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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Asymmetrical bending waves can be obtained by reactivating demembranated sea urchin spermatozoa at high Ca2+ concentrations. Moving-film flash photography shows that asymmetrical flagellar bending waves are associated with premature termination of the growth of the bends in one direction (the reverse bends) while the bends in the opposite direction (the principal bends) grow for one full beat cycle, and with unequal rates of growth of principal and reverse bends. The relative proportions of these two components of asymmetry are highly variable. The increased angle in the principal bend is compensated by a decreased angle in the reverse bend, so that there is no change in mean bend angle; the wavelength and beat frequency are also independent of the degree of asymmetry. This new information is still insufficient to identify a particular mechanism for Ca2+-induced asymmetry. When a developing bend stops growing before initiation of growth of a new bend in the same direction, a modification of the sliding between tubules in the distal portion of the flagellum is required. This modification can be described as a superposition of synchronous sliding on the metachronous sliding associated with propagating bending waves. Synchronous sliding is particularly evident in highly asymmetrical flagella, but is probably not the cause of asymmetry. The control of metachronous sliding appears to be unaffected by the superposition of synchronous sliding.
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PMID:Calcium-induced asymmetrical beating of triton-demembranated sea urchin sperm flagella. 47 7

The within-subject variability of the semen sperm count (n), volume (v) and the total number of spermatozoa (N) was studied on 220 ejaculates from 36 normal subjects after an abstinence of 7 days or less. For each of the three variables, the within-subject standard deviation, sigma, was practically proportional to the mean, mu; the common value of the coefficient of variation sigma/mu for all subjects was very high: 0.39 for n, 0.28 for v and 0.55 for N. The 95% confidence intervals based on a single ejaculate were asymmetrical and very large, the lower and upper limits being respectively 0.5 x n and 2.3 x n; 0.7 x v and 1.8 x v; 0.4 x N and 2.9 x N. The three semen characteristics for a given subject were highly correlated with length of abstinence: for an increase in abstinence of 1 day there were mean increments of 13 x 10(6)/ml for n, 0.4 ml for v, and 87 x 10(6) for N.
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PMID:Within-subject variability of human semen in regard to sperm count, volume, total number of spermatozoa and length of abstinence. 51 28

Spermatozoa of the shrew Suncus murinus, a mammal with abdominal testes, exhibit four unusual features: a giant acrosome; a dorsoventral asymmetry of their spermiation; a dorsoventral asymmetry of their head surface character; and also apparent surface maturity as they enter the epididymis. A Sertoli cell-periacrosomal cisternal complex envelops the giant acrosome during spermatid maturation. Spermiation is heraled by asymmetrical disorganization of the subplasmalemmal components of this complex and is completed by retraction of the Sertoli cell from the ventral and then the dorsal face of the spermatid head. This sequence or release is correlated with an asynchronous acquisition of negative surface charges on the spermatid head-demonstrable on glutaraldehyde-stabilized cells by the binding at pH 1.8 of positively charged colloidal particles of ferric oxide. Mature epididymal spermatozoa exhibit an asymmetry in the patterns of distribution of bound colloid over the dorsal vs. ventral surfaces of the sperm head, as well as regional differences between the tail midpiece and principal piece. Surface distributions of anionic residues and lectin (Con A)-binding sites characteristic of mature Suncus spermatozoa are demonstrable within the testis, unlike the situation in most nannals where distinct modifications of the sperm surface occur during epididymal passage.
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PMID:Asymmetry of spermiation and sperm surface charge patterns over the giant acrosome in the musk shrew Suncus murinus. 126 97

In cuttlefish, as in selachians and mammals, spermiogenesis is characterized by the double nuclear protein transition histones----intermediate protein (protein T)----protamine (protein Sp). The cuttlefish protein T, which consists of two structural variants phosphorylated at different degrees, is the first invertebrate spermatid-specific protein to be fully characterized and sequenced. The primary structures of these two variants were established from sequence analysis and mass spectrometric data of the proteins and their fragments. T1 and T2 are two highly related proteins of 78 and 77 residues, respectively, which differ only by four conservative substitutions, two inversions Ser in equilibrium with Arg, and the deletion of 1 residue of arginine in variant T2. The asymmetrical distribution of the hydrophobic and basic residues determines two well defined domains: an amino-terminal domain (residues 1-21) devoid of arginine and aromatic residues and containing all the aliphatic hydrophobic residues and a highly basic carboxyl-terminal domain (residues 22-77 or 78) that contains 77% of arginine, all the tyrosine residues, and most of the phosphorylated serine residues present in the protein. The complete structural identity of the basic carboxyl-terminal domain of spermatidal proteins T1 and T2 with the protamine variants Sp1 and Sp2 isolated from cuttlefish spermatozoa strongly suggests that T1 and T2 could be precursors of Sp1 and Sp2, respectively.
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PMID:Cuttlefish spermatid-specific protein T. Molecular characterization of two variants T1 and T2, putative precursors of sperm protamine variants Sp1 and Sp2. 189 25

The heads of live spermatozoa of the sea urchin Hemicentrotus pulcherrimus were held by suction in the tip of a micropipette mounted on a piezoelectric device and vibrated either laterally or axially with respect to the head axis. Within certain ranges of frequency and amplitude, lateral vibration of the pipette brought about a stable rhythmic beating of the flagella in the plane of vibration, with the beat frequency synchronized to the frequency of vibration [Gibbons et al. (1987), Nature 325, 351-352]. The sperm flagella, with an average natural beat frequency of 48 Hz, showed stable beating synchronized to the pipette vibration over a range of 35-90 Hz when the amplitude of vibration was about 20 microns or greater. Vibration frequencies below this range caused instability of the beat plane, often associated with irregularities in beat frequency. Frequencies above about 90 Hz caused irregular asymmetrical flagellar beating with a marked decrease in amplitude of the propagated bends and a skewing of the flagellar axis towards one side; the flagella often stopped in a cane shape. In flagella that were beating stably under imposed vibration, the wavelength was reduced at higher frequencies and increased at lower frequencies. When the beat frequency was equal to or lower than the natural beat frequency, the apparent time-averaged sliding velocity of axonemal microtubules, obtained as twice the product of frequency and bend angle, decreased with beat frequency in both the proximal and distal regions of the flagella. However, at vibration frequencies above the natural beat frequency, the sliding velocity increased with frequency only in the proximal region of the flagellum and remained essentially unchanged in more distal regions. This apparent limit to the velocity of sliding in the distal region may represent an inherent limit in the intrinsic velocity of active sliding, while the faster sliding observed in the proximal region may be a result of passive sliding or elastic distortion of the microtubules induced by the additional energy supplied by the vibrating pipette. Axial vibration with frequencies either close to or twice the natural beat frequency induced cyclic changes in the waveform, compressing and expanding the bends in the proximal region, but did not affect bends in the distal region or alter the beat frequency.
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PMID:Effect of imposed head vibration on the stability and waveform of flagellar beating in sea urchin spermatozoa. 205 Nov 39

Spermatozoa of several mammalian species were studied by means of high-speed cinematography and electron microscopy. Three types of motile patterns were observed in mouse spermatozoa. The first type involved an asymmetrical beat which seemed to propel the sperm in circular paths. The second type involved rotation of the sperm and appeared to allow them to maintain straight paths. In the third type of pattern, the sperm appeared to move by crawling on surfaces in a snakelike manner. Spermatozoa of rabbit and Chinese hamster also had an asymmetrical beat which sometimes caused them to swim in circles. In spite of the asymmetry of the beat, these spermatozoa were also able to swim in straight paths by rotating around a central axis as they swam. Spermatozoa of some species appeared very flexible; their flagella formed arcs with a very small radius of curvature as they beat. Spermatozoa of other species appeared very stiff, and their flagella formed arcs with a very large radius of curvature. The stiffness of the spermatozoan appeared to correlate positively with the cross-sectional area of the dense fibers. This suggests that the dense fibers may be stiff elastic elements. Opossum sperm become paired as they pass through the epididymis. Pairs of opossum spermatozoa beat in a coordinated, alternating manner.
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PMID:Comparative analysis of mammalian sperm motility. 502 10

The fine structure of hibernating bat spermatozoa (Vesperugo savi and Rinolophus f.e.) has been studied by SEM and TEM, during their prolonged storage in female reproductive tract. The main morphological aspects of sperm portions: head, neck, middle piece, principal piece and terminal piece have been described. The Author besides comparisons with other mammalian species and Chiroptera, suggests some typical ultrastructural features of these Chiroptera, as the complete absence of vacuoles in the nuclear chromatin and corrugated structures in the post-acrosomal zone. Moreover electron-dense material in the subacrosomal space and three mitochondria in the neck were observed. Two areas of fusion between outer dense fibers 3 and 8 and the inner ends of the respective longitudinal columns of the fibrous sheath and asymmetrical arrangement of the outer dense fibers of the principal piece were found.
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PMID:[The fine structure of spermatozoa from Chiroptera]. 624 6

Motility of sperm flagella as well as of cilia is mechanically based on the principle of 9 + 2-tubules. It functions essentially by coordinated action between microtubules and the adenosine-triphosphatase dynein and was already present at the beginning of the evolution of the eucaryotes. Experimentally induced mutations in algae have resulted in numerous variations of the flagellar 9 + 2-structure. A mutation of this kind is also found in man, as immotile cilia syndrome (ICS) where anomalies in spermatozoa and in cilia (e.g. of the respiratory tract) are observed. Clinical manifestations of the syndrome have long been known (chronic bronchitis, bronchiectasis, sinusitis and male sterility). In addition, half of the patients exhibit situs inversus viscerum, known as Kartagener's syndrome, a subgroup of ICS. Electron microscopy was used to investigate sperm flagella with reduced motility from 9 patients (one with ICS) with primary infertility. Cilia of the respiratory tract from 7 patients (several with ICS) with chronic bronchial problems were analyzed for motility (using video techniques) and ultrastructure. Reduced motility or immotility of spermatozoa and immotile or dyskinetic cilia were always accompanied by ultrastructural anomalies. In spermatozoa, lack of dynein arms, 9 + 0-configuration and extratubuli were most frequently observed. The fibrous sheath was always asymmetrical. Structural ciliary defects resulted in non-parallel arrangements, electron dense matrix substance, extratubuli and lack of radial spokes. In one case, ciliary microtubuli were found in microvilli. In two patients, cilia as well as spermatozoa were analyzed. In the first, immotile spermatozoa without dynein arms and structurally normal cilia were observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Sperm flagella and cilia with pathologic motility and ultrastructure]. 650 61

During development membranous organelles first appeared in the primary spermatocytes of Ancylostoma. They were derived from the Golgi as two separate components. One component, an electron-dense spheroid, quickly fused with other newly-formed cup-shaped, membranous structures to form the asymmetrical organelles. Initially the membranous organelles had a homogeneous matrix but later became filled with quantities to 6- 8-nm filaments. Following the meiotic reduction divisions each cell assumed a bipolar configuration. The membranous organelles and mitochondria were confined to the broad anterior region while the non-membrane bound nucleus became located in the narrow posterior region. Golgi membranes, endoplasmic reticulum, and numerous ribosomes were sloughed from the main cell body. The filaments lost their association with the membranous organelles and attached to the plasma membrane while the membranous portion of each organelle became progressively more complex and assumed a peripheral position in the cytoplasm. The resulting spermatid, with its condensed, posteriorly-projected nucleus, and broad anterior cytoplasm, had a tadpolelike appearance. Subsequent to deposition in the female uterus the membranous organelles fused with the plasma membrane and the mature spermatozoa became pleomorphic and moved in an ameboid manner. Because the pseudopods in the mature cell originated in those areas where the filaments previously attached to the plasma membrane it is surmised that the filaments consist of, or contain, actin. The significance of the fusion of the membranous organelles with the sperm plasma membrane, however, remains unknown.
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PMID:Development and fate of the membranous organelles in spermatozoa of Ancylostoma caninum. 713 Nov 88

The heads of demembranated spermatozoa of the sea urchin Tripneustes gratilla, reactivated at different concentrations of ATP, were held by suction in the tip of a micropipette and vibrated laterally with respect to the head axis. This imposed vibration resulted in a stable rhythmic beating of the reactivated flagella that was synchronized to the frequency of the micropipette. The reactivated flagella, which in the absence of imposed vibration had an average beat frequency of 39 Hz at 2 mmol l-1 ATP, showed stable beating synchronized to the pipette vibration over a range of 20-70 Hz. Vibration frequencies above 70 Hz caused irregular, asymmetrical beating, while those below 20 Hz induced instability of the beat plane. At ATP concentrations of 10-100 mumol l-1, the range of vibration frequency capable of maintaining stable beating was diminished; an increase in ATP concentration above 2 mmol l-1 had no effect on the range of stable beating. In flagella reactivated at ATP concentrations above 100 mumol l-1, the apparent time-averaged sliding velocity of axonemal microtubules decreased when the imposed frequency was below the undriven flagellar beat frequency, but at higher imposed frequencies it remained constant, with the higher frequency being accompanied by a decrease in bend angle. This maximal sliding velocity at 2 mmol l-1 ATP was close to the sliding velocity in the distal region of live spermatozoa, possibly indicating that it represents an inherent limit in the velocity of active sliding.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of beat frequency on the velocity of microtubule sliding in reactivated sea urchin sperm flagella under imposed head vibration. 771 54


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