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Biomedical subjects

I Florén

Publications and source records attributed to I Florén.

17 recordsLinked to original sources
PubMed1996

The results of penetrating keratoplasty for keratoconus.

At the Department of Ophthalmology, University Hospital in Lund, Sweden, keratoconus is the most common indication for penetrating keratoplasty. We studied 77 keratoplasties performed on keratoconic eyes between 1989-1991. Postoperative corrected visual acuity was better than or equal to 0.5 in 65 eyes (84.4%), and 30 eyes (39%) had visual acuity of 1.0. The mean postoperative astigmatism was 3.75 D with a range of 0-12.5 D. Eight patients underwent relaxing incision with satisfactory results in 6 patients. Graft rejection was observed in 6 eyes (7.8%). The most serious complication seen in our group of patients was a retrocorneal fibrous membrane that developed in one patient.

Adolescent↗
PubMed1996

Acanthamoeba keratitis in the south of Sweden.

Eight patients with Acanthamoeba keratitis were diagnosed and treated at our clinic between February 1991 and February 1993. Five of these were contact lens wearers, two had suffered recent corneal trauma and one had recently undergone penetrating keratoplasty. The diagnoses were based on both culture and histological examination of biopsy material in three cases, on culture alone in two cases and on histological examination alone in three cases. In all but one primary treatment was Propamidine isethionate and Neomycin/Polymyxin B topically and Ketoconazole orally. Because of poor healing three patients additionally received Paromomycin and Miconazole or Clotrimazol topically; two of these were further treated with Polyhexamethylene biguanide topically. The interval from initial symptoms to accurate diagnoses varied from one to eleven months. In one patient the eye could not be saved; in the remaining patients visual acuity after healing ranged from hand movements to 1.0.

Acanthamoeba↗
PubMed1991

Visual disturbances in man as a result of experimental and occupational exposure to dimethylethylamine.

Experimental exposure of four volunteers to 40-50 mg/m3 of dimethylethylamine (DMEA) for eight hours caused irritation of the mucous membrane of their eyes, subjective visual disturbances (haze), and slight oedema of the corneal epithelium. The thickness of the cornea showed a slight but consistent increase in all four subjects at these exposures and in two subjects exposed to 10 mg/m3. Concentrations of 80 and 160 mg/m3 for 15 minutes caused eye irritation but no visual disturbances or corneal oedema. Occupational exposure for eight hours to about 25 mg/m3 of DMEA (with peaks above 100 mg/m3) was also associated with eye irritation, haze, and corneal oedema. The divergence between our findings and other reports in which visual disturbances occurred at lower concentrations during occupational exposure may be due to peak concentrations.

Adult↗
PubMed1986

Visual disturbances after industrial triethylamine exposure.

Among 19 workers in a polyurethane foam production plant, visual disturbances ("foggy vision", "blue haze", and sometimes halo phenomena) were reported on a total of 47 occasions by five workers over 11 weeks. The symptoms were associated with triethylamine exposure. Time-weighted average levels of 12 to 13 mg/m3 were recorded at work operations associated with symptoms, and 4 to 5 mg/m3 at other tasks. Twice as high peak levels were recorded. A detailed medical examination of the five affected workers in a free interval did not reveal any signs of permanent eye disease.

Adult↗
PubMed1985

Visual disturbances after experimental human exposure to triethylamine.

Two volunteers were exposed to various airborne concentrations of triethylamine. Levels of 18 mg/m3 for eight hours caused subjective visual disturbances (haze and halos) and objective corneal oedema. The effects faded within hours after the end of exposure. The visual disturbances are unpleasant and may cause accidents at work and in traffic after the end of work.

Adult↗
PubMed1984

Indoleamine-accumulating horizontal cells in the squirrel monkey retina.

Horizontal cells capable of selectively accumulating indoleamines have been found in the retina of Saimiri sciureus, the New World squirrel monkey. The uptake of 3H-serotonin (5HT) in vivo and in vitro has been localized by light and electron microscopic (EM) autoradiography only to horizontal cells. In the central retina up to 50% and in the periphery 15-20% of the somas lying at the scleral border of the inner nuclear layer are labeled. In EM autoradiographs, labeled processes occur as lateral elements in both cone and rod synaptic invaginations, but grain counts show four times as many rods as cones are labeled. The light-dark adaptational state of the retina has no apparent effect on 3H-5HT uptake, but it is temperature dependent, and is saturable as indicated by its inhibition in the presence of an excess of nonradioactive 5HT. The indoleamine-accumulating capacity of this population of horizontal cells also was demonstrated by histofluorescence microscopy. A single row of fluorescent cells with a round soma was found lying at the outer edge of the inner nuclear layer. These cells send fluorescent processes only into the outer plexiform layer. The authors suggest that 5HT is not the native transmitter of these squirrel monkey horizontal cells because they lack intrinsic fluorescence and only could be visualized after uptake of extrinsically applied indoleamines. The true transmitter is likely to be a closely related but nonfluorescent indole.

Animals↗
PubMed1982

Localization of substance P-like immunoreactivity within the monkey retina.

Substance P (SP)--like immunoreactivity has been localized to distinct retinal cell populations in the primate Macaca nemestrina by means of immunohistochemical techniques with a well-characterized monoclonal antiserum directed to SP. The specificity of the immunoreactive staining was established by absorption of the antiserum with 10 micro M synthetic SP. Specific SP-like immunoreactivity was observed within varicose processes located in the outer plexiform layer, inner nuclear layer (INL), and in three bands within the inner plexiform layer (IPL). SP-immunoreactive somata were located in the proximal INL, IPL, and ganglion cell layer. These studies have thus identified SP-containing amacrine cells, interstitial amacrine cells, and displayed amacrine cells. In addition, these studies suggest the existence of SP-containing interplexiform cells and perhaps ganglion cells.

Animals↗
PubMed1980

Fluorescence and electron microscopical observations on the amine-accumulating neurons of the cebus monkey retina.

The organization of the Cebus monkey regina was analysed after the intraocular injection of 5,6-dihydroxytryptamine. This amine was taken up not only by the previously known dopaminergic neurons, but also by a set of indoleamine-accumulating neurons, whose processes are confined to the inner plexiform layer. The synaptic contacts of the dopaminergic neurons were analysed in the electron microscope after the processes of the indoleamine-accumulating neurons were destroyed by the intravitreal injection of the neurotoxic indoleamine, 5,7-dihydroxytryptamine. The subsequent injection of 5,6-dihydroxytryptamine induces certain changes in the dopaminergic neurons which accumulate the substance: electron-dense cores appear in the synaptic vesicles, and increased electron-density of mitochodrial and cellular membranes is often observed. The dopaminergic neurons were found to be presynaptic to amacrine cell perikarya and processes in the inner plexiform layer. In the outer plexiform layer they were presynaptic to both bipolar and horizontal cells, but they did not contact photoreceptors. The dopaminergic neurons received synapses only in the inner plexiform layer, from amacrine cell processes. It is inferred that in Cebus most dopaminergic neurons belong to a special class of retinal neuron, the interplexiform cells, which appear to transmit information centrifugally within the retina, from the inner to the outer plexiform layers. There are considerable similarities between the synaptology of the dopaminergic interplexiform neurons in the Cebus monkey and the goldfish retina, and the function of interplexiform neurons may therefore be similar in these two species.

5,6-Dihydroxytryptamine↗
PubMed1980

Investigations into whether 5-hydroxytryptamine is a neurotransmitter in the retina of rabbit and chicken.

A system of indoleamine-accumulating neurons exists in the retina of several species, but the exact transmitter of these neurons is not known. 5-Hydroxytryptamine (5-HT) is a likely candidate, but there are conflicting reports on its amount in the retina. We have determined the amounts of 5-HT with two sensitive, specific, and independent methods. Because the content was found to be lower than what was expected for a neurotransmitter, the rate-limiting enzyme in the 5-HT synthesis was also estimated, as was the effect of 5-HT on cyclic AMP content of the retina. In the rabbit the 5-HT content was found to be 25 to 35 ng/gm wet weight, with not difference between light- and dark-adapted animals. There was no detectable activity of the rate-limiting enzyme tryptophan hydroxylase. It was not possible to raise the 5-HT concentration by treating the rabbits with a monoamine oxidase inhibitor and L-tryptophan. 5-HT induced no change in the cyclic AMP content of the rabbit retina. In both newly hatched and older chicken retina, the 5-HT concentration was higher than in rabbit. The 5-HT concentrations in all retinas were lower than would be expected for a monoamine neurotransmitter, and these results argue against 5-HT being the neurotransmitter of the indoleamine-accumulating neurons.

Adenosine Monophosphate↗
PubMed1979

Absence of indoleamine-accumulating neurons in the retina of humans and cynomolgus monkeys.

Indoleamine-accumulating neurons have previously been detected in cats, rabbits, goldfish, chicken, pigeons, and Cebus monkeys, and were therefore also looked for in humans and in Old World monkey. Cynomolgus irus. The monkey eyes were injected intravitreally with 50 microgram 5,6-dihydroxytryptamine, 5 microgram alpha-methylnoradrenaline, or both drugs simultaneously. The human retinas were incubated in either drug. Previous observations on the distribution of dopaminergic neurons were confirmed in the two species, but no indoleamine-accumulating neurons were detected. The result emphasizes the similarity between human and Old World monkey retinas and contrasts them with the retina of the New World monkeys.

5,6-Dihydroxytryptamine↗
PubMed1979

Arguments against 5-hydroxytryptamine as neurotransmitter in the rabbit retina.

The indoleamine accumulating retinal neurons are visualized only by uptake of exogenously applied indoleamines but lack fluorescence in the normal retina. These neurons have now been studied in the rabbit after pretreatment with L-tryptophan and a monoamine oxidase inhibitor with an improved histofluorescence method based on perfusion with formaldehyde-glyoxylic acid pH 4.5 containing high amounts of magnesium. The method does not, however, reveal any indoleamine fluorescence in the retina. Also, p-chloroamphetamine has no toxic effect on the neurons. Selective inhibitors of the uptake of 5-hydroxytryptamine have a lower inhibitory effect in the retina than in the hypothalamus. A substance other than 5-hydroxytryptamine is therefore suggested to be the transmitter of the indoleamine accumulating neurons.

Animals↗
PubMed1979

Indoleamine accumulating neurons in the retina of chicken and pigeon. A comparison with the dopaminergic neurons.

Recently a special group of indoleamine accumulating neurons has been described in the retina of some mammals and goldfish. These neurons are characterized by their ability to accumulate indoleamines, whereby they become visible in the fluorescence microscope. They do not show any spontaneuos fluorescence. The indoleamine accumulating neurons are in this study shown to be present in the retina of chicken and pigeon. Their cell bodies differ from the earlier described cell bodies of the same type in other species in being larger and bottle shaped instead of round or oval, and in being situated further cutwards in the inner nuclear layer. Their terminals ramify in three sublayers in the inner plexiform layer. No indoleamine containing neurons could, however, be seen to fluoresce in normal retina of chick embryos, newborn chicken, older chicken or pigeons.

5,6-Dihydroxytryptamine↗
PubMed1976

Indoleamine-accumulating neurons in the retina of rabbit, cat and goldfish.

Special neurons accumulating indoleamines have been detected in the retina of rabbit, cat and goldfish. They have their perikarya in the innermost cell row of the inner nuclear layer, among the amacrine cells, and send their processes to various parts of the inner plexiform layer. The distribution of the processes is different in the different animals investigated. The neurons do not correspond to the previously known dopaminergic retinal neurons, which have a different distribution of their terminals and which can be demonstrated with a specially developed technique, simultaneously with the indoleamine-accumulating neurons.

Animals↗