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Biomedical subjects

U Frey

Publications and source records attributed to U Frey.

At least 91 records · Page 5Linked to original sources
PubMed1989

Domperidone, an inhibitor of the D2-receptor, blocks a late phase of an electrically induced long-term potentiation in the CA1-region in rats.

The influence of the D2-receptorblocker domperidone (DP) at a concentration of 1 microM was investigated on an electrically induced long-term potentiation (LTP) measured as the enhancement of the population spike (PS) amplitude in the hippocampal CA1. It could be shown that the drug does not influence the initiation but the maintenance of LTP. The results once again support the hypothesis that different phases of LTP exist which are realized by different cellular inputs.

Animals↗
PubMed1988

Anisomycin, an inhibitor of protein synthesis, blocks late phases of LTP phenomena in the hippocampal CA1 region in vitro.

Long-term potentiation (LTP) with its extremely long duration has been frequently regarded as an elementary mechanism of information storage in the nervous system or at least as a suitable model for the study of mechanisms underlying functional plasticity and processes of learning and memory formation. Considering the necessity of an increased protein synthesis for memory consolidation and for the maintenance of LTP in granular synapses in vivo it was of interest to determine whether the LTP of the CA1 region of the hippocampus depends on protein synthesis as well. For the solution of this question anisomycin (ANI), a reversible blocker of protein synthesis, was used at a concentration of 20 microM, which blocked the [3H]leucine incorporation in hippocampal slices by at least 85%. It has been shown that in the CA1 region in vitro the maintenance of LTP (i.e. a late phase greater than 5 h) depends on an ongoing protein synthesis. A 3-h treatment with ANI immediately following multiple tetanization resulted in gradually developing loss of field excitatory postsynaptic potential (EPSP) and population spike (PS) potentiation (15 +/- 19% increase of the PS instead of the 96 +/- 14% increase in non-treated control experiments at the 8th h after tetanization). Furthermore, a late PS potentiation (greater than 6 h) of a second non-tetanized pathway to CA1 pyramidal cells has been observed (increase by 64 +/- 18% at the 8th h) for the first time. This potentiation was ANI-sensitive as well and suggests that the maintenance of LTP is dependent on a postsynaptic mechanism.

Action Potentials↗
PubMed1988

Polymyxin B, an inhibitor of protein kinase C, prevents the maintenance of synaptic long-term potentiation in hippocampal CA1 neurons.

The involvement of protein kinase C (PKC)-mediated processes in mechanisms of long-term potentiation (LTP) was suggested by recent studies which have demonstrated a correlation between PKC activation and LTP. However, it was not possible to tell whether there is a causal relationship between the two events. Therefore, we have examined the induction and maintenance of LTP in rat hippocampal slices in the presence of a relatively selective PKC inhibitor, using extracellular electrophysiological techniques. Bath application of 0.1-100 microM polymyxin B did not influence the occurrence of post-tetanic and long-term potentiation usually seen in test responses 1 and 10 min after a 100-Hz/1 s tetanic stimulation of stratum radiatum fibers. However, 20 microM polymyxin B significantly depressed the increase in population spike amplitude and population excitatory postsynaptic potential (EPSP) slope from 30 to 120 min onwards, following repeated tetanization. Immediately after the drug application only weak and reversible effects were seen by the same parameters in test responses of a non-tetanized control input. A late (greater than 6 h) heterosynaptic potentiation of the population spike in the control input was blocked by polymyxin B treatment. Whereas the EPSP-LTP was fully blocked, some potentiation of the population spike still remained, suggesting the independence of PKC of the additional spike (E/S) potentiation for the first 6 h. These results provide direct evidence that the PKC activation is not essential for the initial phase of LTP, but is a necessary condition for a medium and a late, protein synthesis-dependent phase in this monosynaptic pathway, i.e. for the maintenance of synaptic LTP.

Action Potentials↗
PubMed1986

Calcium-induced long-term potentiation in the hippocampal slice: characterization of the time course and conditions.

A transient increase in extracellular calcium concentration causes a long-lasting enhancement of radiatum fibers evoked excitatory postsynaptic potential and population spike responses of CA1 pyramidal neurons which resembles long-term potentiation (LTP). The duration of this potentiation is much longer than described previously and is probably limited by the survival of the preparation itself (greater than 8 hr). Therefore, Ca-induced LTP can be used for the investigation of a postulated late phase of LTP. Ca effects were activity-independent, since the subsequently evoked responses were facilitated even when the presynaptic fibers were not concurrently stimulated during or immediately after superfusion with the high Ca medium. In contrast, if too frequent testing of the synaptic input was done during the high Ca pulse, a short lasting depression instead of potentiation was observed. A lower extracellular magnesium concentration in the standard medium (1.3 instead of 2.0 mM MgSO4) prevents the potentiation of the EPSP at least for the first few hours. Presumably, both tetanus- and Ca-induced LTP share some common mechanisms, since an additional tetanization after Ca induction was not followed by an additional LTP. Compared to the potentiation following tetanization, the Ca-induced LTP was, however, not accompanied by a potentiation of the EPSP/spike ratio within the range of the population spike threshold intensity.

Animals↗
PubMed1985

[Interdisciplinary prevention--a critical analysis of the situation].

We witness a general trend towards increasing specialization and particularism. In Switzerland, this is determined in part by historical and political factors. This trend influences especially the fields of biomedical research, education, the functioning of the health system and the protection of the environment. Preventive medicine is confronted with several obstacles. It certainly is not simple to implement interdisciplinary strategies for prevention and health promotion. It is urgent to make additional resources available, through the creation of a Prevention Fund. Integration and interdisciplinarity are to be promoted in pre and postgraduate training, in research and in the administrations. For the Swiss Society for Social and Preventive Medicine, a consequence is that collaboration has to be strengthened with societies and organisations, medical or not, which have similar purposes.

Humans↗
PubMed1980

[Self treatment through self medication].

Self-treatment of minor ailments is widespread. A lot of people seek advice from nonmedical counsellors or consult a "doctor's book" before applying to a medical practitioner. In Switzerland home made and natural remedies are rather popular whereas the treatment with chemical products is often met with scepticism. The greatest risk involved in uncontrolled self-medication and self-treatment is the unscrupulous consumption of medicines which can lead to addiction. The danger of important diagnoses being delayed is less considerable. From the health economic point of view reasonable self-medication and self-treatment are desirable. An important item is thereby the use of harmless natural remedies.

Diagnosis↗
PubMed1980

[Medical ethics and the public health office].

The Federal Office of Public Health is a governmental administration in charge of control and coordination measures related to the field of health protection. A rough 20% of the 220 officials and employees have university education prevailingly in medicine or natural sciences. Any government is working for the benefit of the general public and ought not to end in itself. Although there is a potential danger of abuse of official authority and power and of corruption, such deviations have proved to be quite rare in Switzerland. The safety guarantees are sufficient and we furthermore dispose in general of a professionally and morally well qualified staff. A governmental institution is as good or as bad as the humans working for it. A careful selection of the civil servants is therefore of utmost importance. On the whole, the quality of our civil service is quite superior to its reputation. Negative global judgements are to be declined. The Federal Office of Public Health aims at respecting the principles of the medical ethics in all its activities.

Confidentiality↗
PubMed1978

[Demonstration of osseous tumor micrometastases: comparison of the value of bone marrow cytology and histology].

In the course of a complete diagnostic work up ("staging") of 404 patients with solid tumors and malignant lymphomas, the bone marrow (BM) was analyzed cytologically (smears) as well as histologically (needle biopsy). 1. In this study both smear and needle biopsy showed an equal percentage of tumor metastases in the BM (14.6% and 16.1% respectively). Considerable differences exist between the various kinds of tumors, and therefore, each type must be viewed separately. 2. BM smear and BM needle biopsy complement each other. Combination of the two shows approximately 20--30% more positive BM finding as compared to each of the methods alone (19.6% positive findings), execpt in Hodgkin's disease.3. In Hodgkin's disease BM biopsy is superior to the smear in detecting BM infiltration. The biopsy yield is not improved on by smear. 4. In patients with oat cell tumors of the lung, the BM smears appear to be superior to biopsy for diagnosis of marrow invasion. The diagnostic yield of BM smears is, however, supplemented by the histology of simultaneous BM needle biopsy. 5. Direct BM examination (smear and needle biopsy) effectively supplements diagnostic radiological and isotope scanning procedures of the skeleton in searching for disseminated BM metastases in lung cancer of the oat-cell type, in non-Hodgkin lymphomas, and in prostatic cancer, but does not do so in patients with other solid tumors and Hodgkin's disease.

Bone Marrow Examination↗
PubMed1978

[Establishing prevention in federal legislation].

History and present situation of legislation on the cantonal and federal levels are briefly discussed. Special attention is given to the planned federal law on prevention which should provide a frame for various measures aiming at primary prevention of illnesses and accidents.

Drug and Narcotic Control↗
PubMed1978

[Is preventive medicine a government task?].

Health care of the citizens (sanitary police) belongs to the classical tasks of the public authorities ( = state). Primary prevention is a joint task of the state and the individual, but it only can be fully effective if the state participates in the organization and coordination. The most significant examples are immunization and prophylaxis of road accidents while preventive medical examinations can be left to the individual's own responsibility. It is no primary task of the state to carry them out and pay for them. The state creates the necessary basis for effective prevention by means of training and further education of the health personnel, continued evaluation of preventive measures, setting up statistical instruments, coordination of nationwide activities, active cooperation in publicity campaigns for preventive measures (mass media) and promoting research. Simultaneously, the citizen's own responsibility should be activated by persuasive measures. As little use as possible should be made of compulsory measures.

Government↗