Tracking the dissolution of calcite single crystals in acid waters: a simple method for measuring fast surface kinetics

Although the dissolution kinetics of calcite in acid waters has been studied for more than a century, the process is not fully understood, and for particles and microcrystals the process is often assumed to be diffusion-controlled. Herein, the dissolution kinetics of calcite single microcrystals in aqueous solution (pH ca. 3) has been investigated for the first time by a combination of real-time optical microscopy coupled with numerical simulations. The small size and well-defined geometry of rhombohedral calcite single crystals enables the measurement of the dissolution rates of the individual crystal faces exposed to the solvent and an assessment of the relative importance of corners and edges compared to the {104} faces. Data are used to parameterise finite element method (FEM) models for the quantitative analysis of dissolution kinetics. The simulations provide an accurate determination of the near-interface concentration of solution species during dissolution, as well as concentration gradients. The intrinsic first-order dissolution rate constant for the attack of protons on the exposed {104} faces, k_surf = (6.4 ± 2.8) × 10^-4 m s^-1, is in good agreement with previous microscopic and macroscopic measurements, corroborating the method. This study is a further demonstration of the power of simple in situ optical microscopy for quantitative interfacial (dissolution/growth) kinetic measurements, using a configuration of practical relevance for processes as diverse as the remediation of acid water and scale removal.

Single-crystal X-ray diffraction and NMR crystallography of a 1:1 cocrystal of dithianon and pyrimethanil

A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile-4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental 1H and 13C chemical shifts are determined from two-dimensional 1H-13C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C-H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a 1H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the 1H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N-H...O and C-H...O hydrogen bonding, while changes of -2.7 and -1.5 ppm are due to ring current effects associated with C-H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.

ACTH and gonadotropin deficiencies predict mortality in patients treated for nonfunctioning pituitary adenoma: long-term follow-up of 519 patients in two large European centres

CONTEXT AND OBJECTIVE

Nonfunctioning pituitary adenomas (NFPAs) are the most common subtype of pituitary tumour. Hypopituitarism is observed in NFPAs due to tumour- or treatment-related factors and may increase mortality risk. Here, we analysed the associations of hypopituitarism, hormone replacement and mortality in a large NFPA cohort derived from two large European centres.

DESIGN, SETTING AND PARTICIPANTS

Case note review of all patients treated for NFPA in University Hospitals Birmingham and Beaumont Hospital Dublin between 1999 and 2014 was performed.

MAIN OUTCOME MEASURES

Clinical presentation, treatment strategies, pituitary function and vitality status were recorded in each patient. A multivariate Cox regression model was used to examine the association between hypopituitarism, hormone replacement and premature mortality.

RESULTS

A total of 519 patients were included in the analysis. Median duration of follow-up was 7·0 years (0·5-43). A total of 81 deaths were recorded (15·6%). On multivariate analysis, adrenocorticotropic hormone (ACTH) and gonadotropin (Gn) deficiencies were associated with an increased relative risk of death (OR 2·26, 95% CI 1·15-4·47, P = 0·01 and OR 2·56, 95% CI 1·10-5·96, P = 0·01, respectively). Increased hydrocortisone (HC) (P-trend = 0·02) and lower levothyroxine (LT4) doses (P-trend = 0·03) were associated with increased risk of death. Mortality increased with the degree of pituitary failure observed (P-trend = 0·04).

CONCLUSION

ACTH and gonadotropin-deficient patients have higher mortality rates compared to those with intact hormonal axes. Excessive HC and suboptimal LT4 replacement may also increase risk of death. Complex associations between hormone deficiency and replacement underpin the increased mortality risk in NFPA patients.

Enzymatic single-chain antibody tagging: a universal approach to targeted molecular imaging and cell homing in cardiovascular disease

RATIONALE

Antibody-targeted delivery of imaging agents can enhance the sensitivity and accuracy of current imaging techniques. Similarly, homing of effector cells to disease sites increases the efficacy of regenerative cell therapy while reducing the number of cells required. Currently, targeting can be achieved via chemical conjugation to specific antibodies, which typically results in the loss of antibody functionality and in severe cell damage. An ideal conjugation technique should ensure retention of antigen-binding activity and functionality of the targeted biological component.

OBJECTIVE

To develop a biochemically robust, highly reproducible, and site-specific coupling method using the Staphylococcus aureus sortase A enzyme for the conjugation of a single-chain antibody (scFv) to nanoparticles and cells for molecular imaging and cell homing in cardiovascular diseases. This scFv specifically binds to activated platelets, which play a pivotal role in thrombosis, atherosclerosis, and inflammation.

METHODS AND RESULTS

The conjugation procedure involves chemical and enzyme-mediated coupling steps. The scFv was successfully conjugated to iron oxide particles (contrast agents for magnetic resonance imaging) and to model cells. Conjugation efficiency ranged between 50% and 70%, and bioactivity of the scFv after coupling was preserved. The targeting of scFv-coupled cells and nanoparticles to activated platelets was strong and specific as demonstrated in in vitro static adhesion assays, in a flow chamber system, in mouse intravital microscopy, and in in vivo magnetic resonance imaging of mouse carotid arteries.

CONCLUSIONS

This unique biotechnological approach provides a versatile and broadly applicable tool for procuring targeted regenerative cell therapy and targeted molecular imaging in cardiovascular and inflammatory diseases and beyond.

Analysis of veterinary drug residues in fish and shrimp composites collected during the Canadian Total Diet Study, 1993–2004

Thirty shrimp, marine fish, freshwater fish, and canned fish composite samples collected and prepared as part of the Canadian Total Diet Study were analysed for 39 different veterinary drug residues. The analyses were undertaken to obtain baseline data that could be used to estimate the dietary exposure of Canadians to these residues. The most frequently observed residue was AOZ (four out of 30 samples), the metabolite of furazolidone, at a range of 0.50 to 2.0 ng g(-1) wet weight. Other residues detected included enrofloxacin (three samples; 0.3-0.73 ng g(-1)), leucomalachite green (three samples; 0.73-1.2 ng g(-1)), oxolinic acid (two samples; 0.3-4.3 ng g(-1)), AMOZ (the metabolite of furaltadone; one sample; 0.40 ng g(-1)), chloramphenicol (one sample; 0.40 ng g(-1)), and SEM (the metabolite of nitrofurazone; one sample; 0.8 ng g(-1)). The results of this survey indicate that Canadians are exposed to low ng g-1 concentrations of some banned and unapproved veterinary drug residues via the consumption of certain fish and shrimp.

'The experience of community mental health case management provided from an acute in-patient psychiatric unit'

In Australia, case management is the cornerstone of mental health service delivery for seriously ill clients living in the community. In this study, case management was provided from an acute, inpatient psychiatric unit; a model thought to be unique. Findings from this qualitative study explicated the experience of case management from client and case manager (CM) perspectives. They note the nature, purpose, processes and outcomes of case management within that context. Findings were positive, suggesting clients and CM's develop a therapeutic alliance through which interventions are implemented and which result in clients experiencing personal (re) integration and enhanced well-being. These findings are discussed and they suggest an alternative model of service delivery well regarded by both clients and CM's.

Effect of biocides commonly used in the hospital environment on the transfer of antibiotic-resistance genes in Staphylococcus aureus

The effect of sub-minimal inhibitory concentrations of biocides, commonly used in the hospital environment, on the conjugation and transduction of plasmid pWG613 was investigated in three strains of Staphylococcus aureus. The highest transfer frequency was obtained in the conjugation experiments. A low concentration of povidone-iodine was found to significantly reduce transfer frequency by 10-fold in S. aureus SAU3/13136 mating, while other biocides had no effect at low concentrations. Cetrimide (0.0001%) was found to increase significantly transduction efficiency in S. aureus RF2 when the biocide was included in the recovery media. A low concentration of chlorhexidine or povidone-iodine reduced transduction efficiency in the same recipient. This study showed that reduction in transduction efficiency was caused by the direct effect of biocides on the recipient strains rather than on the phage 80 alpha particles.

Nurse mentors for preregistration house officers

Newly qualified junior doctors experience 'reality shock' when they start work on the wards. This article describes the development of a nurse mentorship scheme which uses the skills and expertise of senior ward nurses to help them through this transition. It has proved to be both popular and successful.

ACE inhibitor use is associated with hospitalization for severe hypoglycemia in patients with diabetes. DARTS/MEMO Collaboration. Diabetes Audit and Research in Tayside, Scotland. Medicines Monitoring Unit

OBJECTIVE

To evaluate the association between the use of ACE inhibitors and hospital admission for severe hypoglycemia and to explore the effects of potential confounding variables on this relationship.

RESEARCH DESIGN AND METHODS

The association between the use of ACE inhibitors and the incidence of hypoglycemia is controversial. A recent study reported that 14% of all hospital admissions for hypoglycemia might be attributable to ACE inhibitors. We performed a nested case-control study, using a cohort of 6,649 diabetic patients taking insulin or oral antidiabetic drugs, on the Diabetes Audit and Research in Tayside, Scotland (DARTS) database. From 1 January 1993 to 30 April 1994, we identified 64 patients who had been admitted to Tayside hospitals with hypoglycemia and selected 440 control patients from the same cohort.

RESULTS

Hypoglycemia was associated with the use of ACE inhibitors (odds ratio [OR] 3.2, 95% CI 1.2-8.3, P = 0.023), whereas use of beta-blockers and calcium antagonists was not associated with an increased risk of hospitalization for hypoglycemia with ORs of 0.9 (95% CI 0.3-3.3) and 1.7 (95% CI 0.2-2.1), respectively. There were significant differences between case and control patients in type of diabetes treatment, diabetes duration, place of routine diabetes care, and congestive cardiac failure. These differences did not confound the relationship between ACE inhibitors and hypoglycemia (adjusted OR 4.3, 95% CI 1.2-16.0).

CONCLUSIONS

The results show that the association between ACE inhibitor therapy and hospital admission for severe hypoglycemia is not explained by these confounding factors. Although ACE inhibitors have distinct advantages over other antihypertensive drugs in diabetes, the risk of hypoglycemia should be considered.

Axillary brachial plexus block in two hundred consecutive patients

Two hundred consecutive, minimally-sedated patients presenting for upper limb surgery were audited prospectively to determine the overall clinical success rate, extent of cutaneous neural blockade, reliability and complication rate of each indicator of axillary sheath entry, and degree of patient satisfaction. The axillary sheath was identified, using a 22 gauge, short-bevelled needle, by one of four indicators, whichever was elicited first (paraesthesia, arterial or venous puncture, or tethering by the axillary sheath). Alkalinized mepivacaine 1.2%, 50 ml then was injected. The cutaneous distribution of the block was mapped in the presence of minimal sedation. Anaesthesia was supplemented with peripheral nerve blocks where necessary. Patients were followed up with a mailed questionnaire and surgeon interview. The overall clinical success rate was 92.5%, improving to 99% with supplementary nerve blocks. Complete anaesthesia distal to the elbow was achieved in 85% of patients. Complications were common, but generally mild and transient: mild acute local anaesthetic toxicity, 3.5%; axillary tenderness and bruising, 12%; and dysaesthesias, 12.5%. Despite this, patient satisfaction was high (97%).

Congenital syphilis in Maryland, 1989-1991: the effect of changing the case definition and opportunities for prevention

BACKGROUND

The reported incidence of congenital syphilis in the United States rose dramatically during the 1980s. Although lack of prenatal care has been associated with congenital syphilis, little has been published regarding missed opportunities for prenatal intervention.

GOAL OF THIS STUDY

To determine whether congenital syphilis increases in Maryland between 1989 and 1991 resulted from a true increase in congenital syphilis incidence or a change in the surveillance case definition, and to describe missed opportunities for prenatal intervention.

STUDY DESIGN

This was a retrospective cohort study.

RESULTS

When the revised case definition was used, a 473% increase in the number of cases was seen. Among infants who met the revised definition, 45% of mothers had received no prenatal care. Among those whose mothers had received prenatal care, opportunities to intervene were missed for 53%.

CONCLUSIONS

Although a true increase in congenital syphilis incidence occurred before 1990, the increase reported in Maryland between 1989 and 1991 was primarily due to the change in case definition. Many cases of congenital syphilis could have been prevented with early and adequate prenatal care.

Large haplotype-specific differences in inter-genic distances in human MHC shown by pulsed field electrophoresis mapping of healthy and type 1 diabetic subjects

Type 1 diabetes is associated with extended haplotypes defined by combinations of specific alleles of genes in the MHC. We have used pulsed field gel electrophoresis mapping to examine the gross structure of the Class II region of the MHC and its relationship to susceptibility to Type 1 diabetes. We have studied heterozygous members of a family in which susceptibility to Type 1 diabetes is associated with an A1/B8/DR3 haplotype and resistance with A2/B7/DR2, an unrelated diabetic DR3,4 patient and a healthy DR4,w10 subject and a DR2/Dw2 cell line. Digestion was performed with the enzymes Sst II, Mlu I, and Pvu I and hybridization with 21-hydroxylase, DRA, DQB, DOB and DPA probes. Within the DQ/DR region the DR4- and DR7-bearing haplotypes studied contain insertions of 140-150kb relative to the DR3 haplotypes whilst the DR2 haplotype in the family was smaller than the DR3 haplotypes by 130kb, whilst that in the cell line was smaller by up to 220kb. This cell line, previously thought to be homozygous by consanguinity, was also shown to be heterozygous in the DP region. Although no differences between diabetic and healthy subjects were observed within the family, these differences in long-range structure may be of importance to the etiology of Type 1 diabetes, as well as to the evolution of the MHC.

Comparative trial of Nutrizym in chronic pancreatic insufficiency

A cross-over trial of pancreatic replacement therapy was carried out in 12 adults with chronic pancreatic insufficiency. The standard enteric-coated preparation, Pancrex V forte, was compared with Nutrizym, which has an enteric-coated core of pancreatic extract and a shell of bromelains-a mixture of proteolytic enzymes derived from the stem of the pineapple.Nutrizym was significantly more effective than Pancrex V forte in improving fat absorption, and reduced faecal weight. Protein digestion was assessed by measuring the urinary excretion of hydroxyproline after a gelatin meal. Nutrizym produced an earlier and significantly higher peak in hydroxyproline excretion than Pancrex V forte, but the cumulative effect was similar. The value of bromelains was investigated by including a period on the Nutrizym core alone. This was similar to Pancrex V forte in improving fat absorption but had less effect on protein digestion, suggesting that the beneficial effect of Nutrizym compared with Pancrex V forte was due to the added bromelains, and not to differences in enzyme content or enteric coating.

The Effect of Riboflavin on Corneal Vascularization and Symptoms of Eye Fatigue in R.C.A.F. Personnel

Images