Anatomical Organization (anatomical + organization)

Distribution by Scientific Domains

Selected Abstracts

Modulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movement

Romildo Don
Abstract In the present study we investigated the probability, latency and duration of the inhibitory component of the withdrawal reflex elicited by painful electrical stimulation of the index finger in humans. The stimulus consisted of a train of high-intensity pulses. The investigation was carried out in several upper limb muscles during isometric contractions of different strengths and during a motor sequence consisting of reaching, picking up and transporting an object. We used a new algorithm to detect and characterize the inhibitory reflex. The reflex was found in all muscles except the brachioradialis at all the isometric contraction strengths, and showed a distal-to-proximal gradient of latency and duration. Conversely, during movement the reflex probability was high (> 80%) in the anterior deltoid and triceps muscles during reaching, in the extensor carpi radialis muscle during transporting of the object, and in the first interosseous muscle during both picking up and transporting of the object. This modulation of inhibitory reflex transmission in the upper limb muscles suggests that the motor response is organized in such a way as to inhibit the overall ongoing motor task by interrupting motion during reaching and by releasing the object during transporting. This pattern of modulation appears to differ markedly from that previously reported for the excitatory component of the withdrawal reflex. Study of the nociceptive inhibitory reflexes during movement offers new and more profound insights into the functional anatomical organization of the spinal interneuronal network mediating sensory,motor integration. [source]

The Anatomy of the Gastrointestinal Tract of the African Lungfish, Protopterus annectens

Josť M. Icardo
Abstract The gastrointestinal tract of the African lungfish Protopterus annectens is a composite, which includes the gut, the spleen, and the pancreas. The gut is formed by a short oesophagus, a longitudinal stomach, a pyloric valve, a spiraling intestine, and a cloaca. Coiling of the intestine begins dorsally below the pylorus, winding down to form six complete turns before ending into the cloaca. A reticular tissue of undisclosed nature accompanies the winding of the intestinal mucosa. The spleen is located along the right side of the stomach, overlapping the cranial end of the pancreas. The pancreas occupies the shallow area, which indicates on the gut dorsal side the beginning of the intestine coiling. In addition, up to 25 lymphatic-like nodes accompany the inner border of the spiral valve. The mesenteric artery forms a long axis for the intestine. All the components of the gastrointestinal tract are attached to each other by connective sheaths, and are wrapped by connective tissue, and by the serosa externally. We believe that several previous observations have been misinterpreted and that the anatomy of the lungfish gut is more similar among all the three lungfish genera than previously thought. Curiously, the gross anatomical organization is not modified during aestivation. We hypothesize that the absence of function is accompanied by structural modifications of the epithelium, and are currently investigating this possibility. Anat Rec 293:1146,1154, 2010. © 2010 Wiley-Liss, Inc. [source]

Encoding of whisker input by cerebellar Purkinje cells

Laurens W. J. Bosman
The cerebellar cortex is crucial for sensorimotor integration. Sensorimotor inputs converge on cerebellar Purkinje cells via two afferent pathways: the climbing fibre pathway triggering complex spikes, and the mossy fibre,parallel fibre pathway, modulating the simple spike activities of Purkinje cells. We used, for the first time, the mouse whisker system as a model system to study the encoding of somatosensory input by Purkinje cells. We show that most Purkinje cells in ipsilateral crus 1 and crus 2 of awake mice respond to whisker stimulation with complex spike and/or simple spike responses. Single-whisker stimulation in anaesthetised mice revealed that the receptive fields of complex spike and simple spike responses were strikingly different. Complex spike responses, which proved to be sensitive to the amplitude, speed and direction of whisker movement, were evoked by only one or a few whiskers. Simple spike responses, which were not affected by the direction of movement, could be evoked by many individual whiskers. The receptive fields of Purkinje cells were largely intermingled, and we suggest that this facilitates the rapid integration of sensory inputs from different sources. Furthermore, we describe that individual Purkinje cells, at least under anaesthesia, may be bound in two functional ensembles based on the receptive fields and the synchrony of the complex spike and simple spike responses. The ,complex spike ensembles' were oriented in the sagittal plane, following the anatomical organization of the climbing fibres, while the ,simple spike ensembles' were oriented in the transversal plane, as are the beams of parallel fibres. [source]

Do tracheid microstructure and the presence of minute crystals link Nymphaeaceae, Cabombaceae and Hydatellaceae?

Original scanning electron microscopy (SEM) observations are presented for stems of Brasenia schreberi and Cabomba caroliniana of Cabombaceae and three species of Trithuria of Hydatellaceae. End walls of stem tracheids of Brasenia have the same peculiar microstructure that we have reported in Barclaya, Euryale, Nuphar, Nymphaea (including Ondinea) and Victoria of Nymphaeaceae. This feature unites Cabombaceae with Nymphaeaceae. The minute rhomboidal crystals on the surfaces of stellate parenchyma cells of Brasenia reported by Solereder (1906. Oxford: University Press), but not noticed since, are figured. They are like the minute crystals of the often-mentioned astrosclereids of Nymphaeaceae. Neither of these two features has been observed in Hydatellaceae. If the absence of these two features can be confirmed, the reason may be more related to ecology, development, habit and anatomical organization than to degree of phylogenetic relationship as shown by molecular studies. Anatomical observations on the stem anatomy of Trithuria are offered on the basis of paraffin sections prepared for a paper by Cheadle & Kosakai (1975. American Journal of Botany62: 1017,1026); that study is notable for a discrepancy between an illustration of a specialized vessel element on the one hand and tabular data indicating long scalariform perforation plates on the other. Long scalariform perforation plates are mostly found in scalariformly pitted vessels of monocots, whereas the tracheary elements of Trithuria mostly have helical or annular thickenings. We were unable to demonstrate the presence of vessels in Hydatellaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 572,582. [source]