The Synthesis and Stability of Si1−yQy Alloys and Strained Layer Superlattices

We have synthesized Si1−yQy layers and strained layer superlattices on Si (100) with C concentrations of up to a few percent using Solid Source Molecular Beam Epitaxy. The presence of C even in small quantities is known to disrupt the epitaxy of Si. We show that under conditions of high Si flux for a given C/Si flux ratio, defect-free epitaxy results. However, exceeding a critical C/Si flux ratio leads to disruption of epitaxy, initially via twinning and subsequently by amorphous growth. Growth temperature also plays a significant role in preventing twinning and islanding. Low growth temperature also suppresses the precipitation of β-SiC and leads to the formation of pseudomorphic Si1−yQy random alloys. The layers are characterized by X-ray diffraction, Secondary Ion Mass spectroscopy, and Transmission Electron Microscopy. We have also studied the thermal stability of strained layer superlattices and find that the layers are stable to about 800°C (for y = 0.003). Between 800°C and 1000°C, the layers relax by interdiffusion. Above 1000°C, silicon carbide precipitation occurs and the carbide layers nucleate and grow at high C content regions of the film.

Quantitative profiling of the pathological prion protein allotypes in bank voles by liquid chromatography-mass spectrometry

The conversion of the cellular prion protein (PrP(C)) into a misfolded isoform (PrP(TSE)) that accumulates in the brain of affected individuals is the key feature of transmissible spongiform encephalopaties (TSEs). Susceptibility to TSEs is influenced by polymorphisms of the prion gene suggesting that the presence of certain amino acid residues may facilitate the pathological conversion. In this work, we describe a quantitative, fast and reliable HPLC-MS method that allowed to demonstrate that in the brain of 109(Met/Ile) heterozygous bank voles infected with the mouse adapted scrapie strain 139A, there are comparable amounts of PrP(TSE) with methionine or isoleucine in position 109, suggesting that in this TSE model the two allotypes have similar rates of accumulation. This method can be easily adapted for the quantitative determination of PrP allotypes in the brain of other natural or experimental TSE models.

Identification of the pathological prion protein allotypes in scrapie-infected heterozygous bank voles (Clethrionomys glareolus) by high-performance liquid chromatography-mass spectrometry

Cerebral formation of the pathological isoform of the prion protein (PrP) is a crucial molecular event in prion diseases. The bank vole (Clethrionomys glareolus) is a rodent species highly susceptible to natural scrapie. The PrP gene of bank vole is polymorphic (Met/Ile) at codon 109. Here we show that homozygous 109Met/Met voles have incubation times shorter than heterozygous 109Met/Ile voles after experimental challenge with three different scrapie isolates. An HPLC-MS/MS method was optimized and applied to investigate whether in heterozygous animals both PrP allotypes are able to undergo pathological conversion. The results demonstrate that both allotypes of the prion protein participate to pathological deposition.

Creutzfeldt-Jakob disease associated with the R208H mutation in the prion protein gene

The authors investigated a patient who died of apparent sporadic Creutzfeldt-Jakob disease (CJD) but carried a R208H substitution in the prion protein (PrP). The patient phenotype was indistinguishable from typical sporadic CJD (i.e., MM1 subtype). In addition, pathologic PrP, PrP(Sc), originated from both the normal and the mutated PRNP allele and had the same characteristics as PrP(Sc) type 1. The authors propose that the R208H mutation influences disease susceptibility without significantly affecting PrP(Sc) properties or disease phenotype.

Natural specific radioactivity in different soils. Transfer in the soil plant food chain

In order to warrant customer's health we must pay attention to the quality of the environment and production processes; that means look all over alimentary chain. Media speak often about this topics, because of the interest of the public opinion regarding agribusiness; Nether the less much is know about soil radioactivity, but often scant attention is directed to the knowledge of the amount what remains in food and arrives to the man who is the last and main user of the product. As a consequence of that, we have done some originals studies concerning specific radioactivity in alimentary chain: soil-plant-food. These studies have been made in relation with geopedologic position of fields in volcanic, clayey, sandy soils of Latium. We have measured radioactive activity over some alimentary chains both annual (like turnip and garden cress) and pluriannual (such as vine). We made comparisons on the same soils studying the following natural markers: K40, Pb214, and Bi214; and Cs137, one of the main natural markers.

Increased CSF levels of prostaglandin E(2) in variant Creutzfeldt-Jakob disease

The concentration of the cyclooxygenase product prostaglandin E(2) was sixfold higher in CSF samples from 18 cases of variant Creutzfeldt-Jakob disease (CJD) than in a group of eight subjects with other noninflammatory neurologic diseases, and comparable to those found in a group of six patients affected by diseases with a known inflammatory component. This finding suggests that cyclooxygenase activity may have a role in variant CJD pathogenesis, as previously reported in sporadic CJD.

Increased brain synthesis of prostaglandin E2 and F2-isoprostane in human and experimental transmissible spongiform encephalopathies

The levels of 2 arachidonic acid metabolites formed either by enzymatic activity of cyclooxygenase, i.e. prostaglandin E2 (PGE2), or by free radical-catalyzed peroxidation, i.e. F2-isoprostane 8-epi-prostaglandin F2alpha (8-epi-PGF2alpha), were measured in the CSF of subjects with sporadic and familial Creutzfeldt-Jakob disease (CJD) and in brain homogenates of scrapie-infected mice. The CSF levels of both metabolites were increased in sporadic CJD (n = 52) and familial CJD (n = 10) patients when compared with a group of patients with noninflammatory disorders. Similarly, PGE2 and 8-epi-PGF2alpha levels were higher in brain homogenates obtained from C57BL/6J mice infected with the ME7 scrapie strain than in brain homogenates from control animals. As PGE2 is 1 of the most abundant prostaglandins released during inflammation and 8-epi-PGF2alpha is a quantitative marker of lipid peroxidation, our results provide in vivo biochemical evidence for the occurrence of inflammation and oxidative stress in human and experimental transmissible spongiform encephalopathies (TSEs), a concept so far based mainly on histopathological and in vitro evidence. Interestingly, in sporadic CJD patients, high CSF levels of PGE2, but not 8-epi-PGF2alpha, correlated with short survival time, suggesting that the inflammatory response correlates with the clinical duration of disease.

Analysis of EEG and CSF 14-3-3 proteins as aids to the diagnosis of Creutzfeldt-Jakob disease

OBJECTIVE

To improve diagnostic criteria for sporadic Creutzfeldt-Jakob disease (CJD).

METHODS

Pooled data on initial and final diagnostic classification of suspected CJD patients were accumulated, including results of investigations derived from a coordinated multinational study of CJD. Prospective analysis for a comparison of clinical and neuropathologic diagnoses and evaluation of the sensitivity and specificity of EEG and 14-3-3 CSF immunoassay were conducted.

RESULTS

Data on 1,003 patients with suspected CJD were collected using a standard questionnaire. After follow-up was carried out, complete clinical data and neuropathologic diagnoses were available in 805 cases. In these patients, the sensitivity of the detection of periodic sharp wave complexes in the EEG was 66%, with a specificity of 74%. The detection of 14-3-3 proteins in the CSF correlated with the clinical diagnosis in 94% (sensitivity). The specificity (84%) was higher than that of EEG. A combination of both investigations further increased the sensitivity but decreased the specificity.

CONCLUSIONS

Incorporation of CSF 14-3-3 analysis in the diagnostic criteria for CJD significantly increases the sensitivity of case definition. Amended diagnostic criteria for CJD are proposed.

Prion protein glycotype analysis in familial and sporadic Creutzfeldt-Jakob disease patients

Creutzfeldt-Jakob disease (CJD) and other transmissible spongiform encephalopathies (TSEs) are characterised by the accumulation of a pathological conformer of PrP, named PrPsc. Molecular weight and glycosylation of the protease-resistant core of PrPsc (PrP27-30) are heterogeneous in different forms of TSEs. We analysed PrP27-30 glycotypes in a large number of TSE-affected patients: 50 sporadic CJD (sCJD), 1 iatrogenic CJD, 1 Gerstmann-Sträussler-Scheinker syndrome (GSS) with the Pro102Leu mutation of PrP, 3 familial CJD (fCJD) with the Glu200Lys mutation and, for the first time, 7 fCJD with the Val210ll3e mutation. All patients were screened for the polymorphic codon 129 of the PrP gene. PrP27-30 deglycosylation and PrPsc immunohistochemistry were performed in selected cases. We found that two PrP27-30 glycotypes (type 1A and type 2A) are produced in sCJD. Type 1A is more frequently associated with methionine than valine in position 129. Type 1A is also formed in Val210lle fCJD. In Glu200Lys fCJD and GSS patients, we found that PrP27-30 has the same mobility of type 1 but different glycosylation ratios (type 1B). Our findings indicate that the polymorphic residue 129 of PrP has a leading role in determining the proteinase degradation site of PrPsc while mutant residues 102 or 200 influence only the glycosylation pattern.

Highly infectious purified preparations of disease-specific amyloid of transmissible spongiform encephalopathies are not devoid of nucleic acids of viral size

An efficient purification protocol for infectivity causing a transmissible spongiform encephalopathy (TSE) is described. From fractions purified by this protocol about 3 x 10(8) LD50 but only 3 ng of nucleic acids per gram of brain material can be isolated from all TSE-affected brains (hamster, human, sheep, cattle). By PAGE such fractions from brains of infected and control hamsters contained only one distinct nucleic acid band of 1.5 kg together with some broader smear of nucleic acid material. Although distilled water was used for such purifications, quite often a similar nucleic acid band was isolated from blanks containing no brain material. In all instances this material proved to be DNA. The result challenges the potentially important claim that purified infectious preparations of TSE-specific amyloid are free of nucleic acids of viral size. Nucleic acids isolated by other groups from diseased brain were not detected in preparations isolated by the new protocol. The application of this purification protocol in future studies will be helpful to decide whether TSEs are caused by agents containing nucleic acid or by protein only.

Identification of the prion protein allotypes which accumulate in the brain of sporadic and familial Creutzfeldt-Jakob disease patients

A characteristic feature of Creutzfeldt-Jakob disease (CJD) is the accumulation in the brain of the amyloid protease-resistant protein PrPres. PrPres derives from a host-encoded, protease-sensitive isoform, PrPsen. Mutations of this protein are linked to familial variants of the disease, and the presence of a methionine or valine residue at the polymorphic position 129 may be critical in sporadic CJD cases. We found that in the brain of patients heterozygous for the mutation in which isoleucine is substituted for valine at codon 210 (Val21Olle), the PrPres is formed by both the wild-type and mutant PrPsen. We also found that in a sporadic CJD patient, who was heterozygous (Met/Val) at position 129, PrPres is also formed by both allotypes. These data associate transmissible spongiform encephalopathies with other amyloidosis, although the nature of the transmissible agent remains unsettled.

Polymorphism at codon 129 or codon 219 of PRNP and clinical heterogeneity in a previously unreported family with Gerstmann-Sträussler-Scheinker disease (PrP-P102L mutation)

We present a new, large, Italian family affected by Gerstmann-Sträussler-Scheinker syndrome (GSS) associated with the Pro to Leu point mutation at codon 102 of the prion protein gene (PRNP). The affected members of this family show a remarkable phenotypic variability of the disease: three of them had a clinical picture characterized by dementia and a brief illness duration (less than 1 year), while the other five members presented an ataxic, slowly evolving syndrome (a clinical duration of 3 to 4 years) with no evidence of cognitive impairment. Despite these remarkable clinical differences among affected members, we found no correlation between the clinical presentation and the codon 129 or codon 219 genotypes. These data suggest that factors as yet unidentified may influence the clinical expression of the disease.

A panencephalopathic type of Creutzfeldt-Jakob disease with selective lesions of the thalamic nuclei in 2 Swiss patients

Creutzfeldt-Jakob disease (CJD), a subacute spongiform encephalopathy, is generally included among the group of human and animal diseases which is transmissible by a non-conventional agent, the prion, whose expression is conditioned by the host's genome. The process leading to neuropathological changes is still unknown. We report the neuropathological findings in 2 cases of the "panencephalopathic" variant of CJD, which is relatively common in Japan, but extremely rare in Europe and North America. When compared with the classical form this variant is characterized by a relatively long clinical course with persistent vegetative state and primary involvement of the white matter presenting in the form of demyelination and gemistocytic gliosis. The selective involvement of certain thalamic nuclei is a particular pathological feature in both our cases. There was practically complete neuronal loss with diffuse gliosis of the anteroventral (AV) and dorsomedial (DM) nuclei, while the neuronal loss in the pulvinar remained moderate: the other nuclei were apparently spared. A similar involvement of the thalamus has been reported in fatal familial insomnia, a recently described prion disease in which these lesions are predominant. A comparable distribution has also been observed in other degenerative neurological diseases such as Steele-Richardson-Olszewski disease, Alzheimer disease, and thalamic dementia (selective thalamic atrophy or with multisystemic degeneration). The AV and DM nuclei, commonly referred to as "limbic thalamus" represent phylogenetically the most recent thalamic structures and would appear to play an important role in the superior functions in man as memory, attention and awareness. In our cases thalamic lesions are selective, bilateral, and symmetric, not explained by Wallerian degeneration. These lesions may be due to the primary pathogenetic properties of the infectious agent. The rapid clinical evolution in a persistent vegetative state could be consequential to precocious and severe disfunction of the limbic thalamus.

Detection of proteinase-resistant protein (PrP) in small brain tissue samples from Creutzfeldt-Jakob disease patients

We describe a short and a sensitive method to isolate PrP in small samples of brain tissue using a one day procedure. The tissue was homogenized in sarkosyl, cleared by low-speed centrifugation, and then ultracentrifuged. The pellet was suspended in 10 mM Tris-HCl, 10% NaCl, 1% sarkosyl, precipitated by centrifugation and re-suspended in the above solution with proteinase K. After digestion, PrP was spun down, electrophoresed on a 15% SDS-polyacrylamide minigel and then electro-transferred to a nitrocellulose membrane. The blots were processed with rabbit polyclonal antibody against hamster PrP27-30. Four bands of PrP with molecular weights of 28-30 kDa, 24-26 kDa, 19-20 kDa, and 16 kDa were clearly detected by Western blot in two samples obtained by brain biopsy. To test the sensitivity and the specificity of our method we also purified PrP from 20, 50 and 100 mg of cerebral cortical tissues taken from six frozen CJD brains and one Alzheimer's disease brain of our collection. All the CJD samples, but not the Alzheimer's disease one, resulted positive by Western blot. In the smallest sample tested (20 mg), there was at least one band (about 25 kDa) of PrP detectable by Western blot. Thus, this is a valid and efficient method for the diagnosis of CJD in small brain tissue samples.

Influence of lactate on isoproterenol-induced lipolysis and beta-adrenoceptors distribution in human fat cells

The influence of lactate on human adipocytes lipolysis and the possible relationship between lactate-induced metabolic effects and beta-adrenoceptor binding sites were investigated. beta-sites were identified in membranes with (125I)-cyanopindolol and in intact cells with (125I)-cyanopindolol and (3H)-CGP 12177. Lactate reduced isoproterenol-induced lipolysis in a dose-response fashion and such inhibition became significant only at 16 mmol/l lactate. Exposure of human fat cells to 16 mmol/l lactate significantly reduced beta-adrenoceptors density on crude membranes. When the binding assay was performed on intact cells using (125I)-cyanopindolol at 37 degrees C, the radioligand identified the same number of receptors, regardless of the presence of lactate in the preincubation medium. When (3H)-CGP 12177 was used, it bound to about 35% less receptors in lactate pre-treated cells than in control. Seemingly, at 37 degrees C, because of its lipophilicity, (125I)-cyanopindolol can cross the plasma membrane and bind to intracellular sites whereas, (3H)-CGP 1277, due to its hydrophilicity, identifies surface receptors only. Thus, the present in vitro study provides evidence that high levels of lactate, similar to the concentrations usually achieved in overt lactic acidosis, are able per se to inhibit human lipolysis and to redistribute beta-adrenoceptors from cell surface to a domain not accessible to hydrophilic ligands.

[Course of skin allografts in rabbits immunized by heterologous red blood cells]

Skin allografts were done in rabbits previously immunized with sheep red blood cells at 1-10 day intervals. Results showed that mean allograft survival was not delayed, nor was accelerated rejection observed. It is concluded that antigenic competition between sheep erythrocytes and skin allografts does not exist.