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The serotonin and norepinephrine innervation of primary visual cortex in the cynomolgus monkey (Macaca fascicularis).

The morphology and laminar distribution of norepinephrine (NE) and serotonin (5-hydroxytryptamine, 5-HT) axons in the primary visual cortex of cynomolgus monkeys (Macaca fascicularis) have been analyzed by immunocytochemistry with antibodies directed against dopamine-beta-hydroxylase (DBH) and against 5-HT. The NE and 5-HT innervation of primary visual cortex (area 17) in the monkey exhibit highly differentiated laminar patterns. Both of these monoamine axonal systems form tangentially continuous laminar bands that differ in density, morphology, and predominant orientation of constituent fibers. Serotonin axons, present in all cortical layers, form two especially prominent, dense bands of arborizing fibers; one extending from midlayer III through IVC-alpha and the other from VA through VI. NE axons within cynomolgus visual cortex are markedly less dense than 5-HT axons, and laminar differences in NE density are less prominent. NE axons form two broad bands of moderate density extending through deep and superficial cortical layers, separated by layer IVC, which is conspicuously poor in NE fibers. The laminar complementarity of 5-HT and NE innervation that is a notable feature of the squirrel monkey visual cortex is not present in cynomolgus monkey; in this Old World monkey NE and 5-HT axons show considerable overlap such that the same cortical layers appear to be innervated by both neurotransmitters. By virtue of their laminar distribution, 5-HT and NE axons may each have a selective influence on the intrinsic circuitry of primate cerebral cortex, and, for 5-HT in particular, the specific cellular targets of this influence are likely to differ in New and Old World monkeys.

Animals↗

Projections of thalamic gustatory and lingual areas in the monkey, Macaca fascicularis.

The efferent projections of the parvicellular division of the ventroposteromedial nucleus of the thalamus (VMPpc; thalamic taste area) were traced to cortex in Macaca fascicularis by using tritiated amino acid autoradiography. Labeled fascicles could be traced from VPMpc to two discrete regions of cortex. The primary efferent projection was located on ipsilateral insular-opercular cortex adjacent to the superior limiting sulcus and extended as far rostrally as the posterior lateral orbitofrontal cortex. An additional projection was located within primary somatosensory (SI) cortex subjacent to the anterior subcentral sulcus. Following autoradiographic injections in VPM, the trigeminal somatosensory relay, a dense terminal plexus was labeled on SI cortex of both pre- and postcentral gyri, but not within insular-opercular cortex. The autoradiographic data were verified by injecting each cortical projection area with horseradish peroxidase (HRP) and observing the pattern of retrogradely labeled somata within the thalamus. Injections in the precentral gyrus near the anterior subcentral sulcus retrogradely labeled neurons within VPMpc, whereas injections further caudally near the floor of the central sulcus labeled neurons within VPM. Injections of HRP within opercular, insular, or posterior lateral orbitofrontal cortex retrogradely labeled neurons within VPMpc.

Animals↗

Sagittal cytoarchitectonic maps of the Macaca mulatta thalamus with a revised nomenclature of the motor-related nuclei validated by observations on their connectivity.

Cytoarchitectonic atlas plates of the Macaca mulatta thalamus are presented in the sagittal plane of section with a revised nomenclature of the motor thalamic region. The proposed changes in nomenclature are based on the analysis of topographical relationships between nigral, pallidal, and cerebellar projections to the thalamus studied in 13 rhesus monkeys with the use of autoradiography technique. Mapping of the projection zones of these motor-related systems in serial sagittal sections revealed that they are completely segregated with each honoring cytoarchitectonic boundaries of specific nuclear subdivisions. The available data on thalamic connectivity together with the results of the present study allowed us to divide the primate "motor" thalamus into two major territories: (1) the ventral anterior region (VA) and (2) the ventral lateral region (VL). Although the designation of these two areas of the motor thalamus is the same as the classic one, the nuclear subdivisions that compose them differ significantly from those described in previous classifications. As is delineated in the maps, VA represents the basal ganglia territory of the motor thalamus where nigral projections coincide with its magnocellular part (VAmc), and pallidal projections occupy densicellular (VAdc) and parvicellular (VApc) subdivisions. VAdc corresponds closely to VLo of Olszewski; however, we prefer the new term in order to avoid possible conceptual confusions with the ventral lateral region (VL), which does not receive basal ganglia projections. The VL region is characterized as a distinct cytoarchitectonic entity of the motor thalamus that receives cerebellar projections and includes area X, VPLo, VLc, and VLps of Olszewski. The ventral medial region (VM in the present study or VLm in Olszewski terminology) is usually considered together with the basal ganglia territory on a common connectional basis. However, we did not obtain convincing data to support this view, since evidence of terminal labeling was observed only in (or around) fiber bundles passing through the nucleus with other areas free of label. Rather, in this study VM was treated as an intermediate zone between the subthalamus and motor thalamus where fiber bundles from basal ganglia and cerebellum are organized in a topographical manner before reaching their destinations in the VA and VL regions, respectively. Other major thalamic regions represented in the maps were delineated purely on cytoarchitectonic grounds and their traditional nomenclature was maintained.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Distribution of corticotropin-releasing-factor-like immunoreactivity in brainstem of two monkey species (Saimiri sciureus and Macaca fascicularis): an immunohistochemical study.

Immunohistochemical methods were utilized to systematically map the distribution of corticotropin-releasing-factor-like immunoreactivity (CRF-LI) in the diencephalon, mesencephalon, and rhombencephalon of two monkey species (Saimiri sciureus and Macaca fascicularis). A primary antiserum directed against the human form of the peptide was utilized. Immunoreactive neuronal perikarya and processes were evident in numerous areas, and the distributions of these elements were similar for the two species. As previously reported for rats, monkeys, and human, intense immunoreactivity was evident in putative hypophyseal neurons in the parvicellular component of the paraventricular nucleus of the hypothalamus and in fibers extending from this area into the median eminence. The results for other brainstem regions, most of which have been previously examined for CRF-LI only in rats, indicate that many similarities exist between rats and monkeys in the distribution of this peptide in brainstem extrahypophyseal neuronal circuits, although substantial differences are also evident. For example, immunoreactive perikarya previously observed in other hypothalamic nuclei in rats were not evident in monkeys. Conversely, in monkeys, unlike rats, labeled perikarya were evident in several thalamic nuclei, especially in the intralaminar complex. Also, two large groups of immunoreactive neurons which have generally not been observed in rat studies were present in the mesencephalon and rhombencephalon. In the mesencephalon this consisted of a group of neurons just lateral to the mesencephalic tegmentum, extending throughout the rostral-caudal extent of the midbrain. In the rhombencephalon, labeled perikarya were observed throughout the inferior olive. Some of the differences between rats and monkeys in the locations of labeled perikarya may be due to differences in antiserum specificity and/or sensitivity, or they may result from the fact that colchicine pretreatment was not utilized in the present study. The distributions of immunoreactive fibers also exhibited similarities and differences between monkeys and rats. The most striking terminal fields observed in the present study which have not been previously described are a moderate-to-dense field within and adjacent to presumed dopamine-containing neurons in the substantia nigra pars compacta, a dense innervation of certain subdivisions of the interpeduncular nucleus, and a regionally and parasagittally organized distribution of fibers in the Purkinje cell and molecular layers of the cerebellar cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Vasopressin and oxytocin systems in the brain and upper spinal cord of Macaca fascicularis.

This paper describes the vasopressin (VP) and oxytocin (OXT) immunoreactive structures in the brain and upper spinal cord of the adult male and female Macaca fascicularis. Immunocytochemistry following intraventricular application of colchicine displayed VP neurons in the diagonal band of Broca (DBB), bed nucleus of the stria terminalis (BST), medial amygdaloid nucleus, dorsomedial hypothalamic nucleus, area of the locus coeruleus (LC), solitary tract nuclei (NTS), and the dorsal horn of the cervical spinal cord in addition to those known to exist in the paraventricular, supraoptic, and suprachiasmatic hypothalamic nuclei. Furthermore, a dense accumulation of VP fibers was observed in areas such as the DBB, medial septum, BST, amygdala, hippocampus, ventral tegmental area, periaquaductal gray, dorsal and ventral raphe, area of Forel, LC region, parabrachial nuclei, and NTS. The lateral septum and lateral habenula displayed no and very few VP fibers, respectively. No extrahypothalamic OXT neurons were found in the brain of this macaque monkey. Dense concentrations of OXT fibers were demonstrated in the amygdala, NTS, and marginal layer of the cervical spinal cord. No sexual dimorphism was found in this primate VP or OXT system. The results show a distribution of the central VP and OXT systems in this primate which is quite different from that in the rat. However, in various aspects it agrees with current data on the VP and OXT systems of the human brain. The present results suggest, therefore, that this monkey might serve as a better model for the human VP system than the rat.

Animals↗

Musculotopic organization of the facial motor nucleus in Macaca fascicularis: a morphometric and retrograde tracing study with cholera toxin B-HRP.

Morphometric and retrograde tracing methods were used to determine the location and number of motoneurons innervating individual facial muscles in Macaca fascicularis. Intramuscular injections of the cholera toxin B subunit-horseradish peroxidase conjugate produced discrete labeling patterns in the ipsilateral facial motor nucleus with good definition of somata and their processes. The facial nucleus extended rostrocaudally in the pons for about 2 mm, varying in shape and cross-sectional area along this axis. Motoneurons were clustered in subnuclei, but their boundaries were not sharp and they were not segregated by fiber bundles. The length, number, and area of subnuclei varied with rostrocaudal location. Retrograde labeling patterns revealed that individual muscles were innervated by longitudinal columns of motoneurons with each muscle region represented at all rostrocaudal levels of its column. The columns began at different rostrocaudal levels and varied in length. Columns for closely related muscles, such as the orbicularis oris and mentalis of the lower lip, tended to overlap, whereas columns for disparate muscles, such as the perioral and orbital, did not overlap. The dendritic processes of most motoneurons branched extensively among several different columns or subnuclei. Some dendrites extended outside of the nucleus into the surrounding tegmentum. Mean soma diameter (10.4-42.2 microns) was distributed unimodally, reflecting the absence of gamma motoneurons and lack of muscle spindles in the facial muscles. Large and small motoneurons were found in all regions of the nucleus, but the largest ones were located caudally and innervated muscles of the upper and lower lip. The perioral muscles also had more neurons, longer columns, and a lower cell density than the other muscle groups examined. These features may reflect the functions of the perioral muscles in facial expression and vocalization.

Animals↗

Light and electron microscopic analysis of synaptic development in Macaca monkey retina as detected by immunocytochemical labeling for the synaptic vesicle protein, SV2.

The development of synapses has been followed in Macaca monkey fetal and infant retina using immunocytochemical labeling for the transmembrane synaptic vesicle glycoprotein, SV2. Electron microscopy (EM) was used to verify the presence of morphological synapses at selected ages. EM immunocytochemical labeling in adult retina showed that all synaptic types contained SV2 in inner (IPL) and outer (OPL) plexiform layers. In fetal retina, SV2 expression and the appearance of morphological synapses were closely related in time, demonstrating that SV2 is a reliable marker for synaptogenesis. SV2 expression appears along a foveal to peripheral gradient. Both SV2 and synapses appear in the foveal IPL at Fd50-55, and reach the retinal edge by Fd90-103. Cone ribbon synapses and SV2 labeling are not present in the foveal OPL until Fd60. Photoreceptors in the far periphery contain SV2 by Fd119-125. This pattern demonstrates an "inner to outer" direction of synaptogenesis. Cones show SV2 labeling before rods at the same retinal eccentricity. In the cone-dominated fovea, SV2 labeling and bipolar cell ribbon-containing terminals are present at Fd55 when amacrine cell conventional terminals are very scarce, indicating that bipolar synapses precede amacrine synapses in monkey foveal IPL. SV2 labeling and bipolar terminals appear first in the outer IPL which contains "OFF" ganglion and bipolar processes in the adult, suggesting that "OFF" midget bipolar cells may form the first synapses. Both SV2 immunocytochemical labeling and EM morphology find that monkey retina follows a generalized inner before outer, and cone before rod synaptic developmental pattern, similar to that in other mammals. The cone-dominated fovea initiates synaptogenesis, and shows a different synaptic sequence from rod-dominated peripheral retina.

Animals↗

Effect of bone strain on cortical bone structure in macaques (Macaca mulatta).

It has recently been shown that the consistency of food significantly affects levels of bone strain in the mandible during mastication (Hylander, '79a). Mandibular bone histology was examined to test the effects of a diet of hard food compared to a diet of soft food in two groups of monkeys. One group of rhesus macaques (Macaca mulatta) was fed a diet of commercially prepared hard biscuits. The second group was fed a soft diet the consistency of fudge. Both diets were nutritionally adequate for normal growth and development. As a control for other factors influencing cortical bone structure, fibular morphology was also examined. At the end of the test period, mandibular and fibular tissue samples from the two groups were prepared to determine the amount of secondary Haversian bone present. Mandibular depth at M2 and fibular anteroposterior diameter were also measured and compared between the two dietary groups. The soft-diet monkeys showed low levels of remodeling in their mandibles. There were large patches of unremodeled bone and resorption spaces were common. The hard-diet monkeys exhibited more extensive evidence of secondary Haversian remodeling in their mandibles. The hard-diet monkeys also had deeper mandibles. In contrast, the fibulae from the two groups had similar mean diameters and showed comparable levels of secondary remodeling. We infer that the higher mandibular bone remodeling levels in the hard-diet monkeys represent an adaptive response to remove and replace fatigued mandibular bone due to higher stress levels associated with the ingestion and mastication of hard foods. We also infer that greater depth of the mandible at M2 found in the hard-diet group represents an adaptive response to higher stress levels associated with the ingestion and mastication of hard foods.

Animals↗

Teratological and radiocephalometric analysis of craniofacial malformations induced with retinoic acid in rhesus monkeys (Macaca mulatta).

Fifteen pregnant Macaca mulatta were treated with doses of 20 or 40 mg of retinoic acid between 19--45 or 17--45 days of gestation, respectively, for 4--8 consecutive days. Based on gross examination, ten malformed infants, including one stillbirth and one abortus, four normal infants, and one resorption were produced. The most critical sensitive period was between days 24--35 of gestation, and the malformations primarily involved the craniofacial skeleton. Ten treated infants and eight age-matched controls were cephalometrically analyzed using craniometric points as closely correlated as possible with those in humans in order to define the craniofacial malformations induced prenatally by retinoic acid. Although all ten animals had detectable linear and angular deviations from the controls, four had cephalometric patterns which appeared to be of similar developmental origin.

Abnormalities, Drug-Induced↗

A crypto-lymphatic unit at the uvula of the monkey Macaca fascicularis. A light- and electron-microscopic study.

A crypto-lymphatic unit was observed at the left lateral aspect of the uvula of a mature female monkey, Macaca fascicularis. A light- and transmission electron-microscopic investigation revealed that the lumen of the crypt was filled with bacteria, desquamated epithelial cells, lymphocytes and neutrophils. The non-keratinized stratified squamous epithelium of the crypt was fragmented and showed heavy mononuclear cell infiltration and surface discontinuities, exposing lymphoid cells to foreign material. The lymphatic parenchyma consisted of organized lymphatic tissue including germinal centres. The resident cell population included lymphocytes of varying size, blastforming B- and T-lymphocytes and two types of reticular cells resembling the fibroblastic reticulum cell and the follicular dendritic cell, respectively. Occasionally granulocytes were encountered. At its base and laterally the crypto-lymphatic unit was ensheathed by a thin connective tissue capsule. Three other monkeys of the same species failed to reveal similar structures at the same site.

Animals↗

Age-related decline of lymphoid-tissue components in the oral mucosa of the lip, cheek and soft palate of Macaca fascicularis.

In three mature monkeys (Macaca fascicularis; 3.5 +/- 0.3 kg in weight), the labial, buccal and soft-palate mucosae were examined morphologically and stereologically. Using fixation by perfusion, standardized methods of tissue preparation and morphometric analysis at the light-microscopic level, the gross dimensions (i.e., epithelial thickness, width of combined lamina propria/submucosa) and the volumetric composition of the oral mucosae were estimated and compared with those of young animals examined previously. The data show (1) an age-related decline in the volume and prevalence of organized lymphoid tissue (i.e., lymphoid follicles associated with secretory ducts), (2) a stable plasma-cell density in the interglandular connective tissue, and (3) an increase of glandular tissue in mature versus young animals. It is suggested that the lymphoid follicles associated with secretory ducts, providing for plasma-cell generation, mirror the tonsillar lymphoid tissue declining after puberty.

Aging↗

The innervation of the myometrium of the cynomolgus monkey (Macaca fascicularis). A quantitative electron-microscopic study.

The autonomic innervation of the myometrium of Macaca fascicularis consists of bundles of unmyelinated nerve fibres running between the smooth muscle cells, and is therefore considered to be of the "fascicular (= unitary) type". Close contacts between nerve fibres and smooth muscle fibres were not found. Modification of the chromaffin method according to Tranzer and Richards made it possible to visualize the heterogeneity of the nerve fibres in a single bundle. The following fibre types were found to coexist: (1) noradrenergic fibres containing "synaptic" vesicles with a dense granule, (2) cholinergic fibres containing empty "synaptic vesicles", and (3) non-adrenergic non-cholinergic (NANC) fibres containing only or predominantly large dense-cored vesicles, which do not react with this method. Noradrenergic fibres are the most numerous (around 60%), followed by NANC fibres (30%) and cholinergic elements (around 10%). The distribution of these three types is similar in the cervix, the isthmus and the body of the uterus in pregnant and non-pregnant females.

Adrenergic Fibers↗

Structure and composition of the oral mucous membrane on the lips and cheeks of the monkey, Macaca fascicularis.

In seven monkeys (6 Macaca fascicularis, 1 M. mulatta; 2.4 +/- 0.6 kg in weight) the labial and buccal mucosae were studied morphologically and quantitatively. Following fixation by perfusion, the upper and lower lips and entire cheeks were dissected free and processed for light-, scanning and transmission electron microscopy. Established programs (HISTOMEP, MUMANA II) and appropriate morphometric techniques were used to estimate, at the light-microscopic level, the epithelial thickness, the width of the combined lamina propria/submucosa, and the volumetric composition of the gland-containing portions of lip and cheek mucosae. The cheek epithelium was more than twofold thicker than the lip epithelium, on the average 0.46 +/- 0.04 and 0.21 +/- 0.02 mm, respectively, with no differences related to sex or topographical sites. The combined lamina propria/submucosa was 1.32 +/- 0.19 and 1.50 +/- 0.26 mm in width in cheeks and lips, respectively. The main mucosal constituents at both sites were glandular and connective tissue, and lymph follicles associated with secretory ducts. In lips, the volume of plasma cells around gland acini correlated positively with the amount of lymphoid tissue present around topographically related ducts. It is suggested that the duct/lymph follicle assembly may serve as a local antigen-recognition system.

Animals↗

Architecture of associations of minor salivary gland ducts and lymphoid follicles in Macaca fascicularis. An ultrastructural study.

Previous light-microscopic and ultra-immunohistochemical tracer studies revealed the existence of an independent local immune response of the simian oral mucosa. This local response is attributed to the presence of minor salivary gland (MSG) duct-related lymphoid tissue. Semithin sections from a total of 263 Epon-embedded tissue blocks from the labial and buccal mucosae of seven monkeys, Macaca fascicularis, were analysed light-microscopically, and 10 suitable MSG duct/follicle assemblies were investigated ultrastructurally. These duct/follicle assemblies include follicular and parafollicular compartments with distinct fine-structural elements. The follicular area or germinal centre contains numerous small and large lymphoid cells, mitotic figures, plasmablasts, macrophages, and cells resembling the follicular dendritic cells with distinct desmosomal junctions. The parafollicular area, which includes the heavily infiltrated duct wall, contains numerous small lymphocytes, T-lymphoblasts, plasma cells and reticular cells resembling fibroblasts. A distinct feature of this compartment is the presence of high endothelial venules (HEV). The presence of HEV and numerous blast cells, resembling blast-forming T-lymphocytes activated in vitro, in a specific area of the duct/follicle assembly strongly suggests that this area is structurally and physiologically identical to the thymus-dependent area of other lymphoid tissues. In other words, the duct/follicle assemblies of simian MSG contain the various specific fine-structural elements that are suitable for antigen recognition and processing. These elements are distributed in discrete compartments comparable to the B- and T-cell areas of "classical" lymphoid tissue.

Animals↗

Organization of lymphoid tissue in the tonsilla lingualis. An ultrastructural study in Macaca fascicularis (Primates, Cercopithecoidea).

Lymphoid organs are highly organized structures made up of different tissue compartments, each with its own specific cell populations. However, the cellular elements of the lingual tonsil, which forms a significant part of Waldeyer's pharyngeal ring, are not yet documented. This study, therefore, describes the fine structure and tissue organization of tonsilla lingualis in Macaca fascicularis. Ten selected crypto-lymphatic units originating from five perfusion-fixed animals were analysed ultrastructurally. Based on the fine-structural elements contained within, the lymphoid tissue of tonsillar units could be subdivided into follicular (germinal centre) and parafollicular areas. The latter contained predominantly small lymphocytes, lymphoblasts resembling T-blasts, plasma cells, macrophages, occasional neutrophils and many reticular cells resembling fibroblasts. A distinct feature of the parafollicular area was the presence of numerous high endothelial (HEV)- or postcapillary venules (PCV). The follicular areas contained many small and large lymphoid cells, mitotic cells, plasmablasts, macrophages and specialised reticular cells resembling follicular dendritic cells (FDC) with distinct desmosomal junctions. These observations show that the crypto-lymphatic units of the lingual tonsil are, in fact, organised into distinct B- and T-cell compartments with their own specific lymphoid and accessory cells.

Animals↗

Association of microperoxisomes with the endoplasmic reticulum in the granulosa lutein cells of the Rhesus monkey (Macaca mulatta).

Aldehyde fixed tissue from monkey (Macaca mulatta) corpus luteum was incubated in alkaline 3,3inch-diaminobenzidine (DAB), and prepared for electron microscopic histochemical observations. The association of microperoxisomes with the granular (GER) or agranular (AER) endoplasmic reticulum was reconstructed from serially sectioned tissues and by tilting of specimens in the microscope. Out of 107 microperoxisomes, 106 were directly associated with the AER. Two different forms of attachment were found between microperoxisomes and the AER and that of the microperoxisome are confluent. In the second, lingulate type of connection, a blunt-end structure either is inserted into an invagination of the AER, or penetrates into the lumen of the AER. The lumen of the lingula is confluent with the microperoxisome, but not with the AER. In addition to these connections, fine thread-like structures were observed extending between AER and adjacent microperoxisomes.

Animals↗

Developmental study of neuropeptide Y-like immunoreactivity in the neurohypophysis and intermediate lobe of the rhesus monkey (Macaca mulatta).

The purpose of this study was to examine the development and distribution of neuropeptide Y-immunoreactive fibers in the neurohypophysis of the rhesus monkey (Macaca mulatta) throughout life and the relationship of these fibers to the hypothalamo-hypophyseal portal vasculature. In rhesus monkeys, which varied in age from fetal life to 34 years, neuropeptide Y-immunoreactive fibers were present at all ages examined. In adult monkeys, varicose neuropeptide Y-labeled fibers were concentrated in the upper infundibular stem in association with capillary loops of the portal vasculature and the long portal vessels. Other fibers travelled down the infundibular stem and were distributed at the junction of the lower infundibular stem and infundibular process in the vicinity of the short portal vessels. In the infundibular process, neuropeptide Y-immunoreactive fibers were concentrated along the border of the intermediate lobe. Other stained fibers were sparsely distributed in the infundibular process and were often associated with small vessels. Neuropeptide Y-immunoreactivity was also located in a few fibers and cells of the intermediate lobe. Very few labeled fibers were seen in the fetal neurohypophysis, but their number increased gradually during the first postnatal year. At two years of age, a high density of stained fibers was observed, especially in the infundibular process. The number of axons in the infundibular process was lower at 12 years and continued to decline until 34 years of age. Neuropeptide Y may modulate hormone release at these sites and may also be released directly into vessels in the infundibular process. The close association of neuropeptide Y-labeled fibers with capillaries of the portal vasculature strongly suggests that neuropeptide Y is released into the portal blood of monkeys throughout life and may influence hormone secretion from the anterior pituitary gland.

Aging↗

The normal anatomy of the pig tailed macaque (Macaca nemestrina) outflow apparatus with particular reference to the presence of smooth muscle.

The normal anatomy of the pig tailed macaque (Macaca nemestrina) outflow system has until now been undocumented. Tissue from ten monkeys was investigated by light microscopy, transmission electron microscopy and scanning electron microscopy. Although the basic configuration of the outflow apparatus was similar to other subhuman primates it did differ in the following aspects: a) bundles of circumferentially orientated smooth muscle cells were present in the outer and posterior part of the trabecular meshwork near Schlemm's Canal, b) large 'atypical' endothelial cells with microfilament rich cytoplasm were present in the cribriform layer, c) numerous collagenous cords and septae were present in Schlemm's Canal which also appeared to be drained by more than the usual number of collector channels. The possible importance of these anatomical differences is discussed.

Animals↗