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Biomedical subjects

M Holmberg

Publications and source records attributed to M Holmberg.

78 records · Page 5Linked to original sources
PubMedDate not supplied

A comparison of two DNA probes, one specific for Plasmodium falciparum and one with wider reactivity, in the diagnosis of malaria.

The sensitivity and specificity of 2 probes for the detection of malarial infection was studied. 399 blood samples from Gambian children were tested in a deoxyribonucleic acid (DNA) hybridization assay, and the results compared with the microscopical findings from thick blood films. 8 additional pure Plasmodium malariae and 14 pure P. vivax samples were also assayed. One probe, containing a 21 base pair tandem repeat and highly specific for P. falciparum, detected this species in all except 2 of 74 samples with a parasitaemia of 250 per microliter or more; the overall sensitivity of the probe was 76%. The other probe, a 6 kilobase pair organelle DNA, is conserved in all Plasmodium species so far tested. Its sensitivity for P. falciparum was lower than the 21 base pair repeat, but it detected P. vivax and P. malariae at low levels of parasitaemia, and thus could be useful in field studies.

Animals↗
PubMedDate not supplied

Hybridisation of short DNA molecules investigated with in situ atomic force microscopy.

By introducing the complementary DNA (cDNA) strand to a molecular layer of short single stranded DNA (ssDNA), immobilised on a gold surface, we have investigated hybridisation between the two DNA strands through the technique of in situ atomic force microscopy (AFM). Before introduction of cDNA, the ssDNA molecular layer was modulated with the spacer molecule mercaptohexanol (MCH), which makes the ssDNA molecules more accessible for hybridisation. With in situ AFM, we have monitored the formation of a smooth, mixed molecular layer containing ssDNA and MCH. Furthermore, the hybridisation between the two DNA strands has been studied. Introduction of the cDNA strand resulted in an increase in smoothness and thickness of the molecular layer. Both the increase in order and thickness of the molecular layer can be expected if hybridisation occurs, since double stranded DNA molecules have a more rigid and elongated structure than ssDNA molecules.

Biosensing Techniques↗
PubMedDate not supplied

Application in clinical epidemiology of new advances in immunology and molecular biology of malaria.

The first purpose was to study the sensitivity of a spot hybridization assay for P. falciparum with a DNA probe. This assay was compared with light microscopy for the detection of low-grade parasitemia. The second purpose was to study in clinically immune individuals the seroreactivity, against a newly identified P. falciparum antigen, deposited in the erythrocyte membrane during merozoite invasion (Perlmann et al., 1984). This antigen is considered to be a potential component in a future vaccine against the blood stage of the parasite. In a holoendemic village in Yekepa area, Northern Liberia, 28 adult men with a high degree of protective immunity against malaria, were shown to have repeatedly low-grade parasitemias of varying density. The spot hybridization assay with the DNA probe was highly sensitive in detecting parasitic infection. The sensitivity was comparable to that of the examination of a blood film for about 15 min by an experienced microscopist. The seroreactivity against Pf 155 antigen varied between a high positive titer to negativity in different subjects, but the reactivity was constant over a period of 15 months for each subject despite numerous new infections and comparable protective immunity against malaria infection.

Adult↗