Triple check for antigen specificity of B cells during germinal centre reactions

Somatic hypermutation of the immunoglobulin variable genes during germinal reactions might permit the expansion of B-cell clones with unwanted (e.g. autoreactive) specificity. Here, Ernst Lindhout and colleagues propose three antigen-specific checkpoints that ensure the appropriate antigen specificity of activated B cells is maintained by regulating the activation, selection and further differentiation of B cells.     

Nasopharyngeal colonization in Costa Rican children during the first year of life

BACKGROUND: The establishment of the nasopharyngeal flora was followed in Costa Rican children from birth to 1 year of age. METHODS: Nasopharyngeal cultures were obtained at 1 (n = 413), 3 (n = 393), 6 (n = 376) and 12 months (n = 356) of age from children representative of the population in the Puriscal district. Weekly cultures were obtained from a subcohort of these children (n = 101). Mother-infant diads (n = 95) and preschool children (n = 208) attending day-care centers were also studied. RESULTS: The estimated proportion of colonized children in the population differed markedly depending on the frequency of culture. Quarterly cultures showed a slow increase in carrier rates from 3.9% for Haemophilus influenzae, 3.1% for Streptococcus pneumoniae and 6.5% for Moraxella catarrhalis at 1 month of age to 10.1% carrying H. influenzae and 19.4% carrying S. pneumoniae by the end of the first year. By quarterly culture the proportion of children colonized at least once was 36% for S. pneumoniae, 26% for H. influenzae and 28% for M. catarrhalis. In contrast weekly sampling showed that 95 to 100% of the children were colonized at least once during the first year of life with H. influenzae, S. pneumoniae or M. catarrhalis. Nasopharyngeal carriage of H. influenzae, S. pneumoniae and M. catarrhalis was low in the mothers, and very few mother-infant pairs carried identical bacteria at the same time. In contrast carrier rates were high in the siblings attending day care (H. influenzae 27.9%, S. pneumoniae 39.4%, both organisms 26.6%). Infants with siblings had significantly higher bacterial carriage at all ages than infants without siblings. CONCLUSIONS: Quarterly nasopharyngeal cultures showed that Costa Rican infants acquire their nasopharyngeal flora at a rate comparable with that for infants in developed countries and that siblings are an important source of the bacteria. Weekly samplings showed that virtually all children were colonized at least once during the first year of life.     

Clinical oncology nurses' perceptions of research

Within the realm of oncology nursing, research has been an integral part in its development as a specialty practice. Yet despite the growing volume of published nursing research studies, little is known about how nurses working in oncology care settings perceive research. Therefore, the purposes of this study were to examine clinical oncology nurses' perceptions of research and to determine factors influencing their perceptions. Two hundred and eighty-three registered nurses providing cancer care to patients in 40 health care agencies across northern Ontario participated in the survey. Data were collected using a questionnaire developed by Alcock and colleagues (1990) which addressed nurses' perceived value of research, their role, interest and experience in research as well as the research climate of the agency. The findings showed that respondents valued nursing research and perceived a research role for staff nurses. However, the respondents did not perceive strong administrative or collegial support for nurses' involvement in research activities. In addition, the study results indicated that the clinical oncology nurses' perceptions of research were influenced by educational preparation.     

Review of Constructing the subject: Historical origins of psychological research.

Reviews the book, Constructing the subject: Historical origins of psychological research by Kurt Danziger (1990). Kurt Danziger's Constructing the Subject: Historical Origins of Psychological Research is a book of singular importance because it provides such a penetrating analysis, and does so in a manner that is cause for considerable reflection. In brief, Danziger provides a history lesson that not only situates the names and the projects of experimental psychology in the first part of this century, but also aims to clarify the project of knowledge generation both past and present. Indeed, shades of Quine, Kuhn, and Hesse permeate this book in a way that demands psychologists examine their own investigative practices and logics of justification. Through Wundt, through Galton, through Ebbinghaus and others, Danziger illuminates the development of experimental psychology along with the historical and philosophical vicissitudes that have given rise to numerous psychological knowledge claims. If it is true that we must understand our history in order to understand our present, then Danziger's book should be required reading in all research laboratories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In Situ ceramic particle-reinforced aluminum matrix composites fabricated by reaction pressing in the TiO2 (Ti)-Al-B (B2O3) systems

Particulate TiB₂ reinforced aluminum-based metal matrix composites (MMCs) were successfully fabricated by means of the reaction processing method. TiB₂ particulates were formed in situ through the reaction of Ti and B in Ti-Al-B, TiO₂ and B in TiO₂-Al-B, and TiO₂ and B₂O₃ in TiO₂-Al-B₂O₃ systems. The results showed that in situ TiB₂ particulates formed in the Ti-Al-B system had a size of 5 μm and they exhibited block and rodlike structures. Moreover, coarse Al₃Ti blocks several tens of micrometers in size were also formed simultaneously. On the other hand, equiaxed Al₂O₃ and TiB₂ particulates with a size of less than 2 μm were formed in situ in the TiO₂-Al-B and TiO₂-Al-B₂O₃ systems. The Al₃Ti phase was completely eliminated in the TiO₂-Al-B system with increasing B content. Tensile tests revealed that the Al₂O₃ · TiB₂/Al composite fabricated from the TiO₂-Al-B system exhibits excellent mechanical properties. The yield strength of the Al₂O₃ · TiB₂/Al composite appeared to increase with increasing TiB₂ content. The yield strength of the Al₂O₃ · TiB₂/Al composite could be further increased by introducing CuO into the TiO₂-Al-B system. Such an increment in mechanical strength arose from the strengthening effect caused by the Al₂Cu precipitates. The incorporation of CuO had no effect on the in situ reaction process of the TiO₂-Al-B system. Finally, the effect of SiC addition on the microstructure and mechanical properties of the composites fabricated from the TiO₂-Al-B and TiO₂-Al-B-CuO systems was also investigated.     

Laparoscopic operation of a Morgagni hernia

Morgagni hernias are the least common form of diaphragmatic hernias. Although they are congenital, most of them are not diagnosed until later in life. The indication for surgery is based on the patient's symptoms or on the radiological evidence of incarcerated tissue, and until quite recently involved a laparotomy or thoracotomy. Laparoscopy not only permits the suspected diagnosis to be confirmed--which is otherwise often difficult--but also makes it possible to close the hernia site by suturing. For improved security, the hernia site is augmented by fixing in place a non-absorbable mesh. The operative technique employed is described.     

Visualization of mitochondria with green fluorescent protein in cultured fibroblasts from patients with mitochondrial diseases

cDNAs for green fluorescent protein (GFP) and for a GFP fusion protein containing the presequence of human ornithine transcarbamylase (pOTC-GFP) were transfected into cultured human fibroblasts. GFP cDNA gave diffuse fluorescence throughout the cytoplasm and the nucleus, whereas pOTC-GFP cDNA gave mitochondria-associated fluorescence. Fluorescent mitochondrial structures could be classified into five patterns: thread-like mitochondria, fine thread-like ones, rod-like ones, granular ones, and granular ones with weak cytosolic fluorescence. pOTC-GFP mutants resulted in a loss of mitochondrial fluorescence and an appearance of weak fluorescence throughout the cytoplasm. pOTC-GFP cDNA was transfected into fibroblasts from patients with various mitochondrial diseases. Higher ratios of fibroblasts with granular mitochondria and those with fine thread-like ones were observed in a patient with Reye's syndrome and a patient with Kearns-Sayre syndrome. Weak cytosolic fluorescence was sometimes observed in fibroblasts from these patients. This method will be useful to analyze mitochondrial structural alterations and disorders of mitochondrial protein import.