Expert and novice performance in solving physics problems

Although a sizable body of knowledge is prerequisite to expert skill, that knowledge must be indexed by large numbers of patterns that, on recognition, guide the expert in a fraction of a second to relevant parts of the knowledge store. The knowledge forms complex schemata that can guide a problem's interpretation and solution and that constitute a large part of what we call physical intuition.

High prevalence of low plasma thiamine concentration in diabetes linked to a marker of vascular disease

AIMS/HYPOTHESIS

To assess thiamine status by analysis of plasma, erythrocytes and urine in type 1 and type 2 diabetic patients and links to markers of vascular dysfunction.

METHODS

Diabetic patients (26 type 1 and 48 type 2) with and without microalbuminuria and 20 normal healthy control volunteers were recruited. Erythrocyte activity of transketolase, the concentrations of thiamine and related phosphorylated metabolites in plasma, erythrocytes and urine, and markers of metabolic control and vascular dysfunction were determined.

RESULTS

Plasma thiamine concentration was decreased 76% in type 1 diabetic patients and 75% in type 2 diabetic patients: normal volunteers 64.1 (95% CI 58.5-69.7) nmol/l, type 1 diabetes 15.3 (95% CI 11.5-19.1) nmol/l, p < 0.001, and type 2 diabetes 16.3 (95% CI 13.0-9.6) nmol/l, p < 0.001. Renal clearance of thiamine was increased 24-fold in type 1 diabetic patients and 16-fold in type 2 diabetic patients. Plasma thiamine concentration correlated negatively with renal clearance of thiamine (r = -0.531, p < 0.001) and fractional excretion of thiamine (r = -0.616, p < 0.001). Erythrocyte transketolase activity correlated negatively with urinary albumin excretion (r = -0.232, p < 0.05). Thiamine transporter protein contents of erythrocyte membranes of type 1 and type 2 diabetic patients were increased. Plasma thiamine concentration and urinary excretion of thiamine correlated negatively with soluble vascular adhesion molecule-1 (r = -0.246, p < 0.05, and -0.311, p < 0.01, respectively).

CONCLUSIONS/INTERPRETATION

Low plasma thiamine concentration is prevalent in patients with type 1 and type 2 diabetes, associated with increased thiamine clearance. The conventional assessment of thiamine status was masked by increased thiamine transporter content of erythrocytes.

Phase II study of adjuvant gemcitabine plus docetaxel (GD) for completely resected stage I-IV high grade uterine leiomyosarcoma (HGuLMS)

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Background: Patients (pts) with completely resected stage I-IV HGuLMS are at high risk for recurrence, with reported 2-year progression-free survival ranging from 19–30% (Dinh, Gyn Onc 2004; Major, Cancer 1993). No adjuvant treatment has been shown to improve survival, although prospective data are limited. GD achieves objective responses in metastatic uLMS. We sought to determine whether 4 cycles GD given after complete resection of stage I-IV HGuLMS would yield a 2-year PFS of at least 40%, in order to determine whether GD was worth pursuing as an adjuvant strategy in a randomized trial. Methods: Eligible pts with completely resected HGuLMS within 8 weeks of surgery, no prior GD, no evidence of disease on post-resection CT, KPS = 80, and adequate organ function were treated with G 900 mg/m2 over 90 minutes days 1 and 8 + D 75 mg/m2 d8, with GCSF or pegfilgrastim, every 3 weeks for 4 cycles. CT was performed at baseline, after cycle 4, and every 3 months. Progression defined as new evidence of disease on CT. Results: 25 pts (median age 49, range 37–73) enrolled; 23 evaluable (1-never treated, 1-ineligible). Grade 3 related toxicities were: neutropenia (2/23) 8.7%, febrile neutropenia (2/23) 8.7%, anemia (2/23) 8.7%, thrombocytopenia (1/23) 4.3%, diarrhea (1/23) 4.3%, hyperglycemia (2/23) 8.7%, pulmonary (2/23) 8.7%; there were no ≥ grade 4 toxicities. With median follow-up of 29 months (range 0.5 to 45 months) for all pts, PFS at 2 y and 3 y is 45%, and median OS is not yet reached. For the 18 pts with stage I or II uLMS 2-y and 3-y PFS is 58%, and median PFS is 38 months (95%C.I. 6 months to not yet reached). Sites of first recurrence were: lung only-3/23 (13%); pelvis only-5/23 (22%); both-5 (22%). Treatment of recurrence was at physician discretion and included resection, resection plus pelvic radiation, and/or chemotherapy. Conclusions: Pts treated with post-resection GD for stage I-IV HGuLMS had 2-y and 3-y PFS that appears superior to historical rates of PFS. Incorporation of GD into a randomized trial of adjuvant chemotherapy vs adjuvant pelvic radiation for resected stage I and II uLMS is planned.

No significant financial relationships to disclose.

Phase I study of pemetrexed (P) plus gemcitabine (G) in advanced solid tumors (ST)

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Background: P is active in multiple ST types, and preclinical data support P synergy with G. Methods: Eligible advanced ST patients (pts) with no prior P or G, no prior radiotherapy (RT) to ≡ 25% of the marrow, Karnofsky Performance Status ≡ 70%, and adequate organ function enrolled in cohorts (C) of 3, expanding to 6 if dose-limiting toxicity (DLT) occurred. P was given at 300 (C1), 400 (C2), 500 (C3) or 600 (C4) mg/m2 followed by G at 1500 mg/m2 q 14 days (d) without granulocyte-colony stimulating factor. Vitamin B12 and folate supplementation were given. Response was assessed by RECIST Results: 29 pts (median number prior regimens 2, range 1–5; 66% with prior RT) enrolled and are evaluable for safety; 23 are evaluable for response. There were no DLTs in C1. One pt in C2 was replaced after 1 cycle for progression of disease (PD). Among the next 6 pts, 2 had DLTs (1 G3 thrombocytopenia [TP] treatment delay; 1 neutropenic fever [NF]). C2-R (C2, Revised) re-opened after amendment permitting ≡ 2 prior cytotoxic regimens, no history of brain metastases/brain RT. C2-R enrolled 8 pts with 1 DLT (G3 TP with treatment delay) and 2 pts replaced (1 early PD, 1 no documented duration of neutropenia [NP]). C3 had 0/3 pts with DLT. C4 had 2/3 pts with DLTs (1 G4 hyponatremia; 1 herpes zoster-related treatment delay). C3 has been expanded to 5 of 6 planned patients, one with DLT (NF, G4 TP). Toxicities per cycle (n= 189 cycles, 29 patients): include NP-G3 (23%), G4 (14%); TP-G3 (2%); WBC-G3 (30%), G4 (4%); lymphopenia-G3 (11%), Hgb-G3 (4%); G3-NF (1%). 3/23 (13%) had objective partial responses (2 head and neck squamous cell cancer, HNSCC; 1 nasopharyngeal cancer, NPC), 4 stable disease (SD), 16 PD. (1 pt, no measurable disease at baseline; 5 pts, too early for response assesment). Conclusions: G + P is well-tolerated, and yields objective responses in HNSCC and NPC. C3 (P 500 mg/m2 + G 1500 mg/m2 q 14 d) was the phase II recommended dose in another phase I study of this regimen (Melemed ASCO 2005). Our final results will be available for ASCO 2007.

No significant financial relationships to disclose.

The development of novel flexible electrode arrays for the electrochemotherapy of solid tumour tissue. (Potential for endoscopic treatment of inaccessible cancers)

Therapeutic "electroporation" involves application of electric fields to target cells/tissues, thereby rendering their cell membranes transiently porous, thus making feasible the cellular uptake and efficacy of previously impermeant and ineffective therapeutic agents. The objectives of this research are a) the development of flexible electrode arrays for incorporation into microsystem endoscopic devices, and b) the assessment of their efficacy in delivering selected genetic and pharmaceutical anticancer therapies. Gold electrodes were fabricated on flexible polyimide substrates following predictive modeling and simulation of electric fields using FEMLAB software. Subsequent assessment of electroporation efficiency in-vitro involved 1) enumeration of viable tumour cells after delivery of electric pulses and exposure to low concentrations of bleomycin, otherwise known as electrochemotherapy 2) Efficacy of gene delivery by detection of emitted green fluorescence by cells after electroporation with the pEGFP plasmid and 3) In-vivo efficacy of electrochemotherapy in a variety of human solid tumour masses in nude mouse models (xenografts). The flexible electrode system was found to be successful for electrical delivery of plasmids and drugs in-vitro and in-vivo. We found in-vivo complete regression of prostate, colon, oesophageal, and renal cancers with reduced growth rates for fibrosarcoma and breast cell lines. These flexible electrodes are suitable for electrochemotherapy or gene therapy to solid tumours masses and may be fabricated for application to the treatment of some cancers in humans by transcutaneous or endoscopic delivery systems.

Combined electric field and ultrasound therapy as a novel anti-tumour treatment

The permeabilising effects of electric pulses on cell membranes and the use of ultrasound energy of various intensities, for both thermal effects and enhancement of drug and gene delivery, have led to extensive research into the potential applications of these systems in the development of novel anti-cancer treatments. In the present study we have demonstrated for the first time that the application of brief electric pulses 'sensitises' tumour cells to the effects of low intensity ultrasound. The studies were conducted in human tumours established in athymic nude mice and in many instances resulted in the reduction of tumour mass. The combined electric field and ultrasound approach (CEFUS) was applied in vivo to a murine colon adenocarcinoma (C26) and a human oesophageal adenocarcinoma (OE19). The experiments performed demonstrated the anti-tumour effects of the combined therapy. Varying the electrosensitisation parameters used (voltage, waveform, electrode type) contributed to optimise the procedure. Exponential electric pulses with a peak of 1000 V/cm were initially used, but square wave pulses (1000 V/cm, 1 ms, x2, 1 Hz) were found to be just as effective. All ultrasound application parameters were kept constant during the study. The growth rate of C26 tumours treated with CEFUS was significantly reduced with respect to untreated controls at day 7 (96% of average initial tumour volume in CEFUS group versus 615% for controls, P < 0.05). Similar reduction was observed in OE19 tumours treated with CEFUS by day 4 (82% versus 232%, P < 0.032). Our preliminary data suggest that this novel technology could potentially be of wide application in clinical practice for the treatment of solid tumours and is worth further investigation.

Selection of CD4+CD25+ regulatory T cells by self-peptides

Regulatory T cells have been shown to prevent the development of autoimmune disease, and can modulate immune responses during infections or following tissue transplantation. Recently, the processes by which CD4+CD25+ regulatory T cells are produced during immune repertoire formation have begun to be elucidated. This review focuses on the role of self-peptides in mediating CD4+CD25+ regulatory T cell selection in the thymus. How self-peptides continue to have an important influence on the accumulation of CD4+CD25+ regulatory T cells in the periphery is also discussed.

Lack of radiological and clinical benefit over two years of low dose prednisolone for rheumatoid arthritis: results of a randomised controlled trial

BACKGROUND

Evidence for disease modifying activity of low dose corticosteroid treatment in rheumatoid arthritis is contradictory. Studies showing radiological benefit suggest that continued treatment is required to sustain the effect.

OBJECTIVE

To evaluate the effect of low dose oral prednisolone in early rheumatoid arthritis on disease activity over two years.

DESIGN

Double blind placebo controlled trial.

METHODS

Patients with rheumatoid arthritis, duration <3 years (n = 167), were started on a disease modifying antirheumatic drug (DMARD; sulphasalazine) and allocated by stratified randomisation to prednisolone 7 mg/day or placebo. Primary outcome measure was radiological damage, assessed by the modified Sharp method. Clinical benefit was a secondary outcome. A proactive approach to identifying and treating corticosteroid adverse events was adopted. Patients who discontinued sulphasalazine were offered an alternative DMARD.

RESULTS

90 of 257 patients eligible for the study refused to participate (more women than men). Of those enrolled, 84% were seropositive for rheumatoid factor, median age 56 years, median disease duration 12 months, female to male ratio 1.8:1. Prednisolone was given to 84 patients; of these 73% continued prednisolone and 70% sulphasalazine at 2 years. Of the 83 patients on placebo, 80% continued placebo and 64% sulphasalazine at 2 years. There were no significant differences in radiological score or clinical and laboratory measures at 0 and 2 years.

CONCLUSIONS

Low dose prednisolone conferred no radiological or clinical benefit on patients maintained on a DMARD over two years. Low dose corticosteroids have no role in the routine management of rheumatoid arthritis treated with conventional disease modifying drugs.

Activation of fibronectin gene expression by hepatitis B virus x antigen

The development of fibrosis and cirrhosis during chronic hepatitis B virus (HBV) infection correlates with the persistent expression of HBV x antigen (HBxAg), which acts in part, by stimulating selected signal transduction pathways, including nuclear factor kappa B (NF-kappa B). To identify NF-kappa B responsive genes that are differentially expressed in HBxAg-positive cells, HepG2 cells were stably transfected with HBxAg, and then with pZeoSV2 or pZeoSV2-I kappa B alpha. When RNAs from each culture were compared by PCR-select cDNA subtraction, fibronectin (FN) mRNA was shown to be strongly down-regulated by I kappa B alpha. Up-regulated expression of FN and co-expression between FN and HBxAg were observed in liver sections from HBV carriers that were stained for HBxAg and analysed for FN mRNA by in situ hybridization (ISH). In liver cell cultures, HBxAg increased the levels of FN mRNA and protein. This was because of the HBxAg-mediated trans-activation of the FN promoter, which was NF-kappa B-dependent. HBxAg also antagonized the repression of the FN promoter by the tumour suppressor, p53. Hence, the FN gene may be a natural target for HBxAg trans-activation, perhaps through activation of NF-kappa B and inactivation of p53, thereby contributing to the accumulation of FN in the liver over the course of chronic HBV infection.

Overnight central and peripheral temperature changes in normal infants

AIM

To explore the relationship between central and peripheral temperature in normal infants after being put down to sleep.

METHODS

Overnight shin and rectal temperatures of 21 normal infants were continuously recorded at home for three nights at 2 wk, 6 wk, 3 mo and 5 mo of age. Parents documented the start and end of feed/nappy changes during the night.

RESULTS

An initial fall in rectal temperature was recorded on 149 out of 161 nights. This was linearly correlated with a rise in shin temperature for 106/149 (71%) nights (median R2 = 0.95, lower quartile 0.92, upper quartile 0.97). It was not possible to rule out a change in thermal insulation over the shins as a confounding variable in this strong association. However, a similar inverse relationship was seen between shin and rectal temperature during 111 of 121 (92%) feed/nappy changes.

CONCLUSION

The fall in rectal temperature after being put down to sleep may be due to redistribution of heat rather than decreased production or heat loss. If causal, the development in early infancy of an inverse relationship between shin and rectal temperature may be important for cardiovascular homeostasis. Further sleep laboratory work is required to distinguish peripheral temperature changes on falling asleep from those associated with changes in thermal insulation.

Central and peripheral temperature change in normal infants

The purpose was to explore the relationship between the fall in rectal temperature seen in normal infants after being put down to sleep and the concomitant rise in peripheral shin temperature. In this observational study 21 normal infants had continuous overnight peripheral shin and central rectal temperature recorded, for three nights at 2 weeks, 6 weeks, 3 months and 5 months of age. Parents documented the start and end of feed/nappy changing episodes during the night. All recordings were made in the infants' own home. A strong inverse linear correlation (median r2 = 0.95, lower quartile 0.92, upper quartile 0.97) was seen between rectal temperature and shin temperature on falling to sleep when put down on 106 (65%) of 161 nights. On many other nights a significant nonlinear association was present. It was not possible to exclude the process of being put down to sleep as a confounding variable in this strong association. However, a similar inverse relationship between shin and rectal temperature was seen overnight during 111 of 121 (92%) feed/nappy changing episodes. If causal, the development in early infancy of an inverse relationship between shin and rectal temperature may be important for cardiovascular homeostasis. Further sleep laboratory work including video recording is required to separate the peripheral and central temperature changes that take place on falling to sleep from those associated with removal of clothing during a nappy change.

Thoracoscopic repair of instrumental perforation of the oesophagus: first report

BACKGROUND

Perforation of the oesophagus is a life-threatening condition requiring early recognition and repair to prevent mediastinitis and death. Primary closure with mediastinal drainage is recognised as the treatment of choice for patients presenting within 24 hours. Many are frail, however, and unsuitable for major surgery.

AIM

To report the first case of thoracoscopic repair of the oesophagus for oesophageal perforation following instrumentation.

METHODS

Flexible endoscopy revealed a 10cm perforation in the right lower oesophagus. With the gastroscope in the oesophagus, four thoracoports were introduced. Using suction and irrigation, the pleural cavity was suctioned free of debris and a 10cm longitudinal tear of the right lateral aspect of the oesophagus was repaired using interrupted polyglactin sutures through all layers.

RESULTS

The patient tolerated the procedure well and made an uncomplicated recovery.

CONCLUSION

The uncomplicated recovery of this frail patient without need for blood transfusions or assisted ventilation supports the notion that the thoracoscopic approach may have significant advantages. With increased experience and technical refinements there should be less reluctance to refer these patients for earlier definitive surgical repair.

Nuclear translocation of IFN-gamma is an intrinsic requirement for its biologic activity and can be driven by a heterologous nuclear localization sequence

We have previously identified a nuclear localization sequence (NLS) in interferon-gamma (IFN-gamma). This NLS functions intracellularly by forming a complex with its transcription factor Stat1alpha and the nuclear importer of Stat1alpha, the importin-alpha analog NPI-1. The stability of this complex and the subsequent nuclear translocation of the complexed Stat1alpha are dependent on the integrity of this NLS, showing that Stat1alpha nuclear import is mediated by the IFN-gamma NLS. In this study, to directly evaluate the intrinsic requirement of nuclear IFN-gamma toward its biologic activities, we engineered a chimeric in which the IFN-gamma NLS has been substituted by a heterologous NLS, namely, the prototypical NLS of the SV40 large T antigen, which would drive nuclear translocation of IFN-gamma in a sequence-nonspecific manner. The chimeric, IFN-gamma-SV, was equally active in antiviral and antiproliferative assays as the wild-type IFN-gamma. Interestingly, IFN-gamma-SV was also translocated to the nucleus and was also recovered intracellularly as a complex with the Stat1alpha importer NPI-1, like wild-type IFN-gamma. Comparison with an NLS deletion mutant showed that deletion or changes within the NLS motif of IFN-gamma were inconsequential to the high-affinity extracellular binding to the IFN-gamma receptor complex, yet the presence of an NLS was critical to the expression of the biologic activities of IFN-gamma and its NPI-1 complexation ability. Our data conclusively demonstrate that nuclear translocation of IFN-gamma is an intrinsic requirement for the full expression of the biologic activities of IFN-gamma and strengthen the conclusion that nuclear chaperoning of Stat1alpha is the primary role of IFN-gamma nuclear translocation. This type of ligand imprinting by sequestering of activated Stat may contribute to the specificity of Stat nuclear transcription.

Chronic ethanol consumption stimulates hepatitis B virus gene expression and replication in transgenic mice

Epidemiologic observations show a higher frequency of hepatitis B virus (HBV) serologic markers in chronic alcoholics compared with the general population. This may be the result of an increased susceptibility of alcoholics to infection and/or to an ethanol-mediated stimulation of HBV gene expression and replication. To test the latter hypothesis, HBV transgenic SCID mice, which support consistent levels of virus replication, were fed with a standard Lieber-DiCarli or isocaloric diet for 5 weeks. In ethanol-fed mice, the levels of hepatitis B surface antigen (HBsAg) and viral DNA in serum increased by up to 7-fold compared with mice fed the control diet. Ethanol-treated mice also had elevated HBV-RNA levels, and increased expression of surface, core, and X antigens in the liver, especially in the pericentral regions. None of these changes were observed in transgenic mice fed isocaloric diets. Thus, chronic alcohol consumption alters the patterns of HBV gene expression and replication in the serum and liver of HBV transgenic SCID mice, and may provide a partial explanation for the increased frequency of HBV markers among alcoholics.

Differential properties of two putative nuclear localization sequences found in the carboxyl-terminus of human ifn-gamma

Interferon-gamma (IFN-gamma), a protein that uses the Jak-Stat pathway for signal transduction, translocates rapidly to the nucleus in cells treated extracellularly with the cytokine. A nuclear localization sequence (NLS) has been identified and characterized in the C-terminus of IFN-gamma. Both human and murine IFN-gamma contain this NLS. We show in this report that human IFN-gamma (HuIFN-gamma) contains a second NLS at an upstream site, as determined in standard import assays using digitonin-permeabilized HeLa cells. The primary sequence, analogous with the NLS sequence identified in murine IFN-gamma, representing amino acids 122-132 of HuIFN-gamma was capable of mediating the nuclear import of the autofluorescent protein allophycocyanin (APC) in an energy-dependent manner. The second sequence, representing amino acids 78-92 of HuIFN-gamma, was also capable of mediating the nuclear import of APC in an energy-dependent manner but to a greatly reduced extent. The nuclear import of both sequences conjugated to APC was strongly blocked by competition with unconjugated HuIFN-gamma(122-132). Competition by the sequence HuIFN-gamma(78-92) effectively blocked the import of APC-conjugated HuIFN-gamma(78-92) but, at the same concentration, was not capable of inhibiting the nuclear import of APC-conjugated HuIFN-gamma(122-132), suggesting that HuIFN-gamma(78-92) was a less efficient NLS than HuIFN-gamma(122-132). This is consistent with >90% loss of antiviral activity of HuIFN-gamma lacking the downstream NLS in 122-132. The nuclear import of APC-conjugated HuIFN-gamma(122-132) was inhibited by a peptide containing the prototypical polybasic NLS of the SV40 T NLS, which suggests that the same Ran/importin cellular machinery is used in both cases.

Probabilities and polarity biases in conditional inference

A probabilistic computational level model of conditional inference is proposed that can explain polarity biases in conditional inference (e.g., J. St. B. T. Evans, 1993). These biases are observed when J. St. B. T. Evans's (1972) negations paradigm is used in the conditional inference task. The model assumes that negations define higher probability categories than their affirmative counterparts (M. Oaksford & K. Stenning, 1992); for example, P(not-dog) > P(dog). This identification suggests that polarity biases are really a rational effect of high-probability categories. Three experiments revealed that, consistent with this probabilistic account, when high-probability categories are used instead of negations, a high-probability conclusion effect is observed. The relationships between the probabilistic model and other phenomena and other theories in conditional reasoning are discussed.