Pz Values Research Articles

Actividad proteinasa y fosfolipasa como factores de virulencia en especies de Candida aisladas de sangre

The number of nosocomial blood stream infections due to Candida species has increased over the past few decades. In order to establish an infection, opportunistic pathogens have to evade the immune system, survive, divide in the host environment, and spread to other tissues. Proteinase and phospholipase secretion has been implicated as potential virulence factors for some Candida species responsible for catheter related candidemia in intensive care unit (ICU) patients with indwelling devices. We therefore have aimed at demonstrating the secretion of proteinase and phospholipase enzymes as virulent factors by Candida species isolated from blood samples collected from ICUs, dialysis units and oncology units. One hundred and fourteen isolates of Candida species were obtained from the blood samples and the isolates include 37 Candida albicans, 7 Candida glabrata, 5 Candida guilliermondii, 3 Candida kefyr, 45 Candida krusei, 5 Candida parapsilosis, and 12 Candida tropicalis. Proteinase assay was performed by using the Staib et al method. Phospholipase assay was performed by using the method of Samaranayake et al. Precipitation zone (Pz value) was determined. The percentage of isolates which produced detectable amounts of proteinase is 74.56% and 44.73% of isolates produced detectable amounts of phospholipase. We believe that production of both phospholipase and proteinase enzimes could be an important virulence factor for several Candida species.

Diffusion-Weighted Imaging of the Prostate at 3 T for Differentiation of Malignant and Benign Tissue in Transition and Peripheral Zones

To evaluate prospectively the use of apparent diffusion coefficients (ADCs) for the differentiation of malignant and benign tissue in the transition (TZ) and peripheral (PZ) zones of the prostate diffusion-weighted imaging (DWI) at 3 T magnetic resonance imaging (MRI) using a phased-array coil. The DWI at 3-T MRI was performed on a total of 35 patients before radical prostatectomy. A single-shot echo-planar imaging DWI technique with b = 0 and b = 1000 s/mm2 was used. The ADC values were measured in both benign and malignant tissues in the PZ and TZ using regions of interest. Differences between PZ and TZ ADC values were estimated using a paired Student t test. Presumed ADC cutoff values in the PZ and TZ for the diagnosis of cancer were assessed by receiver operating characteristic analysis. The ADC values of malignant tissues were significantly lower than those of benign tissues in the PZ and TZ (P < 0.001; 1.32 +/- 0.24 x 10(-3) mm2/s vs 1.97 +/- 0.25 x 10(-3) mm2/s, and 1.37 +/- 0.29 x 10(-3) mm2/s vs 1.79 +/- 0.19 x 10(-3) mm2/s, respectively). For tumor diagnosis, cutoff values of 1.67 x 10(-3) mm2/s (PZ) and 1.61 x 10(-3) mm2/s (TZ) resulted in sensitivities and specificities of 94% and 91% and 90% and 84%, respectively. The DWI of the prostate at 3T MRI using a phased-array coil was useful for the differentiation of malignant and benign tissues in the TZ and PZ.

Phospholipase activity of Candida albicans isolates from patients with denture stomatitis: The influence of chlorhexidine gluconate on phospholipase production

Background and objectives The extracellular phospholipases of Candida albicans are considered to play a significant role in the pathogenesis of human infections. Therefore 23 clinical oral isolates of C. albicans from patients with denture stomatitis and 22 commensal oral isolates obtained from the palatal mucosa of healthy subjects were assayed for phospholipase activity. It is generally accepted that chlorhexidine gluconate is an appropriate adjunct or an alternative to antimycotic therapy in the management of oral candidiasis. However, the intraoral concentrations of this antiseptic fluctuate considerably due to the dynamics of the oral cavity. So the second main objective of this study was to investigate the effect of brief exposure (30 min) to two sub-therapeutic concentrations (0.002% and 0.0012%) of chlorhexidine gluconate on the value of phospholipase production (Pz) of C. albicans. Method An in vitro phospholipase production was done by plate assay method using an egg yolk–agar medium. Results No significant differences were found in the number of C. albicans isolates producing phospholipase between two groups. However, the mean value of Pz produced by the isolates from patients with denture stomatitis was significantly ( p < 0.05) higher than the commensals. Exposure of the isolates to 0.002% and 0.0012% chlorhexidine led to a significant ( p < 0.001 and p < 0.01, respectively) reduction in the amount of phospholipase. Conclusion The results of this study imply that sub-therapeutic levels of chlorhexidine may modulate candidal phospholipase activity, thereby suppressing pathogenicity of C. albicans.

Role of β-endorphin on phospholipase production inMalassezia pachydermatisin dogs: new insights into the pathogenesis of this yeast

Malassezia spp. are lipophilic yeasts that are part of the normal cutaneous microflora and sometimes act as pathogens causing dermatitis. This study investigated the interactions occurring between beta-endorphin and phospholipase activity in isolates of M. pachydermatis in dogs presenting cutaneous lesions. Phospholipase production was evaluated and quantified on 144 isolates suspended in Dixon broth to which different beta-endorphin concentrations (from 600 to 0.6 pM) were added. The isolates were divided into three groups: group A comprised isolates from lesional skin of dogs with dermatitis confined to one site, group B consisted of isolates from the healthy skin of the same dogs with localized lesions, and group C was made up of isolates from assorted skin sites of healthy dogs. A statistically higher phospholipase activity than that of the controls was recorded in group B at all tested beta-endorphin concentrations. In groups A (Pz=0.62) and C (Pz=0.62) phospholipase activity was statistically higher than the controls only at a concentration of 600 pM. This study suggests that beta-endorphin plays an important role in the production of phospholipase in M. pachydermatis isolates and provides evidence that beta-endorphin concentrations affect the number but not the Pz value of phospholipase-producing isolates. B-endorphin concentrations may play a relevant role in inducing M. pachydermatis cell differentiation towards the production or non-production of phospholipase.

Membrane topology of loop 13–14 of the Na +/glucose cotransporter (SGLT1): A SCAM and fluorescent labelling study

The accessibility of the hydrophilic loop between putative transmembrane segments XIII and XIV of the Na +/glucose cotransporter (SGLT1) was studied in Xenopus oocytes, using the substituted cysteine accessibility method (SCAM) and fluorescent labelling. Fifteen cysteine mutants between positions 565 and 664 yielded cotransport currents of similar amplitude than the wild-type SGLT1 (wtSGLT1). Extracellular, membrane-impermeant MTSES (−) and MTSET (+) had no effect on either cotransport or Na + leak currents of wtSGLT1 but 9 mutants were affected by MTSES and/or MTSET. We also performed fluorescent labelling on SGLT1 mutants, using tetramethylrhodamine-5-maleimide and showed that positions 586, 588 and 624 were accessible. As amino acids 604 to 610 in SGLT1 have been proposed to form part of a phlorizin (Pz) binding site, we measured the K i Pz and K m αMG for wtSGLT1 and for cysteine mutants at positions 588, 605–608 and 625. Although mutants A605C, Y606C and D607C had slightly higher K i Pz values than wtSGLT1 with minimal changes in K m αMG, the effects were modest and do not support the original hypothesis. We conclude that the large, hydrophilic loop near the carboxyl terminus of SGLT1 is thus accessible to the external solution but does not appear to play a major part in the binding of phlorizin.

Comparison of phospholipase and proteinase activity in Candida albicans and C. dubliniensis

Although the production of virulence enzymes by Candida albicans has been extensively explored, little attention has been given to the virulence factors of C. dubliniensis. In the present study, an attempt was made to investigate phospholipase activity (Pz value) and secretory aspartyl proteinase production of C. dubliniensis and compare it with C. albicans. None of the 87 C. dubliniensis isolates tested, produced phosholipases whereas, in contrast all the 52 (100%) C. albicans isolates tested demonstrated varying degree of phospholipase activity (Pz value: 0.37-0.74), with 35 (67.3%) of them eliciting a higher phospholipase activity (Pz values between 0.37 and 0.50). Only 32% of the C. dubliniensis isolates exhibited moderate activity (score of 1+) of secretory aspartyl proteinase whereas a vast majority (68%) of them were non-proteolytic. On the contrary, a strong proteinase activity (score of 2+) was observed for 79% of C. albicans while the remaining 21% isolates showed moderate proteinase activity (score of 1+). As phospholipases and aspartyl proteinases of C. albicans are considered important virulence factors, the absence or lowered expression of these enzymes in C. dubliniensis may indicate the less virulent nature of this novel yeast species when compared with C. albicans.

Investigation of desirable hydrostatic pressure required to sterilize Bacillus stearothermophilus IFO 12550 spores and its sterilization properties in glucose, sodium chloride and ethanol solutions

Desirable hydrostatic pressure required to sterilize Bacillus stearothermophilus IFO 12550 spores and its sterilization properties in glucose, sodium chloride and ethanol solutions were investigated. Spores were inactivated as treatment temperature (35 to 95°C) increased at 50 and 100 MPa. The Pz (pressure z) values were 29.32 MPa under the pressure ranged from 10 to 60 MPa and 545.6 MPa in under 60 to 100 MPa at 95°C. Therefore, 60 MPa was the desirable pressure to sterilize the spores at 95°C. Glucose, sodium chloride and ethanol respectively decrease the inactivation rate of the spores significantly ( P<0.05) except for 6% glucose. The spores were inactivated at 60 MPa, 95°C for 420 to 540 min in the media with various food additives. The PD (pressure D) values ranged from 75.2 min (containing no food additives) to 86.2 min (containing 20% ethanol).

Phospholipase activity in Cryptococcus neoformans: a new virulence factor?

Fifty isolates of Cryptococcus neoformans were examined for extracellular phospholipase production after inoculation onto egg yolk agar; 49 produced a pericolonial precipitate indicative of phospholipase activity. Phospholipase B (PLB), lysophospholipase, and lysophospholipase-transacylase activities were identified by radiometric analysis in supernatants from 4 clinical isolates. The ratio of colony diameter to colony plus precipitate on agar (Pz) correlated with PLB activity. Phospholipase production was similar in 12 environmental and 13 clinical isolates of C. neoformans var. gattii. Environmental strains of C. neoformans var. neoformans (n = 8) produced more phospholipase at 72 h than did 17 clinical isolates (mean Pz, 0.57 vs. 0.72; P < .01); however, Pz values were similar at 96 h. Quantitation of cryptococci in the lungs and brains of BALB/c mice inoculated intravenously with 4 strains expressing high, intermediate, or low phospholipase activity revealed a correlation between phospholipase activity and virulence. Phospholipases secreted by C. neoformans may be implicated in virulence.

Measurement of beam polarization using the D(, p)3H reaction

The D(d, p) reaction was used to measure the vector polarization of the deuteron beam from the atomic beam polarized ion source at King Fahd University of Petroleum and Minerals. The vector polarized deuteron beam was produced using a weak field transition. The polarization pz of the deuteron beam was determined from the measured asymmetry and known analyzing power Ay(θ) of the D(d, p) reaction with 200 keV deuterons. The experimentally determined value of pz was found to be −0.462±0.029 which is 69±6% of the maximum theoretical value. Within the statistical uncertainties, the measured beam polarization agrees with the value given by the manufacturer.

Characterization of the piston gauge to assess the suitability of its use with several working fluids up to 5 MPa

This paper describes the systematic studies carried out to characterize the controlled clearance piston gauge in the pneumatic pressure region up to 5.09 MPa by measuring its fall rate as a function of the jacket pressure (Pj) using different working fluids such as argon, nitrogen, helium, and hydrogen. It is also observed that a small ambient temperature fluctuation does not affect the overall uncertainty in the measured pressure. A relatively better reproducibility in the stall jacket pressure (Pz) values is obtained for helium and hydrogen as compared to that of argon and nitrogen; therefore it is shown that helium can also be used in addition to the commonly used nitrogen in the pneumatic pressure region. But the use of helium requires a higher value of Pj compared to that of nitrogen in order to get a good floating condition of the gauge. In addition, a detailed study is reported of the effective area of the simple piston gauge with different working fluids used during the calibration.

Characterization of a Controlled Clearance Piston Gauge Using Different Working Fluids up to 5 MPa

A systematic study carried out to characterize the controlled clearance piston gauge in the pneumatic pressure region up to 5.09 MPa full-scale pressure using different working fluids such as argon, nitrogen, helium and hydrogen is described. The characterization was conducted/carried out by measuring the fall rate of the piston as a function of the jacket pressure (Pj) in order to determine the stall jacket pressure (Pz) corresponding to the zero clearance between the piston and cylinder. A comparatively greater reproducibility in the Pz values is obtained for helium and hydrogen as compared to that of argon and nitrogen. The effects of the temperature of the operation on the fall rate in this piston gauge using gaseous nitrogen as the working fluid are also reported. It is observed that a small temperature fluctuation does not effect the overall uncertainly in the measured pressure.

Phospholipase activity as a criterion for biotypingCandida albicans

The phospholipase activity of 100 oral isolates of Candida albicans was determined by a plate assay. 94% of the C. albicans isolates were phospholipase producers with varying degrees of activity ranging from Pz values of 0.3 to 0.9. As variations in the degree of phospholipase activity on repeat testing of isolates was high it is concluded that the latter criterion cannot be usefully incorporated into a biotyping system of C. albicans.

Effects of viscosity, temperature, and rate of rotation on pressure generated by a controlled-clearance piston gauge

The calculation of the pressure generated by a controlled-clearance piston gauge depends upon the jacket pressure corresponding to zero clearance between the piston and cylinder Pz. The dependence of Pz on the viscosity of the pressure transmitting fluid, the temperature, and the rate of piston rotation have been measured. The four fluids used in this study have viscosities ranging from 0.7 to more than 10 000 cP. The value of Pz is nearly independent of viscosity below 60 cP. Above 60 cP, Pz depends strongly upon viscosity. Variations of Pz with temperature and rate of rotation are more severe at higher viscosities. The results suggest that the best choice of fluid is the one having the lowest viscosity at the operating pressure. Such a fluid can be selected on the basis of having the most nearly linear plot of Pz as a function of pressure of the candidate fluids. These results are also a clear indication that, for the most accurate pressure measurements, a controlled-clearance piston gauge must be characterized using the same operational and environmental conditions with the same fluid as are used in normal operation.

Factors affecting the phospholipase activity ofCandidaspeciesin vitro

The phospholipase activity of 41 isolates of oral Candida species was determined by a plate assay. Seventy nine per cent of the C. albicans isolates were phospholipase producers whereas none of the C. tropicalis, C. glabrata or C. parapsilosis isolates produced the enzyme. The degree of phospholipase activity (Pz value) of individual isolates was remarkably constant despite the large variation in activity among different isolates. Experiments with 10 phospholipase positive C. albicans isolates indicate that phospholipase production in vitro is limited to a narrow pH range (c. 3.6-4.7) and is suppressed by increasing concentrations of sucrose and galactose in the media (r = 0.9). Hence, candidal phospholipases seem to play a complex role in the aetiopathology of human candidoses.

Effects of Viscosity, Temperature, and Rate of Rotation on the Operation of a Controlled-Clearance Piston Gauge

ABSTRACTThe calculation of the pressure generated by a controlled clearance piston gauge depends upon the jacket pressure corresponding to zero clearance between the piston and cylinder, Pz;. The dependence of Pz; on the viscosity of the pressure transmitting fluid, the temperature, and the rate of piston rotation has been measured.The value of Pz; is nearly independent of viscosity below 60 cp. Above 60 cp, Pz; depends strongly upon viscosity. Variations of Pz; with femperature and rate of rotation are more severe at figher viscosities.These results are a clear indication that for the most accurate pressure measurements, a controlled-clearance piston gauge must be characterized using the same operational and environmental conditions with the same fluid as in normal operation.

Plate method for detection of phospholipase activity in Candida albicans.

Intracellular phospholipase activity has previously been detected in Candida albicans. A plate method is described which allows rapid detection and measurement of the extracellular activity in a number of clinical isolates. The ratio of colony diameter to diameter of the dense white zone of precipitation around phospholipase positive colonies, (Pz value), correlates with hydrolysis of [14C]phosphatidylcholine by concentrated culture filtrates of selected test isolates. A large variation in phospholipase activity is found between different isolates of C. albicans, however the Pz value is constant for any one isolate regardless of the site from which it is recovered in the patient. Fifty five % of fresh blood isolates are positive and these are also the most potent phospholipase producers. Fifth % of wound isolates and 30% of urine isolates are also positive. A larger sample group must be studied, however, before it can be determined whether these differences are highly significant.

Isoelectric points of proteins: A table

We have prepared a table of isoelectric points (pZ) of proteins selected from the literature. Initially, we retrieved a computerized bibliography from the MEDLARS data base covering the time period of January 1970-March 1976. This search, supplemented by an additional search of Biological Abstracts, produced about 3000 citations. From this bibliography we initially screened about 1000 papers and selected 400 for the table. These papers were chosen to be representative rather than comprehensive. Data obtained were collected according to the following scheme: 1. Only named proteins are recorded. Classes of proteins (ribosomal, membrane, etc.) are not included. 2. Only pZ’s obtained by isoelectric focusing in the presence of carrier ampholytes are included in the table. These values are taken directly from the text and have not been normalized for effects of temperature or other factors that might affect the apparent pZ. All values are rounded off to one decimal place. 3. pZ values were determined under nondenaturing conditions except where indicated (** denotes values obtained by isoelectric focusing in the presence of urea). pi’s for protein subunits have not been included. 4. In cases where there are several reports for the pZ of a given protein, we have selected only one of several references. This was usually the most accessible reference. 5. When only one or two major forms were present, those values are listed. With multiple forms, the pZ range is given. In a pZ range with one predominant component, that pZ is listed first and underlined, e.g., 5.7, 5.5-6.0 represents multiple forms with pi’s between 5.5 and 6.0, with the major component at pZ 5.7.

Expressions of gaseous concentration and dilution ratios

Ratios of dilution or concentration of a gas sample are expressed as a pollutant quotient, or, if appropriate, an odorant quotient, Z, denoting the ratio of a pollutant (or odorant) concentration to some target concentration. The expression pZ is defined as + log 10 Z, so that a positive value of pZ implies dilution and a negative value concentration. The effect of particulate matter on the Z function is considered. Various examples are given, including conversions from other common dilution expressions.

RELATIVE REACTIVITIES OF THE GEOMETRICAL ISOMERS OF HEXACHLOROCYCLOHEXANE

The dehydrochlorination of hexachlorocyclohexane to trichlorobenzene in an alcoholic solution of piperidine was investigated, and the relative reactivities of four geometrical isomers of hexachlorocyclohexane determined. Activation energies and PZ values for the alpha, gamma, and delta isomers were obtained; the beta isomer reacted too slowly under the conditions used for convenient rate studies to be made. The order of reactivity was found to be alpha, [Formula: see text]; the order of reactivity is interpreted on the basis of differing degrees of steric hindrance in the isomers.