A prospective analysis of the incidence and risk factors associated with junctional ectopic tachycardia following surgery for congenital heart disease

This study was designed to evaluate the incidence and risk factors associated with the occurrence of junctional ectopic tachycardia (JET) in patients after congenital heart surgery. We prospectively analyzed cardiac rhythm status in 336 consecutive patients undergoing surgery for congenital heart disease at our institution during a 1-year period. The incidence of JET was 8% (27/336). Repairs with the highest incidence of JET were arterial switch operation (3/13, 23%), atrioventricular (AV) canal repair (4/19, 21%), and Norwood repair (2/10, 20%). Compared to patients with no arrhythmias, patients with JET were more likely to be younger (2.75 +/- 2.44 vs 5.38 +/- 7.25 years, p < 0.01), have had longer cardiopulmonary bypass times (126 +/- 50 vs 85 +/- 73, p < 0.01), and have a higher inotrope score (6.26 +/- 7.55 vs 2.41 +/- 8.11, p < 0.01). By multivariate analysis, ischemic time was the only factor associated with JET [odds ratio, 1.01 (confidence interval, 1.005-1.02); p = 0.0014). The presence of JET did not correlate with electrolyte abnormalities. JET is not necessarily related to surgery near the His bundle or hypomagnesemia. Longer ischemic time is the best predictor of JET. Patients undergoing arterial switch operation, AV canal repair, and Norwood repair are at highest risk of postoperative JET and should be considered for prophylactic therapy.

Chronic outpatient sildenafil therapy for pulmonary hypertension in a child after cardiac surgery

We report the case of a 14-month-old male with d-transposition of the great arteries, ventricular septal defect, and pulmonary hypertension successfully treated with long-term sildenafil following cardiac surgery. To our knowledge, this is the first published report of long-term sildenafil treatment in a child after corrective cardiac surgery.

Modified Fontan operation in patients with anomalies of systemic and pulmonary venous connection

The presence of anomalies of the systemic and pulmonary venous connection associated with single ventricle anomalies has been considered a contraindication for the Fontan operation (FO). The aim of this study is to outline the technical considerations associated with the presence of anomalies of systemic and/or pulmonary venous connections and to identify the risk factors for mortality in this group of patients undergoing the modified FO. Between 1989 and 2004, 63 patients (median age, 3.2 years) with anomalous systemic or pulmonary venous connection underwent a Fontan procedure at our institution. Nine patients had a combination of anomalous systemic and pulmonary venous connection, 49 patients had anomalous drainage only from the systemic circulation, and 5 patients had isolated anomalies of pulmonary venous return. Visceral heterotaxy syndrome was diagnosed in 25 patients. Previous palliative operations had been performed in 51 patients (81%). There was 1 early death, and 2 patients required take down of Fontan procedures. Two patients required reoperation for revision of the atrial baffle. At a mean follow-up of 4.6 +/- 3.4 years, there have been 5 late deaths (8%) and 45 patients (71%) have undergone Fontan completion. Actuarial survival was 92% at 1 year and 91% at 5 and 10 years-not significantly different from the overall survival of the Fontan patients. We conclude that the modified FO can be successfully performed in patients with anomalous systemic or pulmonary venous connections, including those with visceral heterotaxy syndrome, with morbidity and mortality rates that do not differ significantly from those achieved in all patients with normal connections.

Repair of tetralogy of Fallot with anomalous coronary arteries coursing across the obstructed right ventricular outflow tract

Anomalous coronary artery (ACA) anatomy occurs in 2-9% of patients with tetralogy of Fallot (TOF), in which the left anterior descending coronary artery (LAD) originates from the right coronary artery (RCA) crossing the right ventricular outflow tract. The purpose of this study was to review our results of repair for TOF with ACA. Between 1978 and 2001, 43 ACA patients (mean age, 4.8 years; range, 5 months-41 years) underwent repair for TC. The ACA anatomy was classified as the single LAD from the RCA (n = 20), a significant conal branch (dual LAD) from the RCA (n = 13), paired anterior descending arteries originating from the left and right coronary arteries (n = 7), and single RCA from the LAD (n = 3). In cases in which the anomalous LAD crossed the obstructed infundibulum, thinning or coring of the endocardium was done. Patch infundibuloplasty was performed in 39 patients, with 10 needing separate RV and pulmonary artery patches, and the pulmonary valve was preserved. Nine patients had the addition of a monocusp to a transannular incision. Two patients had a main pulmonary arterioplasty alone. There was one early (2.3%) and no late deaths. Mean early and late postoperative gradients were 21.5 +/- 10.5 mmHg (4 patients had > or =30 mmHg) and 27.1 +/- 13.7 mmHg (5 patients had >30 mmHg; p = 0.12), respectively. There were four reoperations during a mean follow-up of 4.8 years (range, 6 months to 18 years). Actuarial freedom from reoperation was 90% at 5, 10, and 15 years. At the latest follow-up, all patients were in NYHA functional class I. TOF repair for an ACA can be performed without disturbing the native coronary anatomy and without the use of conduits in most cases. Outcomes are similar to those of other patients with TOF. The presence of ACA does not impose increased risk after this surgical strategy.

Resolution of acquired pulmonary arteriovenous malformations in a patient with total anomalous systemic venous return

An 11-year-old male with total anomalous systemic venous return had surgical repair except for the hepatic venous return, which drained to the left atrium. He developed progressive cyanosis and fatigue and was diagnosed with large pulmonary arteriovenous malformations (PAVMs) during cardiac catheterization with the use of bubble contrast echocardiography. After surgical redirection of hepatic venous flow to the right heart and pulmonary arterial system, resolution of these PAVMs was demonstrated clinically and by contrast echocardiography. This unique case report demonstrates the development of PAVMs with exclusion of hepatic venous return through the pulmonary vascular bed while pulsatile pulmonary blood flow remains intact. It reinforces the likelihood of the absence of an as yet unidentified hepatic vasoactive substance as the source for development of PAVMs.

COPD may increase the incidence of refractory supraventricular arrhythmias following pulmonary resection for non-small cell lung cancer

PURPOSE

This study investigated the association of COPD and postoperative cardiac arrhythmias, specifically supraventricular tachycardia (SVT), as well as mortality in patients undergoing pulmonary resection for non-small cell lung cancer (NSCLC).

METHODS

A retrospective chart review of 244 patients who had undergone lung resection for NSCLC at Indiana University Hospital between 1992 and 1997 was undertaken. COPD, which was defined as an FEV(1) of < or = 70% predicted and an FEV(1)/FVC ratio of < or = 70% based on the results of a preoperative pulmonary function test (PFT), was diagnosed in 78 of the 244 patients (COPD group). In the remaining 166 patients, the results of preoperative PFTs did not meet these criteria (non-COPD group). Both groups were otherwise well-matched with respect to multiple variables, including age, comorbid conditions, extent of pulmonary resection, and final pathologic stage. The incidence of cardiac arrhythmias and operative mortality were compared between the two groups using univariate and multivariate analysis.

RESULTS

Seventy-six patients (31.9%) experienced new onsets of postoperative SVT, with 58 of these patients (76.3%) demonstrating atrial fibrillation. The COPD group had a 58.7% incidence of SVT (n = 44) compared to a 27.0% incidence (n = 44) in the non-COPD group (p < 0.0 0 1). Moreover, following initial digoxin therapy, the COPD group required more second-line antiarrhythmic therapy than did the non-COPD group (66.7% vs 37.8%, respectively; p = 0.0 03). Overall, there were 16 operative deaths (6.6%), and the mortality rate was significantly higher in the COPD group (14.1%) than in the non-COPD group (3.0%; p = 0.0 04). Patients who developed SVT had a significantly longer hospital course than did patients who did not (p < 0.0001). Thirteen of the 16 patients who died experienced SVT; however, SVT was not an independent risk factor for death. Finally, of the 19 variables evaluated, major resection (ie, pneumonectomy and bilobectomy) and COPD were identified as independent risk factors for the development of cardiac arrhythmias (p = 0.0 033 and p = 0.0 009, respectively).

CONCLUSION

Patients with COPD, as defined by the results of preoperative PFTs, are at significantly higher risk for SVT, and in particular SVT refractory to digoxin, following pulmonary resection for NSCLC. Although SVT was not an independent risk factor for death, a significantly longer hospitalization was observed.

Effects of marine sponge extracts on mitogen-activated protein kinase (MAPK/ERK(1,2)) activity in SW-13 human adrenal carcinoma cells

Some species of marine sponge have been shown to produce metabolites with endocrine-altering and cell growth regulatory properties. Since cell division and differentiation are controlled, in part, by the mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK/ERK) cascade, we tested extracts (1.0mg/ml) from six shallow water marine species obtained in the Florida Keys for effects on MAPK/ERK(l,2) (sub-variant of EC 2.7.1.37) activity in incubations with SW-13 human adrenal carcinoma cells in culture. In these short-term incubations, extracts from two species, the purple bleeding sponge (Iotrochota birotulata) and the West Indian bath sponge (Spongia barbara), significantly inhibited MAPK/ERK(1,2) activity (to 51 and 44% of control levels, respectively) without altering cell survival. Western blots for phosphorylated and total ERK showed that ERK(2) predominated over ERK(1) by a factor of about 4:1 and that the phosphorylated forms of these isozymes were strongly suppressed by active extracts from both sponges. Another species, the green sponge (Haliclona veridis), whose extract has been shown previously to activate guanylate cyclase and to inhibit adenylate cyclase in a variety of mammalian tissues, was found not to affect MAPK/ERK(1,2) in human adrenal carcinoma cultures but did lyse and kill most of these cultured cells. Extracts from the sheepswool sponge (Hippospongia lachne) and the bleeding sponge (Oligoceras hemorrhages) did not significantly affect either MAPK/ERK(1,2) activity or the survival of attached cells. An extract from the fire sponge (Tedania ignis) did not alter MAPK/ERK(1,2) activity but did modestly decrease cell viability. These studies document for the first time species-specifc effects of marine sponge extracts on the MAPK/ERK(1,2) cascade and on the growth and survival of human adrenal carcinoma cells in culture.

Multiple snoRNA gene clusters from Arabidopsis

Small nucleolar RNAs (snoRNAs) are involved in precursor ribosomal RNA (pre-rRNA) processing and rRNA base modification (2'-O-ribose methylation and pseudouridylation). In all eukaryotes, certain snoRNAs (e.g., U3) are transcribed from classical promoters. In vertebrates, the majority are encoded in introns of protein-coding genes, and are released by exonucleolytic cleavage of linearized intron lariats. In contrast, in maize and yeast, nonintronic snoRNA gene clusters are transcribed as polycistronic pre-snoRNA transcripts from which individual snoRNAs are processed. In this article, 43 clusters of snoRNA genes, an intronic snoRNA, and 10 single genes have been identified by cloning and by computer searches, giving a total of 136 snoRNA gene copies of 71 different snoRNA genes. Of these, 31 represent snoRNA genes novel to plants. A cluster of four U14 snoRNA genes and two clusters containing five different snoRNA genes (U31, snoR4, U33, U51, and snoR5) from Arabidopsis have been isolated and characterized. Of these genes, snoR4 is a novel box C/D snoRNA that has the potential to base pair with the 3' end of 5.8S rRNA and snoR5 is a box H/ACA snoRNA gene. In addition, 42 putative sites of 2'-O-ribose methylation in plant 5.8S, 18S, and 25S rRNAs have been mapped by primer extension analysis, including eight sites novel to plant rRNAs. The results clearly show that, in plants, the most common gene organization is polycistronic and that over a third of predicted and mapped methylation sites are novel to plant rRNAs. The variation in this organization among gene clusters highlights mechanisms of snoRNA evolution.

Surgical results in patients with double outlet right ventricle: a 20-year experience

BACKGROUND

The objective of this study was to review our surgical strategy in children with double outlet right ventricle and to assess risk factors for early and late mortality and reoperation.

METHODS

Patients (n = 124; June 1980 to January 2000; age range, 7 days to 16 years; mean, 2.8 years) who underwent repair of double outlet right ventricle. The patients were divided into three groups. Group 1 (n = 47) had noncomplex patients with atrioventricular concordance, a single ventricular septal defect, balanced ventricles, no straddling atrioventricular valves, and no major pulmonary artery anomalies. Group 2 (n = 39) included patients with double outlet right ventricle and a subpulmonary ventricular septal defect (Taussig-Bing). Group 3 (n = 38) had patients with complex anomalies including straddling atrioventricular valves, atrioventricular septal defects or a hypoplastic valve or ventricle, or a combination of atrioventricular septal defects and hypoplastic valve or ventricle.

RESULTS

Four types of definitive repairs were performed: (1) intraventricular tunnel repair with a baffle from the left ventricle to the aorta (n = 53); (2) use of a valved or nonvalved conduit (n = 20); (3) arterial switch operation with a patch committing the left ventricle to the neo-aorta (n = 16); and (4) cavopulmonary shunt and Fontan procedures (n = 33). Two patients with late postoperative cardiomyopathy had heart transplantation. Potential risk factors included location of the largest ventricular septal defect, presence of additional ventricular septal defects, ventricular outflow obstruction or hypoplasia, or both ventricular outflow obstruction and hypoplasia, previous palliation, and type of definitive operation. There were six early deaths (4.8%) and four late deaths (3.2%), and two heart transplants (1.6%). Overall 15-year survival was 95.8%, 89.7%, and 89.5% for groups 1, 2, and 3, respectively (p = 0.08). Thirteen patients (11.4%) have required 15 reoperations. Mean follow-up for survivors was 76.6 +/- 52.8 months. Up-to-date follow-ups are available on 114 surviving patients. Ninety-five of these patients (83.3%) were in New York Heart Association class I, and the remaining 19 patients (16.7%) were in New York Heart Association class II. Freedom from reoperation was 87%, 72%, and 100% at 15 years for groups 1, 2, and 3, respectively (p = 0.11).

CONCLUSIONS

Survival was high for all patients with double outlet right ventricle undergoing intraventricular tunnel repair, arterial switch operation, and repair with a conduit or a modified Fontan procedure. Careful attention to preoperative anatomy dictates the best surgical approach and will enhance outcomes.

Clinical outcomes and indicators of normalization of left ventricular dimensions after Ross procedure in children

Between 1993 and 2000, 50 patients (age range, 1 month to 18 years) who had left ventricular outflow tract (LVOT) disease and had undergone a Ross procedure were assessed using echocardiography. Aortic annulus size, valvular gradient, valve insufficiency, LV dimensions at end-systole and end-diastole, LV interventricular septal and posterior wall thickness, and LV mass index (LVMI) were measured. There was 1 early and 2 late deaths, and 5 reoperations. Aortic annulus size increased and degree of aortic insufficiency (AI) decreased, as did LV internal dimensions and LVMI. Peak pressure gradients declined from 73 +/- 18 mm Hg to 7 +/- 7 mm Hg, and LVMI regressed (167 +/- 6 g/m(2) v 108 +/- 6 g/m(2), P <.001) after 3 years. The degree of AI ranged from none to mild, and no patient has LVOT stenosis. Regression of LV dilatation and hypertrophy, good autograft valve function and durability, and a high survival rate suggest that the Ross procedure is preferred for most children who require aortic valve replacement.

Truncus arteriosus repair: outcomes, risk factors, reoperation and management

OBJECTIVES

Truncus arteriosus (TA) continues to be associated with significant morbidity and mortality, but there have been clinically significant improvements with early repair.

METHODS

Sixty patients underwent physiological correction of TA between November 1978 and January 2000. The average age was 76 days (range, 3 days--20 months). Associated cardiac anomalies were frequently encountered, the most common being severe truncal valve regurgitation (n=7), interrupted aortic arch (n=6), coronary artery anomalies (n=6), non-confluent pulmonary arteries (n=4), and total anomalous pulmonary venous return (n=1). Truncal valve replacement was performed initially or subsequently in seven patients with severe regurgitation (mechanical prostheses in six patients and a cryopreserved aortic homograft in one patient). Right ventricle--pulmonary artery continuity was established with an aortic (n=16) or pulmonary homograft (n=32) in 48 patients, a Dacron polyester porcine valved conduit in five, a non-valved polytetrafluoroethylene (PTFE) tube in three, direct anastomosis to the right ventricle with anterior patch arterioplasty in three, and a bovine jugular venous valve conduit in one patient.

RESULTS

There were ten hospital deaths (17%; 70% confidence limit, 7--25%). Multivariate and univariate analyses demonstrated a relationship between hospital mortality and associated cardiac anomalies. In the 43 patients without these associated cardiac anomalies, the early survival was 91% (group I). In the 17 patients with one or more of these risk factors, the survival was 71% (group II, P=0.002). There was one late death. Twenty-three patients (46%) required reoperation for right ventricular outflow tract (RVOT) obstruction at a mean follow-up time of 59.1 months. In 23 patients, the RVOT reconstruction was performed with a PTFE monocusp, and six patients had of a variety of replacement conduits inserted. Postoperatively, there were 34 (68%) patients in New York Heart Association functional class I and 16 (32%) in class II. Twenty-eight surviving patients are reported as doing well without any medication. The freedom of reoperation in the 39 hospital survivors (group I) without risk factors was 64% at 7 years; and 36% at 10 years in the 11 patients (group II) surviving with risk factors.

CONCLUSIONS

Associated cardiac anomalies were risk factors for death after the repair of TA. In the absence of these associated lesions, TA can be repaired with an excellent surgical outcome in the neonatal and early infancy period.

Characterization of RNase P holoenzymes from Methanococcus jannaschii and Methanothermobacter thermoautotrophicus

The partial purification and basic biochemical characterization of the RNase P holoenzymes of two species of methanogenic Archaea, Methanothermobacter thermoautotrophicus (previously Methanobacterium thermoautotrophicum strain deltaH) and Methanococcus jannaschii, are described. The properties of these enzymes, particularly buoyant density in Cs2SO4 and recent information about the subunit composition of the archaeal enzymes, suggest that RNase P enzymes in Archaea are much more alike than earlier studies in Sulfolobus acidocaldarius and Haloferax volcanii suggested.

Arterial switch operation: factors impacting survival in the current era

BACKGROUND

The arterial switch procedure has become the preferred procedure for the transposition of the great arteries (TGA) and Taussig-Bing anomaly. This analysis is intended to identify potential factors affecting survival in the current era.

METHODS

From 1986 to 1999, 201 consecutive patients underwent an arterial switch operation for TGA or Taussig-Bing anomaly. Multivariate analysis of perioperative variables was performed for operative morbidity/ mortality. Patients were separated into two groups. Phase 1 (n = 29) included patients before mid-1989 who underwent an open coronary reimplantation technique. Phase 2 (n = 172) included the patients undergoing a technique of reimplanting coronary buttons after neoaortic reconstruction.

RESULTS

The patient population included TGA with intact ventricular septum (58.7%, 118 of 201), with ventricular septal defect (31.3%, 61 of 201), and Taussig-Bing anomaly (10.0%, 22 of 201). Overall, early mortality was 9.5% (19 of 201) and there were five late deaths (2.7%). One-month, 1-year, and 5-year actuarial survival rates were 90.4%, 87.9%, and 87.9%, respectively. Reoperation rate for late pulmonary stenosis was 2.7% (5 of 182). The freedom from reoperation at 3 and 5 years was 97.5% and 93.3%, respectively. In the analysis by time period, the operative mortality declined from 27.6% (8 of 29) to 6.4% (11 of 172) (p = 0.002). Risk factors for operative death were coronary artery patterns (usual vs retropulmonary left coronary artery, p = 0.009) in phase 1 and preoperative instability in phase 2 (p = 0.002).

CONCLUSIONS

The arterial switch operation for TGA and Taussig-Bing anomaly has early low and late mortality and reoperation rates. Technical modifications in coronary reimplantation have minimized coronary artery pattern-related risks.

Biological versus mechanical aortic valve replacement in children

BACKGROUND

Aortic valve replacement in children remains challenging because of constraints imposed by available prosthetic devices. Potential risks of anticoagulation with mechanical valves and degeneration of other biological substitutes have kindled interest in the Ross procedure. This study outlines the evolution of our 27-year experience with prosthetic devices.

METHODS

Ninety-nine patients who underwent aortic valve replacement (January 1973 through September 2000) were included in this study. Procedures included implantation of pulmonary autograft (PA) (n = 42), aortic homograft (AH) (n = 3), mechanical valves (MV) (n = 41), and xenograft tissue valves (XG) (n = 13).

RESULTS

The mean follow-up times were: 3.8+/-1.3 years for PA, 3.5+/-1.5 years for AH, 7.7+/-4.7 years for MV, and 8.4+/-4.8 years for XG. There were no significant differences in perioperative outcomes among the groups (p < or = 0.05) or early deaths (2 each in the MV, AH, and PA groups). The incidence of valve-related complications and reoperations was high in the MV (n = 5), XG (n = 7), and AH (n = 1) groups as compared with the PA group (n = 3, p < 0.01). Early and late mortality for the series was 8.6% (n = 8). Overall, the reoperation rate was 20.7% (n = 18): 15.2% (5 of 33) MV, 70% (7 of 10) XG, 50% (1 of 2) AH, and 11.9% (5 of 42) for PA. The actuarial survival rate was 87.8% and 100% at 10 years for MV and XG, and 95.2% and 6.6% at 7 years for PA and AH.

CONCLUSIONS

Aortic valve replacement in children can be performed with acceptable mortality and good long-term results. The Ross procedure, although more complicated, has the advantage of not requiring anticoagulation therapy, can be performed in all age groups, possesses inherent growth potential, and exhibits the most normal left ventricular outflow tract hemodynamics.

Expression of intron-containing GUS constructs is reduced due to activation of a cryptic 5' splice site

An intron-containing beta-glucuronidase (GUS) gene has been used widely in promoter analyses and as a plant transformation marker. Maximal plant gene expression requires accurate and efficient removal of the intron from the expressed pre-mRNA transcripts by splicing. Detailed analysis of splicing of potato ST-LS1 and pea legumin introns from GUS constructs revealed the activation of a cryptic 5' splice site in the GUS coding sequence 4 nt upstream from the authentic intron 5' splice site. About 40% of transcripts utilised the cryptic 5' splice site in tobacco protoplasts, reducing the translational potential of expressed pre-mRNA. The same cryptic splicing event was evident in transgenic tobacco leaves but at reduced levels. Mutations that removed the cryptic 5' splice site are associated with a two-fold enhancement in GUS activity in tobacco protoplasts, highlighting the need for careful examination of introns and their sites of insertion into gene constructs to minimise variability in gene activity and maximise gene expression.

Differential expression of potato U1A spliceosomal protein genes: a rapid method for expression profiling of multigene families

The spliceosomal protein, UIA, is a component of the U1snRNP essential to pre-mRNA splicing. From the ubiquitous nature of the splicing machinery, expression of U1A genes is expected to be constitutive. However, many plant genes are organised in multigene families that exhibit variation in expression profiles. Without detailed knowledge of the size of the U1A gene family or their degree of sequence variation, we examined the expression of the U1A genes using a novel approach. The approach was based on 5' RACE with [32P]-labelled primers and separation of products on high-resolution DNA sequencing gels to give a 'snapshot' of the expression of U1A genes. This was followed by sequencing of cloned 5' RACE products and of products re-amplified from excised bands. In combination with RT-PCR/SSCP, these analyses allowed the rapid identification of different gene transcripts and assessment of their relative expression profiles. Transcripts from four U1A genes (U1A-1 to U1A-4) were identified, of which U1A-1 and U1A-2 were expressed much more highly than U1A-3 and U1A-4. Differential expression of the two most highly expressed genes, U1A-1 and UIA-2, was observed in that only U1A-2 was expressed in flowers. Upstream sequences of U1A-1 and U1A-2 were cloned and the gene-specific promoters identified on the basis of the sequence variation defined from the 5' RACE products. The differential expression of these genes may be due to a 1.3 kb insertion less than 200 bp upstream of the U1A-1 coding sequence. This approach can be used more generally to examine expression profiles of multigene families, and in particular to refine information from EST or microarray analyses, and to isolate rapidly gene-specific promoters.

Effects of androgens and estrogens and catechol and methoxy-estrogen derivatives on mitogen-activated protein kinase (ERK(1,2)) activity in SW-13 human adrenal carcinoma cells

We tested the effects of 17beta-estradiol as well as its catechol- and methoxy-derivatives, two androgens (DHEA and testosterone), a glucocorticoid (cortisol), a mineralocorticoid (aldosterone), and progesterone on the activity of ERK(1,2), a key component of the ERK/MAPK enzyme phosphorylation cascade, in SW-13 human adrenal carcinoma cells. After a 24-hour exposure SW-13 cells incubated with 10(-5) M concentrations of 17beta-estradiol, its 2-hydroxy or its 2-methoxy derivative, all had elevated ERK activities (196%, 159%, and 275%, respectively) relative to control cells (p < 0.01). Incubation with testosterone resulted in 162% of control ERK activity (p < 0.01), whereas incubation with the far weaker androgen DHEA or with cortisol, aldosterone, or progesterone had no significant effects. These findings suggest sex steroid-specific influences in the induction or activation of signal transduction pathways known to play a crucial role in cellular proliferation and differentiation.

New insight into RNase P RNA structure from comparative analysis of the archaeal RNA

A detailed comparative analysis of archaeal RNase P RNA structure and a comparison of the resulting structural information with that of the bacterial RNA reveals that the archaeal RNase P RNAs are strikingly similar to those of Bacteria. The differences between the secondary structure models of archaeal and bacterial RNase P RNA have largely disappeared, and even variation in the sequence and structure of the RNAs are similar in extent and type. The structure of the cruciform (P7-11) has been reevaluated on the basis of a total of 321 bacterial and archaeal sequences, leading to a model for the structure of this region of the RNA that includes an extension to P11 that consistently organizes the cruciform and adjacent highly-conserved sequences.

Biosynthesis and metabolism of steroid hormones by human adrenal carcinomas

Over a 15-year period, our university-based laboratory obtained 125 adrenal tumors, of which 15 (12%) were adrenal cortical carcinomas. Of these, 6 (40% of the carcinomas) occurred in patients with clear clinical manifestations of steroid hormone excess. Adrenal cortical carcinoma cells derived from the surgically resected tumors in 4 of these patients were isolated and established in primary culture. Radiotracer steroid interconversion studies were carried out with these cultures and also on mitochondria isolated from homogenized tissues. Large tumors had the lowest steroidogenic activities per weight, whereas small tumors had more moderately depressed enzyme activities relative to cells from normal glands. In incubations with pregnenolone as substrate, 1 mM metyrapone blocked the synthesis of corticosterone and cortisol and also the formation of aldosterone. Metyrapone inhibition was associated with a concomitant increase in the formation of androgens (androstenedione and testosterone) from pregnenolone. Administration of metyrapone in vivo before surgery in one patient resulted in a similar increase in plasma androstenedione, though plasma testosterone levels were not significantly affected. In cultures of two of four tumors examined, dibutyryl cAMP stimulated 11ss-hydroxylase activity modestly; ACTH also had a significant stimulatory effect in one of these tumors. Unlike results obtained with normal or adenomatous adrenal cortical tissues, mitochondria from carcinomatous cells showed a lack of support of either cholesterol side-chain cleavage enzyme complex or steroid 11ss-hydroxylase activity by Krebs cycle intermediates (10 mM isocitrate, succinate or malate). This finding is consistent with the concept that these carcinomas may tend to function predominantly in an anaerobic manner, rather than through the oxidation of Krebs cycle intermediates.