Body composition in aging: a biological perspective

PURPOSE OF REVIEW

Changes in body composition accompany and predict medical and surgical risk; interventions may be considered. Aging affects body composition, particularly in reduction of the body cell mass.

RECENT FINDINGS

The molecular biology of aging has become an active frontier of research in the past 30 years, with acceleration in the past decade. A review of the toxicities of reactive oxygen and nitrogen species, especially at the mitochondria, can now be studied at the molecular, genetic, and proteomic scales, in individual cell components and systems, with major implications for patient management, for planning therapeutic interventions, and for predicting future age spans.

SUMMARY

The intersections between the clinical fields of endocrinology, nuclear medicine/radiology, and geriatrics, with the more fundamental fields of physiology, molecular biology, genetics, and proteomics are indicated.

Scedosporium apiospermum pneumonia and sternal wound infection in a heart transplant recipient

BACKGROUND

The most common fungi that cause invasive infection in transplant recipients are the spp, spp, and the endemic fungi such as and. Recently, however, other fungal pathogens have emerged as important causes of invasive disease in these immunocompromised individuals, including the dematiaceous fungi, such as and the spp, species of and, and the hyalohyphomycoses, such as (Pseudallescheria boydii) (1).

METHODS

We present a single patient case report and literature review.

RESULTS

We illustrate the first reported case of a postoperative sternal wound infection and pneumonia caused by in a heart transplant recipient and review the significant clinical, microbiologic, and therapeutic aspects of infection with this important opportunistic pathogen.

CONCLUSIONS

Postsurgical wound infection should be added to the growing list of infections in the transplant population caused by.

Bioelectrical impedance analysis models for prediction of total body water and fat-free mass in healthy and HIV-infected children and adolescents

BACKGROUND

Bioelectrical impedance analysis (BIA) is an attractive method of measuring pediatric body composition in the field, but the applicability of existing equations to diverse populations has been questioned.

OBJECTIVE

The objectives were to evaluate the performance of 13 published pediatric BIA-based predictive equations for total body water (TBW) and fat-free mass (FFM) and to refit the best-performing models.

DESIGN

We used TBW by deuterium dilution, FFM by dual-energy X-ray absorptiometry, and BIA-derived variables to evaluate BIA models in a cross-sectional study of 1291 pediatric subjects aged 4-18 y, from several ethnic backgrounds, including 54 children with HIV infection and 627 females. The best-performing models were refitted according to criterion values from this population, cross-validated, and assessed for performance. Additional variables were added to improve the predictive accuracy of the equations.

RESULTS

The correlation between predicted and criterion values was high for all models tested, but bias and precision improved with the refitted models. The 95% limits of agreement between predicted and criterion values were 16% and 11% for TBW and FFM, respectively. Bias was significant for some subgroups, and there was greater loss of precision in specific age groups and pubertal stages. The models with additional variables eliminated bias, but the limits of agreement and the loss of precision persisted.

CONCLUSION

This study confirms that BIA prediction models may not be appropriate for individual evaluation but are suitable for population studies. Additional variables may be necessary to eliminate bias for specific subgroups.

Multicomponent methods: evaluation of new and traditional soft tissue mineral models by in vivo neutron activation analysis

BACKGROUND

Practical and accurate methods for quantifying the soft tissue mineral component of multicomponent fat-estimation models are needed.

OBJECTIVES

The aims were to develop a new complete model for estimating soft tissue minerals based on measured total body water (TBW) and extracellular water (ECW) and a simplified new model based on TBW measurements only and to compare these estimates with those determined with 2 traditional models (ie, the Brozek and Selinger models) and with criterion estimates based on in vivo neutron activation (IVNA) analysis.

DESIGN

The subjects were 156 healthy adults and 50 patients with AIDS. Total body potassium, sodium, chlorine, and calcium were measured by IVNA; TBW by (3)H(2)O or D(2)O dilution; ECW by bromide dilution; and bone mineral by dual-energy X-ray absorptiometry.

RESULTS

The mean (+/- SD) mass of total-body soft tissue minerals in healthy adults was 467 +/- 62 g with the IVNA model, 492 +/- 62 g with the new model, and 487 +/- 59 g with the simplified new model. Compared with the IVNA model, the complete and simplified new models overestimated soft tissue minerals by 5.4% and 4.6% (both P < 0.001), respectively. In contrast, the Brozek and Selinger models overestimated overall mean soft tissue minerals by 35% and 99% (both P < 0.001), respectively. Overall results for soft tissue mineral prediction with the 2 new models were less satisfactory for the patients with AIDS, although the results were better than those with the traditional models.

CONCLUSIONS

The physiologically formulated complete new model for estimating soft tissue minerals provides the opportunity to upgrade the accuracy of current multicomponent models for estimating total body fat.

Regional subcutaneous-fat loss induced by caloric restriction in obese women

OBJECTIVE

With anthropometric models using skinfolds and circumferences, we studied changes in the percentage of subcutaneous fat in the total cross-sectional area (SF%) at four body sites in obese women, before and after weight loss induced by 6 months of caloric restriction.

RESEARCH METHODS AND PROCEDURES

In 61 obese women [31 African Americans and 30 whites; ages, 24 to 68 years; body mass index (BMI), > or =28 kg/m(2)], we measured SF% at the midpoint of the upper arm and thigh and the waistline and hipline, and we measured the percentage of total body fat by DXA before (Obs#1) and after (Obs#2) a 6-month nonintervention control period and then after 6 months on a 1200 kcal/d diet (Obs#3).

RESULTS

The mean body weight and BMI increased (1.8 kg and 0.61 kg/m(2); p = 0.0001), but there were no significant changes in any other body composition measurements from Obs#1 to Obs#2. The means of Obs#3 for weight and BMI decreased by 11%, and the percentage of total body fat decreased by 13% of Obs#2 mean values (p = 0.0001). The mean SF% at each site decreased 7.6% to 18.0% of the Obs#2 mean values (p < 0.001). The SF% decreases were greater at mid-arm and mid-thigh than in the cross-sectional regions at the waistline and hipline (p = 0.05). There was no interaction between age or ethnicity (p > 0.2).

CONCLUSIONS

In obese women, caloric restriction alone reduces anthropometrically measured subcutaneous fat proportionally more in peripheral than in central regions.

Successful management of an ABO-mismatched lung allograft using antigen-specific immunoadsorption, complement inhibition, and immunomodulatory therapy

BACKGROUND

Successful management of an ABO-mismatched lung allograft recipient has not previously been described.

METHODS

Because of a clerical error, a 67-year-old blood type B patient with idiopathic pulmonary fibrosis received a left single-lung allograft from a blood type A donor. Cyclophosphamide was added to immunosuppression with anti-thymocyte globulin induction, cyclosporine, mycophenolate mofetil, and prednisone. When increasing anti-A antibody titers were detected, antigen-specific immunoadsorption, anti-CD20 monoclonal antibody, and recombinant soluble complement receptor type 1 (TP10) were administered.

RESULTS

Rising anti-A antibody titers were reduced acutely by immunoadsorption, and remained low during long-term follow-up. Humoral injury to the graft was not detected. Acute cellular rejection and multiple complications were successfully managed. Three years after transplantation the patient is clinically well on stable maintenance immunosuppression and prophylactic photochemotherapy.

CONCLUSIONS

Modulation of anti-A antibody, preserved graft function, and a favorable patient outcome can be achieved for an ABO-mismatched lung allograft.

Prepubertal Asians have less limb skeletal muscle

Skeletal muscle mass in prepubertal Asian children has not been examined previously. The aims of this study were to test the hypotheses that 1) prepubertal Asians have less appendicular skeletal muscle (ASM) mass compared with African-Americans and Caucasians, and 2) ASM is less in prepubertal Asian girls compared with Asian boys. ASM was estimated by using dual-energy X-ray absorptiometry in healthy prepubertal girls (n = 170) and boys (n = 166). The results showed that, after adjusting for age, height, and body weight, 1) Asian girls and boys had less amounts of ASM than African-Americans (P < 0.001); 2) Asian girls had less amounts of ASM than Caucasian girls (P = 0.004); 3) there was a trend towards less ASM in Asian compared with Caucasian boys (P = 0.07); 4) and Asian girls had significantly less ASM than Asian boys (P < 0.001). This study indicates that skeletal muscle mass as a fraction of body weight is smaller in Asian compared with African-American and Caucasian children.

Bone density and amenorrhea in ballet dancers are related to a decreased resting metabolic rate and lower leptin levels

Osteopenia, which is correlated with amenorrhea and poor nutritional habits, has been well documented in elite ballet dancers. Estrogen replacement therapy and recovery from amenorrhea have not been associated with normalization of bone density. Thus, the osteopenia may be related to changes brought about by chronic dieting or other factors, such as a hypometabolic state induced by poor nutrition. The purpose of this study was to investigate the relationship of chronic dieting and resting metabolic rate (RMR) to amenorrhea and bone density. RMR, bone density, eating disorder assessments, leptin levels, and complete menstrual and medical histories were determined in 21 elite ballet dancers and in 27 nondancers (age, 20-30 yr). No significant correlations were found between high EAT26 scores, a measure of disordered eating, and RMR, bone densities, body weight, body fat, or fat-free mass. However, when RMR was adjusted for fat-free mass (FFM), a significant positive correlation was found between RMR/FFM and bone density in both the arms (P < 0.001) and spine (P < 0.05) in ballet dancers, but not in the normal controls. The dancers also demonstrated significantly higher EAT scores (22.9 +/- 10.3 vs. 4.1 +/- 2.4; P < 0.001) and lower RMR/FFM ratios (30.0 +/- 2.2 vs. 32.05 +/- 2.8; P < 0.01). The only variable to predict lower RMR/FFM in the entire sample was ever having had amenorrhea; this group had significantly higher EAT scores (18.0 +/- 13.5 vs. 10.3 +/- 10.2; P < 0.05), lower leptin levels (4.03 +/- 0.625 vs. 7.10 +/- 4.052; P < 0.05), and lower bone mineral density in the spine (0.984 +/- 0.11 vs. 1.10 +/- 0.13; P < 0.05) and arm (0.773 +/- 0.99 vs. 0.818 +/- 0.01; P < 0.05). We hypothesize that the correlation between low RMR and lower leptin levels and bone density may be more strongly related to nutritional habits in ballet dancers, causing significant depression of RMR, particularly for those with a history of amenorrhea.

Sex and race differences in fat distribution among Asian, African-American, and Caucasian prepubertal children

Sexual dimorphism in fat distribution is thought to emerge during puberty. Truncal or android body fat distribution is characteristic of adult males but is also recognized as a human cardiovascular risk factor. Race differences in truncal fat are clearly evident in adults and have been described in prepubertal children but not between Asians and other race groups. The aim of this study in African-American, Asian, and Caucasian prepubertal children was to evaluate sex differences and race differences in body fat distribution. Analysis of covariance was used to explore fat distribution in 358 prepubertal children (176 girls and 182 boys; 143 Asians, 95 African-Americans, and 120 Caucasians), measured by skinfold thickness and dual-energy x-ray absorptiometry (DXA) in a cross-sectional study. Extremity and gynoid fat masses were evaluated after adjustment for trunk or android fat, respectively, and for covariates including age, weight, height, and interactions. In Asian children, sex differences were present in models for gynoid fat by DXA only (P < 0.001), with girls having greater gynoid fat than boys. In African-American and Caucasian children, sex differences were present in models for extremity and gynoid fat masses, measured by both methods. Among girls, Asians had generally lower adjusted extremity and gynoid fat than Caucasians and African-Americans. Among boys, Asians had lower adjusted extremity fat by DXA than Caucasians (P < 0.01) but greater gynoid fat by skinfolds than African-Americans (P < 0.01). This study of prepubertal children demonstrates that: 1) sex differences in body fat distribution are present in prepubertal children but that the specific characteristics for Asians differ from African-Americans and Caucasians, and 2) differences in body fat distribution in Asian children, compared with African-Americans and Caucasians, are present but vary by sex. This comparison of African-American, Asian, and Caucasian prepubertal children suggests phenotypic differences. Additional studies are needed to explore the metabolic and health risk implications of these findings.

Trunk fat and blood pressure in children through puberty

BACKGROUND

Fat distribution is well recognized as a cardiovascular risk factor in adults. The association between android fat distribution and cardiovascular risk factors, such as blood pressure (BP), was previously reported in an African-American and Caucasian pediatric population. The aim of the present study was to investigate the relationship between BP and body fat distribution in a large cross-sectional pediatric sample. The effects of race, sex, and puberty on this relationship were assessed.

METHODS AND RESULTS

BP was measured in 920 healthy children and adolescents (African-American, Asian, and Caucasian, ages 5 to 18 years). Fat distribution was determined by skinfold thickness and dual-energy X-ray absorptiometry (DXA). Pubertal status was assessed by the criteria of Tanner. Regression analysis was used to explore the association between BP and fat distribution. Significant positive relationships between systolic and diastolic BP and trunk fat adjusted for total fat were seen in boys at all pubertal stages in all 3 races by both DXA and skinfold measurements. In girls, trunk fat was not a significant predictor of BP.

CONCLUSIONS

Our results demonstrate a sex difference in the relationship between BP and trunk fat in that a significant positive relationship was present in boys only. These findings, based on 2 independent measures of fat distribution, may help identify the specific features of individuals at risk, allow earlier intervention, and suggest sex-specific determinants for BP.

Postoperative coronary revascularization on LVAD support for surgically inaccessible myocardial ischemia

The authors have used the concept of hybrid revascularization to salvage a patient in persistent cardiogenic shock after incomplete emergent surgical revascularization. While the patient was on left ventricular assist device support, a complex angioplasty was done on a surgically inaccessible right coronary artery, with subsequent cardiac recovery.

Left ventricular assist device implantation via left thoracotomy: alternative to repeat sternotomy

Repeat sternotomy for left ventricular assist device insertion may result in injury to the right heart or patent coronary grafts, complicating intraoperative and postoperative management. In 4 critically ill patients, left thoracotomy was used as an alternative to repeat sternotomy. Anastomosis of the outflow conduit to the descending thoracic aorta provided satisfactory hemodynamic support.

Cardiac surgery in patients with moderate renal impairment

BACKGROUND

There is a paucity of information concerning the results of cardiac surgery in patients with moderate impairment of renal function. We reviewed our recent experience to determine the results of operation and the long-term outcome.

METHODS

Since January 1992, we have performed cardiac surgical procedures utilizing total cardiopulmonary bypass on 57 adult patients with preoperative serum creatinine values > or = 2.0 mg/dL and no history of dialysis. Operative procedures done were coronary artery bypass (39 patients), repeated coronary artery bypass (2), valve replacement with or without coronary artery bypass (12), and other procedures (4).

RESULTS

No operative deaths occurred. There were 3 hospital deaths. Only 5 patients required perioperative dialysis; in 5 additional patients, chronic dialysis was begun from 4 to 24 months postoperatively. The surviving patients who were not receiving dialysis had a mean creatinine value of 2.4 mg/dL at most recent follow-up.

CONCLUSIONS

Adult patients with moderate renal impairment can safely have major cardiac procedures. The majority of patients maintain stable renal function postoperatively. The overall results of cardiac surgery in this patient population are good.

Late cardiac reoperation after cardiac transplantation

BACKGROUND

The intermediate and long-term results of cardiac transplantation continue to improve. Subsequent cardiac procedures may be required to extend patient survival and protect graft function.

METHODS

The medical records of all adult and pediatric cardiac transplant recipients who underwent a subsequent cardiac procedure at our institution were reviewed.

RESULTS

Three hundred sixty patients have undergone primary orthotopic transplantation in our institution. Seventeen patients (12 adults, 5 children) underwent a subsequent procedure requiring cardiopulmonary bypass including cardiac retransplantation (10), coronary artery bypass grafting (3), ascending aortic replacement (2), tricuspid valve repair (1), and myotomy and myomectomy (1 patient). Mean interval from time of transplantation to second procedure was 8.3 years. There was one perioperative death. Two patients, both retransplants, died late postoperatively at 22 and 84 months, respectively. Overall mean follow-up in the late survivors is 26.6 months. All survivors are currently asymptomatic and doing well.

CONCLUSIONS

A variety of subsequent cardiac procedures, in addition to retransplantation, can be performed safely in carefully selected cardiac transplant recipients. The intermediate term results are gratifying in terms of survival and freedom from symptoms.

Cardiac Surgery after Renal Transplantation

Renal transplantation remains a mainstay of therapy for end-stage renal disease. Cardiac disease has a high prevalence in this patient population. This study reviews the factors and outcomes associated with cardiac surgery in renal transplant recipients. We performed a retrospective review of all patients at our institution with a functioning renal allograft at the time of their cardiac surgical procedure. Between June 1971 and April 2000, 2343 patients underwent renal transplantation at Vanderbilt University Medical Center. Twenty-six patients with a functioning renal allograft subsequently underwent a cardiac procedure requiring cardiopulmonary bypass. There were 11 women and 15 men. Twenty-four patients underwent coronary bypass, one had a double valve replacement, and one had a combined coronary bypass/valve replacement. The interval from renal transplant to heart surgery ranged between 0.6 and 227 months (mean 79.1). Operative mortality was zero but there were two hospital deaths: one due to multisystem organ failure and one due to pulmonary embolism. Six additional patients died late with only one due to heart disease. Four patients required perioperative dialysis, and one of these went on to require permanent dialysis. Two additional patients returned to dialysis late postoperatively. The requirement for acute perioperative dialysis was predicted by preoperative creatinine, hematocrit, and intraoperative urine output. The overall survival is 69 per cent (18 of 26) with a median follow-up of 38 months. The majority of long-term survivors have minimal cardiac symptoms. Standard cardiac surgery procedures can be performed with relative safety in patients with functioning renal allografts. The incidence of perioperative and late development of renal failure requiring dialysis is low. The long-term survival and symptomatic improvement achieved are favorable and warrant continued performance of cardiac surgery in patients with functioning renal allografts.

Prevention of cytomegalovirus infection and disease after lung transplantation: results using a unique regimen employing delayed ganciclovir

BACKGROUND

Many lung transplant programs employ lengthy regimens of IV ganciclovir therapy to prevent disease due to cytomegalovirus (CMV). In 1994, we introduced a regimen of delayed ganciclovir prophylaxis for CMV infection. This consisted of 2 weeks of IV ganciclovir therapy, initiated 3 to 4 weeks after transplantation, with subsequent viral monitoring and preemptive therapy as needed. When not receiving ganciclovir, patients received oral acyclovir, 800 mg tid, for 6 months. CMV-seronegative patients with seropositive donors also received four doses of CMV hyperimmune globulin. This study analyzes the CMV outcomes of 54 patients who received the delayed regimen compared to 33 historical control subjects who received only acyclovir prophylaxis (n = 28) or oral acyclovir and 2 to 4 weeks of ganciclovir early after transplantation (n = 5).

METHODS

CMV detection was by shell vial culture or IgG seroconversion; after 1996, CMV detection was by blood antigenemia. The diagnosis of CMV disease also required a typical clinical syndrome or pathologic evidence of CMV. The main outcome was the actuarial incidence of CMV infection and disease. In order to account for the effect of other important risk factors for CMV infection, the time to CMV infection and disease was also studied as dependeant variables in a Cox proportional-hazard analysis, with the delayed regimen and other important risk factors as independent variables.

RESULTS

The delayed regimen reduced the actuarial incidence of CMV infection from 80 to 48% (p < 0.001) and CMV disease from 31 to 10% (p < 0.01). No seropositive patient receiving the delayed regimen developed CMV disease. Twelve of the 54 patients in the study group required additional IV antiviral treatment, but the total use of ganciclovir averaged only 18 days per patient. In a Cox proportional-hazards model, the use of delayed ganciclovir was the only factor that showed a significant association with freedom from CMV infection (hazard ratio [HR], 0.43; 95% confidence interval [CI], 0.24 to 0.75; p = 0.003) and CMV disease (HR, 0.29; 95% CI, 0.10 to 0.86; p = 0.03).

CONCLUSION

A regimen of CMV prophylaxis employing 2 weeks of IV ganciclovir initiated 3 to 4 weeks after lung transplantation followed by virologic monitoring and preemptive therapy as needed provides good protection against CMV disease.

Cardiac surgery after renal transplantation

Renal transplantation remains a mainstay of therapy for end-stage renal disease. Cardiac disease has a high prevalence in this patient population. This study reviews the factors and outcomes associated with cardiac surgery in renal transplant recipients. We performed a retrospective review of all patients at our institution with a functioning renal allograft at the time of their cardiac surgical procedure. Between June 1971 and April 2000, 2343 patients underwent renal transplantation at Vanderbilt University Medical Center. Twenty-six patients with a functioning renal allograft subsequently underwent a cardiac procedure requiring cardiopulmonary bypass. There were 11 women and 15 men. Twenty-four patients underwent coronary bypass, one had a double valve replacement, and one had a combined coronary bypass/valve replacement. The interval from renal transplant to heart surgery ranged between 0.6 and 227 months (mean 79.1). Operative mortality was zero but there were two hospital deaths: one due to multisystem organ failure and one due to pulmonary embolism. Six additional patients died late with only one due to heart disease. Four patients required perioperative dialysis, and one of these went on to require permanent dialysis. Two additional patients returned to dialysis late postoperatively. The requirement for acute perioperative dialysis was predicted by preoperative creatinine, hematocrit, and intraoperative urine output. The overall survival is 69 per cent (18 of 26) with a median follow-up of 38 months. The majority of long-term survivors have minimal cardiac symptoms. Standard cardiac surgery procedures can be performed with relative safety in patients with functioning renal allografts. The incidence of perioperative and late development of renal failure requiring dialysis is low. The long-term survival and symptomatic improvement achieved are favorable and warrant continued performance of cardiac surgery in patients with functioning renal allografts.

CD40-ligand in primate cardiac allograft and viral immunity

Our laboratory has studied the role of CD40 ligand (CD40L, CD154) in the primate immune response to allogenic and infectious challenges. We find that intensive early blockade of CD40L reliably attenuates acute rejection of primate cardiac allografts. Monotherapy fails to prevent late graft loss, which often occurs in association with rising antidonor antibody titers and allograft vasculopathy, despite continuing anti-CD40L therapy. In contrast, the primary humoral response to T helper dependent influenza viral antigen is inhibited during anti-CD40L therapy, and responses to subsequent immunization are blunted after discontinuation of therapy. These results are encouraging with regard to the tolerogenic potential of costimulatory blockade for specific T helper dependent antigens. However, these findings also indicate that pathogenic allograft responses in primates are probably not entirely CD40L-dependent. As such, additional immunomodulatory strategies are needed to facilitate tolerance to a transplanted organ.

Effects of whey protein and resistance exercise on body cell mass, muscle strength, and quality of life in women with HIV

OBJECTIVE

To determine the effects of whey protein, resistance exercise, and combined protein and exercise treatment on body cell mass (BCM), muscle strength, and quality of life (QOL) in HIV-infected women with reduced BCM.

DESIGN AND SETTING

Prospective, randomized, controlled trial at a university hospital in New York City.

METHODS

A volunteer sample of 30 HIV-infected women were randomized to whey protein (PRO), progressive resistance exercise (PRE), or combined treatment (PRO-PRE) for 14 weeks after a 6-week control period. The main outcome measures were body weight, BCM, skeletal muscle, fat mass, muscle strength, and QOL.

RESULTS

There were no significant changes in BCM, strength, or QOL during the control period. PRO patients gained 3.6 kg (P = 0.001), and 2.5 kg fat (P = 0.002) with no change in BCM (0.5 kg; P = 0.07) or skeletal muscle (0.6 kg; P = 0.12). The PRE group increased BCM (0.74 kg;P = 0.03) and skeletal muscle (1.2 kg; P < 0.001) and decreased fat (1.7 kg; P = 0.02). PRO-PRE increased BCM (0.61 kg; P = 0.01) without change in skeletal muscle (0.6 kg; P = 0.30). Strength increased for both exercise groups (range, 40.6-95.3%; P < 0.001). The QOL physical activity score improved for PRE (P = 0.02) and worsened for PRO (P = 0.01).

CONCLUSIONS

Resistance exercise significantly increased BCM, muscle mass, muscle strength, and QOL in HIV-infected women with reduced BCM. Whey protein had little effect on BCM accrual. Combined protein and exercise did not increase BCM in excess of gains achieved by exercise alone.

Role of anti-Gal alpha13Gal and anti-platelet antibodies in hyperacute rejection of pig lung by human blood

BACKGROUND

Previous work has shown that antibodies against porcine antigens are an important trigger of hyperacute lung rejection (HALR). The relative importance of Gal alpha1,3Gal epitopes and other antigens, such as those expressed on pig platelet membranes or lung itself, has not been defined. This study compares the efficiency of three anti-pig antibody depletion strategies, and their efficacy with regard to attenuation of HALR.

METHODS

Plasma pooled from three human donors was adsorbed against Gal alpha1,3Gal disaccharide or porcine platelet extract (PPE), or passed through pig lung vasculature. Whole blood reconstituted using adsorbed plasma was then used to perfuse piglet lung, and results were compared with unmodified human blood.

RESULTS

Depletion of lung-reactive anti-Gal alpha1-3Gal antibodies was most efficient with the alphaGal column (99% +/- 0.5% vs 87% to 93% +/- 11% for PPE and 92% to 95% +/- 8% for lung, p < 0.01 vs alphaGal column). PPE column tended to be more efficient (77% to 84% +/- 12%) in removing anti-PPE antibodies than pig lung (66% to 70% +/- 14%) or the alphaGal column (56% to 63% +/- 16%, p < 0.05). Lung survival and function with each antibody depletion strategy was improved relative to unmodified controls (mean survival > or = 146 minutes vs 8 minutes for controls). Although alphaGal and lung adsorption yielded more consistent lung protection (survival beyond 2 hours) than did PPE, no approach proved significantly superior. Complement C3a elaboration at 10 minutes was attenuated > 80% by each adsorption strategy, an effect that was most pronounced in the lung adsorption group (95%, p < 0.01). Histamine elaboration was blunted significantly by PPE adsorption but not in other groups (p < 0.05). Platelet but not leukocyte sequestration was decreased with antibody depletion compared with the nondepleted group (44% to 50% vs 82%, p < 0.01).

CONCLUSIONS

Each antibody depletion strategy tested significantly prolongs lung xenograft survival and function compared with unmodified human blood, but none was sufficient to reliably prevent HALR. Depletion of antibodies against both alphaGal and additional cell membrane antigens, or control of antibody-independent pathogenic pathways, may be necessary to consistently prevent HALR.

Prepubertal girls with premature adrenarche have greater bone mineral content and density than controls

Body composition in premature adrenarche (PA) has not been described. We hypothesized that the increased adrenal androgens in PA would have a trophic effect on lean body components. We studied 14 PA subjects and 16 controls, all prepubertal Hispanic girls. The body composition parameters tested included height, weight, bone mineral density (BMD), bone mineral content (BMC), nonbone fat-free mass, total body potassium, total body water, and extracellular water. Bone age was determined in all PA subjects. Compared with controls, PA subjects had significantly higher BMC (P = 0.02) and BMD (P = 0.03) when adjusted for age, weight, height, and fat mass, but were not different in the following lean body components: fat-free mass, total body potassium, total body water, and extracellular water. There was no difference in BMD or BMC between the PA subjects with and without advanced bone age. These data suggest a specific effect of PA on bone mineral, but not on other lean body components. The absence of a correlation between bone age and bone mineral in this small group leads us to propose there are separate promoters of bone age advancement and bone mineral accrual. Candidate hormones for these processes include adrenal androgens, E, and IGF-I. The findings of this study suggest that hormonal alterations associated with PA affect bone mineral accrual and may elucidate the mechanisms involved in this process.

Magnitude and variation of ratio of total body potassium to fat-free mass: a cellular level modeling study

Potassium is an essential element of living organisms that is found almost exclusively in the intracellular fluid compartment. The assumed constant ratio of total body potassium (TBK) to fat-free mass (FFM) is a cornerstone of the TBK method of estimating total body fat. Although the TBK-to-FFM (TBK/FFM) ratio has been assumed constant, a large range of individual and group values is recognized. The purpose of the present study was to undertake a comprehensive analysis of biological factors that cause variation in the TBK/FFM ratio. A theoretical TBK/FFM model was developed on the cellular body composition level. This physiological model includes six factors that combine to produce the observed TBK/FFM ratio. The ratio magnitude and range, as well as the differences in the TBK/FFM ratio between men and women and variation with growth, were examined with the proposed model. The ratio of extracellular water to intracellular water (E/I) is the major factor leading to between-individual variation in the TBK/FFM ratio. The present study provides a conceptual framework for examining the separate TBK/FFM determinants and suggests important limitations of the TBK/FFM method used in estimating total body fat in humans and other mammals.

Bone turnover and density in obese premenopausal women during moderate weight loss and calcium supplementation

Bone turnover is increased during weight loss in postmenopausal women and can be suppressed with calcium supplementation. In this study, we assessed the influence of energy restriction with and without calcium supplementation (1 g/day) in premenopausal women. Thirty-eight obese premenopausal women (body mass index [BMI] of 35.0 +/- 3.9 kg/m2) completed a 6-month study of either moderate weight loss or weight maintenance. During weight loss, women were randomly assigned to either a calcium supplementation (n = 14) or placebo group (n = 14) and lost 7.5 +/- 2.5% of their body weight. The control group of women (n = 10) maintained their body weight. Total body and lumbar bone mineral density (LBMD) and content were measured by dual-energy X-ray absorptiometry (DXA) at baseline and after weight loss. Throughout the study, blood and urine samples were collected to measure bone turnover markers and hormones. During moderate energy restriction, dietary calcium intake decreased (p < 0.05) and the bone resorption marker deoxypyridinoline (DPD) increased slightly (p < or = 0.05) without evidence of bone loss. Calcium supplementation during weight loss tended to increase lumbar BMD by 1.7% (p = 0.05) compared with the placebo or weight maintenance groups. In contrast to our previous findings in postmenopausal women, premenopausal obese women who consume a low calcium diet do not lose bone over a 6-month period, whether their weight is stable or decreasing moderately.

Hemorrhagic colitis due to a novel Escherichia coli serotype (O121:H19) in a transplant patient

Infection due to enterohemorrhagic Escherichia coli (EHEC) has not been described in immunosuppressed patients. We recently saw a case of EHEC infection caused by a novel Shiga toxin II-producing Escherichia coli serotype (O121:H19) that caused hemorrhagic colitis in a patient with renal and cardiac transplants. The patient's signs, symptoms, and colon pathology were similar to reports of EHEC infection in immunocompetent patients. This case suggests that the immunosuppressed state may not alter the clinical presentation or histopathologic findings of this disorder. Assays for EHEC are not routinely done at most hospitals. Therefore, clinicians caring for transplant patients should be aware of the typical clinical presentation of EHEC infection, so that they can initiate appropriate laboratory investigation in suspected cases.