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ABSTRACT: Five strains of Candida albicans with previously characterized epidermolytic acid proteinase activity were evaluated for virulence following intravenous (i.v.) injection in mice. Increased proteinase activity was associated with increased virulence in female, NYLAR mice receiving 10(6) cells i.v. Mean mortality times (1.25, 2.0, 2.0, 4.25 and 19.6 days, in groups of 20 mice for each of the five strains) correlated directly with degree of proteinase activity. Three of the strains were selected for additional in vivo study and the association between increased proteinase activity and increased mortality rates was confirmed in dose-response studies in two additional strains of mice. The mean survival times appeared to be independent of fungal growth rate in vitro. These results support the positive correlation between proteinase activity and virulence.
Journal of medical and veterinary mycology: bi-monthly publication of the International Society for Human and Animal Mycology 02/1994; 32(1):59-64.
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ABSTRACT: Volatile anesthetics may depress transmission by altering synaptic concentrations of neurotransmitter. Microdialysis studies have found an increase in brain extracellular dopamine concentration on exposure to volatile anesthetics. We investigated the possibility that synaptosomal dopamine transport is reversibly inhibited by the halothane and isoflurane.
Rat brain synaptosomes were incubated with 5 nM 3H-DA and increasing concentrations of anesthetic in Teflon-sealed microvials. Cocaine (100 microM) was used to quantify non-specific binding/uptake. Uptake was stopped by vacuum filtration and washing; label incorporation into synaptosomes was determined by liquid scintillation counting. 3H-DA release from preloaded synaptosomes also was studied in the presence of the anesthetic to allow distinction between uptake inhibition and release stimulation in the synaptosomes.
Both halothane and isoflurane inhibited the specific 3H-DA uptake in a concentration-dependent fashion with an IC50 of 0.72 +/- 0.14 mM for halothane and 2.24 +/- 0.85 mM for isoflurane. No stereoselectivity of isoflurane's action on Dopamine (DA) uptake was observed. The inhibition produced by halothane and isoflurane was kinetically characterized as noncompetitive, but full reversal was demonstrated after removal of the anesthetic from the incubation mixture. The anesthetics did not stimulate 3H-DA release from preloaded synaptosomes.
These results demonstrate volatile anesthetic-induced inhibition of the dopamine transporter in this preparation of synaptosomes. The calculated IC50S suggest this inhibition occurs with clinically relevant concentrations of halothane but not with isoflurane. The results are consistent with and may explain the increase in extracellular dopamine concentrations demonstrated by microdialysis.
Anesthesiology 05/1993; 78(4):750-6. · 5.36 Impact Factor
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ABSTRACT: The hypothesis that volatile anesthetics act directly on or bind specifically to membrane proteins remains controversial. In earlier in situ electron probe microanalysis studies in cardiac muscle we showed preferential partitioning of halothane into mitochondria. To determine whether partitioning represents saturable binding or simple solubility, a photoaffinity labeling method was developed for halothane to examine binding in rat brain synaptosomes. Radioligand binding assays were then used to determine binding parameters for this important inhalational anesthetic. UV-light exposure of synaptosomes incubated with clinical concentrations of [14C]halothane resulted in sufficient labeling to allow characterization of binding sites. Analysis of saturation and competition curves showed that greater than 60% of [14C]halothane photolysis product binding to synaptosomes was specific, with low affinity (Kd = 0.49 +/- 0.16 mM) and high binding site concentration (Bmax = 1.87 +/- 0.75 nmol/mg of protein). Halothane photoaffinity labeling was partially inhibited by isoflurane (20%), chloroform (44%), 2-bromotrifluoroethane (20%), and dichlorotrifluoroethane (20%) but not by ethanol. The Kd measured with this photoaffinity approach is similar to the concentration of halothane required to produce anesthesia in rats.
Proceedings of the National Academy of Sciences 06/1992; 89(10):4329-32. · 9.68 Impact Factor
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ABSTRACT: Epidermolytic proteases were partially purified from six strains of Candida albicans, four of which were isolated from patients with cutaneous diseases. Two of the strains exhibited a unique time-course of enzyme production compared to that previously reported, with detectable epidermolytic protease levels being significantly delayed. All epidermolytic proteases had pH and temperature optima of 4-4.5 and 35-37 degrees C, respectively. These conditions are consistent with the microenvironment of human skin, a habitat where an epidermolytic protease would appear to be an important advantage to the yeast. Candida epidermolytic proteases were more active against a substrate of normal human epidermis than that obtained from psoriatic patients. When human epidermis replaced bovine serum albumin as the protein source within the culture medium, the epidermolytic activity of the resultant enzyme was reduced by 9 and 25% for normal and psoriatic epidermis substrates, respectively. The proteases were found to contain major protein bands at 42 and 66 kDa. The ability of these same Candida strains to adhere to human epidermal cells was studied and found to be optimal at 35-37 degrees C within neutral pH values. Pepstatin, bovine brain gangliosides, and convalescent human serum all interfered with the adherence of the yeast to epidermal cells. A higher yeast-epidermal-cell adherence for Candida was demonstrated on normal rather than psoriatic epidermal cells, and after treating the cells with partially purified Candida protease.
Clinical and Experimental Dermatology 06/1990; 15(3):183-91. · 1.20 Impact Factor
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ABSTRACT: [3H]Cocaine bound reversibly, with high affinity (KD 2.3 +/- 1.1 nM) and stereospecificity to rat liver microsomes. Little binding was detected in the lysosomal, mitochondrial and nuclear fractions. The binding kinetics were slow (T1/2 for association, 6 min and for dissociation 17 min), and the kinetically calculated KD was 2 nM. Induction of mixed function oxidases by phenobarbital did not produce significant change in [3H]cocaine binding. On the other hand, chronic administration of cocaine reduced [3H]cocaine binding drastically. Neither treatment affected the affinity of the liver binding protein for cocaine. Microsomes from mouse and human livers had less cocaine-binding protein and lower affinity for cocaine than those from rat liver. Binding of [3H]cocaine to rat liver microsomes was insensitive to monovalent cations and greater than 10 fold less sensitive to biogenic amines than the cocaine receptor in rat striatum. However, the liver protein had higher affinity for cocaine and metabolites except for norcocaine. Amine uptake inhibitors displaced [3H]cocaine binding to liver with a different rank order of potency than their displacement of [3H]cocaine binding to striatum. This high affinity [3H]cocaine binding protein in liver is not likely to be a monooxygenase, but may have a role in cocaine-induced hepatotoxicity.
Life Sciences 02/1988; 42(17):1675-82. · 2.53 Impact Factor
