Posts Tagged ‘evidence’

Sea levels rose in bursts during past global warming

“What these fossil reefs show is that the last time Earth warmed like it is today, sea level did not rise steadily…”

Transitional basal cells at the squamous–columnar junction generate Barrett’s oesophagus

In several organ systems, the transitional zone between different types of epithelium is a hotspot for pre-neoplastic metaplasia and malignancy, but the cells of origin for these metaplastic epithelia and subsequent malignancies remain unknown. In the case of Barrett’s oesophagus, intestinal metaplasia occurs at the gastro-oesophageal junction, where stratified squamous epithelium transitions into simple columnar cells. On the basis of a number of experimental models, several alternative cell types have been proposed as the source of this metaplasia but in all cases the evidence is inconclusive: no model completely mimics Barrett’s oesophagus in terms of the presence of intestinal goblet cells. Here we describe a transitional columnar epithelium with distinct basal progenitor cells (p63+KRT5+KRT7+) at the squamous–columnar junction of the upper gastrointestinal tract in a mouse model. We use multiple models and lineage tracing strategies to show that this squamous–columnar junction basal cell population serves as a source of progenitors for the transitional epithelium. On ectopic expression of CDX2, these transitional basal progenitors differentiate into intestinal-like epithelium (including goblet cells) and thereby reproduce Barrett’s metaplasia. A similar transitional columnar epithelium is present at the transitional zones of other mouse tissues (including the anorectal junction) as well as in the gastro-oesophageal junction in the human gut. Acid reflux-induced oesophagitis and the multilayered epithelium (believed to be a precursor of Barrett’s oesophagus) are both characterized by the expansion of the transitional basal progenitor cells. Our findings reveal a previously unidentified transitional zone in the epithelium of the upper gastrointestinal tract and provide evidence that the p63+KRT5+KRT7+ basal cells in this zone are the cells of origin for multi-layered epithelium and Barrett’s oesophagus.

Siberian volcanic eruptions caused extinction 250 million years ago, new evidence shows

The Great Permian Extinction, which occurred approximately 250 million years ago, was caused by massive volcanic eruptions that led to significant environmental changes, new evidence shows.

Have astronomers found the ‘missing link’ of black hole evolution?

Astronomers believe that they have discovered an enormous new black hole thought to be nearly 100,000 more massive than the sun near the center of the Milky Way, and it may be the first ever actual detection of a long-hypothesized-but-never-proven type of space-time phenomena. Writing in the journal Nature Astronomy, a team of researchers led […]

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