Fracturing across the multi-scales of diverse materials.

Everyone has to deal with fracturing of materials at one level or another, beginning from normal household chores and extending to the largest scale of observations reported for catastrophic events occurring on a geological level or even expanded to events in outer space. Such wide perspective is introduced in the current introduction of this theme issue. The follow-on organization of technical articles provides a flavour of the range in size scales at which fracturing occurs in a wide diversity of materials-from 'fracking' oil extraction and earth moving to laboratory testing of rock material and extending to the cracking of tooth enamel. Of important scientific interest are observations made and analysed at the smallest dimensions corresponding to the mechanisms by which fracture is either enhanced or hindered by permanent deformation or other processes. Such events are irrevocably linked to the atomic structure in all engineering materials, a sampling of which is presented, including results for crystalline and amorphous materials. Hooray for the broad subject description that is hoped to be appealing to the interested reader.

Gemcitabine diphosphate choline is a major metabolite linked to the Kennedy pathway in pancreatic cancer models in vivo.

BACKGROUND: The modest benefits of gemcitabine (dFdC) therapy in patients with pancreatic ductal adenocarcinoma (PDAC) are well documented, with drug delivery and metabolic lability cited as important contributing factors. We have used a mouse model of PDAC: KRAS(G12D); p53(R172H); pdx-Cre (KPC) that recapitulates the human disease to study dFdC intra-tumoural metabolism. METHODS: LC-MS/MS and NMR were used to measure drug and physiological analytes. Cytotoxicity was assessed by the Sulphorhodamine B assay. RESULTS: In KPC tumour tissue, we identified a new, Kennedy pathway-linked dFdC metabolite (gemcitabine diphosphate choline (GdPC)) present at equimolar amounts to its precursor, the accepted active metabolite gemcitabine triphosphate (dFdCTP). Utilising additional subcutaneous PDAC tumour models, we demonstrated an inverse correlation between GdPC/dFdCTP ratios and cytidine triphosphate (CTP). In tumour homogenates in vitro, CTP inhibited GdPC formation from dFdCTP, indicating competition between CTP and dFdCTP for CTP:phosphocholine cytidylyltransferase (CCT). As the structure of GdPC precludes entry into cells, potential cytotoxicity was assessed by stimulating CCT activity using linoleate in KPC cells in vitro, leading to increased GdPC concentration and synergistic growth inhibition after dFdC addition. CONCLUSIONS: GdPC is an important element of the intra-tumoural dFdC metabolic pathway in vivo.

Dichloroacetate induces autophagy in colorectal cancer cells and tumours.

BACKGROUND: Dichloroacetate (DCA) has been found to have antitumour properties. METHODS: We investigated the cellular and metabolic responses to DCA treatment and recovery in human colorectal (HT29, HCT116 WT and HCT116 Bax-ko), prostate carcinoma cells (PC3) and HT29 xenografts by flow cytometry, western blotting, electron microscopy, (1)H and hyperpolarised (13)C-magnetic resonance spectroscopy. RESULTS: Increased expression of the autophagy markers LC3B II was observed following DCA treatment both in vitro and in vivo. We observed increased production of reactive oxygen species (ROS) and mTOR inhibition (decreased pS6 ribosomal protein and p4E-BP1 expression) as well as increased expression of MCT1 following DCA treatment. Steady-state lactate excretion and the apparent hyperpolarised [1-(13)C] pyruvate-to-lactate exchange rate (k(PL)) were decreased in DCA-treated cells, along with increased NAD(+)/NADH ratios and NAD(+). Steady-state lactate excretion and k(PL) returned to, or exceeded, control levels in cells recovered from DCA treatment, accompanied by increased NAD(+) and NADH. Reduced k(PL) with DCA treatment was found in HT29 tumour xenografts in vivo. CONCLUSIONS: DCA induces autophagy in cancer cells accompanied by ROS production and mTOR inhibition, reduced lactate excretion, reduced k(PL) and increased NAD(+)/NADH ratio. The observed cellular and metabolic changes recover on cessation of treatment.

DCE and DW MRI in monitoring response to androgen deprivation therapy in patients with prostate cancer: a feasibility study.

Androgen deprivation therapy (ADT) is a key primary treatment for advanced and metastatic prostate cancer and is an important neoadjuvant before radiotherapy. We evaluated 3.0 T dynamic contrast-enhanced MRI and diffusion-weighted (DW) MRI in monitoring ADT response. Twenty-three consecutive patients with prostate cancer treated by primary ADT were included. Imaging was performed at baseline and 3 months posttreatment with ADT. After 3 months therapy there was a significant reduction in all dynamic contrast-enhanced MRI parameters measured in tumor regions of interest (K(trans), k(ep), v(p), IAUGC-90); P < 0.001. Areas of normal-appearing peripheral zone showed no significant change; P = 0.285-0.879. Post-ADT, there was no significant change in apparent diffusion coefficient values in tumors, whilst apparent diffusion coefficient values significantly decreased in areas of normal-appearing peripheral zone, from 1.786 × 10(-3) mm(2) /s to 1.561 × 10(-3) mm(2) /s; P = 0.007. As expected the median Prostate-Specific Antigen (PSA) significantly reduced from 30 ng/mL to 1.5 ng/mL posttreatment, and median prostate volume dropped from 47.6 cm(3) to 24.9 cm(3) ; P < 0.001. These results suggest that dynamic contrast-enhanced MRI and diffusion-weighted MRI offer different information but that both could prove useful adjuncts to the anatomical information provided by T2-weighted imaging. dynamic contrast-enhanced as a marker of angiogenesis may help demonstrate ADT resistance and diffusion-weighted imaging may be more accurate in determining presence of tumor cell death versus residual tumor.

Local anaesthetic toxicity: are we prepared for the consequences in the Emergency Department?

BACKGROUND: Local anaesthetic agents are commonly encountered in the Emergency Department (ED). Local anaesthetic toxicity leading to cardiorespiratory arrest is a rare, but potentially fatal, complication of an overdose of these agents. A recent innovation in the treatment of severe local anaesthetic toxicity has been the introduction of intravenous lipid emulsion therapy (Intralipid 20%). The aim of this study was to gauge the current level of knowledge surrounding the administration and complications associated with commonly used local anaesthetic agents. METHODS: Questionnaires were distributed amongst the training grade doctors working in four Emergency Departments. Results were divided into two groups for ease of analysis. Core Trainees (CT) and Foundation Year 2 (F2) doctors were placed in one group. Specialist Registrars (SPR), Speciality Registrars (StR) and Staff Grades (SG) form the other group. RESULTS: The results showed that less than half of the CT/F2 group knew the maximum dose of lignocaine 1%. 80% of these doctors were unable to calculate the maximum dose of lignocaine 1% for an 80 kg man, and nearly one-third would administer a toxic dose. In addition, only one out of 30 in the CT/F2 group were aware of lipid emulsion therapy. CONCLUSIONS: Those using local anaesthetic should also be able to recognise the signs and symptoms of toxicity should this occur and act accordingly. The lack of knowledge amongst the more junior staff, as demonstrated by this project, highlights failings in teaching the basics of safe practices in the ED.

Taurine: a potential marker of apoptosis in gliomas.

New cancer therapies are being developed that trigger tumour apoptosis and an in vivo method of apoptotic detection and early treatment response would be of great value. Magnetic resonance spectroscopy (MRS) can determine the tumour biochemical profile in vivo, and we have investigated whether a specific spectroscopic signature exists for apoptosis in human astrocytomas. High-resolution magic angle spinning (HRMAS) (1)H MRS provided detailed (1)H spectra of brain tumour biopsies for direct correlation with histopathology. Metabolites, mobile lipids and macromolecules were quantified from presaturation HRMAS (1)H spectra acquired from 41 biopsies of grades II (n=8), III (n=3) and IV (n=30) astrocytomas. Subsequently, TUNEL and H&E staining provided quantification of apoptosis, cell density and necrosis. Taurine was found to significantly correlate with apoptotic cell density (TUNEL) in both non-necrotic (R=0.727, P=0.003) and necrotic (R=0.626, P=0.0005) biopsies. However, the ca 2.8 p.p.m. polyunsaturated fatty acid peak, observed in other studies as a marker of apoptosis, correlated only in non-necrotic biopsies (R=0.705, P<0.005). We suggest that the taurine (1)H MRS signal in astrocytomas may be a robust apoptotic biomarker that is independent of tumour necrotic status.

Pattern recognition of MRSI data shows regions of glioma growth that agree with DTI markers of brain tumor infiltration.

Gliomas are the most common primary brain tumors and the majority are highly malignant, with one of the worst prognoses for patients. Gliomas are characterized by invasive growth into normal brain tissue that makes complete surgical resection and accurate radiotherapy planning extremely difficult. We have performed independent component analysis of magnetic resonance spectroscopy imaging data from human gliomas to segment brain tissue into tumor core, tumor infiltration, and normal brain, with confirmation by diffusion tensor imaging analysis. Our data are consistent with previous studies that compared anomalies in isotropic and anisotropic diffusion images to determine regions of potential glioma infiltration. We show that coefficients of independent components can be used to create colored images for easy visual identification of regions of infiltrative tumor growth.

Metabolites of 2'-fluoro-2'-deoxy-D-glucose detected by 19F magnetic resonance spectroscopy in vivo predict response of murine RIF-1 tumors to 5-fluorouracil.

There is a clinical need for early detection of tumor response to therapy. This study aimed to determine whether metabolites of fluorodeoxyglucose (FDG) detected in solid mouse tumors in situ by I9F magnetic resonance spectroscopy (19F MRS) correlated with response to 5-fluorouracil chemotherapy. After injection of FDG (1.4 mmol/kg i.p.), uptake and metabolism was monitored for 2 h in RIF-1 tumors. FDG was detectable immediately, and after 10 min, a second broad peak was detected 5-6 ppm upfield. 19F MRS analysis of cell and tumor extracts in vitro showed that the upfield peak (> or =15% of the total detectable 19F signal) consisted of the epimer alpha-fluorodeoxymannose (FDM) and various conjugates. Mice treated with 5-fluorouracil (130 mg/kg) received, 48 h later, a repeat dose of FDG. The change in the rate of FDM formation, but not the FDG or total 19F signal, correlated significantly with the response to 5-fluorouracil (P = 0.032), suggesting that 19F MRS of FDM metabolism in vivo may be a novel means of predicting tumor response.

31P-nuclear magnetic resonance spectroscopy studies of the response of rat mammary tumors to endocrine therapy.

We have used 31P-nuclear magnetic resonance spectroscopy to detect the metabolic changes that occur in estrogen-sensitive, N-methyl-N-nitrosourea-induced rat mammary tumors as they regress following ovariectomy. In untreated animals the spectra of the tumors showed a steady loss of high energy phosphates (phosphocreatine and nucleoside triphosphates) and an increase in inorganic phosphate. This was reversed after ovariectomy. Spectral changes occurred before detectable regression of the tumor. Estrogen-insensitive tumors, grown from implanted Rama 600 and 622 cells, did not regress in response to ovariectomy, and their high energy phosphates continued to fall; estrogen-sensitive tumors also failed to respond to sham ovariectomy. These effects are probably due to the reduction in cellular energy requirements that occurs when the hormonal stimulus to growth is removed. Because the nuclear magnetic resonance method is noninvasive, this technique should be applicable clinically as a means of predicting the response of a tumor to endocrine therapy.

Metabolic consequences of a reversed pH gradient in rat tumors.

We have previously demonstrated (M. Stubbs, Z. M. Bhujwalla, G. M. Tozer, L. M. Rodrigues, R. J. Maxwell, R. Morgan, F. A. Howe, and J. R. Griffiths, NMR Biomed., 5: 351, 1992) that the intracellular pH (pHi) of several rat tumors is higher (> pH 7.0) than that of the tumor extracellular fluid (pHe), in contrast to normal tissues (e.g., liver) in which pHi is lower than pHe. In this paper we confirm a pHe of 6.8 +/- 0.07 (SEM) in Morris hepatoma 9618a by an independent method and report the tissue content of other ions by both 31P magnetic resonance spectroscopy and by conventional analysis in hepatomas and livers in rats. Compared with liver, tissue Na+ was 2-fold higher and tissue K+ was lower. Tissue Ca2+ was 8-fold higher (7.4 +/- 4.3 mumol/g wet weight) and tissue Pi was 2-fold higher (8.5 +/- 1.3 mumol/g wet weight) suggesting the presence of insoluble calcium phosphate. Cl- was unchanged (approximately 40 mumol/g wet weight), whereas HCO3- was lower in the hepatoma (12.4 +/- 0.83 compared to 15.5 +/- 0.76 mumol/g wet weight). Total tissue Mg2+ was similar in both tissues, but free [Mg2+] (calculated by two different methods) was approximately 5-fold lower in the hepatoma. The ATP values were 3.5-fold and [NAD]/[NADH] 9-fold lower in the hepatoma. The results are compatible with the hypothesis that the chronic partial hypoxia of tumor tissue involves changes in the linked equilibria of many ions and metabolites and may help explain such pathologies as calcification.

Preclinical evaluation of the fluorinated 2-nitroimidazole N-(2-hydroxy-3,3,3-trifluoropropyl)-2-(2-nitro-1-imidazolyl) acetamide (SR-4554) as a probe for the measurement of tumor hypoxia.

A novel probe, N-(2-hydroxy-3,3,3,-trifluoropropyl)-2-(2-nitro-1-imidazolyl) acetamide (SR-4554), has been used to detect tumor hypoxia noninvasively by 19F magnetic resonance spectroscopy (19F MRS). The compound was designed to undergo a hypoxia-dependent, one-electron reduction to metabolites that are selectively retained in tumors and has attractive pharmacokinetic, toxicological, and detection sensitivity properties. As a prelude to clinical studies, we report here for the first time on the ability to detect a MR signal following SR-4554 administration in various transplantable tumors and describe validation studies, consisting of a correlation between signal retention and radiobiological hypoxic fraction, and the effects of modulating the degree of hypoxia by hydralazine and carbogen breathing. SR-4554 was absorbed and then eliminated from EMT6 tumors with a half-life of 51 min following an injection of 180 mg/kg i.p. of SR-4554. Using a quantitative 19F MRS technique, the 19F retention index (19FRI; 19F signal level at 6 h/45 min) was determined for four commonly used murine tumors (EMT6, SCCVII, KHT, and RIF-1). The retention of high tumor concentrations of fluorinated probe at 6 h, despite the much lower (20-fold) concentration of parent SR-4554 detected by high-performance liquid chromatography, was consistent with the involvement of one or more nitroreduced metabolites and suggested that 19F MRS might give a quantitative measure of tumor hypoxia. In these murine tumors, 19FRI correlated with the reported radiobiological hypoxic fraction of the tumors (r = 0.988; P = 0.01). In addition, changes in tumor microenvironment were detected by 19F MRS. An increase in hypoxia induced by hydralazine treatment of RIF-1 tumor-bearing mice was associated with a 2.4-fold increase in 19FRI compared to untreated controls. In contrast, carbogen breathing by C3H mammary tumor-bearing mice produced a 6-fold decrease in the 19FRI compared to air-breathing mice. The data presented support the preclinical and clinical development of SR-4554 as a noninvasive probe for tumor hypoxia.

Carbogen breathing increases 5-fluorouracil uptake and cytotoxicity in hypoxic murine RIF-1 tumors: a magnetic resonance study in vivo.

The purpose of this study was to examine the effect of carbogen gas (95% O2-5% CO2) on uptake and metabolism of 5-fluorouracil (5FU) in murine RIF-1 tumors and their growth in vivo. In addition, we have explored the mechanisms by which carbogen can transiently affect the physiology of RIF-1 tumors. After i.p. injection of 1 mmol/kg 5FU into C3H mice, the uptake and metabolism of the drug by s.c. RIF-1 tumors was followed for 2 h noninvasively using 19F-magnetic resonance spectroscopy (MRS). In all animals, irrespective of tumor size, carbogen caused a significant increase in the half-life (t(1/2)) of the elimination of 5FU by the tumor and a significant increase in growth inhibition. In 2-3-g tumors (group II), carbogen also caused increased 5FU uptake and metabolism to the cytotoxic 5-fluoronucleotides, whereas in 0.8-1.5-g tumors (group I), only the t(1/2) was slightly increased. These results suggested that tumor size was an important factor in the effect of carbogen on tumor physiology. Measurements of RIF-1 tumor vascular and necrotic volume showed no significant differences between group I and group II tumors. However, 1H-MR images of RIF-1 tumors showed that carbogen caused a transient decrease in signal intensity, which correlated positively (P = 0.02) with tumor size, suggesting that larger tumors responded to carbogen by transiently increasing O2 uptake from the blood. 19F-MRS was used to measure RIF-1 tumor retention of the fluorinated nitroimidazole SR-4554. These studies also showed a positive correlation (P = 0.001) with tumor size, implying greater hypoxia in larger tumors. We propose that carbogen may transiently open nonfunctional blood vessels in the tumor, allowing increased leakage of 5FU from the plasma into the extracellular space. 5FU transport is known to be pH dependent. Intra- and extracellular tumor pH was measured using 31P- and 19F-MRS, which showed that carbogen caused a significant decrease in the extracellular pH of 0.1 unit in group II tumors and a consequent increase in the negative pH gradient across the tumor plasma membrane, which can cause increased 5FU uptake. The pH gradient was unaffected in group I tumors. We conclude that carbogen breathing can increase tumor uptake of 5FU by two independent mechanisms involving changes in tumor blood flow and pH, which consequently cause increased formation of 5-fluoronucleotides and cytotoxicity. The effect seems more pronounced in hypoxic tumors, implying that carbogen would be a valuable aid in clinical chemotherapy.

Vasoactive intestinal peptide stimulates glycolysis in pituitary tumours; 1H-NMR detection of lactate in vivo.

1H- and 31P-NMR spectroscopy has been applied to rats carrying implanted tumours in vivo, and used to observe simultaneous changes in intracellular pH (pHi) and lactate concentration during the stimulatory action of vasoactive intestinal polypeptide (VIP). A maximal decrease in pHi to a mean of 0.29 units below basal values was recorded. At the same time, 11 min after VIP, a maximal increase in tumour lactate was found, with a mean value of 150% of the basal concentration. The magnitude of these changes was compatible with in vitro measurements of basal lactate concentration and buffering capacity made on the same tumour line. It is concluded that VIP stimulates glycolysis by the tumour cells, resulting in an accumulation of lactate and a consequent fall in pHi.

31P-magnetic resonance spectroscopy studies of nucleated and non-nucleated erythrocytes; time domain data analysis (VARPRO) incorporating prior knowledge can give information on the binding of ADP.

Human erythrocytes have no nucleus, mitochondria or endoplasmic reticulum, whereas chicken erythrocytes have a nucleus and mitochondria and are closer in internal morphology, to cells such as the hepatocyte. Erythrocytes were used to test the hypothesis that 31P-MRS invisibility of ADP is associated with the presence of intracellular organelles. Simple frequency domain spectral analysis methods showed that all the acid extractable ADP (and ATP) was MR-visible in human erythrocytes. However, such methods gave variable estimates for 31P-NMR spectra of fresh chicken erythrocytes from which no conclusions could be drawn about the MR-visibility of ADP. Only when the data were fitted by a method incorporating prior knowledge of the ATP and ADP peak structure, using the time domain VARPRO method, was it possible to conclude that in fresh chicken erythrocytes, similar to other nucleated cells (liver, muscle), all the acid extractable ADP appeared to be MRS invisible, indicating binding or sequestration by intracellular organelles.

Investigations in vivo of the effects of carbogen breathing on 5-fluorouracil pharmacokinetics and physiology of solid rodent tumours.

PURPOSE: We have shown previously that carbogen (95% 0(2), 5% CO(2)) breathing by rodents can increase uptake of anticancer drugs into tumours. The aim of this study was to extend these observations to other rodent models using the anticancer drug 5-fluorouracil (5FU). 5FU pharmacokinetics in tumour and plasma and physiological effects on the tumour by carbogen were investigated to determine the locus of carbogen action on augmenting tumour uptake of 5FU. METHODS: Two different tumour models were used, rat GH3 prolactinomas xenografted s.c. into nude mice and rat H9618a hepatomas grown s.c. in syngeneic Buffalo rats. Uptake and metabolism of 5FU in both tumour models with or without host carbogen breathing was studied non-invasively using fluorine-19 magnetic resonance spectroscopy ((19)F-MRS), while plasma samples from Buffalo rats were used to construct a NONMEM pharmacokinetic model. Physiological effects of carbogen on tumours were studied using (31)P-MRS for energy status (NTP/Pi) and pH, and gradient-recalled echo magnetic resonance imaging (GRE-MRI) for blood flow and oxygenation. RESULTS: In both tumour models, carbogan-induced GRE-MRI signal intensity increases of approximately 60% consistent with an increase in tumour blood oxygenation and/or flow. In GH3 xenografts, (19)F-MRS showed that carbogen had no significant effect on 5FU uptake and metabolism by the tumours, and (31)P-MRS showed there was no change in the NTP/Pi ratio. In H9618a hepatomas, (19)F-MRS showed that carbogen had no effect on tumour 5FU uptake but significantly ( p=0.0003) increased 5FU elimination from the tumour (i.e. decreased the t(1/2)) and significantly ( p=0.029) increased (53%) the rate of metabolism to cytotoxic fluoronucleotides (FNuct). The pharmacokinetic analysis showed that carbogen increased the rate of tumour uptake of 5FU from the plasma but also increased the rate of removal. (31)P-MRS showed there were significant ( p

Do junior doctors know where to insert chest drains safely?

BACKGROUND: The safe insertion of a chest drain is a skill doctors across specialties require. Incorrect placement can lead to significant morbidity and even mortality. METHODS: This audit surveyed junior doctors working in a teaching hospital about their specialty and level of experience with intercostal drains. They were then asked to mark on a photograph where they would insert a chest drain for a pneumothorax in a non-emergency situation. RESULTS: Of the 55 junior doctors surveyed, 45% were outside the safe area of chest drain insertion as defined by the British Thoracic Society. The most common error was a choice of insertion site too low (24%). CONCLUSIONS: In this audit 45% of juniors surveyed would have placed a chest drain outside the safe triangle recommended by the British Thoracic Society. The common mistake of a choice of insertion site too low should be discussed in postgraduate teaching programmes.

Understanding the tumor metabolic phenotype in the genomic era.

Now, at the beginning of a new century, 80 years after Warburg's Nobel prize winning discoveries, we are beginning to make sense of the underlying causes of the well known metabolic phenotype of tumor cells. Building on decades of research to understand the interrelationships between respiration and glycolysis in cancer, the tumor metabolic phenotype can now begin to be understood in a genomic context. With the discovery of hypoxia inducible factor-1 (HIF-1), which is widely overexpressed across a broad range of cancers, modern molecular tools have allowed us to put together the pattern of events that might explain the metabolic differences between tumor and normal cells. HIF-1 controls cellular and systemic responses to oxygen availability and coordinates up-regulation of genes involved in many pathways concerned with tumour growth and metabolism including angiogenesis, glucose and energy metabolism, cellular proliferation, differentiation and viability, apoptosis, pH regulation and matrix metabolism. These findings begin to explain how glucose uptake and glycolysis could be up-regulated in cancer cells (through binding to a core DNA recognition sequence) in a co-ordinated and constitutive fashion that may also allow us to elucidate new targets for tumor therapy.

Monitoring pharmacokinetics of anticancer drugs: non-invasive investigation using magnetic resonance spectroscopy.

Magnetic resonance spectroscopy (MRS) offers the unique advantage of detecting, identifying and quantifying chemicals deep within the living body in a totally non-invasive manner. In studies on pharmacology and toxicology of anticancer drugs, MRS and the closely related technique magnetic resonance imaging (MRI) have many uses. MRS in particular, despite its low sensitivity, offers unique insights into pharmacokinetics (the changing concentration of the drug at its site of action) which can be monitored, and metabolism (both activation and detoxification) can be detected in real time. This review considers some recent work on (19)F, (31)P, (1)H and (13)C MRS of anticancer drugs. Future possibilities for (13)C MRS and (1)H MRS studies of drugs and their metabolites are considered in detail.