Bioassay-Guided Isolation and Identification of Cytotoxic Compounds from Melaleuca quinquenervia Fruits.

The fruit extract of Melaleuca quinquenervia yielded a total of 19 compounds, including two novel spiro-biflavonoid enantiomers (1a and 1b) and a chalcone derivative (3). Their structures were determined through spectroscopic analysis. The enantiomers of the racemic mixture of compound 1 were successfully resolved into (+)-1 and (-)-1 using chiral-phase HPLC. Single-crystal X-ray diffraction analysis was also used to confirm the structure of 1. The enantiomeric configurations of 1 and 2 were determined through a comparison of the calculated and experimental electronic circular dichroism spectra. Compounds 2 (melanervin), 14 (methyl betulinate), 15 (3-O-acetylbetulinic acid), and 16 (pyracrenic acid) were found to be highly cytotoxic, with compound 16 showing superior growth inhibition of nonsmall cell lung cancer cells (A549 cells) (IC50 2.8 ± 0.1 µM) compared to cisplatin (IC50 3.3 ± 0.0 µM), a positive control chemotherapeutic drug. Both compound 16 and cisplatin were significantly more cytotoxic toward A549 lung cancer cells compared to nontumorigenic Vero E6 cells.

Identification of candidate genes and pathways in retinopathy of prematurity by whole exome sequencing of preterm infants enriched in phenotypic extremes.

Retinopathy of prematurity (ROP) is a vasoproliferative retinal disease affecting premature infants. In addition to prematurity itself and oxygen treatment, genetic factors have been suggested to predispose to ROP. We aimed to identify potentially pathogenic genes and biological pathways associated with ROP by analyzing variants from whole exome sequencing (WES) data of premature infants. As part of a multicenter ROP cohort study, 100 non-Hispanic Caucasian preterm infants enriched in phenotypic extremes were subjected to WES. Gene-based testing was done on coding nonsynonymous variants. Genes showing enrichment of qualifying variants in severe ROP compared to mild or no ROP from gene-based tests with adjustment for gestational age and birth weight were selected for gene set enrichment analysis (GSEA). Mean BW of included infants with pre-plus, type-1 or type 2 ROP including aggressive posterior ROP (n = 58) and mild or no ROP (n = 42) were 744 g and 995 g, respectively. No single genes reached genome-wide significance that could account for a severe phenotype. GSEA identified two significantly associated pathways (smooth endoplasmic reticulum and vitamin C metabolism) after correction for multiple tests. WES of premature infants revealed potential pathways that may be important in the pathogenesis of ROP and in further genetic studies.

Non-Cystic Fibrosis-Related Meconium Ileus: GUCY2C-Associated Disease Discovered through Rapid Neonatal Whole-Exome Sequencing.

Meconium ileus is caused by cystic fibrosis; however, mutations in the GUCY2C gene also cause this disease. We report non-cystic fibrosis meconium ileus in an infant of non-Middle Eastern origin with compound heterozygous mutations in GUCY2C.

Maternal and neonatal outcomes associated with infertility.

Objective: To investigate perinatal outcomes in a cohort of fertile and infertile nulliparous women. Design: Retrospective cohort study. Setting: Academic medical center. Patients: All nulliparous women delivering singletons ≥24-week gestation at our center from 1 January 2012 to 31 December 2012 were included. Women were classified into two groups - fertile and infertile - based on a chart review at the time of delivery. Outcome measure: Perinatal outcomes of interest included mode of delivery, gestational age at delivery, and birth weight. Results: A total of 3293 mother/infant dyads fulfilled the inclusion criteria. Of these, 277 women (8.4%) were classified as infertile. Infertile women were significantly older than fertile women. In bivariate analyses, infertile women were more likely to undergo cesarean delivery (51.8 versus 36.1%, p < .001) and deliver at an earlier gestational age (38.9 ± 2.3 versus 39.4 ± 1.7 weeks, p < .0001). Infertility was no longer significantly associated with cesarean delivery after adjusting for maternal age. Infertility remained associated with an earlier gestational age at delivery after adjusting for maternal age and maternal race (ß coefficient -0.42, 95%CI -0.64, -0.2). There was no difference in infant birth weight. Late preterm deliveries (34-36 completed gestational weeks) accounted for 8.3% of deliveries for infertile women compared to 4.3% for fertile women (p = .032). Conclusions: We conclude that the increased risk of cesarean section associated with infertility is driven by maternal age. Late preterm infants represent a key cohort for further evaluation in the perinatal outcomes of infertile women.

The genetics of retinopathy of prematurity: a model for neovascular retinal disease.

TOPIC: Retinopathy of prematurity (ROP) is a proliferative retinal vascular disease in premature infants, and is a major cause of childhood blindness worldwide. In addition to known clinical risk factors such as low birth weight and gestational age, there is a growing body of evidence supporting a genetic basis for ROP. CLINICAL RELEVANCE: While comorbidities and environmental factors have been identified as contributing to ROP outcomes in premature infants, most notably gestational age and oxygen, some infants progress to severe disease despite absence of these clinical risk factors. The contribution of genetic factors may explain these differences and allow better detection and treatment of infants at risk for severe ROP. METHODS: To comprehensively review genetic factors that potentially contribute to the development and severity of ROP, we conducted a literature search focusing on the genetic basis for ROP. Terms related to other heritable retinal vascular diseases like "familial exudative vitreoretinopathy", as well as to genes implicated in animal models of ROP, were also used to capture research in diseases with similar pathogenesis to ROP in humans with known genetic components. RESULTS: Contributions across several genetic domains are described including vascular endothelial growth factor, the Wnt signaling pathway, insulin-like growth factor 1, inflammatory mediators, and brain-derived neurotrophic factor. CONCLUSIONS: Most candidate gene studies of ROP have limitations such as inability to replicate results, conflicting results from various studies, small sample size, and differences in clinical characterization. Additional difficulty arises in separating the contribution of genetic factors like Wnt signaling to ROP and prematurity. Although studies have implicated involvement of multiple signaling pathways in ROP, the genetics of ROP have not been clearly elucidated. Next-generation sequencing and genome-wide association studies have potential to expand future understanding of underlying genetic risk factors and pathophysiology of ROP.

A New Model for Non-Lipid Compounded Neonatal Parenteral Nutrition Solution Osmolality.

BACKGROUND: Osmotic stress is a physical risk factor for adverse events related to peripheral parenteral nutrition (PN) administration, such as infiltration. We sought to improve prediction of compounded PN osmolality utilizing basic nutrient solutions available to North American neonatal intensive care units. This study tested the hypothesis that calculated osmolarity underestimates osmolality in compounded PN. METHODS: Osmolarity (mOsm/L) was calculated utilizing commercial software. Osmolality (mOsm/kg) was determined by a freezing-point depression micro-osmometer. The relationship between calculated osmolarity and measured osmolality was modeled from linear or polynomial regression analysis using the least squares method. Regression models were based upon calculated osmolarity and included various combinations of PN components. RESULTS: Calculated osmolarity significantly underestimated measured osmolality in all PN samples (n = 363). Based upon the osmolality of PN and the basic nutrient solutions, we determined a polynomial regression that effectively corrects for the osmolal gap (measured osmolality-calculated osmolarity) in the validation set (R2 = 0.99367). The unbiased analysis corrected for the osmolal gap based on individual solute behaviors, as well as the solute-solute interactions in compounded solutions. CONCLUSIONS: Calculated osmolarity (mOsm/L) significantly underestimates the osmolality (mOsm/kg) in compounded PN. We developed a new algorithm to more accurately predict PN osmolality based upon calculated osmolarity from commercial software and composition of neonatal basic nutrient solutions used in North America. We propose that use of this PN algorithm will facilitate future studies to determine whether a causal association exists between PN osmolality and adverse events, and to establish safe thresholds for PN concentration in neonates.

Colony and Single Cell Level Analysis of the Heterogeneous Response of Cryptococcus neoformans to Fluconazole.

Cryptococcus neoformans is a human fungal pathogen that can cause fatal meningitis in immunocompromised individuals. Fluconazole (FLC) is a fungistatic drug administered to treat cryptococcosis. When exposed to the inhibitory concentration of FLC, C. neoformans exhibits heteroresistance where a small subpopulation of cells develops into FLC-resistant colonies. FLC-resistant cells are aneuploids with regard to specific beneficial chromosomal regions. Factors underlying the potential for only certain C. neoformans cells in a genetically isogenic population to become FLC-resistant are unknown. In this study, we systematically examine the heterogeneous response of C. neoformans to FLC at a colony and individual cell level. We find that the heterogeneity in response to FLC is reflected by variable diminishment of the ergosterol at the plasma membrane. A population of C. neoformans spread on a semi-solid medium displays two types of outcomes following FLC exposure. The first outcome is colonies consisting of non-resistant cells (survivors). The size of colonies consisting of survivors ranges from a few cells to visible colonies, which reflects intrinsic phenotypic heterogeneity of the C. neoformans population. The second outcome is FLC-resistant cells forming colonies of sizes significantly larger as compared to colonies made of survivors. We propose a model that describes how a distribution of these types of cellular responses within a population changes depending on FLC concentration and factors that influence the rate of cellular growth including temperature, media type, growth phase, and the age of cells. Our findings highlight a complex nature of the response to a fungistatic drug and provide insights that may help to optimize FLC therapy.

Pharmacophore Modeling, Synthesis, and Antibacterial Evaluation of Chalcones and Derivatives.

A series of novel chalcone and thiol-Michael addition analogues was synthesized and tested against Mycobacterium tuberculosis and other clinically significant bacterial pathogens. Previously reported chalcone-like antibacterials (1a-c and 2) were used as a training set to generate a pharmacophore model. The chalcone derivative hit compound 3 was subsequently identified through a pharmacophore-based virtual screen of the Specs library of >200 000 compounds. Among the newly synthesized chalcones and thiol-Michael addition analogues, chalcones 6r and 6s were active (minimum inhibitory concentrations (MICs) = 1.56-6.25 µg/mL) against Gram-positive pathogens Bacillus anthracis and Staphylococcus aureus [methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA)]. The chalcone thiol-Michael addition derivatives 7j-m showed good to excellent antibacterial activities (MICs = 0.78-6.25 µg/mL) against Enterococcus faecalis, B. anthracis, and S. aureus. Interestingly, the amine-Michael addition analogue 12a showed promising anti-MRSA activity (MIC = 1.56 µg/mL) with a selectivity index of 14 toward mammalian Vero cells. In addition, evaluation of selected compounds against biofilm and planktonic S. aureus (MSSA and MRSA) revealed that 12a exhibited bactericidal activities in these assays, which was overall superior to vancomycin. These properties may result from the compounds dissipating the proton motive force of bacterial membranes.

Fluconazole-Induced Ploidy Change in Cryptococcus neoformans Results from the Uncoupling of Cell Growth and Nuclear Division.

Cryptococcus neoformans is a pathogenic yeast that causes lethal cryptococcal meningitis in immunocompromised patients. One of the challenges in treating cryptococcosis is the development of resistance to azole antifungals. Previous studies linked azole resistance to elevated numbers of copies of critical resistance genes in aneuploid cells. However, how aneuploidy is formed in the presence of azole drugs remains unclear. This study showed that treatment with inhibitory concentrations of an azole drug, fluconazole (FLC), resulted in a significant population of cells with increased DNA content, through the following defects: inhibition of budding, premature mitosis, and inhibition of cytokinesis followed by replication in the mother cell. Inhibition of and/or a delay in cytokinesis led to the formation of cells with two or more daughter cells attached (multimeric cells). To investigate which part of cytokinesis fails in the presence of FLC, the dynamics of the actomyosin ring (AMR), septins, and Cts1, a protein involved in cell separation, were analyzed with time-lapse microscopy. Following the constriction of the AMR, septins assembled and the septum was formed between the mother and daughter cells. However, final degradation of the septum was affected. Enlarged cells with aberrant morphology, including multimeric cells, exhibited an increased potential to proliferate in the presence of FLC. These findings suggest that pleiotropic effects of FLC on growth and mitotic division lead to an increase in DNA content, resulting in cells less sensitive to the drug. Cells with increased DNA content continue to proliferate and therefore increase the chance of forming resistant populations. IMPORTANCE Azoles are antifungals that are widely utilized due to relatively low toxicity and cost of treatment. One of their drawbacks, however, is that azoles are primarily cytostatic, leaving fungal cells capable of developing drug resistance. The human pathogen Cryptococcus neoformans acquires resistance to the azole drug fluconazole (FLC) through the development of aneuploidy, leading to elevated expression of key resistance genes, a mechanism that is also common for Candida albicans (K. J. Kwon-Chung and Y. C. Chang, PLoS Pathog 8:e1003022, 2012, https://doi.org/10.1371/journal.ppat.1003022; J. Morschhäuser, J Microbiol 54:192-201, 2016, https://doi.org/10.1007/s12275-016-5628-4). However, the exact ways in which FLC contributes to increased resistance in either of these important fungal pathogens remain unclear. Here we found that FLC treatment leads to an increase in DNA content in C. neoformans through multiple mechanisms, potentially increasing the size of a pool of cells from which aneuploids with increased resistance are selected. This study demonstrated the importance of FLC's inhibitory effects on growth and cytokinesis in the generation of cell populations with decreased sensitivity to the drug.

Fertility Treatment Is Associated with Stay in the Neonatal Intensive Care Unit and Respiratory Support in Late Preterm Infants.

Late preterm infants are at risk for short-term morbidities. We report that late preterm singletons conceived with fertility treatment have increased risk for admission to the neonatal intensive care unit and respiratory support compared with spontaneously conceived infants. Fertility treatment may be a risk factor to consider in managing late preterm infants.

Bioactive Constituents from an Endophytic Fungus, Penicillium polonicum NFW9, Associated with Taxus fauna.

BACKGROUND: Endophytic fungi are being recognized as vital and untapped sources of a variety of structurally novel and unique bioactive secondary metabolites in the field of natural products drug discovery. Herein, this study reports the isolation and characterization of secondary metabolites from an endophytic fungus Penicillium polonicum (NFW9) associated with Taxus fuana. METHOD: The extracts of the endophytic fungus cultured on potato dextrose agar were purified using several chromatographic techniques. Biological evaluation was performed based on their abilities to inhibit tumor necrosis factor-alpha (TNF-α)-induced nuclear factor-kappa B (NF-κB) and cytotoxicity assays. RESULTS: Bioactivity-directed fractionation of the ethyl acetate extract of a fermentation culture of an endophytic fungus, Penicillium polonicum led to the isolation of a dimeric anthraquinone, (R)- 1,1',3,3',5,5'-hexahydroxy-7,7'-dimethyl[2,2'-bianthracene]-9,9',10,10'-tetraone (1), a steroidal furanoid (-)-wortmannolone (2), along with three other compounds (3-4). Moreover, this is the first report on the isolation of compound 1 from an endophytic fungus. All purified metabolites were characterized by NMR and MS data analyses. The stereo structure of compound 1 was determined by the measurement of specific optical rotation and CD spectrum. The relative stereochemistry of 2 was confirmed by single-crystal X-ray diffraction. Compounds 2-3 showed inhibitory activities in the TNF-α-induced NF-κB assay with IC50 values in the range of 0.47-2.11 µM. Compounds 1, 4 and 5 showed moderate inhibition against NF-κB and cancer cell lines. CONCLUSION: The endophytic fungus Penicillium polonicum of Taxus fuana is capable of producing biologically active natural compounds. Our results provide a scientific rationale for further chemical investigations into endophyte-producing natural products, drug discovery and development.

Transcatheter Closure of Patent Ductus Arteriosus in Extremely Premature Newborns: Early Results and Midterm Follow-Up.

OBJECTIVES: The goal of this study was to describe early and midterm outcomes of extremely premature newborns (EPNs) who underwent transcatheter echocardiographically guided patent ductus arteriosus (PDA) closure. BACKGROUND: Surgical ligation of PDA in EPNs confers significant risk for procedural morbidity and adverse long-term outcomes. METHODS: The Amplatzer Vascular Plug II was used in all cases. Post-ligation syndrome was defined using previously published parameters. Patients were followed at pre-specified intervals, and prospectively collected data were reviewed. RESULTS: Transcatheter closure was attempted in 24 EPNs (mean procedural age 30 days [range 5 to 80 days], mean procedural weight 1,249 g [range 755 to 2,380 g]) and was successful in 88%. The 3 procedural failures were related to the development of left pulmonary artery (LPA) stenosis caused by the device, and all devices were removed uneventfully. Complications included 2 instances of device malposition, resolved with device repositioning, and 1 instance of LPA stenosis, requiring an LPA stent. There were no procedural deaths, cases of post-ligation syndrome, residual PDA, or device embolization. Survival to discharge was 96% (23 of 24), with a single late death unrelated to the procedure. After a median follow-up period of 11.1 months, all patients were alive and well, with no residual PDA or evidence of LPA or aortic coarctation. CONCLUSIONS: This newly described technique can be performed safely with a high success rate and minimal procedural morbidity in EPNs. Early and midterm follow-up is encouraging. Future efforts should be directed toward developing specific devices for this unique application.

Withanolides derived from Physalis peruviana (Poha) with potential anti-inflammatory activity.

Three new withanolides, physaperuvin G (1), with physaperuvins I (2), and J (3), along with seven known derivatives (4-10), were isolated from the aerial parts of Physalis peruviana. The structures of 1-3 were determined by NMR, X-ray diffraction, and mass spectrometry. Compounds 1-10 were evaluated in lipopolysaccharide (LPS)-activated murine macrophage RAW 264.7 cells. Compounds 4, 5, and 10 with potent nitric oxide inhibitory activity in LPS-activated RAW 264.7 cells, with IC50 values in the range of 0.32-7.8µM. In addition, all compounds were evaluated for potential to inhibit tumor necrosis factor-alpha (TNF-α)-activated nuclear factor-kappa B (NF-κB) activity with transfected human embryonic kidney cells 293. Compounds 4-7 inhibited TNF-α-induced NF-κB activity with IC50 values in the range of 0.04-5.6µM.

Atrial Myxoma Presenting as Myocardial Infarction Diagnosed by Echocardiography, Managed Endoscopically with Robot-Assisted Surgery.

Atrial myxomatous embolization into the coronary arteries is a rare event. Management of large myxomas is usually via surgical resection involving a median sternotomy. Echocardiography is not a routine part of non-ST-elevation myocardial infarction (NSTEMI) management. Here, we present the case of a 70-year-old Caucasian man with a history of hypertension and hyperlipidemia who presented to the emergency department with an NSTEMI. Transthoracic echocardiogram and transesophageal echocardiogram revealed a large and highly mobile atrial mass, traversing through the mitral valve orifice during diastole. Coronary angiography revealed a focal 60% lesion in the right coronary artery and no other significant obstructive coronary artery disease, suggesting that the cause of his presentation was tumor embolization into the coronary circulation. The patient underwent robot-assisted endoscopic resection of his atrial mass and was discharged in stable condition on postoperative day 2. Pathology revealed atrial myxoma. To our knowledge, this is the first reported case of an atrial myxoma presenting with an NSTEMI and managed with a robot-assisted endoscopic approach. This case also highlights the importance of routine early echocardiography in patients presenting with NSTEMI.

Determination of the absolute configuration of chaetoviridins and other bioactive azaphilones from the endophytic fungus Chaetomium globosum.

Chemical investigation of an endophytic fungus Chaetomium globosum isolated from leaves of Wikstroemia uva-ursi led to the isolation of two new azaphilones, chaetoviridins J and K (1 and 3), along with five known derivatives (2 and 4-7). The structures of azaphilones were determined by NMR, X-ray diffraction, Mosher's method, and CD analysis. The isolated compounds were evaluated for their cancer chemopreventive-potential based on their abilities to inhibit tumor necrosis factor alpha (TNF-α)-induced nuclear factor-kappa B (NF-κB). Compounds 4, 5, 7, and synthetic 8 and 9 inhibit nitric oxide (NO) production with IC50 values in the range of 0.3-5.8 µM. Compounds 4, 5, and 9 also displayed (TNF-α)-induced NF-κB activity with IC50 values in the range of 0.9-5.1 µM.

A novel technique for transcatheter patent ductus arteriosus closure in extremely preterm infants using commercially available technology.

OBJECTIVES: To describe a new technique for transcatheter patent ductus arteriosus (PDA) closure in extremely preterm infants using commercially available technology. BACKGROUND: PDA in premature neonates continues to be a significant clinical problem contributing importantly to both morbidity and mortality. Surgical ligation and medical therapy both have their drawbacks. MATERIAL AND METHODS: Hospital records and catheterization reports of all premature neonates (< 32 weeks gestation) who underwent transcatheter PDA closure between March 2013 and February 2014 were reviewed. Particular attention was paid to procedural details, complications, and short and mid-term outcomes. RESULTS: Six premature infants born at gestational ages ranging between 26 and 31 weeks (median, 26 weeks) underwent attempted transcatheter PDA closure using the Amplatzer Vascular Plug II (AVP II). Median age and weight was 21.5 days (16-80 days) and 1,180 g (870-2,240 g), respectively. Fluoroscopy and echocardiography were used to guide device. Contrast angiography was not used in any patient. Complete closure was achieved in all patients with no major procedural complications. Median fluoroscopy and procedural times were 9.4 (0-19.5) and 51.5 (33-87) min, respectively. All patients were alive at the time of this report. There were no instances of device migration, left pulmonary artery (LPA), or aortic coarctation. CONCLUSIONS: This preliminary study demonstrates that transcatheter PDA closure can be successfully performed in extremely preterm neonates using currently available technology with a high success rate and a low incidence of complications. This report also describes a novel transvenous approach using a combination of echocardiography and judicious use of fluoroscopy to avoid arterial access in this fragile patient population. © 2014 Wiley Periodicals, Inc.

Synthesis, structure-activity relationship studies, and antibacterial evaluation of 4-chromanones and chalcones, as well as olympicin A and derivatives.

On the basis of recently reported abyssinone II and olympicin A, a series of chemically modified flavonoid phytochemicals were synthesized and evaluated against Mycobacterium tuberculosis and a panel of Gram-positive and -negative bacterial pathogens. Some of the synthesized compounds exhibited good antibacterial activities against Gram-positive pathogens including methicillin resistant Staphylococcus aureus with minimum inhibitory concentration as low as 0.39 µg/mL. SAR analysis revealed that the 2-hydrophobic substituent and the 4-hydrogen bond donor/acceptor of the 4-chromanone scaffold together with the hydroxy groups at 5- and 7-positions enhanced antibacterial activities; the 2',4'-dihydroxylated A ring and the lipophilic substituted B ring of chalcone derivatives were pharmacophoric elements for antibacterial activities. Mode of action studies performed on selected compounds revealed that they dissipated the bacterial membrane potential, resulting in the inhibition of macromolecular biosynthesis; further studies showed that selected compounds inhibited DNA topoisomerase IV, suggesting complex mechanisms of actions for compounds in this series.

Accelerated identification of halogenated monoterpenes from Australian specimens of the red algae Plocamium hamatum and Plocamium costatum.

Two species of red algae belonging to the genus Plocamium, P. hamatum from Moreton Bay, Queensland, and P. costatum, from Pandalowie Bay, South Australia, were investigated to assess their chemical variation and as potential sources of new halogenated monoterpenes. The hyphenated technique HPLC-UV-MS-SPE-NMR was used to assess the algal extracts and to determine its potential for accelerated identification of halogenated monoterpenes generally. A combination of the hyphenated and traditional chromatographic techniques resulted in the isolation and characterization of a total of 10 halogenated monoterpene metabolites, eight of which are reported for the first time. Their structures, including configurations, were determined through interpretation of their 1D and 2D NMR, mass spectrometric, infrared, and X-ray data. The two species of Plocamium produced different secondary metabolites and contained a significant number of new polyhalogenated monoterpenes. The investigation also showed the hyphenated technique HPLC-UV-MS-SPE-NMR to be useful for preliminary investigation of the chemical content of algal extracts.

Development and Evaluation of Reference Standards for Image-based Telemedicine Diagnosis and Clinical Research Studies in Ophthalmology.

Information systems managing image-based data for telemedicine or clinical research applications require a reference standard representing the correct diagnosis. Accurate reference standards are difficult to establish because of imperfect agreement among physicians, and discrepancies between clinical vs. image-based diagnosis. This study is designed to describe the development and evaluation of reference standards for image-based diagnosis, which combine diagnostic impressions of multiple image readers with the actual clinical diagnoses. We show that agreement between image reading and clinical examinations was imperfect (689 [32%] discrepancies in 2148 image readings), as was inter-reader agreement (kappa 0.490-0.652). This was improved by establishing an image-based reference standard defined as the majority diagnosis given by three readers (13% discrepancies with image readers). It was further improved by establishing an overall reference standard that incorporated the clinical diagnosis (10% discrepancies with image readers). These principles of establishing reference standards may be applied to improve robustness of real-world systems supporting image-based diagnosis.

Influence of lattice interactions on the Jahn-Teller distortion of the [Cu(H2O)6]2+ ion: dependence of the crystal structure of K2(x)Rb(2-2x)[Cu(H2O)6](SeO4)2 upon the K/Rb ratio.

The temperature dependence of the structures of a wide range of mixed-cation Tutton's salts of general formula K2(x)Rb(2-2x)[Cu(H2O)6](SeO4)2 has been determined over the temperature range 90 to 320 K. Crystals with a high proportion of potassium adopt a different structure (form B) from those with a low ratio (form A). In both forms, the [Cu(H2O)6](2+) ion has an orthorhombically distorted tetragonally elongated coordination geometry, but the long and intermediate bonds occur with a different pair of water molecules in form A compared with form B. The alkali metal is surrounded by seven close oxygen atoms in form B but eight oxygen atoms in form A, and this difference in coordination number is associated with the change in the Cu-O bond distances via the hydrogen-bonding network. For crystals with between 32 and ∼41% potassium, a relatively sharp change from form B to A occurs on cooling, and the temperature at which this occurs increases approximately linearly as the proportion of potassium falls. For the whole range of mixed crystals, the bond lengths have been determined as a function of temperature. The data have been interpreted as a thermal equilibrium of the two structural forms of the [Cu(H2O)6](2+) ion that develops gradually as the temperature increases, with this becoming more pronounced as the proportions of the two cations become more similar. The temperature dependence of the bond lengths in this thermal equilibrium has been analyzed using a model in which the Jahn-Teller potential surface of the [Cu(H2O)6](2+) ion is perturbed by lattice strain interactions. The magnitude and sign of the orthorhombic component of this strain interaction depends upon the proportion of potassium to rubidium ions in the structure.