Sperm-induced calcium oscillations. Soluble factor, factors or receptors?
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Animals↗
Biomedical subjects
B Dale
Publications and source records attributed to B Dale.
Intercellular communication in in vivo- and in vitro-produced bovine embryos.
In vivo bovine embryos were obtained by nonsurgical flushing of uterine horns of cows submitted to superovulatory treatment, while in vitro embryos were generated from oocytes collected from slaughtered donors. Lucifer Yellow injected into single blastomeres did not diffuse into neighboring cells until the morula stage in in vivo embryos and the blastocyst stage in in vitro embryos. In both cases diffusion was limited to a few cells. In contrast, diffusion was extensive in microsurgically isolated inner cell mass (ICM) but absent in the trophectoderm (TE). At the blastocyst stage, diffusion was always more extensive in in vivo than in in vitro embryos. Ultrastructural analyses confirmed these functional observations, and gap junction-like structures were observed at the blastocyst stage. These structures were diffuse in the ICM of in vivo embryos, scarce in the ICM of in vitro embryos and in the TE of in vivo embryos, and not observed in the TE of in vitro embryos. Blastomeres at all stages of development from the 2-cell stage to the blastocyst stage in in vitro embryos and at the morula and blastocyst stage in in vivo embryos were electrically coupled, and the junctional conductance (Gj) decreased in in vitro embryos from 4.18 +/- 1.70 nS (2-cell stage) to 0.37 +/- 0.12 nS (blastocyst stage). At each developmental stage, in vivo embryos showed a significantly (P < 0. 05) higher Gj than in vitro-produced embryos. Moreover, a significantly (P < 0.01) higher Gj was found in isolated ICM than in the respective blastocyst in both in vivo- and in vitro-produced embryos (3.5 +/- 1.4 vs. 0.7 +/- 0.3 and 2.6 +/- 1.6 vs. 0.37 +/- 0. 12 nS, respectively). The electrical coupling in absence of dye coupling in the early bovine embryo agrees with observations for embryos from other phyla. The late and reduced expression of intercellular communicative devices in in vitro-produced embryos may be one of the factors explaining their developmental low efficiency.
Animals↗
Ins and outs of meiosis in ascidians.
Ascidian oocytes are blocked in metaphase (M) of the first meiotic division. Fertilization triggers the completion of meiosis without any further arrest. In this review, we have analyzed the mechanisms that regulate the progression through meiosis in these oocytes. A primary signal from the fertilizing spermatozoon, probably soluble sperm factor(s), induces intracellular calcium release by activating the IP3 and CICR pathways and gates the fertilization current by triggering the generation of ADP ribose (ADPr). The calcium oscillations are not required for the inactivation of MPF observed at M-I release; however, ADPr may be indirectly involved in the activity of MPF associated kinase, Cdc2. MPF activity reaches a second peak at M-II followed by subsequent inactivation. Progression to M-II is dependent on the intracellular calcium oscillations. MAP kinase (MAPK) activity decreases at M-I exit and remains low during the completion of meiosis. Finally, although Cdc2, Cyclin B and MAPK-like proteins have been identified in ascidian oocytes, components of CSF still remain to be identified.
Adenosine Diphosphate Ribose↗
Electrocardiographic consequences of a peripatetic lifestyle in gray wolves (Canis lupus).
Cardiac chamber enlargement and hypertrophy are normal physiologic responses to repetitive endurance exercise activity in human beings and domestic dogs. Whether similar changes occur in wild animals as a consequence of increased activity is unknown. We found that free-ranging gray wolves (Canis lupus, n = 11), the archetypical endurance athlete, have electrocardiographic evidence of cardiac chamber enlargement and hypertrophy relative to sedentary captive gray wolves (n = 20), as demonstrated by significant increases in QRS duration, QT interval, and QT interval corrected for heart rate, a tendency towards increased Q, R, and S wave voltages in all leads, and a significant decrease in heart rate. We conclude that exercise activity level and therefore lifestyle affects physiologic variables in wild animals. An immediate consequence of this finding is that physiologic measurements obtained from a captive wild-animal population with reduced exercise activity level may not accurately reflect the normal physiologic state for free-ranging members of the same species.
Adaptation, Physiological↗
Non-specific currents at fertilisation in sea urchin oocytes.
Using the whole-cell voltage-clamp technique to clamp sea urchin oocytes we show that the fertilising spermatozoon triggers an inward current of -521 +/- 56.7 pA (n = 8) at activation. Simultaneously, the plasma membrane depolarises and the conductance increases from 23.4 +/- 1.4 to 40.6 +/- 1.2 nS (n = 8). The I/V curve for the peak activation current is linear and the current reverses between 0 and +20 mV, suggesting a non-specific ion current. Since injection of inositol triphosphate induced an inward current of -1062 +/- 314 pA (n = 4), and the current was inhibited by preloading oocytes with the calcium chelator BAPTA, the non-specific activation current in sea urchin appears to be calcium dependent.
Animals↗
Soluble extracts from ascidian spermatozoa trigger intracellular calcium release independently of the activation of the ADP ribose channel.
We have injected soluble extracts of sperm from the ascidian Ciona intestinalis into oocytes of the same species to test whether these extracts can mimic the events of fertilisation. Injection of ascidian sperm extracts leads, after a delay of approximately 60 s, to a large calcium transient and repetitive pattern of calcium oscillations, mimicking the normal fertilisation response. The response was concentration-independent, suggesting a stimulatory mechanism in triggering the fertilisation response. We tested the pathway of calcium release in ascidian oocytes after injection of sperm extracts by preinjection of calcium release inhibitors. The data demonstrate that dual pathways to calcium release act at fertilisation in ascidians, as in other species. C. intestinalis oocytes are characterised by a ion channel in the plasma membrane that is gated uniquely by ADP ribose. We show that this channel is not gated by the injection of ascidian sperm extracts. Our data suggest that one metabolic pathway triggered by sperm, the release of nitric oxide, is not stimulated by sperm extracts and that several metabolic pathways are stimulated at fertilisation by more than one factor within sperm.
Adenosine Diphosphate Ribose↗
Nucleotide sequence of the inter-structural gene region of feline infectious peritonitis virus.
The sequence of the region located between the S and M glycoprotein genes of the 79-1146 strain of feline infectious peritonitis virus (FIPV) is presented. The inter-structural gene region encodes 3 open reading frames (ORFs), termed ORFs 3a, 3b and 4, with nucleotide sequences conforming to the minimum conserved transcription signal upstream of each. An additional ORF, 3x, partially overlaps the 3' end of ORF 3a. The FIPV interstructural gene region is identical in length when compared to the Insavc-1 strain of canine coronavirus (CCV) but differs from various strains of transmissible gastroenteritis virus (TGEV) by the presence of deletions and insertions. The sizes of ORF 3a and 4 are conserved in FIPV, TGEV and CCV. However, as with CCV, the FIPV ORF 3b is truncated in comparison with TGEV.
Animals↗
Mammalian embryo quality: is it possible to estimate it, and when?
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Animals↗
Intracellular pH regulation in the human oocyte.
We have used fluorescence techniques to study the regulation of intracellular pH during fertilization and preimplantation embryo development in human oocytes. The intracellular pH of human oocytes during maturation and fertilization was always 7.4, suggesting that these processes do not involve long-term changes in intracellular pH. The recovery of intracellular pH of human oocytes and embryos after extracellular acid or alkaline shock was investigated. Fresh metaphase II oocytes and preimplantation embryos showed similar rates of recovery following alkaline shock. However, aged and immature oocytes had a significantly slower rate of recovery to physiological pH. Early embryos up to the morula stage were unable to recover following acidosis, whereas blastocysts could control both acidosis and alkalosis. We assessed the sensitivity of fertilization and early development in the human to extracellular pH. Our results show that insemination in the human is pH-sensitive, whereas intracytoplasmic injection (ICSI) activated oocytes at all pH tested. We suggest that this is due to the pH-sensitivity of the sperm-zona pellucida interaction, which is bypassed during the ICSI procedure. Further development in human embryos is more sensitive to alkalinity than acidity. We discuss these results in terms of the extracellular pH in vivo in the female reproductive tract.
Blastocyst↗
Time to switch from co-culture to sequential defined media for transfer at the blastocyst stage.
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Blastocyst↗
Can nurse practitioners offer a quality service? An evaluation of a year's work of a nurse led minor injury unit.
OBJECTIVE: To evaluate activities of a nurse led minor injuries unit based in a community hospital situated eight miles away from its sister district hospital in Crawley to demonstrate whether nurses can provide an alternative service. DESIGN: "Walk in" service provided by emergency nurse practitioners (ENPs) working within protocols and parameters with supervision from the accident and emergency consultant during the period of May 1995 to April 1996. RESULTS: Within the 12 month period, ENPs treated 6944 new patients. Altogether 234 patients were transferred to Crawley Hospital for further treatment. The ENPs reviewed 1611 patients and the consultant 1342; 1945 patients required radiographs and 793 were given medication; 553 patients were referred to other health care professionals. Almost all patients were happy to see a nurse and all were satisfied with the treatment they received. CONCLUSION: With careful planning, adequate supervision, and support from multidisciplinary teams nurses can provide a worthwhile and effective service for a local community.
Emergency Service, Hospital↗
ADP-ribose gates the fertilization channel in ascidian oocytes.
We report an ion channel in the plasma membrane of unfertilized oocytes of the ascidian Ciona intestinalis that is directly gated by the second messenger ADP-ribose. The ion channel is permeable to Ca2+ and Na+ and is characterized by a reversal potential between 0 and +20 mV and a unitary conductance of 140 pS. Preinjection of the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) or antagonists of intracellular Ca2+ release channels into oocytes did not inhibit the ADP-ribose current, demonstrating that the channel is activated in a Ca2+-independent manner. Both the fertilization current and the current induced by the injection of nicotinamide nucleotides are blocked by nicotinamide, suggesting that the ADP-ribose channel is activated at fertilization in a nicotinamide-sensitive manner. These data suggest that ascidian sperm trigger the hydrolysis of nicotinamide nucleotides in the oocyte to ADP-ribose and that this mechanism is responsible for the production of the fertilization current.
Adenosine Diphosphate Ribose↗
Serum biochemistry of captive and free-ranging gray wolves (Canis lupus).
Normal serum biochemistry values are frequently obtained from studies of captive sedentary (zoo) or free-ranging (wild) animals. It is frequently assumed that values obtained from these two populations are directly referable to each other. We tested this assumption using 20 captive gray wolves (Canis lupus) in Minnesota, USA, and 11 free-ranging gray wolves in Alaska, USA. Free-ranging wolves had significantly (P < 0.05) lower sodium, chloride, and creatinine concentrations and significantly higher potassium and blood urea nitrogen (BUN) concentrations; BUN to creatinine ratios; and alanine aminotransferase, aspartate aminotransferase, and creatine kinase activities relative to captive wolves. Corticosteroid-induced alkaline phosphatase activity (a marker of stress in domestic dogs) was detected in 3 of 11 free-ranging wolves and in 0 of 20 captive wolves (P = 0.037). This study provides clear evidence that serum biochemical differences can exist between captive and free-ranging populations of one species. Accordingly, evaluation of the health status of an animal should incorporate an understanding of the potential confounding effect that nutrition, activity level, and environmental stress could have on the factor(s) being measured.
Animals↗
Nitric oxide gates fertilization channels in ascidian oocytes through nicotinamide nucleotide metabolism.
In this paper we use the nitric oxide (NO) donor sodium nitroprusside to examine the response of the unfertilised oocyte of the ascidian Ciona intestinalis to nitric oxide. We show that the release of NO triggers an inward current that displays similar properties to the ascidian fertilisation current. Furthermore, the production of NO causes the release of intracellular calcium through a ruthenium-red sensitive mechanism. Our data suggest that these effects are due to the stimulation of nicotinamide nucleotide metabolism, but the active second messenger is not cyclic adenosine diphosphate ribose (cADPr). Finally, we show that NO production increases at fertilisation. The results suggest that ascidian sperm trigger the release of NO and this second messenger causes the breakdown of nicotinamide nucleotides leading to the production of a second messenger which induces the fertilisation current and may assist in the production of the increase in calcium.
Adenosine Diphosphate Ribose↗
A soluble extract from human spermatozoa activates ascidian oocytes.
A soluble extract from human spermatozoa induced calcium oscillations and extrusion of the first polar body when injected into oocytes of the ascidian Ciona intestinalis. The properties of calcium oscillations and time of polar body extrusion precisely mimic oocyte activation induced by C. intestinalis sperm or sperm extracts. The data suggest that human sperm extracts can activate oocytes of different phyla by the same mechanism as homologous spermatozoa. Injection of inositol 1,4,5-trisphosphate (IP3) into C. intestinalis oocytes mimicked to some extent the initial stages of oocyte activation, but the results demonstrate that ascidian oocyte activation by human sperm extract cannot be explained solely in terms of IP3-induced calcium release. Injection of other calcium releasing second messengers, cyclic adenosine diphosphate ribose, or calcium ions, does not lead to oocyte activation or release intracellular calcium in ascidian oocyte. It was concluded that human spermatozoa contain one or more molecules than can trigger intracellular calcium release in oocytes from different phyla.
Adenosine Diphosphate Ribose↗
Ambient air and its potential effects on conception in vitro.
Incidences of chemical air contamination (CAC) are common in assisted reproductive technology, but not reported in peer review format. Justified fear of car and industrial emissions clearly exists among reproductive specialists, but standards for air contents and gaseous emission limits have not been reported. Here, we describe air sampling methods and assay systems which can be applied to any laboratory or laboratory item. It was found that unfiltered outside air may be cleaner than high efficiency particulate air filtration (HEPA) filtered laboratory air or air obtained from incubators, due to accumulation of volatile organic compounds derived from adjacent spaces or specific laboratory products such as compressed CO2, sterile Petri dishes and other materials or devices known to release gaseous emissions. Specific groups of products such as anaesthetic gases, refrigerants, cleaning agents, hydrocarbons and aromatic compounds such as benzene and toluene are described. The latter were shown to accumulate specifically in incubators. Isopropyl alcohol was the most dominant product found, though it was not used by the laboratory staff. Concentrations of this agent were low in incubator air, indicating that it was probably absorbed by the water in the pan or by culture medium. Measures to counter CAC are proposed, including the use of activated carbon filters and oxidizing material placed in the central air handling systems, in separate free-standing units or even inside the incubators.
Air Pollution, Indoor↗
Sperm factor: what is it and what does it do?
There are two current hypotheses as to how the spermatozoon triggers the oocyte into activity; a transmembrane receptor mechanism involving G-proteins and a soluble sperm-factor mechanism. In this short review we show that the present data favours the idea of a soluble factor diffusing from the spermatozoon into the oocyte following plasma membrane fusion of the two gametes that triggers calcium release in the oocyte. Two categories of calcium release mechanisms, inositol-1,4,5-triphosphate-induced calcium release (IICR) and calcium induced calcium release (CICR) are found in oocytes from a variety of species and both appear to be activated at fertilization. Since these calcium release pathways are distinct it is possible that sperm cytosol contains more that one activating factor. Finally, the fact that sperm extracts 'activate' oocytes from different phyla and trigger calcium oscillations in somatic cells infers calcium releasing agents common to other cell types.
Animals↗
Polarized distribution of L-type calcium channels in early sea urchin embryos.
Using the whole cell clamp technique, we have measured calcium-dependent currents and steady-state conductance in early sea urchin blastomeres. The calcium currents in M phase decreased from 8.5 microA/cm2 at the four-cell stage to 5.4 microA/cm2 at the eight-cell stage. In 16-cell stage embryos, calcium currents were 7.4 microA/cm2 in the mesomeres, 2.3 microA/cm2 in the macromeres, and were not detected in the micromeres. In contrast, the micromeres had a two- to threefold higher steady-state conductance than the mesomeres or macromeres, which may be due to potassium ion conductivity. Nifedipine, an L-type channel antagonist, delays cleavage division at a concentration of 0.05-0.1 mM and causes developmental defects, such as poor skeletal differentiation in later sea urchin embryos.
Animals↗