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  • pharmacokinetics  (10)
  • Prebiotic  (6)
  • Springer  (16)
  • 2020-2024
  • 2010-2014
  • 1970-1974  (16)
  • 1945-1949
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  • Springer  (16)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 2 (1973), S. 231-234 
    ISSN: 1432-1432
    Schlagwort(e): Phosphorylation ; Nucleotides ; Nucleoside Polyphosphates ; Oligonucleotides ; Urea ; Prebiotic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have analyzed the products formed when mixtures of a nucleoside and ammonium dihydrogen phosphate are heated with an excess of urea. If there is more phosphate than nucleoside in the mixture, compounds containing pyrophosphate bonds are obtained. If uridine, as nucleoside, is in excess over phosphate, di- and oligonucleotides are formed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 1 (1972), S. 249-257 
    ISSN: 1432-1432
    Schlagwort(e): Prebiotic ; Nucleosides ; Dry-phase ; Seawater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The purine nucleosides (adenosine, guanosine, inosine, xanthosine) are formed when the corresponding purine bases and D-ribose are heated together in the presence of certain salts and minerals. The salts remaining after the evaporation of seawater are particularly effective in these syntheses. The relevance of these reactions for prebiological evolution is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 3 (1974), S. 141-150 
    ISSN: 1432-1432
    Schlagwort(e): Adsorption ; Clay ; Montmorillonite ; Phosphoramidates ; Polymerization ; Prebiotic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Nucleoside phosphoramidates derived from polyamines containing at least three amine groups are strongly adsorbed by sodium and magnesium montmorillonite clays even from very dilute solutions. Heating the dried clay-phosphoramidate mixture results in the production of small amounts of the dinucleotides.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 2 (1973), S. 303-316 
    ISSN: 1432-1432
    Schlagwort(e): Polymerization ; Phosphorylation ; Adenosine Cyclic 2′,3′-phosphate ; Oligonucleotides ; Amines ; 2-Aminoethanol ; Amino Acids ; Prebiotic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary When adenosine cyclic 2′,3′-phosphate is evaporated from solution in the presence of simple catalysts such as aliphatic diamines at alkaline pH, and maintained in a dry state at moderate temperatures (25-85°C), self-polymerization to give oligonucleotides of chainlength up to at least 6 is observed. The products contain an excess of [3′→5′]-linkages over [2′→5′]-linkages. The effects of different catalysts and reaction conditions on the efficiency of the reaction are described. The prebiological relevance of these reactions is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 3 (1974), S. 317-321 
    ISSN: 1432-1432
    Schlagwort(e): Thiophosphate ; Thymidine ; Phosphorylation of Nucleosides ; Prebiotic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary It is proposed that inorganic thiophosphate was a versatile and highly reactive constituent of the primitive earth. Some of the ramifications of this assumption with regard to prebiotic chemistry stem from the dual nature of thiophosphate as the most superior nucleophilic agent and an energy rich phosphate. The Michael addition of thiophosphate to acrylonitrile yieldsS-cyanoethylphosphorothioate in high yield. This compound in turn can be used to phosphorylate 2′-deoxythymidine in organic solvents and in the solid state. A mixture of 5′ and 3′-dTMP were identified via chromatography, elementary analysis and NMR spectroscopy.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 1 (1972), S. 241-248 
    ISSN: 1432-1432
    Schlagwort(e): Urea ; Ammonium Dihydrogen Phosphate ; Nucleoside ; Prebiotic ; Polyphosphate ; Trimetaphosphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary When ammonium dihydrogen phosphate is heated with urea to temperatures in the range 85–100°C, it polymerizes almost quantitatively to give polyphosphates containing, on the average, more than ten (PO3) residues. Similar experiments carried out at 72°C give polyphosphate in more than 60% yield. If a nucleoside (thymidine or 3′-deoxythymidine) is added to the reaction mixture, up to 23% of trimetaphosphate can be obtained at 100°C. The prebiotic significance of these reactions is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1432-1041
    Schlagwort(e): Oral antidiabetic drug ; butylbiguanide ; pharmacokinetics ; two-compartment open model ; plasma concentration ; liver concentration ; intestine concentration ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary 50 mg14C-Butylbiguanide was administered intravenously to 4 diabetic patients and 100 mg14C-butylbiguanide orally to 5 further diabetics. The concentrations of the drug in plasma, intestinal fluid, intestinal epithelium and liver tissue were determined and the renal excretion of the biguanide measured. Irregularities in the plasma concentration curve were observed which appeared as systematic deviations from the ideal curve of a biexponential function. Because these deviations occurred only in the middle phase of the plasma concentration curve, it was nevertheless possible to calculate the pharmacokinetic parameters of butylbiguanide by use of a two-compartment open model. The principal pharmacokinetic parameters were determined according to this model after intravenous dosing and the following mean values were obtained:t 1/2 (β)=4.6 h (β=0.15 h−1),C P 0 =0.85µg/ml,V D =218 l,V T =157 l,V P =62 l,k 12=0.69 h−1,k 21=0.44 h−1,k el =0.54 h−1. Within 48 h after administration, an average of 72.4% of the intravenous and 74.4% of the oral dose had been excreted in the urine. Total clearance (Cl tot) averaged 536 ml/min and renal clearance (Cl ren) 393 ml/min. High concentrations of butylbiguanide were observed in the intestinal fluid (100–700 mg/ml) 20–40 min after oral administration. It was found that the drug accumulates in intestinal fluid, intestinal epithelium and liver tissue, and that it is secreted into the intestinal lumen. The concentrations of butylbiguanide in intestinal and liver tissue were 10–46 times higher than in plasma. The secretion of biguanide into the intestinal lumen may occur via the bile or the intestinal mucosa, but there is no evidence of significant biliary excretion of butylbiguanide.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 4 (1972), S. 233-240 
    ISSN: 1432-1041
    Schlagwort(e): Sulphamethoxazole ; trimethoprim ; pharmacokinetics ; uraemia ; sulphonamides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of sulphamethoxazole (SMZ) and trimethoprim (TMP) have been investigated in four healthy volunteers, 15 patients with stable chronic renal failure and 3 patients on regular dialysis. The dosage schedule was 400 mg of SMZ and 80 mg of TMP orally every 12 h. The plasma concentrations and urinary excretion have been analysed in terms of a one compartment open model, allowing for elimination by renal excretion and metabolic processes. — At equilibrium the plasma concentrations of unchanged sulphonamide showed no significant correlation with the degree of renal impairment. The accumulation of TMP increased slightly without affecting the concentration ratio of both agents in plasma. In contrast, increasing accumulation of metabolized SMZ was demonstrated in the presence of renal insufficiency. Indirect evidence indicates that rising metabolite levels under these circumstances may lead to a displacement of unchanged sulphonamide from protein binding sites. — The cumulative urinary excretion amounted to 82.4% of the dose of sulphonamide administered, which probably corresponds to the fraction of the compound absorbed. The urinary concentration of biologically active SMZ was slightly below the plasma level, especially in advanced renal failure, but it remained above the minimum inhibitory concentrations reported in the literature. The concentration of TMP in urine was considerably higher than in plasma, it decreased with loss of renal function as did active SMZ.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 6 (1973), S. 88-92 
    ISSN: 1432-1041
    Schlagwort(e): Noradrenaline pools ; 7-3H-noradrenaline ; neuro-effector junction kinetics ; pharmacokinetics ; sympathoadrenergic activity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A two-compartment model of 73HNA distribution has been developed for studying sympatho-adrenergic activity in intact man. After infusion of 73HNA at constant speed in resting normal subjects, the decay curves of the plasma concentration and urinary excretion of 73HNA were plotted against time. Analysis of the curves yielded constants and indirect indications about noradrenaline exchange processes in the extracellular environment. Complete evaluation of the neuronal pools and of the pathways of biosynthesis and metabolism was impossible, but it seemed likely that 73HNA entered small neuronal pools that underwent rapid exchange with the extracellular environment, a point of some interest in clinical and pharmacologic investigations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 6 (1973), S. 261-267 
    ISSN: 1432-1041
    Schlagwort(e): Alclofenac ; antiphlogistic ; man ; pharmacokinetics ; dosage regimes ; plasma levels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A one compartment open model has been found to fit plasma concentration data previously obtained in man after single oral doses of alclofenac; the parameters of the model are: $${\text{t}}_{\tfrac{{\text{1}}}{{\text{2}}}} $$ abs=1.3±0.7h, $${\text{t}}_{\tfrac{{\text{1}}}{{\text{2}}}} $$ el=3.5±1.2h, Vd/F=17±6. The model has been used successfully to predict steady-state plasma levels of alclofenac after multiple oral doses. One treatment schedule (initial dose 500 mg, maintenance dose 250 mg five times a day) was administered to two volunteers for five days and the plasma levels of alclofenac determined daily. The latter were in good agreement with computer predictions based on the model. It is now possible, therefore, to select the most suitable dosage regimes for this drug.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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