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At least 613 records · Page 34Linked to original sources
PubMed2003

Inertial shear forces and the use of centrifuges in gravity research. What is the proper control?

Centrifuges are used for 1 x g controls in space flight microgravity experiments and in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces contribute significantly to the total force acting on the cells or tissues. The inertial shear force artifact should be dealt with for future experiment hardware development for Shuttle and the International Space Station (ISS) as well as for the interpretation of previous space-flight and on-ground research data.

Acceleration↗
PubMed1990

[Effects of DEAE-dextran, centrifugation, cycloheximide and their combination on infection and growth of Chlamydia psittaci bird isolates].

In order to establish a stable and uniform cultural method in a cell line HaLa 229, we studied the effect of DEAE-dextran, centrifugation, cycloheximide and their combination on infectivity and progeny yields of Chlamydia psittaci isolated mainly from birds. Of 11 strains (10 avian and one human origin Ito strain), 9 showed maximal inclusion formation when host cells were treated with a combination of dextran and cycloheximide. Of the other two strains, one showed maximum inclusion formation with dextran alone and any treatments did not enhance the inclusion formation in another strain. Maximal yields of progeny at 48 hours after infection was observed in 5 (4 avian and Ito) strains when host cells were treated with a combination of dextran and cycloheximide. One avian strain showed maximal yields with a triple treatment; dextran and cycloheximide combined with centrifugation. At 72 hours after infection, three avian and Ito strains showed maximal yields with a double treatment (dextran and cycloheximide) and other two avian strains showed that with a triple treatment (double treatment added with centrifugation). The results suggest that in a cell culture HeLa 229, the treatment with dextran and cycloheximide may provide an efficient isolation and growth pattern for most strains originated from birds.

Animals↗
PubMed1975

Direction finding by hornets under gravitational and centrifugal forces.

The effect of centrifugal and gravitational forces whose resultant ranged between 26 degrees and 45 degrees on comb construction by hornet workers was assessed experimentally. Comb construction by hornets exposed to centrifugation at 1 to 2 days of age differed from that of hornets similarly exposed at 3 to 7 days of age. Juvenile hornets built their cells in the direction of the resultant force, whereas adults resisted the centrifugal force and tried to build in the direction of the gravitational force. Juveniles started their comb from the side walls, whereas adults started from the roof, as did nonspinning, control hornets. The findings suggest that hornets rapidly learn the gravitational force during the first days of life, and that they are aided by geometric cues of the breeding box to build in the direction of the force to which they had become habituated.

Age Factors↗
PubMed1965

Ribosomes: analysis by cesium sulfate gradient centrifugation.

Ribosomes from the cytoplasm of a mammalian tissue, HeLa cells, were partially purified and then concentrated into a zone by prolonged centrifugation in Cs(2)SO(4) solution (density, 1.43 grams per milliliter). Ribosomal preparations treated with bentonite prior to density-gradient centrifugation showed single peaks after centrifugation. Material recovered from the peaks represented aggregates of the original 74S particle.

Aluminum Silicates↗
PubMed1995

Precision and accuracy of recovery of Legionella pneumophila from seeded tap water by filtration and centrifugation.

Determination of the concentration of Legionella pneumophila in environmental water sites may be useful for the prediction of the risk of a particular site's causing Legionnaires' disease as well as for experimental studies of environmental growth or remediation. The precision and accuracy of recovery of two different L. pneumophila strains from seeded tap water samples were studied, with either filtration or centrifugation used to concentrate the bacteria. L. pneumophila grown on BCYE alpha agar or in Acanthamoeba castellanii was used to seed sterile tap water. Water samples were then either filtered (0.2-microns pore size) or centrifuged. An average of 53% (95% confidence interval [CI], 47 to 58%; n = 45) of the seeded L. pneumophila organisms were recovered by filtration with flat polycarbonate membranes. This recovery was significantly higher (P < 0.01) than that obtained by filtration with cast membranes (mean, 13%; 95% CI, 11 to 38%; n = 4) or by centrifugation at 3,800 x g for 30 min (mean, 14%; 95% CI, 2 to 25%; n = 9) or at 8,150 x g for 15 min (mean, 32%; 95% CI, 28 to 36%; n = 19). Recovery of L. pneumophila was not significantly different whether the bacteria were grown on plates or in amoebae. Use of a selective medium did not decrease the recovery efficiency, but preplating acid treatment of specimens caused an approximately 30% bacterial loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Centrifugation↗
PubMed1975

Biohazards assessment in large-scale zonal centrifugation.

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both the centrifuge chamber interior and rotor surfaces.

Air Microbiology↗
PubMed1975

Separation of viable Rickettsia typhi from yolk sac and L cell host components by renografin density gradient centrifugation.

Rickettsia typhi cultivated in the yolk sac of chicken embryos or in L cells irradiated 7 days previously was separated from host cell components by two cycles of Renografin density gradient centrifugation. Preliminary steps involved differential centrifugation and centrifugation over a layer of 10% bovine plasma albumin of infected yolk sac suspensions, or trypsinization and passage through filters of wide porosity of infected L cell suspensions. Rickettsial preparations obtained by these methods appeared to be free from host cell components while retaining high levels of hemolytic activity, egg infectivity, and capacity to catabolize glutamate. Average yields were 3.3 mg of rickettsial protein per yolk sac or 0.44 mg per 16-oz (ca. 475-ml) L cell culture. Extracts from these two preparations displayed malate dehydrogenase activity of electrophoretic mobility identical to each other but quite different in migration patterns from the corresponding host cell enzymes. This method of separation of rickettsiae from host cell constituents appears to be particularly well suited for the study of rickettsial enzymatic activity.

Animals↗
PubMed1982

Concentrated gram stain smears prepared with a cytospin centrifuge.

A Cytospin slide centrifuge was used to concentrate 0.05- to 0.5-ml samples of cerebrospinal and other body fluids for Gram stain. Trials with cerebrospinal fluid containing known numbers of microorganisms indicated that the Cytospin increased the sensitivity of cerebrospinal fluid Gram stains by up to 2 logs compared with unconcentrated and conventional centrifuge smears. Cytospin-concentrated smears were prospectively compared with unconcentrated Gram-stained smears and bacteriological culture results for 80 clinical body fluid specimens. Bacteria were seen in unconcentrated smears of 9 of the 16 (56%) fluids which were infected, whereas Cytospin smears of 12 of the 16 (75%) showed bacteria. Cytospin smears revealed more bacteria and demonstrated better leukocyte morphology than did unconcentrated or conventionally centrifuged samples of small volumes of infected body fluids, allowing early diagnosis of infection.

Bacteriological Techniques↗
PubMed1984

Effect of storage of the du Pont lysis-centrifugation system on recovery of bacteria and fungi in a prospective clinical trial.

A commercially available lysis-centrifugation system was compared with a conventional biphasic brain heart infusion medium in a prospective clinical study of 5,125 fungal blood cultures. Recovery rates were compared between two time periods to assess the effect of 25 degrees C storage before processing by the lysis-centrifugation system. The lysis-centrifugation tubes processed within 9 h showed a significantly higher yield (3.4 versus 1.49%) for yeasts (Candida glabrata), filamentous fungi (Histoplasma capsulatum), and bacteria (8.84 versus 7.34%) (Klebsiella pneumoniae and Serratia marcescens) than did those processed after 9 h.

Bacteria↗
PubMed1986

Rapid detection of herpes simplex virus in clinical specimens by centrifugation and immunoperoxidase staining.

The effect of immunoperoxidase staining and centrifugation on the sensitivity and rapidity of herpes simplex virus detection in mink lung cell cultures was determined with 730 clinical specimens. In standard tube cultures, the use of immunoperoxidase staining resulted in detection of 31 (91%) of 34 positive cultures after overnight incubation, compared with 25 (74%) detected without the stain (P less than 0.05). The effect of centrifugation of specimens onto the monolayer followed by overnight incubation and immunoperoxidase staining was studied with 431 specimens. Of 107 positive specimens, 103 (96%) were detected by this method, compared with 91 (85%) detected in standard cell cultures observed for 5 days (P less than 0.02). Standard cell cultures that were examined after overnight incubation detected only 62 (58%) of the 107 positive specimens (P less than 0.001). Centrifugation of clinical specimens onto cell monolayers followed by overnight incubation and immunoperoxidase staining is more rapid and sensitive than are standard cell culture techniques for the laboratory diagnosis of herpes simplex virus infection.

Animals↗
PubMed1987

Evaluation of a direct fluorescein-conjugated monoclonal antibody for detection of cytomegalovirus in centrifugation culture.

A fluorescein-conjugated murine monoclonal antibody (MAb) reactive with cytomegalovirus (CMV) was evaluated for the detection of CMV in centrifugation culture. Of 188 specimens, 90 were positive for CMV in centrifugation culture. The fluorescein-conjugated MAb detected CMV in 86 of 90 (95%) specimens at 16 h postinoculation, and 88 of 90 (98%) were positive at 36 h. The fluorescein-conjugated MAb can be used in a direct immunofluorescence assay that can be completed in 15 min following cover slip fixation. Use of this antibody in centrifugation culture provides a convenient and rapid assay for the identification of CMV.

Antibodies, Monoclonal↗
PubMed1990

Evaluation of isolator system and large-volume centrifugation method for culturing body fluids.

The Isolator system was compared with the large-volume centrifugation method for processing and recovering organisms from body fluids other than blood, cerebrospinal fluid, and urine. A total of 155 body fluid samples were processed for the recovery of clinically significant organisms. Of the 55 positive cultures, Isolator detected 94% and the large-volume centrifugation method detected 64%. The time necessary to indicate positivity was not significantly different in the two methods; however, in five cases, the Isolator system yielded clinically significant organisms 24 h sooner than the conventional method. The Isolator system was found to be a more sensitive alternative than the conventional large-volume centrifugation method.

Bacteria↗
PubMed1991

Comparison of the lysis-centrifugation and agitated biphasic blood culture systems for detection of fungemia.

Although the detection of fungemia has been improved by the use of vented or biphasic blood culture bottles, the best recovery and earliest detection have been reported in the Isolator lysis-centrifugation system. It was recently demonstrated that improved detection of both bacteria and fungi was accomplished by mechanically agitating blood culture bottles for the first 24 h of incubation. In this study the detection of fungemia by use of the Isolator system was compared with that of an agitated biphasic system. A total of 182 fungi were isolated from blood specimens inoculated into both culture systems. No difference in the overall recovery of fungi or individual species of yeasts was observed between the two systems. However, all seven isolates of Histoplasma capsulatum were recovered in the Isolator system only. The time required to detect fungemia with each of the two systems was also compared. No statistically significant difference was observed. From the data collected during this 18-month study, it can be concluded that the overall recovery and time of detection of yeasts are equivalent in the lysis-centrifugation system and the agitated biphasic blood culture system. The lysis-centrifugation system is still superior for the detection of filamentous fungi such as H. capsulatum.

Blood↗
PubMed1993

Reproducibility of lysis-centrifugation cultures for quantification of Mycobacterium avium complex bacteremia.

While quantitative mycobacterial blood cultures have been accepted as the standard for evaluating response to various Mycobacterium avium complex (MAC) treatment regimens, variability in this methodology has not been evaluated in a rigorous fashion. We thus studied the reproducibility of quantitative MAC cultures by a lysis-centrifugation culture system within and among five institutions. To measure the intralaboratory variation in mycobacterial colony counts, colony counts from duplicate blood specimens collected from 52 AIDS patients with MAC bacteremia were determined. Colony counts ranged from 0 to 50,000 CFU/ml. Nonparametric analyses revealed there was no significant difference in colony counts between the 52 duplicate specimens. The agreement between the intralaboratory paired specimens, as measured by the intraclass correlation coefficient, was 0.997. To measure the interlaboratory variation, multiple 10-ml aliquots from 12 patients were distributed to five institutions and processed within 24 to 32 h by lysis-centrifugation. For the 12 specimens distributed to the five laboratories, two-way analysis of variance for repeated measures revealed no significant difference in an individual patient's colony counts between laboratories (P > 0.2). We conclude that quantitation of mycobacterial colony counts by the lysis-centrifugation system is reproducible within and between institutions. Clinical trials evaluating response to therapeutic interventions for MAC can use multiple laboratories for quantitation of mycobacteremia. Furthermore, a 24- to 32-h delay in processing appeared to have no impact on reproducibility.

AIDS-Related Opportunistic Infections↗
PubMed2000

Comparison of rapid centrifugation assay with conventional tissue culture method for isolation of dengue 2 virus in C6/36-HT cells.

A rapid centrifugation assay was compared with conventional tube cell culture for dengue virus isolation in both sera and autopsy samples from dengue and dengue hemorrhagic fever/dengue shock syndrome fatal cases. The rapid centrifugation assay allowed isolation of virus from 16.6% more samples than the conventional method, and it shortened the time for dengue virus detection. Finally, it allowed the isolation of dengue 2 virus in 42.8% of tissue samples from five fatal cases. Our results suggest that the rapid centrifugation assay may be useful for detection of dengue virus in clinical specimens.

Aedes↗
PubMed2003

Processing sputum specimens in a refrigerated centrifuge does not increase the rate of isolation of Mycobacterium tuberculosis.

A total of 1,047 sputum samples from pulmonary tuberculosis patients was collected in cetyl pyridinium chloride-sodium chloride solution. Each sample was divided into two parts and randomly allocated for the isolation of Mycobacterium tuberculosis, with one part to be processed by the standard method and the other by a modified method. In the standard method, the samples were processed by using nonrefrigerated centrifuges, while in the modified method, they were processed by using a refrigerated centrifuge. Fifty-seven samples that yielded contaminants were excluded, and the remaining 990 samples were taken up for analysis. The rates of isolation of M. tuberculosis with the standard and modified methods were 48.6 and 48.1%, respectively, and the difference was not statistically significant (McNemar's test; P > 0.5). However, 51% of the positive cultures were isolated within 2 weeks with the modified method compared to 37% with the standard method (chi-square test; P < 0.001). The results of the study reveal that processing of sputum samples in a refrigerated centrifuge does not improve the rate of isolation but will result in rapid isolation of M. tuberculosis.

Centrifugation↗