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991.
Carolina E. Reisenman Alicia N. Lorenzo Figueiras Martín Giurfa Claudio R. Lazzari 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(10):961-968
We analysed how the assembling behaviour of Triatoma infestans is modulated by the convergence of chemical cues released by their faeces and the spectral quality of the light associated with refuges. Second-instar larvae were confronted with refuges associated with a visual stimulus (either blue, green or red lights having the same intensity, or darkness) and a chemical cue (presence or absence of faeces). In this context, faeces constitute a major attractant for bugs. In the absence of faeces, bugs always assembled in dark places. Green light was always rejected despite the presence of faeces, i.e. the assembling behaviour was controlled by a photonegative reaction to this light. In the presence of red light, orientation towards the chemical cue dominated over the bugs' photonegative reaction to this light. Such a light was avoided in the absence of faeces but not in their presence. Also, negative phototaxis to blue light could be counteracted by the presence of the chemical cue. Thus, a concrete interaction between visual and olfactory cues occurred in these experiments: the bugs' response changed depending on the specific combination of spectral light and faeces. Finally, bugs responded differentially to blue, red and green lights of the same intensity. They assembled preferentially on red, followed by blue and then by green. Thus, discrimination between lights of different spectral quality is possible, probably through an achromatic mechanism. 相似文献
992.
Peggion Cristina Piazza Claudia Formaggio Fernando Crisma Marco Toniolo Claudio Kaptein Bernard Broxterman Quirinus B. Kamphuis Johan 《International journal of peptide research and therapeutics》2000,7(1):9-16
Summary We synthesized by solution-phase methods the naturally occurring, 10-amino acid residue lipopeptaibol antibiotics trikoningins
KBI and KBII, and the [l-Iva1] KB analogue, in which the amino acid in position 1 is different, with the aim at investigating the effect of hydrophobicity
and chirality in that position. A solution conformational analysis, using FT-IR absorption and CD techniques, indicated that
all of the three decapeptides are predominantly helical in a membrane-mimetic environment. Permeability measurements showed
an increase of the activity from the [Aib1] peptide to the more hydrophobic [Iva1] peptides. Conversely, the effect of a change in chirality, obtained by replacingd-Iva1 withl-Iva, turned out to be of minor significance. 相似文献
993.
Claudia M. Filozof Carlos Murúa Marta P. Sanchez Carlos Brailovsky Mario Perman Claudio D. Gonzalez Eric Ravussin 《Obesity (Silver Spring, Md.)》2000,8(3):205-210
Objective: A low resting metabolic rate for a given body size and composition, a low rate of fat oxidation, low levels of physical activity, and low plasma leptin concentrations are all risk factors for body weight gain. The aim of the present investigation was to compare resting metabolic rate (RMR), respiratory quotient (RQ), levels of physical activity, and plasma leptin concentrations in eight post‐obese adults (2 males and 6 females; 48.9 ± 12.2 years; body mass index [BMI]: 24.5 ± 1.0 kg/m2; body fat 33 ± 5%; mean ± SD) who lost 27.1 ± 21.3 kg (16 to 79 kg) and had maintained this weight loss for ≥2 months (2 to 9 months) to eight age‐ and BMI‐matched control never‐obese subjects (1 male and 7 females; 49.1 ± 5.2 years; BMI 24.4 ± 1.0 kg/m2; body fat 33 ± 7%). Research Methods and Procedures: Following 3 days of weight maintenance diet (50% carbohydrate and 30% fat), RMR and RQ were measured after a 10‐hour fast using indirect calorimetry and plasma leptin concentrations were measured using radioimmunoassay. Levels of physical activity were estimated using an accelerometer over a 48‐hour period in free living conditions. Results: After adjustment for fat mass and fat‐free mass, post‐obese subjects had, compared with controls, similar levels of physical activity (4185 ± 205 vs. 4295 ± 204 counts) and similar RMR (1383 ± 268 vs. 1430 ± 104 kcal/day) but higher RQ (0.86 ± 0.04 vs. 0.81 ± 0.03, p < 0.05). Leptin concentration correlated positively with percent body fat (r = 0.57, p < 0.05) and, after adjusting for fat mass and fat‐free mass, was lower in post‐obese than in control subjects (4.5 ± 2.1 vs. 11.6 ± 7.9 ng/mL, p < 0.05). Discussion: The low fat oxidation and low plasma leptin concentrations observed in post‐obese individuals may, in part, explain their propensity to relapse. 相似文献
994.
The origin of neo-XY sex systems in Acrididae is usually explained through an X-autosome centric fusion, and the behaviour
of the neo-sex chromosomes has been solely studied in males. In this paper we analysed male and female Dichroplus vittatus. The karyotype comprises 2n = 20 chromosomes including 9 pairs of autosomes and a sex chromosome pair that includes a large metacentric neo-X and a small
telocentric neo-Y. We compared the meiotic behaviour of the sex bivalent between both sexes. Mean cell autosomal chiasma frequency
was low in both sexes and slightly but significantly higher in males than in females. Chiasma frequency of females increased
significantly when the sex-bivalent was included. Chiasma distribution was basically distal in both sexes. Behaviour of the
neo-XY pair is complex as a priori suggested by its structure, which was analysed in mitosis and meiosis of diploid and polyploid cells. During meiosis, orientation
of the neo-XY is highly irregular; only 21% of the metaphase I spermatocytes show standard orientation. In the rest of cells,
the alternate or simultaneous activity of an extra kinetochore in the distal end of the short arm (XL) of the neo-X, determined
unusual MI orientations and a high frequency of non-disjunction and lagging of the sex-chromosomes. In females, the neo-XX
bivalent had a more regular behaviour but showed 17% asynapsis in the XL arm which, in those cases orientated its distal ends
towards opposite spindle poles suggesting, again, the activity of a second kinetochore. The dicentric nature and the unstable
meiotic behaviour of the sex neo-chromosomes of D. vittatus suggest a recent origin of the sex determination mechanism, with presumable adaptive advantages which could compensate their
potential negative heterosis. Our observations suggest that the origin of the neo-sex system was a tandem fusion of two original
telocentric X-chromosomes followed by another tandem fusion with the small megameric bivalent and a further pericentric inversion
of the neo-X. The remaining autosomal homolog resulted in the neo-Y chromosome.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
Oxygen uptake rates of undisturbed sediment columns have been used as an integrative measure of the metabolic activities of benthic communities. Since the intensity of metabolic processes of profundal lake is dependent on the production of organic matter in the pelagic zone, oxygen uptake rates reflect the trophic condition of the whole lake. Four small lakes of central Chile, differing strongly in trophic conditions, provided a possibility to compare benthic oxygen uptake rates, under different oxygen conditions (Quiñenco, Grande, Chica and Lleulleu). Our objective was to establish the relationship between the oxygen uptake rates and bottom characteristics of lakes with different trophic conditions. At 8 mg O2 l-1 in the overlying water of the cores studied, the oxygen uptake rates of the sediment were: Quiñenco 51.2–56.0 mg O2 m2 h-1 (eutrophic), Grande 41.2–46.4 mg O2 m2 h-1 (mesotrophic), Chica 23.2–18.1 mg O2 m2 h-1 (mesotrophic) and Lleulleu 11.7–16.0 mg O2 m2 h-1 (oligotrophic). By exposing the sediments to different oxygen levels in the laboratory, it was found that benthic community metabolism decreased with oxygen concentrations. The slope of regression lines, relating oxygen uptake rates to oxygen concentrations, differed for the different sites investigated, closely related with the trophic conditions of the lakes. It was positively correlated with the organic matter content of the sediment of the cores (r
2= 0.78, p<0,05) and the nutrients of the bottom waters (total-P: r
2= 0.73, p<0,05; total-N: r
2= 0.73, p<0,05), and negatively with the redox potential of the sediments (r
2= 0.88, p<0,05). 相似文献
996.
997.
Rashpal S. Dhillon Yiming Qin Paul R. van Ginkel Vivian X. Fu James M. Vann Alexis J. Lawton Cara L. Green Fúlvia B. ManchadoGobatto Claudio A. Gobatto Dudley W. Lamming Tomas A. Prolla John M. Denu 《Aging cell》2022,21(12)
Mitochondrial NAD+‐dependent protein deacetylase Sirtuin3 (SIRT3) has been proposed to mediate calorie restriction (CR)‐dependent metabolic regulation and lifespan extension. Here, we investigated the role of SIRT3 in CR‐mediated longevity, mitochondrial function, and aerobic fitness. We report that SIRT3 is required for whole‐body aerobic capacity but is dispensable for CR‐dependent lifespan extension. Under CR, loss of SIRT3 (Sirt3 −/− ) yielded a longer overall and maximum lifespan as compared to Sirt3 +/+ mice. This unexpected lifespan extension was associated with altered mitochondrial protein acetylation in oxidative metabolic pathways, reduced mitochondrial respiration, and reduced aerobic exercise capacity. Also, Sirt3 −/− CR mice exhibit lower spontaneous activity and a trend favoring fatty acid oxidation during the postprandial period. This study shows the uncoupling of lifespan and healthspan parameters (aerobic fitness and spontaneous activity) and provides new insights into SIRT3 function in CR adaptation, fuel utilization, and aging. 相似文献
998.
Transmissible spongiform encephalopathies are fatal neurodegenerative diseases that involve misfolding of the prion protein. Recent studies have provided evidence that normal prion protein might have a physiological function in neuroprotective signaling, suggesting that loss of prion protein activity might contribute to the pathogenesis of prion disease. However, studies using knockout animals do not support the loss-of-function hypothesis and argue that prion neurodegeneration might be associated with a gain of a toxic activity by the misfolded prion protein. Thus, the mechanism of neurodegeneration in spongiform encephalopathies remains enigmatic. 相似文献
999.
Reinier Oropesa-Nuñez Sandeep Keshavan Silvia Dante Alberto Diaspro Benedetta Mannini Claudia Capitini Cristina Cecchi Massimo Stefani Fabrizio Chiti Claudio Canale 《Biophysical journal》2018,114(6):1357-1367
The deposition of fibrillar protein aggregates in human organs is the hallmark of several pathological states, including highly debilitating neurodegenerative disorders and systemic amyloidoses. It is widely accepted that small oligomers arising as intermediates in the aggregation process, released by fibrils, or growing in secondary nucleation steps are the cytotoxic entities in protein-misfolding diseases, notably neurodegenerative conditions. Increasing evidence indicates that cytotoxicity is triggered by the interaction between nanosized protein aggregates and cell membranes, even though little information on the molecular details of such interaction is presently available. In this work, we propose what is, to our knowledge, a new approach, based on the use of single-cell force spectroscopy applied to multifunctional substrates, to study the interaction between protein oligomers, cell membranes, and/or the extracellular matrix. We compared the interaction of single Chinese hamster ovary cells with two types of oligomers (toxic and nontoxic) grown from the N-terminal domain of the Escherichia coli protein HypF. We were able to quantify the affinity between both oligomer type and the cell membrane by measuring the mechanical work needed to detach the cells from the aggregates, and we could discriminate the contributions of the membrane lipid and protein fractions to such affinity. The fundamental role of the ganglioside GM1 in the membrane-oligomers interaction was also highlighted. Finally, we observed that the binding of toxic oligomers to the cell membrane significantly affects the functionality of adhesion molecules such as Arg-Gly-Asp binding integrins, and that this effect requires the presence of the negatively charged sialic acid moiety of GM1. 相似文献
1000.
Minehira K Young SG Villanueva CJ Yetukuri L Oresic M Hellerstein MK Farese RV Horton JD Preitner F Thorens B Tappy L 《Journal of lipid research》2008,49(9):2038-2044
The liver secretes triglyceride-rich VLDLs, and the triglycerides in these particles are taken up by peripheral tissues, mainly heart, skeletal muscle, and adipose tissue. Blocking hepatic VLDL secretion interferes with the delivery of liver-derived triglycerides to peripheral tissues and results in an accumulation of triglycerides in the liver. However, it is unclear how interfering with hepatic triglyceride secretion affects adiposity, muscle triglyceride stores, and insulin sensitivity. To explore these issues, we examined mice that cannot secrete VLDL [due to the absence of microsomal triglyceride transfer protein (Mttp) in the liver]. These mice exhibit markedly reduced levels of apolipoprotein B-100 in the plasma, along with reduced levels of triglycerides in the plasma. Despite the low plasma triglyceride levels, triglyceride levels in skeletal muscle were unaffected. Adiposity and adipose tissue triglyceride synthesis rates were also normal, and body weight curves were unaffected. Even though the blockade of VLDL secretion caused hepatic steatosis accompanied by increased ceramides and diacylglycerols in the liver, the mice exhibited normal glucose tolerance and were sensitive to insulin at the whole-body level, as judged by hyperinsulinemic euglycemic clamp studies. Normal hepatic glucose production and insulin signaling were also maintained in the fatty liver induced by Mttp deletion. Thus, blocking VLDL secretion causes hepatic steatosis without insulin resistance, and there is little effect on muscle triglyceride stores or adiposity. 相似文献