Beating Patterns of Mammalian Spermatozoa
Claude Gagnon in Controls of Sperm Motility, 2020
Golden hamster spermatozoa beat with an asymmetrical waveform and a slender beat envelope as shown in Figure 1d. The flagellar movement was almost planar when it was observed with an ordinary light microscope from a direction parallel to the beating plane.9 Woolley,33,47 however, has proposed the twisted-plane waveform (the direction of the twist is clockwise as viewed from the proximal end of the flagellum) with the torsions restricted to the interbend segments by examining the spermatozoa in an electron microscope after rapid fixation. According to him, the displacement between a first bend and a second is approximately 6 to 13 μm. Thus, it might be possible to detect this distance by careful examination of the flagellar movement using a conventional light microscope as well.
Infertility Diagnosis and Treatment
Sujoy K. Guba in Bioengineering in Reproductive Medicine, 2020
Movement of flagellar organisms has interested scientists for long. Spermatozoa too has been a subject of study.1 Initially the purpose was mainly to understand how linear progression could be obtained out of the wavelike motion of the tail. Later on spermatozoa motion was linked to the transport within the male and female reproductive tracts. More recently major research impetus in the area has come about on account of the demonstrated value of motility assessment in identifying causes of male infertility and in its management. Spermatozoa motility studies have gone beyond the research laboratories to the clinical centers. Not only the motion of spermatozoa in its natural environment of the seminal fluid is examined, but also the penetration into the cervical mucus is observed.2 So it is now imperative to have appropriate techniques which not only can provide all the details of the motion objectively and accurately but also rapidly in a cost-effective manner.
Giardia
Dongyou Liu in Handbook of Foodborne Diseases, 2018
Members of the Giardia genus have a simple, direct life cycle comprising two biological and morphological differentiated stages, the trophozoite and the cyst (Figure 57.1). Giardia is considered as a primitive eukaryote because of the absence of several organelles, and is a model for evolutionary studies.17 As reviewed previously,5,18 trophozoites contain two nuclei positioned anteriorly that are transcriptionally active and surrounded by nuclear envelopes. They also have a complex cytoskeleton to maintain their shape and anchor the four pairs of flagella that behave differently during motility,19 the median body, and the ventral disk (Figure 57.1a). Flagella are composed of microtubules (eukaryotic 9 + 2 arrangement) and are built from basal bodies located between the nuclei. The median bodies, formed by an irregular set of microtubules, have a comma-shaped structure that varies in size and thickness, and are located transversally, perpendicular to the central axis. Morphological differentiation of Giardia species can be achieved by light and electron microscopy examination of the median bodies.5,18 In the zoonotic species G. duodenalis, the trophozoite is a pear-shaped cell about 12–15 μm long, 6–8 μm wide, and 1–2 μm thick. Median bodies may serve as a reserve of microtubules or in the biogenesis of the ventral disk.
Regulation of flagellar motility and biosynthesis in enterohemorrhagic Escherichia coli O157:H7
Published in Gut Microbes, 2022
Hongmin Sun, Min Wang, Yutao Liu, Pan Wu, Ting Yao, Wen Yang, Qian Yang, Jun Yan, Bin Yang
The bacterial flagellum is a macromolecular machine that consists of a basal body (rotary motor), a hook (universal joint), and a filament (propeller).8 Flagellar-mediated motility confers an important advantage for bacteria in moving toward favorable conditions or in avoiding detrimental environments and allows bacteria to pursue nutrients and to reach and maintain their preferred niches for survival.9 In addition to having locomotive properties, flagellum-mediated motility plays diverse roles in the pathogenesis and progression of EHEC O157:H7 infection. Upon entering the host intestine, EHEC O157:H7 relies on flagellum-mediated motility to reach and adhere to optimal colonization sites in the host.10 Subsequently, EHEC O157:H7 inhibits flagellar biosynthesis to save energy and minimize host immunity (Figure 1).10
Effect of Tagetes minuta oil on larval morphology of Plutella xylostella through scanning electron microscopy and mechanism of action by enzyme assay
Published in Toxin Reviews, 2022
Shudh Kirti Dolma, C. S. Jayaram, Nandita Chauhan, S. G. Eswara Reddy
After 24 h of treatment, setae of thoracic leg initiated to deform followed by rudimentary growth of thoracic leg and extra cuticular growth observed on thoracic legs which are modified into slender and elongated. Initially, the larvae treated with T. minuta oil showed shattering of crochets in pro-legs followed by separation of fleshy two segments of prolegs (planta). Later (72 h), legs of the cuticle initiated to lose granulation and third segment of the proleg were separated. After 96 h of treatment, granulation of the cuticle is fully crumbled and the first pair of the pro-leg is broken. Seta modified into clubbed/globose shaped after 24 h and then broken from the tip (48 h). The clubbed seta has swollen to a higher extent and left with broken bloated seta (after 72 h) and finally, setae fragmented from the hair socket. Similar setal modifications in the vicinity of stemmata, posterior abdominal segments, and ventral part of the mouthparts were also observed. In a similar study, significant deformation was observed on antennal segments after 96 h of treatment. In the flagellum, deformation seen in third flagellar segment which presented filamentous and knotted (Jayaram et al. 2020).
A bacterial polysaccharide biosynthesis-related gene inversely regulates larval settlement and metamorphosis of Mytilus coruscus
Published in Biofouling, 2020
Li-Hua Peng, Xiao Liang, Rui-Heng Chang, Jia-Yi Mu, Hui-E Chen, Asami Yoshida, Kiyoshi Osatomi, Jin-Long Yang
BF formation has reversible and irreversible stages (Dunne 2002; Schlapp et al. 2011). In the reversible stage, flagellum-driven motility is essential for cell adhesion to a surface and low flagellar motility promotes better BF formation (Hoffman et al. 2015). Here, the BFs of Δ01912 had higher bacterial densities. A possible reason is that the decrease in bacterial motility caused more attachment to the glass slide surface during the reversible stage (Figure 6). Polysaccharides also could tether bacterial cells to the surface and help to form a stable BF structure in the irreversible stage of BF formation ( Limoli et al. 2015). Thus, the CA overproduction increased the adhesion of P. marina during the permanent adhesion stage. Moreover, CA contributed to the spatial arrangement of cells on BFs (Prigent-Combaret et al. 2000), which explain why the bacterial cells on Δ01912 BFs were distributed more uniformly than wild-type BFs.
Related Knowledge Centers
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