Prothrombin Time, Activated Partial Thromboplastin Time, and Fibrinogen Reference Intervals for Inbred Strain 13/N Guinea Pigs (Cavia porcellus) and Validation of Low Volume Sample Analysis

Assessment of anticoagulant safety and coagulation analysis in mice using the VETSCAN® VSpro analyzer

Animal models of thrombosis play a critical role in research, helping us understand the mechanisms of hemostasis and thrombus formation, as well as in the screening of anti-thrombotic drugs. This study aimed to evaluate the safety profile of two anticoagulants in murine research and to assess coagulation parameters, including prothrombin time (PT) and activated partial thromboplastin time (aPTT), using the VETSCAN® VSpro coagulation analyzer in wild-type (C57BL/6) mice following administration of anticoagulants. Two experiments were conducted involving a total of sixty wild-type mice that received two common anticoagulants. Warfarin was administered in the drinking water at varying dosages, while dabigatran was incorporated into a custom-chow diet at two dosages (10 mg/g and 15 mg/g chow). The VSpro was used to establish a reference range for PT and aPTT values in untreated wild-type mice and to monitor coagulation changes in mice undergoing anticoagulant therapy. Dabigatran was well tolerated at both concentrations (10 mg/g and 15 mg/g chow), while warfarin was safe at a concentration of 2.5 mg/L, resulting in a doubling of PT and aPTT compared to baseline levels. Although the VSpro effectively detected coagulation abnormalities in murine models, certain limitations were observed, including out-of-range measurements in cases of coagulopathy. This study provides insights into safe anticoagulant dosages for murine models, supporting the use of dabigatran at 10 mg/g and 15 mg/g chow and warfarin at 2.5 mg/L. The VSpro analyzer was able to monitor coagulation parameters under these conditions, making it a feasible tool for murine research.

Establishing New Isosexual Pairs in Adult Male Guinea Pigs (Cavia porcellus) to Facilitate Social Housing

Guinea pigs (Cavia porcellus) are a commonly used species in biomedical research. As social creatures, compatible guinea pigs should be housed together unless scientific objectives or veterinary care require otherwise. Extensive literature suggests that adult male guinea pigs are highly aggressive in the presence of females, but data are lacking regarding the compatibility of cohoused adult males in the absence of females. Most studies that use adult males do not report housing densities. We used serial wound scoring and observations of behavior to determine whether unfamiliar adult male guinea pigs will develop stable, prosocial isosexual pairs. Wound scoring was performed before and 24 h after pairing. Serial behavioral observations assessed affiliative and agonistic behaviors at 0.5, 2, 24, and 48 h after pairing. Wound scoring and behavioral observations continued weekly for 1 mo and monthly thereafter. Wound scores were significantly higher at 24 h after pairing as compared with baseline and all other time points. Wounding was rare after week 2, indicating reduced aggression. Furthermore, affiliative behaviors significantly increased over time while agonistic behaviors were rare. Together, these data suggest that unfamiliar adult male guinea pigs establish stable prosocial pairs after an acclimation period. As was done in the present study, providing ample space, separate shelters for each animal, and the absence of female guinea pigs will likely facilitate successful pairing. We recommend consideration of a social housing program for adult male guinea pigs to provide companionship and enrich their housing environment.

New High-Affinity Thrombin Aptamers for Advancing Coagulation Therapy: Balancing Thrombin Inhibition for Clot Prevention and Effective Bleeding Management with Antidote

Thrombin is a key enzyme involved in blood clotting, and its dysregulation can lead to thrombotic diseases such as stroke, myocardial infarction, and deep vein thrombosis. Thrombin aptamers have the potential to be used as therapeutic agents to prevent or treat thrombotic diseases. Thrombin DNA aptamers developed in our laboratory exhibit high affinity and specificity to thrombin. In vitro assays have demonstrated their efficacy by significantly decreasing Factor II activity and increasing PT and APTT times in both plasma and whole blood. Aptamers AYA1809002 and AYA1809004, the two most potent aptamers, exhibit high affinity for their target, with affinity constants (Kd) of 10 nM and 13 nM, respectively. Furthermore, the in vitro activity of these aptamers displays dose-dependent behavior, highlighting their efficacy in a concentration-dependent manner. In vitro stability assessments reveal that the aptamers remain stable in plasma and whole blood for up to 24 h. This finding is crucial for their potential application in clinical settings. Importantly, the thrombin inhibitory activity of the aptamers can be reversed by employing reverse complement sequences, providing a mechanism to counteract their anticoagulant effects when necessary to avoid excessive bleeding. These thrombin aptamers have been determined to be safe, with no observed mutagenic or immunogenic effects. Overall, these findings highlight the promising characteristics of these newly developed thrombin DNA aptamers, emphasizing their potential for therapeutic applications in the field of anticoagulation therapy. Moreover, the inclusion of an antidote in the coagulation therapy regimen can improve patient safety, ensure greater therapeutic efficacy, and minimize risk during emergency situations.

Evaluation of Citrated Plasma After Thawing for Routine Coagulation Testing

OBJECTIVE

We aim to find the time in which a thawed citrate plasma sample that was preserved can be analyzed for routine coagulation testing without losing precision.

METHODS

Whole blood samples from 30 healthy volunteers were collected in 3.2% sodium citrate vacutainer and centrifuged to separate platelet-poor plasma. Each sample was then aliquoted, one aliquot was used immediately for prothrombin time (PT)-international normalized ratio (INR) and activated partial thromboplastin time (APTT), four were stored at -20°C, and four were stored at -80°C for 24 hours. After 24 hours, the aliquots were taken out and thawed at 37°C in water bath and analyzed after 15, 30, 60, and 120 minutes.

STATISTICAL ANALYSIS

Data were presented as mean with standard deviation (SD). Repeated measures ANOVA with Tukey post-hoc test was performed for multiple comparisons. All analysis was done using GraphPAD Prism 8.0 software (GraphPad Software, San Diego, California, USA).  Results: In the case of PT and INR, no statistically significant difference was found between the mean values after thawing for 120 minutes when compared with the mean baseline value. However, the APTT showed a statistically significant difference (p = 0.0232) after 30 minutes of thawing when the sample was stored at -20°C. Furthermore, a statistically significance difference (p = 0.0001) was found after 60 minutes of thawing when the samples were stored at -80°C.

CONCLUSION

Plasma samples for the PT and INR may be accepted for assessment up to 120 minutes, when stored at -20°C and -80°C for 24 hours. In the case of APTT, the plasma sample can be used for assessment up to 30 minutes after thawing when stored at -20°C and up to 60 minutes when stored at -80°C.

Hemostatic Testing in Companion Exotic Mammals

The mammalian hemostatic system is highly conserved, and companion exotic mammals are commonly used as biomedical models for normal and disordered hemostasis. Challenges associated with sample collection, test validation, and test interpretation have limited the use of these tests in clinical exotic animal practice. However, evaluation of platelet counts, coagulation screening times, and fibrin(ogen) degradation products can be valuable for monitoring exotic patients with a range of disease presentations including intoxications, anemia, systemic viral disease, hepatopathy, and endocrinopathy.

Quantitative proteomics analysis reveals core and variable tick salivary proteins at the tick-vertebrate host interface

Few studies have examined tick proteomes, how they adapt to their environment, and their roles in the parasite-host interactions that drive tick infestation and pathogen transmission. Here we used a proteomics approach to screen for biologically and immunologically relevant proteins acting at the tick-host interface during tick feeding and, as proof of principle, measured host antibody responses to some of the discovered candidates. We used a label-free quantitative proteomic workflow to study salivary proteomes of (i) wild Ixodes ricinus ticks fed on different hosts; (ii) wild or laboratory ticks fed on the same host; and (iii) adult ticks co-fed with nymphs. Our results reveal high and stable expression of several protease inhibitors and other tick-specific proteins under different feeding conditions. Most pathways functionally enriched in sialoproteomes were related to proteolysis, endopeptidase, and amine-binding activities. The generated catalog of tick salivary proteins enabled the selection of six candidate secreted immunogenic peptides for rabbit immunizations, three of which induced strong and durable antigen-specific antibody responses in rabbits. Furthermore, rabbits exposed to ticks mounted immune responses against the candidate peptides/proteins, confirming their expression at the tick-vertebrate interface. Our approach provides insights into tick adaptation strategies to different feeding conditions and promising candidates for developing anti-tick vaccines or markers of exposure of vertebrate hosts to tick bites.

Hemorrhagic Fever Viruses: Pathogenesis and Countermeasures

Before December 2019 and the COVID-19 pandemic, the general public was to some extent aware that zoonotic viruses can spill over into the human population and cause a disease outbreak [...]

Assessing Coagulation Parameters in Healthy Asian Elephants (Elephas maximus) from European and Thai Populations

The Asian elephant population is continuously declining due to several extrinsic reasons in their range countries, but also due to diseases in captive populations worldwide. One of these diseases, the elephant endotheliotropic herpesvirus (EEHV) hemorrhagic disease, is very impactful because it particularly affects Asian elephant calves. It is commonly fatal and presents as an acute and generalized hemorrhagic syndrome. Therefore, having reference values of coagulation parameters, and obtaining such values for diseased animals in a very short time, is of great importance. We analyzed prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen concentrations using a portable and fast point-of-care analyzer (VetScan Pro) in 127 Asian elephants from Thai camps and European captive herds. We found significantly different PT and aPTT coagulation times between elephants from the two regions, as well as clear differences in fibrinogen concentration. Nevertheless, these alterations were not expected to have biological or clinical implications. We have also sequenced the coagulation factor VII gene of 141 animals to assess the presence of a previously reported hereditary coagulation disorder in Asian elephants and to investigate the presence of other mutations. We did not find the previously reported mutation in our study population. Instead, we discovered the presence of several new single nucleotide polymorphisms, two of them being considered as deleterious by effect prediction software.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.