Hemodynamic effects of aerobic vs resistance exercise

Previous studies suggest that aerobic exercise lowers blood pressure (BP), while isometric exercise increases BP, at least transiently. The purpose of this study was to examine the hemodynamic effect of a 6-week training period of aerobic exercise or weight training. Twenty deconditioned healthy males ages 18-36, self-selected a training regimen. The aerobic group exercised 30 min/day, 4 times each week to achieve 60-80% maximal heart rate. The resistance group lifted weights at 65-80% maximal voluntary contraction; 3-4 sets of 8-12 repetitions; 3 day/week using large muscle groups. Hemodynamic measurements of heart rate, BP, venous capacitance, forearm blood flow, and vascular resistance were made at baseline and week 6 by plethysmography and analyzed by 2-way ANOVA. The groups showed no differences in baseline characteristics. A training effect was confirmed by a decrease in resting heart rate in the aerobic group (71.5 +/- 4.4 to 64.5 +/- 3.7, beats per minute, P = 0.004), and an increase in total work capacity in the weight lifting group (6231 vs 7508, P = 0.01). Forearm blood flow increased similarly in both groups, averaging 17% (3.5 +/- 0.2 vs 4.2 +/- 0.2 ml 100 g/min, P = 0.03), while forearm vascular resistance fell 19% (28.8 +/- 1.7 vs 24.3 +/- 1.7 mm Hg/ml/min 100 g, P = 0.08). The main differences between the groups after training was found in their response to isometric stress (1/3 maximal handgrip). The weight-lifting group had a greater increase of forearm blood flow and venous capacitance, less increase in systolic BP (SBP) and a greater fall of forearm vascular resistance, (P < 0.05) while the aerobic group had less increase in SBP and heart rate (P < 0.04) but no significant change of forearm hemodynamics. We conclude that both aerobic and repetitive weight programs have short term favorable effects on resting forearm BP and resistance. The exercise programs differ in altering the individual's physiologic response to subsequent isometric stress. However, exercise training of longer duration or greater intensity or frequency could alter these results.

Estrogen replacement therapy

For decades, observers have noted that women lose their natural resistance to coronary disease following menopause. It is now known that this increase in coronary risk is due to the loss of the protective effect of estrogen. Although still somewhat controversial, estrogen replacement therapy appears to offer significant cardioprotective benefits to postmenopausal women. These benefits extend to women with a history of coronary artery disease as well as to those without. The exact mechanism by which estrogen confers protection is not known, although the primary focus has been on estrogen's effect on serum lipids. Estrogen reduces total cholesterol levels and low-density-lipoprotein cholesterol levels and increases levels of high-density lipoproteins. Recent data suggest that estrogen may also have a beneficial effect on lipoprotein (a), a less studied lipid fraction, and may affect lipid metabolism in the blood-vessel wall. Numerous studies are under way to define better the risks and benefits of estrogen replacement therapy. Until more is known, the decision to recommend estrogen replacement therapy must be made on an individual basis.

A 1996 update on antihypertensive agents

Seven new classes of antihypertensive agents that are currently under development are outlined. Clinical studies of neutral endopeptidase inhibitors and angiotensin II receptor blockers are described. Experimental studies are described involving endothelin inhibitors, and clinical and experimental studies of a new multiple action antihypertensive agent, carvedilol, are presented. Studies demonstrating the efficacy of very low doses of thiazide diuretics added to other antihypertensive agents are described. A meta-analysis that found increased risk of sudden death in hypertensive patients treated with non-potassium-sparing diuretics is reported. The controversy over the use of calcium-channel blockers is reviewed, and current recommendations regarding the use of rapidly-acting nifedipine are given.

Practical aspects of preventing and managing athersclerotic disease in post-menopausal women

Factors that exacerbate the risk of atherosclerotic plaque formation include cigarette smoking, hypertension, hypercholesterolaemia, sedentary lifestyle, and oestrogen deficiency. The potentially important role of oestrogen deficiency in this process is evidenced by the significant increase in cardiovascular risk observed in women after menopause, and in the marked reduction in cardiovascular events observed in women who take hormone replacement therapy. Oestrogen replacement therapy, through an effect on the blood vessel wall and on serum lipids, also appears to stabilize existing atherosclerotic plaques. The combination of oestrogen and progesterone reduces risk of endometrial cancer while possibly delivering the same benefits as oestrogen alone. Other measures, such as antithrombotic therapy, exercise, and smoking cessation, also contribute to reduced risk of cardiovascular disease in older women.

The clinical aspects of estrogen and the cardiovascular system

Extensive epidemiologic and postmortem studies have identified a link between menopause and cardiovascular disease. The relation is especially strong in surgically menopausal women who do not receive estrogen replacement. More than 30 observational studies and one small randomized, controlled clinical trial have provided evidence that estrogen replacement reduces cardiovascular risk by approximately 50%. Four studies that used coronary arteriography to document the presence of coronary atherosclerosis have provided some of the most compelling evidence that estrogen replacement reduces cardiovascular risk in postmenopausal women. One study of survival in women undergoing coronary arteriography found that the greatest improvement in total mortality took place in those women with substantial coronary stenosis; less benefit was observed in those without disease. Angiographic studies have also confirmed the importance of high-density lipoprotein cholesterol in mediating the effect of estrogen and the beneficial effect of estrogen on endothelial function. Although the addition of progestins to estrogen attenuates estrogen's effect on high-density lipoprotein cholesterol, limited observational daa have suggested that the cardioprotective effect is not reduced.

Estrogens, menopause, and coronary artery disease

The incidence of cardiovascular disease increases after menopause as women age. Estrogen-replacement therapy has been found to reduce cardiovascular risk by about 50% in over 30 observational studies. Part of the beneficial effect appears to be due to a reduction of LDL cholesterol and an increase in HDL cholesterol. Another important mechanism is related to the effect of estrogen on endothelial function. In making a decision to use estrogen-replacement therapy, the benefits must be weighed against the risks of endometrial and breast cancer.

A journal of community. Catholic healthcare providers' presence is necessary to sustain a values-based system

Catholic healthcare leaders must use all their will and creative imagination to find a way to maintain a significant Catholic presence in healthcare. Catholic healthcare leaders across the nation are acquiring, consolidating, and merging hospitals; forming alliances and networks of integrated services; and bringing together Catholic healthcare systems on a regional and local basis. The next few years are critical for Catholic sponsors of healthcare services. The unique challenge is to pursue the development of a Catholic network that would include a wide range of health, mental health, home care, long-term care, social, and housing services. The key ingredient to making networks happen will be leadership, and I think CHA and sponsors rightly emphasize the need for continuing leadership formation and development of trustees and executives in Catholic healthcare. A united effort by Catholic healthcare providers could have a penetrating influence on the overall development of healthcare in this nation. Now is the time to exercise imaginative leadership; to reach out to the existing Catholic and community-based providers of health and human services; and to create networks that can provide a continuum of accessible, high-quality, values-based, and cost-efficient services.

Three distinct structural environments of a transmembrane domain in the inwardly rectifying potassium channel ROMK1 defined by perturbation

To probe the protein environment of an ion channel, we have perturbed the structure of a transmembrane domain by substituting side chains with those of two different sizes by using site-specific mutagenesis. We have used Trp and Ala as a high- and a low-impact perturbation probe, respectively, to replace each of 18 consecutive residues within the putative second transmembrane segment, M2, of an inwardly rectifying potassium channel, ROMK1. Our rationale is that a change in the channel function as a consequence of these mutations at a particular position will reflect the structural environment of the altered side chain. Each position can then be assigned to one of three classes of environments, as grated by different levels of perturbation: very tolerant (channel functions with both Trp and Ala substitutions), tolerant (function preserved with Ala but not with Trp substitution), and intolerant (either Ala or Trp substitution destroys function). We identify the very tolerant environment as being lipid-facing, tolerant as protein-interior-facing, and intolerant as pore-facing. We observe a strikingly ordered pattern of perturbation of all three environmental classes. This result indicates that M2 is a straight alpha-helix.

Coronary arteriography in estrogen-treated postmenopausal women

Four cross-sectional studies that used coronary arteriography to determine the extent of coronary atherosclerosis have provided some of the most convincing evidence that estrogen replacement reduces cardiovascular risk in postmenopausal women. One study of outcome in women undergoing coronary arteriography at baseline has found that the greatest improvement in total mortality occurred in women with significant coronary stenosis. Angiographic studies have also confirmed the importance of high-density lipoprotein in mediating the effect of estrogen and the beneficial effect of estrogen on endothelial function.

Osteoporosis as a model for the long-term clinical consequences of the menopause

The decrease in ovarian function culminating in the last menstrual period, the menopause, in women in their forties and fifties takes place over a period of 3 to 5 years. There are several immediate clinical consequences of the menopause that are easy to detect and treat, usually with hormone replacement. In contrast, the longer term consequences of the menopause, cardiovascular disease and osteoporosis, are usually clinically silent during these early postmenopausal years. As a result, it has proven difficult to get physicians and their patients to accept this cause-and-effect relationship between the menopause and the development of osteoporosis or heart disease a decade or more later. The details concerning the menopause and osteoporosis are by now so well established that this disease can serve as a model for studies linking the menopause to heart disease. This article, with its focus on osteoporosis, serves as an introduction to the later articles detailing the cardiovascular consequences of the menopause.

Cloning and characterization of chi-1: a developmentally regulated member of a novel class of the ionotropic glutamate receptor family

Ionotropic glutamate receptors are composed of homomeric or heteromeric configurations of glutamate receptor subunits. We have cloned a member of a novel class of the rat ionotropic glutamate receptor family, termed chi-1. This subunit exhibits an average identity of 27% to NMDA subunits and 23% to non-NMDA subunits. Regional transcript levels of chi-1 are elevated just prior to and during the first postnatal week, with the highest levels present in the spinal cord, brainstem, hypothalamus, thalamus, CA1 field of the hippocampus, and amygdala. The spatial distribution of chi-1 expression is similar from postnatal day 1 (P1) to adulthood. However, transcript levels decline sharply between P7 and P14 and remain attenuated into adulthood. Functional expression studies in Xenopus oocytes injected with in vitro transcribed chi-1 RNA did not demonstrate agonist-activated currents. Pairwise expression of chi-1 with members of the AMPA, KA, or delta class of glutamate recepto subunits either failed to generate agonist-activated currents or failed to alter the underlying current generated by the coexpressed subunit. However, coexpression of chi-1 with subunits forming otherwise functional NMDA receptors resulted in an inhibition of current responses. Since chi-1 did not alter the currents generated by non-NMDA subunits, this suggests that chi-1 may specifically interact with NMDA receptor subunits. Further characterization will be required to establish the precise role of this glutamate receptor subunit in neuronal signaling.

Impact of patency of the left anterior descending coronary artery on long-term survival

This study examines the relative importance of patency of the left anterior descending (LAD) coronary artery on long-term survival when the LAD is the only significantly narrowed coronary artery. From a cardiac disease registry of 21,786 patients, 826 medically treated patients with isolated LAD disease were identified. These patients were followed for > 5 years. Patients were divided into those with open versus those with closed arteries. With the use of univariate and multivariate analysis, the relative importance of the patency of the LAD was determined. All patients with previous anterior wall infarction were analyzed as a separate group, and those with and without a patent LAD were compared. Overall, survival was significantly better in patients with an open LAD. However, multivariate analysis of either the entire study group or the group with myocardial infarction showed that coronary artery patency was not an independent predictor of long-term survival. Analysis of patients with prior anterior myocardial infarction showed significantly improved 5-year survival in younger patients (< 70 years) who had an open (but stenosed) versus a closed LAD without angiographic collateral formation (94% vs 81%, p = 0.025). Furthermore, this survival difference was most striking in patients with left ventricular dysfunction. Survival in younger patients with an open LAD was similar to that of patients with a closed LAD with collateral formation (94% vs 92%, p = 0.55). No differences in survival were observed in the groups without infarction. This study implies that an open LAD improves long-term survival for younger patients with a previous anterior myocardial infarction and no collateral support to the ischemic or infarcted myocardium.

The effect of noncritical coronary artery disease on long-term survival

This study was designed to determine the impact of noncritical (less than 70% narrowing of the luminal diameter) coronary stenoses on the long-term survival rate of patients with coronary artery disease. The survival rate of 3,342 patients with normal coronary arteries (Group 1A) was compared with that of 2,184 patients with only noncritical stenoses (Group 1B). Similarly, the survival rate of 1,128 patients with one or more critical lesions (Group 2A) was compared with that of 5,944 cases with noncritical plus critical lesions (Group 2B). Patients with noncritical lesions had significantly lower 10-year survival rates (85.8%) than did those with normal coronary arteries (90.1%). However, the difference in survival rate was attributable to older age, male sex, and higher prevalence of cigarette smoking, diabetes mellitus, and hypertension in Group 1B than in Group 1A; presence of noncritical stenoses was not a statistically significant independent determinant of survival. Long-term survival rates of the patients with one or more critical lesions (Group 2A) were equivalent to that of patients with critical stenoses plus one or more noncritical lesions (Group 2B). Therefore, 1) patients with only noncritical stenoses have more risk factors for coronary artery disease than do those with normal coronary arteries; 2) these patients have a reduced long-term survival rate that reflects these risk factors rather than the presence of noncritical lesions; and 3) in patients with critical lesions, the presence of additional non-critical stenoses does not affect the long-term survival rate.

In situ human obstetrical ultrasound exposimetry: estimates of derating factors for each of three different tissue models

A specialized in vivo exposimetry system was developed to acquire transabdominal in situ ultrasound exposure quantities in obstetric patients. Under surgical conditions, the sterilized 7-element calibrated linear array hydrophone was introduced into the uterus under direct ultrasound guidance and placed in direct contact with the products of conception, usually in the saggital midplane of the uterine cavity. Twenty-five patients with empty bladders and 10 patients with full bladders were studied at gestational ages between 7 and 20 weeks. In the empty bladder condition, the sound beam traversed the anterior abdominal wall, uterus, amniotic fluid and fetal parts and in the full bladder condition, the sound beam also traversed the fluid-filled bladder. Each study was conducted with a 3 MHz, mechanical sector transducer in combination with an ATL Ultramark 4 diagnostic ultrasound imaging system. Calibration data were recorded after completion of each in vivo patient study. The acquired exposimetry data from the 35 obstetric patients were used to evaluate the appropriateness of three tissue attenuation models, viz., fixed path, homogeneous and overlying. All three tissue models yield a mean attenuation coefficient value of about a factor of 3 to 4 greater than their respective minimum values. In the case of the overlying and homogeneous tissue models, there was a statistically significant correlation between their calculated attenuation coefficients and total distance for the combined data set whereas there was no such dependency for the calculated fixed-path tissue model. In summary, any one of the three tissue models may be used to estimate in utero acoustic quantities during the first and second trimesters of human pregnancy based on this study.

Long-term survival of patients with coronary artery disease during the 1970s. A cohort study

STUDY OBJECTIVE

This study was undertaken to determine the effects of altered risk factors and treatment modalities on the short- and long-term survival of patients with documented coronary artery disease whose conditions were diagnosed from 1972 through 1982.

STUDY DESIGN

The study was a retrospective database analysis of clinical, angiographic, and follow-up information.

SETTING

Data from all patients referred for cardiac catheterization at the Baptist Memorial Hospital, Memphis, Tenn, were studied.

PATIENTS

Risk factors and survival of patients who underwent cardiac catheterization from 1972 through 1982 and who were followed up for at least 5 years were evaluated. Cohort A included 1,821 patients studied from 1972 through 1977; cohort B included 5,369 patients studied between 1977 and the end of 1982. Each cohort was subdivided based on type of therapy (medical or surgical) that the patients received.

MEASUREMENTS AND RESULTS

The 30-day (short-term) and 5-year (long-term) survival rates were compared by life table methods. Short-term survival improved significantly in both medical (from 94.9% to 97.5%, p < 0.001) and surgical (from 95.5% to 97.6%, p < 0.001) groups from cohort A to cohort B. Long-term survival, however, did not differ significantly between the two cohorts. In the medical group, 5-year survival in cohort A was 86.3% and in cohort B it was 86.9% (p = NS); in the surgical group, cohort A it was 89.1% while in cohort B it was 89.4% (p = NS). Prevalence of both cigarette smoking and hypercholesterolemia declined significantly from cohort A to cohort B in both surgical and medical groups. However, advanced age, female gender, and previous myocardial infarction were significantly more common in cohort B than in cohort A for both treatment groups.

CONCLUSIONS

These results indicate that during the study period, a significant decline in short-term mortality occurred for patients with angiographically documented coronary artery disease. Long-term survival did not, however, improve possibly due to a complex interplay between factors that promote coronary artery disease, eg, cigarette abuse and hypercholesterolemia, and factors that determine survival, eg, increase in age and history of prior infarction and advances in medical and surgical therapy.

Clinical practice guidelines: implications for use

The differences between standards and clinical practice guidelines are discussed. Implications for using guidelines in nursing practice in defining scope of practice, evaluating careless or negligent practice, practicing outside of clinical guidelines, and using clinical guidelines for cost containment are presented.

Identification of two cysteine residues that are required for redox modulation of the NMDA subtype of glutamate receptor

Modulation of NMDA-mediated responses by oxidizing and reducing reagents has been described in a variety of neuronal preparations. Here, we report that NMDA-gated currents of oocytes expressing heteromeric NMDA receptors are also modulated by sulfhydryl redox reagents. Each cysteine residue in the NMDAR1 (NR1) subunit and each conserved NMDAR2 (NR2) cysteine residue in a prototypical subunit (NR2B) was tested for its role in redox modulation. We have identified 2 cysteines in the NR1 subunit that are required for redox modulation of NMDA-gated currents in oocytes expressing NR1-NR2B, NR1-NR2C, or NR1-NR2D receptors. Mutation of these same 2 cysteines also eliminated potentiation by spermine and shifted the IC50 for H+ inhibition and the EC50 for NMDA. Redox modulation of heteromeric NR1-NR2A receptors appeared to be different from that of the other heteromeric receptors, indicating the presence of one or more unique redox modulatory sites on NR1-NR2A receptors.

Integrated treatment for the survivor of childhood trauma who is chemically dependent

A substantial percentage of individuals who are chemically dependent also suffer from posttraumatic stress disorder and other survivor syndromes related to childhood abuse. The synergism of these multiple conditions creates unique treatment challenges. An enhanced, integrated treatment approach increases the chances of a successful clinical outcome. This article discusses a treatment model for chemical dependence and trauma-related syndromes that blends mental health and 12-Step and other chemical dependence treatment notions into an integrated approach that treats both disorders simultaneously and comprehensively. The model uses the strategic principle of "safety first" to drive all interventions and has five stages to organize the selection and timing of treatment tactics: crisis, skills, education, integration, and maintenance. This article also presents specific therapeutic tactics for each stage and a composit case example blending the history and recovery process of a survivor to illustrate the model in action.

Care provided by a nurse managed center: polyarteritis nodosa

Polyarteritis nodosa is a form of necrotizing vasculitis involving small and medium size arteries. Nursing care provided by baccalaureate nursing students in a nurse-managed center at San Jose State University's (CA) School of Nursing focuses on monitoring symptoms, preventing complications, and supporting patients and families affected by polyarteritis nodosa.

Protein chemical characterization and immunocytochemical localization of the NMDA receptor subunit NMDA R1

In the rat central nervous system, the mRNA encoding the N-methyl-D-aspartate receptor subunit R1 is the most ubiquitously distributed among the cloned subunit mRNAs of this glutamate receptor subtype. The N-methyl-D-aspartate R1 mRNA is very abundantly expressed and N-methyl-D-aspartate R1 coexpression is necessary for functional expression of all other cloned N-methyl-D-aspartate receptor subunits. Therefore, the R1 subunit is likely to be an essential component of all known N-methyl-D-aspartate receptors in rat brain. By employing sequence specific polyclonal antibodies, we demonstrate that rat brain N-methyl-D-aspartate R1, as well as recombinantly expressed receptor protein, has an apparent molecular mass of 116 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis. The receptor protein is heavily glycosylated. It is specifically localized to the central nervous system, and it co-enriches with synaptic membranes upon subcellular fractionation of the cerebral cortex. Chemical cross-linking of synaptic membrane proteins shows that the N-methyl-D-aspartate R1 protein is part of a receptor protein complex with a molecular mass of 730 kDa. By using immunocytochemical methods, we demonstrate a widespread but distinct distribution of N-methyl-D-aspartate R1 in neurons of the rat brain, with prominent immunostaining in certain layers of the cerebral cortex, in the hippocampus and dentate gyrus, as well as in the cerebellum.

Finite element computations of specific absorption rates in anatomically conforming full-body models for hyperthermia treatment analysis

Finite element techniques for three-dimensional specific absorption rate (SAR) computation in anatomically based human models are presented. The formulations center on Helmholtz weak forms which have been shown to be numerically robust and to afford additional sparsity in the resulting system of algebraic equations. Practical solution of these equations depends critically on the realization of an effective sparse matrix solver. Experience with several conjugate gradient-type methods is reported. The findings show that convergence rate (and even convergence in some cases) degrades significantly with increasing matrix rank and decreasing electrical loss for mesh spacings which adequately resolve the physical wavelengths of the electromagnetic wave propagation. However, with proper choice of algorithm and preconditioning, reliable convergence has been achieved for matrix ranks exceeding 2 x 10(5) on domains having sizeable volumes of electrically lossless regions. An automatic grid generation scheme for constructing meshes which consist of variable element sizes that conform to a predefined set of boundaries is discussed. Example meshes of homogeneous and heterogeneous human anatomies, the boundaries of which have been derived from CT-scan information, are shown. These results highlight the fact that 3D finite element mesh generation remains a difficult problem, but usable meshes with this level of complexity can be generated. Integration of the finite element formulation, the sparse matrix solver, and the mesh generation scheme is shown to lead to algorithms that can be implemented on inexpensive reduced instruction set computer (RISC) workstations with run times on the order of hours. An example of hyperthermia device simulation is presented which suggests that the finite element method is a practical alternative that rivals the impressive finite-difference time-domain (FDTD) computations that have appeared.