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Biomedical subjects

M A Smits

Publications and source records attributed to M A Smits.

60 records · Page 4Linked to original sources
PubMed1985

Sequential expression of antigens on sexual stages of Plasmodium falciparum accessible to transmission-blocking antibodies in the mosquito.

Plasmodium falciparum gametocytes contain specific antigens, some of which (Mr 230,000, 48,000, 45,000) are expressed on the surface of the newly emerged macrogamete. A different antigen (Mr 25,000) surrounds the surface of the ookinete and, although present to some extent in the developing gametocyte, is synthesized in high quantities by the macrogamete/zygote and expressed progressively on the transforming zygote surface. These antigens are targets of transmission blocking antibodies that are effective at two distinct points after gametogenesis: fertilization of the macrogamete and ookinete to oocyst development. The antigens involved in the fertilization blockade are the Mr 48 and 45 proteins, which are expressed on the macrogamete surface. The Mr 230 K coprecipitating protein probably plays no part in transmission block. mAb directed against the Mr 25 K ookinete surface protein blocked transmission without inhibiting ookinete formation, indicating that this protein has an important role in the transformation of ookinete into oocyst. A combination of mAb recognizing different epitopes on the same protein molecule acted synergistically in inhibiting oocyst formation. Using a mixture of two blocking mAb reacting against the Mr 48/45 and 25 K proteins, respectively, an additive blocking effect could be demonstrated.

Animals↗
PubMed1984

Initiation and termination signals for transcription in bacteriophage M13.

Transcription of the infrequently expressed phage M13 genome domain, comprising genes III, VI, I and IV, has been studied in detail by hybridization and S1-nuclease mapping studies. The contiguous genes III and VI are transcribed via an 1800 nucleotide-long RNA molecule that is initiated at a promoter which overlaps with the Rho-independent termination signal between genes III and VIII. Its synthesis is terminated at a Rho-dependent terminator in the proximal part of gene I. Transcription of gene I is not mediated by an independent promoter but most probably by read-through of RNA-polymerase through this terminator. Transcription of gene IV is accomplished by synthesis of four distinct RNAs of about 1500 to 1680 nucleotides long which are initiated at a promoter located immediately in front of gene IV. Termination of these transcripts is generated at least four different sites located in tandem within the intergenic region between genes IV and II.

Base Sequence↗
PubMed1984

Gametocytogenesis of Plasmodium falciparum in vitro: a simple technique for the routine culture of pure capacitated gametocytes en masse.

A technique is described for the growth of pure gametocyte cultures of Plasmodium falciparum. Using the classification of Hawking, Wilson & Gammage (1971) these cultures contain gametocytes of stages III, IV and V alone. Routine sexual cultures, varying from 0.35 ml static cultures to 500 ml shaking cultures, are exposed to an inhibitor of DNA synthesis (mitomycin C at 10 micrograms/ml) on the 11th day of culture, and the culture is harvested on the 14th day when capacitated stage V gametocytes are present. All other stages are killed by the drug and are morphologically degenerate within 2 days of the addition of the inhibitor.

Animals↗
PubMed1978

Expression of bacteriophage M13 dna in vivo. I. Synthesis of phage-specific RNA and protein in minicells.

It is demonstrated that after infection of the appropriate minicell-producing strain of Escherichia coli with the filamentous bacteriophage M13, its replicative form DNA is segregated into minicells. Consequently these minicells have acquired the capability to direct the synthesis of phage-specific RNA and protein. Comparision of the electrophoretic mobilities of phage-specific RNA species made in vitro with those made in M13 replicative form DNA harbouring minicells, have indicated that almost all in vitro synthesized G-start RNAs have an equivalent among the in vivo synthesized RNA products. Furthermore it could be demonstrated that in M13 replicative form DNA harbouring minicells the phage-specific proteins encoded by genes III, IV, V and VIII are made. In addition the synthesis of a phage-specific polypeptide (molecular weight approx. 3000) co-migrating with the recently discovered capsid protein (designated C-protein) could be demonstrated. The meaning of these results for the resolution of the regulatory mechanisms operative during the life cycle of this phage will be discussed.

Bacterial Proteins↗
PubMed1978

Expression of bacteriophage M13 DNA in vivo. Localization of the transcription initiation and termination signal of the mRNA coding for the major capsid protein.

During the infection cycle of the filamentous bacteriophage M13 a phage specific RNA species is made which selectively directs in vitro the synthesis of the precursor of the major capsid protein encoded by gene VIII. This RNA is unstable (its mean half-life is 11 min) and is made in amounts representing at least 2% of the newly synthesized RN. Nucleotide sequence analysis have indicated that the synthesis of this RNA species is initiated and terminated at the same promoter (G0.18) and termination signal (T0.25) of the M13 genome as the 8S RNA species made in vitro under the direction of M13 replicative form DNA.

Base Sequence↗