Telomeres and meiosis in health and disease.
Explore the source record for details and available documents.
Chromosome Disorders↗
Biomedical subjects
D L Keefe
Publications and source records attributed to D L Keefe.
Telomeres and aging-related meiotic dysfunction in women.
Meiotic dysfunction increasingly afflicts women as they age, resulting in infertility, miscarriage and handicapped offspring. How aging disrupts meiotic function in women remains unclear, but as women increasingly delay childbearing, this issue becomes urgent. Telomeres, which mediate aging in mitotic cells, may also mediate aging during meiosis. Telomeres shorten during DNA replication. In mammals, oocytes remain quiescent, but their precursors replicated during fetal oogenesis. Moreover, eggs ovulated from older women entered meiosis later during fetal oogenesis than eggs ovulated when younger, and therefore underwent more replications. Telomeres also shorten from reactive oxygen, which triggers a DNA repair response, so the prolonged interval between fetal oogenesis and ovulation in some women would further shorten telomeres. Mice normally do not exhibit age-related meiotic dysfunction (interestingly, their telomeres are manyfold longer than telomeres in women), but genetic or pharmacologic shortening of mouse telomeres recapitulates the reproductive aging phenotype of women. This has led to a telomere theory of age-related meiotic dysfunction in women, and underlined the importance to human health of a mechanistic understanding of telomeres and meiosis.
Animals↗
Mullerian inhibiting substance levels at the time of HCG administration in IVF cycles predict both ovarian reserve and embryo morphology.
BACKGROUND: Pre-antral and early antral follicles secrete Müllerian inhibiting substance (MIS), suggesting that MIS may directly reflect ovarian reserve. Since little is known about how ovarian reserve affects oocyte quality, we attempt here to assess the predictive value of MIS on embryo morphology and IVF outcome. To do so, we measured MIS at the time of HCG administration 36 h prior to oocyte retrieval. METHODS: A total of 257 patients undergoing IVF were prospectively recruited. We measured MIS levels by enzyme-linked immunosorbent assay at the time of HCG, and compared the MIS values to day 3 FSH levels in the prediction of embryo morphology and IVF outcome. RESULTS: The distribution of MIS levels was skewed, with a median of 2.7 ng/ml (range 0 to 28.5 ng/ml). MIS values at the time of HCG administration inversely correlated with basal FSH levels (P = 0.002), and both correlated significantly with patient age, number of mature follicles, number of oocytes retrieved and serum estradiol levels. MIS levels correlated significantly with a greater number of 6-cell embryos and better embryo morphology score, while basal FSH levels did not correlate with these outcome variables. MIS levels > or =2.7 ng/ml portended improved oocyte quality as reflected in a higher implantation rate (P = 0.001) and a trend toward a better clinical pregnancy rate (P = 0.084). CONCLUSIONS: MIS levels seem to predict not only ovarian reserve, but also embryo morphology. Measurement of MIS at the time of HCG administration may, therefore, in the future improve management of patients undergoing treatments with assisted reproductive technology.
Anti-Mullerian Hormone↗
Safe and cost effective use of alteplase for the clearance of occluded central venous access devices.
PURPOSE: To determine whether cryopreserved solutions of the thrombolytic agent alteplase could be used as a safe, effective, and economically reasonable alternative to urokinase in patients presenting with occluded central venous access devices (CVADs). MATERIALS AND METHODS: Alteplase has been reported as an efficacious alternative to urokinase for treatment of occluded CVADs. However, the practicality of using alteplase as the thrombolytic of choice for this indication remained conjectural. To make this approach economically feasible, alteplase was diluted to 1 mg/mL and 2.5-mL aliquots were stored at -20 degrees C until use. A need to confirm that the cryopreserving and thawing of the reconstituted solution did not compromise the safety and efficacy reported from prior trials was recognized. A quality assessment initiative was undertaken to concurrently monitor the safety and efficacy of this approach. Patients presenting with occluded CVADs received a sufficient volume of the thawed alteplase solution to fill the occluded catheter(s). Data, including efficacy, adverse reactions, dwell time, and catheter type, were collected over a 5-month period. RESULTS: One hundred twenty-one patients accounting for 168 attempted clearances were assessable for safety and efficacy. One hundred thirty-six (81%) of the 168 catheter clearance attempts resulted in successful catheter clearance (95% confidence interval, 74% to 86%). No adverse events were reported. CONCLUSION: Cryopreserved 1-mg/mL aliquots of alteplase are safe and effective in the clearance of occluded CVADs when stored at -20 degrees C for 30 days. The ability to cryopreserve alteplase aliquots makes it an economically reasonable alternative to urokinase in the setting of CVAD occlusion.
Adolescent↗
The spindle observation and its relationship with fertilization after intracytoplasmic sperm injection in living human oocytes.
OBJECTIVE: To image spindles in living human oocytes and to examine the relation between spindles and fertilization after ICSI. DESIGN: The LC polscope was used to examine spindles in an observational study of living oocytes. SETTING: Academic IVF clinic. PATIENT(S): Women being treated for infertility. INTERVENTION(S): Oocytes retrieved from patients for infertility treatment were examined before ICSI. Aged, unfertilized oocytes after IVF or ICSI were examined with polscope and confocal microscopes to compare the two methods. MAIN OUTCOME MEASURE(S): Spindle structure in living oocytes and fertilization after ICSI. RESULT(S): Spindles could be imaged in 61.4% of oocytes. More oocytes with spindles than oocytes without spindles fertilized normally after ICSI (61.8% vs. 44.2%). Spindles in most aged oocytes were partially or completely disassembled, and only a few microtubules around the chromosomes or dispersed microtubules in the cytoplasm were observed. Confocal images of immunostained spindles were almost identical to polscope images of spindle birefringence. CONCLUSION(S): Spindles in living human oocytes can be imaged by using the polscope. A birefringent spindle in human oocytes may clinically predict the quality and age of oocytes. This method also can be used to monitor spindle position during ICSI.
Cellular Senescence↗
Circulatory shock.
Patients with malignancy may present with acute circulatory compromise requiring ICU monitoring and care. The clinician must be familiar with a multiplicity of acute and chronic medical conditions common to the general population and also with conditions directly related to cancer or therapy thereof.
Adrenal Gland Diseases↗
Mitochondrial modulation of calcium signaling at the initiation of development.
Fertilization triggers cytosolic Ca(2+) oscillations that activate mammalian eggs and initiate development. Extensive evidence demonstrates that Ca(2+) is released from endoplasmic reticulum stores; however, less is known about how the increased Ca(2+) is restored to its resting level, forming the Ca(2+) oscillations. We investigated whether mitochondria also play a role in activation-associated Ca(2+) signaling. Mitochondrial dysfunction induced by the mitochondrial uncoupler FCCP or antimycin A disrupted cytosolic Ca(2+) oscillations, resulting in sustained increase in cytosolic Ca(2+), followed by apoptotic cell death. This suggests that functional mitochondria may participate in sequestering the released Ca(2+), contributing to cytosolic Ca(2+) oscillations and preventing cell death. By centrifugation, mouse eggs were stratified and separated into fractions containing both endoplasmic reticulum and mitochondria and fractions containing endoplasmic reticulum with no mitochondria. The former showed Ca(2+) oscillations by activation, whereas the latter exhibited sustained elevation in cytosolic Ca(2+) but no Ca(2+) oscillations, suggesting that mitochondria take up released cytosolic Ca(2+). Further, using Rhod-2 for detection of mitochondrial Ca(2+), we found that mitochondria exhibited Ca(2+) oscillations, the frequency of which was not different from that of cytosolic Ca(2+) oscillations, indicating that mitochondria are involved in Ca(2+) signaling during egg activation. Therefore, we propose that mitochondria play a crucial role in Ca(2+) signaling that mediates egg activation and development, and apoptotic cell death.
Animals↗
Limited recovery of meiotic spindles in living human oocytes after cooling-rewarming observed using polarized light microscopy.
BACKGROUND: Spindles are formed from microtubules and are exquisitely sensitive to changes in temperature. An orientation-independent polarized light microscope, the Polscope, can be used to image spindles in living oocytes allowing analysis of spindle kinetics in the living state. This study examined the effects of cooling on spindle disassembly in living human oocytes and spindle recovery after rewarming. METHODS: Oocytes were imaged continuously with the Polscope during cooling and rewarming. The quantity of microtubules in the spindles was measured by its birefringence using the Polscope. RESULTS: Spindles had completely disassembled by 5 min after cooling and recovered by 20 min after rewarming to 37 degrees C if rewarming started soon after the oocyte's temperature dropped to room temperature. However, when oocytes were cooled and kept at 33, 28 or 25 degrees C for 10 min and then warmed, it was found that warming allowed 5/5, 2/5 and 0/5 oocytes of the spindles to recover respectively. CONCLUSIONS: These results indicate that human meiotic spindles are exquisitely sensitive to alterations in temperature. The maintenance of temperature at 37 degrees C during in-vitro manipulation is important for spindle integrity and, therefore, is likely to be important for normal fertilization and subsequent embryo development.
Cold Temperature↗
Developmental ability of human oocytes with or without birefringent spindles imaged by Polscope before insemination.
BACKGROUND: Birefringent spindles imaged with the Polscope can predict fertilization rates after intracytoplasmic sperm injection (ICSI). The present study examined the development of human oocytes with or without birefringent spindles, imaged with the Polscope before ICSI. METHODS: Oocytes were obtained from stimulated ovaries of consenting patients undergoing oocyte retrieval for ICSI. Spindles were imaged with the Polscope combined with a computerized image analysis system. After imaging and ICSI, oocytes with or without spindles were cultured separately for examination of fertilization and embryo development. A total of 1544 oocytes from 136 cycles were examined with the Polscope and inseminated by ICSI. RESULTS: Spindles were imaged in 82% of oocytes. After ICSI, more oocytes (P < 0.05) with spindles (69.4%) fertilized normally, forming 2 pronuclei, than oocytes without spindles (62.9%). At day 3, more oocytes (P < 0.01) with spindles (66.3%) developed to 4-11 cell stages than oocytes without spindles (55.4%). Significantly more (P < 0.001) oocytes with spindles developed to morula and blastocyst by day 5 (51.1 versus 30.3%) and day 6 (53.2 versus 29.3%) compared with oocytes without spindles. CONCLUSIONS: The results indicate that the presence of a birefringent spindle in human oocytes can predict not only higher fertilization rate, but also higher embryo developmental competence.
Adult↗
Estrogen and progesterone effects on transcapillary fluid dynamics.
The purpose of this study was to determine estrogen (E(2)) and progesterone (P(4)) effects on atrial natriuretic peptide (ANP) control of plasma volume (PV) and transcapillary fluid dynamics. To this end, we suppressed reproductive function in 12 women (age 21-35 yr) using a gonadotropin releasing-hormone (GnRH) analog (leuprolide acetate) for 5 wk. During the 5th week, the women either received 4 days of E(2) administration (17beta-estradiol, transdermal patch, 0.1 mg/day) or 4 days of E(2) with P(4) administration (vaginal gel, 90 mg P(4) twice per day). At the end of the 4th and 5th week of GnRH analog and hormone administration, we determined PV (Evans blue dye) and changes in PV and forearm capillary filtration coefficient (CFC) during a 120-min infusion of ANP (5 ng x kg body wt(-1) x min(-1)). Preinfusion PV was estimated from Evans blue dye measurement taken over the last 30 min of infusion based on changes in hematocrit. E(2) treatment did not affect preinfusion PV relative to GnRH analog alone (45.3 +/- 3.1 vs. 45.4 +/- 3.1 ml/kg). During ANP infusion CFC was greater during E(2) treatment compared with GnRH analog alone (6.5 +/- 1.4 vs. 4.9 +/- 1.4 microl. 100 g(-1) x min(-1) mmHg(-1), P < 0.05). The %PV loss during ANP infusion was similar for E(2) and GnRH analog-alone treatments (-0.8 +/- 0.2 and -1.0 +/- 0.2 ml/kg, respectively), indicating the change in CFC had little systemic effect on ANP-related changes in PV. Estimated baseline PV was reduced by E(2)-P(4) treatment. During ANP infusion CFC was approximately 30% lower during E(2)-P(4) (6.0 +/- 0.5 vs. 4.3 +/- 4.3 microl. 100 g(-1) x min(-1) mm Hg(-1), P < 0.05), and the PV loss during ANP infusion was attenuated (-0.9 +/- 0.2 and -0.2 +/- 0.2 ml/kg for GnRH analog-alone and E(2)-P(4) treatments, respectively). Thus the E(2)-P(4) treatment lowered CFC and reduced PV loss during ANP infusion.
Adult↗
Progesterone does not alter osmotic regulation of AVP.
To test the hypothesis that progesterone, independent of estrogen, decreases the plasma osmotic threshold for arginine vasopressin (AVP) release and thirst onset, we compared AVP and thirst responses to hypertonic saline infusion (HSI) during administration of oral contraceptives (OCs) containing progesterone (OCP) with responses to infusion of OCs containing progesterone and estrogen (OCEP). Eight women (29 +/- 2 yr) were infused with 3% NaCl (120 min, 0.1 ml. kg body wt(-1). min(-1)) and consumed fluid (90 min, 15 ml/kg body wt) in the early follicular and midluteal phases of a 28-day menstrual cycle and also after 4 wk of OCP and after 4 wk of OCEP in a randomized crossover design. Baseline plasma osmolality (P(osm)) was lower in the luteal phase (280 +/- 1 mosmol/kgH(2)O) and during OCEP (283 +/- 1 mosmol/kgH(2)O) than in the follicular phase (286 +/- 1 mosmol/kgH(2)O, P < 0.05) but was unaffected by OCP (284 +/- 1 mosmol/kgH(2)O). P(osm) remained lower in the follicular phase than in the luteal phase and with OCEP throughout the first 50 min of HSI. The mean abscissal plasma AVP concentration-P(osm) intercept was unaffected by OCP (267 +/- 1 mosmol/kgH(2)O) but was greater in the follicular phase (273 +/- 2 mosmol/kgH(2)O) than in the luteal phase (266 +/- 4 mosmol/kgH(2)O) and with OCEP (268 +/- 2 mosmol/kgH(2)O, P < 0.05). There were no differences in osmotic thresholds for thirst onset across experimental days. Despite the lower osmotic threshold for AVP release during the luteal phase and with OCEP, fluid balance, renal free water clearance, and Na(+) regulation during HSI were unaffected by menstrual phase or OC treatment, indicating a lower osmotic operating point for body water balance. OCP did not affect osmotic AVP regulation, suggesting that progesterone does not affect osmotic fluid regulation through a mechanism independent of estrogen.
Adult↗
Sex differences in osmotic regulation of AVP and renal sodium handling.
To determine sex differences in osmoregulation of arginine vasopressin (AVP) and body water, we studied eight men (24 +/- 1 yr) and eight women (29 +/- 2 yr) during 3% NaCl infusion [hypertonic saline infusion (HSI); 120 min, 0.1 ml. kg body wt(-1). min(-1)]. Subjects then drank 15 ml/kg body wt over 30 min followed by 60 min of rest. Women were studied in the early follicular (F; 16.1 +/- 2.8 pg/ml plasma 17beta-estradiol and 0.6 +/- 0.1 ng/ml plasma progesterone) and midluteal (L; 80.6 +/- 11.4 pg/ml plasma 17beta-estradiol and 12.7 +/- 0.7 ng/ml plasma progesterone) menstrual phases. Basal plasma osmolality was higher in F (286 +/- 1 mosmol/kgH(2)O) and in men (289 +/- 1 mosmol/kgH(2)O) compared with L (280 +/- 1 mosmol/kgH(2)O, P < 0.05). Neither menstrual phase nor gender affected basal plasma AVP concentration (P([AVP]); 1.7 +/- 4, 1.9 +/- 0.4, and 2.2 +/- 0.5 pg/ml for F, L, and men, respectively). The plasma osmolality threshold for AVP release was lowest in L (x-intercept, 263 +/- 3 mosmol/kgH(2)O, P < 0.05) compared with F (273 +/- 2 mosmol/kgH(2)O) and men (270 +/- 4 mosmol/kgH(2)O) during HSI. Men had greater P([AVP])-plasma osmolality slopes (i.e., sensitivity) compared with F and L (slopes = 0.14 +/- 0.04, 0.09 +/- 0.01, and 0.24 +/- 0.07 for F, L, and men, respectively, P < 0.05). Despite similar Na+-regulating hormone responses, men excreted less Na+ during HSI (0.7 +/- 0.1, 0.7 +/- 0.1, and 0.5 +/- 0.1 meq/kg body wt for F, L, and men, respectively, P < 0.05). Furthermore, men had greater systolic blood pressure (119 +/- 5, 119 +/- 5, and 132 +/- 3 mmHg for F, L, and men, respectively, P < 0.05) than F and L. Our data indicate greater sensitivity in P([AVP]) response to changes in plasma osmolality as the primary difference between men and women during HSI. In men, this greater sensitivity was associated with an increase in systolic blood pressure and pulse pressure during HSI, most likely due to a shift in the pressure-natriuresis curve.
Adult↗
Anthracycline-induced cardiomyopathy.
The highly active chemotherapeutic agents doxorubicin, duanorubicin, idarubicin, epirubicin, and mitoxantrone are also associated with acute, largely reversible cardiotoxic effects and a dose-related cardiomyopathy. This cardiomyopathy is characterized by minimal left ventricular enlargement and global systolic dysfunction, usually with associated mild to moderate mitral insufficiency. Historically, this was characterized by myocardial biopsy and radionuclide angiography. More recently, echocardiography has become the most widely available and cost-efficient tool for diagnosis. The precise mechanism of this toxicity has not been fully defined. However, the maximum tolerated cumulative dose can by increased by reducing peak drug levels and concurrent administration of the iron chelator, dexrazoxane. Because anthracycline-induced cardiomyopathy is largely irreversible and cumulative, prevention is the preferred strategy. Monitoring by assessment of left ventricular function by the most reproducible method available as patients approach potentially toxic doses can substantially reduce toxicity. Stress studies before major procedures such as bone marrow or stem cell transplants may be of benefit. This syndrome responds well to conventional therapy for congestive heart failure with angiotensin-converting enzyme inhibitors, digoxin, and diuretics. The beta-blocker carvedilol is often associated with significant improvement in ejection fraction and symptoms and spironolactone is well tolerated and often of benefit. The long-term outlook of the syndrome is much better than previously reported because of advances in therapy and prevention.
Anthracyclines↗
A non-invasive method for measuring preimplantation embryo physiology.
The physiology of the early embryo may be indicative of embryo vitality and therefore methods for non-invasively monitoring physiological parameters from embryos could improve preimplantation diagnoses. The self-referencing electrophysiological technique is capable of non-invasive measurement of the physiology of individual cells by monitoring the movement of ions and molecules between the cell and the surrounding media. Here we use this technique to monitor gradients of calcium, potassium, oxygen and hydrogen peroxide around individual mouse preimplantation embryos. The calcium-sensitive electrode in self-referencing mode identified a region of elevated calcium concentration (approximately 0.25 pmol) surrounding each embryo. The calcium gradient surrounding embryos was relatively steep, such that the region of elevated calcium extended into the medium only 4 microns from the embryo. By contrast, using an oxygen-sensitive electrode an extensive gradient of reduced dissolved oxygen concentration was measured surrounding the embryo and extended tens of micrometres into the medium. A gradient of neither potassium nor hydrogen peroxide was observed around unperturbed embryos. We also demonstrate that monitoring the physiology of embryos using the self-referencing technique does not compromise their subsequent development. Blastocyts studied with the self-referencing technique implanted and developed to term at the same frequency as did unexamined, control embryos. Therefore, the self-referencing electrode provides a valuable non-invasive technique for studying the physiology and pathophysiology of individual embryos without hindering their subsequent development.
Animals↗
A reliable, noninvasive technique for spindle imaging and enucleation of mammalian oocytes.
Factors affecting the efficiency of animal cloning remain to be elucidated. Enucleation of recipient oocytes is a critical step in cloning procedures and typically is performed by aspirating a portion of the cytoplasm underlying the first polar body. Enucleation is evaluated using epifluorescence after Hoechst staining for DNA, which may disrupt functions of the cytoplast, especially mitochondria. Mitochondrial DNA in Dolly and other cloned sheep has been shown to derive exclusively from recipient oocytes. Not only might evaluation of the aspirated karyoplast portion inadequately reflect the state of the cytoplast, it is also time consuming. Here we report a reliable, noninvasive technique for spindle imaging and enucleation of oocytes using a new microscope, the Pol-Scope. The efficiency of enucleation was 100%, and only 5.5% of the oocytes' mitochondria entered the karyoplast upon Pol-Scope-directed removal of the spindle. Moreover, Pol-Scope imaging of spindles and micromanipulation did not compromise the developmental competence of reconstituted oocytes and cytoplasts.
Animals↗
Involvement of mitochondria in oxidative stress-induced cell death in mouse zygotes.
Accumulation of reactive oxygen species during aging leads to programmed cell death (PCD) in many cell types but has not been explored in mammalian fertilized eggs, in which mitochondria are "immature," in contrast to "mature" mitochondria in somatic cells. We characterized PCD in mouse zygotes induced by either intensive (1 mM for 1.5 h) or mild (200 microM for 15 min) hydrogen peroxide (H(2)O(2)) treatment. Shortly after intensive treatment, zygotes displayed PCD, typified by cell shrinkage, cytochrome c release from mitochondria, and caspase activation, then terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining in condensed pronuclei. On the other hand, after mild treatment, zygotes arrested developmentally and showed neither cytochrome c release nor caspase activation over 48 h; until 72 h, 46% zygotes exhibited TUNEL staining, and 88% of zygotes lost plasma membrane integrity. Interestingly, mild oxidative treatment induced a decline in mitochondrial membrane potential and disruption of the mitochondrial matrix. Taken together, these results suggest that oxidative stress caused by H(2)O(2) induces PCD in mouse zygotes and that mitochondria are involved in the early phase of oxidative stress-induced PCD. Furthermore, mitochondrial malfunction also may contribute to cell cycle arrest, followed by cell death, triggered by mild oxidative stress.
Animals↗
Cytoplasm mediates both development and oxidation-induced apoptotic cell death in mouse zygotes.
Eggs must be the major locus of reproductive aging in women, because donation of eggs from younger to middle-aged women abrogates the effects of age on fertility. Oxidative stress, mitochondrial dysfunction, and apoptosis are associated with senescence. To develop an animal model of egg senescence, we treated mouse zygotes with 175 microM H(2)O(2) that induced mitochondrial dysfunction and developmental arrest, followed by delayed cell death, consistent with apoptosis. We reconstructed zygotes with nuclei and cytoplasm from treated or untreated zygotes, then followed development and apoptotic cell death in the reconstituted embryos. Pronuclear exchange between untreated, normal zygotes served as nuclear transfer controls. Rates of cleavage and development to morula and blastocysts were significantly lower (P<0.01) in zygotes reconstituted from untreated pronuclei and H(2)O(2)-stressed cytoplasts than those of nuclear transfer controls. Instead, the arrested, reconstituted zygotes displayed TUNEL staining at a similar rate to that of H(2)O(2)-treated controls, suggesting that apoptotic potential could be transferred cytoplasmically. On the other hand, rates of cleavage and development to morula and blastocyst of the reconstituted zygotes, derived from stressed pronuclei and untreated cytoplasm, were significantly increased (P<0.05), compared to those of H(2)O(2)-treated, control zygotes, indicating that healthy cytoplasm could partly rescue pronuclei from oxidative stress. Although oxidation stressed both nuclei and cytoplasm, cytoplasm was more sensitive than nuclei to oxidative stress. It is suggested that cytoplasm, most likely mitochondria, plays a central role in mediating both development and apoptotic cell death induced by oxidative stress in mouse zygotes.
Animals↗
Oxidative phosphorylation-dependent and -independent oxygen consumption by individual preimplantation mouse embryos.
The self-referencing electrode technique was employed to noninvasively measure gradients of dissolved oxygen in the medium immediately surrounding developing mouse embryos and, thereby, characterized changes in oxygen consumption and utilization during development. A gradient of depleted oxygen surrounded each embryo and could be detected >50 microm from the embryo. Blastocysts depleted the surrounding medium of 0.6+/-0.1 microM of oxygen, whereas early cleavage stage embryos depleted the medium of only 0.3+/-0.1 microM of oxygen, suggesting a twofold increase in oxygen consumption at the blastocyst stage. Mitochondrial oxidative phosphorylation (OXPHOS) accounted for 60-70% of the oxygen consumed by blastocysts, while it accounted for only 30% of the total oxygen consumed by cleavage-stage embryos. The amount of oxygen consumed by non-OXPHOS mechanisms remained relatively constant throughout preimplantation development. By contrast, the amount of oxygen consumed by OXPHOS in blastocysts is greater than that consumed by OXPHOS in cleavage-stage embryos. The amount of oxygen consumed by one-cell embryos was modulated by the absence of pyruvate from the culture medium. Treatment of one-cell embryos and blastocysts with diamide, an agent known to induce cell death in embryos, resulted in a decline in oxygen consumption, such that the medium surrounding dying embryos was not as depleted of oxygen as that surrounding untreated control embryos. Together these results validate the self-referencing electrode technique for analyzing oxygen consumption and utilization by preimplantation embryos and demonstrate that changes in oxygen consumption accompany important physiological events, such as development, response to medium metabolites, or cell death.
Animals↗