SMX produced a significant reduction in mortality (P less than 0.0001) and an absence of clinical signs of infection. HBO in combination with TMP/SMX showed similar effect on mortality and no evident clinical disease. The addition of HBO did result in a significant decrease in spiroplasma brain titres but was no more effective in preventing the spiroplasma-induced fatal microcystic encephalopathy than when the antibiotics were used alone. The exclusive use of HBO produced a catastrophic mortality rate in the spiroplasma-infected rats, which is contrary to the effect of HBO on conventional bacterial infections.

Evaluation of [3H]thymidine uptake method for studying growth of spiroplasmas under various conditions.

[3H]thymidine uptake and colony counts are quantitative and inexpensive methods for studying Spiroplasma growth. Using these techniques, we demonstrated subtle effects on the growth of suckling mouse cataract agent of medium alterations, inoculum size, and freezing of cultures. In addition, suckling mouse cataract agent multiplied more actively under aerobic than under anaerobic conditions. These techniques have wide application for the study of Spiroplasma growth and will be useful for the development of a defined medium.

Neurovirulence in an experimental focal herpes encephalitis: relationship to observed seizures.

An animal model of focal herpes simplex encephalitis was used to study several strains of type-1 herpes simplex virus. Rabbits were inoculated in the olfactory bulb by a standardized technique. Virus strains resulting in mortality of greater than 70% produced seizures of 3 types, and all animals that seized became moribund or died. In contrast, a virus strain resulting in a 20% mortality produced no seizures. Administration of 60 mg phenobarbital intramuscularly daily reduced mortality significantly in animals given the epileptogenic viruses. Cultures from temporal and frontal lobes showed viral growth more frequently than did cultures of other brain areas. Microscopic examination of routine and immunoperoxidase-stained brain sections confirmed the focal nature of the infection. Clinical syndromes such as seizures arising from viral brain disease may influence mortality in animal model systems.

Malignant transformation in craniopharyngioma.

Malignant transformation in a craniopharyngioma has not been described previously. A 49-year-old woman presented with recurrence of a suprasellar craniopharyngioma diagnosed 35 years previously. The patient had been treated surgically for recurrence on five occasions. Radiation therapy had been administered 7 years before the final presentation. Tissue obtained from the fifth operation revealed malignant degeneration in a typical craniopharyngioma.

Antiserum to scrapie-associated fibril protein cross-reacts with Spiroplasma mirum fibril proteins.

Protease-resistant fibril proteins purified from Spiroplasma mirum and from Creutzfeldt-Jakob disease-infected brain tissues reacted with antisera to scrapie-associated fibrils on Western immunoblot analysis. These data suggest that there are conformational similarities among spiroplasma proteins and infection-specific proteins of the transmissible spongiform encephalopathies.