Search PubMed⌕ Search

Biomedical subjects

T Eriksson

Publications and source records attributed to T Eriksson.

At least 19 recordsLinked to original sources
PubMed1992

Determination of thalidomide in plasma and blood by high-performance liquid chromatography: avoiding hydrolytic degradation.

Thalidomide was determined in plasma and blood by reversed-phase high-performance liquid chromatography with ultraviolet detection. The coefficient of variation of the assay was 1-2% over the 0.25-4.0 micrograms/ml concentration range. Hydrolysis of thalidomide during storage and work-up of the samples was avoided by the addition of an equal volume of citrate buffer, pH 1.5. The assay could be applied to the determination of blood concentrations of thalidomide in rats for at least 28 h after a single oral dose, with multiple blood sampling from the same animal.

Animals↗
PubMed1992

Chronopharmacology of isoprenaline: the effects on rat plasma concentrations of large neutral amino acids depend on time of day for administration.

This investigation was undertaken in order to test our hypothesis, that the endogenous circadian rhythms in large neutral amino acids (LNAAs) in plasma are partly regulated by beta-adrenergic mechanisms. The beta-adrenoceptor agonist isoprenaline, which is known to decrease the concentrations of rat plasma LNAAs, was given at several time-points over a full 24-h period intraperitoneally to rats, which were killed 1 h later. Isoprenaline, administered in the evening, decreased the plasma amino acid concentrations more than it did in the same doses given in the morning. Also the potency of isoprenaline was in this respect higher in the evening than in the morning. This finding, of a time-of-day dependent relationship between the effects of a beta-adrenoceptor agonist and plasma LNAA concentrations, supports our hypothesis, that beta-adrenergic mechanisms are involved in the endogenous regulation of the plasma LNAA rhythms. We suggest that the known endogenous circadian variation in sympathetic activity, which gives rise to a reciprocal rhythm in beta-adrenoceptor responsiveness, could be one factor explaining that part of the circadian rhythm in plasma LNAA concentrations, which is not due to variations in food intake.

Amino Acids↗
PubMed1992

Is rat brain content of large neutral amino acids (LNAAs) a reflection of plasma LNAA concentrations?

Competition between the large neutral amino acids (LNAAs), including the monoamine precursors tyrosine and tryptophan, for the carrier-mediated transport from plasma into the brain is considered the major regulator of brain LNAA content. The plasma ratio of each LNAA to the sum of all LNAAs, previously, in standardized experiments, has proved an excellent predictor of brain LNAA content. To investigate how diurnal variations in plasma LNAAs are reflected in the brain, we have killed rats, in groups of six, every 1 h throughout one 24 h period. The concentration of each LNAA in both plasma and brain varied with time-of-day. Also the total concentration of LNAAs in brain was shown to vary diurnally. Obviously, variations in total brain LNAA concentration cannot be explained by changes in plasma LNAA ratios. Consequently, other factors, contributing to the regulation of the diurnal rhythm in brain LNAA content, must be considered.

Amino Acids↗
PubMed1992

Diurnal rhythms in rat brain large neutral amino acids (LNAAs), monoamines and monoamine metabolites.

To obtain reliable information on the diurnal rhythms in rat brain large neutral amino acid (LNAA) concentrations, animals were killed, in groups of six, every one h throughout one 24 h period. By using such short sampling intervals, it was possible to detect a statistically significant diurnal variation in the whole brain concentration of each LNAA and to give a more detailed description of these diurnal variations than previously presented. Furthermore, the diurnal variations in whole brain concentrations of the precursor amino acids, tyrosine and tryptophan, were compared with corresponding variations in the respective monoamines and their main metabolites. Similar diurnal patterns were demonstrated for tryptophan, serotonin and 5-hydroxyindoleacetic acid. No such correspondence was detected for tyrosine, dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid.

Amino Acids↗
PubMed1992

Relationship between plasma and brain large neutral amino acids in rats fed diets with different compositions at different times of the day.

Large neutral amino acids (LNAAs) compete with each other for carrier-mediated transport through the blood-brain barrier into the brain. The relative plasma concentration, expressed as the ratio of each LNAA to the sum of LNAAs, is considered the main regulator of brain LNAA concentrations. In order to investigate the consistency of this assumption throughout a 24-h period, we have compared the relationship of plasma LNAAs to brain LNAAs among groups of rats fed diets containing various amounts of protein (in order to obtain a wide range of plasma LNAA levels) at two different phases of the light/dark cycle (0900 and 2100 hours). The relationship between plasma and brain LNAAs was found to be dependent on both diet and the time of day. Similar plasma amino acid concentrations in the morning and in the evening contrasted with different brain concentrations. Furthermore, previous findings that brain LNAA concentrations are influenced by plasma amino acid concentrations were confirmed.

Administration, Oral↗
PubMed1992

Modulation of neutrophil superoxide generation by inhibitors of protein kinase C, calmodulin, diacylglycerol and myosin light chain kinases, and peptidyl prolyl cis-trans isomerase.

To assess the role of protein kinase C (PKC) in the respiratory burst of adherent human polymorphonuclear leukocytes (PMNL), reduction of ferricytochrome C by cells triggered with a phorbol ester (PMA), ionophore A23187, serum-treated zymosan (STZ) or three lipid derivatives, 3-decanoyl-sn-glycerol (G-3-OCOC9), (R,R)-1,4-diethyl-2-O-decyl-L-tartrate (Tt-2-OC10) and 3-decyloxy-5-hydroxymethylphenol (DHP) was examined in a microtiter plate procedure in the presence of inhibitors of PKC and, for comparison, inhibitors of calmodulin, diacylglycerol and myosin light chain kinases and the peptidyl-prolyl cis-trans isomerase activity of fujiphilin. 1) Of the protein kinase inhibitors examined, Ro 31-7549 and staurosporine reduced responses to all stimuli except possibly STZ; in contrast, K252a and the myosin light chain kinase inhibitors ML-7 and ML-9 blocked responses to A23187 and STZ better than those triggered by PMA. H-7 reduced responses to A23187, DHP and G-3-OCOC9, and calphostin, palmitoyl carnitine, sphingosine and the multifunctional drugs TMB-8 and W-7 reduced A23187; they also, when examined, reduced decane derivative-induced O2- production more effectively than PMA- and STZ-triggered responses. Polymyxin B, 4 alpha-PMA and retinal displayed no inhibitory capacity. 2) Of the selective calmodulin antagonists, CGS 9343B, Ro 22-4839 and calmidazolium did not inhibit the oxidative response irrespective of the stimulus used, whereas metofenazate reduced those evoked by A23187, DHP, G-3-OCOC9 and STZ.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Isomerases↗
PubMed1992

Some factors influencing the quantity of prosthodontic treatment performed by general practitioners in public dental service.

For general dentists in public dental service, Orebro county, the numbers of artificial crowns, pontics, RPD:s and CRD:s produced in 1989 were studied in relation to some background factors. The dentist-related factors were: gender, time in profession, working time per week, and place of graduation. Factors related to dental clinics were: location of the clinic, general prosthodontic activity at the clinic. Multiple regression analyses were used. Two different patterns were found; one for fixed prosthodontics, another for removable prosthodontics. Prosthodontic activity at the clinic, the male sex, and (inversely) time in profession were significantly associated with high production of artificial crowns and pontics. The regression models for removable prosthodontics showed no significance.

Crowns↗
PubMed1991

Effects of withdrawal of antiparkinson medication on gait and clinical score in the Parkinson patient.

Objective testing of medication is needed in Parkinson's disease. Gait analysis and clinical evaluation were done before and after a 24-h withdrawal of Parkinson medication. Twelve patients with stable, mild to moderate idiopathic parkinsonism (Hoehn and Yahr 1-3; seven men and five women mean age 59.9 years, mean duration of disease 6 years) were tested with gait analysis walking in five different paces. Velocity of gait, stride length and stride frequency, as well as stride length at constant velocity were calculated. Regression coefficients for the relation between stride length and stride frequency were also calculated. Clinical scoring according to the Webster rating scale and Hoehn and Yahr were performed for each test. Clinical functional assessment with a specially designed rise and gait test, an arm cycle test and the wooden rods test were done. Evaluated clinical score increased significantly (p less than 0.05) using both clinical tests. Maximum gait velocity (p less than 0.01), stride length at max. velocity (p less than 0.01), and stride length at constant velocity (p less than 0.03) were significantly decreased without medication. Stride frequency did not change. In the functional assessment tests only performance on the arm cycle test (p less than 0.03) was less well performed without medication. There was correlation between clinical score, gait and clinical functional assessment. The methods used detected significant changes in variables of gait as well as clinical scoring and some of the clinical functional assessments when medication was withdrawn for a 24-h period. The methods were useful in evaluation of pharmacological treatment.

Aged↗
PubMed1991

Development of tolerance to the plasma amino acid-decreasing effect of ethanol in the rat.

Male Sprague-Dawley rats were treated for one month with daily intraperitoneal injections of ethanol (2 g kg-1), or saline. After this pretreatment, animals from each group were given acute doses of ethanol (2 g kg-1) or saline. Plasma amino acid concentrations and brain tyrosine, tryptophan, dopamine, 5-HT and 5-HIAA concentrations were measured in samples collected 1 h after the injections. Acute administration of ethanol induced a dramatic fall in the concentrations of 18 out of 20 plasma amino acids in animals pretreated with saline. In animals chronically pretreated with ethanol this decrease was much smaller. Furthermore, the decrease was significantly lower for 6 of the measured amino acids in the chronic ethanol group compared with the saline-treated control group. Tolerance to the plasma amino acid decreasing effect of ethanol had thus developed. This acquired tolerance might be explained by both pharmacokinetic and pharmacodynamic mechanisms. Chronic administration of ethanol induced increased concentrations of tyrosine and dopamine in the brain, probably due to increased transport of tyrosine into the brain caused by an increase in the ratio of tyrosine to large neutral amino acids in plasma.

Amino Acids↗
PubMed1990

Structure of a RecA-DNA complex from linear dichroism and small-angle neutron-scattering in flow-oriented solution.

Small-angle neutron-scattering (SANS) and ultraviolet linear dichroism (l.d.) were measured on identical samples of a RecA-double-stranded (ds) DNA complex, including cofactor adenosine 5'-O-thiotriphosphate, which were aligned by flow in two equivalent Couette devices made of niobium and silica, transparent to neutrons and to ultraviolet light, respectively. The SANS anisotropy indicates a modest orientation of the RecA-dsDNA fiber with the helix axis parallel to the flow field. By correlation with the corresponding l.d. of the DNA at the same orientation conditions, it is inferred that the DNA bases have a local orientation that is approximately perpendicular to the helix axis. By comparison with the worse orientation in single-stranded DNA-RecA, this conclusion suggests that the dsDNA in its complex with RecA is not strand separated, and may be accommodated as an essentially unperturbed, straight double helix running along the RecA polymer fiber. The SANS anisotropy is also found to support the assignment of a subsidiary intensity maximum as originating from the pitch of a helical fiber.

Animals↗
PubMed1990

[AIDS and dementia].

Two case histories are presented of patients with AIDS. In both cases, the initial symptom, apart from the generalized symptoms, was rapidly progressive dementia. The most important neurological symptoms in the AIDS dementia complex are reviewed and the CNS complications of AIDS are mentioned. In patients with atypical neurological clinical pictures, the diagnosis of AIDS should be considered.

AIDS Dementia Complex↗
PubMed1990

Dose-dependent decrease in rat plasma amino acids after acute administration of ethanol.

Male rats were given three different doses of ethanol in i.p. injections (0.66, 1.33 and 2.00 g kg-1). A dose-dependent decrease in the concentrations of most plasma amino acids was observed. For the total amino acid concentration this decrease was 5, 16 and 22%, respectively, compared with a saline-treated control group. It has previously been suggested that the oxidation of ethanol plays an important role in the amino acid decreasing effect of ethanol. In this study the lowest dose used (0.66 g kg-1) was calculated to be high enough to keep the enzyme systems involved in ethanol oxidation saturated during the 60 min course of the experiment. The observation that the ethanol-induced decrease in plasma amino acid levels was more pronounced with higher ethanol doses indicates that not only the oxidation of ethanol but also ethanol itself is important in the effect of ethanol on plasma amino acid concentrations.

Amino Acids↗
PubMed1989

Diurnal rhythm in absolute and relative concentrations of large neutral amino acids in human plasma.

In order to obtain detailed information on the diurnal plasma rhythmicity in those large neutral amino acids (LNAA) which compete with each other for carrier-mediated transport from plasma into the brain, blood samples were collected every hour for 24h from six healthy men, aged 25-50 yr. The well-known diurnal rhythm in the concentration of plasma amino acids was confirmed and is described in greater detail in this paper. These data might be helpful in clinical situations where LNAAs (e.g. L-dopa, alpha-methyldopa and tryptophan) are used as therapeutic agents, since these amino acids compete with endogenous LNAAs for carrier-mediated transport from plasma into the brain. Furthermore, it was found that the amplitude of variation differed between the individual LNAAs. In addition the relationships between them, expressed as ratios of the concentrations of each single LNAA to total LNAA concentration also possess diurnal rhythms, different from those observed in absolute LNAA concentrations. This rhythmicity in relative LNAA concentrations might be of importance for brain function, since altered relationships between LNAAs in plasma might bring about altered concentrations of LNAAs in the brain and consequently, in monoamine synthesis.

Adult↗