Nylon Screen Research Articles

A Field Tests of Interspecific Competition on Oviposition of Gall‐Forming Sawflies on Willow

We performed a manipulative field experiment to test for competitive effects of the stem galling sawfly (Euura lasiolepis) on three other gall—forming sawflies on arroyo willow (Salix lasiolepis). Within a willow clone, three branches were left untreated, three branches had E. lasiolepis females placed on them in nylon screen bags during that species' oviposition period, and three branches were bagged during that same period but had no sawflies introduced. When oviposition by E. lasiolepis was completed, bags were removed, and three other sawflies were permitted to oviposit on the branches. We found no significant interspecific competitive effects on the densities of three species in response to 9— and 17—fold increase in densities of galls of the stem—galling sawfly on branches of field plants in 1985 and 1986, respectively. The densities of stem gallers on the experimental branches were high, but were near densities observed on some unmanipulated field plants. The density of the petiole galler in 1985 was higher on branches with the stem galler than was the density of the leaf galler. This suggested a facilitation effect, which was not repeated in 1986. The leaf folder had significantly greater densities than the leaf galler or petiole galler. However, bagging of branches resulted in greatly reduced densities of the leaf folder compared to unbagged control branches in both years. The petiole galler and leaf galler were not affected by bagging in either year, probably due to their later oviposition phenology. Within treatment branches, where stem gall densities were high, these three sawfly species did not significantly avoid oviposition on shoots with stem galls, and in 1986 there were generally positive co—occurrence patterns of each of these species with stem galls on shoots. We conclude that interspecific competitive effects on gall density was not important under these field conditions for the leaf galler and the petiole galler, but bagging effects on the leaf folder density could have reduced the likelihood of detecting competitive effects by the stem galler on this species. Differences in the results of this study with an earlier experiment may be related to compensatory ability of the larger field plants and differences in stem gall densities.

Effects of Leaf Litter on Survival and Growth of Juvenile Coho Salmon

Abstract Juvenile coho salmon (Oncorhynchus kisutch) were raised for a 6-week period from 2 weeks posthatching through yolk-sac absorption in oval tanks with or without a 5-cm layer of leaf litter. Each treatment was conducted in triplicate tanks; each tank initially contained 100 yolk-sac fry. The fish were fed at a reduced ration in order to discern nutritive effects (possibly from invertebrates) due to the presence of leaf litter. In each of the two consecutive years that the experiment was conducted, there was a third experimental condition – in year 1, a nylon screen was placed on top of the leaf litter to separate cover effects from nutritional effects; in year 2, a treatment group was fed full ration. Examination of total treatment mortality suggested that some factor in the leaf litter tended to improve survival, although the added leaf litter did not have any statistically significant effect on growth during the experiment. Thus, leaf litter, a component of the natural habitat of coho salmon fry,...

Evidence that a secretory component of the sea urchin egg is routed to yolk platelets after fertilization

During fertilization the sea urchin egg undergoes a global wave of secretion (the cortical reaction) followed by a period of endocytotic activity involved in membrane retrieval. Using a monoclonal antibody (MAb 1223) that recognizes a 130-kDa glycoprotein found in both the egg and embryo of Strongylocentrotus purpuratus, we recently suggested that glycoproteins bearing the 1223 epitope are stored in the cortical vesicles of the egg, secreted during fertilization, and subsequently endocytosed and routed to yolk platelets, a possible site of degradation.In the current study, to determine whether fertilized eggs could internalize an antibody probe directed at the cell surface, we coupled MAb 1223 to colloidal gold and presented it to eggs that had been stripped of fertilization envelopes and hyaline layers. Gold-conjugated mouse IgG (preimmune), bovine serum albumin (BSA), and goat-antimouse IgG served as controls. Colloidal gold (8 and 15 nm) was prepared and conjugated to BSA or antibody as previously described. For localization of the 1223 antigen in unfertilized eggs MAb 1223-gold was diluted 1:20 in buffer and applied to sections of eggs embedded in Lowicryl K4M. To remove the envelopes and hyaline layers, 20-30 seconds after addition of sperm the eggs were suspended in ice-cold artificial sea water containing 25 mM EGTA and passed through a nylon screen (64 μm mesh). Subsequently, 1 ml aliquots of the denuded eggs [10% suspension (vol/vol)] were gravity settled, removed from the Ca2+-chelator and resuspended in complete sea water. After a second wash, 20 μl aliquots of the eggs were transferred to fresh 1.0 ml volumes of sea water equilibrated at 14°C in the presence of the individual gold probes. The final dilution of the gold probes in sea water was 1:100. After gentle mixing of the eggs and gold probes, at time points 5,15,30 and 60 minutes specimens were fixed and embedded in Spurr resin as previously described.

CORRELATION OF MORTALITY RATES OF AEDES AEGYPTI (DIPTERA: CULICIDAE) AND CHLORPYRIFOS DEPOSITED ON SENTINEL CAGE SCREEN MATERIAL1

A method was developed to provide an alternative to sentinel mosquitoes for assessing efficacy of ultra-low volume (ULV) insecticide applications. A correlation (r2 = 0.793) exists between chlorpyrifos recovered from the screens of sentinel cages and mortality rates of confined adult female Aedes aegypti. Chromatographic methods were modified to accurately measure nanogram quantities of chlorpyrifos. The retention of 11 and 26 ng of chlorpyrifos/cm2 of nylon screen from the sentinel cages correlated with adult female Ae. aegypti mortality rates of 34 and 68%, respectively, 6 h posttreatment.

Effects of screen materials on droplet size frequency distribution of aerosols entering sentinel mosquito exposure tubes*

Aerosol filtration effects of three types of mesh screen used for mosquito cages were evaluated with aerosolized water, mineral oil and chlorpyrifos. The screen materials were two nylon tulles (3 x 4 and 8 x 11 repeats per cm2) and corrosion-resistant steel (7 x 7 repeats per cm2). Open areas of these three mesh materials were, respectively, 94%, 79% and 88%. Aerosol droplet size frequency distributions were altered when passed through test screens of these materials fitted to standard tubes from World Health Organization test-kits for exposure of adult mosquitoes. The alterations included reductions in total droplets and volume median diameter (VmD). Nylon screen with fewer repeats of the mesh altered droplet VmD and frequency distribution the least, allowing the greatest number of droplets to enter sentinel mosquito cages for bioassays of mortality-rates. The greater filtration effect of screens with less open area, giving rise to selective deposition of particular droplet sizes on the screen material, could result in anomalous exposures of test mosquitoes to contact with insecticide filtrate on the screen substrate. This might help to explain the poor correlation often observed between insecticide aerosol impact on wild target mosquito populations as compared with sentinel caged mosquitoes. In addition to other standard test procedures, the need for standardization of materials used for construction of sentinel cages employed for aerosol bioassays is emphasized.

The use of periphyton communities for nutrient removal from polluted streams

The results of experiments on the efficiency of periphyton communities for nutrient removal from polluted streams in a continuous flow-through are given. The artifical stream (5 m × 0.7 m × 0.5 m) was made of wood, with silon (a kind of nylon) screens, as a substratum for periphyton growth. The elimination of nutrients was monitored by ammonium, nitrite, nitrate and orthophosphate analyses. In addition, the elimination of organics and the decrease in trophic state were determined. During two field experiments a marked elimination of nitrogen and phosphorus was demonstrated. The maximum efficiency of ammonium and orthophosphate removal was 80% and 70%, respectively. Organic removal reached 35% (C.O.D.Mn-Kubel) and 54% (B.O.D.5). Inorganic and organic nutrient elimination caused significant changes in periphyton community structure in the outflow portion of the through, evaluated by the saprobic index and the similarity coefficient. The experiments confirmed that periphyton communities are a useful means of nutrient removal from polluted streams.

Inactivation of particle-associated coliforms by chlorine and monochloramine

Sieves and nylon screens were used to separate primary sewage effluent solids into particle fractions of less than 7- or greater than 7-micron size. The efficiency of separation was determined by using a particle counter. Indigenous coliforms associated with the particle fractions were tested for their resistance to chlorine and monochloramine. Coliforms associated with the less than 7-microns fraction were inactivated more rapidly by 0.5 mg of chlorine per liter at 5 degrees C and pH 7 than coliforms associated with the greater than 7-microns fraction. Homogenization of the greater than 7-microns fraction not only resulted in an increase in the number of less than 7-microns particles, but also increased the rate of inactivation to a rate similar to that of the less than 7-microns fraction. With 1 mg of monochloramine per liter at 5 degrees C and pH 7, particle size had no appreciable effect on the rate of inactivation. At pH 8, however, the less than 7-micron fraction was inactivated more rapidly than the greater than 7-micron fraction. The time required for 99% inactivation of the particle fractions with monochloramine at pH 7 or 8 was 20- to 50-fold greater than the time required for the same amount of inactivation with chlorine at pH 7. The results indicate that coliforms associated with sewage effluent particles are inactivated more rapidly with 0.5 mg of chlorine per liter than with 1.0 mg of monochloramine per liter. However, greater than 7-micron particles can have a protective effect against the disinfecting action of chlorine.

Repellency of Textile Assemblies

In a series of studies on the relation between the wettability or repellency of textile assemblies and their structures, apparent contact angles (ϕ) of monofilament nylon and polyester mesh screens to water were measured to clarify the effect of the woven structure on the repellency of textiles. The apparent equilibrium contact angles (ϕ e), not the apparent advancing ones (ϕ A), can be quantitatively predicted by using the theoretical expressions for the liquid-solid and liquid-air interfaces per unit of mac roscopic surface area in the Cassie-Baxter equation ( f1 and f 2, respectively) and the true advancing contact angles (θ A). The effect of the size of sessile water drops on the apparent contact angles (ϕ) was also interpreted in terms of the distortion of the drop surface owing to the gravity effect.

Repellency of Textile Assemblies

In a series of studies on the wettability of textile assemblies, apparent contact angles (ϕ) of wax-coated monofilament nylon and polyester mesh screens to water were measured to investigate the effect of the woven structure on the repellency of textiles. Expressions for the liquid-solid and liquid-air interfaces per unit of macroscopic surface area in the Cassie-Baxter equation ( f 1 and f2, respectively) have been derived for mesh screens using several models to calculate the apparent contact angles (ϕ A) theoretically. Comparison with experimental data has shown that the apparent advancing contact angles of water on wax-coated mesh screens can be quantitatively predicted by the Cassie-Baxter equation when the geometrical structure of the surface is accurately defined.

Isolation of the zona pellucida and purification of its glycoprotein families from pig oocytes

The isolation of the porcine zona pellucida, the glycoprotein envelope surrounding the mammalian oocyte, and the purification of its glycoprotein families is described. The zona pellucida was prepared from oocytes isolated from pig ovaries using a razor blade device and sieving procedures with Teflon or nylon screens. In 6–7 man h, the zona pellucida from 5 × 10 5 oocytes was obtained yielding 12 mg protein and 2.2 mg carbohydrate. The absorptivity of heat solublized and filtered zona pellucida was A 280 nm, 1cm 1% = 10.8. The four glycoprotein families of the zona pellucida were purified by two-dimensional polyacrylamide gel electrophoresis and electrophoretic elution. The electrophoretic purity of these families was greater than 90%. The protein and carbohydrate content and the amino acid and monosaccharide compositions of each of the glycoprotein families were determined.

Arterial line filtration during cardiopulmonary bypass: Neurologic, neuropsychologic, and hematologic studies

One hundred patients who underwent elective cardiac operations were randomized into two groups. Group 1 had a 20 micron nylon screen filter in the arterial line. In Group 2 no filter was used in the arterial line. Neurologic and neuropsychologic examination of the patients was performed with seven psychometric tests of the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale. These tests were conducted before and a mean of 10 days after the operation. Platelet counts and hemoglobin and total protein levels were measured at the onset and at the end of cardiopulmonary bypass. Two patients died during their hospital stay. Neurologic damage with focal signs was found in the postoperative examination in six patients (three in each group). Twenty-eight patients (28.5%) exhibited signs of mild cerebral dysfunction as assessed by the presence of archaic (primitive) reflexes. Fifteen were in Group 1 and 13 in Group 2 (no significant difference). Sixty patients (61%) had decrements greater than one standard deviation in at least one of the three tests that showed most decreased postoperative scores. There were 32 in Group 1 and 28 in Group 2 (no significant difference). When each test was analyzed individually, there were no significant differences between the two groups. Platelet counts decreased, during cardiopulmonary bypass, a mean of 33% in Group 1 and 34.5% in Group 2 (no significant difference). Both hemoglobin and total protein levels remained virtually unchanged. These results indicate that the addition of a small-pore filter in the arterial line does not prevent the neurologic and neuropsychologic disturbances frequently encountered after cardiopulmonary bypass. The filter itself does not appear to have a direct effect on the blood components. Routine use of an arterial line filter remains questionable.

Sieving Techniques in Palynological Sample Processing with Special Reference to the MRA System

Sieving Techniques in Palynological Sample Processing with Special Reference to the MRA System

A technique for the isolation of highly viable pancreatic B-cells from ob/ob mice.

A method has been developed to prepare free islet cells in suspension from adult ob/ob-mice. About 200 collagenase-isolated pancreatic islets were pooled in 4 ml of calcium-free Krebs-Ringer-HEPES buffer supplemented with 1 mM EGTA and 10 micrograms/ml DNAase. The islets were gently shaken in a water-bath for 10 min at 30 degrees C. Then, the cell suspension was filtered through a nylon screen and centrifuged through ice-cold, dense albumin. The isolated cells, of which more than 99% were B-cells, appeared well preserved both in light- and electron-microscopy. Out of the isolated cells, 7.1 +/- 0.5% took up Evans Blue and were thus considered non-viable.

Monitoring extra-matrical hyphae of a vesicular-arbuscular mycorrhizal fungus with an immunofluorescence assay and the soil aggregation technique

An immunofluorescence assay (IFA) was used to compare the amount of extra-matrical hyphae of the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus versiforme (Karst) Berch colonizing seedlings of White Cedar, Chamaecyparis lawsoniana (A. Murr.) Parl., with different root densities in three soil mixes. Restriction (binding) of the root mass with nylon screening decreased root density and also decreased the density of VAM hyphae detected per root length or per soil volume. Top growth of transplanted seedlings was not affected by root restriction. More VAM fungal external hyphae, determined by IFA and the sand aggregation method, formed in river sand than in silt loam with similar percentages of intraradical VAM colonization. More soil aggregates formed in silt loam than in sand regardless of the presence of VAM fungal hyphae. Depending on experimental design, the aggregation method for estimating VAM external hyphae may be limited to use in sandy soil. IFA reacted specifically with G. versiforme hyphae in mineral soil or sand, but was ineffective in peat soil due to nonspecific staining and autofluorescence of organic matter.

Identification and Isolation of Single Cells that Produce Somatic Embryos at a High Frequency in a Carrot Suspension Culture

A system was established in which single cells differentiated to embryos at a high frequency. Small spherical single cells from a carrot (Daucus carota L. cv "Kurodagosun") cell suspension culture were obtained by fractionation through sieving, using nylon screens and then density gradient centrifugation in Percoll solutions. Eighty-five to 90% of these small single cells differentiated to embryos when they were cultured in a medium containing 2,4-dichlorophenoxyacetic acid (5 x 10(-8) molar), zeatin (10(-6) molar), and mannitol (0.2 molar) for 7 days, followed by transfer to a medium containing zeatin (10(-7) molar) but no auxin. This indicates that there are at least two phases in the differentiation of embryos from single cells. The progression of the first phase required exogenous auxin, whereas that of the second phase was inhibited by the same growth regulator. The relationship between the morphology and potency for embryogenesis from single cells was discussed. The system established here is a useful one for investigation of differentiation process from a single cell to a whole plant via embryogenesis, especially in its early stage.

Preparation techniques for concentrating pollen from marine sediments and other sediments with low pollen density

Abstract A procedure that modifies standard preparation techniques was developed to concentrate pollen and spores from intractable sediments. These modifications include sieving samples suspended in 0.001 M sodium pyrophasphate through 7im nylon screens prior to and following chemical treatments. If siliceous sediments require reprocessing with hydroflouric acid (HF), samples are sieved through 7 im screens between HF treatments, using sodium pyrophosphate as a suspension. Samples with large amounts of undigested, fine‐grained organic matter are slowly oxidized with a sodium chlorate mixture. Continuously monitored use of these techniques produces statistically‐significant sums of pollen from sediments which otherwise would be of little value to palynologists.

Evidence for the involvement of the soil microbiota in the exclusion of Fusarium from coniferous forest soils

Fusarium was recovered from only 1 of 14 Pacific Northwest coniferous forest soils but from all 7 nursery soils tested. Assays using high concentrations of Fusarium oxysporum macroconidia added to soil determined that forest soils stimulate macroconidial germination [Formula: see text] often followed by germ-tube lysis or the formation of stunted chlamydospores, while nursery soils support little macroconidial germination [Formula: see text]. Treatment of forest soils with aerated steam (minimum of 45 °C for 30 min), radiation, or propylene oxide reduced the amount of germination in forest soils, suggesting that the forest soil microbiota is involved in the stimulation of macroconidial germination. Bacteria isolated from F. oxysporum hyphae placed in forest, field, or nursery soils on nylon screens did not significantly influence germ-tube lysis when combined with macroconidia in a nutrient broth. Chemical, physical, and nutritional properties of forest soils likely affect the capacity of the forest soil microbiota to influence Fusarium macroconidial germination and germ-tube lysis.

Isolation of oligodendroglial cells from young and adult whole rat brains using an in situ generated percoll density gradient

A method for the isolation of oligodendroglial cells from young and adult whole rat brains, using a Percoll density gradient is presented. The minced tissue, incubated in a balanced salt solution containing 0.1% trypsin is further dissociated by forcing it through nylon screens to 145 and 74 μm pore size. The crude suspension is then mixed with an isosmotic Percoll solution and centrifuged for 15 min. An in situ generated density gradient allows the separation of five bands, only one of which (Band C) lying between δ1.050 and δ1.062 contains cellular elements. The isolated cells show the typical morphological characteristics of oligodendroglia. A detailed morphological study of the cells isolated from whole brains of 10-, 30- and 120-day old rats is presented for the first time in the literature and immunocytochemical characterization is carried out using specific (antigalactocerebroside) and non specific (anti-glial fibrillary acidic protein) anti-sera. The method is simple and rapid and isosmotic conditions are maintained throughout, resulting in a better preservation of cell integrity. It represents an improvement over the two previous methods described in the literature and will be useful for studying different developmental events (biochemical and morphological) occurring in oligodendroglial cells at early stages of myelin formation.

Observations on the removal of microaggregates from stored blood by centrifugation and filtration through a standard 170 micron transfusion filter.

The effect of centrifugation (5 minutes, 6900 X g) on the amount and particle size of blood microaggregates was studied in order to assess whether centrifugation and filtration by a standard (170 micron) transfusion set filter could be used for aggregate removal instead of microfiltration. Aggregates were quantitated using a method based on nylon screens with graded pore sizes. At the beginning of storage, centrifugation increased the particle size of aggregates only slightly. In 7-day-old blood, aggregates capable of passing a 160 micron screen amounted to 308 +/- 107 (SD) mg of debris protein per liter of blood before and 55 +/- 26 (SD) mg of protein (n = 10) after centrifugation. In 14-day-old blood centrifugation increased the size of aggregates even more effectively: 311 +/- 81 (SD) before and 29 +/- 14 (SD) mg of protein following centrifugation. Microaggregates can thus be removed effectively by the centrifugation and filtration method from blood stored for more than 1 week. A standard transfusion set filter can be used instead of a micropore filter.

The mononuclear cell population in rat leg muscle: its contribution to the lysosomal enzyme activities of whole muscle extracts.

The mononuclear cell fraction of rat hind-limb muscle was obtained by digestion with clostridial collagenase in the presence of calcium ions, filtration through nylon screens and washing to remove the enzyme. Final traces of contaminant myofibrillar debris were separated by isopycnic centrifugation in a Percoll density gradient. Whole muscle, washed cells and Percoll-fractionated cells were extracted in the presence of non-ionic detergent and the supernatants assayed for the lysosomal enzymes cathepsins B + L, N-acetyl-beta-glucosaminidase, beta-glucuronidase and protein. The enzyme levels were highest in the muscle from young rats, but the percentage of recovered activity in the mononuclear cell fraction was little altered by the age of the animal. The values obtained were: cathepsin B + L, 2.4-4.0%; N-acetyl-beta-glucuronidase, 4.3-7.6%; and beta-glucuronidase, 6.3-10.3%. Because of unavoidable losses in preparation these are minimal values and the actual levels of activity from the mononuclear cell fraction in muscle would be higher. The specific activity values of the cell lysates were raised after isopycnic centrifugation and were nearly constant over the age range 65-180 days. Substantially higher specific activity values were obtained for the cells from rats of 38 days. When grown in culture the mononuclear cell fractions were seen to contain mainly fibroblasts and myoblasts with only few leucocytes. The cultures reached confluence by the second week, at which time numerous myotubes had formed. In addition there were groups of large, circular cells with a prominent centrosphere. The origin of these latter cells is uncertain. It was concluded that although total lysosomal enzyme activity was higher in young rats there was little effect of age on the distribution of activity between muscle fibres and mononuclear cells in the muscle.