The influence of diet on the growth of Stenonema vicarium (Walker) (Ephemeroptera: Heptageniidae)

Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d⁻¹) than detritus (mean = 1.8% wet wt. d⁻¹). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.     

Failure of bacterial endotoxin to produce the generalized Shwartzman reaction in the Syrian hamster

The ability of bacterial endotoxin to produce the generalized Shwartzman reaction (GSR) in pregnant and nonpregnant hamsters was investigated. Endotoxins prepared from Escherichia coli O127:B8, Salmonella enteritidis, and S. typhosa 0-901 did not produce the GSR in nonpregnant hamsters. Injection of lead acetate did not make the hamsters susceptible to the GSR producing effects of endotoxin. Endotoxin administered to hamsters on either or both the 14th and 15th day of the 16-day gestation period caused fetal death, but did not provoke the GSR. The immunization of hamsters with boiled suspensions of gram-negative bacteria isolated from hamster feces did not protect against the GSR produced in pregnant hamsters by the injection of the antimitotic drug colchicine late in the gestation period. It appeared that colchicine was acting to produce the GSR by a mechanism other than the release of endogenous endotoxin through the damaged intestinal wall. Ascitic fluid, amniotic fluid, and serum obtained from pregnant hamsters developing the GSR after the administration of colchicine did not provoke the GSR in other pregnant hamsters.     

The nutritional ecology of larvae of Alsophila pometaria and Anisota senatoria feeding on early- and late-season oak foliage

The larvae of Alsophila pometaria (Harr.), feeding on the young foliage of oak, has a higher relative growth rate (RGR) and relative nitrogen accumulation rate (RNAR) than the larvae of Anisota senatoria (J. E. Smith), feeding on the mature foliage of oak. Although the young oak foliage is more efficiently digested by A. pometaria (higher AD's), it is not more efficiently assimilated and used for growth (no difference in ECI's). Thus, the higher growth rate of A. pometaria is due entirely to a higher consumption rate (RCR and RNCR). Young foliage is significantly higher in nitrogen and water than mature foliage, but phenol and tannin levels are comparable in young and old foliage. A. pometaria consumes the foliage of different oak species at the same rate, independent of nitrogen content, while A. senatoria increases its consumption rate in response to decreased nitrogen levels. As a result, the growth rate of A. pometaria is directly related to leaf nitrogen content, while the growth rate of A. senatoria is independent of leaf nitrogen. The two species of insects have digestive systems that are very similar biochemically, and that are well-designed for effective protein digestion. Tannins and phenols do not influence the nutrional indices of either species. We suggest that the major benefit of spring feeding is the availability of succulent, high-nitrogen foliage, and not the avoidance of high-tannin foliage. The spring feeder appears to have a feeding strategy that favors rapid growth at the expense of efficiency, while the late summer feeder has a strategy that favors efficiency over rate.

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Résumé Alimentées sur feuillage jeune de chêne, les chenilles d'Alsophila pometaria avaient un taux relatif de croissance (RGR) et un taux relatif d'accumulation d'azote (RNAR) plus élevés que les chenilles d'Anisota senatoria alimentées sur feuillage mûr de chêne. Bien que le jeune feuillage soit plus efficacement digéré par A. pometaria (AD plus élevé), il n'est pas assimilé et utilisé pour la croissance avec de meilleurs rendements (les ECI ne sont pas différents). Ainsi le taux de croissance plus élevé d'A. pometaria est dû entièrement à un taux de consommation plus important (RCR et RNCR). Le feuillage jeune est significativement plus riche en azote et en eau que le feuillage mûr, mais les niveaux de phénol et de tanins sont les mêmes. A pometaria consomme les feuilles de différentes espèces de chênes au même taux, indépendamment de la teneur en azote, tandis que A. senatoria accroît sa consommation en réponse à une diminution de la teneur en azote. Il en résulte que le taux de croissance d'A. pometaria dépend directement de la teneur en azote des feuilles, tandis que celui d'A. senatoria en est indépendant. Les systèmes digestifs des deux insectes sont biochimiquement semblables et sont efficaces pour la digestion des protéines. Les tanins et les phénols n'influent pas sur les indices nutritionnels de ces deux espèces. Nous estimons que le principal intérêt de l'alimentation printanière est la disponibilité en feuillage succulent, riche en azote, et non l'absence de feuilles à haute teneur en tanin. L'alimentation printanière semble correspondre à une strategie alimentaire qui favorise la croissance aux dépens de l'efficacité tandis que l'alimentation en fin d'été est une stratégie qui favorise l'efficacité sur la rapidité.

     

High-performance liquid chromatography of p-nitrophenacyl esters of selected prostaglandins on silver ion-loaded microparticulate cation-exchange resin

A silver ion-loaded microparticulate cation-exchange resin column has been used for high-performance liquid chromatographic (HPLC) separation of the p-nitrophenacyl esters of several series of closely related prostaglandins: 8-iso-PGE₂, 11-epi-PGE₂, 5-trans-PGE₂, PGE₂, PGF_1α, PGE₁, and PGF_2α, PGA₂ and PGB₂; 15 (R)-methyl-PGE₂ and 15 (S)-methyl-PGE₂; 5-trans-PGA₂ and PGA₂; and 5-trans-PGF_2α and PGF_2α. The properties of this column are compared with those of silica-gel and reversed-phase columns.     

Cyclic nucleotide metabolism and reactive oxygen production by macrophages

The production of reactive oxygen species by elicited rat peritoneal macrophages was assessed by $\text{in vitro}$ measurement of chemiluminescence in the presence of luminol. The divalent ion ionophore A23187 stimulated the production of reactive oxygen species. This action was inhibited by monobutyryl and dibutyryl derivatives of cyclic AMP but was not affected by derivates of cyclic GMP. Cyclic AMP and cyclic GMP concentrations increased rapidly in macrophages exposed to A23187 or zymosan. Indomethacin (20 μmol/1) inhibited the increase in cyclic AMP concentration but not the increase in cyclic GMP concentration. Neither A23187 nor zymosan stimulated adenylate cyclase activity in broken cell preparations of macrophages. The observations are consistent with the hypothesis that PGE produced by macrophages after phagocytotic stimuli may inhibit certain macrophage functions and perform a regulatory role in these cells. This action of PGE may be mediated by cyclic AMP.     

Genetic studies of human acidic salivary protein (Pa).

The phenotypic expression of a dominantly inherited human salivary acidic protein (Pa) has been described in acid-urea starch and in Tris-borate acrylamide gel systems. Estimates of the Pa+ allelic frequencies in American Caucasians, American blacks, and Orientals are .21, .14, and .42, respectively. The genetic and biochemical similarities to another series of proline-rich salivary proteins, Pr, and to a pair of similarly staining salivary proteins, Db (double band), are evaluated. It is concluded that either one locus or two (or three) tightly linked loci are viable explanations for this polymorphic system(s). It is suggested that the three factors, Pa, Pr, and Db, be treated as separate loci to allow clarification of their genetic relationships.     

Moisture is required for the termination of egg diapause in the chrysomelid beetle, Homichloda barkeri

Four factors (moisture, light regime, temperature, food type) were examined for their effects on the embryonic diapause of Homichloda (Weiseana) barkeri (Jacoby) (Coleoptera: Chrysomelidae), a biocontrol agent for prickly acacia, Acacia nilotica (L.) Willdenew ex Delile (Mimosaceae). Moisture is critical for termination of diapause. A single wetting of eggs resulted in a low hatch rate while a sequence of wetting events followed by periods of dryness produced a high hatch rate. A relatively constant proportion of embryos within each batch initiated development at each wetting event, with hatching complete after the eighth wetting event in these trials. An extended interval between wetting events, tested at up to 23 days, did not result in a decreased overall hatch rate. A threshold time of exposure to moisture of between 3 to 6 h is required before development proceeds. The response of eggs to the moisture regime is seen as a strategy for taking advantage of available food after rainfall by terminating diapause, rather than merely a quiescent response to the absence of moisture. Temperature affected development time and the proportion of eggs that developed. Experimental manipulations of photoperiod and host-plant availability showed no effect on embryonic development.     

Characterization of glycosphingolipids by supercritical fluid chromatography-mass spectrometry

Gangliosides have been characterized by supercritical fluid chromatography-chemical ionization mass spectrometry (SFC-CIMS) as permethyl and pertrimethylsilyl derivatives, using carbon dioxide as the SFC mobile phase and CI reagent gas. Ganglioside classes and ceramide heterogeneity within each class are well resolved by SFC. Direct SFC-interfacing allows the analytical manipulations of single-ion monitoring, total-ion plots, background subtraction, library searches, and spectral reconstruction algorithms. Addition of ammonia to the CI ion chamber (NH3 as a CI reagent gas) yields abundant molecular-weight-related ions, (MH)+ and (MNH4)+ from analyte derivatives. Substitution of methanol for ammonia yields considerable parent-ion fragmentation, providing structural information on carbohydrate sequence, fatty acid, and sphingoid components. Under these latter conditions a unique alpha-cleavage fragment is observed which differentiates fatty acid from sphingosine heterogeneity. For ganglioside samples, the carboxyl group of neuraminyl residue(s) have been esterified with pentafluorobenzyl bromide and the products analyzed by negative ion chemical ionization MS. This modification improves chemical selectivity and greatly enhances detecting sensitivity. These "soft" ionization conditions provide abundant molecular-weight-related anions for collision-induced dissociation and subpicogram detection.     

Variation in responses to spawning Pacific salmon among three south-eastern Alaska streams

1. Pacific salmon are thought to stimulate the productivity of the fresh waters in which they spawn by fertilising them with marine‐derived nutrients (MDN). We compared the influence of salmon spawners on surface streamwater chemistry and benthic biota among three south‐eastern Alaska streams. Within each stream, reaches up‐ and downstream of barriers to salmon migration were sampled during or soon after spawners entered the streams. 2. Within streams, concentrations of dissolved ammonium and soluble reactive phosphorus (SRP), abundance of epilithon (chlorophyll a and ash‐free dry mass) and biomass of chironomids were significantly higher in reaches with salmon spawners. In contrast, biomass of the mayflies Epeorus spp. and Rhithrogena spp. was significantly higher in reaches lacking spawners. 3. Among streams, significant differences were found in concentrations of dissolved ammonium, dissolved organic carbon, nitrate and SRP, abundance of epilithon, and the biomass of chironomids and Rhithrogena. These differences did not appear to reflect differences among streams in spawner density, nor the changes in water chemistry resulting from salmon spawners. 4. Our results suggest that the ‘enrichment’ effect of salmon spawners (e.g. increased streamwater nutrient concentrations) was balanced by other concurrent effects of spawners on streams (e.g. sediment disturbance). Furthermore, the collective effect of spawners on lotic ecosystems is likely to be constrained by conditions unique to individual streams, such as temperature, background water chemistry and light attenuation.