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Biomedical subjects

W N Arnold

Publications and source records attributed to W N Arnold.

At least 19 recordsLinked to original sources
PubMed1992

Porphyrogenic properties of the terpenes camphor, pinene, and thujone (with a note on historic implications for absinthe and the illness of Vincent van Gogh).

Camphor, alpha-pinene (the major component of turpentine), and thujone (a constituent in the liqueur called absinthe) produced an increase in porphyrin production in primary cultures of chick embryo liver cells. In the presence of desferrioxamine (an iron chelator which inhibits heme synthesis and thereby mimics the effect of the block associated with acute porphyria), the terpenes enhanced porphyrin accumulation 5- to 20-fold. They also induced synthesis of the rate-controlling enzyme for the pathway, 5-aminolevulinic acid synthase, which was monitored both spectrophotometrically and immunochemically. These effects are shared by well-known porphyrogenic chemicals such as phenobarbital and glutethimide. Camphor and glutethimide alone led to the accumulation of mostly uro- and heptacarboxylporphyrins, whereas alpha-pinene and thujone resulted in lesser accumulations of porphyrins which were predominantly copro- and protoporphyrins. In the presence of desferrioxamine, plus any of the three terpenes, the major product that accumulated was protoporphyrin. The present results indicate that the terpenes tested are porphyrogenic and hazardous to patients with underlying defects in hepatic heme synthesis. There are also implications for the illness of Vincent van Gogh and the once popular, but now banned liqueur, called absinthe.

5-Aminolevulinate Synthetase↗
PubMed1991

Xanthopsia and van Gogh's yellow palette.

A survey of van Gogh's work from 1886 to 1890 indicated that paintings with a yellow dominance were numerous, episodic, and multi-regional. His underlying illness, by his own admission, affected his life and work; furthermore, episodes of malnutrition, substance abuse, environmental exposure, and drug experimentation (all evident from correspondence) exacerbated his condition. Accordingly, we reviewed plausible agents that might have modified the artist's colour perception. Xanthopsia due to overdosage of digitalis or santonin is well documented elsewhere, but evidence of useage of either drug by van Gogh cannot be substantiated. It is unlikely that ageing of the human lens was an influence because of the artist's youth. Sunstroke is too restrictive to fit the multiplicity of regions and motifs. Hallucinations induced by absinthe, the popular liqueur of the period, may explain particular canvases but not the majority of 'high yellow' paintings. Van Gogh's proclivity for exaggerated colours and his embrance of yellow in particular are clear from his letters and, in contradistinction to chemical or physical insults modifying perception, artistic preference is the best working hypothesis to explain the yellow dominance in his palette.

Adult↗
PubMed1989

Absinthe.

Explore the source record for details and available documents.

Alcoholic Beverages↗
PubMed1988

Vincent van Gogh and the thujone connection.

During his last two years Vincent van Gogh experienced fits with hallucinations that have been attributed to a congenital psychosis. But the artist admitted to episodes of heavy drinking that were amply confirmed by colleagues and there is good evidence to indicate that addiction to absinthe exacerbated his illness. Absinthe was distilled from an alcoholic steep of herbs. Wormwood (Artemisia absinthium) was the most significant constituent because it contributed thujone. This terpene can cause excitation, convulsions that mimic epilepsy, and even permanent brain damage. Statements in van Gogh's letters and from his friends indicate that he had an affinity for substances with a chemical connection to thujone; the documented examples are camphor and pinene. Perhaps he developed an abnormal craving for terpenes, a sort of pica, that would explain his attempts to eat paints and so on, which were previously regarded as unrelated absurdities.

Alcoholic Beverages↗
PubMed1988

The acid phosphatases of Thermoascus crustaceus, a thermophilic fungus.

Thermoascus crustaceus, a filamentous, thermophilic ascomycete with pathogenic potential was cultured on Sabouraud's liquid medium at temperatures from 27 to 47 degrees C for periods up to 7 days. Growth rate and yield were optimal at 37 degrees C. Morphological changes were confined to the cell walls, the thickness being greatest at 47 degrees C, which were also more resistant to mechanical disruption. Significant amounts of acid phosphatase (EC 3.1.3.2) activity occurred in the spent media of all cultures but were greatest at 37 degrees C. The proportions of acid phosphatase activity which were operationally defined as soluble or bound were also documented; the optimum pH for acid phosphatase activity in all fractions was 5.0. Extracts were subjected to polyacrylamide gel electrophoresis under non-denaturing conditions and the gels were stained for acid phosphatase activity. This revealed four electrophoretically distinct acid phosphatases which had different susceptibilities to inhibition by fluoride, phosphate, or tartrate. Effects of growth temperature, or phosphate supplement in the culture medium, on the acid phosphatase isoenzyme pattern were judged to be minor. Cytochemistry at the electron microscope level indicated acid phosphatase activity on the surface, in the periplasmic space, and in the cytoplasm, but no trends with regard to growth conditions. A substantial temperature range can be tolerated by this species but it is concluded that neither the general shape of the cells nor the acid phosphatase isoenzyme pattern changes substantially; this contrasts with previously documented differences for this class of enzyme in dimorphic Sporotrix schenckii.

Acid Phosphatase↗
PubMed1987

Selective inactivation of an extra-cytoplasmic acid phosphatase of yeast-like cells of Sporothrix schenckii by sodium fluoride.

Suspensions of intact, yeast-like cells of Sporothrix schenckii exhibited an acid phosphatase (EC 3.1.3.2) activity against p-nitrophenyl phosphate of about 5 IU (g dry wt)-1, without recourse to membrane perturbation. This extra-cytoplasmic acid phosphatase was reversibly and competitively inhibited by orthophosphate (Ki = 2 mM at pH 5) but unaffected by L(+)-tartrate (in contradistinction to some of the cytoplasmic acid phosphatases of the same organism). Inactivation by NaF of the extra-cytoplasmic isoenzyme was irreversible and followed first order kinetics; sensitivity to NaF was decreased by the presence of citrate, phosphate or substrate. Neither Km (0.3 mM at pH 5) nor Vmax for this enzyme in acetate buffer was greatly affected by pH in the range 3-5 but the first order rate constant for inactivation by NaF was strongly dependent on pH (maximum at pH 3.5). Crude cell-free extracts of yeast cells had nine electrophoretically distinct acid phosphatase activity bands and, on the basis of the pattern of inhibitors, the extra-cytoplasmic activity was identified as Y-I, an isoenzyme that barely penetrates standard polyacrylamide gel electropherograms. Additional evidence for the assignment came from selective inactivation of this isoenzyme by short treatments of intact cells with NaF under conditions that did not allow penetration of the plasma membrane by the inhibitor and did not kill the cells.

Acid Phosphatase↗
PubMed1987

Media-induced departures from the usual, temperature-dependent cell shapes of Sporothrix schenckii and concomitant changes in the acid phosphatase isoenzyme patterns.

Sporothrix schenckii grew as mycelia at 20 degrees C or yeast at 35 degrees C on a common culture medium, YNG (yeast extract, neopeptone and glucose), in agreement with previous observations that standard media support the mycelial phase at the lower temperature and the yeast phase at the higher temperature. Special media, M-1 and M-2, were used to generate yeast at 20 degrees C and mycelia at 35 degrees C, respectively, i.e. the reverse of the typically-observed, temperature-dependent phases. In this context the M-1 induced (or forced) generation of yeast cells at 20 degrees C was judged to be abnormal yet these cells had a typical yeast ultrastructure including the definitive microfibrillar zone of the cell envelope. Electropherograms of extracts of these cells (M-1 at 20 degrees C) displayed the typical acid phosphatase isoenzyme pattern of yeast grown at 35 degrees C, and that is much more complicated than the typical pattern for extracts of mycelia grown at 20 degrees C on YNG. On the other hand the fungus was held in the mycelial phase on M-2 at 35 degrees C, at least for short term cultures, to complement the study and provide a departure from the cell shape which is expected at the higher temperature. These mycelia were judged to be ultrastructurally abnormal in that they had a thin microfibrillar zone not previously seen in S. schenckii mycelia produced on standard media at lower temperatures. The cell-free extract of these abnormal mycelia grown at 35 degrees C exhibited an isoenzyme pattern which was closer to that of yeast grown at 35 degrees C than to mycelia grown at 20 degrees C, although one isoenzyme showed intermediate electrophoretic mobility. The findings with M-2 medium at 35 degrees C were less meaningful because of the eventual conversion to yeast phase. Overall the results indicate an association between acid phosphatase isoenzyme pattern and cell shape, rather than simply an expression of the various acid phosphatases with growth temperature.

Acid Phosphatase↗
PubMed1986

Acid phosphatases of Sporothrix schenckii.

Sporothrix schenckii cells were grown on a medium containing yeast extract, neopeptone and glucose at 20 degrees C to obtain a mixture of mycelia and conidia, and at 35 degrees C to obtain yeast-like cells. The organism was maintained in the mycelial form, and its transformation to yeast at the higher temperature proceeded via conidia and 'intermediate cells' that then gave rise to yeast by a blastic mechanism. Cell-free extracts were analysed by PAGE at pH 8.0 and acid phosphatases (EC 3.1.3.2) were revealed by a sensitive detection reagent at pH 5.0. Mycelial, conidial and yeast extracts all had some acid phosphatase activity (M-I, C-I and Y-I) at the origin, although the proportion was highest for the yeast extracts. All of the bands that penetrated the gels had different electrophoretic mobilities. Mycelial and conidial extracts each had one other isoenzyme (M-II and C-II), while the yeast extracts had a total of five electrophoretically distinct acid phosphatases. Isoenzyme Y-II was further resolved into five closely related bands (Y-IIa to Y-IIe), the relative intensities of which varied with the phosphate nutrition of the yeast cells and the history of the extracts. The acid phosphatase isoenzymes were inhibited to various extents by sodium fluoride, L(+)-tartrate and phosphate, and showed interactions with citrate as opposed to acetate as the background buffer at pH 5.0.

Acid Phosphatase↗
PubMed1985

Ultrastructure of Candida ingens: a yeast that can assimilate volatile fatty acids.

A defined liquid medium was developed for culture of Candida ingens on either volatile fatty acids or glucose as carbon source. Buffering capacity at pH 5.4 was achieved by inclusion of 50 mM phthalic acid which is not assimilated. The yeast grew on C2-C5 acids, with lags in some cases that were dependent on the cultural history of the inoculum. The cells were notably large for Candida species, or yeasts in general, and were significantly more elongated on glucose substrate compared with butyrate. Traditional aldehyde fixatives and heavy metal staining yielded bland micrographs. However, the periodic acid-thiocarbohydrazide-silver proteinate stain of Thiéry resulted in informative, high contrast electron images for this species. The ultrastructure of the cell envelope was not greatly affected by carbon source or by growth habit except that a slime layer was more prevalent in pellicular cells compared with those grown in submerged culture. The slime layer was apparently stabilized by colloidal iron staining. The other feature of the cell envelope was a microfibrillar zone containing periodic acid reactive constituents. Subcellular organelles were typical of yeast species although there was a propensity for large vacuoles in pellicular cells. When cells were grown on fatty acids there was an increase in the number of microbodies compared with that observed on glucose. Microbodies were best demonstrated by diaminobenzidine-hydrogen peroxide staining of protoplasts, which were generated by dissolution of cell walls with snail digestive enzymes.

Candida↗
PubMed1983

Toxicity of 5-thioglucose towards a pathogenic yeast, Torulopsis glabrata.

5-thioglucose (T-glc) caused premature death of T. glabrata cells after 1- and 2-day culture in defined glucose-containing medium. T-glc equilibrated with 80% of the cell water but did not accumulate in resting or growing cells. The sulfur analog had little or no effect on, 1) the rate of glucose uptake, 2) the kinetics of endogenous trehalose turnover preceding new growth, and 3) the viability of resting cells. A hallmark of cells grown in the presence of T-glc was the retention of abnormally high concentrations of glycogen after 2-day culture. Toxicity of T-glc towards Candida albicans and C. tropicalis was also indicated.

Candida↗
PubMed1982

The cryptic beta-fructofuranosidase of Saccharomyces rouxii.

The synthesis of beta-fructofuranosidase in synchronously dividing cells of S. rouxii was continuous (as opposed to periodic) throughout the budding cycle and followed the increase in cell mass. Similar patterns for cell mass and enzyme increases were observed even in phosphate-deprived cells which did not divide. The beta-fructofuranosidase activity remained physically cryptic throughout the cell cycle as evidenced by analyses on equilibrium density gradient fractions. The beta-fructofuranosidase activity released from mechanically disrupted cells resisted sedimentation when subjected to 131 000 g for 1 h, thus ruling out membrane association. Ethyl acetate was routinely employed to break the crypticity barrier. Enzyme in cell-free extract or in cells was equally sensitive to inactivation at pH values below 5 in the presence of ethyl acetate, which suggested that this is an inherent property of the enzyme in question and not a reflection of proteolytic inactivation. The status of beta-fructofuranosidase in selected species of Saccharomyces was compared with that for S. rouxii and a close similarity with S. bisporus var. mellis was noted. The degree of crypticity encountered in genetically defined strains of S. cerevisiae (e.g. X2180 a/alpha) was relatively high (42%) compared with that for commercially derived bakers' and brewers' strains (about 6%). Extant data on the cryptic beta-fructofuranosidase of S. rouxii are evaluated and the utility of this system for studying enzyme translocation is discussed.

Centrifugation, Density Gradient↗
PubMed1980

Altered purine and pyrimidine metabolism in erythrocytes with purine nucleoside phosphorylase deficiency.

Purine and pyrimidine metabolism was compared in erythrocytes from three patients from two families with purine nucleoside phosphorylase deficiency and T-cell immunodeficiency, one heterozygote subject for this enzyme deficiency, one patient with a complete deficiency of hypoxanthine-guanine phosphoribosyltransferase, and two normal subjects. The erythrocytes from the heterozygote subject were indistinguishable from the normal erythrocytes. The purine nucleoside phosphorylase deficient erythrocytes had a block in the conversion of inosine to hypoxanthine. The erythrocytes with 0.07% of normal purine nucleoside phosphorylase activity resembled erythrocytes with hypoxanthine-guanine phosphoribosyltransferase deficiency by having an elevated intracellular concentration of PP-ribose-P, increased synthesis of PP-ribose-P, and an elevated rate of carbon dioxide release from orotic acid during its conversion to UMP. Two hypotheses to account for the associated immunodeficiency--that the enzyme deficiency leads to a block of PP-ribose-P synthesis or inhibition of pyrimidine synthesis--could not be supported by observations in erythrocytes from both enzyme-deficient families.

Child↗
PubMed1980

Amphotericin B-induced changes in K+ content, viability, and ultrastructure of yeast-phase Histoplasma capsulatum.

Yeast-phase cells of Histoplasma capsulatum were challenged with amphotericin B, and membrane perturbation was monitored by K+ efflux. Suspensions of washed cells readily absorbed about 1.12 microgram of amphotericin B per mg (dry weight) and further nonspecific sites were also apparent. The dose-response curve for initial rate of K+ efflux was sigmoidal within the range 0.1 to 1.0 microgram of amphotericin B per ml. A fungistatic concentration of amphotericin B (0.3 microgram/ml) evoked an efflux of 85 to 90% K+ from the cells within 15 min, but cell viability decreased only 13% (yeast phase) or 33% (transformed to mycelial units). Ultrastructural changes in treated cells were detected within 5 min, and the hallmark was expansion of vacuoles during the 1-h monitoring period. In contradistinction to a previous report, the appearance of the protoplasmic membrane was not altered by fungistatic concentration. When treated cells were returned to a fresh growth medium, there was a pronounced lag (20 h). During this apparent recovery phase, the large vacuoles fragmented and returned to normal size. It is proposed that vacuoles of H. capsulatum act as a spatial buffer of considerable survival value to stressed cells.

Amphotericin B↗
PubMed1979

Isolation and characterization of protoplasts from Saccharomyces rouxii.

Cells of the osmotolerant yeast Saccharomyces rouxii were transformed to protoplasts in good yield (85%) by digesting cell walls with snail-gut enzyme in the presence of 10 mM dithioerythritol, 0.1 M sodium phosphate buffer (pH 6.8), and 2.0 M KCl. The requirement for 2.0 M KCl compares with that for S. bisporus var. mellis (another osmotolerant species) and contrasts with the 0.3 to 0.8 M KCl concentrations used in the preparation of most yeast protoplasts. Short digestions (60 min or less) produced mostly spheroplasts; longer incubations (90 min or more) yielded mostly protoplasts as judged by electron micrographs. These protoplasts could be transferred to 1.0 M KCl or 2.0 M sorbitol without lysing, but lysis was pronounced in 0.5 M KCl or 1.0 M mannitol and complete in 0.02 M KCl. Protoplasts were separated from isolated cell wall remnants and debris by centrifugation on a linear gradient of Ficoll 400 (35 to 17.5%, wt/vol) containing 2.0 M KCl. Both crude and fractionated protoplast preparations contained vesicles which were identified with the periplasmic bodies of whole cells. Some of the periplasmic bodies were connected to protoplasts by fine pedicels; others appeared free. Independent degeneracy of periplasmic bodies was occasionally observed. beta-Fructofuranosidase (EC 3.2.1.26) activity is cryptic (physically) in cells of S. rouxii in contrast to the expressed enzyme (periplasmic space) of other Saccharomyces species. This enzyme remains cryptic in protoplast preparations of S. rouxii but is expressed upon lysis. The same specific activities were found per unit cell or protoplast. The possible association of the cryptic enzyme with periplasmic bodies is discussed.

Organoids↗
PubMed1977

Permeability of the cell envelope and osmotic behavior in Saccharomyces cerevisiae.

Bakers' yeast (Saccharomyces cerevisiae) was equilibrated with distilled water and then packed into standardized pellets by centrifugation. The fractional space (S value) that was accessible to passive permeation was probed with a variety of mono- and divalent salts, mono- and disaccharides, polyols, substrates and products of beta-fructofuranosidase (EC 3.2.1.26) and acid phosphatase (EC 3.1.3.2), and a cross-linked polymer of sucrose (Ficoll 400). A simple but very reproducible method was developed to measure pellet volume. At the limit of zero osmolality for bathing medium, the interstitial space was 0.223 ml/ml of pellet, and the aqueous volume of cell envelopes was 0.117 ml/ml of pellet. Thus the cell envelope for this yeast, under these conditions, was approximately 15% of the total cell volume. At a finite osmolality, the space in a yeast pellet that was accessible to salt was accounted for by the sum of initial interstitial space, the volume of the cell envelopes, and the volume of water abstracted from the cells by osmosis. Plots of S value versus osmolality were linear for uncharged probes and curvilinear for all salts. When Ficoll and potassium thiocyanate were presented to the yeast in admixture, the S values for the salt increased continuously over the range of osmolality studied. However, the S values for Ficoll 400 (which did not penetrate the cell wall) were lower by an amount equilivalent to the cell envelopes; they increased in parallel with the S curve for salt up to 1.15 osmol/kg and then plateaued. The results support the concept of incipient plasmolysis at 1.15 osmol/kg, and the separation of protoplasm from the cell wall is indicated with more concentrated solutions. Such cells were still viable if slowly diluted in distilled water, but they were injured by the shock of rapid dilution. However, shocking the cells did not release beta-fructofuranosidase into the medium. The complete accessibility of salts toward killed cells was demonstrated with yeast that had been pretreated with heat, organic solvents, or glutaraldehyde.

Acid Phosphatase↗