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1: Science. 2008 Feb 15;319(5865):966-8.Click here to read Links
Comment in:
Science. 2008 Jun 27;320(5884):1720.

The critical importance of retrieval for learning.

Karpicke JD, Roediger HL 3rd.

Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, USA. karpicke@purdue.edu

Learning is often considered complete when a student can produce the correct answer to a question. In our research, students in one condition learned foreign language vocabulary words in the standard paradigm of repeated study-test trials. In three other conditions, once a student had correctly produced the vocabulary item, it was repeatedly studied but dropped from further testing, repeatedly tested but dropped from further study, or dropped from both study and test. Repeated studying after learning had no effect on delayed recall, but repeated testing produced a large positive effect. In addition, students' predictions of their performance were uncorrelated with actual performance. The results demonstrate the critical role of retrieval practice in consolidating learning and show that even university students seem unaware of this fact.

PMID: 18276894 [PubMed - indexed for MEDLINE]

2: Science. 2008 Feb 15;319(5865):962-5.Click here to read Links
Comment in:
Science. 2008 Feb 15;319(5865):910-1.

Metal chelation and inhibition of bacterial growth in tissue abscesses.

Corbin BD, Seeley EH, Raab A, Feldmann J, Miller MR, Torres VJ, Anderson KL, Dattilo BM, Dunman PM, Gerads R, Caprioli RM, Nacken W, Chazin WJ, Skaar EP.

Department of Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.

Bacterial infection often results in the formation of tissue abscesses, which represent the primary site of interaction between invading bacteria and the innate immune system. We identify the host protein calprotectin as a neutrophil-dependent factor expressed inside Staphylococcus aureus abscesses. Neutrophil-derived calprotectin inhibited S. aureus growth through chelation of nutrient Mn2+ and Zn2+: an activity that results in reprogramming of the bacterial transcriptome. The abscesses of mice lacking calprotectin were enriched in metal, and staphylococcal proliferation was enhanced in these metal-rich abscesses. These results demonstrate that calprotectin is a critical factor in the innate immune response to infection and define metal chelation as a strategy for inhibiting microbial growth inside abscessed tissue.

PMID: 18276893 [PubMed - indexed for MEDLINE]

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