PubMed Health⌕ Search

Biomedical subjects

S H Hansen

Publications and source records attributed to S H Hansen.

At least 91 records · Page 5Linked to original sources
PubMed1992

On the botanical distribution of chiral forms of gossypol.

Plants belonging to Malvaceae (about 90 species belonging to 33 genera) were analysed for the presence of gossypol by reversed-phase HPLC using absorbance detection at 365 nm, and the chirality and optical purity of gossypol were determined whenever the analysis was positive. Only plants belonging to the cotton tribe (Gossypieae) contained gossypol (detection limit better than 0.001%). In particular, no gossypol could be detected in ABELMOSCHUS ESCULENTUS (ocra), HIBISCUS TILIACEUS, H. SABDARIFFA, and HEREA BRASI-LIENSIS, earlier claimed to contain this compound. Gossypol-containing plants usually produced dextrorotatory gossypol of varying optical purity; an enantiomeric excess of (-)-gossypol was detected in only one plant, GOSSYPIUTN BARBADENSE.

Journal Article↗
PubMed1992

Effects of brefeldin A on endocytosis, transcytosis and transport to the Golgi complex in polarized MDCK cells.

We have studied the effects of brefeldin A (BFA) on endocytosis and intracellular traffic in polarized MDCK cells by using the galactose-binding protein toxin ricin as a membrane marker and HRP as a marker of fluid phase transport. We found that BFA treatment rapidly increased apical endocytosis of both ricin and HRP, whereas basolateral endocytosis was unaffected, as was endocytosis of HRP in the poorly polarized carcinoma cell lines HEp-2 and T47D. Tubular endosomes were induced by BFA both apically and basolaterally in some MDCK cells, comparable with those seen in HEp-2 and T47D cells. In addition, in MDCK cells, BFA induced formation of small (< 300 nm) vesicles, labeled both after apical and basolateral uptake of HRP, as well as some very large (> 700 nm) vacuoles, which were only labeled when HRP was present in the apical medium. In contrast, neither in MDCK nor in HEp-2 or T47D cells, did BFA have any effect on lysosomal morphology. Moreover, transcytosis in the basolateral-apical direction was stimulated both for HRP and ricin. Other vesicular transport routes were less affected or unaffected by BFA treatment. Two closely related structural analogues of BFA (B16 and B21), unable to produce the changes in Golgi and endosomal morphology seen after BFA treatment in a number of different cell lines, were also unable to mimic the effects of BFA on MDCK cells.

Animals↗
PubMed1992

Effect of 5-aminosalicylic acid on myocardial capillary permeability following ischaemia and reperfusion.

OBJECTIVE: The aim was to evaluate the effect of 5-aminosalicylic acid on myocardial capillary permeability for small hydrophilic molecules after ischaemia and reperfusion. METHODS: Open chest anaesthetised dogs were subjected to a 20 min occlusion of the left anterior descending coronary artery followed by 1 h reperfusion. 5-Aminosalicylic acid (bolus injection 12 mg.kg-1, followed by 105 micrograms.kg-1.min-1) (n = 10) or saline (control, n = 12) was given intravenously for 1 h, starting 20 min before ischaemia. The myocardial plasma flow rate, myocardial capillary extraction fraction, and myocardial capillary permeability-surface area (PS) product for 99mTc-DTPA were determined before ischaemia, and 5 and 60 min after the start of reperfusion by employing the single injection residue detection method. Immediately after reperfusion, the reactive hyperaemic plasma flow was measured by the 133Xe washout method. RESULTS: Four dogs (two untreated and two treated with 5-aminosalicylic acid) were eliminated due to ventricular fibrillation at the time of reperfusion. In the remaining animals (10 controls and eight treated) the plasma flow rate, capillary extraction fraction and PS were similar before myocardial ischaemia. After 5 min reperfusion, the plasma flow rate and PS were significantly increased in control animals (p < 0.02 and p < 0.008, respectively), but were unchanged in dogs treated with 5-aminosalicylic acid. In addition, after 5 min reperfusion, PS was significantly higher in the control group than in treated animals (p < 0.005). Microcirculatory variables returned to preocclusive values in both groups by 60 min after reperfusion. 5-Aminosalicylic acid had no significant effect on haemodynamics or on reactive hyperaemic plasma flow. CONCLUSIONS: The results suggest that 5-aminosalicylic acid can attenuate the microvascular changes after reversible myocardial ischaemia. The effect is potentially beneficial, and may be mediated by well recognised anti-inflammatory actions of 5-aminosalicylic acid (ie, scavenging of oxygen free radicals and neutrophil inhibition).

Aminosalicylic Acids↗
PubMed1991

High-performance liquid chromatographic assay of 5-aminosalicylic acid (5-ASA) and its metabolites N-beta-D-glucopyranosyl-5-ASA, N-acetyl-5-ASA, N-formyl-5-ASA and N-butyryl-5-ASA in biological fluids.

A fast, highly sensitive high-performance liquid chromatographic method for the simultaneous determination of 5-aminosalicylic acid (5-ASA) and its metabolites N-beta-D-glucopyranosyl-5-ASA, N-formyl-5-ASA, N-acetyl-5-ASA and N-butyryl-5-ASA has been developed using a dynamically modified silica approach on a 40 mm x 4.6 mm I.D. column packed with 3-microns Hypersil. Plasma proteins are precipitated with acetonitrile. After extraction of the acetonitrile into 1,1,1-trichloroethane an undiluted aqueous phase containing the analytes is obtained. The detection limits are in the range 0.002-0.05 microgram/ml in plasma at a signal-to-noise ratio of 3 using fluorescence detection.

Aminosalicylic Acids↗
PubMed1991

Stability of 5-aminosalicylic acid and its metabolites in plasma at -20 degrees C. Formation of N-beta-D-glucopyranosyl-5-aminosalicylic acid.

The stability of 5-aminosalicylic acid and its metabolites has been investigated when stored frozen. N-beta-D-Glucopyranosyl-5-aminosalicylic acid was formed in considerable amounts concomitant with a decrease in 5-aminosalicylic acid in plasma samples spiked with 5-aminosalicylic acid as well as in standard solutions of 5-aminosalicylic acid buffered with potassium phosphate between pH 5.5 and pH 8.0 with 4.0 mM glucose added and stored at -20 degrees C. Thus N-beta-D-glucopyranosyl-5-aminosalicylic acid might not, as previously described, be a metabolite of 5-aminosalicylic acid but an artifact formed during storage of plasma samples. The N-glucoside formed could be quantitatively degraded to 5-aminosalicylic acid and glucose by adding 0.2 M potassium phosphate buffer pH 3.0 to the sample prior to the analysis. The metabolites of 5-aminosalicylic acid (N-formyl-5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid and N-butyryl-5-aminosalicylic acid) were found to be stable in plasma stored at -20 degrees C for at least eight months.

Aminosalicylic Acids↗
PubMed1991

[Bladder tumors in West Lolland. A case-control study of occupational exposure in a risk region].

The Danish Cancer Register recorded a significant excess incidence of bladder tumours among men in West Lolland during the period 1970 and 1979. No corresponding excess incidence of cancer of the lung was recorded. This might suggest that causes other than increased prevalence of smokers explain the recorded findings. A case-control investigation was carried out to illustrate possible occupational causal factors with the aid of the Cancer Register database concerning cancer and occupation which is based on linking of the Cancer Register with the Supplementary Pension Fund (additional pensions supplementary pension fund awarded via the Labour Market.) Increased risks of bladder tumours were demonstrated in several occupations which are recognized as involving a risk for this disease. A significantly increased risk was demonstrated in the transport occupation. No evidence was found to suggest that the peculiar occupational structure of the region could explain the excess risk registered.

Case-Control Studies↗
PubMed1991

Pharmacokinetics of 5-aminosalicylic acid in man following administration of intravenous bolus and per os slow-release formulation.

The fate of 5-aminosalicylic acid (5-ASA), which is used in the treatment of chronic inflammatory bowel diseases, was studied in six healthy volunteers receiving doses of 100 mg and 250 mg intravenous bolus as well as 250 mg per os (slow release). Following intravenous administration, the drug was rapidly eliminated with a plasma half-life of about 40 min, mainly due to rapid metabolism. No parent drug was recovered in feces, and the total recovery following oral administration (30%) was significantly lower than following the intravenous doses (77% and 72%). Nonlinear pharmacokinetics were suggested as the 2.5-fold increase in intravenous dose was followed by a significant relative increase (greater than 2.5) in the renal elimination of 5-ASA, as well as a significant decrease (less than 2.5) in the elimination of the metabolite N-acetyl-5-ASA. There was also a trend towards a decreasing total body clearance and metabolic ratio. The present study confirms earlier findings on the pharmacokinetics of 5-ASA and suggests a possible saturation of the N-acetylating system in the dose range studied. This may be of interest in the design of controlled-release formulations and dosage regimes for the treatment of diseases of the small-bowel, where 5-ASA is easily absorbed. Further, for the first time, a marked difference in the intestinal fate compared to the systemic fate of the drug is demonstrated, suggesting alternative presystemic metabolism of 5-ASA, which may bear relevance to its mode of action. Further studies on the pharmacokinetics of 5-ASA, preferably in patients, are warranted.

Administration, Oral↗
PubMed1991

The preendosomal compartment comprises distinct coated and noncoated endocytic vesicle populations.

The transfer of molecules from the cell surface to the early endosomes is mediated by preendosomal vesicles. These vesicles, which have pinched off completely from the plasma membrane but not yet fused with endosomes, form the earliest compartment along the endocytic route. Using a new assay to distinguish between free and cell surface connected vesicle profiles, we have characterized the preedosomal compartment ultrastructurally. Our basic experimental setup was labeling of the entire cell surface at 4 degrees C with Con A-gold, warming of the cells to 37 degrees C to allow endocytosis, followed by replacing incubation medium with fixative, all within either 30 or 60 s. Then the fixed cells were incubated with anti-Con A-HRP to distinguish truly free (gold labeled) endocytic vesicles from surface-connected structures. Finally, analysis of thin (20-30 nm) serial sections and quantification of vesicle diameters were carried out. Based on this approach it is shown that the preendosomal compartment comprises both clathrin-coated and non-coated endocytic vesicles with approximately the same frequency but with distinct diameter distributions, the average noncoated vesicle being smaller (95 nm) than the average coated one (110 nm). In parallel experiments, using an anti-transferrin receptor gold-conjugate as a specific marker for clathrin-dependent endocytosis it is also shown that uncoating of coated vesicles plays only a minor role for the total frequency of noncoated vesicles. Furthermore, after perturbation of clathrin-dependent endocytosis by potassium depletion where uptake of transferrin is blocked, noncoated endocytic vesicles with Con A-gold, but not coated vesicles, exist already after 30 and 60 s. Finally, it is shown that the existence of small, free vesicles in the short-time experiments cannot be ascribed to recycling from the early endosomes.

Cell Compartmentation↗
PubMed1991

Ricin transport in brefeldin A-treated cells: correlation between Golgi structure and toxic effect.

Whereas brefeldin A (BFA) protected a number of cell lines against the protein toxin ricin, two of the cell lines tested were not protected but rather sensitized to ricin by BFA. EM studies revealed that upon addition of BFA the Golgi stacks in cells which were protected against the toxin rapidly transformed into a characteristic tubulo-vesicular reticulum connected to the endoplasmic reticulum, and subcellular fractionation experiments showed that galactosyl transferase disappeared from the Golgi fractions where it was normally located. EM and subcellular fractionation also indicated that in contrast to the Golgi stacks, the trans-Golgi network (TGN) remained intact and that internalized ricin was still localized in the TGN both when BFA was added before and after the toxin. Thus, BFA does not prevent fusion of ricin-containing vesicles with the TGN, and unlike resident proteins in Golgi stacks, ricin is not transported back to ER upon treatment of cells with BFA. Two kidney epithelial cell lines, MDCK and PtK2, were not protected against ricin by BFA, and EM studies of MDCK cells revealed that BFA did not alter the morphology of the Golgi complex in these cells. Also, subcellular fractionation revealed that, in contrast to the other cell types tested, the localization of galactosyl transferase in the gradients was not affected by BFA treatment. The data show that there is a correlation between BFA-induced disassembly of the Golgi stacks and protection against ricin, and they demonstrate that the structural organization of the Golgi apparatus is affected by BFA to different extents in various cell lines.

Animals↗
PubMed1991

Availability of mesalazine (5-aminosalicylic acid) from enemas and suppositories during steady-state conditions.

The local and systemic bioavailability of a mesalazine enema (Pentasa, Ferring A/S, Denmark) and a mesalazine suppository (Pentasa, Ferring) was assessed during steady-state conditions. Eleven healthy subjects took 1 g of the enema or the suppository twice daily for 1 week, with a drug-free period of at least 1 week in between. At the end of each treatment period the urine and faeces were collected for 48 h, and the concentrations of mesalazine and the metabolite acetyl-mesalazine were measured. Plasma concentrations of drug and metabolite were measured hourly during a 12-h dose interval. The faecal water concentration of mesalazine was significantly higher after suppository treatment (55.7 mmol/l) compared with enema treatment (31.7 mmol/l) (p less than 0.01). The systemic absorption was low; 15% of daily mesalazine dose was recovered in urine after enema treatment and 10% after suppositores (p less than 0.01). Plasma concentrations were low, and no accumulation of either mesalazine or acetyl-mesalazine occurred. In conclusion, the enema and the suppository can be continuously administered as 1 g of mesalazine twice daily, respectively, giving high faecal water concentrations of mesalazine and a low systemic absorption.

Administration, Rectal↗
PubMed1991

New metabolites of the drug 5-aminosalicylic acid. II. N-formyl-5-aminosalicylic acid.

1. A new metabolite of the drug 5-aminosalicylic acid (5-ASA) has been found in urine from pigs and in plasma of humans. The metabolite has been isolated from pig urine using an XAD-2 column and purified using preparative h.p.l.c. 2. The metabolite has been identified as N-formyl-5-ASA (5-formamidosalicylic acid) using 1H- and 13C-n.m.r. spectrometry and mass spectroscopy and the structure was confirmed by chemical synthesis. 3. N-Formyl-5-ASA is stable in human plasma and in potassium phosphate buffers between pH 3.0 and 9.0. It is hydrolysed below pH 3.0. 4. N-Formyl-5-ASA was readily formed in rat liver homogenate when 5-ASA and N-formyl-L-kynurenine were added. Thus N-formyl-5-ASA might be formed by the actions of formamidase in vivo. 5. N-Formyl-5-ASA has been found in human plasma from healthy volunteers dosed i.v. with 5-ASA (250 mg). N-beta-D-glucopyranosyl-5-ASA, N-acetyl-5-ASA and N-formyl-5-ASA were quantified in human plasma using a h.p.l.c. assay.

Aminosalicylic Acids↗
PubMed1990

Gas chromatographic assay for N,N-dimethylglycine in urine.

A gas chromatographic method for the determination of N,N-dimethylglycine in urine has been developed. After clean-up by cation-exchange, N,N-dimethylglycine was derivatized with ethanol and hydrochloric acid to form the corresponding ethyl ester. After evaporation of solvent, N,N-dimethylglycine ethyl ester was extracted into methylene chloride and chromatographed on a gas chromatograph equipped with a packed column containing 10% Carbowax 20 M. The detection limit of the method is 0.01 mM N,N-dimethylglycine in urine. This method has been used to detect N,N-dimethylglycine in urine from healthy subjects as well as in urine from patients with metabolic disorders. These findings were verified by gas chromatography-mass spectrometry.

Betaine↗
PubMed1990

Localization of urokinase-type plasminogen activator receptor on U937 cells: phorbol ester PMA induces heterogeneity.

The binding of human urokinase-type plasminogen activator (u-PA) to the surface of the human monocytic cell line U937 was studied by immunological detection of bound u-PA or binding of biotinylated diisopropyl fluorophosphate-inactivated human u-PA visualized by light or electron microscopy. Untreated U937 cells showed a characteristic binding pattern, with the majority of the u-PA bound to the microvillar-containing protruding pole of the cells. After treatment with the phorbol ester PMA, the resulting adherent cell population was very heterogeneous with respect to both cellular morphology and u-PA binding. The bound u-PA was distributed on both the dorsal and the substrate side of the cells, and the patches of bound u-PA could not be correlated to any typical membrane conformations or cell-cell or cell-substratum contacts. When a monoclonal antibody directed against the amino-terminal fragment (ATF) of u-PA was used, the results were identical regardless of whether intact u-PA or ATF was used for binding to the cells. In contrast, when a monoclonal antibody recognizing the non-receptor-binding protease domain of u-PA was used, bound ATF showed no staining, while bound intact u-PA was stained as efficiently as above. The alteration of u-PA receptor distribution following treatment with PMA could be related to the changes in glycosylation and ligand affinity of the purified u-PA receptor previously described following PMA treatment of U937 cells.

Cell Line↗
PubMed1990

Relationship between uptake and elimination of toluene and debrisoquin hydroxylation polymorphism.

The toxicokinetics of toluene were studied in six healthy subjects. Three of the subjects were phenotyped as rapid hydroxylators of debrisoquin and three subjects were phenotyped as slow hydroxylators of debrisoquin. The subjects were exposed in an exposure chamber to toluene vapor (3.25 mmol/m3) for 4 hours. Solvent concentrations in blood and the metabolites, hippuric acid and o-cresol, in urine were measured during the exposure period and 3 hours after exposure. The capacity to metabolize debrisoquin was determined in three volunteers who had earlier experimentally been exposed to toluene. The uptake of toluene was about 3 mmol, or 50% of the inhaled dose in both rapid and slow hydroxylators. There were no significant differences between the two phenotypic groups with regard to concentrations of toluene in blood, apparent blood clearance of toluene, or excretion of hippuric acid and o-cresol.

Atmosphere Exposure Chambers↗
PubMed1990

Topical and systemic availability of 5-aminosalicylate: comparisons of three controlled release preparations in man.

The bioavailability of three pure 5-aminosalicylic (5-ASA) preparations (Asacol, Claversal, and Pentasa) was studied in 8 ileostomy patients and 12 normal subjects after 6 days of treatment with 2000 mg 5-ASA. The local bioavailability, reflected by the 5-ASA concentration was thereby measured at two clinically relevant areas of the gut: at the entrance to, and the exit from the colon. Estimates of the systemic bioavailability were obtained from the urinary excretions and the plasma values of 5-ASA and Acetyl-5-ASA (Ac-5-ASA) during the three regimens. The three preparations studied are designed to release 5-ASA at different levels in the intestine, but there was no significant difference in the 5-ASA concentrations in the ileostomy effluents (Asacol 1.8 mmol/L, Claversal 3.4 mmol/L, Pentasa 2.0 mmol/L, median values). However, we found a smaller urinary excretion of 5-ASA and Ac-5-ASA (5.2% vs Claversal 27.9% and Pentasa 23.0%, median values of ingested daily dose) and a lower concentration of Ac-5-ASA in the ileostomy effluents after Asacol treatment (0.8 mmol/L, median value) which indicates a more distal release from this preparation compared with Claversal (2.4 mmol/L, median value) and Pentasa (5.5 mmol/L, median value). In normal subjects a higher faecal water concentration of 5-ASA was found after Asacol (9.8 mmol/L, median value) compared with Claversal (5.0 mmol/L, median value), whereas no difference between the faecal water concentrations of Ac-5-ASA was found (Asacol 21.5 mmol/L, Claversal 21.6 mmol/L, median values). This can be explained by a larger systemic absorption of 5-ASA from Claversal, and accordingly Claversal treatment resulted in the largest urinary excretion of 5-ASA and Ac-5-ASA (43.7% vs Asacol 35.6% and Pentasa 31.6%, median values of ingested daily dose). The high Ac-5-ASA concentration in the ileostomy effluents and in the faeces after Pentasa, and the low plasma values, indicate a slow 5-ASA release from this preparation throughout the small and large intestine. The results of the study indicate that Asacol is released in the distal part of the small intestine, that Pentasa is gradually released in the small and large intestine, and that Claversal shows an intermediate release pattern.

Administration, Topical↗
PubMed1990

Endocytosis, intracellular transport and transcytosis of the toxic protein ricin by a polarized epithelium.

The toxic plant protein ricin binds to both the apical and basolateral surface domains of MDCK (strain I) cells grown on polycarbonate filters. Endocytosis of 125I-labeled ricin was not only higher from the basolateral than from the apical surface--an observation which can be explained by the higher surface area of the basolateral surface--but it also appeared to be more efficient when measured as a percentage of total cell-associated ricin. Monovalent ricin-horseradish peroxidase (Ri-HRP), which is known to behave like native ricin with respect to intracellular transport, also binds to, and is taken up from, both the apical and the basolateral surfaces. Initially, after 10 to 15 min, molecules taken up from the two surface domains at 37 degrees C are present in two separate (basolateral and apical) early endosomal populations. This can also be obtained by incubating for 60 min at 18 degrees C. However, after 30 to 60 min at 37 degrees C, most internalized ligand is found in apical lysosomes, regardless from which surface endocytosis took place. Experiments with endocytosis of cationized ferritin from the apical pole and HRP or Ri-HRP from the basolateral pole showed that intermixing in apical lysosomes (or prelysosomes) of molecules taken up from the two poles occurs. Bidirectional transcytosis involving coated pits of both 125I-labeled ricin and Ri-HRP was demonstrated and was found to be most efficient (as measured in per cent of endocytosed toxin) from the apical pole. Transcytosis was strongly reduced at 18 degrees C, and no transepithelial transport of ricin could be measured at 4 degrees C. Transcytosed ricin was intact and could intoxicate new cells. Finally, delivery of ricin internalized from both the apical and the basolateral surface to the apically localized trans-Golgi network occurred at 37 degrees C but not at 18 degrees C, and ricin inhibited protein synthesis largely with the same kinetics following uptake from the two poles. Incubation at 18 degrees C strongly inhibited the toxic effect of ricin. These data show that ricin can intoxicate epithelia from both sides and also penetrate tight epithelial barriers in intact form.

Animals↗
PubMed1989

Simple and rapid method for the simultaneous determination of the eight main metabolites and conjugates of sulphasalazine in human plasma, urine and faeces using dynamically modified silica.

A simple and rapid method for the simultaneous determination of sulphapyridine, N-acetylsulphapyridine, 5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid, hydroxysulphapyridine, N-acetylhydroxysulphapyridine, sulphapyridine O-glucuronide and N-acetylsulphapyridine O-glucuronide in plasma, urine and faeces is presented. After precipitation of plasma proteins by addition of methanol the samples are injected directly into the liquid chromatographic system. The limit of detection is 1 microgram/ml or less at a signal-to-noise ratio of 5 for all compounds using ultraviolet, fluorescence or electrochemical detection. The advantages of the dynamically modified silica approach in this reversed-phase high-performance liquid chromatographic method are demonstrated with respect to regulation and reproducibility of the selectivity.

Chemical Phenomena↗