We have examined the effects of chlorine gas inhalation (110 and 140 ppm) on cardiovascular and pulmonary function in nine anaesthetised and mechanically ventilated pigs. Four additional pigs, which were similarly treated but not exposed to gas, served as controls. Severe pulmonary dysfunction developed when the animals were exposed to 100 l of 140 ppm chlorine gas for 10 min. Five of six animals died within 6 h of exposure. This dose induced a rapid drop in arterial oxygen tension (P < 0.001 compared with controls, ANOVA), a biphasic decline in lung compliance (P < 0.001) and a gradual increase in pulmonary vascular resistance (P < 0.001) that eventually caused a significant reduction in cardiac output (P < 0.05). Microscopic examination showed sloughing of the bronchial epithelium and early infiltration with leukocytes, but largely intact alveoli. The sequence of events and the microscopic appearance suggested that the initial stage of pulmonary dysfunction (the first 1 or 2 h) was the result of mismatching of ventilation and perfusion. This was followed at a later stage by interstitial oedema and migration of immunocompetent cells into the tissue. We conclude that exposure to 100 l of 140 ppm chlorine gas induces a severe stereotypic lung injury with high mortality within 6 h in this anaesthetised animal model.

Administration, Inhalation↗

PubMedDate not supplied

Mast cells and middle ear effusion.

The mast cell--an important component of connective tissue--carries in its cytoplasmic granules various biologically active substances, such as heparin, histamine, and a broad spectrum of enzymes. This cell type plays a prominent role in inflammatory and allergic conditions. In the middle ear, the mast cells are mainly localized in the pars flaccida of the tympanic membrane and beneath the tracts of secretory and ciliated cells in the middle ear mucosa. Degranulation of the mast cells by the histamine liberator compound 48/80 causes histamine-rich effusion material to accumulate in the middle ear. Plugging of the eustachian tube and/or tympanic isthmus will bring about a similar accumulation. It would thus seem that mast cells in some way participate in the production of middle ear effusion, probably via their potent mediators.

Animals↗

PubMedDate not supplied

The release of histamine from the pars flaccida mast cells one cause of otitis media with effusion?

In this experimental study in the rat, compound 48/80--a potent degranulating drug of mast cells--was instilled in the external auditory meatus towards the tympanic membrane. Moreover, effusion material was produced in the attic space by blocking the tympanic isthmus with a piece of Gelfoam applied through the tympanic bulla. Both these procedures caused a degranulation of the pars flaccida mast cells and subsequently histamine was detected in the rinsing fluid collected from the middle ear cavity. A possible direct cause of the effusion material in the middle ear cavity may be a degranulation of the pars flaccida mast cells, thus resembling an allergic reaction Type I.

Animals↗

PubMedDate not supplied

Fine structure of-and some histochemical observations on-chondroid regions of benign mixed parotid tumours.

Seven cases of mixed parotid tumour were studied at the light-and of these, three-at the electron microscopical level. In the latter group, special attention was paid to the fine structure of the chondroid regions of the tumours. The chondroid regions showed a typical cartilage fine structure-of greater interest was the finding that this tissue was mixed type of both hyaline and elastic cartilage. This was evident with respect to both cell and extracellular matrix. Two cell types were found: (A) cells similar to cells of hyaline cartilage and (B) cells resembling cells shown to be involved in synthesis of elastic fibres (elastic tendon fibroblasts, elastic cartilage chondrocytes and arterial smooth muscle cells). As in normal calcifying cartilage the chondroid regions contain numerous membrane-delimited matrix vesicles. However, mineral deposits within the latter were rare, indicating either a suppressed tendency towards mineralization of a lower stage of tissue maturation at which the mineralization process has not yet started.

Adenoma, Pleomorphic↗

PubMedDate not supplied

Middle ear effusion caused by mechanical stimulation of the external auditory canal. An experimental study in the rat.

Mechanical stimulation of the external auditory canal (EAC) in rat, either by scratching or exposure to a stream of air, caused effusion behind an intact ear-drum both in the experimental ear and in the contralateral one. Histologically the pars flaccida appeared oedematous, especially its lamina propria; and was infiltrated by inflammatory cells indicating a vascular leakage. Determination of the histamine level of the content of the middle ear cavity showed elevated levels, not only in the experimental ear but also in the contralateral. This increased level of histamine was recorded as long as 24 hours after stimulation. Though the mechanisms involved are not known, new ideas about the initiation of otitis media with effusion are inferred.

Animals↗

PubMedDate not supplied

Membrana shrapnelli of maturing rats. The occurrence of mast cells, and histamine content in relation to otitis media with effusion.

The membrana shrapnelli or pars flaccida of 12 day old rats is thick (84 micron) and almost completely fills the lateral attic compartment. Histologically it is characterized by a thickened layer of stratified squamous epithelium and a lamina propria whereas an inner epithelial lining is difficult to discern. Mast cells are numerous and distributed throughout the lamina propria. At day 21 and day 30 the thickness of the pars flaccida is reduced and histologically it resembles that of the adult. Mast cells are mainly located in the vicinity of blood vessels and in a layer just beneath the squamous epithelium. The number of mast cells per unit area of pars flaccida is considerably higher in young rats as compared to adults. At day 12 their number is roughly 2.1 times that of the adult and at day 21 and 30 about 1.5 times. Except for a slightly raised level of histamine at day 30 the concentration of histamine in the pars flaccida of young rats did not differ from values obtained in the adult. Previous experimental studies have indicated that mast cells in the pars flaccida may play an important role in the pathogenesis of OME. It is interesting to note that the pars flaccida of young rats contains more mast cells than that of the adult. Should this also be the case in the pars flaccida of young humans it is tempting to suggest that mast cells may play a role in the pathogenesis of OME in children too.

Animals↗