Evaluation of chemotherapy in experimental toxocarosis by determination of specific immune complexes

Parasitism by the larval phase of Toxocara canis is a chronic process in which the larvae survive in the tissues, resulting in the constant stimulation of the immune system. As a result, the detection of specific antibodies may not reflect the active state of the parasite. We have studied the dynamics of the production of specific immune complexes by ELISA with the monoclonal antibody TC-1 in rabbits inoculated with single and multiple doses of T. canis eggs. We also compared this with the production of specific antibodies and their possible modification after treatment with mebendazole. The specific antibodies against excretory-secretory antigen were detected with peaks at 10 and 12 weeks depending on the dose and remained positive during the entire experiment (62 weeks). Treatment caused an increase in the level of detectable antibodies dropping to similar levels to the controls. Specific immune complexes were detected only in multiple doses, and were then positive during the entire experiment. From the beginning of treatment the values of immune complexes fell quickly, remaining at undetectable levels during the rest of the experiment. For this reason the detection of specific immune complexes is a valid technique for monitoring the efficiency of treatment.     

Amino terminal sequence of heavy and light chains from ratfish immunoglobulin

The ratfish,Callorhinchus callorhinchus, a representative of the Holocephali, has a natural serum hemagglutinin (M _r 960 000), composed of heavy (M _r 71000), light (M _r 22 500), and J (M _r 16 000) chains. To approach the mechanisms that generate diversity at this level of evolution, the amino terminal sequence of the heavy and light chains was determined by automated microsequencing. The chains are unblocked and have modest internal sequence heterogeneity. The heavy chains show sequence similarity with the terminal region of the heavy chain from the horned shark,Heterodontus francisci, and other species. In contrast to the heavy chain, the ratfish light chains display low sequence similarity with their shark kappa counterparts. However, their similarity with the variable region of the chicken lambda light chains is about 75%.     

Responses of benthic macroinvertebrates in small intermittent streams to silvicultural practices

We examined macroinvertebrate communities in small(0.1-1.0 m²) pools of intermittent streams (alwayscontainingsome water but without perennial flow) with small watersheds(2-6 ha) subjected to five types of forest harvest to assesspotential impacts of the different harvest methods. Bufferstrips10 m wide were left on each side of the streams. Each harvesttreatment was coupled with a similar unharvested referencestand.An incomplete block design included three 0.05 m² vacuumsamples from each treatment paired with three from theadjacentreferences. There was a high degree of similarity amongreferencesfor parameters other than taxonomic composition (e.g.macroinvertebrate density, number of species, Shannondiversity,functional groups, etc.). Statistically significantdifferenceswere found between references and treatments and among harvestmethods but the responses varied among response variables(density,Shannon-Weiner diversity, species composition), differentspeciesassemblages (all invertebrates, chironomids,Ephemeroptera-Plecoptera-Trichoptera [EPT], isopods), andfunctional group categories (shredders, collector-gatherers).Wecollected 56 taxa, 7–16 per site, with low communitysimilarity(mean Jaccards=0.18, mean Bray-Curtis percentdissimilarity=81). The most severe harvest treatmentsresultedin the highest diversities of total invertebrates in thesesmallspring pool communities.     

Action Spectra for Conversions of Phycochrome c from Nostoc muscorum

The reversibly photochromic pigment, phycochrome c, was extracted from the blue-green alga Nostoc muscorum strain A. Action spectra were determined for in vitro conversions of the pigment from the short wavelength to the long wavelength form and vice versa. The action peak for the absorbance decrease at 650 nm is at 630 nm. During this decrease there is only a slight increase of the absorbance in the green region. Green and yellow light (maximum efficiency at 580 nm) completely restores absorbance at 650 nm. The observations are explained by the existence of three spectrally different forms of phycochrome c: P^c₆₃₀ and P^c₆₅₀ which equilibrate in darkness and P^c₅₈₀ which is reversibly photoconvertible to P^c₆₃₀. We have also measured the absorbance changes brought about by saturating irradiations with light of various wavelengths (“photostationary state spectrum”). Extreme photostationary states were obtained with about 650 nm and 500 nm light.     

Persistence of immune response in human toxocariasis as measured by ELISA.

The antibody titer was followed in a group of patients, clinically diagnosed with toxocariasis, during a 5 year period. We observed that larvae can survive for at least 5 years in humans. Antigenic stimulation was enough to keep high levels of immunoglobulins over this period. Antibody levels decreased slowly and this pattern is similar to that shown by animal models.     

Hypothalamic action of atrial natriuretic factor to inhibit vasopressin secretion

The ability of synthetic atrial natriuretic factor (ANF) to inhibit vasopressin (AVP) release, as well as its action to inhibit water intake and salt preference in the rat, suggest a role for the peptide in the hypothalamic control of fluid volume in addition to its established actions in the kidney. We report here evidence for a direct, hypothalamic site of action of ANF to inhibit, specifically, AVP secretion. Third cerebroventricular infusion of 1.0 (p less than 0.05) and 2.0 (p less than 0.025) nmoles ANF significantly inhibited AVP release in euvolemic, normally hydrated rats while IV doses of ANF failed to significantly alter AVP release except when 5 nmoles (p less than 0.05) were infused. No significant effects on oxytocin (OT) release were observed. Vasopressin release from median eminence or pituitary, neural lobe explants during static, in vitro incubations was not significantly altered by doses of ANF ranging from 10(-12) to 10(-7) molar. Release of AVP during perifusion of neural lobe explants in the presence of ANF was similarly unaffected. However, AVP and not OT release from hypothalamo-neurohypophysial system explants was significantly inhibited in the presence of 10(-8) and 10(-7) M ANF, suggesting an action of the peptide at the levels of the AVP-producing cell bodies in the included supraoptic nucleus either directly or via an action on an interneuron, and not at the AVP-containing terminal fields in the median eminence or neural lobe.     

The Ultrastructure of the Fungus Trichoderma viride and Investigation of its Growth on Cellulose

Changes in the ultrastructure of Trichoderma viride during growth in shake cultures on cellobiose and cellulose fibres were examined. Electron micrographs of thin sections of germinating conidia, septate hyphae with ascomycete pores and other cell organelles are presented. Extensive autolysis of hyphae was observed after growth for 20 h on cellobiose. The fungus grew in the lumina and within the walls of cellulose fibres. The hyphae followed the directions of the laminar structure but did not grow across them. The observations indicated that the hyphae penetrated the fibres by causing cracks and by dissolving enzymatically the cellulose.     

Thinner bark increases sensitivity of wetter Amazonian tropical forests to fire

Understory fires represent an accelerating threat to Amazonian tropical forests and can, during drought, affect larger areas than deforestation itself. These fires kill trees at rates varying from < 10 to c. 90% depending on fire intensity, forest disturbance history and tree functional traits. Here, we examine variation in bark thickness across the Amazon. Bark can protect trees from fires, but it is often assumed to be consistently thin across tropical forests. Here, we show that investment in bark varies, with thicker bark in dry forests and thinner in wetter forests. We also show that thinner bark translated into higher fire‐driven tree mortality in wetter forests, with between 0.67 and 5.86 gigatonnes CO₂ lost in Amazon understory fires between 2001 and 2010. Trait‐enabled global vegetation models that explicitly include variation in bark thickness are likely to improve the predictions of fire effects on carbon cycling in tropical forests.     

Renin-Angiotensin System Blockers Protect Pancreatic Islets against Diet-Induced Obesity and Insulin Resistance in Mice

Background

The associations between obesity, hypertension and diabetes are well established, and the renin-angiotensin system (RAS) may provide a link among them. The effect of RAS inhibition on type 2 diabetes is still unclear; however, RAS seems to play an important role in the regulation of the pancreas and glucose intolerance of mice fed high-fat (HF) diet.

Methods

C57BL/6 mice fed a HF diet (8 weeks) were treated with aliskiren (50 mg/kg/day), enalapril (30 mg/kg/day) or losartan (10 mg/kg/day) for 6 weeks, and the protective effects were extensively compared among groups by morphometry, stereological tools, immunostaining, Western blotting and hormonal analysis.

Results

All RAS inhibitors significantly attenuated the increased blood pressure in mice fed a HF diet. Treatment with enalapril, but not aliskiren or losartan, significantly attenuated body mass (BM) gain, glucose intolerance and insulin resistance, improved the alpha and beta cell mass and prevented the reduction of plasma adiponectin. Furthermore, enalapril treatment improved the protein expression of the pancreatic islet Pdx1, GLUT2, ACE2 and Mas receptors. Losartan treatment showed the greatest AT2R expression.

Conclusion

Our findings indicate that ACE inhibition with enalapril attenuated several of the deleterious effects of the HF diet. In summary, enalapril appears to be responsible for the normalization of islet morphology and function, of alpha and beta cell mass and of Pdx1 and GLUT2 expression. These protective effects of enalapril were attributed, primarily, to the reduction in body mass gain and food intake and the enhancement of the ACE2/Ang (1-7) /Mas receptor axis and adiponectin levels.