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Biomedical subjects

M Perl

Publications and source records attributed to M Perl.

At least 19 recordsLinked to original sources
PubMed1997

Cardiopulmonary bypass (CPB) for lung transplantation.

Surgeons have often been reluctant to use cardiopulmonary bypass (CPB) during single (SLTx) and double lung (DLTx) transplantation surgery because of the potential adverse sequelae of CPB including haemorrhage and activation of complement leading to sequestration of neutrophils and platelets in the pulmonary capillary bed, endothelial damage, increased capillary permeability and pulmonary oedema. To clarify the effect of CPB on lung transplant recipients, we reviewed our last four years' experience in 74 patients of whom 30 required CPB support. Indications for CPB were mean pulmonary artery pressure of greater than 50 mmHg, haemodynamic instability, hypoxia or hypercarbia. Patients undergoing SLTx were placed on CPB via the femoral artery and vein, while those undergoing DLTx were cannulated in the standard fashion using the ascending aorta and right atrium. All patients were administered aprotinin prior to CPB. Intraoperatively and postoperatively, haemorrhage was not a major problem. The 30-day mortality in the CPB group and the non-CPB group were 20% and 4.6%, respectively which was not statistically significant (p = 0.06). We conclude that CPB during lung transplantation is a safe, effective method to support these severely ill patients and should not be avoided because of concerns over adverse sequelae of CPB on postoperative graft function.

Blood Transfusion↗
PubMed1995

Comparing the cost effectiveness of psychiatric treatments: bulimia nervosa.

We conducted an exploratory post hoc study that compared the cost effectiveness of five treatments for bulimia nervosa: 15 weeks of cognitive behavioral therapy (CB) followed by three monthly sessions, 16 weeks (Med16) and 24 weeks (Med24) of desipramine (< or = 300 mg/day), and CB combined with desipramine for those durations (Combo16 and Combo24). We illustrate how a treatment's cost effectiveness varies according to when evaluation is done and how effectiveness and cost are defined. At 32 weeks, Med16 appears the most cost-effective treatment, and Combo16 appears the least. At 1 year, Med24 appears the most cost-effective treatment, and Combo16 appears the least. Using this post hoc analysis as an example, we discuss the pitfalls and limitations of cost-effectiveness analysis of psychiatric treatments.

Adolescent↗
PubMed1994

Experimental perturbation of the development of sexual size dimorphism in the mouse skeleton.

BALB/c mice were raised for 30 days under nine treatment regimens to determine their effects on sexual dimorphism for size of the femur and of the body. Treatment groups were divided into three experiments: 1) burrowing in a high litter cage; eight times normal gravity for a total of one hour per day; a voluntary exercise control. 2) Unilateral femoral and sciatic nerve ablation; the opposite unoperated leg. 3) Swimming exercise; anabolic steroid; swimming and anabolic steroid; normal exercise control. Traits measured were body weight gain and thirteen femoral characters: moment at failure, length, cross-sectional area, anteroposterior and lateromedial diameters of the cross section, wall thickness for all four quadrants of the shaft, moments of inertia of the cross section in the anteroposterior and lateromedial directions, deflection of the shaft before failure, and total mineral content. Sexual dimorphism of the traits studied varied significantly with treatment. The greatest dimorphism was seen in the controls and the burrowing group. The least dimorphism was seen in the eight times gravity, the steroid, and the exercise and anabolic steroid groups. Reduction in the extent of sexual dimorphism was not correlated with a reduction in the loading regimen but rather seemed mediated by systemic changes in physiology brought on by several factors. Change in the amount of sexual dimorphism for size from the control reflects change in growth rates for males and females in response to different treatments. Change in growth rates of juvenile males and females will likely result in changes in the size of femoral characters and body weight in the adult. Change in the size of femoral characters affects the strength of the femur. In natural populations, a change in the body size of adult males and females could adversely affect reproductive success in groups that normally exhibit strong dimorphism, and hence, select against any conditions that reduce sexual dimorphism. Ordinarily, a significant change in sexual dimorphism--of the magnitude seen here--through natural selection, would take several generations.

Animals↗
PubMed1993

Geodesics as a mechanically optimal fiber geometry for the left ventricle.

Anatomical findings as well as theoretical considerations indicate that the myocardial fibers lie along minimal length geodesics of the left ventricular wall. Based upon this knowledge it is shown that the energy spent by the actively contracting fibers during systole, as well as the passive fiber stresses developed through diastole, are minimal in comparison with any other possible fiber configuration. Subsequently, it is concluded that for a given succession of left ventricular states, fiber shortening course and hence the amount of mechanical work are uniquely determined. Comparison with experimental findings concerning global left ventricular systolic work indicates that a given course of afterload produces a unique course of ventricular volume and of mechanical work.

Diastole↗
PubMed1993

Adaptive modeling in a mammalian skeletal model system.

Juvenile BALB/c mice were used as a model system to test the effects of various loading and exercise regimens on the growth and development of femora. Six treatments and three controls were used to document changes in geometric, mechanical, and material properties of the femora associated with strength. In each age-matched experiment, body weight and the strength, length, anterior and posterior diameters, cross-sectional area, moments of inertia in the anteroposterior and lateromedial directions, cortical wall thickness, and mineral content of the femora were assessed and found to vary significantly among treatment groups. An adaptive interpretation of these data was provided by calculating Pearson correlation coefficients between moment at failure (one measure of strength) and each geometric, mechanical and material property of the femora that contributes to strength. We make the assumption that at the termination of the experiment the greater the coordination between changes in strength and changes in the parameters that contribute to strength (the greater the number of correlations), the more adaptively modeled the femora are. Adaptive modeling here refers to the manner in which the femora grow and develop (adapt) under a given treatment regimen. Absolute strength of whole femora was reflected by our measure of adaptive modeling in all groups with one exception. In each experiment, the voluntary exercise controls were the most adaptively modeled. The least adaptively modeled groups also showed a general retardation of growth. It appears that juvenile mouse femora demonstrate a wide range of responses to different conditions of loading and exercise and that some of these changes are likely permanent. Moreover, at least two major variables--1) mechanical loading and 2) glucocorticoid mediated psychological stress--appear to contribute to the differences seen between the treatment groups.

Adaptation, Physiological↗
PubMed1992

Pharmacologic and cognitive-behavioral treatment for bulimia nervosa: a controlled comparison.

OBJECTIVE: This study examined the relative effectiveness of desipramine, cognitive-behavioral therapy, and their combination in the treatment of bulimia nervosa, together with the effects of withdrawing medication after two different lengths of treatment. METHOD: Seventy-one patients meeting DSM-III-R criteria for bulimia nervosa, recruited from an eating disorders clinic or by advertisements, were assigned at random to one of five groups: desipramine (withdrawn at 16 or 24 weeks), combined treatment (medication withdrawn at 16 or 24 weeks), and cognitive-behavioral therapy (15 sessions). All treatments were conducted individually in an outpatient clinic. The primary outcome measures were binge eating and purging rates assessed at pretreatment, 16, 24, and 32 weeks. The results were analyzed as three groups (medication, cognitive-behavioral therapy, and combined treatment) at 16 weeks and as five groups at subsequent assessments. RESULTS: At 16 weeks, both cognitive-behavioral therapy and the combined treatment were superior to medication given for 16 weeks in reducing binge eating and purging. At 32 weeks, however, only the combined 24-week treatment was superior to medication given for 16 weeks. The combined treatment was also more effective in reducing dietary preoccupation and hunger. Continuing cognitive-behavioral therapy appeared to prevent relapse in patients withdrawn from medication at 16 weeks. CONCLUSIONS: Overall, the results favor the use of a combination of medication and cognitive-behavioral therapy in the treatment of bulimia nervosa, with medication continued for at least 24 weeks.

Adolescent↗
PubMed1989

Structural alterations and breaking strength of mouse femora exposed to three activity regimens.

Mice were used as a model system to correlate loading, changes in cortical and trabecular bone growth and remodeling, and differences in breaking strength of the whole femur. BALB/c mice were raised for 30 days, starting at day 14, under three conditions of loading or exercise: (a) normal exercise control (NE), (b) 4 x normal gravity for a total of one h/day in addition to normal exercises (HG), and (c) chronic digging and burrowing (high-litter cage) (HL). Results indicate that both HG and HL groups significantly increased the cortical cross-sectional area of the mid-shaft of the femur, the moment of inertia in the antero-posterior direction at the mid-shaft, anterior wall thickness of the midshaft cross section, and changed the architecture of trabecular bone in the proximal one-third of the femur. The extent of these structural changes, however, was unique in each group. The HG group (high-intensity, short duration loading) demonstrated the greatest structural changes in the moment of inertia in the antero-posterior direction, which increased by 44% over the control (p less than .001), and in the architecture of trabecular bone. The HL group (lower-intensity, chronic exercise), demonstrated the greatest structural change in cortical bone cross-sectional area, which increased by 27% (p less than .0001). Despite the differences in loading and structural changes in the HG and HL groups, the breaking strength of the whole femur for both groups was approximately 64% greater than the controls (p less than .0001). A mechanical analysis of our data revealed that for our tests the contribution of bending to the total stress on the shaft may be over 50 times greater than that of either compression or tension. Further, the change in the geometry of the cortical bone may account for only approximately 50% of the increase in breaking strength; the remaining increase must be accounted for by changes in material properties and/or placement of trabeculae within the lumen of the shaft.

Animals↗
PubMed1988

Nonlinear incompressible finite element for simulating loading of cardiac tissue--Part I: Two dimensional formulation for thin myocardial strips.

A two-dimensional incompressible plane-stress finite element is formulated for the simulation of the passive-state mechanics of thin myocardial strips. The formulation employs a total Lagrangian and materially nonlinear approach, being based on a recently proposed structural material law, which is derived from the histological composition of the tissue. The ensuing finite element allows to demonstrate the mechanical properties of a single myocardial layer containing uniformly directed fibers by simulating various loading cases such as tension, compression and shear. The results of these cases show that the fiber direction is considerably stiffer than the cross-fiber direction, that there is significant coupling between these two directions, and that the shear stiffness of the tissue is lower than its tensile and compressive stiffness.

Collagen↗
PubMed1988

Structural three-dimensional constitutive law for the passive myocardium.

A three-dimensional constitutive law is proposed for the myocardium. Its formulation is based on a structural approach in which the total strain energy of the tissue is the sum of the strain energies of its constituents: the muscle fibers, the collagen fibers and the fluid matrix which embeds them. The ensuing material law expresses the specific structural and mechanical properties of the tissue, namely, the spatial orientation of the comprising fibers, their waviness in the unstressed state and their stress-strain behavior when stretched. Having assumed specific functional forms for the distribution of the fibers spatial orientation and waviness, the results of biaxial mechanical tests serve for the estimation of the material constants appearing in the constitutive equations. A very good fit is obtained between the measured and the calculated stresses, indicating the suitability of the proposed model for describing the mechanical behavior of the passive myocardium. Moreover, the results provide general conclusions concerning the structural basis for the tissue overall mechanical properties, the main of which is that the collagen matrix, though comprising a relatively small fraction of the whole tissue volume, is the dominant component accounting for its stiffness.

Animals↗
PubMed1987

Home parenteral nutrition and the family.

When a patient begins home parenteral nutrition (HPN), everyone in the patient's family is affected. In the early stages, the predominant issues are unfamiliarity with the HPN equipment and fear of acute complications. Later, adjustments become necessary in routine family activities such as eating, traveling, and recreation. The indwelling catheter used for parenteral feeding is a source of body-image distortion and anxiety for the patient, his or her sexual partner, and family members in general. The role of the consultation-liaison psychiatrist in the multidisciplinary home hyperalimentation team is described.

Catheters, Indwelling↗
PubMed1985

Denial in clinical medicine. A reexamination of the concept and its significance.

It is argued that, due to the diversity of meanings attaching to the term "denial" considerable imprecision exists in the clinical use both of the term itself and of its associated concepts. An obvious danger in this situation is that the term should be rendered unserviceably vague. Less obvious dangers include infringements of patients' rights and a tendency to foster paternalistic decision making. Amending the term's clinical usage is made with recommendations.

Attitude of Health Personnel↗