Search PubMed⌕ Search

Biomedical subjects

G Mulder

Publications and source records attributed to G Mulder.

At least 73 records · Page 4Linked to original sources
PubMed1983

A small DNA molecule containing covalently-linked ribonucleotides originates from the large intergenic region of the cauliflower mosaic virus genome.

We have detected a small DNA molecule (sa-DNA), 725 nucleotides long, in cauliflower mosaic virus (CaMV)-infected, but not non-infected, turnip leaves. Alkali and RNase A treatments shortened sa-DNA by 100 nucleotides and we conclude that it contains covalently-linked ribonucleotides. This DNA co-purified with cellular polyadenylated RNA. It is complementary to the beta-strand of CaMV DNA and of opposite polarity to RNAs transcribed from the alpha-strand. Hybridisation studies suggest that sa-DNA originates from the large intergenic region (IR1) of the CaMV genome. A small double-stranded DNA with three single-stranded components, which co-purifies with cellular DNA, appears to be related to sa-DNA but lacks detectable ribonucleotides.

Cloning, Molecular↗
PubMed1983

The P3 complex as an index of information processing: the effects of response probability.

The amplitude and latency of the late positive (P3b) component of the cortical evoked potential were studied in a visual search task. The main independent variables were memory load, response type and relative response frequency. In the experiment we used the varied mapping procedure, a condition in which the target and distractor stimuli were thoroughly mixed across trials. The main goal of the study was to establish the locus of relative response frequency. In many models of choice reaction time the effect of this task variable is believed to occur in the response selection stage. If the latency of the P3b only indexes stimulus evaluation, independent of response selection and organization processes, relative response frequency should only affect reaction time and not the latency of P3b. The results indicated that the latency of P3b was very sensitive to the number of comparisons, response type and relative response frequency. In addition, only a subset of subjects selectively prepared for the most probable response. Only these subjects showed the effects of relative response frequency in their reaction times too. Response preparation, however, did not affect the latency of P3b. It was concluded that the latency of P3b is a very sensitive index of the search and comparison process, the binary decision process, and the probability of the type of the decision, but insensitive to motor preparation.

Adult↗
PubMed1983

The information processing paradigm: concepts, methods and limitations.

Some characteristics of the information processing paradigm are discussed. Characteristics of fast process research are particularly emphasized. Fast process research deals with elementary information processes, called 'mechanics'. The processes cannot be revealed by introspective methods, but only by chronometric studies. Attentional research has revealed automatic and controlled mechanics. Only the latter require attention resources for their execution. The functional state of the brain is thought to affect in particular the efficiency of controlled mechanics Methods used in fast process research and cognitive psychophysiology could be helpful in deciding if behavioural disturbances result from limitations in the nature of the mechanics or in their efficiency.

Arousal↗
PubMed1981

Late positive components and stimulus evaluation time.

The amplitude and latency of late positive components were, together with reaction time (RT), studied in a task which combines visual and memory search. The visual display contained either one, two or four letters, as did the memory set. Six load combinations, resulting in one, four, eight and 16 comparisons, were examined. The reaction time data indicated a self-terminating search process. Three late positive components were present in the evoked potential: one at 375 msec after the onset of the display, one at 375 msec after the offset of the display and one around 600 msec. Only the latter component appeared to be sensitive to the number of comparisons. Adaptive averaging was applied to this latter component. The latency of this P300 suggested, in contrast to the RT data, an exhaustive search process. In addition there was a negligible correlation between the response latency and P300 latency at single trial level. Several hypotheses are suggested for what P300 could have to tell us.

Adult↗
PubMed1979

Comparison of four commercially available cAMP kits.

In this study four commercially available cAMP kits were compared and shown to differ with respect to reliability, sensitivity, simplicity and expiration time. It is not possible to recommend a particular kit, because the choice depends on the demands of the investigator, which, of course, may vary. However, in our opinion, one of the kits was inferior to the others.

3',5'-Cyclic-AMP Phosphodiesterases↗