Apparent diffusion coefficient as a non-invasive predictor of treatment response and recurrence in locally advanced rectal cancer

AIM

To evaluate the role of pretreatment apparent diffusion coefficient (ADC) as a predictor of treatment response and local recurrence in patients with locally advanced rectal cancer who underwent neoadjuvant therapy.

MATERIALS AND METHODS

Forty-nine patients who underwent preoperative diffusion-weighted magnetic resonance imaging (MRI) followed by neoadjuvant chemoradiation and surgery were enrolled in the study. The mean tumour ADC was measured independently from multiple, non-overlapping regions of interest (ROIs) to cover the entire tumour area on a single section by two radiologists and patients were followed postoperatively for a median of 16.4 months. Diagnostic accuracy of ADC for predicting treatment response and recurrence was evaluated using the area under the receiver-operating characteristic (ROC) curve, sensitivity, specificity, and predictive values. Univariate and multivariate analyses including clinical tumour (cT) staging, carcinoembryonic antigen (CEA) level, lymph-node involvement, tumour grade, surgical margin, vascular involvement, and ADC were performed with respect to recurrence. Interobserver agreement of ADC values was assessed.

RESULTS

Twenty patients showed response to neoadjuvant therapy and recurrence was noted in 17 patients. Low pretreatment ADC, MRI findings of cT4 staging, and node involvement were significantly related to poor treatment response. Sensitivity and specificity of ADC = 0.833 × 10(-3) mm(2)/s for prediction of treatment response was 75 and 48% for reader 1 and 65 and 52% for reader 2, respectively. Univariate and multivariate analyses identified pretreatment tumour ADC as the only predictive factor for recurrence. Sensitivity and specificity of ADC = 0.833 × 10(-3) mm(2)/s for prediction of recurrence was 86 and 77% for reader 1 and 80 and 69% for reader 2, respectively. Interobserver agreement for measuring ADC was good with a kappa value of 0.70.

CONCLUSION

Pretreatment rectal tumour ADC values may be an early biomarker for predicting treatment response and local recurrence in patients who underwent neoadjuvant chemoradiation.

Strong Short-Range Cooperativity in Hydrogen-Bond Chains

Chains of hydrogen bonds such as those found in water and proteins are often presumed to be more stable than the sum of the individual H bonds. However, the energetics of cooperativity are complicated by solvent effects and the dynamics of intermolecular interactions, meaning that information on cooperativity typically is derived from theory or indirect structural data. Herein, we present direct measurements of energetic cooperativity in an experimental system in which the geometry and the number of H bonds in a chain were systematically controlled. Strikingly, we found that adding a second H-bond donor to form a chain can almost double the strength of the terminal H bond, while further extensions have little effect. The experimental observations add weight to computations which have suggested that strong, but short-range cooperative effects may occur in H-bond chains.

Synthetically Diversified Protein Nanopores: Resolving Click Reaction Mechanisms

Nanopores are emerging as a powerful tool for the investigation of nanoscale processes at the single-molecule level. Here, we demonstrate the methionine-selective synthetic diversification of α-hemolysin (α-HL) protein nanopores and their exploitation as a platform for investigating reaction mechanisms. A wide range of functionalities, including azides, alkynes, nucleotides, and single-stranded DNA, were incorporated into individual pores in a divergent fashion. The ion currents flowing through the modified pores were used to observe the trajectory of a range of azide-alkyne click reactions and revealed several short-lived intermediates in Cu(I)-catalyzed azide-alkyne [3 + 2] cycloadditions (CuAAC) at the single-molecule level. Analysis of ion-current fluctuations enabled the populations of species involved in rapidly exchanging equilibria to be determined, facilitating the resolution of several transient intermediates in the CuAAC reaction mechanism. The versatile pore-modification chemistry offers a useful approach for enabling future physical organic investigations of reaction mechanisms at the single-molecule level.

Quantifying Interactions and Solvent Effects Using Molecular Balances and Model Complexes

Where the basic units of molecular chemistry are the bonds within molecules, supramolecular chemistry is based on the interactions that occur between molecules. Understanding the "how" and "why" of the processes that govern molecular self-assembly remains an open challenge to the supramolecular community. While many interactions are readily examined in silico through electronic structure calculations, such insights may not be directly applicable to experimentalists. The practical limitations of computationally accounting for solvation is perhaps the largest bottleneck in this regard, with implicit solvation models failing to comprehensively account for the specific nature of solvent effects and explicit models incurring a prohibitively high computational cost. Since molecular recognition processes usually occur in solution, insight into the nature and effect of solvation is imperative not only for understanding these phenomena but also for the rational design of systems that exploit them.Molecular balances and supramolecular complexes have emerged as useful tools for the experimental dissection of the physicochemical basis of various noncovalent interactions, but they have historically been underexploited as a platform for the evaluation of solvent effects. Contrasting with large biological complexes, smaller synthetic model systems enable combined experimental and computational analyses, often facilitating theoretical analyses that can work in concert with experiment.Our research has focused on the development of supramolecular systems to evaluate the role of solvents in molecular recognition, and further characterize the underlying mechanisms by which molecules associate. In particular, the use of molecular balances has provided a framework to measure the magnitude of solvent effects and to examine the accuracy of solvent models. Such approaches have revealed how solvation can modulate the electronic landscape of a molecule and how competitive solvation and solvent cohesion can provide thermodynamic driving forces for association. Moreover, the use of simple model systems facilitates the interrogation and further dissection of the physicochemical origins of molecular recognition. This tandem experimental/computational approach has married less common computational techniques, like symmetry adapted perturbation theory (SAPT) and natural bonding orbital (NBO) analysis, with experimental observations to elucidate the influence of effects that are difficult to resolve experimentally (e.g., London dispersion and electron delocalization).

The role of fibular fixation in the treatment of tibia diaphysis distal third fractures

INTRODUCTION

Combined fractures of the distal third of tibia diaphysis and fibula diaphysis are a common orthopedic injury. There is an ongoing debate about the necessity of fibular fixation when associated to distal third tibial fracture. This study aims at evaluating the role of fibular fixation in the treatment of distal third tibial fractures.

HYPOTHESIS

We hypothesized that fixation of the fibula increases the stability of fixation in distal third tibial and fibular fractures.

MATERIALS AND METHODS

In a randomized clinical trial, 53 patients with concomitant fractures of tibia and ipsilateral fibula at distal third level were recruited in this study during a 23-month period. Patients were randomized in two groups: patients with fibular fixation (case group) and without fibular fixation (control group). The patients were followed up for at least 6 months postoperatively.

RESULTS

There were seven cases exhibiting malalignment on immediate postoperative radiographs. Six of them were in group II (control group) and one was in group I (case group) (P=0.084). We didn't find nonunion in group I and we found three patients in group II (P=0.141). Infection was one in group I and two in group II on gustillo II injuries (P=0.516).

CONCLUSION

Despite its low count of patients, our study didn't show any advantage to fix the fibula fracture associated to distal third of tibia diaphysis fracture. It didn't show either an increase of complication after fibula open reduction and internal fixation.

LEVEL OF EVIDENCE

Level III. Randomized prospective study.

An RNA-dependent mechanism for transient expression of bacterial translocation filaments

The prokaryotic RNA chaperone Hfq mediates sRNA-mRNA interactions and plays a significant role in post-transcriptional regulation of the type III secretion (T3S) system produced by a range of Escherichia coli pathotypes. UV-crosslinking was used to map Hfq-binding under conditions that promote T3S and multiple interactions were identified within polycistronic transcripts produced from the locus of enterocyte effacement (LEE) that encodes the T3S system. The majority of Hfq binding was within the LEE5 and LEE4 operons, the latter encoding the translocon apparatus (SepL-EspADB) that is positively regulated by the RNA binding protein, CsrA. Using the identified Hfq-binding sites and a series of sRNA deletions, the sRNA Spot42 was shown to directly repress translation of LEE4 at the sepL 5' UTR. In silico and in vivo analyses of the sepL mRNA secondary structure combined with expression studies of truncates indicated that the unbound sepL mRNA is translationally inactive. Based on expression studies with site-directed mutants, an OFF-ON-OFF toggle model is proposed that results in transient translation of SepL and EspA filament assembly. Under this model, the nascent mRNA is translationally off, before being activated by CsrA, and then repressed by Hfq and Spot42.

Relationships between the Na(+)/K(+) pump and ATP and ADP content in mouse pancreatic islets: effects of meglitinide and glibenclamide

We have previously demonstrated that both D-glucose and glibenclamide stimulate the Na(+)/K(+) pump and suggested that this may be part of the membrane repolarization process, following the primary depolarization by these agents. The aim of this study was to investigate whether the non-sulphonylurea meglitinide (HB 699) exerts similar effects as glibenclamide or glucose on the islet Na(+)/K(+) pump and if effects of meglitinide or glibenclamide on this pump activity is paralleled by changes in islet ATP content and/or ATP/ADP ratio. The acyl-amino-alkyl benzoic acid derivative, meglitinide, stimulated the islet ouabain-sensitive portion of (86)Rb(+) influx (Na(+)/K(+) pump) by 53%, while the ouabain-resistant portion was inhibited by 70%. The stimulatory effect was not additive to that caused by D-glucose, suggesting that both agents may activate the Na(+)/K(+) pump via the same mechanism. Glibenclamide (10 microM) decreased the islet ATP and ADP content as well as the ATP/ADP ratio at 0 mM glucose. These effects were no longer observed at 10 mM glucose. Meglitinide (10 or 50 microM) lowered the islet ATP and ADP content at 0 mM glucose without affecting the ATP/ADP ratio. At 10 mM glucose, however, 10 microM of the drug reduced the islet ATP content but not the ATP/ADP ratio, while 50 microM of the drug, besides lowering the ATP content, also reduced the ATP/ADP ratio. Diazoxide (0.5 mM) increased the islet ATP content in the absence of glucose, an effect not seen in the presence of 10 mM glucose. The rate of glucose oxidation at 1, 10 or 20 mM of the sugar was not affected by glibenclamide (0.1 - 10 microM) and at 10 or 20 mM of the sugar not affected by meglitinide (1 - 100 microM). These results suggest that glibenclamide and meglitinide lower the islet ATP level by indirectly activating the beta-cell Na(+)/K(+) pump, which is a major consumer of ATP in the islets, while diazoxide increases the ATP level due to inhibition of the pump.

Ammonia and nitrous oxide emissions from two acidic soils of Nova Scotia fertilised with liquid hog manure mixed with or without dicyandiamide

Gaseous nitrogen (N) loss from field-applied manure in the form of ammonia (NH(3)) and nitrous oxide (N(2)O) has negative agronomic, environmental and health implications. This study was undertaken to evaluate the combined effect of soil type and dicyandiamide (DCD) on NH(3) and N(2)O emissions following application of liquid hog manure. Soil samples (100g) were placed in 500 mL screw-top Mason-jars and de-ionised water was added to bring the soil samples to 50%, 70% and 90% water-filled pore space (WFPS). Slurry and slurry+DCD treatments were applied at a rate of 116000 l ha(-1). The jars were then sealed and incubated at 21 degrees C for 21 d. Ammonia volatilisation was quantified using boric acid traps while N(2)O gas concentrations were analysed using gas chromatography. Results showed that DCD had no effect (p>0.05) on either NH(3) or N(2)O emissions. However, soil type had a significant effect (p<0.05) on both gases. Overall, the Pugwash soil produced 3 and 2.5 times more NH(3) and N(2)O, respectively, than the Acadia soil. N(2)O emissions from both soils increased with an increase in %WFPS, indicating that during the spring and fall in Atlantic Canada, when soils are generally wet, a significant amount of N(2)O may be emitted from these soils. The relationship between cumulative N(2)O and %WFPS was best described by an exponential function R(2)=0.83 and p<0.05 (both soils). Therefore, soil type should be taken into consideration when formulating N(2)O emission factors. The addition of DCD together with slurry may not be a viable strategy to mitigate N(2)O emissions from acidic soils. To reduce emissions of both gases, livestock slurry should not be applied on wet soils.

Effects of leptin, acetylcholine and vasoactive intestinal polypeptide on insulin secretion in isolated ob/ob mouse pancreatic islets

Obesity is often accompanied by hyperleptinemia, hyperinsulinemia, and an increased parasympathetic tone. Obese-hyperglycemic mice (Umeå ob/ob) have functional leptin receptors and a raised parasympathetic tone. We studied insulin release in islets isolated from 9-month-old severely obese ob/ob mice. Leptin (0.5-18 nM) did not affect insulin release together with 2.8-20 mM glucose. Leptin (18 microM) had no effect in the presence of low glucose (2.8-5.5 mM), but increased insulin secretion in islets challenged with 11.1 or 16.7 mM glucose. Leptin at 18 microM increased insulin secretion stimulated by the parasympathetic neurotransmitters acetylcholine (ACh; 10 microM) or vasoactive intestinal peptide (VIP; 10 nM), and by 5 mM theophylline or 2.5 microM forskolin. Overnight culture increased the effect of 18 microM leptin, but no effects were observed with 18 nM leptin. Pretreatment of islets with phorbol 12-myristate 13-acetate (PMA) did not suggest any involvement of protein kinase C. In summary, a high concentration of leptin stimulates insulin release in the presence of stimulatory concentrations of glucose alone and with parasympathetic neurotransmitters. Hyperleptinemia and increased parasympathetic stimulation may in part cause the hyperinsulinemia observed in obesity. This may aggravate insulin resistance and the abnormal metabolism in diabetes mellitus.

Hepatoprotective role of captopril on paraquat induced hepatotoxicity

Paraquat (PQ) is a highly toxic herbicide that is used in most of the countries without restriction. The cytotoxic effect of PQ is mediated by radicals, which are the products of PQ reduction in cells. The anti-oxidative action of captopril, an angiotensin-converting enzyme inhibitor, appears to be through its ability to scavenge reactive oxygen species. In this study, the heptoprotective effect of captopril against PQ-induced hepatotoxicity was evaluated using primary cultured rat hepatocytes. Hepatocytes were isolated from male Wistar rats using a two-step collagenase perfusion, following incubation in the presence of captopril at 0.1, 0.2, 0.4 and 0.8 mM with or without PQ (5 mM). Hepatoprotective effects of captopril were studied indicating glutathione level intensity, thiobarbituric acid reactive substances (TBARs) formation, lactate dehydrogenase (LDH) leakage and cell viability every 70 min for 210 min. Captopril at 0.2 mM concentration maintained the LDH leakage, glutathione level and cell viability in the presence of 5 mM PQ. In spite of a significant elevation in TBARs formation in the PQ group, captopril did not show any significant protection. In conclusion, our data reveals that incubation of freshly isolated rat hepa-tocytes with captopril (0.2 mM) significantly protected the hepatocytes against the cytotoxicity of PQ ( P < 0.05). Human & Experimental Toxicology (2007) 26, 789— 794

Modulation of islet ATP content by inhibition or stimulation of the Na(+)/K(+) pump

High (30 mM) K(+), known to cause beta-cell membrane depolarisation, significantly decreased the islet total ATP content, supporting the view that beta-cell membrane depolarisation can activate the ATP-consuming Na(+)/K(+) pump. Ouabain (1 mM) did not change the islet ATP content after 5-15 min of incubation in the absence or presence of 3 mM glucose but reduced it after 30 min, and in the presence of 20 mM glucose, the reduction by ouabain occurred already after 15 min. Incubation of islets with ouabain for 60 min decreased the islet ATP content in the presence of 3, 10 or 20 mM glucose or 30 mM K(+). Also, the islet glucose oxidation rate was decreased by ouabain. When K(+) deficiency was used to inhibit the Na(+)/K(+) pump, no change in ATP content was observed irrespective of glucose concentration, although K(+) deficiency caused a slight inhibition of the glucose oxidation rate. Diazoxide reduced the islet glucose oxidation rate and increased the islet ATP content in the presence of 20 mM glucose. There may exist a feedback mechanism decreasing the flow of glucose metabolism in response to reduced ATP consumption by the Na(+)/K(+) pump.

Accumulation of phytate in vegetable-type soybean genotypes harvested at four developmental stages

A total of 17 vegetable-type soybean (Glycine max [L.] Merr) genotypes were planted in four-row plots arranged in a randomized complete block design in 1988 and 1989 at Petersburg, Virginia. Each genotype was harvested at four developmental stages and evaluated for phytate content. Highly significant differences for phytate content were observed among the stages of harvest and genotypes, and there was an interaction between genotype x stage of harvest. The significant differences observed for phytate content among genotypes indicated that genetic variation exists among the tested genotypes for selection and improvement through hybridization. Among the genotypes, 'Kingston' and PI 423852 had the highest phytate content in most stages of harvest while PI 416771, 'Emperor', and PI 416982 had the lowest phytate values. A heritability estimate of 81 percent was observed for phytate content. This high heritability value indicates that selecting genotypes for lower phytate content would be effective. Significant correlations were observed for phytate content among genotypes harvested at R6, R7, R8, and overall. The magnitude of association of R6 with the overall phytate mean was especially high. These results illustrate that determining the phytate content of genotypes at the R6 growth stage would be a good predictor of the overall genotypic performance.

Transient myocardial thickening: a retrospective analysis on etiological, clinical, laboratory, therapeutic, and outcome findings in 27 cats

INTRODUCTION/OBJECTIVE

Transient myocardial thickening (TMT) in cats is a poorly characterized clinical entity. Therefore, this study aimed to provide descriptions of additional cats diagnosed with this clinical phenomenon.

ANIMALS, MATERIALS, AND METHODS

For this multicenter observational retrospective study, cats diagnosed with TMT were searched in three medical databases. TMT was defined for cats with at least two echocardiograms showing an increased end-diastolic left ventricular wall thickness (LVWTd; i.e. ≥6 mm) at presentation and subsequent echocardiographic normalization (i.e. LVWTd <5.5 mm). Signalment, history, clinical, laboratory, therapeutic, and outcome data were retrieved.

RESULTS

Twenty seven cats were included. The median age was 3 years. In 9/27 cats, an antecedent event was documented. At admission, 27/27 cats had evidence of myocardial injury (median value of cardiac troponin I 5.5 ng/mL), 25/27 cats had congestive heart failure, 13/27 cats had hypothermia, 8/27 cats had systemic hypotension, 7/27 cats had bradycardia, and 7/27 cats had electrocardiographic evidence of an arrhythmia. The median LVWTd was 6.4 mm. A potential cause of myocardial injury was identified in 14/27 cats. The median time from diagnosis to a significant reduction in LVWTd was 43 days.

DISCUSSION

TMT can be diagnosed in a wide range of cats, including young subjects. An antecedent predisposing event and/or a possible causative trigger can be identified in some. The reduction in LVWTd that defines this phenomenon usually occurs over a variable time frame.

CONCLUSIONS

This study represents the largest investigation of TMT in cats and provides additional information on this uncommon clinical entity.

Comparison of genu varum treating results using open and closed wedge high tibial osteotomy

High tibial osteotomy methods include open and closed wedge techniques. The study aims at comparing results of osteotomy methods in patients suffering from genu varum deformity. In a cohort study, 32 patients with genu varum deformity (42 knees) were evaluated. They were divided into two groups and matched according to age and gender. The patients were treated with open and closed wedge osteotomy. After surgery, they were followed up and compared for 6 months. Thirty two patients with genu varum deformity (10 cases of bilateral deformity (31.2%) including 25 women (87.2%) and 7 men (21.8%) were studied. Incidence of complications was the same after open and closed wedge osteotomy operation (12.5%). Patients overall satisfaction from open and closed wedge methods was 87.5 and 75%, respectively. There was statistically significant difference between two groups considering operation duration, weight bearing duration and return to routine activities (p < 0.001). There was no difference in other parameters including varus angle correction, Lysholm score Tegner activity as well as Insall Salvati index. This study demonstrated that there is no difference between two osteotomy methods considering patients' clinical outcomes and both methods are successful in final treatment results.

Solvent Attenuation of London Dispersion in Polycyclic Aromatic Stacking

Solvent competition for London dispersion attenuates its energetic significance in molecular recognition processes. By varying both the stacked contact area and the solvent, here we experimentally deconvolute solvent attenuation using molecular balances. Experimental stacking energies (phenyl to pyrene) correlated strongly with calculations only when dispersion was considered. Such calculations favoured stacking by up to -27 kJ mol-1 in the gas phase, but it was weakly disfavoured in our solution-phase experiments (+0.5 to +4.6 kJ mol-1). Nonetheless, the propensity for stacking increased with contact area and in solvents with lower bulk polarisabilities that compete less for dispersion. Experimental stacking energies per unit change in solvent accessible area ranged from -0.02 kJ mol-1 Å-2 in CS2, to -0.05 kJ mol-1 Å-2 in CD2Cl2, but were dwarfed by the calculated gas-phase energy of -0.6 kJ mol-1 Å-2. The results underscore the challenge facing the exploitation of dispersion in solution. Solvent competition strongly but imperfectly cancels dispersion at molecular recognition interfaces, making the energetic benefits difficult to realise.