Flagella, flagellum

One of the most fascinating recent developments in biology has been the discovery of numerous highly complex biopolymer assemblies (see also section C2.14.2.3) such as the ribosome or the bacterial flagellum [93, 94 and 95], the envy of nanoteclmologists seeking to miniaturize man-made mechanical devices (note that the word machinery is also sometimes used to refer to multienzyme complexes such as the proteasome [96]), and an entire... 

Namba Kand Vonderviszt F 1997 Moleoular arohiteoture of the baoterial flagellum Q. Rev. Blophys. 30 1-65... 

Geissel, /. flagellum, cilium whip, scourge, -farbung, /. (Micros.) flagellum staining, -tierchen, n. (Biol.) flagellate. 

In mammals, ciliated cells line the respiratory air passages, the fallopian tubes, and the ventricles of the brain. The cilia beat in a coordinated manner in waves that propel fluids, suspended cells, and small particles along a surface. The motility of the sperm cell is provided by a single flagellum. 

Figure 2. Electron micrograph of cross section of flagellum of mouse sperm, taken near the tip. The axoneme contains nine outer pairs of doublet microtubules and two central singlet microtubules. Several dynein arms and the fibrous sheath of the sperm are also shown.

An isolated flagellum will continue to bend actively, indicating that this function is linked to its intrinsic structure. Treatment of cilia from the protozoan Tetra-hymena with the proteolytic enzyme trypsin selectively dissolves the nexin links and radial spokes but leaves unaffected the microtubules and dynein arms. If such a preparation is treated with a small amount of ATP, the loosened microtubule doublets slide against each other and through longitudinal overlap, extend for a distance that is up to nine times the original length of the cilium (Warner and Mitchell, 1981). 

Denique causam morbi seu meteori morbosi finalem exprimit ista definitio esse flagellum Dei pro peccates hominum, ita ut si non esset... 

Flagella are threads of protein often 2fim. long which start as small basal organs just beneath the cytoplasmic membrane. They are responsible for the movement of motile bacteria. Their number and distribution varies. Some species bear a single flagellum, others are flagellate over their whole surface. 

Bacterial motion is generally associated with the presence of organs of locomotion known as flagella (singular, flagellum). They were first observed in stained preparations by Cohn. The presence of flagella does not mean necessarily that the organisms are always motile, but it indicates a potential power to move. 

The number and arrangement of flagella vary with different bacteria, but they are generally constant for each species. Some have only one flagellum others have two or more flagella. 

It is an aerobic, gram-negative, nonsporing, rod-shaped bacterium. It is motile with a single polar flagellum. 

Kawai H, Nakamura S, Mimuro M, Furuya M, Watanabe M. Microspectrophotometry of the autofluorescent flagellum in phototactic brown algal zoids. Protoplasma 1996 191 172-177. 

Axons of antennal ORCs project through the antennal nerve to enter the brain at the level of the ipsilateral antennal lobe (AL) of the deutocerebrum (52). ORC axons project from the flagellum to targets in the AL, but axons from antennal mechanosensory neurons bypass the AL and project instead to an "antennal mechanosensory and motor center" in the deutocerebrum posteroventral (with respect to the body axis of the animal) to the AL (52, 58, 64). In moths and certain other insect groups, sex-pheromonal information is processed in a prominent male-specific neuropil structure in each AL called the macroglomerular complex (MGC) (16, 52, 64, 65). 

In reality, clustering may be a useful process for the cells [352], especially if the chemoreceptors are clustered at the leading pole of the cell or where a flagellum locally thins the boundary layer [114]. 

Kuwajima, G., Kawagishi, I., Homma, M., Asaka, J.-I., Kondon, E., and Macnab, R. (1989). Export of an N-terminal fragment of Escherichia coli flagellin by a flagellum-specific pathway. Proc. Natl. Acad. Sd. U.S.A. 86, 4953—4957. 

In spermatozoa, the phosphocreatine shuttle is present to transfer energy from the mitochondria to the flagellum, which is essential for swimming of the sperm (Figure 9.21) (see also Chapter 19). 

Figure 9.21 The creatine/phosphocreatine shuttle in spermatozoa. This shuttle may not be present in all sperm it will depend upon the distance between the mitochondria and the flagellum. Mitochondria are present in the midpiece just below the head. ATP is required for movement of the flagellum which enables the sperm to swim. Dynein ATPase is the specific motor ATPase, similar to myosin ATPase, that transfers energy from ATP to the flagellum. A deficiency of creatine may explain low sperm motility in some infertile men. CK - creatine kinase. Deficiences of enzymes in the pathway for synthesis of creatine are known to occur (see Appendix 8.3).

Figure 9.30 Flow diagram of the energy chain from food to essential processes in human life. The ATP utilised by the NayK ATPase maintains the ion distribution in nerves that is essential for electrical activity and, in addition, maintains neurotransmitter synthesis, both of which provide communication in the brain and hence consciousness, learning and behaviour (Chapter 14). ATP utilisation by myosin ATPase is essential for movement and physical activity. ATP utilisation by the flagellum of sperm is essential for reproduction and ATP utilisation for synthesis of macromolecules is essential for growth.

The spermatozoon consists of a head, a midpiece and a tail or flagellum. The head contains the nucleus and a vesicle known as the acrosome (Figure 19.4). It contains hydrolytic enzymes that are required during fertilisation of the ovum. 

The midpiece contains the mitochondria which are wrapped around the proximal part of the flagellum. The beating of the flagellum, and hence the swimming of the sperm involves the motor protein known as dynein, which requires ATP hydrolysis. In some species, the diffusion of energy in the spermatozoa is increased by the presence of the creatine/phosphocreatine shuttle (Chapter 9) that is, phosphocreatine and creatine diffuse throughout the cytosol... 

Figure 19.18 The role of cyclic GMP and vasodilation in provision and preparation of spermatozoa for fertilisation. Vasodilation is regulated by the concentration of cyclic GMP by relaxation of smooth muscle. The resultant increase in blood flow to the corpora cavernosa results in erection of the penis for the ejaculation of spermatozoa into the vagina. The increase in blood flow to the vaginal smooth muscle provides more oxygen for diffusion into the lumen. Here it provides for oxidative phosphorylation in the mitochondria of the-mid section of the spermatozoa, which provides the ATP for the beating of the flagellum and hence for swimming to the oviduct for fertilisation.

The same considerations hold for another beautiful object, depicted in Figure 5.18 an axoneme, from abacterial flagellum (Stryer, 1975). This is really a... 

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