Microvascularization of thalamus and metathalamus in common tree shrew (Tupaia glis)

The microangioarchitecture of the thalamus and metathalamus in common tree shrew (Tupaia glis) was studied using vascular corrosion cast/stereomicroscope and SEM technique. The arterial supply of the thalamus and metathalamus was found to originate from perforating branches of the posterior communicating artery, the posterior cerebral artery, the middle cerebral artery, and the anterior choroidal artery. These perforating arteries gave rise to numerous bipinnate arterioles which in turn, with decreasing vessel diameters, branched into a non-fenestrated capillary bed. Venous blood from the superficial parts of the thalamus and metathalamus was collected into the thalamocollicular vein, whereas venous blood from internal aspects of the thalamus was conveyed to the internal cerebral vein. Some venous blood from the most rostral part of the thalamus flowed into tributaries of the middle cerebral vein before draining into the cavernous sinus. Further, the thalamic and metathalamic vascular arrangement was found to be of centripetal type. In addition, thalamic arterial anastomosis was rarely observed. Thus, obstruction of thalamic blood supply could easily lead to thalamic infraction.     

Crystalloid configurations in the adrenal cortex of the Siamese tree shrew (Tupaia glis)

Crystalloids of what appear to be smooth reticulum have been observed in the zona fasciculata and zona reticularis in both the stressed and nonstressed adrenal gland of the Siamese tree shrew (Tupaia glis). No crystalloids are observed in the zona glomerulosa. Similar crystalloids have been described in other steroid-secreting organs, including the antebrachial organ of the lemur (Lemur catta), the parotoid gland of Bufo alvarius and in sebaceous gland cells of the Galagos and Macaques. Moreover, the crystalloids in the present investigation resemble the paracrystalline arrays of smooth reticulum present in the adrenal cortex of the fetal guinea pig. The crystalloids show much variation in degree of organization, sometimes appearing as wavy tubules parallel with one another or as fused tubules having a “donut” configuration. In addition, the crystalloids are nearly identical to configurations which have been described in mitochondrial cristae of the protozoan, Pelomyxa carolinensis.     

Hypophyseal angioarchitecture of common tree shrew (Tupaia glis) revealed by scanning electron microscopy study of vascular corrosion casts

The vascular corrosion cast technique in conjunction with scanning electron microscopy (SEM) was used for the study of pituitary microvascularization in the common tree shrew (Tupaia glis). The pituitary vascular casts were obtained by infusion of low viscosity methyl methacrylate plastic (Batson's no. 17) mixture. It was found that the blood supplies to the pituitary complex were from branches of the circle of Willis and could be divided into two groups. The first group consisted of two to four superior hypophyseal arteries (SHAs) branching off from the internal carotid artery supplying each half of the median eminence (ME), infundibular stalk (IS), and pars distalis (PD). The SHAs supplying the ME branched into internal and external capillary plexi. The internal plexus had a larger capillary size (approximately 15 μm in diameter), was deeper in position, and had denser and more complex capillary loops than those in the external plexus. The capillaries of the external plexus were approximately 10 μm in diameter. The two plexi drained into 15–20 hypophyseal portal veins (HPVs) which were located mainly along the ventral and ventrolateral surfaces of the IS before breaking up into large capillaries (approximately 18 μm in diameter) with an anteroposterior arrangement within the PD. The second group consisted of one inferior hypophyseal artery (IHA) on each side branching off from the internal carotid artery. These arteries gave off branches to pierce the dorsolateral and ventrolateral aspects of infundibular process (IP) before branching off to form a capillary network. They also gave rise to radiating capillaries to supply the pars intermedia (PI) surrounding the cortical area of the IP. The hypophyseal cleft separating the PI from the PD was clearly seen with very few blood vessels. The capillaries in both PD and IP joined to form confluent hypophyseal veins draining the blood into the cavernous sinus.     

Psychosocial stress affects pineal function in the tree shrew (Tupaia belangeri)

Using a recently developed commercially available radioimmunoassay the concentration of the principal melatonin metabolite 6-sulfatoxymelatonin (aMT6s) in the morning urine of male tree shrews was determined. Chronic social confrontation elicited a drastic increase of aMT6s excretion in subordinate tree shrews, whereas there was a tendency to reduced excretion of the melatonin metabolite in dominant animals. These results substantiate the function of the pineal gland in transforming stimuli from the social environment to endocrine information and, therefore, are indicative for the relevant role the gland may play in the physiological reactions to chronic psychosocial stress.     

Callosal projections between areas 17 in the adult tree shrew (Tupaia belangeri)

Summary In the primary visual cortex (area 17) of the tree shrew (Tupaia belangeri) neurons projecting to the contralateral area 17 via the corpus callosum were identified by horseradish peroxidase histochemistry (HRP, WGA-HRP). The distribution of homotopic and heterotopic connections was studied. We found that a narrow stripe of area 17 close to the dorsal area 17/18 border — which corresponds to the visual field along the vertical meridian — is connected via homotopic callosal projections. The adjacent dorsal part of area 17, which largely corresponds to the binocular visual field, is connected via homotopic as well as heterotopic projections. Heterotopic projections originate in the cortical stripe along the area 17/18 border and their contralateral targets are displaced medially. Callosal neurons are located mostly in supragranular but also occur in infragranular layers. The supragranular neurons in general are pyramidal cells. In addition to these findings, we confirmed earlier reports on ipsilateral projections of the primary visual area to the dLGN, the claustrum, area 18 and other visual areas.The authors wish to dedicate this paper to Prof. W. Lierse in honour of his 60th birthday     

A lectin-histochemical study on the seminiferous epithelium of the northern smooth-tailed tree shrew (Dendrogale murina) and the Java tree shrew (Tupaia javanica)

Lectin-binding patterns in the testes of the northern smooth-tailed tree shrew, Dendrogale murina and Java tree shrew, Tupaia javanica were studied by light microscopy and compared the data with those of the common tree shrew. Four lectins (PNA, SBA, BPA and GS-II) were used in this study. Peanut (Arachis hypogaea) agglutinin (PNA), soybean (Glycine max) agglutinin (SBA) and Bauhinia purpurea agglutinin (BPA) showed a strong reaction in the acrosomal region from Golgi to acrosome-phase spermatids in three species of tree shrews. These lectins also showed a granular positive reaction in the cytoplasm from acrosome to maturation-phase spermatids in three species, except that BPA revealed no granular reaction (though it was positive) in the spermatid cytoplasm of the northern smooth-tailed tree shrew and that PNA revealed no reaction in the spermatid cytoplasm of the common tree shrew. While, Griffonia simplicifolia-II agglutinin (GS-II) showed a positive reaction in the acrosomal region of Golgi-phase spermatids in three species of tree shrews. Although GS-II was positive in the spermatocyte cytoplasm of three species, it showed granular in the northern smooth-tailed tree shrew and common tree shrew but not granular in the Java tree shrew. Thus, the lectin-binding patterns in testes were similar among three species belonging to the Order Scandentia. However, slight differences were also detected even among these phylogenetically-close species.     

Mapping of cytoskeletal components in the hippocampal formation of the tree shrew (Tupaia belangeri)

The distribution of the major cytoskeletal components in frontal cryosections of the hippocampal formation of adult male tree shrews (Tupaia belangeri) was immunohistochemically investigated by using commercially available antibodies. Actin-immunolabeling was evident in all layers of the dentate gyrus as well as in the regio superior (CA1) and the regio inferior (CA3). Neurofilament 160 was detected only in the molecular layer of the dentate gyrus and in the axons of the granule cells (mossy fibers). For beta-tubulin, the microtubule associated proteins (MAPs) MAP2AB, MAP2ABC and Tau, immunoreactivity was evident within the granule cells and within the somatodendritic compartment of pyramidal neurons. Granule cells and the somata of the pyramidal neurons were intensely labeled for kinesin. Our findings show the elaborate expression of cytoskeletal proteins in the hippocampal formation of the tree shrew, relatively similar to what is seen in other species but with also some important differences, such as the immunonegativity of the axonal compartment for Tau in the tree shrew, which is contrary to what we see in the mouse (unpublished data). These findings provide useful insights regarding the organization of the hippocampal formation of the tree shrew and are fundamental for further research in this field.     

A cytoarchitectonic study of the hippocampal formation of the tree shrew (Tupaia belangeri)

Tree shrews constitute an interesting animal model to study the impact of stress or aging on the hippocampal formation, a brain structure known to be affected under such environmental or internal influences. To perform detailed investigations of the hippocampal formation, adequate knowledge of its anatomy should be present. Until now, the hippocampal formation of the tree shrew has not yet been studied extensively. The main objective of this study, therefore, was to describe the subfield boundaries in various levels of the dorsoventral hippocampal axis of the tree shrew (Tupaia belangeri) in detail. The secondary aim was to clarify whether a separate CA2 field can actually be distinguished in the tree shrew hippocampus, a fact that was denied in former reports. In addition, we aimed at investigating whether or not a CA4 subfield can be identified in the tree shrew's hippocampus. The immunocytochemical distribution of microtubule-associated protein 2 and the calcium-binding proteins, parvalbumin and calbindin, and the characteristics of Nissl staining in adjacent sections were compared. Because of the rather dorsoventral orientation of the long hippocampal axis in tree shrews, staining patterns were analyzed mainly in horizontal sections. The subiculum and the hippocampal CA1 and CA3 areas were easily identified. Moreover, we were able to demonstrate the existence of a distinct CA2 subfield in the tree shrew's Ammon's horn, contrary to previous reports. However, our results indicate that a CA4 field in the tree shrew hippocampal formation cannot be identified with the methods that we used. Therefore, supposed CA4 pyramidal neurons should be included into the CA3 field.     

Scanning electron microscopic study of the splenic vascular casts in common tree shrew (Tupaia glis)

Summary Splenic vascular casts of the common tree shrew,Tupaia glis, were constructed with Batson's No. 17 plastic mixture and studied with the scanning electron microscope (SEM). Fifteen adult animals of both sexes, weighing between 120 and 180 g were used. Under ether anaesthesia, each animal was injected with 0.05 ml heparin intracardially; the right atrium was cut open and then 250 ml of 0.9% NaCl, followed by 50 ml of 10% neutral formalin, (in four animals) was injected through the left ventricle. Plastic mixture was injected through the same opening. After complete polymerization of the plastic, the spleen and surrounding tissues were removed and macerated in 40% KOH. The air-dried casts were then coated with carbon and gold before viewing and photographing under SEM at 15 kV. It was found that the splenic arteries penetrated deep into the organ before they divided into trabecular arteries and divided again into central arterioles. Each central arteriole sent out 15 to 30 radiating arterioles, called penicillar arterioles, and further divided into smaller vessels entering the marginal zone and red pulp. In this area each arteriole continued directly into either marginal or red pulp sinusoids. The sinusoids emptied into pulp venules which joined to form trabecular veins. Most of the trabecular veins travelled to the cortical area underneath the splenic capsule before approaching the hilum, where they finally drained into splenic and short gastric veins. It is likely that the spleen of the common tree shrew has a closed circulation.This paper is dedicated to Professor Fred Walberg on the occasion of his 70th birthday.     

Behavior alterations in tree shrews (Tupaia glis,Diard 1820) induced by Borna disease virus

Intracerebral injection of Borna disease virus in tree shrews led to a persistent infection that sometimes resulted in clinical symptoms and/or specific alterations in the animals' behavior. Whereas infective virus in the brain and in the serum antibodies were always present after infection, only some of the animals showed signs of clinical disease and behavior changes. Animals kept in pairs showed especially obvious behavior alterations expressed as an exaggeration of all the components of normal social behavior. The division of the roles between males and females was seriously disturbed. The breeding behavior of females was especially impaired, although no stress factors were given and the animals were obviously in good physical condition. Some females that were maintained solitarily showed considerably exaggerated spontaneous locomotor activities (hyperactivity) 4 weeks after infection, followed by a phase of clinical neurologic symptoms (decline phase), spatial and temporal disorientation, and alterations in comfort behavior. Following a slow recovery the animals remained unusually docile and were much less timid than before infection. A recurrence of the clinical illness is possible, as shown by the occurrence of a second decline phase. All the behavior alterations can be interpreted as a disturbance in the balance of approach and avoidance. In paired animals this imbalance results in interference with normal sociosexual behavior. These alterations indicate that BD preferentially involves the limbic system, an interpretation supported by the results of neuropathologic investigations.     

Development of the NADPH-diaphorase-positive neurons in the sympathetic ganglia

Changes in the distribution of NADPH-diaphorase (NADPH-d) were studied in neurons of the superior cervical ganglion (SCG), stellate ganglion (SG) and celiac ganglia (CG) in newborn, 10-, 20-day-old, 1-month-old, 2-month-old and 6-month-old rats, mice and kittens. NADPH-d-positive neurons were revealed in all sympathetic ganglia in kittens but not in rodents from birth onwards. In kittens, the largest population of NADPH-d-positive cells was found in the SG, the smallest in the SCG (<1%) and we observed only a few cells in the CG. The proportion of NADPH-d-positive cells in the SG increased from 3.1±0.15% in newborn kittens to 9.3±0.63% in 20-day-old animals and decreased further from 8.1±0.75% in 30-day-old kittens to 3.4±0.54% in 2-month-old animals. The content of NADPH-d-positive cells in the CG and SCG did not change during development. There were no differences in cross-sectional area between neurons located in different ganglia of animals from the same age group under study. We conclude that the development of NADPH-d-positive neurons in different sympathetic ganglia has its own time dynamics and is completed by the end of the second month of life.     

Neurochemical properties of the middle cervical ganglion in the sheep

The neurochemical properties of the ovine middle cervical ganglion (MCG) were studied using antibodies raised against tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and galanin (GAL). Double-labelling immunocytochemistry revealed that the vast majority (95.5 +/- 0.8%) of postganglionic sympathetic MCG neurons expressed simultaneously both catecholamine-synthesizing enzymes (neurons were TH/DbetaH-positive). A large population of noradrenergic neurons exhibited immunoreactivity (IR) to NPY (62.2 +/- 2.2%), but single NPY-positive perikarya-lacking noradrenergic markers were also observed (2.0 +/- 0.3%). None of the examined MCG neuronal somata contained SP, CGRP, GAL or VIP. A moderate number of noradrenergic nerve fibres located amongst neuronal cell bodies was also found. In small number of these terminals the presence of NPYor GAL (but not CGRP or VIP) was detected. The ovine MCG was numerously innervated with SP-immunoreactive nerve fibres which sometimes formed basket-like formations around postganglionic neurons. The MCG exhibited a sparse CGRP-immunoreactive innervation and lacked VIP-positive nerve terminals. In many aspects the chemical coding of MCG postganglionic neurons and nerve terminals resembles that found in other mammalian cervico-thoracic paravertebral ganglia, but some important species-dependent differences exist. The functional implications of these differences remain to be elucidated.     

Extracellular matrix and development of lamination in the dorsal lateral geniculate nucleus in the tree shrew (Tupaia belangeri).

 In the tree shrew (Tupaia belangeri), the cytoarchitectonic lamination of the lateral geniculate nucleus cannot be detected at birth; it only appears during the early postnatal period. However, a laminated pattern was revealed with rapid Golgi staining and retinal afferents were segregated into the appropriate laminae well before cytoarchitectonic lamination could be seen. Both observations indicate that the extracellular matrix may play a role in the separation of lateral geniculate nucleus cells into laminae. In the present study, the organization of the extracellular matrix was investigated during development using immunohistochemical and in situ hybridization techniques. For immunohistochemistry, peanut agglutinin (PNA) lectin and antibodies against tenascin (TN) were chosen, while for in situ hybridization, mTN riboprobes were used, simultaneously, with antibodies against Vimentin (Vim) and microtubule associated protein (MAP-2). The results showed that the pattern of PNA-binding glycoproteins and that of tenascin were relatively similar, although tenascin appeared later and disappeared earlier. The first interlaminar spaces to be detected were those between layers innervated by opposite eyes. The TN specific mRNA was detected in the lateral geniculate nucleus at P0, but was no longer visible at P7. By comparing TN mRNA and Vim or MAP-2 stainings a correspondence could be observed. The extracellular matrix lamination therefore seems to precede cytoarchitectonic lamination, suggesting that the extracellular matrix may play a role in the development of laminated structures. The TN-producing cells seem to be developing astrocytes and neurons. Accepted: 23 November 1998