Impact of assisted reproductive technologies: a mitochondrial perspective of cytoplasmic transplantation.

Many of the assisted reproductive techniques associated with maternal aging, disease states, or implantation failure aim to correct poor developmental capacity. These techniques are highly invasive and require the exchange of nuclear or cytoplasmic material from a donor oocyte to compensate for deficiencies inherent in the affected individual. These techniques are based on the assumption that the cytoplasm of the donor oocyte can effectively substitute the necessary component(s) to enable development to proceed. Several studies have attempted to inject cytoplasm from "normal" (young) donors, into aged eggs, again assuming that beneficial components of the cytoplasm are transferred to restore developmental capacity. These invasive assisted reproduction technology (ART) procedures aim to eliminate chromosomal abnormalities, improve the quality of oocytes deficient in some important cytoplasmic factors necessary for maturation and/or subsequent development, and eliminate maternally inherited diseases (particularly mitochondrial myopathies). However, in order to develop such ART, understanding the processes involving mitochondrial DNA replication and transcription is imperative, as asynchrony between mitochondrial and nuclear genomes may cause problems in mitochondrial function, localization, and biogenesis.

Mitochondrial DNA deletions in primate embryonic and adult stem cells.

Mitochondrial DNA (mtDNA) mutations occur naturally in skeletal muscle fibers from aged rhesus macaques. In addition, mtDNA mutations have been observed in germinal vesicle oocytes from fertile monkeys. The goal of this study was to determine whether the rhesus macaque mitochondrial common deletion was present in oocytes and embryos generated by in-vitro embryo production (IVP), as well as in rhesus adult and embryonic stem cell lines. The rhesus common deletion was detected in IVP-generated embryos, three IVP-derived embryonic stem cell lines (ORMES 1, 2 and 7), one in-vivo-derived embryonic stem cell line (R4) and multiple passages of an adult bone marrow stromal cell (BMSC) line. Mitochondrial DNA from an adult adipose stromal cell (ATSC) line was compared with mtDNA from an immortalized line transfected with a retroviral vector expressing telomerase, ATSC-TERT. Multiple passages of the ATSC line harboured a dramatically higher level of the rhesus common deletion than the immortalized ATSC-TERT line. Accumulation of mtDNA mutations in oocytes, embryos and subsequent embryonic stem cell lines, as well as adult stem cell lines, may contribute to mitochondrial dysfunction, and thereby impair ATP production. The authors believe this information establishes a compelling argument for the parallel development of embryonic stem cell technology in non-human primates and humans.

Mitochondrial DNA deletions in rhesus macaque oocytes and embryos.

Mitochondria are the most abundant organelles in mammalian oocytes and early embryos. Mitochondrial DNA (mtDNA) mutations, including the common deletion, have been found in skeletal muscle fibres from aged rhesus macaques. The specific aims of this study were to determine whether the mitochondrial common deletion is present in rhesus oocytes after hormonal stimulation and in embryos generated by in vitro production, or whether this deletion is already present in the immature oocyte. Using a nested primer PCR strategy, we found a significant increase in the proportion of mtDNA deletions in stimulated oocytes and embryos from rhesus macaques, compared with mtDNA deletions in immature, unstimulated oocytes derived from necropsied ovaries of age-matched monkeys. The common deletion is larger in the rhesus (5704 bp) than in humans (4977 bp). Accumulation of mtDNA deletions in oocytes may contribute to mitochondrial dysfunction and impaired ATP production. We propose the rhesus to be an excellent model to assess the quality of gametes and embryos and their developmental competence in primates, including humans.

Cardiac and skeletal muscle adaptations to training in systemic hypertension and effect of beta blockade (metoprolol or propranolol).

Cardiovascular and peripheral adaptations to an aerobic conditioning program were studied in 30 hypertensive adults taking either placebo, beta 1-selective beta-adrenergic blocker (metoprolol) or beta 1-nonselective beta-adrenergic blocker (propranolol). The placebo group increased aerobic capacity (VO2max) 24% (p less than 0.002), largely explained by an increased peripheral arteriovenous (AV) oxygen difference with minimal changes in cardiac size and function. Resting blood pressure and total systemic resistance also decreased. The group taking a beta 1-selective beta blocker increased VO2max 8% (p less than 0.05), reduced resting blood pressure but had no significant change of AV oxygen difference or cardiac size or function. The group taking the beta 1-nonselective beta blocker propranolol had no increase in VO2max, no decrease in resting blood pressure and no cardiovascular or peripheral adaptations to the exercise program. Thus, beta 1-selective and beta 1-nonselective beta blockers attenuate conditioning in hypertensive patients to differing degrees, in each case by blocking peripheral mechanisms of conditioning.

ECG abnormalities during excretory urography: the effect of stress.

ECG alterations occurring during IV infusion of contrast agents have been well documented, although the specific causes of these alterations are unknown. Stress and anxiety have been considered important factors, but no prospective evaluation of their impact on ECG alterations has been reported. In order to separate ECG changes resulting from anxiety associated with the procedure itself from those caused by the contrast agent, ECG monitoring was done during IV urography, first when patients were given saline and then again during and after contrast infusion. In both circumstances, the patients were told that they were being given contrast material. One hundred fifty patients undergoing infusion excretory urography with meglumine diatrizoate were studied. Preliminary 12-lead ECGs identified those with initially normal (71) and abnormal (79) tracings. Lead II rhythm strip ECGs were then obtained at 1 and 3 min during a saline infusion and again during contrast infusion; final 12-lead ECGs were done after the contrast infusion. During contrast infusion, PR prolongation (greater than 0.02 sec) occurred in 44% of patients, a change in heart rate (greater than +/- 10 beats/min) occurred in 26%, and benign arrhythmias (premature atrial and ventricular contractions, less than 5/min) occurred in 9%. Saline alone caused no statistically significant ECG alterations (only a single instance of premature atrial contractions). The hypothesis that stress or anxiety may adversely affect ECG reactivity in IV urography is unproved. Although we do not offer proof that it cannot occur, we found no evidence in a study of 150 patients to confirm that stress is an important factor. Only the contrast agent, not saline, produced measurable ECG changes during urography.

Vascular access for acute haemodialysis.

Vascular access for acute haemodialysis was required on 29 occasions in 26 children over a six year period. Comparison was made of the forms of vascular access employed, these being the Scribner shunt, the Hickman line, and percutaneous polyvinylchloride cannulae. The Hickman catheter was used to provide vascular access in 17 patients (mean age 8.8 years (range 2.5-16 years) and mean weight 25.5 kg (range 7.7-60 kg)) and allowed adequate haemodialysis to occur. Only one catheter had to be removed because of infection, and no other serious complications were encountered. These results show the superiority of the Hickman catheter as vascular access for acute haemodialysis in children.

A new echocardiographic model for quantifying three-dimensional endocardial surface area.

A new technique for quantitatively mapping the three-dimensional left ventricular endocardial surface was developed, using measurements from standard cross-sectional echocardiographic images. To validate the accuracy of this echocardiographic mapping technique in an animal model, the endocardial areas of 15 excised canine ventricles were calculated using measurements made from echocardiographic studies of the hearts and compared with areas determined with latex casts of the same ventricles. Close correlation (r = 0.87, p less than 0.001) between these two measures of endocardial area provided preliminary confirmation of the accuracy of the maps. To further characterize the mapping algorithm, it was translated into computer format and used to map the surfaces of idealized hemiellipsoids. Areas measured with this mapping technique closely approximated the actual areas of idealized surfaces with a wide spectrum of shapes; maps were particularly accurate for ellipsoids with shapes similar to those of undistorted human ventricles. Also, the accuracies of area calculations were relatively insensitive to deviation from the assumed positions of the echocardiographic short-axis planes. Finally, although the accuracy of the mapping technique improved as data from more transverse planes were added, the procedure proved reliable for estimating surface areas when data from only three planes were used. These studies confirm the accuracy of the echocardiographic mapping technique, and they suggest that the resulting planar plots might be useful as templates for localizing and quantifying the overall extent of abnormal wall motion.

The ear lobe crease sign and coronary artery disease in aortic stenosis.

Ear lobe creases have been proposed as useful indirect markers of coronary artery disease. To test such a hypothesis, this physical sign was evaluated in 100 patients with symptomatic aortic stenosis undergoing cardiac catheterization to establish the hemodynamic severity of the obstruction and the degree of coronary artery involvement. This is a disorder where the coexistence of cardiac ischemia may play an important part in diagnosis and management. Criteria were established for the degree of ear lobe involvement with a grading of mild (Grade 1), moderate (Grade 2), and severe (Grade 3). Significant coronary artery disease was defined as narrowing greater than or equal to 50% and a coronary score was established. Sensitivity, specificity, positive and negative predictive values were calculated, using Bayesian analysis for three levels of assumed coronary artery disease prevalence. An ear lobe crease score was correlated with a coronary artery disease score, taking into account the variables of age, sex, and body mass index. No useful statistical correlations were found and it is concluded that this physical sign is of little practical value in this clinical setting.

Unruptured sinus of Valsalva aneurysm with right ventricular outflow obstruction diagnosed by two-dimensional and Doppler echocardiography.

This report presents a case of an unusually large unruptured sinus of Valsalva aneurysm complicated by right ventricular outflow tract obstruction, right coronary artery occlusion and incomplete right bundle branch block. Two-dimensional and Doppler echocardiography were instrumental in preoperative diagnosis and postoperative follow-up.

Method for estimating right ventricular volume by planes applicable to cross-sectional echocardiography: correlation with angiographic formulas.

Right ventricular (RV) volumes determined by echocardiography were compared with those measured using established angiographic formulas. RV cast displacement volumes were first correlated with data derived from radiographic images of the casts corresponding to standard angiographic RV views. Four established angiographic formulas (Ferlinz, Boak, Fisher and Thilenius) correlated well with cast volume, with the corrected prism method of Fisher showing a best fit (r = 0.98, y = 1.1 + 0.9 x, standard error of the estimate = 3.6). Cast volumes calculated using our echocardiographic formula were then examined relative to the volumes derived from radiographic images of the RV casts. Volumes calculated using the corrected area-length Thilenius formula correlated best with those obtained using our derived 2-dimensional echocardiographic formula (r = 0.96, y = 4.6 + 1.0 x, standard error of the estimate = 6.8). These data confirm that volume calculated using the suggested optimal echocardiographic formula correlates well with volume obtained using derived angiographic data. Accordingly, confirmation in humans by the use of angiography is a rational step.

Clinical significance of incomplete tricuspid valve closure seen on two-dimensional echocardiography.

Incomplete closure of the tricuspid valve without apparent cusp disease was noted on two-dimensional echocardiography in 31 patients. This abnormality was defined as a failure of the tricuspid valve leaflet tips to reach the plane of the tricuspid valve anulus by at least 1 cm in the standard apical four chamber view at the point of maximal systolic closure. This resulted in a final systolic leaflet position deeper within the right ventricular cavity than is normally seen. The finding was present in the following diagnostic subgroups: Group A, pulmonary hypertension (11 patients); Group B, rheumatic heart disease (4 patients); Group C, dilated cardiomyopathy (9 patients) and Group D, previous myocardial infarction (7 patients). Right atrial, right ventricular and tricuspid anulus measurements were made and compared with those from a group of 67 normal subjects. The results were as follows: right atrial endsystolic area = 27.2 +/- 8.6 cm2 (normal = 13.4 +/- 2.0); right ventricular end-systolic area = 25.6 +/- 8.7 cm2 (normal = 10.9 +/- 2.9); right ventricular end-diastolic area = 31.5 +/- 9.1 cm2 (normal = 20.1 +/- 4.9) and tricuspid valve anular end-systolic dimension = 4.0 +/- 0.6 cm (normal = 2.2 +/- 0.3). The differences from the normal data were all statistically significant (p less than 0.001). Incomplete closure of the tricuspid valve, although a nonspecific diagnostic finding, is primarily associated with right-sided chamber enlargement. Tricuspid regurgitation may be present. The mechanism could be related to geometric changes in valve apparatus dynamics secondary to right-sided cardiac enlargement and tricuspid valve anular dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic efficacy of 24-hour electrocardiographic monitoring for syncope.

The effectiveness of an open referral electrocardiographic monitoring service in identifying an arrhythmogenic cause for syncope was evaluated. Over 5 years, 7,364 patients of all ages underwent ambulatory 24-hour electrocardiographic (Holter) monitoring using a 2-channel recorder. Of these, 1,512 (20.5%) were referred because of syncope. During monitoring, 15 patients had syncope and 7 of the episodes were related to an arrhythmia, usually ventricular tachycardia. Presyncope was reported in 241 patients, with a related arrhythmia in 24. Thus, an arrhythmia-related symptom that could be diagnostic was present in only 2% of the patients monitored. However, syncope or presyncope without an associated arrhythmia might be considered a negative diagnostic clue and occurred in 225 (15%). High-grade atrioventricular block was present in 15 and ventricular tachycardia in 116; only 6 (5%) reported associated symptoms. An age-related incremental increase in atrial and ventricular arrhythmias was found. In 415 of the 1,004 patients (41%) aged 60 years or more, arrhythmias that are conventionally associated with sinoatrial disease were recorded. Using stringent diagnostic criteria, the sick sinus or tachybradycardia syndrome was present in 33 (3%). Many older patients (70%) were taking drugs that could be arrhythmogenic, hypotensive or both. It is concluded that an open referral 24-hour ambulatory monitoring service rarely results in identifying relevant symptom-related arrhythmias in patients with syncope. It records many asymptomatic arrhythmias that can compound rather than resolve the diagnostic problem in older patients, because the data obtained could lead to unnecessary therapy. An iatrogenic cause for syncope should always be considered.