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Ecology and evolution of primate colour vision.

More than one hundred years ago, Grant Allen suggested that colour vision in primates, birds and insects evolved as an adaptation for foraging on colourful advertisements of plants--fruits and flowers. Recent studies have shown that well developed colour vision appeared long before fruits and flowers evolved. Thus, colour vision is generally beneficial for many animals, not only for those eating colourful food. Primates are the only placental mammals that have trichromatic colour vision. This may indicate either that trichromacy is particularly useful for primates or that primates are unique among placental mammals in their ability to utilise the signals of three spectrally distinct types of cones or both. Because fruits are an important component of the primate diet, primate trichromacy could have evolved as a specific adaptation for foraging on fruits. Alternatively, primate trichromacy could have evolved as an adaptation for many visual tasks. Comparative studies of mammalian eyes indicate that primates are the only placental mammals that have in their retina a pre-existing neural machinery capable of utilising the signals of an additional spectral type of cone. Thus, the failure of non-primate placental mammals to evolve trichromacy can be explained by constraints imposed on the wiring of retinal neurones.

Adaptation, Physiological↗

Report on primate supply for biomedical scientific work in the UK. EUPREN UK Working Party.

A Working Party of the UK group of European Primate Resources Network (EUPREN) considered primate supply for scientific work in the UK. Through a questionnaire, which achieved a very good response, it obtained details of primate use, sources and breeding in the UK and it put forward options to ensure that animal welfare is the best possible whilst ensuring continued supply. The questionnaire showed that contract research laboratories and pharmaceutical companies use about 80% of the 4233 primates used annually at the moment, with the rest accounted for by academic establishments and public sector laboratories. Fifty-four per cent are cynomolgus macaques (Macaca fascicularis), of which nearly 90% are captive-bred outside the European Union (EU), the remainder being bred in the UK. Nearly 90% of cynomolgus macaques are used by only five institutions. Thirty-seven per cent of primates used are marmosets (Callithrix jacchus jacchus), all of which are bred in the UK. Most of the rest are rhesus macaques (Macaca mulatta), about half of which are captive-bred outside the EU, the other half being bred in the UK. Overall primate use has increased from about 3000 per year in 1990 and users predict that requirements for all species except baboons (Papio sp.) will be maintained or increase. Marmoset breeding in the UK is already closely matched to use, and it could be increased reasonably easily if necessary. Some of the existing breeding centres of macaques in the UK would be prepared to consider expanding to supply others, although investment and imported breeding stock would be needed and it is likely that a large investment would be needed to breed a significant fraction of the macaque use in the UK. A further problem is that the users of only about 10% of the cynomolgus macaques said that they could replace this species by rhesus macaques, which are easier to breed in the UK. The questionnaire showed that much of the use of macaques would be transferred to other countries equally remote from the natural source countries of the animals, if constraints on primate use became more severe in the UK. Users felt that it is unlikely that much of the work could be transferred to the natural source countries themselves. A review of the literature revealed a paucity of information on the effects of transport on primate welfare. The importance of obtaining this information before making decisions about alternative means of supply is stressed. Current schemes for the accreditation of primate breeders were reviewed. A list of options is presented for discussion. Users vary so much in their requirements that it is unlikely that one means of supply will be applicable to all. Animal welfare will benefit and supply will be more certain if cooperation between those concerned (preferably through the UK group of EUPREN) is maintained.

Animal Welfare↗

Sexual selection and the evolution of brain size in primates.

Reproductive competition among males has long been considered a powerful force in the evolution of primates. The evolution of brain size and complexity in the Order Primates has been widely regarded as the hallmark of primate evolutionary history. Despite their importance to our understanding of primate evolution, the relationship between sexual selection and the evolutionary development of brain size is not well studied. The present research examines the evolutionary relationship between brain size and two components of primate sexual selection, sperm competition and male competition for mates. Results indicate that there is not a significant relationship between relative brain size and sperm competition as measured by relative testis size in primates, suggesting sperm competition has not played an important role in the evolution of brain size in the primate order. There is, however, a significant negative evolutionary relationship between relative brain size and the level of male competition for mates. The present study shows that the largest relative brain sizes among primate species are associated with monogamous mating systems, suggesting primate monogamy may require greater social acuity and abilities of deception.

Animals↗

Histological definition of the vomeronasal organ in humans and chimpanzees, with a comparison to other primates.

The vomeronasal organ (VNO) is a chemosensory structure that has morphological indications of functionality in strepsirhine and New World primates examined to date. In these species, it is thought to mediate certain socio-sexual behaviors. The functionality and even existence of the VNO in Old World primates has been debated. Most modern texts state that the VNO is absent in Old World monkeys, apes, and humans. A recent study on the VNO in the chimpanzee (Smith et al., 2001b) challenged this notion, demonstrating the need for further comparative studies of primates. In particular, there is a need to establish how the human/chimpanzee VNO differs from that of other primates and even nonhomologous mucosal ducts. Histochemical and microscopic morphological characteristics of the VNO and nasopalatine duct (NPD) were examined in 51 peri- and postnatal primates, including humans, chimpanzees, five species of New World monkeys, and seven strepsirhine species. The nasal septum was removed from each primate and histologically processed for coronal sectioning. Selected anteroposterior intervals of the VNO were variously stained with alcian blue (AB)-periodic acid-Schiff (PAS), PAS only, Gomori trichrome, or hematoxylin-eosin procedures. All strepsirhine species had well developed VNOs, with a prominent neuroepithelium and vomeronasal cartilages that nearly surrounded the VNO. New World monkeys had variable amounts of neuroepithelia, whereas Pan troglodytes and Homo sapiens had no recognizable neuroepithelium or vomeronasal nerves (VNNs). Certain unidentified cell types of the human/chimpanzee VNO require further examination (immunohistochemical and electron microscopic). The VNOs of P. troglodytes, H. sapiens, and New World monkeys exhibited different histochemistry of mucins compared to strepsirhine species. The nasopalatine region showed great variation among species. It is a blind-ended pit in P. troglodytes, a glandular recess in H. sapiens, a mucous-producing duct in Otolemur crassicaudatus, and a stratified squamous passageway in all other species. This study also revealed remarkable morphological/histochemical variability in the VNO and nasopalatine regions among the primate species examined. The VNOs of humans and chimpanzees had some structural similarities to nonhomologous ciliated gland ducts seen in other primates. However, certain distinctions from the VNOs of other primates or nonhomologous epithelial structures characterize the human/chimpanzee VNO: 1) bilateral epithelial tubes; 2) a superiorly displaced position in the same plane as the paraseptal cartilages; 3) a homogeneous, pseudostratified columnar morphology with ciliated regions; and 4) mucous-producing structures in the epithelium itself.

Aged↗

Phylogeny of Pneumocystis carinii from 18 primate species confirms host specificity and suggests coevolution.

Primates are regularly infected by fungal organisms identified as Pneumocystis carinii. They constitute a valuable population for the confirmation of P. carinii host specificity. In this study, the presence of P. carinii was assessed by direct examination and nested PCR at mitochondrial large subunit (mtLSU) rRNA and dihydropteroate synthetase (DHPS) genes in 98 lung tissue samples from captive or wild nonhuman primates. Fifty-nine air samples corresponding to the environment of different primate species in zoological parks were also examined. Cystic forms of P. carinii were detected in smears from 7 lung tissue samples corresponding to 5 New World primate species. Amplifications at the mtLSU rRNA gene were positive for 29 lung tissue samples representing 18 different primate species or subspecies and 2 air samples corresponding to the environment of two simian colonies. Amplifications at the DHPS gene were positive for 8 lung tissue samples representing 6 different primate species. Direct sequencing of nested PCR products demonstrated that a specific mtLSU rRNA and DHPS sequence could be attributed to each primate species or subspecies. No nonhuman primate harbored the human type of P. carinii (P. carinii f. sp. hominis). Genetic divergence in primate-derived P. carinii organisms varied in terms of the phylogenetic divergence existing among the corresponding host species, suggesting coevolution.

Air Microbiology↗

Hind limb proportions and kinematics: are small primates different from other small mammals?

Similar in body size, locomotor behaviour and morphology to the last common ancestor of Primates, living small quadrupedal primates provide a convenient model for investigating the evolution of primate locomotion. In this study, the hind limb kinematics of quadrupedal walking in mouse lemurs, brown lemurs, cotton-top tamarins and squirrel monkeys are analysed using cineradiography. The scaling of hind limb length to body size and the intralimb proportions of the three-segmented hind limb are taken into consideration when kinematic similarities and differences are discussed. Hind limb kinematics of arboreal quadrupedal primates, ranging in size between 100 g and 3000 g, are size independent and resemble the hind limb kinematics of small non-cursorial mammals. A common feature seen in smaller mammals, in general, is the horizontal position of the thigh at touchdown and of the lower leg at lift-off. Thus, the maximum bone length is immediately transferred into the step length. The vertical position of the leg at the beginning of a step cycle and of the thigh at lift-off contributes the same distance to pivot height. Step length and pivot height increase proportionally with hind limb length, because intralimb proportions of the hind limb remain fairly constant. Therefore, the strong positive allometric scaling of the hind limb in arboreal quadrupedal primates affects neither the kinematics of hind limb segments nor the total angular excursion of the limb. The angular excursion of the hind limb in quadrupedal primates is equal to that of other non-cursorial mammals. Hence, hind limb excursion in larger cercopithecine primates differs from that of other large mammals due to the decreasing angular excursion as part of convergent cursorial adaptations in several phylogenetic lineages of mammals. Typical members of those phylogenetic groups are traditionally used in comparison with typical primates, and therefore the ;uniqueness' of primate locomotor characteristics is often overrated.

Age Factors↗

Metabolism and pharmacokinetics of N1,N11-diethylnorspermine in a Cebus apella primate model.

The tissue distribution, metabolic profile, and pharmacokinetic parameters of i.v.-administered N1,N11-diethylnorspermine (DENSPM) are evaluated in Cebus apella primates, and the results are compared with data gathered from canine and human studies. Although the metabolic processing of DENSPM (i.e., deethylation and deaminopropylation) in dogs and primates is very similar, there are some significant differences in tissue distribution of the parent drug. In dogs, the organ concentration of DENSPM follows the order kidney >> liver approximately = lung > spleen. In the primate, the order is liver >> kidney approximately = spleen > lung. The difference in pharmacokinetic parameters between the species is profound with (area under the time-concentration curve)primate << (area under the time-concentration curve)dog; (terminal elimination half-life)primate << (terminal elimination half-life)dog; and (mean residence time)primate << (mean residence time)dog. The most notable difference between dogs and primates is seen in the fraction of parent drug excreted unchanged in the urine, 50% in the dog and < 1% in the primate. However, the pharmacokinetic parameters and urinary drug clearance in C. apella primates are remarkably similar to those in humans. Thus, C. apella is established as an excellent model for assessing the metabolism, tissue distribution, and pharmacokinetic properties of polyamine analogues.

Animals↗

Stable infection of primates with Trypanosoma cruzi I and II.

In order to better comprehend the putative association between genotype Trypanosoma cruzi II and primates, an evaluation of the infection in free ranging primates and specimens born in captivity from different geographical areas, the Amazon and the Atlantic forest, was carried out. Seroprevalences of the T. cruzi infection among the primates was similar in both biomes (45.5% and 46%). The parasites were isolated from 8 and 4 different species of primates, respectively from the Amazon and Atlantic forest. Multi-locus enzyme electrophoresis (MLEE) typed the isolates from Amazon as zymodeme 1. Mini-exon gene analysis characterized all these isolates as T. cruzi I, the main genotype circulating in the region. In the Atlantic forest, primates infected with TCI and TCII, as well as a mixed infection (TCI and TCII), were detected. These findings prove that primates may maintain stable infections by both genotypes. Moreover, data show that T. cruzi can occur in a wide range of primate genera, independent of their social behaviour, niches or habitats. Considering the high seroprevalence and stability of T. cruzi infection among the primates, these animals play an important role in the maintenance of the parasite in nature.

Animals↗

Osteological evidence for the evolution of activity pattern and visual acuity in primates.

Examination of orbit size and optic foramen size in living primates reveals two adaptive phenomena. First, as noted by many authors, orbit size is strongly correlated with activity pattern. Comparisons of large samples of extant primates consistently reveal that nocturnal species exhibit proportionately larger orbits than diurnal species. Furthermore, nocturnal haplorhines (Tarsius and Aotus) have considerably larger orbits than similar-sized nocturnal strepsirrhines. Orbital hypertrophy in Tarsius and Aotus accommodates the enormously enlarged eyes of these taxa. This extreme ocular hypertrophy seen in extant nocturnal haplorhines is an adaptation for both enhanced visual acuity and sensitivity in conditions of low light intensity. Second, the relative size of the optic foramen is highly correlated with the degree of retinal summation and inferred visual acuity. Diurnal haplorhines exhibit proportionately larger optic foramina, less central retinal summation, and much higher visual acuity than do all other primates. Diurnal strepsirrhines exhibit a more subtle but significant parallel enlargement of the optic foramen and a decrease in retinal summation relative to the condition seen in nocturnal primates. These twin osteological variables of orbit size and optic foramen size may be used to draw inferences regarding the activity pattern, retinal anatomy, and visual acuity of fossil primates. Our measurements demonstrate that the omomyiforms Microchoerus, Necrolemur, Shoshonius, and Tetonius, adapiform Pronycticebus, and the possible lorisiform Plesiopithecus were likely nocturnal on the basis of orbit diameter. The adapiforms Leptadapis, Adapis, and Notharctus, the phylogenetically enigmatic Rooneyia, the early anthropoids Proteopithecus, Catopithecus, and Aegyptopithecus, and early platyrrhine Dolichocebus were likely diurnal. The activity pattern of the platyrrhine Tremacebus is obscure. Plesiopithecus, Pronycticebus, Microchoerus, and Necrolemur probably had eyes that were very similar to those of extant nocturnal primates, with a high degree of retinal summation and rod-dominated retinae. Leptadapis and Rooneyia likely had eyes similar to those of extant diurnal strepsirrhines, with moderate degrees of retinal summation, a larger cone:rod ratio than in nocturnal primates, and, more speculatively, well-developed areae centrales similar to those of diurnal strepsirrhines. Adapis exhibited uncharacteristically high degrees of retinal summation for a small-eyed (likely diurnal) primate. None of the adapiform or omomyiform taxa for which we were able to obtain optic foramen dimensions exhibited the extremely high visual acuity characteristic of extant diurnal haplorhines.

Animals↗

Masticatory stress, orbital orientation and the evolution of the primate postorbital bar.

A postorbital bar is one of a suite of derived features which distinguishes basal primates from their putative sister taxon, plesiadapiforms. Two hypotheses have been put forward to explain postorbital bar development and variation in circumorbital form: the facial torsion model and visual predation hypothesis. To test the facial torsion model, we employ strain data on circumorbital and mandibular loading patterns in representative primates with a postorbital bar and masticatory apparatus similar to basal primates. To examine the visual predation hypothesis, we employ metric data on orbit orientation in Paleocene and Eocene primates, as well as several clades of visual predators and foragers that vary interspecifically in postorbital bar formation.A comparison of galago circumorbital and mandibular peak strains during powerful mastication demonstrates that circumorbital strains are quite low. This indicates that, as in anthropoids, the strepsirhine circumorbital region is excessively overbuilt for countering routine masticatory loads. The fact that circumorbital peak-strain levels are uniformly low in both primate suborders undermines any model which posits that masticatory stresses are determinants of circumorbital form, function and evolution. This is interpreted to mean that sufficient cortical bone must exist to prevent structural failure due to non-masticatory traumatic forces. Preliminary data also indicate that the difference between circumorbital and mandibular strains is greater in larger taxa.Comparative analyses of several extant analogs suggest that the postorbital bar apparently provides rigidity to the lateral orbital margins to ensure a high level of visual acuity during chewing and biting. The origin of the primate postorbital bar is linked to changes in orbital convergence and frontation at smaller sizes due to nocturnal visual predation and increased encephalization. By incorporating in vivo and fossil data, we reformulate the visual predation hypothesis of primate origins and thus offer new insights into major adaptive transformations in the primate skull.

Animals↗

Toward a molecular paleontology of primate genomes. II. The KpnI families of alphoid DNAs.

KpnI restriction of anthropoid primate DNAs, from a New World monkey to man, releases a series of segments that are remarkable among all of the alphoid DNAs in the constancy of their relative amounts in the various primate genomes, in their long-range organization, and in their internal sequence structure. These segments are labeled the KpnI A, B, C and D segments. Cross-hybridization analysis by Southern filter-transfer hybridization indicates that the KpnI segments represent separate and distinct families of alphoid DNAs. These families are termed the KpnI A, B, C and D families of alphoid sequences, of which only the KpnI A and B families were studied in detail here. - Evidence is presented suggesting that the KpnI segments do not exist as long, tandemly repeated sequences in the primate genome: rather, they may occur interspersed among other, perhaps nonalphoid sequences. From the stained gel patterns and from Southern filter-transfer hybridization experiments, the KpnI families appear to be absent from the genomes of the two prosimians studied - the galago and the black lemur. The KpnI A and B families are found among all of the anthropoid primates, including the New World capuchin monkey. The KpnI C family was detected in the genomes of the Old World anthropoid primates whereas the KpnI D family was detected only among the great apes and man. - The results are in accord with the observation (Musich et al., 1980) that with the continued evolutionary development of the primate Order, there has been a parallel trend toward an increased number and variety of alphoid DNA sequences. The properties of the KpnI families suggest that these sequences, unique among the alphoid DNAs, have been conservatively maintained throughout primate phylogeny and that they are among the most ancient of all primate DNAs.

Animals↗

Forty million years of independent evolution: a mitochondrial gene and its corresponding nuclear pseudogene in primates.

Sequences from nuclear mitochondrial pseudogenes (numts) that originated by transfer of genetic information from mitochondria to the nucleus offer a unique opportunity to compare different regimes of molecular evolution. Analyzing a 1621-nt-long numt of the rRNA specifying mitochondrial DNA residing on human chromosome 3 and its corresponding mitochondrial gene in 18 anthropoid primates, we were able to retrace about 40 MY of primate rDNA evolutionary history. The results illustrate strengths and weaknesses of mtDNA data sets in reconstructing and dating the phylogenetic history of primates. We were able to show the following. In contrast to numt-DNA, (1) the nucleotide composition of mtDNA changed dramatically in the different primate lineages. This is assumed to lead to significant misinterpretations of the mitochondrial evolutionary history. (2) Due to the nucleotide compositional plasticity of primate mtDNA, the phylogenetic reconstruction combining mitochondrial and nuclear sequences is unlikely to yield reliable information for either tree topologies or branch lengths. This is because a major part of the underlying sequence evolution model--the nucleotide composition--is undergoing dramatic change in different mitochondrial lineages. We propose that this problem is also expressed in the occasional unexpected long branches leading to the "common ancestor" of orthologous numt sequences of different primate taxa. (3) The heterogeneous and lineage-specific evolution of mitochondrial sequences in primates renders molecular dating based on primate mtDNA problematic, whereas the numt sequences provide a much more reliable base for dating.

Animals↗

Developmental processes and canine dimorphism in primate evolution.

Understanding the evolutionary history of canine sexual dimorphism is important for interpreting the developmental biology, socioecology and phylogenetic position of primates. All current evidence for extant primates indicates that canine dimorphism is achieved through bimaturism rather than via differences in rates of crown formation time. Using incremental growth lines, we charted the ontogeny of canine formation within species of Eocene Cantius, the earliest known canine-dimorphic primate, to test whether canine dimorphism via bimaturism was developmentally canalized early in primate evolution. Our results show that canine dimorphism in Cantius is achieved primarily through different rates of crown formation in males and females, not bimaturism. This is the first demonstration of rate differences resulting in canine dimorphism in any primate and therefore suggests that canine dimorphism is not developmentally homologous across Primates. The most likely interpretation is that canine dimorphism has been selected for at least twice during the course of primate evolution. The power of this approach is its ability to identify underlying developmental processes behind patterns of morphological similarity, even in long-extinct primate species.

Animals↗

Evolution of DNA sequences has been retarded in Malagasy primates.

It is generally accepted that there are six major groups of living primates: (1) lemurs (including all the primates of Madagascar), (2) lorises (including galago and potto), (3) tarsiers, (4) New World monkeys, (5) Old World monkeys and (6) apes (including man). Tree shrews, once considered to be primates, are now generally recognized as not significantly more closely related to the six groups than other mammals. The first surviving primate lines to diverge from the common primate ancestor are believed to have given rise to one or more of the first three groups. However, the fossil record is insufficient to determine their relative branching order. Furthermore, neither morphological considerations nor studies of protein evolution produce unanimity as to whether tarsiers are more closely related to the prosimians (the lemurs plus lorises) or the simians (the monkeys and apes). In an attempt to resolve these discrepancies, we have measured the DNA sequence difference between several primates. We report here that the evolution of DNA of primates from Madagascar is significantly less than that of all other groups of living primates. This is not expected in the simplest form of the theory of neutral selection and may be important for our understanding of evolution at the molecular level.

Animals↗

Primate origins: plugging the gaps.

Recent discoveries of fossil primate specimens have produced several surprises and challenged prevailing views of early primate evolution. Plesiadapiformes, long regarded as 'archaic primates', may perhaps be linked to the peculiar colugos instead. Inferred relationships of the earliest known undoubted primates (adapids and omomyids) are in turmoil. Both groups have been proposed as sources for the simian primates. Although the origin of the simian primates is obscure, new fossil evidence could push it further back by at least 10 million years. Such uncertainties reflect the low sampling level of the primate fossil record, which can potentially also lead to underestimation of times of origin within the primate tree.

Animals↗

A primer of primate pathology: lesions and nonlesions.

Nonhuman primates are important laboratory animals for biomedical, pharmacology, and toxicology research. To effectively use primates as models, their gross and histologic anatomy, physiology and natural history, as well as common health problems and the source from which the primate is obtained, must be known and understood by pathologists involved in study design and/or interpretation. The first very important lesson in the "primer" is: there is no such thing as a generic monkey. Brand names (ie, species and subspecies) are important. Several taxonomic groups of primates are used in research including: prosimians, such as galagos and lemurs; New World monkeys, particularily marmosets; Old World monkeys, especially macaques and baboons; and the chimpanzee, an African ape. Differences between taxa are exemplified by the glucocorticoid resistance of New World monkeys compared to Old World monkeys, which results in the requirement for Vitamin D3 and their high circulating levels of steroids such as cortisone and progesterone. Differences in ovarian histology between Old and New World monkeys probably relate to steroid receptor biology as well. There are also variations in disease manifestations, even among closely related primate species such as rhesus and cynomolgus macaques (cynos). For example type D retrovirus infection is accompanied by lymphomas in cynos, but not rhesus. The second important lesson in this "primer" is: "not test article related" does not always mean "normal." Lymphoid nodules in bone marrow or salivary gland, a common background finding in macaques, often signal the presence of type D retrovirus. Other histologic changes and normal anatomic variations may be confusing to individuals not routinely examining primate tissues. The objective of this paper is to familiarize pathologists with the use of primates in research as well as lesions and nonlesions (normal anatomy or physiology) of primates that may influence study design and confound interpretation.

Animal Diseases↗

Demand for nonhuman primate resources in the age of biodefense.

The demand for nonhuman primates will undoubtedly increase to meet biomedical needs in this current age of biodefense. The availability of funding has increased the research on select agents and has created a requirement to validate results in relevant primate models. This review provides a description of current and potential biological threats that are likely to require nonhuman primates for the development of vaccines and therapeutics. Primates have been an invaluable resource in the dissection of viral disease pathogenesis as well as in testing vaccine efficacy. DNA vaccine approaches have been studied successfully for Ebola, Lassa, and anthrax in nonhuman primate models. Nonhuman primate research with monkeypox has provided insight into the role of cytokines in limiting disease severity. Biodefense research that has focused on select agents of bacterial origin has also benefited from nonhuman primate studies. Rhesus macaques have traditionally been the model of choice for anthrax research and have yielded successful findings in vaccine development. In plague research, African green monkeys have contributed to vaccine development. However, the disadvantages of current vaccines will undoubtedly require the generation of new vaccines, thus increasing the need for nonhuman primate research. Unfortunately, the current biosafety level (BSL)-3 and BSL-4 facilities equipped to perform this research are limited, which may ultimately impede progress in this era of biodefense.

Animal Experimentation↗

Plasma cortisol transport and primate evolution.

Primates have diverged into three major evolutionary groups: prosimians, Old World primates, and New World primates; the last group is distinguished by high circulating cortisol concentrations and resistance to the action of glucocorticoids. We have studied a large spectrum of primate species within these groups to characterize the phylogenetic relationships of cortisol-binding globulin (CBG) among them. The CBG in each species was found to be glycosylated, as judged from lectin interactions, and to exhibit an electrophoretic mobility similar to that of human CBG. Although the CBG affinity for cortisol differed among species, the effects of changes in temperature on the CBG affinity were similar. Strikingly, the CBG-binding capacity of plasma in the New World primates was 1/10th to 1/100th those in the Old World primates and prosimians, while the CBG-binding affinity for cortisol was lower. The reduced capacity and affinity of CBG result in a markedly higher fraction of unbound plasma cortisol in the New World primates than in the Old World primates or the prosimian species examined. This evolutionary pattern of CBG may be a compensatory mechanism for the target organ resistance to glucocorticoids that characterizes the New World monkeys.

Animals↗