Electrically tunable partial coalescence of oppositely charged drops.

We report the existence of a critical ionic conductivity below which oppositely charged drops only partially coalesce. The extent of coalescence between dissimilarly sized water drops in oil can be tuned from complete coalescence at low electric field strengths to complete noncoalescence at high field strengths, thus providing external control over the daughter droplet size. Strikingly, the size and charge of the daughter droplet are both independent of the ionic conductivity. We present evidence suggesting the charge transfer is instead strongly influenced by convection associated with the capillary-driven penetration of a vortex into the larger drop, and we demonstrate that the size of the daughter droplet is consistent with a scaling model based on a balance between capillary-driven inertia and electrostatic repulsion.

Sedation scoring. Assessment tools.

The changing use of sedative agents, is reviewed. Tools to guide sedation assessment are identified, although only one appears to assess level, quality and depth of sedation. Several issues concerning reliability and validity of sedation assessment tools are discussed. Recommendations for practice are made, which highlight the criteria that sedation assessment tools need to address and the research directions needed for future tool development.

Analysis of polycyclic aromatic hydrocarbons in metered dose inhaler drug formulations by isotope dilution gas chromatography/mass spectrometry.

Organic compounds extracted into metered dose inhalers (MDIs) from the rubber components of the metering valve are of increasing interest in the development of these formulations. Polycyclic aromatic hydrocarbons (PAHs) are a class of extractable organic compounds whose source is the carbon black commonly used as a reinforcing agent in rubber. The analytical method for PAHs described in this report employs "cold filtration" to remove the suspended drug substance and excipients, and gas chromatography/mass spectrometry (GC/MS) for separation and detection of individual PAHs. After filtration, stable isotope labelled analogues of target PAHs are spiked into the drug product to act as internal standards, correcting for recovery (termed "isotope dilution GC/MS"). Validation of the method was accomplished with respect to linearity, precision, limit of detection/quantitation, selectivity and ruggedness. Application to a variety of MDI drug product formulations revealed that certain PAHs are present at the ng/inhaler level.

Cyclobuta-dithymidine induction by solar-simulating UV radiation in human skin: II. Individual responses.

The purpose of this study was to examine cyclobuta-dithymidine (T*T) photoproduct induction and persistence in human skin exposed in situ to simulated solar UV radiation. Small areas of untanned skin in nineteen individuals were exposed using a solar UV apparatus that simulates both the spectrum and intensity of the UV portion of summer midday sunlight at 39 degrees N latitude. The equivalent of approximately 60 min of sunlight exposure (72KJ/m2) was administered, and T*T photoproducts were quantitated by enzyme-linked immunosorbent assay (ELISA) of DNA extracted from skin punch biopsies. Net yields of T*T photoproducts were determined in 10 individuals, with the majority (7 of 10) between 0.02 and 0.12 T*T per kilobase (Kb). The three remaining individuals had higher levels of photoproducts but were not unusually sensitive to solar UV as determined by minimal erythema dose (MED). Percentage loss of T*T photoproducts 4 h after exposure was determined in nine individuals to be 80.2 +/- 14.0%.

Induction and repair of cyclobuta-dithymidine photoproducts in hamster skin by solar-simulated UV radiation.

The induction and repair of cyclobuta-dithymidine (T less than greater than T) photoproducts in hamster skin was measured following exposure to artificial solar radiation. DNA extracted from irradiated hamster epidermis was analyzed by enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody specific for T less than greater than T photoproducts. Between 49% and 58% of T less than greater than T antibody binding sites were eliminated from DNA by 24 h after radiation exposures comparable with approximately 60 - 120 min of midday sunlight, whereas all detectable T less than greater than T binding sites were eliminated by 24 h after a radiation exposure comparable with 30 min of sunlight.

Cyclobuta-dithymidine induction by solar-simulating UV radiation in human skin. I. Protection by constitutive pigmentation.

The induction and persistence of cyclobuta-dithymidine (T less than greater than T) photoproducts in human skin samples was measured following exposure to artificial solar radiation. DNA extracted from human epidermis, irradiated with the equivalent of 15 to 120 min of midday sunlight, was analyzed by enzyme-linked immunosorbent assay (ELISA). Heavily pigmented skin required 2- to 4-fold higher doses than non-pigmented skin to produce similar amounts of T less than greater than T photoproducts. These results demonstrate the effectiveness of constitutive epidermal pigmentation in protecting epidermal cell DNA from solar UV-induced damage.

Immunoassay of dithymidine cyclobutane dimers in nanogram quantities of DNA.

Immunological assays for DNA photoproducts, which have been in use for a number of years, provide a rapid means for quantifying photodamage in DNA. Radioimmunoassays (RIA) are capable of measuring photoproducts in microgram quantities (1-10 micrograms) of DNA extracted from biological samples, e.g., animal skin or cultured cells. We have refined an indirect enzyme-linked immunosorbent assay (ELISA) for the analysis of cyclobutadithymidine (T-T) photoproducts in nanogram quantities (3-100 ng) of DNA. T-T photoproducts were detectable in 30 ng DNA irradiated with a minimum of 10 J/m2 of 254 nm ultraviolet light (UV). The efficiency of T-T induction in DNA was approximately 4000-fold lower per unit dose using a solar-simulating UV radiation source (290-400 nm) than with 254 nm radiation. The assay was used to measure T-T photoproducts induced by solar-simulated UV radiation in hamster skin and human skin and should be useful for the routine analysis of photoproducts in small amounts of DNA (500-1000 ng) available from human skin biopsies.

Mitochondrial lamellated bodies and surfactant depots in the Type II cells of the lung compared by bimetallic staining and X-ray analysis.

After heavy dosages of sensory irritants osmiophilic whorls (mitochondrial lamellated bodies) are found in the mitochondria of the Type II cells of the lung. To obtain evidence of their nature, the lead/osmium (Pb/Os) ratio in these and other bodies after bimetallic staining was studied by electron probe X-ray analysis during transmission electron microscopy. To allow for inter-specimen variation the Pb/Os ratio was divided by the Pb/Os ratio for chromatin in the same cell, to give a "relative ratio". The values of the latter ranged from 1.4 for granules in an eosinophil leucocyte to 0.60-0.77 for lamellated osmiophilic bodies of Type II cells, 0.4 for nerve myelin, and 0.05 for fat globules. The Pb/Os ratio for mitochondrial lamellated bodies did not differ significantly from that for lamellated osmiophilic bodies (which are depots of lung surfactant) in the same cell. This is compatible with the mitochondrial lamellated bodies consisting of excess surfactant produced in response to stress. the method is capable of extension.

The development of the lung and its surfactant in the foal and in other species.

The development of the lung from the glandular through the canalicular to the alveolar stages in the horse fetus is described. Traces of surfactant and occasional lamellated osmiophilic bodies representing intracellular surfactant were found at 150 days of gestation, some 40 to 60 days before the transition to the canalicular stage. During this transition some of the cuboidal cells of the glandular rosettes are transformed into cells of Types I and II, but the surfactant is not fully developed until 300 days or, in some foals, until after delivery.

A technique for preparing human dermal and scar specimens for scanning electron microscopy.

The aims in a current study of dermis and scar tissue using the scanning electron microscope are: (1) to maintain the orientation of the specimen, (2) to preserve the in vivo architecture, and (3) to expose a satisfactory surface. A technique which best fulfils these requirements involves glutaraldehyde fixation of a splinted specimen, freeze-fracturing using a modified pair of pliers, freeze-drying again after washing. Consistently satisfactory specimens have been obtained, which provide information about fibre architecture and cell distribution.