Design of sensitive fluorogenic substrates for human cathepsin D

Cathepsin D is a lysosomal aspartic proteinase that has been implicated in several pathological processes such as breast cancer and Alzheimer's disease. We designed and synthesized a number of quenched fluorogenic substrates with P2 variations in the series AcEE(EDANS)KPIXFFRLGK(DABCYL)E-NH2, where X=cysteine, methylcysteine, ethylcysteine, tert-butylcysteine, carboxymethylcysteine, methionine, valine or isoleucine. Most of the fluorogenic substrates exhibited greater k(cat)/Km ratios than the best cathepsin D substrates described so far. Differences in kinetic constants, which were rationalized using structure-based modeling, might make certain substrates useful for particular applications, such as active site titrations or initial velocity determination using a fluorescent plate reader.

Pharmacological regulation of blood glucose levels in non-insulin-dependent diabetes mellitus

Non-insulin-dependent diabetes mellitus is a metabolic disease that is common and is characterized by insulin insufficiency and resistance. Measures such as body weight reduction and exercise improve the metabolic defects, but pharmacological therapy is the most frequently used and successful therapy. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase disposal and decrease hepatic glucose output without causing hypoglycemia. Acarbose is a dietary aid that spreads the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological agents, either alone or in combination, can improve blood glucose regulation in patients with non-insulin-dependent diabetes mellitus.

Tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta 1 (TGF-beta 1) inhibit the expression and activity of Na+/K(+)-ATPase in FRTL-5 rat thyroid cells

We recently reported that tumor necrosis factor-alpha (TNF-alpha) induction of the synthesis and secretion of transforming growth factor (TGF)-beta 1 by FRTL-5 cells is a thyroid-stimulating hormone (TSH)-dependent and age-dependent process. TNF-alpha is only cytotoxic to aged (> 40 passages) FRTL-5 cells grown in TSH-containing medium, whereas TGF-beta induces programmed cell death (apoptosis) in epithelial cells but not in FRTL-5 cells, which otherwise retain many properties of normal thyroid follicular cells. This cell line is, therefore, a convenient model for studies on the TSH-dependent and age-dependent inhibitory effects of these cytokines on epithelial cell growth, viability, and function. One prominent effect of TNF-alpha (and TGF-beta 1) on FRTL-5 cell function is suppression of iodide uptake, which is markedly stimulated by TSH. In aged FRTL-5 cells, iodide uptake is only about 10% that of young control cells. Na+/K(+)-ATPase activity, which drives iodide uptake by thyroid cells, is inhibited by TNF-alpha and TGF-beta. The following experiments quantitate the effects of TSH, aging, TNF-alpha, and TGF-beta 1 on the expression and activity of Na+/K(+)-ATPase activity in FRTL-5 cells. Young (< 20 passages) and aged (> 40 passages) FRTL-5 cells were treated with various doses (0-100 ng/ml) of recombinant human TNF-alpha or TGF-beta 1 for various times (0-3 days) with and without 2 U/liter TSH. These treatments reduced the rate-limiting Na+/K(+)-ATPase beta 1 mRNA level and Na+/K(+)-ATPase activity in parallel in a dose-dependent and time-dependent fashion. Aged FRTL-5 cells were more sensitive to the inhibitory effects of TNF-alpha, whereas young cells were more sensitive to the suppressive effects of TGF-beta 1 on the expression and activity of Na+/K(+)-ATPase. We conclude that inhibition of Na+/K(+)-ATPase activity by TNF-alpha and TGF-beta in FRTL-5 cells is differentially affected by aging and that this inhibitory effect can be dissociated from effects on cell viability.

Disruption of transcription in vitro and gene expression in vivo by DNA adducts derived from a benzo[a]pyrene diol epoxide located in heterologous sequences

Previous studies indicated a high affinity of the transcription factor Sp1 for DNA adducts derived from benzo[a]pyrene diol epoxide (BPDE) in sequences that are not normal binding sites for Sp1. We tested for functional effects of this phenomenon in three systems in which transcription is Sp1-dependent. In an in vitro, Sp1-dependent transcription system addition of heterologous plasmid DNA containing BPDE adducts abolished production of a specific run-off transcript. This inhibition was not seen with unmodified plasmid DNA, and could be overcome by addition of purified Sp1 protein. In SL2 insect cells, high-level expression of an Sp1-dependent reporter gene, which was dependent on co-transfection of an Sp1 expression vector, was inhibited >95% by co-transfection of heterologous DNA containing BPDE adducts. This inhibition could be partially overcome by increasing the amount of the Sp1 expression vector in the transfections. In human C33A cells, expression of a transfected reporter gene driven by a GC box containing fragment of the human E2F1 promoter was enhanced by co-transfection of an Sp1 expression plasmid. Expression was inhibited 3-6-fold by co-transfection of heterologous DNA containing BPDE-DNA adducts. A similar inhibition was seen in human SAOS-2 cells, which lack functional p53 protein. These data are consistent with functionally significant sequestration of the Sp1 transcription factor by BPDE-DNA adducts in all three systems. Altered availability of transcription factors such as Sp1 in carcinogen-treated cells may disrupt patterns of gene expression.

Oral antidiabetic drug use in the elderly

Non-insulin-dependent diabetes mellitus (NIDDM) is a metabolic disease that is common in the elderly, and is characterised by insulin insufficiency and resistance. Measures such as bodyweight reduction and exercise improve the metabolic defects, but pharmacological therapy is the most frequently used and successful therapy. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase glucose disposal and decrease hepatic glucose output without causing hypoglycaemia. Acarbose is a dietary aid that spreads the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological agents, either alone or in combination, should improve blood glucose regulation in patients with NIDDM.

Cytoskeletal proteins inside human immunodeficiency virus type 1 virions

We have identified three types of cytoskeletal proteins inside human immunodeficiency virus type 1 (HIV-1) virions by analyzing subtilisin-digested particles. HIV-1 virions were digested with protease, and the treated particles were isolated by sucrose density centrifugation. This method removes both exterior viral proteins and proteins associated with microvesicles that contaminate virion preparations. Since the proteins inside the virion are protected from digestion by the viral lipid envelope, they can be isolated and analyzed after treatment. Experiments presented here demonstrated that this procedure removed more than 95% of the protein associated with microvesicles. Proteins in digested HIV-1(MN) particles from infected H9 and CEM(ss) cell lines were analyzed by high-pressure liquid chromatography, protein sequencing, and immunoblotting. The data revealed that three types of cytoskeletal proteins are present in virions at different concentrations relative to the molar level of Gag: actin (approximately 10 to 15%), ezrin and moesin (approximately 2%), and cofilin (approximately 2 to 10%). Our analysis of proteins within virus particles detected proteolytic fragments of alpha-smooth muscle actin and moesin that were cleaved at sites which might be recognized by HIV-1 protease. These cleavage products are not present in microvesicles from uninfected cells. Therefore, these processed proteins are most probably produced by HIV-1 protease digestion. The presence of these fragments, as well as the incorporation of a few specific cytoskeletal proteins into virions, suggests an active interaction between cytoskeletal and viral proteins.

Low level cyclic adenosine 3',5'-monophosphate accumulation analysis of [des-His1, des- Phe6, Glu9] glucagon-NH2 identifies glucagon antagonists from weak partial agonists/antagonists

[des-His1, des-Phe6,Glu9]Glucagon-NH2 is a newly designed glucagon antagonist. This analog has a binding IC50 of 48 nM (compared to glucagon IC50 of 1.5 nM) and demonstrates pure antagonism in an adenylate cyclase assay. Although the number of glucagon antagonists has grown rapidly recently, closer examination suggested that many of these antagonists retained very low, almost imperceptible levels of cAMP accumulation that were sufficient to elicit an in vivo biological response. To investigate more carefully this secondary biological signal, we measured cAMP accumulation in a revised assay using isolated hepatocytes in the presence of the phosphodiesterase (PDE) inhibitor Rolipram. The PDE inhibitors Rolipram and isobutyl-1-methylxanthine (IBMX) increased the sensitivity of the cAMP accumulation assay from approximately 10-fold for the native hormone to 35-fold above basal levels. On the other hand, amrinone, another PDE inhibitor, did not affect the cAMP accumulation caused by glucagon. The use of PDE inhibitors indicated that three glucagon analogs that had previously been reported to have strong antagonist properties in classical adenylate cyclase assays were actually weak partial agonists in this new assay system. [N alpha-Trinitrophenyl-His1, homo-Arg12]glucagon, [des-amino-His1,D-Phe4,Tyr5, Arg12, Lys17,18,Glu21]glucagon, and [des-His1,Glu9]glucagon-NH2 demonstrated 233%, 21%, and 5.5% cAMP accumulation relative to the native hormone in the presence of 25 microM Rolipram. On the other hand, [des-His1,des-Phe6,Glu9]glucagon-NH2, a newly designed glucagon antagonist, did not activate adenylate cyclase in the presence of Rolipram up to a maximal physiological concentration of 1 microM, indicating that it was a pure antagonist of glucagon-induced adenylate cyclase activity and also the first one in this class. This compound and others were tested in a glycogen phosphorylase assay. As [des-His1,des- Phe6,Glu9]glucagon-NH2 did not activate phosphorylase activity, it was chosen as our candidate for in vivo testing in streptozotocin-induced diabetic rats. An initial dose of 0.75 mg/kg was found to cause the greatest lowering of blood glucose levels (to 63% of the initial levels in 15 min) when the bolus was followed by continuous infusion of 25 micrograms/kgxmin for 1 h.

Phase determination from mostly one-sided interferograms

We show how to detect and correct for nonlinear phase shifts in a mainly one-sided interferogram of an emission-line source. We simultaneously detect and correct for an out-of-phase emission background from the spectrometer. The method requires two auxiliary spectra, one of a strong continuum source, and one of an emission-line source with little or no continuum.

Cardiovascular and sympathoadrenal responses to heat stress following water deprivation in rats

This study was designed to characterize the regional and systemic hemodynamic and sympathoadrenal responses to heating after 24 and 48 h of water deprivation in chloralose-anesthetized, male Sprague-Dawley rats (n = 7 per group). Water deprivation produced significant decreases in body weight of 8.1 and 13.7% in the 24- and 48-h groups (P < 0.05), respectively. After water deprivation, rats were exposed to an ambient temperature of 43 degrees C. After correction for body weight differences, heating rates were faster in the 48-h group compared with both euhydrated and 24-h groups. Mean arterial blood pressure (MAP), heart rate, and colonic (Tco) and tail (Ttail) temperatures increased above baseline in all groups during heating. Renal and mesenteric artery blood flow velocities decreased, and vascular resistances increased in response to heating. Compared with euhydrated controls, 48-h water-deprived rats exhibited attenuated pressor (delta MAP = 36 +/- 3 vs. 18 +/- 3 mmHg) and visceral vasoconstrictor (% delta in mesenteric resistance = 122.6 +/- 27.3 vs. 54.9 +/- 6.9%) responses during heating. Tail-skin blood flow estimated from Ttail was also lower at baseline and the onset of heating in water-deprived rats. However, peak Ttail and Tco values were similar across groups. Plasma catecholamines measured in separate groups of rats (n = 6 per group) were significantly higher at baseline and the end of heating in the 48-h group compared with euhydrated and 24-h groups. Despite this exaggerated sympathoadrenal response, the 48-h group exhibited attenuated hemodynamic responses to nonexertional heating compared with euhydrated and 24-h water-deprived rats. These data suggest that cardiovascular and thermoregulatory adjustments can compensate for small changes in hydration state (i.e., 24 h), but more severe levels of hypohydration significantly alter blood pressure and body temperature regulation during heat stress.

Sulfonylurea binding to a low-affinity site inhibits the Na/K-ATPase and the KATP channel in insulin-secreting cells

We have used hamster insulinoma tumor (HIT) cells, an insulin-secreting tumor cell line, to investigate modulation of the Na/K-ATPase and of the ATP-sensitive K channel (K(ATP)) by the sulfonylurea glyburide. Membrane proteins from cells cultured in RPMI with 11 mM glucose have at least two glyburide receptor populations, as evidenced by high and low binding affinity constants, (K(d) = 0.96 and 91 nM, respectively). In these cells K(ATP) channel activity was blocked by low glyburide concentrations, IC(50) = 5.4 nM. At 12.5 nM glyburide the inhibition developed slowly, tau = 380 s, and caused reduction of channel activity by 75 percent. At higher concentrations, however, inhibition occurred at a fast rate, tau = 42 s at 100 nM, and was almost complete. Na/K-ATPase activity measured enzymatically and electrophysiologically was also suppressed by glyburide, but higher concentrations were needed, IC(50) = 20-40 nM. Inhibition occurred rapidly, tau = 30 s at 50 nM, when maximum, activity was reduced by 40 percent. By contrast, cells cultured in RPMI supplemented with 25 mM glucose exhibit a single receptor population binding glyburide with low affinity, K(d)= 68 nM. In these cells inhibition of the Na/K-ATPase by the sulfonylurea was similar to that observed in cells cultured in 11 mM glucose, but K(ATP) channel inhibition was markedly altered. Inhibition occurred only at high concentrations of glyburide and at a fast rate; maximum inhibition was observed at 100 nM. Based on these data, we propose that glyburide binding to the high affinity site affects primarily K(ATP) channel activity, while interaction with the low affinity site inhibits both Na/K-ATPase and K(ATP) channel activities. The latter observation suggests possible functional interactions between the Na/K-ATPase and the K(ATP) channel.

Regulation of E2F-1 gene expression by p130 (Rb2) and D-type cyclin kinase activity

Previous experiments have demonstrated that the regulation of E2F-1 transcription factor activity is critical for the maintenance of normal cell proliferation control. Regulation of E2F-1 is accomplished through at least two mechanisms: posttranslational regulation by binding proteins such as Rb and transcriptional regulation of the E2F-1 gene. The E2F-1 gene promoter has recently been isolated to examine this latter aspect of E2F-1 regulation. Preliminary studies demonstrate that the E2F-1 promoter is under E2F-dependent negative control during the cell growth response, being transcriptionally repressed through E2F sites in G0 and early G1. We now demonstrate that the presence of an E2F DNA-binding complex containing the Rb-related p130 protein (Rb2) correlates with E2F-1 gene repression and that overexpression of p130 inhibits transcription from the E2F-1 promoter. Moreover, D-type cyclin-dependent kinase activity specifically activates the E2F-1 promoter by relieving E2F-mediated repression but is inhibited by coexpression of the cdk4 and cdk6 inhibitor p16 (CDKN2, MTS1, INK4). Taken together, these findings suggest that E2F-1 gene expression is controlled during cell cycle progression by a regulatory network involving at least one oncogene (cyclin D1) and several potential tumor suppressor genes.

Analysis and localization of cyclophilin A found in the virions of human immunodeficiency virus type 1 MN strain

Previous reports have shown that cyclophilin A (CyPA) is found to be specifically associated with human immunodeficiency virus type-1 (HIV-1) virions and is required for infectivity (Franke et al. Nature 372:359; Thali et al. Nature 372:363). We have examined CyPA associated with HIV-1MN virions. Virions from infected human lymphoid cells were analyzed by high-pressure liquid chromatography (HPLC), protein sequence, and immunoblot analysis. At least three forms of CyPA were found: an unmodified form, an N-terminally modified form, and an N-terminally modified form that migrates as a larger isoform on a reducing-SDS polyacrylamide gel. Using a protease digestion procedure, CyPA that is associated with virions was found to be located inside the viral membrane. Similar examination of SIVMne produced by HUT-78 human T cells did not detect specific incorporation of CyPA into SIV virions. Our results are consistent with the role of CyPA acting early in the infectious process of HIV-1.

Unexpected death from enterocolitis after surgery for Hirschsprung's disease

Unanticipated death from enterocolitis occurred in five children 3 weeks to 20 months after uncomplicated reconstruction for Hirschsprung's disease. In each case the presenting symptoms of enterocolitis were mild and were misinterpreted by examining physicians. Within 2 to 12 days of onset of symptoms, unexpected death occurred. Although fatal enterocolitis is a well-known complication of Hirschsprung's disease, emphasis is usually placed on preoperative enterocolitis. Fatal postoperative enterocolitis is not a new entity associated with Hirschsprung's disease, but physician awareness of this possibility is obviously deficient. We strongly recommend extensive parent education and better postoperative communication between the surgeon and the referring physician.

Rectal irrigations for the prevention of postoperative enterocolitis in Hirschsprung's disease

The purpose of this clinical trial was to examine the role of rectal irrigations in the prevention of postoperative enterocolitis in children with Hirschsprung's disease. Over the past 22 years 177 children had surgical treatment for Hirschsprung's disease at a single pediatric hospital. Five children have died of other causes. Of the remaining 172 patients, follow-up clinical information was obtained from 135 (78%). In 1989, all of the children undergoing surgical reconstruction for Hirschsprung's disease were placed on routine postoperative rectal irrigations with normal saline. The parents were instructed in the irrigation technique before leaving the hospital. Irrigations were started 1 to 2 weeks postoperatively and were performed two times a day for 3 months, then once a day for an additional 3 months. There were no complications from the irrigations themselves. A previous report from the authors' institution has documented five sudden deaths over the past 22 years from fulminant postoperative enterocolitis. These five children all had an unremarkable postoperative recovery, then developed a rapidly progressive diarrheal illness. All of these deaths occurred before the institution of routine postoperative irrigations. Of the 135 patients in this review, 40 had the postoperative rectal irrigations. The remaining 95 children serve as historical controls. Data analysis showed that 34 of the 95 children in the nonirrigation cohort developed postoperative enterocolitis compared with 3 of 40 in the rectal irrigation cohort; P < .001 using Fisher's exact test. In the authors' experience, routine postoperative rectal irrigations have significantly decreased the incidence and severity of enterocolitis in children after surgical correction of Hirschsprung's disease.

Gastrointestinal function after surgical correction of Hirschsprung's disease: long-term follow-up in 135 patients

This study is a retrospective review of all children treated for Hirschsprung's disease over the past 22 years at a single pediatric institution. During this time 177 patients had definitive surgical reconstruction. Five children died of causes unrelated to Hirschsprung's disease, and five children died from enterocolitis after an uneventful postoperative course. Clinical follow-up information was obtained from 135 (78%). Demographic data includes the following: sex ratio 74% male, 26% female; current mean age 9.9 years; mean length of follow-up 7.9 years (range, 3 months to 21.5 years). Mean age at surgical reconstruction was 1.6 years. Definitive surgical procedures included endorectal pull-through (Soave), 21%; modified Duhamel, 67%; extended side-to-side ileocolic anastomosis, 8%; rectal myomectomy, 4%. Transition zone was within rectum or rectosigmoid region in 86%. Overall, 32% (43/135) report difficulty with fecal soiling, and 12.6% (17/135) identify this as a severe problem. These numbers include patients with trisomy 21 and total colonic aganglionosis. Severe fecal soiling was reported in 7.1% (2/28) after an endorectal pull-through, and in 12.1% (11/91) after the modified Duhamel. The difference in incidence of soiling after these two procedures is not statistically significant. However, 40% (4/10) of the patients after the long side-to-side anastomosis for total colonic aganglionosis report severe problems with fecal soiling (P = .03). Surgical reconstruction for Hirschsprung's disease provides near-normal gastrointestinal function for the majority of children, but long-term follow-up shows significant residual problems with soiling in 12.6% of the patients. This is consistent with reported experience worldwide.

Cardiovascular, plasma norepinephrine, and thermal adjustments to prolonged exercise in young and older healthy humans

We tested the hypothesis that the whole body energy expenditure, plasma norepinephrine, cardiovascular, and internal body temperature adjustments to prolonged submaximal exercise (i.e., 'cardiovascular drift') performed at the same per cent of peak oxygen uptake (per cent VO2peak) under thermoneutral ambient conditions would be smaller in older compared to young non-physically trained men. Healthy young (25 +/- 1 years; VO2max = 49.3 +/- 1.6 ml kg-1 min-1; n = 6) and older (66 +/- 2 years; VO2max = 31.5 +/- 2.3 ml kg-1 min-1; n = 6) untrained men with similar levels of chronic physical activity were studied during pre-exercise standing rest and serially during 45 min of constant load treadmill walking at approximately 65% VO2peak (Ta = approximately 23 degrees C; approximately 40 RH). There were no group differences at rest. From rest to 5 min of exercise, the increases in heart rate were less (P < 0.05), the changes in arterial blood pressure and per cent delta blood volume were not different, and the rise in plasma norepinephrine concentration was greater (P < 0.05) in the older men vs. young controls. Consistent with our hypothesis, the increases in rectal temperature and plasma norepinephrine concentrations from 5 to 45 min of exercise were smaller in the older men (1.06-0.18 vs. 1.46 +/- 0.16 degrees C and 110 +/- 132 vs. 443 +/- 189%, respectively, P < 0.05). In contrast, the progressive increases in VO2, heart rate, and perceived effort, as well as the time-dependent reductions in systolic, mean and diastolic arterial blood pressure and per cent delta blood volume, were not different in the two groups. Thus, the whole body energy expenditure and selected cardiovascular adjustments to prolonged submaximal treadmill exercise performed at the same per cent VO2peak under comfortable ambient conditions are not different in healthy, physical activity-matched young and older men, despite a smaller elevation in internal body temperature in the latter.

Early lactation responses of Holstein cows fed a rumen-inert fat prepartum, postpartum, or both

Primiparous (n = 22) and multiparous (n = 41) cows were randomly assigned by calving date and parity to one of four dietary sequences of supplemental fat from 14 d prepartum to 151 d postpartum. Partially hydrogenated tallow was added to diets at 0% prepartum and postpartum (control); 1% prepartum and 2% postpartum; 0% prepartum and 2% postpartum; and 0% prepartum, 0% from 1 to 34 d postpartum, and 2% from 35 to 151 d postpartum. Inclusion of partially hydrogenated tallow did not influence yields of milk or 3.5% FCM, milk composition, or DMI during the first 151 d postpartum. During the first 35 d postpartum, cows receiving partially hydrogenated tallow starting at parturition yielded milk with a higher fat content than those receiving fat prepartum and postpartum. Addition of partially hydrogenated tallow to diets starting 35 d postpartum resulted in cows being more persistent in yields of milk and 3.5% FCM from 60 to 151 d postpartum. Reproduction parameters measured were unaffected by time of fat addition to diets. Our data suggest that delaying the addition of partially hydrogenated tallow to diets until 35 d postpartum may improve the persistency of lactation.

Muscle sympathetic nerve activity during postural change in healthy young and older adults

Recent evidence suggests that during orthostatic stress the reflex increase in muscle sympathetic nerve activity may be diminished in older adults. To test this hypothesis, we measured muscle sympathetic nerve activity, plasma noradrenaline concentrations, heart rate, and arterial blood pressure in twelve young (mean, 25 years; range, 19-29 years) adults and 14 older (mean 64 years; range, 60-74 years) healthy adults, while supine and during upright sitting. Supine control levels of muscle sympathetic nerve activity were higher in the older subjects (35 +/- 1 vs. 25 +/- 1 bursts/min, p < 0.05), but there were no differences in plasma noradrenaline concentrations, heart rate or arterial pressure. Despite higher supine control levels in the older group, the absolute unit increases in muscle sympathetic nerve activity in response to upright sitting (p < 0.05 vs. control) were not different in the two groups (7 +/- 1 vs. 7 +/- 1 bursts/min), nor were the increases in plasma noradrenaline concentrations. Heart rate did not increase above supine control in response to sitting in either group. Arterial pressure increased slightly (p < 0.05, supine vs. control), but there were no age-related differences. These results indicate that, contrary to recent findings, the reflex increases in muscle sympathetic nerve activity and plasma noradrenaline concentrations and regulation of arterial pressure during this natural orthostatic stress are well preserved in older healthy men and women.

Oncogenic capacity of the E2F1 gene

Previous experiments have identified the E2F transcription factor as a potential downstream target for the action of cellular regulatory activities, such as the Rb tumor suppressor protein, that control cell growth and that, when altered, contribute to the development of human tumors. In light of these findings, we have assayed the ability of the E2F1 and DP1 genes, which encode heterodimeric partners that together create E2F activity, to act in an oncogenic fashion. We find that E2F1, particularly in combination with the DP1 product, cooperates with an activated ras oncogene to induce the formation of morphologically transformed foci in primary rat embryo fibroblast cultures. In addition, an E2F1 chimeric protein, in which sequences involved in Rb binding have been replaced with the herpesvirus VP16 activation domain, exhibits increased transformation activity. Cells transfected with E2F1 and DP1 or the E2F1-VP16 chimera form colonies in soft agar and induce tumor formation in nude mice. We conclude that deregulated E2F1 expression and function can have oncogenic consequences.

Tracheal reconstruction

Treatment of stenosing malformations of the pediatric airway has progressed from dilatation and occasional localized resection to radical resection or extended tracheoplastic reconstruction. Current preoperative evaluation includes high-contrast radiography, bronchography, often magnetic resonance imaging (MRI) or computed tomography (CT), and intraoperative bronchoscopy. Cardiopulmonary bypass may be essential for complicated reconstructions involving the carina and bronchi, but most other stenoses can be corrected without bypass. Balloon dilatation directed toward forceful posterior split of complete cartilage rings has shown recent promise in small infants. Segmental resection with anastomosis is preferred for localized lesions. Incision tracheoplasty with interposition cartilage grafting is the current choice for long stenoses.

Congenital chest wall mesenchymal hamartoma

The case of an infant with mesenchymal hamartoma of the chest wall is presented, and the role of conservative diagnostic and therapeutic intervention is emphasized. A large mass that involved the right hemithorax and chest wall was detected in utero on routine ultrasonographic studies and diagnosed as mesenchymal hamartoma by percutaneous fine needle biopsy at 4 days after birth. The mass did not enlarge after birth, but surgical debulking was necessary at 1 month because of progressive respiratory compromise. Tumor regrowth was noted over the ensuing 8 months, and a second debulking at 9 months has been followed by a 6-year interval without evidence of recurrence.