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Biomedical subjects

C W Lloyd

Publications and source records attributed to C W Lloyd.

At least 55 records · Page 3Linked to original sources
PubMed1985

Stability of morphine sulfate and meperidine hydrochloride in a parenteral nutrient formulation.

The compatibility, stability, and availability of morphine sulfate and meperidine hydrochloride prepared in total parenteral nutrient (TPN) solution, 5% dextrose injection, and sterile water for injection in polyvinyl chloride (PVC) bags were evaluated. A 300-mg dose of each narcotic was mixed in 0.25-L bags of 5% dextrose injection and sterile water for injection, and in 3-L bags of TPN and sterile water for injection. Each solution was examined visually for precipitation, color change, turbidity, and the evolution of gas immediately after the addition of the drug to the bag and every 12 hours for a 36-hour period. Narcotic concentrations in each solution were determined by high-pressure liquid chromatography before and for 36 hours after the addition of the drugs to the bags. No loss of either drug because of adsorption to the PVC bags was found. Morphine sulfate and meperidine hydrochloride were chemically compatible and stable in TPN and 5% dextrose injection for 36 hours. Solutions of morphine sulfate or meperidine hydrochloride in PVC bags containing TPN or 5% dextrose injection are visually and chemically compatible, as well as stable and available for 36 hours when stored at 21.5 degrees C with no protection from environmental light.

Chemistry, Pharmaceutical↗
PubMed1984

The relationship between the division plane and spindle geometry in Allium cells treated with CIPC and griseofulvin: an anti-tubulin study.

Isopropyl N-(3-chlorophenyl)-carbamate (CIPC), and griseofulvin, were used to perturb mitosis and the subsequent plane of division in meristematic cells of Allium cepa. The effects of these compounds on the microtubule organization throughout the cell cycle were investigated by immunofluorescence techniques. Microtubules were not disassembled by drug treatment, but the spindle organization was disrupted, resulting in tripolar spindles which gave rise to multiple nuclei. Ensuing cell plates, with associated phragmoplast microtubules, were branched. The effects of these drugs with respect to MTOC duplication and function in plant cells are discussed as is the relationship between the pre-prophase band (PPB) and the plane of cell division.

Cell Cycle↗
PubMed1983

CPR skills: achievement and retention under stringent and relaxed criteria.

The ability to deliver proper basic cardiac life support was evaluated in 33 health professional students immediately and three months post CPR training, the latter assessment unsuspected. Statistically significant declines were noted in psychomotor skills. Performance using American Heart Association (AHA) standards was compared to performance under "relaxed" criteria. Results imply that current lengths of training sessions, duration of recertification, and application of established AHA standards may require re-evaluation.

Education, Pharmacy↗
PubMed1982

The detergent-resistant cytoskeleton of higher plant protoplasts contains nucleus-associated fibrillar bundles in addition to microtubules.

Cytoskeletons prepared from carrot protoplasts often retain the nucleus, which is associated with bundles of 7 nm fibrils. These were also seen in cytoskeletons from oil palm, maize and Italian rye grass cells. By examining such cytoskeletons by immunofluorescence, negative staining and stereo scanning electron microscopy it appears that the bundles could be part of a more delicate system of fibrils distal to the nucleus. Optical diffraction of the bundles, staining with heavy meromyosin, drug treatments and phalloidin-staining all confirm that the bundles are not composed of actin. Bundles could not be isolated from such cytoskeletons in quantities sufficient for analysis, but by disrupting protoplasts prepared from stationary-phase cells it was possible to purify fibrillar bundles that appeared in the lysate. These were similar in size and properties to the nucleus-associated bundles. The former were shown by sodium dodecyl sulphate/polyacrylamide gel electrophoresis to be composed of several proteins and were sensitive to reducing agents. Since they are not composed of actin, the possibility was explored that these fibrils are related to the P-proteins of phloem sieve tube and accessory cells.

Cell Adhesion↗
PubMed1980

Thymidine Metabolism and the Measurement of the Rate of DNA Synthesis in Carrot Suspension Cultures: EVIDENCE FOR A DEGRADATION PATHWAY FOR THYMIDINE.

The kinetics of [(3)H]thymidine incorporation into the DNA of carrot suspension cultures were investigated. At a thymidine concentration of 0.1 micromolar, incorporation into DNA is not quantitative but ceases after only 14% of the thymidine has been incorporated. Thymidine incorporation into DNA is resumed following addition of a second aliquot of thymidine, which is consistent with substrate depletion. In vivo tracer experiments indicate that this may be due to a catabolic route for converting thymidine to beta-aminoisobutyric acid. Bearing these observations in mind, conditions for determining the rate of DNA synthesis using [(3)H]thymidine incorporation have been investigated. It is concluded that by increasing the thymidine concentration to 10 micromolar the assay period may be increased, by reducing the influence of the degradative pathway, and that cell density and incubation time are critical factors in establishing a valid measure of the rate of DNA synthesis using this method.

Journal Article↗
PubMed1980

The mode of action of 2,4-D in counteracting the elongation of carrot cells grown in culture.

The growth regulator 2,4-D (2,4-dichlorophenoxyacetic acid) has been used to investigate the inter-relationship between cell elongation and cell division in carrot suspension cells. Maintained in 1 mg/l. 2,4-D, dividing populations of cells remain spheroidal and in clusters. But when subcultured into lower levels or zero, 2,4-D they increasingly elongate at the expense of division. Over the range of 0 to 1.0 mg/l, 2,4-D, elongation and division are therefore inversely related. However, by suppressing the mitogenic effect with FUdR it can be shown that cells do elongate in 1 mg/l. 2,4-D--a concentration which otherwise produces dividing, spheroidal cells. This indicates that mitogenc levels of 2,4-D do not perturb structures which support cellular elongation. This conclusion is confirmed by immuno- and electron-microscopy which show that development of elaborate arrays of cytoplasmic microtubules is unaffected by 1 mg/l. 2,4-D when FUdR is present. It is concluded that over the time periods under study here, 2,4-D regulates cell size (and shape) by stimulating growing cells to enter the division cycle and not by inhibiting elongation per se.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1977

Rapid isolation of plasma membranes in high yield from cultured fibroblasts.

1. A method was developed which allows the rapid preparation of pure plasma membranes in high yield from cultured fibroblasts. 2. Cells are lysed in hypo-osmotic borate/EDTA and, after differential centrifugation, the membranes collected by centrifugation on a sucrose barrier. 3. Electron microscopy of the isolated material shows large membrane vesicles essentially free from contaminating organelles. 4. There is no detectable activity of the endoplasmic-reticulum enzyme marker, NADH2--lipoamide oxidoreductase (EC 1.6.4.3), and that of succinate dehydrogenase (EC 1.3.99.1), a marker for mitochondria, is substantially decreased. Chemical compositions are in good agreement with previous observations. 5. This study confirms the usefulness of applied isotopic markers for isolating plasma membranes.

Borohydrides↗
PubMed1977

Control of grip and stick in cell adhesion through lateral relationships of membrane glycoproteins.

Although cell adhesion to substrate must ultimately depend on 'sticking' by physical forces at the outer surface, we suggest that control is exercised through the 'grip' of the cytoskeleton. Our experiments indicate that grip can be relaxed by agents which release surface glycoproteins from some form of side-to-side organisation, and can be consolidated by suitable cross-linking to augment this organisation.

Animals↗
PubMed1976

Mechanisms of cell adhesion: early-forming junctions between aggregating fibroblasts.

When cultured fibroblasts (16C) are mildly dissociated with EGTA or trypsin/EDTA, they aggregate rapidly. The formation of aggregates has been found to involve junctions of the gap and adhaerens types which are seen by electron microscopy within minutes of allowing cells to come together. The process of adhesion between freshly dissociated, transformed 16C fibroblasts is therefore organized and establishes its usefulness as a model for studying cellular interactions in relation to supracellular organization.

Cell Adhesion↗
PubMed1975

Patterns of LH and FSH release from perifused rat pituitaries in response to infusions of hypothalamic extract.

A continuous flow incubation (perufusion) system was developed in which the secretory responses of pools of hemipituitaries from adult male rats to hypothalamic extract (HE) were characterized by serial radioimmunoassay of LH and FSH in the effluent medium. There was in initial massive release of LH and FSH which, in the absence of HE, declined to low basal levels at a rate which depended on the flow rate. Thereafter, the baseline for LH continued to decline gradually while that for FSH was stable. The rate of LH and FSH release rose abruptly after addition of the HE to the medium and returned promptly to baseline after withdrawal of the HE. During continuous infusion of HE for five hours, LH secretion was maintained at a relatively constant, elevated level. The responses to repeated identical pulses of HE were highly reproducible. The variability between responses by any one pool of tissue was significantly less than between responses of separate pituitary pools including pools comprising right and left halves of the same glands. For any given pool of pituitaries of the relationships were linear between: 1) duration of HE pulses (concentration constant) and increases in LH output, and 2) log of concentration of HE (pulse duration constant) and increases inLH and in FSH output. Consistent responses were obtained for up to 12 hr, the maximum period tested.

Animals↗