| the alpha-2b adrenoceptor in the paraventricular thalamic nucleus is persistently upregulated by chronic psychosocial stress. | stress has been reported to regulate adrenergic receptors but it is not known whether it has an impact on the alpha-2 adrenoceptor subtype b that is strongly expressed in distinct nuclei of the thalamus. so far little is known about effects of stress on the thalamus. using the chronic psychosocial stress paradigm in male tree shrews, we analyzed alpha-2b adrenoceptor expression in the paraventricular and the anteroventral nucleus of the thalamus after a six-week period of daily social stress and ... | 2004 | 15672682 |
| areal specialization of pyramidal cell structure in the visual cortex of the tree shrew: a new twist revealed in the evolution of cortical circuitry. | cortical pyramidal cells, while having a characteristic morphology, show marked phenotypic variation in primates. differences have been reported in their size, branching structure and spine density between cortical areas. in particular, there is a systematic increase in the complexity of the structure of pyramidal cells with anterior progression through occipito-temporal cortical visual areas. these differences reflect area-specific specializations in cortical circuitry, which are believed to be ... | 2005 | 15660232 |
| alterations of neuroplasticity in depression: the hippocampus and beyond. | early hypotheses on the pathophysiology of major depression were based on aberrant intrasynaptic concentrations of mainly the neurotransmitters serotonin and norepinephrine. however, recent neuroimaging studies have demonstrated selective structural changes across various limbic and nonlimbic circuits in the brains of depressed patients. in addition, postmortem morphometric studies revealed decreased glial and neuron densities in selected brain structures supporting the idea that major depressio ... | 2004 | 15550346 |
| chronic stress decreases the number of parvalbumin-immunoreactive interneurons in the hippocampus: prevention by treatment with a substance p receptor (nk1) antagonist. | previous studies have demonstrated that stress may affect the hippocampal gabaergic system. here, we examined whether long-term psychosocial stress influenced the number of parvalbumin-containing gabaergic cells, known to provide the most powerful inhibitory input to the perisomatic region of principal cells. adult male tree shrews were submitted to 5 weeks of stress, after which immunocytochemical and quantitative stereological techniques were used to estimate the total number of hippocampal pa ... | 2005 | 15470372 |
| neural plasticity and the promise of novel pharmacotherapies for depression. commentary on fuchs et al., examining novel concepts of the pathophysiology of depression in the chronic psychosocial stress paradigm in tree shrews. | | 2004 | 15343061 |
| depressed neurogenesis and its role in the genesis of depression. commentary on fuchs et al., examining novel concepts of the pathophysiology of depression in the chronic psychosocial stress paradigm in tree shrews. | | 2004 | 15343060 |
| more questions than answers. commentary on fuchs et al., examining novel concepts of the pathophysiology of depression in the chronic psychosocial stress paradigm in tree shrews. | | 2004 | 15343059 |
| examining novel concepts of the pathophysiology of depression in the chronic psychosocial stress paradigm in tree shrews. | despite decades of research on psychiatric disorders, the aetiology and precise biological mechanisms that underlie depressive diseases are still poorly understood. there is increasing evidence that psychiatric disorders not only have a neurochemical basis but are also associated with morphological alterations in central nervous neurons and/or glial cells. antidepressants may act by restoring structure as well as function of neural networks, meaning that they may, as a fundamental principle, aff ... | 2004 | 15343055 |
| homeostatic maintenance in excitability of tree shrew hippocampal ca3 pyramidal neurons after chronic stress. | the experience of chronic stress induces a reversible regression of hippocampal ca3 apical neuron dendrites. although such postsynaptic membrane reduction will obviously diminish the possibility of synaptic input, the consequences for the functional membrane properties of these cells are not well understood. we tested the hypothesis that chronic stress affects the input-output characteristics and excitability of ca3 pyramidal cells. somatic whole-cell current-clamp recording with parallel intrac ... | 2004 | 15318332 |
| the contribution of vertical and horizontal connections to the receptive field center and surround in v1. | here we review the results of anatomical and physiological studies in tree shrew visual cortex which focus on the contribution of vertical and horizontal inputs to receptive field center and surround properties of layer 2/3 neurons. a fundamental feature of both sets of connections is the arrangement of axon arbors in a fashion that respects both the orientation preference and retinotopic displacement of the target site. as a result, layer 2/3 neurons receive convergent input from populations of ... | 2007 | 15288892 |
| a morphological basis for orientation tuning in primary visual cortex. | feedforward connections are thought to be important in the generation of orientation-selective responses in visual cortex by establishing a bias in the sampling of information from regions of visual space that lie along a neuron's axis of preferred orientation. it remains unclear, however, which structural elements-dendrites or axons-are ultimately responsible for conveying this sampling bias. to explore this question, we have examined the spatial arrangement of feedforward axonal connections th ... | 2004 | 15258585 |
| synaptic plasticity and tianeptine: structural regulation. | stress-induced structural and cellular alterations in the hippocampus can contribute to the pathophysiology of depression. the reversal of these alterations may be a mechanism by which antidepressants achieve their therapeutic effect. the aim of the present study was therefore to investigate the effect of tianeptine on stress-induced structural changes and alterations in cerebral metabolites. to this end, psychosocially stressed male tree shrews were treated with tianeptine. a combination of in ... | 2002 | 15177087 |
| cellular consequences of stress and depression. | stress is known to activate distinct neuronal circuits in the brain and induce multiple changes on the cellular level, including alterations in neuronal structures. on the basis of clinical observations that stress often precipitates a depressive disease, chronic psychosocial stress serves as an experimental model to evaluate the cellular and molecular alterations associated with the consequences of major depression. antidepressants are presently believed to exert their primary biochemical effec ... | 2004 | 22033809 |
| antidepressant treatment with tianeptine reduces apoptosis in the hippocampal dentate gyrus and temporal cortex. | recent clinical and preclinical studies suggest that major depression may be related to impairments of structural plasticity. consequently, antidepressants may act by restoring altered rates of cell birth or death. here, we investigated whether the antidepressant tianeptine would affect apoptosis in an animal model of depression, the psychosocially stressed tree shrew. | 2004 | 15050859 |
| "lipotyphlan" phylogeny based on the growth hormone receptor gene: a reanalysis. | from an evolutionary perspective, "insectivores" have been one of the most important mammalian groups for over a century. morphologists have successively pruned flying lemurs, elephant shrews, and tree shrews from insectivora, but have retained chrysochlorids, tenrecs, erinaceids, soricids, talpids, and solenodontids in crown-group lipotyphla. with the appearance of large molecular data sets, the monophyly of lipotyphla has proved untenable. rather, an emerging consensus is that lipotyphla is a ... | 2004 | 15012955 |
| intrinsic connections in tree shrew v1 imply a global to local mapping. | the local-global map hypothesis states that locally organized response properties--such as orientation preference--result from visuotopically organized local maps of non-retinotopic response properties. in the tree shrew, the lateral extent of horizontal patchy connections is as much as 80-100% of v1 and is consistent with the length summation property. we argue that neural signals can be transmitted across the entire extent of v1 and this allows the formation of maps at the local scale that are ... | 2004 | 14992831 |
| identification of genes regulated by chronic psychosocial stress and antidepressant treatment in the hippocampus. | analysis of differentially expressed genes in the brain is a promising tool for elucidating pathological mechanisms that lead to central nervous disorders. stress is known to be involved in the development of psychopathologies such as depression. in the present study, we searched for differentially expressed genes in the hippocampal formation after chronic psychosocial stress and after treatment with the antidepressant clomipramine. experiments were conducted in male tree shrews, a valid psychos ... | 2004 | 14984416 |
| proportion and cluster analyses of the skull in various species of the tree shrews. | the skull adaptation was functional-morphologically examined in 14 species of the tree shrews. from the data of the proportion indices, the similarities were confirmed between t. minor and t. gracilis, t. tana and t. dorsalis, and t. longipes and t. glis. we demonstrated that the splanchnocranium was elongated in terrestrial t. tana and t. dorsalis and shortened in arboreal t. minor and t. gracilis from the proportion data. in both dendrogram from the matrix of the q-mode correlation coefficient ... | 2004 | 14960803 |
| refractive state of tree shrew eyes measured with cortical visual evoked potentials. | to determine the refractive state of tree shrew eyes using visual evoked potentials (vep's) recorded from primary visual cortex and compare the values with those obtained with streak retinoscopy and with an autorefractor. | 2003 | 14502042 |
| chronic social stress: effects on limbic brain structures. | different types of stressors are known to activate distinct neuronal circuits in the brain. acute physiological stimuli that are life threatening and require immediate reactions lead to a rapid stimulation of brainstem and hypothalamus to activate efferent visceral pathways. in contrast, psychological stressors activate higher-order brain structures for further interpretations of the perceived endangerment. common to the later multimodal stressors is that they need cortical processing and, depen ... | 2003 | 12954436 |
| emergent properties of layer 2/3 neurons reflect the collinear arrangement of horizontal connections in tree shrew visual cortex. | the superficial layers of primary visual cortex, unlike layer 4, have an extensive network of long-range horizontal connections linking sites of similar orientation preference. to identify possible functional consequences of this distinct anatomy, we compared the receptive field properties of layers 2/3 and 4 neurons in tree shrew primary visual cortex with electrophysiological recordings. we found that elongated receptive fields, strong orientation tuning, and length summation (properties predi ... | 2003 | 12684482 |
| alpha2a and alpha2c-adrenoceptor regulation in the brain: alpha2a changes persist after chronic stress. | stress-induced activation of the central nervous noradrenergic system has been suspected to induce depressive disorders. as episodes of depression often occur some time after a stress experience we investigated whether stress-induced changes in the alpha2-adrenoceptor (alpha2-ar) system persist throughout a post-stress recovery period. brains of male tree shrews were analysed after 44 days of chronic psychosocial stress and after a subsequent 10-day recovery period. expression of rna for alpha2a ... | 2003 | 12653968 |
| [different gene expression during hepatocarcinogenesis in tree shrew induced by aflatoxin b1]. | to understand the molecular mechanism and find out the responsible genes for liver cancer by exploring the regulation of gene expression during hepatocarcinogenesis in tree shrew induced by aflatoxin b1 (afb1). | 2003 | 12648405 |
| microscopic anatomy of the orbital harderian gland in the common tree shrew (tupaia glis). | the orbital harderian gland of the common tree shrew (tupaia glis) was investigated at the macroscopic and microscopic levels. in the glands of both sexes only one acinar cell type was found. the cell is characterized by the presence of numerous lipid vacuoles of variable size and by a small number of pas-positive, electron-dense granules distributed throughout the cytoplasm, which are predominant at the basal portion of each acinar cell. the duct system is well developed within the gland. the c ... | 2003 | 12520550 |
| substance p receptor antagonist and clomipramine prevent stress-induced alterations in cerebral metabolites, cytogenesis in the dentate gyrus and hippocampal volume. | the neuropeptide substance p and its receptor, the neurokinin 1 receptor (nk(1)r) have been proposed as possible targets for new antidepressant therapies. the present study investigated the effect of the nk(1)r antagonist l-760,735 and the tricyclic antidepressant clomipramine in the chronic psychosocial stress paradigm of adult male tree shrews. animals were subjected to a 7-day period of psychosocial stress before the onset of daily oral administration of l-760,735 (10 mg kg(-1) day(-1)) or cl ... | 2002 | 12399945 |
| molecular phylogenetic evidence confirming the eulipotyphla concept and in support of hedgehogs as the sister group to shrews. | for more than a century, living insectivore-like mammals have been viewed as little removed from the ancestral mammalian stock based on their retention of numerous primitive characteristics. this circumstance has made "insectivores" a group of special interest in the study of mammalian evolution. included hedgehogs, moles, shrews, solenodons, golden moles, tenrecs, flying lemurs, tree shrews, and elephant shrews in insectivora. subsequently, morphologists excluded flying lemurs, tree shrews, and ... | 2002 | 12383761 |
| histological study on intestinal diverticulum of tree shrew (tupaia javanica). | tree shrews possess an intestinal diverticulum. we investigated this diverticulum with histological and immunohistochemical methods to determine whether this diverticulum was cecum or not. the ratio of the length of diverticulum/small intestine was apparently shorter than that of several primates. in the histological study, mucous membrane of the small intestine was shifted to that of the large intestine at the junction of the diverticulum. histological features of the diverticulum were similar ... | 2002 | 12221937 |
| spatial coding of position and orientation in primary visual cortex. | we examined the spatial distribution of population activity in primary visual cortex (v1) of tree shrews with optical imaging and electrophysiology. a line stimulus, thinner than the average v1 receptive field, evoked a broad strip of neural activity of nearly constant size for all stimulus locations tested within the central 10 degrees of visual space. stimuli in adjacent positions activated highly overlapping populations of neurons; nevertheless, small changes in stimulus position produced ord ... | 2002 | 12195429 |
| the chronic psychosocial stress paradigm in male tree shrews: evaluation of a novel animal model for depressive disorders. | to improve our knowledge of the causal mechanisms of stress-related disorders such as depression, we need animal models that mirror the situation in patients. one promising model is the chronic psychosocial stress paradigm in male tree shrews, which is based on the territorial behaviour of these animals that can be used to establish naturally occurring challenging situations under experimental control in the laboratory. co-existence of two males in visual and olfactory contact leads to a stable ... | 2002 | 12171765 |
| retinoscleral control of scleral remodelling in refractive development: a role for endogenous fgf-2? | studies in avian models of myopia have shown that refractive error development can be influenced by exogenously delivered fibroblast growth factor (fgf)-2. the present study sought to determine whether endogenous fgf-2 was associated with retinoscleral signalling or scleral remodelling during changes in refractive error in a mammalian model of myopia. | 2002 | 12160524 |
| social stress in tree shrews: effects on physiology, brain function, and behavior of subordinate individuals. | social stress is known to be involved in the etiology of central nervous disorders such as depression. in recent years, animal models have been developed that use chronic stress to induce neuroendocrine and central nervous changes that might be similar to those occurring in the course of the development of depressive disorders. the present review gives a summary of observations made in the tree shrew chronic social stress model. during periods of daily social stress, male tree shrews develop sym ... | 2002 | 12076743 |
| chemopreventive effect of oltipraz on afb(1)-induced hepatocarcinogenesis in tree shrew model. | | 2000 | 11819668 |
| expression of igf- ii, p53, p21 and hbxag in precancerous events of hepatocarcinogenesis induced by afb1 and/or hbv in tree shrews. | | 2000 | 11819544 |
| a phylogenetic foundation for comparative mammalian genomics. | a major effort is being undertaken to sequence an array of mammalian genomes. coincidentally, the evolutionary relationships of the 18 presently recognized orders of placental mammals are only just being resolved. in this work we construct and analyse the largest alignments of amino acid sequence data to date. our findings allow us to set up a series of superordinal groups (clades) to act as prior hypotheses for further testing. important findings include strong evidence for a clade of euarchont ... | 2001 | 11791233 |
| gender-specific alterations of cerebral metabolites with aging and cortisol treatment. | excess availability of the adrenocortical glucocorticoid hormone cortisol has been correlated with structural brain changes and a decline of cognitive functions during aging. pertinent studies need to consider gender as a potential confound because of sexual dimorphism in the regulation of hypothalamus-pituitary-adrenal axis activity. in vivo localized proton magnetic resonance spectroscopy of male and female tree shrews revealed similar concentrations of cerebral metabolites in young adult anim ... | 2013 | 11578641 |
| chronic psychosocial stress differentially affects apoptosis in hippocampal subregions and cortex of the adult tree shrew. | we studied the effect of chronic psychosocial stress on cell death and volume changes in the tree shrew hippocampus. in situ end labelling (isel) identified low frequent but convincing apoptosis in many hippocampal subregions. also in entorhinal cortex, apoptosis was found, generally at higher frequencies. after 28 days of chronic stress, apoptosis was significantly reduced in the ca1 stratum radiatum, whereas an increase was observed in the hilus (p < 0.04). with all subregions taken together, ... | 2001 | 11488960 |
| chronic subordination stress in male tree shrews: replacement of testosterone affects behavior and central alpha(2)-adrenoceptors. | subordination stress induced by social defeat in male animals is known to inhibit gonadal functions and it has been discussed whether the resulting deficit in testosterone might play a role in subordination behavior. one of the major transmitter systems involved in regulation of behavior is the noradrenergic system. to analyze whether a testosterone replacement can alter subordination behavior and whether this might be related to changes in the brain noradrenergic system, we quantified alpha(2)- ... | 2001 | 11438354 |
| how to use the optical fractionator: an example based on the estimation of neurons in the hippocampal ca1 and ca3 regions of tree shrews. | until recently, exposure of the hippocampus to prolonged elevated glucocorticoid levels was thought to result in damage and loss of pyramidal neurons. most of the earlier studies were based on measures of neuronal density and used assumptions-based counting methods. using a stereological technique, the optical fractionator, which eliminates potential biases inherent in the assumption-based techniques, we were able to demonstrate that chronic psychosocial stress in tree shrews has no effect on ne ... | 2001 | 11431122 |
| steady state mrna levels in tree shrew sclera with form-deprivation myopia and during recovery. | in tree shrews, visual form deprivation induces myopia and tissue remodeling in the sclera, characterized by decreased levels of collagen and glycosaminoglycans (gags) and increased levels of matrix metalloproteinases (mmps). removal of the visual deprivation allows recovery. this study investigated whether these changes are accompanied by changes in steady state mrna levels in the sclera. | 2001 | 11328721 |
| scleral remodeling during the development of and recovery from axial myopia in the tree shrew. | recent investigations have suggested that scleral thinning in mammalian eyes with axial myopia is a consequence of the loss of scleral tissue, rather than the redistribution of existing tissue as the eye enlarges. the present study investigated whether further changes in the distribution and metabolism of scleral tissue occur during the process of recovery from axial myopia. scleral glycosaminoglycan (gag) synthesis and content as well as scleral dry weight changes were monitored as indicators o ... | 2000 | 11053267 |
| changes in blood-retinal barrier permeability in form deprivation myopia in tree shrews. | to study the correlation between blood-retinal barrier (brb) permeability and development of form deprivation (fd) myopia, fd was induced in tree shrews. the refractive error and the axial dimensions of the optical elements were measured. ocular fluorescence was measured before and after fluorescein-na injection. the inward permeability (p(in)) of the brb was measured before and 15, 30, and 45 days after fd was induced. fd eyes became significantly myopic 15 days after fd was induced (p<0.01), a ... | 2000 | 10927122 |
| osteometrical skull character in the four species of tree shrew. | the skull size and shape were osteometrically examined in the four species of the tree shrews (tupaia tana, t. javanica, t. minor and t. dorsalis). we suggest that the skull characters were affected by the species specific behavior and terrestrial, arbo-terrestrial and arboreal life, among the genus tupaia. the neurocranium was laterally narrower in the braincase area, and the splanchnocranium was longer only on dorsal side in t. tana, and these characters were opposite to t. minor. the principa ... | 2000 | 10852401 |
| effect of chronic psychosocial stress and long-term cortisol treatment on hippocampus-mediated memory and hippocampal volume: a pilot-study in tree shrews. | we investigated the impact of chronic psychosocial stress and long-term cortisol treatment on hippocampus-mediated memory processes and hippocampal volume in male tree shrews. by combining cognitive tests on a hole board, magnetic resonance imaging (mri), and saliva cortisol analysis, we were able to follow in individual animals the stress- and cortisol-induced temporal effects on hpa axis activity and the hippocampus and its executive functions during 15 weeks. four weeks of either cortisol tre ... | 2000 | 10725612 |
| functional specificity of callosal connections in tree shrew striate cortex. | although callosal connections have been shown to link extensive regions of primary visual cortex, the distribution of these connections with respect to the map of visual space and the map of orientation preference remains unclear. here we combine optical imaging of intrinsic signals with injection of fluorescent microspheres to assess the functional specificity of callosal connections in the tree shrew. by imaging both hemispheres simultaneously while presenting a series of spatially restricted ... | 2000 | 10704509 |
| diazepam has no beneficial effects on stress-induced behavioural and endocrine changes in male tree shrews. | the present study evaluated the effect of subchronic oral treatment of psychosocially stressed male tree shrews with diazepam on locomotor activity, marking behavior, avoidance behavior, and urinary cortisol and noradrenaline. to mimic a realistic situation of anxiolytic intervention, the treatment started 14 days after the beginning of psychosocial stress; at that time, the stress-induced behavioral and endocrine alterations had been established. the drug (5 mg/kg/day) was administered orally i ... | 2000 | 10683496 |
| micro-anatomy of the volar skin and interordinal relationships of primates. | paleontological and molecular evidence have been employed to suggest that flying lemurs (dermoptera) and primates form a monophyletic group, in sharp contrast with cranial and postcranial evidence indicating sister group relationships between flying lemurs and bats (chiroptera). new evidence from the epidermis of the volar pads of primates, tree shrews, flying lemurs, bats, and other mammals was examined and mapped on to various hypotheses of archontan relationships. the micro-anatomy of the ski ... | 2000 | 10656778 |
| effects of cortisol on brain alpha2-adrenoceptors: potential role in stress. | it has been proposed that behavioural changes induced by chronic psychosocial stress in male tree shrews might be related to alterations in the central nervous alpha2-adrenoceptor system. in the noradrenergic centres of the brain, alpha2-adrenoceptors function as autoreceptors regulating noradrenaline release. chronic stress downregulates these receptors in several brain regions. since during stress, the activity of the hypothalamus-pituitary-adrenal axis is increased leading to high concentrati ... | 1999 | 10580309 |
| chronic psychosocial stress and antidepressant treatment in tree shrews: time-dependent behavioral and endocrine effects. | social defeat has been shown to cause a number of behavioral, physiological, and central nervous changes in male tree shrews. the present study was designed to assess: (i) a potential time lag in the occurrence of behavioral alterations (locomotor activity, self-grooming, marking behavior, food and water intake, and avoidance behavior) after stress and long-term antidepressant treatment; and (ii) to investigate potential interactions between behavioral and endocrine variables (urinary cortisol a ... | 1999 | 10580308 |
| experimental therapy of a platelet-activating factor antagonist (ginkgolide b) on photochemically induced thrombotic cerebral ischaemia in tree shrews. | 1. the aim of the present study was to investigate the effects of a platelet-activating factor (paf) antagonist (ginkgolide b; gb) on brain oedema, ion homeostasis, monoamine neurotransmitter disturbances in ischaemic penumbra and the neuroprotective mechanisms of the paf antagonist. 2. photochemically induced thrombotic cerebral ischaemia in tree shrews was used as the experimental model and changes in histopathology and the content of monoamine neurotransmitters (measured by a spectrofluoromet ... | 1999 | 10549411 |
| calcium channel heterogeneity among cone photoreceptors in the tree shrew retina. | retinal photoreceptors are depolarized in darkness and release neurotransmitter tonically. they respond to light by hyperpolarization and a concomitant reduction in transmitter release. the calcium-dependent release of transmitter is coupled to graded changes in membrane potential by l-type calcium channels in the photoreceptor terminals. this paper reports the immuno-localization of an l-type channel alpha1d subunit to most, but not all, synaptic terminals of cones in the tree shrew retina. dou ... | 1999 | 10457194 |
| optical correction of induced axial myopia in the tree shrew: implications for emmetropization. | to determine whether an active emmetropization mechanism is involved in the recovery from axial myopia through the use of a mammalian model of refractive development. specifically, we sought to establish whether the emmetropization mechanism is visually guided by the level of clarity of the image falling on the retina, or if recovery is driven by a mechanism sensitive to abnormal eye shape. | 1999 | 10416937 |
| phalangeal morphology of the paromomyidae (?primates, plesiadapiformes): the evidence for gliding behavior reconsidered. | a comparative morphometric analysis of isolated proximal and intermediate phalanges attributed to the paromomyids ignacius graybullianus and phenacolemur simonsi was undertaken to test the hypothesis that these fossil phalanges exhibit evidence of a dermopteran-like interdigital patagium. linear dimensions were collected for the fossil phalanges and a comparative sample of associated proximal and intermediate phalanges representing extant tree squirrels, tree shrews, dermopterans (colugos), glid ... | 1999 | 10407467 |
| volumetric mri measurements of the tree shrew hippocampus. | protocols suitable for repeated magnetic resonance imaging (mri) studies of the tree shrew's brain were established. this included the development of (i) a technique for prolonged inhalation anesthesia by endotracheal intubation; (ii) a reproducible fixation of the animal's head in a stereotaxic frame and finally (iii) the set-up of the hardware (rf coil) and software (mri sequences) of the mri system. the endotracheal intubation as well as the repeated and prolonged anesthesia showed no complic ... | 1999 | 10389665 |
| localization of nitric oxide synthase in the tree shrew retina. | nitric oxide (no) is a novel neuronal messenger that likely influences retinal function by activating retinal guanylyl cyclase to increase levels of cgmp. in the present study, the localization of neuronal nitric oxide synthase (nnos, type i nos) in the cone-dominant tree shrew retina was studied using nadph-d histochemistry and nnos immunocytochemistry. both nadph-d and nnos-immunoreactivity (ir) labeled the inner segments of rods and the myoids of a regular subpopulation of cones, with their c ... | 2006 | 10349961 |
| local excitatory circuits in the intermediate gray layer of the superior colliculus. | we have used photostimulation and whole cell patch-clamp recording techniques to examine local synaptic interactions in slices from the superior colliculus of the tree shrew. uncaging glutamate 10-75 microm from the somata of neurons in the intermediate gray layer elicited a long-lasting inward current, due to direct activation of glutamate receptors on these neurons, and brief inward currents caused by activation of presynaptic neurons. the synaptic responses occurred as individual currents or ... | 1999 | 10085368 |
| modulation of scleral dna synthesis in development of and recovery from induced axial myopia in the tree shrew. | visually modulated scleral extracellular matrix remodelling is associated with the development of, and recovery from, induced axial myopia in the tree shrew, a commonly used mammalian model of refractive error development. the involvement of scleral cell proliferation in this process was investigated using [3h] thymidine. tree shrews were monocularly deprived of pattern vision, using translucent occluders, or the retinal image was optically defocused, using negative lenses, over a period of 5 da ... | 1999 | 10068481 |
| memory performance in tree shrews: effects of stressful experiences. | male tree shrews were exposed to alternating non-stressful and stressful conditions, and their memory performance was tested during three different stress periods and after rest periods of various lengths using a modified holeboard. this paradigm circumvents confounding factors, e.g. food or water deprivation, transport to a special testing arena, and excludes the development of automatic cognitive processes by complex memory tasks. in experimental tree shrews, psychosocial conflict caused eleva ... | 1998 | 9884125 |
| stress, glucocorticoids and structural plasticity of the hippocampus. | sustained stress can have numerous pathophysiological effects. adrenal glucocorticoid hormones are principal effectors in the stress response. they have profound effects on mood and behavior and affect neurochemical transmission and neuroendocrine control. we have used the experimental paradigm of chronic psychosocial stress in tree shrews to investigate the impact of aversive social encounters on brain structures. chronic stress in male tree shrews which is accompanied by constantly elevated le ... | 1998 | 9884123 |
| angioarchitecture of the coeliac sympathetic ganglion complex in the common tree shrew (tupaia glis). | the angioarchitecture of the coeliac sympathetic ganglion complex (cgc) of the common tree shrew (tupaia glis) was studied by the vascular corrosion cast technique in conjunction with scanning electron microscopy. the cgc of the tree shrew was found to be a highly vascularised organ. it normally received arterial blood supply from branches of the inferior phrenic, superior suprarenal and inferior suprarenal arteries and of the abdominal aorta. in some animals, its blood supply was also derived f ... | 1998 | 9877296 |
| adrenal microvascularization in the common tree shrew (tupaia glis) as revealed by scanning electron microscopy of vascular corrosion casts. | the blood supply of the adrenal gland in the common tree shrew (tupaia glis) was studied by use of transmission electron microscopy and vascular corrosion cast/scanning electron microscopy techniques. it was found that the gland receives its blood supply from branches of the inferior phrenic, aorta and renal arteries. upon reaching the gland, these arteries divide into cortical and medullary arteries. the cortical arteries give rise to the subcapsular capillary plexuses which partially enclose t ... | 1998 | 9852352 |
| evolution of neuroendocrine peptide systems: gonadotropin-releasing hormone and somatostatin. | nine vertebrate and two protochordate gonadotropin-releasing hormone (gnrh) decapeptides have been identified and sequenced. multiple molecular forms of gnrh peptide were present in the brain of most species examined, and cgnrh-ii generally coexists with one or more gnrh forms in all the major vertebrate groups. the presence of multiple gnrh forms has been further confirmed by the deduced gnrh peptide structure from cdna and/or gene sequences in several teleost species and tree shrew. high conse ... | 1998 | 9827009 |
| a test of archonta monophyly and the phylogenetic utility of the mitochondrial gene 12s rrna. | the relationships within the superorder archonta, which contains the orders dermoptera (flying lemurs), scandentia (tree shrews), chiroptera (bats), and primates, were examined through the analysis of five newly derived and complete mitochondrial 12s rrna sequences. the new data is combined with 83 additional known mammalian sequences to provide a full phylogenetic sampling. phylogenetic hypotheses are generated using paup 3.1.1 (swofford [1993] illinois natural history survey, champaign, il) th ... | 1998 | 9821489 |
| 5ht1a-receptors and behaviour under chronic stress: selective counteraction by testosterone. | behaviour of chronically stressed male tree shrews is characterized by a reduction in scent marking, self-grooming and overall locomotor activity. it has been proposed that this subordination behaviour is related to the down-regulation of 5ht1a-receptors occurring in distinct brain regions of the animals. the high cortisol concentrations which accompany chronic stress are supposed to induce 5ht1a-receptor down-regulation. because chronic stress in males also decreases androgen levels we investig ... | 1998 | 9767398 |
| testicular microvascularization in the common tree shrew (tupaia glis) as revealed by vascular corrosion cast/sem and by tem. | testicular angioarchitecture in lower primates has not been established and the route of androgens from leydig cells entering the systemic circulation is still a matter of controversy. in the present study, the common tree shrew (tupaia glis) was used as the model for vascular corrosion cast/sem and conventional tem studies. with vascular corrosion cast/sem, it was revealed that while coursing in the spermatic cord, the testicular artery convoluted and gave off branches to supply the epididymis, ... | 1998 | 9764923 |
| optical feedback controlled scleral remodeling as a mechanism for myopic eye growth. | experimental studies of myopia have demonstrated that optical errors imposed on a developing eye will stimulate elongation of the globe, although the mechanism of axial growth is not well understood. in this study, a mathematical model of eye growth is presented in which expansion of the globe occurs as the elastic deformations of the scleral shell are incorporated into the zero stress configuration of the eye during the scleral remodeling process. the rate of remodeling is determined by the ret ... | 1998 | 9745757 |
| opioidergic innervation of the tree shrew pineal gland: an immunohistochemical study. | the tree shrew (tupaia glis) has been described as a missing link relating primate to insectivore stock. the pineal gland of the tree shrew consists of a superficial pineal and a deep pineal, which are connected by a long and slender pineal stalk. a monoclonal antibody against leu-enkephalin was used in an immunohistochemical investigation of the tree shrew pineal gland. a moderate innervation of leu-enkephalin immunoreactive nerve fibers has been demonstrated in both superficial and deep pineal ... | 1998 | 9572529 |
| monoclonal antibody tsd-1 is specific to elongating and matured spermatids in testis of common tree shrew (tupaia glis). | the monoclonal antibody (mab), named tsd-1, specific to spermatogenic cells of the common tree shrew (tupaia glis) was established and characterized using immunohistochemistry and immunoblotting. mab tsd-1 reacted with elongating and matured spermatids in a stage-dependent manner. tsd-1 recognized a 94 kilodalton (kda) peptide in the plasma membrane and cytosol. additionally, an extremely weak 107 kda band was detected only in the cytosol. the reactions were not detected in round spermatids. in ... | 1998 | 9560784 |
| body temperature and behavior of tree shrews and flying squirrels in a thermal gradient. | the daily rhythms of body temperature, temperature selection, and locomotor activity of tree shrews and flying squirrels were studied in a thermal gradient. in accordance with previous observations in other mammalian species, the rhythm of temperature selection was found to be 180 degrees out of phase with the body temperature rhythm in both species. comparison of the amplitude of the body temperature rhythm in the presence and absence of the ambient temperature gradient indicated that behaviora ... | 1998 | 9523893 |
| first evidence of diversity in eutherian chiasmatic architecture: tree shrews, like marsupials, have spatially segregated crossed and uncrossed chiasmatic pathways. | in the optic chiasm of mammals, axons either cross the midline to the opposite side of the brain or remain uncrossed. in the eutherian species studied to date, uncrossed axons in the caudal nerve are found in all regions. in the chiasm, they are dispersed through the hemichiasm, with many axons approaching the midline and then turning back to enter the same side of the brain as the originating eye. in marsupials, by contrast, uncrossed axons never approach the midline; instead, they remain group ... | 1998 | 9453663 |
| carpal development and morphology in archontan mammals. | carpal morphology and development in bats, colugos, tree shrews, murids, and sciurids were studied in order to homologize carpal elements. prenatal coalescence of discrete cartilaginous templates with a loss of a center of ossification appears to be the most common method of reducing carpal elements in these mammals. only bats and colugos showed postnatal ossification between discrete elements as a method of reducing carpal elements. carpal morphology of tree shrews is more diverse than previous ... | 1998 | 9438973 |
| starburst cholinergic amacrine cells in the tree shrew retina. | in all mammalian retinae studied to date, starburst cholinergic amacrine cells are a consistently occurring cell type. here, we show that the cone-dominated retina of the tree shrew also has starburst cells with the characteristic radially symmetric branching pattern known from other species. dendritic field sizes increase from 150 microm in the central retina to 300 microm in the retinal periphery. the characteristic morphology is established early during postnatal development. labelling the st ... | 1997 | 9390767 |
| chronic psychosocial stress does not affect the number of pyramidal neurons in tree shrew hippocampus. | exposure of the hippocampus for prolonged periods to an excess of glucocorticoids is thought to result in damage and finally loss of pyramidal neurons. by applying improved methods for quantifying cell numbers we investigated whether chronic psychosocial stress in tree shrews reduces the total number of hippocampal pyramidal neurons. for 28 days male tree shrews were exposed to subordination stress resulting in constantly elevated cortisol levels. the number of pyramidal neurons in the hippocamp ... | 1997 | 9350847 |
| neurogenesis in the dentate gyrus of the adult tree shrew is regulated by psychosocial stress and nmda receptor activation. | these studies were designed to determine whether adult neurogenesis occurs in the dentate gyrus of the tree shrew, an animal phylogenetically between insectivores and primates, and to explore the possibility that this process is regulated by stressful experiences and nmda receptor activation. we performed immunohistochemistry for cell-specific markers and the thymidine analog bromodeoxyuridine (brdu), a marker of dna synthesis that labels proliferating cells and their progeny, on the brains of a ... | 1997 | 9065509 |
| orientation selectivity and the arrangement of horizontal connections in tree shrew striate cortex. | horizontal connections, formed primarily by the axon collaterals of pyramidal neurons in layer 2/3 of visual cortex, extend for millimeters parallel to the cortical surface and form patchy terminations. previous studies have provided evidence that the patches formed by horizontal connections exhibit modular specificity, preferentially linking columns of neurons with similar response characteristics, such as preferred orientation. the issue of how these connections are distributed with respect to ... | 1997 | 9045738 |
| unusual nature and possible evolutionary implications of the male vesicular gland secretion in the tree shrew, tupaia glis. | whereas the secretion of the male vesicular gland in most mammals is amorphous, that of the tree shrew, tupaia glis, was observed to be stored as globules. | 1997 | 9025999 |
| microvascularization in trigeminal ganglion of the common tree shrew (tupaia glis). | since there is only a limited number of studies of the blood supply to the trigeminal ganglion (tg) in mammalian species, the tg from 16 common tree shrews (tupaia glis) were investigated by light microscope, transmission electron microscope (tem) and the corrosion cast technique in conjunction with scanning electron microscope (sem). it was found that the tg contained clusters of neurons in the peripheral region whereas the bundles of nerve fibers were located more centrally. each ganglionic ne ... | 1997 | 9643657 |
| alterations in the central nervous alpha 2-adrenoceptor system under chronic psychosocial stress. | it has recently been shown for the tree shrew that after 10 days of psychosocial stress, when the central nervous noradrenergic and adrenergic systems are highly activated, alpha 2-adrenoceptors are down-regulated in brain regions which are involved in the regulation of autonomic functions (flügge g. et al. (1992) brain res. 597, 131-137). the present study demonstrates the dynamic changes occurring in the alpha 2-adrenoceptor system during chronic psychosocial stress. male tree shrews were subm ... | 1996 | 8923533 |
| an ultrastructural and lectin-histochemical study on the seminiferous epithelium of the common tree shrew (tupaia glis). | the seminiferous epithelium of the common tree shrew (tupaia glis) was investigated using transmission electron microscopy and lectin-histochemistry. it was compared with that of shrews examined in previous studies. some peculiar structures were detected in the tree shrew spermatid at the electron microscopic level. the most characteristic feature was the disposition of mitochondria in early spermatids. in cap and early acrosome-phase spermatids, mitochondria accumulated in one area of the sperm ... | 1996 | 8771399 |
| form-deprivation myopia induces activation of scleral matrix metalloproteinase-2 in tree shrew. | to investigate whether structural changes to the sclera during form-deprivation myopia are caused by active tissue remodeling, the gelatinase activity of tree shrew scleras was studied in normal animals, form-vision deprived animals, and animals recovering from myopia. | 1996 | 8641841 |
| the m1 muscarinic antagonist pirenzepine reduces myopia and eye enlargement in the tree shrew. | to determine the efficacy of the m1-selective muscarinic antagonist, pirenzepine, in preventing experimentally induced myopia in a mammalian model, the tree shrew. | 1996 | 8641840 |
| the functional organization of local circuits in visual cortex: insights from the study of tree shrew striate cortex. | we have used a combination of anatomical and physiological techniques to explore the functional organization of vertical and horizontal connections in tree shrew striate cortex. our studies of vertical connections reveal a remarkable specificity in the laminar arrangement of the projections from layer iv to layer iii that establishes three parallel intracortical pathways. the pathways that emerge from layer iv are not simple continuations of parallel thalamocortical pathways. layer iv and its co ... | 2007 | 8670661 |
| specificity in the axonal connections of layer vi neurons in tree shrew striate cortex: evidence for distinct granular and supragranular systems. | pyramidal neurons in layer vi of striate cortex are the source of descending projections to the lateral geniculate nucleus (lgn) as well as a major source of axon terminals in the layers of striate cortex that receive lgn projections. this study examines how the connections of layer vi neurons are arranged with respect to the functionally distinct classes of neurons that compose their cortical and subcortical targets. by placing injections of biocytin into layer vi of tree shrew striate cortex, ... | 1996 | 8558249 |
| enamel prism morphology in molar teeth of small eutherian mammals. | data summarizing enamel prism shape, size and spacing are reported for the molar enamel of 55 species of small eutherian mammals including primates, bats, tree shrews, flying lemurs, insectivorans and representatives of a variety of fossil families. confocal photomicrographs reveal that the subsurface enamel of most species is characterized by arc-shaped prisms. the lack of a clear distinction between pattern 2 and pattern 3 prism configurations within single specimens suggests that the broad ca ... | 1996 | 9813617 |
| fluorophotometry with a small animal adapter. | the usefulness of the fluorotron master fluorophotometer fitted with a small animal adapter was evaluated with tree shrews. we also determined that the optimal measurement parameters for these animals, which are regarded as promising for experimental use in ophthalmic research, are: fluorescein-na concentration, 0.5 x 10(-9) to 1.0 x 10(-6) g/ml; fluorescein-na dosage, 2 mg/kg; measurement time, 30 minutes after injection of fluorescein-na into the ocular compartments. results indicated that ult ... | 1996 | 8988420 |
| fine structure of the parotid gland in tree shrew (tupaia glis). | the parotid glands of tupaia glis were examined by light and transmission electron microscopy. the acinar cells were seromucous in nature, and contained many acidophilic granules with strong affinity for periodic acid-schiff (pas) and weak affinity for alcian blue (ab). these granules consisted of a fine granular matrix of moderate density in which a denser corpuscles or semilunar materials were present. intercalated duct cells had a few fine vesicles, vacuoles and very few dense granules in the ... | 1995 | 8575539 |
| cardiac musculature of the cranial vena cava in the common tree shrew (tupaia glis). | cardiac musculature of the cranial vena cava in the common tree shrew (tupaia glis) was examined by light and transmission electron microscopy. the common tree shrew has well developed cardiac myocyte layers in the tunica media of the cranial vena cava, extending from the right atrium to the root of the subclavian vein. because the common tree shrew belongs to a primitive group of mammals, the occurrence of cardiac musculature in the cranial vena cava may be a common feature in lower mammals. th ... | 1995 | 7591997 |
| form deprivation myopia: elastic properties of sclera. | thinning of the posterior sclera may imply that stretching and/or weakening of the sclera plays a role in axial elongation of myopic eyes. we investigated the elastic stress-strain properties of sclera from developing tree shrew eyes made myopic by monocular deprivation (md) of form vision. five days of md induced a relative myopia (mean +/- sem) of -5.6 d +/- 0.6 d (retinoscopy) and a vitreous chamber elongation (deprived minus control) of 106 +/- 14 microns, n = 10 (ultrasonography). posterior ... | 1995 | 8524554 |
| laminar organization of receptive field properties in the dorsal lateral geniculate nucleus of the tree shrew (tupaiaglis belangeri). | a laminar analysis of the receptive field properties of relay cells in the binocular region of the tree shrew dorsal lateral geniculate nucleus (lgn) found three main subdivisions. lamina 1 (receiving ipsilateral eye input) and lamina 2 (contralateral) comprise a pair of layers that contain only on-center neurons. laminae 4 (contralateral) and 5 (ipsilateral) comprise a pair of layers with mostly off-center cells (86%). laminae 3 and 6 (both contralaterally innervated) also form a distinct pair, ... | 1995 | 7560294 |
| reduced extracellular matrix in mammalian sclera with induced myopia. | the purpose of this study was to learn whether visual form deprivation, which produces myopia in the deprived eye, alters the scleral extracellular matrix in tree shrew, a mammal closely related to primates. axial myopia was induced in 10 tree shrews by monocular deprivation imposed with a translucent diffuser. the other eye in each animal was an untreated control. after 21 days of deprivation the refractive state and axial component dimensions were measured and the eyes were assayed for levels ... | 1995 | 7610587 |
| chronic psychosocial stress induces morphological alterations in hippocampal pyramidal neurons of the tree shrew. | the effect of sustained psychosocial stress on the morphology of hippocampal pyramidal neurons was analysed in male tree shrews after 14, 20, and 28 days of social confrontation. a variety of physiological changes such as constantly elevated levels of urinary cortisol and norepinephrine and reduced body weight, which are indicative of chronic stress were observed in the subordinate, but not in the dominant males. light microscopic analysis of nissl-stained hippocampal sections showed that the st ... | 1995 | 7606441 |
| modulation of binding sites for corticotropin-releasing hormone by chronic psychosocial stress. | this study was conducted to determine whether long lasting psychosocial stress would affect corticotropin-releasing hormone (crh) binding sites in the brain, the pituitary, and the adrenal gland. as a model for sustained emotional stress we used chronic psychosocial conflict in male tree shrews. in subordinate tree shrews, repeated confrontation with a dominant conspecific results in constant hyperactivity of the hpa-axis and an elevated neurosympathetic tone. after 24 days of psychosocial confl ... | 1995 | 7838901 |
| a morphological study on the crown dimensions of the mandibular molars in tupaia glis. | the crown dimensions of the mandibular molars in tupaia glis were measured. all the mean values of crown diameters and areas were larger for the m1 molar than for the m2 and m3. the last two molars were more reduced in the talonid component than in the trigonid compared to the m1, and were more reduced in the buccolingual than in the mesiodistal direction. the most common molar size sequence (mss) was m1 > m2 > m3, and this pattern was more frequently observed in the talonid component than in th ... | 1994 | 8041562 |
| crown dimensions of the maxillary molars in tupaia glis. | the crown dimensions of the maxillary molars in tupaia glis were measured, and the most common molar size sequence was m1 > m2 > m3. the m2 and m3 molars were smaller than the m1 in the mesiodistal crown diameters. with regard to the buccolingual diameters, the distal part of m1 and mesial part of m2 were relatively larger and less variable in size. this stable area corresponded to the inflection point of the maxillary arch curve. these results could be explained from a functional morphological ... | 1994 | 8041561 |
| lid-suture myopia in tree shrews with retinal ganglion cell blockade. | to determine whether central communication of retinal signals is necessary for the development of an experimentally induced myopia, tree shrews were exposed to monocular deprivation (md) while the action potentials of retinal cells in the deprived eye were blocked with intravitreally injected tetrodotoxin (ttx-md animals). ttx injections (0.6 microgram in 3 microl) and md began about 15 days after eye opening, at the start of the susceptible period for the development of lid-suture myopia. six i ... | 2016 | 8011577 |
| horizontal cells in the cone-dominated tree shrew retina: morphology, photoreceptor contacts, and topographical distribution. | while most mammalian retinas are rod dominated, in the tree shrew retina 95% of the photoreceptors are cones. we studied three shrew horizontal cells to look for features associated with this unusual photoreceptor arrangement. the morphology of horizontal cells was revealed by intracellular injections of lucifer yellow, and their photoreceptor contacts were assessed by light and electron microscopy. horizontal cell topography was studied in material stained with a neurofilament antibody and with ... | 1993 | 7688042 |
| microvascularization of the common tree shrew (tupaia glis) superior cervical ganglion studied by vascular corrosion cast with scanning electron microscopy. | microvascularization of the superior cervical ganglion (scg) of the common tree shrew (tupaia glis) was investigated by the vascular-corrosion-cast technique in conjunction with scanning electron microscopy. it was found that the scg of the tree shrew is a highly vascularized organ. it receives arterial blood from branches of the external and common carotid arteries which enter the rostral and caudal portions of the ganglion. these arteries give rise to a subcapsular capillary plexus before bran ... | 1993 | 8273447 |
| cytoarchitecture of the common tree shrew (tupaia glis) superior cervical ganglion. a scanning electron microscope study on vascular cast/enzyme-digested superior cervical ganglia. | the cytoarchitecture of the superior cervical ganglion of the common tree shrew was investigated by scanning electron microscopy using the vascular cast technique in conjunction with digestion by collagenase-hyaluronidase/hcl. the main cellular constituents were found to be multipolar neurons that were densely distributed throughout the ganglion. these neurons were covered with a smooth cytoplasmic sheath of satellite cells. after the removal of this sheath by digestion of increased duration, th ... | 1993 | 8116334 |
| [3h]rauwolscine binding sites in the brains of male tree shrews are related to social status. | the aim of the present study was to investigate the influence of social status on central nervous alpha 2-adrenoceptors. using the specific alpha 2-adrenoceptor antagonist [3h]rauwolscine, binding sites in the brains of dominant and subordinate male tree shrews were quantified by in vitro autoradiography. in 5 of the 14 brain structures investigated, subordinates had significantly lower numbers of binding sites than dominants. these structures were the solitary tract nucleus, the dorsal motor nu ... | 1992 | 1335817 |
| psychosocial stress affects urinary pteridines in tree shrews. | | 1992 | 1522923 |
| a molecular perspective on mammalian evolution from the gene encoding interphotoreceptor retinoid binding protein, with convincing evidence for bat monophyly. | the evolutionary relationships of the various orders of placental mammals remain an issue of uncertainty and controversy. molecular studies of mammalian phylogeny at the dna level that include more than just a few orders are still relatively meager. here we report results on mammalian phylogeny deduced from the coding sequence of the single-copy nuclear gene for the interphotoreceptor retinoid binding protein (irbp). analysis of 13 species representing eight eutherian orders and one marsupial yi ... | 1992 | 1342928 |