Peripheral blood telomere content is greater in patients with endometriosis than in controls

The etiology of endometriosis remains poorly understood but circulating stem cells may contribute. Telomeres shorten with cell divisions and age. Stem cells attempt to compensate for telomere attrition through the action of telomerase. Since circulating stem cells may contribute to endometriosis, we compared telomere content in lymphocytes of patients with and without endometriosis.

METHODS

Observational study comparing peripheral lymphocytes telomere content, measured by quantitative polymerase chain reaction, in patients with (n = 86) and without endometriosis (n = 21).

FINDINGS

Patients with endometriosis had longer telomeres than that of matched, endometriosis-free controls (telomere to single copy gene ratio [T/S ratio] of 1.62 vs 1.34, respectively, P = .00002). Patients with endometriosis were 8.1-fold more likely to have long telomeres. (odds ratio = 8.1, 95% confidence interval: 1.28-51.57, P = .0264).

INTERPRETATION

Longer telomeres could be consistent with a stem cell origin of endometriosis.

Antihypertensive treatment in patients with class 3 obesity

BACKGROUND

Even though patients with class 3 obesity (body mass index ≥ 40 kg/m(2)) are prone to arterial hypertension and respond less to antihypertensive drugs, they are not considered in hypertension treatment guidelines and data from prospective clinical trials are lacking.

METHODS

In a post hoc analysis of a clinical trial, we compared patients with class 3 obesity with patients with class 1/2 obesity.

RESULTS AND CONCLUSIONS

Blood pressure control in class 3 obesity was less likely to be achieved with hydrochlorothiazide monotherapy. While addition of amlodipine, irbesartan, or aliskiren to hydrochlorothiazide improved the blood pressure response, amlodipine was less effective and induced peripheral edema in 19% of patients with class 3 obesity.

Aliskiren as add-on therapy in the treatment of hypertensive diabetic patients inadequately controlled with valsartan/HCT combination: a placebo-controlled study

BACKGROUND

Hypertension frequently coexists with diabetes mellitus, resulting in increased cardiovascular risk. Thus, BP control is crucial in decreasing morbidity and mortality in this difficult-to-treat patient population.

OBJECTIVE

The objective of this study was to evaluate the efficacy and safety of aliskiren in hypertensive patients with diabetes not adequately responsive to the combination of valsartan and hydrochlorothiazide (HCT).

METHODS

After a 1- to 4-week washout period, patients with a mean sitting diastolic BP (msDBP) ≥95 mmHg were treated with valsartan 160 mg for 2 weeks followed by valsartan/HCT 160 mg/25 mg for an additional 4 weeks (single-blind active run-in period). Patients whose msDBP remained ≥85 mmHg after the active run-in period were randomized (1 : 1) to receive aliskiren 150 mg (n = 184) or placebo (n = 179) as add-on therapy for 6 weeks. Aliskiren was then force-titrated to 300 mg once daily for another 6 weeks. Efficacy variables were: the change in msDBP and mean sitting systolic BP (msSBP) from baseline to week 12 endpoint, diastolic response (msDBP <80 mmHg or reduction of at least 10 mmHg), and BP control rate (<130/80 mmHg).

RESULTS

Of the 363 patients randomized, 328 (90.4%) completed the study (aliskiren and placebo groups: 89.7% and 91.1%, respectively). At week 12 endpoint, the least squares mean (LSM) changes in msDBP (aliskiren vs placebo: -5.8 vs -4.8 mmHg; p = 0.2767) and msSBP (aliskiren vs placebo: -7.3 vs -4.8 mmHg; p = 0.0725) were numerically greater in patients treated with aliskiren compared with those treated with placebo; however, this difference was not statistically significant. The proportion of diastolic responders (aliskiren and placebo: 68.5% and 72.9%, respectively; p = 0.8482) and patients achieving BP control (aliskiren and placebo: 16.0% and 16.4%, respectively; p = 0.7511) were similar for both groups. Overall, 63 (34%) and 59 (33%) patients in the aliskiren and placebo groups, respectively, experienced adverse events (AEs). The most commonly reported AEs were headache (placebo group: 6.1%) and dizziness (aliskiren group: 4.4%). Aliskiren was well tolerated.

CONCLUSION

The reductions in BP with aliskiren added to valsartan/HCT in this study were numerically greater compared with placebo added to valsartan/HCT, although not statistically significant.

Efficacy, safety, and tolerability of aliskiren monotherapy administered with a light meal in elderly hypertensive patients: a randomized, double-blind, placebo-controlled, dose-response evaluation study

This randomized, double-blind, placebo-controlled study assessed the efficacy, safety, and tolerability of aliskiren 75, 150, and 300 mg to clarify the dose-response relationship and characterize the optimum aliskiren dose when given with a light meal to elderly hypertensive patients. After washout, 754 patients aged ≥65 years with hypertension (mean sitting systolic blood pressure [msSBP] ≥150 and <180 mm Hg; mean sitting diastolic blood pressure [msDBP] <110 mm Hg) were randomized to aliskiren 75, 150, or 300 mg or placebo for 8 weeks; medication was taken each morning with a light meal. The primary efficacy variable was change in msSBP from baseline to week 8 end point. Change from baseline in msDBP and dose-response curves for aliskiren 75, 150, and 300 mg were also assessed. At week 8 end point, all 3 aliskiren doses provided significantly greater least squares mean reductions in msSBP/msDBP (75 mg, 13/5 mm Hg; 150 mg, 15/6 mm Hg; 300 mg, 14/7 mm Hg) compared with placebo (8/4 mm Hg; P < .05). Aliskiren was generally well tolerated at all doses. There was a significant dose-response relationship for aliskiren, with an estimated minimum effective dose of 81.9 mg. In conclusion, aliskiren 150 and 300 mg provided effective blood pressure control in elderly patients when given with a light meal.

Comparison of aliskiren/hydrochlorothiazide combination therapy and amlodipine monotherapy in patients with stage 2 systolic hypertension and type 2 diabetes mellitus

Patients with stage 2 hypertension and diabetes are at high cardiovascular risk and require large blood pressure (BP) reductions to reach treatment goals. This randomized double-blind study compared aliskiren/hydrochlorothiazide (HCTZ) combination therapy with amlodipine monotherapy in 860 patients with mean sitting systolic BP (msSBP) ≥160 mm Hg to <200 mm Hg and type 2 diabetes. Patients received either once-daily aliskiren/HCTZ 150/12.5 mg or amlodipine 5 mg for 1 week then force-titrated to double the doses for 7 weeks. Baseline BP was 167.7/91.4 mm Hg. At week 8 end point, aliskiren/HCTZ provided significantly greater reductions in msSBP than amlodipine (28.8 mm Hg vs 26.2 mm Hg; P<.05). Mean sitting diastolic BP reductions were similar with aliskiren/HCTZ (9.9 mm Hg) and amlodipine (9.0 mm Hg). Achievement of BP control (<130/80 mm Hg) was significantly greater with aliskiren/HCTZ (23.2%) than amlodipine (13.8%; P<.0001). Aliskiren/HCTZ provides substantial msSBP reductions and greater BP control rates than amlodipine, and offers an attractive treatment option for patients with hypertension and diabetes mellitus.

Long-term safety and tolerability of the oral direct renin inhibitor aliskiren with optional add-on hydrochlorothiazide in patients with hypertension: a randomized, open-label, parallel-group, multicentre, dose-escalation study with an extension phase

BACKGROUND

Most patients with hypertension will require combination therapy with at least two agents from different antihypertensive classes to achieve blood pressure (BP) control. Thiazide diuretics, such as hydrochlorothiazide (HCTZ), are widely used in combination therapy. The volume reduction with these agents stimulates the renin-angiotensin system (RAS), making RAS inhibitors such as the direct renin inhibitor aliskiren a logical choice for combination therapy with HCTZ.

OBJECTIVE

The aim of this study was to investigate the long-term safety, tolerability and efficacy of the direct renin inhibitor aliskiren, with or without addition of the diuretic HCTZ.

METHODS

In the 12-month core study, patients with hypertension (mean sitting diastolic BP ≥90 mmHg and <110 mmHg) were randomized in a 3 : 2 ratio to once-daily aliskiren 150 mg or 300 mg. At months 2, 3, 4, 6 and 9, treatment was adjusted in patients not achieving a BP goal of <140/90 mmHg. Patients not at goal on aliskiren 150 mg once daily were up-titrated to aliskiren 300 mg once daily. Patients not at goal with aliskiren 300 mg once daily received add-on HCTZ 12.5 mg once daily, which was up-titrated to 25 mg once daily if BP remained inadequately controlled. At month 12, patients who received aliskiren/HCTZ 300 mg/25 mg once daily for at least 8 months in the core study were eligible to enter a 4-month extension study.

RESULTS

Overall, 1625/1955 patients completed the core study, and 870/1955 patients received add-on HCTZ; 189/198 patients completed the 4-month extension. Aliskiren, with or without add-on HCTZ, was generally well tolerated; the incidence of adverse events (AEs) during the core study was similar among the four final treatment groups. The most frequently reported AEs in the core and extension studies were mild and transient cases of nasopharyngitis, headache and dizziness. Few patients exhibited laboratory abnormalities. Overall, aliskiren, with or without add-on HCTZ, reduced mean BP by 18.0/12.7 mmHg at core study endpoint, and 61.2% of patients achieved BP control. BP reductions with aliskiren/HCTZ 300 mg/25 mg combination therapy at the core study endpoint were maintained during the extension study.

CONCLUSION

In patients with hypertension, long-term treatment with aliskiren, with or without add-on HCTZ, is well tolerated and provides effective BP lowering that is sustained over 12 months.

Safety and tolerability of the direct renin inhibitor aliskiren: a pooled analysis of clinical experience in more than 12,000 patients with hypertension

While the safety of renin-angiotensin system (RAS)-blocking drugs such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers is well known, less is known about the new direct renin inhibitor aliskiren. The authors pooled data from 12 randomized controlled trials of aliskiren in patients with hypertension and analyzed the incidence and types of adverse events (AEs) and laboratory abnormalities. Studies were characterized as short-term (≤2 months) placebo-controlled or long-term (>2 months) active-controlled. Relative risks for AEs of particular interest for RAS blockers were calculated. In short-term studies, AEs occurred in similar proportions of aliskiren 150 mg and 300 mg (33.6% and 31.6%, respectively) and placebo treatment groups (36.8%). In long-term studies, a lower proportion of patients treated with aliskiren 150 mg and 300 mg had AEs (33.7% and 43.2%, respectively) than those treated with ACE inhibitors (60.1%), angiotensin receptor blockers (53.9%), and thiazide diuretics (48.9%). Events of special interest, including angioedema, hyperkalemia, and diarrhea occurred in similar proportions of patients taking aliskiren, placebo, and comparator agents. In studies of up to 36 weeks, patients treated with aliskiren were significantly less likely to develop cough than those treated with ACE inhibitors. At the registered doses of 150 mg and 300 mg daily, aliskiren has safety and tolerability profiles similar to placebo, other RAS blockers, and diuretics. Cough rates are lower with aliskiren compared with ACE inhibitors.

Comparative efficacy of aliskiren monotherapy and ramipril monotherapy in patients with stage 2 systolic hypertension: subgroup analysis of a double-blind, active comparator trial

Aliskiren is the first direct renin inhibitor approved for the treatment of hypertension. Blood pressure (BP) control in stage 2 hypertension with aliskiren monotherapy has not been reported. This was a post hoc analysis of the subgroup of patients with stage 2 systolic hypertension (baseline mean sitting systolic BP [msSBP]≥160 mmHg) who completed the 12-week monotherapy phase of a 6-month, double-blind, randomized study. A total of 175 patients were randomized to aliskiren 150 mg (n = 88) or ramipril 5 mg (n = 87) with optional up-titration to aliskiren 300 mg or ramipril 10 mg, respectively, at weeks 6 and 12. In the subgroup of patients with stage 2 systolic hypertension, aliskiren lowered msSBP and mean sitting diastolic BP (msDBP) by 22.3/12.7 mmHg from baseline to week 12; compared with a reduction of 18.1/10.2 mmHg with ramipril. The maximum BP reductions achieved with aliskiren were 60.0/34.0 mmHg (from a baseline of 172.7/107.3 mmHg). Aliskiren was noninferior (P < 0.0001) to ramipril for SBP reduction with nonsignificant superiority (P = 0.052), and superior (P = 0.043) to ramipril for DBP reduction. The proportion of patients who achieved BP control (<140/90 mmHg) after 12 weeks of monotherapy was larger with aliskiren (34/88, 38.6%) than with ramipril (22/87, 25.3%; P = 0.038). In this post hoc analysis, 12 weeks of monotherapy with aliskiren 150-300 mg provided effective mean BP reductions (22/13 mmHg) and was superior to ramipril 5-10 mg in controlling BP in patients with stage 2 systolic hypertension.

Evaluation of the dose--response relationship of aliskiren, a direct renin inhibitor, in an 8-week, multicenter, randomized, double-blind, parallel-group, placebo-controlled study in adult patients with stage 1 or 2 essential hypertension

BACKGROUND

Aliskiren is approved for the treatment of hypertension at once-daily doses of 150 or 300 mg by the US Food and Drug Administration and the European Commission. It is generally well tolerated and provides 24-hour, dose-dependent blood pressure (BP) reduction; however, the effect of the 75-mg dose has been inconsistent in previous trials.

OBJECTIVES

This study was designed to assess the efficacy and tolerability of once-daily administration of aliskiren 75 mg and to evaluate the dose-response relationship across all 3 doses of aliskiren (75, 150, and 300 mg).

METHODS

In this 8-week, multicenter, randomized, double-blind, parallel-group, placebo-controlled study, patients aged > or =18 years with stage 1 or 2 essential hypertension entered a 3- to 4-week, single-blind, placebo run-in period. Eligible patients were randomized (1:1:1:1) to receive oral, once-daily doses of aliskiren 75, 150, or 300 mg or placebo. The primary efficacy variable was the change from baseline in mean sitting diastolic BP (msDBP) at the week-8 end point. Tolerability was assessed by monitoring and recording all adverse events (AEs).

RESULTS

A total of 642 patients (mean [SD] age, 52.0 [10.73] years; 60.0% male; 80.8% white; mean body weight, 89.2 [18.4] kg [range, 50-160 kg]) were included in the study. Overall, 576 patients (89.7%) completed the double-blind treatment period. The most frequent reasons for discontinuation were unsatisfactory therapeutic effect (27/642 randomized patients [4.2%]) and AEs (17/642 [2.6%]). At end point, aliskiren 150 and 300 mg significantly reduced msDBP (both, P < 0.001) and mean sitting systolic

CONCLUSIONS

This study found a positive linear dose-response relationship in BP reduction with aliskiren 75, 150, and 300 mg dosed once daily, but only aliskiren 150 and 300 mg provided statistically significant reductions from baseline compared with placebo. All 3 doses of aliskiren were generally well tolerated.

Influence of body weight and gender on the pharmacokinetics, pharmacodynamics, and antihypertensive efficacy of aliskiren

Gender and body weight influence the pharmacokinetics and pharmacodynamics of many drugs. This pooled analysis of 17 clinical studies evaluated the effect of gender, body mass index (BMI), body weight, and lean body weight (LBW) on the pharmacokinetics of the direct renin inhibitor aliskiren in healthy volunteers (n = 392). A separate pooled analysis of 5 clinical studies in patients with hypertension (n = 2327) assessed the influence of gender and BMI on the effects of aliskiren on plasma renin activity and blood pressure. Area under the aliskiren plasma concentration-time curve (AUC(τ)) was 22% lower and the peak aliskiren plasma concentration (C(max)) was 24% lower in men than women (P < .05). BMI was not significantly correlated with AUC(τ) (r = 0.005; P = .917); AUC(τ) was negatively correlated with body weight (r = -0.235; P < .0001) and LBW (r = -0.295; P < .0001). Results were similar for C(max). Adjusting individual aliskiren AUC(τ) and C(max) values for overall mean body weight or LBW abolished gender differences. Based on r(2) values, LBW variation accounted for 8.9% of aliskiren AUC(τ) variation. In patients with hypertension, gender and BMI did not significantly influence the effects of aliskiren on plasma renin activity or blood pressure. It was concluded that lower systemic exposure to aliskiren in men versus women relates to differences in body weight; neither gender nor body weight has clinically relevant effects on the pharmacokinetics or pharmacodynamics of aliskiren.

Effects of the direct renin inhibitor aliskiren and atenolol alone or in combination in patients with hypertension

INTRODUCTION

Aliskiren is the first in a new class of direct renin inhibitors to be approved for the treatment of hypertension.

PATIENTS AND METHODS

In this double-blind, multicentre trial, 694 patients with hypertension (mean sitting diastolic blood pressure [BP] > or = 95 and < 110 mmHg) were randomised to once-daily aliskiren 150 mg (n=231), atenolol 50 mg (n=231) or the combination (150/50 mg; n=232) for six weeks, followed by a further six weeks on double the initial doses of aliskiren and atenolol. Efficacy (reduction from baseline in mean sitting systolic and diastolic BP) and tolerability of study treatments were assessed; plasma renin activity (PRA) was measured in a subset of patients.

RESULTS

At Week 12 endpoint, aliskiren, atenolol and aliskiren/atenolol lowered systolic and diastolic BP from baseline by 14.3/11.3, 14.3/13.7 and 17.3/14.1 mmHg, respectively. Systolic BP reductions with aliskiren/atenolol were significantly greater than those with aliskiren (p=0.039) or atenolol (p=0.034) alone, and diastolic BP reductions were greater than with aliskiren alone (p<0.001). Diastolic BP changes were larger with atenolol than with aliskiren (p=0.003, correlating with the large reductions in pulse rate (> 10 bpm) observed with atenolol. Aliskiren, atenolol and aliskiren/atenolol reduced geometric mean PRA from baseline by 65%, 52% and 61%, respectively. In patients with moderate or high baseline PRA (> or = 0.65 ng/ml/hour), PRA was reduced to low levels (< 0.65 ng/ml/hour) at Week 12 endpoint in a greater proportion of patients receiving aliskiren (11/15 patients, 73.3%) or aliskiren/atenolol (18/23, 78.3%) than with atenolol (10/21, 47.6%). Aliskiren treatment was associated with numerically lower rates of adverse events and discontinuations due to adverse events compared with atenolol or combination treatment, and unlike atenolol was not associated with bradycardia.

CONCLUSIONS

Direct renin inhibition with aliskiren may be an appropriate substitute for beta-blocker treatment in patients with uncomplicated hypertension. Aliskiren also represents an attractive option for dual therapy with atenolol to improve systolic BP/pulse pressure reductions and BP control with maintained tolerability compared with atenolol alone.

Decisions and ethical issues among BRCA carriers and the use of preimplantation genetic diagnosis

The lifetime risks for both breast and ovarian cancer for BRCA mutation carriers far exceeds the general population risk of 13% for breast cancer and 1.4% for ovarian cancer. BRCA carriers have unique and medically complicated decisions to make regarding their cancer treatment or risk reduction. As BRCA testing becomes increasingly common among unaffected individuals in families with a previously documented BRCA mutation, there are a growing number of individuals with unique psychosocial needs and concerns. This review paper describes the BRCA 1/2 population, discusses preimplantation genetic diagnosis (PGD), and describes the decisions and ethical issues related to PGD among the BRCA 1/ 2 population.

Comparative effects of aliskiren-based and ramipril-based therapy on the renin system during long-term (6 months) treatment and withdrawal in patients with hypertension

INTRODUCTION

This subgroup analysis assessed the effects of treatment based on the direct renin inhibitor, aliskiren, or the angiotensin-converting enzyme inhibitor, ramipril, on plasma renin activity (PRA), plasma renin concentration (PRC) and other biomarkers in a 26-week randomised, double-blind trial. Changes in PRA and PRC after stopping treatment were also assessed.

METHODS

After placebo run-in, 842 patients (mean sitting diastolic blood pressure (BP) 95-109 mmHg) were randomised to aliskiren 150 mg or ramipril 5 mg. Dose titration and hydrochlorothiazide addition were allowed after Week 6 and 12, respectively, for inadequate BP control. Patients completing active treatment were re-randomised to current regimen or placebo during a 4-week posttreatment phase.

RESULTS

BP reductions were independent of baseline PRA at Week 12, were greater with aliskiren- than ramipril-based therapy at Week 26 (17.9/13.3 vs. 15.2/12.0 mmHg, p<0.05) and persisted for longer after stopping aliskiren. Aliskiren-based therapy reduced geometric mean PRA (-63%, p<0.05; n=103), while ramipril-based therapy increased PRA (+143%, p<0.05; n=100) at Week 26; PRC increased in both groups (aliskiren: +224% [n=33], ramipril: +145% [n=39], both p<0.05). Four weeks after stopping aliskiren-based therapy, PRA remained 52% below pre-treatment baseline; PRA returned to baseline 2 weeks after stopping ramipril-based therapy.

CONCLUSIONS

Aliskiren-based therapy produced sustained BP and PRA reductions over 26 weeks; ramipril-based therapy lowered BP and increased PRA. PRA reductions persisted 4 weeks after stopping aliskiren, suggesting an inhibitory effect beyond the elimination half-life of the drug.

Aliskiren, a novel oral renin inhibitor, provides dose-dependent efficacy and placebo-like tolerability in Japanese patients with hypertension

Aliskiren is a novel orally active renin inhibitor for the treatment of hypertension. This study evaluated the antihypertensive efficacy, safety and tolerability of aliskiren in Japanese patients with hypertension. Forty hundred and fifty-five Japanese men and women with a mean sitting diastolic blood pressure of 95-110 mmHg were randomized to receive once-daily double-blind treatment for 8 weeks with aliskiren 75, 150 or 300 mg or placebo. Aliskiren produced significant, dose-dependent reductions in mean sitting diastolic blood pressure (p<0.0005 vs. placebo for each dose) and mean sitting systolic blood pressure (p<0.001 vs. placebo for each dose). The placebo-corrected reductions in mean sitting systolic/diastolic blood pressure were 5.7/4.0, 5.9/4.5 and 11.2/7.5 mmHg in the aliskiren 75, 150 and 300 mg groups, respectively. After 8 weeks' treatment, 27.8%, 47.8%, 48.2% and 63.7% of patients in the placebo and aliskiren 75, 150 and 300 mg groups, respectively, achieved a successful treatment response (diastolic blood pressure <90 mmHg and/or reduced by > or =10 mmHg from baseline; p<0.005 vs. placebo for each dose). Aliskiren treatment was well tolerated, with the incidence of adverse events reported in the active treatment groups (53-55%) being similar to that in the placebo group (50%). This study, which is the first to assess the antihypertensive efficacy and safety of aliskiren in Japanese patients with hypertension, demonstrates that the once-daily oral renin inhibitor aliskiren provides significant, dose-dependent reductions in blood pressure with placebo-like tolerability.

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.

Direct Renin inhibition with aliskiren in obese patients with arterial hypertension

Current guidelines from the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommend first-line treatment with a thiazide diuretic but do not provide specific guidance for obese patients. The renin system is activated in obesity-associated arterial hypertension. Therefore, we tested the hypothesis that the oral direct renin inhibitor aliskiren could provide additive blood pressure lowering in obese patients with hypertension (body mass index >or=30 kg/m(2); mean sitting diastolic blood pressure: 95 to 109 mm Hg) who had not responded to 4 weeks of treatment with hydrochlorothiazide (HCTZ) 25 mg. After a 2- to 4-week washout, 560 patients received single-blind HCTZ (25 mg) for 4 weeks; 489 nonresponders were randomly assigned to double-blind aliskiren (150 mg), irbesartan (150 mg), amlodipine (5 mg), or placebo for 4 weeks added to HCTZ (25 mg), followed by 8 weeks on double the initial doses of aliskiren, irbesartan, or amlodipine. After 8 weeks of double-blind treatment (4 weeks on the higher dose), aliskiren/HCTZ lowered blood pressure by 15.8/11.9 mm Hg, significantly more (P<0.0001) than placebo/HCTZ (8.6/7.9 mm Hg). Aliskiren/HCTZ provided blood pressure reductions similar to those with irbesartan/HCTZ and amlodipine/HCTZ (15.4/11.3 and 13.6/10.3 mm Hg, respectively), with similar tolerability to placebo/HCTZ. Adverse event rates were highest with amlodipine/HCTZ because of a higher incidence of peripheral edema (11.1% versus 0.8% to 1.6% in other groups). In conclusion, combination treatment with aliskiren is a highly effective and well-tolerated therapeutic option for obese patients with hypertension who fail to achieve blood pressure control with first-line thiazide diuretic treatment.

Aliskiren, an Oral Renin Inhibitor, Provides Dose-Dependent Efficacy and Sustained 24-Hour Blood Pressure Control in Patients With Hypertension

OBJECTIVES

This dose-ranging study evaluated the antihypertensive efficacy and tolerability of aliskiren in patients with mild-to-moderate hypertension.

BACKGROUND

Low blood pressure (BP) control rates among patients with hypertension indicate a need for improved treatment options. This study investigates aliskiren, the first in a new antihypertensive class called renin inhibitors.

METHODS

Patients with mean sitting diastolic BP 95 to 109 mm Hg were randomized to aliskiren 150, 300, or 600 mg or placebo once daily for 8 weeks. Patients completing this treatment phase entered a 2-week treatment-free withdrawal period. Office BP was recorded at baseline, weeks 2, 4, 6, and 8 of treatment, and 4 days and 2 weeks after cessation of treatment. A subgroup of patients underwent ambulatory BP monitoring.

RESULTS

In total, 672 patients were randomized to treatment. After 8 weeks, aliskiren 150, 300, and 600 mg significantly reduced mean sitting BP (systolic/diastolic) by 13.0/10.3, 14.7/11.1, and 15.8/12.5 mm Hg, respectively, versus 3.8/4.9 mm Hg with placebo (all p < 0.0001 for systolic and diastolic BP). The BP-lowering effect of aliskiren persisted for up to 2 weeks after treatment withdrawal. Aliskiren significantly reduced mean 24-h ambulatory BP (p < 0.0001 vs. placebo with all doses) exhibiting smooth, sustained effects and high trough-to-peak ratios. Aliskiren was well tolerated; overall adverse event rates were 40.1%, 46.7%, and 52.4% with aliskiren 150, 300, and 600 mg, respectively, and 43.0% with placebo. Few patients discontinued treatment due to adverse events.

CONCLUSIONS

Aliskiren provides significant antihypertensive efficacy in patients with hypertension, with no rebound effects on blood pressure after treatment withdrawal.

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.

QTc interval prolongation associated with intravenous methadone

Numerous medications prolong the rate-corrected QT (QTc) interval and induce arrhythmias by blocking ionic current through cardiac potassium channels composed of subunits expressed by the human ether-a-go-go-related gene (HERG). Recent reports suggest that high doses of methadone cause torsades de pointes. To date, no controlled study has described an association between methadone and QTc prolongation. The only commercial formulation of parenteral methadone available in the United States contains the preservative chlorobutanol. The objectives of this study are to determine: (1) whether the administration of intravenous (i.v.) methadone causes QTc prolongation in humans; (2) whether methadone and/or chlorobutanol block cardiac HERG potassium currents (IHERG) in vitro. Over 20 months, we identified every inpatient with at least one electrocardiogram (ECG) performed on i.v. methadone. For each patient, we measured QTc intervals for every available ECG performed on and off i.v. methadone. Concurrent methadone doses were also recorded. Similar data were collected for a separate group of inpatients treated with i.v. morphine. In a separate set of experiments IHERG was evaluated in transfected human embryonic kidney cells exposed to increasing concentrations of methadone, chlorobutanol, and the two in combination. Mean difference (+/- standard error) per patient in QTc intervals on and off methadone was 41.7 (+/- 7.8)ms, p<0.0001. Mean difference in QTc intervals on and off morphine was 9.0 (+/- 6.1)ms, p=0.15. The approximately linear relationship between QTc measurements and log-dose of methadone was significant (p<0.0001). Methadone and chlorobutanol independently block IHERG in a concentration-dependent manner with IC50 values of 20 +/- 2 microM and 4.4 +/- 0.3 mM, respectively. Chlorobutanol potentiates methadone's ability to block IHERG. Methadone in combination with chlorobutanol is associated with QTc interval prolongation. Our data strongly suggest that methadone in combination with chlorobutanol is associated with QTc interval prolongation.

Trastuzumab-associated cardiotoxicity

Trastuzumab is a monoclonal antibody used for the treatment of metastatic breast carcinoma in women whose tumors overexpress the HER2 protein. Cardiotoxicity has been reported to occur with trastuzumab when administered alone and in combination with antineoplastic agents, particularly anthracyclines. The risk of cardiotoxicity with trastuzumab has been reported to be 4% with monotherapy and 27% when administered in combination with an anthracycline and cyclophosphamide, but to the author's knowledge severe outcomes, such as death or permanent disability, are uncommon. The majority of reported cardiac effects are mild to moderate, nonspecific, and medically manageable. Signs and symptoms are similar to those observed in patients who develop anthracycline-induced cardiomyopathy and include tachycardia, palpitations, and exertional dyspnea, which may progress to congestive heart failure. The pathogenesis and histologic changes responsible for trastuzumab-associated cardiotoxicity currently are under investigation. Unlike anthracycline-induced toxicity, trastuzumab-associated toxicity usually responds to standard treatment or the discontinuation of trastuzumab, and there is no evidence that the toxicity is dose related. Current methods for the early detection of cardiotoxicity in trastuzumab-treated patients are similar to those used in anthracycline-treated patients. Cardiac function is established at baseline and monitored regularly during treatment by physical examination and measurement of left ventricular ejection fraction. The majority of patients improve with proper treatment, and some are able to continue to receive trastuzumab.

The cardiotoxic potential of the 5-HT(3) receptor antagonist antiemetics: is there cause for concern?

PURPOSE

To review and evaluate the potential cardiac effects of 5-HT(3) antiemetic treatment in patients who may be predisposed to cardiac complications resulting from malignancy, cytotoxic oncologic regimens, or preexisting comorbid conditions.

DESIGN

A literature review was conducted on the negative cardiovascular effects of chemotherapeutic agents, and, more specifically, on the cardiac interactions of the 5-HT(3) receptor antagonists commonly used to treat chemotherapy-induced nausea and vomiting.

RESULTS

Clinical studies in healthy subjects have reported electrocardiograph changes following administration of 5-HT(3) receptor antagonists. However, there are limited data on the use of 5-HT(3) antiemetics when administered with cardiotoxic chemotherapy. Nonetheless, the development of significant electrocardiograph changes with some agents may indicate a potential for significant cardiac effects in patients, particularly those who may be predisposed to cardiac complication.

CONCLUSIONS

As the predicted human life span increases, clinicians will be treating a larger, older oncology population. Because two of the most common major comorbidities are cardiovascular related, we need to be acutely aware of the toxic effects of chemotherapy, as well as the possible cardiac interaction of supportive agents, specifically the 5-HT(3) antiemetics. Until more data are made available, the best antiemetic option for patients receiving emetogenic and cardiotoxic chemotherapy may be the agent with the fewest apparent cardiac effects.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Noninvasive measurement of potassium efflux as an early indicator of cell death in mouse embryos

Programmed cell death (apoptosis) occurs in nearly all cell types examined, including mammalian oocytes and embryos, where it may underlie some forms of infertility in humans. Although the molecular machinery participating in apoptosis have been intensely investigated, the accompanying physiological changes have not received similar attention. In this study, a novel electrophysiology technique has been employed to monitor real-time perturbations in the physiology of mouse embryos undergoing apoptosis evoked by hydrogen peroxide, diamide, and staurosporine. Despite differences in their mode of action, these agents evoked a similar early change in cellular physiology; namely, a pronounced, transient, potassium efflux through tetraethylammonium-sensitive potassium channels accompanied by cell shrinkage. Mouse zygotes exposed to 200 microM H(2)O(2) exhibited potassium efflux that elevated the potassium concentration of the media surrounding embryos by 1.4 +/- 0.1 microM. Pretreatment with tetraethylammonium inhibited this increase (0.2 +/- 0.1 microM). Our results indicate that potassium efflux through potassium channels and concurrent cell shrinkage are early indicators of cell death in embryos and that noninvasive measurements of potassium pathophysiology may identify embryos undergoing cell death prior to the manifestation of other morphological or molecular hallmarks of cell death.

Increased birefringence in the meiotic spindle provides a new marker for the onset of activation in living oocytes

The newly developed Pol-Scope allows imaging of spindle retardance, which is an optical property of organized macromolecular structures that can be observed in living cells without fixation or staining. Experiments were undertaken to examine changes in meiotic spindles during the initial stages of activation of living mouse oocytes using the Pol-Scope. Parthenogenetic activation of oocytes treated with calcium ionophore evoked a dynamic increase in meiotic spindle retardance, particularly of the midregion, before spindle rotation and second polar body extrusion. The pronounced increase in spindle retardance, which could, for the first time to our knowledge, be quantified in living oocytes, was maintained during polar body extrusion. Spindle retardance of newly in vivo fertilized oocytes was significantly higher than that of ovulated, metaphase II oocytes. Pol-Scope imaging of fertilized oocytes did not affect subsequent development. These results establish that increased spindle retardance precedes polar body extrusion and pronuclear formation. The increased birefringence in the spindle provides an early indicator of oocyte activation. Thus, noninvasive, quantitative imaging of the onset of activation in living oocytes might improve the efficiency of assisted fertilization and other embryo technologies.

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.

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.