Epithelial transformations in the establishment of the blood-gas barrier in the developing chick embryo lung

The tall epithelium of the developing chick embryo lung is converted to a squamous one, which participates in formation of the thin blood-gas barrier. We show that this conversion occurred through processes resembling exocrine secretion. Initially, cells formed intraluminal protrusions (aposomes), and then transcellular double membranes were established. Gaps between the membranes opened, thus, severing the aposome from the cell. Alternatively, aposomes were squeezed out by adjacent cells or were spontaneously constricted and extruded. As a third mechanism, formation and fusion of severed vesicles or vacuoles below the aposome and their fusion with the apicolateral plasma membrane resulted in severing of the aposome. The atria started to form by progressive epithelial attenuation and subsequent invasion of the surrounding mesenchyme at regions delineated by subepithelial alpha-smooth muscle actin-positive cells. Further epithelial attenuation was achieved by vacuolation; rupture of such vacuoles with resultant numerous microfolds and microvilli, which were abscised to accomplish a smooth squamous epithelium just before hatching.

Temporal and spatial variation of nitrogen transformations in nitrogen-saturated soils of a central Appalachian hardwood forest

We studied temporal and spatial patterns of soil nitrogen (N) dynamics from 1993 to 1995 in three watersheds of Fernow Experimental Forest, W.V.: WS7 (24-year-old, untreated); WS4 (mature, untreated); and WS3 (24-year-old, treated with (NH4)2SO since 1989 at the rate of 35 kg Nha–1year–1). Net nitrification was 141, 114, and115 kg Nha–1year–1, for WS3, WS4, and WS7, respectively, essentially 100% of net N mineralization for all watersheds. Temporal (seasonal) patterns of nitrification were significantly related to soil moisture and ambient temperaturein untreated watersheds only. Spatial patterns of soil water NO3–of WS4 suggest that microenvironmental variabilitylimits rates of N processing in some areas of this N-saturated watershed, in part by ericaceous species in the herbaceous layer. Spatial patterns of soil water NO3–in treated WS3 suggest that later stages of N saturation may result inhigher concentrations with less spatial variability. Spatial variability in soil N variables was lower in treated WS3 versus untreated watersheds. Nitrogen additions have altered the response of N-processing microbes to environmental factors, becoming less sensitive to seasonal changes in soil moisture and temperature. Biotic processes responsible forregulating N dynamics may be compromised in N-saturated forest ecosystems.

Transformations in French Anti-Semitism?

The increase in the number of anti-Semitic acts since the start of the Second Intifada has sparked off a broad debate on the return of anti-Semitism in France. This article focuses on the question whether this anti-Semitism is still based on the alleged superiority of the Aryan race as in the time of Nazism, or if it represents the birth of a “new Judeophobia” that is more based on anti-Zionism and the polemical mixing of “Jews,” “Israelis,” and “Zionists.” One supposed effect of this transformation is that anti-Semitism is in the process of changing camps and migrating from the extreme right to the extreme left of the political arena, to the “altermondialistes,” the communists, and the “neo-Trotskyists.” The article provides answers to the following questions: Are anti-Jewish views on the increase in France today? Do these opinions correlate with negative opinions of other minorities, notably Maghrebians and Muslims? Do they tend to develop among voters and sympathizers with the extreme right or on the extreme left of the political spectrum? And how are they related to opinions concerning Zionism and the Israeli-Palestinian conflict? My evaluation of the transformations in French anti-Semitism relies on two types of data. The first is police and gendarmerie statistics published by the National Consultative Committee on Human Rights (CNCDH), which is charged with presenting the prime minister with an annual report on the struggle against racism and xenophobia in France. The other is data from surveys, notably surveys commissioned by CNCDH for its annual report and surveys conducted at the Center for Political Research (CEVIPOF) at Sciences Po (Paris Institute for Political Research). The data show that anti-Semitic opinions follow a different logic from acts, that the social, cultural, and political profile of anti-Semites remains very close to that of other types of racists, and that anti-Zionism and anti-Semitism do not overlap exactly.

How fit turns into misfit and back: institutional transformations of pastoral commons in African floodplains

We enlarge the notion of institutional fit using theoretical approaches from New Institutionalism, including rational choice and strategic action, political ecology and constructivist approaches. These approaches are combined with ecological approaches (system and evolutionary ecology) focusing on feedback loops and change. We offer results drawn from a comparison of fit and misfit cases of institutional change in pastoral commons in four African floodplain contexts (Zambia, Cameroon, Tanzania (two cases). Cases of precolonial fit and misfit in the postcolonial past, as well as a case of institutional fit in the postcolonial phase, highlight important features, specifically, flexible institutions, leadership, and mutual economic benefit under specific relations of bargaining power of actors. We argue that only by combining otherwise conflicting approaches can we come to understand why institutional fit develops into misfit and back again. Key Words: African floodplains; governance; institutional change; institutional fit; New Institutionalism; pastoral commons