Regular brief interruptions to sitting after a high-energy evening meal attenuate glycemic excursions in overweight/obese adults.

BACKGROUND AND AIMS: Modern Western lifestyles are characterized by consumption of approximately 45% of total daily energy intake at the evening meal, followed by prolonged sitting while watching television (TV), which may deleteriously impact glycemic control. After a high-energy evening meal (dinner), we examined whether regular, brief activity bouts during TV commercial breaks could acutely lower postprandial glucose and insulin responses in overweight/obese adults, compared to prolonged uninterrupted sitting. METHODS AND RESULTS: Nine overweight/obese adults (29.7 ± 4.06 kg m-2; aged 32 ± 3 years; 5 male) completed two laboratory-based conditions of three and a half hours: prolonged sitting during TV viewing (SIT); and, prolonged sitting interrupted every 20 min with 3 min of light-intensity body-weight resistance activities (active commercial breaks; ACBs). Venous postprandial glucose and insulin responses to dinner were calculated as positive incremental area under the curve (iAUC) from baseline. Interstitial glucose was measured using a continuous glucose monitor and quantified as total AUC (tAUC). Compared to SIT, plasma glucose iAUC was reduced by 33% [3.4 ± 1.0 vs 5.1 ± 1.0 (mean ± SEM) mmol h·L-1, p = 0.019] and plasma insulin iAUC by 41% (813 ± 224 vs 1373 ± 224, p = 0.033 pmol h·L-1) for the ACB condition. During the ACB condition there was a significant reduction in interstitial glucose tAUC (24.4 ± 5.2 vs 26.9 ± 5.2 mmol h·L-1, p < 0.001), but this did not persist beyond the laboratory observation period. CONCLUSIONS: Regular brief light-intensity activity bouts can attenuate glycemic responses during television viewing time following a high-energy evening meal in overweight/obese adults.

Genetic diversity in proteolytic enzymes and amino acid metabolism among Lactobacillus helveticus strains.

Lactobacillus helveticus CNRZ 32 is recognized for its ability to decrease bitterness and accelerate flavor development in cheese, and has also been shown to release bioactive peptides in milk. Similar capabilities have been documented in other strains of Lb. helveticus, but the ability of different strains to affect these characteristics can vary widely. Because these attributes are associated with enzymes involved in proteolysis or AA catabolism, we performed comparative genome hybridizations to a CNRZ 32 microarray to explore the distribution of genes encoding such enzymes across a bank of 38 Lb. helveticus strains, including 2 archival samples of CNRZ 32. Genes for peptidases and AA metabolism were highly conserved across the species, whereas those for cell envelope-associated proteinases varied widely. Some of the genetic differences that were detected may help explain the variability that has been noted among Lb. helveticus strains in regard to their functionality in cheese and fermented milk.

Comparison of two aspirin doses on ischemic stroke in post-myocardial infarction patients in the warfarin (Coumadin) Aspirin Reinfarction Study (CARS).

The Coumadin Aspirin Reinfarction Study demonstrated that combination treatment with fixed dose warfarin (1 or 3 mg) + aspirin 80 mg was not superior to aspirin 160 mg alone after myocardial infarction for reducing nonfatal reinfarction, nonfatal stroke, and cardiovascular death. In this analysis, we examined the importance of aspirin dose in the protection against the secondary end point of ischemic stroke. The comparison arms for this analysis were warfarin 1 mg + aspirin 80 mg versus aspirin 160 mg. In the Coumadin Aspirin Reinfarction Study, 2,028 patients were randomized to aspirin 80 mg plus warfarin 1 mg, and 3,393 were randomized to aspirin 160 mg alone. A predictive model for ischemic stroke was developed using the Cox proportional-hazards model. A reduced Cox proportional-hazards model was developed to test for the effect of aspirin dose on ischemic stroke in predefined subgroups. The incidence of ischemic stroke was lower in patients treated with aspirin 160 mg than in patients treated with aspirin 80 mg + warfarin 1 mg (0.6% vs 1.1%; p = 0.0534). Age, previous stroke or transient ischemic attack, and aspirin dose were independent predictors of ischemic stroke. In addition, the highest risk patients, those with Q-wave myocardial infarction and male patients, appeared to receive greater benefit from aspirin 160 mg than from aspirin 80 mg + warfarin 1 mg. The results of this secondary analysis suggest that aspirin 160 mg is more effective than aspirin 80 mg + warfarin 1 mg in preventing ischemic stroke in post-myocardial infarction patients.

Noninvasive diagnosis of partial anomalous left pulmonary artery.

The branching patterns of the pulmonary arteries may vary, with one or more lobes of the left lung being supplied by a branch originating from the right pulmonary artery-a condition termed partial anomalous left pulmonary artery. If this anomalous branch courses anterior and inferior to the trachea, it is unlikely to result in airway obstruction. It is important that this anomaly not be confused with pulmonary artery sling, where the anomalous branch courses posterior to the trachea, encircling it almost completely. Partial anomalous left pulmonary artery has previously been diagnosed with angiography or by direct visualization during surgery. We present the first cases of noninvasive diagnosis of this anomaly with the use of echocardiography and magnetic resonance imaging. The complementary roles of these two modalities in detecting the anomaly and defining the spatial relationship of the anomalous pulmonary artery to the trachea are emphasized.

Pediatric cardiac retransplantation: intermediate-term results.

BACKGROUND: Cardiac retransplantation (re-CTx) in children is a controversial therapy, yet it remains the best treatment option to recipients with failing grafts. Our objective was to determine the incidence of re-CTx in a large pediatric population of recipients and evaluate the outcome of such therapy. METHODS: Between November 1985 and November 1999, 347 children underwent cardiac transplantation at the Loma Linda University Medical Center. Of these, 32 children were listed for re-CTx. Ten patients died while waiting, and 22 recipients underwent re-CTx. Median age at re-CTx was 7.1 years (range, 52 days to 20.1 years). RESULTS: Indications for re-CTx were allograft vasculopathy (n = 16), primary graft failure (n = 5), and acute rejection (n = 1). Two patients with primary graft failure underwent retransplantation within 24 hours of the first transplantation procedure while on extracorporeal membrane oxygenation support. Median time interval to re-CTx for the others was 7.2 years (range, 32 days to 9.4 years). Operative mortality for all cardiac re-CTx procedures was 13.6%. Causes of hospital mortality were pulmonary hypertension with graft failure (n = 2) and multiorgan failure (n = 1). Median hospital stay after re-CTx was 14.1 days (range, 6 to 45 days). There was one late death from severe rejection. Actuarial survival at 3 years for re-CTx was 81.9% +/- 8.9% compared with 77.3% +/- 2.6% for primary cardiac transplantation recipients (p = 0.70). CONCLUSIONS: Elective re-CTx can be performed with acceptable mortality. Although the number of patients undergoing retransplantation in this report is small and their long-term outcome is unknown, the intermediate-term survival after re-CTx is similar to that of children undergoing primary cardiac transplantation.

Late rejection is a predictor of transplant coronary artery disease in children.

OBJECTIVE: The study objectives were to determine posttransplant coronary artery disease (TxCAD) incidence, predisposing factors and optimal timing for retransplantation (re-Tx) in pediatric heart transplantation (Tx) recipients. BACKGROUND: The TxCAD limits long-term survival following heart Tx, with re-Tx being the primary therapy. Information on risk factors and timing of listing for re-Tx is limited in children. METHODS: The records of children who survived >1 year post-Tx at Loma Linda University were reviewed. Nonimmune and immune risk factors were analyzed. RESULTS: TxCAD was documented in 24 of 210 children. Freedom from TxCAD was 92 +/- 2% and 75 +/- 5% at 5 and 10 years' post-Tx, respectively. The TxCAD diagnosis was established at autopsy in 10 asymptomatic patients who died suddenly within nine months following the most recent negative angiograms. The remaining 14 children had angiographic diagnoses of TxCAD and had symptoms and/or graft dysfunction (n = 10) or positive stress studies (n = 4). Three of 14 died within three months after the diagnosis was made. Eleven patients underwent re-Tx within seven months of diagnosis; nine survived. Univariate and multivariate analyses showed that only late rejection (>1 year posttransplant) frequency (p = 0.025) and severity (hemodynamically compromising) (p < 0.01) were independent predictors of TxCAD development. Freedom from TxCAD after severe late rejection was 78 +/- 8% one year postevent and 55 +/- 10% by two years. CONCLUSIONS: Late rejection is an independent predictor of TxCAD. Patients suffering severe late rejection develop angiographically apparent TxCAD rapidly and must be monitored aggressively. Both TxCAD mortality and morbidity occur early; therefore, we recommend immediate listing for re-Tx upon diagnosis.

Outcome of infants with hypoplastic left heart syndrome who undergo atrial septostomy before heart transplantation.

This study evaluated the procedural and long-term outcome of infants who underwent atrial septostomy while awaiting transplant. The results suggest that septostomy improved outcome in these patients although infants needing a transseptal perforation were at higher risk.

The medium-term findings in coronary arteries by intravascular ultrasound in infants and children after heart transplantation.

OBJECTIVES: The study purposes were to determine 1) whether intravascular ultrasound (IVUS) was more sensitive than angiography for the detection of post-transplant coronary artery disease (PTCAD) in pediatric patients; and 2) whether those transplanted as neonates reacted differently than older patients. BACKGROUND: Experience with IVUS for the diagnosis of PTCAD in children is limited. METHODS: Patients were divided into two groups: those transplanted as neonates (early group) and those transplanted in infancy or childhood (late group). Morphometric analysis was performed, including maximal intimal thickness (MIT) and intimal index (II). Stanford classification was used to grade lesion severity. Acute rejection and cytomegalovirus (CMV) status were correlated with MIT and II. RESULTS: Thirty children were studied (early group, n = 13; late group, n = 17). All segments studied were angiographically normal. Mean MIT and mean II were significantly greater in the late group (0.26 +/- 0.14 vs. 0.13 +/- 0.04 mm, p < 0.001 and 0.11 +/- 0.07 vs. 0.07 +/- 0.03 mm, p = 0.04, respectively). There was a significant correlation between MIT and II in those who had acute rejection in the late group. Patients in the late group who were CMV-positive had a significantly higher MIT compared with those in the late group with negative serology (p = 0.04). CONCLUSIONS: Intravascular ultrasound was more sensitive than angiography in detecting PTCAD after pediatric heart transplantation. There is a possible role for acute rejection and CMV in the development of PTCAD.

Successful myocardial volume reduction in a 9-month-old infant.

Left ventricular reduction has shown promise as a treatment for end-stage dilated cardiomyopathy, with restoration of the physiologic ratio between myocardial mass and left ventricular diameter. We present a case of successful partial left ventriculectomy utilizing both lateral and septal wall excision as treatment of dilated cardiomyopathy in a 9-month-old patient.

Posttransplant recoarctation of the aorta: a twelve year experience.

OBJECTIVES: This study was undertaken to investigate the incidence of posttransplant recoarctation of the aorta, delineate the mode of presentation, identify risk factors that predict recoarctation and examine the results of intervention for posttransplant recoarctation. BACKGROUND: Patients with aortic arch hypoplasia require extended arch reconstruction at transplant, with an inherent possibility of subsequent recoarctation of the aorta. METHODS: This was a retrospective review of all children (age <18 years) who underwent cardiac transplantation over a 10-year period. Collected data included pretransplant diagnosis, details of the transplant procedure and posttransplant data including development of recoarctation of the aorta, interventions for recoarctation and the most recent follow-up assessment of the aortic arch. RESULTS: Two hundred eighty-eight transplants were performed on 279 children (follow-up = 1,075 patient-years; range 0 to 133 months, median 43.7). Thirty-two of 152 patients (21%) who underwent extended aortic arch reconstruction subsequently developed recoarctation. All but one patient developed recoarctation within 2 years after transplant; 87% were hypertensive at presentation. Of 30 patients who underwent intervention for recoarctation (balloon angioplasty [n = 26] and surgical repair of recoarctation [n = 4]), 26 (87%) have remained recurrence-free (follow-up = 133 patient-years; range 8 to 106 months, median 47). CONCLUSIONS: The high frequency of recoarctation after cardiac transplantation with extended aortic arch reconstruction mandates serial echocardiographic evaluation of the aortic arch. Patients typically present with systemic hypertension within the first two years after transplantation. Balloon angioplasty is a safe, effective and durable method of treatment.

Dobutamine stress echocardiography for assessing coronary artery disease after transplantation in children.

OBJECTIVES: The purpose of this study was to determine the feasibility, safety and diagnostic accuracy of dobutamine stress echocardiography (DSE) for evaluating posttransplant coronary artery disease (TxCAD) in children, and to determine the frequency of selected cardiac events after normal or abnormal DSE. BACKGROUND: Posttransplant coronary artery disease is the most common cause of graft loss (late death or retransplantation) after cardiac transplantation (CTx) in children. Coronary angiography, routinely performed to screen for TxCAD, is an invasive procedure with limited sensitivity. The efficacy of DSE for detecting atherosclerotic coronary artery disease is established, but is unknown in children after CTx. METHODS: Of the 78 children (median age 5.7 years, range 3 to 18) entered into the study, 72 (92%) underwent diagnostic DSE by means of a standard protocol, 4.6 +/- 1.9 years after CTx. The results of coronary angiography performed in 70 patients were compared with DSE findings. After DSE, subjects were monitored for TxCAD-related cardiac events, including death, retransplantation and new angiographic diagnosis of TxCAD. RESULTS: No major complications occurred. Minor complications, most often hypertension, occurred in 11% of the 72 subjects. The sensitivity and specificity of DSE were 72% and 80%, respectively, when compared with coronary angiography. At follow-up (21 +/- 8 months), TxCAD-related cardiac events occurred in 2 of 50 children (4%) with negative DSE, versus 6 of 22 children (27%) with positive DSE (p < 0.01). CONCLUSIONS: DSE is a feasible, safe and accurate screening method for TxCAD in children. Positive DSE identifies patients at increased risk of TxCAD-related cardiac events. Negative DSE predicts short-term freedom from such events.

Heart transplantation in infants and children with situs inversus.

BACKGROUND: Recipient situs inversus has always represented a technical challenge during heart transplantation. OBJECTIVE: A simplified operative strategy for heart transplantation in a recipient with atrial situs inversus is described. METHODS: Fifteen pediatric recipients with situs inversus accompanying other complex congenital heart disease or dilated cardiomyopathy having "orthotopic" heart allotransplantation in one center, between 1985 and 1997, were reviewed retrospectively. A nearly uniform, simplified technical approach to transplantation was used and is described. RESULTS: Fourteen of these recipients with complex malformations survived the transplantation. Morbidity relating to surgical technique has been limited to partial (n = 2) or complete (n = 1) late obstruction of superior vena caval drainage; each case was managed successfully by interventional cardiologic techniques. Actuarial survival after transplantation compares favorably with that among 290 infants and children with atrial situs solitus who underwent heart transplantation. CONCLUSIONS: Systemic atrial malposition, including situs inversus, does not limit successful heart transplantation by the simplified method described.

Is optimal angiotensin-converting enzyme inhibitor dosing neglected in elderly patients with heart failure?

BACKGROUND: The benefit of angiotensin-converting enzyme (ACE) inhibitors on mortality in heart failure has been proved in randomized controlled trials. METHODS: We prospectively evaluated the prescribing of ACE inhibitors and the prescribing of target ACE inhibitor doses in 43 ambulatory patients with heart failure to identify differences in ACE inhibitor utilization among elderly and nonelderly patients. The prescribed ACE inhibitor dose and other variables were assessed by direct patient interview and information contained in the medical record. Telephone calls were conducted at 3 months to identify the occurrence of clinical events. RESULTS: Fewer elderly patients were prescribed target ACE inhibitor doses compared with nonelderly patients (21.4% vs 68.8%; p = 0.0136). Elderly patients were more likely to experience an event than nonelderly patients (11 vs 4; p = 0.0074). Elderly patients not receiving target ACE inhibitor doses demonstrated a trend toward more events than elderly patients who were at target doses. CONCLUSION: The data suggest that this group of elderly patients with heart failure who received lower ACE inhibitor doses appeared to be at higher risk for clinical events.

Ability of heart rate variability to predict prognosis in patients with advanced congestive heart failure.

We analyzed heart rate variability from normal RR intervals in patients with advanced congestive heart failure. Although most patients had decreased HRV, patients with a life-threatening cardiac event or death (n = 8) within 18 months had significantly lower heart rate variability than those who did not (n = 18), which may have value in determining prognosis in this population.

Valve perforation and balloon pulmonary valvuloplasty in an infant with tetralogy of Fallot and pulmonary atresia.

We report an infant who had tetralogy of Fallot, hypoplastic pulmonary arteries, and membranous pulmonary atresia who underwent successful perforation of the atretic valve and subsequent balloon pulmonary valvuloplasty. Because of the inability to access the pulmonary arteries via a patent ductus arteriosus, two-dimensional echocardiography was used to confirm wire position prior to perforation. The branch pulmonary arteries initially measured 1.5 mm in diameter and enlarged to 2.8 mm immediately after valvuloplasty. Four months postprocedure, the patient underwent a successful repeat balloon pulmonary valvuloplasty. The pulmonary arteries had grown to approximately 6 mm in diameter. Although it is a rare occurrence, patients with tetralogy of Fallot and membranous pulmonary atresia can be dilated with successful growth of the pulmonary arteries.

Transplantation as a primary treatment for hypoplastic left heart syndrome: intermediate-term results.

BACKGROUND: Hypoplastic left heart syndrome is a lethal malformation. For the last 10 years, orthotopic cardiac transplantation has been our preferred treatment for infants with hypoplastic left heart syndrome. METHODS: One hundred seventy-six infants with hypoplastic left heart syndrome were entered into a cardiac transplant protocol between November 1985 and November 1995. Interventional procedures to stent the ductus arteriosus or enlarge the interatrial communication were performed in 8 and 35 patients, respectively. Thirty-four patients (19%) died during the waiting period, and 142 infants underwent cardiac transplantation. Age at cardiac transplantation ranged from 1.5 hours to 6 months (median, 29 days). The majority of grafts were oversized, and the median graft ischemic time was 273 minutes (range, 60 to 576 minutes). The implantation procedure used a period of hypothermic circulatory arrest ranging from 23 to 110 minutes (median, 53 minutes). Repair of other significant defects included interrupted aortic arch and total or partial anomalous pulmonary venous connection. RESULTS: There were 13 early and 22 late deaths. Patient actuarial survival at 1 month and at 1, 5 and 7 years was 91%, 84%, 76%, and 70% respectively. Half of the late deaths were due to rejection. Severe graft vasculopathy was confirmed in 8 patients. Retransplantation was performed in 5 patients for graft vasculopathy 4 and rejection 1. Lymphoblastic leukemia developed in 1 patient 3 years after cardiac transplantation. CONCLUSIONS: Cardiac transplantation can be performed in infants with hypoplastic left heart syndrome with good operative and intermediate-term results. Improved survival can be achieved with increased donor availability, better management of rejection, and control of graft vasculopathy.

Cardiac pacemakers in pediatric heart transplant recipients: incidence, indications, and associated factors. Pediatric Heart Transplant Group-Loma Linda.

This study was undertaken to assess the incidence, indications, and predisposing factors for pacemaker placement in a pediatric heart transplant population. From November 1985 to May 1994, 246 pediatric patients have undergone cardiac transplantation at Loma Linda University Medical Center. Seven (2.8%) have received pacemaker placement with an 8-50 month follow-up period. Median age at transplant was 462 days (0 days to 2.5 years). The median time to pacemaker placement was 190 days (18-1,672 days) after transplantation. Indications were sick sinus syndrome (SSS) in 5 and heart block in 2 patients (1 during acute rejection). Three patients with SSS underwent electrophysiology studies (EPS); 1 was normal and 2 showed sinus node dysfunction. The mode of pacing was VVIR in 6 patients and VVI in 1 patient. All 6 survivors are doing well and 5 patients' pacemakers still provide support. These 7 patients were compared with 185 pediatric patients (0 days to 12-years-old) transplanted during 1985 through 1993 who survived at least 6 months after transplantation. There was no correlation between the receipt of a pacemaker and graft cold ischemic time, rejection history, donor age, or recipient age at transplantation. The 5 patients with SSS had significantly lower average heart rates in the first month after transplantation (108 +/- 16 vs 130 +/- 12; P = 0.0002). The need for permanent pacemakers in this population is uncommon. Pacemakers, however, can be safely performed when necessary with excellent clinical results.

Pretransplant risk factors and causes of death or graft loss after heart transplantation during early infancy. Pediatric Heart Transplant Team, Loma Linda.

BACKGROUND: This study was performed to report causes of death or graft loss and to identify possible pretransplant risk factors for death or graft loss in infants after heart transplantation. METHODS AND RESULTS: Pretransplant risk factors were compared for 153 infants registered for heart transplantation within 90 days of life and transplanted from November 1985 to June 1994. Factors assessed were diagnosis, age at transplantation, race, weight, blood type, sex, donor/recipient blood type match, sex match, weight ratio, fetal registration, locale of pretransplant waiting period, mechanical ventilation, ischemic time, and the need for atrial septostomy or septectomy pretransplantation. No factor was associated with death or graft loss at 1 month or 1 year. Causes of death or graft loss were determined using clinical course and pathology data when available. Death or grafts lost at 1 month, 1 year, and > 1 year were 14, 13, and 15, respectively. Causes of death or graft loss expressed as a percent (at 1 month, 1 year, and > 1 year, respectively) were acute rejection (14, 23, 27), chronic rejection and posttransplant coronary disease (0, 8, 47), infectious causes (21, 15, 13), early graft failure (21, 0, 0), technical issues (21, 23, 0), chronic graft dysfunction (0, 15, 0), and miscellaneous (21, 15, 13). The graft loss rate at 1 year was significantly correlated (linear regression, r2 = .66; P < .05) with the year of transplantation. Actuarial survival in this population was 91% at 1 month, 81% at 1 year, and 73% at 3 years. CONCLUSIONS: Heart transplantation in the young infant can be performed with acceptable short-term and midterm results. Causes of death or graft loss and survival are similar to adult data. No pretransplant risk factors were identified. The experience level of the transplant team members affects survival. The diagnosis and management of rejection remain a major challenge.

Orthotopic transplantation for total anomalous pulmonary venous connection associated with complex congenital heart disease.

BACKGROUND: When total anomalous pulmonary venous connection is associated with other complex cardiac malformations, early and late postsurgical morbidity and mortality are excessive. METHODS: In an attempt to modify this outcome, twelve children (4 days to 6.8 years of age) with total anomalous pulmonary venous connection and various congenital cardiac defects were treated with orthotopic heart transplantation. Associated cardiac diagnoses included the following: hypoplastic left heart syndrome (n = 2), unbalanced atrioventricular canal with pulmonary atresia (n = 2), and single ventricle with severe pulmonary stenosis (n = 3) or atresia (n = 5). Two patients had situs inversus, and two had dextrocardia with situs ambiguous. Eight patients had asplenia and one had polysplenia. Palliative pretransplantation procedures in five patients included the following: systemic to pulmonary artery shunt (n = 5), atrioventricular valve annuloplasty (n = 1) and classical Glenn shunt (n = 1). The donor left atrium was anastomosed directly to a common pulmonary venous pool in nine patients; whereas three children required complex reconstruction to baffle the pulmonary venous flow to the donor left atrium. RESULTS: There was one operative death related to an oversized heart and vena caval thrombosis. Follow-up ranged from 16 months to 4.5 years (average 3 years). In two patients (18%) pulmonary venous obstruction developed 3 and 4 months after transplantation. Reoperation to relieve the obstruction was successful in one patient. The second patient underwent three such reoperations and died of sepsis 10 months after orthotopic heart transplantation. CONCLUSION: Orthotopic transplantation is a viable option for children with complex total anomalous pulmonary venous connection that precludes a biventricular repair. Transplantation may improve the dismal prognosis of those children, but it does not eliminate the potential for late pulmonary venous obstruction.

Refined crystal structure of lysozyme from the rainbow trout (Oncorhynchus mykiss).

Lysozymes (E.C. 3.2.1.17) are well characterized ubiquitous enzymes that have an antibacterial effect. The lysozymes from rainbow trout (RBTL) (Oncorhynchus mykiss) could be particularly interesting in aquaculture since they show higher activity than egg-white lysozyme and lysozymes from other fish species against a variety of pathogenic bacteria. Two lysozymes, I and II, differing only in a single amino acid, were purified from the kidney of rainbow trout and shown to belong to the c-type class of lysozymes. The type II form was shown to be much more potent against a variety of bacteria than the type I enzyme. We have grown crystals from a mixture containing about 80% type I and 20% type II lysozyme from rainbow trout, and solved the X-ray crystal structure. The crystals are trigonal with a = 76.68, c = 54.46 A and space group P3(1)21. The phase problem was solved by the molecular-replacement method, and the structure was refined to an R-factor of 17.4% using data to 1.8 A resolution. The crystal structure shows that the three-dimensional structure of rainbow trout lysozyme is very similar to the previously solved structures of other c-type lysozymes. The single polypeptide of 129 amino acids is folded into two domains separated by a deep cleft which contains the active site. Secondary-structure elements, four alpha-helices and a three-stranded beta-sheet, are located in the same sequential positions as in the hen, turkey and human enzymes. The beta-sheet is found to be common for structures of both c- and g-type lysozymes. We suggest that differences in antibiotic activity of the two forms of RBTL are probably due to small differences in the hydophobicity of a small surface region.