Adhesión de streptococcus mutans sobre hidroxiapatita in vitro

En el presente trabajo se evalúa la adhesión de Streptococcus mutans a hidroxiapatitas de diferente naturaleza en una solución oral sintética. La adhesión microbiana fue determinada indirectamente por recuento de los microorganismos viables en suspensiones equilibradas con los sustratos. Los resultados obtenidos mostraron que, a baja concentración de inóculo, la adhesión de Streptococcus mutans puede ser descripta, razonablemente, mediante una única isoterma de Langmuir, introduciendo una pequeña corrección en cada muestra para dar cuenta de las diferencias en la macrorugosidad. La constante de afinidad resultó ser aproximadamente igual a 0,25´10- 8 (bacterias/mL)-1. La falta de influencia del sustrato se interpreta en términos del mecanismo de adsorción del S. mutans, y el gran tamaño de la bacteria, que disimula diferencias químicas y morfológicas de la superficie en la dimensión nanométrica. Estos resultados sugieren que la derivatización de la superficie con grandes polímeros puede ser una alternativa más útil para modificar la adhesión bacteriana. A altas concentraciones de inóculo, se dispara una adhesión multicapa, descrita por una ecuación modificada de Hill, con un coeficiente n = 3, que indica fuertes interacciones atractivas entre bacterias.Peer Reviewe

Iminium Salts of ω-Dithiafulvenylpolyenals: An Easy Entry to the Corresponding Aldehydes and Doubly Proaromatic Nonlinear Optic-phores

A short, high-yielding route to ω-dithiafulvenylpolyenals (1) via the corresponding iminium salts (2) and starting from trimethyl-1,3-dithiolium tetrafluoroborate is reported. The Knoevenagel reactions of either 1 or 2 with isoxazolone-containing acceptors afford merocyanines 7 and 9, in a process that is often accompanied by a vinylene-shortening side reaction. Experimental and theoretical studies reveal that compounds 7 and 9, featuring two proaromatic end groups, are strongly polarized and show good second-order nonlinear optical responses

New insights into the genetic etiology of Alzheimer's disease and related dementias.

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

The Thermal Evolution of a Barium Ferrite Precursor Obtained by a New Chemical Coprecipitation Method

The evolution during thermal treatment of the precursor obtained by a new method to synthezise barium hexaferrite by chemical coprecipitation is described; the method involves the precipitation froma strongly alkaline ferrate(VI) solution containing barium chloride. Barium hexaferrite may be formed by heating of the original superparamagnetic precursor at temperatures as low as 700°C as shown by XRD, Mössbauer spectra and DTA-TGA behaviour. The precursor does not contain appreciable amounts of carbonate, thus favouring the formation of the hexaferrite at lower temperatures. Scanning electron microscopy shows that the ferrite particles are less than 0.5 µm in diameter

Adhesión de streptococcus mutans sobre hidroxiapatita in vitro

En el presente trabajo se evalúa la adhesión de Streptococcus mutans a hidroxiapatitas de diferente naturaleza en una solución oral sintética. La adhesión microbiana fue determinada indirectamente por recuento de los microorganismos viables en suspensiones equilibradas con los sustratos. Los resultados obtenidos mostraron que, a baja concentración de inóculo, la adhesión de Streptococcus mutans puede ser descripta, razonablemente, mediante una única isoterma de Langmuir, introduciendo una pequeña corrección en cada muestra para dar cuenta de las diferencias en la macrorugosidad. La constante de afinidad resultó ser aproximadamente igual a 0,25´10- 8 (bacterias/mL)-1. La falta de influencia del sustrato se interpreta en términos del mecanismo de adsorción del S. mutans, y el gran tamaño de la bacteria, que disimula diferencias químicas y morfológicas de la superficie en la dimensión nanométrica. Estos resultados sugieren que la derivatización de la superficie con grandes polímeros puede ser una alternativa más útil para modificar la adhesión bacteriana. A altas concentraciones de inóculo, se dispara una adhesión multicapa, descrita por una ecuación modificada de Hill, con un coeficiente n = 3, que indica fuertes interacciones atractivas entre bacterias.Peer Reviewe