Biomedical subjects

P Marti

Publications and source records attributed to P Marti.

4 recordsLinked to original sources

PubMed1998

An embryonic demethylation mechanism involving binding of transcription factors to replicating DNA.

In vertebrates, transcriptionally active promoters are undermethylated. Since the transcription factor Sp1, and more recently NF-kappaB, have been implicated in the demethylation process, we examined the effect of transcription factors on demethylation by injecting in vitro methylated plasmid DNA into Xenopus fertilized eggs. We found that various transactivation domains, including a strong acidic activation domain from the viral protein VP16, can enhance demethylation of a promoter region when fused to a DNA binding domain which recognizes the promoter. Furthermore, demethylation occurs only after the midblastula transition, when the general transcription machinery of the host embryo becomes available. Nevertheless, transcription factor binding need not be followed by actual transcription, since demethylation is not blocked by alpha-amanitin treatment. Finally, replication of the target DNA is a prerequisite for efficient demethylation since only plasmids that carry the bovine papilloma virus sequences which support plasmid replication after the midblastula transition are demethylated. No demethylation is detectable in the oocyte system where DNA is not replicated. These results suggest that, in the Xenopus embryo, promoters for which transcription factors are available are demethylated by a replication-dependent, possibly passive mechanism.

Amanitins↗

PubMed1998

Structured task analysis in complex domains.

This paper describes the application of MUSE, a human factors structured design method, to the design of systems supporting the work of air traffic controllers at European airport control towers. The paper illustrates the derivation of a generalized task model starting from the analyses performed at four airports and the construction of the composite task model of the future system. Other important concerns of the work are the harmonization of the different tools in the airport control tower and the assessment of the impact of these tools on the human operators. The potentialities and limitations of applying the method are discussed in particular with respect to the complexity of the domain and the nonstandard features of the air traffic control as a MUSE application. Indeed, air traffic management is widely acknowledged as a complex domain to design for, and the documented application of human factors structured methods to design are all referred to the modelling of worksystems (as opposed to working positions or workstations) with a single operator. In the present application one has multiple operators and multiple design goals (design, harmonization, assessment). The work presented is a contribution to the extension and better definition of structured methods and their applicability to the analysis of complex domains.

Aviation↗

PubMed1994

Peri-implant mucosal aspects of ITI implants supporting overdentures. A five-year longitudinal study.

Sixty-six ITI implants placed in the mandible of 33 edentulous elderly patients (mean age: 69 years) were observed longitudinally for 5 years. The implants served as overdenture anchorage either by means of a connecting bar or single spherical attachments. During the study period, 2 implants failed (one because of a peri-implant lesion and one because of a fracture) and had to be removed. At the beginning of the study, all implants were osseointegrated and had successfully been in function for 3-5 months. Oral hygiene practices and the peri-implant mucosal status were assessed according to the criteria of conventional periodontal parameters. Approximately 50% of the implants had been installed into lining mucosa and hence were to surrounded by keratinized mucosa. The peri-implant mucosal tissue was maintained healthy during the whole observation period, and no or only minimal loss of attachment was observed. The probing depths averaged approximately 3 mm. At the end of the study, orthopantomographic radiographs were obtained from all patients to assess the peri-implant bony structures. Small local angular bony defects were detected on 16 implants (22%) in 12 patients. Slightly increased probing depths were observed when angular bony defects were present. Loss of attachment was significantly less frequent when the implants had been placed following a prolonged period of edentulousness (> 5 years). This study demonstrated that advanced age, reduced dexterity of elderly patients and environmental conditions of overdentures do not represent a higher risk for the development of peri-implant lesions.

Aged↗

PubMed1983

[Standardization problems in the monitoring of oral anticoagulants by Quick's thromboplastin time: an attempt to determine the state of the problem in Switzerland].

In comparison with British Comparative Thromboplastin, we examined 11 different reagents which are presently available in Switzerland for surveillance of oral anticoagulation. Frozen plasma samples obtained from 50 patients under oral anticoagulation for at least 6 weeks were used for comparison of the various reagents. From our results the following conclusions emerge: Our present results largely concur with those of a similar study which compared the therapeutic range of thromboplastin reagents available in Switzerland 6 years earlier; therefore, we assume that the reagents which were sold at that time and are now available in Switzerland have remained fairly constant. In contrast to this apparent agreement, the therapeutic ranges indicated by the producers of reagents are, at least in part, comparable neither with the therapeutic range established for the British Comparative Reagent nor among themselves. Thus, the intensity of the induced coagulation defect is obviously variable, depending on a given test system. The calculated "therapeutic range" for a given test system traditionally corresponds to an average risk of thrombosis or bleeding; this range is not of necessity identical with a target zone that has to be established either individually or for certain diseases. Once established, a target value defining the intensity of oral anticoagulation can be more conveniently reproduced by use of suitable control plasmas rather than with reference thromboplastins, at any rate by practitioners or non specialised hospital laboratories.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗