Joyful by nature: approaches to investigate the evolution and function of joy in non-human animals

The nature and evolution of positive emotion is a major question remaining unanswered in science and philosophy. The study of feelings and emotions in humans and animals is dominated by discussion of affective states that have negative valence. Given the clinical and social significance of negative affect, such as depression, it is unsurprising that these emotions have received more attention from scientists. Compared to negative emotions, such as fear that leads to fleeing or avoidance, positive emotions are less likely to result in specific, identifiable, behaviours being expressed by an animal. This makes it particularly challenging to quantify and study positive affect. However, bursts of intense positive emotion (joy) are more likely to be accompanied by externally visible markers, like vocalisations or movement patterns, which make it more amenable to scientific study and more resilient to concerns about anthropomorphism. We define joy as intense, brief, and event-driven (i.e. a response to something), which permits investigation into how animals react to a variety of situations that would provoke joy in humans. This means that behavioural correlates of joy are measurable, either through newly discovered ‘laughter’ vocalisations, increases in play behaviour, or reactions to cognitive bias tests that can be used across species. There are a range of potential situations that cause joy in humans that have not been studied in other animals, such as whether animals feel joy on sunny days, when they accomplish a difficult feat, or when they are reunited with a familiar companion after a prolonged absence. Observations of species-specific calls and play behaviour can be combined with biometric markers and reactions to ambiguous stimuli in order to enable comparisons of affect between phylogenetically distant taxonomic groups. Identifying positive affect is also important for animal welfare because knowledge of positive emotional states would allow us to monitor animal well-being better. Additionally, measuring if phylogenetically and ecologically distant animals play more, laugh more, or act more optimistically after certain kinds of experiences will also provide insight into the mechanisms underlying the evolution of joy and other positive emotions, and potentially even into the evolution of consciousness.     

Biosynthesis and function of membrane bound and secreted forms of recombinant CD11b/CD18 (Mac-1)

Full-length (membrane bound) and truncated (secreted) forms of the beta 2 integrin heterodimer, CD11b/CD18 (Mac-1), were expressed in a human kidney cell line (293) that normally does not express leukocyte adhesion molecules (Leu-CAMs). The biosynthesis of recombinant Mac-1 in 293 cells differed from that reported for leukocytes in that heterodimer formation was not required for CD11b to be exported to the cell surface. A stable cell line was constructed that constitutively secreted the recombinant, truncated Mac-1 heterodimer into growth conditioned cell culture medium. A novel monoclonal antibody that enabled an immunoaffinity method for the selective purification of recombinant Mac-1 heterodimers was identified. Sufficient protein was purified to allow the first measurement of the 50% inhibitory concentration (IC₅₀) for CD11b/CD18 and for the direct comparison of the inhibitory activity of recombinant soluble Mac-1 with that of various CD18 and CD11b specific monoclonal antibodies. Purified recombinant soluble Mac-1 inhibited the binding of neutrophils, activated by opsonized zymosan or fMet-Leu-Phe peptide, to human umbilical vein endothelial cells. Similarly, the recombinant integrin was effective in inhibiting the binding of unactivated neutrophils to tumor necrosis factor (TNF-alpha) activated endothelial cells. The availability of an abundant source of purified, biologically active Mac-1 will enable direct physical and chemical investigations into the relationship between the structure and function of this leukocyte adhesion molecule.     

Mechanisms of cellular resistance to hydrogen peroxide, hyperoxia, and 4-hydroxy-2-nonenal toxicity: the significance of increased catalase activity in H2O2-resistant fibroblasts.

An H2O2-resistant variant (OC14) of the HA1 Chinese hamster fibroblast cell line which demonstrates a 20-fold increase in catalase activity was utilized in the study of mechanisms responsible for cellular resistance to hydrogen peroxide, oxygen, and 4-hydroxy-2-nonenal toxicity. HA1 and OC14 cells were treated with 9 mM aminotriazole which resulted in a 60 to 80% reduction in catalase activity. Pretreatment with aminotriazole resulted in significant sensitization to the toxicity of 1-h exposures to exogenously applied H2O2, which was proportional to the reduction in catalase activity. Treatment with aminotriazole produced significant sensitization to the toxicity of 95% O2 after 45 h of O2 exposure but no sensitization to the toxicity of a 1-h exposure to 50 microM 4-hydroxy-2-nonenal. Inhibition of catalase activity by aminotriazole had no effect on the metabolism of 4-hydroxy-2-nonenal by either cell line tested. These results support the conclusion that in H2O2-resistant cells, catalase activity is a major determinant of cellular resistance to H2O2 toxicity, whereas catalase activity has a limited role in cellular resistance to an acute exposure to 95% O2 and is unrelated to cellular resistance to 4-hydroxy-2-nonenal.     

Enhanced stability in vivo of a thermodynamically stable mutant form of yeast iso-1-cytochrome c

Previous work has established that the N57I amino acid replacement in iso-1-cytochrome c from the yeast Saccharomyces cerevisiae causes an unprecedented increase in thermodynamic stability of the protein in vitro, whereas the N57G replacement diminishes stability. Spectrophotometric measurements of intact cells revealed that the N57I iso-l-cytochrome c is present at higher than normal levels in vivo. Although iso-1-cytochrome c turnover is negligible during aerobic growth, transfer of fully derepressed, aerobically grown cells to anaerobic growth conditions leads to reduction in the levels of all of the cytochromes. Pulsechase experiments carried out under these anaerobic conditions demonstrated that the N57I iso-l-cytochrome c has a longer half-life than the normal protein. This is the first report of enhanced stability in vivo of a mutant form of a protein that has an enhanced thermodynamic stability in vitro. Although the N57I protein concentration is higher than the normal level, reduced growth in lactate medium indicated that the specific activity of this iso-l-cytochrome c in vivo is diminished relative to wild-type. On the other hand, the level of the thermodynamically labile N57G iso-1-cytochrome c was below normal. The in vivo levels of the N57I and N57G iso-l-cytochrome c suggest that proteins in the mitochondrial intermembrane space can be subjected to degradation, and that this degradation may play a role in controlling their normal levels.     

Cortical control of reaching movements

Recent studies provide further support for the hypothesis that spatial representations of limb position, target locations, and potential motor actions are expressed in the neuronal activity in parietal cortex. In contrast, precentral cortical activity more strongly expresses processes involved in the selection and execution of motor actions. As a general conceptual framework, these processes may be interpreted in terms of such formalisms as sensorimotor transformation and ‘internal models’.     

Are Elevated Aminotransferases and Decreased Bilirubin Additional Characteristics of the Metabolic Syndrome?

Abnormal liver tests, as well as morphological changes in the liver, are frequent among obese patients. Other frequent disturbances are visceral fat accumulation, insulin resistance, non-insulin-dependent diabetes mellitus (NIDDM), hypertriglyceridemia, and hypertension; these are a set of aberrations known as the metabolic syndrome. In order to investigate a possible relationship between the metabolic syndrome and impaired liver status we examined associations between liver tests, metabolic variables (insulin, glucose, and triglycerids), body composition and nutrition in 1083 men (BMI 28.8–63.8 kg/m²) and 1367 women (BMI 26.7–68.0 kg/m²) in the ongoing intervention study of Swedish Obese Subjects (SOS). Standard biochemical techniques were used to assess liver status and metabolic variables. Lean body mass (LBM) and masses of visceral and subcutaneous adipose tissue (AT) were estimated by means of computed tomography (CT) calibrated anthropometric equations. In both genders aspartate aminotransferase and alanine aminotransferase were, or tended to be, positively correlated to fasting serum insulin, visceral AT (women), and alcohol intake. In women, the aminotransferases were also correlated with fasting blood glucose. In both genders alkaline phosphatase was, or tended to be, positively associated with visceral AT, insulin (women), and glucose. Bilirubin was negatively correlated to insulin and visceral AT in men and women. Additional multivariate analyses indicated that alcohol had less explanatory power than serum insulin for the examined liver tests, especially among women. These results suggest that pathological liver tests in the obese may represent an expression of the metabolic syndrome.