Joseph M. Lauweryns

Hypoxia-sensitive neuro-epithelial bodies intrapulmonary secretory neuroreceptors, modulated by the CNS

SummaryIn an attempt to further our knowledge about the structure and function of the recently identified intrapulmonary Neuro-epithelial Bodies (NEBs) (Lauweryns et al., 1972a, 1972b), lungs of 84 neonatal rabbits and 6 neonatal mice were studied along four different lines of investigation. Several routine and silver staining methods, Falcks fluorescent amine technic and histochemical and electron microscopical techniques were performed.1. In order to test the probable chemoreceptor function of the NEBs, animals were exposed to hypoxia. Under such circumstances, the corpuscular cells of the NEBs secrete their dense-cored, serotonin-containing vesicles at their basal vascular pole. 2. After reserpine pretreatment, the NEBs of otherwise normal animals reveal a distinct amine depletion, the corpuscular cells exhibiting a decreased yellow fluorescence and ultrastructurally a clearing up of their dense-cored vesicles. 3. Studied on serial sections with the electron microscope, various types of morphologically afferent-like and efferent-like nerve endings, making contact as well with the corpuscular cells as amongst themselves have been detailed. 4. Cytochemically the corpuscular cells react positively with alpha-glycerophosphate dehydrogenase, acetylcholinesterase and Solcias lead hematoxylin stain for endocrine cells producing polypeptides and amines.It is proposed that the NEBs provide an intrapulmonary, hypoxia-sensitive neuro(chemo-) receptor system in addition to the well established central and peripheral (e.g. carotid body) chemoreceptors. They contain and secrete serotonin and probably also related amines or peptides, which could influence the pulmonary vasoconstrictor response. According to classic morphologic criteria, they possess a dual innervation, both afferent and efferent.Various other possible functions of the NEBs in normal and diseased lungs are briefly proposed.

Neuro-epithelial bodies in the respiratory mucosa of various mammals

SummaryLungs of fetal, neonatal and adult rabbits and of various other adult mammals were investigated. Several routine and silver staining methods, Falcks fluorescent amine technic and various electron microscopic techniques were performed.As in the human infant lung (Lauwerynset al., 1972) each of these techniques revealed the occurrence throughout the intrapulmonary airways of intramucosal corpuscles or so-called Neuroepithelial Bodies, composed of more or less parallely oriented, non-ciliated cylindrical cells which reach from the basement membrane to the airway lumen and display a prominent cytoplasmic argyrophilia, a less pronounced argentaffinity and an intense yellow fluorescence. Ultrastructurally, they are granulated, containing mainly two types of dense-cored vesicles of which the first type exhibits a positive reaction for serotonin (technic of Jaim-Etcheverryet al., 1968). They contain intracorpuscular nerve endings which form synaptic end formations upon the granulated cells.Though the functions of these serotonin producing Neuroepithelial Bodies remain furthermore unsettled, they seem to be related also to the recently reported AFG (Argyrophil, Fluorescent and Granulated) cells (Lauwerynset al., 1969, 1970a) and might be involved in various mucosal bronchial and bronchiolar neurosecretory processes; most probably they are chemo-, stretch- and/or tactile neuroreceptor organs modulated by the central nervous system.

Serotonin Producing Neuroepithelial Bodies in Rabbit Respiratory Mucosa

The intrapulmonary lining epithelium of rabbits contains newly identified corpuscles composed of argyrophil, argentaffin, yellow fluorescent, ultrastructurally granulated and innervated epithelial cellular organs. These are proved, by electron microscopic cytochemistry and microspectrography, to be a source for intrapulmonary production of serotonin. Probably they are intrapulmonary neuroreceptor organs modulated by the central nervous system which exhibit local secretory activities.

Cross-circulation studies on the influence of hypoxia and hypoxaemia on neuro-epithelial bodies in young rabbits.

SummaryThe reactions of the previously described neuro-epithelial bodies (NEB) (Lauweryns et al., 1969, 1970, 1972a, b, 1973a, b, c, 1974, 1975) in young rabbits to: (1) hypoxia with normoxaemia in the arteria pulmonalis on the one hand, and (2) hypoxaemia in the arteria pulmonalis with normoxic aeration on the other hand, has been investigated by means of cross-circulation experiments and light microscopical, electron microscopical and morphometrical techniques.Hypoxically aerated young rabbits, which received normoxaemic blood in their arteria pulmonalis from a donor rabbit by means of an arterio-arterial cross-circulation with mutual exchange transfusion, revealed an increased exocytosis of the dense-core vesicles of their NEB. Normoxically aerated young rabbits which received hypoxaemic blood in an identical manner, did not exhibit an increased exocytosis.It is concluded that the NEB apparently react directly to the hypoxia of the inhaled air and not to the hypoxaemia of the pulmonary blood. By the release of serotonin and a polypeptide substance, they may produce a local vasoconstriction in hypoxically aerated lung areas, enabling an intrapulmonary regulation of the V/Q ratio. This is regarded as additional proof that the NEB — while being modulated by the CNS — probably are intrapulmonary chemoreceptors with local secretory activities, reacting to the composition of the inhaled air.

Intrapulmonary neuro-epithelial bodies in newborn rabbits

SummaryNeonatal rabbit neuro-epithelial bodies (NEB) were investigated under various experimental conditions with light microscopy, microspectrography, morphometry and electron microscopy. (1) Hypoxia causes a decreased amine fluorescence intensity and an increased secretory exocytosis of dense core vesicles (DCV). Otherwise the NEB appear structurally normal. (2) Hypercapnia also produces a decreased fluorescence and an increased exocytosis; ultrastructurally, however, the dense core of DCV fragmentizes. (3) Hyperoxia does not appear to affect significantly either fluorescence or exocytosis. (4) The uptake of biogenic amines such as 5-HTP and L-DOPA was demonstrated by fluorometry and electron microscopy. (5) Reserpine, on the other hand, provokes an amine depletion with a decrease of the NEB fluorescence and an ultrastructural palor of the DCV. (6) Intratracheally administered nicotine is accompanied by a decreased fluorescence and a distinct exocytosis of fragmented DCV.The reaction of NEB to hypoxia and hypercapnia suggests that these corpuscles could be intrapulmonary chemoreceptors (in addition to the classically known central and peripheral chemoreceptors), inducing a reflex reaction through the liberation of DCV at the corpuscular sensible nerve endings and via the CNS. In addition, they may subserve a local intrapulmonary effect by modulating directly the hypoxic and hypercapnic pulmonary vasoconstriction and thus the V/Q ratio.

Argyrophil, fluorescent and granulated (peptide and amine producing?) AFG cells in human infant bronchial epithelium. Light and electron microscopic studies.

Abstract Light optical, histochemical and electron microscopical studies have revealed that the epithelium of the bronchi of newborn human infants contains an impressive number of distinctly argyrophil, fluorescent (after freeze-drying and formaldehyde vapour treatment) and ultrastructurally granulated cells. These AFG cells do indeed contain numerous round electronopaque dense-cored vesicles. Intramucosal nerve endings are also present, suggesting a “direct contact” with the AFG cells. It is proposed that these cells in the human lung are related to the growing list of presumably peptide and amine secreting “argyrophil” or APUD, and other cells which have been reported in different other tissues and organs. A possible chemoreceptor-like function may also be possible. The AFG cells could interfere with various pulmonary areas, such as bronchial smooth muscle tone, pulmonary vasomotion, the circulatory adaptation (or failure) of the newborn at birth and pulmonary oncology (carcinoid and oat cell tumors).

Innervation of rabbit intrapulmonary neuroepithelial bodies: Quantitative and qualitative ultrastructural study after vagotomy☆

The purpose of this study was to locate the cell bodies of origin of the intracorpuscular nerve endings of the intrapulmonary neuroepithelial bodies (NEB). Left infra- or supranodosal vagotomy was performed on 35 young rabbits. In control animals, the NEB innervation index (i.e. the ratio of the number of intracorpuscular nerve endings to the number of NEB corpuscular epithelial cells) was 0.3 in both left and right lungs. Left infranodosal vagotomy decreased the NEB innervation index in the left lung to 0.1 by 24 h postoperatively. Degenerating nerve endings displaying neurofilamentous hyperplasia, were found among the few surviving nerve endings. Left supranodosal vagotomy did not influence the innervation of the NEB of the left lung, even at 5 days postoperatively. In the right lungs, neither procedure had significant effects. These findings indicate that the NEB are predominantly innervated by sensory nerve fibers, derived from cell bodies in the nodose ganglion of the vagus nerve. This neuroanatomical argument corroborates our hypothesis that NEB represent intrapulmonary neuroreceptors.

Immunohistochemical localization of serotonin in intrapulmonary neuro-epithelial bodies

SummaryA recently developed immunohistochemical technique for serotonin (Steinbusch et al. 1978) was used in the present investigation to study the occurrence of this indoleamine in the granulated epithelial cells of neuroepithelial bodies (NEB). Lungs from neonatal rabbits and pigs exhibit immunoreactive cell groups identical in morphology and their preferential location (i.e., at bronchiolar bifurcations) to the recently described intrapulmonary NEB. Moreover, in the trachea and lung of rabbits isolated immunoreactive cells, presumably of Kultschitsky type, were found in the lining respiratory mucosa. Such single cells were also frequently observed in the bronchial epithelium of pig lungs. It is concluded that the corpuscular cells, being modulated by the central nervous system, probably represent intrapulmonary neuro(chemo-)receptors with local secretory activities, one of the substances released being serotonin and reacting to the oxygen composition of the inhaled air. It is proposed that the cells of Kultschitsky type exert a more local effect upon the airways.

Tobacco smoking impairs the local immunosurveillance in the uterine cervix. An immunohistochemical study.

Previous reports have supported an association between tobacco smoking and cervical neoplasia. Our observations show an association between smoking and a reduction of the numerical densities of Langerhans cells and of helper/inducer T lymphocytes in the squamous epithelia of the transformation zone of the uterine cervix. This suggests a local impairment of cell-mediated immunity by smoking. This immunosuppressive effect could support the concept that smoking is an independent risk factor for cervical neoplasia.

Effect of Various Vagotomy Procedures on the Reaction to Hypoxia of Rabbit Neuroepithelial Bodies: Modulation by Intrapulmonary Axon Reflexes?

Recent neuroanatomical investigations revealed the intrapulmonary neuroepithelial bodies (NEB) to be innervated to a large extent by sensory nerve fibers, displaying peripheral nerve endings of afferent as well as efferent morphology and having their cell bodies in the nodose ganglion of the vagus nerve. Earlier studies also revealed that upon exposure to acute hypoxia NEB exhibit a distinct secretory response, including as well a decrease in the cytoplasmic fluorescence as an increased basal exocytosis and indicating the secretion of serotonin. In the present study, we have tried to establish whether or not this secretory behavior is neurally controlled by combining an exposure to hypoxia with various vagotomy procedures. After long-term (3 days) infranodose vagotomy, the ipsilateral NEB nerve endings have degenerated. The secretory response to hypoxia is modified: the cytoplasmic fluorescence intensifies, while the basal exocytosis remains unchanged. After short-term (1 hour) infranodose as well as long-term (3 days) supranodose vagotomy, the NEB nerve endings are still intact, though no longer connected to the central nervous system. In these circumstances, the hypoxic NEB secretory behavior is indistinguishable from that of intact NEB. From these experimental findings we conclude that the hypoxic NEB secretory response is neurally controlled, since it no longer occurs when the normal innervation has degenerated. This modulation is however not by CNS motor nerve impulses, but probably by intrapulmonary axon reflexes in sensory nerve fibers.