18F-sodium fluoride positron emission tomography provides pertinent additional information to computed tomography for assessment and management of tarsal pain in horses.

OBJECTIVE: To assess the value of 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) for imaging the tarsus and proximal metatarsus and compare it with CT and lameness evaluation. ANIMALS: 25 horses with lameness localized to the tarsal and proximal metatarsal regions that underwent 18F-NaF PET/CT between 2016 and 2021. METHODS: 18F-NaF PET and CT images were retrospectively independently evaluated by 3 observers. Standardized uptake values (SUV) were used to characterize 18F-NaF uptake. Correlation between PET and CT findings with subjective and objective maximum (Max-D) and minimum pelvic height lameness data was estimated. RESULTS: The inter-observer Kappa-weighted value (κ) was higher for PET (κ = 0.66) than CT (κ = 0.6). CT and PET scores were fairly correlated (R = 0.49; P < 0.05). PET SUVratio (SUV of the main lesion/SUV talus) had the highest correlation with Max-D (R = 0.71; P < .05). PET and CT scores for the plantar region were significantly higher in Quarter Horses (P < .05) and showed consistently higher correlation with objective lameness data (CT plantar grade - Max-D [R = 0.6; P < .05], PET plantar grade - Max-D [R = 0.47; P = .04]) than other regions of the distal tarsal joints. Three Warmbloods presented marked uptake at the medial cochlea of the distal tibia. CLINICAL RELEVANCE: PET had a moderate correlation with CT for assessment of tarsal lesions. The degree of PET uptake can help differentiate active versus inactive lesions. Specific location of the uptake is important in determining clinical relevance.

A Database of Snow on Sea Ice in the Central Arctic Collected during the MOSAiC expedition.

Snow plays an essential role in the Arctic as the interface between the sea ice and the atmosphere. Optical properties, thermal conductivity and mass distribution are critical to understanding the complex Arctic sea ice system's energy balance and mass distribution. By conducting measurements from October 2019 to September 2020 on the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, we have produced a dataset capturing the year-long evolution of the physical properties of the snow and surface scattering layer, a highly porous surface layer on Arctic sea ice that evolves due to preferential melt at the ice grain boundaries. The dataset includes measurements of snow during MOSAiC. Measurements included profiles of depth, density, temperature, snow water equivalent, penetration resistance, stable water isotope, salinity and microcomputer tomography samples. Most snowpit sites were visited and measured weekly to capture the temporal evolution of the physical properties of snow. The compiled dataset includes 576 snowpits and describes snow conditions during the MOSAiC expedition.

Comparison of skeletal scintigraphy and standing 18 F-NaF positron emission tomography for imaging of the fetlock in 33 Thoroughbred racehorses.

This retrospective, methods comparison study aimed to compare skeletal scintigraphy and 18 F-NaF positron emission tomography (PET) for the detection of abnormalities in the fetlocks of Thoroughbred racehorses. Thirty-three horses (72 limbs) imaged with both scintigraphy and 18 F-NaF PET, for investigation of lameness or poor performance related to the fetlock, were included. Seven observers, including experienced racetrack practitioners, surgery and imaging residents, and a board-certified veterinary radiologist, independently reviewed all data for evidence of increased radiopharmaceutical uptake in 10 different regions of interest. The interobserver agreement was higher for PET (Kappa-weighted (K-w) 0.73 (0.51-0.84)) (median (range)) than for scintigraphy (0.61 (0.40-0.77)) (P < 0.0001). When scintigraphy and PET were compared, the agreement was fair (K-w 0.29). More sites of increased uptake were identified using PET compared with scintigraphy. Agreement between the two modalities was higher for the palmar/plantar metacarpal/metatarsal condylar regions (K-w 0.59) than for the proximal sesamoid bones (K-w 0.25). Increased radiopharmaceutical uptake was detected in the medial proximal sesamoid bone in 6.9% and 22.2% of limbs with scintigraphy and PET, respectively. The high interobserver agreement for PET, despite the recent introduction of this technique, demonstrates the ease of clinical interpretation of PET scans. The higher number of lesions detected with PET compared with scintigraphy can be explained by the higher spatial resolution and cross-sectional nature of this modality. Study findings supported using PET in a clinical population of racehorses, in particular for the assessment of the proximal sesamoid bones.

Validation of a dedicated positron emission tomography scanner for imaging of the distal limb of standing horses.

A positron emission tomography (PET) scanner, with an openable ring of detectors, was specifically designed to image the distal limb of standing horses. The goals of this prospective, preclinical, experimental, methods comparison study were to validate the safety of the scanner, assess image quality, and optimize scanning protocols. Six research horses were imaged three times (twice standing, once anesthetized) and six horses in active race training were imaged once under standing sedation. Multiple scans of both front fetlocks were obtained with different scan durations and axial fields of view. A total of 94 fetlock scans were attempted and 90 provided images of diagnostic value. Radiotracer uptake was the main factor affecting image quality, while motion did not represent a major issue. Scan duration and field of view also affected image quality. Eight specific lesions were identified on PET images from anesthetized horses and were all also independently recognized on the PET images obtained on standing horses. Maximal standardized uptake values (SUVmax) had good repeatability for the assessment of specific lesions among different scans. Three feet and six carpi were also successfully imaged. This study validated the safety and practicality of a PET scanner specifically designed to image the distal limb in standing horses. Proper preparation of horses, similar to bone scintigraphy, is important for image quality. A 4-min scan with 12 cm field of view was considered optimal for clinical fetlock imaging. Evaluation of a larger clinical population is the next step for further assessment of the clinical utility of PET imaging in horses.

Bacterial meningitis after dental extraction in a 17-year-old horse.

Dental extractions in horses may result in bacteremia, which can lead to systemic complications. Bacterial meningitis following oral cheek tooth extractions in a 17-year-old Thoroughbred gelding is described in this report. The bacterial meningitis was confirmed by histopathology. The gelding was presented for evaluation of intermittent fever, loose feces, and mild colic signs which started 5 days after cheek tooth extraction. This case illustrates a rare complication associated with oral tooth extraction in a horse and highlights the unusual presenting features of meningitis. Key clinical message: Bacterial meningitis secondary to oral cheek tooth extraction should be considered as differential diagnosis; particularly in cases with the development of pyrexia a few days after the procedure.

Méningite bactérienne après extraction dentaire chez un cheval de 17 ans. Les extractions dentaires chez les chevaux peuvent entraîner une bactériémie, ce qui peut amener des complications systémiques. Un cas de méningite bactérienne à la suite d'extractions buccales de dents jugales chez un hongre pur-sang de 17 ans est décrite dans ce rapport. La méningite bactérienne a été confirmée par histopathologie. Le hongre a été présenté pour évaluation d'une fièvre intermittente, de selles molles et de signes de coliques légers qui ont commencé 5 jours après l'extraction de la dent jugale. Ce cas illustre une complication rare associée à l'extraction dentaire orale chez un cheval et met en évidence des caractéristiques inhabituelles de la méningite.Message clinique clé :La méningite bactérienne secondaire à l'extraction buccale des dents jugales doit être considérée comme un diagnostic différentiel, en particulier dans les cas de développement d'une pyrexie quelques jours après l'intervention.(Traduit par Dr Serge Messier).

Clinical and diagnostic findings, treatment, and short- and long-term survival in horses with peritonitis: 72 cases (2007-2017).

OBJECTIVE: To identify etiology, clinical findings, diagnostic results, treatment, and short- and long-term survival and to report factors associated with nonsurvival and survival in horses with peritonitis. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n = 72). METHODS: Medical records at William R. Pritchard Veterinary Medical Teaching Hospital from 2007-2017 were reviewed for horses diagnosed with peritonitis. The essential inclusion criterion was a peritoneal nucleated cell count of ≥25 000 cells/µL. Gastrointestinal rupture and cases in which peritonitis occurred after abdominal surgery or castration were excluded. Information retrieved from medical records included signalment, history, clinicopathological and peritoneal fluid variables, diagnostic imaging findings, inciting cause, treatment, and short- and long-term survival. Data were analyzed by using Fisher's exact test, Wilcoxon rank sum test, and χ2 test (P < .05). RESULTS: Colic was the most common presenting complaint (34/72 [48%]). A definitive diagnosis could be made in 44 (44/72 [61%]) cases. The most common cause of peritonitis was infectious agents (31/72), followed by trauma (8/72), gastrointestinal thickening (3/72), and eosinophilic peritonitis (2/72). Idiopathic peritonitis was identified in 28 (28/72 [39%]) cases. Sixty (83%) horses survived to hospital discharge. Long-term follow-up was available for 49 horses, with 43 (88%) horses alive 1 year after discharge. Significant differences between nonsurvivors and survivors were history of colic, positive peritoneal fluid culture, and several hematological/peritoneal fluid variables. CONCLUSION: Peritoneal fluid analysis was essential for a definitive diagnosis of peritonitis, and certain variables were useful for predicting outcome. CLINICAL SIGNIFICANCE: Results of this study provide evidence of the value of peritoneal fluid analysis for identification of peritonitis, prediction of outcome, and successful treatment.

Comparison between head-tail-rope assisted and unassisted recoveries in healthy horses undergoing general anesthesia for elective surgeries.

OBJECTIVE: To compare attempts to stand, duration, quality, and occurrence of injuries between head-tail rope assistance and unassisted recoveries in healthy horses undergoing general anesthesia for elective surgeries. STUDY DESIGN: Randomized, prospective, clinical trial. METHODS: Three hundred one healthy horses undergoing elective surgeries were randomly assigned to recover with head-tail rope assistance (group A) or unassisted (group U); 305 recoveries (group A, n = 154; group U, n = 151) were analyzed. Anesthesia was maintained with isoflurane and triple drip. For each recovery, attempts to stand, duration, quality, and recovery-associated injuries were recorded. Data were analyzed by linear regression and analysis of covariance. RESULTS: Anesthesia duration was similar between groups (mean ± SD, 70 ± 29 minutes). Compared with group U, group A had fewer attempts to stand (median [range], group A = 1 [1-7] vs group U = 3 [1-34]) and shorter duration of recovery (mean ± SD, A = 36 ± 12 minutes vs U = 41 ± 15 minutes). Recovery quality in group A (28 points [15-70]) was better than that in group U (38 points [11-87]). More horses had recovery-associated injuries in group U (9 horses) compared with group A (2 horses). One horse per group was euthanized. CONCLUSION: Head-tail rope assistance reduced standing attempts, shortened recovery duration, improved recovery quality, and reduced recovery-associated minor injuries after general anesthesia for elective surgery in healthy horses. Fatalities could not be prevented. CLINICAL SIGNIFICANCE: Head-tail rope assistance may improve recovery in healthy horses after short-duration elective surgeries with isoflurane and triple drip.

Effect of age on Narcotrend Index monitoring during sevoflurane anesthesia in children below 2 years of age.

BACKGROUND: In older children, different electroencephalogram-based algorithms for measuring depth of anesthesia displayed a similar performance as in adults, but in infants they have not displayed the same reliability so far. According to the individual developmental state, the Narcotrend distinguishes "differentiated" electroencephalograms, which can be classified using the full Narcotrend Index scale, from "undifferentiated" electroencephalograms, which are classified using a scale with fewer stages. OBJECTIVE: The objective of this prospective clinical observational study was to assess the feasibility and performance of the Narcotrend monitor in children <2 years within a clinical setting. METHODS: Sixty-one children aged 0-24 months undergoing general anesthesia with sevoflurane and remifentanil for elective pediatric surgery were studied. We investigated the percentage of differentiated electroencephalograms and the correlation between multiples of minimal alveolar sevoflurane concentration and the Narcotrend Index according to age groups. Prediction probability was used to evaluate the performance of the Narcotrend Index for differentiation between consciousness and unconsciousness and between different sevoflurane concentrations. RESULTS: The percentage of differentiated electroencephalograms increased with increasing age (0-3 months: 23.8%, 4-5 months: 87.5%, 6-11 months: 92.3%, 12-24 months: 100%). The overall prediction probability of Narcotrend Index was 1.0 (SE 0.05) for differentiation between awake and loss of consciousness and 1.0 (SE 0.01) for differentiation between anesthetized and return of consciousness. Spearman correlation analysis revealed a significant negative correlation between sevoflurane concentration and the Narcotrend Index (r = -0.78, P < .0001, 95%CI: -0.81 to -0.74). Overall prediction probability of Narcotrend Index to sevoflurane concentration was 0.8 (95%CI: 0.78-0.82). CONCLUSION: The Narcotrend monitor indicated a Narcotrend Index in most infants and young children starting from 4 months with significant correlation to and acceptable prediction probability for minimal alveolar sevoflurane concentration.

Scope and Limitations of Typical Copper-Free Bioorthogonal Reactions with DNA: Reactive 2'-Deoxyuridine Triphosphates for Postsynthetic Labeling.

Four triphosphates of 2'-deoxyuridine that carried the following bioorthogonally reactive groups were synthesized by organic-chemical methods. Two triphosphates with tetrazines and one with a cyclopropene moiety were designed for Diels-Alder reactions with inverse electron demand, and one triphosphate with a tetrazole core was designed for the "photoclick" cycloaddition. These triphosphates were not only successfully applied for oligonucleotide preparation by standard DNA polymerases, including Hemo KlenTaq, Vent, and Deep Vent, but also bypassed for full length primer extension products. Fluorescent labeling of the primer extension products was achieved by fluorophores with reactive counterparts and analyzed by polyacrylamide gel electrophoresis mobility shifts. The tetrazine-oligonucleotide conjugates were reacted with carboxymethylmonobenzocyclooctyne- and bicyclononyne-modified fluorophores. The yield of these postsynthetic reactions could significantly be improved by a more stable but still reactive nicotinic acid-derived tetrazine and by changing the key experimental conditions, mainly the pH of 7.2 and the temperature of 45-55 °C. The cyclopropene-oligonucleotide conjugate could be successfully labeled with a tetrazine-modified rhodamine in very good yields. The "photoclick" cycloaddition between tetrazole-oligonucleotide conjugates and a maleimide-modified dye worked quantitatively. The combination of primer extension, bypass, and bioorthogonal modification works also for double and triple labeling using the cyclopropene-modified 2'-deoxyuridine triphosphate.

Synthesis of Wavelength-shifting DNA Hybridization Probes by Using Photostable Cyanine Dyes.

In this protocol, we demonstrate a method for the synthesis of 2'-alkyne modified deoxyribonucleic acid (DNA) strands by automated solid phase synthesis using standard phosphoramidite chemistry. Oligonucleotides are post-synthetically labeled by two new photostable cyanine dyes using copper-catalyzed click-chemistry. The synthesis of both donor and acceptor dye is described and is performed in three consecutive steps. With the DNA as the surrounding architecture, these two dyes undergo an energy transfer when they are brought into close proximity by hybridization. Therefore, annealing of two single stranded DNA strands is visualized by a change of fluorescence color. This color change is characterized by fluorescence spectroscopy but can also be directly observed by using a handheld ultraviolet (UV) lamp. The concept of a dual fluorescence color readout makes these oligonucleotide probes excellent tools for molecular imaging especially when the described photostable dyes are used. Thereby, photobleaching of the imaging probes is prevented, and biological processes can be observed in real time for a longer time period.

Copper-Free Postsynthetic Labeling of Nucleic Acids by Means of Bioorthogonal Reactions.

Postsynthetic modification of nucleic acids has the advantage that the chemical development of only a few building blocks is necessary, each bearing a chosen reactive functional group that is applicable to its reactive counterpart for a variety of different labeling types. The reactive group is either linked to phosphoramidites for chemical synthesis on solid phase or attached to nucleoside triphosphates for application in primer extension experiments and PCR. Chemoselectivity is required for this strategy, together with bioorthogonality to perform these labelings in living cells or even organisms. Currently, the copper-free reactions include strain-promoted 1,3-dipolar cycloadditions, "photoclick" reactions, Diels-Alder reactions with inverse electron demand, and nucleophilic additions. The majority of these modification strategies show good to excellent reaction kinetics, an important prerequisite for labeling inside cells and in vivo in order to keep the concentrations of the reacting partners as low as possible.

Influence of ice thickness and surface properties on light transmission through Arctic sea ice.

The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance using the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under-ice light field on small scales (<1000 m2), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

"Photoclick" postsynthetic modification of DNA.

A new DNA building block bearing a push-pull-substituted diaryltetrazole linked to the 5-position of 2'-deoxyuridine through an aminopropynyl group was synthesized. The accordingly modified oligonucleotide allows postsynthetic labeling with a maleimide-modified sulfo-Cy3 dye, N-methylmaleimide, and methylmethacrylate as dipolarophiles by irradiation at 365 nm (LED). The determined rate constant of (23±7) M(-1) s(-1) is remarkably high with respect to other copper-free bioorthogonal reactions and comparable with the copper-catalyzed cycloaddition between azides and acetylenes.

Prevention and synergistic control of Ph(+) ALL by a DNA vaccine and 6-mercaptopurine.

Although the outcome of patients with acute lymphoblastic leukemia (ALL) has been improved continuously by chemotherapy and tyrosine kinase inhibitors, prognosis of patients with Philadelphia chromosome positive (Ph(+)) ALL still remains poor. Since further intensification of chemotherapy is limited by toxic side effects and patients with high risk of transplant-related mortality are not eligible for allogeneic stem cell transplantation new treatment strategies are urgently needed for the prevention of Ph(+) ALL relapse. There is increasing evidence that the immune system plays an essential role for the eradication or immunologic control of remaining leukemia cells. We developed several DNA-based vaccines encoding a BCR-ABL(p185) specific peptide and GM-CSF, and CD40-L, IL-27 or IL-12 and evaluated the preventive and therapeutic efficacy against a lethal challenge of syngeneic Ph(+) ALL in Balb/c mice. In vivo cell depletion assays and cytokine expression studies were performed and the efficacy of the DNA vaccine was compared with 6-mercaptopurine (6-MP) alone and the combination of the DNA vaccine and 6-MP. Preventive immunization with the vaccine BCR-ABL/GM-CSF/IL-12 and the TLR-9 agonist dSLIM induced an innate and adaptive immune response mediated by NK-cells, CD4(+) T-cells and CD8(+) T-cells leading to a survival rate of 80%. Therapeutic vaccination resulted in a significantly longer leukemia-free survival (40.7 days vs. 20.4 days) and a higher survival rate (56% vs. 10%) compared to chemotherapy with 6-MP. Remarkably, in combination with the vaccine 6-MP acted synergistically and led to 100% survival. These results demonstrate that minimal residual disease of Ph(+) ALL can be significantly better controlled by a combined treatment approach of immunotherapy and chemotherapy. This provides a rationale for improving maintenance therapy in order to reduce the relapse rate in patients with Ph(+) ALL.