Sleep deprivation induces late deleterious effects in a pharmacological model of Parkinsonism.

Parkinson's disease is a degenerative, chronic and progressive disease, characterized by motor dysfunctions. Patients also exhibit non-motor symptoms, such as affective and sleep disorders. Sleep disorders can potentiate clinical and neuropathological features and lead to worse prognosis. The goal of this study was to evaluate the effects of sleep deprivation (SD) in mice submitted to a progressive pharmacological model of Parkinsonism (chronic administration with a low dose of reserpine). Male Swiss mice received 20 injections of reserpine (0.1 mg/kg) or vehicle, on alternate days. SD was applied before or during reserpine treatment and was performed by gentle handling for 6 h per day for 10 consecutive days. Animals were submitted to motor and non-motor behavioral assessments and neurochemical evaluations. Locomotion was increased by SD and decreased by reserpine treatment. SD during treatment delayed the onset of catalepsy, but SD prior to treatment potentiated reserpine-induced catalepsy. Thus, although SD induced an apparent beneficial effect on motor parameters, a delayed deleterious effect on alterations induced by reserpine was found. In the object recognition test, both SD and reserpine treatment produced cognitive deficits. In addition, the association between SD and reserpine induced anhedonic-like behavior. Finally, an increase in oxidative stress was found in hippocampus of mice subjected to SD, and tyrosine hydroxylase immunoreactivity was reduced in substantia nigra of reserpine-treated animals. Results point to a possible late effect of SD, aggravating the deficits in mice submitted to the reserpine progressive model of PD.

Animal Approaches to Studying Risk Factors for Parkinson's Disease: A Narrative Review.

Despite recent efforts to search for biomarkers for the pre-symptomatic diagnosis of Parkinson's disease (PD), the presence of risk factors, prodromal signs, and family history still support the classification of individuals at risk for this disease. Human epidemiological studies are useful in this search but fail to provide causality. The study of well-known risk factors for PD in animal models can help elucidate mechanisms related to the disease's etiology and contribute to future prevention or treatment approaches. This narrative review aims to discuss animal studies that investigated four of the main risk factors and/or prodromal signs related to PD: advanced age, male sex, sleep alterations, and depression. Different databases were used to search the studies, which were included based on their relevance to the topic. Although still in a reduced number, such studies are of great relevance in the search for evidence that leads to a possible early diagnosis and improvements in methods of prevention and treatment.

Ear identification: A multi-ethnic study sample.

The external human ear is considered to be highly variable among individuals. Hence, forensic applications could be explored for human identification. This research compares the usefulness of Cameriere's ear identification method, in samples originating from six different countries (Brazil, India, Japan, Russia, South Africa and Turkey) in order to examine possible differences in their accuracy values. A sample of 2,225 photographs of the external human ear (1,134 left and 1,091 right ears) from 1,411 individuals (633 females and 778 males) was collected. The samples included healthy subjects with no systemic disorders and without any craniofacial trauma, maxillofacial abnormalities, auricular anomalies, ear diseases or previous auricular surgery. Cameriere's ear identification method was applied and measurements were performed on the images of each ear, considering four anatomic regions: helix, antihelix, concha, and lobe. The quantified measurement values were converted into a proposed coded number system. A search for identical codes was accomplished to find out the distinctiveness of the morphology of the human ear. The combined codes of left and right ears of each of the 814 subjects were not repeated in this multi-ethnic study sample. Dirichlet's distribution and the inherent study equation showed that the probability of two different individuals having the same code (false-positive identification) was found to be <0.0007. Because of the distinctive metrics of the ratios of external human ears, studies with Cameriere's ear identification method may be valuable for human identification. Studying the differences between the left and right ears of the same individual and across different ethnic groups could contribute to the development of supplementary tools for human identification.

Use of non-clinical smile images for human identification: a systematic review.

Human identification using Forensic Dentistry occurs through comparative analysis of ante-mortem (AM) and post-mortem (PM) data. With the constant improvement of technology, photographs became a common source of AM data. When clinical dental records are not available, images showing the smile can be useful in human identification. The aim of this study was to investigate human identification techniques through the analysis of smile images in the available literature. Studies on human identification through the analysis of smile images were searched in the scientific literature. The search resulted in 4,043 studies. After screening, 14 studies were considered eligible. Eleven were case reports, two were pilot studies and one a technical note. From the eligible studies, in addition to the methodological data, information about the sample, used techniques and results regarding human identification were extracted. Three techniques were detected: direct comparison of morphological characteristics, AM/PM image overlap, and the analysis of smile lines. One or more associated techniques were used for human identification. Authors highlighted as a common limitation of the techniques the quality of the available images, the difficulty in reproducing PM the same images AM, and the eventual image modifications performed by the victim before posting in social media. Advantages included the low-cost aspect of the technique, as well as a potential fast and accurate procedure (depending on the quantity and quality of evidence). In general, studies considered the technique useful and adjuvant for human identification.

Radiographic changes in endodontically treated teeth submitted to drowning and burial simulations: is it a useful tool in forensic investigation?

Dental radiographs, endodontic treatment and materials are a source of useful forensic data. The response of dental materials to death-related events are widely studied and provide forensic evidence for experts. This study aimed to analyze the radiographic images of endodontically treated teeth submitted to burial and drowning simulation, verifying its forensic feasibility, applicability and usefulness. MATERIAL AND METHOD: n=20 bovine incisor teeth were endodontically treated then divided into two groups: burial and drowning scenarios. Teeth were radiographed two times (before and after scenario) with an aluminium stepwedge, and optical density (OD) was assessed in each root third, in both radiographs, and then compared (ANOVA and Tukey test) for each scenario. RESULTS: Burial scenario did not significantly alter radiopacity. As for the drowning scenario, there was no difference in radiopacity between the root thirds before the test. After drowning, the apical third demonstrated lower OD (p<.05) than the other two thirds. Comparing the OD before and after drowning, medium third presented lower and cervical third demonstrated higher means (p<.05) after drowning. CONCLUSION: We concluded that drowning conditions could alter the radiopacity of endodontically treated teeth, more specifically in the medium and cervical thirds. There is no evidence that this also occurs in burial situations. This has the potential to be useful in forensic casework as an initial sign of the type of ambient in which the body was supposedly exposed or set.

Sex estimation by maxillary sinus using computed tomography: a systematic review.

Sex estimation is an important part of forensic human identification, and when primary methods cannot be applied, forensic anthropology becomes an important auxiliary method of identification. The maxillary sinus may remain intact even if the skull is severely damaged and could thus be used in forensic investigations. The objective of this study was to verify the effectiveness of the evaluation of the maxillary sinus as a technique for sex estimation. Articles published in the past 10 years were searched using PubMed, Web of Science, Scopus, and Cochrane databases, including those that used computed tomography to perform maxillary sinus measurements with the purpose of sex estimation. Studies that used radiographs to perform the measurements were excluded because they do not allow for a three-dimensional analysis. Studies that did not provide information regarding the origin of the analyzed population were also excluded. The selected articles were evaluated for methodological quality according to the indication of the objective, studied population, inclusion and exclusion criteria, parameters for obtaining the computed tomography image, measurements evaluated, bias discussion, and ethical authorization. From the 52 articles found, 18 were included. The populations studied included Indians, Iraqis, Iranians, Egyptians, Brazilians, French, Dutch, and Turkish. Height, width, length, and volume of the maxillary sinus were measured. The maxillary sinus can act as an auxiliary tool for sex estimation in forensic investigations.

Applicability of forensic facial approximation in the recognition process of unclaimed victims.

BACKGROUND: Identifying bodies in a state of putrefaction, skeletonization or mutilation is often difficult. In these cases, it is possible to use auxiliary methods such as forensic facial approximation, considering the possibility of recognition by a relative or acquaintance, helping to obtain ante-mortem data for the identification process. The aims of the present study were to evaluate the capacity of recognition of individuals from digital facial approximation and to verify the association between the level of understanding of the issue by evaluators and the recognition success index. METHODS: 16 skulls with previous photographic records were selected and then utilized for three-dimensional approximation using the digital technique, scanned by photogrammetry, and reconstructed by computerized method using open-source software. Twenty evaluators tried to recognize the facial approximation performed from images present in the photospreads. RESULTS: The mean overall score was 23.75%, and it was observed that in only five approximations (31.24%) the option of correct recognition of the victim was the one that obtained the highest number of selections. False positives and negatives corresponded, respectively, to 11.56% and 12.5%. CONCLUSIONS: It can be concluded that the methodology can provide recognition albeit in low numbers, and permitting the acquisition of ante-mortem data for the proper process of human identification through primary methods.

Revisiting autopsies of death by mechanical asphyxia in the search for post-mortem pink teeth.

BACKGROUND: In contemporary forensic practice, Medicine and Dentistry combine forces to improve the search for the cause of death and human identification. The pink tooth phenomenon (PTP) is a cadaveric sign that allegedly manifests more often in victims of asphyxia. However, the scientific literature is scarce and controversial on this aspect. OBJECTIVE: This study aimed at screening victims of mechanical asphyxia in order to search for post-mortem pink teeth. MATERIAL AND METHODS: Retrospectively, autopsy reports from a local medico-legal institute in South Brazil were revisited in the search for victims of death by asphyxia. Autopsy reports of twenty one victims aged between 6 and 67 years (mean age: 40.6 years ±19.20; median: 37 years) were found and analyzed. RESULTS: The different modalities of asphyxia included drowning (n=7; 33.33%), strangulation (n=1; 4.76%) and hanging (n=13; 61.91%). A single case of PTP was detected (4.76%) - a 26-year-old male victim of hanging. CONCLUSION: This study illustrates and highlights the unspecific aspect of the PTP. In practice, forensic experts must avoid interpretations of this phenomenon as conclusive evidence of the cause of death, such as asphyxia by drowning, strangulation or hanging.

Cognitive and anxiety-like impairments accompanied by serotonergic ultrastructural and immunohistochemical alterations in early stages of parkinsonism.

Parkinson's disease (PD) is mostly known as a dopamine deficiency syndrome due the structural and functional changes in striatal projection neurons. However, studies have considered this pathology as a multi-systemic disease in which the neurodegenerative process extends beyond the dopaminergic system. Therefore, the purpose of the present study was to investigate the morphological and immunohistochemical changes associated with behavioral and cognitive alterations in a model of parkinsonism induced by low dose of reserpine. Animals showed anxiety-like behavior and deficits in short-term recognition memory. Besides, Tyrosine Hydroxylase (TH) immunoreactive cells decreased in reserpine (RES) group in CA1 and serotonin (5-HT) immunoreactive cells decreased in RES group in CA1, CA3 and medial prefrontal cortex (mPFC). Moreover, an increase in the area (µm2) of 5 H T labeled ultrastructure (axon terminal) was observed in RES group only in CA1 and mPFC. The evidence of alterations in 5-HT immunoreactive in the premotor phase of model of parkinsonism highlights the importance of looking beyond the nigrostriatal system to elucidate the underling mechanisms and deficits in other neurotransmitters systems. This provides vital information regarding novel interventions for the management of non-motor symptoms. Additionally, the low-dose reserpine treatment has an early effect on axonal ultrastructure. As the axonopathy in PD has been increasingly recognized, the focus on axonal neurobiology is noteworthy for both neuroprotective and restorative therapeutics, and the progressive reserpine rat model can be a useful tool in this search.

Colour stability of dental restorative materials submitted to conditions of burial and drowning, for forensic purposes.

The aim of this study was to evaluate the effect of earth and water on the colour stability of tooth-coloured dental restorative materials: composite resin (CR) and glass ionomer cement (GIC). Aiming to distinguish between one and another tooth-coloured material and to estimate the period in which they could be submitted to the factors earth and water, the proposed method may contribute to the proceedings of human identification of victims of burial and submersion in water. Forty bovine incisors were prepared (6 x 6 x 2mm) and restored with CR FiltekTM Z250 XT (3M ESPETM) and GIC KetacTM Fil Plus (3M ESPETM). After initial colour read-outs (VITATM Easyshade spectrophotometer), the samples were separated into two groups (n=10), according to the conditions to which they were submitted: simulations of burying and submersion in water, for periods of 1, 3, 6 and 12 months, when new read-outs were taken. The values of colour change (ΔE, ΔL*, Δa*, and Δb*) were subjected to 3-way ANOVA statistical analysis, repeated measures, Bonferroni (p<.05), and it was verified that both factors produced colour changes in the restorative materials, which were higher for glass ionomer cement (p<.05) after 12 months of burial, and 6 months of submersion in water. The authors concluded that the analysis of colour change in the material contributed to the forensic odontology casework depending on the time during which the victim was submitted to the condition of burial or submersion in water.

Genotype x environment interaction and stability of soybean cultivars for vegetative-stage characters.

In order to obtain the certificate of cultivar protection, it is necessary to prove its distinctiveness, homogeneity, and stability. Currently, there are 37 descriptors for differentiating soybeans cultivars. However, they are still not enough and, as a result, it is necessary to create, identify, and evaluate new descriptors. This study was aimed at evaluating the genotypic and environment interaction (GxE) and determining the stability of eight soybean cultivars for five vegetative-stage descriptors. The research was done in a greenhouse of the Soybean Breeding and Genetic Studies Program of Universidade Federal de Uberlândia. The treatments were composed of eight soybean cultivars, sown in two different growing seasons (January 25, 2014 and November 27, 2014). The experiments were carried out in randomized complete blocks with three replications and each experimental plot consisted of one pot with four soybean plants. The characters evaluated were: length of hypocotyl (LH), length of epicotyl (LE), length of unifoliolate leaf petiole (LUP), length of first trifoliate leaf petiole (LTLP), and rachis length of terminal leaflet of the first trifoliate leaf (RL). The data achieved from the trials were undergone genetic-statistical analyses by the GENES software. For all analyzed characters, the existence of genetic variability was observed emphasizing the vegetative-stage descriptors' utility to differentiate soybean cultivars. The occurrence of GxE interaction was detected for all characters assessed, mainly of complex nature, except by RL, which was of simple nature. The most stable cultivars for the vegetative-stage descriptors analysed were UFUS 7415 and UFUS Impacta.

Age estimation by facial analysis based on applications available for smartphones.

BACKGROUND: Forensic Dentistry has an important role in the human identification cases and, among the analyses that can be performed, age estimation has an important value in establishing an anthropological profile. Modern technology invests for new mechanisms of age estimation: software apps, based on special algorithms, because there is not interference based on personal knowledge, cultural and personal experiences for facial recognition. MATERIALS AND METHODS: This research evaluated the use of two different apps: "How Old Do I Look? - Age Camera" and "How Old Am I? - Age Camera, Do You Look Like in Selfie Face Pic?", for age estimation analysis in a sample of 100 people (50 females and 50 males). Univariate and multivariate statistical methods were used to evaluate data. RESULTS: A great reliability was seen when used for the male volunteers. However, for females, no equivalence was found between the real age and the estimated age. CONCLUSION: These applications presented satisfactory results as an auxiliary method, in male images.

Forensic odontology education:from undergraduate to PhD - a Brazilian experience.

BACKGROUND: Forensic Odontology is a topic present in the majority of Dental Schools in Brazil, and due to this reality, some universities develop activities related to undergraduate and graduate students, from the Dentistry course until the Ph.D. degree. AIM: To present the education experience related to Forensic Odontology at School of Dentistry of Ribeirão Preto (USP - University of São Paulo), showing the strategies and activities in the different degrees (Dental course, Forensic Odontology Specialization Program, Specific Professional Training, Master, and Ph.D.). RESULTS: To the undergraduate students, many activities are developed in order to demonstrate all the possibilities that Forensic Dentistry allow, including theoretical and practical activities; in the Forensic Odontology Specialization Program, the dentists are trained to act as Forensic Odontologists in all its amplitude; in the Specific Professional Training, some courses are available, related to specific topics as DVI, Forensic Facial Reconstruction, Auditor in Dental Care Insurance and others; and in the Master and Ph.D. Programs, the professionals receive training in skills like teaching, research, student's guidance and others. CONCLUSION: In Brazil, Forensic Odontology is a well-known field in Dentistry and universities develop an important role in training a qualified workforce.

Cytocompatibility of HEMA-free resin-based luting cements according to application protocols on dentine surfaces.

AIM: To evaluate the transdentinal cytotoxicity of resin-based luting cements (RBLCs), with no HEMA in their composition, to odontoblast-like cells. METHODOLOGY: Human dentine discs 0.3 mm thick were adapted to artificial pulp chambers (APCs) and placed in wells of 24-well plates containing 1 mL of culture medium (DMEM). Two categories of HEMA-free RBLCs were evaluated: group 1, self-adhesive Rely X Unicem (RU; 3M ESPE), applied directly to the dentine substrate; and group 2, Rely X ARC (RARC; 3M ESPE), applied to dentine previously acid-etched and treated with a bonding agent. In group 3 (control), considered as representing 100% cell metabolic activity, no treatment was performed on dentine. The APC/disc sets were incubated for 24 h or 7 days at 37 °C and 5% CO2 . Then, the extracts (DMEM + dental materials components that diffused through dentine) were applied to cultured odontoblast-like MDPC-23 cells for 24 h. After that, the cell viability (MTT assay), cell morphology (SEM), total protein production (TP) and alkaline phosphatase (ALP) activity were assessed. Data from MTT assay and TP production were analysed by Kruskal-Wallis and Mann-Whitney tests (α = 5%). Data from ALP activity were analysed by one-way anova and Tukey's test (α = 5%). RESULTS: In group 1, a slight reduction in cell viability (11.6% and 16.8% for 24-h and 7-day periods, respectively) and ALP activity (13.5% and 17.9% for 24-h and 7-day periods, respectively) was observed, with no significant difference from group 3 (control) (P > 0.05). In group 2, a significant reduction in cell viability, TP production and ALP activity compared with group 3 (control) occurred (P < 0.05), regardless of incubation time. Alteration in MDPC-23 cell morphology was observed only in group 2. CONCLUSIONS: HEMA-free Rely X ARC cement caused greater toxicity to odontoblast-like MDPC-23 cells than did Rely X Unicem cement when both resin-based luting materials were applied to dentine as recommended by the manufacturer.

Pro- and Anticonvulsant Effects of the Ant Dinoponera quadriceps (Kempf) Venom in Mice.

Epilepsy affects at least 50 million people worldwide, and the available treatment is associated with various side effects. Approximately 20-30% of the patients develop seizures that persist despite careful monitored treatment with antiepileptic drugs. Thus, there is a clear need for the development of new antiepileptic drugs, and the venoms can be an excellent source of probes. In this context, while there are studies on venoms from snakes, scorpions, and spiders, little is known regarding venom from ants. The aim of this study was to investigate the potential pro- and anticonvulsant effects of the venom from the ant Dinoponera quadriceps (Kempf) in Swiss mice. After the injection of the crude venom (DqTx-5, 50, and 500 mg/mL) in the lateral ventricle of mice, we observed a reduction of exploration and grooming behaviors, as well as an increase in immobility duration. In addition, the crude venom induced procursive behavior and tonic-clonic seizures at the highest concentration. Conversely, the preadministration of the denatured venom (AbDq) at the concentration of 2 mg/mL protected the animals against tonic-clonic seizures (66.7%) and death (100%) induced by administration of bicuculline. Taken together, the findings demonstrate that D. quadriceps venom might be potential source of new pro- and anticonvulsants molecules.

Improvement in physiological and psychological parameters after 6 months of yoga practice.

Yoga is believed to have beneficial effects on cognition, attenuation of emotional intensity and stress reduction. Previous studies were mainly performed on eastern experienced practitioners or unhealthy subjects undergoing concomitant conventional therapies. Further investigation is needed on the effects of yoga per se, as well as its possible preventive benefits on healthy subjects. We investigated the effects of yoga on memory and psychophysiological parameters related to stress, comparing yoga practice and conventional physical exercises in healthy men (previously yoga-naïve). Memory tests, salivary cortisol levels and stress, anxiety, and depression inventories were assessed before and after 6 months of practice. Yoga practitioners showed improvement of the memory performance, as well as improvements in psychophysiological parameters. The present results suggest that regular yoga practice can improve aspects of cognition and quality of life for healthy individuals. An indirect influence of emotional state on cognitive improvement promoted by yoga practice can be proposed.

Pre-training anandamide infusion within the basolateral amygdala impairs plus-maze discriminative avoidance task in rats.

Endocannabinoids (eCBs) modulate a variety of brain functions via activation of the widely expressed CB1 receptor. One site of high density of this receptor is the basolateral amygdala (BLA), a structure involved in the formation of aversive memories. The activation and blockade of CB1 receptors by systemic or hippocampal drug administrations have been shown to modify memory processing. However, little is known about the role of the BLA endocannabinoid system in aversive memories. Additionally, BLA endocannabinoid transmission seems to be related to emotional states, but the relevance of these effects to memory formation is still unknown. In this study we investigated the effects of the eCB anandamide (AEA) and the CB1 antagonist/inverse agonist AM251 infused into the BLA on the acquisition of an aversive memory task, concomitantly evaluating basal anxiety levels in rats. Male rats received pre-training micro-injection of AEA, AM251 or vehicle bilaterally into the BLA, and were studied with the plus-maze discriminative avoidance task (a paradigm that allows concomitant and independent evaluation of anxiety-like behavior and the memory of an aversive task). Our results showed that AEA into the BLA before training prevented memory retrieval 24 h later, as evaluated by exploration of the aversive arm of the maze, while AM251 into the BLA did not interfere with animals' performance. In addition, AEA had no effect on anxiety-like behavior (as evaluated by open arm exploration and risk assessment), while AM251 induced an anxiogenic effect. Our data indicate an important role of BLA CB1 receptors in aversive memory formation, and suggest that this involvement is not necessarily related to a possible modulation of anxiety states.

Basolateral amygdala inactivation impairs learned (but not innate) fear response in rats.

Numerous studies have suggested that the amygdala is involved in the formation of aversive memories, but the possibility that this structure is merely related to any kind of fear sensation or response could not be ruled out in previous studies. The present study investigated the effects of bilateral inactivation of the amygdaloid complex in rats tested in the plus-maze discriminative avoidance task. This task concomitantly evaluates aversive memory (by discrimination of the two enclosed arms) and innate fear (by open-arm exploration). Wistar rats (3-5 months-old) were implanted with bilateral guide cannulae into basolateral amygdala. After surgery, all subjects were given 1 week to recover before behavioral experiments. Afterwards, in experiment 1, 15 min prior to training, 0.5 µl of saline or muscimol (1 mg/ml) was infused in each side via microinjection needles. In experiment 2 the animals received injections immediately after the training session and in experiment 3 rats were injected prior to testing session (24 h after training). The main results showed that (1) pre-training muscimol prevented memory retention (evaluated by aversive arm exploration in the test session), but did not alter innate fear (evaluated by percent time in open arms); (2) post-training muscimol impaired consolidation, inducing increased percent in aversive arm exploration in the test session and (3) pre-testing muscimol did not affect retrieval (evaluated by aversive enclosed arm exploration in the test session). The results suggest that amygdala inactivation specifically modulated the learning of the aversive task, excluding a possible secondary effect of amygdala inactivation on general fear responses. Additionally, our data corroborate the hypothesis that basolateral amygdala is not the specific site of storage of aversive memories, since retention of the previously learned task was not affected by pre-testing inactivation.

Aerobic and anaerobic decomposition of Pistia stratiotes leachates from a tropical eutrophic reservoir (Barra Bonita, SP, Brazil).

The present study discussed the kinetic aspects of leachate decomposition from an aquatic macrophyte, Pistia stratiotes L (water lettuce). This species was collected from Barra Bonita Reservoir located in the State of São Paulo (Brazil). Decomposition chambers were prepared with high molecular weight (HMW), low molecular weight (LMW) and integral (INT = HMW + LMW) dissolved organic matter (DOM) diluted with reservoir water. The samples were incubated at 20 degrees C, in darkness and under aerobic or anaerobic conditions. For 79 days, the concentrations of dissolved oxygen (DO) and organic carbon (OC) were measured. For calculating the deoxygenation coefficients (k d) and maximum oxygen consumption (COmax) the concentration of DO was integrated and fitted to a first-order kinetics model, which also applied to the depletion of OC concentrations. The COmax of INT incubations were 4% higher than the sum of HMW and LMW fractions. The deoxygenation coefficients, k d, had the same order of magnitude for all treatments. In relation to carbon decay, regardless of the availability of oxygen, the INT DOM also showed higher mineralisation. These results suggest that the leachate mineralisations are short-term processes; when the fractionation of the leachates occurs, the LMW had organic compounds with more accessibility for heterotrophic metabolism. On the other hand, when compared to INT DOM, the HMW and LMW were less consumed suggesting an interaction of the reactivity of the leachate. Our data suggest that in the Barra Bonita Reservoir the mineralisation of P. stratiotes leachates occurs through two competitive pathways (i.e. mineralisation of the labile compounds and formation of recalcitrant organic resources and their mineralisation) in which the oxygen availability and the molecular mass of DOM can interfere in the rates of reactions.

Aerobic and anaerobic decomposition of Pistia stratiotes leachates from a tropical eutrophic reservoir (Barra Bonita, SP, Brazil) / Decomposição aeróbia e anaerobia de lixiviados de Pistia stratiotes de um reservatório eutrófico tropical (Barra Bonita, SP, Brasil)

The present study discussed the kinetic aspects of leachate decomposition from an aquatic macrophyte, Pistia stratiotes L (water lettuce). This species was collected from Barra Bonita Reservoir located in the State of São Paulo (Brazil). Decomposition chambers were prepared with high molecular weight (HMW), low molecular weight (LMW) and integral (INT = HMW + LMW) dissolved organic matter (DOM) diluted with reservoir water. The samples were incubated at 20 °C, in darkness and under aerobic or anaerobic conditions. For 79 days, the concentrations of dissolved oxygen (DO) and organic carbon (OC) were measured. For calculating the deoxygenation coefficients (k d) and maximum oxygen consumption (COmax) the concentration of DO was integrated and fitted to a first-order kinetics model, which also applied to the depletion of OC concentrations. The COmax of INT incubations were 4 percent higher than the sum of HMW and LMW fractions. The deoxygenation coefficients, k d, had the same order of magnitude for all treatments. In relation to carbon decay, regardless of the availability of oxygen, the INT DOM also showed higher mineralisation. These results suggest that the leachate mineralisations are short-term processes; when the fractionation of the leachates occurs, the LMW had organic compounds with more accessibility for heterotrophic metabolism. On the other hand, when compared to INT DOM, the HMW and LMW were less consumed suggesting an interaction of the reactivity of the leachate. Our data suggest that in the Barra Bonita Reservoir the mineralisation of P. stratiotes leachates occurs through two competitive pathways (i.e. mineralisation of the labile compounds and formation of recalcitrant organic resources and their mineralisation) in which the oxygen availability and the molecular mass of DOM can interfere in the rates of reactions.

Nesse estudo foram discutidos aspectos cinéticos da decomposição de lixiviados da macrófita aquática Pistia stratiotes L (alface-d'água). A macrófita foi coletada no reservatório de Barra Bonita, localizado no Estado de São Paulo (Brasil). As câmaras de decomposição foram preparadas com amostras de água do reservatório e matéria orgânica dissolvida (MOD) de lixiviados com massa molecular alta (MMA), massa molecular baixa (MMB) e integral (INT = MMA + MMB). As amostras foram incubadas a 20 ºC, no escuro e sob condições aeróbias e anaeróbias. Durante 79 dias, as concentrações de oxigênio dissolvido (OD) e de carbono orgânico (CO) foram determinadas. Para os cálculos dos coeficientes de desoxigenação (k d) e das quantidades máximas de oxigênio consumido (OCmax), as concentrações de OD foram integradas e ajustadas a um modelo cinético de primeira ordem, que também foi empregado para os ajustes dos decréscimos das concentrações de CO. O OCmax da incubação com lixiviado integral (INT) foi 4 por cento maior que a soma dos OCmax das frações MMA e MMB. Os coeficientes de desoxigenação foram da mesma ordem de magnitude em todos os tratamentos. Em relação à perda de massa do carbono, independente da disponibilidade de oxigênio, a MOD INT apresentou as mineralizações mais elevadas. Os resultados sugeriram que as mineralizações desses lixiviados foram processos de curto prazo; na ocorrência de fracionamento, os lixiviados com MMB apresentam compostos orgânicos mais acessíveis aos metabolismos dos heterótrofos. Por outro lado, quando comparados com MOD INT, os lixiviados com MMB e MMA foram menos consumidos, sugerindo interação na reatividade dos lixiviados. Os resultados sugerem que no reservatório de Barra Bonita as mineralizações dos lixiviados de P. stratiotes ocorrem por duas rotas competitivas (i.e. mineralização dos compostos lábeis e formação de recursos refratários e sua mineralização), nas quais a disponibilidade de oxigênio e a massa molecular...