α-Aryl substituted GdDOTA derivatives, the perfect contrast agents for MRI?

Enhancing the performance of Gd3+ chelates as relaxation agents for MRI has the potential to lower doses, improving safety and mitigating the environmental impact on our surface waters. More than three decades of research into manipulating the properties of Gd3+ have failed to develop a chelate that simultaneously optimizes all relevant parameters and affords maximal relaxivity. Introducing aryl substituents into the α-position of the pendant arms of a GdDOTA chelate affords chelates that, for the first time, simultaneously optimize all physico-chemical properties. Slowing tumbling by binding to human serum albumin affords a relaxivity of 110 ± 5 mM-1 s-1, close to the maximum possible. As discrete chelates, these α-aryl substituted GdDOTA chelates exhibit relaxivities that are 2-3 times higher than those of currently used agents, even at the higher fields (1.5 & 3.0 T) used in modern clinical MRI.

"There should be one spot that you can go:" BRCA mutation carriers' perspectives on cancer risk management and a hereditary cancer registry

Individuals who carry BRCA1 or BRCA2 pathogenic variants are recommended to have extensive cancer prevention screening and risk-reducing surgeries. Uptake of these recommendations is variable, and there remains room for improvement in the risk management of BRCA carriers. This paper explores female BRCA carriers' experiences with the current model of care and their perspectives on (and interest in) an inherited cancer registry. Findings can inform the development of a dedicated high-risk screening and management program for these patients. Quantitative and qualitative data were gathered through a provincial descriptive survey and semi-structured qualitative interviews to assess BRCA carriers' opinions toward risk management services in the province of Newfoundland and Labrador (NL), Canada. Survey (n = 69) and interview data (n = 15) revealed continuity and coordination challenges with the current system of care of high-risk individuals. Respondents suggested an inherited cancer registry would help identify high-risk individuals and provide a centralized system of risk management for identified carriers. Respondents identified concerns about the privacy of their registry data, including who could access it. Findings suggest BRCA carriers see great value in an inherited cancer registry. Specifically, participants noted it could provide a centralized system to help improve the coordination of burdensome, life-long risk management. Important patient concerns about protecting their privacy and their health data confidentiality must be addressed in patient and public information and informed consent documents about a registry.

Diastereoselective Synthesis of α-Aryl-Substituted LnDOTA Chelates from Achiral Starting Materials by Deracemization Under Mild Conditions

Substituted derivatives of the DOTA framework are of general interest to alter chelate properties and facilitate the conjugation of chelates to other molecular structures. However, the scope of substituents that can be introduced into the α-position has traditionally been limited by the availability of a suitable enantiopure starting materials to facilitate a stereoselective synthesis. Tetra-substituted DOTA derivatives with phenyl and benzoate substituents in the α-position have been prepared. Initial syntheses used enantiopure starting materials but did not afford enantiopure products. This indicates that the integrity of the stereocenters was not preserved during synthesis, despite the homo-chiral diastereoisomer being the major reaction product. The homochiral diastereoisomer could be produced as the major or sole reaction product when starting from racemic or even achiral materials. Deracemization was found to occur during chelation through the formation of an enolate stabilized by the aryl substituent. This general ability of aryl groups to enable deracemization greatly increases the range of substituents that can be introduced into DOTA-type ligands with diastereochemical selectivity.

Identifying risk factors and implications for beach drowning prevention amongst an Australian multicultural community

Multicultural communities in Australia are recognised as a priority area for drowning prevention, but no evidence-based study has addressed their knowledge of beach safety. This study used an online survey tool to identify and examine risk factors relating to swimming ability, beach visitation characteristics and behaviour, and beach safety knowledge of the Australian Southern Asian community to assist in the development of future beach safety interventions. Data was obtained through 249 online and in-person surveys of people aged > 18 years. Most respondents reported poor swimming ability (80%), often swam in in the absence of lifeguards (77%), did not understand the rip current hazard (58%), but reported that they entered the water (76%) when visiting beaches. Close to one-quarter (28%) had not heard, or didn't know the purpose, of the red and yellow beach flags, which identify lifeguard supervised areas on Australian beaches. Length of time living in Australia is an important beach safety consideration for this community, with minimal differences in terms of gender and age. Those who have lived < 10 years in Australia visit beaches more frequently and are less likely to have participated in swimming lessons, be able to swim, heard of the flags or swim between them, understand rip currents, or have participated in a beach safety program. Very few (3%) respondents received beach safety information from within their own community. The importance of beach safety education and swimming lessons within the Southern Asian community should be prioritised for new and recent migrants to Australia.

COVID-19 conundrum: Precepting during a pandemic

In an effort to expedite the publication of articles , AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Audit of waist measurement methods during statutory diving medical assessments

BACKGROUND

Measurement of waist circumference is used to assess abdominal fat and risk of heart disease, type 2 diabetes, cancer and stroke. It is performed in several clinical settings for health promotion and medical assessment purposes, including statutory medical assessments where results may influence decisions on fitness to work. Under the Diving at Work Regulations 1997, working divers must have an annual assessment of their fitness to dive performed by an approved medical examiner of divers (AMED), appointed by the Health and Safety Executive (HSE). The assessment includes measurement of height, weight and waist circumference, the latter used as an indicator of central adiposity and associated health risks.

AIMS

To establish the practice of AMEDs in measuring waist circumference of working divers undergoing medical assessment to determine their fitness to dive.

METHODS

Ninety-seven AMEDs were sent a questionnaire and asked to describe their current practice in measuring waist circumference. The response rate was 79%. The audit standard used was the consensus document published by the World Health Organization (WHO).

RESULTS

Of the 77 responses, 76 were completed sufficiently to allow analysis. When the waist was measured, there was consistency in the diver's level of clothing, stage of breathing and posture for the procedure but variability in the site of measurement. Only 7/76 (9%) respondents carried out waist measurement fully in line with WHO guidance.

CONCLUSIONS

The audit has identified that there is a need for guidance for AMEDs on measuring waist circumference in the statutory medical assessment of working divers.

Analysis of the Relaxometric Properties of Extremely Rapidly Exchanging Gd3+ Chelates: Lessons from a Comparison of Four Isomeric Chelates

Relaxometric analyses and in particular the use of fast-field cycling techniques have become routine in the study of paramagnetic metal complexes. The field dependence of the solvent proton relaxation properties (nuclear magnetic relaxation dispersion, NMRD) can provide unparalleled insights into the chemistry of these complexes. However, analyzing NMRD data is a multiparametric problem, and some sets of variables are mutually compensatory. Specifically, when fitting NMRD profiles, the metal-proton distance and the rotational correlation time constant have a push-pull relationship in which a change to one causes a predictable compensation in the other. A relaxometric analysis of four isomeric chelates highlights the pitfalls that await when fitting the NMRD profiles of chelates for which dissociative water exchange is extremely rapid. In the absence of independently verified values for one of these parameters, NMRD profiles can be fitted to multiple parameter sets. This means that NMRD fitting can inadvertently be used to buttress a preconceived notion of how the complex should behave when a different parameter set may more accurately describe the actual behavior. These findings explain why the effect of very rapid dissociative exchange on the hydration state of Gd³⁺ has remained obscured until only recently.

Moral distress revisited: the viewpoints and responses of nurses

AIM

To present and discuss the main themes that were revealed following an analysis of the qualitative research findings that were extracted from a national survey regarding the causes and effects of moral distress amongst New Zealand nurses.

BACKGROUND/INTRODUCTION

Moral distress continues to be a major concern amongst nurses around the world. In New Zealand, a country where nurses have just been on strike over their working conditions and the deteriorating state of their roles within the health services, it remains a major issue.

METHOD

In the original research project, large numbers of nurses supplied not only quantitative data that revealed the extent and impact of moral distress on their practices, but also extensive notes that more specifically explained the causes and effects of their moral distress. This material has since been thematically analysed and is now presented.

FINDINGS/RESULTS

The data strongly suggested that New Zealand nurses experienced and attempted to respond to several major issues; that is, they were not properly supported by 'the system', frequently experienced problems with managers and bullying, witnessing poor care practices and collegial incompetence, and suffered from ongoing problems caused by moral residue.

CONCLUSION

Under current working conditions, nurses are struggling under an increasing weight of moral residue to maintain their ethical standards within an increasingly difficult ethical climate.

IMPLICATIONS FOR NURSING AND HEALTH POLICY

This research suggests that although nurses clearly seek out and use various ways to cope with moral distress in their practices, there is a continuing need for moral courage and strengthening of moral resilience that involves greater input from not just nurses themselves, but nurse managers, educators and other health services representatives.

Penile Paget's Disease: A Case Report and Review of the Literature

Extramammary Paget's Disease (EMPD) is a rare cutaneous, slow growing, intraepithelial adenocarcinoma that can be either primary (intraepithelial arising within the epidermis) or secondary (intraepithelial spread of a visceral carcinoma). Here we present the case of a 63-year-old male with EMPD of the glans penis stemming from underlying urothelial carcinoma. Our treatment decision elected for management with chemotherapy and local treatment with radiation therapy. Subsequent, review of the literature demonstrated a rare disease with a variety of underlying malignancies causing this secondary pathology. Caregivers should be aware of the association of Paget's disease and urothelial cancer and should have a high index of suspicion that erythematous penile lesions may represent Paget's disease and that penile biopsies should be performed early in this setting.

Crystal Structures of DOTMA Chelates from Ce3+ to Yb3+ : Evidence for a Continuum of Metal Ion Hydration States

The crystal structures of chelates formed between each stable paramagnetic lanthanide ion and the octadentate polyamino carboxylate ligand DOTMA are described. A total of 23 individual chelates structures were obtained; in each chelate the coordination geometry around the metal ion is best described as a twisted square antiprism (torsion angle -25.0°--31.4°). Despite the uniformity of the general coordination geometry provided by the DOTMA ligand, there is a considerable variation in the hydration state of each chelate. The early Ln³⁺ chelates are associated with a single inner sphere water molecule; the Ln-OH₂ interaction is remarkable for being very long. After a clear break at gadolinium, the number of chelates in the unit cell that have a water molecule interacting with the Ln³⁺ decreases linearly until at Tm³⁺ no water is found to interact with the metal ion. The Ln-OH₂ distance observed in the chelates of the later Ln³⁺ ions are also extremely long and increase as the ions contract (2.550-2.732 Å). No clear break between hydrated and dehydrated chelates is observed; rather this series of chelates appear to represent a continuum of hydration states in which the ligand gradually closes around the metal ion as its ionic radius decreases (with decreased hydration) and the metal drops down into the coordination cage.

Differences in the Relaxometric Properties of Regioisomeric Benzyl-DOTA Bifunctional Chelators: Implications for Molecular Imaging

The bifunctional chelator S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane- N, N', N″, N‴-1,4,7,10-tetraacetate (IB-DOTA) is on paper the most attractive of the commercially available bifunctional chelators for magnetic resonance imaging (MRI) applications. The preserved DOTA scaffold is known to produce extremely kinetically and thermodynamically robust chelates with the Gd³⁺ ion. Also, ligation through four acetate pendant arms should ensure that the rapid water exchange kinetics so, crucial to the function of an MRI contrast agent are retained. However, upon ligation of the Gd³⁺ ion, IB-DOTA differentiates into two distinct isomers defined by the positions of the benzylic substituent (corner or side). A relaxometric analysis of these two isomers revealed marked differences in the property and behavior of the two chelates. Most notably the side isomer is found to be substantially more likely to aggregate in aqueous solution than its corner counterpart. This aggregation results in higher relaxivity for the side isomer versus the corner isomer, an observation that potentially obscures the impact of differences in water exchange kinetics between the two isomers. The side isomer is composed of a significant fraction of a twisted square antiprismatic coordination geometry that exchanges water more rapidly than optimal (τ_M = 7 ns) for maximizing relaxivity. The impact of this excessively fast exchange is not observed in the relaxivity of the side isomer only because in isolation this chelate tumbles much more slowly than the corner isomer. However, this situation is not expected to persist when the chelate is employed in a typical bioconjugate. These results imply that the corner isomer of IB-DOTA may represent a better choice of bifunctional chelator for bioconjugation applications in which a large macromolecule is to be tagged for MRI applications.

ParaCEST Agents Encapsulated in Reverse Nano-Assembled Capsules (RACs): How Slow Molecular Tumbling Can Quench CEST Contrast

Although paraCEST is a method with immense scope for generating image contrast in MRI, it suffers from the serious drawback of high detection limits. For a typical discrete paraCEST agent the detection limit is roughly an order of magnitude higher than that of a clinically used relaxation agent. One solution to this problem may be the incorporation of a large payload of paraCEST agents into a single macromolecular agent. Here we report a new synthetic method for accomplishing this goal: incorporating a large payload of the paraCEST agent DyDOTAM3+ into a Reverse Assembled nano-Capsule. An aggregate can be generated between this chelate and polyacrylic acid (PAA) after the addition of ethylene diamine. Subsequent addition of polyallylamine hydrochloride (PAH) followed by silica nanoparticles generated a robust encapsulating shell and afforded capsule with a mean hydrodynamic diameter of 650 ± 250 nm. Unfortunately this encapsulation did not have the effect of amplifying the CEST effect per agent, but quenched the CEST altogether. The quenching effect of encapsulation could be attributed to the effect of slowing molecular tumbling, which is inevitable when the chelate is incorporated into a nano-scale material. This increases the transverse relaxation rate of chelate protons and a theoretical examination using Solomon Bloembergen Morgan theory and the Bloch equations shows that the increase in the transverse relaxation rate constant for the amide protons, in even modestly sized nano-materials, is sufficient to significantly quench CEST.

A cross-sectional analysis of factors associated with the intention to engage in tobacco treatment among inpatients in a state psychiatric hospital

WHAT IS KNOWN ON THE SUBJECT?: People admitted to psychiatric facilities have high rates of tobacco use and hospitalizations present an opportunity for patients to have conversations about tobacco use treatment. Clinicians may believe that people with mental illnesses are not interested in quitting or that they do not understand the importance of treatment. Positive attitudes towards tobacco treatment, viewing that participating in treatment is normal care, and feeling that one is quite able to participate in such treatment predicts intentions to participate in treatment, which, in turn, predicts actual participation. WHAT DOES THIS PAPER ADD TO EXISTING KNOWLEDGE?: Psychiatric patients who use tobacco use report poor prior involvement with tobacco treatment. Positive attitudes towards, encouraging opinions of other people about, and having a sense of control over taking part in tobacco treatment increases plans to engage in treatment. Having a sense of control in taking part in tobacco treatment is strongly associated with prior experiences with evidence-based treatment. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Because psychiatric hospitalizations are an opportunity for addressing tobacco use and treatment, clinicians should be prepared to support willing patients, especially those with prior substance use histories. Support should include providing them with information regarding tobacco treatment options during their hospital stay and ways that they can continue to receive care after discharge. Clinicians should be promoters of pro-tobacco treatment attitudes and supporting patients' sense of control over participating in treatment during hospitalization.

ABSTRACT

Introduction Hospitalized tobacco users with mental illnesses (MI) may face several barriers to stopping smoking. However, motivational factors that affect the intention to engage in tobacco treatment have been shown to predict actual engagement. Aim To use the Theory of Planned Behavior to assess intentions to and prior experiences of engaging in evidence-based tobacco treatment among hospitalized individuals with MI. Method A cross-sectional survey was conducted among 115 patients in a state psychiatric hospital. Multivariate analyses were used to examine associations with the intentions and prior experiences of engaging in tobacco treatment. Results After controlling for demographic and smoking history, attitudes, subjective norms and perceived behavioural control towards engaging in tobacco treatment were significantly associated with intentions towards treatment engagement. Only higher scores on perceived behavioural control and lower education levels were associated with reported prior experiences of tobacco treatment. Discussion The low prior treatment engagement scores, but relatively higher intention to engage scores among participants suggests the need for deliberate support for evidence-based tobacco treatment during psychiatric hospitalizations. Implications for practice Clinician training in tobacco treatment can promote self-efficacy to engage patients while supporting patients' control so that tobacco treatment is an expected component of psychiatric care.

Gadolinium Chelate Safety in Pregnancy: Barely Detectable Gadolinium Levels in the Juvenile Nonhuman Primate after in Utero Exposure

Purpose To determine whether gadolinium remains in juvenile nonhuman primate tissue after maternal exposure to intravenous gadoteridol during pregnancy. Materials and Methods Gravid rhesus macaques and their offspring (n = 10) were maintained, as approved by the institutional animal care and utilization committee. They were prospectively studied as part of a pre-existing ongoing research protocol to evaluate the effects of maternal malnutrition on placental and fetal development. On gestational days 85 and 135, they underwent placental magnetic resonance imaging after intravenous gadoteridol administration. Amniocentesis was performed on day 135 prior to administration of the second dose of gadoteridol. After delivery, the offspring were followed for 7 months. Tissue samples from eight different organs and from blood were harvested from each juvenile macaque. Gadolinium levels were measured by using inductively coupled plasma mass spectrometry. Results Gadolinium concentration in the amniotic fluid was 0.028 × 10^-5 %ID/g (percentage injected dose per gram of tissue) 50 days after administration of one gadoteridol dose. Gadolinium was most consistently detected in the femur (mean, 2.5 × 10^-5 %ID/g; range, [0.81-4.1] × 10^-5 %ID/g) and liver (mean, 0.15 × 10^-5 %ID/g; range, [0-0.26] × 10^-5 %ID/g). Levels were undetectable in the remaining sampled tissues, with the exception of one juvenile skin sample (0.07 × 10^-5 %ID/g), one juvenile spleen sample (0.039 × 10^-5 %ID/g), and one juvenile brain (0.095 × 10^-5 %ID/g) and kidney (0.13 × 10^-5 %ID/g) sample. Conclusion The presence of gadoteridol in the amniotic fluid after maternal injection enables confirmation that it crosses the placenta. Extremely low levels of gadolinium are found in juvenile macaque tissues after in utero exposure to two doses of gadoteridol, indicating that a very small amount of gadolinium persists after delivery. ^© RSNA, 2017.

Pharmacist Impact on Pneumococcal Vaccination Rates through Incorporation of Immunization Assessment into Critical Pathways in an Acute Care Setting

Despite the availability of effective prevention and treatment measures, pneumococcal infection continues to be a significant source of morbidity and mortality. This study evaluated the impact of incorporating the assessment of pneumococcal vaccination status into selected critical pathways of at-risk patients. In a prospective, nonblinded, parallel-group trial, adult inpatients on four critical pathways were randomized into intervention or control groups. Nursing personnel screened all patients for previous pneumococcal vaccination. A pharmacist would then screen all patients for pneumococcal disease risk factors. If vaccination was indicated in the intervention group, the pharmacist educated the patient and/or caregiver, obtained patient consent, and asked the patient's physician for permission to immunize. No further action was undertaken with the control patients. A total of 231 patients were enrolled in the study (107 intervention, 124 control). Initial immunization rates were 46.8% in the control group and 56.1 % in the intervention group. Forty-six patients in the control group and 39 patients in the intervention group were eligible (unvaccinated with indication) for vaccination. Thirty-two (82.1%) of the patients in the intervention group were counseled and 19 (59.4%) were vaccinated. The overall vaccination rates were 73.8% in the intervention group and 56.1% in the control group (P < 0.001). Results indicate that incorporating assessment of pneumococcal immunization status into critical pathways is an effective way to improve immunization rates.

Crosslinked shells for nano-assembled capsules: a new encapsulation method for smaller Gd3+-loaded capsules with exceedingly high relaxivities

Nano-assembled capsules can incorporate large payloads of high relaxivity Gd3+, permitting the development of highly detectable molecular imaging agents for MRI. A new encapsulating shell, based upon cross-linked peptides, is found to afford smaller capsules (127 nm average diameter) with exceptionally high per-Gd3+ relaxivities (70.7 s-1 mmolal-1).

RADIATION DOSE MEASUREMENTS FOR HIGH-INTENSITY LASER INTERACTIONS WITH SOLID TARGETS AT SLAC

A systematic study of photon and neutron radiation doses generated in high-intensity laser-solid interactions is underway at SLAC National Accelerator Laboratory. These laser-solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source's (LCLS) Matter in Extreme Conditions (MEC) facility. Radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser-solid experiments at SLAC MEC in 2014 with peak intensity between 10¹⁸ and 7.1 × 10¹⁹ W cm^-2 are presented.

Balancing Rights and Duties in ‘Life and Death’ Decision Making Involving Children: a role for nurses?

In recent years, increasing pressures have been brought to bear upon nurses and others more closely to inform, involve and support the rights of parents or guardians when crucial ‘life and death’ ethical decisions are made on behalf of their seriously ill child. Such decisions can be very painful for all involved, and may easily become deadlocked when there is an apparent clash of moral ideals or values between the medical team and the parents or guardians. This article examines a growing number of such cases in New Zealand and analyses the moral parameters, processes, outcomes and ethical responses that must be considered when life and death ethical decisions involving children are made. The article concludes with a recommendation that nurses should be recognized as perhaps the most suitable of all health care personnel when careful mediation is needed to produce an acceptable moral outcome in difficult ethical situations.

Relative sensitivities of DCE-MRI pharmacokinetic parameters to arterial input function (AIF) scaling

Dynamic-Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) has been used widely for clinical applications. Pharmacokinetic modeling of DCE-MRI data that extracts quantitative contrast reagent/tissue-specific model parameters is the most investigated method. One of the primary challenges in pharmacokinetic analysis of DCE-MRI data is accurate and reliable measurement of the arterial input function (AIF), which is the driving force behind all pharmacokinetics. Because of effects such as inflow and partial volume averaging, AIF measured from individual arteries sometimes require amplitude scaling for better representation of the blood contrast reagent (CR) concentration time-courses. Empirical approaches like blinded AIF estimation or reference tissue AIF derivation can be useful and practical, especially when there is no clearly visible blood vessel within the imaging field-of-view (FOV). Similarly, these approaches generally also require magnitude scaling of the derived AIF time-courses. Since the AIF varies among individuals even with the same CR injection protocol and the perfect scaling factor for reconstructing the ground truth AIF often remains unknown, variations in estimated pharmacokinetic parameters due to varying AIF scaling factors are of special interest. In this work, using simulated and real prostate cancer DCE-MRI data, we examined parameter variations associated with AIF scaling. Our results show that, for both the fast-exchange-limit (FXL) Tofts model and the water exchange sensitized fast-exchange-regime (FXR) model, the commonly fitted CR transfer constant (K(trans)) and the extravascular, extracellular volume fraction (ve) scale nearly proportionally with the AIF, whereas the FXR-specific unidirectional cellular water efflux rate constant, kio, and the CR intravasation rate constant, kep, are both AIF scaling insensitive. This indicates that, for DCE-MRI of prostate cancer and possibly other cancers, kio and kep may be more suitable imaging biomarkers for cross-platform, multicenter applications. Data from our limited study cohort show that kio correlates with Gleason scores, suggesting that it may be a useful biomarker for prostate cancer disease progression monitoring.

Nano assembly and encapsulation; a versatile platform for slowing the rotation of polyanionic Gd(3+) -based MRI contrast agents

Encapsulating discrete Gd(3+) chelates in nano-assembled capsules (NACs) is a simple and effective method of preparing an MRI contrast agent capable of delivering a large payload of high relaxivity imaging agent. The preparation of contrast agent containing NACs had previously focussed on preparations incorporating GdDOTP(5-) into the internal aggregate. In this report we demonstrate that other Gd(3+) chelates bearing overall charges as low as 2- can also be used to prepare NACs. This discovery opens up the possibility of using Gd(3+) chelates that have inner-sphere water molecules that could further increase the relaxivity enhancement associated with the long τR that arises from encapsulation. However, encapsulation of the q = 1 chelate GdDTPA(2-) did not give rise to a significant increase in relaxivity relative to encapsulation of the outer-sphere chelate GdTTHA(3-). This leads us to the conclusion that in the NAC interior proton transport is not mediated by movement of whole water molecules and the enhanced relaxivity of Gd(3+) chelate encapsulated within NACs arises primarily from second sphere effects.

Effect of Repeated Glucagon Doses on Hepatic Glycogen in Type 1 Diabetes: Implications for a Bihormonal Closed-Loop System

OBJECTIVE

To evaluate subjects with type 1 diabetes for hepatic glycogen depletion after repeated doses of glucagon, simulating delivery in a bihormonal closed-loop system.

RESEARCH DESIGN AND METHODS

Eleven adult subjects with type 1 diabetes participated. Subjects underwent estimation of hepatic glycogen using (13)C MRS. MRS was performed at the following four time points: fasting and after a meal at baseline, and fasting and after a meal after eight doses of subcutaneously administered glucagon at a dose of 2 µg/kg, for a total mean dose of 1,126 µg over 16 h. The primary and secondary end points were, respectively, estimated hepatic glycogen by MRS and incremental area under the glucose curve for a 90-min interval after glucagon administration.

RESULTS

In the eight subjects with complete data sets, estimated glycogen stores were similar at baseline and after repeated glucagon doses. In the fasting state, glycogen averaged 21 ± 3 g/L before glucagon administration and 25 ± 4 g/L after glucagon administration (mean ± SEM) (P = NS). In the fed state, glycogen averaged 40 ± 2 g/L before glucagon administration and 34 ± 4 g/L after glucagon administration (P = NS). With the use of an insulin action model, the rise in glucose after the last dose of glucagon was comparable to the rise after the first dose, as measured by the 90-min incremental area under the glucose curve.

CONCLUSIONS

In adult subjects with well-controlled type 1 diabetes (mean A1C 7.2%), glycogen stores and the hyperglycemic response to glucagon administration are maintained even after receiving multiple doses of glucagon. This finding supports the safety of repeated glucagon delivery in the setting of a bihormonal closed-loop system.

Gadolinium Chelate Contrast Material in Pregnancy: Fetal Biodistribution in the Nonhuman Primate

PURPOSE

To determine the extent to which gadolinium chelate is found in nonhuman primate fetal tissues and amniotic fluid at 19-45 hours after intravenous injection of a weight-appropriate maternal dose of the contrast agent gadoteridol.

MATERIALS AND METHODS

Gravid Japanese macaques (n = 14) were maintained as approved by the institutional animal care and utilization committee. In the 3rd trimester of pregnancy, the macaques were injected with gadoteridol (0.1 mmol per kilogram of maternal weight). Fetuses were delivered by means of cesarean section within 24 hours of maternal injection (range, 19-21 hours; n = 11) or 45 hours after injection (n = 3). Gadolinium chelate levels in the placenta, fetal tissues, and amniotic fluid were obtained by using inductively coupled plasma mass spectrometry. The Wilcoxon rank sum test was used for quantitative comparisons.

RESULTS

Gadoteridol was present in the fetoplacental circulation at much lower quantities than in the mother. At both time points, the distribution of gadolinium chelate in the fetus was comparable to that expected in an adult. The highest concentration of the injected dose (ID) was found in the fetal kidney (0.0161% ID per gram in the 19-21-hour group). The majority of the in utero gadolinium chelate was found in the amniotic fluid and the placenta (mean, 0.1361% ID per organ ± 0.076 [standard deviation] and 0.0939% ID per organ ± 0.0494, respectively). Data acquired 45 hours after injection showed a significant decrease in the gadolinium chelate concentration in amniotic fluid compared with that in the 19-21-hour group (from 0.0017% to 0.0007% ID per gram; P = .01).

CONCLUSION

Amounts of gadolinium chelate in the fetal tissues and amniotic fluid were minimal compared with the maternal ID. This may impact future clinical studies on the safety of gadolinium contrast agent use in pregnancy.

Aggregation in amphiphilic macrocycle-substituted Gd(3+) DOTA-type chelates is affected by the regiochemistry of substitution

Gd(3+) chelates of macrocyclic bifunctional chelators (BFCs) can differentiate into two regioisomers: corner and side. These isomers afford different orientations of chelate relative to conjugate. These differences alter the self-assembly, tumbling, and effectiveness as magnetic resonance imaging contrast agents of the two biphenyl conjugate isomers.

Isomerism in benzyl-DOTA derived bifunctional chelators: implications for molecular imaging

The bifunctional chelator IB-DOTA has found use in a range of biomedical applications given its ability to chelate many metal ions, but in particular the lanthanide(III) ions. Gd(3+) in particular is of interest in the development of new molecular imaging agents for MRI and is highly suitable for chelation by IB-DOTA. Given the long-term instability of the aryl isothiocyanate functional group we have used the more stable nitro derivative (NB-DOTA) to conduct a follow-up study of some of our previous work on the coordination chemistry of chelates of these BFCs. Using a combination of NMR and HPLC to study the Eu(3+) and Yb(3+) chelates of NB-DOTA, we have demonstrated that this ligand will produce two discrete regioisomeric chelates at the point at which the metal ion is introduced into the BFC. These regioisomers are defined by the position of the benzylic substituent on the macrocyclic ring: adopting an equatorial position either at the corner or the side of the [3333] ring conformation. These regioisomers are incapable of interconversion and are distinct, separate structures with different SAP/TSAP ratios. The side isomer exhibits an increased population of the TSAP isomer, pointing to more rapid water exchange kinetics in this regioisomer. This has potential ramifications for the use of these two regioisomers of Gd(3+)-BFC chelates in MRI applications. We have also found that, remarkably, there is little or no freedom of rotation about the first single bond extending from the macrocyclic ring to the benzylic substituent. Since this is the linkage through which the chelate is conjugated to the remainder of the molecular imaging probe, this result implies that there may be reduced local rotation of the Gd(3+) chelate within a molecular imaging probe. This implies that this type of BFC could exhibit higher relaxivities than other types of BFC.

The presence of fast-exchanging proton species in aqueous solutions of paraCEST agents can impact rate constants measured for slower exchanging species when fitting CEST spectra to the Bloch equations

LnDOTA-tetraamide complexes typically exist in solution as a mixture of square-antiprismatic (SAP) and twisted square-antiprismatic (TSAP) coordination isomers. In most cases, the SAP isomer, which is preferred for CEST imaging, predominates, and the presence of the minor TSAP isomer is assumed to have little influence on quantitative measures of the water-exchange rate constant for the SAP isomer. Here, we sought to confirm the validity of this assumption by mixing two chelates with different SAP and TSAP isomer populations while measuring the water-exchange rate constant of the SAP isomer. The results show that an increase in the population of the TSAP isomer in solution results in as much as a 30% overestimation of the water-exchange rate constant for the SAP isomer when CEST spectra are fit to the Bloch equations. This effect was shown to be significant only when the TSAP isomer population exceeded 50%.

The confluence of structure and dynamics in lanthanide(III) chelates: how dynamics help define structure in solution

Coordination exchange processes tend to dominate the solution state behaviour of lanthanide chelates and generally prohibit the study of small conformational changes. In this article we take advantage of coordinatively rigid Eu(3+) chelates to examine the small conformational changes that occur in these chelates as water dissociatively exchanges in and out of the inner coordination sphere. The results show that the time-averaged conformation of the chelate alters as the water exchange rate increases. This conformational change reflects a change in the hydration state (q/r(LnH)(6)) of the chelate. The hydration state has recently come to be expressed as two separate parameters q and r(LnH). However, these two parameters simultaneously describe the same structural considerations which in solution are indistinguishable and intrinsically related to, and dependent upon, the dissociative water exchange rate. This realization leads to the broader understanding that a solution state structure can only be appreciated with reference to the dynamics of the system.

Notizen: Characterisation of Pairs of Isomeric Bisaminohexachlorocyclotetraphosphazatetraenes

The isolation of three pairs of isomeric bisaminohexachlorocyclotetraphosphazatetraenes, N4P4Cl6R2 (R = NHBut, NHEt, NMePh) is described. Structures are proposed for the derivatives on the basis of 81P NMR data.

First results from the LUX dark matter experiment at the Sanford underground research facility

The Large Underground Xenon (LUX) experiment is a dual-phase xenon time-projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota). The LUX cryostat was filled for the first time in the underground laboratory in February 2013. We report results of the first WIMP search data set, taken during the period from April to August 2013, presenting the analysis of 85.3 live days of data with a fiducial volume of 118 kg. A profile-likelihood analysis technique shows our data to be consistent with the background-only hypothesis, allowing 90% confidence limits to be set on spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 × 10(-46) cm(2) at a WIMP mass of 33 GeV/c(2). We find that the LUX data are in disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.

Influence of pre-diagnostic cigarette smoking on colorectal cancer survival: overall and by tumour molecular phenotype

BACKGROUND

Smoking is a risk factor for incident colorectal cancer (CRC); however, it is unclear about its influence on survival after CRC diagnosis.

METHODS

A cohort of 706 CRC patients diagnosed from 1999 to 2003 in Newfoundland and Labrador, Canada, was followed for mortality and recurrence until April 2010. Smoking and other relevant data were collected by questionnaire after cancer diagnosis, using a referent period of '2 years before diagnosis' to capture pre-diagnosis information. Molecular analyses of microsatellite instability (MSI) status and BRAF V600E mutation status were performed in tumour tissue using standard techniques. Multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated with Cox proportional hazards regression, controlling for major prognostic factors.

RESULTS

Compared with never smokers, all-cause mortality (overall survival, OS) was higher for current (HR: 1.78; 95% CI: 1.04-3.06), but not for former (HR: 1.06; 95% CI: 0.71-1.59) smokers. The associations of cigarette smoking with the study outcomes were higher among patients with ≥40 pack-years of smoking (OS: HR: 1.72; 95% CI: 1.03-2.85; disease-free survival (DFS: HR: 1.99; 95% CI: 1.25-3.19), those who smoked ≥30 cigarettes per day (DFS: HR: 1.80; 95% CI: 1.22-2.67), and those with microsatellite stable (MSS) or MSI-low tumours (OS: HR: 1.38; 95% CI: 1.04-1.82 and DFS: HR: 1.32; 95% CI: 1.01-1.72). Potential heterogeneity was noted for sex (DFS HR: 1.68 for men and 1.01 for women: P for heterogeneity=0.04), and age at diagnosis (OS: HR: 1.11 for patients aged <60 and 1.69 for patients aged ≥60: P for heterogeneity=0.03).

CONCLUSIONS

Pre-diagnosis cigarette smoking is associated with worsened prognosis among patients with CRC.

Human whole-blood (1)H2O longitudinal relaxation with normal and high-relaxivity contrast reagents: influence of trans-cell-membrane water exchange

PURPOSE

Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R1 ) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions.

METHODS

Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA.

RESULTS

In plasma, the (1) H2 O R1 [CR]-dependence was nonlinear for gadobenate and gadofosveset secondary to CR interactions with the serum macromolecule albumin, and was well described by an analytical expression for effective 1:1 binding stoichiometry. In whole blood, the (1) H2 O R1 [CR]-dependence was markedly non-linear for all CRs, and was well-predicted by an expression for equilibrium exchange of water molecules between plasma and intracellular spaces using a priori parameter values only.

CONCLUSION

In whole blood, (1) H2 O R1 exhibits a nonlinear relationship with [CR] over 0 to 18 mM CR. The nonlinearity is well described by exchange of water between erythrocyte and plasma compartments, and is particularly evident for high relaxivity CRs.

Detecting human papillomavirus in ocular surface diseases

PURPOSE

Human papillomavirus (HPV) infection has been implicated as a possible inducing factor for benign and neoplastic ocular surface diseases such as pterygia and ocular-surface squamous neoplasia (OSSN). However, the wide range in HPV prevalence previously reported for both diseases adds controversy to, and highlights the limitations of, this field. The aim of this study was to determine the prevalence of HPV in pterygia and OSSN and to devise a standardized approach for detecting viral DNA in ocular tissue samples.

METHODS

DNA was extracted from a variety of specimens (n = 160), including formalin-fixed paraffin-embedded tissue shavings, fresh tissue, and cultured cells. Nested PCR for HPV with consensus and subtype-specific primers was used to detect viral DNA. Confirmatory assays, including molecular sequencing, histology, and immunohistochemistry for HPV E6 protein and p16 were also performed.

RESULTS

HPV was not detected in pterygia or normal conjunctiva. However, 6.5% (3/46) of OSSN samples were HPV-positive by PCR, sequencing, and immunohistochemistry. Positive cases were all squamous cell carcinoma of the conjunctiva (SCCC), the most severe form of OSSN, representing 12.5% (3/24) of SCCCs in our cohort. HPV-16 was the genotype identified in each case and this correlated with the presence of koilocytes and intense immunoreactivity for p16. Our study found no association between pterygia and OSSN with other oncogenic viruses, such as EBV or CMV, as they were just as prevalent in normal conjunctiva.

CONCLUSIONS

The low prevalence of HPV-16 in ocular surface disease suggests infection is not a cause but a cofactor in disease development.

The effect of regioisomerism on the coordination chemistry and CEST properties of lanthanide(III) NB-DOTA-tetraamide chelates

Chemical exchange saturation transfer (CEST) offers many advantages as a method of generating contrast in magnetic resonance images. However, many of the exogenous agents currently under investigation suffer from detection limits that are still somewhat short of what can be achieved with more traditional Gd(3+) agents. To remedy this limitation we have undertaken an investigation of Ln(3+) DOTA-tetraamide chelates (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) that have unusually rigid ligand structures: the nitrobenzyl derivatives of DOTA-tetraamides with (2-phenylethyl)amide substituents. In this report we examine the effect of incorporating hydrophobic amide substituents on water exchange and CEST. The ligand systems chosen afforded a total of three CEST-active isomeric square antiprismatic chelates; each of these chelates was found to have different water exchange and CEST characteristics. The position of a nitrobenzyl substituent on the macrocyclic ring strongly influenced the way in which the chelate and Ln(3+) coordination cage distorted. These differential distortions were found to affect the rate of water proton exchange in the chelates. But, by far the greatest effect arose from altering the position of the hydrophobic amide substituent, which, when forced upwards around the water binding site, caused a substantial reduction in the rate of water proton exchange. Such slow water proton exchange afforded a chelate that was 4.5 times more effective as a CEST agent than its isomeric counterparts in dry acetonitrile and at low temperatures and very low presaturation powers.