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PubMed2005

Comparison of centrifugation and filtration techniques for the size fractionation of colloidal material in soil suspensions using sedimentation field-flow fractionation.

Sedimentation field-flow fractionation (SdFFF) with UV detection is used to systematically investigate the effect of traditional membrane filtration and centrifugation procedures on the isolation of specific size fractions from soil suspensions. Both procedures were used to isolate the nominal <0.45 and <0.2 microm fractions from a clay soil suspension. Results showed that the membrane filtration approach seriously underestimated the total mass of particulate matter present as compared to the centrifugation approach. This has serious implications forthe interpretation of results for "colloidal" and "soluble" fractions from soil suspensions and other environmental matrices obtained using the standard membrane approach. The results also show that sedimentation FFF has great potential as a robust and relatively mild technology for studying size distributions in the "colloidal" range for soil suspensions and other aquatic matrices.

Centrifugation↗
PubMed1991

Inoperable non-small-cell lung cancer (NSCLC): a Medical Research Council randomised trial of palliative radiotherapy with two fractions or ten fractions. Report to the Medical Research Council by its Lung Cancer Working Party.

Two policies of palliative thoracic radiotherapy for non-small-cell lung cancer have been compared in a randomised multicentre controlled trial. A total of 369 patients with inoperable, histologically or cytologically confirmed disease, too advanced for radical 'curative' radiotherapy, and with their main symptoms related to the primary intrathoracic tumour even if metastases were present, were studied. They were allocated at random either to a regimen of 17 Gy given in two fractions of 8.5 Gy 1 week apart (F2 regimen), or to a conventional multifractionated regimen of either 30 Gy in ten fractions or 27 Gy in six fractions (a biologically equivalent dose), given daily except at weekends (FM regimen). On admission, 93% of the patients had cough, 47% haemoptysis, 57% chest pain, 58% anorexia, and 11% dysphagia. As assessed by the clinicians, palliation of the main symptoms was achieved in high proportions of patients ranging in the F2 group from 65% for cough to 81% for haemoptysis and in the FM group from 56% for cough to 86% for haemoptysis. Haemoptysis, chest pain, and anorexia disappeared for a time in well over half the patients with these symptoms, and cough in 37%. For all the main symptoms, the median duration of palliation was 50% or more of survival. Performance status improved in approximately half of the patients with a poor status on admission. All these results were similar in the two treatment groups. As assessed daily by the patients using a diary card, the quality of life deteriorated slightly during treatment but then improved steadily during the next 5 weeks. The proportion of patients with dysphagia increased considerably during treatment, but fell to the pretreatment level during the next 2 weeks. The results were similar in the two groups. Radiation myelopathy was suspected in one (F2) patient. There was no difference in survival between the two groups (log-rank test), the median survival time from the date of allocation being 179 days in the F2 and 177 days in the FM group. In the light of all the findings, the regimen of two fractions of 8.5 Gy given 1 week apart is recommended.

Adult↗
PubMed1983

Fractionation of hagfish slime gland secretions: partial characterization of the mucous vesicle fraction.

This paper deals with the collection, fractionation and partial characterization of the slime gland secretion of the Pacific hagfish (Eptatretus stouti) with emphasis on the mucous fraction. Secretions were collected by electrical stimulation of the glands of anesthetized hagfish and, using three different methods, separated into three fractions: 1) the thread cells, 2) the mucous vesicles of the mucous cells, and 3) the soluble fraction. The methods take advantage of the stabilization of the thread cells and mucous vesicles by ammonium sulfate and sodium citrate.

Amino Acids↗
PubMed2005

Steepness of the radiation dose-response curve for dose-per-fraction escalation keeping the number of fractions fixed.

Clinically, there is growing interest in strategies for intensifying radiation therapy by escalating the dose per fraction. This paper considers the steepness of the dose-response curve in this case. The steepness of a radiation dose-response curve is most conveniently quantified by the normalized dose-response gradient, gamma. Under the assumption of a linear-quadratic dose-effect model, a simple analytical relationship is derived between the gamma-value for a dose-response curve generated by varying the total dose while keeping the number of fractions constant, i.e. escalating the dose per fraction, and the gamma-value for a dose-response curve generated by varying the total dose while keeping the dose per fraction constant. This formulation is compared with clinical dose-response data from the literature and shown to be in good agreement with the observations. Some implications of this formulation for non-uniform dose distributions delivered using 3D conformal radiotherapy or intensity modulated radiotherapy (IMRT) are briefly discussed.

Dose-Response Relationship, Radiation↗
PubMed1996

Comparison between radionuclide ejection fraction and fractional area changes derived from transesophageal echocardiography using automated border detection.

BACKGROUND: Left ventricular fractional area changes (FAC) can be derived from transesophageal echocardiography using an automated border detection system. However, FAC has not yet been compared to left ventricular ejection fraction (EF) evaluated by a reference technique. The aim of this study was to correlate transesophageal echocardiography automated FAC to EF derived from radionuclide angiography to obtain a quantifying method of global left ventricular systolic function at the bedside. METHODS: Ten critically ill patients, whose lungs were mechanically ventilated, were included in this prospective study. Patients were scheduled for radionuclide EF evaluation when at least 75% of the endocardium was clearly visualized on transesophageal echocardiography. Patients with esophageal pathology or cardiac dysrhythmia were excluded. Ejection fraction derived from radionuclide angiography was measured using technetium 99m. Echocardiographic data were obtained using an ultrasound system with automated border capabilities. Simultaneous measurements of left ventricular EF and FAC were obtained for each patient, both before and after starting a dobutamine intravenous infusion to modify left ventricular contractility. RESULTS: Mean values for radionuclide EF and transesophageal echocardiography FAC were, respectively: 55% +/- 19% (range 19-89%) and 46% +/- 18% (range 17-80%). Left ventricular EF and FAC were significantly correlated (r = 0.85, SEE = 9.6%). Variations of EF and FAC, induced by dobutamine, were also correlated (r = 0.70, SEE = 4.9%). CONCLUSIONS: Fractional area changes determined by transesophageal echocardiography using automated border detection correlate well with radionuclide EF and may be used at the bedside to quantify left ventricular function in selected intensive care unit patients.

Echocardiography, Transesophageal↗
PubMed1983

Immunogenic dialyzable factor derived from a ribosomal fraction of Salmonella typhimurium. I. Preparation of the protective dialyzable factor from the ribosomal fraction by the freeze-thaw procedure.

The preparation, properties, and immunogenicity of the dialyzable factor from a ribosomal fraction of Salmonella typhimurium are described. The ribosomal fraction was purified to eliminate O-antigenic components, by affinity chromatography (Sepharose-anti-O antibody conjugates used as immunoadsorbent). The dialyzable factor was obtained in the concentrated dialysate of the purified ribosomal fraction which was alternately frozen in dry-ice acetone and thawed in an 80 C water bath, for a total of five or six cycles. When this preparation was tested for its ability to protect mice against challenge with 1,000 LD50 of the homologous bacteria, it afforded 100% protection at a dose equivalent to 5.0 micrograms of RNA. The protection conferred by this factor was mainly cell mediated but immune serum enhanced this immunity despite the fact that no antibodies were detected in it. The protective activity of this factor was sensitive to RNase digestion but resistant to proteolytic enzymes. Ion exchange chromatography of this factor with DEAE-Sephadex A-25 (in 7 M Urea-0.02 M Tris-HCl buffer, pH 7.5) resulted in a single A260 peak which was found to be immunogenic. Chemical analysis of this peak after it was concentrated and desalted revealed that this immunogenic fraction was composed mainly of mixed nucleotides. The data indicate that protective immunity conferred by a ribosomal vaccine is associated with RNA but may not require the intact RNA molecule.

Animals↗
PubMedDate not supplied

The cardio-renal-anemia syndrome in elderly subjects with heart failure and a normal ejection fraction: a comparison with heart failure and low ejection fraction.

The prevalence and severity of anemia and renal dysfunction in heart failure patients with a normal ejection fraction (HFNEF) is uncharacterized. Two hundred eighty-five consecutive patients admitted to a community hospital with heart failure were stratified by the presence or absence of anemia and a normal or reduced ejection fraction. Comparisons of clinical variables were performed. In this sample, 62% of subjects were anemic, with no difference between those with a normal and a reduced ejection fraction (63% vs. 61%). Anemic HFNEF subjects had a lower glomerular filtration rate (37 +/- 21 mL/min vs. 52 +/- 35 mL/min; p < 0.05) and more severe self-reported symptom scores than nonanemic HFNEF subjects. Multivariate analysis confirmed the association of renal dysfunction and anemia. The authors conclude that the degree and magnitude of anemia in elderly inpatients with heart failure does not differ by ejection fraction. Worse symptoms and more severe renal dysfunction were seen in HFNEF subjects with anemia than in HFNEF subjects without anemia.

Aged↗
PubMed1991

Normal tissue reactions in the British Institute of Radiology Study of 3 fractions per week versus 5 fractions per week in the treatment of carcinoma of the laryngo-pharynx by radiotherapy.

The radiobiological data obtained from a multicentre clinical trial of the British Institute of Radiology, which compared the treatment of carcinoma of the laryngo-pharynx by 3 fractions per week (3F/wk) with 5 fractions per week (5F/wk) radiotherapy, have been studied. The trial involved an intake of 734 patients between 1966 and 1975. The number of fractions, overall treatment time and total doses used by different treatment centres ranges from 9 to 40 fractions, 18 to 70 days and 3880 to 7800 cGy, respectively. An 11-13% reduction in the total radiation dose was applied for treatments with 3F/wk as compared with 5F/wk in centres treating over 6 weeks and 3 weeks, respectively. All patients were followed for 10 years from the start of treatment. Different types of early and late normal-tissue reactions were investigated, ranging from a low percentage incidence of perichondritis to 95% for slight early reactions. Greater than 80% of the late normal-tissue reactions seen were observed within the first year after the start of treatment, and 96% were observed within the first 5 years. There was no statistically significant difference in the normal-tissue event-free rates between the 3F/wk and 5F/wk treatment groups. This finding did not differ when different major treatment centres were studied separately. For a number of end-points, alpha/beta ratios and N- and T-exponents of a modified nominal standard dose (NSD) formula have been calculated.

Adult↗
PubMed1992

DNA ploidy, S-phase fraction, and G2 fraction as prognostic determinants in human pancreatic cancer.

The DNA ploidy, S-phase fraction (SPF), and G2 fraction of pancreatic cancer tissue was measured by flow cytometry in 95 patients. Forty-nine per cent (n = 47) had a diploid DNA index, and 51% (n = 48) of tumours were aneuploid. Aneuploid tumours and high-grade tumours had significantly higher S-phase and G2-fraction values than diploid tumours or low-grade tumours. Diploid and tetraploid tumours had a more favourable prognosis than non-tetraploid aneuploid tumours (p = 0.0020) during the mean follow-up of 6 years. The type of therapy (p = 0.07), histologic grade (p = 0.06), SPF (p = 0.1), and G2 fraction (p = 0.02) had predictive value in survival analysis as well. In multivariate survival analysis, including flow-cytometric, histologic, and clinical variables, diploidy and tetraploidy had independent predictive value. The results suggest that flow cytometry might be used in grading of pancreatic cancer. Such a grading would have practical value if new modes of therapy are being developed. Forty-one per cent of multiple samples had a heterogeneous DNA index when multiple samples were used. Consequently, flow cytometric analysis of pancreatic cancer using multiple samples is recommended.

Adenocarcinoma↗
PubMedDate not supplied

Studies on fractionated hyperthermia in L1A2 tumour cells in vitro: response to multiple equal heat fractions.

The development of thermotolerance in L1A2 cells in vitro was investigated after fractionated hyperthermia at 42 degrees C. A single pretreatment of 90 min at 42 degrees C resulted in maximal thermotolerance at a 10 h fractionation interval with a thermotolerance ratio (TTR) of approximately 4.5. Thermotolerance was maintained at this level if the cells were exposed to 1-3 additional 90 min pretreatments separated by 10 h intervals. At a 6 h fractionation interval, where thermotolerance was still developing, additional 90 min pretreatments raised the level of thermotolerance to the level induced by the 10 h interval; the TTR increased from 2.1 to 4.5. Intervals of 20 and 24 h, at which there was decay but not complete disappearance of thermotolerance, did not induce such a build-up, and the TTR remained constant at 2.5 and 1.6, respectively. With 2 h fractionation intervals, where a single pretreatment did not induce thermotolerance, no thermotolerance was induced by additional pretreatments. With a shorter preheating time (e.g. 45 min at 42 degrees C) administration of a single pretreatment induced maximal thermotolerance after 6 h with a TTR of 3.0; additional 45 min pretreatments separated by 6 h intervals maintained this level. The thermotolerance induced by multifractioned hyperthermia as described above decayed in a similar way to that of cells exposed to a single pretreatment.

Animals↗
PubMed1976

Age trends in human chiasma frequencies and recombination fractions. II. Method for analyzing recombination fractions and applications to the ABO:nail-patella linkage.

A new method is presented for studying the relationship between human recombination fractions and parental age at the time of conception. Assuming the sex specific recombination fraction to be a linear function of age, a feasible computer algorithm is described whereby the likelihood of multigenerational families can be calculated. Using this method and the likelihood ratio test, it is found that for the ABO:nail-patella linkage age (P= .17)is more significant than sex (p= .23) in its effect on the recombination fraction. The age effect, if it is real, appears to be limited to males: the paternal recombination fraction decreases by .0062(+/- .0036) per year.

ABO Blood-Group System↗
PubMed1985

[Course of ejection fraction, regurgitation fraction and ventricular volumes during exertion in chronic aortic insufficiency. Study using technetium 99m gamma-cineangiography].

Previous studies have shown that variations of the ejection fraction (EF) during exercise were representative of the contractile state of the left ventricle: an increased EF on effort is considered to be physiological, whilst a decrease would indicate latent LV dysfunction unmasked during exercise. This hypothesis was tested by performing Technetium 99 gamma cineangiography at equilibrium under basal conditions and at maximal effort in 8 healthy subjects and 44 patients with pure, severe aortic regurgitation to measure the ejection and regurgitant fractions and the variations in end systolic and end diastolic LV volume. In the control group the EF increased and end systolic volume decreased significantly on effort whilst the regurgitant fraction and end diastolic volume were unchanged. In the 44 patients with aortic regurgitation no significant variations in EF, end systolic and end diastolic volumes were observed because the individual values were very dispersed. Variations of the EF and end systolic volume were inversely correlated. The regurgitant fraction decreased significantly on effort. Based on the variations of the EF and end systolic volume three different types of response to effort could be identified: in 7 patients, the EF increased on effort and end systolic volume decreased without any significant variation in the end diastolic volume, as in the group of normal control subjects; in 22 patients, a reduction in EF was observed on effort, associated with an increased end systolic volume. These changes indicated latent IV dysfunction inapparent at rest and unmasked by exercise; in a third group of 15 patients, the EF decreased on effort despite a physiological decrease in end systolic volume due to a greater decrease in end diastolic volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

On tests of equal effect per fraction in microcolony assays of survival after fractionated irradiations.

H. D. Thames, Jr. and H. R. Withers [Br. J. Radiol. 53, 1071-1077 (1980)] propose a test of an equal effect per fraction in microcolony assays after fractionated radiation, in which the total effect is measured by counting microcolonies derived from surviving cells in a tissue. The factors considered to influence the cytocidal effect per fraction are incomplete repair, repopulation, and synchrony. The statistics used in the method are criticized and conditions are given under which the test should not be used. An alternative method of testing for an equal effect per fraction is proposed. The pros and cons of each test are discussed and compared using some mouse jejunal crypt cell survival data.

Animals↗
PubMed1967

Antibiotic production of hyphal fractions of Streptomyces griseus. II. Streptomycin production of different fractions obtained by density gradient centrifugation.

The streptomycin-producing activity (SPA) of hyphal fractions from washed mycelium of submerged cultures of Streptomyces griseus strain 52-1, as obtained by density gradient centrifugation, was investigated. Activity of the various fractions differed strongly in intensity. The highest SPA was evident in the unfractionated mycelium. A synergistic effect upon SPA was found in the interaction of cultures of different ages, and a 55% increase in yield was obtained by mixing the 48- and 72-hr cultures. A synergistic effect occurred in all combinations studied. By use of fractions obtained from 72-hr mycelium for inoculation, differences in streptomycin production were noted. Some inoculum fractions yielded a greater amount of streptomycin (36%) than the unfractionated mycelial inoculum.

Centrifugation, Density Gradient↗
PubMed1980

[Analogies between "fraction P" with immunosuppressive properties in pregnant females and a protein fraction induced by estradiol treatment in the amphibian Salamandra salamandra L].

A "fraction P" analogue possessing immunosuppressive properties during pregnancy in the Salamandra, can be induced by treating males and females with oestradiol. Both fractions possess the same physiochemical characteristics, and equally react against a Rabbit immune serum anti "fraction P" of pregnant Salamandra. But the proteic fraction induced by hormonal treatment does immunosuppressive properties.

Animals↗
PubMed1982

Fractionated irradiation and haematopoiesis. III. Effect of time interval between fractions.

The effect of total single fractionated irradiation with short time interval on haematopoietic regeneration of the bone marrow and spleen was investigated. Also, the importance of first dose, when dose of 600 R was divided in two unequal fractions with time interval of 300s was studied. The investigation was performed on 25 day old rats. The dose of 600 R (X-rays) was divided on: 500 + 100, 400 + 200, 300 + 300, 200 + 400 or 100 + 500 R with time interval of 150, 300 or 600s. Ten days after irradiation the changes in blood, bone marrow and spleen were observed. After unequal fractionated dose with interval of 600s slight effect was found. The results after intervals of 600s and 300s were significant, when the total dose was divided in two equal doses. The first dose has no promoting role in haematopoietic regeneration when total dose was unequally fractionated.

Animals↗
PubMed1980

Fractionated irradiation and haematopoiesis. I. The effect of a differently fractionated radiation dose of 600 R.

The effect of the same dose of irradiation (600 R) divided into two different fractions (500 + 100 R; 400 + 200 R; 300 + 300 R) upon the haematopoietic system of young rats (25 days old) was investigated. Free interval between the first and the second dose was 5 minutes. Changes were observed in bone-marrow, spleen and blood in all the experimental groups of 10 days after the irradiation. Spontaneous regeneration of haematopoiesis after a single dose of 600 R is higher than after division of this dose into two fractions, excluding the group where the dose was divided into two equal fractions. The most intensive haematopoietic repopulation was found in the group of rats irradiated with 300 + 300 R, where the primary dose was the smallest. In fractional conditions, the first dose is of primary importance for the repopulating capacity of the haematopoietic system regardless of the short free interval.

Animals↗
PubMed1979

Fractionation of outdated freeze-dried plasma: a comparative study of cold- and heat-ethanol fractionation procedures.

In a comparative study a total volume of 1435 kg outdated freeze-dried plasma, equivalent to approx. 200,000 kg liquid plasma, was fractionated into albumin (20%): about 30% of the total plasma volume was fractionated following the cold-ethanol procedure and about 70% following the heat-ethanol method. Average albumin recovery following cold-ethanol preparation was 47% of the albumin originally present in the freeze-dried plasma (= 50% of total protein); following heat-ethanol fractionation, 71%. Gelfiltration of heat-ethanol albumin showed a main peak (= 93%) representing albumin monomers and one slightly faster component (= 7%) representing albumin dimers. Gelfiltration of cold-ethanol isolated albumin on the other hand showed four peaks: albumin monomers (= 60%), albumin dimers (= 15%), and two other peaks representing higher molecular weight molecules (= 25%). Hemoglobin present in the reconstituted plasma was reduced about five-fold in the cold-ethanol product and about ten-fold in the heat-ethanol albumin. Stability tests of both products did not differ from equivalent products isolated from normal human plasma. Besides albumin, immunoglobulins may be isolated as Cohn fraction II-III prior to the heating procedure without significant albumin loss.

Blood Banks↗