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  • 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
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  • Springer  (50)
  • AGU
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  • 1975-1979  (50)
  • 1970-1974
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 5 (1975), S. 187-197 
    ISSN: 1432-1432
    Keywords: Evolution ; Cytochrome C ; Substitution ; Covarion ; Monte-Carlo Simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A statistical analysis aimed at obtaining some informations on a possible correlation between simultaneous amino acid substitutions is proposed. This method is applied to a set of cytochromes C, at the level of tandem and triple substitutions separated along the peptide chain by 1 to 15 peptide bonds. Monte-Carlo simulations are performed and the results are compared. We find a significant occurence of three adjacent amino acid substitutions in which the first replacement requires a two nucleotide substitution. A possible explanation of this fact is proposed on the basis of covarions.
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  • 2
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    Journal of molecular evolution 5 (1975), S. 47-55 
    ISSN: 1432-1432
    Keywords: Gene Duplication ; Dipeptides ; Posterior Pituitary Peptide ; Evolution ; Protein Sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have compiled the dipeptide frequencies in 100 known protein sequences. We suggest that dipeptides which occur with low frequencies can be used to locate proteins where partial gene duplication may have taken place. The 48 residue sequence of posterior pituitary peptide contains two Cys Trp pairs. The adjacent portions of the sequence are compatible with a partial gene duplication in the evolutionary history of posterior pituitary peptide.
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  • 3
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    Journal of molecular evolution 6 (1975), S. 309-320 
    ISSN: 1432-1432
    Keywords: Aminoacyl Transfer ; Amino Acid Adenylate ; Imidazole Catalysis ; Evolution ; Peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly (U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly (U). At pH 7.1, transfer to poly (U) was five times as great as to poly (A) and transfer to a poly (A) poly (U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly (U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2′ hydroxyl groups throughout poly (U) and the 2′ (3) hydroxyl groups at the terminus of poly (U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
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  • 4
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    Journal of molecular evolution 6 (1975), S. 149-163 
    ISSN: 1432-1432
    Keywords: Electrophoretic Detectability ; Neutral Mutation Theory ; Evolution ; Mutation Rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Routine electrophoretic surveys for genetic variation in natural populations depend primarily upon detecting differences in the net charge carried by a protein. We have calculated the proportion of base substitutions which would yield an electrophoretically detectable mutant protein, and the relative mutation rates among different charge classes, under a variety of simplifying assumptions. These calculations indicate that: (i) only 25 per cent of all single base mutations would lead to a charge change on a protein molecule. (ii) five distinct classes of electrophoretic variants can be generated from a specified protein by single base substitutions. (iii) the relative mutation rates differ markedly among the different charge classes which can be generated by single base substitutions. The estimates of the proportion of electrophoretically detectable mutant proteins and relative mutation rates among charge classes were relatively robust to changes in assumptions concerned with the kind and site of base substitutions and the amino acid composition of the protein.
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  • 5
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    Journal of molecular evolution 6 (1975), S. 61-76 
    ISSN: 1432-1432
    Keywords: 5S ribosomal RNA ; Translation ; Evolution ; Molecular Architecture ; Conformational Changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An extensive comparative analysis of the available primary sequence data on 5S rRNA has been made. A universal secondary structure is presented for procaryotic 5S rRNA which contains four helical regions. Eucaryotic 5S rRNAs are found to have only three of these helices and thus have a somewhat different architecture. In addition, a highly conserved segment of more than thirty nucleotides is identified in the 5′ half of the procaryotic molecule. This segment includes the oligonucleotide-CGAAC- which presumably binds to the t-RNA “common” sequence-GTΨCG-. Among the eucaryotes, the plants display a procaryotic nature in this region, but no eucaryote has the sequence -CGAAC- in this segment. A functional role for the procaryotic 5S rRNA molecule is discussed in which it is envisioned to undergo conformational change, i.e., coiling and uncoiling of one of the helices, which can result in a cyclic interaction of the 5S rRNA molecule with two t-RNA molecules. A general principle also emerges: the natural rotational motion inherent in coiling and uncoiling of nucleic acid helices can be converted quite simply to linear mechanical motion.
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  • 6
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    Journal of molecular evolution 5 (1975), S. 279-290 
    ISSN: 1432-1432
    Keywords: E.coli ; Mutagenesis ; Evolution ; Gene Transposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The lactose fermenting genes inE.coli have been transposed to various chromosomal locations. The bacterial strains were mutagenized with different chemical mutagens and the frequency of Lac negative mutant colonies was measured as a function of lactose gene location in the chromosome. There appears to be a highly mutable location between 58–60 minutes on theE.coli map. This region does not appear to be correlated with the origin of DNA replication or with the terminus. The possible significance of this mutable region in the evolution of new bacterial genes is discussed.
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  • 7
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    Journal of molecular evolution 5 (1975), S. 25-34 
    ISSN: 1432-1432
    Keywords: Rhodopseudomonas spheroides ; 16S Ribosomal RNA ; T1 Ribonuclease Digest ; Phylogeny ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 16S ribosomal RNA (30S subunit) ofRhodopseudomonas spheroides has been characterized in terms of T1 ribonuclease digestion products. This “fingerprint” ultimately permits the placement ofR. spheroides into a detailed procaryotic phylogenetic tree. Given the number of major procaryotic lines that have been characterized in these terms to date, one can tentatively place the Athiorhodaceae closer to the Vibrio-Enteric group than to the Bacillaceae or Cyanophyta.
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  • 8
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    Journal of molecular evolution 5 (1975), S. 35-46 
    ISSN: 1432-1432
    Keywords: Photobacter Strain 8265 ; 5S Ribosomal RNA ; Primary Structure ; Comparative Characterization ; Evolution ; Energetically Constrained Helix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Comparative sequencing studies provide powerful insights into molecular function and evolution. The sequence for 5S ribosomal RNA from Photobacter strain 8265 is eighteen base replacements removed from that ofEscherichia coli. Of these, the vast majority involve a G or C becoming an A or U. These variations also define unequivocally a hexanucleotide base paired region, which appears to be a universal feature of the 5S RNA molecule. The base composition of this helix seems to be under rather stringent, and so unusual, energetic constraints. The possible implications of this are discussed - in particular the prospect of a 5S RNA molecule that undergoes conformational transitions as a part of the overall state changes that constitute the function of the ribosome.
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  • 9
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    European journal of clinical pharmacology 8 (1975), S. 97-105 
    ISSN: 1432-1041
    Keywords: Di-n-propylacetate ; 2-propyl-valeric acid sodium salt ; pharmacokinetics ; anti-epileptic ; drug monitoring ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the anti-epileptic drug di-n-propylacetate (DepakineR) have been studied in 7 patients, in whom plasma concentrations were determined during and following subchronic treatment. Elimination of the drug appeared to follow a monophasic exponential course; biological half lives were 8 to 15 hours. The data supported the assumption that an open one-compartment model can be used to describe the kinetics of dipropylacetate in man. The drug appeared to have a relatively restricted distribution: calculated relative distribution volumes ranged from 0.15 to 0.40 1/kg. There were large interindividual differences in clearance rate. The therapeutic range was considered to be between 50 and 100 mg/1 plasma. Plasma levels of phenobarbital were markedly raised during treatment with dipropylacetate for an unknown reason. Determination of the plasma concentrations of drugs at accurately fixed times appears to be a reliable method for pharmacotherapeutic monitoring of epileptic patients.
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  • 10
    ISSN: 1432-1041
    Keywords: Sympathetic activity ; plasma catecholamine concentration ; dopamine-β-hydroxylase activity ; graded physical exercise ; heart rate ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 11 healthy untrained volunteers the increase in plasma dopamine-β-hydroxylase (DBH) activity during graded physical exercise has been examined as a true measure of increased activity of the sympathetic nervous system. The correlation between DBH activity, catecholamine concentration (CA) in plasma and heart rate was studied. When work on an electrically braked bicycle ergometer was gradually increased from 12.5 to 100, 200 and 300 watts there was a linear increase in DBH activity and heart rate; the increase in CA concentrations followed an exponential function. The peak values for DBH activity and CA concentration in plasma after the 300 watt work load (as percentages of the resting levels) were 130±3% and 820±71%, respectively; the adrenaline concentration in plasma increased only to 150±19% (p〉0.05). There were significant correlations between heart rate and work load, DBH and work load and log CA and work load. The data imply direct correlations between heart rate and DBH, heart rate and log CA and DBH and log CA. The exponential increase in noradrenaline concentration in plasma might be due either to a greater net “overflow” from sympathetic nerve endings, and/or to increased secretion by the adrenal medulla. In the latter case, the release of noradrenaline would not be accompanied by secretion either of adrenaline or DBH. After work ceased there were sharp falls in heart rate and CA concentration, which indicate an immediate drop in sympathetic activity. DBH activity in plasma returned to normal very slowly; it reached half maximum values after 20 – 22 min. It is concluded that increased sympathetic activity in man can be estimated in vivo as changes in DBH and/or CA concentration in plasma. In contrast, a rapid decrease in sympathetic activity is directly reflected only by a rapid fall in the plasma concentrations of CA.
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  • 11
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    European journal of clinical pharmacology 8 (1975), S. 33-39 
    ISSN: 1432-1041
    Keywords: m-octopamine ; metabolism ; first-pass effect ; man ; enteric absorption ; monohydroxylated phenylalkylamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The diminished sympathomimetic pressor activity of monohydroxylated phenylalkylamines after oral administration has been attributed to incomplete enteric absorption. Therefore, urinary excretion of the unchanged drug and its metabolites has been compared after intravenous and oral administration of3H-m-octopamine to eight patients. Identical amounts of3H-activity (80% of the dose) were excreted after the two routes of dosing, so enteric absorption has been assumed to be complete. Significant differences were found in the fraction of free urinarym-octopamine, which amounted to 10.5% of the dose after infusion and 0.58% after oral administration. The only metabolic pathways form-octopamine are deamination and conjugation. Following oral administration the percentage of conjugates was considerably higher than after intravenous infusion. This metabolic pattern appears typical of all phenylalkylamines with a hydroxyl group in themeta position. Ring hydroxylation to catecholamines was not observed. The enzymes mainly responsible for conjugation after oral administration are located in the gut wall. The resulting “first pass effect”, i.e. metabolism prior to the access to the central compartment, can account for the diminished pharmacodynamic effect after dosing by this route.
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  • 12
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    European journal of clinical pharmacology 8 (1975), S. 161-166 
    ISSN: 1432-1041
    Keywords: Oxyfedrine ; norephedrine ; man ; urinary excretion ; sympathomimetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After oral administration of oxyfedrine to healthy volunteers, norephedrine was identified in the urine by thin layer chromatography and gas liquid chromatography and mass spectrography. 30 hours after single oral doses of 8, 16 or 24 mg of oxyfedrine, about 4, 8 and 9 mg, respectively, of norephedrine were found in the urine, i.e. on a molar base 75–100% of the dose was excreted as norephedrine. The peak of excretion occurred within 2–4 hours after administration of the drug. No accumulation of oxyfedrine and/or its metabolite was observed after administration of 16 mg of oxyfedrine t.i.d. for three days. It could not be decided whether oxyfedrine was metabolized to norephedrine by liver enzymes, as in rats, or was spontaneously degraded to norephedrine, e.g. in duodenal fluid before absorption. 30–150 min after oral oxyfedrine (24 mg) norephedrine was demonstrable in duodenal fluid. Thus, in addition to the directβ-sympathomimetic effects of oxyfedrine, it may also have indirect sympathomimetic effects because of the noradrenaline-releasing properties of its metabolite norephedrine.
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  • 13
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    European journal of clinical pharmacology 8 (1975), S. 249-254 
    ISSN: 1432-1041
    Keywords: Clonazepam ; 7-amino-clonazepam ; pharmacokinetics ; side-effects ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Clonazepam (CNP) and its principal metabolite in plasma, 7-amino-CNP (ACNP), have been investigated in a prospective study of 27 newly diagnosed epileptics and correlated with specified side-effects. At a daily dose of 6 mg, the average plasma levels of both substances were about 50ng/ml, and individual values ranged from 30 to about 80ng/ml. There was a linear correlation between changes in dose and the resulting plasma levels, which indicates first order elimination kinetics. Side-effects were frequent, but neither their severity nor their occurrence could be related to plasma levels or to the rate of increase in plasma concentration of the drug. Three out of five patients who developed serious dysphoria had significantly high CNP levels. The concentration of ACNP was considerably increased in four patients who subsequently suffered from withdrawal symptoms. Drug interaction with diphenylhydantoin, i.e. decreased CNP level, was observed in all five patients who received both compounds. In general it is not yet possible to define an upper limit for the plasma levels of CNP and ACNP at which toxicity occurs. In patients treated with conventional doses of CNP, measurement of plasma concentration is not required, except in special circumstances, because of the lack of correlation between plasma level and side-effects.
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  • 14
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    European journal of clinical pharmacology 8 (1975), S. 343-347 
    ISSN: 1432-1041
    Keywords: Nortriptyline ; pharmacokinetics ; man ; two compartment model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of nortriptyline have been assayed in four subjects after intravenous infusion of 57 mg nortriptyline hydrochloride. The data were evaluated according to a two compartment open model. The calculated best-fitting curves were in good agreement with the experimental data, better than could be expected from a simpler model. This justifies the assumption that the kinetics of nortriptyline in man may be described by this model with an appropriate input function. The data permitted estimation of all the parameters of the model. The meaning of the parameters is discussed, particularly in relation to individual variation.
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  • 15
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    European journal of clinical pharmacology 8 (1975), S. 285-285 
    ISSN: 1432-1041
    Keywords: Lithium ; intoxication ; man ; delayed absorption ; gastric contents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A 55-year old man with lithium intoxication showed increasing serum concentrations in spite of forced diuresis and dialysis. A high lithium content was found in gastric juice three days after the compound had been taken. The serum lithium level began to fall after gastric lavage.
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  • 16
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    European journal of clinical pharmacology 8 (1975), S. 277-282 
    ISSN: 1432-1041
    Keywords: QX-572 ; quaternary ammonium compound ; plasma level ; urinary excretion ; man ; anti-arrhythmic drug
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A quantitative thin layer chromatographic (TLC) method has been developed for determination of the antiarrhythmic quaternary ammonium compound N, N-bis (phenylcarbamoylmethyl) dimethylammonium chloride (QX-572) in biological materials. Prior to chromatography QX-572 was transferred into chloroform as perchlorate by ion pair extraction. Tritium-labelled QX-572 was used as the internal standard and a TLC scanning spectrophotometer equipped with a linear detector system afforded the required accuracy, specificity and simplicity. The method was used to determine QX-572 in plasma from 11 patients with various cardiac diseases who received QX-572 8 mg/kg body wt. as an intravenous infusion over 30 min. There was a rapid initial decay of the plasma levels from 11.0±1.1 µg/ml (mean ± SE) at the end of infusion to 3.5±0.5 µg/ml after 30 min. 240 min after commencement of the infusion the plasma level was 0.7±0.1 µg/ml. In these patients 22±2% (mean±SE) of the total administered dose of QX-572 was excreted unchanged in urine during the 24 hours following infusion of the drug. A second group of 28 patients with acute myocardial infarction also received QX-572 8 mg/kg body wt. Their plasma levels did not differ significantly from those found in the first group of patients. There was a poor correlation between the amount of QX-572 administered and plasma level at the end of the infusion. The study has provided some preliminary data about the pharmacokinetics of QX-572, but before a detailed analysis can be done data from longer periods of observation is required. The present results suggest that in future QX-572 can be administered in a standardized dosage, what would be advantageous in practice.
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  • 17
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    European journal of clinical pharmacology 9 (1975), S. 135-145 
    ISSN: 1432-1041
    Keywords: Anturan® ; 14C-label ; man ; pharmacokinetics ; biotransformation ; C-glucuronidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption, biotransformation and elimination of sulfinpyrazone, 1,2-diphenyl-3,5-dioxo-4-(2′-phenylsufinylethyl)-pyrazolidine, have been studied by administration of single 200 mg oral doses of a14C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and complete and the plasma concentration of unchanged drug reached maximum values of 22.67 and 13.04 µg/ml, respectively, after 1 – 2 hours. The elimination half-life in the two subjects, calculated from the decline between 3 and 8 hours, was 2.7 and 2.2 hours. The integrated concentration of unchanged sulfinpyrazone in plasma, estimated from the area under the concentration curves (AUC), was almost as high as that of total14C-substances, so the proportion of metabolized drug in plasma was low. In no case did the AUC of the three specifically determined metabolites, i.e. the sulphone G 31 442, the “para-hydroxy”-compound G 32 642 and the “4-hydroxy”-compound GP 52 097, exceed 4% of the sulfinpyrazone value. More than 95% of whole blood radioactivity was confined to plasma. The oral dose was rapidly and completely excreted, since within 4 days more than 95% was recovered, 85% from urine and 10% from faeces. A large proportion of the dose was excreted as unchanged drug in the two volunteers: 51 and 54% of total urinary radioactivity was present as sulfinpyrazone; 8.2 and 8.8% was present as “para-hydroxy”-metabolite, 2.7 and 3.0% as sulphone-metabolite, and 0.6 and 0.8% as “4-hydroxy”-metabolite. About 30% of urinary radioactivity consisted of highly polar metabolites. Spectroscopy of them showed that they were the C-β-glucuronides of sulfinpyrazone (28%) and the corresponding sulfone (2%). In these metabolites the C(4) of the pyrazolidine ring was directly attached to glucuronic acid, and thus they represent a new type of biosynthetic conjugate.
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  • 18
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    European journal of clinical pharmacology 9 (1975), S. 155-159 
    ISSN: 1432-1041
    Keywords: Anticonvulsants ; benzazepines ; clonazepam ; pharmacokinetics ; gas chromatography ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Eight healthy volunteers were given single i.v. and oral doses of clonazepam (2 mg). The disposition curves after i.v. administration showed a biexponential decline and the data were applied to a two-compartment open model. The volume of distribution ((Vd)β) ranged between 1.5 and 4.4 l/kg and the plasma half-life (t1/2) between 19 and 60 hours. Absorption after oral administration was fast, with peak plasma concentrations within 4 hours in all subjects. Five of the subjects received repeated oral doses of clonazepam 0.5 mg bid for 15 days. The plasma level during steady state (estimated as Cmin within the dose interval) could be predicted from the constants A, B, α and β obtained in the single dose study with a coefficient of variation of 6%. The plasma half-lives after cessation of the subchronic dosing were of the same magnitude as after single doses.
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  • 19
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    European journal of clinical pharmacology 9 (1975), S. 193-198 
    ISSN: 1432-1041
    Keywords: (−)-[14C]-ephedrine ; metabolism ; urinary excretion ; tolerance ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The metabolic fate of orally administered (−)-[14C]-ephedrine has been studied in 3 human subjects and the urinary excretion of metabolites determined quantitatively by solvent extraction, paper chromatography and reverse isotope dilution procedures. Following an oral dose of the drug (0.35 mg/kg, 1.6 µCi), 97% of the dose was excreted in the urine within 48 h, 88% in the first 24 h. Unchanged drug was the major urinary excretory product (53–74%), with N-demethylation occurring to a variable extent (8–20%) although there was little interindividual variation in urine pH. Oxidative deamination was also variable (4–13%); the main identified products of this were benzoic acid (free and conjugated) and 1,2-dihydroxy-1-phenylpropane (free and conjugated). No phenolic metabolites could be detected, and thus it would appear that these compounds cannot be implicated in the acquisition of tolerance to ephedrine which can occur on repeated dosage.
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  • 20
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    European journal of clinical pharmacology 9 (1975), S. 219-227 
    ISSN: 1432-1041
    Keywords: Rifampicin ; induction of drug metabolism ; hexobarbital kinetics ; tolbutamide kinetics ; plasma concentrations ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy volunteers took 1.2 g rifampicin daily for 8 days, and before and afterwards each received hexobarbital (7.32 mg/kg) and tolbutamide (20 mg/kg) by i.v. infusion on two consecutive days. The plasma concentrations of the two drugs were determined during and after infusion. The average elimination half-life of hexobarbital had decreased from 325 to 122 min and of tolbutamide from 418 to 183 min following rifampicin treatment. It was calculated that the metabolic clearance of hexobarbital had increased about three-fold and that of tolbutamide more than two-fold. Significant changes in the distribution kinetics of the two drugs were not observed. The results suggest that rifampicin is capable of inducing drug metabolism in man, which leads to an increased rate of elimination of drugs that undergo biotransformation in the liver.
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  • 21
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    European journal of clinical pharmacology 9 (1975), S. 229-234 
    ISSN: 1432-1041
    Keywords: Quercetin ; flavonoids ; pharmacokinetics ; absorption ; disposition ; metabolism ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of quercetin, a flavonoid, have been studied in 6 volunteers after single intravenous (100 mg) and oral (4 g) doses. The data after iv administration were analyzed according to a two compartment open model with half lives of 8.8±1.2 min for the α phase and 2.4±0.2 h for the β phase (predominant half life), respectively. Protein binding was 〉98%. The apparent volume of distribution was small at 0.34±0.03 l/kg. Of the intravenous dose 7.4±1.2% was excreted in urine as a conjugated metabolite, and 0.65±0.1% was excreted unchanged. After oral administration no measurable plasma concentrations could be detected, nor was any quercetin found in urine, either unchanged or in a metabolized form. These results exclude absorption of more than 1% of unchanged drug. Recovery in faeces after the oral dose was 53±5%, which suggests extensive degradation by microorganisms in the gut. The data obtained show that oral administration of flavonoids may be of questionable value.
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  • 22
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    European journal of clinical pharmacology 8 (1975), S. 227-231 
    ISSN: 1432-1041
    Keywords: Dixyrazine ; methaqualone ; etodroxizine ; Isonox® ; sleep stages ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Whole night EEG and polygraphic recordings were made in ten young, healthy, male volunteers after dixyrazine (12.5 mg, 25 mg, 50 mg), methaqualone (250 mg) and Isonox® (methaqualone 250 mg + etodroxizine 50 mg). A total of 156 recording nights (36 adaptation nights were not included in the analyses) were scored for different sleep stages according to accepted criteria. The smallest dose of dixyrazine (12.5 mg) had no significant effect upon sleep pattern: the larger doses (25 mg and 50 mg) caused significant decreases in REM-sleep during the first nights of administration. The decrease disappeared during the following two nights of treatment. No withdrawal effects were seen. Methaqualone also caused moderate depression of REM-sleep during the first night of treatment, and this effect, too, disappeared during prolonged administration. Isonox® (methaqualone + etodroxizine) had a somewhat stronger surpressive effect upon REM-sleep than methaqualone alone.
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  • 23
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    European journal of clinical pharmacology 8 (1975), S. 91-96 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; pharmacokinetics ; man ; diphenylhydantoin ; phenobarbital ; plasma binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Carbamazepine (2.7–3 mg/kg) was administered orally as an alcoholic solution (50% v/v) to eight healthy volunteers. Two of the subjects were also given 50 mg and 100 mg of carbamazepine in alcoholic solution and 200 mg as a tablet. Plasma concentrations, which were analysed by mass fragmentography, reached a maximum 1 – 7 hours after dosing, and then declined monoexponentially with half-lives ranging from 24 to 46 hours. The half-lives were independent of dose. The apparent distribution volume ranged from 0.79 to 1.40 l/kg. It was found that 72% of carbamazepine was bound to plasma proteins with little interindividual variation, and this was not influenced by the presence of diphenylhydantoin or phenobarbital in therapeutic concentrations. The pharmacokinetic parameters calculated from single oral doses were used to predict the steady-state plasma concentration expected after treatment with multiple doses of 200 mg three times daily. The predicted steady-state concentration was 2 – 3 times higher than that reported in patients undergoing chronic treatment with carbamazepine at this dose level, i.e. the pharmacokinetics of carbamazepine apparently change during multiple dosing.
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    European journal of clinical pharmacology 8 (1975), S. 167-173 
    ISSN: 1432-1041
    Keywords: Disopyramide ; haemodynamic effect ; negative inotropic effect ; anticholinergic effect ; hear failure ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The haemodynamic effects of disopyramide have been studied in 11 patients with manifest or imminent heart failure. Disopyramide, 2 mg per kg body weight, was given intravenously during right and left heart catheterisation. The cardiac index decreased by an average of 28% (p〈0.01); mean maximal left and right ventricular end-diastolic pressures were increased by 5.0±0.9 mm Hg (〈0.01) and 5.0±0.6 mm Hg (p〈0.05), respectively; and left ventricular systolic pressure fell slightly but significantly (p〈0.05). No significant change in right ventricular systolic pressure was seen. Pulmonary wedge pressure rose on average by 2.7 mm Hg (p〈0.05). No significant change in heart rate was observed in 5 patients with sinus rhythm. In 6 patients with atrial fibrillation, there was a significant (p〈0.01) increase in heart rate; the average increase in heart rate for the entire group was 19,6 heats per minute. The maximum effect on all the parameters occurred 7–11 minutes after the injection, and it gradually subsided during the following 10 minutes. It was concluded that disopyramide had a potentially serious myocardial depressant effect.
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    European journal of clinical pharmacology 8 (1975), S. 353-357 
    ISSN: 1432-1041
    Keywords: Chlormethiazole ; pharmacokinetics ; man ; plasma levels ; gas-liquid chromatography
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of chlormethiazole have been studied in six healthy volunteers following an intravenous infusion of the drug. The log. plasma concentration-time curve of chlormethiazole after cessation of the infusion was found to be curvilinear and was fitted therefore, by a bi-exponential equation computed by non-linear least squares regression analysis. Half-lives for the inital α-phase (0.54±0.05 h) and the terminal β-phase (4.05 ±0.60 h) were calculated together with other pharmacokinetic parameters of the two compartment open model. An explanation for the discrepancy between the presently reported plasma half-lives and those appearing in the literature has been presented. The pharmacokinetic treatment of the plasma concentration-time data obtained following intravenous infusion also enabled the prediction that the maximal systemic availability of an orally administered dose of chlormethiazole would be of the order of 15%.
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    European journal of clinical pharmacology 8 (1975), S. 371-376 
    ISSN: 1432-1041
    Keywords: Digoxin ; bioavailability ; plasma levels ; cumulative urinary excretion ; particle size ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Various brands of digoxin tablets, and even different batches of one brand, may differ greatly in bioavailability. Digoxin-Sandoz® tablets have been compared with Lanoxin® manufactured between 1969 and 1972 and after May 1972. Comparisons were also made between and within batches of Digoxin-Sandoz tablets. Three separate cross-over studies were conducted involving a total of 20 volunteers. Digoxin-Sandoz tablets were shown to have a constant bioavailability and to produce plasma concentrations very similar to “new” Lanoxin. Storage for 2 years of one batch of Digoxin-Sandoz did not alter the bioavailability. Particle size was shown to influence bioavailability. Care should be exercised when plasma data alone are interpreted as an index of bioavailability. Measures of bioavailability based on plasma data obtained up to 6 h after administration differed from those based on cumulative urinary excretion data (in this study by a factor of about 2), which can lead to the belief that a difference in bioavailability is much greater than is actually the case. Data from cumulative urinary excretion, collected over a sufficiently long period of time, are likely to be the most reliable method for determining the bioavailability of a substance such as digoxin.
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    European journal of clinical pharmacology 8 (1975), S. 421-425 
    ISSN: 1432-1041
    Keywords: Proscillaridin ; enteric-coated tablets ; plasma levels ; urine excretion ; 86Rb-erythrocyte assay ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration of proscillaridin was measured by a modified86Rd method during treatment with multiple doses of a commercial preparation of proscillaridin. Despite high doses, very low plasma levels were found, and there were only minute amounts of glycoside activity in urine and faeces. Administration of an enteric-coated proscillaridin preparation gave higher plasma levels, which raises the possibility of inactivation of the glycoside by acid gastric juice. The results suggest that proscillaridin has low biological availability when given orally, and that it is extensively metabolised in the body.
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    European journal of clinical pharmacology 8 (1975), S. 317-322 
    ISSN: 1432-1041
    Keywords: Verapamil ; haemodynamics ; exercise ; man ; vascular resistance ; negative inotropism
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Verapamil, 0.1 mg/kg body wt, was injected i.v. over 2 minutes in 8 subjectively healthy middle-aged men, followed by a continuous infusion of 0.007 mg/kg body wt per minute. Prior to the injection several of the subjects had raised pulmonary or systemic arterial pressures. At rest, the central pressures increased slightly, which was taken as a sign of a moderate negative inotropic effect, but there was no change in pre-ejection period or maximal dp/dt of the aortic pressure. The heart rate increased and there was a small decrease in systemic arterial pressure, probably due to a fall of systemic vascular resistance. The PQ time was prolonged. During exercise, with its positive inotropic stimulation, the moderate negative inotropic effect of verapamil disappeared, whereas the increase in heart rate and decrease in aortic pressures persisted. Some variables that reflected the oxygen demand of the heart decreased. The slight negative inotropic effect does not appear to be a particular contraindication to the use of verapamil, but it should be employed cautiously in conditions with a compensatory rise in systemic vascular resistance, or if atrioventricular conduction is impaired.
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    European journal of clinical pharmacology 8 (1975), S. 337-341 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; carbamamazepine-10,11-epoxide ; pharmacokinetics ; induction of metabolism ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Carbamazepine (Tegretol®) was administered orally to four patients as a single dose, and one week later three times daily for 15–21 days. The plasma half-lives of the drug were shorter in all patients after multiple doses (20.9±5.0 hours) than after the initial single dose (35.6±15.3 hours). During multiple doses the plasma concentrations of the metabolite carbamazepine-10,11-epoxide followed those of the parent drug. The steady-state plasma concentrations expected during multiple doses were calculated from the pharmacokinetic parameters obtained in the single dose studies. The calculated levels were higher (17.2±7.2 µg/ml) than the observed maximal concentrations (8.4±1.6 µg/ml on day 4), which were obtained 3–4 days after starting the multiple doses. The levels tended to decrease further during the experimental period. The results suggest that carbamazepine induces its own metabolism in man.
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    European journal of clinical pharmacology 8 (1975), S. 427-432 
    ISSN: 1432-1041
    Keywords: Methylproscillaridin ; urinary and faecal excretion ; polar and non-polar metabolites ; man ; glucuronides
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 0.5 mg3H-proscillaridin-4-methylether was administered orally to 5 healthy males. Maximum plasma levels of total radioactivity were reached after one to two hours. In two subjects a second peak was observed between 6 and 12 hours. The plasma half life of total radioactivity was 51 hours. 20% and 56% respectively of the dose were eliminated in urine and faeces during the following 7 days. 55% of the total radioactivity in plasma, 80% in urine and 20% in faeces consisted of CHCl3-insoluble compounds. 50 – 60% of the latter in plasma and urine could be hydrolysed by β-glucuronidase. More than 90% of the split products were identified as conjugates of methylproscillaridin. TLC-separation of the CHCl3-soluble fractions of plasma and urine yielded two unidentified metabolites, P2 and P3, as the main compounds, besides methylproscillaridin, proscillaridin and scillarenin. In faeces more than 90% of the non-polar fraction was identified as methylproscillaridin. Shortly after administration of3H-methylproscillaridin, the radioactivity in plasma consisted mainly of CHCl3-in-soluble conjugates and of the metabolite P2.
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    Oxidation of metals 9 (1975), S. 459-472 
    ISSN: 1573-4889
    Keywords: Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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    Oxidation of metals 9 (1975), S. 357-365 
    ISSN: 1573-4889
    Keywords: kinetics ; zirconia ; defect structure ; ionic conductivity ; yttria dopant
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A Zr-0.5 Y alloy was found to oxidize about 6 times faster than pure zirconium over the temperature range of 400 to 565°C. The activation energies were nearly identical (∼32 kcal/mole). The activation energies correspond to grain boundary diffusion of oxygen through the scale. The higher oxidation rate of the alloy was attributed to a higher anion vacancy concentration and the assumption that diffusion sites in the lattice and boundaries were in local equilibrium. Measurements on yttria-doped zirconia showed that ionic conductivity was increased markedly by yttrium and extended over a wide range of oxygen pressure. The defect structure of the doped oxide was changed to one of oxygen vacancies, even at the high end of the oxygen pressure range, 10−8 to 0.2 atm, over which pure ziconia contains oxygen interstitials. The doped oxide was found to be extrinsic over the entire range of oxygen pressure and, although ionic conductivity predominated, electronic conductivity was still appreciable. The electronic conductivity, however, was still sufficiently high so that electron transport was not rate-controlling in the predominantly ionic-conducting scale.
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    Oxidation of metals 9 (1975), S. 99-116 
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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    ISSN: 1573-4889
    Keywords: kinetics ; cobalt and nickel oxidation ; parabolic rate constant
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new fast method is proposed for the determination of parabolic rate constants of metal oxidation as a function of pressure and temperature. The method consists of determining rate constants by oxidation of a single metal sample in a continuous manner, periodically changing the oxidant pressure or temperature. This method eliminates a number of errors inherent in the classical method which involves the use of a new metal specimen in each experiment and it further shortens the time of evaluating the functions k p '' = f (p, T). The method is particularly suitable for the determination of rate constants of slow processes. To verify the proposed method measurements of the kinetics of oxidation of cobalt and nickel at different oxygen pressures over the temperature range 1000–1300° C were carried out.
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    Cell & tissue research 157 (1975), S. 457-465 
    ISSN: 1432-0878
    Keywords: Pecten oculi ; Pigeon ; Surface ; Function ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A scanning electron microscopic study of the pecten reveals the rib-like character of the pectinal folds, the nature of their connections with the base and bridge of the pecten as well as the presence of interconnections between the bundles of superficial collagenous fibres. It has been suggested that the pecten may have a mechanical significance, namely protection of the retina from the excessive movements of the vitreous humour. The relationship between the superficial membrane of the folds which is continuous, the intercellular spaces and the process of diffussion has also been discussed.
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    Cell & tissue research 159 (1975), S. 73-80 
    ISSN: 1432-0878
    Keywords: Osteoblasts ; Collagen orientation ; Parietal bone ; Rat, Rhesus monkey ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Bone was removed from the calvaria of anaesthetized 70 g rats or freshly killed young monkeys and the fibrous periosteum dissected off the inner, formative surface under 0.15 M cacodylate buffer. The bone and undisturbed osteoblasts were fixed in 3% glutaraldehyde in the same buffer for 24 to 48 hours, critical point dried and coated with evaporated carbon and gold for scanning electron microscopy (SEM). Fields of osteoblasts were photographed and chosen cells dissected off the osteoid using a tungsten needle. The control of the dissection was made possible by the use of a system of real-time stereo TV-speed SEM. The fields were rephotographed and the orientations of the osteoblasts were compared with that of the underlying collagen fibres. 62% of all osteoblasts lay with their long axes within 15° of the collagen fibre orientation below and 80% within 30°. Montages of large areas of osteoblasts were also made, and then compared with ones of the same area after the cells had been stripped off on adhesive tape. In general, the orientation of the collagen tended to be the same as the cell that formed it. Collagen fibres below cells at the periphery of a domain sometimes had the orientation of the cells in the adjacent patch. It is not possible to determine whether the cells controlled the orientation of the collagen, or vice versa, from this experiment, but other SEM evidence suggests that the collagen orientation in hard tissue matrices depends on the freedom of cells to move with respect to the matrix surface.
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    Cell & tissue research 159 (1975), S. 233-243 
    ISSN: 1432-0878
    Keywords: Odontoblasts ; Predentine ; Dentine ; Calcification ; Scanning electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary A scanning electron microscopic technique was used to investigate the surface structure of dentinogenically active odontoblasts. Thin pieces of rat incisors were fixed, rapidly frozen, freezedried at -70° C and fractured to expose new surfaces prior to examination in the SEM. Differences in the appearance of odontoblastic cell surfaces were seen, with the most extensive ridge formations at the distal part of the sides of the odontoblasts. The predentine area displayed a spongy structure which contrasted to the compact appearance of dentine. Results are discussed in relation to previous studies at the light microscopic and transmission electron microscopic levels.
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    Cell & tissue research 160 (1975), S. 399-410 
    ISSN: 1432-0878
    Keywords: Lung ; Frog ; Alveolar epithelium ; Mucus layer ; Scanning electron microscopy ; Transmission electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary Scanning and transmission electron microscopy were used to study the inner architecture of the frog lung. In some specimens the alveolar surface mucus layer was removed to permit the examination of underlying features. The inner surface of the frog's lung is covered by a layer of microvilli belonging to only one type of epithelial cells. The boundaries of these epithelial cells are demarcated by small ridges. Different degrees of lung expansion cause variations of the surface topography. The morphology of certain surface features is examined in detail. Several methods of drying the specimens are compared.
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    Cell & tissue research 161 (1975), S. 329-341 
    ISSN: 1432-0878
    Keywords: Spermatozoa ; Boar, bull, ram ; Surface ultrastructure ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé La morphologie comparée des spermatozoïdes éjaculés de Verrat, Taureau et Bélier a été étudiée au microscope à balayage. Le sperme lavé est fixé dans le glutaraldéhyde ou le mélange acide picrique-formaldéhyde-glutaraldéhyde. Les échantillons sont le plus souvent désséchés par la méthode du point critique (Fréon) sur un filtre et aussi dans l'air sur une lamelle de verre. La tête des spermatozoïdes de ces trois espèces présente la même forme en pagaie aplatie formée de trois régions principales: les deux segments, antérieur, entouré d'un épaississement marginal, et équatorial de l'acrosome et la région postacrosomique. La plupart des differentiations de la lame postacrosomique décrites en microscopie électronique à transmission sont visibles à travers la membrane plasmique, particulièrement après dessication à l'air. La morphologie superficielle du cou et des différentes parties du flagelle est aussi observable. Des différences spécifiques sont mises en évidence: chez le verrat seulement, par exemple, la surface de l'acrosome apparaît granuleuse, et aucune bordure antérieure dentelée de la lame postacrosomique n'est visible. La microscopie à balayage permet d'observer les grands traits et de fins détails de la morphologie superficielle d'un échantillon de sperme et aussi d'étudier les effects de traitements sur des spermatozoïdes (congélation, extraction de l'acrosome).
    Notes: Summary The comparative ultrastructure of ejaculated boar, bull and ram spermatozoa is studied by scanning electron microscopy. After washing, the spermatozoa are fixed in glutaraldehyde or in picric acid-formaldehyde-glutaraldehyde mixture. Samples are prepared either by critical point drying (Freon) on Millipore filters or by air drying on glass cover slips. In all the species studied, three regions may be distinguished in the paddle-shaped head of the sperm: an anterior segment (surrounded by the marginal thickening) and an equatorial segment constituting together the acrosome, and the postacrosomal region. Most of the feature of the postacrosomal lamina described in transmission electron microscopy are visible through the plasma membrane, particularly after air drying. The surface morphology of the neck and of the different segments of the flagellum is also evident. Some species differences are encountered, e.g. rough surface of acrosome and absence of serrations in postacrosomal lamina of boar spermatozoa only. The techniques employed result in good general morphology and fine resolution of surface detail of the sperm samples; they also permit analysis of spermatozoa treated by freezing or submitted to acrosomal extraction.
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    Cell & tissue research 163 (1975), S. 125-132 
    ISSN: 1432-0878
    Keywords: Bovine subcommissural organ ; Scanning electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The bovine subcommissural organ was studied by using scanning electron microscopy. The most prominent finding was the existence of protruded and dilated endings of the ependymal cells. The majority of these cells were ciliated with two or more cilia; only a few unciliated cells were seen. Some pore-like structures were also seen on the surface. From the functional point of view, the most interesting finding was an amorphous heterogeneous material on the subcommissural ependyma. Especially in the caudal part of the organ this material accumulated in abundance. No real filamentous structures such as Reissner's fibre could be seen, however, it was assumed that the heterogeneous material corresponds to this formation. No supraependymal neurones were demonstrated.
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    Cell & tissue research 163 (1975), S. 313-325 
    ISSN: 1432-0878
    Keywords: Neurogenesis ; Cerebral cortex ; Scanning electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary Fixed cerebral vesicles of mouse foetuses were fractured and examined with the scanning electron microscope. This method provides a study of the three dimensional developmental features of the pseudostratified columnar epithelium up to the formation of the early cortex plate. Matrix cells are a cell population of homogeneous shape, however, mitotic cells are easily identified by their spherical form. The external surface of the brain is formed by the closely packed end feet of these cells covered by a basal membrane. The formation of the cortical plate is the result of a continuous cell migration in columnar arrangement towards the pia. Glioependymal cells extend along the whole brain wall and most likely provide guidance for the migrating cell cords. The formation of the so-called migratory zone is a consequence of the growth of the basal and the horizontal prolongations of emigrating cells. The significance of the cell to cell contacts for the neuronal migration processes is discussed.
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    Cell & tissue research 159 (1975), S. 379-385 
    ISSN: 1432-0878
    Keywords: Compound eye ; Musca domestica ; Ommatidium ; Distal retinula ; Scanning electron microscopy ; Corneal lens ; Corneal pigment cell ; Pseudocone ; Semper cell ; Basement membrane
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    Topics: Biology , Medicine
    Notes: Summary The distal aspect of the housefly ommatidium was surveyed by the scanning electron microscope. Attention was directed to the somal eminence of the superior central cell and the lens to large pigment cell junction. The underside of each lens facet exhibits six hexagonally arranged incisures. Into each of these indentations are fitted several large pigment cells. This hexagonal indentation appears to be a tenacious anchorage. Two corneal pigment cells laterally encircle the pseudocone and at their proximal extension they enclose the Semper cells and neck of the retinula. The somal eminence of the superior central cell is about 10 μm from the base of the corneal pigment cell enclosure. Micrographs were used to construct a diagram of the ommatidium above the basement membrane. Suggestions are made as to the functional correlates of the observed ommatidial structures.
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  • 43
    ISSN: 1432-0878
    Keywords: Hypothalamo-adenohypophysial region Bufo bufo (L.) ; Portal vessels ; Methyl-methacrylate casts ; Light microscopy ; Scanning electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The vascularization of the hypothalamo-adenohypophysial region of the toad Bufo bufo (L.) (Amphibia, Anura) was studied by means of light- and scanning electron microscopy. Special attention was given to the portal vascular system of the median eminence and the pars distalis. Course and arrangement of these vessels are described.
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    Cell & tissue research 162 (1975), S. 377-385 
    ISSN: 1432-0878
    Keywords: Globiferous pedicellariae ; Psammechinus miliaris ; Microvilli ; Chemoreceptor ; Scanning electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The globiferous pedicellariae of Psammechinus miliaris are described. Two fixation methods giving minimal distortion and rapid tissue hardening were adapted for soft tissue preparation for scanning electron microscopy. The pedicellarial valves are covered by a microvillous epithelium. The outer valve epithelial microvilli overlying red spherulocytes in the epidermis are characterized by a filament matrix radiating out from each microvillus. These microvilli may function in epidermal absorption of organic solutes. The inner valve microvilli are more densely packed and the filament matrix is absent. Ciliation is confined to the inner valve surface where the cilia are concentrated to form a distal sensory pad and sensory hillock. Behavioural evidence suggests a chemo- and mechanosensory role for the inner valve surface.
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    Cell & tissue research 164 (1975), S. 371-385 
    ISSN: 1432-0878
    Keywords: Kupffer cell ; Endothelial cell ; Sinusoid ; Liver ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surface ultrastructure of Kupffer cells in the rat liver has been studied by scanning electron microscopy (SEM). The results demonstrate that Kupffer cells are both significantly different and clearly distinct from endothelial cells. Kupffer cells have neither pores (and/or “sieve plates”) nor fenestrations, all of which are present in endothelial cells. They possess a stellate shape, and only indirectly, with slender and irregular evaginations, contribute to the lining of the sinusoidal wall. Furthermore, the luminal surface in some areas contains a large population of short microvilli, microplicae and invaginations. These elements form a kind of microlabyrinth which may correspond to the “worm-like” structures described by transmission electron microscopy (TEM). In the present study, transition forms between endothelial and Kupffer cells were never found. On the contrary, considering the highly fenestrated nature of the endothelial cells, the Kupffer cells may, by ameboid movements, easily cross the overlapping barrier of the sinusoid and protrude into the lumen. Thus, acting as activated macrophages, the Kupffer cells might function to prevent the entrance of foreign material into the tissues of the liver through the fragile and highly fenestrated endothelium. Finally, the topographical reconstruction of the sinusoid by correlated SEM and TEM studies demonstrates that Kupffer cells, with their protruding cytoplasm and ability to extend into the lumen of the sinusoid, may actually change the caliber of the vessel, and thus function as a “sphincter” which causes a temporary arrest of the blood flow when the diameter of the sinusoidal lumen is reduced.
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    ISSN: 1432-0878
    Keywords: Neuromuscular junctions ; Appendicularia (Oikopleura dioica) ; Connective tissue fibrils ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Critical point dried and fractured appendicularia of the species Oikopleura dioica have been examined in the scanning electron microscope. The dorsal nerve cord with ganglion cells and peripheral nerve fibres could easily be observed. Thick peripheral nerve fibres leave the nerve cord as bilateral pairs at constant intervals along the tail. Most of these fibres branch from the naked nerve cord, but some evidently originate in ganglion perikarya bulging out from the nerve cord itself. These paired peripheral nerves always have elaborate end-arborizations on the medial surface of the lateral muscle cells. They are accordingly interpreted as motor axons. Some thinner peripheral nerve fibres originate at irregular intervals from both the nerve cord and the ganglion cells. Due to the numerous extracellular fibrils that connect the bilateral layers of the epidermal fins and the muscle cells to each other, these thin nerve fibres can seldom be traced to their termination. A few ones can, however, be traced ventrally between the notochord and the muscle cells and seem to end in singular bulb-like expansions. Clusters of synaptic vesicles are present in transmission electron micrographs of such nerves, and they are accordingly believed to carry efferent impulses. The extracellular fibrils are arranged in a highly ordered pattern with thick bundles crossing the gap between the structures to be interconnected and with numerous radiating insertions on the surface of the tissues.
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  • 47
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    Cell & tissue research 164 (1975), S. 467-471 
    ISSN: 1432-0878
    Keywords: Pancreas ; Islets ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surfaces of isolated pancreatic islet cells were studied with the scanning and transmission electron microscopes. Islets were isolated from the pancreas of Wistar rats by collagenase treatment and were incubated either in glucose-free medium or in 300 mg% glucose for one hour. Immunoreactive insulin (IRI) in the media of both control and experimental preparations was assayed. Islets were then transferred to 4% glutaraldehyde, buffered with cacodylate, pH 7.4, and prepared for scanning and transmission electron microscopy. Cell masses average 200 μ in diameter. Alpha cells appear pyramidal in shape, are about 8 μ in diameter and appear in groups. Beta cells are round or oval in shape and have an average diameter of 10 μ. Glucose stimulation raised the IRI value tenfold and increased the number of blebs and other surface irregularities per unit area of beta cell surface. Comparison with transmission electron micrographs suggests that the blebs are related to the process of emiocytosis.
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  • 48
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    Cell & tissue research 163 (1975), S. 29-44 
    ISSN: 1432-0878
    Keywords: Spermatozoa ; Capacitation ; Uterus ; Acrosome Reaction ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surface morphology of rabbit spermatozoa, fixed in situ (female reproductive tract) and prepared for scanning electron microscopy by critical point drying, was studied for as many as 36 hours post coitum. The findings demonstrate that 1) spermatozoa in the reproductive tract following coitus exist as a heterogenous, morphological population and 2) with time, shifts within this population from one predominant morphology to another take place. In the fresh ejaculate, most spermatozoa have intact surfaces free of membranous disruptions. With time, a process of labilization (denudation) of the membranes covering the acrosomal region occurs in a progressively larger proportion of spermatozoa. The labilization originates by a process of vesiculation and/or vacuolation and leads to the appearance of a series of small fenestrations or perforations of the surface membranes. The perforations coalesce, and gradually larger areas of the surface membranes are eroded such that by 15 hours post coitum, the outer acrosomal membrane, as well as other acrosomal areas, are to varying degrees, directly exposed to the uterine milieu. Secretory granules, picked up by cilia and transferred to the spermatozoa become localized over the acrosomal region shortly after coitus. The possible significance of these time-dependent, morphological events with the phenomena of capacitation and the “true” and “false” acrosome reactions are discussed.
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  • 49
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    Cell & tissue research 163 (1975), S. 411-413 
    ISSN: 1432-0878
    Keywords: Cuticle ; Laminae ; Arthropod ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Examination of etched pyramids of decapod crustacean cuticles with the scanning electron microscope indicates that laminae are continuous around the angles of the pyramids. This observation is in direct contrast to the result expected on Bouligand's (1965, 1971) hypothesis and suggests that laminae may be real structures.
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  • 50
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    Journal of pharmacokinetics and pharmacodynamics 3 (1975), S. 277-290 
    ISSN: 1573-8744
    Keywords: sulfobromophthalein (BSP) ; kinetics ; BSP disposition ; mathematical model ; flow-limited
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A linear, flow-limited mathematical model of drug kinetics was used to simulate total sulfobromophthalein (BSP) kinetics in normal anesthetized rats during intravenous infusions and following rapid intravenous injections. Four parameters were used to characterize the distribution and biliary and urinary excretion of BSP: liver- to- plasma concentration ratio, extrahepatic tissue- to- plasma concentration ratio, liver clearance rate constant, and renal plasma clearance rate constant. The same parameters appear to characterize the kinetics of BSP in man through the successful application of “scale- up” techniques utilizing data from experiments in rats. Plasma levels of BSP corresponding to intravenous infusions and rapid intravenous injections in man are approximated by computer simulation.
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