Stem cells reside in a microenvironment or niche that is critical for stem cell maintenance and regulation. But what happens when a stem cell niche is disrupted? In this issue of Cell, two reports (Walkley et al., 2007a, 2007b) demonstrate in mice that alterations in the niche for hematopoietic stem cells lead to the development of myeloproliferative disease.

OBJECTIVES To assess the importance of 2 variables, transducer tip diameter and resection of the round window (RW) niche, affecting the optimization of the mechanical stimulation of the RW membrane with an active middle ear implant (AMEI). MATERIALS AND METHODS Ten temporal bones were prepared with combined atticotomy and facial recess approach to expose the RW. An AMEI stimulated the RW with...

Recent theories in cognitive science have begun to focus on the active role of organisms in shaping their own environment, and the role of these environmental resources for cognition. Approaches such as situated, embedded, ecological, distributed and particularly extended cognition look beyond ‘what is inside your head’ to the old Gibsonian question of ‘what your head is inside of’ and with whi...

Adaptation to a specific niche theoretically constrains a population's ability to subsequently diversify into other niches. We tested this theory using the bacterium Pseudomonas fluorescens, which diversifies into niche specialists when propagated in laboratory microcosms. Numerically dominant genotypes were allowed to diversify in isolation. As predicted, populations increased in fitness throu...

JCB • VOLUME 171 • NUMBER 3 • 2005 406 Divided identities in the niche o maintain a stem cell niche at a fixed size, the niche exerts control over both cell differentiation (how many cells functionally leave the niche) and cell division. G. Venugopala Reddy and Elliot Meyerowitz (Caltech, Pasadena, CA) now show that, in the growing shoots of plants, these two control points are separable in bot...

Increasing evidence points to extracellular matrix (ECM) components playing integral roles in regulating the muscle satellite cell (SC) niche. Even small alterations to the niche ECM can have profound effects on SC localization, activation, self-renewal, proliferation and differentiation. This review will focus on the ECM components that comprise the niche, how they are modulated in health and ...

BACKGROUND A caesarean section (CS) can cause a defect or disruption of the myometrium at the site of the uterine scar, called a niche. In recent years, an association between a niche and postmenstrual spotting after a CS has been demonstrated. Hysteroscopic resection of these niches is thought to reduce spotting and menstrual pain. However, there are no randomised trials assessing the effectiv...

OBJECTIVE To evaluate the effectiveness of a laparoscopic niche resection on niche-related symptoms and/or fertility-related problems, ultrasound findings and quality of life. DESIGN Prospective cohort study. SETTING University hospital. POPULATION Women with a large niche (residual myometrium <3 mm) and complaints of either postmenstrual spotting, dysmenorrhoea, intrauterine fluid accumu...

In the course of an adaptive radiation, the evolution of niche parameters is of particular interest for understanding modes of speciation and the consequences for coexistence of related species within communities. We pose a general question: In the course of an evolutionary radiation, do traits related to within-community niche differences (alpha niche) evolve before or after differentiation of...

Boivin et al.’s (1) article profoundly deepens scientific understanding of anthropogenic global ecological change from Pleistocene to present by offering robust new evidence of early human transformation of the biosphere that should influence discussions on Anthropocene formalization (2, 3). As ecologists and evolutionary theorists, we applaud this work. However, we are also concerned that this...