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Biomedical subjects

J Freund

Publications and source records attributed to J Freund.

At least 37 records · Page 2Linked to original sources
PubMed1992

Assessment of spinal and femoral bone density by dual X-ray absorptiometry: comparison of lunar and hologic instruments.

Clinical application of techniques for assessing bone mineral density (BMD) requires accurate and precise measurements that can be related to clearly defined normal ranges. In this study we investigated the clinical interpretation of BMD values in a group of individuals measured on the same day with two different dual-energy x-ray densitometers (Lunar DPX and Hologic QDR 1000). The BMD results were analyzed as absolute values in g/cm2 and with respect to young and age-specific normals as defined by each manufacturer. Absolute BMD values measured by the two instruments were highly correlated (lumbar spine r = 0.98, femoral neck r = 0.95; p less than 0.0001). In the lumbar spine, the two instruments assigned almost identical values when expressed as a percentage of age-matched values and as a percentage of young normals, despite a small but systematic difference between the values assigned for the latter index. In the femoral neck, however, there were significant differences in assignments between instruments, expressed both as a percentage of young normal (mean difference 6.2%) and with respect to age-matched values (mean difference 3.3%). In particular, in premenopausal subjects femoral neck values with the Hologic instrument were assigned significantly lower values. This study shows effective comparability between these two instruments for absolute and relative values for the lumbar spine, as well as for absolute values at the femoral neck, but important differences for normality assignments at the femoral neck. These latter differences may produce bias in the "diagnosis" of femoral neck osteoporosis and may have important implications for clinical decision making.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

Postmenopausal bone loss in rheumatoid arthritis: effect of estrogens and androgens.

Osteoporosis is a frequent complication of rheumatoid arthritis (RA), especially in postmenopausal women, and may involve both juxtaarticular and generalized bone loss. To examine the effect of exogenous estrogens and endogenous androgens on bone loss in RA we determined rates of bone loss by serial bone density measurement for up to 4 years in 38 postmenopausal women with RA. Serum dehydroepiandosterone sulfate concentrations correlated significantly with the change in femoral neck bone but not in lumbar spine bone. Estrogen therapy prevented lumbar spine bone loss, but did not affect bone loss from the hip. These data suggest adrenal androgen status may influence bone loss in RA and that, although estrogen therapy can prevent bone loss from the spine, it may not prevent bone loss at sites near involved joints.

Androgens↗
PubMed1990

Reproducibility of radionuclide left ventricular ejection fraction in patients awaiting cardiac transplantation.

Radionuclide-derived left ventricular ejection fraction (LVEF) is used to assess LV systolic function, to follow trends in the natural history of dilated cardiomyopathy, and to prioritize patients waiting for cardiac transplantation. Reproducibility of LVEF at extremely low levels has not, however, been reported. To assess the reproducibility of radionuclide LVEF at levels below 0.30 EF U, 17 highly symptomatic patients (NYHA Class III/IV) with dilated cardiomyopathy were studied on two occasions, 72 hours apart. Sequential scans were analyzed by two independent observers. Mean LVEF was 0.18 +/- 0.06 U (scan 1) and 0.17 +/- 0.06 U (scan 2). Interoperator reproducibility (SD) was 0.03 U (R = 0.76), interscan reproducibility (SD) was 0.03 U (R = 0.62), and overall reproducibility (SD) was 0.04 U (R = 0.50). The interobserver variation of 0.03 (actually 0.027) was just over one half that seen in normal volunteers (variation 0.05, n = 29) studied previously in this department. A change of greater than or equal to 0.08 U (2SD) in either direction is highly likely to represent a real change in LV function in those with LVEF less than or equal to 0.30 units, compared with the change of at least 0.10 units required in those with normal LV function. Lower interobserver and interscan reproducibility should be taken into account when interpreting sequential scans in patients with severe LV dysfunction.

Adolescent↗
PubMed1989

Muscle strength, physical fitness, and weight but not age predict femoral neck bone mass.

Hip fractures are the most serious complication of osteoporosis. Although low proximal femoral bone mineral density (BMD) does not cause hip fractures directly, it is clearly a prerequisite for the increased risk associated with aging. To investigate the mechanism of the age-related decline in proximal femoral bone mineral density, we have examined the relative importance of muscle strength, physical fitness, and body mass index (BMI) in addition to age in the determination of proximal femoral BMD in 73 healthy female volunteers age 20-75 years. Muscle strength was an independent predictor of BMD at all three sites in the proximal femur as well as in the lumbar spine and forearm; proximal femur BMD was also predicted by physical fitness. BMI was a positive predictor of bone mass at all sites. In the proximal femur, age was not an independent predictor of BMD at any site. In postmenopausal women muscle strength was a significant predictor of bone mass in the femur and forearm, but not in the spine. However, BMI remained predictive of bone mineral at all sites. Muscle strength, physical fitness, and weight appear to exert independent effects upon bone mass. Age effects may be mediated indirectly through associated changes in these factors. The integrated physical load on the skeleton may be a final common pathway.

Adult↗
PubMed1989

Noninvasive predictors of cardiac events after myocardial infarction. Complementary value of exercise testing and signal-averaged electrocardiography.

Signal-averaged electrocardiography, resting radionuclide ventriculography and Holter monitoring were performed prior to hospital discharge, to assess their value in predicting recurrent cardiac events in 210 survivors of acute myocardial infarction. In addition, 153 of these patients also underwent exercise radionuclide ventriculographic assessment. During median follow-up of 14 months (6-24 months), there were 16 cardiac deaths, 15 patients had recurrent infarction and 7 patients represented with symptomatic ventricular tachycardia. Cox regression analysis identified independent predictors of 'ischemic events' (death or re-infarction) as a previous history of infarction (p = 0.01), Killip class III-IV (p = 0.03) and an abnormal exercise radionuclide study (p = 0.04); and predictors of 'arrhythmic events' (sustained ventricular tachycardia or sudden death) as an abnormal signal-averaged electrocardiograph (p = 0.01) and left ventricular ejection fraction less than 40% (p = 0.03). Patients with an abnormal signal-averaged electrocardiograph and reduced left ventricular ejection fraction had a 34% incidence of arrhythmic events during the first 6 months compared with a 4% incidence among patients without late potentials. In those patients who underwent exercise testing and signal averaging, 85% of total cardiac events and all cardiac deaths were predicted by an abnormality of either noninvasive test. In addition, exercise testing and signal-averaged ECG were independent predictors of outcome. Hence, using a combination of noninvasive tests, patients can be stratified according to the risk of recurrent life-threatening cardiac events after myocardial infarction; such patients may be suitable for intensive investigation and considered for trials involving active intervention.

Electrocardiography↗
PubMed1988

Timing of cardiac transplantation in idiopathic dilated cardiomyopathy.

Seventy-nine patients with idiopathic dilated cardiomyopathy were assessed and followed up to evaluate 9 variables that might predict duration of survival after assessment for cardiac transplantation. Patients with ischemic heart disease, alcoholic and peripartum cardiomyopathy were excluded. There were 38 deaths (48%) during the 18-month (mean) follow-up. Patients underwent determination of left ventricular ejection fraction by radionuclide scan, echocardiography, cardiac catheterization and myocardial biopsy. Only left ventricular ejection fraction determined by radionuclide study correlated significantly with time to death in nonsurvivors (r = 0.38, p less than 0.05). Multivariant analysis and Cox multivariate regression analysis revealed that the single consistent determinant of prognosis was radionuclide-determined ejection fraction. It was an excellent predictor of survival to 3 months (p less than 0.0001) and a reasonable predictor of survival to 6 months (p less than 0.05). There was no variable that efficiently predicted survival for any period greater than 6 months. In 15 of 70 patients (21% of the entire group), clinical status and radionuclide ejection fraction improved after assessment but only one of these had an ejection fraction less than or equal to 0.10. No patient with a radionuclide ejection fraction greater than or equal to 0.20 died within 6 months of assessment. For those with ejection fraction between 0.11 and 0.19, survival after cardiac transplantation exceeded that of the natural history of their disease; this suggests that transplantation should be undertaken within 6 to 12 months of assessment. Left ventricular ejection fraction less than or equal to 0.10 predicts an extremely poor prognosis (6-month survival was 17%) and such patients should be transplanted with minimal delay.

Actuarial Analysis↗
PubMed1988

Bone mineral density in Australia compared with the United States.

Bone density measurements are currently being performed throughout the world in the diagnosis and management of osteoporosis as well as in research into this major health problem. However, it is not clear to what extent bone mineral density (BMD) values determined by dual-photon absorptiometry at one center can be applied to another. This is particularly relevant for the quantitative comparison of results from studies carried out in different laboratories. Furthermore, many centers now acquiring densitometers may not have the resources to determine their own normal range, relying instead on a "normal" range provided by the manufacturer. The question of the comparability of BMD data obtained in different centers was examined by comparing the normal range for the lumbar spine and proximal femur in 203 normal white Australian women and 892 normal white U.S. women, obtained using the same model densitometer. The two populations were compared according to decade. From superimposition of the Australian individual values on the North American normal ranges, only minor differences between the two populations were seen at any of the sites measured at any decade. None of these minor differences were statistically significant. This study shows a close similarity between BMD values in both the proximal femur and lumbar spine in normal white women in Australia and North America, provided the same model densitometer is used. Thus data obtained from different centers in populations with similar ethnic composition may be compared directly. These findings provide for the first time a sound basis for the quantitative comparison of the at times conflicting studies carried out in widely differing settings around the world.

Adult↗
PubMed1987

Dual-photon bone densitometry in normal Australian women: a cross-sectional study.

Osteoporosis is a major health problem in Australia, as it is in most Western societies. Bone mineral density in the spine and femoral neck are accurate indicators of osteopenia and thus useful indicators of the risk of a fracture. Dual-photon absorptiometry is a non-invasive technique that allows the accurate quantitation of bone mineral density in the lumbar vertebrae and proximal femur with a low radiation exposure. The increasing availability of this technique dictates the requirement for "normal" ranges and quality control. We report here lumbar vertebral and proximal femur bone mineral density as measured by dual-photon absorptiometry in 179 normal Australian women. Forearm bone mineral content in these subjects, as measured by single-photon absorptiometry, is also presented. There was a relative stability of lumbar bone mineral density and forearm bone mineral content before the menopause, after which there was an age-related decline. On the other hand, bone mineral density at all three sites in the proximal femur showed an age-related decline throughout adult life. Intraoperator variability in calculated bone mineral density did not exceed 2.3%. The requirement for correct positioning of the patient is illustrated. The data allow statistical analysis and the development of normal ranges. They provide an Australian base against which individual patient values can now be compared.

Adult↗
PubMed1987

Enhanced prediction of major cardiac events after myocardial infarction using exercise radionuclide ventriculography.

Exercise radionuclide ventriculography (RVG) was performed 7-12 days after acute myocardial infarction (MI) in 153 patients to assess its value in identifying those at risk of serious recurrent cardiac events. In addition to electrocardiogram (ECG) features of the exercise test, clinical and hemodynamic features were also considered: the exercise test was abnormal if there was a fall in blood pressure of 10 mmHg or more, development of angina, or inability to complete three minutes of exercise. RVG was used to measure left ventricular ejection fraction and to assess wall motion at rest and at peak exercise. After a median follow-up of 14 months, there were 18 cardiac events: six deaths and 12 patients with recurrent MI. In addition, 18 patients underwent coronary artery bypass surgery; the decision to perform surgery was predicted by ST segment depression or a fall in blood pressure during exercise (p less than 0.005). The sensitivity of the exercise test for identifying patients with a cardiac event increased progressively as additional parameters were considered in a cumulative fashion; hence, ST depression identified 28% of patients with events, whereas addition of clinical and hemodynamic parameters increased this to 61%. The addition of RVG increased the sensitivity further to 88%, but with a specificity of 50%. Although exercise-induced ST depression of up to 1 mm did not predict outcome significantly, a positive exercise RVG did predict cardiac events: 17% of patients with a positive test had an event, compared with 6% of those with a normal study (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Passive immunization: a method of enhancing the immune response against antigen mixtures.

Antigenic competition is known to be a widespread phenomenon when using crude extracts of antigens (e.g., Escherichia coli cytoplasmic proteins) for immunization. This non-specific form of immune suppression can be partially overcome by passive immunization with antibodies against dominant antigens (which are the suppressive molecules) before injection of the antigenic mixture. Blocking these immunodominant antigens or antigenic determinants by a passively administered antibody permits antibody responses against hitherto weakly or non-immunogenic molecules.

Animals↗
PubMed1984

Cascade immunization: a method of obtaining polyspecific antisera against crude fractions of antigens.

Between 20 and 30 precipitation lines are usually obtained by crossed immune electrophoresis of an Escherichia coli cytoplasmic extract against antisera produced against that extract in individual rabbits. With a combination of several such antisera, the number of precipitation lines increases to 30-40. Nevertheless, extracts as used in this work contain many antigens in addition to those thus detected. Intermolecular immune competition may be avoided by removing strong immunogens from the extracts. The remaining antigens which give no immune response in the primary immunization are used for further immunization. New antibody production against 8-14 additional antigens occurs after one such 'cascade immunization' step. Separation of strong from weak immunogens is performed by preparative CIE and the use of immuno-affinity columns. The procedure is called cascade immunization because it involves repeated removal of antigens and production of further antisera directed against antigens in the remainder.

Animals↗
PubMed1981

[The mechanical properties of devices used for the fixation of femoral neck fractures (author's transl)].

The authors have studied the mechanical problems of internal fixation of femoral neck fractures, both from the theoretical and experimental point of view. They have tested stability of several types of fixation according to the obliquity of the fracture line. Three types of strain have been applied to fractured dried bone. Fixation by three parallel screws seemed to give the most stability. The authors conclude that, with this type of fixation, early weight-bearing can be resumed by patients with fractures of Pauwels type I and II, but weight-bearing is still dangerous in type III.

Biomechanical Phenomena↗
PubMed1980

Detection of varicocele by radionuclide blood-pool scanning.

Varicocele is a common and treatable cause of male subfertility. The authors describe a new technique for varicocele detection using radionuclide blood-pool imaging of the scrotum. Of 83 patients studied, 29 had a clinically palpable varicocele of various sizes, and 26 of them were demonstrated by this technique. Two of the false negatives were bilateral varicoceles. In the 41 patients with no clinically detectable varicocele, there were 10 positive and 10 marginally asymmetric studies. The results indicate that this technique detects unilateral varicoceles with high sensitivity, including some which are subclinical. There may be significant implications for treatment of infertility.

Adult↗
PubMed1979

Mapping and ordering of fragments of BK virus DNA produced by restriction endonucleases.

A total of 51 restriction sites were recognized within the BK virus genome by the combination of 10 different restriction endonucleases. These sites were mapped and oriented relative to one another as well as to the five fragments generated by the digestion of BK virus DNA with HindIII and EcoRI. The result was a comprehensive physical map suitable for in-depth characterization of the functions of BK virus at the molecular level.

BK Virus↗
PubMed1979

Parathyroid lesions localized by radionuclide subtraction and ultrasound.

Radionuclide subtraction technique and gray-scale echography were used to localize parathyroid lesions in 6 patients with primary hyperparathyroidism. In 3 cases, surgery verified the scintigraphic findings. All lesions weighed less than 1 g, with the smallest weighing 350 mg. These procedures provide complementary information in preoperative localization of hyperfunctioning parathyroid tissue.

Adenoma↗