Sten Hellström

A new projection from locus coeruleus to the spinal ventral columns: histochemical and biochemical evidence

The locus coeruleus (A6 of Dahlstr6m and Fuxe a) is a large pontine noradrenergic nucleus which projects to many brain regions, including the cerebellum, cerebral cortex, hypothalamus and hippocampus 12-14,21,22. Recently, evidence has also been presented for a coerulospinal projectiont0,21; however, the distribution of these descending fibers within the gray matter of the cord has not been studied. Noradrenergic projections to the spinal cord from the medullary nuclei A1-3 have been described by DahlstrSm and Fuxe 4 and Fuxe. s Our recent work 2 has suggested that a dopaminergic neuronal system is present in the spinal cord, most likely as terminals of axons whose cell bodies originate in the brain stem. In the course of our studies of the dopaminergic neurons which project to the spinal cord, we lesioned several brain stem nuclei, including the locus coeruleus. Dopamine (DA) represents almost 25 ~ of the catecholamines in this nucleus 2a, thus amine level changes after a lesion of this classical noradrenergic system could provide added support for dopaminergic neurons in the cord and indicate the quantity of precursor DA in noradrenergic terminals. Our consistent observation has been a nearly complete absence of fluorescent terminals from the spinal ventral columns following bilateral lesion of the locus coeruleus. In these same animals, there was a concomitant reduction in the cord of norepinephrine (NE), but not of DA. Apparently the coerulospinal projection is almost entirely noradrenergic, and the fibers terminate primarily in the ventral column. Male Sprague-Dawley rats, 125-150 g (Zivic-Miller Laboratories, Inc., Allison Park, Pa.) were anesthetized with ether and placed in a small animal stereotaxic frame. A unipolar stainless steel electrode (0.3 mm diameter) insulated to within 0.5 mm of the tip was stereotaxically placed in the locus coeruleus, according to the coordinates used by Korf et al. 13. The electrode was connected to a Lesion Producing Device (Stoelting Co., Chicago, Ill.). A current of 2.5 mA was passed for 45 sec producing a lesion of about 1 mm in diameter. Ten days later, the animals were anesthetized with sodium

Hyaluronan and Healing of Tympanic Membrane Perforations. An experimental study

Hyaluronan, an extracellular high molecular weight polysaccharide, was applied onto experimentally performed tympanic membrane (TM) perforations in the rat. The hyaluronan-treated perforations closed faster than the untreated controls and showed less scar tissue. Initially the perforation became covered by a sheet of keratin and hyaluronan, which appeared to relax and orientate the retracted collagen fibres at the margin of the perforation. The hypertrophic stratified keratinizing squamous epithelium advanced within the hyaluronan-keratin cover and closed the perforation ahead of an approaching connective tissue. Three months after the closure, the hyaluronan-treated TMs appeared transparent in comparison to the opaque untreated controls. In histological sections the hyaluronan-treated TM was comparably thin and an organized collagen fibre layer was discernible. Hyaluronan of various concentrations (0.75, 1.0, 1.75 and 1.9%) and molecular weights (4 x 10(6) and 6 x 10(6)) were tested. The healing rate and degree of scar tissue was dependent on the concentration, but not on the molecular weight of the hyaluronan. Hyaluronan, at the higher concentration, healed the perforations faster and produced a less opaque TM than hyaluronan at low concentration. The number of applications of hyaluronan also influenced the healing rate; fewer applications resulted in a reduced rate. However, the quality of the healed TM was influenced to a lesser extent by the number of hyaluronan applications. Even single applications caused less scar tissue in comparison with untreated TMs. It is inferred from the study that hyaluronan, exogenously applied, might be valuable also in the clinical situation to enhance the healing of different types of TM perforation.

A rat model for pneumococcal otitis media

The middle ears of 29 male Sprague-Dawley rats were injected with viable pneumococci, type 3 or 6A, and changes were monitored by otomicroscopy and analysis of bacterial samples from middle ear effusions, blood, and the nasopharynx. Depending on the type of pneumococci and its concentration, three responses were noted: otitis media with purulent effusion, otitis media with serous effusion, or no reaction. The mortality rate was low and the animals recovered without permanent deterioration or otomicroscopically discernable change. The results of this study show the rat to be a suitable animal model for the study of bacterial otitis media.

Anatomy of the Rat Middle Ear

The rat is of value in otological research for many reasons. For instance, the middle ear structures are easily approachable. Recently a couple of studies in the rat have been published concerning the

Myringosclerosis Caused by Increased Oxygen Concentration in Traumatized Tympanic Membranes Experimental Study

The purpose of this study was to elucidate possible relationships between the oxygen concentration of the middle ear cavity and the development of myringosclerosis. Three groups of rats with myringotomized tympanic membranes were exposed to different oxygen concentrations of 10%, 15%, and 40%, respectively, for 1 week. A fourth group was kept in ambient air. Two other groups of rats with myringotomized and intubated tympanic membranes were exposed to oxygen concentrations of 10% and 40%, respectively, for the same period of time. Otomicroscopically, all hyperoxic animals had more numerous myringosclerotic lesions compared with the ambient air group, and also displayed a pronounced hyperplasia of the keratinizing epithelium around the perforation border. By contrast, the hypoxic animals showed less pronounced myringosclerotic lesions or even completely lacked them. It is inferred that an increased oxygen concentration in the middle ear cavity will increase the likelihood of myringosclerotic deposits. The mechanism involved could be related to the formation of oxygen radicals.

Ventilation Tube Treatment A Systematic Review of the Literature

Objective. The aim of this review was to study the effectiveness of ventilation tube (VT) treatment in children with secretory otitis media (SOM), assessed by improved hearing, normalized language and quality of life (QoL), and recurrent acute otitis media (rAOM), assessed by number of episodes of AOM and QoL. Data Sources. Cochrane Library, PubMed, and Embase databases were searched for randomized and nonrandomized controlled trials and cohort studies in English, Scandinavian, German, and French languages between 1966 and April 2007. Additional literature was retrieved from reference lists in the articles. Review Methods. A total of 493 abstracts were evaluated independently by 2 members of the project group, 247 full-text versions were assessed for inclusion criteria and quality using structured evaluation forms, and 63 articles were included in the review. Results and Conclusions. This review shows that there is strong scientific evidence (grade 1) that VT treatment of SOM improves hearing for at least 9 months and that QoL is improved for up to 9 months (grade 2 scientific evidence). There was insufficient evidence to support an effect of VT treatment for rAOM. There was also insufficient evidence to determine whether the design or material of the VT or the procedure used for insertion had any influence on the effect; however, there was some evidence (grade 3) that aspiration of secretion at insertion does not prolong VT treatment. Further research is needed to address these issues.

Application of Oxygen Free Radical Scavengers to Diminish the Occurrence of Myringosclerosis

The present study was designed to establish whether or not an increased production of oxygen-derived free radicals is involved in the causation of myringosclerosis. Sclerotic lesions in the tympanic membrane were experimentally elicited by keeping rats with perforated tympanic membranes in an atmosphere containing roughly 40% oxygen. The animals were treated daily with a solution containing either copper zinc-supcroxide dismutase plus catalase, deferoxamine, or copper sulfate plus iron chloride, applied to the traumatized area. After 1 week the extension of myringosclerotic plaques was determined otomicroscopically. The pars tensa and pars flaccida were then dissected free and prepared for light microscopic studies. The results showed that treatment with copper zinc-superoxide dismutase plus catalase and deferoxamine inhibited or reduced the development of myringosclerosis, whereas die ears treated with copper sulfate plus iron chloride appeared unaffected. Consequently, the findings support the hypothesis that the formation of oxygen free radicals contributes significantly to the development of myringosclerosis.

An improved technique for hyaluronan histochemistry using microwave irradiation

SummaryA hyaluronan binding protein (HABP), extracted from cartilage, was biotin-labelled and used for histochemical localization of hyaluronan (HA) in tissue sections. Various tissues were fixed for a mixture of formaldehyde and glutaraldehyde during microwave irradiation. The microwave oven when set at 700 W and 45°C yielded an intense and specific staining of HA. Under these conditions the relative proportion of the two aldehydes did not influence the staining intensity. Aldehyde fixation during microwave irradiation for HA histochemistry, (1) saves time, (2) eliminates the use of cetylpyridinium chloride (CPC), and (3) improves the reproducibility.

The distribution of hyaluronan in human skin and mature, hypertrophic and keloid scars

A hyaluronan-binding protein (HABP) was used to locate the distribution of HA in normal skin and in various types of scar tissue: mature scar tissue, hypertrophic scar tissue and keloids. The study was intended to establish whether or not a deviant HA distribution could explain the different clinical features of these scar tissues. The distribution of HA was found to differ between the various scar tissues. In normal skin an intense HA-staining was observed in the papillary dermis. In mature scar tissue the distribution of HA resembled that of normal uninjured tissue, but the layer of HA was thinner. In hypertrophic scar tissue, HA occurred mainly as a narrow strip in the papillary dermis. Keloid tissue showed the least HA-staining of the papillary layer and resembled that of the bulging reticular dermis. In contrast, the thickened granular and spinous layer of the keloid epidermis exhibited an intense HA-staining. We suggest that the altered distribution and amount of HA in these different scar tissues may contribute to their different clinical characteristics. This histochemical technique for the demonstration of HA in scar tissue could be of use in clinical work to decide on therapeutic strategies.

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

SummaryTwo 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 (0.4 versus 0.9%), mitochondria (14 versus 17%) and nuclei (49 versus 38%).The fingerlike 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.