A comparison of the toxic and sub-lethal effects of fluvalinate and esfenvalerate on the twospotted spider mite (Acari: Tetranychidae)

There was no difference in the direct toxicity of fluvalinate and esfenvalerate to twospotted spider mite (TSSM), Tetranychus urticae Koch. adults. The residual toxicity LC₅₀ of esfenvalerate was lower. Neither pyrethroid was toxic (<10% mortality) to TSSM eggs or adults at their recommended field concentrations. Fluvalinate was twice as toxic (45% mortality) than esfenvalerate to TSSM larvae at 0.01 g.a.i L^-1. The toxicity of the pyrethroids to TSSM protonymphs and deutonymphs was similar (16–28% mortality at 0.1 g a.i. L^-1). Dispersal from the treated surface was the main response to both pyrethroids by TSSM protonymphs, deutonymphs and adults. Maximum run-off by TSSM adults from fluvalinate and esfenvalerate treated surfaces was found with 0.01 and 0.005 g a.i. L^-1 respectively. Spin-down from pyrethroid treated surfaces was positively correlated with concentration. Oviposition was negatively correlated with concentration. Fluvalinate caused greater reductions in oviposition than esfenvalerate. Both pyrethroids reduced TSSM development rate from larval, protonymph and deutonymph stages, but fluvalinate caused larger reductions. Both pyrethroids prevented mating: for ten days oviposition 93% and 98% of offspring were male for esfenvalerate and fluvalinate respectively at 0.1 g a.i. L^-1. These findings are discussed with respect to the incidence of pyrethroid induced mite outbreaks.     

Susceptibility of Ceratitis capitata Wiedemann (Diptera: Tephritidae) to Entomopathogenic Fungi and Their Extracts

The effectiveness of seven strains of entomopathogenic fungi against Ceratitis capitata adults was evaluated in the laboratory. Adults were susceptible to five of seven aqueous suspensions of conidia. Metarhizium anisopliae and strain CG-260 of Paecilomyces fumosoroseus were the most pathogenic fungi, with 10-day LD₅₀ values of 5.1 and 6.1 × 10³ conidia/fly, respectively, when applied topically. Sublethal effects on fecundity and fertility of the fungal-exposed females were also studied. The most effective fungus in reducing fecundity was P. fumosoroseus CECT 2705, with reductions on the order of 65% at 1 × 10⁶ conidia/fly. M. anisopliae and Aspergillus ochraceus also showed significant reductions of fecundity (40–50% for most of the assayed concentrations). Fertility was moderately affected by the fungi. M. anisopliae at 1 × 10⁶ conidia/fly was the most effective fungus, showing egg eclosion reduction of over 50% compared with the control. In addition, culture broth dichloromethane extracts from the entomopathogenic fungi were tested for insecticide activity against C. capitata, including effects on fecundity and fertility. The extract from M. anisopliae was the most toxic, resulting in about 90% mortality at a concentration of 25 mg/g of diet; under these conditions, fecundity and fertility of treated females were reduced by 94 and 53%, respectively, compared with untreated controls.     

Antilisterial activity of lactose monolaurate in milk,drinkable yogurt and cottage cheese

Lactose monolaurate (LML) was previously found to be an antimicrobial against Listeria monocytogenes in culture medium at concentrations between 3 and 5 mg ml^?1. In this study, the microbial inhibitory activity of LML in dairy products inoculated with a 5‐strain cocktail of clinical isolates of L. monocytogenes was investigated. Addition of LML at a concentration of 5 mg ml^?1 resulted in 4·4, 4·0 and 4·2 log reductions in 0·5% fat, 1% fat and 3·25% fat milks, respectively; 4·1, 4·4, and 3·5 log reductions in nonfat, 1% fat, and 1·5% fat yogurts, respectively; and 4·0 log reductions in both nonfat and 2% fat cottage cheese. The inhibitory effect of LML was only observed at 37°C and not 5°C. Experiments suggest that both the lauric acid and the esterified lactose moiety of LML play roles in the growth inhibition.

Significance and Impact of the Study

A novel sugar ester, lactose monolaurate, inhibited the growth of a five‐strain cocktail of Listeria monocytogenes in milk, yogurt and cottage cheese. This is the first report of the use of a sugar ester to inhibit the growth of Listeria in food systems.     

Harmful dinoflagellate Cochlodinium polykrikoides impairs the feeding behavior of larval sheepshead minnows (Cyprinodon variegatus)

Research evaluating the toxicity of the harmful dinoflagellate Cochlodinium (a.k.a. Margalefidinium) polykrikoides has been dominated by acute bioassays while the sublethal effects remain less well understood. This study examined the sublethal effects of C. polykrikoides exposure on the feeding behavior of larval estuarine fish. Sheepshead minnow (Cyprinodon variegatus) larvae were used in feeding experiments which assessed the total consumption of zooplankton prey (i.e., Artemia nauplii) over defined time periods. Larvae exposed to intermediate concentrations (i.e., 10² cells ml⁻¹) of clonal cultures of C. polykrikoides saw statistically significant reductions (range = 10%–81%) in the Artemia consumed compared to controls (i.e., filtered seawater, culture media or nontoxin producing dinoflagellate). These reductions were found independent of whether the larvae were fed or starved prior to experimentation. As these concentrations are similar to those typically found during mild blooms or at the periphery of dense blooms, these findings have significant implications for the feeding behavior of ichthyoplankton.     

Synthesis of (S)- and (R)-3-hydroxy acids using cells or purified (S)-3-hydroxycarboxylate oxidoreductase from Clostridium tyrobutyricum and the NADP(H) regeneration system of Clostridium thermoaceticum

A purified and partially characterized novel NADP⁺-dependent oxidoreductase from Clostridium tyrobutyricum DSM 1460 was applied for the preparative reduction of several 3-oxo acids to (S)-3-hydroxy acids. (R)-3-Hydroxybutyrate was prepared by the same enzyme selectively dehydrogenating the S enantiomer of (R,S)-3-hydroxybutyrate. The enantiomeric purity of the (S)- and (R)-3-hydroxy acids was at least 98% enantiomeric excess (e.e). NADPH for reductions and NADP⁺ for dehydrogenations were regenerated by applying artificial mediator accepting pyridine nucleotide oxidoreductases in the form of a crude extract of C. thermoaceticum cells. For NADP⁺ regeneration also the system 2-oxoglutarate/glutamate dehydrogenase was used for comparison. Instead of the purified (S)-3-hydroxycarboxylate oxidoreductase, resting cells of C. tyrobutyricum were also applied for reductions and dehydrogenations with substrate concentrations of 200–400 mM leading to products with e.e. values above 96%.Dedicated to Prof. H.G. Floss on the occasion of his 60th birthday     

Reduction of grasshopper populations following field application of the fungus Beauveria bassiana

Conidia of the Hyphomycete fungus Beauveria bassiana (Bals.) were applied in an attempt to reduce field populations of grasshoppers, primarily the migratory grasshopper Melanoplus sanguinipes (Fabricius). Dry spores were applied with wheat bran carrier to three fallow fields at a rate of 2.0 × 10¹³ spores ha^?1 in 10 kg bait ha^?1. Examination of culture plates that had been placed in the field to capture spores and of bran carrier with scanning electron microscopy indicated that a substantial portion of the B. bassiana colony—forming units (spores and clumps of spores) did not adhere to the bran and were applied in the field as free particles. Grasshoppers collected from the treated plots at intervals after application were assayed for infection by B. bassiana. The observed rate of mycosis in the treated populations was 70% of those collected after 2 days, declining to 41% by 13 days and 5% by 19 days after application. Analysis of reductions in population density gave results in agreement with the infection data. Treated populations declined 60% and 33% by 9 and 15 days after application respectively. The reductions were significant on both post—treatment sampling dates (p < 0.05) and the three replicated fields gave comparable results. This is the first field demonstration of effectiveness of this fungus as a microbial control agent of grasshoppers.     

Entomogenous Fungi as Promising Biopesticides for Tick Control

When ticks were sealed in nylon tetrapacks and infected with the entomogenous fungi, Beauveria bassiana and Metarizium anisopliae and maintained in potted grass in the field, the fungal oil formulations (10⁹ conidia per ml) induced 100% mortality in larvae of Rhipicephalus appendiculatus and Amblyomma variegatum, whereas mortalities in nymphs varied between 80–100% and in adults 80–90%. The aqueous formulations (10⁹ conidia per ml) induced mortalities of 40–50% and reductions in egg hatchability of 68% (B. bassiana) and 48% (M. anisopliae) when sprayed on Boophilus decoloratus engorging on cattle. The strains of B. bassiana and M. anisopliae isolated from naturally infected ticks were also found to induce high mortalities in both R. appendiculatus and A.variegatum in tetrapacks placed in potted grass. Both aqueous and oil-based formulations were found to be effective, although the latter induced higher mortalities. These fungal strains in aqueous formulation (10⁸ conidia per ml) suppressed on-host populations of adult R. appendiculatus by 80% (B. bassiana) and 92% (M. anisopliae) when sprayed on tick-infested grass once per month for a period of 6 months. The feasibility of using entomogenous fungi for tick control in the field is discussed.     

Modeling Hermissenda: I. Differential contributions of I A and I C to type-B cell plasticity

We developed a multicompartmental Hodgkin-Huxley model of the Hermissenda type-B photoreceptor and used it to address the relative contributions of reductions of two K⁺ currents, I _a and I _C, to changes in cellular excitability and synaptic strength that occur in these cells after associative learning. We found that reductions of g_C, the peak conductance of I _C, substantially increased the firing frequency of the type-B cell during the plateau phase of a simulated light response, whereas reductions of g_A had only a modest contribution to the plateau frequency. This can be understood at least in part by the contributions of these currents to the light-induced (nonspiking) generator potential, the plateau of which was enhanced by g_C reductions, but not by g_A reductions. In contrast, however, reductions of g_A broadened the type-B cell action potential, increased Ca²⁺ influx, and increased the size of the postsynaptic potential produced in a type-A cell, whereas similar reductions of g_C had only negligible contributions to these measures. These results suggest that reductions of I _A and I _C play important but different roles in type-B cell plasticity.     

Deleterious effect of soil‐applied metalaxyl and mancozeb on the mycoparasite Pythium oligandrum

Pythium oligandrum was recovered, identified and quantified from air‐dried soil plated on 1.5% water agar containing 0.1% glucose. Isolations of P. oligandrum over 2 years from soils treated with single applications of metalaxyl plus mancozeb were consistently lower than those from untreated soil from the same fields. In three fields in the first year P. oligandrum was reduced from a range of 43.3–115.0 to 17.0–43.2 isolates g^‐1 soil. In the second year, results from 11 fields showed reductions from 27.8–141.8 to 2.8–44.5 isolates g^‐1 soil. P. oligandrum was sensitive to both metalaxyl and mancozeb, with median effective dose (ED₅₀) values of 0.13 ± 0.02 μg m^‐1 and 3.33 ± 0.12 μg ml^‐1, respectively. In a pot test with three soils treated with metalaxyl, mancozeb or the combination of fungicides, levels of P. oligandrum declined over 3 months, with effects first recorded 2 weeks after treatment. Levels of P. oligandrum were reducd by differing degrees in the three soils. Isolate counts from untreated soils declined from a mean of 58.0 g^‐1 soil at the start of the experiment to 27.5 g^‐1 after 3 months, whereas fungicide treatments caused further reductions to 11.1 (metalaxyl), 9.7 (mancozeb) and 4.8 isolates g^‐1 (metalaxyl plus mancozeb).     

The effects of water deprivation and salt load on water conservation efficiency in two Indian desert gerbils

Summary The effects of water deprivation and intraperitoneal salt loading on urine volume and on various urinary constituents have been examined in two gerbil species of the Rajasthan desert, the Indian desert gerbil (Meriones hurrianae Jerdon) and the Indian gerbil (Tatera indica indica Hardwicke). During summer, hydratedT. indica excreted 0.782 ml urine·100 g^-1·d^-1 which was about 60.5% higher than the volume of urine excreted by hydratedM. hurrianae (0.487 ml·100 g^-1·d^-1). During winter, both species excreted around 1.5 ml urine ·100 g^-1·d^-1. The experimental treatments caused reductions in urine volume inM. hurrianae from 40 to 76% during summer and from 35 to 71% in winter. Similar treatments inT. indica caused reductions in urine volume of 50–82% in summer and 5–60% in winter. The mean increase in urine osmolarity following various salt loading treatments inT. indica ranged from 3800 to 5761 mosmol·l^-1 and from 4034 to 6255 mosmol·l^-1 during summer and winter, respectively. The mean values of urine osmolarity for hydratedT. indica were 2831 and 3189 mosmol·l^-1 during summer and winter, respectively. InM. hurrianae salt loading treatments caused increases of urine osmolarity between 3381 and 5646 mosmol·l^-1 and between 4032 and 5434 mosmol· l^-1, during summer and winter, respectively, over the values recorded for hydrated animals (summer=3292; winter=3294 mosmol·l^-1). A maximum urine osmolarity of around 7000 mosmol·l^-1 was found in both species when subjected to 2% salt-loading treatment. The treatments used in this study increased urinary urea level in bothT. indica (3039–4056 mM) and inM. hurrianae (1900–2180 mM) compared to the level in their respective hydrated controls (T. indica=1628 mM;M. hurrianae=1372 mM). The results indicate thatT. indica may be better adapted to produce more concentrated urine thanM. hurrianae.     

Effect of Pramlintide on Weight in Overweight and Obese Insulin‐Treated Type 2 Diabetes Patients

Objective: Several randomized, placebo‐controlled, double‐blind trials in insulin‐treated patients with type 2 diabetes have shown that adjunctive therapy with pramlintide reduces hemoglobin (Hb)A_1c with concomitant weight loss. This analysis further characterizes the weight‐lowering effect of pramlintide in this patient population. Research Methods and Procedures: This pooled post hoc analysis of two long‐term trials included all patients who were overweight/obese at baseline (BMI > 25 kg/m²), and who were treated with either 120 μg pramlintide BID (n = 254; HbA_1c 9.2%; weight, 96.1 kg) or placebo (n = 244; HbA_1c 9.4%; weight, 95.0 kg). Statistical endpoints included changes from baseline to week 26 in HbA_1c, body weight, and insulin use. Results: Pramlintide treatment resulted in significant reductions from baseline to week 26, compared with placebo, in HbA_1c and body weight (both, p < 0.0001), for placebo‐corrected reductions of ?0.41% and ?1.8 kg, respectively. Approximately three times the number of patients using pramlintide experienced a ≥5% reduction of body weight than with placebo (9% vs. 3%, p = 0.0005). Patients using pramlintide also experienced a proportionate decrease in total daily insulin use (r = 0.39, p < 0.0001). The greatest placebo‐corrected reductions in weight at week 26 were observed in pramlintide‐treated patients with a BMI >40 kg/m² and in those concomitantly treated with metformin (both, p < 0.001), for placebo‐corrected reductions of ?3.2 kg and ?2.5 kg, respectively. Discussion: These findings support further evaluation of the weight‐lowering potential of pramlintide in obese patients with type 2 diabetes.     

Field efficacy of entomopathogenic nematodes against the beetle Maladera matrida (Coleoptera: Scarabaeidae)

Single, double and triple releases of the entomopathogenic nematode Heterorhabditis bacteriophora Poinar, reduced the population of the beetle Maladera matrida Argaman, infesting peanuts (’Shulamit’ cv.) by 70, 75 and 93% respectively in microplot tests. Simultaneous and late (2 weeks after infestation) applications reduced beetle numbers by 63 and 79% respectively, in the microplots, while early application (2 weeks prior to infestation) did not reduce the beetle population. In a field trial, reductions in insect population and damage to the crop were achieved by early treatment with the nematode as well as by Heptachlor, leading to reductions in the insect population of 60 and 90% respectively, when recorded 4 weeks after nematode application. However, the nematode treatment did not maintain its effectiveness for a longer period and pest damage increased to the same level as the untreated control after 7 weeks. When the nematodes were applied at different concentrations (0.25–1.0 x 10⁶ infective juveniles (IJs) m^‐2) their effectiveness was not related to the concentration level. The only significant (P < 0.05) reduction in insect levels was recorded in the treatment with 0.5 X 10⁶ IJs m^‐2. In a second field trial, both H. bacteriophora and Steinernema glaseri reduced insect populations significantly (P < 0.05) by approximately 50% in comparison to the control. In the third trial, treatment with H. bacteriophora resulted in a decrease in insect population of 90% while treatment with S. carpocapsae reduced the grub numbers by 40% in comparison to the control. A differential susceptibility of various grub developmental stages was recorded in the field. The small grubs (I‐4 mm long, lst‐2nd larval stage) were not affected by the nematode treatments while the numbers of medium and large size grubs were reduced by 2‐ and 3‐fold respectively in the various tests. Nematodes were recovered by ‘nematode traps’ containing Galleria mellonella larvae from treated field plots 78 days after application. The implications of the results from the present studies on the use of entomopathogenic nematodes are discussed in relation to the development of an integrated pest management programme.     

Post hoc assessment of an operational biocontrol program: efficacy of the flea beetle Aphthona lacertosa Rosenhauer (Chrysomelidae: Coleoptera), an introduced biocontrol agent for leafy spurge

Mixed populations of Aphthona lacertosa and Aphthona czwalinae were released at more than 50 locations in Alberta in 1997. Two and 3 years post-release, beetle populations were primarily A. lacertosa, with A. czwalinae forming less than 0.5% of the sampled populations. Beetle densities were moderate (10–70 beetles per m²) or high (>70 beetles per m²) at 14% and more than 60% of the sampled sites in 1999 and 2000, respectively. Larger beetles had greater instantaneous egg loads (r²=0.424,P=0.003). In 2000, the largest beetles were found at moderate density sites and there was a significant negative relationship between beetle size and the time taken to accumulate a degree day threshold of 1230 (for females: r²=0.678,P=0.001). Sites with the most rapid accumulation of degree days have the greatest potential for beetle population growth based on potential fecundity. Changes in leafy spurge percent cover, stem density, and canopy height from 1997 to 2000 were assessed across sites with low (<10 beetles per m²), moderate, and high beetle densities in 2000. Sites with high beetle densities had significantly greater reductions of leafy spurge within 5 m of the release point than sites with low beetle densities (P<0.017). Damage caused by the beetles at high-density sites was often visible as a halo-shaped patch of dead leafy spurge stems. The significant overall reduction of leafy spurge within release patches makes A. lacertosa a promising biocontrol agent for leafy spurge in Alberta.     

Effects of managanese salts on the AIDS-related pathogen,Cryptosporidium parvum in vitro and in vivo

The authors examined the effects of manganese salts on the interaction of the AIDS-related pathogen,Cryptosporidium parvum, with human ileoadenocarcinoma (HCT-8) cells in vitro. Manganese (Mn) inhibited binding ofC. parvum sporozoite membrane antigens to intact, fixed HCT-8 cells in a dose-dependent fashion, whereas Ca⁺⁺, Mg⁺⁺, and Zn⁺⁺ salts had no effect. Manganese was also found to affect sporozoite penetration of live HCT-8 cells, which resulted in a dose-dependent inhibition of parasite development. However, the levels of Mn⁺⁺ needed in the live cell assays was approx 10-fold greater than in the fixed-cell assays. This inhibition of parasite development was not reversible when Ca⁺⁺ or Mg⁺⁺ were used as competitors. Oral supplementation of suckling mice infected withC. parvum with MnSO₄ resulted in significant reductions and, in some cases, elimination of intestinally derived oocysts.     

Effects of the paedogenetic mushroom cecid, Heteropeza pygmaea (Diptera:Cecidomyiidae) on cropping of the cultivated mushroom (Agaricus bisporus)

When introduced into a mushroom crop at rates of 2, 20 or 200 larvae/tray (0.56 m²), the mushroom cecid, Heteropeza pygmaea, caused significant reductions in both yield and number of mushrooms in relation to the infestation level. The reductions were greater when the larvae were introduced at spawning rather than at casing. The yield and number of infested (unmarketable) mushrooms increased significantly in relation to the initial infestation level. Just two H. pygmaea larvae, introduced at spawning, resulted in cecid populations that caused a 12% loss in total yield in addition to a 7% loss due to spoilage. Loss assessment in the future, therefore, should take into account both yield suppression and spoilage. There was little effect of cecid infestation on flush timing and mushroom size was only affected in the fourth flush, when a significant reduction (27%) was shown at the highest infestation rate at spawning.     

Studies of the Cultural Physiology of the Lichen Alga Trebouxia

The pholosynthetic growth of three species of Trebouxia was so slow as to preclude the usual inorganic methods of algal cultivation. Heterotrophic growth was much stronger — as many as 0.4 doublings per day were obtained in Bold's solution with glucose and amino acid hydrolysates. Ammonium salts of inorganic acids could not be used in the culture medium because they caused excessive reductions in pH. Although the organisms showed variations in their growth response to amino acids, no specific requirement was found. T. erici produced significantly lower quantities of photosynthetic pigments in the dark. Of the nineteen carbohydrates tested, only glucose, mannitol, and galactosc stimulated growth of the algae. Preliminary studies showed that Trebouxia incorporated ¹⁴CO₂ more slowly than Chlorella pyrenoidosa. However, the carbon fixed by Trebouxia remained soluble in 80% ethanol longer than Chlorella. The carbon incorporated as CO₂ in short term experiments was greater than would be expected from the growth rates of the organisms studied.     

Small reductions in forest cover weaken terrestrial-aquatic linkages in headwater streams

1. We assessed the impacts of deforestation on the energy base of headwater food webs in seven headwater streams in the Upper Chattahoochee basin, GA, U.S.A where percentage forest in catchments ranged from 82 to 96%. We measured terrestrial organic matter standing crop and determined consumer (crayfish and insectivorous fish) dependence on terrestrial versus aquatic energy sources via gut content and stable isotope analyses. 2. Standing crop of coarse particulate organic matter (CPOM) declined with deforestation at large scales (i.e. catchment deforestation and riparian deforestation at the entire stream network scale). Terrestrial plant matter, the dominant component of crayfish guts, declined in crayfish guts with reductions in CPOM standing crop and with deforestation. 3. Crayfish and insectivorous fish δ¹³C showed enrichment trends with deforestation, indicating isotopic divergence from CPOM, the most ¹³C‐depleted basal resource, with reductions in catchment and riparian forest cover. Crayfish δ¹³C also exhibited enrichment with decreased instream CPOM standing crop. 4. A concentration‐dependent mixing model was used to calculate the relative dependence of crayfish and fish on terrestrial versus aquatic basal resources. Results suggested that both allochthonous CPOM and autochthonous production were important basal resources. Consumer dependence on CPOM decreased with reductions in canopy cover. 5. Our data suggest the importance of forest cover to headwater food webs at multiple scales, and that relatively low levels of riparian deforestation along headwater streams can lead to reductions in stream food web dependence on terrestrial subsidies.     

Norway Maple (Acer platanoides) Invasion of a Natural Forest Stand: Understory Consequence and Regeneration Pattern

Norway maple (Acer platanoidesis) is invasive in a natural stand in suburban Ithaca, NY. To determine the understory pattern and consequences of a Norway maple invasion, I compared density and species richness under Norway maples and sugar maples (Acer saccharum). Mean sapling density was significantly lower (P<0.0027) under Norway maples (3.64/100 m²±1.6 SE) than under sugar maples (19.4/100 m²±4.4 SE). Mean sapling species richness was significantly lower (P<0.0018) under Norway maples (0.7/32 m²±0.18 SE) than under sugar maples (2.6/32 m²±0.48 SE). Likewise, Norway maple regeneration is more frequent under sugar maples than sugar maple regeneration: 57% of sugar maple plots had Norway maple saplings while 0% of Norway maple plots had sugar maple saplings. Two significant plot effects were found for presence–absence: Norway maple saplings grow under Norway maples with a significantly lower frequency (P<0.03) than under sugar maples; sugar maple saplings grow under Norway maples with a significantly lower frequency (P<0.000) than under sugar maples. Across the site, Norway maple saplings were the most abundant (29 saplings for 480 m²). The success of Norway maple regeneration and the reductions in total stem density beneath Norway maples is most likely the result of its strong competitive abilities, notably its high shade tolerance and abundant seed crops.     

Carbon isotope discrimination and growth response of old Pinus ponderosa trees to stand density reductions

Stand density reductions have been proposed as a method by which old‐growth ponderosa pine (Pinus ponderosa) forests of North America can be converted back to pre‐1900 conditions, thereby reducing the danger of catastrophic forest fires and insect attacks while increasing the productivity of the remaining old‐growth individuals. However, the duration of productivity response of individual trees and the physiological mechanisms underlying such a response remain speculative issues, particularly in old trees. Tree‐ring measurements of carbon isotope ratios (δ¹³C) and basal area increment (BAI) were used to assess the response of intrinsic water‐use efficiency (the ratio of photosynthesis, A to stomatal conductance, g) and growth of individual> 250‐year‐old‐ponderosa pine trees to stand density reductions. It was hypothesized that reductions in stand density would increase soil moisture availability, thus decreasing canopy A/g and increasing carbon isotope discrimination (Δ). Cellulose‐δ¹³C of annual tree rings, soil water availability (estimated from pre‐dawn leaf water potential), photosynthetic capacity, stem basal growth and xylem anatomy were measured in individual trees within three pairs of thinned and un‐thinned stands. The thinned stands were treated 7 to 15 years prior to measurement. The values of δ¹³C and BAI were assessed for 20 consecutive years overlapping the date of thinning in a single intensively studied stand, and was measured for 3 years on either side of the date of thinning for the two other stands to assess the generality of the response. After thinning, Δ increased by 0.89‰ (± 0.15‰). The trees in the un‐thinned stands showed no change in Δ (0.00‰ ± 0.04‰). In the intensively studied trees, significant differences were expressed in the first growing season after the thinning took place but it took 6 years before the full 0.89‰ difference was observed. BAI doubled or tripled after disturbance, depending on the stand, and the increased BAI lasted up to 15 years after thinning. In the intensively studied trees, the BAI response did not begin until 3 years after the Δ response, peaked 1 year after the Δ peak, and then BAI and Δ oscillated in unison. The lag between BAI and Δ was not due to slow changes in anatomical properties of the sapwood, because tracheid dimensions and sapwood‐specific conductivity remained unchanged after disturbance. The Δ response of thinned trees indicated that A/g decreased after thinning. Photosynthetic capacity, as indexed by foliar nitrogen ([N]) and by the relationship between photosynthesis and internal CO₂ (A–C_i curves), was unchanged by thinning, confirming our suspicion that the decline in A/g was due to a relatively greater increase in g in comparison with A. Model estimates agreed with this conclusion, predicting that g increased by nearly 25% after thinning relative to a 15% increase in A. Pre‐dawn leaf water potential averaged 0.11 MPa (± 0.03 MPa) less negative for the thinned compared with the un‐thinned trees in all stands, and was strongly correlated with Δ post‐thinning (R² = 0.91). There was a strong relationship between BAI and modelled A, suggesting that changes in water availability and g have a significant effect on carbon assimilation and growth of these old trees. These results confirm that stand density reductions result in increased growth of individual trees via increased stomatal conductance. Furthermore, they show that a physiological response to stand density reductions can last for up to 15 years in old ponderosa pines if stand leaf area is not fully re‐established.     

Activity of sodium trimetaphosphate,associated or not with fluoride,on dual-species biofilms

Abstract

A response surface methodology was used to build a model to predict reductions in uropathogenic Escherichia coli biofilms in response to three compounds: cranberry extract [CB] at 3.0–9.0%, and caprylic acid [CAR] and thymol [TM] at 0.01%–0.05%. The predictive model for microbial reduction had a high regression coefficient (R²?=?0.9988), and the accuracy of the model was verified (R²?=?0.9527). Values of CAR, TM, and the quadratic term CAR² were the most significant (P?10 reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37?°C for 1?min. The model could be used to predict the most cost-efficient amounts of antimicrobial agents for anti-urinary tract infection products such as catheter lock solution and antimicrobial coatings for catheters.