Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0026916 (MAC)
 5,226 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Trans-1,2-dichloroethylene (t-DCE), an industrial solvent, proved to be moderately toxic when studied in small laboratory animals. In adult female rats brief (8 h) and prolonged (8 h daily, on 5 consecutive days a week, for more than 16 weeks) inhalation of 200 ppm--the current TLV/MAC in various countries--produced histological evidence of slight to severe fatty degeneration of the liver lobules and Kupffer cells. In addition marked pulmonary hyperaemia and alveolar septal distention were noted. Fibrous swelling of the cardiac muscle (with striation) just barely maintained) and hyperaemia remained detectable for as long as 14 h post-exposure, but only occurred at 3000 ppm/8 h. A concentration of 1000 ppm/8 h was required to produce a fall in blood albumin, urea nitrogen, alkaline phosphatase activities and erythrocyte count. The cited concentrations failed to produce prenarcotic symptoms of narcosis (central nervous system (CNS) depression). The LD50 was found to be 6.0 ml/kg i.p. and 1.0 ml/kg p.o. for female rats, and 3.2 ml/kg i;p. for female mice. In some of the rats killed in these experiments the organ changes were found to be identical to those observed after inhalation.
 ...
PMID:Toxicity studies on trans-1,2-dichloroethylene. 85 30

Tracheal mucociliary flow rates in dogs were measured with a radioactive droplet technique during thiopental anesthesia, and subseqently during halothane anesthesia. Body temperature and inspired gas temperature and humidity were held constant. Ventilation was controlled with 25 per cent oxygen in nitrogen to produce PaCO2 30 torr. Mucociliary flow rate remained constant when halothane concentration was held constant at 1.2 MAC halothane. Mucociliary flow rates at 0.6 MAC halothane were comparable to those after thiopental, 25 mg/kg. Increases in concentration from 0.6 to 1.2 to 1.8 to 2.4 MAC halothane progressively depressed mucociliary flow. Flow at 2.4 MAC halothane was 27 per cent of the control (thiopental) value. Flow returned to previous values as end-tidal halothane concentration was reduced. The depression produced by halothane may represent impairment of an important pulmonary defense mechanism.
 ...
PMID:Halothane depresses mucociliary flow in the trachea. 93 52

Following treatment with nitrosoguanidine, mutant derivatives of Rhizobium leguminosarum strain 3841 were isolated which failed to react with AFRC MAC 203. This monoclonal antibody normally recognizes a strain-specific lipopolysaccharide epitope which is developmentally regulated during legume nodule differentiation. Structural modification of lipopolysaccharide (LPS) was analysed by examining reactivity with a range of monoclonal antibodies with different epitope specificities, and also by analysis of LPS mobility changes after electrophoresis on polyacrylamide gels. One class of these LPS-defective mutants induced normal nitrogen-fixing (Fix+) nodules on peas (Pisum sativum), while another two classes of Fix- mutants were also identified, suggesting that a component of the LPS antigen that is part of the MAC 203 epitope is essential for normal nodule development leading to symbiotic nitrogen fixation. When grown under low-oxygen or low-pH culture conditions, one class of Fix- mutants completely lacked LPS-1 (the species that carries O antigen) and a second class showed a modified and truncated form of LPS-1. Mutants with defective LPS structure were also obtained after Tn5 mutagenesis of R. leguminosarum 3841 and all nine Fix- mutants were also found to lack the MAC 203 epitope. Three of these transposon-induced mutants synthesized a truncated form of LPS-1 that was structurally similar to that of the class of the NTG-induced mutants described above. These transposon-induced mutations, and the nitrosoguanidine-induced Fix- mutations, were closely linked and could be suppressed by the same cloned fragment of chromosomal DNA. The data presented here suggest that a precondition for normal nodule development of R. leguminosarum 3841 within pea nodules is the ability to synthesize relatively long-chain LPS-1 macromolecules under the physiological conditions encountered within the nodule. All mutants that lacked the ability to elongate LPS-1 macromolecules also failed to express the MAC 203 epitope.
 ...
PMID:Molecular dissection of structure and function in the lipopolysaccharide of Rhizobium leguminosarum strain 3841 using monoclonal antibodies and genetic analysis. 138 72

We examined the potential toxicity of desflurane in 13 young 25.0 +/- 2.3 (mean +/- SD) yr-old men, given 7.35 +/- 0.81 MAC-hours of desflurane anesthesia. Hepatic and renal function tests, serum electrolytes, and standard urine and hematologic tests were performed before, during, and after anesthesia. No toxicity was found. There were no changes in tests of hepatocellular integrity (plasma alanine transferase activity), synthetic function (serum albumin, prothrombin time, partial thromboplastin time), or renal function (serum creatinine concentration, blood urea nitrogen concentration). Decreases in red blood cell count, hematocrit, and blood hemoglobin concentration during and immediately after anesthesia were attributed to blood sampling and infusion of intravenous electrolyte solution. These values returned by 4 days after anesthesia to values not different from those before anesthesia. Increased white blood cell counts and blood glucose concentrations noted during anesthesia with other inhaled anesthetics were also seen in these volunteers. Desflurane appears to have no greater toxicity than currently used inhaled anesthetics and, because of its lesser metabolism, may have lesser or not toxicity.
 ...
PMID:Desflurane does not produce hepatic or renal injury in human volunteers. 155 24

The authors' aim was to examine direct cardiac responses to isoflurane, enflurane and halothane, as altered during mild hypoxia by the substitution of nitrogen (N2) for oxygen (O2), and additionally by the substitution of nitrous oxide (N2O) for N2. Heart rate, atrioventricular conduction time, left ventricular pressure (LVP), peak positive and negative derivatives of LVP (dLVP/dtmax), coronary flow, O2 delivery (DO2), percent O2 extraction, and myocardial O2 consumption (MVo2) were examined in 47 isolated guinea pig hearts. Changes in the ratio of DO2 to MVO2 indicated the relationship of autoregulation of coronary flow to myocardial O2 utilization. Each heart was first exposed to 96% O2 and then randomly exposed to 48% N2 and 48% N2O alone and with three equivalent concentrations of one of three volatile anesthetics: isoflurane (n = 15), halothane (n = 16), or enflurane (n = 16). Results were as follows: 1) N2 alone significantly decreased LVP, +dLVP/dtmax and -dLVP/dtmax, DO2 and MVO2; increased coronary flow; and produced no change in heart rate, atrioventricular conduction time, percent O2 extraction, or the DO2/MVO2 ratio. 2) Compared to N2, N2O alone only produced additional significant decreases in LVP and +dLVP/dtmax. 3) In the presence of N2 or N2O, each volatile anesthetic caused significant stepwise decreases in heart rate, LVP, +dLVP/dtmax and -dLVP/dtmax, MVO2, and percent O2 extraction; no additional change in coronary flow or DO2; and a stepwise increase in the DO2/MVO2 ratio. The effects of halothane and enflurane were generally greater than those of isoflurane. 4) Each volatile anesthetic caused an additive, parallel depression of LVP and percent O2 extraction as a function of MAC with N2O compared to N2. This study demonstrates that the direct negative inotropic effects of halothane and enflurane are more pronounced than those of isoflurane and are accompanied by a greater reduction in O2 utilization by halothane and enflurane than by isoflurane in the presence of mild hypoxia alone or with the addition of N2O. The study also demonstrates that N2O accentuates the negative inotropic effects of volatile anesthetics during reduced O2.
 ...
PMID:Comparison of halothane, enflurane, and isoflurane with nitrous oxide on contractility and oxygen supply and demand in isolated hearts. 174 98

Structural and chemical properties of a flavodoxin from Anabaena PCC 7119 are described. The first 36 residues of the amino-terminal amino acid sequence have been determined and show extensive homology with flavodoxins isolated from other sources. Anabaena flavodoxin exhibits a net negative change (-3) in the helix-1 segment as found with other cyanobacterial flavodoxins Synechococcus 6301 (Anacystis nidulans) and Nostoc MAC, but in contrast to the net positive charge found in this region in the case of flavodoxins isolated from nitrogen-fixing bacteria (Azotobacter and Klebsiella). The FMN cofactor can be reversibly resolved from the apoprotein by trichloroacetic acid treatment. Apoflavodoxin, thus prepared, binds FMN with a Kd value of 0.1 nM and binds riboflavin with a decreased affinity (Kd = 5 microM) at pH 7.2. The apoprotein is stable in dilute solutions at pH values around 7 but readily denatures at pH 8 as judged from loss in flavin-binding ability and by ultraviolet circular dichroism spectroscopy. Oxidation-reduction potential studies at pH values of 7 and 8 show OX/SQ couples of -195 mV and -255 mV, respectively, and show SQ/HQ couples of -390 mV and -418 mV, respectively. From these data, the binding constant for the FMN semiquinone is calculated to be approx. 5-fold tighter and the binding of the FMN hydroquinone is approx. 10(5)-fold weaker than that of the oxidized FMN to the apoprotein. Anabaena flavodoxin functions as an effective mediator of electron transfer from ferredoxin-NADP(+)-reductase to cytochrome c with a turnover number [4.5-5) x 10(3) min-1); a values similar to that determined for Anabaena ferredoxin. The flavodoxin binds tightly to the reductase with Kd values of 6.4 and 8.5 microM at pH values of 7.0 and 8.0, respectively.
 ...
PMID:Structural and chemical properties of a flavodoxin from Anabaena PCC 7119. 211 31

Rhizobium leguminosarum bv. viciae 3841 was grown in liquid suspension culture to investigate how culture conditions could affect the expression of a developmentally regulated cell surface antigen associated with lipopolysaccharide. The antigen, which is recognized by monoclonal antibody AFRC MAC 203, was expressed when cultures were grown at neutral pH under low-oxygen conditions (less than 7.5% [vol/vol] O2 in the gas phase). Antigen was also expressed in aerobically grown cultures at pH values below 5.3. The nature of the nitrogen and the carbon sources had no effect on antigen expression except by indirect changes on the pH of the culture medium; similarly, growth in 0.3 M NaCl did not result in antigen expression. The induction of MAC 203 antigen by low-oxygen or low-pH culture conditions is discussed in the context of tissue-specific expression within the legume root nodule.
 ...
PMID:Expression of a cell surface antigen from Rhizobium leguminosarum 3841 is regulated by oxygen and pH. 276 81

Monoclonal antibody AFRC MAC 203 recognizes a developmentally regulated lipopolysaccharide antigen in Rhizobium leguminosarum bv. viciae 3841. Transposon-induced mutants that constitutively expressed MAC 203 antigen were isolated. These strains were morphologically normal, showed no gross abnormalities in lipopolysaccharide size distribution on sodium dodecyl sulfate-polyacrylamide gels, and induced normal nitrogen-fixing nodules. However, the mutants lacked lipopolysaccharide epitopes recognized by another rat monoclonal antibody, AFRC MAC 281, suggesting that the corresponding epitopes may be interconverted or share a common precursor. In conjugational crosses, the transposon insertion associated with both the loss of MAC 281 antigen and the constitutive expression of MAC 203 antigen showed linkage to the chromosomal rif allele. A derivative of strain 3841 with a deletion spanning the nod-fix region of the symbiotic plasmid showed no altered expression pattern for MAC 203 antigen, suggesting that the relevant genetic determinants map to genomic sites that are not associated with nifA or any known genes on the symbiotic plasmid.
 ...
PMID:Genetic derepression of a developmentally regulated lipopolysaccharide antigen from Rhizobium leguminosarum 3841. 276 82

Among the non-depolarizing neuromuscular blocking drugs, atracurium appears to be unique in its ability to produce cerebral stimulation in lightly anaesthetized animals. This effect is attributed to the atracurium metabolite, laudanosine. The following studies were performed to determine if pretreatments with the non-depolarizing neuromuscular blockers pancuronium, atracurium or vecuronium would differ in their effects on the seizure threshold of lignocaine. Adult mongrel cats were anaesthetized with 1.0 MAC halothane in oxygen and nitrogen. Ventilation, blood-gas tensions, acid-base balance and temperature were controlled. Cats received pancuronium 0.2 mg kg 1 i.v. (n = 7), atracurium 1.0 mg kg-1 i.v. (n = 7) or vecuronium 0.2 mg kg-1 i.v. (n = 7). Ten minutes after the administration of the myoneural blocker, all cats received lignocaine 4 mg kg-1 min-1 i.v. until the onset of EEG evidence of generalized seizure activity. At seizure onset, there were no statistically significant differences among the cumulative lignocaine doses or the serum lignocaine concentrations in cats pretreated with pancuronium, atracurium or vecuronium.
 ...
PMID:Effects of atracurium, vecuronium or pancuronium pretreatment on lignocaine seizure thresholds in cats. 289 21

General anesthesia in combination with surgery is known to result in negative nitrogen balance. To determine whether general anesthesia without concomitant surgery decreases whole body protein synthesis and/or increases whole body protein breakdown, two groups of dogs were studied: Group 1 (n = 6) in the conscious state and Group 2 (n = 8) during general anesthesia employing halothane (1.5 MAC) in 50% nitrous oxide and oxygen. Changes in protein metabolism were estimated by isotope dilution techniques employing simultaneous infusions of [4,53H]leucine and alpha-[1-14C]-ketoisocaproate (KIC). Total leucine carbon flux was unchanged or slightly increased in the anesthetized animals when compared to the conscious controls, indicating only a slight increase in the rate of proteolysis. However, leucine oxidation was increased (P less than 0.001) by more than 80% in the anesthetized animals when compared with their conscious controls, whereas whole body nonoxidative leucine disappearance, an indicator of whole body protein synthesis, was decreased. The ratio of leucine oxidation to the nonoxidative rate of leucine disappearance, which provides an index of the catabolism of at least one essential amino acid in the postabsorptive state, was more than twofold increased (P less than 0.001) in the anesthetized animals regardless of the tracer employed. These studies suggest that the administration of anesthesia alone, without concomitant surgery, is associated with a decreased rate of whole body protein synthesis and increased leucine oxidation, resulting in increased leucine and protein catabolism, which may be underlying or initiating some of the protein wasting known to occur in patients undergoing surgery.
 ...
PMID:Anesthesia with halothane and nitrous oxide alters protein and amino acid metabolism in dogs. 304 37


1 2 3 4 5 6 Next >>