Extent and severity of coronary disease and mortality in patients with end-stage renal failure evaluated for renal transplantation

The purpose of this study is to explore the relationship between coronary artery disease (CAD), transplantation status and subsequent mortality in end-stage renal disease (ESRD) patients undergoing evaluation for renal transplantation. Two hundred fifty-three ESRD patients at high risk for CAD underwent coronary angiography as part of a renal transplant evaluation. The cohort was divided into three groups: Group 1 (n = 127) had no vessels with >or=50% stenosis, Group 2 (n = 56) had one vessel with >or=50% stenosis and Group 3 (n = 70) had two or more vessels with >or=50% stenosis. Long-term survival was determined; median follow-up was 3.3 years. The baseline characteristics were similar except for older age and higher proportion of diabetes mellitus, dyslipidemia and peripheral vascular disease in Groups 2 and 3 patients as compared to Group 1. Survival was worse in Group 3 compared to Group 1 (p < 0.0001). Each of the three subgroups had better survival with renal transplantation than those who did not undergo transplantation (p < 0.0001). Although the degree of CAD is related to subsequent mortality, transplantation is associated with better survival regardless of the extent and severity of CAD. Thus, the presence of CAD should not exclude ESRD patients from consideration for this therapy.

Prospective parental consent for autopsy research following sudden unexpected childhood deaths: a successful model

BACKGROUND

Organ retention issues, recent changes in the Coroners' (Amendment) Rules 2005 and the Human Tissue Act have resulted in pessimism regarding prospective consent for paediatric autopsy research in the UK.

OBJECTIVES

To examine the feasibility and acceptability of a prospective telephone consenting model for post-mortem magnetic resonance (MR) imaging research in HM Coroners' cases.

DESIGN

Following each autopsy referral from the HM Coroner, permission to contact the family for research was requested. A family liaison sister, with experience in dealing with bereaved families, then contacted the parents by telephone, explained the study and obtained oral, and then written consent for post-mortem imaging.

SETTING

London and an area south of London.

RESULTS

Of 76 eligible HM Coroners' cases referred during the study period, permission to contact parents (provided by the HM Coroners' Office) was obtained for only 32 cases (42%). The research sister contacted 32 parents during the study period of whom 31 (96.8%) gave oral research consent. "Helping other parents in the future" and "the importance of post-mortem research" were the main reasons for parents wanting to participate in research.

CONCLUSIONS

Prospective consenting for HM Coroners' cases for research is feasible in children, and can be done ethically by parental consenting via telephone contact before autopsy by appropriately trained staff. However, close co-ordination between mortuary staff, HM Coroners, research staff and medical staff is required. This model may be useful in performing post-mortem research in HM Coroners' cases and in developing paediatric tissue and brain banks in the UK.

Immediate clinical and haemodynamic benefits of restoration of pulmonary valvar competence in patients with pulmonary hypertension

OBJECTIVE

To analyse the potential benefit of restoration of pulmonary valvar competence in patients with severe pulmonary regurgitation (PR) and pulmonary hypertension (PH) associated with congenital heart disease.

DESIGN

Retrospective study.

SETTING

Tertiary paediatric and adult congenital heart cardiac centre.

INTERVENTIONS

Percutaneous pulmonary valve implantation (PPVI).

PATIENTS

All patients who underwent PPVI for treatment of PR in the presence of PH (mean PAP >25 mm Hg).

RESULTS

Seven patients with severe PH as a result of congenital heart disease and severe PR underwent PPVI. The valve implantation procedure was feasible and uncomplicated in all seven cases, successfully abolishing PR. There was a significant increase in diastolic (15.4 (7.3) to 34.0 (8.5) mm Hg; p = 0.007) and mean (29.7 (8.1) to 41.3 (12.9) mm Hg; p = 0.034) pulmonary artery pressures, and an improvement in NYHA functional class (from median IV to median III; p<0.008). Peripheral oxygen saturations rose from 85.9% (11.0%) to 91.7% (8.3%) (p = 0.036). Right ventricular (RV) volumes decreased (from 157.0 (44.7) to 140.3 (53.3) ml/m(2)), while effective RV stroke volume increased (from 23.4 (9.3) to 41.0 (11.6) ml/m(2)). During a median follow-up of 20.3 months (range 1.3-47.5), valvar competence was well maintained despite near systemic pulmonary pressures. None of the valved stents were explanted during follow-up.

CONCLUSION

Trans-catheter treatment of PR in patients with PH is well tolerated and leads to clinical and haemodynamic improvement, most probably caused by a combination of increased pulmonary perfusion pressures and RV efficiency.

Cardiac magnetic resonance imaging in patients with systemic lupus erythematosus

Objectives:

To delineate the cardiac magnetic resonance (MR) appearances of cardiovascular disease (CVD) in patients with systemic lupus erythematosus (SLE), in comparison with transthoracic echocardiographs.

Methods:

Cardiac MR was performed on 22 patients with SLE—11 with previous CVD and 11 matched controls—using late gadolinium contrast enhancement (LGE) to identify areas of myocardial scarring; Transthoracic echocardiography (TTE) was performed on the same day.

Results:

Twenty female and two male patients participated. LGE was seen in 5/11 subjects in the CVD group (4/5 with previous myocardial infarction) and 1/11 in the control group. TTE detected myocardial abnormalities in 2/6 patients with LGE.

Conclusion:

The cardiac MR appearance of CVD in these patients with SLE was suggestive of coronary disease, rather than cumulative inflammatory muscle damage. Cardiac MR detected more abnormalities than TTE. Further studies of cardiac MR in patients with SLE are warranted to investigate these preliminary findings.

A role for dorsal and ventral hippocampus in inter-temporal choice cost-benefit decision making

Previous studies suggest a preferential role for dorsal hippocampus (dHPC) in spatial memory tasks, whereas ventral hippocampus (vHPC) has been implicated in aspects of fear and/or anxiety. In this study, we tested the hypothesis that vHPC may be a critical subregion for performance on a delay-based, cost-benefit decision making task. Rats chose between the two goal arms of a T maze, one containing an immediately available small reward, the other containing a larger reward that was only accessible after a delay. dHPC, vHPC, and complete hippocampal (cHPC) lesions all reduced choice of the delayed high reward (HR) in favor of the immediately available low reward (LR). The deficits were not due to a complete inability to remember which reward size was associated with which arm of the maze. When an equivalent 10-s delay was introduced in both goal arms, all rats chose the HR arm on nearly all trials. The deficit was, however, reinstated when the inequality was reintroduced. Our results suggest an important role for both dHPC and vHPC in the extended neural circuitry that underlies intertemporal choice.

High rate flame synthesis of highly crystalline iron oxide nanorods

Single-step flame synthesis of iron oxide nanorods is performed using iron probes inserted into an opposed-flow methane oxy-flame. The high temperature reacting environment of the flame tends to convert elemental iron into a high density layer of iron oxide nanorods. The diameters of the iron oxide nanorods vary from 10 to 100 nm with a typical length of a few microns. The structural characterization performed shows that nanorods possess a highly ordered crystalline structure with parameters corresponding to cubic magnetite (Fe(3)O(4)) with the [100] direction oriented along the nanorod axis. Structural variations of straight nanorods such as bends, and T-branched and Y-branched shapes are frequently observed within the nanomaterials formed, opening pathways for synthesis of multidimensional, interconnected networks.

Deletion of glutamate receptor-A (GluR-A) AMPA receptor subunits impairs one-trial spatial memory

Genetically modified mice lacking the glutamate receptor A (GluR-A) subunit of the AMPA receptor (GluR-A-/- mice) display normal spatial reference memory but impaired spatial working memory (SWM). This study tested whether the SWM impairment in these mice could be explained by a greater sensitivity to within-session proactive interference. The SWM performance of GluR-A-/- and wild-type mice was assessed during nonmatching-to-place testing under conditions in which potential proactive interference from previous trials was reduced or eliminated. SWM was impaired in GluR-A-/- mice, both during testing with pseudotrial-unique arm presentations on the radial maze and when conducting each trial on a different 3-arm maze, each in a novel testing room. Experimentally naive GluR-A-/- mice also exhibited chance performance during a single trial of spontaneous alternation. This 1-trial spatial memory deficit was present irrespective of the delay between the sample information and the response choice (0 or 45 min) and the length of the sample phase (0.5 or 5 min). These results imply that the SWM deficit in GluR-A-/- mice is not due to increased susceptibility to proactive interference.

Control of Frey's syndrome in patients treated with botulinum toxin type A

AIM

To identify the severity of Frey s syndrome and its response to botulinum toxin type A.

METHODS

Minor test was performed in all cases to assess the extent of the affected area, using the contralateral side as control. Severity was assessed according to the proposal of Luna-Ortiz et al. Response was evaluated after 3 and 6 months, and was compared with the basal data.

RESULTS

Frey s syndrome was documented in 38 patients, but only 23 cases accepted the botulinum toxin type A treatment. Severity was moderate in 8 (35%) and severe in 15 (65%) cases. Mean applied dose was 1.41 MU/cm2 in 21 patients (91%), whereas one patient was treated with 10 MU for a 0.8 cm2 affected area (12.5 MU/cm2) and another patient with 10 MU for a 0.5 cm2 affected area (20 MU/cm2) due to severity of their symptomatology. Average affected area at the beginning was 14.2 cm2, while after 3 and 6 months of treatment it was 4.1 cm2 and 4.4 cm2 respectively (p<0.001). The two patients that received higher doses of botulinum toxin A had complete response. Complete response was observed in 13 patients (56.5%) at 3 months, but in only nine (39%) this lack of symptomatology persisted at 6 months. In three cases (13%) no response was obtained at 3 months, and the application of an additional dose of botulinum toxin type A produced no response in two of them after 6 months. Comparison of the severity score of the average basal value vs. that obtained at 3 and 6 months revealed a significant difference (p<0.05); however, no statistically significant difference was found when comparing outcome at 3 vs. 6 months. There were no statistically significant differences using the independent samples test when comparing outcome after treatment in relation to gender, type of surgery, or use of postoperative radiation therapy (p>0.05). In conclusion, botulinum toxin A remains as the treatment of choice for Frey s syndrome.

Assessment of differential branch pulmonary blood flow: a comparative study of phase contrast magnetic resonance imaging and radionuclide lung perfusion imaging

OBJECTIVES

To test whether magnetic resonance (MR) imaging can be used to assess differential lung blood flow as accurately as isotope lung perfusion studies in patients investigated for congenital heart disease.

METHODS AND RESULTS

Radionuclide lung perfusion and MR imaging were performed in 12 children with suspected unilateral branch pulmonary artery stenosis (mean age 12.1 (5.9) years, range 3.1-17.2 years). A non-breath hold, fast gradient echo phase contrast MR sequence was used to measure flow in the pulmonary trunk and one pulmonary artery to calculate differential flow. Good agreement was shown between the two imaging methods by Bland-Altman analysis. There was excellent correlation between the radionuclide and MR phase contrast calculated total lung blood flow (r = 0.98, p < 0.0001).

CONCLUSION

MR phase contrast is an accurate method for measuring differential total right and left lung blood flow. If MR imaging is performed to assess the branch pulmonary arteries, differential lung blood flow can be also measured, avoiding the need for an additional radionuclide lung perfusion scan and reducing the overall radiation burden to this group of patients.

Muscle cell injury, haemolysis and dark urine in children with falciparum malaria in Papua New Guinea

During a prospective study of red cell variants and severe malaria in children, a surprising observation was the occurrence of dark urine. Children were grouped according to urine findings: 22 had dark urine that contained a haem protein (Group I), 93 had urine of normal colour that contained a haem protein (Group II) and 236 had normal urine (Group III). To investigate the cause of dark urine, haemolysis and muscle cell injury were assessed. Intravascular haemolysis was greater in Group I than in Groups II and III. However, anaemia was more severe in Group III and is likely to have resulted mainly from extravascular haemolysis. Median plasma myoglobin concentrations were greater in Groups I and II than Group III (P = 0.00060). Plasma myoglobin was greater in children with cerebral malaria, hyperlactataemia and those who died but was not associated with acidosis. Urine myoglobin was greater in Group I than Groups II and III (P = 0.00054). It is likely that both haemoglobin and myoglobin contributed to dark urine. The association between muscle cell injury and coma suggests sequestration of parasitized red cells as a common underlying pathology. In malaria, hyperlactataemia may result directly from breakdown of muscle protein as well as tissue hypoxia.

Solitary fibrous tumor of the parotid region. Report of a case and review of the literature

Solitary fibrous tumor is a well-recognized entity that most commonly involves the pleura; however, it has been recently described in other locations including the head and neck region, where it occurs as a slowly growing and well-circumscribed lesion. Due to its low frequency it may be confused with other neoplasms, and for this reason microscopic, ultrastructural and immunohistochemical features are necessary to establish its diagnosis. Prognosis of this tumor depends on its location and size. We present a 20-year-old woman with a well circumscribed, rapidly enlarging solitary fibrous tumor located in the parotid region, which protruded into the oral cavity, measured 10 x 8.5 x 5.5 cm and exhibited benign histological features and positive immunoreactivity to CD34.

A practical method for clinical diagnosis of oral mucosal melanomas

OBJECTIVE

To present a practical and technically simple method for clinical diagnosis of oral melanomas that allows to differentiate this neoplasm from other pigmented lesions.

PATIENTS AND METHODS

Thirteen oral pigmented lesions with suspected diagnosis of mucosal melanomas were submitted to a test named "rubbing with a gauze" the surface of the lesion. The test was considered positive when the gauze stained dark brown or black due to the presence of melanin-laden cells on the epithelial surface. In all cases definite diagnosis was confirmed by biopsy.

RESULTS

Positive results were obtained in 11 out of 13 cases (84.6%).

CONCLUSION

Our results establish that the test "rubbing with gauze" the surface of oral pigmented lesions demonstrates a high sensitivity to anticipate clinically the diagnosis of mucosal melanomas. However, a negative result does not exclude this neoplasm, since there are some cases in which malignant cells have not invaded the superficial epithelial layers. In every case the final diagnosis must be established by histopathologic or immunohistochemical analysis.

Malignant odontogenic tumors. A retrospective and collaborative study of seven cases

The frequency, clinico-pathologic features and outcome of malignant odontogenic tumors diagnosed according to the current WHO classification in three pathology services in Mexico City are presented. There were seven cases (5 male and 2 female patients), which represent less than 4% of all odontogenic tumors diagnosed in these services. There were six odontogenic carcinomas (two malignant ameloblastomas, two clear cell odontogenic carcinomas, one primary intraosseous carcinoma and one carcinoma arising in an odontogenic cyst) and one ameloblastic fibrosarcoma. Age ranged from 25 to 72 years (mean: 43.8). Clear cell odontogenic carcinomas occurred in the canine-premolar region, one in the maxilla and one in the mandible (one ia a man and one in a woman), while the remaining lesions affected the posterior region of the mandible, with a male predominance (4:1), which agrees with previously reported cases. Surgical resection was the treatment employed in all carcinomas, while the ameloblastic fibrosarcoma was treated with chemotherapy due to its large extension, but without favorable response. The patient with primary intraosseous carcinoma had submaxillary and cervical metastases and the neoplasm was the cause of death. In spite of their extremely low frequency, malignant odontogenic tumors are an important cause of extensive surgical procedures in the oral and maxillofacial region.

Molecular analysis of single colonies reveals a diverse origin of initial clonal proliferation in B-precursor acute lymphoblastic leukemia that can precede the t(12;21) translocation

The pathogenesis of pediatric B-precursor acute lymphoblastic leukemia is largely unknown, and even with nonrandom chromosomal translocations present, the precise order of clonal molecular events is undefined. We developed an in vitro system using cytokines interleukin (IL)-3, IL-7, IL-10, and FMS-like tyrosine kinase 3 ligand with CD40 ligand-expressing fibroblasts to obtain single blast colonies from which clonal immunoglobulin heavy chain (IgH), T-cell receptor delta gene rearrangements, and, in t(12;21)-positive cases, TEL-AML1 fusion transcripts could be simultaneously PCR amplified. The proliferation of early tumor progenitors increased subclone detection enabling us, in seven diagnostic samples, to determine the stage of differentiation at which each leukemia occurred. Four were derived from the stage before initiation of IgH rearrangement, one during recombination of variable, joining, and diversity segments of the heavy chain gene VDJ(H), and two after completion of IgH rearrangement. Furthermore, analysis of a t(12;21)-positive leukemia with unusually late onset, identified both TEL-AML1-positive and -negative colonies carrying a clonal T-cell receptor delta rearrangement, inferring the presence of clonal expansion before the occurrence of the t(12;21). In contrast, in a typical, early onset t(12;21)-positive leukemia, the t(12;21) appeared to be the first clonal event. In both leukemias, the t(12;21) occurred before recombination of variable, joining and diversity segments of the heavy chain gene VDJ.

Cysteine-directed cross-linking localizes regions of the human erythrocyte anion-exchange protein (AE1) relative to the dimeric interface

The human erythrocyte anion-exchanger isoform 1 (AE1) is a dimeric membrane protein that exchanges chloride for bicarbonate across the erythrocyte plasma membrane. Crystallographic studies suggest that the transmembrane anion channel lies at the interface between the two monomers, whereas kinetic analysis provides evidence that each monomer contains an anion channel. We have studied the structure-function relationship of residues at the dimeric interface of AE1 by cysteine-directed cross-linking. Single cysteine mutations were introduced in 16 positions of putative loop regions throughout AE1. The ability of these residues to be chemically cross-linked to their partner within the dimeric protein complex was assessed by mobility of the protein on immunoblots. Introduced cysteine residues in extracellular loops (ECs) 1-4 and intracellular loop 1 formed disulphide cross-linked dimers. Treatment with homobifunctional maleimide cross-linkers of different lengths (6, 10 and 16 A; 1 A identical with 0.1 nm) also cross-linked AE1 with introduced cysteines in EC5 and close to the start of transmembrane segment (TM) 1. On the basis of these data, tentative positional constraints of TMs 1-4 and 6 relative to the dimeric interface are proposed. Neither disulphide- nor maleimide-mediated cross-linking perturbed AE1 transport function, suggesting that loop-loop contacts across the dimeric interface are not primarily responsible for allosteric interactions between monomers within the functional dimeric protein complex.

Calculation of a subject-specific adaptive motion-correction factor for improved real-time navigator echo-gated magnetic resonance coronary angiography

There has been conflicting data in the literature regarding the use of wide navigator echo (NE) acceptance windows in combination with adaptive motion correction for magnetic resonance coronary angiography (MRCA). This in part may be due to the use of a fixed correction factor when applying the adaptive motion-correction algorithm, which may potentially result in miscorrection of the imaging slice in subjects whose correction factor differs widely from the mean. We have addressed this issue by measuring the superior/inferior correction factor in 25 subjects and assessing the effect of using a subject-specific correction factor (CFss) for MRCA in comparison with no adaptive motion correction (CF0) and erroneous adaptive motion correction with a correction factor of 1.0 (CF1). There was a wide variation in the correction factor between subjects (proximal right coronary artery, 0.49 +/- 0.15, range 0.20-0.70; proximal left coronary artery, mean 0.59 +/- 0.15, range 0.20-0.85). The subject-specific correction factor was accurately calculated from motion of the aortic root in the coronal plane between expiratory and inspiratory breathhold (correction factor calculated from coronal image versus correction factor calculated after localization of coronary arteries, r = 0.92, p < 0.001). MRCA image quality was improved using a subject-specific correction factor, for both a 6-mm NE acceptance window (CFss versus CF0, p = 0.008; CFss versus CF1, p = 0.02) and a 16-mm NE window (CFss versus CF0, p = 0.01; CFss versus CF1, p = 0.007). Furthermore, image quality was maintained between the two NE windows if the subjects-specific correction factor was used (6 versus 16 mm, p = 0.21), with an improvement in scan efficiency (6 versus 16 mm, 49 +/- 17% versus 81 +/- 22% respectively, p < 0.001). Thus, for adaptive motion correction to be implemented, a subject-specific correction factor should be used and calculated from simple coronal expiratory and inspiratory breathholds. For real-time NE-gated cardiac MR with adaptive motion correction, the NE window can be widened to reduce the acquisition period without loss of image quality.

Use of the intravascular contrast agent NC100150 injection in spin-echo and gradient-echo imaging of the heart

This is the first study of the intravascular iron oxide particle contrast agent, NC100150 Injection (Nycomed Imaging AS, Oslo, Norway, a part of Nycomed Amersham) in magnetic resonance imaging of the human heart. Eighteen healthy male volunteers were studied at both 0.5 and 1.5 T before and after the administration of NC100150 Injection. Transaxial spin-echo images were acquired at both field strengths, conventional gradient-echo cine images at 0.5 T, and breathhold Turbo-FLASH cine images at 1.5 T. Optimized cine imaging sequences were used postcontrast, with a high flip angle of 60-70 degrees. In the spin-echo images there was a significant reduction in the blood pool flow artifact at the level of the right atrium (0.5 T, 57%, p < 0.01; 1.5 T, 41%, p = 0.01) and the left ventricle (LV) (0.5 T, 45%, p = 0.01; 1.5 T, 45%, p < 0.01). In the conventional gradient-echo cines at 0.5 T, there was a significant increase in the LV blood pool and myocardial signal difference-to-noise ratio (SDNR) in the diastolic (56%, p = 0.01) and systolic (141%, p < 0.001) frames. There was also a significant increase in the signal intensity (SI) gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p < 0.001). At higher doses of NC100150 Injection (3 and 4 mg/kg), a rim of signal void around the LV blood pool was observed, perfectly defining the LV blood pool-myocardial border. In the Turbo-FLASH breathhold cines at 1.5 T, there was a significant increase in the LV blood pool-myocardial SDNR in the diastolic (221%, p < 0.001) and systolic (916%, p < 0.001) frames. Again, there was also a significant increase in the SI gradient at the LV blood pool-myocardial border in the diastolic and systolic frames (both p = 0.003). In conclusion, NC100150 Injection was given safely to 18 healthy subjects. Image quality and LV blood pool-myocardial definition were improved after the administration of NC100150 Injection. These improvements enable better spin-echo anatomical definition, better definition of myocardial wall motion, and should improve the capability of automated edge detection algorithms.

Chromosome instability syndromes

The chromosome instability syndromes, ataxia telangiectasia (A-T), Fanconi anaemia (FA) and Bloom syndrome (BS) have been known for many years. More recently Nijmegen breakage syndrome (NBS) and ataxia telangiectasia-like disorder (ATLD) have been identified. A-T, ATLD and NBS form a group of disorders all of which show very similar cellular features that result from the consequences of increased sensitivity to ionizing radiation (IR). They also share some clinical features, particularly A-T and ATLD, and all show an immunodeficiency. A-T and NBS both show a predisposition to lymphoid tumours. Fanconi anaemia can be caused by mutations in eight different genes, although the majority of mutations are accounted for by FANCA and FANCC. The very rare Bloom syndrome is caused by mutation in a single gene, BLM. An important feature which all of these disorders have in common is that the genes identified are involved in aspects of recombination repair of DNA damage.

Residual ataxia telangiectasia mutated protein function in cells from ataxia telangiectasia patients, with 5762ins137 and 7271T-->G mutations, showing a less severe phenotype

We have assessed several ataxia Telangiectasia mutated (ATM)-dependent functions in cells derived from ataxia telangiectasia patients, carrying either an ATM 5762ins137 splice site or a 7271T-->G missense mutation, with a less severe phenotype compared with the classical disorder. ATM kinase in vitro, from 5762ins137 cells, showed the same specific activity as ATM in normal cells, but the protein was present at low levels. In contrast, mutant ATM kinase activity in the 7271T-->G cells was only about 6% that of the activity in normal cells, although the level of mutant protein expressed was similar to normal cells. Phosphorylation of the DNA double strand break repair proteins Nbs1 and hMre11, following DNA damage, was observed in normal and 7271T-->G cells but was almost absent in both 5762ins137 and classical ataxia telangiectasia cells. The kinetics of p53 response was intermediate between normal and classical ataxia telangiectasia cells in both the 7271T-->G and 5762ins137 cells, but interestingly, c-Jun kinase activation following DNA damage was equally deficient in cell lines derived from all the ataxia telangiectasia patients. Our results indicate that levels of ATM kinase activity, but not induction of p53 or c-Jun kinase activity, in these cells correlate with the degree of neurological disorder in the patients.

Mutations in the sterol-sensing domain of Patched suggest a role for vesicular trafficking in Smoothened regulation

The tumor suppressor gene patched (ptc) encodes an approximately 140 kDa polytopic transmembrane protein [1-3] [corrected] that binds members of the Hedgehog (Hh) family of signaling proteins [4-6] [corrected] and regulates the activity of Smoothened (Smo), a G protein-coupled receptor-like protein essential for Hh signal transduction [7-9] [corrected]. Ptc contains a sterol-sensing domain (SSD) [10, 11] [corrected], a motif found in proteins implicated in the intracellular trafficking of cholesterol [12] [corrected], and/or other cargoes [13-15] [corrected]. Cholesterol plays a critical role in Hedgehog (Hh) signaling by facilitating the regulated secretion and sequestration of the Hh protein [16] [corrected], to which it is covalently coupled. In addition, cholesterol synthesis inhibitors block the ability of cells to respond to Hh [18, 19] [corrected], and this finding points to an additional requirement for the lipid in regulating downstream components of the Hh signaling pathway. Although the SSD of Ptc has been linked to both the sequestration of, and the cellular response to Hh [16, 20, 21] [corrected], definitive evidence for its function has so far been lacking. Here we describe the identification and characterization of two missense mutations in the SSD of Drosophila Ptc; strikingly, while both mutations abolish Smo repression, neither affects the ability of Ptc to interact with Hh. We speculate that Ptc may control Smo activity by regulating an intracellular trafficking process dependent upon the integrity of the SSD.

Experience with laparoscopic ultrasonography for defining tumour resectability in carcinoma of the pancreatic head and periampullary region

BACKGROUND

Computed tomography (CT) is currently the most widely available staging investigation for pancreatic tumours. However, the accuracy of CT for determining tumour resectability is variable and can be poor. Laparoscopic ultrasonography (LUS) is potentially a more accurate method for disease staging. The authors' experience of LUS for staging carcinoma of the pancreatic head and periampullary region is described.

METHODS

Fifty-one patients with potentially resectable pancreatic tumours defined at CT underwent further investigation with LUS. Twenty-seven patients subsequently had an open laparotomy. The evaluations of tumour resectability at CT and LUS were compared with the operative findings.

RESULTS

At LUS, 24 patients were considered to have resectable tumours, 21 non-resectable tumours and six patients were shown to have no pancreatic tumour mass. Twenty-two patients deemed to have a resectable tumour at LUS underwent surgery. Twenty patients were confirmed to have resectable disease and two patients had non-resectable disease. A further five patients underwent surgery. In all five the ultrasonographic diagnosis was confirmed at surgery (four patients with non-resectable disease and no pancreatic tumour in one patient). LUS prevented unnecessary extensive surgery in 53 per cent of patients. For the 22 patients who underwent surgery for potentially resectable disease, the positive predictive value of LUS for defining tumour resectability was 91 per cent.

CONCLUSION

LUS is an accurate additional investigation for defining tumour resectability and directing management in patients with potentially resectable carcinoma of the pancreatic head or periampullary region.

p53 dysfunction in B-cell chronic lymphocytic leukemia: inactivation of ATM as an alternative to TP53 mutation

The well-established association between TP53 mutations and adverse clinical outcome in a range of human cancers reflects the importance of p53 protein in regulating tumor-cell growth and survival. Although it is theoretically possible for p53 dysfunction to arise through mechanisms that do not involve TP53 mutation, such a phenomenon has not previously been demonstrated in a sporadic tumor. Here, we show that p53 dysfunction in B-cell chronic lymphocytic leukemia (CLL) can occur in the absence of TP53 mutation and that such dysfunction is associated with mutation of the gene encoding ATM, a kinase implicated in p53 activation. Forty-three patients with CLL were examined for p53 dysfunction, as detected by impaired up-regulation of p53 and of the p53-dependent protein p21(CIP1/WAF1) after exposure to ionizing radiation (IR). Thirty (70%) patients had normal p53 responses and underwent progressive IR-induced apoptosis. In 13 (30%) patients, p21 up-regulation was markedly impaired, indicating p53 dysfunction. Six (14%) of these patients with p53 dysfunction had increased baseline levels of p53, were found to have TP53 mutations, and were completely resistant to IR-induced apoptosis. In the other 7 (16%) patients with p53 dysfunction, IR-induced p53 up-regulation and apoptosis were markedly impaired, but baseline levels of p53 were not increased, and no TP53 mutations were detected. Each of these patients was found to have at least one ATM mutation, and a variable reduction in ATM protein was detected in all 4 patients examined. This is the first study to provide a direct demonstration that p53 dysfunction can arise in a sporadic tumor by a mechanism that does not involve TP53 mutation. (Blood. 2001;98:814-822)

trans-dominant inhibition of connexin-43 by mutant connexin-26: implications for dominant connexin disorders affecting epidermal differentiation

Dominant mutations of GJB2-encoding connexin-26 (Cx26) have pleiotropic effects, causing either hearing impairment (HI) alone or in association with palmoplantar keratoderma (PPK/HI). We examined a British family with the latter phenotype and identified a new dominant GJB2 mutation predicted to eliminate the amino acid residue E42 (ΔE42) in Cx26. To dissect the pathomechanisms that result in diverse phenotypes of dominant GJB2 mutations, we studied the effect of three Cx26 mutants (ΔE42, D66H and R75W) identified in individuals with PPK/HI, and another (W44C) present in individuals with non-syndromic HI on gap junctional intercellular communication. We expressed mutant Cx26 alone and together with the epidermal connexins Cx26, Cx37 and Cx43 in paired Xenopus oocytes, and measured the intercellular coupling by dual voltage clamping. Homotypic expression of each connexin as well as co-expression of wild-type (wt) Cx26/wtCx43 and wtCx26/wtCx37 yielded variable, yet robust, levels of channel activity. However, all four Cx26 mutants were functionally impaired and failed to induce intercellular coupling. When co-expressed with wtCx26, all four mutants suppressed the wtCx26 channel activity consistent with a dominant inhibitory effect. However, only those Cx26 mutants associated with a skin phenotype also significantly (P&lt;0.05) inhibited intercellular conductance of co-expressed wtCx43, indicating a direct interaction of mutant Cx26 units with wtCx43. These results demonstrate, for the first time, a trans-dominant negative effect of Cx26 mutants in vitro. Furthermore, they support a novel concept suggesting that the principal mechanism for manifestation of dominant GJB2 mutations in the skin is their dominant interference with the function of wtCx43. This assumption is further corroborated by our finding that Cx26 and Cx43 focally colocalize at gap junctional plaques in affected skin tissue of two carriers of ΔE42.

Ameloblastic fibrosarcoma of the mandible: report of two cases and review of the literature

Ameloblastic fibrosarcoma (AFS) is a rare malignant odontogenic tumour. To date, 60 well-documented cases have been published in the English-language literature. Two additional cases located in the posterior region of the mandible are reported. The relevant clinicopathological features of these cases, as well as those previously reported are discussed. Approximately two-thirds of AFS are malignant tumors de novo, with an average age of the affected patients being 22.9 years. This age is lower than the one observed in AFS developing from a pre-existent benign lesion (mean 33 years). Although regional and distant metastases are very infrequent, AFS is a locally aggressive lesion, with 23 (37%) of the reported cases having at least one recurrence; 12 patients (19.3%) died of the disease. Wide surgical excision with long-term follow-up remains the treatment of choice for this neoplasm.

hMRE11: genomic structure and a null mutation identified in a transcript protected from nonsense-mediated mRNA decay

We showed recently that mutation of the hMRE11 gene identified a new ataxia telangiectasia-like disorder (ATLD). In this report we describe the genomic organization of the hMRE11 gene and the analysis of a promoter region that appears to direct the divergent transcription of hMRE11 and the adjacent gene. The characterization of the genomic organization of the hMRE11 gene allowed us to determine the basis of an apparent null hMRE11 allele present in the mother and two patients in one of our two ATLD families. Polymorphic markers in the hMRE11 gene, including the promoter region, provided evidence that the mutated maternal allele was not deleted. An exon by exon search revealed the presence of a missense mutation in exon 15, the effect of which was to create a premature termination codon. Transcripts derived from the mutant allele were found to be subject to nonsense-mediated mRNA decay (NMD). Therefore, this allele was effectively null, because little if any mRNA from it was available for translation. The ATLD patients carrying this protein-truncating hMRE11 mutation have survived because the null allele they inherited from their mother is present with a missense mutation inherited from their father, which is expressed as normal levels of partially functional MRE11 protein. The mutation in the maternal hMRE11 allele of family 2 was also identified in a further unrelated Italian family with ATLD and also found to be subject to NMD.

Response to radioimmunotherapy correlates with tumor pO2 measured by EPR oximetry in human tumor xenografts

The efficacy of radiation treatment depends upon local oxygen concentration. We postulated that the variability in responsiveness of tumor xenografts to a fixed dose of radioimmunotherapy might be related to the tumor pO2 at the time that radioimmunotherapy was administered. We evaluated the growth of xenografts of CALU-3 tumors, a non-small cell lung carcinoma, in response to an 8.9-MBq dose of 131I-RS-7-anti-EGP-1 and correlated tumor growth rate with initial tumor pO2 measured by EPR oximetry. The greatest growth delay in response to radioimmunotherapy had the highest initial pO2, and the fastest-growing tumors had the lowest initial pO2. We then determined the dynamic effect of radioimmunotherapy on tumor pO2 by serial measurements of pO2 for 35 days after radioimmunotherapy. This information could be important for ascertaining the likelihood that a tumor will respond to additional doses as part of a multiple dose scheme. Serial tumor pO2 measurements may help identify a window of opportunity when the surviving tumor regions will be responsive to a second round of radioimmunotherapy or a second therapeutic modality such as chemotherapy or an anti-vascular agent. After radioimmunotherapy, there was an increase in tumor pO2 followed by a decrease below initial levels in most mice. Thus defined times may exist when a tumor is more or less radiosensitive after radioimmunotherapy.

Autosomal recessive cerebellar ataxia with oculomotor apraxia (ataxia-telangiectasia-like syndrome) is linked to chromosome 9q34

Ataxia with oculomotor apraxia (ataxia-telangiectasia-like syndrome [AOA]; MIM 208920) is an autosomal recessive disorder characterized by ataxia, oculomotor apraxia, and choreoathetosis. These neurological features resemble those of ataxia-telangiectasia (AT), but in AOA there are none of the extraneurological features of AT, such as immunodeficiency, neoplasia, chromosomal instability, or sensitivity to ionizing radiation. It is unclear whether these patients have a true disorder of chromosomal instability or a primary neurodegenerative syndrome, and it has not been possible to identify the defective gene in AOA, since the families have been too small for linkage analysis. We have identified a new family with AOA, and we show that the patients have no evidence of chromosomal instability or sensitivity to ionizing radiation, suggesting that AOA in this family is a true primary cerebellar ataxia. We have localized the disease gene, by linkage analysis and homozygosity mapping, to a 15.9-cM interval on chromosome 9q34. This work will ultimately allow the disease gene to be identified and its relevance to other types of autosomal recessive cerebellar ataxias to be determined.

Patched represses the Hedgehog signalling pathway by promoting modification of the Smoothened protein

Hedgehog (Hh) signalling plays a central role in many developmental processes in both vertebrates and invertebrates [1]. The multipass membrane-spanning proteins Patched (Ptc) [2-4] and Smoothened (Smo) [5-7] have been proposed to act as subunits of a putative Hh receptor complex. According to this view, Smo functions as the transducing subunit, the activity of which is blocked by a direct interaction with the ligand-binding subunit, Ptc [8]. Activation of the intracellular signalling pathway occurs when Hh binds to Ptc [8-11], an event assumed to release Smo from Ptc-mediated inhibition. Evidence for a physical interaction between Smo and Ptc is so far limited to studies of the vertebrate versions of these proteins when overexpressed in tissue culture systems [8,12]. To test this model, we have overexpressed the Drosophila Smo protein in vivo and found that increasing the levels of Smo protein per se was not sufficient for activation of the pathway. Immunohistochemical staining of wild-type and transgenic embryos revealed distinct patterns of Smo distribution, depending on which region of the protein was detected by the antibody. Our findings suggest that Smo is modified to yield a non-functional form and this modification is promoted by Ptc in a non-stoichiometric manner.

Coronary artery imaging in grown up congenital heart disease: complementary role of magnetic resonance and x-ray coronary angiography

BACKGROUND

There is a high incidence of anomalous coronary arteries in subjects with congenital heart disease. These abnormalities can be responsible for myocardial ischemia and sudden death or be damaged during surgical intervention. It can be difficult to define the proximal course of anomalous coronary arteries with the use of conventional x-ray coronary angiography. Magnetic resonance coronary angiography (MRCA) has been shown to be useful in the assessment of the 3-dimensional relationship between the coronary arteries and the great vessels in subjects with normal cardiac morphology but has not been used in patients with congenital heart disease.

METHODS AND RESULTS

Twenty-five adults with various congenital heart abnormalities were studied. X-ray coronary angiography and respiratory-gated MRCA were performed in all subjects. Coronary artery origin and proximal course were assessed for each imaging modality by separate, blinded investigators. Images were then compared, and a consensus diagnosis was reached. With the consensus readings for both magnetic resonance and x-ray coronary angiography, it was possible to identify the origin and course of the proximal coronary arteries in all 25 subjects: 16 with coronary anomalies and 9 with normal coronary arteries. Respiratory-gated MRCA had an accuracy of 92%, a sensitivity of 88%, and a specificity of 100% for the detection of abnormal coronary arteries. The MRCA results were more likely to agree with the consensus for definition of the proximal course of the coronary arteries (P<0.02).

CONCLUSIONS

For the assessment of anomalous coronary artery anatomy in patients with congenital heart disease, the use of the combination of MRCA with x-ray coronary angiography improves the definition of the proximal coronary artery course. MRCA provides correct spatial relationships, whereas x-ray angiography provides a view of the entire coronary length and its peripheral run-off. Furthermore, respiratory-gated MRCA can be performed without breath holding and with only limited subject cooperation.

A comparison between segmented k-space FLASH and interleaved spiral MR coronary angiography sequences

A direct comparison of segmented fast low-angle short (FLASH) imaging and interleaved spiral magnetic resonance coronary angiography (MRCA) during free respiration using navigator echo has been performed. MRCA images were acquired in 30 normal subjects and 15 patients with coronary artery disease (CAD). Images of the right coronary artery were acquired during free respiration using navigator echo gating for both a segmented k-space FLASH sequence (8 views/segment, segment duration 105 msec) and an interleaved spiral sequence (20 interleaves, spiral read-out period 19 msec). Image quality was scored by three independent blinded observers, and coronary artery signal-to-noise ratio (SNR) and coronary artery/epicardial fat contrast-to-noise ratio (CNR) were measured. There was a significant improvement in image quality when coronary images were acquired with the interleaved spiral sequence (spiral 2. 3 vs. FLASH 1.8; P = 0.002). This was associated with an increase in the coronary artery SNR (16.6 +/- 6.9 vs. 11.8 +/- 5.0; P < 0.001), the coronary artery/epicardial fat CNR (12.5 +/- 6.1 vs. 7.4 +/- 4.0, P < 0.001), and the image resolution (256 x 256 vs. 256 x 128). However, there was a 12% increase in acquisition time for the interleaved spiral sequence. Image quality, SNR, CNR, and resolution can be improved using an interleaved spiral sequence. These improvements are secondary to the intrinsic characteristics of spiral imaging and the short acquisition period, which reduces the effects of both cardiac and respiratory motion.

Phase ordering with automatic window selection (PAWS): a novel motion-resistant technique for 3D coronary imaging

Navigator acceptance imaging methods are hindered by the loss in scan efficiency which results from the changes in the breathing pattern of a subject over time. The diminishing variance algorithm (DVA), which does not use a predefined acceptance window, is less influenced by such changes. The use of phase ordering and weighting techniques has been shown to significantly improve image quality over nonordered window methods. However, the use of an acceptance window is inherent in all these techniques as a decision to accept or reject data must still be made. A technique is presented which is resistant to changes in breathing while allowing the use of phase ordering to provide effective motion artifact reduction in optimal time. The basic principle is described and illustrated for this automatic window-selection technique with in vitro results to demonstrate the feasibility of this method. Results of an in vivo study are also presented which demonstrate significant improvement in image quality over the DVA (p < 0.01) and hybrid-ordered phase encoding methods (p < 0.05).

Using language intensity to increase the success of a family intervention to protect children from ultraviolet radiation: predictions from language expectancy theory

BACKGROUND

Even though people are informed about skin cancer prevention, they do not always comply with prevention advice. From Language Expectancy Theory, it was predicted that messages with high language intensity would improve compliance with sun safety recommendations and that this effect would be enhanced with deductive argument style.

METHODS

Parents (N = 841) from a pediatric clinic and elementary schools received sun safety messages (newsletters, brochures, tip cards) by mail that varied in language intensity and logical style. Effects on attitudes and behavior were tested in a pretest-posttest factorial design.

RESULTS

As hypothesized, parents receiving messages with high- as opposed to low-intensity language complied more with sun safety advice. Messages with highly intense language were more persuasive when the arguments were formatted in a deductive style; low language intensity was more persuasive in inductively styled messages.

CONCLUSIONS

By carefully adjusting messages features, health professionals can obtain further compliance beyond that produced by educating people about health risks and creating favorable attitudes and self-efficacy expectations. Highly intense language may be a good general strategy in prevention messages and works better when conclusions and recommendations are offered explicitly to recipients, especially when advice is aimed at reducing their personal risk.

Clonal diversity of Ig and T-cell receptor gene rearrangements in childhood B-precursor acute lymphoblastic leukaemia

The majority of paediatric B precursor acute lymphoblastic leukaemias in children are derived from a single transformed haematopoietic cell with complete or partial VDJ recombination within the immunoglobulin heavy chain gene. A high frequency of patients also show rearrangements within TCRdelta and TCRgamma loci and in up to 40% of children there is an excess of immune system gene rearrangements compared with the number of identified alleles of immune system genes, suggesting the presence of multiple leukaemic subclones -clonal diversity. It has been observed by us and other investigators that in individual patients the pattern of immune system gene rearrangements often changes between presentation and relapse. In order to explore the possibility that clonal diversity plays a biological role during disease progression we optimised methods for subclone detection and analysed the prognostic significance of clonal diversity among 75 children with B precursor-ALL. Our results suggest that clonal diversity plays a role in disease progression as patients with oligoclonal disease showed a significantly shorter disease free survival than patients with monoclonal disease. This trend was of particular importance in the 'standard risk' group of ALL where aggressive disease could not be recognised by other means. In addition, generation of independent subclones from an early, non-rearranged tumour progenitor appears to be a common feature among leukaemias with aggressive clinical behaviour. We speculate on the type of genetic factors which may participate both in the generation of subclones and also in wider genomic instability and which are likely to be required for the aggressive clinical phenotype in children with ALL.

Long-term effects of language intensity in preventive messages on planned family solar protection

A series of sun safety messages containing highly intense language and deductive logical style achieved the most immediate compliance by parents, particularly when they intended to improve protection. Inductive messages were more successful when no intentions existed (D. B. Buller, Borland, & Burgoon, 1998; D. B. Buller et al., 2000). Interviewers recontacted 568 parents during the winter following message dissemination and assessed solar protection. A 2 (language intensity) x 2 (logical style) x 3 (behavioral intention) x 2 (person) mixed-model analysis of variance showed that parents receiving high-intensity, deductive messages reported the most improved solar protection and improvement was greatest when parents intended to improve protection. Over the long term, high language intensity may reinforce decisions to take preventive action and does not appear to provoke psychological reactance or resistance to these highly directive messages.

The DNA double-strand break repair gene hMRE11 is mutated in individuals with an ataxia-telangiectasia-like disorder

We show that hypomorphic mutations in hMRE11, but not in ATM, are present in certain individuals with an ataxia-telangiectasia-like disorder (ATLD). The cellular features resulting from these hMRE11 mutations are similar to those seen in A-T as well as NBS and include hypersensitivity to ionizing radiation, radioresistant DNA synthesis, and abrogation of ATM-dependent events, such as the activation of Jun kinase following exposure to gamma irradiation. Although the mutant hMre11 proteins retain some ability to interact with hRad50 and Nbs1, formation of ionizing radiation-induced hMre11 and Nbs1 foci was absent in hMRE11 mutant cells. These data demonstrate that ATM and the hMre11/hRad50/Nbs1 protein complex act in the same DNA damage response pathway and link hMre11 to the complex pathology of A-T.

The relationship between insulin, IGF-I and weight gain in cystic fibrosis

OBJECTIVE

In cystic fibrosis, reduced body mass is related to low levels of IGF-I and changes in the IGF binding proteins. Our aim was to determine whether these abnormalities are linked to pancreatic endocrine dysfunction.

PATIENTS AND DESIGN

We measured serum levels of insulin, IGF-I, IGFBP-I, IGFBP-3 and IGF bioactivity in 77 fasting subjects (43 male) mean age 9.6 years (range 2.99-17.98 years). Data were analysed with respect of body mass, puberty and stature and compared with control data established in the same laboratory.

RESULTS

The mean height standard deviation score (SDS (SD)) was -0.54 (0.97) and the body mass index SDS -0.24 (1.09). Both body mass index SDS (r = -0.40, P = 0.0003) and IGF-I SDS (r = - 0.32, P = 0.009) declined with age. Insulin levels were also low and correlated with IGF-I and IGFBP-3 (r = 0.42, P = 0.0004, and r = 0.45, P = 0.0002, respectively) whereas levels of IGFBP-I were inversely related to those of IGF-I and insulin (r = - 0.43, P = 0. 0004, r = - 0.52, P < 0.0001). IGF bioactivity was reduced and inversely related to IGFBP-I (r = - 0.31, P = 0.009). In multiple regression analysis, body mass index SDS was negatively related to age (P < 0.0001) and positively related to insulin and IGF-I (P = 0. 04, P = 0.03, respectively). Height SDS was correlated with IGF bioactivity (P = 0.003) and negatively with IGFBP-I (P = 0.01).

CONCLUSIONS

We conclude that progressive insulin deficiency may result in reduced IGF-I levels and IGF-bioactivity and may determine weight gain and statural growth in cystic fibrosis.

First-pass myocardial perfusion imaging and equilibrium signal changes using the intravascular contrast agent NC100150 injection

In this phase I clinical study, the new ultrasmall superparamagnetic iron oxide contrast agent, NC100150 Injection (Nycomed AS, Oslo, Norway, a part of Nycomed Amersham), was assessed for first-pass magnetic resonance myocardial perfusion studies and its ability to produce equilibrium signal changes, as a possible indicator of myocardial blood volume. Data were acquired in 18 healthy male volunteers at 0.5 T and 1.5 T. At both field strengths, first-pass studies using T1-weighted sequences were acquired. Long TE spin-echo echoplanar imaging (EPI) was used at 0.5 T and short TE fast low-angle shot (FLASH) imaging at 1.5 T. With both sequences, T1 effects dominated the images for low doses, and time intensity curves potentially suitable for perfusion analysis were generated. At higher doses, T2 and T2* effects were observed. At 1.5 T, these predominantly affected the blood pool signal; however, at 0.5 T the myocardial signal was also involved, reflecting the relative T2 and T2* sensitivity of the spin-echo EPI sequence as a result of the long TE and long readout window, respectively. Equilibrium changes were assessed at both field strengths using T1-weighted FLASH sequences and in addition at 1.5 T using T2*-weighted gradient-echo EPI. With the T1-weighted images at both field strengths, signal changes were observed in all subjects; however, no dose-response relationship could be shown. With the T2*-weighted EPI there was significantly lower signal (P < 0.05) with the 3 and 4 mg/kg doses than with the 2 mg/kg dose. In conclusion, NC100150 Injection is useful for first-pass myocardial perfusion using T1-weighted sequences; however, low doses in combination with short TE sequences are required to minimize sensitivity to T2* effects. Equilibrium signal changes can also be induced in the myocardium. More work is required to optimize the imaging sequences and dose of NC100150 Injection for first-pass studies and also to determine whether the equilibrium signal changes can be used to measure myocardial blood volume changes in ischemic heart disease.

Binding properties of the stilbene disulfonate sites on human erythrocyte AE1: kinetic, thermodynamic, and solid state deuterium NMR analyses

A novel stilbene disulfonate, 4-trimethylammonium-4'-isothiocyanostilbene-2,2'-disulfonic acid (TIDS), has been chemically synthesized, and the interaction of this probe with human erythrocyte anion exchanger (AE1) was characterized. Covalent labeling of intact erythrocytes by [N(+)((14)CH(3))(3)]TIDS revealed that specific modification of AE1 was achieved only after removal of other ligand binding sites by external trypsinization. Following proteolysis, (1.2 +/- 0.4) x 10(6) TIDS binding sites per erythrocyte could be blocked by prior treatment with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), a highly specific inhibitor of AE1. Inhibition of sulfate equilibrium exchange by TIDS in whole cells was described by a Hill coefficient of 1.10 +/- 0.06, which reduced to 0.51 +/- 0.01 following external trypsinization. The negative cooperativity of TIDS binding following external trypsinization suggests that trypsin-sensitive proteins modulate allosteric coupling between AE1 monomers. Thermodynamic analysis revealed that TIDS binding induces smaller conformational changes in AE1 than is observed following DIDS binding. The similar inhibitory potencies of both TIDS (IC(50) = 0.71 +/- 0.48 microM) and DIDS (IC(50) = 0.2 microM) imply that there is no correlation between the ability of stilbene disulfonates to arrest anion exchange function and the magnitude of ligand-induced conformational changes in AE1. Solid state (2)H NMR analysis of a [N(+)(CD(3))(3)]TIDS-AE1 complex in both unoriented and macroscopically oriented membranes revealed that large amplitude "wobbling" motions describe ligand dynamics. The data are consistent with a model where TIDS bound to AE1 is located exofacially in contact with the bulk aqueous phase.

Spin-label studies of lipid-protein interactions with reconstituted band 3, the human erythrocyte chloride-bicarbonate exchanger

Lipid-protein interactions in reconstituted band 3 preparations were investigated by using spin-labeled lipids in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Purified erythrocyte band 3 was reconstituted into egg phosphatidylcholine liposomes at high protein density with preservation predominantly of the dimeric state. Lipid-protein associations were revealed by the presence of a component in the EPR spectra that, when compared to spectra obtained from protein-free bilayers, indicated that lipid chain motions are restricted by interactions with the protein. From the fraction of the motionally restricted component obtained from the phosphatidylcholine spin-label, a value of 64 +/- 14 annular lipids per band 3 dimer was obtained. This agrees with a value of 62 for the number of lipids that may be accommodated around the electron density map of a band 3 dimer. Selectivity of various spin-labeled lipids for the protein revealed that androstanol had a lower affinity for the band 3 interface, whereas a distinct preference was observed for the negatively charged lipids phosphatidylglycerol and stearic acid over phosphatidylcholine. This preference for negatively charged lipids could not be screened by 1-M salt, indicating that electrostatic lipid-protein interactions are not dominant. Estimates of annular lipid exchange rates from measured acyl chain segmental motions suggested that the rate of exchange between bilayer and boundary lipids was approximately 10(6) s(-1), at least an order of magnitude slower than the rate of lipid lateral diffusion in protein-free bilayers.

Differences between normal subjects and patients with coronary artery disease for three different MR coronary angiography respiratory suppression techniques

A comparison between three magnetic resonance coronary angiography (MRCA) respiratory motion suppression techniques was performed for both normal subjects and patients with coronary artery disease (CAD). MRCA images were acquired in 17 normal subjects and 15 patients with CAD, using conventional breath-hold MRCA, navigator echo (NE)-guided breath-hold MRCA (LED feedback), and NE-gated MRCA during free respiration. Image quality, diaphragm registration, and total acquisition time were assessed. Overall, there was poor diaphragm registration for conventional breath-holding compared with free respiration (P < 0.001). CAD patients found it significantly more difficult to perform a steady breath-hold (P = 0.04) or attain the same diaphragm position over multiple breath-holds than normal subjects (P = 0.02). All normal subjects, but only 3 of the 15 CAD patients, were able to perform the LED feedback technique (P < 0.001). For normal subjects, image quality was similar between the three respiratory suppression techniques (P = 0.3), while for CAD patients there was an improvement in image quality, for images acquired during free respiration (breath-hold vs. free respiration, P < 0.01). There was no significant difference in the total acquisition times between the breath-hold and free respiration techniques (P = 0.2). There were substantial differences in the effectiveness of MRCA respiratory suppression techniques between normal subjects and CAD patients. In patients, only NE-gated MRCA performed well, requiring minimal cooperation with no increase in total acquisition time. Validation of NE-MRCA techniques should always be performed in patients, as well as normal subjects, to ensure correct evaluation of the technique for the target population.

Hydrodynamic properties of human erythrocyte band 3 solubilized in reduced Triton X-100

The oligomeric state and function of band 3, purified by sulfhydryl affinity chromatography in reduced Triton X-100, was investigated. Size exclusion high-performance liquid chromatography showed that a homogeneous population of band 3 dimers could be purified from whole erythrocyte membranes. The elution profile of band 3 purified from membranes that had been stripped of its cytoskeleton before solubilization was a broad single peak describing a heterogeneous population of oligomers with a mean Stokes radius of 100 A. Sedimentation velocity ultracentrifugation analysis confirmed particle heterogeneity and further showed monomer/dimer/tetramer equilibrium self-association. Whether the conversion of dimer to the form described by a Stokes radius of 100 A was initiated by removal of cytoskeletal components, alkali-induced changes in band 3 conformation, or alkali-induced loss of copurifying ligands remains unclear. After incubation at 20 degrees C for 24 h, both preparations of band 3 converted to a common form characterized by a mean Stokes radius of 114 A. This form of the protein, examined by equilibrium sedimentation ultracentrifugation, is able to self-associate reversibly, and the self-association can be described by a dimer/tetramer/hexamer model, although the presence of higher oligomers cannot be discounted. The ability of the different forms of the protein to bind stilbene disulfonates revealed that the dimer had the highest inhibitor binding affinity, and the form characterized by a mean Stokes radius of 114 A to have the lowest.

Automated monitoring of diaphragm end-expiratory position for real-time navigator echo MR coronary angiography

Real-time navigator echo (NE)-gated magnetic resonance coronary angiography (MRCA) during free respiration is now possible. However, the mean diaphragm end-expiratory position (DEEP) drifts over time, and this results in a reduction in scanning efficiency and increased artifacts due to the acquisition of data during periods of high diaphragm velocity. To address these problems, a diaphragm monitoring program that follows the mean DEEP over time has been developed. Fifteen subjects with ischemic heart disease underwent continuous NE monitoring of their diaphragm for 30 minutes. Using these diaphragm traces, theoretical MRCA scans were performed. Several diaphragm monitoring algorithms were developed and compared with the simplest case (a stationary 5 mm NE acceptance window placed around the mean DEEP, as measured by NE monitoring at the outset of the scan). An overall scan efficiency was calculated, and the number of completed scans where the mean DEEP lay within the NE acceptance window was recorded. Of the six algorithms considered, the most effective one monitored the mean DEEP and prospectively placed the upper limit of the NE acceptance window on this position for the subsequent acquisition. Using this algorithm in comparison with the simplest stationary scenario, both scan efficiency (47.9% vs. 38.5%, P = 0.01) and the number of completed scans where the mean DEEP lay within the NE acceptance window (71.2 vs. 30.3, P < 0.001) were improved. The implementation of such a monitoring algorithm, in combination with adaptive motion correction techniques, should improve overall scan efficiency while maintaining the end-expiratory position at the top end of the NE acceptance window, to reduce image artifacts.