Entraining effects of variations in light spectral composition on the rest-activity rhythm of a nocturnal rodent

The ability to predict and adjust physiology and behavior to recurring environmental events has been necessary for survival on Earth. Recent discoveries revealed that not only changes in irradiance but also light spectral composition can stimulate the suprachiasmatic nucleus (SCN), ensuring the body’s synchronization to the environment. Therefore, using a lighting system that modulates spectral composition during the day using combined red-green-blue (RGB) lights, we evaluated the effect of variations in light spectral composition on the rest-activity rhythm of rodents. Male Wistar rats (n = 17) were gestated and raised under different lighting conditions and exposed to a long photoperiod (16 h light: 8 h dark). The difference between groups was the presence of variations in light spectral composition during the day (RGB-v) to simulate daily changes in natural light, or not (RGB-f). After weaning, spontaneous motor activity was recorded continuously for rhythm evaluation. Our results indicated that animals under RGB-v did not present a reactive peak of activity after the beginning of the light phase, suggesting that this group successfully detected the variations aimed at mimicking daily alterations of natural light. Furthermore, RGB-v animals exhibited an earlier activity acrophase in comparison to animals under RGB-f (RGB-v = 12:16 – “hh:mm”, RGB-f = 13:02; p < 0.001), which might have been due to the capability to predict the beginning of the dark phase when exposed to variations in light spectrum. However, this earlier activity acrophase can be also explained by the blue-light peak that occurred in RGB-v. The spectral and waveform analysis of daily patterns of motor activity revealed that rats in the RGB-v group were better entrained to a circadian rhythm throughout the experiment. RGB-v showed higher interdaily stability (IS) values (29.75 ± 6.5, n = 9) than did RGB-f (t₍₁₅₎ = 2.74, p = 0.015). Besides, the highest power content (PC) on the first harmonic (circadian) was reached earlier in the RGB-v group. The circadianity index (CI) of the whole period was higher in the RGB-v group (t₍₁₅₎ = 3.47, p = 0.003). Thus, we could consider that locomotor activity rhythm was entrained to the light-dark cycle in the RGB-v rats earlier compared to the RGB-f rats. Our results provide additional evidence for the effect of variations in light spectral composition on the rest-activity pattern of nocturnal rodents. This suggests that these animals might predict the arrival of the activity phase by its advanced acrophase when exposed to RGB-v, demonstrating a better synchronization to a 24-h rhythm.     

Diacetylcurcumin: a new photosensitizer for antimicrobial photodynamic therapy in Streptococcus mutans biofilms

This study evaluated the effect of antimicrobial photodynamic therapy (aPDT) on S. mutans using diacetylcurcumin (DAC) and verified DAC toxicity. In vitro, S. mutans biofilms were exposed to curcumin (CUR) and DAC and were light-irradiated. Biofilms were collected, plated and incubated for colony counts. DAC and CUR toxicity assays were conducted with Human Gingival Fibroblast cells (HGF). In vivo, G. mellonella larvae were injected with S. mutans and treated with DAC, CUR and aPDT. The hemolymph was plated and incubated for colony counts. Significant reductions were observed when DAC and CUR alone were used and when aPDT was applied. HGF assays demonstrated no differences in cell viability for most groups. DAC and CUR reduced the S. mutans load in G. mellonella larvae both alone and with aPDT. Systematic toxicity assays on G. mellonella demonstrated no effect of DAC and CUR or aPDT on the survival curve.     

Colonization by Macroinvertebrates of Experimentally Disturbed Stones in Three Tropical Streams Differing in Size

We experimentally disturbed stones in three streams of different sizes and followed the macroinvertebrate colonization process in terms of abundance, species richness and similarity over 64 days. We hypothesized that colonization in the smallest and in the largest streams would be slower than in the medium‐sized stream. The small upstream pool of colonists available in the smallest stream could restrict colonization, while in the largest stream predation by the diverse fish assemblage could restrict drifting colonists. The medium‐sized stream did not have these two constraints. We found similar colonization patterns in all three streams, leading to the rejection of the stated hypotheses. Lack of support of the original hypothesis might be due to the weakness of the two hypothesized restrictions on colonization. In addition, colonization by crawling species from undisturbed nearby patches might be of significant importance. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Queens remate despite traumatic mating in stingless bees

Males can control female reproduction using genital plugs to impede access by rivals. In social bees, ants, and wasps, plugging may involve traumatic mating, with females being harmed. In stingless bees, chances are that plugs may promote ovarian activan, and are thought to ensure single mating—a general tendency among the social Hymenoptera. However, understanding on relationships between mating plugs, traumatic mating, and mating systems in stingless bees remains limited. To address this, we (1) compared mated queens of 7 Neotropical species to understand the patterns of copulatory marks in females and (2) compared pre- and post-mating genitalia of males and females in Melipona fasciculata to depict plug functional morphology. Data revealed an unprecedented consequence of mating in stingless bees: the characteristic marks left by mating plugs on female abdomens and the inferences that can be made from them. To our surprise, in 1 species M. fasciculata we found that queens retain the plug long after mating, and may carry it for the rest of their lives. All the other 6 species retained the plug for only a short period. Remated queens were only found in M. seminigra, whose multiple copulatory marks match previous findings of polyandry in this species. Our study shows that queens can remate, and suggests that male genital morphology may determine in part the time persistence of plugs. We conclude that traumatic mating plugs do not fully prevent remating in stingless bees and that mating systems are not uniform in this group. Nonetheless, exceptional cases of facultative polyandry in social insects—for example, when mating plugs fail—may confirm a general tendency for single mating in close link with efficient mating plugs.     

Differences in contribution of biological nitrogen fixation to yield performance of common bean cultivars as assessed by the 15N natural abundance technique

Plant and Soil - Identification of variability in biological N2 fixation (BNF) contribution among common bean (Phaseolus vulgaris L.) cultivars under field conditions requires a reliable...     

Tissue Injury and Astrocytic Reaction,But Not Cognitive Deficits,Are Dependent on Hypoxia Duration in Very Immature Rats Undergoing Neonatal Hypoxia–Ischemia

Neurochemical Research - Preterm birth and hypoxia–ischemia (HI) are major causes of neonatal death and neurological disabilities in newborns. The widely used preclinical HI model combines...     

Vaginal probe transducer: Characterization and measurement of pelvic-floor strength

The pelvic-floor muscles (PFM) play an important role in urinary and fecal continence. Several investigators have studied the PFM using intra-vaginal pressure measurements, but their methods have not been validated. We describe the characteristics of a probe transducer developed to measure PFM strength according to its dynamic response and the effects of temperature variation. This probe transducer was used to evaluate changes in the contraction strength of pelvic muscles in a group of patients who participated in a PFM training program. Experiments allowed the identification of the probe's characteristics at different temperatures, definition of a calibration equation, and measurements of the dynamic response to pressure pulse. Evaluation of patients before and after the PFM training program showed significant differences in the peak pressure achieved during the contraction (p<0.001) and in pressure-rise time (p<0.01). The tests performed with the probe allowed the characterization of the proposed transducer, and the intra-vaginal pressure measurements in volunteers undergoing a PFM training program allowed a quantitative evaluation of the PFM strength.     

OTUB1 co-opts Lys48-linked ubiquitin recognition to suppress E2 enzyme function

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Highlights? Identification of OTUB1 mutants with impaired ability to inhibit E2 enzymes ? Crystal structure of a ubiquitin-charged E2 bound to OTUB1 ? Molecular basis of Lys48-linked ubiquitin chain recognition by OTUB1 determined ? OTUB1 employs product inhibition mimicry to inhibit E2 enzymes     

Leaf area index of a tropical semi-deciduous forest of the southern Amazon Basin

Leaf area index (LAI) is an important ecophysiological variable because leaves are the organs responsible for gas exchange between plants and the atmosphere. This variable can be calculated from primary values of leaf area assessed by destructive or non-destructive methods, which is relatively easy when crop species are investigated, but is not the case when the focus is on natural wood plants communities. In this paper, we analyze the seasonality of LAI estimated by three different methods in the Amazonia-savannah transitional forest, located 50 km north-east of Sinop city, Mato Grosso, Brazil. In the first method, we combine Monsi and Saekis' original method [Monsi M, Saeki T (1953) Jpn J Bot 14:22–52], which measures LAI using the Beer-Lambert extinction law, and the proposition of Goudriaan [Goudriaan J (1988) Agric For Meteorol 43:155–169] to estimate the extinction coefficient from solar height. The second method differed from the first only in the way in which the daily fraction of intercepted photosynthetic active radiation (FPAR) was calculated, as proposed by Charles-Edwards and Lawn (Charles-Edwards DA, Lawn RJ (1984) Plant Cell Environ 7:247–251]. In the third method, we used a remote sensing technique [MOD15_BU-collection 4, produced and distributed by EROS Data Center Distributed Active Archive Center (EDC DAAC)]. We found that the first and the second methods revealed the expected LAI dynamics, which increased during the dry–wet transition and wet season, and decreased during the wet–dry transition and dry season. From 20 randomly distributed sets in a 1.0 ha area, only 3 showed significant differences in LAI estimated from the first two methods; conversely, LAI was overestimated by the third method.