The Role of Aphid Abundance, Species Diversity, and Virus Titer in the Spread of Sweetpotato Potyviruses in Louisiana and Mississippi.

Sweet potato feathery mottle virus (SPFMV), Sweet potato virus G (SPVG), and Sweet potato virus 2 (SPV2) are sweetpotato (Ipomoea batatas) potyviruses nonpersistently transmitted by aphids. Our objective was to determine how aphid abundance, aphid species diversity, and virus titers relate to the spread of SPFMV, SPVG, and SPV2 in Louisiana and Mississippi sweetpotato fields. The most abundant aphid species were Aphis gossypii, Myzus persicae, Rhopalosiphum padi, and Therioaphis trifolii. Aphids were captured during the entire crop cycle but virus infection of sentinel plants occurred mainly during the months of June to August. SPFMV was more commonly detected than SPVG or SPV2 in sentinel plants. Virus titers for SPFMV were higher in samples beginning in late June. Because significant aphid populations were present during April to June when virus titers were low in sweetpotato and there was very little virus infection of sentinel plants, low virus titers may have limited aphid acquisition and transmission opportunities. This is the first study to comprehensively examine aphid transmission of potyviruses in sweetpotato crops in the United States and includes the first report of R. maidis and R. padi as vectors of SPFMV, though they were less efficient than A. gossypii or M. persicae.

Droplet size and spray volume effects on insecticide deposit and mortality of heliothine (Lepidoptera: Noctuidae) larvae in cotton.

Effects of droplet size and volumetric application rate of tractor-applied lambda cyhalothrin (Karate Z 2.08 SC) on larval tobacco budworm, Heliothis virescens (F.), mortality and insecticide deposition on and within the canopy of mature cotton were explored by use of a laboratory bioassay incorporating field-sprayed cotton and a field trial incorporating natural insect infestations. Insecticide was applied in all combinations of three distinct droplet sizes and three volumetric application rates. Mortality of third-instar tobacco budworm occurring in leaf-disk bioassays was highly correlated with insecticide deposits (microg/leaf disk) at upper- and midcanopy levels. At the upper canopy level, mortality was negatively correlated with volumetric application rate and was not significantly correlated with droplet size. Deposit was negatively correlated with volumetric application rate at the lower plant level and larval mortality decreased with increasing droplet size. Results from this study do not support the recommendations of high volumetric application rates; and although droplet size was less influential than volumetric application rate in deposit and insect mortality, the data indicate a significant trend toward increased midcanopy larval mortality with smaller droplets.

Distribution and localization of a novel cholecystokinin-releasing factor in the rat gastrointestinal tract.

The purpose of this study was to examine the distribution and localization of an intestinal cholecystokinin (CCK)-releasing factor, called luminal CCK-releasing factor (LCRF), in the gastrointestinal tract and pancreas of the rat. RIA analysis indicates that LCRF immunoreactivity is found throughout the gut including the pancreas, stomach, duodenum, jejunum, ileum, and colon with the highest levels in the small intestine. Immunohistochemistry analysis shows LCRF immunoreactivity staining in intestinal villi, Brunner's glands of the duodenum, the duodenal myenteric plexus, gastric pits, pancreatic ductules, and pancreatic islets. These results indicate potential sources for secretagogue-stimulated release of luminal LCRF and support the hypothesis that LCRF is secreted into the intestinal lumen to stimulate CCK release from mucosal CCK cells.

Treatment of periorbital wrinkles. A comparison of the SilkTouch carbon dioxide laser with a medium-depth chemical peel.

BACKGROUND: Chemical peels are an effective treatment for wrinkles, but their use is limited because of the associated risk of scarring, hypopigmentation, and the inability to accurately control the depth of tissue injury. High energy, pulsed, or computer scanned continuous wave carbon dioxide (CO2) lasers cause minimal thermal injury, decrease the risk of scarring, and allow for precise control of tissue vaporization to predictable depths. OBJECTIVE: To compare the effectiveness and side effect profile of a medium-depth chemical peel to that of the SilkTouch CO2 laser in the treatment of periorbital wrinkles. METHODS: Twenty-four subjects (nine male, 15 female) with moderate to severe periorbital wrinkles were assigned a wrinkle score (1 = mild through 5 = severe) before treatment and 6 months after treatment. Each subject was treated with Jessner's solution and 35% trichloroacetic acid on one side and the SilkTouch CO2 laser on the other side. RESULTS: The average periorbital wrinkle score decreased from 4.00 +/- 0.78 before laser treatment to 1.75 +/- 0.68 6 months after treatment. The chemical peel wrinkle score decreased from 4.13 +/- 0.85 to 3.29 +/- 0.99. The degree in which the wrinkle score improved after laser treatment compared with after chemical peel treatment was statistically significant. Posttreatment erythema lasted an average of 4.5 months for the laser-treated areas and 2.5 months for the chemical peel-treated areas. CONCLUSION: Treatment of periorbital wrinkles with the SilkTouch CO2 laser resulted in a greater degree of improvement than treatment with a medium-depth chemical peel but had longer lasting posttreatment erythema.

Effect of carboxypeptidase E deficiency on progastrin processing and gastrin messenger ribonucleic acid expression in mice with the fat mutation.

Proforms of gastrointestinal peptides are cleaved at paired basic residues into intermediate forms. Paired basic residues at the C-terminal then are excised by carboxypeptidases before the peptide is amidated. An obese mouse, called Cpe(fat)/Cpe(fat), has a missense mutation in carboxypeptidase E (CPE) with no pancreatic CPE activity and a reduced processing of pancreatic proinsulin to insulin. The purpose of this study was 1) to look for the presence of CPE in the antrum of the stomach, duodenum, and colon in the Cpe(fat)/Cpe(fat) mouse; 2) to determine whether CPE is involved in the processing of progastrin (Pro-G) to its carboxyl-terminal amidated form; and 3) to determine whether a decrease in amidated gastrin results in an up-regulation of stomach gastrin messenger RNA (mRNA) levels. In Cpe(fat)/Cpe(fat) mice, CPE activity was absent in the antrum and colon. In Cpe(fat)/Cpe(fat) mice, amidated gastrin levels were reduced significantly. Levels of the precursor for amidated gastrin (gastrin-Gly-Arg-Arg) were markedly elevated. Gastrin mRNA levels were increased approximately 2-fold over the levels in Cpe(fat)/Cpe(fat) mice. These results indicate that CPE is needed for processing progastrin to gastrin in the stomach and that amidated gastrin exerts an inhibitory feedback effect on gastrin mRNA levels.

Stratum corneum structure and function correlates with phenotype in psoriasis.

Psoriatic epidermis demonstrates a defective program of growth and differentiation, including an abnormal permeability barrier. Despite the fact that damage to the epidermis often initiates the disease, psoriasis is commonly viewed as triggered by aberrant immune phenomena in deeper skin layers. Permeability barrier homeostasis requires the formation and secretion of lamellar body contents, as well as the extracellular processing of lamellar body contents into lamellar bilayers. To address the hypothesis that psoriasis is triggered by exogenous rather than internal factors, we assessed permeability barrier function, lamellar body structure, and extracellular lamellar bilayer formation in untreated patients with different psoriatic phenotypes. Subjects with erythroderma and active plaque phenotypes displayed elevated transepidermal water loss levels, increased numbers of epidermal lamellar bodies (many of which failed to be secreted); i.e., corneocytes displayed retained cytosolic lamellar bodies, and extracellular domains largely devoid of lamellae. In contrast, patients with chronic plaque psoriasis and sebopsoriasis displayed a lesser increase in transepidermal water loss, normal numbers of lamellar bodies with only a few retained organelles, and abundant extracellular lamellar material (although a normal unit bilayer pattern did not form). Thus, both functionally and structurally, permeability barrier homeostasis was more disrupted in erythrodermic and active plaque psoriasis than in chronic plaque psoriasis and sebopsoriasis; i.e., the extent of defective barrier function correlated with abnormalities in the known mechanisms of barrier repair, including lamellar body production and extracellular bilayer formation. These findings are consistent with the hypothesis that both the initial appearance of psoriasis (Koebner phenomenon) and changes in disease phenotype are driven by alterations in barrier function.

Decreased epidermal lipid synthesis accounts for altered barrier function in aged mice.

The epidermis of aged mice displays decreased stratum corneum (SC) lipid content and decreased extracellular bilayers, which result in impaired barrier recovery following the solvent treatment or tape stripping. We assessed the role of altered lipid synthesis as the cause of the abnormal barrier and lipid content in aged epidermis, both under basal conditions and in response to acute barrier perturbations. In aged epidermis ( > or = 18 months), synthesis of one of the three key lipid classes (cholesterol) is decreased under basal conditions, and sterologenesis fails to attain the levels reached in young epidermis following comparable acute perturbations. In contrast, fatty acid and sphingolipid synthesis in aged epidermis increase sufficiently to approach the levels attained in stimulated young epidermis. The abnormalities in sterologenesis in aged epidermis are paralleled by a decrease in activity of its rate-limiting enzyme, 3-hydroxy-3-methylglutaryl-coenzyme A reductase, under basal conditions, and enzyme activity also fails to increase as much as in young epidermis after barrier disruption. That defective lipid generation contributes to the barrier defect is shown directly by the ability of either a cholesterol-containing mixture of SC lipids or cholesterol alone to enhance barrier recovery. Finally, lipid-induced acceleration of barrier recovery in aged epidermis correlates with repletion of the extracellular spaces with normal lamellar structures. Thus, a deficiency in lipid synthesis, particularly in cholesterologenesis, accounts for the barrier abnormality in aged epidermis.

Skin type, but neither race nor gender, influence epidermal permeability barrier function.

BACKGROUND AND DESIGN: Previous studies that compared transepidermal water loss in subjects of different race and sex showed minimal differences in basal permeability barrier function. These studies often did not assess the ability of the stratum corneum to withstand or recover from insults to the epidermal permeability barrier. We compared epidermal permeability barrier function in the following human subjects (age range, 22 to 38 years): white (n = 8) vs Asian (n = 6); male (n = 7) vs female (n = 7); and skin type II/III (n = 14) vs skin type V/VI (n = 7) (scale, I to VI). Basal transepidermal water loss was measured by evaporimetry (three sites) on the volar aspect of the forearm. Barrier integrity then was assessed by determining the number of tape strippings required to reach a transepidermal water loss greater than or equal to 20 g/m2 per hour. The rates of barrier recovery then were compared at 6, 24, and 48 hours and 1 week after abrogation. RESULTS: Neither the number of tape strippings required to perturb the barrier nor the rates of barrier recovery were significantly different in white vs Asian subjects or in female vs male subjects. However, patients with skin types II/III required only 29.6 +/- 2.4 tape strippings to perturb the barrier, while the skin type V/VI group required 66.7 +/- 6.9 tape strippings. Furthermore, while barrier function in skin type II/III recovered by approximately 20% by 6 hours and 55% by 48 hours, barrier function in skin type V/VI, independent of race, recovered more quickly, 43% and 72% at 6 and 48 hours, respectively. Finally, neither the differences in barrier integrity nor in rates of recovery could be attributed to variations in cohesiveness, since stripping appears to remove the same weight of stratum corneum in both groups. CONCLUSIONS: Darkly pigmented skin displays both a more resistant barrier and one that recovers more quickly after perturbation by tape stripping than does the skin of individuals with lighter pigmentation. These findings have potential implications for transdermal delivery of topical or systemic therapeutic agents, the ability of individuals with different skin types to withstand environmental or occupational insults, and the influence of acquired hyperpigmentation or pigment loss to influence permeability.

Field evaluation of arthropod repellent netting as a ground cloth against ticks.

Tick repellent, wide-mesh net ground cloths were tested against Amblyomma americanum (Linnaeus) by the CO2 bait technique. Two repellents, N,N-diethyl-metatoluamide (deet) and 3 acetyl-2-(dimethyl-5-heptenyl)-oxazoladine, and two netting fabrics were compared. All combinations tested provided over 90% protection. The effectiveness of repellent ground cloths against chiggers is discussed.