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T Vanden Driessche

Publications and source records attributed to T Vanden Driessche.

At least 19 recordsLinked to original sources
PubMed1997

Chronobiology of Plasmodium chabaudi chabaudi: analysis of hourly recorded total and differential parasitaemia during a schizogonic cycle.

Detailed total and differential parasitaemia curves of asexual Plasmodium chabaudi chabaudi erythrocytic stages were recorded and analysed. Female, inbred, CBA/Ca mice were infected with the virulent IP-PC1 strain after in vitro synchronization of the parasites. Thin blood smears were made on an hourly basis, and the total and differential parasitaemia of ring forms, trophozoites and schizonts were counted after Giemsa staining. These curves reveal information that remains hidden when less detailed curves are examined: the duration and periodicity of the schizogonic cycle, the existence of a plateau, indications of a schizont withdrawal from the peripheral blood, the timing of the rise of the parasitaemia at each schizogony, and the invasion rate of the merozoites. In the perspective of developing a rational and efficient strategy for chronotherapy of malaria, such information should be taken into account.

Animals↗
PubMed1995

Immunogenization of a murine T-cell lymphoma via transfection with interferon-gamma.

Tumor cell variants were derived from the BW5147 T-cell lymphoma that differ in major histocompatibility complex (MHC) class I antigen expression, tumorigenicity and metastatic potential. In general, increased H-2Kk expression was found to be correlated with a reduced tumorigenicity and spontaneous metastasis. CD8+ T cells were identified in the immune recognition of such variants, implicating a role for H-2Kk in the presentation of tumor-associated antigens. In the present study, H-2Kk+ BW variants were transfected with a gene encoding interferon-gamma (IFN-gamma), a potent inducer of MHC class I expression. The resulting transfectants exhibited an increased expression of H-2Kk and concomitantly an inability to generate visible tumors and a reduced metastatic capacity. Furthermore, immunization with the IFN-gamma transfectants resulted in an increased generation of cytotoxic T lymphocytes (CTLs) that lysed both the transfectants and the parental tumor cells. Based on these results, vaccinations with the IFN-gamma transfectants were performed against the parental tumor cells. The results clearly demonstrated that such vaccinations reduced significantly the tumorigenicity and metastatic capacity of the parental tumor cells. Hence, in this tumor model, IFN-gamma gene transfection provides a means to immunogenize H-2Kk+ BW tumor cells.

Animals↗
PubMed1992

Isolation and characterization of different forms of thioredoxins from the green alga Acetabularia mediterranea: identification of an NADP/thioredoxin system in the extrachloroplastic fraction.

A procedure has been developed for the simultaneous purification to apparent homogeneity of chloroplast thioredoxins f and m, and nonchloroplast thioredoxin h, from the green alga Acetabularia mediterranea. In the chloroplast fraction, three thioredoxins were isolated: one f type thioredoxin (Mr 13.4 kDa) and two m type thioredoxin forms (Mr of 12.9 and 13.8 kDa). A Western blot analysis of crude and purified chloroplast thioredoxin preparations revealed that Acetabularia thioredoxin m was immunologically related to its higher-plant counterparts whereas thioredoxin f was not. In the nonchloroplast fraction, a single form of thioredoxin h (Mr 13.4 kDa) and its associated enzyme NADP-thioredoxin reductase (NTR) were evidenced. Acetabularia NTR was partially purified and shown to be an holoenzyme composed of two 33.0-kDa subunits as is the case for other plant and bacterial NTRs. Similarity was confirmed by immunological tests: the algal enzyme was recognized by antibodies to spinach and Escherichia coli NTRs. Acetabularia thioredoxin h seemed to be more distant from higher-plant type h thioredoxins as recognition by antibodies to thioredoxin h from spinach and wheat was weak. The algal thioredoxin h was also slightly active with spinach and E. coli NTRs. These results suggest that in green algae as in the green tissues of higher plants the NADP and chloroplast thioredoxin systems are present simultaneously, and might play an important regulatory role in their respective cellular compartments.

Acetabularia↗
PubMed1990

Association between MHC class I antigen expression and malignancy of murine T lymphoma variants.

Tumor cell variants were derived from an AKR T-cell lymphoma cell line (BW5147, H-2k haplotype). These variants differed in their malignant potential and in their membrane expression of class I MHC antigens. High tumorigenic and spontaneous metastatic capacity was found to be predominantly associated with a decrease of H-2Kk class I major histocompatibility complex (MHC) antigen expression. In contrast, high experimental metastatic capacity correlated strongly with an increased H-2Dk antigen expression. The in vitro invasive potential and the LFA-1 expression of the BW variants showed no correlation with the differential MHC antigen expression and the differential metastatic and tumorigenic capacity of the BW variants. Furthermore, the susceptibility of the BW 5147 variants to TNF and NK-mediated cytotoxicity was not related to the differential metastatic potential and the expression of the class I MHC antigens.

Animals↗
PubMed1989

Masking in plants.

Circadian rhythms in plants are liable to masking, i.e. alterations by environmental influencing agents. Experiments have been reported for both positive and negative masking, attributed to a Zeitgeber which may either increase or decrease the amplitude of a circadian rhythm (CR). In some instances, the CR may even be unexpressed. This inhibition, however, may be alleviated by synchronizing agents. Reports are also available for changes in the shape or pattern of an oscillation. The latter may be prevented, at least in Acetabularia in certain conditions, by a phytohormone antagonist. Masking may also be brought about by water stress, relative humidity, bacterial infection and alteration in the relative direction of the gravitational force. Finally, subjecting plants to constant conditions, particularly continuous light, alters the physiological state of the organism.

Circadian Rhythm↗
PubMed1989

The molecular mechanism of circadian rhythms.

The endogenous and ubiquitous circadian rhythms (CR) are not understood in molecular terms, in spite of recent interesting advances. They concern, on one hand, protein synthesis, of which a small fraction--possibly a single protein--, formed on cytosolic ribosomes, may be required on each 24 h cycle. On the other hand, the per gene, involved in the control of CR in drosophila has been found to direct the synthesis of 2 (or 3) proteoglycans. Several models have been put forward in order to explain CR generation. Considering the complexity of the cell's organization and the occurrence of partial arrhythmicity, CR generation might result from the integration of a few physiological and metabolic pathways normally involving at least one feed-back loop. Sequentiality would be inherent to the kinetics of both the metabolic pathways and translocators located in the membranes of the various compartments; as a consequence, the peaks of the oscillatory activities would be positioned at particular phase points relative to others. Proteoglycans (or other proteins modified post-transcriptionally) could be involved in the operation of rhythms in controlling not only some plasmalemma (as proposed by Yu et al., 1987) but also intracellular membranes. Finally, reversible enzyme modification occurring on each 24 h cycle could be critically important in circadian rhythms generation.

Animals↗
PubMed1984

Temporal morphology and cap formation in Acetabularia--I. Light-dark cycle perturbations.

Cap formation, a major developmental process in the alga Acetabularia, is influenced by a single perturbation of the entraining light-dark schedule and thus, presumably, of the circadian rhythms. This perturbation is brought about several weeks before cap formation, the most conspicuous expression of morphogenesis in Acetabularia. The effect is more pronounced on cap formation than on growth. It varies in importance with the circadian time at which the perturbation was brought about. The effect is dependent on the developmental state of the alga: transfer carried out during the logarithmic phase of growth produces a delay whose importance decreases with time. When carried out during the phase of slow terminal growth, the transfer induces a transitory acceleration of cap formation. When the algae approach their final length, no effect is elicited. Photoperiodism seems to be involved.

Acetabularia↗
PubMed1984

Temporal morphology and cap formation in Acetabularia--II. Effects of morphactin and auxin.

In order to support the hypothesis that circadian rhythms are implicated in cap formation, experiments were undertaken on the possible time-dependency of the effects of (a) a competitive inhibitor of auxins, morphactin and (b) of auxin (IAA). It was found that: (i) the inhibitory effect of morphactin varies dramatically with the time at which the several weeks' treatment was first begun; (ii) the maximum inhibition varies with development and decreases with time; (iii) IAA accelerates cap formation when the algae are submitted to IAA during the exponential growth phase; the effect is time dependent and decreases with time; (iv) IAA first applied on smaller algae has a transient inhibitory effect which is time dependent; (v) anucleate fragments also respond differentially to an IAA treatment begun at several times in the 24-hr cycle, most clearly when newly formed mRNA have been accumulated and (vi) the effect of iAA is not cumulative with that of a LD shift; that of morphactin is not, or only slightly, improved by a LD shift.

Acetabularia↗
PubMed1978

Changes in the cyclic AMP content during growth and development of Acetabularia.

The 3',5'-adenosine monophosphate (cyclic-AMP) content of the unicellular alga Acetabularia has been examined at various developmental stages. It has been found that very young algae, less than 10mm in length, have a high cAMP content [more than 7 pmoles per 100 mg wet weight (WW)], but that with the growth of the algae, the cAMP content decreases rapidly, reaching the low level of 0.5--1.0 pmoles per 100mg WW. The cAMP content remains at this level until cap differentiation, after which an increase in cAMP content accompanies cap enlargement. It has been shown that these results are unlikely to be affected by changes in the cAMP content induced by variations in circadian rhythm. Treatment with theophylline (2.10(-3) M), a phosphodieterase inhibitor, results in an increase in the cAMP content and delays growth and cap formation. Experiments on the effects of theophylline upon the circadian rhythm of oxygen evolution have shown that the continuous presence of theophylline in the culture medium does not induce a phase shift in the rhythm. The cAMP content of anucleate Acetabularia shows development stage variations parallel to that of the whole algae.

Acetabularia↗
PubMed1976

Acetabulaira mediterranea: circadian rhythms of photosynthesis and associated changes in molecular structure of the thylakoid membranes.

Acetabularia mediterranea algae, grown in three different light-dark regimes, were frozen in liquid nitrogen at c.t.(1) 0 and c.t. 6 and a record made of 77 degrees K fluorescence emission spectra of their chloroplasts. Algae grown under LD cycles exhibited a clear circadian rhythm of oxygen production. The low temperature fluorescence emission spectrum at c.t.0 was different from that at c.t.6 and this difference was increased by submitting the algae to successive "freeze-thaw" treatment. Similar results were obtained in DD, and the photosynthesis rhythm remained fully expressed. Algae grown in LL, where no rhythm of photosynthesis could be detected in the samples because there is a great individual variability in period lenght under these conditions, exhibited a similar difference in their low temperature flourescence emission spectra between c.t.0 and c.t.6. We conclude that the circadian rhythm in low-temperature fluorescence emission of the chloroplasts in Acetabularia is related to the circadian rhythm in photosynthesis.

Acetabularia↗