Rearrangement of allylic alcohols

Three allylic type alcohols were rearranged in sulfuric acid (l, 10 and 50%) at 25 and 100C and their products identified. Specifically, 2-phenyl-lpropen-3-ol, 2-methyl-l-phenyl-l-propen-3-ol and 2-methyl-3-phenyl-l-propen-3-ol were studied. 2-Phenyl-l-propen-3-ol was found to rearrange to 2-phenylpropionaldehyde while 2-methyl-1-phenyl-l-propen-3-ol formed 2-methyl-2-phenylpropanal, isobutyrophenone and 2-methyl-3-phenyl-l-propen-3-ol. The final rearrangement of the 2-methyl-3-phenyl-lpropen- 3-ol allylic alcohol produced 2-methyl-2-phenylpropanal, isobutyrophenone, 2-methyl-l-phenyll- propen-3-ol and 2-(2-phenylisopropyl)-4-phenyl-5- methyl-1, 3-dioxane

Grasshoppers efficiently process C 4 grass leaf tissues: implications for patterns of host-plant utilization

Leaf-chewing insects are commonly believed to be unable to crush the nutrient-rich bundle sheath cells (BSC) of C 4 grasses. This physical constraint on digestion is thought to reduce the nutritional quality of these grasses substantially. However, recent evidence suggests that BSC are digested by grasshoppers. To directly assess the ability of grasshoppers to digest C 4 grass BSC, leaf particles of Bouteloua curtipendula (Poaceae) were examined from the digestive tracts of two grasshopper species: Camnula pellucida (Scudder) (primarily a grass feeder) and Melanoplus sanguinipes (Fabricius) (a forb and grass generalist) (Orthoptera: Acrididae). Transmission electron microscopy was used to make the first observations of BSC crushing by herbivorous insects. Camnula pellucida and M. sanguinipes crushed over 58% and 24%, respectively, of the BSC in ingested leaf tissues. In addition, chloroplast and cell membranes were commonly disrupted in uncrushed BSC, permitting soluble nutrients to be extracted, even when BSC walls remain intact. The greater efficiency with which C. pellucida crushes BSC is consistent with the idea that grass-feeding species are better adapted for handling grass leaf tissues than are generalist species. By demonstrating the effectiveness with which the BSC of B. curtipendula can be crushed and extracted by both species of grasshoppers, this study suggests one reason why C 4 grasses are not generally avoided by grasshoppers: at least some C 4 grasses can be more easily digested than has been hypothesized.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73290/1/j.1570-7458.2005.00324.x.pd

Physiological factors affecting the rapid decrease in protein assimilation efficiency by a caterpillar on newly‐mature tree leaves

Lymantria dispar L. caterpillars have a decreased ability to assimilate protein from mature leaves of red oak ( Quercus rubra ) compared with young, expanding leaves. The present study determines whether the drop in protein assimilation efficiency (PAE) occurs during the rapid phase of leaf maturation. Several mechanisms that might account for decreased PAE are also examined: mature leaf tissues could resist being chewed efficiently, protein in mature leaf tissues could become difficult to extract, and other nutrients in mature leaves might become growth limiting. The entire seasonal decrease in PAE occurs rapidly (in less than 2 weeks), when the leaves finished expanding. The maturation process is characterized by increased levels of fibre and decreased levels of water but no significant changes in the levels of protein or carbohydrates. Despite increased fibre in mature leaves, they are not chewed into larger food particles than are immature leaves. Carbohydrate assimilation efficiencies remain high on mature leaves, and signs of limiting water levels in larvae of L. dispar on mature leaves are not observed. The most important finding in the present study is the decreased extractability of protein in food particles from mature leaves, which plays a major role in explaining the rapid decrease in PAE. It is hypothesized that structural changes in cell walls during the rapid process of leaf maturation decrease protein extractability, which, in turn, greatly decreases the nutritional quality of mature oak leaves for caterpillars. The results of the present study therefore suggest a general mechanism to help explain the widely documented decrease in the nutritional quality of the mature leaves of many tree species for herbivorous insects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106099/1/phen12049.pd

Accident analysis computer code for nuclear reactors

Originally presented as the first author's thesis, (Nucl. E.)--in the M.I.T. Dept. of Nuclear Engineering, 1977Includes bibliographical references (pages 122-123

Fenton-type reactions and iron concentrations in the midgut fluids of tree-feeding caterpillars

Peroxides are formed in the midgut fluids of caterpillars when ingested tannins and other phenolic compounds oxidize. If these peroxides broke down in the presence of redox-active metal ions, they would form damaging free radicals (Fenton-type reactions). Elemental iron is present in relatively large amounts in leaves and artificial diets, but little is known about its concentration and redox state in midgut fluids, or the extent of Fenton-type reactions in these conditions. This study compared the levels of hydroxyl radicals and iron in the midgut fluids of two species of caterpillars: Orgyia leucostigma , in which phenol oxidation is limited, and Malacosoma disstria , in which phenol oxidation is more extensive. We tested two hypotheses: (1) higher levels of hydroxyl radicals are formed in M. disstria (consistent with the higher concentrations of hydrogen peroxide in this species), and (2) lower concentrations of iron are present in O. leucostigma (providing greater protection of its midgut fluids from oxidative damage). Hydroxyl radical levels increased greatly in M. disstria , but not in O. leucostigma , when they consumed a tannin-containing diet, supporting the first hypothesis. Protein oxidation was also significantly increased in the midgut fluids of M. disstria that ingested tannic acid, consistent with hydroxyl radical damage. Contrary to the second hypothesis, similar concentrations of iron (70 μM) remained in solution or suspension in both species of caterpillars on an artificial diet. Over 90% of this iron appeared to be in the reduced (catalytically active) state in both species. We conclude that tree-feeding caterpillars protect their midgut fluids from oxidative damage caused by Fenton-type reactions by limiting the formation of peroxides, rather than by limiting the availability of reduced iron. Arch. Insect Biochem. Physiol. 60:32–43, 2005. © 2005 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48689/1/20079_ftp.pd

C 3 grasses have higher nutritional quality than C 4 grasses under ambient and elevated atmospheric CO 2

Grasses with the C 3 photosynthetic pathway are commonly considered to be more nutritious host plants than C 4 grasses, but the nutritional quality of C 3 grasses is also more greatly impacted by elevated atmospheric CO 2 than is that of C 4 grasses; C 3 grasses produce greater amounts of nonstructural carbohydrates and have greater declines in their nitrogen content than do C 4 grasses under elevated CO 2 . Will C 3 grasses remain nutritionally superior to C 4 grasses under elevated CO 2 levels? We addressed this question by determining whether levels of protein in C 3 grasses decline to similar levels as in C 4 grasses, and whether total carbohydrate : protein ratios become similar in C 3 and C 4 grasses under elevated CO 2 . In addition, we tested the hypothesis that, among the nonstructural carbohydrates in C 3 grasses, levels of fructan respond most strongly to elevated CO 2 . Five C 3 and five C 4 grass species were grown from seed in outdoor open-top chambers at ambient (370 ppm) or elevated (740 ppm) CO 2 for 2 months. As expected, a significant increase in sugars, starch and fructan in the C 3 grasses under elevated CO 2 was associated with a significant reduction in their protein levels, while protein levels in most C 4 grasses were little affected by elevated CO 2 . However, this differential response of the two types of grasses was insufficient to reduce protein in C 3 grasses to the levels in C 4 grasses. Although levels of fructan in the C 3 grasses tripled under elevated CO 2 , the amounts produced remained relatively low, both in absolute terms and as a fraction of the total nonstructural carbohydrates in the C 3 grasses. We conclude that C 3 grasses will generally remain more nutritious than C 4 grasses at elevated CO 2 concentrations, having higher levels of protein, nonstructural carbohydrates, and water, but lower levels of fiber and toughness, and lower total carbohydrate : protein ratios than C 4 grasses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72210/1/j.1365-2486.2004.00833.x.pd

Erratum

The bottom panel of figure number 1 in the article, “Roles of Peritrophic Membranes in Protecting Herbivorous Insects From Ingested Plant Allelochemicals” by Raymond V. Barbehenn, Volume 47, Number 2, June 2001 on pages 86–99 was submitted incorrectly. The corrected figure and legend from page 88 are herein reprinted. The bottom panel is now on the right hand side.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34926/1/10041_ftp.pd

Non-absorption of ingested lipophilic and amphiphilic allelochemicals by generalist grasshoppers: The role of extractive ultrafiltration by the peritrophic envelope

The role of the peritrophic envelope in the non-absorption of three allelochemicals ingested by generalist grasshoppers was examined. This study tested the hypothesis that the association of lipophilic and amphiphilic allelochemicals with lipid aggregates (mixed micelles) reduces their permeability through the peritrophic envelope, a process similar to extractive ultrafiltration. Each of three allelochemicals (digitoxin, ouabain, and xanthotoxin) were solubilized in a lysolecithin suspension and injected separately into the midgut lumens of adult Melanoplus sanguinipes (Orthoptera: Acrididae). The low permeability of digitoxin through the peritrophic envelope was consistent with the extractive ultrafiltration of this compound. By comparison, ouabain and xanthotoxin permeability coefficients were 7- and 12-fold higher, respectively, than those of digitoxin. The results of extractive ultrafiltration assays confirmed that digitoxin is effectively extracted in lysolecithin micelles, but that neither ouabain nor xanthotoxin aggregates efficiently with these micelles. Arch. Insect Biochem. Physiol. 42:130–137, 1999. © 1999 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34925/1/3_ftp.pd