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At least 19 recordsLinked to original sources
PubMed1992

Detection of chronic hepatitis C virus infection by four diagnostic systems: first-generation and second-generation enzyme-linked immunosorbent assay, second-generation recombinant immunoblot assay and nested polymerase chain reaction analysis.

Serum samples from 100 patients with non-A, non-B hepatitis-related chronic liver disease and 100 patients with hepatitis B-related chronic liver disease were tested by first-generation and second-generation enzyme-linked immunosorbent assays, a second-generation recombinant immunoblot assay and the nested polymerase chain reaction. In non-A, non-B hepatitis-related chronic liver disease, second-generation enzyme-linked immunosorbent assay (anti-c22 and/or c200) and second-generation recombinant immunoblot assay showed 98% positivity, whereas first-generation enzyme-linked immunosorbent assay (anti-c100-3) showed 89% positivity. The two second-generation recombinant immunoblot assay-negative samples were positive by nested polymerase chain reaction, but one second-generation recombinant immunoblot assay-positive sample was polymerase chain reaction negative. However, when this second-generation recombinant immunoblot assay-positive sample was tested by polymerase chain reaction using another set of primers, it was polymerase chain reaction positive. Therefore, 100% of the non-A, non-B hepatitis-related chronic liver disease serum samples were hepatitis C virus RNA positive by polymerase chain reaction. Nine hepatitis B-related chronic liver disease samples were first-generation enzyme-linked immunosorbent assay positive. Of the eight second-generation enzyme-linked immunosorbent assay-positive hepatitis B-related chronic liver disease samples, six were first-generation enzyme-linked immunosorbent assay positive and five were second-generation recombinant immunoblot assay positive and polymerase chain reaction positive. One indeterminate second-generation recombinant immunoblot assay sample was polymerase chain reaction negative. Therefore, second-generation recombinant immunoblot assay appears to be as useful as polymerase chain reaction for detecting a chronic hepatitis C virus infection, although some discrepancies were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Analysis of the generation and inhibition of factor Xa. Area under generation curves is independent of enzyme generation rate.

The activation of factor X in the presence of antithrombin has been studied in order to determine the parameters that control the area under the resulting factor Xa generation curve. Generation curves were analyzed using a model containing three parameters: the total generation of factor Xa, Emax; the rate of factor Xa generation, expressed as a first-order rate constant, kappa 1; and the rate of inhibition, expressed as another first-order rate constant, kappa 2. Using factor IXa-VIIIa to activate factor X, we found the area under the generation curve to be proportional to Emax, which was varied by varying the factor IXa concentration, and inversely proportional to kappa 2, which was varied by varying the antithrombin concentration. With this activator, however, kappa 1 varied in parallel with Emax, resulting in a correlation between integrated area and kappa 1. In order to determine whether Emax or kappa 1, or both, was a controlling parameter, similar activations were done with varying concentrations of the factor X-activating enzyme of Russell's viper venom. With this activator it was possible to vary Emax and kappa 1 independently, again at varying antithrombin concentrations. These results showed the integrated area to be proportional to Emax and inversely proportional to kappa 2, as before, but independent of the activation rate, kappa 1. In this system, therefore, the area under the factor Xa generation curve is controlled by the amount of factor Xa generated and its rate of inhibition but is independent of the rate of factor Xa generation.

Animals↗
PubMed1989

Characterization of free radical generation by xanthine oxidase. Evidence for hydroxyl radical generation.

Xanthine oxidase has been hypothesized to be an important source of biological free radical generation. The enzyme generates the superoxide radical, .O2- and has been widely applied as a .O2- generating system; however, the enzyme may also generate other forms of reduced oxygen. We have applied electron paramagnetic resonance (EPR) spectroscopy using the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) to characterize the different radical species generated by xanthine oxidase along with the mechanisms of their generation. Upon reaction of xanthine with xanthine oxidase equilibrated with air, both DMPO-OOH and DMPO-OH radicals are observed. In the presence of ethanol or dimethyl sulfoxide, alpha-hydroxyethyl or methyl radicals are generated, respectively, indicating that significant DMPO-OH generation occurred directly from OH rather than simply from the breakdown of DMPO-OOH. Superoxide dismutase totally scavenged the DMPO-OOH signal but not the DMPO-OH signal suggesting that .O2- was not required for .OH generation. Catalase markedly decreased the DMPO-OH signal, while superoxide dismutase + catalase totally scavenged all radical generation. Thus, xanthine oxidase generates .OH via the reduction of O2 to H2O2, which in turn is reduced to .OH. In anaerobic preparations, the enzyme reduces H2O2 to .OH as evidenced by the appearance of a pure DMPO-OH signal. The presence of the flavin in the enzyme is required for both .O2- and .OH generation confirming that the flavin is the site of O2 reduction. The ratio of .O2- and .OH generation was affected by the relative concentrations of dissolved O2 and H2O2. Thus, xanthine oxidase can generate the highly reactive .OH radical as well as the less reactive .O2- radical. The direct production of .OH by xanthine oxidase in cells and tissues containing this enzyme could explain the presence of oxidative cellular damage which is not prevented by superoxide dismutase.

Cyclic N-Oxides↗
PubMed2001

Electroreception in Gymnotus carapo: differences between self-generated and conspecific-generated signal carriers.

Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish ('local self-generated fields') and on the skin of a conspecific ('local conspecific-generated fields') using a specially designed probe. Local self-generated fields showed a constant pattern along the body of the fish. At the head, these fields were collimated, much stronger than elsewhere on the fish, and had a time waveform that was site-independent. This waveform consisted of a slow head-negative wave followed by a faster head-positive wave. In contrast, time waveforms in the trunk and tail regions were site-specific, with field vectors that changed direction over time. Local conspecific-generated fields were similar to the head-to-tail field, but their spatio-temporal pattern at the skin depended on the relative orientation between the receiving fish and the emitting fish. Because self-generated fields had a slow early component at the head region, they displayed a low-frequency peak in their power spectral density histograms. In contrast, the conspecific-generated fields had time waveforms with a sharper phase reversal, resulting in a peak at higher frequency than in the self-generated field. Lesions in emitting fish demonstrated that waveform components generated by the trunk and tail regions of the electric organ predominate in conspecific-generated fields, whereas waveform components generated by the abdominal region prevail in self-generated fields. Similar results were obtained from Brachyhypopomus pinnicaudatus. These results suggest that, in pulse-emitting gymnotids, electrolocation and electrocommunication signals may be carried by different field components generated by different regions of the electric organ.

Animal Communication↗
PubMed1992

A comparison between one first generation and three second generation anti-HCV ELISAs: an investigation in high- and low-risk subjects in correlation with recombinant immunoblot assay and polymerase chain reaction.

One first generation assay (manufactured by Ortho, test I) and 3 second generation anti-HCV ELISAs (manufactured by Ortho, Abbott, and UBI, tests II-IV) were compared. Sera from 4 different sources were used: (1) intravenous drug-users (IVDUs, n = 50), (2) blood donors (n = 1055), (3) all clinical samples from one day of routine anti-HCV testing (n = 89), (4) hemodialysis patients previously found negative by test I but clinically suspected to have a HCV infection (n = 11). Confirmatory anti-HCV tests were carried out with a second generation recombinant immunoblot assay (RIBA II). In sera positive exclusively by test IV, one antibody consumption test (UBI HCV Neutralization EIA) and one further immunoblot assay (INNO-LIA HCV Ab) were used. PCR for HCV RNA was carried out on all hemodialysis patient sera and in the RIBA II positive blood donor sera. The second generation ELISAs discriminated 11 more positive samples than the first generation test (2 IVDUs, 5 blood donors, 4 clinical samples). The 9 sera from blood donors and clinical samples were all RIBA II positive or indeterminate. The second generation tests thus showed increased sensitivity. The second generation tests also showed increased specificity in that 4 samples that were positive by test I but negative by the second generation tests, were also negative by RIBA II. With few exceptions, all RIBA II-positive and most of the indeterminate samples were positive by the second generation ELISAs. With few exceptions, all the RIBA II-negative samples were negative by the second generation ELISAs. Eleven blood donor sera were positive by test IV exclusively where RIBA II and other supplementary assays were negative. The recently introduced second generation anti-HCV ELISAs were found to have a higher sensitivity than the first generation test. The tests also showed a good concordance with the exception of test IV in the group of blood donor sera.

Blood Donors↗
PubMedDate not supplied

Ocular defects in first generation of ethanol exposed albino rats and its penetrance into third generation.

BACKGROUND: The objective of this study was to observe the ocular teratogenic effects of alcohol on the third generation in albino rats. METHODS: This study was carried out at department of Anatomy, Basic Medical Sciences Institute, JPMC Karachi from 1996--98. 36 pregnant female rats were divided into a treated and a control group (18 in each). The gestation period of albino rats is between 21-23 days (7 days trimester). Treated group was injected 25% alcohol (ethanol) intraperitonealy in a dose of 0.03 ml/gm body weight, while the control group was treated with normal saline in the same dose by same route. This intervention was done on 8th, 9th and 10th gestational day. The first generation (n=115) was crossbred to get second generation (n=104) that was then used to produce the third generation (n=95). Generations of control rats were developed parallel. No treatment was given to the subsequent generations of treated or control groups. RESULTS: Ocular defects (micro/macrophthalmia, cataract, coreanl opacity etc.) were observed in 30% (39/115) of the first generation, 40.38% (42/104) of the second generation and 45.26% (43/95) of 3rd generation of ethanol treated group. No ocular defect was observed in the three generations of controls. CONCLUSION: Alcohol exposure caused ocular defects in three generations of exposed rats. There is a need to study subsequent generations of rats for further penetrance and to develop cohort study in humans.

Animals↗
PubMed1987

Failure to transmit diethylnitrosamine tumorigenicity from transplacentally exposed F1 generation Syrian hamsters to the respiratory tract of F2 and F3 generations.

A multigeneration study with four successive generations of Syrian hamsters was conducted to determine whether a single s.c. injection of different doses of diethylnitrosamine (DEN) (1.25, 2.5, 5, 10, and 20 mg/kg body weight) on day 15 of pregnancy induces respiratory tract tumors not only in the treated P generation mothers and their F1 progeny but also in F2 and F3 generations. In this study, the P generation mothers only were given a single injection of DEN during the period of gestation. Fifty-six % of the 36 DEN-treated mothers and 52% of their F1 generation offspring (total, 233 animals) developed neoplasms in the respiratory tract. A single respiratory tract tumor was found in one DEN-unexposed F1 generation control hamster as well as in one F2 generation animal (total, 209 animals) descended from DEN-exposed P generation. Both tumors were considered to have arisen spontaneously. No respiratory tract tumors were observed in the F3 generation (total, 160 animals) descended from a DEN-exposed P generation. Thus our results indicate that the vertical transmission of the tumorigenic effect of DEN in Syrian hamsters is limited to one generation and does not persist in the F2 and F3 generations.

Animals↗
PubMed1996

The effect on metabolic control of second-generation sulfonylurea drugs in patients with NIDDM after secondary failure to first-generation agents.

BACKGROUND: The literature contains few data examining the results of therapy with second-generation sulfonylurea drugs in subjects with non-insulin-dependent diabetes mellitus (NIDDM) after the onset of secondary failure to first-generation agents. The present study was undertaken to assess the efficacy of therapy with second-generation sulfonylurea in subjects with NIDDM following secondary failure to first-generation agents. METHODS: The study included 55 subjects with NIDDM who manifested secondary failure to first-generation sulfonylurea therapy. Of these, 29 subjects underwent therapy with the second-generation sulfonylurea glipizide, and 26 subjects were treated with glyburide, both drugs administered in the maximum daily dosage. Before initiation of the second-generation sulfonylurea agents and again at the end of 6 months, metabolic control was assessed by determination of fasting plasma glucose, glycosylated hemoglobin (HbA1c), and the lipid profile. RESULTS: Fasting plasma glucose and HbA1c levels were 209 +/- 31 mg/dL and 12.3 +/- 2.1%, respectively, before initiation of glipizide, and did not significantly change following therapy (fasting plasma glucose, 211 +/- 34 mg/dL; HbA1c, 11.7 +/- 1.8%). Similarly, no significant alteration was noted in these metabolic values in the glyburide group (before glyburide therapy, fasting plasma glucose, 180 +/- 16 mg/dL; HbA1c, 11.2 +/- 1.6%; after glyburide therapy, fasting plasma glucose, 184 +/- 20 mg/dL; HbA1c, 11.0 +/- 1.5%). Lipids also were not significantly altered following therapy with either glipizide or glyburide. Finally, for all subjects, fasting plasma glucose and HbA1c were 200 +/- 27 mg/dL and 11.9 +/- 2.0%, respectively, during treatment with first-generation drugs and did not change significantly following therapy with the second-generation agents (fasting plasma glucose, 205 +/- 20 mg/dL; HbA1c, 11.2 +/- 1.2%). P values were > .60 for all comparisons. CONCLUSIONS: Treatment with second-generation sulfonylurea agents for patients with NIDDM following onset of secondary failure to first-generation sulfonylurea drugs achieves no better metabolic control than treatment with first-generation agents.

Adult↗
PubMed2001

Evaluation of the 2nd generation radio-receptional assay for anti-TSH receptor antibodies (TRAb) in autoimmune thyroid diseases. Comparison with 1st generation and anti-thyroperoxidase antibodies (AbTPO).

BACKGROUND: The detection of autoantibodies to the TSH-receptor (TRAb) by radio-receptor assays (RRA) is widely requested in clinical practice for the diagnostic workup of Graves' disease and its differentiation from diffuse thyroid autonomy. Additionally, TRAb measurement can be useful during antithyroid drug treatment of Graves' disease to evaluate the risk of relapse after therapy discontinuation. Nevertheless, some patients affected by Graves' disease are TRAb-negative when 1st generation assay is used. METHODS: In this study we evaluated the diagnostic performance of a newly developed 2nd generation TRAb assay (TRAK human DYNOtest, BRAHMS Diagnostica GmbH, Berlin, Germany) in 74 untreated patients affected by Graves' disease, 53 untreated patients affected by Hashimoto's thyroiditis and 88 patients affected by euthyroid nodular goiter. We also compared the new TRAb assay with the 1st generation test (TRAK Assay, BRAHMS Diagnostica GmbH, Berlin, Germany) and anti-thyroperoxidase assay (AbTPO DYNOtest, BRAHMS Diagnostica GmbH, Berlin). RESULTS: The 2nd generation TRAb assay showed the better diagnostic sensitivity in Graves' disease (97%) with respect to the 1st generation assay (85%) and AbTPO assay (64%). The AbTPO assay was positive in 50 of 53 (94%) patients affected by autoimmune thyroiditis. The 1st and 2nd generation TRAb assays were positive in 4 (7%) and 7 (13%) of 53 patients affected by autoimmune thyroiditis, respectively. No patients affected by nodular goiter showed positive 1st and 2nd generation TRAb assay while AbTPO levels were positive in 8 of 88 patients (specificity 91%). CONCLUSIONS: In conclusion, the 2nd generation TRAb assay is clearly more sensitive than the 1st generation test and should be used in clinical practice to minimize the incidence of TRAb-negative Graves' disease. Long term prospective studies are needed to evaluate the prognostic role of 2nd generation TRAb assay in Graves' disease. The assay of AbTPO is the best marker for autoimmune thyroiditis but is clearly less sensitive than 1st and 2nd generation TRAb assays in Graves' disease. Consequently, AbTPO assay should not be performed in Graves' disease neither alone or in association with TRAb.

Autoantibodies↗
PubMed1994

Early detection of antibodies to human immunodeficiency virus 1 by a third-generation enzyme immunoassay. A comparative study with the results of second-generation immunoassays and western blot.

The aim of the study was to examine the sensitivity and the specificity of a HIV-1/HIV-2 third-generation enzyme immunoassay, the Abbott recombinant HIV-1/HIV-2 third-generation enzyme immunoassay, which is reported to detect simultaneously IgG and IgM. Sensitivity was evaluated with sera from seropositive subjects and a series of samples from eight HIV-1 seroconverting subjects. Results were compared with Western blot, second-generation immunoassays (including Vidas HIV-1 + 2) and an HIV-1 antigen assay. Specificity was studied with sera collected from a low-risk population and sera with false-reactive enzyme immunoassays results. In seven cases, the third-generation immunoassay detected HIV-antibodies several days earlier (range 4 to > or = 9 days) than the Western blot test according to the criteria proposed by the Association of State and Territorial Public Health Laboratory Directors, ie, positive with two of the three bands-gp160 or gp120, gp41, and p24. In the last case detection occurred at the same time as Western blot. The second-generation tests generally detected HIV-antibodies at the same time as Western blot. Antigaenemia was positive in the first samples tested in most cases, prior to or simultaneously with the Abbott third-generation test first reactivity, before the second generation tests and the Western blot test. In most cases, the disappearance of detectable HIV antigen was observed, and was concurrent with the development of the antibodies immune response. For our low-risk population, the current third-generation EIA test obtained a false-reactive rate of 0.26%. Our data indicate that the Abbott third-generation immunoassay is more sensitive than the Western blot test and the second-generation tests. The addition of a third-generation assay to the strategy for HIV-antibody screening may indeed be of interest and could make it possible to decrease the number of false-negative results.

Blotting, Western↗
PubMed2006

Simultaneous measurement of superoxide generation and intracellular Ca2+ concentration reveals the effect of extracellular Ca2+ on rapid and transient contents of superoxide generation in differentiated THP-1 cells.

We invented a simultaneous measuring instrument of fluorescence and chemiluminescence, realizing the analysis of chronological correlation between change in intracellular Ca2+ concentration ([Ca2+]i) and superoxide generation. A human monocytic cell line, THP-1, differentiated to be neutrophil-like cells generated superoxide with increase in intracellular Ca2+ concentration when stimulated with formyl-methionyl-leucyl-phenylalanine (fMLP) whereas PMA, phorbol ester-stimulated superoxide response occurred without change in [Ca2+]i. The cells treated with TMB-8, an intracellular Ca2+ antagonist, generated superoxide rapidly as well as transiently with transient [Ca2+]i elevation after stimulation with fMLP, whereas EGTA-treated cells generated superoxide slowly as well as persistently with transient [Ca2+]i elevation after the stimulation. These results suggest that the rapid and transient contents of superoxide generation are specific for Ca2+ influx from the extracellular domain. Verapamil, voltage-dependent Ca2+ channel blocker, dose-dependently inhibited fMLP-stimulated extracellular Ca2+ influx and superoxide generation without affecting PMA-stimulated superoxide generation. Other channel blockers tested, nifedipine and diltiazem, similarly inhibited these fMLP-stimulated responses. Numerical analysis of the values of the response curves elucidated that TMB-8 or the channel blocker reveals or eliminates the same contents of superoxide generation by the antagonism of intracellular Ca2+ release or extracellular Ca2+ influx, respectively. Taking these results together, the characteristic extracellular Ca2+ influx essential for superoxide generation was first revealed by the simultaneous measurement of superoxide generation and change in [Ca2+]i.

Calcium↗
PubMed1995

Birth weights of infants of first generation Asian women in Britain compared with second generation Asian women.

OBJECTIVES: To compare birth weights of infants of first generation Asian women (women born in the Indian subcontinent) with those of infants of second generation Asian women (born in the United Kingdom). DESIGN: Retrospective case note study. SETTING: Bolton District General Hospital. SUBJECTS: 331 Asian women who gave birth between January 1989 and December 1989: 220 of these women were first generation Asians and 111 were second generation Asians. MAIN OUTCOME MEASURE: Birth weights of babies born to first and second generation Asian women. RESULTS: At all gestational ages at delivery, babies born to second generation Asian women were heavier than those born to first generation women. The mean birth weight for babies of second generation women was 3196 g, 249 g more than the mean birth weight of 2946 g of babies of first generation women (P < 0.001). After a stepwise multiple regression analysis was carried out the adjusted difference in birth weights was 280 g, greater than the crude difference. CONCLUSION: Birth weights are important in relation to perinatal mortality, which is notoriously high among Asians. The results of this study indicate that there is hope for lowering of perinatal mortality and improving postnatal growth in babies of second generation Asians.

Adult↗
PubMed1989

The generation effect extended: memory enhancement for generation cues.

The generation effect is the greater memorability of a response that is actively produced (e.g., in answering a question from memory) than one that is more passively produced (as in reading the answer). The present three experiments addressed a question that is critical to the theoretical interpretation of the generation effect: Is memory enhanced for the cues that are used to elicit generated responses? Using incidental learning procedures, Experiments 1 and 2 gave an affirmative answer (although the effect was substantially weaker than the generation effect for responses). Enhancement of memory for generation cues was observed both in a within-subject/within-list design (reading and generation items within the same trial blocks; Experiment 1) and in a between-subjects design (reading and generation tasks for different groups of subjects; Experiment 2). In Experiment 3, memory enhancement for generation cues was used to produce a previously unobtained result--a generation effect for nonsense responses under incidental learning conditions. These findings provide critical evidence required by theories that interpret the generation effect in terms of enhanced processing of the cue-response item.

Cues↗
PubMed2002

The emergent generation effect and hypermnesia: influences of semantic and nonsemantic generation tasks.

The generation effect is moderated by experimental design, affecting recall in within-subjects designs but typically not in between-subjects designs. However, N. W. Mulligan (2001) found that the generation effect emerged over repeated recall tests in a between-subjects design, calling into question the generality of this limiting condition. In addition, the generate condition but not the read condition produced hypermnesia (increased recall over tests). The present experiments demonstrate that semantic-based (semantic-associate and category-associate) generation tasks produce this pattern of results whereas nonsemantic (letter transposition, rhyme, word fragment) generation tasks do not. Thus, the emergent generation effect appears to be a byproduct of semantic elaboration rather than a direct product of generation. In addition, high- and low-imagery words produced equivalent hypermnesia and emergent generation effects, arguing against a mediating role for imagistic encoding. Finally, there is no evidence of an emergent generation effect for nonwords, another traditional limiting condition of the generation effect.

Attention↗
PubMed1997

Resolution and purification of an aldehyde-generating and an alcohol-generating fatty acyl-CoA reductase from pea leaves (Pisum sativum L.).

Higher plant tissues produce both wax esters generated from fatty alcohols and hydrocarbons generated from fatty aldehydes. If two different reductases are responsible for the synthesis of aldehydes and alcohols, both types of reductases may be present in such tissues. To test for this possibility, pea leaves, known to produce both types of wax components, were examined. Subcellular fractionation showed that acyl-CoA reductase activities were localized mainly in the microsomal fraction. Fatty aldehyde formation was rectilinear for 30 min and subsequently decreased, whereas fatty alcohol formation remained linear for 2 h. The two activities in the microsomes were differently affected by pH; alcohol formation was optimal between pH 5 and pH 6, whereas aldehyde formation was optimal at around pH 7.5. With solubilized microsomes, protein concentration dependence of alcohol formation showed a sigmoidal pattern, possibly suggesting inhibition by hexadecanoyl-CoA at low protein concentrations. Bovine serum albumin (BSA) enhanced alcohol formation. In contrast, the aldehyde generation showed a typical protein concentration dependence, and BSA severely inhibited aldehyde generation. Phosphatidylcholine showed over twofold stimulation for alcohol formation, whereas aldehyde formation was only slightly stimulated. All of this biochemical evidence suggested the presence of two different reductases. Confirming this hypothesis, an aldehyde-generating and an alcohol-generating reductase were resolved from the solubilized microsomal proteins using Blue A agarose, gel filtration, and hexadecanoyl-CoA affinity chromatography. SDS-PAGE of the purified proteins showed that the alcohol-generating enzyme was a 58-kDa protein and the aldehyde-forming one was a 28-kDa protein. It is proposed that two different elongating systems are functionally coupled to the alcohol-generating and aldehyde-generating reductases, which in turn are coupled to the transacylase to produce wax esters and to the decarbonylase to produce hydrocarbons, respectively.

Alcohols↗
PubMed2002

Chemiluminescence of superoxide generated by Candida albicans: differential effects of the superoxide generator paraquat on a wild-type strain and a respiratory mutant.

We previously reported that a respiration-competent parent strain (K) of Candida albicans was more susceptible to the intracellular superoxide radical (O2-) generator paraquat (PQ) than was a respiration-deficient mutant (KRD-19), although both showed a similar sensitivity to extracellularly generated O2-. To clarify the cause of the differential PQ lethality, we developed a chemiluminescence method for measuring O2- generated by C. albicans cells by using the probe methyl-Cypridina-luciferin analogue (MCLA), and examined the effects of PQ on O2- generation in both parent and mutant strains. Endogenous O2- generation without stimulation by PQ was unexpectedly low in both strains. PQ-induced O2- generation in the parent strain was maximal in logarithmic phase cells and lowered in stationary phase cells. In contrast, O2- generation in the mutant remained low throughout the growth phase, even when stimulated by PQ. The extent of PQ-induced O2- generation in the parent strain depended on the carbon source added to the assay mixture; in decreasing order, glucose, glycerol, no carbon source. The inhibitor of the cytochrome respiratory chain, antimycin A, suppressed almost completely the PQ-induced O2- generation in the parent strain. It has been established that PQ is converted to its radical form (PQ+) by receiving a single electron in cells. PQ+ then reduces molecular oxygen to O2- by redox cycling. Thus, the high tolerance to PQ of the respiration-deficient mutant can be explained by minimal PQ+/O2- production due to the limited supply of electrons from the impaired respiratory system.

Candida albicans↗
PubMed2003

Electrical power generation characteristics of piezoelectric generator under quasi-static and dynamic stress conditions.

The electrical characteristics of a piezoelectric power generator are investigated under quasi-static (duration > 100 ms) and dynamic (stress duration < 10 ms) stress applications. The electromechanical model of piezoelectric generator is presented and used to explain the effects of the two stress conditions. A computer simulation of the piezoelectric generator is used to compare the theoretical and experimental results. The simulation predicts that a quasi-static stress will produce a bidirectional generator output voltage, and a dynamic stress will produce a unidirectional output voltage. The simulation also predicts that, when equal stresses are applied to the generator, the dynamic stress will generate a 10X higher output voltage than the quasi-static stress, contradicting results reported by other investigators. The output voltage is different for the two cases because of the generator's resistive capacitive (RC) time constant. The dynamic stress is applied in a time that is less than the generator's RC time constant, and the quasi-static stress is applied in a time greater than the generator's RC time constant. The piezoelectric capacitance has enough time to charge in the quasi-static case, resulting in the lower output voltage. The simulation results are experimentally verified for leaded zirconia titanate PZT 5H and PZT 5A materials. Simulated and experimental results are shown to be in good agreement.

Journal Article↗