Woodchip and biochar amendments differentially influence microbial responses,but do not enhance plant recovery in disturbed semiarid soils

Restoration presents a global challenge in drylands (arid and semiarid ecosystems) where uses can range from exclusive conservation to open‐pit mining and restoration practices are constrained by scarce, unpredictable precipitation, and high ambient temperatures. Adding woodchip amendments to soils is a common strategy for mitigating soil degradation as amendments may enhance soil carbon and increase plant cover. We assessed the effect of surface or incorporated woodchip addition and incorporated wood‐derived biochar on soil carbon dynamics and microbial activities as well as plant cover in semiarid soils that had been removed and replaced. We found that woodchips at the soil surface increased soil organic carbon (SOC), and both surface and incorporated woodchips increased the dissolved organic carbon (DOC) content. The incorporation of woodchips inhibited plant cover yet increased soil CO₂ efflux and dissolved organic matter stoichiometry. Surface woodchips also significantly enhanced microbial activities but not plant cover. A significant amount of the soil efflux in response to incorporating woodchips was explained by plant cover and exoenzyme activities, but this was not the case for other amendment treatments. Biochar, thought to be more resistant to decomposition, neither stimulated nor reduced microbial activities or plant cover and did not influence SOC or DOC. Our findings demonstrate that the influence of woodchip amendments on microbial processes and soil carbon dynamics depends on the location of application and that coarse fast‐pyrolysis biochar has limited influence on soil processes over a 22‐month study in a water‐limited ecosystem.     

Potassium Loss from Chlorhexidine-Treated Bacterial Pathogens is Time- and Concentration-Dependent and Variable Between Species

The membrane-active antimicrobial agent chlorhexidine is used extensively as an antiseptic during infection prophylaxis and treatment. Whilst known to induce membrane damage that results in loss of internal solutes from bacteria, the present study sought to determine the rate and extent of cytoplasmic potassium loss and whether any species-specific differences exist. Direct measurement of potassium was achieved using flame emission spectrophotometry. Exposure of selected species to minimum inhibitory (MIC) or minimum bactericidal concentration (MBC) resulted in solute loss that was both concentration and time dependent. Within 5-min treatment with MIC levels, losses of 3 % from P. aeruginosa, 9 % from E. coli, and 15 % from S. aureus were recorded, whilst at 5 % w/v chlorhexidine, elevated loss of 20, 28, and 41 % occurred, respectively. Nonlinear potassium release was evident from all species when treated with 5 % chlorhexidine over a 60-min period. After this contact time, potassium loss from E. coli and S. aureus rose to 93 or 90 %, respectively; in contrast, P. aeruginosa retained 62 % intracellular potassium. Results confirm lethal concentrations of chlorhexidine induce rapid and substantial loss of cytoplasmic potassium from common pathogens. However, bacterial responses vary between species and should be borne in mind when considering mechanism of action.     

Bird movement patterns in an agricultural landscape are mediated by both habitat conditions and traits

Alterations of the landscape following agricultural expansion and intensification affect animal movement patterns in the resulting mosaic of fragments and surrounding matrix. Here, we analyze the observed movement patterns of 34 individuals from nine tropical bird species from a rapidly changing agricultural landscape in Kenya. We deconstructed the movement patterns into their three components: step length, turn angles, and displacement and categorized them into two states: area restrictive and expansive movement. Using hidden Markov models, mixed models, and species traits, we showed that movement of birds in the fragments comprised of short step lengths and small displacements, characteristic of area restrictive movement to exploit high-quality habitats. On the contrary, movement in the matrix comprised of long step lengths and large displacements, characteristic of area expansive movement to explore or pass-through poorer habitats. The responses of movement components to fragments and the surrounding matrix were mediated by species traits. Habitat specialists showed stronger boundary response, shorter step lengths, and smaller displacements than habitat generalists in both the fragments and the matrix. Their strong preferences for the fragments, coupled with low flight capabilities can make movement in the matrix particularly difficult. Whereas, at the landscape scale, habitat generalist omnivores and habitat specialist frugivores had larger step lengths than the other guilds, as they use the matrix for resources or as a conduit to movement. Therefore, the habitat fragments are intensely utilized and of conservation importance. The matrix quality and permeability can promote animal space use and movement.     

Action of intercostal muscles on the lung in dogs

The action on the lung of interosseous intercostal muscles located in the third and the seventh interspaces was studied in 15 anesthetized-curarized supine dogs. Changes in pleural pressure, airflow rate, and lung volume produced by maximal stimulation of both intercostal muscle layers were measured at and above functional residual capacity (FRC). In five animals measurements were also obtained during isolated stimulation of the internal layer. At FRC, intercostal stimulation in the upper interspaces had invariably an inspiratory effect on the lung but no effect was detectable in the lower interspaces. Qualitatively similar results were obtained during isolated stimulation of the internal layer. Increasing lung volume reduced the inspiratory action of the upper intercostals and conferred an expiratory action to the lower intercostals. These results indicate the following: 1) when contracting in a single interspace, the external and internal intercostals have a qualitatively similar action on the lung; and 2) this action, however, depends critically on their location along the cephalocaudal axis of the rib cage: in the upper portion of the rib cage, both muscle layers have an inspiratory effect at and above FRC; in the lower portion of the rib cage, they have no respiratory action at FRC and act in the expiratory direction at higher lung volumes.     

Ecdysteroid binding sites localized by autoradiography in the central nervous system of precommitment fifth-stadium Manduca sexta larvae

Summary Brains and subesophageal ganglia from day 3.5 fifth stadium larvae of Manduca sexta were incubated in vitro with 4 nM tritiated ponasterone A, a 20-hydroxyecdysone analog, to determine whether uptake and specific binding of ecdysteroids occur at a cellular level. These tissues, which were taken just prior to the commitment peak in the hemolymph-ecdysteroid titer, showed saturable uptake of ³H-ponasterone A after 40–60 min of incubation. Uptake was blocked by the addition of 400 nM unlabelled ponasterone A, or of 500 nM or 1000 nM 20-hydroxyecdysone. RH 5849, a synthetic 20-hydroxyecdysone agonist with a long half-life, for which ecdysteroid receptors have low affinity, also reduced ponasterone A uptake at a concentration of 10 M. Autoradiographs of 4 m sections of brains revealed distinct nuclear concentrations of silver grains over cell populations in the pars intercerebralis, pars lateralis, and ventral tritocerebrum. Nuclear labelling was also found in many small cells around the mushroom bodies and the neuropil, and between the inner and outer larval optic lobes. Nuclear labelling of cells in the subesophageal ganglion was observed in the fronto-medial and lateral regions, in small cells around the neuropil, and caudally in a few large neurons. In addition to cells with nuclear labelling, both brains and ganglia at this development stage contained cells with exclusively cytoplasmic or both nuclear and cytoplasmic labelling. None of these apparent binding sites were observed in the competition experiments, suggesting that the binding is specific.     

Juvenile hormone III biosynthesis by the larval corpora allata of Manduca sexta

A radioimmunoassay (RIA) for juvenile hormone III has been established which quantifies the biosynthesis of this hormone in vitro by the corpora allata of larvae and pupae of the tobacco hornworm, Manduca sexta. The specificity of the RIA for homologues and metabolites of juvenile hormone III was determined and it was found that the antibody was specific for juvenile hormone III and its acid. The juvenile hormone III RIA activity synthesized in vitro by corpora allata from day-5 last-instar larvae was identified as juvenile hormone III by high pressure liquid chromatography. The kinetics of hormone synthesis by corpora allata from selected stages during larval-pupal development revealed differential rates of synthesis, suggesting that juvenile hormone III may have a hormonal function in the larva and that regulation of its synthesis may occur. The significance of these developmental fluctuations in rates of juvenile hormone III synthesis by the corpora allata is discussed in relation to the haemolymph titres of the hormone.     

Enduring antibody responses in "normal" rabbits to maternal immunoglobulin allotypes.

A majority of rabbits born to mothers heterozygous with respect to the b locus allotypic markers "spontaneously" develop antibodies against the noninherited maternal allotypes. Such antibodies generally appear in the 4- to 5-month-old rabbit, after what may be a transient period of tolerance, and persist at constant levels for at least 5 to 6 months. The finding of a high incidence of measurable antimaternal allotype responses in "normal" rabbits, added to similar findings by others in mice, pigs, and man, underscores the generality of this rather unexpected phenomenon and invites further inquiries into biological significance.     

Triangularis sterni muscle use in supine humans

The electrical activity of the triangularis sterni (transversus thoracis) muscle was studied in supine humans during resting breathing and a variety of respiratory and nonrespiratory maneuvers known to bring the abdominal muscles into action. Twelve normal subjects, of whom seven were uninformed and untrained, were investigated. The electromyogram of the triangularis sterni was recorded using a concentric needle electrode, and it was compared with the electromyograms of the abdominal (external oblique and rectus abdominis) muscles. The triangularis sterni was usually silent during resting breathing. In contrast, the muscle was invariably activated during expiration from functional residual capacity, expulsive maneuvers, "belly-in" isovolume maneuvers, static head flexion and trunk rotation, and spontaneous events such as speech, coughing, and laughter. When three trained subjects expired voluntarily with considerable recruitment of the triangularis sterni and no abdominal muscle activity, rib cage volume decreased and abdominal volume increased. These results indicate that unlike in the dog, spontaneous quiet expiration in supine humans is essentially a passive process; the human triangularis sterni, however, is a primary muscle of expiration; and its neural activation is largely coupled with that of the abdominals. The triangularis sterni probably contributes to the deflation of the rib cage during active expiration.     

Dendritic cells permit immune invasion of the CNS in an animal model of multiple sclerosis

Immunization with myelin antigens leads to the development of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. The disease can also be induced by the transfer of encephalitogenic CD4+ T helper (T(H)) lymphocytes into naive mice. These T cells need to re-encounter their cognate antigen in the context of major histocompatibility complex (MHC) class II-bearing antigen-presenting cells (APCs) in order to recognize their target. The cell type and location of the APC mediating T-cell entry into the central nervous system (CNS) remain unknown. Here, we show that APCs of the lymphoreticular system and of the CNS parenchyma are dispensable for the immune invasion of the CNS. We also describe that a discrete population of vessel-associated dendritic cells (DCs) is present in human brain tissue. In mice, CD11c+ DCs alone are sufficient to present antigen in vivo to primed myelin-reactive T cells in order to mediate CNS inflammation and clinical disease development.     

NF kappa B-inducing kinase deficiency results in the development of a subset of regulatory T cells, which shows a hyperproliferative activity upon glucocorticoid-induced TNF receptor family-related gene stimulation

CD4+CD25+ regulatory T cells (T(reg)) play an important role in maintaining immunologic tolerance. Glucocorticoid-induced TNFR family-related gene (GITR) expressed preferentially at high levels on T(reg) has been shown to be a key player of regulating T(reg)-mediated suppression. A recent study reports that NF-kappaB-inducing kinase (NIK) expression in thymic stroma is important for the normal production of T(reg) but not for its suppression capacity. In this report, we have shown that T(reg) from NIK-deficient mice display hyperproliferative activities upon GITR stimulation through an IL-2-independent mechanism. Furthermore, high dose IL-2, anti-CD28 stimulation, or GITR ligand-transduced bone marrow-derived dendritic cells used as APC (culture conditions which drive T(reg) proliferation in vitro) could not ablate this difference in proliferative activity between NIK-deficient and wild-type T(reg). Additional experiments have shown NIK-deficient mice have a higher ratio of CD4+CD25+CD62L(low) T(reg) both in thymus and periphery than their wild-type littermates. This CD62(low) subset is responsible for the hyperproliferative activity upon GITR stimulation. These data suggest a novel role of NIK in controlling the development and expansion of CD4+CD25+ regulatory T cells.