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Biomedical subjects

M Butler

Publications and source records attributed to M Butler.

At least 91 records · Page 5Linked to original sources
PubMed1983

High yields from microcarrier cultures by medium perfusion.

A culture perfusion system is described for the growth of anchorage-dependent cells on microcarriers. The critical component of this system is a column separator, which removes medium while allowing the microcarriers to remain in the culture. Amino acids and ammonia were analysed during cell growth of the perfusion culture. None of the amino acids was completely utilized. The accumulation of ammonia to 2.3 mM was observed and may be responsible for, or coincident with, events limiting further cell growth. It is suggested that oxygen deprivation and growth inhibitor accumulation, rather than nutrient depletion, are the major factors in limiting even higher cell yields.

Amino Acids↗
PubMed1982

Use of phospholipase A to compare phospholipid organization in synaptic membranes, myelin, and liposomes.

The pattern of fatty acid release from rat synaptic membranes in the presence of phospholipase A2 (Vipera russelli) was compared to that from liposomes comprised of phospholipids. Phospholipase A2 more readily attacked myelin and synaptic membranes than liposomes prepared from total phospholipids derived from myelin. Although hydrolysis of liposomal phospholipids occurred in the absence of added calcium, the presence of 2 mM CaCl2 or 2% bovine serum albumin significantly enhanced the phospholipase attack of liposomes, but not synaptic membranes of myelin. Phospholipase exhibited a marked preference for phospholipids containing docosahexaenoic acid (22:6) in the synaptic membranes, while with liposomes the pattern of released fatty acid reflected the fatty acid composition in the two-position of the phospholipids. Although either calcium or albumin markedly increased the phospholipase hydrolysis of liposomes, neither affected the hydrolysis of synaptic membranes or the pattern of fatty acid release from liposomes. It was concluded that the nonlipid constituents, particularly the proteins, of biomembranes were responsible for the organization of the phospholipids and accounted for the observed differences between liposomes and synaptic membranes with respect to enzymic accessibility.

Animals↗
PubMed1982

MDCK microcarrier cultured: seeding density effects and amino acid utilization.

The growth of Madin Darby canine kidney cells on microcarriers was studied at different cell seeding densities. Maximum growth was attained when a cell-to-bead ratio of 7:1 was used. Under these conditions an initial concentration of above 3 X 10(6) cells/ml resulted in a yield of over 2 X 10(6) cell/ml in 2 d. The amino acid utilization of cells from Dulbecco's modified Eagle medium was studied under the above conditions. Eight amino acids (arg, cys, gln, ile, leu, met, ser, and val) showed rapid and near complete depletion from the medium. Five amino acids (his, lys, phe, thr, and tyr) showed limited depletion. Two amino acids (ala and gly) were released into the medium by the cells.

Amino Acids↗
PubMed1982

A comparison of the virucidal properties of chlorine, chlorine dioxide, bromine chloride and iodine.

Chlorine dioxide, bromine chloride and iodine were compared with chlorine as virucidal agents. Under optimal conditions all disinfectants were effective at low concentrations, but each disinfectant responded differently to acidity and alkalinity. Disinfection by chlorine was impaired by the presence of ammonia, but the other disinfectants retained much of their potency. Disinfection of poliovirus by iodine resulted in structural changes in the virions as seen by electron micrroscopy, but the other disinfectants were able to inactivate poliovirus without causing any apparent structural changes.

Bromides↗
PubMed1982

Sidedness of phospholipid synthesis on brain membranes.

We have investigated the localization of the site of incorporation and the subsequent equilibration of newly synthesized phospholipids in brain membranes. Rats were injected intracranially with [3H]glycerol; the animals were killed at varying times afterwards, and microsomal fractions were isolated from the brains. In some cases, microsomes were subfractionated on sucrose gradients. Initially, most of the radioactive phosphatidylethanolamine appeared in a pool that reacted with the impermeable reagent trinitrobenzene sulfonic acid (TNBS). This probe presumably modified only the lipid on the outer face of microsomal vesicles (which may, in large part, consist of pinched-off endoplasmic reticulum). At 5 min after injection, the specific radioactivity of the TNBS-modified phosphatidylethanolamine (cytoplasmic face) was four times that of the unmodified (luminal or inner face) phosphatidylethanolamine. With time, the ratio of the specific activities in the modified and unmodified pools of phosphatidylethanolamine approached 1.0, with kinetics that suggested a half-time on the order of 30 min for in vivo conversion of the TNBS-accessible to the -inaccessible pool. This equilibration in specific activities could be the result of either translocation of phospholipids across endoplasmic reticulum membranes or conversion with time of initially labeled endoplasmic reticulum to other membranous organelles which form randomly oriented vesicles upon homogenization. A similar experimental design, using phospholipase C to hydrolyze outer face phospholipids preferentially, verified this conclusion for phosphatidylethanolamine and yielded similar results for phosphatidylcholine. Control studies measuring radioactive sucrose permeability indicated that neither TNBS nor phospholipase C treatment significantly disrupted microsomal vesicles under the conditions used.

Animals↗
PubMed1982

Isolation of indigenous enteroviruses from chemically treated and dewatered sludge samples.

Samples of wastewater sludge were examined for infectious enteroviruses before and after they had been chemically conditioned and dewatered. The least virus was recovered from the cake produced by filter pressing of sludge, which had a greatly increased solids content (39 to 45% [wt/vol]) relative to the untreated sludge (4.2 to 6.2% [wt/vol]) and in one plant was at pH 11 due to the lime conditioner used. Conditioning with a cationic polyelectrolyte before dewatering by centrifugation produced a watery sludge (2.7 to 5.3% [wt/vol]) from which high titers of infectious virus were recovered which were often greater than those isolated from the untreated sludge (0.6 to 1.4% [wt/vol]). This was thought to be due to saturation of virus and sludge floc adsorption sites by the polyelectrolyte, resulting in the liberation of virions from the sludge solids.

Calcium↗
PubMed1982

Quantitative and functional deficit of suppressor T cells in children with atopic eczema.

Helper (OKT4+) and suppressor (OKT8+) T cells were enumerated in 16 children with severe atopic eczema. Compared to controls (median 1 . 8) the ratio of OKT4+/OKT8+ cells in the patients was significantly higher (median 2 . 65, P less than 0 . 002). Functional suppressor activity in these patients was assessed by concanavalin A (Con A) activation and suppression of pokeweed mitogen (PWM) induced immunoglobulin production by plasma cells and Con A proliferation of T cells. In both assays a lack of suppression was shown (Con A/PWM, P less than 0 . 02; Con A/Con A, P less than 0 . 05). There was a significant inverse correlation between the helper/suppressor ratio and functional suppressor activity (P less than 0 . 01). These results indicate that a defect of T cell regulation does exist in atopic eczema and if it is of primary pathogenic importance, immunotherapy to restore the balance may prove useful.

Adolescent↗
PubMed1981

The extraordinary mutagenicity of nitropyrenes in bacteria.

Nitropyrenes cause frameshift mutations in Salmonella typhimurium. This activity which is restricted to frameshift mutations is unusual in several respects: (a) Nitropyrenes, as a class, are the most mutagenic chemicals reported in the literature; (b) The mutagenicity depends upon the formation of adducts between DNA and nitropyrene metabolites; (c) The penultimate intermediates responsible for mutagenic activity (hydroxylamines) are not obtained in all instances by reduction of the nitro function by the "classical" nitroreductase (the one that acts on nitrofurans and other simple nitrated polycyclic aromatic hydrocarbons) but by another nitroreductase which appears to be specific for higher nitrated polycyclic aromatic hydrocarbons; (d) The mutagenicity of nitropyrenes is enhanced when resting rather than growing bacterial cultures are used.

Escherichia coli↗
PubMed1981

Long-term abnormalities in T and B lymphocyte function in children following treatment for acute lymphoblastic leukaemia.

T and B lymphocyte function as assessed by pokeweed mitogen stimulation and concanavalin A suppression was studied in 40 children with acute lymphoblastic leukaemia who were in remission and off all treatment. Both plasma cell and immunoglobulin production was reduced in off-treatment patients, particularly in those who had received cyclophosphamide as part of their treatment. The ability to suppress immunoglobulin production was also significantly reduced in these patients. These abnormalities were long-standing and were apparent up to 5 years after stopping treatment with no indication of a return to normality. No clinical correlations have been observed.

Adolescent↗
PubMed1981

Recovery of indigenous enteroviruses from raw and digested sewage sludges.

We examined different types of raw sewage sludge treatment, including consolidation, anaerobic mesophilic digestion with subsequent consolidation, and aerobic-thermophilic digestion. Of these, the most efficient reduction in infectious virus titer was achieved by mesophilic digestion with subsequent consolidation, although a pilot-scale aerobic-thermophilic digester was extremely time effective, producing sludges with similarly low virus titers in a small fraction of the time. Although none of the treatments examined consistently produced a sludge with undetectable virus levels, mesophilic digestion alone was found to be particularly unreliable in reducing the levels of infectious virus present in the raw sludge.

Aerobiosis↗
PubMed1981

Trends and differentials in breast feeding: an update.

Analysis of the 1973 National Survey of Family Growth shows a continued downward trend in breast feeding by successive cohorts of American mothers. The downward trend is evident in both measures of incidence (ever-breast feeding) and duration of breast feeding for first and higher-order births. For all cohorts higher-order births are less likely to be breast fed than first births. However, breast feeding of higher-order births is typically of a longer duration. Differentials in breast feeding reveal strong associations with indicators of social class; women who are college graduates, who work as professionals, and who are married to professional husbands are most likely to breast-feed their infants. Differentials in average duration of breast feeding are often reversed from differentials in ever-breast feeding.

Adult↗
PubMed1980

Nitropyrenes: isolation, identificaton, and reduction of mutagenic impurities in carbon black and toners.

Extracts of selected xerographic toners and copies were found to be mutagenic in the Salmonella assay. The activity was independent of the xerographic hardware and process and was traced to nitropyrenes present as impurities in the carbon black, the toner colorant. Manufacturing process changes resulted in a substantial reduction of the nitropyrene content of the carbon black and thus in the mutagenicity of the corresponding toners. Nitropyrenes are potent frameshift mutagens, and possible mechanisms for their biological action are discussed.

Biotransformation↗
PubMed1980

Inactivation of viruses in municipal effluent by chlorine.

The influence of pH and temperature on the efficiency of chlorine inactivation of two unrelated picornaviruses in a typical urban wastewater effluent was examined. Temperature, unlike pH, had relatively little effect on the rate of inactivation. The pH effect was complex and the two viruses differed. The f2 coliphage was more sensitive to chlorine at low pH, but at all values there was a threshold above which additional chlorine resulted in very rapid inactivation. The amount of chlorine required for this was less at low than at high pH, although at pH values above 7 the extent of inactivation was about the same. There was no apparent correlation between pH and rate of inactivation of poliovirus but there was a suggestion that at a pH close to the isoelectric point of the virus it was less sensitive to chlorination.

Chlorine↗
PubMed1980

Inactivation of f2 coliphage in municipal effluent by the use of various disinfectants.

Bromine chloride, chlorine and peracetic acid inactivated f2 coliphages in effluent but in order to achieve 99.99% inactivation the three disinfectants were required at about 1, 10 and 100 mg/l respectively. The activity of chlorine was halved by the presence of added organic matter, whereas bromine chloride and peracetic acid were very little affected. When a second successive dose of virus was added to the reaction mixture, the virus was inactivated only by peracetic acid despite the fact that in the chlorine-treated effluent residual chlorine was detected. The addition of a second dose of disinfectant inactivated residual virus in the same way as the first dose.

Acetates↗
PubMed1980

Differentiation of rubella virus strains by neutralization kinetics.

The neutralization of rubella virus was investigated and shown to proceed by first order kinetics over the first 10 to 15 min. A comparison of the rate constant of neutralization (K) for six strains of rubella virus was carried out over this period of the reaction. Two particularly antibody-sensitive isolates were detected. It was noted that the three strains isolated from in utero infections were poorly neutralized by heterologous antisera when compared to postnatal strains.

Adult↗