Can ends justify the means?: Telomeres and the mechanisms of replicative senescence and immortalization in mammalian cells

Finite replicative lifespan, or senescence, of mammalian cells in culture is a phenomenon that has generated much curiosity since its description. The obvious significance of senescence to organismal aging and the development of cancer has engendered a long-lasting and lively debate about its mechanisms. Recent discoveries concerning the phenotypes of telomerase knockout mice, the consequences of telomerase reexpression in somatic cells, and genes that regulate senescence have provided striking molecular insights but also have uncovered important new questions. The objective of this review is to reconcile old observations with new molecular details and to focus attention on the key remaining puzzles.

Enabling, empowering, inspiring: research and mentorship through the years*

The interrelationship between research and mentorship in an association such as the Medical Library Association (MLA) is revealed through the contributions of individuals and significant association activities in support of research. Research is vital to the well-being and ultimate survival of health sciences librarianship and is not an ivory tower academic activity. Mentorship plays a critical role in setting a standard and model for those individuals who want to be involved in research and, ultimately, for the preparation of the next generation of health sciences librarians. Research and mentorship are discussed in the context of personal experiences, scholarship, and problem solving in a practice environment. Through research and mentorship, we are enabled to enhance our services and programs, empowered to look beyond our own operations for information puzzles to be solved, and inspired to serve society by improving health.

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

We used positron emission tomography (PET) to examine the role of the hippocampal formation in implicit and explicit memory. Human volunteers studied a list of familiar words, and then they either provided the first word that came to mind in response to three-letter cues (implicit memory) or tried to recall studied words in response to the same cues (explicit memory). There was no evidence of hippocampal activation in association with implicit memory. However, priming effects on the implicit memory test were associated with decreased activity in extrastriate visual cortex. On the explicit memory test, subjects recalled many target words in one condition and recalled few words in a second condition, despite trying to remember them. Comparisons between the two conditions showed that blood-flow increases in the hippocampal formation are specifically associated with the conscious recollection of studied words, whereas blood-flow increases in frontal regions are associated with efforts to retrieve target words. Our results help to clarify some puzzles concerning the role of the hippocampal formation in human memory.