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1.
Positive selection is a general phenomenon in the evolution of abalone sperm lysin 总被引:36,自引:21,他引:15
Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole
in the egg vitelline envelope (VE). The interaction of lysin with the VE is
species-selective and is one step in the multistep fertilization process
that restricts heterospecific (cross-species) fertilization. For this
reason, the evolution of lysin could play a role in establishing prezygotic
reproductive isolation between species. Previously, we sequenced sperm
lysin cDNAs from seven California abalone species and showed that positive
Darwinian selection promotes their divergence. In this paper an additional
13 lysin sequences are presented representing species from Japan, Taiwan,
Australia, New Zealand, South Africa, and Europe. The total of 20 sequences
represents the most extensive analysis of a fertilization protein to date.
The phylogenetic analysis divides the sequences into two major clades, one
composed of species from the northern Pacific (California and Japan) and
the other composed of species from other parts of the world. Analysis of
nucleotide substitution demonstrates that positive selection is a general
process in the evolution of this fertilization protein. Analysis of
nucleotide and codon usage bias shows that neither parameter can account
for the robust data supporting positive selection. The selection pressure
responsible for the positive selection on lysin remains unknown.
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2.
Dorofeev IIu Avelev VD Shcherbakova NA Gerasimenko IuP 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2007,93(10):1112-1122
The role of hindpaw skin afferent input in the locomotor pattern formation induced by epidural spinal cord stimulation was investigated in decerebrated cats. Locomotor activity was evoked by continuous 3-5Hz stimulation of dorsal surface of L4-L5 spinal segments. Kinematic and electromyographic activity (EMG) of m. Quadriceps, m. Semitendinosus, m. Tibialis anterior an m. Gastrocnemius lateralis before and after blocking of skin receptors in one hind limb were recorded. In addition, reflex responses in the hind limb muscles to epidural stimulation with frequency 0.5 Hz were analysed. Blocking of skin receptors of the foot with chlorothane paw irrigation or 2 % lidocaine administrated into the hind paw was performed. After blocking of skin receptors of the foot the stepping pattern changed. Stepping with dorsal foot placement and dragging during swing phase was observed. Duration of stance phase significantly decreased. Inhibition of polysynaptic activity of proximal and distal extensor muscles and distal flexor muscles of hind paw during locomotion was found. Monosynaptic responses after blocking of skin receptors of the foot changed insignificantly. 相似文献
3.
The effects of segmental reflexes on descending intersegmental reflexes to stimulation of forelimb afferents were studied in anesthetized cats by recording postsynaptic responses from single motoneurons. Interaction between these influences was found to be reciprocal in character for groups of neurons with primary connections with afferents of the superficial and deep branches of the peroneal nerve and afferents of the nerve to the gastrocnemius muscle. Excitatory postsynaptic responses arising in groups of motoneurons of the peroneal nerve to stimulation of forelimb afferents underwent profound and prolonged inhibition during conditioning stimulation of afferents in the deep and superficial peroneal nerves. Activation of segmental afferents during conditioning stimulation of the gastrocnemius nerve was accompanied by inhibition of excitatory intersegmental responses and deinhibition of inhibitory responses in motoneurons of the gastrocnemius muscle. Segmental inhibition of intersegmental descending impulse activity appeared in the interneuron system of the segmental reflex centers connecting the descending propriospinal tracts with the motoneurons of these centers.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 16872-175, March–April, 1972. 相似文献
4.
Kumar S Jain S Behari J Avelev VD Mathur R 《Indian journal of experimental biology》2010,48(10):982-986
Chronic (2 h/d x 8 weeks) exposure to magnetic field (MF; 50 Hz, 17.9 microT) in complete spinal cord (T13) transected rats restored food intake (FI), water intake (WI) and body weight (BW) which were decreased in the spinal cord injured rats. The results suggest a significant beneficial effect of chronic exposure to magnetic field of paraplegic rats. 相似文献
5.
Mitochondrial DNA and bindin gene sequence evolution among allopatric species of the sea urchin genus Arbacia 总被引:3,自引:1,他引:2
Sea urchins of the genus Arbacia (order Stirodonta) have discontinuous
allopatric distributions ranging over thousands of kilometers.
Mitochondrial DNA (mtDNA) sequences were used to reconstruct phylogenetic
relationships of four Arbacia species and their geographic populations.
There is little evidence of genetic structuring of populations within
species, except in two cases at range extremes. The mtDNA sequence
differentiation between species suggests that divergence occurred about 4-9
MYA. Gene sequences encoding the sperm protein bindin and its intron were
obtained and compared with the mtDNA phylogeny. Sea urchins among the
well-studied echinoid order Camarodonta, with degrees of mtDNA divergence
similar to those of Arbacia species, are known to have remarkable variation
in bindin. However, in Arbacia, little variation in deduced amino acid
sequences of bindin was found, indicating that purifying selection acts on
the protein. In contrast, bindin intron sequences showed much
differentiation, including numerous insertion/deletions. Fertilization
experiments performed between a divergent pair of Arbacia species from the
Atlantic and Pacific Oceans revealed no evidence of blocks to gamete
recognition. In Arbacia, fertilization specificities may have evolved
relatively slowly as a result of extensive gene flow within species,
greater functional constraint on the bindin polypeptide, or reduced
selective pressure for species recognition in singly occurring species.
相似文献
6.
Females of the sea urchin Strongylocentrotus purpuratus differ in the structures of their egg jelly sulfated fucans 总被引:1,自引:0,他引:1
The egg jelly coats of sea urchins contain sulfated fucans which bind to a
sperm surface receptor glycoprotein to initiate the signal transduction
events resulting in the sperm acrosome reaction. The acrosome reaction is
an ion channel regulated exocytosis which is an obligatory event for sperm
binding to, and fusion with, the egg. Approximately 90% of individual
females of the sea urchin Strongylocentrotus purpuratus spawned eggs having
only one of two possible sulfated fucan electrophoretic isotypes, a slow
migrating (sulfated fucan I), or a fast migrating (sulfated fucan II)
isotype. The remaining 10% of females spawned eggs having both sulfated
fucan isotypes. The two sulfated fucan isotypes were purified from egg
jelly coats and their structures determined by NMR spectroscopy and
methylation analysis. Both sulfated fucans are linear polysaccharides
composed of 1-->3-linked alpha-L-fucopyranosyl units. Sulfated fucan I
is entirely sulfated at the O -2 position but with a heterogeneous
sulfation pattern at O -4 position. Sulfated fucan II is composed of a
regular repeating sequence of 3 residues, as follows: [3-alpha-L-Fuc p -
2,4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-
1]n. Both purified sulfated fucans have approximately equal potency in
inducing the sperm acrosome reaction. The significance of two structurally
different sulfated fucans in the egg jelly coat of this species could
relate to the finding that the sperm receptor protein which binds sulfated
fucan contains two carbohydrate recognition modules of the C-type lectin
variety which differ by 50% in their primary structure.
相似文献
7.
During recording of impulse activity from single nerve fibers of electroreceptors of the ampullae of Lorenzini of skates, we studied the responses to electromagnetic radiation (EMR) at a frequency of 37–55 GHz and an intensity of 1–100 mW/cm2.Exposure of the ampullar canal pore to EMR at an intensity of 1–5 mW/cm2 and a distance of 1–10 mm evoked a transient increase in the frequency of low-threshold receptor activity (current threshold was 0.04–0.2 µA). An increase in EMR intensity by more than 8–10 mW/cm2 produced, together with elevation of receptor activity, an inhibition due to a rise in temperature of 1–3°C in the region exposed. The phase of increase in frequency of activity was absent in high current-threshold receptors (0.3–2.0 µA) when exposed to EMR. The receptors responded to irradiation of the ampullar canal pore at a distance of 15–20 mm by an increase in discharge frequency for 20 min. Direct irradiation of the ampullae of Lorenzini induced only inhibitory responses in receptor cells regardless of their excitability.The results obtained indicate that the sensory receptors of vertebrates are sensitive to EMR. It is concluded that the excitatory effects are due to direct reception of EMR by electroreceptors, and the inhibitory effects are related to local heating of the Lorenzini ampullar pore.Neirofiziologiya/Neurophysiology, Vol. 25, No. 5, pp. 325–329, September–October, 1993. 相似文献
8.
Iu P Gerasimenko V D Avelev O A Nikitin I A Lavrov 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2001,87(9):1161-1170
An area initiating locomotor activity under conditions of the spinal cord surface stimulation (SCS) was found at the upper border of the lumbar enlargement (L4-5 spinal segments). Parameters of the SCS for activation of the spinal stepping generator (SSG) were identified. Activation of the SSG under the SCS was shown to occur because of interaction of the spinal and peripheral mechanisms. Primary role in the SSG initiation during the SCS belongs to the propriospinal system of the dorsolateral funiculi. 相似文献
9.
Clinically effective modalities of treatment for spinal cord injury (SCI) still remain unsatisfactory and are largely invasive in nature. There are reports of accelerated regeneration in injured peripheral nerves by extremely low-frequency pulsed electromagnetic field (ELF-EMF) in the rat. In the present study, the effect of (50?Hz), low-intensity (17.96 μT) magnetic field (MF) exposure of rats after-hemisection of T13 spinal cord (hSCI) was investigated on sensori-motor and locomotor functions. Rats were divided into hSCI (sham-exposed) and hSCI+MF (MF: 2?h/d X 6 weeks) groups. Besides their general conditions, locomotor function by Basso, Beattie, and Brenahan (BBB) score; motor responses to noxious stimuli by threshold of tail flick (TTF), simple vocalization (TSV), tail flick latency (TFL), and neuronal excitability by H-reflex were noted. It is found that, in the hSCI+MF group, a statistically significant improvement over the hSCI control group was noted in BBB score from post-SCI wk2 and TFL and TTF by post-hSCI wk1 and wk3, respectively. Correspondingly, TSV gradually restored by post-hSCI wk5.The threshold of H-reflex was reduced on ipsilateral side vs. contralateral side in hSCI and hSCI+MF group. A complete bladder control was dramatically restored on post-hSCI day4 (vs. day7 of hSCI group) and the survival rate was 100% in the hSCI+MF group (vs. 90% of hSCI group). The results of our study suggest that extremely low-frequency (50?Hz), low-intensity (17.96 μT) MF exposure for 2?h/d x 6wks promotes recovery of sensori-motor behavior including locomotion and bladder control both in terms of temporal pattern and magnitude in hemisection injury of (T13) spinal cord rats. 相似文献
10.
L. I. Kolosova G. N. Akoev V. D. Avelev O. V. Ryabchikova K. S. Babu 《Neurophysiology》1993,25(1):22-25
The effect of millimeter-band electromagnetic radiation of low intensity on the regeneration of the sciatic nerve was studied in experiments conducted on rats. The restoration of the functional properties of the nerve following its section and microsurgical suturing was investigated. It was established that irradiation of the site of operation stimulates the growth of nerve fibers and increases the conduction velocity of action potentials along the regenerating nerve.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 27–31, January–February, 1993. 相似文献