Perceived necessity explains the dissociation between logic and meaning: the case of "only if"

The purpose of this article was to investigate why sentences of the form "p only if q" often appear to have a different meaning than sentences of the form "if p, then q," despite their logical equivalence. The results of 3 experiments indicate that when "if ... then" statements were equated with respect to necessity and temporal relations, different pragmatic relations (such as permission, causation, etc.) elicited similar "only if" judgments. However, different necessity relations elicited different "only if" judgments, regardless of the type of pragmatic relation expressed in the "if then" statement. These data suggest that "only if" judgements are primarily mediated by necessity and temporal relations and that pragmatic contexts may play a more indirect role, such as in the interpretation of necessity and temporal relations. Suggestions for how these findings might be incorporated into pragmatic schema theory (P. W. Cheng & K. J. Holyoak, 1985; P. W. Cheng, K. J. Holyoak, R. E. Nisbett, & L. M. Oliver, 1986) and mental models theory (P. N. Johnson-Laird & R. M. J. Byrne, 1991) are discussed.

Myocyte nuclear area as a measure of left ventricular hypertrophy in transplant patients

Transplanted hearts have been reported to increase in size/weight in the first few months after transplant and to remain stable thereafter. An indirect way of assessing the changes in heart weight is through the changes in the area of the myocyte nucleus (MNA). We studied 20 patients who had undergone orthotopic heart transplantation more than 12 months previously; 10 had become hypertensive, and the remaining 10 were normotensive. Myocardial biopsies taken the first week after transplant and 6, 12, 24, and 52 weeks after transplant were assessed. Myocyte nuclear area was measured in 200 myocytes/biopsy with an image analyzer. Individual measurements showed a wide variation in MNA, with significant overlaps among the different biopsies. Assessment of MNA at one year showed increased MNA in 4 10 patients in the hypertensive group and 5 10 in the normotensive group. The remaining patients showed either no statistically significant changes in MNA or a significant (p < 0.0001) decrease in MNA. The presence of systemic hypertension was not a predictive factor for significant hypertrophy and, in some cases, not even for hypertrophy itself. We conclude that although there is often an increase in MNA of the transplanted heart at one year posttransplant, this increase is not systematic, and isolated morphometric results should be viewed cautiously.

Evidence from family studies for autoimmunity in dilated cardiomyopathy

Organ-specific antibodies are found in patients with autoimmune disease and their symptom-free relatives many years before clinical onset. Organ-specific cardiac antibodies can be found in patients with dilated cardiomyopathy (DCM) and their relatives, which supports the idea that DCM is an autoimmune disease. We did non-invasive cardiological assessment and antibody screening in 342 symptom-free relatives (170 male, 172 female, mean [SD] age 31 [16] years). 177 relatives were from 33 families with more than 1 affected individual (familial DCM) and 165 relatives from 31 families with only 1 affected member (non-familial DCM). The frequency of cardiac antibodies was higher among relatives of DCM patients than in controls (20% vs 3.5%, p = 0.0001). In 37 (58%) of the families studied, cardiac antibodies were found in the proband and/or in at least 1 family member and were more common in familial than in non-familial DCM (24% vs 15%, p = 0.036). Antibody-positive relatives were younger (26 [15] vs 33 [17] years, p = 0.01) and had a larger mean echocardiographic left ventricular end-systolic dimension (35 [6] vs 32 [6], p = 0.01 mm) and reduced percentage fractional shortening compared with antibody-negative relatives (31 [6] vs 34 [6], p = 0.008). Presence of cardiac-specific autoantibodies in symptom-free DCM relatives provides evidence of autoimmunity in a subset of our patients (58%), including familial and non-familial forms of DCM. These antibodies are associated with mild left ventricular systolic dysfunction on echocardiography and may be early markers for relatives at risk of DCM.

Physicians and medical students: factors affecting entry into public health

We surveyed members of a recent master of public health (MPH) degree program to learn more about how, when, and why physicians and medical students decided to seek formal training in public health. We interviewed physicians and medical students to determine how and why these MPH students became involved in what they considered public health work; how and why they decided to attend public health school; and what their career plans were following completion of the degree program. All 47 medical students and physicians responded to the survey. Sixty-six percent described previous public health-related work experience. Only 5% decided prior to or during college to attend public health school. A personal contact directed 62% towards public health school. Those with previous public health work experience were more likely to pursue what they considered public health careers after completion of public health school than those without such previous work experience. The continuing need for qualified practitioners and leaders in public health challenges the medical community to characterize further those factors motivating medical students and physicians to formalize their training in public health.

Myocardial disarray in Noonan syndrome

OBJECTIVE

To characterise the histopathology of the left ventricular hypertrophy commonly associated with Noonan syndrome by assessing the extent of myocyte disarray and therefore to define one aspect of the relation between this disease and idiopathic hypertrophic cardiomyopathy.

DESIGN

Blinded histological analysis.

SETTING

Hospital medical school.

PATIENTS

Six hearts of children with the Noonan phenotype and isolated ventricular hypertrophy were compared with age and sex matched controls.

METHODS

Histological analysis was performed with an image analyser under light microscopy. Representative sections from the entire left ventricular free wall were examined. Results were expressed as the percentage of fields showing disarray related to the number of fields evaluated: 100 fields were examined for each patient.

RESULTS

In the patients with Noonan syndrome myocardial disarray was present in the ventricular septum in 24 (5.7)% (mean (SD)) of fields and in the free wall in 22.2 (6.8)%. In the controls disarray was present in the septum in 3.8 (2.3)% of fields and in the free wall in 2.4 (2.8)%. In both regions the extent of disarray was significantly greater in patients with Noonan syndrome (p < 0.0005; 95% confidence interval 14 to 26.3 for the septum: p < 0.005, 95% confidence interval 11.4 to 28.2 for the free wall).

CONCLUSIONS

The ventricular hypertrophy associated with Noonan syndrome is histologically similar to hypertrophic cardiomyopathy but whether the two diseases are the expression of the same genetic defect remains to be determined.

Assessment of rejection in orthotopic human heart transplantation using proliferating cell nuclear antigen (PCNA) as an index of cell proliferation

Myocardial biopsies taken during the management of cardiac transplantation were stained for proliferating cell nuclear antigen (PCNA). Counts of PCNA-positive interstitial cells were compared, in retrospect, with the reported histological grade of rejection. Biopsies without rejection had negligible numbers of PCNA-positive cells. Ascending grades of rejection were paralleled by an increase in the number of PCNA-positive cells [grade 1, 13 +/- 35 (mean +/- SD); grade 2a, 38 +/- 40; grade 2b, 91 +/- 75; grade 3, 170 +/- 78]. While highly significant, in statistical terms, the overlap in the counts between different grades means that prediction of rejection from the PCNA count alone is not feasible. Biopsies graded as 0 or 1 and which immediately preceded more severe rejection episodes showed no increase in PCNA-positive cells. The majority of PCNA-positive cells are fibroblasts, although in grade 2b and 3 rejection a small population of PCNA-positive T lymphocytes occurs. PCNA staining is also seen in cardiac myocytes immediately after transplantation, during rejection episodes, and late after transplantation in the absence of rejection. The positive PCNA staining of cardiac myocytes probably reflects DNA synthesis that occurs with the shift toward polyploidy in hypertrophy.

Myocardial magnesium depletion associated with prolonged hypomagnesemia: a longitudinal study in heart transplant recipients

OBJECTIVES

This study was carried out to establish prospectively the incidence and relation of hypomagnesemia and myocardial magnesium depletion after heart transplantation.

BACKGROUND

No serial in vivo study of the relation of serum with tissue magnesium has been described. Myocardial magnesium depletion is associated with intracellular calcium overload, an increased incidence of cardiac arrhythmia and changes in coronary vasculature similar to those seen in the accelerated atherosclerosis that compromises graft survival after transplantation.

METHODS

In a prospective study in 19 consecutive patients, serum and myocardial magnesium content were measured serially for 9 months after heart transplantation. Blood cyclosporine was assayed simultaneously.

RESULTS

The incidence of hypomagnesemia was 100% during the 9-month study period, with lowest levels at 3 months (mean 0.80 vs. 0.64 mmol/liter, p less than 0.002). Myocardial magnesium depletion developed in 94% and was persistent in 55%; the lowest levels occurred at 6 months (mean 33.6 vs. 30.1, mumol/g, p less than 0.04). Hypomagnesemia predated decreases in myocardial magnesium by 2 to 6 weeks. Peak cyclosporine levels correlated positively with the decrease in serum magnesium. Clinical events were rare.

CONCLUSIONS

This is the first report of serial measurement of tissue magnesium. Persistent hypomagnesemia is invariably accompanied by myocardial magnesium depletion in the transplanted heart. Reciprocal calcium overload and adverse changes in coronary vasculature would be expected from previous studies and merit further investigation. Should the implications of this study extend to the native heart, myocardial magnesium depletion may contribute to the high incidence of fatal arrhythmic events observed in patients with heart failure, who commonly have persistent hypomagnesemia.

Identification of alpha- and beta-cardiac myosin heavy chain isoforms as major autoantigens in dilated cardiomyopathy

BACKGROUND

Immunization with cardiac myosin induces experimental autoimmune heart disease in genetically predisposed mice. These mice produce heart-specific autoantibodies, some of which are directed against the cardiac myosin isoform.

METHODS AND RESULTS

We have reported the presence of circulating heart-specific autoantibodies in 26% of patients with idiopathic dilated cardiomyopathy (DCM) using indirect immunofluorescence. To identify the autoantigen(s) recognized by heart-specific autoantibodies in human disease, we tested, by Western blotting, sera from 26 DCM patients, 14 of whom were cardiac antibody-positive and 12 antibody-negative, as well as sera from 12 patients with cardiac failure from ischemic or valvular heart disease and from 13 normal subjects who were cardiac antibody-negative. Crude myofibrillar proteins and myosin preparations extracted from human atrial or ventricular specimens were used as antigens. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was performed. The proteins were electrophoretically transferred to nitrocellulose sheets. The paper strips were incubated in sera from patients or controls at 1:100 dilution; the reaction was revealed with a peroxidase-labeled second antibody against human immunoglobulin. Twelve of the 14 DCM sera (86%) containing heart-specific antibodies reacted with both the alpha- (atrial specific) and beta- (ventricular and slow skeletal) myosin heavy chain isoforms; none of the 13 normal sera (p = 0.0001) and one of the 24 heart failure-negative control sera (4%, p = 0.0001) contained antibodies against myosin heavy chain.

CONCLUSIONS

These findings indicate that alpha- and beta-cardiac myosin heavy chain isoforms as in the murine model of autoimmune heart disease are major autoantigens in patients with idiopathic DCM.

AIDS--the second decade: a global perspective

The human immunodeficiency virus (HIV) and AIDS epidemic merits its designation as a pandemic: AIDS cases are reported to the World Health Organization from 163 countries, and at least 10 million adults have been infected with HIV. The pandemic is a relatively new phenomenon, and therefore it remains dynamic, unstable, and volatile. Transmission continues in all already-affected countries; HIV is spreading, sometimes quite rapidly, to previously unaffected or little-affected areas of the world; and the epidemic becomes more complex and differentiated. The major impact of the pandemic is yet to come: In the 1990s, a 10-fold increase is anticipated in the numbers of adults (to 10 million) and children (to 5 million) developing AIDS. The social, cultural, economic, and political impacts of the pandemic are also increasing. The community, national, and international approach to control of the pandemic must continue to evolve, taking into account the specific conditions of the modern world, of which the global interdependence of health has become the major new factor.

Global AIDS: critical issues for prevention in the 1990s

A review of the first decade of global experience with the struggle against HIV/AIDS suggests that prevention will require both full application of existing approaches and fundamental changes in concepts and values. The critical deeper issues can be grouped under three headings: behavior, societal action, and globalism. Behavior, individual and collective, will be increasingly recognized as the major challenge for public health. However, for purposes of HIV prevention (and other issues) a sufficient understanding of behavior has not yet been developed. At the societal level, the activism of community organizations has shifted the balance of initiative in public health toward the community. The long-term implications of this evolution for roles and responsibilities at the community, national, and international levels must be explored. Finally, an understanding of global solidarity, based on respect for human rights and on the objective conditions of the modern world, will be critical for the future capability to deal effectively with HIV/AIDS. In summary, the future of HIV/AIDS prevention and control cannot be separated from the major public health and social issues of our time.

Experimental model of left ventricular failure

A model of chronic cardiac failure has undergone extensive hemodynamic investigation. Under anesthesia the homonymous and second diagonal coronary arteries of sheep have been ligated. The resulting myocardial infarction caused significant acute hemodynamic impairment (paired two-tailed t tests), mean pulmonary artery pressure increasing from 7.31 +/- 0.94 to 13.80 +/- 1.19 mm Hg (p less than 0.001), pulmonary artery diastolic pressure increasing from 4.94 +/- 1.03 to 11.13 +/- 1.27 mm Hg (p less than 0.001), and directly measured left ventricular end-diastolic pressure increasing from 9.31 +/- 1.52 to 17.42 +/- 1.82 mm Hg (p less than 0.001) after infarction documented with invasive monitoring. There was a hemodynamically significant left ventricular aneurysm (paired two-tailed t tests) in animals studied 3 months later, with increased mean pulmonary artery pressure from 7.20 +/- 1.15 to 13.80 +/- 2.00 mm Hg (p = 0.009), an increase in pulmonary artery diastolic pressure from 4.60 +/- 1.30 to 12.10 +/- 2.06 mm Hg (p = 0.006), and an increase in left ventricular end-diastolic pressure from 11.00 +/- 1.94 mm Hg before infarction to 17.00 +/- 2.69 mm Hg (p = 0.038). We conclude that this is a useful model of chronic left ventricular failure that is reproducible and applicable to investigations of therapeutic options in chronic heart failure.

Cerebrovascular accidents in infective endocarditis: role of anticoagulation

Anticoagulation is still a matter of debate in infective endocarditis, since it can increase the risk of complications, mostly neurological. In our series of 269 patients with native valve endocarditis studied between 1970 and 1982, 35 were anticoagulated. We observed 14 patients with brain infarcts, of whom five died, and 12 patients with cerebromeningeal or brain haemorrhage of whom six died. In a similar series of 63 patients with prosthetic valve endocarditis, all of whom were on anticoagulation and were studied between 1972 and 1987, we observed five patients with brain infarcts, three of whom died, and two patients with brain haemorrhage, one of whom died. The frequency of cerebrovascular accident (CVA) was similar for both groups (11.1% in prosthetic endocarditis vs 11.5% in native valve endocarditis, P = ns), as was mortality rate (57% vs 48.4%, P = ns). CVA are significantly more frequent among anticoagulated patients (19/94 vs 19/238: P less than 0.01), but the mortality rate in CVA is similar for anticoagulated and non-anticoagulated patients (11/19 vs 8/19: P = ns). The indications for anticoagulation in infective endocarditis remain similar to those in valvular heart disease. In patients with infective endocarditis, anticoagulation with heparin should be maintained whenever a brain infarct is present, unless it is large and/or haemorrhagic.

Human T cell lymphotropic virus type I (HTLV-I) among female prostitutes in Kinshasa, Zaire

Three hundred seventy-seven prostitutes from Kinshasa, Zaire, were enrolled in a study to determine associated risk factors for human immunodeficiency virus type 1 (HIV-1) and human T cell lymphotropic virus type I (HTLV-I) infection. Twelve samples (3.2%) were seropositive for HTLV-I; results for HIV-1 (101 [26.8%]) are reported elsewhere. HTLV-I prevalence increased with age, and seven of the seropositive women originated from the Equateur region, a remote area in northwestern Zaire. The prevalence among women from Equateur (7.2%) was higher than that of women from all other regions (1.8%, P = .02). Presence of HTLV-I antibodies was not associated with frequency or type of sex practice. In a subsequent study, 350 serum samples were obtained from a variety of subjects in the Equateur region in 1986. Nineteen (5.4%) showed antibodies to HTLV-I. These data and a recent report of a cluster of patients with tropical spastic paraparesis from this region suggest that HTLV-I is endemic in the Equateur region of Zaire.

International travel and HIV infection

Although human immunodeficiency virus (HIV) infection is a worldwide problem, its prevalence and pattern vary from country to country. Accordingly, the risk to international travellers of acquiring HIV infection also varies widely in different parts of the world, and depends principally on their behaviour. The risk of sexual acquisition of HIV infection can be virtually eliminated by avoiding penetrative sexual intercourse with intravenous drug users and persons who have had multiple sexual partners (such as prostitutes) or reduced by the use of condoms. The risk of parenteral exposure to HIV can be reduced by avoiding parenteral drug use and behaviour that is likely to lead to injury (with its attendant risk of requiring blood transfusion) and by seeking medical facilities with adequate capabilities to screen blood donors for HIV and to sterilize instruments. HIV screening of international travellers is an ineffective, costly, and impractical public health strategy for limiting the worldwide spread of HIV infection. Travellers infected with HIV require specialized advice regarding health precautions, prophylactic medications, and immunization.