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PubMedDate not supplied

[The study of the growth of tylosin producer using differential centrifugation of mycelium in a sucrose density gradient].

The mycelium of Streptomyces fradiae was fractionated by differential centrifugation in a sucrose density gradient (SDG) using various samples of the inoculation material and aliquots of the cultural broth taken in the course of tylosin production. The mode of mycelium distribution in SDG made it possible to select the most active inoculation material. The mycelium was redistributed from sucrose layers with a high density to those with a lower density in the course of fermentation. The fractions differed in the antibiotic activity but none of them had an activity higher than in the control centrifuged in 30% sucrose and washed off just like the fractions. Therefore, mycelium fractionation in SDG would not elevate its antibiotic activity. The paper presents the cytological characteristics of different fractions changing in the course of fermentation.

Centrifugation, Density Gradient↗
PubMedDate not supplied

[Effect of cardioactive compounds on myocardial actomyosin in the centrifuged rat].

It has been shown that during centrifugation the modulating effect of cardioactive compounds, particularly adrenalin and obsidan, varies in similarity to that of Ca ions. The reactivity of the native actomyosin complex of the heart of white rats to such agents declines during centrifugation. This may be associated with changes in regulatory protein components through which the modulating effect of the above compounds is mediated. Differences in the reactivity to adrenalin and obsidan that persist after 2-month readaptation can be attributed to the heterogeneous recovery of properties of individual subunits of regulatory proteins.

Actomyosin↗
PubMed1977

Bovine lymphocytes: enhanced E-rosette formation after storage or gradient centrifugation.

Incubation of bovine thymus lymphocytes with SRBCs for 1 hr or more at 0 degrees C during the E-rosette test gave higher rosette counts than tests receiving no such incubation. Further enhancement was seen if lymphocytes were stored in foetal calf serum (FCS) or BSA solutions at 4 degrees C for 18 hr prior to rosette tests. Best enhancement due to storage in BSA was seen when cells were subsequently tested in FCS. However, after storage in BSA many rosettes occurred when tests were done in BSA, Albeit few rosettes occurred in BSA without prior storage. Less enhancement was seen after storage in sodium metrizoate (NaM). Enhancement in FCS and 10% BSA occurred after 1 day, but not 2 or more days, of storage at 4 degrees C, but was not seen when cells were stored at 37 degrees C. Rosette formation was about doubled by centrifugation of lymphocytes through BSA gradients prior to rosette tests; centrifugation through NaM gradients had no such effect. It is suggested that rosette formation is a property of an immature bovine T cell, and that on storage some cells develop and subsequently lose the ability to form rosettes.

Animals↗
PubMed1988

Shrinkage of centrifuged cement.

Two postulated mechanisms for the failure of prosthetic implants secured with bone cement are: failure of the cement itself, and loosening at the bone/cement interface. Failure rate with cement can be reduced by increasing the strength of the cement, and loosening can be reduced by minimizing cement shrinkage during polymerization. This paper shows that centrifuging cement to reduce porosity (and presumably increase strength) results in a substantial increase in cement shrinkage over uncentrifuged cement. A second set of experiments demonstrated that pressurization of cement to four atmospheres during polymerization resulted in tensile strengths comparable with those reported for centrifuged cement. Thus, the use of uncentrifuged bone cement, pressurized during polymerization, should minimize implant failure rates.

Atmospheric Pressure↗
PubMed1988

Enucleation of phagocytic cells with adenine, guanine, and their nucleosides in combination with centrifugation.

Several purine compounds, such as adenine, guanine, adenosine, guanosine, and their related compounds, exhibited enucleation activity on adherent mouse peritoneal exudate cells (macrophages) during centrifugation at 25,000 and 35,000 g for 60 min at 34 degrees-36 degrees C in medium containing one of these compounds. Enucleation activity, however, did not occur in cells treated with adenine nucleotides, inosine, xanthine, or any of the tested pyrimidines. The purine compounds also had enucleation activity on mouse macrophage-like cell lines (P388D1 and RAW 264) and mouse polymorphonuclear leukocytes, but not on other typical cell lines such as a human epithelial cell line (HeLa S-3) or a mouse fibroblast cell line (L929). Cytochalasin B (CB) treatment, however, resulted in the enucleation of all cell types tested, even at a centrifugal force as low as 5,000 g. The process of macrophage enucleation was observed by both light microscopy and scanning electron microscopy. In enucleated macrophages that had been treated with purine compounds, but not with CB, a newly formed cytoplasmic crater-like structure (about 3-9 microns in diameter) was observed at the original site of the nucleus. Surface structures, such as microvilli and membrane ruffles, remained relatively intact in macrophages that had been enucleated by treatment with purine compounds. By contrast, these surface structures were markedly changed in CB-treated macrophages. Purine compounds may affect cytoskeletal elements in ways similar to the well characterized effects of CB, and thus result in the enucleation of phagocytes. However, the characteristic differences in the enucleation activity exhibited by purine compounds and CB may indicate that purines have a mechanism of action different from that of CB.

Adenine↗
PubMed1986

Depletion of donor lymphocytes by counterflow centrifugation successfully prevents acute graft-versus-host disease in matched allogeneic marrow transplantation.

Bone marrow from 22 histocompatible siblings was depleted of 98% of the lymphocytes using a combination of density flotation centrifugation followed by counterflow elutriation. Even with the marrow suppressive influence of methotrexate (MTX), the viability of the hematopoietic stem cells was not affected, as indicated by the normal repopulation after grafting in the evaluable patients. One patient (UPN 9) showed a primary graft failure, possibly resulting from persisting septicemia and long-term antibiotic therapy. Two patients have persistent host lymphocytes, one of whom was examined during relapse; the other remains in remission. Two patients did not receive immunosuppression after bone marrow transplantation (BMT), and acute graft-v-host disease (GVHD) developed in both. Nine patients received MTX as immunosuppression following BMT. GVHD did not develop in any of them, but fatal infections in the immediate posttransplant period developed in five patients. Eleven patients received cyclosporine (CsA) after transplantation. Beginning in week 5 after BMT, CsA was gradually replaced by MTX. Acute GVHD, substantial chronic GVHD, or fatal infections did not develop in any of these patients. Removal of 98% of the lymphocytes by counterflow centrifugation prevents development of acute GVHD, provided that immunosuppression is administered after BMT. Graft rejection was not observed, but the number of evaluable patients is limited at present.

Adolescent↗
PubMed1978

Immunofluorescence titres of sperm centrifuged at different speeds.

Two washing procedures were used on spermatozoa to test the effect of centrifugation on immunofluorescent staining. The rapidly centrifuged spermatozoa often exhibited a loss of acrosomal but an increase in tail antigenicity. A standard technique of sperm preparation for immunofluorescence is recommended in order to have reliable and comparable results.

Acrosome↗
PubMed1987

Evaluation of a fully automated centrifugal analyzer for performance of hemostasis tests.

We have evaluated the performance of a centrifugal analyzer, specifically designed for hemostasis tests, for methods based on clotting time as measured by light scattering, or based on splitting of chromogenic substrates. The results were compared with those obtained with a semiautomated coagulometer (clotting tests) or with a manually operated photometer (chromogenic tests). In general, the results with the centrifugal analyzer were at least as precise as those of the comparative methods, with greater output and ease of operation. Disadvantages of the instrument are its partial incompatibility with some commercial reagents and the relative rigidity of the operational parameters, which hinder its use for research.

Antithrombin III↗
PubMed1979

Concentration and separation of erythrocytes infected with Plasmodium falciparum by gradient centrifugation.

Concentration of infected erythrocytes was achieved in cell suspensions derived from long-term culture of Plasmodium falciparum growing asynchronously in human erythrocytes. This new procedure involves the slow centrifugation (at 33 g) of erythrocyte suspensions through 5% Ficoll solutions. Mature asexual erythrocytic forms are preferentially retained in the gradient solution (top fraction). After further gradient centrifugation of these parasitized cells, the concentration of mature forms is increased 15- to 31-fold and a mature form parasitaemia of 71-81% is obtained in the final erythrocyte suspension. Furthermore, at least 75% of the total number of the mature forms can be retrieved by this method. Parasitized cells that are not retained in the gradient are sedimented to the bottom of the tube (bottom fraction) and consist predominantly of ring forms. Parasites from both the top and bottom fractions are viable and have been used to initiate short-term synchronous cultures. By providing purified parasite preparations, this simple procedure will facilitate immunological, chemotherapeutic, and biochemical studies with P. falciparum.

Cell Separation↗
PubMed1985

Efficacy of discontinuous flow centrifugation compared with cascade filtration in Waldenstrom's macroglobulinemia: a pilot study.

In the treatment of Waldenstrom's macroglobulinemia (WM) and lipoprotein or immune complex mediated diseases, centrifugal and membrane plasma separation systems have been successfully employed over the past years. More recently, semiselective double filtration systems have been used in isolated cases. While it is hoped that cascade filtration (CF) will soon become a routine technique, a note of caution came from some investigators because of the lack of any evidence that CF does really deplete patients' plasma of known pathogenic macromolecules. The aim of this study was to test the efficacy of CF in the removal of IgM paraproteins in comparison with discontinuous flow centrifugation (DFC). Eight patients were treated by DFC and seven by CF; there were no significant differences between the two groups in terms of sex, age, clinical severity and IgM plasma concentration. After DFC or CF sessions, IgM concentration diminished by 50% and plasma viscosity by 60%, producing a comparable mean reduction in patients' clinical severity. Our in vivo results thus preliminarily answer the question whether CF is capable of removing known pathogenic macromolecules from patients' plasma, and the technique appears to warrant further investigations.

Centrifugation↗
PubMed1986

Loss of coproporphyrin by centrifuging urine samples before liquid-chromatography.

We have previously reported a "high-performance" liquid-chromatographic procedure for urinary porphyrins. While attempting to automate this procedure, we discovered that coproporphyrin could be partly or completely lost from urine samples if they were centrifuged or filtered before analysis. The loss is related to the amount of precipitate in each sample, acidic urines showing the greatest losses. If samples are alkalinized before centrifugation, the loss is prevented.

Centrifugation↗
PubMed1985

Adherence of human polymorphonuclear leukocytes to endothelial monolayers: effects of temperature, divalent cations, and chemotactic factors on the strength of adherence measured with a new centrifugation assay.

Polymorphonuclear leukocytes (PMNs) adhere to endothelial cells at sites of acute inflammation. To examine this phenomenon in vitro, we have developed a new assay to measure adherence of PMNs to cultured endothelial cells. Human PMNs were labeled with 111indium-oxine and incubated in microtiter wells with monolayers of either human umbilical vein or bovine aortic endothelial cells. Following incubation, the wells were sealed, inverted, and centrifuged at varying speeds. Results are expressed as the percentage of PMNs added initially that remained attached to the monolayers after being subjected to dislodgment forces (ie, relative centrifugal forces) ranging from 1 to 1,200 g. Adherence of PMNs to endothelial monolayers was temperature dependent, dependent on the concentration of extracellular Mg2+ (but not Ca2+), and enhanced significantly by the chemotactic peptides, N-formyl-methionyl-leucyl-phenylalanine (fMLP) and human C5a. It was found that fMLP and C5a not only increased the number of PMNs that adhered to endothelial cells, but also increased the strength of adherence.

Animals↗
PubMed1985

Isolation of bovine eosinophils by density gradient centrifugation.

A method for the isolation of an enriched population (greater than 60%) of bovine eosinophils was developed, using density gradient centrifugation. Eosinophils were isolated from peripheral blood by centrifugation on a density gradient medium of sp gr 1.092. Viability was greater than or equal to 95%, and the isolated eosinophils were found to be functional in chemokinetic and antibody-dependent cellular-cytotoxicity assays. This method represents a simple, rapid method for obtaining bovine eosinophils that can be used in a variety of assays of eosinophil function.

Animals↗
PubMed1977

Biochemical studies of isolated rat hepatocytes from normal and phenobarbital-treated liver as obtained by rate zonal centrifugation.

Cell suspensions from normal and phenobarbital treated livers were analysed by rate zonal centrifugation in ficoll gradients. No difference in the microsomal cytochrome P-450 and NADPH-cytochrome C reductase content and in the incorporation rate of radioactive leucine was noted between light and heavy hepatocytes. After centrifugation of a mixture of radioactive phenobarbital-treated cells and normal liver cells, the specific radioactivity was constant, indicating that the hepatocytes from drug-treated liver had the same density as the normal cells.

Animals↗
PubMed1977

Abnormal oogenesis and embryogenesis resulting from centrifuging Drosophila melanogaster females.

Females of Drosophila melanogaster were centrifuged at 2400 g and 4200 g for 3 h in a number of different orientations. The oocytes in various stages of vitellogenesis become separated into three layers; a centrifugal yolk layer, a central cytoplasmic layer, and a centripetal lipid layer. The direction of layering is related to the orientation of the female. The process of recovery of the ovaries was followed and the development of the eggs laid analysed. Many of the eggs laid over the subsequent 3 days die very early in development and fail to produce any differentiated structures. Some hatch into normal larvae and others produce defective embryos. The most common defect being a misarrangement of the segmentation. The differences in the kinds of experimentally inducible pattern aberrations in Drosophila and other diptera is discussed.

Animals↗
PubMedDate not supplied

New kinetic procedure for the measurement of conjugated bilirubin with a centrifugal analyzer.

A procedure has been developed for the automated measurement of conjugated bilirubin in serum with a centrifugal analyzer. The conjugated bilirubin is measured by a fixed time kinetic method which monitors the reaction between conjugated bilirubin and diazotized sulfanilic acid at 550 nm. Results are calculated based on a comparison of the reagent blank-corrected absorbance changes between 15 seconds and 75 seconds for sample vs changes in an empirical standard. The standard used is N-(1-naphthyl) ethylene diamine dihydrochloride (NEDC) which reacts with diazotized sulfanilic acid at a rate comparable to conjugated bilirubin. The standard is calibrated by comparison with a modified Jendrassik and Grof procedure using a serum blank-corrected centrifugal analyzer reference method. The method is linear to 150 mg per 1 with a sensitivity of 3.0 milliabsorbance units per 1.0 mg per 1 of conjugated bilirubin using a 35 mul sample volume. Within-run precision is 1 percent for elevated concentrations of bilirubin. Hemolysis introduces a negative interference, the nature of which is discussed.

Bilirubin↗
PubMed1979

Separation of normal human bone marrow cells by counterflow centrifugal elutriation. I. Morphological analysis and subfractionation of neutrophilic granulocytes.

We have used counterflow centrifugal elutriation to separate the nucleated cells of normal human bone marrow into their major morphologically identifiable cellular components. Human bone marrow cells were separated simultaneously into the major cell types--lymphocytes, monocytes, granulocytes, and erythroid precursors. Significant concentration of bone marrow cell types could be achieved, including myeloblasts (x 25), promyelocytes (x 43), early myelocytes ( x 22), late myelocytes (x 17), metamyelocytes (x 6), eosinophils (x 40), basophils (x 55), erythroblasts (x 35), monocytes (x 40), and plasma cells (x 35). Cell loss is minimal (85% recovery of input) and random, and cell viability, as measured by trypan blue staining, is high (greater than 95%). Factors interfering with separation are also described: a low loading flow rate, the presence of an excess of mature red cells, and the absence of fetal calf serum resulted in poor cell recovery and viability. The use of heparin as the anticoagulant resulted in cell loss, decrease in cell viability, and an ineffective separation. Separation of cells from normal bone marrow by centrifugal elutriation should facilitate the study of bone marrow cell interactions and the purification of individual types of bone marrow cells.

Bone Marrow↗
PubMed1982

Isolation of human thymocytes differing in maturation state and function by centrifugal elutriation.

A modified centrifugal elutriation technique was used to separate (up to 3 X 10(9)) human thymocytes, according to size in 6 different fractions. Eighty percent of the unfractionated thymocytes were recovered in fractions 1 and 2. The majority of these thymocytes appeared to be small and phenotypically immature as was determined by the high percentage of cells reacting with the monoclonal antibodies OKT-6, Mas-036 and peanut agglutinin. In addition, a relatively low percentage of the cells reacted with a monoclonal antibody directed against HLA-A, B and C determinants (Mas-015). The immaturity of these thymocytes was confirmed by their failure to respond to phytohemagglutinin (PHA) and their negligible responder capacity in mixed leukocyte cultures. Fractions 3-6, representing 20% of the unfractionated thymocytes, were collected arbitrarily and contained thymocytes of various maturation stages as judged by their phenotype. The PHA responsiveness and responder capacity in mixed leukocyte cultures of the thymocytes in these fractions were, in general, considerably higher than those of the unfractionated thymocytes. Our data indicate that centrifugal elutriation is a fast and reproducible method to separate large quantities of functionally inactive and phenotypically immature thymocytes from the more mature and functionally active thymocytes.

Antibodies, Monoclonal↗