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Biomedical subjects

K C Lowe

Publications and source records attributed to K C Lowe.

At least 55 records · Page 3Linked to original sources

Novel fluorinated surfactants for perfluorochemical emulsification: biocompatibility assessments of glycosidic and polyol derivatives.

A novel series of fluoro-surfactants, derived from glycosides (monosaccharides) or polyols (ureas or carbamates), have been produced for use in respiratory gas-carrying perfluorochemical emulsions. Compounds were synthesised via simple, but highly selective, routes using highly fluorinated isocyanates with amino alcohols, polyethoxylated alcohols and partially protected sugars at anomeric carbon; yields were 88-95%. Resultant compounds were perfluoroalkylated with hydroxylic "head" groups. The biocompatibility of surfactants with human blood in vitro was assessed using a conventional haemolysis test. Compounds showing insignificant haemolysis at up to 10 g l-1 were further evaluated (i) for their effects on neutrophil chemiluminescence, and (ii) in a human platelet aggregation assay. Some fluoro-surfactants inhibited spontaneous platelet aggregation, in blood anti-coagulated with hirudin, at concentrations of 0.01% (w/v), suggesting possible applications as antithrombotic agents.

Ampholyte Mixtures↗

Beneficial effects of oxygenated fluorocarbon on the in vitro culture of protoplasts and cell electrofusion products.

Electrofused Passiflora protoplasts (P. edulis, P. giberti) were plated in KPR medium overlaying oxygen-gassed perfluorodecalin (Flutec PP6). Oxygenated PFC significantly (P < 0.05) enhanced protoplast division, as reflected by an increase in mean plating efficiency of up to 62% (P < 0.05) over 14 days. After 21 days of culture, the liquid phase containing dividing protoplast-derived cells, was removed from the PFC surface and overlaid onto MS-based agar medium for callus proliferation. Forty days later, protoplast-derived calli were transferred to one of two regeneration protocols, previously determined using unfused parental protoplasts. Calli derived from electrofusion-treated protoplasts exhibited organogenesis or somatic embryogenesis, depending on the regeneration procedure. The regeneration efficiency after 121 days for protoplasts initially cultured with oxygenated PFC was over 2-fold greater (P < 0.01) than control. These results indicate that oxygenated PFC can enhance growth and regeneration of protoplasts and their fusion products.

Cell Fusion↗

Effects of the co-polymer surfactant, Pluronic F-68, on platelet aggregation in human whole blood.

The effects have been studied of Pluronic F-68 on platelet aggregation in human whole blood. The median spontaneous platelet aggregation in normal blood (n = 15) was 18.4% [interquartile range (IQ) = 10.5-24.2%]. Commercial grade Pluronic F-68 significantly (P < 0.05) reduced platelet aggregation at 7.3 microM (median = 8.4%, IQ = 3.9-13.4; n = 12) and almost eliminated aggregation at concentrations of > 58 microM (median = 2.0%, IQ = 0.0-3.5). Similar results were obtained with a silica gelpurified Pluronic F-68 fraction (n = 3). Pluronic F-68 also accelerated the rate of platelet dis-aggregation in blood treated with 0.3, 1.0 or 3.0 mM adenosine di-phosphate. These results suggest that the therapeutic effects of Pluronic F-68 in ischaemic injury may be due, in part, to inhibition of platelet aggregation in the microcirculation. The beneficial effects of tissue perfusion with oxygen-carrying perfluorochemical emulsions, containing Pluronic F-68, may also involve direct effects of the surfactant on platelets.

Adenosine Diphosphate↗

Haemolytic properties of pluronic surfactants and effects of purification.

The effects of incubating blood from mice, rats, rabbits or hamsters with either a commercial grade or a silica-purified fraction of Pluronic F-68 or Pluronic F-38 have been studied. Incubation of blood with up to 4.0% (w/v) of commercial or purified Pluronic F-68 produced no detectable haemolysis (< 0.1%). Haemolysis did occur with concentrations of commercial Pluronic F-68 above 4.0% (w/v). This was maximal with rat blood incubated with 10.0% (w/v) Pluronic F-68, where the mean haemolysis was 4.7 +/- 1.5%; the mean haemolysis in rat blood was reduced to 0.5 +/- 0.3% (P < 0.05) following incubation with the purified Pluronic F-68 fraction. Neither commercial grade or purified Pluronic F-38 produced any significant haemolysis when incubated with rat or hamster blood. Incubation of rabbit blood with 10.0% (w/v) commercial Pluronic F-38 produced only 0.5% haemolysis.

Animals↗

Enhanced protoplast growth at the interface between oxygenated fluorocarbon liquid and aqueous culture medium supplemented with pluronic F-68.

Protoplasts isolated from cell suspensions of albino Petunia hybrida were grown for 10 d at the interface between aqueous culture medium and oxygenated perfluorodecalin. Protoplasts synthesised new cell walls and divided normally at the fluorocarbon/culture medium interface, the mean division frequency of protoplasts being increased by 37% (P < 0.05) in this system when the perfluorodecalin was saturated with oxygen prior to use. The mean division frequency of protoplasts was further increased to a maximum of 52% above control (P < 0.01) when the medium overlaying the oxygenated perfluorodecalin was supplemented with 0.01% (w/v) of the co-polymer surfactant, Pluronic F-68. These results demonstrate a beneficial and synergistic effect of supplementing protoplast culture systems with oxygenated perfluorodecalin and Pluronic F-68.

Cell Division↗

Uptake of concentrated perfluorocarbon emulsions into rat lymphoid tissues.

The effects of injecting (10-30 mL kg-1) either perfluorodecalin (FDC) emulsions of increasing phase fraction (20-60% w/v) or the commercial formulation, Fluosol, on lymphoid tissues have been studied for up to 7 days in male rats. Tissue weights increased by up to 123% (P < 0.05) in proportion with quantity of perfluorochemical (PFC) injected, with spleen responses consistently greater than those of the liver. PFC droplets recovered from these tissues at 72 h after injection of 30% (w/v) FDC emulsion (10 mL kg-1) had mean diameters in the 1-10 microns range, with those from the spleen being larger than those from the liver. Recovered droplet diameters were considerably greater than freshly-prepared emulsion mean particle sizes (0.21-0.25 microns). These results suggest that coalescence of emulsion droplets following accumulation in lymphoid tissue is a pre-requisite for the eventual excretion of PFC vapour through the lungs.

Animals↗

Emulsified perfluorochemicals as respiratory gas carriers: recovery of perfluorodecalin emulsion droplets from rat tissues.

To further understand the in-vivo biokinetic behaviour of perfluorochemical (PFC) emulsions, male rats were injected (10 mL kg-1) with 30% (w/v) emulsified perfluorodecalin (FDC) and uptake into tissues assessed. At 72 h after injection, the mean (+/- s.e.m.) diameters of FDC droplets recovered from liver and spleen were 2.24 +/- 0.04 and 2.78 +/- 0.10 microns, respectively; droplets recovered from lung after 72 h (mean: 1.73 +/- 0.13 micron) were significantly smaller (P < 0.01). After 7 days, FDC droplet diameters in liver had increased to 3.31 +/- 0.13 microns (P < 0.01) and those in lung to 2.71 +/- 0.14 microns (P < 0.01); droplets in spleen after 7 days (2.22 +/- 0.09 microns) were similar to those at 72 h. These data support the hypothesis that significant initial coalescence of FDC droplets occurs in the rat liver and spleen, with further coalescence in the liver up to 7 days. The mean percentage of the injected FDC dose recovered from the liver after 72 h was 2.2 +/- 0.4%, and after 7 days was 0.07 +/- 0.05% (P < 0.01). A smaller decrease in the percent injected FDC in spleen also occurred over the same period (72 h: 1.9 +/- 0.3%; 7 days: 0.8 +/- 0.5%; P < 0.01). The percent injected FDC in lung was similar at 72 h (0.007 +/- 0.004%) and 7 days (0.005 +/- 0.001%). FDC was undetectable (< 0.001%) in all blood samples. The greater rate of FDC elimination from the liver than from the spleen may be related to differences in the rates of reticuloendothelial system processing between these organs.

Animals↗

Protective effects of a novel perfluorochemical emulsion in photodynamic therapy.

The effects of pre-injection of mice with a novel perfluorodecalin-based emulsion on the responses to photodynamic therapy (PDT) using the photosensitizer, metatetra (hydroxyphenyl) porphyrin (m-THPP), have been studied. Injection of emulsion after m-THPP and before illumination (activating wavelength 648 nm) protected skin against PDT-induced inflammatory effects, as reflected by decreases (P less than 0.05) in vascular permeability and oedema formation. However, there was no protection against epidermal cell loss. In contrast, injection of emulsion before sensitizer had no corresponding effect. A fall in mean dermal temperature of up to 6 degrees C occurred in mice injected with emulsion 1-2.5 h before illumination suggesting a decrease in skin blood flow which would reduce oedema formation. Possible mechanism(s) for this apparent protective effect are discussed.

Animals↗

Biocompatibility studies with perfluorochemical oxygen carriers.

The effects of injecting either a novel perfluorodecalin (FDC)-based emulsion or various perfluorochemical (PFC) oils on liver cytochromes P-450 (P-450) and aryl esterase (LAE) enzymes in male rats have been studied. Mean P-450 concentration increased (P less than 0.05) following injection of the novel emulsion or FDC. In contrast, LAE increased in response to injection of FDC (P less than 0.05) and the C-16 oil, perfluoroperhydrofluoranthrene (P less than 0.01), added to stabilize the emulsion. No corresponding changes in either P-450 or LAE occurred in rats injected with either perfluorotripropylamine, perfluorotributylamine or perfluorooctylbromide. The "sleeping time" of animals injected with the pentobarbital-based anaesthetic, Equithesin, following pretreatment with the novel emulsion was lower (P less than 0.05) than in saline-injected controls. The results are discussed in relation to the effects of PFCs on liver metabolic functions.

Animals↗

Retention of perfluorochemicals in rat liver and spleen.

The uptake and retention of perfluorochemicals (PFCs) into rat liver and spleen have been measured for up to 28 d following injection of either the commercial PFC emulsion, Fluosol, or a novel perfluorodecalin (FDC)-based emulsion. Both quantitative and qualitative differences in the retention of individual PFCs were observed, depending on composition of emulsion administered. Nevertheless, uptake of PFCs into the spleen was consistently greater than into the liver, irrespective of formulation injected.

Animals↗

Lymphoid tissue responses to concentrated perfluorochemical emulsions in rats.

The effects of injecting perfluorochemical (PFC) emulsions of varying concentrations on lymphoid tissues have been studied in rats. Tissue weights were increased in proportion with quantity of PFC injected, with spleen responses consistently greater than those of the liver. PFC droplets recovered from tissues had mean diameters in the 1-10 microns range, with those from the spleen being larger than from the liver. Recovered droplet diameters were considerably greater than freshly-prepared emulsion mean particle sizes (0.20-0.25 microns). This suggests that coalescence of emulsion droplets following accumulation in tissues is a pre-requisite to the eventual excretion of PFC vapour through the lungs.

Animals↗

A novel method for the isolation of nematode larvae using pluronic F-68-treated cellulose strips.

A new method is described for the isolation of cultured nematode larvae. This allows effective separation of larvae from fecal contamination, exsheathed larvae from cast sheaths, and viable larvae from nonviable larvae. The method involves the use of cellulose strips and has been assessed using larvae from 2 hookworm species, Necator americanus and Ancylostoma ceylanicum. Pretreatment of the cellulose strips with 1.0% (w/v) of the nonionic surfactant, Pluronic F-68, significantly increased larval recovery of both species.

Ancylostoma↗