Ouabain-insensitive salt and water movements in duck red cells. II. The role of chloride in the volume response

This paper describes the effect of external chloride on the typical swelling response induced in duck red cells by hypertonicity or norepinephrine. Lowering chloride inhibits swelling and produces concomitant changes in net movements of sodium and potassium in ouabain-treated cells, which resemble the effect of lowering external sodium or potassium. Inhibition is the same whether chloride is replaced with gluconate or with an osmotic equivalent of sucrose. Since changes in external chloride also cause predictable changes in cell chloride, pH, and water, these variables were systematically investigated by varying external pH along with chloride. Lowering pH to 6.60 does not abolish the response if external chloride levels are normal, although the cells are initially swollen due to the increased acidity. Cells deliberately preswollen in hypotonic solutions with appropriate ionic composition can also respond to norepinephrine by further swelling. These results rule out initial values of cell water, chloride, and pH as significant variables affecting the response. Initial values of the chloride equilibrium potential do have marked effect on the direction and rate of net water movement. If chloride is lowered by replacement with the permeant anion, acetate, E(Cl) is unchanged and a normal response to norepinephrine, which is inhibited by furosemide, is observed. Increasing internal sodium by the nystatin technique also inhibits the response. A theory is developed which depicts that the cotransport carrier proposed in the previous paper (W.F. Schmidt and T.J. McManus. 1977b. J. Gen. Physiol. 70:81-97) moves in response to the net electrochemical potential difference driving sodium and potassium across the membrane. Predictions of this theory fit the data for both cations and anions.     

Studies of carbohydrate derivatives having the -CH2F function

The following primary sulphonates have been converted into the corresponding deoxyfluoro derivatives by reaction with potassium fluoride in ethylene glycol:1,2:3,4-di-O-isopropylidene-6-O-tosyl α-D-galactopyranose (1), methyl 2,3-O2-isopropyliden-5-O-tosyl-α,β-D-ribofuranoside (2), 1,2:3,4-di-O-methylene-6-O-tosyl-α-D-glucofuranose (3), 3,5-di-O-benzylidene-1,2-O-isopropylidene-6-O-tosyl-α-D-glucofuranose (4), and 1,2:3,5-di-O-isopropylidene-6-O-tosyl-α-D-glucofuranose (5). The yields were generally poor; in the reaction of 1, a major by-product was 6-O-(2-hydroxyethyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (11). The reaction of the primary hydroxyl precursor of each of the above tosylates with N2-(2-chloro- 1,1,2-trifluoroethyl)-N,N-diethylamine generally yielded the O-chlorofluoroacetyl derivative; however, 1,2:3,5-di-O-methylene-α-D-glucofuranose (12) was converted into the 6-deoxy-6-fluoro derivative (8). The ¹⁹F resonances of compounds containing the CH₂F moiety fall between φ_C +213 and φ_C +235 p.p.m. The differences between the vicinal¹⁹F-¹H couplings of compounds having the D-gluco and D-galacto configurations clearly reflect the influence of the C-4O-4 substitutents on the populations of the C-5C-6 rotamers. A novel type of noise-modulated, heteronuclear decoupling experiment is described.     

Clearing Width and Movements of Understory Rainforest Birds1

We assessed the capacity of three species of disturbance‐sensitive understory birds to traverse a highway (50–75 m width) and large farm clearing (250 m width), by radio‐tracking translocated individuals in central Amazonia, Brazil. Most individuals translocated across the highway (eight of nine birds) or moved within continuous forest (five of seven birds) returned to their home ranges, whereas none of five birds moved across the large clearing returned. Our results suggest that large clearings (>250 m width) can significantly reduce the movements of some understory rainforest birds.     

The discovery of biaryl acids and amides exhibiting antibacterial activity against Gram-positive bacteria

Solid-phase synthetic methods for biaryl-based compounds were developed resulting in the construction of two 1000-member libraries. Numerous compounds were identified by high-throughput screening using whole cell screens to exhibit anti-microbial activity against Gram-positive bacteria. A series of biaryl compounds containing natural and unnatural amino acids were made to explore the SAR of the amino acid functionality.     

Interacting Factors Driving a Major Loss of Large Trees with Cavities in a Forest Ecosystem

Large trees with cavities provide critical ecological functions in forests worldwide, including vital nesting and denning resources for many species. However, many ecosystems are experiencing increasingly rapid loss of large trees or a failure to recruit new large trees or both. We quantify this problem in a globally iconic ecosystem in southeastern Australia – forests dominated by the world''s tallest angiosperms, Mountain Ash (Eucalyptus regnans). Tree, stand and landscape-level factors influencing the death and collapse of large living cavity trees and the decay and collapse of dead trees with cavities are documented using a suite of long-term datasets gathered between 1983 and 2011. The historical rate of tree mortality on unburned sites between 1997 and 2011 was >14% with a mortality spike in the driest period (2006–2009). Following a major wildfire in 2009, 79% of large living trees with cavities died and 57–100% of large dead trees were destroyed on burned sites. Repeated measurements between 1997 and 2011 revealed no recruitment of any new large trees with cavities on any of our unburned or burned sites. Transition probability matrices of large trees with cavities through increasingly decayed condition states projects a severe shortage of large trees with cavities by 2039 that will continue until at least 2067. This large cavity tree crisis in Mountain Ash forests is a product of: (1) the prolonged time required (>120 years) for initiation of cavities; and (2) repeated past wildfires and widespread logging operations. These latter factors have resulted in all landscapes being dominated by stands ≤72 years and just 1.16% of forest being unburned and unlogged. We discuss how the features that make Mountain Ash forests vulnerable to a decline in large tree abundance are shared with many forest types worldwide.     

Avian ecological succession in the Amazon: A long‐term case study following experimental deforestation

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Detecting anthropogenic disturbance in tropical forests

Tropical forests are beleaguered by an array of threats driven by different scales of anthropogenic perturbations, which vary in the degree to which they can be detected by remote sensing. The extent of different patterns of cryptic disturbance often far exceeds the total area deforested, as shown by two recent studies on selective logging in Amazonia. Here, we discuss different forms of disturbance in Amazonian forests and question how much of the apparently intact forest in this region remains relatively undisturbed.