The neurophysiology of dyspnea

Objective – To review the human and veterinary literature regarding the neurophysiology of dyspnea and to provide evidence for the beneficial effects of several novel therapies aimed at the alleviation of dyspneic sensations. Data Sources – Data sources included scientific reviews, case reports, original research publications, and recent research conference proceedings. Human Data Synthesis – The use of blood oxygenation level‐dependent functional magnetic resonance imaging technology has revealed that the brain regions activated by air hunger in humans are also those activated by fear, pain, and thirst perception. In human subjects, it has been found that agents known to enhance the firing of pulmonary slowly adapting receptors (SARs) can alleviate the sensation of dyspnea without altering central respiratory drive. Several small studies have also shown that nebulized opioids can reduce the sensation of dyspnea apparently via activation of peripheral opioid receptors in the lung. Veterinary Data Synthesis – There are several animal models relevant to both small and large animal clinical patient populations. Treatment of rats with a nebulized SAR sensitizing agent (furosemide) enhances SAR firing in response to lung inflation. Behavioral escape responses to airway occlusion are reduced in lightly anesthetized cats when treated with nebulized furosemide. Opioid agonists have been shown to inhibit the release of acetylcholine and other mediators from the airways of dogs and guinea pigs. Studies using a goat model with bilateral destruction of the pre‐Bötzinger Complex do not support current paradigms of air hunger origination. Conclusions – Veterinary patients may benefit from an approach to dyspnea that incorporates an understanding of the origins of the unpleasant sensations associated with the condition. Several novel therapies have shown promise in alleviating dyspneic sensations without altering respiratory drive. Further study is needed to determine the safety and efficacy of these therapies in veterinary patients.     

Alterations in activated T‐cell cytokine expression in healthy dogs over the initial 7 days of twice daily dosing with oral cyclosporine

Cyclosporine is a powerful T‐cell inhibitor used in the treatment of immune‐mediated and inflammatory diseases in the dog. There is limited information on how to best monitor patients on cyclosporine therapy. Currently, pharmacokinetic and pharmacodynamic assays are available. Pharmacokinetic assays that measure the concentration of cyclosporine in the blood are used to assess if an appropriate drug concentration has been achieved; however, target blood drug concentrations have not been shown to reliably correlate with suppression of T‐cell function in the dog. In human transplant recipients, therapeutic drug monitoring has shifted to include pharmacodynamic‐based monitoring. Our laboratory has validated a RT‐qPCR assay to measure the pharmacodynamic effects of cyclosporine in the dog. In this study, activated T‐cell expression of IL‐2 and IFN‐γ was measured using RT‐qPCR daily for 7 consecutive days in 8 healthy Walker hounds receiving oral cyclosporine at a dosage of 10 mg/kg every 12 hr. Cytokine production was found to be markedly decreased within 24 hr after the initiation of cyclosporine and remained significantly decreased for the duration of the project. Based on these results, cyclosporine causes a rapid drop in T‐cell cytokine production that is sustained with continued dosing in healthy dogs. Although performed in healthy dogs, this study demonstrated a marked decrease in cytokine suppression within 24 hr of drug administration, suggesting that pharmacodynamic monitoring of cyclosporine's effects on T cells could be considered within several days of commencing therapy in dogs suffering from life‐threatening immune‐mediated disorders.     

Helium‐oxygen gas‐carrier mixture (heliox): a review of physics and potential applications in veterinary medicine

Background – To review the physics of helium with regard to airway physiology, as well as known human and potential veterinary applications of administration of inhaled helium‐oxygen gas‐carrier mixture (heliox). Data Sources – Human and veterinary studies. Human Data Synthesis – Helium‐oxygen mixtures have been used in human medicine for over 70 years as an adjunct therapy in various upper and lower respiratory disorders. Helium's low density promotes laminar flow through partially obstructed airways, resulting in a decreased work of breathing. Veterinary Data Synthesis – Little to no evidence‐based medicine exists to support or oppose the use of heliox in veterinary species. However, domestic animal species and humans share several common pathophysiologic aspects of various obstructive airway disorders. Thus, veterinary patients may also ultimately and significantly benefit from this novel therapy. Conclusion – Prospective studies are needed in veterinary medicine to determine the utility of heliox in clinical scenarios.     

Immune defense of wild‐caught Norway rats is characterized by increased levels of basal activity but reduced capability to respond to further immune stimulation

Studies of wild animals' immunity often use comparison with laboratory‐raised individuals. Using such an approach, various data were obtained concerning wild Norway rat's immunity. Lower or higher potential of immune system cells to respond to activation stimuli were shown, because of analysis of disparate parameters and/ or small number of analyzed individuals. Inconsistent differences between laboratory and wild rats were shown too, owing to great response variability in wild rats. We hypothesized that wild rats will express more intense immune activity compared to their laboratory counterparts which live in a less demanding environment. To test this, we analyzed the circulating levels of inflammatory cytokine interleukin‐6 (IL‐6), a mediator which has a central role in host immune defense. In addition, we examined the activity of the central immune organ, the spleen, including cell proliferation and production of pro‐inflammatory cytokines interferon‐γ (IFN‐γ) and interleukin‐17 (IL‐17), which are major effectors of cellular adaptive immune response. In order to obtain reasonable insight into the immunity of wild Norway rats, analysis was conducted on a much larger number of individuals compared to other studies. Higher levels of plasma IL‐6, higher spleen mass, cellularity and basal IFN‐γ production concomitantly with lower basal production of anti‐inflammatory cytokine interleukin‐10 (IL‐10) revealed more intense immune activity in the wild compared to laboratory rats. However, lower responsiveness of their spleen cells' proinflammatory cytokine production to concanavalin A (ConA) stimulation, along with preserved capacity of IL‐10 response, might be perceived as an indication of wild rats' reduced capability to cope with incoming environmental stimuli, but also as a means to limit tissue damage.     

Apoptosis: A review of pro‐apoptotic and anti‐apoptotic pathways and dysregulation in disease

Objective – To review the human and veterinary literature on the biology of apoptosis in health and disease. Data Sources – Data were examined from the human and veterinary literature identified through Pubmed and references listed in appropriate articles pertaining to apoptosis. Human Data Synthesis – The role of apoptosis in health and disease is a rapidly growing area of research in human medicine. Apoptosis has been identified as a component of human autoimmune diseases, Alzheimer's disease, cancer, and sepsis. Veterinary Data Synthesis – Research data available from the veterinary literature pertaining to apoptosis and its role in diseases of small animal species is still in its infancy. The majority of veterinary studies focus on oncologic therapy. Most of the basic science and human clinical research studies use human blood and tissue samples and murine models. The results from these studies may be applicable to small animal species. Conclusions – Apoptosis is the complex physiologic process of programmed cell death. The pathophysiology of apoptosis and disease is only now being closely evaluated in human medicine. Knowledge of the physiologic mechanisms by which tissues regulate their size and composition is leading researchers to investigate the role of apoptosis in human diseases such as cancer, autoimmune disease and sepsis. Because it is a multifaceted process, apoptosis is difficult to target or manipulate therapeutically. Future studies may reveal methods to regulate or manipulate apoptosis and improve patient outcome.     

Age‐associated changes to pathogen‐associated molecular pattern‐induced inflammatory mediator production in dogs

Objective – To determine whether older dogs will have a more pronounced pro‐inflammatory response and blunted anti‐inflammatory response to pathogen‐associated molecular patterns (PAMPs) compared with younger dogs. Design – Prospective. Setting – University teaching hospital. Animals – Thirty‐eight privately owned sexually altered dogs of various ages. Interventions – Blood was collected for HCT, WBC count, plasma biochemical analysis, and whole blood culture. Whole blood was stimulated with lipopolysaccharide (LPS) or, lipoteichoic acid or, peptidoglycan or, addition of phosphate‐buffered saline. Tumor necrosis factor (TNF), interleukin (IL)‐6, and IL‐10 production from whole blood were compared among young, middle aged, and geriatric dogs. Measurements and Main Results – LPS, lipoteichoic acid, and peptidoglycan stimulated significant TNF, IL‐6, and IL‐10 production from canine whole blood compared with phosphate‐buffered saline. Whole blood from geriatric dogs had a blunted IL‐10 response to LPS stimulation and middle‐aged dogs had increased LPS‐induced TNF production compared with the other groups. Conclusion – PAMPs from gram‐positive and gram‐negative bacteria stimulate TNF, IL‐6, and IL‐10 production from canine whole blood. The inflammatory mediator response to PAMPs from gram‐negative bacteria alters with age and may be one factor contributing to mortality in geriatric dogs with sepsis.     

Controversies related to red blood cell transfusion in critically ill patients

Objective – To review the evolution of and controversies associated with allogenic blood transfusion in critically ill patients. Data sources – Veterinary and human literature review. Human Data Synthesis – RBC transfusion practices for ICU patients have come under scrutiny in the last 2 decades. Human trials have demonstrated relative tolerance to severe, euvolemic anemia and a significant outcome advantage following implementation of more restricted transfusion therapy. Investigators question the ability of RBCs stored longer than 2 weeks to improve tissue oxygenation, and theorize that both age and proinflammatory or immunomodulating effects of transfused cells may limit efficacy and contribute to increased patient morbidity and mortality. Also controversial is the ability of pre‐ and post‐storage leukoreduction of RBCs to mitigate adverse transfusion‐related events. Veterinary Data Synthesis – While there are several studies evaluating the transfusion trigger, the RBC storage lesion and transfusion‐related immunomodulation in experimental animal models, there is little research pertaining to clinical veterinary patients. Conclusions – RBC transfusion is unequivocally indicated for treatment of anemic hypoxia. However, critical hemoglobin or Hct below which all critically ill patients require transfusion has not been established and there are inherent risks associated with allogenic blood transfusion. Clinical trials designed to evaluate the effects of RBC age and leukoreduction on veterinary patient outcome are warranted. Implementation of evidence‐based transfusion guidelines and consideration of alternatives to allogenic blood transfusion are advisable.     

On the winter enhancement of adaptive humoral immunity: hypothesis testing in desert hamsters (Phodopus roborovskii: Cricetidae,Rodentia) kept under long‐day and short‐day photoperiod

We tested the winter immunity enhancement hypothesis (WIEH) on male desert hamsters (Phodopus roborovskii) kept under long‐day (LD) and short‐day (SD) photoperiods. We assumed that under SD in a laboratory, the adaptive humoral immune responsiveness to the antigenic challenge would be enhanced due to the lack of winter physical stressors and food shortages and/or because of the action of an endogenous winter bolstering mechanism, while under LD the immune responsiveness would be suppressed by the activity of the reproductive system. The results support the WIEH in part. We did not find a difference in antibody production in response to sheep erythrocytes between SD and LD hamsters, but SD males had the lower number of granulocytes and the higher number of lymphocytes in white blood cell counts. Reproductive activity was lower in SD males. These males demonstrated an increase in their mass‐specific resting metabolic rate, their mass‐specific maximal metabolic rate and their level of cortisol. The result of a generalized linear model analysis indicates the negative effect on secondary immunoresponsiveness to sheep erythrocytes of mid‐ventral gland size, the organ characterizing individual reproductive quality, and designates a tradeoff between antibody production and reproductive effort. The mass‐independent maximal metabolic rate also negatively affected antibody production, indicating a tradeoff between maximal aerobic performance and the adaptive immune function. The higher stress in SD males seems to be the most likely reason for the lack of the effect of daylight duration on antibody production.     

A case‐based review of a simplified quantitative approach to acid‐base analysis

Objective – To present a simplified quantitative approach to acid‐base analysis and to demonstrate its clinical utility. Data Sources – Original research articles and textbooks. Data Synthesis – A simplified quantitative approach to acid‐base analysis is presented, which is derived from the Fencl‐Stewart approach and calculates the magnitude of the effect on the standardized base excess (SBE) of 5 separate variables: (1) a free water effect (marked by sodium concentration), (2) an effect marked by the chloride concentration, (3) an albumin effect, (4) a lactate effect, and (5) a phosphate effect. Six clinical cases with acid‐base abnormalities are presented in which the quantitative approach provides information that is not apparent from the traditional approach. Conclusion – This simplified quantitative approach provides a comprehensive evaluation of complex acid‐base disorders, identifies individual processes and their relative influence on SBE, and aids in the development of an appropriate therapeutic plan.     

Histamine: metabolism, physiology, and pathophysiology with applications in veterinary medicine

Objective – To review the human and veterinary literature on histamine physiology and pathophysiology and potential applications for clinical use in veterinary critical care. Data Sources – Human and veterinary clinical studies, reviews, texts, and recent research in histamine receptor and antagonist therapy. Human Data Synthesis – Recent progress in molecular biology has led to a more complete understanding of the enzymes involved in histamine metabolism and histamine receptor physiology. The past decade of research has confirmed the role of histamine in the classical functions (contraction of smooth muscle, increase in vascular permeability, and stimulation of gastric acid secretion) and has also elucidated newer ones that are now under investigation. Data on the roles of histamine in angiogenesis, circadian rhythm, bone marrow regeneration, bacterial eradication, and cancer are emerging in the literature. Newer histamine antagonists are currently in drug trials and are expected to advance the clinical field in treatment of allergic, gastrointestinal, and cognitive disorders. Veterinary Data Synthesis – Veterinary histamine research is directed at identifying the effects of certain pharmacological agents on blood histamine concentrations and establishing the relevance in clinical disease states. Research demonstrates important species differences in regards to histamine receptor physiology and tissue response. Studies in the area of trauma, sepsis, anaphylaxis, allergy, and gastrointestinal disorders have direct applications to clinical veterinary medicine. Conclusions – Histamine plays a key role in the morbidity and mortality associated with allergy, asthma, gastric ulcers, anaphylaxis, sepsis, hemorrhagic shock, anesthesia, surgery, cardiovascular disease, cancer, CNS disorders, and immune‐mediated disease. Histamine antagonism has been in common use to block its adverse effects. With recent advances in the understanding of histamine receptor physiology, pharmaceutical agents targeting these receptors have increased the therapeutic options.     

Tumor necrosis factor‐α‐induced inflammatory responses in cattle

Tumor necrosis factor‐alpha (TNF‐α) is recognized as a cytokine because of its involvement in inflammation‐mediated biological defense functions. Although TNF‐α is primarily produced by macrophages, it is also produced by other cells, including lymphocytes, Kupffer cells, natural killer cells and adipocytes. While TNF‐α has diverse immune system functions, including antitumor activity, antimicrobial activity and mediation of inflammation, it also regulates a number of physiological functions, including appetite, fever, energy metabolism and endocrine activity. Factors such as viruses, parasites, other cytokines, and endotoxins induce TNF‐α production. In combination with other cytokines, TNF‐α plays a clinically important role in cattle by mediating immune inflammatory responses such as mastitis and endotoxic shock. It has been reported that cytokines such as TNF‐α are involved in metabolic disease such as acidosis. On the other hand, several data suggest that lactoferrin (LF) acts to prevent the release of a number of inflammatory mediators from various activated cells, and further suggest that the prophylactic effect of LF involves inhibition of cytokine production, including TNF‐α, that are principal mediators of the inflammatory response leading to death from toxic shock. This review discusses the role of TNF‐α in pathological conditions in cattle, including infections and metabolic diseases caused by perturbation of metabolism and endocrine functions.     

Treatment of primary immune‐mediated hemolytic anemia with mycophenolate mofetil in two cats

Objective – To describe the use of oral mycophenolate mofetil (MMF) as an adjunctive therapy in 2 cats with primary immune‐mediated hemolytic anemia. Case Series Summary – Two cats suffering from presumptive primary immune mediated hemolytic were treated with MMF as part of their treatment regimens. Both cats had improved complete blood counts following therapy. New or Unique Information Provided – This is the first reported use of oral MMF as adjunctive treatment for cats with immune‐mediated hemolytic anemia. Outcome was favorable in both cats and no adverse effects were noted from the MMF.     

Subconjunctival bone marrow‐derived mesenchymal stem cell therapy as a novel treatment alternative for equine immune‐mediated keratitis: A case series

Equine immune‐mediated keratitis (IMMK) leads to increased corneal opacity and inflammation secondary to an alteration of the local immune system. Bone marrow‐derived mesenchymal stem cells (BM‐MSC) have been shown to modulate the immune system by downregulating inflammation. Four horses with unilateral IMMK poorly responsive to traditional medical treatments underwent novel, autologous subconjunctival BM‐MSC therapy. Bone marrow was harvested and processed as previously described for equine orthopedic disease. Horses received autologous subconjunctival BM‐MSC injections approximately every 3‐4 weeks for 1‐5 treatments total. Horses were maintained on their current medical treatment regimen throughout the BM‐MSC treatment period. Three horses had a positive response to therapy as demonstrated by an increase in corneal clarity, a decrease in neovascularization and a reduction in surface irregularity. One horse was nonresponsive to therapy. These experimental results demonstrate the safety and potential efficacy of an innovative solution for IMMK.     

The effects of environmental enrichment and transport stress on the weights of lymphoid organs,cell‐mediated immune response,heterophil functions and antibody production in laying hens

The effects of environmental enrichment and transport stress on the immune system were investigated in laying hens. A total of 48 1‐day‐old chickens were used, half of the chickens were reared in conventional cages (RCC) and the rest in enriched cages (REC). Transport stress was applied in the 17th week. Liver weight decreased, spleen and bursa of Fabricius weights, white blood cell count, CD4+ and CD8+ cell proportions increased due to the transport. Environmental enrichment significantly increased antibody production and tended to increase monocyte percentage and CD8+ cell proportion. The effect of transport on, heterophil (H) and lymphocyte (L) percentages was not significant in RCC chickens. While heterophil percentage and H:L ratio increased, lymphocyte percentage decreased in REC chickens subjected to transport. Transport stress increased heterophil functions both in REC and RCC chickens, but the increase was higher in REC hens than in RCC hens. In conclusion, although environmental enrichment did not neutralize the effect of transport on lymphoid organs, it activated the non‐specific immune system, cellular and the humoral branches of the specific immune system by increasing heterophil functions, CD8+ cells and antibody production, respectively. Therefore, environmental enrichment suggested for improving animal welfare may also be beneficial to improve the immune system of birds exposed to stress.     

Interleukin‐31: its role in canine pruritus and naturally occurring canine atopic dermatitis

Background – Interleukin‐31 (IL‐31) is a member of the gp130/interleukin‐6 cytokine family that is produced by cell types such as T helper 2 lymphocytes and cutaneous lymphocyte antigen positive skin homing T cells. When overexpressed in transgenic mice, IL‐31 induces severe pruritus, alopecia and skin lesions. In humans, IL‐31 serum levels correlate with the severity of atopic dermatitis in adults and children. Hypothesis/Objective – To determine the role of IL‐31 in canine pruritus and naturally occurring canine atopic dermatitis (AD). Animals – Purpose‐bred beagle dogs were used for laboratory studies. Serum samples were obtained from laboratory animals, nondiseased client‐owned dogs and client‐owned dogs diagnosed with naturally occurring AD. Methods – Purpose‐bred beagle dogs were administered canine interleukin‐31 (cIL‐31) via several routes (intravenous, subcutaneous or intradermal), and pruritic behaviour was observed/quantified via video monitoring. Quantitative immunoassay techniques were employed to measure serum levels of cIL‐31 in dogs. Results – Injection of cIL‐31 into laboratory beagle dogs caused transient episodes of pruritic behaviour regardless of the route of administration. When evaluated over a 2 h period, dogs receiving cIL‐31 exhibited a significant increase in pruritic behaviour compared with dogs that received placebo. In addition, cIL‐31 levels were detectable in 57% of dogs with naturally occurring AD (≥13 pg/mL) but were below limits of quantification (<13 pg/mL) in normal, nondiseased laboratory or client‐owned animals. Conclusions – Canine IL‐31 induced pruritic behaviours in dogs. Canine IL‐31 was detected in the majority of dogs with naturally occurring AD, suggesting that this cytokine may play an important role in pruritic allergic skin conditions, such as atopic dermatitis, in this species.     

Taking Advantage of the Positive Side‐Effects of Smallpox Vaccination

From the introduction of smallpox vaccination approximately 200 years ago right up to its discontinuation (1980), reports by physicians and scientists about positive side‐effects such as healing of chronic skin rashes, reduced susceptibility to various infectious diseases, e.g. measles, scarlet fever and whooping cough, and even the prophylactic use of the vaccination, e.g. against syphilis, were published again and again. Comparison with the period after cessation of vaccination confirms the experiences of the above vaccinators. As early as 1956, targeted research on these observations led to evidence of the ‘ring‐zone phenomenon’, i.e. the production of soluble antiviral substances in infected chicken embryos and cell cultures. With the help of modern immunological and bioengineering methods, it was later possible to demonstrate that these effects are based on the activation of lymphoreticular cells and the regulatory effect of certain cytokines within the context of the non‐specific immune system. These findings led to the development of paramunization with paraspecific vaccines from highly attenuated animal pox viruses. During attenuation, deletions in the virus DNA occur. Attenuated animal pox strains are therefore suited for the production of vector vaccines. The fact that these vector vaccines demonstrate an especially high level of paraspecific efficacy and lack harmful effects is likewise the result of the attenuated animal pox viruses. Optimum regulation of the entire immune system leads to increased paramunity already in the first few days after vaccination and to enhanced antigen recognition and thus accelerated commencement of specific immunity.     

Evaluation of immunomodulatory effect of recombinant human granulocyte‐macrophage colony‐stimulating factor on polymorphonuclear cell from dogs with cancer in vitro

The objective of this in vitro study was to evaluate the immunomodulatory effects of recombinant human granulocyte‐macrophage colony‐stimulating factor (rhGM‐CSF) on polymorphonuclear cell (PMN) function in dogs with cancer. PMNs were harvested from dogs with naturally developing cancer as a pre‐clinical model to evaluate the immunomodulatory effects of rhGM‐CSF on PMN phagocytic and cytotoxic functions, cytokine production and receptor expression. Some aspects of cancer‐related PMN dysfunction in dogs with cancer were restored following incubation with rhGM‐CSF including PMN phagocytosis, respiratory burst and LPS‐induced TNF‐α production. In addition, rhGM‐CSF increased surface HLA‐DR expression on the PMNs of dogs with cancer. These data suggests that dysfunction of innate immune response in dogs with cancer may be improved by rhGM‐CSF. The results of this study provided a pathophysiologic rationale for the initiation of clinical trials to continue evaluating rhGM‐CSF as an immunomodulatory therapy in dogs with cancer.     

The use of intravenous lipid emulsion as an antidote in veterinary toxicology

Objective – To review the use of IV lipid emulsion (ILE) for the treatment of toxicities related to fat‐soluble agents; evaluate current human and veterinary literature; and to provide proposed guidelines for the use of this emerging therapy in veterinary medicine and toxicology. Data Sources – Human and veterinary medical literature. Human Data Synthesis – Human data are composed mostly of case reports describing the response to treatment with ILE as variant from mild improvement to complete resolution of clinical signs, which is suspected to be due to the variability of lipid solubility of the drugs. The use of ILE therapy has been advocated as an antidote in cases of local anesthetic and other lipophilic drug toxicoses, particularly in the face of cardiopulmonary arrest and unsuccessful cardiopulmonary cerebral resuscitation. Veterinary Data Synthesis – The use of ILE therapy in veterinary medicine has recently been advocated by animal poison control centers for toxicoses associated with fat‐soluble agents, but there are only few clinical reports documenting successful use of this therapy. Evidence for the use of ILE in both human and veterinary medicine is composed primarily from experimental animal data. Conclusions – The use of ILE appears to be a safe therapy for the poisoned animal patient, but is warranted only with certain toxicoses. Adverse events associated with ILE in veterinary medicine are rare and anecdotal. Standard resuscitation protocols should be exhausted before considering this therapy and the potential side effects should be evaluated before administration of ILE as a potential antidote in cases of lipophilic drug toxicoses. Further research is waranted.     

Can farm animals help to study endocrine disruption?

The phenomenon of endocrine disruption can be regarded as part of the disciplines of toxicology and environmental toxicology. These two disciplines have generated guideline protocols on how various effects of chemicals should be tested as a basis for regulatory decisions. These protocols almost exclusively involve laboratory rodents and the data obtained are then used for human risk assessment. Would it be justifiable, then, to introduce or promote the use of other species in these test protocols? There are, at any rate rationales for studying effects in species other than laboratory rodents: (1) other species may better mimic the human system; (2) they may in some cases be more useful for studying a certain mechanism or phenomenon; (3) they may highlight the diversity of effects or sensitivity between species. However, there are at least two basic criteria that must be met for a species before it can be introduced in this context: (a) we must have a good understanding of the physiological system to be studied; and (b) we must have a number of tools to study effects on this system. When it comes to the reproductive system – regarding which most endocrine disruption has been reported – farm animals are second only, or in some respects superior, to laboratory rodents with respect to these criteria. This review gives examples of how farm animals can be of use in the study of endocrine disruption with a focus on the author's own data from studies in the pig.