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Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

At least 163 records · Page 9Linked to original sources
PubMed1983

The pressure equilibrating function of pars flaccida in middle ear mechanics.

In the adult male rat the precise volumes of the middle ear cavity, the lateral attic compartment and a maximally retracted pars flaccida were calculated to 550 microliter, 21 microliter and 3 microliter respectively, using Woods metal. Small intratympanal pressure or volume changes caused the pars flaccida to move in a medial-lateral direction. As the volume of a maximally retracted or bulging pars flaccida only amounted to about 0.5% of the total middle ear volume and the pars flaccida reacted even at volume changes of 0.1% of the middle ear, it would seem that the pressure equilibrating capacity of the elastic pars flaccida is negligible. On the other hand the pars flaccida is extremely sensitive to pressure and volume changes in the middle ear and may take part in the pressure equilibrating system as a detector for minute pressure and/or volume changes in the middle ear.

Animals↗
PubMed1983

The stapedial artery in the rat. A microscopical study under normal conditions and in otitis media with effusion.

Arteria stapedialis in the rat was studied in healthy rats and in experimental otitis media with effusion (OME). The mean diameters of the vessel was calculated to approximately 460 microns (healthy) and 430 microns (otitic) (no significant difference). The tunica intima consisted of an endothelium and a well-developed elastica interna. The tunica media was composed of 2-3 layers of smooth muscle cells. The adventitia was thicker than the media and consisted of bundles of collagen fibers. The artery in the middle ear cavity was quite naked covered only with the middle ear mucosa. The stapedial artery did not appear to be involved in the production of effusion in experimentally induced OME.

Animals↗
PubMed1982

Effects of neonatal sympathetic denervation on amylase secretion in the adult rat parotid gland: difference in beta 1- and beta 2-adrenoceptor response.

Changes in amylase secretion and cyclic AMP accumulation in response to various secretagogues were studied in parotid glands of adult rats subjected to neonatal sympathetic denervation by unilateral excision of the superior cervical ganglion. Denervation decreased the gland content of amylase and both basal and the stimulated levels of cyclic AMP were elevated. The secretory cells of neonatally denervated glands exhibited enhanced maximal enzyme discharge in response to beta-adrenoceptor agonists. However, the selective beta 1-agonist, prenalterol was not effective in this respect whereas an enhanced maximal secretory response to the beta 2-selective agonist, terbutaline, was particularly prominent. DBcAMP was also more efficient in inducing amylase release from the denervated gland. The result of the present study demonstrate that the usual dominance of the beta 1-adrenoceptor subtype in eliciting amylase release is lost, implying that the differentiation of the beta-adrenoceptor into its subtypes is altered by neonatal sympathetic denervation.

Amylases↗
PubMed1982

Fiber components of the recurrent laryngeal nerve of the rat: a study by light and electron microscopy.

A quantitative study by light and electron microscopy of the recurrent laryngeal nerve (RLN) of the rat has been performed. The diameter of the myelinated fibers displayed a bimodal pattern, with a pronounced peak at 2-3 microns, and with a second peak at 4.5-7 microns. The number of small fibers was reduced at the termination of the nerve, indicating that many of the small fibers are distributed to the trachea and oesophagus as the nerve ascends in the neck. Upon comparison, no difference between right and left side was noted in numbers of myelinated fibers. The RLN was also found to contain numerous unmyelinated fibers. Most of these fibers were of the diameter size range 0.2-0.6 microns. The unmyelinated fibers constituted about 50-60% of all axons in the RLN.

Animals↗
PubMed1982

Structure of the pars flaccida after occlusion of the Eustachian tube or blockade of the tympanic isthmus.

In this experimental study performed on the rat middle ear either the Eustachian tube or the tympanic isthmus was blocked via the tympanic bulla with a polyethylene plug or a piece of Gelfoam, respectively. Effusion material was immediately observed in the attic space and subsequently the pars flaccida was drawn in a medial direction to form a retraction pocket. The initial changes in the pars flaccida structure were a degranulation of the mast cells and concomitantly metaplasia of the mucosal epithelium into cells displaying numerous osmiophilic inclusions, vacuoles and multivesicular bodies. It cannot be excluded that the initial cause of the effusion production is the histamine released from mast cell granules.

Animals↗
PubMed1981

Trophic effect of the sympathetic nervous system on the early development of the rat parotid gland: a quantitative ultrastructural study.

Rats were sympathetically denervated on one side by avulsion of the superior cervical ganglion either immediately after birth (within 4 hr) or when the salivary glands were fully developed. Nine weeks after ganglionectomy the parotid glands were subjects to microscopical studies. As shown by the lack of specific fluorescence, sympathetic denervation caused an almost total depletion of catecholamines in the acini. This was further substantiated at the electron microscopic level using KMnO4 as fixative. No alterations in either gland weight or in acinar cell size were noticeable after adult sympathectomy. On the other hand, neonatal denervation caused a decrease in gland weight as well as ascinar cell hypotrophy. The mean volume of individual acinar cells was reduced by roughly 25% and the granule volume density by about 50%. Also the mean volume of individual granules was decreased. These findings indicate an important role for the sympathetic nerve system in the maturation of the rat parotid gland.

Age Factors↗
PubMed1976

Effects of glucocorticoid treatment on catecholamine content and ultrastructure of adult rat carotid body.

Carotid bodies of dexamethasone-treated (daily injections, 10 days) adult male rats were analyzed with respect to catecholamine content and ultrastructure. Gas chromatographic-mass spectrometric assays demonstrated that norepinephrine (NE) and dopamine (DA) concentrations more than doubled after dexamethasone treatment. The increase in NE was relatively greater than that of DA. No epinephrine (E) could be detected. Morphometry revealed, as for the control carotid bodies, two subclasses of type I cells on the basis of the diameters of their dense-cored vesicles. These groups of cells were termed small vesicle cells (SVC) and large vesicle cells (LVC). Dexamethasone treatment resulted in significantly increased volume densities and diameters of the dense-cored vesicles in both SVC and LVC. The greatest increase occurred in the SVC. If these morphological changes do reflect the change in amine concentrations then it is possible to speculate that the type of cells with the greatest increase of amine storage capacity may store the kind of catecholamine most increased. Thus NE may presumably be stored in the SVC and DA in the LVC. Furthermore, these effects of administered glucocorticoids may also indicate a regulatory function for endogenous glucocorticoids on the carotid body catecholamines.

Animals↗
PubMed1975

Morphometric studies of dense-cored vesicles in type I cells of rat carotid body.

Two subclasses of Type I cells of rat carotid body were recognized by analyzing the diameters of dense-cored vesicles. One group of cells contained vesicles with a mean diameter of about 52 nm; in the other group of cells the vesicles measured about 71 nm. The mean volume of the small vesicle cell (SVC) was roughly 3/4 that of the large vesicle cell (LVC). Furthermore there were significant differences between SVC and LVC in volume densities of vesicles extensions typical of the Type I cells were more common for LVC than for SVC. The majority of the nerve-endings observed terminated on LVC. The significance of these differences has yet to be determined.

Animals↗
PubMed1975

Type I cells of carotid body from rats treated with 5-OH-dopa and L-dopa: an electron microscopical study.

The ultrastructure of the Type I cells in rat carotid bodies was studied after treatment with 5-OH-Dopa and L-Dopa. Type I cells from the L-Dopa treated rats were also analysed by morphometric methods. After 5-OH-Dopa treatment, the majority of dense-cored vesicles of the Type I cells were almost completely filled with very electron-dense material. The vesicles were mainly distributed close to the plasma membrane. After L-Dopa treatment, the ultrastructure of the Type I cells resembled that after 5-OH-Dopa treatment, except that the increase in electron density of the vesicle content was less pronounced. The morphometric analysis revealed, as previously described for normal carotid bodies, two subclasses of Type I cells, small vesicle cells (SVC) and large vesicle cells (LVC). Compared to those of normal rats, the mean profile diameter of the vesicles in the L-Dopa treated rat carotid bodies were enlarged (for SVC from 47 to 55 nm and for LVC from 63 to 76-78 nm). Furthermore, the volume density of vesicles in both SVC and LVS was increased. The mean volume of the SVC was markedly increased after L-Dopa treatment for 60 h. These observations indicate that the Type I cells possess mechanisms for uptake of amine precursors and synthesis of monoamines. Though the vesicle may be involved in an 'endocrine-like' function, they may also be related to the chemoreceptor function of the carotid body.

Animals↗
PubMed1975

Biogenic amines in carotid body of adult and infant rats--a gas chromatographic-mass spectrometric assay.

A gas chromatographic-mass spectrometric method was used for the determination of biogenic amines in carotid body of adult and 10 days old rats. The method is ideally suited for this measurement since only small amounts of tissue were available (dry weight carotid body: adult 8.3 mug; infant 5.6 mug). In adult carotid body large amounts of dopamine (1 950 pmol/mg protein) and norepinephrine (1 140 pmol/mg protein) were found together with a comparatively small concentration of serotonin (505 pmol/mg protein). The carotid bodies of infant rats contained 1 065 pmol dopamine/mg protein and 410 pmol norepinephrine/mg protein. Epinephrine could not be detected. Surgical sympathetic denervation and chemical sympathectomy (6-hydroxydopamine) of adult carotid bodies did not significantly change the catecholamine content as compared to the controls. Reserpine depleted the catecholamines dosedependently. Administration of L-Dopa and pargyline (a monoamineoxidaseinhibitor) drastically increased the concentration of catecholamines. Treatment with a dopamine-beta-hydroxlase-inhibitor resulted in a decreased amount of norepinephrine without a simultaneous increase of dopamine. This may indicate that certain storage sites in this tissue may store dopamine while in other sites dopamine is a precursor of norepinephrine. Probably most of the dopamine and norepinephrine are stored in different cells.

Age Factors↗
PubMedDate not supplied

Carotid-body-like tissue within the recurrent laryngeal nerve: an endoneural chemosensitive micro-organ?

Paraganglia associated with the ninth and tenth cranial nerves have been observed in several locations in the head and neck region. The most studied of these organs, both morphologically and functionally, is the carotid body, a chemoreceptor organ located in the carotid bifurcation. In the present study a microglomus (microparaganglion) composed of islands of carotid-body-like cells was found in the endoneural space of the recurrent laryngeal nerve of rats, 5 to 10 mm from the nerve entrance into the larynx. This microglomus was surrounded by bundles of myelinated and unmyelinated nerve fibers. Fenestrated blood vessels were observed between cells. The cells were characterized by their cytoplasmic membrane-bound granules and dense-core vesicles. Ultrastructurally, these cells seemed to be identical to carotid body chemoreceptor cells and thus to indicate that the cells of the microglomus store catecholamines. Nerve terminals impinging on the cells, classified as both afferent and efferent, were also identified. The recurrent laryngeal endoneural microglomus may have a chemosensitive function influencing the laryngeal physiologic reflex mechanisms.

Animals↗
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↗