Acute inhibition by ethanol of intestinal absorption of glucose and hepatic glycogen synthesis on glucose refeeding after starvation in the rat.

1. Intragastric administration of ethanol (75 mmol/kg body wt.) at 1 h before glucose refeeding of 24 h-starved rats inhibited hepatic glycogen deposition (by 69%) and synthesis (by approx. 70%), but was without significant effect on muscle glycogen deposition and synthesis. 2. Treatment of ethanol-administered rats with methylpyrazole (an inhibitor of alcohol dehydrogenase) did not significantly diminish the inhibitory effect of ethanol on hepatic glycogen deposition after glucose refeeding, suggesting that the inhibition was not dependent on ethanol metabolism. 3. Ethanol delayed and diminished intestinal glucose absorption, at least in part by delaying gastric emptying. 4. At a lower dose (10 mmol/kg body wt.), ethanol inhibited hepatic glycogen repletion and synthesis without compromising intestinal glucose absorption. Ethanol inhibited glycogen deposition (by 40%) in hepatocytes from starved rats provided with glucose + lactate + pyruvate as substrates, consistent with it having a direct effect to diminish hepatic glycogen synthesis by inhibition of gluconeogenic flux at a site(s) between phosphoenolpyruvate and triose phosphate in the pathway. 5. It is concluded that ethanol acutely impairs hepatic glycogen repletion by inhibition at at least two distinct sites, namely (a) intestinal glucose absorption and (b) hepatic gluconeogenic flux.     

Vascular delay and administration of basic fibroblast growth factor augment latissimus dorsi muscle flap perfusion and function

Ischemia of the distal latissimus dorsi muscle flap occurs when the entire muscle is acutely elevated. Although this level of ischemia may not be critical if the muscle is to be used as a conventional muscle flap, the ischemia causes decreased distal muscle function if it is used for dynamic muscle flap transfer. This experiment was designed to determine whether or not the administration of exogenous basic fibroblast growth factor (bFGF), combined with a sublethal ischemic insult (i.e., vascular delay), would further augment muscle perfusion and function. Both latissimus dorsi muscles of nine canines were subjected to a bipedicle vascular delay procedure immediately followed by thoracodorsal intraarterial injection of 100 microg of bFGF on one side and by intraarterial injection of vehicle on the other. Ten days later, both latissimus dorsi muscles were raised as thoracodorsally based island flaps, with perfusion determined by laser-Doppler fluximetry. The muscles were wrapped around silicone chambers, simulating cardiomyoplasty, and stimulating electrodes were placed around each thoracodorsal nerve. The muscles were then subjected to an experimental protocol to determine muscle contractile function. At the end of the experiment, latissimus dorsi muscle biopsies were obtained for measurement of bFGF expression. The results demonstrated that the administration of 100 microg of bFGF immediately after the vascular delay procedure increases expression of native bFGF. In the distal and middle muscle segments, it also significantly increased muscle perfusion by approximately 20 percent and fatigue resistance by approximately 300 percent. The administration of growth factors may serve as an important adjuvant to surgical procedures using dynamic muscle flap transfers.     

Automated real-space refinement of protein structures using a realistic backbone move set

Crystals of many important biological macromolecules diffract to limited resolution, rendering accurate model building and refinement difficult and time-consuming. We present a torsional optimization protocol that is applicable to many such situations and combines Protein Data Bank-based torsional optimization with real-space refinement against the electron density derived from crystallography or cryo-electron microscopy. Our method converts moderate- to low-resolution structures at initial (e.g., backbone trace only) or late stages of refinement to structures with increased numbers of hydrogen bonds, improved crystallographic R-factors, and superior backbone geometry. This automated method is applicable to DNA-binding and membrane proteins of any size and will aid studies of structural biology by improving model quality and saving considerable effort. The method can be extended to improve NMR and other structures. Our backbone score and its sequence profile provide an additional standard tool for evaluating structural quality.     

Liana Abundance,Diversity, and Distribution on Barro Colorado Island,Panama

Lianas are a key component of tropical forests; however, most surveys are too small to accurately quantify liana community composition, diversity, abundance, and spatial distribution – critical components for measuring the contribution of lianas to forest processes. In 2007, we tagged, mapped, measured the diameter, and identified all lianas ≥1 cm rooted in a 50-ha plot on Barro Colorado Island, Panama (BCI). We calculated liana density, basal area, and species richness for both independently rooted lianas and all rooted liana stems (genets plus clones). We compared spatial aggregation patterns of liana and tree species, and among liana species that varied in the amount of clonal reproduction. We also tested whether liana and tree densities have increased on BCI compared to surveys conducted 30-years earlier. This study represents the most comprehensive spatially contiguous sampling of lianas ever conducted and, over the 50 ha area, we found 67,447 rooted liana stems comprising 162 species. Rooted lianas composed nearly 25% of the woody stems (trees and lianas), 35% of woody species richness, and 3% of woody basal area. Lianas were spatially aggregated within the 50-ha plot and the liana species with the highest proportion of clonal stems more spatially aggregated than the least clonal species, possibly indicating clonal stem recruitment following canopy disturbance. Over the past 30 years, liana density increased by 75% for stems ≥1 cm diameter and nearly 140% for stems ≥5 cm diameter, while tree density on BCI decreased 11.5%; a finding consistent with other neotropical forests. Our data confirm that lianas contribute substantially to tropical forest stem density and diversity, they have highly clumped distributions that appear to be driven by clonal stem recruitment into treefall gaps, and they are increasing relative to trees, thus indicating that lianas will play a greater role in the future dynamics of BCI and other neotropical forests.     

Enhanced Uniformity and Area Scaling in Carbon Nanotube–Fullerene Bulk‐Heterojunction Solar Cells Enabled by Solvent Additives

Single‐walled carbon nanotube (SWCNT) fullerene solar cells have recently attracted attention due to their low‐cost processing, high environmental stability, and near‐infrared absorption. While SWCNT–fullerene bulk‐heterojunction photovoltaics employing an inverted architecture and polychiral SWCNTs have achieved efficiencies exceeding 3% over device areas of ≈1 mm², large‐area SWCNT solar cells have not yet been demonstrated. In particular, with increasing device area, spatial inhomogeneities in the SWCNT film have limited overall device performance. Here, 1,8‐diiodooctane (DIO) is utilized as a solvent additive to reduce fullerene domain size and to improve SWCNT–fullerene bulk‐heterojunction morphology. Under optimized conditions, DIO elucidates the influence of SWCNT chiral distribution on overall device performance, revealing a tradeoff between short‐circuit current density and fill factor as a function of the chirality distribution present. The combination of SWCNT chirality distribution engineering and improved spatial homogeneity via solvent additives enables area‐scaling of SWCNT–fullerene solar cells with performance comparable to small‐area cells.     

Inhibition of respiration in mitochondria and in digitonin-treated rat hepatocytes by podophyllotoxin

Summary The effects of the microtubular inhibitor, podophyllotoxin, on mitochondrial respiration were determined using isolated, digitonin-permeabilized hepatocytes and isolated mitochondria. In hepatocytes, podophyllotoxin (1.5 mM) inhibited coupled and uncoupled respiration of both FAD and NAD-linked substrates. In mitochondria, podophyllotoxin inhibited State III respiration, prevented the return to State IV respiration, and inhibited uncoupled respiration. There was no inhibition of ascorbate/TMPD oxidation in either the hepatocytes or the mitochondria. Podophyllotoxin had no effect upon oligomycin inhibition of coupled respiration. Oligomycin had no effect on the podophyllotoxin-inhibition of uncoupled respiration in either hepatocytes or mitochondria. The results indicate that podophyllotoxin alters electron flow at a site early in the electron transport chain.     

Ultraviolet-B radiation reduces the rates of cell division and elongation in the primary leaf of wheat (Triticum aestivum L. cv Maris Huntsman)

The primary leaf of wheat (Triticum aestivum L. cv Maris Huntsman) was used as a model system to examine how elevated ultraviolet‐B (UV‐B; λ= 280–320 nm) radiation affected growth. A reduction in the rate and duration of growth of the primary leaf, in response to UV‐B, was the result of changes in both the rate and extent of cell division and elongation. UV‐B reduced the proportion of mitotically active cells (mitotic index) and increased the time taken for cell division (cell doubling time). Thus the supply of cells into the elongation zone was reduced, and this, coupled to a reduction in the rate of elongation, resulted in reduced leaf growth. This analysis of the spatial distribution of growth provided a means of calculating the age of cells within the leaves. Cells of UV‐B‐treated leaves were found to age more quickly than those of the controls. This analysis will enable future studies to take account of age‐related changes when interpreting the response of plants to any number of environmental stresses that affect leaf development.