Pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension in Cape Town, South Africa

Background

Pulmonary endarterectomy (PEA) is the only definitive and potentially curative therapy for chronic thromboembolic pulmonary hypertension (CTEPH), associated with impressive improvements in symptoms and haemodynamics. However, it is only offered at a few centres in South Africa. The characteristics and outcomes of patients undergoing PEA in Cape Town have not been reported previously.

Objectives

To assess the difference in World Health Organization functional class (WHO-FC) before and at least 6 weeks after surgery.

Methods

We interrogated the adult cardiothoracic surgery database at the University of Cape Town between December 2005 and April 2021 for patients undergoing PEA at Groote Schuur Hospital and a private hospital.

Results

A total of 32 patients underwent PEA, of whom 8 were excluded from the final analysis owing to incomplete data or a histological diagnosis other than CTEPH. The work-up of these patients for surgery was variable: all had a computed tomography pulmonary angiogram, 7 (29%) had a ventilation/perfusion scan, 5 (21%) underwent right heart catheterisation, and none had a pulmonary angiogram. The perioperative mortality was 4/24 (17%): 1 patient (4%) had a cardiac arrest on induction of anaesthesia, 2 patients (8%) died of postoperative pulmonary haemorrhage, and 1 patient (4%) died of septic complications in the intensive care unit. Among the survivors, the median (interquartile range) improvement in WHO-FC was 2 (1 - 3) classes (p=0.0004); 10/16 patients (63%) returned to a normal baseline (WHO-FC I).

Conclusion

Even in a low-volume centre, PEA is associated with significant improvements in WHO-FC and a return to a normal baseline in survivors.

Study synopsis

What the study adds. South African patients undergoing pulmonary endarterectomy (PEA) for chronic thromboembolic pulmonary hypertension (CTEPH) have a marked improvement in functional status, with many returning to a normal functional baseline. However, the small number of patients included in this study indicates that PEA is probably underutilised. Pre- and postoperative assessment is inconsistent, despite availability of established guidelines.Implications of the findings. More patients should be referred to specialist centres for assessment for this potentially curative procedure. Use of guidelines to standardise investigations and monitoring of patients with CTEPH may improve patient selection for surgery.

Protein analysis of purified respiratory syncytial virus particles reveals an important role for heat shock protein 90 in virus particle assembly

In this study, we used imaging and proteomics to identify the presence of virus-associated cellular proteins that may play a role in respiratory syncytial virus (RSV) maturation. Fluorescence microscopy of virus-infected cells revealed the presence of virus-induced cytoplasmic inclusion bodies and mature virus particles, the latter appearing as virus filaments. In situ electron tomography suggested that the virus filaments were complex structures that were able to package multiple copies of the virus genome. The virus particles were purified, and the protein content was analyzed by one-dimensional nano-LC MS/MS. In addition to all the major virus structural proteins, 25 cellular proteins were also detected, including proteins associated with the cortical actin network, energy pathways, and heat shock proteins (HSP70, HSC70, and HSP90). Representative actin-associated proteins, HSC70, and HSP90 were selected for further biological validation. The presence of beta-actin, filamin-1, cofilin-1, HSC70, and HSP90 in the virus preparation was confirmed by immunoblotting using relevant antibodies. Immunofluorescence microscopy of infected cells stained with antibodies against relevant virus and cellular proteins confirmed the presence of these cellular proteins in the virus filaments and inclusion bodies. The relevance of HSP90 to virus infection was examined using the specific inhibitors 17-N-Allylamino-17-demethoxygeldanamycin. Although virus protein expression was largely unaffected by these drugs, we noted that the formation of virus particles was inhibited, and virus transmission was impaired, suggesting an important role for HSP90 in virus maturation. This study highlights the utility of proteomics in facilitating both our understanding of the role that cellular proteins play during RSV maturation and, by extrapolation, the identification of new potential targets for antiviral therapy.

Clarification of ethanol-positive case using urine serotonin metabolite ratio

This paper intends to provide investigators with information useful in determining the presence of postmortem ethanol in fatal accidents and a case history of an accident that involved postmortem alcohol formation is presented. An ethanol-positive fatal case initially reported as being from ingestion was ultimately determined to be from postmortem ethanol production using the ratio of two serotonin metabolites found in urine. This case involved a transportation accident that could have resulted in additional hardships for the victim's family through loss of compensation and reputation.

Experimental Verification of Conformational Variation of Human Fatty Acid Synthase as Predicted by Normal Mode Analysis

Fatty acid synthase (FAS) is a 550 kDa homodimeric enzyme with multiple functional and structural domains. Normal mode analysis of a previously determined 19 A structure of FAS suggested that this enzyme might assume different conformational states with several distinct hinge movements. We have used a simultaneous multiple-model refinement method to search for the presence of the structural conformers from the electron images of FAS. We have demonstrated that the resulting models observed in the electron images are consistent with the predicted conformational changes. This technique demonstrates the potential of the combination of normal mode analysis with multiple model refinement to elucidate the multiple conformations of flexible proteins. Since each of these structures is based on a more homogeneous particle set, this technique has the potential, provided that sufficient references are used, to improve the resolution of the final reconstructions of single particles from electron cryomicroscopy.

Assessing socio-economic factors in relation to stigmatization, impairment status, and selection for socio-economic rehabilitation: a 1-year cohort of new leprosy cases in north Bangladesh

The current leprosy elimination strategy focuses almost exclusively on delivery of leprosy diagnostic services and multi-drug treatment (MDT). However, the specific problems of people newly diagnosed with leprosy or cured with MDT primarily relate to impairment of nerve function and social and economic consequences of the diagnosis of leprosy. This study was carried out to investigate the relation between socio-economic factors and the development of nerve impairments and stigma. In addition the relation between socio-economic factors and selection for socio-economic assistance was studied. The study population was a cohort of 2364 newly diagnosed people with leprosy in rural Bangladesh in 1996, including 42.5% women, with an overall mean age of 31.4 years. Three hundred and sixty people (15.2%) had WHO grade 1 or 2 disability identified at diagnosis, and 50 (2.1%) had stigma identified on interview at home visit conducted within one month of diagnosis. One hundred and eighty-eight people (8%) were selected for specific assistance for rehabilitation, primarily interest-free loans for income generating activities or vocational training. Factors independently associated with WHO grade 1 or 2 disability at diagnosis were multibacillary (MB) classification, adult status, and manual occupations. Smear positivity, female sex, and the presence of dependents were associated with an increase in the experience of stigma. The presence of nerve impairments and stigma, as well as several indices of poverty were clearly associated with selection for inclusion in an integrated program for socio-economic assistance. An increased focus by leprosy services on the socio-economic factors associated with poorer physical and social outcomes is recommended. Where adequate finances and trained staff are available, efforts could be made to identify those at higher risk of poor outcomes, and to provide or to mobilize appropriately targeted socio-economic interventions.

Long-term prognosis of children with papillary thyroid cancer presenting with pulmonary metastases

Background

Papillary thyroid cancer (PTC) has a generally favourable prognosis, but elderly patients with distant metastases or extracapsular invasion fair poorly. In small studies with short follow-up, young patients presenting with such extracapsular invasion and pulmonary metastases have faired well. This retrospective study was undertaken to clarify the long-term prognosis of such patients with advanced PTC.

Methods

Twenty-one children and young adults (median age 14 (range 6–20) years) presenting with PTC and pulmonary metastases were treated at a single institution between 1947 and 1998. Mean maximal tumour diameter was 4·65 cm. Initial surgical treatment consisted of total thyroidectomy (n = 16), subtotal thyroidectomy (n = 4) and isthmectomy (n = 1), coupled with a variety of lymph node dissections (n = 20). After operation, 19 patients were treated with ablative and incremental doses of iodine-131 until disease free. All patients were placed on suppressive thyroid hormone after operation. Mean length of follow-up was 21 years (range 3 months to 47 years). Follow-up was less than 3 years in four patients. All patients have undergone post-treatment radionucleotide and radiological evaluation.

Results

Nine of the 21 patients developed recurrent disease. The risk of recurrence at 5 years was 39 (95 per cent confidence interval 14–57) per cent. Eight had cervical lymph node recurrence and no patient developed recurrent pulmonary disease. All patients with identifiable recurrent disease underwent selective lymph node resection, which involved multiple resections in four. At follow-up, 18 patients remain completely free of disease, one patient has recurrent cervical node disease and two patients have died. The disease-free survival at 5 years was 95 (95 per cent confidence interval 86–100) per cent. Cause-specific death occurred in a single patient who died from extensive local disease at age 29 years after 12 years of multiple cervical lymph node recurrences.

Conclusion

A stepwise treatment approach including total thyroidectomy, high-dose iodine-131 treatment and early surgical reintervention for suspected local recurrent disease allows long-term survival and frequent ‘cure’ for young patients with PTC and concomitant pulmonary metastases.

Domain movements in human fatty acid synthase by quantized elastic deformational model

This paper reports the results of applying a computational method called the quantized elastic deformational model, to the determination of conformational flexibility of the supermolecular complex of human fatty acid synthase. The essence of this method is the ability to model large-scale conformational changes such as domain movements by treating the protein as an elastic object without the knowledge of protein primary sequence and atomic coordinates. The calculation was based on the electron density maps of the synthase at 19 A. The results suggest that the synthase is a very flexible molecule. Two types of flexible hinges in the structure were identified. One is an intersubunit hinge formed by the intersubunit connection and the other is an intrasubunit hinge located between domains I and II. Despite the fact that the dimeric synthase has a chemically symmetric structure, large domain movements around the hinge region occur in various directions and allow the molecule to adopt a wide range of conformations. These domain movements are likely to be important in facilitating and regulating the entire palmitate synthesis by coordinating the communication between components of the molecule, for instance, adjusting the distance between various active sites inside the catalytic reaction center. Finally, the ability to describe protein motions of a supermolecular complex, without the information of protein sequence and atomic coordinates, is a major advance in computational modeling of protein dynamics. The method provides an unprecedented ability to model protein motions at such a low resolution of structure.

Quaternary structure of human fatty acid synthase by electron cryomicroscopy

We present the first three-dimensional reconstruction of human fatty acid synthase obtained by electron cryomicroscopy and single-particle image processing. The structure shows that the synthase is composed of two monomers, arranged in an antiparallel orientation, which is consistent with biochemical data. The monomers are connected to each other at their middle by a bridge of density, a site proposed to be the combination of the interdomain regions of the two monomers. Each monomer subunit appears to be subdivided into three structural domains. With this reconstruction of the synthase, we propose a location for the enzyme's two fatty acid synthesis sites.

Limbic abnormalities in affective processing by criminal psychopaths as revealed by functional magnetic resonance imaging

BACKGROUND

Psychopathy is a complex personality disorder of unknown etiology. Central to the disorder are anomalies or difficulties in affective processing.

METHODS

Functional magnetic resonance imaging was used to elucidate the neurobiological correlates of these anomalies in criminal psychopaths during performance of an affective memory task.

RESULTS

Compared with criminal nonpsychopaths and noncriminal control participants, criminal psychopaths showed significantly less affect-related activity in the amygdala/hippocampal formation, parahippocampal gyrus, ventral striatum, and in the anterior and posterior cingulate gyri. Psychopathic criminals also showed evidence of overactivation in the bilateral fronto-temporal cortex for processing affective stimuli.

CONCLUSIONS

These data suggest that the affective abnormalities so often observed in psychopathic offenders may be linked to deficient or weakened input from limbic structures.

Biocor No- React stentless aortic valve--short-term results

OBJECTIVES

Short-term results of the bioprosthetic Biocor No-React composite porcine stentless aortic valve (Biocor Industria e Pesquisas LTDA, Belo Horizonte, Brazil) implanted in patients in whom anticoagulation was thought to be contraindicated or expected to be non-compliant.

METHODS

Retrospective review of 52 consecutive prospective patients in whom this valve was implanted, between September 1994 and May 1998.

RESULTS

Average age was 44 +/- 17 years; 75% of patients were operated on for rheumatic heart disease and combined procedures were done in 40% of cases. Early mortality was 5.8%, and related to pre-operative ejection fraction ( P < 0.03), New York Heart Association (NYHA) class (P < 0.01), and bacterial endocarditis (P < 0.04). On discharge, 84% of survivors were in NYHA class I and 16% in class II. The average postoperative prosthetic valve peak gradient on echocardiography was 19.9 +/- 11 mmHg and was related to pre-operative ejection fraction and smaller valve sizes. Postoperative residual trivial or mild aortic regurgitation was seen in 19 patients (36.6%), resolved on follow-up in 10 cases, and did not correlate with structural deterioration, re-operation, mortality, or widening of the non-coronary sinus. The non-coronary aortic sinus was widened on closure, because of perceived crowding of the adjacent stentless valve commisures, in 52% of cases. This was thought to be related to the use of an oblique as opposed to transverse aortotomy. Patient survival, inclusive of operative deaths, was 88.5%, and event-free survival was 80.0% at 4 years.

CONCLUSION

The short-term results of this stentless aortic valve in a young predominantly third-world population group are acceptable, and appear to be superior to the results for mechanical valves in a similar patient group. We would recommend a transverse aortotomy above the sinotubular ridge to be the more appropriate aortotomy incision when using stentless aortic valves.

Report of the Xenotransplantation Advisory Committee of the International Society for Heart and Lung Transplantation: the present status of xenotransplantation and its potential role in the treatment of end-stage cardiac and pulmonary diseases

An urgent and steadily increasing need exists world-wide for a greater supply of donor thoracic organs. Xenotransplantation offers the possibility of an unlimited supply of hearts and lungs that could be available electively when required. However, anti-body- mediated mechanisms cause the rejection of pig organs transplanted into non-human primates, and these mechanisms provide major immunologic barriers that have not yet been overcome. Having reviewed the literature on xenotransplantation, we present a number of conclusions on its present status with regard to thoracic organs, and we make a number of recommendations relating to eventual clinical trials. Although pig hearts have functioned in heterotopic sites in non-human primates for periods of several weeks, median survival of orthotopically transplanted hearts is currently ,1 month. No transplanted pig lung has functioned for even 24 hours. Current experimental results indicate that a clinical trial would be premature. A potential risk exists, hitherto undetermined, of transferring infectious organisms along with the donor pig organ to the recipient, and possibly to other members of the community. A clinical trial of xeno-transplantation should not be undertaken until experts in microbiology and the relevant regulatory authorities consider this risk to be minimal. A clinical trial should be considered when approximately 60% survival of life-supporting pig organs in non-human primates has been achieved for a minimum of 3 months, with at least 10 animals surviving for this minimum period. Furthermore, evidence should suggest that longer survival (.6 months) can be achieved. These results should be achieved in the absence of life-threatening complications caused by the immunosuppressive regimen used. The relationship between the presence of anti-HLA antibody and anti-pig antibody and their cross-reactivity, and the outcome of pig-organ xenotransplantation in recipients previously sensitized to HLA antigens require further investigation. We recommend that the patients who initially enter into a clinical trial of cardiac xenotransplantation be unacceptable for allotransplantation, or acceptable for allotransplantation but unlikely to survive until a human cadaveric organ becomes available, and in whom mechanical assist-device bridging is not possible. National bodies that have wide-reaching government-backed control over all aspects of the trials should regulate the initial clinical trial and all subsequent clinical xenotransplantation procedures for the foreseeable future. We recommend coordination and monitoring of these trials through an international body, such as the International Society for Heart and Lung Transplantation, and setting up a registry to record and widely disperse the results of these trials. Xenotransplantation has the potential to solve the problem of donor-organ supply, and therefore research in this field should be actively encouraged and supported.

Transseptal puncture guided by intracardiac echocardiography during percutaneous transvenous mitral commissurotomy in patients with distorted anatomy of the fossa ovalis

Positioning of the transseptal needle during percutaneous transvenous mitral commissurotomy (PTMV) can become a difficult and risky procedure when distortion of the interatrial septum exists. We present two cases where intracardiac echocardiography (ICE) facilitated the transseptal puncture in the presence of bulging of the fossa ovalis into the right atrium.

Ischemic mitral valve repair surgery

BACKGROUND AND AIM OF THE STUDY

The management of concomitant moderate or severe ischemic mitral regurgitation in the presence of ischemic heart disease is important for long-term prognosis. Mitral repair by either a suture or ring annuloplasty method has been advocated, although clear superiority of either method has not been established.

METHODS

Combined coronary artery bypass and mitral valve surgery for ischemic mitral incompetence was performed on 68 consecutive patients between January 1996 and December 1998. The outcome in 63 of these patients (35 females, 28 males) who underwent mitral valve repair was reviewed.

RESULTS

Average patient age was 61+/-9.4 years (range: 39-81 years). Average left ventricular ejection fraction (LVEF) was 42.1%; a suture annuloplasty was used in 84% and a ring in 16%. The average number of distal anastomoses was 3.9+/-1.1 (range: 1-6) and aortic cross-clamp time was 131+/-35 min (range: 58-238 min). Operative mortality rate (<30 days or in-hospital) was 12.7% and only requirement for intra-aortic balloon pumping either before or during surgery (21%) was predictive (p<0.05). On discharge, 98.2% of patients were in NYHA class I or II. Follow up (range: 1-35 months) was complete in 95% of cases. Moderate mitral regurgitation on discharge occurred in nine patients and was not related to the type of annuloplasty. Predictive risk factors were preoperative severe mitral regurgitation (p<0.04), poor LVEF (p = 0.05), and was predictive of deterioration of NYHA class (p<0.02), progression of regurgitation (p<0.05), and poor outcome (p<0.01). Poor outcome was also related to surgeon's experience. Structural valvular deterioration occurred in 21.8% of operative survivors, and there was one reoperation and four late deaths. The survival rate (including operative deaths) at 35 months was 68.3 +/- 13.1%, and event-free survival rate (no mortality, reoperation or angina) 65.2+/-6.2%.

CONCLUSIONS

The type of annuloplasty used did not influence outcome. The risk of structural mitral valve dysfunction on follow up was related to severe preoperative mitral regurgitation, poor LVEF, surgeon's experience, and was predictive of poor outcome.

Semantic and affective processing in psychopaths: an event-related potential (ERP) study

We tested the hypothesis that psychopathy is associated with abnormal processing of semantic and affective verbal information. In Task 1, a lexical decision task, and in Task 2, a word identification task, participants responded faster to concrete than to abstract words. In Task 2, psychopaths made more errors identifying abstract words than concrete words. In Task 3, a word identification task, participants responded faster to positive than to negative words. In all three tasks, nonpsychopaths showed the expected event-related potential (ERP) differentiation between word stimuli, whereas psychopaths did not. In each task, the ERPs of the psychopaths included a large centrofrontal negative-going wave (N350); this wave was absent or very small in the nonpsychopaths. The interpretation and significance of these differences are discussed.

Recombinant immunotoxins directed against the c-erb-2/HER2/neu oncogene product: in vitro cytotoxicity, pharmacokinetics, and in vivo efficacy studies in xenograft models

TAB-250 and BACH-250 are murine and human chimeric antibodies directed at the extracellular domain of the gp185c-erb-2 (HER2/neu) growth factor receptor overexpressed in a variety of tumor types, including ovarian and breast carcinoma. The ribosome-inhibiting plant toxin gelonin (rGel) was chemically coupled to both antibodies, and the resulting immunotoxins were purified and tested in vitro against human tumor cells expressing various levels of HER-2/neu and in vivo against human tumor xenograft models. The binding of both BACH-250 and BACH-250/rGel conjugate to target cells was essentially equivalent. Against SKOV-3 cells, the IC50 of BACH-250/rGel was 97 pM (17 ng/ml), whereas BACH-250 and rGel alone showed no cytotoxic effects. There was a clear correlation between expression levels of HER-2/neu and cytoimmunotoxin. Tissue distribution studies showed that the antibody and immunotoxin both concentrate 2-10-fold higher in tumors than in normal tissues, with optimal tumor uptake occurring 48-96 h after administration. Plasma clearance curves for BACH-250 and BACH-250/rGel showed terminal-phase half-lives of 26 and 72 h, respectively. In athymic mice bearing s.c. or i.p. SKOV-3 tumors, immunotoxin treatment slowed tumor growth by 99 and 94 % at days 35 and 49 after implantation, respectively, and lengthened the median survival by 40% (from 30 to 50 days) in mice bearing lethal i.p. tumors. We conclude that clinical development of BACH-250/rGel may be warranted in patients with HER2/neu-expressing malignancies.

Homologue scanning mutagenesis of heregulin reveals receptor specific binding epitopes

The EGF domain of heregulin has all the receptor binding characteristics of full-length heregulin and has strong homology to the ligands for erbB-1. Despite this, it does not bind erbB-1 but instead binds erbB-3 and erbB-4. The sequence similarity between HRG and the erbB-1 ligands suggest that a few residues are responsible for receptor binding specificity. To determine the sequences involved in receptor binding, we performed homologue scanning mutagenesis on the EGF domain of HRGalpha using sequences of TGFalpha or EGF. We found three sets of mutations in the N-terminal subdomain that were responsible for receptor binding specificity. Mutations in the C-terminal subdomain affected the binding affinity, but did appear to confer any specificity.

Mistaken angiographic diagnosis of traumatic aorto-atrial fistula

A case of angiographically occult traumatic aorto-caval fistula masquerading as aorto-right atrial fistula is presented. The importance of angiographic vigilance in the imaging of arterio-venous fistula is emphasized.

Reduction of charging in protein electron cryomicroscopy

Charging causes a loss of resolution in electron cryomicroscopy with biological specimens prepared without a continuous carbon support film. Thin conductive films were deposited onto catalase crystals prepared across holes using ion-beam sputtering and thermal evaporation and evaluated for the effectiveness of charge reduction. Deposits applied by ion-beam sputtering reduced charging but concurrently resulted in structural damage. Coatings applied by thermal evaporation also reduced charging, and preserved the specimen structure beyond 5 A resolution as judged from electron diffraction patterns and images of glucose-embedded catalase crystals tilted to 45 degrees in the microscope. This study demonstrates for the first time the feasibility of obtaining high-resolution data from unstained, unsupported protein crystals with a conductive surface coating.

Electron crystallographic analysis of two-dimensional streptavidin crystals coordinated to metal-chelated lipid monolayers

Coordination of individual histidine residues located on a protein surface to metal-chelated lipid monolayers is a potentially general method for crystallizing proteins in two dimensions. It was shown recently by Brewster angle microscopy (BAM) that the model protein streptavidin binds via its surface histidines to Cu-DOIDA lipid monolayers, and aggregates into regularly shaped domains that have the appearance of crystals. We have used electron microscopy to confirm that the domains are indeed crystalline with lattice parameters similar to those of the same protein crystallized beneath biotinylated lipid monolayers. Although BAM demonstrates that the two-dimensional protein crystals grown via metal chelation are distinct from the biotin-bound crystals in both microscopic shape and thermodynamic behavior, the two crystal types show similar density projections and the same plane group symmetry.

Negative cooperativity between alpha 3 beta 1 and alpha 2 beta 1 integrins in human mammary carcinoma MDA MB 231 cells

The alpha 3 beta 1 integrin has been implicated as a receptor for several matrix components, including collagen, fibronectin, and laminins. The function of alpha 3 beta 1 seems to be very versatile involving cell adhesion to or migration on ECM, establishment of cell-cell contacts in aggregates, as well as linkage to intracellular tyrosine phosphorylation cascades. Here we report a strong induction of attachment of alpha 3 beta 1 integrin expressing human breast carcinoma cell line MDA MB 231 to matrix proteins by two alpha 3 integrin subunit function-blocking monoclonal antibodies (P1B5 and ASC-1). In contrast, stimulation of adhesion to ECM by inhibitory alpha 3 integrin-specific antibodies was not observed in the alpha 3 beta 1 integrin-expressing nonmalignant human mammary epithelial cell line MCF-10A or the human breast carcinoma cell line MDA MB 468 that expressed relatively low amounts of alpha 3 beta 1 integrin at the cell surface. This increase was specific for collagens and not observed on fibronectin or laminin. Physiological concentrations of bivalent cations were not required. MAb P1B5 did not induce homotypic aggregation of MDA MB 231 cells. The P1B5-induced increase in cell attachment to collagens could be prevented but not reduced below control levels by blocking mAb to the alpha 2 integrin subunit. Function blocking anti-alpha 5 integrin subunit mAb was without effect while anti-beta 1-mAb completely abolished adhesion. Our data indicate that negative cooperativity between integrins results in transdominant inhibition of alpha 2 beta 1 function by alpha 3 beta 1 in human MDA MB 231 but not MDA MB 468 tumor cells or nonmalignant MCF-10A cells.

Evaluation of charging on macromolecules in electron cryomicroscopy

We describe procedures to assess charging of biological specimens under electron irradiation in an electron cryomicroscope. Charging can be observed by an expansion of the illuminating beam, blurring of electron diffraction patterns and by beam "footprints" on the specimen. Discharging can also be seen in the defocused electron diffraction mode. We investigated the influence of a variety of factors on the magnitude and visibility of charging. A reduction of charging is noticed when part of the adjacent carbon film is included in the irradiated specimen area.

Interaction between panel reactive antibodies, auto- and cold reactive antibodies, and a positive B cell cross-match in renal and cardiac allograft survival

We analyzed the influence on allograft survival of pretransplant panel reactive antibodies (PRA) < 10%, PRA > 10%, autoantibodies, cold antibodies and a positive B cell crossmatch in 807 renal and 237 cardiac transplant recipients. Donors and recipients were predominantly of mixed ancestry (Khoi, San, Xhosa and Caucasoid). Log rank analysis showed that PRA < 10%, cold antibodies, and a positive B cell cross-match did not influence allograft survival. Autoantibodies were present only in renal recipients; they appeared to have a beneficial effect on allograft survival (P = 0.06). PRA > 10% appeared to have a detrimental effect on allograft survival in both renal (P = 0.07) and cardiac (P = 0.06) recipients. Since autoantibodies and PRA > 10% had opposing effects, the results of renal recipients were reanalyzed after omission of the recipients with autoantibodies and coexisting PRA > 10%. This resulted in augmentation of the protective effect for autoantibodies (P = 0.027) and of the detrimental effect for PRA > 10% (P = 0.020). Two-year survival curves showed that when autoantibodies coexisted with PRA > 10%, the long term, but not the short-term, detrimental effect of PRA > 10% was attenuated. Patients with a positive B cell cross-match clustered in the PRA > 10% group in both renal (PRA negative vs. PRA < 10%; P = 0.0251; PRA < 10% vs. PRA > 10%: P = 0.0011) and cardiac (PRA negative vs. PRA > 10%: P = 0.0085) recipients. We conclude that PRA > 10% is the best indicator to identify recipients at high risk for rejection, and that the influence of antibodies on graft survival can not reliably be established without taking coexisting antibodies into account.

Pulmonary artery banding: adequacy and long-term outcome

OBJECTIVE

Pulmonary artery banding remains a palliative option for patients with congenital heart disease and excessive pulmonary blood flow, if there is unfavourable anatomy or frail condition. In contrast to more developed countries, our patients at Red Cross Children's Hospital, Cape Town, often present to medical services late and in poor nutritional condition. We retrospectively reviewed patients undergoing pulmonary artery banding to determine major variables that influenced long-term outcome.

METHODS

In a 10-year period ending June 1992, 135 consecutive patients underwent pulmonary artery banding; 89 with ventricular septal defect type non-mixing disorders, and 46 with mixing or complex disorders. The median age was 3.0 months and weight 3.5 kg with 74.8% of patients weighing less than the third percentile (NCHS adapted), and 39.3% had an additional serious medical illness.

RESULTS

Pulmonary banding mortality was 8.1%, and was higher in neonates (22.2%), P = 0.04) but was not related to congenital disorder, associated medical illness, or associated coarctation or interrupted aortic arch. The pulmonary band was inadequate at follow-up in 28.9%, which occurred more commonly if banding was necessary before 3 months of age (41.5%, P = 0.003) but was not related to weight, congenital disorder or associated respiratory infection. Sixty patients (44.4%) have now proceeded to definitive repair with a mortality of 23.3%, which was increased if the pulmonary band was inadequate at the time of definitive repair (44.4%: P = 0.02), but was not related to the congenital disorder.

CONCLUSIONS

An inadequate pulmonary artery band adversely affects outcome and demands further aggressive management prior to definitive repair.

Comparison of induction chemotherapy before radiotherapy with radiotherapy only in patients with locally advanced squamous cell carcinoma of the lung. The Swedish Lung Cancer Study Group

The aim of this randomised trial was to investigate the effect of induction chemotherapy before radiotherapy on survival in 302 patients with non-resectable squamous cell carcinoma of the lung. Radiotherapy, 56 Gy to the chest, was given to 154 patients and combined treatment, with chemotherapy preceding the radiotherapy, to 148 patients. Chemotherapy consisted of three courses of cisplatin (120 mg/m2) and etoposide (100 mg/m2 i.v. for 3 days) administered every fourth week. Median survival was 10.5 months in the radiotherapy arm and 11 months in the combined treatment arm. The 2-year survival rate was 17% in the radiotherapy arm and 21% in the combined treatment arm. Addition of chemotherapy seemed to significantly improve survival, according to the Cox multivariate analysis (P = 0.04), but as only a trend according to life-table analysis (P = 0.11). Chemotherapy also accomplished a trend towards improved local control (P = 0.08) and towards decreased metastatic disease (P = 0.10). 2 patients in the combined treatment arm, but none in the radiotherapy arm, died from toxicity. The conclusion was that the value of the chemotherapy used in this study was very modest, but the results strongly support further research for more efficient drugs and combinations.

Enteroscopy with enteroclysis

The authors conclude that their experiences support the conclusion that the combination of enteroscopy and enterocysis is safe and offers quality small bowel examinations in a more comfortable and convenient single diagnostic setting. Although enteroclysis has identified bleeding sources in only 8% of patients who underwent this study, other lesions than angiodysplasia were confidently excluded in the remainder of patients. The combined procedure is well tolerated in the outpatient setting, more comfortable, and safer by decreasing radiation exposures than enteroclysis alone. Use of small bowel enteroscopy at an earlier stage in the evaluation of patients with obscure gastrointestinal bleeding increases cost effectiveness without compromising quality.

Performance of a slow-scan CCD camera for macromolecular imaging in a 400 kV electron cryomicroscope

The feasibility and limitations of a 1024 x 1024 slow-scan charge-coupled device (CCD) camera were evaluated for imaging in a 400kV electron cryomicroscope. Catalase crystals and amorphous carbon film were used as test specimens. Using catalase crystals, it was found that the finite (24 microns) pixel size of the slow-scan CCD camera governs the ultimate resolution in the acquired images. For instance, spot-scan images of ice-embedded catalase crystals showed resolutions of 8 A and 4 A at effective magnifications of 67,000 x and 132,000 x, respectively. Using an amorphous carbon film, the damping effect of the modulation transfer function (MTF) of the slow-scan CCD camera on the specimen's Fourier spectrum relative to that of the photographic film was evaluated. The MTF of the slow-scan CCD camera fell off more rapidly compared to that of the photographic film and reached the value of 0.2 at the Nyquist frequency. Despite this attenuation, the signal-to-noise ratio of the CCD data, as determined from reflections of negatively-stained catalase crystals, was found to decrease to approximately 50% of that of photographic film data. The phases computed from images of the same negatively-stained catalase crystals recorded consecutively on both the slow-scan CCD camera and photographic film were found to be comparable to each other within 12 degrees. Ways of minimizing the effect of the MTF of the slow-scan CCD camera on the acquired images are also presented.

Acute traumatic rupture of the thoracic aorta. A comparison of techniques

Twenty-eight patients were treated for acute blunt thoracic aortic rupture at Groote Schuur Hospital between January 1984 and March 1994. Aortic arch ruptures occurred in 2 patients and were successfully repaired by means of hypothermic circulatory arrest. Descending aortic ruptures were repaired more safely by insertion of an interposition graft as opposed to direct suture reapproximation, and with the aid of partial heparinless bypass as opposed to simple aortic cross-clamping.

Processing of electron diffraction patterns acquired on a slow-scan CCD camera

We have developed two software packages for the processing of electron diffraction patterns acquired on a slow-scan CCD camera. Automated indexing and processing of these electron diffraction patterns is possible using a program called AUTO. To obtain a set of reliable reflections, AUTO applies a number of corrections, which are necessary due to the acquisition of the patterns with a slow-scan CCD camera. To index and process unknown lattices in electron diffraction patterns obtained from, for instance, a new protein or a new crystal form, an interactive program called EDP is available. It supports indexing in an interactive manner through a graphical user interface. Processing of the electron diffraction pattern is done using a script created by EDP. Both packages run on UNIX platforms, with EDP requiring the X Window System.

Applications of a slow-scan CCD camera in protein electron crystallography

A Gatan 1024 x 1024 slow-scan charge-coupled device (CCD) camera has been interfaced to a JEOL4000EX electron cryomicroscope and explored for its usefulness in the electron crystallographic analysis of thin, glucose-embedded crystals of crotoxin complex kept at -125 degrees C. We show that the camera allows for an on-line assessment of the crystals' crystallinity, flatness, and thickness. Intensities obtained from electron diffraction patterns acquired with the camera have been statistically analyzed and were found to be consistent with theoretically expected values. A quantitative analysis of the diffraction intensity as function of the accumulated electron dose suggests the possibility of recording up to 250 diffraction patterns with 3.5 A resolution from a single crotoxin complex crystal 128 A thick. Tilt series of 125 electron diffraction patterns with 3.5 A data acquired from a single crystal are shown to be practically feasible. The current study demonstrates for the first time the effectiveness of using a slow-scan CCD camera for electron diffraction data collection from thin protein crystals at near atomic resolution.

Measurement of slice sensitivity profiles in spiral CT

In conventional computed tomography (CT), ramps, typically thin sheets of aluminum inclined at 45 degrees, are established tools for measurements of slice sensitivity profiles (SSP). In spiral CT, however, they yield inconsistent results for different positions along the longitudinal axis. It is explained herein how ramp profiles result as a superposition of true SSPs and artifacts, the artifacts being caused by the slice interpolation process due to the difficult interpolation condition in this particular geometry. In direct consequence, ramp tests yield spatially variant results. As an alternative tool for measuring the slice sensitivity profile, the use of a thin high-contrast sheet held between two disks which approximate the ideal test of a delta impulse in the longitudinal direction is suggested. Resulting SSPs are shown for both methods; the delta method, in agreement with theoretical predictions, provided smooth symmetrical SSPs independent of table position in agreement with theoretical predictions. It is concluded that ramps are inadequate test objects to determine SSPs in spiral CT.

Low-dose thickness measurement of glucose-embedded protein crystals by electron energy loss spectroscopy and STEM dark-field imaging

Electron energy loss spectroscopy and dark-field imaging in a scanning transmission electron microscope were used to determine the thickness of glucose-embedded crotoxin complex crystals. The results demonstrate the feasibility of identifying protein crystals with a thickness of half a unit cell (12.8 nm) under low-dose and low-temperature conditions. The accuracy of this method is limited by the amount of surface coating of the crystal's embedding glucose used for preserving the high-resolution structure of the protein. The histogram of the crystal thickness distribution and the spread of the anticipated crystal thickness allow us to make an estimate of the uncertainty in the glucose layer thickness. This approach can be incorporated as part of the experimental procedure in the three-dimensional data collection for structure determination of protein crystals with variable thicknesses. The measurement can be done on areas approximately 200 nm in diameter so that crystals of suitable thickness can be pre-selected before the high-resolution data is recorded. Accurate determination of the crystal thickness will optimize the data collection efficiency by avoiding the collection and subsequent analysis of unmatchable data for the three-dimensional reconstruction.

Die Toon: a Late Holocene site in the Richtersveld National Park, northern Cape

A small excavation in the arid eastern portion of the Richtersveld National Park has produced evidence of hunter-gatherer occupation during the period ca. 3800 to 3100 years ago. These are the earliest Holocene deposits to have been excavated in Namaqualand. The occupation layers are very ephemeral but include microlithic stone tools and evidence for the hunting of small game. The possible presence of blesbok indicates more grassveld in the vicinity of the site than at present.

Computer-controlled spot-scan imaging of crotoxin complex crystals with 400 keV electrons at near-atomic resolution

400 keV electrons yield a better relative image contrast than 100 keV electrons for a beam-sensitive organic crystal when spot-scan imaging is used [J. Brink and W. Chiu, J. Microscopy 161 (1991) 279]. A FORTRAN 77 program has been written to operate the spot-scan imaging system on a computer workstation under the VMS operating system which is interfaced serially to the JEOL4000 electron microscope. We demonstrate the application of this implementation by imaging crotoxin complex crystals embedded in either vitreous ice or glucose to 2.5 A resolution. The intensity strength of the structure factors of this protein crystal are different at low (> 10 A) resolution but similar at high resolution (< 10 A) for the two embedding media as expected from their scattering contrast difference. Based on our experience as judged from the electron diffraction patterns of highly tilted crystals, flat crystals embedded in glucose can be readily obtained. Furthermore, our spot-scan imaging system also has the option of correcting the focus gradient that is present in images of tilted specimens.