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Biomedical subjects

A Pines

Publications and source records attributed to A Pines.

At least 73 records · Page 4Linked to original sources
PubMed1998

The effects of sublingual estradiol on left ventricular function at rest and exercise in postmenopausal women: an echocardiographic assessment.

OBJECTIVE: To evaluate the acute hemodynamic effects of 4 mg estradiol given sublingually. DESIGN: Rest and exercise echocardiographies were performed prior to estradiol administration. Then, another set of tests was done post-dose: rest examination at 1 h post-dose, isometric exercise at 65 min post-dose, and dynamic exercise at 100 min post-dose. RESULTS: The administration of 4 mg sublingual estradiol to 24 postmenopausal women (aged 48-58 years) was followed 60 min post-dose by a surge in mean estradiol serum levels (1759 +/- 704 pg/ml). At rest a slight drop in systolic and diastolic blood pressure was measured after estrogen ingestion: 132 +/- 24 mm Hg versus 127 +/- 21 mm Hg, p < 0.05; 83 +/- 11 mm Hg versus 78 +/- 10 mm Hg, p < 0.02. There were no changes in resting heart rate, double product, or vascular resistance. The left heart cavities became smaller: the left atrium diameter decreased from 33.7 +/- 4 mm to 32.3 +/- 4 mm, p < 0.01; the end-systolic diameter decreased from 24.9 +/- 3 mm to 23.6 +/- 4 mm, p < 0.01; the end-diastolic diameter decreased from 44.5 +/- 4 mm to 42.7 +/- 4 mm, p < 0.01. The peak aortic blood flow velocity fell from 120 +/- 19 cm/s to 116 +/- 22 cm/s (p < 0.05), and the flow velocity integral fell from 26.3 +/- 4 cm to 24.9 +/- 5 cm (p < 0.01); the cardiac output underwent a small change, with borderline significance: 7 +/- 2 L/min versus 6.7 +/- 2 L/min, p = 0.06. Only minor changes in the hemodynamic and echocardiographic parameters were recorded after estrogen for both isometric and dynamic exercises. Analyses were also made for two subgroups: 13 normotensive women were compared with 11 hypertensive women. The post-estrogen decreases in resting blood pressure and in peak blood velocity were observed only in the hypertensive subjects, whereas the changes in heart dimensions and in flow velocity integral were the same in both subgroups. CONCLUSIONS: Sublingual estradiol was associated with acute hemodynamic alterations mainly at rest but also after exercise.

Administration, Sublingual↗
PubMed1997

In vivo NMR and MRI using injection delivery of laser-polarized xenon.

Because xenon NMR is highly sensitive to the local environment, laser-polarized xenon could be a unique probe of living tissues. Realization of clinical and medical science applications beyond lung airspace imaging requires methods of efficient delivery of laser-polarized xenon to tissues, because of the short spin-lattice relaxation times and relatively low concentrations of xenon attainable in the body. Preliminary results from the application of a polarized xenon injection technique for in vivo 129Xe NMR/MRI are extrapolated along with a simple model of xenon transit to show that the peak local concentration of polarized xenon delivered to tissues by injection may exceed that delivered by respiration by severalfold.

Humans↗
PubMed1997

Comparison of left ventricular function using isometric exercise Doppler echocardiography in competitive runners and weightlifters versus sedentary individuals.

It is unclear whether cardiovascular responses to heavy isometric exercise are changed by intensive training. We evaluated the effects of this type of exercise on left ventricular (LV) function in athletes engaged in static and dynamic sport, compared with sedentary persons, and looked for peculiarities in static athletes' responses that might reflect adaptive mechanisms to their specific activity. The study population comprised 45 men (age 24 +/- 5 years): 29 dynamic and 16 static athletes (runners and weightlifters, respectively). The control group consisted of 20 age and gender-matched healthy sedentary persons. All performed 50% of maximal voluntary contraction on a whole-body isometric exercise device for 2 minutes. Echocardiographic calculations were determined at rest and exercise. Upon exercise, stroke volume, cardiac output, end-diastolic volume, and ejection fraction increased significantly in athletes, while end-systolic volume and systemic vascular resistance decreased. In sedentary persons, stroke volume and resistance remained unchanged, cardiac output and LV volumes increased, and ejection fraction decreased from 67 +/- 5% to 60 +/- 5% (p <0.01 compared with rest; p <0.0001 compared with athletes). Whereas peak flow velocity decreased from 103 +/- 10 to 81 +/- 6 cm/s in sedentary persons, it increased from 112 +/- 9 to 126 +/- 8 cm/s in the static group and from 120 +/-3 to 126 +/- 9 cm/s in the dynamic athletes (p <0.0001 compared with the sedentary group). Mean acceleration decreased in the sedentary group, remained unchanged among the dynamic athletes, and increased among the static athletes. We conclude that cardiovascular responses to heavy isometric exercise are modified by intensive training. Athletes, taken as a group, react differently and adapt better than sedentary individuals. Moreover, among them, those involved in static sport show an improved cardiovascular adaptation to this type of exercise.

Adult↗
PubMed1997

Impact of early exercise radionuclide cineangiography on long-term prognosis after CABG.

BACKGROUND: The immediate benefits of coronary artery bypass grafting might be only transient. This prospective study examined the capability of exercise radionuclide cineangiography done shortly after coronary artery bypass grafting to predict outcome and long-term prognosis. METHODS: Results of exercise radionuclide cineangiography at 5.5 +/- 0.7 months (range, 4 to 8 months) postoperatively were correlated with mortality, major surgical and nonsurgical cardiac events, and cardiac event-free survival in 100 consecutive patients who underwent coronary artery bypass grafting. Stepwise logistic regression analysis was used to evaluate the incremental value of radionuclide cineangiography beyond the commonly used variables. RESULTS: Left ventricular ejection fraction at rest was normal (> or = 0.45) in 72 patients and increased on exercise in 58. The exercise radionuclide variables that correlated with future cardiac events were change and fractional change in heart rate, ST segment changes, anginal pain and congestive heart symptoms during exercise, rest ejection fraction, and change and fractional changes in ejection fraction. Predictors of event-free survival were exercise heart rate, rest ejection fraction, and change and fractional change in ejection fraction during exercise. Logistic regression analysis revealed that change in ejection fraction was an independent predictor of cardiac death and surgical interventions, whereas resting ejection fraction was a predictor of nonsurgical cardiac events. CONCLUSIONS: Postoperative exercise radionuclide cineangiography carried out soon after coronary artery bypass grafting had definite independent prognostic value and should be performed routinely to help decide treatment protocol.

Adult↗
PubMed1997

Does hormone replacement therapy inhibit coronary artery calcification?

OBJECTIVE: To determine the association between the use of hormone replacement therapy (HRT) and coronary calcium, in postmenopausal women who had no history of coronary artery disease by double helical computed tomography (CT). METHODS: We used CT to compare the prevalence and extent of coronary calcium in 41 postmenopausal women who were on HRT from the first year of menopause and 37 age-matched controls who had never used HRT. RESULTS: Both groups had a similar rate of smoking, hypertension, a positive family history, and hypercholesterolemia. Coronary calcification was observed in 28.2% of the 78 women studied. The prevalence of coronary calcium was significantly lower among HRT users: six of the 47 (14.6%), compared with 16 of the 37 nonusers (43.2%) (P < .01). The recorded risk factors had no effect on the prevalence of coronary calcium. Stepwise logistic regression analysis, including age, coronary risk factors, and HRT use as independent variables, yielded HRT as the only variable determining the presence of coronary calcium (odds ratio = 0.2; 95% confidence interval 0.06, 0.63; P = .006). CONCLUSION: The lower incidence of coronary calcium in the HRT users suggests that HRT is associated with decreased prevalence of the coronary calcification.

Calcinosis↗
PubMed1997

Hormone replacement therapy and cardioprotection: basic concepts and clinical considerations.

A large body of epidemiological evidence shows that estrogen use after the menopause reduces the incidence of cardiovascular disease up to 50%. The use of progestin as co-medication in HRT appears not to attenuate the cardioprotective effects of estrogen. Menopause-related changes in metabolic cardiovascular risk factors are identifiable, as are HRT-related changes in these factors. Estrogens may act in a gender-specific way on vascular endothelial cells and other components of the vessel wall enhancing the synthesis and release of NO and other vasodilators and by inhibiting the synthesis and release of vasoconstricting agents, thus favoring vasodilation. Angiographic studies demonstrated in postmenopausal women with ischemic heart disease a reduction in coronary stenosis by estrogen monotherapy. Several studies, including the PEPI-trial, failed to demonstrate any major effect of HRT on blood pressure. The information on HRT and cardioprotection which is available so far is very promising and merits recommending HRT not only in healthy women but also in women with cardiovascular disease as well as in women with increased risk for this disease.

Blood Pressure↗
PubMed1997

Multiple-quantum magic-angle spinning and dynamic-angle spinning NMR spectroscopy of quadrupolar nuclei.

Several aspects of the Multiple-Quantum Magic-Angle Spinning (MQMAS) technique (L. Frydman and J.S. Harwood, J. Am. Chem. Soc., 117 (1995) 5367) are compared with Dynamic-Angle Spinning (DAS). Examples of MQMAS spectra are shown for I = 3/2 nuclei with CQ up to 3.6 MHz, and for 27Al (I = 5/2) with CQ up to 10 MHz. The MQMAS linewidth is largely independent of the magnitude of the homonuclear dipolar interaction, while the spinning sideband manifold is similar to that observed in DAS experiments. MQMAS is technically simple and routinely useful for studying nuclei with short spin-lattice relaxation times, but care must be taken in its use for quantitative studies as the excitation of the triple-quantum coherence is not uniform. In this regard, MQMAS is most useful for samples with small quadrupolar coupling constants. In the specific case of 17O, DAS would give spectra with excellent resolution in comparison to MQMAS. The different advantages of DAS and MQMAS make them useful complementary techniques in many cases. Two additional methods are also presented for extracting the chemical shift anisotropy (CSA) directly for quadrupolar nuclei using the multiple-quantum scheme.

Magnetic Resonance Spectroscopy↗
PubMed1997

31P to 77Se cross polarization in beta-P4Se3.

Cross polarization from 31P to 77Se is demonstrated in beta-P4Se3. This material, an inorganic glass, is readily synthesized from the elements and serves as a convenient sample for setting the Hartmann-Hahn condition.

Chemical Phenomena↗
PubMed1997

Acute myocardial infarction in patients who have had coronary artery bypass surgery.

BACKGROUND: Although acute myocardial infarction (AMI) and coronary artery bypass grafting (CABG) are frequently discussed, the issue of AMI in patients who have previously had CABG has not been addressed yet. METHODS: We critically reviewed data obtained from the medical literature on this subject since 1974. RESULTS: The overall incidence of AMI is about 10% during the first 3 years after CABG, though it occurs more frequently in older male patients. It seems that the infarct size is smaller and post-AMI ejection fraction is higher in patients who have had CABG than in those who have not. Although early mortality appears to be lower, on 5-year follow-up, more patients had AMI, angina, and revascularization procedures. CONCLUSIONS: The data abstracted indicate that AMI after CABG appears to be a well-delineated entity. Further studies are necessary to determine the optimal treatment for this population.

Age Factors↗
PubMed1996

Exercise echocardiography in postmenopausal hormone users with mild systemic hypertension.

Rest and exercise echocardiography (at dynamic and isometric exercise) were performed in 30 postmenopausal women (aged 54 +/- 4 years) with borderline to mild hypertension. They were then divided into 2 groups: 17 women who started oral hormone replacement therapy (0.625 mg/day conjugated estrogens or 2 mg/day estradiol) and a control group of 13 nonusers. After 6 to 9 months, a second echocardiography was performed in 26 women (4 withdrew). There were only a few changes in values obtained in the 12 controls at the end of follow-up compared with baseline. Primarily, these changes included a slight decrease in systolic blood pressure at rest and on exercise. Several significant morphologic and hemodynamic alterations appeared in 14 hormone users. Left ventricular cavity dimensions and mass became smaller: mean end-diastolic diameter decreased from 45.9 +/- 3 mm at baseline to 44.4 +/- 3 mm at study termination (p = 0.007). The corresponding values for end-systolic diameter were 25.8 +/- 4 mm and 23.9 +/- 4 mm (p = 0.006); for left atrium diameter, it was 34.5 +/- 4 mm and 32.5 +/- 4 mm (p = 0.001); for left ventricular wall width, it was 19.9 +/- 2 mm and 19.3 +/- 2 mm (p = 0.02); for left ventricular mass, it was 197 +/- 28 g and 179 +/- 32 g (p = 0.006). The resting aortic blood flow velocity and acceleration increased: 119 +/- 18 cm/s before therapy versus 129 +/- 23 cm/s while on hormone substitution (p = 0.04), and 13.6 +/- 3 m/s2 versus 16.5 +/- 4 m/s2 (p = 0.008), respectively. Mean rest to peak exercise systolic blood pressure difference became smaller after hormones: 39 +/- 19 mm Hg versus 28 +/- 13 mm Hg (p = 0.03) during dynamic exercise, and 43 +/- 22 mm Hg versus 25 +/- 13 mm Hg (p = 0.004) during isometric exercise. The above data probably indicate that with hormone replacement therapy, there is an improvement in cardiac function both at rest and during exercise.

Echocardiography, Doppler↗
PubMed1996

NMR of laser-polarized xenon in human blood.

By means of optical pumping with laser light it is possible to enhance the nuclear spin polarization of gaseous xenon by four to five orders of magnitude. The enhanced polarization has allowed advances in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI), including polarization transfer to molecules and imaging of lungs and other void spaces. A critical issue for such applications is the delivery of xenon to the sample while maintaining the polarization. Described herein is an efficient method for the introduction of laser-polarized xenon into systems of biological and medical interest for the purpose of obtaining highly enhanced NMR/MRI signals. Using this method, we have made the first observation of the time-resolved process of xenon penetrating the red blood cells in fresh human blood-the xenon residence time constant in the red blood cells was measured to be 20.4 +/- 2 ms. The potential of certain biologically compatible solvents for delivery of laser-polarized xenon to tissues for NMR/MRI is discussed in light of their respective relaxation and partitioning properties.

Erythrocytes↗
PubMed1996

Solid-state NMR studies of the prion protein H1 fragment.

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically 13C-enriched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly 13C-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases.

Amino Acid Sequence↗
PubMed1996

Ventricular arrhythmias during sexual activity in patients with coronary artery disease.

STUDY OBJECTIVE: Information on appearance or increase of ventricular arrhythmias during intercourse in patients with coronary disease is still inadequate. This prospective study analyzes patients' rhythm disturbances on sexual activity and compares them with occurrences during daily activities and stress testing. PATIENTS: The study included 88 male outpatients with stable coronary disease; ages ranged from 36 to 66 years (mean, 52 years). INTERVENTIONS: Patients underwent ambulatory ECG monitoring, which included sexual activity, and a near-maximal ergometric test. RESULTS: Arrhythmia was found during intercourse in 56% of patients, compared to 38% at exercise. Occurrence or exacerbation of ectopic activity was the dominant pattern in patients with arrhythmia at exercise testing (89%), but this exacerbation was found only in 11% of patients during intercourse. Complex ventricular arrhythmia during sex was detected in 12.5% of patients. CONCLUSIONS: Two main observations may be drawn from the study. First, rhythm disturbances were not exacerbated during intercourse in most patients. Second, if ventricular ectopic activity occurred on intercourse, it was most often simple and essentially similar to disturbances in daily activity.

Activities of Daily Living↗
PubMed1995

Ischemic stroke following an intramuscular injection of diclofenac. Case report.

Nonsteroidal antiinflammatory drugs (NSAIDs) have arterial vasospastic properties. The authors report a stroke that occurred within minutes following an intramuscular injection of diclofenac. A sixty-one-year-old man, a heavy smoker, was admitted for an acute onset of mild hemiparesis thirty minutes after a single intramuscular injection of diclofenac. The neurologic deficit was resolved at one month of follow-up. The authors suggest a temporal causal relationship between the cerebrovascular event and the injection of diclofenac. The mechanism of stroke might be related to a synergistic vasospastic property shared by the use of an NSAID and heavy smoking.

Acute Disease↗