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PubMed1980

The morphology of the diencephalon in the Prosimii. II. The Lemuroidea and Lorisoidea. Part I. Thalamus and metathalamus.

This study (Part I) covers the comparative structure of the thalamus and metathalamus in the prosimian superfamilies, Lorisoidea and Lemuroidea. Several lemuroid specimens, namely Lemus, Cheirogaleus, Microcebus, Avahi and Daubentonia, and lorisoid specimens such as Galago, Perodicticus and Loris have been used in this extensive study. The anterior nuclear group does not show much difference among these species, although attention is focussed on the differentiation of the principal anterior nucleus into anteromedial and anteroventral parts; the latter increases in structural complexity. The anterodorsal nucleus has regressed into a small, flattened cap-line structure covering the dorsal surface of the anteroventral nucleus. The midline thalamic nuclei are more or less the same throughout the entire prosimian primate scale, though the gradual fusion of the nucleus rhomboidalis with the nucleus centralis medialis is observed from Microcebus to Daubentonia. The medial thalamic nuclear region is dominated by the nucleus mediodorsalis which is clearly differentiated into dorsomedial magnocellular and ventrolateral parvocellular protions. A third division consisting of rather large, darkly staining cells have been observed in the caudal region of the nucleus mediodorsalis. The nuclei centrum medianum and parafascicularis are both large in size, but is not completely demarcated from each other. The dorsolateral thalamic nuclei--the nuclei laterales dorsalis, intermedius and posterior, are well developed, but cannot be distinguished from one another. The pulvinar shows a remarkable phylogenetic development; it does not only enlarge, but is differentiated into several distinct parts. The ventrolateral thalamic nuclear group is comparably larger in structural size than the dorsolateral thalamic nuclei. The nuclei ventrales anterior and lateralis are not clearly demarcated from each other, but on both cyto- and myelo-architectonic grounds, are separate entities. The nucleus ventralis posterior is differentiated into lateral, medial and inferior parts. The posterior thalamic nuclei show the beginnings of regression. The nucleus pretectalis remains comparatively large in size and divided into medial and lateral parts. The nucleus posterior thalamicus is either absent or involuted into other nuclei. The nucleus limitans makes its first appearance in the Prosimii. The lateral geniculate body is very variable in size in all respects among the prosimian species, that is, in the dorsoventral shift along the lateral surface of the thalamus, the cellular differentiation of the lateral geniculate nucleus into 5 or 6 layers, the topographical position of the pregeniculate nucleus and the degree of inversion. The medial geniculate body is shown to be clearly subdivided on cyto-architectonic grounds into dorsomedial and ventrolateral parts; a magnocellular protion can be seen on the dorsal region of this nucleus, and appears to be closely related to the nucleus suprageniculatus.

Animals↗
PubMed1994

[A case of hemangioblastoma in the thalamus].

Supratentorial hemangioblastoma is encountered very rarely. About 80 cases in all have been reported. The authors present a case of supratentorial hemangioblastoma in the thalamus with gradually enlarging cysts. The patient was a 45-year-old man with complaints of left hemiparesis and headache. Computed tomographic scans of the brain showed a cystic mass with mural nodule in the right thalamus. Left vertebral angiography demonstrated a vascular tumor fed by a thalamogeniculate artery. A right temporo-parietal craniotomy was performed and the tumor was totally resected through the transcortical approach. The histological diagnosis was hemangioblastoma. Post-operative course was good except for a minor complication of the left lower quadrant homonymous hemianopsia and left hemiparesis which had disappeared at the time of discharge.

Hemangioblastoma↗
PubMed1995

Postnatal development of GABAA receptor function in somatosensory thalamus and cortex: whole-cell voltage-clamp recordings in acutely isolated rat neurons.

GABAergic inhibition synchronizes oscillatory activity in the thalamocortical system. To understand better the role of this neurotransmitter in generation of thalamocortical rhythmicity, the postnatal development of GABAergic function mediated through activation of GABAA receptors was studied in thalamus and cortex. GABA-evoked chloride currents were recorded in dissociated rat cortical and thalamic neurons during postnatal development. Kinetic fits of GABA concentration/response relationships revealed developmental and regional alterations in the potency of GABA. Early in postnatal development (p5-p8), both thalamic and cortical neurons exhibited reduced potency of GABA (27-31 microM KD). Potency increased by p18-p25 in thalamic and cortical neurons (19-22 microM KD), to a level maintained in adult thalamic neurons. Adult cortical neurons exhibited reduced potency of GABA (40 microM KD). Benzodiazepine modulation of GABAA currents was also studied. Kinetic analyses of benzodiazepine augmentation of GABAA currents were best fitted assuming two effective sites with different affinities for clonazepam. The high-affinity site (KD of 0.05-0.27 nM) showed little variation with development in cortical neurons, contributing about 16-23% potentiation at all postnatal ages. Developing thalamic neurons (p5-p25) showed similar potency and efficacy of the high-affinity benzodiazepine site to cortical neurons. High-affinity benzodiazepine effects disappeared in adult thalamic neurons. A lower-affinity benzodiazepine site (25-50 nM KD) was greater in efficacy in cortical neurons compared to thalamic neurons at all ages, with efficacy ranging from 50% to 110% in cortex and from 20% to 60% in thalamus. Knowledge of developmental and regional alterations in GABAA receptor function may aid in understanding mechanisms involved in generation and control of normal and pathological thalamocortical rhythms.

Aging↗
PubMedDate not supplied

[The effect of burn trauma on the microcirculatory bed of the human thalamus].

Alterations in the microcirculatory bed of the thalamus resulting from thermal trauma manifest themselves as dystonia of the arteriolar-venular part of the microcirculatory bed, sharply decreased density of functionally active capillaries, area of their exchange surface and amount of blood in them. Clear distinctions are observed in stages of burn disease. At the stage of burn shock all morphometric parameters of the capillary bed are decreased in anterior, medial, ventro-lateral and posterior (pulvinar) nuclei of the thalamus. At the stage of toxemia in anterior and medial nuclei the parameters were at the level of the control group or even higher. On the contrary, in ventro-lateral and posterior nuclei they remained considerably lower as compared with control figures. It is likely to be associated with the fact that the pathways of pain, tactile and temperature sensitivity which are the first to react to burn trauma are switched over in these groups of nuclei.

Accidents↗
PubMed1994

[Acute encephalopathy with symmetrical lesions of the thalamus, the putamen and the cerebellum on magnetic resonance imaging].

A 19-year-old boy was admitted to our hospital because of impaired consciousness after experiencing fever and headaches for 7 days. The patient was in a deep coma or generalized convulsions, with retrocollis and decorticate posture. He never regained consciousness, remaining in an apallic state. The initial CSF pressure was 290 mm H2O, CSF cell count 18/3 mm3, protein 75 mg/100 ml, and sugar 74 mg/100 ml. There was no significant elevation in the viral titer in the serum or CSF. Plain CT on admission showed marked brain edema. MRI three months thereafter demonstrated symmetrical high intensity in the thalamus, the putamen and the cerebellum on both T1- and T2-weighted images, probably representing petechial bleeding. The lesions in the medial portion of the occipital lobes showed iso intensity on T1-weighted images and high intensity on T2-weighted images. These lesions were consistent with infarction of both posterior cerebral arteries, which may have been due to severe brain edema. The clinical and MRI findings were similar to those of patients with acute encephalopathy with low-density areas in the thalamus or bilateral striatal necrosis in childhood. To the best of our knowledge, there have been no reports of cases like ours in adults.

Acute Disease↗
PubMed1993

A survey of the auditory midbrain, thalamus and forebrain in the chicken (Gallus domesticus) with cytochrome oxidase histochemistry.

The chicken's central auditory nuclei from the inferior colliculus to field L in the forebrain were studied with cytochrome oxidase histochemistry. All stations of the ascending pathway displayed high activity levels, including the inferior colliculus, the nucleus ovoidalis of the thalamus, and field L1 to L3 and the hyperstriatum ventrale caudale which correspond to primary and secondary auditory cortex. In the inferior colliculus a moderately active external nucleus could be distinguished from a more intensely stained central and superficial nucleus. In the central nucleus there was a lateral shell displaying stronger neuropil reactivity than a central core. Unilateral cochlea removal caused no remarkable effect in tectum and thalamus. The auditory forebrain contralateral to the lesion displayed reduced CO reactivity compared with the ipsilateral side. After bilateral cochlea extirpation auditory structures still displayed higher enzyme levels than most other nuclei.

Animals↗
PubMed1996

Influences of the thalamus on the survival of subplate and cortical plate cells in cultured embryonic mouse brain.

The afferent and efferent connections of the cerebral neocortex develop simultaneously toward the end of embryogenesis. At this stage, the neocortex comprises two main cell-dense layers: the thicker and more superficial cortical plate (future layers 2-6) and the thinner underlying subplate. Many early thalamocortical projections temporarily innervate the subplate before leaving it to locate their ultimate targets in the overlying cortical plate. The subplate then disappears. In this study, we performed in vitro experiments on late embryonic murine brain to test whether the thalamus can influence the survival of cortical plate and subplate cells at this stage. In isolated organotypic cortical explants from embryonic day 19 mice, most of the cells that had formed the subplate died. Coculture with a thalamic explant prevented this loss; coculture with additional cortical or cerebellar explants did not. By contrast, many cells in or destined for the cortical plate survived even in isolated cortical explants; coculture with a thalamic explant did not alter the numbers of these cells that survived. Our results suggest that the thalamus provides trophic support for subplate cells but not for late embryonic cortical plate cells. In vivo, a loss of thalamic-derived trophic support for the subplate late in embryogenesis, consequent on the movement of thalamocortical axons into the cortical plate, may contribute to subplate death.

Animals↗
PubMed1996

Changes in the number of astrocytes and microglia in the thalamus of the monkey Macaca fascicularis following long-term subclinical methylmercury exposure.

The effects of long-term subclinical exposure to methylmercury on the number of neurons, oligodendrocytes, astrocytes, microglia, endothelial cells and pericytes within the thalamus from the left side of the brain of the monkey Macaca fascicularis has been determined by use of the Optical Volume Fractionator stereological method. The accumulated burden of inorganic mercury (IHg) within these same cell types has been determined by autometallographic methods. Four groups of monkeys were exposed to methylmercury (MeHg; 50 micrograms Hg/kg body weight/day) by mouth for 6 months, 12 months, 18 months, or 12 months followed by 6 months without exposure (clearance group). Neurons, oligodendrocytes, endothelia, and pericytes did not show a significant change in cell number for any exposure group. Astrocyte cell number exhibited a significant decline for both the 6 month and clearance exposure groups. The microglia, in contrast, showed a significant increase in the 18 month and clearance exposure groups. Results from mercury speciation and quantification analysis of contralateral matched samples from the thalamus of the right side of the brain from these same monkeys indicated that MeHg concentrations plateaued at around 12 months exposure, whereas the inorganic levels, presumably derived from demethylation of MeHg, continued to increase throughout all exposure durations. Autometallographic determination of the distribution of IHg by cell type indicates that both the astrocytes and microglia contain substantially elevated IHg deposits relative to all other cell types. The data suggest that the inorganic mercury present in the brains, accumulating after long-term subclinical methyl mercury exposure, may be a proximate toxic form of mercury responsible for the changes within the astrocyte and microglial populations.

Animals↗
PubMed1996

Suppression of noxious stimulus-evoked activity in the ventral posterolateral nucleus of the thalamus by a cannabinoid agonist: correlation between electrophysiological and antinociceptive effects.

The CNS contains a putative cannabinergic neurotransmitter and an abundance of G-protein-coupled cannabinoid receptors. However, little is known about the function of this novel neurochemical system. Cannabinold agonists produce antinociception in behavioral tests, suggesting the possibility that this system serves in part to modulate pain sensitivity. To explore this possibility, the effects of the cannabinoid agonist WIN 55,212-2 on nociceptive neurons in the ventroposterolateral (VPL) nucleus of the thalamus were examined in urethane-anesthetized rats. After identification of a nociresponsive neuron, a computer-controlled device delivered graded pressure stimuli to the contralateral hindpaw. WIN 55,212-2 (0.0625, 0.125, and 0.25 mg/kg, i.v.) suppressed noxious stimulus-evoked activity of VPL neurons in a dose-dependent and reversible manner. Noxious stimulus-evoked firing was affected more than spontaneous firing. These effects were apparently mediated by cannabinoid receptors, because the cannabinoid receptor-inactive enantiomer of the drug (WIN 55,212-3, 0.25 mg/kg) failed to alter the activity of this population of cells. Administration of morphine (0.5 mg/kg, i.v.) produced effects that were very similar to those produced by the cannabinoid. WIN 55,212-2 (0.25 mg/kg, i.v.) failed to alter the responses of non-nociceptive low-threshold mechanosensitive neurons in the VPL WIN 55,212-2 produced antinociceptive effects with a potency and time course similar to that observed in the electrophysiological experiments, despite the differences in the anesthetic states of the animals used in these experiments. The antinociceptive and electrophysiological effects on VPL neurons outlasted the motor effects of the drug. Furthermore, the changes in nociceptive responding could not be attributed to changes in skin temperature. Taken together, these findings suggest that cannabinoids decrease nociceptive neurotransmission at the level of the thalamus and that one function of endogenous cannabinoids may be to modulate pain sensitivity.

Analgesics↗
PubMed1997

Vascularization of the brain in guinea pig. V. Angioarchitectonics of the thalamus, telencephalon and internal capsule.

The main blood supply of the thalamus constitute internal branches of the posterior cerebral, posterior communicating, middle, and choroid arteries. Branches of these arteries from three groups of vessels: medial, lateral, and posterior. Considering the number of vessels, their diameter and direct origin from the cerebral arterial circle, the thalamus is best vascularized structure of the brain. The telencephalon is supplied by rami of the anterior and middle cerebral, choroid, posterior communicating, and posterior cerebral arteries. The internal capsule and telencephalic nuclei are supplied by the internal branches of the same vessels as the telencephalon as well as by the cortical rami of the middle and posterior cerebral arteries. All these vessels from anteromedial, anterolateral, and superolateral groups. Between the internal and cortical branches anastomotic vessels are seen.

Animals↗
PubMed1997

Germinoma of the basal ganglia and thalamus--CT and MRI findings.

A case of germinoma originating in the basal ganglia and thalamus is presented. This tumour most commonly originates during childhood and adolescence, at pineal and suprasellar regions. In the early stages, the diagnosis of germinoma in the basal ganglion and thalamus is difficult because of its rarity and non-specific findings. The computed tomography (CT) and magnetic resonance imaging (MRI) findings though non-diagnostic, are discussed here. A few differential diagnoses had been discussed with radiological abnormality. Open biopsy done in this case proved to be two-cell pattern germinoma. Early detection of the tumour is desirable, since this tumour is highly sensitive to radio and chemotherapy and is potentially curable. Our patient was treated with combined chemotherapy and the response was well and no residual tumour or recurrence was seen on the repeated imaging modality, however his neurological deficits remained unchanged.

Antineoplastic Agents↗
PubMed1998

Signal transduction correlates of mu opioid agonist intrinsic efficacy: receptor-stimulated [35S]GTP gamma S binding in mMOR-CHO cells and rat thalamus.

This study examined the signal transduction correlates of mu opioid agonist efficacy in two systems: mu receptor-transfected mMOR-CHO cell and rat thalamic membranes. The potency and maximal stimulation of [35S]GTP gamma S binding by various agonists was measured in the presence of excess GDP and compared with receptor binding affinity under identical assay conditions. Results showed that the relative maximal stimulation produced by these agonists was greater in mMOR-CHO cell than in rat thalamic membranes; some drugs that were full agonists in mMOR-CHO cells were partial agonists in the thalamus, and some partial agonists in the transfected cells were full antagonists in the thalamus. Furthermore, there was receptor reserve for G-protein activation by some agonists in mMOR-CHO cell membranes, but no receptor reserve was detected in rat thalamic membranes. Saturation analysis of agonist-stimulated [35S]GTP gamma S binding revealed that full agonists produced both a higher Bmax and apparent affinity of [35S]GTP gamma S binding than partial agonists. Correlation of the Bmax and KD of agonist-stimulated [35S]GTP gamma S binding with agonist intrinsic efficacy revealed only a moderate correlation with either parameter alone, but a highly significant correlation (r > 0.9) with a combination of the two parameters (Bmax/KD). These results suggest that the intrinsic efficacy of agonists at G-protein-coupled receptors is determined primarily by the ability of the agonist-occupied receptor to promote high-affinity GTP binding to the G-protein and to catalytically activate a maximal number G-proteins.

Animals↗
PubMed1998

[A case of Japanese B encephalitis with lesions of thalamus and substantia nigra revealed by MRI].

We report a 6-year-old girl with Japanese B encephalitis. The initial symptoms were high fever, headache and vomiting. On the second day of illness, she developed hemiconvulsion and was admitted to our hospital. Physical examination demonstrated a stiff neck. C-reactive protein elevated to 22.7 mg/dl. CSF examination showed a marked increase in the cell count (10,896/3 mm3). During the course of the treatment, she showed transient hemiparesis and dysphagia, followed by akinetic mutism lasting for about a month. The patient was left with severe cognitive and memory impairment and complex partial seizures but no motor dysfunction. Japanese B encephalitis was diagnosed by means of serological examination. Magnetic resonance imaging revealed cystic lesions in the medial and posterior thalamus and substantia nigra and severe atrophy of the hippocampus. Despite the involvement of substantia nigra, the patient had no parkinsonism. The cognitive impairment may in part be explained by the lesions in the medical and posterior thalamus.

Child↗
PubMed1997

[Expression of c-fos in spinal cord, medulla oblongata and thalamus following epicardial application of adenosine].

Effects of epicardial application of adenosine on the expression of c-fos proto-oncogene in spinal cord, medulla oblongata and thalamus were examined in 12 sinoaortic denervated and vagotomized anesthetized rats. The results showed that following epicardial application of adenosine the Fos-like protein immunoreactive (FLI) neurons were remarkably increased in the dorsal horn of T3 spinal segment, nucleus paragigantocellularis lateralis (PGL) of medulla oblongata, ventral postero-lateral thalamic nucleus (VPL), posterior thalamic nucleus (Po), parafascicular thalamic nucleus (PF) and centrolateral thalamic nucleus (CL), while the blood pressure and heart rate were not affected. Only a few FLI neurons were found in the vehicle-control rats. The results indicate that epicardial application of adenosine may activate the pain-related neurons in spinal cord, medulla oblongata and thalamus.

Adenosine↗
PubMed2000

A lesion of the anterior thalamus producing dystonic tremor of the hand.

BACKGROUND: Thalamic tremor is typically characterized by resting and intention components; a postural element is often present as well. Previously reported cases of acquired thalamic tremor have demonstrated lesions in the posterior thalamus or dentatorubrothalamic tract. OBJECTIVES: To report a case of dystonic-postural tremor of the upper extremity that occurred after a contralateral anterior thalamic infarct, and to discuss potential tremorigenic mechanisms. DESIGN: Case report. SETTING: Municipal hospital neurology clinic. PATIENT: A 65-year-old right-handed woman suddenly developed a dystonic tremor in her left hand after undergoing coronary bypass surgery. The tremor persisted unchanged for 8 months, at which time she was evaluated by us. Cranial magnetic resonance imaging scans demonstrated a right anterior thalamic infarct. CONCLUSION: To our knowledge, this is the first report of focal tremor caused by a lesion of the anterior thalamus.

Aged↗
PubMed2001

Size gradients of barreloids in the rat thalamus.

The spatial organization of the anatomical structures along the trigeminal afferent pathway of the rat conserves the topographical order of the receptor sheath: The brainstem barrelettes, thalamic barreloids, and cortical barrels all reflect the arrangement of whiskers across the mystacial pad. Although both the amount of innervation in the mystacial pad and the size of cortical barrels were shown previously to exhibit increasing gradients toward the ventral and caudal whiskers, whether similar gradients existed in the brainstem and thalamus was not known. Here, the authors investigated the size gradients of the barreloids in the ventral posteromedial nucleus of the rat thalamus. Because the angles used to cut the brain were crucial to this study, the optimal cutting angles were determined first for visualization of individual barreloids and of the entire barreloid field. Individual barreloids, arcs, and rows as well as entire barreloid fields were clearly visualized using cytochrome oxidase staining of brain slices that were cut with the optimal cutting angles. For the first five arcs (including straddlers), the length of barreloids increased in the direction of dorsal-to-ventral whiskers and of caudal-to-rostral whiskers. These gradients reveal an inverse relationship between the size of barreloids and whiskers (length and follicle diameter) along arcs and rows. The largest barreloids in the ventral posteromedial nucleus were those that represent whiskers C2-C4, D2-D4, and E2-E4, which are neither the largest nor the most innervated whiskers in the mystacial pad. This implies that the extended representation is not merely a reflection of peripheral innervation biases and probably serves an as yet unknown processing function.

Animals↗
PubMed1979

Quantitative comparison of the hominoid thalamus. I. Specific sensory relay nuclei.

Studies to date have indicated few differences in sensory perception among hominoids. Sensory relay nuclei in the dorsal thalamus--portions of the medial and lateral geniculate bodies (MGBp, LGBd) and the ventrobasal complex (VB)--in two gibbons, one gorilla, one chimpanzee and three humans were examined for anatomical similarity by measuring and estimating the nuclear volumes, neuronal densities, numbers of neurons per nucleus, and volumes of neuronal perikarya. The absolute volumes of these nuclei were larger in the larger brains; however, with the volume of the dorsal thalamus as a standard, these sensory relay nuclei showed negative allometry. The gibbons had about half as many neurons as did the other hominoids. Although the human VB had slightly more neurons, the numbers of neurons in LGBd and MGBp did not significantly differ between the great apes and humans. The volumetric distribution of the neuronal perikarya were similar among these hominoids. Other thalamic nuclei had much more diverse numbers of neurons and relative frequencies of their neuronal perikarya. The sensory relay nuclei appear to be a group of conservative nuclei in the forebrain. These results suggest that as a neurological base for complex behaviors evolved in hominids, not all parts of the brain changed equally.

Animals↗
PubMed1984

Value of ultrasound for identification of acute hemorrhagic necrosis of thalamus and basal ganglia in an asphyxiated term infant.

An infant with profound intrapartum and postpartum asphyxia demonstrated striking bilateral echodensities in the region of the thalamus and basal ganglia on ultrasound scan. Neuropathological examination confirmed the presence of symmetrical areas of hemorrhagic necrosis involving the thalamus, caudate, putamen, and globus pallidus. The findings demonstrate the value of ultrasonography in the identification of this variety of perinatal hypoxic-ischemic injury.

Asphyxia Neonatorum↗