Adaptive responses during anemia and its correction in lambs.

There is limited information available on which to base decisions regarding red blood cell (RBC) transfusion treatment in anemic newborn infants. Using a conscious newborn lamb model of progressive anemia, we sought to identify accessible metabolic and cardiovascular measures of hypoxia that might provide guidance in the management of anemic infants. We hypothesized that severe phlebotomy-induced isovolemic anemia and its reversal after RBC transfusion result in a defined pattern of adaptive responses. Anemia was produced over 2 days by serial phlebotomy (with plasma replacement) to Hb levels of 30-40 g/l. During the ensuing 2 days, Hb was restored to pretransfusion baseline levels by repeated RBC transfusion. Area-under-the-curve methodology was utilized for defining the Hb level at which individual study variables demonstrated significant change. Significant reciprocal changes (P < 0.05) of equivalent magnitude were observed during the phlebotomy and transfusion phases for cardiac output, plasma erythropoietin (Epo) concentration, oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate concentration. No significant change was observed in resting oxygen consumption. Cardiac output and plasma Epo concentration increased at Hb levels <75 g/l, oxygen delivery and oxygen extraction ratio decreased at Hb levels <60 g/l, and venous oxygen saturation decreased and blood lactate concentration increased at Hb levels <55 g/l. We speculate that plasma Epo and blood lactate concentrations may be useful measures of clinically significant anemia in infants and may indicate when an infant might benefit from a RBC transfusion.     

Schistosoma mansoni: Vaccination of mice with highly X-irradiated cercariae

Vaccination against schistosomiasis with highly X-irradiated Schistosoma mansoni cercariae was studied in mice. The optimum dose of X radiation for the attenuation of cercariae was in the range of 24–48 krad. In selecting the optimum dose, lesions caused by migrating schistosomula in the lungs of the immunized host were considered. Cercariae exposed to 48 krad caused fewer lesions than those exposed to 24 krad but still effected a comparable worm reduction. The percentages of worm reduction in mice immunized with 48-krad X-irradiated cercariae increased with the number of immunizations up to the fifth immunization and then fluctuated in the sixth, seventh, and eighth days without increase. The optimum dose of immunizing cercariae was 500, and the optimum time interval for successive immunizations was 4 weeks. There was no significant difference in susceptibility to infection in the adult mice 161 to 694 days of age. The duration of acquired immunity in immunized mice is long, still evident 545 days from the last immunization. The present studies clearly showed that with the bioengineering method, the worm reduction in the immunized mice reached 91.1%, the effect of immunization was stronger in mice immunized with the highly X-irradiated cercariae than with the low X-irradiated cercariae, and X-irradiated cercariae were demonstrated to be a strong inducing agent for immunity in mice.     

Microelectrode array studies of basal and potassium-evoked release of L-glutamate in the anesthetized rat brain

L-glutamate (Glu) is the predominant excitatory neurotransmitter in the mammalian central nervous system. It plays major roles in normal neurophysiology and many brain disorders by binding to membrane-bound Glu receptors. To overcome the spatial and temporal limitations encountered in previous in vivo extracellular Glu studies, we employed enzyme-coated microelectrode arrays to measure both basal and potassium-evoked release of Glu in the anesthetized rat brain. We also addressed the question of signal identity, which is the predominant criticism of these recording technologies. In vivo self-referencing recordings demonstrated that our Glu signals were both enzyme- and voltage-dependent, supporting the identity of L-glutamate. In addition, basal Glu was actively regulated, tetrodotoxin (TTX)-dependent, and measured in the low micromolar range (approximately 2 microm) using multiple self-referencing subtraction approaches for identification of Glu. Moreover, potassium-evoked Glu release exhibited fast kinetics that were concentration-dependent and reproducible. These data support the hypothesis that Glu release is highly regulated, requiring detection technologies that must be very close to the synapse and measure on a second-by-second basis to best characterize the dynamics of the Glu system.     

Neural Activity Patterns in Response to Interspecific and Intraspecific Variation in Mating Calls in the Túngara Frog

Background

During mate choice, individuals must classify potential mates according to species identity and relative attractiveness. In many species, females do so by evaluating variation in the signals produced by males. Male túngara frogs (Physalaemus pustulosus) can produce single note calls (whines) and multi-note calls (whine-chucks). While the whine alone is sufficient for species recognition, females greatly prefer the whine-chuck when given a choice.

Methodology/Principal Findings

To better understand how the brain responds to variation in male mating signals, we mapped neural activity patterns evoked by interspecific and intraspecific variation in mating calls in túngara frogs by measuring expression of egr-1. We predicted that egr-1 responses to conspecific calls would identify brain regions that are potentially important for species recognition and that at least some of those brain regions would vary in their egr-1 responses to mating calls that vary in attractiveness. We measured egr-1 in the auditory brainstem and its forebrain targets and found that conspecific whine-chucks elicited greater egr-1 expression than heterospecific whines in all but three regions. We found no evidence that preferred whine-chuck calls elicited greater egr-1 expression than conspecific whines in any of eleven brain regions examined, in contrast to predictions that mating preferences in túngara frogs emerge from greater responses in the auditory system.

Conclusions

Although selectivity for species-specific signals is apparent throughout the túngara frog brain, further studies are necessary to elucidate how neural activity patterns vary with the attractiveness of conspecific mating calls.     

Comprehensive analysis of CD4+ T cells in the decision between tolerance and immunity in vivo reveals a pivotal role for ICOS

We have established a comprehensive in vivo mouse model for the CD4(+) T cell response to an "innocuous" versus "dangerous" exogenous Ag and developed an in vivo test for tolerance. In this model, specific gene-expression signatures, distinctive upregulation of early T cell-communication molecules, and differential expansion of effector T cells (Teff) and regulatory T cells (Treg) were identified as central correlates of T cell tolerance and T cell immunity. Different from essentially all other T cell-activation molecules, ICOS was found to be induced in the immunity response and not by T cells activated under tolerogenic conditions. If expressed, ICOS did not act as a general T cell costimulator but selectively caused a massive expansion of effector CD4(+) T cells, leaving the regulatory CD4(+) T cell compartment largely undisturbed. Thus, ICOS strongly contributed to the dramatic change in the balance between Ag-specific Teff and Treg from ～1:1 at steady state to 21:1 at the height of the immune response. This newly defined role for the balance of Teff to Treg, together with its known key function in T cell help for B cells, establishes ICOS as a central mediator of immunity. Given its exceptionally selective induction on CD4(+) T cells under inflammatory, but not tolerogenic, conditions, ICOS emerges as a pivotal effector molecule in the early decision between tolerance and immunity to exogenous Ag.     

Production and purification of a peptide of Fusarium tricinctum that causes conidia of Penicillium to swell

A process is described for production of a cyclodepsipeptide complex (CDPC) from autoclaved white corn grits fermented with Fusarium tricinctum NRRL 3510. Yields of more than 2.5 g CDPC/ kg of medium were obtained. Previously, we described the conspicuous swelling of Pencillium digitatum conidia and hyphal tips incubating in a medium supplemented with the CDPC, a trio of metabolites produced by strains of F. tricinctum and F. roseum. Analysis of the CDPC mass spectra and the amino acid composition indicated one major and two minor cyclodepsipeptides. The two major products differed from the major cyclodepsipeptide only in the substitution of either isoleucine or valine for leucine in the threonyl-alanyl-alanyl-glutaminyl-tyrosyl-leucine peptide portion of the molecule.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

ICOS controls the pool size of effector-memory and regulatory T cells

ICOS is an important regulator of T cell effector function. ICOS-deficient patients as well as knockout mice show severe defects in T cell-dependent B cell responses. Several in vitro and in vivo studies attributed this phenomenon to impaired up-regulation of cell surface communication molecules and cytokine synthesis by ICOS-deficient T cells. However, we now could show with Ag-specific T cells in a murine adoptive transfer system that signaling via ICOS does not significantly affect early T cell activation. Instead, ICOS substantially contributes to the survival and expansion of effector T cells upon local challenge with Ag and adjuvant. Importantly, the observed biological function of ICOS also extends to FoxP3+ regulatory T cells, as can be observed after systemic Ag delivery without adjuvant. In line with these findings, absence of ICOS under homeostatic conditions of nonimmunized mice leads to a reduced number of both effector-memory and FoxP3+ regulatory T cells. Based on these results, we propose a biological role for ICOS as a costimulatory, agonistic molecule for a variety of effector T cells with differing and partly opposing functional roles. This concept may reconcile a number of past in vivo studies with seemingly contradictory results on ICOS function.