PubMed Health⌕ Search

Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

At least 145 records · Page 8Linked to original sources
PubMed1985

Tympanostomy tubes for prevention of purulent otitis media.

A recently developed animal model was used to study the effect of tympanostomy tubes (TTs) on the spontaneous development of purulent otitis media. In 35 rats with soft-palate clefts a TT was inserted into the right tympanic membrane. The left ear was left intact. Serous effusion occurred in the attic space within 2 days after surgery, whether or not the middle ear cavity (MEC) was artificially ventilated. Between days 7 and 21 the intact-ear MEC was gradually filled with effusion material that turned purulent. Effusion material did not develop in the mesotympanum and hypotympanum of the intubated ears. Microbiologic examination of the effusion material showed a microflora similar to that in the nasopharynx. Ventilation through a TT reduced the number of colonized MECs (4 vs. 10) on day 21. In the individual culture-positive MEC with a TT there were fewer colonies than in the corresponding ear without a TT. These results support the contention that a TT may prevent the development of purulent otitis media.

Animals↗
PubMed1984

Short-term effects of local anaesthetic agents on the structure of the rat tympanic membrane.

Four different local anaesthetic agents were tested on the tympanic membrane of the rat in order to detect any structural changes. Specimens were obtained for examination under the light microscope 10 min, 24 h, 1 week, and 2 weeks after exposure to each anaesthetic. The histological changes observed were, in general, rather similar for all agents tested, although certain differences were noted. The initial change observed was damage of the outer epithelial layers, later also accompanied by changes in the corresponding endothelial cover. No perforations were observed macroscopically. The healing process was characterized by hyperplasia of the connective tissue layers of the drum. However, the most prominent feature of this process was the hyperplastic epithelium, ingrowing from the periphery of the membrane to cover denuded areas. During certain stages of the healing process the thickness of the membrane amounted to 40 times that of the normal drum. The initial changes appeared severe both with the clinically more potent and effective anaesthetics (phenol and Bonain's liquid), and with Xylocaine spray.

Anesthetics, Local↗
PubMed1984

Morphometric analysis of glomus cells within the recurrent laryngeal nerve of the rat.

An endoneurial paraganglion located in the recurrent laryngeal nerve of the rat was found in 17 of 20 nerves studied. The median size of the paraganglia was estimated to be 0.8 X 10(6) micron 3. The number of type I like cells within a paraganglion ranged between 8 and 24. Altogether, 120 endoneurial dense-cored vesicle cells from 8 paraganglia were subjected to a morphometric analysis at the ultrastructure level. The mean vesicle profile diameter was estimated to be 101.3 nm and only one type of granulated cell could be distinguished. The volume density of the dense-cored vesicles was estimated to be about 6%, a value amounting to two to three times that in the carotid glomus. Moreover, the mean cell profile area of vesiculated cells of recurrent laryngeal nerve exceeds that of the cells of the carotid glomus.

Animals↗
PubMed1984

Intact and sympathectomized carotid bodies of long-term hypoxic rats: a morphometric ultrastructural study.

The ultrastructure of the carotid body after exposure to hypoxia (10% O2) for one, two or three weeks was investigated morphometrically. The study was performed on rats after unilateral removal of the superior cervical ganglion. The normally occurring bimodal distribution of type I cells, representing cells with small vesicle profile diameters (SVC) and large vesicle profile diameters (LVC) respectively, changed after one week of hypoxia into a unimodal population. After one or two weeks of hypoxia the diameter range of dense-cored vesicle (DCV) profiles in type I cells was not different from that of DCV profiles in control LVC. After three weeks of hypoxia the DCV vesicle size was intermediate between those of control SVC and LVC. The volume density of DCV decreased after one week but returned to initial values after two and three weeks of hypoxia. At two or three weeks of hypoxia, however, the total cell volume was increased about 1.4 times which should reflect an increase of the total content of DCV at these times of exposure to hypoxia. An increased mean area of cell profiles indicates a hypertrophy of the type I cells, but no signs of hyperplasia could be detected. The ganglionectomy did not cause any remarkable changes compared to the intact carotid body except for a higher volume density of DCV during the early periods of hypoxia. It is inferred from the study that the increased total mass of type I cell tissue during long-term hypoxia is due to a hypertrophy of the cells. Furthermore, the type I cells can increase their storage capacity for catecholamines during hypoxia by an increase in the size and number of DCV.

Animals↗
PubMed1984

Experimental background for the use of tympanostomy tubes.

Already within 24 h, splitting of the soft palate in rats caused production of effusion in the attic space. During the next couple of days the effusion material filled the meso- and hypotympanon. The production of a serous fluid in the attic space appeared concomitant with an elevated histamine content in the middle ear cavity, irrespective of whether the ears were ventilated or not. In the artificially ventilated middle ears no effusion appeared in the meso- and hypotympanon and the hypotympanal mucosal lining remained normal. The serous effusion filling the middle ear cavities with the intact tympanic membranes was replaced at about 7 days by a purulent effusion material containing mainly Gram-negative enteric rods. Thus it seems that a serous otitis media and a purulent otitis media occur in a continuum. The change to a purulent infection could be prevented by artificial ventilation, but as soon as the myringotomies were healed or the tympanostomy tubes got clogged a flocculent, pus-like effusion also appeared in these middle ear cavities.

Animals↗
PubMed1984

Chronic propranolol treatment affects parietal cells of the developing rat gastric mucosa.

The nonselective beta-adrenoceptor antagonist propranolol (0.3 mg/kg body weight) was given to rats, twice daily, from the day of birth to 5 weeks of age. The animals were then killed, and sections from gastric mucosa were prepared for light and electron microscopy. Propranolol treatment significantly reduced the thickness of the mucosa as compared with that of the controls. The parietal cell volume density and the number of parietal cells were markedly decreased following propranolol. The volume density of lamina propria and of other epithelial cells in the gastric mucosa were not significantly different from the control group. The secretory canaliculi of the parietal cells seemed markedly increased, indicating enhanced secretory activity. These findings suggest an important role for the adrenergic-sympathetic system in the development of parietal cells in the maturing gastric mucosa.

Animals↗
PubMed1984

The attic space--its development and some species differences.

The attic space of the rat has been described. The lateral attic compartment is connected with the rest of the middle ear through a narrow opening--the isthmus tympanicus. Part of this lateral compartment seems to correspond to Prussak's space in the human. The attic space develops later than the rest of the middle ear cavity and is not fully developed until the external auditory canal is established. Most mammals seem to have an attic space similar to that of the rat. The size of pars flaccida relative to that of pars tensa, however, differs between species. It is interesting to note that an extremely earthbound animal such as the hedgehog has an extremely large pars flaccida, whereas guinea pig, emanating from high altitude life, has its pars flaccida converted into bony lamella. In this context it is also noteworthy that the bird investigated has only a rudimentary pars flaccida. On the basis of the presented findings it is tempting to speculate that the attic space is of importance for the pressure-equilibration of the middle ear cavity. The space needs to be ventilated. If not sufficiently ventilated, pathological conditions affecting this part of the middle ear cavity may start. To obtain conclusive evidence for these suppositions, further research is needed. Such studies are already in progress.

Animals↗
PubMed1983

The anatomy of the eustachian tube in the rat: a macro- and microscopical study.

The rat eustachian tube (ET), from the nasopharyngeal orifice to the tympanal orifice, is about 4.5 mm long, of which the naso-medial membranous part (the nasopharyngeal orifice) measures about 1.5 mm and the occipito-lateral bony portion about 3 mm. The nasopharyngeal orifice is surrounded by two soft, lip-like, mucosal swellings--one ventral and one cranial--both easily mobile. The muscles related to the tubal opening mechanisms are the salpingopharyngeus, the tensor veli palatini and the levator veli palatini muscles. The salpingopharyngeus muscle originates partly from the cranial lip, whereas the palatal muscles originate partly from the ventral lip. The tympanal two thirds of the mucosal lining of the ET is cranially guided by a cartilage and incompletely framed by bony structures. The tympanal orifice is situated in the nasal part of the medial wall, well above the floor of the bulla. The tensor tympani muscle does not seem to take part in the opening and closing mechanisms of the ET. The mucosal lining of the ET consists of a respiratory epithelium with numerous glands in the lamina propria. It is suggested that the tubal muscles control the passage through the ET by moving the lip-like folds of the nasopharyngeal orifice. The anatomy of the rat ET is comparable to that described in Homo and it can be concluded that the rat ET might be a good model for studying the function of the human ET.

Animals↗
PubMed1983

Intact and sympathectomized carotid bodies of long-term hypoxic rats. A morphometric light microscopical study.

Intact and sympathectomized carotid bodies from rats exposed to hypoxia (room-air mixed with N2 to a final oxygen concentration of 10%) for 1, 2 and 3 weeks were analyzed by morphometric methods using the light microscope. Exposure to hypoxia enlarges the carotid bodies, in which the vascularity increases dramatically from the first week. This changed vascularity seems to be due to enhanced vasodilatation. In addition, there is a pronounced profileration of the endothelial tissue, thus suggesting an ingrowth of new blood vessels. The volume density of glomic type I, and type II cells, decreases during hypoxia but when calculated in total volumes this entity is increased 3-fold. Sympathectomy does not modify the structural changes occurring during hypoxia when compared with carotid bodies with intact innervation. Though the primary elements in the mechanism of transduction in carotid body are unknown, a remodelling of the vascular architecture may be a method by which this chemoreceptor alters its sensitivity.

Animals↗
PubMed1983

Clearance of effusion material from the attic space--an experimental study in the rat.

Rat serum with Evan's blue added as a tracer was instilled into the attic through a pars flaccida perforation in rats. At intervals the drainage of the effusion-like material was observed through a hole in the tympanic bulla. The distribution of ciliary cells was studied in the middle ear using light microscopic and scanning electronmicroscopic techniques. It was noted that the effusion material was propelled from the attic to the inlet of the Eustachian tube mainly by hydrostatic forces. It is also concluded that this mechanism might apply in Homo sapiens and that the drainage position of the head may be of importance in preventing and treating otitis media with effusion (OME).

Animals↗
PubMed1983

Appearance of effusion material in the attic space correlated to an impaired Eustachian tube function.

In adult Sprague-Dawley rats a dysfunction or a total blockade of the Eustachian tube was established by various experimental procedures. The appearance of effusion material in the attic was subsequently considered to be evidence of incomplete ventilation of the middle ear cavity. Though the salpingopharyngeus muscle (SPM) seemed to be the muscle which could open the Eustachian tube maximally, splitting of the soft palate and consequent interference with the tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM)--but obviously not with the salpingopharyngeus muscle (SPM)--caused the effusion material to be produced in the middle ear cavity. Neither blockade by about 80% of the tympanal orifice nor severing of the tendon of the tensor tympani muscle (TTM) close to the malleus produced any signs of effusion material whatsoever. Our findings strongly suggest that the most important part of the Eustachian tube, as regards ventilation, is the nasopharyngeal portion, as a normally functioning TVPM and LVPM seems to be an absolute prerequisite to prevent effusion material from developing in the attic.

Animals↗