Absence of female-specific protein in the hemolymph of stable fly Stomoxys calcitrans (L.) (Diptera: Muscidae)

Changes, during the reproductive cycle, in fat body, hemolymph, and ovarian proteins of the stable fly Stomoxys calcitrans were characterized quantitatively and qualitatively using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Protein content of all three tissues increased after blood feeding. Fat body protein increased first, followed by hemolymph and ovarian proteins. SDS-PAGE failed to identify vitellogenin in both female hemolymph and fat body samples. No single protein or group of proteins predominated at any stage of the reproductive cycle. Comparisons between male and female stable fly hemolymph and fat body proteins failed to detect female-specific proteins. Female-specific proteins, however, were detected in the hemolymph of four other species of Diptera.     

14,15N, 13C, 57Fe, and 1,2H Q-band ENDOR study of Fe-S proteins with clusters that have endogenous sulfur ligands.

The benefits of performing ENDOR experiments at higher microwave frequency are demonstrated in a Q-band (35 GHz) ENDOR investigation of a number of proteins with [nFe-mS] clusters, n = 2, 3, 4. Each protein displays several resonances in the frequency range of 0-20 MHz. In all instances, features are seen near v approximately 13 and 8 MHz that can be assigned, respectively, to "distant ENDOR" from 13C in natural-abundance (1.1%) and from 14N (the delta m1 = +/- 2 transitions); the nuclei involved in this phenomenon are remote from and have negligible hyperfine couplings to the cluster. In addition, a number of proteins show local 13C ENDOR signals with resolved hyperfine interactions; these are assigned to the beta carbons of cysteines bound to the cluster [A(13C) approximately 1.0 MHz]. Five proteins show resolved, local delta m1 = +/- 2 ENDOR signals from 14N with an isotropic hyperfine coupling, 0.4 less than or equal to A(14N) less than or equal to 1.0, similar to those seen in ESEEM studies; these most likely are associated with N-H...S hydrogen bonds to the cluster. Anabaena ferredoxin further shows a signal corresponding to A(14N) approximately 4 MHz. Quadrupole coupling constants are derived for both local and distant 14N signals. The interpretation of the data is supported by studies on 15N- and 13C-enriched ferredoxin (Fd) from Anabaena 7120, where the 15N signals can be clearly correlated with the corresponding 14N signals and where the 13C signals are strongly enhanced. Thus, the observation of 14N delta m1 = +/- 2 signals at Q-band provides a new technique for examining weak interactions with a cluster.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of digestive proteinases in the alimentary tract of the european corn borer Ostrinia nubilalis (lepidoptera: Pyralidae)

The distribution of digestive proteinases in either the anterior and posterior midgut or between the midgut epithelium and ectoperitrophic and endo-peritrophic spaces in the midgut were examined in the European corn borer, Ostrinia nubilalis. Trypsin, chymotrypsin, elastase, and aminopeptidase activities were the same in the anterior and posterior halves of the midgut. Of the total aminopeptidase activity, 95% was located in the midgut epithelium, and 90% of the trypsin, 97% of chymotrypsin, and 93% of the elastase activity were found in the midgut lumen. Trypsin, measured by hydrolysis of benzoyl-L-arginine ethyl ester, and chymotrypsin levels were significantly higher in the ectoperitrophic space compared to the endoperitrophic space. Digestion in the midgut is proposed to be sequential with tryptic digestion occurring in the endoperitrophic space. Ingested protein is digested further in the ectoperitrophic space by the action of elastase, chymotrypsin, and a second trypsin. Final digestion occurs by an intracellular aminopeptidase. © 1995 Wiley-Liss, Inc.     

Characterization of the [4Fe-4S]+ cluster at the active site of aconitase by 57Fe, 33S, and 14N electron nuclear double resonance spectroscopy

57Fe, 33S, and 14N electron nuclear double resonance (ENDOR) studies have been performed to characterize the [4Fe-4S]+ cluster at the active site of aconitase. Q-band 57Fe ENDOLR of isotopically enriched enzyme, both substrate free and in the enzyme-substrate complex, reveals four inequivalent iron sites. In agreement with M?ssbauer studies [Kent et al. (1985) J. Biol. Chem. 260, 6371-6881], one of the iron ions, Fea, which is easily removed by oxidation to yield the [3Fe-4S]+ cluster of inactive aconitase, shows a dramatic change in the presence of substrate. The remaining iron sites, Feb1,2,3, show minor changes when substrate is bound. Methods devised by us for analyzing and simulating ENDOR spectra of a randomly oriented paramagnet have been used to determine the principal values and orientation relative to the g tensor for the hyperfine tensors of three of the four inequivalent iron sites of the [4Fe-4S]+ cluster, Fea, Feb2, and Feb3, in the substrate-free enzyme and the enzyme-substrate complex. The full tensor for the fourth site, Feb1, could not be obtained because its signal is seen only over a limited range of the EPR envelope. 33S ENDOR data for the enzyme-substrate complex using enzyme reconstituted with 33S show that the four inorganic bridging sulfide ions of the [4Fe-4S]+ cube have isotropic hyperfine couplings of A(S) less than 12 MHz, and analysis indicates that they can be divided into two pairs, one with couplings of A(S1) approximately less than 1 MHz and the other with A(S2) approximately 6-12 MHz; the analysis further places these pairs within the cube relative to the iron sites. 33S data for substrate-free enzyme is qualitatively similar and can be completely simulated by two types of S2- ion, with A(S1) approximately 7.5 and A(S2) approximately 9 MHz; the full hyperfine tensors have been determined. The hyperfine values for the two enzyme forms correspond to surprisingly small unpaired spin density on S2-. 14N ENDOR at Q-band reveals a nitrogen signal that does not change upon substrate binding.     

Absorption and metabolism of nicotine from cigarettes.

Eight men volunteers each smoked a single cirgarette containing 14C-nicotine and gave arterial blood samples during and for 50 minutes after smoking. The maximum concentration of nicotine in the arterial blood ranged from 31 to 41 mug/l in four regular cigarette smokers who inhaled. Two non-smokers achieved maximum levels of 2 and 4 mug/l. On a separate occasion two of the inhalers received 1 mg. 14C-nicotine in 10 divided doses injected intravenously. In both cases the peak arterial nicotine concentrations bore a similar relationship to the intravenous dose, as did the peak nicotine concentrations to the retained doses during smoking.     

Fossil grebes from the Truckee Formation (Miocene) of Nevada and a new phylogenetic analysis of Podicipediformes (Aves)

Podicipediformes is a cosmopolitan clade of foot‐propelled diving birds that, despite inhabiting marine and lacustrine environments, have a poor fossil record. In this contribution, we describe three new grebe fossils from the diatomite beds of the Late Miocene Truckee Formation (10.2 ± 0.2 Ma) of Nevada (USA). Two postcranial skeletons and an associated set of wing elements indicate that at least two distinct grebe species occupied the large, shallow Lake Truckee during the Miocene. Phylogenetic analysis of morphological data supports a basal divergence between a clade uniting the dabchicks (Tachybaptus, Limnodytes, Poliocephalus) and a clade uniting Podilymbus, Rollandia, Podiceps and Aechmophorus. Missing data, combined with a paucity of informative skeletal characters, make it difficult to place the Truckee grebes within either of these major clades. Given the weak projection of the cnemial crests compared with extant grebes, it also remains plausible that these specimens represent stem lineage grebes. Although more material is needed to resolve the phylogenetic position of the Truckee grebes, our analysis offers insight into the tempo of grebe evolution by placing the Miocene taxon Thiornis sociata within the dabchick clade. Thiornis sociata provides a minimum age calibration of 8.7 Ma for the basal divergence among dabchicks. Based on the recovery of a nonmonophyletic Tachybaptus and placement of the Western Hemisphere ‘Tachybaptus’ dominicus as the basal member of the otherwise exclusively Eastern Hemisphere dabchick clade, we resurrect the genus Limnodytes for this extant species (Limnodytes dominicus). Our results also nest the large, long‐necked Aechmophorus grebes within the genus Podiceps, as the sister taxon to Podiceps major.     

Alternative states and positive feedbacks in restoration ecology

There is increasing interest in developing better predictive tools and a broader conceptual framework to guide the restoration of degraded land. Traditionally, restoration efforts have focused on re-establishing historical disturbance regimes or abiotic conditions, relying on successional processes to guide the recovery of biotic communities. However, strong feedbacks between biotic factors and the physical environment can alter the efficacy of these successional-based management efforts. Recent experimental work indicates that some degraded systems are resilient to traditional restoration efforts owing to constraints such as changes in landscape connectivity and organization, loss of native species pools, shifts in species dominance, trophic interactions and/or invasion by exotics, and concomitant effects on biogeochemical processes. Models of alternative ecosystem states that incorporate system thresholds and feedbacks are now being applied to the dynamics of recovery in degraded systems and are suggesting ways in which restoration can identify, prioritize and address these constraints.     

Cattle grazing in CRP grasslands during the nesting season: effects on avian abundance and diversity

The Conservation Reserve Program (CRP) is a primary tool for restoring grassland in the United States, in part as wildlife habitat, which has benefited declining grassland bird populations. Among potential mid-contract management practices used to maintain early-successional CRP grasslands, cattle grazing had been prohibited and is currently disincentivized during the primary nesting season for birds (much of the growing season), despite the important role that large herbivores historically played in structuring grassland ecosystems. Conservative grazing of CRP grasslands could increase spatial heterogeneity in vegetation structure and plant diversity, potentially supporting higher densities of some grassland bird species and higher bird diversity. Our objective was to determine the effect of experimental cattle grazing on species-specific relative abundance and occupancy, species diversity, and community dissimilarity of grassland birds on CRP grasslands across the longitudinal extent of Kansas, USA (a 63.5-cm precipitation gradient) during the 2017–2019 avian breeding seasons. Fifty-three of 108 fields were grazed by cattle during the growing seasons of 2017 and 2018 and all fields were rested from grazing in 2019. For all analyses, we examined separate model sets for semiarid western versus more mesic eastern Kansas. Using data from line transect surveys, we modeled relative abundances of 5 songbird species: grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), western meadowlark (Sturnella neglecta), and brown-headed cowbird (Molothrus ater). Grazing had delayed yet positive effects on abundances of grasshopper sparrow in western Kansas, and eastern meadowlark in eastern Kansas, but negative effects on dickcissel abundance in western Kansas and especially on burned fields in eastern Kansas. Somewhat counterintuitively, brown-headed cowbirds in western Kansas were more abundant on ungrazed versus grazed fields in the years after grazing began. In addition, we modeled multi-season occupancy of 3 gamebird species (ring-necked pheasant [Phasianus colcicus], northern bobwhite [Colinus virginianus], mourning dove [Zenaida macroura]) and Henslow's sparrow (Centronyx henslowii); grazing did not affect occupancy of these species. In eastern Kansas, species diversity was highest in grazed, unburned fields. In western Kansas, bird communities in grazed and ungrazed fields were dissimilar, as determined from multivariate analysis. Though regionally variable, conservative stocking of cattle on CRP grasslands during the nesting season as a mid-contract management tool might increase bird species diversity by restructuring habitat that accommodates a greater variety of species and decreasing abundances of species associated with taller, denser stands of vegetation.