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Biomedical subjects

A Midelfart

Publications and source records attributed to A Midelfart.

At least 19 recordsLinked to original sources
PubMed1998

Dexamethasone and dexamethasone phosphate detected by 1H and 19F NMR spectroscopy in the aqueous humour.

To apply nuclear magnetic resonance (NMR) spectroscopy to study the penetration of dexamethasone phosphate into the aqueous humour from rabbit following topical administration. After topical administration of 0.1%, 1.0% and 10% dexamethasone phosphate solutions, respectively, samples of aqueous humour were aspirated, freeze-dried, redissolved in deuterium oxide and analyzed by high resolution 1H and 19F NMR spectroscopy. In order to study the lipophilic and hydrophilic metabolites of the drug, samples obtained after application of 1% dexamethasone phosphate were extracted with methanol/chloroform, and then extracted with perchloric acid. In all samples obtained from eyes denuded of the corneal epithelium prior to administration of dexamethasone, signals corresponding to the chemical shifts of the drug were identified in 19F NMR spectra. In the experiments performed with 1% dexamethasone phosphate, both dexamethasone and dexamethasone phosphate were detected in the aqueous humour. Using 10% dexamethasone phosphate solutions, signals from the drug were detected in 1H NMR spectra simultaneously with signals from about twenty other substances present in the aqueous humour. NMR spectroscopy appears to be a valuable method for studying dexamethasone metabolism and penetration into ocular tissues. It provides simultaneous detection of both the drug metabolites and other substances in the sample and might offer a complementary approach to other analytical methods.

Administration, Topical↗
PubMed1998

Refractive errors among young adults and university students in Norway.

PURPOSE: This study was initiated to compare the refractive state in a population sample to that among university students in Norway and to that among the general population in other Nordic countries. METHODS: A population sample of 112 individuals and 224 engineering students were randomly selected and examined using automated and clinical refraction in cycloplegia. RESULTS: Statistically significant differences were found in prevalences of myopia (population sample: 33%, students: 47%, p: 0.016) and prevalences of hyperopia (population sample: 47%, students: 30%, p: 0.001) between the two groups. The mean refractive error among the population sample was -0.1+/-2.0 D compared to -0.6+/-2.2 D among the students (p=0.0013). CONCLUSIONS: The population sample had a significantly lower prevalence of myopia and a higher prevalence of hyperopia than the student population. The state of refraction in the population sample was found to be in agreement with results reported from other Nordic countries.

Adult↗
PubMed1996

Women and men--same eyes?

In ophthalmology, few studies have been designed to investigate possible differences between women and men in a consistent manner. Some evidence is, however, available showing significance male-female differences. The importance of gender in ophthalmological research is emphasized by focusing on some knowledge about sex differences in ocular components in relation to cataract surgery and on the influence of the female hormones on the cornea.

Cataract Extraction↗
PubMed1996

Clinical evaluation of the Allergan Humphrey 500 autorefractor and the Nidek AR-1000 autorefractor.

AIMS/BACKGROUND: The intentions of this study were to estimate agreement between two different autorefractors and standard subjective refraction techniques and to evaluate the clinical implications of relying on the autorefractor measurements. METHODS: Subjective refraction was carried out on 448 cycloplegic eyes and compared with cycloplegic readings with the Allergan Humphrey 500 autorefractor (448 eyes) and the Nidek AR-1000 autorefractor (160 eyes). Each refraction was followed by clinical visual acuity measurement. The study population comprised 224 healthy students, 107 men and 117 women, with a mean age of 20.6 (SD 1.1) years. RESULTS: Both the Nidek and Humphrey autorefractors measured more negative or less positive refractive values compared with subjective refraction and these biases were statistically significant (Humphrey right eye -0.23 D, p = 0.0001, left eye -0.20 D, p = 0.0001), (Nidek right eye -0.13 D, p = 0.0001, left eye -0.11 D, p = 0.0002). Comparing the results of autorefraction with subjective refraction, the Nidek was better than the Humphrey autorefractor in several ways: a smaller mean difference, better agreement between spherical equivalent values, narrower limits of agreements, and better visual acuity obtained with the autorefraction. On the other hand, the Humphrey autorefractor agreed better with subjective refraction concerning cylinder axis. CONCLUSION: The results show that both autorefractors represent a valuable complement to subjective refraction, but cannot be used as a replacement.

Adolescent↗
PubMed1996

Metabolic analysis of the rabbit cornea by proton nuclear magnetic resonance spectroscopy.

Perchloric acid extracts of the rabbit cornea were analyzed by high-resolution 1H NMR spectroscopy, including the two-dimensional shift-correlated (COSY) technique. Numerous metabolites including leucine/isoleucine, 3-hydroxybutyrate, valine, lactate, alanine, lysine, acetate, glutamate, creatine/phosphocreatine, taurine, glycine, inositol, glucose, tyrosine, phenylalanine, histidine, adenosine and formate have been simultaneously detected and identified in the NMR spectra. Concentrations of some of these were also determined. Of particular importance are the detection and identification of hypotaurine in the corneal tissue. Hypotaurine is a precursor of the synthesis of taurine and may act as an antioxidant. Moreover, the presence of choline, a precursor for acetylcholine, was established. This novel metabolite profile of the cornea obtained by high-resolution 1H NMR spectroscopy may be of value in the study of pathologic and toxic disorders.

Acetates↗
PubMed1996

Detection of different metabolites in the rabbit lens by high resolution 1H NMR spectroscopy.

PURPOSE: To investigate the metabolic profile of the rabbit lens using high resolution 1H NMR spectroscopy including two-dimensional shift correlated (COSY) technique. METHODS: Perchloric acid extracts of the rabbit lens were analysed with a Bruker AM-500 spectrometer and the metabolites were assigned in the spectra. Some of these were also quantified. RESULTS: More than 20 metabolites were detected in the perchloric acid extract of a single lens, including amino acids, nucleotides and other related compounds. Of particular importance is the ability to detect and identify glutathione, myoinositol, scyllo-inositol and taurine. CONCLUSIONS: The study demonstrated the potential of 1H NMR spectroscopy for monitoring the metabolic profile of the lens in normal and pathologic conditions.

Amino Acids↗
PubMed1996

Microbial contamination of contact lens cases among medical students.

PURPOSE: We performed a systematic examination of the rate and level of contamination of contact lens cases in a population of asymptomatic contact lens wearers using commercially prepared chemical disinfection solutions. METHODS: Solutions from the lens cases and from the conjunctiva of 21 asymptomatic contact lens wearers were examined. RESULTS: Contamination was found in five (24%) of the lens cases; four of the isolated microorganisms were recognized as potential ocular pathogens, namely Xanthomonas maltophilia, Pseudomonas cepacia, Serratia liquefaciens, and Serratia plymuthica. Serratia organisms have not been previously isolated from lens care solutions preserved with guanide, and, in addition, this was the first time that Serratia plymuthica has been isolated from a lens care system. Acanthamoeba was not detected in any of the examined samples, and no potential pathogens were isolated from the conjunctiva. Among students having contaminated lens cases, all reported problems such as itching, redness, dryness, and coating of the lens. CONCLUSIONS: The percentage of contaminated lens cases in this study was lower than in other studies. However, since the microorganisms identified in 80% of the contaminated lens cases were considered potential ocular pathogens, we feel contact lens wearers should be encouraged to frequently replace their lens cases.

Adult↗
PubMed1995

Clinical usefulness of biopsy in giant cell arteritis.

To evaluate the diagnostic usefulness of temporal artery biopsy in the diagnosis of giant cell arteritis, the clinical records of 98 patients who underwent this procedure between 1984 and 1992 were reviewed. The biopsies were positive for giant cell arteritis in 13 (13%) cases. In addition, 9 patients with negative biopsy were considered to have giant cell arteritis based on clinical examination, while 76 patients had other diagnoses. About 90% of the patients with giant cell arteritis were women. Evaluating the clinical features and laboratory findings, a history of headache, a combination of headache and the erythrocyte sedimentation rate > 40 mm/h and a combination of headache and temporal tenderness were significantly more common among patients with positive diagnosis than among the other patients.

Aged↗
PubMed1995

Low-conductance anion channel activated by cAMP in teleost Cl- -secreting cells.

We studied characteristics and modulation of ion channels in primary cultures of opercular epithelium from the euryhaline marine killifish Fundulus heteroclitus. Primary cultures, 17-28 h old, retain mitochondria-rich Cl- cells identifiable by fluorescence microscopy. Cell-attached patches revealed frequent low-conductance 8.1 +/- 0.35 pS channels that usually became inactive on excision; high-conductance anion channels were not apparent. Ion substitution experiments demonstrated selectivity for Cl- over gluconate of 1:0.07. With addition of 1-isobutyl-3-methylxanthine (0.1 mM) and dibutyryladenosine 3',5'-cyclic monophosphate (1.0 mM) to the bath, incidence of the channel increased from 35.3 to 61.9% of total patches (n = 156 and 21, respectively), and incidence of patches with multiple copies of the channel increased markedly from 2.2 to 38.5%. Epithelial Cl- transport was inhibited by mucosally added diphenylamine-2-carboxylic acid (1.0 mM) but not by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (0.1-1.0 mM). The anion channel was absent from cultured killifish corneal epithelium, a tissue that lacks Cl- cells. We conclude that a low-conductance anion channel of Cl- cells, likely in the apical membrane, may account for adenosine 3',5'-cyclic monophosphate-activated Cl- secretion by marine fish.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

High-resolution 1H NMR spectroscopy of aqueous humour from rabbits.

BACKGROUND: Detection of different substances in aqueous humour is important for evaluation of the disorders affecting the eye. The purpose of the present study was to apply high-resolution proton (1H) nuclear magnetic resonance (NMR) spectroscopy for extensive characterisation of the metabolites in the aqueous humour from rabbits. METHODS: High-resolution 1H NMR spectroscopy, including two-dimensional shift correlated (COSY) technique, was performed on aqueous humour from rabbits. RESULTS: More than 20 metabolites were simultaneously detected and identified in high-resolution 1H NMR spectra of aqueous humour from rabbits. Some of these were also quantified. CONCLUSION: High-resolution 1H NMR spectroscopy is a valuable method for simultaneous detection of many different metabolites in aqueous humour.

Animals↗
PubMed1994

Ocular parameters in elderly in Norway.

A retrospective review of medical records of 434 patients (mean age 76.2 +/- 10.1 years) undergoing cataract surgery was performed to detect possible sex differences for several ocular parameters and their change with age. More women were operated for cataract than men by a 2:1 ratio. Their age was not significantly different. Women had higher intraocular pressure (15.4 +/- 3.5 mmHg), shorter axial length (22.98 +/- 1.31 mm) and steeper cornea (43.64 +/- 1.61D) than men (14.7 +/- 3.6 mmHg, 23.33 +/- 0.97 mm and 42.88 +/- 1.52D, respectively). For both sexes, a negative correlation between the corneal refraction and axial length was revealed. For women, a trend towards shorter eyes in the higher age groups was found. Among those older than 80 years, stronger intraocular lenses were implanted in women than in men. Based on these results, more attention should be paid to the differences between women and men regarding ocular parameters in the elderly.

Adult↗
PubMed1994

Clinical comparison of the ProTon and Tono-Pen tonometers with the Goldmann applanation tonometer.

A clinical evaluation of a new electron ProTon tonometer was performed comparing the values of intraocular pressure (IOP) measured using this instrument with those determined by a similar instrument, Tono-Pen XL, and by Goldmann applanation tonometry. The mean IOP measured in 106 eyes with the ProTon tonometer was not significantly different from that determined with Goldmann applanation, while the IOP values measured with Tono-Pen XL were significantly lower. The 95% limits of agreement between applanation tonometry and ProTon tonometry were between -4 mm Hg and 5 mm Hg and between applanation tonometry and Tono-Pen XL tonometry between -3 mm Hg and 8 mm Hg. The ProTon tonometer appears to have a higher level of accuracy than the Tono-Pen XL tonometer in clinical practice.

Equipment Design↗
PubMed1994

Refractive errors among engineering students in Norway.

This study reveals the prevalence of refractive errors in a group of young adults (mean age 20.6 years) exposed to high educational demands, including much reading. In all, 224 (117 females, 107 males) first-year engineering students were subjectively refracted. A prevalence of myopia of 46.9% (right eye), 49.1% (left eye) and 42.9% (both eyes), and a prevalence of hyperopia of 29.5% (right eye), 28.1% (left eye) and 23.2% (both eyes) was detected. The mean refractive error in the whole group was -0.6 +/- 2.2 D (right eye), -0.7 +/- 2.4 D (left eye) and -0.7 +/- 2.3 D (both eyes). As many as 56.4% (n = 57) of the myopic students had either no corrective lenses (11.9%, n = 12) or had their first corrective lenses prescribed at the age of 16 years or later (44.6%, n = 45). There was no significant difference in the prevalence of myopia between female and male students. No significant difference regarding body height was found among men in the different groups of refractive errors, but a significant difference was detected among women. We found no statistically significant relationship between intraocular pressure and any refractive error among men or women.

Adult↗
PubMed1993

Survey of eye injuries in Norwegian children.

A review of the medical records of 238 children younger than 16 years admitted with ocular injury to the University Hospital in Trondheim during a 10-years period was undertaken to provide information about the causes, circumstances and visual outcome of ocular trauma in young patients. Children with ocular injury represented 14% of all paediatric eye admissions. The majority were boys (77%). The frequency of injuries among boys increased markedly from the age of 8 years, while the frequency was almost the same among girls in all age groups. The most common cause of injury was projectiles (21.5%) followed by sticks, twigs and pencils (10.1%), falls (10.1%), bow and arrows and catapults (9.7%) and balls (8.8%). The most frequent diagnosis was contusion (43%). Perforating eye injuries amounted to 19%. Follow-up examination showed that 49% of children with eye injuries had some visual deficit, including eighteen children (8%) with visual acuity worse than 0.1. Because most of the eye injuries among children are preventable, more appropriate strategies for the prevention of these should be implemented.

Adolescent↗
PubMed1992

Myopia among medical students in Norway.

In this study the prevalence of myopia and age at onset among medical students were determined. Of the 140 senior medical students at The Faculty of Medicine, University of Trondheim, Norway, 133 (75 females, 58 males) were examined. Visual acuity was tested and the refractive error was measured using automated refraction and clinical refractive technique. The prevalence of myopia was found to be 50.3% in the right eye (n = 67) without significant difference between female and male students. The refractive state was unrelated to body height. Among the myopic students, the mean equivalent sphere was -2.34 +/- 2.01 D in the right eye (range -9.25 D to -0.25 D). A clear relationship was detected between the current amount of myopia and the age at which corrective lenses were first prescribed. However, as much as 43.3% of the myopic students wearing corrective lenses first received these at the age of about 20 years, indicating a relatively high prevalence rate of adult-onset myopia.

Adult↗
PubMed1991

[Myopia--a disease or a physiological defect?].

Many investigations have been carried out during the last 150 years to detect factors which cause nearsightedness (myopia). A factor that has been awarded particular attention in addition to hereditary factors is the influence of the environment, especially the amount of close work on the refractive state of the eye. The increasing prevalence of myopia among children and young people revealed in some populations has been related to stressing educational systems, which are suspected of enhancing the changes in the growth of the eye leading to myopia. However, the direct etiological relationship between the myopia and prolonged accommodation during the close work has still to be established. The prevalence of myopia in Norway is not known, but relatively high prevalence was found in a recent study among medical students and physicians. At the present time, increasing interest is being shown for keratorefractive surgery to correct myopia. Both radial keratotomy and excimer laser photorefractive keratomileusis have become available in Norway, and a few hundred patients have been operated. The purpose of this article is to elucidate some important aspects in understanding the etiology, development and correction of myopia.

Eye↗
PubMed1991

Chloride concentrations in the corneal epithelium and stroma from different species.

Using ion chromatography, the concentration of chloride in the corneal stroma and epithelium of ox, pig and rabbit was measured to detect possible species differences. In all three species, the chloride concentration in the stroma was found to be very similar, i.e. 363 +/- 14 mmol kg-1 dry wt in ox, 364 +/- 18 mmol kg-1 dry wt in pig and 358 +/- 24 mmol kg-1 dry wt in rabbit. In contrast, a substantially higher concentration of 232 +/- 33 mmol kg-1 dry wt was found in the corneal epithelium of rabbit in comparison to the values determined in the same tissue of ox, i.e. 137 +/- 4 mmol kg-1 dry wt and of pig, i.e. 128 +/- 24 mmol kg-1 dry wt. Using the results obtained previously for the extracellular volume (Midelfart 1988), an intracellular chloride concentration of 25 +/- 2 mmol kg-1 H2O was calculated in the bovine corneal epithelium. The results obtained in this study indicate that species differences are considered as important in studies of ion transport mechanisms in the cornea.

Animals↗