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Head rotation in human spermatozoa is essential for different swimming modes and fertilisation, as it links the molecular workings of the flagellar beat with sperm motion in three-dimensional (3D) space over time. Determining the direction of head rotation has been hindered by the symmetry and translucent nature of the sperm head, and by the fast 3D motion driven by the helical flagellar beat. Analysis has been mostly restricted to two-dimensional (2D) single focal plane image analysis, which enables tracking of head centre position but not tracking of head rotation. Despite the conserved helical beating of the human sperm flagellum, human sperm head rotation has been reported to be uni- or bi-directional, and even to intermittently change direction in a given cell. Here, we directly measure the head rotation of freely swimming human sperm using multi-plane 4D (3D+t) microscopy and show that: (1) 2D microscopy is unable to distinguish head rotation direction in human spermatozoa; (2) head rotation direction in non-capacitating and capacitating solutions, for both aqueous and viscous media, is counterclockwise (CCW), as seen from head to tail, in all rotating spermatozoa, regardless of the experimental conditions; and (3) head rotation is suppressed in 36% of spermatozoa swimming in non-capacitating viscous medium, although CCW rotation is recovered after incubation in capacitating conditions within the same viscous medium, possibly unveiling an unexplored aspect of the essential need of capacitation for fertilisation. Our observations show that the CCW head rotation in human sperm is conserved. It constitutes a robust and persistent helical driving mechanism that influences sperm navigation in 3D space over time, and thus is of critical importance in cell motility, propulsion of flagellated microorganisms, sperm motility assessments, human reproduction research, and self-organisation of flagellar beating patterns and swimming in 3D space. [ABSTRACT FROM AUTHOR]

In the realm of 3D image processing, accurately representing the geometric nuances of line curves is crucial. Building upon the foundation set by the slope chain code, which adeptly represents intricate two-dimensional curves using an array capturing the exterior angles at each vertex, this study introduces an innovative 3D encoding method tailored for polygonal curves. This 3D encoding employs parallel slope and torsion chains, ensuring invariance to common transformations like translations, rotations, and uniform scaling, while also demonstrating robustness against mirror imaging and variable starting points. A hallmark feature of this method is its ability to compute tortuosity, a descriptor of curve complexity or winding nature. By applying this technique to biomedical engineering, we delved into the flagellar beat patterns of human sperm. These insights underscore the versatility of our 3D encoding across diverse computer vision applications. [ABSTRACT FROM AUTHOR]

• Local BSD and d 32 were analyzed with retrofitted P g /V in a three-phases system. • The presence of mycelial biomass change the BSD from bimodal to unimodal shape. • Air dispersion patterns were different in the three positions analyzed. • The bottom impeller showed a peculiar behavior, suggesting that it was flooded. Data about the effects of mycelium on local air dispersion in stirred tanks are very limited. Available information has been focused in laboratory-scale bioreactors and under constant stirring speed conditions. However, aeration and the biomass cause indirect changes in the actual power consumption. Therefore, studies keeping constant the gassed power input per unit volume (P g /V) are necessary to identify effects not ascribable to this variable. We used the mycelial biomass of the filamentous fungus Trichoderma harzianum , and analyzed its effect on the local bubble size distribution (BSD) and on Sauter mean diameter (d 32) in a pilot scale proto-fermenter having three ports for local measurements. Total P g /V was kept constant by adjusting impeller speed. Without biomass, the local BSD presented a bimodal shape in all locations analyzed. Statistically significant changes in the BSD and its shape were observed when the biomass concentration increased, becoming unimodal in its shape. The local analysis showed that the bubble dispersion had a different pattern in the three locations analyzed indicating that different hydrodynamic conditions prevail in each impeller. The upper and middle impellers behaved similarly: the bubble size decreased as the P g /V increased, whereas, the bottom impeller behaved differently, suggesting a flooding condition. [ABSTRACT FROM AUTHOR]

The reiterative process of lateral root (LR) formation is widespread and underlies root system formation. However, early LR primordium (LRP) morphogenesis is not fully understood. In this study, we conducted both a clonal analysis and time-lapse experiments to decipher the pattern and sequence of pericycle founder cell (FC) participation in LR formation. Most commonly, LRP initiation starts with the specification of just one FC longitudinally. Clonal and anatomical analyses suggested that a single FC gradually recruits neighboring pericycle cells to become FCs. This conclusion was validated by long-term time-lapse live-imaging experiments. Once the first FC starts to divide, its immediate neighbors, both lengthwise and laterally, are recruited within the hour, after which they recruit their neighboring cells within a few hours. Therefore, LRP initiation is a gradual, multistep process. FC recruitment is auxindependent and is abolished by treatment with a polar auxin transport inhibitor. Furthermore, FC recruitment establishes a morphogenetic field where laterally peripheral cells have a lower auxin response, which is associated with a lower proliferation potential, compared to centrally located FCs. The lateral boundaries of the morphogenetic field are determined by phloem-adjacent pericycle cells, which are the last cells to be recruited as FCs. The proliferation potential of these cells is limited, but their recruitment is essential for root system formation, resulting in the formation of a new vascular connection between the nascent and parent root, which is crucial for establishing a continuous and efficient vascular system. [ABSTRACT FROM AUTHOR]

In this study, experimental power input curves were obtained in a four-phase system. Sauter mean diameter of air and oil dispersions obtained in a four-phase Trichoderma harzianum fermentation model (aqueous salt solution, castor oil, air and T. harzianum mycelia) are presented. Experiments allowed to analyze the effect of varying amounts of surfactant (mixture of proteins coming from the biomass and bovine serum albumin) and solid concentration (mycelial biomass) on gassed power input, mean drop and bubble size distributions. Experimental power input measurements showed that the different mixtures of biomass and protein, keeping constant the agitation rate, affected the gassed power consumption by approximately ±10%. By keeping the gassed power input fixed during the dispersion experiments, it was possible to rule out the effects of the power consumption variation and to discern and analyze the impact of the amount of protein and biomass on the dispersion of air bubbles and oil drops. The protein, due to its surface-active properties, caused a considerable decrease in the Sauter mean diameter of air bubbles compared to the system without protein, regardless of the concentration. Protein did not have an effect on oil drops, which maintained a constant Sauter diameter through the studied concentration range (0–1.36 g/L). It was shown that, for comparable biomass concentrations, the gassed power input is the parameter determining the Sauter diameter of air bubbles as well as for the oil drops. It was found that, even by keeping the power input constant, the addition of biomass to the mixtures has additional interactions with the dispersions, decreasing the Sauter mean diameter of bubbles and increasing the value in oil drops. [ABSTRACT FROM AUTHOR]

Water hyacinth ( Eichhornia crassipes) is one of the most problematic invasive macrophyte in the world. Although it has become a key element of the systems where it was introduced several decades ago, there is insufficient information to determine its role on biological interactions. To elucidate water hyacinth-littoral zooplankton-planktivorous fish interactions, we conducted habitat choice experiments in the absence and presence of fish chemical cues (kairomones) for two tropical littoral cladocerans, Chydorus brevilabris and Simocephalus vetulus. We classified habitat selection as a habitat (preference for the plant without predation risk) and/or as a refuge (preference for the plant with predation risk). Our results showed that E. crassipes is used as a habitat by C. brevilabris and as a refuge by S. vetulus against fish predation. Although C. brevilabris did not use the water hyacinth as a refuge in the presence of kairomones, the results suggested that both C. brevilabris and S. vetulus exhibited behavioral responses that further reduced their predation risk. To our knowledge, this study is the first experimental evidence for littoral cladocerans using free-floating macrophytes as a refuge against fish predation in tropical systems. Our results support the assertion that habitat association is not necessarily an evidence of habitat preference. [ABSTRACT FROM AUTHOR]

The presence of foam is an important characteristic of chocolate beverages. In Mexico, which is part of ancient Mesoamerica, the foam in chocolate has been produced since ancient times mainly through two different techniques: by pouring the liquid from one vessel to another and by using the molinillo, which is a chocolate beater widely used nowadays. Knowledge regarding the different designs and modes of use of the molinillo has traditionally been empirical. In this work, the performance of the molinillo during the preparation of a chocolate beverage was characterised through high-speed video, and the foam production at three different levels of immersion (clearance), was measured. Furthermore, the hydrodynamics of the system was analysed. The tip speed reached approximately 3 m -1, and a typical forward-backward cycle lasted approximately 300 ms. A small clearance resulted in a high solid dispersion capacity but a limited foam production, whereas a large clearance improved the foam production but exhibited a poor solid suspension. The results quantitatively revealed the scientific basis underlying the empirical ancestral performance of the molinillo in the dispersion of cocoa solids, the promotion of liquid (water)–liquid (cocoa fat) mixing, and the production of foam. [ABSTRACT FROM AUTHOR]

Thyrotropin-releasing hormone (TRH) is released from the median eminence upon neural stimulation such as cold or suckling exposure. Concomitant with the cold- or suckling-induced release of TRH is a rapid and transient increase in the expression of proTRH mRNA in the paraventricular nucleus (PVN) of the hypothalamus. We employed two strategies to determine whether TRH neurons responding to cold exposure are different from those responding to suckling. First, we attempted to identify a marker of cellular activation in TRH neurons of the PVN. Cold induced c-fos expression in about 25% of TRH neurons of the PVN, but no induction was observed by suckling. Moreover, we explored the expression of a variety of immediate early genes including NGFI-A, fra-1 and c-jun, or CREB phosphorylation but found none to be induced by suckling. The number of cells expressing high levels of proTRH mRNA was counted and compared to total expressing cells. An increased number of cells expressing high levels of proTRH mRNA was observed when both stimuli were applied to the same animal, suggesting that different cells respond separately to each stimulus. We therefore analyzed the distribution of responsive TRH neurons as defined by the cellular level of proTRH mRNA. The proTRH mRNA signal was analyzed within three rostrocaudal zones of the PVN and within six mediolateral columns. Results showed that in response to cold, all areas of the PVN of the lactating rat present increased proTRH mRNA levels, including the anterior zone where few hypophysiotropic TRHergic cells are believed to reside. The distribution of the proTRH mRNA expressing cells in response to cold was quite comparable in female and in male rats. In contrast, the response after suckling was confined to the middle and caudal zones. Our results provide evidence of a functional specialization of TRH cells in the PVN.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Examines the role of the FilM N terminus in the flagellar rotation of Rhodobacter sphaeroides. Proteins composing the flagellar switch complex; Impact of protein interaction with CheY response regulator on the rotation direction; Effect of attractant concentration on stopping frequency.

The article offers a study that focuses on the human sperm which uses asymmetric and anisotropic flagellar controls to regulate swimming symmetry and cell steering. It mentions that the flagellar waves has generated by thousands of asymmetric molecular components yet, paradoxically, forward swimming arises via symmetric side-to-side flagellar movement; also focuses on high-speed three-dimensional (3D) microscopy.

Tracing tubular structures from biomedical images is important for a wide range of applications. Particularly, the spermatozoon is an essential cell whose flagella have a tubular form. Its main function is to fertilize the egg, and the flagellum is fundamental to achieve this task which depends importantly on the dynamics of intracellular calcium ([Ca2+]i). Measuring [Ca2+]i along the flagellum in 3-D is not a simple matter since it requires: 1) sophisticated fluorescence imaging techniques dealing with low intensity and signal to noise ratio (SNR) and 2) tracing the flagellum’s centerline. Most of the algorithms proposed to trace tubular structures have been developed for multi-branch structures not being adequate for single tubular structures with low SNR. Taking into account the prior knowledge that the flagellum is constituted by a single tubular structure, we propose an automatic method to trace and track multiple single tubular structures from 3-D $+ {t}$ images. First, an algorithm based on one-class classification allows enhancement of the flagellum. This enhanced 3-D image permits guiding an iterative centerline algorithm toward the flagellum’s centerline. Each sperm is assigned an ID to keep track of it in 3-D $+ {t}$. Our algorithm was quantitatively evaluated using a ground truth 564 semi-manual traces (six 3-D $+ {t}$ image stacks) comparing them to those obtained from state-of-the-art tubular structure centerline extraction algorithms. The qualitative and quantitative results show that our algorithm is extracting similar traces as compared with ground truth, and it is more robust and accurate to trace the flagellum’s centerline than multi-branch algorithms. [ABSTRACT FROM AUTHOR]

* Background and Aims The Arabidopsis thaliana root is a key experimental system in developmental biology. Despite its importance, we are still lacking an objective and broadly applicable approach for identification of number and position of developmental domains or zones along the longitudinal axis of the root apex or boundaries between them, which is essential for understanding the mechanisms underlying cell proliferation, elongation and differentiation dynamics during root development. * Methods We used a statistics approach, the multiple structural change algorithm (MSC), for estimating the number and position of developmental transitions in the growing portion of the root apex. Once the positions of the transitions between domains and zones were determined, linear models were used to estimate the critical size of dividing cells (LcritD) and other parameters. * Key Results The MSC approach enabled identification of three discrete regions in the growing parts of the root that correspond to the proliferation domain (PD), the transition domain (TD) and the elongation zone (EZ). Simultaneous application of the MSC approach and G2-to-M transition (CycB1;1DB:GFP) and endoreduplication (pCCS52A1:GUS) molecular markers confirmed the presence and position of the TD. We also found that the MADS-box gene XAANTAL1 (XAL1) is required for the wild-type (wt) PD increase in length during the first 2 weeks of growth. Contrary to wt, in the xal1 loss-of-function mutant the increase and acceleration of root growth were not detected. We also found alterations in LcritD in xal1 compared with wt, which was associated with longer cell cycle duration in the mutant. * Conclusions The MSC approach is a useful, objective and versatile tool for identification of the PD, TD and EZ and boundaries between them in the root apices and can be used for the phenotyping of different genetic backgrounds, experimental treatments or developmental changes within a genotype. The tool is publicly available at www.ibiologia.com.mx/MSC_analysis. [ABSTRACT FROM AUTHOR]

The automated detection and measurement of oil drops in multiphase fermentation systems are important for mass transfer analysis. A novel computer technique for automated detection of oil drops in images is presented in the context of a stirred tank containing a three-phase water-oil-air dispersion. The technique is an original feature extraction transform designed for the detection of objects with a characteristic appearance. The proposed transform, denominated gradient-direction-pattern (GDP) transform, utilizes naturally occurring patterns in the orientation of the local gradient appearing in test images. The GDP transform was used to demonstrate the feasibility of automatically estimating oil drop-size unbiased distributions which is an important task in the chemical and other related industries. [ABSTRACT FROM AUTHOR]

Intracellular Ca2+ is a key regulator of cell signaling and sperm are not the exception. Cells often use cytoplasmic Ca2+ concentration ([Ca2+] i) oscillations as a means to decodify external and internal information. [Ca2+] i oscillations faster than those usually found in other cells and correlated with flagellar beat were the first to be described in sperm in 1993 by Susan Suarez, in the boar. More than 20 years passed before similar [Ca2+] i oscillations were documented in human sperm, simultaneously examining their flagellar beat in three dimensions by Corkidi et al. 2017. On the other hand, 10 years after the discovery of the fast boar [Ca2+] i oscillations, slower ones triggered by compounds from the egg external envelope were found to regulate cell motility and chemotaxis in sperm from marine organisms. Today it is known that sperm display fast and slow spontaneous and agonist triggered [Ca2+] i oscillations. In mammalian sperm these Ca2+ transients may act like a multifaceted tool that regulates fundamental functions such as motility and acrosome reaction. This review covers the main sperm species and experimental conditions where [Ca2+] i oscillations have been described and discusses what is known about the transporters involved, their regulation and the physiological purpose of these oscillations. There is a lot to be learned regarding the origin, regulation and physiological relevance of these Ca2+ oscillations. Calcium is a ubiquitous signal that regulates a variety of processes of cell physiology. In many species, sperms are empowered with sperm specific molecular actors which decoy and transmit information from their surroundings, where Ca2+ plays a major role. This review covers some intricacies of the main cellular and molecular processes which govern the sperm function, commonly driven or which withstand within the reign of oscillatory Ca2+-dependent signaling processes. [Display omitted] [ABSTRACT FROM AUTHOR]

A high-speed video system was used for studying multiphase dispersions by image analysis. A high-speed video camera, coupled to a stereomicroscope was used to record the dispersion occurring in a mixing tank. A high intensity direct light probe submerged in the liquid was used for illumination. Sequences of 200 images (512 × 384 pixels) at rates up to 5130 frames/s (fps) and magnification up to 11× were obtained and analyzed. A detailed observation of the mixing dynamics at a high video rate allowed visualizing how oil drops and air bubbles move and interact. Velocity of the objects could be calculated at different focal planes. Rotational movement and trajectories in different directions, depending on the physicochemical properties of the system could be observed and recorded. The implemented methods also allowed the recording of the deformation of complex drops and were useful to discern situations of inclusions of objects (i.e. bubbles inside oil drops) in multiphase dispersions under power inputs up to 0.50 kW/m3. [ABSTRACT FROM AUTHOR]

Abstract: Fermentation bioprocesses typically involve two liquid phases (i.e. water and organic compounds) and one gas phase (air), together with suspended solids (i.e. biomass), which are the components to be dispersed. Characterization of multiphase dispersions is required as it determines mass transfer efficiency and bioreactor homogeneity. It is also needed for the appropriate design of contacting equipment, helping in establishing optimum operational conditions. This work describes the development of image analysis based techniques with advantages (in terms of data acquisition and processing), for the characterization of oil drops and bubble diameters in complex simulated fermentation broths. The system consists of fully digital acquisition of in situ images obtained from the inside of a mixing tank using a CCD camera synchronized with a stroboscopic light source, which are processed with a versatile commercial software. To improve the automation of particle recognition and counting, the Hough transform (HT) was used, so bubbles and oil drops were automatically detected and the processing time was reduced by 55% without losing accuracy with respect to a fully manual analysis. The system has been used for the detailed characterization of a number of operational conditions, including oil content, biomass morphology, presence of surfactants (such as proteins) and viscosity of the aqueous phase. [Copyright &y& Elsevier]

Reports on the isolation of a no hydrotropic response semi-dominant mutant of Arabidopsis that continued to grow downwardly into the medium with lowest water potential. Dependence of plant survival on the capacity of root tips to sense and move towards water and other nutrients in the soil; Primary site for perception of underground signals; Hydrotropic response of plant roots.

A simple and accurate method for determining the distribution of sizes of single cells and aggregates of Azotobacter vinelandii by image analysis has been developed. A staining procedure using methylene blue helps to enhance the contrast between aggregates and background without altering aggregate size distribution. Sample dilution affected the distribution of the population and therefore should be avoided. Mixing and aeration conditions during culture play an important role in the aggregation of A. vinelandii. Cells grown under mild mixing conditions (unbaffled flasks) presented a thick slime layer and formed aggregates of up to 35 μm of average equivalent diameter. In contrast, under strong agitation conditions (baffled flasks) practically no aggregates were formed throughout cultivation. The method described can be used for the characterization of aggregation of other microbial cultures. [Copyright &y& Elsevier]