Cell viability in magnetotactic multicellular prokaryotes

A magnetotactic multicellular prokaryote (MMP) is an assembly of bacterial cells organized side by side in a hollow sphere in which each cell faces both the external environment and an internal acellular compartment in the center of the multicellular organism. MMPs swim as a unit propelled by the coordinated beating of the many flagella on the external surface of each cell. At every stage of its life cycle, MMPs are multicellular. Initially, a spherical MMP grows by enlarging the size of each of its cells, which then divide. Later, the cells separate into two identical spheres. Swimming individual cells of MMPs have never been observed. Here we have used fluorescent dyes and electron microscopy to study the viability of individual MMP cells. When separated from the MMP, the cells cease to move and they no longer respond to magnetic fields. Viability tests indicated that, although several cells could separate from a MMP before completely losing their motility and viability, all of the separated cells were dead. Our data show that the high level of cellular organization in MMPs is essential for their motility, magnetotactic behavior, and viability. [Int Microbiol 2006; 9(4):267-272

Salinity dependence of the distribution of multicellular magnetotactic prokaryotes in a hypersaline lagoon

Candidatus Magnetoglobus multicellularis is an unusual magnetotactic multicellular microorganism composed of a highly organized assemblage of gram-negative bacterial cells. In this work, the salinity dependence of Ca. M. multicellularis and its abundance in the hypersaline Araruama Lagoon, Brazil were studied. Viability experiments showed that Ca. M. multicellularis died in salinities >55‰ and < 40‰. Low salinities were also observed to modify the cellular assemblage. In microcosms prepared with different salinities, the microorganism grew better at intermediate salinities whereas in high or low salinities, the size of the population did not increase over time. The concentrations of Ca. M. multicellularis in the lagoon were related to salinity; sites with lower and higher salinities than the lagoon average contained less Ca. M. multicellularis. These results demonstrate the influence of salinity on the survival and distribution of Ca. M. multicellularis in the environment. In sediments, the abundance of Ca. M. multicellularis ranged from 0 to 103 microorganisms/ml, which represented 0.001% of the counts of total bacteria. The ability of Ca. M. multicellularis to accumulate iron and sulfur in high numbers of magnetosomes (up to 905 per microorganism) suggests that its impact on the sequestration of these elements (0.1% for biogenic bacterial iron) is not proportional to its abundance in the lagoon. [Int Microbiol 2009; 12(3):193-201

Effects of GaAs laser and stretching on muscle contusion in rats

Laser e alongamento são usados para tratar lesões musculares. Este estudo objetivou avaliar os efeitos do laser GaAs e alongamento na morfologia do músculo Tibial anterior (TA) após contusão. Trinta e seis ratos (349±23 g) foram divididos em seis grupos (n=6): grupo controle (GC); grupo lesão e laser (GLL); grupo lesão e alongamento (GLA); grupo lesão, laser e alongamento (GLLA) e grupo alongamento (GA). Foi realizada lesão no TA por meio de um aparato de contusão. O tratamento com laser GAAS foi usado com dose de 4,5 J/cm2 durante 32 s, iniciando 48 h após lesão, por 7 dias. Alongamento passivo manual consistiu de 10 repetições de 1 minuto de duração, iniciando no 8º dia, 3 vezes por semana, durante 3 semanas. Após 4 semanas, os ratos foram eutanasiados para retirada do TA para análise de: peso e comprimento musculares, área de secção transversa das fibras musculares (ASTFM), número de sarcômeros em série (NSS), comprimento dos sarcômeros e porcentagem de tecido conjuntivo. A comparação entre os grupos deu-se por meio da ANOVA e post hoc Tukey, com nível de significância ≤ 0,05. O número de sarcômeros em série do GLLS foi maior que o GLS. O comprimento dos sarcômeros no GLA foi superior ao GLL, GLLA e GA. No GA houve aumento do NSS comparado com o GC, enquanto a porcentagem de tecido conjuntivo do GA diminuiu em comparação com o GLLA. Assim, a sarcomerogênese dos músculos lesionados foi aumentada pelo uso do laser, alongamento e pela associação destes. O alongamento foi suficiente para aumentar o NSS em músculos intactos.Láser y estiramiento son utilizados para sanar lesiones musculares. Este estudio tuvo como objetivo evaluar los efectos del láser GaAs y del estiramiento en la morfología del músculo tibial anterior (TA) después de contusión. Treinta y seis ratones (349±23 g) fueron divididos en seis grupos (n=6): grupo control (GC); grupo lesión y láser (GLL); grupo lesión y estiramiento (GLE); grupo lesión, laser y estiramiento (GLLA) y grupo estiramiento (GA). Se realizó lesión en el TA mediante un aparato de contusión. Se utilizó el tratamiento con láser GaAs con dosis de 4,5 J/cm2 durante 32 s, iniciado 48 h después de la lesión, durante 7 días. El estiramiento pasivo manual consistió de 10 repeticiones de 1 minuto de duración, iniciado en el 8º día, 3 veces por semana, durante 3 semanas. Después de 4 semanas, los ratones sufrieron eutanasia para la retirada del TA para análisis de: peso y longitud musculares, área de sección trasversa de las fibras musculares (ASTFM), número de sarcómeros en serie (NSS), longitud de los sarcómeros y porcentaje de tejido conjuntivo. La comparación entre los grupos ocurrió mediante la Anova y post hoc Tukey, con nivel de significancia de ≤0,05. El número de sarcómeros en serie del GLLS fue mayor que el GLS. La longitud de los sarcómeros en el GLA fue superior al GLL, GLLA y GA. En el GA hubo aumento del NSS en comparación con el GC, mientras el porcentaje del tejido conjuntivo del GA disminuyó en comparación al del GLLA. Así, la sarcomerogénesis de los músculos lesionados fue aumentada por el uso del láser, estiramiento y por su asociación. El estiramiento fue suficiente para aumentar el NSS en músculos intactos.Laser and stretching are used to treat skeletal muscle injuries. This study aimed to evaluate the effects of GaAs laser and stretching in the morphology of the tibialis anterior (TA) muscle after contusion. Thirty-six male rats (349±23g) were divided into six groups (n=6): control group (CG); lesion group (LG); lesion and laser group (LLG); lesion and stretching group (LSG); lesion, laser and stretching group (LLSG); and stretching group (SG). TA was wounded by a contusion apparatus. We used GaAs laser 4.5 J/cm2 dose for 32 s each, beginning 48 h after lesion, for 7 days, once a day. Manual passive stretching was applied by 10 repetitions for 1 minute, initiating on the 8th day, once a day, 3 times a week, during 3 weeks. After 4 weeks, rats were euthanized and we analyzed: muscle weight and length, cross sectional area of muscle fibers (CSAMF), serial sarcomere number (SSN), sarcomere length, and percentage of connective tissue. Comparisons among groups were made by ANOVA and post hoc Tukey tests, with the significance level set at ≤ 0.05. The serial sarcomere number of LLSG was higher than LSG. The sarcomere length of LSG was superior to LLG, LLSG, and SG. SG increased SSN compared to CG, while the percentage of connective tissue of SG decreased in comparison to LLSG. Thus, the sarcomerogenesis of injured muscles was enhanced by laser therapy, stretching, and association of both. The stretching protocol was enough to increase SSN of intact muscles

Intermittent in-situ high-resolution X-ray microscopy of 400-nm porous glass under uniaxial compression: study of pore changes and crack formation

The properties of porous glasses and their field of application strongly depend on the characteristics of the void space. Understanding the relationship between their porous structure and failure behaviour can contribute to the development of porous glasses with long-term reliability optimized for specific applications. In the present work, we used X-ray computed tomography with nanometric resolution (nano-CT) to image a controlled pore glass (CPG) with 400 nm-sized pores whilst undergoing uniaxial compression in-situ to emulate a stress process. Our results show that in-situ nano-CT provides an ideal platform for identifying the mechanisms of damage within glass with pores of 400 nm, as it allowed the tracking of the pores and struts change of shape during compression until specimen failure. We have also applied computational tools to quantify the microstructural changes within the CPG sample by mapping the displacements and strain fields, and to numerically simulate the behaviour of the CPG using a Fast Fourier Transform/phase-field method. Both experimental and numerical data show local shear deformation, organized along bands, consistent with the appearance and propagation of +/- 45 degrees cracks.Comment: 14 pages, 6 figure

Children's exposure to indoor air in schools: Impact on wheezing

Wheezing is a common symptom in childhood and has been associated with air pollution. Children spend a large part of their time in school, this being the most important indoor environment apart from home. However, studies on the impact of children's indoor air pollution exposure at schools on respiratory health are scarce. Thus, this study aimed to assess the impact of children's exposure to indoor air pollution in a total of five urban nursery and primary schools on active wheezing. Multivariate logistic regression models were used to estimate the associations, adjusted for sex, age group (pre-school/primary school) and parental history of asthma. A microenvironmental modelling approach was used to estimate indoor air pollution exposure to each of the pollutants exceeding legislation limit values (CO2, formaldehyde and PM2.5), as the sum of the product of time spent by the child in different indoor school microenvironments and the time-averaged concentration measured in each microenvironment. Measurements were performed in 11 classrooms, two bedrooms and two canteens in Porto, Portugal. A total of 164 completed parent-reported questionnaires derived from the International Study of Asthma and Allergies in Childhood allowed to identify active wheezing (at least one wheeze episode in the previous 12 months) in 16.5% of the studied children. Although not statistically significant, the studied children's exposure to indoor air pollution in nursery and primary schools seemed to be associated with an increase in the odds of having active wheezing especially for PM2.5 (OR = 1.57, p-value = 0.675). These results highlight the importance of applying indoor air pollution mitigation measures in nursery and primary schools. The impacts of those measures, on both indoor air quality and children's respiratory health, should be evaluated in future studies. (c) 2019 WIT Pres

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Bioactive glasses convert to a biomimetic apatite when in contact with physiological solutions; however, the number and type of phases precipitating depends on glass composition and reactivity. This process is typically followed by X-ray diffraction and infrared spectroscopy. Here, we visualise surface mineralisation in a series of sodium-free bioactive glasses, using transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDXS) and X-ray nano-computed tomography (nano-CT). In the glasses, the phosphate content was increased while adding stoichiometric amounts of calcium to maintain phosphate in an orthophosphate environment in the glass. Calcium fluoride was added to keep the melting temperature low. TEM brought to light the presence of phosphate clustering and nearly crystalline calcium fluoride environments in the glasses. A combination of analytical methods, including solid-state NMR, shows how with increasing phosphate content in the glass, precipitation of calcium fluoride during immersion is superseded by fluorapatite precipitation. Nano-CT gives insight into bioactive glass particle morphology after immersion, while TEM illustrates how compositional changes in the glass affect microstructure at a sub-micron to nanometre-level

Chromosome differentiation patterns during cichlid fish evolution

<p>Abstract</p> <p>Background</p> <p>Cichlid fishes have been the subject of increasing scientific interest because of their rapid adaptive radiation which has led to an extensive ecological diversity and their enormous importance to tropical and subtropical aquaculture. To increase our understanding of chromosome evolution among cichlid species, karyotypes of one Asian, 22 African, and 30 South American cichlid species were investigated, and chromosomal data of the family was reviewed.</p> <p>Results</p> <p>Although there is extensive variation in the karyotypes of cichlid fishes (from 2n = 32 to 2n = 60 chromosomes), the modal chromosome number for South American species was 2n = 48 and the modal number for the African ones was 2n = 44. The only Asian species analyzed, <it>Etroplus maculatus</it>, was observed to have 46 chromosomes. The presence of one or two macro B chromosomes was detected in two African species. The cytogenetic mapping of 18S ribosomal RNA (18S rRNA) gene revealed a variable number of clusters among species varying from two to six.</p> <p>Conclusions</p> <p>The karyotype diversification of cichlids seems to have occurred through several chromosomal rearrangements involving fissions, fusions and inversions. It was possible to identify karyotype markers for the subfamilies Pseudocrenilabrinae (African) and Cichlinae (American). The karyotype analyses did not clarify the phylogenetic relationship among the Cichlinae tribes. On the other hand, the two major groups of Pseudocrenilabrinae (tilapiine and haplochromine) were clearly discriminated based on the characteristics of their karyotypes. The cytogenetic mapping of 18S ribosomal RNA (18S rRNA) gene did not follow the chromosome diversification in the family. The dynamic evolution of the repeated units of rRNA genes generates patterns of chromosomal distribution that do not help follows the phylogenetic relationships among taxa. The presence of B chromosomes in cichlids is of particular interest because they may not be represented in the reference genome sequences currently being obtained.</p

Hydrogels Based on Chitosan and Chitosan Derivatives for Biomedical Applications

Chitosan (CS) is a polymer obtained from chitin, being this, after the cellulose, the most abundant polysaccharide. The fact of (i) CS being obtained from renewable sources; (ii) CS to possess capability for doing interactions with different moieties being such capability dependent of pH; (iii) plenty of possibilities for chemical modification of CS; and (iv) tuning the final properties of CS derivatives makes this polymer very interesting in academic and technological points of view. In this way, hydrogels based on CS and on CS derivatives have been widely used for biomedical applications. Other important technological applications can be also cited, such as adsorbent of metals and dyes in wastewater from industrial effluents. In pharmaceutical field, hydrogels based on CS are often used as drugs’ and proteins’ carrier formulations due to the inherent characteristics such as the biocompatibility, nontoxicity, hydrophilicity, etc. This chapter is an attempt for updating and joining the plenty of available information regarding the preparation, characterization, and biomedical application of hydrogels based on chitosan and chitosan derivatives. More than 260 references are provided, being the majority of them published in the last 10 years

Agronomic biofortification of cowpea with selenium: effects of selenate and selenite applications on selenium and phytate concentrations in seeds

BACKGROUNDSelenium (Se) is a nutrient for animals and humans, and is considered beneficial to higher plants. Selenium concentrations are low in most soils, which can result in a lack of Se in plants, and consequently in human diets. Phytic acid (PA) is the main storage form of phosphorus in seeds, and it is able to form insoluble complexes with essential minerals in the monogastric gut. This study aimed to establish optimal levels of Se application to cowpea, with the aim of increasing Se concentrations. The efficiency of agronomic biofortification was evaluated by the application of seven levels of Se (0, 2.5, 5, 10, 20, 40, and 60 g ha−1) from two sources (selenate and selenite) to the soil under field conditions in 2016 and 2017.RESULTSApplication of Se as selenate led to greater plant Se concentrations than application as selenite in both leaves and grains. Assuming human cowpea consumption of 54.2 g day−1, Se application of 20 g ha−1 in 2016 or 10 g ha−1 in 2017 as selenate would have provided a suitable daily intake of Se (between 20 and 55 μg day−1) for humans. Phytic acid showed no direct response to Se application.CONCLUSIONSelenate provides greater phytoavailability than selenite. The application of 10 g Se ha−1 of selenate to cowpea plants could provide sufficient seed Se to increase daily human intake by 13–14 μg d−1. © 2019 Society of Chemical Industr