Biomedical subjects

I de Groot

Publications and source records attributed to I de Groot.

4 recordsLinked to original sources

PubMed1977

The germicidal effect of the open air in different parts of The Netherlands.

Using the microthread technique the survival of Escherichia coli MRE 162 in open air was measured in different parts of The Netherlands. The presence of bactericidal compounds (open air factor = OAF) could be demonstrated on several days and quantitated in relative units of OAF concentration. In the absence of ozone the OAF concentration was always low. In the presence of ozone the OAF concentration was dependent on wind direction. At the selected microthread exposure sites air from areas with high traffic intensity contributed more to OAF production than air from industrial areas. OAF production is probably related to the nature of hydrocarbons in the air.

Air Microbiology↗

PubMed1977

Survival of aerosolized bacteriophage phi X174 in air containing ozone--olefin mixtures.

The effects of ozone and ozonized olefins on aerosol survival of bacteriophage phiX174 were studied. The ozone concentrations used were between 0 and 110 parts/10(9), giving decay rates up to 0-03 min-1. The olefins used were trans-2-butene and cyclohexene in concentrations of 500 parts/10(9) and 2-4 parts/10(6), respectively. Olefins alone have no effect, whereas in combination with ozone, decay rates of 0-1 min-1 and higher were obtained. The results are discussed in relation to the viricidal effect of open air.

Aerosols↗

PubMed1977

Mechanisms of inactivation of bacteriophage phiX174 and its DNA in aerosols by ozone and ozonized cyclohexene.

The mechanisms of inactivation of aerosolized bacteriophage phiX174 in atmospheres containing ozone, cyclohexene, or ozonized cyclohexene were studied by using 32P-labelled phage. The inactivation of the aerosolized phage in clear air or in air containing cyclohexene is due to damage of the protein coat since the deoxyribonucleic acid (DNA) extracted from the inactivated phage retains its biological activity. Inactivation of the phage in air containing ozonized cyclohexene is due both to protein and DNA damage. Sucrose gradient analysis shows that aerosolized inactivated phiX174 releases unbroken DNA. In contrast, the DNA from phage phiX174 inactivated by ozonized cyclohexene is broken. The inactivation of aerosolized phage phiX174-DNA was studied in the same atmospheres using 32P-labelled DNA. phiX174-DNA aerosolized in clear air or air containing cyclohexene at 75% r.h. is inactivated by a factor of 2 in 30 min. The inactivated DNA is broken. Ozone as well as ozonized cyclohexene inactivates KNA very fast causing breaks in the molecule. This is in contrast with the intact bacteriophage in which ozone does not produce breaks in the DNA.

Aerosols↗

PubMed1977

Special lecture: the breast cancer screening controversy: a perspective.

Analysis of the data of the Health Insurance Plan of New York Breast Cancer Screening Study indicates that in patients whose cancers were found by screening, the case fatality rate at all ages is almost half the case fatality rate of controls. The data also strongly suggest that maximal benefit in young women resides in the detection of in situ cancers. Due to relatively low yield of these early lesions, projected 20 year survival in that study may be little different for all women screened compared to controls. We have shown that the yield of these early lesions can be increased by aggressive screening and liberal use of biopsy. Furthermore, where J.C. Bailar has indicated a net gain (or loss) of -4 to +8 lives per 20,000 women using the HIP data, using his method and our data we find a savings of 25-27 lives/20,000 women by 3 year screening to date. These are lives that have been saved by mammography alone.

Adult↗