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Biomedical subjects

M Kalia

Publications and source records attributed to M Kalia.

At least 55 records · Page 3Linked to original sources
PubMed1981

Neurohistochemical methods in tracing central respiratory mechanisms.

Neurohistochemical methods using the retrograde and transganglionic transport of horseradish peroxidase (HRP) have been used to examine differences in the topographic representation in the brainstem of airway stretch receptors in the extrathoracic trachea and intrathoracic trachea of the cat. HRP neurohistochemistry has also been used to trace connections between brainstem respiratory nuclei, e.g., the inspiratory region of the nucleus of the tractus solitarius (nTS). Microiontophoretic deposits of HRP in functionally homogeneous neuronal populations of the medulla, the inspiratory neuronal group of the ventrolateral nTS, permit the examination of specific anatomical projections; distinct differences between the subnuclei of the nTS receiving projections from the extrathoracic and intrathoracic trachea could be identified. The afferents from the extrathoracic trachea (trachealis muscle stretch receptors) terminate in the main inspiratory subnucleus of the nTS, the ventrolateral nTS, whereas an identical region of the intrathoracic trachea sends its afferents to the dorsolateral nTS. The possible functional effects of such topographic differences are discussed. The inspiratory neuronal population in the ventrolateral nTS receives afferent projections from the contralateral rostral ventrolateral medulla. These afferent projections originate in a recently identified location in the rostral end of the nucleus ambiguous lying ventral to the retrofacial nucleus. This region has been identified as a site for respiratory related activity, which is expiratory in nature and anatomically distinct from the nucleus ambiguus and the retrofacial nucleus. This region has been identified as the Bötzinger complex, which corresponds to a collection of expiratory neurons in the rostral medulla.

Animals↗
PubMed1980

Brain stem projections of sensory and motor components of the vagus complex in the cat: I. The cervical vagus and nodose ganglion.

The motor and sensory connections of the cervical vagus nerve and of its inferior ganglion (nodose ganglion) have been traced in the medulla oblongata of 32 adult cats with the neuroanatomical methods of horseradish peroxidase (HRP) histochemistry and amino acid autoradiography (ARG). In 14 of these subjects, an aqueous solution of HRP was applied unilaterally to the central end of the severed cervical vagus nerve. In 13 other cases, HRP was injected directly into the nodose ganglion. Three of these 13 subjects had undergone infranodose vagotomy 6 weeks prior to the HRP injection. A mixture of tritiated amino acid was injected into the nodose ganglion in five additional cats. The retrograde transport of HRP yielded reaction product in nerve fibers and perikarya of parasympathetic and somatic motoneurons in the medulla oblongata. Furthermore, a tetramethyl benzidine (TMB) method for visualizing HRP enabled the demonstration of anterograde and transganglionic transport, so that central sensory connections of the nodose ganglion and of the vagus nerve could also be traced. The central distribution of silver grain following injections of tritiated amino acids in the nodose ganglion corresponded closely with the distribution of sensory projections demonstrated with HRP, thus confirming the validity of HRP histochemistry as a method for tracing these projections. The histochemical and autoradiographic experiments showed that the vagus nerve enters the medulla from its lateral aspect in multiple fascicles and that it contains three major components--axons of preganglionic parasympathetic neurones, axons of skeletal motoneurons, and central processes of the sensory neurons in the nodose ganglion. Retrogradely labeled neurons were seen in the dorsal motor nucleus of X(dmnX), the nucleus ambiguus (nA), the nucleus retroambigualis (nRA), the nucleus dorsomedialis (ndm) and the spinal nucleus of the accessory nerve (nspA). The axons arising from motoneurons in the nA did not traverse the medulla directly laterally; rather, all of these axons were initially directed dorsomedially toward the dmnX, where they formed a hairpin loop and then accompanied the axons of dmnX neurons to their points of exit. Afferent fibers in the vagus nerve reached most of the subnuclei of the nTS bilaterally, with the more intense labeling being found on the ipsilateral side. Labeling of sensory vagal projections was also found in the area postrema of both sides and around neurons of the dmnX. These direct sensory projections terminating within the dmnX may provide an anatomical substrate for vagally mediated monosynpatic reflexes. Following deefferentiation by infranodose vagotomy 6 weeks prior to HRP injections into the nodose ganglion, a number of neurons in the dmnX were still intensely labeled with the HRP reaction product. The axons of these HRP-labeled perikarya may constitute the bulbar component of the accessory nerve.

Afferent Pathways↗
PubMed1980

Brain stem projections of the aortic nerve in the cat: a study using tetramethyl benzidine as the substrate for horseradish peroxidase.

The intra-axonal transport of horseradish peroxidase (HRP) has been used to trace the nodose ganglion and brain stem projections of a physiologically distinct nerve - the aortic depressor nerve - following electrophysiological identification. Tetramethyl benzidine (TMB) has been used as the substrate for demonstrating the centrally transported HRP15, 16. This sensitive method for horseradish peroxidase histochemistry has permitted the visualization of the central projections of aortic nerve afferents and has also provided information regarding the anatomical localization of cell bodies of these sensory nerve fibers within the nodose ganglion. This study demonstrates the usefulness of using TMB as a substrate for HRP histochemistry in anatomical studies where the detection of anterogradely transported HRP is an essential prerequisite. The uptake of HRP from the cut central ends of sensory nerve fibers and the transport of this enzyme to the sensory ganglion and subsequently into the central processes of these sensory neurons have made possible this study of the central projections of a functionally distinct peripheral nerve. Information has been provided by this study that cell bodies of aortic nerve afferent fibers are localized in the rostrolateral pole of the nodose ganglion. Dense central projections of sensory terminals of aortic afferents have been found in the dorsolateral and medial subdivisions of the nucleus of the tractus solitarius. These central projections of aortic afferents extend for 6 mm rostrocaudally in the medulla with the densest projection being found at the level of the obex. These projections are bilateral at all rostrocaudal levels. This anatomical demonstration of the dorsolateral and medial subdivisions of the nucleus of the tractus solitarius confirms earlier reports based on electrophysiological studies. Of particular interest in this study is the new observation that there exists a dense projection of aortic nerve afferents to the area postrema. The possible physiological implications of a direct input of peripheral chemoreceptor afferents to a region of central chemosensitivity are discussed. The complete absence of any retrogradely labeled cell body in the brain stem from exposure of the aortic nerve to horseradish peroxidase is noteworthy. This indicates that the aortic nerve is purely afferent in function and that reflex control of afferent activity in the aortic nerve is not mediated by brain stem neurons projecting down the same nerve.

Animals↗
PubMed1979

Tissue culture of adult human neurons.

Dissociated neurons from adult human trigeminal and superior cervical ganglia were cultured in vitro for more than 2 months. Immediately after dissociation by incubation in 0.06% collagenase for 15--18 h, the cultures consisted of single neurons or clumps of neurons and degenerating fragments of myelinated or non-myelinated axons. After 7--10 days, bipolar Schwann cells, large neurons and fine nerve fibers were observed. Electron microscopic examination of these neurons revealed all the ultrastructural features of healthy adult neurons including those of lipofuscin pigments. By electrophysiological technique, extracellular recording to action potentials generated by these neurons were obtained indicating the neurons were alive and healthy. The availability of adult human neurons in culture should provide a model system for investigation related to the pathomechanism of lipofuscin formation and aging in general.

Action Potentials↗
PubMed1976

Visceral and somatic reflexes produced by J pulmonary receptors in newborn kittens.

The functional efficiency of J pulmonary receptor reflexes was studied in 28 newborn anesthetized kittens. J receptor stimulation was achieved by injecting phenyl diguanide (PDG) solution into the right atrium using a technique established earlier for cats. Control injections of PDG into the aorta were made. Respiration, aortic blood presure, and knee jerk were recorded. The Hering-Breuer reflex was routinely tested in each kitten by inflating the lungs through the tracheal cannula. In the newborn kitten (1-6 days old), it was not possible to elicit any effect on injection of PDG into the right atrium. At 1 wk, the visceral reflexes--apnea, rapid shallow breathing, bradycardia--could be produced by doses much higher (six times) than the adult dose. By the 10th day, the visceral reflexes were fully developed. The motor reflex, i.e., inhibition of EMG and reduction of knee jerk, was elicited after 3 wk. The earliest response was seen in a 3-wk-old kitten. All these reflexes were abolished by bilateral cervical vagotomy. These results suggest that the J receptor reflexes are poorly developed in the newborn kitten and that the motor reflexes develop much later than the visceral reflexes.

Age Factors↗
PubMed1973

The visual areas in the splenial sulcus of the cat.

1. The extreme periphery of the visual field is represented in the upper wall of the splenial sulcus where the sulcus is horizontal, and in its anterior wall more posteriorly where the sulcus runs downwards and laterally. About half the cells whose fields lie between 50 and 90 degrees from the area centralis have a sharply horizontal preferred orientation.2. Beyond the lateral edge of visual I there is a narrow band of visual cortex in which the receptive fields return towards the area centralis as one moves 1-1.5 mm laterally. Their receptive fields are usually about 20-30 degrees degrees across, but all orientations are found. The more central fields may be binocular and those at the area centralis may be as small as 1 degrees in diameter.3. This band has been called the splenial visual area. It does not seem to have properties corresponding to those of visual II nor of visual III.

Animals↗