The relationship between thalamocortical connections and stimulus-evoked metabolic activity in the ventroposterior nucleus of the monkey

Although a highly organized system of reciprocal projections exists between the cerebral cortex and the thalamus, the relationship of the thalamocortical projections to functional activity remains unclear. This study attempts to identify the correlation between thalamic relay cells and functional activity evoked in the ventroposterior nucleus (VP) of cynomolgus and squirrel monkeys. Wheatgerm agglutinin conjugated to horseradish peroxidase (WGA:HRP) was iontophoretically injected into physiologically determined sites in the somatosensory cortex, resulting in retrogradely labeled cells and anterogradely labeled terminals in corresponding somatosensory thalamic regions. In the same animals, 2-deoxyglucose (2DG) experiments were carried out 2 days later, using the somatic stimuli identified as best exciting the cortical neurons. Stimulation to the limbs produced crescent-shaped clusters of metabolic label arranged in a somatotopically organized fashion in the ventral posterior lateral nucleus (VPL). Following WGA:HRP injections into area 3b, the stimulus-evoked 2DG label was colocalized with the retrograde and anterograde tracer. This finding suggests that the location of stimulus-evoked metabolic activity can be predicted by the presence of transported WGA:HRP clusters.

Cholinergic manipulation alters stimulus-evoked metabolic activity in cat somatosensory cortex

The role of acetylcholine (ACh) in cerebral cortical activity has recently been reevaluated. It now seems clear that this neurotransmitter increases the magnitude of cortical responses. Although substantial information has been gathered regarding the role of ACh in sensory information processing, little is known about the participation of ACh in the organization of maps in the cerebral cortex. To address this issue, we used 2 methods to manipulate the supply of ACh in the somatosensory cortex of cats: 1) unilateral neurotoxic lesions of the basal forebrain and 2) unilateral topical applications of the cholinergic antagonist, atropine. For each experimental condition, the animal received an injection of 2-deoxyglucose (2DG) while identical somatic stimuli were delivered to the right and left forepaws. In the somatosensory cortex, the 2DG uptake most often occurred in the form of patches that extended from layer II to IV. When the patches were reconstructed into 2-dimensional maps of activity throughout the somatosensory cortex, they formed strips that ran in the rostrocaudal direction. The reconstructed maps revealed that the 2DG patterns in ACh-depleted and the normal cortex were similar in their overall topographic distribution. Depletion or antagonism of ACh, however, caused the stimulus-evoked metabolic label to be reduced in dimension and density. Measurements of background activity levels were obtained by using 1) cytochrome oxidase histochemistry or 2) metabolic activity values in regions of somatosensory cortex that were not specifically stimulated. This analysis indicated that background values in the ACh-depleted hemispheres were not different from those in the normal hemispheres. The absence of ACh therefore appears to reduce the cortical response to stimulation, while background activity values do not change. These observations indicate that ACh plays a significant role in the processing of sensory information and the organization of somatosensory cortical maps.

[Detection of antibodies to citric acid extract of skeletal muscle (CAE-ab) in the sera of patients with myasthenia gravis using indirect hemagglutination]

In this paper are described the method and results for the demonstration of the antibodies to citric acid extract of skeletal muscle (CAE-ab) in the sera from myasthenia gravis (MG) patients with or without thymoma, in patients with other diseases and in healthy controls by an indirect hemagglutination assay (IHA), were described. The CAE-ab titers were positive in 15 (71.43%) of the 21 MG patients with thymoma, the antibody titers ranging from 1:16 to 1:512. In the 35 MG patients without thymoma, as well as in the 32 healthy controls and 22 patients with other diseases, the antibody titers were all negative A statistically significant difference was found between the CAE-ab titers in the group of MG patients with thymoma and those in the other three groups. It was considered that IHA for the purpose of demonstrating CAE-ab could serve as a supplementary diagnostic method for early detection of thymoma in MG patients at an early stage.

Lesions of the basal forebrain alter stimulus-evoked metabolic activity in mouse somatosensory cortex

The role that acetylcholine plays in processing sensory stimuli is beginning to be characterized; however, morphological correlates of cholinergic effects on activity patterns in sensory cortex are not available. To study this problem, unilateral neurotoxic lesions that depleted the necortex of acetylcholine were made in the basal forebrains of mice. The aim of these experiments was to study the effect of cholinergic depletion on stimulus-evoked activity in the barrel field of the mouse somatosensory cortex. One month following the lesion, 2-deoxyglucose (2DG) experiments were conducted on the lesioned and on normal mice while the animal received bilateral stimulation to the C3 whisker. The tissue was processed for acetylcholinesterase and cytochrome oxidase histochemistry and 2DG autoradiography. Evaluation of the column-like 2DG label evoked in the somatosensory cortex revealed that the activity on the lesioned side was significantly reduced in dimension and intensity from that in the normal hemisphere. On the normal side, the activated barrels averaged 641 microns in tangential width, were 76.5% above background in density, and extended from lamina I-V. On the lesioned side, the activated barrels were 485 microns in tangential width, 65.4% above background in density, and extended from lamina II-V. In other cortical regions, outside the stimulus-evoked barrel field, 2DG activity values were similar on the normal and lesioned side. Additionally, both the pattern and intensity of the cytochrome oxidase staining within the barrel field displayed no differences in either hemisphere. These studies suggest that acetylcholine plays a significant role in the processing of somatosensory information. Neurotoxic lesions that diminish cortical cholinergic innervation cause a reduction of stimulus-evoked activity levels, while underlying metabolic activity is either not affected or recovers over time.

Spino-diencephalic relays through the parabrachial nucleus in the cat

Previous studies have shown that the spinal input to the parabrachial nucleus (PBN) in the cat is limited to certain portions of its lateral division 8,21,45. The purpose of the present study was to determine some of the output targets of PBN neurons located within this spinal terminal domain by means of single, double and triple light microscopic labeling strategies. Combinations of tracers included the retrograde transport of tritiated wheat germ agglutinin, wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) and Fluoro-Gold from the hypothalamus, amygdala or thalamus/zona incerta together with either the anterograde transport of WGA-HRP from the spinal cord or the degeneration of spinal terminals following spinal lesions. The results (summarized in Fig. 10) showed that the spinal terminal domain contains separable populations of neurons projecting to the thalamus/zona incerta and hypothalamus. Only a limited number of amygdala-projecting neurons was located in this domain. Evidence from several laboratories supports the conclusion that these potential spino-diencephalic relays are involved somehow in nociception. More information is needed, however, regarding differences in the response properties of these separable populations of spinal-recipient neurons before more specific hypotheses concerning the precise nature of their nociceptive functions can be formulated.

Spinal input to the parabrachial nucleus in the cat

The projections from the spinal cord to the parabrachial nucleus in the cat were investigated using both the degeneration method and the anterograde transport of wheat germ agglutinin-horseradish peroxidase conjugate. Both methods produced similar results. Spinal input to the parabrachial nucleus was bilateral, with a slight contralateral predominance. The termination area was localized predominantly in the dorsal part of the lateral parabrachial nucleus, with additional limited terminations in the Kölliker-Fuse subnucleus. Projections from different rostrocaudal levels of the spinal cord overlapped completely, suggesting that spinal input to the parabrachial nucleus is not topographically organized. Taking these results together with those of others indicating that spinal input to the parabrachial nucleus arises primarily from nociceptive-specific neurons in lamina I of the dorsal horn, it is concluded that the spinal projections to the parabrachial nucleus are likely to be involved in various generalized aspects of nociception.

An ultrastructural analysis of serotoninergic neurons in the nucleus raphe magnus of the rat

The synaptic organization of serotonin elements in the nucleus raphe magnus of adult rat was investigated by electron microscopic immunocytochemistry with an antiserum against serotonin itself. Immunoreactive somata in the nucleus raphe magnus were usually of the same size (7-15 microns) and showed similar cytological features as their unlabeled congeners. The serotonin perikarya were contacted by a few unlabeled axon terminals containing round synaptic vesicles, and gave rise to dendrites which often ran perpendicularly to the midline. These dendrites received many contacts from axon terminals containing round or pleomorphic synaptic vesicles, but themselves failed to show vesicular aggregates or membrane differentiations suggestive of synaptic specialization. Immunoreactive axon terminals were numerous and mostly contained round or pleomorphic vesicles. Several exhibited synaptic contacts on dendrites, but there were also others which did not show any synaptic membranous differentiation, even when followed in serial sections. Immunostained myelinated as well as unmyelinated axons could be observed. These results provide a first description of the morphology and synaptic organization of the serotonin neurons in adult rat nucleus raphe magnus.

Fine structure of the dorsal part of the nucleus submedius of the rat thalamus: an anatomical study with reference to possible pain pathways

The dorsal portion of the nucleus submedius of the rat thalamus receives spinal and trigeminal projections which may convey noxious inputs. The present study was undertaken to analyse the fine structure of the nucleus with particular reference to a possible trigemino-thalamo-prefrontal cortical pathway relaying in nucleus submedius. Presynaptic terminals in the dorsal portion of the nucleus submedius were classified into three broad categories usually observed in thalamic nuclei: "small round", "flat" and "large round" types. Axonal tracing using either anterograde transport of horseradish peroxidase or degeneration methods indicated that some "small round" terminals originate from the pre-frontal cortex. Some "large round" terminals were labelled from the trigeminal subnucleus caudalis. These "large round" terminals exhibited distinct morphological features when compared with trigeminal terminals in other thalamic nuclei. In particular they made synaptic contacts predominantly with dendritic protrusions and were surrounded by multilamellate astrocytic processes. Double-labelling experiments were performed by means of the combined retrograde transport of horseradish peroxidase and Wallerian degradation techniques. Terminals degrading after lesion of the trigeminal subnucleus caudalis contacted submedius neurons labelled retrogradely from the prefrontal cortex. These observations demonstrate the existence of a direct monosynaptically relayed pathway from subnucleus caudalis to prefrontal cortex which relays in the dorsal part of nucleus submedius.

Spinal and trigeminal projections to the parabrachial nucleus in the rat: electron-microscopic evidence of a spino-ponto-amygdalian somatosensory pathway

The fine structure of spinal and trigeminal projections to the parabrachial area (PB) of the rat was studied using either the anterograde transport of a lectin-peroxidase conjugate or the degeneration technique. Two morphologically different types of terminals were observed. Most labeled terminals contained round vesicles (R type) and formed asymmetrical synapses, usually with large dendrites. Others contained pleomorphic vesicles (P type) and usually made symmetrical contacts with large or medium-size dendrites. A double-labeling strategy was used, combining the retrograde labeling of PB neurons with lectin-peroxidase conjugate from the amygdala and the identification of degenerating terminals after lesions of spinal or trigeminal pathways. These experiments demonstrated that spinal and trigeminal terminals contact PB neurons that project to the central nucleus of the amygdala. The role of this spino(trigemino)-ponto-amygdalian pathway is discussed in relation to some aspects of pain.

The differential synaptic organization of the spinal and lemniscal projections to the ventrobasal complex of the rat thalamus. Evidence for convergence of the two systems upon single thalamic neurons

The synaptic organization of terminals originating either from the spinal cord (spinothalamic) or from the dorsal column nuclei (lemniscal) was investigated in the ventrobasal complex of the rat thalamus. Wheatgerm agglutinin conjugated to horseradish peroxidase was used as an anterogradely transported axonal tracer, using benzidine dihydrochloride as a chromogen for the identification by electron microscopy of spinal and lemniscal projections to the ventrobasal thalamus. A double anterograde tract tracing strategy, based labeling by wheatgerm agglutinin conjugated to horseradish peroxidase of spinal terminals and simultaneous visualization of lemniscal terminals identified by Wallerian degeneration induced by lesion of the neurons of origin in the dorsal column nuclei, was used to compare the postsynaptic elements contacted by the two pathways and to look for a possible convergence of the two pathways onto single thalamic neurons. Spinal and lemniscal terminals are large (2-2.5 microns mean average diameter) terminals containing several mitochondria and numerous rounded vesicles. A quantitative analysis of the mean average diameters of the terminals revealed that one could not differentiate between synapses formed by the two pathways on a morphological basis. Terminals of the two pathways make asymmetrical contacts (Gray type I) with dendrites of varying diameter, dendritic protrusions, and cell somata. A quantitative analysis of the least diameter of the postsynaptic elements demonstrates projections of the two systems to different, partially overlapping regions of thalamic neurons. Lemniscal terminals originating from the dorsal column nuclei frequently contact cell somata; axosomatic spinothalamic contacts are uncommon. In addition, lemniscal projections tend to contact more proximal dendrites than do spinal projections, and this differential synaptic organization is statistically significant. From a functional point of view, this differential synaptic organization might indicate that lemniscal inputs have greater influence than spinal inputs in affecting the activity of thalamic neurons. Labeled spinothalamic terminals contact the same dendritic profile as do degenerating lemniscal terminals in about 10% of single sections. Because the present study did not include a complete reconstruction of ventrobasal complex neurons of the thalamus or even regions of dendritic arbors, the degree of convergence is likely to be significantly underestimated. These findings indicate that the anatomical basis exists for an interaction between nociceptive and non-nociceptive somesthetic systems at the level of single ventrobasal neurons of the thalamus of the rat.

Synaptic glomeruli in the nucleus submedius of the rat thalamus

Synaptic glomeruli in the nucleus submedius of the rat are described and the source of some of the component terminals identified. The glomeruli consist of large terminals with round synaptic vesicles establishing Gray type I contacts with dendrites and surrounded by layers of astrocyte derived membranes. The astrocyte processes may be composed of cell membranes with minimal interventing cytoplasm or, less frequently, contain larger amounts of cytoplasm. Horseradish peroxidase injected into the trigeminal nucleus caudalis labels some of the large astrocyte-enclosed terminals in nucleus submedius.

Fine structure of the spinothalamic projections to the central lateral nucleus of the rat thalamus

The fine structure of labelled spinothalamic terminals in the central lateral nucleus has been studied in the rat following injection of wheat germ agglutinin-horseradish peroxidase into the spinal cord. Myelinated axons gave rise to the labelled terminals, which were large profiles which contained round vesicles, numerous mitochondria, and formed asymmetrical contacts with large dendrites or dendritic protrusions. These profiles are similar to those described in other somatosensory thalamic nuclei, and in many other nuclei of the thalamus.

Swallow syncope after aneurysmectomy of the thoracic aorta

A case of swallow syncope is presented and 30 previously reported cases from the literature in English are reviewed. A 67-year-old male developed syncope on swallowing 3 months after the resection of an aneurysm of the descending thoracic aorta. Electrocardiographic monitoring during eating demonstrated sinus bradycardia and sinus arrest with loss of consciousness. Neither Valsalva's maneuver nor carotid massage could produce bradycardia or syncope. Intravenous administration of edrophonium produced sinus bradycardia and the drinking of water by the patient after edrophonium administration brought about sinus bradycardia and sinus arrest with loss of consciousness. Sinoatrial node and atrioventricular node functions, evaluated by an atropine test, overdrive suppression test, and His bundle electrocardiogram were normal. No pathological changes were observed following a barium swallow. The patient was treated with a permanent pacemaker.

The overlap of spinothalamic and dorsal column nuclei projections in the ventrobasal complex of the rat thalamus: a double anterograde labeling study using light microscopy analysis

Projections from the spinal cord and the dorsal column nuclei (DCN) to the ventrobasal complex of the thalamus (VB) were studied in the rat by using double anterograde labeling strategy. This strategy was based on the injection of 3H-leucine into the DCN and of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the spinal cord and their subsequent transport. Adjacent 30-micron-thick sections were then processed differentially for autoradiography or for HRP by using tetramethyl benzidine (TMB) as a chromogen. Similar areas of the ventrobasal complex were labeled, in adjacent sections, after a large injection of 3H-leucine into the DCN and when wheat germ agglutinin-HRP had been injected in any part of the spinal cord. If, however, a small injection of the radioactive tracer was centered in the gracile nucleus and compared with an injection of WGA-HRP placed in the lumbar enlargement of the cord, the rostral and dorsal portions of the lateral VB were labeled from both sources. On the other hand, if tritiated leucine was injected into the cuneate nucleus, and WGA-HRP placed in the cervical enlargement, then the caudal and ventral portions of the lateral VB demonstrated overlap of both labels. The present results show that, in the rat, areas of termination of both the spinothalamic tract and the lemniscal pathway originating from the DCN overlap in the lateral VB. This overlap is somatotopically organized, thus indicating that the same area of the VB receives somatic inputs from one particular part of the body through both pathways. These results are discussed in comparison to those of comparable studies performed in the cat and in the monkey and with reference to the electrophysiological data that have demonstrated that, in the rat VB, neurons responding to noxious stimulation are intermingled with neurons exclusively responding to non-noxious stimulation.

Electrophysiological identification of serotonergic neurons in the rat nucleus raphe magnus

In the present study, antidromically activated raphe-spinal neurons in the nucleus raphe magnus are found to exhibit a wide range of conduction velocities and spontaneous discharge rates. The unit activities observed in control rats have been compared with those in 5,6-dihydroxytryptamine (a specific neurotoxin to serotonergic cells)-pretreated animals. It is found that the units conducting at slower than 12 m/sec and discharging at rates of less than 3 Hz often found in control rats are not found in drug-pretreated animals, and are thus presumed to be serotonergic. In addition, the regularity of spontaneous discharges of units has been evaluated by testing the coefficient of variability of spike intervals. These results indicate that the slow-conducting units discharge less regularly than the fast-conducting ones.

Factors influencing morbidity and mortality of renal transplantation in a high risk population

A group of 37 patients with 39 renal transplants were studied from January 1971 to June 1974, in which 32 were considered at high risk by well defined cardiovascular, gastrointestinal, cerebral vascular, or pulmonary disease or age categories. Three of the 37 patients have died, and two patients in the high risk group, 92 per cent. Eighty-eight per cent of the entire group have functioning kidneys at present, and 93 per cent of those in the high risk group have functioning kidneys. Evaluation of pretransplant mixed lymphocyte cultures, HL-A antigen, and immune responder status; close follow-up observation of lymphocyte culture and humoral responses by in vitro testing; and the use of antilymphoblast globulin are considered to be the reasons for the improved results.