SEARCH · PubMed Health

Results for “Primates”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources

PubMed1993

Non-human primates used in studies of periodontal disease pathogenesis: a review of the literature.

The inability to examine initiation and progression of periodontal disease and to assess certain therapies in humans has led to a great interest in the use of animal models in periodontal research. Some of the most prominent animals used are non-human primates. This article reviews the characteristics of non-human primate models in periodontal health, in the transition from health to gingivitis to periodontitis, and in experimental gingivitis and periodontitis. Where possible, the results of these studies are compared with results from human studies. Only a few studies have compared in detail the anatomy, physiology, immunology, and tissue interactions in monkeys with those of humans. With the exceptions of differences and variations in size of the dentition, the number of each tooth type as well as larger canines, presence of diastemata between anterior teeth, and an edge-to-edge relationship of the incisors, the dental and periodontal anatomy of non-human primates seem quite similar to that of humans. Clinically healthy gingiva can be established and maintained in non-human primates, and gingivitis as well as periodontitis occur in these animals. It is possible to induce experimental periodontitis by placement of peri-dental silk ligatures or orthodontic elastics as well as by surgical removal of alveolar bone. Although the most appropriate model for studies of periodontal disease pathogenesis in non-human primates appears to involve the application of silk ligatures, some difficulties may occur in establishing periodontal break-down by using this model. Many clinical, histological, microbiological, and immunological characteristics of spontaneous and experimental marginal inflammation in most non-human primates are similar to those in humans. The most significant differences between small non-human primates and humans are the very limited number of lymphocytes and plasma cells in the inflammatory infiltrate of squirrel monkeys (Saimiri sciureus) and marmosets. Therefore, the use of squirrel monkeys and marmosets may not be appropriate in many studies of periodontal disease pathogenesis. The most significant microbial differences between macaque species and humans are a lower proportion of Actinomyces species, the presence of a catalase-producing Prevotella melaninogenica strain, and the high carrier rate for Actinobacillus actinomycetemcomitans in subgingival plaque of macaque species. The significance of these differences is presently unknown. It is concluded that the use of many non-human primate species due to the apparent close anatomic and biologic similarities to humans is appropriate in experimental studies of periodontal disease, provided the use of laboratory animals is requisite and lower species are not applicable.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2000

[Ecology and social organization of African tropical forest primates: aid in understanding retrovirus transmission].

The risk of transmission of primate viruses to humans is great because of their genetic proximity. It is now clear that the HIV group of retroviruses came from primates and that the origin of HIV1 is the chimpanzee subspecies of Central Africa, Pan troglodytes troglodytes. Many African primates are natural hosts of retroviruses and details of the natural history of both hosts and viruses are essential to understand the evolution of the latter. Data on the demography, ecology and behaviour of three species of primates (gorillas, chimpanzees and mandrills), studied in the Lopé Reserve in Central Gabon since 1983, are analysed to identify the factors that allow, or favour, disease transmission within each species, between different species and between primates and humans. The comparison of the relative degree of risk suggests that of the three species, chimpanzees are the most susceptible to exposure to infection both from conspecifics and from other species. With respect to humans, the comparative analysis suggests greater exposure to viruses of mandrills and gorillas than to those of chimpanzees. For primates, major risk factors are: large social groups; bites inflicted in fights; social grooming; and predation on mammals. However, given that contacts between social groups of the same species are rare, the spread of a virus through a population will be slow and uncertain. Hunting wild animals is the behaviour most likely to provide transmission routes for primate viruses into human populations because of the high probability of blood-blood contact. Not only the hunters themselves, but also women who prepare bush meat for cooking and people involved in trade of carcasses are at high risk of transmission of pathogens. Hunting of bush meat is increasing in Central Africa due to the economic recession and the spread of logging into the forests of the interior of the region. To counter the significant risk of transmission of known, as well as new, diseases from primates to humans, urgent measures are needed to attack the root causes of commercial hunting which is not only risk to public health but also a serious threat to biodiversity in the region.

Animals↗

PubMed1995

Comparative sequence analysis of cytokine genes from human and nonhuman primates.

Two major issues severely limit the studies of human recombinant cytokines/growth factors in nonhuman primates. First, assays and reagents specific for the detection and quantitation of human cytokines do not all function when utilized to detect/quantitate the nonhuman primate cytokines. Second, although most of the human cytokines appear to induce similar, if not identical, biologic function when used with cells from nonhuman primates in vitro or in vivo, they invariably induce Ab responses in vivo, precluding their repeated and/or continued use in vivo. Our laboratory has thus initiated studies to clone, sequence, and prepare recombinant cytokines from nonhuman primates and to define assays and reagents for their detection and quantitation at the nucleic acid and protein level. The data that were derived from such studies show that the nonhuman primate cytokines IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12 alpha, IL-12 beta, IL-15, IFN-alpha, IFN-gamma, and TNF-alpha share 93 to 99% homology at the nucleic acid and protein level with the human equivalents. The most prominent differences between human and nonhuman primate cytokine sequences were noted for IL-1 alpha/beta, IL-2, IL-8, IFN-alpha, IFN-gamma, and IL-12 beta. The aligned sequences of cytokines for human and several nonhuman primate species are provided herein, and a phylogenetic analysis of the published sequences of select cytokines from other species, along with those of the nonhuman primates, are described. In addition, comparative analysis of the relative bioactivity of our immunoaffinity-purified recombinant rhesus macaque IL-4, IL-15, and IFN-gamma with commercially available human recombinant cytokines is described herein.

Amino Acid Sequence↗

PubMed1978

The neuroanatomical organization of pathways between the dorsal lateral geniculate nucleus and visual cortex in Old World and New World primates.

Pathways between the dorsal lateral geniculate nucleus (dLGN) and visual cortex in Old World (Macaca, Papio, Erythrocebus, Cercopithecus) and New World (Saimiri, Cebus) primates were studied after injections of horseradish peroxidase and H3 or S35 amino acids into the dLGN or visual cortex. Trans-synaptic autoradiography was also used to study these pathways after an injection of H3 proline-fucose into one eye. The subsequent autoradiographs of visual cortex showed that Old World primates have separate eye inputs (ocular dominance columns) in the striate cortex, whereas New World monkeys have overlapping or non-separated eye inputs. In both primate groups the geniculocortical input to layer IVA formed a pattern which resembled a honeycomb in tangential sections, unlike the solidly labeled layer IVC. Also common to the two primate groups was a projection from dLGN to layer VI. There was no dLGN projection to any prestriate area in any of the primates. However, after an injection limited to the prestriate cortex of Macaca, light autoradiographic labeling was seen in the interlaminar zones and the magnocellular and S laminae, demonstrating a prestriate-dLGN pathway. Our results indicate that the primate visual system differs significantly from the cat in having no dLGN projection to area 18. There are also signficant differences between primates in the level at which the possibility of binocularity (of an excitatory nature) first occurs in the striate cortex because in the species studied thus far with neuroanatomical methods, Old World primates have ocular dominance columns in layer IV but most New World monkeys lack them.

Animals↗

PubMed1981

The topography of primate retina: a study of the human, bushbaby, and new- and old-world monkeys.

The distribution of ganglion cells has been studied in the retinas of four primates: the prosimian bushbaby, the New-World squirrel monkey, the Old-World crab-eating cynamolgous monkey, and the human. The sizes of ganglion cell somas were also measured at a number of retinal locations and compared with similar measurements in the cat retina to test for the presence in primates of retinal specializations such as the visual streak, and for gradients in retinal structure, such as that between temporal and nasal retina. In all four primates, ganglion cell somas in peripheral retina ranged considerably in diameter (6-16 micrometer in the bushbaby, 8-22 micrometer in the squirrel monkey, 8-23 micrometer in the cynamolgous monkey, 8-26 micrometer in the human). It seems likely that the strong physiological correlates of soma size which have been described among cat retinal ganglion cells and among the relay cells of the macaque lateral geniculate nucleus are generally present in primates. In all four primates, evidence was also obtained of a visual streak specialization; the isodensity lines in ganglion cell density maps were horizontally elongated, and small-bodied ganglion cells were relatively more common in the region of the proposed streak than in other areas of peripheral retina. However, the visual streak seems less well developed than in the cat; among the four primate species examined it was best developed in the bushbaby, at least as assessed by the shape of the isodensity lines. All four primates showed a clear foveal specialization, but this feature seemed least developed in the bushbaby. At the fovea, ganglion cells are smaller in soma size than in peripheral retina; they also seemed more uniform in size, although some distinctly larger cells persist in the human and bushbaby. Soma size measurements also provided evidence of a difference between nasal and temporal areas of peripheral retina comparable to that reported for the cat and other species. Thus the primate retinas examined show features, such as the foveal specialization, which seem unique to them among mammals. They also show features, such as nasal-temporal differences in ganglion cell size, and (though weakly developed) a visual streak, which they have in common with other mammals with widely different phylogenetic histories.

Animals↗

PubMed1996

Theories of visual cortex organization in primates: areas of the third level.

This brief review has a few main points. (1) Early proposals on how extrastriate cortex is subdivided were inconsistent with each other, and differences in interpretation were not resolved. (2) Brodmann's proposal of two ring-like areas, 18 and 19, surrounding primary visual cortex gained great acceptance despite the lack of agreement among different investigators considering the same evidence. (3) The concepts of areas 18 and 19, transposed to signify V2 and V3, have had great impact on recent and even current theories of extrastriate visual cortex organization in primates. (4) Nevertheless, Brodmann's areas 18 and 19, as defined in humans and Old World monkeys, correspond to none of the fields currently proposed for these primates. (5) All or most mammals appear to have a V2, and there is now widespread complete agreement over the extent and organization of this area in all studied primates. V2 is commonly referred to as area 18 because of its correspondence to area 18 as defined by Brodmann is some mammals. Yet, we should recognize that V2 is about half the size of Brodmann's area 18 in Old World monkeys and humans. (6) Current concepts of V3 differ greatly from the ring-like area 19 of Brodmann. We question the validity and usefulness of retaining the concept of V3 in primates. Our proposal for DM and other visual areas along the outer border of V2 seems more consistent, not only with the evidence from New World monkeys, but with evidence from Old World and prosimian primates, and even mammals most closely related to primates (see Kaas and Preuss, 1993). In all of these primates and close relatives of primates, the evidence indicates that more than one field forms the outer border of V2.

Animals↗

PubMed1997

Determinants of primate social organization: comparative evidence and new insights from Malagasy lemurs.

The aim of this review is to summarize newly available information on lemur social systems, to contrast it with the social organization of other primates and to relate it to existing models of primate social evolution. Because of their evolutionary history, the primates of Madagascar constitute a natural experiment in social evolution. During millions of years of isolation, they converged with other primates only in the most fundamental way in the evolution of solitary, pair-living and group-living species, but deviate in several respects within these basic categories of social organization. Solitary lemurs remain poorly studied, but their social organization appears to be broadly similar to that of other solitary primates, even though the unexpected lack of sexual dimorphism may indicate that similar types of social organization can give rise to different mating systems. The determinants of a solitary lifestyle remain elusive. Pair-living lemurs show striking convergences with other monogamous primates in several behavioural traits, but also deviate in that the majority of species are at least partly nocturnal and do not exhibit direct paternal care of dependent young. Group-living lemurs have not evolved single-male groups, male-bonded and multi-level societies, and polyandrous groups may also be lacking. Female philopatry is common, but female bonds are generally weakly developed and eviction of females from natal groups is not unusual. Group-living lemurs also differ from anthropoids in that their groups have even adult sex ratios, smaller average size and may split up on a seasonal basis. Feeding competition, predation risk and reproductive competition can not fully explain these unusual aspects of lemur social organization. It has therefore been suggested that the social consequences of the risk of infanticide and of recent changes in activity may be ultimately responsible for these idiosyncracies of group-living lemurs, an explanation largely supported by the available evidence. Thus, social factors and fundamental life-history traits, in addition to ecological factors, contribute importantly to variation in social systems among lemurs, and possibly other primates. However, neither the diversity of lemur social systems, nor the evolutionary forces and mechanisms operating in these and other primates are yet fully understood.

Animals↗

PubMed1994

Comparison of canine and non-human primate animal models for periodontal regenerative therapy: results following a single administration of PDGF/IGF-I.

Two commonly used animal models for evaluating putative periodontal regenerative therapies are the beagle dog model with natural periodontal disease and the non-human primate with ligature-induced attachment loss. The host response, microbiology, and skeletal rates of remodeling of these two models are summarized. In addition, the results of experiments comparing the healing response to periodontal surgery with and without concurrent use of the combination of platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) in these models are presented. At 1 month, PDGF/IGF-I administration resulted in a 64.1% and 51.4% increase in new attachment formation in the non-human primate and canine, respectively, while controls (surgery plus placebo) demonstrated 34.1% and 8.6% increases in new attachment formation in the non-human primate and canine models, respectively. Further, application of PDGF/IGF-I stimulated 21.6% and 65% osseous defect fill in the non-human primate and canine, respectively, while controls demonstrated 8.5% and 14.5% osseous defect fill in the non-human primate and canine, respectively. The osseous response in the canine appears greater than that of the non-human primate, and the new attachment formation was more substantial in the non-human primate than the canine. However, in general these data demonstrate a high degree of consistency in the effects of PDGF/IGF-I in promoting periodontal regeneration. Positive results in these two models--the dog with natural periodontal disease and the non-human primate with ligature-induced attachment loss--justify human clinical trial testing of a putative regenerative therapy.

Alveolar Bone Loss↗

PubMed1983

Selective myocardial cell necrosis in nonhuman primates.

A retrospective study was performed to describe the histologic stages of selective myocardial cell necrosis (SMCN) in nonhuman primates, and to compare the incidence of SMCN in two groups of nonhuman primates. Myocardial tissues taken at the time of autopsy from 50 primates at an experimental center were compared with similar tissues from 50 primates housed in a breeding colony. SMCN was confirmed in 20% of the experimental primates and 30% of the breeding primates, proportions that were not significantly different. The incidence and histologic characteristics of SMCN in nonhuman primates were similar to those described in humans, and resembled the lesion produced in experimental primates by administration of catecholamines of by hypokalemia.

Animals↗

PubMed2000

Habitat alteration and the conservation of African primates: case study of Kibale National Park, Uganda.

Tropical forests and the animals they support are being threatened by accelerating rates of forest conversion and degradation. In a continually fluctuating sociopolitical world, it is often impossible to protect areas from such conversion until the political environment is suitable to pursue conservation goals, by which time, the forests have often been converted to other uses. This reality suggests a need for inquiry into which primate species can persist after different types of disturbances and how quickly primate communities can recover from disturbance. Here we examine the persistence of primate populations in disturbed habitats by providing a case study of patterns of primate abundance in areas of Kibale National Park (766 km2), Uganda, that have been modified by different types and intensities of human activities, primarily commercial logging and agricultural clearing. Distributional surveys at 24 sites and detailed line-transect censuses at six sites demonstrate that primate populations in Kibale are often high and suggest that patterns of population change associated with disturbance are complex. Analysis of the land use coverage of Kibale reveals that abandoned farms (10.3%) and degraded forest (8.7%) now cover 146 km2. Unfortunately, we do not know what proportion of the farms were established on areas that were forest versus grassland. However, if the areas that are now abandoned farms were all once forested, this means that 79 km2 of forest has been lost. Based on density estimates from nearby sites, this would represent a loss of 52,612 monkeys and 200 chimpanzees. Populations would also have been affected by the degradation of the 66 km2 (8.7%) of forest. These estimates of the potential reductions in the primate populations that could have resulted from forest clearing and degradation illustrate the importance of protecting land. A review of the literature illustrates that the biomass of primates found within Kibale is very high in comparison to other locations and thus illustrates the importance of Kibale to regional conservation.

Agriculture↗

PubMed2000

Micro-anatomy of the volar skin and interordinal relationships of primates.

Paleontological and molecular evidence have been employed to suggest that flying lemurs (Dermoptera) and primates form a monophyletic group, in sharp contrast with cranial and postcranial evidence indicating sister group relationships between flying lemurs and bats (Chiroptera). New evidence from the epidermis of the volar pads of primates, tree shrews, flying lemurs, bats, and other mammals was examined and mapped on to various hypotheses of archontan relationships. The micro-anatomy of the skin on the palm and sole of flying lemurs and bats differs fundamentally from that of tree shrews (Scandentia) and primates. The volar skin of flying lemurs and bats lacks the serial arrangement of papillary ridges and grooves ("fingerprints") found in primates, tree shrews, and many other mammals. Moreover, the junction between the epidermis and dermis in flying lemurs and bats is relatively flat and shows little or no development of the internal ridges that occur in primates and tree shrews. When mapped on to a set of cladograms of mammals currently allocated to the superorder Archonta, this new evidence does not support sister group relationships between flying lemurs and primates, regardless of the volar skin morphology that characterized the last common ancestor of Archonta. Micro-anatomical differences that distinguish the volar skin of flying lemurs and bats from that of primates and tree shrews reflect a profound dichotomy in the functional roles fulfilled by the extremities, which could be significant in a phylogenetic context.

Animals↗

PubMed2000

Molecular evolution of cytochrome c oxidase subunit I in primates: is there coevolution between mitochondrial and nuclear genomes?

Phylogenetic analyses carried out on cytochrome c oxidase (COX) subunit I mitochondrial genes from 14 primates representing the major branches of the order and four outgroup nonprimate eutherians revealed that transversions and amino acid replacements (i.e., the more slowly occurring sequence changes) contained lower levels of homoplasy and thus provided more accurate information on cladistic relationships than transitions (i.e., the more rapidly occurring sequence changes). Several amino acids, each with a high likelihood of functionality involving the binding of cytochrome c or interaction with COX VIII, have changed in Anthropoidea, the primate suborder grouping New World monkey, Old World monkey, ape, and human lineages. They are conserved in other mammalian lineages and in nonanthropoid primates. Maximum-likelihood ancestral COX I nucleotide sequences were determined utilizing a near most parsimonious branching arrangement for the primate sequences that was consistent with previously hypothesized primate cladistic relationships based on larger and more diverse data sets. Relative rate tests of COX I mitochondrial sequences showed an elevated nonsynonymous (N) substitution rate for anthropoid-nonanthropoid comparisons. This finding for the largest mitochondrial (mt) DNA-encoded subunit is consistent with previous observations of elevated nonsynonymous substitution/synonymous substitution (S) rates in primates for mt-encoded COX II and for the nuclear-encoded COX IV and COX VIIa-H. Other COX-related proteins, including cytochrome c and cytochrome b, also show elevated amino acid replacement rates or N/S during similar time frames, suggesting that this group of interacting genes is likely to have coevolved during primate evolution.

Amino Acid Sequence↗

PubMed1994

Evolution of the primate cytochrome c oxidase subunit II gene.

We examined the nucleotide and amino acid sequence variation of the cytochrome c oxidase subunit II (COII) gene from 25 primates (4 hominoids, 8 Old World monkeys, 2 New World monkeys, 2 tarsiers, 7 lemuriforms, 2 lorisiforms). Marginal support was found for three phylogenetic conclusions: (1) sister-group relationship between tarsiers and a monkey/ape clade, (2) placement of the aye-aye (Daubentonia) sister to all other strepsirhine primates, and (3) rejection of a sister-group relationship of dwarf lemurs (i.e., Cheirogaleus) with lorisiform primates. Stronger support was found for a sister-group relationship between the ring-tail lemur (Lemur catta) and the gentle lemurs (Hapalemur). In congruence with previous studies on COII, we found that the monkeys and apes have undergone a nearly two-fold increase in the rate of amino acid replacement relative to other primates. Although functionally important amino acids are generally conserved among all primates, the acceleration in amino acid replacements in higher primates is associated with increased variation in the amino terminal end of the protein. Additionally, the replacement of two carboxyl-bearing residues (glutamate and aspartate) at positions 114 and 115 may provide a partial explanation for the poor enzyme kinetics in cross-reactions between the cytochromes c and cytochrome c oxidases of higher primates and other mammals.

Amino Acid Sequence↗

PubMed1994

Coraco-clavicular joint: normal variant in humans. A radiographic demonstration in the human and non-human primate.

The coraco-clavicular joint is a true synovial joint that may become painful in some patients after trauma. Among the descriptions of this entity is the assertion that the coraco-clavicular joint is routinely seen in gorillas and gibbons. We undertook to assess the incidence of this variant among gorillas, gibbons, and other non-human primates. All available radiographs of large primates performed at the International Wildlife Conservation Park/Bronx Zoo (IWCP) over the past 10 years were reviewed by a musculoskeletal radiologist (human radiology). All radiographs were taken during the normal clinical care of the non-human primate population of the IWCP and are a part of each animal's clinical record. Eighty-one non-human primate radiographs were suitable for study as they contained the region of interest. The 81 radiographic examinations included 14 different species of non-human primates. The coraco-clavicular joint was seen in 4 out of 9 silver-leaf langur, 2 out of 8 lowland gorilla, and in 1 out of 6 white-handed gibbon. In all non-human primate cases where the coraco-clavicular joint occurred, it was bilateral. In 1 out of 8 mandrill, there were very wide distal clavicular ends that articulated both with the coracoid and with the acromion. The coraco-clavicular joint differs from an ossified coraco-clavicular ligament. The radiographic appearance is characteristic and is found in both humans and some non-human primate species. It may rarely become painful following trauma. When symptomatic in humans, resection of this anomalous articulation is curative.

Acromioclavicular Joint↗

PubMed1989

Effects of environmental conditions on the psychological well-being of primates: a review of the literature.

Amendments made to the Animal Welfare Act in 1985 require primate researchers to provide "a physical environment adequate to promote the psychological well-being of primates". Regulations have not yet been promulgated, in part because "the psychological well-being" of primates is extremely difficult to define. Ideally, those regulations would be based upon observable changes in behavior rather than assumed psychological changes. Regardless, new primate care regulations pertaining to social environment, cage size, exercise and other forms of environmental enrichment are anticipated. A review of the literature suggests that there is little scientific data to support changing existing regulations. For instance, although it is clear that total social isolation in very young primates can be behaviorally devastating in terms of normal social behaviors, there are few, if any, demonstrable adverse effects of individual housing in adult primates. On the other hand, group housing, particularly with groups changing frequently in composition, increases aggression, trauma and disease transmission. In addition, existing research suggests there are important species differences in terms of social preferences. It is impossible to justify an increase in cage size based upon the available literature. An additional practical consideration is that any change in cage size requirements will necessitate replacement of current primate housing on a national level, an enormously expensive proposition. Regarding environmental enrichment, research suggests that providing a naturalistic environment is not as critical as arranging dynamic events that are contingent upon behavior. However, new research is necessary to specify the types of environmental enrichment that are valuable and appropriate before useless, even damaging, and expensive changes are mandated.

Animal Welfare↗

PubMed2001

Comparative expression of hedonic impact: affective reactions to taste by human infants and other primates.

This study examines behavioral affective reactions elicited by tastes from eight newborn human infants, and from 27 other infant or adult primates. Non-human primates belonged to 11 species: three great apes (chimpanzee, orangutan, gorilla), three Old World monkeys (rhesus monkey, greater spot-nosed monkey, and red-capped mangabey), four New World monkeys (golden-handed tamarin, cotton-top tamarin, white tufted-ear marmoset, and Humboldt's night monkey), and one lemur (mongoose lemur). The taste of sucrose elicited homologous positive hedonic patterns of facial affective reactions from humans and other primates, whereas quinine elicited homologous aversive or negative affective patterns. The degree of similarity between human and other primate affective reaction patterns appeared to be strongly indicative of their phylogenetic relatedness. For example, affective reaction patterns of human infants and great apes were more similar to each other than either were to Old World monkeys or New World monkeys. Certain affective reaction components were found to be shared by humans and all primates, whereas other components were restricted to particular taxonomic groups. Finally, allometric timing parameters for the duration of components indicated that the 'same' affective reaction could have different durations in species of different size. These results show that both positive/negative valence and intensity of affective reaction may be quantitatively assessed in human and non-human primates, and indicate that taste-elicited affective reaction patterns of human infants are related systematically to those of other primate species.

Affect↗

PubMed2000

The connections of the dopaminergic system with the striatum in rats and primates: an analysis with respect to the functional and compartmental organization of the striatum.

This Commentary compares the connections of the dopaminergic system with the striatum in rats and primates with respect to two levels of striatal organization: a tripartite functional (motor, associative and limbic) subdivision and a compartmental (patch/striosome-matrix) subdivision. The topography of other basal ganglia projections to the dopaminergic system with respect to their tripartite functional subdivision is also reviewed. This examination indicates that, in rats and primates, the following observations can be made. (1) The limbic striatum reciprocates its dopaminergic input and in addition innervates most of the dopaminergic neurons projecting to the associative and motor striatum, whereas the motor and associative striatum reciprocate only part of their dopaminergic input. Therefore, the connections of the three striatal subregions with the dopaminergic system are asymmetrical, but the direction of asymmetry differs between the limbic versus the motor and associative striatum. (2) The limbic striatum provides the main striatal input to dopamine cell bodies and proximal dendrites, with some contribution from a subset of neurons in the associative and motor striatum (patch neurons in rats; an unspecified group of neurons in primates), while striatal input to the ventrally extending dopamine dendrites arises mainly from a subset of neurons in the associative and motor striatum (matrix neurons in rats; an unspecified group of neurons in primates). (3) Projections from functionally corresponding subdivisions of the striatum, pallidum and subthalamic nucleus to the dopaminergic system overlap, but the specific targets (dopamine cells, dopamine dendrites, GABA cells) of these projections differ. Major differences include the following. (1) In rats, neurons projecting to the motor and associative striatum reside in distinct regions, while in primates they are arranged in interdigitating clusters. (2) In rats, the terminal fields of projections arising from the motor and associative striatum are largely segregated, while in primates they are not. (3) In rats, patch- and matrix-projecting dopamine cells are organized in spatially, morphologically, histochemically and hodologically distinct ventral and dorsal tiers, while in primates there is no (bi)division of the dopaminergic system that results in two areas which have all the characteristics of the two tiers in rats. Based on the anatomical data and known dopamine cell physiology, we forward an hypothesis regarding the influence of the basal ganglia on dopamine cell activity which captures at least part of the complex interplay taking place within the substantia nigra between projections arising from the different basal ganglia nuclei. Finally, we incorporate the striatal connections with the dopaminergic system into an open-interconnected scheme of basal ganglia-thalamocortical circuitry.

Animals↗

PubMed2000

Nonhuman primate models in biogerontology.

A variety of animal models are utilized in biogerontological studies including yeast, nematodes, fruit flies, hamsters, mice, rats, and nonhuman primates. Species selection for research is based on many factors including economic feasibility, husbandry, generalizability of findings, available background information, adaptability to experimentation, and often, relevance to human aging. Each model offers its own strengths and limitations; however, nonhuman primates offer the unique advantage of phylogenetic proximity to humans. Among others, costs to purchase and maintain research subjects represent major limitations of nonhuman primate models. Although several nonhuman primate species have been utilized in aging research, rhesus monkeys (Macaca mulatta) are the best characterized and most extensively studied in biomedical gerontology. Nonhuman primate models have been employed as models for human aging in many research areas including neurobiology, skeletal, and reproductive aging and age-related diseases such as cardiovascular disease and diabetes. Primate models are now also being utilized to study interventions into aging such as caloric restriction. It will be several more years until definitive conclusions regarding lifespan effects can be made. However, existing data strongly suggest that many of the beneficial effects reported in rodents on CR also occur in primate models thereby strengthening the possibility that this nutritional paradigm may also impact favorably upon human aging.

Aging↗