Utility of Orchidometric Parameters for Assessing Sexual Maturation in Male Cynomolgus Macaques (Macaca fascicularis)

Testicular volume is one of several parameters that have been used in preclinical toxicology to facilitate the identification of sexually mature male cynomolgus macaques when semen evaluation is unavailable. Furthermore, testicular volume provides additional information to pathologists to aid in the interpretation of microscopic findings. Orchidometry has been proposed as a useful tool for assessing testicular volume. To assess its utility for this purpose, we used orchidometry to measure testicular volume in untreated control male cynomolgus macaques during preclinical toxicology studies. Additional parameters including age, body weight, testicular weight, serum testosterone, and testicular histology were also evaluated. Serum inhibin B and the diameter of histologic testicular sections were assessed to determine whether they might provide any additional corroborative evidence for differentiating stages of sexual maturity in males. Orchidometry was easy to use in sedated or awake macaques and, in combination with testicular histology, enabled the establishment of cut-off values by which sexually mature male cynomolgus macaques can be identified with a high degree of confidence. The relative utility of the parameters examined for discriminating sexually mature and immature males was testicular volume ≥ serum testosterone > body weight > age; for differentiation of sexually mature and peripubertal males the order was testicular volume ≥ body weight > serum testosterone > age. Testicular weight and the diameter of histologic testicular sections provided corroborative information for discriminating stages of sexual maturity. Serum inhibin B was of little value in helping to differentiate the different stages of sexual maturation evaluated in this study.

Morphometric examination for development of reproductive organs in male cynomolgus monkeys

We previously reported on a histological classification of cynomolgus monkey testis into six grades (1, immature; 2, prepuberty; 3, onset of puberty; 4, puberty; 5, early adult; 6, adult) based on spermatogenesis development. In this investigation, the accessory reproductive organs from the same animals underwent histomorphometric examination, in addition to being examined histologically and weighed, to evaluate relationships between these parameters and the six grades. Seminiferous tubule diameter increased corresponding to the testicular maturity grade and was notably increased at grade 6. Beginning from grade 3, increases in the areas of the ductus epididymis were noted, and reserved sperm was visible in the lumen. In the prostate, the glandular lumen area per unit area showed an increase beginning from grade 3 but no clear differences between grades 4 and 6; advanced development of epithelial height was observed at grade 6. In the seminal vesicle, development of the epithelial cell layer was markedly increased at grade 6. It was concluded that development of the male accessory reproductive organs began after reserved sperm was observed in the lumen of the ductus epididymis (grade 3) and that these organs were developed notably when the testis reached sexual maturity (grade 6).

Tubular anomalous bones found in both thighs of a long-tailed macaque (Macaca fascicularis)

Tubular anomalous bones were found in both thighs of a 6-year-old male long-tailed macaque (Macaca fascicularis) bred in captivity. The bones had jagged ends and protruded from the skin. Radiographs showed that they developed in the femurs at the middle and elongated. They were removed with surgery under anesthesia. Histological analysis revealed that these bones had the same histological structure as the femur, though they were composed of primary and secondary osteon regions. This finding indicated that the new bones developed from the old bone piece(s), acquired a tubular shape, and elongated. It is suggested that the anomalous bones were produced not by the congenital deformity but by regeneration from fragments of the fractured femur that were embedded in the bone marrow; these acquired a tubular pattern and elongated.

Biologic data of Macaca mulatta, Macaca fascicularis, and Saimiri sciureus used for research at the Fiocruz primate center

Physiological parameters of laboratory animals used for biomedical research is crucial for following several experimental procedures. With the intent to establish baseline biologic parameters for non-human primates held in closed colonies, hematological and morphometric data of captive monkeys were determined. Data of clinically healthy rhesus macaques (Macaca mulatta), cynomolgus monkeys (Macaca fascicularis), and squirrel monkeys (Saimiri sciureus) were collected over a period of five years. Animals were separated according to sex and divided into five age groups. Hematological data were compared with those in the literature by Student's t test. Discrepancies with significance levels of 0.1, 1 or 5% were found in the hematological studies. Growth curves showed that the sexual dimorphism of rhesus monkeys appeared at an age of four years. In earlier ages, the differences between sexes could not be distinguished (p < 0.05). Sexual dimorphism in both squirrel monkeys and cynomolgus monkeys occurred at an age of about 32 months. Data presented in this paper could be useful for comparative studies using primates under similar conditions.

VEGF expression by ganglion cells in central retina before formation of the foveal depression in monkey retina: evidence of developmental hypoxia

In macaque monkeys the foveal depression forms between fetal day (Fd) 105 and birth (Fd 172 of gestation). Before this, the incipient fovea is identified by a photoreceptor layer comprising cones almost exclusively, a multilayered ganglion cell layer (GCL), and a "domed" profile. Vessels are absent from the central retina until late in development, leading to the suggestion that the GCL in the incipient fovea may be transitorily hypoxic. Vascular endothelial growth factor (VEGF), expressed by both glial and neuronal cells and mediated by the hypoxia-inducible transcription factor (HIF)-1, is the principal factor involved in blood vessel growth in the retina. We examined VEGF expression in macaque retinas between Fd 85 and 4 months postnatal. Digoxygenin-labeled riboprobes were generated from a partial-length human cDNA polymerase chain reaction fragment, detected using fluorescence confocal microscopy, and quantified using Scion Image. High levels of VEGF mRNA were detected in astrocytes associated with developing vessels. We also detected strong expression of VEGF mRNA in the GCL at the incipient fovea prior to Fd 105, with peak labeling in the incipient fovea that declined with distance in nasal and temporal directions. By Fd 152 peak labeling was in two bands associated with development of the inner nuclear layer (INL) capillary plexus: in the inner INL where Müller and amacrine cell somas are located, and in the outer INL where horizontal cells are found. The findings suggest that at the incipient fovea the GCL is hypoxic, supporting the hypothesis that the adaptive significance of the fovea centralis is in ensuring adequate oxygen supply to neuronal elements initially located within the avascular region.

Methods for predicting sexual maturity in male cynomolgus macaques on the basis of age, body weight, and histologic evaluation of the testes

In pharmaceutical drug safety testing, sexual maturity is an important experimental parameter. Histologic immaturity of the tissues of the reproductive system can interfere with the interpretation of compound-related effects on the reproductive organs. In female cynomolgus macaques, determination of sexual maturity is simplified by the presence of a menstrual cycle. For male cynomolgus macaques, predicting maturity is much more difficult. In this study, we evaluated methods that would reliably predict sexual maturity in male cynomolgus macaques. The results of histologic examination of testes of control male cynomolgus macaques used for drug safety studies were examined retrospectively for evidence of sexual maturity. These data were compared with age and body weight determinations to establish statistical models for determining the probability that a male cynomolgus macaque is sexually mature. This model presents a simple prospective method of predicting sexual maturity in male cynomolgus macaques.

Between-species variation in the development of hand preference among macaques

This research examined between-species variation in the development of hand preference among Macaca. Specifically, we examined hand preference using juveniles and adults of three macaque species that differ in social and reactive tendencies in order to examine whether the correlation between temperament and handedness that has been noted within Macaca mulatta occurs between closely related species. Each of the species studied exhibited a different pattern of hand preference development. Both juvenile and adult M. mulatta exhibited group-level left-hand bias. Juvenile Macaca nemestrina were not biased towards either hand at the group-level, whereas adults exhibited a group-level left-hand bias. Neither juvenile nor adult Macaca fascicularis exhibited manual bias at the group-level. Analysis of variance indicated statistically significant main effects of species and age class on hand preference measures. Post-hoc analysis indicated greater use of the left- versus right-hand, and greater hand preference strength independent of direction, among M. mulatta and M. nemestrina than among M. fascicularis, and among adults than among juveniles. These results indicate significant between-species variation in the development of hand preference within the genus Macaca, and are inconsistent with any one single-factor theory yet offered to explain the etiology of primate laterality. We hypothesize that the relationship between handedness and temperament that has been shown within M. mulatta may generalize across closely related primate species.

Localization of immunoreactive testosterone and 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase in cynomolgus monkey (Macaca fascicularis) testes during postnatal development

The age-related expression of testosterone and 3beta-HSD in the testes of cynomolgus monkeys was detected using light-microscopic immunocytochemistry. Intense deposits of immunoreactive testosterone were labeled in parts of Leydig cells in neonatal, late infantile, pubertal, and adult testes, and only a few Leydig cells in early infantile testes. The immunoreactive 3beta-HSD was labeled in parts of Leydig cells and in all Sertoli cells in neonatal, late infantile, pubertal, and adult testes, whereas only a few Leydig cells, but no Sertoli cells, were labeled in early infantile testes. The fluctuations of testosterone and 3beta-HSD expression in testes correlated well with those already observed plasma testosterone levels during postnatal development in cynomolgus monkeys.

Distribution and development of short-wavelength cones differ between Macaca monkey and human fovea

Macaca monkey and humans have three cone types containing either long-wavelength (L), medium-wavelength (M), or short-wavelength (S)-specific opsin. The highest cone density is found in the fovea, which mediates high visual acuity. Most studies agree that the adult human fovea has a small S cone-free area, but data are conflicting concerning S-cone numbers in the adult Macaca monkey fovea, and little evidence exists for how either primate fovea develops its characteristic cone pattern. Single- and double-label in situ hybridization and immunocytochemistry have been used to determine the pattern of foveal S cones in both the fetal and adult Macaca and human. Both labels find a clear difference at all ages between monkey and human. Adult humans have a distinct but variable central zone about 100 microm wide that lacks S cones and is surrounded by a ring in which the S-cone density is 8%. This S cone-free zone is detectable at fetal week 15.5 (Fwk15.5), shortly after S opsin is expressed, and is similar to the adult by Fwk20.5. Adult monkey foveas have an overall S-cone foveal density of 10%, with several areas lacking a few S cones that are not coincident with the area of highest cone density. A surrounding zone at 200-microm eccentricity has an S-cone density averaging 25%, but, by 800 microm, this has decreased to 11%. Fetal day 77-135 monkeys all have a distribution and density of foveal S cones similar to adults, although the high-density ring is not obvious in fetal retinas. Estimates of the numbers of S cones missing in the fetal human fovea range from 234 to 328, whereas no more than 40 are missing in the fetal monkey. These results show that, in these two trichromatic primates, S-cone distribution and the developmental mechanisms determining S-cone topography are markedly different from the time that S cones are first detected.

Macaque MDC family of proteins: sequence analysis, tissue distribution and processing in the male reproductive tract

A large number of sequence-related, cysteine-rich membrane proteins containing metalloproteinase-like and disintegrin-like domains (the MDC protein family) have been identified in mammalian tissues from a variety of species. Previous studies in the macaque (Macaca fascicularis) have led to the cDNA cloning and sequence analysis of a number of MDC proteins which are abundantly expressed in the male reproductive tract. We now describe the distribution of seven of these macaque MDC transcripts in a range of different tissues. This description includes a novel macaque testis-derived MDC, tMDC III, whose full-length sequence is reported for the first time. In addition, polyclonal antisera have been used to localize a number of these MDC proteins to spermatogenic cells in testis sections, and to demonstrate their processing on the sperm surface during epididymal transit.

Lack of effect of methylmercury exposure from birth to adulthood on information processing speed in the monkey

Although it is established that developmental methylmercury exposure produces severe motor and sensory impairment, the effect on cognitive function is less clear. To explore this issue, monkeys with robust methylmercury-induced deficits in visual, auditory, and somatosensory function were tested on a series of tasks assessing central processing speed, which is highly correlated with intelligence in humans. Five monkeys (Macaca fascicularis) were dosed from birth to 7 years of age with 50 micrograms/kg/day of mercury as methylmercuric chloride. Blood mercury levels were stable at 0.8-1.1 micrograms/g until cessation of dosing. When they were 20 years old, these monkeys and four age- and rearing-matched controls were tested on a series of simple and complex reaction time tasks. The monkey sat in a primate chair with a stainless steel bar centered at waist height. Four push buttons equidistant from the steel bar were mounted on a vertical Plexiglas panel in front of the monkey. The monkey was required to make contact with the bar, then release the bar and push the appropriate button in response to a change in stimulus conditions. For the first task (simple reaction time), the monkey was required to respond on a button when it changed from unlit to red. The monkey then performed a sequence of complex reaction time tasks: two-button, four-button, and several tasks of increasing complexity using four buttons and multiple colors. For each task, the latency to release the bar after the stimulus change (central processing speed) and to move the hand from the bar to the button (motor speed) were determined. Lastly, the monkey was required to make the quickest possible motor response on the simple reaction time task. There were no differences between groups on any aspect of the experiment. These data provide further evidence for absence of cognitive impairment in monkeys exposed developmentally to methylmercury.

An electrophysiological study of the postnatal development of the corticospinal system in the macaque monkey

Postnatal development of the corticospinal system was investigated in 13 macaques using noninvasive transcranial magnetic stimulation (TMS) of the motor cortex and direct electrical stimulation of corticospinal axons in the medullary pyramid and spinal cord. The latency of antidromic corticospinal volleys evoked from the pyramid and recorded from the motor cortex decreased dramatically during the first postnatal months. Our data predict that conduction velocity (CV) of the fastest corticospinal neurons over their cranial course would reach adult values at approximately 11 months. The CV of corticospinal neurons in the spinal cord increased with age but with a slower time course. In the neonate, the fastest spinal CV was estimated at 7.8 m/sec, approximately 10 times slower than in adults (mean 80.0 m/sec). Our data predict that full myelination of corticospinal axons in the spinal cord would not occur until approximately 36 months. No short-latency EMG responses were elicited in arm and hand muscles by TMS until 3 months of age; TMS thresholds were high initially and then fell progressively with age. When corrected for body size, relative latencies of EMG responses showed an exponential decrease during the first postnatal months. Our data are consistent with the hypothesis that fine finger movements are not observed before functional CM connections are well established and that rapid changes in the physiological properties of the corticospinal system coincide with the period in which precision grip is known to mature (3-6 months). However, corticospinal development continues long after simple measures of dexterity indicate functional maturity, and these changes may contribute to the improved speed and coordination of skilled hand tasks.

Role of directed growth and target selection in the formation of cortical pathways: prenatal development of the projection of area V2 to area V4 in the monkey

In experiments combining retrograde tracers and histochemistry, we have looked at the prenatal development of the cortical pathway linking areas V2 and V4. Transient expression of acetylcholinesterase in fetal area V2 reveals the separate compartments that project to V4 (temporal directed pathway) and V5 (parietal directed pathway). During early stages of pathway formation, V2 neurons projecting to area V4 are clustered in the appropriate compartments. During the phase of rapid axonal growth, there is a selective increase of connections originating from the appropriate compartments leading to a strongly clustered organization at the peak of connectivity. During this phase, injections involving the white matter also showed clustering, but this was somewhat reduced in comparison to that of gray matter injections. The growth phase is followed by an elimination phase during which there is a tendency for a preferential loss of intercluster connections, which may sharpen the early formed pattern. These results demonstrate the primary role of axonal guidance and target recognition mechanisms followed by a limited extent of selective elimination during the formation of functional cortical pathways in the primate isocortex. Compared to previous findings, these results suggest that the developmental restriction of callosal connections is not a universal model of cortical development. In the present report, the directed growth and early specification of feed-forward connections contrast with the prolonged remodelling of monkey feedback projections, suggesting two distinct developmental strategies of pathway formation in the monkey.

Serum kappa and lambda light immunoglobulin chains in cynomolgus macaques (Macaca fascicularis) during the first twenty months of age

Growth is coupled to physiological modifications of the immune system which reaches the functional capabilities according to age-related milestones. Few data are available on the circulating immunoglobulin levels and no data exist on total immunoglobulin light chains in infant macaques. Therefore we studied by a nephelometric assay, the age-dependent variations of kappa and lambda serum light chains in the experimental animal model Macaca fascicularis during the first 20 months of age. Both kappa and lambda showed a marked increase in their concentrations during the first 7-8 months of life. Infants' light chain levels were anyhow significantly lower than those of the nursing dams and of the control group, never attaining, even at the 20th month, the same concentration as the adult, although the value of the kappa/lambda ratio was apparently the same.

Contribution of thalamic input to the specification of cytoarchitectonic cortical fields in the primate: effects of bilateral enucleation in the fetal monkey on the boundaries, dimensions, and gyrification of striate and extrastriate cortex

Bilateral enucleation was performed at different fetal ages during corticogenesis, and the brains were prepared for histological examination. Early-enucleated fetuses (operated prior to embryonic day 77) showed morphological changes at the level of the thalamus and the cortex. In the thalamus, there was a loss of lamination and a decrease in size of the lateral geniculate nucleus. There was a decrease in the size of the inferior pulvinar, but there was no change in the lateral pulvinar. The border of striate cortex was as sharp in the enucleates as it was in the normal monkeys. In three of the four early enucleates, we observed an interdigitation of striate and extrastriate cortex. In three of the early enucleates, we observed a small island of nonstriate cortex near the striate border that was surrounded entirely by striate cortex. Enucleation led to an age-related reduction of striate cortex. This reduction was greater in the operculum than in the calcarine fissure. The reduction of striate cortex was accompanied by an increase in the dimensions of extrastriate visual cortex, so that the overall dimensions of the neocortex remained invariant. The extrastriate cortex in the enucleated animals presented a uniform cytoarchitecture and was indistinguishable from area 18 in the normal animal. There were changes in the gyral pattern that were restricted mainly to the cortex on the operculum. A deepening of minor dimples as well as the induction of a variable number of supplementary sulci led to an increase in the convolution of the occipital lobe. These results are discussed with respect to the specification of cortical areas. They demonstrate that the reduction in striate cortex was not accompanied by an equivalent reduction in the neocortex; rather, there was a border shift, and a large volume of cortex that was destined to become striate cortex appears to be cytoarchitectonically normal extrastriate cortex.

[A feeding experiment on laboratory-bred male cynomolgus monkeys. I. Morphometrical study]

Effects of restricted feeding on the growth of laboratory-bred male cynomolgus monkeys (Macaca fascicularis) aged between one year and four years were studied morphometrically. A series of 11 variables representing physical elements were measured. Before 2.5 years of age, the amount of commercial diet (Type AS, 382kcal/100g and 28.1% of crude protein, Oriental Yeast Co. Ltd.) per day was restricted to 50g (group A), 30g (group B) or 20g (group C) and increased to 100g (group A), 50g (group B) or 40g (group C) respectively at 2.5 years old. Throughout the experimental period ca 100g of apples and oranges per day were provided. Significant differences in body weight between group A and C were detected excepting the early period of the experiment. Although the slight suppression in weight gain was observed in group B during the second trimester of the experiment, body weight increased gradually after increasing the amount of food and no significant difference from A was observed at four years of age. The minimum requirement of diets is judged to be 30g/day before two years old and 50g/day over two years old in the laboratory-bred male cynomolgus monkey. Moreover, the suppressive effects of restricted feeding were most significant on the growth of the limbs and, secondarily, on the growth of the trunk. Practically no effect on the growth of the head was observed.

Early follicle growth in the juvenile macaca monkey ovary: the effects of estrogen priming and follicle-stimulating hormone

The mechanism(s) that drives preantral and early antral follicle growth in the primate ovary is poorly understood. We previously reported that estrogen does not stimulate preantral or early antral follicle growth in juvenile primates. The purpose of the present study was to determine whether estrogen priming may play a role in enhancing FSH-stimulated follicle growth. Eight juvenile monkeys received implants on Day 1 of silastic capsules containing estradiol (or vehicle) to elevate circulating estradiol levels. Daily FSH injections were initiated on Day 4 and continued for up to 12 days. The left ovary was removed on Day 8 and served as a control. Ovulation was induced, and a luteal phase followed. On the first day of menses, the estradiol (vehicle) capsule-FSH protocol was repeated. The remaining ovary was removed on Day 8 of the second cycle. The number and size of all follicles in both ovaries were evaluated by light microscopy. Results indicate that estrogen priming in the first cycle did not enhance growth of preantral or antral follicles, but did result in fewer developing follicles > 1.0 mm in diameter, this was accompanied by an increase in early atretic antral follicles of similar size. In the second cycle, an even further reduction in number and size of developing antral follicles > 1.0 mm in diameter was observed. These data suggest that pretreatment with exogenous estrogen has an anti-follicular action on follicle growth in these primates.

A coordinate-free approach to the analysis of growth patterns: models and theoretical considerations

Developmental biology holds keys to our understanding of morphological pattern formation whether these patterns are expressed in the fossil record or among extant species. Though much is known about osseous growth at the cellular level (e.g. Hall, 1991), we have minimal understanding of the coordinated processes that combine to produce a complex, three-dimensional form. We have proposed a framework for the coordinate-free representation of form, a statistical method for comparing and modelling growth trajectories for complex morphologies, and a means for the eventual elucidation of the role of growth in the evolution of morphology. Our method uses the coordinate locations of biological landmarks to represent form as a matrix of all possible linear distances between landmarks, the form matrix. When two forms are expressed in this way, comparison of these forms is accomplished by computing the ratios of like linear distances, the form difference matrix. When the forms being compared are from a growth series, the matrix of ratios is called a growth matrix. Patterns of growth for two groups can be compared by computing the growth difference matrix. We applied growth difference matrix analysis to the study of sexual dimorphism of ontogeny in the M. fascicularis craniofacial skeleton. Growth matrices describing growth in male and female M. fascicularis were presented along with the growth difference matrix that describes sexual dimorphism of growth to underscore the detailed information available from this analytical technique. The method is quite general and can be applied to two- or three-dimensional data sets of landmark coordinates (cross-sectional or longitudinal) collected from almost any developing structure. The methods that we propose enable us to go beyond a mathematical summary of the comparison of forms and the comparison of growth patterns. We provide examples of how growth patterns might be used in the study of phylogenetic relationships. Our plans for use of this method in the study of evolutionary change assumes that morphological change in the craniofacial skeleton results from evolutionary change in developmental units (as defined by Atchley & Hall, 1991) that underlie morphological structure. We believe we have the basic tools to ultimately propose informed phylogenies based solely on developmental data. This task requires the identification of 'growth features' and the polarization of these features as primitive or derived. It is also advisable to determine a set of primitive growth features for the groups of interest. This will necessitate the inclusion of outgroups in our growth analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

[Relative growth of physiques in laboratory-bred cynomolgus monkeys: a longitudinal study during the first 6 years of life]

Physical growth was studied longitudinally in laboratory-bred cynomolgus monkeys (Macaca fascicularis) aged from birth to 6.0 years in females and to 6.5 years in males. An allometric formula was applied to morphometrical growth data and the relative growth of each morphological site to anterior trunk length was analyzed. The growth patterns of all of the measurement sites in females and most of the sites in males showed monophasic allometry; while those of head length, head breadth and morphological upper face length in males were judged to show diphasic allometry. The growth patterns of morphological total face length, upper arm length and lower arm length in some males showed diphasic allometry. Morphological measurements with negative allometry were head length, head breadth, morphological total face length, total head height, biacrominal breadth hand length and foot length, while the other morphological measurements revealed isometry in both sexes. However, the values of the relative growth coefficient to anterior trunk length were larger in males than in females, except for in the case of biiliac breadth. These differences in growth patterns may cause the morphological differences between genders after sexual maturation in this primate species.

[Morphometrical study of physical growth of laboratory-bred cynomolgus monkeys: a longitudinal study during the first 6 years of life]

Physical growth was studied longitudinally in laboratory-bred cynomolgus monkeys (Macaca fascicularis) aged between zero and 6.0 years (females), and between zero and 6.5 years (males). A series of 17 variables representing physical elements were measured in 12 females and 10 males. Rates of increase in morphological total face length and morphological upper face length were somewhat larger than rates of increase in head length and head breadth. Trunk traits showed relatively high growth rates compared to those of leg and arm traits. Growth functions (Gompertz, logistic and quadratic equations) were applied to the growth data. The quadratic equation had the closest fit to the morphometrical growth data in this primate species.

Postnatal development of skull base, neuro- and viscerocranium in man and monkey: morphometric evaluation of CT scans and radiograms

Postnatal development of the neuro- and viscerocranium with special reference to the maxillodental structures was studied morphometrically by analyzing computer tomograms and radiograms of human and monkey heads of different age groups. The following parameters were used: the prognathic angle, the clivus angle, the palate-incisivus angle, the interincisival angle and the viscerocranial quotient. In the newborn primates including man, all parameters measured were relatively similar; postnatally, however, characteristic differences in the growth pattern between man and monkey were developing. In monkey, a marked prognathic growth of the viscerocranium was found associated with characteristic positional changes of the frontal teeth, whereas the growth of the neurocranium was retarded. Here, unlike the human, a flattening of the skull base was observed. In contrast, the human skull showed no major proportional changes during its postnatal development compared with the original spherical skull form of the newborn.

[Morphometrical study of physical growth of laboratory-bred cynomolgus monkeys aged from zero to 9 years]

The relative growth was examined in laboratory-bred cynomolgus monkeys (Macaca fascicularis) aged from zero to 9 years. The principal component analysis and multivariate allometry were applied to the biometrical data. As the result of the principal component analysis, the cumulative contribution ratio of the 1 st (PC 1) and 2 nd (PC 2) principal components accounted for 99.0 percent. According to the eigen vector values of each morphological site (14 sites), PC 1 was acceptable not only as a size factor but also as a shape factor of the morphological growth changes from birth to the 3rd year of life in both sexes. PC 2 was acceptable as a shape factor of the morphological differences between sexes after the 3rd year of life. As the result of the multivariate allometric analysis applied to the same data, proximate sites of the trunk showed relatively high growth rates compared to distal ones of the trunk. The head, limbs and arms grew slowly in contrast to the trunk. Thus, we could demonstrate the relative growth of cynomolgus monkeys morphometrically.

Lead-induced behavioral impairment on a spatial discrimination reversal task in monkeys exposed during different periods of development

A total of 52 monkeys (Macaca fascicularis) were dosed orally with vehicle or 1.5 mg/kg/day of lead on one of four dosing regimens (13 monkeys/group): Group 1, vehicle only; Group 2, dosed with lead from birth onward; Group 3, dosed with lead from birth to 400 days of age and vehicle thereafter; Group 4, dosed with vehicle from birth to 300 days of age and lead thereafter. Blood lead concentrations averaged 3-6 micrograms/dl when monkeys were not being dosed with lead, 32-36 micrograms/dl when being dosed with lead and having access to infant formula, and 19-26 micrograms/dl when being dosed with lead after weaning from infant formula. When monkeys were 7-8 years old, they were tested on three spatial discrimination reversal tasks: no irrelevant cues, irrelevant form cues, and irrelevant form and color cues. Fifteen reversals were run for each task. Only Group 2 was impaired in the absence of irrelevant cues, while all three treated groups were impaired in the presence of irrelevant cues. These results are in contrast to results from a series of nonspatial discrimination reversal tasks in these monkeys in which Groups 2 and 4 were impaired and Group 3 was unimpaired. The present results are in agreement with results from another spatial task, delayed alternation, in which all three treated groups were impaired.

Lead-induced behavioral impairment on a spatial discrimination reversal task in monkeys exposed during different periods of development

A total of 52 monkeys (Macaca fascicularis) were dosed orally with vehicle or 1.5 mg/kg/day of lead on one of four dosing regimens (13 monkeys/group): Group 1, vehicle only; Group 2, dosed with lead from birth onward; Group 3, dosed with lead from birth to 400 days of age and vehicle thereafter; Group 4, dosed with vehicle from birth to 300 days of age and lead thereafter. Blood lead concentrations averaged 3-6 micrograms/dl when monkeys were not being dosed with lead, 32-36 micrograms/dl when being dosed with lead and having access to infant formula, and 19-26 micrograms/dl when being dosed with lead after weaning from infant formula. When monkeys were 7-8 years old, they were tested on three spatial discrimination reversal tasks: no irrelevant cues, irrelevant form cues, and irrelevant form and color cues. Fifteen reversals were run for each task. Only Group 2 was impaired in the absence of irrelevant cues, while all three treated groups were impaired in the presence of irrelevant cues. These results are in contrast to results from a series of nonspatial discrimination reversal tasks in these monkeys in which Groups 2 and 4 were impaired and Group 3 was unimpaired. The present results are in agreement with results from another spatial task, delayed alternation, in which all three treated groups were impaired.

Nerve growth factor in the primate central nervous system: regional distribution and ontogeny

An enzyme immunoassay for nerve growth factor was developed to determine the regional distribution and ontogenic change in the macaque (Macaca fascicularis) CNS. The standard curve of mouse nerve growth factor paralleled the dilution curves of extracts from the primate CNS at the adult and pre-natal stages. Furthermore, the nerve growth factor immunoreactive material comigrated with mouse nerve growth factor by means of carboxy methyl cellulose chromatography. These findings suggest that the immunoreactive material extracted from the primate CNS is mouse nerve growth factor-like molecules. At the adult stage, the highest level of nerve growth factor was in the hippocampus, with relatively high levels also in the hypothalamus, the cerebral cortex, the amygdala, the basal nucleus of Meynert, the septal nucleus, the cerebellum and the caudate nucleus. No detectable amounts were observed in the spinal cord, the substantia nigra or the dentate nucleus. In addition to the CNS, the pituitary gland contained about four times the level found in the hippocampus. At embryonic day 120, a high level of nerve growth factor already existed in the occipital cortex (80% of the level at the adult stage) and in the hippocampus (70% of the level at the adult stage). Between embryonic day 120 and the newborn stage in the occipital cortex and between embryonic day 120 and postnatal day 60 in the hippocampus, nerve growth factor levels increased about 1.7-fold, and after that, they gradually decreased until the adult stage was reached. In contrast, in the cerebellum, the level was quite high during the pre-natal period and declined to one-third at postnatal day 60. The developmental changes in nerve growth factor and choline acetyltransferase activity in the hippocampus were well correlated (r = 0.963) between embryonic day 120 and postnatal day 60. Our studies reveal that nerve growth factor is present in the primate CNS. The high level of nerve growth factor during embryonic stages and the good correlation with choline acetyltransferase activity suggest a physiological role for nerve growth factor in the development of the primate CNS.

Extrinsic determinants of retinal ganglion cell development in primates

As in all mammals studied to date, primate retina contains morphologically distinct classes of retinal ganglion cells (Polyak: The Retina. Chicago: University of Chicago Press, '41; Boycott and Dowling: Philos. Trans. R. Soc. Lond. [Biol.] 225:109-184, '69; Leventhal et al.: Science 213:1139-1142, '81; Perry et al.: Neuroscience 12:1101-1123, '84; Rodieck et al.: J. Comp. Neurol. 233:115-132, '85; Rodieck: In H.D. Steklis and J. Erwin (eds): Comparative Primate Biology, Volume 4: Neurosciences. New York: Alan R. Liss, Inc., pp. 203-278, '88). We have now studied the morphologies, central projections, and retinal distributions of the major morphological classes of ganglion cells in the normal adult monkey, the newborn monkey, and the adult monkey in which restricted regions of retina were depleted of ganglion cells at birth as a result of small lesions made around the perimeter of the optic disc. Both old-world (Macaca fascicularis) and new-world (Saimiri sciureus) monkeys were studied. Our results indicate that, at birth, the major morphological classes of monkey retinal ganglion cells are recognizable; cells in central regions are close to adult size whereas cells in peripheral regions are much smaller than in the adult. As in the adult (Stone et al.: J. Comp. Neurol. 150:333-348, '73), in newborn monkeys there is a very sharp division between ipsilaterally and contralaterally projecting retinal ganglion cells (nasotemporal division). Consistent with earlier work (Hendrickson and Kupfer: Invest. Ophthalmol. 15:746-756, '76) we find that the foveal pit in the neonate is immature and contains many more ganglion cells than in the adult. In the adult monkey in which the density of retinal ganglion cells in the central retina was reduced experimentally at birth, the fovea appeared immature, and an abnormally large number of retinal ganglion cells were distributed throughout the foveal pit. The cell bodies and dendritic fields of ganglion cells that developed within cell-poor regions of the central retina were nearly ten times larger than normal. In peripheral regions the effects were smaller. The dendrites of the abnormally toward the foveal pit. They did not extend preferentially into the cell-poor region as do the abnormally large cells on the borders of experimentally induced cell-poor regions of cat central retina (Leventhal et al.: J. Neurosci. 8:1485-1499, '88) or, as we found here, in paracentral regions of primate retina.(ABSTRACT TRUNCATED AT 400 WORDS)

[Morphometrical study of physical growth in infant cynomolgus monkeys using multivariate analysis]

We describe the relative growth in infant cynomolgus monkeys (Macaca fascicularis). The multivariate analyses using the principal component analysis and multivariate allometric analysis were applied to biometrical data of laboratory-bred cynomolgus monkeys aged from birth to 12 weeks. All the animals had been bred and reared under uniform environmental conditions at Tsukuba Primate Center for Medical Science, N. I. H., Japan. As the result of the principal component analysis, the cumulative contribution ratio of the 1st and 2nd principal components (PC1 and PC2) accounted for 88.2% and 85.7% in males and females, respectively. This indicates that the morphologic traits (15 traits) grow normally in size, but the analysis did not detect any differences in growth rate among the traits. So, the multivariate allometric analysis was applied to the same data. The traits concerning the face and truck showed relatively high growth rates compared to head breadth, whereas the limbs and arms grew slowly.

Absence of interhemispheric connections of area 17 during development in the monkey

Our understanding of the development of cortical connectivity largely stems from studies of the ontogeny of interhemispheric pathways in carnivores, rodents and lagomorphs. Early in development, cortical neurons projecting to the contralateral hemisphere through the corpus callosum (callosal projection neurons) have a widespread distribution. As maturation proceeds, callosal projection neurons become restricted to those cortical regions that are connected in the adult. In newborn cats and rats, for example, callosal projection neurons are not restricted to the 17-18 border as in the adult, but are found throughout areas 17 and 18. The macaque monkey is an exception, because at birth it has an adult-like distribution of callosal projection neurons in area 18, with practically none in area 17. Here we show that whereas area 17 is devoid of interhemispheric connections throughout prenatal development, the distribution of callosal projection neurons in area 18 shows the common sequence of an early widespread distribution followed by regression. The absence of callosal projection neurons in area 17 throughout ontogeny may well be a feature unique to Old World primates.

[Multivariate analysis of hematological and serum biochemical values in female cynomolgus monkeys (Macaca fascicularis) aged less than a year]

Hematological and serum biochemical data obtained from 91 laboratory-bred cynomolgus monkeys (Macaca fascicularis) aged 11 to 362 days were analyzed by the discriminant analysis. All animals used had been bred and reared under uniform environmental conditions at Tsukuba Primate Center for Medical Science, N. I. H., Japan. The examination items were as follows: red blood cell count (RBC), hematocrit value (Ht), hemoglobin concentration (Hb), mean corpuscular volume (MCV), white blood cell count (WBC), glutamic oxaloacetic transaminase activity (GOT), glutamic pyruvic transaminase activity (GPT), total protein concentration (TP), albumin concentration (ALB), albumin-globulin ratio (A/G), blood urea nitrogen (BUN), glucose concentration (GLU), total cholesterol concentration (TCHO), free cholesterol concentration (FCHO), triglyceride concentration (TG), alkaline phosphatase activity (ALP) and calcium concentration (Ca). The animals were divided into four groups (A: Suckling infants, less than 176 days old. B, C, D: Weanlings and juveniles, 121 to 220 days old, 221 to 280 days old, and 281 to 362 days old, respectively). Discrimination was possible among these four groups on the basis of the Mahalanobis' generalized distance. Regarding the canonical discriminant analysis (discriminant analysis with reduction of dimensionality), discrimination was possible. The suckling infant group could be discriminated from the juvenile groups by the first canonical variate. Concerning the juvenile groups, age was highly correlated to the value of the second canonical variate.2+ Judging from an approximate relative eigenvector value for the second canonical variate, the effective discriminant variables were WBC, TP, ALB, A/G, FCHO, TG, and ALP. It can be concluded that these eight parameters are important and useful for monitoring the physiologicals conditions of growing juvenile monkeys.

Comparative effect of cyclosporin A and G on weight gain of primates during the pubertal growth period

A double-blind study with six cynomolgus monkeys (mean age, 2.0 years) was carried out. All animals received immunosuppression therapy with 16 mg/kg/day of cyclosporin A or G (Norvaline cyclosporine), given intramuscularly in two divided daily dosages. All animals received a small dosage of steroids (0.1 mg/kg/day). After 14 months the dosage of cyclosporin G was increased to 20 mg/kg/day. During the first study year, weight velocity was normal in the cyclosporin G group and impeded in the group receiving cyclosporin A. During the second year of the study, the weight velocity was impeded in both groups. The weight gain was significantly less in the cyclosporin A group than in the group receiving cyclosporin G (p = 0.001). The results suggested that cyclosporine impeded weight gain in primates during the pubertal period. The effect was dosage-related and was less with cyclosporin G than with cyclosporin A. The mechanism is unclear, but the possible effect on the growth hormone merits further studies.

Longitudinal study of craniofacial growth in Macaca fascicularis

This paper is an analysis of normal craniofacial growth in adolescent crab-eating macaques (Macaca fascicularis). Eight female adolescent monkeys were used in this study. Their individual craniofacial growth was studied for a 24-month period utilizing tantalum implants and roentgenographic cephalograms. Throughout the observation period, each monkey consistently showed a class I molar relationship with a good overjet and overbite. The amount of anterior displacement of the maxilla and the mandible was significantly dominant compared to the vertical displacements at every observation period. The midface exhibited a maxillary differential growth pattern in which the premaxilla displaced superiorly and the posterior maxilla moved inferiorly, resulting in a counterclockwise rotation of the entire maxilla. Growth of the lower anterior teeth and alveolar bone compensated for the incremental vertical spaces which were induced by superior displacement of the premaxilla and inferior repositioning of the chin. In addition, the amount of anterior displacement of the upper and lower anterior teeth were significantly larger than that of the premaxilla and the chin. The dentocraniofacial growth pattern in Macaca fascicularis was quite similar to that seen in Macaca mulatta.

Mandibular condylar structure and growth in Macaca fascicularis are related to skeletal rather than dentitional development

Mandibular condyles of eight male monkeys (Macaca fascicularis), ranging in weight from 1.5 to 3.0 kg, were examined using histometric, radioautographic and stereologic techniques. The animals were classified on the basis of their dentitional and, as judged from radiographs of the hand and wrist, of their skeletal development. This allowed morphometric parameter means to be plotted as a function of four dentitional and five skeletal levels of maturation. The influence of dentitional and skeletal age on total parameter variations was examined by calculating factorial analyses of variance. Although consistent and well defined within each method, condylar parameter changes plotted over skeletal age were essentially different from those over dentitional age. Whereas the latter were difficult, if not impossible, to interpret, the former closely resembled the age-related curves displaying the elongation of short bones of the fingers in M. fascicularis. Furthermore these parameter changes were also consistent with longitudinal alterations in mandibular growth as assessed radiographically in man. The analyses of variance suggested that animals exhibiting the same degree of skeletal as compared to dentitional development, particularly at late stages of maturation, were markedly more homogeneous with respect to the majority of the morphometric parameters examined. Therefore, somatic maturation rather than the stage of tooth eruption should be the basis for estimating biological age in growth studies of the mandibular condyle.

Morphometric studies on the structural development of the lung in Macaca fascicularis during fetal and postnatal life

The structural development of the normal monkey lung (Macaca fascicularis) from 61 days of gestation to 14 days postnatal age has been described using quantitative morphometric techniques. The lung of the adult monkey has also been studied. The airway and arterial branching pattern has been traced using serial sections. The alveolar number and size have been estimated and the structure of the arteries after postmortem arterial injection has been assessed. Comparison of lung morphology in monkey and man shows that there are similarities in segmental arrangement, structure and branching pattern of airways, in arterial structure and in changes in the arteries after birth. Although there are differences in the number of lobes, the number of generations of different types of airways and the number and size of alveoli, the overall structure in the monkey is more similar to that in man than is the structure of the lung in species such as sheep, pig or rat. During fetal life the monkey lung passes through the same stages of development as the human fetus but at birth the monkey has a full complement of airways and mature alveoli. Postnatal growth of airways and alveoli is due to increase in size rather than to multiplication. In man there is an increase in the number of alveoli and alveolar ducts after birth as well as an increase in size. Despite the differences between the species it seems appropriate to use the monkey in experimental studies on the lung.

Structural development of the lateral geniculate nucleus and visual cortex in monkey and man

This study concerns the development of the primary visual pathway of the primate. The lateral geniculate nucleus (LGN) is the principal thalamic relay to the visual cortex (area 17), and its neurons have similar morphological characteristics in both monkey and man, as identified by Golgi impregnation. The commonest neuron is the multipolar with a radiate or tufted dendritic tree; next is the bipolar neuron with two or three diametrically opposed dendritic trunks. Less frequent are neurons with beaded dendrites and others with fine, axon-like dendritic processes, possibly interneurons. The dendritic tree of all neurons remains generally within a lamina, but some dendrites cross interlaminar zones. LGN neurons are identifiable before birth and differ from their adult form by the presence of immature features, especially numerous dendritic and somatic spines, most frequent at birth in monkeys and at about 4 months postnatally in man. They disappear almost completely by 3 months in monkeys and 9 months in man. The human LGN has reached its 'adult' volume by this age. Two stages in the development of the human area 17 can be defined. The first is marked by a rapid growth to its 'adult' volume by about 4 months, and by intense synaptogenesis beginning in the foetus and reaching a maximum around 8 months. The second stage is one of stabilization in the volume of area 17 and loss of synapses to reach 'adult' synaptic density around 11 years, at about 60% of the maximum values.

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 antero-posterior 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.

Sex differences in dendritic structure in the preoptic area of the juvenile macaque monkey brain

Quantitative analysis of Golgi-stained neurons in the preoptic area of the brain of prepuberal Macaca fascicularis monkeys indicated structural differences between males and females. Neurons of males had more dendritic bifurcations and a higher frequency of spines. The bifurcation difference appeared in all cell types and was concentrated in the ventrolateral preoptic area. The spine difference was greatest in the central region of the preoptic area. No differences in gross measurements of this brain region were found. These results suggest that sexual dimorphism in the function of the monkey preoptic area may be based on differences in neuronal structure.

Establishment of a cynomolgus monkey (Macaca fascicularis) breeding colony in Malaysia: a feasibility study

A breeding colony utilizing a harem mating system was established to study the feasibility of breeding cynomoglus monkeys, Macaca fascicularis, in Malaysia. Two groups consisting of 10 females and one male each were evaluated over a 3 period. Forty births were recorded; one was stillborn, 11 died while nursing, and 28 were weaned. The average time to wean offspring was 230 days with an average weight at weaning of 0.858 kg. The average time for conception to take place after weaning was 50 days. Of the 20 breeder females, six produced three offspring each, nine produced two offspring each, four produced one offspring each and one remained barren throughout the project. Three different weaning systems were evaluated. The best method was caging the mother-infant pair within or adjacent to the breeding room followed by a two-part cage system which allowed the infant to continue nursing and also obtain solid food inaccessible to the mother.

Bone growth aud development of secondary ossification centers of extremities in the cynomolgus monkey (Macaca fascicularis)

The development of so-called long bones in the extremity has been studied roentgenographically in forty-seven males and fifty-one females cynomolgus monkeys bred and reared at the National Institute of Health. The age of the females ranged from five months to eight years and nine months, and that of the males was from four months to seven years. In addition, the fetuses of six to twenty weeks of gestation age were examined for the time of appearance of ossification centers. As the biological parameters concerning body growth, the body weight and the bone length were measured and the secondary ossification centers were scrutinized and assessed the maturity process on the basis of the criteria that divided the state into eleven stages. Also the allometric analyses of body weight against bone length was conducted. Most of the secondary ossification centers except the proximal fibulal epiphysis appeared during the period from the prenatal stage (15-20 weeks of gestationage) to the postnatal one (several months of age). From four to five months of age, many ossification centers had developed to some extent. But, the appearance of proximal fibulal epiphysis was delayed and often lacking until 10 months of age in female and one year and three months of age in male. The earliest epiphyseal fusion was observed at the distal humeral epiphysis in both sexes. The latest epiphyseal fusion was observed at the distal ulnal epiphysis in both sexes and at the distal ulnal and radial epiphyses in female. From this study, the time of fusion was at five and three guarters years of age in females and at six and a half years of age in males. As a result, it is suggested that the estimation of animal's age might be put to practical use by introducing the assessing method that the score was given from the observation of the secondary ossification center.

Nursery rearing of infant monkeys (Macaca fascicularis) for toxicity studies

At birth, nine infant male cynomolgus monkeys (Macaca fascicularis) weighed an average of 402 g and 16 infant female cynomolgus monkeys weighed an average of 362 g. Both female and male infants last 15-20 g by the fourth day after birth. Female and male infants showed a growth rate of approximately 4 and 5 g body wt/day, respectively, from 4 to 150 days of age. Caloric intake increased from approximately 140 cal/gkg body weight/day in both females and males on the first day after birth to peak values of 325 and 290 cal/kg body weight/day in females and males, respectively, and subsequently declined to about 200 cal/kg/day in males and 250 cal/kg/day for females. Total calories consumed per day increased from 53 cal/day in females and 68 cal/day in males to approximately 200 cal/day after 60 days of age in both females and males. Erythrocyte counts, packed cell volume, and hemoglobin values decreased from birth to 2 weeks of age, then stabilized. An increase in lymphocyte count, with a concomitant decrease in mature neutrophils, was observed from birth to 6 weeks of age. "Temper fits" and certain aggressive behavioral signs were observed as early as 3-4 days after birth, and infants began to develop social orders as early as the 30-40th day. Behavioral abnormalities frequently seen in infants reared in isolation were not observed.

[Nursing procedures for cynomolgus monkey infants (author's transl)]

This paper describes the results of the artificial nursing of 8 infant cynomolgus monkeys (Macaca fascicularis) weighing 230-350 g at birth. The infants were separated from their mothers just after or 2 days after birth and were kept in a specially deviced small cage (Photo 1 & 2). They were fed on 6.4-16.6% solution of a commercially available powdered milk for the human baby. Apple juice also was given to them from the 3rd or 4th week on. In about the 6th week, the infants received solid foods such as small pieces of apple, biscuit and monkey chow. The main part of the dietary regimen was changed to the solid diet around the 12th week. The volume of milk taken was recorded every day, and the daily intake ff three major nutrients was estimated with the milk intake (Fig. 1,2,5,6). The body weights were between 600 and 750 g on the day of weaning, that is at about 12 weeks of age, except No. 2 infant showing a slight growth retardation (Fig.4). Their physical growth can be judged as normal as that of breast-nursed infants of the saame species from our laboratory. On the basis of these results, an example of the artificial feeding schedule for the infant cynomolgus monkeys was introduced (Fig. 7).