Synthesis and toxicological study of chitosan-pirul (Schinus molle L.) essential oil nanoparticles on Aspergillus flavus.

In recent years, the study of essential oils as antifungal alternatives and their encapsulation to increase their properties for greater effects has been tested. In this work, nanoparticles of chitosan-Schinus molle L. essential oil (CS-PEO-Np) with a size of 260 ± 31.1 nm were obtained by ionic gelation and evaluated in some growth phases of Aspergillus flavus, a toxigenic fungus. At a concentration of 250 µg/mL of CS-PEO-Np, the A. flavus mycelial growth was inhibited at 97.1% with respect to control, at 96 h of incubation; the germination and viability of spores were inhibited at 74.8 and 40%, respectively, after exposure to 500 µg/mL of these nanomaterials, at 12 h of incubation. The fluorescence images of stained spores with DAPI showed the affectations caused by nanoparticles in the cell membrane, vacuoles and vacuolar content, cell wall, and nucleic acids. For both nanoparticles, CS-Np and CS-PEO-Np, no mutagenic effect was observed in Salmonella Typhimurium; also, the phytotoxic assay showed low-to-moderate toxicity toward seeds, which was dependent on the nanoparticle's concentration. The acute toxicity of CS-PEO-Np to A. salina nauplii was considered low in comparison to CS-Np (control), which indicates that the incorporation of Schinus molle essential oil into nanoparticles of chitosan is a strategy to reduce the toxicity commonly associated with nanostructured materials. The nanoparticulated systems of CS-PEO-Np represent an effective and non-toxic alternative for the control of toxigenic fungi such as A. flavus by delaying the initial growth stage.

The IV International Symposium on Fungal Stress and the XIII International Fungal Biology Conference.

For the first time, the International Symposium on Fungal Stress was joined by the XIII International Fungal Biology Conference. The International Symposium on Fungal Stress (ISFUS), always held in Brazil, is now in its fourth edition, as an event of recognized quality in the international community of mycological research. The event held in São José dos Campos, SP, Brazil, in September 2022, featured 33 renowned speakers from 12 countries, including: Austria, Brazil, France, Germany, Ghana, Hungary, México, Pakistan, Spain, Slovenia, USA, and UK. In addition to the scientific contribution of the event in bringing together national and international researchers and their work in a strategic area, it helps maintain and strengthen international cooperation for scientific development in Brazil.

Experimental measurement of endocytosis in fungal hyphae.

The present study examines the notion that polarized exocytosis in the tips of growing hyphae creates an excess of plasma membrane and thus the need for its removal by endocytosis. To measure endocytosis experimentally, we developed a photobleaching (FRAP) procedure to count endocytic events in hyphae of Neurospora crassa carrying a fluorescent tag on the actin-binding protein fimbrin (FIM-1-GFP). Given 40 nm as the average diameter of endocytic vesicles, we calculated that about 12.5% of the plasma membrane discharged in the apex becomes endocytosed in the subapex. According to our calculations, the GFP-tagged hyphae of N. crassa, measured under the constrained conditions of confocal microscopic examination, needed about 8800 vesicles/min to extend their plasma membrane or about 9800/min, if we include predicted demands for cell wall growth and extracellular secretion. Our findings support the notion that exocytosis and endocytosis operate in tandem with the latter serving as a compensatory process to remove any excess of plasma membrane generated by the intense exocytosis in the hyphal tips. Presumably, this tandem arrangement evolved to support the hallmark features of fungi namely rapid cell extension and abundant secretion of hydrolytic enzymes.

Microtubules and associated molecular motors in Neurospora crassa.

The cytoskeleton provides structure, shape and movement to various cells. Microtubules (MTs) are tubular structures made of α and ß-tubulin heterodimers organized in 13 protofilaments, forming a hollow cylinder. A vast group of MT-associated proteins determines the function, behavior and interaction of the MTs with other cellular components. Among these proteins, molecular motors such as the dynein-dynactin complex and kinesin superfamily play roles in MT organization and organelle transport. This article focuses on the MT cytoskeleton and associated molecular motors in the filamentous fungus Neurospora crassa In addition to reviewing current available information for this fungus and contrasting it with knowledge of other fungal species, we present new experimental results that support the role of dynein, dynactin and conventional kinesin in MT organization, dynamics and transport of subcellular structures (nuclei and secretory vesicles). In wild type hyphae of N. crassa, cytoplasmic MTs are arranged longitudinally along hyphae and display a helical curvature. They interlace with one another to form a network throughout the cytoplasm. N. crassa dynein and dynactin mutants have a scant and disorganized MT cytoskeleton, an erratic and reduced Spitzenkörper (Spk) and distorted hyphal morphology. In contrast, hyphae of mutants with defective conventional kinesin exhibit only minor disruptions in MT and Spk organization. Although nuclear positioning is affected in all mutants, the MT-associated motor proteins are not major contributors to nuclear movement during hyphal growth. Cytoplasmic bulk flow is the vehicle for nuclear displacement in growing hyphal regions of N. crassa Motors are involved in nuclei saltatory movements in both retrograde or anterograde direction. In the dynein and kinesin mutants, micro and macrovesicles can reach the Spk, although growth is slightly impaired and the Spk displays an erratic path. Hyphal growth requires MTs, and their associated motors are required for their organization and dynamics and Spk integrity.

Septum development in Neurospora crassa: the septal actomyosin tangle.

Septum formation in Neurospora crassa was studied by fluorescent tagging of actin, myosin, tropomyosin, formin, fimbrin, BUD-4, and CHS-1. In chronological order, we recognized three septum development stages: 1) septal actomyosin tangle (SAT) assembly, 2) contractile actomyosin ring (CAR) formation, 3) CAR constriction together with plasma membrane ingrowth and cell wall construction. Septation began with the assembly of a conspicuous tangle of cortical actin cables (SAT) in the septation site >5 min before plasma membrane ingrowth. Tropomyosin and myosin were detected as components of the SAT from the outset. The SAT gradually condensed to form a proto-CAR that preceded CAR formation. During septum development, the contractile actomyosin ring remained associated with the advancing edge of the septum. Formin and BUD-4 were recruited during the transition from SAT to CAR and CHS-1 appeared two min before CAR constriction. Actin patches containing fimbrin were observed surrounding the ingrowing septum, an indication of endocytic activity. Although the trigger of SAT assembly remains unclear, the regularity of septation both in space and time gives us reason to believe that the initiation of the septation process is integrated with the mechanisms that control both the cell cycle and the overall growth of hyphae, despite the asynchronous nature of mitosis in N. crassa.

Recent advances in septum biogenesis in Neurospora crassa.

Hyphae of the Ascomycota are tubular cells compartmentalized by perforated septa, whose central pore allows the flow of organelles and cytoplasm. While in plants and yeast septation leads to cell separation, in filamentous fungi the formation of crosswalls appears to have an architectural role, limits the extent of mechanical damage thus maintaining hyphal integrity, and also is of fundamental importance as part of cell differentiation. The increasing number of available fungal genome sequences, knockout mutants, versatile tools for protein tagging, and the continuous improvement of fluorescence microscopes have allowed scientists to analyze living cells and reveal the molecular and cellular basis of septation with unprecedented detail. This review summarizes the recent advances in septum ontogenesis in Neurospora crassa. A "septal actomyosin tangle" is the first indication of impending septation. It assembles prior to any visible evidence of plasma membrane inward growth, which occurs concomitantly with the formation and constriction of a contractile actomyosin ring and synthesis of the septum wall. One of the key questions in septum biogenesis is how the septation machinery is assembled to construct a centripetally growing crosswall. Most of the machinery utilized in apical cell wall growth can be expected at septation sites to ensure an organized arrival and supply of vesicles leading to the formation of a septum. Yet, the intrinsically different architecture of the septum may require a different organization and regulation of the wall-synthesizing machinery.

Años acumulados de vida productiva potencial perdidos por accidentes de trabajo en Petróleos Mexicanos / Accumulated years of potential productive life lost due to work accidents in Petróleos Mexicanos

Objetivo. Se propone el cálculo de los años acumulados de vida productiva potencial perdidos (AAVPPP) para complementar la evaluación de las pérdidas por accidentes de trabajo. Material y métodos. A partir de los datos obtenidos del Departamento General de Medicina del Trabajo de la Gerencia Médica de Petróleos Mexicanos, se analizaron 8 638 accidentes de trabajo dictaminados entre el 1 de enero de 1990 y el 30 de junio de 1993. Las variables independientes consideradas fueron: sexo, edad, sitio y tipo de lesión, nivel de ingresos, y situación laboral; la variable dependiente fue el porcentaje de incapacidad permanente. A partir del indicador propuesto se calcularon los AAVPPP. Resultados. El 19.5 por ciento de los accidentados quedó con algún grado de secuela; el total de AAVPPP fue de 5 611, con un promedio por caso de 3.2 años; de las variables analizadas el sexo masculino, los niveles de ingreso más bajos, la situación contractual transitoria y las lesiones en mano y muñeca fueron las que más AAVPPP aportaron. Se observaron diferencias al comparar la jerarquización de algunas variables independientes en función de diversos criterios con el de AAVPPP. Conclusiones. Este indicador es aplicable en el área operativa de seguridad e higiene; complementa la información de indicadores similares y se considera útil para la planeación de programas y la evaluación de riesgos de trabajo

There are different indicators to give priority to health problems within the area of occupational health; we propose the calculation of accummulated years of potential productive life lost (AYPPLL) to estimate the loss of material and human resources due to work accidents. Material and methods. A total of 8 638 work accidents were analized using this method. Independent variables were: sex, age, place and type of accident, subject's income and work conditions. The dependent variable was permanent disability. Results. Subjects who had some kind of permanent damage were 19.5%; the total number of AYPPLL was 5 611, with an average of 3.2 YPPLL per accident. Variables associated with the highest AYPPLL were the socio-demographic variables, male sex, lowest income levels, temporary work contracts and injuries of the hand and wrist. Conclusions. The AYPPLL method was found to be a valuable indicator of the safety and hygiene of the worksite and a useful tool for planning and evaluating work accident programs.