Evidence For Negative Feedback Research Articles

Breeder age, group size, and fledgling production in the cooperatively breeding Red-cockaded Woodpecker (Dryobates borealis)

Field studies of the factors that influence reproductive success are crucial to life history theory. We investigate annual fledgling production by the monogamous, cooperatively breeding Red-cockaded Woodpecker (Dryobates borealis) in relation to breeder age, experience, and group size at Brosnan Forest, South Carolina, and evaluate several associated hypotheses. Productivity in both female and male breeders increased nonlinearly with age, peaked at 6 and 7 years, respectively, and then declined. We tested if the early increase in productivity with age was associated with age, per se (general skills), or breeding experience. We found for both males and females that the productivity of novice breeders increased significantly with age, indicating age effects independent of prior experience, but that experienced breeders were no more productive than novices the same age. We conclude that the basic skills that accrue with age, but not prior breeding experience, explain increasing success among young birds. The probability of a group nesting increased nonlinearly with female and male age, reaching 100% among females ≥ 7 and males ≥ 11 years old. We found support for both the constraint and restraint hypotheses for young males, but only for the constraint hypothesis among young females. Declining productivity with senescence counters the restraint hypothesis's prediction of increased effort late in life, while the maximal propensity to nest among older birds supports it. Differential survival failed to explain increasing productivity with age. Holding breeder ages constant, we found a linear effect of group size on annual fledgling production, with productivity increasing by 12% with each added helper through the largest group sizes. This suggests (1) no evidence of net compensation as group size increased, (2) no evidence of negative feedback from reproductive or resource competition in large groups, and (3) inclusive fitness is a selective force in helping.

Star Formation Quenching in Quasar Host Galaxies

Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionised and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ∼2.4 obtained with SINFONI in the H- and K-band. All the quasars show [OIII]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s), which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e. star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50 - 100 M⊙/yr, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

Fulfilling desire: Evidence for negative feedback between men's testosterone, sociosexual psychology, and sexual partner number

Across human societies and many nonhuman animals, males have greater interest in uncommitted sex (more unrestricted sociosexuality) than do females. Testosterone shows positive associations with male-typical sociosexual behavior in nonhuman animals. Yet, it remains unclear whether the human sex difference in sociosexual psychology (attitudes and desires) is mediated by testosterone, whether any relationships between testosterone and sociosexuality differ between men and women, and what the nature of these possible relationships might be. In studies to resolve these questions, we examined relationships between salivary testosterone concentrations and sociosexual psychology and behavior in men and women. We measured testosterone in all men in our sample, but only in those women taking oral contraception (OC-using women) in order to reduce the influence of ovulatory cycle variation in ovarian hormone production. We found that OC-using women did not differ from normally-ovulating women in sociosexual psychology or behavior, but that circulating testosterone mediated the sex difference in human sociosexuality and predicted sociosexual psychology in men but not OC-using women. Moreover, when sociosexual psychology was controlled, men's sociosexual behavior (number of sexual partners) was negatively related to testosterone, suggesting that testosterone drives sociosexual psychology in men and is inhibited when those desires are fulfilled. This more complex relationship between androgens and male sexuality may reconcile some conflicting prior reports.

An Empirical Analysis of Foreign Institutional Investment and Stock Market Returns in India

Augmented Dickey Fuller and Phillips-Perron tests were employed to examine the stationarity of both net foreign institutional investment and NSE market return series. Besides, Instantaneous Granger Causality test was employed to examine the contemporaneous relationship between net foreign institutional investment flows and equity market returns in India for the pre-global financial crisis and during a crisis period. By and large, our analysis reveals that there is an evidence of negative feedback trading hypothesis and positive feedback trading hypothesis by foreign investors before the global financial crisis period and during a crisis period respectively. This implies that foreign institutional investment acts as smoothening effect and destabilizing forces before and during the crisis period respectively. However, such positive feedback trading strategies from foreign institutional investors seem to be rational during the period of global financial crisis.

Suppression of nematodes in a coastal grassland soil

The nematophagous fungi Arthrobotrys oligospora and Myzocytiopsis glutinospora increase to large numbers (>103 propagules/g of soil) when moth larvae killed by entomopathogenic nematodes are added to soil microcosms. In spite of these increases, it is unclear how effective these nematophagous fungi are in suppressing nematodes. We measured nematode mortality in microcosms with small numbers of assay nematodes, and we examined assay nematodes recovered at the end of the experiment for signs of fungal parasites. Because the microcosms did not have a moat or other refuge, the assay nematodes remained vulnerable for the 3 days that they were in the soil. Mortality in this experiment was not substantially increased compared to a previous experiment, which measured the mortality of a larger number of assay nematodes in microcosms surrounded by a moat. Mortality, however, increased from 34 to 50% when recovered assay nematodes were examined and when those with conidia of the nematophagous fungus Hirsutella rhossiliensis were considered dead. The zoosporic fungus M. glutinospora was not detected, perhaps because the soil water potential was too low. Contrary to our expectations, there was no evidence of negative feedback on nematodes (i.e., no evidence of density-dependent mortality) because the addition of dead moth larvae greatly increased numbers of resident nematodes and A. oligospora but did not greatly affect the probability of nematode mortality.

Limitation and Regulation of Ecological Populations: a Meta-analysis ofTipula paludosaField Data

Whether the size of an animal population is environmentally limited or regulated by density dependent negative feedback mechanisms is of ecological interest. Proponents of limitation theory have issued a set of speciflc challenges which are addressed in this paper using fleld data for the insect Tipula paludosa. This species is known to be subject to population crashes caused by adverse environmental conditions and assumed to be limited. We re-examine published data in support of this hypothesis and show that there is also evidence of negative feedback between generations. Meta-analyses of annual count data from individual flelds, and regional surveys provide further evidence of negative feedback and it is concluded that population regulation occurs at both local and regional scales. Evidence from other studies is used to propose that cannibalism is the causative mechanism. Since similar negative feedback responses were apparent under both normal and environmentally limiting conditions when populations crash, a single population model that could simulate the difiering regional dynamics observed from the annual surveys was produced. We conclude that the range of annual ∞uctuations observed in T. paludosa populations is the outcome of both limiting and regulating processes, conflrming from fleld observations that these are not exclusive mechanisms.

Basal and activity-induced release of substance P from primary afferent fibres in NK 1 receptor knockout mice: evidence for negative feedback

The concept that NK 1 receptors are located pre-junctionally on substance P (SP)-containing nerves, acting as autoreceptors to inhibit SP release, has been suggested, but remains a controversial issue. To further investigate the existence of this receptor on central and peripheral terminals of primary afferent fibres, NK 1 receptor knockout mice and an NK 1 receptor antagonist were used in nerve-attached tissue preparations. These were the isolated dorsal horn of the spinal cord with dorsal roots attached, and the hairy skin of the hind paw with attached saphenous nerve. The results reveal that in the dorsal horn preparation, basal release of SP is significantly higher in NK 1 −/− mice than NK 1 +/+ mice ( P<0.05, n=7 mice/strain). However, a difference in SP release evoked in the dorsal horn by electrical stimulation of the dorsal roots or capsaicin application was not observed. In contrast, antidromic electrical stimulation of the saphenous nerve caused a substantially greater release of SP in the skin of NK 1 −/− mice than in NK 1 +/+ mice ( P<0.05, n=5 to 6 mice/strain). These results provide evidence for the existence of NK 1 autoreceptors on sensory nerves in skin, which may be relevant to the modulation of their peripheral pathophysiological effector functions.

Soil pathogenic fungi have the potential to affect the co‐existence of two tallgrass prairie species

Summary 1 Negative feedback may exist between plant species and their biotic soil communities. Two co‐occurring native tallgrass species (Andropogon gerardii, a perennial grass, and Chamaecrista fasciculata, an annual legume) were reciprocally transplanted into pots containing soil from areas dominated by one of the species. Half of the soil derived from each area was microwaved to reduce soil fungi, resulting in four different ‘soil types’. 2 Chamaecrista fasciculata plants were smaller when grown in their native soil vs. that from under A. gerardii, but were unaffected by microwaving (i.e. fungal reduction). Andropogon gerardii plants were shorter with fewer inflorescences in non‐microwaved soil, with the poorest growth occurring in non‐microwaved C. fasciculata soil. 3 Fungi were isolated from roots of A. gerardii growing in the different soil types. We tested whether the fungi found differed between the four soil types and whether any species characteristic of C. fasciculata soil were responsible for the poor growth of A. gerardii in this medium. 4 Fungi unique to the non‐microwaved C. fasciculata soil type reduced tillering and caused an early reduction in growth of A. gerardii. These effects were partially ameliorated when potentially mycoparasitic fungi associated with A. gerardii were also included. By the end of the experiment, both fungal treatments increased above‐ground biomass but greatly reduced below‐ground biomass of A. gerardii compared with controls, suggesting that the exposure to potential fungal pathogens from C. fasciculata soil altered biomass allocation within plants. 5 There was no evidence of negative feedback between the prairie species and their own soils. However, fungi associated with Chamaecrista fasciculata were detrimental to A. gerardii, one of the dominant perennials in the surrounding area, and may facilitate the annual’s long‐term persistence. Arbuscular mycorrhizae did not ameliorate the pathogenic effects of these fungi as there was little colonization of A. gerardii roots in C. fasciculata soil.

Temporal and Spatial Information Diffusion in Real Estate Price Changes and Variances

This article examines patterns of temporal and spatial diffusion of real estate price changes. In addition to means, changes in volatility are tracked in reaction to substantial new information, estimated with GARCH‐M methods. The data covers towns in Connecticut and near San Francisco. There is evidence of negative feedback at short lags, contrary to previous research on housing and other assets. There is also evidence of a moving average error process which tends to reverse recent shocks. Significantly positive spatial information diffusion is found from neighboring towns in Connecticut but none in control tests on nonneighboring towns. The results also include evidence of a risk‐reward tradeoff in housing price changes in the San Francisco area.

Gamma-Aminobutyric acid exerts a local inhibitory action on the axon terminal of bipolar cells: evidence for negative feedback from amacrine cells.

It is well-established morphologically that bipolar cells, the second-order neurons in the vertebrate retina, make reciprocal synapses with amacrine cells in the inner plexiform layer. However, neither the property nor the physiological function of the feedback synapse is understood. Autoradiographic and immunohistochemical studies suggest the presence of gamma-aminobutyric acid (GABA)-ergic amacrine cells, and therefore the bipolar cells are thought to receive GABAergic inputs from amacrine cells. This possibility was investigated in the present study, in which we used solitary bipolar cells dissociated from the goldfish retina enzymatically. Dissociated solitary bipolar cells showed a large variety in morphology. In the present study, we selected the bipolar cells with a huge bulbous axon terminal. Bipolar cells of this subtype were identical in morphology to the on-center cells with rod-dominant inputs as revealed in earlier studies by intracellular staining. Membrane currents were measured under voltage clamp with a patch pipette in the whole cell configuration. In some experiments, GABA-sensitive membrane was excised as an outside-out patch from the axon terminal bulb of solitary bipolar cells. All cells of this type responded to GABA. The highest sensitivity was located at the axon terminal. The minimal effective dose was on the order of 10(-7) M. GABA increased the chloride conductance and evoked a membrane hyperpolarization. Partial desensitization was observed during the application of GABA. The bipolar cells had GABA type A receptors. These results are consistent with the idea that the rod-dominant on-center bipolar cells receive negative feedback inputs from GABAergic amacrine cells.