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Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

At least 73 records · Page 4Linked to original sources
PubMed1993

Mucosal fine structure in experimental sinusitis.

Rabbit maxillary sinuses were inoculated with Streptococcus pneumoniae and Bacteroides fragilis, and the histologic response in the sinus mucosa was observed over a 12-week period. An increased height of the cylindric cells and hyperplasia of the basal cells were frequent findings irrespective of the pathogen inoculated. The disease was found to influence the character of the secretory product from epithelial secretory cells and to degranulate the subepithelial glands. Ciliary loss was a transitional finding. A reduction in the number of mitochondria, the occurrence of deformed short microvilli, and cytoplasmic blebbing were seen in the cells devoid of normal cilia. It is inferred from this study that pneumococcal sinusitis in rabbits is a self-limiting process, and the mucosal sequelae of the acute infection are persisting goblet cells, slight focal fibrosis, and edema. Inoculation with B fragilis produces a chronic inflammatory process, with infiltration of mononuclear cells, luminal dilatation of the glands exhibiting zymogen granule depletion, and an increased thickness of the whole mucosal layer.

Animals↗
PubMed1993

Arachidonic acid metabolites in experimental otitis media and effects of anti-inflammatory drugs.

Previous studies have shown that arachidonic acid (AA) metabolites are important in the pathogenesis of otitis media with effusion. The AA metabolites in 4 different experimental models for otitis media were analyzed, and the effect of anti-inflammatory drugs was studied. Purulent otitis media was induced in rats by inoculation of Streptococcus pneumoniae in the tympanic bulla, serous otitis media by blocking the tympanal orifice of the eustachian tube, and mucoid otitis media by combining the two procedures. Middle ear effusion was also induced by stimulating the external auditory canal with cold air. Indomethacin and hydrocortisone were used to inhibit AA metabolism in the latter model. Lipoxygenase products dominated in the purulent and cold air otitis media models. Cyclooxygenase products dominated in the mucoid and serous models. Indomethacin inhibited accumulation of middle ear effusion in the cold air otitis media model, whereas hydrocortisone did not. Apart from AA metabolites, other mechanisms and mediators appear to be responsible for the increased vessel permeability observed in the cold air otitis media model, such as interactions between mast cells and nerves in the middle ear mucosa.

Animals↗
PubMed1993

Tobacco smoke exposure suppresses radiation-induced inflammation in the lung: a study of bronchoalveolar lavage and ultrastructural morphology in the rat.

Previous studies on patients with breast cancer, who received postsurgical irradiation, displayed a markedly suppressed inflammatory response in the lung of smoking patients compared to nonsmokers. The aim of the present study was to investigate further the effect of exposure to tobacco smoke on the development of irradiation-induced pneumonitis in the rat. Four groups of animals were used: controls (C); those exposed to tobacco smoke (S); those irradiated but not exposed to smoke (RNS); and those irradiated and exposed to tobacco smoke (RS). The rats were exposed to a diluted main stream of cigarette smoke, at a concentration of about 0.4 mg.l-1, in a nose-only exposure system for 1 h.day-1, 5 days.week-1 for 10 weeks. Exposure to tobacco smoke started 3 weeks before irradiation. The basal one third of both lungs was exposed to a single radiation dose of 28 Gy (6 MeV photons). All animals were killed 7 weeks after irradiation. We compared findings in bronchoalveolar lavage (BAL) and tissue morphology. The alveolar tissue showed less inflammation in the RS-group than in the RNS-group. Most strikingly, mast cells were increased one hundredfold in the lung interstitium and thirty fold in the peribronchial area in the RNS-group, whereas no increase was found in the RS-group or in the controls. The alveolar septa of the RNS-group were thickened, with occurrence of inflammatory cells and mast cells, whereas the RS-group displayed no difference as compared to the non-irradiated, nonsmoking group (C).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The use of hyaluronidase and glucosidase to remove mucus from the rat middle ear cavities for SEM studies.

To conduct SEM studies on epithelium containing mucus-producing cells it is essential to remove the mucus which normally obscures the epithelial surface. This study presents a method which effectively removes the covering layer of mucus in the rat middle ear. Healthy Sprague-Dawley rats were decapitated and the middle ears dissected free. Incubation and agitation of the middle ear specimens in hyaluronidase (50 IE ml-1) and/or glucosidase (8%) removed the mucus from the middle ear cavity without altering the surface structures. It was also revealed that substances such as polyvinyl-pyrrolidone (PVP) (used to increase the colloid osmotic pressure of, e.g., the fixative solution) must be omitted when preparing ciliated specimens for SEM.

Animals↗
PubMed1992

Effects of tobacco-smoke on radiation-induced pneumonitis in rats.

To investigate the effect of exposure to tobacco smoke (TS) on the development of irradiation-induced pneumonitis in rats, five groups of animals were investigated including controls (C), tobacco smoke exposed (S), irradiated (RNS) and irradiated and tobacco smoke exposed (RS). An additional group (RS/NS) was exposed to tobacco before irradiation but not afterwards. Rats were exposed to diluted mainstream cigarette smoke at a concentration of about 0.4 mg/l in a nose-only exposure system for 1/day, 5 days/week for 10 weeks. Exposure to TS started 3 weeks before irradiation in which the basal one-third of both lungs was exposed to a single dose of 28 Gy. In previous studies this dose had been shown to cause significant pneumonitis. All the animals were killed at 7 weeks after irradiation. Examination of the morphology of lung sections showed less pulmonary inflammation in the RS group than in the RNS group. This was also reflected in the results of bronchoalveolar lavage (BAL) which showed a decline in cell recovery and a marked decrease in the numbers of mast cells and neutrophils in the RS rats compared with the RNS animals. The concentration of hyaluronan in lavage fluid was increased in the RNS and RS/NS group while no increase was found in the RS group. A marked increase in BAL protein was also seen in the RNS and RS/NS groups as compared with the RS group but all were significantly higher than in unirradiated controls. This indicates that smoking suppresses the radiation-induced inflammation but to a lesser degree affects the radiation-induced increase in membrane permeability as reflected by increased protein levels in BAL. Moreover, the marked effects on the numbers of mast cells and neutrophils in the RS group may indicate that these cells play an important role in the mechanism by which tobacco smoke modulates the effects of irradiation. When exposure to tobacco smoke was terminated immediately after irradiation (RS/NS), the inflammatory response was unaffected.

Animals↗
PubMed1992

Mucosal immunoreactivity in experimental pneumococcal otitis media.

A rat model was used to investigate immunological events in the middle ear mucosa during pneumococcal acute otitis media (AOM). Twelve healthy male Sprague-Dawley rats were challenged in the right middle ear with Streptococcus pneumoniae type 3, the presence of AOM being confirmed by otomicroscopy. Randomly selected rats, four at a time, were sacrificed on days 7, 14 and 56 after bacterial challenge. Immunohistochemical staining for IgG, secretory IgA (SIgA), and IgM was performed on tissue specimens from four separate locations in the middle ear and tubal mucosa. Immunoglobulins, especially IgG, were found around blood vessels in the middle ear mucosa. Immunoreactive lymphoid cells of all three Ig classes investigated, undetectable before bacterial challenge, appeared within 7-14 days after middle ear challenge, and the location of these cells in the middle ear mucosa suggests the presence of IgG, SIgA, and IgM, respectively. On the other hand, reactivity with anti-SIgA (but not with anti-IgG or anti-IgM) in Eustachian epithelial cells, and also in the subepithelial glands of tubal mucosa was present both before and after challenge. The results suggest that the middle ear mucosa is an immunoreactive site only after it has been activated with pathogens. In contrast, the tubal mucosa exhibits immunological activity also prior to the antigenic stimulation of present interest.

Animals↗
PubMed1992

Ventilatory response to hyperoxia in newborn rats born in hypoxia--possible relationship to carotid body dopamine.

1. The influence of postnatal hypoxia on regulation of breathing and turnover rate of carotid body dopamine was examined in newborn rats. The percentage change in frequency, tidal volume and ventilation elicited by transient hyperoxia was assessed by flow plethysmography in unanaesthetized pups. The alteration in ventilation was taken as an index of peripheral chemoreceptor activity. 2. The rats were born and reared in hypoxia. The inspired oxygen fraction (FI,O2) was 0.12-0.14 until 2 days after delivery when the rats were placed into room air and the ventilatory chemoreflex was tested. At 4 days of age, i.e. 2 days after termination of hypoxia, the rats were tested again. The ventilatory data were compared with those from a previous study in normoxic rats. 3. We found a smaller decrease in ventilation (8.8 +/- 3.9%, mean +/- S.D.) in the hypoxic rats at 2 days of age compared with normoxic rats (22.7 +/- 6.4%; P < 0.001). In contrast, at 4 days of age there was no difference in ventilatory response between the posthypoxic rats (19.2 +/- 4.6%) and normoxic pups (18.6 +/- 4.9%). 4. The turnover rates of dopamine in carotid bodies were determined at 0-6, 6-12, 12-24 h and 2 days after birth in hypoxic rats and in 2-day-old posthypoxic rat pups at different time intervals after termination of hypoxia. Postnatal hypoxia sustained a high turnover rate which decreased after termination of the hypoxia. 5. We propose that the weak chemoreflex in hypoxic rat pups is brought about by a high release of carotid body dopamine.

Animals↗
PubMed1992

Immunohistochemical localization of alpha-atrial natriuretic polypeptide in the rat cochlea.

The localization of alpha-atrial natriuretic polypeptide (alpha-ANP) in the rat cochlea was studied by immunohistochemical technique, using a polyclonal antibody against synthetic rat alpha-atrial natriuretic polypeptide (alpha-rANP). The spiral ligament of the lateral cochlear wall exhibited pronounced immunoreactivity to atrial natriuretic polypeptide (ANP), whereas the stria vascularis displayed almost no immunoreaction. ANP immunoreactivity (IR) was also intense in the spiral limbus region. IR was observed in the fibroblast-like cells and in the extracellular matrix, in particular along its fibrous bundles, of both the spiral ligament and the spiral limbus. These results indicate that ANP may participate in the regulation of the water electrolyte balance at these sites, which may imply a role for ANP in the regulation of cochlear fluids.

Animals↗
PubMed1992

Long-term hypoxia induces changes in the substance P immunoreactivity pattern in laryngeal nerve paraganglia.

We previously showed that long-term hypoxia increases the dopamine content in rat laryngeal nerve paraganglia. In the present study paraganglia of rats exposed to hypoxia (10 +/- 0.5% O2) for 14 days were examined immunohistochemically to detect changes in the expression of neuropeptides and catecholamine-synthesizing enzymes. Hypoxia induced an intense cellular substance P (SP)-like immunoreactivity (LI) in some paraganglia and an increase in the number of stromal nerve fibers showing SP-LI in others. The patterns of tyrosine hydroxylase-, dopamine-beta-hydroxylase-, phenylethanolamine-N-methyltransferase-, vasoactive intestinal polypeptide-, neuropeptide-Y and calcitonin gene-related peptide-LI were not changed in response to hypoxia. The results show that hypoxia induces changes in the pattern of SP immunoreactivity in laryngeal nerve paraganglia and may indicate that SP plays a role in the regulation of catecholamine metabolism in this tissue.

Animals↗
PubMed1992

Islet cell surface antibodies in diabetic children determined with 125I-labelled anti-IgG as tracer.

We have developed an assay for ICSA using fixed beta-cells as target cells and 125-I-Anti-IgG as tracer. Interassay variation was 9.5% and intraassay variation was 9.9%. For high titers of ICSA specificity was 100% but sensitivity then only 70%. Our technique enables a laboratory assistant to determine 200 samples in one week. Absorption of the samples with rat beta-cells as well as rat fibroblasts showed that ICSA are beta-cell specific and does not crossreact with rat fibroblasts. We found a significant difference in prevalence of high titer ICSA between healthy school children (4%) and newly diagnosed diabetic children (19%) (p < 0.001). That difference had disappeared after 18 months duration of IDDM when the B-cell mass and thus the amount of antigen had decreased. No difference was seen between healthy children and adult blood donors. There was no seasonal variation of ICSA titers in healthy children.

Adolescent↗
PubMed1992

[Occlusive dressing--s potential treatment for tympanic membrane rupture?].

In a rat study, an occlusive double-layer transparent hydrocolloid dressing, Duo-DERM, was compared with a rice paper dressing in the treatment of tympanic membrane perforation. The Duo-DERM dressing manifested better healing properties, and the healed membrane was histologically similar to spontaneously healed membrane, being generally thin with moderate connective tissue thickening. If this dressing is found to have good healing properties in clinical trials, it would mean a great saving in health care resources. The method is simple, inexpensive, and gives immediate improvement in hearing.

Animals↗
PubMed1992

[Healing of tympanic membrane perforation-a complex process influenced by a variety of factors].

It is known that the healing of a perforated tympanic membrane can be influenced by mechanical procedures as well as drugs. Animal experiments have recently shown that local treatment with steroids delays the healing of a tympanic membrane perforation, whereas hyaluronan (hyaluronic acid) improves the healing rate as well as the quality of the scar. Hyaluronan, a non-sulphated glycosaminoglycan, belongs to the extracellular matrix substances. In the present study another glycosaminoglycan--heparin--was applied on experimental tympanic membrane perforations. This report confirmed that also this extracellular matrix substance improves the healing rate of a tympanic membrane perforation and the scar quality.

Heparin↗
PubMed1992

The microwave oven in temporal bone research.

The microwave oven has recently been introduced in morphological research. It can be used for virtually all procedures in histological processing; fixation, dehydration, embedding, staining, immunotechniques, and the techniques used for electron microscopy. Here we report that the microwave oven histoprocedures also have several advantages in temporal bone research on animals. The microwave oven has been tested for (i) fixation, (ii) decalcification, (ii) staining of semithin plastic sections. The microwave oven procedures are time-saving and results in an excellent preservation of the tissues. The microwave histoprocessing should also be applicable to temporal bone research in human.

Animals↗
PubMed1992

Cochlear effects of hyaluronan applied on ruptured round window membrane.

The purpose of the present experimental study was to determine whether hyaluronan (hyaluronic acid, HYA) exerts any functional or morphologic ototoxic effects on the cochlea when in contact with a ruptured round window membrane (RWM). HYA in 1% solution was applied in the round window (RW) niche of rats (n = 6) prior to perforating the RWM. In a control group (n = 6) the RWM was perforated alone. Cochlear functioning and structure were monitored by recording auditory brainstem responses (ABRs) at 2-31.5 kHz and by scanning electron microscopy. Perforation of the RWM alone resulted in immediate loss of ABR thresholds between 6 and 31.5 kHz in 2 of 6 animals. Similar results were obtained after application of HYA into the RW niche and subsequent RWM perforation. In both treatment groups the mean ABR thresholds and mean latencies for wave II at the ABR threshold returned to the pre-surgical (normal) range after 2 months. Also with respect to the cochlear morphology the results in both treatment groups were alike including minor structural changes in hair cell stereociliae but no loss of hair cells. It is concluded that HYA, when instilled into the middle ear with the inner ear opened, is free from cochlear ototoxic effects. Our present findings enhance the potential usefulness of HYA in otosurgery, even in cases when the inner ear has been opened and/or when one wishes to protect the inner ear.

Animals↗
PubMed1991

Laryngeal nerve paraganglia of the rat are morphologically and biochemically unchanged by long-term hypercapnia.

Exposure to hypercapnia (8.2 +/- 0.7% CO2) for 3 weeks failed to change the morphometric characteristics (mean cell area, nuclear, mitochondria and vesicle volume density) of the recurrent laryngeal nerve paraganglia of the rat. Moreover, this treatment had no effect on the dopamine and noradrenaline content of the superior and recurrent laryngeal nerves. The results are in contrast to what is found after exposure to hypoxia which increases the dopamine content and the cell area of the paraganglia and indicate that the mechanisms of the paraganglia in long-term hypoxia and hypercapnia differ.

Animals↗