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F G Larsen

Publications and source records attributed to F G Larsen.

36 records · Page 2Linked to original sources
PubMed1989

Pharmacokinetics of etretinate in psoriatic patients with liver fibrosis.

A study of the pharmacokinetics of etretinate in 7 psoriatic patients with liver fibrosis or liver cirrhosis is reported. Maximum plasma concentrations occurred within 1.5-4.0 hr. Absorption lag-times ranged from 0.3-2.5 hr, whereas the apparent absorption first order half-times (t1/2ka) were within the range of 0.3-1.2 hr. As judged from the AUC-values corrected for dose and body weight a six-fold interindividual variation existed with regard to the systemic availability of etretinate. Absorption and disposition rates of etretinate in subjects with hepatic fibrosis increasing to cirrhosis were not significantly altered compared with previous results in psoriatic patients with normal liver function.

Acitretin↗
PubMed1988

Epidermis and lymphocyte interactions during a tuberculin skin reaction. I. Increased ETAF/IL-1 like activity, expression of tissue antigens and mixed skin lymphocyte reactivity.

Forty-one persons were tested for tuberculin skin reactivity. Epidermal cells (ECs) were isolated from the tuberculin reaction and from a contra lateral, non injected skin area. We found a significant increase of epidermal thymocyte activating factor (ETAF) in epidermis overlying a positive tuberculin reaction together with an increase of OKT6 and class II (HLA-DR) positive cells. Allogeneic lymphocytes proliferated significantly more when mixed with ECs from a positive tuberculin skin test. Injection of tuberculin per se or a negative reaction did not induce similar changes. The described model seems useful for functional studies of ECs and lymphocytes in patients with contact dermatitis.

Adult↗
PubMed1988

Epidermis and lymphocyte interactions during an allergic patch test reaction. Increased activity of ETAF/IL-1, epidermal derived lymphocyte chemotactic factor and mixed skin lymphocyte reactivity in persons with type IV allergy.

Recently, we have found an increased activity of epidermal-derived thymocyte-activating factor (ETAF/IL-1) and epidermal lymphocyte chemotactic factor (ELCF) in epidermis overlying a positive tuberculin skin reaction. In the present study, we investigated 20 patients with confirmed or suspected allergic contact dermatitis by using the suction blister technique before and during patch testing. The ETAF/IL-1 was found in epidermis before patch testing. Its presence increased 2.8-fold in epidermis overlying a positive patch test compared with pretesting values. This increase was statistically significant. Interestingly, nontested skin also showed a significant increase of ETAF/IL-1, which was 1.9-fold higher than pretest values. The ETAF/IL-1 activity in patch test areas was significantly correlated with the clinical response. ELCF is not present in epidermis from noneczematous persons. We observed a significant content of ELCF in three of seven patients with eczema prior to patch testing. After patch testing, all patients showed ELCF in epidermis. Nontested skin showed a 1.5-fold higher content of ELCF compared with pretest values, and in the test area ELCF was 1.8-fold higher. The increases were statistically significant. We performed mixed skin lymphocyte reactions in seven patients using epidermal cells from the patch test area. All patients with a positive patch test had an increased mixed skin lymphocyte reactivity compared with epidermis coming from a negative reaction.

Adult↗
PubMed1988

Pharmacokinetics of etretin and etretinate during long-term treatment of psoriasis patients.

The aromatic retinoic acid derivative etretin has recently been introduced in the treatment of severe psoriasis and other dyskeratoses. Hitherto, the use of the carboxylic acid ester analogue, etretinate, has been hampered by an extremely long elimination half-life of up to 120 days for this drug. Seven patients of either sex from whom we recently reported single-dose pharmacokinetics have been studied after 1 and 3 months multiple dose administration of the drugs. Four were given etretin and three etretinate. Etretin, both as drug and as metabolite, was absorbed faster than etretinate as judged from t-lag, tm and t 1/2 ka. Etretin as drug was eliminated faster than the metabolite etretin, t 1/2 beta 2.39 +/- 1.16 days compared to 6.51 +/- 2.06 days. In patients receiving etretinate the terminal disposition or elimination half-lives for cisetretin (t 1/2 lambda 3 15.9 +/- 9.9 days) were longer than for the metabolite etretin and exhibit a pronounced interindividual variation from 4.25 to 22.8 days. Similarly, cis-etretin accumulated very marked in comparison to the metabolite etretin of the drug etretinate. Assuming 40% systemic availability for both drugs, the central compartment of distribution constituted about 12-32% in case of etretin and about 0.8-3.6% in case of etretinate of the calculated apparent total volume of distribution at steady state, which showed mean values of 3.5 and 39.6 1.kg.-1, respectively, presumably reflecting the higher lipophilic nature of the latter compound.

Acitretin↗
PubMed1988

Preparation of human epidermal tissue for functional immune studies.

A trypsinization technique was optimized for preparation of human epidermal single-cell suspensions from suction blisters. The conditions which provided the highest epidermal cell yield and viability was Sigma trypsin 0.25% (Type II, crude; cat. no. T8128). The incubation time should be 45 min at 37 degrees C with continuous shaking of the epidermal tissue. The use of suction blisters was evaluated for in vivo determination of epidermal thymocyte activating factor (ETAF/Il-1). Trypsinization of epidermis diminished ETAF/Il-1 activity. Dialysis of epidermal homogenates improves determination of ETAF/Il-1-like activity due to removal of low-weight inhibitors. Determination of ETAF/Il-1-like activity in homogenates of suction blisters constitutes a reliable model with acceptable reproducibility.

Cell Separation↗
PubMed1987

Single dose pharmacokinetics of etretin and etretinate in psoriatic patients.

Etretin, an aromatic retinoic acid derivative, has recently been introduced as a possible substitute for etretinate in the treatment of severe psoriasis and other dyskeratoses. A total of nine patients with psoriasis of either sex in the age range 23-76 years was investigated after single dose oral drug administration, six were given 40 mg of etretin and three 40 mg of etretinate. A newly developed reversed-phase HPLC method was applied for simultaneous determination of etretin and etretinate in plasma. In patients receiving etretinate, the lag-time i.e. the time elapsing until appearance of first-order drug absorption was 1.24 +/- 0.27 for the parent drug and 0.69 hrs +/- 0.16 (mean value +/- S.D.) for its metabolite, etretin. Absorption half-times were 0.86 +/- 0.04 and 0.55 hrs +/- 0.09, respectively. The patients receiving etretin showed a lag-time of 0.42 hrs +/- 0.23 and an absorption half-time of 0.33 hrs +/- 0.28. This suggests that a fraction of etretinate is rapidly hydrolysed to etretin during the absorption process. The mean half-times of the distributory phases of disposition for etretinate and etretin were about 1 and 1.3 hrs and the apparent terminal half-lives were 6.57 +/- 2.09 and 5.52 hrs +/- 1.76, respectively. Assuming 40% systemic availability for both drugs the mean apparent volumes of distributions were calculated to be 1.50 +/- 0.46 and 1.31 l X kg-1 +/- 0.53 and mean plasma clearances were 177.8 +/- 105.8 and 175.9 ml X kg-1 X hr-1 +/- 81.4 for etretinate and etretin, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acitretin↗
PubMed1986

A two-constant equation for multiple albumin-binding isotherms.

It has been found that binding of low molecular weight ligands to human serum albumin is generally nonsaturating. Equations commonly used for describing the binding equilibria, i.e., the Scatchard and Klotz (Adair) equations, are saturation functions. We have accordingly tried to establish an equation which would fit the observed data, i.e., not reach a saturation plateau. An empirical equation, in which the bound ligand is expressed as a function of the free ligand [R(C) = b1 in (b2C + 1)], is shown to give reasonably good fits to observed binding equilibrium data for the binding of several organic ligands to human serum albumin, when the two parameters, b1 and b2, are given suitable values. The curve of bound versus free ligand, as plotted from this equation, has the same slope and curvature as that obtained from the Klotz stepwise binding equation at C = 0, if b1 = K1/[2(K1 - 2K2)] and b2 = 2(K1 - 2K2), where K1 and K2 are the first and second stoichiometric binding constants.

Albumins↗
PubMed1986

Quantification of the 3H-ouabain binding site concentration in human myocardium: a postmortem study.

The 3H-ouabain binding site concentration in the human myocardium was determined by measuring vanadate facilitated binding of 3H-ouabain to necropsy specimens of the left ventricle. The 3H-ouabain binding to samples weighing 4-6 mg was specific and saturable and appeared to take place to only one population of high affinity binding sites. After death the 3H-ouabain binding capacity degraded relatively slowly. From 6 to 24 h after death a mean decrease of 11% was seen in five patients, being significant in only one. In 15 patients aged 64-86 years the concentration of 3H-ouabain binding sites measured 6 h after death varied from 223 to 577 pmol X g-1 wet weight with no obvious relation to age or sex. The mean (SEM) value (413(26) pmol X g-1 wet weight) was 1.7 times higher than that previously reported for human myocardium. The concentrations of 3H-ouabain and 3H-digoxin binding sites were identical, and an excess of unlabelled ouabain completely prevented the specific binding of 3H-digoxin. In necropsy specimens weighing 1-2 mg from the endomyocardium obtained using a biotome the 3H-ouabain binding site concentration was in the same range as that in the myocardium. These findings indicate that it is possible to determine the concentration of Na, K-pumps in the human myocardium by measuring the 3H-ouabain binding capacity of biopsy specimens obtained during heart catheterisation or of specimens obtained within the first 18 h after death. This finding may be of importance for studying conditions in which the Na, K-pump concentration is suspected of undergoing variation.

Aged↗
PubMed1986

Warfarin binding to plasma albumin, measured in patients and related to fatty acid concentrations.

A method for determination of reserve albumin equivalent for binding of warfarin as previously described [1] has been used for assessing the influence of non-esterified fatty acid concentration (NEFA) on binding of warfarin to human serum albumin (HSA). Reserve albumin concentration can be used for calculation of the expected fraction of bound warfarin in serum. It is shown in vitro that binding of warfarin increases with added oleate up to 4 mol of oleate per mol of albumin and then decreases. Twenty-four patients on permanent warfarin treatment showed no correlation of serum albumin and reserve albumin concentrations (r = 0.10, P greater than 0.50) indicating that warfarin binding is governed by other factors. However, in the same patients there was a significant correlation between reserve albumin concentration and NEFA/HSA (r = 0.54, P less than 0.01). In one human volunteer changes of NEFA were provoked by strenuous work and it was found that reserve albumin concentration increased with NEFA concentration as expected from the in vitro findings (r = 0.90, P less than 0.001). Five uraemic patients on permanent warfarin treatment showed increasing reserve albumin concentration with increasing NEFA concentration induced by heparin. These findings indicate that, both in vitro and in vivo, the reserve albumin concentration for binding of warfarin and hence the free warfarin concentration is markedly influenced by NEFA concentration. This may add to the understanding of warfarin dose requirement during anticoagulant therapy.

Adult↗
PubMed1985

Multiple cobinding of two ligands to serum albumin: a stoichiometric description of binding equilibria.

Binding equilibria for simultaneous binding of several molecules of two anionic ligands, sulfamethizole/warfarin in one series and sulfamethizole/diflunisal in another, to human serum albumin were studied by equilibrium dialysis. It was found that Klotz's stepwise binding equilibrium concept, extended to cover interaction of two ligands with one carrier, could be used for a quantitative description of binding equilibria. Reciprocity of ligand effects was established at all levels. Heterotropic anticooperativity was present among these pairs of ligands. The experiments were supplemented with observations of albumin binding equilibria for traces of warfarin in the presence of varying amount of oleate, up to 6 mol/mol albumin, by measuring dialysis rates for unbound warfarin. Binding of warfarin to albumin is enhanced upon binding of oleate up to 4 mol/mol albumin, and decreases at higher oleate concentrations. Using stoichiometric (stepwise) binding constants for oleate previously published by Ashbrook et al. [(1975) J. Biol. Chem. 250, 2333-2338], the reverse effect, of warfarin on binding of oleate, was calculated. Simultaneous binding of these ligands to albumin could be described according to the stoichiometric principles as used above for sulfamethizole/warfarin and sulfamethizole/diflunisal.

Binding, Competitive↗
PubMed1985

Interaction of warfarin with human serum albumin. A stoichiometric description.

Reversible binding of warfarin to defatted serum albumin was studied by equilibrium dialysis at pH 7.4, in a 66 mM sodium phosphate buffer at 37 degrees. The binding isotherm could be described by two stoichiometric binding constants, K1 in the range 141,000 to 192,000 M-1 and K2 at 39,000 to 57,000 M-1. At least two additional molecules could be bound but gave indeterminate binding constants. The product K3 X K4 was about 4.7 X 10(7) M-2. Different site models were possible, either one high affinity and several low affinity sites, or two high affinity sites, cooperative, independent, or anticooperative, together with two low affinity sites. Binding affinity for the first warfarin molecule did not vary with pH in the interval from 6 to 9. The affinity decreased with increasing concentrations of sodium sulfate, sodium chloride, and calcium chloride, depending upon ionic strength. Specific effects of chloride and calcium ions were not observed. Light absorption spectra indicated that the warfarin anion was bound to albumin. All observations were consistent with a binding process involving albumin and the warfarin anion, without participation of hydrogen ions and not influenced by the N-B conformational transition of albumin.

Electrolytes↗
PubMed1984

Serum albumin--a non-saturable carrier.

The shape of binding isotherms for sixteen ligands to human serum albumin showed no signs of approaching saturation at high ligand concentrations. It is suggested that ligand binding to serum albumin is essentially different from saturable binding of substrates to enzymes, of oxygen to haemoglobin, etc. Binding to serum albumin appears to be non-saturable.

Bilirubin↗
PubMed1984

Warfarin-sulfinpyrazone interaction on binding to human serum albumin.

Sulfinpyrazone displacement of warfarin from human serum albumin was studied in-vitro. At low sulfinpyrazone concentrations one molecule of warfarin is displaced on binding by one molecule of sulfinpyrazone. Clinical plasma concentrations of sulfinpyrazone are, however, too low to cause significant displacement.

Binding, Competitive↗
PubMedDate not supplied

Dermatoscopic prediction of melanoma thickness using latent trait analysis and likelihood ratios.

Breslow thickness and Clark level can be used to determine surgical procedures for cutaneous malignant melanoma and patient eligibility for experimental adjuvant therapy. Efforts to predict the thickness of melanomas using dermatoscopy have focused on differences between single dermatoscopic findings. The aim of this study was to develop a method for preoperative identification of melanomas of > or = 1 mm Breslow thickness using the entire range of dermatoscopic findings. Sixty-five melanomas were assessed for the presence of 22 dermatoscopic features. Ten dermatoscopic features showed differences in thick and thin melanomas and were selected for further analysis. A latent trait analysis construct implied that a progression in dermatoscopic features was associated with advancement of melanomas. Early melanomas are characterized by a light brown colour, a pigment network and irregularity or heterogeneity. Gray-blue areas, white scar-like areas and an atypical vascular pattern gradually displace these features. Likelihood ratios were determined for these 6 dermatoscopic findings and an algorithm for calculating the probability of thick malignant melanoma was established.

Denmark↗
PubMedDate not supplied

Comparison of dermatoscopic ABCD rule and risk stratification in the diagnosis of malignant melanoma.

For didactic and documentation purposes the dermatoscopic ABCD rule and the dermatoscopic risk stratification have been proposed. The aim of this investigation was to compare the ability of the 2 methods to separate patients with cutaneous malignant melanoma from individuals with other pigmented skin lesions. Three dermatologists, experienced users of dermatoscopy, assessed macroscopic clinical and dermatoscopic slides from 258 patients referred to the skin cancer outpatient clinic by the ABCD rule and risk stratification methods. Diagnostic performance of the 2 methods was compared by receiver operating characteristics curve analysis. When all pigmented skin lesions were compared, there was a trend for the observers to perform better using risk stratification. When only lesions with a well-defined pigment network were included, the diagnostic performance of the risk stratification method was superior to the dermatoscopic ABCD rule (areas under the receiver operating characteristics curve median 0.93 vs. 0.80, p<0.004) for all observers. The agreement between the 2 methods was moderate to substantial (kappa coefficient 0.53-0.62). More melanomas were identified when the rules were combined. The dermatoscopic ABCD rule has been accepted as a standard for identifying melanomas with the dermatoscope, but should be considered secondary to pigment network analysis.

Biopsy, Needle↗