L-glutamate (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system. Monitoring extracellular Glu is critical to understanding Glu regulation to discriminate physiological and pathological roles. To overcome the limitations of previous in vivo extracellular Glu studies, we developed Glu selective microelectrode arrays with better spatial and temporal resolutions than commonly used techniques like microdialysis. We used these microelectrode arrays to characterize basal and potassium-evoked Glu neurotransmission in the normal rat brain. We then investigated disease-related Glu alterations in a rat model of Parkinson's disease and normal Glu regulation in young and aged rhesus monkeys. In the normal anesthetized rat striatum and frontal cortex, basal Glu was regulated by active release and uptake mechanisms, fully TTX-dependent, and measured at ~2 micromolar levels. Potassium-evoked Glu kinetics were fast, concentration-dependent, and rapidly reproducible at 15-20 seconds intervals. In the unilateral 6-hydroxydopamine-lesioned rat, there were significant bilateral increases in potassium-evoked Glu release in the striatum and frontal cortex compared to hemisphere-matched non-lesioned rats. Ipsilateral striatal effects may have been related to DA loss, while contralateral striatal effects and the bilateral frontal corticaleffects may have resulted from parkinsonian neurotransmitter changes or bilateral neuranatomical connectivity, especially in the cortex. There were also alterations in Glu kinetics in the nucleus accumbens in both non-lesioned and lesioned rats. With appropriate technological and methodological modifications, we successfully recorded normal Glu signaling in anesthetized nonhuman primates in the operating room. Fast potassium-evoked Glu signals were recorded in the motor cortex of all monkeys, and Glu ejections showed robust Glu uptake in the motor and frontal cortices of all monkeys. These findings are comparable to initial rat studies. Slow evoked Glu kinetics and high basal Glu levels with oscillatory behavior were recorded in the frontal cortex. The primary age-related differences between monkeys were the nearly ten-fold increases in the volumes of Glu ejected needed in the aged monkey to achieve amplitude-matched signals in the motor and frontal cortices and a decreased uptake rate in the motor cortex. Preliminary work with excised human tissue and future plans for patient-oriented research and clinical applications are discussed.

Pituitary adenylate cyclase activating polypeptide (PACAP) is associated with Alzheimer's disease (AD), but its age-related effects are unknown. We chose the rhesus macaque due to its closeness to human anatomy and physiology. We examined four variables: aging, cognitive performance, amyloid plaques and PACAP. Delayed nonmatching-to-sample recognition memory scores declined with age and correlated with PACAP levels in the striatum, parietal and temporal lobes. Because amyloid plaques were the only AD pathology in the old rhesus macaque, we further studied human amyloid precursor protein (hAPP) transgenic mice. Aging was associated with decreased performance in the Morris Water Maze (MWM). In wild type (WT) C57BL/ 6 mice, the performance was decreased at age 24-26 month whereas in hAPP transgenic mice, it was decreased as early as 9-12 month. Neuritic plaques in adult hAPP mice clustered in hippocampus and adjacent cortical regions, but did not propagate further into the frontal cortex. Cerebral PACAP protein levels were reduced in hAPP mice compared to age-matched WT mice, but the genetic predisposition dominated cognitive decline. Taken together, these data suggest an association among PACAP levels, aging, cognitive function and amyloid load in nonhuman primates, with both similarities and differences from human AD brains. Our results suggest caution in choosing animal models and in extrapolating data to human AD studies.

archives@tulane.edu / Immune signatures are patterns of gene and protein expression in immune cells that characterize states of activation and response. As such, signatures indicative of viral control during natural infection may guide vaccine development efforts to achieve similar patterns of protection. Here, we used nonhuman primate (NHP) models of Zika virus (ZIKV) and simian immunodeficiency virus (SIV, as a model for HIV) to explore outcomes of infection in these important human pathogens. We employed a multifaceted approach including high dimensional flow cytometry and RNA sequencing to understand cellular responses to ZIKV generally and during pregnancy, as well as to identify the impacts of infection in astrocytes, a neuroglial target of ZIKV thought to be important in the development of neurologic disease. We found that CD8 T cells may restrict ZIKV persistence in tissues but ultimately have a minimal role in protection to either primary or secondary challenge. However, we showed that immune manipulation, either naturally through pregnancy or artificially through depletion experiments, can skew metabolic and innate immune pathways in unexpected ways. While cellular immunity appeared to minimally impact ZIKV infection, such responses in SIV are important in controlling viral replication, which we inversely showed by tracking patterns of viral mutation to evade CD8 responses. We also identified transcriptional signatures in ZIKV infection that may underlie the development of neurologic diseases and found that different virus lineages have unique impacts on gene expression. Together, these experiments showcase the utility of profiling approaches in understanding the immune complexity that accompanies viral infection. / 1 / Blake Schouest

Twenty-one 8-14 kg adult male stumptailed macaques, Macaca arctoides, were fed a standard laboratory diet and divided into 3 groups. The high-dose group and low-dose group were exposed to cigarette smoke at the human equivalent of 3 packs and 1 pack per day, respectively, 7 days per week, for 3-5 years. Eight animals served as cage and sham controls. Peak blood carboxyhemoglobin (COHb) levels measured immediately after smoking showed levels of 0.5 ± 0.1%, 3.6 ± 1.0%, and 5.7 ± 2.8% for. sham controls, low, and high dose smokers, respectively. Hemoglobin and hematocrit values were 2-7% higher (N.S. to P < 0.05) for smoking groups, presumably as a consequence of chronically elevated COHb levels. No significant differences were seen in total plasma cholesterol and lipoprotein cholesterol concentration measured at four intervals over a period of one year. We conclude from these data that, while fed a low fat diet, chronic cigarette smoke inhalation fails to alter plasma lipoprotein levels in this animal model.

Over the past few decades, the dominant view by comparative psychologists of analogical reasoning in nonhuman primates was one of dichotomy between apes, including humans, and monkeys: the distinction between the analogical ape and paleological monkey (Thompson & Oden, 2000). Whereas evidence for analogy proper by representation reinterpretation in monkeys is sparse and debated, the gap between that which is analogic and paleologic has been narrowed by the studies presented here. Representation of relational concepts important for analogy proves difficult for rhesus and capuchin monkeys without the ability to rely on a greater amount of perceptual variability, implicating a perceptually-bound predisposition in problem-solving (Chapters 2-3). A shift in attention from perceptual features to abstract concepts for employment in relational matching is again difficult, but not impossible given cognitive incentive in the form of differential outcomes to refocus attention on conceptual properties (Chapter 4). Finally, chimpanzees unlike monkeys appear more apt to reason by analogy, perhaps due to a more default conceptual focus (Chapter 5). Taken together, these studies provide an account for the emergence of analogical reasoning skills throughout the primate lineage in contrast to views regarding analogy a hallmark of human intelligence.

Humans have a tendency to engage in economically irrational behaviors such as gambling, which typically leads to long-term financial losses. While there has been much research on human gambling behavior, relatively little work has been done to explore the evolutionary origins of this behavior. To examine the adaptive pressures that may have led to this seemingly irrational behavior in humans, nonhuman primates were tested to explore their reactions to gambling type scenarios. Several experiments based on traditional human economic experiments were adapted for use with a wider variety of primate species including chimpanzees and capuchin monkeys. This allowed for testing multiple species using similar methodologies in order to make more accurate comparisons of species abilities. This series of tasks helps to elucidate risky decision-making behavior in three primate species.

Three experiments were conducted to evaluate the relation between age, relative numerousness judgments, and summation in Western lowland gorillas. The findings indicated that most of the gorillas did not perform relative numerousness judgments until after specific training to do so. However, the gorillas did perform summation without specific training and an age-related difference was apparent.

The ability to recognize sameness among objects and events is a prerequisite for abstraction and forming concepts about what one has learned; thus, identity and nonidentity learning can be considered the backbone of higher-order human cognitive abilities. Discovering identity relations between the constituent properties of objects is an important ability that often characterizes the comparisons that humans make so it is important to devote attention to understanding how nonhuman primates process and conceptualize part-identity as well as whole-identity. Because the ability to generalize the results of learning is to what concepts ultimately reduce, the series of experiments herein first investigated responding to part-identity and -nonidentity and whole-identity and -nonidentity and then explored the generality of such learning to the formation of concepts about color, shape, and cardinal number. The data from Experiments 1, 2, and 3 indicated that the two orangutans learned to respond concurrently to color whole-identity and -nonidentity and they responded faster to color whole-identity. Additionally, both subjects learned to respond concurrently to color and shape part- and whole-identity and for the most part, it was easier for them to do so with color part- and whole-identity problems than shape part- and whole-identity problems. Further, their learned responses to color and shape part- and whole-identity fully transferred to novel color part-identity problems for both subjects and fully transferred to novel color and shape whole-identity problems for one orangutan. The data from Experiments 4, 5, and 6 showed that one subject learned to judge numerical identity when both irrelevant dimensions were cue-constant, but the subject did not do the same when one or more irrelevant dimensions were cue-ambiguous. Further, the subject's accuracy was affected by the numerical distance and the numerical total of comparisons during acquisition of the conditional discrimination. The subject subsequently formed a domain-specific concept about numerical identity as evinced by the transfer of learning to novel numerosities instantiated with novel, cue-constant element colors and shapes and novel numerosities instantiated with cue-constant, familiar element colors and shapes. Given the adaptive significance of using concepts, it is important to investigate if and how nonhuman primates form identity concepts for which they categorize or classify the stimuli around them. This dissertation provided evidence about the extent to which orangutans learned to respond to color, shape, and number identity and nonidentity and subsequent concept formation from such learning. The findings from this study will help in understanding the convergence and divergence in the expression abstraction in the primate phylogeny, thus, informing our understanding about the origins and mechanisms of cognition in human and nonhuman primates.

The acquisition of relational concepts plays an integral role and is assumed to be a prerequisite for analogical reasoning. Language and token-trained apes (e.g. Premack, 1976; Thompson, Oden, and Boysen, 1997) are the only nonhuman animals to succeed in solving and completing analogies, thus implicating language as the mechanism enabling the phenomenon. In the present study, I examine the role of meaning in the analogical reasoning abilities of three different primate species. Humans, chimpanzees, and rhesus monkeys completed relational match-to-sample (RMTS) tasks with either meaningful or nonmeaningful stimuli. For human participants, meaningfulness facilitated the acquisition of analogical rules. Individual differences were evident amongst the chimpanzees suggesting that meaning can either enable or hinder their ability to complete analogies. Rhesus monkeys did not succeed in either condition, suggesting that their ability to reason analogically, if present at all, may be dependent upon a dimension other than the representational value of stimuli.

This research investigated a number of issues regarding hepatitis B virus (HBV) in the silvery gibbon (Hylobates moloch). Due to the relatively recent discovery of the virus in nonhuman primate populations, specific knowledge of the biological behaviour of the virus is presently lacking, with current information largely extrapolated from the behaviour of HBV in human infections. In order to manage the captive and wild populations of this critically endangered species, information regarding the behaviour of the virus in gibbons and the likely impact of the viral infection is essential. The research was performed at Perth Zoo, with the study population consisting of the current and historical members of the zoo’s silvery gibbon colony. Because this gibbon species is critically endangered, the study was conducted with minimal intervention to the population with samples collected largely on an opportunistic basis from a small study population. Review of the history of the virus within the Perth Zoo colony provided epidemiological evidence to indicate vertical transmission in three gibbons (Hecla, Uban and Jury). It would appear that vertical transmission is the primary mode of transmission leading to dispersal of the virus through the captive population of silvery gibbons. Elevated concentrations of the liver enzymes alanine aminotransferase and aspartate aminotransferase were found in three gibbons (Perth 2, Uban and Jury), and may suggest a pathogenic role of the virus in this species. Histological examination of the livers of Uban and Perth 2 failed to demonstrate definitive evidence of cirrhosis, however mild fibrosis was seen in both cases and may represent an early stage of liver pathology associated with chronic hepatitis B infection. The vaccination protocol developed at Perth Zoo was successful in preventing neonatal transmission of the virus from a high infectivity carrier mother in at least two individuals, and was also successful in producing a protective level of immunity against the virus in all three of the individuals tested. Sequencing of the complete hepatitis B genome from one gibbon (Hecla) revealed that she was infected with GiHV (Gibbon hepatitis B virus), an indigenous strain of HBV previously identified in a number of gibbon species, but not previously confirmed in the silvery gibbon. Hecla's strain of HBV was shown to be more closely related to other nonhuman primate strains of HBV than to any of the human strains of HBV. 100% nucleotide similarity to two of Hecla’s siblings indicates that infection in all three animals was the result of vertical transmission from their mother. Partial sequencing of the virus from a second gibbon (Uban) identified another strain of GiHBV which supports the results of the epidemiological study. Neither gibbon showed a high sequence similarity to the virus sequenced from Ivan, the father of the third carrier gibbon (Jury), although only limited sequence data was available from Ivan. Consequently it is likely that at least three different strains of GiHBV are present within the silvery gibbon population. The information contained in this thesis will assist in the understanding and management of hepatitis B infection in silvery gibbons, as well as the numerous other species of nonhuman primates now shown to be susceptible to this virus.