Macromolecular synthesis in organ cultures of neonatal rat lung

Organ cultures of newborn rat lungs synthesize and accumulate DNA, RNA, collagen and noncollagenous proteins almost at a linear rate for at least 5 days. During this period the synthesis of collagen consistently exceeds the synthesis of noncollagenous proteins in a pattern similar to neonatal lung growth in vivo. Although some morphological characteristics of lung architecture are distorted after culture, fundamental structural similarities to lungs growing in intact animals are retained. When these cultures are maintained in atmospheres rich in oxygen, increased collagen synthesis is observed, a response similar to that of lungs in intact animals exposed to high oxygen concentrations in vivo. Our studies suggest that lung organ cultures may be a suitable system for investigating the biochemical aspects of lung tissue-environmental interaction. These studies were supported in parts by NIH Grant HL-19668, a contract (68-03-2005) from the U.S. Environmental Protection Agency, and grants from the California Lung Association.     

Hydrocarbons obtained by pyrolysis of some precambrian rocks of minnesota

Drill core samples of 42 Precambrian sedimentary, igneous, and metamorphic rocks were analyzed by heating under partial vacuum at 100°C and at 400°C to release hydrocarbons and other volatile products.The core samples yielded methane in amounts ranging from traces to 3 microliters per gram, but averaged much less. By way of comparison, samples of Middle Devonian Marcellus black shale, from Pennsylvania, yielded methane in amounts up to 7ul/g.Other straight chain hydrocarbons up to C₁₁ were found in the volatile products, especially those obtained at 400°C, and benzene was a common product, also mainly in the 400°C experiments. Carbon dioxide and nitrogen appear to form a large part of the nonhydrocarbon volatiles in at least some of the samples.Spectral data indicate that the straight chain pyrolysis products of the Precambrian rocks are mainly alkenes, whereas those of the Devonian rocks, referred to above, are a mixture of alkanes and alkenes. Alkanes were however, obtained from several algae-bearing Middle Precambrian argillites. Available evidence indicates, although not conclusively, that the alkenes were contained in the rock rather than being produced from alkanes during pyrolysis.The writers believe that surface contamination in most of the drill cores was minimal owing to the low permeability of the rocks studied, and that contamination by drilling was also minimal.There is a reasonable possibility that the volatiles, if not formed from kerogen residues by the pyrolysis experiments, are in part juvenile igneous gases or are substances that were distilled out of the deeperlying rocks during intervals of folding and metamorphism, and subsequently accumulated at higher levels.     

Field studies on the population dynamics of Biomphalaria glabrata, intermediate host of Schistosoma mansoni on the West Indian Island of St. Lucia

Growth curves, calculated for field populations of B. glabrata, were not materially affected by habitat, altitude or season. A mean growth curve was therefore used to estimate the age-frequency distribution of snails in successive field samples. These data permitted the construction of ecological life tables and the estimation of r, the intrinsic rate of natural increase (or decrease) of the different populations. The calculated values of r were inserted in a simple model of unlimited population growth but the resultant curves poorly represented the observed data. A model for unlimited growth was more satisfactory for pond and marsh populations but, apparently, immigration made it less satisfactory for stream and banana drain populations. Nevertheless, r may still be of value in predicting repopulation rates in certain habitats after a mollusciciding which does not kill the entire snail population.     

Vegetation,land use and management of the inner-dune zone in the North-Holland Dune Reserve,The Netherlands

The inner-dune zone between the villages of Bakkum and Egmond in the North-Holland Dune Reserve is one of the few remaining examples of the semi-natural boundary between the dunes and the polders. For several centuries this area has been used for various purposes, in particular for grazing. Large-scale excavating, especially after about 1900, has encroached upon the dunes. Vegetation and land-use history were studied and a provisional scheme on the vegetation development is presented. Management policies discussed are non-intervention, mowing in order to start natural processes such as rabbit grazing, and the continuation of traditional livestock grazing. Proposals for external management policies were made in order to maintain or enhance the original transition zone, based on comprehensive physical-geographical studies of the whole inner-dune zone.