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Biomedical subjects

R S Criddle

Publications and source records attributed to R S Criddle.

At least 19 recordsLinked to original sources
PubMed1992

Susceptibility testing of Cryptococcus neoformans: a microdilution technique.

We studied a series of test conditions in a microtiter system to define the optimal method for determining the susceptibility of Cryptococcus neoformans to antifungal agents. Twenty-one isolates of C. neoformans were grown for 24 or 48 h in four chemically defined media: yeast nitrogen base (BYNB 7); RPMI 1640; synthetic amino acid medium--fungal (SAAMF), buffered at pH 7.0 to select the medium that best supported growth of this fastidious yeast; and yeast nitrogen base, pH 5.4 (YNB 5.4). Maximum growth of C. neoformans, at 35 degrees C, was obtained in YNB 5.4, with the next highest growth levels in BYNB 7, SAAMF, and RPMI. Growth at 24 h was uniformly poor in all media and lacked reproducibility. In contrast, incubation for 48 h gave adequate growth with low standard deviations, and 48 h was selected as the optimal incubation period for this study. Comparison of the relationship between growth kinetics and initial inoculum size for eight cryptococcal isolates showed that 10(4) cells per ml yielded optimal growth in BYNB 7 and YNB 5.4, whereas 10(5) cells per ml was optimal in RPMI and SAAMF. Furthermore, variation of inocula from 10(3) to 10(5) cells per ml showed small but significant inoculum effects in determining MICs of fluconazole, amphotericin B, and flucytosine for C. neoformans. Therefore, 10(4) cells per ml was chosen as the optimal inoculum for susceptibility testing in this study. Mean MICs of fluconazole, amphotericin B, and flucytosine for 21 crytococcal isolates in RPMI and BYNB 7 were low (for example, fluconazole had mean MICs of 1.2 and 1.3 micrograms/ml in RPMI and BYNB 7, respectively) and differed significantly from medium to medium. In contrast, the MICs obtained in SAAMF were significantly higher (e.g., fluconazole had a mean MIC of 2.2 micrograms/ml). Variance in MICs was large with fluconazole and flucytosine but small with amphotericin B, irrespective of the medium used. A microtiter system employing BYNB 7 as the medium, 48 h as the incubation period, and 10(4) cells per ml as the final inoculum is a simple, accurate, and reproducible method for the testing of C. neoformans susceptibility to fluconazole, amphotericin B, and flucytosine.

AIDS-Related Opportunistic Infections↗
PubMed1991

Simultaneous measurement of metabolic heat rate, CO2 production, and O2 consumption by microcalorimetry.

This study describes methods and equipment for measurement of metabolic heat rates of cells and tissues under conditions that provide simultaneous determinations of the flux rates of both O2 and CO2. Isothermal measurement of metabolic heats are conducted in a sealed ampule. A trapping solution is employed to absorb metabolic CO2. Absorption of CO2 produces heat at a rate proportional to the rate of CO2 production. Under these conditions, O2 consumption by the tissue results in a decrease in the partial pressure of O2 within the sealed ampule. The decrease in pressure can be monitored with a pressure sensor and related to O2 consumption rates. The combined measurements of heat rates, CO2, and O2 fluxes provide important information on bioenergetic efficiency of cell metabolism. These data can also suggest possible shifts in metabolic pathways or substrate sources as cells develop, or are exposed to effectors, inhibitors, and environmental factors.

Calibration↗
PubMed1991

Platelet activating factors (AGEPC) from epidermal secretions of the Arabian Gulf catfish, Arius bilineatus, which stimulate wound healing.

High levels of platelet activating factor (PAF) activity were demonstrated by platelet aggregation and serotonin release assays to be present in fright induced epidermal secretions of the Arabian Gulf catfish, Arius bilineatus (Valenciennes, 1840). The PAF activity was purified by thin-layer chromatography. Mass spectral analysis combined with chemical and enzymatic modification of the purified PAF and inhibitor studies indicated that PAF activity was due to the presence of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine (AGEPC) molecules. The total AGEPC concentration in the epidermal secretions based on PAF assays was 8 x 10(8) M, well above the threshold level for platelet activation which is near 5 x 10(-11) M. Thus, stimulated epidermal secretory cells of Arius bilineatus supply platelet activating molecules at physiologically high concentrations to sites of injury.

Animals↗
PubMed1990

Combinations of antifungal and antineoplastic drugs with interactive effects on inhibition of yeast growth.

Interactive effects among antifungal and antineoplastic drugs contributed to toxicities when combinations of these drugs were used to inhibit the growth of five Candida spp. Drug interactions were measured by growth inhibition in both liquid and solid media, by viable cell counts and by examination using scanning electron microscopy. Large cooperative effects on toxicity were demonstrated between some antineoplastic and antifungal drugs. For example, positive cooperativity was seen between the antineoplastic drug 5-fluorouracil and combinations of the antifungal agents amphotericin B and miconazole nitrate. Smaller, and often negative, interactions occurred between the antineoplastic drug cyclophosphamide and antifungal drugs. The levels of drugs required for inhibition in combination drug treatments were critically dependent upon the ratios as well as the absolute concentrations of the drugs tested. Drug combinations were selected which inhibit yeast growth at concentrations far below the individual MIC of the drugs. These combinations may prove of value in clinical treatments of cancer patients infected by Candida.

Antibiotics, Antineoplastic↗
PubMed1989

Histopathological observations on organs from rabbits injected with the skin toxin of the Arabian Gulf catfish (Arius bilineatus, Valenciennes).

Toxicity of soluble protein extracts (skin toxin) from epidermal skin secretions of the catfish, Arius bilineatus (previously identified as Arius thalassinus), was examined in rabbits. Intravenous injections containing doses as low as 2 mg protein/kg body weight caused mortality in most animals tested. Histopathological examination of lung, heart, liver and kidney tissues of rabbits injected with skin toxin indicated that the lungs and livers of treated animals were adversely affected, while heart and kidney tissues appeared to be normal. Lethality of skin toxin was prevented by pretreatment of the rabbits with indomethacin. Histopathological examination of lung and liver tissues of indomethacin pretreated animals showed a significant reduction in the damage observed after injection of skin toxin.

Animals↗
PubMed1989

Comparative biochemical and pharmacological properties of epidermal secretions from Ariid catfish of the Arabian Gulf.

1. Comparative biochemical and pharmacological studies on epidermal secretions from three species of Ariid catfish were carried out to determine whether they share common properties. 2. Protein compositions are generally similar, but show some differences in size and numbers of proteins. 3. Lipids also differ. However, seasonal and dietary changes in lipid compositions exceed the differences among species. 4. Enzymes in the secretions appear common to each fish species, though some differences are noted in relative activities. 5. Toxicity responses of rabbits to injections with secretions from each of the catfish species indicated that two were lethal, with similar lethal dose levels when injected intravenously. 6. Secretions from all three catfish induced changes in plasma enzyme levels indicative of heart and liver damage, and also induced changes in blood glucose and cholesterol levels.

Animals↗
PubMed1989

Multifactorial analysis of effects of interactions among antifungal and antineoplastic drugs on inhibition of Candida albicans growth.

Interactions among antineoplastic and antifungal drugs affecting the inhibition of Candida albicans growth are complex functions of the nature of the drugs used in combination, their absolute concentrations, and also their relative concentrations. Studies of drug interactions involving the use of test drugs in fixed concentration ratios can lead to inaccurate conclusions about synergism or antagonism among the drugs. A multifactorial experimental design procedure in which the concentrations of all drugs in test combinations were simultaneously varied has been used to identify and quantify drug interactions. The methods have been applied to combinations of two, three, and four drugs, including antineoplastic drugs, antifungal drugs, and combinations of antineoplastic and antifungal drugs. Results were obtained which allow predictions of effects of combinations and provide maximum effectiveness in growth inhibition with minimum levels of the test drugs.

Antifungal Agents↗
PubMed1989

Interactive effects of antifungal and antineoplastic agents on yeasts commonly prevalent in cancer patients.

The effects of combinations of antifungal and antineoplastic drugs on inhibition of the growth of yeasts which commonly infect cancer patients have been analyzed. It was shown that (i) inhibitory drug combinations could be selected in which all drugs were at levels far below their individual MICs; (ii) interactive effects among antineoplastic and antifungal drugs may be very large; (iii) optimum combinations of drugs for inhibition of yeast growth depended upon both the relative and absolute concentrations of the drugs in the mixture; (iv) drug combinations which were effective at low levels in inhibiting one test yeast were also generally effective against other species, but the levels of susceptibilities and, to a lesser extent, the best ratios of drugs in the test combinations varied with species; and (v) to quantitatively evaluate drug interactions, it is necessary to carefully define and control all experimental conditions, absolute and relative concentrations of drugs used, and the organisms tested.

Antifungal Agents↗
PubMed1987

Prostaglandin associated mortality following intravenous injection of catfish epidermal secretions in rabbits.

Toxicity of soluble protein extracts from epidermal gel secretions of the catfish, Arius thalassinus, was examined in rabbits. Intravenous injections containing doses as low as 2 mg protein/kg body weight caused mortality in all animals tested. An increase in plasma levels of thromboxane B2 (TXB2) and of 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) were observed following injections. Both the mortality and prostaglandin release were prevented by pretreatment of rabbits with either indomethacin or hydrocortisone. A similar indomethacin sensitive induction of prostaglandin release was noted following the in vitro treatment of arterial tissue sections with gel. Lethality appears to result from gel substances stimulating phospholipase activity to yield arachidonic acid, which is then metabolized to give toxic levels of prostaglandins.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

A hemolytic protein secreted from epidermal cells of the Arabian Gulf catfish, Arius thalassinus (Ruppell).

1. A fright or shock induced toxic secretion (gel) from the epidermis of the Arabian Gulf catfish, Arius thalassinus, exhibits hemolytic activity when tested against red blood cells from many different sources. 2. An enzyme with hemolytic activity, which represents 1.1% of the total soluble gel protein fraction, has been purified to homogeneity. 3. Molecular sieve chromatography and SDS polyacrylamide gel electrophoresis of the purified protein indicate a mol. wt of 34,000. 4. One additional protein component with hemolytic activity was found in the epidermal secretion. 5. Specific activity of the catfish epidermal factor is 20.6 units/mg protein, a level somewhat lower than those of most protein hemolytic factors. 6. The catfish hemolytic factor was not ichthyotoxic when tested against small fish and did not cause lethality when administered intravenously to rabbits.

Animals↗
PubMed1987

Protein composition of the threat induced epidermal secretion from the Arabian Gulf catfish, Arius thalassinus (Ruppell).

1. When threatened or injured, the Arabian Gulf catfish (Arius thalassinus, Ruppell) secretes a thick gel-like layer of proteinaceous material to its skin surface mainly from unicellular glands of the epidermis termed club cells. 2. Since a preparation from this secretion has been implicated in stimulation of the rate of wound healing in man and other test animals, the total gel protein composition was analysed by chemical, chromatographic and electrophoretic techniques. 3. Gel proteins were separated into soluble and insoluble fractions by extractions with increasingly strong solubilizing agents and the most insoluble components were solubilized only upon treatment with 10% SDS or concentrated organic acids. 4. Some of the soluble proteins from the secretion are also present in the insoluble protein fractions, indicating that the insoluble material is formed in part by aggregation of the soluble proteins. 5. The secretion was shown to be distinct from the catfish venom and differed greatly from typical fish mucus secretions in its composition and distribution of protein components.

Amino Acids↗
PubMed1986

Vasoconstrictor components in the Arabian Gulf catfish (Arius thalassinus, Ruppell) proteinaceous skin secretion.

The Arabian Gulf catfish (Arius thalassinus, Ruppell) produces toxic substances from its skin and from venom glands located near the base of the pectoral fins. Investigation of the pharmacological properties of the skin toxin have previously shown cholinergic vasoconstrictor activity in umbilical arteries. Cholinergic vasoconstriction was confirmed in sheep renal arteries. This activity was partially blocked by atropine, while most of the residual contraction was eliminated by simultaneous addition of indomethacin. Skin toxin treatment of arterial specimens caused a release of prostaglandin (PGE2, TXB2 and 6-keto-PGF1 alpha) into the organ bath. Prostaglandin release was blocked by pretreatment with indomethacin. Heat denaturation of skin toxin caused a loss of only the indomethacin-sensitive muscle contraction activity; most of the residual activity was blocked by atropine.

Animals↗
PubMed1986

Purification and properties of a hemagglutination factor from Arabian Gulf catfish (Arius thalassinus) epidermal secretion.

A galactose specific lectin was isolated from an epidermal proteinaceous gel secretion of the Arabian Gulf catfish, Arius thalassinus, Ruppell. The lectin was extracted and purified to near homogeneity by exclusion chromatography, affinity chromatography and isoelectric focusing. The lectin appears to be active as a single polypeptide chain with a mol. wt near 200,000, which can form oligomers and heteropolymers. The lectin comprises about 2% of the total gel protein, lacks carbohydrates and contains no unusual types or amounts of amino acids. The lectin agglutinates a wide range of red blood cell types.

Animals↗
PubMed1986

Lipid composition of the epidermal gel secretion from the Arabian Gulf catfish (Arius thalassinus Ruppell).

Lipids associated with a threat induced epidermal gel secretion from the catfish, Arius thalassinus, have been analyzed. Phospholipids, neutral lipids and glycolipids are all present and each of these subclasses has been analyzed by thin layer and gas chromatography with a general similarity with membrane lipids being noted. The epidermal gel lipids differed from total liver lipids of the catfish. Fatty acid analysis showed the gel lipid to be rich in the unsaturated fatty acids: oleate (omega 7, C18:1), arachidonate (omega 6, C20:4), and docosahexaenoate (omega 3, C22:6). Some prostaglandins were quantitated in lipid extracts from the epidermal gel.

Animals↗
PubMed1985

Isolation and characterization of metmyoglobin reductase from yellowfin tuna (Thunnus albacares).

The isolation, purification, and characterization of metmyoglobin reductase from yellowfin tuna (Thunnus albacares) is described. The enzyme has been purified 120-fold. Characterization of the enzyme includes molecular weight, isoelectric point, substrate specificity, enzyme kinetics, chromatographic behavior, and sensitivity to inhibitors. The physical and catalytic properties of the tuna enzyme are compared to those of bovine and blue-white dolphin metmyoglobin reductase.

Animals↗
PubMed1983

An acyl-thioesterase from yeast mitochondria.

A previously unstudied acyl-coenzyme A thioesterase activity has been demonstrated in submitochondrial particles from Saccharomyces cerevisiae. The preferred substrate for the enzyme activity is oleoyl-coenzyme A. Tests with inhibitors of the thioesterase showed that, in addition to common thiol inhibitors, the oxidative phosphorylation inhibitors oligomycin and venturicidin also blocked thioesterase activity. Purification of the enzyme catalyzing this activity revealed that thioesterase copurified with mitochondrial ATPase. When thioesterase was isolated from oxidative phosphorylation mutants selected for resistance to these two inhibitors, thioesterase activity was also resistant. The results suggest that thioester hydrolysis may be catalyzed by components associated with the isolated ATPase complex. Further attempts to link this activity to in vivo function of ATPase were not successful.

Ethylmaleimide↗