Activation currents, sperm entry and surface contractions in ascidian eggs

Zygote ◽  
1993 ◽  
Vol 1 (2) ◽  
pp. 113-119 ◽  
Author(s):  
C. Pecorella ◽  
E. Tosti ◽  
K. Kyozuka ◽  
B. Dale
Keyword(s):  
Sperm Nucleus ◽  
Initial Slope ◽  
Ostrea Edulis ◽  
Sperm Entry ◽  
Large Conductance Channel ◽  
Vegetal Pole ◽  
Inward Currents ◽  
The Mean ◽  
Contraction Wave ◽  
Surface Generate

SummarySpermatozoa from the mollusc Ostrea edulis are capable of fusing to and entering de-chorionated ascidian eggs. During interaction they generate activation currents, comparable to the fertilisation currents induced by homologous spermatozoa. Activation currents are inward at − 80 mV, with a mean initial slope of 111 ± 124 pA/s for Ciona intestinalis eggs and 47 ± 25 pA/s for Phallusia mammillata eggs, while the mean peak currents are 2782 ± 1132 pA and 1523 ± 1668 pA, respectively. The fertilisation and activation currents reverse at a holding potential of 0 mV to + 20 mV, suggesting that oyster sperm and ascidian sperm gate the same channel precursor, a non-specific, large conductance channel described previously (Dale & DeFelice, 1984). In contrast to homologous fertilisation, the activation current is not followed by a polarised contraction of the egg surface, nor other signs of egg activation. Staining eggs with Hoechst 33342 after insemination shows the female nucleus and a single oyster sperm nucleus at the antipode. This suggests a specialised predetermined site at the vegetal pole for sperm entry. Homologous and heterologous spermatozoa delivered, in a large pipette, to localised areas of the egg surface generate fast inward currents of 200–2000 pA, but do not induce contraction of the egg surface. This shows that although channel precursors are located globally over the egg surface, channel activation does not necessarily trigger the contraction wave. Subsequent induction of both a fertilisation current and a contraction by homologous sperm added to the bath, implies a regionalised activation site with an accumulation of channel precursors and a ‘pacemaker’ for the initiation of the contraction wave.

The sperm entry point defines the orientation of the calcium-induced contraction wave that directs the first phase of cytoplasmic reorganization in the ascidian egg

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3457-3466 ◽  
Author(s):  
F. Roegiers ◽  
A. McDougall ◽  
C. Sardet
Keyword(s):  
Sperm Nucleus ◽  
Cytoplasmic Domains ◽  
Dorsoventral Axis ◽  
Rich Domain ◽  
Sperm Entry ◽  
Vegetal Pole ◽  
Ooplasmic Segregation ◽  
The Relationship ◽  
Ascidian Embryo ◽  
Contraction Wave

Ascidians eggs are spawned with their cytoskeleton and organelles organized along a preexisting animal-vegetal axis. Fertilization triggers a spectacular microfilament-dependant cortical contraction that causes the relocalization of preexisting cytoplasmic domains and the creation of new domains in the lower part of the vegetal hemisphere. We have investigated the relationship between fertilization, the cortical contraction and the localization of cytoplasmic domains in eggs of the ascidian Phallusia mammillata. We have also examined the link between this first phase of ooplasmic segregation and the site of gastrulation. The cortical contraction was found to be initiated on the side of the egg where intracellular calcium is first released either by the entering sperm or by photolysis of caged InsP3. The cortical contraction carries the sperm nucleus towards the vegetal hemisphere along with a subcortical mitochondria-rich domain (the myoplasm). If the sperm enters close to the animal or vegetal poles the cortical contraction is symmetrical, travelling along the animal-vegetal axis. If the sperm enters closer to the equator, the contraction is asymmetrical and its direction does not coincide with the animal-vegetal axis. The direction of contraction defines an axis along which preexisting (such as the myoplasm) or newly created cytoplasmic domains are relocalized. Two microfilament-rich surface constrictions, the ‘contraction pole’ and the ‘vegetal button’ (which forms 20 minutes later), appear along that axis approximately opposite the site where the contraction is initiated. The contraction pole can be situated as much as 55 degrees from the vegetal pole, and its location predicts the site of gastrulation. It thus appears that in ascidian eggs, the organization of the egg before fertilization defines a 110 degrees cone centered around the vegetal pole in which the future site of gastrulation of the embryo will lie. The calcium wave and cortical contraction triggered by the entering sperm adjust the location of cytoplasmic domains along an axis within that permissive zone. We discuss the relation between that axis and the establishment of the dorsoventral axis in the ascidian embryo.

scholarly journals The activation wave of calcium in the ascidian egg and its role in ooplasmic segregation.

1990 ◽  
Vol 110 (5) ◽  
pp. 1589-1598 ◽  
Author(s):  
J E Speksnijder ◽  
C Sardet ◽  
L F Jaffe
Keyword(s):  
Imaging System ◽  
Sperm Nucleus ◽  
Calcium Wave ◽  
Free Calcium ◽  
S Wave ◽  
Animal Pole ◽  
Calcium Dependent ◽  
Sperm Entry ◽  
Vegetal Pole ◽  
Ooplasmic Segregation

We have studied egg activation and ooplasmic segregation in the ascidian Phallusia mammillata using an imaging system that let us simultaneously monitor egg morphology and calcium-dependent aequorin luminescence. After insemination, a wave of highly elevated free calcium crosses the egg with a peak velocity of 8-9 microns/s. A similar wave is seen in egg fertilized in the absence of external calcium. Artificial activation via incubation with WGA also results in a calcium wave, albeit with different temporal and spatial characteristics than in sperm-activated eggs. In eggs in which movement of the sperm nucleus after entry is blocked with cytochalasin D, the sperm aster is formed at the site where the calcium wave had previously started. This indicates that the calcium wave starts where the sperm enters. In 70% of the eggs, the calcium wave starts in the animal hemisphere, which confirms previous observations that there is a preference for sperm to enter this part of the egg (Speksnijder, J. E., L. F. Jaffe, and C. Sardet. 1989. Dev. Biol. 133:180-184). About 30-40 s after the calcium wave starts, a slower (1.4 microns/s) wave of cortical contraction starts near the animal pole. It carries the subcortical cytoplasm to a contraction pole, which forms away from the side of sperm entry and up to 50 degrees away from the vegetal pole. We propose that the point of sperm entry may affect the direction of ooplasmic segregation by causing it to tilt away from the vegetal pole, presumably via some action of the calcium wave.

Preservation of left ventricular function by insulin in experimental catecholamine cardiomyopathy

1980 ◽  
Vol 238 (2) ◽  
pp. H257-H262
Author(s):  
J. C. Werner ◽  
J. C. Lee ◽  
S. E. Downing
Keyword(s):  
Left Ventricular Function ◽  
Ventricular Function ◽  
Myocardial Injury ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Initial Slope ◽  
Histological Findings ◽  
Aortic Constriction ◽  
The Mean ◽  
Lv Volume

We have shown previously that insulin reduces myocardial injury associated with norepinephrine (NE) infusion in the rabbit (Am. J. Pathol. 93:399--353, 1978). In the present study, left ventricular function (LVF) was assessed from afterload curves obtained by progressive aortic constriction 2--4 days following NE infusion. The initial slope of the function curves (SFC), maximum dP/dt and left ventricular end-diastolic pressure at 120 mmHg ((LVEDP120) were used for comparison. In 4 controls, SFC averaged 23.8 mmHg/cmH2O. In 10 rabbits given NE, the mean slope was 8.4 (P less than 0.01). However, animals pretreated with insulin before being given NE did not differ from controls (SFC, 19.7 mmHg/cmH2O). These performance data were supported by measurements of LVEDP120, which were 2.8, 12.3 and 3.1 cmH2O, respectively (P less than 0.05 and less than 0.02). In spite of the higher LVEDP, max dP/dt120 was significantly lower in the NE group than in the group given insulin. Histological findings and postmortem measurements of LV volume and mass were consistent with the observed differences in LVF. It is concluded that NE damage reduces LVF and this is largely prevented by pretreatment with insulin.

Clinical Use of a Portable Bedside Cerebral Blood Flow Machine in the Management of Aneurysmal Subarachnoid Hemorrhage

Neurosurgery ◽  
1984 ◽  
Vol 15 (4) ◽  
pp. 519-525 ◽  
Author(s):  
Jacob Rosenstein ◽  
Mikio Suzuki ◽  
Lindsay Symon ◽  
Sheila Redmond
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Subarachnoid Hemorrhage ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Initial Slope ◽  
Management Decision ◽  
Mean Flow ◽  
Management Decision Making ◽  
Acute Subarachnoid Hemorrhage ◽  
The Mean

Abstract Recent advances in electronics and microprocessors have enabled the development of a compact portable cerebral blood flow (CBF) machine capable of being transported to the patient's bedside. We have used such a device, the Novo Cerebrograph 2a, during the past 7 months on a regular basis in the day to day management of our patients with intracranial aneurysms. One hundred three studies were performed in 23 cases of suspected intracranial aneurysm. Twenty-two cases presented with acute subarachnoid hemorrhage. Patients were studied on admission, preoperatively, in the recovery room, on postoperative Days 1, 5, and 14, and whenever the clinical condition of the patient warranted. The preoperative admission grade was found to correlate well with the mean CBFisi (ISI: initial slope index). Grade III and IV patients had flows significantly lower than those of Grade I and II patients. Serial CBF measurements proved useful in the management of 18 of 22 cases admitted with acute subarachnoid hemorrhage. Delayed ischemic deficits secondary to vasospasm occurred in 6 cases, with a concomitant average fall in mean flow in the symptomatic hemispheres of 27.9%. After volume expansion, an average increase in flow of 29.7% was noted. Low preoperative flows influenced management decision-making in 8 cases. In a further 4 cases, serial CBF measurements were helpful in the differential diagnosis of new neurological signs.

scholarly journals Influence of parentage upon growth in Ostrea edulis: evidence for inbreeding depression

2000 ◽  
Vol 76 (2) ◽  
pp. 159-168 ◽  
Author(s):  
YAMAMA NACIRI-GRAVEN ◽  
SOPHIE LAUNEY ◽  
NICOLAS LEBAYON ◽  
ANDRE GERARD ◽  
JEAN-PIERRE BAUD
Keyword(s):  
Inbreeding Depression ◽  
Genetic Relatedness ◽  
Protozoan Parasite ◽  
Control Population ◽  
Ostrea Edulis ◽  
The Family ◽  
Bonamia Ostreae ◽  
Sib Families ◽  
The Mean ◽  
Selection For

Genetic variability for growth was analysed in three populations of Ostrea edulis, selected for resistance to the protozoan parasite Bonamia ostreae. This study was undertaken first to determine the potential for selection for growth in populations that have never been selected for this character, and second to estimate heterosis versus inbreeding depression. Growth was monitored in culture for 10 months. The selected populations (namely S85-G3, S89I-G2 and S89W-G2), their crossbred population and a control population were composed of full-sib families whose parents were already genotyped using five microsatellite markers. This genotyping allowed the estimation of genetic relatedness among pairs of parents. The parents' relatedness was then correlated with the growth performance of their offspring within each of the three populations, and inbreeding depression was estimated. The population effect for growth was highly significant, with the crossbred population having the highest growth rate, followed by S89I-G2 and S89W-G2, S85-G3 and the control population. The within-populations family effect was also highly significant, indicating, as well as the high value for heritability at the family level (between 0·57 and 0·92), that a potential for a further selection for growth still exists within the three populations. Estimates of inbreeding depression (relative to the mean, for complete inbreeding) were high (1 for S891-G2, 0·44 for S89W-G2 and between 0·02 and 0·43 for S85-G3), which correlates with the apparent heterosis for growth observed in the crossbred population. These results are discussed in the context of the future management of the selected populations.

Augmentation of Cerebral Blood Flow Induced by Hemodilution in Stroke Patients after Superficial Temporal-Middle Cerebral Arterial Bypass Operation

Neurosurgery ◽  
1984 ◽  
Vol 15 (4) ◽  
pp. 535-539 ◽  
Author(s):  
James H. Wood ◽  
Konstantinos S. Polyzoidis ◽  
David B. Kee ◽  
Antonio R. Prats ◽  
Gordon L. Gibby ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebral Perfusion ◽  
Brain Regions ◽  
Initial Slope ◽  
Homologous Region ◽  
Stroke Patients ◽  
Ischemic Brain ◽  
Bypass Patency ◽  
The Mean

Abstract Experimental hemodilutional therapy has been shown to raise collateral perfusion to acutely ischemic brain regions distal to occluded internal carotid (ICA) and middle cerebral (MCA) arteries and to reduce infarct size. Superficial temporal (STA)-MCA anastomosis surgically establishes additional regional collateralization, and this bypass angiographically enlarges over time. Despite bypass patency verification by Doppler recording made at the edge of the craniectomy, the microsurgical STA-MCA anastomosis in 11 stroke patients did not produce early changes in cerebral perfusion parameters in the MCA territory of either hemisphere as determined by 133xenon inhalation. Therefore, hemodilution was initiated in an effort to increase cerebral perfusion during this marginal period when the STA was beginning to dilate progressively. Incremental venesections with equal intravenous volume replacement with 5% human serum albumin caused a significant lowering of the hematocrit from 40 ± 1 to 33 ± 1%. This isovolemic hemodilutional therapy resulted in significant mean regional cerebral blood flow (rCBF) elevations of 23 ± 5% (SE) in the bypassed MCA territory and of 25 ± 6% in the opposite MCA region. The mean gray flow (F1) in the involved and homologous MCA regions significantly increased 27 ± 8% and 30 ± 11%, respectively. Similarly, the initial slope index (ISI2) significantly rose by 17 ± 5% in the bypassed MCA territory and by 18 ± 6% in the homologous region. These data objectively support the premise that reductions in hematocrit without intravascular volume expansion augment cerebral blood flow, probably by reducing blood viscosity. Moreover, inovolemic hemodilution, the effect of which lasts several weeks, may be useful adjunct therapy for the postoperative care of patients with marginal cerebral circulation who undergo cerebral revascularization.

Fertilization of immature frog eggs: cleavage and development following subsequent activation

Development ◽  
1977 ◽  
Vol 37 (1) ◽  
pp. 187-201
Author(s):  
Richard P. Elinson
Keyword(s):  
Sperm Nucleus ◽  
Sperm Entry ◽  
The Difference ◽  
Subsequent Activation

Frog eggs are normally fertilized after reaching metaphase II. When eggs are inseminated prior to that, several sperm enter, but entry does not activate the egg. When such inseminated, immature eggs were maintained until they became mature and then were artificially activated, the eggs began to cleave. The cleavage furrows were irregular and often multiple, but the eggs developed to blastulae or partial blastulae. About 2 → 5% of the eggs developed to tadpoles. Typical asters were not associated with the entering sperm; rather, asters appeared only after activation. The sperm nucleus often formed chromosomes which were attached to small spindles. It is clear that sperm which remain for a time in unactivated egg cytoplasm, retain their ability to promote cleavage and development. Aster formation required not only sperm centrioles but also activated egg cytoplasm. Sperm which entered either near the equator or in the animal half of mature eggs usually produced normal cleavage furrows. Sperm which entered the animal half of immature eggs produced multiple animal half furrows when the egg was subsequently activated. In contrast, sperm which entered near the equator of immature eggs often failed to induce furrowing on subsequent activation or produced unusual equatorial furrows. The difference in the type of furrow between eggs inseminated in the animal half or at the equator is interpreted as a consequence of dissociating sperm entry from the cortical contraction which occurs on activation.

A sedimentation study of gel systems

1964 ◽  
Vol 278 (1375) ◽  
pp. 527-542 ◽  
Keyword(s):  
Induction Period ◽  
Time Lag ◽  
Swelling Pressure ◽  
Initial Slope ◽  
Agar Gel ◽  
True Solution ◽  
Gelatin Gels ◽  
The Mean ◽  
Centre Of Rotation ◽  
Limiting Value

When an agar gel was subjected to a high centrifugal field, a well-defined gel/solvent in terface formed, and moved in the direction of the field, sometimes with a self-sharpening effect. Little non-gelling solute occurred. At high centrifugal fields, there was no observable time lag between application of the field and motion of the boundary. A plot of log x against t ( x being distance of the interface from the centre of rotation and t the time) was almost linear initially but the slope decreased progressively and the curve approached a well-defined limiting value log x ∞ appropriate to the field and initial concentration. This behaviour is probably due to the continuously increasing gel concentration which is caused as the gelling solute is confined to a progressively smaller volume between the gel interface and the bottom of the cell. When no further motion occurs, equilibrium has been attained, a tall levels of the cell, between the partial hydrostatic pressure involved and the swelling pressure of the gels. At low fields, a considerable time lag (induction period), observed between application of the field and motion of the boundary, probably indicates the need for a considerable break ­ down of structure before flow can occur. A plot of initial slope (d log x /d t ) against the square of the rotational speed is linear within experimental error and passes through the origin. The yield point for gels may be associated with the occurrence of the induction period. On the basis of a crude lattice model, the mean pore size for a 1 % agar gel was calculated to be 70 to 100 Å, in fair agreement with previous estimates. Gelatin gels behave similarly to agar in the general features of the curves of log x against t but a much higher proportion of gelatin is observable in true solution (30 to 40% ), sedimenting more slowly than the gel interface.

Vasospasm and Regional Cerebral Blood Flow (rCBF) in Patients with Ruptured Intracranial Aneurysm: Serial rCBF Studies with the Xenon-133 Inhalation Method

Neurosurgery ◽  
1983 ◽  
Vol 13 (4) ◽  
pp. 394-401 ◽  
Author(s):  
Iwao Yamakami ◽  
Katsumi Isobe ◽  
Akira Yamaura ◽  
Takao Nakamura ◽  
Hiroyasu Makino
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Neurological Deficit ◽  
Mean Value ◽  
Initial Slope ◽  
Delayed Ischemic Neurological Deficit ◽  
Ruptured Intracranial Aneurysm ◽  
The Mean ◽  
Xenon 133 ◽  
Head Probe

Abstract To clarify the relationship of vasospasm to the reduction of cerebral blood flow (CBF) and the delayed ischemic neurological deficit, serial rCBF studies with the use of the xenon-133 inhalation method were conducted in 35 postoperative patients with ruptured intracranial aneurysms. The CBF was calculated as an initial slope index (ISI) derived from the desaturation curve of each head probe, and the hemispheric mean value of the ISI (mean ISI) was calculated in both hemispheres. The mean ISI in the hemisphere ipsilateral to the operation was low compared to that of the contralateral hemisphere. In relation to the presence of vasospasm, angiographic findings were classified into the following five types: diffuse, peripheral, proximal-severe, proximal-mild, and no spasm. Patients with vasospasm of the diffuse, peripheral, and proximal-severe types showed a markedly decreased mean ISI, and vasospasm of the diffuse type caused the greatest degree of reduction. The mean ISI of the patients who developed delayed ischemic neurological deficit (DIND) due to vasospasm was significantly decreased (37.4± 4.6) compared to that of the patients who did not develop DIND (52.2± 5.6). None of 3 cases of no spasm and only 1 of 14 cases of proximal-mild spasm developed DIND. On the other hand, all of 4 cases of diffuse, 2 of 3 cases of peripheral, and 2 of 6 cases of proximal-severe spasm developed DIND. Thus, if these three types of vasospasm are joined together as severe vasospasm, 8 of 13 cases with severe vasospasm developed DIND. These results suggest that severe vasospasm causes a reduction of CBF and that the reduced CBF brings about DIND.

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