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Biomedical subjects

B Lindström

Publications and source records attributed to B Lindström.

At least 55 records · Page 3Linked to original sources
PubMed1991

Measurement of human cochlear blood flow.

Cochlear blood flow (CBF) was measured with a laser-Doppler (L-D) flowmeter (Periflux PR2-B) in four unanesthetized human subjects with chronic tympanic membrane perforations and nine anesthetized human subjects undergoing middle ear operations. The L-D recordings were made over the promontory and/or the round window membrane during carbogen breathing and direct electrical stimulation of the cochlea in both groups and with warm water irrigation of the external ear canal in the anesthetized subjects. Carbogen led to little or no change in CBF as monitored with either measurement approach in either subject group. Electrical stimulation yielded an increase (15% to 25%) in CBF as recorded from the promontory in seven of the nine subjects tested. Warm (44 degrees C to 49 degrees C) water irrigation produced changes of 20% to 60% in CBF that were partially recoverable in the 10 minutes available for study. This study demonstrated the feasibility of direct CBF measurement in humans with the L-D method. Moreover, the data indicate that carbogen has little influence on CBF and that electrical stimulation at relatively safe levels and warm water irrigation of the ear canal produce increases in human CBF.

Aged↗
PubMed1991

Youth, disability and quality of life.

When broader aspects of health are considered especially when assessing the life of the disabled it becomes necessary to reach beyond physical measurements to more dynamic aspects including the individual's other resources and demands. In such a context issues of quality of life are important. Quality of life is here defined as a term describing the total existence of an individual or a group and is operationalized in three life spheres: external conditions, interpersonal conditions and personal psychological conditions. National samples of youths aged 12-18 years with cystic fibrosis and myelomeningocele are compared to a reference group of normal youths in the five Nordic countries. The study was based on a mailed questionnaire. The results show that the disabled groups had equal external conditions as their peers while they rated lower on the interpersonal and personal levels. This indicates that the Nordic countries have succeeded in providing a good material support for families with handicapped youths. The fact that these families are also more satisfied with the different life spheres means that both objective and subjective needs are met. The social networks and personal psychological conditions, though, proved to be less sufficient and there is still a lot to be done to give handicapped youngsters a full life.

Adolescent↗
PubMed1990

Clinical pharmacokinetics of intravenous and oral 9-amino-1,2,3,4-tetrahydroacridine, tacrine.

The pharmacokinetics of 9-amino-1,2,3,4-tetrahydroacridine; tacrine, THA, was studied after intravenous administration and following the first and last oral doses of a seven week clinical trial involving 8 patients with amyotrophic lateral sclerosis, ALS. Two surgical patients given intravenous THA for reversal of postoperative sedation were also included. Plasma concentration of THA and in some cases the metabolite, 1-hydroxy-THA, were assayed using a selective and sensitive method with high performance liquid chromatography. After an intravenous dose of 30 mg THA, the plasma concentrations were fitted to a two-compartment model. Plasma clearance showed a threefold interindividual variation with a mean of 2.42 l.h-1. Volume of distribution, V alpha varied 100-680 l with a mean of 349 l. The plasma half-lives of distribution and elimination were 1.8 and 98.2 min, respectively. Oral bioavailability showed large interindividual differences and ranged 6-36% in the four subjects studied. After seven weeks treatment with oral THA, plasma concentrations immediately prior to medication were below 10 ng/ml in three patients and above 100 ng/ml in two patients. At the same occasion the plasma metabolite concentrations considerably exceeded those of THA. THA medication was associated with side effects in the majority of the patients.

Administration, Oral↗
PubMed1990

Liquid scintillation counting of 3H-thymidine incorporated into rat lens DNA.

DNA synthesis in the lens has previously been localized by autoradiography following incorporation of 3H-thymidine. For the quantification of DNA synthesis in the lens, pooling of lenses and extraction of the DNA for liquid scintillation counting, has formerly been adapted. In the present investigation a method has been developed for the extraction of the unincorporated tracer from whole lenses after short time incubation in a medium containing 3H-thymidine. The 3H-thymidine incorporated into individual lenses was then detected by liquid scintillation counting after dissolution of the lenses. The sources of the variation in the method are evaluated.

Animals↗
PubMed1990

Morphine sulphation in children.

The metabolism of morphine was studied in nine children and seven preterm neonates receiving a continuous infusion of morphine. All the neonates and three children had detectable concentrations of morphine-3-sulphate (M3S) in urine. None of the neonates or the children had detectable concentrations of morphine-6-sulphate (M6S) in urine. None of the children had detectable concentrations of M3S in plasma. The M3S/morphine ratios were significantly higher in neonates than children (P less than 0.01), suggesting that morphine sulphation decreases after the neonatal period. The amount of M3S formed, even in neonates, is low suggesting that this is a minor metabolic pathway.

Humans↗
PubMed1990

Functional and pharmacokinetic studies of tetrahydroaminoacridine in patients with amyotrophic lateral sclerosis.

Assuming the presence of clinically significant cholinergic hypofunction in amyotrophic lateral scleroses (ALS), seven patients with ALS were treated with 100-200 mg tetrahydroaminoacridine (THA) together with 11 g lecithin daily for up to 7 weeks. In a separate experiment pharmacokinetics and effects on muscle strength and neurophysiological parameters were studied following the injection of 30 mg THA intravenously. Following the injection of THA an increase in muscle strength was observed in two patients. There were no consistent pharmacokinetic differences that could explain the effect on intravenous THA on muscle strength in these two patients. The plasma clearance of THA was high and the oral bioavailability low with large interindividual differences (6-36%). No beneficial effect was seen during oral medication and side-effects were common. There were no conclusive changes observed regarding neurophysiological parameters after drug administration. THA has probably no place in the treatment of ALS.

Administration, Oral↗
PubMed1990

An objective and rapid method for the determination of light dissemination in the lens.

A method for the objective measurement of light dissemination in the lens was developed. There is an exponential relationship between the concentration of standard solutions and the intensity of light disseminated forwards. The light disseminated in non-pathological lenses from Sprague Dawley rats was registered as the equivalent standard concentration, C, and then transformed to log10 (C + 1) and was found not to deviate from the normal distribution. The tolerance limit for light dissemination was derived by setting the probability to classify a non-pathological lens as pathological. An analysis of variance demonstrated that the inter-animal variation was the dominating source of imprecision. It is anticipated that the developed system will be useful in experimental toxicological risk assessment.

Analysis of Variance↗
PubMed1990

Electrophonic hearing and cochlear implants.

It has been difficult to explain the good speech understanding obtained by some cochlear implant patients fitted with a single-channel electrode and analog transmissions of the speech signal (Vienna/3M implant). It has also been difficult to explain the variation in results reported by different groups using the same implant. One hypothesis asserts that the above differences can be explained by the observation that electric stimulation with an implanted electrode might result in two different auditory sensations, the first resulting from the stimulation of the remaining hair cells (electrophonic component) and the second from the electric stimulation of the auditory nerve (electro-neural component). The two sensations are very different. As a result of different definitions of total deafness (functional or threshold definition), patients with remaining hair cells are operated on by some groups, but not by other groups. Some published results from different studies are discussed with reference to the above hypothesis and the possible consequences for the selection of the patients, the use of extra- or intracochlear electrodes, and the selection of the speech coding strategy are discussed.

Audiometry, Pure-Tone↗
PubMed1989

Inactivation of lactate dehydrogenase by UV radiation in the 300 nm wavelength region.

The effect of UV radiation on lactate dehydrogenase (LDH) was investigated. LDH from bovine heart was exposed to 3.6-18 kJ/m2 of ultraviolet (UV) radiation in the 300 nm wavelength region. The activity of LDH was observed to decrease as a function of the dosage of UV radiation. The inactivation of LDH was independent of exposure rate at constant dosage of UV radiation. The decrease of LDH activity caused by UV 300 nm radiation was coupled to a decrease of the maximal velocity (Vmax) while the Michaelis constant (Km) remained unchanged. The absorption spectrum of the LDH changed during exposure to UV radiation suggesting an alteration of tryptophan in the LDH molecule.

Kinetics↗
PubMed1989

Hyaluronate in healing of corneal alkali wound in the rabbit.

The effect of topically applied 1% and 2% sodium hyaluronate was studied on the healing of a standardized rabbit corneal alkali wound. The healing of the epithelium, the stroma, and the endothelium was evaluated separately by applying quantitative methods. The healing was followed for 8 weeks. Both 1% and 2% sodium hyaluronate have a statistically significant positive influence on the epithelial re-surfacing, especially during the late healing phase. Furthermore, sodium hyaluronate has a positive healing influence on the stromal healing at a certain time interval during the observation period. This was reflected as a better maintained stromal dry mass level compared to control. The stromal healing was parallel to a faster re-surfacing of the endothelium.

Administration, Topical↗
PubMed1989

Dextromethorphan: polymorphic serum pattern of the O-demethylated and didemethylated metabolites in man.

1. The interindividual differences in serum concentrations of dextromethorphan (DM) and its metabolites were studied in 29 healthy subjects given 120 mg orally. They were also phenotyped according to the urinary ratio of debrisoquine and 4-hydroxy-debrisoquine. 2. Four (14%) subjects were found to be poor metabolizers (PM) with a dextromethorphan/dextrorphan metabolite ratio in plasma of 3.6 or more compared with extensive metabolizers (EM) with a ratio of 0.11 or less. Significant levels of 3-hydroxymorphinan were measurable in all individuals except two, both of whom were PMs. This subdivision corresponded to the phenotype determined by the metabolic ratio of debrisoquine (r = 0.92). 3. Twelve of the 29 subjects reported adverse drug reactions after dextromethorphan administration compared with none after placebo.

Adult↗
PubMed1989

Reversal of postoperative somnolence using a two-rate infusion of physostigmine.

In order to antagonize immediate postoperative somnolence, 24 surgical patients were given a two-rate infusion of physostigmine, aiming at a constant plasma concentration in the range of 1 to 10 ng/ml. Plasma concentrations of physostigmine were determined during infusion and after infusion and the effects of physostigmine on analgesia and postoperative sedation, and its side effects were monitored throughout. On the 1st postoperative day some of the patients (n = 8) were given 5 mg physostigmine orally, after which plasma concentrations as well as effects were measured. Steady-state concentrations were generally lower than predicted. Clearance varied between 10 and 85 ml/min x kg with a mean of 40.8 +/- 21.0 ml/min x kg. Oral bioavailability was 25.3 +/- 11.1%. Physostigmine administered as an intravenous infusion antagonized immediate postoperative somnolence in 21 out of 24 patients. Effects were poorly correlated with the established steady-state concentration of physostigmine. The patients' experience of postoperative pain relief was mostly satisfactory and the side effects of physostigmine infusion were generally limited. The effects of physostigmine in the immediate postoperative period seemed dependent on the dose as well as on the time which had elapsed since administration of anticholinergic drugs. After oral physostigmine administration the following morning, the majority of patients experienced side effects such as nausea and abdominal pain. In conclusion, physostigmine given as infusion antagonizes postoperative somnolence. However, the arousal effect was considered not better than that resulting from a bolus dose of the drug, although the infusion regimen allowed a prolonged clinical effect duration.

Administration, Oral↗
PubMed1989

Determination of Na and K in the rat lens by atomic absorption spectrophotometry.

A new procedure is described for determination of sodium and potassium in rat lenses with atomic absorption spectrophotometry. Samples were prepared by soaking of the ground or the intact lens in deionized water. For potassium determinations HNO3 dissolution was also tried. Deionized water or CsCl aqueous solution was adopted for dilution for measurement. At absorbances up to 1.0 absorbance unit only measurements on HNO3 dissolved lenses diluted in deionized water were compatible with a linear absorbance function. At absorbances below 0.2-0.3 absorbance units all combinations were in agreement with a linear absorbance function. Grinding of the lens was found to increase the variability but did not change the level. HNO3 dissolution did not increase the level. Dilution with CsCl increased the sensitivity and decreased the variability. A schedule is proposed for determination of sodium and potassium in which lens samples are obtained by soaking in deionized water. Aqueous solution of CsCl is suggested for dilution.

Animals↗
PubMed1989

Activity distribution of cytochrome oxidase in the rat retina. A quantitative histochemical study.

Cytochrome oxidase (CYO) is a key enzyme in the respiratory chain. Therefore, CYO has an important role in the cell metabolism. In the present study CYO activity in the rat retina was identified by histochemical staining. The density of the staining, corresponding to the activity of the CYO, was evaluated quantitatively by densitometry. A high CYO activity was found in the retinal pigment epithelium, in the inner segment of the photoreceptors, in the outer plexiform layer and in the inner plexiform layer. In the outer segment of the photoreceptors, in the outer nuclear layer, and in the inner nuclear layer the CYO activity was relatively low. An analysis of variance demonstrated that the precision in an estimation of a mean depends on the number of animals and the number of retinal sections per animal.

Animals↗
PubMed1989

Oral mercaptopurine in childhood leukemia: influence of food intake on bioavailability.

Plasma concentrations of 6-mercaptopurine (6-MP) were determined by gas chromatography-mass spectrometry. Ten children (nine with acute lymphatic leukemia) were studied on 2 consecutive days after oral intake of 6-MP. On one day the drug was administered in the fasting state and on the other (in random order) together with breakfast. The peak plasma concentrations of 6-MP after the dose intake with breakfast in percent of that in the fasting state (meal in % of fasting for each individual) varied between 33 and 181% (mean 111), and the area under the plasma concentration-time curve varied between 47 and 186% (mean 103). Thus, there were considerable variations among patients, but, for the group as a whole, there were no statistically significant differences between the two experimental conditions. This study cannot therefore form the basis for a recommendation as to whether 6-MP should be administered on an empty stomach or together with food.

Administration, Oral↗