Percent Inactivation Research Articles

Chlorhexidine: An effective anticovid mouth rinse.

Context:Dentists across the globe are witnessing a completely unforeseen and uncertain professional situation during these times of COVID-19 pandemic. There is conflicting evidence regarding the effectiveness of routinely used mouthwashes and especially Chlorhexidine, to reduce the viral load in oral cavity and the aerosols during oral procedures.Aims:Comparative evaluation of the effectiveness of the current 'gold standard' chlorhexidine and povidone iodine as a control agent, through an in-vitro analysis.Settings and Design:In-vitro laboratory analysis.Methods and Material:All the experiments for analysis of antiviral efficacy of chlorhexidine digluconate (2%)and povidone iodine(1%), against SARS-CoV-2 virus were performed in the BSL3 facility at the Council of Scientific and Industrial Research-Institute of Microbial Technology, using the VeroE6 cell lines. The analysis of the virus inactivation was based on quantification of viral RNA (Cycle threshold (Ct) profile) present in the culture supernatant using Real-Time Quantitative Reverse Transcription PCR (qRT-PCR).Statistical Analysis Used:Descriptive analysis (Statistical package for social sciences (SPSS Inc., Chicago, IL, version 15.0 for Windows).Results:Chlorhexidine digluconate in 0.2% concentration inactivated more than 99.9% of SARS CoV 2 virus, in minimal contact time of 30 seconds, which was considered better efficacy than povidone-iodine utilized for 30 and 60 seconds. Subtle differences were observed in the activity of both the compounds in terms of percent inactivation of virus, though a greater relative change in Ct values was observed for chlorhexidine.Conclusions:Within the limitations of the present study, it can be concluded that Chlorhexidine digluconate in 0.2% concentration inactivated SARS CoV 2 in minimal contact time i.e 30 secs, however both compounds tested i.e Chlorhexidine and povidone-iodine were found to have antiviral activity against SARS CoV2 virus.

Describing The Percent Inactivation Versus Force Relationships And Predicting True Force With Polynomial Regression

PURPOSE: The purpose of this study was to examine the percent voluntary inactivation versus submaximal force relationships with polynomial regression to predict each subjects' true maximal voluntary contraction (MVC) capabilities. METHODS: Nine participants (mean±SD age=21±3 yrs) completed nine randomly-ordered isometric plantar flexions from 10 to 90% of the MVC. Transcutaneous electrical stimuli were delivered to the tibial nerve using a high-voltage constant-current stimulator (Digitimer DS7AH, Herthfordshire, UK). Doublets were administered at a supramaximal stimulus intensity during the submaximal MVC plateau and then again 3-5 s after the submaximal MVC trial at rest. Percent inactivation was calculated for each submaximal MVC. The nine subjects selected for this study demonstrated < 5% voluntary inactivation at the 90% MVC, which suggested that these subjects were highly activated. Percent voluntary inactivation versus force relationships were analyzed on a subject-by-subject basis using polynomial regression (linear, quadratic, and cubic models). The predicted true MVC for each subject was extrapolated with their best fit polynomial model. A paired-samples t test was used to compare the actual MVC to the predicted true MVC. RESULTS: Polynomial regression indicated that 3 of 9 subjects (33%) were best fitted with a linear model, 2 of 9 subjects (22%) were best fitted with a quadratic model, and 4 of 9 subjects (44%) were best fitted with a cubic model. The t test indicated that the actual MVC (mean±SD 446±114 N) was greater than the predicted MVC (mean±SD 405±124 N) values (P = 0.003). Percent difference for each subject between actual MVC versus predicted MVC values ranged from 0.7% to 20.5%. CONCLUSIONS: Fitting the percent inactivation versus force relationships of highly activated subjects resulted in 33% linear and 66% nonlinear relationships. These results suggested that these patterns should be analyzed on a subject-by-subject basis. However, the predicted true MVC values from the best fit polynomial models were significantly less than the actual MVC values.

Stability of murine, chimeric and humanized antibodies against pre-S2 surface antigen of hepatitis B virus

We have constructed a humanized antibody with specificity for the pre-S2 surface antigen of hepatitis B virus (HBV) by grafting the complementarity determining regions (CDRs) of parental murine monoclonal antibody (mAb) into human anti-Sm antibody framework regions. The humanized antibody has a substitution at position 94 in a framework region of the heavy chain variable region, and exhibits the same antigen binding affinity as the parental murine monoclonal and chimeric antibodies. In order to assess the stability of these antibodies, thermal inactivation of the parental, chimeric and humanized antibodies was analyzed. Fifty percent inactivation of the chimeric and humanized antibodies was observed at 63.7 °C and 68.7 °C, respectively, compared to 55.0 °C for murine antibody. The humanized antibody also exhibited increased stability against denaturant. Guanidine-induced unfolding monitored by the changes in fluorescence intensity at 360 nm showed that midpoints of the transition of the chimeric and humanized antibodies were 2.47 M and 2.56 M, respectively, whereas that of the murine antibody was 1.36 M.

The effect of UV light on the inactivation of Giardia lamblia and Giardia muris cysts as determined by animal infectivity assay (P-2951-01)

This study measured the effect of germicidal ultraviolet (UV) light on Giardia lamblia and Giardia muris cysts, as determined by their infectivity in Mongolian gerbils and CD-1 mice, respectively. Reduction of cyst infectivity due to UV exposure was quantified by applying most probable number techniques. Controlled bench-scale, collimated-beam tests exposed cysts suspended in filtered natural water to light from a low-pressure UV lamp. Both G. lamblia and G. muris cysts showed similar sensitivity to UV light. At 3 mJ/cm 2, a dose 10-fold lower than what large-scale UV reactors may be designed to provide, >2-log 10 (99 percent) inactivation was observed. These results, combined with previously published data showing other protozoa and bacteria have similar, high sensitivity to UV light, establish that UV disinfection of drinking water is controlled by viruses which may require over 10-fold more UV dose for the same level of control.

The inactivation of single-chain urokinase-type plasminogen activator by thrombin on cultured human endothelial cells

Single-chain urokinase-type plasminogen activator (scu-PA) is cleaved by thrombin, resulting in an inactive molecule called thrombin-cleaved two-chain urokinase-type plasminogen activator (tcu-PA/T). There is no knowledge about cell-mediated inactivation of scu-PA. We have studied whether scu-PA bound to cultured human umbilical vein endothelial cells (HUVEC) could be inactivated by thrombin. High molecular weight scu-PA was bound to HUVEC and incubated with increasing amounts of thrombin for 30 min at 37°C. Cell-bound urokinase-type plasminogen activator (u-PA) was released and levels of scu-PA, tcu-PA/T and active two-chain u-PA were measured using sensitive bioimmunoassays. Cell-bound scu-PA was efficiently inactivated by thrombin. Fifty percent inactivation of scu-PA occurred at about 0.2 nM thrombin. In the presence of monoclonal anti-urokinase receptor IgG, at least 50% of the binding of scu-PA to HUVEC was inhibited. The relative amount of tcu-PA/T that was generated by thrombin was not affected by the monoclonal antibody. These results indicated that scu-PA bound to HUVEC via the urokinase receptor can be inactivated by thrombin. The efficient inactivation of cell-bound scu-PA suggests that a cofactor for thrombin may be involved, like thrombomodulin or glycosaminoglycans. It is concluded that scu-PA bound to the urokinase receptor on a cell surface can be inactivated by thrombin, which may have profound effects on u-PA-mediated local fibrinolysis and extracellular proteolysis during processes in which thrombin is also involved.

Temperature modulates the Ca 2+ current of HIT-T15 and mouse pancreatic β-cells

The effects of raising temperature on the Ca 2+, currents of insulin-secreting HIT and mouse pancreatic β-cells were studied. Currents were measured in 3 mM Ca 2+ containing solutions using standard whole-cell techniques. Increasing temperature from 22°C to 35°C increased peak Ca 2+, current amplitude, percent (fast) inactivation and decreased the time-to-peak of the current. Ca 2+ currents in HIT and mouse β-cells responded in the same manner to an imposed physiological burstwave with test-pulses: (i) application of the burstwave inactivated the test-pulse Ca 2+ current at both high and low temperatures; (ii) Ca 2+, current inactivation leveled off during the plateau phase at 20–22°C whereas there was an apparent continual decay at 33–35°C; and (iii) recovery from inactivation occurred during the interburst period at both temperatures. Application of a physiological burstwave without test-pulses to mouse β-cells before and after addition of 0.2 mM Cd 2+ resulted in a Ca 2+ difference current. This current activated during the hyperpolarized interburst phase, activated, inactivated and deactivated rapidly and continually during the plateau phase, and recovered from inactivation during the interburst. Although raising temperature strongly modified HIT and mouse β-cell Ca 2+ current, our work suggests that other channels, in addition to Ca 2+ channels, are likely to be involved in the control of islet bursts, particularly at different temperatures. In addition, the effect of temperature on islet cell Ca 2+, current may be partly responsible for the well-known temperature dependence of glucose-dependent secretion.

Cupric and ferric ions inactivate HIV.

Human immunodeficiency virus (HIV-1) was inactivated by either cupric or ferric ions when the virus was free in solution and also 3 hr after cell infection. Fifty percent inactivation of cell-free HIV was achieved with Cu(II) at a concentration between 0.16 and 1.6 mM, or by 1.8 to 18 mM Fe(III). Thus, the dose to inactivate 50% of infectious HIV (D50) by Cu(II) or Fe(III) is higher than that reported for glutaraldehyde (0.1 mM); between the D50 reported for sodium hypochlorite (1.3 mM) and sodium hydroxide (11.5 mM), and significantly lower than that required for HIV inactivation by ethanol (360 mM). Treatment of infected cells for 30 min at 20 degrees C with 6 mM Cu(II) or Fe(III) completely inhibited the formation of syncytia and the synthesis of virus-specific p24 antigen in HIV-infected cells, while still preserving cell viability. The virucidal properties of cupric and ferric ions could be exploited for the development of novel virucidal formulations efficient against HIV.

Auditory cortex neurons: primary culture and ion channel activity in rat.

We have developed a primary dissociated cell culture of the fetal (E17) and post-natal (P0-P10) rat auditory cortex. Pyramidal and non-pyramidal cells had a mean cross-sectional diameter of 12.73 +/- 1.80 microns (mean +/- S.D., n = 25) and 17.58 +/- 1.67 microns (mean +/- S.D., n = 10), respectively, measured at 6 days in culture. These cells were viable for as long as 18-21 days. They expressed voltage-gated sodium and potassium channel currents as early as one day in culture, and at various phases in cell culture. Sodium current, activated at membrane potentials more positive than -60 mV, displayed fast activation and inactivation kinetics. Fifty percent inactivation of sodium channels occurred at a pre-pulse potential of -63 mV. Delayed rectifier potassium channels were activated at potentials positive to -40 mV. Large hyperpolarizing constant current pulses elicited anode break action potentials, and large depolarizing constant current pulses exhibited rectification indicative of the delayed rectifying potassium channel activity.

Aging-related prolongation of calcium spike duration in rat hippocampal slice neurons

Calcium (Ca) spike potentials were investigated in cesium-loaded, tetrodotoxin (TTX)-treated CA1 pyramidal cells in hippocampal slices from young-mature and aged rats. The duration of single Ca spike potentials was prolonged in cells from aged rats, indicating that previously observed age-related changes in Ca-dependent mechanisms (e.g. in the K-mediated after hyperpolarization and in frequency potentiation) may result from an age-related increase of voltage-dependent Ca conductance. Since we recently found that Ca spike duration in hippocampus can be modulated strongly by a form of Ca-dependent inactivation of Ca current, spike inactivation paradigms also were examined. However, following 5- or 10-s-long depolarizing pulses, or during a 2-Hz train of elicited Ca spikes, there were no age differences in percent inactivation. These results do not support (but do not fully rule out) the possibility that impaired Ca-dependent inactivation underlies the increase in the Ca spike with aging. Conceivably, this prolongation of voltage-dependent Ca influx could have implications for our understanding of normal and abnormal brain aging.

Bicarbonate Inhibits Ribulose-1,5-Bisphosphate Carboxylase

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) rapidly extracted from leaves of wheat (Triticum aestivum) and purified activated RuBPCO were incubated in the presence and absence of 20 millimolar HCO(3) (-) and changes in activation state were followed. Rapid inactivation occurred in the presence, but not in the absence, of HCO(3) (-). Effects of CO(2) concentration and pH during preincubation before assay on activation state of RuBPCO were investigated in equilibrium studies. Twenty percent inactivation occurred at high CO(2) concentration if pH was high, but not if it was low, suggesting that RuBPCO was inactivated by HCO(3) (-). The inactivation by HCO(3) (-) was more rapid than the dissociation of activating CO(2) in CO(2)-free buffer (both in the presence of 20 millimolar MgCl(2)), suggesting that HCO(3) (-) was bound to the active enzyme complex. The dissociation of inactivating HCO(3) (-) from the enzyme was slow enough that inhibition could be demonstrated in experiments with HCO(3) (-) treatments during preincubation and constant conditions during assay. Inorganic phosphate did not seem to interfere with the binding of HCO(3) (-).

Ozone Concentration and Temperature Effects on Disinfection Kinetics

Abstract The cysts of the nonpathogenic soil and water amoeba, Naegleriagruberi strain (NEG), were inactivated using aqueous ozone in batch reactors at controlled temperatures (5–30°C) at pH 7. The semi-log plots of survival ratio vs. time consisted of an initial shoulder followed by a linear portion. The log-log plots of ozone concentration against time for 99 percent inactivation were essentially linear. The relationship between the overall inactivation rate and absolute temperature was well expressed by the Arrhenius theory. An empirical relationship was developed between the extent of cyst inactivation, ozone dose, temperature, and contact time.

Inactivation by 6-hydroxydopamine of the cerebral factor(s) responsible for the inhibition of the autoxidation of norepinephrine in vitro

The effect of extracts from rat cerebral cortex was examined on the stability of norepinephrine-HCl (NE) in 16 mM Na-phosphate buffer, pH 7.4, at 37°C. The autoxidation products of NE were detected spectrophotometrically at 480 nm. Dialysed samples from a synaptosomal preparation and from the 100,000 g supernatant of a crude homogenate were tested. Aliquots from these preparations, in the range of 0.005–5.0 or 0.01–10.0 μg protein/ml, respectively, produced up to 80–85% inhibition of the autoxidation of 100 μM NE for a period of at least 3 h. Similar results were obtained with albumin and ovalbumin at 10- and 10 3-times higher concentrations, respectively. After the preparations were exposed to 0.1–1.0 mg 6-hydroxydopamine-HCl/mg protein for 5 min at 25°C followed by rapid dialysis, the maximal inhibitory effect was reduced to between 95% to less than 5% of control values. The percent inactivation by a given quantity of 6-hydroxydopamine (6-OHDA) was inversely related to the potency of the untreated sample. Additional observations are presented which suggest that the destruction of the antioxidant activity is caused by breakdown products of 6-OHDA reacting with nucleophilic sites of the preparation. Similar inactivating substances are expected to be formed from other autoxidizing catecholamines, although at a slower rate.

Inactivation of DNA-polymerase associated with hepatitis B virus.

The effects of heat, sodium hypochlorite, diethyl ether, and ethyl alcohol on the activity of DNA polymerase (DNA-P) associated with hepatitis B virsus (HBV) in serum were evaluated. The response of DNA-P to heating at 60 degrees C for 15, 30, 45, 60, 90, 120, 180, and 240 minutes was studied and the data suggested that there may be two types of DNA-P. The majority of DNA-P was type 'a', and it showed a one log reduction (D60) at 60 degrees C in 36 minutes, while the remaining activity was type 'b' that showed a one log reduction (D60) in 340 minutes. Treatment of DNA-P with sodium hypochlorite at concentrations of 250 and 500 parts per million (ppm) of available chlorine resulted in a 20 to 25% reduction in DNA-P activity within one minute. Complete loss in detectable DNA-P activity occurred within one minute when available Cl- was 2500 ppm or greater. Various concentrations of ethyl alcohol (ranging from 10 to 70%) caused gradually increasing inactivation of DNA-P activity in ten minutes at 4 degrees C. Ninety percent inactivation occurred with 60% alcohol. Overnight treatment of DNA-P-reactive material with diethyl ether at 4 degrees C led to loss of detectable activity. A reduction in the titer of HBsAg was found following treatment with alcohol or ether. The possible use of DNA-P assay as an indicator of the rate of inactivation of HBV is proposed.

Anticoagulant activity of heparin octasaccharide.

Porcine intestinal heparin was partially digested with a purified heparinase and an octasaccharide with high-affinity for antithrombin III was isolated from the digest by gel filtration, followed by affinity chromatography on a column of Sepharose 4B coupled with antithrombin III. The anticoagulant activity determined by the activated partial thromboplastin time method of the octasaccharide was 240 units/mg. Fifty percent inactivation activities of the octasaccharide for thrombin and factor Xa in the presence of antithrombin III were 2 and 6.5 times, respectively, higher than those of the initial heparin. These data indicate that the octasaccharide possesses the critical structural integrities required for manifesting these biological activities.

Properties of soluble and membrane bound dopamine-beta-monooxygenase from bovine adrenal medulla cross-linked with dimethyl suberimidate.

Bovine dopamine-beta-monooxygenase from chromaffin granules in its soluble and membrane-bound forms was cross-linked with the bifunctional reagent dimethyl suberimidate, and its structural and kinetic properties were studied. 1. The cross-linking reaction does not affect the activity of soluble dopamine-beta-monooxygenase; it produces a ten percent inactivation in the membrane-bound enzyme, possibly because the linkage to other membrane proteins hinders its activity. 2. The soluble dopamine-beta-monooxygenase reaction mixture was analyzed by sodium dodecyl sulfate gel electrophoresis, showing appreciable amounts of dimer and tetramer, but only small amounts of trimer. In membrane-bound dopamine-beta-monooxygenase, subjected to the same treatment, appreciable amounts of dimer and higher aggregates were found. 3. The kinetic properties of soluble dopamine-beta-monooxygenase after the crosslinking reaction are the same as those of the native enzyme, with a ping-pong kinetic mechanism and the same real Michaelis constants for tyramine and ascorbate: KmT = 0.36 mM and KmA = 0.32 mM. Membrane-bound dopamine-beta-monooxygenase does not present a ping-pong mechanism before or after cross-linking; its real Michaelis constants are slightly modified by the cross-linking reaction: KmT = 0.4 mM and KMA = 0.4 mM.

Prostaglandin Inactivation in Normal and Sensitized Guinea-pig Lung and its Inhibition by Indomethacin

Based on the evidence of a rapid removal of prostaglandins (PGs) in the lung, inhibition of the pulmonary removal of PGE1 and PGF2α, was studied with isolated guinea-pig lungs. 1) In normal lungs, the average percent inactivation of PGE1 and PGF2α (5ng/ml) were 83.67±8.73% and 80.92±8.49%, respectively. 2) The percent inactivation of PGF1 and PGF2α decreased with increasing doses. 3) In normal lungs, the average percent inactivations of PGE1 and PGF2α, were 20.52±5.33% and 23.31±8.27%, respectively, with continuous infusion of indomethacin. 4) In sensitized lungs, the average percent inactivations of PGE1 and PG2α (5ng/ml) were 37.44±13.13% and 35.12±13.44%, respectively. 5) These results demonstrate that indomethacin has an inhibitory activity on PG inactivation, in addition to its already established activity on PG biosynthesis and that sensitization of lungs also inhibits inactivation of PGs per fused through the pulmonary vasculature.

X-Ray Induced Inactivation of the Capacity for Photosynthetic Oxygen Evolution and Nitrate Reduction in Blue-Green Algae

The level of inactivation of oxygen evolving photosynthesis in the green alga, Chlorella pyrenoidosa was 12 percent in N$sub 2$ at a dose of 100 krad of x irradiation. Under similar conditions, as well as under O$sub 2$, there resulted a 20 percent inactivation of the same function in the blue-green algae, Agmenellum quadruplicatum, strains PR-6 and AQ-6. Nitrate reduction capacity in the mutant AQ-6 was inactivated to 40 percent in N$sub 2$ and to 7 percent in O$sub 2$. Catalase and formate provided some protection from irradiation in O$sub 2$, suggesting some inactivation by H$sub 2$O$sub 2$. Most of the damage to the nitrate reduction system resulted from the direct action of x irradiation on a constitutive subunit of the nitrate reductase complex. Moreover, the slight inactivation of the O$sub 2$ evolving system, a function which is associated with photosystem II, cannot account for the inactivation of nitrate reduction. (auth)

Effect of sodium bisulfite modification on the arginine acceptance of E. coli tRNA Arg.

Escherichia coli tRNA Arg was treated with sodium bisulfite to convert exposed cytosine residues to uracil. This treatment resulted in the loss of amino acid acceptance of the tRNA Arg with pseudo first-order reaction kinetics. The active and inactive molecules were separated after about 60e active and inactive molecules were separated after about 60 percent inactivation and analyzed for U in various positions by finger-printing of the oligonucleotides produced by nucleases. The results show that C to U base transitions in the dihydrouridine loop and in the CCA terminus have no effect on the aminoacylation of this tRNA. Deamination of a cytosine residue at the second position of the anticodon resulted in the loss of amino acid acceptor activity of arginine transfer RNA.

The Effect of Oxygen Toxicity on the Inactivation of Bacteria by the Lung

he effect of prolonged oxygen administration on Thost defense mechanisms in the lung was evaluated by comparing the intrapulmonary inactivation of gram positive and gram negative bacteria. Bacterial viability and radiotracer activity in the lungs of approximately 2500 mice were quantified six hours after exposure to an aerosol of radiolabeled ( 32P ) Staphylococcus aureus or Proteus mirabilis. Control animals (Poz.120 mm Hg) inactivated 92.9 percent of the inhaled staphylococci and 89.5 percent of the Proteus inoculum. Prolonged adrninistration of 100 percent oxygen (Poz.700 mm Hg) resulted in progressive impairment of antibacterial defenses proportional to the duration of oxygen exposure. In those animals in which intrapulmonary bacterial inactivation exceeded intrapulmonary bacterial replication, there was 78.5 percent and 78.2 percent inactivation of the Gram-positive and Gramnegative bacterial challenge, respectively, after 24 hours, 69.2 'percent and 66.9 percent inactivation after 48 hours and 56.0 percent and 47.3 percent inactivation after 72 hours exposure to oxygen. In

Kinetics of quinone inactivation of Tulare apple mosaic virus

A direct assay technique was used to measure the kinetics of o-quinone inactivation of Tulare apple mosaic virus (TAMV). Inactivation occurred at rates measurable in seconds, minutes, or hours depending upon the particular quinone tested and the ratio of benzoquinone equivalents per milligram of virus used. The inactivation rate appeared independent of the absolute virus concentration. Inactivation rates were not linear at any quinone concentration measurable. However, inactivation data plotted according to the equation 1 I = ( b a )( 1 t ) + 1 a where I is the percent inactivation, a and b constants, and t exposure time, gave linear curves from which initial inactivation rates (percent virus inactivated in the first second) and minimum exposure times (times required to cause 100% inactivation) could be determined.