Extensive evaluation of a new LC-MS/MS method to quantify monofluoroacetate toxin in the kidney

Monofluoroacetate (MFA) is a highly lethal toxin which causes death by inhibiting cellular ATP production. The heart and brain are the primary target organs. Acute death is attributed to cardiac fibrillation and/or convulsions. Although it occurs naturally in some plants, a major source of animal intoxication is access to sodium monofluoroacetate (NaMFA) pesticide which continues to be a concern in the US and around the world despite restricted use in some countries including the US. There are also concerns about misuse of this pesticide for malicious poisoning. Currently, a tissue-based diagnostic method for NaMFA intoxication in animals is lacking. There is a critical need by the veterinary diagnostic community for a simple, sensitive, and reliable tissue-based diagnostic test to confirm NaMFA poisoning in animals. We have developed and extensively evaluated a sensitive novel LC-MS/MS method suitable for this purpose. The limits of detection (LOD) and limits of quantitation (LOQ) are 1.7 ng/g and 5.0 ng/g, respectively. The accuracy and precision met or exceeded expectations. The method performance was verified using incurred kidney obtained from animal diagnostic cases. This novel kidney-based method is now available for clinical use and can help with diagnostic purposes, including detecting potential issues related to animal foods.

Comparative evaluation of assay performance for SARS-CoV-2 detection in animal oral samples, lung homogenates, and phosphate-buffered saline using the TaqPath COVID-19 Combo kit

A One Health approach has been key to monitoring the COVID-19 pandemic, as human and veterinary medical professionals jointly met the demands for an extraordinary testing effort for SARS-CoV-2. Veterinary diagnostic laboratories continue to monitor SARS-CoV-2 infection in animals, furthering the understanding of zoonotic transmission dynamics between humans and animals. A RT-PCR assay is a primary animal screening tool established within validation and verification guidelines provided by the American Association of Veterinary Laboratory Diagnosticians (AAVLD), World Organisation for Animal Health (WOAH), and the U.S. Food and Drug Administration (FDA). However, differences in sample matrices, RNA extraction methods, instrument platforms, gene targets, and cutoff values may affect test outcomes. Therefore, targeted validation for a new sample matrix used in any PCR assay is critical. We evaluated a COVID-19 assay for the detection of SARS-CoV-2 in feline and canine lung homogenates and oral swab samples. We used the commercial Applied Biosystems MagMAX Viral/Pathogen II (MVP II) nucleic acid isolation kit and TaqPath COVID-19 Combo kit, which are validated for a variety of human samples, including nasopharyngeal and oropharyngeal swab samples. Our masked test showed a high detection rate and no false-positive or false-negative results, supporting sample extension to include feline oral swab samples. Our study is a prime example of One Health, illustrating how a COVID-19 assay designed for human testing can be adapted and used to detect SARS-CoV-2 in oral swab samples from cats and likely dogs, but not lung homogenates.

Validation and interlaboratory comparison of anticoagulant rodenticide analysis in animal livers using ultra-performance liquid chromatography-mass spectrometry

Anticoagulant rodenticides (ARs) are used to control rodent populations. Poisoning of non-target species can occur by accidental consumption of commercial formulations used for rodent control. A robust method for determining ARs in animal tissues is important for animal postmortem diagnostic and forensic purposes. We evaluated an ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) method to quantify 8 ARs (brodifacoum, bromadiolone, chlorophacinone, coumachlor, dicoumarol, difethialone, diphacinone, warfarin) in a wide range of animal (bovine, canine, chicken, equine, porcine) liver samples, including incurred samples. We further evaluated UPLC-MS in 2 interlaboratory comparison (ILC) studies; one an ILC exercise (ICE), the other a proficiency test (PT). The limits of detection of UPLC-MS were 0.3-3.1 ng/g, and the limits of quantification were 0.8-9.4 ng/g. The recoveries obtained using UPLC-MS were 90-115%, and relative SDs were 1.2-13% for each of the 8 ARs for the 50, 500, and 2,000 ng/g spiked liver samples. The overall accuracy from the laboratories participating in the 2 ILC studies (4 and 11 laboratories for ICE and PT studies, respectively) were 86-118%, with relative repeatability SDs of 3.7-11%, relative reproducibility SDs of 7.8-31.2%, and Horwitz ratio values of 0.5-1.5. Via the ILC studies, we verified the accuracy of UPLC-MS for AR analysis in liver matrices and demonstrated that ILC can be utilized to evaluate performance characteristics of analytical methods.

Successful Detection of Delta and Omicron Variants of SARS-CoV-2 by Veterinary Diagnostic Laboratory Participants in an Interlaboratory Comparison Exercise

BACKGROUND

Throughout the COVID-19 pandemic, veterinary diagnostic laboratories have tested diagnostic samples for SARS-CoV-2 both in animals and over 6 million human samples. An evaluation of the performance of those laboratories is needed using blinded test samples to ensure that laboratories report reliable data to the public. This interlaboratory comparison exercise (ILC3) builds on 2 prior exercises to assess whether veterinary diagnostic laboratories can detect Delta and Omicron variants spiked in canine nasal matrix or viral transport medium.

METHODS

The ILC organizer was an independent laboratory that prepared inactivated Delta variant at levels of 25 to 1000 copies per 50 µL of nasal matrix for blinded analysis. Omicron variant at 1000 copies per 50 µL of transport medium was also included. Feline infectious peritonitis virus (FIPV) RNA was used as a confounder for specificity assessment. Fourteen test samples were prepared for each participant. Participants used their routine diagnostic procedures for RNA extraction and real-time reverse transcriptase-PCR. Results were analyzed according to International Organization for Standardization (ISO) 16140-2:2016.

RESULTS

Overall, laboratories demonstrated 93% detection for Delta and 97% for Omicron at 1000 copies per 50 µL. Specificity was 97% for blank samples and 100% for blank samples with FIPV. No differences in Cycle Threshold (Ct) values were significant for samples with the same virus levels between N1 and N2 markers, nor between the 2 variants.

CONCLUSIONS

The results indicated that all ILC3 participants were able to detect both Delta and Omicron variants. The canine nasal matrix did not significantly affect SARS-CoV-2 detection.

Extensive Evaluation of a Method for Quantitative Measurement of Aflatoxins B1 and M1 in Animal Urine Using High-Performance Liquid Chromatography with Fluorescence Detection

BACKGROUND

Aflatoxins (AFs) are common feed contaminants and are one of the common causes of toxin-related pet food poisoning and recalls.

OBJECTIVE

Currently, there are no validated methods for the detection and quantitation of AFs in biological matrices to diagnose AF exposure in live animals. Following a successful intra-laboratory method development to quantify AFB1 and AFM1 in animal urine by HPLC with fluorescence detection (HPLC-FLD), the present study was conducted to extensively evaluate the method performance in an unbiased manner using blinded samples.

METHODS

The evaluation included two stages. First, the performance was verified in the method-originating laboratory in a single-laboratory blinded method test (BMT-S) trial followed by a multi-laboratory blinded method test (BMT-M) trial.

RESULTS

In both trials, accuracy, repeatability, and reproducibility were satisfactory confirming the relatively good ruggedness and robustness of the method and ensuring that it will perform as expected if used by other laboratories in the future.

CONCLUSIONS

We extensively evaluated the performance of a quantitative method to detect AFB1 and AFM1 in animal urine by HPLC-FLD by two different laboratories in two separate BMT-S and BMT-M trials. Both BMT results demonstrated the satisfactory accuracy and precision of the method. It is now available to be adopted by other diagnostic laboratories for purposes of diagnosing AF intoxication in animals.

HIGHLIGHTS

A simple urine-based diagnostic test method using HPLC-FLD that originated in a single laboratory now has passed a multi-laboratory evaluation and is now available to be shared with other diagnostic laboratories for purposes of diagnosing AF intoxication in animals so better treatment can be rendered.

Comprehensive Evaluation of HPLC-MS/MS Method for Quantitation of Seven Anticoagulant Rodenticides and Dicoumarol in Animal Serum

Anticoagulant rodenticides (ARs) are commonly utilized for controlling rodent populations, however non-target companion and wildlife animals are also exposed. A method was developed for quantitation of seven ARs (chlorophacinone, coumachlor, bromadiolone, brodifacoum, difethialone, diphacinone, and warfarin) and dicoumarol (a naturally occurring anticoagulant) in animal serum. Analytes were extracted with 10% (v/v) acetone in methanol and analyzed by reverse phase high-pressure liquid chromatograph-tandem mass spectrometry (HPLC-MS/MS) using electrospray ionization (negative mode) combined with multiple reaction monitoring (MRM). In-house method validation in the originating laboratory using non-blinded samples revealed method limits of quantitation at 2.5 ng/mL for all analytes. Inter-assay accuracy ranged 99-104% and relative standard deviation ranged 3.5-20.5%. Method performance was then verified in the originating laboratory during an exercise organized by an independent party using blinded samples. The method was successfully transferred to two naïve laboratories and further evaluated for reproducibility among three laboratories by means of Horwitz ratio (HorRat(R)) values. Such extensive validation provides a high degree of confidence that the method is rugged, robust, and will perform as expected if used by others in the future.

Preventive Model of Formation of Health-save Competence of Student Youth with the Use of Natural Physiotherapy

Aim: The aim of the study is to determine the basic conceptual, methodological and organizational-methodological aspects of the process of forming health competence of students using natural physiotherapy, to formalize them in the form of a preventive model. Materials and Methods: The pedagogical experiment lasted during 2019-2021 in Sumy State Pedagogical University named after A.S. Makarenko. The pedagogical research was attended by 128 first- and second-year students majoring in «Physical Education», «Physical Therapy, Occupational Therapy» Sumy State Pedagogical University named after A.S. Makarenko. The research methods were as follows: analysis of special and scientific literature, pedagogical observation, pedagogical experiment, pedagogical testing, methods of statistical data processing. Results: In order to organize and systematize this theoretical and practical experience, we have developed a preventive model of forming health-save competence of students, which allows to form an idea of the determinants of health, ways to strengthen it, guide students to follow the rules of healthy living and application of a wide range of natural physiotherapeutic means. Conclusions: The pedagogical model of formation of health-save competence orients students on observance of rules and norms of a healthy way of life with application of natural physiotherapeutic means (physical exercises, water procedures, air, solar heat and light), systematizes and formalizes representations of integral, multilevel, integrative, interdisciplinary educational process in the conditions of educational institution.

Second round of an interlaboratory comparison of SARS-CoV2 molecular detection assays used by 45 veterinary diagnostic laboratories in the United States

The COVID-19 pandemic presents a continued public health challenge. Veterinary diagnostic laboratories in the United States use RT-rtPCR for animal testing, and many laboratories are certified for testing human samples; hence, ensuring that laboratories have sensitive and specific SARS-CoV2 testing methods is a critical component of the pandemic response. In 2020, the FDA Veterinary Laboratory Investigation and Response Network (Vet-LIRN) led an interlaboratory comparison (ILC1) to help laboratories evaluate their existing RT-rtPCR methods for detecting SARS-CoV2. All participating laboratories were able to detect the viral RNA spiked in buffer and PrimeStore molecular transport medium (MTM). With ILC2, Vet-LIRN extended ILC1 by evaluating analytical sensitivity and specificity of the methods used by participating laboratories to detect 3 SARS-CoV2 variants (B.1; B.1.1.7 [Alpha]; B.1.351 [Beta]) at various copy levels. We analyzed 57 sets of results from 45 laboratories qualitatively and quantitatively according to the principles of ISO 16140-2:2016. More than 95% of analysts detected the SARS-CoV2 RNA in MTM at ≥500 copies for all 3 variants. In addition, for nucleocapsid markers N1 and N2, 81% and 92% of the analysts detected ≤20 copies in the assays, respectively. The analytical specificity of the evaluated methods was >99%. Participating laboratories were able to assess their current method performance, identify possible limitations, and recognize method strengths as part of a continuous learning environment to support the critical need for the reliable diagnosis of COVID-19 in potentially infected animals and humans.

Interlaboratory comparison of SARS-CoV2 molecular detection assays in use by U.S. veterinary diagnostic laboratories

The continued search for intermediate hosts and potential reservoirs for SARS-CoV2 makes it clear that animal surveillance is critical in outbreak response and prevention. Real-time RT-PCR assays for SARS-CoV2 detection can easily be adapted to different host species. U.S. veterinary diagnostic laboratories have used the CDC assays or other national reference laboratory methods to test animal samples. However, these methods have only been evaluated using internal validation protocols. To help the laboratories evaluate their SARS-CoV2 test methods, an interlaboratory comparison (ILC) was performed in collaboration with multiple organizations. Forty-four sets of 19 blind-coded RNA samples in Tris-EDTA (TE) buffer or PrimeStore transport medium were shipped to 42 laboratories. Results were analyzed according to the principles of the International Organization for Standardization (ISO) 16140-2:2016 standard. Qualitative assessment of PrimeStore samples revealed that, in approximately two-thirds of the laboratories, the limit of detection with a probability of 0.95 (LOD95) for detecting the RNA was ≤20 copies per PCR reaction, close to the theoretical LOD of 3 copies per reaction. This level of sensitivity is not expected in clinical samples because of additional factors, such as sample collection, transport, and extraction of RNA from the clinical matrix. Quantitative assessment of Ct values indicated that reproducibility standard deviations for testing the RNA with assays reported as N1 were slightly lower than those for N2, and they were higher for the RNA in PrimeStore medium than those in TE buffer. Analyst experience and the use of either a singleplex or multiplex PCR also affected the quantitative ILC test results.

A Lateral Flow Method for Aflatoxin B1 in Dry Dog Food: An Inter-Laboratory Trial

BACKGROUND

Dogs are highly susceptible to aflatoxins, the mycotoxins which most commonly cause acute dog illnesses and deaths following the consumption of contaminated food.

OBJECTIVE

In this study, a screening method to detect aflatoxin B1 (AFB1) in dry dog food was further evaluated at the FDA action level of 20 ng/g. A fourth-round multi-laboratory trial was performed. In contrast to the previous work, a different source of dog food was used in the multi-laboratory trial and more participants were involved.

METHOD

The tested lateral flow method employs a modified procedure of the "Rosa® AFQ-Fast Test Kit" from Charm Sciences Inc. A total of 60 unfortified blank study samples, 220 study samples fortified at 20 ng/g, and 80 study samples fortified at 9-11 ng/g were prepared by an independent party and analyzed in 10 collaborating laboratories in a blinded manner.

RESULTS

The pass rates were 98.3 and 94.5% for unfortified and 20 ng/g fortified study samples, respectively.

CONCLUSIONS

The method is suitable for aflatoxin B1 screening at the FDA action level of 20 ng/g in a complex matrix such as dry dog food.

HIGHLIGHTS

This work completes extensive method performance evaluation through four rounds of multi-laboratory trials.

Multilaboratory Evaluation of a Lateral Flow Method for Aflatoxin B1 Analysis in Dry Dog Food

BACKGROUND

Aflatoxins are one of the most heavily regulated mycotoxins in agriculture throughout the world. A variety of tests are used for detection, including rapid methods that are preferred when a large number of samples need to be quickly screened to implement an immediate action. However, a method developed for screening a specific commodity for the presence of mycotoxins requires further validation to demonstrate its suitability for additional matrices.

OBJECTIVE

In this study, a study was undertaken to evaluate a rapid screening method for aflatoxin B1 (AFB1) in dry dog food, a product potentially susceptible to aflatoxins contamination.

METHOD

This test method employed lateral flow technology using kits obtained from Charm Sciences Inc. Three different sources of dry dog food were tested at the FDA action level of 20 ppb (ng/g) in three trials of a multi-laboratory study by four participants. A total of 80 unfortified blank samples, 270 samples spiked at 20 ppb, and 60 samples spiked below 20 ppb were analyzed.

RESULTS

The overall pass rates of 100% for unfortified samples and > 97% for 20 ppb-fortified samples meet the FDA guidance acceptance criteria for a limit test of 10-15% false positives and no more than 5% false negatives.

CONCLUSIONS

The method is suitable for screening a large number of dry dog food samples for rapid response.

HIGHLIGHTS

Multi-laboratory evaluation of a rapid method for aflatoxin screening in dog food.

Extensive Evaluation via Blinded Testing of an UHPLC-MS/MS Method for Quantitation of Ten Ergot Alkaloids in Rye and Wheat Grains

BACKGROUND

Ergot alkaloids are mycotoxins produced by the fungus Claviceps, which can contaminate grains and pose a health risk to humans and animals. Validation of an ergot alkaloid method in collaborative projects can be challenging due to instability of analytes, a lack of reliable reference materials, and a fully validated reference method.

OBJECTIVE

To extensively evaluate performance of a quantitative UHPLC-MS/MS method to detect ten ergot alkaloids at concentrations between 16 and 500 ng/g in grains.

METHOD

The method performance was evaluated in the Blinded Method Test (BMT) exercise, which allowed organizers to successfully address the challenges. Forty completely blinded test samples were prepared in an independent laboratory and shipped to a participating laboratory to analyze on two separate days.

RESULTS

Precision, accuracy, and HorRatr values met or exceeded the U.S. Food and Drug Administration recommendations. The design of the BMT exercise provided a high degree of confidence in data and conclusions drawn.

CONCLUSIONS

The method performed in a manner as expected, and the method can be used by the laboratory for routine testing of wheat and rye grains.

HIGHLIGHTS

BMT of laboratory methods facilitate validation of tests by evaluating performance in an unbiased manner.

Evaluation of a Diagnostic Method to Quantify Aflatoxins B1 and M1 in Animal Liver by High-Performance Liquid Chromatography with Fluorescence Detection

Background: Aflatoxins (AFs) are secondary metabolites of fungi and are one of the causes of toxin-related pet food recalls. An intralaboratory method was previously developed to quantify aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1) in animal liver by HPLC with fluorescence detection. Objective: The aim of this study was to extensively evaluate the method performance with a single-laboratory blinded method test (BMT-S) and a multilaboratory blinded method test (BMT-M). Methods: Blinded tissue samples were prepared by a third-party laboratory and sent out to participating laboratories for both BMT-S and BMT-M. Results: In both tests, participants analyzed blinded samples prepared by an independent laboratory. In the BMT-S, accuracy ranged between 111 and 154% for AFB1 and 113 and 159% for AFM1 within the quantitation range of 0.1–0.5 ng/g. The HorRat values for repeatability ranged between 0.1 and 0.3 for AFB1 and 0.3 and 0.6 for AFM1. In the BMT-M, the interlaboratory accuracy ranged between 77 and 81% for AFB1 and 83 and 85% for AFM1 within the quantitation range of 0.2–10 ng/g. The HorRat values for reproducibility ranged between 0.4 and 0.7 for AFB1 and 0.4 and 0.9 for AFM1. Both recovery and reproducibility were acceptable. Conclusions: BMT-M evaluation demonstrated that the method was suitable for quantitation of aflatoxins B1 and M1 in animal liver between laboratories. Highlights: The BMT-S and BMT-M results demonstrated that the method is rugged and reproducible among the participating laboratories.

Evaluation of a Diagnostic Method to Quantify Aflatoxins B1 and M1 in Animal Liver by High-Performance Liquid Chromatography with Fluorescence Detection

Background: Aflatoxins (AFs) are secondary metabolites of fungi and are one of the causes of toxin-related pet food recalls. An intralaboratory method was previously developed to quantify aflatoxin B₁ (AFB₁) and aflatoxin M₁ (AFM₁) in animal liver by HPLC with fluorescence detection. Objective: The aim of this study was to extensively evaluate the method performance with a single-laboratory blinded method test (BMT-S) and a multilaboratory blinded method test (BMT-M). Methods: Blinded tissue samples were prepared by a third-party laboratory and sent out to participating laboratories for both BMT-S and BMT-M. Results: In both tests, participants analyzed blinded samples prepared by an independent laboratory. In the BMT-S, accuracy ranged between 111 and 154% for AFB₁ and 113 and 159% for AFM₁ within the quantitation range of 0.1-0.5 ng/g. The HorRat values for repeatability ranged between 0.1 and 0.3 for AFB₁ and 0.3 and 0.6 for AFM₁. In the BMT-M, the interlaboratory accuracy ranged between 77 and 81% for AFB₁ and 83 and 85% for AFM₁ within the quantitation range of 0.2-10 ng/g. The HorRat values for reproducibility ranged between 0.4 and 0.7 for AFB₁ and 0.4 and 0.9 for AFM₁. Both recovery and reproducibility were acceptable. Conclusions: BMT-M evaluation demonstrated that the method was suitable for quantitation of aflatoxins B₁ and M₁ in animal liver between laboratories. Highlights: The BMT-S and BMT-M results demonstrated that the method is rugged and reproducible among the participating laboratories.

TAIGA - a hybrid array for high energy gamma astronomy and cosmic ray physics

The physics motivations and advantages of the new TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) detector are presented. TAIGA aims at gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. For the energy range 30 – 200 TeV the sensitivity of 10 km2 area TAIGA array for the detection of local sources is expected to be 5 × 10-14 erg cm-2 sec-1 for 300 h of observations. Reconstruction of the given EAS energy, incoming direction and its core position, based on the timing TAIGA-HiSCORE data, allows one to increase a distance between the IACTs up to 600-1000 m. The low investments together with the high sensitivity for energies ≥ 30-50 TeV make this pioneering technique very attractive for exploring the galactic PeVatrons and cosmic rays. At present the TAIGA first stage has been constructed in Tunka valley, 50 km West from the Lake Baikal. The first experimental results of the TAIGA first stage are presented.

Nuclear transport of the human aryl hydrocarbon receptor and subsequent gene induction relies on its residue histidine 291

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor involved in the metabolism of physiological substances and xenobiotics, representing an interesting target in both toxicology and pharmacology. In this study, we investigated the ligand-dependent conjunction of nuclear import of the human AHR in living cells and target gene induction. Our findings strengthen the theory that the AHR triggers a precisely defined and rapid reaction upon binding to endogenous ligands, while the xenobiotic β-naphthoflavone only induces rather unspecific and slow effects. To better illuminate the ligand-mediated responses of the human AHR, we applied site-directed mutagenesis and identified histidine 291 as key residue for AHR functionality, essential for both nuclear import and target gene induction. Contrary, replacing histidine at position 291 by alanine did not affect nucleo-cytoplasmic shuttling, showing that permanent endogenous import and ligand-induced import of the AHR into the nucleus are two independent and differently regulated processes. Combining these observations with our structural investigations using a homology model of the AHR-PAS B domain, we suggest a dual role of histidine 291: (1) a major role for shaping the ligand binding site including direct interactions with ligands and, (2) an essential role for the conformational dynamics of a PAS B loop, which most likely influences the association of the AHR with the AHR nuclear translocator through interference with their protein-protein interface.

Development and Validation of Quantitative Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry Assay for Anticoagulant Rodenticides in Liver

Anticoagulant rodenticides (ARs) are used to control rodent populations; however, exposure to nontarget animals occurs. A sensitive and rugged quantitative method was developed, optimized, and validated for eight ARs in liver. Target analytes comprised two chemical classes: hydroxycoumarins (warfarin, coumachlor, dicoumarol, bromadiolone, brodifacoum, and difethialone) and indanediones (diphacinone and chlorophacinone). In this method, liver extracts were cleaned using dispersive solid phase extraction (d-SPE) to remove matrix interferences and analyzed by reverse phase ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Electrospray ionization in negative ion mode combined with multiple reaction monitoring (MRM) using a triple quadrupole mass spectrometer provided simultaneous confirmation and quantitation. Detection limits spanned 0.75-25 ng/g, and lower quantitation limits were established as 50 ng/g. Interassay method accuracy ranged from 92 to 110% across the analytical range (50-2500 ng/g) using matrix-matched calibrants with good repeatability (relative standard deviations 2-16%). Successful method transfer to another laboratory utilizing an Orbitrap mass analyzer, providing high mass accuracy, was assessed by good method reproducibility during blinded study analyses (6-29%; Horwitz ratios (HORRAT) ≤ 1.5).

An assay to screen bacterial adhesion to mucus biomolecules

AIMS

To develop an assay for rapid screening of bacterial adhesion to various groups of biomolecules present in fish mucus.

METHODS AND RESULTS

A novel assay was developed for investigation of bacterial adhesion to various groups of mucus biomolecules from fish. Lipid-, protein-, carbohydrate- and nucleic acid-rich constituents of mucus were separated using isopycnic density gradient centrifugation techniques. Separated mucus fractions were assayed for bacterial adhesion using a blotting apparatus. The assay was validated using Vibrio vulnificus and skin mucus from hybrid tilapia.

CONCLUSIONS

A novel assay was developed for the screening of bacterial adhesion to major groups of mucus biomolecules. Adhesion of V. vulnificus MLT403 positively correlated with lipid- and protein-rich mucus constituents and negatively correlated with carbohydrate-rich mucus constituents.

SIGNIFICANCE AND IMPACT OF THE STUDY

The assay can be used as an initial approach in a systematic identification of mucus constituent(s) exhibiting the most favourable adhesion properties for bacteria.

Unifying interfacial self-assembly and surface freezing

X-ray investigations reveal that the monolayers formed at the bulk alkanol-sapphire interface are densely packed with the surface-normal molecules hydrogen bound to the sapphire. About 30-35 °C above the bulk, these monolayers both melt reversibly and partially desorb. This system exhibits balanced intermolecular and molecule-substrate interactions which are intermediate between self-assembled and surface-frozen monolayers, each dominated by one interaction. The phase behavior is rationalized within a thermodynamic model comprising interfacial interactions, elasticity, and entropic effects. Separating the substrate from the melt leaves the monolayer structurally intact.

Interaction of mucus with freshly neutralised aluminium in freshwater

This study examined the interaction of mollusc trail mucus, and its biochemical constituents, with environmentally relevant concentrations of freshly neutralised aluminium (Al) in freshwater. Upon neutralisation Al starts to polymerise. In the presence of mucus the metal is rapidly localised into the hydrated mucus gel resulting in a likely reduction of its overall degree of polymerisation. A simple Al binding assay identified large-M(r) glycoconjugates as major Al-complexing molecules in mucus. Subsequent isolation and purification of these mucus glycoconjugates showed the metal readily bound to the carbohydrate portion and, in particular, to acidic components such as those containing carboxyl functionality. It is suggested gel-forming extracellular glycoconjugates play a crucial role in preventing the diffusion of Al into biological systems and thus serve to maintain metabolic homeostasis.

Calcitic microlenses as part of the photoreceptor system in brittlestars

Photosensitivity in most echinoderms has been attributed to 'diffuse' dermal receptors. Here we report that certain single calcite crystals used by brittlestars for skeletal construction are also a component of specialized photosensory organs, conceivably with the function of a compound eye. The analysis of arm ossicles in Ophiocoma showed that in light-sensitive species, the periphery of the labyrinthic calcitic skeleton extends into a regular array of spherical microstructures that have a characteristic double-lens design. These structures are absent in light-indifferent species. Photolithographic experiments in which a photoresist film was illuminated through the lens array showed selective exposure of the photoresist under the lens centres. These results provide experimental evidence that the microlenses are optical elements that guide and focus the light inside the tissue. The estimated focal distance (4-7 micrometer below the lenses) coincides with the location of nerve bundles-the presumed primary photoreceptors. The lens array is designed to minimize spherical aberration and birefringence and to detect light from a particular direction. The optical performance is further optimized by phototropic chromatophores that regulate the dose of illumination reaching the receptors. These structures represent an example of a multifunctional biomaterial that fulfills both mechanical and optical functions.

The role of the natural polyamine putrescine in defense against oxidative stress in Escherichia coli

Putrescine up-regulated, in a concentration-dependent manner, the expression levels of the oxyR and katG genes of Escherichia coli cells exposed to hydrogen peroxide. Its stimulatory effect was more pronounced under conditions of strong oxidative stress. 1,4-Diamino-2-butanone, a specific inhibitor of putrescine synthesis, also inhibited oxyR expression under oxidative stress. When added to inhibited cells, putrescine relieved this inhibitory effect. Addition of putrescine to E. coli cultures exposed to oxidative stress led to increased cell survival.

Misexpression of disrupted HMGI architectural factors activates alternative pathways of tumorigenesis

Cancer arises from aberrations in the genetic mechanisms that control growth and differentiation. HMGI-C and HMGI(Y) are members of the HMGI family of architectural factors expressed in embryonic or undifferentiated cells and highly associated with transformation. Translocations of 12q13-15 in lipomas (fat cell tumors) disrupt HMGI-C and fuse its DNA-binding domains to novel transcriptional regulatory domains. This study shows that in a rare, karyotypically distinct group of human lipomas, rearrangements of 6p21-23 produce internal deletions within HMGI(Y). Activation of the rearranged alleles leads to expression of aberrant HMGI(Y) transcripts in differentiated adipocytes. A molecular analysis of these transcripts demonstrates that fusion of HMGI DNA-binding domains to putative transcriptional regulatory domains was not necessary for lipoma formation. However, such fusions may facilitate tumor development because activation of the wild-type HMGI allele, normally required for tumorigenesis, is bypassed in lipomas which express chimeric HMGI proteins. We hypothesize that HMGI misexpression in a differentiated cell is a pivotal event in benign tumorigenesis, and the molecular pathway of tumor development depends upon the precise nature of HMGI disruption.

Localization of rat K51 keratin-like locus (Krt10l) to human and animal chromosomes by in situ hybridization

The rat K51 locus (gene symbol Krt10l) was mapped using isotopic in situ hybridization to rat chromosome 3, human chromosome 9, pig chromosome 6, cattle chromosome 18, and mink chromosome 1.

Disruption of the architectural factor HMGI-C: DNA-binding AT hook motifs fused in lipomas to distinct transcriptional regulatory domains

Lipomas are one of the most common mesenchymal neoplasms in humans. They are characterized by consistent cytogenetic aberrations involving chromosome 12 in bands q14-15. Interestingly, this region is also the site of rearrangement for other mesenchymally derived tumors. This study demonstrates that HMGI-C, an architectural factor that functions in transcriptional regulation, has been disrupted by rearrangement at the 12q14-15 chromosomal breakpoint in lipomas. Chimeric transcripts were isolated from two lipomas in which HMGI-C DNA-binding domains (AT hook motifs) are fused to either a LIM or an acidic transactivation domain. These results, identifying a gene rearranged in a benign neoplastic process that does not proceed to a malignancy, suggest a role for HMGI-C in adipogenesis and mesenchyme differentiation.

Rapid isolation of tissue-specific and developmentally regulated brain cDNAs using RNA arbitrarily primed PCR (RAP-PCR)

RNA arbitrarily primed PCR (RAP-PCR) was used to isolate cDNAs that represent developmentally regulated brain-specific genes. Five clones with a restricted pattern of expression were identified and sequenced. Four cDNAs had no obvious homology to the sequences in GenBank. One clone had over 95% homology to a Ca2+/calmodulin-insensitive adenylyl cyclase, a recently cloned gene that was isolated from rat brain and was shown to be expressed only in adult brain and lung. Two novel cDNAs were investigated further by Northern blot analysis and were found to be expressed differentially during development; their expression was confined to the forebrain in the adult mouse. Further characterization by in situ hybridization showed that the mRNA corresponding to one clone was localized to a limited number of differentiating functional structures in the developing nervous system. In the adult brain, this message is confined to the forebrain with the highest level of expression in the cortex. These data suggest that the product of this gene is involved in the establishment of neuronal networks during brain development and in synaptic plasticity in the mature cortex. This work demonstrates that RAP-PCR is a powerful method for the simultaneous detection of differences between multiple RNA populations and, as such, can be used to study differential gene expression in the brain.