RESUMEN
Parafermions are generalizations of Majorana fermions that may appear in interacting topological systems. They are known to be powerful building blocks of topological quantum computers. Existing proposals for realizations of parafermions typically rely on strong electronic correlations which are hard to achieve in the laboratory. We identify a novel physical system in which parafermions generically develop. It is based on a quantum constriction formed by the helical edge states of a quantum spin Hall insulator in the vicinity of an ordinary s-wave superconductor. Interestingly, our analysis suggests that Z_{4} parafermions are emerging bound states in this setup in the weakly interacting regime. Furthermore, we identify a situation in which Majorana fermions and parafermions can coexist.
RESUMEN
Despite remarkable progress made in the fields of antiviral therapy and virological laboratory diagnosis, infections with the human cytomegalovirus (CMV) still pose considerable problems in certain patient groups. The variety of available test methods - mostly not standardised - with their different test characteristics, sample types etc. is often confusing for the clinician. There is often great uncertainty as to whether a given laboratory result is pathognomonic. In addition, not only is the diagnostic repertoire growing constantly - for instance through genome quantification and measurement of virus-specific T lymphocytes - but also the available antiviral therapeutic options with the need for adequate surveillance. This paper gives an up-to-date overview about the available diagnostic means with their specific advantages and disadvantages. Concrete recommendations regarding a rational and comprehensive, yet economic approach to CMV diagnosis have to be targeted at the individual patient group and specific diagnostic problem; this is beyond the scope of this paper and the reader is referred to the pertinent expert groups' publications. This review article deals with general and fundamental aspects.
Asunto(s)
Infecciones por Citomegalovirus/diagnóstico , Citomegalovirus/aislamiento & purificación , Distribución por Edad , Anticuerpos Antivirales/análisis , Antígenos Virales/análisis , Citomegalovirus/genética , Citomegalovirus/inmunología , Citomegalovirus/patogenicidad , Infecciones por Citomegalovirus/epidemiología , Infecciones por Citomegalovirus/virología , ADN Viral/análisis , Genoma Viral , Humanos , ARN Mensajero/análisis , Factores de RiesgoRESUMEN
Adherently growing, non-hematopoietic somatic stem cells isolated from human cord blood were stained with the fluorescent dye PKH26 and transplanted into livers of SCID-mice to examine a possible cell fate transition. Already 7 days after transplantation stem cells were well integrated into the liver tissue. Human albumin that was not expressed by the stem cells before transplantation was detectable in the host's livers after injection of cord blood stem cells. Human alpha1-antitrypsin was detectable in stem cells already before transplantation and remained positive in the mouse liver. The most interesting observation in this study was the downregulation of human beta2-microglobulin (beta2M) in the stem cells after transplantation: beta2M is expressed constitutively in our cord blood stem cells. However, beta2M was no longer detectable by RT-PCR in all tissues where human albumin and alpha1-antitrypsin were expressed after stem cell transplantation. beta2M is known to participate as an integral part of the major histocompatibility complex. Absence of beta2M makes the residual heavy chain inactive as an antigen. Thus, downregulation of beta2M may represent an escape mechanism from killer-T cells and may be a molecular mechanism explaining the recently described "immunological blindness" [37] of stem cells. In contrast to the results obtained after direct injection of stem cells as a suspension, no consistent downregulation of beta2M was observed after transplantation of stem cells encapsulated in alginate beads to generate a compartment where stem cells are protected from the host's natural killer cells. No expression of human genes was observed after transplantation of human cord blood derived mononuclear cells (MNC) that were used as a negative control. In conclusion, we have shown that human cord blood somatic stem cells survive and are reprogrammed after transplantation into mouse livers, although a complete transdifferentiation to hepatocytes did not occur within 7 days, since some marker genes (GATA4 and alpha-fetoprotein) were still negative. Switching off expression of beta2M may be part of an intriguing and novel mechanism explaining why stem cells escape the host's immune system.
Asunto(s)
Sangre Fetal/citología , Trasplante de Células Madre Hematopoyéticas , Hígado/citología , Trasplante de Células Madre , Microglobulina beta-2/metabolismo , Anciano , Albúminas/genética , Albúminas/inmunología , Albúminas/metabolismo , Animales , Regulación hacia Abajo , Silenciador del Gen , Humanos , Inmunohistoquímica , Masculino , Ratones , Ratones SCID , ARN Mensajero/biosíntesis , Células Madre/metabolismo , Células Madre/fisiología , Activación Transcripcional , Tolerancia al Trasplante , Microglobulina beta-2/genéticaRESUMEN
In cooperation with the management of the cafeterias of the University of Zurich the Institute of Social and Preventive Medicine intended to show that good eating is not contrary to healthy eating. This message was presented verbally (exhibition and pamphlets) as well as practically (healthy menus). The campaign lasted two weeks. A pamphlet containing the nutritional basics for each of the ten menus was distributed every day. The exhibition presented the nutritional highlights with emphasis on health and environment. The impact of the campaign was evaluated with a written questionnaire.