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Biomedical subjects

G J Harper

Publications and source records attributed to G J Harper.

16 recordsLinked to original sources
PubMed1993

Effect of photon flux density on carbon assimilation and chlorophyll a fluorescence of cold-stored white spruce and lodgepole pine seedlings.

White spruce (Picea glauca (Moench.) Voss) and lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings previously held in dark, frozen storage (-2 degrees C) for 2.5 or 6 months, and nursery-grown white spruce seedlings lifted in summer were exposed to photon flux densities (PFDs) similar to those that might be encountered at planting. Photosynthetic gas exchange and chlorophyll a (chl a) fluorescence were examined in cold-stored and summer-lifted seedlings before and after a 9 h-exposure to artificial illumination of high PFD (2000 micro mol m(-2) s(-1)) or low PFD (ca. 500 micro mol m(-2) s(-1)), and during exposure to 400 micro mol m(-2) s(-1) for 4-9 days. In the 2.5-month-stored and summer-lifted seedlings, the high-PFD treatment caused a small decrease in carbon fixation and a large decrease in the ratio of variable to maximum fluorescence (F(v)/F(m)) relative to the effect of the low-PFD treatment. In contrast, in the 6-month-stored seedlings the high-PFD treatment caused a significant decrease in rate of light-saturated carbon fixation but little decrease in F(v)/F(m) relative to the effect of the low-PFD treatment, indicating that the mechanisms for maintaining integrity of the photochemical apparatus had changed during the storage interval.

Journal Article↗
PubMed1991

Temporal variations in cold sensitivity of root growth in cold-stored white spruce seedlings.

We examined effects of soil temperature on the number of roots produced by white spruce (Picea glauca (Moench.) Voss) seedlings during the first month of growth following 0-30 weeks of storage in darkness at -2 degrees C. After storage, seedlings were planted in pots and placed in a controlled-environment chamber with a constant air temperature of 11 degrees C and a 16-h photoperiod. Water baths were used to keep soil temperature at 3, 7 or 11 degrees C. The number of long roots (> 10 mm) produced was strongly dependent on soil temperature. At soil temperatures of 3 or 7 degrees C, the number of long roots produced was only 11 to 30% that at 11 degrees C. Seedlings that had been stored for 14 weeks and then planted in soil at 11 degrees C produced the greatest number of long roots. For seedlings planted in soil at 11 degrees C, the number of long roots increased with time of storage up to 14-18 weeks and then declined progressively with length of storage. No increase in number of long roots with length of storage up to 18 weeks was evident in seedlings planted in soil at 3 or 7 degrees C. The maximum number of short roots (5-10 mm) was observed in seedlings that had been stored for 17 weeks and then planted in soil at 7 or 11 degrees C.

Journal Article↗
PubMed1984

An assessment of environmental contamination arising from the use of some automated equipment in microbiology.

The generation of aerosols and the contamination of surfaces arising from some equipment used to automate tasks in the microbiology laboratory have been assessed using a microbiological test method. When used for the designed purposes none of the equipment is likely to present any significant aerosol hazard. Some of the equipment gave rise to surface contamination, and it is recommended that decontamination of work surfaces should be carried out at frequent intervals.

Aerosols↗
PubMed1983

An assessment of some hazards associated with the collection of venous blood.

Some potential hazards of three commercially available blood collecting devices are compared with the conventional syringe method. A simulated venous system using blood containing a bacterial spore tracer was used to estimate surface and aerosol contamination. No appreciable difference in potential hazard to the operator was demonstrable by the methods employed.

Aerosols↗
PubMed1983

An assessment of environmental contamination arising from the use of equipment for carrying out the ELISA technique in microtitre plates.

The generation of aerosols and the contamination of surfaces arising from the use of equipment for the filling, diluting in, and washing of microtitre plates used in ELISA techniques have been measured. With the exception of vacuum pump outlets no significant amount of aerosol was generated by any of the equipment tested. The fitting of a small air filter to vacuum pump outlets eliminated any hazard from this source. Some low level contamination of surfaces was detected. Except when working with known, or suspected, highly infectious materials there is no evidence to support the need to operate the equipment within a microbiological safety cabinet.

Aerosols↗
PubMed1981

Contamination of the environment by special purpose centrifuges used in clinical laboratories.

The generation of aerosols and the contamination of surfaces arising from the use of a number of special purpose centrifuges have been measured. Except when sealed containers were used all the equipment tested generated airborne particles and contaminated surrounding surfaces. The magnitude of this contamination was shown to be associated with several factors, and it could be considerably reduced by the use of sealed containers, and by fitting air filters. The significance of these findings and their application are discussed.

Aerosols↗
PubMed1973

The evidence for the airborne spread of Newcastle disease.

Newcastle disease virus has been shown to survive when airborne in small particles, both in the laboratory and in the open air. Field outbreaks have been studied and viable virus has been recovered from the open air short distances downwind of infected premises. Vaccination of birds leads to a great reduction in the amount of virus liberated into the air.

Aerosols↗