Extramedullary hematopoiesis (EMH) is the formation and development of blood cells outside the medullary spaces of the bone marrow. Although widely considered an epiphenomenon, secondary to underlying primary disease and lacking serious clinical or diagnostic implications, the presence of EMH is far from incidental on a molecular basis; rather, it reflects a well-choreographed suite of changes involving stem cells and their microenvironment (the stem cell niche). The goals of this review are to reconsider the molecular basis of EMH based on current knowledge of stem cell niches and to examine its role in the pathophysiologic mechanisms of EMH in animals. The ability of blood cells to home, proliferate, and mature in extramedullary tissues of adult animals reflects embryonic patterns of hematopoiesis and establishment or reactivation of a stem cell niche. This involves pathophysiologic alterations in hematopoietic stem cells, extracellular matrix, stromal cells, and local and systemic chemokines. Four major theories involving changes in stem cells and/or their microenvironment can explain the development of most occurrences of EMH: (1) severe bone marrow failure; (2) myelostimulation; (3) tissue inflammation, injury, and repair; and (4) abnormal chemokine production. EMH has also been reported within many types of neoplasms. Understanding the concepts and factors involved in stem cell niches enhances our understanding of the occurrence of EMH in animals and its relationship to underlying disease. In turn, a better understanding of the prevalence and distribution of EMH in animals and its molecular basis could further inform our understanding of the hematopoietic stem cell niche.

Desert tortoise (Gopherus agassizii) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss, and human and disease-related mortality. Evaluation of hematologic and biochemical responses of desert tortoises to physiologic and environmental factors can facilitate the assessment of stress and disease in tortoises and contribute to management decisions and population recovery. The goal of this study was to obtain and analyze clinical laboratory data from free-ranging desert tortoises at three sites in the Mojave Desert (California, USA) between October 1990 and October 1995, to establish reference intervals, and to develop guidelines for the interpretation of laboratory data under a variety of environmental and physiologic conditions. Body weight, carapace length, and venous blood samples for a complete blood count and clinical chemistry profile were obtained from 98 clinically healthy adult desert tortoises of both sexes at the Desert Tortoise Research Natural area (western Mojave), Goffs (eastern Mojave) and Ivanpah Valley (northeastern Mojave). Samples were obtained four times per year, in winter (February/March), spring (May/June), summer (July/August), and fall (October). Years of near-, above-and below-average rainfall were represented in the 5 yr period. Minimum, maximum and median values, and central 95 percentiles were used as reference intervals and measures of central tendency for tortoises at each site and/or season. Data were analyzed using repeated measures analysis of variance for significant (P Ͻ 0.01) variation on the basis of sex, site, season, and interactions between these variables. Significant sex differences were observed for packed cell volume, hemoglobin concentration, aspartate transaminase activity, and cholesterol, triglyceride, calcium, and phosphorus concentrations. Marked seasonal variation was observed in most parameters in conjunction with reproductive cycle, hibernation, or seasonal rainfall. Year-to-year differences and long-term alterations primarily reflected winter rainfall amounts. Site differences were minimal, and largely reflected geographic differences in precipitation patterns, such that results from these studies can be applied to other tortoise populations in environments with known rainfall and forage availability patterns.

Results of the present study suggested that there were substantial differences in the accuracy of currently available PBGMs when used to determine blood glucose concentration in dogs.

Tortoise mycoplasmosis is one of the most extensively characterized infectious diseases of chelonians. A 1989 outbreak of upper respiratory tract disease (URTD) in free-ranging Agassiz's desert tortoises (Gopherus agassizii) brought together an investigative team of researchers, diagnosticians, pathologists, immunologists and clinicians from multiple institutions and agencies. Electron microscopic studies of affected tortoises revealed a microorganism in close association with the nasal mucosa that subsequently was identified as a new species, Mycoplasma agassizii. Over the next 24  years, a second causative agent, Mycoplasma testudineum, was discovered, the geographic distribution and host range of tortoise mycoplasmosis were expanded, diagnostic tests were developed and refined for antibody and pathogen detection, transmission studies confirmed the pathogenicity of the original M. agassizii isolate, clinical (and subclinical) disease and laboratory abnormalities were characterized, many extrinsic and predisposing factors were found to play a role in morbidity and mortality associated with mycoplasmal infection, and social behavior was implicated in disease transmission. The translation of scientific research into management decisions has sometimes led to undesirable outcomes, such as euthanasia of clinically healthy tortoises. In this article, we review and assess current research on tortoise mycoplasmosis, arguably the most important chronic infectious disease of wild and captive North American and European tortoises, and update the implications for management and conservation of tortoises in the wild.

Background: Despite treatment, many dogs still die of complications related to canine parvoviral (CPV) enteritis. Effective prognostication would be beneficial in managing this disease.Hypothesis: We hypothesize that the occurrence of leukocytopenias at admission and at 24 and 48 hours after admission, and changes in absolute leukocyte counts over time, could be used to predict outcome.Animals: Sixty-two puppies with confirmed CPV. Methods: A prospective study was performed. CBC was performed daily until discharge or death (in which case a postmortem examination was performed).Results: Of the nonsurvivors (10/62; 16%), 9 died because of complications of the disease and 1 was euthanized because of a poor prognosis. There was a statistical significant difference in the occurrence of leukocytopenias between groups at 24 and 48 hours postadmission. The survivors showed a significant increase over time in certain leukocyte types (specifically lymphocytes) compared with values at admission. The positive predictive value for survivors was high. Nonsurvivors had marked thymic and lymphoid atrophy and marked bone marrow hypocellularity.Conclusion: An accurate prognosis could be obtained at 24 hours after admission by evaluating the change in total leukocyte, band neutrophil, lymphocyte, monocyte, and eosinophil counts.