Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar calcified cartilage.

Summary In an attempt to show maturational alterations in the calcified cartilage, mandibular condyles of four growing and four adult male monkeys (Macaca fascicularis) were studied using light microscopy as well as transmission and scanning electron microscopy. All specimens were initially fixed by perfusion in the presence of ruthenium red. For examination of the hard tissue surfaces in the scanning electron microscope, uncalcified tissues were removed with sodium hypochlorite. In growing animals, almost the entire hard tissue surface in the joint region of the condyle was formed by calcified cartilage, while in adult animals, calcified cartilage was confined to load-bearing regions. In growing animals, the appearance of the calcified cartilage surface suggested a continuously advancing mineralizing front similar to that seen in the epiphyseal plate. Chondrocytes mostly exhibited a terminal stage of hypertrophy, and seemed to die and get lost through vascular invasion and subsequent endochondral ossification. In adult animals, most of the calcified cartilage surface appeared comparatively stable, and resembled the tidemark of articular cartilage. Chondrocytes were usually small and appeared viable. However, on the adult condyles, there were always circumscribed islands where chondrocytes and the pattern of mineralization resembled those seen in growing animals. In these regions, prominent chondroclastic activity indicated extensive articular remodelling. These observations suggest that at the end of somatic growth, condylar calcified cartilage undergoes considerable maturation from a type reminiscent of hyaline growth cartilage to a type resembling articular cartilage. Concomitantly, chondrocytes appear to change their developmental program, in that they stop enlarging and lose their commitment to death. However, they may be able to retain, or switch back to, a more immature stage, in case there is need for extensive articular remodelling.     

An experimental study on developmental changes of maternal discrimination of infants in crab-eating monkeys (Macaca fascicularis)

Individually reared mother-infant dyads of crab-eating monkeys (Macaca fascicularis) were observed cross-sectionally in their mother-infant relationship. In infants aged from 0 to 5.0 months, rather drastic changes were found both at 0.5-1.0 and 2.0-3.0 months of age. For an explanation of these changes, developmental processes of discrimination between mother and infant were analyzed cross-sectionally by exchanging mother-infant combinations. The results indicated that the first 0.5 months postpartum was characterized as a behaviorally nondiscriminating stage where nipple discrimination by infants was the only exception. The latter half of the first month was the beginning of a nonaggressive discrimination stage by mothers, indicated by lipsmacking and sniffing and in infants by clinging. When infants reached the age of 2.0-3.0 months, the mothers' nonaggressive discrimination with lipsmacking decreased, and her aggressive discrimination of alien infants increased. In addition to maternal visual discrimination of infants' physical appearances, differences in infants' odor and/or their method of nipple contact were suggested to affect the mothers' differential behaviors.     

The nucleus accumbens in monkeys (Macaca fascicularis)

The nucleus accumbens (NA), which receives inputs from limbic structures and projects to the motor system, may be important for the association of reinforcement with action. There are projections to the NA from the amygdala and hippocampus. Discrimination and reversal learning tasks which are known to be disrupted by lesions to these areas in monkeys were given to monkeys with lesions of the NA. Twelve monkeys (Macaca fascicularis) were used in the present study. Six of these received ibotenic acid lesions which resulted in considerable cell loss in the NA; the remaining six acted as controls. The first group of six monkeys were taught a visual discrimination task pre-operatively. Post-operatively, these monkeys were tested on visual and spatial discrimination and reversal tasks. A second group of six monkeys were tested on a motor reversal task. The results indicate that ibotenic acid lesions of the NA transiently impair spatial but not visual reversal learning in monkeys. The NA lesions did not impair a monkey's ability to perform visual or spatial discriminations, or the ability to perform the motor learning or motor reversal tasks. Our results suggest that bilateral lesions of the NA in monkeys do not disrupt the ability to discriminate basic properties of reward-related stimuli or the formation of visual stimulus-reward associations. In addition, our results argue against theories which suggest that the NA is important for behavioural switching or general behavioural flexibility. We conclude that the NA may play a more specific role in the association of temporal and spatial cues with movement and reward.     

Atherosclerosis research in cynomolgus monkeys (Macaca fascicularis)

This is a review of the utilization of cynomolgus monkeys (Macaca fascicularis) in atherosclerosis research. Naturally occurring and experimentally induced atherosclerosis progression and regression studies are described. This species has been utilized as an animal model to study the effects of immunologic injury, aging, exercise, and drug intervention on atherosclerotic lesions. Cynomolgus macaque atherosclerosis induced by feeding cholesterol is a good model of human atherosclerosis because of similar gender-related differences in susceptibility to coronary artery atherosclerosis, a relatively high incidence of myocardial infarction, and characterized psychosocial factors that influence the development of atherosclerosis.     

The cutaneous branch of the mylohyoid nerve in the crab-eating monkey (Macaca fascicularis)

Cutaneous branches of the mylohyoid nerve were observed in both sides of 25 (83.3%) and in one side of 5 (16.7%) out of 30 crab-eating monkeys (Macaca fascicularis). The branch supply the skin and sinus hairs at the mental part. These sinus hairs seem to be the intermandibular sinus hairs according to the manner of nerve supply.     

Characterization of prenatal growth and development in the crab-eating macaque (Macaca fascicularis) by ultrasound

Diagnostic ultrasound is a valuable tool for the examination of various anatomical structures in vivo. Improvements in technology have increased its effectiveness and provided a noninvasive method for the in utero observation of a variety of structural and functional events. Ultrasound is utilized in our laboratory to monitor a variety of studies during embryonic and fetal development. Basic to these evaluations is the ability to assess normal growth and development. The cynomolgus, or crab-eating macaque (Macaca fascicularis), has been observed in utero by ultrasound from early gestation to term. The earliest detection of implantation is by the identification of a developing gestational sac (GS), which may be visualized on gestational day (GD) 14-15. Positive identification of the GS on GD 16-18 and appearance of the embryo, yolk sac, and cardiac motion on GD 21-25 confirms pregnancy. Once the embryo is evident, measurements of the greatest length (GL) may be used to assess normal growth or to aid in the prediction of gestational age. During the fetal period, a variety of growth parameters aid in fetal evaluation. The gender of the fetus can be accurately identified as early as GD 70-75. An assessment of viability and condition can be determined by the observation of embryonic and fetal heart rates and gross body movement.     

Pathology of inhalation anthrax in cynomolgus monkeys (Macaca fascicularis)

Anthrax is considered a serious biowarfare and bioterrorism threat because of its high lethality, especially by the inhalation route. Rhesus macaques (Macaca mulatta) are the most commonly used nonhuman primate model of human inhalation anthrax exposure. The nonavailability of rhesus macaques necessitated development of an alternate model for vaccine testing and immunologic studies. This report describes the median lethal dose (LD(50)) and pathology of inhalation anthrax in cynomolgus macaques (Macaca fascicularis). Gross and microscopic tissue changes were reviewed in 14 cynomolgus monkeys that died or were killed after aerosol exposure of spores of Bacillus anthracis (Ames strain). The LD(50) and 95% confidence intervals were 61800 (34000 to 110000) colony-forming units. The most common gross lesions were mild splenomegaly, lymph node enlargement, and hemorrhages in various organs, particularly involving the meninges and the lungs. Mediastinitis, manifested as hemorrhage or edema, affected 29% of the monkeys. Microscopically, lymphocytolysis occurred in the intrathoracic lymph nodes and spleens of all animals, and was particularly severe in the spleen and in germinal centers of lymph nodes. Hemorrhages were common in lungs, bronchial lymph nodes, meninges, gastrointestinal tract, and mediastinum. These results demonstrate that the Ames strain of B. anthracis is lethal by the inhalation route in the cynomolgus macaque. The LD(50) of the Ames strain of B. anthracis was within the expected experimental range of previously reported values in the rhesus monkey in an aerosol challenge. The gross and microscopic pathology of inhalation anthrax in the cynomolgus monkey is remarkably similar to that reported in rhesus monkeys and humans. The results of this study are important for the establishment of an alternative nonhuman primate model for evaluation of medical countermeasures against inhalational anthrax.     

Two cases of adreno-hepatic fusion in cynomolgus monkeys (Macaca fascicularis)

In this report we describe 2 cases of adreno-hepatic fusion (AHF) in Cynomolgus monkeys (Macaca fascicularis) used in short-term toxicity studies. AHF is defined as the union of hepatic tissue with the adrenal gland with close intermingling of the respective parenchymal cells. In this condition, a continuous intervening connective tissue septum is lacking. AHF is believed to be a congenital anomaly caused by a defect or delay in the formation of the organ capsules from the intermediate primitive mesenchymal stroma. To our knowledge, this is the first time this anomaly is described in the monkey.     

Pneumocystis infection in macaque monkeys: Macaca fuscata fuscata and Macaca fascicularis

Retrospective examination of lungs from 128 monkey necropsies was attempted for Pneumocystis infection using special stains, including toluidine blue-O and Gomori's methenamine silver nitrate. Four Japanese monkeys (7.7%), Macaca fuscata fuscata, and one crab-eating monkey (7.7%), Macaca fascicularis, were found to have Pneumocystis infection. The organism was found in young and infant animals. At the time of death, one infant and two young monkeys were debilitated and/or emaciated. Pneumocystis infection was considered an important lesion which could have caused reduced respiratory function in two of the Japanese monkeys, but constituted only an incidental finding in the others.Contribution No. 567 from the Department of Medical Zoology, Kyoto Prefectural University of Medicine     

Estrogen and the cholinergic system modulate visuospatial attention in monkeys (Macaca fascicularis)

This study determined the effects of estrogen on attention and motor speed in young monkeys (Macaca fascicularis). Performance on visuospatial attention and reaction time motor tasks was measured before ovariectomy, for 2 months after ovariectomy, and at 14 months after treatment with placebo or estrogen replacement therapy (ERT). Release time on invalid trials in the attention task was increased after ovariectomy and was reduced in monkeys treated with ERT. but not placebo. Simple reaction time was not altered after ovariectomy or treatment. The effects of scopolamine on attention, but not memory, in a delayed response task were dependent on estrogen. These observations indicate that loss of estrogen modulates visuospatial attention in primates and that 1 mechanism of this modulation is through the cholinergic system.     

Social stress-associated depression in adult female cynomolgus monkeys (Macaca fascicularis)

This paper describes a behavior pattern in adult female cynomolgus monkeys that has several behavioral and physiological characteristics in common with human depression including reduced body fat, low levels of activity, high heart rate, hypothalamic-pituitary-adrenal (HPA) axis disturbances, and increased mortality. Under certain circumstances, this depressive behavior appears more common in socially stressed subordinate, than dominant, females. This is the first animal model of social stress-related depression in females and the first primate model of adult depression. It is important to have a female animal model of depression because women are more likely to experience a clinically significant depression than men, and depression in women is often associated with changes in reproductive system function. This model is particularly useful because these monkeys have menstrual cycles that are similar to those of women, and those that exhibit depressive behavior have relatively low levels of ovarian steroids. These monkeys may be a useful model of reproductive system-associated mood disorders in females.     

Motor learning in monkeys (Macaca fascicularis) with lesions in motor thalamus

Summary The study examines the nature of the influence that the basal ganglia exert on frontal cortex via the motor nuclei of the thalamus. Twelve monkeys were trained to pull a handle given one colour cue and to turn it given another. Bilateral lesions were then placed in the ventral thalamus. Four monkeys with large anterior lesions including the VA nucleus and the anterior part of VLo were severely impaired at relearning the task. Monkeys with small lesions in VAmc or with lesions centred on VLo were not impaired. The analysis of the histology suggests that the impairment in the four monkeys did not result from involvement of the cerebellar relay through nucleus X. It is argued that the animals are not impaired because of faulty execution. This suggests that the basal ganglia have an influence on motor learning.     

Testosterone and its metabolites in male cynomolgus monkeys (Macaca fascicularis): behavior and biochemistry

To extend our previous study on the behavioral effects of testosterone propionate (TP) and dihydrotestosterone propionate (DHTP) to a dose-range producing supra-physiological plasma androgen levels, 4 castrated cynomolgus monkeys were tested with the same 4 females during successive 4-week treatment periods while receiving 800 micrograms, 1.6 mg, 3.2 mg, 6.4 mg and 12.8 mg of TP or DHTP SC/day in counterbalanced order (16 pairs, 828 1-hr tests). Both androgens increased male sexual activity, but DHTP was less effective than TP in increasing the numbers of ejaculations per test and failed to restore ejaculations to intact levels. Giving androgen-treated males single injections of 50 micrograms and 100 micrograms estradiol benzoate (EB) was without any additional effect on behavior (16 pairs, 256 tests). To examine hormonal effects in the brain, castrated males were given either 3H-T or 3H-DHT, and tissues were examined by high performance liquid chromatography (hplc). After 3H-T, 3H-E2 and unchanged 3H-T were the major forms of radioactivity in nuclei from hypothalamus, preoptic area and amygdala. After 3H-DHT, unchanged 3H-DHT predominated. The lower behavioral effectiveness of DHT could not be ascribed to its failure to enter the brain. The data suggested a role for unchanged T in the regulation of ejaculatory behavior in a male primate.     

Cryopreservation-induced acrosomal vesiculation in live spermatozoa from cynomolgus monkeys (Macaca fascicularis)

BACKGROUND: Cryopreserved spermatozoa are known to undergo accelerated capacitation and require a shorter incubation time for fertilization. However, details of their acrosomal membranes following cryopreservation remain unclear. METHODS: Percoll density gradient centrifugation was used to remove dead spermatozoa; thus >90% live spermatozoa were recovered after cryopreservation, and acrosomal status was compared among non-incubated and incubated fresh and cryopreserved spermatozoa. RESULTS: Transmission election microscopy (TEM) using microwave methods and fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) staining revealed that 21.1 and 61.6% respectively of non-incubated, cryopreserved spermatozoa were intact, whereas 97.6% (TEM) or 91.9% (FITC-PSA) of non-incubated fresh spermatozoa were intact. TEM revealed that 28.8% of the cryopreserved spermatozoa were swollen, and probably included among those counted as intact by FITC-PSA staining. The non-incubated cryopreserved spermatozoa had fused plasma and outer acrosomal membranes, and 36.4% of them had vesiculation when observed by TEM. FITC-PSA staining indicated that 22% of the live spermatozoa were acrosome reacted. CONCLUSIONS: Acceleration of the acrosome reaction was evident by both TEM and FITC-PSA. Incubation of cryopreserved spermatozoa for 2 h accelerated vesiculation to a state similar to that of fresh spermatozoa that had been incubated for 8 h. These results reveal that in cryopreserved spermatozoa, the process of acrosome reaction begins before incubation.     

Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis)

This study aimed to clarify the development of sulci and gyri on the external surface of the cerebrum of cynomolgus monkeys. Sulcus formation began with the appearance of the lateral fissure on embryonic day (ED) 70, followed by delineations of four cerebral lobes by the emergence of the parietooccipital sulcus, central sulcus, and preoccipital notch on EDs 80–90. The following primary sulci were then visible until ED 120: the superior temporal sulcus on ED 90; the intraparietal sulcus, lunate sulcus, inferior occipital sulcus, and arcuate sulcus on ED 100; and the principle sulcus on ED 110; the occipitotemporal sulcus, anterior middle temporal sulcus, and superior postcentral dimple on ED 120. These sulci demarcated the superior temporal gyrus on ED 90, the precentral gyrus, supramarginal gyrus, and angular gyrus on ED 100, and the inferior and middle temporal gyri, postocentral gyrus, superior parietal lobule, superior, middle and inferior frontal gyri, and inferior occipital gyrus on ED 120. Except for the intermediate and lateral orbitofrontal sulci, the sulci that appeared on ED 130 and thereafter were not related to the gyrus demarcations. Intriguingly, the brain markedly gained weight on EDs 100 and 120, corresponding to the embryonic ages when almost all gyri were visible. The results suggest that a rapid growth of the cerebrum involves convolutions of the gyri by a regular sequence of the sulcus formation in cynomolgus monkeys. This study further provides a standard of reference for normal development in the cerebral cortical morphology of cynomolgus monkeys.     

Behaviorally elicited heart rate reactivity and atherosclerosis in female cynomolgus monkeys (Macaca fascicularis)

We previously reported that the coronary atherosclerosis of cholesterol-fed, male cynomolgus monkeys (Macaca fascicularis) was exacerbated among animals that exhibited the largest heart rate (HR) reactions to a standard laboratory stressor. Here we report a similar relationship between behaviorally induced HR reactivity and atherosclerosis in females of the same species. Twenty-one female monkeys were fed a moderately atherogenic diet for 30 months. Near the end of this period, animals were fitted with electrocardiogram telemetry devices and their HRs were recorded under baseline and stressed conditions. Stress period HR measurements were obtained during a standard challenge involving threatened capture and physical handling of the animals. At necropsy, sections taken from the left anterior descending, left circumflex, and right coronary arteries were examined histologically. Mean intimal area measurements were then compared between animals identified as High (n = 7) and Low (n = 7) HR reactors. High HR reactive animals were found to have significantly greater coronary artery atherosclerosis than Low reactors; atherosclerosis at the right carotid bifurcation also differed significantly between High and Low reactive monkeys. Groups did not differ in baseline HR, blood pressure, and total or HDL cholesterol concentrations. Relative to Low HR reactors, however, High reactive animals weighed less and were less ponderous, had greater heart weights (adjusted for differences in body weight), were behaviorally less aggressive, and had lower luteal phase progesterone concentrations. These relationships were corroborated in correlation analyses employing data of all 21 study animals.     

Structure and growth activities of the mandibular condyle in monkeys (Macaca fascicularis): I. Intracondylar variations

Eight condyles of four growing monkeys (Macaca fascicularis) of estimated ages between 1.6 and 3.6 years (minimum and maximum) were analyzed using radioautographic, histometric, and stereologic techniques. The aim of the study was to examine the relationship between intracondylar variations in structure and growth activities. The animals received ³H-proline (1 mCi/kg body weight) and ³H-thymidine (0.5 mCi/kg body weight) 24 and 3 hours, respectively, prior to sacrifice. The perichondral and chondral layers of the condylar articular covering as well as the subchondral zone of erosion were examined at different sampling sites distributed systematically in the anteroposterior and lateromedial dimension of the articulating surface. Intracondylar variations observed with respect to morphometric and radioautographic parameters suggest the following biologic mechanisms contributing to mandibular growth in a superior-posterior direction. Greater mitotic activity at the central and posterior sites of the condylar perichondrium generates a population of progenitor cells that is larger in these than in other regions. On the other hand, the rate of differentiation of these progenitor cells into chondroblasts and chondrocytes, i.e., the “migration” into and through the chondral layers of the articulating covering, seems to be enhanced in the same superior and posterior areas. Additionally, while “migrating” faster, these cartilage cells become larger and produce greater amounts of extracellular matrix than those in the anterior parts of the condyle. Finally, enhanced resorptive activities in the superior and posterior regions of the subchondral zone of erosion provide an increased “loss” of degenerated chondrocytes, thereby establishing the basis for a cartilaginous drift in the superior-posterior direction.     

Cerebral malaria in the rhesus monkey (Macaca mulatta): Light and electron microscopic changes in blood cells and cerebrovascular endothelia

To assess the interaction between the cellular elements of the blood and neurovascular endothelia in cerebral malaria, brain tissue from adult rhesus moneys (Macaca mulatta) infected with a virulent (W1) strain of Plasmodium knowlesi were studied by light and electron microscopical techniques. Light microscopical examination showed sequestration of macrophages and margination of erythrocytes containing late stages of the parasite in the capillaries and venules throughout the brains of the infected monkeys. Brain microvascular lesions (associated with parasitised erythrocytes and macrophage attachment to vascular walls) seen with the electron microscope, were swelling of the endothelial cells, formation of pseudopodia, increased numbers of pinocytotic vesicles and disorganisation of the mitochondria. Parasitised mature erythrocytes and macrophages adhered to the vascular endothelial lining in equal proportions. The endothelial ultrastructural alterations were similar to those described in experimental rodent and in clinical human cerebral malaria.