In this study of the human palatine tonsil we examined epithelial structures found always in the vicinity of the crypts and closely resembling thymic Hassall's corpuscles. We propose that in the reactive tonsillar lymphoid tissue these corpuscles form as a result of occlusion of fine microcrypts by the expanding lymphoid follicles during antigenic stimulation. The reticulated epithelial cells lining these microcrypts may then loose their polarisation, and gradually degenerate deep in the parenchyma, forming concentrically arranged parakeratotic pearls, rather than desquamate at the free epithelial surface. The structural similarities of the tonsillar and Hassall's corpuscles may be explained by endodermal embryological origin of the primordia of both organs, and by the specific degenerative properties of epithelia in the lymphoepithelial immune organs.

Adolescent↗

PubMed1993

The segmental Bauplan of the rostral zone of the head in vertebrates.

Observations in a wide selection of lower vertebrate embryos have confirmed classical descriptions concerning segmentation of the early head mesoderm. The premandibular (PM) segment is seen as the most rostral representative of a continuous rostro-caudal series of condensations in the paraxial mesoderm, luminisations within which are secondary and variable in occurrence and form. The premandibular condensations are typically in continuity across the midline; the confluence, which comes to lie behind Rathke's pouch, marks the site of first mesoderm formation behind the oral membrane. The underlying consistency of pre-otic segmental pattern throughout the vertebrates is frequently obscured by superimposed variation in morphological detail between species, reflecting the dynamic nature of the morphogenetic tissue processes. Luminisation is one such morphogenetic epiphenomenon. Variations in it account for the terminal (Platt's) vesicle and "proboscis pores": such structures cannot therefore be safely used to infer evolutionary homologies. Many previous difficulties facing segmentation theory are explained as the result of failure to take account of the dynamic nature of the responsible morphogenetic events.

Animals↗

PubMed1992

Repeated antigenic challenge induces earthworm coelomocyte proliferation.

Annelids are able to protect themselves against foreign materials by natural and acquired cellular immunity. The aim of this study was to characterize the kinetic of antigen induced proliferation of earthworm coelomocytes. The proliferative activity of free coelomocytes of Eisenia foetida decreased after a second contact with the same antigen. Precursor cells in the mesenchymal lining of the coelomic cavity responded to stimulation immediately. These results indicate that for a successful triggering of the proliferative response of the free coelomocytes repeated contact with stimulating agents is needed.

Animals↗

PubMed1992

The development and involution of tonsils.

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Animals↗

PubMed1990

[An unusual early complication of tonsillectomy].

The authors describe the observation of a localized tissue emphysema of the right cheek, which developed in an eight-year-old child as the early complication of tonsillectomy performed under local anaesthesia. In addition to reflections on the possible pathways of the gas from the tonsillar bed into interstitial spaces of the cheek, the authors draw attention also to possible concurrent penetration into the soft tissues of the neck and mediastinum.

Cheek↗

PubMed1989

[Radiodiagnostic methods in the postmortem study of a dicephalus masculinus].

With conventional radiography and with CT several malformations were detected in a dicephalus masculinus. The most important were: 2 spinal medullas in a common spinal canal (TH1 to L4), hydrocephalus of both lateral ventricles and of the third ventricle, prolaps of the left hepatic lobe into the left thoracic cavity, two aortic arcs, one large internal jugular vein, and twin bases of the vertebrae TH1 to L5. The dicephalus had not only a double head, but also two cervices connected by a falx.

Abnormalities, Severe Teratoid↗

PubMed1988

Palatine tonsils--their evolution and ontogeny.

The structure of the palatine tonsils in an evolutionary line of mammals and its development in man was studied. The homologies between the thymus and tonsils were pointed out. Both primordia come from the same source and their epithelium reticulizes and can form concentric corpuscles. The tonsil develops from a doubled primordium and consists of two lobes. Attention is drawn to the close relation between tonsils and glands. In the evolution the glands diminish and more crypts are formed. After antigenous stimulation, proliferation of the crypt epithelium takes place which provokes the increase of venules. They bring new populations of lymphoid elements which penetrate into the reticulated epithelium and finally form new follicles.

Animals↗

PubMed1988